【作者】 朱益利；

【导师】 徐龙祥；

【作者基本信息】 南京航空航天大学 ， 机械设计及理论， 2013， 博士

【摘要】 在磁悬浮轴承系统中，需要一套保护轴承作为磁悬浮轴承失效后转子的临时支撑，保护设备不受损坏。传统保护轴承往往无法支撑超高速转子旋转，且难以承受转子跌落后所带来的振动和冲击。针对传统保护轴承的不足，本文提出了将双层滚珠轴承作为保护轴承来使用，并进行了一系列相关研究。在双层滚珠轴承作为保护轴承使用之前，首先对其力学特性进行了分析。基于拟静力学原理，在考虑轴承所承受的径向载荷、轴向载荷、滚珠自身离心力以及陀螺力矩联合载荷作用下，建立了双层滚珠轴承的力学模型，基于MATLAB平台，编制了单、双层滚珠轴承力学特性分析的计算程序，并研究了相关参数对轴承力学特性的影响，最后搭建了转子—轴承系统试验平台，对仿真结果进行了试验验证。研究结果表明：内外层轴承节径比直接影响到双层滚珠轴承的转速分配；在相同的工作状态下，相对于单层滚珠轴承，双层滚珠轴承具有较小的径向和轴向支撑刚度；外载荷和工作转速影响着单、双层角接触球轴承的滚珠接触角的变化，滚珠的离心力使得滚珠与相应的内、外滚道间的接触角不再相等；外载荷、工作转速、滚珠材料、沟曲率半径和滚珠初始接触角对单、双层角接触球轴承轴向和径向变形均有一定的影响；径向游隙、工作转速和径向载荷对单、双层深沟球轴承的径向变形存在一定的影响。在对双层滚珠轴承力学特性研究的基础上，对转子跌落到弹性阻尼器支撑下的双层滚珠轴承上的动力学响应进行了详细的研究。分别建立了磁悬浮轴承失效前后转子的动力学模型、磁悬浮轴承支撑模型、转子—内圈碰撞模型、滚珠的受力模型以及双层轴承的实时支撑弹性力模型，根据所建立的模型，对在不同参数下，磁悬浮轴承失效后各部分的动力学响应进行仿真计算，并在一个五自由度磁悬浮轴承试验台上进行相关的跌落试验研究。研究结果表明：与传统保护轴承相比，双层滚珠轴承作为保护轴承的使用能有效地降低转子跌落后转子与内圈之间的碰撞力、内层滚珠的最大接触应力和发热量；在实际使用中，可以通过改变内、外层轴承的组合来调节双层轴承受转子跌落冲击后的内、外层滚珠的最大接触应力；为了保证转子跌落后，保护轴承滚珠在许用应力范围内，转子的工作转速及偏心距不能超出其安全区域范围；从降低转子跌落后的碰撞力出发，应该尽量减小转子与保护轴承内圈之间的摩擦系数、选择合适的保护间隙和保护轴承的支撑阻尼；当使用内层为面对面安装的角接触球轴承的双层滚珠轴承作为保护轴承使用时，内层轴承应具有较大滚珠初始接触角和较小轴向预紧力；当选用深沟球轴承组成的双层滚珠轴承作为保护轴承使用时，应尽量选取较大的轴承游隙等级；与铝材相比，选用密度较大的45钢作为双层轴承的中圈转接环材料具有更好的缓冲性能；在保证转子跌落后保护轴承的滚珠最大接触应力不超出最大许用应力范围的前提下，应尽量选择轻薄系列的滚动轴承来组合双层轴承；当将公差环安装在保护轴承系统中时，可以通过改变公差环的材料厚度、突起个数等参数来调整支撑特性，以提高其工作性能；金属橡胶环的加入能有效地缓冲了转子跌落后的对保护轴承的冲击；公差环和金属橡胶环的减振效果均得到了证明，但从经济性和装配的难易性出发，应优先选择公差环作为保护轴承系统中的弹性阻尼器来使用；保护轴承的破坏性试验证明合适弹性阻尼器支撑下的双层轴承具有更长的寿命，且破坏性试验过程中轴承的损坏形式均为保持架碎裂。更多还原

【Abstract】 In active magnetic bearing system (AMBs), the catcher bearings (CBs) are indispensable totemporarily support the rotor from directly impact the stators. They prevent damages during themaintenance and destruction of the AMBs. In most cases, traditional catcher bearings cannot bear theultra high speed and the following vibration and impacts after rotor drop. Aiming at the defects oftraditional catcher bearings, double-decker ball bearings (DDBB) are proposed to use as catcherbearings in AMBs, and a series of relevant researches are carried out.The mechanical characteristics of DDBB are analyzed before using them as CBs. The mechanicalmodel of DDBB is established based on the quasi-static method by considering the radial load, axialload, centrifugal force as well as the gyroscopic moment acted on the bearing simultaneously. Thecalculation program is compiled in MATLAB to analyze the influences of various load and structureparameters on the mechanical characteristics of DDBB and single-decker ball bearing (SDBB). A testplatform of rotor-bearing system is established, and the relevant experiments are carried out to verifythe theoretical results. The results show that the relationship between the inner and outer pitchdiameters determines the rotate speed distribution of DDBB. In the same work condition, comparedwith SDBB, DDBB has relatively smaller radial and axial support stiffness. The external loads andworking speed affect the ball contact angles of SDBB and DDBB, and the ball centrifugal force makesthe contact angles between the ball and the corresponding inner and external groove no longer equal.External loads, working speed, ball materials, groove curvature radius and ball initial contact angle allhave certain influence on the axial and radial deformations of both SDBB and DDBB. Radialclearance, working speed and radial load have certain influences on the radial deformation ofsingle-decker and double-decker deep groove ball bearings.Based on the analysis of DDBB, the dynamic responses of rotor drops onto DDBB under the supportof elastic dampers are detailed analyzed. The rotor dynamical modes before and after AMBs failure,support model of active magnetic bearings, impact model between rotor and inner race, ball forcemodel as well as the real-time support force model of DDBB are respectively established. Based onthe established models, the dynamical responses of each part after rotor drop for different parametersare theoretically simulated. And the relevant rotor drop experiments are carried out on a five-degree offreedom (DOF) AMBs test platform. The results indicate that compared with traditional catcherbearing, using DDBB as CB helps to reduce the following collision forces，inner ball contact stress aswell as heat energy. In the actual applications, the inner and outer ball maximum contact stresses canbe regulated by adjusting inner and outer bearing combinations. Rotor work speed and unbalanceshould be in the safe zone to make sure the ball maximum contact stresses do not exceed the allowable stress range after rotor drop. Friction coefficient between rotor and inner ring, suitable protectionclearance and support damping of CBs are beneficial to reducing the collision force after rotor drop. Itis advisable to choose larger ball initial contact angle and smaller pre-tightening force when useface-to-face mounted angular contact bearings as the inner bearing of DDBB used as CB. Largerradial clearance is advisable when the selected DDBB used as CB are composed of deep groove ballbearings. Compared with aluminum, choosing45steel which has larger density as adapter ring of theintermediate ring has better cushion performances. In the guarantee of the maximum ball contactstress in the permission stress range, it is better to choose light and thin series of ball bearings tocombine DDCB. The work performance of tolerance ring in the CB system can be improved bymodulating its thickness, number of waves and some other design parameters. The added metal rubberring can effectively cushion the vibrations after rotor drop. The vibration reduction effects of bothtolerance ring and metal rubber ring are confirmed, but proceed from economy and degree ofassembly difficulties, it is suggested to use tolerance ring. The destructive tests show that DDBBunder the support of suitable elastic damper has longer service life, and all the bearing damage formsduring the destructive tests are cage fragmentation.更多还原