Method for operating an internal combustion engine and device for executing the method

Abstract

A method for operating an internal combustion engine and a device for executing the method provide for diagnostics of the exhaust system in which an exhaust-gas treatment device for converting at least one undesirable exhaust gas component is situated. A measure for the conversion is determined from the exhaust gas component, ascertained upstream from the exhaust-gas treatment-device and measured downstream from the exhaust-gas treatment device and compared to a predefinable threshold value. An error signal is issued when the threshold is not met. The approach makes it possible in particular to detect a manipulation in the exhaust system such as the use of a dummy in the exhaust-gas treatment device or, for example, a deliberately defective lining of a component situated in the exhaust-gas treatment device.

1 . A method for operating an internal combustion engine which provides for diagnostics of an exhaust system of the internal combustion engine, in which an exhaust-gas treatment device for converting at least one undesirable exhaust gas component is situated, the method comprising: 
 determining a measure for the conversion from the exhaust gas component, ascertained upstream from the exhaust-gas treatment device and measured downstream from the exhaust-gas treatment device;    comparing the measure to a predefined threshold value; and    providing an error signal when the threshold value is not met.    
   
   
       2 . The method according to  claim 1 , wherein a degree of efficiency of the exhaust-gas treatment device is ascertained as a measure for the conversion.  
   
   
       3 . The method according to  claim 1 , wherein a reduction of a concentration of the exhaust gas component is ascertained as a measure for the conversion.  
   
   
       4 . The method according to  claim 1 , wherein a measure for the exhaust gas component upstream from the exhaust-gas treatment device is calculated from performance characteristics of the internal combustion engine.  
   
   
       5 . The method according to  claim 1 , wherein the threshold value is set based upon at least one of (a) operating conditions in the exhaust system and (b) operating conditions of the internal combustion engine.  
   
   
       6 . The method according to  claim 5 , wherein at least one of a temperature of the exhaust-gas treatment device and a metering of a reagent introduced into the exhaust system is taken into account.  
   
   
       7 . The method according to  claim 1 , wherein a delay time for delaying the exhaust gas component measured downstream from the exhaust-gas treatment device is provided in order to take into account a transit time of the exhaust gas component in the exhaust system.  
   
   
       8 . The method according to  claim 1 , wherein the error signal is provided when a threshold shortfall lasts at least a predefined period of time.  
   
   
       9 . The method according to  claim 1 , wherein the exhaust gs component includes NOx emissions of the internal combustion engine.  
   
   
       10 . The method according to  claim 1 , further comprising carrying out further diagnostic procedures after the error signal occurs.  
   
   
       11 . A device for operating an internal combustion engine, which provides for diagnostics of an exhaust system of the internal combustion engine, in which an exhaust-gas treatment device for converting at least one undesirable exhaust gas component is situated, the device comprising at least one control unit for performing the following: 
 determining a measure for the conversion from the exhaust gas component, ascertained upstream from the exhaust-gas treatment device and measured downstream from the exhaust-gas treatment device;    comparing the measure to a predefined threshold value; and    providing an error signal when the threshold value is not met.    
   
   
       12 . The device according to  claim 11 , further comprising a sensor for detecting the at least one undesirable exhaust gas component, and wherein an exhaust-gas flap applies the exhaust gas component occurring one of upstream and downstream from the exhaust-gas treatment device to the sensor.