Pneumatic Tire Carcass Structure for Load-Adaptive Vertical Rigidity
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Solution Overview
Problem
Conventional tires with increased vertical spring rigidity suffer from reduced flexibility at light tire loads, leading to inadequate ground contact length and area, which degrades tire performance.
Innovation Solution
A pneumatic tire design featuring a carcass with first and second carcass cords of different Young's moduli, where the second carcass cords have a larger modulus than the first, and are positioned outside the folded-back portions of the first carcass cords, allowing for improved vertical spring rigidity at heavy loads while maintaining flexibility at light loads through a specific manufacturing method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the vertical spring rigidity is increased by increasing the tire inner pressure and increasing the rigidity of the carcass, then the vertical spring rigidity is improved, but the flexibility of the tire at relatively light tire load becomes insufficient
Solution Approach 1:
The carcass is segmented into multiple carcass plies with different cord arrangements and material properties. The first carcass ply has cords extending from the tread to the bead portions, while the second carcass ply has cords arranged differently. This segmentation allows each ply to contribute differently to the tire's mechanical properties, enabling high vertical spring rigidity at heavy loads while maintaining flexibility at light loads.
Solution Approach 2:
Different regions of the carcass are given different local qualities through varying cord arrangements and material properties. The first and second carcass plies have different cord orientations and Young's moduli, creating localized variations in stiffness. This allows the tire to exhibit appropriate flexibility in certain regions under light loads while providing high rigidity in other regions under heavy loads.
2Strength
If the vertical spring rigidity is increased, then the ground contact length and ground contact area are reduced, but the tire performance based on the ground contact is degraded
Solution Approach 1:
The tire structure is designed to dynamically adapt its effective stiffness based on the applied load. Under light loads, the carcass plies allow greater deformation, maintaining larger ground contact area. Under heavy loads, the higher rigidity of the carcass structure provides the necessary vertical spring rigidity. This dynamic behavior resolves the contradiction between rigidity and ground contact area.
Solution Approach 2:
The carcass uses composite construction with multiple plies having different cord materials, arrangements, and Young's moduli. This composite structure enables the tire to exhibit non-linear mechanical behavior, providing both flexibility for ground contact and rigidity for vertical support depending on the load condition, thereby resolving the contradiction between ground contact area and vertical spring rigidity.
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
The tire achieves enhanced vertical spring rigidity at heavy loads while ensuring sufficient ground contact and flexibility at light loads, stabilizing vehicle posture and improving running performance across various speed ranges.
Implementation Method 1
the first carcass cords have a Young's modulus E1, and the second carcass cords have a Young's modulus E2 larger than the Young's modulus E1
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A pneumatic tire (1) comprises a tread portion (2), sidewall portions (3), bead portions (4) each with a bead core (5) embedded therein, and a carcass (6) extending between the bead portions (4) and comprising first carcass cords (63) and second carcass cords (64). The first carcass cord (63) comprises: a main portion (63a) extending from the tread portion (2) to the bead portions (4) via the sidewall portions (3); and folded-back portions (63b) continued from the main portion (63a) and folded back around the bead cores (5) from the inside to the outside in the tire axial direction. The second carcass cord (64) extends from the tread portion (2) to the bead portions (4) and terminates on the axially outside of the folded-back portions (63b) of the first carcass cords (63). Young's modulus of the second carcass cords (64) is larger than Young's modulus of the first carcass cords (63).