Tire Bead Apex Structure for Low Rolling Resistance and Durability
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Solution Overview
Problem
Tires face a challenge in reducing rolling resistance while maintaining durability, as thin sidewalls used to reduce rolling resistance lead to decreased stiffness and potential durability issues.
Innovation Solution
The tire design incorporates a pair of beads with a core and apex, featuring a carcass ply with turned-up portions, an apex body, a strip apex, and an intermediate apex. The intermediate apex is harder than the apex body and softer than the strip apex, strategically located to alleviate stiffness differences and distribute strain evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If thin sidewalls are used to reduce rolling resistance, then rolling resistance is reduced, but the stiffness of each side portion is decreased
Solution Approach 1:
The apex is segmented into three distinct components with different hardness levels: the apex body (softer), the strip apex (hardest), and the intermediate apex (medium hardness). This segmentation allows each component to perform its specific function - the softer apex body provides flexibility, the hardest strip apex maintains steering stability, and the intermediate apex bridges the stiffness difference to reduce strain concentration.
Solution Approach 2:
Different regions of the apex are given different hardness properties to optimize local performance. The strip apex at the outer end has the highest hardness to maintain steering stability where needed most, while the apex body has lower hardness for flexibility. The intermediate apex provides a gradual transition in hardness to distribute strain evenly across the region.
2Stability of the object's composition
If a strip apex is provided between the ply body and the apex body to maintain steering stability, then steering stability is improved, but strain is concentrated around the outer end of the apex body due to large stiffness difference, leading to decreased durability
Solution Approach 1:
The intermediate apex acts as a mediator between the strip apex and the apex body. It has medium hardness that is harder than the apex body but softer than the strip apex, creating a gradual stiffness transition. This intermediate layer distributes the strain that would otherwise concentrate at the interface between the hard strip apex and the softer apex body, thereby improving durability while maintaining steering stability.
3Stability of the object's composition
If the apex body is tapered outward to maintain good steering stability, then steering stability is maintained, but the stiffness difference between the apex body and the strip apex increases, causing strain concentration
Solution Approach 1:
The hardness parameter is changed across different apex components to optimize both steering stability and strain distribution. By introducing the intermediate apex with medium hardness between the hard strip apex and the softer apex body, the patent creates a gradual hardness gradient that reduces strain concentration while maintaining the steering stability provided by the hard strip apex.
Data Source
AI summary
Provided is a tire 2 that can achieve reduction of rolling resistance while reducing a decrease in durability to be small. An apex 32 of each bead 10 includes an apex body 48, a strip apex 50, and an intermediate apex 52. An inner end of the strip apex 50 is located between a ply body 38a of a carcass ply 38 and the apex body 48. An inner end of the intermediate apex 52 is located between the strip apex 50 and the apex body 48. An outer end of the apex body 48 is located between the inner and outer ends of the intermediate apex 52. The intermediate apex 52 is located between the inner and outer ends of the strip apex 50. The intermediate apex 52 is harder than the apex body 48, and the strip apex 50 is harder than the intermediate apex 52.