汽车制动能量回收 中外文翻译.docx

汽车制动能量回收 中外文翻译.docx

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汽车制动能量回收中外文翻译

THEBRAKES

Don'texpectmiraclesfromtuningonthebrakes-improvement,yes-butnomiracles.Therearetworeasonsforthis.First,theracingdiscbrakesystemhasbeendevelopedtoaveryhighstateindeedsothattherejustisn'talotleftinthelineofpracticalimprovementand,second,wejustdon'tspendverymuchtimeunderthebrakes.Ontheaverageroadracingcircuit,somethinglessthantenpercentofthetimerequiredtocompletealapisspentbraking.Therefore,afivepercentimprovementinbrakingperformance（notbrakeefficiency）wouldnetatheoreticalimprovementinlaptimeofonehalfofonepercentoraboutonehalfsecondina90secondlap.Inactuality,theimprovementwouldbesomewhatlessbecausehumanandpracticallimitationsalwayspreventusfromrealizingthefullpotentialbenefitfromanyperformanceimprovement.

Thebigpayoffofawellsortedoutbrakingsystemcomes,notfromanyincreaseinbrakingpoweritself,butintheconfidence,consistencyandcontrolabilitythatitprovidestothedriver.Thisisparticularlytruewhenitcomestocornerentry-entryspeed,placement,precisionandrepeatabilityarealldirectlydependentuponbrakingperformanceandconsistency.

Iwouldbeastonishedtolearnofamodernroadracingcarwhichwasdeliveredwithinadequatebrakes.BadlyarrangedorbadlysetupI'mwillingtobelieve,butinadequate-NO.Thisstatementisvalidonlysolongaswedonotchangetiresize,poweroutputand/orgrossweightalloutofproportiontotheoriginaldesign.ItisdefinitelynottrueinthoseclassesofproductionbasedtouringcarandG.T.Carracingwherethesanctioningbody,throughsheerignoranceand/orbloodymindednessprohibitschangestothebrakingsystem.

BRAKINGPOWER:

WHEREDOESITCOMEFROM?

Ittakesanastonishingamountofenergytodecelerateamovingvehicle-infactittakesthesameamountofenergytodeceleratefromonespeedtoanotherasitwouldtoacceleratebetweenthetwospeeds-exceptthatwecandeceleratefasterbecausemostoftheinertialforcesareworkingforusratherthanagainstus.Theactualenergyrequiredtodecelerateourracerisgivenbytheequation:

Energy（Ib/ft）=.0335x[（mphmax）2（mphmin）2]xgrossweight（lb）.Fora1760Ibcarbrakingfrom150mphto60mphwearetalkingabout.0335x[（150）2_（60）2]x1760=I,I14,344Ib/ft.Nomatterwhatterminologyweuse,thisisahellofalotofenergyabsorbedinaveryshortperiodoftime.SomebodyonceconvertedthebrakingenergyputoutbyaGT40overthetwelvehoursofSebringandcametotheconclusionthatthesameamountofenergycouldsupplytheelectricalrequirementsofafairsizedcityforagoodlyperiodoftime.Sowheredoestheenergycomefrom-whatactuallystopsthecar?

Somecomesfromtherollingresistanceofthetires-notmuch,butsome.Anotableamount,atleastathighroadspeeds,comesfromthevehicle'saerodynamicdrag.Alittlebitcomesfromthefrictiongeneratedbetweenthemovingpartsoftheentiremechanism.Mostofit,however,mustcomefromthevehicle'sbrakingsystemwhichconvertsthekineticenergyofvehicleinertiaintothermalenergywhichmustthenbedissipatedintotheairstream-becausewehaveyettofigureoutapracticalmethodtocollectit,storeit,anduseitforpropulsivethrust.Wereallyaren'tveryefficient.Thischapterisdevotedtoinvestigatingthebrakingsystemitself.Weshallconvenientlyignoretheotherfactorswhichslowthecarbecausewhatwereallywanttodowiththemisminimizethemtoincreasetheaccelerationofthevehicle.

WHATWECANEXPECTFROMTHEBRAKES

Whatexactlyarewelookingforinbrakingsystemperformance?

Firstofallweneedabrakingsystemwhichiscapableofdevelopingenoughbrakingforcetoexceedthedecelerationcapacityofthetires-atanyspeedthatthevehiclecanreach-timeaftertime,forthedurationoftherace.Allracingcars,andmanymodifiedproductioncars,havesuchasystem-providedthatitisproperlyinstalled,adjustedandmaintained.Thebrakingeffortproducedmustbedirectlyandlinearlyproportionaltothepedalpressureexertedbythedriver.Further,thedrivereffortrequiredmustbereasonable,pedalpressuresmustbeneithersogreatthatGodzillaisrequiredtostopthecarnorsolightthatitwillbeeasytolockthetires.Thepedalpositionmustbecorrectlymatchedtothegeometryofthedriver'sfootandankle,mustremainataconstantheightandshouldbereallyfirmandhaveminimumtravel.Thesystemmustdeliveroptimumbalanceofbrakingforcebetweenthefrontandreartiressothatthedrivercanmaintainsteeringcontrolunderveryheavybrakingandyetuseallofthedecelerativecapacityofallfourtires.Lastly,thesystemmustoffercompletereliability.Ifthedriverisbrakingasdeepandashardasheshouldbe,anybrakesystemfailurewillinevitablyresultinthecarleavingthecircuit.Whathappensafterthatisuptothemanupstairs.Brakefailureinaracingcaratthelimithastobeexperiencedtobeunderstood.Thisiswhyeventhemostheroicdriversareliabletogivethebrakepedalareassuringtapbeforetheyarriveattheirbrakingmarker.

Weneedavehiclesuspensionsystemcapableofdealingwiththeloadsandforcesgeneratedbyheavybrakingwithoutwheelhop,suspensionbottoming,compliance,adversecambereffects,pullordarting.Mostofallweneedadriversensitiveandskillfulenoughtobalancethecarontheedgeofthetractioncircleunderbrakingandunderthecombinationofbrakingandcornering.Ifwedonotprovidethedriverwithallofthesystemparameterslistedabove,hecannotprovideuswiththeskillanddaringnecessarytoridetheedgeofthetractioncircle.

EVALUATIONANDDRIVERTECHNIQUE

We'llstartoutwithwhatisprobablythemostdifficultpartofthewholebrakingscene-evaluationofwhatyouhave.Measuringthebrakingperformanceofyourparticularprojectileagainstthatofthecompetitionisnoeasierthancomparinganyotheraspectofvehicleperformance-andforthesamereasons-toomanyvariablesandtoomuchegoinvolved.Thisiswhereinstrumentationisinvaluable.Thebiggestvariableis,ofcourse,thedriver.Theverylastthingthatareallygoodracingdriverlearnstodotrulywellistousethebrakes.Mostpeopletaketoolongtogetthemonhard,leavethemhardontoolongandbraketooheavilytoodeepintothecorner.AlmostinvariablythelaptimesgeneratedbytheKingofTheLateBrakersareslow.Hisadrenalinlevelisliabletobeabnormallyhighandhehasatendencytofallofftheroad.Thereareseveralreasonsforthesecharacteristics.Whenyouleaveyourbrakingtoolateyouareveryliabletoarriveatthepointontheracetrackwhereyoureallywanttostartyourturnonlytofindthatthecarwillnotturn.Itwillnotdosobecause,inyoureffortstosaveyourlife,youhavethebindersonsohardthatallofthefronttires'availabletractionisbeingusedindecelerationandthereisnonelefttoallowthegenerationofthesideforcenecessarytoturnthecar-or,shouldyousomehowsucceedininitiatingaturn,tokeepitinabalancedcorneringstate.Inaddition,thefronttiresareliabletobeverynearlyonfireanddangerouslyclosetothecompoundtemperaturelimit.Thirdly,ifyouarestillhardonthebrakeswhentheturnisinitiated,forwardloadtransferhasunbalancedthecar,thefrontsuspensiontravelisaboutusedup,thefronttiresaresteeplycamberedand,ifthethingturnsatall,thingsaregoingtohappenabitquickly.

Ifyoupersistinbrakingtoolate,thespectatorswill"ooh"and"ahh"andbeimpressednoendandtheannouncerwillmentionyournamefrequently-notingthatyouarereallytryingoutthere.Youwillcomplainpitifullyaboutcornerentryundersteerfollowedbyanincrediblyrapidtransitiontopoweronoversteer.Theotherdriverswillpourbyyou-eitherwhileyouareexploringthegreyareasofthetrackinyourfranticscrabblefortractionoronthewayoutofthecornerwhentheyhavebothhigherexitspeedandabetterbite.Youwilldoalotofexploringasyourselfinducedundersteerforcesyouintounintentionallatecornerentries.Yourteammanagerwilleventuallycatchon,wanderoutonthecourseandobserveyourantics.Iftheensuingfrankdiscussionoftechniquedoesnotinspireyoutomendyourways,hewillseriouslyconsidereitheranotherdriver（ifyoudon'townthecar）oranotherjob（ifyoudo）.

Soanytimethatyouaregoinginnoticeablydeeperthanthecompetentopposition（assumingsimilarcars）butyourlaptimesarenotreflectingthedegreeofheroismthatyoufeeltheyshould-andthecarisenteringcornersbadly-haveagoodthinkaboutthewisdomofyourbrakingpoints.Slowinandfastoutwillbeatfastinandslowouteverytime.Ofcoursefastinandfastoutbeatseitheroftheabove-andthat'swhatwearetryingtoachieve-butyouwon'tcomeoutfastifyougoinwiththecarunbalancedandthefronttiresonfire.Thisisnottosaythatasuperlatebrakeapplicationfollowedbyadeliberateearlycornerentryandabitofslitheringaroundwhichusesupaportionofthetrackthatmightotherwisebeusefultosomeoneelseisnotavaliddesperationmaneuver.Itis,anditwillcontinuetobe-butitisn'tveryoftenfastanditisevenlessoftenrepeatedlyfast.

THEBRAKEPEDAL

Havingdisposedofthesystemactuator,itistimetodiscusshardware.Wewillbeginwiththebrakepedalsinceitistheclosestparttothedriver.Thebrakepedalshouldbeverystrong-andsoshoulditsattachmenttothechassis.Thismaysoundverybasicandabitridiculous-andsoitshould.Anyfoolshouldbeabletofigureoutthatifthebrakepedal,oranyoftheassociatedbits,fractures,