Komatsu PC200-8M0, Shop Manual, Page: 177 / 1254

SEN06120-00
PC200, 200LC, 220, 220LC-8M0 10-402
35
402 Hydraulic system, Part 2
Functions and operation by valve
LS selector valve
LS: Abbreviation for Load Sensing
a
The illustration shows the condition when the
combined operation of swing and R.H. travel is
performed. [When pilot pressure (BP) is sup-
plied]
1. Valve
2. Spring
3. Piston
4. Piston
5. Swing valve spool
6. R.H. travel valve spool
7. Arm valve spool
8. LS shuttle valve
9. LS circuit
Function
q This valve prevents the high LS pressure of the
swing valve from entering the LS circuits of
work equipment valves when the swing and
work equipment are in combined operation.
q This valve serves to improve operability of the
work equipment by blocking the high pressure
generated during swing operation.
Operation
When pilot pressure (BP) is shut off
q
Since pilot pressure (BP) is shut off, piston (3)
is pressed to the left by force of spring (2).
q
If the swing lever is moved, swing LS pressure
(P1) passing through swing spool (5) enters
port (A).
q
Swing LS pressure (P1) presses valve (1) to
the left, and port (A) and port (B) are intercon-
nected.
q
Swing LS pressure (P1) is transmitted from
port (A) to LS shuttle valve (8) through port (B).
When pilot pressure (BP) is supplied
q When pilot pressure (BP) is supplied, pilot
pressure (BP) moves piston (3) to the right
against the force of spring (2).
q When piston (3) moves to the right, valve (1)
disconnects ports (A) and (B).
q Since ports (A) and (B) are disconnected,
swing LS pressure (P1) is not transmitted to LS
shuttle valve (8).
q Swing LS pressure (P1) cannot affect other LS
circuits, even if it rises.