【正文】 r i working procedure operating time (s)。 V speed of flow which permits for the pipeline in (m/s). The mon oil suction pipe takes ~ 5 (m/s)。 nmaxis the oil motor highest rotational speed (r/s). 3 hydraulic pressure parts choice hydraulic pumps determinations with need the power the putation (1) determines the hydraulic pump the biggest working pressure. 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 oil pump loses Sigma Delta p the oil mouth to the cylinder place always pressureΣΔp, namely ???? PPPB 1 () ??P loses, the pipeline including the oil after the flow 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, mon pipeline simple throttle valve velocity modulation system ΣΔp is (2 ~ 5) 105Pa, with the velocity modulation valve and pipeline plex system ??P is (5 ~ 15) 105Pa, ??P also may only consider flows after various control valves pressure loss, but ignores the circuitry along the regulation loss, various valves rated pressure loses may searches from the hydraulic pressure part handbook or the product sample, Also may refer to the table selections The table is monly used, the low pressure each kind of valve pressure loses (Δpn) Valve Δpn (105Pa) Valve Δpn (105Pa) Valve Δpn (105Pa) Valve Δpn (105Pa) Coneway valve ～ Coneway valve 3～ 8 Coneway valve ～ 2 Coneway valve ～ 2 Cross valve ～ 3 Cross valve 2～ 3 Cross valve ～ 3 Cross valve 3～ 5 determines the hydraulic pump current capacityqB Pumps the current capacity qBbasis functional element operating cycle must the maximum current capacity qmaxand the system divulges the determination (1) At the same time when more than hydraulic 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 system divulging wears the volumetric efficiency drop after the hydraulic pump, namely )()( 3m a x smqKq B ?? () In the formula: K is the system leakage coefficient, generally takes ~ , the great current capacity takes the small value, the small current capacity takes the great value ? )max( q。 R is the journal radius (m). (3) moment of inertiaMi. The moment of inertia which in order to revolve the part acceleration or decelerates when produces, its formula is: )( MNtJMi ??? ? () In the formula: ε Is the angle acceleration (r/s2)。 The second kind, the hydraulic cylinder preceding partly makes the uniform accelerated motion in the overall travelling schedule, in another one partly makes the uniform retarded motion, also the acceleration value is equal?？爝M時的流量最大，其值為 30L/min，最小流量在工進時，其值為 ，取 K＝ ， 則： qB＝ 103=36L/min 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 。 正式液壓系統(tǒng)原理圖上要標明各液壓元件的型號規(guī)格。 如果計算出來的 P? 比在初選系統(tǒng)工作壓力時粗略選定的壓力損失大得多， 應該重新調(diào)整有關元件、輔件的規(guī)格，重新確定管道尺寸。 （ 2） 吸箱管和回油管的間距應盡量大。 （ 2） 銅管：紫銅管工作壓力在 ～ 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。 選擇閥類元件應注意的問題 （ 1） 應盡量選用標準定型 產(chǎn)品，除非不得已時才自行設計專用件。 m)； mP? 為液壓馬達進出口壓力差 (3mN)； min?為液壓馬達的機械效率，一般齒輪和柱塞馬達取 ～ ，葉片馬達取 ～ 。 (3) 慣性力矩 Mi 慣性力 矩 Mi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： )( MNtJM i ??? ? () 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 ( 2mKg? )， 。 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。 簽名： 注： 請將該封面與附件裝訂成冊。 在上述工作的基礎上，應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，以下對工況分析的內(nèi)容作具體介紹。 （ 2） 液壓缸運動循環(huán)各階段的總負載力 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、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。 根據(jù)式 ()，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 。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ΣΔ p，即 ???? PPPB 1 () ??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)管路未設計之前，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) ??P為 (2～ 5) 105Pa，用調(diào)速閥及管路復雜的系統(tǒng) ??P 為 (5～ 15) 105Pa， ??P 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 選取。 蓄能器的選擇 （ 1） 蓄能器用于補充液壓泵供油不足時，其有效容積為： )( 3mtqKLAV Bii ?? ? () 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?。耍?； qB為液壓泵供 油流量 (m3/s)； t為動作時間 (s)。一般吸油管取 ～ 5(m/s)；壓力油管取 ～ 5(m/s)；回油管取 ～ 2(m/s)。 （ 2） 過濾精度： 按被保護元件的精度要求確定。 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： )()1(1 1 WtPTP ini bi ??? ?? () 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)。本機床為鉆孔組合機床，為防止鉆通時發(fā)生前沖現(xiàn)象，液壓缸回油腔應有背壓，設背壓 p2=6 105Pa，為使快進快退速度相等，選用 21 2AA? 差動油缸，假定快進、快退的回油壓力損失為Δp=7 105Pa。 (從略 ) （ 4） 確定油箱容量油箱容量可按經(jīng)驗公式估算，取 V＝ (5～ 7)q。 Fi For inertia resistance。 The pressure chooses high somewhat, then part size small, the weight is light, but to the part manufacture precision, the sealing property requests high. Therefore, the hydraulic cylinder working pressure choice has two ways: One, elects according to the mechanical type。 L is the hydraulic cylinder travelling schedule (m)。 When n is the safety coefficient, steel pipe p 7MPa, takes n=8。 m? In order to functional element overall effectiveness index。 η Is the hydraulic pump overall effectiveness index If in a operating cycle has several working procedures, then may act according to each working procedure the calorific capacity, extracts the system unit time the average calorific capacity: )()1(1 1 WtPTP ini bi ??? ?? （ ）