Oxygen Sensor Electrode Gap Design for Thermal Stress Relief
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Solution Overview
Problem
Conventional oxygen sensors using ceramic sintered bodies face issues with thermal stress-induced cracking and electrode detachment due to the coating method and electrode placement on multiple surfaces, leading to poor productivity and stability.
Innovation Solution
The gas sensor employs a ceramic sintered body with paired electrode parts formed on specific surfaces, avoiding regions where adjacent surfaces touch, and uses a manufacturing method involving green sheets and printed electrodes to create gaps between the electrodes and the sensor body, reducing thermal stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If end-surface electrodes are coated on five surfaces of the element ends, then the electrode coverage area is increased, but thermal stress concentration occurs at the edges where adjacent surfaces touch, leading to cracks and electrode detachment
Solution Approach 1:
The patent extracts the electrode parts from the edge regions where adjacent surfaces touch, forming gaps between the electrodes and the edges. This removes the electrodes from the high thermal stress concentration zones, preventing cracks and detachment while maintaining sufficient electrode coverage area for functional performance
Solution Approach 2:
The patent applies different spatial arrangements to different regions of the electrode: electrodes are positioned to avoid edge regions where thermal stress concentrates, creating a local quality difference between edge areas (with gaps) and central areas (with electrode coverage). This localized adjustment prevents failure at critical stress points while maintaining overall electrode functionality
2Ease of manufacture
If the dipping method is used to manufacture electrodes, then the electrode coating process is simplified, but productivity remains poor and requires deep or wide immersion in dipping liquid, causing variation and complicated control
Solution Approach 1:
The patent replaces the traditional dipping method with a printing method for electrode manufacturing. This substitution eliminates the need for deep or wide immersion in dipping liquid, reduces variation in electrode coating, simplifies control parameters, and significantly improves manufacturing productivity while maintaining ease of implementation
Solution Approach 2:
The patent changes the manufacturing parameter from immersion depth/width (in dipping method) to printing pattern parameters (in printing method). This parameter change eliminates the need for deep or wide immersion, reduces variation through precise printing control, and improves productivity by enabling more efficient electrode formation
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 design enhances the sensor's resistance to heat cycles by alleviating thermal stress and preventing electrode cracking, improving stability and productivity by eliminating concentration of thermal stress and ensuring electrode detachment is minimized.
Implementation Method 1
The oxygen sensor using a ceramic sintered body detects oxygen concentration utilizing a hot spot phenomenon that a part of the linear member is red-heated when a voltage is applied
Implementation Method 2
the electrode material expands and contracts in the axial direction of the element and the orthogonal direction thereto, stress is applied particularly on mutually touching portions
Data Source
AI summary
An oxygen sensor for detecting gas concentration based on either an electric current value or a resistance value measured when a voltage is applied to a sensor element includes gaps formed between electrodes arranged in an element main body and ridges where surfaces of an element touch each other. These gaps will be escaping parts for expansion and contraction of electrode material that accompany thermal expansion and contraction of a sensor main body, and concentration of thermal stress at edge parts of the element main body may thus be eliminated, thereby alleviating thermal stress on the oxygen sensor. This allows provision of a gas sensor that controls generation of cracks in the element and that is stably usable over a long period of time.