Pneumatic Tire Bead Crack Suppression via Localized Rubber Modulus
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Solution Overview
Problem
Pneumatic tires experience crack generation from the edge of the carcass folded back portion, which affects durability and requires a countermeasure to improve bead portion durability.
Innovation Solution
A pneumatic tire design featuring a pair of bead portions with bead cores, a carcass supported by these cores, a steel cord reinforcing layer, and specific rubber layers with defined complex modulus and elongation properties to reduce strain and prevent crack generation, while maintaining mountability on a 15° tapered rim.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bead portion structure is used, then the tire can be mounted on the rim, but crack generation occurs from the edge of the carcass folded back portion
Solution Approach 1:
The patent applies local quality by providing a reinforcing rubber layer specifically at the outer edge portion of the carcass folded back portion where cracks tend to generate. This localized reinforcement with different material properties (higher elasticity and tensile strength) addresses the specific problem area without changing the entire bead portion structure, thereby suppressing crack generation while maintaining overall tire functionality.
Solution Approach 2:
The patent uses composite materials by combining the reinforcing rubber layer with the existing bead portion structure. The reinforcing rubber layer has specific elastic modulus and tensile strength properties that differ from the conventional bead rubber, creating a composite structure that enhances durability at the critical edge portion where cracks typically initiate.
2Reliability
If the bead portion structure is modified to prevent cracks, then durability is improved, but the complexity of the bead portion increases
Solution Approach 1:
The patent applies segmentation by dividing the bead portion into functional layers: the conventional bead rubber and the additional reinforcing rubber layer. This segmented approach allows the reinforcing layer to be positioned specifically where needed (at the outer edge of the folded back portion) to prevent cracks, while keeping the rest of the bead portion structure simple and maintaining ease of manufacturing.
3Strength
If the carcass folded back portion is reinforced, then crack resistance is improved, but the flexibility of the bead portion may be reduced
Solution Approach 1:
The reinforcing rubber layer is applied locally at the outer edge portion of the folded back portion rather than throughout the entire bead portion. This localized reinforcement provides crack resistance where it is most needed while preserving the flexibility of the rest of the bead portion, allowing the tire to maintain its ability to deform and conform to the rim during mounting and operation.
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 effectively suppresses crack generation from the carcass folded back portion, maintaining durability and mountability, with optimal rubber layer properties reducing strain and elongation, thus enhancing the tire's performance and longevity.
Implementation Method 1
a complex modulus of the first reinforcing rubber layer being from 6 MPa to 10 MPa, an elongation at break of the first reinforcing rubber layer being from 300% to 450%, a complex modulus of the second reinforcing rubber layer being from 10 MPa to 15 MPa
Implementation Method 2
a complex modulus of the shock absorbing rubber layer being from 2 MPa to 6 MPa
Data Source
AI summary
A pneumatic tire mountable on a 15° tapered specified rim includes a bead core, a carcass, a steel cord reinforcing layer, a bead rubber layer, and a first reinforcing rubber layer. A distance from a second line segment to a third line segment is from 4 mm to 12 mm, a complex modulus of the first reinforcing rubber layer is from 6 MPa to 10 MPa, an elongation at break of the first reinforcing rubber layer is from 300% to 450%, a complex modulus of the second reinforcing rubber layer is from 10 MPa to 15 MPa, and a complex modulus of a shock absorbing rubber layer is from 2 MPa to 6 MPa.