Komatsu PC20R-8 Shop Manual page 54

4. When pump flow is amount demanded by control valve
A
1 4
x
P
LS
LS valve
8
c
d
. Let us take the area receiving the pressure at the
large diameter end of servo piston (4) as A
area receiving the pressure at the small diameter
end as A , the pressure acting on the large piston
2
diameter end as P
EN
small piston diameter end as P
. When the flow of oil from the pump reaches the
flow demanded by the control valve, pump pres-
sure P acting on port b of the LS valve and the
P
combined force of LS pressure P
spring (8) acting on spring chamber a are balanced,
so piston (6) stops at almost the central position.
10-36
G
P
H
P
a b
6
6
e
and the pressure acting on the
.
P
+ force of
LS
A
2
. As a result, port c, port d and port e open approxi-
, the mately the same amount, so the pump pressure
1
flows from port c to port d.
Part flows from port e to the tank case and is
drained, so the pressure is reduced by approx. 1/2
and flows to chamber X at the large diameter end
of servo piston (4).
. At this point, the relationship between the area re-
ceiving the pressure at both ends of servo piston
(4) is A
2
ends of servo piston (4) becomes P
This makes the force acting on both ends of servo
piston (4) 1 : 1, so servo piston (4) stops in that po-
sition and the pump discharge amount is balanced
with the oil flow demanded by the control valve.
M
Control valve
P
P
G G
H
: A =1 : 2, so the pressure applied to both
1
To actuator
P
LS
L
RKP01231
: P =2 : 1.
P EN
PC20R-8 PC27R-8