Multi-Layer Tread Structure for Low Rolling Resistance and Even Wear
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Solution Overview
Problem
Conventional pneumatic tires do not adequately reduce rolling resistance and are prone to uneven wear, despite existing attempts to improve these aspects through tread composition modifications.
Innovation Solution
A pneumatic tire design featuring a tread portion with multiple rubber layers, a circumferential groove, and a belt reinforcing layer, where the complex elastic modulus of the inner layer is lower than the surface layer, and specific groove area ratios and sipe configurations are implemented to enhance contact stability and reduce stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the tread portion is made with a single rubber composition to reduce rolling resistance, then low fuel consumption performance is improved, but uneven wear resistance deteriorates
Solution Approach 1:
The tread portion is divided into multiple rubber layers (first rubber layer and second rubber layer) with different compositions and properties. The first rubber layer has lower hysteresis loss for reduced rolling resistance, while the second rubber layer has higher wear resistance for improved durability. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between reducing energy loss and maintaining reliability.
Solution Approach 2:
Different regions of the tread portion are assigned different rubber compositions tailored to their specific functional requirements. The first rubber layer uses a composition optimized for low hysteresis loss (e.g., high silica content, specific polymer ratio) to reduce rolling resistance, while the second rubber layer uses a composition optimized for wear resistance (e.g., different polymer blend, filler distribution). This local optimization of material properties resolves the contradiction by allowing each region to excel at its primary function.
2Loss of energy
If the tread portion uses a softer rubber composition to improve contact uniformity, then rolling resistance is reduced, but wear resistance deteriorates
Solution Approach 1:
The tread portion is segmented into a first rubber layer with softer, lower hysteresis composition for improved contact uniformity and reduced rolling resistance, and a second rubber layer with harder, more wear-resistant composition for durability. The first layer's softer properties allow better conformability to the road surface, reducing energy loss, while the second layer provides the necessary strength and wear resistance that would be compromised if the entire tread were made soft.
Solution Approach 2:
The tread portion employs a composite structure of two different rubber compositions layered together. The first rubber layer contains materials optimized for low hysteresis (such as specific silica-modified polymers with controlled crosslinking), while the second rubber layer contains materials optimized for wear resistance (such as different polymer blends with enhanced tensile strength). This composite material approach allows the tread to simultaneously achieve softness for uniform contact and hardness for wear resistance in different layers.
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 tire achieves both reduced rolling resistance and improved uneven wear resistance by ensuring uniform ground contact and stress distribution, leading to better fuel efficiency and extended tread life.
Implementation Method 1
when a loss tangent at 30°C of an inner layer of the tread portion is denoted by tan δ 2, tan δ 2 is not greater than 0.10
Implementation Method 2
when a complex elastic modulus at 30°C of the surface layer of the tread portion is denoted by E*
Data Source
Figure 1
AI summary
A pneumatic tire that achieves both reduction of rolling resistance and improvement of uneven wear resistance is provided. The pneumatic tire includes: a tread portion including at least two or more rubber layers including a surface layer and an inner layer in a center region centered at a tire equator line and having a width that is 50% of a ground-contact width of a ground-contact surface; and sidewall portions. The tread portion has a circumferential groove extending in a circumferential direction, and includes a plurality of land portions demarcated by the circumferential groove and ground-contact end portions. An outer portion of each sidewall portion is overlapped on an outer side of an end portion in a tire width direction of the tread portion, and each end portion in the width direction of the inner layer is located in a part of an interface between the surface layer and the sidewall portion. A complex elastic modulus E∗1 (MPa) of the surface layer and a complex elastic modulus E∗2 (MPa) of the inner layer satisfy (E∗2/E∗1)<1.0, and a groove area ratio CR (%) in the center region and a groove area ratio SR (%) in a region obtained by excluding the center region from the ground-contact surface satisfy |CR-SR|≤15.