Pneumatic Radial Tire Reinforcement Layer Fatigue Resistance
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Solution Overview
Problem
Heavy-duty pneumatic radial tires with wide tread widths and low aspect ratios face reduced durability due to increased load on the belt layer, leading to fatigue rupture in the circumferential-direction reinforcement layer, particularly at the edge portions, where repetitive tensile and compressive strains cause failure.
Innovation Solution
A pneumatic radial tire design featuring a main belt layer with intersecting steel cords and a circumferential-direction reinforcement layer with varying steel cord elastic modulus, where the width of the reinforcement layer is between 0.5 to 0.9 times the main belt layer's width, and the elastic modulus in edge portions is set lower than in the center, to ease compressive strain and maintain reinforcing effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a circumferential-direction reinforcement layer is formed by winding steel cords in parallel to the tire circumferential direction, then the tread portion is provided with rigidity in the circumferential direction, but the steel cords are repetitively deformed when the tire is rolling so as to be likely to rupture due to fatigue
Solution Approach 1:
The patent applies local quality by making the steel cords in the edge portions of the circumferential-direction reinforcement layer have a smaller elastic modulus than those in the center portion. This creates a gradient structure where edge cords are more flexible and better at absorbing compressive strains during cornering, while center cords maintain high rigidity for circumferential strength. This resolves the contradiction by locally adapting cord properties to the specific stress conditions at different radial positions.
2Weight of moving object
If the tread width of a single tire is increased to replace dual tires, then weight is reduced and resource saving is achieved, but the load on the belt layer in the tread portion is significantly increased leading to reduced durability
Solution Approach 1:
The patent employs composite material principles by combining steel cords with different elastic moduli in a gradient arrangement within the circumferential-direction reinforcement layer. This composite structure allows the tire to handle increased loads from wider tread design while maintaining durability, as the varying cord stiffness creates a more uniform stress distribution across the belt layer under high-load conditions.
3Strength
If steel cords with high elastic modulus are used in the circumferential-direction reinforcement layer, then the reinforcing effect is maximized, but the steel cords are vulnerable to compression and likely to rupture due to fatigue in edge portions
Solution Approach 1:
The patent applies parameter changes by systematically varying the elastic modulus parameter of steel cords across the width of the circumferential-direction reinforcement layer. Center cords use high elastic modulus for maximum reinforcing effect, while edge cords use lower elastic modulus to reduce compressive strain vulnerability. This continuous or stepped parameter variation resolves the contradiction between reinforcing strength and compression resistance.
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 enhances the fatigue resistance of the circumferential-direction reinforcement layer, prevents separation failures in the edge portions, and improves the overall durability of the tire by uniformly distributing deformation across the tread width, even under high-speed and high-load conditions.
Implementation Method 1
steel cords have a high elastic modulus, and are thus vulnerable to compression. For this reason, when the steel cords are oriented in the tire circumferential direction as in the above-described circumferential-direction reinforcement layer, the steel cords are repetitively deformed when the tire is rolling so as to be likely to rupture due to fatigue
Data Source
AI summary
Provided is a pneumatic radial tire including a main belt layer and at least one circumferential-direction reinforcement layer, which are provided in the tread portion. The main belt layer includes two belt layers in which steel cords are disposed in a manner that the steel cords of a first one of the two belt layers intersect the steel cords of a second one of the two belt layers. In the circumferential-direction reinforcement layer, steel cords are disposed in a substantial tire circumferential direction. The ratio Wo/Wm of the width Wo of the circumferential-direction reinforcement layer to the maximum width Wm of the main belt layer is 0.5 to 0.9. The ratio Ee/Ec of the reinforcement-cord elastic modulus Ee of the steel cords in the edge portions of the circumferential-direction reinforcement layer to the reinforcement-cord elastic modulus Ec of the steel cords in the center portion of the circumferential-direction reinforcement layer is not less than (0.85−0.5 Wo/Wm) and not more than 0.8.