Brake Valve

8. Maintenance standards

8.1 600-hour check

Disassemble the parts above the mount plate, wash and check them. Replace defective parts, and apply grease to the sliding surfaces.

8.2 2000-hour or 1-year check

Disassemble the valve, and clean all the parts. Replace all rubber parts. Replace metal parts that are scratched, worn, or otherwise damaged. Execute all the tests specified.

Booster (Brake)

T-4 Booster (Brake)

[NOTICE]

There is a case that the appearance and so on differ from the parts for this machine. Although there is not so much difference in functions and disassembly procedures, make sure of the serial number of this machine and the part sales unit described in the parts catalog before starting disassembling operations. In some boosters, a switch assembly is installed in place of the plug.

1. Structure

1. Body

2. Filter

3. Nipple

4. O-ring

5. Retaining ring

6. Bleeder

7. Cap

8. Check valve

9. Valve seat

2. Function

Booster (Brake)

10. Spring

11. Cap assy

12. O-ring

13. Air breather assy

14. Mud guard

15. Plug

16. O-ring

17. Spring

18. Plunger assy

The booster increases the pneumatic pressure transmitted from the brake valve through portïA, while converting it into a hydraulic pressure. The increased pressure is out put from portïB to actuate the wheel cylinders to apply brakes.

The booster consists of the following three major components.

2.1 Air cylinder

1. The air cylinder contains an air piston, plunger, and return spring. The chamber formed on the side of the cylinder where the plunger slides is always open to the atmosphere.

2. The chamber formed on the opposite side of the cylinder receives the pneumatic pressure from the brake valve and retains it inside the chamber.

2.2 Cylinder body

1.The cylinder body accommodates a plunger guide, primary cup, secondary cup guide, secondary cup, etc. The secondary side parts serves for guiding and sealing the plunger when it is in sliding motion, whereas the primary side parts serves for retaining fluid pressure and supplying fluid.

2. The fluid pressure retaining section has a mechanism which allows the fluid to freely flow from the center of the check valve to the outside of the booster, but permit the fluid to flow in the reverse direction only through a space around the outer circumference of the check valve. The whole check valve is held pressed by a spring.

19. Piston assy

20. Air cylinder

21. Bolt

22. Nut and washer

23. Primary cup

24. Cup spacer

25. Plunger guide

26. Bushing

27. Cup supporter

28. SpacerïA

29. Guide

30. Secondary cup

31. O-ring

32. Retaining ring

33. SpacerïB

Booster (Brake)

3. Operation of cylinder

3.1 Booster not in operation

1. When no air pressure is applied to the booster, the high-pressure side chamber of the air cylinder is open to the atmosphere. Therefore, the air piston is pressed against the left end of the chamber by the return spring.

2. The plunger which is fixed to the air piston is also placed at the leftmost position where the piston assíy is stopped by the air cylinder end wall.

3. In this state, the fluid holes (Φ 0.7 4 places) of the plunger are positioned on the left side of the primary cup lip, allowing the brake fluid to freely flow from the fluid reservoir to the fluid cylinder.

3.2 Booster in operation

1. The compressed air supplied through the opened brake valve reaches the high-pressure side chamber in the air cylinder. When the air pressure overcomes the force of the return spring, the air piston assíy is pushed to move the plunger rightward.

2. In this state, the fluid holes of the plunger are moved rightward beyond the lip of the primary cup. As a result, the fluid passages are blocked and a fluid pressure is generated in the fluid cylinder, letting the pressurized brake fluid flow into the wheel cylinders.

3.3 Brakes are released

Booster (Brake)

1. When the brake pedal is released, the compressed air that has been acting on the booster is let out from the exhaust port of the brake valve. As a result, the piston assy is moved to the left by the action of the return spring.

2. At this point, the pressure in the fluid cylinder begins to turn negative, and this causes check valve to open, allowing the fluid in the wheel cylinders to go back into the booster.

3. Check valve prevents the pressure in the wheel cylinders from turning negative even after the piston has been moved all the way back, thereby preventing air from entering the piping through joints.

3.4 Operation of stroke switch

1. When the brake shoe clearance increases excessively during braking or when the brake fluid leaks from the brake line, or when air is trapped in the brake system, the air piston moved on a stroke larger than normal and pushes the stroke switch to operate an warning lamp or other alarm to remained the driver of the problem.

4. Removing of booster

1. Park the carrier on a level surface, apply the parking brake, and block wheels with chocks.

2. Open the drain cock of the air reservoir to free it from pressure completely.

3. Disconnect the air and fluid pipings from the booster.

4. Remove the booster from the bracket.

Booster (Brake)

5. Disassembly [NOTICE]

Before disassembling, drain the brake fluid from inside the booster, and remove any mud or dirt adhering to the rear surface. Make alignment marks on all the connections and joints to air reassembly. Keep the removed parts in good order to facilitate reassembly.

5.1 Disassembly of cylinder

1. Unscrew the nuts (with washers) at 6 locations, then disconnect the cylinder body from the air cylinder assy. Bolt Washer assembled nut

2. Loosen cap assembly by setting a spanner on the flats of cylinder body. Take out check valve and spring from inside the cylinder body.

IW404-0020E03

At this time, a spring load of 8 kg is applied to the return spring. Press the air cylinder assy and cylinder body with both hands, and use care when disassembling.

3. Take out valve seat by expanding check valve by hand. IW404-0020E06

4. Use a wrench to remove bleeder.

Booster (Brake)

5. Remove retaining ring at nipple. Filter is then removable.

Nipple

Retainer ring

Cup supporter Cup spacer Plunger guide (include bushing) Spacer (A)

Nipple Retainer ring

O-ring

Filter

IW404-0020E10 ï Spacer (B) ï Secondary cup guide (including secondary cup and O-ring) ï Spacer (A) ï Plunger guide (including bushing) ï Cup spacer ï Primary cup ï Cup supporter

6. Disassembly of primary and secondary cup sections: Remove retaining ring. Then the following parts are removable in the order of mention.

IW404-002011

Primary cup Retaining ring

Secondary cup guide O-ring Spacer (B) Secondary Cup

IW404-0020E12

7. Removal of air breather: Remove air breather assembly through from cylinder body by loosening air breather body.

8. Loosen screw to separate the air breather assy into the following parts: ï Air breather body ï Element ï Cover

IW404-0020E14

Booster (Brake)

9. Remove switch assy by using a wrench on the hexagonal section. Then remove O-ring and retainer.

The switch cannot be disassembled.

[NOTICE]

Boosters which do not include a switch assy have a plug installed in its place.

5.2 Disassembly of air cylinder assembly

1. Remove the spring and piston assy from the air cylinder assy.

6. Check

1. Rubber parts

Check the cup and O-ring for damage, wear and aging.

The rubber parts must be replaced regularly at intervals of one year.

2. Air cylinder

Check the inside surface of the cylinder for corrosion or rust. Remove corrosion or rust with No. 500 emery paper. Replace the air cylinder if it is distorted or has a harmful damage.

3. Piston assy

If the air piston is badly deformed or if there are harmful flaws on the outer surface of the plunger, replace the piston assy with a new one.

4. Bushing

Replace the Bushing if harmful damage is evident.

[NOTICE]

Use care when removing the piston assy rod (plunger) to avoid scratching its periphery.

2. Remove piston cup from the piston, using a spatula or the like.

The piston and rod cannot be separated from each other, as they are welded together.

Booster (Brake)

7. Reassembly

To assemble, refer to the figure below, and follow the disassembly procedure in the reverse order.

Greasing points and types of greases to be used

Red seal

Silicon grease G30M

Rubber grease

Thread size and tightening torque

8. Test

8.1 Testing equipment

Booster (Brake)

8.2 Test method

Test Items Test conditions

Fluid-tight test Apply a pressure of 11.8MPa(1711psi ) to the hydraulic pressure line and close the line. Measure the time requires before the pressure falls to 980kPa(142psi).

Air tightness test when opening

Operation begining pressure test

Apply a compressed air pressure of 590kpa(86psi) to the booster and shut off the compressed air supply. Measure the pressure drop amount in 15 seconds.

Slowly depress the pedal to open the brake valve and measure the service line pressure at the moment when the wheel cylinder pressure begins to rise.

Measure the wheel cylinder fluid pressure when the service line pressure is 686kPa(100psi).

With the booster placed in full-load operation state, close the service line and measure the pressure drop amount in 15 seconds.

Residual pressure test

Stroke switch operation test

Release the brake pedal and measure the wheel cylinder fluid pressure.

Loosen the bleeder screw to apply a 196 to 294kPa (28 to 43psi ) air pressure to the booster. Make sure that the stroke switch operates as the air piston moves by using an electric tester.

To work.

9. Maintenance standards

Booster (Brake)

T-5 Air Dryer [NOTICE]

There is a case that the appearance and so on differ from the parts for this machine. Although there is not so much difference in functions and disassembly procedures, make sure of the serial number of this machine and the part sales unit described in the parts catalog before starting disassembling operations.

33. Cap nut 34. Check valve

35. Check valve spring

49. Screw and washer

50. Cover

51. Oil separator filter

52. O-ring

53. Hexagon socket head bolt and washer

54. Gasket ring

55. Gasket ring

56. O-ring

57. Purge chamber

58. Bolt and washer

59. Heater

60. Thermostat

61.Screw

62. Cord clamp plate

63. Screw Thread

2. Function

1. When the air pressure at the air dryer outlet port (air tank air pressure) reaches the specified release pressure, this governor sends that pressurized air to the control port, opening the air dryer drain valve.

2. When the air pressure at the air dryer outlet port has dropped to the specified intake pressure, the pressurized air at the control port is released to the atmosphere, closing the drain valve.

2.1 Dehumidification

1. During the compressor load cycle, the air from the compressor enters the air dryer inlet port. The compressed air is cooled down as it flows along the body walls. This results in moisture and oil accumulating at the bottom of the body.

2. The air flows through a filter which includes an oil mist separator, which removes minute oil droplets and dust before the air enters the drying tube.

3. In the drying tube, the moisture in the air is removed by a desiccant that has a strong affinity for water.

4. As the air proceeds from the bottom of the drying tube to the top, it contacts a stronger desiccant, which further reduces the moisture. When the air reaches the top of the drying tube, it is dry air.

5. This dry air passes through the check valve and purge chamber at the top of the drying tube, and is supplied to the governor chamber and main tank via the outlet port check valve.

2.2 Regeneration

1. When the air pressure in the system reaches the upper limit pressure of the governor, the governor control pressure passes through the control line and opens the drain valve

2. At this time, the air in the drying tube is released into the atmosphere. Because it is released suddenly, the pressure in the drying tube cleans the oil filter and ejects the oil and water condensate into the atmosphere.

3. After the sudden decrease in pressure, the dry air in the purge chamber passes through the orifice, decompressing and expanding. It becomes super-dry air, which flows backwards through the drying tube, absorbing moisture from the desiccant carrying it out into the atmosphere, completing the regeneration of the desiccant.

4. In addition, because there is no feedback command to the compressor, the compressor continues to supply pressure. For this reason, this pressure is also ejected from the dryer into the atmosphere by the opening of the drain valve.

5. When the load cycle begins again, a command from the governor closes the drain valve, and the dehumidifying process starts.