Steering Circuit - Toro Groundsmaster 3505-D Service Manual

Steering Circuit

A two section gear pump is directly coupled to the the hy-
drostat which is driven by the engine. Gear pump sec-
tion (P2) supplies hydraulic flow for operating the
steering system, raising and lowering the cutting units
and maintaining 100 to 150 PSI (6.9 to 10.3 bar) to the
low pressure side of the traction circuit (charge). The
pump section (P2) takes its suction from the hydraulic
reservoir.
With the engine running and the steering control valve
in the centered position, flow enters the steering control
valve at the IN (P) port and goes through the control
valve, by--passing the rotary meter (V1) and steering
cylinder. Flow leaves the control valve through the AUX
(E) port to be available for the lift circuit and then to the
hydrostat (charge).
Right Turn
When a right turn is made with the engine running, the
turning of the steering wheel positions the control valve
so that flow goes through the bottom of the valve. Flow
entering the steering control valve at the IN (P) port goes
through the valve and is routed to two places. First, most
of the flow through the valve is by--passed out the AUX
(E) port back through the lift control valve to the hydros-
tat. Second, the remainder of the flow is drawn through
the rotary meter (V1) and out port (R) to the steering cyl-
inder. Flow to the steering cylinder retracts the piston for
a right turn. The rotary meter (V1) ensures that the oil
flow to the cylinder is proportional to the amount of the
turning on the steering wheel. Fluid leaving the steering
cylinder flows back through the steering control valve
then through the OUT (T) port and to the hydrostat
(charge).
The steering control valve returns to the neutral position
when turning is complete.
Groundsmaster 3505--D
Left Turn
When a left turn is made with the engine running, the
turning of the steering wheel positions the steering con-
trol valve so that flow goes through the top of the valve.
Flow entering the steering control valve at the IN (P) port
goes through the spool and is routed to two places. As
in a right turn, most of the flow through the valve is by--
passed out the AUX (E) port back through the lift control
and to the hydrostat (charge). Also like a right turn, the
remainder of the flow is drawn through rotary meter (V1)
but goes out port (L) to the steering cylinder. Flow ex-
tends the steering cylinder piston for a left turn. The
rotary meter (V1) ensures that the oil flow to the cylinder
is proportional to the amount of the turning on the steer-
ing wheel. Fluid leaving the steering cylinder flows back
through the steering control valve then through the OUT
(T) port and to the hydrostat (charge).
The steering control valve returns to the neutral position
when turning is complete.
Page 4 - - 17 Hydraulic System