Pneumatic Tire Bead Core Tapered Shape Rim Disengagement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Pneumatic tires with side reinforcing layers on the sidewall face challenges in reducing weight while maintaining durability and preventing rim disengagement during run-flat conditions, as existing weight reduction methods compromise tire rigidity and increase the risk of rim disengagement.
Innovation Solution
The tire design incorporates a bead core with a specific shape and structure, including a carcass layer and side reinforcing layer, where the bead core has a tapered shape with a radially outward wedge shape, reducing the number of bead wire turns and optimizing the cross-sectional area to enhance rim disengagement resistance without increasing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a side reinforcing layer is provided on the sidewall portion to support load during puncture, then run-flat capability is improved, but tire weight increases due to increased thickness near the bead portion
Solution Approach 1:
The side reinforcing layer is designed with non-uniform thickness distribution, being thickest at the equatorial region and gradually thinning toward the bead portions. This local quality variation allows the layer to provide maximum support where needed (equatorial region for load bearing) while minimizing weight contribution near the bead portions, thus resolving the contradiction between run-flat capability and weight reduction.
2Reliability
If a side reinforcing layer is provided on the sidewall portion, then run-flat capability is improved, but rim disengagement resistance deteriorates due to increased rigidity around the rim flange contact portion
Solution Approach 1:
The side reinforcing layer's thickness is locally optimized to be thinner near the bead portions and rim flange contact areas, reducing excessive rigidity in these regions. This prevents the generation of rotational forces that could cause rim disengagement during run-flat traveling, while maintaining sufficient thickness at the equatorial region to support run-flat loads, thus resolving the contradiction between run-flat capability and rim disengagement resistance.
3Weight of moving object
If the bead core shape is modified to reduce weight by eliminating the bead filler, then tire weight is reduced, but rigidity near the bead portion deteriorates
Solution Approach 1:
The bead core is designed with a tapered shape that is wider at the equatorial region and narrower near the bead portions. This local variation in dimensions, combined with the optimized side reinforcing layer thickness distribution, concentrates the rigidity-providing structure where it is most needed (equatorial region for load bearing) while minimizing material usage near the bead portions, thus achieving weight reduction without sacrificing essential rigidity.
4Strength
If the bead core width is reduced to improve rim disengagement resistance, then rim disengagement resistance is improved, but tire durability deteriorates
Solution Approach 1:
The bead core employs a tapered width design with maximum width at the equatorial region and reduced width near the bead portions. This local quality differentiation allows the bead core to provide sufficient rim disengagement resistance at the equatorial region while maintaining adequate structural dimensions for durability. The optimized thickness distribution of the side reinforcing layer further complements this design by providing localized support where needed.
Data Source
AI summary
In a pneumatic tire including a side reinforcing layer, the maximum width W0 of a bead core and the widths W1, W2 of the bead core at innermost and outermost sides in the radial direction, respectively, satisfy W1>W2 and W2≤0.5×W0. W0 is toward the inside of the center of the bead core in the radial direction. A carcass is folded and curved along the bead core, and a folded back portion of the carcass extends toward the sidewalls while contacting a body of the carcass. A rubber occupancy ratio in a region formed by the body and the folded back portion of the carcass is 0.1% to 15%. The cross-sectional area S2 of a filler toward the outside of the carcass in the lateral direction, the hardness H2 of the filler, the cross-sectional area S1 of a side reinforcing layer and the hardness H1 of the side reinforcing layer satisfy 0.15≤(S2×H2)/(S1×H1)≤0.60.