液压系统及液压缸-外文翻译

1、实用文案标准液压传动第十讲制动器 力流体动力系统的优秀的特性之一是由电源产生，通过适当的控制和指导，并 通过电线传输，就可以轻松转换到几乎任何类型的机械运动所需要用到的地方。 使用一个合适的驱动装置，可以获得线性（直线）或者是旋转运动。驱动器是 一种转换流体动力机械力和运动的装置。缸、马达和涡轮机是最常见的将流体 动力系统应用于驱动设备的类型。这一章描述了各种类型的动作汽缸和他们的 应用程序、不同类型的流体汽车和使用流体动力系统的涡轮机。汽缸制动汽缸是一种将流体动力转换成线性或直线、力和运动的装置。因为线性运 动是沿着一条直线前后移动的往复运动。这种类型的制动器有时被称为一个往 复、或线性、电

2、动机。由ram或活塞组成的汽缸在一个圆柱孔内操作。制动汽 缸可以安装，以便汽缸被固定在一个固定的结构，ram或活塞被连接到该机制ram和活塞来操作，或者是活塞和ram可能被固定到固定结构，汽缸附加到机械装置来操 作。制动汽缸气动和液压系统的设计和操作是类似的。一些变化的 式制动汽缸的内容将在后面的段落中描述。冲压式缸术语ram和活塞通常可以互换使用。然而，一个冲压式缸通常被认为是一个截 面积活塞杆超过一半的截面积活动元件。在大多数这种类型的制动汽缸中，杆 和活动元件各占一半。这种类型的活动元件经常被称为柱塞。冲压式缸主要是 用来推动而不是拉。一些应用程序需要 ram的一部分在平坦的外部来推动或

3、升 降单位操作。其他应用程序需要一些机械装置的附件，如一个U型夹或有眼螺栓。冲压式缸的设计在很多其他方面不同，以满足不同应用程序的要求。单作用千斤顶单作用千斤顶（如图：10-1 ）试用力只在一个方向。流体定向的汽缸取代ram 和他外部的弹性元件，将物体举起放在上面。Fi|iiiV ID 1.riuiMhpcEliuih卑 ryliTiiki.当流体压力释放后，由于没有规定由流体动力缩回ram。物体的重量或者是一些机械设备，比如一个弹簧，迫使ram回到汽缸。这种流体能量就倒回到容器。 单作用冲压式汽缸通常用于液压千斤顶。用于移动飞机的飞行甲板和机库甲板 航空母舰的升降机也使用这种类型的汽缸。在这

4、些升降机中，汽缸是水平安装 的，通过一系列的电缆和捆运行升降机。流体压力产生ram的外在能量使升降机运行。当从ram中释放出流体压力，升降机的重量迫使 ram回到汽缸。反过 来，这迫使流体回容器。双作用千斤顶一个双作用冲压式缸如图10-2。在这个汽缸中，两个中风的ram都是由加压流 体产生的。它有两个流体端口，每一个都在或是接近汽缸的两端。针对流体压 力的封闭端缸扩展ram和应用力。撤销ram和减少力、流体是指向截然相反的 汽缸。一个四通换向阀是通常用于控制双作用ram。当阀门定位来扩展ram，加压流体进入端口 A，作用于ram的地面，加强ram的外部力量。 535 dUTCTLthDLqHU

5、 LIPHyud 10 i,- IXhiUt Kdng ram typcaLluiitmg (vliiHhT.对于在液压系统中的回流管，或者气动系统中的大气，通过控制阀门，高于ram 边缘的流体是免费流出端口 B的。通常情况下，流体的压力和ram的中风是相 同的。记得第二章中，力等于压力乘以面积（F=PA）。注意到不同的领域上的压力如图10-2所示。在扩展中风期间，在ram适用力的同时，对抗大的表面 积的压力是来自于ram的地下。在收缩行程的过程中，ram不需要很大的动力。 作用于ram顶面的小面积的压力为收回ram提供了必要的动力。伸缩式千斤顶图10-3显示了一个可伸缩的冲压式气缸。一系列的

6、ram是嵌在可伸缩的装配中。除了最小的ram,每一个ram都是中空的，作为下一个较小的ram的油缸壳。ram装配主要包括活塞部件，它还提供了流体端口。尽管这个装配需要一个小空间的ram收回,但是当ram扩展的时候，伸缩式行动的组装提供了一个相对长 的冲程。这种型号的汽缸的一个很好的例子是应用在自动倾卸卡车上。它是用 来解除前端的卡车床和转储负载。在吊运作业，最大的力量是所需的初始提升的 负载。Fl甘uii? lU 3.-T(?k5jplJiyJiAtn山igLylhiihT.FOHT ftA吐raiseRut I 一 _ 加 M HI9随着负载的提升并开始转储，所需的力量越来越少，直到负载是完

7、全抛弃。在提高 循环时，加压流体通过端口 A进入气缸，然后作用在ram的底部表面。Ram 1有一个更大的表面积，因此提供了更大的力的初始负载，正如Ram 1完成它的行程所需的力是减少的，当 Ram 2移动时，提供较小的力需要继续提高负载。当ram 2完成它的行程，一个更小的力量是必需的。是然后 Ram 3往外移动完成提高和倾销负载。一些可伸缩的冲压式的汽缸的单作用类型，像前面所讨论 的单作用千斤顶，这些可伸缩的冲压式汽缸通过重力或机械力收回。一些液压 千斤顶配备了可伸缩的ram。这样的千斤顶是用来提升车辆通过更小的间隙到达所需的高度。其他类型的可伸缩的汽缸，如图10-3所示，是双作用类型。在这

8、种类型中，流体压力用于扩展和收缩中风。一个四通换向阀是常用的控制操作 的双作用类型。注意在墙上的ram1和2的小通路。他们提供了一个路径流体 流向，在汽缸上面边缘的ram2和3之间。在附加行程中，返回流体通过那些 小通路和汽缸外面到达B端口。然后流经换向阀来返回线路或蓄水池。撤销ram，流体压力是通过B端口直接进入气缸的，然后反作用于三个ram的边缘的表面 区域。这迫使ram收回了位置。流离失所的流体从 ram的另一侧通过A端口流出汽缸，通过换向阀来返回线路或蓄水池。Fluid PowerNAVEDTRA 14105CHAPTER 10ACTUATORSOne of the outsta nd

9、ing features of fluid po wer systems is that force, gen erated by the po wer supply, con trolled and directed by suitable val uing, and transp orted by lin es, can be conv erted with ease to almost any kind of mecha ni cal moti on desired at the very p lace it is n eeded. Either lin ear (straight li

10、ne) or rotary moti on can be obta ined by using a suitable actuat ing device. An actuator is a device that conv erts fluid po wer into mecha ni cal force and moti on. Cyli nders, motors, and turb ines are the most com mon types of actuati ng devices used in fluid po wer systems. This cha pter descri

11、bes various types of actuat ing cyli nders and their app licati ons, differe nt types of fluid motors, and turb ines used in fluid po wer systems.CY LINDERSAn actuati ng cyli nder is a device that conv erts fluid po wer to lin ear, or straight line, force and motio n. Since lin ear moti on is a back

12、-a nd-forth moti on along a straight line, this type of actuator is sometimes referred to as a recip rocati ng, or lin ear, motor. The cyli nder con sists of a ram or p ist on op erati ng within a cyli ndrical bore.Actuati ng cyli nders may be in stalled so that the cyli nder is an chored to a stati

13、 onary structure and the ram or p ist on is attached to the mecha nism to be op erated, or the p ist on or ram may be an chored to the stati onary structure and the cyli nder attached to the mecha nism to be op erated. Actuat ing cyli nders for pn eumatic and hydraulic systems are similar in desig n

14、 and op erati on. Some of the variati ons of ram- and piston-type actuat ing cyli nders are described in the follow ing p aragra phs.RAM-T YPE CY LINDERSThe terms ram and piston are often used interchangeably. However, a ram-t ype cyli nder is usually con sidered one in which the cross-secti onal ar

15、ea of the p isto n rod is more tha n on e-half the cross-secti onal area of the movable eleme nt. In most actuati ng cyli nders of this type, the rod and the movable eleme nt have equal areas. This type of movable eleme nt is freque ntly referred to as a plun ger. The ram-ty pe actuator is used p ri

16、marily to push rather tha n to p ull. Some app licati ons require simply a flat surface on the exter nal part of the ram for p ush ing or lifting the un it to be op erated. Other app licati ons require some mecha ni cal means of attachme nt, such as a clevis or eyebolt. The desig n of ram-t ype cyli

17、 nders varies in many other resp ects to satisfy the requireme nts of differe nt app licati ons.Si ngle-Acti ng RamThe sin gle-act ing ram (fig. 10-1) app lies force in on ly one directi on. The fluid that is directed into the cyli nder dis places the ram and forces it outward, lift ing the object p

18、 laced on it.TVICWINDERfllhdSUP PLYFlgLre lOLSingh?-aft 11 rmn type artuaimo blinderSi nee there is no pro visi on for retracti ng the ram by fluid po wer, whe n fluid p ressure is released, either the weight of the object or some mecha ni cal means, such as a spring, forces the ram back into the cy

19、li nder. This forces the fluid back to the reservoir. The sin gle-act ing ram-t ype actuat ing cyli nder is ofte n used in the hydraulic jack. The elevators used to move aircraft to and from the flight deck and han gar deck on aircraft carriers also use cyli nders of this type. In these elevators, t

20、he cyli nders are in stalled horiz on tally and op erate the elevator through a series of cables and sheaves. Fluid p ressure forces the ram outward and lifts the elevator. Whe n fluid p ressure is released from the ram, the weight of the elevator forces the ram back in to the cyli nder. This, in tu

21、r n, forces the fluid back in to the reservoir. Double-Acti ng RamA double-act ing ram-t ype cyli nder is illustrated in figure 10-2. In this cyli nder, both strokes of the ram are p roduced by p ressurized fluid. There are two fluid p orts, one at or n ear each end of the cyli nder. Fluid un der p

22、ressure is directed to the closed end of the cyli nder to exte nd the ram and apply force. To retract the ram and reduce the force, fluidHU UHCKEtl meCTLlMDfH HflOflitnUMaiAMDi Winis directed to the opp osite end of the cyli nder. A four-way directi onal con trol valve is nor mally used to con trol

23、the double-act ing ram. Whe n the valve is po siti oned to exte nd the ram, pr essurized fluid en ters port A (fig. 10-2), acts on the bottom surface of the ram, and forces the ram outward.AErMfeCTlON-APT3ST fe IPDAT fluid 5LJPPU :FiLirv 1 ft ,=Dou1j1i Kling nLwhpciitwuilngolinMei.Fluid above the ra

24、m lip is free to flow out of port B, through the con trol valve, and to the return line in hydraulic systems or to the atmos phere in pn eumatic systems. Normally, the p ressure of the fluid is the same for either stroke of the ram. Recall from cha pter 2 that force is equal to p ressure times area

25、(F= P A). Notice the differe nee of the areas upon which the pr essure acts in figure 10-2. The pr essure acts aga inst the large surface area on the bottom of the ram duri ng the exte nsion stroke, duri ng which time the ram app lies force. Since the ram does not require a large force duri ng the r

26、etractio n stroke, p ressure act ing on the small area on the top surface of the ram lip pro vides the n ecessary force to retract the ram.Telesc oping RamsFigure 10-3 shows a telesc oping ram-t ype actuat ing cyli nder. A series of rams is n ested in the telesc oping assembly. With the exce pti on

27、of the smallest ram, each ram is hollow and serves as the cyli nder hous ing for the next smaller ram. The ram assembly is contained in the main cyli nder assembly, which also pro vides the fluid p orts. Although the assembly requires a small sp ace with all the rams retracted, the telesc oping acti

28、 on of the assembly pro vides a relatively long stroke whe n the rams are exte nded. An excelle nt exa mple of the app licati on of this type of cyli nder is in the dump truck. It is used to lift the forward end of the truck bed and dump the load. During the lift ing op erati on, the greatest force

29、is required for the in itial lifti ng of the load.HAISEIIlFiuiv 1IL3TMewpli里 runi lypi dLtudoQlltidrt,As the load is lifted and beg ins to dump, the required force becomes less and less un til the load is comp letely dump ed. Duri ng the raise cycle, p ressurized fluid en ters the cyli nder through

30、port A (fig. 10-3) and acts on the bottom surface of all three rams. Ram 1 has a larger surface area and, therefore, pro vides the greater force for the in itial load, As ram 1 reaches the end of its stroke and the required force is decreased, ram 2 moves, pro vid ing the smaller force n eeded to co

31、ntinue rais ing the load. Whe n ram 2 compi etes its stroke, a still smaller force is required. Ram 3 the n moves outward to fin ish rais ing and dumping the load. Some telesc oping ram-t ype cyli nders are of the sin gle-act ing type. Like the sin gle-act ing ram discussed prev iously, these telesc oping ram-t ype cyli nders are retracted by gravity or mecha ni cal force. Some hydraulic jacks are equipped with telesc oping rams. Such jacks are used to lift vehicles with low cleara nces to the requi