Denso Corporation

Nippondenso Co., Ltd.

Toyota Jidosha Kabushiki Kaisha

Yasumichi Hotta

Namitsugu Fujii

Hiromi Sano

Kiyomi Kobayashi

Naoto Miwa

Motoaki Satou

Tooru Katafuchi

Masatoshi Suzuki

Toshitaka Saito

Satoru Nomura

Hiroshi Sugino

Gang E

Jiro Nakano

Takao Akatsuka

Masahiro Shibata

Takao Ishibashi

Masao Kawaguchi

Xin Fu, Legal Representative

The present invention provides a gas sensor element and its production method, in which poisons are trapped in a porous protective layer to prevent them from reaching a measured gas side electrode, thereby making it possible to maintain a stable sensor output over a long period of time. The gas sensor element of the present invention is composed of a solid electrolyte, and a measured gas side electrodethat contacts a measured gas and a reference gas side electrodethat contacts a reference gas provided on said solid electrolyte; wherein, the above measured gas side electrodeis covered with a porous protective layercomposed of a heat-resistant metal oxide containing a getter, and the above getter is an alkaline silicate.

Gas sensor element containing a getter

A gas sensing element has a solid electrolytic body, a reference gas side electrode provided on a surface of the solid electrolytic body so as to be exposed to a reference gas, and a measured gas side electrode provided on another surface of the solid electrolytic body so as to be exposed to a measured gas. A crystal face strength ratio of the measured gas side electrode according to X-ray diffraction is 0.7&#x2266;{I(200)/I(111)} or 0.6&#x2266;{I(220)/I(111)}.

Gas sensing element and method for manufacturing the same

A method of manufacturing a gas sensor element which includes a solid electrolyte body, a target gas electrode a reference gas electrode provided on a surface of the solid electrolyte body so as to be exposed to a reference gas and the manufacturing method includes exposing the gas sensor element to a gas atmosphere containing at least one of a hydrocarbon gas, a CO gas, and a H gas and applying an ac voltage to said target gas electrode and the reference gas electrode. Each of the target gas electrode and the reference gas electrode is made up of a plurality of crystal grains defined by grain boundaries having a total length of 1000 &mgr;m or more in a surface area of 100 &mgr;m .

Method of producing a gas sensor element

An oxygen sensor element is provided which may be used in an oxygen sensor designed to measure the concentration of oxygen contained in exhaust gasses of an automotive internal combustion engine. The gas sensor element includes a solid electrolyte body, a target gas electrode, a reference gas electrode, and a catalytic layer formed over the target gas electrode. The catalytic layer is made of heat resisting ceramic grains which hold thereon catalytic metal grains whose average grain size is 0.3 to 2.0 &mgr;m, a weight of catalytic metal grains per unit area of the catalytic layer, as defined by projecting the target gas electrode on a plane, is 10 to 200 &mgr;g/cm . This facilitates the reaction of exhaust gasses such as H , NOx, and HC with O over the target gas electrode, thus resulting in improved accuracy of a sensor output over a wide temperature range.

Oxygen sensor element

A second protective layer is a ceramic porous protective layer comprising coarse particles and fine particles structurally arranged in such a manner that interparticle cavities formed between the coarse particles are filled with the fine particles. At least either of the coarse particles and the fine particles contain at least one selected from the group consisting of &ggr;-Al2O3, &thgr;-Al2O3, &dgr;-Al2O3 and solid solution having the same crystal structure as those of &ggr;-Al2O3, &thgr;-Al2O3, &dgr;-Al2O3.

Gas sensing element incorporated in a gas sensor for an internal combustion engine

A gas sensor element is provided which is used in a gas sensor such as an oxygen sensor. The gas sensor element includes a solid electrolyte body, a target gas electrode provided on a surface of the solid electrolyte body so as to be exposed to a gas to be measured, and a reference gas electrode provided on a surface of the solid electrolyte body so as to be exposed to a reference gas. Each of the target gas electrode and the reference gas electrode is made up of a plurality of crystal grains defined by grain boundaries. The total length of the grain boundaries in each of the target gas electrode and the reference gas electrode is 1000 &mgr;m or more in a surface area of 1000 &mgr;m . This ensures a sufficient degree of diffusion of the gasses in the target and reference gas electrodes, thereby providing a rapid response rate to the gas sensor element.

Gas sensor element

A gas sensing element has a solid electrolytic body, a reference gas side electrode provided on a surface of the solid electrolytic body so as to be exposed to a reference gas, and a measured gas side electrode provided on another surface of the solid electrolytic body so as to be exposed to a measured gas. A crystal face strength ratio of the measured gas side electrode according to X-ray diffraction is 0.7&lE;&lcub;I( )/I( )&rcub; or 0.6&lE;&lcub;I( )/I( )&rcub;.

A sensor element has a solid electrolyte body holding a reference gas side electrode and a measurement gas side electrode on surfaces thereof. The measurement gas side electrode is covered with a porous protective layer including a component as a lead getter, which reacts with lead contained in measurement gas. Accordingly, lead is removed from measurement gas by the protective layer not to be attached to the measurement gas side electrode. As a result, the sensor element can be used in measurement gas containing lead, without deteriorating responsibility and output thereof.

Gas sensor element with lead-proof effect

An improved structure of an oxygen sensing element installed in an oxygen sensor designed to measure an oxygen content in gases is provided. The structure includes a cup-shaped solid electrolyte body, an inner electrode, and an outer electrode. The solid electrolyte body has a portion exposed to the gases which has a given length. The inner electrode is formed on an inner wall of the solid electrolyte body and exposed to air. The outer electrode is formed on an outer wall of the solid electrolyte body and exposed to the gases through a protective layer. The oxygen content in the gases is measured based on output signals from the inner and outer electrodes. The outer electrode occupies an area on the outer wall of the solid electrolyte body within a range of 80% of the given length of the gas-exposed portion of the solid electrolyte body and has a thickness ranging from 1.2 to 3.0 &mgr;m. This allows the oxygen sensing element to determine the oxygen content in the gases precisely and to have an improved heat-resistance.

Structure of oxygen sensing element

In a method for forming an inside electrode within a cup-type electrolyte member of an O.sub.2 sensor element, firstly, a nozzle having a paste discharge hole is prepared. The nozzle is inserted into an inside space of the electrolyte member. Then, the paste discharge hole of the nozzle is relatively rotated with respect to the electrolyte member along an inside surface of the electrolyte member while discharging paste therefrom onto the inside surface. Accordingly, the inside electrode formation portion is formed. After forming the inside electrode formation portion, the electrolyte member is baked. As a result, the inside electrode can be disposed on a required portion of the electrolyte member with a uniform thickness.

Method for manufacturing O.sub.2 sensor with solid electrolyte member

An oxygen concentration detector element 2 includes a cup-shaped solid electrolyte 20 with an inside chamber 25 opened at one end and closed at the other end. An external electrode 21 is formed on an outer surface of solid electrolyte 20 by dipping solid electrolyte 20 in first chemical plating liquid 81, while an internal electrode 22 is formed on an inner surface of solid electrolyte 20 by introducing second chemical plating liquid 82 into inside chamber 25. First, in an injecting step, an injection needle 11 is inserted into inside chamber 25 and second chemical plating liquid 82 is introduced into inside chamber 25 via injection needle 11, and then injection needle 11 is pulled out of inside chamber 25. Next, in a plating step, internal electrode 22 is formed on the inner surface of inside chamber 25 using second chemical plating liquid 82. Then, in a discharging step, residual second chemical plating liquid 82 is discharged from inside chamber 25.

Method of manufacturing an oxygen concentration detector element

An oxygen concentration detecting device comprises a solid electrolyte body, inner and outer electrodes formed on the opposite sides of the solid electrolyte body, and a protective layer formed on the outer electrode and comprised of coarse particles and fine particles mutually bonded through an inorganic binder while substantially keeping the original forms of the both types of particles. A ratio of an average particle size, RB, of the coarse particles to an average particle size, RA, of the fine particles of 30:1 or above, and a content, WA, of the fine particles in the protective layer based on the total content, W, of the content, WA, of the fine particles and the content, WB, of the coarse particles on the weight basis is in the range of 15 to 80 %. A method for fabricating the detecting device having such a protective layer as set out above is also described.

Oxygen concentration detecting device and method for fabricating the same

According to the present invention, an oxygen sensor element includes a solid electrolyte having a side surface at one side thereof, the side surface being contactable with a gas to be measured, a skeletal electrode provided on the side surface and having a plurality of pore portions, each of the pore portions passing through the skeletal electrode up to the solid electrolyte, and a reactive electrode made of a porous film and provided in each of the pore portions, a thickness of the porous film being smaller than that of said skeletal electrode. An area percentage (SH/SZ) which is a ratio of a total area (SH) of the reactive electrode to a total area (SZ) of the skeletal electrode and the reactive electrode is in a range from 10 to 50%, an average area (SA) of the pore portions is 100 .mu.m.sup.2 or less, a film thickness of the skeletal electrode is in a range from 1.5 to 4 .mu.m, and the film thickness of the reactive electrode is in a range from 0.6 to 1.5 .mu.m. The oxygen sensor element is superior in the heat resistance characteristics and the response characteristics.

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 concentration detector provides high durability by increasing the thermal stability of coating layers applied to an electrode face thereof. A catalyst layer is formed on an outer surface of an electrode at the analysis gas side of a partition wall made of an ion oxygen conductive ceramic for generating electromotive force according to the difference between the concentration of oxygen in the analysis gas and the concentration of oxygen in the reference gas. The catalyst layer is composed of heat resistant ceramic particles and a particulate metallic catalyst made of platinum, rhodium or the like, supported by the surface of the heat resistant ceramic particles. The catalyst layer is formed so that the catalyst is supported by the heat resistant support particles. The support particles are heat treated to grow to a particle size so that particle growth can be restrained when the support particles are exposed to the exhaust gas from an internal combustion engine. The outside of the electrode of the partition wall is covered with support particles having such heat treated large cohered catalyst particles, and good responsivity of the sensor is thereby maintained.

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Mie-ken, Japan

Yasumichi Hotta