Komatsu PC500LC-10R Shop Manual page 215

10 STRUCTURE AND FUNCTION
OPERATION OF MAIN PUMP PC VALVE
Operation of PC-EPC valve solenoid (1) when the pump controller is normal, the
actuator load is small, and the pump pressures (PP1) and (PP2) are low.
1.
Command current (X) flows from the pump controller into PC-EPC valve solenoid (1).
2.
Command current (X) acts on PC-EPC valve and outputs signal pressure to change the force to push pis-
ton (2).
3.
Spool (3) stops at a position where the spring set force of springs (4) and (6) is balanced with the pump
pressure (PP1) (self pressure) and (PP2) (other pump pressure) which pushes spool (3).
The pressure output from PC valve "pressure of port (C)" varies depending on the position.
4.
The level of command current (X) depends on the contents of work (lever operation), selected working
mode, and set value and actual value of the engine speed.
REMARK
The other pump pressure means the pressure of the pump on the opposite side.
The other pump pressure for the front pump is the rear pump pressure, and that for the rear pump is the front
pump pressure.
PC500LC-10R
COMPONENT PARTS OF HYDRAULIC SYSTEM
AEP19357
10-121