内燃机专业英语教案

1内燃机专业英语自编讲义局部：一、教学内容：在该局部内容中主要表达内燃机、汽油发动机、柴油发动机等的相关学问。包括：1.EngineClassificationandOverallMechanics，发动机的分类和总体构造；2.Four-stage-engineOperation，四行程发动机工作过程；3.Two-stage-engineOperation，二行程发动机工作过程；4.DieselEngineOperatingFeatures，柴油发动机工作特点；5.EngineCylinderBlockCrankcase，发动机气缸体曲轴箱；6.PistonConnectingRod，活塞连杆；7.CrankshaftFlywheel，曲轴飞轮；8.ValvesandValesTrain，气门与气门传动组；9.EngineFuelSystem，发动机燃油系统；10.EngineLubricatingSystem，发动机润滑系统；11.EngineCoolingSystem，发动机冷却系统；12.EngineIgnitionSystem，EngineStarting二、教学时数：18学时。EngineClassificationandOverallMechanics〔1学时〕发动机的分类和总体构造Four-stage-engineOperation〔1学时〕四行程发动机工作过程Two-stage-engineOperation〔1学时〕二行程发动机工作过程DieselEngineOperatingFeatures〔1学时〕柴油发动机工作特点EngineCylinder BlockCrankcase〔1学时〕发动机气缸体 曲轴箱PistonConnectingRod〔1学时〕活塞 连杆Crankshaft Flywheel〔1学时〕曲轴飞轮气门与气门传动组EngineFuelSystem〔1学时〕发动机燃油系统EngineLubricatingSystem〔1学时〕发动机润滑系统EngineCoolingSystem〔1学时〕发动机冷却系统EngineIgnitionSystem〔1学时〕发动机点火系统EngineStartingSystem〔1学时〕发动机起动系统Locomotives〔2学时〕机车DieselTraction〔3学时〕内燃牵引三、教学难点与重点：重点内容有：EngineClassificationandOverallMechanics，发动机的分类和总体构造；2.Four-stage-engineOperation，四行程发动机工作过程；4.DieselEngineOperatingFeature5.EngineCylinderBlockCrankcase轴箱；7.CrankshaftFlywheel，曲轴飞轮；8.ValvesandValesTrain，气门与气门传动组；9.EngineFuelSystem，发动机燃油系统；10.EngineLubricatingSystem，发动机润11.EngineCoolingSystem，发动机冷却系统；13.EngineStartingSystem，发动机起动系统；14.Locomotives，机车；15.DieselTraction，内燃牵引。四、作业三篇翻译10EngineClassificationandOverallMechanics发动机的分类和总体构造Theautomobileenginescanbeclassifiedaccordingto:1.numberofcylinders;2.arrangementofcylinders;3.arrangementofvalves;4.typeofcooling;5.numberofcycles(twoorfour);6.typeoffuelburned;7.typeofignition.汽车发动机可以按以下几种状况分类：燃料分类；7．按点火方式分类。Theengineisthesourceofpowerthatmakesthewheelsgoaroundandthecarmove.Theautomobileengineisaninternal-combustionenginebecausethefuel(gasoline)isburnedinsideit.Theburningofgasolineinsidetheengineproduceshighpressureintheenginecombustionchamber.Thishighpressureforcespistontomove,themovementiscarriedbyconnectingrodstotheenginecrankshaft.Thecrankshaftisthusmadetorotate;therotarymotioniscarriedthroughthepowertraintothecarwheelssothattheyrotateandthemoves.〔汽油〕是在发动机内燃烧的。汽油的燃烧在发动机燃烧室中产系统将发动机的转动运动传给汽车车轮，从而使车轮及整车转动起来。Theenginerequiresafuelsystemtosupplyitwithamixtureofairandfuel.Thefuelsystemdoesthisbypumpingliquidgasolinefromatankintothecarburetor,amixingdevicethatmixesthegasolinewithair.Themixtureisdeliveredtotheenginewhereitisburned.抽出来，通过化油器--一种把汽油空气进展混合的装置--将可燃混合气输送到发动机，并在那里进展燃烧。Theenginealsoneedsacoolingsystem,thecombustionoftheair-fuelmixtureintheenginecreatesaveryhightemperature(ashighas2023to2700 ℃).Thecoolingsystemtakesheatawayfromtheenginebycirculatingaliquidcoolant(watermixedwithantifreeze)betweentheengineandaradiator.Thecoolantgetshotasitgoesthroughtheengine.Itcoolsoffasitgoesthroughtheradiator.Thus,thecoolantcontinuallytakesheatawayfromtheengine,whereitcoulddodamage,anddeliversittotheradiator.Airpassingthroughtheradiatortakesheatawayfromtheradiator.发动机还配备有冷却系统，发动机内部的混合气燃烧会产生高温〔2，，700℃。冷却系统通过在发动机和散热器之间流淌的液体冷却液〔加了〕使发动机降温。当冷却液流经发动机时，冷却液就会变热。而流到空气，将热量从散热器中带走。Theenginealsoincludesalubricatingsystem.Thepurposeofthelubricatingsystemistosupplyallmovingpartsinsidetheenginewithlubricatingoil;theoilkeepsmovingpartsfromwearingexcessively.润滑油。润滑油可是运动零件免于过度磨损。Theenginerequiresafourthsystem,theignitionsystem.Theignitionsystemprovideshigh-voltageelectricsparksthatignite,orsetfireto,thechargesofair-fuelmixtureintheenginecombustionchambers.燃烧室中的可燃混合气起燃。Thefifthisstartingsystemanditspurposeistochangetheelectricalcurrentintothemechanicalenergytopushthecrank-shaftaround.Bymeansofthis,theenginecanbestarted.动曲轴转动。发动机借助这种方法启动。Thesefivesystemsarediscussedbrieflyinfollowingsections.这五个系统将在以后的章节中具体争论。WordsandExpressionscombustionchamberignition.powertrainantifreeze防冻的；coolant冷却剂〔液态；crankshaft曲轴Four-stage-engineOperation四行程发动机工作过程Theactiontakingplaceintheenginecylindercanbedividedintofourstages,orstrokes.“Strokeferstopistonmovement;asstrokeoccurswhenthepistonmovesfromonelimitingpositiontotheother.TheupperlimitofpistonmovementiscalledTDC〔topdeadcenter〕.ThelowerlimitofpistonmovementiscalledBDC(bottomdeadcenter).AstrokeispistonmovementfromTDCtoBDCorfromBDCtoTDC.Inotherwords,thepistoncompletesastrokeeachtimeitchangeitsdirectionofmotion.TDC〔上止点BD〔下止点。一个行程就是活塞从上止点到下次其运动的方向。Wheretheentirecycleofeventsinthecylinderrequiresfourstrokes(ortwocrankshaftrevolutions),theengineiscalledafour-stroke-cycleengine,orafour-cycleengine.Thefourpistonstrokesareintake,compression,power,andexhaust.发动机气缸中的全部工作过程分为四个行程的〔或者曲轴旋转两周的，叫排气。Intakestroke.Ontheintakestroke,theintakevalvehasopened,thepistonismovingdownward,andamixtureofairandvaporizedgasolineisenteringthecylinderthroughthevalveport.Themixtureofairandvaporizedgasolineisdeliveredtothecylinderbythefuelsystemandcarburetor.进气行程：在进气行程中，进气门翻开，活塞向下移动，可燃混合气通过进气门进入气缸。适当浓度可燃混合气是由燃料系统和化油器供给的。Compressionstroke.AfterthepistonreachesBDC,orthelowerlimitofitstravel,itbeginstomoveupward.Asthishappens,theintakevalvecloses.Theexhaustvalveisalsoclosed,sothatthecylinderissealed.Asthepistonmovesupward(pushednowbytherevolvingcrankshaftandconnectingrod),theair-fuelmixtureiscompressed.BythetimethepistonreachesTDC,themixturehasbeencompressedtoaslittleasone-tenthofitsoriginalvolume,orevenless.Thiscompressionoftheair-fuelmixtureincreasesthepressureinthecylinder.Whenthe air-fuelmixtureiscompressed,notonlydoesthepressureinthecylindergoup,butthetemperatureofthemixturealsoincreases.时〔这是由转动的曲轴和连杆推动活塞，可燃混合气被压缩。当活塞到达上止料被压缩时，不仅气缸里的压力上升，可燃混合气的温度也随之增加了。Powerstroke.AsthepistonreachesTDConthecompressionstroke,anelectricsparkisproducedatthesparkplug.Theignitionsystemdeliversahigh-voltagesurgeofelectricitytothesparkplugtoproducethespark.Thesparkignites,orsetsfireto,theair-fuelmixture.Itnowbeginstoburnveryrapidly,andthecylinderpressureincreasestoasmuchas3-5MPaorevenmore.Thisterrificpushagainstthepistonforcesitdownward,andapowerimpulseistransmittedthroughtheconnectingrodtothecrankpinonthecrankshaft.Thecrankshaftisrotatedasthepistonispusheddownbythepressureaboveit.合气开头发生猛烈燃烧，气缸内压力到达3-5兆帕，甚至更高。作用于活塞上强上。因此，当活塞受压向下运动时，推动曲轴转动。Exhauststroke.AsthepistonreachesBDCagain,theexhaustvalveopens.Now,asthepistonmovesupontheexhauststroke,itforcestheburnedgasesoutofthecylinderthroughtheexhaust-valveport.Then,whenthepistonreachesTDC,theexhaustvalveclosesandtheintakevalveopens.Now,afreshchargeofair-fuelmixturewillbedrawnintothecylinderasthepistonmovesdownagaintowardBDC.Theabovefourstrokesarecontinuouslyrepeated.把废气经排气门排出气缸。随后活塞到达上止点，排气门关闭，进气门翻开。当程又连续重复。WordsandExpressionsstroke行程，冲程；BDC 上止点；TDC 下止点；surge 了不起的，绝妙的；crankpin 曲柄销，连杆轴颈；intakestroke 吸气冲程；compressionstroke 压缩冲程；powerstroke 做功冲程；exhauststroke 程；freshcharge 〔发动机〕吸入的颖混合油气Two-stage-engineOperation二行程发动机工作过程Inthefour-stroke-cycleengine,alreadydiscussedinlesson1 、2,thecompletecycleofeventsrequiresfourpistonstrokes(intake,compression,power,andexhaust).Inthetwo-stroke-cycle,ortwo-cycle,engine,theintakeandcompressionstrokesandpowerandexhauststrokesareinasensecombined.Thispermitstheenginetoproduceapowerstrokeeverytwopistonstrokes,oreverycrankshaftrotation.成一次工作循环。Inthetwo-cycleengine,thepistonactsasavalve,clearingvalveportsinthecylinderwallasitnearsBDC.Afreshair-fuelchargeentersthroughtheintakeport,andtheburnedgasesexitthroughtheexhaustport.Thecompletecycleofoperationisasfollows:AsthepistonnearsTDC,ignitiontakesplace.Thehighcombustionpressuresdrivethepistondown,andthethrustthroughtheconnectingrodturnsthecrankshaft.AsthepistonnearsBDC，itpassestheintakeandexhaustportsinthecylinderwall.Burnedgases,stillundersomepressure,begintostreamoutthroughtheexhaustport.Atthesametime,theintakeport,nowclearedbythepiston,beginstodeliverair-fuelmixture,underpressure,tothecylinder.Thetopofthepistonisshapedtogivetheincomingmixtureanupwardmovement.Thishelpstosweeptheburnedgasesaheadandoutthroughtheexhaustport.动活塞向下运动，通过连杆，推动曲轴转动。当活塞接近下止点时，经过气缸壁口排出。AfterthepistonhaspassedthroughBDCandstarsupagain,itpassesbothports,thussealingthemoff.Nowthefreshair-fuelchargeabovethepistoniscompressedandignited.Thesameseriesofeventstakesplaceagainandcontinueaslongastheengineruns.会反复不断地发生。Wementionedthattheair-fuelmixtureisdeliveredtothecylinderunderpressure.Inmostengines,thispressureisputonthemixtureinthecrankcase.Thecrankcaseissealedexceptforaleaf,orreed,valveatthebottom.Thereedvalveisaflexible,flatmetalplatethatrestssnuglyagainstthefloorofthecrankcase.Thereareholesunderthereedvalvethatconnecttotheenginecarburetor.Whenthepistonismovingup,apartialvacuumisproducedinthesealedcrankcase.Atmosphericpressureliftsthereedvalveofftheholes,andair-fuelmixtureentersthecrankcase.AfterthepistonpassesTDCandstartsdownagain,pressurebeginstobuildupinthecrankcase.Thispressureclosesthereedvalvesothatfurtherdownwardmovementofthepistoncompressesthetappedair-fuelmixtureinthecrankcase.Thepressurewhichisbuiltupontheair-fuelmixturethencausesittoflowupthroughtheintakeportintotheenginecylinderwhenthepistonmovesdownfarenoughtocleartheintakeport.〔片簧阀〕之外，曲轴箱是密封的。片出进气口，可燃混合气所具有的压力使其上升，通过进气口进入气缸。Thetwo-strokeengineisnotonlyverysimplebutgivesnearlytwicethepowerofafourstrokeenginefromacylinderofgivensize,butitiswastefulofgasoline,assomemixtureinevitablyfindsitswayintotheexhaustsystemonthecombinesintake/exhauststroke,andtherearealwayssomecombustionproductsleftinthecylinderwhichreducetherapidburningofthefuel.Thiskindofengineisalwaysusedinmotorcycles.行程发动机耗油较大。通常使用在摩托车上。WordsandExpressionssweep 扫气；connectingrod 连杆；crankcase 曲轴箱；sealoff 密封；leaf〔reed〕valve 片簧阀；air-fuelcharge 可燃混合油气DieselEngineOperatingFeatures柴油发动机工作特点Weallknowthatdieselengines,inprinciple,workinthesamewayasgasolineenginesdo.Bothkindsofenginesareinternal-combustionengines,buteachofthemhasitscharacteristicfeatures.Astheirnamessuggestthistypeofenginesburntheirpartsoftheengines.“Internal”means“inside”,“combustion”means“catchingfireorburning”.Inanyinternalcombustionengine,burningfuelheatsairwhichconsequentlyexpands,andinexpandingexistsapushtoapistonwhich,inturn,rotatestheenginecrankshaftthroughaconnectingrod.我们都知道柴油机和汽油机的工作原理是一样的。这两种发动机都是内燃燃料是在发动机工作部件的内部燃烧的。“internal”意思是“内部”，“combustion””。在任何内燃机中，燃烧的燃料使空气受热并快速膨胀，产生推力推动活塞，通过连杆推动发动机的曲轴。Nowletuscomparethedieselenginewiththegasolineengine.Firstly,theexplosivemixtureofthegasolineengineisprovidedbyacarburetor,butinthecaseofthedieselenginethesupplyisaffectedbyaninjectionor“jerk”pumpwhichforcesa“short”offuelintoeachcylinderinturnaccordingtothecorrectfiringsequence.Secondly,thefundamentaldifferencebetweengasolineanddieselenginesisthatinthegasolineenginethesourceoftheheatforignitingthecharge,namely,anelectricspark,isgeneratedoutsidetheengine,andistaken,asitwere,intothewaitingchargeattherequiredinstant.Inthedieselenginethesourceofheatforignitingthechargeiscreatedwithintheenginebycompressingpureairtoadegreethatwillinitiatecombustionandtheninjectingthefuelattherighttimeinrelationtothemovementofthecrankshaft.Bothclassesofenginesareofverysimilarconstruction.Butasthedieselengineiscalledupontowithstandverymuchgreaterstressesduetohigherpressuresincylinders,ithastobeofmoresubstantialconstruction,andisthusheavier.Ingeneral,thedieselenginemayweighabout9.25kilogramsperkilowatt.Themostimportantadvantageofthegasolineengineisitslowerweightperkilowatt.Thegasolineengineforautomobilesweighsabout6.17kilogramsperkilowatt,andgasolineenginesforairplanesmayweighaslittleas0.77kilogramsperkilowatt.Thisadvantagepreventsthedieselenginefromreplacingthegasolineengineinsomeautomobilesandairplanes.大。一般来说，柴油机比质量约为9.25公斤每千瓦。汽油机最重要的优点是每千瓦的质量较轻。汽车用汽油发动机比质量为6.17公斤每千瓦，而飞机用汽油发动机的比质量小到0.77公斤每千瓦。汽油机的这一优点使柴油机无法代替某些汽车以及飞机上使用的汽油发动机。However,thedieselengineismoreefficient,becauseithashighercompressionration.Itsratiomaybeashighas16to1.Upto40percentofthechemicalenergyoftheburningfuelmaybechangedintomechanicalenergy.Inaddition,thedieselenginerunscoolerthanthegasolineengine.Thisadvantageisespeciallyobviousatlowerspeeds.Dieseloilisnotonlycheaperthangasoline,butalsosafertostore.但是，柴油发动机的效率更高些，由于柴油机具有较高的压缩比—161。宜，而且贮存更为安全。WordsandExpressionsdiesel：柴油机；internal-combustionengines：内燃机；jerkpump：脉动史喷油泵；compressionration：压缩比EngineCylinder BlockCrankcase发动机气缸体 曲轴箱Wehaveseenhowthemixtureofairandfuelisdeliveredbythefuelsystemtotheenginecylinder,whereitiscompressed,ignited,andburned.Wehavenotedthatthiscombustionproducesahighpressurethatpushesthepistondownsothatthecrankshaftisrotated.Nowletusexaminethevariouspartsoftheengineindetail.动曲轴转动。现在让我们具体争论一下发动机的各局部构造。EnginecylinderblockThecylinderblockofliquid-cooledenginesformsthebasicframeworkoftheengine.Otherpartsareattachedtothecylinderblockorareassembledinit.Theblockiscastinonepiecefromgrayironorironalloyedwithothermetals,suchasnickelorchromium.Someblocksarecastfromaluminum.Theblockcontainsnotonlythecylindersbutalsothewaterjacketsthatsurroundthem.Inaluminumblocks,cast-ironorsteelcylindersleeves(alsocalledborelines)areused.Thesemetalshavebetterwearingqualitiesthanaluminum andcanbetterwithstandthewearingeffect ofthepistonsandringmovingupanddowninthecylinders.Formostengines,castironhasbeenfoundtobeasatisfactorycylinder-wallmaterial.However,insomesmallengines,thecylinderwallsareplatedwithchromium,averyhardmetal,toreducewallwearandlengthentheirlife.发动机气缸体水冷发动机的气缸体是发动机的根本构件，其它部件都支承或安装在它上铁或钢制的气缸套〔或称之为气缸衬套。这类金属的耐磨性比铝更好，能更好种格外耐磨的金属，可削减气缸壁的磨损并延长使用寿命。CylinderHeadThecylinderheadisusuallycastinonepiecefromiron,fromironalloyedwithothermetals,orfromaluminumalloy.Aluminumhastheadvantageofcombininglightnesswithhighheatconductivity.Thatis,analuminumheadtendstoturncooler,otherfactorsbeingequal.Therearetwotypesofhead,LheadandIhead.Cylinderheadcontainswaterjacketsforcooling;intheassembledengine,thesewaterjacketsareconnectedthroughopeningstothecylinder-blockwaterjackets.Spark-plugholesareprovided,alongwithpocketsintowhichthevalvescanmoveastheyopen.气缸盖就是说，其它因素一样时，铝盖更简洁冷却。有两种气缸，LI型气缸气缸盖上留有火花塞口和凹槽，凹槽使气门翻开时可以移动。GasketsThejointbetweenthecylinderblockandtheheadmustbetightandabletowithstandthepressureandheatdevelopedinthecombustionchambers.Theblockandheadcannotbemachinedflatandsmoothenoughtoprovideanadequateseal.Thus,gasketsareused.Headgasketsaremadeofthinsheetsofsoftmetalorasbestosandmetal.Allcylinder,water,valve,andhead-boltopeningsarecutout.Whenthegasketisplacedontheblockandtheheadinstalled,tighteningoftheheadbolts(ornuts)squeezesthesoftmetalsothatthejointiseffectivelysealed.Gasketsarealsousedtosealjointsbetweenotherparts,suchasbetweentheoilpan,manifolds,orwaterpumpandtheblock.气缸垫体之间的密封。OilPanTheoilpanisusuallyformedofpressedsteel.Itusuallyholds5to10litresofoil,dependingontheenginedesign.Theoilpanandthelowerpartofthecylinderblocktogetherarecalledthecrankcase;theyenclose,orencase,thecrankshaft.Theoilpumpinthelubricatingsystemdrawsoilfromtheoilpanandsendsittoallworkingpartsintheengine.Theoildrainsoffandrunsdownintothepan.Thus,thereisconstantcirculationofoilbetweenthepanandtheworkingpartsoftheengine.油盘510升盘。这样，机油就在和发动机的各个部件之间不断循环流淌。WordsandExpressionscylinderblockblockcrankcaseframework构造，车架；grayiron灰铸铁；waterjacketplate…with镀金属；cylindergasketsasbestosmanifoldoilpan油盘；pocket凹槽；boreliner气缸衬套Piston ConnectingRod活塞 连杆PistonThepistonisessentiallyacylindricalplugthatmovesupanddownintheenginecylinder.Itisequippedwithpistonringstoprovideagoodsealbetweenthecylinderwallandpiston.Thepistonabsorbsheatfromthegas,andthisheatmustbecarriedawayifthemetaltemperatureistobecarriedawayifthemetaltemperatureistobeheldwithinsafelimits.Theconstantreversalofthepistontravelsetsupinertialforces,whichincreasebothwiththeweightofthepistonandwithitsspeed.Forthisreason,designerstrytokeeppistonweightlow,particularlyinhigh-speedengines.Aslowerhoodlinesandover-squareenginesbecamepopular,thesemi-slipperandfull-slipperpistonscameintouse.Onthesepistonsthenumberpistonringswasreducedtothree,twocompressionandoneoil-control.Onereasonfortheslipperpistonisthat,ontheshortstroke,over-squareengine,thepistonskirthadtobecutawaytomakeroomforthecounterweightsonthecrankshaft.Also,theslipperpiston,beingshorterandhavingpartofitsskirtcutaway,islighter.Thisreducestheinertialloadontheenginebearingsand,inaddition,makesforamoreresponsiveengine.Thelighterthepiston,thelessthebearingloadandthelongerthebearingswilllast.Anotherwaytolightenthepistonistomakeitoflight metal.Theidea pistonmaterialwouldbelightandstrong,conductheatwill,expandonlyslightwhenheated,resistwear,andbelowincost.Thus,mostautomotive-enginepistonstodayaremadeofaluminum,whichislessthanhalfasheavyasiron.Ironpistonswerecommonintheearlierengines.Aluminumexpandsmorerapidlythanironwithincreasingtemperature,however,andsincethecylinderblockisofiron,specialprovisionsmustbemadetomaintainproperpistonclearanceatoperatingtemperatures.Totakecareofit,thecrownismachinedonslighttaper,thediameterbeinggreatestwherethecrownmeetstheskirtandbecominglesstowardthetop.活塞体，即活塞顶部与活塞裙部交接处直径最大，愈向顶部，直径愈小。PistonRingsAgoodsealmustbemaintainedbetweenthepistonandcylinderwalltopreventblow-by.“Blow-by”isthenamethatdescribestheescapeofburnedgasesfromthecombustionchamber,pastthepiston,andintothecrankcase.Inotherwords,thesegases“blowby”thepiston.Itisnotpracticaltofitthepistontothecylindercloselyenoughtopreventblow-by.Thus,pistonringsmustbeusedtoprovidethenecessaryseal.Theringsareinstalledingroovesinthepiston.Actually,therearetwotypesofrings,compressionringsandoil-controlrings.Thecompressionringssealintheair-fuelmixtureasitiscompressedandalsothecombustionpressuresasthemixtureburns.Theoil-controlringsscrapeoffexcessiveoilfromthecylinderwallandreturnittotheoilpan.活塞环“漏气”这一名称是指生的压力不外溢。油环的作用是刮去气缸壁上多余的机油，使之流回油底壳。Theringshavejoints(theyaresplit)sothattheycanbeexpandedandslippedoverthepistonheadandintotherecessedgroovescutinthepiston.Ringsforautomotiveenginesusuallyhavebuttjoints,butinsomeheavy-dutyengines,thejointsmaybeangles,lapped,orofthesealedtype.活塞环有接口〔也就是有一缝隙。这样可以使端部扩张并滑入活塞上的凹口可以是斜角接口、搭接式或是密封式的。Theringsaresomewhatlargerindiameterthantheywillbewheninthecylinder.Then,whentheyareinstalled,theyarecompressessothatthejointsarenearlyclosed.Compressingtheringsgivesthemaninitialtension;theypresstightlyagainstthecylinderwall.在气缸壁上。ConnectingRodTheconnectingrodisattachedatoneendtoacrankpinonthecrankshaftandattheothertoapiston,throughapistonpinorwristpin.Theconnectingrodmustbeverystrongandrigidandalsoaslightaspossible.Theconnectingrodcarriesthepowerthrustsfromthepistontothecrankpin.Atthesametime,therodisineccentricmotion.Tominimizevibrationandbearingloads,therodmustbelightinweight.Tomaintaingoodenginebalance,connectingrodsandcapsarecarefullymatchedinsetsforengines.Allrodsinanenginemustbeofequalweight;iftheyarenot,noticeablevibrationmayresult.Inoriginalassembly,rodsandcapsareindividuallymatchedtoeachotherandusuallycarryidentifyingnumberssotheywillnotbemixediftheengineisdisassembledforservice.Theymustnotbemixedduringanyservicejob,sincethiscouldresultinpoorbearingfitandbearingfailure.连杆给连杆轴颈。同时，连杆做偏心运动。为了把振动和轴承负荷减小到最低限度，配套。发动机连杆的质量都必需相等，否则，就会产生明显的振动。在进展装套及轴承的损坏。WordsandExpressionscounterweight 平衡重；groove 凹槽；recess 凹口；lap 搭接；eccentric 心的；lowerhoodlines 低发动机罩；over-squareengine 短行程发动机；semi-slipperpiston 半裙式活塞；full-slipperpiston 全裙式活塞；matchinset配套；blow-by 漏气；initialtension 初张力；poorbearingfit 轴承不配套；bearingfailing 轴承故障。Crankshaft Flywheel曲轴飞轮CrankshaftThecrankshaftisaone-piececastingorforgingofheat-treatedalloysteelofconsiderablemechanicalstrength.Thecrankshaftmustbestrongenoughtotakethedownwardthrustsofthepistonsduringthepowerstrokeswithoutexcessivedistortion.Inaddition,thecrankshaftmustbecarefullybalancedtoeliminateunduevibrationresultingfromtheweightoftheoffsetcranks.Toprovidebalance,crankshaftshavecounterweightsoppositethecranks.Crankshaftshavedrilledoilpassagesthroughwhichoilcanflowfromthemaintotheconnecting-rodbearings.Thefrontendofthecrankshaftcarriesthreedevices,thegearorsprocketthatdrivesthecamshaft,thevibrationdamper,andthefanbeltpulley.Thepulleydrivestheenginefan,waterpump,andgeneratorwithaVbelt.曲轴凸轮轴的齿轮或链轮、减震器和风扇皮带轮。皮带轮通过V形皮带驱动发动机风扇，水泵和发电机。FlywheelTheflowofpowerfromtheenginecylindersisnotsmooth.Althoughthepowerimpulsesoverlap(onsix-andeight-cylinderengines),therearetimeswhenmorepowerisbeingdeliveredthanatothertimes.Thistendstomakethecrankshaftspeedupandthenslowdown.However,theflywheelcombatsthetendency.Theflywheelisacomparativelyheavywheelboltedtotherearendofthecrankshaft.Theinertiaoftheflywheeltendstokeepitturningatconstantspeed.Thus,theflywheelabsorbsenergyasthecrankshafttriestospeedupandgivesbackenergyasthecrankshafttriestoslowdown.Ineffect,theflywheelabsorbspowerfromtheengineduringthepowerstroke(orspeeduptime)andthengivesitbacktotheengineduringtheotherthreestrokes(orslowdowntime)ofthecycle.飞轮〔或加速过程〕中贮存动能，而在其它三个行程〔或减慢过程〕中，把动能释放出来。WordsandExpressionsforgingsprocket扣链齿〔链轮上与链条结合的齿〕damper减震器；flywheel飞轮；bolt螺栓；one-piece整体ValvesandValesTrain气门与气门传动组ValvesandValveTrainTherearetwoopenings,orports,intheenclosedendofthecylinder.Oneoftheportspermitsthemixtureofairandgasolinevaportoenterthecylinder.Theotherportpermitstheburnedgases,aftercombustion,toexhaust,orescape,fromthecylinder.Thetwoportshavevalvesassembledintothem.Thesevalvescloseoffoneortheotherport,orbothports,duringthevariousstagesofengineoperation.Thatistosay,eachcylinderhastwovalves,anintakevalveandexhaustvalve.Thecamlobesonthecamshaftaresorelatedtothecrankshaftcrankpinsthroughthegearorsprocketsandchainastocausethevalvestoopenandclosewiththecorrectrelationshiptothepistonstrokes.气门和气门机构〔或另一个开口门依据活塞行程的正确挨次开启和关闭。Thevalvesarenothingmorethanaccuratelymachinedmetalplugs(onlongstems)thatclosetheopeningswhentheyareseated(havemovedupintotheopenings).Whenthevalvecloses,itmovesupsothattheouteredgerestsontheseat.Inthisposition,thevalveportisclosedsothatairorgascannotescapefromthecylinder.〔向上移动阀口，即可将气门关闭。气门关闭时，气门向上移动，这样气门的边缘就正好落在气门座上。在这一位置上，气门口关闭，混合气就不会从气缸中逸出。Aspringonthevalvestemtendstoholdthevalveonitsseat(closed).Thelowerendofthespringrestsagainstthecylinderhead.Theupperendrestsagainstaflatwasher,orspringretainer,whichisattachedtothevalvestembyaretainerlock(alsocalledakeeper).Thespringisundercompression,whichmeansthatittriestoexpandandthereforespring-loadsthevalveintheclosedposition.气门杆上的弹簧使气门保持在气门座上〔关闭状态。弹簧的下端抵在气缸盖上。上端抵在弹簧座上，在弹簧座的下面用拴销〔或叫做定位销〕加以定位。压缩”Avalve-openingmechanismopensthevalve,orliftsitoffitsseat,atcertaintimes.Onmostengines,thismechanism,calledthevalvetrain,includesacamonthecamshaft,avalvelifter,apushrod,andarockerarm.Asthecamshaftturns,thecamlobecomesaroundunderthevalvelifter.Thisraisesthelifter,whichinturnpushesupwardonthepushrod.Thepushrod,asitislifted,causestheendoftherockerarmtomoveup.Therockerarmpivotsarounditssupportingshaftsothatthevalveenoftherockerarmisforceddownward.Thisdownwardmovementforcedthevalvetomovedownwardoffitsseatsothatitopens.Afterthecamlobemovesoutfromunderthevalvelifter,thevalvespringforcesthevalveupontoitsseatagain.回到气门座上。Intheotherkindofvalvemechanismforanengine,thevalvesarelocatedinthecylinderblockinsteadofthehead.Withthisarrangement,thecamshaftisdirectlybelowthevalvelifter,andnopushrodsorrockerarmsarenecessary.Althoughthevalve-in-block arrangement is a simple design, most automotive engines valve-in-headtype.Thevalve-in-headenginehascertainadvantages.有优点。CamandCamshaftAcamisadevicethatcanchangerotarymotionintolinear,orstraight-line,motion.Thecamhashighspot,orlobe;afollowerridingonthecamwillmoveawayfromortowardthecamshaftasthecamrotates.Intheengine,camsonthecamshaftcausetheintakeandexhaustvalvestoopen.Thereisacamonthecamshaftforeachvalve,ortwocamspercylinder.Thecamshaftisdrivenbygears,orbya