Run-Flat Tire Sidewall Structure for Ride Comfort and Durability
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Solution Overview
Problem
Run flat tires with side-reinforcing rubber experience a decrease in ride comfort due to an increase in the vertical spring coefficient.
Innovation Solution
The tire design incorporates a low elastic modulus portion in the side-reinforcing rubber, located in specific areas of the tire cross-section, and a high crack-resistant inner layer rubber to reduce bending rigidity and enhance durability while maintaining ride comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If side-reinforcing rubber with high elastic modulus is used to ensure run-flat durability, then run-flat durability is improved, but ride comfort deteriorates due to increased vertical spring coefficient
Solution Approach 1:
The side-reinforcing rubber is designed with non-uniform thickness: thicker at the bead portion (higher elastic modulus region) to ensure run-flat durability and load support, and thinner at the equatorial portion (lower elastic modulus region) to reduce vertical spring coefficient and improve ride comfort. This local variation in thickness creates different mechanical properties in different regions of the same component.
Solution Approach 2:
The side-reinforcing rubber is segmented into two functional regions based on thickness: a bead portion with greater thickness for structural support and run-flat capability, and an equatorial portion with lesser thickness for ride comfort. This segmentation allows each region to optimize its performance for its specific function.
2Strength
If side-reinforcing rubber with high elastic modulus is used to support load during run-flat driving, then load support capability is improved, but vertical spring coefficient increases causing ride discomfort
Solution Approach 1:
The side-reinforcing rubber exhibits local quality variations through thickness differentiation: the bead portion has greater thickness providing high load support capability during run-flat driving, while the equatorial portion has lesser thickness reducing the vertical spring coefficient to maintain ride comfort during normal driving conditions.
3Ease of manufacture
If uniform thickness side-reinforcing rubber is used, then manufacturing is simplified, but run-flat durability and ride comfort cannot be simultaneously optimized
Solution Approach 1:
Rather than using uniform thickness, the invention applies local quality by varying the thickness of the side-reinforcing rubber: greater thickness at the bead portion for run-flat durability and lesser thickness at the equatorial portion for ride comfort. This resolves the contradiction by accepting increased manufacturing complexity to achieve optimized performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design maintains run-flat durability and reduces ride discomfort, without increasing weight or impairing fuel economy, by moderating the elastic modulus and tension of the side-reinforcing rubber and adding a crack-resistant inner layer.
Implementation Method 1
a low elastic modulus portion in the side-reinforcing rubber, located in specific areas of the tire cross-section
Implementation Method 2
a high crack-resistant inner layer rubber to reduce bending rigidity and enhance durability
Data Source
Figure 1
Figure 2
AI summary
The run flat tire according to this disclosure comprises a tread portion, sidewall portions, bead portions, a side-reinforcing rubber having a crescent-shaped cross section, and a carcass. A part of the side-reinforcing rubber is a low elastic portion with a lower elastic modulus than other portion, and the low elastic portion is located in an area, in the tire radial direction, of 50% or more and 80% or less of the tire cross-sectional height from the bead baseline. In a reference condition, an elastic modulus of the low elastic portion is 80% or less of an elastic modulus of the other portion. When the maximum thickness of the low elastic portion, measured in the direction of a perpendicular line from the carcass down to the tire inner surface, is t1 and the thickness of the other portion, measured in the direction of the perpendicular line, is t2, the ratio t1/t2 is 0.2 or more and 3 or less. The tire maximum width in the reference condition is the center value or more and the upper limit or less of the tire maximum width specified in the standard, and the tire maximum width position in the reference condition is located at the position, with a distance of more than 50% of the tire cross-sectional height, outward in the tire radial direction from the bead baseline.