COMPONENT OPERATION / HST Pump Constant Torque Control The engine stop due to overloading is prevented by using the command signal current from the HST controller for HST pump displacement angle control. When the engine is loaded and the engine speed decreases, the HST controller reduces the command signal current to the DE pump solenoid valve. Therefore, the displacement of the HST pump is reduced and the inlet torque of the pump is also reduced. The pump displacement is balanced with the engine torque. When the load is increased, the engine speed is slightly decreased, and the HST controller makes the HST pump displacement angle control effective use of the engine torque without the engine stop.
Torque T
P Engine Torque
Overloading State
P’
Stable State
Pump Torque
N N’ N
Engine Speed T81S-03-01-011
T3-4-9
