Toro Groundsmaster 360 - Traction Circuits

TractionCircuits
ThetractionsystemoftheGroundsmaster360machinesconsistsofa
transmissionthatisdirectlyconnectedto,anddrivenbyacouplerattachedto
theengineywheel.Thetractioncomponentsincludeatransmissionwith2
independentclosedloopcircuits,2rearwheelmotors,2frontwheelmotors,
andCrossTrax™tractionmanifoldassembly.Eachoftheclosedloopcircuits
includesavariabledisplacement,slipperfootdesignpistonpumpwhichprovides
hydraulicowfor2wheelmotors.Onepistonpumpprovidesowtotheright
rearandleftfrontwheelmotor,andtheotherpistonpumpsuppliesowtotheleft
rearandrightfrontwheelmotor.Theswashplateineachofthesepistonpumps
iscontrolledbytheoperatortractionpedalthroughalinkagesystem.
Theangleoftheswashplatedeterminesthepumpowandultimatelytraction
speed.Whenatractionpedalismovedasmallamount,asmallswashplate
rotationresultsinlowpumpoutputandlowertractionspeed.Whenthetraction
pedalismovedfully,thepumpswashplaterotatesfullytoprovidemaximum
pumpoutputowandtractionspeed.
WiththeenginerunningandthetractionpedalintheNEUTRALposition,the
swashplatesofthepistonpumpareheldintheverticalposition,providingno
owtoeitherofthewheelmotorsandthemachineremainsstationary.The
transmissionreversecheckvalvesincludeanoricewhichmakesiteasierto
locatethetransmissionneutralposition.
ForwardDirection
Whenthetractionpedalispushedforward,therodconnectedtothetraction
linkagepositionstheswashplatesinthepistonpumpstoprovidehydraulicuid
owfromthetransmission(portAandC).Thisuidowstotherearwheel
motorsandthentotheoppositefrontwheelmotor(e.g.,rightrearthenleftfront)
andturnsthemotorsintheforwarddirection.Theuidowfromthefrontwheel
motorreturnstothetransmission(portBorD)andiscontinuouslypumped
whilethetractionpedalispushedforward.Asthetractionloadincreases,the
forwardtractioncircuitpressurecanincreasetotherelief-valvesettingof27,600
kPa(4,000psi).Ifthecircuitpressureismorethantherelief-valvesetting,uid
owsthroughtheforwardreliefvalveinthetransmissiontothelow-pressure
sideoftheclosedlooptractioncircuit.
Thepistonpumpsuseasmallamountofhydraulicuidforinternallubrication.
Theuidisdesignedtoleakacrossthepumppartsintothetransmissioncase
drain.Thisleakageresultsinthelossofhydraulicuidfromtheclosedloop
tractioncircuitsthatmustbereplaced.Achargepumpinthetransmission
supplieshydraulicowformaintaining810to850kPa(117to123psi)
tothelow-pressuresideofthe2tractioncircuits.Thechargepumpalso
providespressureforthetransmissionPTOdrivesystem.Thechargepump
replenishestheclosedlooptractioncircuitswithuidfromthehydraulictank.
Thecharge-reliefvalveinthetransmissionmaintainssufcientpressuresothat
thecharge-pumpowisguidedpastcheckvalvestothelow-pressuresideof
eachtractioncircuit.Thecharge-pumpowinexcessofsystemrequirementsis
releasedthroughthecharge-reliefvalvebacktothehydraulictank.
Whenoperatingthemachineinaforward,straightdirection(notturning),
transmissionuidowtothe2tractioncircuitsroutesfromarearwheelmotorto
theoppositefrontwheelmotor.Boththetractioncircuitsrequiresimilarowto
drivethewheelmotorssominimalcircuitowchangeisprovidedthroughthe
tractionmanifoldassemblyandbalancinguidlines.
Whenturningthemachineinaforwarddirection,the4wheelmotorsrequire
differentowsduetodifferentwheeldistancestraveledgoingaroundthecorner.
Thebalancinglinesandthetractionmanifoldassemblyallowthe2traction
circuitstobeconnectedsodifferencesinthewheelmotorowscanbeachieved.
Groundsmaster360
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HydraulicSystem:HydraulicFlowDiagrams
16225SLRevC