机械英语ppt讲解

1、 滁州学院滁州学院12级机械本一班级机械本一班 主讲：胡恩生主讲：胡恩生 编辑：金冉编辑：金冉 贾富文贾富文 资料搜集：胡恩生资料搜集：胡恩生 蒋杉杉蒋杉杉 1432514325 Gears 我的翻译：齿轮是一个旋转的机械零件，有削减的齿，它与我的翻译：齿轮是一个旋转的机械零件，有削减的齿，它与 另一个齿的一部分，以便传输扭矩。两个或多个齿轮同步另一个齿的一部分，以便传输扭矩。两个或多个齿轮同步 工作被称为传动系统，并且能够产生通过机械传动比的优工作被称为传动系统，并且能够产生通过机械传动比的优 势，因此可以被认为是简单的机械。减速装置可以改变的势，因此可以被认为是简单的机械。减速装置可以改变

2、的 速度，规模，以及一个电源方向。最常见的情况是谦卑地速度，规模，以及一个电源方向。最常见的情况是谦卑地 与另一个齿轮，齿轮，齿轮也不过一目了非旋转式齿形的与另一个齿轮，齿轮，齿轮也不过一目了非旋转式齿形的 一部分，称为机架，从而产生传动，而不是旋转。一部分，称为机架，从而产生传动，而不是旋转。 Gearsaredirect-contactbodies, operatinginpairs,thattransmitmotion andforcefromonerotatingshaftto another,orfromashafttoaslide（滑动（滑动 部件）部件）(rack), bymea

3、nsofsuccessivelyengaging Projections（突出物）（突出物）calledteeth. Therearefourmaintypesofgears：spur， helical，worm，andbevel。 spurandhelicalgears 直齿轮和斜齿轮直齿轮和斜齿轮 Agearhavingtoothelementsthatares traightandparalleltoitsaxisisknown sasaspurgear.Aspurpaircanbeus edtoconnectparallelshaftsonly.Para llelshafts,howe

4、ver,canalsobeconne ctedbygearsofanothertype,andasp urgearcanbematedwithagearofadif ferenttype. Topreventjammingasaresultofthermalex pansion,toaidlubricationandtocompensat eforunavoidableinaccuraciesinmanufactur e,allpowertransmittinggearsmusthavebac klash.thismeansthatonpitchcirclesofama tingpair,th

5、espacewidthonthepinionmust beslinghtlygreatherthanthetooththicknes sonthegear,andviceversa（反之亦然）。（反之亦然）。 Oninstrumentgears,backlashcanbeelimina thedbyusingagearsplitdownthemiddle,o nehalfbeingratabletotheother.A,springfo rcesthesplitgearteethtooccupythefullwi dthofthepinionspace. Helicalgearshavecer

6、tainadvantages,forexample, whenconnectingparallelshafts,theyhaveahigherl oad-carryingcapacitythanspurgearswiththesame toothnumbersandcutwiththesamecutter. Becauseoftheoverlappingactionoftheteeth,they aresmootherinactionandandcanoperateathigher pitchlinevelocitiesthanspurgears. Thepitchlinevelocityis

7、thevelocityinthepitch circle.Sincetheteethareinclinedtothexisofrotatio n,helicalgearscreateanaxialthust. Ifusedsinglarly,thisthrustmustbeabsorbedinthe shaftbearings.Thethrustproblemcanbeovercome bycuttingtwosetsofopposinghelicalteethonthes ameblank.（注释：（注释：PitchCircleisthereferencecirclefrom whichal

8、ltransversesplinetoothdimensionsareconstructed. 节圆是一个参考圆节圆是一个参考圆,花键的键齿的所有的横向尺寸都是以节圆为基础开始计算的花键的键齿的所有的横向尺寸都是以节圆为基础开始计算的.） Dependingonthemethodofmanufacture,thegear manybeofthecontinuous- toothherringbonevarintyoradouble- helicalgearwithaspacebetweenthetwohalvestop emitthecuttingtooltorunout. Doublehel

9、icalgearsarewellsuitedfortheefficient transmissionofpowerathighspeeds.Helicalgears canalsobeusedtoconnectnonparallel,non- intersectingshaftsatanyangletooneanother. Ninetydegreesisthemostcommonangle,atwhich suchgearsareused. When the shafts are parallel, the contact between the teeth on mating gears

10、is “line contact” regardless of whether the teeth ar straight or helical. When the shafts are inclined, the contact become “point contact.” For this reason, crossed-axis helical gears do not have as much load- carrying capacity as parallel-shaft helicals. They are frequently employed in instruments

11、and positioning mechanisms where friction is the only force opposing their motion. WormandBevelGears 蜗轮和锥齿轮传动蜗轮和锥齿轮传动 Inordertoachievelinecontactandimprovetheload carryingcapacityofthecrossed-axishelicalgears,the gearcanbemadetocurvepartiallyaroundthepinion,in somewhatthesamewaythatanutenvelopsascre

12、w. Theresultwouldbeacylindricalwormandgear.Worms arealsomadeintheshapeofanhourglass,insteadof cylindrical,sothattheypartiallyenvelopthegear.This resultsinafurtherincreaseinload-carryingcapacity. Wormgearsprovidethesimplestmeansofobtaininglarg eratiosinasinglepair.Theyareusuallylessefficientthan para

13、llel-shaft gears,however, becauseofanadditional sliding movementalongtheteeth. Becauseoftheirsimilarity,theefficiencyofawormandge ardependsonthesamefactorsastheefficiencyofascrew. Single- threadwormsoflargediameterhavesmalllead angles and lowefficiencies.Multiple-thread wormshave largerleadanglesand

14、higherefficiencies. Forleadangles ofabout15degreesanda coefficientoffrictionlessthan 0.15, theefficiencyrangesfromabout55percentto95 percent, andthegearcandrivetheworm.Such units make compactspeedincreases;theyhavebeenusedfor driving superchargersonaircraftengines. Inself-locking worms,thegearcannot

15、drivetheworm,andtheefficiency islessthan50percent. Fortransmittingrotarymotionandtorquearoundcorners,be velgearsarecommonlyused.Theconnectedshafts,whose axeswouldintersectifextended,areusuallybutnotnecessa rilyatrightanglestooneanother.Thepitchsurfacesofgears arerolling,truncatedcones,andtheteeth,wh

16、ichmustbe taperedinbothandheight,areeitherstraightorcurved. Althoughcurved-toothbevelgearsarecalledspiralbevel gears,thecurveoftheteethisusuallyacirculararc.The curvatureoftheteethresultsinoverlappingtoothactionand asmoothertransmissionofpowerthanwithstraightteeth. Forhighspeedsandtorques,spiralbeve

17、lgearsaresuperior tostraightbevelgearsinmuchthesamewaythathelical gearsaresuperiortospurgearsforconnectingparallel shafts. Whenadaptedforshaftsthatdonotintersect,spiralbevel gearsarecalledhypoidgears.Thepitchsurfacesofthese gearsarenotrollingcones,andtheratiooftheirmean diametersisnotequaltothespeed

18、ratio.Consequently, thepinionmayhavefewteethandbemadeaslargeas necessarytocarrytheload.Thispermitshigherspeed justascrossed-axisratioshelicalsandwormgearscan providehigherthanparallelhelicals.Theabsenceofthe proportionalrolling-pitchsurfacerequirementisabenefit. Theprofilesoftheteethonbevelgearsaren

19、otinvolutes;theyareof suchashapethatthetoolsforcuttingtheteethareeasiertomake andmaintain（保养）（保养）thaninvolutescuttingtools.Sincebevelgears comeinpairs,aslongastheyareconjugatetooneanotherthey neednotbeconjugatetoothergearswithdifferenttoothmembers. WordsandExpressions Helicalgear Spurgear Backlash P

20、inion Herringbone Coefficientoffriction Truncatedcone Spiral Hypoidgear conjugate 斜齿轮，螺旋齿轮斜齿轮，螺旋齿轮 正齿轮正齿轮 齿间隙齿间隙 小齿轮小齿轮 人字形，交叉缝式人字形，交叉缝式 摩擦系数摩擦系数 截头圆锥体截头圆锥体 螺旋形的：螺线螺旋形的：螺线 偏轴伞齿轮偏轴伞齿轮 成对的，共轭的成对的，共轭的 Summary 总结 Intheforceanalysisofspurgears,theforcesareassumedtoactin asingleplane.Inthislessonweshallst

21、udygearsinwhichtheforce shavethreedimensions.在直齿圆柱齿轮的受力分析中，假定各力 作用在单一平面的在这一课中，我们将研究承受三维作用力的齿 轮 Thereasonforthis,inthecaseofhelicalgears,isthattheteethare notparalleltotheaxisofrotation.就斜齿轮而言，是因为其轮齿是与 其回转轴线不平行而产生的。 Andinthecaseofbevelgears,therotationalaxesarenotparallelt oeachother.而就锥齿轮而言，是因为各回转轴线

22、互相不干行。 Therearealsootherreasons,asweshalllearn.当然像我们将。要 讨论的那样，还有其他的原因 Helicalgearsareusedtotransmitmotionbetweenparallelshafts. 斜齿轮用于传递平行轴之间的运动。 Thehelixangleisthesameoneachgear,butonegearmusthave aright-handhelixandtheotheraleft-handhelix.两个齿轮的螺旋角 相等，但一个齿轮必须右旋，而另一个齿轮必须是左旋。 Theshapeofthetoothisaninv

23、olutehelicoid.轮齿的形状是一渐开 线螺旋面。 Ifapieceofpapercutintheshapeofaparallelogramiswrappedar oundacylinder,theangularedgeofthepaperbecomesahelix.如 果一张被剪成平行四边形(矩形)的纸张包围在圆柱体上，这张纸的斜 边就是一螺旋线。 Ifweunwindthispaper,eachpointontheangularedgegeneratesa ninvolutecurve.如果我们展开这张纸，在斜边上的每一个点就发生 一条渐开线曲线。 Thesurfaceobtain

24、edwheneverypointontheedgegeneratesanin voluteiscalledaninvolutehelicoid.由斜边上每一点产生的渐开线组 成面叫做渐开线螺旋面。 Theinitialcontactofspur- gearteethisalineextendingallthewayacrossthefaceofthetoot h.直齿圆柱齿轮轮齿的初始接触处是贯穿整个齿面的一条直线。 Theinitialcontactofhelicalgearteethisapoint,whichchangesint oalineastheteethcomeintomoree

25、ngagement.斜齿轮轮齿的初始 接触是一点，当轮齿进一步啮合时，它就变成线。 Inspurgearsthelineofcontactisparalleltotheaxisoftherotatio n;inhelicalgears,thelineisdiagonalacrossthefaceofthetooth. 在直齿圆柱齿轮中，接触线是平行于回转轴线的。在斜齿轮中，该线 是穿过齿面的对角线 Itisthisgradualengagementoftheteethandthesmoothtransfero floadformonetoothtoanother,whichgivehelica

26、lgearstheabilityt otransmitheavyloadsathighspeeds.正是轮齿逐渐进行啮合并平稳 地从一个齿到另一个齿传递运动，那样就使斜齿轮具有高速重载下平 稳传递运动的能力 Helicalgearssubjecttheshaftbearingstobothradialandthrustloa ds.斜齿轮使轴承承受径向力和轴向力。 Whenthethrustloadsbecomehighorareobjectionableforotherre asons,itmaybedesirabletousedoublehelicalgears.当轴向力过大 或由于别的原

27、因而产生不利影响时，那就可能需要使用人字齿轮。 Adoublehelicalgear(herringbone)isequivalenttotwohelicalgear sofoppositehand,mountedsidebysideonthesameshaft.双斜齿 轮(人字齿轮)相当于反向的并排地装在同一轴上的两个斜齿轮 Theydevelopoppositethrustreactionsandthuscanceloutthethru stload.他们产生相反的轴向推力作用，这样就抵消了轴向推 Whentwoormoresinglehelicalgearsaremountedonthe

28、samesh aft,thehandofthegearsshouldbeselectedsoastoproducethem inimumthrustload.当两个或更多个的单一斜齿轮被装在同一轴上时， 齿轮的齿向应作选择，以便保证最小的轴向力。 Crossed- helical,orspiral,gearsarethoseinwhichtheshaftcenterlinesaren eitherparallelnorintersecting.交错轴斜齿轮或螺旋齿轮，他们的轴 中心线既不相交也不平行 Wormgearsaresimilartocrossedhelicalgears.蜗轮蜗杆与交

29、错轴 斜齿轮相似。 Thepinionorwormhasasmallnumberofteethusuallyonetofour, andsincetheycompletelywraparoundthepitchcylindertheyareca lledthreads.小齿轮即蜗杆具有较少的齿数，通常是一到四齿，由于 它们完全缠绕在节圆柱上，因此它们又被称为螺纹齿。 Itsmatinggeariscalledawormgear,whichisnotatruehelicalgea r.与其配对的齿轮叫做蜗轮，蜗轮不是真正意义上的斜齿轮。 Awormandwormgearareusedtoprov

30、ideahighangular- velocityreductionbetweennonintersectingshaftswhichareusually atrightangle.蜗杆和蜗轮通常是用于向垂直相交轴之间的传动提供大 的角速度减速比。 Thewormgearisnotahelicalgearbecauseitsfaceismadeconcav etofitthecurvatureoftheworminordertoprovidelinecontactinst eadofpointcontact.因为其齿顶面做成中凹形状以适配蜗杆曲率， 目的是要形成线接触而不是点接触。 Howev

31、er,adisadvantageofwormgearingisthehighslidingvelociti esacrosstheteeth,thesameaswithcrossedhelicalgears.然而， 蜗杆蜗轮传动机构正像交错轴斜齿轮那样，存在齿间有较大滑移速度 的缺点。 Wormgearingareeithersingle-ordouble-enveloping.Asingle- envelopinggearingisoneinwhichthegearwrapsaroundorpartiall yenclosestheworm.杆蜗轮机构有单包围和双包围机构单包围机 构就是蜗轮

32、包裹着蜗杆或部分地包围着蜗杆的一种机构 Agearinginwhicheachelementpartiallyenclosestheotheris,ofco urse,adouble-envelopingwormgearing.当然，如果每个构件各自 局部地包围着对方的蜗轮机构就是双包围蜗轮蜗杆机构。 Theimportantdifferencebetweenthetowisthatareacontactexists betweentheteethofdouble- envelopinggearswhileonlylinecontactbetweenthoseofsingle- envelop

33、inggears.这两者之间的重要区别是，在双包围蜗轮蜗杆机 构的轮齿间是面接触，而在单包围蜗轮蜗杆机构的轮齿间只有线接 触。 Thewormandwormgearofasethavethesamehandofhelixasfo rcrossedhelicalgears,butthehelixanglesareusuallyquitedifferen t.蜗轮蜗杆传动副正像交错轴斜齿轮副那样具有相同的螺旋线头数， 但是其螺旋角是极不相同的 Thehelixangleonthewormisgenerallyquitelarge,andthatonthe gearverysmall.蜗杆上的螺旋升

34、角通常很大，而蜗轮上的则极小 Becauseofthis,itisusualtospecifytheleadangleontheworm,wh ichisthecomplementofthewormhelixangle,andthehelixangleo nthegear;thetowanglesareequalfora90-degshaftangle.因此， 通常规定蜗杆导程角就是蜗杆螺旋角的余角；也规定了蜗轮上的螺旋 角，该两角和等于90度的轴交角。 Whengearsaretobeusedtotransmitmotionbetweenintersecting shafts,somefor

35、mofbevelgearisrequired.当需要传递相交轴之间 的运动时，就可采用某种形式的锥齿轮 Althoughbevelgearsareusuallymadeforashaftangleof90deg.,t heymaybeproducedforalmostanyshaftangle.虽然锥齿轮传动通 常制造成90度轴交角，但它们也可以制造成任何角度的轴交角 Theteethmaybecast,milled,orgenerated.Onlythegeneratedteet hmaybeclassedasaccurate.轮齿可以铸出、铣制或滚切加工只 有滚齿可以说是精加工 Inatypicalbevelgearmounting,oneofthegearisoftenmountedo utboardofthebearing.在典型的锥齿轮安装中，其中一个锥齿轮常常 装于支承的外侧。 Thismeansthatshaftdeflectioncanbemorepronouncedandhave agreatereffectonthecontactoftheteeth.这意味着轴的挠曲情况 更加明显从而在轮齿接触上产生更大的影响 Anotherdifficulty,whichoccursin