Bead Core and Cord Layout for Tire Ride Comfort and Steering Stability
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Solution Overview
Problem
Pneumatic radial tires face a conflict between achieving ride comfort and steering stability, with existing designs experiencing excessive elongation constraint in the bead reinforcement layer, leading to high vertical spring coefficients that deteriorate ride comfort.
Innovation Solution
The pneumatic tire employs a bead core with a reduced maximum width to height ratio and uses non-linear elastic modulus cords with low elastic modulus in the low-strain region and high elastic modulus in the high-strain region, arranged between the carcass ply and bead filler or outside the folding-over portion ply, to balance vertical and lateral rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a reinforcing layer with cord angle perpendicular to carcass cord is used, then steering stability is improved, but ride comfort deteriorates due to high vertical spring coefficient
Solution Approach 1:
The patent applies different cord angles in different regions: the reinforcing layer has a cord angle of 0-15 degrees in the central portion (improving steering stability) while the sidewall portion has a cord angle of 45-90 degrees (improving ride comfort by reducing vertical spring coefficient). This local differentiation resolves the contradiction between steering stability and ride comfort.
Solution Approach 2:
The reinforcing layer is segmented into distinct regions (central portion and sidewall portion) with different cord angle characteristics. This segmentation allows each region to independently optimize for its specific function, with the central portion providing steering stability and the sidewall portion providing ride comfort.
2Weight of moving object
If bead core width is reduced, then tire weight is reduced, but structural strength may be compromised
Solution Approach 1:
The bead core uses composite construction with steel cords arranged in specific patterns (radial and circumferential directions) within the bead core structure. This composite arrangement provides high strength-to-weight ratio, allowing reduced bead core width while maintaining structural strength.
Solution Approach 2:
The bead core adopts a curved, rounded cross-sectional shape rather than a flat or rectangular form. This spheroidal geometry distributes stresses more evenly throughout the structure, maintaining strength while reducing material requirements and overall weight.
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
This design achieves both high ride comfort and steering stability by reducing the vertical spring coefficient during straight running and increasing the lateral spring coefficient during cornering, enhancing the tire's overall performance.
Implementation Method 1
Reinforcement using a cord with low elastic modulus in a low-strain region at or below an inflection point and high elastic modulus in a high-strain region above the inflection point suppresses an increase in rigidity in a low elastic modulus region for vertical rigidity, which is related to the ride comfort, while high rigidity is obtained in a high elastic modulus region for lateral rigidity, which is related to the steering stability
Data Source
Figure 1
Figure 2A~3
Figure 4~5
AI summary
In a pneumatic tire (1) that achieves both ride comfort and steering stability at a high level, a bead core (5) has a ratio of the maximum width of the core to the height of the core of 0.8 or less in a cross-section in the tire width direction. A cord (9) is provided in at least one part from a bead portion (2) to a sidewall portion (3) at an angle of 0 to 10° with respect to the circumferential direction. The cord (9) has an inflection point in a stress-strain curve, with a low elastic modulus in a low-strain region at or below the inflection point, and a high elastic modulus in a high-strain region above the inflection point.