Tire Bead Design for Low Rolling Resistance and Robustness
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Solution Overview
Problem
High-load index passenger vehicle tires face challenges in achieving low rolling resistance and high cornering stiffness without compromising industrial robustness, particularly when implementing rubber compounds with specific elastic and viscous moduli in '4×4' tires, which can lead to increased tire failures due to rubber movement during curing.
Innovation Solution
A tire design featuring a wide annular reinforcing structure with a bead filler and outer strip made of rubber compounds with elastic and viscous moduli less than or equal to 15 MPa, and a thickness variation that is shorter and wider, positioned radially and axially within specific distance ranges relative to the tire's height, to maintain industrial robustness and reduce rolling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If rubber compounds with elastic modulus G' less than or equal to 15 MPa and viscous modulus G'' such that G'' less than or equal to 0.2·G'−0.2 MPa are used in the outer strip and bead filler, then rolling resistance is reduced, but industrial robustness deteriorates due to rubber movement during curing causing increased tire failures
Solution Approach 1:
The patent applies parameter changes by precisely controlling the elastic modulus (G' ≤ 15 MPa) and viscous modulus (G'' ≤ 0.2·G'−0.2 MPa) of the rubber compound, while also controlling the thickness variation parameter (dE/dr ≤ -0.25 mm/mm). This multi-parameter optimization achieves low rolling resistance while preventing rubber movement during curing, thus maintaining industrial robustness.
Solution Approach 2:
The patent applies local quality by creating a specific thickness profile E(r) that varies radially across the outer strip and bead filler. The thickness is optimized at different radial positions to provide the right balance between flexibility (for low rolling resistance) and stability (for preventing rubber movement during curing), thereby resolving the contradiction between energy loss and reliability.
2Loss of energy
If the thickness E(r) of the rubber compound portion is reduced to create a 'squat' entity (shorter and wider), then rolling resistance is reduced, but the quantity of rubber compound decreases which may affect cornering stiffness
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness E(r) profile with a specific gradient (dE/dr ≤ -0.25 mm/mm in the range r=20-50 mm). This controlled thickness reduction creates a 'squat' geometry that lowers rolling resistance while the precise gradient ensures sufficient rubber compound quantity is maintained in critical areas to preserve cornering stiffness.
Solution Approach 2:
The patent applies dimensionality change by transitioning from a uniform thickness design to a radially varying thickness profile E(r). This dimensional optimization allows the entity to be shorter radially while wider axially, achieving low rolling resistance through the squat shape while maintaining adequate material volume for cornering stiffness through the optimized radial distribution.
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 achieves a 5% reduction in rolling resistance and a 15% improvement in manufacturing productivity while maintaining cornering stiffness and endurance, with no negative impact on tire endurance.
Implementation Method 1
The outer strip and possibly the bead filler are made using rubber compounds that have an elastic modulus G′ less than or equal to 15 MPa and a viscous modulus G′′ such that: G′′[MPa]≦0.2·G′[MPa]−0.2 MPa, the elastic and viscous moduli being measured at 23° C.
Implementation Method 2
the carcass reinforcement comprising a plurality of carcass reinforcing elements and being anchored in the two beads by being wrapped around the annular reinforcing structure so as to form, within each bead, a main portion and a wrapped-around portion
Data Source
AI summary
Tire comprising two beads comprising an annular reinforcing structure and a carcass reinforcement which is anchored in the two beads by being wrapped around the annular reinforcing structure so as to form, in each bead, a main portion and a wrapped-around portion, in which each bead comprises a bead filler situated between the main portion and the wrapped-around portion of the carcass reinforcement, and an outer strip positioned axially on the outside of the carcass reinforcement and of the bead filler in which the entity formed by the bead filler and the outer strip has a thickness E(r), the thickness E(r) changes as a function of the distance r such that, in the range of distances r comprised between 25 and 45% of the height H of the tire, the variation in thickness∂E(r)∂rIs less than or equal to −0.25 mm/mm over at least 4% of the height H of the tire, and in which the annular reinforcing structure has a maximum axial width DE such that the ratioE(r)max-DEE(r)max,where E(r)max is the maximum value of the thickness E(r), is less than or equal to 10%.