Lightweight Wheel Bearing with Dissimilar Materials for Vehicle 2019-01-2134
Limited fossil fuel resources, air pollution, and global warming all drive strengthening of fuel economy and vehicle emission standards globally. Much R&D continues to be dedicated to improve fuel efficiency of automobiles and to reduce exhaust gasses. These include improvement of engine/driveline performance for higher efficiency, development of alternative energy, and minimization of air resistance through aerodynamic design optimization. OEM weight reduction-focused research has extended into chassis components (steering knuckle, brakes, control arms, etc.) in sequence from body-in-white(BIW). Wheel bearings, one of the core components of a driveline and part of a vehicle’s unsprung mass, are also being required to reduce weight. Conventionally, wheel bearings have achieved “lightweighting” primarily through design optimization methods. They have been highly optimized today using steel based materials. Opportunities for further mass optimization are increasingly limited and so the focus of this study is integration of lighter-materials into steel bearing components for weight savings. Both aluminum and CFRP were considered in the study for partial integration into the steel hub flange which interfaces directly with the wheel. The application of lightweight materials was targeted on the specific area of the hub which is relatively less affected by impact loads. Hot forging and compressive molding were applied to induce denser bonding of the dissimilar materials. The slope angle design having an inverse draft at the combined boundary was applied to reinforce physical bonding and to enhance joint integrity. In addition, a Zinc-based coating was partially applied on the surface of the combined boundary to protect against galvanic corrosion between dissimilar materials. Bearings containing the new composite hubs achieved a 20% weight reduction compared to conventional wheel bearings made of full steel.