Tubular Gas Sensor Porous Protective Layer Peeling Prevention
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Solution Overview
Problem
The existing porous protective layers in tubular gas sensor elements are prone to peeling due to stress differences between the solid electrolyte body and the protective layer, especially when vibrations are applied, as they have a higher porosity inside region and lower porosity outside region, which compromises their adhesion and durability.
Innovation Solution
A gas sensor element with a porous protective layer comprising an inside region and an outside region, where the outside region is formed as a sintered body of ceramic and glass, enhancing bonding strength and maintaining the porosity difference to effectively capture pollutants and manage heat insulation, while the inside region can be of similar or different ceramic and glass composition to improve adhesion and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous protective layer with higher porosity inside region and lower porosity outside region is applied to a tubular gas sensor element, then heat insulating effect is improved and pollutant capture is enhanced, but the protective layer is easily peeled from the solid electrolyte body
Solution Approach 1:
The invention changes the material composition parameter of the outside region by incorporating glass particles (5-20 mass%) in addition to ceramic particles. This parameter change modifies the bonding characteristics at the interface between the protective layer and solid electrolyte body, preventing peeling while preserving the porosity gradient structure needed for heat insulation and pollutant capture.
Solution Approach 2:
The outside region is formed as a composite material consisting of ceramic particles and glass particles. This composite structure provides both the mechanical strength needed for peeling resistance and the controlled porosity required for capturing poisonous substances. The glass component specifically enhances adhesion to the solid electrolyte body.
2Object-affected harmful factors
If the outside region has lower porosity to capture poisonous substances, then pollutant capture is improved, but heat insulation performance may be compromised
Solution Approach 1:
The protective layer is designed with spatially varying porosity: the inside region has higher porosity (50-70%) for heat insulation, while the outside region has lower porosity (20-40%) for pollutant capture. This local quality differentiation allows each region to optimize its function without compromising the other.
Solution Approach 2:
The protective layer is segmented into two distinct regions with different porosity characteristics: an inside region for heat insulation and an outside region for pollutant capture. This segmentation allows independent optimization of each region's properties to fulfill different functional requirements.
3Ease of manufacture
If the porous protective layer is made with ceramic particles only, then manufacturing is simplified, but adhesion to the solid electrolyte body is insufficient causing peeling
Solution Approach 1:
The outside region uses a composite of ceramic particles and glass particles. The glass component specifically enhances adhesion to the solid electrolyte body, preventing peeling under vibration. While this adds manufacturing complexity compared to ceramic-only formulations, it is achieved through standard co-firing processes.
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 prevents peeling of the protective layer from the solid electrolyte body, maintains effective pollutant capture and heat insulation, and improves the overall durability and reliability of the gas sensor element under stress conditions.
Implementation Method 1
since the glass is melted upon firing of the outside region and is thus interposed between the ceramic particles, the bonding between the ceramic particles is strengthened
Implementation Method 2
the outside region is formed of a sintered body of ceramic and glass
Implementation Method 3
a heat insulating effect of the inside region is increased, and loss of the heat of the detection element to the porous protective layer can be suppressed
Implementation Method 4
since the porosity of the outside region is lower than the porosity of the inside region, a poisonous substance adhering to the porous protective layer can be effectively caught in the outside region
Implementation Method 5
water droplets adhering to the porous protective layer have difficulty penetrating the inside region, but can be allowed to effectively penetrate into the outside region
Data Source
AI summary
A gas sensor element (3) includes: a solid electrolyte body (3s) having a bottomed tubular shape and a closed front end, and extending in the direction of an axial line O; an inside electrode (50) which is provided on an inner surface of the solid electrolyte body; an outside electrode (51) which is provided on an outer surface of the solid electrolyte body; and a porous protective layer (80) which covers the outside electrode, the porous protective layer has an inside region (81) which covers the outside electrode and an outside region (82) which covers the inside region and has a lower porosity than the inside region, and the outside region is formed of a sintered body of ceramic and glass.