US 11,899,002 B2Granted

Gas sensor and method for controlling operation of gas sensor

AssigneeNGK Insulators, Ltd.

InventorsYusuke Watanabe, Takayuki Sekiya

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Abstract

A limiting-current type gas sensor including a sensor element including a base part made of an oxygen-ion conductive solid electrolyte and measuring concentration of NOx in a measurement gas includes: a pump cell including a first electrode disposed to be capable of being in contact with a gas introduced into the element and a second electrode disposed so that a part made of the solid electrolyte is located between the first electrode and the second electrode; and a pumping diagnostic part to determine whether an inter-electrode electric field produced in the part made of the solid electrolyte through application of a predetermined pump voltage between the electrodes exceeds a first threshold, and, when the inter-electrode electric field exceeds the first threshold, the predetermined pump voltage is reduced so that the inter-electrode electric field falls below the first threshold.

Claims20

Dependent claims

A limiting-current type gas sensor measuring concentration of NOx in a measurement gas, said gas sensor comprising:

a sensor element including:
a base part made of an oxygen-ion conductive solid electrolyte;
at least one pump cell as an electrochemical pump cell including:
a first electrode disposed to be capable of being in contact with said measurement gas introduced into said sensor element;
and
a second electrode disposed so that a part made of said solid electrolyte is located between said first electrode and said second electrode,
and said at least one pump cell capable of externally pumping out oxygen from a region that said first electrode faces through application of a predetermined pump voltage between said first electrode and said second electrode;
and
a heater part buried in said sensor element and heating said sensor element;
and
a controller controlling operation of said gas sensor, said controller being configured to:
apply said predetermined pump voltage between said first electrode and said second electrode,
determine an inter-electrode electric field produced in said part made of said solid electrolyte between said first electrode and said second electrode through the application of said predetermined pump voltage between said first electrode and said second electrode, and
determine whether the inter-electrode electric field exceeds a first threshold, wherein
upon a temperature of the sensor element being lower than an element driving temperature at a start of the gas sensor, the controller controls said heater part to raise the temperature of said sensor element to said element driving temperature and applies said predetermined pump voltage between said first electrode and said second electrode, and upon determining said inter-electrode electric field exceeds said first threshold, the controller is configured to reduce said predetermined pump voltage so that said inter-electrode electric field falls below said first threshold.

12 more elements

A method for controlling operation of a limiting-current type gas sensor measuring concentration of NOx in a measurement gas, wherein

said gas sensor includes a sensor element including:
a base part made of an oxygen-ion conductive solid electrolyte;
at least one pump cell as an electrochemical pump cell including:
a first electrode disposed to be capable of being in contact with said measurement gas introduced into said sensor element;
and
a second electrode disposed so that a part made of said solid electrolyte is located between said first electrode and said second electrode,
and said at least one pump cell being capable of externally pumping out oxygen from a region that said first electrode faces through application of a predetermined pump voltage between said first electrode and said second electrode;
and
a heater part buried in said sensor element and heating said sensor element,
said method including:
a) applying said predetermined pump voltage between said first electrode and said second electrode;
and
b) making a first diagnosis to determine whether an inter-electrode electric field produced in said part made of said solid electrolyte between said first electrode and said second electrode through application of said predetermined pump voltage between said first electrode and said second electrode in said step a) exceeds a first threshold, wherein
upon a temperature of the sensor element being lower than an element driving temperature at a start of the gas sensor, controlling said heater part to raise the temperature of said sensor element to said element driving temperature and applying said predetermined pump voltage between said first electrode and said second electrode, and upon determining said inter-electrode electric field exceeds said first threshold in said step b), said predetermined pump voltage applied in said step a) is reduced so that said inter-electrode electric field falls below said first threshold.

11 more elements

Dependencies are inferred from the claim text.

Facts

Application: 17/208,060Filed 22 Mar 2021
Priority: JP 2020-05400225 Mar 2020
Published: US 2021/0302400 A130 Sep 2021
Granted: 13 Feb 2024
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

G01N 33/0037
Specially adapted to detect a particular component: nox
G01N 27/4073
For investigating or analysing gases: composition or fabrication of the solid electrolyte
G01N 27/409
For investigating or analysing gases: oxygen concentration cells
G01N 27/41
For investigating or analysing gases: oxygen pumping cells