EP0369238A2 — Oxygen sensor and method for producing same

Claim 1

Independent Claim 88 words

An oxygen sensor for detecting oxygen concentration within an exhaust gas comprising a sensor element (1), the sensor element having a protective layer which is made of heat-resistant metal oxide (5b) and which carries a component (5a) consisting of a IIa subgroup element in the international periodic table (termed hereinafter a "IIa subgroup component") on the side exposed to the exhaust gas of the sensor element (1), at least a part of said protective layer being present as a nonstoichiometric compound with respect to the heat-resistant metal oxide.

Claim 2

Dependent Claim 88 words

An oxygen sensor for detecting oxygen concentration within an exhaust gas comprising a sensor element (1), the sensor element having a protective layer which is made of heat-resistant metal oxide (5b) and which carries a component (5a) consisting of a IIa subgroup element in the international periodic table (termed hereinafter a "IIa subgroup component") on the side exposed to the exhaust gas of the sensor element (1), at least a part of said protective layer being present as a nonstoichiometric compound with respect to the heat-resistant metal oxide.

Claim 3

Dependent Claim 26 words

An oxygen sensor for detecting oxygen concentration in an exhaust gas according to claim 1 further comprising a heater (6) for heating the sensor element (1).

Claim 4

Dependent Claim 24 words

An oxygen sensor according to Claim 1 or 2 wherein the protective layer also includes a noble metal at least in a part thereof.

Claim 5

Dependent Claim 77 words

An oxygen sensor according to claim 3 in which the protective layer which is made of a heat-resistant metal oxide carries a IIa subgroup component and a noble metal at the side exposed to the exhaust gas of the sensor element, and a part of the protective layer in which said noble metal is carried being disposed closer to an electrode (3) than a part of the protective layer in which said IIa subgroup component is carried.

Claim 6

Dependent Claim 38 words

An oxygen sensor according to one of the preceding claims, wherein the nonstoichiometric compound is titanium oxide which forms said protective layer in which the IIa subgroup component is dispersed and carried by particles of the titanium oxide.

Claim 7

Dependent Claim 25 words

An oxygen sensor according to one of the preceding claims wherein the main body of the sensor element is made of a ZrO₂ solid electrolyte.

Claim 8

Dependent Claim 72 words

An oxygen sensor according to one of the preceding claims, wherein an inner protective layer (4) not including the IIa subgroup component is provided on the inner side within said protective layer, said inner protective layer includes a noble metal, and the surface at the side of a measuring electrode (3) of the main body (1) of the sensor element has a roughness in a depth of not less than 10 µm.

Claim 9

Dependent Claim 58 words

An oxygen sensor for detecting oxygen concentration in an exhaust gas comprising a sensor element (1) having a protective layer which includes at least one kind of components (5a) consisting of IIa subgroup elements in the international periodic table (termed hereinafter "IIa subgroup components") on the side exposed to the exhaust gas of the oxygen sensor element (1).

Claim 10

Dependent Claim 58 words

An oxygen sensor for detecting oxygen concentration in an exhaust gas comprising a sensor element (1) having a protective layer which includes at least one kind of components (5a) consisting of IIa subgroup elements in the international periodic table (termed hereinafter "IIa subgroup components") on the side exposed to the exhaust gas of the oxygen sensor element (1).

Claim 11

Dependent Claim 17 words

An oxygen sensor according to claim 8, wherein the IIa subgroup component is mainly Ca and/or Mg.

Claim 12

Dependent Claim 58 words

An oxygen sensor having a pair of electrodes on both surfaces of an oxygen-ion conductor for detecting oxygen concentration in an exhaust gas, said oxygen sensor comprising: a protective layer which includes at least one kind of IIa subgroup components at least covering the elecrode (3) on the side exposed to the exhaust gas of the oxygen-ion conductor.

Claim 13

Dependent Claim 58 words

An oxygen sensor having a pair of electrodes on both surfaces of an oxygen-ion conductor for detecting oxygen concentration in an exhaust gas, said oxygen sensor comprising: a protective layer which includes at least one kind of IIa subgroup components at least covering the elecrode (3) on the side exposed to the exhaust gas of the oxygen-ion conductor.

Claim 14

Dependent Claim 14 words

An oxygen sensor according to claim 10, wherein the IIa subgroup components are nonoxides.

Claim 15

Dependent Claim 63 words

An oxygen sensor according to claim 10, wherein the protective layer is formed of a first protective layer (4) which neighbors the electrodes (3) to directly protect the electrodes (3) and which is made of a heat-resistant metal oxide (5b) and a second protective layer which exists independently of the first protective layer and which is made of a IIa subgroup component (5a).

Claim 16

Dependent Claim 40 words

An oxygen sensor according to claim 8, wherein the protective layer for protecting the electrodes is made of spinel and/or alumina, and wherein a further protective layer including a IIa subgroup component is provided at least on the outside thereof.

Claim 17

Dependent Claim 43 words

An oxygen sensor according to one of claims 8 to 13, wherein said at least one kind of components consisting of the IIa subgroup elements are included as chloride, nitric salt, carbonate and the like, and each is present as an independent component.

Claim 18

Dependent Claim 29 words

An oxygen sensor according to claim 13, wherein a noble metal is included in an amount not more than 5 wt% within the protective layer of spinel and/or alumina.

Claim 19

Dependent Claim 23 words

An oxygen sensor according to one of claims 8 to 15, wherein a ceramic heater (6) for heating the sensor element is provided.

Claim 20

Dependent Claim 24 words

An oxygen sensor according to one of claims 8 to 16, wherein the oxygen sensor element (1) is made of a ZrO₂ solid electrolyte.

Claim 21

Dependent Claim 23 words

An oxygen sensor according to one of claims 8 to 16, wherein the oxygen sensor element (1) is made of an oxide semiconductor.

Claim 22

Independent Claim 64 words

A method of producing an oxygen sensor element in which a process for providing a protective layer for an electrode on the side exposed to an exhaust gas of an oxygen-ion conductor comprising the steps of: (a) forming an air-permeable first protective layer with a heat-resistant metal oxide, and (b) forming a second protective layer with a ceramic composition comprising a IIa subgroup component.

Claim 23

Independent Claim 64 words

A method of producing an oxygen sensor element in which a process for providing a protective layer for an electrode on the side exposed to an exhaust gas of an oxygen-ion conductor comprising the steps of: (a) forming an air-permeable first protective layer with a heat-resistant metal oxide, and (b) forming a second protective layer with a ceramic composition comprising a IIa subgroup component.

Claim 24

Dependent Claim 47 words

A method of producing an oxygen sensor element according to claim 19, wherein in said step (b), as the ceramic composition a slurry is formed by mixing the IIa subgroup component and a heat-resistant metal oxide powder, and said second protective layer is formed by said slurry.

Claim 25

Dependent Claim 42 words

A method of producing an oxygen sensor element according to claim 19, wherein, in said step (b), the second protective layer including the IIa subgroup component is formed by dipping the first protective layer into a liquid including the IIa subgroup component.

Claim 26

Dependent Claim 55 words

A method of producing an oxygen sensor element according to claim 19, wherein, in said step (b), the second protective layer is formed with a slurry prepared by adding the IIa subgroup component to a powdery mixture of a heat-resistant metal oxide powder and a noble metal dispersedly carried on the heat-resistant metal oxide powder.

Claim 27

Dependent Claim 52 words

A method of producing an oxygen sensor element according to claim 19, wherein, in said step (b), the second protective layer is formed by coating a slurry of a heat-resistant metal oxide powder dispersedly carrying a noble metal followed by dipping the resultant product in a solution containing the IIa subgroup component.

Claim 28

Independent Claim 42 words

A method of producing an oxygen sensor element according to any one of claims 19 to 23, wherein the IIa subgroup component is at least one selected from the group consisting of chloride, nitric salt and carbonate of the IIa subgroup elements.

Claim 29

Dependent Claim 21 words

A method of producing an oxygen sensor element according to claim 24, wherein the IIa subgroup elements are Ca and/or Mg.

Claim 30

Independent Claim 25 words

A method of producing an oxygen sensor element according to one of claims 19 to 25 wherein said heat-resistant metal oxide is spinel and/or alumina.

Oxygen sensor and method for producing same

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag