Method for warming up a catalytic converter arranged downstream from a spark-ignition, direct injection internal combustion engine

Abstract

The invention relates to a method for warming up at least one catalytic converter that is arranged downstream from a spark-ignition, direct injection internal combustion engine. To this end, an exhaust gas temperature is at least temporarily increased by at least one measure, which is executed by the engine, after the conclusion (t 1 ) of the engine start of the internal combustion engine. The measures, which are executed by the engine, consist of a multiple injection during which at least two fuel injections into the cylinder are carried out within an induction cycle and compression cycle of a cylinder of the internal combustion engine, and/or said measures consist of a spark retarding. The invention provides that the measure executed by the engine or a combination of measures having the strongest heating action is available, at the earliest, after a retardation of at least two working cycles of the internal combustion engine after the conclusion (t 1 ) of the engine start. The method makes it possible to keep jumps in torque low, which result from the initiation of heating measures, and to provide these in a manner that can be reproduced and easily regulated. Moreover, a reliable ignition and combustion can be guaranteed during the entire warming up phase.

1 . Method for warming up at least one catalytic converter arranged downstream of a spark-ignition, direct injection internal combustion engine, whereby after a conclusion of an engine start (t 1 ) of the internal combustion engine an exhaust gas temperature is increased at least temporarily by at least one engine-related measure, and whereby the engine-related measures comprise a multiple injection, wherein at least two fuel injections into the cylinder are performed within an intake and compression stroke of a cylinder of the internal combustion engine and/or a retardation of an ignition angle, characterized in that the engine-related measure or combination of measures with the most profound heating effect occurs at the earliest after a delay of at least two operating cycles of the internal combustion engine after the conclusion of the engine start (t 1 ).  
     
     
         2 . Method according to  claim 1 , characterized in that the engine-related measure or the combination of measures with the most profound heating effect occurs at the earliest after a delay of at least three, in particular of at least five, operating cycles of the internal combustion engine after the conclusion of the engine start (t 1 ).  
     
     
         3 . Method for warming up at least one catalytic converter arranged downstream of a spark-ignition, direct injection internal combustion engine, whereby after an end of an engine start (t 1 ) of the internal combustion engine an exhaust gas temperature is increased at least temporarily by at least one engine-related measure, and the engine-related measures comprise a multiple injection, wherein at least two fuel injections into the cylinder are performed within an intake and compression stroke of a cylinder of the internal combustion engine, and/or a retardation of an ignition angle, characterized in that after the conclusion of the engine start (t 1 ), a single injection operation with at least temporary retardation of the ignition angle is performed during a first phase, and a changeover into a multiple injection operation occurs during a subsequent second phase.  
     
     
         4 . Method for warming up at least one catalytic converter arranged downstream of a spark-ignition, direct injection internal combustion engine, whereby after an end of an engine start (t 1 ) of the internal combustion engine an exhaust gas temperature is increased at least temporarily by at least one engine-related measure, and the engine-related measures comprise a multiple injection, wherein at least two fuel injections into the cylinder are performed within an intake and compression stroke of a cylinder of the internal combustion engine, and/or a retardation of an ignition angle, characterized in that after the conclusion of the engine start (t 1 ), an operation with 30 to 100% of an injected fuel quantity occurs during a first phase with an essentially homogeneous mixture preparation at an ignition time, and a multiple injection operation occurs in a subsequent second phase, wherein at the ignition time at least 35% of an injected fuel quantity is present as stratified charge and at least 20% of the fuel quantity is present in homogeneous distribution.  
     
     
         5 . Method according to one of the preceding claims, characterized in that the multiple injection comprises two injections, wherein a first early injection occurs essentially during an intake stroke and a second, late injection occurs during a subsequent compression stroke, and that the fuel supplied during the early injection has at the ignition time an essentially homogeneous distribution in the combustion chamber of the cylinder and the fuel supplied during the late injection is concentrated at the ignition time essentially as a stratified charge in a region around a spark plug.  
     
     
         6 . Method according to  claim 5 , characterized in that the early injection takes place in particular during a first half of the intake stroke and the late injection during a second half of the compression stroke.  
     
     
         7 . Method according to one of the  claims 3  to  6 , characterized in that the first phase is started initially with an early ignition angle (α Z ), in particular with an ignition angle (α Z ) before the upper dead center (U.D.C.), and that thereafter the ignition angle is adjusted progressively, continuously and/or stepwise towards a later ignition point, in particular up to an ignition angle (α Z ) after the upper dead center (U.D.C.).  
     
     
         8 . Method according to  claim 7 , characterized in that the changeover to a multiple injection operation occurs at an ignition angle (α Z ) of between 0 and 20° after U.D.C., in particular of 10° after U.D.C.  
     
     
         9 . Method according to  claim 8 , characterized in that the changeover into a multiple injection operation occurs around 4°, in particular around 2° before an ignition angle (α Z ) at which an exclusively homogeneous operation is still barely possible.  
     
     
         10 . Method according to one of the  claims 7  to  9 , characterized in that at the changeover to the multiple injection operation the last ignition angle (α Z ) of the first phase is adopted and the progressive retardation of the injection angle is continued after the changeover to the multiple injection operation.  
     
     
         11 . Method according to  claim 10 , characterized in that the progressive retardation of the injection angle occurs at a maximum ignition angle (α Z ) of 20 to 45° after U.D.C., in particular at a maximum ignition angle (α Z ) of 35° after U.D.C.  
     
     
         12 . Method according to one of the preceding claims, characterized in that an injection angle (α EE ) of the late injection of the multiple injection is retarded essentially synchronously with the progressive retardation of the ignition angle.  
     
     
         13 . Method according to  claim 12 , characterized in that an injection end (α EE ) of the late injection is adjusted with an essentially constant difference of 50 to 100°, in particular of 60 to 80°, relative to the ignition angle (α Z ).  
     
     
         14 . Method according to  claim 13 , characterized in that the difference between the injection end (α EE ) of the late injection and the injection angle (α Z ) is varied as a function of the engine rotation speed (n) and/or an injection pressure.  
     
     
         15 . Method according to one of the  claims 12  to  14 , characterized in that the injection end of the late injection is initially set to an angle (α EE ) of 40 to 90° before U.D.C., in particular 50 to 80° before U.D.C., and subsequently adjusted to an angle (α EE ) of 30 to 50° before U.D.C., in particular 40° before U.D.C.  
     
     
         16 . Method according to one of the preceding claims, characterized in that the initiation of the engine-related measure or the combination of measures with the most profound heating effect and/or the changeover to the multiple injection operation is identified based on a measured and/or or modeled engine and/or exhaust gas and/or catalytic converter temperature, and/or a time elapsed after the conclusion of the engine start and/or since a number of crankshaft revolutions after the conclusion of the engine start and/or a distance traveled after the conclusion of the engine start and/or a cumulative exhaust gas heat flow since the conclusion of the engine start.  
     
     
         17 . Method according to one of the preceding claims, characterized in that when the internal combustion engine is in a phase with an essentially constant load, in particular in idle, after at least partial warm-up of at least a first catalytic converter, the ignition angle (α Z ) and/or the injection angle (α EE ) is progressively advanced and the multiple injection is terminated and a changeover to the single injection operation occurs as soon as the ignition angle (α EE ) permits a homogeneous operation.  
     
     
         18 . Method according to  claim 17 , characterized in that the changeover to the single injection operation occurs at an ignition angle (α Z ) of 5 to 15° after U.D.C., in particular 10° after U.D.C.  
     
     
         19 . Method according to  claim 17  or  18 , characterized in that the progressive advancement of the ignition angle continues after the changeover to the single injection operation.  
     
     
         20 . Method according to one of the preceding claims, characterized in that when the internal combustion engine is in a load demand phase, in particular in a startup and/or acceleration phase, after at least partial warm-up of at least a first catalytic converter, the multiple injection and/or the retardation of the ignition angle is immediately terminated and a changeover to a single injection operation occurs.  
     
     
         21 . Method according to one of the  claims 17  to  20 , characterized in that the completed warm-up is identified based on a measured and/or or modeled exhaust gas and/or catalytic converter temperature and/or a time elapsed after the conclusion of the engine start and/or since a number of crankshaft revolutions after the conclusion of the engine start and/or a distance traveled after the conclusion of the engine start and/or a cumulative exhaust gas heat flow since the conclusion of the engine start.