Exhaust gas purification control apparatus of engine

Abstract

An exhaust gas purification control apparatus is used for an engine provided with a NOx catalyst absorbing or adsorbing NOx when an air fuel ratio of exhaust gas from the engine is lean and reducing the absorbed or adsorbed NOx when the exhaust gas is at the stoichiometric air fuel ratio or richer in fuel, and an exhaust sensor arranged upstream or downstream of the NOx catalyst, and characterized in that thed exhaust gas purification control apparatus comprises a sulphur component calculating means for calculating or estimating a quantity of sulphur components in the exhaust gas and an operation mode changing means for changing an air fuel ratio of the engine on the basis of the detected value of the sulphur components, and the calculated or estimated value of sulphur components is a prescribed value or more, the operation changing means decreases frequencies of lean mode operation of the engine, shortens continuation time of the lean mode operation or prohibits the lean mode operation.

What is claimed is:  
     
         1 . An exhaust gas purification control apparatus of an engine, having a NOx catalyst absorbing or adsorbing NOx when an air fuel ratio of exhaust gas from the engine is lean and reducing the absorbed or adsorbed NOx when the exhaust gas is at the stoichiometric air fuel ratio or richer in fuel, and an exhaust sensor arranged upstream or downstream of said NOx catalyst, 
 wherein said exhaust gas purification control apparatus comprises; 
 sulphur component calculating means for calculating or estimating a quantity of sulphur components in the exhaust gas; and  
 operation mode changing means for changing an air fuel ratio of the engine on the basis of the detected value of the sulphur components.  
   
     
     
         2 . An exhaust gas purification control apparatus of an engine according to    claim 1   , wherein a sulphur concentration sensor for detecting the concentration of sulphur is arranged in an exhaust duct of the engine.  
     
     
         3 . An exhaust gas purification control apparatus of an engine according to    claim 1   , wherein said sulphur component calculating means calculates or estimates the concentration of sulphur on the basis of an output signal of said sulphur concentration sensor or said exhaust sensor.  
     
     
         4 . An exhaust gas purification control apparatus of an engine according to    claim 2   , wherein said sulphur component calculating means calculates or estimates the concentration of sulphur on the basis of an output signal of said sulphur concentration sensor or said exhaust sensor.  
     
     
         5 . An exhaust gas purification control apparatus of an engine according to    claim 3   , wherein said sulphur component calculating means estimates that the slower the response time of said exhaust sensor becomes, the higher the concentration of sulphur is.  
     
     
         6 . An exhaust gas purification control apparatus of an engine according to    claim 4   , wherein said sulphur component calculating means estimates that the slower the response time of said exhaust sensor becomes, the higher the concentration of sulphur is.  
     
     
         7 . An exhaust gas purification control apparatus of an engine according to    claim 1   , wherein when the calculated or estimated value of sulphur components is a prescribed value or more, said operation changing means decreases frequencies of lean mode operation of the engine, shortens continuation time of the lean mode operation or prohibits the lean mode operation.  
     
     
         8 . An exhaust gas purification control apparatus of an engine according to    claim 2   , wherein when the calculated or estimated value of sulphur components is a prescribed value or more, said operation changing means decreases frequencies of lean mode operation of the engine, shortens continuation time of the lean mode operation or prohibits the lean mode operation.  
     
     
         9 . An exhaust gas purification control apparatus of an engine according to    claim 3   , wherein when the calculated or estimated value of sulphur components is a prescribed value or more, said operation changing means decreases frequencies of lean mode operation of the engine, shortens continuation time of the lean mode operation or prohibits the lean mode operation.  
     
     
         10 . An exhaust gas purification control apparatus of an engine according to    claim 4   , wherein when the calculated or estimated value of sulphur components is a prescribed value or more, said operation changing means decreases frequencies of lean mode operation of the engine, shortens continuation time of the lean mode operation or prohibits the lean mode operation.  
     
     
         11 . An exhaust gas purification control apparatus of an engine according to    claim 5   , wherein when the calculated or estimated value of sulphur components is a prescribed value or more, said operation changing means decreases frequencies of lean mode operation of the engine, shortens continuation time of the lean mode operation or prohibits the lean mode operation.  
     
     
         12 . An exhaust gas purification control apparatus of an engine according to    claim 6   , wherein when the calculated or estimated value of sulphur components is a prescribed value or more, said operation changing means decreases frequencies of lean mode operation of the engine, shortens continuation time of the lean mode operation or prohibits the lean mode operation.