Layered Tire Tread Layout for Stable Wet Braking Through Wear
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Solution Overview
Problem
Tires with rubber layers of different loss tangents tend to experience sudden changes in wet performance in the middle stage of tread wear life, failing to maintain good wet performance from the initial to the final stage.
Innovation Solution
A tire design featuring circumferential grooves that divide the tread portion into first and second land portions, with specific loss tangents and distances for the cap, intermediate, and base tread rubber layers, ensuring gradual exposure of the intermediate tread rubber layer as the tire wears, thereby stabilizing wet performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tread portion comprises rubber layers with different loss tangents to improve wet performance, then wet braking performance is improved, but wet performance changes suddenly in the middle stage of wear life
Solution Approach 1:
The tread rubber is divided into three distinct layers with different loss tangent values: a cap tread rubber layer (0.15≤tanδ1<0.35), an intermediate tread rubber layer (0.30≤tanδ2<0.50), and a base tread rubber layer (0.05≤tanδ3<0.25). This segmentation allows each layer to contribute differently to wet performance at various stages of wear, preventing sudden performance changes.
Solution Approach 2:
Different regions of the tread portion are designed with specific layer configurations. The first land portion has the cap tread rubber layer extending to the groove bottom, while the second land portion has the intermediate tread rubber layer extending closer to the groove bottom. This local quality differentiation ensures gradual exposure of layers with appropriate loss tangents during wear.
2Loss of energy
If the cap tread rubber layer has low loss tangent for low rolling resistance, then rolling resistance is reduced, but wet performance deteriorates
Solution Approach 1:
The tread portion uses a composite structure of three rubber layers with different loss tangent characteristics. The cap layer (low tanδ) provides low rolling resistance, the intermediate layer (high tanδ) provides wet friction, and the base layer (low tanδ) maintains stability. This composite material approach resolves the contradiction between rolling resistance and wet performance.
Solution Approach 2:
The solution moves from a single-layer uniform material to a multi-layer structured material with vertical differentiation. By adding the radial dimension of layering with progressively different loss tangents, the patent simultaneously achieves low rolling resistance (cap layer) and good wet performance (intermediate layer exposure during wear).
3Reliability
If the intermediate tread rubber layer is positioned closer to the groove bottom in the second land portion, then wet performance is maintained during wear, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter ranges for the rubber layers to balance performance and manufacturability. The loss tangents are constrained to specific ranges (tanδ1: 0.15-0.35, tanδ2: 0.30-0.50, tanδ3: 0.05-0.25), and the distance ratio L1/L2 is set between 0.5-2.0. These parameter specifications make the design achievable with standard manufacturing tolerances while ensuring the desired gradual layer exposure effect.
Data Source
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AI summary
A tire comprises a tread portion provided with circumferential grooves and including a circumferential first land portion and a circumferential second land portion on the tire equator side of the first land portion. Each of the first land portion and the second land portion comprises a cap tread rubber layer and an intermediate tread rubber layer. The loss tangent δ2 of the intermediate tread rubber layer is larger than the loss tangent δ1 of the cap tread rubber layer. The shortest distance L2 from the ground contacting surface of the second land portion to the radially outer surface of the intermediate tread rubber layer of the second land portion is smaller than the shortest distance L1 from the ground contacting surface of the first land portion to the radially outer surface of the intermediate tread rubber layer of the first land portion.