Exhaust system of internal combustion engine

Abstract

An object of the present invention is to provide a technology that enables efficient utilization of the purification capability of an exhaust gas purification apparatus. To achieve the object, according to the present invention, in an exhaust system of an internal combustion engine provided with a reducing agent supply apparatus that supplies a reducing agent to the exhaust gas before it flows into an exhaust gas purification apparatus, an extension chamber is provided downstream of the position at which the reducing agent supply apparatus supplies the reducing agent to the exhaust gas and upstream of the exhaust gas purification apparatus. The extension chamber is provided with a back step flow creating portion that creates a back step flow of the exhaust gas in the extension chamber and a swirling flow creating portion that creates a swirling flow. As the exhaust gas and the reducing agent flow into the extension chamber as described above, the mixing of the exhaust gas and the reducing agent is promoted by a combined effect of the back step flow and the swirling flow, and partial localization of the distribution of the flow rate is eliminated.

1 . (canceled) 
     
     
         2 . An exhaust system of an internal combustion engine comprising:
 an exhaust gas purification apparatus disposed in an exhaust pipe of the internal combustion engine;   an extension chamber provided in the middle of the exhaust pipe upstream of the exhaust gas purification apparatus, the extension chamber having an internal space with a cross sectional area larger than a cross sectional area of a passage in the exhaust pipe;   a reducing agent supply apparatus that supplies a reducing agent to exhaust gas flowing into said extension chamber;   a back step flow creating portion that creates a back step flow of exhaust gas in the interior space of said extension chamber; and   a swirling flow creating portion that changes the flow of exhaust gas flowing into the interior space of said extension chamber into a swirling flow,   wherein said back step flow creating portion comprises an inlet port that brings the interior of the exhaust pipe located upstream of said extension chamber and the interior space of said extension chamber into communication with each other through a step, and said swirling flow creating portion comprises a guide wall surface that is oriented obliquely to the inflowing direction of the exhaust gas flowing into said extension chamber.   
     
     
         3 . An exhaust system of an internal combustion engine according to  claim 2 , wherein said extension chamber is disposed in such a way that the axis of said extension chamber is oriented obliquely to the inflowing direction of the exhaust gas flowing into said extension chamber, and said guide wall surface is an inner wall surface of said extension chamber. 
     
     
         4 . An exhaust system of an internal combustion engine according to  claim 2 , wherein said guide wall surface is a surface of a projection provided on an inner wall surface of said extension chamber. 
     
     
         5 . An exhaust system of an internal combustion engine comprising:
 an exhaust gas purification apparatus disposed in an exhaust pipe of the internal combustion engine;   an extension chamber provided in the middle of the exhaust pipe upstream of said exhaust gas purification apparatus, the extension chamber having an internal space with a cross sectional area larger than a cross sectional area of the passage of the exhaust pipe; and   a reducing agent supply apparatus that supplies a reducing agent to exhaust gas flowing into said extension chamber,   wherein said extension chamber is disposed in such a way that the axis of said extension chamber is oriented obliquely to the inflowing direction of the exhaust gas flowing into said extension chamber, and said extension chamber has an inlet port that brings the interior of the exhaust pipe located upstream of said extension chamber and the interior space of said extension chamber into communication with each other through a step.   
     
     
         6 . An exhaust system of an internal combustion engine comprising:
 an exhaust gas purification apparatus disposed in an exhaust pipe of the internal combustion engine;   an extension chamber provided in the middle of the exhaust pipe upstream of said exhaust gas purification apparatus, the extension chamber having an internal space with a cross sectional area larger than a cross sectional area of the passage of the exhaust pipe; and   a reducing agent supply apparatus that supplies a reducing agent to exhaust gas flowing into said extension chamber,   wherein said extension chamber has an inner wall surface that is oriented obliquely to the inflowing direction of the exhaust gas flowing into said extension chamber, and an inlet port that brings the interior of the exhaust pipe located upstream of said extension chamber and the interior space of said extension chamber into communication with each other through a step.   
     
     
         7 . An exhaust system of an internal combustion engine according to  claim 2 , wherein said step is provided only in the portion other than the portion by which the inner bottom surface of the inlet port. 
     
     
         8 . An exhaust system of an internal combustion engine according to  claim 2 , wherein the distance from the upstream end of the interior space of said extension chamber to the downstream end thereof is equal to or smaller than seven times the height of said step. 
     
     
         9 . An exhaust system of an internal combustion engine according to  claim 2 , wherein said extension chamber is configured to have a hollow cylindrical shape. 
     
     
         10 . An exhaust system of an internal combustion engine according to  claim 5 , wherein said step is provided only in the portion other than the portion by which the inner bottom surface of the inlet port. 
     
     
         11 . An exhaust system of an internal combustion engine according to  claim 6 , wherein said step is provided only in the portion other than the portion by which the inner bottom surface of the inlet port. 
     
     
         12 . An exhaust system of an internal combustion engine according to  claim 5 , wherein the distance from the upstream end of the interior space of said extension chamber to the downstream end thereof is equal to or smaller than seven times the height of said step. 
     
     
         13 . An exhaust system of an internal combustion engine according to  claim 6 , wherein the distance from the upstream end of the interior space of said extension chamber to the downstream end thereof is equal to or smaller than seven times the height of said step. 
     
     
         14 . An exhaust system of an internal combustion engine according to  claim 5 , wherein said extension chamber is configured to have a hollow cylindrical shape. 
     
     
         15 . An exhaust system of an internal combustion engine according to  claim 6 , wherein said extension chamber is configured to have a hollow cylindrical shape.