Steering Circuit (Machine Serial Number Above 316000000) - Toro Groundsmaster 3280-D Service Manual

Steering Circuit (Machine Serial Number above 316000000)

Left Turn
Right Turn
Groundsmaster ® 3280-D/3320
05138SL Rev B
The charge pump supplies flow for the steering circuit and for the lift circuit. The
pump output flows to the steering control valve before reaching the lift manifold
so that the steering circuit has priority. The steering circuit pressure is limited to
7,239 kPa (1,050 psi) by a relief valve located in the steering control valve.
When the steering wheel is not being turned and the engine is running (hydraulic
pump input shaft being rotated), charge pump flow enters the steering control
valve at the P port and by-passes the rotary meter and steering cylinder. Flow
leaves the steering control valve through the E port and is directed to the lift
manifold.
When a left turn is made with the engine running, the turning of the steering
wheel positions the steering control spool valve so that the flow goes through
the bottom of the spool. Flow entering the steering control valve at the P port
passes through the rotary meter and is directed out the L port. Pressure retracts
the steering cylinder for a left turn. The rotary meter ensures that the fluid flow to
the cylinder is proportional to amount of steering wheel rotation. The fluid leaving
the steering cylinder flows back through the spool valve, then out the T port and
returns to the hydraulic reservoir (front axle).
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 goes through the
top of the spool. Flow entering the steering control valve at the P port passes
through the rotary meter and is directed out port R. Pressure extends the
steering cylinder for a right turn. The rotary meter ensures that the fluid flow to
the cylinder is proportional to the amount of steering wheel rotation. The fluid
leaving the steering cylinder flows back through the spool valve, then out the T
port and return to the oil cooler and the hydraulic reservoir (front axle).
Page 5–37 Hydraulic System: Hydraulic Flow Diagrams