Face gear drive manufacturing: Pinion/cutter design for a crowned contact pattern

Abstract

Face gear drives are special angular gears in which an involute pinion and face gear wheel mesh. They enable high transmission ratios in small construction spaces. The face gear is typically manufactured by gear hobbing or gear shaping using an involute pinion-type cutter. Face gear drives with identical pinion and cutter parameters form a conjugated pairing. Conjugate pairings tend to have unfavourable edge contact, which is usually counteracted by geometric flank modifications during manufacture. A common modification technique is the crowning of the flanks. This usually requires changes to the machine kinematics. Due to their geometry and manufacturing process, face gear drives offer an easy way to achieve a crowned contact pattern in the facewidth direction without changing the machine kinematics, making them promising for multiple applications. Using a pinion with fewer teeth than the cutter results in a crowned contact pattern (lead crowning). The position of the contact point along the facewidth can be adjusted by varying the profile shift coefficient of the pinion or the cutter. This paper presents a straightforward method for selecting proper design parameters depending on the contact distances. The contact distances can be estimated analytically to evaluate the chosen design parameters. Example calculations are given as proof of the developed method presented in this paper. Overall, this study offers a novel evaluation strategy for an ideal cutter/pinion design for manufacturing durable face gear drives with optimised contact patterns.