Investigation of Dynamic Characteristics Experiments and Stability Evaluation Criterion of Space Ball Bearing Cage

The operation stability of the oil-impregnated cage, which serves as the lubrication and operation core of space ball bearings, is linked to the stability of the bearing dynamic friction moment. A cage dynamic characteristics test rig based on a high-speed camera system is created in this study to achieve synchronous monitoring of the cage centroid trajectory and bearing dynamic friction torque without changing the bearing structure. The centroid trajectory of the cage is separated into aggregation and discrete areas based on the distribution density of centroid trajectory points. To establish the mapping relationship between the shape and fluctuation of the cage centroid trajectory and the stationarity of the bearing dynamic friction moment, a new characteristic quantity, centroid trajectory fluctuation ratio (the ratio of the distance between the track points in the discrete area and the boundary of the aggregation area to the average width of the aggregation area), is adopted. In addition, a criterion based on the distribution density of the centroid trajectory points is proposed for evaluating the cage's operation stability. The findings of the study led to two primary conclusions: (1) The sudden jump of bearing dynamic friction torque is caused by the fluctuation of the cage centroid trajectory, which is independent of the trajectory shape. (2) The fluctuation ratio of centroid trajectory might effectively reflect the operation stability of the cage.