3 - 4
Section H
9803/3280
Section H
3 - 4
Issue 1
Basic System Operation
A401120
4 Wheel Steer Machines
Hydraulic Operation
The main components of the steering system are the priority
valve
7
, load sensing steer unit
42
, hydraulic tank
T
, front
power track rod ram
10
and rear power track rod ram
11
.
When the steering wheel is turned, a pressure demand is
sensed at the priority valve
7
via load sensing line
LS
.
Oil from the hydraulic pump
P2
is then distributed via the
priority valve to the steer unit
42
.
When left turn is selected, oil is distributed from steer unit
42
to the rear power track rod ram
11
via the steer mode
control valve
8
. When right turn is selected, oil is delivered
directly to the front power track rod ram
10
.
When the steering lock is held, the pressure signal
LS
ceases, flow from the hydraulic pump is now distributed to
the main hydraulic circuit via the priority valve
7
.
Maximum steering system pressure is controlled by a relief
valve located in the steering unit
42
.
LS
7
8
7
T
42
42
10
11
A396570
P2
8