Theoretical And Experimental Investigations On Dynamics Of Two-Stage Planetary Transmission System With Thin-Walled Ring Gear On Elastic Supports

As views of the energy density and load sharing, the rim thickness of the ring gear has a greater impact on the power weight ratio and load sharing characteristics of planetary transmission system, the support stiffness of the ring gear affects not only the planetary transmission system’s load sharing but also its dynamic characteristics. This dissertation mainly studies the dynamic characteristics of a dual-clutch two-stage planetary gears box of a hybrid coupling system. It focuses on the dynamic modeling, dynamic characteristics and experimental research of two-stage planetary transmission system with thin-walled ring gear on elastic supports. This research works are listed as follow:The elastic supporting structure is simplified for the tangential and radial stiffness constraints, the thin-walled ring gear is viewed as a standard thin ring to build the differential equation of motion in which only considering its inextensible in-plane vibration.The translational-torsional dynamic model of planet setⅠis established where the time-varing position angle of the planet gear and mesh stiffness of each gear pairs are considered, the lumped parameter-rigid elastic coupled dynamic model of two-stage planetary transmission system with thin-walled ring gear on elastic supports are established through inter-stage coupled method, after including the elasticity of the ring gear of planet setⅡand analyzing the relative deflections of various components.The planetary transmission system stiffness matrix is sorted out and the internal and external time-varying mesh stiffness of each stage are analyzed. It lays the foundation for the later research works.The natural frequencies of the planetary transmission system with three, four, five and six planet gears are calculated, it is found that the natural frequencies and vibration modes of the planetary transmission system are related to numbers of the planet gears, seven kinds of vibration modes are summarized: Ⅰ/Ⅱstage coupled rotational mode, Ⅰstage translational mode, Ⅰstage planet mode, Ⅱ stage translational mode, Ⅱ stage degenerate planet mode, Ⅱ stage distinct planet mode and purely ring gear mode. Specially, this seven vibration modes characteristics are analyzed in detail.The finite difference method and modal energy are used to study the sensitivity of the natural frequencies of the planetary transmission system with four planet gears on each stage gear pairs mesh stiffness and interstage coupled torsional stiffness, the influences of the natural frequencies of the planetary transmission system with four planet gears by the radial support stiffness and bending stiffness of the ring gear of planet set Ⅱ are analyzed. It is found that the influences of the natural frequencies of the planetary transmission system by stiffness parameters are not the same, but there is an obvious regularity. The mode transition phenomenon is also discussed, preliminarily.The dynamic differential equations of the planetary transmission system are solved by numerical method, the time-domain and frequency-domain response characteristics of the ring gear and planet gears of planet set Ⅰ and Ⅱ are particularly analyzed, the dynamic characteristics influences of the planetary transmission system by the radial support stiffness and bending stiffness of the ring gear of planet set Ⅱ, interstage coupled torsional stiffness and working conditions(input rotational speeds and load torques) are mainly analyzed. This characteristics influence laws of the planetary transmission system of stiffness parameters and working conditions are obtained.Based on the theoretiacal studies of the dynamic charateristics of the planetary transmission system, the vibration testing platform of two-stage planetary gears box are set up. The vibration charateristics influences of the radial support stiffness and bending stiffness of the ring gear of planet set Ⅱ, and working condition are experimentally studied. The experiments indicate that the vibrations of two-stage planetary gears box have been suppressed in certain situations as increasing its radial support stiffness and bending stiffness of the ring gear of planet setⅡ, the vibration influences of planet setⅠand Ⅱ by the working condition are not exactly the same.