966G Series II Wheel Loader and 972G Series II Wheel Loader Hydraulic System Pilot Valve (Oil Manifold) - Electrohydraulic Machines Caterpillar


Pilot Valve (Oil Manifold) - Electrohydraulic Machines
`
1.1. Lift Function
2.1. Tilt Function
3.1. Auxiliary Function

The pilot valve (oil manifold) is part of the valve group that is located in the front end frame. The pilot valve (oil manifold) controls the flow of pilot oil to the main control valve.




Illustration 1g00818898

Section View of the Pilot Valve (Oil Manifold)

(1) Shuttle valve

(2) Port to the steering system

(3) Passage (primary pilot pressure)

(4) Supply port from the pilot/brake pump

(5) Primary pressure reducing valve

(6) Secondary pressure reducing valve

(7) Passage to hydraulic oil tank

(8) Solenoid valve (Pilot proportioning) (DUMP)

(9) Solenoid valve (Pilot proportioning) (LOWER)

(10) Port to the main control valve (LOWER)

(11) Port to the main control valve (DUMP)

(12) Passage (pilot pressure)

(13) Port from the lift cylinder

(14) Port to the lowering control valve

(15) Passage (secondary pilot pressure)

(16) Passage from the lift valve spool

(17) Vent port from the makeup valve

(18) Supply port to the ride control solenoid valve

(19) Solenoid valve (hydraulic lockout)

(20) Port to the main control valve (TILT BACK)

(21) Solenoid valve (Pilot proportioning) (TILT BACK)

(22) Return port to the hydraulic oil tank

(23) Solenoid valve (Pilot proportioning) (RAISE)

(24) Port to the main control valve (RAISE)

(25) Float valve

Oil enters the pilot valve (oil manifold) at port (4) from the pilot/brake pump. Primary pressure reducing valve (5) reduces the pressure of the pilot oil to 3450 ± 200 kPa (500 ± 30 psi). When the adjustment of the primary reducing valve is set above the secondary reducing valve, the shuttle valve will shift. This will allow the pilot oil from the pilot/brake pump to flow through passage (3) to shuttle valve (1). Also, pilot oil for the steering system flows through passage (3) to port (2) .

Secondary pressure reducing valve (6) supplies pilot oil when the engine is stopped. The secondary pilot oil allows an operator to lower the lift arms when the engine is stopped. In order to lower the lift arms with the lift control lever, the engine start switch key must be in the ON position.

If there is an electrical failure the lift arms can be lowered manually. The engine start switch key does not need to be in the ON position. Opening the ball valve (dead engine lower) causes the lift arms to slowly lower.

When the lowering control valve is open, hydraulic oil from the lift cylinders flows through port (14) to the lowering control valve. The oil then returns to the hydraulic tank.

Secondary pressure reducing valve (6) receives high pressure oil from the lift cylinder through port (13). A shuttle valve (ball resolver) allows the oil to flow from the end of the lift cylinder with higher pressure. The shuttle valve is located in the manifold that is attached to the main control valve.

The pressure of the oil is reduced to 2070 ± 200 kPa (300 ± 30 psi) by secondary pressure reducing valve (6). The pilot pressure oil then flows through passage (15) to shuttle valve (1) .

Excess oil from pressure reducing valves (5) and (6) flows to port (22). The oil then flows to the hydraulic tank.

Shuttle valve (1) senses the two reduced pressures. The shuttle valve then sends pilot pressure oil through passage (12) to the solenoid valve (hydraulic lockout) (19). Also, pilot oil is supplied to the ride control solenoid valve through port (18) .

The solenoid valve (hydraulic lockout) (19) controls the flow of pilot oil to the solenoid valve (pilot proportioning). When the hydraulic lockout switch is in the LOCKED position the solenoid valve (hydraulic lockout) is closed. When the implement lockout switch is in the UNLOCKED position the solenoid valve (hydraulic lockout) is open and pilot oil will flow to the solenoid valve (pilot proportioning).

When the engine is not running and when all control levers are in the HOLD position, the solenoid valve (hydraulic lockout) is closed. No oil will flow to the solenoid valves (pilot proportioning). The implement cylinders will not operate.

When the engine is running and the solenoid valve (hydraulic lockout) has been energized oil will flow through the solenoid valve (pilot proportioning) (8), (9), (21), and (23). The flow of oil increases with an increase in movement of the control lever or the joystick control from the HOLD position. The oil then flows to the appropriate stem in the main control valve in order to allow pump supply oil to flow to the implement cylinders.

Lift Function

When the lift control lever or the joystick control is pulled backward into the RAISE position, oil will flow through port (24) to the lift valve spool in the main control valve.

As the lift valve spool moves, oil from the chamber at the LOWER end of the lift valve spool returns through port (10). The return oil flows through the solenoid valve (pilot proportioning) (9) and back to return port (22) .

When the lift control lever or the joystick control is pushed forward into the LOWER position, oil will flow to the solenoid valve (pilot proportioning) (9) through port (10) to the lift valve spool in the main control valve.

As the lift valve spool moves, oil from the chamber at the RAISE end of the lift valve spool in the main control valve returns through port (24). The return oil then flows through the solenoid valve (pilot proportioning) (23) and back to return port (22) .

If the lift linkage is below the lower kickout position and the lift control lever is moved to the detent for the LOWER position, the lift arms will be in the FLOAT position. The pilot pressure to the LOWER end of the lift valve spool in the main control valve will increase to pilot system pressure.

This increase in pilot pressure will be sensed in passage (16). Float valve (25) opens in order to vent oil from a makeup valve in the main control valve. The oil flows through port (17) to return port (22).

Oil from both ends of the lift cylinders can flow to the hydraulic oil tank. This allows the work tool to move up and down with the contour of the ground as the machine travels.

Tilt Function

When the tilt control lever or the joystick control is pulled backward into the TILT BACK position, oil will flow to the solenoid valve (pilot proportioning) (21) through port (20) to the tilt valve spool in the main control valve.

As the tilt valve spool moves, oil from the chamber at the DUMP end of the tilt valve spool returns through port (11). The return oil flows through the solenoid valve (pilot proportioning) (8) to return port (22) .

When the tilt control lever or the joystick control is pushed forward into the DUMP position oil will flow to the solenoid valve (pilot proportioning) (8) through port (11) to the tilt valve spool in the main control valve.

As the tilt valve spool moves, oil from the chamber at the TILT BACK end of the tilt valve spool returns through port (20). The return oil flows through the solenoid valve (pilot proportioning) (21) to return port (22) .

Auxiliary Function

Machines with an auxiliary function (logging fork, side dump bucket, multipurpose bucket, etc) have a valve group that is mounted to the right side of the pilot valve (oil manifold).

The valve group contains two solenoid valves (pilot proportioning). The solenoid valves control the movement of the auxiliary valve spool in the main control valve. The auxiliary function operates similarly to the lift function and tilt function. Except, the auxiliary function is not equipped with detent coils in the pilot valve.

Information System:

3054E Industrial Engine Speed/Timing Sensor - Remove and Install
AD30 Underground Articulated Truck Engine Oil Level - Check
AD30 Underground Articulated Truck Transmission Oil Level - Check
3054E Industrial Engine Inlet Air Temperature Sensor - Remove and Install
2003/04/07 Latest Version of Payload Control System (PCS) Software Is Now Available {7620}
2003/04/14 Special Instruction, REHS1640, "Additional Documentation for the Payload Control System" Is Available {0374, 7494}
953C Track-Type Loader Hydraulic System Oil - Change
IT62G Integrated Toolcarrier and 950G and 962G Wheel Loaders Additional Messages
966G Series II Wheel Loader and 972G Series II Wheel Loader Steering System Metering Pump (HMU)
966H Wheel Loader and 972H Wheel Loader Braking and Hydraulic Fan System Service Brakes
IT62G Integrated Toolcarrier and 950G and 962G Wheel Loaders Hydraulic System Oil Sample - Obtain
3054E Industrial Engine Boost Pressure Sensor - Remove and Install
IT62G Integrated Toolcarrier and 950G and 962G Wheel Loaders Operator Controls
Bench Test Procedure for a D9 and D9R Track-Type Tractor Transmission {3030, 3073}
2003/05/19 Additional Information for Testing and Adjusting , "Pump Flow - Test" on the Wheel Skidders {4268, 5070}
2003/11/17 New Fan Guards Are Now Used {1360}
953C Track-Type Loader Hydrostatic Transmission and Hydraulic System Filters - Replace
3054E Industrial Engine Electronic Control Module - Remove and Install
966G Series II Wheel Loader and 972G Series II Wheel Loader Hydraulic System Lift Kickout - Adjust
AD30 Underground Articulated Truck Frame and Body - Inspect
AD30 Underground Articulated Truck Engine Oil and Filter - Change
AD30 Underground Articulated Truck Frame and Body Support Pads - Clean/Inspect
AD30 Underground Articulated Truck Fuel System Primary Filter - Clean/Replace
Procedure for Reinforcing the Mounting Area of the Steering Cylinder on the Rear Frame{7051}