Steering Circuit - Toro Groundsmaster 4300-D Service Manual

Steering Circuit

Left Turn
Right Turn
Hydraulic System: Hydraulic Flow Diagrams
A 4-section gear pump is coupled to the piston (traction) pump. The gear pump
section P3 supplies hydraulic flow to the steering control valve and for the
traction charge circuit. The steering control valve receives the pump supply first,
ensuring pressure and volume is always available for steering control, no matter
the charge circuit demand. The gear pump takes its suction from the hydraulic
reservoir. The steering circuit pressure is limited to 6,900 kPa (1,000 psi) by a
relief valve (R10) located in the steering control valve.
With the steering wheel in the neutral position and the engine running, the
hydraulic flow enters the steering control valve at the P port and goes through
the steering control spool valve, bypassing the rotary meter (V1) and steering
cylinder. The flow leaves the control valve through the T port to the transmission
oil filter and traction charge circuit.
When a left turn is made with the engine running, the turning of the steering
wheel, positions the steering control spool valve so that flow is directed through
the bottom of the spool. The 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 bypassed 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 through the L port. The pressure retracts the steering
cylinder piston for a left turn. The rotary meter ensures that the fluid flow to the
steering cylinder is proportional to the amount of turning on the steering wheel.
The 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.
When a right turn is made with the engine running, the turning of the steering
wheel, positions the steering control spool valve so that the flow is directed
through the top of the spool. The 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 through 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 meter (V1) but goes out through
port R. The pressure extends the steering cylinder piston for a right turn. The
rotary meter ensures that the fluid flow to the steering cylinder is proportional to
the amount of the turning on the steering wheel. The 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 4–30 Groundsmaster ® 4300-D
16226SL Rev C