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毕 业 设 计（论 文）任 务 书1本毕业设计（论文）课题应达到的目的： 本毕业设计课题的主要目的是培养学生综合运用所学的基础理论、专业知识和专业基本技能分析和解决实际问题，训练初步工程设计的能力。根据机械设计、制造及其自动化专业的特点，着重地培养以下几方面能力：1调查研究、中外文献检索、阅读与翻译的能力；2综合运用基础理论、专业理论和知识分析解决实际问题的能力；3查阅和使用专业设计手册的能力；4设计、计算与绘图的能力，包括使用计算机进行绘图的能力；5撰写设计说明书（论文）的能力。2本毕业设计（论文）课题任务的内容和要求（包括原始数据、技术要求、工作要求等）： 试设计用于流水线上箱体内孔加工的专用镗床的液压动力系统。镗床采用液压进给系统自动化加工。机床加工过程的工作循环为：工件安装夹紧到位，刀头快速接近工件，工进速度镗削内孔，加工到位停止，刀头快速退回。进给刀头及拖板最大行程500mm，最大加工进给力12kN，最小进给速度2 mm/s ，最大进给速度不大于20 mm/s ，快进速度60mm/s，快进行程150 mm。要求保证加工质量，自动化，能效高，调速稳定。 毕 业 设 计（论 文）任 务 书3对本毕业设计（论文）课题成果的要求包括图表、实物等硬件要求： 1毕业设计开题报告（文献综述2000字以上，列表附参考文献16篇以上）；2毕业设计外文专业文献阅读及翻译（原文和译文，译文3000汉字以上）；3论文大纲（撰写论文章节目录等）；4液压系统原理图；5液压系统工况图；6液压系统液压站总装配图；7部件装配图及零件图；8设计计算说明书。4主要参考文献： 1液压与气压传动 姜继海编 高等教育出版社 2009年5月 第二版 2.液压与气压传动 左健民主编 机械工业出版社 2009年6月 第四版3液压传动设计指导书 周诵明 编 华中理工大学出版社 1997年12月第一版4. 液压与气压传动 王积伟主编 机械工业出版社 2008年8月 第二版5机械设计手册（下册） 机械工业出版社 1974年1月 第一版6新编液压工程手册 雷天觉主编 北京理工大学出版社 1998年1月第一版7动力机械与液压装置 朱学敏编 机械工业出版社 2004年4月第一版 毕 业 设 计（论 文）任 务 书5本毕业设计（论文）课题工作进度计划：15121616.01.101602.25-1603.09160309-1604.251604.26-1605.061605.06-1605.131605.13-1605.26完成任务书、开题；毕业设计调研；毕业实习调研；完成开题报告、外文阅读与翻译、论文大纲；提交论文草稿，4月中旬中期检查；毕业设计优化；提交论文定稿；准备答辩；答辩，修改完成最终稿；所在专业审查意见：通过负责人： 2015 年 12 月23 日 毕 业 设 计（论文） 开 题 报 告 1结合毕业设计（论文）课题情况，根据所查阅的文献资料，每人撰写不少于1000字左右的文献综述： 流水线专用镗床液压动力系统设计-液压站设计文献综述面对我国经济近年来的快速发展，机械制造工业的壮大，在国民经济中占重要地位的制重造业领域得以健康快速的发展。制造装备的改进，使得作为制造工业重要设备的各类机加工艺装备也有了许多新的变化，尤其是孔加工，其在今天的液压系统的地位越来越重要。镗床液压系统的设计，除了满足主机在动作和性能方面规定的要求外，还必须符合体积小、量轻、成本低、效率高、结构简单、工作可靠、使用和维修方便等一些公认的普遍设计原则。液压系统的设计主要是根据已知的条件，来确定液压工作方案、液压流量、压力和液压泵及其它元件的设计。近五十年来，在工业中有两个学科分支发展极快。其一是电子学中的计算机技术；其二是机械学中的液压控制与传动技术。这两门技术互相渗透和融合，是现代机械的设计、制造和使用突飞猛进。作为现代机械设备实现传动与控制的重要技术手段，液压技术在国民经济各领域得到了广泛的应用。与其他传动控制技术相比，液压技术具有能量密度高配置灵活方便调速范围大工作平稳且快速性好易于控制并过载保护易于实现自动化和机电液一体化整合系统设计制造和使用维护方便等多种显著的技术优势，因而使其成为现代机械工程的基本技术构成和现代控制工程的基本技术要素。目前，仅有以下三种基本方法传递动力：电气、机械和流体。大多数应用系统实际上是将三种方法组合起来而得到最有效地最全面的系统。为了合理地确定采取哪种方法，重要的是了解各种方法的显著特征。例如液压系统在长距离上比机械系统更能经济地传递动力。然而液压系统与电气系统相比，传递动力的距离较短。液压动力传递系统涉及电动机、调节装置和压力，流量控制。总的来说，该系统包括： l 泵：将原动机的能力转换成作用在执行部件上的液压能。 2 阀：控制泵产生流体的运动方向、产生的功率的大小，以及到达执行部件液体的流量。功率大小取决于对流量和压力大小的控制。 3 执行部件：将液压能转换成可用的机械能。 4 介质即油液：可进行无压缩传递和控制，同时可以润滑部件，使阀体密封和系统冷却。 5联接件：联接各个系统部件，为压力流体提供功率传输通路，将液体返回邮箱。 6 油液贮存和调节装置：用来确保提供足够质景和数量并冷却的液体。液压系统在工业中应用广泛，例如冲压，钢类工件的磨削及一般加工业、农业、矿业、航大技术、深海勘探、运输、海洋技术，近海天然气和石油勘探等行业，简而言之，在日常生活中很少有人不从液压技术中得到某种益处。我国液压（含液力，下同）、气动和密封件工业发展历程，大致可分为三个阶段，即：20世纪50年代初到60年代初为起步阶段：60-70 年代为专业化生产体系成长阶段；80-90年代为快速发展阶段。其中，液压工业于50年代初从机床行业生产仿苏的磨床、拉床、仿形车床等液压传动起步，液压元件由机床厂的液压车间生产，自产自用进入60年代后，液压技术的应用从机床逐渐推广到农业机械和工程机械等领域，原来附属于主机厂的液压车间有的独立出来，成为液压件专业生产厂。到了60年代末、70年代初，随着生产机械化的发展，特别是在为第二汽车制造厂等提供高效、自动化设备的带动下，液工压元件制造业出现了迅速发展的局面，一批中小企业也成为液压件专业制造厂。进入80年代，在国家改革开放的方针指引下，随着机械工业的发展，基础件滞后于主机的矛盾日益突出，并引起各有关部门的重视。为此，原一机部于1982年组建一通用基础件工业局，将原有分散在机床、农业机械、工程机械等行业归口的液压、气动和密封件专业厂，统一划归通用基础件局管理，从而使该行业在规划、投资、引进技术和科研开发等方面得到基础件局的指导和支持。从此进入了快速发展期，先后引进了60余项国外先进技术，其中液压40余项、气动7项，经消化吸收和技术改造，现均己批量生产，并成为行业的主导产品。目前我国己和美国、日本、德国等国家著名厂商合资或由外国厂商独资建立了柱塞泵马达、行星减速机、转向器、液压控制阀、液压系统、静液压传动装置、液压件铸造、气动控制阀、气缸、气源处理三联件、机械密封、橡塑密封等类产品生产企业50多家，液压技术也趋于完善，正逐步向世界水平靠近。液压传动技术广泛应用了如自动控制技术、计算机技术、微电子技术、及新工艺和新材料等高技术成果，使传统技术有了新的发展，也使液压系统和元件的质量、水平有一定的提高。尽管如此，走向二十一世纪的液压技术不可能有惊人的技术突破，应当主要靠现有技术的改进和扩展，不断扩大其应用领域以满足未来的要求。综合国内外专家的意见，其主要的发展趋势将集中在以下几个方面： （1）减少能耗,充分利用能量液压技术在将机械能转换成压力能及反转换方面，已取得很大进展，但一直存在能量损耗，主要反映在系统的容积损失和机械损失上。如果全部压力能都能得到充分利用，则将使能量转换过程的效率得到显著提高。 （2）主动维护，液压系统维护已从过去简单的故障拆修，发展到故障预测，即发现故障苗头时，预先进行维修，清除故障隐患，避免设备恶性事故的发展。另外，还应开发液压系统自补偿系统，包括自调整、自润滑、自校正，在故障发生之前，进市补偿，这是液压行业努力的方向。 （3）机电一体化，电子技术和液压传动技术相结合，使传统的液压传动与控制技术增加了活力，扩大了应用领域。实现机电一体化可以提高工作可靠性，实现液压系统柔性化、智能化，改变液压系统效率低，漏油、维修性差等缺点，充分发挥液压传动出力大、贯性小、响应快等优点。液压系统的设计方法并无严格的顺序，各步骤间往往要相互穿插进行。一般来说，在明确设计要求之后，大致按如下步骤进行。 1）确定液压执行元件的形式； 2）进行工况分析，确定系统的主要参数； 3）制定基本方案，拟定液压系统原理图； 4）选择液压元件； 5）液压系统的性能验算； 6）绘制工作图，编制技术文件。 本课题主要是设计用于流水线上箱体内孔加工的专用镗床的液压动力系统。镗床采用液压进给系统自动化加工。机床加工过程的工作循环为：工件安装夹紧到位，刀头快速接近工件，工进速度镗削内孔，加工到位停止，刀头快速退回，其大致工作过程为：定位夹紧快进工进快退停止。根据课题任务书得到主要设计参数及要求如下：进给刀头及拖板最大行程500mm，最大加工进给力12kN，最小进给速度2 mm/s ，最大进给速度不大于20 mm/s ，快进速度60mm/s，快进行程150 mm。要求保证加工质量，自动化，能效高，调速稳定。 参考文献： 1 王积伟，黄谊，章宏甲液压传动 M北京：机械工业出版社，2006 2 张利平液压传动系统及设计 M北京：化学工业出版社，2005 3 雷天觉，新编液压工程手册 M北京：北京理工大学出版社，1998 4 路甬祥，液压气动技术手册 M北京：机械工业出版社，2002 5 成大先，机械设计手册 M北京：化学工业出版社，2002 6 王春行，液压控制系统 M北京：机械工业出版社，2002 7 李状云，液压元件与系统 M北京：机械工业出版社，2002 8 陈书杰.气动传动与控制，北京：冶金工业出版社，1991. 9 张利平，周兰午，齐习娟，制造技术与机床J, 2000(10):11-13. 10 盛小明, 165F曲轴箱组合镗床液压站设计J,2003(1):177-178. 11 李长志, WHC-160数控铣镗床液压系统故障分析两例J, 设备管理与维修, 2003(11):41-41. 12王运炎 朱莉主编机械工程材料机械工业出版社2008 13左健民主编液压与气压传动机械工业出版社2007 14梁俊彦,李玉翔.机电一体化技术的发展及应用J.科技资讯,2007(9). 15芮延年.机电一体化系统设计M.北京机械工业出版社,2004. 16章浩,张西良,周士冲.机电一体化技术的发展与应用J.农机化研究,2006(7). 毕 业 设 计（论文） 开 题 报 告 2本课题要研究或解决的问题和拟采用的研究手段（途径）： 一.课题的内容本课题主要是设计用于流水线上箱体内孔加工的专用镗床的液压动力系统。镗床采用液压进给系统自动化加工。机床加工过程的工作循环为：工件安装夹紧到位，刀头快速接近工件，工进速度镗削内孔，加工到位停止，刀头快速退回，其大致工作过程为：定位夹紧快进工进快退停止。根据课题任务书得到主要设计参数及要求如下：进给刀头及拖板最大行程500mm，最大加工进给力12kN，最小进给速度2 mm/s ，最大进给速度不大于20 mm/s ，快进速度60mm/s，快进行程150 mm。要求保证加工质量，自动化，能效高，调速稳定。二.课题的目的液压传动与机械传动、电气传动为当代三大传动形式，是现代发展起来的一门新技术，液压传动是工科机械类专业的重点课程之一，既有理论知识学习，又有实际技能训练，为此，在教学中安排一至二周的课程设计，本课题具有如下几点意义： 1.综合运用液压传动及其他先修课的理论知识和物产实际知识，进行液压传动设计实践，从而使这些知识得到进一步的巩固加深和发展 2.熟悉和掌握拟定液压传动系统图，液压缸结构设计，液压元件选择以及液压系统的计算方法 3.通过此次毕业设计，提高设计、计算和绘图的基本技能，熟悉设计资料和设计手册，培养独立分析问题和解决问题的能力，为之后毕业设计及设计工作打下必要的基础。 4. 提高撰写设计说明书（论文）的能力。三.课题设计方案（1）液压系统工作流程动作方案：夹紧油缸：快进 慢进 达到夹紧力后启动进给油缸工作进给油缸：快进 慢进 到达进给终点 快速退回（2）根据动作方案及工况分析得到原理如下图所示： 毕 业 设 计（论文） 开 题 报 告 指导教师意见：1对“文献综述”的评语：检索了相关资料并进行了综述。 2对本课题的深度、广度及工作量的意见和对设计（论文）结果的预测：设计课题难度适中，工作量中等，预计能够完成任务。 3.是否同意开题： 同意 不同意 指导教师： 2016 年 03 月 07 日所在专业审查意见：同意 负责人： 2016 年 03 月 08 日Hydraulic systemChapter 1 IntroductionHydraulic Pump Station also known as the stations are independent h- ydraulic device. It requested by the oil gradually. And controlling the hydraulic oil flow direction, pressure and flow rate, applied to the mainframe and hy- draulic devices separability of hydraulic machinery. Users will be provided after the purchase hydraulic station and host of implementing agencies (motor oil or fuel tanks) connected with tubing, Hydraulic machinery can be realized from these movements and the work cycle.Hydraulic pump station is installed, Manifold or valve combination, t- anks, a combination of electrical boxes.Functional components :Pump device - is equipped with motors and pumps, hydraulic station is the source of power. to mechanical energy into hydraulic oil pressure can be. Manifold - from hydraulic valve body and channel assembled. Right direction for implementation of hydraulic oil, pressure and flow control.Valve portfolio - plate valve is installed in up board after board conn-ects with the same functional IC. Tank - plate welding semi-closed containers, also loaded with oil filtering network, air filters, used oil, oil filters and cooling. Electrical boxes - at the two patterns. A set of external fuse terminal plate; distribution of a full range of electrical control.Hydraulic Station principle : motor driven pump rotation, which pump oil absorption from the oil tank. to mechanical energy into hydraulic pressure to the station, hydraulic oil through Manifold (or valve combinations) realized the direction, pressure, After adjusting flow pipe and external to the cylinder hydraulic machinery or motor oil, so as to control the direction of the motive fluid transformation force the size and speed the pace of promoting the various acting hydraulic machinery.1.1 A development course China Hydraulic (including hydraulic, the same below), pneumatic and seals industrial development process can be broadly divided into three phases, namely : 20 early 1950s to the early 1960s, the initial stage; 60s and 70 for specialized production system ;8090s growth stage for the rapid development stage. Which, hydraulic industry in the early 1950s from the machine tool industry production of fake Su-grinder, broaching machine, copying lathe, and other hydraulic drive started, Hydraulic Components from the plant hydraulic machine shop, self-occupied. After entering the 1960s, the application of hydraulic technology from the machine gradually extended to the agricultural machinery and mechanical engineering fields, attached to the original velocity of hydraulic shop some stand out as pieces of hydraulic professional production. To the late 1960s, early 1970s, with the development of mechanized production, especially in the second automobile factory in providing efficient, automated equipment, along with the Hydraulic Components manufacturing has experienced rapid development of the situation, a group of SMEs have become professional hydraulic parts factory. 1968 Chinas annual output of hydraulic components have nearly 200,000 in 1973, machine tools, agricultural machinery, mechanical engineering industries, the production of hydraulic parts factory has been the professional development of more than 100 and an annual output more than one million. an independent hydraulic manufacturing industry has begun to take shape. Then, hydraulic pieces of fake products from the Soviet Union for the introduction of the product development and technical design combining the products to the pressure, Hypertension, and the development of the electro-hydraulic servo valves and systems, hydraulic application areas further expanded. Aerodynamic than the start of the industrial hydraulic years later, in 1967 began to establish professional pneumatic components factory, Pneumatic Components only as commodity production and sales.Sealed with rubber and plastics, mechanical seals and sealing flexible graphite sealing industry, the early 1950s from the production ordinary O-rings.rubber and plastics extrusion, such as oil seal sealing and seal asbestos products start to the early 1960s, begun production of mechanical seals and flexible graphite sealing products. 1970s, the burning of the former Ministry, a Ministry, the Ministry of Agricultural Mechanization System, a group of professional production plants have been established, and the official establishment of industries to seal industrial development has laid the foundation for growth.Since the 1980s, in the countrys reform and opening up policy guidelines, with the development of the machinery industry, based mainframe pieces behind the conflicts have become increasingly prominent and attracted the attention of the relevant departments. To this end, the Ministry of the original one in 1982, formed the basis of common pieces of Industry, will be scattered in the original machine tools, agricultural machinery, mechanical engineering industries centralized hydraulic, pneumatic and seals specialized factories, placing them under common management infrastructure pieces Bureau, so that the industry in the planning, investment, technology and scientific research and development in areas such as infrastructure pieces Bureau of guidance and support. Since then entered a phase of rapid development, has introduced more than 60 items of advanced technology from abroad, including more than 40 items of hydraulic, pneumatic 7. After digestion and absorption and transformation, now have mass production, and industry-leading products. In recent years, the industry increased the technological transformation efforts, in 1991, Local enterprises and the self-financing total input of about 20 billion yuan, of which more than 1.6 billion yuan Hydraulic. Through technological transformation and technology research, and a number of major enterprises to further improve the level of technology, technique and equipment to be greatly improved. In order to form a higher starting point, specialization, and run production has laid a good foundation. In recent years, many countries in the development of common ownership guidelines, under different ownership SMEs rapid rise showing great vitality. With the further opening up, three-funded enterprises rapid development of industry standards for improving and expanding exports play an important role. Today, China has and the United States, Japan, Germany and other countries famous manufacturers joint ventures or wholly-owned by foreign manufacturers to establish a piston pump / motor, planetary reduction gears, steering gear, hydraulic control valve, hydraulic system, hydrostatic transmission, hydraulic Casting. pneumatic control valve, cylinder, gas processing triple pieces, mechanical seals, rubber and seal products more than 50 production enterprises, attracting foreign investment over 200 million U.S. dollars. 1.2 the current situation 1.21Basic Profiles After 40 years of efforts, China hydraulic, pneumatic and sealing industry has formed a relatively complete categories. a certain level of technical capacity and the industrial system. According to the 1995 Third National Industrial Census statistics, hydraulic, Pneumatic seals and industrial 370,000 annual sales income of 100 million yuan in state-owned, village-run, private and cooperative enterprises, individual, three capital enterprises with a total of more than 1,300, of which about 700 hydraulic, Pneumatic seals and the approximately 300 thousand. By 1996 with the international trade statistics, the total output value of Chinas industry hydraulic 2.348 billion yuan, accounting for the worlds 6; Pneumatic industry output 419 million yuan, accounting for world No. 10. 1.22the current supply and demand profiles Through the introduction of technology, independent development and technological innovation, and high-pressure piston pump, gear pumps, vane pump, General Motors hydraulic valves, tanks, Non-lubricated aerodynamic pieces and various seals of the first large technology products has increased noticeably. stability of the mass production may, for various mainframe products provide a level of assurance. In addition, hydraulic and pneumatic components of the CAD system, pollution control, proportional servo technology has scored some achievements, and is already in production. Currently, hydraulic, pneumatic and seals products total about 3,000 species, more than 23,000 specifications. Among them, there are 1,200 hydraulic varieties, more than 10,000 specifications (including hydraulic products 60 varieties 500 specifications); Pneumatic are 1,350 varieties, more than 8,000 specifications; Rubber seal 350 species more than 5,000 specifications have been basically cater to the different types of mainframe products to the general needs, complete sets of equipment for major varieties of matching rate was over 60%, and started a small amount of exports. 1998 pieces of homemade hydraulic output 4.8 million.sales of about 28 billion (of which about 70% mechanical systems); aerodynamic pieces yield 3.6 million. sales of about 5.5 billion (of which about 60% of mechanical systems); Seals output of about 800 million. sales of about 10 billion (of which about 50% mechanical systems). According to the China Hydraulic Pneumatic Seals Industry Association 1998 annual report, hydraulic product sales rate of 97. 5% (101% for hydraulic), pneumatic 95.9%, 98.7% sealed. This fully reflects the basic marketing convergence.My hydraulic, pneumatic and sealing industry has attained a great deal of progress, but with mainframe development needs, and the worlds advanced level, there are still many gaps, mainly reflected in the product variety, performance and reliability, and so on. Hydraulic products as an example, products abroad only one-third, life for half abroad. In order to meet key mainframe, and mainframe imports of major technology and equipment needs, every year a large number of hydraulic, pneumatic and sealing products imports. According to customs statistics and the analysis of data, in 1998 hydraulic, pneumatic and seals in the import about 200 million U.S. dollars, Hydraulic which about 1.4 billion dollars, aerodynamic nearly 030 million U.S. dollars, sealed about 030 million U.S. dollars. compared with a slight decline in 1997. By sums, currently imported products on the domestic market share of about 30%. 1998 pieces of the domestic market demand for hydraulic total of about six million, the total sales of nearly 40 billion; aerodynamic pieces of the total demand of about 5 million, with sales more than 700 million yuan; Seals total demand of about 1.1 billion. total sales of about 1.3 billion. 1.3 the development trend of the future 1.31affect the development of the main factors (1) product development ability, and the level of technological development and speed can not completely meet the advanced mainframe products, major equipment and technology imported equipment and maintenance support; (2) the number of enterprises manufacturing technology, the level of equipment and management standards are comparatively backward, coupled with a strong sense of quality, resulting in low levels of product performance, quality, Reliability poor services in a timely manner, lack of user satisfaction and trust of the brand-name products;(3) industry specialization of production low, scattered strength, low repeat serious, between regions and enterprises of convergence products, blindly compete with each other, driving down prices, the decline of enterprise returns, lack of funds, liquidity difficulties, product development and technological transformation is inadequate and seriously restricted the industry to improve the overall level of competition and the increase of strength; (4) The internationalization of the domestic market and the increasing degree of foreign companies have entered the Chinese market and participate in competition with the domestic private and cooperative enterprises, individuals, foreign-funded enterprises, such as the rise of state-owned enterprises due to the growing impact. 1.32the development trend As the socialist market economy continues to deepen, hydraulic, pneumatic and sealing products in the market supply and demand and there is a greater change, long ago to a shortage of the sellers market has basically become a structural surplus of the characteristics of the buyers market place . Overall capacity, is already in oversupply situation, in particular the general low level of hydraulic, pneumatic and seals, the general oversupply; and the host of urgent high-tech high-parameter, high value-added high-end products, and they do not satisfy the market needs, only dependent on imports. China joins the WTO, its impact may be even greater. Therefore, the 15 during the growth of the output value of industry, must not depend on volume growth and the industry should address the structural problems of their own, increase the intensity of the adjustment of the industrial structure and product mix, is, we should rely on the improvement of quality, and promote technical upgrading of products to meet market demand and stimulating, seek greater development.2 The application of hydraulic power sliding stage2.1 Power sliding Taiwan introducedThis paper deals with the investigation for slide units impact and motion stability in modular machine tool fay means of the method of power bond graph and state space analysis. The dynamic mathematical model of self-adjusting back pressure speed control system used to drive slide unit is established. Main reasons and affecting factors for slide unit impact and motion unstability are analysed through computer digital simulation, It is concluded from those that, if the structural dimensions of hydraulic cylinder and back pressure valve are designed rationally, the slide units dynamics will markedly be improved.NOMENCLATURESfflow sourceSeisliding friction force in slide unitRequivalent viscous friction coefficient in slide unitIimass of slide unit and cylinderhmass of SABP valve spoolCi,C2hydraulic capacitances of rod chamber and non-rod chamber in cylinder re-spec-tivelyC3spring compliance of SABP valveRrR2hydraulic resistances of damping holesR9hydraulic resistance of orifice of SABP valveSe2presetting force of spring in SABP valveI4J5equivalent liquid inertia in pipe linesCCgequivalent hydraulic capacitances in pipe linesequivalent hydraulic resistances in pipe linesV-j Voil-containing volumes in non-rod chamber and rod chamber respectivelyP,r:, P-ioil pressures in non-rod chamber and rod chamber respectivelyFload acted on slide unitVslide unit velocity* Department of Mechanical Engineering, Dalian Ur.iversity of Technology, Dalian. China.2.2 IntroductionDuring operation of modular machine tool, the changes of slid units speed and load acted on it in both magnitude and direction will affect working performar.ee to a different extent Particularly the impact caused by sudden vanishing of load and the motion unstability due to periodical change of load in operation will affect the surface quality of the workpiece machined, and the tool would be broken off under serious conditions, By using the method of power bond graph and state space analysis, the dynamic mathematical model of the system used to drive slide unit is established, that is called as self-adjusting back pressure speed control system and abbreviated to SABP system. In order to improve slide units dynamics, it is necessary to find out the main reasons and affecting factors, that must be based on computer digital simulation and study on the results.2.3Dynamic MathematicaModeldThe schematic diagram of SABP system is shown in Fig.l, the system is used to perform the cycle of feeding, stopping and returning. Four way control valve works in the right position during slide units feeding. The supply pressure of the pump is approximately constant under the action of pressure relief valve, the oil through the control valve and pressure compensated flow control valve enters the non-rod chamber to put slide unit forward. At the same time, the oil from the rod chamber is discharged through SABP valve and directional control valve to tank. In this process, the state of two check valves and pressure relief valve is not changed, To establish the mathematical model as reasonably and simply as possible, consideration must be focused on main affecting factors for a complex non-linear system such as the SABP system. It is illustrated by theoretical analysis and test result , that the transient time of the system is much longer than that of the flow control valve, and the flowrate overshoot of the valve in transients affects very small to slide unit speed because of the ;large effective sectional area of non-rod chamber in cylinder. For investigating the systems dynamics widely and deeply, the initial modeltn is further simplified in this paper, and so the study can be efficiently made with microcomputer. It is assumed that the flowrate through the flow control valve isconstant in the whole transient process, and is denoted to a flow source.Fig.2 shows the structure diagram of the dynamic model of the system, it is composed of cylinder, slide unit, SABP valve and pipe line; etc.By using the method of power bond graph and state space analysis in this paper, the dynamic mathematical model of the system is to be established- The power bond graph is a power flow diagram, which expresses abstractly the actions among sub-systems as three effects, i.e. resistance effect, capacitive effect and inertia effect, according to the way of energy transform, on the basis of practical structure and by means of method of lumped parameters. The model is characterized by a clear conception in physics, and non-linear system can be accurately analysed in combination with method of state space analysis, thus it is a effective method used in the dynamic investigation of complex non-linear system in thetimedomain.From main performances of components in SAEP system, the power bond graph of the system has been formed by means of the rule of model establishing and is shown in Fig.3. Half arrow in each bond indicates a direction of power How, two variahles of power are effort variable and flow variable. O-junction illustrates algebraic summation of flow variables at common effort, i.e. parallel connection, 1-junction does algebraic summation of effort variables at common flow, i.e. series connection. The symbol TF represents power transformer between two types of energy, and transforming modulus between efforts or flows is noted below the symbol TF. Short transverse bar across one end of each bond shows causality between two variables. A full arrow expresses a control action. Among three actions, there is an integration or differential form in capacitive effect and inertia effect between two variables. So state equation may be derived from Fig.3, there are nine state variables in this complex nonlinear equation. Studying on the slide units dynamics is started with impact and motion stability. The equation is simulated by using the method of 4th order Runge-Kutta integration procedure on IBM-PC computer. Fig.4 and Fig.5 illustrate the results respectively.Slide units impact phenominon results from loads vanishing in the transients, for example, the situation of drilling through workpiece, Fig.4 expounds the variations of the load and speed of slide unit, the pressures of chambers in cylinder. When slide unit motions evenly under the action of load, the oil pressure in non-rod chamber is very high, and there is a lot of hydraulic energy accumulated in side. The pressure decreases at once with loads discharging rapidly. During the process of oil pressure converting from high to low, the system absorbs some of the energy, so slide unit impacts forward with high speed. And then the oil in rod chamber iscompressed to increase back pressure, some of the energy is consumed, which plays a part of restraining the impact of the slide unit. It must be noted that inlet pressure of SABP valve telys on the interaction of pressures of two chambers, and increases rapidly at the instant of loads vanishing, and then stabilizes at some value greater than initial one. This pressure is also greater than one of traditional speed control system, therefore the energy can be absorbed much more in the rod chamber. In result, the impact of slide unit in SABP system is 20% lawer than in traditionals. It is thus clear that slide unit with SABP system for driving has a good performance in restraining the impact and SABP valve plays an important part in that,2.4Motion stabilityWhen load acting on slide unit varies periodically, such as the situation of milling, slide units speed will bring about some pulse. In order to meet the requirements of manufacturing quality, the magnitude of the speed pulse must be reduced as small as possible. The variation of the load is assumed to be of sine wave, in order to simplify discussion of the problem, The result of digital simulation is shown in Fig.5 It can be seen that, the response of the system is the sameastraditionls and the differences between them are very small. The reason for this is that the variation of the load is not targe, there the pressures in chambers vary very little that is, the effect of the SABP valve is not obvious.2.5 ImprovementIt is shown by studying, that dynamics of slide unit which used SABP speed control system as driving system is better than that of traditional system. To reduce the slide units impact, the back pressure of rod chamber has to be increased rapidly in the transients of loads vanishing; on the other hand, to enhance the slide units motion stability, it is necessary to raise the system rigidity. However, main recommendation lies in decreasing the volume of oil. It is known from system structure that, there is a lot of oil-containing volume between the rod chamber and drain pipe as shown in Fig.6a. Because the volume exists, not only the effect of SABP valve is delayed and reduced, hut also the rigidity of the system is decreased. Therefore, it is hindered to further improve the impact and motion stability. To make the slide unit dynamics better, the structural dimensions of cylinders chamber and the SABP valve must be designed suitably. Based on simulations under the various structural dimensions and comparison among the results, the following two measures can be taken for improvements:The ratio between volumeV4 and V3 is changed from 5.5 to 1 approximately, as shown in Fig,6b;15the bottom diameter of spool of the SABP valve is increased from 10 mm to 13 mm andthe length of side of triangular damping slot is decreased from 1 mm to 0.7mm the slide unites impact quantity can be reduced by 30%, and the time of dynamic response is shortened. In addition, slide units motion stability may be improved obviously. It is thus evident that improvements are very effective.液压系统1绪论液压站又称液压泵站，是独立的液压装置。它按逐级要求供油。并控制液压油流的方向、压力和流量，适用于主机与液压装置可分离的各种液压机械上。用户购后只要将液压站与主机上的执行机构（油缸或油马达）用油管相连，液压机械即可实现各种规定的动作和工作循环。液压站是由泵装置、集成块或阀组合、油箱、电气盒组合而成。各部件功能为：泵装置上装有电机和油泵，是液压站的动力源，将机械能转化为液压油的压力能。集成块由液压阀及通道体组装而成。对液压油实行方向、压力和流量调节。阀组合板式阀装在立板上，板后管连接，与集成块功能相同。油箱板焊的半封闭容器，上还装有滤油网、空气滤清器等，用来储油、油的冷却及过滤。电气盒分两种型式。一种设置外接引线的端子板；一种配置了全套控制电器。液压站的工作原理：电机带动油泵转动，泵从油箱中吸油供油，将机械能转化为液压站的压力能，液压油通过集成块（或阀组合）实现了方向、压力、流量调节后经外接管路并至液压机械的油缸或油马达中，从而控制液动机方向的变换、力量的大小及速度的快慢，推动各种液压机械做功。1.1发展历程我国液压（含液力，下同）、气动和密封件工业发展历程，大致可分为三个阶段，即：20世纪50年代初到60年代初为起步阶段；6070年代为专业化生产体系成长阶段；8090年代为快速发展阶段。其中，液压工业于50年代初从机床行业生产仿苏的磨床、拉床、仿形车床等液压传动起步，液压元件由机床厂的液压车间生产，自产自用。进入60年代后，液压技术的应用从机床逐渐推广到农业机械和工程机械等领域，原来附属于主机厂的液压车间有的独立出来，成为液压件专业生产厂。到了60年代末、70年代初，随着生产机械化的发展，特别是在为第二汽车制造厂等提供高效、自动化设备的带动下，液压元件制造业出现了迅速发展的局面，一批中小企业也成为液压件专业制造厂。1968年中国液压元件年产量已接近20万件；1973年在机床、农机、工程机械等行业，生产液压件的专业厂已发展到100余家，年产量超过100万件，一个独立的液压件制造业已初步形成。这时，液压件产品已从仿苏产品发展为引进技术与自行设计相结合的产品，压力向中、高压发展，并开发了电液伺服阀及系统，液压应用领域进一步扩大。气动工业的起步比液压稍晚几年，到1967年开始建立气动元件专业厂，气动元件才作为商品生产和销售。含橡塑密封、机械密封和柔性石墨密封的密封件工业，50年代初从生产普通O型圈、油封等挤压橡塑密封和石棉密封制品起步，到60年代初，开始研制生产机械密封和柔性石墨密封等制品。70年代，在原燃化部、一机部、农机部所属系统内，一批专业生产厂相继成立，并正式形成行业，为密封件工业的发展成长奠定了基础。 进入80年代，在国家改革开放的方针指引下，随着机械工业的发展，基础件滞后于主机的矛盾日益突出，并引起各有关部门的重视。为此，原一机部于1982年组建了通用基础件工业局，将原有分散在机床、农业机械、工程机械等行业归口的液压、气动和密封件专业厂，统一划归通用基础件局管理，从而使该行业在规划、投资、引进技术和科研开发等方面得到基础件局的指导和支持。从此进入了快速发展期，先后引进了60余项国外先进技术，其中液压40余项、气动7项，经消化吸收和技术改造，现均已批量生产，并成为行业的主导产品。近年来，行业加大了技术改造力度，19911998年国家、地方和企业自筹资金总投入共约20多亿元，其中液压16亿多元。经过技术改造和技术攻关，一批主要企业技术水平进一步提高，工艺装备得到很大改善，为形成高起点、专业化、批量生产打下了良好基础。近几年，在国家多种所有制共同发展的方针指引下，不同所有制的中小企业迅猛崛起，呈现出勃勃生机。随着国家进一步开放，三资企业迅速发展，对提高行业水平和扩大出口起着重要作用。目前我国已和美国、日本、德国等国著名厂商合资或由外国厂商独资建立了柱塞泵/马达、行星减速机、转向器、液压控制阀、液压系统、静液压传动装置、液压件铸造、气动控制阀、气缸、气源处理三联件、机械密封、橡塑密封等类产品生产企业50多家，引进外资2亿多美元。 1.2目前状况 1.21基本概况 经过40多年的努力，我国液压、气动和密封件行业已形成了一个门类比较齐全，有一定生产能力和技术水平的工业体系。据1995年全国第三次工业普查统计，我国液压、气动和密封件工业乡及乡以上年销售收入在100万元以上的国营、村办、私营、合作经营、个体、“三资”等企业共有1300余家，其中液压约700家，气动和密封件各约300余家。按1996年国际同行业统计，我国液压行业总产值23.48亿元，占世界第6位；气动行业总产值4.19亿元，占世界第10位。 1.22当前供需概况通过技术引进，自主开发和技术改造，高压柱塞泵、齿轮泵、叶片泵、通用液压阀门、油缸、无油润滑气动件和各类密封件第一大批产品的技术水平有了明显的提高，并可稳定的批量生产，为各类主机提高产品水平提供了保证。另外，在液压气动元件和系统的CAD、污染控制、比例伺服技术等方面也取得一定成果，并已用于生产。目前，液压、气动和密封件产品总计约有3000个品种、23000多个规格。其中，液压有1200个品种、10000多个规格（含液力产品60个品种、500个规格）；气动有1350个品种、8000多个规格；橡塑密封有350个品种、5000多个规格，已基本能适应各类主机产品的一般需要，为重大成套装备的品种配套率也可达60%以上，并开始有少量出口。 1998年国产液压件产量480万件，销售额约28亿元（其中机械系统约占70%）；气动件产量360万件，销售额约5.5亿元（其中机械系统约占60%）；密封件产量约8亿件，销售额约10亿元（其中机械系统约占50%）。据中国液压气动密封件工业协会1998年年报统计，液压产品产销率为97 .5%（液力为101%），气动为95.9%，密封为98.7%。这充分反映了产销基本衔接。 我国液压、气动和密封工业虽取得了很大的进步，但与主机发展需求，以及和世界先进水平相比，还存在不少差距，主要反映在产品品种、性能和可靠性等方面。以液压产品为例，产品品种只有国外的1/3，寿命为国外的1/2。为了满足重点主机、进口主机以及重大技术装备的需要，每年都有大量的液压、气动和密封产品进口。据海关统计及有关资料分析，1998年液压、气动和密封件产品的进口额约2亿美元，其中液压约1.4亿美元，气动近0.3亿美元，密封约0.3亿美元，比1997年稍有下降。按金额计，目前进口产品的国内市场占有率约为30%。1998年国内市场液压件需求总量约600万件，销售总额近40亿元；气动件需求总量约500万件，销售总额7亿多元；密封件需求总量约11亿件，销售总额约13亿元。 1.3今后发展走势 1.31影响发展的主要因素 (1)企业产品开发能力不强，技术开发的水平和速度不能完全满足先进主机产品、重大技术装备和进口设备的配