Root Fillet Geometry of Spur, Helical, Spiral Bevel and Hypoid Gears 962230

As modern vehicular applications demand higher power density gears, accurate analytical tools to predict gear stress are required. The finite element method has been successfully applied to the analysis and design of components and structures of a vehicle. However, it is still difficult to apply to gears due to very complicated geometry, especially in the root fillet area. Since a good knowledge of the gear root geometry is required to calculate bending stress, the purpose of this paper is to present the root fillet geometry of spur, helical, spiral bevel, and hypoid gears.

The gear root fillet equations are derived based on the simulation of cutting tool motion on the gear blank during the manufacturing process. For spur and helical gears, the root fillet geometry cut by a rack with and without cutter tip radius is discussed. The phenomenon of undercut is discussed as well. For the more complicated spiral bevel and hypoid gears, the root fillet geometry by Gleason modified roll method is discussed. The Gleason pinion cutters consist of three parts: main profile, TOPREM, and cutter tip fillet profile. This paper shows examples that pinion root fillet geometry generated by both TOPREM and cutter tip fillet profile. It also shows pinion root fillet geometry generated by cutter tip fillet profile only. In addition, the effect of undercut to the root fillet geometry is discussed.