采用磁流体的液压伺服阀力矩马达三维有限元分析

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Jun.2013机 床 与 液 压Hydromechatronics Engineering V0l41 No.12DOI：10.3969/j.issn.1001-3881.2013.12.003Analysis of Hydraulic Servo Valve Torque M otor withM agnetic Fluid Using 3--Dimensional Finite Element M ethodZHANG Zhen ，ZENG Wen，HAN Hasiaoqier，LI SongjingHarbin Institute of Technology，School of Mechanical and Electrical Engineering，Harbin 150001，China1.IntroductionAbstract：As the electric-mechanism convefler。torque motor；s the key component of the electrohydraulic servo valve。lts characteristics jnfluence the performance of servo valve significantly。

Since magnetic fluids have larger magnetic permeability and bigger magnetization intensity underan external magnetic field，the magnetic circuit eficiency of the torqMe motor and the dynamicperformance of the servo-valve can be improved by applying a magnetic fluid.This paper pro-posed a three-dimensiona1.finite-element analysis modeI of torque motor with magnetic fluid.Themagnetic field distribution and the torqMe characteristics of the torque motor are studied with orwithout magnetic fluids by using three-dimensional finite element and analytical methods.Theconclusion ls drawn that the torqMe characteristics of the torqMe motor with magnetic fluid couldimprove markedly as compared with that without magnetic fluid。

Key words：torque motor，servo valve，magnetic fluid，three-dimensional finite element methodServo valve is an indispensable element to hy·draulic control systems and its performance has sig-nifcant influence on the perform ance of the systems。

Torque motor，which converts electric signal to me-chanical movement，is a key element of the electric-hydraulic servo valve[1].The magnetic fluid(MF)is a colloidal solution that is made from nanoscalemagnetic particles which are wrapped and dispersedsymmetrically in the continuous liquid through surfac-tant[2].Since magnetic fluid has larger magneticpermeability and greater magnetization intensity underan external magnetic field，the eficiency of torquemotor magnetic circuit can be improved by pouringmagnetic fluid into the working gaps of servo valvetorque motor between the arm ature and cores.There-fore，the magnetic torque output of torque motor canReceived：2012-11-26National Natural Science Foundation of China(50035004)ZHANG Zhen.E-mail：cqgzzxc### 163.con。

be increased and the dynamic performance of torquemotor can be improved simultaneously. The torquemotor of servo valve is the polarized electromagneticmechanism with the interaction between permanentmagnets and electromagnets.Only by using the meth-od of finite element analysis.can precise results ofmagnetic field distribution be achieved.This paper il-lustrated the structure and the working principle ofservo valve torque motor to which magnetic fluids areadded.The electromagnetic field of torque motor isanalyzed by using the Ansoft Maxwell 3D software。

The paper compared the simulation results of outputtorque of the torque motor between the cases with andwithout magnetic fluids。

2.Structure and working principle of tor-que motorThe construction of a torque motor with magneticfluids is shown in Fig.1.The torque motor consistsof cores， an arm ature， two coils， two perm anentmagnets and magnetic fluids which are filled into fourworking gaps between the cores and the armature。

ZHANG Zhen，et al：Analysis of Hydraulic Servo Valve Torque Motor withMagnetic Fluid Using 3-Dimensional Finite Element Method l1The armature is supported by a spring pipe whichkeeps the armature at middle position between the upand down cores and can rotate around rotation centerof the spring pipe slightly. The space between theupper and lower ends of the arm ature and the coresforms the four working air gap①，②，③，④，withtwo controlled coils trapped on the arm ature。

①(④aM FFig.1 Construction of torque motor with MFIf the electric power of the coils is turned of。

the magnetic fields in the four working clearances aredistributed symmetrically. Theoreticaly.there wil1not be any output torque from the motor and thetorque motor wil stay at the middle position.If the e-lectric power of the coils is turned on.the torque no。

tor will work under the interaction between the elec。

tromagnets and the perm anent magnets.As shown inFig.1，the magnetic intensity in 2，4 working gapswil be increased and become larger than those in 1。

3 working gaps.There will be an output torque sup-plied from the torque motor to the armature. Thetorque motor arm ature wil rotate and drive the flap toproduce a pressure difference to both sides of thespoo1.1le spool will move to a new position wherethe output torque of the motor equals the total of theload torque from the spring pipe and the feedbacktorque from the feedback rod due to the movement ofthe spoo1。

When the electric power of the coils is turnedof，the magnetic fluids will be absorbed in workingclearances under the influence of magnetic field in。

tensity which is caused by perm anent magnets.Whenthe electric power of the coils is turned on，the mag-netic fluids in different clearances wil be magnetizedto different magnetic intensity under the interactionbetween the electromagnets and the perm anent mag-nets.As the permeability of magnetic fluid is greaterthan that of air.magnetic field intensity in the work。

ing clearances wil be increased and the working effi。

3.Parameters of the torque motorThe structural parameters of the torque motor ofthe servo valve are as listed in Tab.1。

Tab.1 Parameters of torque motorparameters valueLength of magnet/mmWidth of magnet/mmWidth of core/mmThickness of core/mmLength of armature/mmWidth of armature/ramThickness of armature/mmHeight of clearance/mmCross sectional area of clearance/mm2Number of turns of the c0i110.418.8324.22322.91.330.253.9 x2.94 Ooo4.Three·dimensional finite element analy-sis of the torque motorThis paper applied the Ansofl Maxwel 3 D soft-ware to analyze the magnetic circuit of the torque no-tor.The analysis consists of three parts：Preprocess-ing，Solution，and Post processing。

To begin with，the paper defined the physicalgeometry and material properties and set up the entiremodel of the finite element analysis.The model of thetorque motor was established according to parametersin Tab.1 and the 3-D model is shown in Fig.2。

Fig.2 Model of torque motor using Maxwel 3DFurthermore，the simulation boundary conditionsare described，including the handling of boundaryconditions，stimulation and time changes.The typeof steady electromagnetic field(Magneto static)ana1。

ysis is chosen to solve the problem of torque motor.Akind of steel in the software materials library is se。

Hydromechatronics Engineeringlected as the material of the armature and the core：Alnico 9 is a substitute of the permanent magnet；thecoil is generally set for the copper material：the airand adding the magnetic fluid is set for the gap mate-ria1.Since there is no magnetic fluid in Ansoft material library。and the main function of magnetic fluidapplication is to changing the magnetic perm e-ability，so the B-H curve of magnetic fluid needs tobe set.B-H curve of magnetic fluid whose saturationmagnetization is 400 Gs is shown in Fig.3。

1 5l O0 5O0 2 000 4 000 6 000 8 000日Fig.3 B-H eurve of magnetic fluid whose saturationmagnetization is 400 GsAs for the loading of the excitation source，thispaper used the current excitation source as the formof the excitation source.The input value of the cur。

rent is the production of the coil turns of the torquemotor and the current value which is actually appliedto the coil.For example，given that the number ofcoil turns is 4 000 and the applied curent is 0.01 A，the setting current in the simulation analysis is 40 A。

The setting of the boundary conditions can constrainthe distribution of the magnetic lines of force so thatthe background can be excluded from the solution re。

Ansoft has the function of adaptive mesh，whichis an advantage of the software.Moreover，adaptivetechnology can achieve a reasonable distribution ofthe grid unit，resulting in the improvement of the cal-culation accuracy.Adaptive meshing is an iterativeprocess：the program first generates an initial dwith fewer units， calculates the field parameters，separates the d further in some regions according tothe distribution of field parameters。then calculatesthe field again5]。

4.2.SolutionSolving procedure is used to build the algebraicequations from the mathematical simulation of physi-cal processes and to obtain the solutions，resulting ina set of magnetic function value which describes themagnetic field in the entire mode1.Maxwel 3 D canbe solved automatically based on the torque motormodel and the given parameters。

Post-processing can achieve the mathematicaloperation of the existing data and display the simula-tion results graphically.If we regard finite element a-nalysis to simulate experiment， post-processingshould be used to identify which method should beprovided and what kind of results will be recorded[6].In the post-processing options，we can observethe single point of the magn etic field strength，themagnetic induction value.the distribution of the vari。

OUS components of the overall magnetic field.For ex。

ample，arm ature field intensity distribution of thetorque motor which we study in this case is shown inFig.4。

Fig.4 Distribution of armatures magnetic induction5.Analysis results5.1.M agnetic field distributionThrough finite element analysis of magneticfield，the vector distribution map of the magnetic in。

duction of torque motor is shown in Fig.5 and Fig.6。

Fig.5 illustrates the vector distribution of magneticinduction when the armature is in the middle positionwith the coil not electrified.while Fig.6 shows thevector distribution of the magnetic induction when thearm ature is in the middle position with the current ofthe coil 0.01 A.Fig.7 shows the vector distributionof magnetic induction when the arm ature is in themiddle position by adding magnetic fluid with the coilnot electrified，whereas Fig.8 shows the vector dis。

tribution of magnetic induction when the armature isin the middle position after adding magnetic fluid andthe curent of the coil is 0.01 A.As we can see fromthe comparison of the situations before and afterZHANG Zhen，et al：Analysis of Hydraulic Servo Valve Torque Motor withMagnetic Fluid Using 3-Dimen 呈 !兰! 2adding magnetic fluid，the magnetic induction vectorof the torque motor armature becomes more intensiveafter adding magnetic fluid，leading to an increase inmagnetic induction intensity values。

Fig.5 Distribution of armatures magnetic inductionwhen the coil without currentFig.6 Distribution of armatures magnetic inductionwhen the curent is 0.01 AF嘻 7 Distribution of magnetic intensity when workingclearances is filed with magnetic fluidFig.8 Distribution of magnetic induction with magneticfluid and the coilS current is 0.01 A5.2.M agnetic field strength valuesTaking the two cases that the gap of the torquemot0r is filled with air and the 400 Gs magnetic flu-id，respectively，as an example，we can analyze themagnetic field strength values of the middle positions0f the four gaps in the case of applying different cur-rent intensitv to the torque motor.The results are lis-ted in Tab.2。

Tab.2 Magnetic fluxes in the working clearancesof torque motorHydromechatronics Engineering续表0 0350 030- 0 025z 0 0200.015O O100 0050O 0 002 0 004 0 006 0 008 0.0l0current/A1.Magnetic fluid with saturation magnetization 400 Gs，2.AirFig.9 output torque when the cleaI彻 ce is airand 400Gs MF6.ConclusionsFrom the above，it can be1)When magnetic fluidsconcluded as follows：are filled into the ar。

mature working air gap of torque motor，magnetic cir-cuit efficiency of the torque motor，the magnetic fieldstrength and the armature output torque value in-crease more significantly than those without magneticfluids。

2)The material properties of armature and corehave great influence on the torque output.The torquevalue of the armature will be changed with the materi-anf the aYlnature。

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0 0350.030- O 025Z O 020善 0.015 0 O100 oo5O0 0 002 0 004 0 006 0 008 0 010current/A1.Material of armature and core are iron.2.Material ofarmature and core are stee1.1010Fig.10 output torque when diferent material of armatureand core are usedHYDRAUL ICS，2007，35(7)：66-79。

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低速重载齿轮箱箱体性能评价的新方法王海霞洛阳理工学院，河南 洛阳 471023[7] YANG chengyun，LIN Tengjiao，LI Runfang，et a1.Fi-nite element analysis and structure optimization for centerdrive gearbox[J].HEAVY MACHINERY，2001，2：42- 45。

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Structural optimization of high-power marine gearbox[J]。

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com/ edu/students/html/publiccontent/03- -FEM- -FEA- - Static- -Analysis- -of- -Ge arbox- -Casings- -Greaves- -Cotton。

摘要：基于弹性变形理论，考虑低速重载齿轮箱箱体弹性 变形对传动 系统的影响，提出同轴偏移度的概念和计算公式。提出了采用同轴偏移度对箱体进行性能评价的新方法。以某款中心驱动减速器为例，将有限元法的分析结果与实际情况进行了对比，验证了该评价方法的可行性。

关键词 ：低速重载齿轮箱 ；箱体评价方法；同轴偏移度 ；弹性变形理论中图分类号：TH13(Continued OU 14 page)采用磁流体的液压伺服阀力矩马达三维有限元分析张 振 ，曾 文，韩哈斯敖其尔，李松晶哈尔滨工业大学 机电工程学院，哈尔滨 150001摘要：力矩马达是电液伺服阀的关键元件之-，其输出力矩特性对伺服阀性能具有较大的影响。利用磁流体(magnetic fluid，MF)具有较大的磁导率和在外加磁场作用下具有较大磁化强度的特点，通过在液压伺服阀力矩马达的工作气隙中添加磁流体来改善伺服阀力矩马达磁路效率，提高伺服 阀动态性能。给出了添加磁流体的力矩马达磁路三维有限元分析模型。利用电磁场三维有限元分析方法对添加磁流体和不添加磁流体的力矩马达的磁场分布及力矩特性进行 了分析♂果表 明：添加磁流体后力矩马达的磁场强度及衔铁输出力矩值有明显改进。

关键词：力矩马达；伺服阀；磁流体；三维有限元分析中图分类号 ：TH137.53 2