液压英文文献及翻译

1、液压系统(文献翻译) 15液压系统1.绪论液压站称液压泵站，是独立的液压装置。它是按逐级要求供油。并控制液压油流方向、压力和流量，适用在主机与液压装置可分离的各种液压机械上面。用户在购后只要将液压站与主机上执行机构（油缸或油马达）用不同的油管相连，液压机械即实现各种规定的动作与工作循环。液压站是由集成块、泵装置或阀组合、电气盒、油箱电气盒组合而成。各个部件功能为：泵装置上装有电机和油泵，其是液压站的动力源，能将机械能转化为液压油压力能。阀组合其板式阀装在立板上，板后管连接，与集成块的功能相同。油集成块是由液压阀及通道体组装而成。其对液压油实行压力、方向和流量调节。箱是板焊的半封闭容器，上面还装

2、有滤油网、空气滤清器等，是用来储油与油的冷却及过滤。电气盒分两种型式：一种是设置外接引线的端子板；一种是配置了全套控制电器。液压站工作原理：电机带动油泵转动，然后泵从油箱中吸油并供油，将机械能转化为液压站压力能，液压油通过集成块（或阀组合）实现方向、压力、流量调节后经过外接管路并至液压机械里的油缸或油马达中，从而控制液动机方向变换、力量的大小及速度的快慢，来推动各种液压机械做功。(1)液压的发展历程 在我国液压（含液力，下同）、气动和密封件工业的发展历程，大致可分成三个阶段，即：在20世纪50年代初到60年代初是起步阶段；60-70年代为专业化生产体系的成长阶段；80-90年代为快速发展阶段。

3、在其中，液压工业始于50年代初从机床行业生产的仿苏的磨床、拉床、仿形车床等液压传动来起步，液压元件由机床厂里的液压车间生产，自产自用。在进入60年代后，液压技术应用从机床逐渐推广到农业机械与工程机械等领域，原来附属于主机厂里的液压车间有些独立出来，成为液压件的专业生产厂。在60年代末、70年代初，随着生产机械化的不断发展，特别是在为第二汽车制造厂等提供了高效、自动化设备的带动下，液压元件制造业出现了不断迅速发展的局面，一批中小企业也开始成为液压件专业制造厂。1968年中国的液压元件年产量已接近20万件；而在1973年在机床、农机、工程机械等行业里，生产液压件的专业厂已发展到100余家，其年产量

4、超过100万件，这样一个独立的液压件制造业已初步形成。于此这时，液压件产品已从开始的仿苏产品发展为引进技术和自行设计相结合的产品，压力向中、高压发展，开发了电液伺服阀及系统，液压的应用领域进一步扩大。而气动工业的起步比液压稍晚几年，到1967年开始才建立气动元件专业厂，气动元件才开始作为商品生产和销售。其含橡塑密封、柔性石墨密封和机械密封的密封件工业，从50年代初生产普通O型圈、油封等挤压橡塑密封和石棉密封制品起步，在到60年代初，开始研制生产柔性石墨密封和机械密封等制品。70年代，原燃化部、一机部、农机部所属系统内，一批批专业生产厂开始相继成立，正式形成行业，为密封件工业发展成长奠定了基础。

5、 在进入80年代，国家改革开放的方针指引下，随着机械工业的不断发展，基础件滞后于主机的矛盾日益突出，引起各有关部门的重视。为此，原一机部在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、工程机械等的行业归口的气动、液压和密封件专业厂，统一划归为通用基础件局管理，从而使该行业在规划、投资、引进技术以及科研开发等方面得到基础件局的指导和支持。由此进入了快速发展期，其先后引进了60余项国外先进技术，而其中液压40余项、气动7项，经过消化吸收和技术改造，现均已批量生产，并成为了行业的主导产品。近年来，行业加大技术改造力度，1991-1998年国家、地方及企业自筹资金总投入共约20多亿元，

6、而其中液压16亿多。经过不断技术改造和技术攻关，一批主要企业技术水平进一步提高，工艺装备也得到很大改善，为形成了高起点、专业化、批量生产打下良好基础。近几年来，在国家多种所有制共同发展的方针指引下，各种不同所有制的中小企业迅猛崛起，展现出勃勃生机。随着国家进一步的开放，三资企业迅速发展，这对提高行业水平和扩大出口起着重要作用。目前为止我国已和美国、德国、日本等国著名厂商合资或直接由外国厂商独资建立了柱塞泵/马达、行星减速机、液压控制阀、转向器、液压系统、静液压传动装置、液压件的铸造、气动控制阀、气缸、气源处理的三联件、橡塑密封、机械密封等类产品生产企业50多家，总共引进外资2亿多美元。 (2)

7、目前状况 1.基本概况 在经过40多年的努力，我国的液压、气动和密封件行业已形成了一个门类比较齐全，并有一定生产能力与技术水平的工业体系。据1995年的全国第三次工业普查统计，我国在液压、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、私营、合作经营、村办、个体、“三资”等企业总共有1300余家，而其中液压约700家，气动和密封件各约300余家。在按1996年国际同行业的统计，我国液压行业总产值约23.48亿元，占世界第6位；气动行业总产值约4.19亿元，占世界第10位。 2.当前供需概况 在通过技术引进，自主开发和技术改造下，高压柱塞泵、叶片泵、齿轮泵、通用液压阀门、油缸、无油润

8、滑气动件与各类密封件第一大批产品的技术水平有了显著的提高，并可以稳定的批量生产，为各类主机提高产品水平提供保证。另外，在液压气动元件与系统的CAD、污染控制、比例伺服技术等方面也取得了一定成果，并已用于生产。目前为止，液压、气动和密封件产品总计大概有3000个品种、23000多个规格。其中，液压约有1200个品种、10000多个规格（其中含液力产品60个品种、500个规格）；气动约有1350个品种、8000多个规格；橡塑密封也有350个品种、5000多个规格，现已基本能适应各类主机产品的一般需要，为重大的成套装备的品种配套率也可达60%以上，并开始有了少量出口。 1998年国产的液压件产量48

9、0万件，销售额约为28亿元（其中机械系统占70%）；气动件产量有360万件，销售额约为5.5亿元（其中机械系统约占60%）；密封件产量约有8亿件，销售额约为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在1998年年报统计中，液压产品产销率为97 .5%（液力为101%），气动为95.9%，密封有98.7%。这充分反映了产销的基本衔接。 我国液压、气动和密封工业虽然取得了很大的进步，但与主机发展的需求，以及和世界先进水平相比较下，还存在不少差距，主要反映在产品的品种、性能和可靠性等方面。如以液压产品为例，产品的品种只有国外1/3，寿命为国外1/2。为了满足重点主机、进口主机和

10、重大技术装备的需要，我国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，在1998年液压、气动和密封件产品的进口额约为2亿美元，其中液压约为1.4亿美元，气动有0.3亿美元，密封约为0.3亿美元，与1997年相比稍有下降。按金额计，目前进口产品国内市场占有率约30%。1998年国内市场的液压件需求总量约600万件，销售总额有40亿元；气动件的需求总量约500万件，销售总额有7亿多元；密封件的需求总量约11亿件，销售总额约为13亿元。 (3)今后发展走势 1.影响发展的主要因素 (1)企业产品的开发能力不强，技术开发的水平与速度不能完全满足当前先进主机产品、重大技术装备与进口设

11、备的配套和维修需要； (2)不少企业制造工艺、装备水平和管理水平都较为落后，加上质量意识感不强，导致产品性能的水平低、质量不稳定、可靠性差，及服务不及时，缺乏使用户能满意和信赖的名牌产品； (3)行业内的生产专业化程度低，力量较为分散，低水平重复严重，地区与企业之间产品趋同，导致盲目竞争，相互压价，从而使企业效益下降，资金缺乏、周转困难等，产品开发和技术改造的投入不足，严重地制约了行业整体水平提高以及竞争实力的增强； (4)当国内市场国际化程度日益提高，国外公司陆续进入中国市场参与竞争，再加上国内私营、合作经营、三资、个体等企业的崛起，从而给国有企业造成愈来愈大的冲击。 2.发展走势 随着社会

12、主义市场经济不断深化，液压、气动与密封产品的市场供求关系发生了较大变化，长期以来“短缺”为特征的卖方市场已基本成为了以“结构性过剩”为特征的买方市场所取代。而从总体能力看，已处于供大于求的态势，而且特别是一般低档次的液压、气动和密封件，普遍供过于求；而像主机急需的技术含量高的高参数与高附加值的高档产品，又不能满足市场的需要，只能依赖进口。在我国加入WTO后，其受冲击有可能更大。因此，在“十五”期间行业产值的增长，决不能只依赖于量的增长，而是应针对行业自身结构性矛盾，加大力度调整产业结构和产品结构，就是应依靠质的提高来促进产品技术升级，以适应和拉动市场的需求，而求得更大的发展。2.液压在动力滑台

13、上的应用(1) 动力滑台介绍利用有束缚力曲线图和状态空间分析法来对组合机床滑台的滑动影响与运动平稳性问题进行分析和研究，从而建立起滑台的液压驱动系统自调背压调速系统的动态数学模型。通过计算机数字的仿真系统，分析滑台产生滑动影响与运动不平稳的原因和主要影响因素。从那些当中可以得出什么样的结论，如果能合理地设计出液压缸与自调背压调压阀的结构尺寸.文中所使用的符号如下： s1流源，即调速阀出口流量； Sel滑台滑动摩擦力； R滑台等效粘性摩擦系数； I1滑台与油缸的质量； 12自调背压阀阀心质量； C1、c2油缸无杆腔及有杆腔的液容； C2自调背压阀弹簧柔度； R1, R2自调背压阀阻尼孔液阻； R

14、9自调背压阀阀口液阻； Se2自调背压阀弹簧的初始预紧力； I4, I5管路的等效液感； C5、C6管路的等效液容； R5, R7管路的等效液阻； V3, V4油缸无杆腔及有杆腔内容积； P3, P4油缸无杆腔及有杆腔的压力； F滑台承受负载； V滑台运动速度；文中采用的是功率键合图和状态空间分折法来建立系统的运动数学模型，而滑台的动态特性可以得到显著的改善。 在组合机床正常工作中，滑台的运动速度大小和它的方向及所承受负载变化都将以程度不同地影响着其工作性能。特别是工进过程中，滑台上负载突然消失引起的前进及负载的周期性变化从而引起的运动不平稳性，都将影响被加工件的表面质量，在严重的情况下会使刀

15、具折断。根据大连机床厂的要求，作者采用有束缚力的曲线图与状态空间分析法来建立组合机床滑台的新型液压驱动系统自调背压调速系统的动态数学模型。为改善滑台的动态特性，有必要分析找出滑台产生的前冲和运动不平稳的原因及主要的影响因素，但那必须通过计算机的数字仿真和研究得出的最后结果。(2)动态数学模型 组合机床滑台液压驱动系统自调背压调速系统的工作原理图如图所示。这系统是用来完成"工进停止快退”的工作循环。当滑台在工进时，三位四通换向阀处于图示位置，油泵的供油压力会在滥流阀的有效作用下近似地保持恒定，该油液流经过换向阀与调速阀后进入油缸的无杆腔，来推动滑台向前移动。与此同时，从油缸有杆腔排出的

16、压力油将经自调背压阀和换向阀流回油箱。在这个过程中，两个单向阀和溢流阀工作状态始终都没有任何改变。对像组合机床滑台的液压驱动系统自调背压调速系统这种复杂非线性系统，为便于研究它的动态特性，建立一个仅着重考虑主要影响因素的简单合理的动态数学模型是尤为重要的12。从理论上分析和试验研究的列举中可得知：该系统过程时间是远大于调速阀的过程时间，当油缸的无杆腔有效承压面积很大时，在调速阀出口流量瞬时的超调反映为滑台运动速度变化是很小的2。为了来更加拓宽和深入研究系统动态特性，使研究工作能在微型的计算机上有效地进行，本文章将对原模型2做出进一步简化处理，假定调速阀在系统整个通过过程中输出时候恒定的流量，这

17、被看成其为流源。这样系统的动态模型结构简图如图2所示，它是由油缸、滑台、自调背压阀和联接管路等组成的。 功率键合图是一功效流图，是按着系统能量的传递方式，以实际结构作为基础，用集中参数把子系统间的作用关系抽象表示为阻性元R、感性元I和容性元C的三种作用元。采用此方法建模物理概念清晰，能结合状态空间分析法可较准确地描述和分析线性系统，该方法在时域中研究复杂的非线性系统动态特性的一种有效方法。 据自调背压调速系统各元件的主要特性及建模规则1，得出了系统的功率键合图。图中每根键上半箭头表示功率流向，构成了功率的两个变量是力变量（油压P与作用力F）和流变量（流量q与速度v）。O结点表示在该系统中属于并

18、联连接，各键上力变量相等而流变量之和为零；1结点表示在该系统中属于串联连接，各键上的流变量相等而力变量之和为零。TF表示在不同能量形式间的变换器，TF下标的字母表示流变量或力变量的转换比值。键上短横杠表示该键上两变量间因果关系。全箭头则表示控制关系。在三种作用元中容性元与感性元的力变量和流变量之间具有积分或微分关系。因此，根据图3可推具有九个状态变量的复杂非线性状态方程。文中对滑台动态特性研究是从滑台的前冲与运动平稳性两方面入手的，用四阶定步长Runge-Kutta在IBM-PC微型计算机上来进行数字仿真。(3)滑台前冲 滑台的前冲现象是作用在滑台上负载突然消失（如钻削工作情况)引起的。在此过

19、程中，滑台负载F、运动速度V、油缸两腔压力P3与P4的变化可从图4中仿真结果看出。当滑台在负载作用下作匀速运动时，油缸无杆腔油液压力较高，油液中聚集大量的能量；而当负载突然消失时，该腔的油压随之迅速降低，油液从高压态转入低压态过程中向系统释放出很多能量，从而致使滑台高速的向前冲击。然而滑台前冲使油缸有杆腔油液受压而引起背压升高，从而耗掉系统中的一部分能量，对滑台的前冲起到了一定的抑制作用。我们应当看出，在所研究系统中，自调背压阀入口压力要受到油缸两腔油压综合性作用。在负载突然消失之时，自调背压阀的压力会迅速地上升，并稳定地在高于初始背压数值以上。从图可见，自调背压的调速系统在负载消失之时油缸背

20、压力升高幅度大于传统调速系统，所以其油缸的有杆腔中油液吸收的能量就多，结果滑台的前冲量将比传统调速系统要小约20%。由此可见采用自调背庄调速系统来作为驱动系统滑台在抑制前冲方面具有良好特性，其中自调背压阀起了非常大的作用。(4)滑台的运动平稳性 当作用在滑台上的负载作周期变化时（比如像铣削加工的情况），滑台运动速度将要产生一定波动。为保证加工质量要求，必须尽可能减小其速度波动范围。而从讨论问题的方便性出发看，假设负载按正弦波规律变化，从而得出的数字仿真结果如图5所示。由此看出这个系统与传统调速系统有着相同变化规律以及非常接近的数值数字。其中原因是负载的变化幅度不大时，油缸两腔的压力也就没有较大

21、的变化，从而最终导致自调背压阀作用不够明显显示。(5)改善措施通过研究的结果表明，以自调背压调速系统来作为驱动系统的滑台，其动态特性会比传统的调速系统好。要减少滑台前冲量，就必须在负载消失瞬间之时迅速提高油缸有杆腔的背压力。提高滑台的运动平稳性就需增加系统刚性，主要措施在于减小油液体积。从系统结构知道，油缸有杆腔与排油管间有一很大容积，如图6a所示。它在存在方面的延迟和衰减了自调背压阀作用，另一方面也降低系统的刚性，它会限制前冲特性与运动平稳性的进一步改善。由此，改善滑台动态特性可以从两个方法进行处理：即改变油缸容积或改变自调背压阀结构尺寸。通过系统结构性参数的仿真计算及结果的比较可得出这样的

22、结果：当把油缸有杆腔与排油管间的容积V4同无杆腔与进油管间的容积V3之比由原来5.5改为1时，如图所示，同时把自调背压阀的阀芯底端直径由原来的10mm增加为13mm,阻尼三角槽边长从原来lmm减小到0.7mm时，将可使滑台前冲量减小30%,过渡过程时间明显的缩短，滑台运动平稳性也将会得到很大的改善。Hydraulic systemChapter 1 IntroductionHydraulic Pump Station also known as the stations are independent h- ydraulic device. It requested by the oil gr

23、adually. 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 w

24、ith 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 sou

25、rce 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 sam

26、e 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 p

27、rinciple : 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 m

28、achinery 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 p

29、rocess can be broadly divided into three phases, namely : 20 early 1950s to the early 1960s, the initial stage; 60's and 70 for specialized production system ;8090's growth stage for the rapid development stage. Which, hydraulic industry in the early 1950s from the machine tool industry prod

30、uction 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 machine

31、ry 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,

32、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 China's annual output of hydraulic components have nearly 200,000 in 1973, machine tools, agricultural

33、 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

34、 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 ind

35、ustrial 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 ordi

36、nary 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 Sy

37、stem, 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 country's reform and opening up policy guidelines, with the development of the machinery i

38、ndustry, 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, agri

39、cultural 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 suc

40、h 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 p

41、roduction, 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

42、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 developme

43、nt 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

44、, 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, cy

45、linder, 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 h

46、as 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, priva

47、te 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 China's industry hydraul

48、ic 2.348 billion yuan, accounting for the world's 6; Pneumatic industry output 419 million yuan, accounting for world No. 10. 1.22 the current supply and demand profiles Through the introduction of technology, independent development and technological innovation, and high-pressure piston pump, g

49、ear 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

50、 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 hydraul

51、ic 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 t

52、o 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. sal

53、es 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% (

54、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 world's advanced level, there are still many gaps, mainly refl

55、ected 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, pneumat

56、ic 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. dollar

57、s. 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 milli

58、on, 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 1.31 affect 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,