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| Illustration 1 | g03632964 |
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The hydrostatic system contains the following top-level components: (1) Hydrostatic pump (2) Hydrostatic motor (3) Hydraulic oil filter (4) Transmission (5) Hydraulic charge pump (6) Hydrostatic drive pressure sensor | |
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| Illustration 2 | g03632468 |
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(1) Hydrostatic pump
(2) Hydrostatic motor (3) Hydraulic oil filter (4) Transmission (5) Hydraulic charge pump (6) Hydrostatic drive pressure sensor (7) Hydrostatic pump control valve (8) Hydrostatic pump control valve (9) Pump actuator (10) Hydraulic cooler (11) Charge pressure relief vale (12) Cross over relief valve (13) Cross over relief valve (14) Hydrostatic inter lock valve (15) Hydrostatic motor control solenoid valve (16) Hydrostatic motor flushing valve (17) Hydraulic oil cooler bypass | |
The hydrostatic pump (1) supplies oil to the hydrostatic motors (2) . The hydrostatic motor (2) is mounted to the transmission (4). The transmission is connected to the rear axle. The transmission is connected with a drive shaft to the front axle.
Charge pump (5) provides control oil to the transmission (4). Charge pump (5) provides oil to the hydrostatic system and pilot oil to the implement system through the hydraulic oil filter (5).
When the machine is started and in the NEUTRAL position, the hydrostatic pump (1) has no displacement until a direction of travel is selected.
Cross Over Relief (COR)/makeup check (12) and (13) protect the hydrostatic system by limiting the pressure spikes in the drive loop. The check valves in the crossover relief COR/makeup valves (12) and (13) open and supply oil to the drive loop. The check valves in the COR/makeup valves (12) and (13) also supply oil to the flushing valve. The COR/makeup valves (12) and (13) supply make oil that is flushed by the flushing valves. The COR/makeup valves (12) and (13) make any oil lost through internal leakage. Charge relief valve (11) limits the charge pressure.
Charge pump (5) sends oil through the hydraulic oil filter (3) and then to various components of the hydrostatic drive system. Oil flows from the hydraulic oil filter (3) to the interlock valve manifold. Oil in the hydrostatic pump control valve manifold flows to the charge relief valve and to the cross over relief/makeup valves. Within the interlock manifold is the hydrostatic interlock solenoid valve (14). The hydrostatic interlock solenoid valve (14), when energized, allows oil to the hydrostatic pump control valves (7) and (8). The hydrostatic interlock solenoid valve (14) is powered on when the machine is running and the parking brake is disengaged. The charge oil pressure is set by the charge pressure relief valve (11) in the pump. Charge oil is supplied to the hydrostatic pump control valves (7) and (8). Hydrostatic pump control valves (7) and (8) controls the flow of oil to the actuator cylinder (9) of the hydrostatic drive pump (1). Charge oil is also supplied to hydrostatic motors (2) for bearing lube.
The three position Forward, Neutral, and Reverse (FNR) switch on the joystick allows the operator to select the direction of travel. The left pedal position and right (accelerator) pedal position are monitored by the ECM. The following information describes machine functions when selecting Forward with the FNR switch after start-up.
As the operator depresses the accelerator pedal, an increasing PWM signal is sent to the solenoid on the pump control valve (7). The machine speed increases. When the pump nears maximum displacement, the ECM increases PWM signal to motor solenoid (14) to further increase speed.
Pump And Motor Flushing In The Neutral Position
While the machine is in the Neutral position, the flushing valve (16) is closed, not allowing oil to pass. The charge pump (5) supplies oil to the drive loop through the COR/makeup valves. Case drain oil flows through the hydrostatic motor (2) to the hydraulic oil tank .
Drive Loop Flushing In The Forward Or Reverse Direction
The oil pressure difference from the high and low-pressure sides will shift the flushing valve spools . When flushing valves (16) shift, oil flows from the flushing valves to the case drain of piston motor (2). From the case drain, oil flows through hydraulic oil cooler (10) and to the tank.