Komatsu F30791, Shop Manual

Page: 51 / 298

2. When opening area of control valve is maximum (lever operated freely)
. When control lever is operated fully(that is, when
the area of opening of the control valve becomes
larger), the difference between pump pressure P
P
and LS pressure P
LS
( LS differential pressure
D P
LS
) becomes smaller.
. LS pressure P
LS
brought to spring chamber a of the
LS valve becomes close to pump pressure P
P
, and
piston (6) is pushed to the right ( ) bythe combined
force of LS pressure P
LS
+ force of spring (8).
This closes port c and interconnects port d and port e .
. As the result, the pressurized oil acting on chamber
X at the large diameter end of servo piston (4) flows
from port d to port e and is connected to port f of
the TCC valve.
. At this point, port f of the TCC valve is drained in-
side the pump case through the inside of the pis-
ton, so the pressure in chamber X at the large dia-
meter end of servo piston (4) also becomes the
drain pressure.
. Because of this, servo piston (4) is moved to the left
( ) in the direction of the maximum swash plate
angle bypump pressure P
P
acting on chamber Y
at the small diameter end of the piston.
10-33
PC20R-8 PC27R-8
Control valve
To actuator
LS valve
a
d
RKP01251
4
P
P
M
G
H
G
L
P
LS
P
LS
c e
G
H
8 6
P
P
x
f
G
L
y
b
6