Abstract:
A device and a method for connecting housing sections ( 5   a,    5   b,    5   c ) of soot particle filters uses a yoke-like clamping U-bolt ( 17 ) which has, disposed along the two longitudinal sides thereof, gripper-like bulges ( 29 ), for the mutual alignment and pressing against one another of end regions of adjacent housing sections ( 5   a,    5   b,    5   c ), which end regions are joined together without overlapping. A sealing tape ( 31 ), disposed at the inside of the clamping U-bolt ( 17 ), seals the gap between mutually adjoining housing sections ( 5   a,    5   b    5   c ) when the clamping U-bolt ( 17 ) is tightened.

Description:
BACKGROUND 
       [0001]    The subject matter of the invention is a device and a method for connecting housing sections for soot particle filters, as well as a clamping U-bolt. 
         [0002]    In the case of vehicles with combustion engines, filters and catalytic converters are being used to an increasing degree for treating exhaust gases. In this way, the environmental load due to pollutants such as soot particles, hydrocarbons, carbon monoxide, or nitrogen oxides can be greatly reduced. For treating diesel exhaust gases, catalytically active soot particle filters are also known in which soot particles are first held on the filter surface and then—when the temperature is sufficiently high—converted catalytically. As a rule, filters and catalytic converters comprise a ceramic carrier or monolith that is provided with a so-called wash coat making the surface larger. This monolith is held in a metallic housing or the so-called canning that is installed rigidly in the exhaust-gas line. 
         [0003]    In the case of diesel particle filters, as a rule the combustion of the particles does not take place completely without residue. Over time, additives contained in motor oil and in diesel fuel can lead to ash deposits in the filter. Metal wear debris in the engine likewise leads to the formation of ash. This increases the exhaust gas back pressure of the filter and thus the fuel consumption. Soot particle filters therefore must be regularly serviced or cleaned, e.g., annually or after reaching a predetermined number of miles traveled. For this purpose, soot particle filters must be separated from the exhaust-gas line and can be reattached after cleaning. 
         [0004]    From DE 20012812 U1, an exhaust-gas cleaning device is known with a housing constructed from several cylindrical modules in which a filter unit is installed in at least one of these modules. The individual modules can be placed one in the other or joined to each other by flange-like fastening elements. In the case of metallic housings, the modules are welded for mutual attachment. Because the housing modules are welded to each other, the filter unit can be removed only when the housing is separated. Even without welding, flanges that project outward on the housing take up a lot of space. In the case of housing modules pushed one inside the other, space and play for movements are likewise required in the direction of the housing axis, so that the individual modules can be separated from each other. 
       SUMMARY 
       [0005]    The objective of the present invention is to create a device and a method for the production of a detachable connection for housing sections of soot particle filters. Another objective of the invention is for allowing a simple removal and re-insertion of a filter unit for an exhaust-gas line, even when the spatial relationships are dimensioned narrowly. Another objective of the invention is for forming the fastening device that is insensitive relative to vibrations and exhaust-gas back pressures. 
         [0006]    These objectives are met by a device and a method for connecting housing sections in the case of soot particle filters as well as a clamping U-bolt according to the features of Claims  1 ,  6 , and  7 . 
         [0007]    The device according to the invention comprises a multiple-part cylindrical housing, wherein the individual housing sections have peripheral beads or seams impressed from the inside on the lateral surface in the region of the end faces. Every two adjacent housing sections are held together by a yoke-like clamping U-bolt with a bracket-like shoulder along each of the two longitudinal sides. When the clamping U-bolt is tightened, its shoulders press elastically from the outside against the outward-projecting bead rings on the housing sections. The housing sections are therefore aligned coaxially and pressed against each other. One or both ends or end faces of the tube-like housing sections could have an inward-projecting step that increases the mutual contact surface area and improves the sealing properties of the connection. Alternatively, the housing sections could also be constructed without such collars reducing the inner diameter. Between the shoulders, a temperature-resistant sealing tape is formed on the inside of the clamping U-bolts made from sheet metal or stainless steel. In the assembled state, this sealing tape covers the gap between the joined-together housing sections and is pressed by the clamping force of the U-bolt from the outside tightly against the end regions of the housing sections. 
         [0008]    In the case of a three-part housing, its middle part could be constructed for housing the soot particle filter. After detachment and shifting or removal of the two clamping U-bolts, this middle part can be pulled out without a problem laterally or in a plane vertical to the housing axis and thus separated from the two end parts of the housing connected to the feed or discharge lines. Here, movement of the middle housing section in the direction of the housing axis is not required. After cleaning or regeneration of the filter, it can be reinstalled in an analogous way. With the fastening device according to the invention, housings for soot particle filters could feature maintenance-friendly installation and construction even in the case of narrow spatial relationships. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The invention will be described in greater detail below with reference to a few figures. Shown here are: 
           [0010]      FIG. 1  a front view of a filter unit with a cylindrical housing comprising three housing sections, 
           [0011]      FIG. 2  a side view of the filter unit from  FIG. 1 , 
           [0012]      FIG. 3  a detail of the housing from  FIG. 1  in the region of two adjacent housing sections without a clamping U-bolt, 
           [0013]      FIG. 4  a cross section of the housing from  FIG. 1  in the region of the connecting point of two housing sections, 
           [0014]      FIG. 5  a side view of the clamping U-bolt in the region of a turnbuckle, 
           [0015]      FIG. 6  a top view of the clamping U-bolt in the region of the turnbuckle, and 
           [0016]      FIG. 7  a cross section of the clamping U-bolt along the line A-A in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]      FIG. 1  shows a front view of a filter unit  1  with a housing  3  that comprises three housing sections  5   a ,  5   b ,  5   c  with essentially cylindrical lateral surfaces  7   a ,  7   b ,  7   c  with the outer diameters D 1 , D 2 , and D 3 . 
         [0018]    Typically, the outer diameters D 1 , D 2 , D 3  each lie, according to the application, on the order of magnitude of approximately 100 mm to approximately 400 mm. The end faces of the housing  5  or the inlet-side housing section  5   a  and the outlet-side housing section  5   c  are formed by annular plates  9   a ,  9   b , each having a cylindrical connection port  11   a ,  11   b  with the diameters D 4  and D 5  arranged coaxial to the housing axis H. These diameters typically lie on the order of magnitude of approximately 40 mm to approximately 150 mm. Alternatively, connection ports  13   a ,  13   b  projecting radially on the corresponding lateral surfaces  7   a ,  7   c  are also formed on the housing sections  5   a  and  5   c , as is shown in  FIGS. 1 and 2  by dashed lines. Obviously, in this variant, passage openings in the lateral surfaces  7   a ,  7   c  would be formed in the region of the connection ports  13   a ,  13   b  and the plates  9   a ,  9   b  closing the housing  5  laterally would be closed. The shape, arrangement, and size of the connection ports  11   a ,  11   b  are aligned according to the conditions of the corresponding exhaust-gas line in which the filter unit  1  is to be installed (as a rule by welding). 
         [0019]    The invention comprises an arbitrary number of additional constructions of housings  5 , wherein these comprise at least two adjacent housing sections  5   a ,  5   b  or  5   b ,  5   c  and in which these housing sections  5   a ,  5   b ,  5   c  have an essentially cylindrical shape at least in the adjacent regions. In the embodiment shown in  FIGS. 1 to 4 , all of the housing sections  5   a ,  5   b ,  5   c  comprise a cylindrical casing-like steel sheet with the thickness 1.25 mm. The wall thickness of the closing plates  9   a ,  9   b  equals 3 mm. Obviously, other wall thicknesses or wall thickness combinations are also possible. In particular, the wall thicknesses of the individual housing sections  5   a ,  5   b ,  5   c  could be equal or different. The outer diameters D 1 , D 2 , D 3  of the three cylindrical housing sections  5   a ,  5   b ,  5   c  are all of equal size in the shown example. Passage openings  15  that can be closed and that are provided, e.g., with threading on the lateral surface  7   a  and on the closing plate  9   a  are formed on the first housing section  5   a . There, e.g., connection cables for sensors can be guided into the interior of the housing  3 . 
         [0020]    Every two adjacent housing sections  5   a ,  5   b  or  5   b ,  5   c  are connected detachably to each other by a clamping U-bolt  17 . The clamping U-bolt  17  comprises a band  19  with a yoke-like cross section with metallic band loops  21  welded on both ends each for holding a cylindrical insert  24 . These inserts  24  belong to the turnbuckle  22  ( FIGS. 5 ,  6 , and  7 ). 
         [0021]      FIG. 3  shows a partial diagram of the housing  3  with two adjacent housing sections  5   a  and  5   b  without the clamping U-bolt  17 . The arrows marked with “P” in the connection ports  11   a ,  13   a  indicate the direction of flow of the exhaust gases.  FIG. 4  shows a region of the housing  3  marked in  FIG. 3  by the dash-dot line G as a section diagram, but this time including the clamping U-bolt  17 . 
         [0022]    Alternatively, the outer diameters D 1 , D 2 , D 3  of the housing sections  5   a ,  5   b ,  5   c  or the adjacent regions of the housing sections  5   a ,  5   b ,  5   c  could also be different. At axial distances S 1  and S 2  from adjacent end faces  20   a ,  20   b  of two housing sections  5   a ,  5   b , respectively, peripheral seams  23  could be formed on the insides or peripheral beads  25  could be formed on the outsides of the lateral surfaces  7   a ,  7   b . Adjacent to a middle region  27  of the clamping U-bolt  17 , wherein this middle region has an approximately straight-line cross section, there are bracket-like or gripper-like bulges  29  or shoulders that contact the outsides of the bead  25  elastically when the clamping U-bolt  17  is tightened and thus press together the two housing sections  5   a ,  5   b  in the direction of the housing axis H and simultaneously also align these sections relative to each other. In an analogous way, other deformations arranged at a distance to the housing section ends  20   a ,  20   b  or joints and projecting to the lateral surfaces  7   a ,  7   b  and/or set in these surfaces could be used as stops for corresponding structures or deformations on the clamping U-bolt  17  for the overlap-free connection of the housing sections  5   a ,  5   b . Instead of deformations of the lateral surfaces  7   a ,  7   b , e.g., rings or other structures could also be fused with the lateral surfaces  7   a ,  7   b  and used as stop elements for the bracket-like edges of the clamping U-bolt  17 . 
         [0023]    The abutting ends  20   a ,  20   b  of the housing sections  5   a ,  5   b  are provided in the example of  FIG. 4  with inward projecting steps  33   a ,  33   b , wherein a larger contact surface is produced for the two housing sections  5   a ,  5   b . The joint or the gap  35  between the two housing parts  5   a ,  5   b  can also be sealed by a sealing tape  31  made from ceramic, glass fibers, or a different, thermally resistant material. As shown in  FIG. 4 , this sealing tape  31  is clamped tight between the clamping U-bolt  17  and the hoop-shaped end regions of the housing sections  5   a ,  5   b  when the clamping U-bolt  17  is tightened. The sealing tape  31  can be fixed, e.g., on the inside of the band  19  by a temperature-resistant adhesive. The attachment points for the seams  23  or beads  25  are arranged at an axial distance h 1  (advantageously 1 mm&lt;h 1 &lt;50 mm, e.g., h 1 =12 mm) from the corresponding ends  20   a ,  20   b  of the housing sections  5   a ,  5   b . The seams  23  or beads  25  have a width h 2 , wherein the position with the maximum height h 3  of the bead  25  or the maximum depth h 3  of the depression of the seams  23  is arranged, as a rule, approximately in the middle. As a rule, a height h 3  on the order of magnitude of a few millimeters, for example, 3 mm, is sufficient. The geometry of the clamping U-bolt  17  is aligned to the mass and shape of the adjacent housing sections  5   a ,  5   b , so that—in the case of beads  25  projecting outward on the lateral surfaces  7   a ,  7   b —the bulges  29  surround the beads  25  and the housing section ends  20   a ,  20   b  and optionally the steps  33   a ,  33   b  are aligned relative to each other or coaxially and are pressed against each other. Outside of the tightening device of the clamping U-bolt  17 , the connection device thus has a very small projection h 4  of, e.g., 5 mm to 10 mm, advantageously less than 7.5 mm, past the outer diameter D 1 , D 2 , D 3  of the housing sections  5   a ,  5   b ,  5   c . Therefore, assembly and disassembly are possible even under narrow spatial relationships. This applies analogously also in the case of holding structures in the shape of seams  23  that are set from the outside into the lateral surfaces  7   a ,  7   b ,  7   c  of the housing sections  5   a ,  5   b ,  5   c . In this case, the bulges  29  are adapted along the longitudinal sides of the band  19  to the shape of the lateral surfaces  7   a ,  7   b , so that they engage in the seams  23  of adjacent housing sections  5   a ,  5   b  when the clamping U-bolt  17  is tightened. Therefore, the housing sections  5   a ,  5   b  are aligned coaxially and pressed against each other (not shown). The clamping U-bolt  17  thus must have regions engaging only in the seams  23 . An overlap or surrounding of the seams  23  in the axial direction is not absolutely necessary. 
         [0024]    The band length of the clamping U-bolt  17  is directed according to the outer diameter D 1 , D 2 , D 3  of the housing sections  5   a ,  5   b ,  5   c  to be connected. It is advantageously dimensioned so that, for a tightened clamping U-bolt  17 , a distance of a few millimeters up to a few centimeters—according to the extent of the lateral surfaces ( 7   a ,  7   b ) to be enclosed—remains between the two end faces of the band  19 .  FIG. 5  shows a side view of the clamping U-bolt  17  in the region of the turnbuckle  22 ,  FIG. 6  shows a top view of this clamping U-bolt  17 , and  FIG. 7  shows a cross section of the clamping U-bolt  17  along the line A-A in  FIG. 5 . 
         [0025]    The first insert  24  comprises a radial through hole for guiding a screw  26 . The second insert  24  is formed as a nut with an inner thread for the screw  26 . When the screw  26  is tightened, the diameter of the band  19  bent into a ring shape is reduced. In the region of one band end, a tab  28  overlapping this band end is connected to the band  19  by weld points  30  on the bottom side of the band  19  (the weld points  30  between the band  19  and the band loops  21  on the top side of the band  19  are also visible). The tab  28  overlaps the band end and grips under the opposing other band end, without, however, being connected rigidly to this end. The tab  28  is used as a stop for the sealing tape  31 . 
         [0026]    In the case of alternative constructions, the length of the band  19  could be dimensioned so that its two end faces just touch for a correctly tightened clamping U-bolt  17  or leave only a small intermediate space in the range of millimeters. In the case of another alternative construction, the two ends of the band  19  could also overlap. 
         [0027]    Soot particle filters that are installed in a housing  3  with several housing sections  5   a ,  5   b ,  5   c  that can be connected according to the invention and can be disassembled, cleaned, and then reassembled in a simple way. After the clamping U-bolts  17  are loosened, these can be shifted axially, so that they no longer overlap the connection points. Alternatively, the clamping U-bolts  17  could also be opened completely and then removed. Because adjacent housing sections  5   a ,  5   b ,  5   c  do not overlap, the middle housing section  5   b  that is not connected rigidly to the exhaust-gas line could be pushed forward laterally or radially without axial displacement and then separated from the rest of the housing  3 . After the cleaning or maintenance of the filter element that is arranged in the middle housing section  5   b , this housing section  5   b  could be integrated back into the housing  3  in the reverse sequence.