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2)
OPERATION
The steering unit consists of a rotary valve and a rotary meter.
Via a steering column the steering unit is connected to the steering wheel of the machine.
When the steering wheel is turned, oil is directed from the steering system pump via the rotary
valve (spool and sleeve) and rotary meter(gear wheel set) to the cylinder ports L or R, depending
on the direction of turn. The rotary meter meters the oil flow to the steering cylinder in proportion to
the angular rotation of the steering wheel.
Spool(12) is connected directly to the drive shaft of steering wheel. It is connected to sleeve(11) by
cross pin(13) (not in contact with the spool when the steering wheel is at neutral) and center
spring(14).
Cardan shaft(8) is meshed at the top with cross pin(13) and forms one unit with sleeve(11).
At the same time, it is meshed with gear rim(5) of the gerotor set by spline.
There are four ports in valve body. They are connected to the pump circuit, tank circuit, and the
head, and left and right steering cylinder. In addition, the pump port and tank port are connected
inside the body by the check valve. Therefore, if there is any failure in the pump of engine, oil can
be sucked in directly from the tank through the check valve.
5-7
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