Exhaust emission control device of internal combustion engine

Abstract

An exhaust emission control device of an internal combustion engine includes a fuel supply unit provided in a fuel supply passage, for supplying a reducing agent directly to a NOx trap catalytic converter; an addition pressure detection unit for detecting the supply pressure of the reducing agent supplied by the fuel supply unit; and a controller for calculating the amount of NOx adsorbed by the catalytic converter. When the supply pressure of the reducing agent is almost zero, the controller prohibits calculation of NOx adsorption amount depending on the supply of the reducing agent, creates a rich state in a cylinder, carries out calculation of NOx adsorption amount depending on the created rich state, and causes release and reduction of the adsorbed NOx.

1 . An exhaust emission control device of an internal combustion engine, comprising: 
 an exhaust passage connected with a cylinder of the engine,    a NOx trap catalytic converter provided in the passage, capable of adsorbing NOx contained in exhaust in lean operation and releasing and reducing the adsorbed NOx in rich operation,    a supply means provided in the passage, for supplying a reducing agent directly to the catalytic converter,    a detection means for detecting the supply pressure of the reducing agent supplied by the supply means, and    a controller for calculating the amount of NOx adsorbed by the catalytic converter, wherein    when the supply pressure of the reducing agent is almost zero, the controller prohibits calculation of NOx adsorption amount depending on the supply of the reducing agent, creates a rich state in the cylinder, carries out calculation of NOx adsorption amount depending on the created rich state, and causes release and reduction of the adsorbed NOx.    
   
   
       2 . The exhaust emission control device of the internal combustion engine according to  claim 1 , wherein 
 when the supply pressure of the reducing agent is almost zero, the controller treats the amount of NOx emitted by the supply of the reducing agent, as zero, to negate it in the calculation of the amount of adsorbed NOx.    
   
   
       3 . The exhaust emission control device of the internal combustion engine according to  claim 1 , wherein 
 when the supply pressure of the reducing agent is almost zero, the controller performs rich spike by post injection under specific restrictions.    
   
   
       4 . The exhaust emission control device of the internal combustion engine according to  claim 3 , wherein 
 the number of times that the rich spike by post injection is performed or the accumulated time of the rich spike by post injection is restricted to the number of times or the time which does not cause lubricating oil for the engine to exceed a dilution limit.    
   
   
       5 . The exhaust emission control device of the internal combustion engine according to  claim 3 , wherein 
 the rich spike by post injection is restricted to the engine operation with medium load or lower.    
   
   
       6 . An exhaust emission control device of an internal combustion engine, comprising: 
 an exhaust passage connected with a cylinder of the engine,    a NOx trap catalytic converter provided in the passage, capable of adsorbing NOx contained in exhaust in lean operation and releasing and reducing the adsorbed NOx in rich operation,    a supply means provided in the passage, for supplying a reducing agent directly to the catalytic converter,    a detection means for detecting the supply pressure of the reducing agent supplied by the supply means, and    a controller for calculating the amount of NOx adsorbed by the catalytic converter, wherein    when the supply pressure of the reducing agent is less than a specific pressure, the controller calculates the amount of the reducing agent supplied, on the basis of the detected supply pressure, carries out calculation of NOx adsorption amount depending on the supply of the reducing agent, and causes release and reduction of the adsorbed NOx.