Komatsu PC500LC-10R Shop Manual page 209

10 STRUCTURE AND FUNCTION
STRUCTURE OF MAIN PUMP LS VALVE
Sectional view
PA: Pump port
PDP: Drain port
PLP: LS control pressure output port
PLS: LS pressure input port
1: Sleeve
2: Piston
3: Spool
4: Spring
FUNCTION OF MAIN PUMP LS VALVE
• The LS (load sensing) valve detects the load of the actuator and controls the pump discharged volume.
• This valve controls pump discharged volume (Q) according to differential pressure (∆PLS) = "(PP) - (PLS)"
(called LS differential pressure) between pump discharged pressure (PP) and control valve outlet port pres-
sure (PLS).
• This valve receives main pump pressure (PP), pressure (PLS) (called LS pressure) from the control valve
output, and pressure (PSIG) (called LS set selector pressure) from the proportional solenoid valve.
• The relationship between differential pressure (∆PLS) =
"(PP) - (PLS)", the difference between main pump pres-
sure (PP) and LS pressure (PLS), and discharged volume
(Q) varies with LS set pressure selector current (ISIG) of
LS-EPC valve as shown in the figure.
• When (ISIG) varies from 0A to 1A, the set pressure of the
spring changes, and the selector point for pump dis-
charged volume changes as shown in the figure below.
PC500LC-10R
COMPONENT PARTS OF HYDRAULIC SYSTEM
PP: Pump port
PPL: Control pressure input port
PSIG: LS mode selector pilot port
5: Seat
6: Sleeve
7: Plug
8: Lock nut
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