A method for point-contact conjugate tooth surfaces with a constant instantaneous transmission ratio generated by point-contact conjugate involute helicoids

Point-contact conjugate tooth surfaces are insensitive to manufacturing errors and assembly er-rors and have no transmission errors. However, design conditions for the current method of generating point-contact conjugate tooth surfaces are strict or lacking. This study proposed a method for point-contact conjugate tooth surfaces with a constant instantaneous transmission ratio generated by point-contact conjugate involute helicoids. According to relative motions of single-and two-degree-of-freedom in generating, design criteria were given and a mathematical model of the method was established. The mechanism of point-contact conjugate tooth surfaces was obtained by investigating the relationship between the engagement lines/surfaces, and ki-nematics was studied, in which the mechanism with a constant instantaneous transmission ratio was geometrically analysed. Based on this method, four types of point-contact conjugate worm drives were studied, in which two novel types of worm drives were developed, i.e., a point -contact conjugate toroidal involute (TI) worm drive, and a point-contact conjugate involute cy-lindrical (ZI) worm drive. The method was validated for correctness using numerical simulations and meshing tests and the influence of adjustable parameters on the meshing performance was outlined.