Komatsu PC200-8M0, Shop Manual

Page: 163 / 1254

SEN06120-00
PC200, 200LC, 220, 220LC-8M0 10-402
21
402 Hydraulic system, Part 2
Functions and operation by valve
Introduction of LS pressure
LS: Abbreviation for Load Sensing
1. Main pump
2. Main spool
3. Pressure compensation valve
4. Valve
5. Check valve
6. LS circuit
7. LS shuttle valve
Function
q The upstream pressure (spool meter-in down-
stream pressure) of pressure compensation
valve (3) is transmitted and led to LS shuttle
valve (7) as LS pressure.
q Connected to actuator port (B) through valve
(4), and makes LS pressure
C
actuator load
pressure.
q In main spool (2), leading hole (a) with a small
diameter also acts as an orifice.
q LS pressure works as source pressure when
closing unload vale while control lever is oper-
ated, and this pressure also functions as oper-
ating pressure when pressure compensation
valve is compensated.
Operation
q When main spool (2) is operated, the pump
pressure is transmitted to port (c) through lead-
ing hole (a) and is led to LS circuit.
q When the pump pressures rises to reach the
load pressure of port (B), check valve (5)
opens and the pressurized oil flows.