Komatsu F30791, Shop Manual

Page: 75 / 298

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
+16 bar (16
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) (16 bar (16 kg/cm
2
)) the unload valve opens, so LS differential pressure D P
LS
becomes 16 bar (16 kg/
cm
2
).
OPERATION
During fine control of control valve
. When fine control is carried out on the control
valve, 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 differ-
ence between LS pressure P
LS
and pump dis-
charge pressure P
P
.
. When the difference in pressure between pump
discharge 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 connected.
. In other words, pump discharge pressure P
P
is set
to a pressure equal to the force of spring (2) (16 bar
(16 kg/cm
2
))+ LS pressure P
LS
, and LS differential
pressure D P
LS
becomes 16 bar (16 kg/cm
2
).
10-57
PC20R-8 PC27R-8
RKP00730
1
P
P
B S
3
S
2
T
T A
S
1
2
P
LS