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| Illustration 1 | g00500971 |
Piston Motor (Typical Illustration) (1) Drive shaft (2) Motor case (3) Port for flushing (4) Retainer (5) Piston (6) Stop for the minimum displacement (7) Head (8) Lens control (9) Stop for the Maximum displacement (10) Spring (11) Barrel (12) Pivot pin | |
The hydrostatic motors are bidirectional. The motors have a displacement that is variable. The motors have a bent axis. The motor and the actuator convert the hydraulic power into mechanical power. The power is transferred into a hydrostatic drive box that is mounted to the rear axle. Power is also sent to the front axle by a drive shaft.
The actuator piston controls the motor displacement by changing the angle of the rotating group relative to the output shaft. As the stroke of the pistons increases, the stroke creates a higher torque and a lower speed. As the stroke of the pistons decreases, the stroke creates a lower torque and a higher speed.
There are five hoses that are connected to the motor. There are two hoses for the high pressure oil of the drive loop. There is a hose for the signal pressure, a hose for the oil supply of the motor bearing, and a hose for the case drain.
Drive shaft (1), retainer (4), pistons (5) and barrel (11) rotate. Motor case (2), head (7) and lens control (8) do not rotate. Spring (10) pushes barrel (11) against lens control (8) in order to make a high pressure seal between the barrel and the lens control. This also creates a high pressure seal between the barrel and the head.
Lens control (8) has two control slots. One control slot is for the high pressure loop. The other control slot is for the low pressure loop.
When the high pressure oil is at the high pressure loop port, oil from the port flows through the control slot in lens control (8). Oil in the control slot flows into the cylinders of barrel (11) that are over the control slot.
The spherical piston heads are held in the sockets in drive shaft (1) by retainer (4). Seven pistons (5) are held by barrel (11). The barrel rotates around pivot pin (12), which is at an angle to the axis of drive shaft (1). As pressure oil enters the cylinders and pressure oil exits the cylinders, the seven pistons move in the cylinders and out of the cylinders. This rotates the pistons, the barrel and the drive shaft.
As the pistons, the barrel and the drive shaft continue to rotate, the piston reaches the top center (fully retracted position). At the same time, the cylinder begins to overlap the control slot in lens control (8) on the low pressure side of the loop. At this point, the piston starts to move down. This pushes oil out of the cylinder through the control slot to the low pressure loop.
The motor bearings receive lubrication from port (3) and cooling oil from port (3). The remaining internal components are lubricated by oil leakage from the pistons and barrel.
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| Illustration 2 | g00777980 |
(13) Motor signal control valve (14) Flushing valve (15) Large variable displacement motor (16) Actuator for the motor (17) Motor displacement control for the large motor (18) Forward signal line (19) Reverse signal line (20) Shuttle valve (21) Motor displacement control for the small motor (22) Actuator for the motor (23) Small variable displacement motor (24) Drive loop (25) Pin | |
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| Illustration 3 | g00516263 |
(15) Large variable displacement motor. (17) Motor displacement control for the large motor. (18) Forward signal line. (19) Reverse signal line. (21) Motor displacement control for the small motor. (23) Small variable displacement motor. (24) Signal line from the motor signal control valve. | |
Small variable displacement motor (23) has a motor displacement control (21). When a direction is selected the forward/neutral/reverse valve sends a signal from the speed sensing valve to the pump actuator. The signal also flows through the actuator to the shuttle valve (20) in the small motor. The shuttle valve shifts in order to send the signal to the right side of the motor displacement control. The oil pressure works against the oil pressure of the drive loop and spring on the left side of the motor displacement control.
The motor displacement control (21) compares the signal pressure with the high pressure oil of the drive loop in order to control the actuator for the motor (22). When the accelerator is depressed, the signal pressure increases and the motor destrokes. If the machine goes up an incline then the drive pressure increases and the motor upstrokes. This causes the machine speed to decrease and this causes the torque to increase.
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| Illustration 4 | g00516766 |
Motor Signal Control Valve (13) The motor signal control valve is located on the front of the fuel tank for (S/N: 9WM1-12981WN1-898). | |
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| Illustration 5 | g00516767 |
Motor Signal Control Valve (13) The motor signal control valve is located on the top of the fuel tank for (S/N: 9WM1299-UP1WN899-UP). | |
Large variable displacement motor (15) has a motor displacement control. The motor displacement control (17) receives signal pressure from motor signal control valve (13). The motor displacement control (17) determines the position of the actuator for the motor (16) from the signal pressure from motor signal control valve (13). The electronic control module (ECM) determines the amount of spool movement of motor signal control valve (13). This will vary the signal pressure to the motor displacement control (17). The ECM monitors the engine speed and the drive shaft speed. The ECM then uses these inputs in order to determine the position of the actuator piston.
When the SLOW speed mode is selected, the ECM de-energizes motor signal control valve (13). If motor signal control valve (13) is not energized the large variable displacement motor (15) remains at the maximum displacement position. In this mode, the speed of the machine is reduced in order to improve the performance of loading.
When the direction control lever is moved to the FORWARD position, the pump sends signal oil to signal line (18). The signal causes the shuttle valve (20) to shift to the left. Then, shuttle valve (20) will direct signal oil to the actuator for the motor (22) .
When the direction control lever is moved to the REVERSE position, the pump sends signal oil from the forward/neutral/reverse valve and the pump actuator to signal line (19). The signal causes the shuttle valve (20) to shift to the right. Signal oil is directed to the actuator for the motor (22). The shuttle (20) senses the position of the forward/neutral/reverse valve.
The flushing valve (14) continuously drains some oil from the low pressure side of the drive loop. The oil then drains through the motor to the case drain. The action purges heat, debris and air from the drive loop. The flushing valve (14) also limits the maximum pressure in the low pressure drive loop.
The pin (25) is part of the head group of each motor. Different slots are on the end of each pin. The pin controls the time for stroking the pump. The pins restrict the flow of oil to the actuator piston of the motor. The pins control the acceleration or deceleration of the machine. The pins are self-cleaning because flow direction occurs in both directions.
If the pin is assembled incorrectly, testing the machine will reveal abnormal deceleration. The pin of the large motor has a slot. The pin of the small motor has two slots. The slot on one end is 0.8 mm (0.0315 inch). The other slot is 0.45 mm (0.0177 inch).