DE102009045884B4 - Method for operating an internal combustion engine and internal combustion engine - Google Patents

Abstract

Method for operating an internal combustion engine (10), wherein in a stratified lean operation when detecting knock events, the fresh air mass in the combustion chamber (12) is increased.

Description

The invention relates to a method for operating an internal combustion engine. Furthermore, the invention relates to an internal combustion engine for carrying out the method.

State of the art

Combustion engines with direct fuel injection into the combustion chamber as well as an engine controller for displaying multiple operating modes and multiple injection sequences per cycle, such as double / triple injection, are known in the art. In the context of consumption-reducing or CO ₂ -absenkender measures is currently working on concepts to expand the stratified or lean operating range of gasoline engines.

In addition to optimized injection and control strategies, the combination of charging and charge stratification is one possible way. The actually usable layer area is limited thereby u. a. by emission requirements, in which case in particular the particles and nitrogen oxide emissions are of importance. From an engine-internal point of view, the usable inner operating range of the stratified operation and in particular of the charged lean operation is limited by knocking of the burns. Since this knocking or knock events have an effect on the inner operating range, it is necessary to respond appropriately when knocking occurs.

From the DE 28 52 715 C2 It is already known in internal combustion engines to respond to the occurrence of knock by an enrichment of the mixture in the combustion chamber. From the DE 100 43 694 A1 It is already known that when knocking occurs due to a particular time distribution of the injection, a cooling effect is achieved and as a result the knocking is reduced. Such a method is also from the JP H11-241 626 A known. From the DE 10 2006 029 279 B3 It is known to reduce the amount of air for a cylinder when knocking occurs. But this is a system, which is operated with λ = 1.

It thus sets itself the task of avoiding occurring in high-load conditions, especially in the charged and stratified engine operation knock events by appropriate control intervention of the engine control.

Disclosure of the invention

Against this background, a method having the features of claim 1 and an internal combustion engine having the features of claim 7 are presented. Embodiments of the method emerge from the dependent claims.

Thus, especially in the charged and stratified engine operation at high load conditions occurring knock events are avoided by appropriate control actions of the engine control by the knock tendency, d. H. Self-ignition properties of the air / fuel mixture, specifically reduced.

By a functionality adapted to the stratified lean operation of the internal combustion engine reliable detection of unwanted knock events is ensured. If knocking events are detected or detected, in particular during supercharged shift operation, measures must be taken to reduce the self-ignition properties of the air / fuel mixture immediately.

In homogeneous engine operation, this is typically done via a Zündwinkelspätzug, by the knock tendency can be reduced. In stratified engine operation, however, the ignition angle can be varied only within very narrow limits, the influence on the self-ignition characteristics being insufficient.

By the method described here, the reduction of the tendency to knock by increasing the fresh air mass supplied and possibly adjusting the inert gas rate is possible, which can be represented in the underlying supercharged layer motors, eg. By increasing the boost pressure.

After engine-critical knock events have been detected, a targeted dilution of the air / fuel mixture takes place in the combustion chamber, for example by increasing the charge pressure. By additionally guided into the combustion chamber fresh air is a targeted reduction of the tendency to knock due to internal cooling and by avoiding local fat zones. Furthermore, z. B. from emission point of view, an adaptation of the exhaust gas recirculation rates to the changed fresh air mass in the combustion chamber be useful.

If knock events still occur despite the maximum permissible increase in the fresh air portion and the maximum permissible adjustment of the exhaust gas recirculation rate, the stratified lean operation should be temporarily prohibited as a final countermeasure and changed to an alternative homogeneous (firing variable) operating mode.

Further advantages and embodiments of the invention will become apparent from the accompanying drawings and the description.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations or alone, without departing from the scope of the present invention.

Short description of the drawing

1 shows an embodiment of the described internal combustion engine.

Embodiment of the invention

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described below in detail with reference to the drawings.

In 1 is an embodiment of the proposed internal combustion engine, in total with the reference numeral 10 provided, shown. This internal combustion engine 10 includes a combustion chamber 12 , in which the combustion of an air / fuel mixture takes place. This can lead to knocking events.

The illustration also shows a device 14 for recording and evaluation of knocking events. This device 14 has a knock sensor 16 who is in the combustion chamber 12 located, and an evaluation unit 18 on. With the device 14 Thus, knock events in the combustion chamber 12 detected and evaluated. Depending on the specification, suitable countermeasures are initiated either immediately upon the occurrence of a knock event or upon reaching a critical limit of the number or frequency of knock events.

This is to a unit 20 to set the boost pressure sent a corresponding signal, so that the boost pressure and thus the fresh air mass is increased.

Claims (7)

Method for operating an internal combustion engine ( 10 ), in which, in the case of a stratified lean-burn mode, when knocking events are detected, the fresh air mass in the combustion chamber ( 12 ) is increased. The method of claim 1, wherein the increase of the fresh air mass is achieved by increasing the boost pressure. The method of claim 1 or 2, wherein upon detection of knock events, an inert gas rate is adjusted. Method according to one of claims 1 to 3, wherein the knock events with at least one knock sensor ( 16 ). Method according to one of claims 1 to 4, wherein an adaptation of the exhaust gas recirculation rates to the changed fresh air mass takes place. Method according to one of claims 1 to 5, in which, if further knock events occur, the stratified lean operation is temporarily excluded and changed to an alternative homogeneous operating mode. Internal combustion engine with a device ( 14 ) for detecting and evaluating knock events, which causes an increase in the fresh air mass in a stratified lean operation when detecting knock events.

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