专业英语9-10专题省名师优质课赛课获奖课件市赛课一等奖课件.ppt

单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,本资料仅供参考，不能作为科学依据。谢谢,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,*,本资料仅供参考，不能作为科学依据。谢谢,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,本资料仅供参考，不能作为科学依据。谢谢,单击此处编辑母版标题样式,特别申明：本电子教案中所有素材的版权归原创作者国防科技大学潘存云教授所有。购买方有权复制多份光盘用于本单位的教学。但不得提供给第三方。未经作者同意，也不得在公开出版物中引用其中的素材，违者应承担相应的法律责任。作者：潘存云 教授 2004年2月,第二级,第三级,第四级,第五级,本资料仅供参考，不能作为科学依据。谢谢,东华大学机械学院 作者：孙志宏,本资料仅供参考，不能作为科学依据。谢谢,机 械 工 程 专 业 英 语,Unit 9 Gear Transmission,第1页,1,2,3,Introduction,Spur Gears,Helical Gears,4,5,Bevel Gears,Worm Gearing,6,Gear Geometry,第2页,A gear drive system is one where a motor turns a series of gears to do work.It plays a very important role of transmitting power,achieving conveying and adjusting torque in numerous industrial equipment like machine tool,automobile,engineering machinery,agriculture machinery and construction machinery.,1,introduction,第3页,Typically,shaft orientation,efficiency,and speed determine which of these types should be used for a particular application.This section on gearing and gear drives describes the major gear types;it,evaluates(,评定，评价,),how the various gear types are combined into gear drives and considers the principal factors that effect gear drive.,轴方位、效率和速度决定了在实际应用中应该采取上述哪一类齿轮。这一节主要介绍齿轮传动中主要齿轮类型。它评定了不一样类型齿轮是怎样组合起来组成齿轮驱动以及影响齿轮驱动主要原因。,1,introduction,第4页,Helical Gears,（斜齿轮）,Bevel Gears,（锥齿轮）,Worm Gears,（蜗轮蜗杆）,Spur Gears,（直齿轮）,Gear Types,Hypoid Gears,（双曲面齿轮）,1,introduction,第5页,Near the root of the tooth,however,the tool traces a,trochoidal(,摆线,),path,Fig.9.2,providing a heavier,and stronger,root section.Because of this geometry,contact between the teeth occurs mostly as rolling rather than sliding.,在靠近齿根处，刀具轨迹呈摆线，这使吃根除更厚实。因为采取这种几何曲线，齿轮接触处主要是滚动摩擦而不是滑动摩擦。,And because contact is simultaneously across the entire width of the,meshing,（啮合）,teeth,a continuous series of shocks is produced by the gear.,因为接触是沿着整个啮合齿宽同时发生，所以齿轮就会产生连续冲击。,Spur Gears,2,第6页,External-tooth gears,.The most common type of spur gear has teeth cut on the outside,perimeter(,周围,),of mating cylindrical wheels,with the larger wheel called gear and the smaller wheel the,pinion(,小齿轮,),.The simplest arrangement of spur gears is single pair of gears called,a single reduction stage(,一级减速装置,),where output rotation is in a direction opposite that of the input.,图,9.3,所表示是最普通直齿轮类型，其轮齿是切削加工在配对齿轮外圆周上。大齿轮称为,gear,，小齿轮称为,pinion,。直齿轮最简单布置就是一级减速装置，其输入转向于输出转向相反。,Spur Gears,2,第7页,Higher net reduction is produced with multiple stages in which the driven gear is rigidly connected to a third gear.This third gear then drives a mating fourth gear that,serves,as(,充当，担任,),output for the second stage.,In this manner,several output speeds on different shafts can be produced from a single input rotation.,更大减速比能够采取多级减速来实现，齿轮第四个齿轮以实现二级减速。采取这种方式，输入一个旋转运动就能够在不一样轴上取得不一样输出转速。,Spur Gears,2,第8页,Internal(ring)gears,.As the name implies(,顾名思义,),teeth are cut on the inside surface of a cylindrical ring,inside of which are mounted a single external-tooth spur gear or set of external-tooth spur gears,typically consisting of three or four larger gears(planets)usually surrounding a smaller central pinion(sun).,顾名思义，在内啮合传动方式中，轮齿是在圆柱环内表面加工出来。在它里面还安装有一个或一套外啮合齿轮，最经典是由三个到四个大齿轮（行星轮）围绕一个较小中心小齿轮（太阳轮）。,Spur Gears,2,第9页,Normally,the ring gear is stationary,causing the planets to,orbit,(,在,轨道上运行,)the sun in the same rotational direction as that of the sun.for this reason,this class of gear if often referred to as a planetary system.,普通情况下，环形齿轮是静止，它使行星轮绕中心齿轮转动，其选装方向与中心轮一致。因为这个原因，这一类齿轮经常被称为行星齿轮系。,Spur Gears,2,第10页,Rack-and-pinion gears,.A straight bar with teeth cut straight across it,Fig.9.5,is called a rack.Basically,this rack is considered to be spur gear,unrolled(,展开,),and laid out flat.Thus,the rack-and-pinion is a special case of spur gearing.The rack-and-pinion is useful in converting rotary motion to linear and,vice versa(,反之亦然,),.,Conversely,in machine tools,lift trucks,升降机,power shovels,挖土机,and other heavy machinery where rotary motion of the pinion drives the straight-line action of a,reciprocating(,往复,),part.4,Spur Gears,2,第11页,Helical gearing,differs from spur gearing in that helical teeth are cut across the gear face at an angle rather than straight.Thus,the,contact line of,the meshing teeth progresses across the face from the,tip(,尖端、末端,),at one end to the root of the other,reducing the noise and vibration characteristic of spur gears.,斜齿轮传动与直齿轮传动区分在于斜齿轮轮齿是沿齿面呈某一角度而不是垂直于端面切削加工出来。如此，啮合齿接触线是由端面一端齿顶抵达另一端齿根处，相比直齿轮传动而言，降低了噪声和振动。,Helical Gears,3,第12页,Also,several teeth are in contact at any one time,producing a more gradual loading of the teeth that reduces wear substantially.The increased amount of,sliding action,between helical gear teeth,however,places greater demands on the lubricant to prevent metal-to-metal contact and resulting,premature,gear failure,.,另外，在啮合过程中，几个齿同时接触，而且是逐层加载，这么有利于大幅度降低磨损。斜齿轮滑动摩擦增加，对润滑提出了更高要求以防止金属间接触而造成过早齿轮失效。,Helical Gears,3,第13页,Also,since the teeth mesh at an angle,a side,thrust(,推力,),load is produced along each gear shaft.Thus,thrust bearings must be used to absorb this load so that the gears are held in proper,alignment(,对齐，排成直线,),.,另外，因为轮齿是沿一定角度进入啮合，沿每个齿轮轴线方向都会产生一个侧向推力载荷，所以，要采取推力球轴承来吸收这个载荷以确保齿轮正常啮合。,Helical Gears,3,第14页,A special class of bevels called,miter gears,have gears of the same size with their shafts at right angles.Often there is no room to support bevel gears at both ends because the shafts,intersect,（相交）,.,还有一类特殊锥齿轮称之为等径锥齿轮，它们尺寸相同而且轴相交成直角。因为齿轮轴相交，轴两端经常没有空间来支撑锥齿轮。,4,Bevel Gears,第15页,This overhang load(OHL)may deflect the shaft and misalign the gears,which causes poor tooth contact and accelerates wear.Shaft deflection may be overcome with,straddle(,跨越,两边,),mounting in which a bearing is placed on each side of the gear provided space permits.,这个悬臂载荷就可能使齿轮轴挠曲，使它们不能对准（错位），会造成轮齿接触不好，从而加速磨损。假如空间允许话，能够采取跨越式结构，在齿轮两端各装一个轴承，就能够处理齿轮轴挠曲变形问题。,4,Bevel Gears,第16页,4,Bevel Gears,Straight-tooth bevels,直齿锥齿轮,Also known as plain(简单)bevels,have teeth cut straight across the face of the gear.They are subject to much of the same operating conditions as spur gears in that straight-tooth bevels are efficient but somewhat(稍微,有点)noisy.They produce thrust(推力)loads in a direction that tends to separate the gears.,Spiral-bevels,螺旋锥齿轮,Curved teeth provide an action somewhat like that of a helical gear.This produces smoother,quieter operation than straight-tooth bevels.Thrust loading depends on the direction of rotation and whether the spiral angle at which the teeth are cut is positive or negative.,第17页,Straight and Spiral Bevel Gears,第18页,Worm gearing,5,WORM AND WORM GEAR,第19页,Worm gear sets consist of a screw-like worm(comparable to a pinion)that meshes with a larger gear,usually called a wheel5,In this way,a wide range of speed ratios up to 60:1 and higher can be obtained from a,single reduction,.Most worms are cylindrical in shape with a uniform,pitch diameter,.However,a,double-enveloping worm,has a variable pitch diameter that is narrowest in the middle and greatest at the end.,Worm gearing,5,第20页,However,a reversible worm-gear has the worm and wheel pitches so,proportioned(,均衡,),that movement of the wheel rotates the worm.In most worm gears,the wheel has teeth similar to those of a helical gear,but the tops of the teeth curve,inward(,向内,),to,envelop(,包络,),the worm.,在可逆式涡轮蜗杆传动过程中，二者节距百分比要适当，蜗杆才能驱动蜗杆。在大多数蜗轮中，其轮齿与斜齿轮轮齿相同，不过轮齿曲线顶部是向内包络蜗杆。,Worm gearing,5,第21页,Because of this high level of,rubbing(,摩擦,),between the worm and wheel teeth,the efficiency of worm gearing is lower than other major gear types.One of the worm gear is low wear,due mostly to the full-fluid lubricant film that tends to be formed between tooth surfaces by the worm sliding action.,Worm gearing,5,第22页,Gear Geometry,6,Nomenclature,of Spur Gears,第23页,Gear Geometry,6,Module(,m,),Pressure angle(,),Base circle(,d,b,),Pitch circle(,d,),Addendum circle(,d,a,),Root circle(,d,f,),Addendum(,h,a,),Dedendum(,h,f,),Whole depth(,h,),Face width(,B,),Pitch,Pitch point,模数,压力角,基圆,节圆,齿顶圆,齿根圆,齿顶高,齿根高,齿全高,齿宽,节距,节点,第24页,r,b,O,齿顶圆,(addendum circle),齿根圆,(dedendum circle),齿厚,(tooth thickness),齿槽宽,(tooth space),齿距,(,周节,),(space width),r,a,s,k,e,k,r,f,p,k,Nomenclature of Spur Gears,第25页,r,b,O,p,n,齿顶高,(Addendum),齿根高,(Dedendum),齿全高,(Tooth depth),齿宽,(Face width),h,a,h,f,h,B,p,r,a,分度圆,(Reference circle),s,e,s,k,e,k,p,b,r,f,r,p,k,Nomenclature of Spur Gears,第26页,Gear Geometry,6,Module(,m,),模数,Pressure angle(,),压力角,Base circle(,d,b,),基圆,Pitch circle(,d,),节圆,Addendum circle(,d,a,),齿顶圆,Root circle(,d,f,),齿根圆,Addendum(,h,a,),齿顶高,Dedendum(,h,f,),齿根高,Whole depth(,h,),齿全高,Face width(,B,),齿宽,Pitch,节距,Pitch point,节点,第27页,Gear Geometry,6,Circular pitch(p),周节,Gear center,齿轮中心,Diametral pitch,径节,Line of center,中心线,Axial pitch,轴向节距,Line of action,啮合线,Base pitch,基节,Line of contact,接触线,Axial base pitch,轴向基节,Point of contact,接触点,Tooth surface,轮齿表面,Center distance,中心距,Tooth profile,齿廓,Lead,导程,Flank,齿侧,Backlash,侧隙,第28页,r,b2,r,2,O,2,2,r,b1,r,1,O,1,1,p,b2,p,b,1,=p,b,2,p,b,1,能正确啮合,!,P,N,1,N,2,B,2,B,1,主要结论：,一对渐开线齿轮正确啮合条件是：它们模数和压力角应分别相等。,第29页,Gears being an important part of a machine have immense usage within various industries.These industries include automotive industry,coal power plants,(,热电厂,),steel plants,paper mills,（造纸厂）,mines and many more.,They are used as,conveyors(,传送带,),elevators(,升降机,),separators(,分离器,),cranes(,起重机,),and lubrication system.,6,Gear Geometry,第30页,第31页,