Exhaust emission control device with additive injector

Abstract

An exhaust emission control apparatus is provided which is equipped with an additive injector to inject additive such as a urea aqueous solution into an exhaust pipe through which exhaust emissions flow. The exhaust pipe includes a straight section and a bent section. A catalyst such as a SCR (Selective Catalytic Reduction) catalyst is disposed downstream of the straight section. A hollow protrusion is formed on an outer peripheral wall of the bent section substantially in parallel to a longitudinal center line of the straight section. The protrusion has an opening formed in one of opposed ends thereof which communicates with inside the bent section. The additive injector is designed to produce a cone-shaped spray of additive and installed on the other end of the protrusion to inject the cone-shaped spray of additive into the exhaust pipe without interfering with at least a downstream edge of the opening.

1 . An exhaust emission control apparatus comprising:
 an exhaust pipe through which exhaust emission flow, said exhaust pipe including a straight section and a bent section extending from the straight section in an upstream direction of a flow of the exhaust emissions;   a catalyst disposed downstream of the straight section of said exhaust pipe in connection therewith;   a hollow protrusion having a length extending outside the said exhaust pipe from a peripheral wall of the bent section substantially in parallel to a longitudinal center line of the straight section, said protrusion having a first end and a second end opposed to the first end, said protrusion having an opening formed in the first end which communicates with inside the bent section of said exhaust pipe; and   an additive injector designed to produce a cone-shaped spray of additive, said additive injector being installed in the second end of said protrusion and oriented to inject the cone-shaped spray of additive into said exhaust pipe through the opening of said protrusion without interfering with at least a downstream edge of the opening, the additive being carried by the flow of the exhaust emissions downstream to said catalyst and used in a given exhaust emission purification reaction, as induced by said catalyst, to purify the exhaust emissions.   
   
   
       2 . An exhaust emission control apparatus as set forth in  claim 1 , wherein said additive injector is so oriented by said protrusion as to avoid interference of the cone-shaped spray of additive with an entire edge of the opening of said protrusion. 
   
   
       3 . An exhaust emission control apparatus as set forth in  claim 1 , wherein said protrusion has a cylindrical inner wall. 
   
   
       4 . An exhaust emission control apparatus as set forth in  claim 1 , wherein said additive injector has a head in which a spray hole is formed, and wherein a distance between the downstream edge of the opening of said protrusion and the head of said additive injector is so selected as a function of an angle of spread of the additive, as sprayed from said additive injector, as to avoid interference of the cone-shaped spray of the additive with the downstream edge of the opening of said protrusion. 
   
   
       5 . An exhaust emission control apparatus as set forth in  claim 1 , wherein said additive injector is oriented in alignment of an axis thereof with that of the straight section of said exhaust pipe. 
   
   
       6 . An exhaust emission control apparatus as set forth in  claim 1 , wherein said additive injector is oriented in alignment of an axis with that of said catalyst. 
   
   
       7 . An exhaust emission control apparatus as set forth in claim  4 , wherein said additive injector is designed to change the angle of spread of the additive, and wherein said additive injector is oriented to avoid interference of the cone-shaped spray of additive with at least the downstream edge of the opening when the angle of spread of the additive is maximized. 
   
   
       8 . An exhaust emission control apparatus as set forth in  claim 1 , wherein said exhaust pipe also includes a second bent section through which the exhaust gas flows, said second bent section communicating with the bent section and the straight section at a branch joint, and wherein the opening of said protrusion leading inside said exhaust pipe through a wall of the branch joint, said protrusion extending outside said exhaust pipe substantially in parallel to the longitudinal center line of the straight section. 
   
   
       9 . An exhaust emission control apparatus as set forth in  claim 1 , wherein the bent section is curved. 
   
   
       10 . An exhaust emission control apparatus as set forth in  claim 1 , wherein the bent section is flexed to a right angle.