Pneumatic Tire Bead Bottom Surface Geometry
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Solution Overview
Problem
Conventional pneumatic tires experience deteriorated steering stability and engagement with the rim due to reduced rigidity of bead portions caused by gaps between the rim and bead portions under large lateral forces, making it difficult to mount the tire effectively.
Innovation Solution
The pneumatic tire design features bead portions with inclined bead bottom surfaces, including toe-side and heel-side portions, and a heel-side arc portion, along with specific angles and rubber thickness distributions to enhance engagement and steering stability by improving contact with the rim, and incorporates a combination of rubber portions with varying butyl rubber content for improved adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rigidity of bead portions is increased to increase tightening force on the rim, then adhesion between rim and bead portions is improved, but mounting difficulty increases and engagement deteriorates
Solution Approach 1:
The bead bottom surface is divided into distinct regions with different inclinations: a toe-side portion with a first inclination angle and a heel-side portion with a second inclination angle. This local differentiation allows the toe-side to provide mounting ease while the heel-side enhances engagement, resolving the contradiction between mounting ease and engagement quality.
Solution Approach 2:
The bead bottom surface is segmented into multiple functional zones including the toe-side portion, heel-side portion, and heel-side arc portion. Each segment serves a specific function: the toe-side portion facilitates initial mounting, the heel-side portion ensures proper engagement, and the arc portion provides smooth transition. This segmentation allows simultaneous optimization of mounting ease and engagement quality.
2Stability of the object's composition
If the rigidity of bead portions is increased to suppress gap formation between rim and bead portions, then steering stability is improved, but mounting difficulty increases
Solution Approach 1:
Different regions of the bead bottom surface are assigned different inclination angles to fulfill conflicting requirements: the toe-side portion's first inclination angle facilitates mounting by allowing easier insertion, while the heel-side portion's second inclination angle provides greater rigidity and resistance to gap formation under lateral forces, thereby improving steering stability.
Solution Approach 2:
The solution moves from a single uniform inclination angle to a two-dimensional surface with varying slopes. By introducing the heel-side arc portion with a specific radius of curvature, the design adds a third dimension (curvature) to the bead bottom surface geometry, enabling smooth transition and stress distribution that maintains stability while facilitating mounting.
3Stability of the object's composition
If the bead bottom surface geometry is optimized for engagement, then steering stability improves, but mounting difficulty increases
Solution Approach 1:
The bead bottom surface incorporates local quality variations through different inclination angles in different regions. The toe-side portion has a gentler slope that facilitates mounting operations, while the heel-side portion has a steeper slope that optimizes engagement with the rim flange, thereby achieving both ease of manufacture and steering stability.
Solution Approach 2:
The heel-side arc portion introduces a curved surface with a specified radius of curvature between the heel-side portion and the flange contacting surface. This curvature provides a smooth transition that facilitates mounting while maintaining optimal engagement geometry, resolving the contradiction between ease of manufacture and steering stability.
Data Source
AI summary
A pneumatic tire includes bead portions, each having a bead bottom surface. The bead bottom surface includes a toe-side portion extending axially outwardly from a bead toe at an angle α in a range of from 17 to 24 degrees with respect to the tire axial direction, a heel-side portion positioned axially outside the toe-side portion and extending axially outwardly at an angle β in a range of from 3 to 7 degrees with respect to the tire axial direction, and a heel-side arc portion smoothly connecting between the heel-side portion and a flange contacting surface with a radius of curvature (R) in a range of from 1.5 to 3.5 mm.