Komatsu PC500LC-10R Shop Manual page 210

COMPONENT PARTS OF HYDRAULIC SYSTEM
OPERATION OF MAIN PUMP LS VALVE
When control valve is in NEUTRAL position
1.
LS valve is a 3-way selector valve, and LS pressure (PLS) (actuator load pressure) at the control valve out-
let is supplied to the spring chamber (B), and the pump discharged pressure (PP) is supplied to the port (H)
of the sleeve (8).
The position of spool (6) is determined corresponding to forces caused by LS pressure (PLS), the spring
(4), and the pump discharged pressure (self-pressure) (PP).
The position of the spool (6) varies with the output pressure (PSIG) (also called LS setting selector pres-
sure) entering the port (G) of EPC valve for LS valve. (set force of the spring changes)
2.
Servo piston (12) is pushed to the left before the engine
starts. (See the figure below)
3.
When the engine is started with the control lever in NEU-
TRAL, the LS pressure (PLS) is 0 MPa {0 kg/cm
terconnected with the drain circuit via the control valve
spool).
4.
Spool (6) is pushed to the right, and port (C) and port (D)
are connected.
5.
Pump discharged pressure (PP) is sent from the port (K) to
the large diameter side of piston.
6.
The same pump discharged pressure (PP) is sent to the small diameter side of piston.
10-116
2
} . (It is in-
10 STRUCTURE AND FUNCTION
PC500LC-10R
AEP19353
A4P21604