Tyre Protective Layer with High Resistivity Elastomer
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Solution Overview
Problem
Heavy-duty tires face challenges in endurance and wear performance, especially when driven at high speeds and on uneven terrain, due to shear stresses and corrosion issues that can lead to cracking and damage during retreading.
Innovation Solution
A tire design with a radial carcass reinforcement featuring a crown reinforcement structure including two working layers and a protective layer made of metallic elements, where the protective layer has an elastomeric mixture with specific properties such as low elastic modulus and high volume electrical resistivity, reducing corrosion and improving cohesion and rolling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer with conventional elastomeric mixture is used, then mechanical protection is provided, but corrosion of metallic elements occurs and endurance is reduced
Solution Approach 1:
The patent applies parameter changes by modifying the elastomeric mixture composition to achieve a volume electrical resistivity greater than 10 ohm.cm (log(ρ) > 10), which is significantly higher than conventional mixtures. This parameter change in electrical resistivity creates a protective electrical barrier that prevents corrosion of metallic reinforcing elements while maintaining mechanical protection functions.
Solution Approach 2:
The patent uses composite materials by combining metallic reinforcing elements with a specially formulated elastomeric mixture that has high volume electrical resistivity. This composite structure provides both mechanical protection and electrical isolation, preventing corrosion while maintaining the structural integrity and protective functions of the protective layer.
2Reliability
If the protective layer has high electrical resistivity, then corrosion is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent achieves high electrical resistivity (log(ρ) > 10) through parameter changes in the elastomeric mixture composition, specifically by selecting rubber compounds and additives that provide inherent high resistivity. This approach integrates corrosion protection into the base material properties rather than requiring separate manufacturing steps, thereby reducing overall manufacturing complexity despite the specialized material requirements.
3Loss of energy
If the elastomeric mixture has low elastic modulus, then rolling resistance is improved, but structural strength may be compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the elastomeric mixture to achieve a low elastic modulus while maintaining adequate structural strength through careful selection of rubber compounds, filler types and amounts, and curing conditions. The balance is achieved by using fillers that provide reinforcement without significantly increasing stiffness, and by optimizing the compound formulation to maintain strength while reducing rolling resistance.
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 enhances endurance and wear resistance, allowing for safer retreading and improved rolling resistance, while reducing corrosion and damage from mechanical and chemical attacks.
Implementation Method 1
at least said outermost radial calendered layer of at least one protective layer having a volume electrical resistivity ρ, measured statically in accordance with ASTM D 257, such that log(ρ) is greater than 8
Implementation Method 2
modulus measurements are carried out in tension according to the AFNOR-NFT-46002 standard of September 1988: the nominal secant modulus (or apparent stress, in MPa) is measured in the second elongation (i.e., after an accommodation cycle) at 10% elongation
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 skim coat has a electrical volume resistivity ρ such that log(ρ) is greater than 8.