Heavy-Duty Tire Carcass Curvature for Bead Strain Reduction
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Solution Overview
Problem
Heavy duty tires face a challenge in improving bead durability without increasing rolling resistance, which is essential for better fuel economy and environmental considerations.
Innovation Solution
A heavy duty tire design featuring a pair of beads with a carcass extending between them, including a core and apex, with a specific contour and structure that incorporates steel cords and a production method involving a pressurized and heated mold process 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 defining precise ratios for the position of the inflection point (axial distance ratio 70-85% and radial distance ratio 15-22%). This parameter optimization allows the carcass to efficiently bear and distribute loads, improving bead durability without requiring additional material or increased mass.
Solution Approach 2:
The invention utilizes curved geometry in the carcass contour with a specifically designed inflection point that creates an outwardly bulging curved portion and an inwardly recessed inversely curved portion. This curvature design optimizes the structural efficiency of the carcass, enabling it to withstand bead portion loads effectively while maintaining lower mass compared to straight or overly thick designs.
2Reliability
If the mass of the tire is increased to improve bead durability, then bead durability is improved, but rolling resistance increases
Solution Approach 1:
By optimizing the carcass contour parameters (inflection point position ratios and curvature characteristics), the invention achieves improved bead durability through enhanced structural efficiency rather than increased mass. This prevents the increase in rolling resistance that would otherwise result from added weight, thereby reducing energy loss and improving fuel economy.
3Reliability
If the thickness of the apex is increased to reduce strain on the bead portion, then bead durability is improved, but the mass of the tire increases
Solution Approach 1:
The invention applies local quality optimization by concentrating structural reinforcement precisely where needed through the strategically positioned inflection point and curved contour design. This localized structural optimization reduces strain on the bead portion and improves durability without requiring uniform increases in thickness across the entire tire, thereby avoiding unnecessary mass increase.
Data Source
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. A part 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%.