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内燃机连杆加工工艺及夹具设计【13张CAD图纸+毕业论文】【答辩通过】

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内燃机连杆加工工艺及夹具设计【全套CAD图纸+毕业论文】【答辩通过】.rar

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关键词：: 内燃机连杆加工工艺夹具设计全套 cad 图纸毕业论文答辩通过

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摘要

连杆是内燃机的主要传动件之一，正文主要论述了连杆的加工工艺及夹具设计。连杆的尺寸精度、形状精度以及位置精度的要求都很高，而连杆的刚性比较差，容易产生变形，因此在安排工艺过程时需要把各主要表面的粗精加工工序分开。逐步减少连杆加工余量、切削力及内应力的作用，以及修正加工后的变形，最后就能达到连杆的技术要求。连杆的主要加工表面为大、小头孔和两端面，较重要的加工表面为连杆体和盖的结合面及连杆螺栓孔定位面，次要加工表面为大头两侧面及螺栓座面等。

在连杆加工中有两个主要因素影响加工精度：

（1）连杆本身的刚度比较低，在外力（夹紧力、切削力）的作用下容易变形。

（2）连杆是模锻件，孔的加工余量较大，切削时将产生较大的残余内应力，并引起内应力重新分布。

通过对内燃机连杆的机械加工工艺及对粗加工大头孔夹具和铣结合面夹具的设计，主要归纳为以下两个方面：

第一方面：连杆件外形较复杂，而刚性较差。其技术要求很高，所以适当的选择机械加工中的定位基准,是能否保证连杆技术要求的重要问题之一。在连杆的实际加工过程中，选用连杆的大小头端面及小头孔作为主要定位基面，同时选用大头孔两侧面作为一般定位基准。为保证小头孔尺寸精度和形状精度，可采用自为基准的加工原则；保证大小头孔的中心距精度要求，可采用互为基准原则加工。

第二方面：关于夹具的设计方法及其步骤。

关键词：连杆；变形；加工工艺；夹具设计

ABSTRACT

The connecting rod is one of the main driving medium of diesel engine, this text expounds mainly the machining technology and the design of clamping device of the connecting rod. The precision of size, the precision of profile and the precision of position , of the connecting rod is demanded highly , and the rigidity of the connecting rod is not enough, easy to deform, so arranging the craft course, need to separate the each main and superficial thick finish machining process. Reduce the margin of processing, cutting force and internal stress progressively, revise the deformation after processing, can reach the specification requirement for the part finally .

In the Connecting rod is one of the main processing surface is large, the small head hole and both ends of the machined surface, is important for the connecting rod body and cover joint surface and the connecting rod bolt hole locating surface, secondary processing surface for bearing locking grooves, oil hole, head and body and a cover on the two sides of the bolt seat surface.

Machine of connecting rod are two major factors that affect the machining precision:

(1) Connecting rod itself stiffness is relatively low, in the external forces (cutting force, clamping force ) under the action of easy deformation.

(2) Connecting rod is die forgings, hole machining allowance, cutting will produce bigger residual stress, and stress redistribution caused by.

The automobile connecting rod machining process and the rough machining and milling combined with big hole clamp surface fixture design, mainly divided into the following two aspects:

The first aspect: connecting rod parts with complicated shape, while the poor rigidity. And the very high technical requirements, so the appropriate selection of mechanical processing in the locating datum, can ensure the connecting rod is one of the important problems of technical requirements. The connecting rod in the practical production process, selection of connecting rod to the size of the head end and the small head hole as the main positioning datum, and choice of big hole two side as a general locating datum. In order to ensure the size precision and shape precision of the small head hole, can be used for reference from the processing principle; ensure that the size of the first hole center distance accuracy requirements, can be used for reference each other the principle of processing.

Second: mainly on the fixture design method and steps.

Key words: Connecting rod;Deformation;Process;Fixture design

摘要III

ABSTRACTIV

目录V

1 绪论1

1.1 本课题的研究内容和意义1

1.2 国内外的发展概况1

1.3 本课题应达到的要求3

2 连杆的分析4

2.1 连杆的作用4

2.2 连杆的机械分析4

2.3 连杆的结构特点4

2.4连杆的主要技术要求5

2.4.1 大、小头孔的尺寸精度、形状精度5

2.4.2 大、小头孔轴心线在两个互相垂直方向的平行度5

2.4.3 大、小头孔中心距5

2.4.4 连杆大头孔两端面对大头孔中心线的垂直度5

2.4.5 大、小头孔两端面的技术要求5

2.4.6 有关结合面的技术要求5

2.5 连杆的材料和毛坯分析5

3 连杆的加工工艺规程的制定7

3.1 加工工艺的基本概念7

3.2 选择定位基准7

3.3 确定加工余量8

3.4 拟订机械加工工艺路线8

3.5 连杆工艺计算10

3.5.1 粗铣两平面10

3.5.2 粗磨两平面11

3.5.3 钻小头小孔13

3.5.4 粗镗小头孔14

3.5.5 车大头外圆15

3.5.6 粗镗大头孔17

3.5.7 粗铣螺栓孔端平面17

3.5.8 精铣螺栓孔端平面17

3.5.9 铣开连杆大头18

3.5.10 精铣体盖分开面18

3.5.11 钻扩铰螺栓孔18

3.5.12 精磨体盖分开面20

3.5.13 精磨两端平面21

3.5.14 精镗小头孔21

3.5.15 粗镗大头孔22

3.5.16 精镗大头孔22

3.5.17 精镗小头孔22

4 夹具设计23

4.1 机床夹具的分类22

4.2 工件的加工工艺分析23

4.3 确定定位方案23

4.4 夹具的机构设计24

4.5 夹具的使用26

5 结论与展望28

6 致谢29

7.参考文献30

1 绪论

1.1 本课题的研究内容和意义

本课题研究的内容是：K2500内燃机车发动机NDS5主连杆工艺规程设计和系列夹具设计，其中包括了工艺流程的设计、工序的编写、系列夹具的设计，并有相关计算和说明书。

连杆的作用是将活塞承受的力传给曲轴，并使活塞的往复运动转变为曲轴的旋转运动。连杆由连杆体、连杆盖、连杆螺栓和连杆轴瓦等零件组成，连杆体与连杆盖为连杆小头、杆身和连杆大头。连杆小头用来安装活塞销，以链接活塞。连杆大头与曲轴的连杆轴颈相连。一般做成分开式，与杆身切开的一半称为连杆盖，二者靠连杆螺栓链接为一题。连杆轴瓦安装在连杆大头孔座中，与曲轴上的连杆轴颈装和在一起，是发动机中最重要的配合副之一。常用的减磨合金主要有白合金、铜铅合金和铝基合金。

不难看出，连杆对于内燃机来说是不可或缺并且起到关键性作用的零件。所以本课题的研究对于生产出优秀耐用的连杆起到至关重要的作用。同时对内燃机的安全性也起到关键作用。

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内容简介：: 编号无锡太湖学院毕业设计（论文）相关资料题目：内燃机连杆加工工艺及夹具设计信机系机械工程及自动化专业学号： 0923012学生姓名：朱斌指导教师：高汉华（职称：副教授）（职称：）2013年5月25日目录一、毕业设计（论文）开题报告二、毕业设计（论文）外文资料翻译及原文三、学生“毕业论文（论文）计划、进度、检查及落实表”四、实习鉴定表无锡太湖学院毕业设计（论文）开题报告题目：内燃机连杆加工工艺及夹具设计信机系机械工程及自动化专业学号： 0923012 学生姓名：朱斌指导教师：高汉华（职称：副教授）（职称：）2012年11月14日课题来源课题来源于生产实际。科学依据（包括课题的科学意义；国内外研究概况、水平和发展趋势；应用前景等）（1）课题科学意义本课题研究的内容是：K2500内燃机车发动机NDS5主连杆工艺规程设计和系列夹具设计，其中包括了工艺流程的设计、工序的编写、系列夹具的设计，并有相关计算和说明书。连杆的作用是将活塞承受的力传给曲轴，并使活塞的往复运动转变为曲轴的旋转运动。连杆由连杆体、连杆盖、连杆螺栓和连杆轴瓦等零件组成，连杆体与连杆盖为连杆小头、杆身和连杆大头。连杆小头用来安装活塞销，以链接活塞。连杆大头与曲轴的连杆轴颈相连。一般做成分开式，与杆身切开的一半称为连杆盖，二者靠连杆螺栓链接为一题。连杆轴瓦安装在连杆大头孔座中，与曲轴上的连杆轴颈装和在一起，是发动机中最重要的配合副之一。常用的减磨合金主要有白合金、铜铅合金和铝基合金。不难看出，连杆对于内燃机来说是不可或缺并且起到关键性作用的零件。所以本课题的研究对于生产出优秀耐用的连杆起到至关重要的作用。同时对内燃机的安全性也起到关键作用（2）内燃机连杆的研究状况及其发展前景曲柄连杆机构是发动机中直接将燃油的化学能转化为机械能的运动机构，他将活塞的往复运动转变为曲轴的旋转运动，并通过曲轴输出发动机的功率，是发动机的主要运动机构。曲柄连杆机构包括活塞、连杆组及曲轴组三部分。连杆组件包括连杆体、螺栓、连杆盖、村套及螺母等件。连杆上接活塞，下连曲轴，将活塞的往复直线运动转换为曲轴的回转运动。连杆的计算分析多采用经验公式。目前在国内，连杆生产线大多由组合专用机床和通用机床组成流水生产线，同国外相比，工序能力指数及自动化程度均较低。有些关键工序也有采用高精设备和新工艺的，比如螺栓孔枪钻、枪铰和冷剂，拉削技术的应用，体盖组立扭矩+转角，刀具自动补偿功能的大小孔精镗，电子综合测量技术等。大的生产厂家主要有一汽集团、二汽集团、上柴、康明斯等。连杆是汽车发动机中的的重要零件，连杆最大的应用市场在于汽车工业。中国是全球汽车生产和消费大国。我国汽车产量快速增长，占世界汽车总产量的比重也在快速提升，我国汽车工业在世界的地位正在快速加强。汽车工业的迅速发展，零部件国产化逐步提升，也给我国汽车零部件产业带来巨大的市场空间和发展机会。研究内容（1）熟悉内燃机连杆的发展趋势，了解内燃机连杆在生产生活中的应用。（2）熟悉零件的加工工艺过程及工序，根据内燃机连杆给出连杆的加工工艺过程卡片及工序卡。（3）熟悉并掌握CAD制图软件，根据连杆的尺寸绘制出连杆的毛柸图、连杆装配图及连杆盖的图纸。（4）熟悉并掌握自由度，夹紧力的相关知识。（5）熟悉并掌握专用夹具设计的相关知识，对连杆进行专用的夹具设计。（6）熟悉螺纹螺母间的配合。拟采取的研究方法、技术路线、实验方案及可行性分析（1）连杆加工工艺分析根据连杆机构特点和精度要求，结合“基准统一”和“基准重合”的原则分析如何对连杆加工基准进行合理选择；在保证加工精度的前提下如何确定夹紧力的方向和着力点；怎样合理选择连杆个部位加工方式及工艺流程。（2）连杆加工余量和工序尺寸分析给出了各工序加工余量的确定方法；工序尺寸与设计尺寸标注方法相同和不同两种情况下如何确定各工序加工尺寸及偏差。研究计划及预期成果研究计划：2012年11月12日-2012年12月2日：按照任务书要求查阅论文相关参考资料，填写毕业设计开题报告书。2012年12月3日-2013年1月20日：填写毕业实习报告。2013年2月11日-2013年2月16日：按照要求制定设计方案。2013年2月18日-2013年3月25日：绘制装配图、零件图、毛坯图等相关图纸。2013年3月25日-2013年4月1日：连杆加工工艺设计及工艺过程卡片。2013年4月2日-2013年4月15日：专用夹具设计。2013年4月16日-2013年5月25日：毕业论文撰写和修改工作。预期成果：达到预期的设计效果：完成连杆加工工艺的设计并对相应的零件进行专业的夹具设计。特色或创新之处使用CAD制图能够准确快速的绘制出连杆的相关图纸。对零件进行专用的夹具设计能够使得生产加工更加的便捷，产品的质量得以提高，节省更多的人力物力。已具备的条件和尚需解决的问题实验方案思路已经非常明确，已经具备使用CAD软件和对部分零件夹具设计的知识。使用CAD的能力尚需加强。指导教师意见指导教师签名：年月日教研室（学科组、研究所）意见教研室主任签名：年月日系意见主管领导签名：年月日英文原文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 machines 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 Devices. 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 most 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 for 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 wrist 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; 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 reciprocating 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 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 already 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 systematic 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 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. 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 rods 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 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 perfectly 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-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 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 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 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. 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, which increases vibration in a vee engine.The usual solution for high-performance aero-engines is a forked connecting rod. One rod is split in two at the big end and the other is thinned to fit into this fork. The journal is still shared between cylinders. The Rolls-Royce Merlin used this style.Crank linkage of the type and characteristicsThe use of the internal combustion engine crank linkage of many types, according to kinematics perspective can be divided into three categories, namely: Heart crank linkage, the eccentric crank linkage and the main vice-link crank linkage. Centre crank linkage is characterized by the cylinder through the centerline of the crankshaft rotation centre and perpendicular to the axis of rotation of the crank. This type of linkage in the internal combustion engine crank in the most widely used. The single-engine general, tied for linkage with the use of the V-shaped chaxing link the internal combustion engine, and the home of the piston internal combustion engine crank linkage fall into this category. Eccentric crank linkage is characterized by vertical cylinder centerline of the crankshaft rotating in the center, but not by crankshaft rotary centre, the cylinder centerline distance between the crankshaft with a rotary axis offset e. This crank linkage institutions can reduce the swelling in the itinerary of the piston and cylinder intramural largest lateral pressure so that the pistons in the expansion programme and pressure reduction programme in the cylinder wall at the role of lateral pressure on both sides of the relatively uniform size. Vice-link the main crank linkage is characterized by: the internal combustion engine cylinder with a main link, the other out vice-link cylinder used, these are not direct link to the bottom of the crank pins, but on sale through the deputy link with in the main link of the big heads, formed a joint movement, such institutions also sometimes referred to as joint song stalk linkage .Crank linkage in the joint, a crank can put a few of connecting rod and piston, This structure will shorten the length of the internal combustion engine, compact and widely used in high-power locomotives used tanks and V-shaped internal combustion engine.Boring In machining, boring is the process of enlarging a hole that has already been drilled (or cast), by means of a single-point cutting tool (or of a boring head containing several such tools), for example as in boring a cannon barrel. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole.The term boring is also sometimes used for drilling a hole.Machine BoringThe boring process can be carried out on a lathe for smaller operations, but for larger production pieces a special boring mill (work piece rotation around a vertical axis) or a horizontal boring machine (rotation around horizontal axis) are used. A tapered hole can also be made by swiveling the head.The boring machines (similar to the milling machines such as the classic Van Norman) come in a large variety of sizes and styles. Work piece diameters are commonly 1-4m (3-12 ft) but can be as large as 20m (60ft). Power requirements can be as much as 200 hp. The control systems can be computer-based, allowing for automation and increased consistency.Because boring is meant to decrease the product tolerances on pre-existing holes, several design considerations must be made. First, large length-to-bore-diameters are not preferred due to cutting tool deflection. Next, through holes are preferred over blind holes (holes that do not traverse the thickness of the work piece). Interrupted internal working surfaceswhere the cutting tool and surface have discontinuous contactshould be avoided. The boring bar is the protruding arm of the machine that holds cutting tool(s), and must be very rigid.ForgingForging is the term for shaping metal by using localized compressive forces. Cold forging is done at room temperature or near room temperature. Hot forging is done at a high temperature, which makes metal easier to shape and less likely to fracture. Warm forging is done at intermediate temperature between room temperature and hot forging temperatures. Forged parts can range in weight from less than a kilogram to 170 metric tons.Forged parts usually require further processing to achieve a finished part. TheselectionofbaseandpositioningThebasepositionisprotocolmachiningline,determinetheprocessingplanoftheimportantworktodofirstMake.Choosecorrectly,theyankeeswilldirectlyinfluencethereasonableornot,themachiningofqualityandproductivity.Whenselectingpositionintheplane,needtoconsiderthefollowingquestions:(1)inwhichasurfaceastheessenceandsurfaceorunifiedstandards,(2)toensuremachiningprecision,(3)Makethemachiningprocesssmoothly?(4)forprocessingthepureplaneorunity,(5)shouldbeadoptedasaroughsurfaceplane?(6)whetherindividualprocessesforspecialprocessingrequirements,(7)needtoemployunifiedstandardsofplaneoutside?Accordingtotheessenceandtheyankeeschoice:fine,fineandselectionprinciplesshouldbeconsideredwhenthefirst,thebenchmarkoverlapInmay,namely,underthesituationofthemachinedsurfaceshouldbechosenforthelocatingdatumdesignstandards.Intheprocessofconnectingthemachiningprocess,mostofaspecifiedprocessselectionofendandsmallheadholeAsthemainbase,withbigholeinthesideoutsidethedesignatedasanotherroundfaceincludessurface.Thisisduetotheface.Largearea,morestable,Withlittleheadpositioncandirectlycontrolsizeholeholecenterdistanceofthehead.ItmakesTheprocessoflocatingdatum,reducepositioningerror.Furtherstudy:again,Accordingtothedrawing,thesizeoftheconnectingpartshaveaheadholesurface(namelytherightend)inaflatsurface,Therefore,butcanalsobeprocessedanotherend(left)isnotanend,fortheplaneasItisdisadvantageouspositiondatum.Therefore,intheprocessofthelocalizationplantoidea.Astheyankeesroundholesmallhead,solittleheadoutsidesurfaceprocessingroundholearrangementearly.InsmallheadandlargeBeforetheyankeesheadholeasorientationofthemachiningprocessesanddrilling,reaming,theseproceduresforprocessingaftertheholeTheholeisparallelwiththatsometimesaffectstheprocessingprecisionfollow-upprocesses,therefore,shouldbeinprocessingNotethatchoosesreasonablepositioningscheme.Intheprocedureoftheworkpieceineachsurfaceisblanksurface,positioningandclampingconditionsarepoor,butLimits.butandcuttingforceisbigger,ifitmeetstheworkpiece,therigiddifferentialitselfformachiningaccuracycanhaveveryBigeffect,thereforetheprocedureofthepositioningandclampingthechoiceofmethods,forthewholeprocessofprocessingDegreeoftenfar-reachingeffects.Processingis.ConnectingInroughmillingofhowtheworkpieceposition?AmethodisIntheend,withblanksideandendmillingaclamping,roughsurface,withgoodsurfacemilling,positioning.Anotherblank,milling.Butbecausetheblanksurfacesmooth,connectingrod,therigidlocalizationclampingworkpiece.May,aftertheroughsurfacedeformationmilling,asmoothseemstorelax,workpieceandrestoredistortion,influencesubsequentprocessesPositioningaccuracy.中文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。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

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