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2)
FUNCTION
1
2
3
8
9
1
Drive shaft
2
Swash plate
3
Shoe plate
4
Counter piston
5
Piston
The steering pump and attachment pump are variable displacement piston pump. The steering
pump and attachment pump are flow controlled by LS signal. When the steering and attachment
are not being used, the pumps are at low pressure standby.
The load sensing pressure that is sensed from steering and attachment hydraulic systems flows
to flow compensator spool (13). This spool keeps the pump output at a level that is necessary to
fulfill the requirements for the system flow and for the pressure.
The pressure compensator spool (12) also limits maximum system pressure. The pressure
compensator spool (12) prevents damage to the steering and attachment hydraulic components
from excessive pressure.
The swivel angle of the pumps is controlled by counter piston (4) and control piston (10). Counter
spring (6) cause swash plate (2) to move at maximum displacement or causes swash plate (2) to
upstroke.
Control piston (10) has a larger area (diameter) than counter piston (4). Control piston (10) causes
swash plate (2) to destroke the pump.
Flow compensator spool (13) and/or pressure compensator spool (12) changes pump output by
regulating the pump discharge pressure that is acting on control piston (10).
4 5
6
10
7
X
13
6
Counter spring
7
Pressure & flow compensator valve
8
Piston shoe
9
Cylinder
10 Control piston
LS pressure
12
11
L
L1
12
11 Control plate
12 Pressure compensator spool
13 Flow compensator spool
6-11
13
X
B
S
4
10
75796WE33
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