汽車發動機外文翻譯文獻（文檔含中英文對照即英文原文和中文翻譯）AUTOMOTIVEENGINElEngineClassificationandOverallMechanicsTheautomobileenginescanbeclassifiedaccordingto:(1)cycles,(2)coolingsystem,(3)fuelsystem,(4)ignitionmethod,(5)valvearrangement,(6)cylinderarrangement,(7)enginespeed.Enginesusedinautomobilesaretheinternalcombustionheatengines.Theburningofgasolineinsidetheengineproduceshighpressureintheenginecombustionchamber.Thishighpressureforcepistontomove,themovementiscarriedbyconnectingrodstotheenginecrankshaft.Thecrankshaftisthusmadetorotate:therotarymotioniscarriedthroughthepowertraintothecarwheelssothattheyrotateandthecarmoves.Theenginerequiresfourbasicsystemstorun(Fig.2-1).Dieselenginesrequire threeofthesesystems.Theyarefuelsystem,ignitionsystem(exceptdiesel),lubricatingsystemandcoolingsystem.However,threeotherrelatedsystemsarealsonecessary.Thesearetheexhaustsystem,theemission-controlsystem,andthestartingsystem.Eachperformsabasicjobinmakingtheenginerun.Fig.2-1Theengineconstruction2EngineOperatingPrinciplesIS— 盤L3USvalveTheengineconstruction2EngineOperatingPrinciplesIS— 盤L3USvalvepistonCTflljkFig.2-2EnginetermsTheterm“stroke”uiedtodescribethemovementofthepistonwithinthecylinder.Themovementofthepistonfromitsuppermostposition(TDC,topdeadcenter)toitslowestposition(BDC,bottomdeadcenter)iscalledastroke.Theoperatingcyclemayrequireeithertwoorfourstrokestocomplete.Mostautomobileenginesoperateonthefourstrokecycle(Fig.2-2).Infour-strokeengine,fourstrokesofthepistoninthecylinderarerequiredtocompleteonefulloperatingcycle.Eachstrokeisnamedaftertheaction.Itperformsintake,compression,power,andexhaustinthatorder(Fig.2-3).Intakestroke CompressionstrokePowerstroke ExhauststrokeFig.2-3Four-stroke-cyclegasolineengineTheintakestrokeTheintakestrokebeginswiththepistonnearthetopofitstravel.Asthepistonbeginsitsdescent,theexhaustvalveclosesfully,theintakevalveopensandthevolumeofthecombustionchamberbeginstoincrease,creatingavacuum.Asthepistondescends,anair/fuelmixtureisdrawnfromthecarburetorintothecylinder throughtheintakemanifold.Theintakestrokeendswiththeintakevalveclosejustafterthepistonhasbegunitsupstroke.CompressionstrokeAsthepistonismovedupbythecrankshaftfromBDC,theintakevalvecloses.Theair/fuelmixtureistrappedinthecylinderabovethepiston.Futurepistontravelcompressestheair/fuelmixturetoapproximatelyone-eighthofitsoriginalvolume(approximately8:1compressionratio)whenthepistonhasreachedTDC.Thiscompletesthecompressionstroke.PowerstrokeAsthepistonreachesTDConthecompressionstroke,anelectricsparkisproducedatthesparkplug.Theignitionsystemdeliversahigh-voltagesurgeofelectricitytothesparkplugtoproducethespark.Thesparkignites,orsetsfireto,theair/fuelmixture.Itnowbeginstoburnveryrapidly,andthecylinderpressureincreasestoasmuchas3-5MPaorevenmore.Thisterrificpushagainstthepistonforcesitdownward,andapowerfulimpulseistransmittedthroughtheconnectingrodtothecrankpinonthecrankshaft.Thecrankshaftisrotatedasthepistonispusheddownbythepressureaboveit.ExhauststrokeAttheendofthepowerstrokethecamshaftopenstheexhaustvalve,andtheexhauststrokebegins.Remainingpressureinthecylinder,andupwardmovementof thepiston,forcetheexhaustgasesoutofthecylinder.Attheendoftheexhauststroke,theexhaustvalveclosesandtheintakevalveopens,repeatingtheentirecycleofeventsoverandoveragain.EngineBlockandCylinderHeadEngineBlockTheengineblockisthebasicframeoftheengine.Allotherenginepartseitherfitinsideitorfastentoit.Itholdsthecylinders,waterjacketsandoilgalleries(Fig.2-4).Theengineblockalsoholdsthecrankshaft,whichfastenstothebottomoftheblock.Thecamshaftalsofitsintheblock,exceptonoverhead-camengines.Inmostcars,thisblockismadeofgrayiron,oranalloy(mixture)ofgrayironandothermetals,suchasnickelorchromium.Engineblocksarecastings.Fig.2-4V6engineblockSomeengineblocks,especiallythoseinsmallercars,aremadeofcastaluminum.Thismetalismuchlighterthaniron.However,ironwearsbetterthanaluminum.Therefore,thecylindersinmostaluminumenginesarelinedwithironorsteelsleeves.Thesesleevesarecalledcylindersleeves.Someengineblocksaremadeentirelyofaluminum.CylinderSleevesCylindersleevesareusedinengineblockstoprovideahardwearingmaterialforpistonsandpistonrings.Theblockcanbemadeofonekindofironthatislightandeasytocastwhilethesleevesusesanotherthatisbetterabletostandupwearandtear.Therearetwomaintypesofsleemaintypesofsleeves:dryandwet(Fig.2-5).DrysleeveWetsleeveFig.2-5CylindersleeveCylinderHeadThecylinderheadfastenstothetopoftheblock,justasarooffitsoverahouse.Theundersideformsthecombustionchamberwiththetopof thepiston. Inlineengineoflightvehicleshavejustonecylinderheadforallcylinders;largerin-lineenginescanhavetwoormore.Just aswithengineblocks,cylinderheads canbemadeofcastironoraluminumalloy.Thecylinderheadcarriesthevalves,valvespringsandtherockersontherockershaft, thispartofvalvegearbeingworkedbythepushrods.Sometimesthecamshaftisfitteddirectlyintothecylinderheadandoperatesonthevalveswithoutrockers.Thisiscalledanoverheadcamshaftarrangement.GasketThecylinderheadisattachedtotheblockwithhigh-tensilesteelstuds.Thejointbetweentheblockandtheheadmustbegas-tightsothatnoneoftheburningmixturecanescape.Thisisachievedbyusingcylinderheadgasket.Gasketsarealsousedtosealjoinsbetweentheotherparts,suchasbetweentheoilpan,manifolds,orwaterpumpandtheblocks.OilPanTheoilpanisusuallyformedofpressedsteel.Theoilpanandthelowerpartofcylinderblocktogetherarecalledthecrankcase;theyenclose,orencase,the

crankshaft.Theoilpumpinthelubricatingsystemdrawsoilfromtheoilpanandsendsittoallworkingpartsintheengine.Theoildrainsoffandrundownintothe pan.Thus,thereisaconstantcirculationofoilbetweenthepanandtheworkingpartsoftheengine.PistonAssembly,pistonrings,Thepistonpin,ConnectingRods,CrankshaftsAndFlywheelPistonPistonringsandthepistonpinaretogethercalledthepistonassembly(Fig.2-6).Fig.2-6Piston,pistonringsandconnectingrodFig.2-6Piston,pistonringsandconnectingrodThepistonisanimportantpartofafour-strokecycleengine.Mostpistonsaremadefromcastaluminum.Thepiston,throughtheconnectingrod,transferstothecrankshafttheforcecreatedbytheburningfuelmixture.Thisforceturnsthecrankshaft.Towithstandtheheatofthecombustionchamber,thepistonmustbestrong.Italsomustbelight,sinceittravelsathighspeedsasitmovesupanddowninsidethecylinder.Thepistonishollow.Itisthickatthetopwhereittakesthebruntoftheheatandtheexpansionforce.Itisthinatthebottom,wherethereislessheat.Thetoppartofthepistonisthehead,orcrown.Thethinpartistheskirt.Mostpistonshavethreeringgroovesatthetop.Thesectionsbetweentheringgroovesarecalledringlands.pistonringspistonringsfitintoringgroovesnearthetopofthepiston.Insimplestterms,pistonInringsarethin,circularpiecesofmetalthatfitintogroovesinthetopsofthepistons.Inmodernengines,eachpistonhasthreerings.(Pistoninolderenginessometimeshadfourrings,orevenfive.)Theinsidesurfaceoftheringfitsinthegrooveonthepiston.Thering'soutsidesurfacepressesagainstthecylinderwalls.Ringsprovidetheneededsealbetweenthepistonandthecylinder walls.Thatis,onlytheringscontactthecylinderwalls.Thetoptworingsareto keepthegasesinthecylinderandarecalledcompressionrings.Theloweronepreventstheoilsplashedontothecylinderborefromenteringthecombustionchamber,andiscalledanoilring.ThepistonpinThepistonpinholdstogetherthepistonandtheconnectingrod.Thispinfitsintothepistonpinholesandintoaholeinthetopendoftheconnectingrod.Thetopendoftherodismuchsmallerthantheendthatfitsonthecrankshaft.Thissmallendfitsinsidethebottomofthepiston.Thepistonpinfitsthroughonesideofthepiston,throughthesmallendoftherod,andthenthroughtheothersideofthepiston.Itholdstherodfirmlyinplaceinthecenterofthepiston.Pinsaremadeofhigh-strengthsteelandhaveahollowcenter.Manypinsarechrome-platedtohelpthemwearbetter.Apistonpinfitsintoaroundholeinthepiston.Thepistonpinjoinsthepistontotheconnectingrod.Thethickpartofthepistonthatholdsthepistonpinisthepinboss.ConnectingRodsTheconnectingrodlittleendisconnectedtothepistonpin.Abushmadefromasoftmetal,suchasbronze,isusedforthisjoint.Thelowerendoftheconnectingrodfitsthecrankshaftjournal.Thisiscalledthebigend.Forthisbig-endbearing,steel-backedleadortinshellbearingsareused.Thesearethesameasthoseusedforthemainbearings.Thesplitofthebigendissometimesatanangle,sothatitissmallenoughtobewithdrawnthroughthecylinderbore.Theconnectingrodismadefromforgedalloysteel.CrankshaftsThecrankshaftisregardedasthe“backbone%ftheengine(Fig.2-7).Thecrankshaft,inconjunctionwiththeconnectingrod,convertsthereciprocatingmotionofthepistontotherotarymotionneededtodrivethevehicle.Itisusuallymadefromcar-bonsteelwhichisalloyedwithasmallproportionofnickel.Themainbearingjournalsfitintothecylinderblockandthebigendjournalsalignwiththeconnectingrods.Attherearendofthecrankshaftisattachedtheflywheel,andatthefrontendarethedrivingwheelsforthetiminggears,fan,coolingwaterandalternator.Thethrowofthecrankshaft,i.e.thedistancebetweenthemainjournalandthebigendcenters,c

ontrolsthelengthofthestroke.Thestrokeisdoublethethrow,andthestrokelengthisthedistancethatthepistontravelsfromTDCtoBDCandviceversa.Fig.2-7ThecrankshaftFlywheelTheflywheelismadefromcarbonsteel.Itfitsontotherearofthecrankshaft.Aswellaskeepingtheenginerotatingbetweenpowerstrokesitalsocarriestheclutch,whichtransmitsthedrivetothegearbox,andhasthestarterringgeararounditscircumference.Thereisonlyoneworkingstrokeinfoursoaflywheelisneededtodrivethecrankshaftduringthetimethattheengineisperformingthenon-powerstrokes.ValveSystemBearings-Fig.2-8PartsofthevalvetrainThevalveoperatingassemblyincludestheliftersorcamfoilowers,pushrods,rockerarmsandshaftsorpivot,valveandspringsetc.Thepurposeofthistoopenandclosetheintakeandexhaustportsthatleadtothecombustionchambersasrequired(Fig.28).Valvemechanismsvarydependingonthecamshaftlocation.Whenthecamshaftispositionedintheengineblock,valveliftersaremountedintheopeningsabove thecamshaft.Pushrodsareconnectedfromeachvalveliftertoapivotedrockerarmmountedaboveeachvalve.Alobeonthecamshaftispositioneddirectlybeloweachvalvelifter.Atypicalcamshaftdrive has asprocket bolted to the endofthecamshaft,andamatchingsprocketisattachedtotheendofthecrankshaft.Thosetwosprockets maybemeshed togetheror surroundeda steel chain to havethecamshaftdrive.Whenthelowerpartofthecamshaftlobeisrotatingunderthevalvelifter,thevalvespringholdsthevalveclosed.汽車發動機1發動機的分類和整體力學汽車發動機可根據如下因素進行分類：10循環系統，（2）冷卻系統，（3）燃油系統，（4）點火方式，（5）氣門布置，（6）氣缸排列，（7）發動機轉速。用于汽車的發動機是內燃機。汽油在發動機內部燃燒，產生的高壓力使活塞移動，這一運動通過連桿傳遞到曲軸，使它旋轉。動力通過動力總成傳遞到車輪，從而帶動汽車前進。發動機需要四個基本系統來運行（圖2-1）。柴油發動機需要其中的三個基本系統來運行。它們是燃油系統、點火系統（柴油除外）、潤滑系統和冷卻系統。 然而，其他三個相關系統也是必要的。這些是排氣系統，排放控制系統，啟動系統。每個系統執行一項基本工作，使發動機正常運行。

圖2-1發動機結構2發動機工作原理“沖程”一詞是用來形容汽缸內活塞的運動。活塞從最高位置（TDC,上止點）運動到其最低位置（BDC上，下止點）的運動過程被稱為一個沖程。做功周期可能需要兩個或四沖程來完成。大多數汽車發動機為四沖程循環（圖2-2）。exhauEtvalve*BDC：Dotuieccin.g：rodstileLvanecrinlL圖exhauEtvalve*BDC：Dotuieccin.g：rodstileLvanecrinlL圖2-2發動機簡圖在四沖程發動機中，活塞在汽缸內的動作都需要完成一個完整的運行周期。每個行程按所完成的動作命名。分別是進氣，壓縮，做功，和排氣（圖2-3）。進氣沖程 壓縮沖程 做功沖程 排氣沖程圖2-3四沖程循環汽油發動機1、 進氣沖程進氣沖程開始運動到活塞行程的頂端附近。當活塞開始下降，排氣門完全關閉，打開進氣門，創造一個真空，燃燒室里進氣量開始增加。當活塞下降，空氣/燃料混合物從化油器通過進氣歧管進入氣缸。活塞已經開始上行后，進氣行程結束進氣門即將關閉。2、 壓縮行程當活塞通過曲軸從BDC位置開始移動，進氣門關閉。在汽缸中活塞上面的空氣/燃料混合物被壓縮。活塞行程壓縮空氣/燃料混合物約為原體積的1/8（大約8:1的壓縮比）時，這時候活塞已經達到TDC的八分之一。這就完成了壓縮沖程。3、 做功沖程在壓縮沖程中當活塞到達TDC時，火花塞產生電火花。點火系統提供給火花塞一個高壓脈沖使產生火花。火花點燃（放火）空氣/燃料混合物，開始迅速燃燒，氣缸壓力增加多達3-5MPa。這壓力推動活塞下降，并通過連桿曲軸的曲柄銷傳送到一個強大的沖動。活塞上面的壓力推動它從而使曲軸旋轉。4、 排氣沖程在動力沖程結束時，凸輪軸打開排氣門，排氣沖程開始。活塞向上運動，氣缸內的壓力迫使廢氣排出氣缸。在排氣沖程結束時，排氣門關閉進氣打開，一遍又一遍地重復整個循環。3發動機缸體和缸蓋3.1發動機缸體

發動機缸體是發動機的基本框架。所有其他發動機零部件裝進或擰緊在缸體上。它擁有冷卻回路、潤滑油道（圖2-4），發動機缸體，還擁有曲軸，機油底殼。除了頂置凸輪發動機外，凸輪軸也屬于這部分。在大多數汽車中，此缸體是由灰鑄鐵和其他金屬，如鎳或銘，合金（混合物）鑄造成的。圖2-4V6發動機缸體有些發動機缸體，尤其是那些小型車使用鑄鋁，這種金屬比鑄鐵輕得多。然而，鐵的耐磨性比鋁好。因此，在大多數鋁制發動機汽缸內襯有鐵或鋼材質的套 管。這些軸套叫做氣缸套。一些發動機缸體完全由鋁做成。3.2氣缸套氣缸套用于發動機缸體內，用來防止活塞和活塞環對缸體的磨損。缸體可以由一種既輕也易于成型的金屬制成，而缸套則用來承受活塞跟活塞環的磨損。有兩種主要類型的缸套：干缸套和濕缸套（圖2-5）。干缸套濕缸套圖2-5缸套3.3缸蓋氣缸蓋是缸體的頂部，相當于一所房子的屋頂與活塞頂部形成燃燒室。直列式輕型車輛的發動機氣缸只有一個缸蓋；較大的直列式發動機可以有兩個或兩個以上。正如發動機缸體，缸蓋也可由鑄鐵或鋁合金制成。氣缸蓋攜帶閥門，氣門彈簧，搖臂軸，搖臂，推動氣門齒輪工作的推桿。有時，凸輪軸直接安裝在缸蓋上，不用搖臂控制氣門工作。這被稱為頂置凸輪軸布置。3.4墊片缸蓋與高強度鋼螺栓連接缸體。缸體和頭部之間的聯合，必須不透氣，使燃燒的混合物不能泄漏。這是通過使用氣缸蓋墊片實現。密封墊片還可以用于連接的其他部分，如油底殼，歧管，或水泵和缸體之間。3.5油底殼油底殼通常由鋼沖壓形成。油底殼和缸體下部一同被叫做曲軸箱；它們把曲軸封閉起來。潤滑系統中的油泵，抽出油底殼中的油，并把它傳送到發動機的所有工作部件。機油流出再通過管道流回油底殼。因此，機油要在發動機的工作部件不斷地循環流動。