第33卷第4期 2OO8年12月 广西大学学报(自然科学版) J0urml 0f Guangxi University(Nat sci Ed) V01.33。No.4 Dec.,2OO8 文章编号:1OO1—7445(2OO8)O4一O378—05 Simulati0n research 0n resp0nse characteristics 0f l0ad sensing system CHEN Yuan一1ing ,FU Yu—lin '。 (1.C0llege 0f Mechanical Engineering,Guangxi University,Nanning 53OOO4,China; 2.Armor Technique Institute 0f PLA,Changchun 130117,China) Abstract:The resp0nse characteristics 0f the load sensing system are simu1ated using AMESim after the analysis 0f the c0ntr0l principle.The results show that the f10w rate 0f the system has nothing to do with the load before the pressure of the system rises to the setting 0f the pressure regulator va1ve and is decided only by the opening 0f the throttle valve,the load sensing valve will regulate the displacement of the pump automatical1y acc0rding t0 the opening 0f the thr0ttle valve. When the pressure of the system rises t0 the setting of the pressure regulat0r va1ve,the pressure 0f the system has nothing to d0 with the 1oad and is restricted only by the setting,the load sensing valve w.1l regu1ate the disp1acement of the pump automatically to supply the just fl0w rate the l0ad needed. Key words:load sensing;variable disp1acement pump;energy saVing;dynamic responses CLC number:TH137 D0cument cOde:A 负载敏感系统响应特性仿真研究 陈远玲 ,付玉林 。 (1.广西大学机械工程学院,广西南宁53O0o4;2.装甲兵技术学院,吉林长春13Oll7) 摘要:在对负载敏感变量泵工作原理进行分析的基础上,基于AMESim平台对系统的响应特性进行了仿真研 究.结果表明,在系统压力达到调压阀设定压力之前,系统的流量仅取决于流量阀的开口而与负载无关,负载 敏感阀将根据流量阀的开口自动调节变量泵的排量.在系统压力达到调压阀设定压力之后,系统压力仅取决 于调压阀的设定值而与负载无关,此时负载敏感阀将自动凋节变量泵的排量使之恰好与负载的需要相适应. 关键词:负载敏感;变量泵;节能;动态响应 中图分类号:TH137 文献标识码:A Load sensing variable displacement pumps have been increasingly used abroad f0r the good control performance and effect on energy saVing, pumps used in the dOmestic construction machinery are generaUy imported products, therefore, it is necessary to speed up the but the l0ad sensing technology is not yet mature jn home and sti11 in the testing stage[ 一4。. Currently,load sensing variable disp1acement localization of the products. Due to the large damping 0f the hydraulic systems,the settings of the parameters w订l play an important role in l Received date:2OO8一O1—16 F0undati0n item:National Natural Science Foundation of China(5O3650O1),Guangxi NSF(O778OO6-12) Bi0graphy:Chen Yuan—ling(1964一),female,native 0f Guangxi pr0vince,associate profess0r 0f Guangxi university; E—mai1:cylgxdx@gxu.edu.cn. 第4期 陈远玲等:负载敏感系统响应特性仿真研究 379 deciding the perf0rmances of the system[ ‘引. ConsequentIy,in order to supply some references for pump design, a load sensing Variable displacement pump with a maximum sensing valve returns to the middle of the valve, then the system is in equilibrium again with a lower flow rate than eVer.If the opening of the throttle valve 1 is increased,the contro1 Drocess will be an opp0site one. Once the thrOttle vaIve 1 is set,the system displacement 0f 90 mL was modeled in AMESim and the parameters concerned were set accordingly,then the resp0nse characteristics of will be in equinbrium. If the load decreases,the the load sensing system were studied by the simulating in AMESim. 1 Control principle The control principle of the load sensing system is showed in Fig.1.The pressure and flow rate of the system are reguIated by pr0portional pressure regulator Valve 2 and proportional throttle valve 1 respectively.The system is loaded by proportional throttle valve 9. 。Ig・l C0IltrOl principIe 0f the 10ad sensing VariabIe displacement pump 1.1 COntrOl 0f the fIOw rate When the system is in equnibrium,the differential Dressure of the two ends 0f the load sensing Valve 3 just balances out its spring f0rce,s0 the spool is in the middle of the valve.If the opening 0f the thrott1e valve 1 is reduced,its differential pressure (eq ua1s to the differential pressure of the load sensing valve)will increase and the spool will shift upwards,which will cause the connection of the right chamber of the cylinder 1O with the outlet of the pump,as a result,the flow rate of the pump wnl decrease,so win its pressure. It is not until the differential Dressure of the throttle valve 1 reduces to the value bef0re the change that the sp00l of the load differential pressure of the two ends of the load sensing va1ve will increase and its spoo1 w订l shift upwards,which will cause the connection of the right chamber of the cylinder with the outlet of the pump,c0nsequently,the flow rate of the pump will decrease,so wn1 its pressure. It is not until the differential pressure of the throttle ValVe 1 reduces to the value before the change that its flow rate rec0vers to the original value. If the load increases,the result is the same one. That is,once the thr0ttle vaIve is set,the flow rate of the system is invariable,even the load changes. 1.2 ContrOl Of the pressure When the pressure of load rises to the cracking pressure of the proporti0nal pressure regu1ator valve,the valve will be opened,as the valve and damping 0rifice 4 form a B—type hydraunc hemi—brjdge, the pressure 0f the chamber with spring in the load sensing valve will decrease and the spool will shift upward, which w订l cause the c0nnection of the right chamber in the cylinder with the out1et 0f the pump,hence the fl0w rate of the pump will decrease, so will its pressure. When the differential pressure of the two ends of the load sensing valve reduces to the value before the shift (because of the existence of the B—type hydraulic hemi—bridge,the value is bigger than the differential Dressure of throttle valve 1 now),the spool returns to the middle of the valve. Then the system wiIl be in equmbrium again with a comparatively lower flow rate, therefore,the 1oad sensing variable displacement pump can automatically regulate its fIow rate to need the changes of the load. If the 1oad further increase after the 380 广西大学学报(自然科学版) 第33卷 proportional pressure regulator valve has been opened,for the existence of B—type hydraulic hemi—bridge,the pressure will be invariable and can increase any more unless the current of the proportional pressure regulator va1ve is 3.1 Static characteristics 0f the system The input signal of the loading valve 9 is sh0wed in fig.3 (abscissa units: s,the same below). Responses of the pressure and fl0w rate of the pump are showed in fig.4. increased. In order to avoid the setting of the proportional pressure regu1ator Valve is so high as to damage the system, a safety valve (equipped at the outlet of the pump)is needed. 2 System mode1ing The model of the load seI1sing system to be 攀 simulated using AMESim is showed in Fig.2. 1 n n n a n n Fig.2 M0deI of lOad sensing variable displacement pump based On AMESim 3 Simulati0n and analysis The main parameters of the simulation are showed in Tab1e 1. Tab.1 Main parameters 0f the simuIatjOn Parameters Value Va1ueDiameter of damping 0r.fice 4 mm 1.4 Setting 0f safety valve bar 35O Piston diameter 0f the cylinder mm 25 Po1e diameter of the cv1inder mm 1 2 Spring rate 0f the cy“nder N/m 4 OOO Engine speed rev/min 1 5OO Diameter of damping ormce 7 mm l_4 Spring rate 0f the 10ad sensing va1ve N/mm l1 Preload of spring in l0ad sensing va1ve N 42 Diameter 0f damping 0r.fice 5 mm O.45 Diameter 0f damping or.fice 6 mm 1.8 Equivalent quality of the inc¨ned plate kg 1.2 The maximum opening of thr0ttle valve 1 mm 8 Setting of pressure regulator va1ve bar 2OO Fig.3 Input signal Of 10ading valve 。pf墩乳Ⅱe 0r廿1e阻JTplDarl ’。’’。’ 。。。’‘’’:。。。。’。 } P ‘_‘ 。IL ’{ 、 、, ……2一一 一… …一- ……‘=三熹 辱 蔓 量 6f 啼r… 0 2 4 6 8 10 。ig・4 Statjc cllaracteristics Of the punlp As is shown in fig。4,the pump keeps the flow rate constant ti1l the pressure comes to setting of the proportional pressure regulator ValVe (2OO bar). When the regulator valve is opened,the flow rate of the pump decreases, however,the pump can still keep it constant. At the same time,the pressure will fluctuate near 20O bar within a small range,the possible reason is that there is always an output in the B—type hydrauIic hemi—bridge since the pressure comes to 200 bar. 3.2 Dynamic characteristics 0f the system (1)Responses when the system pressure lower than the setting 1nput a negative step signal to the loading va1Ve(fig.5),which will make its flow area step from 1 9.63 mm to 3.14 mm .Set the Dressure of the proportional pressure regulator valve to 330 bar,responses of the spool displacement of the load sensing valve and the flow rate of the pump are showed in fig.6 and fig.7,the pressure 第4期 陈远玲等:负载敏感系统响应特性仿真研究 381 responses of both pump and load are showed in fig.8. showed in fig. 6,shifts downward first and finally stops in the position of equ订ibrium after fluctuating seVeral times because of the sp ring force. Accordingly,the flow rate of the pump,as showed in fig.7,also fluctuates several times and then resumes the originaI value. The pressure responses are showed in fig.8 in which curve 1and curve 2 are responses of the pump and the load,curve 3 is the difference of them. The results indicate that the pump can automatically adjust the pressure to need the change of the Fjg.5 Step signal Of loading ValVe load pressure and the pressure l0ss is no m0re than 10 bar.For the highest pressure during the 们0.3 who1e process is 326 bar, the proportional pressure regulator ValVe is not open,the rise 潜≤ §啦time of the pressure is O.2 s and the adjustment time O.5 s,the 0vershoot is 11%. (2) Responses when the system pressure : :1 : : ・ ・ ' ・’ rises to the setting 。 I 。 l ’ I 。 - ’ I ’ ■ R 日 1 Reset the cracking pressure of the proportional pressure regu1ator valve to 2OO bar Fig.6 SpO0l dispIacement Of the 10ad sensing ValVe and input a step current signal as is showed in fig.9 to it,other parameters unchanged. The response curves of the load pressure and the fl0w rate of the pump are showed in fig.10 and fig.11. 。 辆 rvaI 【m.1J Fig.7 Fl0w rate resp0nse Of the pump ● ........●...一...▲一--..-.L.-. …J……。 t 量’ig・9 Step current sjgna1 0f the pressure reguIatOr vaIve Due to the negative current step 0f the proportional pressure regulator valve at the seventh second,the pressure of the load steps from 2O0 bar to 15O bar and the response time is Fig.8 Pressure resp0nses Of the pump and the lOad about 0.5 s,which can be seen in fig.1O.The As the positive step of the load at the fifth negative step of the flow rate showed in fig.1 1 at second,the spool of the load sensing valve,as the fifth second is attributed to the opening of 382 广西大学学报(自然科学版) 第33卷 the prop0rtiotla1 pressure regulator valve,but it is largely constant before the seVenth second. Because of the decreases of the pressure at the seventh second,the spool of the load sensing valve shifts upward, which leads to the connection of the right chamber 0f the cylinder with the outlet 0f the pump,as a result,the angIe of the inclined plate of the pump decreases。so does thc f10w rate.Then,after the adjustment time of about O. 4 s,the pump maintains the flow rate in a constant state again. : p|ess¨ of岫bad l : j i 0 2 4 6 8 10 Fig.1 O Pressure respOnse Of the lOad 1 1 1 1 1 Fig・1 1 Resp0nse 0f the fIow rate of the pump 4 Conclusions Conclusions drawn from the study of the load sensing system are as folIows. (1)The pump can adjust its pressure and flow rate automatically to need the change of the load,the pressure loss is no more than 1O bar. That is,the system is perfect in energy saving. (2)The flow rate 0f the system is constant before the pressure rises to the setting 0f the proportional pressure reguIator vaIve and the pressure is stable; when the pressure c0mes to the setting,the pressure and flow rate will be somewhat fluctuant but they,by and large,are still constant. (3)The time of dynamic responses of the system is short and the main function 0f the lOad sensing system can be realized,which indicate the parameters set in this paper are correct. References : [1] Gao L H,QIA0 F L,LU C J, nZ.Simulation of contr0l characteristics 0f load—sensitive variable discharges of electro—hydraulic proportiona1 radial pist0n pump[J]. Journal 0f Gansu University of Technology,2OO2,28(3):59—63. [2] An G C,Liu X H,Wang M L, n .The simu1ation ana1ysis and experiment study 0n electric—hydraulic proportional load sensor contr0l radial piston pump [J]. Fluid Power Transmission and Contr0l,20O6 (1):8—1O. [3] QIAO F L,LU K,XIE H B.Theoretical analysis of static characteristics of variable pump system with l0ad sensing[J]. J0urnal of Lanzhou University of Technology,2OO6,32(3):S9—62. [4] Liu Z,LU K,LU C J.Design and analysis 0f load- sensitive valve in Load—sensible variable displacement pump [J]. Journal 0f Lanzh0u University of Technology,2OO5,31(6):55—58. [5] Wu G M,Qiu M X, Wang Q F, 口Z. Electrohydraulic pr0portional technique in the0ry and application [M]. Hangzhou: Zhejiang University Press,20O6:3O5—3O6. [6] K0ng X W,Qiu M X,Wei J H.Experimental study 0f l0ad sensing system with l0ng pipes[J].Chinese Journa1 of Mechanical Engineering,2OO5,1 8(1): 118—122. [7] Hu Y P,Peng Y D,Wu G M.Hydrau1ic Resistance Netw0rk Systems[M].Beijing:China Machine Press,20O2. [8] Ji H,Fu X,Yang H Y.Ana1ysis and calcu1ati0n 0n typical shape orifjce areas in hydrau1ic valve[J]. Machine Tool&Hydraulics,20o3(5):14—1 6. (责任编辑梁碧芬)