差速器和车桥中英文翻译.docx
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差速器和车桥中英文翻译.docx
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差速器和车桥中英文翻译
DIFFERENTIALANDREARAXLES
Thedifferentialispartoftherear-axle-housingassembly,whichincludesthedifferential,rearaxles,wheels,andbearing.
Ifthecarweretobedriveninastraightlinewithouthavingtomaketurns,thennodifferentialwouldbenecessary.However,whenthecarroundsaturn,theouterwheelmusttravelfartherthantheinnerwheel.Thedifferentialpermitsthetworearwheelstorotatedifferentamountswhenthecargoesaroundaturn,whilestilldeliveringpowertobothrearwheels.
Therearaxlesareattachedtothewheelsandhavebevelsidegearsontheirinnerends.Thedifferentialcaseisassembledontheleftaxlebutcanrotateonabearingindependentlyoftheaxle.Thedifferentialcasesupportsthedifferential-piniongearonashaft,andthisgearmesheswiththetwobevelgears.Thefinggearisattachedtothedifferentialcasesothatthecaserotateswiththefinggearwhenthelatterisdrivenbythedrivepinion.
Thedrivingpowerentersthedifferentialthroughthedrivepinionontheendofthepropellershaft.Thedrivepinionismeshedwithalargeringgearsothattheringgearrevoveswiththepinion.
Attachedtotheringgearisadifferential-pinionshaftonwhichareassembledtwodifferential-piniongears.Eachrearcarwheelhasaseparateaxle,andtherearetwosidegearssplinedtotheinnerendsofthetwowheelaxles.Thetwosidegears.Whenthecarisonastraighetroad,thetwodifferential-piniongearsdonotrotateonthepinionshaft,buttheydoexertpressureonthetwosidegearsturnatthesamespeedastheringgear,causingbothrearwheelstoturnatthesamespeed,also.
Whenthecarroundsacurve,theouterwheelmustturnfasterthantheinnerwheel,Topermitthis,thetwopininogearsrotateontheirpinionshaft,transmittingmoreturningmovementtotheoutersidegearthattotheinnersidegear.Thus,thesidegearontheouter-wheelaxleturnsmorerapidlythanthesidegearontheinnerwheelaxle.Thispermitstheouterwheeltoturnmorerapidlywhilethecarisroundingthecurve.
Therearetwobasictypesofaxle:
deedaxlesandliveaxle.Thedeadaxledoesnotrotate;thewheelrotatesonit.Acommonexmpleistheaxleonahorse-drawnwagon.Liveaxlesareattachedtothewheelsothatboththewheelandtheaxlerotatetogether.Liveaxlesareclassifiedaccordingtothemannerinwhichtheyaresupported:
semifloating,three-quarer-floating,andfull-floating.
AUTOMOBILESYSTEM
Thefuelsystemhasthejobofsupplyingacombustiblemixtureofairandfueltotheengine.Thefuelsystemmustvarytheproportionsofairandfueltosuitdifferentoperatingconditions.Whentheengineiscold,forexample,thenthemixturemustberich(haveahighproportionoffuel).Thereasonforthisisthatthefueldoesnotvaporizerapidlyatlowtemperatures.Therefore,extrafuelmustbeaddedtothemixturesothattherewillbeenoughvaporizedfueltoformacombustiblemixture.
Thefuelsystemconsistsofthefueltank,fuelpump,fuelfilter,carburetor,intakemanifold,andfuellines,ortubes,connectingthetank,pump,andcarburetor.Somegasolineenginesuseafuel-injectionsystem;inthissystem,afuel-injectionpumpreplacesthecarburetor.
Thefueltank,inwhichgasolineisstored,isnormallylocatedattherearofthevehicle.Itismadeofsheetmetalandisattachedtotheframe.
Afuelpumpdeliversfuelfromthetanktothecarburetor.Therearetwogeneraltypesoffuelpump,mechanicalandelectric.
Thefuelsystemhasfiltersandpreventdireinthefuelfromenteringthefuelpumporcarburetor.Dirtcould,ofcourse,preventnormaloperationoftheseunitsandcausepoorengineperformance.
Thecarburetorisessentiallyamixingdevicewhichmixesliquidgasolinewithair.Inthisprocess,itthrowsafinesprayofgasolineintoairpassingthroughthecarburetoronitswaytotheengine.Thegasolinevaporizesandmixeswiththeairtoformahighlycombustionchambers,whereitisignited.Itburns,causingtheenginetoproducepower.Themixturemustbeofvaryingdegreesofrichnicetosuitengineoperatingconditions.Itmustberich(haveahigherpercentageoffuel)forstarting,acceleration,andhigh-speedoperation.Anditshouldleanto(becomelessrich)foroperationatintermediatespeedwithawormengine.Thecarburetorhasseveraldifferentcircuits,orpassages,throughwhichfuelandair-fuelmixtureflowunderdifferentoperatingconditionstoproducethevaryingrichnessoftheair-fuelmixture.
Thepurposeofthecoolingsystemistokeeptheengineatitsmostefficientoperatingtemperatureatallenginespeedsandalldrillingconditions.
Agreatdealofheatisproducedintheenginebytheburningoftheair-fuelmixture.Someofthisheatescapesfromtheenginethroughtheexhaustgases(thehotgasesleftafterthegasolineisburned).Butenoughremainsintheenginetocauseserioustroubleunlessremovedbysomeothermeans.Thecoolingsystemtakescareofthisadditionalheat.
Thecoolingsystemisbuiltintotheengine.Therearehollowspacesaroundeachenginecylinderandcombustionchamber.Thesehollowspacesarecalledwaterjackets,sincetheyarefilledwithwater.Whentheengineisrunning,thewatertakesheatfromtheengine,becominghotintheprocess.Awaterpumppumpsthehotwaterfromtheenginewaterjacketsintotheradiator.Theradiatorhastwosetsofpassages.Onesetcarriesair(pulledthroughbycarmotionandtheenginefan).Asthehotwaterpassesthrough,itgivesupitsheattotheairpassingthrough.Thecooledwaterthenreenterstheengine,whereitcanpickupmoreheat.Inoperation,watercontinuouslycirculatesbetweentheengineandradiator,carryingheatfromtheenginetemperaturesareprevented.
Twogeneraltypesofcoolingsystemsareused,aircoolingandliquidcooling.Theliquidcoolingsystemconsistsofwaterpumps,waterjackets,enginefan,radiatorandsoon.Thewaterpump,drivenbyabeltfromtheenginecrankshaft,circulatesthecoolingliquidbetweentheradiatorandenginewaterjackets.Thecoolingliquidiswater.Antifreezecompoundsareaddedtothewaterduringthewinter.Thewaterjacketarecastintothecylinderblocksandheats.Theenginefanisusuallymountedonthewater-pumpshaftandisdrivenbythesamebeltthatdrivesthepumpshaftandthegenerator.Thepurposeofthefanistoprovideapowerfuldraftofairthroughtheradiator.Theradiatorisadeviceforholdingalargevolumeofairsothatheatwilltransferfromthewatertotheair.Theradiatorcoreisdividedintotwoseparatecompartments;waterpassesthroughone,andairpassesthroughtheother.
Theignitionsystemispartoftheelectricsystemoftheautomobile.Itspurposeistoproducehigh-voltagesurges(upto20000volts)andtodeliverthemtothecombustionchambersintheengine.Thesehigh-voltagesurgesurgesthencauseelectricsparksinthecombustionchambers.Thesparksignite,orsetfireto,theair-fuelmixtureinthecombustionchamberssothatitburnsandcausetheenginetonoperate.
Theignitionsystemconsiststhreebasicparts:
theignitiondistributor,theignitioncoil,andthesparkplug,togetherwiththeconnectingwires.Whentheengineisrunning,theignitioncoilisrepeatedlyconnected,itbecomesloadedwithelectricalenergy.Then,whenitisdisconnected,the“load”ofelectricalenergyisreleasedinahigh-voltage.Thissurgeflowsthroughthewiringtothesparkplugintheenginecylinderthatisreadytofire.
Youmustunderstandthatallthistakesplaceveryrapidly.Athighspeed,thewholeseriesofeventshappensinlessthanonethree-hundredthofasecond.Thatis,therewillbeasmanyas300oftheseeventseverysecondthattheengineisrunningathighspeed.
Somesystemsusetransistorstoreducetheloadonthedistributorcontractpoints.Othersystemsdonothavecontractpointsuseinsteadacombinationoftransistorsandamagneticpick-upinthedistributor.
Theignitiondistributorhastwojobs.First,itclosesandopensthecircuitbetweenthebatteryandtheignitioncoil.Thedistributorssecondjobistodistributeeachhigh-voltagesurgetothecorrectsparkplugatthecorrectinstantbymeansofthedistributorrotorandcapandsecondarywiring.
Therearetwobasictypesofdistributor:
(1)thetypeusingcontactpointstocloseandopenthecoilprimarycircuit;
(2)thetypeusingamagneticpick-upandatransistorcontrolunittointerruptthecurrentflowofthecoilprimarycircuit.
Automobileenginesarenotself-starts.Inordertostartthem,theenginecrankshaftmustbeturnedoverbysomeoutsidemeanssoasto(a)admitair-fuelmixturetothecylinder,and(b)causethemixturetofire.
Inthecaseofautomobileengines,themixtureinthecylinder,afterbeingcompressed,mustbenotenoughtoignite.Thisrequiresthattheenginebeturnedoverwithsufficientspeed.Iftheengineisturnedovertooslowly,theunavoidablesmallleakspastthepistonringsandalsothroughtheintakeandexhaustvalvesoffour-circleengineswillpermitasubstantialpartofthefuel-airmixturetoescapeduringthecompressionstroke.Also,theheatlossfromthecompressedairtothecylinderwallswillbegreateratlowspeedbecauseofthelongerexposure.Theescapeofairandthelossofheatbothresultinalowertemperatureattheendofcompression.Therefore,thereisaminimumspeedwhichtheenginemustattainbeforeignitionwilloccurandtheenginewillbeginfiring.Thestartingspeeddependsuponthetypeandsizeoftheengine,itscondition,andthetemperatureoftheairenteringengine.
Thestartingsystemcontainsacranking,orstarting,motorandotheraccessories.
Thestartingmotorelectri
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