Komatsu PC20R-8 Shop Manual page 77

2. Introduction of LS pressure
FUNCTION
. The LS pressure is the actuator load pressure at the outlet port end of the control valve.
. It actually reduces pump pressure P
sure as actuation circuit pressure A, and sends it to the LS circuit P
. With the boom swing and blade valves, pump pressure P
pressure A by one reducing valve (3) used for both systems, and the pressure is sent to the LS circuit P
1
From PPC valve
2
OPERATION
1) Boom, arm, bucket, travel valve
. When spool (1) is operated, pump pressure P
flows from control valve (2) and notch a in spool
(1) through bridge passage b to actuator circuit A.
. At the same time, reducing valve (3) also moves to
the right, so pump pressure P
duced by the pressure loss at notch C. It is intro-
duced to LS circuit P
chamber P .
LS1
. When this happens, LS circuit P
tank circuit T from LS by-pass plug (4) (see the sec-
tion on the LS by-pass plug).
PC20R-8 PC27R-8
at reducing valve (3) of the pressure compensation valve to the same pres-
P
A
P
P
has its pressure re-
P
, and then goes to spring
LS
is connected to
LS
.
LS
is reduced to the same pressure as actuator circuit
P
b a
C
. Actuator circuit pressure P
P
end of reducing valve (3); the reduced pump pres-
sure P acts on the other end.
P
. As a result, reducing valve (3) is balanced at a po-
sition where actuator circuit pressure P
pressure of spring chamber P
Pump pressure P
tuator circuit pressure A and is taken to LS circuit
P .
LS
T
To PPC valve
P
A
P
LS1
3
P
LS
4
T
(=A) acts on the left
A
A
are the same.
LS1
reduced at notch C becomes ac-
P
.
LS
RKP00392
and the
10-59