Gas sensor

Patent metadata

Field	Value
Publication number	US-10845327-B2
Application number	US-201916253243-A
Country	US
Kind code	B2
Filing date	Jan 22, 2019
Priority date	Aug 9, 2016
Publication date	Nov 24, 2020
Grant date	Nov 24, 2020

Abstract

A sensor element includes: a sensing cell including a sensing electrode and a reference electrode; an oxygen pump cell configured to pump out oxygen in an internal space when a predetermined voltage is applied between an inner side pump electrode formed facing to the internal space and an outer side pump electrode formed on an outer surface of the sensor element; and a heater capable of heating the sensing cell and the oxygen pump cell. The concentration of a target gas component in measurement gas is specified based on a sensor output generated at the sensing cell and a pump current at the oxygen pump cell while the heater heats the sensing cell to a temperature of 400° C. to 600° C. and heats the oxygen pump cell to a temperature of 580° C. to 850° C. determined in accordance with a diffusion resistance provided to the measurement gas by a gas introduction part.

First claim

The invention claimed is:

1. A gas sensor of a mixed-potential type including a sensor element formed of a solid electrolyte having oxygen-ion conductivity and configured to measure a concentration of a predetermined gas component in measurement gas, wherein
said sensor element includes:
an internal space that is communicated with an external space through a gas introduction part provided on one leading end part side and to which said measurement gas is introduced from said external space;
a sensing electrode provided at a part of said sensor element where said sensing electrode is contactable with the measurement gas;
a reference gas introduction space to which reference gas is introduced;
a reference electrode provided in said reference gas introduction space;
a sensing cell including said sensing electrode and said reference electrode;
an oxygen pump cell including an inner side pump electrode formed facing to said internal space, an outer side pump electrode formed on an outer surface of said sensor element, and said solid electrolyte between said inner side pump electrode and said outer side pump electrode, and configured to pump out oxygen in said internal space when a predetermined oxygen pump voltage is applied between said inner side pump electrode and said outer side pump electrode; and
a heater capable of heating at least said sensing cell and said oxygen pump cell,
said gas sensor further includes:
an oxygen pump power source configured to apply said predetermined oxygen pump voltage between said inner side pump electrode and said outer side pump electrode; and
an electronic control unit (ECU) configured to specify the concentration of said predetermined gas component in said measurement gas,
wherein, while said measurement gas is in contact with said sensing electrode and introduced in said internal space, said heater heats said sensing cell to a first heating temperature of 400° C. or higher and 600° C. or lower and heats said oxygen pump cell to a second heating temperature of 580° C. or higher and 850° C. or lower in a temperature range determined in accordance with a diffusion resistance provided to said measurement gas by said gas introduction part, and said oxygen pump cell pumps out oxygen in said measurement gas in said internal space, said ECU specifies the concentration of a measurement target gas component in said measurement gas based on:
a sensor output value as a potential difference occurring between said sensing electrode and said reference electrode in accordance with the concentration of said predetermined gas component in said measurement gas; and
the concentration of oxygen in said measurement gas specified based on a magnitude of a pump current flowing between said inner side pump electrode and said outer side pump electrode when oxygen in said measurement gas in said internal space is pumped out by said oxygen pump cell.

2. The gas sensor according to claim 1 , wherein
said oxygen pump cell and said heater are stacked in a thickness direction of said sensor element,
said heater extends in a longitudinal direction of said sensor element, and
said sensing cell is disposed at a position where said heater exists in said longitudinal direction.

3. The gas sensor according to claim 2 , wherein said gas introduction part includes a diffusion control part.

4. The gas sensor according to claim 3 , wherein the diffusion resistance provided to said measurement gas by said gas introduction part is 500 cm −1 or more and 900 cm −1 or less.

5. The gas sensor according to claim 2 , wherein the diffusion resistance provided to said measurement gas by said gas introduction part is 500 cm −1 or more and 900 cm −1 or less.

6. The gas sensor according to claim 2 , wherein said first heating temperature is 500° C. or higher and 550° C. or lower.

7. The gas sensor according to claim 2 , wherein said sensing electrode is provided on a front surface of said sensor element.

8. The gas sensor according to claim 2 , wherein said sensor element further includes:
a second internal space that is communicated with an external space through a gas introduction hole provided to a front surface of the sensor element and to which said measurement gas is introduced from said external space; and
said sensing electrode is provided in said second internal space.

9. The gas sensor according to claim 1 , wherein
said oxygen pump cell and said heater are stacked in a thickness direction of said sensor element,
said heater extends in a longitudinal direction of said sensor element, and
said sensing cell is disposed at a position where said heater does not exist in said longitudinal direction.

10. The gas sensor according to claim 9 , wherein the diffusion resistance provided to said measurement gas by said gas introduction part is 500 cm −1 or more and 900 cm −1 or less.

11. The gas sensor according to claim 9 , wherein said first heating temperature is 500° C. or higher and 550° C. or lower.

12. The gas sensor according to claim 9 , wherein said sensing electrode is provided on a front surface of said sensor element.

13. The gas sensor according to claim 9 , wherein said sensor element further includes:
a second internal space that is communicated with an external space through a gas introduction hole provided to a front surface of the sensor element and to which said measurement gas is introduced from said external space; and
said sensing electrode is provided in said second internal space.

14. The gas sensor according to claim 1 , wherein said gas introduction part includes a diffusion control part.

15. The gas sensor according to claim 14 , wherein the diffusion resistance provided to said measurement gas by said gas introduction part is 500 cm −1 or more and 900 cm −1 or less.

16. The gas sensor according to claim 1 , wherein the diffusion resistance provided to said measurement gas by said gas introduction part is 500 cm −1 or more and 900 cm −1 or less.

17. The gas sensor according to claim 16 , wherein said second heating temperature is 580° C. or higher and 700° C. or lower.

18. The gas sensor according to claim 1 , wherein said first heating temperature is 500° C. or higher and 550° C. or lower.

19. The gas sensor according to claim 1 , wherein said sensing electrode is provided on a front surface of said sensor element.

20. The gas sensor according to claim 1 , wherein said sensor element further includes:
a second internal space that is communicated with an external space through a gas introduction hole provided to a front surface of the sensor element and to which said measurement gas is introduced from said external space; and
said sensing electrode is provided in said second internal space.

Assignees

• Ngk Insulators Ltd

Inventors

• Nakayama Yuki
• Hirata Noriko
• Okamoto Taku
• MONNA Kosuke

Classifications

• G01N27/409

  Oxygen concentration cells · CPC title

• G01N27/416

  Systems (G01N27/27 takes precedence) · CPC title

• G01N27/419 Primary

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

• G01N27/407

  for investigating or analysing gases {(G01N27/411 takes precedence)} · CPC title

• G01N27/4071

  using sensor elements of laminated structure · CPC title