液氣壓傳動(dòng) 第一章 概述.ppt

1、液氣壓傳動(dòng)及控制Fluid Power with Applications,劉 甦,第一章 概述（Introduction） 1.1 什么是流體傳動(dòng)？（WHAT IS FLUID POWER?） 1.流體傳動(dòng)與控制（Fluid power and control） 流體傳動(dòng)是一門利用有壓力的流體實(shí)現(xiàn)動(dòng)力的產(chǎn)生、控制和傳輸?shù)募夹g(shù)?？梢赃@么說流體傳動(dòng)是運(yùn)動(dòng)機(jī)器的動(dòng)力。這是因?yàn)榱黧w傳動(dòng)被用來實(shí)現(xiàn)現(xiàn)代工業(yè)所有機(jī)器的推、拉、調(diào)節(jié)或驅(qū)動(dòng)（Fluid power is the technology which deals with generation, control, and transmission

2、of power using pressurized fluids. It can be said that fluid power is the muscle that moves industry. This is because fluid power is used to push, pull，regulate, or drive virtually all the machines of modern industry.）。例如：流體傳動(dòng)操縱和制動(dòng)汽車、發(fā)射宇宙飛船、運(yùn)輸,土方、收割莊稼、采煤、驅(qū)動(dòng)機(jī)床、操縱飛機(jī)、加工食品、甚至于鉆牙等。事實(shí)上， 在產(chǎn)品的加工或銷售過程的某些環(huán)節(jié)離開

3、了流體傳動(dòng)與控制幾乎是不可能實(shí)現(xiàn)的（For example, fluid power steers and brakes automobiles, launches spacecrafts, moves earth, harvests crops, mines coal, drives machine tools, controls airplanes, processes food, and even drills teeth. In fact, it is almost impossible to find a manufactured product which hasnt been “

4、fluid-powered” in some way at some stage of its production or distribution.）。,2.流體傳動(dòng)的介質(zhì)（Fluid power medium） 鑒于流體既可以是液體也可以是氣體，流體傳動(dòng)與控制包含液壓傳動(dòng)和氣壓傳動(dòng)。液壓系統(tǒng)使用像石油基潤(rùn)滑油、水、合成油甚至金屬溶液這樣的液體。氣壓傳動(dòng)以空氣作為傳動(dòng)介質(zhì)，因?yàn)榭諝夥浅ＸS富并且在完成指定的工作后容易排入大氣（Since a fluid can be either a liquid or a gas, fluid power is actually the general te

5、rm used for hydraulics and pneumatics. Hydraulic systems use liquids such as petroleum oils, water, synthetic oils, and even molten metals. Pneumatic systems use air as the gas medium because air is very abundant and can be readily exhausted into the atmosphere after completing its assigned task）。 3

6、.流體系統(tǒng)的類型（Types of fluid systems） 認(rèn)識(shí)到，實(shí)際上有兩種不同類型的流體系統(tǒng)：流體,輸送和流體傳動(dòng)。（It should be realized that there are actually two different types of fluid systems: fluid transport and fluid power）。 流體輸送系統(tǒng)（Fluid transport systems）：其唯一目的是將流體從某個(gè)地方輸送到另一地方以滿足某些用途。例子包括抽水站抽水到家，跨國(guó)的天然氣管道，化學(xué)處理系統(tǒng)中的各種流體匯集。（Fluid transport sys

7、tems have as their sole objective the delivery of a fluid from one location to another to accomplish some useful purpose. Examples include pumping stations for pumping water to homes, cross-country gas lines, and systems where chemical processing takes place as various fluids are brought together.）。

8、 流體傳動(dòng)與控制系統(tǒng)（Fluid power and control systems）：為完成工作而專門設(shè)計(jì)的。這個(gè)工作是由,直接承受壓力流體的工作缸或流體（液壓）馬達(dá)來完成的，依次為希望的動(dòng)作提供動(dòng)力。當(dāng)然，需要控制元件以確保工作平穩(wěn)、準(zhǔn)確、高效、安全地完成（Fluid power systems are designed specifically to perform work. The work is accomplished by pressurized fluid bearing directly on an operating cylinder or fluid motor, wh

9、ich, in turn, provides the muscle to do the desired work. Of course, control components are also needed to ensure that the work is done smoothly, accurately, efficiently, and safely）。,4.流體傳動(dòng)與控制的應(yīng)用范圍（Fluid power and control application range） 功率（Power）：操作員輕觸按鈕就能控制數(shù)百馬力的功率并通過管路將其傳遞到任何位置（A feather touch

10、 by an operator can control hundreds of horsepower and transmit it to any location where a hose or pipe can go）。 精密度（Precision）：像在機(jī)床工業(yè)中的應(yīng)用，能夠重復(fù)達(dá)到萬分之一英寸的公差（In terms of precision such as applications in the machine tool industry, tolerances of one ten-thousandth of an inch can be achieved and repeated

11、 over again）。 流體傳動(dòng)與控制不僅僅是動(dòng)力的源泉，它同時(shí)對(duì)完成所需的工作提供平穩(wěn)、高效、安全和準(zhǔn)確并可控、可變的動(dòng)力（Fluid power is not merely a powerful muscle;,it is a controlled，flexible muscle which provides power smoothly, efficiently, safely, and precisely to accomplish useful work）。,1.2 流體傳動(dòng)的優(yōu)點(diǎn)（ADVANTAGES OF FLUID POWER） 現(xiàn)在有三種基本的傳動(dòng)方式：電力、機(jī)械和流體傳

12、動(dòng)。在大多數(shù)實(shí)際應(yīng)用中，都是這三種方法進(jìn)行組合以使整個(gè)系統(tǒng)的效率最高。掌握每一類型的特點(diǎn)對(duì)正確決定使用哪種方法是很重要的。例如：流體傳動(dòng)系統(tǒng)能夠比機(jī)械傳動(dòng)更經(jīng)濟(jì)地遠(yuǎn)程傳輸動(dòng)力。但是, 與電力系統(tǒng)相比流體傳動(dòng)系統(tǒng)傳輸距離受到限制（There are only 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 ef

13、ficient overall system. To properly determine which principle method to use, it is important to know the salient features of each type. For example, fluid systems can transmit power more economically over,greater distances than can mechanical types. However, fluid systems are restricted to shorter d

14、istances than are electrical systems）。 流體傳動(dòng)成功和廣泛應(yīng)用的奧秘是它的變化多端和控制容易。流體傳動(dòng)不受通常的機(jī)械系統(tǒng)中機(jī)器的幾何關(guān)系阻礙。并且，功率能夠幾乎無限量的傳遞因?yàn)榕c電力系統(tǒng)相比流體傳動(dòng)系統(tǒng)不受材料自身的物理性能的限制。例如：電磁鐵的特性受到鋼材的磁性飽和的限制。另一方面，流體傳動(dòng)系統(tǒng)的功率僅受材料強(qiáng)度大小的限制（The secret of fluid powers success and widespread use is its versatility and manageability. Fluid power is not hinder

15、ed 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 l

16、imited 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）。 為了提高生產(chǎn)率工業(yè)生產(chǎn)越來越依賴工業(yè)自動(dòng)化。這包含了對(duì)生產(chǎn)操作，制造過程和材料輸送的遠(yuǎn)程和直接控制。流體傳動(dòng)因以下四個(gè)突出優(yōu)點(diǎn)在工業(yè)自動(dòng)化中發(fā)揮著重要的作用（Industry is going to depend more and more on automation in order to i

17、ncrease productivity. This includes remote and direct control of production operations, manufacturing processes, and materials handling. Fluid power is the muscle of automation because of advantages in the following four major categories.）。,1.控制簡(jiǎn)單和精確（Ease and accuracy of control） 借助于簡(jiǎn)單的桿件和按鈕的使用，流體傳動(dòng)

18、系統(tǒng)的操作人員很容易進(jìn)行開始、停止、加速和減速操作，并且對(duì)于提供的任何所需功率其位置精度都可達(dá)到十萬分之一英寸（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 position forces which provide any desired horsepower with tolerances as precise as one ten-thousandth of an i

19、nch）。 2.力的放大（Multiplication of force） 一個(gè)液壓系統(tǒng)（不使用笨重的齒輪、皮帶輪和操縱桿）能簡(jiǎn)單而有效地將力從幾分之一盎司放大到數(shù)百噸對(duì)外輸出（A fluid power systems （without using cumbersome gears, pulleys, and levers）can multiply forces simply and efficiently from a fraction of an ounce,to several hundred tons of output）。 3.恒定的力或轉(zhuǎn)矩（Constant force or t

20、orque） 只有流體傳動(dòng)系統(tǒng)能夠提供不受速度變化影響的恒定力或轉(zhuǎn)矩。不論工作速度是每小時(shí)幾英寸還是每分鐘幾百英寸，每小時(shí)幾轉(zhuǎn)還是每分鐘上千轉(zhuǎn)，力或轉(zhuǎn)矩都能保持恒定（Only fluid power systems are capable of providing constant force or torque regardless of speed changes. This is accomplished whether the work output moves a few inches per hour, several hundred inches per minute, a fe

21、w revolutions per hour, or thousands of revolutions per minute）。 4.簡(jiǎn)便、安全、經(jīng)濟(jì)（Simplicity, safety, economy） 流體傳動(dòng)系統(tǒng)與機(jī)械或電力系統(tǒng)相比僅使用少量的運(yùn)動(dòng)部件。所以，操作和維修保養(yǎng)更加簡(jiǎn)便。其次，安全性高，體積小和可靠性好（In general fluid power,systems use fewer moving parts than comparable mechanical or electrical systems. Thus，they are simpler to maintai

22、n and operate. This, in turn maximizes safety, compactness, and reliability）。 流體傳動(dòng)系統(tǒng)另外的優(yōu)點(diǎn)包括即時(shí)的反向運(yùn)動(dòng)，自動(dòng)過載保護(hù)和無級(jí)調(diào)速。在任何已知的動(dòng)力源中流體傳動(dòng)系統(tǒng)具有最高的功率重量比（Additional benefits of fluid power systems include instantly reversible motion, automatic protection against overloads, and infinitely variable speed control. Flu

23、id power systems also have the highest horsepower per weight ratio of any known power source）。 盡管液壓傳動(dòng)有這些優(yōu)點(diǎn)，它也不是所有動(dòng)力傳遞問題的靈丹妙藥。液壓系統(tǒng)總有一些缺點(diǎn)。液壓油是骯臟的，并且泄漏是不可能完全避免的。如果設(shè)計(jì)錯(cuò)誤，,液壓管道可能破裂，飛散的物體能夠?qū)е氯松韨?。此外，如果液壓油泄漏進(jìn)高溫設(shè)備中，很多液壓油能夠引起火災(zāi)。因此，為了確定最好的總體設(shè)計(jì)每一種使用狀況都必須被徹底地研究（In spite of all these highly desirable features of

24、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. Hydraulic lines can burst, possibly resulting in human injury due to flying objects, if proper design is not

25、implemented. Also, most hydraulic oils can cause fires if an oil leak occurs in an area of hot equipment. Therefore, each application must be studied thoroughly to determine the best overall design.）。,1.3 流體傳動(dòng)系統(tǒng)的組成（COMPONENTS OF A FLUID POWER SYSTEM） 事實(shí)上所有的液壓回路基本上是相同的與其使用無關(guān)。液壓回路中由6個(gè)基本元件組成（Virtually

26、all hydraulic circuits are essentially the same regardless of the application. There are six basic components required in a hydraulic circuit）： 油箱（Tank）：盛裝液體（通常是液壓油）（A tank（reservoir）to hold the liquid, which is usually hydraulic oil）。 泵（Pump）：為系統(tǒng)中液體加載（A pump to force the liquid through the system）。

27、 電機(jī)或其它動(dòng)力源（Motor or other power source）：驅(qū)動(dòng)泵（An electric motor or other power source to drive the pump）。,控制閥（Control valve）：控制液體流動(dòng)方向、壓力和流量 （Valves to control liquid direction, pressure, and flow rate）。 執(zhí)行元件（Actuator）：將液體能量轉(zhuǎn)換為工作所需的力或力矩（實(shí)現(xiàn)直線運(yùn)動(dòng)的液壓缸或?qū)崿F(xiàn)旋轉(zhuǎn)運(yùn)動(dòng)的液壓馬達(dá)）（An actuator to convert the energy of the li

28、quid into mechanical force or torque to do useful work. Actuators can be either cylinders to provide linear motion or motors（hydraulic） to provide rotary motion）。 管道（Piping）：使液體由一處流到另一處的管道（Piping which carries the liquid from one location to another）。 當(dāng)然，液壓系統(tǒng)的復(fù)雜程度和組成根據(jù)其用途的差異而不同。液壓系統(tǒng)組成中包括特殊元件也是可以的,（O

29、f course, the sophistication and complexity of hydraulic systems will vary depending on the specific application. This is also true of the individual components which comprise the hydraulic system）。,1.4 流體傳動(dòng)系統(tǒng)的類型（TYPES OF A FLUID POWER SYSTEM） 我們已經(jīng)知道了包括液壓和氣壓系統(tǒng)的兩種流體傳動(dòng)。流體傳動(dòng)能進(jìn)一步細(xì)分為兩種類型：開環(huán)（開式）和閉環(huán)（閉式）系統(tǒng)（

30、We have already established that fluid power includes both hydraulic and pneumatic systems. The field of fluid power can be further subdivided into two additional major categories: open-loop and closed-loop systems）。 閉環(huán)系統(tǒng)（Closed-loop system）：有反饋的。系統(tǒng)輸出端的狀況自動(dòng)地反饋到輸入端或被稱為反饋傳感器的裝置，該裝置產(chǎn)生控制信號(hào)。如果控制信號(hào)和反饋信號(hào)不同

31、，直到它對(duì)比了需求后裝置將得到正確的系統(tǒng)輸出施加于系統(tǒng)。閉環(huán)系統(tǒng)時(shí)常稱為“伺服系統(tǒng)”，并且常常直接稱控制執(zhí)行元件的閥為“伺服閥” （A closed-loop,system is one which uses feedback. This means that the state of the output from the system is automatically sampled and compared（fed back） to the input or command signal by means of a device called a feedback transducer. If there is a difference between the command and feedback signals, action is taken to correct the system output until it matches the requirement imposed on the system. Closed-loop system are frequently called servo system,