Gas Sensor Counter Plate With Gradient Sintered Density
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Solution Overview
Problem
Gas sensors face issues with cracking in the counter plate due to thermal stress, and existing solutions either prevent cracking by increasing the counter plate thickness, which increases activation time, or fail to adequately manage temperature distribution in the measurement-gas chamber.
Innovation Solution
A gas sensor design with a ceramic counter plate having a sintered density 0.8 to 5.0% lower in the inside portion contacting the measurement-gas chamber compared to the outside portion, reducing thermal stress and maintaining compressive stress to prevent cracking while improving heat retention and temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the counter plate is increased to prevent cracking, then cracking resistance is improved, but activation time increases due to heat absorption
Solution Approach 1:
The counter plate is designed with non-uniform sintered density: the inside portion (0.95-0.98) has lower sintered density for stress management and heat retention, while the outside portion (0.98-1.00) has higher sintered density for structural strength. This local differentiation allows the plate to prevent cracking without requiring uniform thickness increase that would delay activation.
2Strength
If the counter plate thickness is increased to prevent cracking, then structural strength is improved, but heat retention worsens causing increased temperature distribution
Solution Approach 1:
The inside portion of the counter plate with lower sintered density (0.95-0.98) provides better heat retention and reduced thermal conductivity, while the outside portion with higher sintered density (0.98-1.00) provides structural strength. This gradient structure manages temperature distribution locally without requiring uniform thickness increase.
Solution Approach 2:
The sintered density parameter is varied across the counter plate thickness and radial position, creating a gradient from 0.95-1.00. This parameter change optimizes both thermal properties (heat retention, temperature distribution) and mechanical properties (strength, cracking resistance) simultaneously.
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 prevents cracking in the counter plate and reduces temperature distribution in the measurement-gas chamber, enhancing the precision of gas concentration detection without increasing activation time.
Implementation Method 1
a ceramic heater substrate that is provided with a heat-generating layer that generates heat by electric conduction
Implementation Method 2
the heat from the heater substrate is transferred to the second spacer, the solid electrolyte substrate and the first spacer by heat conduction
Data Source
AI summary
A gas sensor includes a solid electrolyte substrate that has oxygen-ion conductivity, and a counter plate, made of ceramic, that is arranged so as to face a first surface of the solid electrolyte substrate. The gas sensor further includes a first spacer, made of ceramic, that is held between the counter plate and the solid electrolyte substrate, a heater substrate, made of ceramic, that is arranged so as to face a second surface of the solid electrolyte substrate, and a second spacer, made of ceramic, that is held between the heater substrate and the solid electrolyte substrate. Of the counter plate, the sintered density of an inside portion that comes in contact with a measurement-gas chamber is 0.8 to 5.0% lower than the sintered density of an outside portion that comes in contact with the first spacer.