Method for operating an injector on an internal combustion engine, control device for an internal combustion engine configured to carry out such a method, and internal combustion engine having such a control device

Abstract

The present invention relates to a method for operating an injector (7) at an internal combustion engine (1), wherein: ·‑fuel is introduced into a combustion chamber (3) of the internal combustion engine (1) by means of the injector (7), wherein: ·‑wear values ​​for the injector (7) are detected for a plurality of introduction events, wherein: ·‑each detected wear value is assigned a wear value level from a plurality of wear value levels, wherein: ·‑for each wear value level of the plurality of wear value levels, a level frequency of the detected wear values ​​assigned to the wear value level is calculated, wherein: ·‑based on the level frequency of the wear value levels, a total wear value for the injector (7) is calculated, and wherein: ·‑the injector state of the injector (7) is evaluated based on the total wear value.

Description

Technical Field

[0001] The invention relates to a method for operating an injector on an internal combustion engine, a control device for an internal combustion engine, and an internal combustion engine which is designed to carry out such a method. Background Art

[0002] In such a method or such an internal combustion engine, fuel is introduced into the combustion chamber of the internal combustion engine by means of an injector. Here, there is the problem that such an injector may be subject to wear due to the introduction of fuel, in particular the injection of fuel. The life of such an injector is particularly limited by the cavitation wear of the injection nozzle, wherein material erosion and / or corrosion effects gradually occur at the nozzle blind hole and at the transition portion in the injection hole, and also in the injection hole, which affect the injection diagram of the injector and the flow through the injector. A damage diagram can also be caused at the pilot valve (Pilotventil) of the injector, which also depends on the number of connections (Schaltanzahl) and the pressure ratio at the injector. That is to say, damage can also occur in particular at the actuator inside the injector. If cavitation damage continues to develop in the area of ​​the injection nozzle, this can even lead to spontaneous fracture and cracking of the nozzle top. The damage at the injector leads to uncontrolled introduction of fuel into the combustion chamber. In order to reliably rule out such damage and problems, injectors have hitherto been provided with fixed, pre-set maintenance intervals which are selected to be relatively short. Experience has shown in particular that such injectors can be operated many times longer without problems than the prescribed maintenance intervals. Therefore, premature replacement of injectors is uneconomical and often unnecessary. On the other hand, the replacement interval cannot simply be extended, since this would then present a significant risk to the operation of the internal combustion engine. Injector-specific sensors for monitoring the functionality of the injectors are expensive and complex. Summary of the invention

[0003] The invention is based on the object of providing a method for operating an injector on an internal combustion engine, a control device for an internal combustion engine, and an internal combustion engine, in which the aforementioned disadvantages do not occur.

[0004] This object is achieved by providing the present technical teaching, in particular the teaching of the independent claim and the embodiments disclosed in the dependent claims and the description.

[0005] The object is solved in particular by providing a method for an injector operating at an internal combustion engine, wherein fuel is introduced into the combustion chamber of the internal combustion engine by means of an injector, wherein a wear value for the injector is detected for a plurality of introduction events. Each detected wear value is assigned a wear value level from a plurality of wear value levels. For each wear value level in a plurality of wear value levels, the level frequency of the detected wear value assigned to the wear value level is calculated. Based on the level frequency of the wear value level, a total wear value for the injector is calculated, and the injector state of the injector is evaluated based on the total wear value. Thus, the injector state for the injector can be evaluated in a simple and cost-effective manner without complex sensor mechanisms, so that it can be determined whether the injector can continue to be used or must be replaced. The injector service life (Injektorstandzeit) can be variably selected depending on the calculated injector state, so that the life cycle cost of the injector is reduced. The method can be retrofitted into an existing internal combustion engine in a simple manner, in particular by the operation of a corresponding computer program product. For this purpose, preferably no hardware components are required which are not present in the internal combustion engine anyway.

[0006] In particular, for each of a plurality of introduction events, a wear value for the injector is detected. Here, it is possible to detect a wear value for each introduction event of the injector. However, it is also possible to detect a wear value only for a selected plurality of introduction events (thus for a small number of introduction events).

[0007] An introduction event is particularly understood as the injection or spraying of fuel into the combustion chamber by means of an injector. Such an introduction event can particularly be a main injection, a pre-injection and / or a re-injection.

[0008] Introducing the fuel into the combustion chamber means, in particular, that the fuel is introduced into the combustion chamber indirectly or directly. The injector can in particular be directly introduced into the combustion chamber. However, it is also possible that the injector introduces the fuel into the boost path or air path of the internal combustion engine upstream of the combustion chamber, in particular upstream of the intake valve. Thus, the introduction of the fuel can in particular be designed as a single-point introduction, a multi-point introduction or can also be designed as a direct introduction. When the fuel is liquid, in particular when the fuel is liquid under standard conditions (that is, at 1013 mbar and 25° C.), the introduction of the fuel is in particular injection. The injector can in particular be configured as a liquid fuel injector, in particular as a diesel injector. However, it is also possible that the introduction is the injection of a combustible gas.

[0009] Assigning each detected wear value to a wear value class from a plurality of wear value classes means, in particular, that the detected wear values ​​are histogrammed. The wear value classes are preferably formed, in particular, by dividing the wear value scale into preferably directly adjacent wear value ranges, wherein the wear value ranges form the wear value classes. Assigning the detected wear value to a wear value class means that the class factor of the wear value class into which the wear value falls is counted, that is, increased. This ultimately results in a frequency distribution of the detected wear values ​​with respect to the wear value classes, wherein the injector state can be evaluated, in particular, based on the frequency distribution.

[0010] According to a preferred design, the wear value scale is divided into a plurality of wear value levels with the same level width. However, according to another design, it is also possible that the wear value scale is divided into a plurality of wear value levels with different level widths.

[0011] Preferably, the wear value is additionally assigned to the wear value level depending on at least one other parameter, in particular on the fuel pressure at the injector or on the difference between the fuel pressure and the back pressure relative to which the fuel is drawn. The fuel pressure and the back pressure can also be used individually as further additional parameters for the assignment relative to the wear value level. As at least one other parameter, the introduction duration or at least one information about whether the injector is operated in the ballistic range or in the linear range in a single introduction event can also be used additionally or alternatively. The ballistic range is understood here as the following operating mode of the injector, in which the injector needle does not reach its final position in the open position before it closes again. Alternatively or additionally, the following information can also be used as at least one other parameter, which information is about which introduction event the observed wear value is assigned to, in particular about whether the introduction event involves a main injection, a re-injection, in particular a first re-injection or a second re-injection or a pre-injection.

[0012] In this way, a multidimensional histogram is particularly preferably performed, that is to say, in particular a multidimensional histogram of the wear values ​​is generated. However, it is also possible, alternatively or additionally, to perform a weighting of the wear values ​​as a function of at least one further parameter. The weighting can, for example, cause an inherently lower wear value to be assigned to a higher wear value class due to a further parameter assigned thereto, or vice versa.

[0013] That is to say, for each wear value class in the plurality of wear value classes, the class frequency of the wear value associated with the wear value class is now calculated. The total wear value is then calculated from the class frequencies of the wear value classes.

[0014] The injector condition is in particular the degree of damage and / or wear of the injector. Evaluating the injector condition means in particular determining whether the injector can continue to be used or whether it must be replaced. However, the injector condition is preferably taken into account to determine how badly and / or in what manner the injector is damaged and / or worn.

[0015] The total wear value for the injector is calculated in particular from the class frequencies of the wear value classes.

[0016] Preferably, the method is performed continuously during operation of the internal combustion engine.

[0017] It is possible that the total wear value is recalculated or updated after each introduction event. However, it is also possible that the total wear value is recalculated or updated after a certain number of introduction events. It is also possible that the total wear value is recalculated or updated after a certain number of operating hours. It is also possible that the evaluation of the injector state is not performed continuously, but in a time-dependent and / or event-dependent manner, in particular after each introduction event, after a predetermined number of introduction events, or after a certain number of operating hours.

[0018] Preferably, the method is carried out individually for each of a plurality of injectors of the internal combustion engine. Typically, the internal combustion engine has a plurality of injectors, wherein the method described here can be carried out individually for each of the plurality of injectors without any problems. Preferably, the method is restarted for an injector, in particular after the injector has been replaced (if necessary earlier).

[0019] Preferably, the method is performed only when a static operating state of the internal combustion engine is present. Otherwise, it is preferably waited until a static operating state is present. The method is then continued again. In particular, persuasive wear values ​​for the injectors can be obtained in static operating points.

[0020] However, it is alternatively possible according to a preferred embodiment that the method is carried out independently of whether the internal combustion engine is currently operating in a static operating state or in a transient operating state. The method can in particular also be carried out expediently in a transient operating state.

[0021] According to a preferred embodiment, a maximum damage to the injector is assumed for (time-dependent) transient operating states. This means, in particular, that a maximum wear value is detected for each introduction event of the injector within the transient operating state or that a maximum wear value level is assigned to the respective introduction event. The operating method enables particularly simple detection of transient operating states.

[0022] According to a further development of the invention, it is provided that as a wear value a cavitation coefficient is detected, which characterizes the cavitation occurring at the injector during the introduction event. Since cavitation represents the main wear mechanism of the injector, it is advantageous to quantify the cavitation and to be able to determine the injector state based on the quantified cavitation, that is to say the cavitation coefficient.

[0023] According to a further development of the invention, it is provided that the cavitation factor is calculated as a function of the pressure ratio at the injector. It has been shown that the pressure ratio at the injector is important for the occurrence of cavitation and thus also for the wear of the injector. Particularly preferably, the cavitation factor is calculated as a function of the fuel pressure at the injector, in particular as a function of the fuel pressure at the injector.

[0024] The cavitation factor is preferably calculated as a quotient, wherein the difference between the fuel pressure at the injector and the back pressure is the numerator of the quotient, wherein the back pressure is the denominator of the quotient. The cavitation factor is particularly preferably calculated as a quotient.

[0025] The fuel pressure is, in particular, the pressure at which the fuel is present at the injector and at which the fuel is discharged from the injector. In particular, the high-pressure storage pressure in a common high-pressure storage for a plurality of injectors, in particular in the so-called rail of a common rail system, which is also referred to as rail pressure, can also be used as the fuel pressure. Alternatively or additionally, the individual storage pressure in the individual fuel storages assigned to the injectors can also be used as the fuel pressure.

[0026] The back pressure is in particular the pressure which is present in the volume into which the fuel is introduced via the injector. When the injector is provided and arranged for direct injection or direct injection into the combustion chamber, the back pressure can in particular be the combustion chamber pressure.

[0027] The fuel pressure is preferably detected, in particular measured, by means of a fuel pressure sensor. The back pressure can be measured by means of a back pressure sensor, in particular by means of a combustion chamber pressure sensor. However, it is also possible that the back pressure, in particular the combustion chamber pressure, is read out from a characteristic domain, in particular depending on the current operating point of the internal combustion engine. It has been shown that this enables the back pressure to be determined with sufficiently high accuracy, so that measurement is not absolutely necessary. According to another preferred design, it is also possible to assume that the back pressure is constant, wherein, in a preferred design, a predetermined pressure value, in particular an estimated value, is used for the back pressure. The latter is particularly advantageous when the fuel pressure is much greater than the back pressure.

[0028] To calculate the cavitation factor, in particular, the difference is first formed as the numerator of the quotient, wherein the back pressure is subtracted from the fuel pressure at the injector. The back pressure is then taken into account as the denominator of the quotient, that is, the previously calculated difference is divided by the back pressure. The result is then the cavitation factor.

[0029] In particular, the cavitation coefficient is calculated according to the following equation:

[0030]

[0031] Wherein, in equation (1), p1 is the fuel pressure at the injector, p2 is the back pressure, and K is the cavitation coefficient.

[0032] According to a further development of the invention, it is provided that the total comparison value is calculated as the sum of the (preferably weighted) class frequencies for the wear value class. As a result, the injector state is evaluated in particular as a function of the number of frequencies at which a determined wear value, in particular a determined cavitation coefficient, occurs. This allows in particular a reliable estimation of the wear, in particular the cavitation wear.

[0033] The weighting preferably performed with respect to the wear value classes allows the wear relevance to be determined differently for different wear value classes. For example, it is obvious that not every value of the cavitation coefficient represents an equally relevant damage or influence on the injector state. It is therefore sensible to weight the wear value classes according to their relevance.

[0034] According to a further development of the invention, it is therefore provided that the class frequencies are weighted by a class frequency maximum value (in particular associated with the wear value class) for calculating the total wear value. Preferably, each wear value class is assigned a predetermined class frequency maximum value, which can be intuitively interpreted as the maximum number of wear values ​​occurring in the respective wear value class which is just still acceptable for the injector or from which maintenance measures, such as replacing the injector, should be taken. Particularly preferably, the class frequencies are respectively divided by the class frequency maximum value assigned to them.

[0035] Particularly preferably, the total wear value is calculated according to the following equation:

[0036]

[0037] Where, in equation (2), S is the total wear value, n i is the corresponding level frequency of wear value level i and S i are the respective class frequency maxima assigned to the wear value class i, wherein j is designated as the highest wear value class, and wherein the summation is accordingly performed over the wear value classes.

[0038] According to a further development of the invention, it is provided that a predetermined maximum value of the class frequency for each wear value class is read out from the characteristic field (preferably as a function of the introduction duration, in particular as a function of the injection or injection duration). This means in particular that there is a characteristic field in which the cavitation coefficients assigned to the wear value class (or directly the wear value class) are plotted against a predetermined maximum value of the class frequency. Thus, for each wear value class, the predetermined maximum value of the class frequency assigned thereto can be read out from the characteristic field.

[0039] Preferably, different such characteristic fields are present for a plurality of different introduction durations, wherein, if the introduction duration does not correspond exactly to the introduction duration for which a characteristic field entry is stored, an extrapolation between the characteristic field entries is preferably possible. The corresponding characteristic field can in particular have a Weller curve Particularly preferably, a high cavitation factor is associated with a low predetermined maximum value of the class frequency, wherein a low cavitation factor is associated with a high predetermined maximum value of the class frequency.

[0040] In a simplified preferred embodiment, different characteristic ranges can also exist solely as a function of a particularly binary parameter which indicates whether the injector is operated in the ballistic or linear range.

[0041] According to a further development of the invention, it is provided that the injector state is evaluated by comparing the total wear value with a predetermined total wear value maximum value. The total wear value defined above according to equation (2) increases in particular during the operating period of the internal combustion engine or the injector. The injector state can therefore be advantageously evaluated by checking to what extent the total wear value approaches the predetermined total wear value maximum value. According to a preferred embodiment, it is possible that the total wear value maximum value is equal to 1.

[0042] According to a further development of the invention, it is provided that the remaining service life for the injector is calculated based on the total wear value, in particular based on a comparison of the total wear value with a total wear value maximum. As a result, a prediction can be made of the further possible operating time of the injector until repair, in particular until replacement of the injector. This is preferably done taking into account the (in particular past, that is to say historical) load characteristics and / or speed of the internal combustion engine, wherein it is preferably assumed that the future load characteristics of the internal combustion engine are at least similar to the past load characteristics. As a result, an extrapolation of further development trends is performed, in particular based on past development trends of the (aus) total wear value, in particular development trends in the direction of the total wear value maximum, in particular taking into account the question of when the total wear value reaches the total wear value maximum. This then leads to conclusions about the remaining service life of the injector.

[0043] According to the improved scheme of the present invention, it is arranged that different introduction events within the working cycle of the internal combustion engine are individually assigned different wear value levels. The assignment of wear values ​​to wear value levels can be designed differently for different introduction events in particular. That is to say, different histograms are generated in particular for different introduction events. Different introduction events within the working cycle are particularly understood to be events such as pre-injection, main injection, re-injection, in particular first re-injection and second re-injection. For the different introduction events, typically, different conditions exist at the injector, so it is advantageous to treat the introduction events individually and draw histograms for them individually with respect to different wear value levels.

[0044] According to a further development of the invention, it is provided that all different introduction events within a working cycle are taken into account together for calculating the total wear value. Thus, when summing up, in particular all wear value levels of all introduction events are summed up. This allows a particularly simple and easy-to-calculate evaluation of the injector state.

[0045] The object is also achieved by providing a control device for an internal combustion engine, which is designed to detect a wear value for an injector for a plurality of introduction events, to assign a wear value class from a plurality of wear value classes to each detected wear value, to calculate a class frequency of the detected wear value assigned to the wear value class for each of the plurality of wear value classes, and to calculate a total wear value for the injector as a function of the class frequency of the wear value classes. The control device is further designed to evaluate an injector state of the injector as a function of the total wear value. In particular, the advantages already explained in connection with the method result in the control device.

[0046] The control unit is designed in particular to carry out the method according to the invention or a method according to one of the above-described specific embodiments.

[0047] The object is also achieved by providing an internal combustion engine having at least one combustion chamber and at least one injector, which is designed to introduce fuel into at least one combustion chamber of the internal combustion engine. The internal combustion engine has a control device according to the invention or a control device according to one of the previously described embodiments.

[0048] With regard to the internal combustion engine, in particular the advantages already explained with regard to the method and the control device result.

[0049] Preferably, the internal combustion engine has a fuel pressure sensor, which is designed to detect the fuel pressure present directly at the injector, in particular the fuel pressure at the injector, or the fuel pressure associated with the fuel present at the injector, for example the fuel pressure in a common rail of a common rail system, or the pressure in a single reservoir of the injector. The fuel pressure sensor is preferably operatively connected to the control device so that the detected fuel pressure can be received by the control device.

[0050] According to a preferred embodiment, it is possible that the internal combustion engine has a back pressure sensor which is designed to detect the back pressure, in particular the combustion chamber pressure, for the volume into which the fuel is introduced via the injector. The back pressure sensor can in particular be a combustion chamber pressure sensor. The back pressure sensor is preferably operatively connected to the control device so that the detected back pressure can be received by the control device.

[0051] Alternatively, however, it is also possible for the control device to be designed to read out or calculate the back pressure from the characteristic range (in particular depending on the operating point), or to apply a predetermined, constant value for the back pressure.

[0052] The control device is preferably set up to detect, in particular calculate, a cavitation coefficient that characterizes cavitation occurring at the injector during the introduction event as a wear value, wherein the cavitation coefficient is preferably calculated, in particular calculated, as a function of the pressure ratio at the injector, preferably calculated, in particular calculated as a function of the fuel pressure at the injector, in particular as a quotient of the difference between the fuel pressure and the back pressure divided by the back pressure.

[0053] Preferably, the control device is configured to output a message or warning indicating the injector status, in particular a repair or replacement recommendation, depending on the injector status. Alternatively or additionally, the control device is preferably configured to calculate the remaining service life for the injector and preferably output this remaining service life.

[0054] The control device is particularly preferably designed to calculate a total wear value in the sense of the method explained above and to compare it with a predetermined total wear value maximum value and to output a replacement or repair recommendation, preferably if the total wear value is greater than or equal to the total wear value maximum value. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In the following, the invention is explained in more detail with reference to the accompanying drawings.

[0056] Figure 1 A schematic illustration shows an exemplary embodiment of an internal combustion engine and an exemplary embodiment of a control device for an internal combustion engine, and

[0057] Figure 2 In the form of a flow chart, a method for operating an internal combustion engine, in particular according to Figure 1 Schematic illustration of one specific embodiment of a method for an injector at an internal combustion engine. DETAILED DESCRIPTION

[0058] Figure 1 A schematic illustration of an embodiment of an internal combustion engine 1 is shown, which has at least one combustion chamber 3, in which a piston 5 can be displaced in a reciprocating manner. In the embodiment shown here, the internal combustion engine 1 is therefore designed as a reciprocating piston motor. The internal combustion engine 1 also has an injector 7, which is set up and arranged for introducing fuel into the combustion chamber 3 of the internal combustion engine 1. In the embodiment shown here, the injector 7 is set up for injecting or injecting fuel directly (in the form of direct injection or direct spraying) into the combustion chamber 3.

[0059] The internal combustion engine 1 further comprises a control device 9 which is designed to detect a wear value for the injector 7 for each of a plurality of introduction events, wherein in such an introduction event fuel is introduced into the combustion chamber 3 via the injector 7, to assign each detected wear value to one of a plurality of wear value classes, and to calculate for each of the plurality of wear value classes a class frequency of the wear value respectively assigned to the wear value class. The control device 9 is furthermore designed to calculate a total wear value for the injector 7 as a function of the class frequencies of the wear value classes, and to evaluate the injector state of the injector 7 as a function of the total wear value. In this way, it is possible to determine individual maintenance intervals for the injectors 7, that is, the injectors, for example, do not need to be replaced unnecessarily after a specified, fixed period of time. However, expensive and complex injector-specific sensor systems do not have to be used in this case.

[0060] If the internal combustion engine 1 has a plurality of such injectors 7, the method is carried out individually for each injector 7, and thus a different injector service life and thus a reduction in the life cycle costs are obtained for the different injectors 7. Particularly preferably, the internal combustion engine 1 has a plurality of preferably identically designed combustion chambers 3, wherein particularly preferably a separate injector 7 is assigned to each of the combustion chambers 3.

[0061] The control device 9 is operatively connected to the injector 7 , in particular for the purpose of controlling the injector.

[0062] Preferably, the control device 9 is designed to determine the fuel pressure of the fuel present at the injector 7. For this purpose, the control device 9 is operatively connected to a fuel pressure sensor 11. In the exemplary embodiment shown here, the fuel pressure sensor is designed to detect the fuel pressure in a fuel supply line 13 to the injector 7. Alternatively, it is possible that the fuel pressure sensor 11 is designed to detect the high pressure in a common high-pressure rail for a plurality of injectors 7, in particular in a so-called common rail, wherein such a fuel pressure is also referred to as rail pressure. Further alternatively, it is possible that the fuel pressure sensor 11 is designed to detect the fuel pressure in a single reservoir of the injector 7.

[0063] Furthermore, the control device 9 is preferably configured to determine the back pressure, relative to which the fuel is introduced by the injector 7 during the introduction event into the volume in which the back pressure is present. In the exemplary embodiment shown here, the control device 9 is operatively connected to this end with a combustion chamber pressure sensor 15, which detects the combustion chamber pressure in the combustion chamber 3 as the back pressure. Alternatively, it is also possible in particular that the control device 9 is configured to determine or calculate the back pressure, in particular the combustion chamber pressure, from a characteristic field as a function of at least one other parameter, in particular as a function of the current operating state of the internal combustion engine 1, or to apply a predetermined, constant value for the back pressure.

[0064] Control unit 9 is designed, in particular, to carry out a method, which is explained in greater detail below, for operating injector 7 on internal combustion engine 1 .

[0065] Within the scope of the method, for a plurality of introduction events, wear values ​​are respectively detected for the injector 7, wherein each detected wear value is assigned to a wear value level from a plurality of wear value levels, wherein for each wear value level from the plurality of wear value levels a level frequency of the detected wear values ​​assigned to the wear value level is calculated, wherein a total wear value for the injector 7 is calculated based on the level frequencies of the wear value levels, and wherein an injector state of the injector 7 is evaluated based on the total wear value.

[0066] In this case, a cavitation coefficient which characterizes the cavitation occurring at the injector 7 during the introduction event is preferably detected as the wear value.

[0067] Preferably, the cavitation coefficient is calculated from the pressure ratio at the injector 7, in particular as the quotient of the difference between the fuel pressure and the back pressure at the injector 7 divided by the back pressure, in particular according to equation (1) described above.

[0068] Preferably, the total wear value is calculated as the sum of the preferably weighted class frequencies for the wear value classes. Preferably, the class frequencies are weighted with a predetermined class frequency maximum value for calculating the total wear value. The calculation of the total wear value is preferably performed according to equation (2) described above.

[0069] The predetermined maximum value of the class frequency is preferably read out of the characteristic field for each wear value class, in particular as a function of the introduction duration.

[0070] Preferably, the injector state is evaluated by comparing the total wear value with a predetermined maximum total wear value.

[0071] Preferably, the remaining service life for the injector 7 is calculated from the total wear value, in particular from a comparison of the total wear value with a total wear value maximum, preferably taking into account the load characteristics and / or the rotational speed of the internal combustion engine 1 .

[0072] Preferably, different wear value classes are respectively assigned to different initiation events within a working cycle of internal combustion engine 1 .

[0073] Preferably, all different introduction events within a working cycle are taken into account together to calculate the overall wear value.

[0074] Figure 2 A schematic illustration of one specific embodiment of the method is shown as a flow chart.

[0075] Here, the method starts in a first step S1 during operation of the internal combustion engine 1. In a second step S2, it is optionally checked whether a static operating state of the internal combustion engine 1 currently exists. If this is not the case, the second step S2 is optionally repeated in the form of a continuous cycle until a static operating state exists. If this is the case, the method continues in a third step S3. However, it is also possible to carry out the method in such a way that either transient operating states are also taken into account or whether the internal combustion engine is currently operating in a static operating state or in a transient operating state is not taken into account at all.

[0076] In a third step S3 , the fuel pressure p1 and the back pressure p2 are calculated, in particular detected, read in or read out from the characteristic range, or (in the case of the back pressure p2 ) assumed as predetermined, constant values.

[0077] In a fourth step S4 , a wear value, in particular as a cavitation coefficient, is calculated, in particular according to equation (1) from the fuel pressure p1 and the back pressure p2 .

[0078] In a fifth step S5 , the wear values ​​are classified, ie are assigned one of a plurality of wear value classes. In particular, the cavitation coefficients obtained from a plurality of runs of the method, which are preferably repeated continuously, are histogrammed.

[0079] In the sixth step S6, it is checked whether at least one condition for calculating the total wear value is met, wherein the condition is preferably that a predetermined time, in particular a predetermined number of operating hours has passed since the last calculation of the total wear value, or a certain number of executed introduction events after the last calculation of the total wear value, or the occurrence of another event. If the condition is met, the method continues in the seventh step S7, otherwise the method jumps back to before the second step S2 and thus continues with the second step S2. That is, in this embodiment of the method, the total wear value is not calculated after each operation of steps S3 to S5. However, it is also possible to omit the sixth step S6 or to adapt the condition accordingly so that the total wear value is calculated after each operation of steps S3 to S5. By means of the condition in step S6, time can be saved on the one hand, and on the other hand, sufficiently convincing statistics can be provided for drawing a histogram of the cavitation coefficient.

[0080] In the seventh step S7, the total wear value is calculated based on the level frequencies of the wear value levels, in particular according to equation (2), i.e. as the sum of the preferably weighted level frequencies of the wear value levels, wherein the level frequencies are weighted in particular with a predetermined maximum level frequency value assigned to them.

[0081] In an eighth step S8 , the injector state is then evaluated by comparing the total wear value with a predetermined total wear value maximum value GW.

[0082] If it is determined in the eighth step S8 that the total wear value is greater than or equal to the total wear value maximum value, a maintenance recommendation is output in a ninth step S9 , in particular a recommendation to replace the injector 7 , and the method ends in a tenth step S10 .

[0083] If, on the other hand, it is determined in the eighth step S8 that the total wear value is not greater than or equal to the total wear value maximum value GW, then preferably in an eleventh step S11 a prediction is made about the remaining service life of the injector 7, in particular taking into account the past load characteristics and / or the speed of the internal combustion engine 1. Preferably, the result of this prediction, i.e. in particular the remaining service life, is output. The method then continues with the second step S2.

[0084] Particularly preferably, the method continues during the operation of the internal combustion engine 1 , in particular is iterated, either until the operation of the internal combustion engine 1 ends or until a maintenance recommendation for the injector 7 is generated in a ninth step S9 .

Claims

1. A method for operating an injector (7) at an internal combustion engine (1), wherein: - introducing fuel into the combustion chamber (3) of the internal combustion engine (1) by means of the injector (7), wherein: - for a plurality of introduction events, respectively detecting a wear value for the injector (7), wherein: - Each detected wear value is assigned a wear value class from a plurality of wear value classes, wherein: - for each wear value class of the plurality of wear value classes, determining a class frequency of detected wear values ​​assigned to the wear value class, wherein: - calculating a total wear value for the injector (7) based on the class frequencies of the wear value classes, and wherein: - based on the total wear value, evaluating the injector condition of the injector (7), wherein: - a cavitation coefficient characterizing the cavitation occurring at the injector (7) during the introduction event is detected as a wear value, wherein: The cavitation coefficient is calculated based on the pressure ratio at the injector (7), and is calculated as a quotient of a difference between a fuel pressure and a back pressure at the injector (7) divided by the back pressure.

2. The method according to claim 1, characterized in that The total wear value is calculated as the sum of the class frequencies for the wear value classes.

3. The method according to claim 1 or 2, characterized in that: The class frequencies are weighted with a predetermined class frequency maximum value for calculating the total wear value.

4. The method according to claim 3, characterized in that A predetermined maximum value of the class frequency for each wear value class is read out from the characteristic field.

5. The method according to claim 1 or 2, characterized in that: The injector state is evaluated by comparing the total wear value with a predetermined maximum total wear value.

6. The method according to claim 5, characterized in that The remaining service life of the injector (7) is calculated based on the total wear value.

7. The method according to claim 1 or 2, characterized in that: Different wear value classes are respectively assigned to different initiation events within a working cycle of the internal combustion engine (1).

8. The method according to claim 1 or 2, characterized in that: To calculate the total wear value, all different introduction events within a working cycle are taken into account.

9. The method according to claim 2, characterized in that: The total wear value is calculated as the sum of the weighted class frequencies for the wear value classes.

10. The method according to claim 4, characterized in that A predetermined maximum value of the class frequency for each wear value class is read out from the characteristic field as a function of the introduction duration.

11. The method according to claim 6, characterized in that Based on the comparison of the total wear value with the total wear value maximum, a remaining service life for the injector (7) is calculated.

12. The method according to claim 6 or 11, characterized in that: The remaining service life of the injector (7) is calculated taking into account a load characteristic and / or a rotational speed of the internal combustion engine (1).

13. A control device (9) for an internal combustion engine (1), wherein: The control device (9) is configured to detect wear values ​​for the injector (7) for a plurality of introduction events of fuel into the combustion chamber (3) of the internal combustion engine (1), assign one of a plurality of wear value levels to each detected wear value, calculate a level frequency of the detected wear values ​​assigned to the wear value level for each of the plurality of wear value levels, calculate a total wear value for the injector (7) based on the level frequencies of the wear value levels, evaluate an injector state of the injector (7) based on the total wear value, detect a cavitation coefficient characterizing cavitation occurring at the injector (7) during the introduction event as a wear value, and calculate the cavitation coefficient based on a pressure ratio at the injector (7) as a quotient of a difference between a fuel pressure and a back pressure at the injector (7) divided by the back pressure.

14. An internal combustion engine (1) comprising at least one combustion chamber (3) and at least one injector (7) which is designed to introduce fuel into the at least one combustion chamber (3), and comprising a control device (9) according to claim 13.

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