機械設計專業(yè)外文資料翻譯

1、<p><b>　　附錄A</b></p><p><b>　　齒輪</b></p><p>　　齒輪是直接接觸，成對工作的實體，在稱為齒的凸出物的連續(xù)嚙合作用下，齒輪能將運動和力從一個旋轉軸傳遞到另一個旋轉軸，或從一個軸傳遞到一個滑塊(齒條)。</p><p>　　齒形輪廓。齒輪的接觸面必須以一定的方向排齊，這

2、樣可以使得傳動是正向的，也就是傳遞的載荷不必依靠表面的摩擦作用進行傳遞。如處理直接接觸的實體一樣，要求垂直于表面的公法線不必經(jīng)過主動軸或從動軸的軸線。</p><p>　　和我們所知道的直接接觸的實體一樣，擺線和漸開線輪廓也都提供了一個正方向的驅動和一個均勻的速度比，即共軛作用。</p><p>　　基本關系式。一對齒輪中較小的齒輪稱為小齒輪，較大的齒輪稱為大齒輪，當小齒輪安裝在傳動軸上，

3、則這對齒輪用作減速器；反之，若大齒輪安裝在傳動軸上，則這對齒輪用作加速器。齒輪一般經(jīng)常用于減速而不是加速。</p><p>　　如果齒輪有 N 個齒，并以每分鐘 n 轉的速度旋</p><p>　　轉，乘積 N* n 表示的是每分鐘旋轉的齒數(shù)，如果每個齒都是通過嚙合作用傳動另一個齒輪，那么這個乘積對于一對嚙合齒輪的兩個齒輪來說是相等的。 </p><p>　　對于各

4、種不同類型的共軛齒輪，齒輪比和速度比都可以通過大齒輪和小齒輪上的齒數(shù)比獲得。如果一個大齒輪的齒數(shù)為100，小齒輪的齒數(shù)為20，齒數(shù)比為 100/20=5。這樣不管大齒輪的旋轉速度為多少，小齒輪的旋轉速度總是大齒輪旋轉速度的 5 倍。大小齒輪的接觸點稱為節(jié)點，由于節(jié)點位于中心線上，因此節(jié)點是齒形輪廓線上唯一做純滾動接觸的點。非平行的齒輪，非交叉?zhèn)鲃拥妮S也有節(jié)圓，但是不存在純滾動節(jié)圓概念。</p><p>　　齒輪的

5、類型在很大程度上由軸的不同排列決定，另外，即使速度發(fā)生改變，原有類型的齒輪傳動一般來說也肯定好于采用其他類型的齒輪傳動。這就意味著當軸的排列布置形</p><p>　　式?jīng)Q定后，齒輪的類型或多或少也就定下來了。另一方面，如果齒輪的速度變化及類型一定的話，那么軸的排列布置形式基本上也就定下來了。</p><p>　　直齒輪和螺旋齒輪。齒形輪廓是直的并且平行于傳動軸的齒輪稱為直齒輪，直齒輪只

6、能用于連接平行軸。</p><p>　　如果一個漸開線直齒小齒輪是用橡皮制成的，能均勻扭曲，從而一端會繞另一端為軸進行旋轉，這樣小齒輪上的齒開始將是直的并行于傳動軸，最后會變成螺旋形。</p><p>　　蝸桿和傘形齒輪。為了得到線接觸和改進螺旋齒輪的橫向軸向的傳動載荷能力，大齒輪可能被做成彎曲形狀以圍繞小齒輪，有時類似于螺帽套在螺釘上，這樣的結果就是圓柱</p><p

7、>　　形的蝸輪蝸桿。蝸桿有時也做成沙漏形狀，而非圓柱狀，目的是為了使蝸桿部分接觸蝸輪，結果可以進一步增高承載能力。</p><p>　　蝸輪蝸桿是用一對齒輪就可以提供較大速度比的最簡單方法，但是蝸輪蝸桿的傳動總是比平行軸傳動的齒輪效率更低，因為沿著齒面方向存在滑動現(xiàn)象。</p><p><b>　　V 形帶</b></p><p>　　人

8、造纖維和橡膠V 形帶廣泛應用于動力傳送。V 形帶一般做成兩個系列：標準V 形帶和重型V 形帶。V 形帶能用于傳動的中心距離較短的場合，能做成無縫的，因此避免了連</p><p><b>　　接設備的麻煩。</b></p><p>　　首先，V 形帶成本低，通過并排增加V 形帶的數(shù)量可以增加傳動的功率，傳動中的所有 V 形帶被拉伸相同的長度的目的是為了保持每條 V 形帶

9、中載荷均勻。當一條 V 形帶斷裂時，通常所有V 形帶都被調(diào)換。帶輪可以是從上到下以一個任意角度傳動的。由于V 形帶工作在一個相對小的帶輪中，因此采用一個帶輪就可以進行較大的減速。</p><p>　　其次，帶輪槽的傾斜角度通常為 34°到38°。V 形帶在槽中的嵌入作用可以大大增加 V 形帶的牽引力。</p><p>　　第三，帶輪可以用鑄鐵、鋼、鍛壓等材料制成。在帶輪

10、槽的底部需要留有足夠的間隙，以保證V 形帶不接觸帶輪槽的底部，因為那樣的話容易磨損。有時較大的帶輪沒有輪槽，這時靠帶的內(nèi)表面來獲得牽引力，從而帶輪上加工槽的成本可以省下來。帶輪運行一定時間后槽的寬度可以調(diào)節(jié)，這樣帶輪的節(jié)距是變化的，因此需要進行適當?shù)恼{(diào)整以滿足速度比的要求。</p><p><b>　　鏈傳動</b></p><p>　　第一條鏈傳動或稱為“安全”自行

11、車出現(xiàn)在 1874 年，那時，鏈用于驅動早期自行車的后輪。今天，隨著現(xiàn)代設計和制造方法的改進，鏈傳動越來越比原來的傳動應用得更有效和廣泛，已經(jīng)極大地提高了農(nóng)業(yè)機械、鉆探設備、礦業(yè)和建筑機械的效率，大約從 1930 年以來，鏈傳動已經(jīng)變得日益普遍，尤其是在動力鋸子、摩托車和自動扶梯等設備上。</p><p>　　有至少 6 種類型的動力傳送的鏈，本文介紹其中的 3 種，分別命名為滾柱鏈條、齒型鏈條或低噪音鏈條和滾子

12、鏈條。滾柱鏈條傳動的基本組成部分有側板、銷軸、套筒、滾柱、兩個或多個鏈輪，每個鏈輪上有類似齒輪形狀的齒。滾柱鏈條是用銷軸和滾柱等進行裝配而成的，用兩個銷軸插入兩個側板中的孔可以連接兩邊側板，銷軸緊緊地插入孔中，形成壓緊連接，滾柱是由兩個側板和兩個壓緊的套筒組成的，硬的鋼質(zhì)滾柱可以自由地轉動。當全部裝配完成后，滾柱是一個組合件，可以相對于套筒輕松地轉動，這樣鏈條可以在鏈輪上傳動。 </p><p>　　標準滾柱鏈條

13、可以是單排的也可以是多排的，如果是多排的，那么兩條或多條鏈條一起連接在同一個銷軸上，這時要使?jié)L柱以一定的排列方式對齊，單個驅動的速度比一般控制在 10 ∶1 范圍內(nèi)，比較合適的軸中心距離一般為 30 到35 倍滾柱與滾柱之間的距離，鏈條速度一般不要超過每分鐘2500 英尺(每分鐘 800 米)。當幾個平行軸一起驅動時，滾柱鏈條傳動尤為合適。</p><p>　　齒型鏈條或低噪音鏈條基本上就是齒輪齒條的組合件，每個

14、齒條有兩個齒，軸向連接形成一個封閉的、內(nèi)面有齒的鏈條，鏈輪上有共軛齒。鏈條連接采用銷子連接平鋼板，平鋼板上通常是傾角為 60°的直齒，這是因為許多鏈條同時傳遞動力。相對于前面的滾柱鏈條來說，這種類型的鏈條噪音較低，能在較高速度下工作，同樣的寬度能傳遞更大的載荷。有時汽車就采用這種低噪音的凸輪軸驅動的鏈條。</p><p>　　滾子鏈條提供了一種在傳動的速度和動力相對較低時，用于連接平行或非平行軸價格便宜

15、且很靈活的方式。鏈輪含有球形或錐形凹槽的，滾子可以在凹槽內(nèi)活動，鏈條看上去像一串串鏈子一樣，用普通碳鋼、不銹鋼或實心的塑料滾子做在鏈條上，滾子鏈條用于計算機、空調(diào)、電視調(diào)諧器、百葉窗簾等場合，鏈輪可以是鋼、鍛壓或鑄造的鋅、或尼龍等。</p><p><b>　　附錄B</b></p><p><b>　　Gears</b></p>

16、<p>　　[1]Gears are direct contact bodies，operating in pairs，that transmit motion and force from one rotating shaft to another, or from a shaft to a slide (rack)，by means of successively engaging projections called t

17、eeth ．</p><p>　　Tooth profiles. The contacting surfaces of gear teeth must be aligned in such a way that the drive is positive；i.e., the load transmitted must not depend on frictional contact．As shown in the

18、 treatment of direct contact bodies，this requires that the common normal to the surfaces not to pass through the pivotal axis of either the driver or the follower.</p><p>　　As it is known as direct contact b

19、odies，cycloidal and involute profiles provide both a positive drive and a uniform velocity ratio ；i．e．，conjugate action．</p><p>　　Basic relations．The smaller of a gear pair is called the pinion and the large

20、r is the gear. When the pinion is on the driving shaft the pair acts as a speed reducer；When the gear drives，the pair is a speed increaser ．Gears are more frequently used to reduce speed than to increase it ．</p>

21、<p>　　If a gear having N teeth rotates at n revolutions per minute，the product N*n has the dimension “teeth per minute”. This product must be the same for both members of a mating pair if each tooth acquires a partn

22、er from the mating gear as it passes through the region of tooth engagement．</p><p>　　For conjugate gears of all types，the gear ratio and the speed ratio are both given by the ratio of the number of teeth on

23、 the gear to the number of teeth on the pinion．If a gear has 100 teeth and a mating pinion has 20，the ratio is l00/20=5． -Thus the pinion rotates five times as fast as the gear，regardless of the speed of the gear．Their p

24、oint of tangency is called the pitch point， and since it lies on the line of centers，it is the only point at which the tooth profiles have pure rolling contact</p><p>　　Gear types are determined largely by t

25、he disposition of the shafts；in addition，certain types are better suited than others for large speed changes．This means that if a specific disposition of the shafts is required，the type of gear will more or less be fixed

26、．On the other hand，if a required speed change demands a certain type，the shaft positions will also be fixed．</p><p>　　Spur gears and helical gears．A gear having tooth elements that are straight and parallel

27、to its axis is known as a spur gear．A spur pair can be used to connect parallel shafts only．</p><p>　　If an involute spur pinion were made of rubber and twisted uniformly so that the ends rotated about the a

28、xis relative to one another，the elements of the teeth，initially straight and parallel to the axis，would become helices．The pinion then in effect would become a helical gear．</p><p>　　Worm and bevel gears．In

29、order to achieve line contact and improve the load carrying capacity of the crossed axis helical gears，the gear can be made to curve partially around the pinion，in somewhat the same way that a nut envelops a screw．The re

30、sult would be a cylindrical worm and gear．Worms are also made in the shape of an hourglass, instead of cylindrical，so that they partially envelop the gear．This results in a further increase in load-carrying capacity． <

31、;/p><p>　　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 an additional sliding movement along th

32、e teeth ．</p><p><b>　　V-belt</b></p><p>　　The rayon and rubber V-belt are widely used for power transmission．Such belts are made in two series：the standard V-belt and the high capaci

33、ty V-belt．The belts can be used with short center distances and are made endless so that difficulty with splicing devices is avoided．</p><p>　　First，cost is low，and power output may be increased by operating

34、 several belts side by side．All belts in the drive should stretch at the same rate in order to keep the load equally divided among them. When one of the belts breaks, the group must usually be replaced. The drive may be

35、inclined at any angle with tight side either top or bottom. Since belts can operate on relatively small pulleys, large reductions of speed in a single drive are possible.</p><p>　　Second，the included angle f

36、or the belt groove is usually from 34°to 38°.The wedging action of the belt in the groove gives a large increase in the tractive force developed by the belt.</p><p>　　Third，pulley may be made of ca

37、st iron, sheet steel, or die-cast metal. [3]Sufficient clearance must be provided at the bottom of the groove to prevent the belt from bottoming as it becomes narrower from wear. Sometimes the larger pulley is not groove

38、d when it is possible to develop the required tractive force by running on the inner surface of the belt. The cost of cutting the grooves is thereby eliminated. Pulleys are on the market that permit an adjustment in the

39、width of the groove. The effec</p><p>　　Chain Drives</p><p>　　The first chain-driven or “safety” bicycle appeared in 1874, and chains were used for driving the rear wheels on early automobiles.

40、[4]Today, as the result of modern design and production methods, chain drives that are much superior to their prototypes are available, and these have contributed greatly to the development of efficient agricultural mach

41、inery, well-drilling equipment, and mining and construction machinery. Since about 1930 chain drives have become increasingly popular, especially fo</p><p>　　There are at least six types of power-transmissio

42、n chains; three of these will be covered in this article, namely the roller chain, the inverted tooth, or silent chain, and the bead chain. The essential elements in a roller-chain drive are a chain with side plates, pin

43、s, bushings (sleeves), and rollers, and two or more sprocket wheels with teeth that look like gear teeth. Roller chains are as sembled from pin links and roller links. A pin link consists of two side plates connected by

44、two pins in</p><p>　　Standard roller chains are available in single strands or in multiple strands, In the latter type, two or more chains are joined by common pins that keep the rollers in the separate stra

45、nds in proper alignment. The speed ratio for a single drive should be limited to about 10 ∶1; the preferred shaft center distance is from 30 to 35 times the distance between the rollers and chain speeds greater than abou

46、t 2500 feet (800 meters) per minute are not recommended. Where several parallel shafts are to </p><p>　　An inverted tooth, or silent chain is essentially an assemblage of gear racks, each with two teeth, piv

47、otally connected to form a closed chain with the teeth on the inside, and meshing with conjugate teeth on the sprocket wheels. The links are pin-connected flat steel plates usually having straight-sided teeth with an inc

48、luded angle of 60 degrees. As many links are necessary to transmit the power and are connected side by side. Compared with roller-chain drives, silent-chain drives are quieter, </p><p>　　Bead chains provide

49、an inexpensive and versatile means for connecting parallel or nonparallel shafts when the speed and power transmitted are low. The sprocket wheels contain hemispherical or conical recesses into which the beads fit. The c

50、hains look like key chains and are available in plain carbon and stainless steel and also in the form of solid plastic beads molded on a cord. Bead chains are used on computers, air conditioners, television tuners, and V