機械零件齒輪中英文對照外文翻譯文獻

1、 (文檔含英文原文和中文翻譯)中英文資料對照外文翻譯Machine Parts (I)GearsGears are direct contact bodies, operating in pairs, that transmit motion and forcefrom one rotating shaft to another or from a shaft to a slide (rack), by means ofsuccessively engaging projections called teeth.Tooth profiles. The contacting surfaces o

2、f gear teeth must be aligned in such away that the drive is positive; i.e., the load transmitted must not depend on frictionalcontact. As shown in the treatment of direct contact bodies, this requires that the1 common normal to the surfaces not to pass through the pivotal axis of either the driveror

3、 the follower.As it is known as direct contact bodies, cycloidal and involute profiles profilesprovide both a positive drive and a uniform velocity ratio;i.e., conjugate action.Basic relations. The smaller of a gear pair is called the pinion and the larger isthe gear. When the pinion is on the drivi

4、ng shaft the pair is called the pinion and thelarger is the gear. When the pinion is on the driving shaft the pair acts as a speedreducer; When the gear drives, the pair is a speed incrreaser. Gears are morefrequently used to reduce speed than to increase it.If a gear having N teeth rotates at n rev

5、olutions per minute, the product N*n hasthe dimension “teeth per minute”. This product must be the same for both members ofa mating pair if each tooth acquires a partner from the mating gear as it passes throughthe region of tooth engagement.For conjugate gears of all types, the gear ratio and the s

6、peed ratio are both givenby the ratio of the number of teeth on the gear to the number of teeth on the pinion. Ifa gear has 100 teeth and a mating pinion has 20, the ratio is 100/20=5. Thus the pinionrotates five times as fast as the gear, regardless of the gear. Their point of tangency iscalled the

7、 pitch point, and since it lies on the line of centers, it is the only point atwhich the profiles have pure roling contact. Gears on nonparallel, non-intersectingshafts also have pitch circles, but the rolling-pitch circle concept is not valid.Gear types are determined largely by the disposition of

8、the shafts; in addition,certain types are better suited than others for large speed changes. This means that if aspecific disposition of the shafts is required, the type of gear will more or less be fixed.On the other hand, if a required speed change demands a certain type, the shaftpositions will a

9、lso be fixed.Spur gears and helical gears. A gear having tooth elements that are straight andparallel to its axis is known as a spur gear. A spur pair can be used to connect parallelshafts only.If an involute spur pinion were made of rubber and twisted uniformly so thatthe ends rotated about the axi

10、s relative to one another, the elements of the teeth,initially straight and parallel to the axis, would become helices. The pinion then ineffect would become a helical gear.Worm and bevel gears. In order to achieve line contact and improve the loadcarrying capacity of the crossed axis helical gears,

11、 the gear can be made to curve2 partially around the pinion, in somewhat the same way that a nut envelops a screw.The result would be a cylindrical worm and gear. Worms are also made in the shape ofan hourglass, instead of cylindrical, so that they partially envelop the gear. This resultsin a furthe

12、r increase in load-carrying capacity.Worm gears provide the simplest means of obtaining large ratios in a single pair.They are usually less efficient than parallel-shaft gears, however, because of anadditional sliding movement along the teeth.V-beltThe rayon and rubber V-belt are widely used for pow

13、er transmission. Such beltsare made in two series: the standard V-belt and the high capacity V-belt. The belts canbe used with short center distances and are made endless so that difficulty withsplicing devices is avoided.First, cost is low, and power output may be increased by operating several bel

14、tsside by side. All belts in the drive should stretch at the same rate in order to keep theload equally divided among them. When one of the belts breaks, the group mustusually be replaced. The drive may be inclined at any angle with tight side either topor bottom. Since belts can operate on relative

15、ly small pulleys, large reductions ofspeed in a single drive are possible.Second，the included angle for the belt groove is usually from 34to 38.Thewedging action of the belt in the groove gives a large increase in the tractive forcedeveloped by the belt.Third，pulley may be made of cast iron, sheet s

16、teel, or die-cast metal. Sufficientclearance must be provided at the bottom of the groove to prevent the belt frombottoming as it becomes narrower from wear. Sometimes the larger pulley is notgrooved when it is possible to develop the required tractive force by running on theinner surface of the bel

17、t. The cost of cutting the grooves is thereby eliminated. Pulleysare on the market that permit an adjustment in the width of the groove. The effectivepitch diameter of the pulley is thus varied, and moderate changes in the speed ratiocan be secured.Chain DrivesThe first chain-driven or “safety” bica

18、ypcpleeared in 1874, and chains wereused for driving the rear wheels on early automobiles. Today, as the result ofmodern design and production methods, chain drives that are much superior totheir prototypes are available, and these have contributed greatly to the3 development of efficient agricultur

19、al machinery, well-drilling equipment, and miningand construction machinery. Since about 1930 chain drives have become increasinglypopular, especially for power saws, motorcycle, and escalators etc.There are at least six types of power-transmission chains; three of these will becovered in this artic

20、le, namely the roller chain, the inverted tooth, or silent chain, andthe bead chain. The essential elements in a roller-chain drive are a chain with sideplates, pins, bushings (sleeves), and rollers, and two or more sprocket wheels withteeth that look like gear teeth. Roller chains are assembled fro

21、m pin links and rollerlinks. A pin link consists of two side plates connected by two pins inserted into holesin the side plates. The pins fit tightly into the holes, forming what is known as apress fit. A roller link consists of two side plates connected by two press-fittedbushings, on which two har

22、dened steel rollers are free to rotate. When assembled, thepins are a free fit in the bushings and rotate slightly, relative to the bushings when thechain goes on and leaves a sprocket.Standard roller chains are available in single strands or in multiple strands, Inthe latter type, two or more chain

23、s are joined by common pins that keep the rollers inthe separate strands in proper alignment. The speed ratio for a single drive shouldbe limited to about 10 1; the preferred shaft center distance is from 30 to 35 timesthe distance between the rollers and chain speeds greater than about 2500 feet (8

24、00meters) per minute are not recommended. Where several parallel shafts are to bedriven without slip from a single shaft, roller chains are particularly well suited.An inverted tooth, or silent chain is essentially an assemblage of gear racks,each with two teeth, pivotally connected to form a closed

25、 chain with the teeth on theinside, and meshing with conjugate teeth on the sprocket wheels. The links arepin-connected flat steel plates usually having straight-sided teeth with an includedangle of 60 degrees. As many links are necessary to transmit the power and areconnected side by side. Compared

26、 with roller-chain drives, silent-chain drives arequieter, operate successfully at higher speeds, and can transmit more load for the samewidth. Some automobiles have silent-chain camshaft drives.Bead chains provide an inexpensive and versatile means for connectingparallel or nonparallel shafts when

27、the speed and power transmitted are low. Thesprocket wheels contain hemispherical or conical recesses into which the beads fit.The chains look like key chains and are available in plain carbon and stainless steeland also in the form of solid plastic beads molded on a cord. Bead chains are used on4 c

28、omputers, air conditioners, television tuners, and Venetian blinds. The sprockets maybe steel, die-cast zinc or aluminum, or molded nylon.5 Machine Parts (II)FastenerFasteners are devices which permit one part to be joined to a second part and,hence, they are involved in almost all designs.There are

29、 three main classifications of fasteners, which are described as follows：(1) Removable. This type permits the parts to be readily disconnected withoutdamaging the fastener. An example is the ordinary nut-and-bolt fastener.(2) Semi permanent. For this type, the parts can be disconnected, but somedama

30、ge usually occurs to the fastener. One such example is a cotter pin.(3) Permanent. When this type of fastener is used, it is intended that the partswill never be disassembled. Examples are riveted joints and welded joints.The importance of fasteners can be realized when referring to any complexprodu

31、ct. In the case of the automobile, there are literally thousands of parts whichare fastened together to produce the total product. The failure or loosening of a singlefastener could result in a simple nuisance such as a door rattle or in a serioussituation such as a wheel coming off. Such possibilit

32、ies must be taken into account inthe selection of the type of fastener for the specific application.Nuts, bolts, and screws are undoubtedly the most common means of joiningmaterials. Since they are so widely used, it is essential that these fasteners attainmaximum effectiveness at the lowest possibl

33、e cost. Bolts are, in reality, carefullyengineered products with a practically infinite use over a wide range of services.An ordinary nut loosens when the forces of vibration overcome those of friction.In a nut and lock washer combination, the lock washer supplies an independentlocking feature preve

34、nting the nut from loosening. The lock washer is useful onlywhen the bolt might loosen because of a relative change between the length of the boltand the parts assembled by it. This change in the length of the bolt can be caused by anumber of factors-creep in the bolt, loss of resilience, difference

35、 in thermal expansionbetween the bolt and the bolted members, or wear. In the above static cases, theexpanding lock washer holds the nut under axial load and keeps the assembly tight.When relative changes are caused by vibration forces, the lock washer is not nearly aseffective.Rivets are permanent

36、fasteners. They depend on deformation of their structurefor their holding action. Rivets are usually stronger than the thread-type fastener andare more economical on a first-cost basis. Rivets are driven either hot or cold,6 depending upon the mechanical properties of the rivet material. Aluminum ri

37、vets, forinstance, are cold-driven, since cold working improves the strength of aluminum.Most large rivets are hot-driven, however.ShaftVirtually all machines contain shafts. The most common shape for shafts iscircular and the cross section can be either solid or hollow (hollow shafts can result inw

38、eight savings).Shafts are mounted in bearings and transmit power through such devices as gears,pulleys, cams and clutches. These devices introduce forces which attempt to bend theshaft; hence, the shaft must be rigid enough to prevent overloading of the supportingbearings. In general, the bending de

39、flection of a shaft should not exceed 0.01 in. per ft.of length between bearing supports.For diameters less than 3 in., the usual shaft material is cold-rolled steelcontaining about 0.4 percent carbon. Shafts are either cold-rolled or forged in sizesfrom 3 in. to 5 in. .For sizes above 5 in. , shaft

40、s are forged and machined to size.Plastic shafts are widely used for light load applications. One advantage of usingplastic is safety in electrical applications, since plastic is a poor conductor ofelectricity.Another important aspect of shaft design is the method of directly connectingone shaft to

41、another. This is accomplished by devices such as rigid and flexiblecouplings.BearingA bearing can be defined as a member specifically designed to supportmoving machine components. The most common bearing application is the supportof a rotating shaft that is transmitting power from one location to an

42、other. Since thereis always relative motion between a bearing and its mating surface, friction isinvolved. In many instances, such as the design of pulleys, brakes, and clutches,friction is desirable. However, in the case of bearings, the reduction of friction is oneof the prime considerations：Frict

43、ion results in loss of power, the generation ofheat, and increased wear of mating surfaces.The concern of a machine designer with ball bearings and roller bearings isfivefold as follows：(1) Life in relation to load; (2) stiffness, i.e. deflections under load;(3) friction; (4) wear; (5) noise. For mo

44、derate loads and speeds the correct selection ofa standard bearing on the basis of load rating will usually secure satisfactory7 performance. The deflection of the bearing elements will become important whereloads are high, although this is usually of less magnitude than that of the shafts orother c

45、omponents associated with the bearing. Where speeds are high specialcooling arrangements become necessary which may increase frictional drag. Wearis primarily associated with the introduction of contaminants, and sealingarrangements must be chosen with regard to the hostility of the environment.Notw

46、ithstanding the fact that responsibility for the basic design of ball bearingsand roller bearings rests with the bearing manufacturer, the machine designermust form a correct appreciation of the duty to be performed by the bearing and beconcerned not only with bearing selection but with the conditio

47、ns for correctinstallation.The fit of the bearing races onto the shaft or onto the housings is of criticalimportance because of their combined effect on the internal clearance of the bearingas well as preserving the desired degree of interference fit. Inadequate interferencecan induce serious troubl

48、e from fretting corrosion. The inner race is frequently locatedaxially by abutting against a shoulder. A radius at this point is essential for theavoidance of stress concentration and ball races are provided with a radius or chamferto allow space for this.A journal bearing, in its simplest form, is

49、a cylindrical bushing made of a suitablematerial and containing properly machined inside and outside diameters. The journalis usually the part of a shaft or pin that rotates inside the bearing.Journal bearings operate with sliding contact, to reduce the problems associatedwith sliding friction in jo

50、urnal bearings, a lubricant is used in conjunction withcompatible mating materials. When selecting the lubricant and mating materials, onemust take into account bearing pressures, temperatures and also rubbing velocities.The principle function of the lubricant in sliding contact bearings is to preve

51、ntphysical contact between the rubbing surfaces. Thus the maintenance of an oil filmunder varying loads, speeds and temperature is the prime consideration in slidingcontact bearings.8 Introduction to Machinery DesignMachinery design is either to formulate an engineering plan for thesatisfaction of a

52、 specified need or to solve an engineering problem. It involves a rangeof disciplines in materials, mechanics, heat, flow, control, electronics and production.Machinery design may be simple or enormously complex, easy or difficult,mathematical or nonmathematical, it may involve a trivial problem or

53、one of greatimportance. Good design is the orderly and interesting arrangement of an idea toprovide certain results or effects. A well-designed product is functional, efficient,and dependable. Such a product is less expensive than a similar poorly designedproduct that does not function properly and

54、must constantly be repaired.People who perform the various functions of machinery design are typicallycalled industrial designers. He or she must first carefully define the problem, using anengineering approach, to ensure that any proposed solution will solve the rightproblem. It is important that t

55、he designer begins by identifying exactly how he or shewill recognize a satisfactory alternative, and how to distinguish between twosatisfactory alternatives in order to identify the better. So industrial designers musthave creative imagination, knowledge of engineering, production techniques, tools

56、,machines, and materials to design a new product for manufacture, or to improve anexisting product.In the modern industrialized world, the wealth and living standards of a nationare closely linked with their capabilities to design and manufacture engineeringproducts. It can be claimed that the advan

57、cement of machinery design andmanufacturing can remarkably promote the overall level of a countrys industrization.Our country is playing a more and more vital role in the global manufacturingindustry. To accelerate such an industrializing process, highly skilled design engineershaving extensive know

58、ledge and expertises are needed.Machinery ComponentsThe major part of a machine is the mechanical system. And the mechanicalsystem is decomposed into mechanisms, which can be further decomposed intomechanical components. In this sense, the mechanical components are thefundamental elements of machine

59、ry. On the whole, mechanical components can beclassified as universal and special components. Bolts, gear, and chains are the typicalexamples of the universal components, which can be used extensively in differentmachines across various industrial sectors. Turbine blades, crankshaft and aircraft9 pr

60、opeller are the examples of the special components, which are designed for somespecific purposes.Mechanical Design ProcessProduct design requires much research and development. Many concepts of anidea must be studied, tried, refined, and then either used or discarded. Althoughthe content of each eng