Cured Tread Axial Thickness Profile for Irregular Wear Control
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Solution Overview
Problem
The bonding surface of a base tire, formed by buffing a used tire, results in uneven curvature, leading to irregular wear in the tire's outer and middle areas due to mismatched ground contact lengths, causing either excessive or inadequate contact with the road surface.
Innovation Solution
A cured tread with a configuration of gradually decreasing thickness from the equator to the outermost groove edge and then increasing or maintaining thickness from that edge, optimizing the ground contact shape to ensure balanced contact and prevent irregular wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cured tread of fixed thickness or thinner from axial center toward each side is bonded to a base tire with bonding surface curvature radius decreasing away from axial center, then the bonding process is simplified, but the cured tread bends in an arc causing grooves to stretch and ground contact length to become longer than designed, leading to irregular wear in axially outer areas
Solution Approach 1:
The cured tread is designed with varying thickness along the axial direction, where the thickness is greater at axially outer positions compared to the axial center. This local variation in thickness compensates for the arc bending caused by bonding to the curved base tire surface, ensuring that grooves maintain their intended shape and ground contact length matches the design specifications, thereby preventing irregular wear.
2Ease of repair
If the bonding surface is formed by buffing the tread portion of a used tire, then the base tire can be obtained for reuse, but the bead portions spread wider than rim width causing the tread surface to bend further when fitted, resulting in smaller radius at axial sides and extremely shorter ground contact length, raising likelihood of irregular wear in axially middle area
Solution Approach 1:
The cured tread incorporates a thickness profile that is greater at axially outer positions to compensate for the additional bending effect caused by bead portion spreading during buffing of used tires. This local thickness variation ensures that even when the tread surface bends further due to rim fitting, the ground contact length in axially middle areas remains consistent with design requirements, preventing irregular wear.
3Device complexity
If a cured tread with fixed thickness is bonded to a base tire with curved bonding surface, then the tread structure is simplified, but the tread bends in an arc causing radius difference between inner and outer edges of grooves to increase, leading to stretched groove shapes and irregular wear
Solution Approach 1:
The cured tread is designed with a thickness profile that varies along the axial direction, being greater at axially outer positions. This local thickness variation compensates for the arc bending that occurs when bonding to the curved base tire surface, ensuring that grooves maintain their intended shape and size, thereby preventing irregular wear while keeping the overall tread structure relatively simple.
Data Source
AI summary
The invention provides a cured tread and a tire capable of controlling irregular wear of the tread. A base tire which is to be the base for the tire and a cured tread which is to be bonded to the base tire are molded separately, and they are integrated with each other to produce the tire. The tread is provided in its width (axial) direction with a plurality of grooves extending in its length (circumferential) direction. The thickness of the tread in a width cross section gradually decreases from the equator to the equator-side edge of the outermost groove located at an axially outermost position and gradually increases from the outer edge of the outermost groove outward in the axial direction.