Pneumatic Tire Bead Core Layout for Carcass Cord Durability
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Solution Overview
Problem
Existing pneumatic tires face durability issues at the bead portion due to stress concentration and rubbing between the bead core corners and the carcass, particularly in vehicles requiring high traction, leading to carcass cord breakage.
Innovation Solution
A pneumatic tire design featuring a bead core with a polygonal cross-section, specifically an octagonal shape, and a carcass structure with aligned bead wires and controlled misalignment, along with a carcass folded back over the bead core, to enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a bead core with a polygonal cross-section is used to maintain structural integrity, then the bead core provides sufficient strength, but stress concentration occurs at the corners causing carcass cord breakage
Solution Approach 1:
The patent applies curvature by rounding the corner portions of the bead core cross-section. Instead of sharp corners in the polygonal shape, the corner portions are formed with a curved surface having a specific radius of curvature. This curvature eliminates stress concentration at the corners while maintaining the overall polygonal structure for structural integrity, preventing carcass cord breakage.
2Reliability
If a nylon cover is wound around the bead core to protect against stress concentration, then some protection is provided, but the distance between the corner and carcass is insufficient causing rubbing and cord breakage
Solution Approach 1:
The patent extracts and eliminates the nylon cover component entirely. Instead of using a separate protective layer, the solution is achieved by modifying the bead core geometry itself through rounded corners. This simplifies the structure by removing the nylon cover while still providing the necessary protection against stress concentration and rubbing.
3Force
If the bead core has a flat shape in the tire meridian cross-section for traction performance, then traction is improved, but the corner and carcass rubbing increases leading to cord breakage
Solution Approach 1:
The patent applies local quality by differentiating the geometry of different portions of the bead core. The side portions are maintained with a relatively flat shape to provide good traction, while the corner portions are specifically rounded with a controlled radius of curvature. This local differentiation allows the flat sides to provide traction while the rounded corners prevent stress concentration and rubbing.
Data Source
AI summary
A pneumatic tire includes a bead core including end portions in a width direction formed as a vertical line along a radial direction, the vertical line has a length of 31% to 45% of a core height, in two adjacent bead core layers of first, second and third layers of the bead core, the number of bead wires in the radially outer layer is larger by two or more than the number of bead wires in the radially inner layer, and a misalignment amount between bead wires located at an end portion on one side in the width direction is one-half of the bead wire, and a side on which the one-half misalignment amount between the bead wires in the first and second layers is opposite in the width direction to a side of the one-half misalignment amount between the second and third layer bead wires.