Tyre Carcass Reinforcement Cords with Variable Rubber Thickness
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Solution Overview
Problem
Heavy-duty tires for worksite applications face issues with endurance due to severe rolling conditions, leading to fatigue-fretting and corrosion of carcass reinforcement cords, which results in reduced lifespan and increased manufacturing costs, particularly due to the need for thicker rubber layers for sealing and the risk of buckling under under-inflated conditions.
Innovation Solution
The tire design incorporates carcass reinforcement cords with a permeability test flow rate of less than 10 cm³/min, featuring a reduced thickness of the rubber compound between the tire cavity and the reinforcement elements, and a localized increase in rubber thickness to combat buckling and curvature stresses, while using crosslinkable rubber compositions and specific cable constructions to enhance durability and reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the rubber layer forming the inner wall of the tire cavity is increased to minimize permeability, then the airtightness and resistance to corrosion is improved, but the manufacturing cost increases
Solution Approach 1:
The patent applies local quality by varying the rubber layer thickness in different zones of the tire cavity. The inner wall features localized thickening at specific positions (such as near the bead areas and crown regions) where permeability and corrosion resistance are most critical, while maintaining thinner sections in areas where structural support is already provided by the reinforcement cords. This selective thickening approach achieves the required airtightness and corrosion protection while minimizing the overall rubber material usage and manufacturing cost.
2Strength
If the diameter of wires in carcass reinforcement cables is reduced to improve flexibility and bending endurance, then the flexibility and bending resistance is improved, but the resistance to fatigue-corrosion deteriorates
Solution Approach 1:
The patent employs composite materials by combining multiple wire diameters and material compositions within the carcass reinforcement cable structure. The cable incorporates a core of finer wires optimized for bending flexibility, surrounded by an outer layer of coarser wires providing enhanced corrosion resistance. This composite cable structure integrates the advantages of both wire types, achieving optimal balance between bending endurance and fatigue-corrosion resistance.
Solution Approach 2:
The patent applies parameter changes by systematically varying wire diameter, material composition, and structural configuration of the carcass reinforcement cables. Different cable constructions with specific wire diameter ranges (0.15-0.30mm) and material properties are selected for different tire zones based on the specific mechanical and environmental demands, optimizing the balance between flexibility and corrosion resistance.
3Ease of manufacture
If the thickness of the rubber compound between the tire cavity and reinforcement elements is reduced, then the manufacturing cost is reduced, but the risk of buckling under under-inflated conditions increases
Solution Approach 1:
The patent applies local quality by implementing variable rubber compound thickness in different tire zones. The rubber layer is thickened in critical areas such as the bead regions and crown areas where buckling risk is highest under under-inflated conditions, while maintaining reduced thickness in less critical zones. This localized reinforcement approach provides adequate buckling resistance only where necessary, minimizing overall rubber material usage and manufacturing cost.
Solution Approach 2:
The patent applies preliminary action by incorporating design features that proactively prevent buckling before it occurs. The variable rubber thickness distribution and reinforcement cord arrangement are specifically designed to maintain structural integrity and prevent cord buckling under anticipated under-inflation conditions, addressing the potential failure mode in advance rather than reacting to actual damage.
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
This design maintains or exceeds the endurance performance of existing solutions under normal and under-inflated conditions, reduces manufacturing costs, and minimizes corrosion and buckling risks, achieving a compromise between tire durability and production expenses.
Implementation Method 1
the cables are penetrated by the rubber compound in a cured state, to a depth such that the cables exhibit in a so-called permeability test a flow rate of less than 20 cm³/min
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
The invention relates to a tyre with a radial carcass reinforcement comprising a crown reinforcement in turn capped radially by a tread. According to the invention, the metal reinforcement elements of the carcass reinforcement are non-hooped cords which, during so-called permeability testing, have a flow rate of less than 20 cm3/mn over at least 50% of the axial profile of the tyre. The rubber mixture thickness between the internal surface of the tyre cavity and the point of a metal reinforcement element of the carcass reinforcement is between 1.0 and 3.0 mm and the same thickness on the orthogonal projection of the shoulder ends of the tyre on the internal surface is between 2.4 and 3.9 mm, the ratio of said thicknesses being greater than 1.10.