齿轮机构中英文翻译、外文文献翻译.doc

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1、翻译部分英文原文GearmechanismsGearmechanismsareusedfortransmittingmotionandpowerfromoneshafttoanotherbymeansofthepositivecontactofsuccessivelyengagingteeth.Inabout2,600B.C.,ChineseareknowntohaveusedachariotincorporatingacomplexseriesofgearslikethoseillustratedinFig.2.7.Ari

2、stotle,inthefourthcenturyB.C.wroteofgearsasiftheywerecommonplace.InthefifteenthcenturyA.D.,LeonardodaVincidesignedamultitudeofdevicesincorporatingmanykindsofgears.Incomparisonwithbeltandchaindrives,geardrivesaremorecompact,canoperateathighspeeds,andcanbeusedwherepr

3、ecisetimingisdesired.Thetransmissionefficiencyofgearsisashighas98percent.Ontheotherhand,gearsareusuallymorecostlyandrequiremoreattentiontolubrication,cleanliness,shaftalignment,etc.,andusuallyoperateinaclosedcasewithprovisionforproperlubrication.Gearmechanismscanbe

4、dividedintoplanargearmechanismsandspatialgearmechanisms.Planargearmechanismsareusedtotransmitmotionandspatialgearmechanisms.Planargearmechanismsareusedtotransmitmotionandpowerbetweenparallelshafts,andspatialgearmechanismsbetweennonparallelshafts.Typesofgears(1)Spur

5、gears.ThespurgearhasacylindricalpitchsurfaceandhasstraightteethparalleltoitsaxisasshowninFig.2.8.Theyareusedtotransmitmotionandpowerbetweenparallelshafts.Thetoothsurfacesofspurgearscontactonastraightlineparalleltotheaxesofgears.Thisimpliesthattoothprofilesgointoand

6、outofcontactalongthewholefacewidthatthesametime.Thiswillthereforeresultinthesuddenloadingandsuddenunloadingonteethasprofilesgointoandoutofcontact.Asaresult,vibrationandnoiseareproduced.(2)Helicalgears.Thesegearshavetheirtoothelementsatanangleorhelixtotheaxisofthege

7、ar(Fig.2.9).Thetoothsurfacesoftwoengaginghelicalgearsinnplanargearmechanismscontactonastraightlineinclinedtotheaxesofthegears.Thelengthofthecontactlinechangesgraduallyfromzerotomaximumandthenfrommaximumtozero.Theloadingandunloadingoftheteethbecomegradualandsmooth.H

8、elicalgearsmaybeusedtotransmitmotionandpowerbetweenparallelshafts[Fig.2.9(a)]orshaftsatanangletoeachother[Fig.2.9(d)].Aherringbonegear[Fig.2.9(c)