An analytical approach for calculating thin-walled planet bearing load distribution

Abstract

With the development of planetary gear trains (PGTs), more planet gears are designed as thin-walled structures to reduce the weight and accommodate the larger bearings so that the transmission system can achieve higher power density, improved reliability, and better compactness. However, this would make the planet gear fragile, where it could easily deform and thus influence the load distribution on the bearing. To address this problem, this study investigates the effect of the planet gear rim deformation on the bearing load distribution and its service life. By incorporating the Timoshenko three-dimensional (3D) curved beam theory and the transfer matrix method, a novel analytical model was developed that computes the planet gear rim deformation and the bearing loads. The validation of the model was conducted using a finite element (FE) simulation. Based on the proposed model, the internal states, including forces and deformations, of the planet gear rim along the circumference were examined, and the effects of the planet gear parameters and the bearing clearance on the bearing load distribution and service life were analyzed. The results show that the deformation of the planet gear rim has a significant effect on the contact load, pressure distribution, and service life of the bearing. On this basis, an optimal rim thickness that gives the maximum bearing life was obtained for different planet helix angles and bearing clearances, which can provide design guidance for the planet gear bearing with higher reliability.