Ngk Insulators, Inc.

Ngk Ceramic Device Co., Ltd.

Tetsuya Ishikawa

Sumiko Horisaka

Shota Kageyama

Yosuke Adachi

Shinji Ohtsubo

Yuji Okuda

Kazuhito Sakakibara

Jumpei Tanaka

An inner protective coverof a gas sensor forms an element-chamber inlethaving a first outside opening, a second outside opening, and an element-side opening. The second outside openingis disposed such that the path of a measurement-object gas from the first outside openingto the element-side openingof the element-chamber inletcommunicates in the middle thereof with a first gas chamber, and that there is a path shorter than the shortest path of the measurement-object gas extending from an outer inletthrough the first outside openingto a gas inlet

Gas sensor

A sensor element mainly contains an oxygen ion conductive solid electrolyte. By applying, across a first electrode formed on a surface of an internal space into which a measurement gas is introduced from an outside and a second electrode formed on an external surface of the element, a predetermined voltage determined based on a potential difference between the first electrode and a reference electrode provided inside the element, oxygen in the internal space can be pumped out. In a case where pump reference processing is performed, a DC voltage having a maximum value of 1.4 to 2.0 V inclusive is applied across the reference and second electrodes for 10 to 1200 seconds inclusive in a state in which the reference and second electrodes are respectively electrically connected to negative and positive terminals of an external DC power supply, and an element temperature is set to 700 to 850&#xb0; C. inclusive.

Method for performing processing on gas sensor

To provide a method for manufacturing a sensor element, by which stabilization of an electrode, which is performed prior to inspecting element characteristics, can be performed for a shorter time period and in a more reliable manner than in the conventional. The sensor element includes: an oxygen-ion conductive solid electrolyte layer; a first electrode that is formed on a surface of the oxygen-ion conductive solid electrolyte layer; and a second electrode that is formed in a space provided inside the oxygen-ion conductive solid electrolyte layer, and that is configured to reduce said predetermined gas component. As the pre-treatment, by an external power source, a voltage is applied between the first electrode and the second electrode, to thereby decompose and remove a gas component attached to the second electrode.

Method for manufacturing sensor element for use in gas sensor, inspecting electrical characteristics of sensor element, and pre-treating sensor element

A method of processing a sensor element includes the steps of: (a) preparing a gas atmosphere containing hydrocarbon, having an air-fuel ratio of 0.80 to 0.9999, and having a small amount of oxidizing gas added thereto; and (b) subjecting a sensor element to a heat treatment in the gas atmosphere at a temperature of 500&#xb0; C. or higher for 15 minutes or longer. The sensor element includes an electrochemical pumping cell constituted of an oxygen-ion conductive solid electrolyte and an electrode having a NOx reduction ability. A NOx gas in a measurement gas is reduced or decomposed in the electrode. A NOx concentration in the measurement gas is obtained based on a current which flows in the electrochemical pumping cell at a time of the reduction or decomposition.

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Kasugai, Japan

Tetsuya Ishikawa