The control valve is used to shift the control lens to the desired angle for optimum performance of the piston motor.
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| Illustration 1 | g01957671 |
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(3) Setscrew
(5) Locknut | |
A certain amount of current is needed in order to cause each motor to begin destroking. This is the initiation current for the motor. When the ECM begins sending current to the solenoids for the motors, the ECM does not instantly start at the initiation current for each motor. The current rises from zero to the initiation current for each motor. The motor with a higher initiation current may begin destroking a moment later than the other motor. This causes the tractor to turn briefly in the direction of the motor with the higher initiation current. Adjustment screw (3) and locknut (5) in Illustration 1 are used for setting the initiation current.
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| Illustration 2 | g01957407 |
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Control lens at maximum displacement (1) Solenoid (2) Valve (4) Passage (6) Passage (7) Spring (8) Bushing (9) Spring (10) Spring collar (11) Spring collar (12) Spring (13) Control lens (14) Passage (15) Pin (16) Cavity (17) Shift actuator piston (18) Cavity (19) Passage | |
High pressure oil from the drive loop flows into cavity (16) and the pressure oil forces shift actuator piston (17) downward. Pressure oil also flows through passage (14) to passage (4). The oil flows through passage (4) to valve (2). Also, the oil in cavity (18) flows through passage (19) to passage (6). The oil flows through passage (6) to valve (2).
When there is no signal from the ECM to solenoid (1), valve (2) does not move. Since valve (2) does not move, the pressure oil in passage (4) is blocked. Also, the oil in passage (6) flows past valve (2) in the motor case.
When the angle of the lens plate matches the required displacement, the actuator spring applies force on the control spring. When the force of the actuator spring equals the force that is applied by solenoid (1), the spool closes off flow to chamber (18).
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| Illustration 3 | g01957409 |
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Control lens at minimum displacement (1) Solenoid (2) Valve (4) Passage (6) Passage (7) Spring (8) Bushing (9) Spring (10) Spring collar (11) Spring collar (12) Spring (13) Control lens (14) Passage (15) Pin (16) Cavity (17) Shift actuator piston (18) Cavity (19) Passage | |
When the ECM sends a signal to solenoid (1), solenoid (1) overcomes the force of spring (7) and valve (2) moves downward. As valve (2) moves downward, a path between passage (4) and passage (6) opens. Regulated pressure oil flows from passage (4) past valve (2) into passage (6). Then, the oil flows from passage (6) through passage (19) into cavity (18).
Since the surface area of shift actuator piston (17) in cavity (18) is greater than the surface area of shift actuator piston (17) in cavity (16), shift actuator piston (17) moves upward. Since pin (15) is connected to shift actuator piston (17), pin (15) moves upward and pin (15) moves control lens (13) to the desired angle.
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| Illustration 4 | g01649076 |
Edge filters (20) are located under displacement control valve (21). The edge filters help to keep contamination out of displacement control valve (21).
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| Illustration 5 | g01957411 |
When solenoid (1) is activated, control pressure is routed through motor control regulation valve (22) to the head end of the shift actuator piston. This causes the motor to destroke in order to match the command by solenoid (1). If the control pressure to the pressure regulator is higher than the pressure setting of the regulator valve, the valve spool will shift in order to regulate the output pressure to the head end of the shift actuator piston to the pressure setting of the regulator valve.