Abstract: Taking the planetary gear system as the research object， which contains lightening hole of sun gear， pin support of ring gear and the flexible carrier arm， a finite element model of planetary gear system with gear tip relief was established on the basis of ANSYS software. Based on the model， the influence of the gear tip relief and gear structure， such as lightening hole of sun gear， the rim thickness of ring gear and the flexible carrier arm， on the mesh stiffness was analyzed. The results show that the gear tip relief changes the shape and value of the mesh stiffness curve. Mesh stiffness decreases with the increase of lightening hole size. However， with the increase of the backup ratio of ring gear， the mesh stiffness increases gradually. Meanwhile， the more flexible the carrier arm is， the smaller the gear meshing stiffness fluctuates. The research results may provide a theoretical basis for the design of planetary gear system considering gear modification in actual production.

Key words: planetary gear system, mesh stiffness, gear tip relief, gear structure