Kubota WSM STa-30, Workshop Manual

Page: 262 / 359

8-M6
ST
α
-30, ST
α
-35, WSM STEERING
5. OIL FLOW
■
Neutral Position
When the steering wheel (2) is not being turned, valve
plate (3) is held in the neutral position by centering
springs (4). Under this condition, an oil passage is
formed between P port (from pump) and T port (to
transmission case) in the control valve, and all oil from
the hydraulic pump flows to T port.
The full hydrostatic power steering systems are
divided into two types: non-load reaction type and load
reaction type. They are distinguished by whether the
cylinder port is blocked or not with the controller in
neutral. In these models, the load reaction type is used.
With the load reaction type power steering, the steering
wheel returns almost to the straight forward position as
with an automobile when the operator releases his hands
from the steering wheel.
W1013776
■
Right Turn
When the steering wheel is turned to the right, the
action is transmitted through the drive plate, gerotor, and
drive link to the control valve. Valve plate (3) then rotates
to the right on manifolds, located on the opposite faces
of the valve plate (3). Thus, the P port passage in the
control valve is connected with gerotor (5).
The stator of gerotor (5) turns by the amount
corresponding to the turn of the steering wheel (2), and
the gerotor performs the metering function and lets oil
through it, the amount of which corresponds to the turn
of the steering wheel (2).
The oil which has passed through gerotor (5) flows
back to the control valve, in which it is directed to cylinder
port R to operate steering cylinder (6). Consequently,
the front wheels are moved to the right through the angle
corresponding to the amount of the oil.
When steering cylinder (6) operates, oil returning to
cylinder port L flows back to the transmission case
through the passage connected to T port in the control
valve.
W1013914
(1) Steering Controller
(2) Steering Wheel
(3) Valve Plate
(4) Centering Spring
(5) Gerotor
(6) Steering Cylinder P : Pump Port
T : Tank Port
R : Cylinder Port R
L : Cylinder Port L
(1) Steering Controller
(2) Steering Wheel
(3) Valve Plate
(4) Centering Spring
(5) Gerotor
(6) Steering Cylinder P : Pump Port
T : Tank Port
R : Cylinder Port R
L : Cylinder Port L
KiSC issued 11, 2006 A