1、Todaysaveragecarcontainsmorethan15,000separate,individualpartsthatmustworktogether.Thesepartscangroupedintofourmajorcategories:engine,body,chassisandelectricalequipment.1layoutThebodylayoutofapassengercarisdesignedtokeeppassengerssafeandcomfortable.Thebodystylingprovidesanattractive,colorful,moderna

2、ppearanceforthevehicle.1.1汽車車身的設(shè)計(jì)還應(yīng)該保證乘員的安全舒適。車身的造型（款式）使得汽車看起來漂亮迷人、色彩斑斕、時(shí)尚前衛(wèi)。Theengineactsasthepowerunit.Theinternalcombustionengineismostcommon:thisobtainsitspowerbyburningaliquidfuelinsidetheenginecylinder.Therearetwotypesofengine:gasoline（alsocalledaspark-ignitionengine）anddiesel（alsocalledacompr

3、ession-ignitionengine）.Bothenginesarecalledheatengines;theburningfuelgeneratesheatwhichcausesthegasinsidethecylindertoincreaseitspressureandsupplypowertorotateashaftconnectedtothepowertrain.1.2發(fā)動(dòng)機(jī)作為動(dòng)力設(shè)備，常見的類型是內(nèi)燃機(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)氣壓上升，產(chǎn)生的能量驅(qū)動(dòng)軸旋轉(zhuǎn)，

4、并傳遞給動(dòng)力傳動(dòng)系。Thechassisincludesthepowertrain,steering,suspension,andbrakingsystems.1.3Powertrainsystem:conveysthedrivetothewheelsSteeringsystem:controlsthedirectionofmovementSuspensionandwheelsabsorbtheroadshocksBrakingslowsdownthevehicleThepurposeofthecompletesuspensionsystemistoisolatethevehiclebodyf

5、romroadshocksandvibrations,whichwillotherwisebetransferredtothepassengersandload.Itmustalsokeepthetiresincontactwiththeroadregardlessofroadsurface.Abasicsuspensionsystemconsistsofsprings,axles,shockabsorbers,arms,rodsandballjoints.1.3.3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

6、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)向機(jī)構(gòu)。Drumbrakeshaveadrumattachedtothewheelhub,andbrakingoccursbymeansofbrakeshoesexpandingagainsttheinsideofthedrum.Withdiscbrakes,adiscattachedtothewheelhubisclenchedbetweentwobrakepads.1.3.4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。Linking

7、thepistonbyaconnectingrodtoacrankshaftcausesthegastorotatetheshaftthroughhalfaturn.2.1.2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。Whenavehicleistobemovedfromresttheclutchmustengageastationarygearboxshaftwiththeengine;thismustberotatingatahighspeedtoprovidesufficientpowerorelsetheloadwillbetoogreatandtheenginewillsta

8、ll（cometorest）.3.2.1當(dāng)汽車原地起步時(shí)，離合器要將靜止的變速器軸同發(fā)動(dòng)機(jī)接合起來，此時(shí)發(fā)動(dòng)機(jī)必須高速旋轉(zhuǎn)以提供足夠大的功率，否則載荷過大將引起發(fā)動(dòng)機(jī)熄火。Thedrivingmember:Thedrivingmemberconsistsoftwoparts:theflywheelandthepressureplate.Theflywheelisbolteddirectlytotheenginecrankshaftandrotateswhenthecrankshaftturns.Thepressureplateisboltedtotheflywheel.Theresultist

9、hatbothflywheelandpressureplaterotatetogether.主動(dòng)部分由飛輪和壓盤兩部件組成。飛輪用螺栓直接連接到發(fā)動(dòng)機(jī)曲軸上，隨曲軸旋轉(zhuǎn)而旋轉(zhuǎn)。壓盤與飛輪連接，這樣飛輪和壓盤一起旋轉(zhuǎn)。Thedrivenmember:Thedrivenmember,orclutchdisc,islocatedbetweentheflywheelandpressureplate.Thedischasasplinedhubthatlockstothesplinedinputshaftonthegearbox.Anyrotationoftheclutchdiscturnstheinpu

10、tshaft.從動(dòng)部分（或從動(dòng)盤）位于飛輪和壓盤之間。從動(dòng)盤上有花鍵轂，連接著變速器上帶花鍵的輸入軸。從動(dòng)盤的旋轉(zhuǎn)帶動(dòng)變速器輸入軸隨之轉(zhuǎn)動(dòng)。Thedrivenmember:Theinnerpartoftheclutchdisc,calledthehubflange,hasanumberofsmallcoilsprings.Thesespringsarecalledtorsionalsprings.Theyletthemiddlepartoftheclutchdiscturnslightlyonthehub.Thus,thespringsabsorbthetorsionalvibrationso

11、fthecrankshaft.Whenthespringshavecompressedcompletely,theclutchmovesbackuntilthespringsrelax.Inotherwords,theclutchabsorbstheseenginevibrations,preventingthevibrationsfromgoingthroughthedrivetrain.當(dāng)從動(dòng)盤的內(nèi)側(cè)（轂緣）有一些叫作扭轉(zhuǎn)彈簧的小螺旋彈簧，這些彈簧使得從動(dòng)盤中部相對從動(dòng)盤轂?zāi)苡休p微轉(zhuǎn)動(dòng)，從而吸收曲軸的扭轉(zhuǎn)振動(dòng)。壓緊彈簧完全壓縮時(shí)，離合器向后移動(dòng)直到彈簧開始伸張為止。也就是說，離合器吸收發(fā)動(dòng)

12、機(jī)的振動(dòng)，防止振動(dòng)傳遞給傳動(dòng)系。operatingmembers:Thesearethepartsthatreleasepressurefromtheclutchdisc.Theoperatingmembersconsistoftheclutchpedal,clutchreturnspring,clutchlinkage,clutchfork,andthrowoutbearing.Theclutchlinkageincludestheclutchpedalandamechanicalorhydraulicsystemtomovetheotheroperatingmembers.操縱機(jī)構(gòu)釋放離合

13、器盤的壓力。操縱機(jī)構(gòu)由離合器踏板、回位彈簧、離合器桿系、分離叉和分離軸承等組成。離合器桿系包括離合器踏板以及用來操縱其它部件的機(jī)械式或液壓式操縱系統(tǒng)。operatingmembers:Whentheclutchpedalisdepressed,theclutchlinkageoperatestheclutchfork.Theclutchfork,orreleasefork,movesthethrowoutbearingagainstthepressureplatereleaselevers.Theseleversthencompressspringsthatnormallyholdtheclu

14、tchdisctightlyagainsttheflywheel.踩下離合器踏板，離合器桿系操縱分離叉。分離叉帶動(dòng)分離軸承壓向壓盤上的分離杠桿，分離杠桿壓縮壓緊彈簧。通常情況下，壓緊彈簧使從動(dòng)盤和飛輪緊密接合。operatingmembers:Whentheclutchpedalisreleased,thepressureplateforcestheclutchdiscagainsttheflywheel.Theclutchreturnspringhelpsraisethepedal.釋放離合器踏板，壓盤使從動(dòng)盤同飛輪接合，回位彈簧使離合器踏板抬起。Therearethreetypesofma

15、nualtransmissionsSliding-meshTransmission、Constant-meshTransmission、Synchro-meshTransimission。3.3.1Inthecaseofasliding-meshgearbox,gearchangingdemandsskillifnoiseistobeavoided.Crashing(orclashing)ofthegearsastheresultofabadchangesuggeststhereasonwhythistypeisoftencalledacrashtypegearbox.對滑動(dòng)嚙合變速器來說，換

16、擋時(shí)要避免噪聲是需要技巧的。齒輪打齒是由換擋不當(dāng)引起的，這也是滑動(dòng)嚙合變速器經(jīng)常被稱為“碰撞”型變速器的原因。MT:ManualTransmissionAMT:AutomaticMannuallyTransmissionsCVT:ContinuouslyVariableTransmissionsAT:AutomaticTransmissionThesuspensionconnectsthefinaldriveassemblytothecarbody.Thefinaldrivemovesupanddowninrelationtotheengineandtransmission.Acoupling

17、isneededthatpermitsmovementbetweenthefinaldriveandtransmission.Theuniversaljoints(U-joints)andslidingjointsFig.3-8providethiscoupling.3.4.2懸架連接著主減速器總成和車身。主減速器相對于發(fā)動(dòng)機(jī)和變速器上下運(yùn)動(dòng)，這樣在主減速器和變速器之間就需要萬向節(jié)和滑動(dòng)聯(lián)軸節(jié)等連接裝置來允許其相對運(yùn)動(dòng)。Therearetwotypesofuniversaljointscrosstypejointandconstant-velocityuniversaljoint.Heretw

18、oU-shapedpiecesareplacedperpendiculartooneanotherandjoinedwithasimplecrossFig.3-16.TheU-shapedpiecesarecalledyokes.Thecrossthatconnectsthemiscalledaspider.Thearmsthatextendfromthespiderarecalledtrunnions.Thetwoyokesareata90angletooneanother.Mostcarshavetwouniversaljoints,oneateachendofthepropellersh

19、aft.兩個(gè)U形片垂直布置，通過十字叉連接在一起。U形片稱為萬向節(jié)叉，連接萬向節(jié)叉的十字叉叫作十字軸，從十字軸延伸出的臂叫作耳軸，兩個(gè)萬向節(jié)叉成90布置。多數(shù)汽車采用兩個(gè)萬向節(jié)，在傳動(dòng)軸的每一端各有一個(gè)萬向節(jié)。Ashaftwhichreceivesthedrivefromacrosstypejointvariesitsspeedduringrotation;thegreaterthedriveanglethegreaterthespeedvariation.Aconstantrotationalspeedcanberestoredbyfittingasecondjointinawaysucht

20、hatwhenthefirstjointincreasesitsspeedthesecondjointdecreasesitsspeed.傳動(dòng)軸接收十字軸式萬向節(jié)傳來的動(dòng)力，轉(zhuǎn)動(dòng)時(shí)其速度發(fā)生變化。傳動(dòng)角越大，速度變化越大。要實(shí)現(xiàn)等速，必須以某種方式安裝第二個(gè)萬向節(jié)，這樣第一個(gè)萬向節(jié)使轉(zhuǎn)速增大，第二個(gè)萬向節(jié)就使轉(zhuǎn)速減少。Largecrownwheelsreducethegroundclearanceunderthedifferential.Inthecaseofpinionaxlesandplanetaryhubreductionaxles,thedifferentialandthehalf-s

21、haftscanbemadesmallerbysplittingthereduction.Thismakesitpossible,eveninthecaseofhighpoweroutputs,toachievesufficientgroundclearanceofthevehicle.從動(dòng)錐齒輪尺寸大，就降低了汽車的離地間隙。如果采用圓柱齒輪式和行星齒輪式輪邊減速器，通過兩級減速的形式可極大減小差速器和半軸的尺寸。這樣，汽車就可以獲得足夠大的離地間隙，即使輸出功率要求較大也可以。Planetarygearsareusedmainlyinfinaldrives,rear-mountedspli

22、tterboxesand,aboveall,inautomatictransmissions.Thesimplestformofplanetarygear(theplanetary-geartrain)consistsofsungear,ringgearandarmwithplanetgears.Eachofthethreeelementsmayactasdrive,outputormaybeatrest.Therefore,greatvariationispossibleasregardsthetransmissionratio,rangingasfarasareversalofthedir

23、ectionofrotation.Theparallelmeshingofseveralgearsunderloadpermitsacompactconstruetion.行星齒輪系主要應(yīng)用在主減速器、后置副變速器和自動(dòng)變速器上。最簡單的行星齒輪系統(tǒng)由太陽輪、齒圈和行星輪組成。三部件中任意一個(gè)都可作輸入、輸出或保持靜止。這樣，依照變速比的不同可得到較大的變速范圍，汽車的倒行也能實(shí)現(xiàn)。承載齒輪的平行嚙合使行星輪系結(jié)構(gòu)較緊湊。Whenavehicleiscorneredtheinnerwheelmovesthroughashorterdistancethantheouterwheel.Thisme

24、ansthattheinnerwheelmustslowdownandtheouterwheelmustspeedup.Duringthisperioditisdesirablethateachdrivingwheelmaintainsitsdrivingaction.Thedifferentialperformsthesetwotasks.3.6當(dāng)汽車轉(zhuǎn)彎時(shí)，內(nèi)側(cè)車輪比外側(cè)車輪行駛的距離要短，這說明內(nèi)側(cè)車輪比外側(cè)車輪轉(zhuǎn)得要慢。在此期間，維持每個(gè)驅(qū)動(dòng)車輪的行駛狀態(tài)是很重要的。這兩個(gè)任務(wù)由差速器來完成。Whenthevehicleistravellingstraight,theleverwill

25、dividethedrivingforceequallyandbothdiscswillmovethesameamount.Whenthevehiclecorners,thedrivingforcewillstillbedividedequallybuttheinnerdiscwillnowmovethroughasmallerdistance;thiswillcausethelevertopivotaboutitscenterwhichwillprizeforwardtheouterdisctogiveitagreatermovement.Thisactionshowsthatthetorq

26、ueappliedtoeachdrivingwheelisalwaysequalhencethedifferentialissometimescalledatorqueequalizer.汽車直行時(shí)，杠桿平均分配驅(qū)動(dòng)力，兩個(gè)圓盤移動(dòng)相同的距離。汽車轉(zhuǎn)彎時(shí)驅(qū)動(dòng)力仍然會平均分配，但是內(nèi)側(cè)圓盤移動(dòng)的距離要小一些，這使得杠桿繞中心轉(zhuǎn)動(dòng)，推動(dòng)外側(cè)圓盤使之移動(dòng)更大的距離。這個(gè)過程表明扭矩總是平均分配給每個(gè)驅(qū)動(dòng)輪，因此差速器有時(shí)也叫做扭矩平衡裝置。Energyisrequiredwhenavehicleisacceleratedfromresttoacertainspeed.Aproportionoftha

27、tenergyisnowstoredinthevehicleandiscalledkineticenergy.Inordertoreducethespeedofthevehicle,thebrakeshavetoconvertthekineticenergytoheatenergy;thespeedofconversiongovernstherateatwhichthevehicleslowsdown.4.1汽車從原地起步加速到某一速度需要能量。儲存在汽車中的那部分能量稱為動(dòng)能。要降低車速，制動(dòng)器必須把汽車的動(dòng)能轉(zhuǎn)換為熱能；轉(zhuǎn)換的速度決定了汽車減速的快慢。Abrakingsystemconsi

28、stsofanenergysupplyingdevice,acontroldevice,atransmissiondeviceandthebrake.Thethreetypesofbrakingsystemsareinusetoday:servicebrakingsystem,parkingbrakingsystemandadditionalretarding-brakingsystem.目前使用的制動(dòng)系統(tǒng)有三種類型：行車制動(dòng)系，住車制動(dòng)系和輔助制動(dòng)系.Twotypesofbrakesareusedinmoderncars:drumbrakesanddiscbrakes.目前使用的制動(dòng)器有兩種

29、類型：鼓式制動(dòng)器和盤式制動(dòng)器.Twotypesofhydraulicbrakesystemsareused.1、Themanualbrakesystemisthesimples.2、Thepowerbrakesystem.Exposedtotheair,discbrakesradiatetheheattotheairbetterthandrumbrakes:Thismeansthatthebrakecanbeoperatedcontinuouslyforalongerperiod,i.e.theyhaveagreaterresistancetofade(fall-offinbrakeeffic

30、iencyduetoheat).4.2.2由于暴露于空氣中，盤式制動(dòng)器的散熱效果比鼓式的要好：這意味著盤式制動(dòng)器能持續(xù)使用更長的時(shí)間，也就是說其抗熱衰退性(因受熱導(dǎo)致制動(dòng)效能下降)要好得多。Discbrakesasusedinmostpassengercarsareslowlybeginningtobeusedincommercialvehiclesaswell.Asidefromtheiruseinfastcoaches,currentuseofdiscbrakesincommercialvehiclesisprimarilylimitedtofront-axlebrakesforcomme

31、rcialvehiclesuptoaweightofapprox.7.5twhicharedriveninamannersimilartopassengercars.常用在許多乘用車上的盤式制動(dòng)器正逐漸被用于商用車它們除用于快速客車外，目前盤式制動(dòng)器在商用車上的用途基本限制在前軸制動(dòng)，因?yàn)樯逃密囍亓考s等于7.5噸時(shí)驅(qū)動(dòng)方式與乘用車相似TherearetwomainwaysofbuildingautomobilesTheyarebuiltusingbody/frameconstructionandunitizedbodyconstruction.Aseparateframemustbelight

32、yetstrongenoughtoresistthevariousloadsandroadforces.Commercialvehiclesnormallyuseaseparatesteelframetoprovidetherigidityneededtosupportthevariousloads.Thetwolongsidemembersofchannelsectionarerivetedtoanumberofcrossmemberstogivealowweightframewhichoffersgreatresistancetobending,twisting.4.9分離式車架必須足夠輕

33、巧而且結(jié)實(shí)，以承受變化的載荷和路面作用力。商用車通常使用分離式鋼質(zhì)車架，以獲得較好的剛度來承受變化的載荷。兩根槽形的長縱梁鉚接著很多橫梁，這使車架重量較輕，具有較好的抗彎和抗扭能力。Mostcarsuseaunitizedbodyconstruetion,acombinedbodyandframe.Unitizedbodyconstruetionislighterthanbody/frameconstruetion,butnoisier.Rubbermountsareusedbetweenthebodysectionandmechanicalpartstoabsorbvibrations.Th

34、efloorpanismadeofsectionsthatsupporttherearsuspensionandthetransmission.多數(shù)轎車采用承載式車身，也就是車身和車架融為一體。承載式車身比非承載式車身質(zhì)量輕，但噪聲大。在車身和機(jī)械部件之間安裝橡膠塊以吸收振動(dòng)。地板由一些支撐后懸架和變速器的部件組成。Thepurposeofventingsystemsistodrawinfreshairandremovestaleairfromtheinteriorofthecar.Freshairventingsystemsdirectairtotwodifferentplaces.Firs

35、t,theycandirectoutsideairintotheheaterhousing.Thisaireithercanbypassthecoiloritcanbeheatedbythecoil.Second,theaircanmovedirectlyintothepassengercompartmentthroughsmallventdoorsinthedashpaneloratfloorlevel.Ventingalsocantakeplacebyopeningthewindows.通風(fēng)系統(tǒng)吸入新鮮的空氣，排除車內(nèi)不新鮮的空氣。通風(fēng)系統(tǒng)將新鮮空氣引入兩個(gè)地方。首先，通風(fēng)系統(tǒng)將外部空氣引

36、入加熱器殼里，空氣從線圈旁流過或被線圈加熱。其次，空氣可通過前圍板或地板上的小風(fēng)門直接將空氣引入車廂打開車窗也可實(shí)現(xiàn)通風(fēng)。Thebasicsteeringsysteminmostcarsisthesame.Thesteeringgearofsteeringboxistheheartofthesteeringsystem.Thisusuallyisnexttotheengine.Ashaftextendsfromthebackofthesteeringgear.Thisshaftisconnectedtothesteeringcolumnorsteeringshaft.Thesteeringwh

37、eelisatthetopofthesteeringcolumn.Anothershaftcomesfromthebottomofthesteeringgear.Thisshaftconnectstothearms,rods,andlinks.Thispartsassembly,calledthesteeringlinkage,connectsthesteeringgeartothepartsatthewheels.Thewheelsandtiresmounttothesteeringknuckles.AsshowninFig.5-1,theknucklesarepivotedatthetop

38、andbottom.Thus,thewheelsandtirescanturnfromsidetoside.5.1多數(shù)汽車的轉(zhuǎn)向系基本上是一樣的。轉(zhuǎn)向系的核心是轉(zhuǎn)向器，一般位于發(fā)動(dòng)機(jī)附近。一根軸從轉(zhuǎn)向器后部伸出，連接著轉(zhuǎn)向柱。方向盤在轉(zhuǎn)向柱的頂端。另一根軸從轉(zhuǎn)向器低端伸出，連接著轉(zhuǎn)向臂、轉(zhuǎn)向拉桿和轉(zhuǎn)向桿系，這些部件總稱為轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)，連接轉(zhuǎn)向器和車輪上的部件。車輪和輪胎安裝在轉(zhuǎn)向節(jié)上。如圖5-1所示，轉(zhuǎn)向節(jié)的上下端可自由轉(zhuǎn)動(dòng)，這樣車輪可從一側(cè)轉(zhuǎn)到另一側(cè)。Whilethesteeringsystemmaylookcomplicated,itworksquitesimply.Whenadriver

39、drivesacarstraightdowntheroad,thesteeringgeariscentered.Thegearholdsthelinkagecenteredsothatthewheelsandtirespointstraightahead.Whenthedriverturnsthesteeringwheel,thesteeringshaftrotatesandthesteeringgearmovestowardthatside.Theshaftcomingoutthebottomofthesteeringgearturns,aswell.Whentheshaftturns,it

40、pullsthelinkagetoonesideandmakesthesteeringknucklesturnslightlyabouttheirpivotpoints.Thus,thesteeringknuckle,spindle,wheels,andtiresturntooneside,causingthecartoturn.轉(zhuǎn)向系看起來復(fù)雜，工作原理卻很簡單。汽車直行時(shí)，轉(zhuǎn)向器處于中間位置，轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)也處于中間位置，車輪直行。駕駛員轉(zhuǎn)動(dòng)方向盤，轉(zhuǎn)向軸旋轉(zhuǎn)，轉(zhuǎn)向器向同側(cè)轉(zhuǎn)動(dòng)，同時(shí)轉(zhuǎn)向器底部的輸出軸也會旋轉(zhuǎn)。輸出軸轉(zhuǎn)動(dòng)時(shí)，會向一側(cè)拉動(dòng)拉桿，使得轉(zhuǎn)向節(jié)繞其支點(diǎn)旋轉(zhuǎn)。這樣，轉(zhuǎn)向節(jié)、轉(zhuǎn)向節(jié)軸端、

41、車輪和輪胎都會向一側(cè)旋轉(zhuǎn)，汽車實(shí)現(xiàn)轉(zhuǎn)向。Thesuspensioncoversthearrangementusedtoconnectthewheelstothebody.Thepurposeistopreventlargeshocks,causedbythewheelsstrikingbumpsintheroad,beingpassedtothevehicleoccupantsandcomponents;otherwisediscomfortanddamagewouldoccur.5.6懸架是車架（車身）與車橋（車輪）之間一切連接傳力裝置的總稱。其目的是防止車輪遇到路面不平產(chǎn)生的巨大沖擊傳給車

42、內(nèi)的貨物和乘客；否則會產(chǎn)生不舒適的感覺和貨物的損壞Thesuspensionsystemhastwosubsystemsthefrontsuspensionandtherearsuspension.懸架系統(tǒng)有兩個(gè)子系統(tǒng)一前懸架和后懸架hesuspensionsystemhastwosubsystemsthefrontsuspensionandtherearsuspension.Thefrontsuspensionismorecomplicatedthantherearsuspension.Thisisbecausethefrontwheelsmustmoveinseveraldifferentdir