Gas Sensor Metal Ring Caulking for Thermal Expansion
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Solution Overview
Problem
Gas tightness between the sensor element and housing in existing gas sensors deteriorates upon thermal cycling, allowing detected gases to leak into the sensor due to the expansion of the metal housing exceeding that of the ceramic sealing materials, causing the caulking to loosen.
Innovation Solution
A gas sensor design featuring a cylindrical housing with a sensor element, a sealing material, a cylindrical insulation member, and an annular metal ring where the metal ring's outer peripheral portion projects radially outward, allowing it to spring back and maintain caulking pressure when heated, preventing loosening of the sealing material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the housing is made of metal and the sealing members are made of ceramic, then the housing has high strength and durability, but the metal housing expands more than the ceramic sealing members when heated, causing the caulking to loosen and gas tightness to deteriorate
Solution Approach 1:
The patent changes the material parameter of the caulking portion from ceramic to metal, utilizing the metal's higher thermal expansion coefficient to compensate for the differential expansion between the housing and sealing members. This parameter change allows the caulking portion to maintain contact pressure with the sealing members during thermal cycling, preventing gas leakage while preserving the strength benefits of metal housing.
2Stability of the object's composition
If the caulking portion is made of ceramic to match the sealing members, then thermal expansion is uniform, but the caulking portion cannot provide sufficient contact pressure to maintain sealing when the metal housing expands
Solution Approach 1:
The patent deliberately changes the material parameter of the caulking portion from ceramic to metal, accepting differential thermal expansion as beneficial. The metal caulking portion's higher thermal expansion coefficient allows it to expand more than the ceramic sealing members when heated, maintaining contact pressure and sealing effectiveness despite the housing expansion.
3Reliability
If the sealing material is compressed firmly during assembly, then initial gas tightness is achieved, but the sealing material cannot compensate for thermal expansion differences during thermal cycling
Solution Approach 1:
The patent incorporates a metal caulking portion that is preliminarily positioned to provide continuous contact pressure on the sealing members during assembly. This preliminary action ensures that the sealing members are pre-compressed and maintained in a sealed state throughout thermal cycling, allowing the metal caulking portion to compensate for thermal expansion differences and maintain sealing durability.
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 design effectively suppresses the deterioration of gas tightness by ensuring the caulking pressure is maintained even when the sensor is heated, preventing gas leaks and maintaining sealing integrity.
Implementation Method 1
when the gas sensor is heated, the housing 200 made of metal expands larger than the sealing material 6 and the insulation member 50 both of which are made of ceramic
Implementation Method 2
the metal ring springs back in the direction opposite to the direction that the stress is applied
Data Source
AI summary
A gas sensor suppresses the deterioration of gas tightness caused by failure of a sealing material. The gas sensor includes: a housing; a sensor element arranged inside the housing; a sealing material filling a gap between the sensor element and the housing; an insulation member arranged on a proximal end side of the sealing material; and an annular metal ring arranged on a proximal end side of the insulation member. The sealing material, the insulation member and the metal ring are fixed under pressure by caulking from a proximal end side to a distal. A proximal-end facing surface of an inner peripheral portion of the metal ring is spaced apart from the caulking portion in an opposing region where an inner end of the caulking portion and the metal ring face each other in an opposed manner.