Infinitely variable speed

Basicmeaning

CVTmeanscontinuouslyvariabletransmission,itsEnglishnameisContinuouslyVariableTransmission,orCVTforshort.ItwastheDutchwhoinventedthiskindofvariablespeedtransmissionmechanism,andthetransmissionwithitsdeviceisalsocalledacontinuouslyvariabletransmissionoracontinuouslyvariabletransmission.Thebiggestdifferencebetweenthiskindoftransmissionandordinaryautomatictransmissionisthatiteliminatestheneedforcomplexandheavygearcombinedvariabletransmission,andonlyusestwosetsofpulleysforvariabletransmission.Thedesignconceptisveryingeniousbychangingthecontactradiusofthedrivingwheelandthedrivenwheeltransmissionbelttochangespeed.BecausetheCVTcanachievecontinuouschangesinthetransmissionratio,soastoobtainthebestmatchbetweenthedrivetrainandtheengineoperatingconditions,improvethefueleconomyandpowerofthevehicle,andimprovetheconvenienceofthedriverandtheridecomfortoftheoccupants,soitItisanidealautomobiletransmissiondevice.TheCVTcaralsohasitsowngears,suchasparkinggearP,reversegearR,neutralgearN,forwardgearD,etc.,butthecarforwardsautomaticallyshiftsverysmoothly,withoutthefeelingofsuddenjump.

Classification

Inordertorealizecontinuouslyvariabletransmission,accordingtothetransmissionmode,threemodes:liquidtransmission,electrictransmissionandmechanicaltransmissioncanbeadopted.

Liquidtransmission

Liquidtransmissionisdividedintotwocategories:oneishydraulictype,whichismainlycomposedofpumpsandmotorsorvariablespeedtransmissiondevicescomposedofvalvesandpumps,suitableforsmallandmedium-sizedPowertransmission,hydraulictypeincludestwokindsofhydrostatictypeandhydraulicmechanicaltype.Theothertypeishydraulictype,whichadoptshydrauliccouplingorhydraulictorqueforvariablespeedtransmission,whichissuitableforhighpower(afewhundredtoseveralthousandkilowatts).Themainfeaturesofliquidtransmissionare:largespeedrange,shockabsorptionandoverloadprevention,hightransmissionefficiency,longlife,andeasyautomation:highmanufacturingaccuracyisrequired,thepriceismoreexpensive,theoutputcharacteristicisconstanttorque,andthesliprateisrelativelyhigh.Large,oilleakageislikelytooccurduringoperation.

Electricdrive

Electricdriveisbasicallydividedintothreecategories:oneiselectromagneticslidingtype,whichistoinstallanelectromagneticslipclutchintheasynchronousmotor,bychangingitsexcitationcurrentToadjustthespeed,whichisarelativelybackwardmethodofspeedadjustment.Itscharacteristicsaresimplestructure,lowcost,convenientoperationandmaintenance:maximumsliding,lowefficiency,seriousheatgeneration,notsuitableforlong-termloadoperation,soitisgenerallyonlyusedforlow-powertransmission.ThesecondtypeistheDCmotortype,whichrealizesspeedregulationbychangingthemagneticfluxorchangingthearmaturevoltage.Itischaracterizedbyalargespeedrangeandhighaccuracy,buttheequipmentiscomplicated,costly,anddifficulttomaintain.Itisgenerallyusedinthemediumpowerrange(tenstohundredsofkilowatts),andhasbeengraduallyreplacedbyACmotors.ThethirdtypeisACmotortype,whichadjustsspeedthroughpolechange,voltageregulationandfrequencyconversion.Themostpracticalapplicationisvariablefrequencyspeedregulation,thatis,avariableamplitudeconverterisusedtoobtainthevariableamplitudepowersupply,andthenthemotorisdriventochangespeed.Itischaracterizedbygoodspeedregulationperformance,largerange,highefficiency,automaticcontrol,smallsize,andwideapplicablepowerrange:mechanicalcharacteristicsareconstanttorqueinthespeedreductionsection,lowefficiencyatlowspeeds,andoperationisnotstableenough,thepriceishigh,andmaintenanceProfessionalsarerequired.Inrecentyears,thefrequencyconverterhasdevelopedrapidlyasanadvancedandexcellenttransmissiondevice,whichhashadacertainimpactonthemechanicalcontinuouslyvariabletransmission.

Mechanicaltransmission

Themaincharacteristicsoftraditionalmechanicaltransmissionare:stablespeed,lowsliprate,reliablework,constantpowermechanicalcharacteristicsandpoorimpact,soitisgenerallysuitableformedium,Lowpowertransmission,hightransmissionefficiency,simplestructure,convenientmaintenance,andrelativelycheapprice;butthepartsprocessingandlubricationrequirementsarehigh,theloadcapacityislow,theoverloadresistanceandimpactresistancearepoor,soitisgenerallysuitableformedium,Low-powertransmission.

InthenewCVTmechanism,asectorgearisinstalledontheadjustablegearhubandlocatedontheoutercircumferenceofthesynchronousgearthroughaconnectingshaft.Thegearonthesectorgearmesheswiththegearontheoutercircleofthesynchronousgear.Theoutersideofthegearisfixedwithoneendofthegearrod,thusforminganadjustablegear.Whentheadjustablegearrotatesaroundthebendingdirectionofthegearrodtodrivetheringgear,theservomechanismisusedtoadjustthegearshaftandtheringgearshaft.Inthisway,thenumberofteethoftheinnerringgearactingbetweentwoadjacentracksischanged,thetransmissionratioischanged,andthesteplessspeedchangecanberealized.

ThenewCVThasacompactstructure,smallfootprint,lowcost,hightransmissionefficiency,canrealizeeffectivetransmissionunderhighloads,isveryconvenienttouse,andisconvenientforlarge-scalepopularization.

Theperformanceofthevariable-inclinecontinuouslyvariabletransmissionismoresuperior,andmanytechnicalindicatorsexceedpeople'srequirementsforthecontinuouslyvariabletransmission.

Typeofvehicletype.

Commoncontinuouslyvariabletransmissionsincludehydraulicmechanicalcontinuouslyvariabletransmissionsandmetalbeltcontinuouslyvariabletransmissions(VDT-CVT).AudiA6thatcanbeseeninthedomesticmarketandadoptsthistechnologySomemodels,BYD(G3),Nissan(Sunshine,Teana,Sylphy,Qashqai,Tiida),Palio(Sienna,WeekendWind),HondaCivicand,Fit(newonly),MG3SW,Cowin,GreatWall(Tengyiseriescars),Emgrand(EC7,EC7-RV/Vision)andothermodels,preferlarge-scaleVolvo-producedbuses.

Historicalorigins

Theoriginsofcontinuouslyvariabletransmissionsandautomatictransmissions

Automatictransmissionsarebornforeasyoperationandreducedrivingfatigue.Thegear-shiftingsystemThecontrolmodecanbedividedintohydraulicallycontrolledhydraulicautomatictransmissionandelectronicallycontrolledhydraulicautomatictransmission;accordingtothechangemodeoftransmissionratio,itcanbedividedintosteppedautomatictransmissionandcontinuouslyvariableautomatictransmission.Therefore,thecontinuouslyvariabletransmissionisactuallyakindofautomatictransmission,butitismuchmorecomplicatedthanthecommonautomatictransmission,andthetechnologyismoreadvanced.

Thebiggestdifferencebetweenthecontinuouslyvariabletransmissionandthecommonhydraulicautomatictransmissionisinthestructure.Thelatteriscomposedofahydraulicallycontrolledgeartransmissionsystemwithgears.WhatitcanachieveisbetweentwoContinuouslyvariabletransmissionbetweengears,whilethecontinuouslyvariabletransmissioniscomposedoftwosetsofvariablespeedwheelsandatransmissionbelt,whichissimplerinstructureandsmallerthantraditionalautomatictransmissions.Inaddition,itcanfreelychangethetransmissionratio,soastorealizethefull-rangesteplessspeedchange,sothatthespeedchangeismorestable,withoutthefeelingof"pause"whenthetraditionaltransmissionshifts.

Continuouslyvariabletransmission

AudiMultitroniccontinuouslyvariable/manualintegratedtransmission

Audi’sMultitronictransmissionisbasedontheoriginalcontinuouslyvariabletransmissionAtransmissioncomponentcalledamulti-piecechainbeltisinstalledonthebasis.Thiscomponentgreatlyexpandstheuserangeofthecontinuouslyvariabletransmission.Itcantransmitandcontrolthepeakpoweroutputupto280N·m,anditstransmissionratioexceedsthepreviousLimitvalues​​ofvariousautomatictransmissions.Theobviousadvantagesofthistransmissionarelessenergyconsumptionandfasterresponse.Fromtheperspectiveoftheoverallperformanceofthevehicle,the0-100km/haccelerationtimeoftheAudiA62.8sedanequippedwithMultitronictransmissionis1.3fasterthanthatofordinaryautomatictransmissionmodelsofthesamelevel.s,thefuelconsumptionper100kilometershasbeenreducedby0.9L.

Multitronicalsousesabrand-newelectroniccontrolsystemtoovercometheshortcomingsoftheoriginalcontinuouslyvariabletransmission.Forexample,whengoingupanddown,thesystemcanautomaticallydetecttheslopeandassistthevehicleindrivingbyadjustingthespeedratiotoincreasethepoweroutputorincreasetheengine'sbrakingtorque.

Comparedwithtraditionalautomatictransmissions,Multitronichashigherflexibility.Whenaddingordeletingshiftingmodes,youonlyneedtochangethecomputerprogramtochangethegearratioandradius,soitcanbemoreflexibleDifferenttypesofengineswithdifferentoutputcharacteristicsareusedtogether.

CowinCVT

CowinCVTusestheVT1FcontinuouslyvariabletransmissionproducedbytheGermanZFcompany.Togetherwithitsexcellentengine,thissetofpowerandtransmissionThesystemsallcomefromBMWMINICOOPER.Thecontinuouslyvariabletransmissionhas4drivingmodes:continuouslyvariabletransmission,automaticcruise,sportsmodeand6-speedmanual.Whencombinedwithelectronicthrottle,itisclosertointelligentcontrol.Cowin'sfuelconsumptionperhundredkilometerswithCVTtransmissionisonly0.3Lincreasefromtheoriginal.(Manufacturer'snumber).

PalioSpeedgear

Palio(Siena,weekendwind)Speedgearisahand/self-integratedelectronicallycontrolledcontinuouslyvariabletransmission(ECVT),NanjingFiattooktheleadinapplyingittosmallcars.Itprovidestwoshiftmodes:electronicallycontrolledsteplessautomaticshiftmodeand6-speedsequentialmanualshiftmode.Driverscanchoosedifferentshiftmethodsaccordingtotheirpreferences.Speedgearconsistsofahydraulictorqueconverter,twovariable-diametersteelpulleysandatransmissionmetalbelt(acertainnumberofsteelsheetsandtwo9-layersteelbelts).Ithasawidertransmissionratioandacontinuouslyvariabletransmission.Featuresofsimplestructureandcompactsize.

FitCVT

Fit’sCVTcontinuouslyvariabletransmissionisspeciallydesignedforsmallcars.Itbelongstoanewgenerationofsteelbeltcontinuouslyvariableautomatictransmission,whichallowstwoHightorquetransmissionbetweenthetwopulleys,smoothoperation,hightransmissionefficiency,isbetterinsmallcars.Fit'sCVTtransmissionalsohasSgear(sportsmode),whichnotonlypursuessmoothness,lowfuelconsumption,butalsohasnoshortageofdrivingpleasure.

CVTtechnologyhasonlybeenusedinautomobilesformorethantenyears,butitsadvantagesovertraditionalmanualandautomatictransmissionsareobvious:

1.SimplestructureandvolumeSmall,fewparts,thecostaftermassproductionisdefinitelylowerthanthecostofthecurrentordinaryautomatictransmission;

2.Ithasawideworkingspeedratiorange,whichiseasytoformanidealmatchwiththeengine,therebyimprovingcombustionProcess,therebyreducingfuelconsumptionandemissions;

3.Ithashightransmissionefficiency,lowpowerloss,andhigheconomy.

Ofcourse,CVTtechnologyalsohasitsweaknesses.Forexample,thetransmissionbeltiseasilydamagedandcannotwithstandlargeloads.Thesetechnicaldifficultieshavemadeitmostlyusedinsmall-displacement,low-powercars.superior.

CVTtechnologyhasdevelopedrapidly,andmajorautomakersarestrengtheningresearchanddevelopmentinthisfield.Especiallyinthefuturewhenhybridelectricvehicleshavebroadprospects,thestatusandroleofCVTareirreplaceable,anditwillbethegeneraltrendoffuturetransmissiondevelopment.

Othermodels:jointventurevehiclessuchasVolkswagenTiguan.

Balancedplanetarygearstepless(stage)transmission

Technicalintroduction:ThistechnologyusestwosetsofgearsetstoformaThebalanceendofthecontrolthusrealizesthespeedchange.Thebalanceendislikeabalanceinabalancedstate.Itonlyneedsasmallforcetobreakthebalanceandmakethebalanceendrotate.Bychangingthemagnitudeofthisforce,therotationspeedofthebalanceendcanbecontrolledtoachieveshifting.

Schematicdiagramdescription:1istheinputshaftand13istheoutputshaft.Thebevelsungear7andthesungear14arefixedlyconnectedbyanintermediateshaft.Thetwoendsoftheintermediateshaft15arerespectivelyinsertedinthemiddleoftheinputshaft1andtheoutputshaft13tobeslidablyconnected.Theplanetarygearcarrier19isinslidingconnectionwiththeconnectingshaft18oftheinputshaft1andthebevelgears3and4.Thebevelgears3and4arefixedlyconnectedbyashaft.Thebalanceendbracket9isfixedlyconnectedwiththeconicalgearring5andslidinglyconnectedwiththeplanetarygear11.Thebalancegear6isslidablyconnectedtotheintermediateshaftandfixedlyconnectedtothebalancebracket9.Theoutputshaft13isfixedlyconnectedwiththeringgear10.16isthatthecontrollerisadamperoramotor.

Workingprinciple:Assumingthatthebevelgear5isfixedanddoesnotrotate,whentheinputshaft1drivesthebevelgear2torotateinthepositivedirection,thebevelgears3and4makethebevelThesungear7andthesungear14arereversed.Atthistime,thebevelgear4givesthebevelringgear5apositiveforce.Thereversalofthesungear14causestheplanetarygearcarrier9(balanceendbracket9)toproduceareversalforce.Atthistime,thereversalforceandtheforwardrotationforceontheconegear5areequalinmagnitudeandoppositetoeachothertoformabalance.End,sothebevelgear5andthebalancebracket9donotrotate.Atthistime,aslongastheconegear5andthebalancebracket9rotateundertheactionofexternalforceandchangethespeed,theoutputendwillchangespeed.Theimagepointofviewisthatthebalanceendislikeabalanceinabalancedstate,onlyasmallexternalforcecanbreakthebalance.Bycontrollingthisverysmallforce,thespeedofthebalanceendcanbecontrolledtoachieveshifting.Ifthemotorisusedtocontrolthebalanceendreverserotation,thefunctionoftheclutchcanalsoberealized.

Useasetofdatatoexplain:thebevelgear5ofthedifferentialgearsethas50teeth,andtheotherbevelgearshave10teeth.Theplanetaryreductiongearsetsungear14has10teeth,andtheinternaltoothsungear10has30teeth.Atthistimethebalancedendisformed.Assumingthatthebalanceenddoesnotmove,theinputshaft1rotatesforward6timesperunittime,theconicalsungear7andthesungear14reverse4times,andtheoutputshaftrotatesforward1.33times.Theinput/outputratiois4.5to1,whichactsasareducer.Atthistime,ifthebalanceendreversestheoutputend,itwillslowdown.Whenthebalanceendreversespeedandtheinputendspeedreachacertainratio,theoutputenddoesnotrotate,sothatthefunctionoftheclutchisrealized.Atthistime,ifthebalanceendrotatesforwardandaccelerates,theoutputendacceleratesuntiltheinputend,balanceendandoutputendhavethesamespeedandreacharatioofonetoone.

Controlinstructions:Thedampercontrolispreferredinthisdesign,becausethehigherthedampercontrolspeed,thelowertheloss.Inthedesign,theforcethatmakesthebevelgear5rotateintheforwarddirectionisgreaterthantheforceinthereversedirectionoftheplanetarygearcarrier9tocausethebalanceendtorotateforward.Inthisway,onlythedampercanbeusedtocontrolthebalanceendtoachieveshifting.Theexcessforcewillnotbewasted,itwillbetransferredthroughthebevelgear7andfinallyactontheoutputend.Motorcontrolwillreduceefficiencyduetotheneedforadditionalpower,butitcanbeusedforclutchcontrol.

Efficiencyanalysis:Themostcriticalaspectofthistechnologyisthestabilityofthebalanceendandtheefficiencyofthegear.Thebetterthestability,thesmallerthecontrolforce,thehighertheefficiency.Intermsofstability,thesystemmustusehelicalgears.Thereareotherwaystoimprovestability.Inthegeartransmission,itisassumedthateveryone-stagegearconsumes1%oftheforce,thentheefficiencyofthetransmissionwiththisstructureiscloseto94%whenthevehiclestartsthroughthefive-stagegeartransmission.Whenthevehiclespeedreaches40kilometersperhour,theefficiencyiscloseto97%.Whenreachingspeedsabove80kilometersperhour,theefficiencyiscloseto100%.Atthistime,thespeedattheinputendandtheoutputendarethesame,andthetransmissionislikeadriveshaftwithonlyaslightresistanceconsumptionduetothebearing.

Technicaladvantages:ThistechnologyhasthecommonadvantagesofCVTcontinuouslyvariabletransmissionandgeartransmission.Therefore,thistechnologycanshowitssuperiorityevenmoreintermsofspeedincrease,hightorqueandhighspeed.Thistechnologycanalsorealizethefunctionoftheclutchatthesametime.

Costadvantage:Themaincomponentsofthistechnologyaregears,andthecontrolcomponentsaredampersandmotors.Fewerparts.

Marketadvantage:Thistechnologycannotonlybeappliedtovariousvehicles,butalsotovariousothermachinerythatrequiresdifferentgearratios.Iftheinputendandtheoutputendarereversed,itcanalsobeusedasasteplessspeedincreaserforlargewindturbines,makingiteasiertochangespeed.Theapplicationrangeisverywide.

Technologystatus:Thistechnologyiscurrentlyinthetheoreticalstage,andsampledesignandsoftwaresimulationareinprogress.