Muffler

Abstract

A muffler including an inner pipe through which exhaust gas flows and communication portions formed in a peripheral wall of the inner pipe and including holes that communicate a gas flow path of the inner pipe with a muffling chamber. Each of the communication portions further include an inside deformation portion formed by deforming a portion of the peripheral wall toward the pipe inside, and having a downstream side end portion separated from the peripheral wall; and an outside deformation portion formed by deforming a portion of the peripheral wall adjacent to the downstream side of the inside deformation portion toward the pipe outside, and having a upstream side end portion separated from the peripheral wall. The holes are formed by the downstream side end portion of the inside deformation portion and the upstream side end portion of the outside deformation portion.

What is claimed is: 
     
         1 . A muffler comprising:
 an inner pipe which has an interior through which exhaust gas flows; and   a plurality of communication portions formed in a peripheral wall of the inner pipe, each of the communication portions including
 holes that place an exhaust gas flow path of the inner pipe interior in communication with a muffling chamber at the inner pipe exterior, 
 an inside deformation portion formed by deforming a portion of the peripheral wall toward the inner pipe inside, and that has a gas flow downstream side end portion separated from the peripheral wall, and 
 an outside deformation portion formed by deforming a portion of the peripheral wall adjacent to the gas flow downstream side of the inside deformation portion toward the inner pipe outside, and that has a gas flow upstream side end portion separated from the peripheral wall; 
   wherein the holes are formed by the downstream side end portion of the inside deformation portion and the upstream side end portion of the outside deformation portion.   
     
     
         2 . The muffler of  claim 1 , wherein the profile of the holes is substantially an ellipse with the direction of the major axis aligned with the peripheral direction of the inner pipe. 
     
     
         3 . The muffler of  claim 1 , wherein the profile of the holes is a substantially rectangular shape with a length direction aligned with the peripheral direction of the inner pipe. 
     
     
         4 . The muffler of  claim 1 , wherein the amount of deformation of the inside deformation portion toward the inner pipe inside is less than the amount of deformation of the outside deformation portion toward the inner pipe outside. 
     
     
         5 . The muffler of  claim 1 , wherein the cross-section profiles of the inside deformation portion and the outside deformation portion taken along planes orthogonal to the inner pipe peripheral direction are shaped approximately as arcs of a circle or an ellipse. 
     
     
         6 . The muffler of  claim 1 , wherein the inside deformation portion and the outside deformation portion include a parallel portion that runs parallel to the direction of gas flow. 
     
     
         7 . The muffler of  claim 1 , further comprising:
 an outer shell;   wherein the inner pipe is provided within an interior of the outer shell.   
     
     
         8 . A muffler comprising:
 an outer shell including a plurality of muffling chambers;   a plurality of inner pipes, each inner pipe having an interior through which exhaust gas flows, the plurality of inner pipes provided transverse to the muffling chambers within an interior of the outer shell; and   a plurality of communication portions formed in a peripheral wall of at least one of the inner pipes, each of the communication portions including
 holes that place an exhaust gas flow path of the inner pipe interior in communication with a muffling chamber at the inner pipe exterior, 
 an inside deformation portion formed by deforming a portion of the peripheral wall toward the inner pipe inside, and that has a gas flow downstream side end portion separated from the peripheral wall, and 
 an outside deformation portion formed by deforming a portion of the peripheral wall adjacent to the gas flow downstream side of the inside deformation portion toward the inner pipe outside, and that has a gas flow upstream side end portion separated from the peripheral wall; 
   wherein the holes are formed by the downstream side end portion of the inside deformation portion and the upstream side end portion of the outside deformation portion.   
     
     
         9 . An inner pipe of a muffler comprising:
 a plurality of communication portions formed in a peripheral wall of the inner pipe, each of the communication portions including
 holes that place an exhaust gas flow path of the inner pipe interior in communication with a muffling chamber at the inner pipe exterior, 
 an inside deformation portion formed by deforming a portion of the peripheral wall toward the inner pipe inside, and that has a gas flow downstream side end portion separated from the peripheral wall, and 
 an outside deformation portion formed by deforming a portion of the peripheral wall adjacent to the gas flow downstream side of the inside deformation portion toward the inner pipe outside, and that has a gas flow upstream side end portion separated from the peripheral wall; 
   wherein the holes are formed by the downstream side end portion of the inside deformation portion and the upstream side end portion of the outside deformation portion.