TCM 820-3 Wheel Loader Technical Manual SEW-62M-MAE - PDF DOWNLOAD

No.SEW-62M-MAE

Operational Principle

TECHNICAL MANUAL

Operational Principle

E820-3

No.SEW-62M-MAE

INTRODUCTION TO THE READER • This manual is written for an experienced technician to provide technical information needed to maintain and repair this machine.

• Be sure to thoroughly read this manual for correct product information and service procedures.

ADDITIONAL REFERENCES • Please refer to the other materials (operator’s manual, parts catalog, engine technical material and Hitachi training material etc.) in addition to this manual.

MANUAL COMPOSITION • This manual consists the Technical Manual and the Workshop Manual.

• Information included in the Technical Manual: technical information needed for redelivery and delivery, operation and activation of all devices and systems, operational performance tests, and troubleshooting procedures.

• Information included in the Workshop Manual: technical information needed for maintenance and repair of the machine, tools and devices needed for maintenance and repair, maintenance standards, and removal/installation and assemble/disassemble procedures.

PAGE NUMBER • Each page has a number, located on the center lower part of the page, and each number contains the following information: Example : T 1-3-5 Consecutive Page Number for Each Group Group Number Section Number T: Technical Manual

W: Workshop Manual

IN-01

INTRODUCTION SAFETY ALERT SYMBOL AND HEADLINE NOTATIONS In this manual, the following safety alert symbol and signal words are used to alert the reader to the potential for personal injury of machine damage.

This is the safety alert symbol. When you see this symbol, be alert to the potential for personal injury.

Never fail to follow the safety instructions prescribed along with the safety alert symbol.

The safety alert symbol is also used to draw attention to component/part weights.

To avoid injury and damage, be sure to use appropriate lifting techniques and equipment when lifting heavy parts.

•

CAUTION: Indicated potentially hazardous situation which could, if not avoided, result in personal injury or death.

• IMPORTANT: Indicates a situation which, if not conformed to the instructions, could result in damage to the machine.

•

NOTE: Indicates supplementary technical information or know-how.

UNITS USED • SI Units (International System of Units) are used in

Example : 24.5 MPa (250 kgf/cm2, 3560 psi)

this manual.

MKSA system units and English units are also indicated in parenthheses just behind SI units.

Quantity Length Volume

Weight Force Torque

To Convert From mm mm L L m3 kg N N N⋅m N⋅m

Into in ft US gal US qt yd3 lb kgf lbf kgf⋅m lbf⋅ft

A table for conversion from SI units to other system units is shown below for reference purposees.

Multiply By 0.03937 0.003281 0.2642 1.057 1.308 2.205 0.10197 0.2248 1.0197 0.7375

Quantity Pressure Power Temperature Velocity Flow rate

IN-02

To Convert From MPa MPa kW kW °C km/h min-1 L/min mL/rev

Into

Multiply By 2

kgf/cm psi PS HP °F mph rpm US gpm cc/rev

10.197 145.0 1.360 1.341 °C×1.8+32 0.6214 1.0 0.2642 1.0

SECTION AND GROUP CONTENTS

SECTION 1 GENERAL Group 1 Specifications Group 2 Component Layout Group 3 Component Specifications

SECTION 2 SYSTEM TECHNICAL MANUAL (Operational Principle)

Group 1 Control System Group 2 Hydraulic System Group 3 Electrical System

SECTION 3 COMPONENT OPERATION Group 1 Priority Valve Group 2 Control Valve Group 3 Steering Valve Group 4 HST Pump Group 5 HST Motor Group 6 Reduction Group 7 Axle Group 8 Brake Master Cylinder Group 9 Others TECHNICAL MANUAL (Troubleshooting)

All information, illustrations and specifications in this manual are based on the latest product information available at the time of publication. The right is reserved to make changes at any time without notice.

SECTION 4 OPERATIONAL PERFORMANCE TEST Group 1 Introduction Group 2 Standard Group 3 Engine Test Group 4 Wheel Loader Test Group 5 Component Test Group 6 Adjustment

SECTION 5 TROUBLESHOOTING Group 1 Diagnosing Procedure Group 2 Component Layout Group 3 Troubleshooting A Group 4 Troubleshooting B Group 5 Troubleshooting C Group 6 Electrical System Inspection

←これ以下 記載しない

(Blank)

SECTION 1

GENERAL ―CONTENTS― Group 1 Specifications

Group 3 Component Specifications

Specifications ........................................... T1-1-1

Engine ...................................................... T1-3-1 Engine Accessories .................................. T1-3-5

Group 2 Component Layout Main Component Layout (Overview)......... T1-2-1 Main Component Layout (Body) ............... T1-2-2

Hydraulic Component ............................... T1-3-6 Electrical Component................................ T1-3-9

Main Component Layout (Travel System) ...................................... T1-2-3 Electrical System (Overview).................... T1-2-4 Electrical System (Inside of Cab).............. T1-2-5 Engine .................................................... T1-2-10 HST Pump / Main Pump ......................... T1-2-10 Reduction Gear / HST Motor ...................T1-2-11 Control Valve ...........................................T1-2-11

4FGET-1-1

(Blank)

4FGET-1-2

GENERAL / Specifications SPECIFICATIONS (STANDARD)

M4FGE-12-001

Model Bucket Type Bucket Capacity : heaped m3 (yd3) Operating Weight(Canopy/Cab) kg (lb) Static Tipping Load (Straight) Static Tipping Load (Full 40 Turn) Engine

kgf kgf

E820-3 Pin Type

Coupler Type 0.9 (1.2) (with BOC*)

5245 / 5405 (11570/11920) 3650 3110

5380/5540 (11860/12220) 3350 2840 KUBOTA V3307-DI-T 45.6 kW/2200 min-1 〔62 PS/2200 rpm〕

A: Overall Length

mm (ft⋅in)

B: Overall Width (Bucket)

mm (ft⋅in)

1990 (6’6”)

C: Overall Height

mm (ft⋅in)

2860 / 2850 (9’3”/9’4”)

D: Wheel Base

mm (ft⋅in)

2200 (7’3”)

E: Tread

mm (ft⋅in)

1470 (4’10”)

F: Ground Clearance

mm (ft⋅in)

340 (1’1”)

G: Bucket Hinge Height

mm (ft⋅in)

3160 (10’4”)

H: Dumping Clearance (45°)

mm (ft⋅in)

2500 (8’2”)

2390 (7’10”)

I: Dumping Reach (45°)

mm (ft⋅in)

880 (2’11”)

990 (3’3”)

5220 (17’2”)

5380 (17’8”)

R1: Minimum Turning Radius

3795 (12’5”)

mm (ft⋅in) R2: Minimum Turning Radius mm (ft⋅in) Travel Speed Forward/Reverse km/h (mph) Transmission Speeds (F/R) Articulation Angle (Left/Right) deg Tire Size

4475 (14’8”)

4540 (14’11”) 34.0 / 34.0 (21/21) 2/2

(°)

40

-

17.5/65-20-10PR

NOTE: • * BOC (Bolt-On Cutting Edge) • These specifications are subject to change without notice.

T1-1-1

GENERAL / Specifications (Blank)

T1-1-2

GENERAL / Component Layout MAIN COMPONENT LAYOUT (OVERVIEW) 4

3 2

1

8

7

6

5

M4FGE-01-001

12 9 11

1 - Bucket

2 - Bell Crank 3 - Bucket Cylinder

10

M4FGE-01-002

4 - Head Light / Turn Signal / Hazard Light / Clearance Light 5 - Fuel Tank 6 - Lift Arm Cylinder

7 - Lift Arm

8 - Bucket Link 9 - Hydraulic Oil Tank

T1-2-1

10 - Rear Combination Light (Turn Signal Light / Hazard Light / Clearance Light / Brake Light) 11 - Reverse Light 12 - Backup Buzzer

GENERAL / Component Layout MAIN COMPONENT LAYOUT (BODY)

3

2

1

4

5

6

7

8

9 10 11

12

23

13 22 21 14

20 19 18

17

16

15 T4FG-01-02-005

123456-

Bucket Cylinder Lift Arm Cylinder Steering Valve Priority Valve Brake Master Cylinder Parking Brake Solenoid Valve

7 - Hydraulic Oil Tank 8 - Hydraulic Oil Return Filter 9 - Hydraulic Oil Suction Filter 10 - Brake Oil Tank 11 - Air Cleaner 12 - Coolant Reservoir

13 - Oil Cooler 14 - Radiator 15 - Fuel Pre-Filter 16 - Fuel Filter 17 - Fuel Pump 18 - Engine

T1-2-2

19 - HST Pump 20 - Gear Pump 21 - HST Filter 22 - Fuel Tank 23 - Control Valve

GENERAL / Component Layout MAIN COMPONENT LAYOUT (TRAVEL SYSTEM)

2

1

3 4 5

6

T4FG-01-02-006

1 - Front Axle 2 - Steering Cylinder

34-

HST Motor Reduction Gear

5-

T1-2-3

Rear Axle

6-

Propeller Shaft

GENERAL / Component Layout ELECTRICAL SYSTEM (OVERVIEW) 2

1

Inside of Cab Refer to T1-2-5.

3

4 5 6

17

16 7

15 8

14

9 13 12

11

10 T4FGE-01-02-007

1 - Horn 2 - Brake Light Switch 3 - Brake Pedal Angle Sensor 4 - HST Controller 5 - Air Cleaner Restriction Switch

6 - Coolant Temperature Sensor 7 - Reverse Buzzer 8 - Battery 9 - Engine Speed Sensor 10 - Starter Relay 1

11 - Glow Relay

16 - Speed Sensor

12 - Fusible Link (100 A ) (2 Used) 13 - Brake Oil Level Sensor 14 - Starter Relay 2 15 - Fuel Level Sensor

17 - Bucket Proximity Switch

T1-2-4

GENERAL / Component Layout ELECTRICAL SYSTEM (INSIDE OF CAB) 1

2

3

Front Console Refer to T1-2-7.

Right Console Refer to T1-2-6.

Rear Console Refer to T1-2-8.

T4FG-01-02-008

1-

Radio (Optional)

2-

Rotary Beacon Switch (Optional)

3-

T1-2-5

Auxiliary

GENERAL / Component Layout Right Console 1

2 3 4 5 6

7

9 8 M4FG-01-009

1 - Loader Control Lever 2 - Auxiliary Control Lever (Optional) 3 - Auxiliary Control Lever Lock (Optional)

4 - Auxiliary 5 - Ride Control Switch (Optional)

6 - eco Mode Switch 7 - Heater Switch (Optional)

T1-2-6

8 - Key Switch 9 - Loader Control Lever Lock

GENERAL / Component Layout Front Console 1

13

2

3

4

5 12 6

11

7 10 8 9

T4FG-01-02-009

1 - Monitor Panel (Refer to T1-2-9.)

2 - Horn Switch 3 - Steering Wheel

5 - Front Wiper Switch (Cab)

8 - Light Switch

6 - Rear Wiper Switch (Cab)

9 - Neutral Lever Lock (Forward/Reverse Lever) 10 - Forward/Reverse Lever

7 - Turn Signal Lever / Dimmer Switch

4 - Parking Brake Switch

T1-2-7

11 - High-Low Selector Switch 12 - Work Light Switch (Cab) 13 - Hazard Light Switch

GENERAL / Component Layout Rear Console 3

2

1

4

5

6 7 8 9

1-

10

T4FG-01-02-010

11

Fuse Box

4-

Parking Brake Relay [1]

7-

Buzzer (Overrun Alarm) 3 - Fuse Box (Cab)

5-

Parking Brake Relay [2]

8-

6-

Alternator Indicator Relay [3]

2-

12

HST Control Relay [4]

Emergency Parking Brake Relay [5] 9 - Flasher Unit (Turn Signal/ Hazard Light)

T1-2-8

10 - Front Work Light Relay (Cab) 11 - Rear Work Light Relay (Cab) 12 - Front Wiper Relay (Cab)

GENERAL / Component Layout Monitor Panel

1

2

3

4

5

6

8

7

9

10

11

22 12

21

20

19

18

17

16

15

14

13 M4FG-01-010

1 - Coolant Temperature Gauge 2 - Left Turn Signal Indicator

7 - Stop Indicator

13 - Not Used

19 - Overheat Indicator

8 - Service Indicator

3 - High Beam Indicator

9 - Parking Brake Indicator

14 - Discharge Warning Indicator 15 - Error Code Readout Switch

4 - Monitor Display 5 - Work Light Indicator (Optional) 6 - Right Turn Signal Indicator

10 - Clearance Light Indicator 11 - Fuel Gauge

20 - Engine Oil Low Pressure Indicator 21 - Air Filter Restriction Indicator 22 - HST Warning Indicator

12 - Brake Oil Low Level Indicator

16 - Preheat Indicator 17 - Monitor Display Selector (Up) 18 - Monitor Display Selector (Down)

T1-2-9

GENERAL / Component Layout ENGINE 3

5

4

6

7

8

9

2

1

T4FG-01-02-011

1 - Starter 2 - Engine Speed Sensor

45-

Engine Oil Filter Alternator

67-

Fuel Pre-Filter Fuel Filter

89-

Fuel Pump Coolant Temperature Sensor

3 - Engine Oil Pressure Switch

HST PUMP, MAIN PUMP 1

2

3

5

4

2

6

7 T4FG-01-02-012

1 - Main Pump 2 - High-Pressure Relief Valve

3-

Forward Selection Solenoid Valve 4 - DE Pump Solenoid Valve

5-

Low-Pressure Relief Valve

6-

Displacement Angle Control Cylinder

T1-2-10

7-

Reverse Selection Solenoid Valve

GENERAL / Component Layout REDUCTION GEAR, HST MOTOR

3

2

1

T4FG-01-02-013

CONTROL VALVE

8 9

7

10

6

5

4 T4FGE-01-02-014

1-

HST Motor

4 - Electromagnetic Detent (Bucket)

2-

EP Motor Solenoid Valve

5 - Overload Relief Valve (Bucket: Rod Side)

3 - Reduction Gear

7 - Overload Relief Valve (Auxiliary (Coupler): Rod Side) 8 - Overload Relief Valve (Auxiliary (Coupler): Bottom Side)

6 - Make-Up Valve (Lift Arm: Rod Side)

T1-2-11

9-

Overload Relief Valve (Bucket: Bottom Side)

10 - Main Relief Valve

GENERAL / Component Layout (Blank)

T1-2-12

GENERAL / Component Specifications ENGINE Manufacturer.......................................... KUBOTA Model ..................................................... V3307-DI-T Type....................................................... Diesel, 4-Cycle Water-Cooled, Inline, Direct Injection, Turbo Charged Cyl. No.-Bore×Stroke ............................. 4-94 mm×120 mm (3.7 in×4.7 in) Piston Displacement .............................. 3331 cm3 (203 in3) Rated Output ......................................... 45.6 kW/2200 min-1 (62 PS/2200 rpm) Compression Ratio ................................ 20 Dry Weight ............................................. 268 kg (591 lb) Firing Order............................................ 1-3-4-2 Rotation Direction .................................. Clock Wise (Viewed from Crank Pulley) Dimensions Length×Width×Height......... 655×557×738 mm (26 in×22 in×29 in) (Without Fan) COOLING SYSTEM Fan Pulley Ratio..................................... 1.18 Thermostat............................................. Cracking Temperature at Atmospheric Pressure: 76.5 °C (170 °F) Full Open Temperature: 90 °C (194 °F) LUBRICATION SYSTEM Method................................................... Pressure Lubrication Type Lubrication Pump Type .......................... Trochoid Type Filter....................................................... Full Flow Paper Elemnt Cooler .................................................... Water-Cooled

T1-3-1

GENERAL / Component Specifications STARTING SYSTEM Method.............................................................Self-Starter Type Voltage/Output .................................................12 V/3.0 kW PREHEAT SYSTEM Method.............................................................Glow Plug, QGS Type (4 Used, 12V/12.6 A) ENGINE STOP SYSTEM Type.................................................................Fuel Shut Off (Solenoid Valve) ALTERNATOR Method.............................................................Regulator Integrated IC Type Voltage/Output .................................................12 V/80 A SUPERCHARGING SYSTEM Type.................................................................Exhaust Turbocharger Type, EGR (Exhaust Gas Recirculation) System Lubricating System ..........................................Pressure Lubrication/Water-Cooled Type FUEL SYSTEM Governor..........................................................Mechanical Type Injection Pump .................................................Bosch, K-type Minipump Injection Nozzle................................................Bosch, P-type Hole Nozzle (2-Stage Injection-Valve Opening Pressure Nozzle)

T1-3-2

GENERAL / Component Specifications IMPORTANT: The list shows the design specifications, which are not servicing standard.

Fuel Consumption Ratio ..................................250±13 g/kW⋅h (184±5% g/PS⋅h) at 2200 min-1 Maximum Output Torque..................................233±12 N⋅m (23.7±1.2 kgf⋅m, 170±9 lbf⋅ft) at 1500 min-1 -1 No Load Speed ................................................Slow: (At Full Load: 1150±50 min ) -1 Fast: (At Full Load: 2400±50 min )

T1-3-3

GENERAL / Component Specifications Engine Performance Curve (KUBOTA V3307-DI-T) Test conditions: 1. In conformity with SAE J1349/JIS D0006-1 (Earth-moving machinery-Engines-Part 1: Test code of net power) under standard atmospheric pressure only.

2. Equipped with the air cleaner, muffler, and fan.

Torque (N⋅m)

Output (kW)

Fuel Consumption Ratio (g/kW⋅h)

-1

Engine Speed min (rpm)

T1-3-4

T4FG-01-03-001

GENERAL / Component Specifications ENGINE ACCESSORIES RADIATOR ASSEMBLY Type.................................................................Radiator/Oil Cooler (Parallel Type) Radiator Oil Cooler Capacity...........................................................5.0 L (1.1 US gal) 3.3 L (0.9 US gal) Air-Tight Test Pressure.....................................100 kPa (1.0 kgf/cm2, 14.5 psi) 1500 kPa (15 kgf/cm2, 220 psi) Cap Opening Pressure ....................................49 kPa (0.5 kgf/cm2, 7.0 psi) Weight..............................................................6.3 kg (14 lb) 8.3 kg (18 lb) BATTERY Nominal Voltage...............................................12 V Capacity...........................................................64 Ah (5-Hour Rating) Weight..............................................................Approx. 19.7 kg (43 lb)

T1-3-5

GENERAL / Component Specifications HYDRAULIC COMPONENT HST PUMP Type

HST Pump: Direct Operating Proportional Solenoid Control Charge Pump: Trochoid Type Maximum Flow Rate (Theoretical) ...................HST Pump: 0 to 198 L/min (0 to 52 US gpm) Charge Pump: 43 L/min (11.4 US gpm) High-Pressure Relief Valve Set Pressure.........46.5±1.0 MPa (474±10 kgf/cm2, 6740±145 psi) Pressure Difference: 44 MPa (448 kgf/cm2, 6380 psi) Low-Pressure Relief Valve Set Pressure..........2.5±0.1 MPa (26±1 kgf/cm2, 360±14.5 psi) Cutoff Valve Set Pressure ................................43.7±1.0 MPa (445±10 kgf/cm2, 6340±145 psi) 2 Pressure Difference: 41.2 MPa (420 kgf/cm , 5980 psi) Weight..............................................................Approx. 60 kg (132 lb)

PUMP DEVICE (GEAR PUMP) Type.................................................................Constant Capacity Type Gear Pump Function ...........................................................Main Pump Maximum Flow Rate (Theoretical) ...................Main Pump: 80 L/min (21 US gpm) Weight..............................................................5.9 kg (13 lb) PRIORITY VALVE 2 Relief Set Pressure ..........................................20.6 MPa (210 kgf/cm , 2990 psi) at 100 L/min CONTROL VALVE Type.................................................................Mono-Lever Direct Operating Type (3-Spool, with Electromagnetic Detent) Main Relief Set Pressure .................................20.6 MPa (210 kgf/cm2, 2990 psi) at 80 L/min Overload Relief Set Pressure...........................23.6 MPa (230 kgf/cm2, 3220 psi) at 30 L/min (Bucket Tilt) 2 23.6 MPa (230 kgf/cm , 3220 psi) at 30 L/min (Bucket Dump) Weight..............................................................8 kg (18 lb) STEERING VALVE Type.................................................................Orbitroll Type 2 Overload Relief Set Pressure...........................23.1 MPa (235 kgf/cm , 3350 psi) at 1 L/min Weight..............................................................6.4 kg (14 lb) SOLENOID VALVE Function ...........................................................Parking Brake BRAKE VALVE Type.................................................................Master Cylinder Size..................................................................1” 1/4 Stroke ..............................................................40 mm (1.6 in)

T1-3-6

GENERAL / Component Specifications • Travel System HST MOTOR Type.................................................................Bent-Axis Type Variable Displacement Axial Plunger Motor Control System ................................................Proportional Solenoid Control Weight..............................................................Approx. 64 kg (141 lb) STANDARD AXLE (FRONT) Model ...............................................................Two Stage Reduction Brake Type.......................................................Wet-Type Spring Set Hydraulic Released Multi-Disc Brake Parking Brake Type..........................................Built-In Negative Type (SAHR Type) 2 Parking Brake Release Pressure .....................2.5 MPa (26 kgf/cm , 363 psi) Final Reduction Ratio.......................................13.7 Weight..............................................................235 kg (518 lb) STANDARD AXLE (REAR, Reduction) Model ...............................................................One-Stage Reduction Final Reduction Ratio.......................................13.7 Reduction Reduction Ratio ...............................................1.77 Weight..............................................................270 kg (595 lb) STANDARD PROPELLER SHAFT Type.................................................................Cruciform Joint Type Dimension Between Flanges ...........................1509 mm (59.4 in) STEERING CYLINDER Rod Outer Diameter.........................................25 mm (1.0″) Tube Inner Diameter ........................................45 mm (1.8″) Stroke ..............................................................340 mm (1′ 1″) Fully Retracted Length .....................................605 mm (1′ 12″) Plating Thickness.............................................30 μm (1.18 μin) Weight..............................................................8 kg (18 lb)

T1-3-7

GENERAL / Component Specifications • Front Attachment CYLINDER Lift Arm (Left/Right) Rod Outer Diameter.........................................50 mm (2.0″) Tube Inner Diameter ........................................85 mm (3.3″) Stroke ..............................................................552 mm (2′) Fully Retracted Length .....................................898 mm (2′ 11″) Plating Thickness.............................................30 μm (1.18 μin) Weight..............................................................37 kg (82 lb)

T1-3-8

Bucket 45 mm (1.8”) 80 mm (3.1”) 457 mm (1′ 6″) 785 mm (2′ 7″) 30 μm (1.18 μin) 30 kg (66 lb)

GENERAL / Component Specifications ELECTRICAL COMPONENT ENGINE OIL PRESSURE SWITCH Operating Pressure..........................................45 kPa (0.5 kgf/cm2, 6.5 psi) COOLANT TEMPERATURE SENSOR (FOR COOLANT TEMPERATURE GAUGE) Operating Temperature ....................................25 to 120°C (77 to 248°F) AIR FILTER RESTRICTION SWITCH Operating Pressure..........................................6.2±0.6 kPa (635±58 mm H2O) FUEL LEVEL SENSOR Resistance .......................................................Empty: 90+100 Ω, Full: 100-4 Ω ENGINE SPEED SENSOR Voltage.............................................................12 V STARTER RELAY 1 Voltage.............................................................12 V GLOW RELAY Voltage/Current ................................................12 V STARTER RELAY 2 Voltage.............................................................12 V HORN Consumption Current.......................................4 A or less at 12V Sound Pressure ...............................................111 dB (A) at 2 m Frequency........................................................(High): 440±20 Hz (Low): 370±20 Hz ILLUMINATION Work Light (Cab)..............................................12 V, 55 W Cab Light (Cab) ...............................................12 V, 10 W Head Light .......................................................12 V, 45/45 W Front Combination Light Turn Signal Light ..........................................12 V, 21 W Clearance Light ............................................12 V, 21 W Rear Combination Light Turn Signal Light ..........................................12 V, 21 W Tail Light .......................................................12 V, 5 W Brake Light ...................................................12 V, 21 W License Plate Light...........................................12 V, 10 W Reverse Light...................................................12 V, 21 W

T1-3-9

GENERAL / Component Specifications (Blank)

T1-3-10

MEMO .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... ....................................................................................................................................................................

MEMO .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... ....................................................................................................................................................................

SECTION 2

SYSTEM —CONTENTS— Group 1 Control System

Group 3 Electrical System

Outline...................................................... T2-1-1

Outline ...................................................... T2-3-1

HST Control.............................................. T2-1-3

Main Circuit............................................... T2-3-2

Other Controls .........................................T2-1-11

Electric Power Circuit (Key Switch: OFF).. T2-3-3

Control by Electric and Hydraulic

Indicator Light Check Circuit

Combined Circuit .................................. T2-1-17

(Key Switch: ON) .................................... T2-3-5 Preheat Circuit (Key Switch: HEAT) .......... T2-3-6

Group 2 Hydraulic System

Starting Circuit (Key Switch: START) ........ T2-3-8

Outline...................................................... T2-2-1

Charging Circuit (Key Switch: ON) .......... T2-3-14

Main Circuit .............................................. T2-2-3

Engine Stop Circuit ................................. T2-3-18

Steering Circuit ......................................... T2-2-5

Lamplight Circuit ..................................... T2-3-19

HST Circuit ............................................. T2-2-13

Head Light Circuit ................................... T2-3-20

Brake Circuit........................................... T2-2-20

Turn Signal Circuit .................................. T2-3-24 Brake Light Circuit .................................. T2-3-27 Hazard Light Circuit ................................ T2-3-28 Horn Circuit............................................. T2-3-31 Revrse Light / Buzzer Circuit .................. T2-3-32 Parking Brake Circuit .............................. T2-3-34 Emergency Parking Brake Circuit ........... T2-3-38 Indicator Circuit....................................... T2-3-41

4FGET-2-1

(Blank)

4FGET-2-2

SYSTEM / Control System OUTLINE There are two types of controllers.

• •

The HST control unit and the monitor unit are used for various operation controls of the machine.

HST Control Unit Monitor Unit

The monitor unit and the HST control unit display information on the monitors and control the machine travel function by using received analog signals and detected signals by sensors and switches.

Sensors and Switches for Traveling

Each controller computes various control programs by using the detected data, outputs the driving signals to the solenoid valve for traveling, and controls the HST pump and the HST motor.

Engine

HST Control Unit

HST Pump

DE Pump Solenoid Valve

Engine Speed Seneor

Sensors, Switches

Sensors and Switches for Monitor Monitor Unit

Reduction Gear

HST Motor

Relays

EP Motor Solenoid Valve Light Emitting Diode

Speed Sensor

T2-1-1

T4FG-02-01-001

SYSTEM / Control System The sensors and switches for HST control unit to detect the signals for various operation controls and their controls are as shown below.

Input Signal

• Forward/Reverse Lever • Engine Speed Sensor • Speed Sensor • High-Low Selector Switch • Brake Angle Sensor • ECO Mode Switch

→ → → → →

HST Control Unit

T2-1-2

Operation Control HST Control →High-Low Selection Control (HST Motor) →Inching Control (HST Pump) →ECO Mode Control (HST Pump) →Overrunning control (HST Motor) →Engine protection control (HST Pump, HST Motor) Control by Electric and Hydraulic Combined Circuit →Bucket Auto Leveler Control

SYSTEM / Control System HST Control The HST control consists of the followings.

• High-Low Selection Control (HST Motor) • ECO Mode Control (HST Pump) • Inching Control (HST Pump) • Overrunning Control (HST Motor) • Engine Protection Control (HST Pump, HST Motor)

T2-1-3

SYSTEM / Control System High-Low Selection Control (HST Motor) Purpose: The High-Low selection control controls the HST motor displacement angle according to the selected speed.

Operation: Displacement Angle Control of HST Motor 1. When the HST control unit detects the machine speed, it computes the most suitable HST motor displacement angle.

2. The current equivalent to the computed displacement angle operation is supplied to the EP motor solenoid valve of the HST motor and changes the displacement angle.

3. The HST motor displacement angle is controlled by repeating step 1 to step 2.

NOTE: The speed selection is carried out by the High-Low selector switch. When the Low mode is selected, the signal of the selected speed (Low mode) is sent to the HST control unit.

A

When Low mode is selected: • The ON signal is sent to the HST control unit from the High-Low selector switch.

• The HST motor displacement angle is controlled among A-B-C and the machine speed increases (decreases).

When High mode is selected: • The OFF signal is sent to the HST control unit from the High-Low selector switch.

• The HST motor displacement angle is controlled among A-B-D and the machine speed increases (decreases).

B

HST Motor Displacement Angle

C

D E

0 Selected Speed Range

Low Mode

Machine Speed

High Mode

T2-1-4

T4FC-02-01-101

SYSTEM / Control System

Engine Speed Sensor

HST Control Unit

Engine

HST Pump

Reduction Gear

HST Motor

Monitor Unit

High-Low Selector Switch Lo

EP Motor Solenoid Valve

Hi

Speed Sensor

NOTE: The illustration shows the signal flow when the Low mode of the High-Low selector switch is selected.

T2-1-5

T4FG-02-01-002

SYSTEM / Control System ECO Mode Control (HST Motor) Purpose: When the ECO mode of the ECO mode switch is selected, engine speed can be limited. Therefore, the fuel consumption is less than the normal mode Operation: When ECO mode is selected: • When the ECO mode of the ECO mode switch is selected, the ON signal is sent to the HST control unit.

• According to the input signal the HST control unit controls the displacement angle in order to limit the HST motor maximum displacement angle.

When normal mode is selected: • When the normal mode of the ECO mode switch is selected, no signal is sent to the HST control unit.

• Therefore, the HST motor maximum displacement angle is not limited.

ECO Mode Normal Mode

HST Motor Displacement Angle

HST Motor Rotation Speed (rpm)

T2-1-6

T4FG-02-01-006

SYSTEM / Control System Inching Control (HST Pump) Purpose: Inching control limits the HST pump delivery flow rate according to the brake pedal depressing amount and applies the HST brake.

Operation: 1. The brake pedal depressing amount (angle) is transmitted to the brake pedal angle sensor through the link and converted into the signal.

2. The signal is sent to the HST control unit from the brake pedal angle sensor. The signal varies according to the brake pedal depressing amount (angle).

3. The HST control unit converts into 0 to 100% for the inching angle converted value according to the input signal.

4. The HST control unit computes the inching angle converted value according to the signal from the brake angle sensor, and controls the displacement angle in order to limit the HST pump displacement angle according to the inching angle converted value. (Refer to Hydraulic System / Inching Circuit.)

Brake Pedal

Brake Pedal Angle Sensor

HST Control Unit T4FG-02-01-004

Brake pedal is not depressed.

Brake pedal is depressed fully.

HST Brake Applied Range Brake Pedal

T4FG-02-01-005

T2-1-7

SYSTEM / Control System Overrunning Control (HST Motor) Purpose: When the machine speed is exceeds the allowable maximum speed, it forcibly decreases the machine speed within the speed range.

Operation: 1. The HST control unit computes the machine speed on the basis of the signal from the speed sensor.

2. When the computed machine speed exceeds the allowable maximum speed, the HST control unit controls the motor to make displacement angle larger. Therefore, the machine speed decreases forcibly.

3. When the computed machine speed decreases within the speed range, the HST control unit releases the overrunning control and performs normal motor displacement angle control.

NOTE: When it is under overrunning control, the HST warning indicator and the service indicator blink and the buzzer souds continuously.

Displacement Angle after Control

HST Motor Displacement Angle

Displacement Angle before Control 0 Machine Speed

T2-1-8

T4FC-02-01-101

SYSTEM / Control System Engine Protection Control (HST Pump, HST Motor) Purpose: In order to prevent overrunning of the engine caused by HST brake, the engine protection control controls the HST motor displacement angle, and controls the engine speed to 2800 min-1.

Operation: 1. When releasing the accelerator while traveling in fast speed, the HST brake is applied. The HST pump is forcibly rotated by the pressure oil in the HST circuit.

2. The HST pump and the engine are connected with the shaft. Therefore, the rotation of the HST pump is transmitted to the engine as well. The engine runs in fast speed.

3. The HST control unit detects the signal from the engine speed sensor. When the engine speed is -1 over 2800 min , the HST control unit controls so that the HST motor displacement angle should be reduced in stages.

4. This control releases the HST brake and prevents the engine from overrunning.

NOTE: This control is available when the High-Low selector switch is set to the High mode.

NOTE: This control is given priority over Overrunning Control (T2-1-8). Therefore, the machine may travel in fast speed.

Maximum Displacement Angle Displacement Angle before Control HST Motor Displacement Angle

Displacement Angle after Control

Minimum Displacement Angle

Machine Speed Speed after Control Speed before Control

T2-1-9

T4FC-02-01-019

SYSTEM / Control System (Blank)

T2-1-10

SYSTEM / Control System OTHER CONTROLS Other control systems consist of the followings: • HST Warning Indicator Control • Parking Brake Operation Control (Emergency)

T2-1-11

SYSTEM / Control System HST Warning Indicator Control Purpose:

In order to protect the HST system, the HST warning indicator on the monitor unit lights when malfunction of the parts that lead to HST system breakage occur.

Operation: When any of the parts below becomes faulty, the HST control unit lights the HST warning indicator on the monitor unit.

NOTE: The monitor unit lights the service indicator as well as the HST warning indicator at the same time.

• • • • • • •

EP Motor Solenoid Valve Engine Speed Sensor Speed Sensor Forward / Reverse Lever Brake Angle Sensor Overrun Buzzer DE Pump Solenoid Valve

T2-1-12

SYSTEM / Control System

Brake Pedal (Inching)

Brake Angle Sensor

Forward/Reverse Selection Solenoid Valve

Engine Speed Sensor HST Control Unit

Engine HST Pump 20

DE Pump Solenoid Valve

Monitor Unit HST Warning Indicator

Reduction Gear

F

2A-11 HST Motor

N R

EP Motor Solenoid Valve

HST Relay

Forward / Reverse Lever SpeedSensor

Fuse #13

T4FG-02-01-006

T2-1-13

SYSTEM / Control System Parking Brake Operation Control (Emergency) Purpose: The parking brake operation control lights the brake oil low level indicator on the monitor unit and spplies the parking brake when the brake oil level is below the lower limit.

Operation: 1. The brake oil level sensor is turned ON when the brake oil level in the brake oil tank is below the lower limit.

2. The monitor unit lights the brake oil low level indicator and the stop indicator.

3. Emergency parking brake relay (5) is excited and the parking brake is applied when the signal from the brake oil level sensor is input to the HST control unit.

4. The monitor unit lights the HST warning indicator and the parking brake indicator.

T2-1-14

NOTE: As for the operation circuit of the parking brake, refer to SYSTEM/Hydraulic System/ Brake Circuit.

SYSTEM / Control System

Emergency Parking Brake Relay (5)

Parking Brake Relay (1)

HST Control Unit

Brake Oil Level Sensor

Monitor Unit

Parking Brake Solenoid

Parking Brake Service Brake

ON OFF Parking Brake Switch

Front Axle

T2-1-15

T4FG-02-01-007

SYSTEM / Control System (Blank)

T2-1-16

SYSTEM / Control System CONTROL BY ELECTRIC HYDRAULIC COMBINED CIRCUIT

AND

The electric and hydraulic combined circuit consists of the followings: • Bucket Auto Leveler Control

T2-1-17

SYSTEM / Control System Bucket Auto Leveler Control Purpose: The bucket auto leveler control automatically sets the bucket at a proper (horizontal) digging start angle when returning the bucket to the tilting position Operation: 1. During bucket dump operation, the bar is located in front of the bucket proximity switch.

While the bar passes near the bucket proximity switch, the bucket proximity switch is turned ON. Therefore, the electromagnet on the bucket tilting side in the control valve is also excited.

2. When the loader control lever is operated farther than the bucket tilting detent position (position operated farther than the tilting position), the loader control lever is held by the electromagnet on the bucket tilting side, and the bucket spool in the control valve is held.

3. Pressure oil from the main pump flows to the bottom side of the bucket cylinder through the bucket spool in the control valve, and extends the bucket cylinder. When the bucket cylinder is extended, the bar also passes near the bucket proximity switch at the same time.

4. When the bar moves apart from the bucket proximity switch, the bucket proximity switch is turned OFF. Therefore, the electromagnet on the bucket tilting side is turned OFF and the loader control lever is returned to the neutral position. As the bucket spool in the control valve are also returned to the neutral position, the bucket cylinder stops. Consequently, the bucket is set at the proper (horizontal) digging start angle.

T2-1-18

SYSTEM / Control System

Bar

Bucket Proximity Switch

Bucket Cylinder

Control Valve

Lift Arm

Bucket

From Fuse Box Terminal #10

Main Pump

Hydraulic Oil Tank

T2-1-19

Electromagnet on Bucket Tilting Side

T4FG-02-01-008

SYSTEM / Control System (Blank)

T2-1-20

SYSTEM / Hydraulic System OUTLINE The hydraulic system is broadly divided into the main circuit, the steering circuit, the HST circuit, and the brake circuit.

• Main Circuit Consists of the neutral circuit ,the front attachment operation circuit, and the auxiliary front attachment operation circuit (optional) - composed of the main pump, the control valve, the bucket cylinder,and the lift arm cylinder.

• Steering Circuit Consists of the steering circuit and the steering stop circuit - composed of the priority valve, the steering valve, and the steering cylinder.

• HST Circuit Consists of the charging circuit, the neutral circuit, the forward travel circuit, the reverse travel circuit, and the inching circuit - composed of the HST pump and the HST motor.

• Brake Circuit Consists of the service brake circuit and the parking brake circuit - composed of the brake oil tank, the brake master cylinder, and the parking brake solenoid valve.

T2-2-1

SYSTEM / Hydraulic System (Blank)

T2-2-2

SYSTEM / Hydraulic System MAIN CIRCUIT Outline: • The main pump draws and delivers hydraulic oil from the hydraulic oil tank through the suction filter.

• Delivered pressure oil flows to the control valve through the priority valve.

• Pressure oil to the control valve flows to the cylinders in response to operation of the spool in the control valve, and the returning oil flows back to the hydraulic oil tank through the control valve.

Bucket Cylinder

Lift Arm Cylinder

Control Valve Bucket Spool Lift Arm Spool

Priority Valve

Main Pump

Suction Filter

Hydraulic Oil Tank T4FG-02-02-001

T2-2-3

SYSTEM / Hydraulic System Neutral Circuit

Front Attachment Circuit

• When the loader control lever is in neutral, pressure oil from the main pump returns to the hydraulic oil tank through the neutral circuit of the control valve.

• Pressure oil from the main pump flows to the control valve, and flows to the each spool of lift arm and bucket.

NOTE: The illustration shows oil flow without operation while the engine is running.

Auxiliary Front Attachment Operation Circuit (Optional) • Pressure oil from the main pump flows to the control valve, and flows to the auxiliary actuator (optional) spool.

Auxiliary Actuator (Optional)

Control Valve

Auxiliary Actuator (Optional)

Lift Arm Cylinder

Lift Arm

Bucket Cylinder

Bucket

Hydraulic Oil Tank Main Pump

T2-2-4

T4FG-02-02-002

SYSTEM / Hydraulic System STEERING CIRCUIT Outline: • Delivered pressure oil from the main pump is divided through the priority valve. One flows to the steering valve and the other flows to the control valve.

• Pressure oil to the steering valve flows to the steering cylinders in response to operation of the spool in the steering valve, and the returning oil flows back to the hydraulic oil tank through the steering valve.

Steering Cylinder

Steering Valve Control Valve

Priority Valve

Main Pump

Suction Filter

Hydraulic Oil Tank

T4FG-02-02-003

T2-2-5

SYSTEM / Hydraulic System Priority Valve Circuit (When steering is in neutral) • When the engine is stopped, the priority valve spool is pushed rightward by the spring force.

• When the engine is started, pressure oil from the main pump flows to the steering valve through the priority valve spool, and also flows to ports LS1 and LS2 through orifices 1 and 2 respectively at the same time.

• When steering is in neutral, as pressure oil to port LS2 flows to the hydraulic oil tank through orifice 3 and the steering valve spool, port LS2 is not pressurized.

• As pressure at port LS1 is larger than the spring force, the priority valve spool moves leftward, and all pressure oil from the main pump flows to the control valve.

• The priority valve spool is provided with a notch to lead pressure oil from the main pump to the steering valve and a notch to lead pressure oil to the control valve, which are both connected to the main pump delivery port constantly.

• When the priority valve spool moves leftward, the notch to lead pressure oil from the main pump to the steering valve moves until the delivery port on the steering valve side in the priority valve is closed. The pressure balance is obtained and the spool stops moving.

T2-2-6

NOTE: Orifice 2 of the priority valve is installed in order to warm up the circuit by flowing pressure oil to the hydraulic oil tank from port LS2 at neutral of the steering valve.

Although diameter of port 2 is small and temperature of the oil passing through it rises rapidly, pressure is not raised enough to influence movement of the priority valve spool.

SYSTEM / Hydraulic System Steering Cylinder

Steering Valve

P Control Valve Priority Valve

Orifice 3

Orifice 2 LS

CF

EF

Orifice 1

LS1 Spool

LS2 Spring

Main Pump

When Engine Stops T4FG-02-02-004

NOTE: The illustration shows the pressure oil flow without operation while the engine is running.

T2-2-7

SYSTEM / Hydraulic System Steering Circuit (When Steering is Operated) • When the steering wheel is operated, the oil passage (orifice 4) between the spool and the sleeve of the steering valve is opened in proportion to the steering wheel rotation speed. Port P is connected to the gerotor in the steering valve.

• When the steering wheel is operated quickly, the orifice 4 opening becomes large and pressure oil flow rate to the steering valve increases. When the steering wheel is operated slowly, the orifice 4 opening becomes small and pressure oil flow rate to the steering valve decreases.

• Orifice 4 is opened at the moment when the steering wheel is operated, pressure oil between LS1 and port CF in the priority valve and orifice 4 in the steering valve flows to the gerotor.

• As pressure oil flows to the gerotor, the oil pressure between LS1 and port CF in the priority valve and orifice 4 in the steering valve decreases, the spool in the priority valve moves rightward.

• The spool in the priority valve becomes balanced at the position where pressure oil corresponding to orifice 4 open area the priority valve flows to the steering valve.

• At this time, pressure oil from the main pump flows to both the steering valve and the control valve.

• Pressure oil from the main pump flows to the gerotor through the spool and sleeve in the steering valve. The gerotor delivers pressure oil while rotating as a hydraulic motor. Pressure oil from gerotor flows to the steering cylinder and the machine turns.

• When the rotation of the steering wheel is stopped, the oil passage between the spool and the sleeve in the steering valve is closed. The spool and the sleeve are returned to the neutral position by the spring force completely. Pressure oil from the pump does not flow to the gerotor and the steering cylinder is stopped. (Refer to COMPONENT OPERATION/Steering Valve.)

T2-2-8

NOTE: Load sensing control is performed by using the combinations of orifice 4 and the spool in priority valve. The spool in the priority valve corresponds to the flow rate control valve.

NOTE: As the gerotor is connected to the middle shaft of the steering valve, powered steering effect is generated. (Refer to COMPONENT OPERATION/Steering Valve.)

SYSTEM / Hydraulic System

Steering Cylinder

Steering Valve Sleeve

Gerotor

Spring Steering Wheel

P

Spool Sleeve

Orifice 4 Control Valve Priority Valve

LS

CF

EF

LS1 Hydraulic Oil Tank

Spool

Spring Main Pump

NOTE: The illustration shows the pressure oil flow when the steering wheel is turned to the right.

T2-2-9

T4FG-02-02-005

SYSTEM / Hydraulic System Steering Stop Circuit (When steering cylinder is at stroke end) • When the steering wheel is operated, the oil passage (orifice 4) between the spool and the sleeve of the steering valve is opened in proportion to the steering wheel rotation speed.Pressure in port LS1, LS2, and CF decreases, the priority valve moves rightward.

• When the steering cylinder reaches the stroke end, the pressure in LS 2 in the priority valve increases due to pressure oil from the main pump.

• When the pressure in LS 2 exceeds the specified level, the relief valve in the priority valve is operated, and the pressure oil acting on LS2 flows from the relief valve to the hydraulic oil tank.

• When the relief valve is operated, the pressure oil in LS2 in the priority valve flows to the hydraulic oil tank. Therefore, the pressure difference between LS1 and LS2 occurs due to orifice 2.

• Therefore, the spool in the priority valve moves leftward and pressure oil from the main pump flows to the control valve.

T2-2-10

SYSTEM / Hydraulic System Steering Cylinder

Steering Valve

Steering Wheel

Orifice 3 Priority Valve

Control Valve LS

CF

EF

LS1 Hydraulic Oil Tank

Spool

Spring Relief Valve

Main Pump

NOTE: The illustration shows the pressure oil flow when the relief valve in the priority valve is operated.

T2-2-11

T4FG-02-02-006

SYSTEM / Hydraulic System (Blank)

T2-2-12

SYSTEM / Hydraulic System HST CIRCUIT Outline: • The HST (Hydro-Static Transmission) circuit is a closed circuit, and consists of the HST pump and the HST motor.

• The HST pump is directly driven by the engine power. The HST motor turned by pressure oil from the HST pump.

• The output power of the HST motor is transmitted to the reduction gear / rear axle → the propeller shaft → the front axle → the tire in sequence.

NOTE: The reduction gear is connected to the rear axle.

• The HST pump has a built-in HST charging pump.

The HST charging pump is directly driven by the engine power and draws hydraulic oil from the hydraulic oil tank. The hydraulic oil is added to the low pressure side in the closed circuit in the HST pump and the HST motor through the HST filter.

• Pressure oil from the HST charging pump also cools the HST pump and the HST motor. Pressure oil from the HST charging pump is the oil pressure source of the HST pump displacement angle control.

HST Pump Engine HST Charging Pump

HST Filter

Hydraulic Oil Tank HST Motor

Reduction Gear

Rear Axle

Front Axle

T4FG-02-02-007

Propeller Shaft

T2-2-13

SYSTEM / Hydraulic System Charge Circuit

Neutral Circuit

• Pressure oil from the HST charging pump flows to the orifice in the DE pump solenoid valve through the HST filter.

• A pressure difference occurs between the front and the rear of the orifice by the delivery flow rate of the HST charging pump. The DE pump solenoid valve reduces oil pressure from the HST charging pump according to this pressure difference and provides the control pressure for the HST pump displacement angle.

• The DE pump solenoid valve controls the HST pump displacement angle by supplying the reduced pressure oil to the displacement angle control cylinder.

• The high pressure relief valve provides the function of a check valve. When the flow rate on the low pressure side in the HST close circuit is insufficient, the check valve is opened and pressure oil from the HST charging pump is added.

• The forward/reverse selection solenoid valve is located between the DE pump solenoid valve and the displacement angle control cylinder. When the forward/reverse lever is in neutral, the forward/reverse selection solenoid valve is kept neutral as the forward/reverse selection solenoid valve is not excited.

• Therefore, the pressure oil reduced by the DE pump solenoid valve is not supplied to the displacement angle control cylinder. The HST pump displacement angle is kept neutral.

• Therefore, pressure oil is not delivered from HST pump. The HST motor does not rotate.

NOTE: The delivery flow rate of the HST charged pump is changed in proportion to the engine speed. Therefore, the control pressure for the HST pump displacement angle is changed almost in proportion to the engine speed.

T2-2-14

NOTE: When the forward/reverse lever is in neutral, the EP motor solenoid valve is excited.

SYSTEM / Hydraulic System DE Pump Solenoid Valve

Forward/Reverse Selection Solenoid Valve

HST Filter

HST Pump

Displacement Angle Control Cylinder

Orifice

Engine

HST Charging Pump High-Pressure Relief Valve EP Motor Solenoid Valve

HST Motor

T4FG-02-02-008

T2-2-15

SYSTEM / Hydraulic System Forward Travel Circuit

Reverse Travel Circuit

• When setting the forward/reverse lever to the forward position, the forward selection solenoid valve of the forward/reverse selection solenoid valve is excited and the spool moves rightward.

• Therefore, the circuit between the DE pump solenoid valve and the displacement angle cylinder is connected, and pressure oil from the HST charging pump is supplied to the displacement angle control cylinder.

• As pressure oil from the HST charging pump is supplied to the left side of displacement angle control cylinder, the piston of the displacement angle cylinder moves rightward.

• Therefore, the HST pump displacement angle is changed from the neutral position and the HST pump delivers pressure oil.

• Pressure oil from the HST pump is supplied to the HST motor.

• Therefore, the HST motor rotates to the forward direction.

• When setting the forward/reverse lever to the reverse position, the reverse selection solenoid valve of the forward/reverse selection solenoid valve is excited and the spool moves leftward.

• As pressure oil from the HST charging pump is supplied to the right side of displacement angle cylinder, the HST pump displacement angle direction is reversed in a forward circuit case.

• Therefore, the HST motor rotates to the reverse direction.

T2-2-16

SYSTEM / Hydraulic System DE Pump Solenoid Valve

Forward/Reverse Selection Control Valve

HST Pump

Displacement Angle Control Cylinder

HST Motor

T4FG-02-02-009

NOTE: The illustration shows the forward travel circuit.

T2-2-17

SYSTEM / Hydraulic System Inching Circuit • The signal from the HST control unit excites the DE pump solenoid valve and moves the spool.

The circuit between the DE pump solenoid valve and the forward/reverse selection solenoid valve is connected to the hydraulic oil tank. (Refer to Control System / HST Brake (Inching) Control.)

• Therefore, as the control pressure in the HST pump displacement angle decreases, the displacement angle control cylinder is operated in order to return to the neutral position.

• Consequently, the HST pump displacement angle is changed to neutral and the HST pump delivery flow rate is reduced.

• As the HST pump delivery flow rate is reduced, the rotation speed of the HST motor decreases and the machine is slowed down.

• The control pressure in the HST pump displacement angle is changed according to the depressing amount of the brake pedal. When depressing the brake pedal fully, the HST pump displacement angle becomes neutral.

T2-2-18

SYSTEM / Hydraulic System

Brake Pedal

Brake Pedal Angle Sensor

DE Pump Solenoid Valve

HST Control Unit

Forward/Reverse Selection Solenoid Valve

Displacement Angle Control Cylinder

HST Pump T4FG-02-02-010

NOTE: The illustration shows the pressure oil from when the brake pedal is depressed.

T2-2-19

SYSTEM / Hydraulic System BRAKE CIRCUIT Service Brake Circuit (Refer to COMPONENT OPERATION / Brake Master Cylinder.)

• The brake pedal is connected to the master cylinder via the link.

• The brake master cylinder is filled with brake oil in the brake oil tank.

• Pressure oil from the brake master cylinder is routed to the front brake and the service brake is applied when the brake pedal is depressed.

NOTE: The service brake circuit is held due to the brake master cylinder with the engine stopped.

Parking Brake Circuit • Pressure oil from the HST charging pump is routed to the parking brake solenoid valve.

• When the parking brake switch is turned OFF, the parking brake solenoid valve is excited and pressure oil flows to the parking brake cylinder so that the parking brake is released.

• When the parking brake switch is turned ON, the parking brake solenoid valve is not excited and pressure oil stops being supplied to the parking brake so that the parking brake is applied.

T2-2-20

SYSTEM / Hydraulic System

HST Charging Pump

Parking Brake Solenoid Valve Signal for Parking Brake Release

Brake Pedal

Brake Oil Hydraulic Oil Tank Tank

Brake Master Cylinder

Parking Brake Service Brake

T4FGE-02-02-011

NOTE: The illustration shows the pressure oil flow when the parking brake solenoid valve is excited and the parking brake is released, and the pressure oil flow of the service brake circuit when the brake pedal is depressed.

T2-2-21

SYSTEM / Hydraulic System (Blank)

T2-2-22

SYSTEM / Electrical System OUTLINE The electrical circuit is broadly divided into the main circuit, the lamplight circuit, and the control circuit

• Main Circuit Circuit for engine start/stop, circuit for battery charging

• Lamplight Circuit Circuit for traveling (composed of headlights, turn signals, brake lights, and horn)

• Control Circuit (Refer to SYSTEM/Control System.)

Control circuit for engine, HST pump, HST motor, and valves [composed of actuator as solenoid valve, HST control unit, monitor unit, switch, sensor, and pressure switch] Functions and compositions of the main circuit and the lamplight circuit are explained in this group.

T2-3-1

SYSTEM / Electrical System MAIN CIRCUIT • Electric power circuit: It provides electric power source for the electrical system.

• Indicator light check circuit: It checks the bulbs for monitor warning lamp and indicators.

• Preheat circuit: It assists the engine in starting in cold weather.

• Starting circuit: It starts the engine.

• Charging circuit: It supplies electricity to the battery and charges the battery.

• Engine stop circuit: It stops the engine.

T2-3-2

SYSTEM / Electrical System ELECTRIC POWER SWITCH: OFF)

CIRCUIT

(KEY

The battery ground terminal is connected to the body.

Current from the battery plus terminal flows as shown below when the key switch is in the OFF position.

Battery ↓ Fusible Link

Although the key switch is in the OFF position, very small amount of current is supplied to the circuit.

Disconnect the battery ground terminal when the machine is stopped for long periods.

→Fuse Box

→ Fuse #13 → Fuse #14 → Fuse #19 → Fuse #20

HST Controller Relay [4] Montir Unit (Backup Power) (Option Power) Hazard Switch, Turn Signal Lever

→Fuse Box (Cab)

→ Fuse # 6 → Fuse # 7 → Fuse # 8 → Fuse # 9 → Fuse # 10

(Option Power) (Option Power) Cab Light, Radio (Optional), (Backup Power) Work Light (Front) Work Light (Rear)

→Key Switch

Fuse Box

Fuse Box (Cab)

Monitor Unit

6 7 8 9 10

1A-1

Key Switch

13 14

19 20

Starter Motor Fusible Link (100A)

Engine

(Power)

Battery T4FG-02-03-001

T2-3-3

SYSTEM / Electrical System (Blank)

T2-3-5

SYSTEM / Electrical System INDICATOR LIGHT CHECK CIRCUIT (KEY SWITCH: ON) • When the key switch is turned to the ON position,

• The monitor unit starts the liquid crystal display as

terminal B is connected to terminal ACC in the key switch.

• Current from terminal ACC in the key switch flows to terminal 1A-2 in the monitor unit through fuse #11 in fuse box.

well as checks the indicator bulbs by lighting the warning lamp and indicators.

Fuse Box Monitor Unit 1A-2

11 Key Switch

Starter Motor Fusible Link (100A)

Engine

(Power) Battery T4FG-02-03-002

T2-3-6

SYSTEM / Electrical System PREHEAT CIRCUIT (KEY SWITCH: HEAT) • When the key switch is turned to the HEAT position, terminal B is connected to terminal R1 in the key switch.

• Current from terminal R1 excites the glow relay.

Battery power is supplied to the glow plug from the glow relay through the fusible link (100A).

• While the glow relay is excited, the pre-heating is carried out as the power is supplied to the glow plug from the glow relay.

• While the pre-heating is carried out, the glow plug relay is ON so that current is supplied to the monitor unit and lights the preheat indicator.

• Even if the pre-heating is not carried out, the preheat indicator lights for 2 seconds in order to check the indicator bulbs.

T2-3-7

SYSTEM / Electrical System

Key Switch Preheat Indicator

Monitor Unit

2A-1

Glow Plug Relay

Glow Plug Engine

Starter Motor

Fusible Link (100A)

(Power) Battery T4FG-02-03-003

NOTE: The illustration shows the current flow when preheating is carried out with the glow plug relay excited and power supplied to the glow plug.

T2-3-8

SYSTEM / Electrical System STARTING START)

CIRCUIT

(KEY

SWITCH:

Forward/Reverse Lever in Neutral • When the key switch is turned to the START position, terminal B is connected to terminals ACC and C in the key switch.

• Current from terminal ACC is supplied to terminal R in the starter relay 2 through fuse #9 in fuse box.

• Current from terminal C in the key switch is supplied to the starter relay 1 coil through the neutral circuit in the forward/reverse lever, and to terminal S in the starter relay 2.

• Therefore, starter relay 1 is excited and battery power is supplied to terminal S in the starter motor from starter relay 1.

• Consequently, the relay in the starter motor is turned ON so that the starter motor rotates.

• When the engine has started, the current from terminal L in the alternator stops.

• One current from terminal BR in the key switch is supplied to the fuel pump through fuse #8 in fuse box so that it is operated. Another current is supplied to the engine stop solenoid holding side so that the plunger is held.

T2-3-9

SYSTEM / Electrical System Fuse Box

Key Switch B

R1 R2 BR ACC C

HEAT OFF ON START

8 9

Forward/Reverse Lever Starter Relay 1 F N

Starter Relay 2 R R L S P

Starter Motor

Engine Stop Solenoid

Engine Alternator

E S

B R L

P B

Fuel Pump

Fusible Link (100A)

(Starting/ Charging)

＋ (Power)

－

Battery

T4FG-02-03-005

NOTE: The illustration shows the current flow when the forward/reverse lever is in the neutral position and the engine speed is 1150 min-1 or less.

T2-3-10

SYSTEM / Electrical System (Blank)

T2-3-11

SYSTEM / Electrical System Starter Relay 2 Operation • When the key switch is turned to the START position, continuity between terminals B and ACC in the key switch is found. Current is supplied to the base in transistor Tr3 through resistance R in the starter relay 2. Transistor Tr3 is turned ON and current is supplied to coil R in starter relay 1.

Consequently, battery power is supplied to terminal S in the starter motor from starter relay 1 so that the starter is operated.

• When the engine is started, the alternator begins charging and the pulse wave pattern of the frequency in proportion to the engine speed is output from terminal P in the alternator.

• When this frequency reaches 170 Hz (alternator rotation speed is 1700 r/min), transistor Tr3 is turned OFF as no current is supplied to the base in transistor Tr3.

Current to coil R in starter relay 1 is stopped at this time so that the starter is turned OFF.

Alternator

Starter Switch B

R

R Starter Relay 2 L

L

R R

P

P

Starter Relay 1

S

Tr3

Battery

E

To Starter Motor Terminal S

T4FG-02-03-004

T2-3-12

SYSTEM / Electrical System Forward/Reverse Lever at Operated Position

• Starting Circuit • When the key switch is turned to the START position, terminal B is connected to terminals ACC and C in the key switch.

• Battery power is supplied to starter relay 1 through terminal B in the starter motor and the fusible link (100A).

• When either the forward/reverse lever is in the forward or the reverse position, starter relay 1 is not excited as current from terminal C in the key switch is not supplied to the neutral circuit in the forward/reverse lever.

Therefore, battery power is stopped at starter relay 1.

• Therefore, in case when either the forward/reverse lever is in the forward or the reverse position, the starter motor is not operated even the key switch is turned to the START position

T2-3-13

SYSTEM / Electrical System Fuse Box

Key Switch B

R1 R2 BR ACC C

HEAT OFF ON START

9

Forward/Reverse Lever

Starter Relay 1 F N

Starter Relay 2 R R L S P

Starter Motor

Engine Stop Solenoid

Engine Alternator

E S

B R L

P B

Fuel Pump (Starting/ Charging) Fusible Link (100A) ＋

－

(Power) Battery T4FG-02-03-006

NOTE: The illustration shows the current flow when the forward/reverse lever is in the reverse position.

T2-3-14

SYSTEM / Electrical System CHARGING CIRCUIT (KEY SWITCH: ON) • After the engine starts and the key switch is released, the key switch returns to the ON position.

• Terminal B is connected to terminal ACC in the key switch with the key switch ON. • Current from terminal ACC in the key switch excites charge lamp relay [3] through fuse #9 in the fuse box.

• The alternator starts generating electricity with the engine running. Current from terminal B in the alternator is supplied to the battery through the slow blow fuse (starting/charging), starter motor terminal B, and charges the battery.

• When current from terminal a in charge lamp relay [3] is supplied to terminal 1A-14 in the monitor unit as the generating electricity start signal of alternator terminal L, the alternator indicator lights. When no current is supplied to terminal 1A-14, the alternator indicator goes off.

T2-3-15

SYSTEM / Electrical System

Alternator Indicator

Fuse Box Monitor Unit

Key Switch B

R1 R2 BR ACC C

HEAT OFF ON START

1A-14

9

Charge Lamp Relay ［3］

a

Fusible Link

Starter Motor

(Starting/ Charging)

Alternator Engine

B

R L

P ＋

－

B

Battery

(Power)

T4FG-02-03-007

T2-3-16

SYSTEM / Electrical System Alternator Operation • The alternator consists of field coil FC, stator coil SC and diode D. • At the beginning, no current is flowing through field coil FC. When the rotor starts rotating, alternate current is generated in stator coil SC by the rotor remanent magnetism.

• When current flows through field coil FC, the rotor is further magnetized so that the generating voltage increases. Therefore, current flowing through field coil FC increases. Therefore, generating voltage increases further and the batteries start charging.

Regulator Operation • The regulator is an IC chip, which maintains generated voltage at a constant level.

• When generating voltage exceeds the set voltage, the regulator reduces current through field coil FC. This reduces generating voltage of stator coil SC. • When generating voltage becomes lower than the set voltage, the regulator increases current through field coil FC. This increases generating voltage of stator coil SC. • The above operation is repeated so that the alternator generating voltage is kept constant.

T2-3-17

SYSTEM / Electrical System

Alternator

Starter Switch IC Regulator

SC

B R

D

Starter Relay 2 Starter Relay1

L Ds

R R

D P

FC Tr1

Tr3

Battery

Tr2 To Starter Motor Terminal S

E T4FG-02-03-004

T2-3-18

SYSTEM / Electrical System ENGINE STOP CIRCUIT • Current from terminal BR is supplied to the engine

• When the key switch is changed ON into OFF,

stop solenoid holding side through fuse #8 in fuse box with the key switch ON so that the plunger of the engine stop solenoid is held.

current from terminal BR is not supplied and the plunger of the engine stop solenoid is not held so that the control rack is pushed by the spring force and the engine is stopped.

• In addition, current is not supplied to the fuel pump and it is stopped.

Fuse Box

Key Switch B

R1 R2 BR ACC C

HEAT OFF ON START

Battery Power

8

Fuel Pump

Engine

Engine Stop Solenoid

Holding Side

T4FG-02-03-009

NOTE: The illustration shows the current flow when the key switch is in the ON position.

T2-3-19

SYSTEM / Electrical System LAMPLIGHT CIRCUIT • Headlight circuit: It turns on or off the headlight, the clearance light and the license-plate light (optional).

• Turn signal circuit: It operates the turn signal.

• Brake light circuit: It turns on and off the brake light.

• Hazard light circuit: It operates the hazard light.

• Horn circuit: It operates the horn.

• Reverse light/buzzer circuit: It operates the reverse light and the reverse buzzer.

• Parking brake circuit: It applies and releases the parking brake.

T2-3-20

SYSTEM / Electrical System HEADLIGHT CIRCUIT Clearance Light Lighting Circuit • When the key switch is turned to the ON position, terminal B is connected to terminal ACC in the key switch.

• Current from terminal ACC is supplied to the headlight switch through fuse #12 in fuse box.

• When the headlight switch is positioned at the Clearance Light, one of power from terminal (1) in the headlight switch is supplied to terminal 1B-21 in the monitor unit and the clearance light indicator lights.

• Another power to fuse box is divided and supplied to fuse #4 and fuse #5. Power from fuse #4 lights the left front clearance light, right rear clearance light, and license-palte light.

Power from fuse #5 lights the right front clearance light and left rear clearance light.

T2-3-21

SYSTEM / Electrical System Key Switch B

Monitor Unit

R1 R2 BR ACC C

HEAT OFF ON START

Clearance Light Indicator 1B-21

Fuse Box

4 5

12 Headlight Switch

Clearance Light (Front Right Side)

Tail Light (Right Side) License-Plate Light Tail Light (Left Side)

Clearance Light (Front Left Side)

Fusible Link

Starter Motor Engine

Battery T4FG-02-03-010

T2-3-22

SYSTEM / Electrical System Headlight Lighting Circuit

• When the key switch is turned to the ON position, terminal B is connected to terminal ACC in the key switch.

• Current from terminal ACC is supplied to the headlight switch through fuse #12 in fuse box.

• When the headlight switch is positioned at Headlight, power lights each clearance light.

(Refer to Clearance Light Lighting Circuit.) Power from terminal #2 in the headlight switch is supplied to the dimmer switch.

• When the dimmer switch is set to Low (low beam), power is divided and supplied to fuse #1 and fuse #2 in fuse box.

• Power from fuse #1 in the fuse box lights the low beam of right headlight.

• Power from fuse #2 in the fuse box lights the low beam of left headlight.

• When the dimmer switch is set to High (high beam), power lights the high beam of head lights through fuse #3 in fuse box.

• Another power is supplied to terminal 1B-22 in the monitor unit and lights the high beam indicator in it.

T2-3-23

SYSTEM / Electrical System Key Switch B

Monitor Unit

R1 R2 BR ACC C

HEAT OFF ON START

High Beam Indicator

1B-22

Fuse Box 1 2 3

12 Headlight Switch

Dimmer Switch

High Beam Headlight (Right Side) Low Beam High Beam Headlight (Left Side) Low Beam

Fusible Link

Starter Motor Engine

Battery T4FG-02-03-011

T2-3-24

SYSTEM / Electrical System TURN SIGNAL CIRCUIT • Battery power is supplied to the flasher unit through fuse #20 in fuse box with the key switch OFF. • Battery power is supplied to the turn signal switch through terminal L in the flasher unit.

• When the turn signal switch is turned to left (L), power from the turn signal switch is supplied to the left turn signal light and terminal 1-19 in the monitor unit.

• Consequently, the left front and rear turn signal lights and the left turn signal indicator on the monitor unit blink.

T2-3-25

SYSTEM / Electrical System Key Switch Turn Signal Indicator (Left Side)

Monitor Unit

B

R1 R2 BR ACC C

HEAT OFF ON START

1A-19

Turn Signal Indicator (Right Side)

1A-20

Fuse Box

Hazard Light Switch

Flasher Unit

20

Turn Signal Light (Front Right Side)

Turn Signal Light (Rear Right Side)

Turn Signal Light (Front Left Side)

Fusible Link

Starter Motor

Turn Signal Light (Rear Left Side)

Engine

Battery T4FG-02-03-012

NOTE: The illustration shows the current flow when the turn signal switch is in left (L).

T2-3-26

SYSTEM / Electrical System (Blank)

T2-3-27

SYSTEM / Electrical System BRAKE LIGHT CIRCUIT • When the key switch is turned to the ON position, current from terminal ACC in the key switch is supplied to the brake light switch through fuse #7 in fuse box.

• When the brake pedal is depressed, the brake light is grounded.

• Therefore, battery power lights the brake light.

Key Switch B

R1 R2 BR ACC C

HEAT OFF ON START

Brake Pedal Fuse Box Brake Light Switch.

7

Brake Light (Right Side)

Fusible Link

Starter Motor Engine

Battery

Brake Light (Left Side)

T4FG-02-03-013

T2-3-28

SYSTEM / Electrical System HAZARD LIGHT CIRCUIT • Battery power is supplied to the flasher relay through fuse #20 in fuse box with the key switch OFF. • Battery power is supplied to the hazard light switch through terminal L in the flasher unit.

• When the hazard light switch is turned to the ON position, battery power is supplied to all of turn signal lights and terminal 1A-19 and terminal 1A-20 in the monitor unit.

• Consequently, all of turn signal lights and left/right turn signal indicator on the monitor unit blink.

T2-3-29

SYSTEM / Electrical System Key Switch Turn Signal Indicator (Left Side)

Monitir Unit

B

R1 R2 BR ACC C

HEAT OFF ON START

1A-19

Turn Signal Indicator (Right Side)

1A-20

Fuse Box

Hazard Light Switch

Flasher Unit

20 Turn Signal Light (Front Right Side) Turn Signal Light (Rear Right Side)

Turn Signal Light (Front Left Side)

Fusible Link

Stater Motor Engine

Turn Signal Light (Rear Left Side)

Battery T4FG-02-03-014

T2-3-30

SYSTEM / Electrical System (Blank)

T2-3-31

SYSTEM / Electrical System HORN CIRCUIT • When the key switch is turned to the ON position,

• When the horn switch is pushed, it is grounded.

• Therefore, battery power is supplied to the horn

power from terminal ACC is supplied to the horn relay through fuse #7 in fuse box.

and it sounds.

Key Switch B

R1 R2 BR ACC C

HEAT OFF ON START

Horn Switch

Fuse Box

Low 7

Horn

High

Fusible Link

Starter Motor Engine

Battery

T4FG-02-03-015

T2-3-32

SYSTEM / Electrical System REVERSE LIGHT / BUZZER CIRCUIT When Forward/Reverse lever is operated • When the key switch is turned to the ON position, power from terminal ACC is supplied to parking brake relay [2] through fuse #7 in the fuse box.

• Current through parking brake relay [2] is supplied to the forward/reverse lever through parking brake relay [1].

• When the forward/reverse lever is set to the reverse position, battery power is divided and one of power is supplied to the reverse light and the reverse buzzer.

• Another power is supplied to the reverse side of forward/reverse selection solenoid valve in the HST pump so that the signal is sent to the HST control unit and [R] on the forward/reverse and shift position indicator on the monitor LCD is displayed.

T2-3-33

SYSTEM / Electrical System

Forward/Reverse Lever FN R

Key Switch Parking Brake Relay [1]

B

Parking Brake Relay [2]

R1 R2 BR ACC C

HEAT OFF ON START

Fuse Box

6

Reverse Light

Fusible Link

Reverse Buzzer

Starter Motor Engine

Battery

T4FG-02-03-016

T2-3-34

SYSTEM / Electrical System PARKING BRAKE CIRCUIT Parking brake switch is changed into OFF from ON after engine starts

• When the key switch is turned to the ON, current from terminal ACC is supplied to the parking brake switch through fuse #9 in the fuse box and charge lamp relay [3].

• In addition, current through fuse #6 in the fuse box is supplied to parking brake relay [1] from parking brake relay [2].

• Power through terminal #b in parking brake relay [2] is supplied to terminal #b in parking brake relay [1] and terminal #4 in the parking brake switch through terminal #a in parking brake relay [2].

• The parking brake switch consists of the three circuits (ON-Neutral-OFF). If turning to the ON, the switch is kept ON. If turning to the OFF, the switch returns to neutral position when releasing the switch.

• When the parking brake switch is turned to the OFF, power through terminal #4 in the parking brake switch is not supplied to terminal #2 in it so that parking brake relay [1] is not excited.

• Power through terminal #b in parking brake relay [1] is supplied to the parking brake solenoid valve through terminal #e in parking brake relay [1].

IMPORTANT: The parking brake cannot be released unless the engine is running.

• Consequently, the parking brake is released as the parking brake solenoid valve is activated.

T2-3-35

SYSTEM / Electrical System

OFF Neutral ON

Key Switch Parking Brake Switch

B Parking Brake Relay [1]

Parking Brake Relay [2]

Charge Lamp Relay [3]

R1 R2 BR ACC C

HEAT OFF ON START

Monitor Unit

Parking Brake Indicator

Fuse Box

1A-17

6 9

Starter Motor

Alternator Engine

Parking Brake Solenoid Valve Fusible Link

Battery

T4FG-02-03-017

NOTE: The illustration shows the current flow when the parking brake switch is turned to the OFF position and the parking brake switch is not released while running the engine.

T2-3-36

SYSTEM / Electrical System Parking brake switch is changed into ON from OFF after engine starts

• When the parking brake switch is turned to the ON, power through terminal #4 in the parking brake switch is supplied to terminal #c in parking brake relay [1] through terminal #2 in the parking brake switch.

• As parking brake relay [1] is excited, power to the parking brake solenoid valve through terminal #e in the parking brake relay [1] is stopped.

• Power from terminal #a in parking brake relay [1] lights the parking brake indicator on the monitor unit.

• Consequently, as the parking brake solenoid valve is not excited, the parking brake is applied.

T2-3-37

SYSTEM / Electrical System OFF Neutral ON

Key Switch Parking Brake Switch

B Parking Brake Relay [1]

Parking Brake Relay [2]

Charge Lamp Relay [3]

R1 R2 BR ACC C

HEAT OFF ON START

Monitor Unit Parking Brake Indicator

Fuse Box

1A-17

6 9

Starter Motor

Alternator Engine

Parking Brake Solenoid Valve Fusible Link

Battery

T4FG-02-03-018

T2-3-38

SYSTEM / Electrical System EMERGENCY PARKING BRAKE CIRCUIT • When the service brake system is abnormal and the brake pedal is depressed excessively, the HST control unit excites the emergency parking brake relay.

• Consequently, as the parking brake solenoid valve is not excited, the parking brake is applied.

T2-3-39

SYSTEM / Electrical System

OFF Neutral

Parking Brake Switch

ON

Parking Brake Relay [1]

Charge Lamp Relay [3] Emergency Parking Brake Prking Brake Relay [2] Relay

B

Key Switch R1 R2 BR ACC C

HEAT OFF ON START

Monitor Unit Parking Brake Indicator

Fuse Box

1A-17

6 9

29

HST Control Unit

Starter Motor

Alternator Engine

Brake Pedal Angle Sensor Parking Brake Solenoid Valve Fusible Link

Battery

T4FG-02-03-024

T2-3-40

SYSTEM / Electrical System (Blank)

T2-3-41

SYSTEM / Electrical System INDICATOR CIRCUIT The indicator circuit consists of the followings: • Overheat Indicator • Engine Oil Low Pressure Indicator • Brake Oil Low Level Indicator • Air Filter Restriction Indicator

T2-3-42

SYSTEM / Electrical System Overheat Indicator Purpose: It lights the overheat indicator on the monitor unit in order to inform the abnormal rising in the engine coolant temperature to the operator.

NOTE: The monitor unit lights the stop indicator as well as the overheat indicator at the same time.

Operation: • The overheat indicator lights when the coolant temperature needle of the monitor unit reaches the red zone.

• The overheat indicator goes off when the coolant temperature needle of the monitor unit is below the red zone.

Monitor Unit

Engine

Water Temperature Unit

Overheat Indicator 2A-9

Stop Indicator

T4FG-02-03-019

T2-3-43

SYSTEM / Electrical System Engine Oil Low Pressure Indicator Purpose: It lights the engine oil low pressure indicator on the monitor unit in order to inform the pressure lowering in engine lubricant oil to the operator.

Operation: 1. When the engine lubricant oil pressure becomes lower than the normal range, the engine oil pressure switch is grounded.

2. When the engine oil pressure switch is grounded, the monitor unit lights the engine oil low pressure indicator.

3. When the engine lubricant oil pressure returns to the normal range, the engine oil pressure switch is disconnected from the ground.

4. When the engine oil pressure switch is disconnected form the ground, the monitor unit goes off the engine oil pressure indicator.

Monitor Unit

NOTE: The monitor unit lights the stop indicator as well as the engine oil low pressure indicator at the same time.

Engine Engine Oil Pressure Switch

Engine Oil Low Pressure Indicator

1A-8

Stop Indicator

T4FG-02-03-020

T2-3-44

SYSTEM / Electrical System Brake Oil Low Level Indicator Purpose: It lights the brake oil low level indicator on the monitor unit in order to inform the brake oil lowering to the operator.

Operation: 1. When the brake oil level becomes lower than the normal value, the brake oil level switch is grounded.

2. When the brake oil level switch is grounded, the monitor unit lights the brake oil low level indicator.

3. When the brake oil level returns to the normal value, the brake oil level switch is disconnected from the ground.

4. When the brake oil level switch is disconnected from the ground, the monitor unit goes off the brake oil low level indicator.

NOTE: The monitor unit lights the stop indicator as well as the brake oil low level indicator at the same time.

Brake Oil Level Switch

Monitor Unit

Brake Oil Low Level Indicator

1A-13

Stop Indicator

21

T4FG-02-03-021

T2-3-45

SYSTEM / Electrical System Air Filter Restriction Indicator Purpose: It lights the air filter restriction indicator on the monitor unit in order to inform the clogged air filter to the operator.

Operation: 1. When the air filter is clogged, the air cleaner restriction switch is grounded.

2. When the air cleaner restriction switch is grounded, the monitor unit lights the air filter restriction indicator.

3. When the clogged air filter is recovered, the air cleaner restriction switch is disconnected from the ground.

4. When the air cleaner restriction switch is disconnected form the ground, the monitor unit goes off the air filter restriction indicator.

NOTE: The monitor unit lights the service indicator as well as the air filter restriction indicator at the same time.

Air Cleaner Restriction Switch

Monitor Unit Air Filter Restriction Indicator

Engine Engine Oil Pressure Switch

1A-9

Service Indicator

T4FG-02-03-022

T2-3-46

SYSTEM / Electrical System (Blank)

T2-3-47

MEMO .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... ....................................................................................................................................................................

MEMO .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... .................................................................................................................................................................... ....................................................................................................................................................................

SECTION 3

COMPONENT OPERATION —CONTENTS— Group 1 Priority Valve

Group 5 HST Motor

Outline...................................................... T3-1-1

Outline ...................................................... T3-5-1

Structure................................................... T3-1-2

Operation .................................................. T3-5-4

Operation ................................................. T3-1-3

Regulator .................................................. T3-5-6 EP Motor Solenoid Valve .......................... T3-5-6

Group 2 Control Valve Outline...................................................... T3-2-1

Group 6 Reduction

Hydraulic Circuit ....................................... T3-2-4

Outline ...................................................... T3-6-1

Operation ................................................. T3-2-6

Construction ............................................. T3-6-2

Main Relief Valve.................................... T3-2-15 Overload Relief Valve ............................. T3-2-17 Make-Up Valve ....................................... T3-2-19

Group 3 Steering Valve

Group 7 Axle Outline ...................................................... T3-7-1 Differential ................................................ T3-7-2 Limited Slip Differential (LSD)

Outline...................................................... T3-3-1

(Optional) ................................................ T3-7-6

Structure................................................... T3-3-2

Service Brake ........................................... T3-7-8

Operation ................................................. T3-3-3

Parking Brake ......................................... T3-7-10

Overload Relief Valve ............................... T3-3-6

Final Drive / Axle Shaft............................ T3-7-12

Make-Up Valve ......................................... T3-3-6

Group 4 HST Pump

Group 8 Brake Master Cylinder Outline ...................................................... T3-8-1

Outline...................................................... T3-4-1

Structure ................................................... T3-8-2

Forward / Reverse Selection

Operation .................................................. T3-8-3

Solenoid Valve ........................................ T3-4-7 DE Pump Solenoid Valve.......................... T3-4-8

Group 9 Others

Cutoff Valve ............................................ T3-4-10

Gear Pump ............................................... T3-9-1

High Pressure Relief Valve ......................T3-4-11

Propeller Shaft .......................................... T3-9-2

Low Pressure Relief Valve.......................T3-4-11

Parking Brake Solenoid Valve ................... T3-9-3

HST Charging Pump............................... T3-4-12

4FGET-3-1

(Blank)

4FGET-3-2

COMPONENT OPERATION / Priority Valve OUTLINE The priority valve delivers pressure oil from the main pump to the steering valve and the control valve in proportion to the steering valve operation. (Refer to SYSTEM / Hydraulic System.)

The relief valve is provided in the priority valve. When the steering cylinder is at the stroke end, the relief valve prevents the circuit pressure between priority valve and steering valve from increasing more than the set pressure.

Relief Valve Port P (From Main Pump)

Port T (To Hydraulic Oil Tank)

Port LS (To Steering Valve)

Port EF (To Control Valve)

T3-1-1

Port CF (To Steering Valve)

W4FC-03-11-003

COMPONENT OPERATION / Priority Valve STRUCTURE The priority valve consists of the relief valve, the spool, the spring, orifice A, orifice B, and orifice C. The illustration shows the spool position when the engine stops. The spool is pushed to the right by the spring.

Port P is connected to the main pump. Port CF is connected to the steering valve. Port EF is connected to the control valve.

Relief Valve Spring

Spool Port P

Port T

Port LS

Orifice C

Orifice B

Port EF

T3-1-2

Port CF

Orifice A

W4FC-03-11-003

COMPONENT OPERATION / Priority Valve OPERATION When steering is in neutral: 1. Pressure oil from the main pump flows to port P and is divided into three directions in the inner passage of the spool.

2. When the steering valve is in neutral (the steering wheel is not operated), pressure oil from port CF to the steering valve is blocked by the steering valve so that pressure in port CF increases.

3. As the pressure in port CF increases, pressure oil from the main pump flows to chamber A and chamber B respectively through orifice A and orifice B.

4. As pressure oil in chamber B flows to the hydraulic oil tank through port LS and the steering valve, pressure in chamber B becomes lower than that in chamber A due to orifice B. 5. When the pressure difference overcomes the spring force, the spool moves to the left.

6. Therefore, pressure oil from the main pump flows to the control valve through port EF.

Steering Valve Port P (From Main Pump) Chamber B

Spring

Spool Priority Valve Chamber A

Port LS (To Steering Valve)

Orifice C

Orifice B

Port EF (To Control Valve) Port CF (To Steering Valve)

Orifice A

T487-03-01-007

Port P (From Main Pump)

Port EF (To Control Valve)

T3-1-3

T487-03-01-003

COMPONENT OPERATION / Priority Valve When steering is operated: NOTE: Orifice D in the steering valve is a variable orifice so that the open area becomes large in proportion to the steering wheel rotation angle.

1. The spool in the steering valve moves at the moment when the steering wheel is rotated, so that orifice D is opened.

2. Pressure oil in the circuit between orifice D in the steering valve and chamber A and port CF in the priority valve flows to the gerotor.

3. As pressure oil flows to the gerotor, pressure in the circuit between chamber A and port CF in the priority valve and orifice D in the steering valve decreases so that the spool in the priority valve moves to the right.

4. The spool in the priority valve becomes stable at the position where pressure oil flows to the steering valve in proportion to the orifice D open area.

5. At this time, pressure oil from the main pump flows to the steering valve and the control valve respectively through the spool.

6. Pressure oil from the main pump flows to the gerotor through the spool and the sleeve in the steering valve.

7. The gerotor delivers pressure oil while rotating as a hydraulic motor. Pressure oil from gerotor flows to the steering cylinder and the machine turns.

T3-1-4

COMPONENT OPERATION / Priority Valve

Steering Cylinder

Steering Valve Gerotor

Sleeve Orifice D

Steering Wheel

Spool Sleeve Port P (From Main Pump) Priority Valve

Spool

Chamber A

Port EF (To Control Valve)

T3-1-5

Port CF (To Steering Valve)

T487-03-01-004

COMPONENT OPERATION / Priority Valve When steering cylinder is at stroke end: 1. Pressure oil to port P in the steering valve is divided inside the spool. One flows to the gerotor.

The other flows to port LS in the priority valve and acts on chamber B through orifice C. 2. As pressure in port P increases when the steering cylinder reaches the stroke end, pressure in chamber B in the priority valve also increases through port LS. 3. When pressure in chamber B increases more than the set pressure, the relief valve in the priority valve is operated and pressure oil acting on chamber B flows to the hydraulic oil tank through the relief valve.

4. As pressure oil in chamber B flows to the hydraulic oil tank when the relief valve is operated, the pressure difference between chamber A and chamber B occurs due to orifice B. 5. When the pressure difference overcomes the spring force, the spool in the priority valve moves to the left.

6. Pressure oil from the main pump flows to the control valve through port EF and the spool in the priority valve.

7. Therefore, when the steering cylinder is at the stroke end, pressure oil flows to the control valve.

At this time, pressure acting on the steering cylinder is as much as the set pressure of the relief valve.

T3-1-6

COMPONENT OPERATION / Priority Valve

Steering Cylinder

Steering Valve

Gerotor

Spool Port P (From Main Pump) Priority Valve Relief Valve

Chamber A

Port LS (From Steering Valve)

Orifice C Chamber B

OrificeB

Port EF (To Control Valve) Spring

T3-1-7

T487-03-01-005

COMPONENT OPERATION / Priority Valve (Blank)

T3-1-8

COMPONENT OPERATION / Control Valve OUTLINE The control valve controls the pressure, flow rate, and flow direction in the hydraulic circuit.

The major parts of the control valve are the main relief valve, the overload relief valve, and the spool. The spool is manually operated by the control lever.

Make-Up Valve (Lift Arm: Rod Side)

Overload Relief Valve (Auxiliary (Coupler): Rod Side)

Overload Relief Valve (Auxiliary (Coupler): Bottom Side)

Lift Arm

Machine Front

Main Relief Valve

Overload Relief Valve (Bucket: Rod Side)

Overload Relief Valve (Bucket: Bottom Side)

T3-2-1

Bucket

T4FGE-03-02-001

COMPONENT OPERATION / Control Valve Component Layout 1

2

9

3

5

8

4

7

6 T4FGE-03-02-002

1 - Overload Relief Valve (Coupler: Rod Side) 2 - Overload Relief Valve (Coupler: Bottom side) 3 - Make-Up Valve (Lift Arm: Rod Side)

4 - Overload Relief Valve (Bucket: Rod Side) 5 - Overload Relief Valve (Bucket: Bottom Side)

6 - Main Relief Valve 7 - Load Check Valve (Bucket Circuit)

T3-2-2

8 - Load Check Valve (Lift Arm Circuit) 9 - Load Check Valve (Coupler Circuit)

COMPONENT OPERATION / Control Valve

A B

B A

C

C

1

T4FGE-03-02-003

Section B-B

Section A-A 3

2

5

4

6

T4FG-03-02-004

T4L1-03-02-005

Section C-C 7

8

9

T4FG-03-02-005

1 - Main Relief Valve 2 - Overload Relief Valve (Coupler: Rod Side) 3 - Load Check Valve (Coupler Circuit)

4 - Overload Relief Valve (Coupler: Bottom side) 5 - Make-Up Valve (Lift Arm: Rod Side)

6 - Load Check Valve (Lift Arm Tandem Circuit) 7 - Overload Relief Valve (Bucket: Rod Side)

T3-2-3

8 - Load Check Valve (Bucket Tandem Circuit) 9 - Overload Relief Valve (Bucket: Bottom Side)

COMPONENT OPERATION / Control Valve HYDRAULIC CIRCUIT Main Circuit The main circuit contains a parallel circuit, which enables combined operations.

The main circuit (between the pump and the cylinder) is provided with the main relief valve. The main relief valve prevents the pressure in main circuit from increasing over the set pressure when the spool is in operation (or when the control lever is in operation).

The overload relief valves are provided in the bucket circuit and the auxiliary (coupler) circuit (between the control valve and the cylinder). The overload relief valve prevents circuit pressure developed by external loads in the front attachment circuit from increasing over the set pressure when the spool is in neutral (when the control lever is neutral).

The make-up valve is provided in the lift arm lower circuit (between the control valve and the cylinder).

When pressure in the lift arm lower circuit decreases, the make-up valve draws oil from the hydraulic oil tank and prevents cavitation.

T3-2-4

COMPONENT OPERATION / Control Valve Overload Relief Valve

Coupler Cylinder

Auxiliary (Coupler)

Lift Arm Cylinder

Make-Up Valve

Lift Arm Parallel Circuit

Bucket Cylinder

Bucket

Overload Relief Valve

Main Relief Valve Main Pump

T3-2-5

Hydraulic Oil Tank

T4FGE-03-02-002

COMPONENT OPERATION / Control Valve OPERATION When bucket is in neutral • Bucket spool (1) blocks cylinder port A1 (rod side) and port B1 (bottom side) when the loader control lever is in neutral (N) position.

Pressure oil from main circuit (2) is routed to drain circuit (4) and the hydraulic oil tank through neutral circuit (3). Consequently, the bucket cylinder rod is kept at this position.

Bucket

Bucket Cylinder Ａ1

Ｂ1

2 1

4

Hydraulic Oil Tank

3 T4L1-03-02-006

T3-2-6

COMPONENT OPERATION / Control Valve When bucket tilts Operation: 1. Bucket spool (1) moves to the right (illustrated below) when the loader control lever is in the TILT position.

2. Pressure oil from main circuit (2) is routed to the bucket cylinder bottom side from port B1 through load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the bucket cylinder rod side is routed to drain circuit (4) and the hydraulic oil tank through port A1.

4. Consequently, the bucket cylinder rod is extended so that the bucket tilts.

Bucket

Bucket Cylinder

Ａ1

Ｂ1

1

5

4 Hydraulic Oil Tank

3

2 T4L1-03-02-007

T3-2-7

COMPONENT OPERATION / Control Valve When bucket dumps Operation: 1. Bucket spool (1) moves to the left (illustrated below) when the loader control lever is in the DUMP position.

2. Pressure oil from main circuit (2) is routed to the bucket cylinder rod side from port A1 through load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the bucket cylinder bottom side is routed to drain circuit (4) and the hydraulic oil tank through port B1.

4. Consequently, the bucket cylinder rod is retracted so that the bucket dumps.

Bucket

Bucket Cylinder

Ａ1

Ｂ1

1

5

4

Hydraulic OilTank

3

2 T4L1-03-02-008

T3-2-8

COMPONENT OPERATION / Control Valve When lift arm is in neutral • Lift arm spool (1) blocks cylinder port A2 (rod side) and port B2 (bottom side) when the loader control lever is in the neutral (N) position.

Pressure oil from main circuit (2) is routed to drain circuit (4) and the hydraulic oil tank through neutral circuit (3). Consequently, the lift arm cylinder is kept in that position.

Lift Arm

Lift Arm Cylinder

Ａ2

Ｂ2

1 4

2

Hyfraulic Oil Tank

3 T4FG-03-02-00

T3-2-9

COMPONENT OPERATION / Control Valve When lift arm raises Operation: 1. Lift arm spool (1) moves to the right (illustrated below) when the loader control lever is in the RAISE position.

2. Pressure oil from main circuit (2) is routed to the lift arm cylinder bottom side from port B2 through load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the lift arm cylinder rod side is routed to drain circuit (4) and the hydraulic oil tank through port A2.

4. Consequently, the lift arm cylinder rod is extended so that the lift arm raises.

Lift Arm

Lift Arm Cylinder Ａ2

Ｂ2

1

5 4

Hydraulic Oil Tank

2 3

T3-2-10

T4FG-03-02-010

COMPONENT OPERATION / Control Valve When lift arm lowers Operation: 1. Lift arm spool (1) moves to the left (illustrated below) when the loader control lever is in the LOWER position.

2. Pressure oil from main circuit (2) is routed to the lift arm cylinder rod side from port A2 through load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the lift arm cylinder bottom side is routed to drain circuit (4) and the hydraulic oil tank through port B2.

4. Consequently, the lift arm cylinder rod is retracted so that the lift arm lowers.

Lift Arm

Lift Arm Cylinder

Ａ2

Ｂ2

1

Hydraulic Oil Tank

5 4

T3-2-11

2 3

T4FG-03-02-01

COMPONENT OPERATION / Control Valve When lift arm floats Operation: • Lift arm spool (1) moves to the left (illustrated below) when the loader control lever is in the FLOAT position.

• Pressure oil from main circuit (2) is routed to drain circuit (4) and the hydraulic oil tank through neutral circuit (3). In addition, port A2 and port A1 are connected to drain circuit (4) so that pressure oil is also routed to the lift arm cylinder bottom and rod sides.

• Therefore, pressure oil in the lift arm cylinder bottom and rod sides are routed to drain circuit (4) and the hydraulic oil tank through port A2 and port A1.

• Consequently, the lift arm cylinder rod is extend or retracted freely by the external force.

Lift Arm

Lift Arm Cylinder

Ｂ2

Ａ2

T4FG-03-02-012

1 4

Hydraulic Oil Tank

T3-2-12

2 3

COMPONENT OPERATION / Control Valve When coupler pin is locked Operation: 1. Bucket spool (1) moves to the right (illustrated below) when the auxiliary control lever is in the INSTALLATION position.

2. Pressure oil from main circuit (2) is routed to the coupler cylinder bottom side through port B3 and load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the coupler cylinder rod side is routed to drain circuit (4) and the hydraulic oil tank through port A3.

4. Consequently, the coupler cylinder rod is extended so that the coupler pin is inserted into the pin hole of the bucket.

Bucket

Coupler Cylinder

Ｂ3

1

5

Ａ3

4

Hydraulic Oil Tank

3

2 T4FGE-03-02-009

T3-2-13

COMPONENT OPERATION / Control Valve When coupler pin is unlocked Operation: 1. Auxiliary spool (1) moves to the left (illustrated below) when the auxiliary control lever is in the REMOVAL position.

2. Pressure oil from main circuit (2) is routed to the coupler cylinder rod side through port A3 and load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the coupler cylinder bottom side is routed to drain circuit (4) and the hydraulic oil tank through port B3.

4. Consequently, the coupler cylinder rod is retracted so that the coupler pin comes out from the pin hole of the bucket.

Bucket

Coupler Cylinder

Ａ3

Ｂ3

1

5

4

Hydraulic Oil Tank

3

2 T4FGE-03-02-010

T3-2-14

COMPONENT OPERATION / Control Valve MAIN RELIEF VALVE The main relief valve prevents pressure inside the main circuit from increasing over the set pressure during the cylinder operation.

This function prevents oil leakage from the hoses and piping fittings as well as cylinder breakage.

Relief Operation 1. Pressure in port HP (main circuit) acts on the pilot poppet through orifice A in the main poppet and orifice B in the seat.

2. When pressure in port HP reaches the set force of spring B, the pilot poppet is opened, pressure oil from passage A flows to port LP (hydraulic oil tank) through the outer circumference of the sleeve.

3. At this time, a pressure difference occurs between port HP and the spring chamber due to orifice A. 4. When this pressure difference reaches the set force of spring A, the main poppet is opened and pressure oil from port HP flows to port LP. 5. Consequently, pressure in Port HP (main circuit) decreases.

6. When pressure in Port HP (main circuit) decreases to the specified level, the main poppet is closed by the force of spring A.

T3-2-15

COMPONENT OPERATION / Control Valve During Normal Operation:

Orifice A

Main Poppet

Seat

Orifice B

Passage A

Spring B

HP

Sleeve

LP

Spring A

Spring Chamber

Pilot Poppet

T4FG-03-02-013

During Relief Operation: Main Poppet

Orifice A Seat

Orifice B

Passage A

Spring B

HP

Sleeve

LP

Spring A

Spring Chamber

T3-2-16

Pilot Poppet

T4FG-03-02-014

COMPONENT OPERATION / Control Valve OVERLOAD RELIEF VALVE (WITH MAKE-UP FUNCTION) The overload relief valves are provided with the circuits in the bottom and the rod sides of the bucket and in the bottom and the rod sides of the coupler (auxiliary). The overload relief valve controls pressure in each front attachment circuit in order not to rise abnormally when each front attachment is operated by external load.

It also makes make-up operation by drawing oil from the hydraulic oil tank in order to prevent cavitation when pressure in the front attachment circuit decreases.

Make-Up Operation 1. When pressure in port HP (front attachment circuit) decreases lower than pressure in port LP (hydraulic oil tank), the sleeve moves to the right.

2. Hydraulic oil in port LP flows to port HP and cavitation is prevented.

3. When pressure in port HP increases more than the specified level, the sleeve is closed by the force of spring C.

Bottom Side and Rod Side Circuits of Bucket Relief Operation 1. Pressure in port HP (front attachment circuit) acts on the pilot poppet through the orifice in the piston.

2. When pressure in port HP reaches the set force of spring B, the pilot poppet is opened, pressure oil from passage A flows to port LP (hydraulic oil tank) through the outer circumference of the sleeve.

3. At this time, a pressure difference occurs between port HP and the spring chamber due to the orifice.

4. When this pressure difference reaches the set force of spring A, the main poppet is opened and pressure oil from port HP flows to port LP. 5. Consequently, the pressure in Port HP (front attachment circuit) decreases.

6. When pressure in Port HP (front attachment circuit) decreases to the specified level, the piston and the main poppet are closed by the force of spring A. The circuit in the bottom and the rod sides of the coupler (auxiliary) are also relieved in the same way.

T3-2-17

COMPONENT OPERATION / Control Valve During Normal Operation: Sleeve

Main Popet

Spring A

Passage A

Spring B

HP

LP Orifice

Piston

During Relief Operation:

T4GB-03-02-030

Spring Chamber

Main Poppet

Pilot Poppet

Sleeve

Spring A

Spring C

Passage A Spring B

HP

LP Orifice

Piston

T4GB-03-02-031

Pilot Poppet

Spring Chamber

During Make-Up Operation:

Sleeve

HP

LP

T4GB-03-02-032

Spring C

T3-2-18

COMPONENT OPERATION / Control Valve MAKE-UP VALVE The make-up valve prevents cavitation in the lift arm lower circuit.

As for other cylinder circuits, cavitation is prevented by the make-up function of each overload relief valve.

Operation: 1. Pressure oil in port HP (actuator circuit) acts on spring chamber (4) through passage (2) in poppet (1). Therefore, pressure in port HP is equal to that in spring chamber (4).

2. Thereby, as pressure in port HP is high and the force to close poppet (1) (pressure in spring chamber (4) × pressure receiving area S2) is larger than the force to open poppet (1) (pressure at cylinder side × pressure receiving area S1), poppet (1) is closed.

3. When pressure in port HP is lower than that in port LP, the force to close poppet (1) is equal to the spring (3) force.

4. Thereby, when the force to open poppet (1) (pressure in port T × (pressure receiving area S2 S1) is larger than the force to close poppet (1) (spring (3) force), poppet (1) is opened and hydraulic oil is supplied to port HP. 5. Therefore, cavitation in port HP is prevented.

In Neutral 1

S1

S2

2

3

4

HP

LP

T4FG-03-02-015

In Operation 1

2

3 4

S1

S2

HP

LP

T4FC-03-02-016

1 - Poppet 2 - Passage

T3-2-19

34-

Spring Spring Chamber

COMPONENT OPERATION / Control Valve (Blank)

T3-2-20

COMPONENT OPERATION / Steering Valve OUTLINE The steering valve is located between the priority valve and the steering cylinder.

The steering valve supplies pressure oil from the main pump to the steering cylinder through the priority valve in response to the movement of the steering wheel.

(Refer to SYSTEM / Hydraulic System / Steering Circuit.)

Port L (for Left Steering)

Port LS

The overload relief valve and the make-up valve are provided in the steering valve.

The overload relief valve is operated when the circuit pressure between the steering cylinder and the steering valve is beyond the set pressure.

The make-up valve is operated when the circuit pressure between the steering cylinder and the steering valve is lower than the pressure in the hydraulic oil tank.

Port R (for Right Steering)

Steering Wheel

T4FC-03-04-001

Port T (to Hydraulic Oil Tank)

Port P (from Priority Valve)

T3-3-1

COMPONENT OPERATION / Steering Valve STRUCTURE 11

The steering valve consists of gerotor (8), drive (7), sleeve (3), spool (4), pin (5), housing (1), and centering springs (2).

12

10

When the steering wheel is rotated, spool (4) rotates and an oil passage is provided between spool (4) and sleeve (3). Pressure oil from the main pump is controlled by spool (4) and sleeve (3), and flows to the steering cylinder.

Centering springs (2) are installed to both spool (4) and sleeve (3). When the steering wheel is released, centering spring (2) returns sleeve (3) to the neutral position.

9

1

2

5

4

3

6

8

T4FG-03-03-004

4

2

1

7

3

Port R

Port L

5 Port P Port T

10 9

8

7

6 T4FC-03-04-002

1 - Housing 2 - Centering Spring 3 - Sleeve

456-

Spool Pin Plate

789-

T3-3-2

Drive Gerotor Spacer

10 - Cap 11 - Check Valve 12 - Check Valve

COMPONENT OPERATION / Steering Valve OPERATION Sleeve (3), spool (4), and drive (7) are mutually connected by pin (5). When the steering wheel (spool (4)) is rotated, a relative displacement angle arises between sleeve (3) and spool (4) due to the long hole of spool (4).

The movement of the steering wheel is transmitted to only spool (4), and port P (from the main pump) is connected to port R (to the main valve) or port L through sleeve (3) and spool (4).

Port L

Port R

7

4

3

Steering Wheel

Port T Port P

T4FG-03-03-006

Steering Wheel

T4FG-03-03-005

5

4

3

T3-3-3

7

COMPONENT OPERATION / Steering Valve Left Steering 1. When the steering wheel is rotated to the left, spool (4) rotates. Pressure oil from the main pump flows in the order of port P - sleeve (3) - spool (4) sleeve (3) - housing (1) - gerotor (8).

2. Pressure oil from gerotor (8) flows in the order of housing (1) - sleeve (3) - spool (4) - sleeve (3) port L – the steering cylinders. The steering cylinders direct the machine to the left.

3. Returning oil from the steering cylinders flows to port R, flows in the order of housing (1) - sleeve (3) - spool (4) - sleeve (3) - port T, and returns to the hydraulic oil tank.

4. When pressure oil from the main pump flows to gerotor (8), gerotor (8) rotates to the left. Rotation of gerotor (8) is transmitted to sleeve (3) through drive (7), and sleeve (3) rotates to the left.

5. When sleeve (3) rotates by the same amount of spool (4), the passage between sleeve (3) and spool (4) is closed and the operation of the steering cylinders is stopped.

6. Therefore, gerotor (8) rotates in response to rotation of the steering wheel, and the steering cylinders are operated in response to the amount of turns of the steering wheel.

Steering Cylinders

T

L

R

P

Steering Pump

1 8 7

4

T4FG-03-03-001

2

3

Steering Valve

T3-3-4

COMPONENT OPERATION / Steering Valve Right Steering

Neutral

When the steering wheel is rotated to the right, pressure oil from the main pump flows in the order of port P - port R – the steering cylinders, operates the steering cylinders, and directs the machine to the right.

Returning oil from the steering cylinders flows in the order of port L - port T and returns to the hydraulic oil tank.

When the steering wheel is not rotated, pressure oil from the main pump acts on port P in the steering valve. However, pressure oil does not flow to the steering cylinders as they are blocked by spool (4).

Therefore, the steering cylinders are not operated.

Right Steering: T

L

R

P

T4FG-03-03-002

In Neutral: T

P

4

T4FG-03-03-003

T3-3-5

COMPONENT OPERATION / Steering Valve OVERLOAD RELIEF VALVE Make-Up Valve

The overload relief valves are located in the steering valve and prevent the circuit pressure between the steering cylinder and the steering valve from increasing beyond the set pressure.

When an external force is applied to the left and right steering directions, surge oil pressure is developed in the circuit. When the circuit pressure exceeds the set spring force of the overload relief valve, the poppet in the overload relief valve moves to the right and the oil passage is opened so that pressure oil flows to the hydraulic oil tank.

When the circuit pressure decreases, the poppet moves to the left due to the spring force so that the oil passage is closed again.

Overload Relief Valve

Overload Relief Valve

Port T T4FG-03-03-006

MAKE-UP VALVE The make-up valves are located in the steering valve.

When the circuit pressure between the steering cylinder and the steering valve is lower than the pressure in hydraulic oil tank, the make-up valve draws the hydraulic oil from port T in order to prevent the cavitation.

When the circuit pressure between the steering cylinder and the steering valve is lower than the pressure in the hydraulic oil tank, the ball of the make-up valve moves to the right and the oil passage is opened. Therefore, hydraulic oil from port T is drawn and delivered to the circuit between the steering cylinder and the steering valve.

When the circuit pressure between the steering cylinder and the steering valve increases, the ball is moved to the left by pressure oil and the oil passage is closed again.

T3-3-6

COMPONENT OPERATION / Steering Valve B

Poppet

Spring

Overload Relief Valve

A A

Section A-A

A

T4FC-03-04-011

A B T4FC-03-04-009

C

Section B-B

T4FG-03-03-004

Ball

Make-Up Valve

D D

Section D-D D

D View C

T4FC-03-04-010

T3-3-7

T4FC-03-04-012

COMPONENT OPERATION / Steering Valve (Blank)

T3-3-8

COMPONENT OPERATION / HST Pump OUTLINE The HST pump is a two-direction displacement angle swash plate type variable displacement plunger pump.

The forward/reverse selection solenoid valve (3), the DE pump solenoid valve (2), the cutoff valve (4), the high pressure relief valves (5,10), the low pressure relief valve (8), and the HST charging pump (7) are provided in the HST pump.

The HST pump (6) consists of the shaft, the plunger, the cylinder block, the displacement angle control cylinder, and the swash plate.

Engine power is transmitted to the shaft of the HST pump directly. The shaft rotation of the HST pump is also transmitted to the main pump unit through the coupling.

2

3

A

4 5

1

View A

15 16

6 7

17

8 9

14

13

12

10

11

T4FG-03-04-001

1 - Displacement Angle Control Cylinder 2 - DE Pump Solenoid Valve 3 - Forward/Reverse Selection Solenoid Valve 4 - Cutoff Valve 5 - High-Pressure Relief Valve

6 - Port MB

11 - Port S

16 - Port Fa

7 - HST Charging Pump

12 - Port G

17 - Port B (Port A at Opposite Side)

8 - Low-Pressure Relief Valve

13 - Port T2

9 - Port MA 10 - High-Pressure Relief Valve

14 - Port PS (T1) 15 - Port Fe

T3-4-1

COMPONENT OPERATION / HST Pump 2

3

Port T2

Port Fa

Port Fe

Port T1

Port B

1 4

Port A

7 1 - Displacement Angle Control Cylinder 2 - Forward/Reverse Selection Solenoid Valve 3 - DE Pump Solenoid Valve 4 - HST Charging Pump

6

Port S

5

T4FG-03-04-002

5 - Cutoff Valve

9 - Swash Plate

12 - Pin

6 - Low-Pressure Relief Valve

10 - Plunger

13 - Displacement Angle Piston

7 - High-Pressure Relief Valve 8 - Shaft

11 - Cylinder Block

14 - Spring

1

3

2

5

7

4 8

6 7 T4FG-03-04-003

T3-4-2

COMPONENT OPERATION / HST Pump Rotary Group Part:

12

8

9

10

11 T4FG-03-04-004

Displacement Angle Control Cylinder Part: 3

2 1 1

13

14

12

13

12

9 T4FG-03-04-005

T3-4-3

COMPONENT OPERATION / HST Pump Operation The shaft is splined to the cylinder block. The plungers are installed in the cylinder block.

Engine power is transmitted to the shaft of the HST pump directly. As the shaft is rotated, the plungers rotate with the cylinder block together.

The plungers slide on the swash plate so that the plungers reciprocate in the cylinder block as the swash plate is positioned at an angle toward the plungers. By this reciprocation, hydraulic oil is drawn and delivered. Either port A or port B is selected as a delivery port by the displacement angle control of the swash plate.

Delivery Flow Rate Increasing and Decreasing Operation HST pump delivery flow rate is varied by changing the displacement angle of the swash plate and changing the stroke of the plunger.

As the swash plate is connected to the displacement angle piston of the displacement angle cylinder through the pin, the swash plate operates according to the movement of the displacement angle piston.

The displacement angle piston has the built-in spring, which acts on the direction of the displacement angle piston to return to neutral. The displacement angle piston position is moved by the displacement angle control pressure applied to the displacement angle cylinder. Therefore, the displacement angle of the swash plate is changed.

T3-4-4

COMPONENT OPERATION / HST Pump Rotary Group Part:

Inlet Pin A

Shaft

B Plunger Swash Plate

Cylinder Block

Outlet

T4FG-03-04-004

Displacement Angle Control Cylinder Part:

Displacement Angle Piston

Spring

Pin

Displacement Angle Piston

T3-4-5

Pin

Swash Plate

T4FG-03-04-005

COMPONENT OPERATION / HST Pump Recovery Moment Function 1. α (alpha) and β (beta) are the range of pressure oil applied to the plunger through the valve plate.

The comparison between α and β is shown below. α<β 2. When the HST motor is loaded, the pressure in the circuit from the HST pump to the HST motor increases. Increased pressure acts on the plunger of the HST pump.

3. As there is a rage difference between α (alpha) and β (beta) on the high-pressure port of the valve plate, the pressure oil force acting on the plunger through β (beta) is larger than that through α (alpha). The range difference of (β - α) × Circuit pressure force pushes the bottom of the swash plate as moment around the displacement angle center. Then, the swash plate is moved to neutral.

(Recovery moment.)

4. The moving amount (angle) of the swash plate is in proportion to the HST circuit (between HST pump and HST motor) pressure.

When pressure is low, the moving angle is small.

When pressure is high, the moving angle is large.

Swash Plate

Plunger

Valve Plate

T4FG-03-04-007

Low-Pressure Port

High-Pressure Port

Range α

Displacement Angle Center

Range β

Valve Plate T487-03-04-068

T3-4-6

COMPONENT OPERATION / HST Pump FORWARD / REVERSE SELECTION SOLENOID VALVE

Reverse Selection Solenoid Valve

Spool

The forward/reverse selection solenoid valve controls the pump displacement angle direction and changes the delivery direction (port A or port B) of pressure oil.

Pressure oil from the DE pump solenoid valve to control the displacement angle control cylinder acts on the forward/reverse selection solenoid valve. The forward or the reverse selection solenoid valve is excited and the spool is operated according to the signal from the FNR lever. Then, the hydraulic circuit to the corresponding displacement angle control cylinder is connected.

Therefore, the pump displacement angle is controlled and the delivery direction of pressure oil is changed.

Forward Selection Solenoid Valve

To Port B (Reverse) From Charging Pump

HST Pump

To Port A (Forward) T4FC-03-08-005

Displacement Angle Control Cylinder

Displacement Angle Control Cylinder

A

Forward/Reverse Selection Solenoid Valve Reverse Selection Solenoid Valve View A

Port B (Port A at Opposite Side)

Forward Selection Solenoid Valve

T4FG-03-04-001

T3-4-7

COMPONENT OPERATION / HST Pump DE PUMP SOLENOID VALVE The DE pump solenoid valve is a proportional solenoid valve and controlled by the command signal from the HST control unit.

The command signal is a current value. The pump displacement angle is the maximum at the maximum current value and is the minimum at the minimum current value.

The spool position is changed by changing a current value so that the servo piston operation is controlled.

Max. Displacement Angle Motor Displacement Angle

Min. Displacement Angle Max. Current Min. Current Value Value Command Signal Current

T4FG-03-04-009

DE Pump Solenoid Valve

P2

P1 T4FG-03-04-010

DE Pump Solenoid Valve

P1

P1 Q

Forward/Reverse Selection Solenoid Valve (Forward Side)

P2

T3-4-8

P2

Forward/Reverse Selection Solenoid Valve (Reverse Side)

T4FG-03-04-008

COMPONENT OPERATION / HST Pump Constant Torque Control The engine stop due to overloading is prevented by using the command signal current from the HST controller for HST pump displacement angle control.

When the engine is loaded and the engine speed decreases, the HST controller reduces the command signal current to the DE pump solenoid valve.

Therefore, the displacement of the HST pump is reduced and the inlet torque of the pump is also reduced. The pump displacement is balanced with the engine torque.

When the load is increased, the engine speed is slightly decreased, and the HST controller makes the HST pump displacement angle control effective use of the engine torque without the engine stop.

Torque T

P Engine Torque

Overloading State

P’

Stable State

Pump Torque

N N’ N

Engine Speed T81S-03-01-011

T3-4-9

COMPONENT OPERATION / HST Pump CUTOFF VALVE Control Pressure of Displacement Angle Control Cylinder

The cutoff valve regulates the maximum circuit pressure and protects the circuit on the high pressure side.

When the high-pressure side in the travel circuit reaches the specified circuit pressure, the control pressure acting on the displacement angle control cylinder through the forward/reverse selection solenoid valve is reduced.

When the control pressure of the displacement angle control cylinder is reduced, the pump displacement angle is controlled in order to deliver only the pressure oil flow rate corresponding to the specified pressure.

The heat generation can be minimized as the circuit pressure on the high-pressure side is regulated by the pump flow rate control.

The cutoff valve regulates circuit pressure on the high-pressure side. Therefore, the cutoff valve 2 pressure is usually set at 2 to 3 MPa (20 to 31 kgf/cm , 290 to 435 psi) lower than that of the high pressure relief valve.

Hexagon Nut

Spring

To Forward/Reverse Selection Solenoid Valve

B

A

T81S-03-01-019

To Hydraulic Oil Tank

To HST Close Circuit A

To HST Close Circuit B

T81S-03-01-022

Screw with Hexagon Hole

Guide

Spool

Piston

Barrel

T3-4-10

Spool

Valve Seat

COMPONENT OPERATION / HST Pump HIGH-PRESSURE RELIEF VALVE The high-pressure relief valve regulates the maximum pressure of the travel circuit and protects the circuit on the high-pressure side. The high-pressure relief valve has the check valve function for HST charge. When the pressure oil flow rate to the inlet circuit is insufficient, the HST charge pressure oil is routed to the inlet circuit.

LOW-PRESSURE RELIEF VALVE The low-pressure relief valve regulates the HST charge pressure.

The low-pressure relief valve always operates during machine operation. The relieved oil returns to the hydraulic oil tank through the pump housing for lubrication and cooling.

Hexagon Nut

T81S-03-01-020

Spring

Spring Seat

Piston

Adjusting Screw

NOTE: The illustration shows the low-pressure relief valve.

T3-4-11

Plug

COMPONENT OPERATION / HST Pump HST CHARGING PUMP The HST charging pump is coaxially connected to the shaft of the HST pump. Therefore, when the engine runs, the HST charging pump rotates with the HST pump together. The HST charging pump is a trochoid type pump. The inner rotor and the outer rotor rotates together by engaging so that hydraulic oil is drawn to chamber A and delivered from chamber B.

Inner Rotor

Chamber B Outer Rotor

Chamber A T4FC-03-08-100

T3-4-12

COMPONENT OPERATION / HST Motor OUTLINE HST motor is a bent-axis type variable displacement axial plunger motor and consists of the regulator, the shaft, the plunger, the rotor, and the valve plate.

The EP motor solenoid valve is provided in the regulator of the HST motor.

HST Motor: Port T1

View X

Regulator

Port A

Port B

X

Port T2

EP Motor Solenoid Valve T4FG-03-05-001

1

2

Port T1 Port B

Port A Port T2 T4FG-03-05-002

1 - Regulator

2 - EP Motor Solenoid Valve

T3-5-1

COMPONENT OPERATION / HST Motor HST Motor: View X

1

X

2 T4FG-03-05-001

Rotary Group Part:

4

5

3

6 10 7

9 8

T4FC-03-09-006

1 - Regulator 2 - EP Motor Solenoid Valve 3 - Shaft

4 - Plunger 5 - Rotor 6 - Valve Plate

7 - Control Rod 8 - Spring

T3-5-2

9 - Center Pin 10 - Bearing

COMPONENT OPERATION / HST Motor (Blank)

T3-5-3

COMPONENT OPERATION / HST Motor OPERATION The output shaft of the rotary group is supported to the motor casing by two bearings. The center pin connects the output shaft to the rotor and is located in the rotor center hole. The valve plate is provided in the rotor end.

The spring applies the appropriate force to the rotor and brings the rotor into contact with the valve plate.

There are seven plungers in the rotor. Rotation direction of the HST motor is determined by entering pressure oil into either port A or port B. When traveling forward, pressure oil from the pump flows to the rotor through port B of the valve plate. When the plunger is pushed by pressure oil, component force (FV) of pushing force (F) rotates the output shaft.

As the output shaft rotates the rotor, the plungers reach port A in sequence. When a plunger reaches port A, pressure oil in the rotor is pushed by the plunger. Therefore, pressure oil is returned to the HST circuit.

The valve plate is connected to the regulator through the control rod. The valve plate position is changed by the operation of the regulator. Thus, the HST motor speed is changed.

T3-5-4

COMPONENT OPERATION / HST Motor

Output Shaft

Rotor

Bearing

Spring

Valve Plate

Center Pin

Plunger

T202-03-06-003

FV

F

FR Plunger

Port B Output Shaft

Valve Plate

Rotor

Port A

T487-03-05-006

T3-5-5

COMPONENT OPERATION / HST Motor REGULATOR The regulator consists of the servo piston, the control rod, the balance spring, the spring, and the spool.

The EP motor solenoid valve is provided in the regulator of HST motor.

The servo piston of the regulator is connected to the motor valve plate via the control rod. When operating the servo piston, the valve plate position is changed.

Therefore, the motor displacement angle is changed and the motor speed is controlled.

The servo piston operation is controlled by the EP motor solenoid valve.

Valve Plate

Servo Piston Control Rod

Balance Spring

Spring

Spool

EP Motor Solenoid Valve

T4FC-03-09-003

EP MOTOR SOLENOID VALVE The EP motor solenoid valve is a proportional solenoid valve and controlled by the command signal from the HST control unit. The command signal is a current value. The motor displacement angle is the maximum at the maximum current value and is the minimum at the minimum current value. The spool position is changed by changing a current value so that the servo piston operation is controlled.

Maximum Displacement

Motor Displacement Angle

Minimum Displacement

Minimum Current Value Command Current

T3-5-6

Maximum Current Value

COMPONENT OPERATION / HST Motor Displacement Angle Control (From Large Displacement Angle to Small Displacement Angle) 1. One pressure oil from port B (or port A) flows to the plunger through the valve plate. The other pressure oil opens the check valve, and flows to the spool and the small chamber of the servo piston.

2. The EP motor solenoid valve receives the signal from the HST control unit. When the spool moves upward, pressure oil in the large chamber of the servo piston flows to the hydraulic oil tank through the spool.

Spool

3. Therefore, the servo piston moves downward and the motor displacement angle decreases.

4. Consequently, the motor rotates at fast speed.

From HST Control Unit

EP Motor Solenoid Valve

Check Valve

B

Motor Circuit Pressure

A

Servo Piston

NOTE: The illustration shows the circuit when traveling forward.

T3-5-7

T4FG-03-05-003

COMPONENT OPERATION / HST Motor Displacement Angle Control (From Small Displacement Angle to Large Displacement Angle) 1. One pressure oil from port B (or port A) flows to the plunger through the valve plate. The other pressure oil opens the check valve, and flows to the spool and the small chamber of the servo piston.

2. The EP motor solenoid valve receives the signal from the HST control unit. When the spool moves downward, pressure oil from port B (or port A) flows to the large chamber side of the servo piston through the spool.

Spool

3. As for the pressure receiving area in the servo piston, as that in the large chamber is larger than that in the small chamber, the servo piston moves upward to the position where the servo piston balances with the balance spring so that the motor displacement angle increases.

4. Consequently, the motor rotates at slow speed.

EP Motor Solenoid Valve

From HST Control Unit

Balance Spring

Check Valve

B Motor Circuit Pressure

A

Servo Piston

NOTE: The illustration shows the circuit when traveling forward.

T3-5-8

T4FG-03-05-004

COMPONENT OPERATION / Reduction OUTLINE The reduction consists of the HST motor input shaft, input gear, output shaft, and output gear.

The reduction transmits the output power from the HST motor to the output shaft.

The front of the output shaft is connected to the propeller shaft and the back is connected to the pinion shaft of the rear axle respectively.

Air Breather

Rear Axle HST Motor Mounting Port

Filler (Level) Plug

Drain Plug

Filler (Level) Plug

T4FG-03-06-001

T3-6-1

COMPONENT OPERATION / Reduction CONSTRUCTION 2

1

3

4

5

HST Motor Mounting Port Pinion Shaft (Rear Axle)

Rear Axle

12 Rear Axle Support

11

10

8

9

7

6 T4FG-03-06-002

1 - HST Motor Input Shaft 2 - Roller Bearing 3 - Housing

456-

Input Gear Roller Bearing Oil Seal

789-

T3-6-2

Roller Bearing Output Gear Roller Bearing

10 - Oil Seal 11 - Output Shaft 12 - Output Flange

COMPONENT OPERATION / Axle OUTLINE The axle consists of the differential, final drive, axle shaft, and brake.

(The brake is equipped with only the front axle.)

Final Drive

Power from the reduction is transmitted to the front axle and the rear axle via the propeller shaft. Inside the axle, power is transmitted to the differential, divided into left and right, and drives the final drive and the wheels through the axle shaft.

Axle Shaft

Differential

Brake

A

View A

T4FG-03-07-001

T3-7-1

COMPONENT OPERATION / Axle DIFFERENTIAL When the machine is steered or traveling on bumpy roads, the differential enables the left and the right drive wheels to rotate at different rotating speeds.

1

2

3

4

5

6

7

8

9

10 11 12

16

13 15

14 Speed Sensor Mounting Part

T4FG-03-07-002

12345-

Roller Bearing Side Gear A Ring Gear Differential Gear Body Pinion Gear

6789-

Spider Differential Gear Case Side Gear B Roller Bearing

10 - Pinion Shaft 11 - Roller Bearing 12 - Spacer 13 - Roller Bearing

T3-7-2

14 - Output Flange 15 - Oil Seal 16 - Ring Nut

COMPONENT OPERATION / Axle Function

• Purpose of Differential When the machine is steered, as the inner wheel turns with a smaller radius, the outer wheel needs to rotate faster for smooth steering.

Suppose the rear wheel drives by directly installing the gear to the propeller shaft with a shaft having no differential. Suppose the rear wheel, with installing gear to propeller shaft directly is driven by the shaft having no differential.

In this case, the outer wheel and the inner wheel rotate the same amount. So when the machine is steered, the outer wheel cannot rotate more than the inner wheel, and skidding sideways or tire wear takes place. As the axle shaft is subjected to torsional stress, transmission of drive force becomes unstable.

On the other hand, in case a differential is installed, as the inner and the outer wheels can rotate at different rotating speeds, the problem mentioned above can be eliminated.

Extension Line of Rear Wheel Centers

In Turning of Machine

In Traveling of Machine on Rough Roads T202-03-05-005

T3-7-3

COMPONENT OPERATION / Axle • Principle of Differential Operational principle of the differential is explained comparing it to the racks and the pinion gear in the drawing.

When load W is equally applied to racks A and B, if C is moved upward by the distance of H, racks A and B move by the same distance of H in unison with the pinion together.

If moved by removing the load to rack B, the pinion rotates on rack A (with load applied) and moves rack B upward. At this time, the distance where rack B moves is longer than the distance where the pinion moves while rotating.

Distance where rack B moves can be calculated by using the equation of H+H=2H. This principle is applied to the differential.

W

W

W C

C H

H

H

2H

Rack (A)

Rack (B)

Rack (A)

Pinion

Rack (B)

Pinion T202-03-05-006

• Operation of Differential In Traveling Straight In case resistances applied to axle shafts (7, 8) connected by spline to differential side gears (2, 3) are the same, or in case the machine is traveling straight on plane roads, differential pinion gears (1, 4) do not rotate.

Differential pinion gears (1, 4) and side gears (2, 3) remain fixed by being mutually geared, and rotate with housing (6) connected with ring gear (9).

In case all parts are rotating solidly like this, differential function of the differential does not work, and gears (1, 2, 3, 4) play only the role of joints to connect axle shafts (7, 8).

10

9

1

8

2

3 4

7

6

T487-03-06-014

T3-7-4

COMPONENT OPERATION / Axle In Steering When the machine is turned, uneven resistances are applied to the drive wheels. Therefore, due to the difference of the resistances applied to the inner and outer wheels, differential pinion gears (1, 4) start revolving on side gears (2, 3), while rotating round the pinion shaft. Consequently, in case the resistance force applied to shaft (7) is large, pinion gears (1, 4) rotate in the same direction as the rotational direction on side gear (2) of shaft (7). The speed of shaft (7) is lowered, the amount of the speed reduction is applied to shaft (8) and the differential function is performed.

Suppose ring gear (9) is driven by drive pinion (10) at the speed of 100. In the condition of the machine traveling straight, the drive wheels on the both sides rotate at the same speed.

However, in case the machine is turned and the speed of the right drive wheel is lowered to 90, the left wheel turns at the speed of 100+(100−90)=110 as the speed of 10(100−90=10) is added to the speed of the left wheel.

If ring gear (9) rotates at the speed of 100, the summation of the speeds of the left and right wheels becomes always 200 regardless of movement of the respective wheels.

T3-7-5

10

9

1

8

2

3 4

7

6

T487-03-06-014

COMPONENT OPERATION / Axle LIMITED SLIP DIFFERENTIAL (LSD) (OPTIONAL)

Operational Principle

The wheel loader must be operated on slippery ground condition like sand and muddy soil. In places like these, the tires can slip. As rotation is transmitted to the slipping tire and not to the tires contacting the road, not only the funtion of the wheel loader is worsened but the tire lives are shortened.

In order to avoid this, the limited slip differential (LSD) provided with the differential movement restriction device in order to avoid different movement of the left and right wheels is adopted.

LSD is so constructed that the clutch disc is inserted between the side gear and the differential gear case, which makes restriction of different movement by keeping the tire speeds the same by the resistances of the friction surfaces.

Ring Gear

Pinion Gear Side Gear

Spider

Differential Gear Case

Disc Friction Washer

T3-7-6

Clutch Disc

T4FG-03-07-011

COMPONENT OPERATION / Axle Traveling Straight with the Same Road Resistances to Left and Right Tires As the differential pinion gear and the left and right pinion gears rotate solidly, the driving forces of the left and right tires are the same.

Pinion Gear Side Gear Differential Gear Case

Traveling on Soft Ground (Different Road Resistances to Left and Right Tires) Driving force is transmitted to the differential gear case, pinion gear and side gear through the ring gear.

At this time, thrust force (P) occurs due to rotation of the pinion gear so that the side gear is pushed by the pinion gear. The clutch disc is geared with the differential gear case through the friction washer. As the side gears fitted to the clutch disc by spline rotate solidly with the differential gear case, the left and right gears rotate at the same speed.

Like this, the left and right axle shafts fitted to the side gears by spline tend to rotate solidly with the case, and the differential movement restriction works.

In case the driving force provided for the slipping tire is larger than the road resistance, part of the torque of the slipping tire is added to the tire contacting ground by the differential movement restriction (because of the same speed of the left and right tires), and the tire contacting ground is provided with more torque.

Until the difference of the resistances between the left and right tires exceeds certain value (until the clutch disc begins to slip), the left and right gears solidly rotate at a constant speed.

T3-7-7

P

T4FG-03-07-012

Friction Washer

Clutch Disc

Disc

COMPONENT OPERATION / Axle SERVICE BRAKE The brake is a wet-type spring set hydraulic released multi-disc brake and is assembled in the axle case.

The disc brake is installed to the front wheels of the machine.

• When bake is applied Oil pressure from the brake valve acts on the back of brake piston (5) and moves brake piston (5).

Brake disc (2) and brake plate (3) are fitted tightly via end plate (4).

The inner surface of brake disc (2) is fitted to differential gear case B(8). The outer surface of brake plate (3) is fixed to axle case (1). Therefore, the rotation of brake disc (2) stops and differential gear case B(8) stops.

In addition, brake piston (5) pushes return spring (6) via end plate (4). When piston (11) is pushed further, clutch disc plate (9) and clutch disc (10) are fitted tightly.

The inner surface of clutch disc (10) is fitted to shaft (7). The outer surface of clutch disc plate (9) is fixed to differential gear case B(8).

• When brake is released When oil pressure from the brake valve is decreased, brake piston (5) is returned by return spring (6).

Brake disc (2) is freed and the machine can travel.

T3-7-8

COMPONENT OPERATION / Axle

2

1

10

9

11

3

8

4

Brake Oil Pressure

5

6

7

T4FG-03-07-003

1 - Axle Case 2 - Brake Disc 3 - Brake Plate

4 - End Plate 5 - Brake Piston 6 - Return Spring

7 - Axle Shaft 8 - Differential Gear Case B 9 - Clutch Disc Plate

• When brake is applied 2

3

2

10 - Clutch Disc 11 - Piston

• When brake is released 2

4

3

2

4

From Brake Valve

10

9

11

6

To Brake Valve

10

5 T4FG-03-07-004

T3-7-9

9

11

6

5 T4FG-03-07-005

COMPONENT OPERATION / Axle PARKING BRAKE The parking brake is a wet-type spring set hydraulic released multi-disc brake. The brake is released when the parking brake release pressure acts on the oil chamber in the parking brake piston.

The parking brake is used in combination with the service brake and is installed in the front axle.

• When brake is applied When the parking brake switch is set to the ON position, the brake release pressure from the parking brake solenoid valve does not act on the oil chamber in parking brake piston (5). Spring (6) moves parking brake piston (5) to the left so that piston pin (7) is moved to the left. Then, brake disc (2) and brake plate (3) are fitted tightly.

The inner surface of brake disc (2) is splined to shaft (8) through differential gear case (10). The outer surface of brake plate (3) is fixed to axle case (1). Therefore, the rotation of brake disc (2) stops so that the parking brake is applied.

• When brake is released When the parking brake switch is set to the OFF position, the brake release pressure from the parking brake solenoid valve acts on the oil chamber in parking brake piston (5). Parking brake piston (5) moves to the right so that piston pin (7) is moved to the right by return spring (9). Then, brake disc (2) is freed so that the parking brake is released.

T3-7-10

COMPONENT OPERATION / Axle 1

3

2

Parking Brake Release Pressure

4

Oil Chamber

5 6

10

9

8

7 T4FG-03-07-003

1 - Axle Case 2 - Brake Disc 3 - Brake Plate

4 - End Plate 5 - Parking Brake Piston 6 - Spring

7 - Piston Pin 8 - Shaft

• When brake is applied 2

3

2

9 - Return Spring 10 - Differential Gear Case B

• When brake is released 4

To Parking Brake Solenoid Valve

5

6

2

3

2

4

9

7 T4FG-03-07-006

T3-7-11

From Parking Brake Solenoid Valve

5

6

7 T4FG-03-07-007

COMPONENT OPERATION / Axle FINAL DRIVE / AXLE SHAFT The final drive is the device finally to reduce the speed in the power transmission system, and is a planetary gear type. As for power transmission, power from the differential, is transmitted from the shaft, rotates three planetary gears in the ring gear, and transmits rotation of the planetary gear to the planetary carrier.

Final Drive Axle Shaft

Ring Gear

Planetary Gear

Planetary Carrier Shaft

Housing

T4FG-03-07-010

T4GD-03-10-002

T3-7-12

COMPONENT OPERATION / Brake Master Cylinder OUTLINE The brake master cylinder supplies pressure oil in proportion to brake pedal depressing amount and operates the front wheel service brake.

The brake master cylinder is connected to the brake pedal via the lik.

When the brake pedal is depressed, the HST controller receives the signal from the brake angle sensor and acts on the DE pump control valve in the HST pump so that delivery flow rate from the HST pump is reduced.

(Refer to SYSTEM / Hydraulic System.)

Brake Pedal

Brake Light Switch

Brake Pedal

Brake Angle Sensor

Brake Valve T4FG-03-08-001

T3-8-1

COMPONENT OPERATION / Brake Master Cylinder STRUCTURE The brake master cylinder consists of the pressure chamber and reservoir chamber. Then, they are connected via the relief port. The brake master cylinder has the push rod, piston, return spring, the P (primary) cup which seals and pressure chamber, and the S (secondary) cup which seals the reservoir.

From Brake Oil Tank

Push Rod

S (Secondary) Cup

Reservoir Chamber

Relief Port

Piston

To Front Axle Brake Pedal

T4FG-03-08-002

P (Primary) Pressure Cup Chamber

T3-8-2

Return Spring

COMPONENT OPERATION / Brake Master Cylinder OPERATION • When brake pedal is operated 1. When the brake pedal is not depressed, piston (3) is pushed to the left by return spring (4).

2. Consequently, when the brake pedal is in neutral, the pressure chamber and the reservoir chamber are connected via the relief port, and are connected to brake oil tank.

3. When the brake pedal is depressed, push rod (1) pushes piston (3) to the right and pushes return spring (4).

4. Therefore, the pressure chamber and the reservoir chamber are blocked and brake oil in the pressure chamber is routed to the brake front axle side.

Brake Oil Tank

3

2

Reservoir Chamber

1

Relief Port

To Front Axle Brake Pedal

5

Pressure Chamber

4

T4FG-03-08-003

1 - Push Rod 2 - S (Secondary) Cup

3-

Piston

4-

T3-8-3

Return Spring

5-

P (Primary) Cup

COMPONENT OPERATION / Brake Master Cylinder (Blank)

T3-8-4

COMPONENT OPERATION / Others GEAR PUMP The gear pump (main pump) is connected to the HST pump in tandem. Engine output power is transmitted to the HST pump shaft directly. The rotation of the HST pump shaft is transmitted to the gear pump.

Drive Gear

The gear pump (main pump) supplies pressure oil to the main and steering circuit.

When the shaft rotates, the drive gear rotates, so that the driven gear is rotated. Pressure oil drawn to the pump fills the spaces between the gear teeth and housing, and is delivered to the outlet port along the inside of the housing.

Outlet Port

Inlet Port

Housing

Driven Gear T487-03-01-006

Drive Gear

HST Pump

Driven Gear

T3-9-1

T4FG-03-09-001

COMPONENT OPERATION / Others PROPELLER SHAFT The propeller shaft is installed between the reduction and the front axle.

The propeller shaft transmits the power from the reduction to the front axle. The universal joint, most commonly used, is provided.

Between Front Axle and Reduction

Universal Joint

Universal Joint

T4GD-03-12-001

T3-9-2

COMPONENT OPERATION / Others PARKING BRAKE SOLENOID VALVE Pressure oil from the HST charging pump is accumulated in the HST pump and its pressure always acts on the inlet of the parking brake solenoid valve.

When the parking brake solenoid valve is activated, pressure oil in the HST charging pump flows to the parking brake through the spool and releases the parking brake.

1

From HST Pump

To Hydraulic Oil Tank

2

3

4

5

6

7

T4FC-03-06-004

1 - Parking Brake Piston Chamber (Front Axle) 2 - Plug

3 - Body

5 - Spool

4 - Spring

6 - O-Ring

T3-9-3

7 - Solenoid

COMPONENT OPERATION / Others (Blank)

T3-9-4

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No. SEW-62M-MAE Issued: March, 2010

TCM

CORPORATION

MARKETING GROUP:

All rights reserved

1-15-5, Nishi-shimbashi,Minato-ku,Tokyo 105-0003,Japan FAX: JAPAN +81-3-35918154 X-1003005(OS) Printed in Japan