Airless Tire Tread Ring Recess for Lateral Load Durability
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Solution Overview
Problem
Conventional airless tires experience separation at the adhesion portion between the tread ring and spoke when large lateral forces are applied, leading to durability issues during sharp cornering or similar maneuvers.
Innovation Solution
The airless tire design features a recessed inner circumferential surface on the tread ring, which is recessed outward in the tire radial direction, distributing shearing forces and stress concentrations, and includes a spoke assembly with an outer cylindrical portion and projection matching the recess shape, ensuring even strain distribution and improved adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a straight cylindrical adhesion portion is used to connect the tread ring and spoke, then the structure is simple and easy to manufacture, but separation occurs at the adhesion portion when large lateral force is applied
Solution Approach 1:
The adhesion portion is designed with a curved cross-sectional shape instead of a straight cylindrical shape. The curvature allows the adhesion portion to better distribute lateral forces along its length, preventing stress concentration and separation at the connection between the tread ring and spoke, thereby improving durability while maintaining manufacturing simplicity
Solution Approach 2:
The adhesion portion has different geometric properties at different locations: it features a curved cross-section with varying radius along its length, creating different local stiffness and stress distribution characteristics. This local variation in geometry optimizes the force distribution pattern to prevent separation under lateral loading conditions
2Reliability
If the adhesion portion is made thicker to prevent separation, then durability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
By using a curved cross-sectional shape with optimized radius of curvature, the adhesion portion achieves improved force distribution and separation resistance without requiring increased thickness. The geometric curvature provides mechanical advantage in stress distribution, maintaining durability while keeping the structure simple and easy to manufacture
Data Source
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AI summary
An airless tire 1 includes a tread ring 2 having a ground-contact surface, a hub 3 disposed inward of the tread ring 2 in a tire radial direction and to be fixed to an axle, and a spoke 4 for connecting the tread ring 2 and the hub 3. The spoke 4 includes a plurality of spoke plates 5. The tread ring 2 has an inner circumferential surface 6 facing an inner side in the tire radial direction. A recess 7 is formed on the inner circumferential surface 6 so as to be recessed outward in the tire radial direction beyond a reference straight line BL connecting both ends in a tire axial direction of the inner circumferential surface 6 in a tire meridional cross-section. The recess 7 is formed over an entire range in the tire axial direction of the inner circumferential surface 6.