【正文】 （ 2）裝配因素： 液壓元件在裝配中應(yīng)杜絕野蠻操作，如果過度用力將使零件產(chǎn)生變形，特別是用銅棒等敲打缸體、密封法蘭等；裝配前應(yīng)對零件進(jìn)行仔細(xì)檢查，裝配時應(yīng)將零件蘸少許液壓油，輕輕壓入，清洗時應(yīng)用柴油，特別是密封圈、防塵圈、 O 形圈等橡膠元件，如果用汽油則使其易老化失去原有彈性，從而失去密封機(jī)能。 一、泄漏的分類： 工程機(jī)械液壓系統(tǒng)的泄漏主要有兩種，固定密封處泄漏和運動密封處泄漏，固定密封處泄漏的部位主要包括缸底、各管接頭的連接處等，運動密封處主要包括油缸活塞桿 部位、多路閥閥桿等部位。液體比氣體具有更人的粘性．這會岡為內(nèi)摩擦而引起更人的壓力和功率損失：另外．由于液壓系統(tǒng)使用的液體要與大氣隔絕，故它們需要特殊的油箱和無泄漏系統(tǒng)設(shè)計。壓縮機(jī)一般有活塞式、葉片式和螺旋式等類型。岡為轉(zhuǎn)向部件是全液壓的，沒有萬向節(jié)、軸承、減速齒輪等機(jī)械連接，這使得系統(tǒng)簡單緊湊。液壓動力之所以成為自動化的重要組成部分，是岡為它有如下主要的四種優(yōu)點： 1．控制方便精確通過操作一個簡單的操縱桿和按鈕，液壓系統(tǒng)的操作者便能立即起動、停 止、加減速和能提供任意功率、位置精度為萬分之一英寸的位置控制力。其次，在工作原理上，所有的代的閥口大小，閥進(jìn)間的壓差以及通過閥的流量之 設(shè)計巴巴工作室 間的關(guān)系都是符合孔口流量的公式。聯(lián)接件：聯(lián)接各個系統(tǒng)部件，為壓力流體提供功率傳輸通路，將液體返回油箱 (貯油器 )。 例如液壓系統(tǒng)在長距離上比機(jī)械系統(tǒng)更能經(jīng)濟(jì)地傳遞動力。automatic． protection against overloads， and infinitely variable speed contr01． Fluid power systems also have the highest horsepower per weight rati0 of any known power source． In spite of al 1 these highly desirable features of fluid power， it is not a panacea for all power transmission problems． work revolves as the table moves along the ways, a helical or spiral cut is produced。 設(shè)計巴巴工作室 設(shè)計巴巴工作室 Hydraulic System There are only three basic methods of transmitting power： Electrical，mechanical． and fluid power． Most applications actually use a bination of the three methods to obtain the most efficient overall system． To properly determine which principle method to use。 as shown in millingcutters, helical gears, twist drills and similar worm are produced in this way. The milling of such items requires a particular relationship between the motions of the dividing head and associated gear train, to control the distance the worm will travel while making one plete revolution. Before the helix can be machined the lead and angle of helix are twist drills and similar worm are produced in this way. The milling of such items requires a particular relationship between the motions of the dividing head and associated gear train, to control the distance the worm will travel while making one plete revolution. Hydraulic oil s are messy． and leakage is impossible to pletely eliminate． Also， most hydraulic oil s Carl cause fires if an oil 1eak occur in an area of hot equipment． Pneumatic System Pneumatic systems use pressurized gases to transmit and control power． As the name implies， pneumatic systems typically use air(rather than some other gas)as the fluid medium because air is a safe， low cost， and readily available fluid． It is particularly safe in environment s where an e1 electrical spark could ignite leaks from system ponent s． Worm wheel are similar to bevel gears and are generally used to connect skew shafts transmitting high velocity rations. The worm wheel give line contact between mating teeth unlike a point contact in the case of bevel gears. This improves the load carrying capacity of the gear train. In pneumatic systems pressors are used to press and supply the necessary quantities of air． Compressors are typically of the piston， vane or Screw type． Basically a pressor． Increase the pressure of a gas by reducing its v01ume as described by the perfect gas 1aws． 設(shè)計巴巴工作室 In connecting shafts belonging to separate devices(such as an electrical motor and gearbox) precise aligning of the shafts is diffcult and a flexible coupling is used. This coupling connects the shafts is such a way as to minimize the harmful effects of shaft misalignment. Flexible couplings also permit the shafts to defect under their separate systems of loads and to move freely in the axial direction without interfering with one another. Flexible couplings can also serve to reduce the intensity of shock load and vibrations transmitted from one shaft to another. Pneumatic systems normally use a large centralized air pressor which is considered to be an infinite。然而液壓系統(tǒng)與電氣系相比，傳遞動力的距離較短。閥：控制泵產(chǎn)生流體的運動方向、產(chǎn)生的功率的大小，以及到達(dá)執(zhí)行部件液體的流量。 只是各種閥控制的參數(shù)各不相同而已。 圖 13 一 l是一個使飛機(jī)駕駛員升起和落下起落架的液壓系統(tǒng)，當(dāng)飛行員向某方向移動控制閥，壓力油流人液壓缸的某一腔從而降下起落架。 另外，只需輸入很小的扭矩就能產(chǎn)生滿足極惡劣工作條件所需的控制力．這對操作空間限制而需要小方向盤的場合很重要，這也是減輕司機(jī)疲勞度所必需的。壓縮機(jī)基本上是根據(jù)理想氣體法則，通過減小氣體體積來增加氣體壓力的。氣 設(shè)計巴巴工作室 壓系統(tǒng)使用可以直接排到周圍環(huán)境中的空氣，一般來說氣壓系統(tǒng)沒有液體系統(tǒng)昂貴。從油液的泄漏上也可分為外泄漏和內(nèi)泄漏，外泄漏主要是指液壓油從系統(tǒng)泄漏到環(huán)境中，內(nèi)泄漏是指由于高低壓側(cè)的壓力差的存在以及密封件失效等原因，使液壓油在系統(tǒng)內(nèi)部由高壓側(cè)流向低壓側(cè)。 （三）油液污染及零部件的損傷 （ 1）氣體污染 在大氣壓下，液壓油中可溶解 10％左右的空氣，