擺動活塞式發(fā)動機的結構設計,擺動,活塞,發(fā)動機,結構設計 Mechanical Engineering in the Information Age In the early 1980s, engineers thought that massive research would be needed to speed up product development. As it turns out, less research is actually needed because shortened product development cycles encourage engineers to use available technology. Developing a revolutionary technology for use in a new product is risky and prone to failure. Taking short steps is a safer and usually more successful approach to product development. Shorter product development cycles are also beneficial in an engineering would in which both capital and labor are global. People who can design and manufacture various products can be found anywhere in the world, but containing a new idea is hard. Geographic distance is no longer a barrier to others finding out about your development six months into the process. If you’ve got a short development cycle, the situation is not catastrophic－as long as you maintain your lead. But if you’re in the midst of a six-year development process and a competitor gets wind of your work, the project could be in more serious trouble. The idea that engineers need to create a new design to solve every problem is quickly becoming obsolete. The first step in the modern design process is to browse the Internet or other information systems to see if someone else has already designed a transmission, or a heat exchanger that is close to what you need. Through these information systems, you may discover that someone already has manufacturing drawings, numerical control programs, and everything else required to manufacture your product. Engineers can then focus their professional competence on unsolved problems. Many engineers have as their function the designing of products that are to be brought into reality through the processing or fabrication of materials. In this capacity they are a key factor in the material selection-manufacturing procedure. A design engineer, better than any other person, should know what he or she wants a design to accomplish. He knows what assumptions he has made about service loads and requirements, what service environment the product must withstand, and what appearance he wants the final product to have. In order to meet these requirements he must select and specify the material(s) to be used. In most cases, in order to utilize the material and to enable the product to have the desired form, he knows that certain manufacturing processes will have to be employed. In many instances, the selection of a specific material may dictate what processing must be used. At the same time, when certain processes are to be used, the design may have to be modified may dictate what processing must be used. At the same time, when certain processes are to be used, the design may have be modified in order for the process to be utilized effectively and economically. Certain dimensional tolerances can dictate the processing. In any case, in the sequence of converting the design into reality, such decisions must be made by someone. In most instances they can be made most effectively at the design stage, by the designer if he has are a son ably adequate knowledge concerning materials and manufacturing processes. Otherwise, decisions may be made that will detract from thee effectiveness of the product, or the product may be needlessly costly. It is thus apparent that design engineers are a vital factor in the manufacturing process, and it is indeed a blessing to the company if they can design for producibility—that is, for efficient production. Manufacturing engineers select and coordinate specific processes and equipment to be used, or supervise and manage their use. Some design special tooling that is used so that standard machines can be utilized en producing specific products. These engineers must habe abroad knowledge of machine and process capabilities and of materials, so that desired operations can be done effectively and effi8ciently without overloading or damaging machines and without adversely affecting the materials being processed. These manufacturing engineers also play an important role en manufacturing. A relatively small group of engineers design the machines and equipment used en manufacturing. They obviously are design engineers and, relative to their products, they have the same concerns of the interrelationship of design, materials, and manufacturing processes. However they have an even greater concern regarding the properties of the materials that their machines are going to process and the interrelations of the materials and machines. Still another group of engineers—the materials engineers—devote their major efforts toward developing new and better materials. They, too, must be concerned with how these materials can be processed and with the effects the processing will have on the properties of the materials. Although their roles may be quite different, it is apparent that a large proportion of engineers must concern themselves with the interrelationship between materials and manufacturing processes. Low-cost manufacture does not just happen. There is a close and interdependent relationship between the design of a product, selection of materials, selection of processes and equipment, and tooling selection and design. Each of these must be carefully considered, planned, and coordinated before manufacturing starts. This lead time, particularly for complicated products, may take months, even years, and the expenditure of large amount of money may be involved. Typically, the lead time for a completely new model of an automobile is about 2 years, for amodern aircraft it may be 4years. In tackling such problems, the availability of high-powered personal computers and access to the information highway dramatically enhance the capability of the engineering team and its productivity. These information age tools can give the team access to massive databases of material properties, standards, technologies, and successful designs. Such protested designs can be downloaded for direct use or quickly modified to meet specific needs. Remote manufacturing, in which product instructions are sent out over a network, is also possible. You could end up with a virtual company where you don’t have to see any hardware. When the product is completed, you can direct the manufacturer to drop-ship it to your customer. Periodic visits to the customer can be made to ensure that the product you designed is working according to the specifications. Although all of these developments won’t apply equally to every company, the potential is there. Custom design used to be left to small companies. Big companies sneered at it－they hated the idea of dealing with niche markets or small-volume custom solutions. “Here is my product,” One of the big companies would say. “ This is the best we can make it－you ought to like it. If you don’t, there’s smaller company down the street that will work on your problem. ” Today, nearly every market is a niche market, because customers are selective. If you ignore the potential for tailoring your product to specific customers’ needs, you will lose the major part of your market share－perhaps all of it. Since these niche markets are transient, your company needs to be in a position to respond to them quickly. The emergence of niche markets and design on demand has altered the way engineers conduct research. Today, research is commonly directed toward solving particular problems. Although this situation is probably temporary, much uncommitted technology, developed at government expense or written off by major corporations, is available today at very low cost. Following modest modifications, such technology can often be used directly in product development, which allows many organizations to avoid the expense of an extensive research effort. Once the technology is free of major obstacles, the research effort can focus on overcoming the barriers to commercialization rather than on pursuing new and interesting, but undefined, alternatives. When viewed in this perspective, engineering research must focus primarily on removing the barriers to rapid commercialization of known technologies. Much of this effort must address quality and reliability concerns, which are foremost in the minds of today’s consumers. Clearly, a reputation for poor quality is synonymous with bad business. Everything possible－including thorough inspection at the end of the manufacturing line and automatic replacement of defective products－must be done to assure that the customer receives a properly functioning product. Research has to focus on the cost benefit of factors such as reliability. As reliability increases, manufacturing costs and the final cost of the system will decrease. Having 30 percent junk at the end of a production line not only costs a fortune but also creates an opportunity for a competitor to take your idea and sell it to your customers. Central to the process of improving reliability and lowering costs is the intensive and widespread use of design software, which allows engineers to speed up every stage of the design process. Shortening each stage, however, may not sufficiently reduce the time required for the entire process. Therefore, attention must also be devoted to concurrent engineering software with shared databases that can be accessed by all members of the design team. As we move more fully into the Information Age, success will require that the engineer possess some unique knowledge of and experience in both the development and the management of technology. Success will require broad knowledge and skills as well as expertise in some key technologies and disciplines; it will also require a keen awareness of the social and economic factors at work in the marketplace. Increasingly, in the future, routine problems will not justify heavy engineering expenditures, and engineers will be expected to work cooperatively in solving more challenging, more demanding problems in substantially less time. We have begun a new phase in the practice of engineering. It offers great promise and excitement as more and more problem－solving capability is placed in the hands of the computerized and wired engineer. To assure success, the capability of our tools and the unquenched thirst for better products and systems must be matched by the joy of creation that marks all great engineering endeavors. Mechanical engineering is a great profession, and it will become even greater as we make the most of the opportunities offered by the Information Age. 信息時代的機械工程 在80年代初期，工程師們曾經(jīng)認為要加快產(chǎn)品的研制開發(fā)，必須進行大量的研究工作。結果是實際上只進行了較少的研究工作，這是因為產(chǎn)品開發(fā)周期的縮短，促使工程師們盡可能地利用現(xiàn)有的技術。研制開發(fā)一種創(chuàng)新性的技術并將其應用在新產(chǎn)品上，是有風險的，并且易于招致失敗。在產(chǎn)品開發(fā)過程中采用較少的步驟是一種安全的和易于成功的方法。 對于資金和從略都處于全球性環(huán)境中的工程界而言，縮短產(chǎn)品研制開發(fā)周期也是有益的。能夠設計和制造各種產(chǎn)品的人可以在世界各地找到。但是，具有創(chuàng)新思想感情的人則比較難找。對于你已經(jīng)進行了6個月的研制開發(fā)工作，地理上的距離已經(jīng)不再是其他人發(fā)現(xiàn)它的障礙。如果你的研制周期較短，只要你仍然保持領先，這種情況親不會造成嚴重后果。但是如果你正處于一個長達6年的研制開發(fā)過程的中期，一個競爭對手了解到你的研究工作的一些信息，這個項目將面臨比較大的麻煩。 工程師們在解決任何問題時都需要進行新的設計這種觀念很快就過時了。在現(xiàn)代設計中的第一步是瀏覽因特網(wǎng)或者其他信息系統(tǒng)，看其他人是否已經(jīng)設計了一種類似于你所需要的產(chǎn)品，諸如傳動裝置或者換熱器等。通過這些信息系統(tǒng)，你可能發(fā)現(xiàn)有些人已經(jīng)有了制造圖紙，數(shù)控程序和制造你的產(chǎn)品所需要的其他所有東西。這樣，工程師們就可以把他們的職業(yè)技能集中在尚未解決的問題上。 許多工程師的職責是進行產(chǎn)品設計，而產(chǎn)品是通過對材料的加工制造而生產(chǎn)出來的。設計工程師在材料選擇——制造方法等方面起著關鍵的作用。一個設計工程師應該比其他的人更清楚地知道他的設計需要達到什么目的。他知道他對使用荷載和使用要求所做的假設，產(chǎn)品的使用環(huán)境，產(chǎn)品應該具有的外觀形貌。為了滿足這些要求，他必須選擇和規(guī)定所使用的材料。通常，為了利用材料并使產(chǎn)品具有所期望的形狀，設計工程師知道應該采用哪些制造方法。在許多情況下，選擇了某種特定材料就可能意味著已經(jīng)確定了某種必須采用的加工方法。同時，當決定采用某種加工方法后，很可能需要對設計進行修改，以使這種加工方法能夠被有效而經(jīng)濟地應用。某些尺寸公差可以決定產(chǎn)品的加工方法?？傊?，在將設計轉變?yōu)楫a(chǎn)品的過程中，必須有人作出這些決定。在大多數(shù)情況下，如果設計人員在材料和加工方法方面具有足夠的知識，他會在設計階段作出最為合理的決定。否則，作出的決定可能會降低產(chǎn)品的性能，或者使產(chǎn)品變得過于昂貴。顯然，設計工程師是制造過程中的關鍵人物，如果他們能夠進行面向生產(chǎn)（即可以進行高效率生產(chǎn)）的設計，就會給公司帶來效益。 制造工程師們選擇和調整所采用的加工方法和設備，或者監(jiān)督和管理這些加工方法和設備的使用。一些工程師進行專用工藝裝備的設計，以使通用機床能夠被用來生產(chǎn)特定的產(chǎn)品。這些工程師們在機床、工藝能力和材料方面必須具有廣泛的知識，以使機器在沒有過載和損壞，而且對被加工材料沒有不良影響的情況下，更為有效地完成所需要的加工工序。這些制造工程師們在制造業(yè)中也起到重要作用。 少數(shù)工程師們設計在制造業(yè)中使用的機床和設備。顯然，他們是設計工程師。而且對于他們的產(chǎn)品而言，他們同樣關心設計、材料和制造方法之間的相互關系。然而，他們更多地關心他們所設計的機床將要加工的材料的性能和機床與材料之間的相互作用。 這有另外一些工程師——材料工程師，他們致力于研制新型的和更好的材料，他們也應該關心這些材料的加工方法和加工對材料性能的影響。 盡管工程師們所起的作用可能會有很大差別，但是，大部分工程師們都必須考慮材料與制造工藝之間的相互關系。 低成本制造并不是自動產(chǎn)生的。在產(chǎn)品設計、材料選擇、加工方法和設備的選擇，工藝裝備選擇和設計之間都有著非常密切的相互依賴關系。這些步驟中的每一個都必須在開始制造前仔細地加以考慮、規(guī)劃和協(xié)調。這種從產(chǎn)品設計到實際生產(chǎn)的準備工作，特別是對于復雜產(chǎn)品，可能需要數(shù)月甚至數(shù)年的時間，并且可能花費很多錢。典型的例子有，對于一種全新的汽車，從設計到投產(chǎn)所需要的時間大約為2年，而一種現(xiàn)代化飛機則可能需要4年。 在解決這類問題時，利用高性能微型計算機和進入信息高速公路可以大大增強工程小組的能力和效率。這些信息時代的工具可以使工程小組利用大規(guī)模的數(shù)據(jù)庫。數(shù)據(jù)庫中有材料性能、標準、技術和成功的設計方案等信息。這些經(jīng)過驗證的設計可以通過下載直接應用，或者通過對其進行快速、簡單的改進來滿足特定的要求。將產(chǎn)品的技術要求通過網(wǎng)絡送出去的遠程制造也是可行的。你可以建立一個沒有任何加工設備的虛擬公司。你可以批示制造商，在產(chǎn)品加工完成后，將其直接送給你的客戶。定期訪問你的客戶可以保證你設計的產(chǎn)品按照設計要求進行工作。盡管這些研制開發(fā)方式不可能對每個公司都完全適用，但是這種可能性是存在的。 過去客戶設計的產(chǎn)品通常是由小公司來制造。大公司不屑于制造這種產(chǎn)品——它們討厭瞄準機會的市場，或者是與客戶設計的小批量產(chǎn)品打交道。“這就是我的產(chǎn)品”，一家大公司這樣說：“這是我們能夠制造出來的最好產(chǎn)品——你應該喜歡它。如果你不喜歡，順這條街走有一家小公司，它會按你的要求去做”。 今天，因為顧客們有較大的選擇余地，幾乎所有的市場都是瞄準機會的市場。如果你不能使你的產(chǎn)品滿足某些特定客戶的要求，你將失掉你的市場份額中的一大部分，或者失掉全部份額。由于這些瞄準機會的市場是經(jīng)常變化的，你的公司應該對市場的變化作出快速的反應。 瞄準機會的市場和根據(jù)客戶要求進行設計這種現(xiàn)象的出現(xiàn)改變了工程師們進行研究工作的方式。今天，研究工作通常是針對解決特定問題進行的。現(xiàn)在許多由政府資助或者由大公司出資開發(fā)的技術可以在非常低的成本下被自由使用，盡管這種情況可能是暫時的。在對這些技術進行適當改進后，它們通常能夠被直接用于產(chǎn)品開發(fā)，這使得許多公司可以節(jié)省昂貴的研究經(jīng)費。在主要的技術障礙被克服后，研究工作應該主要致力于產(chǎn)品的商品化方面，而不是開發(fā)新的，有趣的，不確定的替換產(chǎn)品。 采用上述觀點看問題，工程研究應該致力于消除將已知技術快速商品化的障礙。工作的重點是產(chǎn)品的質量和可靠性，這些在當今的顧客的頭腦中是最重要的。很明顯，一個質量差的聲譽是一個不好的企業(yè)的同義詞。企業(yè)應該盡最大的努力來保證顧客得到合格的產(chǎn)品，這個努力包括在生產(chǎn)線的終端對產(chǎn)品進行嚴格的檢驗和自動更換有缺陷的產(chǎn)品。研究工作應該著重考慮諸如可能性等因素對成本帶來的益處。當可能性提高時，制造成本和系統(tǒng)的最終成本將會降低。如果在生產(chǎn)線的終端產(chǎn)生了30%的廢品，這不僅會浪費金錢，也會給你的競爭對手創(chuàng)造一個利用你的想法制造產(chǎn)品，并將其銷售給你的客戶的良機。 提高可能性和降低成本這個過程的關鍵是深入、廣泛地利用設計軟件。設計軟件可以使工程師們加快每一階段的設計工作。然而，僅僅縮短每一階段的設計時間，可能不會顯著地縮短整個設計過程的時間。因而，必須致力于采用并行工程軟件，這樣可以使所有設計組的成員都能使用共同的數(shù)據(jù)庫。 隨著我們步入信息時代，要取得成功，工程師們在技術開發(fā)和技術管理方面都應該具有一些獨特的知識和經(jīng)驗。成功的工程師們不但應該具有寬廣的知識和技能，而且還應該是某些關鍵技術或學科的專家，他們還應該在日常工程問題上的費用將會減少，工程師們將會在一些更富有挑戰(zhàn)性，更亟待解決的問題上協(xié)同工作，大大縮短解決這些問題所需要的時間。我們已經(jīng)開始了工程實踐的新階段。計算機和網(wǎng)絡使工程師們具有了越來越強的解決問題的能力，這也給他們的工作帶來了很大的希望和喜悅。為了確保成功，我們所使用的工具的性能和對更好的產(chǎn)品與系統(tǒng)的不斷追求應該與標志著在工程方面所有巨大努力的創(chuàng)新工作所帶來的喜悅相適應。機械工程是一個偉大的行業(yè)，在我們盡可能多地利用了信息時代所提供的機遇后，它將變得更加偉大。