Meshing limit line of face worm gear drive with hardened cylindrical worm

Abstract

This paper systematically establishes the computation method of the meshing limit line for the face worm gear drive with a hardened cylindrical worm. The meshing theory based on the reference point in the tooth surfaces is developed for the face worm gear drive. The reference point is reasonably determined based on the study of the meshing limit line characteristics. The calculation method of the coordinates of the reference point is proposed. The formula for the limit pressure angle at the reference point is obtained. Numerical results show that two meshing limit lines can be obtained on each flank of the worm tooth surface by iteratively solving the system of non-linear equations with four unknowns. These two meshing lines are near the inner end of the worm addendum. When the meshing limit lines are outside the worm tooth surface, the conjugacy of the worm tooth surface is good. Besides, studies of numerical examples find that poorly matched parameters of the face worm gear drive can result in the meshing limit line entering the worm tooth surface first from the inner end of the addendum, which reduces the conjugacy of the worm tooth surface. To avoid this, the conjugacy of the worm tooth surface can be checked by examining the limit pressure angle of the reference point when designing the face worm gear drive.