5-7
OPERATION
OPERATION
Neutral
Neutral
2)
2)
(1)
(1)
EF
T
P
LS
Ts
P
T
R
L
Ps
Pressure
reducing
valve
KV2
S3
KV1
CL
CR
Shock valves
Suction valves
18A
18
16
17
15
CF
7607SE12
In neutral position, the oil will pass from the pump across the integrated priority valve (18) in the
steering valve for discharge through the EF port. When the steering unit is in neutral, flow through
it is blocked and all flow through the priority valve (18) in steering valve is directed out the EF port
and passed to the main control valve.
When the engine is turned off, the priority valve spool (18) is pushed to the right by the spring. The
passage to the EF port is blocked while the passage to the CF port is open.
When the machine is started, EF port of the steering valve may be connected to the working
hydraulic. Maximum pressure on the EF port = 250 bar.
The operating pressure in the loader system has not effected on the operation of the priority
valve(18) of steering valve. Independently of operation of the loader actuated in relief, the priority
valve(18) will not shift until the machine is steered.
A part of flow through the priority valve spool (18) will flow to P port of steering unit through pres-
sure reducing valve. Also flow as pilot signal of steering through the priority valve spool (18) pass-
es from the P port through the dynamic orifice and into the LS line. It flows to the tank through the
LS orifice in main spool.
In neutral position, the main spool will be in its center position. This means that knocks and
impacts from the cylinder are not transmitted to the steering unit. The steering valve is thus of the
non-reaction type.
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Summary of Contents for HL955
Page 557: ...7 6 MEMORANDUM MEMORANDUM ...
