Gas sensor

Patent metadata

Field	Value
Publication number	US-10514355-B2
Application number	US-201615290063-A
Country	US
Kind code	B2
Filing date	Oct 11, 2016
Priority date	Nov 17, 2015
Publication date	Dec 24, 2019
Grant date	Dec 24, 2019

Abstract

A mixed-potential gas sensor for measuring a concentration of a predetermined gas component of a measurement gas includes sensing electrodes mainly made of an oxygen-ion conductive solid electrolyte and located on a surface of a sensor element, and at least one reference electrode including a cermet including Pt and an oxygen-ion conductive solid electrolyte. The sensing electrodes each include a cermet including a noble metal and an oxygen-ion conductive solid electrolyte. The noble metal includes Pt and Au. A Au abundance ratio, which is an area ratio of a portion covered with the Au to a portion at which the Pt is exposed in a surface of noble metal particles forming each of the sensing electrodes, differs among the sensing electrodes. The gas sensor determines a concentration of the predetermined gas component based on a potential difference between each of the sensing electrodes and the at least one reference electrode.

First claim

What is claimed is:

1. A mixed-potential gas sensor for measuring a concentration of a predetermined gas component of a measurement gas, said gas sensor comprising:
a sensor element mainly made of an oxygen-ion conductive solid electrolyte;
a plurality of sensing electrodes located on a surface of said sensor element, each of said plurality of sensing electrodes configured to sense said predetermined gas component; and
at least one reference electrode including a cermet including Pt and an oxygen-ion conductive solid electrolyte,
wherein
said plurality of sensing electrodes each include a cermet including a noble metal and an oxygen-ion conductive solid electrolyte,
said noble metal includes Pt and Au,
a Au abundance ratio, which is an area ratio of a portion covered with said Au to a portion at which said Pt is exposed in a surface of noble metal particles forming each of said plurality of sensing electrodes, differs among said plurality of sensing electrodes, and
said gas sensor determines a concentration of said predetermined gas component based on a potential difference between each of said plurality of sensing electrodes and said at least one reference electrode.

2. The gas sensor according to claim 1 , wherein
said plurality of sensing electrodes comprise a first sensing electrode and a second sensing electrode,
said Au abundance ratio of said first sensing electrode is 0.7 or more,
said Au abundance ratio of said second sensing electrode is 0.1 or more and less than 0.7, and
said gas sensor determines the concentration of said predetermined gas component based on a first sensor output that is a potential difference between said first sensing electrode and said at least one reference electrode or a second sensor output that is a potential difference between said second sensing electrode and said at least one reference electrode.

3. The gas sensor according to claim 2 , wherein
said at least one reference electrode comprises a first reference electrode and a second reference electrode, and
a potential difference between said first sensing electrode and said first reference electrode is said first sensor output, and a potential difference between said second sensing electrode and said second reference electrode is said second sensor output.

4. The gas sensor according to claim 2 , wherein said first and second sensing electrodes are adjacent to each other in a longitudinal direction of said sensor element on one surface of said sensor element.

5. The gas sensor according to claim 2 , wherein said first and second sensing electrodes are respectively located on two opposite surfaces of said sensor element.

6. The gas sensor according to claim 3 , wherein said first and second sensing electrodes are adjacent to each other in a direction perpendicular to a longitudinal direction of said sensor element on one surface of said sensor element.

7. The gas sensor according to claim 2 , wherein said gas sensor is configured to
determine the concentration of said predetermined gas component based on said first sensor output when an emission source of said measurement gas is in a normal operation, and
determine the concentration of said predetermined gas component based on said second sensor output when the emission source of said measurement gas emits said predetermined gas component at a concentration higher than a concentration in the normal operation.

8. The gas sensor according to claim 2 , wherein said gas sensor is configured to
determine the concentration of said predetermined gas component based on said first sensor output when an absolute value of a time differential value of said first sensor output is not smaller than an absolute value of a time differential value of said second sensor output, and
determine the concentration of said predetermined gas component based on said second sensor output when the absolute value of the time differential value of said first sensor output is smaller than the absolute value of the time differential value of said second sensor output.

9. The gas sensor according to claim 2 , wherein
at least one of a first sensitivity characteristic and a second sensitivity characteristic is experimentally identified in advance, said first sensitivity characteristic representing a functional relationship between the concentration of said predetermined gas component and said first sensor output, said second sensitivity characteristic representing a functional relationship between the concentration of said predetermined gas component and said second sensor output,
in a case where said first sensitivity characteristic has been identified, an upper limit value for said first sensor output in use of said first sensor output to calculate the concentration is set based on said first sensitivity characteristic,
in a case where said second sensitivity characteristic has been identified, a lower limit value for said second sensor output in use of said second sensor output to calculate the concentration is set based on said second sensitivity characteristic, and
said gas sensor is configured to
calculate the concentration of said predetermined gas component based on said first sensor output and said first sensitivity characteristic when said first sensor output is not greater than said upper limit value, and calculate the concentration of said predetermined gas component based on said second sensor output and said second sensitivity characteristic when said first sensor output exceeds said upper limit value, or
calculate the concentration of said predetermined gas component based on said second sensor output and said second sensitivity characteristic when said second sensor output is not smaller than said lower limit value, and calculate the concentration of said predetermined gas component based on said first sensor output and said first sensitivity characteristic when said second sensor output is smaller than said lower limit value.

10. The gas sensor according to claim 1 , further comprising
at least one electrode protective layer that is a porous layer covering at least said plurality of sensing electrodes.

11. The gas sensor according to claim 1 , wherein
said sensor element further includes a reference gas introduction space separate from a space containing said measurement gas, into which a reference gas is introduced, and
said at least one reference electrode is placed under an atmosphere of said reference gas.

12. The gas sensor according to claim 11 , wherein
said sensor element further includes a reference gas introduction layer that is a porous layer in communication with said reference gas introduction space, and
said at least one reference electrode is covered with said reference gas introduction layer.

13. The gas sensor according to claim 11 , wherein said at least one reference electrode is exposed to said reference gas introduction space.

14. The gas sensor according to claim 1 , wherein said predetermined gas component comprises at least one of a hydrocarbon component or a carbon monoxide component.

15. The gas sensor according to claim 3 , wherein said first and second sensing electrodes are adjacent to each other in a longitudinal direction of said sensor element on one surface of said sensor element.

16. The gas sensor according to claim 3 , wherein said first and second sensing electrodes are respectively located on two opposite surfaces of said sensor element.

17. The gas sensor according to claim 3 , wherein said gas sensor is configured to
determine the concentration of said predetermined gas componen

Assignees

• Ngk Insulators Ltd

Inventors

• Okamoto Taku
• Hirata Noriko
• Nakayama Yuki
• Nakasone Osamu

Classifications

• G01N27/419

  Measuring voltages or currents with a combination of oxygen pumping cells and oxygen concentration cells · CPC title

• G01N27/4075

  Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts · CPC title

• G01N27/4071

  using sensor elements of laminated structure · CPC title

• G01N27/4074

  for detection of gases other than oxygen · CPC title

• G01N27/4073

  Composition or fabrication of the solid electrolyte · CPC title