Exhaust Gas Purifying Device Of An Internal Combustion Engine

Abstract

There is provided an oxidizing catalyst located in the upstream of the exhaust gas purifying catalyst. The catalyst capacity of the oxidizing catalyst is set so that, in the relationship between a value obtained by dividing exhaust flow velocity by the catalyst capacity (exhaust flow velocity/catalyst capacity) and catalyst activatibility, when the exhaust flow velocity is exhaust flow velocity at the time of idle operation of the internal combustion engine, the catalyst activatibility is maximum (prescribed maximum activation range) and the value obtained by dividing the exhaust flow velocity by the catalyst capacity is maximum or close to the maximum.

1 . An exhaust gas purifying device of an internal combustion engine, comprising: 
 an exhaust gas purifying catalyst interposed in an exhaust passage of an internal combustion engine for purifying a harmful component contained in exhaust gas; and    an oxidizing catalyst disposed in an upstream of the exhaust gas purifying catalyst, wherein:    catalyst capacity of the oxidizing catalyst is set so that, in relationship between a value obtained by dividing exhaust flow velocity by the catalyst capacity and catalyst activatibility, when the exhaust flow velocity is exhaust flow velocity at the time of idle operation of the internal combustion engine, the catalyst activatibility is maximum and the value obtained by dividing the exhaust flow velocity by the catalyst capacity is maximum or close to the maximum.    
   
   
       2 . The exhaust gas purifying device of an internal combustion engine according to  claim 1 , wherein the exhaust gas purifying catalyst includes a NOx catalyst.  
   
   
       3 . The exhaust gas purifying device of an internal combustion engine according to  claim 1 , wherein: 
 the internal combustion engine is a diesel engine having a throttle valve in an intake system, and includes engine control means that has throttle control means arranged for performing an opening/closing operation of the throttle valve and controls operation of the diesel engine;    the throttle control means closes the throttle valve down to prescribed opening when the internal combustion engine is in the idle operation; and    the catalyst capacity of the oxidizing catalyst is set so that, when the internal combustion engine is in the idle operation and the exhaust flow velocity is exhaust flow velocity in a state where the throttle valve is closed down to the prescribed opening by the engine control means, the catalyst activatibility is maximum and the value obtained by dividing the exhaust flow velocity by the catalyst capacity is maximum or close to the maximum.    
   
   
       4 . The exhaust gas purifying device of an internal combustion engine according to  claim 3 , wherein: 
 the engine control means further includes fuel injection control means arranged for controlling a fuel injection amount and fuel injection timing; and    when the internal combustion engine is in the idle operation, the fuel injection control means retards the fuel injection timing of main injection to be later than normal timing, and carries out pilot injection in which the fuel injection amount is smaller than that of the main injection immediately before the main injection at least once or more.    
   
   
       5 . The exhaust gas purifying device of an internal combustion engine according to  claim 4 , wherein the fuel injection control means retards the fuel injection timing of the main injection to the vicinity of a misfire limit when the internal combustion engine is in the idle operation.  
   
   
       6 . The exhaust gas purifying device of an internal combustion engine according to  claim 1 , wherein: 
 the internal combustion engine is a diesel engine, and includes engine control means that has fuel injection control means arranged for controlling a fuel injection amount and fuel injection timing, and that controls operation of the diesel engine; and    when the internal combustion engine is in the idle operation, the fuel injection control means retards fuel injection timing of main injection to be later than normal timing and carries out pilot injection in which the fuel injection amount is smaller than that of the main injection immediately before the main injection at least once or more.