COMPONENT

OPERATION ／ Control Valve

・Detent operation

Lift plunger section

１．When the control lever is pushed forward to set it in the "FLOAT" position, the lift spool (1) is fully pulled. At the same time the detent pin (2) installed to the spool end is moved and 4-pieces of the detent balls (3) are dropped into the groove on the detent sleeve (4).

２．As the detent balls (3) are pushed by the detent spring (5), the lift spool (1) is held in "FLOAT" position and the detent mechanism is activated.

３．When the detent operation is cancelled, pull the control lever. The detent ball (3) exits the groove and the detent operation is cancelled.

Tilt plunger section

１．For the detent mechanism on the tilt spool section, an electromagnetic detent mechanism has been equipped. For the electric circuit, the current goes from the battery to the proximity switch on the auto-lever through the coil assembly (4) in the tilt section.

２．When the bucket is tilted forward from the level position, the proximity switch is closed and acts the coil assembly (4).

３．When the control lever is moved fully to the "TILT BACK" direction, the tilt spool is pressed in to the end. At the same time the pin (2) attached to the spool end is pressed in, so that the plate (3) touches the coil (4). Therefore the tilt spool (1) position is held and the detent mechanism is activated.

４．When the detent operation is cancelled, operate the control lever manually to cancel.

COMPONENT OPERATION ／ Control Valve

・ Relief valve

This control valve has one main and two port relief valves. The main relief valve is equipped between the neutral passage in the inlet section and the low-pressure passage. The 2-port relief valves are equipped, one is between the rod side of the tilt cylinder port and the low-pressure passage, another one is between the bottom side of tilt cylinder port and the low-pressure passage.

Main Relief Valve

The main relief valve is located in the circuit between port P (the pump side port) and port T (the hydraulic oil tank side port) and prevents the loader circuit pressure from increasing more than the set pressure.

The oil pressure in port P acts on pilot poppet (8) via orifice (2) in main poppet (1) and orifice (7) in sleeve (6). If the oil pressure in the loader circuit increases more than the set pressure by spring (9), pilot poppet (8) opens so that a small quantity of the pressure oil flows to port T through the outer diameter of sleeve (3). Then, a differential pressure arises between port P and spring chamber (5) as orifice (2) is provided. If the differential pressure increases so that main poppet (1) is pushed to the right by a force greater than spring (4) force, main poppet (1) opens, allowing the pressure oil to flow from port P directly to port T. When the oil pres-sure in port P decreases, main poppet (1) is closed again by spring (4) force.

COMPONENT OPERATION ／ Control Valve

Overload Relief Valve

The overload relief valve is located in the circuit be-tween the cylinder and port T (hydraulic oil tank side port) and prevents the circuit oil pressure from being increased excessively even if the cylinder is forcibly moved by external force.

The oil pressure in the cylinder acts on pilot poppet (5) through the passage in poppet valve (1). If the oil pressure increases more than the set pressure by spring (6), pilot poppet (5) opens so that a small quantity of the pressure oil flows to port T through the outer diameter of sleeve (3). Then, a differential pressure arises between the cylinder side port and chamber (4). Then, poppet valve (1) is pushed to the right so that main poppet (2) opens, allowing the pressure oil to flow from the cylinder side port to directly port T. In addition, this overload relief valve draws hydraulic oil from port T (hydraulic oil tank side) when the cylinder circuit pressure becomes negative, preventing the occurrence of cavitation in the cylinder circuit (Anti-void valve)

COMPONENT OPERATION ／ Control Valve

・ Anti-void valve

When a negative pressure is created on the rod side of the lift cylinder, the anti-void valve refill the rod side directly with the oil in the tank port.

Operation

１．The oil from the cylinder port HP is sent into the anti-void valve through the hole in the poppet (1).The poppet (1) is positioned as shown due to the difference in area between (A) and (B).

２．When the pressure in the cylinder port HP is lower than in the tank port LP, the poppet (1) moves to the right due to the difference in area between (A) and (B).At this time, sufficient oil flows to the cylinder port HP from the tank port LP to prevent a cavitation in the cylinder.

COMPONENT OPERATION ／ Main pump

・ Main Pump

The main pump is a double gear pump with the main pump coupled with the charging pump. This pump, installed to the HST pump via the coupling, rotates with the engine. The main pump doubles as a steering pump. The main pump sucks up hydraulic fluid from the hydraulic fluid tank and supplies it to the orbitroll (VP valve). Hydraulic fluid is split into the main hydraulic circuit and steering hydraulic circuit by the orbitroll (VP valve). With the main charging pump operated, the hydraulic fluid in the hydraulic fluid tank fills the space made of the gear bottom and inside walls of housings (9) and (17) by suction power generated when the drive gear (1) engaged with the driven gear (8) and drive gear (15) engaged with driven gear (18) rotate. The hydraulic fluid is pushed out to the discharge side when engagement of gears starts again. The main pump, to prevent oil leaks from the clearance between gears and side plates by high pressure, uses bushings (7) and (16) to achieve pressure balance and make the clearance smaller by leading discharge pressure to surfaces of the bushings (7) and (16), resulting in increased pump efficiency (volume efficiency).