Exhaust gas purification apparatus

Abstract

An adhesion preventing member 21 formed in a substantially circular-cylindrical shape is provided in an exhaust pipe 2. Urea water injected from an injection nozzle 6 is introduced into an inner peripheral side of the adhesion preventing member 21 through an opening portion 21 a, and hence adhesion of the urea water to an inner peripheral surface 2 a of the exhaust pipe 2 is inhibited. In the adhesion preventing member 21, there are provided five dispersion members 22 each having a plurality of through-holes 22 a and urea water is dispersed in the exhaust pipe 2 by flowing through through-holes 22 a. The adhesion preventing member 21 and the dispersion members 22 are arranged at a part spaced apart from the inner peripheral surface 2 a of the exhaust pipe 2, that is, at a part which is heated to high temperature in the exhaust pipe 2.

What is claimed is: 
     
         1 . An exhaust gas purification apparatus, comprising:
 an exhaust pipe in which an exhaust gas discharged from an internal combustion engine flows;   urea-water addition means for injecting urea water into the exhaust pipe; and   a reduction catalyst for purifying nitrogen oxides contained in the exhaust gas by using ammonia generated from the urea water as a reducing agent,   wherein the exhaust pipe comprises therein at least one of:
 a plate-like adhesion preventing member extending along a flow direction of the exhaust gas; and 
 a plate-like dispersion member extending along the flow direction of the exhaust gas and provided with a plurality of through-holes through which the urea water injected from the urea-water addition means is flowable, and 
   wherein the adhesion preventing member and the dispersion member are arranged at a part that faces the urea-water addition means and is heated to high temperature in the exhaust pipe.   
     
     
         2 . An exhaust gas purification apparatus according to  claim 1 , comprising the adhesion preventing member,
 wherein the adhesion preventing member is formed of a substantially cylindrical member, and includes a urea-water introducing portion for introducing the urea water injected from the urea-water addition means into an inner peripheral side of the adhesion preventing member.   
     
     
         3 . An exhaust gas purification apparatus according to  claim 1 , wherein the urea-water addition means injects the urea water into a fan shape substantially flat in a direction substantially perpendicular to the flow direction of the exhaust gas. 
     
     
         4 . An exhaust gas purification apparatus according to  claim 1 , further comprising a NO x  sensor for detecting concentration of the nitrogen oxides contained in the exhaust gas on an upstream side of the reduction catalyst,
 wherein the NO x  sensor is arranged at a part separated from the urea-water addition means by the adhesion preventing member.   
     
     
         5 . An exhaust gas purification apparatus according to  claim 1 , comprising both the adhesion preventing member and the dispersion member, wherein the dispersion member is arranged between the urea-water addition means and the adhesion preventing member. 
     
     
         6 . An exhaust gas purification apparatus according to  claim 1 , comprising a plurality of the dispersion members.