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黑龍江科技學(xué)院 畢業(yè)設(shè)計（論文）任務(wù)書 姓名：吳建芳 任務(wù)下達日期： 2006 年 3 月 13 日 設(shè)計（論文）開始日期： 2006 年 3 月 13 日 設(shè)計（論文）完成日期： 2006 年 6 月 20 日 一、設(shè)計（論文）題目：小汽車維修用液壓升舉裝置 二、專題題目： 高速切削技術(shù)及其應(yīng)用 三、設(shè)計的目的和意義：隨著中國經(jīng)濟的蓬勃發(fā)展，小客車將逐步進入中國的家庭市場。鑒于中國市場的廣闊性，及其中國基礎(chǔ)設(shè)施的滯后性，給小客車的維修帶來了不便，特別是轎車底部的維修，給維修師傅帶來很多不便，浪費人力物力，還有占地面積，為了解決上屬的所有問題，為未來社會的發(fā)展帶來方便。小客車維修用升舉裝置主要應(yīng)用于家庭和出租車類。應(yīng)用十分的廣泛，主要用途是通過升舉實現(xiàn)維修的方便和安全。 四、設(shè)計（論文）主要內(nèi)容：小汽車維修用液壓升舉機總裝配圖（1張0號）、托舉裝置裝配圖（1張0號）、液壓缸裝配圖（1張1號）、液壓原理圖（1張3號）、活塞零件圖（1張2號）、液壓缸后端蓋零件圖（一張2號）. 五、設(shè)計目標：實現(xiàn)液壓傳動裝置的平穩(wěn)升舉 六、進度計劃： 2006年3月13日至3月31日進行為期3周的生產(chǎn)實習(xí)；4月1日至4月15日完成對設(shè)計題目的資料收集與查詢；4月16日至5月13日完成對設(shè)計圖紙的繪制；5月14日至6月10日完成畢業(yè)設(shè)計說明書的編寫；6月11日至6月20日最后的審稿及說明書和圖紙的打印。 七、參考文獻資料： [1] 許福玲、陳堯明主編 《液壓與氣壓傳動》 機械工業(yè)出版社 2000 [2] 王憲軍、趙存友主編 液壓傳動[M] 哈爾濱工業(yè)大學(xué)出版社2002 [3]龐振基、黃其圣主編 精密機械設(shè)計[M] 機械工業(yè)出版社 2000 [4]劉鴻文主編材料力學(xué)（第二版）[M] 高等教育出版社 1992 [5]黃靖遠、龔劍霞主編 機械設(shè)計學(xué)[M] 機械工業(yè)出版社 2002 [6]袁績乾、李文貴主編 機械制造技術(shù)基礎(chǔ)[M] 機械工業(yè)出版社2001 [7]朱龍根主編 機械系統(tǒng)技術(shù)（第二版）[M] 機械工業(yè)出版社2001 [8]馮辛安主編 機械制造裝備設(shè)計[M] 機械工業(yè)出版社 2002 [9]曹德芳主編 汽車維修[M] 人民交通出版社,1999. 70- 78. [10]王靜文主編 汽車診斷與檢測技術(shù)[M] 人民交通出版社 1998. 90- 120 [11]邵松明主編 汽車維護與修理[M]人民交通出版社 2003, (1): 1- 2。 指 導(dǎo) 教 師： 院（系）主管領(lǐng)導(dǎo)： 年 月 日 2 I 摘要 雙柱式舉升機是一種汽車修理和保養(yǎng)單位常用的舉升設(shè)備 廣泛用于轎車 等小型車的維修和保養(yǎng) 它是一種把整車裝備重量不大于 3 噸的各種轎車 面 包車 工具車等舉升到一定高度內(nèi)供汽車維修和安全檢查作業(yè)的保修設(shè)備 關(guān)鍵詞 升舉機 液壓執(zhí)行元件 起重鏈 槽輪 鋼絲繩 II Abstract A pillar type raises to rise the machine is a kind of automobile to fix and maintain the unit to raise to rise the equipments in common usely extensively used for the car etc the compact car maintains and maintains It is a kind of is no bigger than 3 tons the whole car material weight of various car bread car the tool car etc raise to rise the certain height to be provided for car maintenance and safeties to check the homework protect to fix the equipments keyword UP hydraulic power WRAPT hydraulic pressure action element hoisting chain grooved pulley wire rope 1 目 錄 摘要 I ABSTRACT II 第 1 章 緒論 6 1 前言 6 2 升舉機的概述 7 第 2 章 總體設(shè)計 8 第 3 章 主要技術(shù)特點及其技術(shù)參數(shù) 9 1 技術(shù)特點 9 2 技術(shù)參數(shù) 9 第 4 章 液壓系統(tǒng)的傳動計算 10 1 液壓系統(tǒng)的設(shè)計步驟與設(shè)計要求 10 2 進行工況分析 確定液壓系統(tǒng)的主要參數(shù) 11 3 制定基本方案和繪制液壓系統(tǒng)圖 20 4 液壓元件的選擇與專用件設(shè)計 22 5 液壓系統(tǒng)性能驗算 27 第 5 章 液壓執(zhí)行元件 34 1 液壓缸 34 2 液壓馬達 45 2 第 6 章 液壓輔助元件及液壓泵站 46 1 管件 46 2 液壓軟管接頭 46 3 油箱及其附件 47 4 UP 液壓動力包 47 6 液壓油的選擇 51 第 7 章 鋼絲繩的選擇計算 52 1 鋼絲繩的計算 52 2 鋼絲繩的選擇 52 第 8 章 滑輪的選擇和計算 54 1 滑輪結(jié)構(gòu)和材料 54 2 滑輪的主要尺寸 54 3 滑輪直徑與鋼絲繩直徑匹配關(guān)系 54 4 滑輪形式 54 5 滑輪技術(shù)條件 54 6 滑輪強度計算 55 第 9 章 起重鏈條和槽輪 56 1 板式鏈條和槽輪的選擇 56 2 板式鏈及端接頭 56 3 板式鏈用槽輪 56 第 10 章 使用說明 57 1 使用說明 57 3 2 使用時注意事項 57 3 升舉機安全操作規(guī)程 57 第 11 章 經(jīng)濟效益分析 58 總 結(jié) 59 謝 辭 60 參考文獻 61 專題 62 附錄 68 本科畢業(yè)論文(設(shè)計)開題報告 論文題目 專業(yè)名稱 年 級 學(xué)生學(xué)號 學(xué)生姓名 指導(dǎo)教師(職稱) 填表時間 年 月 日 教 務(wù) 處 制  填 表 說 明 一、開題報告各項內(nèi)容要實事求是，逐條認真填寫，表達要明確、嚴謹。外來語應(yīng)用中文和英文同時表達，第一次出現(xiàn)的縮寫詞，須注出全稱。 二、開題報告需用計算機打印，一律為A4開本，于左側(cè)裝訂成冊。各欄空格不夠時，請自行加頁。 三、開題報告需在第八學(xué)期開學(xué)之前完成。 指導(dǎo)教師基本情況 指導(dǎo)教師姓名 性 別 年 齡 學(xué)歷或?qū)W位 專業(yè)技術(shù) 職務(wù)或職稱 工 作 單 位 課題來源 1、導(dǎo)師課題的一部分； 2、其它（須具體說明）： 。 1、該研究的目的、意義 現(xiàn)代汽車工業(yè)隨著科學(xué)技術(shù)的飛速發(fā)展而日新月異, 新工藝、新材料、新技術(shù)廣泛運用, 特別是電子技術(shù)、液壓技術(shù)在汽車上應(yīng)用, 使當(dāng)今的汽車是集各種先進技術(shù)的大成, 新穎別致的汽車時時翻新。而現(xiàn)代汽車的故障診斷不再是眼看、耳聽、手摸, 汽車維修也不再是師傅帶徒弟的一門手藝, 而是利用各種新技術(shù)的過程。隨著汽車技術(shù)的快速發(fā)展, 日益呈現(xiàn)出汽車維修的高科技特征, 與其同時汽車維修理念也不斷更新。 鑒于中國市場的廣闊性，及其中國基礎(chǔ)設(shè)施的滯后性，給汽車的維修帶來了不便，特別是轎車底部的維修，給維修師傅帶來很多不便，浪費人力物力，還有占地面積，為了解決上屬的所有問題，為未來社會的發(fā)展帶來方便。汽車維修用升舉裝置主要應(yīng)用于家庭和出租車類。應(yīng)用十分的廣泛，主要用途是通過升舉實現(xiàn)維修的方便和安全。 2、國內(nèi)外研究現(xiàn)狀及發(fā)展趨勢 汽車維修行業(yè)規(guī)模不斷擴大 ,結(jié)構(gòu)不斷優(yōu)化 十年來 ,我國的維修行業(yè)整體規(guī)模有了較大的發(fā)展和提高。目前 ,我國已從根本上解決了 長期存在的“修車難”問題,取而代之的是一些不成形的小企業(yè) ,由于維修設(shè)備不完善、人員技術(shù)能力差而無法在競爭的環(huán)境下生存。國內(nèi)維修企業(yè)已從傳統(tǒng)的單一車輛維修發(fā)展為車輛維修、車輛檢驗、配件 銷售三位一體的綜合體系。近年來 ,配件市場有了 較大的發(fā)展 ,配件銷售規(guī)模越來越大。車輛檢測也 從無到有 ,建成了汽車綜合檢測站 ,擁有了完整先進的檢測設(shè)備。車輛維修也從過去只能修中型車、國產(chǎn)車、汽油車發(fā)展到能維修重型車、小型車、柴油車 和進口車。維修企業(yè)小而全、全能的經(jīng)營方式已向 專業(yè)化分工方向發(fā)展。十年來 ,各類專業(yè)維修中心近 60 家 ,產(chǎn)業(yè)結(jié)構(gòu)優(yōu)化布局更趨合理 ,高檔車維修可就地完成，維修網(wǎng)絡(luò)系統(tǒng)完善 ,為汽車使用單位提 供了便利條件。 目前國內(nèi)汽車維修技術(shù)水平、管理能力、經(jīng)營方式、生產(chǎn)規(guī)模、從業(yè)人員的綜合素質(zhì)和服務(wù)意識, 與發(fā)達國家相比還存在較大差距, 如在實現(xiàn)汽修業(yè)的配件送貨及全方位的零庫存等。我國汽車維修的經(jīng)營方式將逐步與國際接軌, 多種經(jīng)營方式已全面展開, 如特約維修、代理維修、現(xiàn)場維修、專項總成維修, 也將實 現(xiàn)連鎖經(jīng)營維修、定點維修、會員制方式維修及俱樂部方式的維修等。充分體現(xiàn)低成本, 以專一保證質(zhì)量和服務(wù)的優(yōu)越性。 現(xiàn)在汽車維修，大多采用地溝作業(yè)，工作空間狹小，積油積水后排出困難，溝內(nèi)陰暗，需人工采光，通風(fēng)不良，工作起來極其不便。有了此類升舉裝置，將會給維修帶來效率，還能減輕工人師傅的勞動強度。 故此，小較車維修用升舉機具有很大的市場前景。 3、主要參考文獻 見說明書 4、該研究的簡要內(nèi)容，重點解決的問題，預(yù)期結(jié)果或成果 預(yù)期成果：小汽車維修用液壓升舉機總裝配圖（1張0號）、托舉裝置裝配圖（1張0號）、液壓缸裝配圖（1張1號）、液壓原理圖（1張3號）、活塞零件圖（1張2號）、液壓缸后端蓋零件圖（一張2號）. 5、擬采取的研究方法或?qū)嶒灧椒?，步驟，可能出現(xiàn)的技術(shù)問題及解決辦法 經(jīng)過調(diào)研了解到，國內(nèi)市場對于維修用升舉機的需求量比較大，考慮到國內(nèi)的特點，從實用角度出發(fā)，確定如下方案： 1. 考慮到大多數(shù)維修是屋內(nèi)作業(yè)，野外作業(yè)有，但是少，故采用兩立柱升舉，盡量在滿足升舉條件的情況下，節(jié)省空間。 2. 為了減少噪音及其達到升降的平穩(wěn)性采用液壓動力升舉裝置。 3. 由于升舉的同時，兩個同步液壓缸的設(shè)計不可能完全一樣，將導(dǎo)致升舉的同時車會發(fā)生傾斜，故采用鋼絲繩平穩(wěn)系統(tǒng)，以消除該影響。 4. 在滿足上述要求的同時，盡量結(jié)構(gòu)簡單，操作方便，適用于整體或解體搬運盡量做到標準化，通用化，系列化。 6、完成該研究已具備的條件 1.大量相關(guān)課題資料的收集與整理 2.機械設(shè)計專業(yè)知識學(xué)習(xí) 3.計算機輔助設(shè)計軟件的熟練掌握 指導(dǎo)教師意見 簽名: 年 月 日 教研室意見 教研室負責(zé)人： 時間： 年 月 日 教學(xué)院系部意見 教學(xué)院系部負責(zé)人： 時間： 年 月 日 附錄 (外文翻譯——原文) Fundamentals of Mechanical Design Mechanical design means the design of things and systems of a mechanical nature—machines, products, structures, devices, and instruments. For the most part mechanical design utilizes mathematics, the materials sciences, and the engineering-mechanics sciences. The total design process is of interest to us. How does it begin? Does the engineer simply sit down at his desk with a blank sheet of paper? And, as he jots down some ideas, what happens next? What factors influence or control the decisions which have to be made? Finally, then, how does this design process end? Sometimes, but not always, design begins when an engineer recognizes a need and decides to do something about it. Recognition of the need and phrasing it in so many words often constitute a highly creative act because the need may be only a vague discontent, a feeling of uneasiness, of a sensing that something is not right. The need is usually not evident at all. For example, the need to do something about a food-packaging machine may be indicated by the noise level, by the variations in package weight, and by slight but perceptible variations in the quality of the packaging or wrap. There is a distinct difference between the statement of the need and the identification of the problem. which follows this statement. The problem is more specific. If the need is for cleaner air, the problem might be that of reducing the dust discharge from power-plant stacks, or reducing the quantity of irritants from automotive exhausts. Definition of the problem must include all the specifications for the thing that is to be designed. The specifications are the input and output quantities, the characteristics of the space the thing must occupy and all the limitations on these quantities. We can regard the thing to be designed as something in a black box. In this case we must specify the inputs and outputs of the box together with their characteristics and limitations. The specifications define the cost, the number to be manufactured, the expected life, the range, the operating temperature, and the reliability. There are many implied specifications which result either from the designer's particular environment or from the nature of the problem itself. The manufacturing processes which are available, together with the facilities of a certain plant, constitute restrictions on a designer's freedom, and hence are a part of the implied specifications. A small plant, for instance, may not own cold-working machinery. Knowing this, the designer selects other metal-processing methods which can be performed in the plant. The labor skills available and the competitive situation also constitute implied specifications. After the problem has been defined and a set of written and implied specifications has been obtained, the next step in design is the synthesis of an optimum solution. Now synthesis cannot take place without both analysis and optimization because the system under design must be analyzed to determine whether the performance complies with the specifications. The design is an iterative process in which we proceed through several steps, evaluate the results, and then return to an earlier phase of the procedure. Thus we may synthesize several components of a system, analyze and optimize them, and return to synthesis to see what effect this has on the remaining parts of the system. Both analysis and optimization require that we construct or devise abstract models of the system which will admit some form of mathematical analysis. We call these models mathematical models. In creating them it is our hope that we can find one which will simulate the real physical system very well. Evaluation is a significant phase of the total design process. Evaluation is the final proof of a successful design, which usually involves the testing of a prototype in the laboratory. Here we wish to discover if the design really satisfies the need or needs. Is it reliable? Will it compete successfully with similar products? Is it economical to manufacture and to use? Is it easily maintained and adjusted? Can a profit be made from its sale or use? Communicating the design to others is the final, vital step in the design process. Undoubtedly many great designs, inventions, and creative works have been lost to mankind simply because the originators were unable or unwilling to explain their accomplishments to others. Presentation is a selling job. The engineer, when presenting a new solution to administrative, management, or supervisory persons, is attempting to sell or to prove to them that this solution is a better one. Unless this can be done successfully, the time and effort spent on obtaining the solution have been largely wasted. Basically, there are only three means of communication available to us. There are the written, the oral, and the graphical forms. Therefore the successful engineer will be technically competent and versatile in all three forms of communication. A technically competent person who lacks ability in any one of these forms is severely handicapped. If ability in all three forms is lacking, no one will ever know how competent that person is! The competent engineer should not be afraid of the possibility of not succeeding in a presentation. In fact, occasional failure should be expected because failure or criticism seems to accompany every really creative idea. There is a great to be learned from a failure, and the greatest gains are obtained by those willing to risk defeat. In the find analysis, the real failure would lie in deciding not to make the presentation at all. Introduction to Machine Design Machine design is the application of science and technology to devise new or improved products for the purpose of satisfying human needs. It is a vast field of engineering technology which not only concerns itself with the original conception of the product in terms of its size, shape and construction details, but also considers the various factors involved in the manufacture, marketing and use of the product. People who perform the various functions of machine design are typically called designers, or design engineers. Machine design is basically a creative activity. However, in addition to being innovative, a design engineer must also have a solid background in the areas of mechanical drawing, kinematics, dynamics, materials engineering, strength of materials and manufacturing processes. As stated previously, the purpose of machine design is to produce a product which will serve a need for man. Inventions, discoveries and scientific knowledge by themselves do not necessarily benefit people; only if they are incorporated into a designed product will a benefit be derived. It should be recognized, therefore, that a human need must be identified before a particular product is designed. Machine design should be considered to be an opportunity to use innovative talents to envision a design of a product is to be manufactured. It is important to understand the fundamentals of engineering rather than memorize mere facts and equations. There are no facts or equations which alone can be used to provide all the correct decisions to produce a good design. On the other hand, any calculations made must be done with the utmost care and precision. For example, if a decimal point is misplaced, an otherwise acceptable design may not function. Good designs require trying new ideas and being willing to take a certain amount of risk, knowing that is the new idea does not work the existing method can be reinstated. Thus a designer must have patience, since there is no assurance of success for the time and effort expended. Creating a completely new design generally requires that many old and well-established methods be thrust aside. This is not easy since many people cling to familiar ideas, techniques and attitudes. A design engineer should constantly search for ways to improve an existing product and must decide what old, proven concepts should be used and what new, untried ideas should be incorporated. New designs generally have “bugs” or unforeseen problems which must be worked out before the superior characteristics of the new designs can be enjoyed. Thus there is a chance for a superior product, but only at higher risk. It should be emphasized that, if a design does not warrant radical new methods, such methods should not be applied merely for the sake of change. During the beginning stages of design, creativity should be allowed to flourish without a great number of constraints. Even though many impractical ideas may arise, it is usually easy to eliminate them in the early stages of design before firm details are required by manufacturing. In this way, innovative ideas are not inhibited. Quite often, more than one design is developed, up to the point where they can be compared against each other. It is entirely possible that the design which ultimately accepted will use ideas existing in one of the rejected designs that did not show as much overall promise. Psychologists frequently talk about trying to fit people to the machines they operate. It is essentially the responsibility of the design engineer to strive to fit machines to people. This is not an easy task, since there is really no average person for which certain operating dimensions and procedures are optimum. Another important point which should be recognized is that a design engineer must be able to communicate ideas to other people if they are to be incorporated. Initially the designer must communicate a preliminary design to get management approval. This is usually done by verbal discussions in conjunction with drawing layouts and written material. To communicate effectively, the following questions must be answered: (1) Does the design really serve a human need? (2) Will it be competitive with existing products of rival companies? (3) Is it economical to produce? (4) Can it be readily maintained? (5) Will it sell and make a profit? Only time will provide the true answers to the preceding questions, but the product should be designed, manufactured and marketed only with initial affirmative answers. The design engineer also must communicate the finalized design to manufacturing through the use of detail and assembly drawings. Quite often, a problem well occur during the manufacturing cycle. It may be that a change is required in the dimensioning or tolerancing of a part so that it can be more readily produced. This falls in the category of engineering changes which must be approved by the design engineer so that the product function will not be adversely affected. In other cases, a deficiency in the design may appear during assembly or testing just prior to shipping. These realities simply bear out the fact that design is a living process. There is always a better way to do it and the designer should constantly strive towards finding that better way. Machining Turning The engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. Today these lathes are used primarily in small shops where smaller quantities rather than large production runs are encountered. The engine lathe has been replaced in today's production shops by a wide variety of automatic lathes such as automatic of single-point tooling for maximum metal removal, and the use of form tools for finish and accuracy, are now at the designer's fingertips with production speeds on a par with the fastest processing equipment on the scene today. Tolerances for the engine lathe depend primarily on the skill of the operator. The design engineer must be careful in using tolerances of an experimental part that has been produced on the engine lathe by a skilled operator. In redesigning an experimental part for production, economical tolerances should be used. Turret Lathes Production machining equipment must be evaluated now, more than ever before, in terms of ability to repeat accurately and rapidly. Applying this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating. In designing for low quantities such as 100 or 200 parts, it is most economical to use the turret lathe. In achieving the optimum tolerances possible on the turret lathe, the designer should strive for a minimum of operations. Automatic Screw Machines Generally, automatic screw machines fall into several categories; single-spindle automatics, multiple-spindle automatics and automatic chucking machines. Originally designed for rapid, automatic production of screws and similar threaded parts, the automatic screw machine has long since exceeded the confines of this narrow field, and today plays a vital role in the mass production of a variety of precision parts. Quantities play an important part in the economy of the parts machined on the automatic to set up on the turret lathe than on the automatic screw machine. Quantities less than 1000 parts may be more economical to set up on the turret lathe than on the automatic screw machine. The cost of the parts machined can be reduced if the minimum economical lot size is calculated and the proper machine is selected for these quantities. Automatic Tracer Lathes Since surface roughness depends greatly upon material turned, tooling ,and fees and speeds employed, minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances. Is some case, tolerances of ±0.05mm are held in continuous production using but one cut. Groove width can be held to ±0.125mm on some parts. Bores and single-point finishes can be held to ±0.0125mm. On high-production runs where maximum output is desirable, a minimum tolerance of ±0.125mm is economical on both diameter and length of turn. Milling With the exceptions of turning and drilling, milling is undoubtedly the most widely used method of removing metal. Well suited and readily adapted to the economical production of any quantity of parts, the almost unlimited versatility of the milling process merits the attention and consideration of designers seriously concerned with the manufacture of their product. As in any other process, parts that have to be milled should be designed with economical tolerances that can be achieved in production milling. If the part is designed with tolerances finer than necessary, additional operations will have to be added to achieve these tolerances——and this will increase the cost of the part. Grinding Grinding is one of the most widely used methods of finishing parts to extremely close tolerances and low surface roughness. Currently, there are grinders for almost for almost every type of grinding operation. Particular design features of a part dictate to a large degree the type of grinding machine required. Where processing costs are excessive, parts redesigned to utilize a less expensive, higher output grinding method may be well worthwhile. For example, wherever possible the production economy of centerless grinding should be taken advantage of by proper design consideration. Although grinding is usually considered a finishing operation, it is often employed as a complete machining process on work which can be ground down from rough condition without being turned or otherwise machined. Thus many types of forgings and other parts are finished completely with the grinding wheel at appreciable savings of time and expense. Classes of grinding machines include the following: cylindrical grinders, centerless grinders, internal grinders, surface grinders, and tool and cutter grinders. The cylindrical and centerless grinders are for straight cylindrical or taper work; thus splines, shafts, and similar parts are ground on cylindrical machines either of the common-center type or the centerless machine. Thread grinders are used for grinding precision threads for thread gages, and threads on precision parts where the concentricity between the diameter of the shaft and the pitch diameter of the thread must be held to close tolerances. The internal grinders are used for grinding of precision holes, cylinder bores, and similar operations where bores of all kinds are to be finished. The surface grinders are for finishing all kinds of flat work, or work with plain surfaces which may be operated upon either by the edge of a wheel or by the face of a grinding wheel. These machines may have reciprocating or rotating tables. (外文翻譯——漢文) 機械設(shè)計基礎(chǔ) 機械設(shè)計基礎(chǔ)是指機械裝置和機械系統(tǒng)——機器、產(chǎn)品、結(jié)構(gòu)、設(shè)備和儀器的設(shè)計。大部分機械設(shè)計需要利用數(shù)學(xué)、材料科學(xué)和工程力學(xué)知識。 我們對整個設(shè)計過程感興趣。它是怎樣開始的？工程師是不是僅僅坐在鋪著白紙的桌旁就可以開始設(shè)計了呢？當(dāng)他記下一些設(shè)想后，下一步應(yīng)該做些什么？什么因會影影響或者控制著應(yīng)該做出的決定？最后，這一設(shè)計過程是怎樣結(jié)束的呢？ 有時，雖然并不總是如此，工程師認識到一種需要并且決定對此做一些工作時，設(shè)計就開始了。認識到這種需要，并用語言將其清楚地敘述出來，常常是一種高度創(chuàng)造性的工作。因為這種需要可能只是一個模糊的不滿，一種不舒服的感覺，或者是感覺到了某些東西是不正確的。 這種需要往往不是很明顯的。例如，對食品包裝機械進行改進的需要，可能是由于噪音過大、包裝重量的變化、包裝質(zhì)量的微小的但是能夠察覺得出來的變化等表現(xiàn)出來的。 敘述某種需要和隨后要解決的問題之間有著明顯的區(qū)別。要解決的問題是比較具體的。如果需要干凈的空氣，要解決的問題可能是降低發(fā)電廠煙囪的排塵量，或者是降低汽車排除的有害氣體。 確定問題階段應(yīng)該制訂設(shè)計對象所有的要求。這些設(shè)計要求包括輸入量、輸出兩特性、設(shè)計對象所占據(jù)的空間尺寸以及這些參量的所有制約因素。我們可以把設(shè)計對象看作是黑箱中的某種東西。在這種情況下，我們必須具體確定黑箱的輸入和輸出，以及它們的特性和制約因素。這些設(shè)計要求將規(guī)定生產(chǎn)成本、產(chǎn)量、預(yù)期壽命、工作范圍、操作溫度和可靠性。 還存在著許多由于設(shè)計人員所處的特定環(huán)境或者由于問題本身的性質(zhì)所產(chǎn)生的隱含設(shè)計要求。某個工廠中可利用的制造工藝和設(shè)備會對設(shè)計人員的工作有所限制，因而成為隱含的設(shè)計要求的一部分。例如，一個小工廠中可能沒有冷變形加工機械設(shè)備。因此，設(shè)計人員就必須選擇這個工廠中能夠進行的其他的金屬加工方法。工人的技術(shù)水平和市場上的競爭情況也是隱含的設(shè)計要求的組成部分。 在確定了要解決的問題，并且形成了一系列的書面的和隱含的設(shè)計要求之后，設(shè)計工作的下一階段是進行綜合以獲得最優(yōu)的結(jié)果。因為只有通過對所設(shè)計的系統(tǒng)進行分析，才能確定其性能是否滿足設(shè)計要求。因此，不進行分析和優(yōu)化就不能進行綜合。 設(shè)計工作是一個反復(fù)進行的過程。在這個過程中，我們要經(jīng)歷幾個階段，在對結(jié)果進行評價后，再返回到前面的階段。因此，我們可以先綜合系統(tǒng)中的幾個零件，對它們進行分析和優(yōu)化，然后再進行綜合，看它們對系統(tǒng)的其他部分有時么影響。分析和優(yōu)化都要求我們建立或者做出系統(tǒng)的抽象模型，以便對此進行數(shù)學(xué)分析。我們將這些模型稱為數(shù)學(xué)模型。在建立數(shù)學(xué)模型時，我們希望能夠找到一個可以很好地模擬實際物理系統(tǒng)的數(shù)學(xué)模型。 評價是整個設(shè)計過程中的一個重要階段。評價是對一個成功的設(shè)計的最后檢驗，通常包括樣機的實驗室實驗。在此階段我們希望弄清楚設(shè)計能否真正滿足所有的要求。它是否可靠？在與類似的產(chǎn)品的競爭中它能否獲勝？制造和使用這種產(chǎn)品是否經(jīng)濟？它是否易于維護和調(diào)整？能否從它的銷售或使用中獲得利潤？ 與其他人就設(shè)計方案進行交流和溝通是設(shè)計過程的最后和關(guān)鍵階段。毫無疑問，有許多偉大的設(shè)計、發(fā)明或創(chuàng)造之所以沒有為人類所利用，就是因為創(chuàng)造者不善于或者不愿意向其他人介紹自己的成果。提出方案是一種說服別人的工作。當(dāng)一個工程師向經(jīng)營、管理部門或者其主管人員提出自己的新方案時，就是希望向他們說明或者證明自己的方案是比較好的。只有成功地完成這項工作，為得出這個方案所花費的大量時間和精力才不會被浪費掉。 人們基本上只有三種表達自己思想的方式，即文字材料、口頭表述和繪圖。因此，一個優(yōu)秀的工程師除了掌握技術(shù)之外，還應(yīng)該精通這三種表達方式。如果一個技術(shù)能力很強的人在上述三種表達方式中的某一種的能力較差，他就會遇到很大的困難。如果上述三種能力都很差，那將永遠沒有人知道他是一個多么能干的人！ 一個有能力的工程師不應(yīng)該害怕在提出自己的方案時遭到失敗的可能性。事實上，偶然的失敗肯定會發(fā)生的，因為每一個真正有創(chuàng)造性的設(shè)想似乎總是有失敗或批評伴隨著它。從一次失敗中可以學(xué)到很多東西，只有不怕遭受失敗的人們才能取得最大的收獲。總之，決定不把方案提交出來，才是真正的失敗。 機械設(shè)計概論 機械設(shè)計是一門通過設(shè)計新產(chǎn)品或者改進產(chǎn)品來滿足人類需求的應(yīng)用技術(shù)科學(xué)。它是一個廣闊的工程技術(shù)領(lǐng)域，不僅要研究產(chǎn)品在尺寸、形狀和詳細結(jié)構(gòu)等方面的基本構(gòu)思，還要考慮產(chǎn)品在制造、銷售和使用等方面的有關(guān)問題。 進行各種機械設(shè)計工作的人員通常被稱為設(shè)計人員或者設(shè)計工程師。機械設(shè)計是一項創(chuàng)造性的工作。設(shè)計工程師不僅在工作上要有創(chuàng)新性，還必須在機械制圖、運動學(xué)、工程材料、材料力學(xué)和機械制造工藝等方面具有深厚的基礎(chǔ)知識。 如前面所述，機械設(shè)計的目的是生產(chǎn)能夠滿足人類需求的產(chǎn)品。發(fā)明、發(fā)現(xiàn)和科學(xué)知識本身并不一定能給人類帶來益處，只有當(dāng)它們被用在產(chǎn)品上才能產(chǎn)生效益。因而，應(yīng)該認識到再一個特定產(chǎn)品進行設(shè)計之前，必須先確定人們是否需要這種產(chǎn)品。 應(yīng)當(dāng)把機械設(shè)計看成是設(shè)計人員運用創(chuàng)造性的才能進行產(chǎn)品設(shè)計、系統(tǒng)分析和制訂產(chǎn)品的制造工藝的一個良機。掌握工程基礎(chǔ)知識要比熟記一些數(shù)據(jù)和公式更為重要。僅僅使用數(shù)據(jù)和公式是不足以再一個好的設(shè)計中做出所需的全部決定。另一方面，應(yīng)該認真精確地進行所有運算。例如，即使將一個小數(shù)點的位置放錯，也會使正確的設(shè)計變成錯誤的。 一個好的設(shè)計人員應(yīng)該勇于提出新的想法，而且愿意承擔(dān)一定的風(fēng)險，當(dāng)新的方法不適用時，就恢復(fù)采用原來的方法。因此，設(shè)計人員必須要有耐心，因為所花費的時間和努力并不能保證帶來成功。一個全新的設(shè)計，要求屏棄許多陳舊的，為人們所熟知的方法。由于許多人易于墨守成規(guī)，這樣做并不是一件容易的事情。以為設(shè)計工程師應(yīng)該不斷的探索改進現(xiàn)有產(chǎn)品的辦法，在此過程中應(yīng)該認真選擇原有的、經(jīng)過驗證的設(shè)計原理，將其與未經(jīng)過驗證的新觀念結(jié)合起來。 新設(shè)計本身會有許多缺陷和未能預(yù)料的問題發(fā)生，只有當(dāng)這些缺陷和問題被解決之后，才能體現(xiàn)出新產(chǎn)品的優(yōu)越性。因此，一個性能優(yōu)越的產(chǎn)品誕生的同時，也伴隨著較高的風(fēng)險。應(yīng)該強調(diào)的是，如果設(shè)計本身不要求采用全新的辦法，就沒有必要僅僅為了變革的目的而采用新辦法。 在設(shè)計的初始階段，應(yīng)該允許設(shè)計人員充分發(fā)揮創(chuàng)造性，不受各種約束。即使產(chǎn)生了許多不切合實際的想法，也會在設(shè)計的早期，即繪制生產(chǎn)圖紙之前被改正掉。只有這樣， 才不至于堵塞創(chuàng)新得思路。通常要提出幾套設(shè)計方案?然后加以比較。很有可能在最后選定的方案中?采用了某些未被接受的方案中的一些想法。心理學(xué)家經(jīng)常談?wù)撊绾问谷藗冞m應(yīng)他們所操作的機器。設(shè)計人員的基本職責(zé)是努力使機器來適應(yīng)人們。這并不是一項容易的工作，因為實際上并不存在著一個對所有人來說都是最優(yōu)的操作范圍和操作過程。 另一個應(yīng)該被認識到的重要問題是，設(shè)計工程師必須能夠同其他有關(guān)人員進行交流和溝通。在開始階段，設(shè)計人員必須就初步設(shè)計同管理人員進行交流和溝通，并得到批準。這一般是通過口頭討論，草圖和文字材料進行的。為了有效地進行交流，需要解決下列問題： （1） 所要設(shè)計的這個產(chǎn)品是否真正為人們所需要？ （2） 此產(chǎn)品與其他公司的現(xiàn)有產(chǎn)品相比有無競爭能力？ （3） 生產(chǎn)這種產(chǎn)品是否經(jīng)濟？ （4） 產(chǎn)品的維修是否方便？ （5） 產(chǎn)品有無銷路？是否可以盈利？ 只有時間才能對上述問題給出正確的答案。但是，產(chǎn)品的設(shè)計、制造和銷售只能在對上述問題的初步肯定答案的基礎(chǔ)上進行。設(shè)計工程師還應(yīng)該通過零件圖和裝配圖，與制造部門一起對最終設(shè)計方案進行溝通。 通常，在制造過程中會出現(xiàn)某個問題?？赡軙髮δ硞€零件尺寸或公差作一些修改，使零件的生產(chǎn)變得容易。但是，工程上的修改必須要經(jīng)過設(shè)計人員批準，以保證不會損傷產(chǎn)品的功能。有時，在產(chǎn)品的裝配時或者裝配外運前的試驗中才發(fā)現(xiàn)設(shè)計中的某些缺陷。這些事例恰好說明了設(shè)計是一