Tire Tread Groove Depth Layout for Steering Stability

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Solution Overview

Problem

Tires with uniform and deep circumferential grooves suffer from reduced tread rigidity, impacting steering stability while maintaining wear resistance, necessitating an improvement in tread rigidity to enhance steering stability performance.

Innovation Solution

A tire design with a crown ground contact length between 0.95 to 1.05 times the shoulder ground contact length, and groove depths determined by specific equations to prevent excessive wear, optimizing groove depth distribution across the tread to improve rigidity and cornering power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If uniform and deep circumferential grooves are provided in the tread portion, then wear resistance is improved, but tread rigidity is reduced

Engineering Contradiction:
Improvewear resistanceVSAvoidtread rigidity
Core Design Contradiction:
Duration of action of stationary objectVSStrength

Solution Approach 1:

The groove depth is varied according to the axial position in the tread portion. Specifically, the groove depth increases from the shoulder portion toward the center portion, creating local variations in groove depth that optimize both wear resistance and tread rigidity. This local quality variation allows different regions of the tread to have appropriate groove depths for their specific functional requirements.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The groove depth parameter is changed based on the axial position. The groove depth is set to increase from the shoulder portion to the center portion, with specific relationships defined between groove depths at different axial positions. This parameter change strategy enables the tread to maintain rigidity while achieving uniform wear characteristics.

Inventive Principle:
Principle #35Parameter changes

2Duration of action of stationary object

If large groove depth is used to improve wear resistance, then cornering power is reduced due to decreased tread rigidity

Engineering Contradiction:
Improvewear resistanceVSAvoidcornering power
Core Design Contradiction:
Duration of action of stationary objectVSForce

Solution Approach 1:

The groove depth is locally optimized at different axial positions to maintain tread rigidity while ensuring wear resistance. By making grooves shallower at the shoulder portions and deeper toward the center, the tread maintains sufficient rigidity for cornering while achieving uniform wear patterns that improve long-term performance.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The groove depth parameter is systematically varied across the axial position, with specific mathematical relationships defined. This controlled parameter change ensures that the tread portion maintains adequate rigidity for cornering power while achieving the wear resistance benefits of grooved structures.

Inventive Principle:
Principle #35Parameter changes

3Ease of manufacture

If uniform groove depth is provided across the tread, then manufacturing is simplified, but steering stability is compromised

Engineering Contradiction:
Improvegroove uniformityVSAvoidsteering stability
Core Design Contradiction:
Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The groove depth is designed to vary locally according to axial position, with the center portion having greater groove depth than the shoulder portions. This local variation improves steering stability and cornering performance while maintaining reasonable manufacturing complexity through defined geometric relationships.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The groove depth distribution is intentionally made asymmetric across the axial position, with the center portion featuring deeper grooves than the shoulder portions. This asymmetric design optimizes steering stability and cornering power by creating appropriate rigidity distribution across the tread width.

Inventive Principle:
Principle #4Asymmetry

Data Source

PatentEP4015244B1tire
Publication Date: 2023.12.06 SUMITOMO RUBBER INDUSTRIES LTD
  • EP4015244B1 patent drawingFigure 1
  • EP4015244B1 patent drawingFigure 2
  • EP4015244B1 patent drawingFigure 3

AI summary

A tire has a tread portion provided with grooves. The ground contact area of the tread portion has ground contact lengths in the tire circumferential direction which include a crown ground contact length LC at the tire equator C and a shoulder ground contact length LS at a position spaced apart from the tire equator C by 80% of a half tread width Tw. The crown ground contact length LC is 0.95 to 1.05 times the shoulder ground contact length LS. Groove depths of the respective grooves are determined so as to satisfy specific mathematical equations based on a reference virtual groove G0 having a predetermined groove depth d0 and defined at the tire equator C.