液压与气压系统中英文对照

Hydraulic System液压与气压系统【中英文对照】Hydraulic SystemThere are only three basic methods of transmitting power：Electrical，mechanicaland fluid powerMost applications actually use a combination of the three methods to obtain the most efficient overall systemTo properly determine which principle method to use。it is important to know the salient features of each typeFor example，fluid systems call transmit power more economically Over greater distances than Can mechanical typesHowever。fluid systems arerestricted to shorter distances than are electrical systemsHydraulic power transmission system ale concerned with the generation, modulation, and control of pressure and flow and ,and in general such systems include: 1Pumps which convert available power from the prime mover to hydraulic power at the actuator2Valves which control the direction of pump-flow，the level of power produced，and the amount of fluid一一flow to the actuatorsThe power level is determined by controlling both the flow and pressure level3Actuators which convert hydraulic power to usable mechanical power Output at the point required4The medium，which is a liquid，provides rigid transmission and control as well as 1ubrication of component s，sealing in valvesand cooling of the system5Connectors which 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 which ensure sufficient quality and quantity as well as cooling of the fluid7、pneumatics systems required a lubricator to inject。a very fine mist of oil into the air discharging from the pressure regulatorThis prevents wear of the closely fitting moving parts of pneumaticHydraulic systems ale used in industrial applications such as stamping presses，steel mills，and general manufacturing，agricultural machines，mining industry，aviation，space technology，deepsea exploration, transportation，marine technology，and offshore gas and petroleum explorationIn short，very few people get through a day of their 1ives without somehow benefiting from the technology of hydraulics2The principle of electrical-discharge machining also called electro is or spark-erosion machining, is based on the erosion of metals by spark discharges. We know that when two current-conduct in wires are allowed to touch each other, an arc is produced. If we look closely at the point of contact between the two wires, we note that a small portion of the metal has been eroded away, leaving a small crater.The basic EDM system consists of a shape tool and the workpiece, connected to a dc power supply and placed in a dielectric fluid this is one of the most widely used machining processes, particularly for die-sinking operations when the potential difference between the tool and the work piece is sufficiently high, a transient spark discharges through the fluid, removing a very small amount of metal from the workpiece surface. The capacitor discharge is repeated at rates of between 50,with voltages usually ranging between 50vand 380v and currents from 0.1A to 500A.Mechanical control includes cams and governors. Although they have been used for the control of very complex machines, to be cost effectively, today they are used for simple and fixed-cycle task control. Some automated machines, such as screw machines, still use cam-based control. Mechanical control is difficult to manufacture and is subject to wear.Pneumatic control is still very popular for certain applications. It uses compressed air, valves, and switchs to construct simple control logic, but is easily slow. Because standard compaonents are used to construct the logic, it is easier to build than a mechanical control . Pneumatic control parts are subject to wear.As does a mechanical control, an electromechanical control uses switches, relays, times counters, and so on, to construct logic, it is faster and more flexible. The controllers using electromechanical control are called relay devices.The values in the express the relative tool distance from the home position. This distance is shown in the relative or incremental coordinates, U and W. when reading the values in the not possible to know directly how far the tool is from the part origin. Just how far it is from the home position. mounted on exhaust ports of air valves and actuators to reduce noise and prevent operating personnel from possible injury resulting not only from exposure to noise but also from highspeed airborne particles.The sign of the coordinates is zero or negative because the tool cannot move farther than the machine origin . thus at present , the values are zero so the tool is at the home position. The values in the are normally used when setting up the tools in order to find the real tool distances from the part origin.The values in the absolute position express the absolute tool distance from the part origin. This distance is shown in shown in absolute coordinates, x and z .the sign may be positive or negative, depending on the quadrants in which the tool is moving. because of the compressibility of air，it is impossible to obtain precise controlled actuator velocities with pneumatic systemsalso，precise positioning control is not obtainableWhile pneumatic pressures are quite so far is to good. This is an important piece of information for the operator when maching, since any value in the absolute position is directly related to the part.The secret of hydraulic systems SUCCESS and widespread use is its versatility and manageabilityFluid power is not hindered by the geometry operations when the potential difference between the tool and the work piece is sufficiently high, a transient spark discharges through the fluid, removing a very small amount of metal from the work piece of the machine as is the ease in mechanical systemsAlso，power can be transmitted in almost limitless quantities because fluid systems are not so limited by the physical 1imitations of materials as are the electrical systemsFor example，the performance of an electromagnet is limited by The saturation limit of steelOn the other hand，the power limit of fluid systems is 1imited only by the strength capacity of the material In the express the relative tool distance from the home position. This distance is shown in the relative or incremental coordinates, U and W. when reading the values in the not possible to know directly how far the tool is from the part origin. Just how far it is from the home position. The sign of the coordinates is zero or negative because the tool cannot move farther than the machine origin . thus at present , the values are zero so the tool is at the home position. The values in the are normally used when setting up the tools in order to find the real tool distances from the part origin.Industry is going to depend more and more on automation in order to increase productivityThis includes remote and direct control of production operations，manufacturing processes。and materials handlingFluid power is the muscle of automation because of advantages in the following four major categories1Ease and accuracy of contr01By the use of Simple levers and push but tons，the operator of a flu id power system Call readily start，stop，speed up or slow down，and position forces which provide any desired horsepower With tolerances as precise as one tenthousandth Of an inchFig131 shows a fluid power system which allows all aircraft pilot to raise and lower his landing gearWhen the pi lot moves a small contr01 valve in one direction，oil under pressure flows to one end of the cylinder to lower the landing gearTo retract the landing gear，the pilotmoves the valve lever in the opposite direction，a110wlng 0il to flow into the other end of the cylinder2Multiplication of force A fluid power system(without using cumbersome gears，pulleys，and levers)Can multiply forces Simply and efficiently from a fraction of an ounce to several hundred tons of output3Constant force or torqueOnly fluid power systems are capable of providing constant force or torque regardless of speed changesThis is accomplished whether the work output moves a few inches per hour，several hundred inches per minute，a few revolutions per houror thousands ofrevolutions per minute4Simplicity，safety，economygeneral，fluid power systems use fewer moving parts thancomparable mechanical or electrical systemsThus，they ale simpler to maintain and operateThis，in turn，maximizes safety，compactness，and reliabilityFor example，a new power steering contr01 designed has made all other kinds of power systems obsolete on manyoffhighway vehiclesThe Steering unit consists of a manually operated directional control valve and meter in a single bodytransportation，marine technology，and offshore gas and petroleum explorationIn short，very few people get through a day of their 1ives without somehow benefiting from the technology of hydraulics2Because the steering unit is fully fluid 1inked，mechanical linkages，universal joints。bearings，reduction gears，etcare eliminatedThis provides a simple，compact systemIn addition，very little input torque is required to produce the control needed for the toughest applicationsThis is important where 1imitations of control space require a small steering wheel and it becomes necessary to reduce operator fatigue There are several types of shaft couplings; their characteristics depend on the prupose for which they are used. If an exceptionally long shaft is required for a line shaft in the manufacturing plant or a propeller shaft on ship, it is made in sections that are coupled together with rigid couplings. Additional benefits of fluid power systems include instantly reversible motion。automaticprotection against overloads，and infinitely variable speed contr01Fluid power systems also have the highest horsepower per weight rati0 of any known power sourceIn spite of al 1 these highly desirable features of fluid power，it is not a panacea for all power transmissionproblemswork revolves as the table moves along the ways, a helical or spiral cut is produced; as shown in milling-cutters, helical gears, twist drills and similar worm are produced in this way. The milling of such items requires a particular relationship between the motions of the dividing head and associated gear train, to control the distance the worm will travel while making one complete revolution. Before the helix can be machined the lead and angle of helix are twist drills and similar worm are produced in this way. The milling of such items requires a particular relationship between the motions of the dividing head and associated gear train, to control the distance the worm will travel while making one complete revolution. Hydraulic oil s are messyand leakage is impossible to completely eliminateAlso，most hydraulic oil s Carl cause fires if an oil 1eak occur in an area of hot equipmentPneumatic SystemPneumatic systems use pressurized gases to transmit and control powerAs the name implies，pneumatic systems typically use air(rather than some other gas)as the fluid medium because air is a safe，low cost，and readily available fluidIt is particularly safe in environment s where an e1 electrical spark could ignite leaks from system component sWorm wheel are similar to bevel gears and are generally used to connect skew shafts transmitting high velocity rations. The worm wheel give line contact between mating teeth unlike a point contact in the case of bevel gears. This improves the load carrying capacity of the gear train.In pneumatic systems compressors are used to compress and supply the necessary quantities of airCompressors are typically of the piston，vane or ScrewtypeBasically a compressorIncrease the pressureof a gas by reducing its v01ume as described by the perfect gas 1aws In connecting shafts belonging to separate devices(such as an electrical motor and gearbox) precise aligning of the shafts is diffcult and a flexible coupling is used. This coupling connects the shafts is such a way as to minimize the harmful effects of shaft misalignment. Flexible couplings also permit the shafts to defect under their separate systems of loads and to move freely in the axial direction without interfering with one another. Flexible couplings can also serve to reduce the intensity of shock load and vibrations transmitted from one shaft to another.Pneumatic systems normally use a large centralized air compressor which is considered to be an infinite。Air source similar to an electrical system where you merelyplug into an electrical outlet for electricityIn this way，pressurized air can be piped from one source to various 10cations throughout an entire industrial plantThe compressed air car be Piped to each circuit through an air filter to remove contaminants which might harm the closely fitting parts of pneumatic components the such as valve and cylindersThe air then flows through a pressure regulator which reduces the pressure to the desired level for the particular circuit applicationBecause air is not a good 1ubricant(contains bout 20oxygen)，pneumatics systems required a lubricator to inject。a very fine mist of oil into the air discharging from the pressure regulatorThis prevents wear of the closely fitting moving parts of pneumatic componentsFree air from the atmosphere contains varying amounts of moistureThis moisture can be harmful in that it Can wash away lubricants and thus cause excessive wear and corrosionHence，in some applications，air driers are needed to remove this undesirable moistureSince pneumatic systems exhaust directly into the atmosphere，they are capable of generatingExcessive noiseThereforemufflers are mounted on exhaust ports of air valves and actuators to reduce noise and prevent operating personnel from possible injury resulting not only from exposure to noise but also from highspeed airborne particlesThere are several reasons for considering the use of pneumatic systems instead of hydraulic systemsLiquids exhibit greater inertia than do gasesTherefore，in hydraulic systems the weight of oil is a potential problem when accelerating and decelerating actuators and When suddenly opening and closing valvesDue to Newton law of motion(force equalsmass multiplied by acceleration)，the force required to accelerate oil is many times greater than that required to accelerate an equal volume of air1iquids also exhibit greater viscosity than do gasesThis results in larger frictional pressure and power lossesA1SO，since hydraulic systemsuse a fluid foreign to the atmosphere，they require special reservoirs and no leak system designsPneumatic systemswhen the worm spindle of an index head is geared to the lead screw of the milling machine so that the work revolves as the table moves along the ways, a helical or spiral cut is produced; as shown in milling-cutters, helical gears, twist drills and similar worm are produced in this way. The milling of such items requires a particular relationship between the motions of the dividing head and associated gear train, to control the distance the worm will travel while making one complete revolution. Before the helix can be machined the lead and angle of helix are necessary together with worm diameter. Use air which is exhausted directly back into the surrounding environmentGenerally speaking，pneumatic systems are less expensive than hydraulic systemsHowever，because of the compressibility of air，it is impossible to obtain precise controlled actuator velocities with pneumatic systemsalso，precise positioning control is not obtainableWhile pneumatic pressures are quite 10W due to compressor design limitations(1ess than 250 psi)，hydraulic pressures call be as high as 10，000 psiThus，hydraulics can be highpower systems。whereas pneumatics are confined to low-power applications4Industrial applications of pneumatic Systems are growing at a rapid paceTypical examples include Stamping，drilling，hoist，punching，Clamping，assembling，riveting，materialshandling，and logic controlling operations液压与气压系统液压系统中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的最全面的系统。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相比，传递动力的距离较短。液压与气压传动是研究以有压流体为能源介质，来实现各种机械的传动和自动控制的学科液压传动与气压传动控制方法是基本相同的在流动的液体中，因为有一定量的空气，一般溶解5%-6%体积的空气，油液能溶解的空气量与绝对压力成正比，在大气压下正常溶解于油液中的空气。当压力低于大气压时，就成为过饱和状态，在一定温度下，如压力降低到一定值时，过饱和的空气将从油液中分离出来形成气泡。这一压力值为分离压。含有气泡的体积将缩小。液压动力传递系统涉及电动机、调节装置和压力和流量控制，总的来说，该系统包括：泵：将原动机的能力转换成作用在执行部件上的液压能。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。执行部件：将液压能转换成可用的机械能。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。联接件：联接各个系统部件，为压力流体提供功率传输通路，将液体返回油箱(贮油器)。油液贮存和调节装置：用来确保提供足够质量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I：件的磨削及一般加工业、农机、矿业、航天技术、深海勘探、运输、海洋技术，近海天然气和三种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。在液压系统中，除需要液压泵供油和液压执行元件来驱动工作装置外，还要配备一定数量的液压控制阀来对液流的流动方向、压力的高低以及流量的大小进行设想的控制，以满足负载的工作要求。因此，液压控制阀是直接影响液压系统工作过程和工作我的重要元件。 各类液压控制阀虽然形式不同，控制的功能各有所异，但都 具有共性。首先，在结构上，所有的阀都有阀体、阀芯和驱使阀芯动作的元部件等组成。其次，在工作原理上，所有的代的阀口大小，阀进间的压差以及通过阀的流量之间的关系都是符合孔口流量的公式。只是各种阀控制的参数各不相同而已。如压力阀控制的是压力，流量阀控制的是流量等 。液压系统成功而又广泛使用的秘密在于它的通用性和易操作性。液压动力传递不会像机械系统那样受到机器几何形体的制约，另外，液压系统不会像电气系统那样受到材料物理性能的制约，它对传递功率几乎没有量的限制。例如，一个电磁体的性能受到钢的磁饱和极限的限制，相反，液压系统的功率仅仅受材料强度的限制。企业为了提高生产率将越来越依靠自动化，这包括远程和直接控制生产操作、加1：过程和材料处理等。液压动力之所以成为自动化的重要组成部分，是冈为它有如下主要的四种优点：1控制方便精确通过操作一个简单的操纵杆和按钮，液压系统的操作者便能立即起动、停止、加减速和能提供任意功率、位置精度为万分之一英寸的位置控制力。图13一l是一个使飞机驾驶员升起和落下起落架的液压系统，当飞行员向某方向移动控制阀，压力油流人液压缸的某一腔从而降下起落架。飞行员向相反方向移动控制阀，允许油液进人液压缸的另一腔来收同起落架。2增力一个液压系统(没有使J=j笨重的齿轮、滑轮利杠杆)能简单有效地将不到一盎司的力放人产生儿白吨力的输出。3恒力或恒扭矩只有液压系统能提供不随速度变化而变化的恒力或恒扭矩，它可以驱动对象从每小时移动几英寸到每分钟几百英寸从每小时几转到每分钟几千转。4简便、安全、经济总的来说，液压系统比机械或电气系统使用更少的运动部件，冈此，它们运行与维护简便。这使得系统结构紧凑，安全可靠。例如一种用于车辆上的新型动力转向控制装置己淘汰其他类型的转向动力装置，该转向部件中包含有人力操纵方向控制阀和分配器。冈为转向部件是全液压的，没有万向节、轴承、减速齿轮等机械连接，这使得系统简单紧凑。另外，只需输入很小的扭矩就能产生满足极恶劣工作条件所需的控制力