Gas sensor

Patent metadata

Field	Value
Publication number	US-9910023-B2
Application number	US-201615198458-A
Country	US
Kind code	B2
Filing date	Jun 30, 2016
Priority date	Jul 10, 2015
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

A gas sensor having a heater layer; and a gas detector that is heated by the heater layer to detect a measurement target gas. The gas detector has a gas sensing layer, a diffusion layer that covers a surface of the gas sensing layer, and an absorption layer that covers a surface of the diffusion layer. The absorption layer has greater absorption of the measurement target gas than the diffusion layer, and the diffusion layer has greater diffusion of the measurement target gas than the absorption layer.

First claim

What is claimed is:

1. A gas sensor for detecting a target gas to be measured when desorbed, comprising:
a heater layer; and
a gas detector that is heated by the heater layer for desorption of the target gas in use, and that is comprised of:
a gas sensing layer provided proximate to the heater layer and comprised of a material effective for sensing the target gas when desorbed;
at least one diffusion layer positioned to cover the gas sensing layer and comprised of a porous material which has a pore size effective for diffusion of the target gas there through; and
an absorption layer positioned to cover the at least one diffusion layer and comprised of a porous material which has a pore size effective for absorption of the target gas,

wherein the absorption layer has greater absorption of the target gas than the at least one diffusion layer and the at least one diffusion layer has greater diffusion of the target gas than the absorption layer due to a difference there between of at least one of average pore size, average particle size, specific surface area, polarity, film thickness, supported metal, and constituent porous material.

2. The gas sensor according to claim 1 , wherein the porous material of the absorption layer has an average pore size that is smaller than that of the porous material of the at least one diffusion layer.

3. The gas sensor according to claim 2 , wherein the at least one diffusion layer comprises two or more layers, and one layer of the two or more layers that is closer to the gas sensing layer has a greater average pore size.

4. The gas sensor according to claim 1 , further comprising a controller that controls is electrically connected to the heater layer and to the gas sensing layer, that is programmed to control the heater layer to intermittently drive the heater layer in use, and that obtains a sensor output from the gas sensing layer,
wherein the controller controls the heater layer to intermittently drive the heater layer, and the target gas supplied from the diffusion layer is detected when a reaction occurs between the target gas and the gas sensing layer, and
wherein, when the heater layer is at ambient temperature, the target gas is absorbed by the absorption layer and, when the heater layer is driven by the controller and is heated, the target gas is thermally desorbed from the absorption layer and diffuses into the diffusion layer toward the gas sensing layer.

5. The gas sensor according to claim 1 , wherein the absorption layer and the at least one diffusion layer are each composed of at least one metal oxide selected from the group consisting of Al 2 O 3 , Cr 2 O 3 , Fe 2 O 3 , Ni 2 O 3 , ZrO 2 and SiO 2 , as a main ingredient.

6. The gas sensor according to claim 1 , further comprising an oxygen supply layer formed at least on the surface of the gas sensing layer between the gas sensing layer and the at least one diffusion layer.

7. The gas sensor according to claim 1 , wherein the gas sensing layer is formed of a metal oxide layer containing a dopant.

8. The gas sensor according to claim 1 , further comprising:
a substrate;
a heat insulating layer formed on a surface of the substrate;
the heater layer formed on a surface of the heat insulating layer;
an electric insulating layer formed on a surface of the heater layer;
the gas sensing layer formed on a surface of the electric insulating layer;
an electrode layer connected to the gas sensing layer;
the diffusion layer formed on the surface of the gas sensing layer; and
the absorption layer formed on the surface of the diffusion layer,
wherein the substrate has defined therein a through hole formed to communicate with the heat insulating layer or has a closed-end cavity formed between the substrate and the heat insulating layer.

9. A gas sensor for detecting a target gas to be measured when desorbed, comprising:
a heater layer; and
a gas detector that is heated by the heater layer for desorption of the target gas in use, and that is comprised of:
a gas sensing layer provided proximate to the heater layer and comprised of a metal oxide layer containing a dopant that is effective for sensing the target gas;
at least one diffusion layer positioned to cover the gas sensing layer and comprised of a porous material which is effective for diffusion of the target gas there through; and
an absorption layer positioned to cover the at least one diffusion layer and comprised of a porous material which has a pore size effective for absorption of the target gas; and

a controller that is electrically connected to the heater layer and to the gas sensing layer, that is programmed to control the heater layer to intermittently drive the heater layer in use, and that obtains a sensor output from the gas sensing layer,
wherein the absorption layer has greater absorption of the target gas than the diffusion layer and the diffusion layer has greater diffusion of the measurement target gas than the absorption layer due to a difference there between of at least one of average pore size, average particle size, specific surface area, polarity, film thickness, supported metal, and constituent porous material; and
wherein the absorption layer and the at least one diffusion layer are each composed of at least one metal oxide selected from the group consisting of Al 2 O 3 , Cr 2 O 3 , Fe 2 O 3 , Ni 2 O 3 , ZrO 2 and SiO 2 , as a main ingredient.

10. The gas sensor according to claim 9 , wherein the porous material of the absorption layer has an average pore size that is smaller than that of the porous material of the at least one diffusion layer.

11. The gas sensor according to claim 10 , wherein the at least one diffusion layer comprises two or more layers, and one layer of the two or more layers that is closer to the gas sensing layer has a greater average pore size.

12. A gas sensor for detecting a target gas to be measured when desorbed, comprising:
a substrate;
a heat insulating layer formed on a surface of the substrate;
a heater layer formed on a surface of the heat insulating layer;
an electric insulating layer formed on a surface of the heater layer;
a gas detector that is intermittently heated by the heater layer for desorption of the target gas in use, and that is comprised of:
a gas sensing layer formed on a surface of the electric insulating layer proximate to the heater layer and comprised of a material effective for sensing the target gas when desorbed;
an electrode layer connected to the gas sensing layer;
at least one diffusion layer formed on a surface of the gas sensing layer to cover the gas sensing layer and comprised of a porous material which has a pore size effective for diffusion of the target gas there through; and
an absorption layer formed on a surface of the diffusion layer to cover the surface of the at least one diffusion layer and comprised of a porous material which has a pore size effective for absorption of the target gas,

wherein the substrate has defined therein a through hole formed to communicate with the heat insulating layer or has a closed-end cavity formed between the substrate and the heat insulating layer, and
wherein the absorption layer has greater absorption of the target gas than the diffusion layer and the at least one diffusion layer has greater diffusion of the target gas than the absorption layer due to a difference there between of at least one of average pore size, average particle size, specific surface area, polarity, film thickness, supported metal, and constituent porous material.

13. The gas sensor according to claim 12 , wherein the porous material of the absorption layer has an average por

Assignees

• Fuji Electric Co Ltd
• Univ Tokyo

Inventors

• Ui Fumi
• Suzuki Takuya
• Delaunay Jean Jacques

Classifications

• G01N33/0016

  by regulating a physical variable, e.g. pressure or temperature · CPC title

• G01N33/0047 Primary

  Organic compounds · CPC title

• G01N33/0073

  Control unit therefor · CPC title

• G01N27/123 Primary

  for controlling the temperature (temperature control per se G05D23/00) · CPC title