Electrically heatable catalytic converter and method for manufacturing same
An electrically heatable catalytic converter ( 100, 200, 300, 400 ) for treating a gas stream, especially of the exhaust gas stream of an internal combustion engine, the electrically heatable catalytic converter ( 100, 200, 300, 400 ) has a tubular housing ( 101, 201, 301, 401 ), an interior space enclosed by the tubular housing ( 101, 201, 301, 401 ), and a porous structure, which is arranged in the interior space of the tubular housing ( 101, 201, 301, 401 ) and can be heated by an electric heater, in which the electric heater is a mineral-insulated heater ( 103, 203, 303, 403 ) with a heat conductor ( 104, 204, 304, 404 ), with at least one front-side connection opening ( 109, 209, 210, 309, 409 ) and with at least one outer metal jacket ( 108, 208, 308, 408 ), the mineral-insulated heater ( 103, 203, 303, 403 ) has at least one section ( 103, 203 a, 203 b, 303 a ), which is passed through a housing wall.
1. A method for manufacturing an electrically heatable catalytic converter, the method comprising the steps of:
providing a flat, porous structure with a mineral-insulated heater;
arranging at least a portion of said mineral-insulated heater on said flat, porous structure, said portion of said mineral-insulated heater being in contact with said flat, porous structure, said mineral-insulated heater having at least one front-side connection opening and at least one outer metal jacket and said mineral-insulated heater being arranged on said flat, porous structure such that said at least one front-side connection opening projects over a flat honeycomb structure;
rolling up of said flat, porous structure with said mineral-insulated heater after arranging said portion of said mineral-insulted heater on said flat, porous structure to provide a rolled-up structure;
soldering said rolled-up porous structure with said at least one outer metal jacket of said mineral-insulated heater;
inserting said rolled-up structure into a tubular housing, such that said at least one front-side connection opening projecting over said porous structure projects from said interior space of said tubular housing through a duct opening in a housing wall; and
welding or soldering of said at least one outer metal jacket of said mineral-insulated heater to said tubular housing directly or via a mineral-insulated, vacuum-tight duct, such that said duct opening is closed in a vacuum-tight manner.
2. The method in accordance with claim 1 , wherein said soldering is carried out under vacuum.
3. The method in accordance with claim 1 , wherein said mineral-insulated heater comprises a heat conductor, at least a portion of said heat conductor being helically arranged in a compacted insulation in said interior space of said housing, said at least one outer metal jacket comprising at least one section located outside of said interior space, said at least one section comprising an outer metal jacket portion, said outer metal jacket portion being connected to said tubular housing via a soldered or welded connection, said soldered or welded connection being located outside of said interior space.
4. The method in accordance with claim 1 , wherein said mineral-insulated heater has a smaller cross section in a direction in which a gas flows than in a direction facing walls of said flat, porous structure.
5. The method in accordance with claim 4 , wherein in said direction in which said gas flows, an extension of said mineral-insulated heater has a dimension that is at least four times larger than a dimension of an extension in said direction facing walls of said porous structure.
6. The method in accordance with claim 3 , wherein said heat conductor of said mineral-insulated heater is connected at one end to said tubular housing in an electrically conducting manner, so that said tubular housing acts as a return conductor, said heat conductor comprising a plurality of helical portions, wherein a portion of said porous structure is arranged between one of said plurality of helical portions and another one of said plurality of helical portions.
7. The method in accordance with claim 1 , wherein said tubular housing comprises an Inconel alloy material with a nickel content of at least 25%.
8. The method in accordance with claim 3 , wherein a plurality of mineral-insulated heaters are arranged in said flat, porous structure, said compacted insulation being a ceramic insulation.