Chamfered Solid Electrolyte Edge for Gas Sensor Thermal Stress

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Solution Overview

Problem

Oxygen sensors with a plate-shaped solid electrolyte body face thermal stress issues due to concentrated stress at the edges, leading to cracking and deterioration of their oxygen concentration-detecting function, particularly when exposed to high-temperature measurement gases.

Innovation Solution

A method for producing a gas sensor with a rectangular solid structure of a ceramic solid electrolyte body, where the edges are chamfered using a guide plate and cutter, heated to the glass transition point, to relax thermal stress and improve thermal shock resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the solid electrolyte body is heated to high temperature for oxygen detection, then the oxygen-detecting function is sufficient, but thermal stress concentrates at the edges causing cracking

Engineering Contradiction:
Improveoxygen-detecting functionVSAvoidthermal shock resistance
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent applies chamfering treatment specifically to the edge portions of the solid electrolyte body, creating a local structural modification at the edges while maintaining the original plate shape in the central region. This local quality change redistributes thermal stress away from the sharp edges, preventing cracking while preserving the oxygen detection function.

Inventive Principle:
Principle #3Local quality

2Strength

If the edge portions are chamfered to relax stress concentration, then thermal shock resistance is improved, but the manufacturing process becomes more complex

Engineering Contradiction:
Improvethermal shock resistanceVSAvoidchamfering process complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent replaces complex multi-step mechanical chamfering operations with a simplified single-step cutting process using a straight blade. The blade is inserted into a groove formed by V-shaped guides, automatically creating the chamfered edge geometry through a straightforward linear cutting motion rather than complex angular positioning.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If the solid electrolyte body is miniaturized for easy production, then manufacturing is simplified, but thermal stress concentration at edges increases

Engineering Contradiction:
ImproveminiaturizationVSAvoidedge stress resistance
Core Design Contradiction:
Ease of manufactureVSStrength

Solution Approach 1:

The patent applies chamfering treatment specifically to the edge portions of the miniaturized solid electrolyte body, creating a local structural modification that addresses stress concentration without affecting the overall miniaturized dimensions. This allows the compact sensor to maintain both small size and improved thermal shock resistance.

Inventive Principle:
Principle #3Local quality

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 chamfering process enhances the thermal shock resistance of the gas sensor, preventing edge cracking and maintaining the oxygen concentration-detecting function even at high temperatures, thus improving the sensor's reliability and performance.

Implementation Method 1

The solid electrolyte body is heated to raise its temperature to the glass transition point or higher in the chamfering step

Methodology Applied
Scientific EffectGlass transition:

Implementation Method 2

The chamfering process enhances the thermal shock resistance of the gas sensor, preventing edge cracking and maintaining the oxygen concentration-detecting function even at high temperatures

Methodology Applied
Scientific EffectThermal stress relaxation: Stress Relaxation

Data Source

PatentEP1965203B1Method for producing gas sensor
Publication Date: 2013.09.11 NGK INSULATORS LTD
  • EP1965203B1 patent drawingFigure 1
  • EP1965203B1 patent drawingFigure 2
  • EP1965203B1 patent drawingFigure 3

AI summary

A solid electrolyte body (11) is placed on and fixed to an upper plate (120) of a press jig (116) such that a major surface (an upper surface) of the solid electrolyte body (11) faces one major surface (114a) of a guide plate (114) having a through-hole (112). The upper plate (120) is rotated by a transfer mechanism to incline the solid electrolyte body (11) in one direction, and the inclined solid electrolyte body (11) is moved toward the other major surface (114b) of the guide plate (114) such that a first edge (106a) of the solid electrolyte body (11) protrudes from the through-hole (112). Then, a cutter (118) is slid along the other major surface (114b), so that the first edge (106a) is chamfered to form a first chamfered portion (104a) .