Komatsu PC500LC-10R Shop Manual page 224

COMPONENT PARTS OF HYDRAULIC SYSTEM
When signal current from pump controller is low (coil energized)
1.
When low signal current flows through coil (2), coil (2) is
energized, and the thrust force to the right is generated in
plunger (7).
2.
Rod (6) pushes spool (5) to the right, and the pressurized
oil from port (P) flows to port (C).
3.
When the pressure in port (C) increases, the total of the
force acting on the surface of spool (5) and the reaction
force of spring (4) becomes larger than the thrust of plung-
er (7).
4.
Spool (5) is pushed to the left, and port (P) and port (C)
are disconnected.
5.
Port (C) is connected to port (T).
6.
Spool (5) so moves that the thrust of plunger (7) is bal-
anced with the total of the pressure in port (C) and the re-
action force of spring (4).
7.
The circuit pressure between the EPC valve and LS valve
is controlled in proportion to the amperage of signal cur-
rent.
When signal current from pump controller is maximum (coil energized)
1.
When signal current flows through coil (2), coil (2) is ener-
gized.
Since the signal current is maximum at this time, the thrust
force of plunger (7) also becomes the maximum.
2.
Spool (5) is pushed to the right by spring (6).
3.
The pressurized oil flows from port (P) to port (C) at the
maximum rate, and the circuit pressure between the EPC
valve and LS valve is maximized.
4.
The pressurized oil does not flow to the tank since the port
(T) is closed.
MAIN PUMP PC-EPC VALVE
PC
Abbreviation for Pressure Compensation
10-130
10 STRUCTURE AND FUNCTION
PC500LC-10R