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| Illustration 1 | g00443491 |
(1) Piston pump ( hydrostatic) (2) Charge pump (3) Hydraulic oil filter | |
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| Illustration 2 | g00443706 |
(4) Piston motor ( hydrostatic) | |
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| Illustration 3 | g00455451 |
(5) Transfer drive (6) Rear axle | |
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| Illustration 4 | g00444085 |
(7) Drive shaft (8) Front Axle | |
The hydrostatic system contains the following items: piston pump ( hydrostatic) (1), charge pump (2), hydraulic oil filter (3), piston motor ( hydrostatic) (4), hydrostatic drive box (5), rear axle (6), drive shaft (7) and front axle (8) .
The piston pump supplies oil to the piston motor. The piston motor is mounted to the hydrostatic drive box. The hydrostatic drive box is connected to the rear axle. The hydrostatic drive box is connected with a drive shaft to the front axle.
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| Illustration 5 | g00434721 |
Hydrostatic system in NEUTRAL (1) Fluid level sensor (2) Oil returns To tank (3) Test port for the service brake (4) Line to the brake master cylinder (5) Oil line from the oil cooler to the motor case (6) Piston motor ( hydrostatic) (7) Oil line from the motor case to the hydraulic tank (8) Motor group (9) Reverse solenoid (10) "M1" Test port for the motor (11) Actuator for the motor (12) POR valve (13) Charge relief valve (14) Oil line from the housing of the pump to the hydraulic tank (15) Oil line from the gear motor ( fan) to the tank (16) Crossover relief valve for FORWARD (17) Speed sensing valve (18) Hydraulic oil filter (19) Hydraulic oil filter bypass valve (20) Test port for the hydraulic oil filter (21) Scheduled oil sampling valve (22) Forward/Neutral/Reverse valve (23) Pump actuator (24) Hydraulic oil line from the hydraulic tank to the gear pump ( work tool and steering) (25) Line from the hydraulic tank to the fan pump and to the charge pump (26) Oil line from the gear pump ( fan) to the gear motor ( fan) (27) Oil line from the gear pump ( work tool and steering) to priority valve (28) Gear pump ( work tool and steering) (29) Charge pump (30) Piston pump ( hydrostatic) (31) Pump group (32) "PS" Test port for pump signal pressure (33) Test port for charge pressure (34) Oil line to the pilot valve ( joystick) (35) Crossover relief valve for Reverse (36) "T2" Test port for pressure in the pump case (37) "MH" Test port for high pressure (38) Flushing valve (39) Motor displacement control (40) Valve for the speed control (41) Slow speed control valve (If equipped) (42) Brake valve (AA) High pressure oil of the drive loop (BB) Low pressure oil of the drive loop (CC) Charge oil pressure (DD) Signal oil pressure (EE) Blocked oil (FF) Return to tank oil | |
The hydraulic oil flows from the hydraulic tank to the charge pump (29). The charge oil (CC) flows through the hydraulic oil filter (18) to the speed sensing valve (17) .
Most of the charge oil to the speed sensing valve enters the charge circuit. The oil then goes to the crossover relief valves (16) and (35) .
The makeup valves in each crossover relief valve open. The charge oil flows through the drive loop to the following components: gear pump ( work tool and steering) (28), piston motor ( hydrostatic) (8), flushing valve (38), reverse solenoid valve (9) and motor displacement control (39). When the system is full of charge oil, the relief valve for the charge pump (13) opens. Most of the charge oil goes to the pump case. The oil then goes back to the tank.
The oil also flows through the speed sensing valve. The oil provides signal pressure (DD) to the Forward/Neutral/Reverse valve (22). When the direction control is in the NEUTRAL position, the oil is blocked to the pump actuator at the Forward/Neutral/Reverse valve (22).
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| Illustration 6 | g00441219 |
Hydrostatic system in FORWARD (1) Fluid level sensor (2) Oil returns To tank (3) Test port for the service brake (4) Line to the brake master cylinder (5) Oil line from the oil cooler to the motor case (6) Piston motor ( hydrostatic) (7) Oil line from the motor case to the hydraulic tank (8) Motor group (9) Reverse solenoid (10) "M1" Test port for the motor (11) Actuator for the motor (12) POR valve (13) Charge relief valve (14) Oil line from the housing of the pump to the hydraulic tank (15) Oil line from the fan motor to the tank (16) Crossover relief valve for Forward (17) Speed sensing valve (18) Hydraulic oil filter (19) Hydraulic oil filter bypass valve (20) Test port for the hydraulic oil filter (21) Scheduled oil sampling valve (22) Forward/Neutral/Reverse valve (23) Pump actuator (24) Hydraulic oil line from the hydraulic tank to the gear pump ( work tool and steering pump) (25) Line from the hydraulic tank to the fan pump and to the charge pump (26) Oil line from the gear pump ( fan) to the gear motor ( fan) (27) Oil line from the gear pump ( work tool and steering) to priority valve (28) Gear pump ( work tool and steering) (29) Charge pump (30) Piston pump ( hydrostatic) (31) Pump group (32) "PS" Test port for pump signal pressure (33) Test port for charge pressure (34) Oil line to the pilot valve ( joystick) (35) Crossover relief valve for REVERSE (36) "T2" Test port for pressure in the pump case (37) "MH" Test port for high pressure (38) Flushing valve (39) Motor displacement control (40) Valve for the speed control (41) Slow speed control valve (if equipped) (42) Brake valve (AA) High pressure oil of the drive loop (BB) Low pressure oil of the drive loop (CC) Charge oil pressure (DD) Signal oil pressure (EE) Blocked oil (FF) Return to tank oil | |
When the operator moves the direction control switch to the FORWARD position, the Forward/Neutral/Reverse valve shifts to the FORWARD position and signal oil from the speed sensing valve flows to the pump actuator. The signal pressure acts against the centering springs of the pump. Because the signal pressure is too low, the pump will not upstroke and the machine will not move.
As the operator depresses the accelerator pedal, the engine speed increases causing the signal pressure to increase. The increase of pressure causes the pump to upstroke. As the pump upstrokes, the speed of the machine increases.
As the engine speed continues to increase, the signal pressure from the speed sensing valve also increases. The increase in signal pressure will move the displacement control valve of the motor. This allows the high pressure oil to flow to the actuator of the motor to destroke the motor. Destroking the motor causes the motor to rotate faster. When the motor is fully destroked, the pump is fully upstroked and the engine is at maximum rpm. The machine speed is maximum.
Any resistance to the rotation of the motor increases the drive pressure. The increase of pressure causes the engine to slow down. The slowing down of the engine causes the signal pressure to decrease. As the signal pressure decreases, the pump destrokes. As the pump destrokes the speed of the machine is reduced.
The displacement control valve of the motor continually balances the signal pressure and the drive pressures. The pressure must be continually balanced in order to prevent the engine lugging.
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| Illustration 7 | g00443063 |
Hydrostatic system in REVERSE (1) Fluid level sensor (2) Oil returns To tank (3) Test port for the service brake (4) Line to the brake master cylinder (5) Oil line from the oil cooler to the motor case (6) Piston motor ( hydrostatic) (7) Oil line from the motor case to the hydraulic tank (8) Motor group (9) Reverse solenoid (10) "M1" Test port for the motor (11) Actuator for the motor (12) POR valve (13) Charge relief valve (14) Oil line from the housing of the pump to the hydraulic tank (15) Oil line from the fan motor to the tank (16) Crossover relief valve for FORWARD (17) Speed sensing valve (18) Hydraulic oil filter (19) Hydraulic oil filter bypass valve (20) Test port for the hydraulic oil filter (21) Scheduled oil sampling valve (22) Forward/Neutral/Reverse valve (23) Pump actuator (24) Hydraulic oil line from the hydraulic tank to the gear pump work tool and steering (25) Line from the hydraulic tank to the fan pump and to the charge pump (26) Oil line from the gear pump ( fan) to the gear motor ( fan) (27) Oil line from the gear pump work tool and steering to priority valve (28) Gear pump work tool and steering (29) Charge pump (30) Piston pump ( hydrostatic) (31) Pump group (32) "PS" Test port for pump signal pressure (33) Test port for charge pressure (34) Oil line to the pilot valve ( joystick) (35) Crossover relief valve for Reverse (36) "T2" Test port for pressure in the pump case (37) "MH" Test port for high pressure (38) Flushing Valve (39) Motor displacement control (40) Valve for the speed control (41) Slow speed control valve (if equipped) (42) Brake valve (AA) High pressure oil of the drive loop (BB) Low pressure oil of the drive loop (CC) Charge oil pressure (DD) Signal oil pressure (EE) Blocked oil (FF) Return to tank oil | |
When the operator moves the direction control switch to the REVERSE position, the Forward/Neutral/Reverse valve shifts to the REVERSE position and signal oil from the speed sensing valve flows to the pump actuator. The signal pressure acts against the centering spring of the pump actuator. Because the signal pressure is too low, the pump will not upstroke and the machine will not move.
As the operator depresses the accelerator pedal, the engine speed increases causing the signal pressure to increase flow. The increase of flow causes the motor to turn faster. As the motor turns faster, the speed of the machine increases.
As the engine speed continues to increase, the signal pressure from the speed sensing valve also increases. The increase in signal pressure will move the displacement control valve of the motor. This allows the high pressure oil to flow to the actuator of the motor to destroke the motor. Destroking the motor causes the motor to rotate faster. When the motor is fully destroked, the pump is fully upstroked and the engine is at maximum rpm. The machine speed is maximum.
Any resistance to the rotation of the motor increases the drive pressure. The increase in pressure causes the engine to slow down. The slowing down of the engine causes the signal pressure to decrease. As the signal pressure decreases, the pump destrokes. As the pump destrokes the speed of the machine is reduced.
The displacement control valve of the motor continually balances the signal pressure and the drive pressures. The pressures must be continually balanced in order to prevent the engine lugging.