最新汽車專業(yè)英語原文及翻譯課件PPT

1、汽車工程專業(yè)英語,李俊玲羅永革版（原文與翻譯）,todaysaveragecarcontainsmorethan15000separate,individualpartsthatmustworktogether.thesepartscanbegroupedintofourmajorcategories:body,engine,chassisandelectricalsystem.,現(xiàn)在的汽車一般都由15000多個(gè)分散、獨(dú)立且相互配合的零部件組成。這些零部件只要分為,四類：車身、發(fā)動(dòng)機(jī)、底盤和電氣設(shè)備。,anautomobilebodyisasheetmetalshellwithwindows,

2、ahoodandatrunkdeckbuiltintoit.itprovidesaprotectivecoveringfortheengine,passengersandcargo.thebodyisdesignedtokeeppassengerssafeandcomfortable.thebodystylingprovidesanattractive,colorfulmodernappearanceforthevehicle.,轎車車身是一個(gè)鈑金件殼體，它上面有車窗、車門、發(fā)動(dòng)機(jī)罩和行李艙門等部件，它給發(fā)動(dòng)機(jī)、乘客和行李提供防護(hù)。車身設(shè)計(jì)是為了確保乘客乘坐的安全和舒適。車身造型設(shè)計(jì)使得汽車有

3、一個(gè)華美、現(xiàn)代、吸引人的外觀。,asedanhasanenclosedbodywithamaximumof4doorstoallowaccesstothepassengercompartment.thedesignalsoallowsforstorageofluggageorothergoods.asedancanalsobereferredtoasasaloonandtraditionallyhasafixedroof.therearesoft-topversionsofthesamebodydesignexceptforhaving2doors,andtherearecommonlyref

4、erredtoasconvertibles.轎車車身為封閉式，轎車最多有4個(gè)車門，乘員通過車門進(jìn)出。另外車身的設(shè)計(jì)還應(yīng)考慮行,李和貨物的存放。傳統(tǒng)的轎車都是硬頂車身。活頂乘用車（敞篷車）的車頂是軟頂，車身設(shè)計(jì)與普通轎車類似，但只有兩個(gè)車門。,theutilityorpick-upcarriesgoods.usuallyithasstrongerchassiscomponentsandsuspensionthanasedantosupportgreatergrossvehiclemass.,皮卡一般用來運(yùn)載貨物。為能承載更大的總質(zhì)量，皮卡的底盤部件和懸架比轎車更結(jié)實(shí)。,lightvehiclev

5、anscanbebasedoncommonsedandesignsorredesignssothatmaximumcargospaceisavailable.,輕型貨車一般是基于普通轎車設(shè)計(jì)的，或是重新設(shè)計(jì)使可用載貨空間最大化。,thebodiesofcommercialvehiclesthattransportgoodsaredesignedforthatspecificpurpose.tankerstransportfluids,tipperscarryearthorbulkgrains,flatbedsandvansareusedforgeneralgoodstransport.,用于運(yùn)

6、輸貨物的商用車車身必須滿足具體要求，例如運(yùn)輸液體的油罐車、運(yùn)輸泥土或散裝谷物的自卸車、運(yùn)輸一般貨物的平板車或貨車。,busesandcoachesareusually4-wheelrigidvehices,butalargenumberofwheelsandaxlescanbeused.sometimesarticulatedbusesareusedtoincreasecapacity.busesandcoachescanbesingle-deckordouble-deck.busesarecommonlyusedincitiesascommutertransportswhilecoaches

7、aremoreluxurioususedforlongdistances.,客車和長途汽車一般是有4個(gè)車輪的整體式車輛，也能配備更多的車輪和車橋。為了增加客,車的載客量往往使用由鉸鏈連接的客車。公共汽車和長途汽車有單層和雙層兩種。公共汽車一般用城市內(nèi)公共交通，而長途汽車一般用于長距離的旅行。,1.2Engine,Theengineactsasthepowerunit.Theinternalcombustionengineismostcommon:this,obtainsitspowerbyburningaliquidfuelinsidetheenginecylinder.Therearetwo

8、typesof,engine:gasoline,(also,called,a,spark-ignition,engine),and,diesel(also,called,a,compression-ignitionengine).Bothenginesarecalledheatengines;theburningfuelgeneratesheatwhichcausesthegasinsidethecylindertoincreaseitspressureandsupplypowertorotateashaftconnectedtothepowertrain.發(fā)動(dòng)機(jī)作為動(dòng)力設(shè)備，常見的類型是內(nèi)燃

9、機(jī)，其原理是通過發(fā)動(dòng)機(jī)缸內(nèi)的液體燃料燃燒而產(chǎn)生能量。發(fā)動(dòng)機(jī)可分為兩類：汽油機(jī)（點(diǎn)燃式）和柴油機(jī)（壓燃式），都屬于熱力發(fā)動(dòng)機(jī)。燃料燃燒產(chǎn)生熱量使缸內(nèi)氣體氣壓上升，從而產(chǎn)生能量，驅(qū)動(dòng)與動(dòng)力傳動(dòng)系相連接的軸旋轉(zhuǎn)。Thewayenginecylindersarearrangediscalledengineconfiguration.In-lineengineshavethecylindersinaline.Thisdesigncreatesasimplycastengineblock.Invehicleapplications,thenumberofcylindersisnormallyfrom2up

10、to6.Usually,thecylindersarevertical.Asthenumberofthecylindersincrease,thelengthoftheblockandcrankshaftcanbecomeaproblem.OnewaytoavoidthisiswithaVconfiguration.Thisdesignmakestheenginesblockandcrankshaftshorterandmorerigid.發(fā)動(dòng)機(jī)的布置即發(fā)動(dòng)機(jī)氣缸的排列方式。發(fā)動(dòng)機(jī)缸體按直線排列的即直列式，這種布置使得發(fā)動(dòng)機(jī)缸體結(jié)構(gòu)簡單。汽車發(fā)動(dòng)機(jī)一般為26缸，通常氣缸是垂直放置的，但氣缸數(shù)量

11、的增加會(huì)導(dǎo)致缸體和曲軸的長度過大，解決問題的措施之一就是采用V型布置，這種布置方式可以使發(fā)動(dòng)機(jī)缸體和曲軸長度尺寸更短，從而大大增加剛度。Anenginelocatedatthefrontcanbemountedlongitudinallyandcandriveeitherthefrontortherearwheels.Rearenginevehicleshavetheenginemountedbehindtherearwheels.Theenginecanbetransverseorlongitudinalandusuallydrivestherearwheelsonly.前置發(fā)動(dòng)機(jī)可以縱向布

12、置，能夠驅(qū)動(dòng)前輪或后輪。后置發(fā)動(dòng)機(jī)布置在后輪后側(cè)，發(fā)動(dòng)機(jī)即可縱向布置又可橫向布置，一般只能驅(qū)動(dòng)后輪。1.3chassis底盤thechassisisanassemblyofthosesystemsthatarethemajoroperatingpartsofavehicle.thechassisincludesthepowertrain,steering,suspension,andbrakingsystems.底盤由汽車的主要操作系統(tǒng)組裝而成。包括傳動(dòng)系、行駛系、轉(zhuǎn)向系和制動(dòng)系四部分。1）Powertrainsystemconveysthedrivetothewheels.傳動(dòng)系-將驅(qū)動(dòng)力傳

13、遞到車輪。2）Steeringsystemcontrolsthedirectionofmovement.轉(zhuǎn)向系-控制汽車的行駛方向。3）Suspensionandwheelsabsorbstheroadshocks.懸掛系-吸收路面震動(dòng)4）Brakeslowsdownthevehicle.制動(dòng)系-使汽車減速緩行。1.3.1powertrainsystem動(dòng)力傳動(dòng)系統(tǒng)Thepowertraintransfersturningeffortfromtheenginetothedrivingwheels.apowertraincanincludeaclutchmanualtransmissionora

14、torqueconverterforautomatictransmission,adriveshaft,finaldriveanddifferentialgearsanddrivingaxles.Alternatively,atransaxlemaybeused.Atransaxleisaself-containedunitwithatransmission,finaldrivegearsanddifferentiallocatedinonecasing.傳動(dòng)系把發(fā)動(dòng)機(jī)輸出的扭矩傳遞給驅(qū)動(dòng)輪。傳動(dòng)系包括離合器（對應(yīng)機(jī)械變速器）或液力變矩器（對應(yīng)液力自動(dòng)變速器）、變速器、驅(qū)動(dòng)軸、主減速器、差速器

15、和驅(qū)動(dòng)橋。另外有些傳動(dòng)系采用由變速器、主減速器和差速器組成的一體式的變速驅(qū)動(dòng)橋。（或者采用一個(gè)獨(dú)立的變速驅(qū)動(dòng)橋，即變速器在同一個(gè)箱體內(nèi)。）Avehiclewithamanualtransmissionusesaclutchtoengageanddisengagetheenginefromthepowertrain.Enginetorqueistransmittedthroughtheclutchtothetransmissionortransaxle.thetransmissioncontainssetsofgearsthatincreaseordecreasethetorquebeforei

16、tistransmitted,totherestofthepowertrain.thelowerthegearratioselected,thehigherthetorquetransmissioned.avehiclestartingfromrestneedsalotoftorque,butonceitismoving,itcanmaintainspeedwithonlyarelativelysmallamountoftorque.ahighergearratiocanthenbeselected,andenginespeedisreduced.,對于采用機(jī)械變速器的汽車，其發(fā)動(dòng)機(jī)扭矩由離合

17、器傳遞給變速器或變速驅(qū)動(dòng)橋，并通過離合器來控制發(fā)動(dòng)機(jī)和傳動(dòng)系的嚙合或分離。變速器包含了不同傳動(dòng)比的齒輪副，能夠增加或減小扭矩。選擇的齒輪速比越小，傳遞的扭矩最大。汽車起步時(shí)需要較大的扭矩，一旦起動(dòng)后，僅需要較小的扭矩就可維持速度，此時(shí)應(yīng)該換用較高的檔位，以降低發(fā)動(dòng)機(jī)轉(zhuǎn)速。,aconventionalvehiclewiththeengineatthefrontanddrivingwheelsattherearusesadriveshaft,calledapropellershaft,totransmittorquefromtransmissiontothefinaldrive.,傳統(tǒng)的汽車采用前

18、置發(fā)動(dòng)機(jī)、后輪驅(qū)動(dòng)，因此需要傳動(dòng)軸把動(dòng)力從變速器傳遞給主減速器。,thefinaldriveprovidesafinalgearreductiontomultiplythetorquebeforeapplyingtothedrivingaxles.onfrontenginerearwheeldrivevehicles,thefinaldrivechangesthedirectionofdriveby90degrees.insidethefinaldrive,adifferentialgearsetdividesthetorquetotheaxlesandallowsforthedifferen

19、ceinspeedofeachwheelWhencornering.axlesshaftstransmitthetorquetothedrivingwheels.inarear-wheeldrivevehicle,theaxlescanbesolidorcontainjointstoallowformovementofsuspension.forafront-wheeldrivevehicle,thedriveshafthasuniversaljointstoallowforsuspensionandsteeringmovement.,主減速器的作用就是在把動(dòng)力傳遞給驅(qū)動(dòng)輪之前，降低轉(zhuǎn)速并增加

20、扭矩。對于前置后驅(qū)的汽,車，主減速器還將驅(qū)動(dòng)的旋轉(zhuǎn)方向改變了90度。主減速器內(nèi)的差速器齒輪副，把動(dòng)力分給,兩個(gè)驅(qū)動(dòng)軸，并允許兩邊車輪在轉(zhuǎn)向時(shí)具有不同的轉(zhuǎn)速。動(dòng)力最終由驅(qū)動(dòng)軸傳遞給車輪。后輪驅(qū)動(dòng)汽車的驅(qū)動(dòng)橋應(yīng)能滿足懸架的運(yùn)動(dòng)，可以是剛性的或包含運(yùn)動(dòng)副。為滿足懸架和轉(zhuǎn)向的要求，前輪驅(qū)動(dòng)汽車驅(qū)動(dòng)軸上需安裝萬向節(jié)。,anautomatictransmissionortransaxleperformssimilarfunctionstoamanualtransmissionortransaxleexceptthatgearselectioniscontrolledeitherhydraulicallyo

21、relectronically.theautomatictransmissionusesatorqueconverter,whichactsasahydrauliccouplingtotransferthedrive.,自動(dòng)變速器或自動(dòng)變速驅(qū)動(dòng)橋的功能和機(jī)械式基本類似，區(qū)別在于檔位的選擇是液力或電力控制的。液力自動(dòng)變速器采用液力變矩（耦合）器作為連接器以傳遞動(dòng)力。,1.3.2steeringsystem轉(zhuǎn)向系統(tǒng),Thedirectionalmotionofvehicleiscontrolledbyasteeringsystem.Abasicsteeringsystemhas3mainparts

22、:asteeringboxconnectedtothesteeringwheel,thelinkageconnectingthesteeringboxtothewheelassemblyatthefrontwheelsandfrontsuspensionpartstoletthewheelassembliespivot.Whenthedriverturnsthesteeringwheel,ashaftfromthesteeringcolumnturnsthesteeringgear.Thesteeringgearmovestie-rodsthatconnecttothefrontwheels.

23、Thetie-rodsmovethefrontwheelstoturnthevehiclerightorleft.,轉(zhuǎn)向系控制汽車行駛方向，一般由三部分組成：與轉(zhuǎn)向盤相連的轉(zhuǎn)向器、連接車輪和轉(zhuǎn)向器的傳動(dòng)結(jié)構(gòu)、允許車輪轉(zhuǎn)動(dòng)的前懸架部件。當(dāng)駕駛員轉(zhuǎn)動(dòng)方向盤時(shí)，轉(zhuǎn)向柱內(nèi)的軸帶動(dòng)轉(zhuǎn)向器運(yùn)動(dòng)，然后通過轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)來轉(zhuǎn)動(dòng)車輪，從而使得汽車向左或向右行駛。,1.3.3suspensionsystem懸架系統(tǒng),Thepurposeofthecompletesuspensionsystemistoisolatethevehiclebodyfromroadshocksandvibrations,whichwill

24、otherwisebetransferredtothepassengersandload.Itmustalsokeepthetiresincontactwiththeroadregardlessofroadsurface.Abasicsuspensionsystemconsistsofsprings,axles,shockabsorbers,arms,rodsandballjoints.,整個(gè)懸架系統(tǒng)的作用是隔離來自路面的沖擊和振動(dòng)對車身的影響，防止傳遞給乘員和貨物。另外不論路面如何，懸架系統(tǒng)都應(yīng)該保持輪胎和路面接觸。懸架系統(tǒng)的基本組成包括彈性元件、車橋、減震器、桿系（臂、桿）和球副組成的導(dǎo)向

25、機(jī)構(gòu)。,thespringistheflexiblecomponentofthesussuspension.basictypesare:leafspring,coilspringandtorsionbars.modernpassengervehiclesandcanhavecoilspringsatthefrontandleafspringsattherear.heavycommercialvehiclesusuallyuseleafspringsorairsuspension.,彈簧是懸架的彈性元件，常見的彈簧類型有：鋼板彈簧、螺旋彈簧和扭桿彈簧?，F(xiàn)代汽車大多采用小的螺旋彈簧，輕型商用車常采

26、用的螺旋彈簧比一般乘用車的大得多，或者前懸架采用螺旋彈簧，后懸架采用鋼板彈簧。重型商用車則通常采用鋼板彈簧或空氣彈簧。,wheelsmustbestrongenoughtosupportthevehicleandwithstandtheforcescausedbynormaloperation.atthesametime,theymustbeaslightaspossibletohelpkeepunsprungweighttoaminimum.,車輪必須能支撐整車重量，并能承受正常工況下的載荷。同時(shí)車輪必須盡可能地輕，有助于最小化簧下質(zhì)量。,wheelscanbemadefrompressed

27、-steelingtwosections,andalsobemadefromcastaluminiumalloy.alloywheelsarepopularbecauseoftheirappearanceandbecausetheyarelighterthansimilarsteelwheels.aluminiumisabetterconductorofheat,soalloywheelscandissipateheatfrombrakeesandtiresmoreeffectivelythansteelones.,車輪可采用雙面鋼化板壓制而成，也可采用鑄造的鋁合金材料。除了外觀漂亮之外，鋁合

28、金比鋼更輕，因此鋁合金車輪應(yīng)用較廣。另外鋁合金導(dǎo)熱性更好，因此相比鋼制車輪，制動(dòng)器和車輪產(chǎn)生的熱量更容易被鋁合金車輪散發(fā)。,thetireprovidesacushionbetweenthevehicleandtheroadtoreducethetransmissionofroadshocks.italsoprovidesfrictiontoallowthevehicletoperformitsnormaloperations.moderntiresaremanufacturedfromarangeofmaterials.therubberismainlysynthetic.twotypeso

29、ftireconstructionarecommon:cross-plyandradial.mostpassengercarsnowuseradialtires,andradialsarereplacingcross-plytireson4-wheeldrivesandheavyvehicles.,輪胎在汽車和路面之間起緩沖作用，能減小路面沖擊。同時(shí)輪胎也提供了車輪正常行駛所需的摩擦力。輪胎是由多種材料加工而成，橡膠多是人工合成的。最常見的輪胎類型是子午線輪胎和斜交輪胎?，F(xiàn)在大部分乘用車都采用子午線輪胎，在四輪驅(qū)動(dòng)和商用車上，子午線輪胎也正在取代斜交胎。,tubetiresrequireani

30、nnertubetosealairinsidethetire.tubelesstiresareeliminatingtheinnertubebymakingthecompletewheelandtireassemblyairtight.aspecialairtightvalveassemblyisneeded.thiscanbetightfitintotherimorcanbeheldwithanutandsealingwashers.,有內(nèi)胎的輪胎用內(nèi)胎來密封內(nèi)部氣體。無內(nèi)胎的輪胎則要求車輪和輪胎具有很好的密封性，這就需要專用的密封件，可以緊固在輪緣上，也可用螺釘和密封圈來固定。,1.3.4

31、Brakingsystem制動(dòng)系統(tǒng),Drumbrakeshaveadrumattachedtothewheelhub,andbrakingoccursbymeansofbrakeshoesexpandingagainsttheinsideofthedrum.Withdiscbrakes,adiscattachedtothewheelhubisclenchedbetweentwobrakepads.onlightvehicles,bothofthesesystemsarehydraulicallyoperated.thebrakepedaloperatesamastercylinder.hydr

32、auliclinesandhousesconnectthemastercylindertobrakecylindersatthewheels.mostmodernlightvehicleshaveeitherdiscbrakesonthefrontwheelsanddrumbrakesontherearordiscbrakesonall4wheels.discbrakesrequiregreaterforcestooperatethem.abrakeboosterassistthedriverbyincreasingtheforceappliedtothemastercylinderwhent

33、hebrakeisoperated.,鼓式制動(dòng)器的制動(dòng)鼓和輪轂連接，制動(dòng)蹄張開壓緊制動(dòng)鼓內(nèi)側(cè)從而產(chǎn)生制動(dòng)。在盤式制動(dòng)器上，連著輪轂的制動(dòng)盤被緊緊夾在兩個(gè)制動(dòng)塊之間。輕型汽車上都采用液壓制動(dòng)系統(tǒng)，制動(dòng)踏板控制制動(dòng)主缸，通過液壓管路與車輪上的制動(dòng)輪缸相連。現(xiàn)在輕型汽車上的制動(dòng)器，前輪采用盤式，后輪采用鼓式，或全部采用盤式。相比鼓式制動(dòng)器，盤式制動(dòng)器需要更大的作用力。在制動(dòng)時(shí)采用增壓器輔助駕駛員提高施加在主缸上的制動(dòng)力。,pressedairoperatingonlargediameterdiaphragmsprovidesthelargeforcestothebrakeassemblythatar

34、eneeded.anaircompressorpumpsairtostoragetanks.drivercontrolledvalvesthendirectthecompressedairtodifferentwheelunitstooperatethefrictionbrakes.onarticulatedvehicles,anydelayinapplyingthetrailerbrakeshouldbeminimize.thisisachievedbyusingarelayvalveandaseparatereservoironthetrailer.thisarrangementalsoa

35、ppliesthebrakesifthetrailerdisconnectedfromtheprimemover.,重型商用車多采用氣壓制動(dòng)系統(tǒng)，壓縮氣體作用在直徑較大的膜片上時(shí)能為制動(dòng)總成提供較大的制動(dòng)力。氣壓制動(dòng)系統(tǒng)靠空氣壓縮機(jī)把氣體吸入儲(chǔ)氣罐。駕駛員控制閥門開啟，使壓縮氣體進(jìn)入車輪制動(dòng)氣室進(jìn)行制動(dòng)。在鉸接車輛的拖車上采用繼動(dòng)閥和單獨(dú)的儲(chǔ)氣罐，以減小拖車制動(dòng)系統(tǒng)的時(shí)間延遲，這種布置方式還可以在拖車失去動(dòng)力時(shí)制動(dòng)拖車。,allvehiclesmustbefittedwithatleast2independentsystems.theywereoncecalledtheservicebrake

36、andtheemergencybrake.nowtheyareusuallyreferredtoasthefootbrakeandtheparkbrake.mostlightvehiclesuseafootbrakethatoperatesthroughahydraulicsystemonallwheelsandahandoperatedbrakethatactsmechanicallyontherearwheelsonly.onecommonuseofthehandbrakesystemistoholdthevehiclewhenitisparked.thesystemaredesigned

37、tobeindependentSothatifonefails,theotherisstillavailable.,所有汽車必須安裝至少兩套獨(dú)立的制動(dòng)系統(tǒng)，即行車制動(dòng)系統(tǒng)與緊急制動(dòng)系統(tǒng)，一般被稱之為腳制動(dòng)和停車制動(dòng)。大部分輕型汽車的腳制動(dòng)通過液壓系統(tǒng)作用在四個(gè)車輪上，而其手制動(dòng)則是機(jī)械式的，且僅作用在后輪。手制動(dòng)的一個(gè)普通用途就是停車時(shí)對汽車進(jìn)行制動(dòng)。設(shè)計(jì)兩套獨(dú)立的制動(dòng)系統(tǒng)的目的就是當(dāng)一套失效時(shí)，另一套仍可工作。,1.4.1Electricalsystem電器系統(tǒng),Theelectricalsystemsupplieselectricityforthestarter,ignition,ligh

38、tsandheater.Theelectricitylevelismaintainedbyachargingcircuit.,電器系統(tǒng)為起動(dòng)機(jī)、點(diǎn)火系、照明和加熱設(shè)備提供電流，電流的大小由充電電路來維持。,Thechargingsystemprovideselectricalenergyforalloftheelectricalcomponentsonthevehicle.themainpartsofthechargingsysteminclude:thebattery,thealternator,thevoltageregulatorwhichisusuallyintegraltotheal

39、ternator,achargingwarningorindicatorlightandwiringthatcompletethecircuits.thebatteryprovideselectricalcomponentsofthevehicle.italsochargesthebattertoreplacetheenergyusedtostarttheengine.thevoltageregulatorpreventsovercharging.,充電系統(tǒng)為汽車上所有的電器系統(tǒng)提供電能。充電系統(tǒng)主要組成部分有：蓄電池、交流發(fā)電機(jī)、穩(wěn)壓器（多集成在發(fā)電機(jī)中），充電指示燈和組成電路的電線。汽車起

40、動(dòng)時(shí)由蓄電池提供能量，一旦發(fā)動(dòng)機(jī)開始工作，交流電機(jī)為電氣設(shè)備供電，同時(shí)還對蓄電池進(jìn)行充電，以補(bǔ)償起動(dòng)所消耗的電能。穩(wěn)壓器則防止過載。,1.4.2Starting啟動(dòng)系統(tǒng),Thestaringsystemconsistsofthebattery,cables,startermotor,flywheelringgearandtheignitionswitch.duringstarting,twoactionsoccur.thepinionofthestartermotorengageswiththeflywheelringgearandthestartermotorthenoperatestocr

41、anktheengine.thestartermotoris,anelectricalmotormountedontheengineblockandoperatedfromthebattery.,起動(dòng)系統(tǒng)包括電池、電纜、啟動(dòng)電機(jī)、飛輪齒圈和點(diǎn)火開工。起動(dòng)需要兩個(gè)動(dòng)作，啟動(dòng)電機(jī)齒輪和飛輪齒圈嚙合，從而帶動(dòng)發(fā)動(dòng)機(jī)轉(zhuǎn)動(dòng)。起動(dòng)電機(jī)安裝在發(fā)動(dòng)機(jī)殼體上，靠電池工作。,1.4.3Ignition點(diǎn)火系統(tǒng),Abasicignitionsystemconsistsofthebattery,low-tensioncables,theignitioncoil,distributor,coilhigh-tension

42、cable,sparkplukcablesandsparkplugs.theignitionsystemprovideshighintensesparkstosparkplugstoignitethefuelchargesinthecombustionchambers.thesparksmustbesuppliedattherighttimeandtheymusthavesufficientenergyoverarangeofconditionstoignitethecharges.theenergycomesfromthebatteryandalternator,andvoltageisin

43、creasedbytheignitioncoil.thesystemhastwocircuits.theprimaryorlow-tensioncircuitinitiatesthespark.thesecondaryorhigh-tensioncircuitproducesthehighvoltageanddistributesittosparkplugs.,點(diǎn)火系統(tǒng)包括電池、低壓電纜、點(diǎn)火線圈、分電器、高壓電纜、火花塞連線和火花塞。點(diǎn)火系統(tǒng)在火花塞處產(chǎn)生高壓火花，點(diǎn)燃發(fā)動(dòng)機(jī)燃燒室內(nèi)的燃油混合物。點(diǎn)火系統(tǒng)必須在恰當(dāng)?shù)臅r(shí)刻提供火花，并且能量滿足各種工況的要求。電池和交流發(fā)電機(jī)為點(diǎn)火系統(tǒng)供電，點(diǎn)

44、火線圈提高電壓。點(diǎn)火系統(tǒng)由兩級電路組成，初級電路（低壓電路）初始化火花，次級電路（高壓電路）產(chǎn)生高壓電，并分到各個(gè)火花塞。,2.1principleofoperation工作原理2.1.1energyandpower能源和動(dòng)力,Engineisusedtoproducepower.Thechemicalenergyinfuelisconvertedtoheatbytheburningofthefuelatacontrolledrate.Thisprocessiscalledcombustion.Ifenginecombustionoccurswiththepowerchamber.,theen

45、gineiscalledinternalcombustionengine.Ifcombustiontakesplaceoutsidethecylinder,theengineiscalledanexternalcombustionengine.,能源用于產(chǎn)生動(dòng)力。燃料以控制的速率燃燒，燃料中的化學(xué)能轉(zhuǎn)換為熱能。這個(gè)過程叫做燃燒。如果發(fā)動(dòng)機(jī)燃燒發(fā)生在動(dòng)力室內(nèi)，這種發(fā)動(dòng)機(jī)叫做內(nèi)燃機(jī)。如果燃燒發(fā)生在氣缸外，這樣的發(fā)動(dòng)機(jī)叫做外燃發(fā)動(dòng)機(jī)。,Engineusedinautomobilesareinternalcombustionheatengines.Heatenergyreleasedinthecomb

46、ustionchamberraisesthetemperatureofthecombustiongaseswithinthechamber.Theincreaseingastemperaturecausesthepressureofthegasestoincrease.Thepressuredevelopedwithinthecombustionchamberisappliedtotheheadofapistontoproduceausablemechanicalforce,whichisthenconvertedintousefulmechanicalpower.,汽車使用的發(fā)動(dòng)機(jī)是內(nèi)燃發(fā)動(dòng)

47、機(jī)。在燃燒室內(nèi)釋放的熱能提高了室內(nèi)燃燒氣體的溫度。氣體溫度的增肌使氣體的壓力增加。在燃燒室內(nèi)產(chǎn)生的壓力作用于活塞的頂部，產(chǎn)生機(jī)械力，這個(gè)力轉(zhuǎn)換成有用的機(jī)械動(dòng)力。,2.1.2EngineTerms,Linkingthepistonbyaconnectingrodtoacrankshaftcausesthegastorotatetheshaftthroughhalfaturn.Thepowerstroke“usesup”thegas,someansmustbeprovidedtoexpeltheburntgasandrechargethecylinderwithafreshpetrol-airmi

48、xture:thiscontrolofgasmovementisthedutyofthevalves；aninletvalveallowsthenewmixturetoenterattherighttimeandanexhaustvalveletsouttheburntgasafterthegashasdoneitsjob.Enginetermsare：,活塞通過連桿和曲軸連接，使得氣體帶動(dòng)曲軸旋轉(zhuǎn)半圈。作功沖程耗盡了所以的氣體，這樣就必須采取相應(yīng)的措施排出廢氣以及向氣缸內(nèi)充入新鮮的可燃混合氣：氣體的運(yùn)動(dòng)由氣門來控制。進(jìn)氣閥允許新的混合氣體在適當(dāng)?shù)臅r(shí)間進(jìn)入，排氣閥在作功完成后，可以放出燃燒后的

49、氣體。引擎術(shù)語：,TDC(TopDeadCenter):thepositionofthecrankandpistonwhenthepistonisfartherawayfromt,hecrankshaft.,上止點(diǎn)：活塞處于離曲軸最遠(yuǎn)處時(shí)，曲柄和活塞所處的位置。,BDC(BottomDeadCenter):thepositionofthecrankandpistonwhenthepistonisnearesttothe,crankshaft.,下止點(diǎn)：活塞處于離曲軸最近處時(shí)，曲柄和活塞所處的位置。,Stroke:thedistancebetweenBDCandTDC;strokeiscontr

50、olledbythecrankshaft.行程：上止點(diǎn)和下止點(diǎn)間的距離;行程由曲軸控制。,Bore:theinternaldiameterofthecylinder.,缸徑：氣缸的內(nèi)徑,Sweptvolume:thevolumebetweenTDCandBDC.有效容積：上止點(diǎn)和下止點(diǎn)間的容積Enginecapacity:thisisthesweptvolumeofallthecylinders.e.g.afour-cylinderenginehavingacapacityoftwoliters(2000cm3)hasacylindersweptvolumeof500cm3.發(fā)動(dòng)機(jī)排量：所有氣

51、缸的有效容積之和.例如一四缸發(fā)動(dòng)機(jī)有能力兩升（2000cm3）有一個(gè)氣缸排量500cm3。Clearancevolume:thevolumeofthespaceabovethepistonwhenitisatTDC.燃燒室容積：活塞處于上止點(diǎn)時(shí)，活塞上方的體積Compressionratio=(sweptvol+clearancevol)(clearancevol)壓縮比：（有效容積+燃燒室容積）/燃燒室容積Two-stroke:apowerstrokeeveryrevolutionofthecrank.兩沖程：曲柄旋轉(zhuǎn)一圈作功一次。Four-stroke:apowerstrokeeveryo

52、therrevolutionofthecrank.四沖程：曲柄旋轉(zhuǎn)兩圈作功一次。2.1.3TheFour-strokeSpark-ignitionEngineCycleThespark-ignitionengineisaninternal-combustionenginewithexternallysuppliedinignition,whichconvertstheenergycontainedinthefueltokineticenergy.Thecycleofoperationsisspreadoverfourpistonstrokes.Tocompletethefullcycleitt

53、akestworevolutionsofthecrankshaft.火花點(diǎn)火式發(fā)動(dòng)機(jī)是由外部提供點(diǎn)火的內(nèi)燃機(jī)，從而將含在燃料內(nèi)的能量轉(zhuǎn)化成動(dòng)能。發(fā)動(dòng)機(jī)的一個(gè)工作循環(huán)分布在活塞的四個(gè)行程中，一個(gè)完整的工作循環(huán)曲軸需要轉(zhuǎn)動(dòng)兩圈。Thedownward-movingpistonincreasesthevolumeinthecylinderanddrawsinfreshair-fuelmixturethroughtheopenintakevalve.向下運(yùn)動(dòng)的活塞使氣缸里的體積增大，并且將新的空氣燃料混合物通過節(jié)氣門吸進(jìn)氣缸。Theupward-movingpistonreducesthevolume

54、inthecylinderandcompressestheair-fuelmixture.ShortlybeforeTDCisreached,thesparkplugignitesthecompressedair-fuelmixtureandthusinitiatesthecombustionprocess.Ahighercompressionratiomeansbetterutilizationofthefuel.Theextentofcompressionisrestrictedbytheknocklimit.向上運(yùn)動(dòng)的活塞使氣缸里的體積減小，從而壓縮空氣燃料混合物。在活塞即將到達(dá)上止點(diǎn)的

55、瞬間，火花塞點(diǎn)燃壓縮的空氣燃油混合氣，從而燃燒過程開始了。壓縮比越高，燃料利用率越高，但是壓縮的程度受到爆震極限的限制。Aftertheignitionsparkatthesparkplughasignitedthecompressedair-fuelmixture,thetemperatureincreasesastheresultofcombustionofthemixture.Thepressureinthecylinderincreasesandforcesthepistondownwards.Thepistontransferspowertothecrankshaftviatheco

56、nnectingrod.當(dāng)火花塞噴出的火花點(diǎn)燃壓縮的空氣燃料混合物后，空氣燃料混合物開始然后，隨之氣缸內(nèi)的溫度開始升高。氣缸里的壓力也隨之增加，使得活塞向下運(yùn)動(dòng)。這樣活塞就把動(dòng)力通過連桿傳遞給曲軸。,Theupward-movingpistonexpelsthecombustedgases（exhaustgas）throughtheopenexhaustvalve.Afterthis4thstroke,thecycleisrepeated.,向上運(yùn)動(dòng)的活塞使燃燒后的氣體（廢氣）通過排氣門排出氣缸。在這第四個(gè)行程后，整個(gè)工作工程將重復(fù)進(jìn)行。,2.1.4EngineOverallMechanics

57、發(fā)動(dòng)機(jī)的總體構(gòu)造,Theenginehashundredsofotherparts.Themajorpartsofengineareengineblock,engineheads,pistons,connectingrods,crankshaftandvalves.Theotherpartsarejoinedtomakesystems.Thesesystemsarethefuelsystem,intakesystem,ignitionsystem,coolingsystem,lubricationsystemandexhaustsystem.Eachofthesesystemshasadefi

58、nitefunction.Thesesystemswillbediscussedindetaillater。,發(fā)動(dòng)機(jī)有上百個(gè)其它部件。發(fā)動(dòng)機(jī)的主要部件是發(fā)動(dòng)機(jī)缸體、發(fā)動(dòng)機(jī)頭、活塞、連桿、曲軸和閥門。其他部分也加入到系統(tǒng)中。這些的系統(tǒng)是燃油系統(tǒng)、進(jìn)氣系統(tǒng)、點(diǎn)火系統(tǒng)、冷卻系統(tǒng)、潤滑系統(tǒng)和排氣系統(tǒng)。這些系統(tǒng)中的每一個(gè)都有一個(gè)明確的功能。這些系統(tǒng)以后將進(jìn)行詳細(xì)論述。,2.2EngineBlockandCylinderHead2.2.1EngineBlock,Theengineblockisthebasicframeoftheengine.Allotherenginepartseitherfitinsi

59、deitorfastentoit.Itholdsthecylinders,waterjackets,andoilgalleries.Theengineblockalsoholdsthecrankshaft,whichfastenstothebottomoftheblock.Thecamshaftalsofitsinsidetheblock,exceptonoverhead-camengines(OHC).Inmostcars,thisblockismadeofgrayiron,oranalloy(mixture)ofgrayironandothermetals,suchasnickelorch

60、romium.Engineblocksarecastings.,氣缸體是發(fā)動(dòng)機(jī)的基本框架。發(fā)動(dòng)機(jī)的其他零件都安裝在它里面或者固定在它上。缸體里有,氣缸，水套和油道。曲軸也固定在氣缸體底部。除了頂置凸輪(OHC)發(fā)動(dòng)機(jī)以外，凸輪軸都安裝在氣缸體里面。在大多數(shù)汽車?yán)?，氣缸體由灰鑄鐵或者一種灰鑄鐵和其他金屬的合金(混合物)做成，例如鎳或鉻。氣缸體是鑄件。,Someengineblocks,especiallythoseinsmallercars,aremadeofcastaluminum.Thismetalismuchlighterthaniron.However,ironwearsbetterth