Komatsu F30791, Shop Manual

Page: 59 / 298

3. Action of spring
. The spring load of spring (1) in the TCC valve is
changed bythe swash plate angle. In addition,
spring (1) consist of 2 types of pitch: rough and fine.
. When servo piston (4) moves, the compression of
spring (1) changes bythat amount.
. If piston (4) moves to the right ( ), first, both the
rough and fine pitch of spring (1) are compressed.
If it moves further to the right ( ) the fine pitch
portion comes into close contact, so onlythe rough
pitch portion functions as a spring from this point.
In other words, the spring load is changed bypiston
(4) extending or contracting spring (1).
. The pump absorption torque curve, which shows
the relationship between pump discharge pressure
P
P
and discharge amount Q , is a bent curve as
shown in the diagram on the right because spring
(1) has different spring pitches.
10-41
PC20R-8 PC27R-8
Control valve
To actuator
LS valve
RKP01171
4
1
3
P
P
M
P
LS
G
H
G
L
RKP01181
Pump discharge pressure
Pump discharge amount Q
P
P