Toro Groundsmaster 360 - Steering Circuit

SteeringCircuit
TheGroundsmaster360QuadSteer™allwheelsteeringsystemuses
Ackermannfourwheelsteering.Ackermannsteeringenablestheinsideand
outsidewheelstoturnaroundacommonpivotpoint.Thisresultsinreducedturf
damageandgreateroperatorresponsewhenturning.
Asingle-sectiongearpumpisdirectlycoupledtothetransmissionwhichisdriven
bytheengine.Thisgearpumpsupplieshydraulicowforboththesteering
andlift/lowercircuits.Thehydraulicpumpowfromthegearpumpisrouted
tothesteeringcontrolvalverstsothatthesteeringcircuithaspriority.The
pumptakesitssuctionfromthehydraulictank.Thesteeringcircuitpressureis
limitedto12,500kPa(1,800psi)byareliefvalvelocatedinthegearpump.Two
steeringcylindersareusedtoprovide4wheelsteering:onecylinderturnsthe
frontwheelsandthesecondcylinderturnstherearwheels.
g036195
Figure28
1.Cylinderpiston2.Checkvalveassembly
Thesteeringcontrolvalveincludesacheckvalvethatallowssteeringoperation
whentheengineisnotrunning.Thesteeringwheelrotationwiththeengineshut
offcausestheuidowfromthesteeringcontrolgerotor.Thecheckvalveopens
inthissituationtoallowtheuidowfromthesteeringcontroltothesteering
cylinderinaclosedloop.
Toallowforsynchronizationofthefrontandrearsteeringcylinders,boththe
steeringcylindersincludeaninternalre-phasingcheckvalveassemblyinthe
cylinderpiston(Figure28).Whilerotatingthesteeringwheelforaturnwhenin
4wheelsteer(eitherrightorleft),thecylindercheckvalvewillopenwhenthe
cylinderisfullyextendedorretracted.Afterbothcylindershavemovedfully,the4
wheelsteeringsystemhasbeensynchronized.Ifthesteeringwheelcontinuesto
beturned,thecheckvalveswillstayopenandwillallowowthroughthecircuit.
Withthesteeringwheelintheneutralpositionandtheenginerunning,gear
pumpowentersthesteeringcontrolvalveatthePportandgoesthroughthe
steeringcontrolspoolvalve,bypassingtherotarymeterandsteeringcylinders.
TheowleavesthecontrolvalvethroughtheEportandisroutedtothelift/lower
circuit,oilcooler,andtransmissioncase.Thetransmissioncasedrainallows
uidtoreturntothehydraulictank.
TheGroundsmaster360machineincludesthefeatureofallowingtheoperator
tochoosebetween2or4wheelsteering.Thesteeringselectorswitchonthe
controlpanelisusedtocontrolthehydraulicsteeringsystemforthisfeature.
2WheelSteering
Whenthefrontofthesteeringselectorswitchispressedwiththewheelsdirected
straightforward,thesteeringwillonlybeactiveonthefrontwheels.Thisposition
Groundsmaster360
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HydraulicSystem:HydraulicFlowDiagrams
16225SLRevC