Abstract: A sensor element used to detect, using a limiting current method, the specific gas concentration in a rich-atmosphere measurement-object gas. The sensor element includes a layered body in which a measurement-object gas distribution portion is provided, an adjustment pump cell that has an adjustment pump electrode arranged in an oxygen concentration adjustment space in the measurement-object gas distribution portion. The adjustment pump electrode contains Pt and Au, and a Au/Pt ratio (=the area of a portion where Au is exposed/the area of a portion where Pt is exposed) measured using X-ray photoelectron spectroscopy (XPS) is greater than or equal to 0.3 but not greater than 0.63.

Abstract: A gas sensor includes a sensor element made of an oxygen-ion conductive solid electrolyte, at least one electrode provided to the sensor element so as to contact a measurement gas, and a controller configured to control the gas sensor. The sensor element is heated, by a heater provided to the sensor element, at a temperature higher than an operating temperature set in advance for a predetermined time period at start of the gas sensor, and then the temperature of the sensor element is decreased to the operating temperature.

Abstract: A catalyst deterioration diagnosis system includes an air-fuel ratio detection element and a NOx detection element on a downstream side with respect to a catalyst, and a control element. The control element causes an engine to perform diagnosis operation performed with an exhaust gas temperature being kept at 600° C. or higher, such that at a timing when a downstream air-fuel ratio in a lean operation state reaches a threshold value, the engine is transitioned to a rich operation state, and at a timing that is a predetermined period after a downstream air-fuel ratio in a rich operation state reaches a threshold value, the engine is transitioned to a lean operation state. The diagnosis element compares NOx concentration during the rich operation state to a diagnosis threshold value, thereby to diagnose a degree of deterioration of NOx reduction capability of the catalyst.

Abstract: 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).

Abstract: 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.

Abstract: A catalyst deterioration diagnosis method is a method for a system. The system includes a stepped transmission or a continuously variable transmission connected to an internal combustion engine, a catalyst into which an exhaust gas from the internal combustion engine is introduced, and a gas sensor having sensitivity to ammonia that outputs a detection value corresponding to a component of an exhaust gas that has passed through the catalyst. The catalyst deterioration diagnosis method includes the following steps. Monitoring of temporary increase of a detection value of the gas sensor is started, and thereby a temporarily increased amount of the detection value of the gas sensor is acquired. The monitoring is started when upshifting of the stepped transmission or pseudo-upshifting of the continuously variable transmission is performed. Whether or not the temporarily increased amount is larger than a threshold amount is determined.

Abstract: A method of inspecting an electrode provided in a gas sensor element includes the steps of: producing, in advance, a calibration curve representing a relation between an Au maldistribution degree defined based on a ratio of an area of a portion at which Au is exposed on a noble metal particle surface and calculated from a result of XPS or AES analysis on an inspection target electrode, and a predetermined alternative maldistribution degree index correlated with the Au maldistribution degree and acquired in a non-destructive manner from the gas sensor element heated to a predetermined temperature; acquiring a value of the alternative maldistribution degree index for the inspection target electrode of the gas sensor element while the gas sensor element is heated to the predetermined temperature; and determining whether the Au maldistribution degree satisfies a predetermined standard based on the calibration curve and the acquired inspection value.

Abstract: Provided is a gas sensor having simpler configuration than a conventional multi-gas sensor, and being capable of measuring NOx and NH3 simultaneously. In the gas sensor determining a NOx concentration in a measurement gas based on a pump current flowing between a NOx measurement electrode and an outer pump electrode, the outer pump electrode has catalytic activity inactivated for NH3 so that a sensor element further includes a NH3 sensor part having a mixed potential cell constituted by the outer pump electrode, a reference electrode, and a solid electrolyte between these electrodes, and determination of a NH3 concentration based on a potential difference occurring between the outer pump electrode and the reference electrode and determination of a NOx concentration based on the pump current and the NH3 concentration can be performed simultaneously or selectively when the sensor element is heated to 400° C. or higher and 600° C. or lower.

Abstract: 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 ±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.

Abstract: 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).

Abstract: A gas sensor includes an element body, an inner main pump electrode, an inner auxiliary pump electrode, an inner preliminary pump electrode, a measurement electrode, a reference electrode, a measurement voltage detection device, a specific gas concentration detection device. The inner preliminary pump electrode, the inner main pump electrode, the inner auxiliary pump electrode and the measurement electrode include each contain a noble metal having catalytic activity. At least one of the inner preliminary pump electrode and the inner main pump electrode contains no noble metal having a catalytic activity suppression ability, the catalytic activity suppression ability being an ability to suppress the catalytic activity of the noble metal having the catalytic activity from being exhibited to the specific gas. The inner auxiliary pump electrode contains a noble metal having the catalytic activity suppression ability.

Abstract: A gas sensor detects the concentration of a specific gas on the basis of a pump current that flows when oxygen is pumped out from a measurement chamber, so that an oxygen concentration in the measurement chamber becomes a predetermined low concentration, the oxygen that is pumped out being oxygen that is generated when the specific gas is reduced in measurement chamber in a case where the specific gas is an oxide or being oxygen that is generated when a gas obtained as a result of conversion of the specific gas to an oxide is reduced in the measurement chamber in a case where the specific gas is a non-oxide. Further, the gas sensor corrects the pump current or the concentration of the specific gas on the basis of the oxygen concentration of the measurement-object gas when the measurement-object gas is in a rich atmosphere.

Abstract: A gas sensor includes an element body, an adjustment pump cell, a preliminary pump cell, a measurement electrode, a reference electrode, a specific gas concentration detection device. The element body provides a measurement-object gas flow section to allow a measurement-object gas to be introduced into and flow through the measurement-object gas flow section. The adjustment pump cell adjusts an oxygen concentration of an oxygen concentration adjustment chamber in the measurement-object gas flow section. The preliminary pump cell pumps oxygen into a preliminary chamber to prevent the measurement-object gas in a low-oxygen atmosphere from reaching the oxygen concentration adjustment chamber, the preliminary chamber being provided upstream of the oxygen concentration adjustment chamber in the measurement-object gas flow section.

Abstract: A gas sensor that is unlikely to have Au evaporation from an external electrode even when used under a high temperature atmosphere is provided. The gas sensor includes a sensor element mainly made of an oxygen-ion conductive solid electrolyte; an external electrode provided on the sensor element and containing a Pt—Au alloy; and an electrode evaporation preventing film provided on the sensor element while being insulated from the sensor element and separated from the external electrode, and made of Au or a Pt—Au alloy having an Au composition ratio not smaller than an Au composition ratio of the Pt—Au alloy contained in the external electrode. A protection cover is provided so that at least part of the sensor element, at which the external electrode and the electrode evaporation preventing film is positioned, is inside the protection cover, and so that a measurement gas is introduced inside the protection cover.

Abstract: A mixed-potential gas sensor for measuring a concentration of a predetermined gas component of a measurement gas includes sensing electrodes mainly made of an oxygen-ion conductive solid electrolyte and located on a surface of a sensor element, and at least one reference electrode including a cermet including Pt and an oxygen-ion conductive solid electrolyte. The sensing electrodes each include a cermet including a noble metal and an oxygen-ion conductive solid electrolyte. The noble metal includes Pt and Au. A Au abundance ratio, which is an area ratio of a portion covered with the Au to a portion at which the Pt is exposed in a surface of noble metal particles forming each of the sensing electrodes, differs among the sensing electrodes. The gas sensor determines a concentration of the predetermined gas component based on a potential difference between each of the sensing electrodes and the at least one reference electrode.

Abstract: In a gas sensor configured to measure the concentrations of a plurality of components in the presence of oxygen, in the interior of a structural body made from an oxygen ion conductive solid electrolyte, a preliminary chamber having a mixed potential electrode, an oxygen concentration adjustment chamber having a main pump electrode, and a measurement chamber having a measurement electrode are formed in a manner communicating in this order. While oxygen within the gas to be measured is being discharged by the main pump electrode and the measurement electrode, the NH3 concentration within the gas to be measured is measured by a mixed potential V0 of the mixed potential electrode.

Abstract: A gas sensor includes a structural body made up from a solid electrolyte that exhibits oxygen ion conductivity, a gas introduction port formed in the structural body, a preliminary chamber communicating with the gas introduction port and equipped with a preliminary pump electrode, a main chamber communicating with the preliminary chamber and equipped with a main pump electrode, and a measurement chamber communicating with the main chamber and equipped with a measurement electrode. In the gas sensor, at least a surface of the preliminary pump electrode is made of a material which exhibits a low activity with respect to a reaction between ammonia and oxygen.

Abstract: A first gas sensor includes a main pump cell that pumps oxygen inside a main oxygen concentration adjustment chamber, by applying a main pump voltage between a main interior side electrode and an exterior side electrode, and causing a main pump current to flow, a preliminary pump cell that pumps the oxygen inside a preliminary adjustment chamber by applying a preliminary pump voltage between an interior side preliminary electrode and the exterior side electrode, and causing a preliminary pump current to flow, and a constant control unit that controls the preliminary pump voltage of the preliminary pump cell in a manner so that the main pump current of the main pump cell becomes constant.

Abstract: A apparatus 70 for measuring ammonia concentration includes an electromotive force acquisition section 75 configured to acquire information about an electromotive force EMF of a mixed potential cell 55 while a detection electrode 51 is exposed to a target gas, an oxygen concentration acquisition section 76 configured to acquire information about oxygen concentration pO2 in the target gas, and a control section 72. The control section 72 derives ammonia concentration pNH3 in the target gas from the acquired information about the electromotive force EMF, the acquired information about the oxygen concentration pO2, and the relationship represented by formula (1): EMF=? loga(pNH3)?? logb(pO2)+B??(1) where ?, ?, and B each represent a constant, and a and b each represent any base (provided that a?1, a>0, b?1, and b>0).

Abstract: A apparatus 70 for measuring combustible-gas concentration includes an electromotive force acquisition section 75 configured to acquire information about an electromotive force of a mixed potential cell 55 while a detection electrode 51 is exposed to a target gas, an oxygen concentration acquisition section 76 configured to acquire information about oxygen concentration pO2 in the target gas, and a control section 72. The control section 72 derives combustible-gas concentration pTHC in the target gas from the acquired information about the electromotive force EMF, the acquired information about the oxygen concentration pO2, and the relationship represented by formula (1): EMF=? loga(pTHC)?? logb(pO2)+B??(1) where ?, ?, and B each represent a constant, and a and b each represent any base (provided that a?1, a>0, b?1, and b>0).