轴承间隙及柔性特征对机构动态误差的影响分析

为能够准确、有效地揭示轴承间隙与柔性特征对机构动态误差的影响规律,基于多体动力学理论与Hertz接触理论,提出一种计及轴承间隙与柔性特征影响的多体系统建模方法。该方法采用力约束替代运动约束,构建多体系统环境下的轴承精细化模型。基于该方法,可深入揭示轴承微观动力特性与多体系统宏观动态性能及运动精度之间的映射关系。在此基础上,以含深沟球轴承的曲柄滑块机构为仿真算例,分析轴承间隙与柔性特征对该机构运动位置与速度误差的影响规律。研究表明,轴承内外圈中心形成的相对偏心轨迹的变化特征是由多体系统动态环境下的轴承受载特性决定的;在轴承偏心影响下的机构运动位置与速度误差大小会随曲柄转角位置不同而变化。     

Stability Analysis of Floating Ball Bearing

Conventional disk drive motors supported on ball bearings (BBs) cause nonrepeatable runout (NRRO) due to the surface imperfections on balls and raceways. NRRO is a source of track misregistration between head and disk that inhibits high track density in a hard disk drive. Fluid dynamic bearings with herringbone grooves either on the rotating or stationary surfaces are a suitable replacement for conventional ball bearings. Herringbone grooved bearings have considerably lower noise level than ball bearings and have better stability compared to plain journal bearings at concentric operating position. However, herringbone-grooved patterns are difficult to manufacture because groove depth is of the order of bearing clearance. The major limitation of the BBs is the direct contact between the rotating and stationary parts and also lack of damping effects. This present work attempts to overcome these drawbacks in BBs by eliminating the metal-to-metal contact using a layer of fluid film, and a theoretical analysis of stability characteristics of a floating BB is presented. Results indicate that there is an improvement in the stability of floating BB rotor systems with increase in outer to inner film clearance ratio (β) from 0.7 to 1.3, and with decrease in ratio of outer race radius to inner race radius (δ) from 3.0 to 1.2.     

基于赫兹理论的大型负游隙四点接触球轴承的接触分析

给出了用赫兹接触理论对大型负游隙四点接触球轴承进行接触分析的方法,并以3-645K转盘轴承为例,计算空载时不同负游隙下钢球与内、外圈滚道之间的法向接触压力.结果表明:轴承4个接触点处的接触载荷随负游隙绝对值的增大而增大,负游隙的微小变化对接触力的影响很大.     

Identification of Mechanism Stiffness of Autoeliminating Clearance for Auxiliary Bearing

In this article, a method for identification of equivalent stiffness was proposed based on a genetic algorithm by studying the stiffness characteristics of autoeliminating clearance auxiliary bearing devices (ACABDs) in static condition. Subsequently, the equivalent stiffness damping model and the Hertz contact theory were combined to establish the theoretical equations of the ACABD. Moreover, the linear equivalent model of the ACABD was established to eliminate the influence of contact of the revolute pair on mode shape and mode frequency of the rotor. In addition, simulations and experiments were carried out to verify the effectiveness of the genetic algorithm–based stiffness identification method. The results indicated that the relative errors between the equivalent stiffness in the X and Y directions identified by the linear equivalent model and the theoretical values were 6.22 and 7.19% respectively, demonstrating the feasibility of this identification method.     

一种外间隙结构辅助轴承

介绍了与主动电磁轴承相关的一种外间隙结构辅助轴承,叙述了其选型依据和试验情况,得出了转子系统在主动电磁轴承失效后坠落在外间隙结构辅助轴承支承上的运动模式,并探讨了这种外间隙结构辅助轴承的功能可行性。     

带弹性环保护轴承的动力学特性

提出在传统保护轴承外圈加弹性环来提高其在主动磁悬浮轴承(Active magnetic bearing,AMB)系统中的工作性能。为完善转子跌落仿真模型,得到AMB失效前转子准确的运动状态,理论推导得到AMB的支撑动刚度曲线,进而基于有限元分析方法得到转子在其支撑下的模态,并与试验结果进行对比,验证所得刚度曲线的正确性。在刚性转子理论基础上,建立转子在AMB系统中的动力学模型。基于Hertz接触理论,分别建立AMB失效后转子与保护轴承内圈之间的碰撞模型和保护轴承的实时动刚度模型。根据所建立的模型,对不同弹性环支撑刚度阻尼在不同初始转速下跌落后的动力学响应进行仿真计算,并与无弹性环状态下跌落结果进行对比。仿真分析结果表明,选用合适的弹性环有利于降低转子跌落后的振动幅值和碰撞力。分别在不同初始状态下进行跌落试验研究,试验结果与理论分析结果基本相符。     

Dynamic responses of rotor drops onto double-decker catcher bearing

In an active magnetic bearing(AMB) system,the catcher bearings(CBs) are indispensable to protect the rotor and stator in case the magnetic bearings fail.Most of the former researches associated with CBs are mainly focused on the dynamic responses of the rotor drops onto traditional single-decker catcher bearings(SDCBs).But because of the lower limited speed of SDCB,it cannot withstand the ultra high speed rotation after rotor drop.In this paper,based on the analysis of the disadvantages of SDCBs,a new type of double-decker catcher bearings(DDCBs) is proposed to enhance the CB work performance in AMB system.In order to obtain the accurate rotor movements before AMB failure,the dynamic characteristics of AMB are theoretically derived.Detailed simulation models containing rigid rotor model,contact model between rotor and inner race,DDCB force model as well as heating model after rotor drop are established.Then,using those established models the dynamic responses of rotor drops onto DDCBs and SDCBs are respectively simulated.The rotor orbits,contact forces,spin speeds of various parts and heat energies after AMB failure are mainly analyzed.The simulation results show that DDCBs can effectively improve the CBs limit rotational speed and reduce the following vibrations,impacts and heating.Finally,rotor drop experiments choosing different types of CBs are carried out on the established AMB test bench.Rotor orbits,inner race temperatures as well as the rotating speeds of both inner race and intermediate races after rotor drop are synchronously measured.The experiment results verify the advantages of DDCB and the correctness of theoretical analysis.The studies provide certain theoretical and experimental references for the application of DDCBs in AMB system.     

游隙对滚滑轴承内部载荷及应力影响的研究

滚滑轴承是一种新型轴承,可应用于风力发电机齿轮箱。根据滚动轴承基本原理和接触力学原理,建立滚滑轴承有限元模型,研究滑块与内外套圈滚道之间的游隙对滚滑轴承内部载荷及应力的影响,得到不同游隙时不同大小载荷工况下典型工作位置处滚滑轴承的内部载荷与应力分布规律。在研究中,提出滚滑轴承临界载荷的概念。研究结论可以为滚滑轴承的基础理论研究和参数优化提供参考。     

Modeling and Analysis of Novel Integrated Radial Hybrid Magnetic Bearing for Magnetic Bearing Reaction Wheel

Conventional ball bearing reaction wheel used to control the attitude of spacecraft can't absorb the centrifugal force caused by imbalance of the wheel rotor,and there will be a torque spike at zero speed,which seriously influences the accuracy and stability of spacecraft attitude control.Compared with traditional ball-bearing wheel,noncontact and no lubrication are the remarkable features of the magnetic bearing reaction wheel,and which can solve the high precision problems of wheel.In general,two radial magnetic bearings are needed in magnetic bearing wheel,and the design results in a relatively large axial dimension and smaller momentum-to-mass ratios.In this paper,a new type of magnetic bearing reaction wheel(MBRW) is introduced for satellite attitude control,and a novel integrated radial hybrid magnetic bearing(RHMB) with permanent magnet bias is designed to reduce the mass and minimize the size of the MBRW,etc.The equivalent magnetic circuit model for the RHMB is presented and a solution is found.The stiffness model is also presented,including current stiffness,position negative stiffness,as well as tilting current stiffness,tilting angular position negative stiffness,force and moment equilibrium equations.The design parameters of the RHMB are given according to the requirement of the MBRW with angular momentum of 30 N ? m ? s when the rotation speed of rotor reaches to 5 kr/min.The nonlinearity of the RHMB is shown by using the characteristic curves of force-control current-position,current stiffness,position stiffness,moment-control current-angular displacement,tilting current stiffness and tilting angular position stiffness considering all the rotor position within the clearance space and the control current.The proposed research ensures the performance of the radial magnetic bearing with permanent magnet bias,and provides theory basis for design of the magnetic bearing wheel.     

数字式轴承游隙测量仪

本文介绍了一种代替传统轴承游隙测量装置的新型仪器─-数字式轴承游隙测量仪,并简要叙述了它的基本原理,软件、硬件设计思想,功能、先进性和重要的应用价值。     

高压转子支承刚度计算

通过分析球轴承的负荷在滚动体之间的分配,得到了高压转子球轴承在运行过程中两个极限位置时的刚度,考虑了游隙对轴承刚度的影响,为研究转子系统振动性能提供了参考。     

应用新型可控轴承改善转子系统稳定性的研究

介绍了一种动态特性可在线调整的新型可控径向轴承工作原理,其特征是具有一个由挠性板、控制油腔和流体阻尼器组成的可动部分。给出了转子－轴承系统非线性数学模型,分析了系统的稳定性,并着重研究了阻尼器参数对系统稳定性的影响。计算机仿真结果表明,在较大的转子偏心范围内,应用该轴承可有效地消除或降低系统的自激振荡。     

Characteristics analysis of aero-engine whole vibration response with rolling bearing radial clearance

For the influence of rolling bearing radial clearance on the whole vibration in the aero-engine whole system, a real engine rotorbearing- casing whole model is established. The rotor and casing systems are modeled by means of FEM; the support systems are modeled by lumped-mass model; rolling bearing radial clearance and strong-nonlinearity of Hertz contact force at four different supports are considered. The coupled system response is obtained by the numerical integral method. The characteristics of the whole vibration response are analyzed. For rolling bearing at a typical support, the rotor, outer ring of rolling bearing and casing response characteristics at different rotating speeds are analyzed. The changing law of contact forces for each ball and the global contact forces at different speeds are analyzed. The influence of the radical clearance on the contact forces on the whole vibration is analyzed. The results show that the contact forces will be larger and the acceleration amplitude jumps obviously when the radial clearance is increased, and due to the variable stiffness of the rolling bearing, the natural frequency will appear when the stiffness changes fiercely, that is frequency-locked phenomenon. When the radical clearance is larger and the rotating speed is between two critical speeds, the rotor squeezes the outer ring now and then. Reducing the radical clearance can reduce the whole vibration and increase the rotor’s stability.     

Effect of rotational speed fluctuations on the dynamic behaviour of rolling element bearings with radial clearances

The behaviour of rolling element bearings is of major importance to the vast majority of rotating machines. Due to the varying assembly compliance and the internal clearance existing in the bearing in most cases, a highly non-linear behaviour of the rotor bearing system appears. Thus, a dynamic model of a horizontal rotor supported on ball bearings with radial internal clearance is considered, taking into account contact forces between the balls and the races, as well as the effect of varying compliance and of the internal radial clearance. However, since rotational speed fluctuations of various levels practically appear in all rotating equipment, their effect is now additionally considered. Their effect is examined in two characteristic rotor bearing cases. The analysis includes all the characteristic states of the dynamic behaviour of the rotor, such as periodic, unstable periodic and chaotic responses, using methods like frequency spectra, phase spaces, higher-order Poincare maps and Lyapunov exponents. All results presented show a dominant stabilization effect of the speed fluctuations with respect to the system behaviour. From the analysis performed, it is concluded that even a minimum fluctuation of the rotor speed may result in major changes of the system dynamics, indicating that speed fluctuations of the rotor are a governing parameter for the dynamic behaviour of the system.     

基于ANSYS的主动磁轴承电磁场的有限元分析

在介绍主动磁轴承转子的数学模型及其简化计算的基础上,给出了有限元计算模型及其边界条件,并用有限元分析软件ANSYS对主动磁轴承电磁场的耦合现象及转子偏心量和控制电流对磁场分布的影响进行了仿真,给出定子和转子中的二维磁力线分布图、磁通密度分布图及电磁力随转子位移和控制电流的变化规律.所得结论对磁轴承的设计具有一定的指导意义.     

球轴承涡轮增压器轴承-转子系统动力学分析与应用

相比于普遍使用的浮动轴承,在涡轮增压器中使用球轴承具有机械效率高和加速响应快的优势。以车用球轴承涡轮增压器为研究对象,用有限元法对轴承-转子系统进行了转子动力学特性的研究,对轴承-转子系统的临界转速进行了计算与分析,这是判断转子工作转速是否稳定和涡轮增压器工作是否可靠的重要依据;建立了增压器模型,并对比了计算结果和试验结果,证明了方法的可行性。通过整机试验表明,球轴承涡轮增压器能够满足当前车用发动机的需求,能够提高发动机的工作性能。     

转子轴承失效分析

对转子轴承的受力情况进行了分析,指出了转子轴承非正常失效的原因。最后,从理论和实用角度提出了消除轴承附加反力的措施,对机械传动中轴承的设计和轴系的安装、调试具有一定的指导作用。     

柔性支承结构对可倾瓦轴承稳定性的影响

为了进一步提高可倾瓦轴承支承转子系统的稳定性，提出由弹簧支承的柔性可倾瓦轴承结构。设计制造单层弹簧和双层弹簧支承的2种柔性可倾瓦轴承试样，在转子-轴承实验台上开展稳定性实验研究。实验结果表明：由弹簧支承的柔性可倾瓦轴承综合支承刚度小于普通可倾瓦轴承的支承刚度，新型柔性可倾瓦轴承具有降低转子临界转速的作用；相比于普通可倾瓦轴承，柔性支承可倾瓦轴承明显降低轴频振幅，能够有效提高转子-轴承系统的运行稳定性，且双层弹簧支承的可倾瓦轴承稳定性提高更为显著。     

Effect of Bearing Surroundings on the High-Speed Spindle-Bearing Compliance

This paper investigates the effect of bearing assembly tolerance on spindle-bearing compliance. In a high-speed spindle system, the bearing characteristics are influenced significantly by the initial assembly tolerances and the thermal deformation of the bearing surroundings. In the very early stage of spindle operation, spindle bearings could be under hazardous conditions owing to the rapid change of the internal pressure resulting from thermal deformation or centrifugal force-oriented deformation. The bearing’s internal clearance also may be changed by the operating conditions such as external load, rotational speed, and operating cycle time. To determine the initial tolerance and the optimal cooling regimen, a comprehensive dynamic modelling and analysis of a high-speed spindle system in terms of bearing pressure, bearing compliance, and heat generation is required with consideration of those effects. Moreover, in order to predict spindle characteristics in operation, all of these parameters should be monitored and recalculated in real-time. For this purpose, very simple and effective equations are suggested, representing the bearing stiffness in accordance with the thermal deformation. Most former bearing analyses were based on the Hertzian contact model, without considering the radial elastic defor-mation of the races. In this paper, analytical and experimental investigations of the bearing compliance are conducted with consideration of both the elastic deformation of the race and the thermal deformation of the housing in terms of the bearing stiffness. The experimental results show the effectiveness of the proposed equations, which are simple and useful for fast calculation of the bearing stiffness by dynamic simulation.     

Dynamic responses after rotor drops onto a new-type active eliminating protective clearance touchdown bearing

Journal of Mechanical Science and Technology - A new-type active touchdown bearing (TDB) system integrated with a centering device to eliminate the protective clearance after rotor drop in an...