Komatsu PC500LC-10R Shop Manual page 216

COMPONENT PARTS OF HYDRAULIC SYSTEM
Operation of spring when the pump controller is normal, the actuator load is
small, and the pump pressures (PP1) and (PP2) are low.
1.
The spring load of springs (4) and (6) in the PC valve is determined by the angle of the swash plate.
2.
When servo piston (9) moves to the right, spring (6) is compressed.
When the servo piston moves to the right further, it touches seat (5) and spring (6) is fixed.
After this, only spring (4) is operated.
3.
The servo piston (9) expands or compress the springs (4) and (6) to change the spring loads.
4.
As the command current (X) inputted to PC-EPC valve solenoid (1) changes, the force pressing piston (2)
changes.
5.
The spring loads of the springs (4) and (6) varies also with the command current (X) of PC-EPC valve sole-
noid.
6.
The port (C) of PC valve is connected to the port (E) of LS valve.
7.
The self-pressure (PP1) is sent to the small diameter piston side of servo piston (9) and port (B), and other
pump pressures (PP2) are transmitted to the port (A).
8.
When the pump pressures (PP1) and (PP2) are low, the spool (3) is at the left position.
9.
The port (C) is connected to port (D), and the pressure entering LS valve is to be drain pressure (PT).
10. When port (E) and port (G) of LS valve are connected, the pressure entering from port (J) to large diameter
piston side becomes drain pressure (PT), and servo piston (9) moves to the left.
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10 STRUCTURE AND FUNCTION
PC500LC-10R
AEP19358