Nippondenso Co., Ltd.

Denso Corporation

Nippon Soken, Inc.

Toyota Jidosha Kabushiki Kaisha

Masahiro Shibata

Hiromi Sano

Tomio Sugiyama

Syuichi Nakano

Isao Watanabe

Naoto Miwa

Makoto Nakae

Masaya Fujimoto

Masatoshi Suzuki

Daisuke Makino

Shinichiro Imamura

Masataka Naito

Minoru Ohta

Keigo Mizutani

Namitsugu Fujii

Toshitaka Saito

Yoshiki Chujo

Akio Tanaka

Yasumichi Hotta

Kazunori Suzuki

Masanori Yamada

Hiroshi Sugino

Tomoji Fukaya

Hisayoshi Ohta

Mitihiro Yamakawa

Midori Shibata, Legal Representative

Natsumi Shibata, Legal Representative

Raina Shibata, Legal Representative

A multilayered air-fuel ratio sensor consists of a plurality of substrate layers. At least one heterogeneous boundary layer is interposed between the plurality of substrate layers. The heterogeneous boundary layer has a thickness in a range of 10 to 100 &#x3bc;m. The heterogeneous boundary layer absorbs thermal shocks or any other stresses acting on the substrate layers and stops the growth of cracks.

Multilayered air-fuel ratio sensor

A composite gas sensor comprises a pump cell, a NOx sensor cell and an oxygen sensor cell. The NOx sensor cell is connected to a first ammeter and a constant power source to measure the NOx concentration of a sample gas. The pump cell is connected to a second ammeter and a variable power source to measure an air-fuel ratio of the sample gas. The oxygen sensor cell is connected to a voltmeter. A controller adjusts the variable power source to produce a constant value from the voltmeter.

Composite gas sensor

A multilayered air-fuel ratio sensing element has a zirconic solid electrolytic body and a heat-generating portion including an alumina substrate located adjacent to the zirconic solid electrolytic body. The zirconic solid electrolytic body is made of a partially stabilized zirconia containing 5&tilde;7 mol % yttria and having a mixed phase structure including a cubic phase, a monoclinic phase and a tetragonal phase. The zirconic solid electrolytic body has a relative density of 94&tilde;100% with a mean sintered grain size R,of 0.5&tilde;3.0 &mgr;m. The alumina substrate has a relative density of 95&tilde;100% with a mean sintered grain size R,of 0.5&tilde;4.0 &mgr;m. And, the partially stabilized zirconia has an M/C ratio in a range from 0.05 to 0.25.

Multilayered air-fuel ratio sensing element

An air-fuel ratio sensor of a limit current type is used for an air-fuel ratio feedback control. When the air-fuel ratio sensor is in a semi-activated state, the air-fuel ratio sensor is driven into an electromotive force generating mode by a current externally applied thereto thereby to shift an electromotive force changing point so that an air-fuel ratio at which the electromotive force changes stepwisely is shifted from the stoichiometric ratio point to a lean zone. When the air-fuel ratio sensor is in a completely activated state, the air-fuel ratio sensor is applied with a voltage to produce a limit current varying with an air-fuel ratio so that a feedback control is performed based on the advanced control theory by using a linear current output characteristics.

Air fuel ratio control apparatus having air-fuel ratio control point

A gas concentration detector comprises a plate sensor element including a sensing action and a signal output section. A flange section is formed between the sensing section and the signal output section so as to protrude in the lateral direction thereof. A cylindrical housing has an inside space for receiving the sensor element. Powder is disposed in the inside space of the cylindrical housing at a predetermined position adjacent to the flange section so that the sensor element is airtightly fixed to the housing by applying a pressing force on the powder. Furthermore, a cross-sectional area of the signal output section is larger than a cross-sectional area of the sensing section.

Gas concentration detector

An air-fuel ratio sensor comprises a platelike oxygen sensing section made of a solid electrolyte and a heater sheet heating the oxygen sensing section. The oxygen sensing section and the heater sheet are stacked via spacers to constitute a multilayer construction. The heater sheet comprises a first platelike insulating sheet chiefly containing at least one component selected from the group consisting of .alpha.-alumina, steatite and mullite, a filmy resistance element disposed on the first insulating sheet and having a resistance-temperature coefficient within a range of 0.5.times.10.sup.3 to 2.0.times.10.sup.3 ppm/.degree.C., and a second platelike insulating sheet covering the resistance element and chiefly containing at least one component selected from the group consisting of .alpha.-alumina, steatite and mullite.

Air-fuel ratio sensor

a limiting current type oxygen concentration sensor element includes a measured gas side electrode formed at one side of a solid electrolyte, and a diffusion resistance portion formed on the measured gas side electrode to provide diffusion resistance to passing measured gas therein. The diffusion resistance portion includes a concave portion formed at a position at least corresponding to a position of the measured gas side electrode. In the concave portion, a porous trap layer is disposed to trap contamination in measured gas. The side wall of the concave portion contacts with the trap layer. The area of a contact surface becomes larger than that without the concave portion, which can effectively prevent the trap layer from being peeled off and dropping down. The trap layer can be easily made thicker. By changing the depth of the concave portion appropriately, diffusion resistance of the diffusion resistance portion can be easily adjusted.

Oxygen concentration sensor element

An air-fuel ratio detecting element is composed of an oxygen pump portion and an oxygen sensor portion which are provided on a single solid electrolyte sheet, a heating element, and a spacer. The oxygen pump portion is composed of a pair first of electrodes provided on opposite sides of the solid electrolyte sheet, and a communication hole which is formed through the solid electrolyte sheet and the electrodes. Electrodes are disposed on the solid electrolyte sheet on the same side as the second electrode, whereby the oxygen sensor portion is formed. The spacer has an opening and a slit-like opening. The heating element 4, the spacer, and the solid electrolyte sheet are stacked from bottom to top, and then the stacked assembly is baked. In this case, they are stacked such that the opening faces the first electrodes and the second electrode. By disposing the oxygen pump portion and the oxygen sensor portion on the same solid electrolyte sheet, structure can be made simpler compared with a conventional air-fuel ratio detecting element in which a solid electrolyte sheet is used for each of an oxygen pump portion and an oxygen sensor portion.

Air-fuel ratio detecting device

An oxygen concentration detector includes a one-end closed cylindrical oxygen sensing element having an inside electrode, outside electrode provided on the inner side and outer side respectively, an electrode protecting layer made up of ceramics porous member provided further outside the outside electrode, and a trap layer 1 of ceramics porous member having a surface roughness of 20 to 100 .mu.m measured according to a 10 point mean roughness measurement and provided outside the electrode protecting layer is employed. By dipping the to-be-detected gas side surface of an oxygen sensing element into a slurry with coarse heat-resisting metal oxide particles, 2 to 50 .mu.m in average grain size, dispersed, depositing the slurry on the surface of a protective layer of an oxygen sensor element, thereafter drying and baking the deposit, a porous poisonous substance trap layer, 10 to 500 .mu.m thick, is formed. The dipping is performed after a previous degassing and strong stirring of said slurry and the stop of stirring.

Oxygen concentration detector

An oxygen sensor capable of accelerating electrochemical reactions and practically working at a low temperature comprises a solid electrolyte 5, and an outer electrode 31 and an inner electrode 32, provided on the surfaces of the solid electrolyte 5, wherein mixed conductors 11 and 12 capable of adsorbing oxygen molecules and conducting an ionization reaction are provided between the solid electrolyte 5 and the outer electrode 31 and between the solid electrolyte 5 and the inner electrode 32, respectively. The mixed conductors 11 and 12 are porous and have a higher oxygen ion conductivity than that of the solid electrolyte 5 and an electron conductivity substantially equivalent to the oxygen ion conductivity and are made of a fluorite-type oxide or a perovskite-type oxide.

Oxygen sensor

An oxygen concentration sensor of this invention comprises an element and a diffusion hole. The element is exposed to a gas to be measured and has a chamber portion formed together with an oxygen ion conductive solid electrolyte. The diffusion hole is provided for restricting the flow of said gas to be measured into said chamber portion. Furthermore, the relationship 1.ltoreq.S/(L.multidot.V).ltoreq.5 is established with the diffusion hole having a cross sectional area S (mm.sup.2) and a length L (mm) and the chamber portion having a volume V (mm.sup.3). To do so, the oxygen concentration sensor can provide a stable output even if a pressure of the gas to be measured is abruptly changed.

Oxygen concentration sensor

In an oxygen concentration detector which comprises an oxygen ion-conducting solid electrolyte, a pair of electrodes, provided on both sides of the solid electrolyte, as counterposed against each other, at least one of the electrodes being exposed to a sample gas, an oxygen ion-conducting diffusion-resistant layer, provided on the electrode exposed to the sample gas and having a predetermined porosity thereby to promote the diffusion of the sample gas, the present oxygen concentration detector is characterized by an electrically insulating porous layer, made of an electrically insulating material, provided between the electrode exposed to the sample gas and the diffusion-resistant layer and having a lower porosity than that of the diffusion-resistant layer and can accurately detect an oxygen concentration of the sample gas with current-voltage characteristics free from hysteresis.

An apparatus for determining oxygen concentration in exhaust gases from an automotive engine is provided which includes a solid electrolytic member of oxygen ion conductive material disposed between a pair of first and second electrodes. In this apparatus, a porous insulating layer is formed on a cylindrical heater made of ceramics and a first electrode is formed on the outer periphery of the porous insulating layer. A solid electrolytic member is formed as a thin film form on the outer periphery of the first electrode layer and a second electrode is formed on the outer periphery of the solid electrolytic film member. Since the solid electrolytic film is formed such that it overlies the outer periphery of the cylindrical heater, it has an adequate structural strength even if formed to be a thinner film.

Apparatus for determining the oxygen content in gases

An oxygen gas concentration-sensing device comprises a solid electrolyte body which is prepared from an oxygen ion-permeable metal oxide and whose first surface is exposed to the gas to be sensed and the second surface is exposed to a reference gas. First and second electrodes are respectively pressed against the first and second surface of the solid electrolyte body. The first electrode exposed to the gas is covered with a porous gas diffusion-resisting layer. This gas diffusion-resisting layer is chosen to have an average pore-size ranging from 300 .ANG. to 400 .ANG..

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Nagoya, Japan

Masahiro Shibata