Gas Sensor Protective Layer with Concave Corner Geometry

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Solution Overview

Problem

Conventional gas sensors face issues with peeling of the porous protective layer due to repeated water exposure, leading to reduced water exposure resistance and delayed activation, especially in environments with increased water exposure stress.

Innovation Solution

A gas sensor element with a long plate-like body and a porous protective layer featuring a concave shape on its outer surface, where the layer thickness increases towards the corners, reducing heat capacity and preventing thermal stress concentration, thereby enhancing water resistance and rapid activation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the protective layer has a uniform thickness, then the manufacturing process is simple, but the layer peels off due to thermal stress concentration at corners during repeated water exposure

Engineering Contradiction:

Improvewater exposure resistanceVSAvoidprotective layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protective layer is designed with non-uniform thickness, specifically thicker at corner parts and thinner at central parts of the end face. This local variation in thickness distributes thermal stress more effectively during repeated water exposure, preventing peeling at the corners while maintaining manufacturing feasibility through controlled deposition processes.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The protective layer incorporates a concave shape on its outer surface, creating a curved geometry that reduces stress concentration at the corners. This curvature design allows thermal expansion and contraction forces to be distributed more evenly throughout the layer during temperature cycles associated with water exposure, enhancing reliability without significantly complicating the overall structure.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If the protective layer is thick, then water exposure resistance is improved, but activation time is delayed due to increased heat capacity

Engineering Contradiction:

Improvewater exposure resistanceVSAvoidactivation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The protective layer thickness is optimized locally rather than uniformly throughout. Corner regions have greater thickness to provide enhanced protection against water-induced peeling, while central regions have reduced thickness to minimize heat capacity and allow faster thermal activation. This spatially varying thickness achieves both protection and rapid response.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of making the entire protective layer uniformly thick for maximum protection, the design applies thicker material only where most needed (at corners susceptible to peeling) and thinner material elsewhere. This partial application of the protective function reduces overall heat capacity and activation time while maintaining adequate protection where required.

Inventive Principle:

Principle #16Partial or excessive action

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 concave shape design of the protective layer reduces peeling and thermal stress, enabling the gas sensor to withstand repeated water exposure and achieve rapid activation while maintaining water exposure resistance, allowing for improved detection of specific gas components.

Implementation Method 1

the layer thickness increases toward the corner parts... preventing thermal stress concentration

Methodology Applied

Scientific EffectThermal stress: Thermal Expansion

Implementation Method 2

reducing heat capacity and preventing thermal stress concentration, thereby enhancing water resistance and rapid activation

Methodology Applied

Scientific EffectHeat capacity reduction: Heat Sink

Data Source

PatentUS11555463B2Gas sensor element and gas sensor

Publication Date: 2023.01.17 DENSO CORP

AI summary

A gas sensor element comprising a long plate-like element body and a porous protective layer protecting a surface of the element body, wherein the element body has a gas detection part at an end thereof on one end face side in a longitudinal direction, and the protective layer includes an end face part covering the one end face in laminate, side face parts covering side faces connected to the one end face in laminate, and corner parts where two adjacent ones of the end face part and the side face parts meet. An outer surface of one or more of the end face part and the side face parts has a concave shape that is smoothly continuous with the corner parts and configured such that a layer thickness increases toward the corner parts.