COMPONENT OPERATION / HST Motor Displacement Angle Control (From Large Displacement Angle to Small Displacement Angle) 1. One pressure oil from port B (or port A) flows to the plunger through the valve plate. The other pressure oil opens the check valve, and flows to the spool and the small chamber of the servo piston. 2. The EP motor solenoid valve receives the signal from the HST control unit. When the spool moves upward, pressure oil in the large chamber of the servo piston flows to the hydraulic oil tank through the spool. Spool
3. Therefore, the servo piston moves downward and the motor displacement angle decreases. 4. Consequently, the motor rotates at fast speed.
From HST Control Unit
EP Motor Solenoid Valve
Check Valve
B
Motor Circuit Pressure
A
Servo Piston
NOTE: The illustration shows the circuit when traveling forward.
T3-5-7
T4FG-03-05-003
