Kart Tire Reinforcing Layer Layout for Thin Tread Durability

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Solution Overview

Problem

Racing kart tires face a trade-off between wear resistance and durability, as thick treads extend service life but increase weight, while thin treads improve motion performance but may lead to cracks and tears during cornering due to low elongation at break of high-modulus crosslinked rubber.

Innovation Solution

A tire design featuring a tread with reinforcing layers positioned radially inward of the carcass, with a bias structure and cord or rubber reinforcing layers that enhance wear resistance without compromising durability, allowing for a thinner tread and improved motion performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If a thick tread is adopted, then the service life of the tire can be extended, but the tire becomes heavy and affects the motion performance of the vehicle

Engineering Contradiction:
Improveservice lifeVSAvoidtire weight
Core Design Contradiction:
Duration of action of stationary objectVSWeight of moving object

Solution Approach 1:

The patent applies composite materials by combining crosslinked rubber with high elongation at break (50% or more) and high 200% modulus (6.0 MPa or more) with specific reinforcing structures. The tread uses a composite formulation that achieves both thin profile (reducing weight) and high wear resistance (extending service life), resolving the contradiction between thickness/durability and weight/performance.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent changes the physical-chemical parameters of the rubber material by specifying crosslinking density, elongation at break (50% or more), and 200% modulus (6.0 MPa or more). These parameter changes enable the tread to achieve high wear resistance with reduced thickness, thereby reducing weight while maintaining or extending service life.

Inventive Principle:
Principle #35Parameter changes

2Strength

If a crosslinked rubber having a high modulus is adopted for a tread, then wear resistance is improved, but the elongation at break is low and damage such as cracks and tears may occur in the tread of a shoulder portion during cornering

Engineering Contradiction:
Improvewear resistanceVSAvoiddurability
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent precisely controls the parameter balance by specifying elongation at break of 50% or more and 200% modulus of 6.0 MPa or more. This parameter optimization allows the rubber to have both high strength for wear resistance and sufficient elasticity to prevent cracking during cornering, resolving the contradiction between wear resistance and durability.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent uses composite rubber materials that combine high-modulus components for wear resistance with high-elongation components for flexibility. This composite approach ensures the tread can resist wear while maintaining sufficient elasticity to avoid damage during dynamic cornering operations.

Inventive Principle:
Principle #40Composite materials

Data Source

PatentEP3922485B1Tire for kart
Publication Date: 2024.06.05 SUMITOMO RUBBER INDUSTRIES LTD
  • EP3922485B1 patent drawingFigure 1
  • EP3922485B1 patent drawingFigure 2
  • EP3922485B1 patent drawingFigure 3

AI summary

A tire (2) for a kart includes a pair of reinforcing layers (16) disposed with an equator plane therebetween in an axial direction. In a radial direction, the reinforcing layers (16) are located inward of a tread (4) and stacked outward of a carcass (10). In the axial direction, an inner end (34) of each reinforcing layer (16) is located inward of an end TE of a tread surface (18). In the axial direction, a position of an outer end (36) of each reinforcing layer (16) coincides with a position of the end TE of the tread surface (18), or the outer end (36) of each reinforcing layer (16) is located outward of the end TE of the tread surface (18). Each reinforcing layer (16) is a cord reinforcing layer (40) including a plurality of reinforcing cords (38) aligned in a circumferential direction or a rubber reinforcing layer (60).