液压与气动系统外文翻译

Hydraulic System

There are only following three basic methods of transmitting power : electrical，mechanical ,and fluid power. Most applications actually use a combination of the three methods to obtain the most efficient overall system. To properly determine which principle method to use, it is important to understand the characteristic of each method. For example，hydraulic systems on the long distance economically deliver power more than mechanical systems. However, fluid systems are restricted to shorter distances than electrical systems. Hydraulic power transmission systems are concerned with the generation, modulation, and control of sculptress and flow, and in general such systems include:

l. Pumps convert available power from the prime mover to hydraulic power at the actuator.

2. Valves control the direction of pump- flow, the level of produced power, and the amount of fluid-flow to the actuators. The power level is determined by controlling both the flow and pressure level.

3. Actuators convert hydraulic power to usable mechanical power output at the point required.

4. The medium is a liquid, provides rigid transmission and control as well as lubrication of components, sealing in valves, and cooling of the system.

5.Connectors link the various system components, provide power conductors for the fluid under pressure, and fluid flow return to tank（reservoir).

6. Fluid storage and conditioning equipment ensure sufficient quality and quantity as well as cooling of the fluid. Hydraulic systems are used in industrial applications such as stamping presses, steel mills and general manufacturing, agricultural machines, mining industry, aviation, space technology, deep-sea exploration, transportation, Narine technology, and offshore gas and petroleum exploration. In short, many people get somehow benefiting from the technology of hydraulics.

The secret of the success and widespread use of the hydraulic system is its versatility and manageability. Fluid power is not hindered by the geometry of the machine as is the case in mechanical systems. Also, power can be transmitted in almost limitless quantities because fluid systems are not so limited by the physical limitations of materials as are the electrical systems. For example, the performance of an electromagnet is limited by the saturation limit of steel. On the other hand, the power limit of fluid systems is limited only by the strength capacity of the material. Industry is going to depend more and more on automation in order to increase productivity. This includes remotion and direct control of production operations, manufacturing processes, and materials handling. Fluid power is the muscle of automation because of the advantages in the following four major categories.

1. Ease and accuracy of control. By the use of simple levers and push buttons, the operator of

a fluid power system can readily start , stop ,speed up or slow down, and provide any desired

horsepower with tolerances as precise as one ten-thousandth of an inch.

2. Multiplication of force. A fluid power system (without using cumbersome gears, pulleys, and levers) can multiply force simply and efficiently create the output from a fraction of an ounce to several hundred tons.

3. Constant force or torque. Only fluid power systems are capable of providing constant force or torque regardless of speed changes. It produces the work output moving from a few inches per hour to several hundred inches per minute, or from a few revolutions per hour to thousands of revolutions per minute.

4. Simplicity, safety, economy. In general, fluid power systems use fewer moving parts than comparable mechanical or electrical systems. Thus, they are simpler to maintain and operate. This, in turn, maximizes safety, compactness, and reliability. For example, a new power steering control design has made all other kinds of power systems obsolete on many off-highway vehicles. The steering unit consists of a manually operated directional control valve and meter in a single body. Because the steering unit is fully fluid-linked, without the link of mechanical linkages, universal joints, bearings, reduction gears, etc. This provides a simple, compact system. In addition, very little input torque is required to produce the control needed for the toughest applications. This is important where limitations of control space require a small steering wheel and it becomes necessary to reduce operator fatigue. Additional benefits of fluid power systems include instantly reversible motion, automatic protection against overloads, and infinitely variable speed control. Fluid power systems also have the highest horsepower per weight ratio of any known power source. In spite of all these highly desirable features of fluid power, it is not a panacea for all power transmission problems. Hydraulic systems also have some drawbacks. Hydraulic oils are messy, and leakage is impossible to completely eliminate. Also, most hydraulic oils can cause tires if an oil leak occurs in an area of hot equipment.Now, a concrete example is following - we use hydraulic stations to introduce the advantages of the hydraulic system.

Hydraulic Station and the development of hydraulic components Profiles Hydraulic Pump Station also known as the stations is independent hydraulic device. It is requested by the oil gradually and controls the hydraulic oil flow direction, pressure and flow rate, applied to the mainframe and hydraulic devices ability of hydraulic machinery. Users just need to connect hydraulic station and host of implementing agencies (motor oil or fuel tanks) with tubing. Hydraulic machinery can realize these specified movements and the work cycle. Hydraulic pump station is equipped with Pump device, manifold or valve portfolio, tanks, electrical boxes.

Pump device -- is equipped with motors and pumps. Hydraulic station is the source of power and can translate mechanical energy into hydraulic oil pressure.

Manifold -- is installed by hydraulic valve and assembled channel. It has the function of adjusting the direction for implementation of hydraulic oil, pressure and flow.

Valve portfolio -- plate valve is installed in up board, the back board connects and has the

same functional with IC.

Tank -- plate welding semi-closed containers, also is loaded with oil filtering network, air filters ans is used to save oil, oil filters and cooling.

Electrical boxes -- has the two patterns. A set of external fuse terminal plate and a full range of control electrical.

The principle of the hydraulic Station: the motor drives pump rotation, pump absorbs oil from the oil tank, then translates mechanical energy into hydraulic pressure of the station. Hydraulic oil through Manifold (or valve combinations) realized the direction, pressure. After adjusting flow pipe, it external flows to the cylinder hydraulic machinery or motor oil, so as to control the direction of the motive fluid, the size of transformation force and the speed of the pace, finally it promotes hydraulic machinery to the various acting.

Firstly, A development course

China Hydraulic (including hydraulic, the same below), pneumatic and seals industrial development process can be broadly divided into three phases, namely : the early 1950s to the early 1960s is the initial stage. The 60s and 70s is the growth stage for specialized production system.The80s-90s is the growth stage for the rapid development .Meanwhile, hydraulic industry started in the early 1950s from the machine tool industry production of fake us-grinder, broaching machine, copying lathe, and other hydraulic drive. Hydraulic Components from the plant hydraulic machine shop is self-occupied. After entering the l960s, 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 the second automobile factory provides efficient, automated equipment. The Hydraulic Components manufacturing has experienced rapidly development of the situation. Groups of SME have become professional hydraulic parts factory. China annual output of hydraulic components has nearly 200.000 in 1968. Machine tools, agricultural machinery, mechanical engineering industries, the production of hydraulic parts factory have been the professional development of more than 100 and an annual output more than one million in 1973 and an independent hydraulic manufacturing industry has begun to take shape. Then , hydraulic pieces of fake products has developed from the Soviet Union for the introduction of the product and combining the products .Hypertension has developed to medium and high pressure and the development of the electro-hydraulic servo valves and systems, hydraulic application areas further expanded .Pneumatic industry started later than the industrial hydraulic years. Until 1967 professional pneumatic components factory began to establish . Pneumatic Components looked only as commodity production and sales. It deal with rubber and plastics, mechanical seals and sealing flexible graphite . In the early 1950s, it produced ordinary 0-rings, rubber and plastics extrusion, such as oil seal sealing and seal asbestos. Until the early 1960s,it begun to production of

mechanical seals and flexible graphite sealing products. In 1970s, under 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 l980s, under the guidelines of country’s reform and opening up policy , 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 originating in 1982 and formed the basis of common pieces of Industry, will centralize hydraulic, pneumatic and seals specialized factories original machine tools scattered in agricultural machinery, mechanical engineering industries and place them under common management infrastructure pieces Bureau, so that the industry in the planning, investment, technology and scientific research and development in areas got the guidance and support of infrastructure pieces Bureau. Since then it entered a phase of rapid development and 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 they have mass production, and industry-leading products. In recent years, the industry has increased the technological transformation efforts.Fom1991 to 1998,state,Local enterprises and the self-Financing have fund total input of about 20 billion ￥, of which Hydraulic was more than I .6 billion￥. Through technological transformation and technology research, a number of major enterprises have further improved the level of technology, technique and equipment, which has laid a good foundation in order to form a higher Starting point, specialization, and run production . In recent years, under the guidelines of development of common ownership, different ownership SME rapidly have rise to show great vitality. With the further opening up, three-funded enterprises developed rapidly which played an important role to the development of industry standards and expanding exports. Today, China and the United States, Japan, Germany and other countries famous manufacturers have established joint ventures or wholly-owned by foreign manufacturers which involved in 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. It has more than 50 production enterprises and attracted foreign investment over 200 million U.S. dollars.

Secondly, the current situation

（1）Basic Profiles

After 40 years of efforts, China hydraulic, pneumatic and sealing industry have formed the industrial system with a relatively complete categories, a certain level of technical capacity. According to the 1995, Third National Industrial Census statistics said that state-owned, village-run, private and cooperative enterprises, individual, “three capital” enterprises with a total of more than 1,300 engaged in hydraulic Pneumatic and sealing parts industry with annual sales

income of 100 million￥, of which hydraulic is about 700, Pneumatic and sealing parts industry is approximately300. By 1996 with the international trade statistics, the total output value of China’s hydraulic industry is 2.348 billion￥, accounting for the world’s 6, the output of Pneumatic industry is 419 million￥, accounting for world No. 10.

（2）The current supply and demand profiles

Through the introduction of technology, independent development and technological innovation, 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 have increased noticeably and they can have stability mass production and provide a level of assurance for various mainframe products. In addition, they scored some achievements at hydraulic and pneumatic components of the CAD system, pollution control, proportional servo technology, and have been already in production. Currently, hydraulic, pneumatic and seals products totally have about 3,000 species, more than 23.000 specifications. Among them, there are 1,200 hydraulic varieties, more than I 0,000 specifications (including hydraulic products 60 varieties,500 specifications): Pneumatic has 1 .350 varieties, more than 8,000 specifications: Rubber seal has 350 species, more than 5,000 specifications, they basically cater to the different types of mainframe products to the general needs. The complete sets of equipment for major varieties of matching rate was over 60%, and it started a small amount of exports. In 1998 the output of homemade hydraulic is 4.8 million, the sales of which is about 28 billion (of which about 70% is mechanical systems);The yield of aerodynamic is 3.6 million, Sales of which is about 5.5 billion (of which about 60% is mechanical systems). Seals output is about 800 million, sales of which is about 10 billion (of which about 50% is mechanical systems). According to the China 1998 annual Hydraulic Pneumatic Seals Industry Association, the rate of hydraulic product sales is 97. 5% (101% for hydraulic), pneumatic 95.9%, sealed 98.7%. This fully reflects the basic marketing convergence. Our country hydraulic, pneumatic and sealing industry have attained a great deal of progress, but compared with mainfra me development needs, and the world’s advanced level, there are still many gaps, mainly reflected in the product variety, performance and reliability, and so on. Hydraulic products as an example, is the same one-third of products abroad. life is for half abroad. In order to meet key mainframe, and mainframe imports of major technology and equipment needs, every year we import a large number of hydraulic, pneumatic and sealing Products. According to customs statistics and the analysis of data, in 1998,the import sales of hydraulic, pneumatic and seals is about 200 million U.S. dollars, which Hydraulic is about 1.4 billion dollars, aerodynamic is nearly 0.3million U.S. dollars, sealed industry is about 0.3million U.S. dollars. It is a slight decline compared with 1997 . By sums, currently the domestic market share of the imported products is about 30%. In 1998 ,the demand of domestic hydraulic market is total of about six million, the total sales is nearly 40 billion. The total demand of aerodynamic is about 5 million, with sales more than 0.7 billion ￥The total demand of Seals is

about 1.1 billion, the total sales is about 1.3 billion.

Thirdly, the development trend of the future

1.the main factors of affecting the development

(1) The 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 manufacturing technology, the level of equipment and management standards of A number of enterprises are comparatively backward, along with a week sense of quality, which result in low levels of product performance quality, reliability poor services in a timely manner, lack of satisfaction and trust of the brand-name products:

(3) The production low of industry specialization, scattered strength, low repeat serious, the convergence products between regions and enterprises, blindly competing with each other, driving down prices, the decline of enterprise returns, lack of funds, difficult liquidity, the inadequate product development and technological transformation seriously have restricted the industry to improve the overall level of competition and competitive strength.

(4) As the internationalization of the domestic market is increasing, foreign companies have entered the Chinese market and participate in competition with the domestic private and cooperative enterprises, individuals, foreign-funded enterprises and so on. As the rise of state-owned enterprises has more and more big impact to state-owned enterprises.

2 .The development trend

As the socialist market economy continues to deepen, the relationship of supply and demand of hydraulic, pneumatic and sealing products in the market has a greater change. Long ago, the characterized by "shortage" of the seller's market has basically become the characterized by excess "structural" buyer's market. Look from the overall ability, it is in oversupply situation, especially the supply of the generally low grade of hydraulic, pneumatic and sealing parts, generally exceeds the demand, but the host need high parameters of high technical content, high value-added high-end products, and can't meet the needs of the market, it can only rely on imports. After China's accession to the WTO, its impact could be bigger. Therefore, during "15" , the growth of the industry output value must not be dependent on the amount of growth and should increase, adjust the industrial structure and product structure according to the structural contradiction of industry , namely we should rely on quality, technology upgrade, promote products to meet the market demand and pull, seek a bigger development.

Pneumatic pressure system

Pneumatic pressure system is pressure gas transmission system and control power, as the name suggests, usually it uses air pressure (no other gas) as the fluid medium. Because air is a safe, low cost and widely available fluid. It is safe that Air in system components may ignite the leakage situation (using air as medium) in particular. In pneumatic systems, compressors are used

for compressed air and supply the required. Usually it has a piston compressor, screw and vane type. Compressor is basically according to the ideal gas law, by reducing its volume to increase the gas pressure. Pneumatic system is usually considered using large central air compressor as an unlimited source, this is similar that as long as the plug in the power system lift up into the socket and power can be obtained. Using this method, the gas pressure can be transmitted from the source to every corner of the whole factory. The gas pressure can remove dirt through the air cleaner. the dirt is likely to damage the gas components of precision parts such as valve and cylinder, etc, and then is transported to each loop, and then the air flowing through the pressure reducing valve to reduce the pressure value is suitable for a primary circuit. Because air is not a good lubricant (including 20% oxygen), air pressure system needs a oil mist detector , then uses it to inject oil mist to air for reducing valve and pressure relief in the air, this will help reduce precision pneumatic components with moving parts wear and tear.

Air from the atmosphere contains different amounts of water. The water can be harmful, it can take lubricants to cause excessive wear and corrosion. Therefore, in some occasions, we use air dryer to remove these harmful moisture because the air pressure system directly discharges into the atmosphere, it can produce too much noise, so components can be performed in the valve and vent installed muffler to reduce noise, to prevent the operator due to exposure to noise and high speed air particles may cause damage. Using pneumatic system has the following several reasons instead of the hydraulic system:

liquid inertia is far larger than gas. Therefore, in fluid system, the acceleration deceleration and valve open shut down suddenly when we execute components, the quality of the oil is a potential problem. According to the Newton's laws of motion (force equals mass times acceleration), the force accelerating motion acceleration required to the number of produce oil that are equally many times the volume needed for the air force. Gas liquid ratio has a larger viscosity, it causes more pressure and power loss because of the cold brush. In addition, due to the using of the liquid will cut off from the atmosphere in hydraulic system , so they need special mailbox and leak proof system design. Pneumatic systems can be used directly into the surrounding environment in the air. In general no liquid pressure system is more expensive. However, due to the compressibility of air, the air system execution components may not get a precise speed control and position control. Due to limited compressor of air pressure system, the system pressure is low (less than 250 ops), but fluid pressure is of up to 10000 pa. So it can be a large power system. Air pressure system is used only for small power system. A typical example, it apples for punching, drilling, promoting, punching and clamping, the assembly and riveting, material processing and logic control operation, etc.