Abstract: Limacon gear is a new kind of gear whose pitch-curve varies in cosine rule. In order to select the proper cutting method and cutter and realize different CNC processing methods, theoretical analysis calculation and simulation are done. According to the formula of the new kind of gear’s radius of pitch-curve cavature, pitch-curve’s convex and concave discriminants are given; According to the distribution disciplinarian of the gear’s normal on the pitch-curve, the equations of the gear’s tooth evolute are set up by analytic method; By the geometry relation between the vector of a point on tooth and the vector of the corresponding point on pitch-curve, the equations of the gear tooth are deduced from the equations of the pitch-curve. Based on above, the graphics simulation of the evolute and tooth are finished, which provides theory basis for this new kind of gears. Gears based on these theories have been used in practice and achieved good results.

Key words: Convex-concave, Evolutes, Gear making, Non-circular gear, Pitch-curve, Tooth-profile