Ngk Insulators, Inc.

Nobukazu Ikoma

Taku Okamoto

Nobuhide Kato

Osamu Nakasone

Koichi Masuda

Kenji Isaka

Takeya Miyashita

Hirohito Kiyota

Kunihiko Nakagaki

Yasuhiko Hamada

Hiroshi Kurachi

Sang Jae Lee

Satoshi Nishikawa

Koji Egawa

Akihiro Muroguchi

Takehiro Koganei

Miyoshi Makino

Shodai Hirata

Yutaka Nakane

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.

Sensor element and gas sensor

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.

Gas sensor

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.

Gas sensor and sensor element

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.

Gas sensor and method of producing gas sensor

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.

A sealing pin includes a distal end portion that is inserted into the cylindrical body and that presses the sealant in the sealing step and a slit that is provided to allow the sealing pin to avoid the sensor element when the sealing pin is inserted into the cylindrical body, that extends through the distal end portion in a direction perpendicular to an axial direction of the distal end portion, and that has a width larger than a thickness of the sensor element.

Sealing pin, method of manufacturing assembly, and method of manufacturing gas sensor

The inequality Voff&#x3c;Va&#x3c;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.

Gas sensor and method of controlling gas sensor

Provided is a method for manufacturing a gas sensor which suppresses a defective product caused by a defective posture of a sensor element therein. The method includes a step of obtaining an assembled body constituting the gas sensor, including steps of: causing one end of the sensor element to come to abut to a positioning member for positioning the sensor element; and applying a first force to the annularly-mounted members including a powder compact annularly mounted to the sensor element under a state that the sensor element is positioned and thereby compressing the powder compact so as to fix the sensor element inside of the tubular body, and the compression is performed while constraining the sensor element in a predetermined constraining region in the other end side of the sensor element.

Gas sensor manufacturing method and gas sensor manufacturing apparatus

Provided is a method for manufacturing a gas sensor capable of securing airtightness without a chip in a sensor element. The method includes a step of obtaining an assembled body constituting the gas sensor, including steps of: causing one end of the sensor element to abut to a positioning member for positioning the sensor element; applying a force Fto the annularly-mounted members including a powder compact annularly mounted to the sensor element under a state that the sensor element is positioned and thereby compressing the powder compact so as to fix the sensor element inside of the tubular body, applying a force Flarger than the force Fto the annularly-mounted members under a state that the sensor element is not positioned and thereby further compressing the powder compact, so as to hermetically seal inside of the tubular body.

A method for fitting a protection tube to a gas sensor includes: a step for engaging tube-end opening jigs which have been inserted into the inside of a protection tube through its one end portion, with this end portion, for maintaining this end portion at an opened state, a step for bringing tube-end holding jigs into contact with this engagement portion from outside for holding the tube through pinching between these jigs, and a step for inserting the sensor into the inside of the tube being held through pinching, wherein the insertion of the sensor into the inside of the tube is continued even after an end portion of the sensor comes into contact with the inner surface of the tube, while the engagement of the tube with the tube-end opening jigs is gradually released, thereby fitting the tube to the sensor.

Method for fitting protection tube to gas sensor

Among first and second swaged sections, the second swaged section begins to be swaged prior to the first swaged section. Hence, a strong force can be prevented from acting on a rubber plug in a free state at a time and the first swaged section can begin to be swaged in such a state that a portion of the rubber plug that corresponds to the second swaged section is aligned as compared to the case where the first and second swaged sections begin to be simultaneously swaged. This prevents the position of the rubber plug from being significantly varied during swaging and also prevents the rubber plug from protruding from an outer tube.

Method for manufacturing gas sensor

In resistance welding, an end portion and a flange portion are welded together at contact surfaces thereof by applying a voltage between a first electrode and a second electrode while an inner casing and a main metal piece are pressed in directions toward each other. When a shearing stress due to the pressure is applied to a ceramic guide pin, the guide pin is more resistant to wear compared to a phenolic resin guide pin. In addition, a clearance is between a large-diameter portion of the guide pin and an inner surface of a guide-pin insertion hole. Accordingly, the guide pin is capable of tilting in the radial direction, so that the guide pin can tilt so as to partially absorb the shearing stress. Therefore, the guide pin is more resistant to breakage compared to a guide pin made of ceramic that is not capable of tilting.

Resistance welding method and resistance welding jig

An outer tube and a rubber plug are swaged at two sites, a first swaged section located on the side of connections between contact fittings of a connector and leads and a swaged section located closer to an open end of the outer tube than the first swaged section, such that the inside diameter of a portion of the outer tube is greater than the inside diameter. This prevents reduction of the detection accuracy of a gas sensor because sealing properties can be enhanced by heavily swaging at the second swaged section than the first swaged section. Additionally, excessive force can be prevented on the connections and the leads by lightly swaging the first swaged section rather than the second swaged section. Thus, the disconnection between the connector and the leads can be prevented.

To provide a gas sensor which can stably carry out a securement of an electric continuity between a sensor element and a contact member. A contact member in which an electric connection to a sensor element is obtained by pinching and fixing the sensor element in an inserting port formed by a pair of housing members includes a constraint member which is provided in an outer periphery of a pair of housing members. The constraint member constrains a displacement of a pair of housing members within a predetermined range before the sensor element is pinched and fixed by a pair of housing members, and exists in a state of being pinched between the annular member and a pair of housing member without generating any reaction force with respect to the external force, after the sensor element is pinched and fixed.

Contact member for gas sensor, gas sensor, constraint member, connecting method of sensor element and contact member of gas sensor, manufacturing method of gas sensor

In a gas sensor, when an arithmetical mean roughness Ra of an inner periphery of a metal tubeis 1 &#x3bc;m or less and end portionsandof U-springsare formed as curved contact portions, the end portionsandof the U-springscan slide smoothly along the inner periphery of the metal tube. Therefore, when vibration is applied to the gas sensor, the U-springscan be prevented from being caught in the inner periphery of the metal tube, and the vibration can be absorbed by an elastic function of the U-springs. Even if the gas sensor vibrates, defective contact between a sensor elementand contact fittingsand wear and cracks in the sensor elementare less likely to occur. That is, the gas sensor resistant to vibration can be obtained.

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Nagoya, Japan

Nobukazu Ikoma