Tubular Gas Sensor Element with Curved Bottom

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Solution Overview

Problem

Existing gas sensor elements with a plate-shaped configuration are prone to damage from thermal shock due to corner portions, and those with a hollow cylindrical heater body suffer from stress concentration at the boundary between the heater body and solid electrolyte layer, leading to potential cracks and electrode damage.

Innovation Solution

A gas sensor element with a bottomed tubular basal body made of electrically insulative ceramic material, where the solid electrolyte portion is integrally formed within the side or bottom wall, minimizing the surface level difference to less than 30 μm, and preferably less than 10 μm, to prevent stress concentration and corner-related damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a plate-shaped configuration is used for the gas sensor element, then it is easy to manufacture by laminating layers, but corner portions are formed that are easily damaged by thermal shock from water in the exhaust pipe

Engineering Contradiction:

Improveease of manufactureVSAvoidreliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention replaces the plate-shaped configuration with a bottomed tubular configuration where the bottom surface is formed as a curved surface. This curvature eliminates corner portions that are prone to damage from thermal shock, while the tubular structure maintains manufacturability through conventional forming processes for the basal body.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Quantity of substance

If a hollow cylindrical heater body with a groove and through-hole is used to minimize solid electrolyte amount, then manufacturing cost is reduced, but stress concentration occurs at the boundary between heater body and solid electrolyte layer causing cracks and electrode lead wire breakage

Engineering Contradiction:

Improveamount of solid electrolyteVSAvoidreliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The invention extracts the groove and through-hole structure from the heater body design. By eliminating these features, the solid electrolyte portion can be integrally formed with the basal body without creating boundary discontinuities, thereby preventing stress concentration while still minimizing solid electrolyte usage through the integrated design.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention merges the heater body and solid electrolyte portion into an integral structure. The solid electrolyte portion is formed as an integral part of the basal body, eliminating the boundary between these components and preventing stress concentration that would occur at interfaces during firing or thermal shock.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If the solid electrolyte layer is formed to cross over the opening of the groove in the heater body, then the sensor structure is completed, but a difference in surface level is created that causes stress concentration during firing or thermal shock

Engineering Contradiction:

Improveease of manufactureVSAvoidsurface level uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention merges the solid electrolyte portion with the basal body into an integral structure. This integration eliminates the surface level difference that would occur at the boundary between separately formed components, as the solid electrolyte is formed as part of the basal body itself through conventional forming processes.

Inventive Principle:

Principle #5Merging (Combining)

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 solution effectively prevents cracks and damage during the firing process and thermal shock, ensuring the reliability and sensitivity of the gas sensor element by maintaining a flat surface and reducing thermal stress, while also eliminating corner-related issues.

Implementation Method 1

The at least one solid electrolyte portion is formed in the bottom wall or the side wall of the basal body. The pair of electrodes are opposed to each other with the at least one solid electrolyte portion interposed therebetween.

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 2

The basal body has a bottomed tubular shape and is made of an electrically insulative ceramic material.

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Implementation Method 3

for the bottomed tubular gas sensor elements, it is possible to configure a bottom surface thereof as a curved surface. Consequently, with the curved bottom surface, it is possible to alleviate thermal shock caused by water generated in the exhaust pipe, thereby preventing the gas sensor elements from being damaged by the water.

Methodology Applied

Scientific EffectThermal shock resistance: Thermal Shock

Data Source

PatentUS9540282B2Gas sensor element and its manufacturing method

Publication Date: 2017.01.10 DENSO CORP

AI summary

A gas sensor element includes a basal body, at least one solid electrolyte portion and a pair of electrodes. The basal body has a bottomed tubular shape and is made of an electrically insulative ceramic material. The basal body has a side wall and a bottom wall. The at least one solid electrolyte portion is formed in the bottom wall or the side wall of the basal body. The pair of electrodes are opposed to each other with the at least one solid electrolyte portion interposed therebetween. The difference in surface level between the basal body and the at least one solid electrolyte portion at a boundary therebetween is less than or equal to 30 μm.