Service Manual

Groundsmaster 4300--D Hydraulic SystemPage 4 -- 21
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
hydraulicreservoir.Steering circuit pressure islimitedto
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
controlspool valve, bypassingthe rotarymeter (V1)and
steering cylinder. Flow leaves the control valve through
theTporttothetransmissionoil filterandtractioncharge
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-
tomofthespool.Flowenteringthesteeringcontrolv alve
at the P port goes through the spool and is routed to two
places. First, most of the flow through the v alve is by-
passed out the T port back to the transmission oil filter
andtractionchargecircuit.Second,theremainderofthe
flowis directed throughthe rotary meter(V1) and outthe
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 w heel. 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.
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 s o 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
valveisbypassed outtheTportbacktothetransmission
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 portR. Pressureextends the steer-
ing cylinder piston for a right turn. The rotary meter
ensures that the oil flow to the s teering 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.
Hydraulic
System