Komatsu F30791, Shop Manual

Page: 80 / 298

4. Pressure compensation valve
FUNCTION
. During compound operations, if the load pressure becomes lower than the other actuator and the oil flow tries to
increase, compensation is received. (When this happens, the other actuator being used for compound operation
(right side) is at a higher load than the actuator on this side (left side)).
OPERATION
. If the load pressure of the other actuator (right side)
becomes higher during compound operations, the
oil flow in actuator circuit A on this side (left side)
tries to increase.
. If this happens, the LS pressure P
LS
of the other ac-
tuator acts on spring chamber P
LS1
, and reducing
valve (1) and flow control valve (2) are pushed to
the left ( ).
. Flow control valve (2) throttles the area of opening
between pump circuit P
P
and spool upstream
P
PA
, and pressure loss is generated between P
P
and P
PA
.
. Flow control valve (2) and reducing valve (1) are ba-
lanced in position where the difference in pressure
between P
LS
and P
A
acting on both ends of redu-
cing valve (1) and the pressure loss between P
P
and P
PA
on both sides of flow control valve (2) are
the same.
. In this way, the pressure difference between up-
stream pressure P
PA
and downstream pressure
P
A
of both spools used during compound opera-
tions is the same, so the pump flow is divided in
proportion to the area of opening of notch a of each
spool.
10-62
PC20R-8 PC27R-8
W W
RKP00403
Side receiving
compensation Side providing
compensation
P
PA
2
A a T
P
A
P
LS1
1
P
P
P
LS
P
A
T
a
P
PA