Exhaust gas purification apparatus for internal combustion engine

Abstract

An apparatus including an exhaust passage that forks at a separating portion and joins at a joining portion, exhaust gas purification catalysts between the separating portion and the joining portion, a filter downstream of the joining portion, reducing agent supply units supplying reducing agent to the respective exhaust passages at positions upstream of the exhaust gas purification catalysts, and control units controlling quantity of the exhaust gas passing through the exhaust gas purification catalysts. When regenerating the filter, the reducing agent is supplied by one reducing agent supply unit, and the quantity of exhaust gas passing through the exhaust gas purification catalyst provided in the exhaust passage to which the reducing agent is supplied is made smaller.

1 - 10 . (canceled) 
   
   
       11 . An exhaust gas purification apparatus for an internal combustion engine comprising:
 an exhaust passage that forks, at a separating portion, into a plurality of exhaust passages, which join together at a joining portion downstream of said separating portion;   exhaust gas purification catalysts that are provided respectively in the exhaust passages between said separating portion and the joining portion;   a particulate filter provided in the exhaust passage downstream of said joining portion, said particulate filter supporting a catalyst that has an oxidizing ability or being anteceded by a catalyst that has an oxidizing ability provided upstream thereof;   reducing agent supply units for supplying a reducing agent to the respective exhaust passages at positions downstream of said separating portion and upstream of said exhaust gas purification catalysts;   control units for controlling the quantity of exhaust gas passing through said exhaust gas purification catalysts,   wherein when regeneration of said particulate filter is performed, the reducing agent is supplied from one reducing agent supply unit, and the quantity of exhaust gas passing through one exhaust gas purification catalyst provided in the exhaust passage to which the reducing agent is supplied is made smaller than the quantity of exhaust gas passing through other exhaust gas purification catalyst(s).   
   
   
       12 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 11 , wherein the quantity of exhaust gas passing through said one exhaust gas purification catalyst is made smaller until the quantity of reducing agent adhering to said one exhaust gas purification catalyst becomes equal to or smaller than a threshold value. 
   
   
       13 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 11 , wherein said exhaust gas purification catalysts comprise NOx storage reduction catalysts, and regeneration of said particulate filter is performed simultaneously with reduction of NOx stored in said one exhaust gas purification catalyst. 
   
   
       14 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 12 , wherein said exhaust gas purification catalysts comprise NOx storage reduction catalysts, and regeneration of said particulate filter is performed simultaneously with reduction of NOx stored in said one exhaust gas purification catalyst. 
   
   
       15 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 11 , wherein the quantity of exhaust gas passing through said one exhaust gas purification catalyst is made smaller so that the quantity of oxygen in the ambient atmosphere in said one exhaust gas purification catalyst becomes equal to or smaller than a specific value. 
   
   
       16 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 12 , wherein the quantity of exhaust gas passing through said one exhaust gas purification catalyst is made smaller so that the quantity of oxygen in the ambient atmosphere in said one exhaust gas purification catalyst becomes equal to or smaller than a specific value. 
   
   
       17 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 11 , wherein said control units comprises control valves that are provided respectively in the exhaust passages between the separating portion and the joining portion to control channel section areas of the exhaust passages, the quantity of exhaust gas passing through said exhaust gas purification catalyst is made smaller by operating said control valve in a closing direction, and supply of reducing agent by said one reducing agent supply unit is started during a period since the control valve starts to be closed until it is fully closed. 
   
   
       18 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 12 , wherein said control units comprises control valves that are provided respectively in the exhaust passages between the separating portion and the joining portion to control channel section areas of the exhaust passages, the quantity of exhaust gas passing through said exhaust gas purification catalyst is made smaller by operating said control valve in a closing direction, and supply of reducing agent by said one reducing agent supply unit is started during a period since the control valve starts to be closed until it is fully closed. 
   
   
       19 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 11 , wherein supply of reducing agent by the reducing agent supply unit is performed in multiple installments at regular intervals, and the quantity of supplied reducing agent in each installment is not larger than a specific quantity. 
   
   
       20 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 12 , wherein supply of reducing agent by the reducing agent supply unit is performed in multiple installments at regular intervals, and the quantity of supplied reducing agent in each installment is not larger than a specific quantity. 
   
   
       21 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 11 , wherein a process of supplying the reducing agent by said reducing agent supply unit and making the quantity of exhaust gas passing through the exhaust gas purification catalyst to which the reducing agent is supplied smaller than the quantity of exhaust gas passing through other exhaust gas purification catalyst(s) is performed in the plurality of exhaust passages in rotation. 
   
   
       22 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 12 , wherein a process of supplying the reducing agent by said reducing agent supply unit and making the quantity of exhaust gas passing through the exhaust gas purification catalyst to which the reducing agent is supplied smaller than the quantity of exhaust gas passing through other exhaust gas purification catalyst(s) is performed in the plurality of exhaust passages in rotation. 
   
   
       23 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 11 , wherein said one reducing agent supply unit supplies the reducing agent at such a position that even if the reducing agent, when supplied, evaporates to thereby flow back in the exhaust passage, it does not reach the exhaust passage(s) in which other exhaust gas purification catalyst(s) is provided. 
   
   
       24 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 12 , wherein said one reducing agent supply unit supplies the reducing agent at such a position that even if the reducing agent, when supplied, evaporates to thereby flow back in the exhaust passage, it does not reach the exhaust passage(s) in which other exhaust gas purification catalyst(s) is provided. 
   
   
       25 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 11 , wherein members on which the reducing agent supplied into the exhaust passages by said reducing agent supply units strikes are provided in the respective exhaust passages. 
   
   
       26 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 12 , wherein members on which the reducing agent supplied into the exhaust passages by said reducing agent supply units strikes are provided in the respective exhaust passages. 
   
   
       27 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 11 , further comprising:
 an air-fuel ratio sensor that senses the air-fuel ratio of exhaust gas flowing in the exhaust passage downstream of said exhaust gas purification catalyst and upstream of said joining portion;   a temperature sensor that senses the temperature of exhaust gas flowing in the exhaust passage downstream of said exhaust gas purification catalyst and upstream of said joining portion; and   an abnormality determination unit that determines that an abnormality occurs in a certain member if a value sensed by either said air-fuel ratio sensor or said temperature sensor falls out of a specific range.   
   
   
       28 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 12 , further comprising:
 an air-fuel ratio sensor that senses the air-fuel ratio of exhaust gas flowing in the exhaust passage downstream of said exhaust gas purification catalyst and upstream of said joining portion;   a temperature sensor that senses the temperature of exhaust gas flowing in the exhaust passage downstream of said exhaust gas purification catalyst and upstream of said joining portion; and   an abnormality determination unit that determines that an abnormality occurs in a certain member if a value sensed by either said air-fuel ratio sensor or said temperature sensor falls out of a specific range.