WO2018108301A1

WO2018108301A1 - Method for operating an internal combustion engine and internal combustion engine

Info

Publication number: WO2018108301A1
Application number: PCT/EP2017/001309
Authority: WO
Inventors: Johannes Bauer; Tim SPÄDER; Roland Werner
Original assignee: Mtu Friedrichshafen Gmbh
Priority date: 2016-12-13
Filing date: 2017-11-10
Publication date: 2018-06-21
Also published as: DE102016224833A1; DE102016224833B4

Abstract

The invention relates to a method for operating an internal combustion engine (1), having the following steps: introducing a first defined quantity of a first gaseous fuel into a combustion chamber (3) of the internal combustion engine (1), in a first operating mode; introducing a second defined quantity of a second liquid fuel into the combustion chamber (3) at a defined injection time, inflaming the fuels in the combustion chamber (3), and detecting a knocking signal for the combustion chamber (3) in order to determine a knocking intensity, wherein, in the first operating mode of the internal combustion engine (1), the defined injection time is moved later within a first postponement range (VB1) if the determined knocking intensity exceeds a first smaller threshold value, wherein the determined injection time is moved later within a second postponement range (VB2), which is expanded in comparison to the first postponement range (VB1), if the determined knocking intensity exceeds a second, larger threshold value.

Description

DESCRIPTION Method for operating an internal combustion engine and internal combustion engine

The invention relates to a method for operating an internal combustion engine and an internal combustion engine. If a first, gaseous fuel as well as a second, liquid fuel are supplied to a combustion chamber of an internal combustion engine, it is basically possible to react in different ways to a knocking combustion in the combustion chamber. It is possible to determine a time of ignition, typically by an injection time of the second, liquid fuel is determined to postpone; Additionally or alternatively, a quantity of the first gaseous fuel introduced into the combustion chamber can be reduced. A corresponding method is apparent, for example, from the German patent application DE 10 2011 089 292 AI. The various reaction options have different, generally undesirable side effects, for example on the emissions, the efficiency and / or the operating costs of the internal combustion engine. Furthermore, the different measures have different speeds. In addition, a variety of constraints to consider if the internal combustion engine is to be operated optimally. Known methods are in particular in view of the consideration of such constraints and optimal operation of the internal combustion engine in need of improvement. The invention is therefore based on the object, a method for operating a

Internal combustion engine and to provide an internal combustion engine in which the disadvantages mentioned do not occur.

The object is achieved by providing the subject matters of the independent claims. Advantageous embodiments emerge from the subclaims.

The object is achieved in particular by a method for operating a

Internal combustion engine is created with the following steps: It is in a first mode, a first specific amount of first gaseous fuel in a combustion chamber of Internal combustion engine introduced. A second specific amount of second, liquid fuel is introduced into the combustion chamber at a specific injection time. The fuels are ignited in the combustion chamber. A knock signal for determining a knock intensity for the combustion chamber is detected. The knock signal is preferably evaluated to determine the knock intensity. In the first operating mode of the internal combustion engine, the specific injection time within a first shift range is late

shifted when the determined knock intensity exceeds a first, smaller threshold, wherein the determined injection timing is delayed within a second, extended compared to the first shift range shift range when the determined knock intensity exceeds a second, larger threshold. The method has advantages over the prior art. In particular, the method allows a multi-stage escalation chain in response to knocking combustion in the combustion chamber: Thus, the injection timing within the first displacement range, which is preferably tuned to minimum or legally allowable emissions of the internal combustion engine, shifted as long as the knock intensity of the second, larger

Threshold, wherein the shift range can be extended when the knock intensity exceeds the second, larger threshold. In this way it is possible to respond more flexibly to the actual intensity of a knocking combustion, wherein in particular an emission-damaging extension of the displacement range for the specific injection time is only performed when this is actually necessary to protect the internal combustion engine. Previously, the injection timing can be shifted within narrow limits, namely in the first displacement range, while ensuring safe operation of the internal combustion engine and allowable emissions can be met.

The first gaseous fuel used is in particular a fuel which is gaseous under normal conditions, that is to say in particular at 1013 mbar and 298 K,

in particular a fuel gas, preferably a methane-containing fuel gas, particularly preferably CNG (compressed natural gas), LPG (liquid petroleum gas), natural gas, in which

Extracting gas, in particular source gas, landfill gas, biogas, or any other suitable gas. The first, gaseous fuel is preferably introduced upstream of the combustion chamber in a charging path or air path of the internal combustion engine, in particular in a suction tube, preferably by Mehrpunkteindüsung, Einzelpunkteindüsung or by means of a gas mixer, preferably upstream of a arranged in the charging path Compressor, so that by the compressor, a mixture of charge air and gaseous fuel is compressed, or in another suitable manner.

As a second, liquid fuel in particular a fuel is used, the under

Normal conditions, that is, in particular at 1013 mbar and 298 K liquid, particularly preferably an ignition oil, in particular diesel, dimethyl ether or the like. The second, liquid fuel is preferably introduced directly into the combustion chamber, in particular injected, in particular via a dedicated injector. The ignition of the fuels in the combustion chamber is preferably carried out by auto-ignition of the second, liquid fuel, which takes place in particular in very close temporal relation to the injection time, in particular to the injection time. The injection time thus defines the time of ignition of the fuels. In particular, the beginning of the injection of the second fuel into the combustion chamber is referred to below the injection time.

The first operating mode of the internal combustion engine is in particular a two-fuel operation, in which the combustion chamber both the first, gaseous fuel and the second liquid fuel are supplied.

The internal combustion engine is operated in particular so that not only a minimum, necessary for the ignition ignition amount of the second liquid fuel in the combustion chamber

is introduced, but that also the second certain amount of the second, liquid

Fuel for power generation in the combustion chamber contributes more than marginally. In this case, the first specific amount of first fuel is preferably different from the second specific amount of second fuel. It is possible for the first quantity and the second quantity to be chosen as a function of the operating point. In the operation of the internal combustion engine, a substitution of the second, liquid fuel to a certain proportion is preferably carried out by the first, gaseous fuel, which can be done in particular operating point-dependent. This substitution is preferably infinitely or discretely possible, with preferably from 0% of the second, liquid fuel to nearly 100% of the second, liquid

Fuel can be replaced by the first, gaseous fuel. An amount of fuel is understood in particular to mean a fuel mass. Preferably, the knock signal is evaluated by being filtered. The filtered one

Tapping signal can be used as knock intensity. However, the knock signal can also be used directly as a knock intensity, being compared only with the determined threshold value.

If an internal combustion engine is operated, which has a plurality of combustion chambers, the knock signal is preferably detected individually for the combustion chamber, either by means of a

Plurality of sensors, or by means of a sensor whose sensor signal is preferred

Crankshaft angle dependent is evaluated. Preferably, the knock intensity is determined combustion chamber individually, with the displacement of the particular

Injection timing is performed individually for each combustion chamber. On the other hand, the selection of the first or second shift range preferably takes place globally for the entire internal combustion engine, so that in particular the second shift range extended in comparison to the first shift range is released as soon as the knock intensity in one of the combustion chambers exceeds the second, larger threshold value.

For detecting the knock signal, preferably at least one structure-borne sound sensor, at least one cylinder pressure sensor, or at least one other suitable sensor is used. The fact that the specific injection timing is delayed, means in particular that this - preferably indicated on a crankshaft angle scale closer to a top dead center of a piston displaceable in the combustion chamber is moved zoom, wherein the top dead center separates a compression stroke of a power stroke of the combustion chamber , The determined injection time is preferably iteratively, in particular incrementally, postponed if the determined knock intensity is the first and / or the second threshold value

exceeds.

The fact that the second displacement region is widened in comparison to the first displacement region preferably means, in particular, that the second displacement region overlaps the first displacement region, but it extends a larger interval - in particular late - for permissible injection times, in particular on the

Crankshaft angle scale includes. It is preferably provided that the first

Shift range and the second shift range have a common, earliest allowable injection timing quasi as the lower limit of the interval, but with a the latest permissible injection time for the second shift range is closer to the top dead center than the latest allowable injection time for the first

Displacement range. Thus, the two shift ranges differ

in particular by their upper limit for the late shift of the particular

Injection timing.

Specifically, the fact that the particular injection timing is delayed within the second shift range extended compared to the first shift range when the knock intensity exceeds the second, larger threshold means that the latest allowable injection timing is retarded when the knock intensity is second , exceeds larger threshold.

According to one development of the invention, it is provided that the first specific quantity of the first gaseous fuel is reduced if the specific injection time exceeds a first specific injection time threshold value - in the direction of late, that is, in the direction closer to top dead center. It is thus possible to reduce the amount of fuel gas introduced into the combustion chamber, if the shifting of the injection timing indicates an increased knocking tendency, which is in particular due to the properties of the fuel used

Fuel gas can be. Preferably, the first particular injection timing threshold is selected to be equal to the latest allowable injection time of the first

Displacement range is, so that in particular when the knock intensity exceeds the second, larger threshold, not only the injection timing can be moved to late, but also the combustion chamber in the extended second shift range less fuel gas is supplied. Alternatively or additionally, it is preferably provided that the first specific amount of the first gaseous fuel is reduced when the knock intensity exceeds the second, larger threshold value, preferably independently of the instantaneous value of the specific injection time point.

According to one embodiment of the invention, it is provided that the second specific amount of the second, liquid fuel, when the first predetermined amount of the first gaseous fuel is reduced, is increased such that a power and / or torque of the internal combustion engine - in particular to a certain, in particular momentary load point - is kept constant / are. The reduction of the combustion chamber supplied Quantity of fuel gas is thus compensated by an increased amount of the combustion chamber supplied ignition oil.

According to one embodiment of the invention, it is provided that the first specific quantity of the first, gaseous fuel is reduced as a function of the injection time, in particular currently valid. Particularly preferably, it is provided that the first specific quantity is reduced as a function of a difference between the particular injection time, in particular currently valid, and the first specific injection time threshold value. This allows a gradual reduction of the first specific amount when a knocking combustion occurs. The reduction of the first specific amount of the first gaseous fuel may depend on the

certain injection timing and / or the difference between the determined

Injection time and the first specific injection timing threshold in a map deposited.

According to one embodiment of the invention, it is provided that the introduction of the first amount of the first gaseous fuel in a second operating mode of the internal combustion engine is omitted when the knock intensity exceeds a third threshold, wherein the third threshold is greater than the second, larger threshold. In particular, the third threshold value is therefore greater than the first, smaller threshold value, which is smaller than the second, larger threshold value. This second operating mode is in particular a pure Zündölbetrieb, in particular diesel operation of the internal combustion engine without admixture of fuel gas. This second mode corresponds to a third escalation stage of the then three-stage escalation chain in response to a knocking combustion, the

Internal combustion engine can be efficiently protected at high knock intensity, that is switched to a pure diesel operation. The switching to the second operating mode is preferably carried out independently of the current specific injection time and / or the current specific amount of first, gaseous fuel which is supplied to the combustion chamber. Thus, it depends preferably exclusively on the knock intensity, whether in the second operating mode of the internal combustion engine and thus the introduction of the first gaseous fuel is omitted.

According to one embodiment of the invention, it is provided that the specific injection time and / or a latest permissible injection time for the second shift range after is shifted early if the knock intensity is smaller than the second, larger threshold value, after which the knock intensity before, that is in particular in one

previous work cycle of the combustion chamber has exceeded the second, larger threshold. This allows a withdrawal of the late shift of

Injection timing and thus its return to a favorable in terms of the emissions of the internal combustion engine area when knocking combustion no longer occurs. The second, extended shift range is thus released only briefly and

in particular cyclically deactivated again. In this way, it can be prevented, in particular, that incorrectly recognized knocking does not erroneously permanently release the extended, second shift range, which is detrimental to the emissions of the engines

Internal combustion engine would affect. This preferably means that the particular

Injection time and / or the latest allowable injection time for the second

Shift range is moved to early if the specified

Injection time exceeds a second specific injection timing threshold and at the same time the knock intensity is smaller than the second, larger threshold value. The second specific injection time threshold value may preferably be equal to the first

be determined injection timing threshold, ie in particular equal to the latest allowable injection timing of the first shift range. Thus, the momentarily valid shift range can be reduced and, in particular, attributed to the first shift range if knocking combustion no longer occurs whose intensity is greater than the second, larger threshold value. Preferably, the shift of the specific injection timing and / or the latest injection timing is gradual, in particular such that a plurality of steps for returning the

Injection timing to the first, smaller shift range are needed. In particular, it is possible that a smaller increment is provided for the injection timing shift to early than for the injection timing shift late when the

Knock intensity exceeds the first or second threshold. This prevents too fast a return of the injection timing with the associated risk of sudden, intense knocking.

The object is also achieved by providing an internal combustion engine which has at least one combustion chamber and at least one first introduction means for introducing a first specific quantity of a first, gaseous fuel into the combustion chamber

Combustion chamber of the internal combustion engine in a first mode, and at least a second Introducing means for introducing a second predetermined amount of a second liquid fuel into the combustion chamber at a particular injection timing. Furthermore, at least one detection means is provided for detecting a knock signal for the at least one combustion chamber, and an evaluation means for determining a knock intensity for the at least one combustion chamber and preferably for evaluating the knock signal. The internal combustion engine also has a control device which is adapted to the particular

To retard injection timing within a first displacement range when the determined knock intensity exceeds a first, smaller threshold, the controller being arranged to retard the determined injection timing within a second displacement range extended compared to the first displacement range determined knock intensity a second, larger

Threshold exceeds. With regard to the internal combustion engine, the advantages which have already been explained in connection with the method result in particular. Preferably, the internal combustion engine is arranged to be operated with an embodiment of the method described above.

According to one embodiment of the invention, the internal combustion engine has a plurality of combustion chambers, wherein the at least one detection means is adapted to the

Detect knock signal combustion chamber individual, and wherein the control device is arranged to move the specific injection timing combustion chamber individual. It is possible that a plurality of detection means are provided, for example, a plurality of structure-borne sound sensors and / or cylinder pressure sensors, wherein in particular each combustion chamber may be associated with a detection means. However, it is also possible for a combustion chamber-individual detection of the knock signal to take place with a number of detection means which is smaller than the number of combustion chambers, in particular also with only one

Detection means or a detection means per cylinder bank, when the internal combustion engine having a plurality of cylinder banks, wherein the assignment of the knock signal can be made to a combustion chamber, in particular based on the crankshaft angle. According to one embodiment of the invention, it is provided that the internal combustion engine is designed as a dual-fuel engine, wherein the dual-fuel engine is in particular designed and configured for simultaneous operation with a fuel gas and an ignition oil in the at least one combustion chamber. The description of the method on the one hand and the internal combustion engine on the other hand are to be understood as complementary to one another. Features of the internal combustion engine that have been explicitly or implicitly described in connection with the method are preferably individually or combined features of a preferred embodiment of the

Internal combustion engine. Method steps which have been described explicitly or implicitly in connection with the internal combustion engine are preferably individually or combined with one another Steps of a preferred embodiment of the method. This is preferably characterized by at least one method step, which is due to at least one feature of an inventive or preferred embodiment of the internal combustion engine. The internal combustion engine is preferably characterized by at least one feature, which is due to at least one step of an inventive or preferred embodiment of the method.

The invention will be explained in more detail below with reference to the drawing. Showing:

Figure 1 is a schematic representation of an embodiment of a

Internal combustion engine;

FIG. 2 shows a schematic representation of the scope of an embodiment of the invention

Method used shift ranges;

Figure 3 is a first schematic representation of an embodiment of the method, and

Figure 4 is a second schematic representation of an embodiment of the method.

Fig. 1 shows a schematic representation of an embodiment of an internal combustion engine 1, which is in particular designed as a dual-fuel engine, which is adapted for operation with a fuel gas and an ignition oil. The internal combustion engine 1 has at least one

Combustion chamber 3 and a first introduction means 5 for introducing a first specific amount of a first gaseous fuel into the combustion chamber 3 in a first mode and a second introduction means 7 for introducing a second specific amount of a second liquid fuel in the combustion chamber 3 to a certain

Injection time on. The first introduction means 5 opens here into a suction pipe 9 of the internal combustion engine 1. In this case, the first introduction means 5 for Einzelpunkteindüsung or provided for Mehrpunkteindüsung and arranged. Through the suction pipe 9 is the combustion chamber 3 - as shown schematically by an arrow - preferably a mixture of preferably compressed charge air and the first, gaseous fuel fed. The second introduction means 7 is designed as an injector for the direct injection of the second, liquid fuel into the combustion chamber 3. During operation of the internal combustion engine 1, the two fuels are ignited in the combustion chamber 3, wherein in a conventional manner in the combustion chamber 3 movably arranged piston 11 in a working cycle of an upper

Dead center is urged toward a bottom dead center, and wherein exhaust gas from the

Combustion of the fuels in a subsequent Ausschiebetakt via an exhaust pipe 13 is discharged from the combustion chamber 3. The representation of the internal combustion engine 1 is extremely schematically as already mentioned, whereby numerous elements are not shown,

For example, at least one inlet valve and at least one outlet valve, which are preferably associated with the combustion chamber 3. Likewise, the first and second injection means 5, 7 are preferably in fluid communication with respective fuel reservoirs for the first fuel and the second fuel, which is also not shown here.

The internal combustion engine 1 also has at least one detection means 15 for detecting a knock signal for the combustion chamber 3. The detection means 15 may be designed in particular as a structure-borne noise sensor or as a cylinder pressure sensor, or in another suitable manner. It is preferably operatively connected to an evaluation means 17, which is set up for evaluating the knock signal, in particular for filtering it, wherein - in particular by filtering - a knock intensity can be determined from the knock signal. Furthermore, the internal combustion engine 1, a control device 19, which in turn the

Evaluation means 17 or is operatively connected to the evaluation means 17, wherein the control device 19 is further preferably operatively connected to the first introduction means 5 and the second insertion means 7 and arranged to delay in the first mode, the specific injection timing within a first displacement range, if the determined knock intensity exceeds a first, smaller threshold, and is further configured to extend the determined injection timing within a second, compared to the first shift range

Delay shift range when the knock intensity exceeds a second, larger threshold. The internal combustion engine 1 preferably has a plurality of combustion chambers 3, wherein the at least one detection means 15 is arranged to detect the knock signal combustion chamber individually, wherein the control device 19 is adapted to the particular

Injection timing to shift combustion chamber individual.

The controller 19 is preferably further configured to reduce the first predetermined amount of the first gaseous fuel when the determined injection timing exceeds a first predetermined injection timing threshold and / or when

Knock intensity exceeds the second, larger threshold. In this case, the second specific quantity of the second, liquid fuel is preferably increased in such a way that a power and / or a torque of the internal combustion engine 1 is / are kept constant.

In a second mode of operation, preferably, the introduction of the first quantity of the first gaseous fuel is omitted if the knock intensity exceeds a third threshold value. The third threshold is greater than the second threshold.

If the first specific quantity of the first fuel is reduced, this preferably takes place as a function of the currently valid specific injection time, particularly preferably as a function of a difference between the currently valid specific injection time and the first specific injection time threshold value.

The particular injection timing and / or a latest allowable injection timing for the second shift range is / are preferably advanced after the

Knock intensity is smaller than the second, larger threshold after it has previously exceeded the second, larger threshold, especially if the particular

Injection timing exceeds a second specific injection timing threshold, which may be equal to or different from the first specific injection timing threshold, and at the same time the knock intensity is smaller than the second, larger

Threshold.

Fig. 2 shows a schematic representation of the shift ranges. A working cycle of the combustion chamber 3 is intended as a full circle, of which only one segment is shown here.

In this case, an upper dead center OT is excellent, which is a compression stroke - counterclockwise before top dead center - from a power stroke - in Clockwise lying behind the top dead center - separates. The angular distances between the events to be explained here are greatly exaggerated in order to increase the clarity of the diagram. Shown by double arrows are here on the one hand, the first shift range VB 1 and on the other the second, in comparison to the first shift range VB1 extended shift range VB2, which overlap each other and in particular have a common earliest allowable injection time EZP1. The first shift range VB1 is limited by a first latest allowable injection time point EZP2.1. The second

Displacement range VB2 is bounded laterally by a second latest allowable injection time EZP2.2, wherein the second latest allowable injection timing EZP2.2 later, that is closer to the top dead center OT is arranged, as the first latest allowable injection time EZP2.1. The first displacement range VB1 preferably corresponds to a desired range with a view to favorable or legally permissible emissions of the

Internal combustion engine 1, wherein in particular in the over the first latest permissible

Injection time EZP2.1 outgoing range of the second shift range VB2 degraded emissions of the internal combustion engine 1 may occur. Therefore, this area is only entered, if necessary, to protect the internal combustion engine 1 due to correspondingly strong knocking combustion from damage. 3 shows a first schematic representation of an embodiment of the method for operating the internal combustion engine 1. In this case, a state ZI is shown, in which the first shift range VB1 is valid. If a knock intensity is detected which is greater than the first, smaller value, but smaller than the second, larger threshold value, the specific injection time within the first shift range VB1 is delayed. By a first arrow PI is shown that the procedure in a second

State Z2 in which the second shift range VB2 is valid, if in any combustion chamber 3 of the internal combustion engine 1, the knock intensity exceeds the second, larger threshold. In this case, the specific injection time within the second shift range VB2 is retarded, so it can in particular be moved to the second, latest allowable injection time EZP2.2.

In particular, when the specific injection timing is in the range between the first latest allowable injection time EZP2.1 and the second latest allowable injection time EZP2.2, preferably the first predetermined amount of first gaseous fuel is reduced, in particular depending on the currently valid one certain injection timing or depending on a difference between the currently valid particular injection timing and the first specific injection timing threshold value, which may be equal to the first latest allowable injection time EZP2.1. In this case, preferably the second specific amount of the second, liquid

Increased fuel so that a power and / or torque of the internal combustion engine is kept constant / are.

A second arrow P2 shows that the method can change to a third state Z2-1 if, in the second state Z2, the knock intensity no longer exceeds the second, larger threshold value. In the third state Z2-1, the specific injection time and / or the second latest allowable injection time EZP2.1 for the second shift range VB2 is then gradually decreased, so that the state of the internal combustion engine 1 is slowly changed in the direction of the first shift range VB1. It is shown by a third arrow P3 that this - unless the meantime, the second, larger threshold value of the knock intensity is exceeded again - means that finally the first state ZI is reached again, in which the first

Shift range VB 1 is valid. A fourth arrow P4 indicates that, starting from the third state Z2-1, the method can again change to the second state Z2 if the knock intensity exceeds the second, larger threshold value in any combustion chamber of the internal combustion engine 1. In this case, then the second shift range VB2 applies again with the original second latest permitted

Injection time EZP2.2.

4 shows a second schematic representation of the method. In this case, the knock signal is detected in a first step S 1 - preferably combustion chamber-specific - which is filtered in a second step S2, wherein a knock intensity is determined. In a third step S3, it is checked whether the knock intensity exceeds the third threshold, which is greater than the second, larger threshold value. If this is the case, in a fourth step S4 is changed to the second mode, and the introduction of the first gaseous fuel is omitted, so that the internal combustion engine 1 is operated in a pure diesel operation.

If, on the other hand, the knock intensity does not exceed the third threshold value, the method continues in a fifth step S5, in which it is checked whether the knock intensity exceeds the second, larger threshold value. If this is the case, in a sixth step S6 the second shift range VB2 is enabled, and the process proceeds to a seventh step S7. On the other hand, the knock intensity exceeds the second, larger one

Threshold, it is checked in an eighth step S8 whether the current valid injection timing has exceeded the second specific injection timing threshold, which may, for example, be equal to the first determined injection timing threshold and, in particular, equal to the first latest allowed injection timing EZP2.1. If this is the case, ie at the same time the particular injection time has exceeded the second specific injection time threshold and the knock intensity is smaller than the second, larger threshold, in a ninth step S9 the determined injection time and / or a later allowable injection time for the second

Shift range VB2 moved to early. The method is then continued in the seventh step S7.

On the other hand, if it is determined in the eighth step S8 that the specific injection timing has not exceeded the second specific injection timing threshold, this becomes

Procedure continues from the eighth step S8 in the seventh step S7.

In the seventh step S7, it is checked whether the knock intensity is the first, smaller

Threshold exceeds. If this is the case, in a tenth step S10 the specific injection timing is delayed, depending on the valid shift range within the first shift range VB1 or within the second shift range VB2. This shift is preferably carried out for individual combustion chambers.

Subsequently, it is checked in an eleventh step Si l whether the currently valid certain injection timing exceeds the first specific injection timing threshold. If this is the case, in a twelfth step S12, the first specific amount of the first gaseous fuel is reduced, wherein preferably at the same time the second specific amount of the second, liquid fuel is increased such that a power and / or a

Torque of the internal combustion engine 1 - in particular with respect to a certain momentary load point - is kept constant / be. Subsequently, the process ends in a thirteenth step S13.

If it is found in the eleventh step Si l that the currently valid certain

Injection timing does not exceed the first specific injection timing threshold, the process ends directly in the thirteenth step S13. Likewise, the method preferably ends directly in the thirteenth step S13 if it is determined in the seventh step S7 that the knock intensity does not exceed the first, smaller threshold value. The method is preferably carried out iteratively, that is, it starts again in the first step S1 after its termination in the thirteenth step S13.

Overall, it is found that with the method proposed here and the internal combustion engine 1, an improved control with regard to a knocking combustion of

Internal combustion engine 1 is possible, this being optimally operated and a variety of

Nebenbedingungen can be mastered.

Claims

Method for operating an internal combustion engine (1), comprising the following steps:

- Introducing a first predetermined amount of a first gaseous fuel in a combustion chamber (3) of the internal combustion engine (1) in a first mode;

- Introducing a second specific amount of a second liquid fuel in the combustion chamber (3) at a certain injection time;

- Ignition of the fuels in the combustion chamber (3), and

Detecting a knock signal for the combustion chamber (3) for determining a knock intensity, wherein in the first operating mode of the internal combustion engine (1)

a) the particular injection timing within a first shift range (VB1) is delayed when the determined knock intensity exceeds a first smaller threshold, wherein

b) the determined injection timing is retarded within a second shift range (VB2) extended in comparison to the first shift range (VB1) when the determined knock intensity exceeds a second larger threshold.

A method according to claim 1, characterized in that the first predetermined amount of first gaseous fuel is reduced when the determined injection timing exceeds a first predetermined injection timing threshold or when

Knocking intensity exceeds the second, larger threshold value, wherein preferably the second specific amount of second, liquid fuel is increased such that a power and / or torque of the internal combustion engine is kept constant / are.

Method according to one of the preceding claims, characterized in that the first predetermined amount of the first gaseous fuel is reduced depending on the particular injection timing, preferably depending on a difference between the determined injection timing and the first specific injection timing threshold. Method according to one of the preceding claims, characterized in that the introduction of the first predetermined amount of the first gaseous fuel in a second operating mode of the internal combustion engine (1) is omitted if the determined knock intensity exceeds a third threshold, wherein the third threshold value is greater than the second threshold.

Method according to one of the preceding claims, characterized in that the specific injection timing and / or a latest allowable injection timing for the second shift range (VB2) is postponed early if the

Knock intensity is less than the second, larger threshold after the

Knock intensity has previously exceeded the second, larger threshold.

Internal combustion engine (1), with

- at least one combustion chamber (3);

- At least a first introduction means (5), adapted for introducing a first predetermined amount of a first gaseous fuel in the combustion chamber (3) in a first operating mode of the internal combustion engine (1);

- At least a second introduction means (7), adapted for introducing a second specific amount of a second liquid fuel into the combustion chamber (3) at a certain injection time;

- At least one detection means, adapted for detecting a knock signal for the combustion chamber (3);

- an evaluation means (17) arranged to determine a knock intensity; and with

- A control device (19) which is adapted to in the first mode of the

Internal combustion engine (1)

a) to retard the determined injection timing within a first displacement range (VB1) when the determined knock intensity exceeds a first, smaller threshold, and

b) delaying the determined injection timing within a second shift range (VB2) extended in comparison to the first shift range (VB1) when the determined knock intensity exceeds a second, larger threshold value.

7. Internal combustion engine (1) according to claim 6, characterized by a plurality of combustion chambers (3), wherein the at least one detection means (15) is adapted to detect the knock signal combustion chamber individually, wherein the control device (19) is adapted to the particular Injection timing to shift combustion chamber individual.

8. Internal combustion engine (1) according to any one of claims 6 and 7, characterized in that the internal combustion engine (1) is designed as a dual-fuel engine and is adapted for operation with a fuel gas and an ignition oil.