Method for operating a fuel injection system

Abstract

Method for operating a fuel injection system (11) for an internal combustion engine (10), in which pressurized fuel is provided in a pressure accumulator (16) and the fuel pressure (19) present in the pressure accumulator (16) is determined by means of a pressure sensor (20), and in which the fuel enters a combustion chamber (12) of the internal combustion engine (10) through at least one fuel injection device (14), characterized in that a slope (51) of a curve (52) is determined via a control and / or regulating device (22), which links a pressure difference (35) in the pressure accumulator (16) during fuel injection with an injected quantity of fuel (40),wherein the pressure difference (35) and the injected fuel quantity (40) are supplied to the control and / or regulating device (22) and the fuel pressure (19) prevailing in the pressure accumulator (16) is inferred from the slope (51) via the control and / or regulating device (22), wherein the fuel quantity (40) injected by the fuel injection device (14) is cyclically changed to determine the slope (51).

Description

State of the art

[0001] The invention relates to a method according to the preamble of claim 1, as well as a control and / or regulating device, a computer program and a storage medium according to the dependent claims.

[0002] Internal combustion engines are known on the market for their ability to monitor operating conditions and / or values ​​of parameters critical to operation using so-called "on-board diagnostics." Among other things, a correctly set fuel pressure in the pressure accumulator of the internal combustion engine's fuel system is important. Fuel pressure is often determined using a pressure sensor (rail pressure sensor, RDS). To test or monitor the proper functioning of the pressure sensor, it is conceivable, for example, to install a second, identical pressure sensor on the pressure accumulator and use it for comparison. A patent publication in this field is, for example, DE 10 2008 043 592 A1.

[0003] Patent DE 10 2006 023 468 B3 discloses a method and a device for controlling injection valves in internal combustion engines. To minimize deviations caused by manufacturing tolerances and aging at small fuel quantities, a test injection is performed during overrun fuel cut-off. By measuring the pressure difference in the fuel rail before and after the injection, a correction factor is determined and applied to subsequent injections.

[0004] A method for monitoring fuel pressure in a fuel injection system of an internal combustion engine is known from German patent application DE 10 2009 046 419 A1. A target fuel pressure is set, followed by two fuel injections in quick succession. The amount of fuel injected during the second injection is determined. If this amount deviates from the target quantity, an action is triggered.

[0005] From US patent specification 6,234,148 B1, a method and a device for monitoring a pressure sensor, particularly in a fuel supply system for internal combustion engines (e.g., common-rail systems), are known. By calculating an expected pressure value and comparing it with the value measured by the sensor, malfunctions can be detected. The invention requires no additional sensors and allows for easy integration into the engine control unit. The method monitors the pressure sensor by comparing an expected pressure value with a measured pressure value and reporting a malfunction in the event of deviations. Disclosure of the invention

[0006] The problem underlying the invention is solved by a method according to claim 1, as well as by a control and / or regulating device, a computer program, and a storage medium according to the dependent claims. Advantageous embodiments are specified in the dependent claims. Further features important to the invention are found in the following description and in the drawings, whereby the features may be important to the invention both individually and in various combinations, without this being explicitly stated again.

[0007] The method according to the invention has the advantage that the fuel pressure in a pressure accumulator (fuel accumulator, "rail") of a fuel system ("fuel injection system") for an internal combustion engine can be determined to be correct without the need for additional sensors or actuators, such as a pressure control valve. In particular, a pressure sensor arranged on the pressure accumulator can also be tested or monitored for correct function. Optionally, devices or algorithms in a control and / or regulating unit for the internal combustion engine, which detect dynamic pressure changes in the pressure accumulator resulting from injections into the combustion chambers of the internal combustion engine, can also be used for the method. Furthermore, the invention is comparatively flexible and adaptable to existing fuel systems.The method according to the invention requires comparatively little computing time and / or data storage space and can be carried out on a single – generally any – combustion chamber (“cylinder”) of the internal combustion engine. This can reduce harmful effects on the operation of the internal combustion engine (for example, on the driving behavior of a motor vehicle) and / or on exhaust emissions.

[0008] The invention relates to a method for operating the fuel injection system for an internal combustion engine, in which pressurized fuel is supplied to the pressure accumulator and the fuel pressure present in the pressure accumulator is determined by means of a pressure sensor, and in which the fuel enters a combustion chamber of the internal combustion engine through at least one fuel injection device (injector valve, injector). According to the invention, a control and / or regulating device determines the slope of a curve that relates a pressure difference in the pressure accumulator during fuel injection to a quantity of injected fuel. The pressure difference and the quantity of injected fuel are supplied to the control and / or regulating device. The control and / or regulating device then uses the slope to infer the fuel pressure prevailing in the pressure accumulator.For example, data values ​​that can be used to determine the fuel pressure in the pressure accumulator or the proper functioning of the pressure sensor can be determined during a test procedure and stored in a data memory of the control and / or regulating device. These values ​​can include a multitude of parameters such as the injected fuel quantity, the pressure differential, and the fuel pressure, with the option of using and storing other parameters as well. This will be described in more detail below. It is intended that, to determine the slope, the amount of fuel injected by the fuel injection device is preferably varied cyclically. Thus, in a first step, an initial amount of fuel is injected, and in a second step, a second, different amount of fuel is injected.This can occur alternately from injection cycle to injection cycle, or the injected fuel quantity can be kept constant over several successive injection cycles. This describes a "stimulation" method particularly suitable for the process. Preferably, the injected fuel quantity is not determined directly (by measurement) but indirectly, for example, by using the actuation duration of an electromagnetic actuator of the fuel injection device. This allows the control and / or regulating device to assume a so-called "desired quantity" for the injected fuel quantity, which characterizes a current target value for the amount of fuel to be injected.

[0009] Additionally, the injected fuel quantity can be varied by a preferably cyclical change in an injection pattern. This allows for a particularly simple variation of the injected fuel quantity by cyclically switching between preferably two injection patterns.

[0010] The impact on the operation of the internal combustion engine can be reduced by switching back and forth between a (first) injection pattern with near pre-injection and a (second) injection pattern without near pre-injection. For example, this can keep the operating noise of the internal combustion engine comparatively low.

[0011] Alternatively or additionally, it can be provided that switching occurs between an injection pattern with late post-injection and an injection pattern without late post-injection. Preferably, a "torque-neutral" post-injection is used for this purpose, so that the effects on the drive torque generated by the internal combustion engine are minimized.

[0012] A further embodiment of the method provides that, during overrun operation of the internal combustion engine, switching occurs between an operating mode in which a comparatively small injection quantity is injected and an operating mode in which no injection takes place. The possibility of using overrun operation makes the invention particularly versatile and flexible in its application.

[0013] Another embodiment of the method involves varying the injection quantity at a single combustion chamber to determine the slope, and measuring the amount of fuel injected into the remaining combustion chambers of the internal combustion engine such that the total torque generated by the engine remains at least approximately constant. Preferably, this is done in such a way that there is no or only a minimal effect on the exhaust emissions of the internal combustion engine. This allows the effort required to implement the method to be kept particularly low, while minimizing any potentially adverse effects on the operation of the internal combustion engine.

[0014] Additionally, it can be provided that when inferring the pressure prevailing in the fuel storage tank from the slope, the fuel temperature and / or fuel type are also taken into account. These parameters can, for example, be used in the context described below, thereby improving the accuracy of the method. However, the fuel temperature and / or fuel type are often unknown in the control and / or regulating device, as these values ​​are comparatively complex to determine. Furthermore, because the fuel pressure or the pressure sensor is also checked according to the invention, the fuel temperature and / or fuel type cannot be inferred from the aforementioned slope of the curve. The method according to the invention operates, in principle, independently of the fuel temperature and fuel type.However, if these quantities are known – for example, by measuring them – they may further improve the accuracy of the procedure.

[0015] Furthermore, it can be provided that a relationship between the slope of the curve linking the pressure difference in the pressure accumulator during fuel injection with the injected fuel quantity is determined in a test environment (e.g., in a laboratory) and / or in a new condition of the internal combustion engine and / or in a new condition of the pressure sensor, and preferably stored in the form of equations, tables, characteristic curves, maps, and / or models. Thus, the method comprises a first process step in the test environment and a second process step in subsequent "normal" operation of the internal combustion engine or a motor vehicle powered by the internal combustion engine. In the test environment, a relationship is determined from the respective pressure differences of the fuel pressure in the pressure accumulator and the associated injection quantities and the corresponding actual measured values ​​of the fuel pressure.This relationship encompasses, for example, a multitude of curves that quantitatively relate pressure differences, injection quantities, fuel pressures, and consequently, the slope(s), which are stored in the data memory of the control and / or regulating device. During normal operation of the internal combustion engine, the respective slope is then determined from at least two pairs of values ​​for the pressure difference and the injected fuel quantity. This slope—and, if applicable, also the pressure differences and injection quantities—can be fed as input to the relationship stored in the data memory, and the corresponding fuel pressure in the pressure accumulator can be determined from this. The fuel pressure determined in this way is considered comparatively accurate, as it was measured precisely and accurately in the test procedure described above.The fuel pressure determined from the data can then be compared with a current reading from the pressure sensor, thus verifying the function of the pressure sensor located on the pressure accumulator. The computational effort required for this is relatively low, and additional components – such as a second pressure sensor or a pressure regulating valve – are not necessary.

[0016] The accuracy of the procedure can be increased by performing time-averaging and / or series averaging of the respective parameters when the procedure is repeated cyclically. This applies, for example, to determining the pressure difference in the pressure accumulator. Disturbances in electrical signals or fluctuations in fuel pressure caused by potential pressure pulsations can thus be averaged out simply and accurately.

[0017] Preferably, the method according to the invention is carried out using the control and / or regulating device for the internal combustion engine. This is done in a particularly cost-effective and efficient manner by means of a computer program which is programmed accordingly to carry out the method.

[0018] Exemplary embodiments of the invention are explained below with reference to the drawing. The drawing shows: Fig. 1 a simplified diagram of an internal combustion engine and a fuel system; Fig. 2 a time diagram with a fuel pressure in a pressure accumulator of the fuel system; Fig. 3 a first fuel injection pattern; Fig. 4 a second fuel injection pattern; Fig. 5 a diagram showing a pressure difference as a function of an injected quantity of fuel; and Fig. 6. A flowchart for operating the fuel system.

[0019] The same reference symbols are used for functionally equivalent elements and sizes in all figures, even in different embodiments.

[0020] The Fig. Figure 1 shows a simplified diagram of a fuel system 11 (“fuel injection system”) for an internal combustion engine 10, which in this case has four combustion chambers 12 (“cylinders”) and associated injectors 14 (“fuel injection device”) for injecting fuel. For example, the internal combustion engine 10 is a gasoline engine or a diesel engine of a motor vehicle (not shown in the drawing). The injectors 14 can each be actuated by an electromagnetic actuator 13. Alternatively, the electromagnetic actuator 13 can also be designed as a piezoelectric actuator 13.

[0021] The drawing shows a pressure accumulator 16 (high-pressure accumulator, "rail") above the injectors 14, which is supplied with fuel from a high-pressure line 18. A fuel pressure 19 ("rail pressure") in the pressure accumulator 16 is monitored by a pressure sensor 20. In the upper right part of the Fig. Figure 1 shows a control and / or regulating device 22 together with indicated outgoing and incoming control lines, as well as a data storage device 24 and a computer program 26 contained therein.

[0022] During operation, a fuel pump (not shown) feeds the pressure accumulator 16 via the high-pressure line 18, with the pressure sensor 20 reporting the current fuel pressure 19 to the control and / or regulating unit 22 via an indicated signal line. Depending on a control signal from the electromagnetic actuating device 13, the four injectors 14 deliver a specific quantity of fuel 40 (see Fig. 3) into the combustion chambers 12.

[0023] Fig. Figure 2 shows a time diagram of the fuel pressure 19 in the pressure accumulator 16 over a time t. A depicted time course 28 of the fuel pressure 19 shows a substantially constant first mean value 30 in a left-hand area of ​​the drawing, and a substantially constant second mean value 32 in a right-hand area of ​​the drawing.

[0024] In a horizontally central area of ​​the drawing, the time course 28 exhibits a sudden drop from the first mean value 30 to the second mean value 32. A pressure difference 35, characterizing this sudden drop, can be determined from the two mean values ​​30 and 32. This pressure difference 35 is essentially proportional to the injected fuel quantity 40 and is also essentially proportional to the activation duration of the electromagnetic actuator 13 and the fuel pressure 19.

[0025] The first mean value 30 is averaged over a first time interval 34 (evaluation window), and the second mean value 32 is averaged over a second time interval 36 (evaluation window). The timing and duration of the respective mean values ​​30 and 32 are preferably predetermined depending on any disturbances superimposed on the time course 28, as is the case here.

[0026] Fig. Figure 3 schematically shows a first injection pattern 37 of the fuel into one of the combustion chambers 12 of the internal combustion engine 10. An injection rate 38 (ordinate) is shown as a function of a crankshaft angle 39 (abscissa). In the drawing, from left to right, the first injection pattern 37 comprises a first pre-injection 42, a second pre-injection 44 ("near pre-injection"), and a main injection 46.

[0027] An integral over the injection rate 38 characterizes the respective injected fuel quantity 40 ("injection quantity"), whereby the fuel quantity 40 can be determined for each of the partial injections 42, 44 and 46 individually or for the sum of the partial injections 42, 44 and 46. By converting the crankshaft angle 39 using a rotational speed of the internal combustion engine 10, a time integral can also be determined, whereby the injected fuel quantity 40 can be quantitatively determined.

[0028] Fig. 4 shows a schematic similarity to the Fig. 3 a second injection pattern 48 of the fuel into the combustion chamber 12. In contrast to the Fig. 3 shows the second injection pattern 48 of the Fig. 4 only the first pre-injection 42 and the main injection 46. Alternatively or additionally to the second pre-injection 44, the first or second injection pattern 37 or 48 can include a torque-neutral late post-injection. This is shown in the Fig. 3 and Fig. 4, however, is not shown.

[0029] Fig. Figure 5 shows a diagram with five curves, which characterize the relationship between the pressure difference 35 (ordinate) and the injected fuel quantity 40 (abscissa) as a function of the fuel pressure 19 (used as a parameter) in the pressure accumulator 16. An arrow 50 points in the direction of a high fuel pressure 19. In this case, the fuel pressure 19 has values ​​in the range of approximately 250 bar to approximately 1600 bar.

[0030] The diagram of Fig. 5 is preferably first determined in a test mode and / or in a new state of the internal combustion engine 10 and / or in a new state of the pressure sensor 20 and stored in the data storage device 24 in the form of equations, tables, characteristic curves, maps and / or models. For this purpose, in the test mode of the internal combustion engine 10, which is essentially stationary and in which a torque generated by the internal combustion engine 10 and a temperature of the fuel can be assumed to be approximately constant, the injection of fuel is carried out alternately ("cyclically") by switching back and forth between the first and the second injection pattern 37 and 48. Preferably, this is done in such a way that there is no or only a minor effect on the exhaust gas values ​​and the operating noise of the internal combustion engine.

[0031] For a given number of fuel pressures 19 (parameters) in the pressure accumulator 16, a family of curves similar to the one described above is generated. Fig. 5. For this purpose, a relationship between the injected fuel quantity 40 and the pressure difference 35 is determined point by point for each of the curves. Using the first and second injection patterns 37 and 48, the slopes 51 of the curves can be determined. This is explained in more detail below using an example of a section or two points of a curve 52.

[0032] In a first step, injection pattern 37 is used, see the corresponding arrow in the drawing of Fig. 5. The first injection pattern 37 corresponds - with the fuel pressure 19 underlying curve 52 - to a value 54 of the pressure difference 35 and a value 56 of the injected fuel quantity 40.

[0033] In a second step, injection pattern 48 is used; see also the corresponding arrow in the drawing. A value of 58 corresponds to a pressure difference of 35 for the second injection pattern 48, and a value of 60 corresponds to the injected fuel quantity 40. Therefore, equation (1) can be stated: ΔΔp=Δp2−Δp1, where Δp1 value 54 of the pressure difference 35; Δp2 value 58 of the pressure difference 35; and ΔΔp Difference between Δp1 and Δp2.

[0034] Accordingly, an equation (2) can be given for the injected fuel quantity 40: Δq=q1−q2, where q1 value 56 of the injected fuel quantity 40; q2 value 60 of the injected fuel quantity 40; and Δq Difference between q1 and q2.

[0035] It is understood that, depending on the (arbitrary) choice of the indices (1; 2), the quantities ΔΔp and Δq may also be negative. In the present case, the injected fuel quantity 40 is not determined directly, but indirectly, for example by using the actuation duration of the electromagnetic actuator 13. Preferably, this determination of the injected fuel quantity 40 is carried out in the aforementioned test operation and in normal operation (see Fig. 6) of the internal combustion engine 10 in the same way. The value 56 of the injected fuel quantity 40 does not correspond to the actual injected fuel quantity 40, as this is not known exactly. Therefore, during test operation and normal operation of the internal combustion engine 10, a so-called "desired quantity" of the control and / or regulating device 22 is assumed for the injected fuel quantity, which characterizes a current target value of the fuel quantity 40 to be injected.

[0036] The slope 51 corresponding to a respective fuel pressure 19 (“rail pressure”) can be specified using equation (3) as follows: ψ=ΔΔpΔq⇒ψ=KL(p), where ψ respective slope 51; KL "characteristic curve", i.e., a functional relationship; and p Fuel pressure 19 in the pressure accumulator 16.

[0037] The characteristic curve KL therefore uses the fuel pressure 19, determined using a correctly functioning pressure sensor 20, as its input variable. Preferably, the values ​​of the slope 51, which depend on the fuel pressure 19, are stored in the data memory 24 in a characteristic curve inversely proportional to equation (3), according to equation (4): pMESS=KL−1(ψ), where p MESS Fuel pressure 19 determined with a correctly functioning pressure sensor 20 in the test operation; KL -1 inverse characteristic curve to equation (3); and ψ slope 51, which can be determined according to equations (1) to (3).

[0038] Additionally, for example, fuel temperature and / or fuel type can be determined and stored as further parameters of the characteristic curve in the data memory 24. However, the method according to the invention operates in principle independently of the fuel temperature and fuel type.

[0039] The characteristic curve determined in this way can be used at a later time (see Fig. 6) can be used in a normal operating condition of the internal combustion engine 10 to infer the existing fuel pressure 19 in the pressure accumulator 16. From this, in particular, the condition of the pressure sensor 20 can be inferred and thus its function or accuracy can be monitored.

[0040] If necessary, several of the above-mentioned quantities or parameters can be averaged using time averaging and / or batch averaging. This can increase the accuracy of the method. Compare, for example, mean values ​​30 and 32 in the Fig. 2.

[0041] The Fig. Figure 6 shows the execution of the procedure, similar to the test operation described above, in normal operation of the internal combustion engine 10 by means of a flowchart. It is understood that the flowchart of the Fig. 6 can be applied analogously and at least partially to the test operation described above, and conversely, that the equations (1) to (4) described above can be applied analogously to the implementation of the procedure in normal operation.

[0042] The race begins in starting block 62. Fig. The procedure shown in section 6 is similar to the test operation described above. In a subsequent block 64, it is checked whether the internal combustion engine 10 is operating in a steady-state condition and whether the torque generated by the internal combustion engine 10 and the temperature of the fuel are approximately constant. Otherwise, the process branches back to the beginning of the same block 64. Preferably, the operating state selected for the method in normal operation and the torque of the internal combustion engine 10, as well as the temperature of the fuel, are approximately constant compared to that observed during the Fig. The test operation described in section 5 is comparable.

[0043] Optionally, if the steady-state operating condition cannot be maintained for a sufficiently long period, values ​​or results determined in the interim can be temporarily stored in data storage 24 and used at a later time when a suitable, comparable operating condition is again available. This reduces the requirements, particularly regarding the duration of the steady-state operating condition, and thus allows the described method to be applied optimally with respect to the prevailing operating conditions.

[0044] In a subsequent block 66, one of the combustion chambers 12 ("test cylinder") is alternately ("cyclically") injected with the injection patterns 37 and 48 according to the Fig. 3 and Fig. 4. The remaining combustion chambers 12 are continuously operated with the second injection pattern 48 according to the Fig. 4 operated. Because a higher quantity of fuel 40 is injected in the test cylinder as a result of the first injection pattern 37 on a time-averaged basis, the quantity of fuel 40 injected in the other combustion chambers 12 is reduced accordingly so that the total quantity of fuel injected 40 and thus the torque remains constant.

[0045] It is particularly advantageous for the process if the alternating use of the first and second injection patterns 37 and 48 takes place in an operating condition of the internal combustion engine 10 in which there is the least possible influence on the torque of the internal combustion engine 10 or on the exhaust gas values ​​of the internal combustion engine 10. In addition, the process is preferably carried out on only one of the combustion chambers 12.

[0046] In a subsequent block 68, the slope 51 is calculated according to the scheme of Fig. 5 is determined from the values ​​54, 56, 58, and 60. If the slope 51 has a stable value, the procedure continues in a subsequent block 70. Otherwise, it branches back to the beginning of the same block 68. Disturbances in electrical signals from the pressure sensor 20 or fluctuations in fuel pressure 19 caused by possible pressure pulsations can be reduced, if necessary, by time averaging and / or fraction averaging.

[0047] In block 70, according to equation (5), a fuel pressure 19 in the pressure accumulator 16 is determined (“calculated”) using data stored in the test operation described above: pCALC=KL−1(ψ), where p CALC In normal operation of the internal combustion engine, 10 "calculated" fuel pressure 19; KL -1 inverse characteristic curve as in equation (4); and ψ with the above equations (1) to (3) in normal operation of the internal combustion engine 10 determined (“measured”) slope 51.

[0048] For this purpose, the slope 51 used in equation (5) is also used as an input variable in equation (4) (or in tables, characteristic curves, maps and / or models stored in data memory 24), so that the quantity p MESS of equation (4) with size p CALC can be compared to equation (5). This corresponds to equation (6): pERR=pMESS−pCALC, where p ERR Errors determined by comparison of fuel pressure 19 and pressure sensor 20.

[0049] In a subsequent block 72, depending on the determined error p, the following occurs ERR This may trigger a response in a system for so-called "on-board diagnostics" (OBD). For example, this occurs when an amount of p ERRIf a threshold value is exceeded, after a sufficiently long "debouncing time" an entry is made in an error memory and / or a warning light or similar is sent to the driver of the motor vehicle.

[0050] After carrying out the described procedure, an injection pattern 48 comparable to that used in the other combustion chambers 12 is also used in the test cylinder of block 74 for the continued normal operation of the internal combustion engine 10. The procedure therefore has no influence on the continued normal operation of the internal combustion engine 10 until the procedure for monitoring the pressure sensor 20 is carried out again at a later time, if necessary. In a subsequent end block 76, the process described in the Fig. 6. Procedure shown.

[0051] In a further embodiment of the method, it is possible to operate the remaining combustion chambers 12 – and, after the method has been carried out, all combustion chambers 12 – with the first injection pattern 37. The fuel quantities 40 are adjusted accordingly during the method, so that the total torque remains constant.

[0052] In a further embodiment, the method is carried out in overrun mode of the internal combustion engine 10. A small quantity of fuel 40 is injected alternately ("cyclically") into the test cylinder for a first number of operating cycles of the internal combustion engine 10 and then not injected for a second number of operating cycles.

[0053] In a further embodiment, one or more moment-neutral partial injections are introduced into the test cylinder for a first number of operating cycles and then not for a second number of operating cycles. Preferably, this is done by means of a so-called "late post-injection", which follows the main injection 46 in time.

Claims

[1] Method for operating a fuel injection system (11) for an internal combustion engine (10) in which pressurized fuel is provided in a pressure accumulator (16) and the fuel pressure (19) present in the pressure accumulator (16) is determined by means of a pressure sensor (20), and in which the fuel is supplied to a combustion chamber (12) of the internal combustion engine (10) by means of at least one fuel injection device (14), characterized by, that a slope (51) of a curve (52) is determined via a control and / or regulating device (22), which links a pressure difference (35) in the pressure accumulator (16) during fuel injection with an injected fuel quantity (40), wherein the pressure difference (35) and the injected fuel quantity (40) are supplied to the control and / or regulating device (22) and the fuel pressure (19) prevailing in the pressure accumulator (16) is inferred from the slope (51) via the control and / or regulating device (22), wherein the fuel quantity (40) injected by the fuel injection device (14) is cyclically changed to determine the slope (51). [2] Method according to claim 1, characterized by , that the injected fuel quantity (40) is changed by a preferably cyclical change of an injection pattern (37, 48). [3] Method according to claim 2, characterized by, that switching back and forth between an injection pattern (37) with near pre-injection (44) and an injection pattern (48) without near pre-injection (44). [4] Method according to claim 2, characterized by , that switching occurs between an injection pattern (37, 48) with late post-injection and an injection pattern (37, 48) without late post-injection. [5] Method according to claim 1, characterized by , that in a boost operation of the internal combustion engine (10) the system switches back and forth between an operating mode in which a comparatively small amount of fuel (40) is injected and an operating mode in which no injection takes place. [6] Method according to at least one of the preceding claims, characterized by, that the injection quantity (40) at a single combustion chamber (12) is changed to determine the slope (51), and that a fuel quantity (40) injected into the other combustion chambers (12) of the internal combustion engine (10) is measured such that the total torque generated by the internal combustion engine (10) is at least approximately constant. [7] Method according to any one of the preceding claims, characterized by , that when the slope (51) is used to infer the pressure (19) prevailing in the fuel storage tank (16), a fuel temperature and / or a fuel type is taken into account. [8] Method according to at least one of the preceding claims, characterized by, that a relationship between the slope (51) of the curve (52), which links the pressure difference (35) in the pressure accumulator (16) during fuel injection with the injected fuel quantity (40), is determined in a test operation and / or in a new state of the internal combustion engine (10) and / or in a new state of the pressure sensor (20) and is preferably stored in the form of equations, tables, characteristic curves, maps and / or models. [9] Method according to at least one of the preceding claims, characterized by , that when it is performed cyclically, a time averaging and / or a set averaging of respective quantities (30, 32; 54, 58; 56, 60; 51) is carried out. [10] Control and / or regulating device (22) for an internal combustion engine (10), characterized by that she is trained to carry out a process according to at least one of the preceding claims. [11] Computer program (26), characterized bythat it is programmed to perform a method according to at least one of claims 1-9. [12] Storage medium, characterized by that it comprises a computer program (26) according to claim 11.

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