Patent Publication Number: US-6659222-B1

Title: Multi-chambered muffler

Description:
This application claims the benefit of provisional application No. 60/122,881 filed on Mar. 5, 1999. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention relates to exhaust systems and, in particular, to mufflers for quieting the exhaust noise of vehicle engines. More particularly, this invention relates to mufflers having outer shells and passageways for conducting exhaust product through a region defined by the outer shells to quiet noise associated with the exhaust product. 
     In accordance with the present invention, a muffler is created by joining two half shells at their peripheries to form an internal chamber therebetween. A baffle plate extends between the two shells to divide the chamber into two subchambers. The baffle is provided with an aperture into which a pair of inner plates are inserted to further divide the subchambers. An inlet and an outlet pipe extend through the shells and are supported by additional apertures in the baffle. The pair of inner plates define a passageway between two of the subchambers as well as a pair of tuning chambers between subchambers for noise reduction. 
     Other features of the present invention will become apparent to those skilled in the art from the following detailed description of preferred embodiments of the invention exemplifying the best mode of carrying out the invention as presently perceived. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The detailed description particularly refers to the accompanying figures in which: 
     FIG. 1 is a perspective exploded view of a muffler including horizontal top and bottom outer shells, vertical first and second inner plates, an inlet tube, an outlet tube and a baffle plate; 
     FIG. 2 is a perspective view of the baffle plate, the vertical first and second inner plates, the inlet tube, and the outlet tube, with portions broken away, showing the vertical first and second inner plates mated together and positioned to extend through the baffle plate to form a lower tuning throat, a middle conductor tube, and an upper tuning throat, the inlet tube positioned to extend through the baffle plate, and the outlet tube positioned to extend through the baffle plate so that the vertical first and second inner plates, the baffle, the inlet tube, and the outlet tube cooperate to form a subassembly; 
     FIG. 3 is a cross-sectional view of the muffler taken along line  3 — 3  of FIG. 4 after the subassembly of FIG. 2 is positioned between the horizontal top and bottom outer shells showing the baffle plate including a central plate-receiving aperture sized and shaped to receive the vertical first and second inner plates therein after the plates are mated together, an inlet tube-receiving aperture to the right of the central plate-receiving aperture sized to receive the inlet tube, and an outlet tube-receiving aperture to the left of the central plate-receiving aperture sized to receive the outlet tube; 
     FIG. 4 is a top plan view of the muffler of FIG. 3, with portions of the top outer shell, inlet tube, and outlet tube broken away, showing the top and bottom outer shells cooperating to define a chamber, the vertical first and second inner plates cooperating with the baffle plate to partition the chamber into first, second, third, and fourth subchambers so that the inlet tube receives exhaust gases generated by an engine, communicates the exhaust gas through the lower-left first subchamber, and “dumps” the exhaust gas into the lower-right second subchambers the middle conductor defined by the vertical first and second inner plates communicates the exhaust gases “diagonally” from the second subchamber to the upper-left third subchamber, and the outlet tube communicates the exhaust gases through the upper-right fourth subchamber into the remainder of the exhaust system including a tailpipe; 
     FIG. 5 is a transverse sectional view of the muffler of FIG. 1 taken along lines  5 — 5  of FIG.  2  and after the installation of the subassembly of FIG. 2 in the chamber defined by the top and bottom outer shells showing the upper tuning throat defined by the vertical first and second inner plates including a first open end communicating with the upper-left third subchamber and a second open end communicating with the upper-right fourth subchamber to permit communication of noise between the third and fourth subchambers so that the fourth subchamber acts as a Helmholtz tuning subchamber; 
     FIG. 6 is a transverse sectional view of the muffler similar to FIG. 5, taken along lines  6 — 6  of FIG. 2, showing the middle conductor tube defined by the vertical first and second plates including a first opening communicating with the second subchamber and a second opening communicating with the third subchamber so that exhaust gases flow diagonally from the second subchamber to the third subchamber and the second and third subchambers act as first and second transfer subchambers and the middle conductor acts as a conduit therebetween; and 
     FIG. 7 is a transverse sectional view of the muffler, taken along lines  7 — 7  of FIG. 2, showing the lower tuning throat defined by the vertical first and second inner plates including a first opening communicating with the second subchamber and a second opening communicating with the first subchamber to permit communication of noise between the second and first subchambers so that the first subchamber acts as a Helmholtz tuning subchamber. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     A stamp-formed muffler  10  according to the present invention is shown in FIG.  1 . Muffler  10  includes a stamped top outer shell  12 , a stamped bottom outer shell  14 , a stamped vertical first inner plate  16 , a stamped vertical second inner plate  18 , a vertical baffle plate  20 , an inlet tube  22 , and an outlet tube  24  as shown in FIG.  1 . 
     Vertical first and second inner plates  16 ,  18 , inlet tube  22 , and outlet tube  24  are positioned to extend through baffle plate  20  to form a subassembly  31  as shown in FIG.  2 . Top and bottom outer shells  12 ,  14  define a chamber  33 . Subassembly  31  is positioned between top and bottom outer shells  12 ,  14  and partitions chamber  33  into first, second, third, and fourth subchambers  35 ,  37 ,  39 ,  41 . 
     After assembly, muffler  10  is installed in a vehicle (not shown) as part of an exhaust system  43  as shown diagrammatically in FIG.  4 . An engine  29  generates exhaust gas that flows through exhaust system  43  and into inlet tube  22  of muffler  10 . Inlet tube  22  communicates exhaust gas through first subchamber  35  into second subchamber  37 . First and second vertical inner plates  16 ,  18  cooperate to define a middle conductor tube  45  that communicates the exhaust gas “diagonally” across muffler  10  from second subchamber  37  to third subchamber  39 . Outlet tube  24  then communicates the exhaust gas from third subchamber  39  through fourth subchamber  41  into the remainder of exhaust system  43  including a tail pipe  27  where the exhaust gas is dissipated in the atmosphere. 
     Muffler  10  is assembled by placing first and second inner plates  16 ,  18  together, inserting first and second inner plates  16 ,  18  through a plate-receiving aperture  26  formed in baffle plate  20 , and inserting inlet and outlet tubes  22 ,  24  through respective inlet and outlet tube-receiving apertures  28 ,  30  formed in baffle plate  20  to create subassembly  31  as shown in FIG.  2 . Top and bottom shells  12 ,  14  cooperate to accept subassembly  31  therebetween and top and bottom shells  12 ,  14  are welded or otherwise mechanically fastened together to define muffler  10 . When top and bottom shells  12 ,  14  are mated together, they define chamber  33  and secure baffle plate  20 , first and second inner plates  16 ,  18 , and inlet and outlet tubes  22 ,  24  between top and bottom shells  12 ,  14  as shown in FIGS. 3-7. 
     Top shell  12  is shaped to include various contours and edges as shown, for example, in FIG.  1 . Top shell  12  includes a top wall  32 , first and second end walls  34 ,  36 , first and second side walls  38 ,  40  extending between first and second end walls  34 ,  36 , and a flange  42  appended to side walls  38 ,  40  and end walls  34 ,  36  as shown in FIG.  1 . First and second end walls  34 ,  36  and first and second side walls  38 ,  40  are appended to top wall  32  and extend from top wall  32  to flange  42  at a perimeter edge  46  as shown in FIG.  1 . Top wall  32 , first and second end walls  34 ,  36 , and first and second side walls  38 ,  40  are formed to include stiffening ribs  44 . In preferred embodiments, ribs  44  raise the resonant frequency of the top shell  12  which reduces the vibration of and noise created by top shell  12 . First end wall  34  is formed to include an inlet passageway  48  and second end wall  36  is formed to include an outlet passageway  50  as shown in FIGS. 1 and 4. 
     Similar to top shell  12 , bottom shell  14  is formed to include various contours and edges as shown, for example, in FIG.  1 . Bottom shell  14  includes a bottom wall  52 , first and second end walls  54 ,  56 , first and second side walls  58 ,  60  extending between first and second end walls  54 ,  56 , and a flange  62  appended to end walls  54 ,  56 , and side walls  58 ,  60 . First and second end walls  54 ,  56  and first and second side walls  58 ,  60  are appended to bottom wall  52  and extend from bottom wall  59  to flange  62  at a perimeter edge  66  as shown, for example, in FIG.  1 . Bottom wall  52 , first and second end walls  54 ,  56 , and first and second side walls  58 ,  60  are formed to include stiffening ribs  64 . In preferred embodiments, ribs  64  raise the resonant frequency of the bottom shell  14  which reduces the vibration of and noise created by bottom shell  14 . First end wall  54  is formed to include an inlet passageway  68  and second end wall  56  is formed to include an outlet passageway  70  as shown in FIGS. 1 and 5. 
     Baffle plate  20  is formed to include edges and contours to interact with top and bottom shells  12 ,  14 , first and second innerplates  16 ,  18 , and inlet and outlet tubes  22 ,  24 . Baffle plate  20  includes a base  29 , a first inner flange  74  defining plate-receiving aperture  26 , a second inner flange  71  defining inlet tube-receiving aperture  28 , a third inner flange  75  defining outlet tube-receiving aperture  30 , and an outer flange  76  at a perimeter edge  78  as shown, for example, in FIGS. 1 and 3. First and second inner plates  16 ,  18  extend through plate-receiving aperture  26  as shown, for example, in FIG.  2 . First and second inner plates  16 ,  18  are secured to baffle plate  20  by a press-fit with first inner flange  74 . 
     Outer flange  76  of baffle plate  20  engages top and bottom shells  12 ,  14  as shown in FIGS. 5-7. More specifically, outer flange  76  is positioned to lie in a groove  80  defined by ribs  44 ,  64  of top and bottom shells  12 ,  14  as shown, for example, in FIGS. 5-7. In alternative embodiments, the outer flange of the baffle plate may be welded or otherwise coupled to the top and bottom shells. In other alternative embodiments, the outer flange of the baffle plate is not nested in grooves but “free-floats” between the top and bottom shells. 
     As previously mentioned, baffle plate  20  cooperates with first and second inner plates  16 ,  18  to divide plate-receiving chamber  33  into first, second, third, and fourth subchambers  35 ,  37 ,  39 ,  41  as shown, for example, in FIG.  4 . Subchambers  35 ,  37 ,  39 ,  41  are created without a drawing process being performed on either top wall  32  or bottom wall  52  of top and bottom shells  12 ,  14 , respectively. Top and bottom walls  32 ,  52  are referred to as creaseless top and bottom walls  32 ,  52  because no drawing processes are performed on creaseless top and bottom walls  32 ,  52  to form subcharnbers  35 ,  37 ,  39 ,  41 . Stiffening ribs  44 ,  64  formed on top and bottom walls  32 ,  52  serve the limited purpose of reducing the vibration of and noise created by top and bottom shells  12 ,  14  and do not define subchambers between top and bottom shells  12 ,  14 . 
     Inlet tube  22  includes a first end  122 , a second end  124  spaced apart from first end  122 , and a plurality of perforations  126 . Similarly, outlet tube  24  includes a first end  128 , a second end  130  spaced apart from first end  128 , and a plurality of perforations  132 . Inlet and outlet tubes  22 ,  24  extend through respective inlet and outlet tube-receiving apertures  28 ,  30  of baffle plate  20  as shown in FIG.  2 . Inlet and outlet tubes  22 ,  24  are then secured to baffle plate  20  by a press-fit with respective second and third inner flanges  71 ,  75 . 
     When inlet tube  22  is positioned to lie in chamber  33  defined by top and bottom shells  12 ,  14 , first end  122  of inlet tube  22  is positioned to lie between inlet passageways  48 ,  68  of top and bottom shells  12 ,  14 . Similarly, second end  130  of outlet tube  24  is positioned to lie between outlet passageways  50 ,  70  of top and bottom shells  12 ,  14 . 
     First and second inner plates  16 ,  18  are stamped from a sheet of stainless steel in the shape as shown in FIGS. 1 and 3. In alternative embodiments, the components of the muffler may be stamped from sheets of cold-rolled, stainless steel, aluminized stainless steel, and any other appropriate type of material. First inner plate  16  includes a base  90  having an outer periphery  91 , a first channel  92 , a second channel  94 , and a third channel  96  as shown, for example, in FIG.  1 . Second inner plate  18  is similar to first inner plate  16  and includes a base  98  having an outer periphery  99 , a first channel  110 , a second channel  112 , and a third channel  114  as shown, for example, in FIG.  1 . 
     Outer peripheries  91 ,  99  are positioned to lie in a groove  81  defined by ribs  44 ,  64  of top and bottom shells  12 ,  14  as shown, for example, in FIGS. 5-7. In alternative embodiments, the first and second inner plates include outer flanges (not shown) coupled to the outer peripheries of respective bases and positioned in groove  81 . 
     After first and second inner plates  16 ,  18  are positioned in plate-receiving aperture  26  of baffle plate  20 , a plane defined by bases  90 ,  98  of first and second inner plates  16 ,  18  is substantially perpendicular to a plane defined by base  21  of baffle plate  20  as shown in FIG.  4 . After positioning subassembly  31  into chamber  33  defined by top and bottom outer shells  12 ,  14 , the plane defined by base  21  of baffle plate  20  is substantially perpendicular to top wall  32  of top outer shell  12  and bottom wall  52  of bottom outer shell  14  and the plane defined by bases  90 ,  98  of first and second inner plates  16 ,  18  is substantially perpendicular to top wall  32  of top outer shell  12  and bottom wall  52  of bottom outer shell  14 . The respective axes of inlet and outlet tubes  22 ,  158  are substantially parallel to top wall  32  and bottom wall  52 , substantially perpendicular to the plane defined by base  21  of baffle plate  20 , and substantially parallel to and spaced apart from the plane defined by bases  90 ,  98  of first and second inner plates  16 ,  18 . 
     Inlet tube  22 , first and second inner plates  16 ,  18 , and outlet tube  24  cooperate to form a path for exhaust gas to flow through muffler  10 . When first and second inner plates  16 ,  18  mate together, first channels  92 ,  110  cooperate to define a lower first tuning throat  116  as shown in FIG. 7, second channels  94 ,  112  cooperate to define a middle tube  118  as shown in FIG. 6, and third channels  96 ,  114  combine to define an upper second tuning throat  120  as shown in FIG.  5 . In preferred embodiments of the present invention, first and second inner plates  16 ,  18  are connected together by seam welding between and along the length of the respective cooperating channels  92 ,  110 ;  94 ,  112 ; and  96 ,  114 . As shown in FIG. 3, inlet tube  22 , outlet tube  158 , and middle tube  118  are coplanar in a horizontal plane defined therethrough and spaced apart from bottom wall  52  of bottom outer shell  14  by a substantially equal vertical distance. First tuning throat  116  is vertically lower than the plane defined by inlet tube  22 , outlet tube  158 , and middle tube  118 . Whereas, second tuning throat  120  is vertically higher than the plane defined by inlet tube  22 , outlet tube  158 , and middle tube  118 . 
     Exhaust gas flows from first end  122  of inlet tube  22  to second end  130  of outlet tube  24  along a serpentine path  53  through inlet tube  22 , tube  118  of vertical first and second inner plates  16 ,  18 , and outlet tube  24  as best shown in FIGS. 4 and 6. Inlet tube  22  is formed to permit communication of exhaust gas from exhaust system  43  to second subchamber  37 . Second end  124  of inlet tube  22  is formed to include an opening  134  that communicates with second subchamber  37 . 
     Middle tube  118  of inner plates  16 ,  18  is formed to permit communication of exhaust gas from second subchamber  37  to third subchamber  39 . Tube  118  includes a first end  138  positioned to lie adjacent to second end walls  36 ,  56  of top and bottom shells  12 ,  14  and a second end  140  positioned to lie adjacent to first end walls  34 ,  54  of top and bottom shells  12 ,  14  as shown, for example, in FIG.  5 . 
     At first end  138  of tube  118 , second channel  94  of first inner plate  16  is formed to include an open end  142  that defines an opening  144  through which exhaust gas travels between second subchamber  37  and tube  118 . At second end  140  of tube  118 , second channel  112  of second inner plate  18  is formed to include an open end  146  that defines an opening  148  through which exhaust gas travels between tube  118  and third subchamber  39 . At first end  138  of tube  118 , second channel  112  of second inner plate  18  is formed to include a closed end  141  that prevents gas from passing into fourth subchamber  41  from tube  118 . Similarly, at second end  140  of tube  118 , second channel  94  of first inner plate  16  is formed to include a closed end  145  that prevents gas from passing into first subchamber  35  from tube  118 . 
     Outlet tube  158  is formed to permit communication of exhaust gases from muffler  10  to the remainder of exhaust system  43  including tail pipe  27  as shown in FIG.  4 . First end  128  of outlet tube  24  is formed to include an opening  136  that communicates with third subchamber  39  as shown in FIG.  5 . Exhaust gas enters outlet tube  158  through opening  136  then exists muffler  10  through second end  130  to the remainder of exhaust system  43 . 
     First tuning throat  116  is formed to permit communication of noise from second subchamber  37  to first subchamber  82  as shown in FIG.  7 . First tuning throat  116  includes a first end  150  positioned to lie adjacent to second end walls  36 ,  56  of top and bottom shells  12 ,  14  and a second end  152  positioned to lie adjacent to first end walls  34 ,  54  of top and bottom shells  12 ,  14 . 
     At first end  150  of first tuning throat  116 , first channel  92  of first inner plate  16  is formed to include an open end  154  that defines an opening  156  through which noise enters first tuning throat  116  from second subchamber  37  as shown in FIG.  7 . At second end  152  of first tuning throat  116 , first channel  92  of first inner plate  16  is formed to include an open end  158  defining an opening  160  through which noise that entered first tuning throat  116  exits into first subchamber  35 . At first end  150  of first tuning throat  116 , first channel  110  of second inner plate  18  is formed to include a closed end  153  that prevents gas from entering fourth subchamber  41  from first tuning throat  116 . At second end  152  of first tuning throat  116 , first channel  110  of second inner plate  18  is formed to include a closed end  157  that prevents gas from entering third subchamber  39  from tuning throat  116 . Thus, first tuning throat  116  allows low frequency noise to pass from second subchamber  37  into first subchamber  35  so that first subchamber  35  acts as a first Helmholtz tuning subchamber  159  for the attenuation of such low frequency noise. 
     Second tuning throat  120  is formed to permit communication of noise from third subchamber  39  to fourth subchamber  41  as shown in FIG.  5 . Second tuning throat  120  includes a first end  162  positioned to lie adjacent to first end walls  34 ,  54  of top and bottom shells  12 ,  14  and a second end  164  positioned to lie adjacent to second end walls  36 ,  56  of top and bottom shells  12 ,  14 . 
     At first end  162  of second tuning throat  120 , third channel  114  of second inner plate  18  is formed to include an open end  166  that defines an opening  168  through which noise enters second tuning throat  120  from third subchamber  39 . At second end  164  of second tuning throat  120 , third channel  114  of second inner plate  18  is formed to include an open end  170  defining an opening  172  through which noise that entered second tuning throat  120  exits into fourth subchamber  41 . At first end  162  of second tuning throat  120 , third channel  96  of first inner plate  16  is formed to include a closed end  165  that prevents gas from entering first subchamber  35  from second tuning throat  120 . At second end  164  of second tuning throat  120 , third channel  96  of first inner plate  16  is formed to include a closed end  169  that prevents gas from entering second subchamber  37  from second tuning throat  120 . Thus, second tuning throat  120  allows low frequency noise to pass from third subchamber  39  into fourth subchamber  41  so that fourth subchamber  41  acts as a second Helmholtz tuning subchamber  161  for the attenuation of such low frequency noise. 
     First and second tuning throats  116 ,  120  having respective lengths  117 ,  121  and inside diameters  119 ,  123  as shown in FIGS. 7 and 4. Lengths  117 ,  121  and inside diameters  119 ,  123  are selected to attenuate a specific range of frequencies. Length  117  and inside diameter  119  of first tuning throat  116  may be the same or different than respective length  121  and diameter  123  of second tuning throat  120 . 
     Exhaust gas travels through muffler  10  along serpentine path  53  until it exits muffler  10 . Exhaust gas enters muffler  10  through first end  122  of inlet tube  22  in direction  174  as shown in FIG.  5 . Exhaust gas flows through inlet tube  22  and exits inlet tube  22  in direction  176  through opening  134  into second subchamber  37 . Inlet tube  22  is formed to include perforations  126  through which exhaust gas in inlet tube  22  also communicates with second subchamber  37 . Perforations attenuate high frequency noise and aid in “tuning” the muffler. As previously mentioned, first tuning throat  116  permits exhaust gas to communicate between second subchamber  37  and first subchamber  35 . 
     Exhaust gas continues flowing in direction  180  from second subchamber  37  through opening  144  of tube  118  as shown in FIG.  5 . Exhaust gas flows diagonally through middle tube  118  and exits tube  118  in direction  182  through opening  168  into third subchamber  34  as shown in FIG. 5. A portion of tube  118  lying in second subchamber  84  is formed to include a plurality of perforations  186  through which exhaust gas in inlet tube  22  communicates with second subchamber  37 . A portion of tube  118  lying in third subchamber  88  is formed to include perforations  178  through which exhaust gas also communicates with third subchamber  39 . 
     Exhaust gas exits third subchamber  39  in direction  184  through opening  136  into outlet tube  24  as shown in FIG.  5 . Outlet tube  24  is formed to include perforations  132  through which exhaust gas in outlet tube  24  communicates with third subchamber  39 . As previously mentioned, second tuning throat  120  permits exhaust gas to communicate between third subchamber  39  and fourth subchamber  41 . 
     Exhaust gas then exits muffler  10  in direction  190  through second end  130  of outlet tube  24  as shown in FIG. 5 into the remainder of exhaust system  43 . In alternative embodiments of the present invention, the inlet tube, outlet tube, and the tube may be formed to include louvers (not shown) instead of perforations. 
     Although the invention has been described in detail with reference to certain embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.