Komatsu PC200-8M0, Shop Manual, Page: 129 / 1254

SEN06119-00
PC200, 200LC, 220, 220LC-8M0 10-401
17
401 Hydraulic system, Part 1
Hydraulic pump
2. PC valve
PA : Pump port
PA2 : Pump pressure pilot port
PDP : Drain port
PM : Mode selector pressure pilot port
PPL : Control pressure output port (to LS valve)
1. Plug
2. Servo piston assembly
3. Pin
4. Spool
5. Retainer
6. Sheet
7. Cover
8. Wiring
Function
q
When the pump discharge pressure (PP1)
(self-pressure) and (PP2) (other pump pres-
sure) are high, the PC valve controls the pump
so that the volume of oil beyond the discharge
pressure-based specific flowrate may not be
conducted however you may increase the con-
trol valve stroke. Namely it is intended at con-
trolling the horse power for the pumps so that it
may not exceed the engine hose power.
q
If the pump discharge pressure increases due
to increased load during operation, this valve
decreases the pump discharge.
q
And if the pump discharge pressure goes low,
it increases the pump discharge.
q
In this case, relation between the mean dis-
charge pressure of the front and rear pumps
[(PP1) + (PP2)]/2 and the pump discharge (Q)
will become as shown in the diagram if the
relation is represented as the parameter the
current value (X) to be given to PC-EPC valve
solenoid.
q
The controller continues counting the actual
engine speed.
q
If the engine speed is slowed down due to
increased load, the controller reduces the
pump discharge to recover the speed.
q
If the engine speed goes below the specified
value because of increased load, the controller
sends a command current to PC-EPC valve
solenoid in order to reduce the slope angle in
proportion to reduction in the engine speed.