mechanicalengineeringAnintroductionto1Lecturer:LiuJu-rongCHAPTER3MachineComponentsandToolsOVERVIEW1ROLLINGELEMENTBEARINGS23FLEXIBLESHAFTCOUPLINGS

2GEARTYPESANDTERMINOLOGY4GEARTYPESANDTERMINOLOGY5MACHZNETOOLS6Vocabulary3buildingblock標(biāo)準(zhǔn)部件off-the-shelf現(xiàn)成的;通用件的Transistor晶體管Bearing忍耐;軸承Shaft軸Gear齒輪Belt帶rollingcontactbearing滾動(dòng)接觸軸承innerracen.內(nèi)座圈outerrace外座圈;外環(huán)Vocabulary4rollingelementn.滾動(dòng)體Journalbearingn.滑動(dòng)軸承polishedsleeve拋光軸套;襯套thinfilm薄膜Crankshaft曲柄軸thrustforce推力boltholes螺栓孔Hardened淬硬precision-ground精加工steelsphere鋼球manufacturingandassemblyprocess制造和裝配工藝machinetool機(jī)床1OVERVIEW----disciplineofmechanicalengineering5First,andfromourprimarystandpointinthistextbook,aworkingknowledgeofthishardwareisimportantforyoutodevelopatechnicalvocabulary.Second,havingsuchabackgroundisnecessarytoselectthepropercomponentforanapplicationandtospecifytheappropriatemachinetoolforaproductionprocess.Finally,thischapterisagoodplaceforyoutobeginthejourneyofunderstandingtheinnerworkingsofmechanicalhardware.Asolidappreciationofmachinecomponentsandtoolsisvaluableatthreelevels.1OVERVIEW----disciplineofmechanicalengineering6FIGURE3.1Thespurandhelicalgeargrinderiscomputercontrolledandusedtomanufacturegearstohighstandardsofquality.Source:ReprintedwithpermissionofNiagaraGearCorporation.1OVERVIEW---Theabilitytobeavailableinthischapter7Afterstudy,whatshouldyoubeabletohave?Describethestructureandcharacteristicsofball,straightroller,taperedroller,andthrustbearings.Understandthepurposeofflexibleshaftcouplings.Describethestructureandcharacteristicsofspur,rack,bevel,helical,andwormgears.Describethedifferencesbetweenv-beltsandtimingbelts.Explainthecircumstancesinwhichonetypeofbearing,gear,ordrivebeltwouldbeselectedforuseinsteadofanother.Describehowdrillpresses,bandsaws,lathes,andmillsareusedinmachineshopsformanufacturing.2ROLLINGELEMENTBEARINGS8journalbearingrollingcontactbearingBallbearingsStraightrollerbearingsTaperedrollerbearingsThrustrollerbearingsbearing2ROLLINGELEMENTBEARINGS9FIGURE3.2Journalbearing2ROLLINGELEMENTBEARINGS10FIGURE3.3Asampleinstallationofabearinginatransmission'shousing.2ROLLINGELEMENTBEARINGS11FIGURE3.4Pillowblockbearingscanbeusedtosupportapowertransmissionshaft.2ROLLINGELEMENTBEARINGS12FIGURE3.5ElementsofastandardballbearingBallOuterraceInnerraceSeparator2ROLLINGELEMENTBEARINGS13FIGURE3.6Structureofastraightrollerbearing.TheinnerracehasbeenremovedinordertoshowtherollersandseparatorRollerOuterraceInnerraceSeparator2ROLLINGELEMENTBEARINGS14FIGURE3.7structureofataperedrollerbearingRollerOuterraceInnerraceSeparator2ROLLINGELEMENTBEARINGS15FIGURE3.8afour-rowtaperedrollerthatiswidelyusedinautomotivefrontwheels,differentials,andmachinetoolspindles.Source:ReprintedwithpermissionofTheTimkenCompany.2ROLLINGELEMENTBEARINGS16FIGURE3.9afour-rowtaperedrollerbearingusedinsheetmetalrollingmillsandotherheavy-dutyapplications.Source:ReprintedwithpermissionofTheTimkenCompany.2ROLLINGELEMENTBEARINGS17RollerhigherthrustplateLowerthrustplateSeparatorFIGURE3.10Structureofathrustrollerbearing.2ROLLINGELEMENTBEARINGS18FIGURE3.11Athrustbearingcomprisedoftaperedrollers,twothrustraces,andaseparator.Source:ReprintedwithpermissionofTheTimkenCompany.3.FLEXIBLESHAFTCOUPLINGS19Toovercomethisproblem,aflexiblecouplingcanbeusedtoconnectthetwoshafts.Thesecouplingseffectivelytransmitrotation,andatthesametimetheyarerelativelycompliantwithrespecttosidewaysbendingWhentheoutputshaftfromonemachineisconnectedtotheinputshaftofanother,youmightinitiallyexpectthattheshaftswouldalwaysberigidlyconnected..Fromapracticalstandpoint,however,itisdifficulttoaligntwoshaftsprecisely,andany(evenslight)angularoroffsetmisalignmentcancausethebearingstobecomeoverloadedanddamaged.203FLEXIBLESHAFTCOUPLINGSFIGURE3.12Theshaftofanelectricmotorisconnectedtoageartrain.Theamountofmisalignmentandbendingareexaggeratedforclarity.(a)Thetwoshaftsareperfectly(butunrealistically)aligned.(b)Whenshaftsaresubjectedtolargeforces.(c)Aflexiblecouplingplacedbetweenthetwoshaftsaccommodatesmisalignmentwhilestilltransmittingrotation.213FLEXIBLESHAFTCOUPLINGSFIGURE3.13Samplesofflexibleshaftcoupling.Source:ReprintedwithpermissionofW.M.Berg,Incorporated.22BevelgearsHelicalgearsSpurgearsRackandpinionGearWormgearsets4GEARTYPESANDTERMINOLOGY4GEARTYPESANDTERMINOLOGY--SpurGears23FIGURE3.14Terminologyforaspurgearsetandgeometryofitsteeth.4GEARTYPESANDTERMINOLOGY--

SpurGears24FIGURE3.15Apairofengaginganddisengagingspurgearteeth.4GEARTYPESANDTERMINOLOGY--

SpurGears25FIGURE3.16Drawingtheinvolutetoothprofileofaspurgearbyunwrappingastringsegmentfromthebasecircle.264GEARTYPESANDTERMINOLOGY---RackandPinionFIGURE3.17Arackandpinionmechanism.4GEARTYPESANDTERMINOLOGY---Bevel27FIGURE3.18Twobevelgearsinmesh..Source:PhotographreprintedwithpermissionofBostonGearCompany.4GEARTYPESANDTERMINOLOGY--HelicalGears28FIGURE3.19Ahelicalgearandintegralshaft.4GEARTYPESANDTERMINOLOGY--WormGearsets29FIGURE3.20Awormgearset.5BELTANDCHAINDRIVES30BELTv-beltstimingbeltsChaindrive5BELTANDCHAINDRIVES31FIGURE3.21v-beltsandv-beltwheel.5BELTANDCHAINDRIVES32FIGURE3.21timingbelts

andtimingbeltwheel.5BELTANDCHAINDRIVES33FIGURE3.21Chainandchaindrive.6MACHINETOOLS34Theassemblylinewillbesetupsothatonlyasmallnumberofoperationsneedtobeperformedinanyoneworkareabeforetheenginemovesontothenextstage.Thefabricationtechniquesthatanengineerselectsforacertainproductwilldepend,inpart,onthetimeandexpenseofsettingupthetooling.Massproductionmightbewhatyoufirstimaginetotakeplaceinalargefactory,andthemanufactureofautomobileenginesisaprimeexample.6MACHINETOOLS35BandsawDrillpressLatheMillLeadscrewCNCmillMachinetools6MACHINETOOLS36FIGURE3.38Majorelementsofadrillpress.6MACHINETOOLS37FIGURE3.40Majorelementsofabandsaw.6MACHINETOOLS38FIGURE3.41Majorelementsofamachinist’slathe.6MACHINETOOLS39FIGURE3.42Majorelementsofamillingmachine.6MACHINETOOLS40FIGURE3.43Aleadscrewconvertsamotor’srotationintothestraight-linemotionofthetableandworkpieceinamill.6MACHINETOOLS41FIGURE3.45Acomputer-controlledmillcanproducehardwaredirectlyfromthemachininginstructionscreatedbycertaincomputer-aidedengineeringsoftwarepackages.SUMMARY42Inthischapter,wehavedescribedasamplerofthemachinecomponentsandtoolsthatariseinmechanicalengineering.Althoughnotexhaustive,thesesummariesofbearings,gears,andpowertransmissioncomponentsontheonehand--andofshoptoolsontheother--shouldhelpyouunderstandandbetterdescribetootherstheanatomyandfunctionofcommonmachines.Bearings,gears,shafts,andthelikeeachhavespecialpropertiesandterminology,andmechanicalengineersneedtobefluentwithsuchbuildingblocksinordertoselectthecomponentthatisbestsuitedtoaparticularapplication.wewillapplyphysicallawsandthetoolsofengineeringscience(namely,thenumbersandequationssideofengineering)toanalyzeengineeringproblemsthatarebasedinpartonsomeofthecomponentsandtoolsdescribedinthischapter.SELF-STUDYANDREVIEW43Whatshouldyourev