Pneumatic Tire Belt Layout for Crack-Resistant High-Speed Durability
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Solution Overview
Problem
Conventional pneumatic tire designs face challenges in balancing vehicle movement performance and durability, particularly due to high rigidity leading to failures like crack development and separation at the end portions of the belt in the tire width direction, which are exacerbated at high speeds.
Innovation Solution
A pneumatic tire configuration featuring a pair of bead portions, a carcass with folded-up plies, and multiple inclined belt layers where the carcass and belt cords cross each other in the same direction, with specific inclination angles and widths to enhance durability and movement performance by managing in-plane rigidity and overlap widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rigidity of the belt is heightened by using hard materials or increasing the number of belt cords, then vehicle movement performance is improved, but failures such as crack development and separation easily occur in the end portion of the belt in the tire width direction
Solution Approach 1:
The patent applies different rigidity characteristics to different regions of the belt structure. The belt layers have higher rigidity in the central region for vehicle movement performance, while the end portions are designed with lower rigidity to prevent crack development. This is achieved by controlling the number of belt cords and their arrangement density in different width-direction positions, creating a gradient rigidity distribution that resolves the contradiction between overall strength and local durability.
Solution Approach 2:
The belt structure is segmented into multiple independent belt layers with different cord arrangements. Each layer can deform independently to some extent, and the layered structure allows stress distribution. The end portions of different layers are positioned at different widths, so when cracking occurs in one layer, it does not necessarily propagate to other layers, preventing catastrophic failure and improving overall reliability.
2Reliability
If the inclination angle of the inclined belt layer is optimized to suppress distortion around the end portion, then durability is improved, but vehicle movement performance may decrease
Solution Approach 1:
Different inclination angles are applied to different regions of the belt layers. The central portions use steeper inclination angles for optimal vehicle movement performance and cornering characteristics, while the end portions use shallower inclination angles to reduce distortion and prevent cracking. This spatial variation in inclination angle resolves the contradiction between movement performance and durability.
Solution Approach 2:
The patent introduces the tire width direction as an additional dimension for optimizing belt layer configuration. Instead of using a single inclination angle for the entire belt width, the inclination angle is optimized independently for the central region and end regions. This dimensional approach allows simultaneous optimization of both vehicle movement performance (central region) and durability (end regions) without compromise.
3Reliability
If a belt reinforcement layer is added to cover the end portions of inclined belt layers, then durability is improved, but the reinforcement layer lacks binding force in the tire width direction when core failure occurs
Solution Approach 1:
The belt reinforcement is segmented into multiple layers with different orientations and functions. The cap layer provides circumferential reinforcement, while additional belt layers provide width-direction support. This multi-layer segmented reinforcement system ensures that when failure occurs in one layer, other layers maintain structural integrity and provide continued binding force in the tire width direction.
Solution Approach 2:
The belt structure uses composite construction with multiple material types and orientations. Steel cords are embedded in rubber matrices, and multiple cord layers are stacked with different orientations. This composite structure provides both the needed binding force in the width direction and the flexibility to accommodate thermal and mechanical stresses, resolving the contradiction between reinforcement strength and flexibility.
Data Source
Figure 1
Figure 2~3
AI summary
Provided is a pneumatic tire comprising a pair of bead portions, a carcass including one or more carcass plies, and a belt including two or more inclined belt layers, and an end of a carcass folded-up portion of the carcass ply located on an outermost side of the tire in the carcass folded-up portion is located in a tire width direction inside an end in the tire width direction of the inclined belt layer on an outermost side in the tire radial direction, in the tire radial direction between a carcass main body portion and the inclined belt layer on an innermost side in the tire radial direction. A carcass cord in the carcass folded-up portion of the carcass ply located on the outermost side of the tire in the carcass folded-up portion and a belt cord of the inclined belt layer on the outermost side in the tire radial direction cross each other to be inclined in the same direction in a tire circumferential direction as being from one side toward the other side in the tire width direction, a difference in inclination angle is 30° or less, a width in the tire width direction of the inclined belt layer on the outermost side in the tire radial direction is larger than a width in the tire width direction of the inclined belt layer on the innermost side in the tire radial direction, and in-plane rigidity per unit width of the inclined belt layer on the innermost side in the tire radial direction is higher than in-plane rigidity per unit width of the inclined belt layer on the outermost side in the tire radial direction.