High Twist Polyester Carcass for Runflat Tires
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Solution Overview
Problem
Conventional runflat tires face heat build-up issues, leading to failure, especially at high speeds and prolonged use, due to the sensitivity of rubber to heat and the high cost of rayon carcass reinforcement, which affects rolling resistance and durability.
Innovation Solution
A pneumatic radial runflat tire design incorporating a high twist polyester cord with a specific cord construction (2200 dtex/2 8.5/8.5 tpi) treated with an aqueous polyepoxide and RFL emulsion, providing improved interfacial strength and adhesion, and featuring a carcass ply structure with a fabric overlay and sidewall inserts for enhanced stiffness and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rayon is used as carcass reinforcement to improve runflat performance, then runflat capability is enhanced, but cost increases and rolling resistance increases
Solution Approach 1:
The patent replaces expensive rayon carcass reinforcement with a more economical polyester cord construction (2200 dtex/2 8.5/8.5 tpi). This substitution maintains runflat capability while reducing material cost, directly addressing the technical contradiction between reliability and manufacturing cost.
Solution Approach 2:
The patent modifies the polyester cord parameters (dtex, twist per inch, cord density between 16-28 epi) to optimize performance. By adjusting these parameters, the polyester cord achieves runflat performance comparable to rayon while maintaining lower cost and reduced rolling resistance.
2Reliability
If rubber is used to stiffen sidewall members to improve runflat performance, then runflat capability is enhanced, but heat build-up increases leading to failure
Solution Approach 1:
The patent changes the material parameter from rubber-dependent sidewall stiffening to a cord-density-based structural approach. By optimizing cord density (16-28 epi) and twist specifications, the tire achieves sidewall stiffness through cord arrangement rather than excessive rubber, reducing heat generation while maintaining runflat capability.
3Ease of manufacture
If polyester cord is used instead of rayon to reduce cost, then manufacturing cost decreases, but interfacial strength at elevated temperatures deteriorates
Solution Approach 1:
The patent optimizes polyester cord parameters including twist per inch (8.5/8.5 tpi) and linear density (2200 dtex/2) to enhance interfacial strength. These parameter adjustments improve the cord's bonding strength with rubber at elevated temperatures while maintaining cost advantages over rayon.
Solution Approach 2:
The patent creates a composite structure by combining polyester cords with rubber compounds in specific configurations. This composite approach enhances the interfacial strength between polyester and rubber, allowing the use of cost-effective polyester while achieving performance comparable to rayon through optimized material combination.
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 runflat mileage and durability while maintaining tenacity and modulus benefits at a lower cost than rayon, reducing rolling resistance and improving high-temperature performance.
Implementation Method 1
an improvement of the interfacial strength of polyester cords in rubber, and more specifically such strength at elevated temperatures
Data Source
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AI summary
A pneumatic radial runflat tire (10) includes a pair of parallel annular beads (20a,20b), a carcass ply structure (22), a belt reinforcement structure (14), a tread (12), and a pair of sidewalls (16,18). The carcass ply structure (22) comprises a polyester fabric with a cord construction of 2200 dtex/2 8.5/8.5 tpi with a cord density of between 16 and 28 epi. The belt reinforcement structure (14) is disposed radially outward of the carcass ply structure (22) in a crown area of the tire. The tread (12) is disposed radially outward of the belt reinforcement structure (14). The pair of sidewalls (16,18) comprises part of the carcass ply structure (22). The pair of sidewalls (16,18) is disposed between the tread (12) and the pair of parallel annular beads (20a,20b).