Hyundai HL955 Manual page 481

(3) Low pressure standby
1 2
10
16
LS pressure oil
System pressure oil
Return oil
1 Drive shaft
2 Swash plate
4 Counter piston
6 Counter spring
10 Control piston
12 Pressure compensator spool
Low pressure standby constitutes the following condition: a running engine and inactive steering
and loader. There are no flow demands on the pump or pressure demands on the pump.
Therefore, there is no LS pressure in line (19).
Before you start the engine, counter spring (6) holds swash plate (2) at the maximum angle. As the
pump begins to turn, oil begins to flow and pressure increases in the system.
Because of close centered steering control valve and close centered loader hydraulic system.
As this pressure increase, the pressure pushes flow compensator spool (13) against spring (18).
This causes flow compensator spool (13) to move left. This opens passage (23) in order to allow
pressure oil to flow to control piston (10).
The oil acts against control piston (10) in order to overcome the force of counter spring (6). The oil
causes control piston (10) to move to the left.
When control piston (10) moves to the left, the piston moves swash plate (2) toward the minimum
angle. Control piston (10) continues to move to the left until cross-drilled hole (24) allows the oil to
drain to the case.
14
4 6
24
17 18 19 20 23 13
13 Flow compensator spool
14 Case drain
15 Passage
16 Passage
17 Spring
18 Spring
6-17
15
LS pressure
21
22
L
L1
12
19 LS line from the metering pump
20 Cavity
21 Passage
22 Passage
23 Cavity
24 Cross-drilled hole
12 13
X
B
S
4 10
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