Gas sensor and gas concentration measuring method using the same

Patent metadata

Field	Value
Publication number	US-2018059046-A1
Application number	US-201715686239-A
Country	US
Kind code	A1
Filing date	Aug 25, 2017
Priority date	Aug 26, 2016
Publication date	Mar 1, 2018
Grant date	—

Abstract

A gas sensor in which an electrode is prevented from being poisoned is provided. A mixed-potential type gas sensor includes a sensor element composed a solid electrolyte. The sensor element includes: a measurement gas introduction space having an open end at a distal end and extending in a longitudinal direction; a sensing electrode provided on an inner side of the measurement gas introduction space; and a heater configured to heat the sensor element. The concentration of the gas component is determined based on a potential difference between the sensing electrode and a reference electrode, while the heater heats the sensor element so that a place having a temperature higher than the temperature of the sensing electrode and the melting point of a poisoning substance exists between the open end and the sensing electrode and the temperature decreases toward the sensing electrode.

First claim

What is claimed is:

1 . A mixed-potential type gas sensor for sensing a predetermined gas component in a measurement gas, said sensor comprising a sensor element composed of an oxygen-ion conductive solid electrolyte, said sensor element including:
a measurement gas introduction space having an open end at a distal end of said sensor element and extending in an element longitudinal direction; a sensing electrode formed of a cermet of a noble metal and an oxygen-ion conductive solid electrolyte and provided on a side opposite to said open end in said measurement gas introduction space; a reference electrode formed of a cermet of Pt and an oxygen-ion conductive solid electrolyte; and a heater configured to heat said sensor element,
wherein
said gas sensor is configured to determine a concentration of said predetermined gas component based on a potential difference between said sensing electrode and said reference electrode, and
when said gas sensor determines the concentration of said predetermined gas component, said heater heats said sensor element so that a high temperature place having a temperature higher than a temperature of said sensing electrode and a melting point of a poisoning substance which is determined or estimated in advance exists between said open end and said sensing electrode and so that the temperature decreases toward said sensing electrode between said high temperature place and said sensing electrode in a direction toward said sensing electrode from said open end.

2 . The gas sensor according to claim 1 , further comprising an electrode protective layer as a porous layer covering said sensing electrode.

3 . A method of measuring a concentration of a predetermined gas component in a measurement gas through a mixed-potential type gas sensor including a sensor element composed of an oxygen-ion conductive solid electrolyte,
said sensor element including: a measurement gas introduction space having an open end at a distal end of said sensor element and extending in an element longitudinal direction; a sensing electrode formed of a cermet of a noble metal and an oxygen-ion conductive solid electrolyte and provided on a side opposite to said open end in said measurement gas introduction space; a reference electrode formed of a cermet of Pt and an oxygen-ion conductive solid electrolyte; and a heater configured to heat said sensor element,
and said method comprising the processes of:
a) contacting the distal end of said sensor element with said measurement gas and contacting said reference electrode with a reference gas;
b) heating, in a contact state achieved through said process a), said sensor element by said heater, so that a high temperature place having a temperature higher than a temperature of said sensing electrode and a melting point of a poisoning substance which is determined or estimated in advance exists between said open end and said sensing electrode and so that the temperature decreases toward said sensing electrode between said high temperature place and said sensing electrode in a direction toward said sensing electrode from said open end; and
c) determining the concentration of said predetermined gas component based on a potential difference between said sensing electrode and said reference electrode while said sensor element is heated through said process b).

Assignees

• Ngk Insulators Ltd

Inventors

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

Classifications

• G01N27/4077 Primary

  Means for protecting the electrolyte or the electrodes · CPC title

• G01N27/4067 Primary

  Means for heating or controlling the temperature of the solid electrolyte · CPC title

• G01N27/00 Primary

  Investigating or analysing materials by the use of electric, electrochemical, or magnetic means (G01N3/00 – G01N25/00 take precedence; measurement or testing of electric or magnetic variables or of electric or magnetic properties of materials G01R) · CPC title

• G01N27/4074

  for detection of gases other than oxygen · CPC title

• G01N27/4076

  Reference electrodes or reference mixtures · CPC title