A Procedure for the Static Design of Activated Carbon-Filled Air Springs

Abstract

Compared to conventional coil springs in passenger vehicles, air springs allow the vehicle body to be leveled independently of the load while maintaining an almost constant spring rate. However, while vehicle masses are increasing, the usable installation space for the suspension and especially the body springs is constantly decreasing as battery packs for electric vehicles tend to become larger. This leads to a conflict of objectives in the design of the air spring, as a low spring rate is mainly achieved by a large air volume in the spring. By introducing adsorbents into the enclosed air volume, the spring rate can be lowered while maintaining the same installation space. Conversely, it is possible to reduce the required installation space while achieving the specified stiffness. This work provides an analytical approach for the determination of the spring stiffness of air springs filled with activated carbon. In contrast to complex numerical approaches based on substitute tests, the presented method provides a simple and application-oriented stiffness prediction for adsorbent-filled air springs under quasi-static excitation. With the validation measurements presented, this provides a robust design tool for industrial use.