Komatsu F30791, Shop Manual

Page: 71 / 298

2. BASIC PRINCIPLE
1) Control of pump swash plate angle
. The pump swash plate angle (pump discharge amount) is so controlled that the LS differential pressure D P
LS
,
which is the difference between the pump discharge pressure P
P
and the LS pressure P
LS
at the outlet port of the
control valve (actuator load pressure), is maintained at a constant level.
( LS differential pressure D P
LS
=Pump discharge pressure P
P
± pressure P
LS
).
. If the LS differential pressure D P
LS
becomes lower than the setting pressure of the LS valve, the pump swash
plate angle becomes larger, and if it becomes higher, the pump swash plate angle becomes smaller.
M For the details of this action, refer to the descriptions of «HYDRAULIC PUMP».
10-53
PC20R-8 PC27R-8
Actuator
Control valve
Pump passage
Main pump
LS passage
P
LS
Min.
Max.
P
LS
∆
LS valve
Differential pressure
large (high)
Differential
pressure
small (low)
Pump pressure high
Pump
pressure low
TCC valve
RKP00651
Servo piston