The-Dynamic-Simulation-and-Analysis-of-a-Cycloidal

Proceedingsofthe11thASMEInternationalPowerTransmissionandGearingConferenceDETC2011August28-31,2011,Washington,DC,USAPaperNumber:DETC2011-48494THEDYNAMICSIMULATIONANDANALYSISOFACYCLOIDALSPEEDREDUCERSandeepV.ThubeSumitomoDriveTechnologiesEngineeringDepartment4200HollandBlvd.Chesapeake,Virginia23323UnitedStatesP:757-485-3355F:757-485-5784e-mail:[e-mail]logiesEngineeringDepartment4200HollandBlvd.Chesapeake,Virginia23323UnitedStatesP:757-485-3355F:757-485-5784e-mail:[e-mail],digitalprototypinghasbecomeavaluabletoolforthedesignandsubsequentanalysisofcomponentsforaproposeddesign.Priortoitsmaturationasadesigntool,itwascommontogothroughrepeatedphysicaliterationsofagivendesigntoassessform,fitandfunction.Investmentsindesigntime,prototypeprocurementandsubsequenttestingyieldedlongtermproductincubationperiodsfrominitialconcepttofinalproduction.Currentdesignmodelingsoftwareallowsforpartdesign,unitassembly,loadinganddynamicsimulationofacomponentelectronically–allwithouttheprocurementofaphysicalprototype.Theresultsfromsuchdynamicsimulationcanthenbeanalyzedthroughfiniteelementanalysistoassesscomponentfunctionalityinitsintendedoperationalenvironmentwithaneyetowardsdesignoptimization.Fromtheperspectiveofgeardesign,digitalprototypingcertainlyaffordsthesameadvantagesashasbeendescribed.Indeed,itiscommontofindelectronicexamplesof3Dgearsetwithmotionandloadingconditionimposedonthem.Itislesscommon,however,tofindsimilardynamicexamplesoftheoperationofacycloidaltypespeedreducerwherethekinematicsofthereductionmechanismiscompletelydifferentfromthatofthetraditionalinvolutegearing.Thispaperwillexploreamethodofdynamicallysimulatingacycloidaltypespeedreducerwherethegeneratedinternalloadswillbeusedtoassessthestressesactingontheoneofthemajorreductioncomponentscontainedwithin–namely,thecycloiddisc.INTRODUCTIONAsthenameimplies,aspeedreducerisamechanicaldevicewhosefunctionistodecreasethespeedofaprimemover(i.e.:electricmotor)whileincreasingthetorqueproducedbythesameprimemover.Thisincreaseintorqueisdirectlyproportionaltothedecreaseinspeedachievedthroughthespeedreducer.Sincetheinventionofrotatingmachines,themostcommon(andnearexclusive)methodofachievingthisreductionofrotationalspeedhasbeenthroughtheinteractionofgearsinmeshwithoneanother.Typically,theprofileofageartoothfollowsaninvoluteform(seeFigure1)and,overthecourseofyears,techniqueshavebeenoptimizedtoconsistentlyreproducethisinvoluteformduringthemanufacturingprocess.FIGURE1:INVOLUTETOOTHFORMDespitethisoptimization,pitfallsremaininsuchtraditionalgearing.Asanexample,wheninmesh,onlyafewoftheteethofonegearareactuallyengagedwiththoseofthematinggearatanygiventime.Becauseofthis,overloads(evenifmomentaryinnature)maybreakoneormoreoftheteethonthesegears.Additionally,inordertoachievehigherreductionratios,multiplegearsmayneedtobeincorporatedintoasinglereducertherebymakingitphysicallylargeincomparisontotheamountoftorquethatitisabletodeliver.EntertheCycloidaltypeofspeedreducer.Thecycloidalreducerisacompletelyuniquetypeofmechanismthatachievesthereductionofspeed/increaseoftoquewithouttheuseofinvolutegearing.Aswillbediscussedinthefollowingpaper,theuniqueoperatingprincipalanddesignofthecycloidalreducereffectivelyeliminatesseveralofthepitfallsfoundincounterpartsthatincorporatetheinvolutegearing.Inthispaper,theseuniquefeatureswillbeverifiedbysimulatingpartmovementsthroughdynamicanalysisandobserving/analyzingforcesinthefiniteelementanalysisenvironmentusingdedicated3Dmodelingsoftware.FEATURESANDBENEFITSSincetheirinceptioninthe1930’s,cycloidaltypespeedreducershavebeensuccessfullyincorporatedintoamultitudeofpowertransmissionapplications.Giventherobustnatureoftheproduct,itisnotuncommontofindexamplesthathavesuccessfullybeeninoperationforperiodsofupto25years!Tounderstandhowtomodelthemechanismdigitally,onefirstneedstounderstandthebasiccomponentsofacycloidalgearboxandhowtheyinteractwitheachother.InreferencingFigure2itcanbeseenthatthespeedreductionisachievedthroughtheinteractionofonlythreeseparatemovingparts(thehighspeedshaftassembly,thecycloiddiscsandtheslowspeedshaftassembly):FIGURE2:COMPONENTSOFACYCLOIDALSPEEDREDUCERTheeccentriccamispressedontothehigh-speedshafttocompletethesub-assemblyand,asitrotates,itrollstheCycloidDiscsaroundtheinnercircumferenceoftheRingGearHousing.Withthisrotationofthecycloiddiscs,thereoccurstwopointsofcontactwithotherreductioncomponentsoftheassembly.First,thereisaslidingmotionoftheexternalsurfaceofthedisc(s)againsttherollersofthe(fixed)RingGearHousingandsecond,thereisarotationalmotionofthedisc(s)interactingwiththeRollersoftheSlowSpeedShaft.TheCycloidalDiscsthemselvesrotateinadirectionoppositethatoftheHighSpeedshaftand,whiledoingso,thelobesonouteredgeofthediscsprogressivelyengagewithInvoluteFormBaseCircleEccentricCamAssemblySlowSpeedShaftAssemblyRingGearHousing(fixed)HighSpeedShaftAssemblyCycloidDiscstherollersattachedtotheinnerperimeteroftheRingGearHousing.Thisinteractionproducesareversedrotationatareducedspeed.Foreachcompleterevoluti