Pneumatic Tire Bead Core Geometry for Rim Slippage
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Solution Overview
Problem
Pneumatic tires on construction vehicles experience rim slippage due to insufficient fastening force, which can lead to wear and damage, and existing solutions that increase fastening force often compromise mountability.
Innovation Solution
A pneumatic tire design featuring a hexagonal bead core with an inclined bead core bottom, a linearly formed bead base portion, an arc-shaped heel portion, and a specific range of rim cushion rubber modulus, displacement, and compression ratio to ensure both effective fastening and mountability on 5°-tapered rims.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the inner diameter of the bead core or the circumferential length of the bead heel portion is reduced to increase fastening force, then rim slippage is suppressed, but mountability on the rim wheel deteriorates
Solution Approach 1:
The bead base portion is designed with a specific inclination angle (8° or more and 12° or less) relative to the tire rotation axis, creating a localized geometric property that optimizes both fastening force and mountability. This local geometric quality allows the bead to engage the rim effectively while maintaining ease of installation.
Solution Approach 2:
The invention changes the geometric parameters of the bead structure, specifically the inclination angle of the bead base portion and the shape of the bead core bottom, to achieve an optimal balance between fastening force and mountability. By adjusting these parameters within specific ranges, both contradictory requirements are satisfied.
2Strength
If the bead base portion is made steeper to increase fastening force, then rim slippage is suppressed, but the bead portion becomes difficult to mount on the rim
Solution Approach 1:
The invention optimizes the inclination angle of the bead base portion within a specific range (8° or more and 12° or less) to achieve the best balance between fastening force and mountability. This parameter optimization ensures that the bead is steep enough to prevent rim slippage but not so steep that it becomes difficult to mount.
Solution Approach 2:
The bead base portion inclination is designed to be partially steep (within the specific angle range) rather than maximally steep, achieving sufficient fastening force while maintaining acceptable mountability. This partial action approach avoids the extremes that would cause either rim slippage or mounting difficulties.
3Ease of operation
If the bead core inner diameter is increased to improve mountability, then ease of mounting is enhanced, but fastening force becomes insufficient causing rim slippage
Solution Approach 1:
The bead core bottom is designed with a specific shape and inclination (0° or more and 5° or less) to create a localized geometric property that compensates for the larger inner diameter. This local geometric quality ensures that even with a larger bead core diameter that facilitates mounting, sufficient fastening force is generated to prevent rim slippage.
4Power
If excessive torque is transmitted from the rim wheel to the bead portion, then power transmission is improved, but rim slippage occurs due to insufficient fastening force
Solution Approach 1:
The invention optimizes the geometric parameters of the bead structure, including the bead base portion inclination angle and bead core bottom shape, to enhance fastening force. This allows the bead portion to withstand excessive torque from high-power construction vehicles without experiencing rim slippage.
Solution Approach 2:
The bead core bottom is designed with a curved surface having a large radius of curvature, which distributes the transmitted torque more evenly across the bead-rim interface. This curvature helps prevent localized stress concentration that could lead to rim slippage under high torque conditions.
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 effectively suppresses rim slippage while maintaining excellent mountability, ensuring a balance between fastening force and ease of mounting, as demonstrated by performance evaluation tests.
Implementation Method 1
a compression factor and a ratio of a bead core effective width to a bead core maximum width, which are each set to fall within a predetermined range to improve a rim slip resistance without causing weight increase. The compression factor is defined by dividing a compression allowance, which is a difference between a total thickness before mounting on a rim of only a rubber part on an inner side in a radial direction than a bead core and a total thickness after mounting on the rim
Data Source
AI summary
In a pneumatic tire mountable on a 5°-tapered rim, a bottom of a bead core is inclined from 0°-5° in a direction in which the bottom diverges toward an outer side in a radial direction as the bottom extends from an inner side in the width direction toward an outer side in the width direction. Each bead portion includes a base, a toe, and a heel. The base is inclined from 8°-12° in a direction in which the bead base portion diverges toward the outer side in the radial direction as the base extends from the inner side toward the outer side in the width direction. The heel has a radius of curvature from 25-30 mm. A rim cushion rubber has a modulus at 100% elongation within a range from 5.0-8.0 MPa. The toe has a displacement between before and after mounting on the rim from 9.0-13.5 mm.