6-5
WHEN THE RCV LEVER IS IN THE RAISE POSITION
When the RCV lever (4, boom) is pulled back, the boom spool is moved to raise position by pilot oil
pressure from EH control block (6).
The oil from main pump (1) flows into main control valve (3) and then goes to the large chamber of
boom cylinder (13) by pushing the load check valve of the boom spool.
The oil from the small chamber of boom cylinder (13) returns to hydraulic oil tank (22) through the
boom spool at the same time.
When this happens, the boom goes up.
·
·
·
·
1
T
A1
P1
X1
X2
X3
S1
B2
L3
L4
B1
L1
L2
S1
S2
X1
X2
PS
Aux
Bucket
Boom
Joystick
4
1
EH20
EH19
EH22
EH21
P
T
6(4)
3(2)
5(3)
2(1)
( ) : 2 Spool
EH18
EH17
To MCV
a3 b3 a1 b1 a2
b2
Return line
Fan & brake pump
Steering system
Return line
Steering valve
(EHPS) EF port
Steering valve
(EHPS) LS port
3
LH
RH
B1
A1
B2
A2
LS
a2
b2
b1
a1
Pst
B3
A3
b3
a3
T
P
PS
PS
Dump
Roll back
Up
Down
Floating
Bucket
Boom
Aux
23
22
25
24
12
11
26
28
28
29
6
5
4
4'
40
14
13
29
29
Control unit
(Electro-Hydraulic & Joysick steering)
1)
757F6WE03
Summary of Contents for HL955
Page 557: ...7 6 MEMORANDUM MEMORANDUM ...