Pneumatic Tire Belt Width and Rubber Modulus Design
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Solution Overview
Problem
Conventional ultralow-profile radial tires for heavy loads face issues with handling stability and uneven wear due to insufficient shear rigidity, which is exacerbated by hardening the rubber around the belt to compensate for rigidity, leading to increased energy loss and deterioration in durability and rolling resistance.
Innovation Solution
A pneumatic tire design featuring a circumferential belt with an intersecting belt layer where the intersecting belt has a maximum width of 80% or more of the carcass width, with a specific width difference between belts, and interposed rubber with a low elastic modulus, along with a side-lower rubber and high-hardness rubber member to enhance stability and reduce rolling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the rubber around the belt is hardened to compensate for insufficient shear rigidity, then handling stability is improved, but energy loss increases and durability against heat deteriorates
Solution Approach 1:
The patent applies different rubber hardness levels to different regions: hard rubber is used specifically in the belt end portion where rigidity is needed for handling stability, while soft rubber is used in the shoulder portion to reduce energy loss. This local differentiation resolves the contradiction by providing rigidity only where necessary rather than hardening the entire tire structure.
Solution Approach 2:
The tire is segmented into distinct regions with different rubber properties: a belt end portion with hardened rubber for rigidity, and a shoulder portion with softer rubber for energy efficiency. This segmentation allows each region to perform its specific function optimally, resolving the contradiction between stability and energy loss.
2Stability of the object's composition
If the rubber around the belt is hardened to compensate for insufficient shear rigidity, then handling stability is improved, but durability against heat deteriorates
Solution Approach 1:
Hard rubber is applied locally only to the belt end portion where structural rigidity is critical for handling stability, while the shoulder portion maintains soft rubber composition to preserve heat resistance and durability. This localized approach resolves the contradiction by limiting the negative thermal effects to the minimum necessary area.
Solution Approach 2:
The tire structure is divided into functional segments: the belt end portion with hard rubber for stability, and the shoulder portion with soft rubber for heat resistance. This segmentation allows the tire to achieve both handling stability and durability against heat simultaneously.
3Ease of operation
If the belt width of the intersecting belt is narrowed to reduce shear rigidity, then the circumferential belt can stretch more easily, but shear rigidity cannot be sufficiently obtained causing deterioration in handling stability
Solution Approach 1:
The circumferential belt is designed with different properties at different locations: the belt end portion has enhanced rigidity through hard rubber to maintain handling stability, while other portions maintain flexibility for stretchability. This local differentiation resolves the contradiction between ease of stretching and handling stability.
4Ease of operation
If the belt width of the circumferential belt is narrowed to suppress deformation, then the circumferential belt can stretch more easily, but rigidity of the entire belt cannot be sufficiently obtained causing advancement of uneven wear
Solution Approach 1:
Hard rubber is applied specifically to the belt end portion to provide localized rigidity that prevents deformation and ensures uniform wear, while allowing other portions of the belt to maintain flexibility for stretchability. This resolves the contradiction between ease of stretching and uniformity of wear.
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
This design enhances handling stability and reduces uneven wear without compromising durability or rolling resistance, by distributing stress effectively and reducing hysteresis loss in the rubber, thus improving tire longevity and fuel efficiency.
Implementation Method 1
interposed rubber disposed between both end portions of the circumferential belt and respective end portions of the intersecting belt layer... having a modulus of 100% elongation of 4 MPa or less and a loss tangent of 0.3 or less... reducing hysteresis loss in the rubber
Implementation Method 2
interposed rubber... having a modulus of 100% elongation of 4 MPa or less... side-lower rubber disposed at a side of and a lower portion of the end portion of the circumferential belt and having an elastic modulus not more than the elastic modulus of a coating rubber coating the circumferential belt
Data Source
AI summary
A belt width of an intersecting belt 15a having the maximum belt width is set to 80% or more of the maximum width of a carcass line; a difference in belt widths between the intersecting belt 15a and an intersecting belt 15b is set in the range of 10 mm to 50 mm on one side of the belt in the width direction; the intersecting belt 15a is not narrower than the circumferential belt 14, and the circumferential belt 14 is not narrower than the intersecting belt 15b; and a pneumatic tire according to the present invention has an interposed rubber 16 having a thickness increasing toward the widthwise outer side of the tire to be 3 mm or more, and a side-lower rubber 17 having an elastic modulus less than the elastic modulus of a coating rubber coating the circumferential belt 14.