Airless Tire Tread Ring Shear Layer Moduli Ratio
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Solution Overview
Problem
Airless tires face challenges in reducing rolling resistance and maintaining steering stability due to the inherent high hysteresis losses in solid tread components, which are 2.5 times higher than those of pneumatic tires, necessitating a different tread structure and component properties.
Innovation Solution
The airless tire employs a sandwich structure with a shear rubber layer sandwiched between first and second reinforcing cord layers, optimizing the ratios of tensile moduli to shear modulus and using specific rubber compositions to achieve low deformation and reduced rolling resistance, while ensuring steering stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solid tread components are used in airless tires, then the structural integrity is improved, but the hysteresis losses increase to 2.5 times that of pneumatic tires
Solution Approach 1:
The tread ring is segmented into multiple functional layers: tread rubber layer, first reinforcing cord layer, shear rubber layer, second reinforcing cord layer, and topping rubber layer. This segmentation allows each layer to perform its specific function - the cord layers provide structural integrity while the rubber layers control hysteresis losses through their viscoelastic properties
Solution Approach 2:
The patent uses composite material structures combining rubber layers with reinforcing cord layers. The composite structure of the tread ring, with alternating rubber and cord layers, optimizes the balance between structural strength and energy loss by leveraging the complementary properties of rubber (low hysteresis) and cord (high strength) materials
2Loss of energy
If the tread ring structure is optimized to reduce rolling resistance, then energy efficiency is improved, but maintaining steering stability becomes more difficult
Solution Approach 1:
Different regions of the tread ring are given different properties: the tread rubber layer provides low hysteresis for rolling resistance reduction, while the reinforcing cord layers provide high strength for steering stability. The local optimization of each layer's properties allows simultaneous achievement of low rolling resistance and high steering stability
Solution Approach 2:
The patent optimizes specific parameters including the tensile modulus of the reinforcing cord layers (Eb1, Eb2), the shear modulus of the rubber layer (Ee), and the ratio Eb1/Ee ≥ 100. These parameter changes enable the tread ring to exhibit low rolling resistance while maintaining sufficient stiffness for steering stability
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
This configuration effectively reduces rolling resistance and enhances steering stability, bringing the performance of airless tires closer to that of pneumatic tires by leveraging a shear rubber layer and reinforcing cord layers with tailored properties.
Implementation Method 1
the inherent high hysteresis losses in solid tread components, which are 2.5 times higher than those of pneumatic tires
Implementation Method 2
a ratio Eb1/Ee between a tire circumferential direction tensile modulus Eb1 of the first reinforcing cord layer and a shear modulus Ee of the shear rubber layer is 100 or greater
Data Source
AI summary
An airless tire includes a tread ring, a hub formed on radial direction inner side of the ring to be fixed to an axle, and a spoke structure connecting the ring and hub. The ring includes a tread rubber layer, a first reinforcing cord layer, a second reinforcing cord layer and a shear rubber layer between the first and second cord layers, the first and second cord layers and shear layer are formed such that ratio Eb1/Ee between tire circumferential direction tensile modulus Eb1 of the first cord layer and shear modulus Ee of the shear layer is 100 or greater and ratio Eb2/Ee between tire circumferential direction tensile modulus Eb2 of the second cord layer and shear modulus Ee is 100 or greater, and each cord layer has topping rubber having loss tangent tan δb of 0.03 to 0.10 and tensile modulus E*b of 4 to 20 MPa.