Exhaust Gas Control Apparatus for Internal Combustion Engine

Abstract

When the temperature of exhaust gas control means ( 3 ), which is provided in an exhaust passage ( 2 ) of an internal combustion engine ( 1 ) and which has oxidation function, is increased to a target temperature in order to recover an exhaust gas control ability of the exhaust gas control means ( 3 ), the method of increasing the temperature of the exhaust gas control means ( 3 ) is switched between a method in which the temperature of the exhaust gas control means ( 3 ) is increased by controlling an amount of fuel supplied to the exhaust gas control means ( 3 ) and a method in which the fuel supply to the exhaust gas control means ( 3 ) is prohibited and the temperature of the exhaust gas control means ( 3 ) is increased by controlling an amount of air taken in the internal combustion engine ( 1 ), based on an operation state of the internal combustion engine ( 1 ).

1 . An exhaust gas control apparatus for an internal combustion engine, comprising: 
 an exhaust gas control device which is provided in an exhaust passage of an internal combustion engine, and which has oxidation function;    fuel supply device for supplying fuel to the exhaust gas control device from a position upstream of the exhaust gas control device; and    intake air amount control device for controlling an amount of air taken in the internal combustion engine, wherein,    when a temperature increasing condition for increasing a temperature of the exhaust gas control device to a target temperature in order to recover an exhaust gas control ability of the exhaust gas control device has been satisfied, if an engine load of the internal combustion engine is lower than a predetermined engine load, the temperature of the exhaust gas control device is increased to or maintained at the target temperature by controlling an amount of fuel supplied from the fuel supply device to the exhaust gas control device, and the intake air amount control device controls the amount of air taken in the internal combustion engine to an intake air amount that is set based on an engine rotational speed of the internal combustion engine and the engine load of the internal combustion engine; and    when the temperature increasing condition has been satisfied, if the engine load of the internal combustion engine is equal to or higher than the predetermined engine load, fuel supply from the fuel supply device is prohibited, and the intake air amount control device controls the amount of air taken in the internal combustion engine, whereby the temperature of the exhaust gas control device is increased to or maintained at the target temperature.    
     
     
         2 . The exhaust gas control apparatus for an internal combustion engine according to  claim 1 , wherein 
 the exhaust gas control device includes at least one of a filter which supports an oxidation catalyst, a filter which supports a NOx storage reduction catalyst, and a NOx storage reduction catalyst.    
     
     
         3 . The exhaust gas control apparatus for an internal combustion engine according to  claim 1 , wherein 
 the fuel supply device performs sub-fuel injection in a cylinder of the internal combustion engine during a power stroke or an exhaust stroke after main fuel injection is performed, thereby supplying fuel to the exhaust gas control device from a position upstream of the exhaust gas control device.    
     
     
         4 . The exhaust gas control apparatus for an internal combustion engine according to  claim 3 , wherein 
 even in a case where the engine load of the internal combustion engine is lower than the predetermined engine load when the temperature increasing condition has been satisfied, if the engine rotational speed of the internal combustion engine is equal to or higher than a predetermined engine rotational speed, the fuel supply from the fuel supply device is prohibited, and the intake air amount control device controls the amount of air taken in the internal combustion engine, whereby the temperature of the exhaust gas control device is increased to or maintained at the target temperature.    
     
     
         5 . The exhaust gas control apparatus for an internal combustion engine according to  claim 1 , wherein 
 the fuel supply device supplies fuel by using a fuel supply valve that is provided in the exhaust passage at a position upstream of the exhaust gas control device, thereby supplying the fuel to the exhaust gas control device.    
     
     
         6 . The exhaust gas control apparatus for an internal combustion engine according to  claim 1 , wherein, 
 as the engine rotational speed of the internal combustion engine that is obtained when the temperature increasing condition has been satisfied becomes higher, the predetermined engine load is set to a lower value.    
     
     
         7 . The exhaust gas control apparatus for an internal combustion engine according to  claim 1 , wherein 
 there is further provided learning device for learning a relationship between the amount of air taken in the internal combustion engine and the temperature of the exhaust gas control device in a state where the fuel supply from the fuel supply device is not performed, wherein    in a case where the temperature increasing condition has been satisfied, when an operation state of the internal combustion engine is shifted from an operation region where the amount of fuel supplied from the fuel supply device to the exhaust gas control device is controlled, whereby the temperature of the exhaust gas control device is increased to the target temperature, to an operation region where the intake air amount control device controls the amount of air taken in the internal combustion engine, whereby the temperature of the exhaust gas control device is increased to the target temperature, the relationship between the amount of air taken in the internal combustion engine and the temperature of the exhaust gas control device is learned by the learning device after the fuel supply from the fuel supply device is stopped and the temperature of the exhaust gas control device is brought to a steady state; and    the amount of air taken in the internal combustion engine is controlled by the intake air amount control device based on the relationship between the amount of air taken in the internal combustion engine and the temperature of the exhaust gas control service that is obtained by learning performed by the learning device such that the temperature of the exhaust gas control device is controlled to the target temperature.