Komatsu F30791, Shop Manual

Page: 76 / 298

3) When the control valve is being operated and the demand flow for the actuator becomes greater than the pump
discharge from the minimum swash plate angle, the flow of the oil out, to tank circuit T is shut off, and all of pump
discharge amount Q flows to the actuator circuit.
OPERATION
Control valve operated
. When the control valve is operated to a larger
stroke, LS pressure P
LS
is generated and acts on
area S3 at the right end of spool (1).
When this happens, the area of the opening of the
control valve spool is large, so the difference be-
tween LS pressure P
LS
and pump discharge pres-
sure P
P
is small.
. For this reason, the difference in pressure between
pump discharge pressure P
P
and LS pressure P
LS
does not reach the load of spring (2) (19.69.8 bar
(2010 kg/cm
2
)), so spool (1) is pushed to the left
byspring (2).
. As a result, pump circuit P
P
and tank circuit T are
shut off, and all the pump discharge amount Q
flows to the actuator circuit.
10-58
PC20R-8 PC27R-8
RKP00740
1 P
P
B S
3
S
2
T T A S
1
2
P
LS