汽车专业英语-3 cha

复习提问（教师说发动机汉语部件名称，同学回答英文名称）用英语说明内燃机分类方式和类别Whatarefourstrokesinafour-stroke-cycleengine?编辑ppt学习内容本次课学习内容、目标和重点难点学习目标难点重点2.4Pistons,ConnectingRodsandCrankshaft2.5ValveSystem1.掌握曲柄连杆机构主要组成、零件英文名称；2.了解VVT系统的主要功能1.重点为记忆曲柄连杆机构主要组成、零件英文专业术语2.难点需要记忆的生词偏多3.汉译准确表达也是难点编辑pptChapter2InternalCombustionEngine

2.4Pistons,ConnectingRodsandCrankshaft

bearing['bεəriŋ]n.轴承journal['ʤə:nəl]n.轴颈throw[θrou]n.&v.投掷，扔；n.投掷距离，偏心距离，摆幅；（pl.）曲柄attach[ə'tæt∫]v.附着，连接，固定（to）reciprocating[ri'siprəkeitiŋ]a.往复的2.4.1

NewWordsandPhrases编辑ppt

2.4.1PistonandconnectingrodThepistonmustmovedownthroughthecylindertoproduceavacuumtodrawafuelchargeintothecylinder.Itthentravelsupinthecylinderandcompressesthemixture.Whenthemixtureisfired,thepressureoftheexpandinggasistransmittedtothetopofthepiston.Thisdrivesthepistonbackdownthroughthecylinderwithgreatforce,transmittingtheenergyoftheexpandinggastothecrankshaft.Thepistonthentravelsupthroughthecylinderandexhauststheburnedfuelcharge.Pistonsareusuallymadeofaluminum.Often,aluminumpistonsaretin-platedtoallowproperbreak-inwhentheengineisstarted.Aluminumpistonscanbeforged,buttheyaremorecommonlycast.Castironisagoodmaterialforpistonsusedinaslow-speedengine.Ithasexcellentwearcharacteristicsandwillprovidegoodperformance.Chapter2InternalCombustionEngine

2.4Pistons,ConnectingRodsandCrankshaft2.4.2Text编辑pptFig.2-5Pistons,connectingrodsandcrankshaft编辑ppt

Asthenameimplies,connectingrodsareusedtoconnectpistonstothecrankshaft(Fig.2-5).Theupperendoftherodhasaholethroughitforthepistonpin.Thebottomofthelargeendoftheconnectingrod(Fig.2-6)mustberemovedsotherodcanbeinstalledonthecrankshaftjournal.Thesectionthatisremovediscalledtheconnectingrodcap.Connectingrodsarenormallymadeofalloysteel.Theyaredrop-forgedtoshapeandthenmachined.Fig.2-6ConnectingrodChapter2InternalCombustionEngine

2.4Pistons,ConnectingRodsandCrankshaft编辑ppt

2.4.2CrankshaftTheenginecrankshaft(Fig.2-7)providesaconstantturningforcetothewheels.Ithasthrowstowhichconnectingrodsareattached,anditsfunctionistochangethereciprocatingmotionofthepistontoarotarymotiontodrivethewheels.Crankshaftsaremadeofalloysteelorcastiron.

Thecrankshaftisheldinpositionbyaseriesofmainbearings.Themaximumnumberofmainbearingsforacrankshaftisonemorethanthenumberofcylinders.Itmayhavefewermainbearingsthancylinders.Chapter2InternalCombustionEngine

2.4Pistons,ConnectingRodsandCrankshaft编辑ppt

Mostenginesuseprecisioninsertbearingsthatareconstructedliketheconnectingrodbearings,butaresomewhatlarger.Inadditiontosupportingthecrankshaft,oneofthemainbearingsmustcontroltheforwardandbackwardmovement.Fig.2-7Crankshaft编辑ppt

Chapter2InternalCombustionEngine

2.5ValveSystem

lifter['liftə]n.挺杆clearance['kliərəns]n.间隙2.5.1

NewWordsandPhrases编辑ppt

Thecamshaftmustturnatone-halfcrankshaftspeed.Thecamshaftislinkedwithcrankshaftbyoneofthreeways:beltdrive,chaindriveandgeardrive.Themaincomponentsofthevalvesystemare:

Camshaft.Itisusedtoopenandclosethevalves.Generallyonlyonecamshaftisusedinmostengines.Newerenginesareincreasinglyequippedwithtwoormorecamshafts(Figure2-8).Valves.Eachenginecylinderordinarilyhastwovalves.However,modernenginesoftenusefourvalvespercylinder(twointakevalvesandtwoexhaustvalves).Inordertopreventburning,thevalvemustgiveoffheattothevalveseatandtothevalveguide.Thevalvemustmakegoodcontactwiththeseatandmustrunwithminimumclearanceintheguide.Chapter2InternalCombustionEngine

2.5ValveSystem2.5.2Text编辑ppt

Valvelifters.Mechanicalvalvelifterswereusedinolderengines.Mostvalvetrainsthatcontainmechanicalliftershavesomeprovisionforadjustingclearance.Hydraulicvalveliftersperformthesamejobasmechanicallifters.However,hydraulicliftersareself-adjusting,operatewithnolifter-to-rockerarmclearance,andusesengineoilunderpressuretooperate.Hydraulicliftersarequietinoperation.Chapter2InternalCombustionEngine

2.5ValveSystem编辑pptFig.2-8Dualoverheadcamshaft（DOHC）编辑ppt补充：

Threetypesofcamshaftdrive凸轮轴三种传动方式：Beltdrive带传动Geardrive齿轮传动Chaindrive链传动编辑ppt

variablevalvetimingsystemeliminatesthecompromiseofconventionalvalvetimingwiththeintroductionofVVT.Bycontinuouslyvaryingintakevalvetiming(upto60crankangledegrees),Toyotaoptimizeslow-tomid-speedtorque,improvesfueleconomyandlowersemissionswithouthavinganegativeimpactonidle.

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

补充：

ContinuouslyVariableValveTiming（CVVT）编辑pptTheheartofthesystemistheintakecampulley,whichconsistsofaninnerandoutersection.Theinnerportionisfixedtothecamshaftandnestsinsidethebelt-drivenouterpulleyviahelicalsplinegears.Anelectronicallycontrolledhydraulicpistonmovesthepulleyhalvesrelativetooneanother,causingth