Exhaust emission control device

Abstract

An exhaust emission control device includes a reducing agent adding valve for injecting a reducing agent into an exhaust pipe. The adding valve has a tip end portion having a nozzle and facing an internal space of the exhaust pipe. The tip end portion is disposed outwardly of an inner circumferential surface of the exhaust pipe. The adding valve is kept out of direct striking contact with the exhaust gas and hence is substantially free from thermal degradation and adhesion of deposits.

1 . An exhaust emission control device comprising:
 an exhaust pipe for the passage therethrough of exhaust gas; and   a reducing agent adding valve for injecting a reducing agent into the exhaust pipe,   wherein the reducing agent adding valve has a tip end portion having a nozzle and facing an internal space of the exhaust pipe, the tip end portion being disposed outwardly of an inner circumferential surface of the exhaust pipe.   
   
   
       2 . The exhaust emission control device according to  claim 1 , further comprising: a collision scattering mechanism disposed in the exhaust pipe at a position intersecting with an injecting direction of the reducing agent for collision with the injected reducing agent to scatter the reducing agent into the exhaust gas. 
   
   
       3 . The exhaust emission control device according to  claim 2 , wherein the exhaust pipe has a tubular wall portion and a mounting portion formed integrally with the tubular wall portion, the reducing agent adding valve being mounted to the mounting portion of the exhaust pipe. 
   
   
       4 . The exhaust emission control device according to  claim 2 , wherein the reducing agent adding valve is disposed in such a manner as to inject the reducing agent in a direction perpendicular to an axial direction of the exhaust pipe, and the collision scattering mechanism is disposed directly beneath the nozzle of the reducing agent adding valve. 
   
   
       5 . The exhaust emission control device according to  claim 3 , wherein the reducing agent adding valve is disposed in such a manner as to inject the reducing agent in a direction perpendicular to an axial direction of the exhaust pipe, and the collision scattering mechanism is disposed directly beneath the nozzle of the reducing agent adding valve. 
   
   
       6 . The exhaust emission control device according to  claim 2 , wherein the collision scattering mechanism is configured to convert a stream of exhaust gas flowing in the axial direction of the exhaust pipe into a swirling flow of exhaust gas running in a circumferential direction of the exhaust pipe. 
   
   
       7 . The exhaust emission control device according to  claim 6 , wherein the collision scattering mechanism includes a plurality of fan-shaped fins tilted in a downstream direction of the exhaust pipe and arranged successively in a circumferential direction of the exhaust pipe so as to convert the stream of exhaust gas into the swirling flow of exhaust gas. 
   
   
       8 . The exhaust emission control device according to  claim 6 , wherein the nozzle of the adding valve has a longitudinal axis offset from a longitudinal axis of the exhaust pipe. 
   
   
       9 . The exhaust emission control device according to  claim 7 , wherein the nozzle of the adding valve has a longitudinal axis offset from a longitudinal axis of the exhaust pipe.