Komatsu Utility PC12R-8 MISTRAL, Shop Manual

Page: 95 / 324

2) During fine control of the control valve, when the demand flow for the actuator is within the amount discharged
by the minimum swash plate angle of the pump, pump discharge pressure P
P
is set to LS pressure
P
LS
+19.6
9.8
bar (20
10
kg/cm
2
).
When the difference in pressure between pump discharge pressure P
P
and LS pressure P
LS
reaches the load of
spring (2) (19.6
9.8
bar (20
10
kg/cm
2
)) the unload valve opens, so LS differential pressure D P
LS
becomes
19.6
9.8
bar (20
10
kg/cm
2
).
OPERATION
During fine control of control valve
. When fine control is carried out on the control val-
ve, LS pressure P
LS
is generated and acts on area
S3 at the right and of spool (1).
When this happens, the area of the opening of the
control valve spool is small, so there is a big diffe-
rence between LS pressure P
LS
and pump dischar-
ge pressure P
P
.
. When the difference in pressure between pump di-
scharge pressure P
P
and LS pressure P
LS
reaches
the load of spring (2), spool (1) moves to the right,
and pump circuit P
P
and tank circuit T are connec-
ted.
. In other words, pump discharge pressure P
P
is set
to a pressure equal to the force of spring (2)
(19.6
9.8
bar (20
10
kg/cm
2
))+ LS pressure P
LS
,
and LS differential pressure D P
LS
becomes
19.6
9.8
bar (20
10
kg/cm
2
).
10-77
PC12R-8 PC15R-8
RKP00730
1
P
P
B S
3
S
2
T T A
S
1
2
P
LS