Ngk Insulators, Inc.

Takeya Miyashita

Nobukazu Ikoma

Nobuhide Kato

Hiroshi Kurachi

Satoshi Nishikawa

Akihiro Muroguchi

Kunihiko Nakagaki

Sang Jae Lee

Shiho Iwai

Takashi Ito

Yuichi Sasaki

Kimie Kato

A manufacturing method for a sensor element includes a forming step. The forming step includes: a step (a) of forming an unfired electrode on one of plural green sheets; a step (b) of forming an unfired electrode lead and an unfired lead insulating layer on the same green sheet as in the step (a), the unfired electrode lead and to be connected to the unfired electrode, the unfired lead insulating layer surrounding at least part of the unfired electrode lead; and a step (c) of forming an unfired bonding layer so as to fill at least part of a region without the unfired lead insulating layer on the green sheet subjected to the step (b) and so as to overlap at least part of an edge portion of the unfired lead insulating layer.

Manufacturing method for sensor element

A gas sensor and nitrogen oxide sensor, which, when fitted to the exhaust system of an internal combustion engine, can suppress the influence of harmful substances contained in a measurement gas and can prevent the reduction in sensitivity over time. A harmful substance-trapping layer is formed at a gas inlet for introducing a to-be-measured gas from an external space into an internal space, and in a buffering space formed between diffusion resistance portions. In a trap-formed portion of a gas passage in which the harmful substance-trapping layer is formed, the measurement gas can pass in an amount of 80% or more of when the harmful substance-trapping layer is not formed in the trap-formed portion. A diffusion resistance is attained in the diffusion resistance portions; a harmful substance is trapped in the harmful substance-trapping layer; and the measurement gas is allowed to flow into a detection electrode side.

Gas sensor and nitrogen oxide sensor

A gas sensor for detecting a predetermined gas component in a measurement gas includes a sensor element in which an opening of a first gas inlet and an opening of a second gas inlet for introducing the measurement gas from an outside are provided at one end. The openings are elongated and substantially rectangular. A sum of sizes in a lateral direction of the openings is greater than or equal to 8 &#x3bc;m and less than or equal to 60 &#x3bc;m, and a sum of areas of the openings is greater than or equal to 0.02 mmand less than or equal to 0.1 mm. The sizes in the lateral direction and the areas of the openings are set to be within a preferable range so that the water droplets attached on the forward end surface can be prevented from entering into the sensor element through the openings.

Gas sensor

A protective cover of a gas sensor includes an inner protective cover which covers at least an end portion of a sensor element, an outer protective cover which covers the inner protective cover, and an intermediate protective cover which is installed between the inner protective cover and the outer protective cover. A/A&#x2267;1 provided that Arepresents a total opening area of the inner gas inlet holes provided for the inner protective cover, and Arepresents a total opening area of the outer gas inlet holes provided for the outer protective cover.

A gas sensor includes a first space for a measurement gas from a gas-introducing hole via a first diffusion rate-determining section, a main pumping means for controlling a partial pressure of oxygen in the measurement gas introduced into the first space to have a predetermined value, a second space for the measurement gas from the first space via a second diffusion rate-determining section, and a measuring pumping means for reducing or decomposing a NOx component in the measurement gas introduced from the second space via a third diffusion rate-determining section so that oxygen produced thereby is pumped out to detect a current generated by pumping out the oxygen. A ratio (Wc/We) between a width (We) of an end of a sensor element and a width (Wc) of the gas-introducing hole is not less than 0.3 and less than 0.7.

Temperature of a heater is controlled by switching an increasing rate of a resistance value of heating unit of the heater. During a period Tfrom a time point when heating of the heater is started until the resistance value of the heating unit reaches a reference value, the increasing rate is changed in multiple heating stages. In this manner, the temperature and the resistance value of the heating unit are increased. During a period Tfrom a time point when the resistance value of the heating unit reaches the reference value, feedback control is performed such that the resistance value is kept at the reference value as a target value.

Gas sensor and method of heating the same

One of a pair of temperature sensor sections in a combustible gas sensor is covered with porous oxidizing catalytic layers ( ) for oxidizing a combustible gas, and the other is not covered with the oxidizing catalyst layers. The temperature sensor sections each have temperature sensitive portions ( ) made of a dense ceramic material, resistors ( ) buried therein and having a positive resistance temperature coefficient, current leads ( ) and voltage leads ( ). A method for detecting the deterioration of a catalyst which intends to eliminate the combustible gas, by the use of this combustible gas sensor is further disclosed. When a difference between temperatures of the pair of resistors or a difference between powers fed to the pair of resistors is in excess of a predetermined value, it is judged that the catalyst has been deteriorated.

Method for detecting deterioration of catalyst

A gas sensor is disclosed in order to decrease the offset value to a degree in which no trouble occurs in the measurement without causing any reduction of NOx so that the measurement accuracy for NOx is improved. In the gas sensor, NOx contained in a measurement gas introduced into a second chamber is decomposed by means of catalytic action and/or electrolysis to pumping-process oxygen produced by the decomposition so that NOx is measured on the basis of a pumping current flowing through a measuring pumping cell thereby. The gas sensor has the following pattern of a heater. That is, a minute pitch is provided for a pattern at a portion corresponding to the forward end of a sensor element, a coarse pitch is provided for a pattern at a central portion, and a pattern is removed at a portion corresponding to the backward end of the sensor element. Thus, the measuring pumping cell is allowed to have a resistivity of electronic conduction of not less than 1 M&OHgr; after conversion into a resistance value.

A combustible gas sensor having a pair of temperature sensor sections is here disclosed. One of the pair of temperature sensor sections is covered with porous oxidizing catalytic layers (23, 24) for oxidizing a combustible gas, and the other is not covered with the oxidizing catalyst layers. In the one temperature sensor section, the combustible gas is burned, and in the other temperature sensor section, the temperature of a gas to be measured is compensated. The temperature sensor sections each comprises temperature sensitive portions (13, 14) made of a dense ceramic material, resistors (21, 22) buried therein and having a positive resistance temperature coefficient, current leads (31, 32, 41, 42) and voltage leads (33, 34, 43, 44). A method for measuring the concentration of the combustible gas by the use of this combustible gas sensor is also disclosed. A method for detecting the deterioration of a catalyst which intends to eliminate the combustible gas, by the use of this combustible gas sensor is further disclosed. When a difference between temperatures of the pair of resistors or a difference between powers fed to the pair of resistors is in excess of a predetermined value, it is judged that the catalyst has been deteriorated.

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Kasugai, Japan

Takeya Miyashita