机械外文翻译外文文献英文文献液压机械及泵

1、Hydraulic machinery and pumpHydraulic machinery are machines and tools which use fluid power to do work. Heavy equipment is a common example.In this type of machine, high-pressure liquid - called hydraulic fluid - is transmitted throughout the machine to various hydraulic motors and hydraulic cylind

2、ers. The fluid is controlled directly or automatically by control valves and distributed through hoses and tubes.The popularity of hydraulic machinery is due to the very large amount of power that can be transferred through small tubes and flexible hoses, and the high power density and wide array of

3、 actuators that can make use of this power.Hydraulic machinery is operated by the use of hydraulics, where a liquid is the powering medium. Pneumatics, on the other side, is based on the use of a gas as the medium for power transmission, generation and control.Hydraulic circuitsFor the hydraulic flu

4、id to do work, it must flow to the actuator and or motors, then return to a reservoir.The fluid is then filtered and re-pumped. The path taken by hydraulic fluid is called a hydraulic circuit of which there are several types. Open center circuits use pumps which supply a 10continuous flow. The flow

5、is returned to tank through the control valves open center; that is, when the control valve is centered, it provides an ope n retur n path to tank and the fluid is not pumped to a high pressure. Otherwise, if the control valve is actuated it routes fluid to and from an actuator and tank. The fluids

6、pressure will rise to meet any resista nee, since the pump has a con sta nt output. If the pressure rises too high, fluid returns to tank through a pressure relief valve.Hydraulic pumps supply fluid to the components in the system. Pressure in the system develops in reaction to the load. Hence, a pu

7、mp rated for 5,000 psi is capable of maintaining flow aga inst a load of 5,000 psi.Pumps have a power density about ten times greater than an electric motor (by volume). They are powered by an electric motor or an engine, conn ected through gears, belts, or a flexible elastomeric coupling to reduce

8、vibration.Common types of hydraulic pumps to hydraulic machinery applicati ons are;Gear pump: cheap, durable, simple. Less efficie nt, because they are con sta nt displaceme nt, and mainly suitable for pressures below 20 MPa (3000 psi).Vane pump: cheap and simple, reliable (especially in g-rotor for

9、m). Good for higher-flow low-pressure output.Axial piston pump: many designed with a variable displacement mecha ni sm, to vary output flow for automatic con trol of pressure.There are various axial pist on pump desig ns, in cludi ng swashplate and checkball. The most com mon is the swashplate pump.

10、Radial piston pump: A pump that is normally used for very high pressure at small flows.Piston pumps are more expensive than gear or vane pumps, but provide Ion ger life operat ing at higher pressure, with difficult fluids and Ion ger con ti nu ous duty cycles. Pist on pumps make up one half of a hyd

11、rostatic tran smissi on.Con trol valvesDirectional control valves route the fluid to the desired actuator.They usually con sist of a spool in side a cast iron or steel hous ing.Directional control valves are usually designed to be stackable, with one valve for each hydraulic cyli nder, and one fluid

12、 in put supplying all the valves in the stack.The spool positi on may be actuated by mecha ni cal levers, hydraulic pilot pressure, or sole no ids which push the spool left or right.The main valve block is usually a stack of off the shelf directional control valves chosen by flow capacity and perfor

13、manee. Some valves are designed to be proportional (flow rate proportional to valve position), while others may be simply on-off. The control valve is one of the most expe nsive and sen sitive parts of a hydraulic circuit.Pressure relief valves are used in several places in hydraulic machinery; on t

14、he return circuit to maintain a small amount of pressure for brakes, pilot lines, etc. On hydraulic cylinders, to prevent overloading and hydraulic line rupture. On the hydraulic reservoir, to maintain a small positive pressure which excludes moisture and con tam in ati on.Pressure reduc ing valves

15、reduce the supply pressure as n eeded for various circuits.Check valves are one-way valves, allowing an accumulator to charge and maintain its pressure after the machine is turned off, for example.Coun terbala nee valves are in fact a special type of pilot con trolled check valve. Whereas the check

16、valve is open or closed, the coun terbala nce valve acts a bit like a pilot con trolled flow con trol.Hydraulic pump typesGear pumpsGear pumps (with external teeth) (fixed displacement) are simpleand economical pumps. The swept volume ordisplacement of gear pumps for hydraulics will be between about

17、 1 cm 3 (0.001 litre) and 200 cm3 (0.2 litre). These pumps create pressure through the meshing of the gear teeth, which forces fluid around the gears to pressurize the outlet side. Some gear pumps can be quite noisy, compared to other types, but modern gear pumps are highly reliable and much quieter

18、 tha n older models.Rotary vane pumpsRotary vane pumps (fixed and simple adjustable displacement) have higher efficie ncies tha n gear pumps, but are also used for mid pressures up to 180 bars in gen eral. Some types of vane pumps can change the centre of the vane body, so that a simple adjustable p

19、ump is obtained. These adjustable vane pumps are in general constant pressure or constant power pumps: the displacement is in creased un til the required pressure or power is reached and subseque ntly the displaceme nt or swept volume is decreased un til an equilibrium is reached.Screw pumpsScrew pu

20、mps (fixed displacement) are a double Archimedes screw , but closed. This means that two screws are used in one body. The pumps are used for high flows and relatively low pressure (max 100 bar). They were used on board ships where the constant pressure hydraulic system was going through the whole sh

21、ip, especially for the control of ball valves, but also for the steering gear and help drive systems. The adva ntage of the screw pumps is the low sound level of these pumps; the efficiency is not that high.Bent axis pumpsBent axis pumps, axial piston pumps and motors using the bent axis principle,

22、fixed or adjustable displacement, exists in two differe ntbasic desig ns. The Thoma-pri nciple(engin eer HansThoma, Germa ny, pate nt 1935) with max 25 degrees an gle and the Wahlmark-pri nciple(Gunnar Axel Wahlmark, pate nt 1960) withspherical-shaped pistons in one piece with the piston rod, piston

23、 rin gs, and maximum 40 degrees betwee n the driveshaft cen terl ine and pist ons (Volvo Hydraulics Co.). These have the best efficie ncy of all pumps. Although in general the largest displacements are approximately one litre per revolution, if necessary a two-liter swept volume pump can be built. O

24、ften variable-displacement pumps are used, so that the oil flow can be adjusted carefully. These pumps can in gen eral work with a work ing pressure of up to 350 420 bars in con ti nu ous work.Axial pist on pumps swashplate prin ciple(fixed andAxial piston pumps using the swashplate principle adjust

25、able displaceme nt) have a quality that is almost the same as the bent axis model. They have the advantage of being more compact in desig n. The pumps are easier and more econo mical to manufacture; the disadvantage is that they are more sensitive to oil con tam in ati on.Radial pist on pumpsRadial

26、piston pumps (fixed displacement) are used especially for high pressure and relatively small flows. Pressures of up to 650 bar are normal. In fact variable displacement is not possible, but sometimes the pump is desig ned in such a way that the plun gers can be switched off one by one, so that a sor

27、t of variable displaceme nt pump is obta ined.Peristaltic pumpsPeristaltic puiare not gen erally used for high pressures.Pumps for ope n and closed systemsMost pumps are working in open systems. The pump draws oil from a reservoir at atmospheric pressure . It is very important that there is no cavit

28、ation at the suction side of the pump. For this reas on the conn ecti on of the sucti on side of the pump is larger in diameter than the connection of the pressure side. In case of the use of multi-pump assemblies, the sucti on conn ecti on of the pump is ofte n comb in ed. It is preferred to have f

29、ree flow to the pump(pressure at inlet of pump at least 0.8 bars). The body of the pumpis often in open connection with the suction side of the pump.In case of a closed system, both sides of the pump can be at high pressure. The reservoir is often pressurized with 6-20 bars boost pressure. For close

30、d loop systems, no rmally axial pist on pumps are used. Because both sides are pressurized, the body of the pump n eeds a separate leakage conn ecti on.Multi pump assemblyIn a hydraulic in stallatio n, one pump can serve more cyli nders and motors. The problem however is that in that case a constant

31、 pressure system is required and the system always needs the full power. It is more economic to give each cylinder and motor its own pump. In that case multi pump assemblies can be used. Gearpumps can often be obtained as multi pumps. The different chambers (sometimes of differe nt size) are moun te

32、d in one body or built together. Also vane pumps can often be obtained as a multi pump. Gerotor pumps are often supplied as multi pumps. Screw pumps can be built together with a gear pump or a vane pump. Axial pist on swashplate pumps can be built together with a sec ond pump of the same or smaller

33、size, or can be built together with one or more gear pumps or vane pumps (depe nding on the supplier).Axial plunger pumps of the bent axis design can not be built together with other pumps.翻译液压机械及泵液压机械是机械和工具，它使用流体的力量去做的工作。重型设备是一种常见的 例子。在这种类型的机器，高压液-所谓的液压油-是整个传送机各种液压马达和液 压缸。流体是直接控制或自动通过控制阀，并通过软管和管分配。

34、液压机械的普及是由于应用非常的大量， 可以通过小管和软管转移，高功率密度 和广泛的执行机构，可以使这项技术广泛的使用。液压机械是由水力学，其中以液体为介质供电使用。气动，在另一边，是基于一 种气体作为动力传输，发电和控制媒介的使用。液压回路对于液压油做的工作，它必须对执行机构的马达，然后返回到一个水库。流体过 滤，然后再抽水。由液压油所采取的路径称为一个液压回路，其中有几种类型。开放中心电路用泵的供应源源不断。 流返回到油箱，通过控制阀的开放中心，也 就是说，当控制阀为中心，它提供了一个开放的返回路径坦克和流体是不是被泵 到高的压力。否则，如果控制阀的流体驱动它的路线和从驱动器和坦克。流体的压

35、力将上升，以应付任何反抗，因为该泵具有恒定的输出。如果压力上升过高， 流体返回舱通过泄压阀。液压泵液供应系统中的组成部分。发展中的系统压力与负载的反应。因此，5000 磅额定泵是维持对 5000磅潮流有一个约十倍以上的电动马达（体积比）的功 率密度更大的能力。它们均采用了电动马达或引擎，通过齿轮，皮带，弹性联轴 器或柔性连接以减少振动。液压泵的常用类型转换为液压机械应用；齿轮泵：便宜，耐用，操作简单。效率较低，因为他们是恒位移，主要用于低于20兆帕（3000磅）的压力下使用。叶片泵：便宜，简单，可靠（特别是在 G -转子的形式）。良好的高流量低压力输 出。轴向活塞泵：很多人用一个变量的机制设计

36、，来改变输出流量的压力自动控制。 有各种轴向活塞泵的设计，包括斜盘。最常见的是活塞泵斜盘：通常是用于一个 非常高的压力容器用在小流量泵。活塞泵比齿轮泵或叶片昂贵，但提供更长的运行在更高的生活压力，困难的液体 和更长的连续工作周期。活塞泵组成的一个静液压传动的一半。控制阀方向控制阀路由到所需的驱动器的液体。 它们通常由一个内部的铸铁或不锈钢外 壳阀芯。方向控制阀通常设计成可堆叠每一个阀液压缸和一个液体输入提供所有堆栈中 的阀门。阀芯位置可能由机械驱动的杠杆，液压试验压力或螺线管这推动阀芯左或右。主阀块通常是一堆现成的定向控制流量阀的容量和性能选择。有些阀门被设计成比例（流量成比例阀的位置），而其

37、他可能会在过简单。控制阀是液压回路的最 昂贵的和敏感的地区之一。泄压阀用于液压机械在几个地方；在回路保持刹车的压力，中试线等少量.对液压 缸，防止超载和液压管破裂。对液压水库，以维持一个小的正压力，排除水分和 污染。减压阀减少供应压力，对各种电路的需要。止回阀是单向阀，允许蓄电池充电和维持其压力后机关闭，例如。平衡阀的其实是一种液控单向阀的特殊类型。而单向阀打开或关闭，平衡阀的行为像一个飞行员控制流量控制位。液压泵类型编辑齿轮泵齿轮泵（带外齿）（固定位移）既简单又经济的泵。波及体积或液压齿轮泵的排 量将由约一立方厘米（0.001升）和二百立方厘米（0.2升）。这些泵创建通过齿 轮啮合，这迫使各地的齿轮流体加压出口侧的压力。一些齿轮泵可以很嘈杂，相对于其他类型，但现