Patent Publication Number: US-7708114-B2

Title: Sound-attenuating muffler having reduced back pressure

Description:
FIELD AND BACKGROUND OF THE INVENTION 
   The present invention relates to sound-attenuating mufflers for internal combustion engines and, more particularly, to sound-attenuating mufflers generating reduced back pressure. 
   Numerous muffler constructions have been proposed for the attenuation of the sound component of an exhaust gas stream from an internal combustion engine. The present invention is an improvement to the low back-pressure sound-attenuating mufflers of U.S. Pat. Nos. 6,286,623 and 6,776,257 to the present inventor and incorporated herein by reference. 
   The low back-pressure sound-attenuating mufflers of U.S. Pat. Nos. 6,286,623 and 6,776,257 are well suited for sports cars. 
   There is therefore a need for a low back-pressure sound-attenuating muffler having a lower decibel output than the previous mufflers so as to be usable on regular passenger vehicles. 
   SUMMARY OF THE INVENTION 
   The present invention is a low back-pressure sound-attenuating muffler having a lower decibel output than the previous mufflers so as to be usable on regular passenger vehicles. 
   According to the teachings of the present invention there is provided, a muffler for an internal combustion engine comprising: (a) a housing having an inlet end with an inlet opening formed for a flow of exhaust gases into the housing and an outlet end with an outlet opening formed for a discharge of exhaust gases from the housing; (b) a first chamber and a second chamber sequentially arranged within the housing; (c) a perforated pipe passing longitudinally through a central region of both the first and the second chambers such that the perforated pipe extends partially into the first chamber, extends a full length of the second chamber; wherein the perforations allow the exhaust gases to enter the perforated pipe so as to be directed through an interior of the perforated pipe and into the third chamber and a partition separating the first and the second chambers includes a hole that enables some of the exhaust gases to pass from the first chamber into the second chamber without passing through the central perforated pipe. 
   According to a further teaching of the present invention, the perforated pipe has a diameter that is 105%-110% of the diameter of the inlet opening. 
   According to a further teaching of the present invention, an upstream end of the perforated pipe is partially sealed. 
   According to a further teaching of the present invention, an upstream end of the perforated pipe is 60%-80% open. 
   According to a further teaching of the present invention, perforations in the perforated pipe extending partially into the first chamber cover 25%-35% of the surface of the perforated pipe and, perforations in the perforated pipe extending the full length of the second chamber cover 60%-75% of the surface of the perforated pipe. 
   According to a further teaching of the present invention, there is also provided: (d) a third chamber containing a deflection element, the perforated t 0  pipe extending so as to open at its downstream end into a third chamber, thereby directing the exhaust gases toward the deflection element; and (e) a fourth chamber configured to channel the flow of gas to the outlet opening. 
   According to a further teaching of the present invention, the deflection element is a hollow pyramid having interior surfaces and exterior surfaces joining at a first end to form a pyramidal apex, the pyramidal apex pointing toward the inlet end of the muffler and extending at a second end to form an open base interconnected to a partition separating the third and the fourth cambers. 
   According to a further teaching of the present invention, the deflection element is a dome-shaped partition having an exterior surface, a first end of the exterior surface pointing toward the inlet end of the muffler, and widening out at a second end to form a base interconnected to a partition separating the third and the fourth cambers. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
       FIG. 1  is a perspective, cut open view of the muffler of U.S. Pat. No. 6,286,623; 
       FIG. 2  is a perspective, cut-open view of the muffler of U.S. Pat. No. 6,776,257; 
       FIG. 3  is a perspective, cut-open view of a first preferred embodiment of a muffler constructed and operational according to the teachings of the present invention; 
       FIG. 4  is a perspective, cut-open view showing the flow path of exhaust gases through the embodiment of  FIG. 3 ; 
       FIG. 5  is a perspective, cut-open view of a second preferred embodiment of a muffler constructed and operational according to the teachings of the present invention; and 
       FIG. 6  is a perspective, cut-open view showing the flow path of exhaust gases through the embodiment of  FIG. 5 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention is a low back-pressure sound-attenuating muffler having a lower decibel output than the previous mufflers so as to be usable on regular passenger vehicles. 
   The principles and operation of low back-pressure sound-attenuating muffler according to the present invention may be better understood with reference to the drawings and the accompanying description. 
   By way of introduction reference is made to the prior art low back-pressure sound-attenuating mufflers of U.S. Pat. Nos. 6,286,623 and 6,776,257 to the present inventor 
     FIG. 1  shows a cut open view of the muffler  200  of U.S. Pat. No. 6,286,623. The muffler  200  consists of an elongated housing  202  having an inlet  206  for introducing the exhaust gases, an outlet  208  for discharging the exhaust gases, a pyramidal partition  250  and converging partitions  240  and  260 . 
   The exhaust gases from the internal combustion engine are introduced into the muffler  200  through the inlet  206 . The exhaust gases enter the housing  202  and flow longitudinally through the length of muffler  200  passing first through chamber  212 . The exhaust gases exit chamber  212  through an opening in partition  240 . Partition  240  is shaped like a funnel (or truncated pyramid), disposed such that the opening in the partition  240  centers the flow of exhaust gases within housing  202 . The flow exhaust gases then enters the second chamber  214  and encounters the apex  230  of pyramidal partition  250 , causing the flow to be deflected along the exterior faces of pyramidal partition  250  and towards the interior surface of the outer wall of housing  202 . 
   The exhaust gases flow through the four spaces  252  formed by the rugose base of the pyramidal partition  250 . A substantial first portion of the exhaust gases continue to flow in the direction of the outlet pipe  208 , thereby creating a low pressure region inside the pyramidal partition  250 . Consequently, a second portion of the exhaust gases changes direction and enters (is drawn into) the inside region of pyramidal partition  250  before continuing toward the outlet pipe  208 . The exhaust gases flow through converging partition  260 , which is substantially identical in shape and in disposition to converging partition  240 . Thus, the flow of exhaust gases enters the third chamber  216  and is again centered within the housing  202  by the partition outlet  224  before being discharged through outlet pipe  208 . 
     FIG. 2  shows a perspective, cut-open view of the muffler  300  of U.S. Pat. No. 6,776,257. Muffler  300  includes an elongated housing  302  having an inlet  306  for introducing the exhaust gases, an outlet  308  for discharging the exhaust gases, a main partition  350 , and an aligning partition  340 . 
   The exhaust gases from the internal combustion engine are introduced through the inlet  306 . The exhaust gases enter housing  302  and flow longitudinally through the length of muffler  300  passing first through chamber  312 . The exhaust gases exit chamber  312  through an opening in partition  340 . Partition  340  is preferably shaped like a funnel (or truncated pyramid), and most importantly, is disposed such that the exhaust gas flow is centered within the housing  302  as the exhaust gases enter the second chamber  314  and the flow of exhaust gases encounters the top of domed partition  350 , causing the flow to be deflected along the exterior face of domed partition  350 . 
   The exhaust gases flow through openings  352  in the sides of domed partition  350  Openings  352  are preferably disposed on opposite sides of domed partition  350 . 
   Subsequently, the exhaust gases continue to flow in the direction of S outlet pipe  308 , thereby creating a low pressure region inside domed partition  350 . Consequently, a portion of the exhaust gases change direction and enter (are drawn into) the inside of domed partition  350  before continuing in the direction of outlet pipe  308 . The exhaust gases flow through converging partition  360 , which is advantageously similar in shape and in disposition to converging partition  340 , and enter the third chamber  316  before being discharged through outlet pipe  308 . 
   Generally speaking, the embodiments of U.S. Pat. Nos. 6,286,623 and 6,776,257 as briefly described above include an inlet chamber, a deflection chamber in which a deflection element is deployed and an outlet chamber. 
   The present invention relates to an improvement that may be used to benefit both of the previous muffler embodiments described above. Specifically, the present invention includes an improved inlet configuration having first and second sequential chambers with a perforated central pipe passing longitudinally through a central region of both chambers for directing the exhaust gases into the third chamber in which the deflection element is deployed. Additionally, the partition separating the first and second chamber has a hole that enables some of the gas to pass from the first chamber into the second chamber not through the central pipe. 
   Described below are two exemplary embodiments of the present inventor The embodiment of  FIGS. 3 and 4  relates to a muffler combining the features of the present invention with the pyramidal partition deflection element of U.S. Pat. No. 6,286,623. The embodiment of  FIGS. 5 and 6  relates to a muffler combining the features of the present invention with the domed partition deflection element of U.S. Pat. No. 6,776,257 
   Referring now to the drawings,  FIGS. 3 and 4  illustrate a muffler  2  generally defined by a housing  4 . An inlet  6  is provided in the inlet end of the muffler for introducing exhaust gases into the first chamber  10 . The improved inlet configuration has the first chamber  10  and a second chamber  12  sequentially arranged within muffler  2 . A perforated pipe  20 , with its upstream end  22  partially sealed, passing longitudinally through a central region of both the first  10  and the second  12  chambers such that perforated pipe  20  extends partially into the first chamber  10  and extends the full length of the second chamber  12 . Perforated pipe  20  extends at its downstream end  24  through partition  40  and opens into the third chamber  14 . The perforations  26   a  allow the exhaust gases to enter the perforated pipe  20  from the first chamber  10 , while perforations  26   b  allow the exhaust gases to enter the perforated pipe  20  from the second chamber  12 . Once the exhaust gases enter perforated pipe  20  they are directed through the interior of perforated pipe  20  and into the third chamber  14 . As illustrated here, the perforations  26  are formed over a predetermined percentage of the surface of pipe  20 . 
   The partition  30  separating the first and second chambers includes a preferably round hole  32  that enables some of the gas to pass from the first chamber  10  into the second chamber  12  without passing through the central perforated pipe  20 . Exhaust gases that enter the second chamber  12  then pass through the perforations  26  in the section of perforated pipe  20  deployed in second chamber  12 . It will be appreciated that hole  32  may be of substantially any suitable size and shape. 
   With this basic understanding of the general structure of the first two chambers of the muffler, it will be appreciated that inlet  6  is configured for attachment to the exhaust pipe of the vehicle on which the muffler is deployed and therefore may vary in diameter depending on the specifications of the of the vehicle manufacturer. It will be appreciated that inlet  6  may be configured as more that one inlet pipe. It will be readily understood that in such an embodiment, the percentages listed herebelow are applied to the combined size of all inlet pipes. Similarly, the outlet pipe  8  may be configured as more that one outlet pipe and the percentages listed herebelow are applied to the combined size of all outlet pipes. 
   In order for the muffler of the present invention to perform at an optimum level, perforated pipe  20  has a diameter that is 100%-130% of the diameter of inlet pipe  6 . It will be appreciated that perforated pipe  20  may be implemented as more than one perforated pipe as long as the ratio of 100%-130% of the diameter of inlet pipe  6  is maintained. The upstream end  22  of the perforated pipe  20  is partially sealed so as to be 60%-80% open. The perforation holes in the perforated pipe  20  may range from 15 mm-55 mm in diameter. Perforations  26   a  cover between 20%-40% of the surface of perforated pipe  20 , while perforations  26   b  cover 50%-90% of the surface of perforated pipe  20 . Hole  32  configured in partition  30  has a diameter that is 60%-80% of the diameter of perforated pipe  20 . It will be appreciated that hole  32  may be implemented as a plurality of holes configured in partition  30 , however, the combined size of the opening still falls within the range of 60%-80% of the diameter of perforated pipe  20 . Further, embodiments in which the second chamber  12  is subdivided into a number of chambers through which perforated pipe  20  passes are within the scope of the present invention. It should be noted that these specifications apply to the embodiment of the present invention described bellow with regard to  FIGS. 5 and 6 , as well as any muffler constructed and operational according to the teachings of the present invention. 
   Similar to the muffler of  FIG. 1 , the flow of exhaust gases is centered within the housing  4  as the exhaust gases leaves the downstream end  24  of the perforated pipe  20 , enters the third chamber  14 . The flow of exhaust gases encounters the apex of pyramidal partition  50 , which is spaced a distance of 20 mm-60 mm from the downstream end  24  of the perforated pipe  20 , causing the flow to be deflected along the exterior faces of pyramidal partition  50  and towards the interior surface of the outer wall of housing  4 . 
   The exhaust gases flow then through the four spaces  52  formed by the rugose base of the pyramidal partition  50 . A substantial first portion of the exhaust gases continue to flow in the direction of the outlet pipe  120 , thereby creating a low pressure region inside the pyramidal partition  150 . Consequently, a second portion of the exhaust gases changes direction and enters (is drawn into) the inside region of pyramidal partition  50  before continuing toward the outlet pipe  8 . The exhaust gases flow through partition  60  and is again centered within the housing  100  as the exhaust gases enter the fourth chamber  16  before being discharged through outlet pipe  8 , formed in the outlet end of the muffler. 
   The arrows in  FIG. 4  illustrate the flow path of the exhaust gases through this embodiment of the muffler of the present invention. 
     FIGS. 5 and 6  illustrate a muffler  102  generally defined by a housing  4 , which includes an inlet configuration similar to the embodiment of  FIGS. 3 and 4 , therefore, the same reference numerals are used here to refer to corresponding components. It will be appreciated that the specifications relating to component size detailed above apply equally here as well. 
   An inlet  6  is provided in the inlet end of the muffler for introducing exhaust gases into the first chamber  10 . The improved inlet configuration of this embodiment also has the first chamber  10  and a second chamber  12  sequentially arranged within muffler  102 . A perforated pipe  20 , with its upstream end  22  sealed, passing longitudinally through a central region of both the first  10  and the second  12  chambers such that perforated pipe  20  extends partially into the first chamber  10  and extends the full length of the second chamber  12 . Perforated pipe  20  extends at its downstream end  24  through partition  40  and opens into the third chamber  14 . The perforations  26  allow the exhaust gases to enter the perforated pipe  20  so as to be directed through the interior of perforated pipe  20  and into the third chamber  14 . 
   The partition  30  separating the first and second chambers includes a preferably round hole  32  that enables some of the gas to pass from the first chamber  10  into the second chamber  12  without passing through the central perforated pipe  20 . Exhaust gases that enter the second chamber  12  then pass through the perforations  26  in the section of perforated pipe  20  deployed in second chamber  12 . It will be appreciated that in this embodiment as well, hole  32  may be of substantially any suitable size and shape. 
   Similar to the muffler of  FIG. 2 , the exhaust gas flow is centered within the housing  4  as the exhaust gases leaves the downstream end  24  of the perforated pipe  20 , and enters the third chamber  14  and the flow of exhaust gases encounters the top of domed partition  150 , causing the flow of exhaust gases to be deflected along the exterior face of domed partition  150 . Dome-shaped partition  150  having an exterior surface, a first end of the exterior surface points toward the inlet end of the muffler, and widening out at a second end to form a base, said dome-shaped partition having at least two partition openings disposed between said first end and said second end of said exterior surface 
   The exhaust gases flow through openings  152  in the sides of domed partition  150 . Openings  152  are preferably disposed on opposite sides of domed partition  150 . 
   Subsequently, the exhaust gases continue to flow in the direction of outlet pipe  8  formed in the outlet end of the muffler, thereby creating a low pressure region inside domed partition  150 . Consequently, a portion of the exhaust gases change direction and enter (are drawn into) the inside of domed partition  150  before continuing in the direction of outlet pipe  8 . The exhaust gases flow through an opening (not shown) partition  160 , and enter the fourth chamber  16  before being discharged through outlet pipe  8 . 
   The arrows in  FIG. 6  illustrate the flow path of the exhaust gases through this embodiment of the muffler of the present invention. 
   It will be appreciated that the above descriptions are intended only to serve as examples and that many other embodiments are possible within the spirit and the scope of the present invention.