Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Reexamination Certificate
1997-04-21
2001-08-14
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
C422S177000, C422S179000
Reexamination Certificate
active
06274099
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for the catalytic conversion of exhaust gases in an exhaust system, in particular in an exhaust system of a combustion engine, including a catalyst carrier body having a multiplicity of channels through which an exhaust gas can flow. The invention also relates to a process for manufacturing such a device.
In order to attain conversion of hydrocarbons and carbon monoxide contained in a combustion engine which is as complete as possible, the catalytic converter must be at a minimum temperature at which the catalytic conversion of components of the exhaust gas can take place. In general, that temperature is described as a so-called initiation temperature. The catalyst is heated during a cold starting phase by hot exhaust gas. It is also known to at least partially electrically heat the catalyst carrier body. In order to ensure that the output of pollutants is as low as possible during the cold starting phase, and for mechanical reasons, it has been proposed that the catalyst carrier body be constructed with an internal insulation in order to reduce heat loss to a housing and into the surroundings.
A device for catalytic conversion of exhaust gases in an exhaust system, in particular in an exhaust system of combustion engines, is known from German Published, Non-Prosecuted Patent Application DE 36 02 134 A1. That device is provided with a metallic catalyst carrier body disposed in a housing. The carrier body is provided with a large number of channels through which an exhaust gas can flow. The internal insulation of the catalyst carrier body is created according to German Published, Non-Prosecuted Patent Application DE 36 02 134 A1 in such a way that a radially inward facing collar is disposed in front of the catalyst carrier body. The height of the collar is 3-15% of the diameter of the catalytic converter, but at least 1 mm. A zone of eddy current is produced in the exhaust gas flow through the use of that collar and in that way direct contact of the hot exhaust gas with an outer annular region is avoided.
A device for the catalytic conversion of exhaust gases in an exhaust system is known from German Utility Model DE G 87 12 267.7 U1. The device includes a catalyst carrier body which is provided with a large number of flow channels for an exhaust gas and which is fitted into a sleeve-like housing. The housing is thermally insulated with respect to the catalyst carrier body. The insulation is obtained by placing the catalyst carrier body between end rings which close at least an outer layer of a metallic matrix body and thereby the outer flow channels in the matrix. In that way the outer region of the catalyst carrier body is provided with a closed air gap, through which exhaust gas does not flow and which serves as heat insulation.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device for catalytic conversion of exhaust gases in an exhaust system and a process for manufacturing such a device, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and processes of this general type and in which the manufacture of a catalyst carrier body with an internal insulation is simplified.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for catalytic conversion of exhaust gases in an exhaust system, in particular in an exhaust system of combustion engines, comprising a catalyst carrier body having an outer annular region and having channel walls defining a multiplicity of channels with free flow cross-sections through which an exhaust gas can flow in a given direction, at least a part of the free flow cross-sections of the channels being closed in the given direction in the outer annular region by plastic deformation of the channel walls.
In contrast to the known devices for catalytic conversion of exhaust gases, an air gap enclosed in an outer region of the catalyst carrier body is not created by additional rings or the like, but instead the free flow cross-section of the channels is closed in part, that is to say in at least an axial part, by plastic deformation of the channel walls in the direction of flow of the exhaust gas. In this way the manufacture of the device is simplified, since a collar or end ring no longer has to be fitted in the housing. If the catalyst carrier body is composed of several wound layers of sheet metal, the plastic deformation can already be carried out during winding. This simplifies the manufacturing process for wound catalytic converters, since the winding procedure and the plastic deformation can take place at the same time.
In accordance with another feature of the invention, the channels are closed in the vicinity of a waste gas inlet. The plastic deformation of the channels is advantageously carried out prior to the application of a catalytically active layer on the catalyst carrier body. The coating (wash coat) is usually applied through the use of a suspension flowing through the catalyst carrier body. The catalyst carrier body can be disposed in such a way that the suspension flows into the channels which are closed on one side. The wash coat then fills up the channels. It forms a thermal insulation. If the catalyst carrier body is disposed in such a way that the closed channels are in the region where the suspension enters the catalyst body, the channels cannot be filled with the suspension. This improves the insulation since the heat conductivity of the catalyst carrier layer which completely fills up the channel is better than that of the atmosphere in the channels.
In accordance with a further feature of the invention, the channels are closed in the vicinity of the exhaust gas intake and outlet. If the plastic deformation does not completely close individual channels, this is compensated for by the subsequent coating, which closes small gaps.
In accordance with an added feature of the invention, the channels in the catalyst carrier body are configured in layers on top of one another, and up to five layers of the channels, preferably two, are closed. In this way an advantageous compromise between the necessity of having catalytically active surfaces and of heat insulation is obtained, without the external dimensions of the catalyst carrier body having to be substantially enlarged.
With the objects of the invention in view there is also provided a process for manufacturing a device for catalytic conversion of exhaust gases in an exhaust system, in particular in an exhaust system of combustion engines, which comprises dividing a catalyst carrier body into a multiplicity of channels having free flow cross-sections through which an exhaust gas can flow in a given flow direction; and plastically deforming the channels in an outer annular region of the catalyst carrier body for closing at least a part of the free flow cross-sections in the given direction.
In accordance with another mode of the invention, the plastic deformation is carried out in such a way that the catalyst carrier body is compressed in a die. When the catalytic converter carrier body is compressed, the outer region of the carrier body is deformed, so that the channels are closed.
In accordance with a further mode of the invention, the compression die is provided with a conical or annular wall.
In accordance with an added mode of the invention, instead of compressing the catalyst carrier body in a die, the plastic deformation of the channel walls is carried out in such a way that a force is exerted upon an outer annular region through the use of a stamp, which results in plastic deformation of the channel walls.
In accordance with an additional mode of the invention, the tamp is annular or has a wall sloping from the inside to the outside. If the stamp is provided with a wall sloping from the inside to the outside, the free flow cross-section of the channels can be closed by bending the channel walls. With an annular stamp, the channel walls are crushed.
In accordance with yet
Bruck Rolf
Maus Wolfgang
Emitec Gesellschaft fuer Emissionstechnologies mbH
Greenberg Laurence A.
Lerner Herbert L.
Stemer Werner H.
Tran Hien
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