NOx Sensor Thermal Insulation via Annular Gas Space
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The accuracy of gas sensors in detecting gas concentrations is compromised by temperature deviations due to ambient temperature changes, affecting the reliability of the detection process.
Innovation Solution
A gas sensor design featuring a detection element, a metal accommodation member, and a metal protector with a tubular space formation member, creating a thermal insulation layer that reduces ambient heat conduction to the detection cell, thereby stabilizing its temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detection element is directly exposed to the ambient environment, then the gas sensor responds quickly to gas concentration changes, but the detection element temperature fluctuates with ambient temperature changes, reducing detection accuracy
Solution Approach 1:
The patent introduces a metal accommodation member as an intermediary between the detection element and the ambient environment. This accommodation member acts as a thermal buffer that mediates heat transfer, reducing the direct impact of ambient temperature fluctuations on the detection element while still allowing gas molecules to reach the detection element through the gas permeable wall.
Solution Approach 2:
The patent employs a gas permeable wall (thin film structure) that selectively allows gas molecules to pass through while providing thermal insulation. This thin film structure enables mass transfer of target gases to the detection element while restricting heat transfer from the ambient environment, thereby stabilizing the detection element temperature.
2Temperature
If a thermal insulation structure is added around the detection element, then the temperature stability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The metal accommodation member serves multiple functions simultaneously: it provides structural support for the detection element, acts as a thermal insulation barrier, and forms the housing of the gas sensor. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity despite the added thermal insulation capability.
Solution Approach 2:
The patent utilizes composite material structures, particularly the combination of the metal accommodation member with the gas permeable wall and the detection element assembly. This composite approach integrates thermal insulation, gas permeability, and mechanical support functions into a unified structure, simplifying manufacturing compared to assembling multiple separate components.
3Temperature
If the detection element is enclosed in a metal accommodation member, then the temperature stability improves, but the gas diffusion path length increases, potentially slowing response time
Solution Approach 1:
The gas permeable wall of the accommodation member is designed with local quality variations, featuring regions of different permeability and thickness. The wall directly facing the detection element has optimized properties to maximize gas diffusion efficiency, while other regions provide sufficient thermal insulation. This localized optimization maintains fast response times in critical areas while providing thermal protection elsewhere.
Solution Approach 2:
The thin film gas permeable wall minimizes the diffusion path length for gas molecules while still providing effective thermal insulation. The film's molecular-level thickness allows rapid gas permeation but presents significant thermal resistance, thereby decoupling the gas diffusion process from thermal transfer and maintaining fast response speeds despite the enclosing structure.
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
This configuration effectively restrains temperature changes of the detection element, maintaining accurate gas concentration detection by minimizing the impact of ambient temperature fluctuations.
Implementation Method 1
Gas is lower in thermal conductivity than metal. Thus, in the gas sensor of the present disclosure, ambient heat of the gas sensor is unlikely to be conducted to the detection cell by way of the stack section, whereby a temperature change of the detection cell can be restrained.
Data Source
AI summary
An NOx sensor includes a gas sensor element, a body member made of metal, and a protector made of metal. The body member is formed into a tubular shape extending in an axial direction and accommodates a gas sensor element internally of the same. The NOx sensor is formed into a tubular shape extending in the axial direction and includes an attachment member disposed such that a space extending in the axial direction is formed between the attachment member and the body member. The gas sensor element includes an oxygen concentration detection cell having an oxygen ion-conductive solid electrolyte layer and a detection electrode and a reference electrode formed on the solid electrolyte layer and forming a pair, and a heater for heating the oxygen concentration detection cell to a predetermined temperature. The oxygen concentration detection cell is disposed in the space.