Tyre Protective Layer with Low Modulus Elastomer
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Solution Overview
Problem
Heavy-duty tires face challenges in endurance and wear performance, especially when driven at high speeds on long journeys, due to shear stresses and corrosion issues that lead to cracks and breakage of reinforcing elements during retreading.
Innovation Solution
A tire design with a radial carcass reinforcement featuring a crown reinforcement of multiple layers, including a protective layer with a specific elastomeric mixture having a modulus of elasticity under tension less than 8.5 MPa and a high macro dispersion Z score, which reduces shear stresses and enhances corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer with conventional elastomeric mixture is used, then the tread provides adequate mechanical protection, but shear stresses cause cracks and breakage of reinforcing elements during high-speed long journeys
Solution Approach 1:
The patent changes the physical-chemical parameters of the elastomeric mixture by specifying a modulus of elasticity under tension less than 8.5 MPa and a macro dispersion Z score greater than 85. These parameter changes optimize the protective layer's ability to reduce shear stresses while maintaining mechanical protection, resolving the contradiction between endurance and shear resistance.
Solution Approach 2:
The patent uses a composite elastomeric mixture containing specific fillers and additives that work together to achieve the desired modulus of elasticity and macro dispersion characteristics. This composite material provides both the mechanical protection needed and the shear stress reduction necessary for improved endurance during high-speed operation.
2Strength
If the elastomeric mixture has high modulus of elasticity, then the protective layer provides strong mechanical protection, but corrosion of reinforcing elements increases during retreading
Solution Approach 1:
The patent specifies a modulus of elasticity under tension less than 8.5 MPa, which is a deliberate parameter change from conventional higher modulus materials. This reduction in stiffness allows the protective layer to better accommodate reinforcing elements during retreading operations, reducing corrosion while maintaining adequate mechanical protection through optimized macro dispersion.
3Reliability
If the macro dispersion Z score is low, then the elastomeric mixture is easier to manufacture, but shear stresses are not adequately reduced leading to crack propagation
Solution Approach 1:
The patent establishes a macro dispersion Z score greater than 85 as a critical parameter threshold. This parameter change ensures adequate mixing uniformity while providing sufficient shear stress reduction to prevent crack propagation. The specific filler types and quantities are selected to achieve this dispersion level without excessive manufacturing complexity.
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 design improves endurance and wear resistance, allowing for safer retreading and reduced corrosion of reinforcing elements, while maintaining satisfactory rolling resistance and cohesion.
Implementation Method 1
shear stresses between the top layers, combined with a significant rise in operating temperature at the ends of the axially shortest top layer, which result in the appearance and propagation of cracks in the rubber at said ends
Implementation Method 2
the tire's durability, and particularly that of the tread, is compromised... solutions relating to the structure and quality of the layers and/or profiles of rubber compounds which are arranged between and/or around the ends of plies
Data Source
Figure 1
AI summary
The invention relates to a tyre comprising a crown reinforcement formed by at least two working crown layers of reinforcing elements and at least one protective layer. According to the invention, the tensile modulus of elasticity at 10% elongation of at least the radially outermost skim coat of at least one protective layer is less than 8.5 MPa, and at least said radially outermost skim coat of at least one protective layer has a macro dispersion rating Z greater than 85.