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附錄A:譯文
液壓系統(tǒng)
一般僅有以下三種基本方法傳遞動力:電氣、機械和液壓。大多數(shù)應用系統(tǒng)實際上是將三種方法組合起來而得到最有效的最全面的系統(tǒng)。為了合理地確定采取哪種方法,重要的是了解各種方法的顯著特征。例如液壓系統(tǒng)在長距離上比機械系統(tǒng)更能經(jīng)濟地傳遞動力。然而液壓系統(tǒng)與電氣系相比,傳遞動力的距離較短。
液壓傳動有許多突出的優(yōu)點,它被廣泛的應用,如一般工業(yè)用的塑料加工機械,壓力機械,機床等;應用機械設備工程機械,建筑機械,農(nóng)業(yè)機械,汽車等;鋼鐵行業(yè)的冶金機械,起重機械,還有軋輥調(diào)整裝置等;水利工程中的控制閘門裝置,河床升降裝置,橋梁和其他操作機構(gòu);發(fā)電廠高速渦輪裝置,核電站等;船舶甲板用的起重機械(絞車),船頭門,艙壁閥、船尾推進器等;特殊技術用的巨型天線控制裝置、測量浮標、升降旋轉(zhuǎn)舞臺等;軍事工業(yè)用的火炮操縱裝置、船舶減搖裝置、飛行器仿真、飛機起落架的收放裝置和方向舵控制裝置等。特殊技術的天線控制裝置,測量浮標,升降旋轉(zhuǎn)舞臺;軍用的火炮操縱裝置,船舶減搖裝置,飛行器仿真,飛機起落架收放裝置和方向舵控制裝置和其他設備。
液壓系統(tǒng)的作用為通過改變壓強增大作用力。一個液壓系統(tǒng)的好壞取決于系統(tǒng)設計的合理性、系統(tǒng)元件性能的優(yōu)劣,系統(tǒng)的污染防護和處理,而最后一點尤為重要。近年來我國國內(nèi)液壓技術有很大的提高,不再單純地使用國外的液壓技術進行加工。
一個完整的液壓系統(tǒng)由五個部分組成,即動力元件、執(zhí)行元件、控制元件、輔助元件(附件)和液壓油。
動力元件的作用是將原動機的機械能轉(zhuǎn)換成液體的壓力能,指液壓系統(tǒng)中的油泵,它向整個液壓系統(tǒng)提供動力。液壓泵的結(jié)構(gòu)形式一般有齒輪泵、葉片泵和柱塞泵。
執(zhí)行元件(如液壓缸和液壓馬達)的作用是將液體的壓力能轉(zhuǎn)換為機械能,驅(qū)動負載作直線往復運動或回轉(zhuǎn)運動。
控制元件(即各種液壓閥)在液壓系統(tǒng)中控制和調(diào)節(jié)液體的壓力、流量和方向。根據(jù)控制功能的不同,液壓閥可分為壓力控制閥、流量控制閥和方向控制閥。壓力控制閥又分為益流閥(安全閥)、減壓閥、順序閥、壓力繼電器等;流量控制閥包括節(jié)流閥、調(diào)整閥、分流集流閥等;方向控制閥包括單向閥、液控單向閥、梭閥、換向閥等。根據(jù)控制方式不同,液壓閥可分為開關式控制閥、定值控制閥和比例控制閥。
輔助元件包括油箱、濾油器、油管及管接頭、密封圈、快換接頭、高壓球閥、膠管總成、測壓接頭、壓力表、油位油溫計等。
液壓油是液壓系統(tǒng)中傳遞能量的工作介質(zhì),有各種礦物油、乳化液和合成型液壓油等幾大類。
液壓系統(tǒng)的作用是幫助人類工作,主要通過執(zhí)行元件將壓力轉(zhuǎn)換為旋轉(zhuǎn)或往復運動。
液壓原理:它由兩個不同大小的缸體充滿了水或油。充滿水的稱為“水壓機”,充滿油的稱為“液壓機”。兩個液缸每個都有一個可動的活塞,如果在小活塞上加點壓力,根據(jù)帕斯卡定律,小活塞的壓力通過液體的壓力傳遞到大活塞,頂端的活塞將前進很長的距離?;拘』钊臋M截面積為S1,外加一個小活塞上一個向下的力F1。因此,小活塞對液體的壓強P=F1/S1的,可以在所有方向上傳輸同樣大小。通過大活塞的壓力也為P。如果大活塞的橫截面積為S2,活塞的壓強P向上的壓力F2=P*S2,橫截面積是小活塞的幾倍,加給小活塞小的力,活塞會有大的壓力,由此用液壓機壓制膠合板,油,提起重物,鍛造煉鋼。
液壓系統(tǒng)成功而又廣泛使用的秘密在于它的通用性和易操作性。液壓動力傳遞不會像機械系統(tǒng)那樣受到機器幾何形體的制約,另外,液壓系統(tǒng)不會像電氣系統(tǒng)那樣受到材料物理性能的制約,它對傳遞功率幾乎沒有量的限制。例如,一個電磁體的性能受到鋼的磁飽和極限的限制,相反,液壓系統(tǒng)的功率僅僅受材料強度的限制。
企業(yè)為了提高生產(chǎn)率將越來越依靠自動化,這包括遠程和直接控制生產(chǎn)操作加工過程和材料處理等。液壓動力之所以成為自動化的重要組成部分,是因為它有如下主要的四種優(yōu)點:
1 控制方便,精確通過操作一個簡單的操縱桿和按鈕,液壓系統(tǒng)的操作者便能立即起動、停止、加減速和能提供任意功率、位置精度為萬分之一英寸的位置控制力。一個使飛機駕駛員升起和落下起落架的液壓系統(tǒng),當飛行員向某方向移動控制閥,壓力油流入液壓缸的某一腔從而降下起落架。飛行員向相反方向移動控制閥,允許油液進入液壓缸的另一腔來收起落架。
2 增力,一個液壓系統(tǒng)沒有使用笨重的齒輪、滑輪杠桿就能簡單有效地將不到一盎司的力放大產(chǎn)生兒上百噸力的輸出。
3 恒力或恒扭矩,只有液壓系統(tǒng)能提供不隨速度變化而變化的恒力或恒扭矩,它可以驅(qū)動對象從每小時移動幾英寸到每分鐘幾百英寸.從每小時幾轉(zhuǎn)到每分鐘幾千轉(zhuǎn)。
4 簡便、安全、經(jīng)濟,總的來說,液壓系統(tǒng)比機械或電氣系統(tǒng)使用更少的運動部件,因此,它們運行與維護簡便。這使得系統(tǒng)結(jié)構(gòu)緊湊,安全可靠。例如一種用于車輛上的新型動力轉(zhuǎn)向控制裝置己淘汰其他類型的轉(zhuǎn)向動力裝置,該轉(zhuǎn)向部件中包含有人力操縱方向控制閥和分配器。因為轉(zhuǎn)向部件是全液壓的,沒有萬向節(jié)、軸承、減速齒輪等機械連接,這使得系統(tǒng)簡單緊湊。另外,只需輸入很小的扭矩就能產(chǎn)生滿足極惡劣工作條件所需的控制力.這對操作空間限制而需要小方向盤的場合很重要,這也是減輕操作者疲勞所必需的。
液壓系統(tǒng)的其他優(yōu)點包括雙向運動、過載保護和無級變速控制,在已有的任何動力系統(tǒng)中液壓系統(tǒng)亦具有最大的單位質(zhì)量功率比。
液壓系統(tǒng)也有三個弱點:
1 由于傳動介質(zhì)(液壓油)流動的過程中部分位置流速不同,導致液體內(nèi)部出現(xiàn)摩擦,同時液體與管道內(nèi)壁也有摩擦,這都是液壓油溫度升高的原因。溫度過高會導致更多的內(nèi)部和外部的泄漏,減少其機械效率。同時由于較高的溫度,液壓油會膨脹。導致可壓縮增大,使操作不能很好的控制傳輸。解決方法:高溫是液壓系統(tǒng)的自身問題,只能最大減輕不能根除。使用質(zhì)量更好的液壓油,液壓管的布局盡量避免出現(xiàn)彎曲,使用高品質(zhì)的管材和管件,液壓閥等。
2 液壓系統(tǒng)的震動也是弱點之一。由于液壓油在管道中流動的高速沖擊和控制閥的打開關閉的過程中的影響是系統(tǒng)振動的原因。強烈震動會導致系統(tǒng)的控制動作錯誤,也會使系統(tǒng)中一些更復雜精密設備出現(xiàn)錯誤,從而導致系統(tǒng)故障。解決方案:液壓管應該是固定的,以避免急彎。為了避免頻繁流動方向的變化,無法避免時應將減震措施應該做到最好。整個液壓系統(tǒng)應具有良好的減振措施,同時避免在系統(tǒng)外部振蕩器的影響。
3 液壓系統(tǒng)有內(nèi)泄露和外泄露,內(nèi)泄漏是指發(fā)生在系統(tǒng)中的泄露過程,如液壓活塞 - 缸的泄漏,控制閥滑閥與閥體之間的泄漏,如兩側(cè)。內(nèi)泄漏雖然沒有液壓油的損失,但是由于泄露,已經(jīng)確定的控制動作會受到影響,直至系統(tǒng)故障。外泄露是指發(fā)生在系統(tǒng)與外部環(huán)境之間的泄露。液壓油直接泄露到環(huán)境中,除了會影響工作環(huán)境,沒有足夠的動力將導致系統(tǒng)故障。液壓油泄露到環(huán)境中也有火災的危險。解決方案:使用質(zhì)量更好的密封件,以提高設備的加工精度。
在液壓系統(tǒng)及其系統(tǒng)中,密封裝置用來防止工作介質(zhì)的泄漏及外界灰塵和異物的侵入。其中起密封作用的元件,即密封件。外漏會造成工作介質(zhì)的浪費,污染機器和環(huán)境,甚至引起機械操作失靈及設備人身事故。內(nèi)漏會引起液壓系統(tǒng)容積效率急劇下降,達不到所需要的工作壓力,甚至不能進行工作。侵入系統(tǒng)中的微小灰塵顆粒,會引起或加劇液壓元件摩擦副的磨損,進一步導致泄漏。
因此,密封件和密封裝置是液壓設備的一個重要組成部分。它的工作的可靠性和使用壽命,是衡量液壓系統(tǒng)好壞的一個重要指標。除間隙密封外,都是利用密封件,使相鄰兩個偶合表面間的間隙控制在需要密封的液體能通過的最小間隙以下。在接觸式密封中,分為自封式壓緊型密封和自封式自緊型密封(即唇形密封)兩種。
附錄B:外文文獻
Hydraulic System
There are only three basic methods of transmitting power:Electrical,mechanical.a(chǎn)nd 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 know the salient features of each type.For example,fluid systems call transmit power more economically Over greater distances than Can mechanical types.However。fluid systems are restricted to shorter distances than are electrical systems.
Hydraulic transmission there are many outstanding advantages, it is widely used, such as general industrial use of plastics processing machinery, the pressure of machinery, machine tools, etc.; operating machinery engineering machinery, construction machinery, agricultural machinery, automobiles, etc.; iron and steel industry metallurgical machinery, lifting equipment, such as roller adjustment device; civil water projects with flood control and dam gate devices, bed lifts installations, bridges and other manipulation of institutions; speed turbine power plant installations, nuclear power plants, etc.; ship from the deck heavy machinery (winch), the bow doors, bulkhead valve, stern thruster, etc.; special antenna technology giant with control devices, measurement buoys, movements such as rotating stage; military-industrial control devices used in artillery, ship anti- rolling devices, aircraft simulation, aircraft retractable landing gear and rudder control devices and other devices.
The role of the hydraulic system to increase the force by changing the pressure. A hydraulic system is good or bad depends on the system design is reasonable, the merits of the performance system components, system, pollution prevention and treatment, while the last point is particularly important. In recent years, China's domestic hydraulic technology has greatly improved, not simply using hydraulic technology from abroad for processing.
A complete hydraulic system consists of five parts, namely, power components, the implementation of components, control components, auxiliary components (Annex) and the hydraulic oil.
The role of dynamic components is the original motivation of the mechanical energy into fluid pressure energy, the hydraulic system of pumps, which provide power to the entire hydraulic system. Structures of hydraulic pumps generally have gear pumps, vane pumps and piston pumps.
Implementation of components (such as hydraulic cylinders and hydraulic motors) is to pressure the liquid can be converted to mechanical energy to drive the load for a linear reciprocating movement or rotational movement.
Control components in the hydraulic system control and regulation of fluid pressure, flow and direction. According to the different control functions, hydraulic valves can be divided into pressure control valves, flow control valves and directional control valve. Pressure control valve is divided into benefits flow valve (safety valve), pressure relief valve, sequence valve, pressure switch, etc.; flow control valves including throttle, adjusting valves, flow diversion valve assembly; Directional control valve includes a check valve, check valve, shuttle valve, valve and so on. Under the control of different ways, hydraulic valves can be divided into switching control valves, control valves and the fixed value proportional control valve.
Auxiliary components, including fuel tanks, filters, tubing and pipe joints, seals, quick couplings, high pressure ball valve, hose assembly, pressure fittings, pressure gauge, oil level, oil temperature meter and so on.
Hydraulic system of hydraulic oil is the work of the energy transfer medium, a variety of mineral oil, emulsion, oil hydraulic molding Hop categories
The role of the hydraulic system is to help humanity work. Mainly by the implementation of components to rotate or pressure into a reciprocating motion.
Hydraulic principle :It consists of two cylinders of different sizes and composition of fluid in the fluid full of water or oil. Water is called "hydraulic press"; the said oil filled "hydraulic machine." Each of the two liquid a sliding piston, if the increase in the small piston on the pressure of a certain value, according to Pascal's law, small piston to the pressure of the pressure through the liquid passed to the large piston, piston top will go a long way to go. Based cross-sectional area of the small piston is S1, plus a small piston in the downward pressure on the F1. Thus, a small piston on the liquid pressure to P = F1/SI, Can be the same size in all directions to the transmission of liquid. "By the large piston is also equivalent to the inevitable pressure P. If the large piston is the cross-sectional area S2, the pressure P on the piston in the upward pressure generated F2 = PxS2 Cross-sectional area is a small multiple of the piston cross-sectional area. From the type known to add in a small piston of a smaller force, the piston will be in great force, for which the hydraulic machine used to suppress plywood, oil, extract heavy objects, such as forging steel.
The secret of hydraulic systems success and widespread use is its versatility and manageability.Fluid 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 systems.Also,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 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 1imited 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 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 The precise convenient control by operating a simple joystick and buttons, the operators of the hydraulic system and can immediately start, stop, and deceleration and can provide any power, position precision for one over ten thousand inch position control. A make the pilot rises and fall the landing gear on the hydraulic system, when the pilot to a certain direction control valves, pressure oil into hydraulic cylinder of a cavity and came down on the landing gear. The pilot to move in the opposite direction control valves, allow the oil into the hydraulic cylinder of another chamber to take back on the landing gear.
2 Multiplication 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 output.
3 Constant force or torque.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 few revolutions per hour.or thousands of revolutions per minute.
4 Simplicity,safety,economy.general,fluid power systems use fewer moving parts than comparable mechanical or electrical systems.Thus,they ale simpler to maintain and operate.This,in turn,maximizes safety,compactness,and reliability.For example,a new power steering control designed 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.transportation,marine technology,and offshore gas and petroleum exploration.
In addition,very little input torque is required to produce the control needed for the toughest applications.This is important where 1imitations 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.
The three hydraulic system diseases.
1 As result of heat transmission medium (hydraulic oil) in the flow velocity in various parts of the existence of different, resulting in the existence of a liquid within the internal friction of liquids and pipelines at the same time there is friction between the inner wall, which are a result of hydraulic the reasons for the oil temperature. Temperature will lead to increased internal and external leakage, reducing its mechanical efficiency. At the same time as a result of high temperature, hydraulic oil expansion will occur, resulting in increased compression, so that action can not be very good control of transmission. Solution: heat is the inherent characteristics of the hydraulic system, not only to minimize eradication. Use good quality hydraulic oil, hydraulic piping arrangement should be avoided as far as possible the emergence of bend, the use of high-quality pipe and fittings, hydraulic valves, etc.
2 The vibration of the vibration of the hydraulic system is also one of its malaise. As a result of hydraulic oil in the pipeline flow of high-speed impact and the control valve to open the closure of the impact of the process are the reasons for the vibration system. Strong vibration control action will cause the system to error, the system will also be some of the more sophisticated equipment error, resulting in system failures. Solutions: hydraulic pipe should be fixed to avoid sharp bends. To avoid frequent changes in flow direction, can not avoid damping measures should be doing a good job. The entire hydraulic system should have good damping measures, while avoiding the external local oscillator on the system.
3 The leakage of the hydraulic system leak into inside and outside the leakage. Leakage refers to the process with the leak occurred in the system, such as hydraulic piston-cylinder on both sides of the leakage, the control valve spool and valve body, such as between the leakage. Although no internal leakage of hydraulic fluid loss, but due to leakage, the control of the established movements may be affected until the cause system failures. Outside means the occurrence of leakage in the system and the leakage between the external environments. Direct leakage of hydraulic oil into the environment, in addition to the system will affect the working environment, not enough pressure will cause the system to trigger a fault. Leakage into the environment of the hydraulic oil was also the danger of fire. Solution: the use of better quality seals to improve the machining accuracy of equipment.
In the hydraulic system and its system,the sealing device to prevent leakage of the work of media within and outside the dust and the intrusion of foreign bodies. Seals played the role of components, namely seals. Medium will result in leakage of waste, pollution and environmental machinery and even give rise to malfunctioning machinery and equipment for personal accident. Leakage within the hydraulic system will cause a sharp drop in volumetric efficiency, amounting to less than the required pressure, can not even work. Micro-invasive system of dust particles can cause or exacerbate friction hydraulic component wear, and further lead to leakage.
Therefore, seals and sealing device is an important hydraulic equipment component. The reliability of its work and life is a measure of the hydraulic system an important indicator of good or bad. In addition to the closed space, are the use of seals, so that two adjacent coupling surface of the gap between the need to control the liquid can be sealed following the smallest gap. In the contact seal, pressed into self-seal-style and self-styled self-tight seal (is, sealed lips) two.
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