汽车发动机外文翻译文献.docx

汽车发动机外文翻译文献.docx

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汽车发动机外文翻译文献

汽车发动机外文翻译文献

（文档含中英文对照即英文原文和中文翻译）

AUTOMOTIVEENGINE

1EngineClassificationandOverallMechanics

Theautomobileenginescanbeclassifiedaccordingto:

（1）cycles,

（2）coolingsystem,（3）fuelsystem,（4）ignitionmethod,（5）valvearrangement,（6）cylinderarrangement,（7）enginespeed.

Enginesusedinautomobilesaretheinternalcombustionheatengines.Theburningofgasolineinsidetheengineproduceshighpressureintheenginecombustionchamber.Thishighpressureforcepistontomove,themovementiscarriedbyconnectingrodstotheenginecrankshaft.Thecrankshaftisthusmadetorotate:

therotarymotioniscarriedthroughthepowertraintothecarwheelssothattheyrotateandthecarmoves.

Theenginerequiresfourbasicsystemstorun（Fig.2-1）.Dieselenginesrequirethreeofthesesystems.Theyarefuelsystem,ignitionsystem（exceptdiesel）,lubricatingsystemandcoolingsystem.However,threeotherrelatedsystemsarealsonecessary.Thesearetheexhaustsystem,theemission-controlsystem,andthestartingsystem.Eachperformsabasicjobinmakingtheenginerun.

Fig.2-1Theengineconstruction

2 Engine OperatingPrinciples

Fig.2-2Engineterms

Theterm“stroke”isusedtodescribethemovementofthepistonwithinthecylinder.Themovementofthepistonfromitsuppermostposition（TDC,topdeadcenter）toitslowestposition（BDC,bottomdeadcenter）iscalledastroke.Theoperatingcyclemayrequireeithertwoorfourstrokestocomplete.Mostautomobileenginesoperateonthefourstrokecycle（Fig.2-2）.

Infour-strokeengine,fourstrokesofthepistoninthecylinderarerequiredtocompleteonefulloperatingcycle.Eachstrokeisnamedaftertheaction.Itperformsintake,compression,power,andexhaustinthatorder（Fig.2-3）.

IntakestrokeCompressionstrokePowerstrokeExhauststroke

Fig.2-3Four-stroke-cyclegasolineengine

1.Theintakestroke

Theintakestrokebeginswiththepistonnearthetopofitstravel.Asthepistonbeginsitsdescent,theexhaustvalveclosesfully,theintakevalveopensandthevolumeofthecombustionchamberbeginstoincrease,creatingavacuum.Asthepistondescends,anair/fuelmixtureisdrawnfromthecarburetorintothecylinderthroughtheintakemanifold.Theintakestrokeendswiththeintakevalveclosejustafterthepistonhasbegunitsupstroke.

2.Compressionstroke

AsthepistonismovedupbythecrankshaftfromBDC,theintakevalvecloses.Theair/fuelmixtureistrappedinthecylinderabovethepiston.Futurepistontravelcompressestheair/fuelmixturetoapproximatelyone-eighthofitsoriginalvolume（approximately8:

1compressionratio）whenthepistonhasreachedTDC.Thiscompletesthecompressionstroke.

3.Powerstroke

AsthepistonreachesTDConthecompressionstroke,anelectricsparkisproducedatthesparkplug.Theignitionsystemdeliversahigh-voltagesurgeofelectricitytothesparkplugtoproducethespark.Thesparkignites,orsetsfireto,theair/fuelmixture.Itnowbeginstoburnveryrapidly,andthecylinderpressureincreasestoasmuchas3-5MPaorevenmore.Thisterrificpushagainstthepistonforcesitdownward,andapowerfulimpulseistransmittedthroughtheconnectingrodtothecrankpinonthecrankshaft.Thecrankshaftisrotatedasthepistonispusheddownbythepressureaboveit.

4.Exhauststroke

Attheendofthepowerstrokethecamshaftopenstheexhaustvalve,andtheexhauststrokebegins.Remainingpressureinthecylinder,andupwardmovementofthepiston,forcetheexhaustgasesoutofthecylinder.Attheendoftheexhauststroke,theexhaustvalveclosesandtheintakevalveopens,repeatingtheentirecycleofeventsoverandoveragain.

3EngineBlockandCylinderHead

3.1EngineBlock

Theengineblockisthebasicframeoftheengine.Allotherenginepartseitherfitinsideitorfastentoit.Itholdsthecylinders,waterjacketsandoilgalleries（Fig.2-4）.Theengineblockalsoholdsthecrankshaft,whichfastenstothebottomoftheblock.Thecamshaftalsofitsintheblock,exceptonoverhead-camengines.Inmostcars,thisblockismadeofgrayiron,oranalloy（mixture）ofgrayironandothermetals,suchasnickelorchromium.Engineblocksarecastings.

Fig.2-4V6engineblock

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

3.2CylinderSleeves

Cylindersleevesareusedinengineblockstoprovideahardwearingmaterialforpistonsandpistonrings.Theblockcanbemadeofonekindofironthatislightandeasytocastwhilethesleevesusesanotherthatisbetterabletostandupwearandtear.Therearetwomaintypesofsleeves:

dryandwet（Fig.2-5）.

DrysleeveWetsleeve

Fig.2-5Cylindersleeve

3.3CylinderHead

Thecylinderheadfastenstothetopoftheblock,justasarooffitsoverahouse.Theundersideformsthecombustionchamberwiththetopofthepiston.In-lineengineoflightvehicleshavejustonecylinderheadforallcylinders;largerin-lineenginescanhavetwoormore.Justaswithengineblocks,cylinderheadscanbemadeofcastironoraluminumalloy.Thecylinderheadcarriesthevalves,valvespringsandtherockersontherockershaft,thispartofvalvegearbeingworkedbythepushrods.Sometimesthecamshaftisfitteddirectlyintothecylinderheadandoperatesonthevalveswithoutrockers.Thisiscalledanoverheadcamshaftarrangement.

3.4Gasket

Thecylinderheadisattachedtotheblockwithhigh-tensilesteelstuds.Thejointbetweentheblockandtheheadmustbegas-tightsothatnoneoftheburningmixturecanescape.Thisisachievedbyusingcylinderheadgasket.Gasketsarealsousedtosealjoinsbetweentheotherparts,suchasbetweentheoilpan,manifolds,orwaterpumpandtheblocks.

3.5OilPan

Theoilpanisusuallyformedofpressedsteel.Theoilpanandthelowerpartofcylinderblocktogetherarecalledthecrankcase;theyenclose,orencase,thecrankshaft.Theoilpumpinthelubricatingsystemdrawsoilfromtheoilpanandsendsittoallworkingpartsintheengine.Theoildrainsoffandrundownintothepan.Thus,thereisaconstantcirculationofoilbetweenthepanandtheworkingpartsoftheengine.

4PistonAssembly,piston rings,The piston pin,ConnectingRods,CrankshaftsAndFlywheel

4.1Piston

Pistonringsandthepistonpinaretogethercalledthepistonassembly（Fig.2-6）.

Fig.2-6Piston,pistonringsandconnectingrod

The piston is an important part of a four-stroke cycle engine. Most pistons are made from cast aluminum. The piston, through the connecting rod, transfers to the crankshaft the force created by the burning fuel mixture. This force turns the crankshaft. 

To withstand the heat of the combustion chamber, the piston must be strong. It also must be light, since it travels at high speeds as it moves up and down inside the cylinder. The piston is hollow. It is thick at the top where it takes the brunt of the heat and the expansion force. It is thin at the bottom, where there is less heat. The top part of the piston is the head, or crown. The thin part is the skirt. Most pistons have three ring grooves at the top. The sections between the ring grooves are called ring lands. 

4.2 piston rings

 piston rings fit into ring grooves near the top of the piston. In simplest terms, piston rings are thin, circular pieces of metal that fit into grooves in the tops of the pistons.

 In modern engines, each piston has three rings. （Piston in older engines sometimes had four rings, or even five.） The inside surface of the ring fits in the groove on the piston. The ring's outside surface presses against the cylinder walls. Rings provide the needed seal between the piston and the cylinder walls. That is, only the rings contact the cylinder walls. The top two rings are to keep the gases in the cylinder and are called compression rings. The lower one prevents the oil splashed onto the cylinder bore from entering the combustion chamber, and is called an oil ring. 

4.3The piston pin

The piston pin holds together the piston and the connecting rod. This pin fits into the piston pin holes and into a hole in the top end of the connecting rod. The top end of the rod is much smaller than the end that fits on the crankshaft. This small end fits inside the bottom of the piston. The piston pin fits through one side of the piston, through the small end of the rod, and then through the other side of the piston. It holds the rod firmly in place in the center of the piston. Pins are made of high-strength steel and have a hollow center. Many pins are chrome-plated to help them wear better.A piston pin fits into a round hole in the piston. The piston pin joins the piston to the connecting rod. The thick part of the piston that holds the piston pin is the pin boss.

4.4ConnectingRods

 The connecting rod little end is connected to the piston pin. A bush made from a soft metal, such as bronze, is used for this joint. The lower end of the connecting rod fits the crankshaft journal. This is called the big end. For this big-end bearing, steel-backed lead or tin shell bearings are used. These are the same as those used for the main bearings. The split of the big end is sometimes at an angle, so that it is small enough to be withdrawn through the cylinder bore. The connecting rod is made from forged alloy steel. 

4.5Crankshafts

Thecrankshaftisregardedasthe“backbone”oftheengine（Fig.2-7）.The crankshaft, in conjunction with the connecting rod, converts the reciprocating motion of th