Dual Porous Gas Sensor Protection Layer for Cracking Resistance
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Solution Overview
Problem
Conventional gas sensor elements face issues with cracking due to water adhesion, particularly when exposed to exhaust gases containing poisoning substances, and struggle to maintain strength while providing thermal insulation.
Innovation Solution
A gas sensor element is designed with a dual porous protection layer structure, where the inner layer has a higher porosity and contains ceramic particles and fiber filaments, and the outer layer has a lower porosity, effectively trapping water and poisoning substances while enhancing the inner layer's strength and thermal insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the porosity of the porous protection layer is increased to provide thermal insulation, then thermal insulation performance is improved, but the strength of the layer decreases due to reduced bonding sites between particles
Solution Approach 1:
The invention uses a composite porous protection layer consisting of multiple layers with different porosity values. The first porous layer has a higher porosity (50-80%) for thermal insulation, while the second porous layer has a lower porosity (20-50%) for strength and bonding. This composite structure resolves the contradiction by combining materials with different properties to achieve both thermal insulation and structural strength simultaneously.
2Strength
If fine particles are used to increase the number of bonding sites and layer strength, then layer strength is improved, but cracking occurs due to reduced solvent amount and increased surface tension during drying
Solution Approach 1:
The invention applies different porosity characteristics to different regions (layers) of the porous protection layer. The first porous layer uses fine particles with high porosity for thermal insulation, while the second porous layer uses particles with lower porosity for strength. This local differentiation allows each layer to be optimized for its specific function, preventing cracking while maintaining strength.
3Device complexity
If a single-layer porous protection layer is used to cover the detection element, then the structure is simple, but it cannot simultaneously provide effective thermal insulation and sufficient strength
Solution Approach 1:
The invention divides the porous protection layer into multiple segments (first porous layer and second porous layer) with different porosity values. The first porous layer with higher porosity (50-80%) provides thermal insulation, while the second porous layer with lower porosity (20-50%) provides strength and bonding. This segmentation allows each layer to be optimized for its specific function, achieving both thermal insulation and structural integrity.
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 dual-layer structure effectively suppresses cracking and maintains the gas sensor element's integrity by preventing sudden cooling and damage from water adhesion, while ensuring the inner layer's strength and thermal insulation properties are enhanced.
Implementation Method 1
the total volume of voids (empty spaces) contained in the lower layer increases, thereby imparting a thermal insulation property to the lower layer. Therefore, even when the upper layer is cooled by adhesion of water, the gas sensor element on the inner side is unlikely to be suddenly cooled.
Implementation Method 2
the outer surface of the gas sensor element is covered with a porous protection layer. That is, the detection element, which is exposed to a gas-to-be-measured (exhaust gas), is entirely covered with the porous protection layer.
Data Source
AI summary
A gas sensor element and a gas sensor incorporating the gas sensor element. The gas sensor element (100) includes a detection portion (150) including a solid electrolyte body (105) and a pair of electrodes (104) and (106) disposed on the solid electrolyte body; and a porous protection layer (20) covering the detection portion. The porous protection layer includes an inner porous layer (21) and an outer porous layer (23). The inner porous layer has a higher porosity than the outer porous layer. Further, the inner porous layer contains, as main components, ceramic particles (21a), and ceramic fiber filaments (21b), and the amount of the ceramic fiber filaments is 25 to 75 vol % based on the total amount of the ceramic particles and the ceramic fiber filaments taken as 100 vol %.