Tire Casing Reinforcement with Variable Rubber Thickness
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Solution Overview
Problem
Heavy-duty tires face challenges with endurance due to 'fatigue-fretting-corrosion' phenomena, leading to reduced lifespan and increased manufacturing costs, especially when used underinflated, where buckling of carcass reinforcement cables occurs, affecting performance and longevity.
Innovation Solution
A tire design with a radial carcass reinforcement featuring uncoated cables with a permeability test flow rate less than 20 cm³/min, where the rubber mixture thickness between the tire cavity and the metal reinforcing elements is optimized to minimize corrosion and buckling risks, with a ratio of thicknesses greater than 1.15, and a crosslinkable rubber sheath based on diene elastomers to enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rubber mixture thickness between the tire cavity and the metal reinforcing elements is increased to reduce corrosion, then the endurance is improved, but the manufacturing cost increases
Solution Approach 1:
The patent applies different rubber mixture thicknesses at different locations: thicker rubber mixture (greater than 3.5mm) at the bead areas where corrosion protection is most critical, and thinner rubber mixture (less than or equal to 3.5mm) at other areas. This local differentiation protects the most vulnerable regions while reducing overall material usage and cost.
Solution Approach 2:
The patent segments the tire structure into distinct zones with different rubber mixture thicknesses: a first zone at the bead area with thicker rubber mixture for corrosion protection, and a second zone with thinner rubber mixture. This segmentation allows optimized protection where needed while reducing overall material consumption.
2Quantity of substance
If uncoated cables are used to reduce manufacturing cost, then the material cost is reduced, but the risk of fatigue-fretting-corrosion increases
Solution Approach 1:
The patent provides corrosion protection specifically where it is most needed (at the bead areas with thicker rubber mixture) rather than uniformly across the entire cable length. This local protection approach maintains cost-effectiveness while addressing the critical corrosion risk zones.
Solution Approach 2:
The rubber mixture acts as an intermediary protective layer between the corrosive environment (tire cavity) and the uncoated metal cables. By optimizing the rubber mixture thickness and composition, the patent provides adequate corrosion protection without requiring expensive cable coatings.
3Quantity of substance
If the tire is used underinflated to reduce operating cost, then the operating cost is reduced, but the cables buckle and performance deteriorates
Solution Approach 1:
The thicker rubber mixture at the bead areas provides预先 cushioning and support to the cables in the most vulnerable regions. This prior protection helps prevent cable buckling when the tire is operated underinflated, maintaining performance even under suboptimal operating conditions.
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 tire exhibits improved endurance and reduced manufacturing costs, maintaining performance under normal and under-inflated conditions, with extended lifespan and reduced risk of corrosion and buckling, while maintaining a lower material cost structure.
Implementation Method 1
The cables are of the type allowing penetration by a rubber mixture, and thus limiting the dimension of the passage of oxidizing agents
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
The invention relates to a tire having a radial casing reinforcement, consisting of at least one layer of metal reinforcement elements, said tire including a top reinforcement (5), itself radially covered with a tread (6), said tread being joined to two beads (3) via two sidewalls. According to the invention, the metal reinforcement elements of at least one layer of the casing reinforcement (2) are non-reinforced cables having, in the so-called perviousness test, a displacement of less than 20 cm3/mn, and in a radial plane, at least on a portion of the meridional profile of the tire, the rubber mixture thickness (E) between the inner surface of the tire cavity and the point of a metal reinforcement element of the casing reinforcement nearest to said inner surface of the cavity is less than or equal to 3.5 mm, and the rubber mixture thickness ratio between the inner surface of the tire cavity and the point of a metal reinforcement element of the casing reinforcement nearest said inner surface of the cavity of two separate portions of the tire is greater than 1.15.