Ngk Spark Plug Company, Limited

Yoshiro Noda

Takao Kojima

Nobuhiro Hayakawa

Yoshiaki Kuroki

Yutaka Adachi

Toshihiko Aoyama

Ryohei Aoki

Koichi Imaeda

Yoshiro Suematsu

Sinya Awano

Takafumi Oshima

Noboru Ishida

Satoshi Ishikawa

Masashi Ando

Norihiko Nadanami

Satoshi Sugaya

Hiroshi Miyata

Toshitaka Matsuura

Yukihiro Kimura

Tessho Yamada

Shoji Akatsuka

Takaki Otsuka

Kikuo Sakurai

Yoshitake Kawachi

Kazuho Tatemasu

Syogo Kawajiri

A solid electrolyte layer or body capable of being co-fired with an insulating ceramic substrate or body to be used as a gas sensor laminate. The gas sensor laminate is preferably composed of an alumina substrate () and an oxygen-ion conductive solid electrolyte layer () bonded to the alumina substrate () by firing. The oxygen-ion conductive solid electrolyte layer or body is formed from partially or wholly stabilized zirconia, which layer contains alumina in an amount of 10% to 80% by weight, particularly 30% to 75% by weight. In this manner, another ceramic layer; particularly, a ceramic layer () of alumina can further be bonded to the oxygen-ion conductive solid electrolyte layer. The relative density of the ceramic layer can be 60% to 99.5%, preferably 80% to 99.5%.

Solid electrolyte containing insulating grains for gas sensor

A solid electrolyte layer or body capable of being co-fired with an insulating ceramic substrate or body to be used as a gas sensor laminate. The gas sensor laminate is preferably composed of an alumina substrate ( ) and an oxygen-ion conductive solid electrolyte layer ( ) bonded to the alumina substrate ( ) by firing. The oxygen-ion conductive solid electrolyte layer or body is formed from partially or wholly stabilized zirconia, which layer contains alumina in an amount of 10% to 80% by weight, particularly 30% to 75% by weight. In this manner, another ceramic layer; particularly, a ceramic layer ( ) of alumina can further be bonded to the oxygen-ion conductive solid electrolyte layer. The relative density of the ceramic layer can be 60% to 99.5%, preferably 80% to 99.5%.

Solid electrolyte containing insulating ceramic grains for gas sensor

An apparatus and method using a two-serial space sensor (having first and second internal spaces ) for accurately measuring NOx concentration in gas, e.g., exhausted from an internal combustion engine. Both NOx (nitrogen oxide) and oxygen are forced to be partially dissociated in the first space to an oxygen concentration level of 2&times;10 to 2&times;10 atm by pumping out oxygen from the first space . The NOx concentration is determined based on the second current measured in the second space and based on the NO dissociation percentage in the first chamber which is 0.5-50%, or preferably 2-20%. The NOx measurement accuracy is further improved when the above oxygen concentration level is maintained from 2&times;10 to 2&times;10 and the temperature drift of the sensor is maintained within &plusmn;5&deg; C. under a sensor temperature range of 700-900&deg; C.

Method for measuring NOx concentration and NOx concentration sensor

A ceramic heater with a specified ratio of electric resistance for the heat generating portion and the lead portion of a heat generating resistor is provided. The ceramic heater has a ceramic substrate comprising alumina as a main ingredient and a heat generating resistor composed only of tungsten, or a heat generating resistor comprising at least one of 3 to 30% by weight of alumina and 10 to 40% by weight of rhenium, and at least one of tungsten and molybdenum. Particularly, the ratio of the electric resistance can be controlled and the adhesion of ceramic substrates for sandwiching the heat generating resistor can be improved, for example, by means of disposing slits to the lead portion and/or changing ingredients constituting the lead portion. The ceramic heater is capable of reaching a predetermined temperature in a short time, has high adhesion between the heat generating resistor and ceramic substrates and excellent durability and can be used in an oxygen sensor.

Ceramic heater and oxygen sensor using the same

A ceramic heater has a structure in which a resistance heating element mainly composed of a metal having a high melting point is embedded in a ceramic substrate. With an average grain size for component grains of the ceramic substrate taken as dB and that for component grains of the resistance heating element taken as dH, a dH/dB ratio is adjusted to not greater than 0.8.

Ceramic heater

A shaft-like heating member is inserted into and fixed to an oxygen sensing element of a hollowed shaft-like member, together with of a terminal member. A heating portion is located at a portion of the heating member closer to the extreme end thereof. The surface of the heating portion is resiliently pressed on the element inner wall in a side-abutting fashion. In this case, a guide mainly gives rise to the elastic force. With such a side-abutting structure, heat generated in the heating portion is directly transferred to the oxygen sensing element, and heats it. Heat radiated from a portion in the vicinity of its contact position additively heats the oxygen sensing element. Temperature of the oxygen sensor quickly reaches an activation temperature.

Oxygen sensor with a heater

An alumina-based sintered material for ceramic heater having a resistance heater embedded in its ceramic material. With the total amount of Al.sub.2 O.sub.3, SiO.sub.2, MgO and CaO being 100 wt %, the sintered material contains 91 to 97 wt % of Al.sub.2 O.sub.3, 1 to 8 wt % of SiO.sub.2, 0.2 to 1.2 wt % of MgO and 0.2 to 1.2 wt % of CaO, the total amount of MgO and CaO being 0.4 to 1.8 wt %, whereas, for the total amount of Al.sub.2 O.sub.3, MgO and CaO of 100 wt %, 0.1 to 15 wt % of (a) at least one of rare earth elements and groups IVa excluding Ti, Va and VIa of the Periodic Table are contained in the sintered material. In place of (a), 0.2 wt % or less of other elements (Na, K, Fe, Ti etc.) may also be contained in an amount not more than 0.2 wt %, calculated in terms of oxides.

Alumina-based sintered material for ceramic heater

The invention relates to a ceramic heater element consisting of a sintered body of a silicon nitride base ceramic and a resistance heating wire such as a tungsten wire embedded in the ceramic body. The ceramic contains Al.sub.2 O.sub.3 and AlN besides Si.sub.3 N.sub.4 and is produced by using Y.sub.2 O.sub.3 as sintering aid. The ceramic body is improved in strength and also in stability of the ceramic structure at temperatures up to about 1300.degree. C. by rendering the grain boundary phase of the sintered ceramic a crystalline phase comprising either 2Y.sub.2 O.sub.3.Si.sub.2-x Al.sub.x N.sub.2-x O.sub.1-x (0.ltoreq.x&lt;2) or 3Y.sub.2 O.sub.3.5Al.sub.2 O.sub.3. The heater element is produced by preparing a powder mixture in which (Si.sub.3 N.sub.4 +Al.sub.2 O.sub.3 +AlN) amounts to 90-98 wt %, the balance being the sintering aid, with proviso that (Al.sub.2 O.sub.3 +AlN)/Si.sub.3 N.sub.4 is from 0.02 to 0.08 by weight and that (Al.sub.2 O.sub.3 /AlN) is from 0.2 to 2.0 by weight, compacting the powder mixture into a desirably shaped body with insertion of the heating wire and sintering the shaped body preferably by a hot press sintering method. For example, the heater element is used in a glow plug for a diesel engine.

Silicon nitride base ceramic heater element and method of producing same

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Gifu, Japan

Yoshiro Noda