Vibration Characteristics of Defected Sun Gear Bearing in Planetary Gearbox

Planetary gear transmission has the characteristics of an immense power-to-weight ratio, compact structure. It has been widely used in various industrial fields. Due to the complex load conditions, bearings are easily damaged during the operation process. However, in real applications, vibration characteristics of the defect bearings in gearboxes are too weak that it is challenging to extract useful information. This paper presents a dynamic model for an inner-race defect sun gear bearing in a planetary gearbox, from which the simulation results are validated using our planetary gearbox test bench and can be implemented in feature extraction in vibration signals. Specifically, time-varying stiffness during gear meshing and the slippage between raceways and balls are considered. Simulation results show dominant ball passing frequencies of inner-race defect, which are validated by the experimental results. Besides, the capability of our model to extract bearing defect frequencies from strong gear vibrations is proved by the envelope analysis.