外文翻譯--汽車發(fā)動機凸輪軸

1、<p>　　Automotive engine camshaft</p><p>　　Brief introduction</p><p>　　The camshaft is a part of the piston engine. Its role is to control the opening and closing operation of the valve. Alt

2、hough the camshaft rotational speed in a four-stroke engine is a half of the crankshaft (the same as the camshaft rotational speed in a two-stroke engine with the crankshaft), but usually it is still very high speed, but

3、 also need to withstand the large torque, so the design right demanding camshaft in terms of strength and support material is generally a special cast iron, occa</p><p><b>　　Structure</b></p&g

4、t;<p>　　The main body of the camshaft is the same as the one with the cylinder length of the cylindrical rod. The above sets have several cam for driving the valve. One end of the camshaft camshaft bearing support

5、 and the other end is connected to the drive wheels.</p><p>　　Cam side was egg-shaped. The design aims to ensure the the cylinder sufficient air intake and exhaust, specifically, within the shortest possible

6、 time to complete the valve opening and closing movements. In addition, taking into account the durability of the engine and the smoothness of operation, the valve can not be generated due to the deceleration process of

7、opening and closing movements too much too large the impact of serious wear and tear of the valve, otherwise it will cause an increase </p><p>　　Generally inline engine, a cam corresponding to a valve V-type

8、 engine or horizontal opposed type engine, every two valves share a cam. The rotary engine the valveless with gas engine because of its special structure, does not need to cam</p><p><b>　　Position</

9、b></p><p>　　In the long period of time, the bottom-mounted camshaft in an internal combustion engine is most common. Typically such engines, the valve is located in the top of the engine camshaft machine,

10、 i.e., so-called the OHV (Over Head Valve, OHV) engines. Usually camshaft located on the side of the crankcase, through the gas distribution agencies (such as tappet, push rod, rocker, etc.) valve control. Bottom-mounted

11、 camshaft general also called side-mounted camshaft. Far distance valve, and each cylind</p><p>　　Now most of the production car's engine is equipped with overhead camshaft. The overhead camshafts struct

12、ure closer to the camshaft valve, to reduce the kinetic energy of the waste caused by the bottom-mounted camshaft due to the larger distance between the camshaft and the valve shuttle. Overhead camshaft of the engine val

13、ve opening and closing action is relatively rapid, and hence higher speed, and the smooth running is also better. The engine of the the overhead camshafts structure appeared e</p><p>　　Classification</p&g

14、t;<p>　　According to the the camshaft number of how many, can be divided into single overhead camshaft (SOHC) and double overhead camshaft (DOHC), two kinds. The single overhead camshaft camshaft is only one camsh

15、aft, double overhead camshaft is two, this is too straightforward explanation.</p><p>　　The single overhead camshaft with a camshaft in the cylinder head, direct drive into the exhaust valve, it has a simple

16、 structure, suitable for high-speed engine. Generally used in the past side camshaft, the camshaft in the cylinder side, is driven directly by a timing gear. The valve lifter to the rotation of the camshaft is converted

17、into reciprocating motion of the valve must be used to transfer power. Thus, more parts of the reciprocating motion, the inertial mass, is not conducive to high-</p><p>　　DOHC cylinder head equipped with two

18、 camshafts, one is used to drive the intake valve, the other for driving the exhaust valve. Double overhead camshaft camshaft and valve spring design less demanding, especially for the hemispherical combustion chamber of

19、 the valve V-shaped configuration, but also facilitate and used in conjunction with four-valve gas distribution agencies.</p><p><b>　　Fault</b></p><p>　　Camshaft common faults includ

20、ing abnormal wear and tear, abnormal wear of the symptoms often first appear before the occurrence of abnormal sound as well as fracture, abnormal sound and fracture. </p><p>　　(1) Camshaft almost at the end

21、 of the engine lubrication system, lubrication situation is not optimistic. If the oil pump is too long and so insufficient oil pressure or the lubricants Road blockage caused by lubricating oil can not reach the camshaf

22、t bearing cap fastening bolts tightening torque caused by excessive oil can not enter the the camshaft gap will causing abnormal wear of the camshaft.</p><p>　　(2) the abnormal wear of the camshaft causes th

23、e gap increases between the camshaft bearing, the camshaft movement occurs when the axial displacement, resulting in abnormal noise. Abnormal wear will lead to increased gap between the drive cam with hydraulic tappets,

24、cam combined with hydraulic tappets will collide, resulting in abnormal noise.</p><p>　　(3) camshaft sometimes fracture and other serious fault, common causes of hydraulic tappet cracked or severely worn, se

25、rious poor lubrication the camshaft poor quality and camshaft timing gear rupture.</p><p>　　(4) In some cases, the failure of the camshaft is man-made causes, in particular the maintenance of the engine cams

26、haft not correct disassembly. Such as demolition of the camshaft bearing caps with a hammer strength knocking or prying with a screwdriver, or install the bearing cap installed the wrong position does not match the resul

27、t in the bearing cap and bearing, or bearing cover the fastening bolt tightening torque is too large. Install bearing cap should pay attention to the direction of th</p><p><b>　　Refit</b></p&g

28、t;<p>　　In order to enhance the power of the engine, some converted stores a modified camshaft engine face lift high angle camshaft (Hi-camshaft CAM) is a common form of modified method. This modification operatio

29、n is not complicated, but because of the lack of understanding of some modification cam on the camshaft angle and works so that the modified effect is not obvious even lead to the deterioration of the performance of the

30、engine.</p><p>　　High angle camshaft relative to ordinary camshaft cam angle of about 240°, high angle camshaft cam angle can often reach over 280°. The large angle of the camshaft can extend the v

31、alve open time, increase the valve lift, the intake valve and the exhaust valve open as early and late off, so that more air into the cylinder, in order to improve the engine, the power of the high speed output. Should c

32、hoose for civilian vehicles, modified cam camshaft angle 278, will be a significant increase in work</p><p>　　Production technology</p><p>　　The camshaft is one of the key parts of the engine, t

33、he hardness of the camshaft peach apical and white layer depth is to determine the key technical indicators camshaft life and engine efficiency. , Should be considered to ensure that the cam has a sufficiently high hardn

34、ess and a fairly deep white layer premise journal does not appear high carbide, so that it has a better cutting performance.</p><p>　　Currently, the main method of domestic and foreign production camshaft: s

35、teel forging blank by cutting the cam peach tip martensitic layer formed some of the high-frequency quenching process. The end of the 1970s, Germany and France have developed a new camshaft argon arc remelting process; h

36、ardened cast iron camshaft otherwise dominated by the United States; chilled cast iron camshaft mainly to Japan and France; well cam parts of the Cr-Mn-Mo alloy coatings casting surface alloying production.</p>&l

37、t;p><b>　　汽車發(fā)動機凸輪軸</b></p><p><b>　　簡介</b></p><p>　　凸輪軸是活塞發(fā)動機里的一個部件。它的作用是控制氣門的開啟和閉合動作。雖然在四沖程發(fā)動機里凸輪軸的轉速是曲軸的一半（在二沖程發(fā)動機中凸輪軸的轉速與曲軸相同），不過通常它的轉速依然很高，而且需要承受很大的扭矩，因此設計中對凸輪軸在強度和支

38、撐方面的要求很高，其材質一般是特種鑄鐵，偶爾也有采用鍛件的。由于氣門運動規(guī)律關系到一臺發(fā)動機的動力和運轉特性，因此凸輪軸設計在發(fā)動機的設計過程中占據著十分重要的地位。</p><p><b>　　構造</b></p><p>　　凸輪軸的主體是一根與汽缸組長度相同的圓柱形棒體。上面套有若干個凸輪，用于驅動氣門。凸輪軸的一端是軸承支撐點，另一端與驅動輪相連接。　　<

39、;/p><p>　　凸輪的側面呈雞蛋形。其設計的目的在于保證汽缸充分的進氣和排氣，具體來說就是在盡可能短的時間內完成氣門的開、閉動作。另外考慮到發(fā)動機的耐久性和運轉的平順性，氣門也不能因開閉動作中的加減速過程產生過多過大的沖擊，否則就會造成氣門的嚴重磨損、噪聲增加或是其它嚴重后果。因此，凸輪和發(fā)動機的功率、扭矩輸出以及運轉的平順性有很直接的關系?！　?lt;/p><p>　　一般來說直列式發(fā)動機中

40、，一個凸輪都對應一個氣門，V型發(fā)動機或水平對置式發(fā)動機則是每兩個氣門共享一個凸輪。而轉子發(fā)動機和無閥配氣發(fā)動機由于其特殊的結構，并不需要凸輪。</p><p><b>　　位置</b></p><p>　　在以前很長的一段時間里，底置式凸輪軸在內燃機中最為常見。通常這樣的發(fā)動機中，氣門位于發(fā)動 機的頂部，即所謂的OHV（Over Head Valve，頂置氣門）式發(fā)

41、動機。此時通常凸輪軸位于曲軸箱的側面，通過配氣機構（如挺桿、推桿、搖臂等）對氣門進行控制。因此底置式凸輪軸一般也叫側置式凸輪軸。由于在這樣的發(fā)動機中凸輪軸距離氣門較遠，而且每個氣缸通常只有兩個氣門，因此轉速通常較慢，平順性不佳，輸出功率也比較低。不過這種結構的引擎輸出扭矩和低速性能比較出色，結構也比較簡單，易于維修?！　‖F在大多數量產車的發(fā)動機配備的是頂置式凸輪軸。頂置式凸輪軸結構使凸輪軸更加接近氣門，減少了底置式凸輪軸由于凸輪軸和氣門

42、之間較大的距離而造成的往返動能的浪費。頂置式凸輪軸的發(fā)動機由于氣門開閉動作比較迅速，因而轉速更高，運行的平穩(wěn)度也比較好。較早出現的頂置式凸輪軸結構的發(fā)動機是SOHC（Single Over Head Cam，頂置單凸輪軸）式發(fā)動機。這種發(fā)動機在頂部只安裝了一根凸輪軸，因此一般每個汽缸只有兩到三個氣門（進氣一到兩個，排氣一個），高速性能受到了限制。而技術更新一些的則是DOHC式（Double O</p><p>&

43、lt;b>　　分類</b></p><p>　　按凸輪軸數目的多少，可分為單頂置凸輪軸(SOHC)和雙頂置凸輪軸(DOHC)兩種。單頂置凸輪軸就是 只有一根凸輪軸，雙頂置凸輪軸就是有兩根，這是太直白的解釋?！　?lt;/p><p>　　單頂置凸輪軸在氣缸蓋上用一根凸輪軸，直接驅動進、排氣門，它具有結構簡單，適用于高速發(fā)動機。以往一般采用的側置凸輪軸，即凸輪軸在氣缸側面，由正

44、時齒輪直接驅動。為了把凸輪軸的轉動變換為氣門的往復運動，必須使用氣門挺桿來傳遞動力。這樣，往復運動的零件較多，慣性質量大，不利于發(fā)動機高速運動。而且，細長的挺桿具有一定的彈性，容易引起振動，加速零件磨損，甚至使氣門失去控制?！　?lt;/p><p>　　頂置雙凸輪軸是在缸蓋上裝有兩根凸輪軸，一根用于驅動進氣門，另一根用于驅動排氣門。采用雙頂置凸輪軸對凸輪軸和氣門彈簧的設計要求不高，特別適用于氣門V形配置的半球形燃燒室

45、，也便于和四氣門配氣機構配合使用。</p><p><b>　　傳動</b></p><p>　　底置式凸輪軸通常采用星形齒輪組（即所謂的“控制輪”），輥子鏈或齒條與曲軸相連。為了控制噪聲，直徑較大的凸輪軸端傳動輪通常由塑料或者輕金屬制造，而相對直徑較小的曲軸端傳動輪則大多采用鋼材。 </p><p>　　鏈條連接也比較多見。這種方式在底置式

46、和頂置式凸輪軸上都可以看到。為了減小噪聲（一般是鏈條在運動中產生的“振擺噪聲”），通常還會附帶一個液壓壓緊裝置和塑料材質的導軌。　　</p><p>　　頂置式凸輪軸結構中比較多見的是用一個塑料齒條鏈連接。這個齒條鏈位于發(fā)動機機油腔外，附帶有鋼質的嵌入部件，通過一個可調的輥子幫助張緊?！　?lt;/p><p>　　還有一種結構由于動力在傳輸過程中損耗過大且過于復雜，現在已經比較少見。這種結構通

47、過一個偏心連桿、星形齒輪組或帶中間軸的錐形齒輪組來連接頂置式凸輪軸與曲軸?！　⊥馆嗇S與曲軸之間的常見傳動方式包括齒輪傳動、鏈條傳動以及齒形膠帶傳動。下置凸輪軸和中置凸輪軸與曲軸之間的傳動大多采用圓柱形正時齒輪傳動，一般從曲軸到凸輪軸只需要1對齒輪傳動，如果傳動齒輪直徑過大，可以再增加1個中間惰輪。為了嚙合平穩(wěn)并降低工作噪聲，正時齒輪大多采用斜齒輪?！　?lt;/p><p>　　鏈條傳動常見于頂置凸輪軸與曲軸之間，但其

48、工作可靠性和耐久性不如齒輪傳動。近年來在高轉速發(fā)動機上廣泛使用齒形膠帶代替?zhèn)鲃渔湕l，但在一些大功率發(fā)動機上仍然使用鏈條傳動。齒形膠帶具有工作噪聲小、工作可靠以及成本低等特點。對于雙頂置凸輪軸，一般是排氣凸輪軸通過正時齒形膠帶或鏈條由曲軸驅動，進氣凸輪軸通過金屬鏈條由排氣凸輪軸驅動，或進氣凸輪軸和排氣凸輪軸均由曲軸通過齒形膠帶或鏈條驅動?！　?lt;/p><p>　　安裝凸輪軸時，一定要注意凸輪軸帶輪或鏈輪上的正時標記

49、。有些發(fā)動機沒有明顯的正時標記，維修人員可以在拆卸凸輪軸之前標記出曲軸和凸輪軸的準確位置，有些發(fā)動機則是需要專用工具才能進行正時的調校。</p><p><b>　　故障</b></p><p>　　凸輪軸的常見故障包括異常磨損、異響以及斷裂，異響和斷裂發(fā)生之前往往先出現異常磨損的癥狀。 </p><p>　　凸輪軸幾乎位于發(fā)動機潤滑系統(tǒng)的末

50、端，因此潤滑狀況不容樂觀。如果機油泵因為使用時間過長等原因出現供油壓力不足，或潤滑油道堵塞造成潤滑油無法到達凸輪軸，或軸承蓋緊固螺栓擰緊力矩過大造成潤滑油無法進入凸輪軸間隙，均會造成凸輪軸的異常磨損。　　 凸輪軸的異常磨損會導致凸輪軸與軸承座之間的間隙增大，凸輪軸運動時會發(fā)生軸向位移，從而產生異響。異常磨損還會導致驅動凸輪與液壓挺桿之間的間隙增大，凸輪與液壓挺桿結合時會發(fā)生撞擊，從

51、而產生異響。　　</p><p>　　凸輪軸有時會出現斷裂等嚴重故障，常見原因有液壓挺桿碎裂或嚴重磨損、嚴重的潤滑不良、凸輪軸質量差以及凸輪軸正時齒輪破裂等?！　?lt;/p><p>　　有些情況下，凸輪軸的故障是人為原因引起的，特別是維修發(fā)動機時對凸輪軸沒有進行正確的拆裝。例如拆卸凸輪軸軸承蓋時用錘子強力敲擊或用改錐撬壓，或安裝軸承蓋時將位置裝錯導致軸承蓋與軸承座不匹配，或軸承蓋緊固螺栓擰緊

52、力矩過大等。安裝軸承蓋時應注意軸承蓋表面上的方向箭頭和位置號等標記，并嚴格按照規(guī)定力矩使用扭力扳手擰緊軸承蓋緊固螺栓。</p><p><b>　　改裝</b></p><p>　　為了提升發(fā)動機的動力，有些改裝店對發(fā)動機的凸輪軸進行了改裝，其中換裝高角度凸輪軸（Hi－CAM）是常見的一種改裝方法。這種改裝操作并不復雜，但由于一些改裝人員對凸輪軸上凸輪的工作角度和工作

53、原理了解不足，使得改裝后的效果并不明顯甚至導致發(fā)動機的性能惡化?！　?lt;/p><p>　　高角度凸輪軸是相對于普通凸輪軸的240°左右的凸輪工作角度而言的，高角度凸輪軸的凸輪工作角度通常可以達到280°以上。大角度的凸輪軸可以延長氣門的開啟時間，增大氣門的升程，使進氣門和排氣門實現早開和晚關，使更多空氣進入氣缸，以提高發(fā)動機中、高轉速的動力輸出。對于民用車來說，改裝時應該選擇凸輪工作角度在27

54、8°以下的凸輪軸，因為工作角度大于278°的凸輪軸會大幅度增加氣門重疊角，使發(fā)動機高轉速時的動力提升很多，但發(fā)動機在低轉速時會因為氣缸密封性不好而導致怠速嚴重抖動甚至熄火，這樣的車輛無法適應日常使用，而只能用于競賽用途。</p><p><b>　　生產技術</b></p><p>　　凸輪軸是發(fā)動機的關鍵零件之一，凸輪軸桃尖部位的硬度和白口層深度

55、是決定凸輪軸使用壽命和發(fā)動機效率的關鍵技術指標。在保證凸輪有足夠高的硬度和相當深的白口層的前提下，還應考慮軸頸不出現較高的碳化物，使其具有較好的切削加工性能。　　目前，國內外生產凸輪軸的主要方法有：采用鋼質鍛造毛坯經切削加工后，凸輪桃尖部分經高頻淬火形成馬氏體層的工藝。20世紀 70年代末，德國和法國相繼開發(fā)了凸輪軸氬弧重熔新工藝；另有以美國為主的可淬硬鑄鐵凸輪軸；以日本和法國為主的冷硬鑄鐵凸輪軸；以及凸輪部位用 Cr-Mn-Mo 合金