Toro Groundsmaster 4500-D Series - Page 140

Afoursectiongearpumpiscoupledtothepiston(traction)pump.Thethird
gearpumpsectionsupplieshydraulicowtothesteeringcontrolvalveand
thelift/lowercontrolvalve.Pumphydraulicowisdeliveredtothetwocircuits
throughaproportionalowdividerlocatedinthefancontrolmanifold.Steering
circuitpressureislimitedto72bar(1050PSI)byareliefvalvelocatedinthe
steeringcontrolvalve.
Withthesteeringwheelintheneutralpositionandtheenginerunning,gear
pumpsectionowentersthesteeringcontrolvalveatthePportandgoes
throughthesteeringcontrolspoolvalve,bypassingtherotarymeterandsteering
cylinder.FlowleavesthecontrolvalvethroughtheEporttotheoillterand
tractionchargecircuit.
PISTON MOVEMENT
STEERING CYLINDER
PISTON MOVEMENT
STEERING CYLINDER
LEFT TURN
NEUTRAL POSITION
RIGHT TURN
NO PISTON MOVEMENT
STEERING CYLINDER
1050
EP T
R
6.1
CIR
L
CONTROL
VALVE
STEERING
PSI
1050
EP T
R
6.1
CIR
L
CONTROL
VALVE
STEERING
PSI
1050
EP T
R
6.1
CIR
L
CONTROL
VALVE
STEERING
PSI
g308198
Figure56
RightTurn
Whenarightturnismadewiththeenginerunning,theturningofthesteering
wheelpositionsthespoolvalvesothatowgoesthroughthebottomofthespool.
FlowenteringthesteeringcontrolvalveatthePportgoesthroughthespooland
isroutedtotwoplaces.First,mostoftheowthroughthevalveisbypassedout
theEportbacktotheoillterandtractionchargecircuit.Theremainderofthe
owisdrawnthroughrotarymeterandthenisdirectedoutportR.Pressure
extendsthesteeringcylinderforarightturn.Therotarymeterensuresthatthe
oilowtothecylinderisproportionaltotheamountoftheturningonthesteering
wheel.Fluidleavingthecylinderowsbackthroughthespoolvalvethenthrough
theTportandtothehydraulicreservoir.
Thesteeringcontrolvalvereturnstotheneutralpositionwhenturningis
completed.
LeftTurn
Whenaleftturnismadewiththeenginerunning,theturningofthesteering
wheelpositionsthespoolvalvesothatowgoesthroughthetopofthespool.
FlowenteringthesteeringcontrolvalveatthePportgoesthroughthespooland
isroutedtotwoplaces.Asinarightturn,mostoftheowthroughthevalveis
bypassedouttheEportbacktotheoillterandtractionchargecircuit.The
remainderoftheowisdrawnthroughtherotarymeterandouttheLport.
HydraulicSystem:HydraulicFlowDiagrams
Page5–38
Groundsmaster
®
4500-D/4700-D
19245SLRevA