STRUCTUREOFAUTOMOBILEENGINE汽車(chē)發(fā)動(dòng)機(jī)構(gòu)造汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)STRUCTUREOFAUTOMOBILEENGIChapter1:TheInternalCombustionEngine§1-1General

●Definition:TheInternalCombustionengineVSTheExternalCombustionEngine------Thecombustion(orburning)fueltakesplaceinsidetheengine.

●Fuel:1.Mostautomobileengineproducepowerbyburningamixtureofairandgasoline;2.somekindsofenginebydieselfuel;3.somebyalternativefuelssuchasCNG（天然氣）,LNG（液化石油氣）,Methanol(甲醇）,ethanol(乙醇）andetc.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月Chapter1:TheInternalCombusMainobjection:

Tostudytheinternalcombustionengine汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月Mainobjection:

Tostudythe§1-2Gasolineasafuelknowaboutfollowingpoints:●NO.1Howtheburningofgasolineproducesmechanicalpower?(1)Gasolineinliquidformisnoncombustible(non-burning)(2)however,gasolineVapordoesburn,combinedwithair(oxygeninair),gasolinevaporburnsinsidetheenginetoproducepower.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)§1-2Gasolineasafuelkno●NO.2Howdoestheliquidgasolineinthegastankbecomegasolinevapor?Evaporation:Gasolinebecomesavaporbyevaporation,whichistheprocessofturningaliquidintoavapor.Gasolinebeginstoevaporateatamuchlowertemperaturethanwater:

Tevaporationofgasoline﹤Tevaporationofwateritmeans:Gasolineismoreeasytovaporizethanwater.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)●NO.2HowdoestheliquidgasoEvaporate

Evaporationtakesplaceabovethesurfaceofaliquidwhenitisexposedtotheair.-----thus,gasolinevaporwillfillthespaceabovethesurfaceofgasoline.letshaveanexperiment:seeFig.1-1★Remember:thereisalwaysvaporabovethesurfaceofgasoline.Whiletheliquidmaynotburn,thevaporwill.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)EvaporateEvaporationtakesplAtomizedparticlesAtomizer1-1:thevapormadebyasprayevaporatesquickly.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)AtomizedparticlesAtomizer1-1:SprayingthegasolineintotheairThebestwaytoevaporategasolineistoexposetotheairasmuchofitssurfaceaspossible------tomakeliquidgasolineintothetinydroplets.e.gFig.1—2Thevapormadebyasprayevaporatesquickly.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)SprayingthegasolineintothefuseFuel-airmixturestopper1-2:Inthisexperiment,gasolinevaporburninginacanhasenoughpowertohavethestopperout.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月fuseFuel-airmixturestopper1-2No.3Whathappenswhengasolineevaporates?Theevaporatinggasolinemixedwithair.Theevaporatinggasolineexpandstofillmorespacethanitdidasaliquid.Ifaflameistouchedtothismixture,thegasolinevaporandairburnrapidlyproducingintenseheat.Whenveryhot,themixturequicklyexpandsevenmore.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)No.3WhathappenswhengasolinNo.4Whathappenstothemixturewhenitisburnedinsideaclosedcontainer?Fig.1---3Suppose:①attheopenendofatincan------putacork(塞子）；②throughtheclosedend------ranafuse(引線，導(dǎo)火線）③closedspace

filledwithfuel-airmixtureinside汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月No.4WhathappenstothemixtuSparkplugExhaustvalveIntakevalveCombustionchamberpistoncylinder1-3:Inthisengine.Atight-fittingpistonmovesupanddowninthecylinder.Theintakevalvetakesinvapor.Theexhaustvalvereleasestheburnedmixture.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月SparkplugExhaustvalveIntakeMakeanexperiment:

First:sprayedinamixtureofvaporizedgasolineandairwithatomizer.Second:litthefuseThen:thefusewillignitethegasolinevapor.Thelast:theburningvaporwouldexpandwithsuchforcethatitwouldblowthestopper

off---that’s“explosion”★conclusion:Internalcombustionengineburnsgasolinevaporandairtoproducepower.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)Makeanexperiment:

First:spr§1-3AOne-cylinderInternalCombustionengineThetincan------LikethecylinderofengineThestopperinthetincan------LikeapistonThefuseinthetincan------LikeasparkplugSpacebetweenthetopofthepistonandthetopofthecylinder.------Thecombustionchamber汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)§1-3AOne-cylinderInternalCIntakevalve------themixtureisletinandignitedExhaustvalve------exhaustgaswasreleasedfromthecylinderthroughtheexhaustvalveCrankshaft(曲軸）-----lookslikeastraightbarwithanoffset(n.偏置）sectioninthecenterofit(crankshaft)function:tochangepiston’supanddownmotiontotherotationofthecrankshaft●Aconnectingrod------joinsthepistonandthecrankshaft

PistonConnectingrodcrankshaft1-4:thecrankshaftisstraight,withanoffsetsectioninthemiddleofit.Itisjoinedtothepistonmovesthecrankshaft.Thisconvertstheverticalmotionofthepistonintotherotarymotionofthecrankshaft.汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)Intakevalve------themixture汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件§1-5Boreandstroke汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月§1-5Boreandstroke汽車(chē)運(yùn)用教研組汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)§1-6pistonstrokesIntakestroke(進(jìn)氣行程)Compressionstroke(壓縮行程)Powerstroke(做功行程)Exhauststroke(排氣行程)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)§1-6pistonstrokesIntakestro第二節(jié)四沖程發(fā)動(dòng)機(jī)工作原理四沖程柴油機(jī)工作過(guò)程汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月第二節(jié)四沖程發(fā)動(dòng)機(jī)工作原理四沖程柴油機(jī)汽車(chē)運(yùn)用教研組汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)§1-7enginedisplacement

汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)2003年8月§1-7enginedisplacement

汽車(chē)運(yùn)用教汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)CompressionratioCompressionratioisacomparisonbetweenthevolumeinthecylinderwhenthepistonstandsatBDCagainstthevolumeatTDC.ε=Va/Vccar(gasoline)ε:8:1-11:1;someracingcar:13:1-14:1汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)CompressionratioCompressionr汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)Reviewquestion1.Whymustgasolinebevaporizedinanengine?2.Whereistheair-fuelmixtureignited?3.WhatdoestheabbreviationTDCstandfor?4.whatisthefinalstrokesinanenginecycle?5.listthefourenginestrokes.6.howisdisplacementmeasured?7.howdoyoucalculatecompressionratio?汽車(chē)運(yùn)用教研組黃銀娣開(kāi)發(fā)Reviewquestion1.WhymustgaCH2:EnginefundamentalsCH2:Enginefundamentals§2－1Enginesystems§2－1Enginesystems§2－2Engineconfiguration

thein-lineengineThewaytoarrangecylindersinagroupistolinethemupinastraightrow.Usuallyhaveevennumber(four,six,eightlinecylinders,it’sbalanced.Butsometimehave3or5cylinders.2－1：Anexampleofanin-lineenginethathasfourcylindersinaline.§2－2Engineconfiguration

the汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件TheV-typeengineTheV-8enginewasdesignedtoproducethepowerofthein-lineeightinasmallerengine.Hastwofour-cylinderin-lineenginesplacedbesideeachotherintheshapeofaVHasonlyonecrankshaft,withalleightcylindersconnected.IntheUnitedStates,itwasforyearsthemoatpopularengine.Today,thereareV-4enginejusttwocylinderlong;V-6type;V-8,evensomeexpensiveforeigncarshaveV-12engines,whichhavetwobankofsixcylinderseach.TheV-typeengineTheV-8engin2-2:

AutomanufacturesmakeV-typeenginesoffour,six,andeightcylinders.AV-6configurationisshownhere.2-3:

thehorizontally-opposedenginehastwobanksofcylinderspointinginoppositedirections.Becausethebankshavea180anglebetweenthem,thisengineiscalledaflatengine.2-2:AutomanufacturesmakeV-汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件Theflatengine

SeeFig.2-3Ithastwobanksofcylindersoppositeoneanother.JustliketheV-typebecomeaflathorizontalline.Eg.Air-cooledVolkswagens(大眾）usetheflat-fourengine.ManyPorschesusetheflat-six.TheflatengineSeeFig.2-3§2－3Engineplacement發(fā)動(dòng)機(jī)驅(qū)動(dòng)：Frontengine,rearwheeldrive(truck,jeepetc.)Rearengine,rearwheeldrive(Passengercars)Frontengine,frontwheeldrive(mostcar)發(fā)動(dòng)機(jī)位置：In-linepowertrain（縱向發(fā)動(dòng)機(jī)）:theengineiscenteredandtheshaftsrunthelengthofthecar.（與車(chē)軸垂直）Transverseengine(橫向發(fā)動(dòng)機(jī)）:theengineiscrosswiseinthecar.Inthiscase,theengineisrightoverthefrontaxle.Whichitdrives.Acarwithsuchadesignhasatransverseengine.（與車(chē)軸平行)§2－3Engineplacement發(fā)動(dòng)機(jī)驅(qū)動(dòng)：ABEngineEngineDriveshaftDrivingaxleDrivingaxle2-4:(A)Manycarshaveanin-lineenginearrangementwiththeengineanddriveshaftrunningfront-to-rear.(B)Intransverseenginearrangementtheenginerunsfromsidetoside.ABEngineEngineDriveshaftDr§2－4Theenginesystem

thefuelsystemAsshowinFig.2-5Function:thefuelsystemstoresfuelanddeliversittotheengineasneeded.Composition:fourbasicpartsmakeupthefuelsystem.Theyarethefueltank,fuellines,fuelpumpsandthefuelfilter.§2－4Theenginesystem

thefu汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件FueltankFuellineFuelpumpFuelfilter2-5:Thefuelsystemstoresthefuelanddeliversittotheengineasneeded.FueltankFuellineFuelpumpFue§2－5TheintakesystemSeeFig.2-6Function:takesfuelfromthefuelsystem,mixesitwithjusttherightamountofair,andthendeliversittothecombustionchamber.Composition:theaircleaner,theairfilter,thecarburetor,theintakemanifold,theintakepartsetc.§2－5Theintakesystem汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件AircleanerAirfiltercarburetorIntakemanifoldblock2-6:themainpartsoftheintakesystem.AircleanerAirfiltercarbureto§2－6Theignitionsystem

Seefig.2-7Function:theignitionsystemignites(orfires)theair-fuelmixtureinthecombustionchamberatjusttherightinstant.thisinstantisattheendofthecompressionstrokeandthebeginningofthepowerstroke.Unlessthefuelisignitedatthecorrectmoment,theenginewillnotrunproperly.Composition:battery,sparkplugs,thecoil,andthedistributoretc.§2－6TheignitionsystemSeefCoilwirebatteryCoilSparkplugwiresdistributorSparkplugs2-7:theignitionsystemtakeselectricityfromthebatteryanddeliversittothesparkplugstoignitethefuel-airmixture.CoilwirebatteryCoilSparkplu汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件§2－7thecoolingsystem

Seefig.2-8,2-9Function:tocarryawaytheheatproducedbythecombustionengineinsidethechamber.Types:a.theair-cooledengine（風(fēng)冷發(fā)動(dòng)機(jī)）(mostmotorcycle)b.andthewatercooledengine（水冷發(fā)動(dòng)機(jī)）(mostcars)Thewatercooled:alsocalledliquid-cooled.amixtureofwaterandachemical，theliquidpreventsfreezinginthewinterandboilinginthesummer.thechemical:isantifreeze(防凍劑）(it’sscientificnameisethyleneglycol)§2－7thecoolingsystemSeefiairairfanCoolingfins2-8:Anair-cooledengineusestheoutsideairpassingovertheenginetocarryawaytheheatproducedbytheburningmixture.airairfanCoolingfins2-8:AnaWaterjacketWaterpumpcoolantradiator2-9:Awater-cooledengineusesaliquidtocooltheengine.Thenitusesairtocooltheliquid.WaterjacketWaterpumpcoolantr§2－8ThelubricationsystemSeeFig.2-10,11Partsofthelubricationsystem:1.Theoilpan(油底殼）:istheholder,orsump,forthe3-6qts.(about3-5L)ofoil.2.anoilpump（油泵）:drawstheoilfromthepanandpushesitthroughtheoilfilter.3.theoilfilter（濾清器）:removesdirtfromtheoil.4.oilgalleries(油道）：passagestheoilthroughintheenginepartsthatneedlubrication.§2－8ThelubricationsystemSeePushingforce

forceoffriction

2-10:frictionistheforcethatresistsmotionbetweentwosurfacesincontact.Oilgalleries

Oilpan

OilpickupOilpumpOilfilter2-11:thelubricationsystemprovidesoiltoallinternalengineparts,toreduceheatinsidetheengine.

Pushingforceforceoffrictio§2－9Theexhaustsystem(排氣系統(tǒng)）

Function:takestheburnedgasesfromthecylinder,carriesthemawayfromtheengine,anddischargesthemintotheair.Seefig.2-12Partsoftheexhaustsystem:exhaustmanifold（排氣歧管）,exhaustpipe（排氣管）,intermediatepipe（中間排氣管）,muffle（消聲器）,andtailpipe（排氣尾管）.§2－9Theexhaustsystem(排氣系統(tǒng)）TailpipemufflerIntermediatepipeExhaustpipeExhaustmanifold2-12:theexhaustsystemCarriestheburnedgasesawayfromtheengineandoutintotheair.Italsolessenstheloudnoiseproducedbytheengine.TailpipemufflerIntermediatepReviewquestions1.Whatisengineconfiguration?2.whatisahorizontally-opposedengine(水平對(duì)置，平置發(fā)動(dòng)機(jī)）?3.listthesixenginesystems.4.Whatisatransverseengine(橫置發(fā)動(dòng)機(jī)）?5.whatdoesthedistributordo?6.whyisliquidcoolingneededinmodernengines?7.whyisoilneededinanengine?Reviewquestions1.WhatisengiChapter3:engineblocksandcylinderheads（發(fā)動(dòng)機(jī)機(jī)體和汽缸蓋）Seefig.3-1Chapter3:engineblocksandcIntakemanifolddistributorPistonandrodcrankshaftblockOilpanWaterpumpCylinderheadHeadcover3-2:theblockisthemainsupportpiecefortheengine.Allotherenginepartsfitinsidetheblockorfastentoit.IntakemanifolddistributorPistTheengineblock

Engineblockisthebasicframeoftheengine.Allotherenginepartseitherfitsinsideitorfastentoit.

Itholdsthecylinders（汽缸),waterjackets(水套）,andoilgalleries(油道）；Italsoholdsthecrankshaft,whichfastenstothebottomoftheblock.Thecamshaftalsofitsinsidetheblock,exceptonoverhead-camengine(OHC)(頂置式凸輪軸）。Inthemostcars,theblockismadeofgrayiron(灰鐵）,oranalloy（合金）(mixture)ofgrayironandothermetals,suchasnickel（鎳）orchromium（鉻）.Engineblocksarecastings（鑄造).Acastingisproducedbyheatingmetaluntilitbecomesaliquidandthenpouringitintoamold(模子),whereithardensintothecorrectshape.Someengineblocksinthesmallcars,aremadeofcast

aluminum(鑄鋁），thismetalislighterthantheiron.however,ironwearsbetterthanaluminum.therefore,thecylindersinmostaluminumenginearelinedwithironorsteelsleeves(襯套）。Thissleevesarecalledcylinderlinersorcylindersleeves.(缸套）Someblocksaremadeentirelyofaluminum.Theengineblock

EngineblockCastironblockaluminumblocksleeves3-3:theengineblockismadeofcastironorcastaluminum.Inmostaluminumengines,thecylindersarelinedwithironorsteel.CastironblockaluminumblocksThecylinderhead

Seefig.3-2,thecylinderheadfastenstothetopoftheblock,justasarooffitsoverahouse.Theheadisthewidthandlengthoftheblock.Mostcylinderheadsaremadeofcastiron,thoughsomeareofcastaluminum.,insomeengines,theblockandthecylinderheadaremadeofdifferentmaterials.Seefig.3-4,v-8enginehastwocylinder

heads,eachbankhavefourcylinders.ThecylinderheadSeefig.3-2,HeadHeadblockblockblockV-8In-linefourFlatfour3-4:thenumberofcylinderheadsonanenginedependsonthenumberofbanksofcylindersithas,Eachbankrequiresonehead.HeadHeadblockblockblockV-汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件CombustionchamberOilandwaterpassagesValvesetsExhaustportsPushrodguideholesValveguidesSparkplugHolesIntakeports3-5:theundersideoftheheadhaspocketsforthetopofthecombustionchamber.Thetopoftheheadcontainsvalveseatsandrockerstands.CombustionchamberOilandwateRockershaft

Headbolthole

ValvespringRockerarm

portPushrodguideholevalve3-6:Afullyassembledcylinderheadhasmanyparts.RockershaftHeadboltholeVafinsHeadsurfaceHeadsurfaceBlockdeckBlockdeckgasketNogasket3-8:pressedbetweentwosurfaces,agasketfillsintheirregularitiesandprovidesatightseal.3-7:anair-cooledheadhasfinsbutnowaterjacketpassages.finsHeadsurfaceHeadsurfaceBl汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件BoltholesOilpassageholesWaterpassageholesCylinderholesboltholes3-9:theheadgaskethasholescutintofittheholesinthedeckandheadsurfaces.Onceaheadgasketisremoved,youshouldreplaceitwithanewone.BoltholesOilpassageholesWaValvecoverExhaustmanifoldheadcarburetorIntakemanifold3-10:thevalvecover,exhaustmanifold,andintakemanifoldarefastenedtothecylinderhead.ValvecoverExhaustmanifoldheacarburetorIntakemanifoldheadheadExhaustmanifoldLittervalleyExhaustmanifoldTimingcoverOilpanblockOilpan3-11:AsingleintakemanifoldfitsintothecentralpartofaV-8engine,coveringtheliftervalley.Anexhaustmanifoldboltstotheoutsideofeachhead.3-12:theoilpanandthetimingcover.carburetorIntakemanifoldheadhhemiwedgeSemi-HemihemiwedgeSemi-Hemi3-13:thethreemostcommontypesofautomobileengineheadarethehemi,wedge,andsemi-hemi.hemiwedgeSemi-HemihemiwedgeSemfrontFrontofcarfrontfrontflywheelflywheelflywheelflywheelrearrearFrontofengineBackofengineSteeringwheelleftright3-14:3-15:3-16:3-17:frontFrontofcarfrontfrontflyReviewquestion1.Whatisacasting?2.Whyisacylinderheadneeded?3.Wherearetheintakeandexhaustportslocated?4.Howisthecylinderheadsealedtotheblock?5.Whatarethethreemostcommoncylinderheadshapes?6.listthemajorpartsthatarefastenedtotheblock?Reviewquestion1.WhatisacChapter4:

Connectingrods,bearings,

andcrankshafts連桿,軸瓦.曲軸Connectingrodslinkthepistontothecrankshaft.theserodsconvertthereciprocating(up-and-down)motionofthepistonintotherotarymotionofthecrankshaft.fig.4-1.Theconnectingrodsareprotectedbybearings.Chapter4:

Connectingrods,b汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件4-1:

theconnectingrodlinksthepistontothecrankshaft.Thischangesreciprocatingmotiontorotarymotion.4-2:4-1:theconnectingrodlinksConnectingrodsSeefig.4-2Composition:mainpartofrod(連桿),rodcap(連桿蓋),,rodboltsandnut(連桿螺栓與螺母)Connectingrod’srequirements:mustbestrongandlight.inthepassengercar:theyaremadeofforgedorcaststeel;Engineforracingcar:theyaremadeofaluminumorotheralloys.＊Eachrodcapmustmatchedwith

rodbystampingwithanumber.Seefig.4-3CylindernumberAlignmentnotch4-3:Anumberstampedonthebigendofeachrodmatchesanumberontherodcapthatgoeswithit.ConnectingrodsSeefig.4-2CyConnecting-rodjournals(連桿軸徑)Seefig.4-4,5Connecting–rodjournal,rodjournal,orcrankpin(連桿軸徑)Thissmooth,shapedpieceisoffset(偏置)fromthecenterlineofthecrankshaft.Theamountofoffsetequalshalfoftheenginestroke(偏置量等于發(fā)動(dòng)機(jī)行程的一半).seefig.4-5Connecting-rodjournals(連桿軸徑)Rodjournal(crankpin)Crankshaftcenterline4-4:

theconnectingrodfastenstotheconnecting-rodjournalofthecrankshaft.Rodjournal(crankpin)CrankshaborestrokeCrankshaftoffsetCrankshaftoffsetFig4-5theoffsetofthecrankshaftequalshalfthestrokeoftheengine.Attopdeadcenter,theoffsetpointsstraightup.Atbottomdeadcenter,itpointsstraightdown.borestrokeCrankshaftoffsetCrRodbearings(連桿軸承)Function:arodbearingisusedtolessenfrictionbetweenthecrankshaftandtheconnectingrod.Seefig.4-6,7therodbearingisathinsheetofsoft,smoothmetalthatfitsaroundtherodjournal.Thereisasmallamountofclearance(間隙),whichisoil-filled.thesebearingsseparateintotwohalvesforsimpleinstallation.Rodbearingarecalledinsertbearingbecausetheyareinsertedbetweentherodandtherodjournal.Rodbearings(連桿軸承)Function:a汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件BearinginsertrodRodcapFig4-6theconnecting-rodbearingfitsbetweenthebigendoftherodandtheconnecting-rodjournalofthecrankshaft.bearingrodRodjournalFig4-7therodbearingisalsocalledaninsertbearing,becauseitisinsertedbetweenthecrankpinandtherod.BearinginsertrodRodcapFig4-6Rodbearingconstruction

Seefig.4-8therodbearingfitsbetweentherodandtherodjournal.Thebearingdoesnotturnwiththecrankshaft.Instead,alocating,orlockingtab,holdsthebearingintheplacesintherod.thislocatingtab(定位鍵或鎖止鍵)fitsintoaslot(槽)

intherodcap(連桿蓋).bearingTab(定位鍵)slotRodcapFig4-8whentherodfastentothecrankshaft,alockingtabonthebearinglinesupwithaslotintherodcap.RodbearingconstructionSeeBearingcrush(軸承抱緊,擠壓,壓碎)Seefig.4-9Everybearingmusthavetheproperbearingcrush.WHY?Toensuretheproperbearingcrush,eachhalfofthebearingisslightlylargerthantherodhalves.Thus,whentherodcapfastensontotherod,theendsofthebearinghalvesmeetbeforetherodcapcontactstherod.whentherodcapjoinstherod,theforcetotightentheboltswillslightlycrushthebearinghalves.Thispressureforcesthebearingtightlyintoplace.bearingFig4-9Bearinghalvesaremadelongerthantheinnersurfacesoftherod’sbigend.Thebearinghalvesarecrushedintoplacewhentherodcapistightenedagainsttherod.Bearingcrush(軸承抱緊,擠壓,壓碎)Seef汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件Crushheight4-10.Theamountofcrushisknownasthecrushheight.Crush4-10.TheamountofcruBearingmaterialsThebearingusedintoday’senginesmustbe:Strongenoughtowithstandthepressuresofthemotionofthepistonandconnectingrod;Long-wearingenoughtolastfortensofthousandsofmiles;Softenoughtoshapethemselvestothejournalwithoutdamagingthejournal.Thefoundationofamodernbearingisahalf-circlesteelshell(半圈鋼片)calledthebackingshell(基片)orbearingshell(軸承片).Asecondmetalismeltedontotheinsideofthisshelltofromtheinnersurfaceofthebearing.Thissecondmentalisaluminum(鋁),tin(錫),acopper-leadalloy(銅鉛合金),orbabbitt(巴比合金,一種銅,銻,錫合金,(機(jī))巴比合金軸承襯)(asoftalloyoftin,copper,andantimony(銻)).Somebearinghavelayersofdifferentmaterials.Seefig.4-11,bearingmadeofthreemetalsarecalledtri-mentalbearings.Therealsoarebabbittbearings,aluminum-coated(鍍,涂層)bearing,andcopper-leadbearings(銅鉛軸承).BearingmaterialsThebeariBearingmetalSteelbackingshellFig4-11Bearingshaveasteelshell.Alayerofoneormoresoftmetalsgivesthebearingasmoothinnersurface.BearingmetalSteelbackingsheThefunctionofbearingsLoad-carryingcapacity(承載能力)Highcompressionratio----ashighasseveralthousandpoundspersquareinch(1000psi=6895Kpa)Fatigueresistance(抗疲勞性)

themetalmakinguptheinnersurfaceofthebearingmustbesoftenoughtowithstandfatigue.Embeddability(吸收小顆粒能力)istheabilityofbearingtoabsorbsmallpiecesofdirt.Conformability(與軸徑尺寸的變形一致)Thebearingmustbesoftenoughtoconformtotheshapeofthejournal.Corrosionresistance(抗腐蝕性)

tocombatcorrosionproducedbyacidsthatcombustioncreates.Wearability(磨損性)

mustbehardenoughtowearwell.ThefunctionofbearingsLoad-cMainbearingsSeeFig4-12CrankshafthasanothersetofjournalscalledMainjournalsormain-bearingjournals(主軸徑)#seeFig4-13Inthebodyofengine,thebearingsthatfitaroundthemainjournalsarecalledmainbearingsor(主軸承)mains.#seeFig4-14,15Onemainbearingdiffersfromtheothers.Thisiscalledthrustbearing(推力軸承),

ithaslips,orflanges.Theseflangesrubagainstapolishedsurfaceontheedgeofthemainjournal.Thefront-to-backcrankshaftmovementiscalledcrankshaftthrust.Thethrustbearingstopsexcessivecrankshaftthrust(曲軸推力)andendplay.(曲軸軸向間隙).MainbearingsSeeFig4-12汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件汽車(chē)構(gòu)造（發(fā)動(dòng)機(jī)）中英文ppt課件MainbearingcapsSeeFig4-16Semicircularcapscalledmain-bearingcapsbolttothebottomoftheengineblock.Inmostpassengercarengineusemaincapswithtwobolts(帶有兩個(gè)螺栓的主軸承蓋).seeFig4-16Manyhigh-dutyandhigh–performanceengineshavefourmaincapboltstofastenthecapstotheblock.seeFig4-17MainbearingcapsSeeFig4-16MainbearingcapboltsMainjournalEngineblockMaincap

Fig4-16mainbearingcapsbolttothebottomoftheengineblock.Thesecapsfitaroundthemainbearingsandhelpsupportthecrankshaft.Fig.4-17inacross-bolted,twoboltsgothroughthesideoftheengineblock.Theothertwoboltsgoinfromthebottom.MainbearingcapboltsMainjoucounterweightsCounterweightshelpbalancetheweightoftherodjournal,rodsandpistons.Theypreventvibrationasthecrankshaftturns.Withoutcounterweights,vibrationwouldoccur.Thiswoulddamagetheengine.Fig4-18thethreemajorpartsofthecrankshaftarethemainjournals,rodjournals,andcounterweights.MainjournalsRodjournalscounterweightscounterweightsCounterweightshNumberingthecrankshaftmainjournalsandtherodjournalsFrontofengineBackofenginepistoncylindersConnectingrod

RodjournalsMainjournalsFig4-19themainjournalsonacrankshaftarenumberedinorderfromfronttoback.ThiscrankshafthasfivemainjournalsFig4-20InaV-8,thecylindersinonebankareslightlyforwardofthecylindersintheotherbank.thus,theconnectingrodsofoppositecylinderscanattachtothesamerodjournalofthecrankshaft.NumberingthecrankshaftmainCylinderfiringorderRodjournalarrangementandfiringorderTDCTDCTDCcrankpinBDCBDCFig4-21whenthecrankthrowpointsstraightuptowardthecylinder,thepistonstandsatTDC.Fig4-22whenthecrankthrowpointsstraightdown,awayfromthecylinder,thepistonstandsatBDC.Fig4-23whenthecrankthrowpointsawayfromthecylinderata90°angle,thepistonishalfwayupthecylinder.CylinderfiringorderRodjournIntervalbetweencrankshaftthrows

(1)forfour-cylinderengine=180°

(2)forin-linesix-cylinderengine=120°

(3)inav-8,thecrankshaftthrowsareat90°intervals.seefig4-24

90°Fig4-24theVangleinav-8equals90.This90keepstheproperfiringinterval