【正文】 液壓執(zhí)行器的背壓力系統(tǒng)類型 背壓力(MPa)簡單系統(tǒng)和和一般輕栽節(jié)流調(diào)速系統(tǒng) ?回油帶背壓閥 調(diào)整壓力一般為 回油路設(shè)流量調(diào)節(jié)閥的進給系統(tǒng)滿載工作時 設(shè)補油泵的閉式系統(tǒng) ?高壓系統(tǒng) 初算是可忽略不計 液壓執(zhí)行器主要結(jié)構(gòu)參數(shù)的計算Ⅰ工位夾緊缸主要結(jié)構(gòu)參數(shù)的確定本設(shè)計將Ⅰ工位夾緊缸的有桿腔作為主工作腔，則有公式： 121maxcPAF???（2－1）公式中 ——液壓缸無桿腔的有效面積 ；214AD????2 ——液壓缸有桿腔的有效面積 ；??2d?畢業(yè)設(shè)計（論文）5——液壓缸的最大負載力 ；maxF??N——液壓缸的機械效率（一般取 ）本設(shè)計取 ；? ——液壓缸工作腔壓力；1p ——系統(tǒng)的背壓，本設(shè)計取 。??則由上表查得 d=。 調(diào)速方案的分析和選擇調(diào)速方案對主機的性能起到?jīng)Q定性的作用。畢業(yè)設(shè)計（論文）9 容積調(diào)速是靠改變液壓泵或液壓馬達的排量來達到調(diào)速的目的。容積節(jié)流調(diào)速一般是用變量泵供油，用流量控制閥調(diào)節(jié)輸入或輸出液壓執(zhí)行元件的流量，并使其供油量與需油量相適應(yīng)。 調(diào)速回路一經(jīng)確定，回路的循環(huán)形式也就隨之確定了。容積調(diào)速大多采用閉式循環(huán)形式。 液壓動力源的分析與選擇液壓系統(tǒng)的工作介質(zhì)完全由液壓源來提供，液壓源的核心是液壓泵。對在工作循環(huán)各階段中系統(tǒng)所需油量相差較大的情況，一般采用多泵供油或變量泵供油。為防止系統(tǒng)中雜質(zhì)流回油箱，可在回油路上設(shè)置磁性過濾器或其他型式的過濾器。 3）合成系統(tǒng) 選定液壓基本回路之后，配以輔助性回路，如控制油路，潤滑油路、測壓油路等，可以組成一個完整的液壓系統(tǒng)。 液壓泵的確定液壓泵的最大工作壓力： = ＋ （4－1）p1maxp??其中 ——液壓執(zhí)行元件最大工作壓力；1maxp ——液壓泵出口大執(zhí)行元件入口之間所有的沿程壓力損失和局部壓力??損失之和?，F(xiàn)取泵的容積效率 ＝，當選用轉(zhuǎn)速 n＝1400 r/min 的驅(qū)動電機v?時，泵的流量為： ＝Vnpqv ＝12 mL/rev1400r/min 310? ＝14L/min由前面的計算可知泵的最大功率出現(xiàn)在Ⅱ工位夾緊階段，現(xiàn)取泵的總效率為 ＝，則： ＝p?pNpq? ＝???? ＝840W選用電動機型號：Y90S—4B5 型封閉式三相異步電動機滿足上述要求，其轉(zhuǎn)速為 1400r/min，額定功率為 。t 閥類的選擇 選擇依據(jù)選擇依據(jù)為：額定壓力，最大流量，動作方式，安裝固定方式，壓力損失數(shù)值，工作性能參數(shù)和工作壽命等。將數(shù)值代入公式（43）得Ⅰ工位夾緊液壓缸： ＝d無???? ＝畢業(yè)設(shè)計（論文）17 ＝d有???? ＝Ⅱ工位夾緊液壓缸：＝d無34106???????? ＝ ＝d有34106???? ＝根據(jù) JB827－ 66，同時考慮到制作方便， Ⅰ工位夾緊液壓缸兩根油管同時選用 101（外徑 10mm，壁厚 1mm）的 10 號冷拔無縫鋼管。其他油管，可直接按所連接的液壓元、輔件的接口尺寸決定其管徑的大小。油箱設(shè)計要點：1）油箱應(yīng)有足夠的容積以滿足散熱，同時其容積應(yīng)保證系統(tǒng)中油液全部流回油箱時不滲出，油液液面不應(yīng)超過油箱高度的 80%；2）吸箱管和回油管的間距應(yīng)盡量大，之間應(yīng)設(shè)置隔板，以加大液流循環(huán)的途徑，這樣能提高散熱、分離空氣及沉淀雜質(zhì)的效果。吸油管可安裝 100μm 左右的網(wǎng)式或線隙式過濾器，安裝位置要便于裝卸和清洗過濾器。本設(shè)計取 =6，將數(shù)值代如公式（45）得：? V＝614 ＝84 L畢業(yè)設(shè)計（論文）205 估算液壓系統(tǒng)性能 液壓系統(tǒng)壓力損失驗算由于系統(tǒng)的管路布置尚未具體確定，整個系統(tǒng)的壓力損失無法全面的計算，故只能先估算閥類元件的壓力損失，待設(shè)計好管路布置圖后，加上管路的沿程損失和局部損失即可。因為Ⅱ工位夾緊缸的運動過程是一樣的，使用對此油缸的壓力校驗過程和上面的計算過程是一樣的。為此，必須對系統(tǒng)進行發(fā)熱和溫升計算，以便對系統(tǒng)溫升進行控制。當只考慮油箱散熱時，其散熱量 可按下式計算：0H ＝KA 0H??（5－6）式中 K——散熱系數(shù)（ ） ，計算時可選用推薦值：通風(fēng)很差 K＝8；通/WmC?A風(fēng)良好 K＝14－20；風(fēng)扇冷卻時，K＝20－25；用循環(huán)水冷卻時，K＝110－175； A——油箱散熱面積； ——系統(tǒng)溫升。畢業(yè)設(shè)計（論文）246 結(jié)論在本次關(guān)于數(shù)控銑床兩工位夾緊裝置液壓系統(tǒng)的畢業(yè)設(shè)計中，我通過查閱現(xiàn)有資料，應(yīng)用液壓傳動的一般原理及液壓系統(tǒng)的設(shè)計原理，進行了液壓系統(tǒng)的功能原理設(shè)計、執(zhí)行元件的選擇、閥類元件的選型、集成塊設(shè)計、密封及液壓油的選擇等工作。在今后的工作學(xué)習(xí)中我會更加詳盡的學(xué)習(xí)，提高設(shè)計的科學(xué)性和效率。老師廣博的專業(yè)學(xué)識、嚴謹?shù)闹螌W(xué)態(tài)度以及執(zhí)著的事業(yè)追求使我受益匪淺，他嚴緊的科學(xué)作風(fēng)和實事求是的科學(xué)態(tài)度給我留下了深刻的印象。 Technological Literature Publishers, 1995.[18] Schneider R T. Don’t Fet to Congsider Accumulators. Hydraulics amp。de 101DK9220 Aalb. DenmarkEmail: mmuniet. auc. dkThe goal of the thesis described in this paper is to improve the control of mobile hydraulic cranes. The thesis is split into five parts: a requirements analysis, an analysis of the current systems and their problems, an analysis of different possibiilities for system topologies, development of a new control system for the near future based on electrohydraulic separate meter in / separate meter out valves, and finally an analysis of more advanced and plex solutions which can be applied in the more distant future. The work of the thesis will be done in cooperation with industry so the thesis will have more of an industrial focus than a purely theoretical focus.Key words: Mobile Hydraulic Cranes, Control strategies, Separate Meterin/Separate Meterout.1 INTRODUCTIONThe goal of the thesis described in this paper is to improve the control of mobile hydraulic cranes. A mobile hydraulic crane can be thought of as a large flexible mechanical structure which is moved by some sort of control system, The control system takes its input from a human operator and translates this mand into the motion of actuators which move the mechanical structure.The definition of this control system is purposely left vague in order not to impose any constraints on its design. The control system consists of actuators which move the mechanical structure, a means of controlling the actuators, a means of supplying power to the actuators, and a way of accepting inputs from the operator. It is this control system which is the target of this thesis. The goal is to analyze the requirments made on the control system and present guidelines for the gesign of new control systems.The thesis will be split into five parts:1. Analysis of the requirements of the control system, from the perspective of the operator, the mechanical system, efficiency, stability, and safety requirements.2. Analysis of current control systems and what their problems are.3. Analysis of the different options for the control system: different types of actuators different types of control strategies, and different ways of anizing ponents.4. Presentation of a new type of control system, which is mercially implementable. A system that will meet the needs of industry in the near 畢業(yè)設(shè)計（論文）28future.5. Analysis of more optimized systems, with higher performance, better efficiency, more flexible control, etc. This will be less mercially applicable but will be a starting point for more research.2 SECTIONS OF THE THESIS Requirements Analysis of the Control SystemBefore starting detailed work on developing new control systems, it is important to analyze what the exact demands are on the control system. The control system is influenced by many example: the mechanical structure it is controlling, the human operator, efficiency, stability, and industry requlations. Industry regulations are the first requirements that have to be addressed. Things like hose rupture protection and runaway load protection make a lot of demands on the control system. After regulations, stability is the next most important requiremen