Pneumatic Tire Bead Core Local Quality for Low Fitting Pressure
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Solution Overview
Problem
Conventional pneumatic tires require high fitting pressure to secure the bead portion over the rim due to the non-stretchable core, which complicates the fitting process and can lead to tire displacement or detachment, especially in run-flat tires with reinforced sidewalls.
Innovation Solution
Incorporating a core with a combination of hard and soft units, where the soft unit is more easily stretchable than the hard unit, allowing for easier deformation and reduced fitting pressure without compromising the tightening force, by arranging these units in a specific configuration within the bead to facilitate easier passage over the rim's hump during fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a non-stretchable cord is used for the core to enhance tightening force, then the tire can be secured to the rim, but the bead portion becomes difficult to pass over the hump during fitting, requiring excessively high fitting pressure
Solution Approach 1:
The core is designed with non-uniform cord arrangement where cords are sparsely arranged in the axial direction at the outer radial side (first region) to facilitate bead deformation and passage over the hump, while cords are densely arranged at the inner radial side (second region) to provide sufficient tightening force. This local quality differentiation resolves the contradiction between ease of fitting and tightening force.
2Reliability
If a core with enhanced tightening force is used, then the tire is prevented from displacement or detachment, but the core becomes difficult to deform, requiring high fitting pressure
Solution Approach 1:
The core structure implements local quality by varying cord density in different radial regions. The sparse cord arrangement at the outer radial side allows easy deformation for passing over the hump, while the dense cord arrangement at the inner radial side ensures reliable tightening force to prevent tire displacement or detachment during operation.
3Ease of manufacture
If the cord is arranged uniformly in the core, then the structure is simple, but the bead portion cannot easily stretch to pass over the hump without compromising tightening force
Solution Approach 1:
The core adopts non-uniform cord arrangement with different densities in different regions. This local quality differentiation allows the bead portion to easily stretch at the outer radial side for hump passage while maintaining sufficient tightening force through dense cord arrangement at the inner radial side, resolving the contradiction between manufacturing simplicity and operational ease.
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 configuration allows for a low fitting pressure to be achieved while maintaining a sufficient tightening force, enhancing the ease of tire installation and reducing the risk of displacement or detachment, particularly in run-flat tires.
Implementation Method 1
a stretchable portion formed from a crosslinked rubber. The stretchable portion is located inward of the main body in an axial direction
Implementation Method 2
formed from a crosslinked rubber
Data Source
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AI summary
[Object] To provide a pneumatic tire 22 that allows a low fitting pressure to be achieved without impairing a tightening force. [Solution] The tire 22 includes a pair of beads 30 and a carcass 32 extending on and between both beads 30. Each bead 30 includes a core 48. The core 48 includes: a main body 56 including a cord 60 extending in a circumferential direction; and a stretchable portion 58 formed from a crosslinked rubber. The stretchable portion 58 is located inward of the main body 56 in an axial direction. The stretchable portion 58 has a size with which at least one cross-section of the cord 60 can be included therein in a cross-section of the bead 30. Preferably, in the tire 22, the main body 56 includes a hard unit and a soft unit. The soft unit is located outward of the hard unit in a radial direction. A hard cord of the hard unit stretches more easily than a soft cord of the soft unit.