Geometry design, tooth wear evaluation and pressure angle influence analysis of asymmetric face gear considering load sharing of multi-pair contact

In response to the new requirements for face gear transmissions in the latest heavy-load helicopters, this paper investigates the impact of pressure angle variations on the geometric contact and performance of asymmetric face gears. Firstly, using meshing theory, the tooth surface equations for asymmetric rack cutter, shaper, and face gear are derived, and the parameterized 3D models are created. Secondly, the line of action (LOA), contact ratio, contact point curvature, and load sharing ratio considering multi-pair contact (MPC) under different pressure angles are analyzed. Then, a wear calculation model based on the Archard wear equation is developed, detailing the tooth surface wear depth calculation. Finally, a case study calculates the contact stress and wear depth under different pressure angles is presented. The results indicate that appropriately increasing the pressure angle effectively lower the contact stress and wear depth on tooth surface, although further increases degrade meshing performance. The gear pair with a pressure angle of 30° in the case study exhibits optimal performance. This study provides a reference for optimizing asymmetric face gear meshing performance under various pressure angles.