汽车专业英语课件-与汽车专业英语读译教程课件、参考译文3-U2TB

UNIT2ENGINEMECHANICALTEXTBValveSystems,PROFESSIONALENGLISH,UNIT2ENGINEMECHANICALTEXTBValveSystemsOperationofValveSystemVVTToyotasContinuouslyVariableValveTimingVTECHondaVariableValveTimingandLiftElectronicControlMIVECMitsubishiInnovativeValvetimingElectronicControlElectronicValveControlSystemSmartValves,本次课学习内容,本次课学习目标,掌握可变气门定时机构主要部件的英文名称掌握可变气门定时机构的基本原理掌握常用术语（phrasesandexpressions）了解相关术语（relatedterms）,NEWWORDS,bumpbmpn.撞击，（因撞击而起的）肿块；v.碰，撞，颠簸camkmn.凸轮lobeloubn.凸起integralintigrla.完整的，整体的，积分的stemstemn.杆，茎powertrainpautreinn.动力系统，动力装置，传动系统dynodainoun.=dynamometer测功机，测力计breathebri:v.呼吸，发出certifications:tifikeinn.证明，鉴定，检验证明书compromisekmprmaizv.&n.妥协，折衷,essenceesnsn.基本，本质，实质，精华，要素pulleypulin.滑轮，带轮helicalhelikla.螺旋状的splinesplainn.花键，方栓spoolspu:ln.线轴，卷轴；滑阀；线圈mpg=milepergallon（英里/加仑）actuatorktjueitn.执行器，执行元件strategystrtiin.策略，谋略flexibilityfleksbilitin.灵活性，柔性，适应性eageri:gv.渴望着，热心于multiplexmtipleksa.多元的，多重的，多样的；n.多路传输，多路通信,nominalnminla.有名无实的；极微小的；标定的，额定的busbsn.总线innovationinouveinv.改进，革新，创新，新发明技术，方法residualrizidjula.剩余的，残余的,camlobe凸轮的凸起部分valvestem气门杆variablevalvetiming（VVT）可变气门定时inessence本质上，实质上spoolvalve滑阀electronicvalvecontrol(EVC)电子式气门控制centralizedsystem集中系统distributedsystem分布系统camlessengine无凸轮发动机smartvalve智能气门,PHRASESANDEXPRESSIONS,ValveSystemsOperationofValveSystemYouhaveseenthattheintakevalvemustbeopenedfortheintakestroke,bothvalvesmustremainclosedduringthecompressionandpowerstrokes,andtheexhaustvalveopensduringtheexhauststroke.Thedesignermustdesignadevicetoopenandclosethevalvesatthepropertimes.Theshaftwillhaveanegg-shapedbumpcalledacamlobe.Thecamlobeismachinedasanintegralpartoftheshaft.Thisshaftiscalledacamshaft.Thedistancethevalvewillberaised,howlongitwillstayopen,andhowfastitopensandclosescanallbecontrolledbytheheightandshapeofthelobe1.Asyouwillseelater,itisimpracticaltohavethecamlobecontacttheendofthevalvestemitself.Youhaveplacedthecamshaftsomedistanceabovetheendofthevalvestem.,Whenthecamshaftisturn,thelobeswillnoteventouchthevalvestem.Thelifterisinstalledbetweenthecamlobeandthevalvestem.Theupperendridesonthelobeandthelowerendalmosttouchesthevalvestem.Thelifterslidesupanddowninaholeboredintheheadmetalthatseparatesthevalvestemfromthecamshaft2.Youhavedevelopedamethodofopeningandclosingthevalves.Thenextproblemishowandatwhatspeedtoturnthecamshafts.Eachvalvemustbeopenforonestroke.Theintakevalveisopenduringtheintakestrokeandremainsclosedduringthecompression,power,andexhauststrokes.Thiswouldindicatethatthecamlobemustturnfastenoughtoraisethevalveeveryfourthstroke.Youcanseethatittakesonecompleterevolutionofthecamlobeforeveryfourstrokesofthepiston.,Rememberthatfourstrokesofthepistonrequiretworevolutionsofthecrankshaft.Youcansaythatforeverytworevolutionsofthecrankshaft,thecamshaftmustturnonce.Ifyouarespeakingofthespeedofthecamshaft,youcansaythatthecamshaftmustturnatone-halfcrankshaftspeed.Ifthecrankshaftisturningandthecamshaftmustturnatone-halfcrankshaftspeed,itseemslogicaltousethespinningcrankshafttoturnthecamshaft.Oneverysimplewaytodrivethecamshaftwouldbebymeansofgearsandabelt.Onegearisfastenedontheendofthecrankshaft,andtheotherisfastenedontheendofthecamshaft.Thesmallercrankshaftgeardrivesthelargercamshaftgearthroughthebelt.If,forinstance,thesmallgearonthecrankshafthas10teethandthelargegearonthecamshafthas20teeth,thecrankshaftwillturnthecamshaftatexactlyone-halfcrankshaftspeed.,VVT-ToyotasContinuouslyVariableValveTimingThemostsignificantandsatisfyingchangestotheLexusGSlineareintheareaofpowertrain.InthecaseoftheGS300,Lexusbreathesnewlifeintolastyears3.0Linlinesix,byintroducingVVTcontinuouslyvariablevalvetimingsystem.Onthedyno,VVTshowsupasonlyfiveadditionalhorsepowerand10lb-ftoftorque.Butinthecaritmeansfueleconomyimprovementsof1.6mpg,smootheridle,CaliforniaTLEV(transitionallow-emissionsvehicle)certificationandzero-to-60mphahalfsecondquicker.ToyotaeliminatesthecompromiseofconventionalvalvetimingwiththeintroductionofVVT.Bycontinuouslyvaryingintakevalvetiming(upto60crankangledegrees),Toyotaoptimizeslow-tomid-speedtorque,improvesfueleconomyandlowersemissionswithouthavinganegativeimpactonidle.,Inessence,thesystemcontrolsvalveoverlap,whichmeansitcaneliminateitcompletelyforaglasssmoothidle,ormaximizeittoboostvolumetricefficiencyandreducepumpinglossesthistranslatesintopower,economyandcleanerrunningatallenginespeeds.Theheartofthesystemistheintakecampulley,whichconsistsofaninnerandoutersection.Theinnerportionisfixedtothecamshaftandnestsinsidethebelt-drivenouterpulleyviahelicalsplinegears.Anelectronicallycontrolledhydraulicpistonmovesthepulleyhalvesrelativetooneanother,causingthecamportiontorotatewithintheouterpulley.Thisrotationadvancesorretardsintakevalvetiming.AspoolvalvereactingtosignalsfromtheECUcontrolshydraulicpressure.,VTEC-HondaVariableValveTimingandLiftElectronicControlBydesigningahighervalvelift,widervalve-timing,andlargervalvediameter,itispossibletoobtainahighervolumetricefficiencytocopewithhigheroutputenginespeeds.TheVTECisusedtoimprovevolumetricefficiencyfromlowenginespeedtohighenginespeed.WithVTEC,thevalvetimingandliftcanbeadjustedatlowenginerotationtoincreasetorqueandpreventairfrombeingforcedbackthroughtheintake.VTECLayoutInFig.2-3thestructureoftheVTECisshown.Theenginehasoneextracamprofileandrockerarm(midrockerarm)forhighenginespeed.Thecamhas3differentprofileslocatedattheintakeandexhaustofeachcylinder.Thecentercamisusedexclusivelyforhighspeedandthe2outsidecamsforlowspeed.,Therockerarmassemblyiscomposedofamidrockerarmwithprimaryandsecondaryrockerarmsoneachside.Insidetherockerarmsare2hydraulicpistons,astopperpin,andareturnspring,whichmakeupthechangeovermechanism.Themidrockerarmhasalostmotionspringsothatthevalveoperatessmoothlyathighspeedsandalsostopsthearmatlowspeeds.ThewholesystemisoperatedbyahydraulicactuatorwhichiscontrolledbytheEngine-ControlUnit(ECU).,1Camshaft2CamLobeforLowSpeedRange3CamLobeforHighSpeedRange4PrimaryRockerArm5MidRockerArm6SecondaryRockerArm7HydraulicPistonA8HydraulicPistonB9StopperPin10Lost-motionSpring11ExhaustValve12IntakeValve,Fig.2-3VTECSystemConstruction,VTECOperationFig.2-4showstheVTECmechanismwhileoperatingatlowenginespeeds.Inthelow-speedmodethe3rockerarmsareseparatedandusecamsA&Bonly.Atthistimethemidrockerarmisincontactwiththehighspeedcamduetothespringforceinthelostmotionmechanism.Itisseparatedfromtheprimaryandsecondaryrockerarmandthusisnotactuatingthevalves.Fig.2-5showstheVTECmechanismwhileoperatinginthehighspeedmode.Duringhighspeedengineoperationthe3rockerarmsareconnectedandmovetogetherduetothe2hydraulicpistonswhichhavemovedoverduetoincreasedhydraulicpressure.,Fig.2-4RockerArmOperation(LowSpeedRange),Fig.2-7operationofcamshaftadjustment,BMWVariablecamshaftcontrol(VANOS)Thesystemconsistsofhydraulicadjuster,mechanicaladjusterandsolenoidvalveforhydraulicactuation(Fig.2-6).ThissystemissimilartoToyotasVVTdescribedaboveindesignandoperation.Withthissystemtheinletcamshaftisrotatedintheoppositedirectiontothecamshaftgear.Dependingonthepositionofthesolenoidvalve,thehydraulicpistonisdisplacedtotheleftorright.Theaxialmovementofthehydraulicpistoncausescamshaftadjust(turn)intheAdvanceorRetarddirectioninthemechanicaladjusterbymeansofthehelicalteeth(Fig.2-7).Adjustmentcanbeperformedsteplessly.,Fig.2-6Designofcamshaftadjustment,Fig.2-7operationofcamshaftadjustment,VaneCamavane-typeadjusterAdditionaladjustmentoftheexhaustcamshaftbringsaboutanincreaseintorqueinthelowertomiddlespeedrangeaswellasinthemiddletoupperspeedrange.Avane-typeadjuster(VaneCam)isshowninFig.2-8.Theouterrotorispermanentlyconnectedtothesprocketandtheinnerrotortothecamshaftrespectively.Theouterrotorandinnerrotorcanberotatedinopposingdirections.Theoilpressureintherespectiveoilchamberisvariablycontrolledbythehydraulicvalves.Thecamshaftsareadjustedinthisway.Themaximumturningangleoftheinnerrotortotheouterrotoris,forexample,52CAfortheinletcamshaftand22CAfortheexhaustcamshaft.,Fig.2-8Avane-typeadjuster,ElectronicValveControlSystemAnelectronicvalvecontrol(EVC)systemreplacesthemechanicalcamshaft,controllingeachvalvewithactuatorsforindependentvalvetiming.TheEVCsystemcontrolstheopeningandclosingtimeandliftamountofeachintakeandexhaustvalvewithindependentactuatorsoneachvalve.Changingfromamechanicalcamshaftdrivenvalveintoindependentlycontrolledactuatorvalvesprovidesahugeamountofflexibilityinenginecontrolstrategy.VehiclesutilizingEVCcanrealizeseveralbenefitsincluding:1)increasesenginepowerandfueleconomy.2)allowscentralizedanddistributedEVCsystemstoperformattheirfullpotential.3)adaptstoenginesofvariedcylindercounts.,Withalloftheimprovedefficienciesandconsumerbenefits,automanufacturersareeagertogettheirfirstEVCsystemsontheroad.TheEVCsystemistargetedtooperateintemperaturesupto125,whiletheactuatoristargetedtorunupto6000r/min.Theactuatorcanbecontrolledinacentralizedsystemwithahigh-speedmultiplexbus(upto10Mbps)orinadistributedsystemwithanominalspeedbus.EVCsystemsmustbecompactinsize,specificallytheactuatorsthatmustbesmallenoughtofitintheenginespace.Avehiclethatusesa42VsystemisidealforEVCbecauseitrequireshighvoltagetocontrolthevalveactuators,andEVCistargetedforV8andV12engines.SmartValvesValeoisactivelydevelopingtechnologyforreducingfuelconsumptionandemissionswithanenginecylinder-headdesignthatusesitsSmart