Patent ID: 11899002
Assignee: NGK INSULATORS, LTD.
Field: Measurement (Instruments)
Classification: CPC G  Y | IPC G

Claim 0:
1. 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.