Patent Publication Number: US-2007102236-A1

Title: Muffler

Description:
FIELD OF THE INVENTION  
      The present invention relates to a muffler for an exhaust system of an internal combustion engine. The invention also relates to an exhaust system equipped with such a muffler.  
     BACKGROUND OF THE INVENTION  
      Mufflers are known in general in exhaust systems of internal combustion engines and are generally used to reduce the noise emission by the internal combustion engine. For targeted suppression of certain frequencies, there are known mufflers that operate with a Helmholtz resonator. Such a Helmholtz resonator has a resonator chamber that is connected via a connecting pipe, the so-called resonator throat, to the sound source to be suppressed. The Helmholtz resonator acts in the manner of a spring-mass oscillator in which the “spring” is formed by the volume of the resonator chamber and the “mass” is determined by the volume of the resonator throat. The spring-mass oscillator, i.e., the Helmholtz resonator, has a resonator frequency at which the damping effect with regard to airborne sound is especially pronounced.  
      Mufflers that work with a Helmholtz resonator are usually limited to a relatively narrow frequency range with regard to their damping effect. In addition, production of such mufflers is usually comparatively complex.  
     SUMMARY OF THE INVENTION  
      The present invention relates to a muffler and/or an exhaust system equipped with a muffler, characterized in particular by an improved damping effect and/or by simplified production.  
      The invention is based on the general idea that several resonator chambers are provided in a single housing of the muffler, and several branch pipes which open into various resonator chambers branch off from a common exhaust-carrying pipe in a single branch section. The muffler therefore has several Helmholtz resonators, each being formed by a resonator chamber and a branch pipe being formed as a resonator throat, whereby these Helmholtz resonators are so adapted that they have different resonance frequencies. Due to the at least two resonance frequencies, the muffler may thus dampen at least two different frequencies and/or frequency ranges.  
      Due to the branching of the branch pipes in a common branch section of the exhaust-carrying pipe and the fact that all the resonator chambers are accommodated in a common housing, the inventive muffler is also characterized by a comparatively simple design and thus by being relatively inexpensive to manufacture.  
      The compact design of the muffler can be improved by additional measures and/or features, which can be implemented cumulatively or alternatively. For example, the exhaust-carrying pipe may pass through the housing and/or through at least one or all resonator chambers. One or more or all branch pipes may run inside the housing or may pass through one or more resonator chambers. The individual resonator chambers may be situated one after the other in the longitudinal direction of the housing and in particular may have the same cross sections along this longitudinal direction. The branch section in which all the branch pipes branch off from the exhaust-carrying pipe may be arranged completely inside one of the resonator chambers.  
      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 indicated but also in other combinations or alone without going beyond the scope of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Preferred exemplary embodiments of the invention are depicted in the drawings and explained in greater detail in the following description, where the same reference numerals refer to the same or similar or functionally identical components.  
       FIG. 1  is a simplified basic longitudinal section through a muffler;  
       FIG. 2  is a cross section through the muffler according to sectional lines II in  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      According to  FIGS. 1 and 2 , an exhaust system  1  includes at least one exhaust line  2  to which a muffler  3  is connected. The exhaust system  1  belongs to an internal combustion engine (not shown) and is used to remove exhaust gases during operation of the internal combustion engine.  
      The muffler  3  has an exhaust-carrying pipe  4 , which is connected and/or tied to the tubular exhaust line  2  in the installed state of the muffler  3 . The exhaust gases from the internal combustion engine thus pass through the pipe  4 . In the example shown here, the pipe  4  runs in a straight line.  
      The muffler  3  also has a housing  5 . The pipe  4  preferably extends through the housing  5 , thus going into and/or out of the housing  5  at axial ends thereof. In the illustrated embodiment, the pipe  4  is arranged in the housing  5  in such a way that it is at a distance radially along its entire circumference from a jacket of the housing  5  situated between the end faces. The housing  5  contains at least two resonator chambers. In the embodiment shown here, for example, three resonator chambers are provided, namely a first resonator chamber  6 , a second resonator chamber  7  and a third resonator chamber  8 . More than three resonator chambers may also be accommodated in the housing  5 . The individual resonator chambers  6 ,  7 ,  8  are separated from one another and are preferably partitioned off from one another so they are airtight. In the exemplary embodiment shown here, the resonator chambers  6 ,  7 ,  8  are arranged in succession axially with respect to the longitudinal direction of the housing  5 , which preferably runs parallel to the longitudinal direction of the pipe  4 . In this way, the second resonator chamber  7  is arranged axially between the first resonator chamber  6  and the third resonator chamber  8 .  
      For axial separation of adjacent resonator chambers  6 ,  7 ,  8 , partitions are provided in the housing  5 , namely a first partition  9  for separating the first resonator chamber  6  from the second resonator chamber  7  and a second partition  10  for separating the second resonator chamber  7  from the third resonator chamber  8 . The partitions  9 ,  10  are preferably designed and arranged in the housing  5  in such a way that they separate the mutually adjacent resonator chambers  6 ,  7 ,  8  from one another in an airtight manner. The pipe  4  passes through the partitions  9 ,  10 , to which end the partitions  9 ,  10  have corresponding passage openings. In the example, the partitions  9 ,  10  run parallel to one another and parallel to the axial end faces of the housing  5 . In this way, the pipe  4  passes through all the resonator chambers  6 ,  7 ,  8  at the same time.  
      The muffler  3  is also equipped with several branch pipes. In the exemplary embodiment, three branch pipes are provided, namely a first branch pipe  11 , a second branch pipe  12  and a third branch pipe  13 . A number of branch pipes  11 ,  12 ,  13  equal to the number of resonator chambers  6 ,  7 ,  8  is preferably provided. Each branch pipe  11 ,  12 ,  13  branches off from the pipe  4  in an axially limited branch section  14  of the pipe  4 . Each branch pipe  11 ,  12 ,  13  is open at its end remote from the branch section  14 . Each branch pipe  11 ,  12 ,  13  opens into a different resonator chamber  6 ,  7 ,  8 . In the present example, the first branch pipe  11  opens into the first resonator chamber  6 . The second branch pipe  12  opens into the second resonator chamber  7  and the third branch pipe  13  opens into the third resonator chamber  8 . In this way, three Helmholtz resonators are designed, each consisting of exactly one resonator chamber  6 ,  7 ,  8  and exactly one branch pipe  11 ,  12 ,  13  as the resonator throat. The three Helmholtz resonators of the muffler  3  shown here are labeled as  6 - 11 ,  7 - 12  and  8 - 13 , respectively, according to their components. The three Helmholtz resonators  6 - 11 ,  7 - 12 ,  8 - 13  have different resonance frequencies, so that the muffler  3  in the present example can dampen three different frequencies and/or frequency ranges.  
      The branch pipes  11 ,  12 ,  13  are preferably arranged completely inside the housing  5 , preferably at a distance from the jacket of the housing  5  in the radial direction around the circumference. The branch section  14  is preferably arranged completely inside the housing  5 . In the present case, the branch section  14  is arranged completely inside one of the resonator chambers, here in the first resonator chamber  6 . Accordingly, the second branch pipe  12  extends through the first resonator chamber  6  to open into the second resonator chamber  7 . The third branch pipe  13  extends through the first resonator chamber  6  and through the second resonator chamber  7  to open into the third resonator chamber  8 . Accordingly, the second branch pipe  12  passes through the first partition  9 , while the third branch pipe  13  passes through both partitions  9 ,  10 . In the exemplary embodiment, the individual branch pipes  11 ,  12 ,  13  in the branch section  14  branch off essentially radially from the pipe  4 . The individual branch pipes  11 ,  12 ,  13  in the branch section  14  preferably branch off at a distance apart in the circumferential direction of the pipe  4 , i.e., they are each distributed separately in the circumferential direction from the pipe  4 . This yields more or less a star-shaped arrangement of the branch pipes  11 ,  12 ,  13  in the branch section  14 . While the first branch pipe  11  has a straight radial path with respect to the pipe  4 , the second branch pipe  12  and the third branch pipe  13  are each bent by an angle of approximately 90°. These two branch pipes  12 ,  13  thus have a radial section, and also an axial section. The respective radial section extends from the branch section  14  in a straight line radially with respect to the pipe  4  and develops into the axial section running parallel to the longitudinal direction of the pipe  4  via a 90° bend within the first resonator chamber  6 .  
      In order for the three Helmholtz resonators  6 - 11 ,  7 - 12 ,  8 - 13  to have different resonant frequencies, they may differ from one another with regard to the volumes of the resonator chamber  6 ,  7 ,  8  and/or the branch pipes  11 ,  12 ,  13 . In the example, the three branch pipes  11 ,  12 ,  13  are of different lengths and are also equipped with different cross sections. The resonator chambers  6 ,  7 ,  8  in the exemplary embodiment have the same cross sections with regard to the longitudinal direction of the housing  5 . To nevertheless achieve different volumes for the resonator chambers  6 ,  7 ,  8 , they may have different axial extents in the longitudinal direction of the housing. For example, the first resonator chamber  6  is longer in the longitudinal direction of the housing than the other two resonator chambers  7 ,  8 . In this example, the volumes of the second resonator chamber  7  and the third resonator chamber  8  are approximately equal.  
      Due to the fact that the resonator chambers  6 ,  7 ,  8  of the pipe  4  and the branch pipes  11 ,  12 ,  13  are accommodated in a shared housing  5 , the muffler  3  has a comparatively simple design which can be implemented relatively inexpensively. The shared branch section  14  in which all the branch pipes  11 ,  12 ,  13  branch off from the pipe  4  contributes to this. The axial dimension of the branch section  14  in the exemplary embodiment shown here corresponds to the diameter of one of the branch pipes measured in the longitudinal direction of the pipe  4 , namely here the first branch pipe  11 . Therefore, the branch section  14  is extremely short. The branch section  14  may preferably be a pipe section that is produced separately with respect to the axial sections of the pipe  4  adjacent thereto, this separate pipe section being pre-mountable in particular with the radial sections of the branch pipes  11 ,  12 ,  13  or with the complete branch pipes  11 ,  12 ,  13 . This creates a pre-mountable unit which can be installed relatively easily into the pipe  4  and into the housing  5  within the context of the final assembly.  
      In an exemplary embodiment illustrated herein, the muffler  3  also has an absorption chamber  15  communicating with the pipe  4 . The absorption chamber  15  is arranged in the housing  5 . To form the absorption chamber  15 , a sleeve  16  is provided, preferably being arranged in the housing  5  in such a way that it surrounds the pipe  4  in an axially parallel direction, preferably concentrically, in a longitudinal section. In this way, the absorption chamber  15  is formed radially between the pipe  4  and the sleeve  16 . The sleeve  16  is sealed on its axial ends with plates, with the pipe  4  passing through them. The sleeve  16  is preferably dimensioned and arranged with respect to the pipe  4  in such a way that the absorption chamber  15  in the longitudinal section completely surrounds the pipe  4  in the circumferential direction. In addition, the sleeve  16  is preferably of such dimensions and arranged in the housing  5  in such a way that it dose not touch the jacket of the housing  5 .  
      The sleeve  16  and thus the absorption chamber  15  are of such dimensions in the axial direction, i.e., in the longitudinal direction of the pipe  4  and/or in the longitudinal direction of the housing  5  in the present case that they extend through both partitions  9 ,  10 . At the same time the absorption chamber  15  and/or the sleeve  16  passes through the second resonator chamber  7  and into the first resonator chamber  6  at one end and also into the third resonator chamber  8  at the other end.  
      To facilitate entry of the airborne sound entrained in the exhaust gas into the absorption chamber  15 , the pipe  4  is designed to be permeable for airborne sound in the longitudinal section surrounded by the absorption chamber  15 . This is achieved with the help of perforation  17 , for example, which may be formed by a plurality of individual holes  18 , for example. The absorption chamber  15  is sealed airtight with respect to the resonator chambers  6 ,  7 ,  8 . With the help of the absorption chamber  15 , high-frequency and higher-frequency sound components can be suppressed. The absorption chamber  15  may be filled with a suitable absorption material  19 .  
      As already mentioned above, the pipe  4 , the sleeve  16  and the branch pipes  12 ,  13  may extend through the axial end faces of the housing  5  and/or through the partitions  9 ,  10  and/or through the plates of the sleeve  16 , and airtight connections are possible in particular. Likewise, sliding seats may be provided in at least some cases to be able to compensate for thermally induced expansion effects. Such sliding seats can be implemented in a sufficiently airtight manner. The individual components of the muffler  3 , in particular the pipe  4 , the sleeves  16 , the branch pipes  11 ,  12 ,  13 , the housing  5  and the partitions  9 ,  10  are preferably made of metal, in particular steel or stainless steel.