Steering Circuit - Toro GroundsmasterR 4300-D Service Manual

Steering Circuit

A four section gear pump is coupled to the piston (trac-
tion) pump. Gear pump section P3 supplies hydraulic
flow to the steering control valve and for the traction
charge circuit. The gear pump takes its suction from the
hydraulic reservoir. Steering circuit pressure is limited to
1000 PSI (70 bar) by a relief valve (R10) located in the
steering control valve.
With the steering wheel in the neutral position and the
engine running, hydraulic flow enters the steering con-
trol valve at the P port and goes through the steering
control spool valve, bypassing the rotary meter (V1) and
steering cylinder. Flow leaves the control valve through
the T port to the transmission oil filter and traction charge
circuit.
Left Turn (Fig. 20)
When a left turn is made with the engine running, the
turning of the steering wheel positions the steering con-
trol spool valve so that flow is directed through the bot-
tom of the spool. Flow entering the steering control valve
at the P port goes through the spool and is routed to two
places. First, most of the flow through the valve is by-
passed out the T port back to the transmission oil filter
and traction charge circuit. Second, the remainder of the
flow is directed through the rotary meter (V1) and out the
L port. Pressure contracts the steering cylinder piston
for a left turn. The rotary meter ensures that the oil flow
to the steering cylinder is proportional to the amount of
turning on the steering wheel. Fluid leaving the steering
cylinder flows back through the steering control spool
valve and then out of the steering control valve through
the T port.
The steering control valve returns to the neutral position
when turning is completed.
Groundsmaster 4300--D
Right Turn (Fig. 20)
When a right turn is made with the engine running, the
turning of the steering wheel positions the steering con-
trol spool valve so that flow is directed through the top
of the spool. Flow entering the steering control valve at
the P port goes through the spool and is routed to two
places. As in a left turn, most of the flow through the
valve is bypassed out the T port back to the transmission
oil filter and traction charge circuit. Also like a left turn,
the remainder of the flow is directed through rotary me-
ter (V1) but goes out port R. Pressure extends the steer-
ing cylinder piston for a right turn. The rotary meter
ensures that the oil flow to the steering cylinder is pro-
portional to the amount of the turning on the steering
wheel. Fluid leaving the steering cylinder flows back
through the steering control spool valve then through
the T port and to the hydraulic reservoir.
The steering control valve returns to the neutral position
when turning is completed.
Page 4 - - 21 Hydraulic System