Hexagonal Bead Core Angle for Heavy-Duty Tire Durability
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Solution Overview
Problem
Heavy-duty pneumatic tires experience a reduction in bead durability and rolling resistance due to rotational displacement of the bead core when inflated, leading to a decrease in fitting pressure and angle between the bead core and rim, which affects performance during both unloaded and loaded conditions.
Innovation Solution
A heavy-duty pneumatic tire design featuring a hexagonal bead core with specific geometric and material properties, including a radially inner surface angle range of 0 ± 3 degrees relative to the rim, a center of gravity height within 0.40 to 0.85 times the rim flange height, and a bead apex rubber with a complex modulus of 60 to 80 MPa, maintains consistent fitting pressure and prevents bead core rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radially inner surface of the bead core is designed to be substantially parallel to the rim sheet surface (angle α1 of substantially 0 degrees), then the fitting pressure uniformly increases and bead durability is improved, but when inflated the carcass ply tension turns out the bead core and the angle becomes 3 to 5 degrees, causing the bead core to rotate and fitting pressure to decrease
Solution Approach 1:
The bead core is designed with an asymmetric hexagonal cross-section where the radially inner surface is inclined at a specific angle (5 to 15 degrees) relative to the rim sheet surface, rather than being parallel. This asymmetric geometry creates an optimal balance between maintaining uniform fitting pressure and preventing rotation caused by carcass ply tension during inflation.
Solution Approach 2:
The invention changes the critical parameter of the bead core geometry from a parallel configuration (0 degrees) to an inclined configuration (5 to 15 degrees). This parameter change optimizes the balance between achieving uniform fitting pressure distribution and maintaining bead core position stability under inflation pressure, thereby simultaneously improving bead durability and preventing rotation.
2Ease of operation
If the bead core rotates during running, then the fitting pressure decreases especially in toe-side of the bead portion, but this rotation causes heat generation and deterioration of bead durability and rolling resistance property
Solution Approach 1:
The asymmetric hexagonal cross-section of the bead core with the radially inner surface inclined at 5 to 15 degrees prevents rotation by creating an optimal geometric configuration that resists the turning force from carcass ply tension, thereby maintaining stable fitting pressure and reducing heat generation during operation.
Solution Approach 2:
The bead core is pre-configured with the optimal inclination angle (5 to 15 degrees) before mounting on the rim. This preliminary geometric configuration ensures that the bead core maintains stable position and prevents rotation during operation, thereby maintaining consistent fitting pressure and preventing heat generation that would deteriorate bead durability and rolling resistance.
3Stability of the object's composition
If the angle between radially inner surface and rim sheet surface is increased to prevent rotation, then position stability is improved, but the fitting pressure distribution becomes non-uniform and bead durability decreases
Solution Approach 1:
The invention identifies and optimizes the critical parameter of the bead core inclination angle, setting it within the specific range of 5 to 15 degrees. This parameter optimization achieves the best balance between maintaining position stability (preventing rotation) and ensuring uniform fitting pressure distribution for bead durability.
Solution Approach 2:
The hexagonal cross-section of the bead core is designed with different surface orientations, where the radially inner surface has a specific inclination angle (5 to 15 degrees) optimized for preventing rotation, while other surfaces maintain configurations that ensure uniform fitting pressure distribution. This local quality differentiation resolves the contradiction between position stability and bead durability.
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A heavy-duty pneumatic tire (1) comprises a carcass (6) comprising a carcass ply (6A) extending from a tread portion (2) through a sidewall portion (3) and turned up around a bead core (5) of a bead portion (4). The bead core (5) comprises a radially inner surface (5a) extending along a bottom surface (4a) of the bead portion (4) in the radial direction of the tire. Under both conditions that include an unloaded standard condition where the tire is mounted on a standard rim (R) and inflated to regular internal pressure and a loaded standard condition where the tire in the unloaded standard condition above is loaded with a regular load and grounded at a camber angle of 0 degrees, the tire has an angle (θ1) between the radially inner surface (5a) of the bead core (5) and a rimsheet surface (13) of the standard rim (R) being in a range of 0 plus/minus 3 degrees.