Procedure and control unit for heating up a catalyst arranged in the exhaust gas system of a supercharged combustion engine

Abstract

Suggested is a procedure for heating up a catalyst in the exhaust gas system of a charged combustion engine by adding air to the exhaust gas system, whereby the added air is taken from a suction system of the combustion engine in the direction of the air current behind a compressor of an exhaust gas turbo charger that is arranged in the suction system. The procedure distinguishes itself thereby that the combustion engine is driven with a direct injection of fuel in its combustion chambers, whereby it is driven after a start-up with an apportionment of a fuel amount, which has to be injected before the beginning of a combustion, into at least two partial injections per ignition, and with a suboptimal ignition angle efficiency. A second independent claim concerns a control unit, which is customized for controlling the course of the procedure.

1 . A method of heating up a catalyst in an exhaust gas system of a charged combustion engine, the method comprising:
 adding air to the exhaust gas system, wherein the added air is taken from a suction system of the combustion engine in a direction of air current behind a compressor of an exhaust gas turbo charger that is arranged in the suction system;   driving the combustion engine with a direct injection of a fuel into a plurality of combustion chambers, wherein the combustion engine is driven:   after a start-up with an apportionment of a fuel amount injected before a beginning of a combustion, and wherein the fuel amount is apportioned into at least two partial injections per ignition per combustion chamber; and   with a suboptimal ignition angle efficiency.   
   
   
       2 . A method according to  claim 1 , further comprising injecting the fuel into each of the plurality of combustion chambers such that a rich fuel/air mixture develops in each of the plurality of combustion chambers. 
   
   
       3 . A method according to  claim 2 , further comprising injecting the fuel into each of the plurality of combustion chambers such that an exhaust gas lambda value is greater than or equal to 1 after adding air. 
   
   
       4 . A method according to  claim 1 , further comprising operating the combustion engine in an almost completely throttled state. 
   
   
       5 . A method according  claim 1 , further comprising operating the combustion engine after a start-up with an increased idle engine speed. 
   
   
       6 . A method according to  claim 1 , further comprising detecting an engine speed of the combustion engine at a start-up; and activating the heating-up of the catalyst when the engine speed exceeds a start-up engine speed threshold value. 
   
   
       7 . A method according to  claim 1 , further comprising using a combustion engine that is compatible with a jet-formed gasoline direct injection. 
   
   
       8 . A method according to  claim 7 , further comprising operating the combustion engine during an idle with an ignition angle between 25 degrees and 40 degrees after a top dead center. 
   
   
       9 . A control unit, especially a control unit of a supercharged combustion engine, configured to implement steps of a method of heating up a catalyst in an exhaust gas system of a charged combustion engine, the method comprising: adding air to the exhaust gas system, wherein the added air is taken from a suction system of the combustion engine in a direction of air current behind a compressor of an exhaust gas turbo charger that is arranged in the suction system; driving the combustion engine with a direct injection of a fuel into a plurality of combustion chambers, wherein the combustion engine is driven: after a start-up with an apportionment of a fuel amount injected before a beginning of a combustion, and wherein the fuel amount is apportioned into at least two partial injections per ignition per combustion chamber; and with a suboptimal ignition angle efficiency. 
   
   
       10 . The control unit of  claim 9 , further configured to implement steps comprising at least one of:
 injecting the fuel into the combustion chamber such that a rich fuel/air mixture develops in the plurality of combustion chambers;   injecting the fuel into the plurality of combustion chambers such that an exhaust gas lambda value is greater than or equal to 1 after adding air;   operating the combustion engine in an almost completely throttled state;   operating the combustion engine after a start-up with an increased idle engine speed;   detecting an engine speed of the combustion engine at a start-up; and activating the heating-up of the catalyst when the engine speed exceeds a start-up engine speed threshold value; and   operating the combustion engine during an idle with an ignition angle between 25 degrees and 40 degrees after a top dead center.