一种基于权重的某车用液力变矩器闭锁品质优化方法

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Mar.2013机 床 与 液 压Hydromechatronics Engineering Vol41 No.6DOI：10.3969/j.issn.1001-3881.2013.06.008A Weight·based Optimization Method of Lockup Quality foran Automotive Hydrodynamic Torque ConverterYAN Qingdong，YANG Aihua ，LIU Shucheng，WEI WeiSchool of Mechanical Engineering，Beo'ing Institute of Technology，Bering 100081，ChinaAbstract：In order to improve the Iockup quality of hydrodynamic torque conveers，this paperoptimized the Iockup point of an automotive hydrodynamic torque converter.This paper took theinfluences of turbine torque changes and engine inertial energy release on Iockup quality into consideration.On the basis of goal programming method，the previous unified objective function wasmodified according to the influences at diferent turbine speeds，a weight-based unified objectivefunction was put forward，and a reasonable Iockup point was obtained.The Iockup performancesimulation modeI of a hydrodynamic torque converter was built in Matlab/Simdriveline.and thesimulation was conducted in the study.The simulation results show that the optimized Iockuppoint is more reasonable than the previous one。

Key words：fluid power transmission and control theo，hydrodynamic torque converter，Iockuppoint，unified objective functionOn the basis of hydrodynamic torque converter，lockup hydrodynamic torque converter has both theadvantages of hydrodynamic transmission and thecharacteristics of high efficiency of mechanical trans。

mission，and it also ensures both vehicle power andeconomy，by adding a lockup clutch[1].Due to thechanges of turbine torqueinertial energy，which areand the release of enginedelivered to transmissionsystem in the form of torque vibration，the lockup im-pact is formed.A great many researches[2-6]showthat making a reasonable lockup point is of great re-search importance to decrease lockup impact and im-prove the lifetime of transmission system as well asriding comfort，because the frequency of lock/unlockprocess[7-8]is very high。

Taking the effects of turbine torque change andengine inertial energy release on lockup quality intoReceived：2012-11-27National Natural Science Foundation of China(50905016)，Ministerial pre-research project(40402050202)$YANG Aihua.E-mail：1 3466307020### 163.comconsideration，this paper researches on the lockupquality of a certain hydrodynamic torque converterand presents the lockup point optimization designmode1。

1.Traditional lockup point design modelIn the hydromechanical transmission，the method of traditional two-parameter lockup point design isthat the intersection point of turbine output torquecurves of both hydrodynamic and mechanical condi-tions is used as the lockup point at a certain throtleopening，according to the equivalence principle ofturbine output torques of the two conditions beforeand after lockup，as shown in Fig.1。

Theoretically，the power is considered beingtransferred without interruption and the lockup impactis very smal，because of the equality of turbine out-put torques both before and after lockup.But due tothe sudden decrease of engine speed，large quantityof engine inertial energy is released，causing greatimpact to the transmission system，which means thatthe lockup quality is still very poor。

YAN Qingdong，et al：A Weight-based Optimization Method of Loekup Quality foran Automotive Hydrodynamic Torque Converter 435 O004O0o3O0020oo500 1 000 1 500 2000 2 500 3000 3500 4000Turbine speed/(r·min 。)Fig.1 Traditional lockup point design2.Lockup point optimization design modelGiven conditions：engine net external character-istic，hydrodynamic torque converter original charac。

Optimization interval：turbine speed n undermechanical condition A，and turbine speed r underhydrodynamic condition c，namely[ ， c]。

2.1-Turbine torque changes before and aRerlockupUnder hydrodynamic conditions，engine workstogether with hydrodynamic torque converter.Speedratioiand turbine speed n口are already known in theco-operation point. Both torque coeficient A andtorque ratioKare the function of speed ratioi，that isAA(i)，K：K(i).Theturbine output torque Mpressed as follows。

(1(1(1a)b)c)Where，P is the density of working oil，gis the acce1。

eration of gravity，and D is the effective diameter ofcirculatory circle。

And then turbine torque can be described in thefollowing。

2 5： ( ) (2)Under mechanical condition，when the impellerand the turbine are locked together，the output speedand torque of both impeller and turbine are the same，which is expressed by the following equation。

nBM M ME·iqiq AE/nB(3(3(3a)b)c)W here，i q is the front drive ratio，M E is the outputtorque of engine which can be calculated as the fol-lowing equation： fa0alnEa2n2E 3 3a4n4E， n≤ ≤bob1 ， ≤ ≤nmaxa (0≤i≤4)and 6 (J0，1)are the fiting coefi-cients of engine，AE is the engine speed，and A i 、AⅣ、Am are the lowest stable speed，rated speed andthe highest speed of engine respectively。

And then turbine torque can be described by thefollowing equation。

Turbinelockup can becorded as theM7 (AT) (4)torque change ratio before and afterdefined as the folowing function，re-first objective function(Ⅳ) (5)2.2.Engine inertial energy release before and af-ter lockupUnder hydrodynamic condition，inertial energyrestored by engine can be calculated as follows。

芝1 I [20n ) (6)Where， and EH are the engine inertial energy andthe speed respectively under hydrodynamic condi。

： 1，E( ) (孚凡 ) g (凡 ) (7)Under mechanical condition，the inertial energyrestored by engine can be calculated as follows。

2～7r )。 (8)Where， and M are the engine inertial energy andthe speed respectively under mechanical condition。

( ) (iqnr) (9)The engine inertial energy release ratio beforeand after lockup can be defined as the folowing func-tion，recorded as the second objective function。

厂2(N) gH(nr)g (凡 ) (n ) (10)2.3.Modifed unifed objective functionAccording to the optimal design theory，multi-objective function can be transformed to single objec--暑 .Z ；bJ0 自Iq鲁-LD2 宣A K n -n 口 ll HHydromechatronics Engineeringrive function to simplify calculation. During theprocess，target programming method can make theseobiective functions achieve their optimal values con-sistently[9]By analysis，when the first objectivefunction obtains optimal value at traditional lockuppoint，the second objective function may not achieveits optimal value.If two objective functions obtainoptimal values at the same time，these two functionsneed to make a concession in order to achieve the o-verall best。

A common unifed objective function is shown asfollows。

2Ⅳ)∑J1 ]Where， is the optimal value of the j-th objectivefunction。

When (N)and (N)achieve its optimal val-ue respectively，八N)can obtain its optimal value。

However，this unifed objective function doesnttake the contribution of these objective functions intoconsideration.So the objective function should bemodifed by adding weighting factors.Weighting fac-tors are changing with turbine speeds，and the princi。

pie of weight changes is that when the turbine speedis closer to its optimal value，the corresponding ob-jective function contributes less to the unifed objec-tire function.Then unifed objective function consid-ering weighting factors can be expressed as follows。

N) 奎1 [ 1 ]20 I nr-n1(12)(13)Where， (0< <1)is weighting factor，01/2，is the optimal turbine speed of function (N)，and n is the optimal turbine speed offunction (N)。

3.Numerical simulationBy programming in Matlab，under full throtle o-pening，the first objective function is monotonicalydecreased with the increase of the turbine speed。

When the change of turbine torque before and afterlockup is the smalest，the first objective function a-chieves the optimal value，that is， 1，and thecoresponding turbine speed is n 2 453.14 r/min，as shown in Fig.2。

2 001 75l 501 25l 00O.750 50O 250l 500 1 750 2000 2250 2 500 2750 3000 3250 3 500Turbine speed/(r·min。)Fig.2 The First Objective FunctionThe second obiective function is monotonicallydecreased with the increase of the turbine speed。

When the engine inertial energy release is the least，the second function obtains the optimal value，thatis， 1.037 8，and the coresponding turbinespeed is n ：3 420.0 r/rain，as shown in Fig.3。

4 003.753 503 253 0O2 752.502 252 001 751 501 251 001 500 1 750 2 000 2 250 2 500 2750 3 000 3 250 3 500Turbine speed/(r·min )Fig.3 The Second Objective FunctionBy the three methods，namely.traditional de。

sign method，unifed objective function method，whose weight can be thought of as l 2 1/2，and weight.based unifed objective function method，under 100% throttle opening，the lockup points andthe corresponding function values are shown in Tab。

1.and the curve of weight.based unifed objectivefunction value is shown in Fig.4。

Tab.1 The Unified Objective Function Value0；霉 00 0 目-qJ0 口芒 靛目里譬 目 TB岛u 曰。 R 司YAN Qingdong，et al：A Weight-based Optimization Method of Lockup Quality foran Automotive Hydrodynamic Torque Converter 450 270 250 23竺 0 210 192 0.17目 0 15。工 0 13O 11O 092 500 2600 2 700 2 800 2900 3 000 3100 3 200 3 300Turbine speed/(r·min。)Fig.4 The unified objective function based on weightsBy analyzing the results，the lockup point deter-mined by weight-based unifed objective function is alitle bit bigger than the one by unifed objectivefunction，but the function value is lower，that is，thelockup quality is improved with lesser engine inertialenergy release and smaller turbine torque changes。

4.M odel validationBy the idea of modular，the lockup performancesimulation model of a certain hydrodynamic torqueconverter is established in Matlab，including enginemodule，hydrodynamic torque converter module，ve-hicle dynamic module and lockup control module。

The purpose is to compare the influence of the lockuppoints determined by weight-based unifed objectivefunction，unifed objective function and traditionaldesign method，to both vehicle power and lockupquality，as shown in Fig.5。

When the lockup points determined by thesethree methods are being verified，the same engine[10]and lockup hydrodynamic torque converter areused，the throtle opening is full，and the character-istic of lockup control oil stays the same，in the samehydrodynamic torque converter lockup perform ancesimulation mode1.The lockup control parameters areturbine speed and throttle opening。

The influence of lockup points determ ined bythese three methods to vehicle power and lockupquality is shown in Tab.2。

Fig.5 The Lockup Quality Simulation Model of Hydrodynamic Torque ConverterTab.2 The Influence of Lockup point on Vehicle Dynamics and Lockup QualityHydromechatronics EngineeringSeen from the simulation results.the changes ofengine torque，speed and inertial energy release beforeand after lockup，which are determined by weight.basedunifed objective function，are smaller，compared withthose determined by unifed objective function and tra-ditional method.In the meantime，the lockup impact，the peak torque，the friction work and the friction poweralso decrease.The friction power，the engine inertialenergy release and the turbine peak torque，determinedby weight-based unifed objective function are decreasedby 89.08%，79.00% and 42.49%，respectively，COB-pared with these determined by traditional method，andare decreased by 63.66% ，58.47% and 23.66% ，re-spectively，compared with these determined by unifiedobjective function.So lockup quality is improved。

Taking throttle opening and turbine speed as con-trol parameters，lockup points at diferent throttle open-ings are established by the way of weight-based unifedobjective function. e lockup law of hydrodynamictorque converter is shown below in Fig.6。

1 00 90.80.70.60.50 4Hydraulieconditionunified objectivefunotionW eight-based unifiedobjective functionTraditional methodM echanicalcondition0 3 I.....-.....I......·.....J.....·.....JL....--.....-L.....-.....I.- 1 000 l 400 l 800 2 200 2 600 3 000Turbine speed/(r·min )Fig.6 The loekup law at diferent throttle openingsAs it can be seen from Fig.6，the lockup law es-tablished by weight.based unified obiective function isabout 100 r/min bigger than those established by bothtraditional method and unifed objective function。whichmeans that mechanical condition is narrower.However。

the vehicle lockup quality has be en improved greatly，with the decreases of lockup impact by 4% an d frictionwork by 80% 。

1)When the hydrodynamic torque converter locksup at diferent turbine speeds，the turbine torque chan-ges and the engine inertial energy release have diferentefects on loekup qu ality，which should be taken intoaccount reasonably.It is not feasible to consider simplythat the two efects on lockup qu ality are the same，when the lockup points are made。

2)By the way of unifed objective function，con-sidering the efects of both turbine torqu e changes andenne inertial energy release on lockup quality at dif-ferent turbine speeds，ideal lockup points can be ob-tmned so that it improves the lockup qu ality.Th e re-search result shows that the new method is reasonableand feasible。

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