液壓與氣壓傳動外文翻譯-預覽頁

　

【正文】 olled actuator velocities with pneumatic systems. Also, precise positioning control is not obtainable. While pneumatics pressures are quite low due to pressor design limitations(less than 250 psi), hydraulic pressures can be as high as 10000 psi. Thus, hydraulics can be highpower systems, whereas pneumatics are confined to lowpower applications. Industrial applications of pneumatics systems are growing at a rapid pace. Typical examples include stamping, drilling, hoist, punching, clamping, assembling, riveting, materials handling, and logic controlling operations. 翻譯： 流體和液壓系統 水力的歷史由來已久，始于人類為利用它周圍的能源而做出的努力。 (2) high torque at low speed in required。 that is, its constituent particles may continuously change their positions relative to one another. Moreover, it offers no lasting resistance to the displacement, however great, of one layer over another. This means that, if the fluid is at rest, no shear force (that is a force tangential to the surface on which it acts) can exist in it. Fluid may be classified as Newtonian or nonNewtonian. In Newtonian fluid there is a linear relation between the magnitude of applied shear stresses and the resulting rate of angular deformation. In non— Newtonian fluid there is a nonlinear relation between the magnitude of applied shear stress and the rate of angular deformation. The flow of fluids may be classified in many ways, such as steady or non steady, rotational or irrotational, pressible or inpressible, and viscous or no viscous. All hydraulic systems depend on Pascal’s law, such as steady or pipeexerts equal force on all of the surfaces of the container. In actual hydraulic systems, Pascal’s law defines the basis of results which are obtained from the system. Thus, a pump moves the liquid in the system. The intake of the pump is connected to a liquid source, usually called the tank or reservoir. Atmospheric pressure, pressing on the liquid in the reservoir, forces the liquid into the pump. When the pump operates, it forces liquid from the tank into the discharge pipe at a suitable pressure. The flow of the pressurized liquid discharged by the pump is controlled by valves. Three control functions are used in most hydraulic systems: (1) control of the liquid pressure, （ 2） control of the liquid flow rate, and (3) control of the direction of flow of the liquid. Hydraulic drives are used in preference to mechanical systems when(1) powers is to be transmitted between point too far apart for chains or belts。(5) easy control of speed and direction is necessary。從 15 世紀早期，水車圖畫就出現在大宮殿的 馬賽克上。 流體是可以流動的物體，與就是說，構成物質的粒子可以連續地改變它們之間的相對位置，而且，它提供流體層間流動非連續的阻力。在非牛頓流體中，流體層間作用的剪切力和角度變形總量的大小成非線性關系。 在實際液壓系統中，帕斯卡定律是解釋從系統中獲得的各種結果的基礎。 由油泵泵出的壓縮液體通過各種閥門來控制。通過閥門控制油的流動，壓力油流產生線性的或旋轉的機械運動。在任一時間里的油流量可以通過調節閥門或采用變量泵來改變。其中一個是液壓驅動在廣泛的范圍內提供無限變化的速度。除了運行平穩外，還發現了許多改進，如工件表面光潔度的改善，在不損壞刀具的前提下能加大刀具的負荷，并能在刃磨刀具的情況下工作更長時間。例如液壓系統在長距離上比機械系統更能經濟地傳遞動力。功率大小取決于對流量和壓力大小的控制。 油液儲存和調節裝置：用來確保提供足夠質量和數量并冷卻的液體。例如，一個電磁體的性能受到鋼的磁炮和極限的限制，相反，液壓系統的功率僅僅受材料強度的限制。 3. 恒力或橫扭矩 只有液壓系統能提供不到速度變化而變化的恒力或橫扭矩，它可以驅動對象從每小時移動幾英寸到每分鐘幾百英寸，從每小時幾轉到每分鐘幾千轉。因為轉向部件是全液壓的，沒有萬向節、軸承、減速齒輪等機械連接，這使得系統簡單緊湊。液壓系統也有些缺點，液壓油又污染，比且泄流不可能完全避免，另外如果油液 滲漏發生在灼熱設備附近，大多數液壓油能引起火災。壓縮機基本上是根據理想氣體法則，通過減小氣體體積來增加氣體壓力的。 由于來自大氣的空氣含有不同數量的水分，這些水分是有害的，它可以帶走潤滑劑引起過 分磨損和腐蝕，因此，在一些試用場合中，要用空氣干燥器來除去這些有害的水分。氣壓系統使用可以直接排到周圍環境中的空氣，一般來說氣壓系統沒有液體