Backlash analysis of a new planetary gearing with internal gear ring

Due to low carrying capacity and short life of current ring reducer, we proposed a new planetary gearing with internal gear ring, which consisted of two stages. One was an involute planetary drive and the other was an N-type planetary drive with small teeth difference. The kinematic calculation was conducted based on the analysis of structural composition and working principle. Formulas of backlash calculation for the new planetary gearing were derived by using probabilistic theory and the analytical model was created at the same time. Then, main factors that affect the systematic backlash were introduced and the effects of manufacture error, misaligments and roller bearing parameters on the distribution of backlash were presented. The influence of gear backlash on systematic return difference was performed based on the backlash mathematic model proposed. The results show that the backlash is a little large, of which the backlash of bearing takes a greater part than two gearing stages. So we presented some practical methods to reduce the systematic backlash.