Metal working – Method of mechanical manufacture – Catalytic device making
Reexamination Certificate
2000-08-11
2002-10-22
Zimmerman, John J. (Department: 1775)
Metal working
Method of mechanical manufacture
Catalytic device making
C428S593000, C502S527220
Reexamination Certificate
active
06467169
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates in particular to a process for the production of a honeycomb body using a hard metal sheet, especially for exhaust gas catalytic converters. The invention also relates to a semi-manufactured honeycomb body.
It is known for honeycomb bodies to be formed by stacking and/or winding sheet metal layers, at least some of which are structured sheet metal layers. Such honeycomb bodies are used, for example, as support bodies for catalytically active coatings.
In order to produce such a honeycomb body, at least one metal sheet is used, which is at least partially structured. The metal sheet or metal sheet portions is or are stacked and/or wound, in dependence on the structure of the honeycomb body. Different structural configurations of a honeycomb body as a catalytic carrier support body are described, for example, in European Patent Application 0 245 738 A1.
The honeycomb body is then subjected to a brazing material-coating operation. Thereafter the sheet metal layers are brazed together. The operation of brazing the sheet metal layers is implemented in particular in a vacuum brazing furnace.
It is known that honeycomb bodies of that kind are produced from metal sheets which have a thickness of about 110 &mgr;m. It is known for the metal sheet to be subjected to a soft-annealing operation after the cold rolling operation so that a certain degree of elasticity is imparted to the metal sheet. Such elasticity ensures that the metal sheet can be provided with a structure, without the metal sheet suffering damage. The structures involved are in particular corrugation configurations which are formed in the metal sheet by way of suitable corrugating rollers. The fact that the metal sheet has been subjected to a heat treatment operation, the soft-annealing procedures, means that the shaping tools are also not subjected to an excessive loading.
It is also known (from a paper entitled “The Development and Application of a Metal Supported Catalyst for Porsche's 911 Carrera 4” by Stephan Pelters et al., in SAE Technical Paper Series 890488) that metal honeycomb bodies can be made from thin metal sheets or metal foils having a thickness of about 50 &mgr;m. Such metal sheets have also been subjected to a soft-annealing operation.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a process for producing a honeycomb body using a hard metal sheet and a semi-manufactured honeycomb body, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and products of this general type and in which the expenditure involved in the production of the honeycomb body can be reduced, the semi-manufactured honeycomb body is easier to produce and the metal sheet is particularly suitable for the production of a honeycomb body.
With the foregoing and other objects in view there is provided, in accordance with the invention, a process for the production of a honeycomb body, in particular for an exhaust gas catalytic converter, which comprises at least partially producing a structure in at least one hard metal sheet having a thickness of at most 80 &mgr;m by cold-shaping the at least one hard metal sheet without a previous soft-annealing; and layering and winding, or winding, the at least one at least partially structured hard metal sheet.
Surprisingly, it was found that on one hand, the nature of a hard metal sheet having a thickness of at most 80 &mgr;m is such that it permits a cold shaping operation to be implemented to provide a structure without the hard metal sheet being excessively mechanically loaded by the cold shaping operation. On the other hand, it was also found that, when dealing with such a hard metal sheet, during a winding operation, the structure introduced into the hard metal sheet is substantially retained, which was not guaranteed when dealing with soft-annealed sheets having a small thickness. This is a matter of particular importance, especially in regard to the use of honeycomb bodies as exhaust gas catalytic converters. That is because in exhaust catalytic converters the flow passages that the honeycomb body has have a significant influence on the flow characteristics and therewith also on the catalytic performance of the exhaust gas catalytic converter.
The fact that the honeycomb body is formed from a hard metal sheet which is subjected to a cold shaping operation without previous soft-annealing provides that there is also a markedly lower degree of variation in the cell density. That is to be attributed to the fact that the structure of the hard metal sheet is retained in the winding operation, which is not the case when using a metal sheet which was subjected to a soft-annealing treatment prior to the cold shaping operation. A further advantage of the production process according to the invention is that it provides a honeycomb body which enjoys a higher level of brazing quality, after a brazing operation in which the hard metal sheets are joined together. By virtue of the fact that the hard metal sheet has a relatively high strength, the honeycomb body which is disposed in a layered configuration and wound, or merely wound, can be introduced into a tubular casing with a higher degree of prestressing than is the case when using metal sheets having a small thickness, which were subjected to a soft-annealing operation. Higher levels of contact forces between the hard metal sheets can be achieved by virtue of the higher level of prestressing effect. That is also the case even if a smooth metal sheet is introduced between two adjacent hard metal sheets.
It is known that, in order to provide a structure in a metal sheet, the metal sheet is prepared in the form of a winding or coil and the metal sheet is transported from the winding or coil by way of suitable transport rollers to a cold shaping station. In that case, the metal sheet is unwound from the winding or coil. The metal sheet is subjected to a tensile loading during the process of transporting it to and away from the cold shaping station. The process according to the invention for the production of a honeycomb body also achieves a reduction in stretching of the metal sheet when it is transported to and away from the cold shaping station. That is also the case during the operation of winding or coiling up the hard metal sheet.
In accordance with another mode of the invention, a hard metal sheet having a thickness of between 50 &mgr;m and 80 &mgr;m, preferably between about 60 &mgr;m and 80 &mgr;m, is subjected to an at least two-stage cold shaping operation. That alternative mode of implementation of the process provides that the tools for forming a structure which is, for example, a corrugation configuration that is produced in the metal sheet through the use of suitable corrugated rollers, are not exposed to an excessive loading or involve a low level of wear. A multi-stage cold shaping procedure also ensures that the hard metal sheet is not exposed to an excessive loading during the cold shaping operation thereof, so that the hard metal sheet is not damaged or destroyed.
In accordance with a further mode of the invention, a hard metal sheet having a thickness of at most 50 &mgr;m, in particular 35 &mgr;m, and preferably 20 &mgr;m, is subjected at least in part to a cold shaping operation without a previous soft-annealing procedure. The hard metal sheet which has a thickness of at most 50 &mgr;m is provided with a structure by the cold shaping operation, in such a way that the structure is formed in a one-stage cold shaping operation. In this case the cold shaping operation is implemented through the use of suitable tools of a tool profile which is also adapted to the thickness of the metal sheet.
In accordance with an added mode of the invention, in order to simplify the production of a honeycomb body which, for example, involves a honeycomb body wound in an S-shape, the hard metal sheet is divided into portions after the cold shaping operation, and the portions are disposed in a layered configuration
Emitec Gesellschaft fuer Emissions-technologie mbH
Zimmerman John J.
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