Pneumatic Tire Pad Rubber Modulus and Thickness Design
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Solution Overview
Problem
Pneumatic tires with chafer layers in the bead part experience distortion concentration at the rolled-up end, which is not effectively suppressed by existing pad rubber arrangements, leading to potential separation and reduced rolling resistance performance.
Innovation Solution
A pneumatic tire design featuring a pad rubber with a higher modulus than the side wall rubber, arranged between the side wall rubber and the carcass ply adjacent to the rolled-up end of the chafer layer, with a constant thickness portion covering 7% to 26% of the tire reference cross-section height, and a tapered thickness portion to disperse distortion and prevent excessive length or reduced adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pad rubber is arranged on the outside in the tire radial direction further than the chafer layer, then the pad rubber does not effectively contribute to suppression of the concentration of distortion at the rolled-up end of the chafer layer, but the structure is simpler to manufacture
Solution Approach 1:
The pad rubber is positioned specifically adjacent to the rolled-up end of the chafer layer in the tire width direction, with its inner-diameter-side end positioned at a specific radial location. This localized positioning ensures the pad rubber directly supports the rolled-up end where distortion concentrates, rather than being positioned further outward where it would not effectively contribute to distortion suppression.
2Reliability
If the constant thickness portion of the pad rubber covers a height range smaller than 7% of the tire reference cross-section height, then the distortion dispersion effect is reduced, but the side wall rubber proportion is increased improving rolling resistance performance
Solution Approach 1:
The height range of the constant thickness portion of the pad rubber is specified to be 7% to 26% of the tire reference cross-section height. This parameter range optimizes the balance between distortion dispersion effect and rolling resistance performance by ensuring sufficient constant thickness portion for distortion dispersion while limiting the pad rubber proportion to maintain side wall rubber performance.
3Reliability
If the constant thickness portion of the pad rubber covers a height range larger than 26% of the tire cross-section height, then the distortion dispersion effect is enhanced, but the proportion of the side wall rubber is excessively decreased degrading fuel consumption
Solution Approach 1:
The upper limit of the constant thickness portion height range is set at 26% of the tire reference cross-section height. This parameter limitation prevents the pad rubber from occupying excessive space that would displace side wall rubber, thereby maintaining the side wall rubber's contribution to rolling resistance performance and fuel efficiency while still providing sufficient distortion dispersion capability.
4Reliability
If the pad rubber has a modulus value higher than that of the side wall rubber, then the distortion at the rolled-up end is reduced, but the side wall rubber proportion is decreased
Solution Approach 1:
The pad rubber with higher modulus value is positioned specifically adjacent to the rolled-up end of the chafer layer, providing localized reinforcement where distortion concentrates. This localized high-modulus region reduces distortion at the critical rolled-up end while limiting the overall volume of high-modulus material, thereby preserving the proportion of side wall rubber for maintaining fuel efficiency.
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 reduces distortion at the rolled-up end of the chafer layer, enhances rolling resistance, and maintains fuel efficiency by dispersing distortion over a predetermined range, while preventing excessive pad rubber proportion that could degrade side wall rubber performance.
Implementation Method 1
the pad rubber having a modulus value higher than that of the side wall rubber. The pad rubber includes a constant thickness portion having a substantially constant thickness over a range of 7% or more but not exceeding 26% of a tire reference cross-section height
Data Source
AI summary
A pneumatic tire includes a pair of bead cores; a pair of bead fillers; a carcass ply that is suspended between the pair of bead cores; a side wall rubber that is arranged on a tire-outer-surface-side of the carcass ply and constitutes a tire outer surface; a chafer layer that is rolled up from a tire-inner-surface-side to the tire-outer-surface-side of the carcass ply around the bead cores and the bead fillers; and a pad rubber that is arranged between the side wall rubber and the carcass ply to be adjacent to a rolled-up end of the chafer layer in a tire width direction, the pad rubber having a modulus value higher than that of the side wall rubber. The pad rubber includes a constant thickness portion having a substantially constant thickness over a range of 7% or more but not exceeding 26% of a tire reference cross-section height.