Hyundai HL955 Manual page 485

5. EH (electro hydraulic) CONTROL BLOCK
STRUCTURE
1)
T
EH18
10-4 10-1
4
2) OPERATION
The proportional pressure reducing valve
(10-1~6) is a direct-acting spool-type valve.
When de-energized, port 2 is closed and
port 1 (delivery) is connected to port 3
(tank). When the inlet pressure fluctuates it
provides an almost constant outlet
pressure-depending on the energization of
the coil. When the control current
increases, the coil solenoid exerts a force
on the control piston which is proportional
to the control current and thereby defines
the regulated pressure at port 1. This
setting is proportional to the control current.
Pressures at tank port 3 are additive to the
set pressure. If, as a result of external
factors, the pressure at port 1 rises above
the preset pressure, the valve opens from
port 1 to tank port 3.
10-4 10-5
10-1 10-2
1 2
4 5
EH17 EH20 EH19 EH22
10-6(4) 10-3(2) 10-5(3) 10-2(1)
1 6 (4) 3 (2) 5 (3)
Hydraulic circuit
10-6
Proportional pressure
reducing valve
10-3
3
6
EH21
T Port
P
1 ~ 6
( ) : 2-spool
2 (1)
DS
1
3 2
6-21
P
DS
Filter screen
Size
9/16-18UNF
9/16-18UNF
DS
3/4-16UNF
P,T
760F6WE33
3
2
1
7809A6WE33