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| Illustration 1 | g00759243 |
(1) Shaft housing (2) Rotor housing (3) Rotor (4) Piston assembly (5) Brake housing (6) Clutch pack (7) Brake piston (8) Belleville washer (9) Roller bearing (10) Roller bearing (11) Shaft | |
The piston motor ( hydrostatic) is of a radial piston type. The piston motor consists of three sections. These sections are the shaft housing (1), the rotor housing (2) and the brake housing (5). Rotor (3) is connected to shaft (11) by splines. Clutch pack (6) is engaged by brake piston (7) and belleville washer (8) when there is no hydraulic pressure. When there is hydraulic pressure, the pressure forces brake piston (7) against belleville washer (8). This allows clutch pack (6) to disengage.
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| Illustration 2 | g00816478 |
(A) Pressure port (B) Pressure port (L) Case drain port (Z) Brake port | |
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| Illustration 3 | g00884297 |
(A) Pressure port (B) Pressure port (C) Annular passages (D) Exposed port (L) Case drain port | |
The hydraulic oil from the piston pump flows through ports (A) and (B). One port will be high pressure and the other port will be low pressure. The high pressure port is determined by the desired direction of rotation. For this explanation of the motor, port (A) is considered to be the high pressure port.
Hydraulic oil flows through the axial bore of port A and into the annular passage (C). Hydraulic oil then flows through the exposed ports (D). The exposed ports (D) are below the piston assemblies. As the pressure increases, the piston is forced outward. As the piston is forced outward, the piston rollers roll on the inner diameter of the cam.
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| Illustration 4 | g00599046 |
As the pistons move along the inner diameter of the cam, the pistons turn the rotor. The rotor turns the shaft. The rotor is connected to the shaft by splines. Illustration 4 shows the rotational motion of the pistons as the pistons rotate about the shaft.
As the rotor turns, the previously exposed ports are covered and previously covered ports are exposed. The fully extended piston assembly next passes over an exposed port.
The piston rollers, which follow the inner diameter of the rotor, force the piston assembly toward the shaft. This is due to the shape of the inner diameter of the rotor. The hydraulic oil is forced through the exposed port by the inward motion of the piston assembly. The hydraulic oil then returns to an annular passage (C) which then directs the oil through an axial bore and out of port (B) .
Port (L) is a case drain for oil that leaks by the piston assemblies and for the flushing valve. The flushing valve uses the oil in order to cool the motor. The flushing valve also uses the oil in order to flush harmful particles from the motor.
Oil for the flushing valve flows from the low pressure side of the drive loop. If the oil pressure in the forward drive cavity increases, the pressure increase shifts the spool toward the reverse drive cavity. Oil from the reverse drive cavity flows through the center passage. The oil pressure in the center passage opens the relief poppet. The oil flows through port (L) to the return manifold and the oil is routed through the oil cooler. Then, the oil returns to the tank.
If the oil pressure in the reverse drive cavity increases, the pressure increase shifts the spool toward the forward drive cavity. Oil from the forward drive cavity flows through the center passage. The oil pressure in the center passage opens the relief poppet. The oil flows through port (L) to the return manifold and the oil is routed through the oil cooler. Then, the oil returns to the tank.