초록 ▼

An oxygen sensor element with a ceramic heater, having a cylindrical element body formed of an oxygen ion permeable solid electrolyte with one end closed, inner and outer electrodes formed on the inner and outer surfaces of the element body, and an electrode protective layer covering at least one of

An oxygen sensor element with a ceramic heater, having a cylindrical element body formed of an oxygen ion permeable solid electrolyte with one end closed, inner and outer electrodes formed on the inner and outer surfaces of the element body, and an electrode protective layer covering at least one of the inner and outer electrodes, the ceramic heater including a bar-like ceramic core member, a ceramic covering layer which covers the outer surface of the ceramic core member and a heating member disposed in the interface between the core member and the covering layer.

대표청구항 ▼

1. An oxygen sensor element having a ceramic heater, said oxygen sensor element comprising: (a) a hollow, cylindrical sensor element body made of an oxygen permeable material, said sensor element body having one closed end and one open end; (b) inner and outer electrodes provided on the inner an

1. An oxygen sensor element having a ceramic heater, said oxygen sensor element comprising: (a) a hollow, cylindrical sensor element body made of an oxygen permeable material, said sensor element body having one closed end and one open end; (b) inner and outer electrodes provided on the inner and outer surface of said sensor element body, respectively; (c) a fitting member made of metal, said fitting, member being mounted in the open end of said sensor element body in electrical contact with said inner electrode, said fitting member having an axial opening therethrough; (d) a ceramic heater mounted in the axial opening in said fitting member, said ceramic heater having a first end and a second end, the first end of said ceramic heater axially projecting from said fitting member into said hollow, cylindrical sensor element body, said ceramic heater comprising: (i) a bar-like ceramic core, said bar-like ceramic core having an axial opening therethrough for introducing a reference gas into the inside of said hollow, cylindrical sensor element body so as to be in contact with said inner electrode; (ii) a ceramic layer disposed around said ceramic core and in contact with the outer surface of said ceramic core; (iii) a metallized layer formed on a portion of the outer surface of said ceramic layer, said ceramic heater being joined to said fitting member by brazing said metallized layer to said fitting member, thereby longitudinally positioning said ceramic heater; and (iv) a heating member hermetically sealed between said ceramic core and said ceramic layer, said heating member having a heating portion positioned near the end of said ceramic heater remote from said fitting member; and (e) first means for exposing said outer electrode to a gas the oxygen content of which is to be sensed. 2. An oxygen sensor element as recited in claim 1 wherein said first means comprises an oxygen permeable protective layer provided on the outer surface of said outer electrode. 3. An oxygen sensor element as recited in claim 1 or claim 2 wherein: (a) the outer surface of said fitting member is stepped, having a greater diameter at the end thereof near the open end of said sensor element and a lesser diameter at the end thereof remote from the open end of said sensor element body, and (b) the open end of said sensor element body is internally stepped to match the outer surface of said fitting member, whereby said fitting member may be spring-biased into axially abutting engagement with said sensor element body. 4. An oxygen sensor element as recited in claim 3 wherein said ceramic core is cylindrical in shape. 5. An oxygen sensor element as recited in claim 4 wherein the second of said ceramic heater extends through said fitting member and projects from said fitting member away from said sensor element body. 6. An oxygen sensor element as recited in claim 3 wherein the second of said ceramic heater extends through said fitting member and projects from said fitting member away from said sensor element body. 7. An oxygen sensor element as recited in claim 1 or claim 2 wherein said ceramic core is cylindrical in shape. 8. An oxygen sensor element as recited in claim 5 wherein the second of said ceramic heater extends through said fitting member and projects from said fitting member away from said sensor element body. 9. An oxygen sensor element as recited in claim 1 or claim 2 wherein the second end of said ceramic heater extends through said fitting member and projects from said fitting member away from said sensor element body. 10. A process for manufacturing an oxygen sensor element having a ceramic heater, said oxygen sensor element comprising: (a) a hollow, cylindrical sensor element body made of an oxygen permeable material, said sensor element body having one closed end and one open end; (b) inner and outer electrodes provided on the inner and outer surfaces of said sensor element body, respectively; (c) a fitting member made of metal, said fitting member being mounted in the open end of said sensor element body in electrical contact with said inner electrode, said fitting member having an axial opening therethrough; (d) a ceramic heater mounted in the axial opening in said fitting member, said ceramic heater having a first end and a second end, the first end of said ceramic heater axially projecting from said fitting member into said hollow, cylindrical sensor element body, said ceramic heater comprising: (i) a bar-like ceramic core, said bar-like ceramic core having an axial opening therethrough for introducing a reference gas into the inside of said hollow, cylindrical sensor element body so as to be in contact with said inner electrode; (ii) a ceramic layer disposed around said ceramic core and in contact with the outer surface of said ceramic core; and (iii) a heating member hermetically sealed between said ceramic core and said ceramic layer, said heating member having a heating portion positioned near the end of said ceramic heater remote from said fitting member; and (e) first means for exposing said outer electrode to a gas the oxygen content of which is to be sensed, said process comprising the steps of: (f) providing a metallized layer on a portion of the outer surface of said ceramic layer; (g) positioning said fitting member over said metallized layer; (h) integrally bonding said ceramic heater to said fitting member by means of brazing said metallized layer to said fitting member, thereby longitudinally positioning said ceramic heater with respect to said fitting member; and (i) mounting said fitting member inside the open end of said hollow, cylindrical sensor element body. 11. A process as recited in claim 10 wherein: (a) the outer surface of said fitting member is stepped, having a greater diameter at the end thereof near the open end of said sensor element body and a lesser diameter at the end thereof remote from the open end of said sensor element body, and (b) the open end of said sensor element body is internally stepped to match the outer surface of said fitting member, said process comprising the further step of spring biasing said fitting member into axially abutting engagement with said sensor element body.