英文及譯文 翻譯英文原文： Accumulators An accumulator is found in many hydraulic systems. As the name suggests, it is a storage device. The various types of accumulators are studied in this chapter. A simple accumulator is sometimes used in household water system. It may consist of a tee with a side branch pipe that is capped. The air that is trapped in the side branch pipe is compressed, and then acts like a compressed spring. As a faucet is either opened or closed quickly, a sudden change in pressure and flow occurs. The trapped air acts as cushion, or shock absorber, to prevent water hammering in the piping system. The storage batter in a car is a typical example of an electrical or chemical accumulator. Chemical energy is stored in the batter is not in use. The stored chemical energy is converted into electricity that is used to start the engine. Hydraulic Accumulators A hydraulic accumulator may be used for a variety of purposes. Some of its uses are: ( 1 ) as a shock absorber； (2) to provide oil makeup in a closed system； (3) to compensate for leakage in a system； (4) to provide a source of emergency power in event of failure of the normal power supply；(5 ) to maintain steady delivery pressure over a period of time without keeping the pump operating continuously； and (6) as a transfer barrier device to separate the oil from some other fluid in the system. Types Of Accumulators Accumulators may be divided into three general types: ( 1 ) weight-loaded, (2) spring-load, and (3) air-or gas-type accumulators. The air-or gas-type Accumulators can be subdivided further into the separator and non-separator types. Weight Loaded or Gravity Types The weight-loaded or gravity-type accumulator consists of a cylinder, a movable position, a ram or plunger, and a weight. The dead weight ( which may be placed in a container) may be concrete, iron, steel, water, or other heavy material. The position should have a precision fit inside the cylinder in order to reduce leakage. The inner cylinder wall should have a honed or ground finish in order to reduce friction and wear. As hydraulic oil is pumped into the cylinder, the piston pushes the weight to a higher level. Thus the potential or stored energy of the weight is increased. The energy stored in the weight is released in the downward motion as it is required by the demands of the system. An accumulator of this type may be custom-built for a particular installation. The weight is adjusted so that the ram rises when the fluid pressure reaches a set level. The travel of the ram can be controlled by an arrangement of a cam on the plunger and limit switches. The gravity force of the piston on the oil provides a nearly constant oil pressure level for the full stroke of the piston. By providing adequate piston area and ample length of piston stroke, a large volume of fluid can be supplied at high pressure. A single large accumulator may provide service for a number of different machines. Spring-loaded Type A spring-loaded type of accumulator is illustrated. This device consists of a cylinder, a piston, and a spring. One or more springs may be used. The springs may be arranged to provide various adjustments by means of bolts. As the oil is pumped into the accumulator, the piston or plunger compresses the spring； The energy stored in the spring is released as it is required by the demands of the system. The pressure on the oil is not constant for all the positions of the piston, because the spring force depends on the movement of the spring. Usually, this type of accumulator delivers only a small amount of oil at low pressure. Air or Gas Type Hydraulic fluid or oil is nearly incompressible. This means that a large increase in oil pressure results in only a small, or negligible, decrease in the volume of oil. On the other hand, a large increase in air or gas pressure results in a large decrease in the volume of the air or gas. Relatively speaking, hydraulic oil is less elastic or spring-like than air. Oil cannot be used effectively to store energy by compressing it, whereas air or gas can be compressed to store energy. Thus, one general type of accumulator used gas or air, rather than a mechanical spring or a weight, to provide the spring-like action. Air or gas types of accumulators can be divided into two subdivisions: (1) the non-separator type, and (2) the separator type. In the non-separator type of accumulator, the oil is in direct contact with the air or gas. In the separator types of accumulator, either a solid or a flexible barrier is placed between the oil and the gas to separate the two different types of fluids. Non-separator Type A non-separator type of air or gas accumulator consists of a fully enclosed cylinder, adequate ports, and a charging valve. A portion of oil must be trapped in the bottom of the cylinder before this type of accumulator can be placed in operator. Air, nitrogen, or an inert gas is then forced into the cylinder, and the accumulator precharged to the minimum pressure requirement of the system. A so-called free surface exists between the oil and the air or gas. As a greater quantity of oil is pumped into the accumulator, the air or gas above the oil is compressed still further. The energy is stored in the compressed gas, and it is released as required by the demands of the system. This type of accumulator should be mounted in a vertical position, because the gas must be retained in the top of the cylinder. To prevent the air or gas being exhausted into the hydraulic system, only about two-thirds of the accumulator volume can be used for the air or gas volume. Approximately one-third of the remaining accumulator volume should be reserved for the oil, to prevent the air or gas from being drawn out of the accumulator to the hydraulic system. Aeration, or mixing, of the oil or air or gas may result in diminishing the precharge of the accumulator. If the air or gas is absorbed by the oil, the accumulator requires an air or gas compressor for the precharging operation of the accumulator. Separator Type ( with piston) A separator type of accumulator with a free or floating piston acting as the barrier between the air or gas and the oil is illustrated in Figure. High-pressure air or gas is charged into the space on one side of the piston, and hydraulic oil is charged into the space on the opposite side. The tube should be machined with precision. The piston packing keeps the oil and gas separated. This type of accumulator may be installed in any position. The preferred position, however, is to place the cylinder axis vertically, with the gas connection at the top. The wearing action of the packing between the piston and the cylinder should be checked after extended use, because this may result in significant leakage. A floating piston within a cylindrical accumulator is illustrated in Figure. In the design, the double-shell construction provides a pressure-balanced inner shell that contains the position and serves as a separator between the precharged air or gas and the working hydraulic fluid. The outer shell serves as a gas container. Rapid decompression of the precharged air or gas, resulting from a rapid discharge of the working hydraulic fluid, provide a coolant for the entire corking area of the inner shell. Pressure balancing ports in the piston provide equal pressure to either side both rings； this prevent pressure lock between seals. Separator Type (with diaphragm) A diaphragm-type accumulator involves two hemispheres that are made from steel forgings. The hemispheres are locked together and a flexible, convoluted, rubber diaphragm is clamped around the periphery. An air or gas precharge is applied to one of the two hemispheres； oil, under pump pressure, is applied to the opposite hemispheres to compress the sir or gas charged. As the air or gas is compressed, the pressure rises； then the gas acts as a spring. Oil pressure and gas pressure are equal, because the separating member is flexible. Bag Type The type, or bladder, type of accumulator is a seamless steel shell that is cylindrical in shape and spherical at both ends. A gas valve is located at one end of the shell and opens into the shell. A large opening through which the bag can be inserted is located at the opposite end. The bladder is made of synthetic rubber and is pear-shaped. The fully enclosed bladder, including a molded air stem, is fastened by means of a lock nut to the upper end of the shell. On the opposite end of the shell, a plug assembly containing the oil port and a pop pet valve is mounted. The accumulator cannot be disassembled while a gas charge is inside the bag. The accumulator should be installed with the end that contains the air at the top to avoid trapping the oil when discharging. Contamination As with the other components in a hydraulic system, care should be taken to avoid contamination when installing the accumulator. The accumulator should be cleaned completely before installation in the system. Since an accumulator usually forms a dead-end in the pipeline, it may not be flushes as well as some other components during system operation. The piston-type accumulator can be studied to better understand accumulator construction. The piston may be sealed with an O-ring groove, causing wear or damage to the O-ring and allowing the gas charge to leak into the oil. An arrangement in which an O-ring seal is placed between Teflon piston rings provides a means by which the piston rings can scrape contaminants from the cylinder walls, and thus protect the O-ring seal. It is a good practice to install a filter in the air or gas charging system of the accumulator. Accumulators In Systems The accumulator is often installed in a hydraulic system to absorb shocks. The hydraulic oil from a pump is piped to a four-way valve, which directs the oil flow to a cylinder containing a piston. If the valve is closed quickly, the sudden stoppage may result in oil shock waves, or a hammering effect. A violent hammering action may damage the fittings and piping. The accumulator is capable of absorbing the shocks, thus protecting the entire system. During periods when no flow of oil is required in the hydraulic system, pump delivery can be returned, or bypassed, to the reservoir at low pressure. This arrangement serves to reduce electric power requirement, oil heating, and wear of the moving parts. The accumulator can be used as a power-saving device. A piston provides a loading force-as for a clamping operation or a rolling mill operation, in which the force moves only a short distance. After the oil pressure is built up at the piston face, the accumulator can supply the loading force for a period of time. During this period it is unnecessary to keep the pump delivering at high pressure. Therefore, an unloading valve is provide to return the pump delivery to the reservoir at low outlet pressure. During the unloading process, the pump discharge pressure is a low level, while the accumulator pressure is at a high level to provide the loading force. Thus, the accumulator is a power-saving device, and also provides for absorption of shock waves. 蓄壓器儲壓器 在很多水壓設備中都能發(fā)現(xiàn)有一個蓄壓器。正如它的名字所暗示的，它是一個存儲設備。在這一章中要學習各種不同種類的蓄壓器。 有時候在家庭存水設備中就會用到一個簡單的蓄壓器。它可以被認為是一個球坐和一個被覆蓋住頭的分支管組成?？諝饩驮谀莻€被蓋住的分支管里，然后按壓。隨著蓋帽的迅速打開蓋上，氣壓突然改變，然后就產生了氣流。里面的空氣就充當了氣墊或者是減弱沖擊的緩沖器，用來防止管子里的水溢出。 汽車里的存儲設備是一種電的或化學成分的蓄壓器。不使用的化學能儲存在儲存器里面。儲存的化學 能被轉化成電能后供發(fā)動引擎使用。 水壓蓄壓器可能被用作不同的目的。它們的一些用途有：（ 1）作為一個減弱沖擊的緩沖器；（ 2）在一個關閉的系統(tǒng)里提供汽油；（ 3）補充系統(tǒng)內的滲漏物；（ 4）在不能達到正常的引力情況下，提供緊急能量的來源；（ 5）當泵不能繼續(xù)運轉的時候，在一段時期內維持傳送過來壓力的穩(wěn)定；（ 6）作為一個傳輸障礙物，在系統(tǒng)中將汽油和其他液體分離。 蓄壓器的種類 蓄壓器一般分為三種類型：（ 1）重量裝載類型，（ 2）彈簧支撐類型，（ 3）空氣或氣體類型?？諝饣驓怏w類型的蓄壓器又可以進一步 劃分為分離的和非分離的。 重量裝載或重力類型 重量裝載或重力類型的蓄壓器是由一個圓柱體，一個可移動位置的撞擊物或活塞和一個重物組成。那個無生命的重物（可能被放在容器中）可能是具體的鐵，鋼，水，或其他重質材料的東西。在圓柱體里的那個位置要固定準備，用來減少滲漏物。圓柱體的內壁上應該有一個磨砂的或毛的物質來減少摩擦和磨損。當水力油抽入圓筒，活塞推擠重量對高水平。 因而增加重量的潛力或儲能。當它由系統(tǒng)的要求，需要在重量存放的能量在向下運動被釋放。這個類型蓄壓器也許是定制的為特殊設施。因為重量裝載是被校正過 的，所以當液體壓力到達設定的值的時候，活塞就會上升。撞擊物的移動可能受放在活塞和計時器上的凸輪的控制?；钊闹亓υ谟偷臑榛钊某浞值臎_程提供一個幾乎恒定的油壓水平。 通過提供充分活塞區(qū)域和活塞沖程的寬裕的長度，大容量流體可以被供應在高壓。 一臺唯一大蓄壓器也許為一定數量不同的機器提供服務。 彈簧支撐類型 蓄壓器的一種彈簧支撐類型被說明。這種類型是由圓柱、活塞、彈簧組成的?；蛟S一根或更多根彈簧要被用到。這種類型的蓄壓器也許通過螺栓提供各種各樣的調整。當油抽入蓄壓器，活塞或柱塞擠壓彈簧；當系統(tǒng)需要時， 儲存在彈簧內的能量就被釋放。因為彈簧的力量取決于彈簧的運動，在油的壓力為活塞的所有位置不是恒定的。 通常，這種類型的蓄壓器交付僅少量油以低壓。 空氣或氣體類型 液壓機液體或油是幾乎不可壓縮的。 這意味著油壓的大增量，導致只有一點點，或幾乎不能地降低油的容量。換句話說，空氣或氣體壓力的大增量，能導致空氣或氣體體積的大幅度下降。相對來說，水力油比空氣較不有彈性或象彈簧的。油不可能通過壓縮它有效地用于存放能量，而空氣或氣體可以被壓縮存放能量。 因此，蓄壓器的一種一般類型使用氣體或空氣，而不是機械的彈簧或重 量裝置，提供像彈簧的作用。 蓄壓器的空氣或氣體類型可以被劃分成二細分： (1)非分離器類型和 (2)分離器類型。在蓄壓器的非分離器類型中，石油是直接與空氣或氣體聯(lián)系。 在蓄壓器的分離器類型中，一個堅實或一個靈活的障礙被安置在石油和氣體之間分離流體的二種不同類型。 非分離類型 空氣或氣體的非分離蓄壓器類型由一個充分的附上的圓筒、充分口岸和一個充氣閥組成。在此種蓄壓器能被操作員使用之前，一部分油必須在圓筒的底部被困住?？諝?、氮氣或者惰性氣體然后被強迫入圓筒，蓄壓器預加壓力滿足系統(tǒng)需要的最小壓力。所謂的自 由表面存在石油和空氣或者氣體之間。 當一個質量更好的油被壓入蓄壓器中，在油之上的空氣或氣體被進一步壓縮。能量存儲在壓縮氣體中，當系統(tǒng)需要是被釋放。 這種類型的蓄壓器應該安裝在一個垂直的位置上，因為氣體必須保留在圓筒的上面。為了防止被用盡的空氣或氣體進入水壓系統(tǒng)中，只有三分之二的圓筒的容量才能被空氣或氣體使用。剩余的三分之一的圓筒的容量是為油后備的，為了防止空氣或氣體從蓄壓器發(fā)揮出來進到系統(tǒng)中去。通風或者混合的油或空氣或氣體可能導致減少蓄壓器的預壓力。如果空氣或氣體被油吸收了，蓄壓器就需要一個空氣的或 氣體的壓氣機來對蓄壓器進行預加壓。 分離類型（帶活塞的） 帶有自由浮動活塞的分離類型的蓄壓器，在空氣或氣體和油之間是一個障礙，這在圖中有被說明。高壓空氣或氣體被加壓在活塞一邊的空間中，并且水力油被加壓在反面的空間中。 應該用機器制造管與精確度。 活塞包裝使油和氣體相分離。 此種蓄壓器在所有位置也許被安裝。然而， 首選的位置，是垂直安置圓筒軸，與在上面的氣體連接。因為這也許導致重大漏出，應該在延長用途以后檢查在活塞和圓筒之間的包裝的佩帶的活動。 在一臺圓筒柱型蓄壓器內，一個浮動的活 塞被用圖說明了。在設計中，雙殼構造的蓄壓器保持內殼層壓力的平衡。內殼層包含了分離預加壓的空氣或氣體和工作液壓機液體的位置和服務。外殼則作為氣體容器。 被預先加壓的空氣或氣體的迅速解壓，起因于工作液壓機液體的迅速放電，為內殼層的整個塞住的區(qū)域提供蓄冷劑。 在活塞的壓力平衡口岸提供相等的壓力給任一邊兩個圓環(huán) ； 這防止在封印之間的壓力鎖。 分離類型（帶膜片的） 膜片類型的蓄壓器包含兩個由鋼鍛造的半球。兩個半球鎖在一起，然后一張靈活，復雜，橡膠膜片在周圍附近被夾緊。 空氣或氣體預加壓后被放到其中的一個半球里 ；油，在泵浦壓力下，被放于相反半球來壓縮 填充的空氣或氣體。當空氣或氣體被壓縮，壓力就變大；然后空氣就相當于是彈簧。因為分離的成員是靈活的，油壓和氣體壓力是相等的。 包類型 這種類型的蓄壓器是一根無縫的鋼毛管。而這個包或者囊是一個圓柱體在有形的球狀的兩個末端。排氣閥位于殼的一個末端并且打開入殼。一個可以通過包插入的開口在相反的末端。囊由合成橡膠制成并且是梨狀的。包含一個模塑的空氣的閥桿緊附在囊上。它通過螺帽被緊固在殼的上端。在殼的相反方，安裝有一個包含供油港和流行石油閥門裝置的塞子。當氣體加壓是在 袋子里面時，蓄壓器不可能被拆卸。這種蓄壓器應當安裝在頂端有空氣的部分，以免當釋放時油被困住。 污染 當安裝蓄壓器時，在液壓機系統(tǒng)中裝有其他零組件時，應當注意避免污染。蓄壓器被安裝到系統(tǒng)之前應當徹底的清洗。因為在管道內，蓄壓器通常是一種固定的形式，因此，在系統(tǒng)運作是，它可能不能像其他零部件那樣沖洗。學習活塞式的蓄壓器能更好的理解蓄壓器的構造?；钊苍S密封成 O 環(huán)凹線，造成對 O 環(huán)的磨損或傷害而且使得空氣加壓流入油中。O 環(huán)封印安置在聚四氟乙烯活塞環(huán)之間，提供活塞環(huán)可能刮從圓筒墻壁的污染物的方法和因而保護 O 環(huán) 封印。 在空氣或氣體的蓄壓器系統(tǒng)中安裝過濾器是一種很好的練習。 蓄壓器在系統(tǒng)中 蓄壓器經常被安裝在一種液壓系統(tǒng)中來緩沖震動。從泵浦的水力油被用管道輸送到一個四種方式的閥門，指揮著油流到包含活塞的圓筒。 如果閥門迅速被關閉，突然的停止也許導致石油危機波浪或者一個錘擊的作用。 一次猛烈錘擊的行動也許損壞配件和管道系統(tǒng)。 蓄壓器能夠承受震動，因而可以保護整個系統(tǒng)。當液壓系統(tǒng)沒有需要油流動的這段期間內，泵排量可以以低壓返回或者被繞過，到水庫。 這個措施能減少對電力和運動機件的油熱和磨損。 蓄壓器可以使用作為力量挽救設備。 活塞為夾緊的操作或軋板機操作提供裝貨力量，力量移動僅一個短的距離。 在油壓被加強在活塞面孔之后，蓄壓器可能在一段時間提供裝貨力量。 在這個期間內泵浦持續(xù)交付在高壓是不必要的。因此，一個卸荷閥是提供以低出口壓力退回泵排量到水庫的。 在卸載的過程期間，泵浦釋放的壓力在一個低水平上，而蓄壓器的壓力在一個高水平上，來提供裝貨力量。因此，蓄壓器是一個力量挽救設備，并且提供沖擊波的吸收。 第八課 數字信號處理器（ DSPs） 在很多情況下，模擬信號要被不同的方式處理， 像過濾和光譜分析。由于對性能的要求，靈活性的需要和需要減少發(fā)展或測試的時間，設計模式硬件執(zhí)行這些作用是可能的，但是變得越來越不實用了。換句話說，設計執(zhí)行對信號的先進的分析的模式是難得。抽樣一個模擬信號到數字式領域里的行為，和申請?zhí)幚碓谑褂糜嬎愕乃惴ǖ臄底质桨姹静⑶以谔幚砗罂赡芑謴托盘柕侥Ｊ筋I域的過程叫做數字信號處理。處理器涌現(xiàn)了在為嵌入信號處理操作被專門研究的過去 15 年期間內，并且這種處理器稱 DSP，代表數字信號處理器。 如今，有許多來自不同產方設計的數字信號處理器，每一種都是為特定價錢 /性能 /使用群體設 計的。像德州儀器和摩托羅拉這些大型產商，即為特定領域提供特定的數字信號處理器，像電動機控制或調制解調器，而且還提供一般的高性能的數字信號處理器，這中處理器能處理廣域范圍內的處理任務。升級工具和軟件也是可用的，而且有商家為數字信號處理做升級軟件，這種處理器能夠允許程序員用簡的 drag n drop統(tǒng)計分析法來處理復雜的程序算法。 根據下面的定點和浮點的體系結構，數字信號處理器或多或少被歸入兩個類別。定點設備通常起作用于 16 位的字，而浮點設備起作用于 3240 位的浮點字。不用說，定點設備通常更加便 宜。 另一個重要的體系結構的區(qū)別就是，當只有一臺“通用”記數器，使他們相當棘手而且更加重要的處理時，定點處理器只傾向于有累加器的體系結構。 這使得 C 編譯器本質上地效率低。浮點數字信號處理器更像帶有寄存器組的普通的通用 CPUs。在市場上，有成千上萬種不同的數字信號處理器，而且很難為某個項目找到一個適合的數字信號處理器。最好的辦法大概就是設定一個限制條件，然后和大的產商生產的處理器進行比較。數字信號處理器的四大產商是：德州儀器，摩托羅拉， AT&T 和模擬設備。 數模變換 在 MPEG 音頻解碼情況下， 數字式壓縮的數據被投向執(zhí)行解碼的 DSP，然后被解碼的樣品必須轉換回到模式領域和發(fā)生的信號被投向放大器或相似的音響器材里。 這種數模變換（ DAC）別具有相同名字的電路執(zhí)行。不同的數字信號處理提供不同的操作和質量，如測量由位的 THD (總諧波畸變 )，數字，線性、速度、過濾器特征和其他東西。 德州儀器的 TM320 家庭數字信號處理器 TM320 家庭型的包括定點，浮點，多重處理機數字信號處理器 (DSPs)和定點 DSP 控制器。 TM320 的數字信號處理器有一個特別為實時信號處理明確地設計的體系結構。 DSP 控制器的 C24x 系列與控制器外圍設備