Komatsu Utility PC12R-8 MISTRAL, Shop Manual

Page: 68 / 324

3) Engine speed sensing function
. All the pump discharge amount Q flows through the
orifice (3) of spool (1). On the fixed pump system,
the relation between engine speed and pump di-
scharge amount Q is in proportion. Therefore when
engine speed is high, pump discharge amount is
much, and little pump discharge amount flows at
engine speed low.
. For this reason, oil flow through the orifice (3) of
spool (1) is different when engine speed is high
and low. At that time, the pressure loss D P
P
is va-
ried.
. The balance of unload valve is:
( P
P2
x S1 )=( P
P1
x S2 )+( P
LS
x S3 )+spring force of
spring (2).
Developing above formula, LS differential pressure
D P
LS
= P
P1
± P
LS
is expressed:
P
P1
± P
LS
= D P
LS
x S1 / S3 +spring force of spring.
Therefore LS differential pressure D P
LS
is varied
according to P
LS
. In other words, when engine
speed varies, LS differential pressure also varies.
. LS differential pressure D P
LS
varies as figure
shown.
10-50
PC12R-8 PC15R-8
To actuator
RKP00781
1
P
P1
S
3
T
S
S
1
2
P
LS
P
P2
T
3
S
2
RKP00771
1,6 (16)
0
1300 2800
0,7 (7)
M
PA
(kg/cm
2
)
rpm
LS
∆
PLS