Laminated Gas Sensor Element with Non-Uniform Protective Layer Thickness

Solution Overview

Problem

Existing laminated gas sensor elements face cracking due to thermal shock at the boundary parts between layers, and thickening the protective layer to prevent cracking leads to increased volume and longer activation times, hindering speedy startup.

Innovation Solution

A laminated gas sensor element design where the protective layer on the vertical surface is thicker than on the horizontal surface, with specific thickness ranges (300 μm to 500 μm for vertical and 150 μm to 250 μm for horizontal surfaces) to slow down water penetration and reduce temperature gradients, while maintaining a thinner layer at corners and porous parts to prevent cracking and minimize volume increase.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the protective layer thickness is increased to prevent cracking at boundary parts, then cracking suppression is improved, but the volume increases and activation time increases

Engineering Contradiction:

Improvecracking suppressionVSAvoidactivation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The protective layer is designed with non-uniform thickness: thicker (300-500 μm) at vertical surfaces where cracking occurs, and thinner (150-250 μm) at horizontal surfaces. This local variation provides enhanced protection at critical locations without uniformly increasing volume and activation time across the entire sensor element.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The protective layer is segmented into different thickness regions corresponding to different surfaces (vertical vs. horizontal). This segmentation allows each region to be optimized for its specific function: vertical surfaces get thicker protection against thermal shock, while horizontal surfaces maintain thinner profiles for faster heating.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the protective layer thickness is increased to prevent cracking at boundary parts, then cracking suppression is improved, but the volume increases

Engineering Contradiction:

Improvecracking suppressionVSAvoidsensor element volume

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The protective layer is designed with non-uniform thickness: thicker (300-500 μm) at vertical surfaces where cracking occurs, and thinner (150-250 μm) at horizontal surfaces. This local variation provides enhanced protection at critical locations without uniformly increasing volume and activation time across the entire sensor element.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The protective layer is segmented into different thickness regions corresponding to different surfaces (vertical vs. horizontal). This segmentation allows each region to be optimized for its specific function: vertical surfaces get thicker protection against thermal shock, while horizontal surfaces maintain thinner profiles for faster heating.

Inventive Principle:

Principle #1Segmentation

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 effectively suppresses thermal shock at boundary parts, reduces activation time, and prevents cracking, allowing for faster and more accurate gas detection while maintaining sensor efficiency.

Implementation Method 1

water drops penetrate through the pores of the thicker protective layer coating the vertical surface more slowly

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

a heater layer having an embedded resistance heating body

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 3

a solid electrolyte such as zirconia used in this laminated gas sensor element becomes active at a high temperature of 300° C. or more

Methodology Applied

Scientific EffectIonic conduction: Fast Ion Conductor

Data Source

PatentUS8038861B2Laminated gas sensor element and gas sensor

Publication Date: 2011.10.18 NITERRA CO LTD

AI summary

A laminated gas sensor element extending in a longitudinal direction and having a detection part including a plate-shaped element body which has a heater layer having an embedded resistance heating body and a detection layer laminated to the heater layer and having a vertical surface along a lamination direction and a horizontal surface perpendicular to the lamination direction; and a porous protective layer coating the vertical surface and the horizontal surface of the element body constituting the detection part, wherein a thickness of the protective layer formed on the vertical surface is thicker than a thickness of the protective layer formed on the horizontal surface.