汽車(chē)專業(yè)英語(yǔ)讀譯教程 第3版 課件 3-U2TB Valve Systems

UNIT2

ENGINEMECHANICAL

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ValveSystemsPROFESSIONALENGLISH

UNIT2

ENGINEMECHANICAL

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ValveSystems

OperationofValveSystem

VVT—Toyota'sContinuouslyVariableValveTiming

VTEC—HondaVariableValveTimingandLiftElectronicControl

MIVEC—MitsubishiInnovativeValvetimingElectronicControl

ElectronicValveControlSystem

SmartValves本次課學(xué)習(xí)內(nèi)容本次課學(xué)習(xí)目標(biāo)掌握可變氣門(mén)定時(shí)機(jī)構(gòu)主要部件的英文名稱掌握可變氣門(mén)定時(shí)機(jī)構(gòu)的基本原理掌握常用術(shù)語(yǔ)（phrasesandexpressions）了解相關(guān)術(shù)語(yǔ)（relatedterms）NEWWORDSbump[b?mp]n.撞擊，（因撞擊而起的）腫塊；v.碰，撞，顛簸cam[k?m]n.凸輪lobe[loub]n.凸起integral['intigr?l]a.完整的，整體的，積分的stem[stem]n.桿，莖powertrain['pau?trein]n.動(dòng)力系統(tǒng)，動(dòng)力裝置，傳動(dòng)系統(tǒng)dyno['dainou]n.=dynamometer測(cè)功機(jī)，測(cè)力計(jì)breathe[bri:e]v.呼吸，發(fā)出certification[?s?:tifi'kei∫?n]n.證明，鑒定，檢驗(yàn)證明書(shū)compromise['k?mpr?maiz]v.&n.妥協(xié)，折衷NEWWORDSessence['esns]n.基本，本質(zhì)，實(shí)質(zhì)，精華，要素pulley['puli]n.滑輪，帶輪helical['helik?l]a.螺旋狀的spline[splain]n.花鍵，方栓spool[spu:l]n.線軸，卷軸；滑閥；線圈mpg

=milepergallon（英里/加侖）actuator['?ktjueit?]n.執(zhí)行器，執(zhí)行元件strategy['str?ti?i]n.策略，謀略flexibility[?fleks?'biliti]n.靈活性，柔性，適應(yīng)性eager['i:g?]v.渴望著，熱心于multiplex['m?tipleks]a.多元的，多重的，多樣的；n.多路傳輸，多路通信NEWWORDSnominal['n?minl]a.有名無(wú)實(shí)的；極微小的；標(biāo)定的，額

定的bus[b?s]n.總線innovation[inou'vei∫?n]v.改進(jìn)，革新，創(chuàng)新，新發(fā)明（技術(shù)，方法）residual[ri'zidju?l]a.剩余的，殘余的

PHRASESANDEXPRESSIONScamlobe凸輪的凸起部分valvestem氣門(mén)桿variablevalvetiming（VVT）可變氣門(mén)定時(shí)inessence本質(zhì)上，實(shí)質(zhì)上spoolvalve滑閥electronicvalvecontrol(EVC)電子式氣門(mén)控制centralizedsystem集中系統(tǒng)distributedsystem分布系統(tǒng)camlessengine無(wú)凸輪發(fā)動(dòng)機(jī)smartvalve智能氣門(mén)OperationofValveSystemYouhaveseenthattheintakevalvemustbeopenedfortheintakestroke,bothvalvesmustremainclosedduringthecompressionandpowerstrokes,andtheexhaustvalveopensduringtheexhauststroke.Thedesignermustdesignadevicetoopenandclosethevalvesatthepropertimes.Theshaftwillhaveanegg-shapedbumpcalledacamlobe.Thecamlobeismachinedasanintegralpartoftheshaft.Thisshaftiscalledacamshaft.Thedistancethevalvewillberaised,howlongitwillstayopen,andhowfastitopensandclosescanallbecontrolledbytheheightandshapeofthelobe[1].

ValveSystems

ValveSystemsAsyouwillseelater,itisimpracticaltohavethecamlobecontacttheendofthevalvestemitself.Youhaveplacedthecamshaftsomedistanceabovetheendofthevalvestem.Whenthecamshaftisturn,thelobeswillnoteventouchthevalvestem.Thelifterisinstalledbetweenthecamlobeandthevalvestem.Theupperendridesonthelobeandthelowerendalmosttouchesthevalvestem.Thelifterslidesupanddowninaholeboredintheheadmetalthatseparatesthevalvestemfromthecamshaft[2].Rememberthatfourstrokesofthepistonrequiretworevolutionsofthecrankshaft.ValveSystemsYoucansaythatforeverytworevolutionsofthecrankshaft,thecamshaftmustturnonce.Ifyouarespeakingofthespeedofthecamshaft,youcansaythatthecamshaftmustturnatone-halfcrankshaftspeed.Youhavedevelopedamethodofopeningandclosingthevalves.Thenextproblemishowandatwhatspeedtoturnthecamshafts.Eachvalvemustbeopenforonestroke.Theintakevalveisopenduringtheintakestrokeandremainsclosedduringthecompression,power,andexhauststrokes.Thiswouldindicatethatthecamlobemustturnfastenoughtoraisethevalveeveryfourthstroke.Youcanseethatittakesonecompleterevolutionofthecamlobeforeveryfourstrokesofthepiston.

ValveSystemsIfthecrankshaftisturningandthecamshaftmustturnatone-halfcrankshaftspeed,itseemslogicaltousethespinningcrankshafttoturnthecamshaft.Oneverysimplewaytodrivethecamshaftwouldbebymeansofgearsandabelt.Onegearisfastenedontheendofthecrankshaft,andtheotherisfastenedontheendofthecamshaft.Thesmallercrankshaftgeardrivesthelargercamshaftgearthroughthebelt.If,forinstance,thesmallgearonthecrankshafthas10teethandthelargegearonthecamshafthas20teeth,thecrankshaftwillturnthecamshaftatexactlyone-halfcrankshaftspeed.ValveSystemsVVT-Toyota'sContinuouslyVariableValveTimingThemostsignificantandsatisfyingchangestotheLexusGSlineareintheareaofpowertrain.InthecaseoftheGS300,Lexusbreathesnewlifeintolastyear's3.0Linlinesix,byintroducingVVT—continuouslyvariablevalvetimingsystem.Onthedyno,VVTshowsupasonlyfiveadditionalhorsepowerand10lb-ftoftorque.Butinthecaritmeansfueleconomyimprovementsof1.6mpg,smootheridle,CaliforniaTLEV(transitionallow-emissionsvehicle)certificationandzero-to-60mphahalfsecondquicker.ToyotaeliminatesthecompromiseofconventionalvalvetimingwiththeintroductionofVVT.Bycontinuouslyvaryingintakevalvetiming(upto60crankangledegrees),Toyotaoptimizeslow-tomid-speedtorque,improvesfueleconomyandlowersemissionswithouthavinganegativeimpactonidle.

Inessence,thesystemcontrolsvalveoverlap,whichmeansitcaneliminateitcompletelyforaglasssmoothidle,ormaximizeittoboostvolumetricefficiencyandreducepumpinglosses—thistranslatesintopower,economyandcleanerrunningatallenginespeeds.

ValveSystemsValveSystemsTheheartofthesystemistheintakecampulley,whichconsistsofaninnerandoutersection.Theinnerportionisfixedtothecamshaftandnestsinsidethebelt-drivenouterpulleyviahelicalsplinegears.Anelectronicallycontrolledhydraulicpistonmovesthepulleyhalvesrelativetooneanother,causingthecamportiontorotatewithintheouterpulley.Thisrotationadvancesorretardsintakevalvetiming.AspoolvalvereactingtosignalsfromtheECUcontrolshydraulicpressure.VTEC-HondaVariableValveTimingandLiftElectronicControl

Bydesigningahighervalvelift,widervalve-timing,andlargervalvediameter,itispossibletoobtainahighervolumetricefficiencytocopewithhigheroutputenginespeeds.TheVTECisusedtoimprovevolumetricefficiencyfromlowenginespeedtohighenginespeed.WithVTEC,thevalvetimingandliftcanbeadjustedatlowenginerotationtoincreasetorqueandpreventairfrombeingforcedbackthroughtheintake.ValveSystemsValveSystemsVTECLayoutInFig.2-3thestructureoftheVTECisshown.Theenginehasoneextracamprofileandrockerarm(midrockerarm)forhighenginespeed.Thecamhas3differentprofileslocatedattheintakeandexhaustofeachcylinder.Thecentercamisusedexclusivelyforhighspeedandthe2outsidecamsforlowspeed.ValveSystemsTherockerarmassemblyiscomposedofamidrockerarmwithprimaryandsecondaryrockerarmsoneachside.Insidetherockerarmsare2hydraulicpistons,astopperpin,andareturnspring,whichmakeupthechangeovermechanism.Themidrockerarmhasalostmotionspringsothatthevalveoperatessmoothlyathighspeedsandalsostopsthearmatlowspeeds.ThewholesystemisoperatedbyahydraulicactuatorwhichiscontrolledbytheEngine-ControlUnit(ECU).ValveSystems1Camshaft2CamLobeforLowSpeedRange3CamLobeforHighSpeedRange4PrimaryRockerArm5MidRockerArm6SecondaryRockerArm7HydraulicPistonA8HydraulicPistonB9StopperPin10Lost-motionSpring11ExhaustValve12IntakeValveFig.2-3VTECSystemConstructionValveSystemsVTECOperationFig.2-4showstheVTECmechanismwhileoperatingatlowenginespeeds.Inthelow-speedmodethe3rockerarmsareseparatedandusecamsA&Bonly.Atthistimethemidrockerarmisincontactwiththehighspeedcamduetothespringforceinthelostmotionmechanism.Itisseparatedfromtheprimaryandsecondaryrockerarmandthusisnotactuatingthevalves.Fig.2-5showstheVTECmechanismwhileoperatinginthehighspeedmode.Duringhighspeedengineoperationthe3rockerarmsareconnectedandmovetogetherduetothe2hydraulicpistonswhichhavemovedoverduetoincreasedhydraulicpressure.Fig.2-4RockerArmOperation(LowSpeedRange)ValveSystemsValveSystemsFig.2-7operationofcamshaftadjustmentValveSystemsBMWVariablecamshaftcontrol(VANOS)Thesystemconsistsofhydraulicadjuster,mechanicaladjusterandsolenoidvalveforhydraulicactuation(Fig.2-6).ThissystemissimilartoToyota’sVVTdescribedaboveindesignandoperation.Withthissystemtheinletcamshaftisrotatedintheoppositedirectiontothecamshaftgear.Dependingonthepositionofthesolenoidvalve,thehydraulicpistonisdisplacedtotheleftorright.Theaxialmovementofthehydraulicpistoncausescamshaftadjust(turn)inthe"Advance"or"Retard"directioninthemechanicaladjusterbymeansofthehelicalteeth(Fig.2-7).Adjustmentcanbeperformedsteplessly.ValveSystemsFig.2-6DesignofcamshaftadjustmentValveSystemsFig.2-7operationofcamshaftadjustmentValveSystemsVaneCam—avane-typeadjuster

Additionaladjustmentoftheexhaustcamshaftbringsaboutanincreaseintorqueinthelowertomiddlespeedrangeaswellasinthemiddletoupperspeedrange.Avane-typeadjuster(VaneCam)isshowninFig.2-8.Theouterrotorispermanentlyconnectedtothesprocketandtheinnerrotortothecamshaftrespectively.Theouterrotorandinnerrotorcanberotatedinopposingdirections.Theoilpressureintherespectiveoilchamberisvariablycontrolledbythehydraulicvalves.Thecamshaftsareadjustedinthisway.Themaximumturningangleoftheinnerrotortotheouterrotoris,forexample,52°CAfortheinletcamshaftand22°CAfortheexhaustcamshaft.Fig.2-8Avane-typeadjusterValveSystemsValveSystemsElectronicValveControlSystemAnelectronicvalvecontrol(EVC)systemreplacesthemechanicalcamshaft,controllingeachvalvewithactuatorsforindependentvalvetiming.TheEVCsystemcontrolstheopeningandclosingtimeandliftamountofeachintakeandexhaustvalvewithindependentactuatorsoneachvalve.Changingfromamechanicalcamshaftdrivenvalveintoindependentlycontrolledactuatorvalvesprovidesahugeamountofflexibilityinenginecontrolstrategy.VehiclesutilizingEVCcanrealizeseveralbenefitsincluding:1)increasesenginepowerandfueleconomy.ValveSystems2)allowscentralizedanddistributedEVCsystemstoperformattheirfullpotential.3)adaptstoenginesofvariedcylindercounts.

Withalloftheimprovedefficienciesandconsumerbenefits,automanufacturersareeagertogettheirfirstEVCsystemsontheroad.TheEVCsystemistargetedtooperateintemperaturesupto125℃,whiletheactuatoristargetedtorunupto6000r/min.Theactuatorcanbecontrolledinacentralizedsystemwithahigh-speedmultiplexbus(upto10Mbps)orinadistributedsystemwithanominalspeedbusValveSystemsEVCsystemsmustbecompactinsize,specificallytheactuatorsthatmustbesmallenoughtofitintheenginespace.Avehiclethatusesa42VsystemisidealforEVCbecauseitrequireshighvoltagetocontrolthevalveactuators,andEVCistargetedforV8andV12engines.SmartValvesValeoisactivelydevelopingtechnologyforreducingfuelconsumptionandemissions