外文翻译--卡车和货车.doc

附录1：英文原文TrucksandWagons3.1GeneralTrucksarehaulingunitswhich,becauseoftheirhighspeedswhenoperatingonsuitableroads,havehighcapacitiesandproviderelativelylowhaulingcosts.Theyprovideahighdegreeofflexibility,asthenumberinservicemaybeincreasedordecreasedeasilytopermitmodificationsinthetotalhaulingcapacityofafleet.Mosttrucksmaybeoperatedoveranyhaulroadforwhichthesurfaceissufficientlyfirmandsmoothandonwhichthegradesarenotexcessivelysteep.Someunitsnowinusearedesignatedasoff-highwaytrucksbecausetheirsizesandtotalloadsarelargerthanthatarepermittedonhighways.Thesetrucksareusedforhaulingmaterialsonlargeprojects,wherethesizesandcostsarejustified.Trucksmaybeclassifiedaccordingtoagreatmanyfactors,includingthefollowing:1.Sizeandtypeofengine-gasoline,diesel,butane,propane.2.Numberofgears.3.Kindofdrivetwo-wheel,four-wheel,six-wheel,etc.4.Numberofwheelsandaxlesandarrangementofdrivingwheels.5.Methodofdumpingtheloadrear-dump,side-dump.6.classofmaterialhauledearth,rock,coal,ore,etc.7.Capacity,intonorcubicmeter(cubicyards).8.Methodofdumpingtheloadforreardumps，hydraulicorcableIftruckaretobepurchasedforgeneralmaterialhauling，thepurchasershouldselectunitsthatareadaptabletothepurposesforwhichtheywillbeusedHowever，iftruckaretobeusedonagivenprojectforagivenpurpose，thepurchasershouldselecttrucksthatmostnearlyfittherequirementoftheproject1RearDumpTrucks2Rear-dumptrucksaresuitableforuseinhaulingmanytypesofmaterialsTheshapeofthebody，suchastheextentofsharpangles，corners，andthecontouroftherear，throughwhichthematerialsmustflowduringdumping，willaffecttheeaseordifficultyofdumpingj41ThebodiesoftruckthatwillbeusedtohaulwetclayandsimilarmaterialsshouldbefreeofsharpanglesandcornersDrysandandgravelwillfloweasilyfromalmostanyshapeofbodyIfquarryrockistobehauled，bodiesshouldbeshallowwithslopingsideboards2BottomDumpWagonsIfunitsaretobeusedtohaulmaterials，suchassand，gravel，reasonabledryearth,coal,etcwhichfloweasily，theuseofbottomdumpwagonswillreducethetimerequiredtounloadtheunitsSuchunitsareparticularlysuitableforusewherethematerialsaredistributedinlayersonafilloraredischargedthroughgrizzliesintohoppersWhendischargingtheloadontofills，thewagonscandumptheirloadswhilemovingWhendischargingthroughgrizzlies，theywillneedtostopforonlyafewsecondsTherapidrateofdischargingtheloadgivesthesewagonsatimeadvantageoverreardumptrucksAsthedoorsthroughwhichtheseunitsdischargetheirloadhavelimitedopenings，difficultiesmaybeexperiencedindischargingsuchmaterialsaswet，stickyclay，especiallyiftheyareinlargelumpsThesewagonsaresatisfactoryhaulingunitsonprojectssuchasearthendams，levees，highwaysandairports，wherelargequantitiesofmaterialsaretobetransportedandhaulroadscanbekeptinreasonablygoodconditionTheymaybeloadedbypowershovels,draglines，orportablebeltloaders3CapacitiesofTrucksandWagonsThereareatleastthreemethodsofexpressingthecapacitiesoftrucksandwagons：bytheloadwhichitwillcarry，expressedintons；byitsstruckvolume；andbyitsheapedvolume。thelattertwoexpressedincubicmeter(orcubicyards)Thestruckcapacityofatruckisthevolumeofmaterialwhichitwillhaulwhenitisfilledtothetopofthesides，withnomaterialabovethesidesTheheapedcapacityisthevolumeofmaterialwhichitwillhaulwhentheloadisheapedabovethesidesThecapacityshouldbeexpressedincubicmetersWhilethetruckcapacityremainsfixedforanygivenunit，buttheheapedcapacitywillvarywiththeheighttowhichthematerialmayextendabovethesidesandwiththelengthandwidthofthebodyWetearthorsandyclaymaybehauledwithaslopeof1：1，whiledrysandorgravelmaynotpermitaslopegreaterthan3：1Inordertodeterminetheprobableheapedcapacityofaunit，itisnecessarytoknowthestruckcapacity，thelengthandwidthofthebody，andtheslopeatwhichthematerialwillremainstablewhiletheunitismoving.Smoothhaulroadswillpermitalargeheapedcapacitythanroughhaulroads.Becauseofvariationsintheheapingcapacitiesofunitsitmaybebettertocomparethemonthebasisoftheirstruckcapacities.Inaneeventthecapacitiesshouldbedeterminedorcomparedinarealisticmanner.Theweightcapacitymaylimitthevolumeoftheloadwhenaunitisusedtohaulheavymaterial，suchasironoreHowever，whenthespecificgravityofthematerialissuchthatthesafeloadisnotexceeded，aunitmaybefilledtoitsheapedcapacityInsomeinstancesitispossibletoaddsideboardstoincreasethedepthofthebodyofatruckorwagon，therebypermittingittohaulalargerloadThispracticeprobablywillincreasethehourlycostofoperatingaunit，becauseofhigherfuelconsumption，reducedtirelifemorefrequentfailuresofparts，suchasaxles，gears，brakes，andclutches，andhighermaintenancecostsHowever，ifthevalueoftheextramaterialhauledisgreaterthanthetotalincreaseinthecostofoperatingavehicle，theoverloadingisjustifiedInconsideringhaulinglargervolumesofmaterials，themaximumsafeloadsonthetiresshouldbecheckedtopreventexcessiveoverloading，whichmightresultinconsiderablelosttimeduetotirefailures.32DesignandPrincipalMechanismsofTracksTheprincipalmechanismsofmostmoderntruckshaveaverysimilardesignandlayoutEachtruckconsistsessentiallyofthreecomponentparts：engine，chassisandbodyTrucksarepoweredmainlybycarburetorordieselenginesThebodyisintendedtocarryloadorpeopleThedriverscabisusuallyseparatedfromthebody，anditsformanddesignconformtothepurposethetruckistoserveThechassiscarriestheengine，body，transmission.runninggearandcontrolsThepowertrainofatruckisacombinationofmechanismsfortransmittingthetorquedevelopedbytheenginecrankshafttothedrivingwheelsThepowertrainofamass-producedtruck(Fig3-1)incorporatesthefollowingmainmechanisms，thepurposeanddesignofmostofwhichdonotdifferinprinciplefromthecorrespondingmechanismsintractors：engine1，clutch2，transmissionbox3，universaljointshaft4，finaldrive8withdifferential5anddrivingwheels6withaxleshafts7Whentheresistancemetbythetruckincreases，forexampleinclimbinguphill，thetransmissionboxisusedtoincreasethetorqueattheexpenseofalowerspeed6jThetransmissionboxesoftrucksandtractorsaredesignedsimilarlyandthefunctionsperformedbytheengineclutcharethesameTheuniversaljointshafttransmitstorquefromthetransmissionboxtothefinaldrive.Thetransmissionboxisattachedrigidlytothetruckframe，whilethefinaldriveandtherearaxleareconnectedtotheframebymeansofspringAsthetyresofthetruckhitbumpsintheroadtherearaxleoscillatescontinuously，changingtheanglebetweenthetransmissionboxandfinaldriveshaftsForthisreason，themainpurposeoftheuniversaljointshaftisthetransmissionoftorquebetweenshaftincludedatdifferentanglesThefinaldriveamplifiesthetorqueandtransmitsitfromthelongitudinaluniversal-jointshafttothedrivingaxleshaftsandthewheelsThefinaldrivesintrucksandtractorsservethesamepurposeThedifferentialusedintruckfinaldrivesallowsthedrivingwheelstorotateatdifferentspeeds，whichisnecessarywhenthetruckturnsorgoesoverunevenroadandtherightandleftwheelstraveldifferentdistancesduringthesametimeInatruckmovingstraightonasmoothroadthismayOccurwhentheradiioftherightandleftwheelsareunequalPhenomenoniscausedbyanunequalpressureinthetyres，nonuniformwearofthetyresordifferentloadactingonthewheelsTherunninggearofatruckcomprisesaframesupportingthebodyandallothermechanisms，aswellasthefrontandrearaxlesspringsforanelasticsuspensionoftheaxlestotheframe，andair-tyredwheelsThespringsandtyrestransmitloadfromtheframetotheroad，andatthesametimedampjerksandshockswhenthetruckhitsbumpsintheroad.TheresultantoscillationsaredampedbyspecialshockabsorbersThesteeringcontrolincludessteeringgear，brakesystem，enginecontrolandpowertraincontro1Thesteeringgearisusedtochangethedirectionofmotionbyturningthewheels.WhicharelinkedwiththesteeringwheelbyasystemofleversandrodsThebrakesystemcontributestowardssafetyandslowsdownatruckgoingdownaslope.Thebrakesaremountedonthetruckwheelsandsometimesontheuniversal-jointshaft.Thebrakesareconnectedwiththebrakepedalorleverbymeansofmechanical，hydraulicorair-operateddevicesEnginecontrolallowsachangeinthenumberofrevolutionstobeeffectedinaccordancewiththedemands，whilethepowertraincontrolboilsdowntoengaginganddisengagingtheclutchandchangingspeeds.EffortstoimprovethepropertiesoftrucksoradaptthemforspecialpurposescontinuouslychangeandimproveboththeindividualelementsandthegenerallayoutForallthat,anddespitethegreatdiversityoftypes，alltrucksconsistessentiallyofthemainelementsdescribedabove33PowerTrainofTrucks1、ClutchInconformitywithitsfunction,theclutchshouldsmoothlyengageandjustassmoothlyandrapidlycomeoutofengagement.Drydiskclutchesaremostwidespread.Thedesignoftheclutchpressureassemblysubdividesallclutchesintospring-loadedandovercentreclutches.Intheformertypethepressuredisksareconstantlycompressedbyspringsandtheclutchcanbedisengagedbydepressingthepedalwhich,overcomingthespringtension,willdrawapartthefrictionsurfaces.Assoonasthepedalisreleasedthediskswillbeagainbroughtincontactbythesprings.Inthelattertypethedrivinganddrivendisksarepressedtogetherbyalevermechanismandtheclutchleverorpedalneednotbeconstantlydepresse.Effortisappliedtotheleveronlyduringengagementordisengagement.Theseclutchesareemployedmainlyingeneralpurposecrawleragriculturaltractorswhereshort-timestoppagesareaffectedbydisengagingtheclutch,becausethetransmissiongearcannotbechangedwhilerunningandaresomewhatdifficulttoengageanddisengageinviewoftheirlargesize.Spring-loadedclutchesareusedpredominantlyintrucks.Fig.3-2illustratesoneofthemostwide-spreadandsimpletypesofsingle-diskspring-loadedclutch.Clutchshaft13(transmissionboxdrivingshaft)ismountedintwoballbearings,itsfrontendrestingintheflywheelopeningandtherearendinthefrontwallofthetransmissionbox.Housing3isattachedtoengineflywheel1.Thepressureondrivendisk2fittedontothesplintedportionofshaft13isprovidedbysprings5installedbetweenthehousingandpressuredrivingdisk4.Threereleaselevers11aremountedonspindles12attachedt