局部变速曲面无保持架陶瓷球轴承滚动体自动离散机理研究

With the development of micro turbine engines for unmaned aerial vehicale, the requirements of high speed and high temperature resistant performance for bearings are getting higher and higher. Recently, conventional bearings with cage limit the speed of the bearings because of the friction heat. They can no longer meet the requirements any more. For the reason, this study proposes a new technology of local speed transformation surface cageless ceramic ball bearings, and demonstrates the automatic discrete mechanism of non-contact between rolling elements by analyzing the speed-change principle of speed transformation surface. Firstly, we analyze the motion distribution regular pattern of the rolling body, and study the automatic discrete principle. We also design the position and geometrical parameters of the speed transformation surface, and establish the contact point locus equation of the rolling body and the speed transformation surface. The research studies the friction and wear mechanism of speed transformation surface through experiments. We'll determine the influence factors of wear on the automatic dispersion of rolling body. A mathematical model for rolling body sliding and discrete failure boundary conditions will be established. The contact dynamics characteristics of automatic discrete bearing will be studied. The model of multi-body contact quasi-kinetics of the system is established. The optimal value of speed transformation parameters and the number of rolling bodies that can reduce the bearing vibration to a minimum will be determined. Finally, we carry out parametric design to different types of automatic discrete bearings, and propose the design method of the system. A predictive model for the life and vibration of the new type bearing will be established. It provides theoretical support for the development of automatic discrete cageless bearing and its application in the field of micro-aero engine and unmanned aerial vehicle.

随着无人机微型涡轮发动机的发展，对轴承的高速、耐高温性能要求越来越高，目前带有保持架的常规轴承因摩擦发热限制了轴承的极限转速，已经不能满足要求，为此，本研究提出局部变速曲面无保持架陶瓷球轴承新技术，通过分析变速曲面变速原理，论证滚动体互不接触自动离散机理。首先，分析滚动体的运动分布规律，研究自动离散原理，设计变速曲面位置及几何参数，建立滚动体与变速曲面接触点轨迹方程；通过实验研究变速曲面的摩擦磨损机理，确定磨损对滚动体自动离散的影响因素，建立滚动体打滑及离散失效边界条件的数学模型；研究自动离散轴承接触动力学特性，建立系统的多体接触拟动力学模型，确定可以将轴承振动降低到最小的变速曲面参数及滚动体数量的最优值；最后，对不同型号自分散轴承进行参数化设计，提出系统的设计方法，建立该新型轴承的寿命和振动的预测模型，为自动离散无保持架轴承的开发及在微型航空发动机、无人机领域中的应用提供理论支撑。

无保持架轴承具有滚动体数量多高刚性和高承载能力特点，作为磁浮轴承的保护轴承能更好地处理下落转子冲击，但因没有保持架的隔离滚动体运动复杂，滚动体间存在不连续接触碰撞及滑移，导致轴承性能恶化及转子系统的不稳定。因此，本项目针对无保持架轴承开展滚动体离散机理分析、非线性系统动力学建模方法及试验研究。针对无保持架轴承滚动体运动随机性导致的碰撞接触问题，建立了滚动体运动姿态及轴承各部件相互作用关系坐标系，基于欧拉运动学理论建立了单个滚动体 6 自由度运动方程及所有14个滚动体分布规律模型；以此为依据在外圈滚道上设计了双曲面形状及椭圆形状的局部变速曲面实现滚动体离散，结合空间几何理论建立了滚动体与变速曲面接触点轨迹方程，基于Gupta轴承动力学理论完成了无保持架轴承滚动体自动离散模型的建立。针对滚动体经过变速曲面打滑引起磨损影响滚动体离散问题，建立了滚动体及变速曲面接触宏观相对滑移速度方程及摩擦力模型，提出了微观分析粘滑区摩擦系数确定变速曲面接触应力最大值的数值方法，结合动态接触应力基于改进的Archard模型建立了变速曲面磨损模型，给出了变速曲面轴承滚动体自动离散失效边界条件。针对损伤变速曲面轴承工作过程可能存在振动问题，提出了考虑时变位移、时变刚度、接触力及碰撞力的损伤演变振动模型。给出了外部激励作用下轴承系统全局坐标系模型，建立了无保持架自动离散轴承系统的多体非光滑接触动力学模型，完成了无保持架自动离散轴承变速曲面参数化设计及仿真试验验证。针对变速曲面轴承滚动体间非连续接触导致求解难收敛问题，提出了用拟动力学确定初值结合ADAMS预测校正算法，提高了计算精度并降低运算时间。本项目研究成果提供的无保持架轴承滚动体自动离散机理、开发的变速曲面轴承系统建模及试验数据，为无保持架变速曲面轴设计及应用提供理论指导。