Pneumatic Tire Belt Structure for High-Speed Durability and Stability
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Solution Overview
Problem
Increasing the strength of steel cords in the belt ply of pneumatic tires to improve high-speed durability leads to increased rigidity, deteriorating road tracking ability and driving stability.
Innovation Solution
A pneumatic tire design with a belt layer having steel cords angled to the tire circumferential direction and a belt reinforcing layer with organic fiber cords in the circumferential direction, adhering to specific rigidity and load relationships represented by Expressions (I) and (II), balances high-speed durability with improved driving stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the strength of steel cords in the belt ply is increased to improve high-speed durability, then the rigidity of the belt layer increases, but the road tracking ability deteriorates and driving stability decreases
Solution Approach 1:
The belt structure is segmented into two distinct layers: a belt ply with steel cords for high-speed durability and a belt reinforcing layer with organic fiber cords for driving stability. This segmentation allows each layer to perform its specialized function without compromising the other, resolving the contradiction between durability and stability
Solution Approach 2:
The patent uses composite material construction with two different cord types (steel and organic fiber) in separate layers. The steel cords provide strength and durability at high speeds, while the organic fiber cords provide flexibility and road tracking ability, achieving both requirements simultaneously
2Strength
If the in-plane rigidity of the belt ply is increased to ensure high-speed durability, then the structural strength improves, but the road tracking ability deteriorates
Solution Approach 1:
Different regions of the belt structure have different rigidity characteristics. The belt ply has high in-plane rigidity (4.0 kN/inch or more) for structural strength, while the belt reinforcing layer has lower rigidity to maintain road tracking ability. This local differentiation of mechanical properties resolves the contradiction
Data Source
AI summary
A pneumatic tire 1 including a belt layer (20) having a belt ply (21) and a belt reinforcing layer (30) having belt reinforcing ply (31) in which organic fiber cords are arranged in a tire circumferential direction, in which the belt ply (21) has an in-plane rigidity of 4.0 [kN/inch] or more in a tire width direction, and A, B, C, and D satisfy relationships represented by the following Expression (I) and Expression (II),2.0≤C/(A×(90-B))Expression (I)Expression (II): 8.0≤D/(A×(90−B))≤30.0 where: A [N/inch] is a bending load per unit width of a sheet of the belt ply (21); B [deg] is a belt angle; C [N/25 mm] is a product of a load at 2% elongation of each organic fiber cord and the number of the organic fiber cords; and D [N/25 mm] is a product of a load at 5% elongation of the organic fiber cord and the number of the organic fiber cords.