5-7
The steering unit is composed of the control valve(rotary valve) and the metering device. The control
valve controls the flow of oil from the pump in the interior of the unit depending on the condition of the
steering wheel. The metering device is a kind of hydraulic motor composed of a stator and a rotor. It
meters the required oil volume, feeds the metered oil to the power cylinder and detects cylinder’s
motion value, that is, cylinder’s motion rate.
When the steering wheel is turned, the spool turns, the oil path is switched and the oil is fed into the
metering device. As a result, the rotor is caused to run by oil pressure, and the sleeve is caused to run
through the drive shaft and cross pin. Therefore, when the spool is turned, the spool turns by the
same value in such a manner that it follows the motion of the spool. Steering motion can be
accomplished when this operation is performed in a continuous state.
If the hoses of the steering system are incorrectly connected, the steering wheel can turn very
rapidly when the key switch is ON. Keep clear of the steering wheel when the key switch is
ON.
The centering spring for the spool and sleeve is provided to cause the valve to return to the neutral
position. It is therefore possible to obtain a constant steering feeling, which is transmitted to the hands
of the driver. Return to the center position occurs when the steering wheel is released.
OPERATION
2)
