- 0 - 本科生畢業(yè)設(shè)計 (論文 ) 外 文 翻 譯 原 文 標(biāo) 題 Oil pressure pump cover 譯 文 標(biāo) 題 油壓泵簡介 作者所在系 別 機(jī)械工程系 作者所在專業(yè) 機(jī)械設(shè)計制造及其自動化 作者所在班級 機(jī)本 1007 作 者 姓 名 作 者 學(xué) 號 指導(dǎo)教師姓名 指導(dǎo)教師職稱 完 成 時 間 2014 年 5 月 20 - 1 - 譯文標(biāo)題 油壓泵 原文標(biāo)題 Oil pressure pump cover 作 者 譯 名 國 籍 原文出處 原文 A hydraulic pump is a mechanical device which converts mechanical energy into hydraulic energy.More specifically ,a pump converts the kinetic(moving) energy of a rotating shaft into the kinetic energy of fluid flow. The fluid flow also has potential energy that allows it to overcome the resistance of the system to fluid flow .Remember that a pump provides the force produce flow and transmit power . Hydraulic pressure is caused by the load on the system and by the resistance of the hydraulic system to fluid flow. When operating , a hydraulic pump performs two functions. First, it creates a partial vacuum at its inlet ,permitting the atmospheric pressure in the fluid reservoir to push the hydraulic fluid through the inlet strainer and line into the pump .Second, its mechanical action delivers the fluid to its outlet and into the hydraulic systems, as shown in Fig.5-1. As the fluid leaves the pump, it encounters the working pressure in the system. This pressure is produced by the pressure regulating valve, the system work load ,and flow losses in the hydraulic tubing A pump is classified on the basis of the physical arrangement of its pumping mechanism and its basic principle of operating. Pumps classified by principle of operation include positive displacement and nonpositive-displacement types. Positive-displacement pumps are equipped with a mechanical separation(gears,vanes,or impellers) between the inlet and outlet, which minimizes internal leakage or slippage. Therefore,the output of positive-displacement pumps is almost unaffected by variations in system pressure Nopositive-displacement pumps(such as centrifugal pumps) do not have a positive internal separation against leakage or slippage. Because of this slippage,the delivery of these pump is reduced as the working pressure of a - 2 - system is increased. However, nonpositive-displacement pumps deliver a continuous flow, while positive-displacement pumps deliver an intermittent(pulsating) flow. These pulsations are small and can be smooth out by the accumulator or the system piping. Most hydraulic pumps are positive-displacement pumps of the rotary type. Positive-displacement pumps have either a fixed or variable displacement. The volume of delivery ,or gpm, of a fixed-displacement pump can be changed only by changing the speed of the pump, because the physical arrangement of the pumping mechanism cannot be changed, (This does not mean that the flow in other portions of the system cannot be adjusted by valves.) The flow of a variable-displacement pump can be changed by changing the physical arrangement of the pumping mechanism with a built-in controlling device. This device often functions in response to system pressure or other signals. Variable-displacement pumps are more complex than fixed-displacement pumps and,therefore,cost more. In addition, the efficiency of a variable-displacement pump is lower than that of a fixed-displacement pump. This is offset somewhat by the higher overall efficiency of a system powered by a variable-displacement pump. Most positive-displacement pumps are classified as rotary pumps. This is because the assembly that transfers the fluid from the pump inlet to the pump outlet has a rotating motion. Rotary pumps are further classified according to the mechanism that transfers the fluid-such as gears,vanes,or screws. A different kind of positive-displacement pump is piston pump. This pump uses a reciprocating (back-and-forth) motion of the piston, alternately to receive fluid on the inlet side, and to discharge fluid on the outlet side. A radial-piston pump has a revolving assembly with several piston assemblies built into it, and can be classified as a rotary pump. Several types of piston pumps will be discussed later in this chapter. The performance of different pumps is evaluated on the basis of many factors, inculding physical characteristics, operating characteristics,and cost. When selecting a pump, the follow pump rating and selection factors are considered； Capacity Pressure Energy consumption Drive speed Efficiency - 3 - Reliability Fluid characteristics Size and weight Control adaptability Service life Installation and maintenance costs Some of the performance characteristics of different pumps are given in Table 5-1.Each of these selection factors is described briefly in the following paragraph. The primary rating of a pump is its capacity. This is also called the delivery rate ,flow rate, or volumetric output. The capacity usually is given in gallons per minute (gpm), cubic inches per minute( min/3in ) ,or cubic inches per revolution at specified operating conditions. Pump capacity ratings usually are given at standard atmospheric inlet pressure and various output pressures, as well as at approximate fluid service temperatures. The pressure rating of a pump generally is based on the ability of the pump to withstand pressure without an undesirable increase in its internal leakage( or slippage) or damage to pump parts. Pumps are pressure-rated under the same conditions( speed,temperrature,and inlet pressure) at which they are capacity-rated. Most pumps are pressure-rated at 100,500,1000,1500,2000,3500,or 5000 psi. Energy consumption is an important consideration not only in the selection of a pump, but also in the operating performance of the pump after the system is installed. The energy requirement for pumping depends on the pumping pressure, and on the mass of fluid pumped in a given time. The fluid pumping horsepower is determined as follow: Hp=(gpm* galb1*psi)/(14286*n) Where n is the overall effciency of the pump, motor, and drive. As you can see from this equation, reducing gpm and psi results in a proportional reduction in pumping horsepower. Control of pump delivery can be accomplished either manually or automatically, using handwheel,levels, or variable-speed motors or transmission actuated by load-sensing controls. Pumps often are rated at the commonly available electric motor speed of 1200 or 1800 rpm.They also may be rated at speeds other than motor speeds. For instance, higher speeds occur in mobile hydraulic pumps driven from internal combustion engines. These engines usually operate at a constant speed - 4 - and include speeds of 2000 rpm and higher. Some industrial hydraulic pumps are rated at speeds of up to 4000 rpm. The maximum safe speed for a rotating pump is limited by the pump s ability to avoid cavitation and high outlet pressures. Most rotating pumps also require a minimum operating speed. Although these speeds usually are not critical, pumps operating at high pressures require a minimum speed in order to prevent overheating or internal slippage. Maximum speed and pressure ratings for pumps often are given for both intermittent and continuous operation. Continuous ratings describe the maximum speed and pressure at which a pump can be operated for a normal design life (about 10000 hours). Intermittent ratings are maximum speed and pressure at which a pump can be operated safely for short times and still have a satisfactory service life. Operating a hydraulic pump beyond its drive speed ratings usually reduces its service life. As pointed out earlier, the pressure a system exerts on the hydraulic pump directly affects the delivery rate of the pump. As the pressure increases, the flow rate of the pump decreases. The amount of decrease varies depending on the type of pump used. This change in flow affects the pump s efficiency. Pump efficiency is described in two ways: Volumetric efficiency- the ratio of the actual delivery rate to the theoretical displacement Overall efficiency-the ratio of the hydraulic power output to the mechanical power input. The reliability of a pump is determined by how well the characteristics of the pump are matched to the requirements of the system. Reliability can also be measured in maintenance time. Items such a how much fluid is required, how well the system is designed and maintained, where the pump is located, and how durable it is, all are related to reliability. The service life of a pump is rated in hours of operation. Many hydraulic pumps hava a service life of 10000 hours, or about one year. Other operate for three or five years at about 5000 hours per year, for a total of 15000 or more hours. The service life depends on the design and construction of the pump as well as on the application. - 5 - 翻譯 液壓 泵是 能把機(jī)械能轉(zhuǎn)化為液壓能的機(jī)械裝置， 更具體地說 ,一個泵將旋轉(zhuǎn)柱塞的動能轉(zhuǎn)換為流動的液壓能。這些流體也有潛在的能量能夠克服系統(tǒng)阻力進(jìn)行流動，記住 液壓 泵提供了一個產(chǎn)生流量和輸出功率的力。液壓是由系統(tǒng)負(fù)載和液壓系統(tǒng)阻力的流體流動。 當(dāng)液壓 泵工作時，它執(zhí)行兩個功能， 首先 ,它在其入口創(chuàng)建了一個局部真空， ,允許大氣壓力作用下推動液壓油通過入口過濾器和油路進(jìn)入泵的吸油腔。第二 ,它的機(jī)械作用傳遞液壓油到出口并進(jìn)入液壓系統(tǒng)，正如表 5-1所示。當(dāng)液壓油離開 泵 時，它就會遭遇系統(tǒng)的工作壓力，這種壓力是由調(diào)壓閥、系統(tǒng)的外負(fù)載和液流的管路損失所產(chǎn)生的。 液壓 泵是基于他的物理排油機(jī)制和基本操作原理來分類的。泵按操作原理分配包括正排量泵和負(fù)排量泵。正排量泵在入口和出口之間裝備了一個機(jī)械分離裝置（齒輪、葉片或葉輪）來最大限度的減少內(nèi)部泄漏和滑移。因此 ,正排量泵的輸出是幾乎不受系統(tǒng)壓力變化的影響。 負(fù)排量泵沒有一個確切的內(nèi)部分離裝置來減少泄漏和滑動，由于這種滑動，這些泵的排油量減少正如系統(tǒng)的工作壓力增加。然而，負(fù)排量泵是持續(xù)性排油，正排量泵是間歇（脈動）的排油，這些脈動很小， 可以通過蓄能器和系統(tǒng)管路消除。大多數(shù)液壓泵是回轉(zhuǎn)型的正排量容積泵。 正排量泵分為定量泵和變量泵。定量泵的流量只能通過改變泵的轉(zhuǎn)速來調(diào)節(jié)，因?yàn)楸玫某槲b置的物理機(jī)制是無法改變的。（這并不意味著液壓系統(tǒng)的其他部分不可以通過閥門來調(diào)節(jié)。） 變量泵可以通過一個內(nèi)置的控制裝置來改變泵的抽吸裝置的物理機(jī)制，這個控制裝置通常是用來相應(yīng)系統(tǒng)壓力和其他信號。變量泵比定量泵更復(fù)雜，因此成本更高。此外變量泵的效率也比定量泵的效率要低。這些變量泵更低的效率有些時候抵消了部分更高的系統(tǒng)整體效率。 大多數(shù)正排量泵被分 類為旋轉(zhuǎn)泵。這是因?yàn)橐簤河蛷娜肟诒坏匠隹谟幸粋€旋轉(zhuǎn)的過程。旋轉(zhuǎn)泵通過它的排油機(jī)制進(jìn)一步劃分為齒輪泵、葉片泵、螺桿泵。 柱塞泵是一種不同的正排量泵，這種泵是使用一種往復(fù)（來回）式運(yùn)動的柱塞，交替的在吸油口吸油，出油口排油。一個旋轉(zhuǎn)裝置和數(shù)個活塞組構(gòu)成了一個徑向柱塞泵，因此它能被分類為旋轉(zhuǎn)泵。 幾種類型的柱塞泵將在本章后面討論 。 不同泵的性能的評估是基于許多因素，包括物理特性、運(yùn)行機(jī)制以及成本。當(dāng)選者一個泵時，應(yīng)考慮遵循泵的功率選擇因素。 排量 壓力 - 6 - 能耗 轉(zhuǎn)速 效率 可靠性 流量 大小和重量 操作適應(yīng)性 使用壽命 安裝和維護(hù)成本 我們主要通過一個泵的容量來評價它。這也可以被稱作供油速度、流量、容積輸出。這種能力通常是在制定操作條件下每分鐘多少加侖，多少立方英寸，或者一次循環(huán)輸出多少立方英寸。泵能力的評級通常在標(biāo)準(zhǔn)大氣進(jìn)氣壓力和各種輸出壓力 ,以及在相似的流體使用溫度下。 一個泵壓力等級的一般是基于