wsm STW37 Workshop Manual page 355

STW34, STW37, STW40, WSM
4. STEERING CONTROLLER
[1] CONTROL VALVE
[2] METERING DEVICE (GEROTOR)
The steering controller mainly consists of a control
valve, a metering device and a relief valve.
The metering device comprises a set of special
gears called "Gerotor".
(1) Dowel Pin
(2) Check Valve
(3) Gerotor
(4) Housing
(5) Bearing Assembly
The control valve is a rotating spool type. When the
steering wheel is not turned, the valve is kept in the
neutral position by the centering spring (3).
Then, the oil flow from the hydraulic pump to the
steering cylinder and from the steering cylinder to the
transmission case is stopped. Oil from the hydraulic
pump is sent to the transmission case through the
control valve.
When the steering wheel is turned clockwise or
counterclockwise, the control valve, together with the
gerotor, changes the direction of oil flow to the steering
cylinder according to the direction, the steering wheel
was turned.
(1) Dowel Pin
(2) Spool
All oil sent from the hydraulic pump to the steering
cylinder, passes through the metering device (Gerotor).
Namely, when the rotor is drive, three chambers suck in
oil due to volumetric change in the pump chambers
formed between the rotor (2) and the stator (3), while oil
is discharged from other three chambers. On the other
hand, rotation of the steering wheel is directly
transmitted to the rotor through the steering shaft, spool,
drive shaft, etc..
Accordingly, the gerotor serves to supply the
steering cylinder with oil, amount of which corresponds
to the rotation of the steering wheel. The wheels are thus
turned by the angle corresponding to the rotation of the
steering wheel.
When the engine stops or the hydraulic pump
malfunctions, the gerotor functions as a manual trochoid
pump, which makes manual steering possible.
(1) Drive Plate
(2) Rotor
7-M4
STEERING
(6) Centering Spring
(7) Sleeve
(8) Spool
(9) Centering Spring
9Y1211109STM0005US0
(3) Centering Spring
(4) Sleeve
9Y1211109STM0006US0
(3) Stator
9Y1211109STM0007US0
KiSC issued 11, 2014 A