汽车构造ENGLISH.docx

汽车构造ENGLISH.docx

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汽车构造ENGLISH

CHAPTER1AUTOMOTIVEBASICS

1.1 PrincipalComponents

Today'saveragecarcontainsmorethan15,000separate,individualpartsthatmustworktogether.Thesepartscangroupedintofourmajorcategories:

engine,body,chassisandelectricalequipment.

1.2 Engine

Theengineactsasthepowerunit.Theinternalcombustionengineismostcommon:

thisobtainsitspowerbyburningaliquidfuelinsidetheenginecylinder.Therearetwotypesofengine:

gasoline（alsocalledaspark-ignitionengine）anddiesel（alsocalledacompression-ignitionengine）.Bothenginesarecalledheatengines;theburningfuelgeneratesheatwhichcausesthegasinsidethecylindertoincreaseitspressureandsupplypowertorotateashaftconnectedtothetransmission.

1.3 Body

Anautomobilebodyisasheetmetalshellwithwindows,doors,ahood,andatrunkdeckbuiltintoit.Itprovidesaprotectivecoveringfortheengine,passengers,andcargo.Thebodyisdesignedtokeeppassengerssafeandcomfortable.Thebodystylingprovidesanattractive,colorful,modernappearanceforthevehicle.

1.4 Chassis

Thechassisisanassemblyofthosesystemsthatarethemajoroperatingpartofavehicle.Thechassisincludesthetransmission,suspension,steering,andbrakesystems.

Transmissionsystems―conveysthedrivetothewheels.Themaincomponentsareclutch,gearbox,driveshaft,finaldrive,anddifferential.

Suspension―absorbstheroadshocks.

Steering―controlsthedirectionofthemovement.

Brake―slowsdownthevehicle.

1.5 Electrical Equipment

Theelectricalsystemsupplieselectricityfortheignition,horn,lights,heater,andstarter.Theelectricitylevelismaintainedbyachargingcircuit.Thiscircuitconsistsofthebattery,alternator（orgenerator）.Thebatterystoreselectricity.Thealternatorchangestheengine'smechanicalenergyintoelectricalenergyandrechargesthebattery.

NewWords

Principalcomponent 主要部件

category 种类，类型

body 车身

chassis 底盘

layout 布置

powerunit 动力装置

internalcombustionengine 内燃机

cylinder 汽缸

gasoline 汽油

spark 火花

ignition 点燃，点火

diesel 柴油机

compression 压缩

shaft 轴

transmission 传动系

sheetmetal 金属板

shell 外壳

hood （发动机）罩

trunkdeck 行李舱盖

cargo 货物

styling 样式

assembly 总成，装配

suspension 悬挂，悬置

shock 冲击

steering 转向，操纵

brake 刹车，制动器

clutch 离合器

gearbox 变速器

driveshaft 传动轴

finaldrive 主减速器，后桥

differential 差速器

slowdown （使）慢下来，减速

horn 喇叭

starter 起动机

charge 充电

alternator 交流发电机

ReviewQuestions

1.Listthemainpartsofanautomobile?

2.Whatarethecommontypesofavehicleaccordingtobodystyling?

3.Whichsystemsdoesachassisincludeandwhatarethemainfunctionsofthechassis?

4.Whyaresuspensionsystemsusedonvehicles?

CHAPTER2INTERNALCOMBUSTIONENGINE

2.1principleofoperation

2.1.1Engineandpower

Engineisusedtoproducepower.Thechemicalenergyinfuelisconvertedtoheatbytheburningofthefuelatacontrolledrate.Thisprocessiscalledcombustion.Ifenginecombustionoccurswiththepowerchamber.,theengineiscalledinternalcombustionengine.Ifcombustiontakesplaceoutsidethecylinder,theengineiscalledanexternalcombustionengine.

Engineusedinautomobilesareinternalcombustionheatengines.Heatenergyreleasedinthecombustionchamberraisesthetemperatureofthecombustiongaseswiththechamber.Theincreaseingastemperaturecausesthepressureofthegasestoincrease.Thepressuredevelopedwithinthecombustionchamberisappliedtotheheadofapistontoproduceausablemechanicalforce,whichisthenconvertedintousefulmechanicalpower.

2.1.2EngineTerms

Linkingthepistonbyaconnectingrodtoacrankshaftcausesthegastorotatetheshaftthroughhalfaturn.Thepowerstroke“usesup”thegas,someansmustbeprovidedtoexpeltheburntgasandrechargethecylinderwithafreshpetrol-airmixture:

thiscontrolofgasmovementisthedutyofthevalves;aninletvalveallowsthenewmixturetoenterattherighttimeandanexhaustvalveletsouttheburntgasafterthegashasdoneitsjob.Enginetermsare:

TDC（TopDeadCenter）:

thepositionofthecrankandpistonwhenthepistonisfartherawayfromthecrankshaft.

BDC（BottomDeadCenter）:

thepositionofthecrankandpistonwhenthepistonisnearesttothecrankshaft.

Stroke:

thedistancebetweenBDCandTDC;strokeiscontrolledbythecrankshaft.

Bore:

theinternaldiameterofthecylinder.

Sweptvolume:

thevolumebetweenTDCandBDC.

Enginecapacity:

thisisthesweptvolumeofallthecylindere.g.afour-strokehavingacapacityoftwoliters（2000cm）hasacylindersweptvolumeof50cm.

Clearancevolume:

thevolumeofthespaceabovethepistonwhenitisatTDC.

Compressionratio=（sweptvol+clearancevol）\（clearancevol）

Two-stroke:

apowerstrokeeveryrevolutionofthecrank.

Four-stroke:

apowerstrokeeveryotherrevolutionofthecrank..

2.1.3TheFour-strokeSpark-ignitionEngineCycle

Thespark-ignitionengineisaninternal-combustionenginewithexternallysuppliedinignition,whichconvertstheenergycontainedinthefueltokineticenergy.

Thecycleofoperationsisspreadoverfourpistonstrokes.Tocompletethefullcycleittakestworevolutionsofthecrankshaft.

Theoperatingstrokesare:

Thisstrokeintroducesamixtureofatomizedgasolineandairintothecylinder.Thestrokestartswhenthepistonmovesdownwardfromapositionnearthetopofthecylinder.Asthepistonmovesdownward,avacuum,orlow-pressurearea,iscreated.

Duringtheintakestroke,oneoftheportsisopenedbymovingtheinletvalve.Theexhaustvalveremainstightlyclosed.

Compressionstroke

Asthepistonmovesupwardtocompressthefuelmixturetrappedinthecylinder,thevalvesareclosedtightly.Thiscompressionactionheatstheair/fuelmixtureslightlyandconfinesitwithinasmallareacalledthecombustionchamber.

Powerstroke

Justbeforethepistonreachesthetopofitscompressionstroke,anelectricalsparkisintroducedfromasparkplugscrewedintothecylinderhead.

Thesparkignitesthecompressed,heatedmixtureoffuelandairinthecombustionchambertocauserapidburning.Theburningfuelproducesintenseheatthatcausesrapidexpansionofthegasescompressedwithinthecylinder.Thispressureforcesthepistondownward.Thedownwardstroketurnsthecrankshaftwithgreatforce.

Exhauststroke

Justbeforethebottomofthepowerstroke,theexhaustvalveopens.Thisallowsthepiston,asitmovesupward,topushthehot,burnedgasesoutthroughtheopenexhaustvalve.

Then,justbeforethepistonreachesitshighestpoint,theexhaustvalveclosesandtheinletvalveopens.Asthepistonreachesthehighestpointinthecylinder,knownasTDC,itstartsbackdownagain.Thus,onecycleendsandanotherbeginsimmediately.

2.1.4EngineOverallMechanics

Theenginehashundredsofotherparts.Themajorpartsofengineareengineblock,engineheads,pistons,connectingrods,crankshaftandvalves.Theotherpartsarejoinedtomakesystems.Thesesystemsarethefuelsystem,intakesystem,ignitionsystem,coolingsystem,lubricationsystemandexhaustsystem.Eachofthesesystemshasadefinitefunction.Thesesystemswilldiscussedindetaillater.

NEWWORD

Piston活塞

Connectingrod连杆

Crankshaft曲轴

Powerstoke活塞行程

Expel排出

Valve气阀

inlet（intake）valve进气阀

exhaustvalve排气阀

term术语

TDC上止点

BDC下止点

Bore缸径

sweptvolume有效容积

enginecapacity发动机排量

clearancevolume余隙容积,燃烧室容积

compressionratio压缩比

revolution旋转,转数

everyother每隔一个

cycle循环

spreadover分布,遍及

intakestroke进气行程

compressionstroke压缩行程

knock敲缸,敲打

exhauststroke排气行程

engineblock发动机缸体

lubrication润滑

2.2EngineBlockandCylinderHead

2.2.1 EngineBlock

Theengineblockisthebasicframeoftheengine.Allotherenginepartseitherfitinsideitorfastentoit.Itholdsthecylinders,waterjackets,andoilgalleries.Theengineblockalsoholdsthecrankshaft,whichfastenstothebottomoftheblock.Thecamshaftalsofitsinsidetheblock,exceptonoverhead-camengines（OHC）.Inmostcars,thisblockismadeofgrayiron,oranalloy（mixture）ofgrayironandothermetals,suchasnickelorchromium.Engineblocksarecastings.

Someengineblocks,especiallythoseinsmallercars,aremadeofcastaluminum.Thismetalismuchlighterthaniron.However,ironwearsbetterthanaluminum.Therefore,thecylindersinmostaluminumenginesarelinedwithironorsteelsleeves.Thesesleevesarecalledcylindersleeves.Someengineblocksaremadeentirelyofaluminum.

2.2.2 CylinderHead

Thecylinderheadfastenstothetopoftheblock,justasarooffitsoverahouse.Theundersideformsthecombustionchamberwiththetopofthepiston.Themostcommoncylinderheadtypesarethehemi,wedge,andsemi-hemi.Allthreeofthesetermsrefertotheshapeoftheengine'scombustionchamber.Thecylinderheadcarriesthevalves,valvespringsandtherockersontherockershaft,thispartofthevalvegearbeingworkedbythepush-rods.Sometimesthecamshaftisfitteddirectlyintothecylinderheadandoperatesonthevalveswithoutrockers.Thisiscalledanoverheadcamshaftarrangement.Likethecylinderblock,theheadismadefromeithercastironoraluminumalloy.

2.2.3 Gasket

Thecylinderheadisattachedtotheblockwithhigh-tensilesteelstuds.Thejointbetweentheblockandtheheadmustbegas-tightsothatnoneoftheburningmixturecanescape.Thisisachievedbyusingcylinderheadgasket.Thisisasandwichgasket,i.e.asheetofasbestosbetweentwosheetsofcopper,boththesematerialsbeingabletowithstandthehightemperatureandpressureswithintheen