外文翻译--齿轮和齿轮传动

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1、设计巴巴工作室www.88doc88.comGearsandgeardriveGearsarethemostdurableandruggedofallmechanicaldrives.Theycantransmithighpoweratefficienciesupto98%andwithlongservicelives.Forthisreason,gearsratherthanbeltsorchainsarefoundinautomotivetransmissionsandmostheavy-dutymachinedrives.Ontheotherhand,gear

2、saremoreexpensivethanotherdrives,especiallyiftheyaremachinedandnotmadefrompowermetalorplastic.Gearcostincreasessharplywithdemandsforhighprecisionandaccuracy.Soitisimportanttoestablishtolerancerequirementsappropriatefortheapplication.Gearsthattransmitheavyloadsorthanoperateathighspeedsa

3、renotparticularlyexpensive,butgearsthatmustdobotharecostly.Silentgearsalsoareexpensive.Instrumentandcomputergearstendtobecostlybecausespeedordisplacementratiosmustbeexact.Attheotherextreme,gearsoperatingatlowspeedinexposedlocationsarenormallytermednocriticalandaremadetominimumqualityst

4、andards.Fortoothforms,size,andquality,industrialpracticeistofollowstandardssetupbytheAmericanGearManufacturesAssociation(AGMA).ToothformStandardspublishedbyAGMAestablishgearproportionsandtoothprofiles.Toothgeometryisdeterminedprimarilybypitch,depth,andpressureangle.Pitch：Standardspitch

5、esareusuallywholenumberswhenmeasuredasdiametralpitchP.Coarse-pitchgearinghasteethlargerthan20diametralpitch–usually0.5to19.99.Fine-pitchgearingusuallyhasteethofdiametralpitch20to200.Depth:Standardizedintermsofpitch.Standardfull-depthhaveworkingdepthof2/p.Iftheteethhaveequaladdenda(asin

6、standardinterchangeablegears)theaddendumis1/p.Stubteethhaveaworkingdepthusually20%lessthanfull-depthteeth.Full-depthteethhavealargercontractratiothanstubteeth.Gearswithsmallnumbersofteethmayhaveundercutsothantheydonotinterferewithoneanotherduringengagement.Undercuttingreduceactiveprofi

7、leandweakensthetooth.Matinggearswithlongandshortaddendumhavelargerload-carryingcapacitythanstandardgears.Theaddendumofthesmallergear(pinion)isincreasedwhilethatoflargergearisdecreased,leavingthewholedepththesame.Thisformisknowasrecess-actiongearing.PressureAngle:Standardanglesareand.