Ngk Insulators, Inc.

Takayuki Sekiya

Yusuke Watanabe

Shota Kageyama

Mika Murakami

Kei Kosaka

Naoya Saito

Takeshi Sakuma

Shiho Iwai

Yuki Nakayama

Tomoya Seimori

Daichi Ichikawa

Shodai Hirata

Taku Okamoto

Yoshio Terasawa

Nobuhiko Mori

Naohiro Shimizu

Sang Jae Lee

Yoshinari Kozuka

Hiroki Fujita

Sumiko Horisaka

Shingo Sokawa

Takeshi Omori

Hiroaki Abe

Yuichi Kakizaki

Shoji Tange

Yosuke Okabe

Souzaburou Hotta

A gas sensor detects a specific gas concentration in a measurement-object gas and includes an element body and one or more pump cells. The element body includes an oxygen-ion-conductive solid electrolyte layer and is provided with a measurement-object gas flow section therein. The measurement-object gas flow section receives a measurement-object gas and allows the measurement-object gas to flow therethrough. The one or more pump cells each have an inner electrode and an outer pump electrode and pump out oxygen from around the inner electrode to around the outer pump electrode. The inner electrode is disposed in the measurement-object gas flow section and contains a catalytically-active noble metal. At least one pump cell of the one or more pump cells pumps out the oxygen by applying a repeatedly on-off controlled pump current between a measurement electrode and the outer pump electrode.

Gas sensor

A sensor element includes: a base part containing an oxygen-ion conductive solid electrolyte as a constituent material; at least one internal space into which a measurement gas is introduced; and at least one pump cell including an internal electrode disposed to face the at least one internal space, an out-of-space pump electrode disposed at a location other than the at least one internal space, and a portion of the base part located between these electrodes, the internal electrode includes: an upper layer consisting of a noble metal, the solid electrolyte, and a pore; and a lower layer consisting of the noble metal and the solid electrolyte, and a volume ratio of the solid electrolyte in the lower layer is greater than a volume ratio of the solid electrolyte in the upper layer.

Sensor element of NOsensor and method for manufacturing sensor element of NOsensor

A sensor element includes a base part including a plurality of oxygen-ion-conductive solid electrolyte layers stacked; a measurement-object gas flow part for introduction and flow of a measurement-object gas through one end part in a longitudinal direction of the base part; a main pump cell including an inner main pump electrode disposed on an inner surface of the measurement-object gas flow part, and an outer pump electrode; a target-gas-decomposing pump cell including a target-gas-decomposing pump electrode disposed at a position farther from the one end part than the inner main pump electrode, and an outer pump electrode; a residual-oxygen-measuring pump cell including a residual-oxygen-measuring electrode disposed at a position farther from the one end part than the inner main pump electrode, and an outer pump electrode; and a reference electrode. The target-gas-decomposing pump electrode comprises a metal material that has catalytic activity of decomposing a target gas to be measured.

Sensor element and gas detection method using sensor element

A sensor element includes: a base part containing an oxygen-ion conductive solid electrolyte as a constituent material; at least one internal space into which a measurement gas is introduced; and at least one pump cell including an internal electrode disposed to face the internal space, an out-of-space pump electrode disposed at a location other than the internal space, and a portion of the base part located between these electrodes, the internal electrode includes a noble metal, the solid electrolyte, and a pore, and, in the internal electrode, a degree of variation of a boundary of a first region formed of the base part or the solid electrolyte contiguous with the base part and a second region occupied by the noble metal and the pore in a thickness direction of the element is 0.5 μm or more and 6.5 μm or less.

Sensor element of NOx sensor

A sensor element includes a base part containing a solid electrolyte as a constituent material; at least one internal space into which a measurement gas is introduced; and at least one pump cell including an internal space electrode disposed to face the internal space, an out-of-space pump electrode disposed at a location other than the internal space, and a portion of the base part located between these electrodes, the internal space electrode includes a noble metal, the solid electrolyte, and a pore, and, in the internal space electrode, a ratio of a length of a boundary of a first region formed of the base part or the solid electrolyte contiguous with the base part and a second region occupied by the noble metal and the pore to a length of a boundary of the solid electrolyte and the internal space electrode is 1.1 or more.

Sensor element of gas sensor

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.

Gas sensor and gas sensor operation control method

In a gas sensor, oxygen pumping control is performed to pump oxygen from the surroundings of an outer side pump electrode into the surroundings of a reference electrode. In addition, during execution of the oxygen pumping control, a pump current Ipis measured when oxygen originating from NOx is pumped out from the surroundings of a measurement electrode so that a voltage Vreaches a target voltage V*. Then, the NOx concentration of a measurement-object gas is calculated based on Ip. In the gas sensor, the NOx concentration is corrected based on DVref which is the difference between Vrefand Vref, wherein Vrefis the voltage across the reference electrode and the outer side pump electrode when the oxygen pumping control is not performed, and Vrefis the voltage across the reference electrode and the outer side pump electrode when the oxygen pumping control is performed.

A sensor element includes an element body having a measurement-object gas flow section being provided therein, a first measurement pump cell that includes a first measurement electrode being disposed in a first measurement chamber and a first outer measurement electrode and that pumps out oxygen produced in a first measurement chamber, and a second measurement pump cell that includes a second measurement electrode being disposed in a second measurement chamber and a second outer measurement electrode and that pumps out oxygen produced in a second measurement chamber. The measurement-object gas flow section is configured such that a measurement-object gas passes through an oxygen concentration adjustment chamber and a first measurement-electrode diffusion-rate-controlling section in this order and reaches the first measurement chamber and that the measurement-object gas passes through the first measurement chamber and a second measurement-electrode diffusion-rate-controlling section in this order and reaches the second measurement chamber.

Sensor element and gas sensor

A limiting-current type gas sensor including a sensor element including a base part made of an oxygen-ion conductive solid electrolyte and measuring concentration of NOx in a measurement gas includes: a pump cell including a first electrode disposed to be capable of being in contact with a gas introduced into the element and a second electrode disposed so that a part made of the solid electrolyte is located between the first electrode and the second electrode; and a pumping diagnostic part to determine whether an inter-electrode electric field produced in the part made of the solid electrolyte through application of a predetermined pump voltage between the electrodes exceeds a first threshold, and, when the inter-electrode electric field exceeds the first threshold, the predetermined pump voltage is reduced so that the inter-electrode electric field falls below the first threshold.

Gas sensor and method for controlling operation of gas sensor

A gas sensor element in which oxidation of electrodes and a heater occurring with continued use is suppressed is provided. The gas sensor element includes a plurality of solid electrolyte layers stacked one over another, and includes an electrochemical cell including a pair of electrodes and a portion of the plurality of solid electrolyte layers existing between the pair of electrodes; a heater part capable of heating the gas sensor element; and a gettering layer located between the plurality of solid electrolyte layers and between the plurality of solid electrolyte layers and each of the pair of electrodes, and gettering impurities in a metal component of the electrodes and the heater part during driving of the gas sensor element.

Gas sensor element

A sensor element for detecting a specific gas concentration in a measurement-object gas includes: an element body including an oxygen-ion-conductive solid electrolyte layer, and having inside a measurement-object gas flow portion that introduces and flows a measurement-object gas and a reference gas chamber used to store a reference gas that is a reference for detecting a specific gas concentration; a reference electrode disposed in the reference gas chamber; and an electrically conductive portion which includes a reference electrode terminal and a reference electrode lead portion that provides electrical continuity between the reference electrode terminal and the reference electrode. The reference gas chamber is provided inside the sensor element in an isolated form, and at least part of the electrically conductive portion is densely formed so as to block movement of oxygen between the reference gas chamber and the outside of the sensor element via the electrically conductive portion.

A sensor element includes: a main pump cell constituted by an inner electrode provided to face a first inner space into which a measurement gas is introduced, an external electrode provided on an element surface, and a solid electrolyte therebetween; and a measurement pump cell constituted by a measurement electrode provided to face a second inner space communicated with the first inner space, an external electrode, and a solid electrolyte therebetween. A diffusion resistance from a gas inlet to the inner electrode is 200 to 1000 cm. For the first inner space and a unit electrode part of the inner electrode, a space length is 2.5 to 10 mm, a space thickness is 50 to 300 &#x3bc;m, an electrode length/the space length is 0.5 to 1.0, and an electrode width/the space width is 0.5 to 1.0.

A method of operation of a gas sensor includes applying a control voltage that is set between the reference electrode and the measurement-object gas side electrode; and detecting the specific gas concentration in the measurement-object gas on the basis of a voltage between the reference electrode and the measurement electrode during a second period, from among a first period that is started upon setting of the control voltage to on state, during which a potential difference between the reference electrode and the measurement-object gas side electrode is large, and the second period that is started upon setting of the control voltage to off state after the potential difference falls from the first period. Tf, a fall time of the potential difference between the first period and the second period, and T, a second time that is a length of the second period, satisfies Tf&#x2264;T

Method of operation of a gas sensor

A method of operation of a gas sensor includes applying a control voltage that is repetitively set to on state and off state between the reference electrode and the measurement-object gas side electrode to pump in oxygen to the periphery of the reference electrode; and detecting the specific gas concentration in the measurement-object gas on the basis of a voltage between the reference electrode and the measurement electrode during a second period, from among a first period that is started upon setting of the control voltage to on state, during which a potential difference between the reference electrode and the measurement-object gas side electrode is large, and the second period that is started upon setting of the control voltage to off state after the potential difference falls from the first period.

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Nisshin, Japan

Takayuki Sekiya