文章通过相对运动关系分析，给出了超环面行星蜗杆传动中共轭运动零件行星轮与定子、行星轮与蜗杆之间相对滑动率的计算方法，得出了凸峰接触时行星轮与定子及蜗杆之间摩擦系数的计算公式；以弹流润滑理论为基础，给出了液体润滑时行星轮与定子及蜗杆之间齿面摩擦系数的计算公式；进而给出了混合摩擦状态下行星轮与定子及蜗杆之间摩擦系数的计算公式。然后，运用上述公式讨论了液体润滑时行星轮与定子及蜗杆之间齿面摩擦系数的相对大小及其随传动参数的变化规律；给出了行星轮与定子全部为凸峰接触时摩擦系数随传动参数的变化规律；讨论了混合摩擦状态下，行星轮与定子之间摩擦系数随膜厚比的变化规律。

In this paper, by analyzing the relationship between relative motions of the toroidal drive, the method for calculation of the sliding factors between the planet and stator or worm is given. Based on above-mentioned results, formulae of the friction coefficient between the planet and stator or worm under profile peak contact are presented. Based on EHL theory, formulae of the friction coefficient between the planet and stator or worm under hydrodynamic lubrication are introduced. Then, formulae of the friction coefficient between the planet and stator or worm under mixed friction are also introduced. Finally, by making use of the above-mentioned formulae, the friction coefficients between the planet and stator or worm under hydrodynamic lubrication are compared, and the dependences of them on parameters are discussed. Dependences of the friction coefficient between the planet and stator on the parameters under profile peak contact are given. And dependences of the friction coefficient between the planet and stator on the ratio of the film thickness to roughness under mixed friction are also discussed. These results are useful for manufacture and design of the drive.