Valve Seal Lip Geometry for Low-Stress EVAP Valve Closing
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Solution Overview
Problem
Existing flow control valves in evaporative fuel processing systems face issues with internal stress leading to potential damage of the rubber seal member due to high stress concentrations, which compromises the durability and sealing performance when trying to improve sealing by reducing the curvature radius of the lip portion.
Innovation Solution
The valve member design incorporates a bottom wall portion with an annular convex portion having a curvature radius larger than the lip portion, and a flat plate portion with a corresponding annular lip portion that projects towards the valve seat, reducing internal stress and preventing the convex portion from breaking through the lip portion, thus enhancing durability and sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the curvature radius of the lip portion is reduced to improve sealing performance, then sealing performance is improved, but internal stress increases causing the convex portion to break through the lip portion
Solution Approach 1:
The patent applies local quality by creating different curvature radii at different locations: the lip portion has a smaller curvature radius for sealing contact, while the convex portion has a larger curvature radius to reduce stress concentration. This localized differentiation allows the sealing surface to have high curvature for good sealing while the support structure has low curvature to prevent stress-induced failure.
Solution Approach 2:
The convex portion with larger curvature radius acts as a stress-distributing structure that cushions the concentrated loads before they reach the lip portion. This pre-cushioning effect prevents the lip portion from being subjected to excessive stress that would cause it to break through, thereby protecting the sealing structure in advance.
2Reliability
If the curvature radius of the lip portion is reduced to improve sealing, then seal margin increases, but internal stress concentration damages the rubber seal member
Solution Approach 1:
The patent implements local quality by assigning different curvature characteristics to different functional zones: the lip portion uses small curvature radius to maximize seal margin and sealing contact, while the convex portion uses large curvature radius to minimize stress concentration. This spatial differentiation resolves the conflict between achieving high seal margin and avoiding stress-induced damage.
Solution Approach 2:
The patent converts the potentially harmful stress concentration into a beneficial stress-distributing feature by designing the convex portion with larger curvature radius. This structure transforms what would be a stress concentration point into a stress-distributing zone that protects the lip portion, turning a harmful effect into a protective mechanism.
Data Source
AI summary
A bottom wall portion of a valve member has an annular convex portion projecting from a bottom surface toward a valve seat. A rubber seal member has a flat plate portion in contact with the bottom wall portion, and an annular lip portion formed to project toward the valve seat at a position corresponding to the convex portion in the flat plate portion so as to abut on the valve seat at the time of valve closing. A projecting tip of the lip portion forms an arc-shaped part in the axial cross section of the valve member. A projecting tip of the convex portion forms an arc-shaped part having a curvature radius larger than a curvature radius of the arc-shaped part of the lip portion in the axial cross section of the valve member.