原 文 标 题 | Oil pressure pump cover | |||||
译 文 标 题 | 油压泵简介 | |||||
作者所在系别 | 机械工程系 | |||||
作者所在专业 | 机械设计制造及其自动化 | |||||
完 成 时 间 | 2014 | 年 | 5 | 月 | 20 | |
译文标题 | 油压泵 | ||||
原文标题 | Oil pressure pump cover | ||||
作 者 | 译 名 | 商铺风水 国 籍 | |||
原文出处 | |||||
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 caud 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 rervoir 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 loss 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 paration(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 paration against leakage or slippage. Becau of this slippage,the delivery of the pump is reduced as the working pressure of a system is incread. However, nonpositive-displacement pumps deliver a continuous flow, while positive-displacement pumps deliver an intermittent(pulsating) flow. The 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, becau 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 respon 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 offt 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 becau the asmbly 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 us 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 asmbly with veral piston asmblies built into it, and can be classified as a rotary pump. Several types of piston pumps will be discusd 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 lecting a pump, the follow pump rating and lection factors are considered; 传统文化的手抄报Capacity Pressure Energy consumption Drive speed Efficiency 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 the lection 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() ,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 rvice temperatures. The pressure rating of a pump generally is bad on the ability of the pump to withstand pressure without an undesirable increa 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 lection 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 horpower is determined as follow: Hp=(gpm* *psi)/(14286*n) Where n is the overall effciency of the pump, motor, and drive. As you can e from this equation, reducing gpm and psi results in a proportional reduction in pumping horpower. Control of pump delivery can be accomplished either manually or automatically, using handwheel,levels, or variable-speed motors or transmission actuated by load-nsing 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. The engines usually operate at a constant speed 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 the 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 rvice life. Operating a hydraulic pump beyond its drive speed ratings usually reduces its rvice 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 increas, the flow rate of the pump decreas. The amount of decrea varies depending on the type of pump ud. 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. 心肌梗塞急救The rvice life of a pump is rated in hours of operation. Many hydraulic pumps hava a rvice 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 rvice life depends on the design and construction of the pump as well as on the application. 翻译 春意无限 液压泵是能把机械能转化为液压能的机械装置，更具体地说,一个泵将旋转柱塞的动能转换为流动的液压能。这些流体也有潜在的能量能够克服系统阻力进行流动，记住液压泵提供了一个产生流量和输出功率的力。液压是由系统负载和液压系统阻力的流体流动。 当液压泵工作时，它执行两个功能，首先,它在其入口创建了一个局部真空，,允许大气压力作用下推动液压油通过入口过滤器和油路进入泵的吸油腔。第二,它的机械作用传递液压油到出口并进入液压系统，正如表5-1所示。当液压油离开泵时，它就会遭遇系统的工作压力，这种压力是由调压阀、系统的外负载和液流的管路损失所产生的。 液压泵是基于他的物理排油机制和基本操作原理来分类的。泵按操作原理分配包括正排量泵和负排量泵。正排量泵在入口和出口之间装备了一个机械分离装置（齿轮、叶片或叶轮）来最大限度的减少内部泄漏和滑移。因此,正排量泵的输出是几乎不受系统压力变化的影响。 负排量泵没有一个确切的内部分离装置来减少泄漏和滑动，由于这种滑动，这些泵的排油量减少正如系统的工作压力增加。然而，负排量泵是持续性排油，正排量泵是间歇（脉动）的排油，这些脉动很小，可以通过蓄能器和系统管路消除。大多数液压泵是回转型的正排量容积泵。 正排量泵分为定量泵和变量泵。定量泵的流量只能通过改变泵的转速来调节，因为泵的抽吸装置的物理机制是无法改变的。（这并不意味着液压系统的其他部分不可以通过阀门来调节。） 变量泵可以通过一个内置的控制装置来改变泵的抽吸装置的物理机制，这个控制装置通常是用来相应系统压力和其他信号。变量泵比定量泵更复杂，因此成本更高。此外变量泵的效率也比定量泵的效率要低。这些变量泵更低的效率有些时候抵消了部分更高的系统整体效率。 大多数正排量泵被分类为旋转泵。这是因为液压油从入口被到出口有一个旋转的过程。旋转泵通过它的排油机制进一步划分为齿轮泵、叶片泵、螺杆泵。 柱塞泵是一种不同的正排量泵，这种泵是使用一种往复（来回）式运动的柱塞，交替的在吸油口吸油，出油口排油。一个旋转装置和数个活塞组构成了一个径向柱塞泵，因此它能被分类为旋转泵。几种类型的柱塞泵将在本章后面讨论。 不同泵的性能的评估是基于许多因素，包括物理特性、运行机制以及成本。当选者一个泵时，应考虑遵循泵的功率选择因素。 排量 压力 能耗 转速 学雷锋手抄报内容效率 可靠性 流量 大小和重量 操作适应性 使用寿命 安装和维护成本 邂逅意思 我们主要通过一个泵的容量来评价它。这也可以被称作供油速度、流量、容积输出。这种能力通常是在制定操作条件下每分钟多少加仑，多少立方英寸，或者一次循环输出多少立方英寸。泵能力的评级通常在标准大气进气压力和各种输出压力,以及在相似的流体使用温度下。 一个泵压力等级的一般是基于的泵能够承受的压力能力并且没有一个不良的内部泄漏(或滑脱)或泵零件损坏的增加。 泵额定压力是在相同条件下（速度、温度、和入口压力）进行的的能力的评估。大多数泵额定压力在100，500，1000，1500，2000，3500或5000青春之歌读后感磅每平方英寸。 能耗是一个重要的考虑因素，不仅仅是在泵的选择上，而且还是在系统安装完成后泵的操作性能上。这个能耗取决于泵压力，和给定时间内的泵的输送流量。 液压泵马力确定如下: Hp=(gpm* *psi)/(14286*n) 这里n是整体效率的泵、马达、驱动器，正如您可以从这个方程看到，减少能耗和流量将会成比例的减少泵的抽送马力。控制泵输送可以通过手轮、阶梯控制的手动完成，也可以通过负载传感器控制变速马达和传输驱动来自动完成。 泵通常的可用的电动马达一般额定在1200-1800转/分钟。这一可以是其他的额定的速度而不是电动机速度。例如,更高的速度发生在由内燃机驱动的变速液压泵。这些引擎通常运行在一个恒定的速度，包括2000转/分钟甚至更高的速度。一些工业液压泵额定速度甚至高达4000转/分钟。 旋转泵的最大安全速度是有限的，它使得泵有能力去避免气穴现象和过高的出口压力。大多数旋转泵还需要一个最低运转速度。尽管这些速度通常都不是关键，泵在高压下需要最低速运转以避免过热和内部滑移。 泵最大额定速度和最大额定压力是在间歇和连续操作中共同确定的，连续额定运转叙述在最大速度和最大压力下，泵在一个正常的使用寿命（大约1000小时）运转。间歇运转是在最大速度和最大压力下，泵能够在短时间内安全运行并且有一个符合要求的使用寿命。操作一个液压泵超出其额定速度通常会减少它的使用寿命。 早些时候就已经指出，液压系统施加在液压泵上的压力直接影响泵的供油速度。随着压力的增加,泵的流量减少，减少这种数量的变化取决于泵的使用种类。这种变化继而影响泵的效率。泵效率是用两种方式来叙述： 容积效率-实际流量和理论流量的比值 总效率-输出功率和输入功率的比值 泵的可靠性取决于如何使泵的特点与系统需求相的系统需求。可靠性也可以从维修时间来判断。所有的项目包括额定流量、液压系统设计的优劣和维护，泵的安装位置以及它的持久性，这些都与可靠性有关。 乳疾灵胶囊一个泵的使用寿命是认定操作的时间。许多有液压泵的使用寿命是10000小时,或者大约一年。其他的泵运转三到五年，每年大约5000小时,总计15000小时甚至更多。使用寿命取决于设计和泵的结构以及它的用途 | |||||
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