Pneumatic Tire Bead Core Wire Arrangement for Rim Fit
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Solution Overview
Problem
Pneumatic tire beads experience rim slip and separation due to variations in rim diameter, leading to increased fitting pressure and effort, and insufficient fastening force, which can result in rim slip or separation from the rim, especially when the rim diameter deviates from the standard value.
Innovation Solution
The tire design incorporates a core with a non-stretchable wire wound in a circumferential direction, featuring two or more rows of wire cross-sections stacked in a specific arrangement, with a controlled angle and distance between the core's bottom side and bead base line, and a specific octagonal outer shape, to reduce the fastening force gradient and improve fitting pressure and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bead is designed to have a great fastening force, then rim slip and separation from rim can be reduced, but high fitting pressure is required and time and effort are needed to mount the tire
Solution Approach 1:
The bead core is segmented into multiple wire rows (first row with fewer cross-sections, second row with more cross-sections) arranged in a specific configuration. This segmentation allows different regions of the bead to contribute differently to fastening force, enabling sufficient holding power while reducing the peak fitting pressure required during mounting.
Solution Approach 2:
The bead core exhibits local quality variation through its multi-row wire structure, where the first row (with fewer cross-sections) and second row (with more cross-sections) provide different mechanical properties at different locations. This local differentiation optimizes the balance between fastening force and fitting pressure by concentrating strength where needed while reducing resistance during the fitting process.
2Reliability
If the bead has great fastening force, then rim slip and separation from rim can be reduced, but the bead may be locally twisted due to high fitting pressure leading to imperfect fitting
Solution Approach 1:
Dividing the bead core into multiple wire rows with different numbers of cross-sections distributes the mechanical loads more evenly during the fitting process. This segmentation prevents concentration of stress that would cause local twisting, while still providing sufficient overall fastening force to prevent rim slip and separation.
Solution Approach 2:
The invention changes the structural parameters of the bead core by specifying different numbers of wire cross-sections in different rows (first row has fewer, second row has more). This parameter variation optimizes the bead's response to fitting pressure, reducing twisting deformation while maintaining the necessary fastening force for reliable rim attachment.
3Manufacturing precision
When the rim diameter varies due to production error, a bead with large fastening force gradient causes greater deviation from appropriate fastening force, increasing fitting pressure and required mounting effort
Solution Approach 1:
The invention optimizes the structural parameters of the bead core, specifically the arrangement of wire cross-sections in multiple rows, to reduce the fastening force gradient. This parameter optimization ensures that the bead maintains appropriate fastening force across a range of rim diameters, reducing sensitivity to manufacturing variations while minimizing the fitting pressure required.
4Manufacturing precision
When the rim diameter is smaller than standard value, a bead with large fastening force gradient results in insufficient fastening force, causing rim slip or separation from bead
Solution Approach 1:
The optimized bead core structure with multiple wire rows and specific cross-section arrangements adjusts the fastening force gradient to an appropriate level. This ensures that even when rim diameter is smaller than the standard value, the bead maintains sufficient fastening force to prevent rim slip and separation, while avoiding excessive fastening force that would require high fitting pressure.
Data Source
AI summary
In a tire, in a cross-section of a core of a bead taken at a plane perpendicular to the circumferential direction, two or more rows of wire cross-sections aligned in the axial direction are stacked. When the radially innermost row is a first row and a row immediately outside the innermost row in the radial direction is a second row, the number of the cross-sections of the wire in the first row is less than that in the second row. An inner end of the second row is axially inward of a line drawn from an inner end of the first row and is perpendicular to a direction in which the first row extends. In the cross-section of the core taken at a plane perpendicular to the circumferential direction, an angle between a bottom side of the core and a bead base line is 2° to not greater than 9°.