Bead-Reinforced Tire Structure for Strain Dispersion and Mass Reduction
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Solution Overview
Problem
Conventional tires with reinforcing rubber layers face challenges in balancing durability and mass reduction, as the stiffness of the rubber layer increases at portions with the reinforcing rubber, leading to strain concentration and potential durability issues.
Innovation Solution
A tire design featuring a carcass with turned-up portions and reinforcing rubber layers between the turned-up portions and protective rubber layers, where the protective rubber layer thickness is reduced at the center portion and increased at other portions, dispersing strain and reducing the tire's mass while maintaining durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the protective rubber layer is set based on conventional art concepts, then the tire mass increases, but the stiffness of the rubber layer outward of the carcass increases at portions including the reinforcing rubber layer, leading to strain concentration and decreased durability
Solution Approach 1:
The protective rubber layer is designed with non-uniform thickness: thinner at the center portion (radial direction center of reinforcing rubber layer) and thicker at other portions. This local variation in thickness allows the tire to reduce overall mass while preventing strain concentration at critical locations, thereby maintaining durability without uniformly increasing mass throughout the protective layer
Solution Approach 2:
The invention changes the thickness parameter of the protective rubber layer from a uniform conventional design to a variable thickness design. By adjusting the thickness parameter locally (thinner at center, thicker at edges), the solution optimizes the balance between mass reduction and durability prevention of strain concentration
2Strength
If a reinforcing rubber layer is provided between the turned-up portion and protective rubber layer, then durability is improved through enhanced bead stiffness, but the stiffness of the rubber layer outward of the carcass increases at reinforcing rubber layer portions, causing strain concentration
Solution Approach 1:
The protective rubber layer thickness is locally optimized: thinner at the center portion where the reinforcing rubber layer provides sufficient stiffness support, and thicker at other portions to prevent strain concentration. This local quality variation allows the reinforcing rubber layer to maintain bead stiffness while the protective layer adapts its thickness to prevent strain concentration at critical areas
Solution Approach 2:
The invention uses a composite structure combining the reinforcing rubber layer (hard crosslinked rubber) with the protective rubber layer of variable thickness. The composite design allows the harder reinforcing layer to provide bead stiffness while the softer, variable-thickness protective layer prevents strain concentration, creating a synergistic effect that improves both strength and durability
Data Source
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AI summary
A tire 2 includes a pair of beads 8, a carcass 10, a pair of protective rubber layers 6, and a pair of reinforcing rubber layers 22. A carcass ply 42a of the carcass 10 includes a ply body 48a and a pair of turned-up portions 50a. Each reinforcing rubber layer 22 is located between the turned-up portion 50a and the protective rubber layer 6. An outer end PA of an apex 40 of each bead 8 is located between an outer end PRS and an inner end PRU of the reinforcing rubber layer 22 in a radial direction. A thickness of the protective rubber layer 6 in a zone from a rim contact end PF to the outer end PRS of the reinforcing rubber layer 22 is small at a center portion in the radial direction of the reinforcing rubber layer 22 and is large at another portion.