1、Gears are vital factors in machinery. One of the first mechanism invented using gears was the clocks. In fact, a clock is little more than a train of gears.Considerable study and research have been made on gears in recent years because of their wide use under exacting conditions. They have to transm

2、it heavier loads and run at higher speeds than ever before. The engineers and the machinists all consider gearing the prime elementin nearly all classes of machinery.齒輪在機(jī)械中占有極其重要的作用。第一個(gè)利用齒輪做成的機(jī)械裝置就是鐘表，事實(shí)上，它只不過是用了一系列的齒輪。對(duì)于它可以在嚴(yán)格的條件下的廣泛使用，在齒輪上做了大量的學(xué)習(xí)和研究。相比過去，它們現(xiàn)在必須在更高的速度下傳遞更重的負(fù)荷。工程師和機(jī)器操縱工人都認(rèn)為齒輪在幾乎所有的機(jī)

3、器的零件中占有首要的因素。1. Spur gearsSpur gears are used to transmit power and rotary motion between parallel shafts. Theteeth are cut parallel to the axis of the shaft on which the gears are mounted. The smaller of two gears in mesh is called the pinion and the larger is customarily Designated as the gear. In

4、 most applications, the pinion is the driving element whereas the gear is the driven element.1.直齒圓柱齒輪直齒圓柱齒輪用于平行軸之間傳遞力和回轉(zhuǎn)運(yùn)動(dòng)，輪齒被切制成與安裝齒輪的軸之軸線相平行。兩嚙合齒輪中較小的叫小齒輪，大的習(xí)慣上叫齒輪，在大多數(shù)情況下，小齒輪是主動(dòng)輪，大齒輪叫從動(dòng)輪。2. Helical gearsHelical gears have certain advantages, for example, when connecting parallel shafts they have

5、a higher load-carrying capacity than spur gear with the same tooth numbers and cut with the same cutter.2斜齒圓柱齒輪斜齒圓柱齒輪具有特定的優(yōu)點(diǎn)，比如，當(dāng)連接平行軸的用相同刀具切削出來的并齒數(shù)相同的斜齒輪比直齒輪具有較高的承載能力。斜齒輪也能用于連接相互成任意角度的非平行軸。Helical gears can also be used to connect nonparallel , non-intersecting shaftsat any angle to one another.斜齒輪

6、也能用于連接相互成任意角度的非平行軸。The maximum gear ratio obtainable with a single pair of gears varies with the type of gear and the application. The following are approximate maxim a for the various type for average load conditions: spur, 8; parallel-shaft helical, 10; straight bevel , 6; spiral bevel, 8;hypoid ,

7、 12; and worm , 80. For lightly loaded, instrument, and positioning gears, these rations can be exceeded. Rations as high as 400 or higher can be obtained with gears that resemble tapered worms meshing with hypoid gear. For heavily loaded gear, the given rations may be so high that a reasonable gear

8、 size precludes a satisfactory pinion.一對(duì)齒輪能獲得的最大傳動(dòng)比隨齒輪類型和應(yīng)用的變化而變化，以下是各種類型的齒輪的平均載荷條件的近似最大化，直齒是8，平行軸斜齒輪是10，直齒錐齒是6，曲線齒錐齒輪8，準(zhǔn)雙曲面12，蝸輪蝸桿8，對(duì)于輕載荷和定位齒輪這些傳動(dòng)比被超出，類似于成錐形的蝸輪蝸桿，和準(zhǔn)雙曲面齒輪能夠獲得的傳動(dòng)比高達(dá)400 或更高，如此高以至于00 的齒輪尺寸不可能令人滿意。Since the ratio in a single pair of gears is the quotient of the tooth number, and since

9、there usually are limitations on both the minimum and maximum numbers of teeth on the available gears,it follows that the number of ratios obtainable in a single pair is limited. To enlarge the coverage it is necessary to use multiple pairs, or trains. The overall speed ratio in a train is the produ

10、ct of the ratios in each pair. In certain cases an exact ratio cannot be obtained with gears, but by using two or more parts, the desired ratio can be approximated to any degree of precision.一對(duì)齒輪的傳動(dòng)比齒數(shù)的商，它們通常是限制在有效齒輪的最大和最小齒數(shù)之間，因此，一對(duì)齒輪獲得的傳動(dòng)比是受限制的，為了擴(kuò)大范圍，用多級(jí)齒輪副或系列是必要的，在一個(gè)系列中，總速比是每對(duì)齒輪產(chǎn)生的傳動(dòng)比。As a conven

11、ience for machine builders and users, packaged speed reducers, following an industry-accepted pattern , are manufactured in a wide variety of types,configurations , speed ratios, and capacities; these consist of a box or housing containing bearings, shafts, lubricant and shaft oil seals. Speed incre

12、asers are usually custom build.在某種情況下，一個(gè)確切的傳動(dòng)比不能由齒輪副獲得，但是用兩對(duì)或更多對(duì)時(shí)，要求的傳動(dòng)比能達(dá)到精確等級(jí)，為了對(duì)機(jī)器制造者和使用者方便起見，各種整裝式減速器，根據(jù)工業(yè)通用的試樣被大量的多樣化的類型的組合的速度比的生產(chǎn)制造，這些由箱子組成或給含有軸承軸潤滑劑和軸油封裝外罩增速器通常被定別。All speed reducers when operating continuously become hot because of friction in the teeth, in the lubricant, in the bearings, an

13、d in the oil seals. If the heat is generated at a faster rate than it can be dissipated to the atmosphere, the lubricant may deteriorate and the gear or bearing fail.所有的減速器當(dāng)被連續(xù)使用時(shí)，由于輪齒在潤滑劑軸承和油封件的摩擦?xí)儫?，如果熱量的產(chǎn)生在空氣中散逸的速度還快的話，潤滑劑不能損壞，并且軸承和齒輪失效。Worm gear sets are widely used because of the many advantage

14、s obtained by their tooth action and load carrying capacity. A large speed reduction or a high increase oftorque can be attained with the worm gear set. Compactness of design is easy to obtain with such a combination, Worm gear drives are quiet and vibration free.蝸輪裝置由于嚙合作用和傳遞載荷能力獲得的許多優(yōu)點(diǎn)而被廣泛應(yīng)用，大量轉(zhuǎn)矩的

15、減速或增速裝置由蝸輪裝置完成，設(shè)計(jì)的緊湊，用這樣一個(gè)結(jié)合體是容易得到的，蝸輪是平穩(wěn)且無振動(dòng)的。A worm gear set consists of the worm, which is very similar to a screw, and the wormgear, which is a helical gear. The shafts upon which the worm and the gear are mounted are usually at right angels but not in the same plane. The usual practice is to ha

16、ve the worm drive the worm gear. With same ratios, it is possible to have a gear driver the worm. However, with large ratios, it is impossible for the gear to drive the worm.一個(gè)蝸輪裝置由蝸桿非常類似于螺絲和蝸輪一個(gè)斜齒輪組成的，安裝蝸桿和蝸輪的軸通常相互垂直而不在同一平面中，通常習(xí)慣上使蝸桿驅(qū)動(dòng)蝸輪。小的傳動(dòng)比，使一個(gè)齒輪驅(qū)動(dòng)蝸桿是有可能的，但是，大的傳動(dòng)比，使一個(gè)齒輪驅(qū)動(dòng)蝸桿是不可能的。The worm can be

17、made with either right-hand or left-hand thread. Also, like a screw, it can be made with single, double, triple, or quadruple thread. A single-thread worm advances the worm gear a distance equal to pitch for each complete worm rotation. The distance advanced is called the lead. Thus, the pitch equal

18、s the lead for a single thread. A double-threaded worm has a lead which is twice the pitch.蝸桿可以被制成右螺紋或左螺紋，同樣像螺絲一樣，蝸桿可以被制成單、雙螺紋，三重或四重螺紋，單螺紋的蝸桿推進(jìn)蝸輪等節(jié)距前進(jìn)來完成每個(gè)完整的蝸桿轉(zhuǎn)動(dòng)，間距的推進(jìn)稱為節(jié)距。因而節(jié)距等于單螺紋的螺距，雙螺紋的蝸桿螺距是兩倍的節(jié)距。The geometry of a worm is similar to that of a power screw. Rotation of the wormsimulates a linearl

19、y advancing involute rack The geometry of worm gear(sometimes called a worm wheel) is similar to that of a helical gear, except that the teeth are curved to envelop the worm. Sometimes the worm is modified to envelop the gear. This gives a greater area of contact, but requires extremely precise moun

20、ting.蝸桿的幾何形狀類似于機(jī)械螺紋，蝸桿的轉(zhuǎn)動(dòng)與一個(gè)漸開線導(dǎo)軌直線移動(dòng)是相仿的。蝸輪幾何形狀（有時(shí)被稱為蝸輪）類似于斜齒輪，除了包圍在蝸輪上的齒是彎曲的以外。有時(shí)把蝸桿齒制成包裹在蝸輪，這就提供了更大的接觸面積，但安裝精度要求更高了。A rotary cam is part on a machine which mechanically changes cylindrical motion to straight-line motion. The cam, which is mounted on a shaft, is usually driven by a motor either ap

21、plied directly to the cam shaft or connected by pulleys orgears. The purpose of a cam is to transmit various kinds of motions to other parts of amachine.一個(gè)轉(zhuǎn)動(dòng)的凸輪是機(jī)械的一部分，也就是用機(jī)械的方式使回轉(zhuǎn)運(yùn)動(dòng)變?yōu)橹本€運(yùn)動(dòng)。凸輪被安裝在軸上通常由直接用到凸輪軸或是由皮帶輪或齒輪聯(lián)結(jié)成的任一原動(dòng)力驅(qū)動(dòng)。凸輪的目的是傳遞各種各樣的運(yùn)動(dòng)到機(jī)械的其他部分。Practically every cam must be designed and manuf

22、actured to fit special requirements. Though each cam appears to be quite different from the other, all the cams work in a similar ways. In each case, as the cam is rotated or turned, another part in contact with the cam, called a follower, is moved either left and right, up and down, or in and out.

23、The follower is usually connected to other parts on the machine to accomplish the desired action. The direction the follower move depends upon the position of the framework which attaches the cam and follower to the machine. If thefollower loses contact with the cam, it will fail to work.幾乎每個(gè)凸輪必須被設(shè)計(jì)

24、和制造以適合特殊的要求，雖然每個(gè)凸輪顯現(xiàn)的十分不同于其他凸輪。但是所有的凸輪都以類似的方式工作。在任何情況下，與凸輪轉(zhuǎn)動(dòng)或旋轉(zhuǎn)時(shí)，與凸輪接觸的另一部分成為從動(dòng)件，向左或向右，向上或向下，向里或向外移動(dòng)。從動(dòng)件通常聯(lián)結(jié)機(jī)械的其他部分以完成要求的運(yùn)動(dòng)，從動(dòng)件運(yùn)動(dòng)的方向取決于結(jié)構(gòu)的位置也就是在機(jī)械中聯(lián)結(jié)凸輪和從動(dòng)輪。如果從動(dòng)件與凸輪不接觸，它將不能工作。The faster the cam turns, the more rapid is the motion of the follower. The motion of the follower caused by rotating the cam

25、 is exactly the same for each complete turn of the cam. 凸輪旋轉(zhuǎn)越快，從動(dòng)輪的運(yùn)動(dòng)越迅速，從動(dòng)件的運(yùn)動(dòng)是由凸輪轉(zhuǎn)動(dòng)導(dǎo)致的并且這種運(yùn)動(dòng)與每個(gè)凸輪整個(gè)旋轉(zhuǎn)運(yùn)動(dòng)是正好相反。Belt drives offer a maximum of versatility as power transmission elements. They allow the designer considerable flexibility in location of driver and driven machinery,and tolerances are not

26、 critical as is the case with gear drives. Another advantage of belt drives is that they reduce vibration and shock transmission. Furthermore, belt drives are relatively quiet.皮帶傳動(dòng)裝置作為傳遞動(dòng)力的元件用途極廣。這種裝置使設(shè)計(jì)人員在確定主動(dòng)機(jī)械與從動(dòng)機(jī)械的位置時(shí)有相當(dāng)大的靈活性，而且公差要求也不像齒輪傳動(dòng)裝置那樣嚴(yán)格。皮帶傳動(dòng)另一個(gè)優(yōu)點(diǎn)是可以減少振動(dòng)及其傳播。不僅如此，皮帶傳動(dòng)噪聲也比較小。Large flat le

27、ather belts were in general use many years ago, when the usual practice was to use one large engine to driver several different pieces of machinery. Some leather belts are in use at this time as well as flat steel, rubber, plastic, and fabric belts. Light, thin flat belts are practical on high speed

28、 machinery where vibration may be a problem用皮革制成的大的平皮帶在許多年前曾用得很普遍，那時(shí)，通常是用一臺(tái)大功率的發(fā)動(dòng)機(jī)驅(qū)動(dòng)好幾臺(tái)不同的機(jī)器?，F(xiàn)在，除了平鋼帶、橡皮帶、塑料帶和布帶外，一些皮革做的皮帶還在使用。輕質(zhì)薄型平皮帶在高速機(jī)械上很實(shí)用，因?yàn)檫@里振動(dòng)可能是一個(gè)問題。V belts are probably the most common means of transmitting power between electric motor and driven machinery. Conventional V belts are made of

29、 rubber. Most often, both driver and driven pulleys lie in the same vertical plane, and the speed ration is constant.三角皮帶大概是在電動(dòng)機(jī)與從動(dòng)機(jī)械之間傳遞動(dòng)力的最為普通的手段。普通的三角皮帶用橡皮制造。通常，主動(dòng)輪與從動(dòng)輪位于同一個(gè)垂直面上，速比是恒定的。Smooth flat belt and V belts depend on friction on the pulleys and some slippage isInherent in their operation.

30、Therefore, speed ratios are not precise. Most heavy dutypulleys are made of cast iron or formed steel.平皮帶和三角皮帶依靠在皮帶輪上的摩擦進(jìn)行傳動(dòng)，所以在傳動(dòng)中總是有一些滑動(dòng)，因此，速比就不精確。大多數(shù)大的皮帶輪是用鑄鐵和型鋼制造的。Note that the capacity of the belt drive is determined by the angle of wrap on the smaller pulley, and that this is particularly cri

31、tical for drives involving pullets of greatly differing size,special closely together. Screws have been used as fasteners for a long time . As indicated in the section on single machine, a screw acts with a wedging action and consists of a circular cylinder (or truncated cone) with a helical Groove

32、in it. When used for fastening, all screws are provided with means for applying a torque(twisting moment) to them; this may consist of a square of hexagonal head for a wrench, a head with a slot or a cross-shaped recess for a screwdriver, a cylindrical head with a recess fitting a special wrench, or

33、 a slot or recess on one end fitting a screwdriver or special wrench and no head.螺釘已經(jīng)被用來作為一種長期有效的緊固件。如本章的機(jī)床剖視圖，螺釘?shù)墓δ茴愃朴谝环N楔緊作用，由具有螺紋的圓柱體（或者圓錐體）組成。當(dāng)用于固定作用時(shí)，所有的螺釘都提供了一種施加扭矩的方式，這些方式有用于扳手的等邊六角形，用于改錐的一字槽或者十字槽，用于配合特殊扳手的圓頭凹槽，或者甚至沒有螺釘頭但配合特殊改錐或特殊扳手的槽或凹坑。Screws with screwdriver slots have heads of several shap

34、es, such as flat, oval round, and fillister(cylindrical with a round top). Wood screws are tapered, and self-tappingscrews have tapered ends and a variety of special points. The latter are usually hardened and cut or form a mating internal thread when screwed into the proper size hole.Screws with he

35、xagonal heads are usually known as cap screws . Screws with other types of heads are also known as cap screws in the larger sizes and as machine screws in the small sizes. All of these screws are used to clamp machine parts together when one of the parts has an internal thread. If neither part is th

36、readed ，a bolt must be used: this consist of screw with a hexagonal head, a Nut (hexagonal ring with an internal thread), and usually a washer(flat 扁 ring).帶有六角形頂端的螺釘通常稱為有頭螺釘。這類螺釘用于當(dāng)零件之一有內(nèi)螺紋時(shí)把機(jī)器的零件加緊在一起。如果零件上未切出螺紋，則必須使用螺栓。螺栓由帶有六角形頂端的螺釘、螺母（是一個(gè)有內(nèi)螺紋的六角環(huán)）、通常還有一個(gè)墊圈組成。In operation, shafts are subjected to

37、 a shearing stress , whose magnitude depends on the torque and the dimensions of the cross section. This stress is a measure of the resistance that the shaft material offers to the applied torque. All shafts that transmit a torque are subjected to torsional shearing stress .軸在轉(zhuǎn)動(dòng)時(shí)承受剪應(yīng)力，其大小取決于扭轉(zhuǎn)和斷面的尺寸

38、。這個(gè)剪應(yīng)力是軸的材料對(duì)作用扭矩所產(chǎn)生的抗力的一種量度。所有傳遞扭矩的軸都承受扭轉(zhuǎn)剪應(yīng)力。In addition to the shearing stresses, twisted 扭曲shafts are also subjected to shearingdistortions. The distorted state is usually defined by the angle of twist per unitlength, i.e., the rotation of one cross section of a shaft relative to another cross sec

39、tion at a unit distance from it.軸的某一截面相對(duì)于間隔一個(gè)單位長度的另一截面的旋轉(zhuǎn)角度。除剪應(yīng)力之外，傳遞扭轉(zhuǎn)的軸還會(huì)產(chǎn)生剪切變形。扭轉(zhuǎn)的狀態(tài)通常用每單位長度的扭轉(zhuǎn)角來表示，即用軸的某一截面所轉(zhuǎn)過的角度來表示。A coupling is a device for connecting the ends of adjacent shafts. In machine construction, couplings are used to effect a semipermanent connection between adjacent rotating shaft

40、s. The connection is permanent in the sense that it is not meant to be broken during the useful life of the machine, but it can be broken and restored in an emergency or when worn parts are replaced.聯(lián)軸器是一種聯(lián)接兩根相鄰軸末端的裝置。機(jī)械構(gòu)件中，聯(lián)軸器可以用來實(shí)現(xiàn)相鄰兩根旋轉(zhuǎn)軸的半永久性聯(lián)接。在機(jī)器的正常使用周期內(nèi)，聯(lián)軸器通常不必拆開，在這個(gè)意義上可以說聯(lián)軸器的聯(lián)接是永久性的，而在緊急情況下或者

41、需要更換已磨損的零件時(shí)，可先把聯(lián)軸器拆開并重新聯(lián)接上。There are several types of shaft couplings; their characteristics depend on the purposefor which they are used. If an exceptionally long shaft is required for a line shaft in amanufacturing plant or a propellershaft on a ship, it is made in sections that are coupled togeth

42、er with rigid couplings. A common type of rigid coupling consists of two mating radial flanges(disks) that are attached by key-driven hubs to the ends of adjacent shaft sections and bolted together through the flanges to form a rigid connection. Alignment of the connected shafts is usually effected

43、by means of a rabbet joint on the face of the flanges, i.e., a short cylindrical projection on the face of one flange fits snugly in a circular recess on the face of the other flange。聯(lián)軸器有幾種類型，其特性隨其用途而定。如果制造廠中或者船舶的螺旋槳需要一根特別長的軸時(shí)，可以分段制造，然后采用剛性聯(lián)軸器將這些軸聯(lián)接起來。常用的剛性聯(lián)軸器包括兩個(gè)匹配的徑向法蘭（盤），他們是通過靠鍵傳動(dòng)的輪轂來連接到相鄰兩軸的兩端，然

44、后用螺栓穿過法蘭聯(lián)接起來形成了剛性聯(lián)接。相互聯(lián)接的兩軸是靠法蘭面上的槽口來對(duì)準(zhǔn)的，也就是說，在其中一個(gè)法蘭面上的短圓柱上的凸起部分與另一個(gè)法蘭面上的圓形凹進(jìn)部分相互緊貼。In connecting shafts belonging to separate devices (such as an electric motor and a gear-box), precise aligning of the shafts is difficult and a flexible coupling is used. This coupling connects the shafts in such a

45、 way as to minimize the harmful effects of shaft misalignment.Flexible couplings also permit the shafts to deflect under their separate systems of loads and to move freely (float) in the axial direction without interfering with one another. Flexible couplings can also serve to reduce the intensity o

46、f shock loads and vibrations transmitted from one shaft to another.在把兩個(gè)屬于不同設(shè)備（如電機(jī)和變速箱）的軸聯(lián)接起來時(shí)，要把這些軸精確對(duì)準(zhǔn)是很困難的，因此可以采用彈性聯(lián)軸器。采用這種聯(lián)軸器聯(lián)接兩軸時(shí)，可以把由于軸聯(lián)接中軸線不重合所造成的損害降到最小。彈性聯(lián)軸器還可允許被聯(lián)接的軸在各自載荷系統(tǒng)中偏斜和在軸向上自由移動(dòng)（浮動(dòng)），而不相互干擾。彈性聯(lián)軸器還能用來減小從一根軸傳到另一根軸的沖擊載荷和振動(dòng)強(qiáng)度。A clutch is a device for quickly and easily connecting or discon

47、necting a rotatable shaft and a rotating coaxialkEu5AksEl shaft. Clutches are usually placed between the input shaft to a machine and the output shaft from the driving motor, and provide a convenient means for starting and stopping the machine and permitting the driver motor or engine to be started

48、in an Unloaded state.離合器是一個(gè)用來使從動(dòng)軸與位于同一軸線上的主動(dòng)軸進(jìn)行快速和順利的聯(lián)接或脫開的裝置。離合器通常位于機(jī)器的輸入軸和驅(qū)動(dòng)電機(jī)的輸出軸之間，以提供一個(gè)方便地啟動(dòng)和停止機(jī)器的手段，并使得驅(qū)動(dòng)電機(jī)或發(fā)動(dòng)機(jī)在無荷載的狀態(tài)下啟動(dòng)。The rotor (rotating member) in an electric motor has rotational inertia, and a torque is required to bring it up to speed when the motor is started. If the motor shaft is r

49、igidly connected to a load with a large rotational inertia, and the motor is started suddenly by closing a switch, the motor may not have sufficient torque capacity to bring the motor shaft up to speed before the windings in motor are burned out by the excessive current demands. A clutch between the motor and the load shafts will restrict the starting torque on the motor to that required to accelerate the rotor and parts of the clutch only.電機(jī)中的轉(zhuǎn)子有轉(zhuǎn)動(dòng)慣量，當(dāng)電機(jī)啟動(dòng)時(shí)需要一