Gas Sensor Element Protective Layer for Thermal Insulation and Strength
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Solution Overview
Problem
Conventional gas sensor protective layers face a trade-off between thermal insulating properties and structural strength, with increased porosity leading to reduced strength and longer heating-up times, while thicker layers increase heat capacity.
Innovation Solution
A laminated protective layer structure comprising an inner layer with coarse voids and fine pores, and an outer layer with lower porosity, achieving a porosity range of 40% to 90% and coarse porosity of 1% to 55%, enhancing water resistance and reducing thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If porosity of the protective layer is increased to reduce thermal conductivity, then thermal insulating properties are improved, but strength of the protective layer deteriorates
Solution Approach 1:
The protective layer is divided into multiple layers with different porosity levels. The first protective layer has high porosity (50-90%) for thermal insulation, while the second protective layer has lower porosity (20-50%) for mechanical strength. This segmentation allows each layer to optimize its function without compromising the other.
Solution Approach 2:
Different regions of the protective layer structure have different porosity characteristics. The first protective layer region has high porosity to provide thermal insulation, while the second protective layer region has lower porosity to provide structural support. This local differentiation of quality resolves the contradiction between thermal performance and mechanical strength.
2Strength
If thickness of the protective layer is increased to secure strength, then strength is improved, but specific heat increases leading to longer heating-up time
Solution Approach 1:
The protective layer is segmented into two distinct layers with different thicknesses and porosity levels. The first layer can be thinner with high porosity for thermal insulation, while the second layer provides additional strength without requiring excessive thickness. This segmentation allows optimization of both strength and heating-up time.
Solution Approach 2:
The porosity parameter is changed across different layers of the protective structure. By varying porosity from high in the first layer to lower in the second layer, the invention achieves both sufficient strength and reduced heat capacity for faster heating-up time.
3Loss of energy
If porosity is increased to reduce thermal conductivity, then thermal insulating properties are improved, but water resistance deteriorates
Solution Approach 1:
The protective layer is segmented into an inner high-porosity layer for thermal insulation and an outer low-porosity layer for water resistance. This segmentation allows the system to achieve both low thermal conductivity and high water resistance simultaneously.
Solution Approach 2:
The protective structure uses a composite arrangement of porous materials with different porosity levels. The combination of high-porosity and low-porosity layers creates a composite structure that exhibits both excellent thermal insulation and superior water resistance properties.
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 sensor element achieves high water resistance and reduced thermal conductivity, with improved adhesion and strength, allowing for faster heating-up times and protection against thermal shock.
Implementation Method 1
A porous material including, as a framework, zirconia particles and a dissimilar material on the surfaces thereof and having many fine pores with a nano-order pore diameter to have high thermal insulating performance
Implementation Method 2
the inner leading-end protective layer has: an overall porosity of 40% or more and 90% or less; and a coarse porosity of 1% or more and 55% or less
Data Source
AI summary
A sensor element includes: an element base which has a gas inlet in one end portion thereof and into which a measurement gas is introduced through the gas inlet; and a leading-end protective layer disposed around an outer periphery of the element base in a predetermined range from the one end portion, having a laminated structure of: an inner layer having coarse voids with a size of 1 μm or more in a matrix region having a framework structure formed by porous pieces each having fine pores with a pore diameter of 10 nm or more and less than 1 μm; and an outer layer disposed to cover the inner leading-end protective layer, and having a lower porosity than the inner layer, and the inner layer has: an overall porosity of 40% or more and 90% or less; and a coarse porosity of 1% or more and 55% or less.