Abstract:
A machine tool for manufacturing exhaust gas cleaning devices, in particular diesel particulate filters and catalysts that have a housing and a gas-traversed insert clamped in the housing, comprises at least one tool, in which the insert is clamped in the housing. A heating device that heats the housing is integrated in the tool. In a method for manufacturing exhaust gas cleaning devices, the heated housing is plastically deformed in a machine tool, and the insert is inserted into the housing.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority to DE 10 2009 012 348.2, which was filed Mar. 9, 2009. 
       FIELD OF THE INVENTION 
       [0002]    This invention relates to a method and a machine tool for manufacturing exhaust gas cleaning devices, in particular diesel particulate filters or catalysts. 
       BACKGROUND 
       [0003]    In such devices, inserts which are very sensitive to radial pressure and which are chiefly axially traversed ceramic substrates, are held in an outer housing by radial clamping. Between the ceramic insert and the outer housing, an insulation mat is arranged, which forms an elastic element. Various methods exist for so-called “canning,” i.e. for introducing or arranging the insert into the housing. Some of these methods will be explained below. 
         [0004]    A first method for manufacturing the device is the so-called “calibrating” or “shrinking” method, where the insert with the insulation mat is put into an oversized, peripherally closed tube referred to as a jacket, and subsequently the unit obtained is placed in a tool. The tool is provided with numerous radially inwardly movable pressure jaws. When the pressure jaws are moved radially inwards, they plastically deform the jacket to such an extent that the insert is clamped in the jacket. 
         [0005]    Another method for manufacturing the device is the so-called “stuffing” method, where the outer housing is first brought to the desired outer radius; and subsequently, the insert wrapped with the insulation mat is placed or introduced into the outer housing through a funnel-shaped tool. 
         [0006]    Other methods include the so-called “wrapping” method, wherein a sheet metal is wrapped around the insert and welded in the desired end position in the overlap region of the sheet-metal edges, and the so-called “clamping” method, in which the housing is divided into two half-shells between which the insert is clamped. 
         [0007]    An important characteristic of the insulation mats is the gap bulk density (GBD). It designates the compression of a certain mass of the material in the gap between insert and housing. Due to the resilience of the housing material, a lower GBD can be obtained by the canning method, so that the insulation mats must be compressed more during the canning method. A thermal expansion of the housing and hence a lower GBD in operation of the exhaust gas cleaning device must be compensated during the manufacture by a correspondingly greater compression of the housing and the insulation mat in the cold condition. 
         [0008]    One objective is to create a machine tool for manufacturing an exhaust gas cleaning device and to provide a method for manufacturing exhaust gas cleaning devices by which the inserts are very safely held in the housing. 
       SUMMARY 
       [0009]    A machine tool for manufacturing exhaust gas cleaning devices, in particular diesel particulate filters and catalysts, includes a housing and a gas-traversed insert clamped in the housing. The machine tool includes at least one tool in which the insert is clamped in the housing, wherein a heating device for heating the housing is integrated in the tool. In this way, it is possible to directly heat the housing in the machine tool during the canning method, whereby the material properties of the components for the manufacturing method are positively changed. For example, the resilience of the housing material is reduced, and the housing is thermally expanded during the manufacturing method, whereby the insert and/or insulation mat must be compressed to a smaller extent. In addition, the required plastic deformation of the housing is smaller than in the prior art. 
         [0010]    In one example, the heating device includes at least one electric heating element. This provides for a simple construction of the heating device. 
         [0011]    The heating device can include at least one induction element. Thus, induced eddy currents provide for a direct heating of the housing material. 
         [0012]    Alternatively, it is possible that heating ducts are provided in the tool, through which a heating fluid flows. A heating fluid provides for heating a plurality of tools via one central heating device. 
         [0013]    If the tool itself is heated, the housing can be heated selectively by contact with the tool. 
         [0014]    In one example, the tool includes a thermal insulation of the heating device. In this way, the housing and the part of the tool adjacent to the housing can be heated, while other regions of the machine tool are not heated due to the thermal insulation. 
         [0015]    It is possible that cooling ducts are provided in the tool, through which a cooling fluid flows. Thus, a plurality of tools can also be cooled via one central cooling device. 
         [0016]    In accordance with a preferred embodiment, the tool is a calibrating tool for reducing the outside dimensions of the housing. 
         [0017]    In accordance with another preferred embodiment, the tool is a stuffing tool in which the insert is stuffed into the heated housing. Here as well, the load acting on the insert during the manufacture is reduced. 
         [0018]    Alternatively, the tool is a wrapping tool in which the insert is wrapped with heated sheet metal. 
         [0019]    In one example, the heating device is constructed such that a tool-side housing receptacle is heated to temperatures of at least 150° C. The elevated temperature facilitates forming of the housing. 
         [0020]    The heating device can be constructed such that a housing receptacle is maximally heated to temperatures of 630° C., more specifically 500° C. At these temperatures, the housing has sufficient mechanical stability, without requiring additional supporting mechanisms. 
         [0021]    In one example, the heating device is constructed such that a housing receptacle is heated to temperatures between 300° C. and 500° C., in particular between 400° C. and 500° C. This temperature range provides for easier forming of the housing with a sufficient mechanical stability at the same time. 
         [0022]    It is possible that temperature sensors are provided in the tool. This provides for a control or regulation of the temperature of the housing, and of the housing receptacle, and provides a protection against overheating of the machine tool. 
         [0023]    This invention also relates to a method for manufacturing exhaust gas cleaning devices, in particular diesel particulate filters and catalysts, which include a housing and a gas-traversed insert clamped in the housing. The housing is formed in a machine tool, the insert is introduced into the housing, and the housing is heated in the machine tool. By heating the housing, the material properties of the housing are changed, for example the resilience of the material is reduced. Another advantage of heating during the manufacturing method is the thermal expansion of the housing, whereby for example the insert and/or insulation mat must be compressed to a smaller extent. 
         [0024]    In one example, the housing is heated to at least 150° C. In this way, a sufficient change in the material properties for improving the manufacturing method becomes possible. 
         [0025]    Advantageously, the housing is heated to not more than 630° C., more specifically not more than 500° C. 
         [0026]    In accordance with a preferred method variant, the housing is heated to temperatures between 300° C. and 500° C., more specifically between 400° C. and 500° C. This provides for a better formability with sufficient strength of the housing. 
         [0027]    In accordance with a further variant, an insulation mat containing a binder is clamped between insert and housing. The temperature of the heated housing liquefies the binder in the insulation mat. By liquefying the binder, the friction between housing and insert is reduced, whereby less shear forces are introduced into the insulation mat. 
         [0028]    Heating of the housing can be effected by induction. 
         [0029]    In one example, the method is, e.g. a stuffing method, with the following method steps. The insert is wrapped with an insulation mat, the housing is heated, and the wrapped insert is introduced into the heated housing. Due to the expansion of the housing, the stuffing method is simplified, since the wrapped insert must only be reduced to the diameter of the expanded housing. 
         [0030]    Alternatively, the insert might also be wrapped by a heated sheet metal. 
         [0031]    The insert can be measured at the beginning of the method and the housing diameter can be reduced or adapted to the respective insert. 
         [0032]    In one example, the housing is cooled in a controlled manner after introducing the wrapped insert. 
         [0033]    In accordance with an alternative method variant, the method is a calibrating method with the following method steps. The insert is wrapped with an insulation mat, the housing is heated, the wrapped insert is introduced into the heated housing, and the outside dimensions of the housing are reduced. Due to the thermal expansion of the hot housing, the required outside dimensions of the calibrated housing are greater than in a cold housing, whereby the calibrating method is simplified and the pressure load acting on the insert is reduced. The reduced resilience of the material of the hot housing provides a further simplification of the method. 
         [0034]    The insert can be measured at the beginning of the method, whereby the outside dimensions of the housing are specifically reduced to the respective insert. 
         [0035]    In one example, heating the housing and reducing the outside dimensions of the housing are performed by a hot tool. Thus, heating the housing and reducing the outside dimensions of the housing substantially can be performed in the same method step. 
         [0036]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  shows a schematic view of an exhaust gas cleaning device. 
           [0038]      FIG. 2  shows a machine tool in accordance with a first embodiment of the invention. 
           [0039]      FIG. 3  shows a sectional view through a tool of the machine tool of  FIG. 2 . 
           [0040]      FIG. 4  shows a sectional view through the tool along line IV-IV in  FIG. 3 . 
           [0041]      FIG. 5  shows a sectional view through the tool along line V-V in  FIG. 3 . 
           [0042]      FIG. 6  shows a part of a machine tool in accordance with a second embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0043]      FIG. 1  shows an exhaust gas cleaning device  30 , for example a diesel particulate filter or a catalyst, which includes a cylindrical housing  32  and a gas-traversed insert  34  clamped in the housing  32 , for example a ceramic monolith. Between the insert  34  and the housing  32  an insulation mat  36  is provided, which forms an elastic element. At each axial end of the insert  34 , funnels  38  are attached to the housing  32  as an inlet or outlet, or the funnels  38  are integrally formed with the same. 
         [0044]      FIG. 2  shows a machine tool  11  in accordance with a first embodiment of the invention with a plurality of tools  10  in the form of jaws which can be moved by the machine tool  11 . The tools  10  form a housing receptacle for the housing  32  of the exhaust gas cleaning device  30 . The illustrated machine tool  11  is a calibrating machine with tools  10  constituting pressure jaws which in radial direction press on the exhaust gas cleaning device  30  introduced into the machine tool  11  and thus reduce the outside dimensions of the housing  32 . 
         [0045]    A tool  10  of the machine tool  11  shown in  FIG. 2  is illustrated in  FIG. 3  to  FIG. 5 . The tool  10  has a side  12  facing the housing  32  (the workpiece) and a side  14  facing the machine tool  11 . On the side  12  facing the housing  32  a heating device  16  is integrated in the tool  10 . The heating device  16  consists of two electric heating elements  18  oriented parallel to each other. Alternatively, it is possible that heating ducts are provided in the tool  10 , through which a heating fluid flows. 
         [0046]    The heating device  16  is constructed such that, for example due to the number and arrangement of the electric heating elements  18 , the tool  10  is uniformly heated on the side  12  facing the housing  32 . 
         [0047]    It is also possible that the heating device  16  includes an induction element by which the housing  32  is directly heated by induction. 
         [0048]    Between the side  14  facing the machine tool  11  and the side  12  of the tool  10  facing the housing  32  a thermal insulation  20  is provided. The heating device  16  only heats the part of the tool  10  directly engaging the housing  32 , while other components of the machine tool  11  are isolated from the heating device  16 . 
         [0049]    An optional cooling device  22  on the side  14  of the tool  10  facing the machine tool  11  includes a plurality of cooling ducts  24 , through which a cooling fluid flows. The cooling device  22  is provided to maintain the temperature of the machine tool  11 , independent of the temperature of the housing  32  determined by the heating device  16 , in a certain range which ensures an optimum function of the machine tool  11 . 
         [0050]    A first temperature sensor  28  is provided on the side  12  of the tool  10  facing the housing  32 . This temperature sensor  28  serves the temperature control of the tool  10  and hence of the contact surface for the housing  32 . A further temperature sensor  28  is provided on the side  14  of the tool  10  facing the machine tool  11 , wherein this temperature sensor  28  serves the control of the cooling device  22  and/or as protection against overheating of the machine tool  11 . 
         [0051]    It is of course also possible that other temperature sensors are provided, for example those which directly measure the temperature of the housing  32 . 
         [0052]      FIG. 6  shows a part of a machine tool  11  in accordance with a second embodiment of the invention, wherein the tool  10  is a stuffing tool by which the insert  34  is stuffed into the housing  32 . A heating device  16  consists of an induction element  26  which is arranged around the housing  32 . A funnel-shaped tool part  40  is arranged at an axial end of the housing. The funnel-shaped tool part  40  and the induction element  26  form the housing receptacle of the tool  10 . 
         [0053]    In the illustrated embodiment, the heating device  16  serves to directly heat the housing  32  by induction. It is also possible that the heating device also heats the funnel-shaped tool part  40  to a specific temperature. 
         [0054]    In the following, a method for manufacturing exhaust gas cleaning devices  30  will be explained with reference to  FIGS. 1 to 6 . 
         [0055]    A first variant of the manufacturing method is the stuffing method. The insert  34  of the exhaust gas cleaning device  30  is measured at the beginning of the method, and the housing  32  is brought to the required dimensions, for example by a calibrating method. In this way, it is possible to compensate manufacturing tolerances of the insert  34 . 
         [0056]    In the following method step, the insert  34  is wrapped with an insulation mat  36 . It is also possible to choose material and/or volume of the insulation mat  36 , for example in dependence on the dimensions of the insert  34 , to individually weigh the insulation mat or individually measure the unit of insulation mat  36  and insert  34 . 
         [0057]    The housing  32  is inserted in the tool  10  of the machine tool  11 , wherein the housing  32  rests against the funnel-shaped tool part  40  with an axial end thereof and is surrounded by the induction element  26 , as is shown in  FIG. 6 . The housing  32  is then heated by the induction element  26 . 
         [0058]    The insert  34  wrapped with the insulation mat  36  subsequently is introduced into the heated housing  32  through the funnel-shaped tool part  40 . The insulation mat  36  surrounding the insert  34  is compressed by the funnel-shaped tool part  40  such that the diameter of the unit comprising the insert  34  and insulation mat  36  maximally corresponds to the inside dimensions of the housing  32  or is smaller than the same. 
         [0059]    By heating the housing  32 , the housing  32  is thermally expanded, whereby the inside dimensions of the housing  32  are increased, which simplifies introducing the wrapped insert  34 . 
         [0060]    During introduction of the insert  34 , the housing  32  is heated to at least 150° C., whereby the binder in the insulation mat  36  is liquefied and the friction between insulation mat  36  and housing  32  is reduced. 
         [0061]    After introducing the insert  34  into the housing  32 , the exhaust gas cleaning device  30  is cooled, and the funnels  38  can be attached or molded to the housing  32 . 
         [0062]    The heating device  16  with the induction element  26  is controlled such that the temperature of the housing  32  is not more than 630° C. The housing  32  in one example is heated to a temperature between 300° C. and 500° C. 
         [0063]    It is also possible that the housing  32  is heated already during the calibration of the empty housing  32  at the beginning of the method. 
         [0064]    In accordance with a second method variant, the manufacture of the exhaust gas cleaning device  30  is effected by a calibrating method. The insert  34  is wrapped with the insulation mat  36 . The housing  32 , possibly together with the insert  34 , is heated in the machine tool  11 , with the dimensions of the housing  32  being larger than the wrapped insert  34 . 
         [0065]    In the following method step the outside dimensions of the housing  32  are reduced. The housing  32  is held in the machine tool  11  by a plurality of tools  10  constituting pressure jaws, and is heated by the heating devices  16  integrated in the tools  10 . The temperature range of the heated housing  32  is similar to the stuffing method described above. 
         [0066]    Due to the material and the thin walls of the housing  32 , heating the housing  32  is effected very quickly upon contact with the hot tool  10 , whereby heating the housing  32  and reducing the outside dimensions of the housing  32  substantially can be performed at the same time in the same method step. 
         [0067]    In the calibrating method it is also possible that the insert  34  and/or the insulation mat  36  are measured at the beginning of the method, in order to correspondingly reduce the outside dimensions of the housing  32  adapted to the respective insert  34 . 
         [0068]    As an alternative to the above embodiments, a wrapping tool can also be used, in which the housing is placed around the insert  34  and contracted as a sheet metal part. In the contracted end position, the sheet metal then is welded along the edge, in order to create a closed cylinder. The tool shown in  FIG. 2  can also be used as wrapping tool, in that the jaws  10  tightly close the sheet metal around the insert. The sheet metal then is welded within the tool. 
         [0069]    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.