Exhaust Gas Purification Apparatus for an Internal Combustion Engine

Abstract

In an exhaust gas purification apparatus for an internal combustion engine, there is provided a technique that can perform the addition of a reducing agent to an exhaust gas in a more appropriate manner; in an exhaust gas purification apparatus for an internal combustion engine having a fuel addition valve that adds fuel to an exhaust gas upstream of a filter arranged in an exhaust passage of the internal combustion engine, an internal pressure in a cylinder of the internal combustion engine upon opening of an exhaust valve for the cylinder is detected, and a flow speed or temperature of the exhaust gas passing a fuel addition position of the fuel addition valve in the exhaust passage is estimated based on the detected cylinder internal pressure; an amount of addition of fuel is adjusted based on the estimated flow speed or temperature of the exhaust gas.

1 . An exhaust gas purification apparatus for an internal combustion engine having a reducing agent addition unit that adds a reducing agent to an exhaust gas upstream of an exhaust gas purification unit arranged in an exhaust passage of said internal combustion engine, said apparatus comprising:
 a cylinder internal pressure detection unit that detects an internal pressure in a cylinder of said internal combustion engine when an exhaust valve for said cylinder is opened;   an estimation unit that estimates a flow speed or temperature of said exhaust gas passing a reducing agent addition position of said reducing agent addition unit in said exhaust passage based on said cylinder internal pressure detected by said cylinder internal pressure detection unit; and   an addition control unit that adjusts an amount of addition of said reducing agent based on the flow speed or temperature of said exhaust gas estimated by said estimation unit.   
   
   
       2 . The exhaust gas purification apparatus for an internal combustion engine as set forth in  claim 1 , wherein
 said estimation unit estimates that the higher said cylinder internal pressure detected by said cylinder internal pressure detection unit, the higher the flow speed or temperature of said exhaust gas becomes; and   said addition control unit increases the amount of addition of said reducing agent in accordance with the higher flow speed or temperature of said exhaust gas estimated by said estimation unit.   
   
   
       3 . The exhaust gas purification apparatus for an internal combustion engine as set forth in  claim 1 , wherein
 said estimation unit estimates timing at which the flow speed of said exhaust gas discharged per one exhaust stroke period becomes maximum; and   said addition control unit adjusts the timing of addition of said reducing agent based on said timing estimated by said estimation unit.   
   
   
       4 . The exhaust gas purification apparatus for an internal combustion engine as set forth in  claim 2 , wherein
 said estimation unit estimates timing at which the flow speed of said exhaust gas discharged per one exhaust stroke period becomes maximum; and   said addition control unit adjusts the timing of addition of said reducing agent based on said timing estimated by said estimation unit.