汽车发动机凸轮轴外文文献翻译@中英文翻译@#外文翻译

Automotive engine camshaft Brief introduction The camshaft is a part of the piston engine. Its role is to control the opening and closing operation of the valve. Although 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 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, occasionally using forgings. Valve motion law related to engine power and operation characteristics, the design in the design process of the engine camshaft occupies a very important position. Structure 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 and the other end is connected to the drive wheels. Cam side was egg-shaped. The design aims to ensure the the cylinder sufficient air intake and exhaust, specifically, within the shortest possible 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 opening and closing movements too much too large the impact of serious wear and tear of the valve, otherwise it will cause an increase in noise or other serious consequences. Therefore, the cam and the power of the engine torque output as well as the operation of the ride there is a direct relationship. Generally inline engine, a cam corresponding to a valve V-type 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 Position 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, 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 camshaft general also called side-mounted camshaft. Far distance valve, and each cylinder is usually only two valves in such an engine camshaft, so the speed is usually slower, ride comfort is poor, the output power is also relatively low. However, the engine output torque and low-speed performance of this structure is relatively good, relatively simple structure and easy maintenance. Now most of the production cars engine is equipped with overhead camshaft. The overhead camshafts structure 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 valve 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 earlier the SOHC (Single Over Head Cam, overhead single camshaft) engine. This engine is only installed at the top of a camshaft, and therefore generally only two to three valves of each cylinder (the intake air a to two exhaust), the high-speed performance has been limited. Technology updates DOHC (Double Over Head Cam, double overhead camshaft) engine, this engine with a two camshafts per cylinder can be installed four to five valves (intake two to three, Pai gas two), high-speed performance significantly improved, but at the same time the low-speed performance will be affected to some degree, the structure will be complicated and difficult to repair. Classification 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 camshaft, double overhead camshaft is two, this is too straightforward explanation. The single overhead camshaft with a camshaft in the cylinder head, direct drive into the exhaust valve, it has a simple 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 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-speed movement of the engine. Moreover, the slender tappet has a certain degree of flexibility, prone to vibration, accelerated component wear, even the valve control is lost. DOHC cylinder head equipped with two 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 the valve V-shaped configuration, but also facilitate and used in conjunction with four-valve gas distribution agencies. Fault Camshaft common faults including 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. (1) Camshaft almost at the end 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 camshaft bearing cap fastening bolts tightening torque caused by excessive oil can not enter the the camshaft gap will causing abnormal wear of the camshaft. (2) the abnormal wear of the camshaft causes the 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, cam combined with hydraulic tappets will collide, resulting in abnormal noise. (3) camshaft sometimes fracture and other serious fault, common causes of hydraulic tappet cracked or severely worn, serious poor lubrication the camshaft poor quality and camshaft timing gear rupture. (4) In some cases, the failure of the camshaft is man-made causes, in particular the maintenance of the engine camshaft 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 result 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 the arrow and the position number marked on the surface of the bearing cap, and in strict accordance with the provisions of torque using the torque wrench tighten the bearing cap fastening bolts. Refit 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 operation 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 engine. 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 valve 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 choose for civilian vehicles, modified cam camshaft angle 278, will be a significant increase in working an angle greater than 278 camshaft valve overlap angle, so that the power of the engine high speed improve a lot, but engine cylinder seal is not good at low speed and cause the idling serious jitter or even turn off, so that the vehicle can not adapt to everyday use, and can only be used for competition purposes. Production technology The camshaft is one of the key parts of the engine, the 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 hardness and a fairly deep white layer premise journal does not appear high carbide, so that it has a better cutting performance. Currently, the main method of domestic and foreign production camshaft: steel 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； hardened 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. 汽车发动机凸轮轴 简介 凸轮轴是 活塞 发动机里的一个部件。它的作用是控制气门的开启和闭合动作。虽然在 四冲程发动机 里凸轮轴的转速是 曲轴 的一半（在 二冲程发动机 中凸轮轴的转速与曲轴相同），不过通常它的转速依然很高，而且需要承受很大的 扭矩 ，因此设计中对凸轮轴在强度和支撑方面的要求很高，其材质一般是特种铸铁，偶尔也有采用锻件的。由于气门运动规律关系到一台发动机的动力和运转特性，因此凸轮轴设计在发动机的设计过程中占据着 十分重要的地位。 构造 凸轮轴的主体是一根与汽缸组长度相同的圆柱形棒体。上面套有若干个 凸轮 ，用于驱动气门。凸轮轴的一端是 轴承 支撑点，另一端与驱动轮相连接。 凸轮的侧面呈鸡蛋形。其设计的目的在于保证汽缸充分的进气和排气，具体来说就是在尽可能短的时间内完成气门的开、闭动作。另外考虑到发动机的耐久性和运转的 平顺性，气门也不能因开闭动作中的加减速过程产生过多过大的冲击，否则就会造成气门的严重磨损、噪声增加或是其它严重后果。因此，凸轮和发动机的功率、 扭矩 输出以及运转的平顺性有很直接的关系。 一般来说直列式发动机中，一个凸轮都对应一个气门， V 型发动机 或水平对置式发动机则是每两个气门共享一个凸轮。而 转子发动机 和无阀配气发动机由于其特殊的结构，并不需要凸轮。 位置 在以前很长的一段时间里，底置式凸轮轴在 内燃机 中最为常见。通常这样的发动机中，气门位于发动 机的顶 部，即所谓的 OHV（ Over Head Valve，顶置气门）式发动机。此时通常凸轮轴位于 曲轴箱 的侧面，通过 配气机构 （如挺杆、推杆、摇臂等）对气门进行控制。因此底置式凸轮轴一般也叫侧置式凸轮轴。由于在这样的发动机中凸轮轴距离气门较远，而且每个 气缸 通常只有两个气门，因此转速通常较慢，平顺性不佳，输出功率也比较低。不过这种结构的引擎输出扭矩和低速性能比较出色，结构也比较简单，易于维修。 现在大多数量产车的发动机配备的是顶置式凸轮轴。顶置式凸轮轴结构使凸轮轴更加接近气门，减少了底置式凸轮轴由于凸轮轴和气门之间较大的距离而造成的往返动能的浪费。顶置式凸轮轴的发动机由于气门开闭动作比较迅速，因而转速更高，运行的平稳度也比较好。较早出现的顶置式凸轮轴结构的发动机是 SOHC（ Single Over Head Cam，顶置 单凸轮轴 ）式发动机。这种发动机在顶部只安装了一根凸轮轴，因此一般每个汽缸只有两到三个气门（进气一到两个，排气一个），高速性能受到了限制。而技术更新一些的则是 DOHC 式（ Double Over Head Cam，顶置双凸轮轴）发动机，这种发动机由于配备了两根凸轮轴，每个 汽缸 可以安装四到五 个气门（进气二到三个，排气二个），高速性能得到了显著的提升，不过与此同时低速性能会受到一定的影响，结构也会变得复杂，不易维修。 分类 按凸轮轴数目的多少，可分为单顶置凸轮轴 (SOHC)和 双顶置凸轮轴 (DOHC)两种。单顶置凸轮轴就是 只有一根凸轮轴，双顶 置凸轮轴就是有两根，这是太直白的解释。 单顶置凸轮轴 在气缸盖上用一根凸轮轴，直接驱动进、排气门，它具有结构简单，适用于 高速发动机 。以往一般采用的侧置凸轮轴，即凸轮轴在气缸侧面，由正时齿轮直接驱动。为了把凸轮轴的转动变换为气门的往复运动，必须使用气门挺杆来传递动力。这样，往复运动的零件较多，惯 性质量大，不利于发动机高速运动。而且，细长的挺杆具有一定的弹性，容易引起振动，加速零件磨损，甚至使气门失去控制。 顶置双凸轮轴是在缸盖上装有两根凸轮轴，一根用于驱动进气门，另一根用于驱动排气门。采用双顶置凸轮轴对凸轮轴和气门弹簧的设计要求不高，特别适用于气门 V 形配置的半球形 燃烧室 ，也便于和四气门配气机构配合使用。 传动 底置式凸轮轴通常采用星形齿轮组（即所谓的 “控制轮 ”），辊子链或 齿条 与曲轴相连。为了控制噪声，直径较大的凸轮轴端传动轮通常由塑料或者轻金属制造，而相对直径较小的曲轴端传动轮则大多采用钢材。 链条连接也比较多见。这种方式在底置式和顶置式凸轮轴上都可以看到。为了减小噪声（一般是链条在运动中产生的 “振摆噪声 ”），通常还会附带一个液压压紧装 置和塑料材质的导轨。 顶置式凸轮轴结构中比较多见的是用一个塑料齿条链连接。这个齿条链位于发动机 机油腔外，附带有钢质的嵌入部件，通过一个可调的辊子帮助张紧。 还有一种结构由于动力在传输过程中损耗过大且过于复杂，现在已经比较少见。这种结构通过一个偏心连杆、星形齿轮组或带中间轴的锥形齿轮组来连接顶置式凸轮轴与曲轴。 凸轮轴与曲轴之间的常见传动方式包括齿轮传动、链条传动以及齿形胶带传动。下置凸轮轴和中置凸轮 轴与曲轴之间的传动大多采用圆柱形正时齿轮传动，一般从曲轴到凸轮轴只需要1 对齿轮传动，如果传动齿轮直径过大，可以再增加 1 个中间惰轮。为了啮合平稳并降低工作噪声，正时齿轮大多采用斜齿轮。 链条传动常见于顶置凸轮轴与曲轴之间，但其工作可靠性和耐久性不如齿轮传动。近年来在高转速发动机上广泛使用齿形胶带代替传动链条，但在一些大功率发动机上仍然使用链条传动。齿形胶带具有工作噪声小、工作可靠以及成本低等特点。对于双顶置凸轮轴，一般是排气凸轮轴通过正时齿形胶带或链条由曲轴驱动，进气凸轮轴通过金属链条由排气凸轮轴驱动，或 进气凸轮轴和排气凸轮轴均由曲轴通过齿形胶带