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Hybrid05 Chassis.pdf

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HYBRID05 CHASSIS
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TOYOTA Hybrid System - Course 071 5-1 Toyotahybridvehiclesuseanumberofspecializedchassissystems including: w Ashift-by-wiresystemwithelectronictransmissioncontrol. w Aregenerativebrakingsystemthatrecoversmuchoftheenergy normallylosttoheatandfrictionduringbraking. w AnElectricPowerSteering(EPS)systemthatimprovesfuel economybecauseitonlyconsumesenergywhenitisinuse. The’01-’03Priususesashift-by-wiresystem.Theshiftpositionsensor isconnectedtoacolumn-mountedshiftleverandoutputstwovoltage signals:amainsignalandasubsignal.Bothcontaininformationabout shiftposition.TheHVECUdeterminesshiftpositionwhenboth signalsmatch. The’04&laterPriususesadifferentshift-by-wiresystem.Itusestwo sensorstomonitorshiftlevermovement:aSelectSensorthatdetects thelateralmovementandaShiftSensorthatdetectsthelongitudinal movement.Thecombinationofthesesignalsisusedtodetermineshift position.Whenshiftselectioniscomplete,thereactiveforceofaspring returnsthelevertoitshomeposition. Shift Control (’01-’03 Prius) Figure 5.1 T071f501c Section 5 Chassis Overview Shift Control (’01-’03 Prius) Shift Control (’04 & later Prius)Section 5 5-2 TOYOTA Technical Training Shift Lock (’01-’03 Prius) Figure 5.2 T071f502c Shift Assembly (’04 & later Prius) Figure 5.3 T072f107c The’04&laterPriususesanelectronicShiftControlActuatorto engagetheparkingpawl.WhentheShiftControlActuatorreceivesa locksignalfromthetransmissionECUitrotates,whichmovesthe parkinglockrodandforcestheparkinglockpawltoengagethe parkinggear.TheShiftControlActuatordetectsitsownpositionwhen thebatteryisreconnected,soitdoesnotrequireinitialization. Shift Control Actuator (’04 & later Prius)Chassis TOYOTA Hybrid System - Course 071 5-3 Shift Control Actuator (’04 & later Prius) Figure 5.4 T072f406c Ifthereisamalfunctionintheshiftcontrolactuator,thevehiclewill notgointopark.TheMasterWarningLightwillilluminate,theshift positionindicatorsonthedashwillflash,andtheParkbuttonlight willflash. Inthiscase,thevehiclecannotbeturnedOFFunlesstheparking brakeisapplied.ThenthevehiclecanbeturnedOFFbutcannotbe turnedbackONagain. TheShiftControlActuatorincludesacycloidgearreduction mechanismthatincreasestheactuator’storque,ensuringthatthe parkinglockwillreleasewhenthevehicleisparkedonaslope. Thismechanismconsistsofaneccentricplatemountedonthemotor’s outputshaft,a61-toothfixedgearthatissecuredtothemotorhousing anda60-toothdrivengear.Astheoutputshaftrotates,theeccentric platepressesthedrivengearagainstthefixedgear.Thedrivengear, whichhasonetoothlessthanthefixedgear,rotatesonetoothforevery completerotationoftheeccentricplate.Theresultisagearreduction ratioof61:1,alongwithanequivalentincreaseintorque. SERVICE TIP Cycloid Reduction Mechanism (’04 & later Prius)Section 5 5-4 TOYOTA Technical Training Cycloid Reduction Mechanism 1. Eccentric shaft rotates with motor shaft, pressing driven gear against fixed gear. 2. Driven gear rotates one tooth for every full rotation of the motor shaft. 3. Reduction Ratio: 61:1. Figure 5.5 T071f505c TheDiagnosticTestercannotturnofftheshiftcontrolsystem.To powerdownthesystemremovethe30-ampmainfuselocatedonthe leftsideofthefuseboxonthedriver’ssideoftheenginecompartment. Thismaybenecessaryifthevehicleneedstobepushedoutoftheshop. Fuse Location Removing the 30A PCON MTR fuse disables the shift control system. Figure 5.6 T071f506c SERVICE TIPChassis TOYOTA Hybrid System - Course 071 5-5 Thehybridvehiclebrakesystemincludesbothhydraulicbrakesanda uniqueregenerativebrakingsystemthatusesthevehicle’smomentum torechargetheHVbattery.Assoonastheacceleratorpedalis released,theHVECUinitiatesregenerativebraking.MG2isturnedby thewheelsandusedasageneratortorechargetheHVbattery.During thisphaseofbraking,thehydraulicbrakesarenotused.Whenmore rapiddecelerationisrequired,thehydraulicbrakesareactivatedto provideadditionalstoppingpower. Toincreaseenergyefficiencythesystemusestheregenerativebrakes wheneverpossible.SelectingB“ontheshiftleverwillmaximize regenerativeefficiencyandisusefulforcontrollingspeedsdownhill. In‘B’mode,about30%oftheenergyisrecovered. Ifeithertheregenerativeorhydraulicbrakingsystemfails,the remainingsystemwillstillwork.However,thebrakepedalwillbe hardertopressandthestoppingdistancewillbelonger.Inthis situation,thebrakesystemwarninglightwillilluminate. Thebatterywillacceptchargeuptoaninstantaneousrateof20to21 KWH.Muchoftheenergyfromlightbrakingathighspeedsand harderbrakingatlowerspeedscanberecovered.Excessenergyover thecharginglimitsiswastedasheatinthebrakes.Atthistimethere isnowayforthedrivertoknowthelimitofregenerativeenergy recovery. Brake System Components (’01-‘03 Prius) Figure 5.7 T071f507c Brake System NOTESection 5 5-6 TOYOTA Technical Training Brake System Diagram (’01-‘03 Prius) Figure 5.8 T071f508c The’01-’03Priusapplieshydraulicpressurefromthemastercylinder directlytothefrontbrakes.Fortherearbrakes,itusesahydraulic brakeboostertoincreasebrakeforce.Withinthehydraulicbrake booster,apumpdrawsbrakefluidfromthereservoirtankandforcesit intotheaccumulatorunderhighpressure.Theaccumulatorstoresthe high-pressurefluiduntilitisneeded. Tomakesuresystempressurestaysattherightlevel,twopressure switchesmonitorhydraulicpressurecomingfromtheaccumulator: w PressureSwitchPH-controlspumpactivation. w PressureSwitchPLgeneratesawarningwhensystempressureis toolow. Ifoneofthepressureswitchesmalfunctionsitcancausethepumpto operatecontinuously,creatingexcessivepressureinthesystem.Ifthat happens,areliefvalveshuntsbrakefluidtothereservoirtankto relievetheexcesspressure. Ifthebrakeboosterfails,theBrakeSystemWarningLightandBuzzer willilluminate.PressingthebrakepedalrepeatedlymayturnONthe BrakeSystemWarningLightandBuzzerbriefly.Ifthebrakeboosteris operatingnormally,thelightandbuzzerwillturnOFFafterafew secondsafterstartup. Hydraulic Brake Booster (’01-’03 Prius)Chassis TOYOTA Hybrid System - Course 071 5-7 Inthe’04&laterPrius,theconventionalbrakeboosterhasbeen replacedbyahydraulicpowersourcethatiscontrolledbytheSkid ControlECU. Thehydraulicpowersourceusesmanyofthesamecomponentsused ontheprevioussystem,includingapump,pumpmotor,accumulator, reliefvalve,2motorrelays,andanaccumulatorpressuresensor.To improvethesystem,theaccumulatorhasbeenmademoregas-tight, andaplunger-typepumphasbeenadopted. Thecontrolportionofthebrakeactuatorincludes: w 2mastercylindersolenoidvalves w 4pressureappliancevalves w 4pressurereductionvalves w 2mastercylinderpressuresensors w 4wheelcylinderpressuresensors Inthe’01-’03Prius,theBrakeECUcontrolsthefollowingbrake functions: w Conventionalbrakecontrol w ABSwithEBDcontrol w Regenerativebrakecooperativecontrol TheBrakeECUexchangessensorinformationwiththeHVECU. Brake Actuator (’04 & later Prius) Brake ECU (’01-’03 Prius)Section 5 5-8 TOYOTA Technical Training Brake Control Components (’01-‘03 Prius) Figure 5.9 T071f509c Inthe’04&laterPrius,brakecontrolprocessingismovedtotheSkid ControlECU,whichhandles: w Conventionalbrakecontrol w ABSwithEBDcontrol w BrakeAssist w EnhancedVSC w Regenerativebrakecooperativecontrol TheSkidControlECUexchangessensorinformationEPSECUand theHVECU. Skid Control ECU (’04 & later Prius)Chassis TOYOTA Hybrid System - Course 071 5-9 Brake Control Components (’04 & later Prius) Figure 5.10 T071f510c The’04&laterPriususesanElectronicallyControlledBrake(ECB) system.Todeterminetheamountofbrakeforcerequested,theBrake PedalStrokeSensorusesavariableresistortodetecttheamountof brakepedalmovement,andthentransmitsthatinformationtothe SkidControlECU. WheninstallingaBrakePedalStrokeSensor: w Initially,thesensorleverislockedintothe0“strokepositionbya smallpin. Donot detachthepin untiltheinstallationhasbeen completed. w Installthesensor. w Then,firmlypressthebrakepedaloncetobreakoffthepin. w Makesurethebrokenpindoesnotremaininthesensorlever. Brake Pedal Stroke Sensor (’04 & later Prius) SERVICE TIPSection 5 5-10 TOYOTA Technical Training Brake Pedal Stroke Sensor Figure 5.11 T071f511c Duringregenerativebrakingfluidflowtothefrontcalipersislimited. Toretainanormalpedalstrokeduringregenerativebraking,the StrokeSimulatorconsumessomeofthefluidflowfromthemaster cylindersothatthepedalcanmovenormally. Thestrokesimulatorislocatedbetweenthemastercylinderandthe brakeactuator.Itusestwocoilspringswithdifferentspringconstants toprovidepedalstrokecharacteristicsintwostages. Stroke Simulator Figure 5.12 T072f112c Stroke SimulatorChassis TOYOTA Hybrid System - Course 071 5-11 Inthe’04&laterPriusaPowerSourceBackupUnithasbeenaddedso thattheECBwillfunctionlongenoughtostopthevehicleevenifthe 12Vbatteryiscompromised.Theunitcontains28capacitorcellsthat storeanelectricalchargeprovidedbythevehicle’s12Vpowersupply. ThecapacitorcellsdischargewhenthepowerswitchisturnedOFF. IfthePowerSourceBackupUnitisremoved,itmustfirstbechecked forresidualvoltage. Power Source Backup Unit Figure 5.13 T072f605c Power Source Backup Unit (’04 & later Prius)Section 5 5-12 TOYOTA Technical Training Regenerativebrakecooperativecontrolbalancesthebrakeforceofthe regenerativeandhydraulicbrakestominimizetheamountofkinetic energylosttoheatandfriction.Itrecoverstheenergybyconvertingit intoelectricalenergy. Onthe’04&laterPrius,theincreasedpoweroutputofMG2provides increasedregenerativebrakeforce.Inaddition,thedistributionofthe brakeforcehasbeenimprovedthroughtheadoptionoftheECB system,effectivelyincreasingtherangeoftheregenerativebrake. Theseattributesenhancethesystem’sabilitytorecoverelectrical energywhichcontributestofueleconomy. Regenerative Brake System To convert kinetic energy to electrical energy, the system uses MG2 as a generator. The drive axle and MG2 are joined mechanically. When the drive wheels rotate MG2, it tends to resist the rotation of the wheels, providing both electrical energy and the brake force needed to slow the vehicle. The greater the amperage (battery charging amperage), the greater the resistance. Figure 5.14 T072f047c Regenerative Brake Cooperative ControlChassis TOYOTA Hybrid System - Course 071 5-13 Inthe’04&laterPrius,brakeforcedistribution(whichwasperformed mechanicallyinthepast)isnowperformedunderelectricalcontrolof theskidcontrolECU.TheskidcontrolECUpreciselycontrolsthe brakingforceinaccordancewiththevehicle’sdrivingconditions. Generally,whenthebrakesareappliedthevehicle’sweightshifts forward,reducingtheloadontherearwheels.WhentheSkidControl ECUsensesthiscondition(basedonspeedsensoroutput)itsignalsthe brakeactuatortoregulaterearbrakeforcesothatthevehiclewill remainundercontrolduringthestop.Theamountofbrakeforce appliedtotherearwheelsvariesbasedtheamountofdeceleration. Theamountofbrakeforcethatisappliedtotherearwheelsalsovaries basedonwhetherornotthevehicleiscarryingaload. Front/Rear Brake Force Disk Figure 5.15 T072f511c Whenthebrakesareappliedwhilethevehicleiscornering,theload appliedtotheinnerwheeldecreaseswhiletheloadappliedtotheouter wheelincreases.WhentheSkidControlECUsensesthiscondition (basedonspeedsensoroutput)itsignalsthebrakeactuatortoregulate brakeforcebetweentheleftandrightwheelstopreventaskid. Electronic Brake Distribution (EBD) Control (’04 & later Prius) Brake Force Distribution - Front/Rear (’04 & later Prius) Brake Force Distribution - Left/Right (’04 & later Prius)Section 5 5-14 TOYOTA Technical Training Inemergencies,driversoftenpanicanddonotapplysufficientpressure tothebrakepedal.Soonthe’04&laterPrius,theBrakeAssistsystem interpretsaquickpushofthebrakepedalasemergencybrakingand supplementsbrakingpoweraccordingly. Todeterminetheneedforanemergencystop,theSkidControlECU looksatthespeedandtheamountofbrakepedalapplicationbasedon signalsfromthemastercylinderpressuresensorsandthebrakepedal strokesensor.IftheSkidControlECUdeterminesthatthedriveris attemptinganemergencystopitsignalsthebrakeactuatortoincrease hydraulicpressure. AkeyfeatureoftheBrakeAssistsystemisthatthetimingandthe degreeofbrakingassistancearedesignedtoensurethatthedriver doesnotdiscernanythingunusualaboutthebrakingoperation.As soonasthedrivereasesuponthebrakepedal,thesystemreducesthe amountofassistanceitprovides. Brake Assist Figure 5.16 T072f512c Brake Assist System (’04 & later Prius)Chassis TOYOTA Hybrid System - Course 071 5-15 TheEnhancedVSCsystemavailableonthe’04&laterPriushelps maintainstabilitywhenthevehicle’stiresexceedtheirlateralgrip. Thesystemhelpscontrolthevehiclebyadjustingthemotiveforceand thebrakesateachwheelwhen: w Thefrontwheelslosetractionbuttherearwheelsdon’t. (frontwheelskidtendencyknownas‘understeer’) w Therearwheelslosetractionbutthefrontwheelsdon’t. (rearwheelskidtendency,or‘oversteer’) WhentheSkidControlECUdeterminesthatthevehicleisin understeeroroversteer,itdecreasesengineoutputandappliesthe brakestotheappropriatewheelsindividuallytocontrolthevehicle. w WhentheskidcontrolECUsensesundersteer,itbrakesthefront andrearinsidewheel.Thisslowsthevehicle,shiftstheloadtothe outsidefrontwheelandlimitsfrontwheelskid. w WhentheskidcontrolECUsensesoversteer,itbrakesthefront andrearoutsidewheel.Thisrestrainstheskidandmovesthe vehiclebacktowarditsintendedpath. EnhancedVSCprovidestheappropriateamountofsteeringassist basedondrivingconditionsbycoordinatingEPSandVSCcontrol. Cooperative Control with EPS Figure 5.17 T072f111c Enhanced VSC System (’04 & later Prius) Cooperative Control with EPS (’04 & later Prius)Section 5 5-16 TOYOTA Technical Training A12VmotorpowerstheEPSsystemsothatsteeringfeelis
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