Method and device for exhaust gas aftertreatment in an internal combustion engine

Abstract

A device for exhaust gas aftertreatment in an internal combustion engine can be connected to an outlet of the internal combustion engine. The device comprises an exhaust gas system with an exhaust gas channel in which a three-way catalytic converter is arranged, and an exhaust gas burner with which hot burner exhaust gases can be fed into the exhaust gas channel at a feed point upstream from the three-way catalytic converter. The three-way catalytic converter is configured as a lambda probe catalytic converter and comprises a first catalyst volume and a second catalyst volume, whereby a lambda probe is arranged downstream from the first catalyst volume and upstream from the second catalyst volume, whereby the first catalyst volume has a lower oxygen storage capacity than the second catalyst volume. A method for exhaust gas aftertreatment in an internal combustion engine has such an exhaust gas aftertreatment device.

1 . A device for exhaust gas aftertreatment in an internal combustion engine, which device can be connected to an outlet of the internal combustion engine, comprising:
 an exhaust gas system with an exhaust gas channel in which a three-way catalytic converter is arranged, and   an exhaust gas burner,   a feed point for burner exhaust gases from the exhaust gas burner, on the exhaust gas channel upstream from the three-way catalytic converter,   wherein the three-way catalytic converter is configured as a lambda probe catalytic converter, and   a lambda probe arranged downstream from a first catalyst volume of the three-way catalytic converter and upstream from a second catalyst volume of the three-way catalytic converter, whereby the first catalyst volume has a lower oxygen storage capacity than the second catalyst volume.   
     
     
         2 . The device for exhaust gas aftertreatment according to  claim 1 , wherein the first catalyst volume makes up 15% to 35% of the total volume of the three-way catalytic converter, and the second catalyst volume makes up 65% to 85% of the total volume of the three-way catalytic converter. 
     
     
         3 . The device for exhaust gas aftertreatment according to  claim 1 , wherein the lambda probe is configured as a step change sensor. 
     
     
         4 . The device for exhaust gas aftertreatment according to  claim 1 , wherein the lambda probe is configured as a broadband probe. 
     
     
         5 . The device for exhaust gas aftertreatment according to  claim 1 , wherein the exhaust gas channel is configured without a lambda probe downstream from the feed point and upstream from the three-way catalytic converter. 
     
     
         6 . The device for exhaust gas aftertreatment according to  claim 1 , further comprising a secondary air system associated with the exhaust gas burner in order to control the quantity of fresh air that is fed to the exhaust gas burner. 
     
     
         7 . The device for exhaust gas aftertreatment according to  claim 1 , wherein the exhaust gas burner comprises a fuel injector with which fuel can be introduced into a combustion chamber of the exhaust gas burner. 
     
     
         8 . The device for exhaust gas aftertreatment according to  claim 1 , further comprising a turbine of an exhaust gas turbocharger arranged in the exhaust gas system upstream from the three-way catalytic converter. 
     
     
         9 . A method for exhaust gas aftertreatment in an internal combustion engine having a device for exhaust gas aftertreatment according to  claim 1 , comprising the following steps:
 activating the exhaust gas burner, whereby the quantity of fuel fed to the exhaust gas burner and/or the quantity of fresh air fed to the exhaust gas burner is pilot-controlled,   detecting the air-fuel ratio downstream from the first catalyst volume and upstream from the second catalyst volume of the three-way catalytic converter, and   changing the quantity of fuel and/or the fresh air quantity when a rich blow-out or a lean blow-out is detected at the lambda probe.   
     
     
         10 . The method for exhaust gas aftertreatment according to  claim 9 , wherein:
 in a first operating state of the exhaust gas burner, the quantity of fuel of the exhaust gas burner is pilot-controlled in such a way that the exhaust gas burner is operated with a sub-stoichiometric air-fuel ratio (λ B <1) and   in a second operating state of the exhaust gas burner, the quantity of fuel of the exhaust gas burner is pilot-controlled in such a way that the exhaust gas burner is operated with a super-stoichiometric air-fuel ratio (λ B >1).   
     
     
         11 . The method for exhaust gas aftertreatment according to  claim 10 , wherein the exhaust gas burner is operated alternately with a sub-stoichiometric air-fuel ratio (λ B <1) and with a super-stoichiometric air-fuel ratio (λ B >1). 
     
     
         12 . The method for exhaust gas aftertreatment according to  claim 10 , wherein the sub-stoichiometric air-fuel ratio (λ B ) is pilot-controlled in the range from 0.93 to 0.98. 
     
     
         13 . The method for exhaust gas aftertreatment according to  claim 10 , wherein the sub-stoichiometric air-fuel ratio (λ B ) is pilot-controlled in the range from 1.02 to 1.07. 
     
     
         14 . The method for exhaust gas aftertreatment according to  claim 9 , further comprising deactivating the exhaust gas burner once the three-way catalytic converter has reached a threshold temperature (T S ).