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本科生畢業(yè)設(shè)計專業(yè)外文翻譯
原 文： Hydraulic cylinders
譯 文： 液壓缸
指導(dǎo)教師 ： 王菡 職稱： 講師
學(xué)生姓名 ： 張 亮 學(xué)號：1102130432
專 業(yè) ： 機(jī)械設(shè)計制造及其自動化
院（系） ： 機(jī)電工程學(xué)院
2015年4月10日
Hydraulic cylinders
????Hydraulic cylinders are hydraulic energy into mechanical energy, make a linear reciprocating motion (or swing movement) of the hydraulic actuators. Simple structure, reliable work. Use it to achieve reciprocating motion, can be removed from deceleration devices, and no transmission gap, smooth movement, and therefore widely used in various mechanical hydraulic system. Hydraulic cylinder output force and the effective area of the piston and the pressure is proportional to both sides; consisting essentially of hydraulic cylinders and cylinder head, piston and piston rod, seals, cushioning device component and exhaust. Cushioning device and the exhaust depending on the specific application may be, other devices are essential.
One . Type
According to the form of the structure of a conventional hydraulic cylinder, which can be divided into three types: structural forms sanitation garbage truck hydraulic cylinder varied, there are a variety of classification methods: by movement can be divided into linear reciprocating and rotary swing ; by the liquid-pressure situation can be divided into single-acting and double-acting; form of the structure can be divided into piston, piston, multi-stage telescoping; rack and pinion, etc; can be divided according to the installation form for rod, earrings, foot, hinge shaft; pressure level can be divided according to 16Mpa, 25Mpa, 31.5Mpa so on.
Piston
????Single rod cylinder is only one end of the piston rod. As shown is a single hydraulic cylinder piston. Both ends of the import and export of oil through ports A and B can pressure oil or oil return to two-way movement, it is known as double-acting cylinders.
Only one-way movement of the piston, the opposite direction from the force required to complete. But its stroke hydraulic cylinder piston generally more big.
Hydraulic cylinder piston works
Hydraulic cylinder piston rod can be divided into single and double rod two structures fixed by way of fixed and fixed two cylinder piston rod, according to the role of fluid pressure in the case of a single-acting and double-acting. In a single-acting hydraulic cylinder, the pressure oil chamber is for a hydraulic cylinder, by hydraulic pressure of the cylinder to achieve a single direction of movement, the movement in the opposite direction by an external force (e.g. spring force, its own weight or external loads, etc.) to achieve; and bis acting hydraulic cylinder piston movement in both directions through the two chambers alternately into the oil, by the action of hydraulic pressure to complete.
Plunger
(1) piston hydraulic cylinder is a single-acting hydraulic cylinder, hydraulic pressure can only be achieved by a direction of movement of the plunger return to rely on other external or plunger weight;
(2) does not support the piston and cylinder liner rely on contact, so that the liner easily processed, it is suitable for making long-stroke hydraulic cylinders;
(3) working the plunger of the total pressure, so it must have sufficient rigidity;
(4) tend to be larger piston weight, easy to sag due to its own weight when placed horizontally, causing the seal and guide unilateral wear, so the vertical use of more favorable.
Telescopic
Telescopic hydraulic cylinder piston has two or more stages, telescopic hydraulic cylinder piston out of style in descending order, while the load is normally retracted the order from small to large. Telescopic cylinders can achieve a longer stroke, while retraction length is shorter, more compact structure. Such cylinders commonly used in the construction machinery and agricultural machinery. There are a plurality of primary motion of the piston, each piston during successive movement, the output speed and output power are changing.
Swing
Swing hydraulic cylinder is an actuator output torque and to achieve a reciprocating motion, also called the swing hydraulic motor. There are two forms of single and double leaf blades. The stator is fixed to the cylinder block, and the blades and rotor are connected together. According inlet direction, will drive the rotor blades for reciprocating swing.
Two . buffer device
Used in the hydraulic system having a hydraulic cylinder driving mechanism of a certain quality, having a large kinetic energy when the hydraulic cylinder is moved to the stroke end, the Failing deceleration process, the hydraulic cylinder piston and the cylinder head will occur mechanical impact, an impact, noise, there destructive. To mitigate and prevent such harm occurs, it can be set up in the hydraulic circuit deceleration device or in the cylinder equipped with cushioning devices.
?Three . Processing
Cylinder as the main components of hydraulic cylinders, single pillar mining, hydraulic support, barrel and other products, and its processing quality directly affects the entire product life and reliability. Cylinder high processing requirements, the inner surface roughness is Ra0.4 ~ 0.8 & um, concentricity, wear resistance demanding. The basic characteristics of the cylinder is the deep processing, the processing has been plagued by processing staff.
Using rolling processing, leaving the surface because the surface layer of residual compressive stress, helps a closed surface microcracks, impede erosion expansion. Thereby enhancing the corrosion resistance of the surface, and can delay fatigue cracks or expanded, thus increasing the fatigue strength of the cylinder. By roll forming, cold rolling the surface layer of the hardened layer, the elastic and plastic deformation to reduce the grinding surface of the auxiliary contact, thereby improving the wear resistance of the inner wall of the cylinder, while avoiding burns caused by grinding. After rolling, the reduction of the surface roughness can be improved with the nature.
Cylinder is a mechanical engineering major parts, the traditional processing methods are: Broaching cylinder - fine boring cylinder - grinding cylinder. Using rolling method is: Broaching cylinder - fine boring cylinder - rolling cylinder, step three parts, but the contrast in time: grinding cylinder about 1 m in 1-2 days, rolling cylinder 1 meter in about 10-30 minutes. Investment comparison: quilting grinder or mill (tens of thousands - millions), rolling knife (a thousand - tens of thousands). After rolling, the surface roughness of the hole by rolling before Ra3.2 ~ 6.3um buildings reduced to Ra0.4 ~ 0.8 & surface hardness um, hole by about 30%, the cylinder surface fatigue strength by 25%. If only consider the cylinder cylinder life impact, increased by 2 to 3 times rolling process is relatively boring grinding efficiency is about 3 times. The above data shows that the rolling process is efficient and can greatly improve the surface quality of the cylinder.
After rolling the cylinder surface is no small sharp edge for a long time and will not damage the movement friction seals or seals, which is especially important in the hydraulic industry.
Four . Diagnosis and treatment
1, A malfunction or failure of the action
Causes and treatment methods are the following:
(1) spool valve stuck or clogging. When the flow direction of the valve spool valve or valve stuck or clogging, hydraulic cylinders prone to malfunction or failure of the operation. You should check the oil pollution; check whether dirt or gelatinous precipitates stuck valve or blockage of the valve hole; check valve wear, cleaning, changing the system filter, cleaning the tank, replace the hydraulic medium.
(2) the piston rod and cylinder or a hydraulic cylinder jammed blockage. At this point in any case manipulation, or action hydraulic cylinder does not operate even micro. Then check the piston and piston rod seal is tight, whether to enter the dirt and glial sediment: the axis of the piston rod and the cylinder is on, the wearing parts and seals if failure load carried it too great.
(3) control the hydraulic system pressure is too low. Throttling resistance in the control line may be too large, improper flow regulating valve, the control pressure is inappropriate, the pressure source is disturbed. You should check the control pressure source, ensure that the pressure is adjusted to the specified value of the system.
(4) in the hydraulic system into the air. Mainly because the system has a leak. You should check the hydraulic oil tank level, seals and fittings suction side of the pump, suction strainer is dirty. If so, you should add hydraulic oil, seals and fittings handle, clean or replace the coarse filter.
(5) hydraulic cylinder initial slow. At lower temperatures, the hydraulic oil viscosity, poor mobility, resulting in slow hydraulic cylinder. Improvement approach is to replace the good viscosity-temperature performance of hydraulic oil at low temperatures can make use of the heater or heating oil with the machine itself to raise start-up, the system work the oil temperature should be maintained at around 40 ℃.
2, when the work can not drive the load
????Mainly for piston stop bit inaccurate, insufficient thrust, speed drops, job insecurity, etc. The reason is:
(1) hydraulic cylinder internal leakage. Internal leakage of hydraulic cylinders including hydraulic cylinder seals, rod seals and piston seals and closures are due to wear and tear such as excessive leakage.
The reason piston seal leakage and closures that seal wrinkles, squeezing, tearing, abrasion, aging, deterioration, distortion, etc., and you should be replaced with new seals.
Piston seal wear is mainly due to excessive speed control valve to adjust properly, causing excessive back pressure and seal improperly installed or hydraulic oil contamination. Followed by a foreign substance enters the assembly and sealing materials is not good quality. The consequence is slow, weak, can also cause serious damage to the piston and the cylinder, a "pull-cylinder" phenomenon. Approach is to adjust the speed control valve, the control installation instructions shall make the necessary operations and improvements.
(2) a hydraulic circuit leakage. Including valves and hydraulic piping leaks. Repair method is to check and eliminate leaking hydraulic valve connecting pipe through manipulation.
(3) hydraulic oil through the relief valve bypass back to the tank. If the relief valve stuck into the dirt, so that the relief valve normally open, hydraulic oil will pass through the relief valve directly back into the tank, causing no oil into the cylinder. If the load is too large, adjust the pressure relief valve has exceeded the maximum rating, but still not the thrust hydraulic cylinder continuous action without action required. If you adjust the lower pressure, due to insufficient pressure is still not up to the required load vertebral strength, showed enough thrust. You should check and adjust the pressure relief valve.
3, the piston sliding or crawling
Hydraulic cylinder piston sliding or crawling make hydraulic cylinders unstable. The main reasons are:
(1) internal stagnation and hydraulic cylinders. Cylinder internal parts improper assembly, parts deformation, wear or geometric tolerance overrun, the resistance movement is too large, the hydraulic cylinder piston speed varies with changes in stroke position, slippage, or crawl. Mostly due to poor quality parts assembly, surface scratches or sintered iron produced, so that the resistance increases, the rate of decline. For example: a piston rod bending and different heart or rod, the rod of the hydraulic cylinder or rail mounting position offset, seal ring fitted too tight or too loose and so on. The workaround is to re-repair or adjustment, replacement parts and remove iron damage.
(2) poor lubrication or hydraulic cylinder aperture processing tolerance. Because such as the piston and cylinder, the piston rod guide and have relative motion, if poor lubrication or hydraulic cylinder aperture ultra-poor, will be increased wear, so the cylinder centerline straight decreases. Thus, when the hydraulic cylinder piston work, friction will be large, sometimes small, slip or crawl. Pre-ground approach is to exclude hydraulic cylinders, then meet the requirements of the preparation of the piston, the piston rod grinding, configuration guide sleeve.
(3) the hydraulic pump or a hydraulic cylinder into the air. Air compression or expansion will cause the piston sliding or crawling. Remedy is to check the pump, set up a special exhaust, fast travel back and forth several times to exhaust the whole operation.
(4) the seal of quality and is directly related to slip or crawl. O-rings when used at a low pressure, compared with the U-shaped ring, due to the higher surface pressure, the difference between static and dynamic friction large, prone to slippage or creeping; U-ring seal surface pressure with increasing pressure is increased, although the sealing effect is increased accordingly, but the difference between static and dynamic frictional resistance becomes large, the internal pressure increases, the impact of rubber elasticity, since the contact resistance is increased lip, the lip seals will rollover and elongation, also prone to slip or crawl, to prevent it tipping support ring can maintain its stability.
液壓缸
液壓缸是將液壓能轉(zhuǎn)變?yōu)闄C(jī)械能的、做直線往復(fù)運(yùn)動（或擺動運(yùn)動）的液壓執(zhí)行元件。它結(jié)構(gòu)簡單、工作可靠。用它來實現(xiàn)往復(fù)運(yùn)動時，可免去減速裝置，并且沒有傳動間隙，運(yùn)動平穩(wěn)，因此在各種機(jī)械的液壓系統(tǒng)中得到廣泛應(yīng)用。液壓缸輸出力和活塞有效面積及其兩邊的壓差成正比；液壓缸基本上由缸筒和缸蓋、活塞和活塞桿、密封裝置、緩沖裝置與排氣裝置組成。緩沖裝置與排氣裝置視具體應(yīng)用場合而定，其他裝置則必不可少。
1．類型
根據(jù)常用液壓缸的結(jié)構(gòu)形式，可將其分為三種類型：環(huán)衛(wèi)垃圾車的液壓缸的結(jié)構(gòu)形式多種多樣，其分類方法也有多種：按運(yùn)動方式可分為直線往復(fù)運(yùn)動式和回轉(zhuǎn)擺動式；按受液壓力作用情況可分為單作用式、雙作用式；按結(jié)構(gòu)形式可分為活塞式、柱塞式、多級伸縮套筒式；齒輪齒條式等；按安裝形式可分為拉桿、耳環(huán)、底腳、鉸軸等；按壓力等級可分為16Mpa、25Mpa、31.5Mpa等。
活塞式
單活塞桿液壓缸只有一端有活塞桿。如圖所示是一種單活塞液壓缸。其兩端進(jìn)出口油口A和B都可通壓力油或回油，以實現(xiàn)雙向運(yùn)動，故稱為雙作用缸。
活塞僅能單向運(yùn)動，其反方向運(yùn)動需由外力來完成。但其行程一般較活塞式液壓缸大。
活塞式液壓缸的工作原理
活塞式液壓缸可分為單桿式和雙桿式兩種結(jié)構(gòu)，其固定方式由缸體固定和活塞桿固定兩種，按液壓力的作用情況有單作用式和雙作用式。在單作用式液壓缸中，壓力油只供液壓缸的一腔，靠液壓力使缸實現(xiàn)單方向運(yùn)動，反方向運(yùn)動則靠外力（如彈簧力、自重或外部載荷等）來實現(xiàn)；而雙作用液壓缸活塞兩個方向的運(yùn)動則通過兩腔交替進(jìn)油，靠液壓力的作用來完成。
柱塞式
（1）柱塞式液壓缸是一種單作用式液壓缸，靠液壓力只能實現(xiàn)一個方向的運(yùn)動，柱塞回程要靠其它外力或柱塞的自重；
（2）柱塞只靠缸套支承而不與缸套接觸，這樣缸套極易加工，故適于做長行程液壓缸；
（3）工作時柱塞總受壓，因而它必須有足夠的剛度；
（4）柱塞重量往往較大，水平放置時 容易因自重而下垂，造成密封件和導(dǎo)向單邊磨損，故其垂直使用更有利。
伸縮式
伸縮式液壓缸具有二級或多級活塞，伸縮式液壓缸中活塞伸出的順序式從大到小，而空載縮回的順序則一般是從小到大。伸縮缸可實現(xiàn)較長的行程，而縮回時長度較短，結(jié)構(gòu)較為緊湊。此種液壓缸常用于工程機(jī)械和農(nóng)業(yè)機(jī)械上。有多個一次運(yùn)動的活塞，各活塞逐次運(yùn)動時，其輸出速度和輸出力均是變化的。
雙作用單活塞桿式液壓缸
擺動式
擺動式液壓缸是輸出扭矩并實現(xiàn)往復(fù)運(yùn)動的執(zhí)行元件，也稱擺動式液壓馬達(dá)。有單葉片和雙葉片兩種形式。定子塊固定在缸體上，而葉片和轉(zhuǎn)子連接在一起。根據(jù)進(jìn)油方向，葉片將帶動轉(zhuǎn)子作往復(fù)擺動。
2．緩沖裝置
在液壓系統(tǒng)中使用液壓缸驅(qū)動具有一定質(zhì)量的機(jī)構(gòu)，當(dāng)液壓缸運(yùn)動至行程終點時具有較大動能，如未作減速處理，液壓缸活塞與缸蓋將發(fā)生機(jī)械碰撞，產(chǎn)生沖擊、噪聲，有破壞性。為緩和及防止這種危害發(fā)生，因此可在液壓回路中設(shè)置減速裝置或在缸體內(nèi)設(shè)緩沖裝置。
3．加工
缸筒作為液壓缸、礦用單體支柱、液壓支架、炮管等產(chǎn)品的主要部件，其加工質(zhì)量的好壞直接影響整個產(chǎn)品的壽命和可靠性。缸筒加工要求高，其內(nèi)表面粗糙度要求為Ra0.4～0.8&um，對同軸度、耐磨性要求嚴(yán)格。缸筒的基本特征是深孔加工，其加工一直困擾加工人員。
采用滾壓加工，由于表面層留有表面殘余壓應(yīng)力，有助于表面微小裂紋的封閉，阻礙侵蝕作用的擴(kuò)展。從而提高表面抗腐蝕能力，并能延緩疲勞裂紋的產(chǎn)生或擴(kuò)大，因而提高缸筒疲勞強(qiáng)度。通過滾壓成型，滾壓表面形成一層冷作硬化層，減少了磨削副接觸表面的彈性和塑性變形，從而提高了缸筒內(nèi)壁的耐磨性，同時避免了因磨削引起的燒傷。滾壓后，表面粗糙度值的減小，可提高配合性質(zhì)。
油缸是工程機(jī)械最主要部件，傳統(tǒng)的加工方法是：拉削缸體——精鏜缸體——磨削缸體。采用滾壓方法是：拉削缸體——精鏜缸體——滾壓缸體，工序是3部分，但時間上對比：磨削缸體1米大概在1-2天的時間，滾壓缸體1米大概在10-30分鐘的時間。投入對比：磨床或絎磨機(jī)（幾萬——幾百萬），滾壓刀（1仟——幾萬）。滾壓后，孔表面粗糙度由幢滾前Ra3.2～6.3um減小為Ra0.4～0.8&um，孔的表面硬度提高約30%，缸筒內(nèi)表面疲勞強(qiáng)度提高25%。油缸使用壽命若只考慮缸筒影響，提高2～3倍，鏜削滾壓工藝較磨削工藝效率提高3倍左右。以上數(shù)據(jù)說明，滾壓工藝是高效的，能大大提高缸筒的表面質(zhì)量。
油缸經(jīng)過滾壓后，表面沒有鋒利的微小刃口，長時間的運(yùn)動摩擦也不會損傷密封圈或密封件，這點在液壓行業(yè)特別重要。
4.故障診斷及處理
1、誤動作或動作失靈
原因和處理方法有以下幾種：
(1)閥芯卡住或閥孔堵塞。當(dāng)流量閥或方向閥閥芯卡住或閥孔堵塞時，液壓缸易發(fā)生誤動作或動作失靈。此時應(yīng)檢查油液的污染情況；檢查臟物或膠質(zhì)沉淀物是否卡住閥芯或堵塞閥孔；檢查閥體的磨損情況，清洗、更換系統(tǒng)過濾器，清洗油箱，更換液壓介質(zhì)。
(2)活塞桿與缸筒卡住或液壓缸堵塞。此時無論如何操縱，液壓缸都不動作或動作甚微。這時應(yīng)檢查活塞及活塞桿密封是否太緊，是否進(jìn)入臟物及膠質(zhì)沉淀物：活塞桿與缸筒的軸心線是否對中，易損件和密封件是否失效，所帶負(fù)荷是否太大。
(3)液壓系統(tǒng)控制壓力太低?？刂乒苈分泄?jié)流阻力可能過大，流量閥調(diào)節(jié)不當(dāng)，控制壓力不合適，壓力源受到干擾。此時應(yīng)檢查控制壓力源，保證壓力調(diào)節(jié)到系統(tǒng)的規(guī)定值。
(4)液壓系統(tǒng)中進(jìn)入空氣。主要是因為系統(tǒng)中有泄漏發(fā)生。此時應(yīng)檢查液壓油箱的液位，液壓泵吸油側(cè)的密封件和管接頭，吸油粗濾器是否太臟。若如此，應(yīng)補(bǔ)充液壓油，處理密封及管接頭，清洗或更換粗濾芯。
(5)液壓缸初始動作緩慢。在溫度較低的情況下，液壓油黏度大，流動性差，導(dǎo)致液壓缸動作緩慢。改善方法是，更換黏溫性能較好的液壓油，在低溫下可借助加熱器或用機(jī)器自身加熱以提升啟動時的油溫，系統(tǒng)正常工作油溫應(yīng)保持在40℃左右。
2、工作時不能驅(qū)動負(fù)載
主要表現(xiàn)為活塞桿停位不準(zhǔn)、推力不足、速度下降、工作不穩(wěn)定等,其原因是：
(1)液壓缸內(nèi)部泄漏。液壓缸內(nèi)部泄漏包括液壓缸體密封、活塞桿與密封蓋密封及活塞密封均磨損過量等引起的泄漏。
活塞桿與密封蓋密封泄漏的原因是，密封件折皺、擠壓、撕裂、磨損、老化、變質(zhì)、變形等，此時應(yīng)更換新的密封件。
活塞密封過量磨損的主要原因是速度控制閥調(diào)節(jié)不當(dāng)，造成過高的背壓以及密封件安裝不當(dāng)或液壓油污染。其次是裝配時有異物進(jìn)入及密封材料質(zhì)量不好。其后果是動作緩慢、無力，嚴(yán)重時還會造成活塞及缸筒的損壞，出現(xiàn)“拉缸”現(xiàn)象。處理方法是調(diào)整速度控制閥，對照安裝說明應(yīng)做必要的操作和改進(jìn)。
(2)液壓回路泄漏。包括閥及液壓管路的泄漏。檢修方法是通過操縱換向閥檢查并消除液壓連接管路的泄漏。
(3)液壓油經(jīng)溢流閥旁通回油箱。若溢流閥進(jìn)入臟物卡住閥芯，使溢流閥常開，液壓油會經(jīng)溢流閥旁通直接流回油箱，導(dǎo)致液壓缸沒油進(jìn)入。若負(fù)載過大，溢流閥的調(diào)節(jié)壓力雖已達(dá)到最大額定值，但液壓缸仍得不到連續(xù)動作所需的推力而不動作。若調(diào)節(jié)壓力較低，則因壓力不足達(dá)不到仍載所需的椎力，表現(xiàn)為推力不夠。此時應(yīng)檢查并調(diào)整溢流閥。
3、活塞滑移或爬行
液壓缸活塞滑移或爬行將使液壓缸工作不穩(wěn)定。主要原因如下：
(1)液壓缸內(nèi)部澀滯。液壓缸內(nèi)部零件裝配不當(dāng)、零件變形、磨損或形位公差超限，動作阻力過大，使液壓缸活塞速度隨著行程位置的不同而變化，出現(xiàn)滑移或爬行。原因大多是由于零件裝配質(zhì)量差，表面有傷痕或燒結(jié)產(chǎn)生的鐵屑，使阻力增大，速度下降。例如：活塞與活塞桿不同心或活塞桿彎曲，液壓缸或活塞桿對導(dǎo)軌安裝位置偏移，密封環(huán)裝得過緊或過松等。解決方法是重新修理或調(diào)整，更換損傷的零件及清除鐵屑。
(2)潤滑不良或液壓缸孔徑加工超差。因為活塞與缸筒、導(dǎo)軌與活塞桿等均有相對運(yùn)動，如果潤滑不良或液壓缸孔徑超差，就會加劇磨損，使缸筒中心線直線性降低。這樣，活塞在液壓缸內(nèi)工作時，摩擦阻力會時大時小，產(chǎn)生滑移或爬行。排除辦法是先修磨液壓缸，再按配合要求配制活塞，修磨活塞桿，配置導(dǎo)向套。
(3)液壓泵或液壓缸進(jìn)入空氣。空氣壓縮或膨脹會造成活塞滑移或爬行。排除措施是檢查液壓泵，設(shè)置專門的排氣裝置，快速操作全行程往返數(shù)次排氣。
(4)密封件質(zhì)量與滑移或爬行有直接關(guān)系。O形密封圈在低壓下使用時，與U形密封圈比較，由于面壓較高、動靜摩擦阻力之差較大，容易產(chǎn)生滑移或爬行；U型密封圈的面壓隨著壓力的提高而增大，雖然密封效果也相應(yīng)提高，但動靜摩擦阻力之差也變大，內(nèi)壓增加，影響橡膠彈性，由于唇緣的接觸阻力增大，密封圈將會傾翻及唇緣伸長，也容易引起滑移或爬行，為防止其傾翻可采用支承環(huán)保持其穩(wěn)定。
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