內(nèi)燃機專業(yè)英語教案

1內(nèi)燃機專業(yè)英語自編講義局部：一、教學(xué)內(nèi)容：在該局部內(nèi)容中主要表達內(nèi)燃機、汽油發(fā)動機、柴油發(fā)動機等的相關(guān)學(xué)問。包括：1.EngineClassificationandOverallMechanics，發(fā)動機的分類和總體構(gòu)造；2.Four-stage-engineOperation，四行程發(fā)動機工作過程；3.Two-stage-engineOperation，二行程發(fā)動機工作過程；4.DieselEngineOperatingFeatures，柴油發(fā)動機工作特點；5.EngineCylinderBlockCrankcase，發(fā)動機氣缸體曲軸箱；6.PistonConnectingRod，活塞連桿；7.CrankshaftFlywheel，曲軸飛輪；8.ValvesandValesTrain，氣門與氣門傳動組；9.EngineFuelSystem，發(fā)動機燃油系統(tǒng)；10.EngineLubricatingSystem，發(fā)動機潤滑系統(tǒng)；11.EngineCoolingSystem，發(fā)動機冷卻系統(tǒng)；12.EngineIgnitionSystem，EngineStarting二、教學(xué)時數(shù)：18學(xué)時。EngineClassificationandOverallMechanics〔1學(xué)時〕發(fā)動機的分類和總體構(gòu)造Four-stage-engineOperation〔1學(xué)時〕四行程發(fā)動機工作過程Two-stage-engineOperation〔1學(xué)時〕二行程發(fā)動機工作過程DieselEngineOperatingFeatures〔1學(xué)時〕柴油發(fā)動機工作特點EngineCylinder BlockCrankcase〔1學(xué)時〕發(fā)動機氣缸體 曲軸箱PistonConnectingRod〔1學(xué)時〕活塞 連桿Crankshaft Flywheel〔1學(xué)時〕曲軸飛輪氣門與氣門傳動組EngineFuelSystem〔1學(xué)時〕發(fā)動機燃油系統(tǒng)EngineLubricatingSystem〔1學(xué)時〕發(fā)動機潤滑系統(tǒng)EngineCoolingSystem〔1學(xué)時〕發(fā)動機冷卻系統(tǒng)EngineIgnitionSystem〔1學(xué)時〕發(fā)動機點火系統(tǒng)EngineStartingSystem〔1學(xué)時〕發(fā)動機起動系統(tǒng)Locomotives〔2學(xué)時〕機車DieselTraction〔3學(xué)時〕內(nèi)燃牽引三、教學(xué)難點與重點：重點內(nèi)容有：EngineClassificationandOverallMechanics，發(fā)動機的分類和總體構(gòu)造；2.Four-stage-engineOperation，四行程發(fā)動機工作過程；4.DieselEngineOperatingFeature5.EngineCylinderBlockCrankcase軸箱；7.CrankshaftFlywheel，曲軸飛輪；8.ValvesandValesTrain，氣門與氣門傳動組；9.EngineFuelSystem，發(fā)動機燃油系統(tǒng)；10.EngineLubricatingSystem，發(fā)動機潤11.EngineCoolingSystem，發(fā)動機冷卻系統(tǒng)；13.EngineStartingSystem，發(fā)動機起動系統(tǒng)；14.Locomotives，機車；15.DieselTraction，內(nèi)燃牽引。四、作業(yè)三篇翻譯10EngineClassificationandOverallMechanics發(fā)動機的分類和總體構(gòu)造Theautomobileenginescanbeclassifiedaccordingto:1.numberofcylinders;2.arrangementofcylinders;3.arrangementofvalves;4.typeofcooling;5.numberofcycles(twoorfour);6.typeoffuelburned;7.typeofignition.汽車發(fā)動機可以按以下幾種狀況分類：燃料分類；7．按點火方式分類。Theengineisthesourceofpowerthatmakesthewheelsgoaroundandthecarmove.Theautomobileengineisaninternal-combustionenginebecausethefuel(gasoline)isburnedinsideit.Theburningofgasolineinsidetheengineproduceshighpressureintheenginecombustionchamber.Thishighpressureforcespistontomove,themovementiscarriedbyconnectingrodstotheenginecrankshaft.Thecrankshaftisthusmadetorotate;therotarymotioniscarriedthroughthepowertraintothecarwheelssothattheyrotateandthemoves.〔汽油〕是在發(fā)動機內(nèi)燃燒的。汽油的燃燒在發(fā)動機燃燒室中產(chǎn)系統(tǒng)將發(fā)動機的轉(zhuǎn)動運動傳給汽車車輪，從而使車輪及整車轉(zhuǎn)動起來。Theenginerequiresafuelsystemtosupplyitwithamixtureofairandfuel.Thefuelsystemdoesthisbypumpingliquidgasolinefromatankintothecarburetor,amixingdevicethatmixesthegasolinewithair.Themixtureisdeliveredtotheenginewhereitisburned.抽出來，通過化油器--一種把汽油空氣進展混合的裝置--將可燃混合氣輸送到發(fā)動機，并在那里進展燃燒。Theenginealsoneedsacoolingsystem,thecombustionoftheair-fuelmixtureintheenginecreatesaveryhightemperature(ashighas2023to2700 ℃).Thecoolingsystemtakesheatawayfromtheenginebycirculatingaliquidcoolant(watermixedwithantifreeze)betweentheengineandaradiator.Thecoolantgetshotasitgoesthroughtheengine.Itcoolsoffasitgoesthroughtheradiator.Thus,thecoolantcontinuallytakesheatawayfromtheengine,whereitcoulddodamage,anddeliversittotheradiator.Airpassingthroughtheradiatortakesheatawayfromtheradiator.發(fā)動機還配備有冷卻系統(tǒng)，發(fā)動機內(nèi)部的混合氣燃燒會產(chǎn)生高溫〔2，，700℃。冷卻系統(tǒng)通過在發(fā)動機和散熱器之間流淌的液體冷卻液〔加了〕使發(fā)動機降溫。當(dāng)冷卻液流經(jīng)發(fā)動機時，冷卻液就會變熱。而流到空氣，將熱量從散熱器中帶走。Theenginealsoincludesalubricatingsystem.Thepurposeofthelubricatingsystemistosupplyallmovingpartsinsidetheenginewithlubricatingoil;theoilkeepsmovingpartsfromwearingexcessively.潤滑油。潤滑油可是運動零件免于過度磨損。Theenginerequiresafourthsystem,theignitionsystem.Theignitionsystemprovideshigh-voltageelectricsparksthatignite,orsetfireto,thechargesofair-fuelmixtureintheenginecombustionchambers.燃燒室中的可燃混合氣起燃。Thefifthisstartingsystemanditspurposeistochangetheelectricalcurrentintothemechanicalenergytopushthecrank-shaftaround.Bymeansofthis,theenginecanbestarted.動曲軸轉(zhuǎn)動。發(fā)動機借助這種方法啟動。Thesefivesystemsarediscussedbrieflyinfollowingsections.這五個系統(tǒng)將在以后的章節(jié)中具體爭論。WordsandExpressionscombustionchamberignition.powertrainantifreeze防凍的；coolant冷卻劑〔液態(tài)；crankshaft曲軸Four-stage-engineOperation四行程發(fā)動機工作過程Theactiontakingplaceintheenginecylindercanbedividedintofourstages,orstrokes.“Strokeferstopistonmovement;asstrokeoccurswhenthepistonmovesfromonelimitingpositiontotheother.TheupperlimitofpistonmovementiscalledTDC〔topdeadcenter〕.ThelowerlimitofpistonmovementiscalledBDC(bottomdeadcenter).AstrokeispistonmovementfromTDCtoBDCorfromBDCtoTDC.Inotherwords,thepistoncompletesastrokeeachtimeitchangeitsdirectionofmotion.TDC〔上止點BD〔下止點。一個行程就是活塞從上止點到下次其運動的方向。Wheretheentirecycleofeventsinthecylinderrequiresfourstrokes(ortwocrankshaftrevolutions),theengineiscalledafour-stroke-cycleengine,orafour-cycleengine.Thefourpistonstrokesareintake,compression,power,andexhaust.發(fā)動機氣缸中的全部工作過程分為四個行程的〔或者曲軸旋轉(zhuǎn)兩周的，叫排氣。Intakestroke.Ontheintakestroke,theintakevalvehasopened,thepistonismovingdownward,andamixtureofairandvaporizedgasolineisenteringthecylinderthroughthevalveport.Themixtureofairandvaporizedgasolineisdeliveredtothecylinderbythefuelsystemandcarburetor.進氣行程：在進氣行程中，進氣門翻開，活塞向下移動，可燃混合氣通過進氣門進入氣缸。適當(dāng)濃度可燃混合氣是由燃料系統(tǒng)和化油器供給的。Compressionstroke.AfterthepistonreachesBDC,orthelowerlimitofitstravel,itbeginstomoveupward.Asthishappens,theintakevalvecloses.Theexhaustvalveisalsoclosed,sothatthecylinderissealed.Asthepistonmovesupward(pushednowbytherevolvingcrankshaftandconnectingrod),theair-fuelmixtureiscompressed.BythetimethepistonreachesTDC,themixturehasbeencompressedtoaslittleasone-tenthofitsoriginalvolume,orevenless.Thiscompressionoftheair-fuelmixtureincreasesthepressureinthecylinder.Whenthe air-fuelmixtureiscompressed,notonlydoesthepressureinthecylindergoup,butthetemperatureofthemixturealsoincreases.時〔這是由轉(zhuǎn)動的曲軸和連桿推動活塞，可燃混合氣被壓縮。當(dāng)活塞到達上止料被壓縮時，不僅氣缸里的壓力上升，可燃混合氣的溫度也隨之增加了。Powerstroke.AsthepistonreachesTDConthecompressionstroke,anelectricsparkisproducedatthesparkplug.Theignitionsystemdeliversahigh-voltagesurgeofelectricitytothesparkplugtoproducethespark.Thesparkignites,orsetsfireto,theair-fuelmixture.Itnowbeginstoburnveryrapidly,andthecylinderpressureincreasestoasmuchas3-5MPaorevenmore.Thisterrificpushagainstthepistonforcesitdownward,andapowerimpulseistransmittedthroughtheconnectingrodtothecrankpinonthecrankshaft.Thecrankshaftisrotatedasthepistonispusheddownbythepressureaboveit.合氣開頭發(fā)生猛烈燃燒，氣缸內(nèi)壓力到達3-5兆帕，甚至更高。作用于活塞上強上。因此，當(dāng)活塞受壓向下運動時，推動曲軸轉(zhuǎn)動。Exhauststroke.AsthepistonreachesBDCagain,theexhaustvalveopens.Now,asthepistonmovesupontheexhauststroke,itforcestheburnedgasesoutofthecylinderthroughtheexhaust-valveport.Then,whenthepistonreachesTDC,theexhaustvalveclosesandtheintakevalveopens.Now,afreshchargeofair-fuelmixturewillbedrawnintothecylinderasthepistonmovesdownagaintowardBDC.Theabovefourstrokesarecontinuouslyrepeated.把廢氣經(jīng)排氣門排出氣缸。隨后活塞到達上止點，排氣門關(guān)閉，進氣門翻開。當(dāng)程又連續(xù)重復(fù)。WordsandExpressionsstroke行程，沖程；BDC 上止點；TDC 下止點；surge 了不起的，絕妙的；crankpin 曲柄銷，連桿軸頸；intakestroke 吸氣沖程；compressionstroke 壓縮沖程；powerstroke 做功沖程；exhauststroke 程；freshcharge 〔發(fā)動機〕吸入的穎混合油氣Two-stage-engineOperation二行程發(fā)動機工作過程Inthefour-stroke-cycleengine,alreadydiscussedinlesson1 、2,thecompletecycleofeventsrequiresfourpistonstrokes(intake,compression,power,andexhaust).Inthetwo-stroke-cycle,ortwo-cycle,engine,theintakeandcompressionstrokesandpowerandexhauststrokesareinasensecombined.Thispermitstheenginetoproduceapowerstrokeeverytwopistonstrokes,oreverycrankshaftrotation.成一次工作循環(huán)。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.動活塞向下運動，通過連桿，推動曲軸轉(zhuǎn)動。當(dāng)活塞接近下止點時，經(jīng)過氣缸壁口排出。AfterthepistonhaspassedthroughBDCandstarsupagain,itpassesbothports,thussealingthemoff.Nowthefreshair-fuelchargeabovethepistoniscompressedandignited.Thesameseriesofeventstakesplaceagainandcontinueaslongastheengineruns.會反復(fù)不斷地發(fā)生。Wementionedthattheair-fuelmixtureisdeliveredtothecylinderunderpressure.Inmostengines,thispressureisputonthemixtureinthecrankcase.Thecrankcaseissealedexceptforaleaf,orreed,valveatthebottom.Thereedvalveisaflexible,flatmetalplatethatrestssnuglyagainstthefloorofthecrankcase.Thereareholesunderthereedvalvethatconnecttotheenginecarburetor.Whenthepistonismovingup,apartialvacuumisproducedinthesealedcrankcase.Atmosphericpressureliftsthereedvalveofftheholes,andair-fuelmixtureentersthecrankcase.AfterthepistonpassesTDCandstartsdownagain,pressurebeginstobuildupinthecrankcase.Thispressureclosesthereedvalvesothatfurtherdownwardmovementofthepistoncompressesthetappedair-fuelmixtureinthecrankcase.Thepressurewhichisbuiltupontheair-fuelmixturethencausesittoflowupthroughtheintakeportintotheenginecylinderwhenthepistonmovesdownfarenoughtocleartheintakeport.〔片簧閥〕之外，曲軸箱是密封的。片出進氣口，可燃混合氣所具有的壓力使其上升，通過進氣口進入氣缸。Thetwo-strokeengineisnotonlyverysimplebutgivesnearlytwicethepowerofafourstrokeenginefromacylinderofgivensize,butitiswastefulofgasoline,assomemixtureinevitablyfindsitswayintotheexhaustsystemonthecombinesintake/exhauststroke,andtherearealwayssomecombustionproductsleftinthecylinderwhichreducetherapidburningofthefuel.Thiskindofengineisalwaysusedinmotorcycles.行程發(fā)動機耗油較大。通常使用在摩托車上。WordsandExpressionssweep 掃氣；connectingrod 連桿；crankcase 曲軸箱；sealoff 密封；leaf〔reed〕valve 片簧閥；air-fuelcharge 可燃混合油氣DieselEngineOperatingFeatures柴油發(fā)動機工作特點Weallknowthatdieselengines,inprinciple,workinthesamewayasgasolineenginesdo.Bothkindsofenginesareinternal-combustionengines,buteachofthemhasitscharacteristicfeatures.Astheirnamessuggestthistypeofenginesburntheirpartsoftheengines.“Internal”means“inside”,“combustion”means“catchingfireorburning”.Inanyinternalcombustionengine,burningfuelheatsairwhichconsequentlyexpands,andinexpandingexistsapushtoapistonwhich,inturn,rotatestheenginecrankshaftthroughaconnectingrod.我們都知道柴油機和汽油機的工作原理是一樣的。這兩種發(fā)動機都是內(nèi)燃燃料是在發(fā)動機工作部件的內(nèi)部燃燒的?！癷nternal”意思是“內(nèi)部”，“combustion””。在任何內(nèi)燃機中，燃燒的燃料使空氣受熱并快速膨脹，產(chǎn)生推力推動活塞，通過連桿推動發(fā)動機的曲軸。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。一般來說，柴油機比質(zhì)量約為9.25公斤每千瓦。汽油機最重要的優(yōu)點是每千瓦的質(zhì)量較輕。汽車用汽油發(fā)動機比質(zhì)量為6.17公斤每千瓦，而飛機用汽油發(fā)動機的比質(zhì)量小到0.77公斤每千瓦。汽油機的這一優(yōu)點使柴油機無法代替某些汽車以及飛機上使用的汽油發(fā)動機。However,thedieselengineismoreefficient,becauseithashighercompressionration.Itsratiomaybeashighas16to1.Upto40percentofthechemicalenergyoftheburningfuelmaybechangedintomechanicalenergy.Inaddition,thedieselenginerunscoolerthanthegasolineengine.Thisadvantageisespeciallyobviousatlowerspeeds.Dieseloilisnotonlycheaperthangasoline,butalsosafertostore.但是，柴油發(fā)動機的效率更高些，由于柴油機具有較高的壓縮比—161。宜，而且貯存更為安全。WordsandExpressionsdiesel：柴油機；internal-combustionengines：內(nèi)燃機；jerkpump：脈動史噴油泵；compressionration：壓縮比EngineCylinder BlockCrankcase發(fā)動機氣缸體 曲軸箱Wehaveseenhowthemixtureofairandfuelisdeliveredbythefuelsystemtotheenginecylinder,whereitiscompressed,ignited,andburned.Wehavenotedthatthiscombustionproducesahighpressurethatpushesthepistondownsothatthecrankshaftisrotated.Nowletusexaminethevariouspartsoftheengineindetail.動曲軸轉(zhuǎn)動。現(xiàn)在讓我們具體爭論一下發(fā)動機的各局部構(gòu)造。EnginecylinderblockThecylinderblockofliquid-cooledenginesformsthebasicframeworkoftheengine.Otherpartsareattachedtothecylinderblockorareassembledinit.Theblockiscastinonepiecefromgrayironorironalloyedwithothermetals,suchasnickelorchromium.Someblocksarecastfromaluminum.Theblockcontainsnotonlythecylindersbutalsothewaterjacketsthatsurroundthem.Inaluminumblocks,cast-ironorsteelcylindersleeves(alsocalledborelines)areused.Thesemetalshavebetterwearingqualitiesthanaluminum andcanbetterwithstandthewearingeffect ofthepistonsandringmovingupanddowninthecylinders.Formostengines,castironhasbeenfoundtobeasatisfactorycylinder-wallmaterial.However,insomesmallengines,thecylinderwallsareplatedwithchromium,averyhardmetal,toreducewallwearandlengthentheirlife.發(fā)動機氣缸體水冷發(fā)動機的氣缸體是發(fā)動機的根本構(gòu)件，其它部件都支承或安裝在它上鐵或鋼制的氣缸套〔或稱之為氣缸襯套。這類金屬的耐磨性比鋁更好，能更好種格外耐磨的金屬，可削減氣缸壁的磨損并延長使用壽命。CylinderHeadThecylinderheadisusuallycastinonepiecefromiron,fromironalloyedwithothermetals,orfromaluminumalloy.Aluminumhastheadvantageofcombininglightnesswithhighheatconductivity.Thatis,analuminumheadtendstoturncooler,otherfactorsbeingequal.Therearetwotypesofhead,LheadandIhead.Cylinderheadcontainswaterjacketsforcooling;intheassembledengine,thesewaterjacketsareconnectedthroughopeningstothecylinder-blockwaterjackets.Spark-plugholesareprovided,alongwithpocketsintowhichthevalvescanmoveastheyopen.氣缸蓋就是說，其它因素一樣時，鋁蓋更簡潔冷卻。有兩種氣缸，LI型氣缸氣缸蓋上留有火花塞口和凹槽，凹槽使氣門翻開時可以移動。GasketsThejointbetweenthecylinderblockandtheheadmustbetightandabletowithstandthepressureandheatdevelopedinthecombustionchambers.Theblockandheadcannotbemachinedflatandsmoothenoughtoprovideanadequateseal.Thus,gasketsareused.Headgasketsaremadeofthinsheetsofsoftmetalorasbestosandmetal.Allcylinder,water,valve,andhead-boltopeningsarecutout.Whenthegasketisplacedontheblockandtheheadinstalled,tighteningoftheheadbolts(ornuts)squeezesthesoftmetalsothatthejointiseffectivelysealed.Gasketsarealsousedtosealjointsbetweenotherparts,suchasbetweentheoilpan,manifolds,orwaterpumpandtheblock.氣缸墊體之間的密封。OilPanTheoilpanisusuallyformedofpressedsteel.Itusuallyholds5to10litresofoil,dependingontheenginedesign.Theoilpanandthelowerpartofthecylinderblocktogetherarecalledthecrankcase;theyenclose,orencase,thecrankshaft.Theoilpumpinthelubricatingsystemdrawsoilfromtheoilpanandsendsittoallworkingpartsintheengine.Theoildrainsoffandrunsdownintothepan.Thus,thereisconstantcirculationofoilbetweenthepanandtheworkingpartsoftheengine.油盤510升盤。這樣，機油就在和發(fā)動機的各個部件之間不斷循環(huán)流淌。WordsandExpressionscylinderblockblockcrankcaseframework構(gòu)造，車架；grayiron灰鑄鐵；waterjacketplate…with鍍金屬；cylindergasketsasbestosmanifoldoilpan油盤；pocket凹槽；boreliner氣缸襯套Piston ConnectingRod活塞 連桿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.活塞體，即活塞頂部與活塞裙部交接處直徑最大，愈向頂部，直徑愈小。PistonRingsAgoodsealmustbemaintainedbetweenthepistonandcylinderwalltopreventblow-by.“Blow-by”isthenamethatdescribestheescapeofburnedgasesfromthecombustionchamber,pastthepiston,andintothecrankcase.Inotherwords,thesegases“blowby”thepiston.Itisnotpracticaltofitthepistontothecylindercloselyenoughtopreventblow-by.Thus,pistonringsmustbeusedtoprovidethenecessaryseal.Theringsareinstalledingroovesinthepiston.Actually,therearetwotypesofrings,compressionringsandoil-controlrings.Thecompressionringssealintheair-fuelmixtureasitiscompressedandalsothecombustionpressuresasthemixtureburns.Theoil-controlringsscrapeoffexcessiveoilfromthecylinderwallandreturnittotheoilpan.活塞環(huán)“漏氣”這一名稱是指生的壓力不外溢。油環(huán)的作用是刮去氣缸壁上多余的機油，使之流回油底殼。Theringshavejoints(theyaresplit)sothattheycanbeexpandedandslippedoverthepistonheadandintotherecessedgroovescutinthepiston.Ringsforautomotiveenginesusuallyhavebuttjoints,butinsomeheavy-dutyengines,thejointsmaybeangles,lapped,orofthesealedtype.活塞環(huán)有接口〔也就是有一縫隙。這樣可以使端部擴張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.在氣缸壁上。ConnectingRodTheconnectingrodisattachedatoneendtoacrankpinonthecrankshaftandattheothertoapiston,throughapistonpinorwristpin.Theconnectingrodmustbeverystrongandrigidandalsoaslightaspossible.Theconnectingrodcarriesthepowerthrustsfromthepistontothecrankpin.Atthesametime,therodisineccentricmotion.Tominimizevibrationandbearingloads,therodmustbelightinweight.Tomaintaingoodenginebalance,connectingrodsandcapsarecarefullymatchedinsetsforengines.Allrodsinanenginemustbeofequalweight;iftheyarenot,noticeablevibrationmayresult.Inoriginalassembly,rodsandcapsareindividuallymatchedtoeachotherandusuallycarryidentifyingnumberssotheywillnotbemixediftheengineisdisassembledforservice.Theymustnotbemixedduringanyservicejob,sincethiscouldresultinpoorbearingfitandbearingfailure.連桿給連桿軸頸。同時，連桿做偏心運動。為了把振動和軸承負(fù)荷減小到最低限度，配套。發(fā)動機連桿的質(zhì)量都必需相等，否則，就會產(chǎn)生明顯的振動。在進展裝套及軸承的損壞。WordsandExpressionscounterweight 平衡重；groove 凹槽；recess 凹口；lap 搭接；eccentric 心的；lowerhoodlines 低發(fā)動機罩；over-squareengine 短行程發(fā)動機；semi-slipperpiston 半裙式活塞；full-slipperpiston 全裙式活塞；matchinset配套；blow-by 漏氣；initialtension 初張力；poorbearingfit 軸承不配套；bearingfailing 軸承故障。Crankshaft Flywheel曲軸飛輪CrankshaftThecrankshaftisaone-piececastingorforgingofheat-treatedalloysteelofconsiderablemechanicalstrength.Thecrankshaftmustbestrongenoughtotakethedownwardthrustsofthepistonsduringthepowerstrokeswithoutexcessivedistortion.Inaddition,thecrankshaftmustbecarefullybalancedtoeliminateunduevibrationresultingfromtheweightoftheoffsetcranks.Toprovidebalance,crankshaftshavecounterweightsoppositethecranks.Crankshaftshavedrilledoilpassagesthroughwhichoilcanflowfromthemaintotheconnecting-rodbearings.Thefrontendofthecrankshaftcarriesthreedevices,thegearorsprocketthatdrivesthecamshaft,thevibrationdamper,andthefanbeltpulley.Thepulleydrivestheenginefan,waterpump,andgeneratorwithaVbelt.曲軸凸輪軸的齒輪或鏈輪、減震器和風(fēng)扇皮帶輪。皮帶輪通過V形皮帶驅(qū)動發(fā)動機風(fēng)扇，水泵和發(fā)電機。FlywheelTheflowofpowerfromtheenginecylindersisnotsmooth.Althoughthepowerimpulsesoverlap(onsix-andeight-cylinderengines),therearetimeswhenmorepowerisbeingdeliveredthanatothertimes.Thistendstomakethecrankshaftspeedupandthenslowdown.However,theflywheelcombatsthetendency.Theflywheelisacomparativelyheavywheelboltedtotherearendofthecrankshaft.Theinertiaoftheflywheeltendstokeepitturningatconstantspeed.Thus,theflywheelabsorbsenergyasthecrankshafttriestospeedupandgivesbackenergyasthecrankshafttriestoslowdown.Ineffect,theflywheelabsorbspowerfromtheengineduringthepowerstroke(orspeeduptime)andthengivesitbacktotheengineduringtheotherthreestrokes(orslowdowntime)ofthecycle.飛輪〔或加速過程〕中貯存動能，而在其它三個行程〔或減慢過程〕中，把動能釋放出來。WordsandExpressionsforgingsprocket扣鏈齒〔鏈輪上與鏈條結(jié)合的齒〕damper減震器；flywheel飛輪；bolt螺栓；one-piece整體ValvesandValesTrain氣門與氣門傳動組ValvesandValveTrainTherearetwoopenings,orports,intheenclosedendofthecylinder.Oneoftheportspermitsthemixtureofairandgasolinevaportoenterthecylinder.Theotherportpermitstheburnedgases,aftercombustion,toexhaust,orescape,fromthecylinder.Thetwoportshavevalvesassembledintothem.Thesevalvescloseoffoneortheotherport,orbothports,duringthevariousstagesofengineoperation.Thatistosay,eachcylinderhastwovalves,anintakevalveandexhaustvalve.Thecamlobesonthecamshaftaresorelatedtothecrankshaftcrankpinsthroughthegearorsprocketsandchainastocausethevalvestoopenandclosewiththecorrectrelationshiptothepistonstrokes.氣門和氣門機構(gòu)〔或另一個開口門依據(jù)活塞行程的正確挨次開啟和關(guān)閉。Thevalvesarenothingmorethanaccuratelymachinedmetalplugs(onlongstems)thatclosetheopeningswhentheyareseated(havemovedupintotheopenings).Whenthevalvecloses,itmovesupsothattheouteredgerestsontheseat.Inthisposition,thevalveportisclosedsothatairorgascannotescapefromthecylinder.〔向上移動閥口，即可將氣門關(guān)閉。氣門關(guān)閉時，氣門向上移動，這樣氣門的邊緣就正好落在氣門座上。在這一位置上，氣門口關(guān)閉，混合氣就不會從氣缸中逸出。Aspringonthevalvestemtendstoholdthevalveonitsseat(closed).Thelowerendofthespringrestsagainstthecylinderhead.Theupperendrestsagainstaflatwasher,orspringretainer,whichisattachedtothevalvestembyaretainerlock(alsocalledakeeper).Thespringisundercompression,whichmeansthatittriestoexpandandthereforespring-loadsthevalveintheclosedposition.氣門桿上的彈簧使氣門保持在氣門座上〔關(guān)閉狀態(tài)。彈簧的下端抵在氣缸蓋上。上端抵在彈簧座上，在彈簧座的下面用拴銷〔或叫做定位銷〕加以定位。壓縮”Avalve-openingmechanismopensthevalve,orliftsitoffitsseat,atcertaintimes.Onmostengines,thismechanism,calledthevalvetrain,includesacamonthecamshaft,avalvelifter,apushrod,andarockerarm.Asthecamshaftturns,thecamlobecomesaroundunderthevalvelifter.Thisraisesthelifter,whichinturnpushesupwardonthepushrod.Thepushrod,asitislifted,causestheendoftherockerarmtomoveup.Therockerarmpivotsarounditssupportingshaftsothatthevalveenoftherockerarmisforceddownward.Thisdownwardmovementforcedthevalvetomovedownwardoffitsseatsothatitopens.Afterthecamlobemovesoutfromunderthevalvelifter,thevalvespringforcesthevalveupontoitsseatagain.回到氣門座上。Intheotherkindofvalvemechanismforanengine,thevalvesarelocatedinthecylinderblockinsteadofthehead.Withthisarrangement,thecamshaftisdirectlybelowthevalvelifter,andnopushrodsorrockerarmsarenecessary.Althoughthevalve-in-block arrangement is a simple design, most automotive engines valve-in-headtype.Thevalve-in-headenginehascertainadvantages.有優(yōu)點。CamandCamshaftAcamisadevicethatcanchangerotarymotionintolinear,orstraight-line,motion.Thecamhashighspot,orlobe;afollowerridingonthecamwillmoveawayfromortowardthecamshaftasthecamrotates.Intheengine,camsonthecamshaftcausetheintakeandexhaustvalvestoopen.Thereisacamonthecamshaftforeachvalve,ortwocamspercylinder.Thecamshaftisdrivenbygears,orbya