Textron JACOBSEN R-311 69166, Technical/Repair Manual

Page: 243 / 402

6-12 4203781 First Edition
HYDRAULICS
6
Theory of Operation and
Diagnostic Information
Steering Circuit Schematic and
Theory of Operation
System Conditions:
• Engine running
• Steering wheel turned to the right or left (right turn
shown)
Oil Supply to Steering Valve
Hydraulic oil is drawn from the hydraulic oil tank by
section 1 of the gear pump assembly. Before entering the
gear pump assembly, the inlet oil is filtered by a
100-mesh screen to remove any debris. Operating
pressure oil from section 1 of the four-section gear pump
is routed to port “P” of the control valve, flows through the
4.5 gpm (17 lpm) priority valve and out port “ST” to the
steering valve.
The priority valve will supply oil flow to the steering valve
before allowing oil flow to the lift valve, to ensure
maximum steering control at any engine rpm range.
Steering Circuit
Operating pressure oil enters the steering unit at port “P,”
and is routed to the pilot line of the 1500 psi (103 bar)
relief valve, against the check valve, and to the steering
valve. With the steering wheel turned to the right, the
steering valve is moved, allowing oil to flow through the
valve to the gerotor metering section. Oil is then routed
through port “RT” of the steering unit to the steering
cylinder, moving the rear wheels in the desired direction.
Oil from the opposite end of the steering cylinder flows
back into the steering unit through port “LT” and back
through the steering valve, exiting through the steering
unit port “T.” Oil exiting the steering unit then flows
through the charge filter, and supplies charge pressure
oil to the traction pump and other systems.