Multi-Cap Tire Tread with Notched Outer Layer for Wet Grip and Rolling Resistance
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Solution Overview
Problem
As a tire wears, the volume of the tread decreases, leading to reduced non-skid capabilities and impaired wet road performance due to decreased groove volume, which limits the tire's ability to channel water away, even if the tread has not worn down to the legal minimum non-skid depth.
Innovation Solution
A pneumatic tire with a tread comprising a radially outer tread cap layer for improved wet properties, a middle tread cap layer for low rolling resistance, and a base tread compound, featuring notched areas that allow the outer cap layer to extend inward, maintaining contact and performance as the tire wears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer tread cap is used, then the structure is simple and manufacturing is easier, but wet grip performance and rolling resistance performance cannot both be optimized throughout the tire's life
Solution Approach 1:
The tread cap is divided into multiple layers (first tread cap layer and second tread cap layer) with different rubber compounds optimized for different functions. The first layer provides wet grip properties while the second layer provides rolling resistance properties, allowing both performance aspects to be optimized simultaneously throughout the tire's service life.
Solution Approach 2:
Different regions of the tread cap have different material properties tailored to their specific functions. The first tread cap layer uses a rubber compound formulated for wet grip, while the second tread cap layer uses a different compound formulated for rolling resistance, creating local optimization of performance characteristics.
2Loss of energy
If the outer tread cap layer is made thin, then rolling resistance improves, but wet grip performance deteriorates
Solution Approach 1:
The tread cap is segmented into multiple layers with distinct thicknesses and material properties. The first tread cap layer can be optimized for wet grip with appropriate thickness and compound, while the second tread cap layer is optimized for rolling resistance, allowing both requirements to be satisfied without compromise.
Solution Approach 2:
The tread cap uses a composite structure with at least two different rubber compounds in separate layers. This composite approach allows each layer to contribute its specialized properties (wet grip or rolling resistance) to the overall performance, achieving a balance that neither single material could provide alone.
3Reliability
If the tread cap layer is made thick, then wet grip performance improves, but rolling resistance increases
Solution Approach 1:
The tread cap is divided into multiple layers where the first layer can be made sufficiently thick to provide wet grip performance, while the second layer compensates for rolling resistance. This segmentation allows the wet grip layer to be optimized for thickness without unnecessarily increasing overall rolling resistance.
Solution Approach 2:
The multi-layer composite structure allows the first tread cap layer to be optimized for wet grip with appropriate thickness and compound formulation, while the second tread cap layer uses a different compound to balance the rolling resistance, achieving overall performance optimization that a single thick layer could not provide.
4Device complexity
If groove volume decreases as the tire wears, then the structure remains simple, but wet road performance is severely limited
Solution Approach 1:
The tread groove is designed with a preliminary geometry that anticipates wear. The groove cross-sectional area is increased at the bottom relative to the top, creating a trapezoidal or triangular shape. This preliminary design ensures that even as the tire wears and groove volume decreases, the remaining groove structure maintains adequate water channeling capability throughout the tire's service life.
Solution Approach 2:
The groove geometry incorporates curved or tapered sides rather than straight vertical walls, creating a trapezoidal or triangular cross-section. This curved geometry allows the groove to maintain effective water channeling capacity as wear progresses, with the wider bottom section providing reserve capacity that compensates for material loss during tire life.
Data Source
Figure 1
AI summary
A tire tread (10) comprising one or more grooves (19, 22, 24, 28) having a groove depth and at least one rib (18, 20, 26) is disclosed. The tread (10) has a radially outer surface and a non-skid tread depth as measured from the radially outer surface of the tread (10) to the radially innermost surface of the one or more grooves (19, 22, 24, 28). The tread (10) further has a radially innermost layer (70) comprising of a base tread compound, a radially outer tread cap layer (50) and a middle tread layer (60) located between the base layer (70) and the outer tread cap layer (50). The rib (18, 20, 26) comprises a dividing line (A) formed between the radially outer tread cap layer (50) and the middle tread layer (60). The dividing line (A) has a notched area in which the radially outer tread cap layer (50) extends radially inward to a depth in a range of from 80% to 110% of the groove depth (D) or the non-skid depth. Also, a pneumatic tire comprising such a tire tread is disclosed.