Abstract:
A muffler for an exhaust system of an internal combustion engine, in particular in a motor vehicle, with an exhaust pipe which has an end section that is permeable for airborne sound and which is surrounded by a jacket in this end section to form a reflective chamber. To make it inexpensive to manufacture the exhaust pipe with the reflective chamber, the jacket and the end section are manufactured in one piece.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a muffler for an exhaust system of an internal combustion engine, especially in a motor vehicle. The invention also relates to a method for manufacturing a reflective chamber enclosing an end section of an exhaust pipe that is permeable for airborne sound, especially for a muffler of an exhaust system of an internal combustion engine.  
       BACKGROUND OF THE INVENTION  
       [0002]     Mufflers for exhaust systems are known in general. In certain embodiments of such mufflers, an exhaust pipe having an end section that is permeable for airborne sound may be situated in a housing of the muffler. This end section may be sheathed by a jacket to thereby form a reflective chamber. During operation of the exhaust system, exhaust gases flow through the muffler and through the exhaust pipe. Airborne sound then propagates in the exhaust gas. Airborne sound can enter the reflective chamber through the end section which is permeable for airborne sound, thereby resulting in attenuation of airborne sound in a predetermined frequency range.  
         [0003]     For production of such reflective chambers, it is essentially possible to push a sleeve that forms the jacket onto the outside of the end section of the exhaust pipe and secure it on the exhaust pipe in a suitable manner.  
         [0004]     The present invention relates to the problem of finding a method for an exhaust pipe equipped with a reflective chamber such that the method is characterized by inexpensive manufacturability in particular.  
       SUMMARY OF THE INVENTION  
       [0005]     The invention is based on the general idea of manufacturing the jacket of the reflective chamber and the end section of the exhaust pipe in one piece. Therefore, no separate jacket need be attached to the exhaust pipe to assemble the muffler. This integral design thus simplifies assembly and therefore reduces the cost of manufacturing the muffler.  
         [0006]     An embodiment in which the jacket is formed by a pipe section of the exhaust pipe that is bent or rolled back over the end section on the outside is especially advantageous. As an alternative, it is also possible for the end section to be formed by a pipe section of the exhaust pipe that is bent or rolled back through the jacket on the inside. In both alternatives, both the jacket and the end section each form an integral component of the exhaust pipe. In the starting state of the exhaust pipe, i.e., in the case of a starting pipe, the two pipe sections which form the jacket and the end section of the finished exhaust pipe after the sections have been bent or rolled back are situated directly side-by-side in the longitudinal direction of the pipe. After bending or rolling back the pipe sections, the two pipe sections are arranged concentrically to one another. The pipe section on the outside then forms the jacket of the reflective chamber while the pipe section on the inside forms the end section of the exhaust pipe which is permeable for airborne sound. The design of the reflective chamber by bending or rolling back a pipe section of the exhaust pipe can be implemented especially inexpensively and in a manner that is reliable for the process. Furthermore, there are no tolerance problems for the design of the reflective chamber. Moreover, no additional operation is required for attaching a separate jacket to the exhaust pipe.  
         [0007]     It is self-evident that the features mentioned above and those yet to be explained below may be used not only in the particular combination given but also in other combinations or even alone without going beyond the scope of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE FIGURES  
       [0008]     Preferred exemplary embodiments of the present invention are depicted in the drawings and explained in greater detail in the following description, where the same reference notation refers to the same or similar or functionally similar components.  
         [0009]      FIG. 1  illustrates a schematic diagram of a highly simplified basic longitudinal section through a muffler with a reflective chamber according to this invention,  
         [0010]      FIG. 2  illustrates a schematic diagram of an enlarged detail view of the muffler according to  FIG. 1  in the area if the reflective chamber but in a different embodiment,  
         [0011]      FIGS. 3   a - 3   c  illustrate schematic diagrams of highly simplified longitudinal sections of an exhaust pipe in different manufacturing states, and  
         [0012]      FIGS. 4   a - 4   c  illustrate schematic diagrams of views like those shown in  FIGS. 3   a - 3   c,  but in a different embodiment of the exhaust pipe.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]     According to  FIG. 1 , an inventive muffler  1  includes at least one exhaust pipe  2 . This exhaust pipe  2  is designed here as an outlet pipe leading out of a housing  3  of the muffler  1 . The muffler  1  here also includes an inlet pipe  4  and at least one connecting pipe  5 . As an example, three chambers are formed in the housing  3 , namely an inlet chamber  6 , an outlet chamber  7  and a muffler chamber  8 . The inlet pipe  4  passes through the outlet chamber  7  and the muffler chamber  8  and ends in the inlet chamber  6 . The at least one connecting pipe  5  passes through the muffler chamber  8  and connects the inlet chamber  6  to the outlet chamber  7 . The outlet pipe, i.e., the exhaust pipe  2  begins in the outlet chamber  7  and passes through the muffler chamber  8  and the inlet chamber  6 .  
         [0014]     The inlet pipe  4  may be designed to be permeable for airborne sound in the area of the muffler chamber  8 , which may be accomplished by means of a perforation  9 , for example. This perforation  9 , i.e., the permeability for airborne sound, is symbolized in  FIG. 1  by double arrows. Similarly, the at least one connecting pipe  5  may also be designed to be permeable for airborne sound in the area of the muffler chamber  8 . This is preferably also accomplished with the help of a perforation  9 , again symbolized by double arrows. A suitable muffler material (not shown here) may be arranged in the muffler chamber  8 .  
         [0015]     The exhaust pipe  2  of the inventive muffler  1  has a reflective chamber  10 . To this end, an end section  11  of the exhaust pipe  2  is sheathed by a jacket  12  in such a way that the reflective chamber  10  is formed radially between the end section  11  and the jacket  12 . The end section  11  is designed to be permeable for airborne sound, which is again symbolized by double arrows in the figures. The permeability for airborne sound may preferably be achieved through a suitable perforation  9  of the end section  11 .  
         [0016]     According to an embodiment of the invention, the jacket  12  and the end section  11  are manufactured of one piece. This means that the jacket  12  is not a separate component with regard to the end section  11  and the exhaust pipe  2  and instead the jacket  12  is an integral component of the exhaust pipe  2 .  
         [0017]     In the embodiment shown in  FIG. 1 , the jacket  12  is formed by a pipe section  13  of the exhaust pipe  2  which is bent back radially on the outside over the end section  11 , preferably rolled back, thereby enclosing and/or sheathing the end section  11 . Furthermore, the jacket  12  and/or the pipe section  13  forming the jacket  12  has a ring collector  15  on its end which is remote from an opening  14  in the exhaust pipe  2 , said ring collar protruding inward radially and being in contact with the exhaust pipe  2 . In this way, the reflective chamber  10  is closed on the end remote from the opening  14 . On the end facing the opening  14 , the reflective chamber  10  is necessarily sealed by the seamless transition between the interior end section  11  and the exterior jacket  12 .  
         [0018]     The ring collar  15  may essentially be in loose contact with the exhaust pipe  2 . Leakage is not critical here. Essentially however it is possible through suitable measures to mount the ring collar  15  in an airtight mount on the exhaust pipe  2  and/or to attach it to the exhaust pipe  2 . For example, this may be accomplished through an appropriate flanging and/or by soldering and/or welding.  
         [0019]     In the alternative embodiment illustrated in  FIG. 2 , the end section  11  which is perforated or permeable for airborne sound is formed by the pipe section  13  which in this case is bent back radially on the inside through the jacket  12 , especially being rolled back to thereby form the reflective chamber  10 . In this variant the ring collar  15  protrudes radially outward away from the end section  11  and is in contact with the exhaust pipe  2  on the inside. Here again essentially a loose or airtight and/or tight contact between the ring collar  15  and the exhaust pipe  2  is/are possible.  
         [0020]     Preferred embodiments of a method for producing the reflective chamber  10  on the exhaust pipe  2  are explained in greater detail below.  
         [0021]      FIG. 3   a  illustrates a starting state with a starting pipe  2 ′ having a pipe opening  16 . A first pipe section  13  begins at this pipe opening  16 , with a second pipe section  17  being connected thereto.  
         [0022]     According to  FIG. 3   b,  in a first process step, the second pipe section  17  is made permeable for airborne sound, symbolized here again by the double arrows. The second pipe section  17 , for example, is provided with a perforation  9 .  
         [0023]     Then the first pipe section  13  is bent back on the outside over the second pipe section  17 , preferably by rolling it back, thereby achieving the state illustrated in  FIG. 3   c.  The ring collar  15  may be formed by bending back the first pipe section  13  or subsequent thereto and brought into contact with the exhaust pipe  2 . Then the finished exhaust pipe  2  is obtained, with the two pipe sections  13 ,  17  starting at the opening  14  of the exhaust pipe  2 . The second pipe section  17  on the inside then forms the end section  11  while the first pipe section on the outside forms the jacket  12 . Then the reflective chamber  10  is formed between the end section  11  and the jacket  12 .  
         [0024]     According to  FIGS. 4   a  through  4   c,  the exhaust pipe  2  equipped with the reflective chamber  10  may also be produced as described below.  
         [0025]     In the starting state according to  FIG. 4   a,  the starting pipe  2 ′ again has the pipe opening  16 , the first pipe section  13  and the second pipe section  17 .  
         [0026]     In a first processing step according to  FIG. 4   b,  the first pipe section  13  is then designed to be permeable for airborne sound and to this end is equipped in particular with a perforation  9 .  
         [0027]     Following that, according to  FIG. 4   c,  the first pipe section  13  is bent back on the inside through the second pipe section  17 , preferably by rolling it back. At the same time or subsequently, the ring collar  15  is formed and brought into contact with the exhaust pipe  2 . In the finished state of the exhaust pipe  2 , the two pipe sections  13 ,  17  here again begin at the opening  14 . The first pipe section  13  is situated on the inside, forming the end section  11  of the exhaust pipe  2 , while in this variant the second pipe section  17  is situated on the outside and subsequently forms the jacket  12 . The reflective chamber  10  is again formed between the jacket  12  and the end section  11 .  
         [0028]     Suitable tools or machines are known for bending or rolling back a pipe section. This bending or rolling process can be designed to be adequately reliable, in which case comparatively narrow shape tolerances can be maintained in particular. The integral design of the reflective chamber  10  on the exhaust pipe  2  makes implementation of such a reflective chamber  10  comparatively inexpensive. In particular, this eliminates the need for any additional processing steps for attaching a jacket designed as a separate component to the exhaust pipe  2 .