Dual-Compound Tire Tread for Wet Grip and Wear Stability
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Solution Overview
Problem
Tires experience a decline in hydroplaning performance and grip on wet surfaces as they wear down, due to reduced tread height, increased rolling resistance, and rigidity, with existing solutions either degrading rolling resistance or requiring complex and costly tire molds.
Innovation Solution
A tire design featuring two rubber mixtures that constitute 90% of the tread's volume, with specific mechanical properties to maintain grip and reduce rolling resistance, including a second rubber mixture that is more rigid and hysteretic, and a first rubber mixture that deforms more, ensuring consistent wear and improved adhesion, while minimizing the impact on rolling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rubber compound with high hysteresis at 0°C is used for the tread to improve wet grip and hydroplaning performance, then wet grip performance is improved, but rolling resistance significantly degrades because the rubber compound also has high hysteresis at 23°C
Solution Approach 1:
The tread is divided into multiple rubber compounds with different hysteresis characteristics. The first rubber compound (40-60% volume) has high hysteresis at 0°C for wet grip, while the second rubber compound (40-60% volume) has lower hysteresis at 23°C for reduced rolling resistance. This segmentation allows each material to optimize its performance in its designated region.
Solution Approach 2:
Different regions of the tread are assigned different rubber compounds based on their functional requirements. The first rubber compound is placed in regions requiring high wet grip (higher hysteresis at 0°C), while the second rubber compound is placed in regions where lower rolling resistance is prioritized (lower hysteresis at 23°C). This local differentiation resolves the contradiction by making each location's material property match its operational demand.
2Reliability
If complex tread patterns are used to recreate cutouts as the tire wears to maintain wet grip, then wet grip performance is maintained, but the tire requires complex, expensive molds that are difficult to demold and susceptible to rubber tearing
Solution Approach 1:
Instead of changing the geometric complexity of the tread pattern, the invention changes the material parameter (hysteresis) of the rubber compounds. By using a first rubber compound with high hysteresis at 0°C, the tread maintains effective cutout functionality and wet grip performance without requiring complex geometric patterns, thus avoiding the manufacturing complexities associated with such patterns.
3Loss of energy
If the tread depth decreases with wear, then rolling resistance decreases, but hydroplaning performance reduces because the water storage capacity decreases
Solution Approach 1:
The tread is designed with a first rubber compound having high hysteresis at 0°C and specific mechanical properties (secant modulus ratio between 0.9 and 1.1) that maintain tread depth and water storage capacity throughout the tire's service life. This preliminary design ensures that even as the tire wears, the tread structure maintains sufficient depth to store water and prevent hydroplaning, countering the natural tendency of tread depth reduction.
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 maintains excellent grip on wet surfaces at the end of its life while limiting the increase in rolling resistance, with a synergy of rigidity and adhesion that enhances performance and reduces irregular wear, as demonstrated by improved wet braking and reduced rolling resistance penalties.
Implementation Method 1
the second rubber compound having a dynamic loss tanD0_2, measured according to ASTM D 5992 - 96, at a temperature of 0°C at 10 Hz, at least equal to the dynamic loss tanD0_1 of the first rubber compound measured according to ASTM D 5992 - 96, at a temperature of 0°C at 10 Hz, the dynamic loss tanD23_1 of the first rubber compound, measured according to ASTM D 5992 - 96, at a temperature of 23°C at 10 Hz, being at most equal to the dynamic loss tanD23_2 of the second rubber compound, measured according to ASTM D 5992-96, at a temperature of 23°C at 10 Hz
Implementation Method 2
The tread is thus constituted by the rubber compound(s) radially outside the outermost radially reinforcing layer of the crown reinforcement
Data Source
Figure 1
AI summary
The invention is a tyre for a vehicle comprising a tread (2), in which the central portion of the tread (2) comprises at least two rubber mixtures (221, 222), making up at least 90% of its volume. The first mixture (221) is radially outside the second mixture (222) and makes up at least 40% and at most 60% of the volume of the central portion. The second rubber mixture (222) has a Shore hardness DS2 at least equal to 5 plus the Shore hardness DS1 of the first mixture (221). The second rubber mixture (222) has dynamic losses at a temperature of 0°C and at a temperature of 23°C at least equal to those of the first rubber mixture (221).