US 11,531,014 B2 · Gas sensor and gas sensor operation control method

Abstract

A controller of the gas sensor can perform diagnostic processing of diagnosing a situation of control to the gas sensor in a case that the gas sensor in an operation state is determined to satisfy a predetermined diagnostic condition and adjustment processing of adjusting a condition for controlling the gas sensor in accordance with a result of diagnosis. In the diagnostic processing, a main pump voltage and a diagnostic threshold as a value of a voltage not causing decomposition of NOx in the main pump cell are compared. In the adjustment processing, temperature adjustment processing to cause, in a case that the main pump voltage is diagnosed to be equal to the threshold or more, the main pump voltage to be less than the threshold, at least in a way that the heater part increases the element driving temperature in the operation state by a predetermined increase amount is performed.

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

a sensor element having a base part made of an oxygen-ion conductive solid electrolyte, said sensor element including:
a gas inlet through which said measurement gas is introduced from an external space;
a first internal space communicating with said gas inlet under predetermined diffusion resistance;
a main pump cell as an electrochemical pump cell including an inner pump electrode located to face said first internal space, an out-of-space pump electrode located to face a space other than said first internal space, and said solid electrolyte located between said inner pump electrode and said out-of-space pump electrode;
a measurement electrode located inside said sensor element, at least one diffusion control part being located between said measurement electrode and said first internal space;
a measurement pump cell as an electrochemical pump cell including said measurement electrode, said out-of-space pump electrode, and said solid electrolyte located between said measurement electrode and said out-of-space pump electrode;
a reference electrode located inside said sensor element and capable of being in contact with a reference gas;
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 including a processor and a memory and being configured to:
perform condition determination processing of determining whether said gas sensor satisfies a predetermined diagnostic condition when said gas sensor is in an operation state capable of measuring a NOx concentration;
perform diagnostic processing of diagnosing a situation of control to said gas sensor in a case that said gas sensor is determined to satisfy said diagnostic condition;
and
perform adjustment processing of adjusting a condition under which said gas sensor is controlled in accordance with a result of diagnosis in said diagnostic processing, wherein
said gas sensor is put into said operation state capable of measuring said NOx concentration at least when:
said heater part heats said sensor element to a predetermined element driving temperature;
a main pump voltage is applied to said main pump cell so that an oxygen concentration in said first internal space is constant;
and
a measurement pump voltage is applied to said measurement pump cell so that oxygen generated through decomposition of NOx in said measurement electrode is pumped out,
in said diagnostic processing, said main pump voltage is compared with a diagnostic threshold set in advance as a value of a voltage not causing decomposition of NOx in said main pump cell,
a temperature adjustment element performs temperature adjustment processing as said adjustment processing,
said temperature adjustment processing is processing to cause, in a case that said main pump voltage is diagnosed to be equal to said diagnostic threshold or more in said diagnostic processing, said main pump voltage to be less than said diagnostic threshold, at least in a way that said heater part increases said element driving temperature in said operation state by a predetermined increase amount,
said controller is further configured to:
perform electromotive force adjustment processing as said adjustment processing;
and
perform auxiliary pump current adjustment processing as said adjustment processing,
said electromotive force adjustment processing is processing to promote pumping out of oxygen with an auxiliary pump cell and thereby to cause said main pump voltage to be less than said diagnostic threshold, in a way of increasing a target value of electromotive force generated between an auxiliary pump electrode and said reference electrode set in accordance with a target oxygen concentration in a second internal space,
said auxiliary pump current adjustment processing is processing to promote pumping out of oxygen with said auxiliary pump cell and thereby to cause said main pump voltage to be less than said diagnostic threshold, in a way of increasing a target value of an auxiliary pump current flowing through said auxiliary pump cell, and
said adjustment processing includes at least one of said electromotive force adjustment processing and said auxiliary pump current adjustment processing in addition to said temperature adjustment processing.

27 more elements

Description11,635 words

Summary1,381 words

#The present application claims priority from Japanese applications JP 2019-155704, filed on Aug. 28, 2019 and JP 2020-104695, filed on Jun. 17, 2020, the contents of which is hereby incorporated by reference into this application.

#The present invention relates to a gas sensor for determining concentration of nitrogen oxides (NOx), and, in particular, to operation control to secure measurement accuracy in a high NOx concentration range.

#A limiting-current type gas sensor (NOx sensor) including a sensor element containing an oxygen-ion conductive solid electrolyte as a main component has already been known (see, for example, Japanese Patent No. 3050781). In determining a NOx concentration using such a gas sensor, a measurement gas is first introduced into a space (an internal space) inside the sensor element under predetermined diffusion resistance, and oxygen in the measurement gas is pumped out by a two-stage electrochemical pump cell, for example, referred to as a main pump cell and an auxiliary pump cell (a first electrochemical pump cell and a second electrochemical pump cell in Japanese Patent No. 3050781) to sufficiently reduce an oxygen concentration of the measurement gas in advance. NOx in the measurement gas is then reduced or decomposed by a measurement electrode (third inner pump electrode in Japanese Patent No. 3050781) functioning as a reduction catalyst, and oxygen thus generated is pumped out by an electrochemical pump cell (a third electrochemical pump cell in Japanese Patent No. 3050781) different from the above-mentioned electrochemical pump cell, including the measurement electrode, and, for example, referred to as a measurement pump cell. The NOx concentration is determined using a constant functional relationship between a current (NOx current) flowing through the measurement pump cell and the NOx concentration.

Brief description of the drawings11 figures

#FIG. 1 schematically shows one example of a configuration of a gas sensor 100 including a vertical sectional view taken along a longitudinal direction of a sensor element 101;

#FIG. 2 shows a functional configuration of a controller 110;

#FIG. 3 shows an example of a functional relationship between a NOx concentration and a NOx current Ip2 showing sensitivity characteristics;

Detailed description10,000 words

#<General Configuration of Gas Sensor>

#A general configuration of a gas sensor 100 including a sensor element 101 according to a first embodiment of the present invention will be described first. In the present embodiment, the gas sensor 100 is a limiting-current type NOx sensor to sense NOx and measure concentration thereof using the sensor element 101. The gas sensor 100 further includes a controller 110 to control operation of each part and identify the NOx concentration based on a NOx current flowing through the sensor element 101.

#FIG. 1 schematically shows one example of a configuration of the gas sensor 100 including a vertical sectional view taken along a longitudinal direction of the sensor element 101.

Facts

Application

16/998,003Filed 20 Aug 2020

Priority

JP JP2019-15570428 Aug 2019

Published

US 2021/0063369 A14 Mar 2021

Granted

20 Dec 2022

Term ends

20 Jan 2041

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 153 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification6 codes

G01N 33/0037
Specially adapted to detect a particular component: nox
G01N 27/4074
Composition or fabrication of the solid electrolyte: for detection of gases other than oxygen
G01N 27/419
Using cells , i.e. more than one cell and probes with solid electrolytes: measuring voltages or currents with a combination of oxygen pumping…
Y02A 50/20
In human health protection, e.g. against extreme weather: air quality improvement or preservation, e.g. vehicle emission control or emission…

Timeline

28 Aug 2019Priority claimedJP JP2019-155704
20 Aug 2020Application filedUS 16/998,003
20 Aug 2020Assigned to Ngk Insulators, Ltd.assignment of assignor's interest
4 Mar 2021PublishedUS 2021/0063369 A1
20 Dec 2022GrantedUS 11,531,014 B2
12 Oct 2026TodayWithin its term
20 Jan 2041Term endsEstimated, includes 153 days of adjustment

Gas sensor and gas sensor operation control method

Life of this patent

Gas sensor and gas sensor operation control method

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims10

Description11,635 words

Drawings

Classification6 codes

Life of this patent

Description11,635 words