Patent Application
20070048198
This nonprovisional application claims priority under 35 U.S.C. § 119(a) on German Patent Application No. DE 2005041512, which was filed in Germany on Sep. 1, 2005, and which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a method for inserting a ceramic functional body in a tubular metal housing. The invention further relates to a device thus produced.
2. Description of the Background Art
Ceramic functional bodies are used as catalysts and as diesel exhaust particulate filters in exhaust systems for motor vehicles with internal combustion engines. The ceramic functional bodies are located in a metal housing, which has a sheet metal jacket, an intake cone, and an outlet cone. In order to be able to compensate for the different coefficients of thermal expansion of metal and ceramic, the ceramic bodies are wrapped in a suitable support mat and inserted in the housing. So that the ceramic functional body remains fixed in place in the metal housing when the ambient temperature drops to −30° C., for example, or when the exhaust temperatures reach temperatures of up to 900° C., the dimensions of the metal housing, the support mat, and the ceramic functional body must be precisely matched to one another.
Unfortunately, ceramic functional bodies have large diameter tolerances on account of the manufacturing process. It is necessary, therefore, to measure each ceramic body in order to be able to determine the appropriate metal housing for it. This is rather costly.
It has already been proposed to utilize an oversized metal housing and to size the metal housing after the insertion of the ceramic body wrapped with the support mat. U.S. Pat. No. 5,055,274 shows such a sizing process using a sizing tool having sizing dies. EP 0 768 451 A shows a method in which the metal housing is sized with the aid of pressure rollers.
Since the sheet metal of the housing has the property of springing back subsequent to the sizing, i.e. after the reduction in diameter, the diameter must first be reduced to an increased degree. This presents the risk that the ceramic functional body will be damaged. Since the housing is already closed, this damage can no longer be detected. Moreover, the function of the support mat is significantly damaged by the brief overcompression. Consequently, the methods for after-the-fact sizing of the metal housing described in the above cited documents have not achieved implementation.
It is therefore an object of the present invention to provide a method by which an after-the-fact sizing of the housing can be performed without the risk of damage to the ceramic functional body or to the support mat.
At least two advantages are achieved thanks to the heating of the housing before the reduction in diameter. Firstly, the heated and the thus softened sheet metal material can be deformed with the application of little force, and has only a minimal tendency to spring back. Secondly, the diameter of the housing only needs to be reduced to the maximum diameter value that the housing will take on in operation under the greatest heating, as a result of which only minimal forces are exerted on the support mat and ceramic body, precluding any damage. As soon as the housing is cooled to ambient temperature, the ceramic functional body sits correctly in the housing.
The heating of the housing preferably takes place by inductive heating. Alternatively, or in addition, the housing can also be heated by, for example, a flame.
The housing is preferably heated to red or white heat, corresponding to temperatures up to 900° C.
The heated housing can be sized in a manner known per se by sizing tools or also by pressure rollers.
The subject matter of the invention also includes devices produced in accordance with the invention for treating exhaust gases of internal combustion engines. These are catalytic converters or exhaust particulate filters with ceramic functional bodies. In order to keep the mechanical stress on the ceramic as low as possible, the housing is heated up to, for example, 900° C. during the sizing process and is sized to a dimension calculated from the diameter of the functional body and the thickness of the support mat.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:
The sequence of the inventive method is described in a purely schematic fashion on the basis of
First, a ceramic functional body 1, for example a catalytic converter or diesel exhaust particulate filter, is measured. The diameter d, in particular, is determined in this process. In the case of oval functional bodies, multiple diameters are measured.
The ceramic functional body 1 is then wrapped with a support mat 2.
In
After the wrapped ceramic body 1, 2 has been slid in, the housing 3 is heated to red or white heat in approximately 5 seconds, as shown in
During the subsequent cooling, the housing 3 shrinks to the desired final dimension, during which process the support mat 2 is compressed to the desired value in the safest manner. Neither the ceramic body 1 nor the support mat 2 can be damaged in this process. The ceramic functional body 1 retains its operating position within the housing 3 in all operating states.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 041 512 | Sep 2005 | DE | national |
