齿轮机构 毕业论文外文翻译

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

2、C.wroteofgearsasiftheywerecommonplace.InthefifteenthcenturyA.D.,LeonardodaVincidesignedamultitudeofdevicesincorporatingmanykindsofgears.Incomparisonwithbeltandchaindrives,geardrivesaremorecompact,canoperateathighspeeds,andcanbeusedwhereprecisetimingisdesired.Thetransmissionefficiencyofgearsi

3、sashighas98percent.Ontheotherhand,gearsareusuallymorecostlyandrequiremoreattentiontolubrication,cleanliness,shaftalignment,etc.,andusuallyoperateinaclosedcasewithprovisionforproperlubrication.Gearmechanismscanbedividedintoplanargearmechanismsandspatialgearmechanisms.Planargearmechanismsareus

4、edtotransmitmotionandspatialgearmechanisms.Planargearmechanismsareusedtotransmitmotionandpowerbetweenparallelshafts,andspatialgearmechanismsbetweennonparallelshafts.Typesofgears(1)Spurgears.ThespurgearhasacylindricalpitchsurfaceandhasstraightteethparalleltoitsaxisasshowninFig.2.8.Theyareused

5、totransmitmotionandpowerbetweenparallelshafts.Thetoothsurfacesofspurgearscontactonastraightlineparalleltotheaxesofgears.Thisimpliesthattoothprofilesgointoandoutofcontactalongthewholefacewidthatthesametime.Thiswillthereforeresultinthesuddenloadingandsuddenunloadingonteethasprofilesgointoandou

6、tofcontact.Asaresult,vibrationandnoiseareproduced.(2)Helicalgears.Thesegearshavetheirtoothelementsatanangleorhelixtotheaxisofthegear(Fig.2.9).Thetoothsurfacesoftwoengaginghelicalgearsinnplanargearmechanismscontactonastraightlineinclinedtotheaxesofthegears.Thelengthofthecontactlinechangesgrad

7、uallyfromzerotomaximumandthenfrommaximumtozero.Theloadingandunloadingoftheteethbecomegradualandsmooth.Helicalgearsmaybeusedtotransmitmotionandpowerbetweenparallelshafts[Fig.2.9(a)]orshaftsatanangletoeachother[Fig.2.9(d)].Aherringbonegear[Fig.2.9(c)