Komatsu PC20R-8 Shop Manual page 51

2. When opening area of control valve is maximum (lever operated freely)
4
x
f
P
LS
LS valve
8
c
d
. 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
and LS pressure P
DP ) becomes smaller.
LS
. LS pressure P brought to spring chamber a of the
LS
LS valve becomes close to pump pressure P
piston (6) is pushed to the right (
force of LS pressure P
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.
PC20R-8 PC27R-8
G P
H P
a 6 b
G
L
6
e
(LS differential pressure
LS
P
) by the combined
+ force of spring (8).
LS
y
. 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-
P
meter end of servo piston (4) also becomes the
drain pressure.
. Because of this, servo piston (4) is moved to the left
, and ( ) in the direction of the maximum swash plate
angle by pump pressure P
at the small diameter end of the piston.
M
Control valve
P
P
G G
H L
acting on chamber Y
P
To actuator
P
LS
RKP01251
10-33