Pneumatic Tyre Bead Apex Geometry for Load Durability
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Solution Overview
Problem
High load capacity tires face challenges in maintaining durability while suppressing the deterioration of rolling resistance performance, as conventional approaches to enhance load capacity often lead to reduced durability and increased rolling resistance.
Innovation Solution
A pneumatic tire with an improved carcass structure, featuring a carcass main portion and bead apex rubbers with specific geometric ratios and angles, along with a carcass turn-up portion, which maintains a low carcass-maximum-width height and optimal bead thickness distribution to enhance durability and rolling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reinforcing plies are added or gauges are thickened to improve load capacity and durability, then durability is improved, but rolling resistance deteriorates
Solution Approach 1:
The invention applies local quality by providing a bead apex rubber only at the bead apex portion rather than uniformly throughout the entire bead portion. This localized reinforcement strengthens the critical high-stress area where the carcass cord terminates, improving durability under high load conditions without adding unnecessary material elsewhere that would increase rolling resistance. The bead apex rubber has a specific geometric configuration (height h1/H ≤ 50%, angle θ between 55-75 degrees) optimized for local stress distribution.
Solution Approach 2:
The invention segments the bead portion into distinct functional zones: the bead apex portion with the bead apex rubber for durability enhancement, and the rest of the bead portion with standard construction for maintaining low rolling resistance. This segmentation allows differential optimization of different regions based on their specific functional requirements, preventing uniform over-reinforcement that would harm rolling resistance performance.
2Force
If the carcass structure is strengthened to support high load, then load capacity is improved, but durability under high load conditions deteriorates
Solution Approach 1:
The invention applies parameter changes by specifically controlling the geometric parameters of the bead apex rubber: height h1/H ≤ 50%, and angle θ between 55-75 degrees. These parameter optimizations ensure that the bead apex rubber effectively distributes high load stresses and prevents carcass cord detachment, thereby improving durability under high load conditions while maintaining appropriate load capacity.
Solution Approach 2:
The invention uses composite materials by combining the bead apex rubber with the carcass cord and bead core to create a composite bead apex portion. This composite structure leverages the complementary properties of different materials to simultaneously achieve high load capacity and enhanced durability, with the rubber providing flexibility and stress distribution while the cord provides tensile strength.
Data Source
AI summary
A pneumatic tyre includes a carcass extending between bead cores disposed in respective bead portions through a tread portion and sidewall portions, and bead apex rubbers each extending radially outwardly from the respective bead cores, each bead apex rubber having an inner side surface in a tyre axial direction. In a tyre cross-section under a standard inflated state, a ratio h1/H of a carcass-maximum-width height h1 to a carcass-maximum height H is equal to or less than 50%, and in at least one bead portion, an angle of a tangent line touching the inner surface of the bead apex rubber at an intersection of a tyre radial reference line passing a rim-width location of the standard wheel with the inner side surface of the bead apex rubber is in a range of from 55 to 75 degrees to the tyre radial reference line.