Toro Groundsmaster 5900 Series Service Manual page 134

Left Turn
Right Turn
Hydraulic System: Hydraulic Flow Diagrams
A three (3) section gear pump is coupled to the piston (traction) pump. The
gear pump section furthest from the piston pump supplies hydraulic flow to the
steering, cutting deck lift and traction charge circuits. Hydraulic flow from the final
pump section is directed to the appropriate circuits by a pressure compensator
valve located in the steering/deck lift control manifold.
The steering control valve is a closed center, load sensing valve. The steering
control valve senses the oil flow that is needed for steering and the pressure
compensator valve (LC) in the steering/deck lift control manifold will supply the
correct amount of oil. Gear pump oil flow that is not used for the steering circuit
is available for the traction charge and deck lift circuits.
When the steering wheel is in the neutral, at rest position and the engine is
running, hydraulic oil from the final gear pump section enters the steering/deck lift
control manifold port P1, flows through the pressure compensator valve (LC) and
is routed to the steering control valve where it dead heads at the control valve
spool. Oil is also sent to both ends of the (LC) spool. On one end of the spool, oil
is directed to both the steering relief valve (RV1) and also to the OR1 orifice and
out the manifold LS port to the steering control valve. This flow provides steering
load sensing that is directed through a small passage in the steering control
valve spool and sleeve before returning to the hydraulic reservoir. As long as
this load sense flow is returning to the reservoir due to no steering input, the
pressure compensator valve (LC) spool is shifted to direct pump section flow to
the traction charge and deck lift circuits.
When a left turn is made with the engine running, the turning of the steering
wheel positions the steering unit spool valve so that the load sense flow is
blocked off. Without load sense flow, pressures on the ends of manifold pressure
compensator valve (LC) start to equalize causing (LC) to move toward its neutral
position which allows the needed oil to the steering control valve for turning. Oil
is routed out manifold port CF, into steering valve port P, through the steering
control spool, is drawn through the rotary meter section and out the L port to the
steering cylinders. The rotary meter ensures that the oil flow to the cylinders is
proportional to the amount of the turning on the steering wheel. Fluid leaving
the cylinders flows back through steering valve R port, the spool valve, out the T
port and is then returned to the hydraulic reservoir.
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 unit spool valve so that the load sense flow is
blocked off. Without load sense flow, pressures on the ends of manifold pressure
compensator valve (LC) start to equalize causing (LC) to move toward its neutral
position which allows the needed oil to the steering control valve for turning. Oil
is routed out manifold port CF, into steering valve port P, through the steering
control spool, is drawn through the rotary meter section and out the R port to the
steering cylinders. The rotary meter ensures that the oil flow to the cylinders is
proportional to the amount of the turning on the steering wheel. Fluid leaving the
cylinders flows back through the steering valve L port, the spool valve, out the T
port and is then returned to the hydraulic reservoir.
The steering control valve returns to the neutral position when turning is
completed.
Page 5–34 Groundsmaster ® 5900 & 5910
16227SL Rev B