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液压两工位加紧装置的分析与计算

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摘要

　　液压传动是用液体作为工作介质来传递能量和进行控制的传动方式。液压传动和气压传动称为流体传动，是根据17世纪帕斯卡提出的液体静压力传动原理而发展起来的一门新兴技术，是工农业生产中广为应用的一门技术。如今，流体传动技术水平的高低已成为一个国家工业发展水平的重要标志。液压传动凭借与其他传动方式相比较具有独特的技术优势，应用领域几乎囊括了国民经济各工业部门。

　　近30年来，由于控制技术、微电子技术、计算机技术、传感检测技术及材料科学的发展，极大的推动了液压传动与控制技术的发展，使其成为集传动、控制、计算机、传感检测、机电液为一体化的全新的自动控制技术。

　　本文根据液压系统的技术指标对数控铣床两工位夹紧装置液压系统进行整体方案设计，对其功能和工作原理进行动力分析和运动分析，初步确定了系统各回路的基本结构及主要元件，按照所给机构性能参数和液压性能参数进行元件的选择计算，通过对系统性能的验算和发热校核，以满足该铣床所要达到的要求。

关键词：液压系统；工位夹紧；性能参数

摘要III

AbstractIV

目录V

1 绪论1

1.1 液压传动的现状及展望1

1.2 液压传动的优点缺点1

2 液压系统的设计3

2.1 技术要求3

2.2 动力分析和运动分析3

2.2.1 Ⅰ工位夹紧缸的负载计算3

2.3 液压系统主要参数的确定5

2.3.1系统工作压力的确定5

2.4 液压执行器主要结构参数的计算6

2.4.1 Ⅰ工位夹紧缸主要结构参数的确定6

2.4.2 Ⅱ工位夹紧缸主要结构参数的确定7

2.4.3 液压缸工作循环中各阶段的压力、流量和功率8

3 液压系统原理图的拟定和方案论证10

3.1 制定基本方案10

3.2 油路循环方式的分析和选择10

3.3 调速方案的分析和选择10

3.4 液压动力源的分析与选择12

3.5 液压回路的分析、选择与合成12

3.6 液压原理图的拟定与设计12

4 计算和选择液压元件14

4.1 液压泵的选择14

4.1.1 液压泵站组件的选择14

4.1.2 液压泵的计算与选择14

4.2 液压控制阀的选择16

4.2.1 选择依据16

4.2.2 选择阀类元件应注意的问题16

4.3 液压附件的计算和选择17

4.3.1 确定管件的尺寸17

4.3.2 确定油箱容积19

5 液压系统性能验算20

5.1 液压系统压力损失验算20

5.1.1 Ⅰ工位夹紧缸的压力损失验算20

5.2 估算系统效率21

5.3 系统的发热和温升22

6液压动力源装置设计..... 24

6.1 液压泵站的结构形式24

7 液压装置的总体配置26

7.1 液压控制阀的块式集成26

7.2 集成块设计26

8 密封装置的选择28

9 液压系统安装29

9.1 液压系统安装............................. 29

9.1.1 在液压系统中安装液压元件时注意事项...29

9.1.2 在液压系统中安装液压泵时注意事项..... 29

10 结论........................................... 30

致谢31

参考文献.......................................... 32

1 绪论

1.1 液压传动的现状及展望

目前，液压传动及控制技术不仅用于传统的机械操纵、助力装置，也用于机械的模拟加工、转速控制、发动机燃料进给控制，以及车辆动力转向、主动悬挂装置和制动系统，同时也能够扩展到航空航天和海洋作业等领域。当前液压技术正在继续向以下几个方面发展。

1）节能

近年来，由于世界能源的紧缺，各国都把液压传动的节能问题作为液压技术发展的重要课题。20世纪70年代后期，德、美等国相继研制成功负载敏感泵及低功率电磁铁等。最近美国威克斯公司又研制成功用于功率匹配系统的CMX阀。

2）液压与微电子、计算机技术相结合

20世纪80年代以来，逐步完善和普及的计算机控制技术和集成传感技术为液压技术与电子技术相结合创造了条件。随着微电子、计算机技术的发展，出现了各种数字阀和数字泵，并出现了把单片机直接装在液压组件上的具有位置或力反馈的闭环控制液压元件及装置。

3）提高液压传动的可靠性

由于有限元法在液压元件设计中的应用，可靠性实验、研究工作的广泛开展以及新材料、新工艺的发展等，是液压元件的寿命得到提高。由于对飞机、船舶、冶金等一些重要液压系统采用多裕度设计，并在系统中设置旁路净化回路及具有初级智能的自动故障检测仪表等，加强了油液的污染度控制。上述领域内的一些重要成果，使液压系统的可靠性逐年提高。9 液压系统安装

9.1 液压系统安装

在设计结束并且专用件、外购件和标准件全部齐全后，第一步需要做的就是按照图纸对液压站进行装配。在装配前需要做以下几个准备工作：

1）需装配液压系统的液压件必须在循环冲洗合格后，方可进入装配状态；

2）液压驱动的主机设备全部安装完毕，运动部件状态良好并经检查合格后，进入装配状态；

3）控制液压系统的电气设备及线路全部安装完毕并检查合格；

4）熟悉调试所需技术文件，如液压原理图、管路安装图、系统使用说明书、系统调试说明书等。根据以上技术文件，检查管路连接是否正确、可靠、选用的油液是否符合技术文件的要求，油箱内油位是否达到规定高度，根据原理图、装配图认定各液压元器件的位置；

9.1.1 在液压系统中安装液压元件时的注意事项

　　　液压元件安装前，要用煤油清洗，自制的重要元件应进行密封盒耐压试验，试验压力可取工作压力的2倍，或取最高工作压力的1.5倍。试验时要分级进行，不要一下子升到试验压力，每升一级检查一次；

　　　方向控制阀应保证轴线呈水平位置安装；

　　　板式元件安装时，要检查进出油口的密封圈是否合乎要求，安装前密封圈应突出安装平面，保证安装后有一定的压缩量，以防泄露；

　　　板式元件安装时，固定螺钉的拧紧力要均匀，使元件的安装平面与元件底板平面能很好的接触。

9.1.2 在液压系统中安装液压泵时的注意事项

　　　1）液压泵传动轴与电动机驱动轴同轴度偏差小于0.1MM，一般采用挠性联轴节联结，不允许用V带直接带动泵轴转动，以防泵轴受径向力过大，影响泵的正常运转；

　　　2）液压泵的旋转方向和进，出油口应按要求安装；

　　　3）各类液压泵的吸油高度，一般小于0.5M。

QQ截图20131202154214.gif

液压两工位加紧装置的分析与计算.gif

内容简介：: 无锡太湖学院信机系机械工程及自动化专业毕业设计论文任务书一、题目及专题：1、题目液压两工位夹紧装置的分析与计算 2、专题二、课题来源及选题依据课题来源：工厂。选题依据：液压传动在机械设备中的应用非常广泛。有的设备是利用其能传递大的动力，且结构简单、体积小、重量轻的优点，如工程机械、矿山机械、冶金机械等；有的设备是利用它操纵控制方便，能较容易地实现较复杂工作循环的优点，如各类金属切削机床、轻工机械、运输机械、军工机械、各类装载机等。所以研究液压系统有很好的应用价值和广阔的前景。我国进入世界贸易组织之后，对我国的机械行业是个机遇，更是一个艰难的挑战。因此作为二十一世纪的主人，我们更应该通过作大量的设计制造和广泛地使用各种先进的机器，以便能加快我国国民经济的增长速度，加快我国现代化建设。三、本设计（论文或其他）应达到的要求：本设计是完成某机床需要对零件进行两工位装夹装置（装夹装置静动摩擦因数，）的设计，拟采用缸筒固定的液压缸驱动夹紧装置，完成工件装夹运动。夹紧装置由液压与电气配合实现的自动循环要求为：工位夹紧缸夹紧工位夹紧缸松开工位夹紧缸夹紧工位夹紧缸松开。四、接受任务学生：机械91 班姓名张佳睿五、开始及完成日期：自2012年11月7日至2013年5月25日六、设计（论文）指导（或顾问）：指导教师签名签名签名教研室主任学科组组长研究所所长签名系主任签名2013年05月25日英文原文 Machinery, Machina Mechine derived from the Greek and Latin, Mechanical gear (figure 1) means clever design, as a general mechanical concept, can be traced back to the Roman period, main is to distinguish and hand tools. Of modern Chinese language the word Machine is organization is (Mechanism) of the English and the floorboard of the Machine (the Machine). Mechanical characteristics are: machinery is a combination of physical components. To determine the relative motion of mechanical parts. So the Machine can convert mechanical energy or accomplish useful mechanical work, is the most basic concept in modern mechanical principle, the modern concept of Chinese machinery more derived from the word Machine of the Japanese, Japanese machinery should supplies to do the following definition (that is, in accordance with the following three characteristics is called mechanical Machine) :1, the machinery is a collection of objects, concentration to the various parts are also difficult to deformation.2, the object must implement the mutual movement, single, regulations.3, to exert energy into a useful form, or converted into mechanical work effectively.Mechanism and machine definition is derived from the mechanical engineering, belongs to the most basic concept of modern mechanical principles, mechanical more modern concepts derived from Chinese of the word machine in Japanese.All have certain sports machine and the floorboard of the system. Such as machine tools, tractors, etc. Mechanical engineering is related to the theoretical basis of natural science and technology, Mechanical gear (figure 2) combined with the accumulation of technical experience in the production practice, study and solve in the development, design, manufacture, installation, use and repair of all kinds of machinery an applied subject of theoretical and practical problems. Every development in the field of engineering requirements in mechanical engineering has adapted to the development, need mechanical engineering provides the necessary machinery. Some mechanical invention and improvement, and could lead to new engineering technology and the emergence and development of new industry. Large machinery manufacturing success, for example, led to the establishment of electric power system; The invention of the locomotive led to the rise of railway engineering and railway undertakings; The invention of the internal combustion engines, gas turbines, rocket engines, etc and progress, as well as the successful development of aircraft and spacecraft has led to the rise of aviation and aerospace business; The development of high voltage equipment lead to the success of many new synthetic chemical engineering and so on. Mechanical engineering is in all respects under the pressure of rising demand for development, at the same time from different disciplines and the advancement of the technology improved and innovative ability. Machinery is a simple device, it can transfer energy, force from one place to another place. Mechanical gear (FIG. 3) it can change the shape of the object structures to create new objects. In life, all around us there are thousands of different kinds of machinery in the work for us.Everyday understanding of mechanical is a mechanical device, which is all kinds of machines and equipment. From the point of view of mechanical professional: machinery has a very important basic position. Machinery is a modern society the five factors of production and service (that is, people, money, energy, materials and machinery). When Marx to industrial society, industrial society, especially in big industrial society, which is machine production machine age. Whether from life in contact with all kinds of physical devices, such as telephones, electric lights, television, refrigerator, elevator and so on contains the machine, or included in the general machinery, and from the point of production, all kinds of machine tools, automation equipment, aircraft, ships, god five, six, and so on, are short of machinery. So, machinery is one of the foundations of modern society. If someone say agriculture is the foundation, also understandable, but in modern society, mechanical serve as the basis for the rest of the industry and engineering, it is no exaggeration to think is the big pillar in society. Any modern industrial and engineering applications require machinery, is the Peoples Daily life, are increasingly used all kinds of machinery, such as cars, bicycles, watches and clocks, cameras, washing machine, refrigerator, air conditioner, vacuum cleaners, etc. The first machine is defined as the Roman architect vitruvius pollio (Vitruvii) in it Mechanical gear (figure 4) for building ten book mainly for carrying heavy things work machinery and tools: the difference between mechanical (machane) and tools (organon) seem to have the following differences between. The machine is most artificial and very big power and effect, such as heavy ballista and grapes press. While the tool is a manipulation of the staff carefully processing, to achieve the purpose of such as were the shape of light range ballista or circular spiral device. Thus, tools and machinery are used in the indispensable thing. The ancient Greek for cylindrical gears. Alexandria, Mr Hiro (Heron of Alexandria) in the 1st century first discussed the basic elements of machinery, mechanical elements considered to be five classes: wheel and shaft, lever, pulley, wedge, spiral. Hiros discourse reflects the classical mechanical characteristics. BC China has guidelines on the application of complex gear system, the incense burner in the application of the permanent control level of the bogie and other parts of a cross. Annotations, said: the machine, the crossbow tooth; enclosed, the arrow around. Said wen jie zi explanation of machine is machine, the main mover , refers to the crossbow. Mechanical in leipzig, Germany in 1724 and liao poulter (Leopold) is defined as machines or tools is a kind of artificial device, use it to produce favorable movement; at the same time cant use other ways to save time and power, it can save. British mechanics, Willis (truly illis) in its agency theory (The Principle of Mechanism, 1841) give The definition of: Machinery gear speed reducer any machine (machine) are made in a variety of different ways of connecting a set of artifacts that make it a component, the component will happen in a certain sport, these artifacts and the initial movement of the components of relative motion relationship depends on the nature of the connections between them. German machinery at le loro (F.R euleaux) in the theory of kinematics (Theoretische Kinematik, Grundzuge einer Theorie China is the worlds first national machinery development. Chinese mechanical engineering technology not only has a long history and splendid achievements in Chinese is not only the material culture and social economic development plays an important role in the world, and to promote the progress of civilization, technology has made great contribution to Chinese traditional machine. And in a long period ahead in the world. In modern times, especially from the early 18th century, due to the nineteen forties, due to the economic and social reasons, such as the China machinery industry, stagnation, in the 100 years is western bourgeois political revolution and industrial revolution, mechanical science and technology is developing rapidly, and far more than the level of China. So, China mechanical development level and the western gap widens, sharply to the 19th century middle behind western one hundred years. After the founding of new China, especially in the past 30 years, our countrys mechanical science and technology development speed. To the mechanical product large-scale, precision, automation and discusses the trend of development. In some aspects has reached or exceeded the world advanced level. Generally speaking, currently China mechanical science and technology achievement is huge, developing fast, high level of unprecedented. In this period, China has no end of mechanical science and technology will develop to a higher level. As long as we can adopt the correct policy, with good technology development and innovation, our machinery industry and mechanical technology can revitalize, leading to the development trend of mechanical industry.Just small ramming machinery: In the 1960s, China mechanical very small tamp lack, many small venues ramming basically USES artificial ramming. Early 1960s, changsha construction machinery institute and Beijing architectural engineering institute, etc., the technical innovation achievements in mass on the basis of summing up Chinese characteristic invented the breaststroke ramming machine, 1962 exceeded national science and technology. The breaststroke ramming machine structure is simple, easy to use and maintenance in 1960s, soon became the dominant products to consolidate machinery. According to not complete count breaststroke tamp cumulative yield reached more than 50,000 machine, in the economic development of our country has played an important role. Since 1970s, the breaststroke ramming machine was gradually more advanced performance of vibration shock ram and vibrating plate ram, now replaced by laying machine has rarely breaststroke, basically be eliminated. In 1964, changsha construction machinery institute HB120 developed movable type, type of Shanghai began laying machine, engineering machine production mainly by tianjin municipal later, annual production engineering machinery dongting about 200. In the 1980s, movable type ramming machine product quality has increased greatly, have exported to southeast Asia and Africa. Since 1990s, internal-combustion type ramming machine production sales, and gradually decreased in only a few small private enterprise production. In 1977, changsha construction machinery factory buildings and developed in liuzhou HZR250 type and the HZR70 type vibrating plate ram, these two kinds of products in 1979 and 1982 passed by the ministry of construction of the organization. Then yiwu building construction machinery factory, siping, anyang vibrators factory, tianjin municipal engineering machinery dongting and other enterprises have started producing vibrating plate ram. In 1986, changsha construction machinery research and develop a larger HZR450 type of vibrating plate ram. Since 1990s, vibrating plate ram in our country has developed very quickly, varieties of products, specifications and increase production enterprises, foreign vibrating plate ram gradually to enter the Chinese market. In 1983, changsha construction machinery institute and the joint development of hubei vibration in the first HZR70 type vibration shock ramming, 1984, passed by the ministry of construction, organization construction technology progress in 1985 won prizes. Due to the vibration impact compaction result has good ramming, productivity, high volume and weight of small, lightweight flexible outstanding characteristics, deeply user etc, obtained a rapid promotion, and soon ZiJiang development to the factory, xinxiang municipal engineering machine tool plant and tianjin dozens of dongting production factory etc. Vibration shock ramming although than vibrating plate ram, but later development speed of development, production and use of extensive than vibrating plate ram, has become the largest in China in the ramming machinery products. Since 1990s, foreign vibrating plate ram gradually to enter the Chinese market. Vibration shock ramming and vibrating plate ram the successful development in our country, not only for our construction department provides advanced performance of mechanical, laying have achieved good economic benefit and social benefit, and make our ramming mechanical technology into a big step forward, shorten the gap with the advanced world level, promoting the development of compaction machine.The mechanical processing: According to the archaeological discovery, hot-working casting in Beijing pinggu, changping and so have proved that the 16th century BC shang dynasty (bronze objects. Ming yongle (1403-1424 years), Beijing produce world-renowned Ming yongle great 3-ton bell made (46.5 tons) and tower (63 tons of great 3-ton bell made of iron clock (25) and the furnace of melting, pit TaoFan model and method of casting. In the 1950s, Beijing based on clay sand castings in manual. In 1955, Beijing first machine tool plant began using leakage mould modelling, double-sided model and iron plate type plate and standard sand box modelling. In 1965, start using plastic model. In 1980, the institute and Beijing municipal electrical factory has successfully developed line frequency coreless bathroom plug stem bottom note type electric insulation casting. In 1982, hospital and Beijing the casting machine research cupola tuyere oxygen blowing technology. 1985-1988, Beijing institute of machine of floating end face seal ring by die successful test pressure casting process. In 1959, Beijing second metalforming machinery general factory changed (Beijing) built 2500 ton heavy-duty hydraulic press. In 1971, the factory produced 6,000 tons, which is then Beijing hydrtesting biggest metalforming equipment. 1968-1979, Beijing hoisting machine factory has 300 tons of using hydraulic press 2000 tons and create crane and large panel. In the 1980s, Beijing institute of electrical and developed a series of Beijing mould centre high-precision cutting die, the multistage close to or to import mould level, changed Beijing precision punching moulds dependence on imports. Before 1949, Beijing has heat treatment furnace, salt dissolved by thermocouples means furnace, quenching and tempering, parts of annealing, normalizing, quenching and tempering, carburizing and etc. In 1956, Beijing first began using high-frequency quenching machine tool plant. In 1961, the Beijing second machine tool plant began using gas nitriding quenching. In 1969, the following enterprise by Beijing gage start light quenching. In 1978, the complete machine tool research institute of Beijing guide surface contact quenching process and equipment, quenching condition of quality inspection. In 1979, scientific research institute of China academy of railway and mechanical institute of high-power diesel engine cylinder collaboration of surface modification of laser. In 1979, Beijing institute of electrical carbon dioxide laser is developed, and the kilowatt in early 1980s respectively applied in cylinder and stamp printing equipments of laser treatment. Among them, tsinghua university, Beijing, Beijing institute of electrical YouPiaoChang jointly completed YouPiaoChang seven color machine DaKongQi laser surface strengthening research. From 1984 to 1990, Beijing institute of vacuum heat treatment research, gas carburizing microcomputer control technology (Beijing university of aeronautics &astronautics and cooperation), rare earth soft nitriding, powder metallurgy products surface strengthening, kerosene and methanol small drops of microcomputer control method of carburizing, solid boriding and carburizing process computer aided process planning and tracking control system, and the application of new technology heat in production. Welding and cutting in 1949, Beijing has geo-drilling, electric welding and cutting etc oxyacetylene flame manual operation. In 1963, Beijing metal structure and YiJiBu mechanical science research cooperation to develop tungsten argon arc welding, and realize the nitrogen plasma cutting stainless steel. In 1964, the use of dc argon arc welding and tungsten wire alloying technology solved by tilting electrolysis industry worse pure nickel welding. In 1966, Beijing metal structure factory developed by rotating sphere of the submerged arc welding automatic welding. In 1968, the plant began to liquefied petroleum gas (LPG) instead of acetylene cutting. In the early 1980s, tsinghua university invented new MIG welding arc arc technology in control, control a breakthrough. In the early 1980s, the Beijing urban construction design completed liquefied petroleum gas (LPG) mobile pneumatic rail welding technology research and application. In 1990, Beijing metal structure factory to adopt CNC precision cutting and with photo-electricity tracking and CNC pursuit of high input automatic programming technology plasma cutting. Visible, China mechanical development in modern development of its rapid.中文原文机械，源自于希腊语之Mechine及拉丁文Machina，机械齿轮（图1）原指“巧妙的设计”，作为一般性的机械概念，可以追溯到古罗马时期，主要是为了区别与手工工具。现代中文之“机械”一词为机构为英语之（Mechanism）和机器（Machine）的总称。机械的特征有：机械是一种人为的实物构件的组合。机械各部分之间具有确定的相对运动。故机器能转换机械能或完成有用的机械功，是现代机械原理中的最基本的概念，中文机械的现代概念多源自日语之“机械”一词，日本的机械应用品对机械概念做如下定义（即符合下面三个特征称为机械Machine）：1、机械是物体的组合，假定力加到其各个部分也难以变形。2、这些物体必须实现相互的、单一的、规定的运动。3、把施加的能量转变为最有用的形式，或转变为有效的机械功。机构和机器的定义来源于机械工程学，属于现代机械原理中的最基本的概念，中文机械的现代概念多源自日语之“机械”一词。一切具有确定的运动系统的机器和机构的总称。如：机床、拖拉机等。机械工程就是以有关的自然科学和技术科学为理论基础。机械齿轮（图2）结合在生产实践中积累的技术经验，研究和解决在开发设计、制造、安装、运用和修理各种机械中的理论和实际问题的一门应用学科。各个工程领域的发展都要求机械工程有与之相适应的发展，都需要机械工程提供所必需的机械。某些机械的发明和完善，又会导致新的工程技术和新的产业的出现和发展。例如大型动力机械的制造成功，促成了电力系统的建立；机车的发明导致了铁路工程和铁路事业的兴起；内燃机、燃气轮机、火箭发动机等的发明和进步，以及飞机和航天器的研制成功导致了航空、航天事业的兴起；高压设备的发展导致了许多新型合成化学工程的成功等等。机械工程就是在各方面不断提高的需求的压力下获得发展动力，同时又从各个学科和技术的进步中得到改进和创新的能力。机械是简单的装置，它能够将能量、力从一个地方传递到另一个地方。机械齿轮（图3）它能改变物体的形状结构创造出新的物件。在生活中，我们周围有数不清的不同种类的机械在为我们工作。机械的日常的理解是机械装置，也就是各种机器与器械。从机械专业的角度来说：机械具有相当重要的基础地位。机械是现代社会进行生产和服务的五大要素（即人、资金、能量、材料和机械）之一。在马克思说到工业社会时候，说工业社会，尤其是大工业社会，即用机器生产机器的时代。无论从生活中接触的各种物理的装置，如电灯、电话、电视机、冰箱、电梯等等都包含有机器的成分，或者包含在广义的机械之中，而从生产中来看，各种机床、自动化装备、飞机、轮船、神五、神六等等，都缺不了机械。所以，机械是现代社会的一个基础。如果有人要说农业也是基础的话，也无可厚非，但是在现代的社会来说，机械作为整个工业和工程的基础，可以毫不夸张地认为也是社会一根大柱子。任何现代产业和工程领域都需要应用机械，就是人们的日常生活，也越来越多地应用各种机械了，如汽车、自行车、钟表、照相机、洗衣机、冰箱、空调机、吸尘器等等。最早的“机械”定义为古罗马建筑师维特鲁威（Vitruvii）在其著机械齿轮（图4）作建筑十书主要对于搬运重物发挥效力的机械和工具作了区别：“机械（machane）和工具（organon）之间似乎有着以下的区别。即机械是以多数人工和很大的力量而发生效果的，如重弩炮和葡萄压榨机。而工具则是一名操纵人员慎重地处理来达到目的的，如蝎形轻弩炮或不等圆的螺旋装置。因此工具和机械都是利用上不可缺少的东西。”古希腊已有圆柱齿轮。亚历山大利亚希罗（Heron of Alexandria）在1世纪最早讨论了机械的基本要素，他认为机械的要素有五类：轮与轴，杠杆，滑车，尖劈，螺旋。希罗的论述反映了古典机械的特征。公元前中国已在指南车上应用复杂的齿轮系统，在被中香炉中应用了能永保水平位置的十字转架等机件。释文称：“机，弩牙；括，箭括。”说文解字对“机”的解释是“机，主发者也”，指弩机。 1724年德国莱比锡机械士廖波尔特（Leopold）给出的定义为“机械或工具是一种人造的设备，用它来产生有利的运动；同时在不能用其他方法节省时间和力量的地方，它能做到节省”。英国机械学家威利斯（R.Willis）在其机构学原理（The Principle of Mechanism，1841年）所给的定义是：机械齿轮减速机“任何机械（machine）都是由用各种不同方式连接起来的一组构件组成，使其一个构件运动，其余构件将发生一定的运动，这些构件与最初运动之构件的相对运动关系取决于它们之间连接的性质。”德国机械学家勒洛（F.Reuleaux ）在其理论运动学（Theoretische Kinematik ，Grundzge einer Theorie des Maschienenwesens，1875年）中的定义为“机械是多个具有抵抗力之物体的组合体，其配置方式使得能够借助它们强迫自然界的机械力做功，同时伴随着一定的确定运动。”总体来讲，机械就是能帮人们降低工作难度或省力的工具装置，像筷子、扫帚以及镊子一类的物品都可以被称为机械，他们是简单机械。而复杂机械就是由两种或两种以上的简单机械构成。通常把这些比较复杂的机械叫做机器。中国是世界上机械发展最早的国家之一。中国的机械工程技术不但历史悠久，而且成就十分辉煌，不仅对中国的物质文化和社会经济的发展起到了重要的促进作用，而且对世界技术文明的进步做出了重大贡献.传统机械方面，我国在很长一段时期内都领先于世界。到了近代由于特别是从18世纪初到19世纪40年代，由于经济社会等诸多原因，我国的机械行业发展停滞不前，在这100多年的时间里正是西方资产阶级政治革命和产业革命时期，机械科学技术飞速发展，远远超过了中国的水平。这样，中国机械的发展水平与西方的差距急剧拉大，到十九世纪中期已经落后西方一百多年。新中国建立后特别是近三十年来，我国的机械科学技术发展速度很快。向机械产品大型化，精密化、自动化和成套化的趋势发展。在有些方面已经达到或超过了世界先进水平。总的来说，就目前而言中国机械科学技术的成就是巨大的，发展速度之快，水平之高也是前所未有的。这一时期还没有结束，我国的机械科学技术还将向更高的水平发展。只要我们能够采取正确的方针、政策、用好科技发展规律并勇于创新，我国的机械工业和机械科技一定能够振兴，重新引领世界机械工业发展潮流。就小型夯实机械而言：上世纪60年代以前，我国小型夯实机械非常缺乏，很多小型场地的夯实基本上采用人工夯实。上世纪60年代初期，长沙建设机械研究所与北京建筑工程学院等单位合作，在群众性技术革新成果的基础上总结发明了具有中国特色的蛙式

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