Abstract:
A method of manufacturing an exhaust gas carrying device, in particular an exhaust gas purification device, and a tool provided therefor include segment-like jaws that are used to deforma an outer housing. The jaws have indentations or projections adjacent to each other, and which are complementary to form a continuously surrounding indentation/projection. The reshaped outer housing is provided with one or more surrounding projections or indentations by the deformation.

Description:
RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 13/063,020, filed Mar. 9, 2011, which is the U.S. national phase of International Patent Application PCT/EP2009/006581, filed 10 Sep. 2009, which claims priority to German Application No. 10 2008 046 527.5, filed 10 Sep. 2008. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a method of manufacturing an exhaust gas carrying device, in particular an exhaust gas purification device, which has an outer housing with an insert clamped therein, as well as an appropriate tool. 
       BACKGROUND 
       [0003]    It is known from the prior art to clamp exhaust gas carrying devices, which more particularly include catalytic converters and diesel particulate filters, in an outer housing. The insert typically consists of a brittle ceramic substrate, also referred to as a monolith, and a flexible, compensating bearing mat. 
         [0004]    The prior art according to WO 2008/064860 A1 discloses the provision of point-shaped extensions in the segment-like pressure jaws of a tool to fix neighboring substrates in place, the extensions pressing the outer housing in sections to clamp the substrate. In the closed condition, the inner faces of the pressure jaws have an inner contour that corresponds to the outer contour to be attained of the outer housing. 
         [0005]    But in these so-called “shrinking methods,” which operate using segment-like pressure jaws that extend around the outer housing and move inwards to deform the outer housing, it is generally a problem that this deformation causes the outer housing to lengthen in the axial direction. This means that there are certain tolerance problems or that an axial mechanical machining operation is required after the shrinking process. 
         [0006]    The objective is to provide a method and a tool for carrying out the method, in which the machining process is effected in a simpler and more precise fashion. 
       SUMMARY 
       [0007]    A method of manufacturing an exhaust gas carrying device includes the following steps: providing a tool having segment-like jaws which are adapted to be moved inwards against an outer housing; providing an indentation or a projection on an inside of each jaw, with indentations or projections of all jaws being oriented in relation to each other such that a continuously surrounding indentation or a continuously surrounding projection is obtained; placing the outer housing and an insert positioned therein into the tool; deforming the outer housing by closing the jaws to clamp the insert in the outer housing; and producing a surrounding projection or a surrounding indentation on the outer jacket remote from the ends thereof when closing the jaws. 
         [0008]    By producing a continuously surrounding projection or a continuously surrounding indentation, the outer jacket becomes shorter in the axial direction than without the projection or indentation. The “unnecessary” material is, as it were, accommodated in the projection or indentation. 
         [0009]    A rolling process or the like is no longer needed, which would constitute a later machining of the outer housing. Instead, the projection or the indentation is produced during the clamping process itself, i.e. during shrinking. 
         [0010]    To increase the stability of the outer housing, more particularly a projection is produced. With a view to stability, such projection is even preferred to an indentation. This means that the material will give way and move into the indentations of the jaws during the shrinking process. 
         [0011]    In one example, a plurality of projections (or indentations) spaced axially from each other are provided on the outer jacket. Accordingly, this results in a kind of rings which surround the outer jacket to stabilize it and provide for its exact length. 
         [0012]    As viewed in cross-section, the projections/recesses more particularly have an arcuate radial end, which is simpler for the plastic deformation. 
         [0013]    According to one example embodiment, the outer housing is configured as a circumferentially closed tube into which the insert is inserted. As an alternative, a kind of wrapping of a sheet metal strip would, of course, also be possible, which is placed around the insert and is welded and closed on the edges after the segments are closed. 
         [0014]    For an exact adjustment of the axial length, provision is made according to the preferred embodiment that the outer housing is positioned in the tool between two axial stops before the jaws are moved inwards. The stops define the axial length of the outer housing after reshaping since the outer housing rests against the stops after the reshaping process. 
         [0015]    The tool according to the invention for manufacturing an exhaust gas carrying device includes appropriately designed jaws having projections and extensions which complement one another on the circumference to form a continuously surrounding indentation or projection. 
         [0016]    These and other features of the present invention can be best understood from the following specification and drawings, of which the following is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Further features and advantages of the invention will be apparent from the description below and from the accompanying drawings, to which reference is made. In the drawings: 
           [0018]      FIG. 1  shows a perspective view of an exhaust gas carrying device manufactured in accordance with the invention, prior to putting on and attaching the funnel-shaped inlets and outlets; 
           [0019]      FIG. 2  shows a side view of a tool according to the invention; 
           [0020]      FIG. 3  shows a view of a longitudinal section taken through the tool according to the invention, more precisely through an upper half of the tool; and 
           [0021]      FIG. 4  shows a single jaw utilized in the tool according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  shows an exhaust gas carrying device manufactured in accordance with the invention, in the form of a catalytic converter or a diesel particulate filter. The exhaust gas carrying device comprises a tubular outer housing  10  and an insert  12  which is clamped in the tube and includes a substrate  14  (see  FIG. 3 ) which comprises ceramics and is preferably catalytically coated, as well as a bearing mat  16  surrounding the substrate  14 . The outer housing  10  preferably is, from the start, a closed tube made of metal. 
         [0023]    As can be seen in  FIG. 1 , the outer housing  10  is provided with a plurality of circumferentially continuously surrounding annular projections  18  spaced from its axial ends, which are produced by deformation of the outer housing  10 . 
         [0024]      FIG. 2  illustrates a tool which is used for plastically deforming the outer housing  10  and radially clamping the insert  12  in the outer housing  10 . This tool is a so-called “shrinking tool” having a plurality of pressure jaws  20  which are segment-like as seen in a side view and which can be closed inwards in the direction of the arrows. In the closed condition, the inner faces of the pressure jaws have an inner contour that corresponds to the outer contour to be attained of the outer housing  10 . One of these jaws  20  is illustrated in  FIG. 4 . Like the others, this jaw  20  is elongate and extends beyond the outer housing  10  in the axial direction, i.e. it is longer than the outer housing. 
         [0025]    As can be seen in  FIGS. 2 to 4 , the jaws  20  have indentations  22  on their inner faces. 
         [0026]    These indentations  22  are complementary in the circumferential direction. When the tool is in the closed condition or has been moved inwards, a recess  22  of a jaw  20  continues into the respective recesses  22  of the adjacent jaws  20  in the circumferential direction, so as to form a circumferentially closed, at least largely closed groove. 
         [0027]      FIG. 3  shows that the indentations run out in an arc shape at their deepest point, i.e. they have an arcuate radial bottom or an arcuate radial end. 
         [0028]    In addition, the tool has axial stops  24  (see  FIG. 3 ), which may be optionally formed in the jaws  20  or are in the form of separate parts possibly adapted to be fed. 
         [0029]    The manufacturing method will now be explained in greater detail below. 
         [0030]    At first the substrate  14  and the bearing mat  16  are pushed as a unit into the outer housing  10 , and this unit is subsequently introduced into the open tool. A correct orientation of the insert  12  in relation to the outer housing  10  must be provided in the axial direction. 
         [0031]    The unit is then positioned between the stops  24 ; preferably, the axial ends of the outer housing  10  even rest against the stops  24 . But it may also be expedient in this connection to provide a small gap axially in advance so that, irrespective of the axial length tolerances of the outer housings  10  installed, as related to the initial condition, the same axial length will always be obtained after manufacture. 
         [0032]    It is also possible to additionally fix the substrate  14  in its position by using stops  26 . These stops  26  can be moved uniformly to the substrate  14  to align the substrate  14  axially in relation to the tool. This uniform movement may be attained, for example, by coupling the stops  26  to a shared spindle or a scissors-type linkage. 
         [0033]    When the jaws  20  are then closed, i.e. in the case of a circular cylindrical outer housing  10  where the jaws  20  are closed radially inwards, the outer housing  10  is plastically deformed. Due to the plastic deformation, the outer housing  10  will tend to become longer. In so doing, it will, however, strike against the stops  24 , and the material will move into the recesses  22  to form the surrounding projections  18 . 
         [0034]    Alternatively or additionally to the projections  18 , the outer housing  10  could, of course, also have a surrounding indentation. But this would then require the provision of projections  40  on the jaws  20 , which complement one another circumferentially.  FIG. 2  shows such a projection  40  on a jaw  20 , for example, and further shows an indentation  30  in the outer housing  10 , which is illustrated by broken lines in  FIG. 2  in the plastically deformed condition. 
         [0035]    The deformation and the continuously surrounding projections  18  provide the outer housing  10  with a distinctly better stability. In addition, the axial tolerances during shrinking are practically reduced to zero, because all outer housings may have the same axial length; with an appropriate adjustment of the stops  24 , the outer housings will always rest against them after deformation. 
         [0036]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.