Polymer Gear Development to Improve Efficiency and NVH Performance of an Engine Mass Balance System

A joint development program between Metaldyne and Victrex Polymer Solutions was established with the goal of developing a cost effective net shape injection molded gear that provides improvements in NVH (Noise Vibration and Harshness) and operating efficiency over conventional high quality iron gears. A detailed DOE (Design of Experiments) evaluating NVH performance of machined gears was performed in a calibrated NVH test cell. Variables in the DOE included material, gear geometry and backlash variation. The DOE showed the PEEK material gears had different geometric sensitivities, such as helix angle effects, on NVH performance. The results of the DOE were then used to develop an optimal injection molded PEEK polymer gear design. A production quality injection molding gear tool was constructed. Net shape production quality PEEK polymer gears were injection molded and the gears were evaluated in a current production mass balance unit for NVH, mechanical efficiency and durability. The study shows when compared to the baseline gears a net shape injection molded PEEK polymer gear provides a 3db noise reduction, as much as 9% reduction in power consumption, a 69% mass reduction and meets the application durability requirements.