SPRING 8E7581 - Caterpillar

Illustration 1 g00401038
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) Control valve (8) Head (9) Lens control (10) Stop for the Maximum displacement (11) Spring (12) Barrel (13) Pivot pin
Illustration 2 g00642107
(1) Piston motor (14) Speed selector valve (15) Relief valve (16) Displacement control valve (17) Flushing valve (18) Actuator (19) Shuttle spool (20) Direction control valve (A) Signal pressure from the speed sensing valve (B) Port for the main loop (C) Oil for the motor bearing from the hydraulic oil cooler (D) Oil to the hydraulic tank (E) Port for the main loopThe hydrostatic motor (1) is bidirectional. The motor has a variable displacement. The power is transferred into a hydrostatic drive box that is mounted to the rear axle. Power is also transferred to the front axle by a drive shaft. The actuator piston (18) controls the motor displacement by changing the angle of the rotating group relative to the output shaft. As the stroke of the pistons (5) 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.The shuttle spool (19) controls the stroking of the motor. The orifice in the shuttle spool slows the movement of the actuator. The orifice causes the movement of the actuator to slow from the minimum stroke to the maximum stroke.The motor displacement control (16) senses the pump signal pressure. The valve compares the signal pressure with the pressure of the drive loop in order to control the actuator piston. When the accelerator is depressed more, the signal pressure increases in order to destroke the motor. If the drive pressure increases, the motor upstrokes. This causes the displacement control valve to shift to the right. The actuator then upstrokes the motor and the machine speed will decrease.When the SLOW speed is selected, the speed selector valve (14) is energized. Signal oil (A) is blocked from reaching the motor displacement control (16). The motor displacement control (16) is shifted to the right by the system pressure. The motor will upstroke. Upstroking the motor provides the maximum displacement of the oil. When the motor is upstroked, the speed of the machine is reduced in order to improve the performance of the loading. The output torque is increased as a result of the increase in the displacement.In the FORWARD position, the direction control valve (20) is de-energized. When the direction control switch is moved to the REVERSE position, the direction control valve allows the pressure from the high pressure side of the drive loop to go to the motor displacement control and the actuator. By stroking the motor with the higher pressure from the drive loop, the response of the driving is improved. During the hydrostatic braking, the stability of the system is maximized.The flushing valve (17) continuously drains some oil from the low pressure side of the drive