Exhaust device of engine

Abstract

A muffler in an exhaust device of an engine includes a casing, a first expansion chamber, a second expansion chamber, and a third expansion chamber separately formed in the casing, and a first communication pipe, a second communication pipe, and a third communication pipe provided in the casing. The rear exhaust pipe is connected to the first expansion chamber, the first expansion chamber communicates with the third expansion chamber via the first communication pipe, the first expansion chamber communicates with the second expansion chamber via the second communication pipe, and the second expansion chamber communicates with an outside of the casing via the third communication pipe. The third expansion chamber does not communicate with an outside of the third expansion chamber except that the third expansion chamber communicates with the first expansion chamber via the first communication pipe.

What is claimed is: 
     
         1 . An exhaust device of an engine, the exhaust device comprising: an exhaust pipe through which an exhaust gas from the engine flows; and a muffler provided on a downstream side of the exhaust pipe,
 the muffler including   a casing,   a first expansion chamber, a second expansion chamber, and a third expansion chamber separately formed in the casing, and   a first communication pipe, a second communication pipe, and a third communication pipe provided in the casing, wherein   the exhaust pipe is connected to the first expansion chamber, the first expansion chamber communicates with the third expansion chamber via the first communication pipe, the first expansion chamber communicates with the second expansion chamber via the second communication pipe, the second expansion chamber communicates with, via the third communication pipe, another chamber separately formed from any of the first expansion chamber, the second expansion chamber, and the third expansion chamber outside or inside the casing, and the third expansion chamber does not communicate with an outside of the third expansion chamber except that the third expansion chamber communicates with the first expansion chamber via the first communication pipe.   
     
     
         2 . The exhaust device of an engine according to  claim 1 , wherein the second expansion chamber is arranged between the first expansion chamber and the third expansion chamber in the casing. 
     
     
         3 . The exhaust device of an engine according to  claim 2 , wherein the muffler is provided on a rear side of the engine in a vehicle provided with the engine, the casing has a shape long in a front-rear direction of the vehicle, and the first expansion chamber is arranged on a rear side of the third expansion chamber in the casing. 
     
     
         4 . The exhaust device of an engine according to  claim 3 , wherein the first expansion chamber is arranged in a rearmost part in the casing, and the third expansion chamber is arranged in a frontmost part in the casing. 
     
     
         5 . The exhaust device of an engine according to  claim 1 , wherein an opening area of an end portion opening to the first expansion chamber in the first communication pipe is equal to or larger than an opening area of an end portion opening to the first expansion chamber in the exhaust pipe. 
     
     
         6 . The exhaust device of an engine according to  claim 1 , wherein the first communication pipe is one of a plurality of first communication pipes, and the muffler includes the plurality of the first communication pipes. 
     
     
         7 . The exhaust device of an engine according to  claim 6 , wherein a total of opening areas of end portions opening to the first expansion chamber in the plurality of first communication pipes is equal to or larger than an opening area of an end portion opening to the first expansion chamber in the exhaust pipe.