Ngk Insulators, Inc.

Noriyuki Ina

Nobuhide Kato

Toshio Yamada

Takao Murase

Yoshihiko Mizutani

Naoya Saito

Yasushi Watanabe

Kazuki Takegawa

Provided is a method of inspecting an assembly defect of a gas sensor in a mass-production process. The sensor element included in a second constituting member includes a heater therein and an electrode terminal for a heater in its surface, and the first constituting member includes a contact point member contacting the terminal in a state where the sensor element is inserted into its opening. A first heater resistance value before incorporated is measured to associate the resistance value with an identification information of the sensor element, a second heater resistance value is measured via a contact point member, in a state where the first and second constituting members are integrated with each other, to associate the resistance value with the identification information of the sensor element, and when a difference value between these resistance values associated with the identical identification information exceeds a threshold value, it is determined that an assembly defect occurs.

Method of inspecting gas sensor and method of manufacturing gas sensor

A sensor for measuring nitrogen oxide (NOx) in a gas by decomposing NOx in the gas and measuring an amount of oxygen generated by the decomposition includes: means for introducing the gas to a first inner space under a first diffusion resistance and connected with an external space, means for controlling an oxygen partial pressure in an atmosphere in the first inner space to be a predetermined low value at which NO is not decomposed substantially by a main pump means, means for introducing a controlled atmosphere of the first inner space into a second inner space which is connected with the first inner space and which is under a second diffusion resistance, and means for converting the atmosphere into an electric signal corresponding to the quantity of oxygen generated by decomposition or reduction of NOx contained in the atmosphere by an electric signal conversion means. A first oxygen concentration detecting means is disposed for detecting an oxygen partial pressure in the second inner space, and a control voltage to be applied to the main pump means is adjusted on the basis of an output of the first oxygen concentration detecting means.

Sensor for measuring nitrogen oxide

Disclosed are a gas sensor and a gas concentration controller each comprising a comparative amplifier for comparing a reference voltage with a terminal voltage between a reference electrode and an inner pumping electrode to obtain a difference therebetween, and amplifying the difference with a predetermined gain to make an output. Wiring connection is arranged so that the output voltage from the comparative amplifier is applied, as a pumping voltage to an oxygen pump, between the electrode and an outer pumping electrode. A resistor for detecting a pumping current is inserted and connected between an output terminal of the comparative amplifier and the electrode of the oxygen pump. A short circuit is formed between both ends of the resistor by using a capacitor. One electrode of the capacitor is connected to a non-inverting terminal of a differential amplifier, and the other electrode is connected to an inverting terminal of the differential amplifier. Accordingly, it is possible to effectively avoid the oscillation phenomenon of the feedback control system for the oxygen pump, and absorb the error in the amount corresponding to voltage drop resulting from the impedance of the oxygen pump.

Gas sensor and gas concentration controller

A system is constructed such that a voltage between an inner pumping electrode and a reference electrode is measured to determine a difference between a measured voltage and a reference voltage so that a pumping voltage is controlled by using the differential voltage. Specifically, a comparative amplifier is provided for comparing the reference voltage with the terminal voltage between the reference electrode and the inner pumping electrode, and amplifying the difference therebetween with a predetermined gain to make an output. The system is wired and connected such that the output voltage (differential voltage) from the comparative amplifier is applied, as the pumping voltage supplied to an oxygen pump, between the inner pumping electrode and an outer pumping electrode. The inner pumping electrode is grounded. Accordingly, for example, when the oxygen pump is used, it is possible to effectively avoid the oscillation phenomenon in the feedback control system for the control voltage for the oxygen pump.

Gas sensor, method for controlling gas sensor, gas concentration

A method for measuring nitrogen oxide (NOx) in a gas by decomposing NOx in the gas and measuring an amount of oxygen generated by the decomposition includes: introducing the gas to a first inner space under a first diffusion resistance and connected with an external space, controlling an oxygen partial pressure in an atmosphere in the first inner space to be a predetermined low value at which NO is not decomposed substantially by a main pump means, introducing a controlled atmosphere of the first inner space into a second inner space which is connected with the first inner space and which is under a second diffusion resistance, and converting the atmosphere into an electric signal corresponding to the quantity of oxygen generated by decomposition or reduction of NOx contained in the atmosphere by an electric signal conversion means. A first oxygen concentration detecting means is disposed for detecting an oxygen partial pressure in the second inner space, and a control voltage to be applied to the main pump means is adjusted on the basis of an output of the first oxygen concentration detecting means.

Method for measuring nitrogen oxide

A gas sensor for measuring a quantity of specific component in a measuring gas includes a main pump means which has an electrochemical pump cell. The electrochemical pump cell includes a solid electrolyte partition exposed to external space, an inner pump electrode and an outer pump electrode formed on the inner surface and outer surface of the solid electrolyte partition, respectively. The main pump means treats oxygen contained in the measuring gas introduced from the outer space by pumping processing on the basis of a control voltage applied between the inner pump electrode and the outer pump electrode. An RLC element which has a specific electric characteristic value corresponding to a characteristic value of the electrochemical pump cell is connected in parallel with the electrochemical pump cell.

Gas sensor and method of measuring quantity of specific compounds in

A system for detecting deterioration of an exhaust gas control catalyst provided in an exhaust gas passage through which a combustion exhaust gas is discharged, including a processing zone communicating with a portion of the passage which is downstream of the catalyst and a pumping cell including an oxygen ion conductive solid electrolyte layer and a pair of electrodes one of which is exposed to the processing zone, wherein the pumping cell pumps oxygen out of the processing zone so as to control oxygen partial pressure in the processing zone which corresponds to a monitor voltage, at a value at which the combustible gas component within the processing zone cannot be burned, and the oxygen concentration in the combustion exhaust gas is obtained based on a pumping current flowing between the pair of electrodes of the pumping cell, whereby the degree of deterioration of the catalyst is determined on the basis of the obtained oxygen concentration.

Method and system for detecting deterioration of exhaust gas control

Disclosed is a method and a sensing device capable of measuring a predetermined measurement gas component continuously and accurately with good response over a long period of time without being affected by a high oxygen concentration in a measurement gas. The measurement gas is introduced into a first processing zone. A first electrochemical pumping cell is used to lower a partial pressure of oxygen in an atmosphere thereof to a degree sufficient to control a partial pressure of oxygen in a subsequent second processing zone. The gas is introduced into the second processing zone. Oxygen in an atmosphere is pumped out by using a second electrochemical pumping cell so that the partial pressure of oxygen in the atmosphere is controlled to have a low value of partial pressure of oxygen which does not substantially affect measurement of an amount of the measurement gas component. The gas is introduced into a third processing zone. Oxygen produced by reducing or decomposing the measurement gas component is pumped out by using a third electrochemical pumping cell. The amount of the measurement gas component is determined from a detected value of a pumping current flowing through the third electrochemical pumping cell. The amount of the measurement gas component may be also determined by measuring an electromotive force by using an electrochemical sensor cell, in place of the third electrochemical pumping cell.

Method and sensing device for measuring predetermined gas component in

A method of evaluating properties of an oxygen sensor used for detecting air-fuel ratio of exhaust gas from internal combustion engine comprises steps of preparing a burnt gas having a predetermined excess air ratio, supplying additional oxidation gas and/or reduction gas into the burnt gas, and detecting an output from the sensor exposed to the mixed gas flow. The supply amount of the additional gas is increased and decreased with a frequency of at least 10 Hz, and a ratio of a supply increasing period to a supply decreasing period is changed to change the supply amount of the additional gas, so that an excess air ratio .lambda. can be controlled similarly to exhaust gas from an actual engine.

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Okazaki, Japan

Noriyuki Ina