Method and device for operating internal combustion engine

Abstract

The invention relates to a device for operating an internal combustion engine with fuel. The device is configured to determine a standard ignition angle based on ignition angle characteristic data for an actual operating point of the internal combustion engine and to determine a knock limit distance of the standard ignition angle from a knock limit of the internal combustion engine based on knock limit distance characteristic data for the actual operating point of the internal combustion engine. The device is also configured to determine an actual ROZ value of the fuel and / or an operating ignition angle for operating the internal combustion engine on the basis of the standard ignition angle and on the basis of the knock limit distance.

Description

Technical Field

[0001] The invention relates to a method and a corresponding device for determining an ignition angle for operating an internal combustion engine, in particular for pilot controlling the internal combustion engine. Background Art

[0002] An internal combustion engine of a vehicle, in particular a gasoline engine, is preferably operated as close to the knock limit as possible in order to optimize the efficiency of the internal combustion engine. The knock limit is usually determined by the quality of the fuel, in particular the octane number (i.e., the ROZ value). A high-quality fuel with a relatively high ROZ value allows the internal combustion engine to be operated without knock at a relatively early ignition time (i.e., a relatively "early" ignition angle), thereby improving the efficiency of the internal combustion engine.

[0003] In order to determine the earliest possible ignition time or ignition angle that allows the internal combustion engine to run without knock, a previously determined ignition angle characteristic diagram (Kennfeld) (e.g., by experiments and / or based on simulations) can be used. The ignition angle characteristic diagram can be determined for fuels with relatively high ROZ values. In addition, the ignition angle characteristic diagram can be determined for a specific standard temperature (e.g., a standard temperature of the fuel, the intake air, the coolant, and / or the direct environment of the combustion chamber). In general, the ignition angle characteristic diagram can be determined for one or more standard boundary conditions. The one or more standard boundary conditions can also be alternatively referred to as design boundary conditions (because the ignition angle characteristic diagram is designed for the one or more boundary conditions).

[0004] If the vehicle is operated with a fuel having a lower actual ROZ value (lower than the standard ROZ value on which the ignition angle characteristic map was designed), a difference value can be determined according to knock adaptation for correcting the ignition angle specified in the ignition angle characteristic map. Furthermore, if the actual temperature of the fuel deviates from the standard temperature (in particular if the actual temperature (e.g. of the fuel, the intake air, the coolant and / or the immediate surroundings of the combustion chamber) is higher than the standard temperature), an offset value can be determined according to the temperature model for correcting the ignition angle specified in the ignition angle characteristic map.

[0005] It is foreseeable that the quality of available fuel, ie the ROZ value, will further increase, wherein the increased ROZ value should be used as a standard ROZ value for the ignition angle characteristic map in order to effectively utilize the increase in engine efficiency that can be achieved by the increase in fuel quality.

[0006] However, it has been found that the ignition angle characteristic diagram of fuels with such high ROZ values ​​(e.g. ROZ>100) can no longer be determined experimentally at all operating points at a standard temperature (e.g. at 20° C.). In particular, at certain operating points (e.g. due to limitations on the maximum permissible operating pressure and / or maximum permissible operating temperature of the internal combustion engine), the ignition time or the ignition angle can no longer be set so far in advance that the knock limit is reached.

[0007] Thus, the ignition angle characteristic diagram determined for a fuel with a particularly high ROZ value shows, at certain operating points (in particular for relatively high engine loads), ignition angles which are caused by the operating limits of the internal combustion engine (with respect to the operating pressure and / or with respect to the operating temperature) and which do not correspond to the earliest possible ignition angle at the knock limit. As a result, the internal combustion engine cannot be operated in an efficiency-optimized manner at certain operating points even if the actual fuel conditions (in particular the actual temperatures, such as the fuel temperature, the temperature of the intake air, the coolant temperature and / or the temperature of the immediate surroundings of the combustion chamber) deviate from standard boundary conditions (in particular the standard temperature). Summary of the invention

[0008] The technical object to be achieved here is to enable efficiency-optimized operation of an internal combustion engine even with fuels having particularly high ROZ values, in particular when the actual boundary condition or conditions deviate from the standard boundary condition or conditions for which the ignition angle characteristic map has been determined.

[0009] The task is solved by the features of the independent claim. Advantageous embodiments are described in the dependent claims. It should be noted that the additional features of the claims dependent on the independent claim can constitute an independent invention independent of the combination of all features of the independent claim without the features of the independent claim or in combination with only part of the features of the independent claim, which can be the technical solution of the independent claim, divisional application or subsequent application. The same applies to the technical teachings described in the specification, which can form an invention independent of the features of the independent claim.

[0010] According to one aspect, a device for operating an internal combustion engine, in particular a gasoline engine, with a fuel, in particular gasoline, is described. The fuel has an actual ROZ value. The device can be used to determine an operating ignition angle, by means of which the internal combustion engine can be operated in a manner that is as efficiency-optimized as possible when using the fuel with the actual ROZ value. The operating ignition angle can be used for precontrolling (ignition angle) of the internal combustion engine, in particular ignition angle regulation of the internal combustion engine.

[0011] The device can be used to determine a standard ignition angle based on ignition angle characteristic data of an actual operating point of the internal combustion engine (currently present). The actual operating point can be defined by a combination of an actual load and an actual speed. The ignition angle characteristic data can respectively provide standard ignition angles for a plurality of different possible operating points. The ignition angle characteristic data can be determined by experiments and / or based on simulations before the operation of the internal combustion engine. If necessary, different ignition angle characteristic data can be provided for different operating modes of the internal combustion engine (such as valve electronic control operation (load control by valve lift), standard operation, throttle operation, Miller operation, etc.).

[0012] The ignition angle characteristic data may be based on one or more standard boundary conditions for operating the internal combustion engine. Exemplary standard boundary conditions include standard temperatures (e.g., standard temperatures of the fuel, intake air, coolant, and / or the immediate surroundings of the combustion chamber) and / or standard lambda values ​​(i.e., a standard ratio of the amount of combustion air to the amount of fuel in the combustion chamber of the internal combustion engine).

[0013] In addition, the ignition angle characteristic data can be based on the operation of the internal combustion engine when using a fuel with a standard ROZ value. The standard ROZ value can also be referred to as a design ROZ value instead, because the ignition angle characteristic data is already designed for the standard ROZ value (i.e., for the design ROZ value). The purpose of determining the ignition angle characteristic is to provide a standard ignition angle for each of a plurality of possible operating points of the internal combustion engine, and the standard ignition angle (when the one or more standard boundary conditions exist) is at the knock limit of the internal combustion engine. Therefore, the ignition angle characteristic data can be determined in such a way that the ignition angle characteristic data for each operating point can respectively give such an ignition angle as far as possible, which is directly at the knock limit of the internal combustion engine when using a fuel with a standard ROZ value and when the one or more standard boundary conditions exist and / or the ignition angle can achieve efficiency-optimized operation of the internal combustion engine.

[0014] However, the standard ROZ value may be so high that, based on one or more physical limit values ​​of the internal combustion engine (e.g., pressure limit value and / or temperature limit value), the ignition angle characteristic data respectively specifies a standard ignition angle for at least some of the multiple possible operating points, which standard ignition angle has an ignition angle difference from the knock limit of the internal combustion engine (when the one or more standard boundary conditions exist). In other words, when using a fuel with a relatively high standard ROZ value (e.g., ROZ>100), the internal combustion engine may not be able to be operated directly at the knock limit at least for some of the possible operating points (especially at relatively high engine loads). Therefore, the ignition angle characteristic data does not specify an ignition angle at the knock limit for this part of the possible operating points, but rather specifies an ignition angle that differs from the knock limit by a certain ignition angle difference.

[0015] Furthermore, the device is configured to determine a knock limit distance (in particular an ignition angle difference) between a standard ignition angle and a knock limit of the internal combustion engine based on knock limit distance characteristic data for an actual operating point of the internal combustion engine. The knock limit distance may represent an ignition angle difference that deviates between the standard ignition angle at the actual operating point of the internal combustion engine and the knock limit of the internal combustion engine (when the one or more actual boundary conditions exist or when the one or more standard boundary conditions exist) (and the standard ignition angle may be further adjusted in an “advanced” direction before reaching the knock limit of the internal combustion engine by the ignition angle difference).

[0016] The knock limit distance characteristic data can respectively provide knock limit distances for a plurality of possible operating points of the internal combustion engine. The knock limit distance characteristic data can be determined by experiments and / or simulations before the internal combustion engine is operated. If necessary, different knock limit distance characteristic data can be respectively provided for different operating modes of the internal combustion engine (such as valve electronic control operation (load control through valve lift), standard operation, throttle operation, Miller operation, etc.).

[0017] The device may be configured to determine a knock limit distance of a standard ignition angle from a knock limit of the internal combustion engine as a function of the one or more actual boundary conditions, in particular as a function of a deviation of the one or more actual boundary conditions from the one or more corresponding standard boundary conditions. In this way, the knock limit distance may be determined in a particularly precise manner.

[0018] Furthermore, the device is configured to determine an operating ignition angle and / or an actual ROZ value of the fuel for operating the internal combustion engine based on a standard ignition angle and based on a knock limit distance. By taking into account the knock limit distance, which is dependent on the ignition angle difference between the standard ignition angle and the knock limit of the internal combustion engine, an efficiency-optimized operation of the internal combustion engine can be achieved in an efficient and reliable manner even with particularly high-quality fuels (with particularly high actual ROZ values) (at least when the one or more actual boundary conditions deviate from the one or more corresponding standard boundary conditions).

[0019] The device can be configured to determine one or more (currently existing) actual boundary conditions for operating the internal combustion engine, which at least partially deviate from the one or more corresponding standard boundary conditions. In this case, an offset value can be determined with the aid of a correction unit, in particular a model-based correction unit, and based on the one or more actual boundary conditions. The actual ROZ value of the operating ignition angle and / or the fuel for operating the internal combustion engine can then be determined in a particularly precise manner based on the offset value. This can further increase the efficiency of the internal combustion engine.

[0020] The device is provided for determining an adapted ignition angle difference between a standard ignition angle and a knock limit of the internal combustion engine (when one or more actual boundary conditions are present) according to knock adaptation (e.g. according to knock control). In this case, the one or more limit values ​​of the internal combustion engine can be taken into account within the scope of knock adaptation. In particular, it can be ensured within the scope of knock adaptation that one or more limit values ​​of the internal combustion engine are not exceeded. This (when using fuels with relatively high actual ROZ values) can result in the actual knock limit of the internal combustion engine not being reached within the scope of knock adaptation.

[0021] The actual ROZ value for the operating ignition angle and / or the fuel for operating the internal combustion engine can also be determined in a particularly precise manner based on the adapted ignition angle difference. The device can be configured in particular to determine the actual ROZ value for the fuel by subtracting a first differential ROZ value associated with the adapted ignition angle difference from a standard ROZ value and adding a second differential ROZ value associated with the knock limit distance. In this way, the actual ROZ value for the fuel can be determined in a particularly precise manner.

[0022] Thus, the device can be configured to determine an actual ROZ value for the fuel used when operating the internal combustion engine. The actual ROZ value can be compared with a ROZ threshold value (the ROZ threshold value can be different for different operating points of the internal combustion engine if necessary). It can then be decided based on the comparison whether the knock limit distance is to be taken into account when determining the operating ignition angle. The device can in particular be configured to take the knock limit distance into account when determining the operating ignition angle, in particular only when the actual ROZ value is equal to or greater than the ROZ threshold value. In this way, the reliability of operating the internal combustion engine (in particular with regard to knock-free operation of the internal combustion engine) can be further increased in an efficiency-optimized manner.

[0023] According to a further aspect, a (road) motor vehicle, in particular a passenger car, a truck, a bus or a motorcycle, is described, which comprises a device as described herein.

[0024] According to another aspect, a method for operating an internal combustion engine with a fuel, in particular gasoline, is described. The method comprises determining a standard ignition angle for an actual operating point of the internal combustion engine based on ignition angle characteristic data, determining a knock limit distance of the standard ignition angle from a knock limit of the internal combustion engine based on knock limit distance characteristic data and for the actual operating point of the internal combustion engine. Furthermore, the method comprises determining an actual ROZ value for an operating ignition angle and / or a fuel for operating the internal combustion engine based on the standard ignition angle and based on the knock limit distance.

[0025] According to another aspect, a software (SW) program is described. The SW program can be configured to be executed on a processor (for example on a control unit of a vehicle) and thereby implement the method described herein.

[0026] According to another aspect, a storage medium is described. The storage medium may include a SW program which is arranged to be executed on a processor and thereby implements the method described herein.

[0027] It should be noted that the methods, devices and systems described herein can be used not only individually but also in combination with other methods, devices and systems described herein. In addition, each aspect of the methods, devices and systems described herein can be combined with each other in a variety of ways. In particular, the features of the claims can be combined with each other in a variety of ways. In addition, the features listed in brackets should be understood as optional features. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is described in detail below with reference to embodiments. The accompanying drawings are as follows:

[0029] Figure 1a shows exemplary components of a vehicle having an internal combustion engine;

[0030] Figure 1b An exemplary ignition angle characteristic diagram is shown;

[0031] Figure 1c An exemplary device for determining an ignition angle or ignition time for operating an internal combustion engine is shown;

[0032] Figure 2 A device is shown for determining an ignition angle or ignition time for operating an internal combustion engine while taking into account a fuel having a particularly high ROZ value; and

[0033] Figure 3 A flow chart of an exemplary method for determining an ignition angle for operating an internal combustion engine is shown. DETAILED DESCRIPTION

[0034] As mentioned at the outset, the present invention relates to increasing the efficiency of an internal combustion engine when operating on fuels having a particularly high ROZ value (eg ROZ>100). Figure 1a An exemplary vehicle 100 is shown having an internal combustion engine 102 which is configured to drive the vehicle 100 and which is operated with a fuel such as gasoline. A (control) device 101 of the vehicle 100 may be configured to determine an ignition angle for operating the internal combustion engine 102. It should be noted that in this document, the terms "ignition angle" and "ignition timing" are used interchangeably.

[0035] The vehicle 100 includes one or more sensors 104, which are configured to determine one or more operating conditions for operating the internal combustion engine 102 (i.e., the operating point of the internal combustion engine 102), such as the load and / or the speed of the internal combustion engine 102. The vehicle 100 may also include one or more sensors 103, which are configured to detect one or more actual boundary conditions for operating the internal combustion engine 102, such as temperatures (e.g., the fuel temperature, the temperature of the intake air, the coolant temperature, and / or the temperature of the immediate surroundings of the combustion chamber). The device 101 may be configured to determine an ignition angle for operating the internal combustion engine 102 as a function of the operating point of the internal combustion engine 102 and / or as a function of the one or more actual boundary conditions.

[0036] Figure 1b An exemplary ignition angle characteristic diagram 110 is shown, which has been determined before the operation of the internal combustion engine 102 (for example, by experiments and / or based on simulations). The ignition angle characteristic diagram 110 specifies a standard ignition angle 113 for each combination of one or more operating parameters of the internal combustion engine 102 (for example, load 112 and / or speed 111) (i.e., for the operating point of the internal combustion engine 102). The ignition angle characteristic diagram 110 may have been determined for a fuel with a standard ROZ value. In addition, the ignition angle characteristic diagram 110 may be determined for one or more standard boundary conditions. The standard ignition angle 113 may be the earliest possible ignition angle when using a fuel with a standard ROZ value and when the one or more standard boundary conditions exist, so as to achieve efficiency-optimized operation of the internal combustion engine 102.

[0037] If the fuel used during operation has a standard ROZ value and if the one or more standard boundary conditions are present, the internal combustion engine 102 can be operated with a standard ignition angle 113. If, on the other hand, the actual ROZ value deviates from the standard ROZ value and / or the one or more actual boundary conditions deviate from the one or more corresponding standard boundary conditions, it is generally necessary to adjust the standard ignition angle 113 in order to continue to achieve efficiency-optimized operation of the internal combustion engine 102.

[0038] Figure 1c An exemplary adjustment of the standard ignition angle 113 is shown. With the aid of the correction unit 120, an offset value 122 can be determined, with the aid of which the standard ignition angle 113 is adjusted, in particular (towards "retardation"), in order to determine an operating ignition angle 123 for operating the internal combustion engine 102. The (model-based) correction unit 120 can be configured to determine the offset value 122 based on one or more actual boundary conditions 121, in particular based on actual temperatures (e.g. actual temperatures of the fuel, intake air, coolant and / or the immediate surroundings of the combustion chamber) and / or based on an actual ROZ value. In combination Figure 1cThe described adjustment of the standard ignition angle 113 is based on the assumption that the actual ROZ value of the fuel is always smaller than the standard ROZ value (ie, smaller than the design ROZ value).

[0039] The development of new fuels makes available fuels with particularly high ROZ values ​​(e.g., ROZ>100). As a result, the standard or design ROZ value increases, for which the ignition angle characteristic diagram 110 needs to be determined and stored in the vehicle 100. As mentioned at the beginning, the internal combustion engine 102 usually has one or more limit values ​​that should not be exceeded during the operation of the internal combustion engine 102, such as pressure limit values ​​(e.g., for pistons, connecting rod bearings, spark plugs, etc.) and / or temperature limit values ​​(e.g., for pistons, connecting rod bearings, spark plugs, etc.). This in turn has the result that when using fuels with relatively high standard ROZ values ​​and when the one or more standard boundary conditions exist, at least for some of the possible operating points, an efficiency-optimized standard ignition angle 113 (which is at the knock limit of the internal combustion engine 102) cannot be determined. For these operating points, a standard ignition angle 113 is then usually stored in the characteristic diagram 110, which is generated by the one or more limit values ​​of the internal combustion engine 102.

[0040] If the internal combustion engine 102 is operated with an actual temperature that deviates from the standard temperature, in particular with a fuel that is above the standard temperature, the correction unit 120 determines an offset value 122 by which the standard ignition angle 113 in the ignition angle characteristic diagram 110 is increased, i.e. adjusted in the “retarded” direction. Such a correction of the standard ignition angle 113 may not be necessary if the standard ignition angle 113 shown by the characteristic diagram 110 is not at the knock limit due to a relatively high standard ROZ value. The internal combustion engine 102 is therefore not operated in an efficiency-optimized manner when the actual boundary conditions 121, in particular the actual temperature (e.g. the actual temperature of the fuel, the intake air, the coolant and / or the immediate surroundings of the combustion chamber) deviate from the corresponding standard boundary conditions.

[0041] Figure 2 An exemplary device 200 is shown which enables efficiency-optimized operation of an internal combustion engine 102 even based on an ignition angle characteristic map 110 for a fuel having a particularly high standard ROZ value. For this purpose, the device 200 comprises a compensation unit which is provided for determining a knock limit distance 222 for different operating points of the internal combustion engine 102, in particular for different combinations of load 112 and speed 111. The compensation unit can be based on a predetermined compensation characteristic map or knock distance characteristic map 220 which specifies the knock limit distance 222 for different operating points.

[0042] The knock limit distance 222 of the operating point can depend on the degree of deviation between the standard ignition angle 113 (based on the one or more limit values ​​of the internal combustion engine 102) and the knock limit (and thus the efficiency-optimized operation of the internal combustion engine 102) displayed by the ignition angle characteristic diagram 110. The knock limit distance 222 can be different for different operating points (and, if necessary, for different operating modes of the internal combustion engine 102). The compensation characteristic diagram 220 for determining the corresponding knock limit distance 222 can be determined before the internal combustion engine 102 is operated (by experiments and / or based on simulations).

[0043] Therefore, an offset value 122 of a standard ignition angle 113 displayed by the ignition angle characteristic diagram 110 (for the current operating point) can be determined based on the one or more actual boundary conditions 121. In addition, a knock limit distance 222 can be determined for the current operating point of the internal combustion engine 102 (if necessary taking into account the one or more actual boundary conditions 121). The standard ignition angle 113 can then be adjusted based on the offset value 122 and based on the knock limit distance 222 to determine an operating ignition angle 123 for operating (in particular for precontrolling) the internal combustion engine 102. For example, the operating ignition angle 113 Z B It can be determined as Z B = Z N + O - K, where Z N is the standard ignition angle 113 , O is the offset value 122 , and K is the knock limit distance 222 .

[0044] As mentioned at the outset, the internal combustion engine 102 should be operated at the knock limit in an efficiency-optimized manner throughout the entire operating range (i.e., for all operating points). The knock resistance of the fuel (i.e., the ROZ value of the fuel) is further improved by technical improvements in production. The measures described herein make it possible to utilize the efficiency-related potential provided by these fuels in terms of knock resistance in an effective and reliable manner.

[0045] By means of the control and / or regulation method during operation of the internal combustion engine 102, it is possible to infer the quality of the currently used fuel, i.e. the actual ROZ value, by measuring the knock limit (which is detected by the knock detection and regulation device). The determined fuel quality can be used to appropriately correct the ignition pilot control (i.e. the operating ignition angle 123). In addition, a model can be used to correct the ignition pilot control (i.e. the determination of the operating ignition angle 123), which takes into account the intake air temperature (i.e. the actual temperature) and / or the engine temperature.

[0046] If early ignition cannot be selected for the fuel without restriction over the entire range of the characteristic map (for example, because otherwise the component temperature limit of the spark plug would be exceeded), the measured knock limit usually no longer effectively reflects the quality of the fuel used (especially with regard to the actual ROZ value). Therefore, these operating ranges of the engine 102 cannot be taken into account when determining the fuel quality, so that the fuel quality cannot be determined in these ranges.

[0047] As mentioned above, when using highly knock-resistant fuels (ROZ value>100), the knock limit may no longer be measurable in the high load range, because under boundary conditions that are favorable to the knock tendency (low ambient and engine temperatures), in particular because under one or more of the standard boundary conditions, the maximum permissible pressure in the combustion chamber (i.e., the limit value of the internal combustion engine 102) would otherwise be exceeded. This maximum permissible pressure is defined, for example, by the component strength limits of the components involved in the combustion (such as components of the piston assembly, spark plug, connecting rod bearing, etc.) and components of the valve and crank mechanism. Therefore, the required distance from the knock limit makes it no longer possible to achieve the general application and / or error-free function of the above-mentioned fuel quality detection.

[0048] Under actual boundary conditions that are knock-critical due to an increase in temperature (e.g., fuel temperature, intake air temperature, or engine 102 temperature), the ignition is usually corrected in the "retard" direction (by the correction unit 120). If the same retardation of the ignition angle is used at those operating points where (under the one or more standard boundary conditions) there is a knock-limited distance to comply with the maximum permissible pressure (i.e. the one or more limit values ​​of the internal combustion engine 102) when using fuels with a relatively high octane number, the efficiency potential of the fuel will not be fully utilized. As a result, the fuel consumption and / or CO2 emissions and / or the exhaust gas temperature of the internal combustion engine 102 will usually increase, although this would not be necessary under actual boundary conditions that deviate from the standard boundary conditions.

[0049] As described above, knock adaptation can transmit an offset value 122 adapted to the currently used fuel mass to the ignition pilot control. This offset value 122 can additionally be corrected by a knock limit distance 222 (for example, in the form of a value read from a speed / load-dependent characteristic diagram 220). Thus, even in operating ranges where the knock limit cannot be reached with all fuel (for example, due to a maximum permissible pressure limit in the combustion chamber), the fuel mass can be determined or the fuel mass can be continuously correctly calculated.

[0050] Alternatively or additionally, the operating ignition angle 123 can be determined by comparing a correction of the ignition pilot control (e.g., a correction due to deviations from standard boundary conditions, such as a standard temperature) with the knock limit distance 222. This may be done only when certain activation conditions are met. An exemplary activation condition is that the actual ROZ value of the fuel based on the knock adaptation detection reaches or exceeds a certain ROZ threshold value (the ROZ threshold value can be different for different operating points of the internal combustion engine 102). By taking into account the knock limit distance 222, the ROZ potential of the high-octane fuel can be fully utilized to minimize carbon dioxide emissions and / or fuel consumption and / or minimize the negative effects of degradation measures.

[0051] Figure 3 A flow chart of a method 300 (possibly computer-implemented) for operating an internal combustion engine 102 with a fuel having an actual ROZ value is shown. Method 300 may be designed in particular for determining an operating ignition angle 123 for operating internal combustion engine 102 (in particular for pilot control of an ignition angle regulation).

[0052] Method 300 includes determining 301 a standard ignition angle 113 for an actual operating point of internal combustion engine 102 based on (predetermined) ignition angle characteristic data 110. The ignition angle characteristic data 110 may specify a standard ignition angle 113 for a plurality of different possible operating points. Possible operating points may correspond to a combination of load 112 and speed 111 of internal combustion engine 102, if necessary. The ignition angle characteristic data 110 may have been determined for a fuel having a standard ROZ value. Furthermore, the ignition angle characteristic data 110 may have been determined for operating internal combustion engine 102 when one or more standard boundary conditions exist, for example when a standard temperature of fuel and / or intake air exists, when a standard temperature of the internal combustion engine exists, and / or when a standard lambda value (i.e., a standard ratio of combustion air to fuel) exists.

[0053] During current operation of internal combustion engine 102 , one or more actual boundary conditions may exist which deviate from the one or more corresponding standard boundary conditions.

[0054] Method 300 further comprises determining 302 a knock limit distance 222 of the standard ignition angle 113 from the knock limit of the internal combustion engine 102 based on the knock limit distance characteristic data 220 and for the actual operating point of the internal combustion engine 102. The knock limit distance 222 may represent an ignition angle difference by which the standard ignition angle 113 deviates from the knock limit of the internal combustion engine 102 at the (current) actual operating point (and when the one or more actual boundary conditions exist). The knock limit distance 222 may depend on the one or more actual boundary conditions, in particular on a deviation of the one or more actual boundary conditions from the one or more corresponding standard boundary conditions.

[0055] Furthermore, method 300 includes determining 303 an actual ROZ value for operating ignition angle 123 and / or fuel for operating internal combustion engine 102 based on standard ignition angle 113 and based on knock limit distance 222 .

[0056] The measures described in this document allow efficiency-optimized operation of internal combustion engine 102 to be achieved in an efficient and reliable manner even with fuels having particularly high ROZ values.

[0057] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and the drawings are intended only to illustrate the principles of the proposed methods, devices and systems by way of example.

Claims

1. A device (101) for operating an internal combustion engine (102) with fuel, the device (101) being configured to - determining a standard ignition angle (113) based on ignition angle characteristic data (110) for an actual operating point of the internal combustion engine (102); - determining a knock limit distance (222) between a standard ignition angle (113) and a knock limit of the internal combustion engine (102) based on knock limit distance characteristic data (220) for an actual operating point of the internal combustion engine (102); and - determining an operating ignition angle (123) and / or an actual ROZ value of the fuel for operating the internal combustion engine (102) based on the standard ignition angle (113) and based on the knock limit distance (222).

2. The device (101) according to claim 1, wherein: The ignition angle characteristic data (110) are based on one or more standard boundary conditions for operating the internal combustion engine (102), and the device (101) is configured to - determining one or more actual boundary conditions for operating the internal combustion engine (102), the one or more actual boundary conditions at least partially deviating from the corresponding one or more standard boundary conditions; - determining an offset value (122) by means of a correction unit (120), in particular based on a model, and based on the one or more actual boundary conditions; and - also determining an operating ignition angle (123) and / or an actual ROZ value of the fuel for operating the internal combustion engine (102) based on the offset value (122).

3. The device (101) according to any of the preceding claims, wherein: The device (101) is configured to - determining an adapted ignition angle difference between a standard ignition angle (113) and a knock limit of the internal combustion engine (102) according to knock adaptation, in particular when one or more actual boundary conditions are present; and - determining an operating ignition angle (123) and / or an actual ROZ value of the fuel for operating the internal combustion engine (102) also based on the adapted ignition angle difference value.

4. The device (101) according to claim 3, wherein: - the ignition angle characteristic data (110) are based on operation of the internal combustion engine (102) using a fuel having a standard ROZ value; and The device (101) is configured to determine an actual ROZ value of the fuel used to operate the internal combustion engine (102) by subtracting a first differential ROZ value associated with the adapted ignition angle differential from the standard ROZ value and adding a second differential ROZ value associated with the knock limit distance (222).

5. The device (101) according to any one of the preceding claims, wherein The device (101) is configured to - determining an actual ROZ value of the fuel used to operate the internal combustion engine (102); - Compare the actual ROZ value with the ROZ threshold; and - depending on the comparison, taking the knock limit distance (222) into account or not taking it into account when determining the operating ignition angle (123).

6. The device (101) according to claim 5, wherein: The device (101) is configured to take into account the knock limit distance (222) when determining an operating ignition angle (123), in particular only when an actual ROZ value is equal to or greater than a ROZ threshold value.

7. The device (101) according to any one of the preceding claims, wherein - the ignition angle characteristic data (110) are based on one or more standard boundary conditions for operating the internal combustion engine (102); The one or more standard boundary conditions include in particular: - standard temperature of the fuel; - standard temperature of the air sucked in by the internal combustion engine (102); - a standard temperature of a coolant used to cool the internal combustion engine (102); and / or - a reference temperature of the internal combustion engine (102); and / or - Standard lambda value; - the ignition angle characteristic data (110) are based on operation of the internal combustion engine (102) using a fuel having a standard ROZ value, - the purpose of determining the ignition angle characteristic data (110) is to provide a standard ignition angle (113) for each of a plurality of possible operating points of the internal combustion engine (102), the standard ignition angle being at the knock limit of the internal combustion engine (102) when the one or more standard boundary conditions are present; and - the standard ROZ value is such that, based on one or more physical limit values ​​of the internal combustion engine (102), the ignition angle characteristic data (110) respectively specify a standard ignition angle (113) for at least a portion of the plurality of possible operating points, which standard ignition angle has an ignition angle difference from the knock limit of the internal combustion engine (102) when the one or more standard boundary conditions exist.

8. The device (101) according to any one of the preceding claims, wherein The device (101) is configured to - determining one or more actual boundary conditions for operating the internal combustion engine (102), the one or more actual boundary conditions at least partially deviating from the corresponding one or more standard boundary conditions; - determining a knock limit distance (222) of a standard ignition angle (113) from a knock limit of the internal combustion engine (102) as a function of the one or more actual boundary conditions, in particular as a function of a deviation of the one or more actual boundary conditions from the corresponding one or more standard boundary conditions.

9. The device (101) according to any one of the preceding claims, wherein The ignition angle characteristic data (110) and / or the knock limit distance characteristic data (220) are determined experimentally and / or based on simulations before the internal combustion engine (102) is operated.

10. A method (300) for an internal combustion engine operated with fuel, the method (300) comprising: - determining (301) a standard ignition angle (113) for an actual operating point of the internal combustion engine (102) based on the ignition angle characteristic data (110); - determining (302) a knock limit distance (222) between the standard ignition angle (113) and a knock limit of the internal combustion engine (102) based on the knock limit distance characteristic data (220) and for an actual operating point of the internal combustion engine (102); and - determining (303) an operating ignition angle (123) and / or an actual ROZ value of the fuel for operating the internal combustion engine (102) based on the standard ignition angle (113) and based on the knock limit distance (222).

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