Komatsu F30791, Shop Manual

Page: 58 / 298

2. When actuator load becomes smaller (pump discharge pressure P
P
drops)
. When the load on the actuator becomes smaller
and pump discharge pressure P
P
drops, piton (3)
is pushed to the right ( ) bythe pressure in cham-
ber X .
. As a result, chamber Y and port f are shut off, and
at the same time, port f is connected to the drain
circuit.
. When this happens, if the LS valve is acting to in-
crease the pump discharge pressure, the limit of
the TCC valve disappears, so the pressurized oil
in chamber X at the large diameter end of servo pis-
ton (4) passes from port d of the LS valve to port e ,
and flows from port f of the TCC valve to the drain
circuit as explained in the section on the LS valve.
. For this reason, servo piston (4) is moved to the left
( ) in the direction of the maximum swash plate
angle bythe pressure in chamber Y at the small
diameter end.
10-40
PC20R-8 PC27R-8
Control valve
To actuator
LS valve
f
y
x
RKP01211
4
1
3
P
P
M
G
H
G
L
P
LS
P
LS
c e
d