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編號
學(xué)院
畢業(yè)設(shè)計（論文）
相關(guān)資料
題目： 內(nèi)燃機(jī)連桿加工工藝及夾具設(shè)計
信機(jī) 系 機(jī)械工程及自動化專業(yè)
學(xué) 號： 0923012
學(xué)生姓名： 朱斌
指導(dǎo)教師： 高漢華 （職稱：副教授 ）
（職稱： ）
2013年5月25日
目 錄
一、畢業(yè)設(shè)計（論文）開題報告
二、畢業(yè)設(shè)計（論文）外文資料翻譯及原文
三、學(xué)生“畢業(yè)論文（論文）計劃、進(jìn)度、檢查及落實(shí)表”
四、實(shí)習(xí)鑒定表
無錫太湖學(xué)院
畢業(yè)設(shè)計（論文）
開題報告
題目： 內(nèi)燃機(jī)連桿加工工藝及夾具設(shè)計
信機(jī) 系 機(jī)械工程及自動化 專業(yè)
學(xué) 號： 0923012
學(xué)生姓名： 朱斌
指導(dǎo)教師： 高漢華（職稱：副教授）
（職稱： ）
2012年11月14日
課題來源
課題來源于生產(chǎn)實(shí)際。
科學(xué)依據(jù)（包括課題的科學(xué)意義；國內(nèi)外研究概況、水平和發(fā)展趨勢；應(yīng)用前景等）
（1）課題科學(xué)意義
本課題研究的內(nèi)容是：K2500內(nèi)燃機(jī)車發(fā)動機(jī)NDS5主連桿工藝規(guī)程設(shè)計和系列夾具設(shè)計，其中包括了工藝流程的設(shè)計、工序的編寫、系列夾具的設(shè)計，并有相關(guān)計算和說明書。
連桿的作用是將活塞承受的力傳給曲軸，并使活塞的往復(fù)運(yùn)動轉(zhuǎn)變?yōu)榍S的旋轉(zhuǎn)運(yùn)動。連桿由連桿體、連桿蓋、連桿螺栓和連桿軸瓦等零件組成，連桿體與連桿蓋為連桿小頭、桿身和連桿大頭。連桿小頭用來安裝活塞銷，以鏈接活塞。連桿大頭與曲軸的連桿軸頸相連。一般做成分開式，與桿身切開的一半稱為連桿蓋，二者靠連桿螺栓鏈接為一題。連桿軸瓦安裝在連桿大頭孔座中，與曲軸上的連桿軸頸裝和在一起，是發(fā)動機(jī)中最重要的配合副之一。常用的減磨合金主要有白合金、銅鉛合金和鋁基合金。不難看出，連桿對于內(nèi)燃機(jī)來說是不可或缺并且起到關(guān)鍵性作用的零件。所以本課題的研究對于生產(chǎn)出優(yōu)秀耐用的連桿起到至關(guān)重要的作用。同時對內(nèi)燃機(jī)的安全性也起到關(guān)鍵作用
（2）內(nèi)燃機(jī)連桿的研究狀況及其發(fā)展前景
曲柄連桿機(jī)構(gòu)是發(fā)動機(jī)中直接將燃油的化學(xué)能轉(zhuǎn)化為機(jī)械能的運(yùn)動機(jī)構(gòu)，他將活塞的往復(fù)運(yùn)動轉(zhuǎn)變?yōu)榍S的旋轉(zhuǎn)運(yùn)動，并通過曲軸輸出發(fā)動機(jī)的功率，是發(fā)動機(jī)的主要運(yùn)動機(jī)構(gòu)。曲柄連桿機(jī)構(gòu)包括活塞、連桿組及曲軸組三部分。
連桿組件包括連桿體、螺栓、連桿蓋、村套及螺母等件。連桿上接活塞，下連曲軸，將活塞的往復(fù)直線運(yùn)動轉(zhuǎn)換為曲軸的回轉(zhuǎn)運(yùn)動。連桿的計算分析多采用經(jīng)驗公式。
目前在國內(nèi)，連桿生產(chǎn)線大多由組合專用機(jī)床和通用機(jī)床組成流水生產(chǎn)線，同國外相比，工序能力指數(shù)及自動化程度均較低。有些關(guān)鍵工序也有采用高精設(shè)備和新工藝的，比如螺栓孔槍鉆、槍鉸和冷劑，拉削技術(shù)的應(yīng)用，體蓋組立扭矩+轉(zhuǎn)角，刀具自動補(bǔ)償功能的大小孔精鏜，電子綜合測量技術(shù)等。大的生產(chǎn)廠家主要有一汽集團(tuán)、二汽集團(tuán)、上柴、康明斯等。
連桿是汽車發(fā)動機(jī)中的的重要零件，連桿最大的應(yīng)用市場在于汽車工業(yè)。中國是全球汽車生產(chǎn)和消費(fèi)大國。我國汽車產(chǎn)量快速增長，占世界汽車總產(chǎn)量的比重也在快速提升，我國汽車工業(yè)在世界的地位正在快速加強(qiáng)。汽車工業(yè)的迅速發(fā)展，零部件國產(chǎn)化逐步提升，也給我國汽車零部件產(chǎn)業(yè)帶來巨大的市場空間和發(fā)展機(jī)會。
研究內(nèi)容
（1）熟悉內(nèi)燃機(jī)連桿的發(fā)展趨勢，了解內(nèi)燃機(jī)連桿在生產(chǎn)生活中的應(yīng)用。
（2）熟悉零件的加工工藝過程及工序，根據(jù)內(nèi)燃機(jī)連桿給出連桿的加工工藝過程卡片及工序卡。
（3）熟悉并掌握CAD制圖軟件，根據(jù)連桿的尺寸繪制出連桿的毛柸圖、連桿裝配圖及連桿蓋的圖紙。
（4）熟悉并掌握自由度，夾緊力的相關(guān)知識。
（5）熟悉并掌握專用夾具設(shè)計的相關(guān)知識，對連桿進(jìn)行專用的夾具設(shè)計。
（6）熟悉螺紋螺母間的配合。
擬采取的研究方法、技術(shù)路線、實(shí)驗方案及可行性分析
（1） 連桿加工工藝分析
根據(jù)連桿機(jī)構(gòu)特點(diǎn)和精度要求，結(jié)合“基準(zhǔn)統(tǒng)一”和“基準(zhǔn)重合”的原則分析如何對連桿加工基準(zhǔn)進(jìn)行合理選擇；在保證加工精度的前提下如何確定夾緊力的方向和著力點(diǎn)；怎樣合理選擇連桿個部位加工方式及工藝流程。
（2）連桿加工余量和工序尺寸分析
給出了各工序加工余量的確定方法；工序尺寸與設(shè)計尺寸標(biāo)注方法相同和不同兩種情況下如何確定各工序加工尺寸及偏差。
研究計劃及預(yù)期成果
研究計劃：
2012年11月12日-2012年12月2日：按照任務(wù)書要求查閱論文相關(guān)參考資料，填寫畢業(yè)設(shè)計開題報告書。
2012年12月3日-2013年1月20日：填寫畢業(yè)實(shí)習(xí)報告。
2013年2月11日-2013年2月16日：按照要求制定設(shè)計方案。
2013年2月18日-2013年3月25日：繪制裝配圖、零件圖、毛坯圖等相關(guān)圖紙。
2013年3月25日-2013年4月1日：連桿加工工藝設(shè)計及工藝過程卡片。
2013年4月2日-2013年4月15日：專用夾具設(shè)計。
2013年4月16日-2013年5月25日：畢業(yè)論文撰寫和修改工作。
預(yù)期成果：
達(dá)到預(yù)期的設(shè)計效果：完成連桿加工工藝的設(shè)計并對相應(yīng)的零件進(jìn)行專業(yè)的夾具設(shè)計。
特色或創(chuàng)新之處
① 使用CAD制圖能夠準(zhǔn)確快速的繪制出連桿的相關(guān)圖紙。
② 對零件進(jìn)行專用的夾具設(shè)計能夠使得生產(chǎn)加工更加的便捷，產(chǎn)品的質(zhì)量得以提高，節(jié)省更多的人力物力。
已具備的條件和尚需解決的問題
① 實(shí)驗方案思路已經(jīng)非常明確，已經(jīng)具備使用CAD軟件和對部分零件夾具設(shè)計的知識。
② 使用CAD的能力尚需加強(qiáng)。
指導(dǎo)教師意見
指導(dǎo)教師簽名：
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教研室（學(xué)科組、研究所）意見
教研室主任簽名：
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系意見
主管領(lǐng)導(dǎo)簽名：
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英文原文
Connecting rod
In 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 rods
Many-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 characteristics
The 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 Boring
The 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 surfaces—where the cutting tool and surface have discontinuous contact—should be avoided. The boring bar is the protruding arm of the machine that holds cutting tool(s), and must be very rigid.
Forging
Forging 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.
The?selection?of?base?and?positioning?
The?base?position?is?protocol?machining?line,?determine?the?processing?plan?of?the?important?work?to?do?first?
Make.?Choose?correctly,?the?yankees?will?directly?influence?the?reasonable?or?not,?the?machining?of?quality?and?productivity.?
When?selecting?position?in?the?plane,?need?to?consider?the?following?questions:?
(1)?in?which?a?surface?as?the?essence?and?surface?or?unified?standards,?(2)?to?ensure?machining?precision,?(3)?Make?the?machining?process?smoothly??
(4)?for?processing?the?pure?plane?or?unity,?(5)?should?be?adopted?as?a?rough?surface?plane??(6)?whether?individual?processes?for?special?processing?requirements,?(7)?need?to?employ?unified?standards?of?plane?outside??
According?to?the?essence?and?the?yankees?choice:?fine,?fine?and?selection?principles?should?be?considered?when?the?first,?the?benchmark?overlap?In?may,?namely,?under?the?situation?of?the?machined?surface?should?be?chosen?for?the?locating?datum?design?standards.?In?the?process?of?connecting?the?machining?process,?most?of?a?specified?process?selection?of?end?and?small?head?hole?As?the?main?base,?with?big?hole?in?the?side?outside?the?designated?as?another?round?face?includes?surface.?This?is?due?to?the?face.??Large?area,?more?stable,?With?little?head?position?can?directly?control?size?hole?hole?center?distance?of?the?head.?It?makes?The?process?of?locating?datum,?reduce?positioning?error.?
Further?study:?again,?
According?to?the?drawing,?the?size?of?the?connecting?parts?have?a?head?hole?surface?(namely?the?right?end)?in?a?flat?surface,?
Therefore,?but?can?also?be?processed?another?end?(left)?is?not?an?end,?for?the?plane?as?
It?is?disadvantageous?position?datum.?Therefore,?in?the?process?of?the?localization?plan?to?idea.
As?the?yankees?round?hole?small?head,?so?little?head?outside?surface?processing?round?hole?arrangement?early.?In?small?head?and?large?
Before?the?yankees?head?hole?as?orientation?of?the?machining?processes?and?drilling,?reaming,?these?procedures?for?processing?after?the?hole?The?hole?is?parallel?with?that?sometimes?affects?the?processing?precision?follow-up?processes,?therefore,?should?be?in?processing?Note?that?chooses?reasonable?positioning?scheme.?
In?the?procedure?of?the?workpiece?in?each?surface?is?blank?surface,?positioning?and?clamping?conditions?are?poor,?but?
Limits.but?and?cutting?force?is?bigger,?if?it?meets?the?workpiece,?the?rigid?differential?itself?for?machining?accuracy?can?have?very?
Big?effect,?therefore?the?procedure?of?the?positioning?and?clamping?the?choice?of?methods,?for?the?whole?process?of?processing?
Degree?often?far-reaching?effects.?Processing?is.?Connecting?In?rough?milling?of?how?the?workpiece?position??A?method?is?In?the?end,?with?blank?side?and?end?milling?a?clamping,?rough?surface,?with?good?surface?milling,?positioning.?
Another?blank,?milling.?But?because?the?blank?surface?smooth,?connecting?rod,?the?rigid?localization?clamping?workpiece.
May,?after?the?rough?surface?deformation?milling,?a?smooth?seems?to?relax,?workpiece?and?restore?distortion,?influence?subsequent?processes?Positioning?accuracy.
中文譯文
連 桿
在活塞往復(fù)式發(fā)動機(jī)內(nèi)，連桿連接著裝在曲柄或曲軸上的活塞?！肚擅畹臋C(jī)械裝置知識》一書這樣寫道：“連桿發(fā)明于1174年至1200年的某個時候，當(dāng)一個名為阿拉-賈扎里的穆斯林發(fā)明家、工程師和工匠，制造了5個機(jī)器來為土耳其阿爾圖格王朝的一位國王泵水——這些機(jī)器的其中之一就使用了連桿。將旋轉(zhuǎn)運(yùn)動轉(zhuǎn)變成往復(fù)運(yùn)動可能需要依靠連接到曲柄上的連桿?！彪p作用往復(fù)活塞泵是第一個提供自動運(yùn)動的機(jī)器，但其機(jī)構(gòu)和其他如凸輪一類的機(jī)構(gòu)也有助于工業(yè)革命的開啟。
內(nèi)燃機(jī)
在現(xiàn)代汽車內(nèi)燃發(fā)動機(jī)里，用于發(fā)動機(jī)的連桿通常由鋼制造，但也可以用鋁（目的是為了減輕重量和獲得在犧牲耐久度的條件下吸收強(qiáng)沖擊的能力）或鈦（目的是為了在需要支持力時提供一種既輕又有足夠強(qiáng)度的組合）來制造高性能發(fā)動機(jī)的連桿，或使用鑄鐵，如制造摩托車連桿時就使用鑄件。它們不會嚴(yán)格地固定于一端，于是當(dāng)連桿作上下運(yùn)動和繞曲柄旋轉(zhuǎn)時連桿與活塞之間的夾角就發(fā)生改變。
連桿較小的一端連接活塞銷，活塞銷（英國用語）或腕銷，這通常會給連桿以經(jīng)常性的壓力，但連桿仍能相對于活塞轉(zhuǎn)動即“浮動腕銷”。連桿的大端連接于曲柄上的軸頸處，并隨著由連桿螺栓固定的可更換的軸瓦轉(zhuǎn)動，螺栓將軸承“蓋”固定在連桿的大端處;通常要鉆一個通過軸瓦和連桿的大端小孔，以便使增壓潤滑油能噴到筒壁的一側(cè)，來使活塞和活塞環(huán)的運(yùn)動得到潤滑。
連桿承受著巨大的壓力，這些壓力來自于由活塞產(chǎn)生的循環(huán)載荷，而事實(shí)上這些壓力來自于每次旋轉(zhuǎn)時的拉伸與松弛，以及隨發(fā)動機(jī)轉(zhuǎn)速增大而急劇增大的載荷。一個失效的連桿，通常被稱為“扔棒”，它是引起汽車引擎災(zāi)難性故障最常見的原因之一，經(jīng)常使失效的連桿穿過曲軸軸箱的一側(cè)，發(fā)動機(jī)會遭受無法彌補(bǔ)的損壞；它可能源于連桿的疲勞缺陷、軸瓦失去潤滑而導(dǎo)致的失效，或源于連桿螺栓的缺陷、不適當(dāng)?shù)木o固，或重復(fù)利用已經(jīng)使用過的（已變形的）螺栓（這是不允許的）。盡管這些經(jīng)常發(fā)生在競爭激烈的汽車運(yùn)動中，但在為日常駕駛生產(chǎn)的汽車中，這種失效是十分罕見。這是因為汽車零部件的生產(chǎn)中要使用一個比較大的安全系數(shù)，同時往往還使用更系統(tǒng)的質(zhì)量控制體系。
當(dāng)制造一個高性能發(fā)動機(jī)時，連桿應(yīng)給予極大的關(guān)注，應(yīng)采取一些技術(shù)來消除應(yīng)力，例如磨削連桿的邊緣以達(dá)到表面粗糙度的要求，噴丸以使表面產(chǎn)生壓應(yīng)力（防止裂紋萌生），裝配時平衡所有連桿、活塞組合件的重量使每對的重量相同以及采用磁力探傷法來探測材料內(nèi)部的微小裂紋，這些看不見的微小裂縫將會產(chǎn)生破壞應(yīng)力造成連桿失效。此外，扭緊連桿螺栓時，應(yīng)非常注意扭矩的大??；通常這些螺栓必須更換，而不是重復(fù)使用。連桿的大端被制造成一個整體，并使其在機(jī)械加工之后能與大端軸瓦準(zhǔn)確裝配。因此，大端的“帽子”在連桿與連桿之間不具有互換性，而且當(dāng)重新制造一個引擎時，必須小心，以確保不同連桿的軸瓦不被亂用。無論是連桿還是與其相配合的軸瓦，通常都會在發(fā)動機(jī)缸體上刻上相應(yīng)的型號。
目前有一些發(fā)動機(jī)（如福特的4.6升引擎，還比如克萊斯勒的2.0升引擎）其連桿采用粉末冶金技術(shù)制造，粉末冶金技術(shù)不僅能精確控制尺寸和重量以減少機(jī)械加工工作量而且還能減少額外的機(jī)械配平。軸瓦因擠壓而與連桿分離，結(jié)果導(dǎo)致了不平滑的斷裂面，這是由于粉末金屬的顆粒造成的。這確保了重新裝配后，軸瓦能與連桿精確地配合，而傳統(tǒng)加工方法制造的連桿與軸瓦，只有當(dāng)兩者的接觸面表面的表面粗糙度都很小時才能達(dá)到較小的誤差。
發(fā)動機(jī)磨損的一個主要原因是由于曲軸通過連桿施加于活塞的側(cè)向力，通常將汽缸磨成橢圓形截面，而不是圓形截面，因此不可能使活塞環(huán)與氣缸側(cè)壁緊密接觸。從力學(xué)角度來說延長連桿的長度可相應(yīng)地減少上述側(cè)向力，這樣一來會使引擎壽命延長。然而，對一已知的發(fā)動機(jī)缸體來說，連桿的長度加上活塞行程，其和是一個固定的值，這個固定值由曲軸和氣缸座（氣缸座用來固定活塞蓋）頂部之間的固定距離來決定。因此，對一個已知的氣缸而言能得到更長的行程，可提供更大的排量和功率。相反，較短的連桿（或較小壓縮行程的活塞），會導(dǎo)致氣缸加速地磨損。
復(fù)合連桿
眾多多缸布局的發(fā)動機(jī)——如V – 12型發(fā)動機(jī)——幾乎沒有可用于在有限長度的曲軸上安裝連桿軸頸的空間。這是一個難以調(diào)和的矛盾，而且若按普通的方式安裝，其往往會導(dǎo)致發(fā)動機(jī)的失敗。
最簡單的解決辦法是使用簡單的連桿，這種最簡單的方法通常用于汽車引擎。這就要求連桿軸瓦要更窄，但對于一個高性能的引擎來說其會增加軸瓦的負(fù)荷及失效的風(fēng)險。這也意味著對置的氣缸不完全位于一條直線上。
在某些類型的引擎內(nèi)，主動連桿帶有一個或多個環(huán)形銷，環(huán)形銷用來連接其他氣缸上的從動連桿相對小一些的大端。徑向引擎的每一邊通常是一個氣缸有一個主動連桿，余下的其它氣缸則配有從動連桿。對于確定設(shè)計的V形引擎，一對對置的氣缸使用一對主/從動連桿。這樣的一個缺點(diǎn)是，輔助連桿的行程稍微短于主動連桿，從而使V形發(fā)動機(jī)產(chǎn)生更大的振動。
高性能航空發(fā)動機(jī)的通常解決方案是使用一個“叉狀”連桿。一個連桿在大端處一分為二，另一個變薄以與這個叉狀連桿相配。軸頸仍然由多個氣缸共用。勞斯萊斯默林發(fā)動機(jī)就使用這種形式。
曲柄連桿機(jī)構(gòu)的類型及特點(diǎn)
內(nèi)燃機(jī)中采用曲柄連桿機(jī)構(gòu)的型式很多，按運(yùn)動學(xué)觀點(diǎn)可分為三類，即:中心曲柄連桿機(jī)構(gòu)、偏心曲柄連桿機(jī)構(gòu)和主副連桿式曲柄連桿機(jī)構(gòu)。中心曲柄連桿機(jī)構(gòu)的特點(diǎn)是氣缸中心線通過曲軸的旋轉(zhuǎn)中心，并垂直于曲柄的回轉(zhuǎn)軸線。這種型式的曲柄連桿機(jī)構(gòu)在內(nèi)燃機(jī)中應(yīng)用最為廣泛。一般的單列式內(nèi)燃機(jī)，采用并列連桿與叉形連桿的V形內(nèi)燃機(jī)，以及對置式活塞內(nèi)燃機(jī)的曲柄連桿機(jī)構(gòu)都屬于這一類。
偏心曲柄連桿機(jī)構(gòu)的特點(diǎn)是氣缸中心線垂直于曲軸的回轉(zhuǎn)中心線，但不通過曲軸的回轉(zhuǎn)中心，氣缸中心線距離曲軸的回轉(zhuǎn)軸線具有一偏移量e。這種曲柄連桿機(jī)構(gòu)可以減小膨脹行程中活塞與氣缸壁間的最大側(cè)壓力，使活塞在膨脹行程與壓縮行程時作用在氣缸壁兩側(cè)的側(cè)壓力大小比較均勻。主從連桿式曲柄連桿機(jī)構(gòu)的特點(diǎn)是:內(nèi)燃機(jī)的一列氣缸用主動連桿，其它各列氣缸則用從動連桿，這些連桿的下端不是直接接在曲柄銷上，而是通過從動連桿銷裝在主連桿的大端上，形成了“關(guān)節(jié)式”運(yùn)動，所以這種機(jī)構(gòu)有時也稱為“關(guān)節(jié)曲柄連桿機(jī)構(gòu)”。在關(guān)節(jié)曲柄連桿機(jī)構(gòu)中，一個曲柄可以同時套上幾副連桿和活塞，這種結(jié)構(gòu)可使內(nèi)燃機(jī)長度縮短，結(jié)構(gòu)緊湊，廣泛地應(yīng)用于大功率的坦克和機(jī)車用 V形內(nèi)燃機(jī)。
鏜
在機(jī)械加工，鏜削加工的過程是一個擴(kuò)孔的過程，這個孔可以是鉆出來的（或鑄造得到的），鏜孔通過單點(diǎn)切削刀具（或一個鏜頭含有若干個這樣的刀具）來加工，例如用鏜削方法加工炮桶。鏜削加工能使孔達(dá)到更精確的尺寸，而且還可以用于錐形孔的加工。
鏜削有時也用于孔的加工。
鏜孔機(jī)
對較小的鏜削加工過程可以在車床上進(jìn)行，但對于較大工件的加工則需要使用特殊的鏜床（工件圍繞一個垂直軸旋轉(zhuǎn)）或臥式鏜床（圍繞水平軸旋轉(zhuǎn)）。通過轉(zhuǎn)動變換刀具的安裝角度也可以加工錐形孔。
鏜床（