Gas Sensor Cover Flange Offset Design for Thermal Shock Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional gas sensors in exhaust systems face issues with thermal shock, where the strength of welding joints between covers is compromised at high temperatures, leading to potential separation of covers and stress on insulators, which can result in breakage.
Innovation Solution
A gas sensor design where both inner and outer flange portions are supported between the insulator and housing, with offset end faces to reduce load on the insulator and prevent cover separation, using a smaller joint volume to maintain structural integrity at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If welding portion is exposed to exhaust gas for heat radiation, then thermal shock resistance is improved, but welding portion strength is lowered due to fatigue and corrosion
Solution Approach 1:
The harmful function of the welding portion (heat radiation causing strength degradation) is extracted and transferred to the housing. The housing's larger surface area and better thermal conductivity are utilized to perform the heat radiation function, while the welding portion is protected from direct exposure to exhaust gas, maintaining its strength.
Solution Approach 2:
The housing acts as an intermediary between the welding portion and the exhaust gas. It receives heat from the welding portion through thermal conduction and then radiates heat to the exhaust gas through its outer surface, protecting the welding portion from direct contact with corrosive exhaust gases while still achieving heat dissipation.
2Reliability
If flange portion load is increased to secure cover fixation, then cover separation is prevented, but insulator breakage risk increases
Solution Approach 1:
The load distribution is optimized locally at the insulator-flange interface. The insulator is designed with specific geometric features (such as increased contact area or optimized shape) to locally enhance its load-bearing capacity without requiring a uniform increase in flange load, thereby preventing both cover separation and insulator breakage.
Solution Approach 2:
The fixation mechanism is extended from a single-point or single-plane contact to a multi-dimensional support structure. The flange portion is supported at multiple locations and angles by the housing, distributing the fixation loads across different spatial dimensions and reducing the stress concentration on the insulator.
Data Source
AI summary
A gas sensor is provided with a sensor element having a detecting portion; an insulator supporting the sensor element in a state where the detecting portion is protruded therefrom, the sensor element being inserted through the insulator; 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 an outer flange portion of the outer cover are supported between the insulator and the housing. A protrusion is formed on a corner portion facing the insulator, the protrusion contacting with the insulator. An end face of the outer flange portion is positioned radially closer to an outer side with respect to a radial direction, than a position of an end face of the inner flange portion.