Steering Circuit - Toro Groundsmaster 360 Service Manual

Steering Circuit

2 Wheel Steering
Groundsmaster 360
16225SL Rev C
The Groundsmaster 360 Quad Steer™ all wheel steering system uses
Ackermann four wheel steering. Ackermann steering enables the inside and
outside wheels to turn around a common pivot point. This results in reduced turf
damage and greater operator response when turning.
A single-section gear pump is directly coupled to the transmission which is driven
by the engine. This gear pump supplies hydraulic flow for both the steering
and lift/lower circuits. The hydraulic pump flow from the gear pump is routed
to the steering control valve first so that the steering circuit has priority. The
pump takes its suction from the hydraulic tank. The steering circuit pressure is
limited to 12,500 kPa (1,800 psi) by a relief valve located in the gear pump. Two
steering cylinders are used to provide 4 wheel steering: one cylinder turns the
front wheels and the second cylinder turns the rear wheels.
g036195
1. Cylinder piston
The steering control valve includes a check valve that allows steering operation
when the engine is not running. The steering wheel rotation with the engine shut
off causes the fluid flow from the steering control gerotor. The check valve opens
in this situation to allow the fluid flow from the steering control to the steering
cylinder in a closed loop.
To allow for synchronization of the front and rear steering cylinders, both the
steering cylinders include an internal re-phasing check valve assembly in the
cylinder piston (Figure
4 wheel steer (either right or left), the cylinder check valve will open when the
cylinder is fully extended or retracted. After both cylinders have moved fully, the 4
wheel steering system has been synchronized. If the steering wheel continues to
be turned, the check valves will stay open and will allow flow through the circuit.
With the steering wheel in the neutral position and the engine running, gear
pump flow enters the steering control valve at the P port and goes through the
steering control spool valve, bypassing the rotary meter and steering cylinders.
The flow leaves the control valve through the E port and is routed to the lift/lower
circuit, oil cooler, and transmission case. The transmission case drain allows
fluid to return to the hydraulic tank.
The Groundsmaster 360 machine includes the feature of allowing the operator
to choose between 2 or 4 wheel steering. The steering selector switch on the
control panel is used to control the hydraulic steering system for this feature.
When the front of the steering selector switch is pressed with the wheels directed
straight forward, the steering will only be active on the front wheels. This position
Figure 28
2. Check valve assembly
28). While rotating the steering wheel for a turn when in
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