Toro Groundmaster Series - Page 100

Thehydraulictractioncircuitisaclosedloopsystemconsistingofavariable
displacementhydraulicpiston(traction)pumpandaseriesofhydraulicwheel
motors.Thehydraulicuidpassesthroughthehydraulicmanifoldonitswayto
andfromthewheelmotors.Thetractionpumpisdrivenbytheengineviaa
multi-rowV-belt.V-belttensioniscontrolledautomaticallybyaspringloaded
idler.
ForwardDirection
Pushingthetopofthetractionpedalanglesthepiston(traction)pump(P1)
swashplatetocreateaowofoil.Thisoilowisdirectedtothewheelmotors
viaahydraulictubetodrivethefrontwheelsintheforwarddirection.Forward
tractionpressureislimitedto25,000kPa(3625psi)bytheforwardtractionrelief
valve(R1)locatedinthetractionpump.
Theangleoftheswashplatedeterminesthestrokeofthepumppistonsand
thereforethevolumeofhydraulicuidowandultimatelytractionspeed.When
thetractionpedalispressedasmallamount,theswashplateangleisslight
resultinginlowpumpoutputandlowertractionspeed.Whenthetractionpedalis
pressedfully,thepumpswashplateangleisdramaticprovidingmaximumpump
outputandmaximumtractionspeed.
For2WDmachines,thehydraulicuidowsfromthefrontwheelmotorsand
passesthroughthehydraulicmanifold.Acontroloriceinthehydraulicmanifold
(ORatmanifoldportOR)equalizestractionsystempressuretoreducetire
scufngwhenturning.Hydraulicuidexitsthemanifoldandreturnstothe
variabledisplacementpump.Hydraulicuidiscontinuouslypumpedthroughthe
closedlooptractioncircuitaslongasthetractionpedalispressedforward.
For4WDmachines,thehydraulicuidowsfromthefrontwheelmotorsand
passesthroughthehydraulicmanifold.Acontrolorice(ORatmanifoldport
OR)andabidirectionalreliefvalve(CRV)inthehydraulicmanifoldequalize
tractionsystempressuretoreducetirescufngwhenturning.Checkvalvesin
thehydraulicmanifoldallowtherearwheelmotorstoover-runduringtightturns.
Hydraulicuidexitsthemanifoldandreturnstothevariabledisplacementpump.
Hydraulicuidiscontinuouslypumpedthroughtheclosedlooptractioncircuitas
longasthetractionpedalispressedforward.
Thepiston(traction)pumpisequippedwithacasedraintoallownormalinternal
leakagetoberemovedfromthepump.Thepistonpumpalsoincludesaushing
valvethatbleedsoffasmallamountofhydraulicuidfromthelowpressure
sideofthecircuitforcoolingoftheclosedlooptractioncircuit.Thecasedrain
andushingvalveareconnectedtothehydraulicreservoir.Thechargesystem
replenishesoilthatisbledfromthetractioncircuitbythecasedrainandthe
ushingvalve.
Gearpump(P2)suppliesoilowforthesteeringcircuitandliftcircuit,andalso
providesaconstantsupplyofchargeoiltotheclosedlooptractioncircuit.Gear
pumpowbeyondtheneedsofthesteering,lift,andchargecircuitsexitsthe
manifold.Acheckvalve(CV2)inthemanifoldmayopentoprovideanadditional
pathforchargecircuituidtoexitthemanifold.Thisfeatureprotectstheoil
coolerfromhighpressurewhentheoiliscold.Thehydraulicuidreturningfrom
themanifoldprovidesmostoftheuidforthegearpump(P2).Theremainder
oftheuidnecessaryissuppliedthroughthesuctionlterandsuctionhose
fromthehydraulicreservoir.
Thechargeoilprovideslubricationfortractioncircuitcomponentsandalso
replenishestractioncircuitoilthatislostduetointernalleakageandcooling
(ushing)inthetractioncircuit.Chargepumpowisdirectedtothelowpressure
sideoftheclosedlooptractioncircuit.Chargepressureislimitedbythecharge
reliefvalve(R3)locatedinthepiston(traction)pumpto896kPa(130psi).
HydraulicSystem:HydraulicFlowDiagrams
Page5–14
Groundsmaster
®
3200,3300and3310
19240SLRevA