Pneumatic Tire Bead Durability via Segmented Carcass Ply Structure
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Solution Overview
Problem
Conventional tires with higher load indices (above 77) face challenges in enhancing the durability of bead portions under higher load and pressure conditions, where existing structures do not adequately address the need for improved durability.
Innovation Solution
A pneumatic tire design featuring a bias structure with at least three layers of carcass plies, including two turn-up plies folded around the bead cores and one down ply terminating on the outer side, along with strand bead cores arranged in six rows and four columns, and a cover member to prevent fretting and enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional carcass ply structures are used in tires with load index higher than 77, then the tire can be manufactured with standard structures, but the durability of bead portions deteriorates under higher load and pressure conditions
Solution Approach 1:
The carcass is divided into multiple layers with different configurations: inner carcass plies are wound up around bead cores while the outer carcass ply extends without being wound up. This segmentation allows each layer to perform specific functions - inner layers provide bead anchoring while the outer layer maintains case rigidity, thereby improving bead portion durability without requiring complete structural redesign
Solution Approach 2:
Different regions of the tire have different carcass ply configurations tailored to local requirements. The bead portion area has wound-up plies for anchoring, while the side wall and tread area has extending plies for rigidity. This local differentiation optimizes durability where needed without unnecessarily complicating the entire structure
2Reliability
If the outer carcass ply is wound up around the bead cores, then the bead portion durability is improved, but the manufacturing complexity and molding difficulty increase
Solution Approach 1:
The carcass plies are segmented into two groups: inner plies that are wound up around bead cores to improve durability, and the outer ply that extends without winding to simplify manufacturing. This segmentation allows the tire to achieve enhanced bead durability while maintaining ease of molding operation
Solution Approach 2:
Instead of winding up all carcass plies around the bead cores (excessive action), only the inner plies are wound up (partial action). This partial application of the winding configuration provides sufficient durability improvement while avoiding the manufacturing complexity that would result from winding all plies
Data Source
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Figure 3
AI summary
Provided is a pneumatic tire for two-wheeled motor vehicles in which the durability of bead portions is improved than in conventional tires. This pneumatic tire includes: a tread portion formed in an annular shape; side wall portions and bead portions, which continuously extend on the respective ends of the tread portion; a carcass 1 composed of at least three layers of carcass plies 1a, 1b and 1c which toroidally extend on the tire radial-direction inner side of the tread portion; a belt 2 composed of at least two belt layers 2a and 2b which are arranged on the tire radial-direction outer side of the carcass 1; and bead cores 3 embedded in the bead portions. In this pneumatic tire, the carcass plies 1a, 1b and 1c have a bias structure and include at least two layers of turn-up carcass plies 1a and 1b which are folded back around the bead cores 3, and at least one layer of down carcass ply 1c which is arranged on the tire radial-direction outer side of the turn-up carcass plies and terminated on the tire width-direction outer side of the bead portions without being folded back around the bead cores 3.