Abstract: A system of diagnosing a deterioration of a catalyst, which includes a precious metal component and a ceramic part and purifies an exhaust gas emitted from an engine, includes: a diagnosis means comparing a diagnosis object value corresponding to an output from an NOx sensor provided on a downstream side with respect to the catalyst and a predetermined diagnosis threshold value stored in a storage means, thereby diagnosing a degree of deterioration of the catalyst, wherein the diagnosis threshold value is previously determined based on a correlationship between the diagnosis object value and a total weight value of NOx and THC in the exhaust gas through the catalyst in a state where the vehicle travels under a constant threshold value setting condition, and the diagnosis means diagnoses that a deterioration occurs in the precious metal component when the diagnosis object value exceeds the diagnosis threshold value.

Abstract: A gas sensor includes a main pump cell, a storage unit that stores information about a zero point in a first correspondence relationship, where the first correspondence relationship is a linear correspondence relationship between the oxygen concentration in a measurement-object gas and the main pump current, an oxygen-concentration-detecting unit that detects the oxygen concentration in a measurement-object gas, based on a measured value p of the main pump current and the information about the zero point, and a measured-value-obtaining unit that performs a second control process and that obtains a measured value b1 at a measurement point B1 at which a known value of the oxygen concentration and the main pump current are relevant to each other with a measurement timing. The oxygen-concentration-detecting unit makes zero point correction such that a divergence of the zero point from the first correspondence relationship is corrected based on the measured value b1.

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 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: A sensor element includes an element main body having an oxygen ion-conducting solid electrolyte body, a detection electrode which is disposed on an outer surface of the element main body and contains Pt and Au, a reference electrode which is disposed in the element main body, a connecting terminal for detection electrode which is disposed on the outside of the element main body, a lead portion for detection electrode which contains Pt, is disposed on the outside of the element main body, and electrically connects between the detection electrode and the connecting terminal for detection electrode, a lower insulating layer which is disposed between the lead portion for detection electrode and the element main body and insulates the two from each other, and an upper insulating layer which covers a surface of the lead portion for detection electrode and has a porosity of 10% or less.

Abstract: A particular-gas concentration-measuring apparatus measures a particular gas concentration being the concentration of a particular gas in a measurement-object gas. The particular-gas concentration-measuring apparatus comprises a particular-gas concentration derivation unit. The particular-gas concentration derivation unit causes an electromotive-force acquisition unit to acquire an electromotive force and derives a correction value compensating for the difference between a correction-value derivation electromotive force that is the electromotive force and the reference electromotive force at a correction-value derivation time. The correction-value derivation time is a time during which a sensing electrode is exposed to a correction-value derivation gas, the correction-value derivation gas being the measurement-object gas where neither ammonia nor a combustible gas is assumed to be included.

Abstract: In a method of performing active control between a lean operation state and a rich operation state on a vehicle engine including a three way catalyst in an exhaust path, on a downstream side with respect to the three way catalyst in the exhaust path, a limited current type NOx sensor having NH3 interference and also capable of detecting a change in an oxygen concentration on the downstream side is disposed, and an operation state of the vehicle engine is switched between a lean operation state and a rich operation state at a timing when a detection of a change in an oxygen concentration in an exhaust air flowing out from the three way catalyst or a detection of NOx or NH3 is performed first by the NOx sensor.

Abstract: A system of diagnosing a deterioration of a catalyst, which includes a precious metal component and a ceramic part and purifies an exhaust gas emitted from an engine, includes: a diagnosis means comparing a diagnosis object value corresponding to an output from an NOx sensor provided on a downstream side with respect to the catalyst and a predetermined diagnosis threshold value stored in a storage means, thereby diagnosing a degree of deterioration of the catalyst, wherein the diagnosis threshold value is previously determined based on a correlationship between the diagnosis object value and a total weight value of NOx and THC in the exhaust gas through the catalyst in a state where the vehicle travels under a constant threshold value setting condition, and the diagnosis means diagnoses that a deterioration occurs in the precious metal component when the diagnosis object value exceeds the diagnosis threshold value.

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: Provided is a gas sensor which is capable of preferably sensing an ammonia gas, and has excellent durability. A mixed-potential gas sensor includes a sensor element composed of an oxygen-ion conductive solid electrolyte, and a heater provided inside the element. The sensor element includes on a surface thereof a sensing electrode formed of a cermet including Pt, Au and an oxygen-ion conductive solid electrolyte, and also includes a reference electrode formed of a cermet of Pt and an oxygen-ion conductive solid electrolyte, and a porous electrode protective layer whose porosity is 5 to 40% covering at least the sensing electrode. The Au abundance ratio in a surface of noble metal particles forming the sensing electrode is 0.4 or more. The concentration of an ammonia gas is determined on the basis of a potential difference occurring between the sensing electrode and the reference electrode when the sensor element is disposed in a measurement gas and heated to 400° C. to 800° C.

Abstract: A mixed-potential gas sensor includes: a first sensing electrode containing a Pt—Au alloy and a second sensing electrode containing Pt, the first and second sensing electrodes being provided on a surface of a sensor element made of an oxygen-ion conductive solid electrolyte on one leading end part side; a reference electrode provided inside the sensor element to be made contact with air; a protective cover that surrounds the one leading end part of the sensor element and into which measurement gas flows; and concentration identification element configured to identify a concentration of a sensing target gas component based on potential differences between both of the first sensing electrode and the second sensing electrode and the reference electrode. The first and second sensing electrodes are disposed so that the measurement gas flowing into the protective cover reaches the first sensing electrode earlier than the second sensing electrode.

Abstract: A mixed-potential type gas sensor includes: a first sensing electrode containing a Pt—Au alloy and a second sensing electrode containing Pt, both sensing electrodes being provided on the surface of a sensor element made of an oxygen-ion conductive solid electrolyte; a reference electrode provided inside the sensor element to be made contact with air; a first protective layer group covering the first sensing electrode; a second protective layer group covering the second sensing electrode; and concentration identification element configured to identify the concentration of a sensing target gas component based on potential differences between both of the first sensing electrode and the second sensing electrode and the reference electrode. The response times of the first and second sensing electrodes are both equal to or shorter than 10 seconds, and the response time difference therebetween is 2 seconds or shorter.

Abstract: The inequality Voff<Va<Vb is satisfied, assuming that Va is a first voltage applied to a preliminary oxygen concentration control unit at a time of a first operation thereof, Vb is a second voltage applied to the preliminary oxygen concentration control unit at a time of a second operation thereof, and Voff is a voltage applied thereto at a time when the preliminary oxygen concentration control unit is stopped.

Abstract: 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° C. to 600° C. and heats the oxygen pump cell to a temperature of 580° C. to 850° C. determined in accordance with a diffusion resistance provided to the measurement gas by a gas introduction part.

Abstract: A gas sensor capable of measuring a high concentration range is provided. A sensing electrode provided in a sensor element of a mixed-potential gas sensor for measuring the concentration of a predetermined component in a measurement gas is formed of 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 Au to a portion at which Pt is exposed in a surface of noble metal particles forming the sensing electrode, is 0.1 or more and less than 0.3.

Abstract: A gas sensor with excellent detection sensitivity is provided. A sensing electrode, which is provided in a mixed-potential gas sensor for measuring a concentration of a predetermined gas component of a measurement gas to sense the predetermined gas component, is formed of a cermet of a noble metal and an oxygen-ion conductive solid electrolyte. The noble metal includes Pt and Au. A range of at least 1.5 nm from a surface of a noble metal particle included in the sensing electrode is a Au enriched region having a Au concentration of 10% or more.

Abstract: A gas sensor includes a sensor element made of an oxygen-ion conductive solid electrolyte and is configured to determine a concentration of a measurement target gas component based on a sensitivity characteristic as a predetermined functional relation held between a sensor output and the concentration of the gas component. The sensor output is a potential difference generated between a sensing electrode of the sensor element heated to a predetermined sensor drive temperature and a reference electrode. At the reference electrode, Au is concentrated at a predetermined maldistribution degree on the surface of a noble metal particle. In the present invention, the sensitivity characteristic is calibrated so as to suit the maldistribution degree at the reference electrode, based on the value of a predetermined alternative maldistribution degree index acquired in a non-destructive manner by performing predetermined measurement while the sensor element is heated to the predetermined temperature.

Abstract: A gas sensor includes an element body including oxygen-ion-conductive solid electrolyte layers and having a measurement-object gas flow section inside the element body; a main pump cell configured to adjust the oxygen concentration in a first internal cavity; an auxiliary pump cell configured to adjust the oxygen concentration in a second internal cavity; a measurement electrode disposed on an inner peripheral surface of a third internal cavity; and a reference electrode. An inner pump electrode of the main pump cell does not contain a noble metal having a catalytic activity inhibition ability. An auxiliary pump electrode of the auxiliary pump cell contains the noble metal having the catalytic activity inhibition ability.

Abstract: A sensor element includes a NOx sensor part, a NH3 gas sensor part, and a single common electrode shared by the both parts. The former has a pump cell including a measurement electrode facing an internal space, a pump electrode formed on a surface of the element, and a solid electrolyte therebetween. The latter includes a sensing electrode formed on a surface of the element and having catalytic activity inactivated for a NH3 gas. The common electrode is located to be in contact with a reference gas. The NOx concentration is determined based on a potential difference occurring between the sensing electrode and the common electrode, and a current flowing through the pump cell in a state of controlling a voltage applied across the electrodes to maintain a potential difference between the measurement electrode and the common electrode constant.