Kubota WSM STa-30, Workshop Manual

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8-M4
ST
α
-30, ST
α
-35, WSM STEERING
4. STEERING CONTROLLER
The steering controller mainly consists of a control valve, a metering device and a relief valve with check valve.
The metering device comprises a set of special gear called “Gerotor”.
[1] CONTROL VALVE
The control valve is a rotary plate type valve. When
the steering wheel is not turned, the position of the valve
plate (1) and the manifolds (2), (3) is kept neutral by the
centering springs (4). This causes the forming of a
“Neutral” oil circuit.
When the steering wheel is turned either clockwise or
counterclockwise, the position of the valve plate (1) and
manifolds (2), (3) changes against the centering spring.
This allows the forming of a “Right Turning” or “Left
Turning” oil circuit. At the same time, the gerotor rotates
with the valve plate and sends the oil to the cylinder
corresponding to the rotation of the steering wheel.
W1013464
[2] METERING DEVICE (GEROTOR)
All oil directed from the hydraulic pump to the steering
cylinder passes through the metering device (gerotor) on
its way. This metering device is a trochoid pump. As the
steering wheel is turned, the action is transmitted directly
to stator (2) through drive plate (1). Thus, the gerotor
sends the amount of oil corresponding to the turn of the
steering wheel to the hydraulic cylinder, and the front
wheels are moved through the angle corresponding to
the turn of the steering wheel.
When the engine is not operating or the hydraulic
pump fails. The gerotor serves as a manual pump, and
thus the machine can be steered manually.
W1013598
(1) Valve Plate
(2) Port Manifold
(3) Isolation Manifold (4) Centering Spring
(5) Hex. Drive Assembly
(6) Valve Ring
(1) Drive Plate
(2) Stator (3) Rotor
(4) Commutator
KiSC issued 11, 2006 A