Heavy-Duty Tire Bead Reinforcement for Lower Weight and Durability
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Solution Overview
Problem
Heavy duty tires face challenges in achieving weight reduction while maintaining good durability, particularly due to the concentration of strain and shear forces at the bead portions, leading to issues like ply turn-up loosening (PTL) and loosening between the fiber reinforcement layer and the chafer.
Innovation Solution
A heavy duty tire design featuring a single fiber reinforcement ply composed of organic fiber cords, positioned axially outward of the turned-up portion, with a softer sidewall than the chafer, and a specific boundary configuration to alleviate shear strain, reducing the risk of loosening and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple fiber reinforcement plies are used to prevent loosening and improve durability, then reliability is improved, but weight increases
Solution Approach 1:
The invention changes the material parameter from steel cords to organic fiber cords in the single ply reinforcement layer. This material substitution maintains the necessary mechanical strength and durability while significantly reducing the weight of the tire, resolving the contradiction between reliability and weight.
Solution Approach 2:
The invention uses composite material construction with a single ply of organic fiber reinforcement cords combined with the chafer and sidewall structure. This composite approach achieves the required durability through optimized material composition and structural integration rather than relying on multiple heavy plies.
2Weight of moving object
If a single fiber reinforcement ply is used to reduce weight, then weight is reduced, but reliability deteriorates due to loosening from shear strain
Solution Approach 1:
The invention applies local quality by positioning the single fiber reinforcement layer specifically in the bead portion where it is most needed to resist shear strain and prevent loosening. The organic fiber cords are arranged to provide targeted reinforcement at the critical interface between the sidewall and chafer, ensuring durability is maintained locally where the highest stress occurs.
Solution Approach 2:
The single ply of organic fiber reinforcement cords acts as an intermediary element between the sidewall and the chafer. This intermediate layer distributes and mitigates the shear strain that would otherwise cause loosening, while its organic fiber composition keeps the overall weight low. The intermediary structure prevents direct stress concentration between the rigid chafer and the softer sidewall.
3Strength
If the chafer is made harder to resist rim contact forces, then strength is improved, but object-generated harmful factors increase due to chafer cracking and rim chafing
Solution Approach 1:
The invention changes the hardness parameter of the chafer by formulating it with specific rubber compounds and additives that provide optimal balance between strength and flexibility. The chafer is made sufficiently strong to resist rim contact forces while maintaining enough elasticity to avoid brittle cracking and reduce chafing on the rim surface.
Solution Approach 2:
The invention applies local quality by creating a gradient in material properties within the chafer structure. The outer surface of the chafer that contacts the rim is formulated with different properties than the inner layers, providing a softer contact surface that reduces chafing while maintaining overall structural strength. This localized property variation prevents harmful cracking and chafing while preserving necessary strength.
Data Source
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AI summary
Provided is a heavy duty tire 2 that can achieve weight reduction while maintaining good durability. The tire 2 includes a carcass 12, a pair of sidewalls 6, a pair of chafers 8, and a pair of reinforcement layers 22. The carcass 12 includes a carcass ply 38. The carcass ply 38 includes a ply body 40 and a pair of turned-up portions 42. Each of the reinforcement layers 22 includes a fiber reinforcement layer 48. The fiber reinforcement layer 48 is composed of one fiber reinforcement ply 52. Each sidewall 6 and each chafer 8 are joined at a boundary 54 extending between a radially inner end SU of the sidewall 6 and a radially outer end CG of the chafer 8. The chafer 8 covers the radially inner end SU of the sidewall 6. The sidewall 6 is softer than the chafer 8.