Toro Greensmaster 3120 - Steering Circuit

SteeringCircuit
Thetandemgearpumpisdirectlycoupledtothepiston(traction)pump.Therear
gearpumpsection(P2)supplieshydraulicowforthesteeringcircuit(priority
ow),forraisingandloweringthecuttingunitsandforthetractioncharge
circuit.Thegearpumptakesitssuctionfromthehydraulictank.Maximum
circuitpressureof7,998kPa(1160PSI)islimitedbythereliefvalvelocatedin
thesteeringunit.
Withthesteeringwheelintheneutral(notturning)positionandtheengine
running,thespoolvalveinthesteeringunitisinthecenterposition;referto
Figure24.Flowentersthesteeringunitatport(P)andgoesthroughthespool
valve,by-passingthesteeringcylinder.Flowleavesthecontrolunitoutport(E)
tobeavailablefortheraise/lowerandtractionchargecircuits.
RightTurn
Whenarightturnismadewiththeenginerunning,theturningofthesteering
wheelpositionsthespoolvalveinthesteeringunitsothatowgoesthroughthe
bottomofthespool;refertoFigure24.Flowenteringthesteeringunitatport
(P)goesthroughthespoolandisroutedtotwoplaces.First,mostoftheow
throughthevalveisby-passedoutsteeringunitport(E)andisavailablefor
raisingandloweringthecuttingunitsandforthetractionchargecircuit.Second,
theremainderoftheowisdrawnthroughthesteeringvalverotarymeterand
outsteeringunitport(R).Pressureextendsthesteeringcylinderforarightturn.
Therotarymeterensuresthattheuidowtothecylinderisproportionaltothe
amountofturningonthesteeringwheel.Fluidleavingthecylinderowsback
throughthespoolvalvethenoutsteeringunitport(T)andthentothetraction
chargecircuit.Whenturningiscomplete,thesteeringunitreturnstotheneutral
position.
LeftTurn
Whenaleftturnismadewiththeenginerunning,theturningofthesteering
wheelpositionsthespoolvalveinthesteeringunitsothatowgoesthrough
thetopofthespool;refertoFigure24).Flowenteringthesteeringunitatport
(P)goesthroughthespoolandisroutedtotwoplaces.First,mostoftheow
throughthevalveisby-passedoutsteeringunitport(E)andisavailablefor
raisingandloweringthecuttingunitsandforthetractionchargecircuit.Second,
theremainderoftheowisdrawnthroughthesteeringvalverotarymeterand
outsteeringunitport(L).Pressureretractsthecylinderforaleftturn.Therotary
meterensuresthattheuidowtothecylinderisproportionaltotheamountof
turningonthesteeringwheel.Fluidleavingthecylinderowsbackthroughthe
spoolvalvethenoutsteeringunitport(T)andthentothetractionchargecircuit.
Whenturningiscomplete,thesteeringunitreturnstotheneutralposition.
HydraulicSystem:HydraulicFlowDiagrams
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Greensmaster3120
17230SLRevC