Pneumatic Tire Bead Load Distribution via Carcass Contour
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Solution Overview
Problem
Pneumatic tires face durability issues due to edge damage (BEL) and increased load on the bead portion, leading to potential separation and reduced durability, which is exacerbated by weight increases from additional carcass plies or reinforcing layers to address these issues.
Innovation Solution
The tire design features a carcass with a turned-up portion between the first and second apexes, where the inner surface contour projects outward from a natural equilibrium shape curve, alleviating load on the bead portion and inhibiting belt movement, thus enhancing durability without adding weight or increasing rolling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the carcass projects outward of the natural equilibrium shape curve in the region from the vicinity of the maximum width position to the vicinity of each edge of the belt, then BEL is inhibited and belt durability is improved, but load on the bead portion is increased causing separation damage
Solution Approach 1:
The invention applies different geometric characteristics to different regions of the carcass cross-section. Specifically, the carcass contour is designed to project outward in the region from maximum width position to belt edge (to inhibit BEL) while maintaining a different profile in the bead region (to protect against separation). This localized differentiation of geometric properties resolves the contradiction by allowing each region to optimize for its specific functional requirement.
Solution Approach 2:
The invention transitions from considering only the radial dimension to incorporating the axial dimension in the carcass profile design. By defining the carcass contour in the radial-axial plane and specifying its relationship to the natural equilibrium shape curve, the invention uses dimensional geometry to simultaneously address both belt edge stability and bead portion load distribution, resolving the contradiction through spatial configuration.
2Strength
If additional carcass plies or reinforcing layers are added to improve bead portion durability, then bead strength is improved, but tire weight increases
Solution Approach 1:
Instead of changing the quantity of material (adding plies or layers), the invention changes the geometric parameters of the existing carcass structure. By modifying the carcass cross-sectional contour to project outward in specific regions, the invention achieves improved load distribution and bead portion durability through dimensional optimization rather than material addition, thereby avoiding weight increase.
3Strength
If additional carcass plies or reinforcing layers are added to improve bead portion durability, then bead strength is improved, but rolling resistance increases
Solution Approach 1:
The invention optimizes the geometric parameters of the carcass contour to achieve improved bead portion durability without adding material layers. By adjusting the cross-sectional shape and projection characteristics, the invention reduces energy loss through optimized structural efficiency, avoiding the increased rolling resistance that would result from additional plies or reinforcing layers.
Data Source
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Figure 2
AI summary
A tire having low weight, low rolling resistance, and excellent durability is provided. Each bead 10 of the tire 2 includes a first apex 30 and a second apex 32. A turned-up portion of a carcass ply passes between the first apex 30 and the second apex 32. In a state where the internal pressure of the tire 2 is set to be not less than 8% and not greater than 15% of a normal internal pressure, when a circular arc that has a center on a reference line L passing through a maximum width position P of a carcass 12 and extending in an axial direction and passes through an axially outer edge Q of a portion where the carcass 12 and the belt 14 are in contact with each other and a position R, which is a position on an inner surface of the carcass 12 and to which a distance in a radial direction from a bead base line is 1.5 times of a distance in the radial direction from the bead base line to an edge 36 of the first apex 30, is defined as a reference circular arc C0, a contour of the inner surface of the carcass 12 is located outward of the reference circular arc C0, between the position P and the position Q.