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

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 (t1) 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 (t1), 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.

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 (t1) 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 (t1), 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.

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.

Method according to one of the preceding claims, characterized in that an injection angle (αEE) of the late injection of the multiple injection is retarded essentially synchronously with the progressive retardation of the ignition angle.

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.

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 (αZ) and/or the injection angle (αEE) is progressively advanced and the multiple injection is terminated and a changeover to the single injection operation occurs as soon as the ignition angle (αEE) permits a homogeneous operation.

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.