Dynamic modeling and analysis of Ravigneaux planetary gear set with unloaded floating ring gear

A Ravigneaux planetary gear set (RPGS) system with an unloaded floating ring gear is studied in this paper. Aiming at investigating the three-dimensional vibration response of the long planet and the dynamic load on the floating ring gear, a flexible-rigid coupling dynamic (FRCD) model is proposed by coupling the condensed substructure of finite element (FE) flexible bodies with rigid dynamic model. Relative positions of different force elements are taken into consideration, as well as time-varying mesh stiffness and gear backlash. Based on this model, the effect of sun gear positions on the dynamic response of the long planet is performed and the mechanism for the vibration of the floating ring gear is revealed. The results show that the bearing force of the long planet varies nearly linearity with sun gear positions, and dynamic loads on the floating ring gear are induced by gear mesh excitations and carrier vibrations, while the former affects impact amplitudes and the latter influences impact frequencies. A further investigation is conducted on the effects of gear backlash and support stiffness, and it is indicated that increasing the support stiffness of the floating ring gear can reduce its dynamic load significantly.