机械外文翻译连杆内燃机.docx

1、机械外文翻译连杆内燃机 毕业设计(论文)外文资料翻译系部： 机械工程系 专 业： 机械工程及自动化 姓 名： 学 号： 外文出处： http:/www.wikipedia.org/ 附 件： 1.外文资料翻译译文；2.外文原文。 指导教师评语： 签名： 年 月 日附件1：外文资料翻译译文连杆在活塞往复式发动机内，连杆连接着装在曲柄或曲轴上的活塞。巧妙的机械装置知识一书这样写道：“连杆发明于1174年至1200年的某个时候，当一个名为阿拉-贾扎里的穆斯林发明家、工程师和工匠，制造了5个机器来为土耳其阿尔图格王朝的一位国王泵水这些机器的其中之一就使用了连杆。将旋转运动转变成往复运动可能需要依靠连接

2、到曲柄上的连杆。”双作用往复活塞泵是第一个提供自动运动的机器，但其机构和其他如凸轮一类的机构也有助于工业革命的开启。内燃机在现代汽车内燃发动机里，用于发动机的连杆通常由钢制造，但也可以用铝（目的是为了减轻重量和获得在牺牲耐久度的条件下吸收强冲击的能力）或钛（目的是为了在需要支持力时提供一种既轻又有足够强度的组合）来制造高性能发动机的连杆，或使用铸铁，如制造摩托车连杆时就使用铸件。它们不会严格地固定于一端，于是当连杆作上下运动和绕曲柄旋转时连杆与活塞之间的夹角就发生改变。连杆较小的一端连接活塞销，活塞销（英国用语）或腕销，这通常会给连杆以经常性的压力，但连杆仍能相对于活塞转动即“浮动腕销”。连杆

3、的大端连接于曲柄上的轴颈处，并随着由连杆螺栓固定的可更换的轴瓦转动，螺栓将轴承“盖”固定在连杆的大端处;通常要钻一个通过轴瓦和连杆的大端小孔，以便使增压润滑油能喷到筒壁的一侧，来使活塞和活塞环的运动得到润滑。连杆承受着巨大的压力，这些压力来自于由活塞产生的循环载荷，而事实上这些压力来自于每次旋转时的拉伸与松弛，以及随发动机转速增大而急剧增大的载荷。一个失效的连杆，通常被称为“扔棒”，它是引起汽车引擎灾难性故障最常见的原因之一，经常使失效的连杆穿过曲轴轴箱的一侧，发动机会遭受无法弥补的损坏；它可能源于连杆的疲劳缺陷、轴瓦失去润滑而导致的失效，或源于连杆螺栓的缺陷、不适当的紧固，或重复利用已经使用

4、过的（已变形的）螺栓（这是不允许的）。尽管这些经常发生在竞争激烈的汽车运动中，但在为日常驾驶生产的汽车中，这种失效是十分罕见。这是因为汽车零部件的生产中要使用一个比较大的安全系数，同时往往还使用更系统的质量控制体系。当制造一个高性能发动机时，连杆应给予极大的关注，应采取一些技术来消除应力，例如磨削连杆的边缘以达到表面粗糙度的要求，喷丸以使表面产生压应力（防止裂纹萌生），装配时平衡所有连杆、活塞组合件的重量使每对的重量相同以及采用磁力探伤法来探测材料内部的微小裂纹，这些看不见的微小裂缝将会产生破坏应力造成连杆失效。此外，扭紧连杆螺栓时，应非常注意扭矩的大小；通常这些螺栓必须更换，而不是重复使用。

5、连杆的大端被制造成一个整体，并使其在机械加工之后能与大端轴瓦准确装配。因此，大端的“帽子”在连杆与连杆之间不具有互换性，而且当重新制造一个引擎时，必须小心，以确保不同连杆的轴瓦不被乱用。无论是连杆还是与其相配合的轴瓦，通常都会在发动机缸体上刻上相应的型号。目前有一些发动机（如福特的4.6升引擎，还比如克莱斯勒的2.0升引擎）其连杆采用粉末冶金技术制造，粉末冶金技术不仅能精确控制尺寸和重量以减少机械加工工作量而且还能减少额外的机械配平。轴瓦因挤压而与连杆分离，结果导致了不平滑的断裂面，这是由于粉末金属的颗粒造成的。这确保了重新装配后，轴瓦能与连杆精确地配合，而传统加工方法制造的连杆与轴瓦，只有当

6、两者的接触面表面的表面粗糙度都很小时才能达到较小的误差。发动机磨损的一个主要原因是由于曲轴通过连杆施加于活塞的侧向力，通常将汽缸磨成椭圆形截面，而不是圆形截面，因此不可能使活塞环与气缸侧壁紧密接触。从力学角度来说延长连杆的长度可相应地减少上述侧向力，这样一来会使引擎寿命延长。然而，对一已知的发动机缸体来说，连杆的长度加上活塞行程，其和是一个固定的值，这个固定值由曲轴和气缸座（气缸座用来固定活塞盖）顶部之间的固定距离来决定。因此，对一个已知的气缸而言能得到更长的行程，可提供更大的排量和功率。相反，较短的连杆（或较小压缩行程的活塞），会导致气缸加速地磨损。复合连杆众多多缸布局的发动机如V 12型发

7、动机几乎没有可用于在有限长度的曲轴上安装连杆轴颈的空间。这是一个难以调和的矛盾，而且若按普通的方式安装，其往往会导致发动机的失败。 最简单的解决办法是使用简单的连杆，这种最简单的方法通常用于汽车引擎。这就要求连杆轴瓦要更窄，但对于一个高性能的引擎来说其会增加轴瓦的负荷及失效的风险。这也意味着对置的气缸不完全位于一条直线上。在某些类型的引擎内，主动连杆带有一个或多个环形销，环形销用来连接其他气缸上的从动连杆相对小一些的大端。径向引擎的每一边通常是一个气缸有一个主动连杆，余下的其它气缸则配有从动连杆。对于确定设计的V形引擎，一对对置的气缸使用一对主/从动连杆。这样的一个缺点是，辅助连杆的行程稍微短

8、于主动连杆，从而使V形发动机产生更大的振动。高性能航空发动机的通常解决方案是使用一个“叉状”连杆。一个连杆在大端处一分为二，另一个变薄以与这个叉状连杆相配。轴颈仍然由多个气缸共用。劳斯莱斯默林发动机就使用这种形式。曲柄连杆机构的类型及特点内燃机中采用曲柄连杆机构的型式很多，按运动学观点可分为三类，即:中心曲柄连杆机构、偏心曲柄连杆机构和主副连杆式曲柄连杆机构。中心曲柄连杆机构的特点是气缸中心线通过曲轴的旋转中心，并垂直于曲柄的回转轴线。这种型式的曲柄连杆机构在内燃机中应用最为广泛。一般的单列式内燃机，采用并列连杆与叉形连杆的V形内燃机，以及对置式活塞内燃机的曲柄连杆机构都属于这一类。偏心曲柄连

9、杆机构的特点是气缸中心线垂直于曲轴的回转中心线，但不通过曲轴的回转中心，气缸中心线距离曲轴的回转轴线具有一偏移量e。这种曲柄连杆机构可以减小膨胀行程中活塞与气缸壁间的最大侧压力，使活塞在膨胀行程与压缩行程时作用在气缸壁两侧的侧压力大小比较均匀。主从连杆式曲柄连杆机构的特点是:内燃机的一列气缸用主动连杆，其它各列气缸则用从动连杆，这些连杆的下端不是直接接在曲柄销上，而是通过从动连杆销装在主连杆的大端上，形成了“关节式”运动，所以这种机构有时也称为“关节曲柄连杆机构”。在关节曲柄连杆机构中，一个曲柄可以同时套上几副连杆和活塞，这种结构可使内燃机长度缩短，结构紧凑，广泛地应用于大功率的坦克和机车用

10、V形内燃机。镗在机械加工，镗削加工的过程是一个扩孔的过程，这个孔可以是钻出来的（或铸造得到的），镗孔通过单点切削刀具（或一个镗头含有若干个这样的刀具）来加工，例如用镗削方法加工炮桶。镗削加工能使孔达到更精确的尺寸，而且还可以用于锥形孔的加工。 镗削有时也用于孔的加工。镗孔机对较小的镗削加工过程可以在车床上进行，但对于较大工件的加工则需要使用特殊的镗床（工件围绕一个垂直轴旋转）或卧式镗床（围绕水平轴旋转）。通过转动变换刀具的安装角度也可以加工锥形孔。 镗床（类似于铣床，如经典的范诺曼型）拥有多种尺寸和类型。工件直径通常是1 4米（ 3-12英尺） ，但也可达20米（六十英尺）。对电力的需求可高达

11、200匹马力。其控制系统可以以计算机为基础，允许自动控制和提高一体性。由于镗削加工可以降低产品上已有孔的公差，因此一些设计的注意事项必须得注意。首先，大的长径比是不希望的，因为这样会使刀具变形。其次，不能加工盲孔（孔的深度不超过工件的厚度）。中断的内部工作表面（即在刀具与加工表面间有不连续的接触）应该避免。装有刀头的镗杆是一个悬臂梁，必须有非常高的刚度。锻造 锻造是一种利用局部压力使金属成型的方法。冷锻是在室温下或接近室温下进行的锻造。热锻是在高温下进行，高温使金属更容易成形和降低断裂的可能性。温锻是在室温和热锻温度之间的温度下进行。锻造可对从不足1千克到170吨的工件进行加工。经锻造加工的零

12、部件通常还需作进一步处理，以便得到最终的产品。附件2：外文原文Connecting rodIn a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. The connecting rod was invented sometime between 1174 and 1200 when a Muslim inventor, engineer and craftsman named al-Jazari built five machine

13、s to pump water for the kings of the Turkish Artuqid dynasty one of which incorporated the connecting rod. Transferring rotary motion to reciprocating motion was made possible by connecting the crankshaft to the connecting rod, which was described in the Book of Knowledge of Ingenious Mechanical Dev

14、ices. The double-acting reciprocating piston pump was the first machine to offer automatic motion, but its mechanisms and others such as the cam, would also help initiate the Industrial Revolution.Internal combustion engines In modern automotive internal combustion engines, the connecting rods are m

15、ost usually made of steel for production engines, but can be made of aluminium (for lightness and the ability to absorb high impact at the expense of durability) or titanium (for a combination of strength and lightness at the expense of affordability) for high performance engines, or of cast iron fo

16、r applications such as motor scooters. They are not rigidly fixed at either end, so that the angle between the connecting rod and the piston can change as the rod moves up and down and rotates around the crankshaft.The small end attaches to the piston pin, gudgeon pin (the usual British term) or wri

17、st pin, which is currently most often press fit into the conrod but can swivel in the piston, a floating wrist pin design.The big end connects to the bearing journal on the crank throw, running on replaceable bearing shells accessible via the con rod bolts which hold the bearing cap onto the big end

18、; typically there is a pinhole bored through the bearing and the big end of the con rod so that pressurized lubricating motor oil squirts out onto the thrust side of the cylinder wall to lubricate the travel of the pistons and piston rings.The con rod is under tremendous stress from the reciprocatin

19、g load represented by the piston, actually stretching and relaxing with every rotation, and the load increases rapidly with increasing engine speed. Failure of a connecting rod, usually called throwing a rod is one of the most common causes of catastrophic engine failure in cars, frequently putting

20、the broken rod through the side of the crankcase and thereby rendering the engine irreparable; it can result from fatigue near a physical defect in the rod, lubrication failure in a bearing due to faulty maintenance, or from failure of the rod bolts from a defect, improper tightening, or re-use of a

21、lready used (stressed) bolts where not recommended. Despite their frequent occurrence on televised competitive automobile events, such failures are quite rare on production cars during normal daily driving. This is because production auto parts have a much larger factor of safety, and often more sys

22、tematic quality control.When building a high performance engine, great attention is paid to the con rods, eliminating stress risers by such techniques as grinding the edges of the rod to a smooth radius, shot peening to induce compressive surface stresses (to prevent crack initiation), balancing all

23、 con rod/piston assemblies to the same weight and Magnafluxing to reveal otherwise invisible small cracks which would cause the rod to fail under stress. In addition, great care is taken to torque the con rod bolts to the exact value specified; often these bolts must be replaced rather than reused.

24、The big end of the rod is fabricated as a unit and cut or cracked in two to establish precision fit around the big end bearing shell. Therefore, the big end caps are not interchangeable between con rods, and when rebuilding an engine, care must be taken to ensure that the caps of the different con r

25、ods are not mixed up. Both the con rod and its bearing cap are usually embossed with the corresponding position number in the engine block.Recent engines such as the Ford 4.6 liter engine and the Chrysler 2.0 liter engine, have connecting rods made using powder metallurgy, which allows more precise

26、control of size and weight with less machining and less excess mass to be machined off for balancing. The cap is then separated from the rod by a fracturing process, which results in an uneven mating surface due to the grain of the powdered metal. This ensures that upon reassembly, the cap will be p

27、erfectly positioned with respect to the rod, compared to the minor misalignments which can occur if the mating surfaces are both flat.A major source of engine wear is the sideways force exerted on the piston through the con rod by the crankshaft, which typically wears the cylinder into an oval cross

28、-section rather than circular, making it impossible for piston rings to correctly seal against the cylinder walls. Geometrically, it can be seen that longer con rods will reduce the amount of this sideways force, and therefore lead to longer engine life. However, for a given engine block, the sum of

29、 the length of the con rod plus the piston stroke is a fixed number, determined by the fixed distance between the crankshaft axis and the top of the cylinder block where the cylinder head fastens; thus, for a given cylinder block longer stroke, giving greater engine displacement and power, requires

30、a shorter connecting rod (or a piston with smaller compression height), resulting in accelerated cylinder wear.Compound rodsMany-cylinder multi-bank engines such as a V-12 layout have little space available for that many connecting rod journals on a limited length of crankshaft. This is a difficult

31、compromise to solve and its consequence has often led to engines being regarded as failures.The simplest solution, almost universal in road car engines, is to use simple rods. This requires the rod bearings to be narrower, increasing bearing load and the risk of failure in a high-performance engine.

32、 This also means the opposing cylinders are not exactly in line with each other.In certain types of engine, the master rod carries one or more ring pins to which are bolted the much smaller big ends of slave rods on other cylinders. Radial engines typically have a master rod for one cylinder and slave rods for all the other cylinders in the same bank. Certain designs of V engines use a master/slave rod for each pair of opposite cylinders. A drawback of this is that the stroke of the subsidiary rod is slightly shorter than the master