Ngk Insulators, Inc.

Soichiro Yoshida

Taku Okamoto

Ryo Hashikawa

Yuki Nakayama

Kunihiko Nakagaki

A gas sensor includes a sensor element and a pump cell controller. The pump cell controller performs a normal time control process after a heater control process is started, the normal time control process including a main pump control process, an auxiliary pump control process of controlling an auxiliary pump cell so that a voltage for auxiliary pump reaches a target value, and a normal time measurement pump control process of pumping out oxygen in a measurement chamber by controlling the measurement pump cell so that a measurement voltage reaches a normal time target value. In an early stage of the normal time control process, the pump cell controller performs a correction process of correcting the target value of the voltage for auxiliary pump to a value higher than a target value in a period after the early stage.

Gas sensor

A gas sensor includes a sensor element including an element body, a measurement pump cell being configured to pump out oxygen from surroundings of an inner measurement electrode to surroundings of an outer measurement electrode, and a measurement voltage detection sensor cell that detects a measurement voltage between a reference electrode and the inner measurement electrode, and a pump cell controller that executes a normal time measurement pump control process of pumping out oxygen in the measurement chamber during a normal operation time of the sensor element so that the measurement voltage reaches a normal time target value, and executes a start-up time measurement pump control process of pumping out oxygen in the measurement chamber at a start-up time of the sensor element earlier than the normal operation time so that the measurement voltage reaches a start-up time target value higher than the normal time target value.

A gas sensor includes a sensor element and a pump cell controller. During a normal operation time of the sensor element, the pump cell controller executes a normal time measurement pump control process of pumping out the oxygen in a measurement chamber by controlling a measurement pump cell so that voltage for measurement reaches a normal time target value. At the start-up time of the sensor element, the pump cell controller executes a start-up time measurement pump control process of pumping out the oxygen in the measurement chamber by controlling the measurement pump cell so that the voltage for measurement reaches a start-up time target value higher than the normal time target value. When determining that the oxygen concentration in the measurement chamber is stabilized, the pump cell controller makes switching from the start-up time measurement pump control process to the normal time measurement pump control process.

A gas sensor includes a laminated body constituted by at least two ceramic layers laminated thereon, and having at least one gas introduction port, and at least one internal vacancy, and an outer side electrode formed on the laminated body, and provided in order to discharge oxygen from the internal vacancy, wherein a slit portion connected to an external space, and which is formed in the laminated body in covering relation to the outer side electrode, is interposed between the ceramic layers and the outer side electrode.

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.

Gas sensor calibration method

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.

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Nagoya, Japan

Soichiro Yoshida