Hyundai HL955 Manual page 470

2) WHEN THE RCV LEVER IS IN THE LOWER POSITION
Bucket Boom
Aux
4
5
Control unit
(Electro-Hydraulic & Joysick steering)
EH18 EH20 EH19 EH22 EH21
EH17
6
4
1 6(4) 3(2) 5(3)
To MCV
a3 b3 a1 b1 a2 b2
Steering valve
(EHPS) EF port
Steering valve
(EHPS) LS port
Return line
1
29
PS
Steering system
B1
S1
·
When the RCV lever (4, boom) is pushed forward, the boom spool is moved to lower position by
pilot pressure from EH contril block (6).
·
The oil from main pump (1) flows into main control valve (3) and then goes to small chamber of
boom cylinder (13) by pushing the load check valve of the boom spool.
·
The oil returned from large chamber of boom cylinder (13) returns to hydraulic tank (22) through
the boom spool at the same time.
·
When the lowering speed of boom is faster, the return oil from the large chamber of boom cylinder
combines with the oil from the pump through the regeneration check valve, and flows into the small
chamber of the cylinder.
This prevents cylinder cavitation by the negative pressure when the pump flow cannot match the
boom down speed.
P
3
LS
Joystick
4' Pst
T
T
P
2(1)
( ) : 2 Spool
28 28 11
12
S1
X1 X2
P1 T
X3
X1 X2
B2
L2 S2 L4 L3
L1
14
40
a1
B1
A1
Bucket
Regeneration
check valve
b1
A1
Return line
23
25
24
26
22
Fan & brake pump
6-6
13
LH RH
29
29
a2 a3
B3
A2 B2 A3
Boom Aux
b2 b3
757F6WE04