A Full-System Approach to Maximise Energy Efficiency of a Wheel Bearing 2020-01-1631
Environmental sustainability is morphing Automotive technical development strategies and driving the evolution of vehicles with a speed and a strength hardly foreseeable a decade ago. The entire vehicle architecture is impacted, and energy efficiency becomes one of the most important parameters to reach goals, which are now not only market demands, but also based on regulatory standards with penalty consequences. Therefore, rolling drag from all bearings in multiple rotating parts of the vehicle needs to be reduced; wheel bearings are among the biggest in size regardless of the powertrain architecture (ICE, Hybrid, BEV) and have a significant impact.
The design of wheel bearings is a complex balance between features influencing durability, robustness, vehicle dynamics, and, of course, energy efficiency. Whereas the driving efficiency and durability have always been main drivers for wheel hub designs, the upcoming development of BEVs, which use large battery packs, has introduced additional needs for compactness and increased carrying capacity. The ability to extend the range of such electric powered vehicles is much more stringent than for ICEs and Hybrids, and, they still require weight and friction reductions.
The keys to an optimum design are:
1. Ability to optimize setup within the given performance requirements
2. Full system approach: reducing friction from all the single components and functions within a wheel hub unit, including the integration of the wheel bearing into the corner layout
In this paper, an optimization strategy for the bearing design will be described, focusing on design approach, calculation tool development, interaction between parameters, and criteria selection for best configuration versus desired output.
The second part of the paper will focus on rolling surface characteristics and cage design for reduced friction.
The work presented will demonstrate how it is possible, through a full system approach, to achieve a significant decrease in wheel bearing friction without compromising the overall functional requirements, and, finally, to contribute to a lower environmental impact of the vehicle.
Paolo Re, Francesco Lamboglia, Giorgio Missiaggia