Twisted Bead Wire Structure for Pneumatic Tire Rim Mounting
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Solution Overview
Problem
The existing bead structure in pneumatic tires, which divides the bead core into axially inner and outer core pieces, faces issues with deformation during rim mounting due to its thinness, leading to plastic deformation that does not return to its original shape, and lacks sufficient air-leak resistance and corrosion resistance.
Innovation Solution
The use of a bead wire comprising multiple twisted steel strands with a core part made of two or more strands and a sheath part made of three or more strands, all with the same diameter and embossed in a wave shape, provides increased flexibility and stability, preventing deformation during rim mounting and enhancing air-leak resistance and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single bead wire is used in a spiral-wound body, then the radial height of the bead core is maximized and the area of contact with the carcass ply is increased, but the bead core becomes axially thin and undergoes plastic deformation during rim mounting that does not return to its original shape
Solution Approach 1:
The bead wire is constructed as a composite structure with a core part made of steel strands and a sheath part made of steel strands, where the core part and sheath part have different diameters. This composite structure provides both the necessary radial height for maximum contact area and the axial stiffness to prevent plastic deformation during rim mounting.
Solution Approach 2:
The invention changes the structural parameters of the bead wire by specifying that the core part has a smaller diameter than the sheath part, creating a hollow or annular cross-section. This parameter change allows the bead core to maintain axial rigidity while preserving the spiral-wound contact area with the carcass ply.
2Area of stationary object
If the bead wire is made axially thin to maximize contact area, then the area of contact with the carcass ply is increased, but the bead core lacks sufficient flexibility and undergoes permanent deformation
Solution Approach 1:
The composite bead wire structure with core and sheath parts of different diameters creates a hollow configuration that enhances flexibility while maintaining contact area. The hollow structure allows the bead wire to bend and deform elastically during rim mounting operations without permanent damage.
3Ease of manufacture
If a single-core bead wire structure is used, then the manufacturing process is simplified, but the bead core provides insufficient air-leak resistance and corrosion resistance
Solution Approach 1:
The two-part composite bead wire structure with core and sheath components provides enhanced air-leak resistance and corrosion resistance through the layered construction. The sheath part acts as a protective barrier while the core part provides structural support, creating a more reliable seal against the rim flange.
Solution Approach 2:
The bead wire is segmented into distinct core and sheath parts with different diameters, allowing each component to perform its specific function. The core provides structural integrity while the sheath provides protective functions, improving overall reliability without significantly complicating the manufacturing process.
Data Source
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AI summary
The present invention prevents core deformation at a time of mounting a tire on a rim while corrosion resistance and air-leak resistance are assured in a tire made with a inner molding process. A bead core comprises axially inner and outer core pieces, and a radially inner end part of a carcass ply is held therebetween. The axially inner and outer bead pieces are composed of a spiral-wound body in which a bead wire has been spirally wound and overlapped. The bead wire comprises a core part in which core strands have been twisted together and a sheath part in which sheath strands have been twisted together around the core part. The core strands and/or the sheath strands comprise an embossed strand. The twisting direction and twisting pitch (Pc) of the core strands are the same as the twisting direction and twitching pitch (Ps) of the sheath strands.