Method for modeling an input current of a pump and control unit

Abstract

A method for modeling an input current of a pump (110), comprising the following steps: - controlling the pump (110) to apply pressure to at least part of an evaporation system (100); - determining a pressure curve in the evaporation system (100); and - modelling a curve (350) of the input current of the pump (110) based on the pressure curve by means of a model; - wherein the modelling of the curve (350) of the input current comprises multiplying by a proportionality factor; and - wherein the proportionality factor is determined by means of a reference operation (353) of the pump (110) in which a reference leakage is pressurized by the pump (110).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to tank ventilation systems and methods for operating them. Specifically, it relates to a method for modeling an input flow of a pump and a corresponding control unit. BACKGROUND OF THE INVENTION

[0002] According to various country-specific legal regulations and for safety reasons, it is necessary to ensure and diagnose the functionality of the fuel tank ventilation system, including the fuel tank, in motor vehicles. Typically, the entire evaporative system, including the fuel tank up to the tank vent valve, must be checked for leaks. Furthermore, blockages in an evaporative line between the fuel tank and the activated carbon canister, or refueling during diagnostic procedures, for example, can be detected. Legal requirements vary from country to country, for example, regarding the smallest leak cross-section to be diagnosed.

[0003] The leak test of the evaporative system, required by various regulations, is carried out for tank systems with or without a tank shut-off valve using leak detection pumps. These leak detection pumps pressurize the evaporative system at a defined time. The electrical power consumed by the leak detection pump, based on the pump's current consumption, for example, is then used as an evaluation criterion to determine the leak diameter. The power consumed by such a leak detection pump or a corresponding pump input current can also be used for the aforementioned blockage diagnosis and refueling detection.

[0004] For example, document EP 1 169 564 B1 discloses a method for testing the leaks of a tank system, in particular a tank ventilation system, of a vehicle. A pressure source introduces an overpressure or a negative pressure relative to atmospheric pressure into the tank system, and the temporal profile of at least one operating parameter of the pressure source, in particular the pump flow, is recorded during the introduction of the overpressure / negative pressure until a first point in time or a first pressure level is reached. A leak is concluded if the recorded temporal profile deviates from an expected diagnostic profile by at least a predetermined value.

[0005] Likewise, document DE 102 43 807 A1 describes a method and device for leak testing a tank and tank ventilation system of a motor vehicle, whereby the tank is subjected to a predeterminable pressure above or below atmospheric pressure. If an averagely constant gas mass flow is established that is greater than a predeterminable limit, the presence of a leak can be concluded. SUMMARY AND EMBODIMENTS

[0006] It is therefore an object of the present disclosure to enable particularly reliable and accurate modeling of an input current of a pump.

[0007] This problem is solved by a method for modeling a pump's input current and a control unit according to the independent patent claims. Advantageous embodiments and further developments emerge from the respective dependent claims, the following description, and the drawings.

[0008] Thus, according to a first aspect, a method for modeling an input flow of a pump is provided. The method comprises the following steps: (i) controlling the pump to apply pressure to at least part of an evaporation system, (ii) determining a pressure profile in the evaporation system, and (iii) modeling a profile of an input flow of the pump based on the pressure profile using a model. Modeling the profile of the input flow comprises multiplying by a proportionality factor, and the proportionality factor is determined using a reference operation of the pump in which a reference leak is pressurized by the pump.

[0009] According to a further aspect, a control unit for a motor vehicle is provided, wherein the control unit is configured to carry out the method described above.

[0010] According to a further aspect, a computer program product is provided which comprises instructions which, when executed by a computer, cause the computer to carry out the method described above.

[0011] In the context of the present disclosure, an evaporative system can be defined as a system configured to discharge vent gases from a tank, in particular a fuel tank. It can be configured to supply the vent gases to a retention filter, in particular a fuel vapor retention filter, and / or to supply them to an air path of an internal combustion engine via at least one purge path. The evaporative system can be a venting system, in particular a tank venting system.

[0012] The evaporative system may include a tank vent line. The tank vent line may include multiple regions, for example, a tank region, a filter region, and / or an engine region. The tank region may extend between the tank and a tank shut-off valve or, if no tank shut-off valve is present, between the tank and a filter region of the tank vent line. The filter region may include a supply line from the tank to the retention filter, in particular a supply line between the tank shut-off valve and the retention filter, a discharge line between the retention filter and the tank vent valve, and / or a fresh air connection of the retention filter. The engine region may include one or more purge paths between the tank vent valve and an air path of the internal combustion engine. The purge paths may open into the air path downstream or upstream of a throttle valve.

[0013] The evaporative system may include a tank vent valve. The tank vent valve may be configured to adjust the gas flow from the retention filter to the air path of the combustion engine. For this purpose, the tank vent valve may be controllable by the control unit. The tank vent valve may be arranged between a filter region and an engine region of the tank vent line.

[0014] The evaporation system may include a tank shut-off valve. The tank shut-off valve may be configured to retain vent gases generated in the fuel tank, such as hydrocarbon vapors, in the tank, in particular to feed them to the retention filter in a controlled manner.

[0015] The evaporation system may comprise the tank or at least a partial area of ​​the tank, in particular a partial area in which vent gases evaporate from a tank content.

[0016] Pressurizing at least a portion of the evaporative system may include pressurizing the entire evaporative system, in particular with the exception of the engine area of ​​the tank vent line. It may include pressurizing at least a portion of the tank, in particular the entire tank. Whether the tank area of ​​the tank vent line and / or the tank is pressurized may depend on whether the tank shutoff valve is closed.

[0017] A pump can be configured to apply pressure to at least a portion of the evaporative system, in particular to enable a leak test and / or leak diagnosis of the evaporative system. The pump can be a leak diagnosis pump. In one embodiment, the pump is arranged between the retention filter and a fresh air connection.

[0018] Determining the pressure profile can comprise evaluating a signal from a pressure sensor. The pressure sensor can be arranged in at least that part of the evaporative system which is pressurized by the pump. The pressure sensor can be arranged, for example, in a filter region of the tank venting line. The pressure sensor can be arranged in a tank venting line between the retention filter and the tank venting valve. The pressure sensor can be arranged between the tank venting valve and the tank and / or between the tank venting valve and the tank shut-off valve in the tank venting line. The pressure sensor can be arranged in the tank, for example, on an upper side of the tank which is in contact with the venting gases. Determining the pressure profile can comprise determining a profile of a variable representative of the pressure.

[0019] Modelling a profile of an input current of the pump may comprise modelling a profile of a quantity representative of the input current, for example an electrical power.

[0020] The method described above can be advantageous for enabling accurate and reliable modeling of the pump's input flow. This can be useful, for example, for leak testing of the evaporative system, for clogging diagnosis, or for refueling detection. In particular, discontinuities in the correlation between the pressure curve and the measured pump input flow curve can remain harmless. Such discontinuities can result, for example, from current fluctuations that are not caused by pressure changes in the volume to be diagnosed. For example, they can be caused by component tolerances such as varying bearing friction, by changing temperature conditions, or by fluctuations in the pump's supply voltage.The influence of such discontinuities on the analysis result can be reduced in particular by not measuring the input current curve but modeling it based on the pressure curve.

[0021] The described method can therefore be advantageous for avoiding repeat tests for faulty components, for example, by avoiding multiple leak tests during a shutdown process of the executing control unit. This can reduce energy consumption and / or noise emissions. Furthermore, it can be possible to avoid diagnostic aborts and thus increase the execution frequency of successful leak diagnoses. Overall, the robustness of the diagnostic results for monitoring leaks in the evaporation system can be increased, for example by avoiding false pass and / or fail tests. This can be achieved by suppressing current consumption fluctuations, caused, for example, by deficiencies in the leak diagnostic hardware. In one embodiment, fluctuations in the pump's supply voltage can also be compensated and / or suppressed.

[0022] According to one embodiment, the method further comprises: determining whether a leak exists in the evaporative system based on a comparison of the modeled profile of the input flow with at least one reference value.

[0023] In the context of the present disclosure, a leak may be defined as a leak in the evaporative system through which vent gases can escape into an environment. A leak may be defined by a smallest cross-section to be diagnosed and / or a smallest diameter to be diagnosed. The smallest cross-section to be diagnosed and / or the smallest diameter to be diagnosed may be specified due to legal and / or technical specifications. Determining whether a leak exists in the evaporative system may include determining the leak diameter and / or the leak cross-section and / or the total cross-section of all existing leaks in the examined area.

[0024] In the context of the present disclosure, a reference value may be a comparison value, for example a value of an input current of the pump that is characteristic of a leak in the evaporation system, in particular for a leak with a predetermined cross-section or diameter, for example 0.5 mm diameter.

[0025] In one embodiment, the at least one reference value is determined by pumping into a reference leak, in particular during reference operation. The one or more reference values ​​can be derived from the electrical power consumed by the pump and / or the electrical current consumed by the pump. The multiple reference values ​​can be distributed over a time interval in which the reference leak is pressurized, in particular continuously distributed. The reference leak can be part of the tank system, in particular the pump.

[0026] In one embodiment, the at least one reference value is determined anew for each leak test. This allows for temperature fluctuations, such as the ambient temperature, and / or hardware changes to be compensated for.

[0027] According to the subject matter of the invention, modeling the input flow curve based on the pressure curve involves multiplying it by a proportionality factor. For example, the pressure curve and / or the gradient of the pressure curve can be multiplied by the proportionality factor. The proportionality factor can represent a linear or at least approximately linear relationship between pressure and input flow. The proportionality factor can at least partially characterize the pump, for example, with regard to production deviations or special operating conditions of individual pumps.

[0028] This approach can be advantageous because the input current relevant for leak analysis is simply related to the measured pressure. This makes pressure a particularly suitable measurement variable for leak testing.

[0029] According to the subject matter of the invention, the proportionality factor is determined using a reference pump operation, wherein a reference leak is pressurized by the pump during the reference operation. For example, the proportionality factor can be determined based on a reference current consumption. The proportionality factor can be determined by measuring limit sample and / or nominal sample hardware. It can be determined based on the measured pump current consumption curve and the pressure curve in the evaporation chamber. The relationship between the reference current consumption and the proportionality factor can be stored in a characteristic map.

[0030] In the context of the present disclosure, a reference operation is understood to mean, in particular, an operating mode of the pump in which a reference leak is pressurized by the pump. The reference operation can precede a test operation for leak testing of the evaporation system. The reference operation can be performed before each test operation or only under certain conditions before the test operation.

[0031] The map can be determined using limit sample and / or nominal sample hardware. The proportionality factor can be stored in the map as a function of one or more operating conditions, for example, an ambient temperature.

[0032] Such an embodiment can be advantageous in order to determine the relationship between pressure curve and current curve particularly precisely, in particular depending on the respective operating conditions.

[0033] According to one embodiment, the proportionality factor is determined based on at least one of the following parameters: a current intensity of a measured input current of the pump before switching a valve of the pump, in particular immediately before switching the valve, and a change in the measured input current of the pump during and / or after switching the valve of the pump, in particular a change in the measured input current caused by switching the valve. The switching of the valve can mark the end of the reference operation. The proportionality factor can be stored in the characteristic map depending on at least one of the mentioned parameters.

[0034] According to one embodiment, the method further comprises adapting the model, in particular the proportionality factor, during a test operation of the pump, wherein during the test operation, at least a portion of the evaporation system is pressurized by the pump. Adapting the model during the test operation can be advantageous to enable an even more precise and reliable leak test of the evaporation system.

[0035] In the context of the present disclosure, a test mode is understood, in particular, to be an operating mode of the pump in which at least a portion of the evaporation system is pressurized. In this case, the reference leak may expediently be pressurized only slightly or not at all, in particular at a lower pressure than in reference mode. The test mode can be configured to detect one or more leaks in the evaporation system. The test mode can be connected downstream of a reference mode. The transition from reference mode can be effected by switching a corresponding valve.

[0036] According to one embodiment, the characteristic map with which the proportionality factor is determined in reference operation is updated after the proportionality factor has been adapted.

[0037] According to one embodiment, adapting the model, in particular the proportionality factor, comprises the following steps: (i) checking whether an operating condition of the pump satisfies a predetermined stability criterion between two predetermined points in time, (ii) determining a difference between the modeled input current and the measured input current of the pump at the two predetermined points in time, and (iii) correcting the model, in particular the proportionality factor, based on the differences at the two predetermined points in time if the stability criterion is met between the two predetermined points in time.

[0038] The operating condition can be, for example, a supply voltage of the pump, a battery voltage, a gradient of the measured profile of the pump's input current, or a gradient of the pressure profile in at least a part of the evaporation system pressurized by the pump. According to a further development, respective stability criteria are specified for several, in particular all, of these operating conditions. This allows the previously mentioned discontinuities to be determined particularly reliably.

[0039] Such an embodiment can be advantageous for permanently ensuring the quality of the modeled current profile, for example, to compensate for any changes in the hardware characteristics. The difference between a current swing of the modeled input current between the two points in time and a current swing of the measured input current between the two points in time and / or the difference between the modeled and measured input current at the two points in time can be characteristic of deviations in the model, in particular the proportionality factor.

[0040] According to one embodiment, correcting the proportionality factor comprises determining the difference between the two differences between the modeled and measured input current at the two points in time and relating this difference to a difference in the measured input current at the two points in time. The result can be a proportional deviation of the proportionality factor, which can be at least partially, in particular completely, taken into account in further leak tests.

[0041] According to one embodiment, the operating condition comprises at least one of the following parameters: a supply voltage of the pump, a gradient of a measured profile of the pump's input current, and a gradient of the pressure profile. According to one embodiment, all of these parameters must meet a respective stability criterion. Such an embodiment can be advantageous because the stability of at least one, in particular all of the mentioned parameters, can be an indication that the model is being adapted appropriately.

[0042] According to a further embodiment, the method further comprises: measuring a profile of the input current of the pump.

[0043] According to a further embodiment, the method further comprises: receiving, in particular by the control unit, a measured profile of the input current of the pump.

[0044] According to a further embodiment, the method further comprises determining an initial value of the modeled profile of the input current, wherein the initial value is based on a current value of the measured profile of the input current at which a gradient of the measured profile of the input current exceeds a predetermined threshold value. The initial value can, for example, be set equal to the current value. The initial value can indicate the temporal start of the modeled profile. The further profile can be determined by the proportionality factor. Such an embodiment can be advantageous because exceeding the threshold value can signal the start of pressurization of the evaporation system by the pump.

[0045] According to a further embodiment, model properties of the model, in particular a functional dependency between the pressure curve and the modeled current curve and / or the initial value, are selected such that a fluctuation in the measured curve of the input current is more pronounced than a corresponding fluctuation in the modeled curve of the input current if the fluctuation in the measured curve is not caused by a change in the pressure in the evaporation system. The modeled current may not exhibit a corresponding fluctuation. Such an embodiment can be advantageous because discontinuities between the measured current curve and the pressure curve are at least partially detected and taken into account during the leak test.

[0046] According to another embodiment, the method further comprises: performing a fault diagnosis of the evaporation system, wherein the fault diagnosis takes into account the modeled profile of the pump's input flow. For example, a leak test, a blockage test, and / or refueling detection can be performed.

[0047] According to a further embodiment, the fault diagnosis takes the modeled input current profile into account if at least one of the following conditions is met: (i) a gradient change of the measured input current profile exceeds a predetermined discontinuity threshold; (ii) an absolute value of a gradient of the measured input current profile exceeds a predetermined further discontinuity threshold; (iii) a fluctuation of a supply voltage of the pump exceeds a predetermined voltage threshold.

[0048] According to one embodiment, the fault diagnosis only considers the modeled input current profile if at least one of the aforementioned conditions is met. Otherwise, i.e., if none of the aforementioned conditions is met, the fault diagnosis can be performed based on a comparison of the measured input current profile with the at least one reference value.

[0049] Such an embodiment may be advantageous in order to save memory and computing capacity when modeling the current curve by using the measured current for leak testing if there is no discontinuity in the relationship between the current curve and the pressure curve.

[0050] According to one embodiment, the discontinuity threshold and / or the further discontinuity threshold are dependent on a volume to which the pressure is applied. Such an embodiment can particularly reliably detect and classify discontinuities relevant for the leak test in the relationship between the measured current profile and the pressure profile.

[0051] In an advantageous further development, the discontinuity threshold value and / or the further discontinuity threshold value are stored in a characteristic map, for example depending on a current tank level and a volume to be diagnosed.

[0052] According to one embodiment, during each leak test, the determination of whether a leak exists in the evaporation system is based on a comparison of the modeled input flow profile with the at least one reference value. Such a method can be advantageous because the potentially time-consuming query of conditions, as described above, is eliminated.

[0053] According to one embodiment, if a leak is present, a leak size of the leak is determined. The leak size can result from a comparison of the modeled current profile with the at least one reference value. The leak size can be determined by a cross-sectional area of ​​the leak and / or by a diameter, for example, an average diameter. According to one embodiment, only ranges are determined, for example, whether a leak has a diameter between 0.5 mm and 1.0 mm, including the boundaries, or whether a leak has a diameter greater than or equal to 1.0 mm.

[0054] According to one embodiment, a method for detecting blockages in an evaporation system based on the pressure profile and / or the modeled profile of the input flow is provided, which method, in addition to the steps of the previously described methods, comprises the following steps: (i) determining the measured flow gradient, the measured pressure gradient in the tank, and the measured pressure gradient in the purge line during test operation; (ii) detecting a blocked line when the following conditions are met: (a) the measured flow gradient is greater than an adjustable threshold; (b) the measured pressure gradient in the tank and / or the gradient of the modeled flow profile is smaller than a respective adjustable threshold; (c) the measured pressure gradient in the purge line is greater than an adjustable threshold.In particular, the described method can be used to detect a blockage between the fuel tank and the retention filter.

[0055] Alternatively, under (i) and (ii), absolute values ​​can be evaluated after a predetermined, in particular adjustable, time interval instead of the respective gradients. The use of the measured pressure gradient in the flushing line or the measured pressure gradient in the tank can also be considered optional in a further embodiment.

[0056] According to one embodiment, a method for refueling detection based on the pressure curve and / or on the modeled curve of the input flow is provided, which, in addition to the steps of the previously described methods, comprises the following steps: (i) determining the measured current gradient change, the measured pressure gradient change in the tank, and the measured pressure gradient change in the purge line during test operation; (ii) detecting a refueling operation if the following conditions are met: (a) the measured current gradient change is greater than an adjustable threshold; (b) the measured pressure gradient change in the tank and / or the gradient change of the modeled current curve are greater than a respective adjustable threshold; (c) the measured pressure gradient change in the purge line is greater than an adjustable threshold. Refueling detection can occur, in particular, during the leak test.

[0057] Alternatively, absolute values ​​of the gradients can be evaluated under (i) and (ii) at a point in time during the test operation. If the measured current gradients and the measured pressure gradients each reach an adjustable threshold during the test operation, refueling can be concluded. The use of the measured pressure gradient change in the purge line can also be considered optional in another embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Further advantages and advantageous embodiments and further developments of the method and of the control device emerge from the following exemplary embodiments shown in conjunction with the figures.

[0059] They show: Fig. 1 shows an evaporation system with a control device for carrying out a leak testing method according to a first embodiment of the present disclosure; Fig. 2 shows a flowchart for selecting different variants of the method for incorporating the modeled power consumption into a fault diagnosis of the evaporative system according to the first embodiment of the present disclosure; Fig. 3 shows the modeled curve of the input current of a pump during a reference operation and a test operation in the method according to the first embodiment of the present disclosure; Fig. 4 and Fig. 5 shows a comparison between the modeled input current profile and the measured input current profile in the method according to the first embodiment of the present disclosure; Fig. 6 and Fig. 7 show characteristics of the current consumption of the leak diagnosis pump when adapting a proportionality factor between the pressure curve and the modeled curve of the input current in the method according to the first embodiment of the present disclosure.

[0060] Identical, similar, or functionally identical elements are provided with the same reference symbols in the figures. In some figures, individual reference symbols have been omitted for clarity. The figures and the relative sizes of the elements depicted in the figures are not to scale. Rather, individual elements may be exaggerated for clarity and / or clarity. DETAILED DESCRIPTION OF EMBODIMENTS

[0061] Fig. 1 shows an evaporation system 100 with a control unit 120 that is configured to perform a leak test method according to a first embodiment. Fig. The evaporative system 100 shown in Figure 1 is equipped with a leak detection pump 110 at the fresh air inlet of the fuel vapor retention filter 109, in this case an activated carbon filter. Hydrocarbons released from the tank 130 are trapped in the activated carbon filter 109.

[0062] The evaporative system includes a tank vent valve 106, which can be configured as a switching or linear valve. The tank vent valve 106 is controlled by the control unit 120, in this case an engine control unit, to regulate the gas flow from the activated carbon filter 109 to the air path 140 of the combustion engine. Typically in pressure tank variants, but not in conventional tank variants, the tank system also includes a tank shutoff valve 107. The tank shutoff valve 107 can be used to retain the hydrocarbon vapors generated in the fuel tank in the tank 130, in order to subsequently feed them to the activated carbon filter 109 in a controlled manner under suitable operating conditions.

[0063] The tank system further comprises (i) a vent line (tank area) 102 between the fuel tank 130 and the tank shut-off valve 112, (ii) a tank vent line (filter area) 101, through which the hydrocarbon gases are conducted from the fuel tank 130 into the activated carbon filter 109 and further to the tank vent valve 106, and (iii) a tank vent line (engine area) 103, through which the hydrocarbon gases are introduced from the activated carbon filter 109 into the air path 140 of an internal combustion engine downstream of the tank vent valve 106. A pressure sensor 111 is arranged in the tank vent line (filter area) 101 between the activated carbon filter 109 and the tank vent valve 106. A further pressure sensor 111 and optionally a temperature sensor or a combined pressure / temperature sensor are arranged in the fuel tank 130.

[0064] The electronic control unit 120 is configured to perform a method for modeling an input flow of a pump 110. The method comprises the following steps: applying pressure to at least a portion of an evaporation system 100 by means of the pump 110; determining a pressure profile in the evaporation system 100; and modeling a profile of the input flow of the pump 110 based on the pressure profile using a model.

[0065] The control unit 120 can also be configured to perform at least one, in particular all, of the following steps or methods: (a) determine a target value for the purge flow from the activated carbon filter 109 to the internal combustion engine for the current operating state; (b) determine an intake manifold pressure using a pressure sensor in the intake tract; (c) read the values ​​from the pressure sensor; (d) determine a PWM (pulse width modulation) value for controlling the tank venting valve 106 from a pressure gradient between the fresh air connection of the activated carbon filter 109 and the pressure at the inlet point in the air path 140 of the internal combustion engine from the specified purge flow; (e) calculate the amount of fuel to be injected for the current operating state of the engine; (f) control the leak diagnosis pump 110 and measure the current consumption; (g) control the tank shut-off valve 107, if present.

[0066] Fig. Figure 2 shows a flowchart for incorporating the modeled current consumption of the leak diagnostic pump into a diagnostic procedure of the evaporative system, for example, a tank leak test procedure, a blockage test, and / or refueling detection. In order to resolve problematic discontinuities in the correlation between the pressure curve and the electrical current consumption of the pump 110 with regard to the quality of the diagnostic result, a correlating current curve is calculated based on the measured gas pressure curve. The pressure curve is measured and evaluated in the tank or filter area, depending on whether the tank area including the filter area is to be diagnosed using the tank pressure sensor 111 or exclusively the filter area is to be diagnosed using the pressure sensor 111 in the filter area.According to a first variant of the method, the current curve corrected via the measured gas pressure curve can be included continuously to form the diagnostic result (step S1).

[0067] In a further variant of the method, which is queried in step S2, the current curve corrected via the measured gas pressure curve is only included if current fluctuations (or continuous current gradients) are detected that cannot be caused by the gas pressure curve in the volume to be diagnosed. To detect current fluctuations, the current curve is measured and the gradient change of the measured current curve is compared with an adjustable threshold. The threshold is stored in the control unit in the form of a map value depending on the current tank level and the volume to be diagnosed (tank and filter area or filter area only). To detect high current gradient values, the gradient of the measured current curve is compared with an adjustable threshold.The threshold is stored in the control unit in the form of a map value depending on the current tank level and the volume to be diagnosed (tank and filter area or filter area only).

[0068] The method for determining whether the leak test is carried out based on the modeled or the measured curve of the pump's input current comprises the following steps: In a first step S1, a query is made as to whether the leak test is always carried out based on the modeled current curve and not the measured current curve. If not (n), a second step S2 queries whether a current fluctuation or a high value of the measured current gradient was detected. If not (n), a third step S3 queries whether a battery fluctuation was detected. If this question is also answered with no (n), then in a further step S4 the leak test is carried out based on the measured current curve. However, if only one of the questions S1, S2, S3 was answered with yes (y), the leak test in step S5 is carried out based on the modeled current curve.

[0069] In Fig. Figure 3 shows the curve of the input current 350 over time 352 during different diagnostic phases 353, 354 of the method according to the first exemplary embodiment. Specifically, the curve of the input current of a pump is shown during a reference operation 353 and a test operation 354. In order to calculate a current curve corrected or modeled based on the pressure curve, it is first necessary to determine the proportionality factor between pressure and current, whereby the proportionality factor characterizes the underlying pump hardware. This characterization should take place within the first diagnostic phase, a reference operation 353.During reference operation 353, a reference current consumption of the measured pump input current is determined, whereby the level of the resulting reference current consumption and / or the change in the measured pump current consumption during the switching of a valve of the leak diagnosis pump determines the proportionality factor. The quantitative relationship is stored within a characteristic map and was previously determined by measuring limit sample and / or nominal sample hardware.

[0070] The Fig. The drop in current consumption apparent in Figure 3 results from the activation of a switching valve and marks the transition between reference operation 353 and test operation 354. The switching valve switches from a reference operation 353 in which a reference leak is pressurized to the test operation 354 in which at least part of the evaporative system is pressurized.

[0071] After determining the proportionality factor, further steps are carried out, which will be explained using the following figures.

[0072] Fig. Figure 4 illustrates the determination of an initial value 456 for the modeled curve 350 of the pump's input current in the method according to the first exemplary embodiment. After switching the switching valve from reference mode 353 to test mode 354, the current curve 455 of the pump's input current is measured, filtered, and the gradient is subsequently determined. If the gradient of the determined filtered measured current curve 455 is greater than an adjustable threshold value, the initial value 456 is formed for the subsequent calculation of the modeled current curve 350. The initial value 456 is set equal to the filtered measured current value at the described time.

[0073] To create the modeled current profile 350, the measured pressure in the evaporation chamber is first filtered, for example, using a low-pass filter. Subsequently, the gradient of the filtered measured pressure in the evaporation chamber is calculated at equidistant time intervals (e.g., 1 s). This gradient of the filtered measured pressure in the evaporation chamber is then multiplied by the previously defined proportionality factor at the same equidistant time interval. A final filtering of this product defines the modeled current profile 350.

[0074] Fig. Figure 5 shows the measured current waveform 455 and the corresponding modeled current waveform 350 in the method according to the first embodiment. A current fluctuation caused by deficiencies in the pump hardware can be seen at the discontinuity 557 in the measured current waveform 455. In contrast, the modeled current waveform 350 suppresses this current fluctuation, which is detrimental to the leakage diagnosis evaluation algorithm.

[0075] In the Fig. 6 and Fig.Figure 7 shows characteristic values ​​of the measured and modeled input current profile 455, 350 when adapting a proportionality factor between the measured input current profile 455 and the pressure profile in the method according to the first exemplary embodiment. In order to permanently ensure the quality of the modeled current profile 350, an adaptation of the proportionality factor is required so that any changes in the hardware characteristics can be compensated. The adaptation is carried out with the aid of four physical quantities continuously determined during the diagnostic run in test mode: 1) Integral 661 of the measured current gradient; 2) Integral 662 of the modeled current gradient; 3) Difference 663 between the integral of the measured and the integral of the modeled current gradient at a first time 664 and a second time 665; and 4) Filtered measured pump input current 455.

[0076] To determine the error in the current modeling process of the current waveform, the following steps can be performed, for example: (i) Determining the stability of the battery voltage, in particular the supply voltage of the pump; (ii) Determining the stability of the measured current gradient and the measured gas pressure gradient, for example by continuously comparing a weakly and a strongly damped or filtered measured current or pressure gradient; (iii) Determining whether conditions (i) and (ii) are present for at least a configurable time;(iv) after conditions (i) and (ii) have been met for at least the adjustable time, equating at this first time 664 the initial value of the difference between the integrals of the measured and the modeled current gradient with the currently prevailing difference between the integrals of the measured and modeled current gradient and equating the initial value of the measured pump input current at the same time 664 with the currently prevailing value; (v) as long as stability criteria (i) and (ii) are met, retaining the stored initial values; (vi) if stability criteria (i) and (ii) are no longer met, forming at this time 665 a final value of the physical quantities mentioned under (iv) by equating them with the currently prevailing value, while retaining the initial values ​​from step (iv);(vii) Determining the error in percent of the applied proportionality factor if the stability criteria under points (i) and (ii) were met for an adjustable minimum time, for example according to the formula: 100% * [(Difference 663 between the integral of the measured current gradient and the integral of the modeled current gradient at the second time point 665) - (Difference 663 between the integral of the measured current gradient and the integral of the modeled current gradient at the first time point 664)] / [(Filtered measured pump input current at the second time point 665) - (Filtered measured pump input current at the first time point 664)].;

[0077] The determined error can then be used proportionally or 100% to adapt the proportionality factor for the next modeling cycle.

[0078] The invention is not limited to the embodiments described herein. Rather, the invention encompasses any novel feature and any combination of features, including, in particular, any combination of features in the embodiments and claims. REFERENCE SYMBOL 100 evaporation system 101 Tank ventilation line (filter area) 102 Tank ventilation line (tank area) 103 Tank ventilation line (engine area) 104 first flushing path 105 second flushing path 106 Tank vent valve 107 Tank shut-off valve 108 Check valve 109 Fuel vapor retention filter 110 Leak diagnosis pump 111 Pressure sensor 112 Flow direction 120 control unit 121 Signal line 130 fuel tank 140 Air path of the combustion engine 141 Air filter 142 throttle valve 350 modeled current flow 351 amperage 352 time 353 Reference company 354 Testing operation 455 measured current curve 456 Initial value 557 Discontinuity 661 Integral of the measured current gradient 662 Integral of the modeled current gradient 663 Difference of the integrals of the measured and modeled current gradient 664 first point in time 665 second point in time

Claims

[1] A method for modeling an input flow of a pump (110), comprising the following steps: - controlling the pump (110) to apply pressure to at least part of an evaporation system (100); - determining a pressure curve in the evaporation system (100); and - modelling a curve (350) of the input current of the pump (110) based on the pressure curve by means of a model; - wherein the modelling of the curve (350) of the input current comprises multiplying by a proportionality factor; and - wherein the proportionality factor is determined by means of a reference operation (353) of the pump (110) in which a reference leakage is pressurized by the pump (110). [2] Method according to the preceding claim, wherein the proportionality factor is determined based on at least one of the following parameters: a current intensity of a measured input current of the pump (110) before switching a valve of the pump (110) and a change in the measured input current of the pump (110) during and / or after switching the valve of the pump (110). [3] Method according to one of the preceding claims, further comprising adapting the model during a test operation (354) of the pump (110), wherein during the test operation (354) the at least part of the evaporation system (100) is pressurized by the pump (110). [4] Method according to the preceding claim, wherein adapting the model comprises Checking whether an operating condition of the pump (110) satisfies a predetermined stability criterion between two predetermined points in time; Determining a difference between the modeled input current (350) and a measured input current (455) of the pump (110) at the two predetermined times (664, 665); and Correcting the model based on the differences at the two specified time points (664, 665) if the stability criterion is met between the two specified time points (664, 665). [5] Method according to the preceding claim, wherein the operating condition comprises at least one of the following parameters: a supply voltage of the pump (110), a gradient of the measured curve (455) of the input current of the pump (110) and a gradient of the pressure curve. [6] Method according to one of the preceding claims, further comprising receiving a measured profile (455) of the input current of the pump (110). [7] Method according to the preceding claim, further comprising determining an initial value (456) of the modeled profile (350) of the input current, wherein the initial value (456) is based on a current value of the measured profile (455) of the input current at which a gradient of the measured profile (455) of the input current exceeds a predetermined threshold value. [8] Method according to claim 6 or 7, wherein model properties of the model are selected such that a fluctuation in the measured profile (455) of the input flow is more pronounced than a corresponding fluctuation in the modeled profile (350) of the input flow if the fluctuation in the measured profile (455) is not caused by a change in the pressure in the evaporation system (100). [9] Method according to one of the preceding claims, further comprising: performing a fault diagnosis of the evaporation system, wherein the fault diagnosis takes into account the modeled profile (350) of the input current of the pump (110). [10] Method according to the preceding claim, wherein the fault diagnosis takes into account the modelled course of the input current if at least one of the following conditions is met: (i) a gradient change of the measured waveform (350) of the input current exceeds a predetermined discontinuity threshold; (ii) an amount of a gradient of the measured waveform (350) of the input current exceeds a predetermined further discontinuity threshold; (iii) a fluctuation of a supply voltage of the pump (110) exceeds a predetermined voltage threshold. [11] Method according to the preceding claim, wherein the discontinuity threshold and / or the further discontinuity threshold are dependent on a volume to which the pressure is applied. [12] Control unit (120) for a motor vehicle, which is designed to carry out a method according to one of claims 1 to 11. [13] A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of claims 1 to 11.

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