Gas Sensor Shell Crimping for High-Temperature Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Residual stress in metal shells manufactured by forging can lead to a decrease in sealing performance when exposed to high temperatures, causing the crimped portion to loosen and compromise the airtightness between the sensor element and the metal shell in gas sensors.
Innovation Solution
A gas sensor design featuring a stainless steel metal shell with a brim portion and crimp portion, where the crimp portion is formed by bending inward and pressing down a sealing member, and the metal shell undergoes a heating process to release residual stress, ensuring a Micro Vickers hardness of 140 to 210 Hv to maintain sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the metal shell is formed by forging, then material wastage is reduced, but residual stress occurs in the metal shell causing loosening of the crimped portion at high temperature
Solution Approach 1:
The patent applies preliminary action by performing a heating process before the crimping operation to release residual stress in advance. The metal shell is heated to a predetermined temperature range (Ac3 transformation point to Ac1 transformation point) before crimping, which eliminates the residual stress that would otherwise cause loosening at high temperature, thereby ensuring long-term sealing reliability while maintaining the forging process's material efficiency.
Solution Approach 2:
The patent utilizes parameter changes by controlling the temperature parameter during the heating process. By heating the metal shell to a specific temperature range (Ac3 to Ac1 transformation points) and then cooling it, the material's microstructure and stress state are changed, transforming the residual stress condition into a stress-free state that maintains sealing performance under subsequent high-temperature exposure.
2Reliability
If the crimp portion is formed by bending inward, then sealing performance is improved, but residual stress causes loosening when exposed to high temperature
Solution Approach 1:
The heating process is performed as a preliminary action before crimping to eliminate residual stress in the metal shell. This ensures that when the crimp portion is formed by bending inward, the material is in a stress-free state, preventing future loosening and maintaining the stability and integrity of the crimp portion structure under high-temperature conditions.
Solution Approach 2:
By changing the temperature parameter of the metal shell to the Ac3-Ac1 transformation range before crimping, the material's mechanical properties and stress state are modified. This parameter change ensures that the crimped structure maintains its integrity and does not loosen when subsequently exposed to high temperatures during sensor operation.
3Reliability
If heating is applied to release residual stress, then sealing performance is maintained, but additional manufacturing steps are required
Solution Approach 1:
The patent merges the heating process for stress relief with the existing manufacturing workflow by positioning it between the forging and crimping operations. This integration ensures that the additional heating step becomes part of the standard manufacturing sequence, and the crimping operation itself serves the dual purpose of forming the sealing structure while utilizing the stress-free state achieved through heating.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses the decrease in sealing performance between the sensor element and the metal shell, even when exposed to high temperatures, by releasing residual stress and maintaining the crimp portion's integrity through controlled heating and crimping.
Implementation Method 1
a heating process that heats the forged body or the proto-metal shell body
Implementation Method 2
The residual stress, especially, occurring at the crimped portion, is afterwards released when the gas sensor is exposed to high temperature
Implementation Method 3
the crimp portion being bent inwards in the radial direction and pressing down a rear end of the sealing member toward the top end side
Implementation Method 4
ensuring airtightness between the sensor element and the metal shell
Implementation Method 5
The metal shell is formed by forging a tubular material. With this forging, the metal shell can be formed without wastage of material
Data Source
AI summary
A gas sensor (1) has a sensor element (21) extending in an axis direction and having, at a top end side thereof, a detecting portion (22) that detects gas; a stainless steel-made tubular metal shell (11) enclosing a radial direction periphery of the sensor element (21) and holding the sensor element (21) and having (a) a brim portion (14) protruding outwards in a radial direction and (b) a crimp portion (16) formed at a rear end side of the metal shell (11); and a sealing member (41) placed between the sensor element (21) and the metal shell (11). The crimp portion (16) is bent inwards in the radial direction and pressing down a rear end of the sealing member (41) toward the top end side. A Micro Vickers hardness of a cross section along the axis direction of the crimp portion (16) is 140 to 210 Hv.