EQ1050NJ20D3高空作业车的机构设计-液压系统含CAD图.zip
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EQ1050NJ20D3
高空作业
机构
设计
液压
系统
CAD
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EQ1050NJ20D3高空作业车的机构设计-液压系统含CAD图.zip,EQ1050NJ20D3,高空作业,机构,设计,液压,系统,CAD
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附录外文文献原文：The commonly used sources of power in hydraulic systems are pumps and accumulators .Similarly,accumulator connected to atmosphere will dischange oil at atmosphere pressure until it empty. only when connected to a system having resistance to flow can pressure be developed.Three types of pumps find use in fluid-power systems:rotary,reciprocating or piston-type, and 3,centrifugal pumps.Simple hydraulic system may use but one type of pump . The trend is to use pumps with the most satisfactory characteristics for the specific tasks involved . In matching the characteristics of the pump to the requirements of the hydraulic system , it is not unusual to find two types of pumps in series . For example , a centrifugal pump may be to supercharge a reciprocating pump , or a rotary pump may be used to supply pressurized oil for the contronls associated with a reversing variabledisplacement pumps . Most power systems require positive displacement pumps . At high pressure , reciprocating pumps are often preferred to rotary pumps .1、Rotary pumpsThese are built in many differnt designs and extremely popular in modern fluid power system . The most common rotay-pump designs used today are spurgear , internal gear ,generated rotor , sliding vane ,and screew pumps . Ehch type has advantages that make it most suitable for a given application .2、Gear pumpsGear pumps are the simplest type of fixed displacement hydraulic pump available . This type consists of two external gear , generally spur gear , within a closed-fitting housing . One of the gear is driven directly by the pump drive shaft . It ,in turn , then drives the second gear . Some designs utilize helical gears ,but the spur gear design predominates . Gear pumps operate on a very simple principle . As the gear teeth unmesh , the volume at the inlet port A expands , a partial vacuum on the suction side of the pump will be formed . Fluid from an external reservoir or tank is forced by atmospheric pressure into the pumpinlet . The continuous action of the fluid being carried from the inlet to the discharge side one of the pump forces the fluid into the system .3、Vane pumpsThe vane pump consists of a housing that is eccentric or offset with respect to the drive shaft axis . In some models this inside surface consists of a cam ring that can be rotated to shift the relationship between rotor are rectangular and extend radially from a center radius to the outside diameter of the rotor and from end to end . A rectangular vane that is essentially the same size as the slot is inserted in the slot and is free to slide in and out .As the rotor turns , the vanes thrust outward , and the vane tips track the inner surface of the housing , riding on a thin film of fluid . Two port or end plates that engage the end face of the ring provide axial retention .Centrifugal force generally contributes to outward thrust of the vane . As they ride along the eccentric housing surface , the vane move in and out of the rotor slots . The vane divide the area between the rotor and casing into a series of chambers .The sides of each chamber are formed by two adjacent vanes ,the port or end plates , the pump casing and the rotor . These chambers change in change in volume depending on their respective position about the shaft .As each chamber approaches the inlet port , its vanes move outward and its volume expands , causing fluid to flow into the expanded chamber . Fluid is then carried within the chamber around to the dischange port . As the chamber approaches the discharge port , its vanes are pushed inward ,the volume is reduced , and the fluid is forced out the discharge port .Vane pump speed is limited by vane peripheral speed . High peripheral speed will cause cavitation in suction cavity . which results in pump damage and reduced flow .An imbalance of the vanes can cause the oil film between the vane tips and the cam ring to break down , resulting in metal-to-metal contact and subsequent increased wear and slipage . One metheod applied to eliminate high vane thrust loading is a dual-vane construction .4、Piston-type pumpAll piston pumps operate by allowing oil to flow into a pumping cavity as a piston retreats and then forcing the oil out into another chamber as the piston advances . Design differences among pumps lie primarily in the methods of separating inlet from outlet oil .5、In-line piston pumpThe siplest typeof axial piston pump is the swash plate in-line design .The cylinder are connected though piston shoes and a retracting ring , so that the shoes beat anainst an angled swash plate . As the block turns ,the piston shoes follow the swash plate ,causing the piston to reciprocate . The ports are arranged in the valve plate so that the pistons pass the inlet port as they are being pulled out and pass the outlet port as they are being forcing back in .The angle of the swash plate controls the delibery . Where the swash plate is fixed , the pump is of the constant-displacement type . In the variable-displacement , inline piston pump , the swash plate is moumted on a pivoted yoke . As the swash plate angle is increased , the cylinder stroke is increase , resulting in a greater flow . A pressure compensator control can position the yoke automatically to maintain a constant output pressure .6、BENT-axis piston pumpAs the shaft roates , distance between any one piston and the valving surface changes continually . Each piston moves away from the valving surface during one half of the revolution and toward the valving surface during the other half . The inlet chamber is in line as the pistons move away , and the outletr chamber is in line as the pistons move closer , thus drawing liquiring in during one half of the inlet chamber as the pistons are moving away from the pintle . Thereforce , during rotation , pistons draw liquid into the cylinder bores as they pass the inlet side of the pinntle and force that liquid out of the bores as they pass the outlet side of the pintle . The displacement of this pump varies with the offset angle , the maximum angle being 30 degree ,the minimum zero . Fixed displacement models are usually avaiable with 23 degree angle .In the variable displacement construction a yoke with an external control is used to change the angle . With some contronls , the yoke can be moved over center to reverse the direction of flow from the pump .7、Pump/system interactionPressure-compensated variavle delivery pumps do not require a relief valve in the high pressure line . The pressure compensation feature eliminates the need for the relief valve . In nearly all working systems ,however , at least one is used on just-in-case basis . The use of a pressure compensator , while avoiding dependence on a relief valve , brings on its own problems . The actuator -spring-spool arrangement in the compensator is a dynamic , damped-mass-spring arrangement . However , when the system calls for a chang in axhievetheir maxmum volume as they reach the inlet port , the maximum volume of fluid will ve moved . If the relationship between housing and rotor is changed such that the chambers achieve their minimum of zero volume as they reach the inlet port , the pump delivery will be reduced to zero .Vane pump speed is limited by vane peripheral speed . High peripheral speed will cause cavitation in suction cavity , which results in pump damage and reduced flow . An imbalance of the vanes can cause the oil film between the cane tips and the cam ring to break down , resulting in metal-to-metal contact and subsequent increased wear and slipage . One method applied to eliminate high vane thrust loading is a dual-vane construction . In the dual-vane construction , tow independent vanes are located in each totor slot chmbered edges along the sides and top of each vane from a channel that essentially balances the hydraulic pressure on the top and bottom of each pair of vanes .Centrifugal force cause the vane to follow the contour of the cam-shaped ring .There is just sufficient seal between the vanes and ring without destroying the thin oil film .45外文文献中文翻译：常用的液压系统的动力源是泵和蓄能器。一般情况下，一个蓄能器在正常的大气压力下，连续的向各系统中压入液压油， 直至将所储存的能量全部用完为止。 只有当其连接的系统中，具有抗流压力时才能够得到补充。在液压系统和液力系统中，常使用液压泵有回转式、往复式、活塞式或者离心式三种类型：简单液压系统一般使用的都是第一类液压泵。目前的发展趋势是针对具体的工作任务和工况，选用最佳的液压泵类型。在符合特性和要求的液压泵中，找到两种不同类型的液压泵式很常见的。 例如，离心泵，往复泵都可以可对系统增压，旋转泵和变量液压泵联合使用也可以提供高压的液压油。大部分动力系统还需要采取容积式液压泵泵。而在较高的体统压力下，往复泵往往要优于回转泵。1、回转泵这些形式的液压泵因为具有许多不同的设计形式而极受欢迎，在现代流体动力系统。 最常见的旋转泵的设计形式，包括内部使用齿轮的、内部使用转子的、内部采用滑动叶片的和使用螺杆的。 其中，每一种类型都有其独特的优点，都有其最适合的一定的应用场合。2、齿轮泵齿轮泵是可以提供的最简单的一种液压泵。这一类型的液压泵一般包括两个外啮合的齿轮，一般是圆柱直齿轮，安装在一个密封的壳体里面。 其中一个齿轮由液压泵的传动轴直接驱动， 第一个齿轮然后再推动第二轮。还有一些设计中利用螺旋齿轮， 但是一般以齿轮设计为主。 齿轮泵的动作的原理非常简单，如插图 7.3 所示。 由于在齿轮的轮齿在脱开啮合时，进气道扩大， 液压泵将会形成局部真空的具有吸力的空腔。 流体在系统的压力下被从外部油箱或罐体中压入， 连续运动的液压油在液压泵的作用下，从真空的吸力空腔中被送入排出液压油的一侧B 侧。3、叶片泵叶片泵一般是由一个相通的腔体，是偏心或抵消对传动轴轴线。在一些模型内的表面设有一个凸轮环，一个可旋转移动的长方形的转子，转子的径向延长，从一个中心，半径为外径的转子，到末端结束。 上面是尺寸大小相同的插槽，矩形叶片一般插入到插槽中，并且可以自如的滑入和滑出。当转子转动时，叶片被向外甩出， 而叶片尖端则贴紧其运动轨道空腔的内表面， 处于液压油的薄膜的上面。 两个油口或端板，向环形的端面提供轴向的存储。通常离心有助于叶片的向外推出。当叶片处于偏心空腔的表面上时，叶片从转子的缝隙中甩出和甩。 叶片将套管和转子之间的区域分成一系列的小空腔。每一个小空腔都是由两个相邻叶片，油口或者端盘，液压泵壳体和转子形成。 这些空腔的容积的变化取决于他们相对于轴的相对位置。当每个厅内靠近进内气孔的时候，其叶片向外移动，其空腔的容积膨胀， 造成液压油流入扩大空腔。 流体随后被带入围绕着排油孔的空腔内。当这些空腔靠近排油孔时，叶片被甩入腔内，空腔的容积减小，液压油随即被压出排油孔。叶片泵的速度一般要受到叶片圆周速度的限制。过高的圆周速度将导致空腔内出现负压，从而导致液压泵损坏和流量减小。一个不平衡的叶片将会引起叶片顶端和凸轮环之间的油膜的破坏，从而进一步导致金属和金属之间的直接接触，因而增加了磨损和叶片泵的动力传动损耗 。消除这种叶片泵的叶片的高推力负荷的方法之一就是采用双叶片结构。4、活塞式泵所有的活塞式液压泵的运行原理，都是通过液压油流入泵腔而推动活塞向后面移动，然后活塞再向前移动，从而将液压油排出，使得液压油进入泵的另一个腔室中。不同的泵的设计差异泵主要在于活塞进入和推出从而将液压油分离的方法。5、直轴式柱塞泵最简单的轴向柱塞泵是将冲板进行线性化设计。气缸与活塞的回缩盘之间相连，
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