Gas Sensor Flange Offset Design for Thermal Shock Resistance
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Solution Overview
Problem
Conventional gas sensors face challenges in maintaining high accuracy and air tightness, particularly under severe thermal conditions, where the strength of welding joints between covers is compromised, leading to potential separation and reduced detection accuracy due to gas leakage.
Innovation Solution
A gas sensor design featuring an inner and outer cover with flange portions supported between the insulator and housing, where the flange portions are offset or protrude to form a corner or protrusion, eliminating the need for large welding joints and ensuring high air tightness without gaps, thus preventing separation and maintaining detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding portions are used to fix the inner cover and outer cover, then the covers are securely attached, but the strength of the welding portion is lowered due to fatigue from thermal shock and heat propagation
Solution Approach 1:
The patent replaces the welding connection (thermal/mechanical system) with a mechanical support structure where flange portions are supported between the housing and insulator. This substitution eliminates the welding portion entirely, avoiding the fatigue and strength degradation issues associated with welded joints under thermal cycling conditions.
Solution Approach 2:
The patent introduces flange portions as intermediary elements that are mechanically supported between the housing and insulator. These flange portions serve as mediators to secure the inner and outer covers without requiring direct welding between them, thereby eliminating the welding portion's vulnerability to thermal fatigue.
2Reliability
If the flange portion structure is designed to prevent separation, then attachment reliability is improved, but the design complexity increases
Solution Approach 1:
The flange portions serve multiple functions simultaneously: they provide structural support for the inner and outer covers, ensure air-tight sealing between the insulator and housing, and eliminate the need for welding portions. This multi-functionality reduces overall structural complexity while maintaining high reliability.
3Temperature
If welding portions are exposed to exhaust gas, then heat radiation is improved, but the welding portion strength is lowered due to high temperature exposure
Solution Approach 1:
The patent eliminates the welding portion entirely by replacing it with a mechanical support structure where flange portions are held between the housing and insulator. This substitution removes the component that would otherwise be exposed to high temperatures and exhaust gas, thereby avoiding strength degradation while still allowing heat radiation to occur through other pathways.
Data Source
AI summary
A gas sensor includes a sensor element having a detecting portion; an insulator supporting the sensor element inserted therethrough; a housing supporting the insulator; an inner cover covering the detecting portion; and an outer cover covering the inner cover. An inner flange portion of the inner cover and the outer flange portion of the outer cover are supported between the insulator and the housing. An end face of the inner flange portion is positioned towards outer side R1 with respect to the radial direction R than the position of an end face of the outer flange portion. A corner portion between the end face and a surface in the outer flange portion protrudes into a surface of the inner flange portion.