Ngk Insulators, Inc.

Kosuke Monna

Taku Okamoto

Noriko Hirata

Yuki Nakayama

Osamu Nakasone

Yoshinobu Nakada

Takayuki Sakurai

Nobuhiko Mori

A catalyst deterioration diagnosis device includes: a unit configured to obtain a temperature of a catalyst; a unit configured to obtain a sensor output from a gas sensor disposed between the catalyst and an exhaust port; and a unit configured to determine the catalyst to be faulty when the temperature of the catalyst obtained when the sensor output becomes a preset evaluative output is equal to or higher than an evaluative catalyst temperature.

Catalyst deterioration diagnosis device and catalyst deterioration diagnosis method

Provided is a method of suitably judging necessity of a recovering process carried out on a mixed-potential gas sensor based on an extent of reversible deterioration occurring in a sensing electrode. The method includes the steps of: (a) performing impedance measurement between a sensing electrode exposed to a measurement gas and a reference electrode exposed to a reference atmosphere, which are provided in the gas sensor; and (b) judging necessity of a recovering process based on electrode reaction resistance or a diagnosis parameter correlating with the electrode reaction resistance wherein the electrode reaction resistance and the diagnosis parameter are obtained based on a result of the impedance measurement. The two steps are intermittently or periodically repeated during use of the gas sensor, and it is judged that a recovering process is necessary when the judge parameter satisfies a predetermined threshold condition in the step (b).

Gas-sensor diagnosing method

A catalyst deterioration diagnosis method is a method for a system. The system includes a gas sensor having ammonia interference property that measures an air-fuel ratio and nitrogen oxide concentration of an exhaust gas that has passed through a catalyst. Monitoring of temporary increase of nitrogen oxide concentration to be detected by the gas sensor is started, and thereby a temporarily increased amount of the nitrogen oxide concentration is acquired. The monitoring is started when a fuel injection device restarts fuel injection after a fuel cut in a case where an air-fuel ratio most recently obtained by the gas sensor is larger than a predetermined threshold air-fuel ratio. The predetermined threshold air-fuel ratio is larger than a stoichiometric air-fuel ratio. Whether or not the temporarily increased amount is larger than a threshold amount is determined.

Catalyst deterioration diagnosis method and catalyst deterioration diagnosis system

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&#xb0; C. to 600&#xb0; C. and heats the oxygen pump cell to a temperature of 580&#xb0; C. to 850&#xb0; C. determined in accordance with a diffusion resistance provided to the measurement gas by a gas introduction part.

Gas sensor

A method of diagnosing a degree of degradation of a catalyst located along an exhaust path of an internal combustion engine, and oxidizing or adsorbing a target gas included in an exhaust gas and including at least one of HC and CO is disclosed. The method includes: a) determining whether an oxygen concentration of the exhaust gas is in a range of 15% to 20% or whether the oxygen concentration is 10% or more and varies in a range of &#xb1;2% or less of a predetermined value in a predetermined period of time; and b) diagnosing whether the catalyst is degraded when criteria in the step a) are satisfied. The step b) is performed by comparing a diagnostic indicator value calculated using an output value from a target gas detection component provided at a location downstream from the catalyst and a threshold corresponding to temperature of the catalyst.

Catalyst degradation diagnostic method and catalyst degradation diagnostic system

A apparatusfor measuring ammonia concentration includes an electromotive force acquisition sectionconfigured to acquire information about an electromotive force EMF of a mixed potential cellwhile a detection electrodeis exposed to a target gas, an oxygen concentration acquisition sectionconfigured to acquire information about oxygen concentration pin the target gas, and a control section. The control sectionderives ammonia concentration pin the target gas from the acquired information about the electromotive force EMF, the acquired information about the oxygen concentration p, and the relationship represented by formula (1):EMF=&#x3b1; log()&#x2212;&#x3b2; log()+&#x2003;&#x2003;(1)where &#x3b1;, &#x3b2;, and B each represent a constant, and a and b each represent any base (provided that a&#x2260;1, a&#x3e;0, b&#x2260;1, and b&#x3e;0).

Apparatus for measuring ammonia concentration, system for measuring ammonia concentration, system for treating exhaust gas, and method for measuring ammonia concentration

A apparatusfor measuring combustible-gas concentration includes an electromotive force acquisition sectionconfigured to acquire information about an electromotive force of a mixed potential cellwhile a detection electrodeis exposed to a target gas, an oxygen concentration acquisition sectionconfigured to acquire information about oxygen concentration pin the target gas, and a control section. The control sectionderives combustible-gas concentration pin the target gas from the acquired information about the electromotive force EMF, the acquired information about the oxygen concentration p, and the relationship represented by formula (1):EMF=&#x3b1; log()&#x2212;&#x3b2; log()+&#x2003;&#x2003;(1)where &#x3b1;, &#x3b2;, and B each represent a constant, and a and b each represent any base (provided that a&#x2260;1, a&#x3e;0, b&#x2260;1, and b&#x3e;0).

Apparatus for measuring combustible-gas concentration, system for measuring combustible-gas concentration, system for treating exhaust gas, method for measuring combustible-gas concentration, and method for deriving constant

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.

Gas sensor and gas concentration measuring method using the same

Provided is a method for diagnosing whether an oxidation catalyst has degraded, based on an output value from one diagnostic sensor with higher accuracy. When a ratio of nitrogen monoxide that is oxidized by a catalyst and discharged downstream of the catalyst as nitrogen dioxide, with respect to nitrogen monoxide contained in an exhaust gas supplied upstream of the catalyst in an exhaust path is defined as a NO conversion rate, a diagnostic sensor configured to output an electromotive force corresponding to the NO conversion rate as a diagnostic output is provided downstream of the catalyst in the exhaust path, and whether the catalyst has degraded beyond an acceptable limit is diagnosed by comparing the diagnostic output with a threshold value predetermined depending on a temperature of the catalyst.

Method for diagnosing degradation in catalyst

A mixed-potential type gas sensor capable of preferably determining the concentration of THC including a kind of gas having a large C number is provided. A sensor element composed of an oxygen-ion conductive solid electrolyte is provided with, on its surface, a sensing electrode formed of a cermet of Pt, Au, and an oxygen-ion conductive solid electrolyte, and includes a reference electrode and a porous surface protective layer that covers at least said sensing electrode. An Au abundance ratio on a surface of noble metal particles forming the sensing electrode is 0.3 or more. The surface protective layer has a porosity of 28% to 40%, a thickness of 10 to 50 &#x3bc;m, and an area ratio of a coarse pore having a pore size of 1 &#x3bc;m or larger of 50% or more; or has a porosity of 28% to 40% and a thickness of 10 to 35 &#x3bc;m.

A slope &#x394;in a linear area of sensor output characteristics for a mixed atmosphere of CO and THC and a slope &#x394;in the linear area of the sensor output characteristics for NHare specified in advance at a time when a time thas elapsed since a start of use of an engine. In performing calibration of an NHsensor when a time t(greater than the time t) has elapsed, a slope &#x394;in the linear area of the sensor output characteristics for the mixed atmosphere is specified, a value &#x394;is calculated from an equation &#x394;=&#x394;/(&#x394;/&#x394;), and the calculated value &#x394;is determined as a new slope in the linear area of the sensor output characteristics for an NHgas.

Ammonia sensor calibration method

An apparatus for measuring ammonia concentration measures ammonia concentration in a target gas with a sensor element including a mixed potential cell. The apparatus for measuring ammonia concentration includes an electromotive force acquisition section, an oxygen concentration acquisition section, and an ammonia concentration derivation section. The ammonia concentration derivation section derives the ammonia concentration in the target gas from the relationship represented by formula (1):EMF=&#x3b1; log()&#x2212;&#x3b2; log()+&#x3b3; log()&#xd7;log()+B&#x2003;&#x2003; (1)

Provided is a method for accurately diagnosing a degree of degradation of an oxidation catalyst. A target gas detecting element configured to output an electromotive force corresponding to a concentration of a target gas is provided downstream of a catalyst in an exhaust path of an internal combustion engine. A sum of change amounts of an electromotive force in a time-variable profile thereof after the introduction of a gas atmosphere for diagnosis into the catalyst is set as a diagnosis index value. The gas atmosphere has been intentionally created in the engine and includes a target gas having a concentration higher than the concentration of a target gas during a steady operation state of the engine. The index value is then compared with a threshold corresponding to the temperature of the catalyst to diagnosis whether degradation exceeding an acceptable degree has occurred in the catalyst.

Method for diagnosing degradation of catalyst and catalyst degradation diagnosis system

Provided is a method for accurately diagnosing a degree of degradation of an oxidation catalyst. A target gas detecting element configured to output an electromotive force corresponding to a concentration of a target gas is provided downstream of a catalyst in an exhaust path of an internal combustion engine. A maximum change amount of an electromotive force after the introduction of a gas atmosphere for diagnosis into the catalyst is set as a diagnosis index value. The gas atmosphere has been intentionally created in the engine and includes a target gas having a concentration higher than the concentration of a target gas in a steady operation state of the engine. The index value is then compared with a threshold corresponding to the temperature of the catalyst to diagnosis whether degradation exceeding an acceptable degree has occurred in the catalyst.

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Aichi, Japan

Kosuke Monna