发动机英文翻译

“中南林业科技大学”热能与动力工程专业“不落的星尘”全力打造，华丽的一个金币，传说中的物美价廉发动机英文翻译、内燃机英文翻译、汽车英文翻译、热动英文翻译由于上传失败，现将两幅插图放在另一个文档中期待各位的指正，谢谢！分割线„„„„割了烦恼„„„„毕业愉快„„„„工作愉快Theengineisanimportantpartoftheautomobile;itactsastheheartofaperson,whichprovidesthepowerthatthecarsneedtorunontheroad.AlltheautomotiveenginestodayaretheInternalCombustionEngines(ICEs)becausethefuelisburntinsidetheircylindersandtheenergyisprovided.ICEsarethoseheatenginesthatburntheirfuelinsidetheenginecylinder.InICEs,thechemicalenergystoredintheirfuelconvertedintoheatenergyduringtheburningpartoftheiroperation.Theheatenergyisconvertedintomechanicalenergybytheexpansionofgasesagainstthepistonattachedtocrankshaftthatcanrotate.Theenginesthatburnpetrolareknownaspetrolengine.OthertypesofICEsburnheavieroils,ofthesetypesthedieselenginehascomeintothewidestuse.Dieselandpetrolengineshavethesamemechanicalparts,exceptthatdieselcomponentsaregenerallystrongerandheavier.Bothenginesareinternalcombustionengines,buttheyhavedifferentfuelsystemandusedifferentfuels.Withadiesel,onlyairentersthecylinderduringtheintakestroke.Apetrolenginetakesinanair-fuelmixture.Followingaresomegeneralcomparisonsbetweendieselandpetrolengines:Inadiesel,thefuelisinjectedintothecylinderasafinespraynearthetopofthecompressionstroke.Withapetrolengine,thefuelisinjectedintotheexhaustportsatthestartoftheinductionstroke.Ignitioninadieselisbythehightemperaturefromthehighlycompressedair.Apetrolengineneedsasparkforignition.Dieselenginesgenerallyoperateatlowerenginerpmthanpetrolengines.Dieselenginesusedistillateforfuel,whichislessvolatilethanpetrol.Thedesignofdieselenginesmakesthemnoisierthanpetrolenginesandtheyhaveauniquedieselknock.Smalldieselengines,aswellaspetrolengines,areusedinpassengercarsandlightcommercialvehicles.Largerdieselenginesareusedinallheavycommercialvehicles,earthmovingequipment,andfarmmachinery..EngineConfigurationsThetermengineconfigurationreferstothewaythatthecylindersofanenginearearranged.Thecylinderscanbein-line,oratanangle(V-type).Withinthesethreebasicarrangements,thereareanumberofvariations.In-lineengineWithin-lineengines,thecylindersarearrangedinastraightline,onebehindtheother.Mostin-lineengineshavetheircylindersvertical,butsomeareslanted.Thatis,theengineistiltedatanangletoreducetheoverallheight.Theseenginesaresometimesreferredtoasslantedengines.Somein-lineengineshavetheircylindershorizontal,sothattheengineismoreorlessonitsside.Thisreducestheoverallheightoftheengine.Thisarrangementis＜插图位置＞usedmainlyinlargercommercialvehicleswiththeenginemountedunderpartofthecab.Themechanicalarrangementofafour-cylinderin-lineforapassengercarisshowninFig.1-9.Thecut-awayviewinFig.1-10enablesthevariouspartstobeidentified.HorizontallyopposedengineThisarrangementhasitscylindersarrangedintwoflatblankswiththecrankshaftbetweenthem.Theengineshownhasashortrigidcrankshaftwithfivebearings.Ahorizontallyopposedenginehasevenfiringimpulsesandgoodbalance.Movementofapistonindirectionisopposedbymovementofapistonintheoppositedirection.Horizontallyopposedengines,withtheirflatdesign,givetheenginealowheightandalsohelptokeepthecenterofgravityofthevehiclelow.Alowcenterofgravitygivesthevehiclestability.V-typeenginesWithV-typeengines,thecylindersarearrangedintwoblanksatanangle.Thisreducesthelengthoftheengineandmakesitmorecompact.Thisalsoreducesthelengthofthecrankshaft,whichcanbedesignedtobemorerigidthanalongshaft..TheEngineAssemblyandComponentsThecompleteengineassemblyconsistsofthemechanicalcomponentsthatmakeuptheengineitselfandalsoanumberofassociatedsystems.Thesearethesystemsthatareneededtostarttheengineandalsotocontrolitandkeepitrunning.Themechanicalpartsoftheengineassemblycanbebrokendownintoanumberofsub-assemblies,orgroupsofassociatedcomponents,althoughtheseareusuallyreferredtomerelyasassemblies,forexample,cylinder-headassemblyandpistonassembly.Somepartsofanengineareinternal,otherpartsareexternal,thisillustrationidentifiesanumberofexternalparts.Thevariouscomponentsofanengineareassembledtogetherduringmanufacturedandmostofthesearesecuredbymeansofbolts,nutsandothertypesoffasteners.Somepartsareinternalandothersareattachedtotheoutsideoftheengine.Thecylinderblockisthelargestpartofengine.Theotherpartsareeitherfittedintotheblockorattachedtoit.Asitsnamesuggests,itisbasicallyablockofcastmetal,usuallycastiron,butitcanbealuminumalloywithcastironorsteelliners.Aluminumisusedtoreducetheweight.Thecylinderblockhasaccuratelyboredcylinderstotakethepistons.Thelowerpartoftheblockisknownasthecrankcaseandthishasbearingsthatcarrythecrankshaft.Thewater-jacketsthatsurroundthecylindersarefilledwithcoolant.Thetopofthecylinderblockhasamachinedsurfaceforthecylinderheadandthebottomofthecylinderblockismachinedtoprovideamountingfortheoilpan,orsump.Thecylinderscanbearrangedintheblocksothattheyareinline,asshown,ortheycanbesetatangle(V-typeengine).Thecrankshaftismountedinbearingsinthelowerpartofthecylinderblock(thecrankcase).Theconnectingrodsconnectthepistonstothecrankshaft,whichisrotatedbythepowerstrokesofthepistonswhentheengineisrunning.Theup-and-down,orreciprocating,motionofthepistonsischangedtorotarymotionbythecombinationactionoftheconnectingrodsandthecranksofthecrankshaft.Thetermcrankshaftcomesfromthewordcranked,whichalsomeansbent.Itisashaftwithanumberofcranksorbends.Within-lineengines,thereacrankforeachcylinder,butwithsomeV-typeengines,thereisonlyonecrankforeachpairofcylinders.Theflywheelisaheavycastironwheelattachedtotherearofthecrankshaft.Itreducesenginevibrationsbysmoothingoutthepowerimpulsesofthepistons.Theflywheelabsorbsenergyduringthepowerstrokeandgivesupenergyduringtheotherstrokesandthishelpstokeeptheenginerunningsmoothly.Aringgearfittedtotherimoftheflywheelsothattheenginecanberotatedbythestarterpinionwhenstartingtheengine.Withautomatictransmissions,adriveplateandtorqueconvertertaketheplaceoftheflywheelandperformthesamefunctionsasaflywheel,asfarastherunningoftheengineisconcerned.Thepistonhasgroovesthatcarrythepistonringsandtheseprovideasealbetweenthepistonandthecylinderwall.Compressionringsareusedasagassealandtheoilringisusedtopreventexcessoilfromfindingitswayuppastthepistonintothecombustionchamber.Theconnectingrodhasaremovablecapandasplitbearingatitslowerendwhereitisconnectedtothecrankshaft.Itsupperhasapistonpinthatprovidesawrist-typeofactionwiththepiston.Becauseofitsaction,thepistonpinissometimesreferredtoasawristpin.Thecylinderheadismadeofcastaluminumalloy.Itisboltedtothetopofthecylinderblocksothatitenclosesthecylinders.Ithascombustionchambersabovethecylindersinwhichtheair-fuelmixtureisburnt.Cylinderheadscanbemadeofcastiron,whichismoreresistanttocorrosion,butaluminumalloyisusedforpetrolenginesbecauseithasadvantagesofbetterheattransferandlighterweight.Thecylinderheadhasintakeportsandexhaustports.Theintakevalvesopentheintakeportstoadmitthefuelchargeintothecylinderduringtheintakestroke.Theexhaustvalvesopentheexhaustportstoallowtheburntgasestoleavethecylinderfollowingtheexhauststroke.Thecamshaftandthevalvemechanismareusedtoopenandclosethevalvesatthecorrecttime.Thecamshaftisdrivenfromthecrankshaftathalfthecrankshaftspeed.Thevalvecover,alsocalledthecylinder-headcover,isfittedtothetopofthecylinderhead.Thisenclosesthevalvemechanism.Anadditionalcoverontopoftheenginecoverstheignitioncoils.Thiscylinder-headarrangement,forafour-cylinderengine,hastwocamshaftsandsixteenvalves.Otherfour-cylinderenginescanhavetwocamshaftsandtwelvevalves,oronecamshaftandeightvalves.Thetimingbeltandpulleysdrivethecamshaftathalfthecrankshaftspeed(enginespeed).Atootheddrivebeltisoftenused,butgearsandchainsarealsoused-insomeinstancesabeltandchainarebothused.Onsomeengines,thetimingchainisusedtodrivetheoilpump.Ondieselengines,atimingchainoratiminggearisusedtodrivetheinjectionpumpaswellasthecamshaft.Theoilpan,orsump,holdstheoilfortheenginelubricatingsystem.Theoilpanismadeofsteelthathasbeenpressedtoshape.Otheroilpansaremadeofaluminumalloythathasbeencasttoshape.Theoilpanisboltedtotheundersideoftheenginesothatitclosesoffthecrankcase.Onlytheendsofthecrankshaftthatextendbeyondthecylinderblockareexposed.Variousformsofgasketsandsealsareusedbetweenthesurfaceswherethepartsareboltedtogether.Someoftheseareusedtosealagainstoil,someagainstcoolantandsomeagainstheatandpressure.Someprovideasealonflatsurfaces,othersealagainstrotatingshafts.Aswellasthelargerpartsofanengine,therearenumeroussmallparts.Theseincludebolts,washers,retainers,springandbracketswhichgotomakeupthemechanicalcomponentsoftheengine..EngineSystemsTheenginesystemsthatenabletheenginetostartandtocontinuetooperateareasfollows:Startingsystem;Fuelsystem;Ignitionsystem;Coolingsystem;Lubricatingsystem;Intakesystem;Exhaustsystem;Chargingsystem;Engine'selectroniccontrolsystem.Thesearethesystemsforpetrolengines.Dieselengineshavesimilarsystemsexceptforthefuelandignitionsystems.Somepartsofthesystemsarebuiltintotheengine,somepartsareattachedtotheengineandotherpartsarelocatedonthebodypanelsintheenginecompartment.StartingsystemThestarterisusedtorotatetheengineduringstarting.Itconsistsofanelectricmotorandadrive.Thedrivehasasmallpinionthatmesheswiththeringgearontheflywheelduringstarting.Thebatterysuppliestheelectricalenergytooperatethestarterandrotatetheengineuntilitfiresandrunsonitsown.FuelsystemThesearefourbasictypesoffuelsystems:carburetorsystemsforpetrolengines,fuelinjectionsystemsforpetrolengines,gasfuelsystems(LPGorNGV),anddieselinjectionsystems.Allthesesystemsoperateindifferentways,buttheyallhavesomewheretostorefuel(afueltankoracylinder)andawayofsupplyingtheenginewiththefuel.Theyalsohaveawayofsupplyingairandfuelmixedinthecorrectproportionsothatitcanbeeffectivelyburninthecombustionchambers.IgnitionsystemPetrolenginesandenginesoperatingongasrequireanignitionsystem.Thisisneededtoprovidethesparksthatfirethechargesinthecombustionchambers.Forthisreason,petrolenginesaresometimesreferredtoasspark-ignitionengines.Thisdistinguishesthemfromthemdieselenginesthatdonotneedasparkbecausetheyusecompressionignition.Combustioninadieseloccurswhenthefuelissprayedintothecombustionchamber.Theairinthecylinderisathightemperaturefrombeingcompressed-highenoughtoignitethefuelthatissprayedfromtheinjector.CoolingsystemAconsiderableamountofheatisproducedinanenginebytheburningair-fuelmixture.Someoftheheatisusedtodousefulwork,someistransferredtootherpartsoftheengineandsomeiscarriedawaywithexhaustgases.However,thereisstillenoughheattocausedamageunlessitisremoved.Thisisstillthefunctionofthecoolingsystem,whichremovesaboutone-thirdoftheheatthatisproduced.Thecoolingsystemdoesnotjustremoveheat;itmaintainstheengineatadesirableoperatingtemperature.Inaliquid-cooledengine,thisisdonebycirculatingcoolantthroughthewater-jackets.Inanair-cooledengine,coolingisbyairovercoolingfins.LubricatingsystemTheengine-lubricatingsystemconsistsofanoilpump,areliefvalveandafilter;alsopipes,passagesanddrillingsinvariouspartsofenginethroughwhichtheoilcanflow.Aquantityofoilisheldintheoilpan.Fromthis,oilistakenbytheoilpumpandcirculatedthroughouttheenginebeforereturningtotheoilpan.Theoillubricatesallthemovingpartsandthisisnotonlyreducesfriction,butitpreventswearanddamage.Theoilpumpisdrivendirectlybythecrankshaft.Thissystemhasanoilcooler,locatedatthefiltermountingunderthefilter.IntakesystemInpetrolenginewithelectronicfuelinjection,theintakesystemincludestheaircleaner,thethrottlevalveassemblyandtheintakemanifold.Theintakesystemprovidescleanairandcarriesitintotheenginethroughtheintakemanifold.Nozzlesofthefuelinjectorssprayfuelintotheairpassingfromtheintakemanifoldintotheintakeports.Withcarburetorfuelsystems,amixtureofairandfueliscarriedfromthecarburetor,throughtheintakemanifoldandintotheenginethroughtheintakeports.Forenginesthatoperateongas,amixtureofairandgasiscarriedintotheenginebytheintakemanifold.Inpetrolengineswithfuelinjection,andindieselengines,cleanaironlyisprovidedbytheintakesystem.ExhaustsystemTheexhaustsystemcarriestheburntgasesawayfromtheengineandalsoreducesnoise.Thesystemconsistsoftheexhaustmanifold,exhaustpipes,acatalyticconverterandamuffler.Arrangementsvarywithdifferentengines,theremaybemorethanonemufflerandmorethanonecatalyticconverter.EnginesthatrunonLeadReplacementPetrol(LRP)donothaveacatalyticconverter,neitherdodieselengines.ChargingsystemThealternator,whichisdrivenbytheengine,convertsmechanicalenergytoelectricalenergy.Thebatterysuppliesenergyforthestarter,theignitionsystemandelectricfuelpumpduringthestartingperiod(petrolengine),butoncetheengineisrunning,thealternatorsuppliesalltheelectricalenergy.Italsorechargesthebatterytoreplacetheenergyusedduringstarting.Engine'selectroniccontrolsystemTheengine'selectroniccontrolsystemconsistsofsensors,acontrolunitandactuators.Thecontrolunitreceivessignalsfromthesensorsandthensendssignalstovariousactuators.Therearesensorsontheengine,intheintakesystemandintheexhaustsystem.Theinjectorsareactuatorsthatadjustthesprayoffuel.Therearealsoactuatorsintheignitionsystemthatadvanceandretardthespark.Thesearejusttwoexamplesofwhereelectroniccontrolisused..EngineOperationDuringthedownwardmotionofthepiston,theair-fuelmixtureissuckedfromthecarburetorintothecylinder.Duringtheupwardmotionthemixtureiscompressedbythepistoninthecylinderandignitedbyanelectricspark.Whenthemixtureisburnedinthecylinder,theresultingheatcausesthegasestoexpandwhichexertpressureonthecylinderwallsandonthepiston.Thepiston,beingmovable,ispusheddownwardbythispressuretothefulllengthofitsstroke.Thepressureexertedonthepistonistransmittedthroughtheconnectingrodtothecrankshaftthatismadetorevolve.Thecrankshaftturnsthroughone-halfofarevolutionasthepistonmovesdownward.Aflywheelattachedtothecrankshaftstoresupenergy.Themomentumoftheflywheelcarriesthepistonthroughthebalanceofitsmotionuntilitreceivesanotherpowerimpulse.Theprocessisrepeatedoverandoveragain,thecrankshaftisturningcontinuouslyandtheengineisrunning.Theeventsthatarerepeatedmakeupthecycleoftheengine.Thenumberofstokesofthepistonrequiredtocompletethecyclevarieswiththetypeofengine.Inmodernvehicles,thecycleisextendedthroughfourstrokeofthepistonortworevolutionsofthecrankshaft.Thisiscalledafour-strokecycleengine.Intwostrokecycleengines,thecycleiscompletedintwostrokesofthepistonoronerevolutionofthecrankshaft.Inthefour-strokecycleengine,thefourstrokesarenamedsuction,compression,power,andexhaustinaccordancewiththeoperationofthecyclewhichoccurduringeachparticularstroke.Suctionstroke:duringsuctionstroke,thepistonismoveddownwardbythecrankshaft,whichisrevolvedeitherbythemomentumoftheflywheelorbythepowergeneratedbytheelectricstartingmotor.Theinletvalveremainsopenandtheexhaustvalveisclosedduringthisstroke.Thedownwardmovementofthepistonsucksair-fuelmixtureinthecylinderfromthecarburetorthroughtheopeninletvalve.Herethefuelispetrolmixedwithair,brokenupintoamist,andpartiallyvaporizedinthecarburetor.Compressionstroke:duringcompressionstroke,thepistonmovesupward,thuscompressingthecharge.Ignitionandmuchofthecompressionalsotakeplaceduringthisstroke.Theheatproducedbythecompressionmakesmorehomogeneousmixtureofairandpetrolinsidethecylinder.Theheatmakesthepetroleasiertoburn,whilethecompressionforcesitintoclosercombinationwiththeair.Themixture,undercompression,isignitedbythesparkproducedbyasparkplug,andthecombustionisoverhalf-completedwhenthepistonisatTopDead-Centre(TDC).Boththeinletandexhaustvalvesremainclosedduringthecompressionstroke.Working,powerorexpansionstroke:theexpansionofthegasesduetotheheatofcombustionexertsapressureonthecylinderandpiston.Underthisimpulsethepistonmovesdownwardthusdoingusefulwork.Boththevalvesremainclosedduringthisstroke.Exhauststroke:duringthisstroke,theinletvalveremainsclosedandtheexhaustvalveopens.Thegreaterpartoftheburntgasesescapesbecauseoftheirownexpansion.Thepistonmovesupwardandpushestheremaininggasesoutoftheopenexhaustvalve.Onlyasmallquantityofexhaustgasesremainsintheclearancespacewhichwilldilutethefreshincomingcharge.Thus,inthistypeofengine,fourstrokesofthepistonarerequiredtocompletethecycle,andthefourstrokesmaketworevolutionsofthecrankshaft.Theoperationsarerepeatedoverandoveragaininrunningtheengine.发动机的组成发动机是汽车的重要组成部分，它为汽车提供行驶的动力，对汽车而言它就像心脏对人一样重要。现今所有的汽车发动机都是内燃机（ICEs）,这种发动机的燃料在气缸内燃烧，燃烧产生的能量直接提供给发动机。内燃机是将燃料在发动机气缸里面燃烧的热机。在内燃机运转过程中，储存在燃料中的化学能通过燃烧转变为热能。内燃机的活塞通过连杆连接在可以旋转的曲轴上，热能使气体膨胀推动活塞转变为机械能。燃烧汽油的发动机叫汽油机。其它形式的内燃机燃烧重油，其中以柴油机的应用最为广泛。柴油机与汽油机具有相似的构造，其区别在于柴油机比较笨重。这两种发动机都是内燃机，但是两者具有不同的燃烧系统，并且使用不同的燃料。对于柴油机，在进气行程中只有空气进入气缸。而对于汽油机，在进气行程中是吸入空气和燃料的混合物。通常，柴油机和汽油机具有以下区别：在柴油机中，燃料是在压缩行程末期以很好的雾状形态喷入气缸。而在汽油机中，燃料在进气行程初期被吸入到排气孔附近。在柴油机中，燃料是被高压空气的高温点燃的。而在汽油机中，燃料需要火花才能点燃。柴油机正常运转时的转速通常比汽油机的低。柴油机一般使用比汽油挥发性小的蒸馏物作为燃料。柴油机的构造使其噪声比汽油机大，并且会产生特有的爆震。小型柴油机和汽油机一样，都被应用于乘用车和轻型商用车上。大型柴油机被应用于所有的重型商用车、工程用车以及农用机械。1.发动机的类型发动机的类型是指发动机气缸的排列形式。气缸可以排列在一条直线上，可以对置排列，还可以呈一定角度排列（V型）。以这三种排列形式为基础，又发展了多种排列形式。直列式发动机顾名思义，直列式发动机中各气缸排成一直列，一个紧邻一个，在一条直线上。大多数直列式发动机其气缸都是垂直的，但也有一些是倾斜的。气缸倾斜设置可以降低发动机的整体高度，这类发动机有时叫做倾斜发动机。有些直列式发动机的气缸是水平放置的，这类发动机的横向尺寸会比较大，不过这样可以降低发动机整高。这类发动机主要用于大型商用车上，其发动机架位于驾驶室底部。如图1-9显示的是轿车用直列四缸发动机的构造。图1-10是侧面剖视图，可以看到更多零部件，便于分别。水平对置式发动机这种排列方式将气缸布置在曲轴两侧的平面上，曲轴是刚性较大的短轴，其上有五个轴承。水平对置式发动机有相当好的输出脉冲和平稳性。活塞的运动方向与对面的活塞运动方向相反。由于水平对置式发动机的平面布置，大大降低了发动机的高度，有利于降低＜插图位置＞汽车的重心，这样可以使汽车更稳定。V型发动机在V型发动机中，气缸被布置在两个成一定角度的平面上。这样减小了发动机的长度，使其更紧凑。同时也减小了曲轴的长度，使之刚性增强。2・发动机的构造及其零部件发动机总成由许多构成它本身的零部件和相关系统组成。这些系统是发动机起动和维持运转所必需的。组成发动机的各个零部件可以分成一系列分总成或者相关的组件，通常也叫它们总成，例如缸盖总成、活塞总成。有些零部件在发动机里面，有些在外面，本文的插图展示了一些发动机外面的零部件。发动机各种各样的零部件通过螺栓、螺母和其它的紧固件装配在一起。有些零部件安装在发动机里面，还有些固定在外面。机体是发动机中最大的零件。其它零部件都是安装或连接在机体上的。顾名思义，机体是一块金属铸体，通常是铸铁，但也可以是铸铝合金或者铸钢。机体中精确加工了气缸，可以使活塞在里面运动。机体的下部是曲轴箱，里面有安装曲轴的轴承。在气缸周围的水套里充满了冷却液。机体顶部是一个机械加工面，用来装配气缸盖，底部装配油底壳或机油箱。在机体中气缸可以布置成一列直线，也可以成一定角度布置（V型发动机）。曲轴安装在机体下部的轴承上（曲轴箱里面）。活塞和曲轴之间用连杆连接，发动机运转时曲轴靠活塞的做功行程旋转。活塞的往复运动通过连杆和曲轴上曲柄的共同作用转变为旋转运动。曲轴这个词源于英文单词“cranked”，它是转动曲柄的意思，包含有弯曲的意思，通俗地讲，曲轴是一根包含若干曲柄的轴。在直列式发动机中，每个气缸对应一个曲柄，但是在某些V型发动机中，一对气缸会共用一个曲柄。飞轮是一个笨重的盘形铸铁件，它安装在曲轴后端。它通可以使活塞输出的动力脉冲更平滑，从而减少发动机的振动。它在做功行程吸收能量，在其它行程释放能量，这样可以保持发动机平稳地运转。飞轮的边缘装有一圈齿圈，在发动机起动时，起动机上的小齿轮通过齿圈带动飞轮旋转。对于自动变速器，在发动机起动时，是用传动盘和变矩器代替飞轮实现发动机的起动。活塞和气缸壁之间靠活塞环来密封，活塞环装在活塞上的凹槽中。气环用来密封气体，油环用来阻止多余的机油从活塞上进入燃烧室。连杆上有一个可以拆掉的连杆盖，其下端通过一个剖分的连杆轴承与曲轴连接。连杆上端通过与活塞销组成转动副而与活塞相连。因为可以转动，所以有时候也称活塞销为肘节销。气缸盖通常是铝合金铸件，通过螺栓将它固定在缸体顶部并且与气缸相吻合。在气缸的上部是燃烧空气与燃料混合物的燃烧室。气缸盖也可以是铸铁，这样具有更强的抗腐蚀性，但是由于铝合金有较好的热传导性和较轻的重量，因而用于汽油机上。气缸盖上有进气孔和排气孔。在进气行程，进气门打开，燃料从进气孔进入气缸。在排气行程，排气门打开，燃烧后的废气从排气孔排出。凸轮轴和配气机构使气门在正确的时刻打开和关闭。凸轮轴由来自曲轴的动力驱动，其转速是曲轴的一半。气缸盖罩装在气缸盖的上面，将配气机构封在里面，并且为发动机顶部的点火线圈提供额外的保护。四气缸发动机的气缸盖包含两根凸轮轴和十六个气门。在另一种四气门发动机上，含有两根凸轮轴和十二个气门。还有一种发动机只有一根凸轮轴和八个气门。皮带轮通过正时皮带以一半的曲轴转速(曲轴转速即发动机转速)驱动凸轮轴。常常将有齿轮的皮带用在这里，但是齿轮和链条也会用于某些发动机，甚至同时使用皮带和链条。在某些发动机上，会用正时链条来驱动油泵。在柴油机中，喷油泵和凸轮轴都是用正时链条或正时齿轮来驱动。油底壳或者机油箱用来盛放发动机润滑系统的机油。油底壳用薄钢板压制成型，有些油底壳用铝合金精密铸造成型。油底壳用螺栓固定在发动机下面以便使曲轴箱密封，我们只能看到延伸至曲轴箱外面的曲轴末端。用螺栓连接的零件贴合表面常常要用到各种各样的垫圈或密封条。有些地方是为了防止泄漏机油，有些地方是为了防止泄漏冷却液，还有些地方是为了绝热和保持压力。有些密封条用于平整表面，还有些用于转轴上。发动机除了这些大部件，还有许许多多小零件。包括螺栓、垫圈、止动垫圈、弹簧，还有组成发动机部件的支架。3・发动机的组成系统以下是发动机起