Tyre Bead Reinforcement Using Low Modulus Polymer
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Solution Overview
Problem
Heavy-duty tires face issues with endurance under excessive loads and inflation pressure, leading to carcass reinforcement unwinding and damage, particularly due to high rolling resistance and stress on the stiffener's radially outer end, which can result in cracking and premature wear.
Innovation Solution
A tire design with a radial carcass reinforcement featuring a layer of uncoated metal cables with saturated layers and a polymeric mixture separating the carcass reinforcement from the stiffener, where the stiffener's radially interior end is engaged under the rod, and the polymeric mixture's modulus of elasticity is less than 8 MPa, reducing stress and improving rolling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If layers of reinforcing elements or stiffeners are arranged axially outside the turnaround of the carcass reinforcement to protect against excessive stresses, then the resistance of the tire to excessive loads and inflation pressure is improved, but the risk of damage to the stiffener increases, including breakages in compression zones and cracking of the surrounding polymeric mixtures
Solution Approach 1:
A polymeric mixture layer is introduced as an intermediary element between the carcass reinforcement turnaround and the stiffener. This intermediate layer absorbs and distributes stresses, preventing direct stress concentration at the stiffener ends and turnaround region, thereby reducing cracking and damage while maintaining protective function
Solution Approach 2:
The polymeric mixture's elastic modulus is specifically controlled to be less than 8 MPa, making it more compliant than traditional stiffer materials. This parameter change allows the material to deform under stress without transmitting excessive forces to the stiffener, preventing breakages and cracking while still providing structural support
2Reliability
If the ends of the carcass reinforcement reversal and stiffener are offset significantly in the radial direction to avoid damage propagation, then crack propagation is prevented, but the protection against unwinding during excessive heating is reduced
Solution Approach 1:
The polymeric mixture layer serves as a mediator that connects the carcass reinforcement turnaround and stiffener while accommodating radial movements. This intermediate compliant layer allows for thermal expansion and contraction during heating without causing unwinding, while still preventing crack propagation through its damage-absorbing properties
3Strength
If the carcass reinforcement is made with polymeric mixtures having elastic moduli of at least 12 MPa to combat unwinding under excessive stress, then resistance to unwinding is improved, but the rolling resistance increases due to unfavorable viscous moduli
Solution Approach 1:
The elastic modulus of the polymeric mixture is reduced to less than 8 MPa, inverting the traditional approach of using high-modulus materials for unwinding resistance. This lower modulus reduces viscous losses and rolling resistance while the geometric configuration and reinforcement architecture maintain adequate resistance to unwinding under normal 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 design enhances endurance and reduces rolling resistance, preventing unwinding and cracking, while maintaining the tire's structural integrity under extreme conditions, as demonstrated by improved performance in tests with excessive loads and prolonged braking.
Implementation Method 1
a polymeric mixture separating the end of the carcass reinforcement reversal from the stiffener, the radially exterior end of which is radially exterior to the end of the turnaround
Implementation Method 2
the reinforcing elements of at least one stiffener being uncoated metal cables with saturated layers having a flow rate of less than 5 cm³
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
The invention relates to a tyre with a radial carcass reinforcement made up of at least one layer of reinforcing elements which is anchored in each of the beads by being wrapped around a bead wire, said wrapped-around portion of carcass reinforcement being reinforced by at least one layer of reinforcing or stiffening elements the radially outer end of which is radially on the outside of the end of the wrapped-around portion. According to the invention, the reinforcing elements of at least one stiffener are unwrapped metal cords with saturated layers which on the test known as the permeability test return a flowrate of less than 5 cm3/min, the radially inner end of said stiffener being radially on the inside of that point of the bead wire that is radially closest to the axis of rotation, and the elastic modulus of the polymer compounds in the calendered layers of the carcass reinforcement is less than or equal to 8 MPa.