Research on the mass unbalance response of an inner planetary gear reducer

A new inner planetary gear reducer with three axes is introduced. Three constructions and fixing techniques of the planetary gears are also introduced and compared with each other. Considering the meshing stiffness and damping of the gear pairs and the stiffness of the bearings, the dynamic governing equations of an inner planetary gear reducer with three axes are established based on the lumped mass method and corresponding deformation conditions. According to the different constructions of the reducer, the natural frequency and the mass unbalance response is investigated in frequency field. It is found that the natural frequency of the reducer with different numbers of inner planetary gears has almost the same frequency value. Mass unbalance force can not only result in bending vibrations, but also result in twisting vibrations. When the reducer has three inner planetary gears, the amplitude of the dynamic response is smallest.