Heavy-Duty Tire Carcass Contour for Bead Durability and Low Rolling Resistance
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Solution Overview
Problem
Existing heavy duty tires face a challenge in improving bead durability without increasing rolling resistance, which affects fuel economy.
Innovation Solution
A heavy duty tire design featuring a specific carcass contour with a bulging and recessed shape, steel cords, and controlled ratios and angles, along with a reduced apex volume, to enhance bead durability without increasing mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of components in the bead portion is increased or additional components are added to improve bead durability, then bead durability is improved, but the mass of the tire increases
Solution Approach 1:
The invention changes the geometric parameters of the carcass contour, specifically creating an outwardly bulging curved portion with controlled ratios (axial distance ratio 0.70-0.85, radial distance ratio 0.15-0.22) to optimize stress distribution in the bead portion. This parameter optimization improves bead durability without adding mass by efficiently utilizing the existing structural geometry rather than increasing component thickness.
Solution Approach 2:
The invention applies curvature by designing the carcass contour with an outwardly bulging curved portion and inwardly recessed inversely curved portion. This curved geometry redistributes mechanical stresses more effectively in the bead region, enhancing durability through optimized stress flow patterns rather than through increased material quantity.
2Reliability
If the mass of the tire is increased to improve bead durability, then bead durability is improved, but the rolling resistance increases
Solution Approach 1:
The invention optimizes the carcass contour parameters (curved portion ratios, inflection point positions) to achieve the dual benefit of improved bead durability and reduced rolling resistance. The specific geometric parameters create a structure that is both mechanically stronger in the bead region and more efficient in terms of energy loss during rolling.
Solution Approach 2:
The curved portion of the carcass contour improves bead durability through optimized stress distribution while simultaneously reducing rolling resistance by creating a more efficient contact patch geometry and reducing hysteresis losses during the rolling cycle.
3Loss of energy
If the thickness of the apex is reduced to decrease tire mass, then rolling resistance is reduced, but bead durability may be compromised
Solution Approach 1:
The invention changes the apex thickness parameter to a specific range (0.30-0.45 times the total tire thickness at the inflection point) that balances durability and energy efficiency. This optimized thickness provides sufficient structural support for bead durability while minimizing the mass that would contribute to rolling resistance.
Solution Approach 2:
The invention applies local quality by creating a curved portion with specific geometric characteristics in the critical bead region. This localized geometric optimization ensures that the apex provides adequate durability where needed while maintaining overall mass efficiency for reduced rolling resistance.
Data Source
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AI summary
A contour CL of a carcass 12 includes a curved portion 44 and an inversely curved portion 46. A boundary between the curved portion 44 and the inversely curved portion 46 is an inflection point PV. Apart or an entirety of the curved portion 44 is represented by a first arc. A part or an entirety of the inversely curved portion 46 is represented by a second arc. The first arc and the second arc are tangent to each other at the inflection point PV. A ratio (X/W) of a distance X in an axial direction to a distance W in the axial direction is not less than 70% and not greater than 85%. A ratio (Y/H) of a distance Y in a radial direction to a distance H in the radial direction is not less than 15% and not greater than 22%.