Tooth-Trace Crowning in Form Grinding of Helical Gears.

Abstract

A method for modifying tooth traces (crowning) of helical gears finished in form grinding is described. Three kinds of additional motion in grinding process, (a) the approaching motion between the grinding wheel and work axes, (b) the additional Screw motion of the work gear, and (c) the shifting motion of the grinding wheel. are introduced for crowning of helical gears. Equations for calculating the tooth profiles of the crowned helical gears ground with these additional motions are derived. The shapes of the tooth surfaces of the crowned helical gears are illustrated using the contour lines which indicate the distance from the theoretical involute tooth surface. From the results of numerical calculation, it is shown that use of the approaching motion between the grinding wheel and work axes is the most practical method of crowning because it produces both tooth surfaces at the same time, accomplishing suitable profile modification at the tooth ends where the contact between the meshing teeth starts.