Two-Layer Multi-Strand Cord for Tyre Reinforcement

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Solution Overview

Problem

Conventional multi-strand cords used in tyre reinforcement are ineffective against larger obstacles due to high shear stress, as they become sheared easily despite their stiffness, which leads to damage in the crown reinforcement of heavy industrial vehicle tyres.

Innovation Solution

A two-layer multi-strand cord design with specific helix angles and strand configurations, achieving a lower modulus value (50 GPa to 160 GPa) to hug obstacles rather than opposing deformation, reducing the risk of breakage and maintaining sufficient steering capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the cord stiffness is increased to resist deformation from obstacles, then the cord can better oppose small and medium obstacles, but the cord becomes more susceptible to shearing by larger obstacles

Engineering Contradiction:

Improveresistance to deformationVSAvoidresistance to shearing

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent changes the modulus parameter from high (>160 GPa) to low (50-160 GPa) range, transforming the cord's mechanical behavior from rigid to flexible. This parameter change allows the cord to hug larger obstacles without shearing while maintaining sufficient stiffness for small obstacles and steering capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Instead of making the cord stiffer to resist obstacles (conventional approach), the patent inverts the approach by making the cord more flexible. This allows the cord to adapt to obstacle shapes through hugging rather than rigid opposition, reducing shear stress and preventing breakage

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If the cord modulus is reduced to hug obstacles, then the risk of breakage from large obstacles is reduced, but the steering capability may be compromised

Engineering Contradiction:

Improveresistance to breakageVSAvoidsteering capability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent identifies and optimizes specific structural parameters (helix angles α, β, γ; number of strands J, L; thread diameters D1, D2) to achieve the target modulus range. These parameter changes enable the cord to maintain adequate steering capability while achieving the flexibility needed to hug obstacles and resist breakage

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11401656B2Two-layer multi-strand cords having very low, low and medium moduli

Publication Date: 2022.08.02 MICHELIN & CO (CIE GEN DES ESTAB MICHELIN)

AI summary

A two-layer multi-strand cord (60) comprises an internal layer (CI) of the cord made up of J>1 internal strands (TI) and an external layer (CE) of the cord made up of L>1 external strands (TE). The cord satisfies the relationship 100≤MC≤175, where MC=(J×MI+L×ME)/(J+L); MI=200×cos4(α)×[Q×(D1/2)2×cos4(β)+N×(D2/2)2×cos4(γ)]/[Q×(D1/2)2+N×(D2/2)2]; and ME=200×cos4(α′)×[Q′×(D1′/2)2×cos4(β′)+N′×(D2′/2)2×cos4(γ′)]/[Q′×(D1′/2)2+N′×(D2′/2)2], where D1, D1′, D2, D2′ are in mm, α and α′ are the helix angle of each internal and external strand (TI), β and β′ are the helix angle of each internal thread (F1, F1′), and γ and γ′ are the helix angle of each external thread (F2, F2′).