Tread Rubber Hardness Profile for Consistent Tire Grip
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Solution Overview
Problem
Tires exhibit insufficient grip performance before running-in, despite techniques to increase tan δ peak temperature or incorporate resins, as the tread rubber surface hardens during storage due to oxygen penetration and low antioxidant content.
Innovation Solution
Adjusting the Martens hardness ratio of tread rubber to satisfy a specific relationship (a/b ≥ 0.75) within a 10 um to 200 um deep region, using a rubber composition with phenylenediamine antioxidants, liquid plasticizers, and amide compounds or nonionic surfactants to maintain a soft surface and prevent hardening, ensuring consistent grip performance before and after running-in.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tread rubber surface is made soft to improve grip performance, then grip performance is improved, but the surface hardens during storage due to oxygen penetration
Solution Approach 1:
The patent applies preliminary action by incorporating antioxidants (specifically 3.4 parts by mass or more of phenylenediamine type antioxidants per 100 parts by mass of rubber component) and liquid plasticizers (20 parts by mass or more per 100 parts by mass of rubber component) into the rubber composition before tire manufacturing. These additives pre-protect the rubber surface from oxidation and maintain softness during storage, preventing the hardening that would otherwise occur before the tire is put into service.
Solution Approach 2:
The patent employs parameter changes by carefully controlling the composition ratios of antioxidants, liquid plasticizers, and other additives in the rubber compound. Specifically, it uses 3.4 parts by mass or more of phenylenediamine antioxidants and 20 parts by mass or more of liquid plasticizers per 100 parts by mass of rubber component, which transforms the rubber's resistance to oxidation and its surface hardness characteristics over time.
2Stability of the object's composition
If antioxidants are increased to prevent surface hardening, then surface stability is improved, but grip performance may be compromised
Solution Approach 1:
The patent optimizes the parameter of antioxidant content by specifying 3.4 parts by mass or more of phenylenediamine type antioxidants per 100 parts by mass of rubber component. This specific quantity ensures sufficient oxidation protection to maintain surface stability while preserving the rubber's grip performance characteristics.
Solution Approach 2:
The patent creates a composite rubber composition that combines multiple functional additives: phenylenediamine antioxidants for oxidation protection, liquid plasticizers for maintaining softness, and optionally amide compounds or nonionic surfactants. This composite formulation achieves both surface stability and grip performance simultaneously.
3Stability of the object's composition
If liquid plasticizers are increased to maintain surface softness, then surface flexibility is improved, but the rubber composition complexity increases
Solution Approach 1:
The patent controls the parameter of liquid plasticizer content by specifying 20 parts by mass or more per 100 parts by mass of rubber component. This specific quantity ensures sufficient surface softness maintenance while managing the complexity of the rubber composition formulation.
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 tires achieve satisfactory grip performance both before and after running-in by maintaining a soft surface layer that conforms to road irregularities, reducing deformation and lifting of block edges, and enhancing actual contact area.
Implementation Method 1
the tread rubber surface hardens during storage due to oxygen penetration and low antioxidant content
Implementation Method 2
the tread rubber is formed from a rubber composition which comprises, per 100 parts by mass of a rubber component therein, 20 parts by mass or more of at least one liquid plasticizer
Implementation Method 3
measuring a Martens hardness of the measurement face of the specimen prepared in the specimen preparation step along the tire radial direction using a microhardness tester
Data Source
Figure 1
Figure 2~3
Figure 4(a)~4(c)
AI summary
The present invention aims to provide tires which exhibit satisfactory grip performance both before and after running-in. The present invention relates to tires including a tread rubber, the tread rubber satisfying the following relationship (I): a/b≥0.75 wherein the symbols (a) and (b) represent the minimum and maximum Martens hardnesses, respectively, of a tire tread contact portion measured in a region from 10 µm to 200 µm deep in the tire radial direction from the tire surface.