第7章圆柱齿轮公差与配合应用Chapter7Cylindricalgear'stoleranceandfitapplication基本要求Basicrequirements•目的：了解圆柱齿轮的公差标准•Aim:TounderstandtolerancestandardsofCylindricalgear•初步掌握：Grasppreliminarily:•1.应用要求、加工误差•Applicationrequirementsandmanufacturingerror•2.评定指标Evaluationindex•3.图样标注Labelsofpattern•4.齿轮精度设计Designofgearaccuracy•操作技能：评定指标的检验Manipulativeskill:Thetestofevaluationindex.特点Traits1结构紧凑Compactstructure2恒定的传动比Constanttransmissionratio3传动效率高Hightransmissionefficiency4可实现平行轴、相交轴和交错轴之间的传动Itcouldrealizethetransmissionbetweenparallelaxles,intersectantaxlesandinterlacedaxles5使用寿命长Longworkinglife6维护保养简单Sampletomaintain作用：传递空间任意两轴（平行、相交、交错）的旋转运动，或将转动转换为移动。Founction:Totransmittherevolvingmovementsofanytwoaxles(parallel,intersectantandinterlaced)inspace.Andtoconvertturntoshift.缺点：要求较高的制造和安装精度，加工成本高、不适宜远距离传动。Disadvantages:Itneedshigheraccuraciesofmanufactureandinstallment.Conversioncostishighanditisnotsuitableforlongdistancetransmission.齿轮传动的类型Typesofgeardrive•传动齿轮：转速较高，功率较大（汽车飞机等变速装置）•Drivegear:Higherrotationrateandpower(Speedvariatorsinautomobilesandairplanes)•动力齿轮：转速不高，传递扭矩（矿山机械起重机械）•Powergear:Thespeedofrevolutionisnothighandittransmitstorque(miningmachineandhoistingmachinery)•分度齿轮：精确回转（精密机床仪表中的分度装置）•Dividinggear:Preciserotation(precisionmachinetoolanddividingdeviceininstrumentation)齿轮传动机构组成Theformofgeartransimissionmechanism齿轮副、轴、轴承、箱体…pairofgears,axles,bearingsandboxes…失效形式failuremode轮齿折断toothbreakage1.由于多次重复的弯曲应力和应力集中造成的疲劳折断；Thefatiguefracturewhichiscausedbyoft-repeatedbendingstressesandstressconcentration.2.由于突然严重过载或冲击载荷作用引起的过载折断。Theoverloadbreakwhichiscausedbysuddensevereoverloadorimpactload.直齿轮：齿宽较小的往往发生全齿折断,齿宽较大的直齿轮或斜齿轮则容易发生局部折断。Straightgear:Thegearswithsmallerbreadthoftoothoftenemergewholetoothfracturewhilethestraightgearsorhelicalgearswithbiggerbreadthoftoothareeasytoemergelocalbreak.一、轮齿的失效形式失效形式齿面点蚀Toothsurfacepitting原因：由于在齿面啮合处脉动循环变接触应力长期作用下，当应力峰值超过材料的接触疲劳极限，经过一定应力循环次数后，先在节线附近的齿廓表面产生细微的疲劳裂纹。随着裂纹的扩展，将导致小块金属剥落，产生齿面点蚀。Reason:Becauseofthelongtermeffectofpulsatingcyclicvariablecontactstressonmeshingpointoftoothsurface.Whenpeakstressexceedsmaterial’scontactfatiguelimit,hairlikefatiguecrackswillappearontoothprofilesurfacearoundnodellineaftercertainnumberoftimesofstresscycle.Withtheextendingofflaws.Scrapmetalwillpeelofftoproducetoothsurfacepitting.点蚀不良影响：影响轮齿正常啮合，引起冲击和噪声，造成传动的不平稳。Harmfuleffectsofpitting:Influencingthenormalengagementofgearteeth,causingconcussionsandnoise,creatingun-stationarytransmission.一、轮齿的失效形式失效形式齿面胶合Toothsurfacebonding高速重载传动中，常因啮合区温度升高而引起润滑失效，致使齿面金属直接接触而相互粘连。当齿面相对滑动时，较软的齿面沿滑动方向被撕下而形成沟纹。Onhighspeedandheavyloadtransmission.Theraiseofmeshingzone’stemperatureusuallycauseslubricationlosingefficacytoleadtothedirectcontactsoftoothsurfacemetalandadhes...
