Komatsu PC200-8M0 Shop Manual page 136

SEN06119-00
(2) When the main pump is under heavy load
q If the emergency pump drive switch is turned
on in the same way as in above, the command
current (X) sent to PC-EPC valve solenoid (1)
becomes constant.
q For this reason, the force of piston (2) pushing
spool (3) is constant.
q If main pump pressures (PP1) and (PP2)
increase, spool (3) moves further to the right
than when the main pump load is light, and is
balanced at the position in the figure above.
q In this case, the pressure from port (B) flows to
port (C), so servo piston (9) moves to the right
(smaller pump discharge) and stops at a posi-
tion to the further to the right then when the
load on the pump is light.
q When the emergency pump drive switch is
turned on, too, the pump pressure (PP) and
pump discharge (Q) have a relationship as
shown with the curve in the figure correspond-
ing to the current sent to the PC-EPC valve
solenoid through the resistor.
24
10-401
401 Hydraulic system, Part 1
q The curve resulting when the emergency pump
drive switch is ON is situated further to the left
(B) than when the pump controller is normal
(A).
PC200, 200LC, 220, 220LC-8M0
Hydraulic pump