Method and device for controlling an exhaust gas post-treatment

Abstract

In a method and device for controlling an exhaust gas post-treatment for an internal combustion engine with at least one cylinder (Z 1 -Z 4 ) and one combustion chamber ( 26 ) and one exhaust gas tract ( 14 ) in which is disposed an SCR catalyst ( 34 ), a humidity parameter (HDT EXH) of an exhaust gas in the exhaust gas tract ( 14 ) is determined upstream of the SCR catalyst ( 34 ) of the internal combustion machine. A control signal for an actuator for introducing ammonia into the exhaust gas is determined as a function of the humidity parameter (HDT_EXH) of the exhaust gas, and the actuator is adjusted accordingly.

1 . A method for controlling an exhaust gas post-treatment process for an internal combustion engine having at least one cylinder with a combustion chamber and an exhaust gas tract in which is arranged an SCR catalytic converter, the method comprising:
 determining a parameter for a water content of an exhaust gas in the exhaust gas tract upstream of the SCR catalytic converter of the internal combustion engine, and   depending on the parameter for the water content of the exhaust gas, determining a control signal for an actuator for introducing ammonia into the exhaust gas and the actuator is set.   
     
     
         2 . The method according to  claim 1 , wherein the parameter for the water content of the exhaust gas is determined depending on the air humidity content of the ambient air fed to the internal combustion engine. 
     
     
         3 . The method according to  claim 1 , wherein the parameter for the water content of the exhaust gas is determined depending on the temperature of the ambient air fed to the internal combustion engine. 
     
     
         4 . The method according to  claim 2 , wherein at least one of the air humidity content and the temperature are/is determined by means of one or more sensors, the measurement signal from which is representative or the measurement signals from which are representative of at least one of the air humidity content and the temperature of the ambient air fed to the internal combustion engine. 
     
     
         5 . The method according to  claim 1 , wherein a setting of the actuator has an effect on an ammonia mass which is fed to the SCR catalytic converter. 
     
     
         6 . A device for controlling an exhaust gas post-treatment process for an internal combustion engine having at least one cylinder with a combustion chamber and an exhaust gas tract in which is arranged an SCR catalytic converter, whereby the device is configured to,
 determine a parameter for a water content of an exhaust gas in the exhaust gas tract upstream of the SCR catalytic converter of the internal combustion engine,   depending on the parameter for the water content of the exhaust gas, to determine a control signal for an actuator for introducing ammonia into the exhaust gas and to set the actuator.   
     
     
         7 . The device according to  claim 6 , wherein the parameter for the water content of the exhaust gas is determined depending on the air humidity content of the ambient air fed to the internal combustion engine. 
     
     
         8 . The device according to  claim 6 , wherein the parameter for the water content of the exhaust gas is determined depending on the temperature of the ambient air fed to the internal combustion engine. 
     
     
         9 . The device according to  claim 7 , wherein at least one of the air humidity content and the temperature are/is determined by means of one or more sensors, the measurement signal from which is representative or the measurement signals from which are representative of at least one of the air humidity content and the temperature of the ambient air fed to the internal combustion engine. 
     
     
         10 . The device according to  claim 6 , wherein a setting of the actuator has an effect on an ammonia mass which is fed to the SCR catalytic converter. 
     
     
         11 . A motor vehicle, comprising:
 an internal combustion engine having an intake tract, an engine block, a cylinder head and an exhaust gas tract,   an SCR catalytic converter arranged in the exhaust gas tract;   a control device;   sensors associated with said control device, said sensors sensing different measurement variables, wherein the control device is configured to determine correcting variables depending on at least one of the measurement variables, which correcting variables can be converted into one or more control signals for controlling actuators by means of corresponding final control elements; and   wherein the control device is further configured:
 to determine a parameter for a water content of an exhaust gas in the exhaust gas tract upstream of the SCR catalytic converter of the internal combustion engine, 
 depending on the parameter for the water content of the exhaust gas, to determine a control signal for an actuator for introducing ammonia into the exhaust gas and to set the actuator. 
   
     
     
         12 . The motor vehicle according to  claim 11 , wherein the intake tract comprises a throttle valve and an induction manifold, wherein the induction manifold leads to a cylinder in the intake port into a combustion chamber of the engine block. 
     
     
         13 . The motor vehicle according to  claim 12 , wherein the engine block comprises a crankshaft which is coupled by way of a connecting rod to a piston in the cylinder, and wherein the cylinder head comprises a valve operating mechanism having a gas inlet valve and a gas outlet valve. 
     
     
         14 . The motor vehicle according to  claim 13 , wherein the cylinder head also comprises an injection valve and a spark plug. 
     
     
         15 . The motor vehicle according to  claim 11 , wherein the actuators are selected from the group consisting of a throttle valve, a gas inlet valve, a gas outlet valve, an injection valve, and a spark plug. 
     
     
         16 . The motor vehicle according to  claim 11 , wherein the sensors comprise at least one of: a pedal position sensor which senses an accelerator pedal position of an accelerator pedal, a humidity sensor which is arranged upstream of the throttle valve, a temperature sensor upstream of the throttle valve, an NOx sensor arranged downstream of the SCR catalytic converter. 
     
     
         17 . The motor vehicle according to  claim 11 , wherein the parameter for the water content of the exhaust gas is determined depending on the air humidity content of the ambient air fed to the internal combustion engine. 
     
     
         18 . The motor vehicle according to  claim 11 , wherein the parameter for the water content of the exhaust gas is determined depending on the temperature of the ambient air fed to the internal combustion engine. 
     
     
         19 . The motor vehicle according to  claim 17 , wherein at least one of the air humidity content and the temperature are/is determined by means of one or more sensors, the measurement signal from which is representative or the measurement signals from which are representative of at least one of the air humidity content and the temperature of the ambient air fed to the internal combustion engine. 
     
     
         20 . The motor vehicle according to  claim 11 , wherein a setting of the actuator has an effect on an ammonia mass which is fed to the SCR catalytic converter.