Seal Device Backup Ring Curvature Reduces Mises Stress
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Solution Overview
Problem
Conventional seal devices for high-pressure carbon dioxide gas in car air conditioners experience excessive stress and reduced service life due to high Mises stress at the seal lip corner, leading to potential fractures.
Innovation Solution
A seal device with a tapered backup ring featuring a rounded surface with a curvature radius (R-1) at the boundary between the tapered and distal ends, and a convex surface with a curvature radius greater than (R-1) to increase the contact surface area, reducing equivalent Mises stress and preventing misalignments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tapered backup ring is used to maintain seal lip alignment, then sealing reliability is improved, but excessive Mises stress occurs at the seal lip corner leading to reduced service life
Solution Approach 1:
The invention applies curvature by forming a rounded surface with a specific curvature radius at the boundary between the tapered part and distal end part of the backup ring. This curved transition replaces the sharp corner geometry, distributing stress more evenly and preventing excessive Mises stress concentration that would otherwise occur at the seal lip corner, thereby extending service life while maintaining sealing reliability.
2Strength
If the backup ring is pressed into the seal lip to ensure joining, then structural integrity is improved, but the seal lip is lifted off the shaft surface compromising sealing capacity
Solution Approach 1:
The invention applies local quality by creating a rounded surface with specific curvature radius at the boundary region of the backup ring. This localized geometric modification allows the backup ring to be pressed into the seal lip with sufficient joining strength while the rounded transition prevents excessive deformation that would lift the seal lip off the shaft surface, thereby maintaining sealing capacity.
Data Source
AI summary
A seal device where a seal lip reliably maintains shaft sealing relative to high-pressure fluid that is to be sealed and where the equivalent Mises stress occurring in the seal lip is reduced to extend the durable term of the seal lip longer. A backup ring has a tapered section continuously extending from a fixation section of the backup ring and also has a forward end section. A rounded surface (E) with a curvature radius (R-1) is formed at least at a boundary where a surface (D) of the tapered section changes to a surface (F) of the forward end section. A portion of the surface (D) of the tapered surface, which portion is in contact with the rounded surface (E) at the boundary, is a projected curvature surface having a curvature radius greater than the curvature radius (R-1) of the boundary.