Pneumatic Tire Bead Durability via Carcass Cord Spacing
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Solution Overview
Problem
Construction vehicle tires face increased fatigue fractures at the carcass ply fold-up portion due to large collapse-deformation and heavy loads, which reduces durability, especially with smaller rim flange heights and larger tire sizes, making it difficult to suppress compression strain and maintain bending rigidity.
Innovation Solution
The tire design features a carcass ply fold-up portion with a cord distance that gradually decreases from the bead core to a minimum value and then increases to a maximum value, with specific height ratios and internal pressure settings to control compression and shear strains, ensuring the carcass ply fold-up portion is positioned closer to the neutral axis of bending while maintaining adequate bending rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the carcass ply fold-up portion is disposed close to the carcass main body to suppress compression strain, then compression strain at the carcass ply fold-up portion is reduced, but shear strain of rubber between the carcass ply fold-up portion and the carcass main body increases, causing rubber separation
Solution Approach 1:
The patent applies local quality by creating a transitional zone between the carcass ply fold-up portion and the carcass main body. The cord distance is specifically controlled to gradually change from a first distance at the fold-up portion to a second distance at the main body, with the ratio between these distances falling within 0.5 to 2.0. This gradual transition locally modifies the structural properties to reduce shear strain concentration while maintaining compression strain suppression.
2Strength
If the carcass ply fold-up portion is disposed close to the carcass main body to suppress compression strain, then compression strain is reduced, but bending rigidity of the carcass ply fold-up portion deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the cord distance parameters between the carcass ply fold-up portion and the carcass main body. The first distance (at the fold-up portion) and second distance (at the main body) are optimized such that their ratio falls within 0.5 to 2.0. This parameter optimization allows the structure to maintain adequate bending rigidity while suppressing compression strain through the controlled gradual transition.
3Weight of moving object
If the tire size increases and rim flange height decreases to reduce tire weight, then tire weight is reduced, but collapse-deformation of the bead portion increases, facilitating fatigue fracture at the carcass ply fold-up portion
Solution Approach 1:
The patent applies local quality by creating a transitional zone between the carcass ply fold-up portion and the carcass main body. The cord distance is specifically controlled to gradually change from a first distance at the fold-up portion to a second distance at the main body, with the ratio between these distances falling within 0.5 to 2.0. This gradual transition locally modifies the structural properties to reduce shear strain concentration while maintaining compression strain suppression.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the optimal cord distance distribution before the tire undergoes collapse-deformation. The cord distances are designed in advance such that the ratio between the first distance (at the fold-up portion) and second distance (at the main body) falls within 0.5 to 2.0, creating a structural buffer that preliminarily reduces shear strain and prevents fatigue fracture under subsequent heavy loading conditions.
Data Source
AI summary
An of object of the present invention is to provide a pneumatic tire which exhibits improved durability of a bead portion due to further suppressing compression strain at a carcass ply fold-up portion and, in particular, suppressing fatigue fracture at the carcass ply fold-up portion. Cord distance between the carcass main body and the carcass ply fold-up portion gradually decreases from the bead core toward the outer side in the tire radial direction to reach the minimum value a, then gradually increases to the maximum value b; provided that height Hf of a flange of an application rim, measured from a base line of the application rim in a state where the tire is assembled with the rim and inflated at a prescribed internal pressure, is 1, heights HA and HB measured from the base line to the positions on the carcass main body corresponding to the minimum and the maximum values, respectively, and the maximum height HT of the tire satisfy relationship formulae below,HT≧8.001.26≦HA≦2.142.43≦HB≦3.75; anda value of ratio (b/a) of the maximum value b with respect to the minimum value a of distance between cords of the carcass main body and the carcass ply fold-up portion exceeds 1.00.