完整版汽车制动系统机械车辆工程毕业论文英文文献及翻译.docx
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完整版汽车制动系统机械车辆工程毕业论文英文文献及翻译
AutomobileBrakeSystem
Thebrakingsystemisthemostimportantsystemincars.Ifthebrakesfail,theresultcanbedisastrous.Brakesareactuallyenergyconversiondevices,whichconvertthekineticenergy（momentum）ofthevehicleintothermalenergy（steppingonthebrakes,thedrivercommandsastoppingforcetentimesaspowerfulastheforcethatputsthecarinmotion.Thebrakingsystemcanexertthousandsofpoundsofpressureoneachofthefourbrakes.
Twocompleteindependentbrakingsystemsareusedonthecar.Theyaretheservicebrakeandtheparkingbrake.
Theservicebrakeactstoslow,stop,oraseparateparkingbrakefootpedalorextremeconditions,fillsthesystem.“Shoes”and“pads”arepushedbytheslavecylinderstocontactthe“drums”and“rotors”thuscausingdrag,which（frontandeitherdiskordrumbrakesintherearconnectedbyasystemoftubesandbrakes.Whenthedriverappliesthebrake,thecontroldeviceforcesbrakeshoes,orpads,againsttherotatingbrakedrumordisksatwheel.Frictionbetweentheshoesorpadsandthedrumsordisksthenslowsorstopsthewheelsothatthecarisbraked.
Inmostmodernbrakesystems（seeFigure15.1）,thereisafluid-filledcylinder,calledmastercylinder,whichcontainstwoseparatesections,thereisapistonineachsectionandbothpistonsareconnectedtoabrakepedalinthedriver’scompartment.Whenthebrakeispusheddown,brakefluidissentfromthemastercylindertothewheels.
Atthewheels,thefluidpushesshoes,orpads,againstrevolvingdrumsordisks.Thefrictionbetweenthestationaryshoes,orpads,andtherevolvingdrumsordisksslowsandstopsthem.Thisslowsorstopstherevolvingwheels,which,inturn,sloworstopthecar.
Thebrakefluidreservoirisontopofthemastercylinder.Mostcarstodayseethelevelwithoutopeningthecover.Thebrakefluidlevelwilldropslightlyasthebrakepadswear.Thisisanormalconditionandnocauseforconcern.Iftheleveldropsnoticeablyoverashortperiodoftimeorgoesdowntoabouttwothirdsfull,aspossible.Keepthereservoircoveredexceptfortheamountoftimeyouneedtofillitandneverleaveacamofbrakefluiduncovered.Brakefluidmustmaintainaveryplacesthatrequireflexibility,suchasatthefrontwheels,whichmoveupanddownaswellassteer.Therestofthesystemusesnon-corrosiveseamlesssteeltubingwithspecialfittingsatallattachmentpoints.Ifasteellinerequiresarepair,thebestprocedureistoreplacethecompeteline.Ifthisisnotpractical,alinecanberepairedusingspecialsplicefittingsthataremadeforbrakesystemrepair.Youmustneverusecoppertubingtorepairabrakesystem.Theyaredangerousandillegal.
Drumbrakes,itconsistsofthebrakedrum,anexpander,pullbacksprings,astationarybackplate,twoshoeswithfrictionlinings,andanchorpins.Thestationarybackplateissecuredtotheflangeoftheaxlethewheeltheinnersurfaceofthedrumandtheshoelining.Toapplybrakes,thedriverpushespedal,theexpanderexpandstheshoesandpressesthemtothedrum.Frictionbetweenthebrakedrumandthefrictionliningsbrakesthewheelsandthevehiclestops.Toreleasebrakes,thedriverreleasethepedal,thepullbackspringretractstheshoesthuspermittingfreerotationofthewheels.
Diskbrakes,iteachsideofthedisk.Theshoessqueezetherotatingdisktostopthecar.Fluidfromthemastercylinderforcesthepistonstomovein,towardthedisk.Thisactionpushesthefrictionpadstightlyagainstthedisk.Thefrictionbetweentheshoesanddiskslowsandstopsit.Thisprovidesthebrakingaction.Pistonsaremadeofeitherplasticormetal.Therearethreegeneraltypesofdiskbrakes.Theyarethefloating-calipertype,thefixed-calipertype,andthesliding-calipertype.Floating-caliperandsliding-caliperdiskbrakesuseasinglepiston.Fixed-caliperdiskbrakestheparkingbrakesfittedinallautomobile.Whenthebrakepedalisdepressed,therodpushesthepistonofbrakemastercylinderwhichpressesthefluid.Thefluidflowsthroughthepipelinestothepowerbrakeunitandthentothewheelcylinder.Thefluidpressureexpandsthecylinderpistonsthuspressingtheshoestothedrumordisk.Ifthepedalisreleased,thepistonreturnstotheinitialposition,thepullbackspringsretracttheshoes,thefluidisforcedbacktothemastercylinderandbrakingceases.
Theprimarypurposeoftheparkingbrakeistoaseparateparkingbrakingthecarthe“on”position.Thecarmaynowbeleftwithoutfearofitsrollingaway.Whenthedriverwantstomovethecaragain,beforethelevercanbereleased.Thetheeventofthefootbrakefailing.Forthisreason,itisseparatefromthefootbrakeusescableorrodsinsteadoftheslipperypavementorduringapanicstop.
Anti-lockbrakesystemsusedonaircraftforyears,andsomedomesticcarwereofferedwithanearlyformofanti-lockbrakinginlate1990’s.Recently,severalautomakersEurope,whereanti-lockbrakingsystemsavailableforadecade,andaforceseveraltimespersecondtobasicallythesameway.Oneormorespeedsensorsgeneratealternatingcurrentsignalwhosefrequencyincreaseswiththewheelrotationalspeed.Anelectroniccontrolunitcontinuouslymonitorsthesesignalsandifthefrequencyofasignaldropstoorapidlyindicatingthatawheelisabouttolock,thecontrolunitinstructsamodulatingdevicetoreducesensorsignalsindicatethewheelisagainrotatingnormally,thecontrolunitallowsincreasedadditiontotheirbasicoperation,anti-locksystemscommon.First,theydonotoperateuntilthebrakesareappliedwithenoughforcetolockornearlylockawheel.Atallothertimes,thesystemstandsreadytofunctionbutdoesnotinterferewithnormalbraking.Second,iftheanti-locksystemfailinanyway,thebrakescontinuetooperatewithoutanti-lockcapability.Awarninglightontheinstrumentpanelalertsthedriverwhenaproblemexistsintheanti-locksystem.
ThecurrentBoschcomponentAnti-lockBrakingSystem（ABSⅡ）,isasecondgenerationdesignwildlyusedbyEuropeanautomakerssuchasBWM,Mercedes-BenzandPorsche.ABSⅡsystemconsistsof:
fourwheelspeedsensor,electroniccontrolunitandmodulatorassembly.
Aspeedsensorisfittedateachwheelsendssignalsaboutwheelrotationtocontrolunit.Eachspeedsensorconsistsofasensorunitandagearwheel.Thefrontsensormountstothesteeringknuckleanditsgearwheelispressedontothestubaxlethatrotateswiththewheel.Therearsensormountstherearsuspensionmemberanditsgearwheelispressedontotheaxle.Thesensoritselfisawindingwithamagneticcore.Thecorecreatesamagneticfieldaroundthewinding,andastheteethofthegearwheelmovethroughthisfield,analternatingcurrentisinducedinthewinding.Thecontrolunitmonitorstherateochangeinthisfrequencytodetermineimpendingbrakelockup.
Thecontrolunit’sfunctioncanbedividedintothreeparts:
signalprocessing,logicandsafetycircuitry.Thesignalprocessingsectionistheconverterthatreceivesthealternatingcurrentsignalsformthespeedsensorsandconvertsthemintodigitalformforthelogicsection.Thelogicsectionthenanalyzesthedigitizedsignalstocalculateanybrakepressurechangesneeded.Ifimpendinglockupissensed,thelogicsectionsendscommandstothemodulatorassembly.
Modulatorassembly
Theitreceivescommandsfromthecontrolutuit.Themodulatorassemblycanmaintainorreducepressureoverthelevelitreceivesfromthemastercylinder,italsocanneverapplythebrakesbyitself.Themodulatorassemblyconsistsofthreedeliverypumpequippedwithinletandoutletcheckvalves.Themodulatorelectricalconnectorandcontrollingrelaysareconcealedunderaplasticcoveroftheassembly.
Eachfrontwheelisservedbyelectricsolenoidvalvemodulatedindependentlybythecontrolunit.Therearbrakesareservedbyasinglesolenoidvalveandmodulatedtogetherusingtheselect-lowprinciple.Duringanti-brakingsystemoperation,thecontrolunitcyclesthesolenoidvalvestoeitherpressureisreleasedfromthebrakelinesduringanti-brakingoperation,itisroutedtoafluidreservoir.Thereisonereservoirforthefrontbrakecircuit.Thereservoirsarelow-pressureaccumulatorsthatstorefluidunderslightspringpressureuntilthereturndeliverypumpcanreturnthefluidthroughthebrakelinestothemastercylinder.
汽车制动系统
制动系统是汽车中最重要的系统。
如果制动失灵，结果可能是损失惨重的。
制动器实际就是能量转换装置，它将汽车的动能（动量）转化成热能（热量）。
当驾驶员踩下制动踏板，所产生的制动力是汽车运动时动力的10倍。
制动系统能对四个刹车系统中的每个施加数千磅的力。
每辆汽车上使用两个完全独立的制动系统，即行车制动器和驻车制动器。
行车制动器起到减速、停车、或保持车辆正常行驶。
制动器是由司机用脚踩、松制动器踏板来控制的。
驻车制动器的主要作用就是当车内无人的时候，汽车能够保持静止。
当独立的驻车制动器—踏板或手杆，被安装时，驻车制动器就会被机械地操作。
制动系统是由下列基本的成分组成:
位于发动机罩下方，而且直接地被连接到制动踏板的“制动主缸”把驾驶员脚的机械力转变为液压力。
钢制的“制动管路”和有柔性的“制动软管”把制动主缸连接到每个轮子的“制动轮缸”上。
制动液,特别地设计为的是工作在极端的情况，填充在系统中。
“制动盘”和“衬块”是被制动轮缸推动接触“圆盘”和“回转体”如此引起缓慢的拖拉运动,（希望）使汽车减慢速度。
典型的制动系统布置有前后盘式，前盘后鼓式，各个车轮上的制动器通过一套管路系统连接到制动主缸上。
基本上讲，所有的汽车制动器都是摩擦制动器。
当司机刹车时，控制装置会迫使制动蹄，或制动衬片与车轮处的旋转的制动鼓或制动盘接触。
接触后产生的摩擦使车轮转动减慢或停止，这就是汽车的制动。
在最基本的制动系统中，有一个制动主缸，这个主缸内部填充制动液，并包含两个部分，每个部分里都有一个活塞，两个活塞都连接驾驶室里的制动踏板。
当制动踏板被踩下时，制动液会从制动主缸流入轮缸。
在轮缸中，制动液推动制动蹄或制动衬片与旋转的制动鼓或制动盘接触。
静止的制动蹄或制动衬片与旋转的制动鼓或制动盘之间产生摩擦力使汽车的运动逐渐减缓或停止。
制动液的装置位于主缸的顶部。
目前大多数的车都有一个容易看见的装制动液的装置，为的是不用打开盖子就可以看得见制动液的油面。
随着制动踏板的运动制动液就会缓慢的下降，正常情况下是这样的。
如果制动液在很短的时间内下降得明显或者下降了三分之二，那么就要尽快的检查你的制动系统了。
保持制动液装置充满制动液除非你需要维修它，制动液必须保持很高的沸点。
位于在空气中的制动液就会吸收空气中的潮气引起制动液低于沸点。
制动液通过一系列的管路从主缸到达各车轮。
橡胶软管只用在需要弹力的地方，比如应用在前轮。
在车的行进中上下来回运动。
系统的其它部分在所有的连接点上都应用了无腐蚀性的无缝钢管。
如果钢线需要修理的话，最好的方法就是代替这条线。
如果这不符合实际，那么为了制动系统可以用特殊的装置修理它。
你不可以用铜管来修理制动系。
它们是危险也是不正确的。
鼓式制动器包括制动鼓，一个轮缸，回拉弹簧，一个制动底版，两个带摩擦层的制动蹄。
制动底版固定在轮轴外部的法兰或转向节。
制动鼓固定在轮毂上。
制动鼓的内部表面与制动蹄的内层之间有空隙。
要使用制动器时，司机就要踩下踏板，这时轮缸扩大制动片，对其施加压力，是制动蹄触碰制动鼓。
制动鼓与摩擦片之间产生的
升级会员 