Patent ID: 8215450

Claim:
An exhaust muffler device for reducing sounds associated with pressure waves of combustion gases exhausted from an internal combustion engine through an exhaust pipe, comprising: an outer housing having inlet-side and outlet-side walls disposed to be spaced apart from each other in a longitudinal direction to define a sealed chamber; an inlet pipe extending through said inlet-side wall so as to permit entry of exhaust gas into said sealed chamber; an outlet pipe which is disposed in said outlet-side wall and which extends along an outlet axis into said sealed chamber, said exhaust muffler device further comprises: an initial expansion subchamber disposed in said sealed chamber, and having a first proximate wall which is spaced apart from said inlet-side wall by a first distance, and which is disposed to permit said inlet pipe to extend therethrough, a first distal wall which is spaced apart from said first proximate wall in the longitudinal direction to serve as a barrier to obstruct flow path of main stream of the exhaust gas, and a first surrounding partition wall which is disposed between said first proximate wall and said first distal wall; and a pre-outlet subchamber disposed in said sealed chamber, and having a second proximate wall which is spaced apart from said inlet-side wall by a second distance, a second distal wall which is spaced apart from said second proximate wall in the longitudinal direction, and which is disposed to permit said outlet pipe to extend therethrough, and a second surrounding partition wall which is disposed between said second proximate wall and said second distal wall to define a tubular passage, said tubular passage being configured to have a direction change region which is juxtaposed to said first surrounding partition wall in a direction transverse to the longitudinal direction, and which is disposed downstream of said initial expansion sub-chamber by virtue of an internal port in said second surrounding partition wall that extends through said first surrounding partition wall, and a rejoining region which is disposed downstream of said direction change region and upstream of said outlet pipe, and which extends along the outlet axis of said outlet pipe, said second surrounding partition wall having a plurality of second communicating perforations such that portion of the exhaust gas from the main stream flowing out of said second communicating perforations at an upstream side into said sealed chamber is permitted to re-enter into said rejoining region through said second communicating perforations at a downstream side to be thereby entrained in the main stream before flowing out of said outlet pipe.