Study on the effect of bearing position and stiffness on the dynamic behavior of output stage of CHT system based on the cylindrical gear meshing

The internal and external rotor shafts are important components to transfer power in coaxial helicopters, and bearing supports could affect the dynamic behavior of the transmission system. In order to explore the influence of bearing support structure, bearing position and support stiffness on the dynamic behavior of the output stage of coaxial helicopter transmission (CHT) system based on the cylindrical gear meshing, a rigid-flexible coupled dynamic model is established under cantilever-cantilever support structure and cantilever-simple support structure considering the flexibility of rotor shaft based on Timoshenko beam theory, and time-varying mesh stiffness (TVMS), comprehensive meshing error are also considered. Newmark-beta numerical method was applied to calculate the dynamic response. The result indicates that the load sharing performance of gear pair using cantilever-simple support structure is better than that of cantilever-cantilever structure, but the maximum vibration displacement of bull gears is reduced apparently. Simultaneously, the bearing positions and stiffness can be adjusted to achieve better performance in load distribution and maximum vibration displacement of bull gears.