机械毕业设计英文外文翻译549载货汽车主减速器文档格式.docx
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TruckMainReductionGear
Inthehighlycompetitiveperiodfollowingtheenergycrisisoftheearly1970'
s,theautomotiveindustryhadtoshiftattentionincreasinglytowardsimprovementofthequalityoftheproduct,yetstillkeepingitspricesaslowaspossible.PriortothatGKNAxlesLtd,totakeoptimumadvantageofeconomiesofscale,hadbeenproducingathighlycompetitivepricesastandardrangeofaxlesofdifferenttypesandsizes,fromwhichallcustomers'
needscouldbesatisfied.Becausevehiclemanufacturershadnothithertohadtoplacesuchagreatemphasisonfueleconomy,andthereforeonlightweight,thesestandardaxlescouldcaterreliablyforallconditionslikelytobemetinawidevarietyofapplications.Nowvehiclemanufacturersrequireaxlesdesignedanddevelopedfortheirspecificapplications.Asaxledesignisbecomingincreasinglyspecialised,customersareincreasinglyraisingtheiraspirationsintermsofperformanceanreliability.Forthisreason,theyareturningtospecialistssuchasGKNAxlesLtdwhohavetheabilitytoprovideaxlesforawidevarietyofvehicles。
Sincethe1970s,however,incommonwithvirtuallyallothersupplierstothehighvolumeproducersinthemotorindustry,GKNhasradicallymodifieditsapproachtosuittheprevailingconditionsastheychangethroughthe1980sandonintothe1990s.Itsaimnowisatsupplyingcompleteaxleassembles,including,forexample,thebrakes,alldesignedandfullydevelopedforandintegrated,asamatterofcourse,intospecificvehicledesignsincluding,inparticular,thoseforthespecialistmarket.
Emphasisisnowonrationalizationofmaterials,methodsandcomponents.Thisoverallchangehasbeennecessarybecauseofthegreatlyincreasedsophisticationdemandedofthemodernvehicle,intermsofoverallefficiency,compactness,lightweight,reliability,durability,refinementandmaintenance-freeoperation.AnotherareaintowhichGKNAxleshasexpandedisthesupplyofcomponentsandassembliessuchaslimited-slipdifferentials,ball-joints,transferboxes,gearsandsometypesofsuspension.
Foroff-roadoperation,thedutycyclesmaybeentirelydifferentinbothtorsionalandbeamloading-denpendingontheapplication.Forexample,sometypesofvehiclespendaconsiderableproportionoftheirrunningtimeathightorqueinlowgear.Inmostcircumstances,theterrainmaybesuchthatthetyrestendtoslipmorereadilythanontarmac;
inothers,however,forexampleinfairlyfirmsandyscrees,itmayallowtyrestobiteintoit,andthusleadtotorsionalfatigueloadingsignificantlygreaterthanonsmoothroads.Verticalandlateralloading,too,maybemuchmoresevere,thoughthisdosedependtoamajorextentonspeeds.Shockloadingcanalsoaffectbrakingandaccelerationtorquesthough,again,sucheffectsarespeed-dependent.
Hypoidgearsystemsaremorecommonlyusedthanspiralbevels.Theirprincipleadvantagesarethatpinionsofaspecificratioarebigger,theirteethprofilesareoflargeradius,theyareinherentlystrongerandmoredurable,theirmeshingareasarelarger,andtheygeneratelessnoise
Hostreductiongeareffectistobeusedtoreducetherotationratethatthetransmissionshaftsendsinbuttoenhancerevolutionmomentoftorsion,changesdrivedirectionwithmomentoftorsion,passesontohalfaxesafterdifferentialmechanismand.Thehostreductiongearstructureformisthattheformisdifferentbutdifferentaccordingtogearwheeltype,reductiongearmainly.Hostreductiongeargearwheelhashelixconeformssuchasgearwheel,hypoidgear,columngearwheelandwormgearwormmainly.
Pairoflevelhostreductiongeariscomparedwithsinglestage,thegapmaybe7~12transmissionratio,i0eachotheratthesametimeinsweartobeawayfromafield12.Butthedimension,massarewithoutexceptionbigger,costishigher.Itappliestomiddle,heavytypefreighttrain,go-anywherevehicleandmotorbusmainlygoahead.
Dyadicoverallpairoflevelhostreductiongearhasthevariousstructurescheme:
Firstorderisaconegearwheel,thesecondstageisacolumngearwheel;
Firstorderisaconegearwheel,thesecondstageisepicyclicgear;
Firstorderisepicyclicgear,thesecondstageisaconegearwheel;
Firstorderisacolumngearwheel,thesecondstageisaconegearwheel.
Horizontal,askew,faceanddroopovertothethreekindstofirstorderfortheconegearwheel,thesecondstagearethatpairofcolumngearwheellevelbetokensreductiongear,buthasdirectionarrangementscheme.
Directionlevelarrangementcanusetheassemblydroopingovertooutlinedimensiondiminution,reducingtheautomobilequalityheartaltitudethereby,makesthedirectiondimensionincreasebybut,thattheuseonlongdistancebetweenshaftsautomobilebutappropriatediminut