Tire Reinforcing Layer Stiffness Balance for Ride and Durability
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Solution Overview
Problem
Existing wide heavy-duty tires face issues with ride quality and durability due to significant differences in outer diameter growth rates between the center and edge portions of the tread, leading to potential cord breakage and reduced performance.
Innovation Solution
A tire design incorporating a circumferential reinforcing layer with a wound bundle of two or more parallel cords and a cap tread, where the ratio of bundle stiffness to tread portion stiffness is maintained at 10.6 or lower, enhancing durability and ride quality by reducing stress concentration and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a circumferential reinforcing layer with steel cords is added to reduce outer diameter growth difference, then structural stability is improved, but ride quality and durability deteriorate due to stress concentration and cord breakage
Solution Approach 1:
The patent applies local quality by creating a tread portion with different stiffness characteristics than the circumferential reinforcing layer. Specifically, the tread portion has a lower stiffness (S/G ≤ 10.6) compared to the reinforcing layer, allowing the tread to flex and absorb stress while the reinforcing layer maintains overall structural stability. This local differentiation prevents stress concentration at the interface and reduces cord breakage.
Solution Approach 2:
The patent changes the stiffness parameter of the tread portion by controlling the ratio S/G to be 10.6 or lower. This parameter adjustment allows the tread to have sufficient flexibility to accommodate road irregularities and reduce vibration, while the circumferential reinforcing layer maintains its high stiffness for structural support. The optimized stiffness ratio prevents excessive stress transfer to the cords.
2Reliability
If the tread portion stiffness is increased to improve durability, then cord breakage resistance is improved, but ride quality deteriorates due to increased vibration and harshness
Solution Approach 1:
The patent optimizes the stiffness parameter by setting S/G ≤ 10.6, which balances durability and ride quality. This parameter change ensures the tread portion is stiff enough to prevent cord breakage and improve durability, while remaining flexible enough to absorb vibrations and maintain comfortable ride quality. The specific threshold of 10.6 represents an optimized balance point.
Solution Approach 2:
The patent creates a composite structure combining the circumferential reinforcing layer with the tread portion, where each layer has different stiffness characteristics. The reinforcing layer provides high stiffness for structural integrity, while the tread portion with optimized stiffness (S/G ≤ 10.6) provides flexibility for ride comfort. This composite approach allows both durability and ride quality to be improved simultaneously.
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 tire design improves ride quality and durability by minimizing cord breakage and stress concentration, ensuring consistent performance even under rough road conditions.
Implementation Method 1
provided that the cords each have a flexural stiffness F (cm × g); the parallel cords of a bundle consist of a number N (number) of cords; the circumferential reinforcing layer has a bundle stiffness S (cm × g × number) defined by F × N
Implementation Method 2
the cap tread includes a rubber composition having a complex modulus of elasticity E (MPa) as measured at a temperature of 70°C, an initial strain of 10%, a dynamic strain of ± 1%, a frequency of 10 Hz, and elongation mode
Implementation Method 3
the tread portion has a stiffness G (N/mm) defined by E × D, the tire has a ratio of the bundle stiffness S of the circumferential reinforcing layer to the stiffness G of the tread portion, S/G (10g × mm 2
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
Provided is a tire with excellent overall performance in terms of ride quality and durability. The tire includes a circumferential reinforcing layer including a wound bundle of two or more parallel cords and a cap tread, wherein, provided that the cords each have a flexural stiffness F (cm·g); the parallel cords consist of a number N (number) of cords; a tread portion has a thickness D (mm) on a straight line extending from an edge of the circumferential reinforcing layer in a tire width direction to a surface of the tread portion; the cap tread includes a rubber composition having a complex modulus of elasticity E (MPa) as measured at a temperature of 70°C, an initial strain of 10%, a dynamic strain of ± 1%, a frequency of 10 Hz, and elongation mode; the circumferential reinforcing layer has a bundle stiffness S (cm·g·number) defined by F × N; and the tread portion has a stiffness G (N/mm) defined by E × D, the tire has a ratio of the bundle stiffness S of the circumferential reinforcing layer to the stiffness G of the tread portion, S/G (10 g·mm2·number/N), of 10.6 or lower.