Hyundai HL955 Manual page 480

(2) Destroking
1
2 4
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
The decreased flow demand causes a LS pressure in line (19). The LS pressure in line (19)
combines with the force of spring (18) in cavity (20).
This combination of LS pressure and of spring force is less than the pump pressure in passage
(21). This causes flow compensator spool (13) to move left.
Pump oil now flows through passage (15). The oil then flows past flow compensator spool (13),
through passage (22), and then to control piston (10).
The pump pressure behind control piston (10) is now greater than the combined force of counter
piston(4) and of counter spring (6). The angle of swash plate (2) decreases.
This decreases the pump output and the system pressure.
When the lower flow requirements are met, flow compensator spool (13) moves right up to the
balanced position. Swash plate (2) maintains an angle that is sufficient to provide the lower
required pressure. If the operator does not turn the steering wheel and does not move RCV, then
the pump will return to low pressure standby.
※ Control piston → Changes pump displacement ; influenced by controller.
Counter piston → Helps to change pump displacement but no possible to control this piston.
14
6
15
10
16
17 18 19 20 13 23
13 Flow compensator spool
14 Case drain
15 Passage
16 Passage
17 Spring
18 Spring
6-16
LS pressure
12
21
22
L
L1
4
12
19 LS line from the metering pump
20 Cavity
21 Passage
22 Passage
23 Cavity
13
X
B
S
10
75796WE34