Toro Groundsmaster 4500-D Series Service Manual page 140

R L
6.1
CIR
1050
PSI
P T E
NEUTRAL POSITION
g308198
Right Turn
Left Turn
Hydraulic System: Hydraulic Flow Diagrams
A four section gear pump is coupled to the piston (traction) pump. The third
gear pump section supplies hydraulic flow to the steering control valve and
the lift/lower control valve. Pump hydraulic flow is delivered to the two circuits
through a proportional flow divider located in the fan control manifold. Steering
circuit pressure is limited to 72 bar (1050 PSI) by a relief valve located in the
steering control valve.
With the steering wheel in the neutral position and the engine running, gear
pump section flow enters the steering control valve at the P port and goes
through the steering control spool valve, bypassing the rotary meter and steering
cylinder. Flow leaves the control valve through the E port to the oil filter and
traction charge circuit.
R
6.1
CIR
STEERING
CONTROL 1050
PSI
VALVE
P
RIGHT TURN
When a right turn is made with the engine running, the turning of the steering
wheel positions the spool valve so that flow goes through the bottom 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 bypassed out
the E port back to the oil filter and traction charge circuit. The remainder of the
flow is drawn through rotary meter and then is directed out port R. Pressure
extends the steering cylinder for a right turn. The rotary meter ensures that the
oil flow to the cylinder is proportional to the amount of the turning on the steering
wheel. Fluid leaving the cylinder flows back through the 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.
When a left turn is made with the engine running, the turning of the steering
wheel positions the spool valve so that flow goes 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 right turn, most of the flow through the valve is
bypassed out the E port back to the oil filter and traction charge circuit. The
remainder of the flow is drawn through the rotary meter and out the L port.
L
STEERING
CONTROL
VALVE
T E
Figure 56
Page 5–38
R L
6.1
CIR
STEERING
CONTROL
1050
VALVE
PSI
P T E
LEFT TURN
Groundsmaster ® 4500-D/4700-D
19245SL Rev A