Two-Layer Multi-Strand Tire Cord for Bending Endurance
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Solution Overview
Problem
Existing cords with a single layer of N=4 strands have a high structural elongation but require improvement in endurance criterion to enhance endurance performance while reducing shear in the polymer matrix, particularly for applications in crown plies like hooping crown plies.
Innovation Solution
A multi-strand cord with two layers of multi-strand elements, each comprising internal and external metal threads wound in a helix, optimized for endurance criterion and structural elongation, allowing for improved resistance to tensile stress and bending stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a single layer of N=4 strands is used, then structural elongation is high (2.8%), but endurance criterion is insufficient (3635 N×m/g)
Solution Approach 1:
The cord is divided into multiple independent strands (K≥2) within a single multi-strand element, rather than using a single solid core. This segmentation allows stress to be distributed across multiple threads, improving endurance criterion while maintaining flexibility and structural elongation comparable to single-layer designs.
Solution Approach 2:
The patent implements a nested structure where multiple strands are wound together to form multi-strand elements, which are then nested within a two-layer cord configuration. The internal layer contains multi-strand elements with K≥2 strands, while the external layer provides additional protection and structural support, creating a compact nested architecture that enhances endurance without excessive complexity.
2Reliability
If cord diameter is increased to improve endurance, then resistance to tensile stress improves, but shear in polymer matrix increases
Solution Approach 1:
The patent optimizes the parameters of individual metal threads including diameter (d1, d2, d3), length (L1, L2, L3), and winding pitch (p1, p2, p3) to achieve the desired balance. By carefully selecting these parameters, the cord achieves sufficient endurance performance while controlling the shear stress transmitted to the polymer matrix, particularly in crown ply applications.
Solution Approach 2:
Different regions of the cord have different structural characteristics. The internal layer multi-strand elements have specific strand configurations optimized for flexibility and elongation, while the external layer provides enhanced protection and structural support. This local differentiation allows the cord to achieve high endurance performance in critical regions while maintaining acceptable shear characteristics in the polymer matrix.
3Reliability
If metal thread mass is increased to improve endurance, then resistance to tensile stress improves, but cord stiffness increases reducing flexibility
Solution Approach 1:
Instead of using a single heavy metal thread, the patent segments the metal content into multiple thinner strands (K≥2) within each multi-strand element. This segmentation maintains the total metal mass for endurance performance while the distributed structure preserves flexibility and allows the cord to bend and flex more easily, which is critical for tyre building operations.
Solution Approach 2:
The cord combines metal threads with polymer matrix in a composite structure where the metal provides tensile strength and endurance while the polymer provides flexibility and shock absorption. The multi-strand configuration optimizes this composite effect by ensuring good interfacial bonding between the segmented metal strands and the polymer matrix, achieving both high endurance and maintained flexibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The multi-strand cord design enhances endurance performance by reducing stress levels and extending tire life, achieving a balanced trade-off between shear and endurance, while maintaining flexibility and structural integrity.
Implementation Method 1
each strand having at least two layers comprising: an internal layer made up of Q1 internal metal thread(s) of diameter d1, and an external layer made up of Q3 external metal threads of diameter d3 wound around the internal layer
Data Source
AI summary
The invention relates to a multi-strand cord (50) having two multi-strand layers, the cord (50) comprising:a cord internal layer (CI) made up of X=1 multi-strand element (M1) comprising K>1 strands (T1) wound in a helix about a main axis (A), each strand (T1) having at least two layers (C1, C3); anda cord external layer (CE) made up of Y>1 multi-strand elements (M2) wound around the internal layer (C1) of the cord, each multi-strand element (M2) comprising L>1 strands (T2) wound in a helix about a main axis (A′), each strand (T2) having at least two layers (C1′; C3′), with the multi-strand elements (M2) being wound in a helix about the main axis (A).The cord (50) has an endurance criterion V1=Δσ bending(M/D)<3000 N×m/g.The cord (50) has a structural elongation As such that As≥1.0%.