非常好的关于减速机及齿轮啮合的资料

,HowstuffworksInthiscaseGearUnits,AllinformationaretakenfromtheInternetpage,TECHNICALINFORMATION:GEARS,HOWDIFFERENTGEARSWORK,SPURGEARisusedwhenshafts(white)mustrotateinthesameplane.Theteetharestraightandparalleltotheshaft.Thepinion(yellow)isthesmallerofagearpair.,ThedifferentkindofGears,INTERNALGEARallowsthepinion(yellow)torotateontheinsideofaringtypegearwithstraightteethonitsinnersurface.Thisisatypeofspurgearinwhichboththepinionandthegearturninthesamedirection,unlikeordinaryspurgears.,ThedifferentkindofGears,HELICALGEARhascurvedteethatanangletotheshaft.Theseteethgripwithlessnoisethanstraightteeth,especiallywhentheyareturningathighspeeds.,ThedifferentkindofGears,HERRINGBONEGEARhasteeththatareV-shaped,likeadoublehelicalgear.Theshaftsrotateinoppositedirectionsasinanordinaryspurgear.,ThedifferentkindofGears,BEVELGEARhasteeththatslopealongonesurfaceofthedisc.Thepinion(yellow)rollsatanangletothetopofthegear,notalongitsedge.Thistypeofgearisusedwhentheshaftstobeturnedmeetatanangle.,ThedifferentkindofGears,WORMGEARhasascrewpinion(theworm)whichturnsalongaspurgear.Motioncanbetransmittedbetweenshaftsthatareatrightangles.,ThedifferentkindofGears,PLANETARYGEARisasystemwherebyPLANETspurgearsturnonacentralSUNgearandaninternalringgear.Thissystemisusedinautomaticcars.,ThedifferentkindofGears,Youseegearsinjustabouteverythingthathasspinningparts.Carenginesandtransmissionscontainlotsofgears.IfyoueveropenupaVCRandlookinside,youwillseeitisfullofgears.Wind-up,grandfatherandpendulumclockscontainplentyofgears,especiallyiftheyhavebellsorchimes.,Youprobablyhaveapowermeteronthesideofyourhouse,andifithasasee-throughcoveryoucanseethatitcontains10or15gears.Gearsareeverywherewherethereareenginesandmotorsproducingrotationalmotion.,PuttingGearstoWorkGearsaregenerallyusedforoneoffourdifferentreasons:ToreversethedirectionofrotationToincreaseordecreasethespeedofrotationTomoverotationalmotiontoadifferentaxisTokeeptherotationoftwoaxessynchronized,Youcanseeeffects1,2and3inthefigureabove.Inthisfigure,youcanseethatthetwogearsarerotatinginoppositedirections,thatthesmallergearisspinningtwiceasfastasthelargergear,andthattheaxisofrotationofthesmallergearistotherightoftheaxisofrotationofthelargergear.,Thefactthatonegearisspinningtwiceasfastastheotherisbecauseoftheratiobetweenthegears-thegearratio.Inthisfigure,thediameterofthegearontheleftistwicethatofthegearontheright.Thegearratioistherefore2:1(pronouncedtwotoone).Ifyouwatchthefigure,youcanseetheratio:Everytimethelargergeargoesaroundonce,thesmallergeargoesaroundtwice.Ifbothgearshadthesamediameter,theywouldrotateatthesamespeedbutinoppositedirections.,UnderstandingtheConceptofGearRatioUnderstandingtheconceptofthegearratioiseasyifyouunderstandtheconceptofthecircumferenceofacircle.KeepinmindthatthecircumferenceofacircleisequaltothediameterofthecirclemultipliedbyPi(Piisequalto3.14159.).Therefore,ifyouhaveacircleoragearwithadiameterof1inch,thecircumferenceofthatcircleis3.14159inches.,Thefollowingfigureshowshowthecircumferenceofacirclewithadiameterof1.27inchesisequaltoalineardistanceof4inches:,Letssaythatyouhaveanothercirclewhosediameteris0.635inches(1.27inches/2),andyourollitinthesamewayasinthisfigure.Youllfindthat,becauseitsdiameterishalfofthecirclesinthefigure,ithastocompletetwofullrotationstocoverthesame4-inchline.Thisexplainswhytwogears,onehalfasbigastheother,haveagearratioof2:1.Thesmallergearhastospintwicetocoverthesamedistancecoveredwhenthelargergearspinsonce.,Mostgearsthatyouseeinreallifehaveteeth.Theteethhavethreeadvantages:Theypreventslippagebetweenthegears.Therefore,axlesconnectedbygearsarealwayssynchronizedexactlywithoneanother.Theymakeitpossibletodetermineexactgearratios.Youjustcountthenumberofteethinthetwogearsanddivide.Soifonegearhas60teethandanotherhas20,thegearratiowhenthesetwogearsareconnectedtogetheris3:1.Theymakeitsothatslightimperfectionsintheactualdiameterandcircumferenceoftwogearsdontmatter.Thegearratioiscontrolledbythenumberofteethevenifthediametersareabitoff.,DetailsonInvoluteGearProfilesOnaninvoluteprofilegeartooth,thecontactpointstartsclosertoonegear,andasthegearspins,thecontactpointmovesawayfromthatgearandtowardtheother.Ifyouweretofollowthecontactpoint,itwoulddescribeastraightlinethatstartsnearonegearandendsupneartheother.Thismeansthattheradiusofthecontactpointgetslargerastheteethengage.,Thepointofcontactdescribesastraightlinethatstartsnearonegearandendsupneartheotherfrombasecircletobasecircle,341,278,303,408,446,316,473,325,535,323,534,366,596,349,DetailsofanInvoluteGearProfile1.)Onaninvoluteprofilegeartooth,thecontactpointstartsclosertoonegear,andasthegearspins,thecontactpointmovesawayfromthatgearandtowardtheother.Ifyouweretofollowthecontactpoint,itwoulddescribeastraightlinethatstartsnearonegearandendsupneartheother.Thismeansthattheradiusofthecontactpointgetslargerastheteethengage.,341,278,303,408,446,316,473,325,535,323,534,366,596,349,2.)Thebaselinediameteristheeffectivecontactdiameter.Sincethecontactdiameterisnotconstant,thepitchdiameterisreallytheaveragecontactdistance.Astheteethfirststarttoengage,thetopgeartoothcontactsthebottomgeartoothinsidethepitchdiameter.Butnoticethatthepartofthetopgeartooththatcontactsthebottomgeartoothisveryskinnyatthispoint.,341,278,303,408,446,316,473,325,535,323,534,366,596,349,3.)Asthegearsturn,thecontactpointslidesupontothethickerpartofthetopgeartooth.Thispushesthetopgearahead,soitcompensatesfortheslightlysmallercontactdiameter.Astheteethcontinuetorotate,thecontactpointmovesevenfurtheraway,goingoutsidethepitchdiameter-buttheprofileofthebottomtoothcompensatesforthismovement.,GearTrainsTocreatelargegearratios,gearsareoftenconnectedtogetheringeartrains,asshownhere.,Theright-hand(purple)gearinthetrainisactuallymadeintwoparts,asshownabove.Asmallgearandalargergearareconnectedtogether,oneontopoftheother.Geartrainsoftenconsistofmultiplegearsinthetrain,asshownonthenexttwopages.,Inthecaseabove,thepurplegearturnsataratetwicethatofthebluegear.Thegreengearturnsattwicetherateofthepurplegear.Theredgearturnsattwicetherateasthegreengear.Thegeartrainshownbelowhasahighergearratio:,Inthistrain,thesmallergearsareone-fifththesizeofthelargergears.Thatmeansthatifyouconnectthepurplegeartoamotorspinningat100revolutionsperminute(rpm),thegreengearwillturnatarateof500rpmandtheredgearwillturnatarateof2,500rpm.Inthesameway,youcouldattacha2,500-rpmmotortotheredgeartoget100rpmonthepurplegear.Ifyoucanseeinsideyourpowermeteranditsoftheolderstylewithfivemechanicaldials,youwillseethatthefivedialsareconnectedtooneanotherthroughageartrainlikethis,withthegearshavingaratioof10:1.Becausethedialsaredirectlyconnectedtooneanother,theyspininoppositedirections(youwillseethatthenumbersarereversedondialsnexttooneanother).,PlanetaryGearsTherearemanyotherwaystousegears.Onespecializedgeartrainiscalledaplanetarygeartrain.Planetarygearssolvethefollowingproblem.Letssayyouwantagearratioof6:1withtheinputturninginthesamedirectionastheoutput.Onewaytocreatethatratioiswiththefollowingthree-geartrain:,PlanetaryGearsetstheSIunitistheNewton-meter.Noticethatthetorqueunitscontainadistanceandaforce.Tocalculatethetorque,youjustmultiplytheforcebythedistancefromthecenter.Inthecaseofthelugnuts,ifthewrenchisafootlong,andyouput200poundsofforceonit,youaregenerating200pound-feetoftorque.Ifyouusea2-footwrench,youonlyneedtoput100poun