Gas Sensor Element Corner Protection via Localized Layer Thickness
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Solution Overview
Problem
Existing gas sensor elements for internal combustion engine exhaust systems face challenges in withstanding water droplets, which cause thermal shock and potential cracking due to uneven protective layer application, leading to increased heat capacity and delayed activation.
Innovation Solution
A gas sensor element design with a laminated structure including a solid electrolyte body, measurement and reference electrodes, and a porous diffusion-resistant layer, featuring an inner and outer protective layer with varying thickness and porosity to ensure high water resistance at corner portions while minimizing heat capacity, achieved through specific ceramic particle sizes and application methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the slurry material is applied on the entire outer surface of the main body by dipping, then the protective layer is formed to protect against water drops, but the thickness of the protective layer becomes smaller at corner portions than at plane portions, resulting in insufficient protection at corners
Solution Approach 1:
The patent applies a thicker protective layer specifically at corner portions where water drops cause greater thermal shock, while maintaining a thinner layer at plane portions. This localized thickness variation optimizes protection where needed while minimizing overall heat capacity. The corner portions are identified as critical areas requiring enhanced protection due to their geometric susceptibility to water accumulation and thermal stress.
Solution Approach 2:
The protective layer is segmented into different thickness zones: a first thickness at corner portions and a second thickness at plane portions. This segmentation allows the design to address the specific protection needs of different surface regions independently, ensuring adequate protection at corners without unnecessarily increasing the thickness and heat capacity across the entire sensor body.
2Reliability
If the slurry material is repeatedly applied to increase the protective layer thickness at corner portions, then water resistance at corners is improved, but the protective layer thickness at plane portions also increases, resulting in increased heat capacity and delayed activation
Solution Approach 1:
The protective layer thickness is locally optimized by making it thicker at corner portions and thinner at plane portions. This local differentiation ensures that corner portions receive adequate protection against water drops without increasing the overall protective layer thickness across the entire sensor, thereby minimizing the increase in heat capacity and activation time.
Solution Approach 2:
The protective layer is segmented into different thickness zones: a first thickness at corner portions and a second thickness at plane portions. This segmentation allows the design to address the specific protection needs of different surface regions independently, ensuring adequate protection at corners without unnecessarily increasing the thickness and heat capacity across the entire sensor body.
3Reliability
If the protective layer thickness is increased to ensure sufficient protection at corner portions, then water resistance is improved, but the heat capacity of the gas sensor element increases, making it difficult to ensure prompt activation
Solution Approach 1:
The protective layer thickness is locally optimized by making it thicker at corner portions and thinner at plane portions. This local differentiation ensures that corner portions receive adequate protection against water drops without increasing the overall protective layer thickness across the entire sensor, thereby minimizing the increase in heat capacity and activation time.
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 provides reliable protection against water damage at critical corner portions while ensuring prompt activation of the solid electrolyte body, maintaining high durability and performance of the gas sensor element.
Implementation Method 1
a porous diffusion-resistant layer through which the measurement gas is introduced to the measurement electrode
Implementation Method 2
a heater layer that includes an electrical heating element
Implementation Method 3
a large thermal shock may be applied to the gas sensor element, thereby causing cracks to occur in the gas sensor element
Data Source
AI summary
A gas sensor element includes a main body and a protective layer. The main body has four plane portions and four corner portions each of which is formed between one adjacent pair of the plane portions. The four corner portions include a pair of first corner portions that are formed on a porous diffusion-resistant layer side in a lamination direction of the main body and a pair of second corner portions that are formed on a heater layer side in the lamination direction. The protective layer is comprised of an inner protective layer that covers at least the first corner portions of the main body and an outer protective layer that covers the entire outer periphery of the main body and the inner protective layer. The protective layer has a larger average thickness at the first corner portions than at the plane portions of the main body.