外文翻譯--液壓傳動系統(tǒng)設(shè)計與計算

1、<p>　　畢業(yè)設(shè)計(論文)外文資料翻譯</p><p>　　系　　部： 機械工程系 </p><p>　　專 業(yè)： 機械工程及自動化 </p><p>　　姓 名： </p><p>　　學(xué)

2、 號： </p><p>　　外文出處：http://www.proesky.com/read-htm- tid-25296.html </p><p>　　附 件： 1.外文資料翻譯譯文；2.外文原文。 </p><p>　　注：請將該封面與附件裝訂成冊。</p&g

3、t;<p>　　附件1：外文資料翻譯譯文</p><p>　　液壓傳動系統(tǒng)設(shè)計與計算</p><p>　　1 明確設(shè)計要求進行工況分析</p><p>　　在設(shè)計液壓系統(tǒng)時，首先應(yīng)明確以下問題，并將其作為設(shè)計依據(jù)。</p><p>　　主機的用途、工藝過程、總體布局以及對液壓傳動裝置的位置和空間尺寸的要求；</p>

4、<p>　　主機對液壓系統(tǒng)的性能要求，如自動化程度、調(diào)速范圍、運動平穩(wěn)性、換向定位精度以及對系統(tǒng)的效率、溫升等的要求；液壓系統(tǒng)的工作環(huán)境，如溫度、濕度、振動沖擊以及是否有腐蝕性和易燃物質(zhì)存在等情況。</p><p>　　在上述工作的基礎(chǔ)上，應(yīng)對主機進行工況分析，工況分析包括運動分析和動力分析，對復(fù)雜的系統(tǒng)還需編制負載和動作循環(huán)圖，由此了解液壓缸或液壓馬達的負載和速度隨時間變化的規(guī)律，以下對工況分析的

5、內(nèi)容作具體介紹。</p><p><b>　　1.1 運動分析</b></p><p>　　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。</p><p>　　1.1.1 位移循環(huán)圖L—t</p><p>　　圖1.1為液壓機的液

6、壓缸位移循環(huán)圖，縱坐標(biāo)L表示活塞位移，橫坐標(biāo)t表示從活塞啟動到返回原位的時間，曲線斜率表示活塞移動速度。</p><p>　　圖1.1 位移循環(huán)圖</p><p>　　1.1.2 速度循環(huán)圖v—t(或v—L) </p><p>　　工程中液壓缸的運動特點可歸納為三種類型。圖1.2為三種類型液壓缸的v—t圖，第一種如圖1.2中實線所示，液壓缸開始作勻加速運動，然后勻速

7、運動， </p><p>　　圖1.2 速度循環(huán)圖</p><p>　　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。v—t圖的三條速度曲線，不僅清楚地表明了三種類型液壓缸的運動規(guī)律，也間接地表明了三種工況的動力特性。</p>&l

8、t;p><b>　　1.2 動力分析</b></p><p>　　動力分析，是研究機器在工作過程中，其執(zhí)行機構(gòu)的受力情況，對液壓系統(tǒng)而言，就是研究液壓缸或液壓馬達的負載情況。</p><p>　　1.2.1 液壓缸的負載及負載循環(huán)圖</p><p>　?。?） 液壓缸的負載力計算工作機構(gòu)作直線往復(fù)運動時，液壓缸必須克服的負載由六部分

9、組成：</p><p><b>　　(1.1)</b></p><p>　　式中：Fc為切削阻力；Ff為摩擦阻力；Fi為慣性阻力；Fg為重力；Fm為密封阻力；Fb為排油阻力。</p><p>　?。?） 液壓缸運動循環(huán)各階段的總負載力</p><p>　　液壓缸運動循環(huán)各階段的總負載力計算，一般包括啟動加速、快進、工進、

10、快退、減速制動等幾個階段，每個階段的總負載力是有區(qū)別的。 </p><p>　　(a) 啟動加速階段：這時液壓缸或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(dǎo)軌的摩擦力、密封裝置的摩擦力(按缸的機械效率=0.9計算)、重力和慣性力等項，即：</p><p><b>　　(1.2)</b></p><p>　　(b) 快速階段：

11、 </p><p>　　 　(1.3)</p><p>　　(c) 工進階段： </p><p><b>　　(1.4) </b></p><p>　　(d) 減速： 　　　　　　　　　　　　　　　　　　　　　　

12、　　　　　　　　　　　</p><p><b>　　(1.5)</b></p><p>　　對簡單液壓系統(tǒng)，上述計算過程可簡化。例如采用單定量泵供油，只需計算工進階段的總負載力，若簡單系統(tǒng)采用限壓式變量泵或雙聯(lián)泵供油，則只需計算快速階段和工進階段的總負載力。</p><p>　　1.2.2 液壓馬達的負載</p><p&g

13、t;　　工作機構(gòu)作旋轉(zhuǎn)運動時，液壓馬達必須克服的外負載為：</p><p>　　 　　　 (1.6)</p><p>　　(1) 工作負載力矩Me</p><p>　　工作負載力矩可能是定值，也可能隨時間變化，應(yīng)根據(jù)機器工作條件進行具體分析。</p><p>　　(2) 摩擦力矩Mf</p><

14、;p>　　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：</p><p><b>　　(1.7)</b></p><p>　　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)。</p><p>　　(3) 慣性力矩Mi</p><p>　　慣性力矩Mi

15、為旋轉(zhuǎn)部件加速或減速時產(chǎn)生的慣性力矩，其計算公式為： </p><p><b>　　(1.8) </b></p><p>　　式中：ε為角加速度(r/s2)；Δω為角速度的變化(r/s)；Δt為加速或減速時間(s)；J為旋轉(zhuǎn)部件的轉(zhuǎn)動慣量()，。</p><p>　　式中：為回轉(zhuǎn)部件的飛輪效應(yīng)()。</p><p>　　

16、各種回轉(zhuǎn)體的可查《機械設(shè)計手冊》。</p><p>　　根據(jù)式(1.6)，分別算出液壓馬達在一個工作循環(huán)內(nèi)各階段的負載大小，便可繪制液壓馬達的負載循環(huán)圖。</p><p>　　2 確定液壓系統(tǒng)主要參數(shù)</p><p>　　2.1 液壓缸的設(shè)計計算</p><p>　　2.1.1 初定液壓缸工作壓力 </p><p&

17、gt;　　液壓缸工作壓力主要根據(jù)運動循環(huán)各階段中的最大總負載力來確定，此外，還需要考慮以下因素：</p><p>　?。?） 各類設(shè)備的不同特點和使用場合</p><p>　?。?） 考慮經(jīng)濟和重量因素，壓力選得低，則元件尺寸大，重量重；壓力選得高一些，則元件尺寸小，重量輕，但對元件的制造精度，密封性能要求高。所以，液壓缸的工作壓力的選擇有兩種方式：一是根據(jù)機械類型選；二是根據(jù)切削負載選。

18、</p><p>　　如表2.1、表2.2所示。</p><p>　　表2.1 按負載選執(zhí)行文件的工作壓力</p><p>　　表2.2 按機械類型選執(zhí)行文件的工作壓力</p><p>　　2.2 液壓馬達的設(shè)計計算</p><p>　　2.2.1 計算液壓馬達排量 </p><p>

19、　　液壓馬達排量根據(jù)下式?jīng)Q定：</p><p><b>　　(2.1)</b></p><p>　　式中：T為液壓馬達的負載力矩(N·m)；為液壓馬達進出口壓力差()；為液壓馬達的機械效率，一般齒輪和柱塞馬達取0.9～0.95，葉片馬達取0.8～0.9。</p><p>　　2.2.2 計算液壓馬達所需流量液壓馬達的最大流量<

20、/p><p><b>　　(2.2)</b></p><p>　　式中：Vm為液壓馬達排量(m3/r)；nmax為液壓馬達的最高轉(zhuǎn)速(r/s)。</p><p>　　3 液壓元件的選擇</p><p>　　3.1 液壓泵的確定與所需功率的計算</p><p>　　3.1.1 液壓泵的確定<

21、/p><p>　　確定液壓泵的最大工作壓力。液壓泵所需工作壓力的確定，主要根據(jù)液壓缸在工作循環(huán)各階段所需最大壓力p1，再加上油泵的出油口到缸進油口處總的壓力損失ΣΔp，即</p><p>　　 (3.1) </p><p>　　包括油液流經(jīng)流量閥和其他元件的局部壓力損失、管路沿程損失等，在系統(tǒng)管路未設(shè)計之前

22、，可根據(jù)同類系統(tǒng)經(jīng)驗估計，一般管路簡單的節(jié)流閥調(diào)速系統(tǒng)為(2～5)×105Pa，用調(diào)速閥及管路復(fù)雜的系統(tǒng)為(5～15)×105Pa，也可只考慮流經(jīng)各控制閥的壓力損失，而將管路系統(tǒng)的沿程損失忽略不計，各閥的額定壓力損失可從液壓元件手冊或產(chǎn)品樣本中查找，也可參照表1.3選取。</p><p>　　表3.1 常用中、低壓各類閥的壓力損失(Δpn)</p><p>　　3.1.

23、2 確定液壓泵的流量qB</p><p>　　泵的流量qB根據(jù)執(zhí)行元件動作循環(huán)所需最大流量qmax和系統(tǒng)的泄漏確定。</p><p>　?。?） 多液壓缸同時動作時，液壓泵的流量要大于同時動作的幾個液壓缸(或馬達)所需的最大流量，并應(yīng)考慮系統(tǒng)的泄漏和液壓泵磨損后容積效率的下降，即</p><p><b>　　(3.2)</b></p&

24、gt;<p>　　式中：K為系統(tǒng)泄漏系數(shù)，一般取1.1～1.3，大流量取小值，小流量取大值；為同時動作的液壓缸(或馬達)的最大總流量(m3/s)。</p><p>　?。?） 選擇液壓泵的規(guī)格：根據(jù)上面所計算的最大壓力pB和流量qB，查液壓元件產(chǎn)品樣本，選擇與pB和qB相當(dāng)?shù)囊簤罕玫囊?guī)格型號。</p><p>　　表3.2 液壓泵的總效率</p><p&g

25、t;　　按上述功率和泵的轉(zhuǎn)速，可以從產(chǎn)品樣本中選取標(biāo)準(zhǔn)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)。</p><p>　　3.2 閥類元件的選擇</p><p>　　3.2.1 選擇依據(jù)</p><p>　　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。</p><p>

26、;　　3.2.2 選擇閥類元件應(yīng)注意的問題</p><p>　?。?） 應(yīng)盡量選用標(biāo)準(zhǔn)定型產(chǎn)品，除非不得已時才自行設(shè)計專用件。</p><p>　　（2） 閥類元件的規(guī)格主要根據(jù)流經(jīng)該閥油液的最大壓力和最大流量選取。選擇溢流閥時，應(yīng)按液壓泵的最大流量選??；選擇節(jié)流閥和調(diào)速閥時，應(yīng)考慮其最小穩(wěn)定流量滿足機器低速性能的要求。</p><p>　　3.3 蓄能器的選擇

27、</p><p>　?。?） 蓄能器用于補充液壓泵供油不足時，其有效容積為：</p><p><b>　　(3.3)</b></p><p>　　式中：A為液壓缸有效面積(m2)；L為液壓缸行程(m)；K為液壓缸損失系數(shù)，估算時可取Ｋ＝1.2；qB為液壓泵供油流量(m3/s)；t為動作時間(s)。</p><p>　　（

28、2） 蓄能器作應(yīng)急能源時，其有效容積為：</p><p><b>　　(3.4)</b></p><p>　　當(dāng)蓄能器用于吸收脈動緩和液壓沖擊時，應(yīng)將其作為系統(tǒng)中的一個環(huán)節(jié)與其關(guān)聯(lián)部分一起綜合考慮其有效容積。</p><p>　　根據(jù)求出的有效容積并考慮其他要求，即可選擇蓄能器的形式。</p><p>　　3.4 管道

29、的選擇</p><p>　　3.4.1 油管類型的選擇</p><p>　　液壓系統(tǒng)中使用的油管分硬管和軟管，選擇的油管應(yīng)有足夠的通流截面和承壓能力，同時，應(yīng)盡量縮短管路，避免急轉(zhuǎn)彎和截面突變。</p><p>　?。?） 鋼管：中高壓系統(tǒng)選用無縫鋼管，低壓系統(tǒng)選用焊接鋼管，鋼管價格低，性能好，使用廣泛。</p><p>　?。?） 銅管：

30、紫銅管工作壓力在6.5～10MPa以下，易變曲，便于裝配；黃銅管承受壓力較高，達25MPa，不如紫銅管易彎曲。銅管價格高，抗震能力弱，易使油液氧化，應(yīng)盡量少用，只用于液壓裝置配接不方便的部位。</p><p>　　3.4.2 油管尺寸的確定</p><p>　?。?） 油管內(nèi)徑d按下式計算：</p><p>　　d=

31、 (3.5)</p><p>　　式中：q為通過油管的最大流量(m3/s)；v為管道內(nèi)允許的流速(m/s)。一般吸油管取0.5～5(m/s)；壓力油管取2.5～5(m/s)；回油管取1.5～2(m/s)。</p><p>　?。?） 油管壁厚δ按下式計算：</p><p><b>　　(3.6)</b></

32、p><p>　　式中：p為管內(nèi)最大工作壓力；n為安全系數(shù)，鋼管p＜7MPa時，取n=8；p＜17.5MPa時，取n=6；p＞17.5MPa時，取n=4。</p><p>　　根據(jù)計算出的油管內(nèi)徑和壁厚，查手冊選取標(biāo)準(zhǔn)規(guī)格油管。</p><p>　　3.5 油箱的設(shè)計</p><p>　　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

33、體。</p><p>　　3.5.1 油箱設(shè)計要點</p><p>　?。?） 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%。</p><p>　　（2） 吸箱管和回油管的間距應(yīng)盡量大。</p><p>　?。?） 油箱底部應(yīng)有適當(dāng)斜度，泄油口置于最低處，以便排油。<

34、/p><p>　　3.6 濾油器的選擇</p><p>　　選擇濾油器的依據(jù)有以下幾點：</p><p><b>　?。?） 承載能力：</b></p><p>　　按系統(tǒng)管路工作壓力確定。</p><p><b>　?。?） 過濾精度：</b></p><

35、p>　　按被保護元件的精度要求確定。</p><p><b>　?。?） 通流能力：</b></p><p>　　按通過最大流量確定。</p><p><b>　　（4） 阻力壓降：</b></p><p>　　應(yīng)滿足過濾材料強度與系數(shù)要求。</p><p>　　4

36、液壓系統(tǒng)性能的驗算</p><p>　　為了判斷液壓系統(tǒng)的設(shè)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。</p><p>　　4.1 管路系統(tǒng)壓力損失的驗算</p><p>　　當(dāng)液壓元件規(guī)格型號和管道尺寸確定之后，就可以較準(zhǔn)確的計算系統(tǒng)的壓力損失，壓力損失包括：油液流經(jīng)管道的沿程壓力損失、局部壓力損失和流經(jīng)閥類元件的壓力損失，即：&

37、lt;/p><p><b>　　(4.1)</b></p><p><b>　　系統(tǒng)的調(diào)整壓力：</b></p><p>　　(4.2) </p><p>　　式中：P0為液壓泵的工作壓力或支路的調(diào)整壓力；P1為執(zhí)行件的工作壓力。</p><p&

38、gt;　　如果計算出來的比在初選系統(tǒng)工作壓力時粗略選定的壓力損失大得多，應(yīng)該重新調(diào)整有關(guān)元件、輔件的規(guī)格，重新確定管道尺寸。</p><p>　　4.2 系統(tǒng)發(fā)熱溫升的驗算</p><p>　　系統(tǒng)發(fā)熱來源于系統(tǒng)內(nèi)部的能量損失，如液壓泵和執(zhí)行元件的功率損失、溢流閥的溢流損失、液壓閥及管道的壓力損失等。</p><p>　　系統(tǒng)發(fā)熱功率P的計算:</p>

39、<p><b>　　(4.3)</b></p><p>　　式中：PB為液壓泵的輸入功率(W)；η為液壓泵的總效率。</p><p>　　若一個工作循環(huán)中有幾個工序，則可根據(jù)各個工序的發(fā)熱量，求出系統(tǒng)單位時間的平均發(fā)熱量：</p><p><b>　　(4.4)</b></p><p>

40、;　　式中：T為工作循環(huán)周期(s)；ti為第i個工序的工作時間(s)；pi為循環(huán)中第i個工序的輸入功率(W)。</p><p>　　4.3 系統(tǒng)效率驗算</p><p>　　液壓系統(tǒng)的效率是由液壓泵、執(zhí)行元件和液壓回路效率來確定的。</p><p>　　液壓回路效率nc一般可用下式計算：</p><p><b>　　(4.5)&l

41、t;/b></p><p>　　式中：p1，q1；p2，q2；……為每個執(zhí)行元件的工作壓力和流量；pB1，qB1；pB2，qB2為每個液壓泵的供油壓力和流量。</p><p><b>　　液壓系統(tǒng)總效率：</b></p><p><b>　　(4.6)</b></p><p>　　式中：為液壓

42、泵總效率；為執(zhí)行元件總效率；為回路效率。</p><p>　　5 繪制正式工作圖和編寫技術(shù)文件</p><p>　　經(jīng)過對液壓系統(tǒng)性能的驗算和必要的修改之后，便可繪制正式工作圖，它包括繪制液壓系統(tǒng)原理圖、系統(tǒng)管路裝配圖和各種非標(biāo)準(zhǔn)元件設(shè)計圖。</p><p>　　正式液壓系統(tǒng)原理圖上要標(biāo)明各液壓元件的型號規(guī)格。對于自動化程度較高的機床，還應(yīng)包括運動部件的運動循環(huán)圖

43、和電磁鐵、壓力繼電器的工作狀態(tài)。</p><p>　　5.1 確定液壓系統(tǒng)參數(shù)</p><p>　　由工況分析中可知，工進階段的負載力最大，所以，液壓缸的工作壓力按此負載力計算，根據(jù)液壓缸與負載的關(guān)系，選p1=40×105Pa。本機床為鉆孔組合機床，為防止鉆通時發(fā)生前沖現(xiàn)象，液壓缸回油腔應(yīng)有背壓，設(shè)背壓p2=6×105Pa，為使快進快退速度相等，選用差動油缸，假定快進

44、、快退的回油壓力損失為Δp=7×105Pa。</p><p>　　5.2 選擇液壓元件</p><p>　?。?） 確定液壓泵的工作壓力。</p><p>　　前面已確定液壓缸的最大工作壓力為40×105Pa，選取進油管路壓力損失Δp=8×105Pa，其調(diào)整壓力一般比系統(tǒng)最大工作壓力大5×105Pa，所以泵的工作壓力PB＝(

45、40＋8＋5)×105＝53×105Pa</p><p>　　這是高壓小流量泵的工作壓力。</p><p>　　液壓缸快退時的工作壓力比快進時大，取其壓力損失Δp′＝4×105Pa，則快退時泵的工作壓力為： </p><p>　　PB=(16.4＋4)×105＝20.4×10

46、5Pa</p><p>　　這是低壓大流量泵的工作壓力。</p><p>　?。?） 液壓泵的流量?？爝M時的流量最大，其值為30L/min，最小流量在工進時，其值為0.51L/min，取K＝1.2，</p><p>　　則： qB＝1.2×0.5×10-3=36L/min</p><p&g

47、t;　　由于溢流閥穩(wěn)定工作時的最小溢流量為3L/min，故小泵流量取3.6L/min。</p><p>　　根據(jù)以上計算，選用YYB-AA36/6B型雙聯(lián)葉片泵。</p><p>　?。?） 確定管道尺寸:根據(jù)工作壓力和流量，按式(3.5)、式(3.6)確定管道內(nèi)徑和壁厚。(從略)</p><p>　?。?） 確定油箱容量油箱容量可按經(jīng)驗公式估算，取V＝(5～7)q

48、。</p><p>　　本例中：V＝6q＝6(6＋36)＝252L有關(guān)系統(tǒng)的性能驗算從略。附件2：外文原文（復(fù)印件）</p><p>　　Hydraulic actuation system design and computation</p><p>　　1 Is clear about the design request to carry on the op

49、erating mode analysis.</p><p>　　When design hydraulic system below, first should be clear about the question, and takes it as the design basis.</p><p>　　Main engine use, technological process, o

50、verall layout as well as to hydraulic gear position and spatial size request; The main engine to the hydraulic system performance requirement, like the automaticity, the velocity modulation scope, the movement stability,

51、 the commutation pointing accuracy as well as the request which to the system efficiency, warm promotes; Hydraulic system working conditions, like temperature, humidity, vibration impact as well as whether has situation

52、and so on corrosive</p><p>　　In in the above work foundation, should carry on the operating mode analysis to the main engine, the operating mode analysis including the movement analysis and the mechanical an

53、alysis, also must establish the load and the operating cycle chart to the complex system, from this understood the hydraulic cylinder or the oil motor load and the speed change as necessary the rule, below makes the conc

54、rete introduction to the operating mode analysis content</p><p>　　1.1 movements analyses</p><p>　　The main engine functional element according to the technological requirement movement situatio

55、n, may use the displacement circulation chart (L—t), the speed circulation chart (v—t), or the speed and the displacement circulation chart indicated, from this carries on the analysis to the movement rule.</p>&l

56、t;p>　　1.1.1 displacements circulation attempts L—t</p><p>　　The chart 1.1 is the hydraulic press hydraulic cylinder moves the circulation chart, the y-coordinate L expression piston moves, the x-coordina

57、te t expression starts from the piston to the reposition time, the rate of curve expression movement of plunger speed.</p><p>　　Chart 1.1 displacements circulation chart</p><p>　　1.1.2 speeds c

58、irculation chart v—t (or v—L)</p><p>　　In the project the hydraulic cylinder movement characteristic may induce is three kind of types. The chart 1.2 is three kind of types hydraulic cylinders v —t chart, th

59、e first kind of like chart 1.2 center solid lines show, the hydraulic cylinder starts to make the uniform accelerated motion, then uniform motion,</p><p>　　Chart 1.2 speeds circulation chart</p><p

60、>　　Finally uniform retarded motion to end point; The second kind, the hydraulic cylinder preceding partly makes the uniform accelerated motion in the overall travelling schedule, in another one partly makes the unifor

61、m retarded motion, also the acceleration value is equal; The third kind, the hydraulic cylinder one most above makes the uniform accelerated motion in the overall travelling schedule by a smaller acceleration, then unifo

62、rm decelerates to the travelling schedule end point. V—t chart thr</p><p>　　1.2 mechanical analyses</p><p>　　1.2.1 hydraulic cylinders loads and duty cycle chart</p><p>　　(1) hydr

63、aulic cylinders load strength computations</p><p>　　When the operating mechanism makes the straight reciprocating motion, the hydraulic cylinder must overcome the load is composed by six parts</p><

64、;p><b>　　(1.1)</b></p><p>　　In the formula: Fc In order to resistance to cutting; Ff In order to friction drag; Fi For inertia resistance; Fg For gravity; Fm In order to seal the resistance; Fb

65、 In order to drain the oil the resistance.</p><p>　　(2 ) hydraulic cylinders cycle of motion various stages overall load strength</p><p>　　The hydraulic cylinder cycle of motion various stages o

66、verall load strength computation, 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

67、has the difference.</p><p>　　(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 streng

68、th including guide rail friction force, packing assembly friction force (according to cylinder mechanical efficiency ηm=0.9 computation), gravity and so on item, namely:</p><p><b>　　(1.2)</b><

69、/p><p>　　(b) fast stage:</p><p>　　 (1.3)</p><p>　　(c) the labor enters the stage:</p><p>　?。?.4） (d) decelerates:</p><p>&l

70、t;b>　　(1.5)</b></p><p>　　To the simple hydraulic system, the above computation process may simplify. For example uses the single proportioning pump to supply the oil, only must calculate the labor t

71、o 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 lab

72、or enters the stage the overall load strength.</p><p>　　1.2.2 oil motors load</p><p>　　When the operating mechanism makes the rotary motion, the oil motor must overcome the outside load is:<

73、/p><p><b>　　(1.6)</b></p><p>　　(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

74、 on the concrete analysis according to the machine working condition.</p><p>　　(2) friction moments. In order to revolve the part journal place friction moment, its formula is:</p><p><b>　

75、　(1.7)</b></p><p>　　In the formula: G is revolves the part weight (N); F is the rubbing factor, when the start for the factor, after the start for moves the rubbing factor; R is the journal radius (m).

76、</p><p>　　(3) moment of inertiaMi. The moment of inertia which in order to revolve the part acceleration or decelerates when produces, its formula is:</p><p><b>　　(1.8) </b></p>

77、;<p>　　In the formula: ε Is the angle acceleration (r/s2);is the acceleration or decelerates the time (s); J is revolves the part rotation inertia (),</p><p>　　In the formula: In order to rotate the p

78、art the flywheel effect ().</p><p>　　Each kind may look up <Machine design Handbook></p><p>　　According to the type (1.6), separately figures out the oil motor in a operating cycle various

79、 stages load size, then may draw up the oil motor the duty cycle chart</p><p>　　2 determinations hydraulic system main parameter</p><p>　　2.1 hydraulic cylinders design calculations</p>

80、<p>　　2.1.1 initially decides the hydraulic cylinder working pressure</p><p>　　In the hydraulic cylinder working pressure main basis cycle of motion various stages biggest overall load strength determi

81、ned, in addition below, but also needs to consider the factor:</p><p>　　(1) each kind of equipment different characteristic and use situation.</p><p>　　(2) considerations economies and the weigh

82、t factor, the pressure elects lowly, then part size big, the weight is heavy; The pressure chooses high somewhat, then part size small, the weight is light, but to the part manufacture precision, the sealing property req

83、uests high.</p><p>　　Therefore, the hydraulic cylinder working pressure choice has two ways: One, elects according to the mechanical type; Two, according to cuts the load to elect.</p><p>　　If t

84、he table 2.1, the table 2.2 shows.</p><p>　　The table 2.1 presses the load to choose the execution file the working pressure</p><p>　　The table 2.2 presses the mechanical type to choose the ex

85、ecution file the working pressure</p><p>　　2.2 oil motors design calculation</p><p>　　2.2.1 computations oil motor displacement</p><p>　　Under oil motor displacement according to

86、the type decided that,</p><p><b>　　(2.1)</b></p><p>　　In the formula: T is the oil motor load moment of force (N·m); For oil motor import and export pressure difference (n/m3);i

87、s the oil motor mechanical efficiency, the common gear and the plunger motor takes 0.9 ~ 0.95, the leaf blade motor takes 0.8 ~ 0.9.</p><p>　　2.2.2 computations oil motor needs the current capacity oil moto

88、r the maximum current capacity</p><p><b>　　(2.2)</b></p><p>　　In the formula: is the oil motor displacement (m3/r); is the oil motor highest rotational speed (r/s).</p><p&

89、gt;　　3 hydraulic pressure parts choice</p><p>　　3.1 hydraulic pumps determinations with need the power the computation</p><p>　　(1) determines the hydraulic pump the biggest working pressure.

90、The hydraulic pressure pumping station must the working pressure determination, mainly acts according to the hydraulic cylinder in the operating cycle various stages to have most tremendous pressure p1, in addition the o

91、il pump loses Sigma Delta p the oil mouth to the cylinder place always pressureΣΔp, namely</p><p>　　 (3.1) </p><p>　　loses, the pipeline including the oil after the flo

92、w valve and other parts local pressures along the regulation loss and so on, before system pipeline design, may act according to the similar system experience to estimate, common pipeline simple throttle valve velocity m

93、odulation system ΣΔp is (2 ~ 5) ×105Pa, with the velocity modulation valve and pipeline complex system is (5 ~ 15) ×105Pa, also may only consider flows after various control valves pressure loss, but ignores

94、the circuitry along</p><p>　　The table 3.1 is commonly used, the low pressure each kind of valve pressure loses (Δpn)</p><p>　　3.1.2 determines the hydraulic pump current capacityqB</p>

95、<p>　　Pumps the current capacity basis functional element operating cycle must the maximum current capacity and the system divulges the determination</p><p>　　(1) At the same time when more than hydrau

96、lic cylinders movement, the hydraulic pump current capacity must be bigger than the maximum current capacity which at the same time the movement several hydraulic cylinders (or motor) needs, and should consider the syste

97、m divulging wears the volumetric efficiency drop after the hydraulic pump, namely</p><p><b>　　(3.2)</b></p><p>　　In the formula: K is the system leakage coefficient, generally takes

98、1.1 ~ 1.3, the great current capacity takes the small value, the small current capacity takes the great value; For at the same time movement hydraulic cylinder (or motor) is biggest (m3/s).</p><p>　　(2) choo

99、ses the hydraulic pump the specification </p><p>　　Table 3.2 hydraulic pumps overall effectiveness indices</p><p>　　Rotational speed and pumps which according to the above power, may select the

100、standard electric motor from the product sample, again carries on, causes when the electric motor sends out the maximum work rate, in permission scope.</p><p>　　3.2 valves class parts choice</p><

101、;p>　　3.2.1 choices bases</p><p>　　The choice basis is: Rated pressure, maximum current capacity, movement way, installment fixed way, pressure loss value, operating performance parameter and working life

102、 and so on.</p><p>　　3.2.2 selector valves class parts should pay attention question</p><p>　　(1) should select the standard stereotypia product as far as possible, only if does not have alread

103、y time only then independently designs special-purp</p><p>　　(2) valves class parts specification main basis class after this valve fat liquor most tremendous pressure and maximum current capacity selection.

104、 When chooses the overflow valve, should according to the hydraulic pump maximum current capacity selection; When chooses the throttle valve and the velocity modulation valve, should consider its minimum stable current c

105、apacity satisfies the machine low-speed performance the request</p><p>　　3.3 accumulators choices</p><p>　　3.3.1 accumulators use in to supplement when the hydraulic pump supplies the oil insu

106、fficiency, its dischargeable capacity is</p><p><b>　　(3.3)</b></p><p>　　In the formula: A is the hydraulic cylinder active surface (m2); L is the hydraulic cylinder travelling schedu

107、le (m); K is the hydraulic cylinder loss coefficient, when the estimate may take K = 1.2; Supplies the oil current capacity for the hydraulic pump (m3/s); T is the operating time (s).</p><p>　　3.3.2 accumul

108、ators make the emergency energy, its dischargeable capacity is:</p><p><b>　　(3.4)</b></p><p>　　When the accumulator uses in absorbs the pulsation to relax the hydraulic pressure impa

109、ct, should take it as in the system a link if to be connected partially together synthesizes considers its dischargeable capaci</p><p>　　According to the dischargeable capacity which extracts and considered

110、other requests, then chooses the accumulator the form</p><p>　　3.4 pipelines choices</p><p>　　3.4.1 drill tubings types choice</p><p>　　In the hydraulic system uses the drill tubi

111、ng 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 extre