Analysis of Load-Sharing and Contact Characteristics of the Concentric Face Gear Split-Torque Transmission System with Elastic Supports

The concentric face gear split-torque transmission system (CFGSTTS) is a new form of drive that is primarily used in helicopter transmission systems. Its load-sharing performance among different branches and tooth contact characteristics have a great impact on the service life of helicopter transmissions. It contains ten meshing pairs, the load distribution is complicated, and the tooth contact areas are difficult to determine. Therefore, based on the multi-point constraint method and nonconforming grid, a quasi-static analysis model of the CFGSTTS coupled with flexible supports was established and the load-sharing performance and contact characteristics were studied. The model considered the support stiffness, backlash, installation error, and web structure of the upper face gear, which could comprehensively reflect the meshing state of the system. The load-sharing coefficient curves, tooth contact area diagram, and meshing force were obtained. The results indicated that (1) a larger idler support stiffness and a smaller input gear support stiffness could achieve better load equalization performance; (2) better load equalization between idler gears could be acquired with a lower face gear support stiffness factor of approximately 0.9; (3) increasing the axial mounting error caused the contact area to shift to the top and inner end of the face gear tooth, which was detrimental to the transmission; and (4) adjusting the backlash of the idler gears, input gears, and tail gear had little influence on the load balance and contact.