【正文】 活塞處于由靜止到啟動并加速到一定速度，其總負載力包括導軌的摩擦力、密封裝置的摩擦力(按缸的機械效率=)、重力和慣性力等項，即： ()(b) 快速階段：  　()(c) 工進階段：  　() (d) 減速： 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 ()對簡單液壓系統(tǒng)，上述計算過程可簡化。 運動分析主機的執(zhí)行元件按工藝要求的運動情況，可以用位移循環(huán)圖(L—t)，速度循環(huán)圖(v—t)，或速度與位移循環(huán)圖表示，由此對運動規(guī)律進行分析。 指導教師評語：此翻譯文章較詳細地介紹了液壓傳動系統(tǒng)的設計與計算，闡述了從工況分析入手，確定液壓系統(tǒng)主要參數(shù)和如何選擇液壓元件，并對液壓系統(tǒng)的性能進行了示范驗算，翻譯用詞基本準確，文筆也較為通順，具備一定的英語閱讀能力?！猼圖，液壓缸開始作勻加速運動，然后勻速運動， 速度循環(huán)圖最后勻減速運動到終點；第二種，液壓缸在總行程的前一半作勻加速運動，在另一半作勻減速運動，且加速度的數(shù)值相等；第三種，液壓缸在總行程的一大半以上以較小的加速度作勻加速運動，然后勻減速至行程終點。(2) 摩擦力矩Mf摩擦力矩Mf為旋轉(zhuǎn)部件軸頸處的摩擦力矩，其計算公式為： ()式中：G為旋轉(zhuǎn)部件的重量(N)；f為摩擦因數(shù)，啟動時為靜摩擦因數(shù)，啟動后為動摩擦因數(shù)；R為軸頸半徑(m)。 按負載選執(zhí)行文件的工作壓力負載/N＜5000500～1000010000～2000020000～3000030000～50000＞50000工作壓力/MPa≤～1～2～33～44～5＞5 按機械類型選執(zhí)行文件的工作壓力機械類型機 床農(nóng)業(yè)機械工程機械磨床組合機床龍門刨床拉床工作壓力/MPaa≤23～5≤88～1010～1620～32 液壓馬達的設計計算 計算液壓馬達排量 液壓馬達排量根據(jù)下式?jīng)Q定： 　　　 ()式中：T為液壓馬達的負載力矩(N 液壓泵的總效率液壓泵類型齒輪泵螺桿泵葉片泵柱塞泵總效率～～～～ 按上述功率和泵的轉(zhuǎn)速，可以從產(chǎn)品樣本中選取標準電動機，再進行驗算，使電動機發(fā)出最大功率時，其超載量在允許范圍內(nèi)。 管道的選擇 油管類型的選擇液壓系統(tǒng)中使用的油管分硬管和軟管，選擇的油管應有足夠的通流截面和承壓能力，同時，應盡量縮短管路，避免急轉(zhuǎn)彎和截面突變。 油箱的設計油箱的作用是儲油，散發(fā)油的熱量，沉淀油中雜質(zhì)，逸出油中的氣體。4 液壓系統(tǒng)性能的驗算為了判斷液壓系統(tǒng)的設計質(zhì)量，需要對系統(tǒng)的壓力損失、發(fā)熱溫升、效率和系統(tǒng)的動態(tài)特性等進行驗算。液壓系統(tǒng)總效率： ()式中：為液壓泵總效率；為執(zhí)行元件總效率；為回路效率。液壓缸快退時的工作壓力比快進時大，取其壓力損失Δp′＝4105Pa，則快退時泵的工作壓力為： PB=(＋4)105＝105Pa這是低壓大流量泵的工作壓力。 The main engine to the hydraulic system performance requirement, like the automaticity, the velocity modulation scope, the movement stability, the mutation pointing accuracy as well as the request which to the system efficiency, warm promotes。 Fb In order to drain the oil the resistance.(2 ) hydraulic cylinders cycle of motion various stages overall load strengthThe hydraulic cylinder cycle of motion various stages overall load strength putation, generally includes the start acceleration, quickly enters, the labor enters, quickly draws back, decelerates applies the brake and so on several stages, each stage overall load strength has the difference.(a) starts the acceleration period: By now the hydraulic cylinder or the piston were in from static enough to starts and accelerates to the certain speed, its overall load strength including guide rail friction force, packing assembly friction force (according to cylinder mechanical efficiency ηm= putation), gravity and so on item, namely: 　　　　()(b) fast stage: ()(c) the labor enters the stage: 　　　　　　　　?。ǎ? (d) decelerates: ()To the simple hydraulic system, the above putation process may simplify. For example uses the single proportioning pump to supply the oil, only must calculate the labor to enter the stage the overall load strength, if the simple system uses the limiting pressure type variable displacement pump or a pair of association pumps for the oil, then only must calculate the fast stage and the labor enters the stage the overall load strength. oil motors loadWhen the operating mechanism makes the rotary motion, the oil motor must overe the outside load is: ()(1) operating duties moment of force Me. The operating duty moment of force is possibly a definite value, also possibly as necessary changes, should carry on the concrete analysis according to the machine working condition.(2) friction moments. In order to revolve the part journal place friction moment, its formula is: 　　　 　 ()In the formula: G is revolves the part weight (N)。 For oil motor import and export pressure difference (n/m3)。 T is the operating time (s). accumulators make the emergency energy, its dischargeable capacity is: ()When the accumulator uses in absorbs the pulsation to relax the hydraulic pressure impact, should take it as in the system a link if to be connected partially together synthesizes considers its dischargeable capaciAccording to the dischargeable capacity which extracts and considered other requests, then chooses the accumulator the form pipelines choices drill tubings types choiceIn the hydraulic system uses the drill tubing divides the hard tube and the hose, the choice drill tubing should have enough passes flows the section and the bearing pressure ability, simultaneously, should reduce the pipeline as far as possible, avoids the extreme turn and the section sudden change.(1) steel pipes: Center the high tension system selects the seamless steel pipe, the low pressure system selects the welded steel pipe, the steel pipe price lowly, performance good, the use is widespread(2) copper pipes: The copper tube working pressure below ~ 10MPa, the instable tune, is advantageous for the assembly。 P1In order to execution working pressure.If calculates in the primary election system working pressure time the is sketchier than designation pressure to lose is much bigger than, should remove entire related part, auxiliary specification, again definite pipeline size. systems give off heat The system gives off heat originates from the system interior energy loss, like the hydraulic pump and the functional element power loss, the overflow valve overflow loses, the hydraulic valve and the pipeline pressure loss and so on.The system gives off heat the power P putation ()In the formula: PB is the hydraulic pump power input