CAT液壓內(nèi)部培訓(xùn)教程

1、objectives 目標(biāo)目標(biāo) understand 當(dāng)功能在使用時(shí)當(dāng)功能在使用時(shí),將油缸壓力發(fā)送到泵控制將油缸壓力發(fā)送到泵控制. the pump control adjusts swashplate angle to maintain a pressure drop from pump to pressure signal. 泵控制調(diào)整斜盤(pán)角度來(lái)維持泵到壓力信號(hào)的壓力的下降。泵控制調(diào)整斜盤(pán)角度來(lái)維持泵到壓力信號(hào)的壓力的下降。 this means that when the function is in use margin pressure is held constant across

2、 the pump to cylinder area. 這就意味著當(dāng)功能在使用時(shí)這就意味著當(dāng)功能在使用時(shí),邊緣壓力在泵到油缸區(qū)保持為常量邊緣壓力在泵到油缸區(qū)保持為常量 pump controls load sensing 泵控制泵控制 負(fù)載敏感的負(fù)載敏感的 load sensing control 載荷敏感控制載荷敏感控制 面積面積area = apcre 面積面積area = apche 面積面積area = actre 面積面積area = acthe pressure 壓力壓力 delta pressure delta 壓力壓力 flow 流量流量 command to achieve

3、flow 完成流動(dòng)命令完成流動(dòng)命令 if op cmd = 0 p = p tank 油箱 if op cmd is non zero p = p cylinder 油缸 pressure 壓力壓力 pressure from working function 來(lái)自工作功能的壓力來(lái)自工作功能的壓力 operator command 駕駛員命令駕駛員命令 - physical locations of controls load sensing control and high pressure cut off on the pump signal network in the implemen

4、t valve signal line sends signal from valve to pump return to tank signal to pump case drain suction tank implement valve pump load sensing control high pressure cut off cylinder cylinder lines pump to valve vickers load sensing compensator and pressure limiter sample system return to tank signal to

5、 pump case drain suction tank implement valve pump load sensing control high pressure cut off cylinder cylinder lines pump to valve in the next several slides we will examine a single circuit in neutral, actuated, and at high pressure cut off. we will examine the pump control action for each situati

6、on. system in neutral signal pressure = tank pressure pump controls assure pump pressure = margin return to tank signal to pump case drain suction tank implement valve pump load sensing control high pressure cut off cylinder cylinder lines pump to valve variable pump neutral mode load sensing spool

7、meters pump near 0 has sufficient flow to compensate for leakage and maintain output = margin load sense control signal = tank high pressure cut off control system actuated signal pressure = cylinder pressure pump controls assure pump pressure = margin plus cylinder return to tank signal to pump cas

8、e drain suction tank implement valve pump load sensing control high pressure cut off cylinder cylinder lines pump to valve variable pump actuated mode load sensing spool meters pump at displacement needed to provide sufficient flow to maintain pressure drop from pump to signal (cylinder) output pres

9、sure = margin plus cylinder load sense control signal = cylinder high pressure cut off control system at high pressure cut function stalled cylinder not moving cylinder pressure = pump pressure (no flow across valve) signal pressure = pump pressure pump controls assure pump pressure = high pressure

10、cut off setting return to tank signal to pump case drain suction tank implement valve pump load sensing control high pressure cut off cylinder cylinder lines pump to valve load sense control signal = pump high pressure cut off control variable pump pressure limit mode pressure cut off spool meters p

11、ump near 0 has sufficient flow to compensate for leakage and maintain output = high pressure cut pressure pump controls 627h tier 4 interim high pressure cut off compensator pump controls 980h interim pump discharge sent to control piston pump controls 988h electronic pump control no signal pressure

12、 pilot pressure sent to control spool pump pilot supply tank controlled pressure hydrac valve solenoid actuated how do we generate the load sensing signal? signal generation 信號(hào)的產(chǎn)生 1a1b2a2b signal additional passages are added to the spool to create signals to send to the pump controls. in multi-func

13、tion applications like wheel loaders that have tilt and lift the signals are resolved and the highest is sent to the pump. 額外的通道被增加到閥芯中 產(chǎn)生信號(hào)，并將其發(fā)送到 泵控制。在像裝載機(jī)這種 具有舉升及翻斗的多功能 應(yīng)用中，信號(hào)被分解，最 高的信號(hào)被發(fā)送到泵中 neutralneutral signal generation 信號(hào)的產(chǎn)生 1a1b2a2b signal in neutral signal is connected to tank, when shift

14、ed signal is connected to cylinder 額外的通道被增加到閥芯中 產(chǎn)生信號(hào)，并將其發(fā)送到 泵控制。在像裝載機(jī)這種 具有舉升及翻斗的多功能 應(yīng)用中，信號(hào)被分解，最 高的信號(hào)被發(fā)送到泵中 neutral actuated work at white board show circuit discuss performance characteristics neutral deadband velocity vs lever 627 tier 4h interim 980 closed center valve parallel circuit tank pump s

15、ummary variable pumps are used to gain efficiency especially during modulation or when pressure reaches relief excess flow is controlled by destroking the pump rather than sending oil over the pump to tank area or the relief valve savings of 3 10 % can be realized in a truck loading cycle operator l

16、oses two control features ability to limit system pressure with the lever tool speed doesnt change with load operator loses “feel” for load pump controls two controls are needed load sensing & high pressure cutoff signal relief is also used in place of high pressure cutoff controls can be hydromecha

17、nical or electronic valve/electronic modifications signaling network needs to be added for hydromechanical controls solenoids and software need to be added for electronic controls fundamentals closed center systems 基礎(chǔ)知識(shí)基礎(chǔ)知識(shí)-閉芯式系統(tǒng)閉芯式系統(tǒng) 1.what are the sources of inefficiency in an open center hydrauli

18、c system? for your machine estimate the amount of energy used to raise a load from bottom to top at full speed and the amount of energy lost in each source of inefficiency. repeat if you are raising at half speed. repeat again if a cylinder is stalled when reaching the top for 5 seconds. compute the

19、 overall system efficiency for all three cases. 在開(kāi)芯式液壓系統(tǒng)里面在開(kāi)芯式液壓系統(tǒng)里面,無(wú)效率的來(lái)源是什么無(wú)效率的來(lái)源是什么? 估算一下你的車(chē)在全速時(shí)估算一下你的車(chē)在全速時(shí),將載荷從底部舉升到頂部時(shí)所使將載荷從底部舉升到頂部時(shí)所使 用的能量的量以及在每一個(gè)無(wú)效率來(lái)源中用的能量的量以及在每一個(gè)無(wú)效率來(lái)源中,能量損失的數(shù)量能量損失的數(shù)量.重復(fù)以上的估算重復(fù)以上的估算,當(dāng)車(chē)在半速行駛時(shí)當(dāng)車(chē)在半速行駛時(shí).估算一下估算一下 ；當(dāng)油缸到達(dá)頂部停止；當(dāng)油缸到達(dá)頂部停止5秒鐘后秒鐘后.油缸處于失速狀態(tài)時(shí)，再次估算一下；計(jì)算這三種情況的總系統(tǒng)效率油缸處于失速狀態(tài)

20、時(shí)，再次估算一下；計(jì)算這三種情況的總系統(tǒng)效率. 2.what sources of inefficiency described in one above are corrected by a closed center load sensing system with a high pressure cut off control? what are the main operating conditions where the improved efficiencies are most beneficial? repeat exercise 1 for a closed center l

21、oad sensing system with a margin pressure of 1500 kpa. 以上所描述的無(wú)效率來(lái)源中以上所描述的無(wú)效率來(lái)源中,哪一種可以被帶有高壓截止控制的閉芯式載荷感應(yīng)系統(tǒng)來(lái)校正哪一種可以被帶有高壓截止控制的閉芯式載荷感應(yīng)系統(tǒng)來(lái)校正? 在什么主要在什么主要 的操作條件下的操作條件下,改進(jìn)后的效率是最有益的改進(jìn)后的效率是最有益的? 重復(fù)練習(xí)一重復(fù)練習(xí)一: 用帶有用帶有1500 kpa.邊緣壓力的閉芯式載荷感應(yīng)系邊緣壓力的閉芯式載荷感應(yīng)系 統(tǒng)統(tǒng) 3.what variable can an operator control with an open center

22、 system that he cannot control with a closed center system? name one application where this is important. 什么變量在開(kāi)芯式系統(tǒng)中什么變量在開(kāi)芯式系統(tǒng)中,駕駛員可以控制但是在閉芯式系統(tǒng)中不能控制駕駛員可以控制但是在閉芯式系統(tǒng)中不能控制? 列舉一個(gè)應(yīng)用實(shí)例列舉一個(gè)應(yīng)用實(shí)例 fundamentals closed center systems 基礎(chǔ)知識(shí)基礎(chǔ)知識(shí)-閉芯式系統(tǒng)閉芯式系統(tǒng) 4.what determines the valve spool deadband for a closed c

23、enter circuit with a resistive load? if your machine has a closed center circuit how much is the deadband for one of the circuits? compare your estimate to measured data from ppg or to data from a dynasty model or both. 什么決定了帶有阻力載荷的中位封閉回路的閥芯死區(qū)什么決定了帶有阻力載荷的中位封閉回路的閥芯死區(qū)?如果你們的車(chē)有一個(gè)中位封閉回路如果你們的車(chē)有一個(gè)中位封閉回路,那么

24、其中一個(gè)回那么其中一個(gè)回 路的死區(qū)是多少路的死區(qū)是多少? 比較一下你的估計(jì)數(shù)字和從比較一下你的估計(jì)數(shù)字和從ppg里或者從里或者從dynasty模型或者同時(shí)從兩者中測(cè)得的數(shù)字模型或者同時(shí)從兩者中測(cè)得的數(shù)字 5.what determines the valve spool deadband for an overrunning load condition for a closed center circuit? how much is the deadband for one of the circuits on your machine? compare your estimate to m

25、easured data from ppg or to data from a dynasty model or both. 對(duì)于一個(gè)中位封閉的回路對(duì)于一個(gè)中位封閉的回路,在超載條件下在超載條件下,是什么決定了閥芯的死區(qū)是什么決定了閥芯的死區(qū)? 其中一個(gè)回路的死區(qū)是多少其中一個(gè)回路的死區(qū)是多少? 比較一比較一 下你的估計(jì)數(shù)字和從下你的估計(jì)數(shù)字和從ppg里或者從里或者從dynasty模型或者同時(shí)從兩者中測(cè)得的數(shù)字模型或者同時(shí)從兩者中測(cè)得的數(shù)字 fundamentals closed center systems 基礎(chǔ)知識(shí)基礎(chǔ)知識(shí)-閉芯式系統(tǒng)閉芯式系統(tǒng) 6.what feedback does a

26、n operator lose when going from an open center system to a closed center system? name one application where this is important. 從開(kāi)芯式系統(tǒng)到閉芯式系統(tǒng)從開(kāi)芯式系統(tǒng)到閉芯式系統(tǒng),駕駛員失去的是什么反饋駕駛員失去的是什么反饋?列舉一個(gè)應(yīng)用實(shí)例列舉一個(gè)應(yīng)用實(shí)例 7.can an operator use engine speed to gain hydraulic modulation with a closed center system? explain your an

27、swer. 在閉芯式系統(tǒng)里面在閉芯式系統(tǒng)里面,駕駛員能否利用發(fā)動(dòng)機(jī)轉(zhuǎn)速獲取液壓調(diào)制駕駛員能否利用發(fā)動(dòng)機(jī)轉(zhuǎn)速獲取液壓調(diào)制? 解釋一下你的答案解釋一下你的答案 fundamentals closed center systems 基礎(chǔ)知識(shí)基礎(chǔ)知識(shí)-閉芯式系統(tǒng)閉芯式系統(tǒng) 8.what are the key differences between a closed center hydromechancical load sensing system and a conventional open center system? consider efficiency, controllability

28、, feedback to the operator regarding load, force capability, etc. 閉芯式液壓機(jī)械載荷感應(yīng)系統(tǒng)與常規(guī)的開(kāi)芯式系統(tǒng)有什么主要的區(qū)別閉芯式液壓機(jī)械載荷感應(yīng)系統(tǒng)與常規(guī)的開(kāi)芯式系統(tǒng)有什么主要的區(qū)別1?考慮有效率考慮有效率,可控制性可控制性, 載荷及力能載荷及力能 等的對(duì)駕駛員的反饋等的對(duì)駕駛員的反饋 9.the 980h interim machine has a high pressure cut off control on the pump. the system also has a load sensing relief. wh

29、y cant we eliminate the relief and rely on the high pressure cut off to control the pump displacement when a function is at relief pressure? pressure compensation 980h interim closed center ls - post compensation valves in neutral 980h interim closed center ls - post compensation shifted valves 1900

30、0 kpa 1000 kpa 19000 kpa 19000 kpa1000 kpa goal 19000 kpa + 2300kpa 21300 kpa actual 21300 if we have a parallel supply and no compensation we get a lot of flow to the low pressure circuit and very little flow to the high pressure circuit. for example, assume circuit 1 has a 1000 kpa load, circuit 2

31、 has a 19000 kpa load, and pump margin is 2300. the pump pressure will be 21300. if both valves are shifted wide open all flow will go to circuit 2. 如果我們有個(gè)平行的供應(yīng)且沒(méi)有補(bǔ)償?shù)脑挘诘蛪夯芈分形覀?獲取了很多流量但是在高壓回路中獲取的就很少。比如說(shuō)，假設(shè) 回路1有1000kpa的載荷，回路2有19000kpa的載荷，泵邊界是1400。 那么泵壓是20400。如果兩個(gè)泵進(jìn)行相同量的換檔，那么在回路1中 的穿過(guò)p-c的壓力下降為19400，在回

32、路2中僅為1400。 所以大多數(shù)的 流動(dòng)將會(huì)進(jìn)入到回路1中。 this needs edited 0 flow full flow mg closed center ls - post compensation valves in neutral mg closed center ls - post compensation valve shifted load cases 1.resistive a & b portsa = 19000 kpa, b = 1000 kpa pump capability = 300 lpmdemand a = 100 lpm b = 100 lpm 2.re

33、sistive a & b portsa = 19000 kpa, b = 1000 kpa pump capability = 300 lpmdemand a = 200 lpm b = 200 lpm 3.resistive a port, overrunning b porta = 19000 kpa, b = vacuum pump capability = 300 lpmdemand a = 100 lpm b = 100 lpm 4.resistive a port, overrunning b porta = 19000 kpa, b = vacuum pump capabili

34、ty = 300 lpmdemand a = 200 lpm b = 200 lpm 5.stall a port, resistive b porta = 35000 kpab = 1000 kpa pump capability = 300 lpmdemand a = 100 lpm b = 100 lpm 6.stall a port, overrunning b porta = 35000 kpab = vacuum pump capability = 300 lpmdemand a = 100 lpm b = 100 lpm 980h interim closed center ls

35、 - post compensation case 1 demand 100 lpm in both circuits 19000 kpa 19000 kpa 19000 kpa 1000 kpa 1000 kpa 19000 kpa + 2300kpa 21300 kpa 19000 kpa 19500 kpa 19500 kpa 100 lpm 100 lpm 19000 kpa 980h interim closed center ls - post compensation case 2 demand 200 lpm in both circuits 19000 kpa 19000 k

36、pa 19000 kpa 1000 kpa 1000 kpa goal 19000 kpa + 2300kpa 21300 kpa actual p 21300 19000 kpa 19500 kpa 19500 kpa 150 lpm 150 lpm 19000 kpa 980h interim closed center ls - post compensation case 3 demand 100 lpm in both circuits 19000 kpa 19000 kpa 19000 kpa 0 kpa 0 kpa 19000 kpa + 2300kpa 21300 kpa 19

37、000 kpa 19500 kpa 19500 kpa 100 lpm 100 lpm 19000 kpa 980h interim closed center ls - post compensation case 4 demand 200 lpm in both circuits 19000 kpa 19000 kpa 19000 kpa 0 kpa 0 kpa 19000 kpa 19500 kpa 19500 kpa 150 lpm 150 lpm goal 19000 kpa + 2300kpa 21300 kpa actual p 21300 19000 kpa 0 lpm sma

38、ll flow to signal relief 980h interim closed center ls - post compensation case 5 demand 100 lpm in both circuits, one circuit stalled, one resistive pressure keeps increasing until relief blows 35000 kpa 37300 kpa 1000 kpa 1000 kpa 35000 kpa + 2300kpa 37300 kpa 35000 kpa 35500 kpa 37300 kpa due to stall 100 lpm 0 lpm small flow to signal relief 980h interim closed center ls - post compensation cas