Run-Flat Tire Sidewall Rubber Tuning for Lower Rolling Resistance
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Solution Overview
Problem
Pneumatic tires with run-flat capabilities face challenges in reducing rolling resistance while maintaining ride comfort under normal travel conditions, as increased rubber volume in the side reinforcing layer leads to heat build-up and increased side rigidity, deteriorating ride comfort.
Innovation Solution
A pneumatic tire design featuring a side reinforcing layer and bead filler with specific rubber physical properties (modulus at 100% elongation between 8.4 MPa to 10.2 MPa, tan δ at 60° C. between 0.04 to 0.08, and JIS hardness at 20° C. between 75 to 79) to prevent peeling and heat build-up, along with an outer reinforcing layer and optimized geometry to reduce rolling resistance and improve run-flat durability and ride comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the volume of rubber in the side reinforcing layer is increased to suppress deflection under run-flat travel conditions, then run-flat durability is improved, but heat build-up is promoted and rolling resistance is increased
Solution Approach 1:
The patent applies parameter changes by precisely controlling the physical properties of the rubber compound within specific ranges: tan δ at 60°C between 0.04-0.08, modulus at 100% elongation between 8.4-10.2 MPa, and JIS hardness between 75-79. This optimization allows the rubber to provide sufficient reinforcement for run-flat durability while minimizing heat build-up and rolling resistance, resolving the contradiction between reliability and energy loss.
Solution Approach 2:
The patent employs composite materials by formulating a specific rubber compound composition including natural rubber (50-80 parts by weight), polybutadiene rubber (20-50 parts by weight), and controlled amounts of sulfur, zinc oxide, and other additives. This composite formulation achieves the desired balance between run-flat performance and reduced rolling resistance through synergistic material properties.
2Reliability
If the volume of rubber in the side reinforcing layer is increased to suppress deflection under run-flat travel conditions, then run-flat durability is improved, but ride comfort under normal travel conditions deteriorates due to an increase in side rigidity
Solution Approach 1:
The patent resolves this contradiction by optimizing the rubber compound parameters within specific ranges: JIS hardness controlled at 75-79, modulus at 100% elongation at 8.4-10.2 MPa, and tan δ at 60°C at 0.04-0.08. These parameter optimizations ensure the side reinforcing layer provides adequate stiffness for run-flat durability while maintaining sufficient flexibility for comfortable normal driving conditions.
Solution Approach 2:
The patent applies local quality by positioning the side reinforcing layer with a crescent-shaped cross-section specifically in the sidewall region where it is needed for run-flat support, while controlling its thickness and material properties to avoid excessive rigidity in areas that would compromise ride comfort. The layer is disposed on the inner side in the tire width direction of the carcass layer, providing localized reinforcement only where required.
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 reduced rolling resistance and improved run-flat durability and ride comfort by balancing the physical properties of the rubber in the side reinforcing and bead filler layers without increasing the rubber's cross-sectional area or thickness, while maintaining effective casing stiffness and deformation suppression.
Implementation Method 1
since the rubbers have the tan δ at 60° C. in the range from 0.04 to 0.08 and are low heat build-up rubbers, heat build-up under run-flat travel conditions is suppressed
Implementation Method 2
since the modulus at 100% elongation is in the range from 8.4 MPa to 10.2 MPa, the generation of peeling off of the carcass layer located between the side reinforcing layer and the bead filler can be prevented
Data Source
AI summary
A pneumatic tire is provided. A bead filler is disposed on an outer circumferential side of each bead core in bead portions, a side reinforcing layer having a crescent-shaped cross-section is disposed on an inner side in a tire width direction of a carcass layer in a sidewall portion, and as physical properties of a rubber that constitutes the side reinforcing layer and a rubber that constitutes the bead filler, a modulus at 100% elongation is in a range from 8.4 MPa to 10.2 MPa, a tan δ at 60° C. is in a range from 0.04 to 0.08, and JIS hardness at 20° C. is in the range from 75 to 79.