Pneumatic Tire Bead Core Segmentation for Rim Disengagement
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Solution Overview
Problem
Run-flat tires face challenges in achieving reduced weight while maintaining sufficient rim disengagement resistance and low engagement pressure, as the side reinforcing layer increases rim rigidity and rotational forces can cause rim disengagement, necessitating higher engagement pressure which compromises mountability.
Innovation Solution
The pneumatic tire features a bead core with a reduced number of bead wire winds near the vertex and a bottom side, a single-vertex external contour shape, and a carcass layer folded back to minimize rigidity and stress concentration, along with a core lower material compression ratio and specific taper angles to enhance rim disengagement resistance and reduce engagement pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the side reinforcing layer is added to increase rim disengagement resistance, then rim disengagement resistance is improved, but tire weight increases
Solution Approach 1:
The bead core is segmented into multiple regions with different bead wire winding densities: a first region with a higher number of winds and a second region with a lower number of winds. This segmentation allows different parts of the bead core to provide different levels of rigidity, reducing overall tire weight while maintaining sufficient rim disengagement resistance in critical areas.
Solution Approach 2:
Different regions of the bead core are designed with locally optimized properties: the first region (where rim disengagement resistance is critical) has higher bead wire winding density for increased rigidity, while the second region has lower winding density to reduce weight. This local quality differentiation resolves the contradiction between overall weight reduction and localized strength requirements.
2Strength
If engagement pressure is increased to prevent rim disengagement, then rim disengagement resistance is improved, but mountability deteriorates
Solution Approach 1:
The bead core structure is designed to be dynamically adaptive: during mounting, the lower bead wire winding density in the second region allows easier deformation and engagement with the rim, improving mountability. During operation, the higher winding density in the first region provides sufficient rigidity to prevent rim disengagement, effectively resolving the contradiction between mountability and rim disengagement resistance.
3Weight of moving object
If the bead core structure is simplified to reduce tire weight, then tire weight is reduced, but durability may deteriorate
Solution Approach 1:
The bead core employs local quality differentiation with higher bead wire winding density in the first region to ensure durability and structural integrity where needed, while using lower winding density in the second region to reduce overall weight. This localized optimization maintains tire durability while achieving weight reduction goals.
Data Source
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AI summary
A pneumatic tire including a side reinforcing layer in a sidewall portion, the pneumatic tire having an enhanced bead portion structure, reduced tire weight, and good engagement pressure and rim disengagement resistance. In a meridian cross-section, an external contour shape of the bead core (5) is a polygon formed by common tangent lines of a plurality of circumferential portions of a bead wire (5A), the external contour shape includes a single vertex (51) located toward the outside in a tire radial direction, an internal angle θ1 formed by two sides sandwiching the vertex (51) is an acute angle, a bottom side (52) of the external contour shape is inclined with respect to the tire lateral direction by from 2° to 9°, and the carcass layer (4) is bent and folded back along a circumference of the bead core (5) in a bead portion (3), a folded back portion (4B) of the carcass layer (4) from a position of an outer end of the bead core (5) in the tire radial direction extends toward a sidewall portion (2) in contact with a body portion (4A).