Toro Groundsmaster 4500-D Series - Page 143

Afoursectiongearpumpiscoupledtothepiston(traction)pump.Thenal
gearpumpsection(farthestfromthepistonpump)supplieshydraulicowfor
thehydraulicenginecoolingfanmotor.
Thefancontrolmanifoldcontrolstheoperationofthehydraulicmotorthatdrives
theenginecoolingfaninadditiontoincludingtheowdividerforthesteering
andliftcircuits.Theelectronicallycontrolledproportionalreliefvalve(PRV)in
themanifoldcontrolstheoilowtothefanmotor.Thefancontrolmanifold
controlsthespeedanddirectionofthefanmotorbasedonelectricaloutput
fromtheTECcontroller(T1).
Oilowfromthegearpumpsectiontothecoolingfanmotoriscontrolledbythe
proportionalreliefvalve(PRV)inthefancontrolmanifold.Thisvalveadjustsfan
circuitowbasedonaPWM(PulseWidthModulation)signalfromtheTEC
controller(1).Thecontrollerusesenginecoolantandhydraulicoiltemperatures
asinputstodeterminetheproperPWMsignalforthePRVvalve.Thefancircuit
owdeterminesthespeedofthecoolingfanmotor.
•Thefanmotorrunsathalfspeeduntilcoolantreachesapproximately74ºC
(165ºF).Thefanmotorincreasestofullspeed(approximately2800RPM)
ascoolantreaches82ºC(180ºF).
•Thefanmotorautomaticallyreversesifcoolantreaches95ºC(203ºF)or
hydraulicoilreaches100ºC(212ºF).
Ifthecoolingfanmotorisstalledforanyreason,themanifoldproportional
reliefvalve(PRV)hasasecondaryfunctionasacircuitrelieftolimitfanmotor
pressureto207bar(3000PSI).
Whentheengineisshutoff,theover-runninginertialoadofthefanblades
keepsdrivingthefanmotorandturnsitintoapump.Thecheckvalve(CV)in
thefancontrolmanifoldwillopentokeepthemotorcircuitfullofoilsothefan
motorwillnotcavitate.
Note:IfPWMcurrentisnotavailabletothefancontrolmanifoldproportional
reliefvalve(PRV),thecoolingfanmotorwillrunatfullspeedinthenormal
(forward)direction.
ForwardDirectionFanOperation
Oilowfromthegearpumpsectionissentthroughthede-energizedsolenoid
valveS1torotatethecoolingfanmotor.Returnowfromthemotorre-enters
themanifold(portM2),throughthede-energizedsolenoidvalveS1,outofthe
manifold(portT)andthenisroutedthroughthedeckcontrolmanifold,oilcooler
andoillter.
Groundsmaster
®
4500-D/4700-D
Page5–41
HydraulicSystem:HydraulicFlowDiagrams
19245SLRevA