Study on clarification of the mechanism for tire force generated in airless tire during rolling motion

In recent years, the research on airless tire (Non-pneumatic tire, NPT) for passenger cars has received extensive attention. The background to this is the development of autonomous driving technology. Autonomous driving of Level 4 and above is un-manned driving, so it is more important to reduce the frequency of maintenance due to accidental failures, and punctureless airless tires are expected as tires for autonomous driving vehicles. Rolling resistance of tires is a highly important property for tire development. The reduction of rolling resistance of tires has become more significant in the tire industry, because it has close relation to the fuel consumption efficiency. As for conventional pneumatic tire, the rolling resistance is mainly generated by energy loss of tire components during tire deformation and it is well known that to reduce the rolling resistance, tanδ of rubber should be decreased. The purpose of this study is to clarify the contributing factors of airless tires to rolling resistance. As a result of measuring the tire force generated by a rolling experiment using a scale model airless tire, it was confirmed that the wheel load fluctuated impulsively. Therefore, we observed the tire deformation during rolling with a high-speed video camera and clarified the mechanism of tire force generation.