Tyre Bead Core and Apex Rubber Layout for Carcass Cord Protection
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Solution Overview
Problem
In pneumatic tyres, carcass cords often suffer damage or breakage due to contact with bead cores when they rotate under standard load conditions, leading to reduced bead durability.
Innovation Solution
The design includes bead cores with an inner surface inclined at 20 degrees plus/minus 2 degrees to the tyre axial direction, paired with bead apex rubbers having a first rubber portion covering the bead core circumference and a second rubber portion tapering outward, where the first rubber portion is harder and larger in size to minimize contact and absorb shear strain, thereby reducing damage to the carcass cords.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bead core has a radially inner surface inclined at 20 degrees with respect to the tyre axial direction, then bead durability is improved, but carcass cords come into contact with and rub against the bead cores causing damage or breakage
Solution Approach 1:
A bead apex rubber is introduced as an intermediary component between the bead core and the carcass cord. This rubber portion covers the apex of the bead core and prevents direct contact between the carcass cord and the rotating bead core, thereby eliminating the harmful friction and damage to the carcass cord while maintaining the beneficial bead durability improvement from the inclined bead core surface
Solution Approach 2:
The bead apex rubber is positioned in advance at the apex region of the bead core to provide protective cushioning before any contact between the carcass cord and bead core can occur. This preventive measure ensures that the carcass cord is shielded from damage during the rotation of the bead core under load
Data Source
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AI summary
A pneumatic tyre includes a pair of bead portion 4, a pair of bead cores 5, a carcass 6 extending between the pair of bead cores 5, and a pair of bead apex rubbers. Each bead core 5 includes a core inner surface on an inner side in the tyre radial direction of the bead core 5. In a pre-assemble state, each core inner surface has an angle of 20 degrees plus/minus 2 degrees to the tyre axial direction, and is inclined outwardly in the tyre radial direction toward an outer side in the tyre axial direction. The bead apex rubber includes a first rubber portion 10 arranged so as to cover a circumference of the bead core 5 and having a circular or substantially elliptical outline, and a second rubber portion 11 tapering outwardly in the tyre radial direction from the first rubber portion 10. The first rubber portion 10 is greater in hardness than the second rubber portion 11.