Internal combustion engine silencer

Abstract

A muffler for internal combustion engines, in order to achieve a high attenuating effect without reducing the attenuating effect in the high revolution range of the engine, comprising one or more expanding chambers 11 through 13 formed in a muffler 1 , an inlet pipe 5 which opens into a expanding chamber 11 and introduces exhaust gas into the muffler 1 , and an outlet pipe 6 which opens into other expanding chamber 13 and introduces exhaust gas out of the muffler 1 . In the muffler, the exhaust gas discharged through an aperture 5 a of this inlet pipe 5 is inverted once or more times in the muffler 1 and is introduced into an aperture 6 a of the outlet pipe 6 . In a contraflow area L 2 in which the flowing direction C of exhaust gas flowing in the expanding chambers 11 through 13 and the flowing direction E of exhaust gas flowing in the outlet pipe 6 are not the same, interference holes 7 composing of a plurality of small holes communicating with the expanding chambers 11 through 13 are bored in the outlet pipe 6 . The aperture area of the small holes 7 is kept at not less than 1% but not more than 5% of the surface area of the outlet pipe in the contraflow area L 2.

1 . A muffler for internal combustion engines comprising at least one expanding chamber formed within the muffler, an inlet pipe opening into said expanding chamber to introduce exhaust gas into the muffler, and an outlet pipe opening into said expanding chamber to introduce exhaust gas out of the muffler, in which exhaust gas discharged from an opening in said inlet pipe is inverted once or more and then introduced into an opening in said outlet pipe, wherein, in a contraflow area in which a flowing direction of exhaust gas flowing in said expanding chamber and a flowing direction of exhaust gas flowing in said outlet pipe are different, interference holes composed of a plurality of small holes communicating with said expanding chamber are bored in said outlet pipe, and the total aperture area of said interference holes is not less than 1% but not more than 5% of a surface area of said outlet pipe in said contraflow area.  
   
   
       2 . The muffler for internal combustion engines as claimed in  claim 1 , wherein said at least one expanding chamber is a plurality of expanding chambers, said inlet pipe is disposed to open into one of them to introduce exhaust gas into the muffler, and said outlet pipe is disposed to open into other one to introduce exhaust gas out of the muffler.  
   
   
       3 . The muffler for internal combustion engines as claimed in claim, wherein said interference holes are disposed in a range of not less than 75% of a length of said outlet pipe in said contraflow area.  
   
   
       4 . The muffler for internal combustion engines as claimed in  claim 1 , wherein bypass holes composing of a plurality of small holes communicating with said expanding chamber are bored downstream from a part of said outlet pipe in said contraflow area, and a total aperture area of said interference holes and said bypass holes together is not greater than a sectional area of a passage in said outlet pipe.  
   
   
       5 . The muffler for internal combustion engines as claimed in  claim 1 , wherein interference holes composing of a plurality of small holes communicating with said expanding chamber are bored in said contraflow section of said inlet pipe.