Method for operating an electric fuel pump

Abstract

Method for operating an electric fuel pump (102) of an injection system (100), wherein a maximum limit (48) is provided for a voltage for controlling a pressure of fuel to be pumped, which is applied to the electric fuel pump (102), and a maximum limit (64) is provided for a current flowing through the electric fuel pump (102), wherein a value (62) of an electric current required by the electric fuel pump (102) is measured, and wherein the maximum limit (48) provided for the voltage applied to the electric fuel pump (102) is reduced depending on the measured value (62) of the current if the measured value (62) exceeds the provided maximum limit (64).

Description

[0001] The invention relates to a method and a control device for operating an electric fuel pump. State of the art

[0002] The functions of an injection system for an internal combustion engine can be controlled by a control unit. An EDC (Electronic Diesel Control) control unit can be used to inject diesel into the combustion chambers of an internal combustion engine. The output stage of the EDC control unit is typically designed to easily meet the power requirements of an actuator in the injection system, even under adverse operating conditions. A monitoring module is also provided, which can shut down the output stage in the event of a fault, such as a short circuit or excessive temperature.

[0003] An actuator of the injection system can be designed as an electric fuel pump (EKP), which, under normal operation and taking all specified boundary conditions into account, has only a limited power requirement. However, in exceptional cases, this power requirement can rise sharply. However, in exceptional cases, such as an increased pressure drop in the fuel filter due to exceptionally contaminated fuel or partial gelling of the fuel, the power requirement increases sharply. In the case of an FPC system (FPC: Feed Pump Control), the rail pressure of the injection system is controlled via the electric fuel pump (EKP), whereby the power requirement of the electric fuel pump depends significantly on an operating point of the injection system.

[0004] In such an injection system, which has a fuel reservoir (common rail), the fuel pressure depends, among other things, on the amount of fuel delivered by a fuel pump, for example a high-pressure pump, the fuel pressure at the fuel pump inlet, and the current required to operate the electric fuel pump. The voltage required at the fuel pump for an operating point varies considerably from model to model, as well as depending on the ambient conditions. The design of the injection system therefore requires a wide permissible voltage range for the electric fuel pump. In exceptional cases, for example in the event of an increased pressure drop, e.g. at the fuel filter, this can lead to a significantly higher current at the fuel pump than normal.However, designing the final stage of the electric fuel pump for this maximum possible current within the injection system is relatively cost-intensive compared to designing it for the currents that only occur under normal circumstances.

[0005] The publication DE 10 2010 030 872 A1 describes a method for determining a correction characteristic curve for adapting a characteristic curve of an injection system, wherein the correction characteristic curve comprises at least one deviation of a measured characteristic curve from a target characteristic curve. The at least one deviation comprises a total tolerance of at least two components of the injection system that influence the characteristic curve.

[0006] DE 10 2006 004 296 A1 discloses a method for detecting fault conditions in fuel delivery systems of internal combustion engines. By comparing the hydraulic power in the fuel system with the electrical power of the fuel pump, deviations from specified values ​​or thresholds are detected, and fault conditions are derived. Current drops in the pump with simultaneous pressure drops indicate prefilter loading. If the voltage curve versus current exceeds a limiting characteristic curve with poor efficiency, the cause is carbon buildup or a worn fuel pump collector.

[0007] DE 10 2011 015 154 A1 discloses a method for monitoring an electric motor-driven fuel pump of a fuel delivery unit for a motor vehicle. The pump current is monitored as a function of a pump voltage or pump speed. By comparing the pump current with the pump voltage or pump speed, it is possible to determine whether the fuel pump is leaking or running dry. The fuel delivery unit does not require a pressure sensor for this purpose and is therefore particularly simple in design.

[0008] DE 10 2004 019 152 A1 discloses a method in which a first voltage is initially applied to a coil of a solenoid valve up to a first point in time, followed by a second voltage which is lower in value than the first voltage. The switchover to the second voltage at the first point in time occurs before the solenoid valve reaches an end position. The coil current and thus also the magnetic force are built up quickly with the first applied voltage, resulting in the solenoid valve starting to move quickly. By switching to a second, lower voltage value, an unnecessary increase in the coil current is avoided. The first point in time can be either before or after a certain force value is reached at which the magnet armature starts to move. In principle, the method can be applied to both normally open and normally closed valves.By switching to a second voltage which is lower in value than the first voltage, it is avoided that the coil current exceeds a maximum permissible current when the solenoid valve is activated again. Disclosure of the invention

[0009] Against this background, a method and a control device with the features of the independent patent claims are presented. Further embodiments of the invention emerge from the dependent patent claims and the description.

[0010] The method makes it possible to limit a current level of an electric fuel pump (EKP), which is designed as a component of an injection system, to a maximum permissible value by designing an output stage and thus to protect the output stage.

[0011] The electric fuel pump delivers a quantity of fuel to a fuel reservoir (common rail) of the injection system, whereby the quantity depends, among other things, on a voltage value applied to the fuel pump and / or a current value flowing through the fuel pump. The pressure (rail pressure) of the fuel in the fuel reservoir is regulated by the quantity delivered as well as the current and / or the voltage. The voltage can therefore be used as a manipulated variable for controlling the pressure. A value range is provided for the voltage which is defined by a minimum and maximum limit value for the voltage. In one embodiment, a current value of the voltage at an operating point of the fuel pump is restricted to the value range by a limiting function.

[0012] It is also provided that a value of the current flowing through the fuel pump can also be influenced by, among other things, a current value of the fuel pressure. This can lead to the value of the current increasing as a function of the pressure and exceeding a maximum limit value provided for the current. In this case, the value range for the voltage, usually the maximum limit value for the voltage, is reduced in a design of the method via a closed control loop with a reduction function by an amount that can depend on the currently measured value of the current, until the current value of the current is lower than the maximum limit value provided for this purpose. Furthermore, the maximum limit value for the voltage can be reduced depending on a predetermined gradient of the measured voltage over time and therefore depending on a temporal change in the voltage.

[0013] Here, the voltage applied to the electric fuel pump is limited based on a measured current demanded or required by the electric fuel pump that flows through the electric fuel pump. Typically, an outgoing voltage value is limited by the limiting function to a value range defined by a maximum limit and a minimum limit. The voltage value range specified by the limiting function can be continuously reduced and, based on the closed control loop that checks whether the measured current value is greater than the limit or not, can be precisely adjusted to a currently required value range. This usually involves reducing the maximum voltage limit. This ensures that the performance of the injection system is maintained within the maximum permissible range.In this way, the availability of the injection system of an internal combustion engine and thus of a motor vehicle powered by it can be ensured even in the event of an unexpectedly high pressure drop of fuel in a low-pressure circuit of the injection system.

[0014] When the procedure is implemented, the outgoing voltage value in an initial state is set to the maximum limit by the limiting function, thus limiting it. Furthermore, a reduction function is activated if the current flowing through the electric fuel pump exceeds a specified limit. This maximum limit can be determined, for example, by the design of the power amplifier.

[0015] The reduction function first detects the current voltage value. The reduction function is then started, and the maximum voltage limit is reduced by the reduction function based on this maximum voltage limit, based on a predefined voltage gradient over time, usually based on the measured voltage and / or on previously reduced maximum voltage limits. This gradient can also depend on the measured current value and / or a temporal change in the current.

[0016] It is also possible to tolerate brief exceedances of the current limit, such as those that may occur during dynamic operation of the injection system and / or fuel pump. In this case, after the current has exceeded the limit, a certain period of time, which can be measured and / or monitored by a timer module, is waited for before the reduction function is activated. If the currently measured current value falls below the limit during this period, the reduction function is not activated, and a timer module for the period is also stopped and reset.

[0017] To reduce the voltage, an integrator is activated, among other things. This integrator is designed to reduce a maximum voltage limit based on the current voltage value until the current value again reaches the permissible range below the specified limit. As soon as this happens, the integrator is deactivated and the limitation of the voltage value range is set to the maximum limit reached. If the current value increases at a later time and lies outside the permissible range, the integrator is activated again and the voltage limit is reduced further. A closed control loop is used here, but it is only activated temporarily, depending on whether the current value lies within or outside the permissible range.

[0018] A control of the fuel pressure in the fuel reservoir (rail) of the injection system, which specifies a control value for the voltage of the electric fuel pump in the injection system, remains fully active. However, if a reduced limit value for the voltage is set, an operating range of the injection system and / or the combustion engine can be restricted, whereby, for example, an injection quantity of the injection system and / or a torque of the combustion engine can be reduced. This can prevent control deviations of a pressure, i.e. the pressure of the fuel in a fuel reservoir of the injection system, from being monitored. This can be carried out as a fault response by an error message that is set by the reduction function provided within the framework of the method and / or by the limiting function for the voltage, or independently thereof by a special type of rail pressure monitoring.If the low-pressure range is manipulated, for example, by an adjustable throttle, the implementation of the method may result in a voltage limiting of the electric fuel pump of the injection system.

[0019] If the fuel pressure in the low-pressure range of the injection system increases due to partial fuel gelling and / or a fuel filter blockage, thus increasing the power requirement of the electric fuel pump, the implementation of the method makes it possible to change the operating point of the electric fuel pump by adjusting, usually reducing, the voltage and thus returning the power requirement to a normal operating range. This reduces the delivery rate of the electric fuel pump and, as a result, the pressure drop in the low-pressure range of the injection system, so that the power requirement of the electric fuel pump is reduced and can be returned to a permissible value range defined by a maximum limit and, if applicable, a minimum limit for the current.

[0020] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0021] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention. Short description of the drawings Fig. 1 shows diagrams of a first embodiment of the presented method. Fig. 2 shows a diagram of a second embodiment of the method. Fig. 3 shows a schematic representation of an example of an injection system with an electric fuel pump and an embodiment of the control unit presented. Embodiments of the invention

[0022] The invention is illustrated schematically in the drawings using embodiments and is described in detail below with reference to the drawings.

[0023] The figures are described coherently and comprehensively; the same reference symbols refer to the same components.

[0024] Fig. 1 comprises a total of five diagrams, namely a first pressure-time diagram 2 and a second pressure-time diagram 4, wherein the time in milliseconds is plotted along an abscissa 6 and a fuel pressure in an injection system in bar is plotted along an ordinate 8. Furthermore, Fig. 1 shows a first current-time diagram 10 and a second current-time diagram 12, each of which also has an abscissa 6 along which the time is plotted in milliseconds. Furthermore, the two current-time diagrams 10, 12 each include an ordinate 14 along which a current flowing through an electric fuel pump of the injection system is plotted in amperes. In the middle between the first pressure-time diagram 2 and the first current-time diagram 10 on the left, as well as the second pressure-time diagram 4 and the second current-time diagram 12 on the right, Fig. 1 shows another diagram 15, which includes an abscissa 16 along which the fuel pressure is plotted in bar. A fuel delivery rate in liters per hour is plotted along a first ordinate 18 of diagram 15, and the current flowing through the fuel pump in amperes is plotted along a second ordinate 20.

[0025] In the first embodiment of the method presented here, it is provided that, due to a blockage of a fuel filter in the injection system, as the first pressure-time diagram 2 illustrates, a pressure value increases from a first operating point 22, at which a pressure of 4.2 bar prevails here, within a time period 24 of 50 ms and reaches an increased value at a second operating point 26. This results, as the first current-time diagram 10 shows, in an increase in the current flowing through the electric fuel pump from the first operating point 22, at which a current of 7.5 A flows here, to a significantly increased value at the second operating point 26 within the time period 24 of 50 ms, wherein it is provided that the current value at the second operating point 26 is greater than a limit value provided for this purpose.A voltage applied to the electric fuel pump has a first duty cycle 27 of 95% at both operating points 22, 26.

[0026] As a countermeasure to an increase in the current value above the specified limit, a permissible maximum limit of the voltage applied to the electric fuel pump is reduced. In addition, the first duty cycle of the voltage is reduced from 95% to a second duty cycle 29 of 85%. Reference is made to diagram 15, which shows a first pressure-dependent curve 28 of the current at the first duty cycle 27 of 95% and a second pressure-dependent curve 30 of the current at the second duty cycle 29 of 85%. For comparison, diagram 15 also shows a curve 32 of a constant current of 7.5 A. Due to the reduction in the maximum limit of the voltage, which results, among other things, from the reduction of the first duty cycle 27 from 95% to the second duty cycle 29 of 85%, the current level is also reduced.This also reduces the fuel delivery rate delivered by the electric fuel pump and the fuel pressure. Diagram 15 shows a first pressure-dependent curve 34 of the delivery rate at the first duty cycle 27 of 95% and a second pressure-dependent curve 36 of the delivery rate at the second duty cycle 29 of 85%. The second pressure-dependent curve 36 of the delivery rate at the second, lower duty cycle 29 of 85% is lower than the first pressure-dependent curve 34 at the first, higher duty cycle 27 of 95%.

[0027] The reduction of the duty cycle 27, 29 of the voltage from 95% to 85% during voltage regulation, which is carried out as part of the method, also affects the pressure and the current at a third operating point 38, at which the second duty cycle 29 of 85% exists. By reducing the duty cycle 27, 29 and thus the voltage, the pressure value prevailing at the second operating point 26 is reduced to a lower value at the third operating point 38, as the second pressure-time diagram 4 shows. In addition, the increased current at the second operating point 26 is reduced again to the comparatively lower value of 7.5 A at the third operating point 38.

[0028] With the diagram from Fig. Figure 2 shows a structure of the second embodiment of the presented method. The structure of the method illustrated in the diagram can be implemented as software in a control unit for carrying out the method.

[0029] The proposed structure for implementing the second embodiment of the presented method comprises a limiting function 56 controlled by the control unit, which limits an incoming value 42 of a voltage applied to an electric fuel pump to a value range between a minimum, lower limit value 46 and a maximum, upper limit value 48 for the voltage. The two limit values ​​46, 48 for the value range of the voltage are specified by a voltage-dependent control (rail pressure control) of a fuel pressure in a fuel reservoir (rail) of an injection system. The fuel pressure in the fuel reservoir depends, among other things, onfrom a quantity of fuel that is pumped from the electric fuel pump to the fuel reservoir as a function of a voltage applied to the electric fuel pump and as a function of a current flowing through the electric fuel pump.

[0030] The incoming, currently measured voltage value 42 is fed to the limiting function 56 via an input signal. In addition, an outgoing, resulting voltage value 44 is provided by the limiting function 56 via an output signal. The outgoing voltage value 44 corresponds to the incoming voltage value 42 as long as the incoming voltage value 42 is within the specified limit values ​​46, 48 of the voltage value range. In contrast, the outgoing voltage value 44 provided by the limiting function 56 via the output signal corresponds to the minimum limit value 46 as long as the incoming voltage value 42 is less than the minimum limit value 46. If, on the other hand, the incoming voltage value 42 is greater than the maximum limit value 48, the outgoing voltage value 44 is limited to the maximum limit value 48 by the limiting function 56.

[0031] As long as a reduction function is not activated, a first switch 59 for switching the voltage is in a first position shown here. In this case, a predetermined maximum value 47 for the voltage is used as the maximum limit value 48 of the limiting function 56. A measured value 62 of the current of the electric fuel pump is compared with a limit value 64 for the current in a module 70 designed for comparison. If the measured value 62 of the current exceeds the limit value 64, a second switch 52 for switching the current is switched and a timer module 72 is started, wherein the timer module 72 measures how long the measured value 62 of the current is greater than the limit value 64 provided for this purpose. In this case, it is monitored whether the measured value 62 of the current is greater than the limit value 64 for longer than a defined period of time.

[0032] The second switch 52 for switching the current also passes on a difference 68 between the measured value 62 and the specified limit value 64 of the current, which difference 68 is formed in a module 78 for calculating this difference 68, to an integrator 54. As long as the measured value 62 is greater than the limit value 64 for the current, a negative difference 68 results. If the negative difference 68 is present, a value 49 originating from an integrator 54 for specifying the maximum limit value 48 for the voltage is continuously reduced by an amount that depends on the difference 68 and thus on the measured value 62 of the current, which in this case is greater than the specified maximum limit value 64. This amount, by which the maximum limit value 48 for the voltage is reduced, can also be reduced depending on a gradient of the voltage over time.The specified gradient can be used to take into account a temporal progression of the measured voltage values ​​and / or a temporal progression of maximum voltage limit values ​​that have already been reduced during the process.

[0033] If the measured current value 62 is greater than the limit value 64 after the time period specified by the timer module 72 has elapsed, a trigger 74 is set, thereby switching a third switch 58 to switch the integrator 54 and setting an output of a flip-flop module 76. By switching the switch 58, the integrator 54 is initialized once with the outgoing voltage value 44 currently provided by the limiting function 56. The output of the flip-flop module 76 switches the first switch 59 to a second position and holds the first switch 59 in this position, with the outgoing value 49 provided by the integrator 54 being continuously passed on to the limiting function 56 to update the maximum voltage limit value 48.Since the integrator 54, as already explained, continuously reduces its outgoing value 49, this results in a continuous reduction of the maximum limit value 48 for the value range of the voltage and thus also a continuous reduction of the outgoing value 44 for the voltage.

[0034] If the measured current value 62 falls below the limit value 64, the output of the comparison module 70 is reset, whereby the second switch 52 for switching the current is returned to its initial position. This sets the input of the integrator 54 to zero, so that the currently outgoing value 49 of the integrator 54 is maintained and not changed further. The maximum limit value 48 of the limiting function 56 is thus set to the reduced value 49 provided by the integrator 54 and thus maintained. If the measured current value 62 exceeds the limit value 64 again, the second switch 52 for switching the current is switched again and the negative difference 68 between the measured value 62 and the limit value 64 for the current is passed on to the input of the integrator 54, whereby the value 49 outgoing from the integrator 54 for setting the voltage limit value 48 is further reduced.

[0035] For the outgoing voltage value 44, the described embodiment of the method results in the maximum voltage limit 48, updated and / or initialized by the integrator 54 via its outgoing value 49, being set to the currently outgoing value 44 by activating the reduction function. Subsequently, a continuous reduction of the maximum limit 48 and, concomitantly, a reduction of the outgoing value 44 is carried out as long as the measured current value 62 is greater than the limit 64 provided for this purpose.

[0036] Irrespective of this, it is generally possible for the outgoing value 44 of the voltage to follow the specified and / or incoming value 42 for the voltage, wherein the incoming value 42 is specified by the control (rail pressure control) of the pressure of the fuel in a fuel reservoir of the injection system and / or is dependent on an operating point of the injection system, as long as the incoming value 42 is within the value range between the minimum limit value 46 and the maximum limit value 48.

[0037] Fig. 2 also shows a counter 80 that counts how often the maximum limit value 48 for the voltage is reduced depending on the measured value 62 of the current, depending on the difference 68 between the measured value 62 and the intended maximum limit value 64 of the current and / or depending on a temporal gradient of the voltage. At least some of the values ​​determined based on Fig. The modules described in Figure 2, which are designed to implement the method, can be implemented by the control unit presented and / or be designed as components of the control unit. This applies, among other things, to the switches 52, 58, 59, the comparison module 70, the timer module 72, the module 78 for calculating the difference 68, the integrator 54, the trigger 74, the flip-flop module 76, and the counter 80. Furthermore, the control unit can have at least one component for implementing the limiting function 56 and the reduction function.

[0038] In Fig. Figure 3 schematically illustrates an example of an injection system 100 for an internal combustion engine of a motor vehicle. This injection system 100 includes an electric fuel pump 102 as a component, which is designed to deliver fuel to a fuel reservoir 104 (common rail) of the injection system 100. Fig. 3 further schematically illustrates the embodiment of the control unit 106, which is designed to monitor and thus control and / or regulate a function of at least one component of the injection system 100, ie at least of the electric fuel pump 102. In this case, the control unit 106 can, among other things, control, generally monitor and / or adjust operating parameters of the electric fuel pump 102, for example a voltage applied to the electric injection pump 102 and a current flowing through the fuel pump 102. In addition, the control unit 106 is designed to carry out at least one step of at least one embodiment of the Fig. 1 and Fig. 2 presented procedure.

[0039] In the method to be performed by the control unit 106 for operating the electric fuel pump 102 of the injection system 100, a maximum limit value is provided for a voltage applied to the electric fuel pump 102 for regulating a pressure of fuel to be delivered, and a maximum limit value is provided for a current flowing through the electric fuel pump 102. Furthermore, a value of an electric current required by the electric fuel pump is measured. The maximum limit value provided for the voltage applied to the electric fuel pump 102 is reduced based on the value of the measured current and / or as a function of this value if the measured current value exceeds the provided maximum limit value.

[0040] The proposed method can reduce the maximum voltage limit applied to the electric fuel pump depending on a specified voltage gradient over time. The voltage gradient or a temporal change in the voltage can be related to a temporal change in the measured voltage and / or to a temporal change in the maximum voltage limit, which is or has already been reduced over time when the method is implemented.

[0041] The amount by which the maximum voltage limit is reduced can depend on the difference between the measured current value and the maximum current limit. In one embodiment, the amount by which the maximum voltage limit is to be reduced is determined by a function for the magnitude of this voltage, which depends on the difference between the measured value and the specified maximum value and / or on the specified voltage gradient.

[0042] In addition, it is possible that the specified maximum limit value for the voltage applied to the electric fuel pump is reduced continuously or gradually, for example using a reduction function, until the current falls below or has fallen below the specified maximum limit value again.

[0043] To reduce the voltage limit, a duty cycle for the voltage applied to the electric fuel pump 102 can also be reduced.

[0044] In a further embodiment, the maximum limit value for the voltage applied to the electric fuel pump 102 can be reduced if the predetermined maximum limit value of the current is exceeded at least for a predetermined and / or definable period of time.

[0045] In addition, the maximum limit for the voltage applied to the electric fuel pump 102 can be reduced to a minimum value when the current falls below the limit, while maintaining the minimum value for the voltage.

[0046] The control unit 106 for operating and thus controlling the operation of the electric fuel pump 102 and / or the injection system 100 is designed to measure the current required by the electric fuel pump 102 using an ammeter provided for this purpose in the control unit 106 and to reduce the maximum limit value provided for the voltage applied to the electric fuel pump 102 in the event that the current exceeds the provided maximum limit value, based on and consequently as a function of the currently measured current and / or the gradient for the voltage.

[0047] The control unit 106 may comprise and / or implement an integrator configured to reduce the maximum limit value for the voltage depending on a difference between a measured value of the current and the intended maximum limit value of the current until the current has fallen below the permissible maximum limit value.

Claims

[1] Method for operating an electric fuel pump (102) of an injection system (100), wherein a maximum limit value (48) is provided for a voltage for regulating a pressure of fuel to be delivered, which voltage is applied to the electric fuel pump (102), and a maximum limit value (64) is provided for a current flowing through the electric fuel pump (102), at which a value (62) of an electric current required by the electric fuel pump (102) is measured, and at which the maximum limit value (48) provided for the voltage applied to the electric fuel pump (102) is reduced depending on the measured value (62) of the current in the event that the measured value (62) of the current exceeds the provided maximum limit value (64). [2] Method according to claim 1, wherein the provided maximum limit value (48) for the voltage applied to the electric fuel pump (102) is reduced as a function of a predetermined gradient of the voltage over time. [3] Method according to claim 1 or 2, wherein the provided maximum limit value (48) for the voltage applied to the electric fuel pump (102) is reduced until the measured value (62) of the current falls below the provided maximum limit value (64). [4] Method according to one of the preceding claims, in which the provided maximum limit value (48) for the voltage applied to the electric fuel pump (102) is continuously reduced. [5] Method according to one of the preceding claims, in which the provided maximum limit value (48) for the voltage applied to the electric fuel pump (102) is reduced with a reduction function. [6] Method according to one of the preceding claims, in which a duty cycle for the voltage applied to the electric fuel pump (102) is reduced. [7] Method according to one of the preceding claims, in which the maximum limit value (48) for the voltage applied to the electric fuel pump (102) is reduced if the provided maximum limit value (64) is exceeded by the measured value (62) of the current for at least a predetermined period of time. [8] Method according to one of the preceding claims, in which the maximum limit value (48) for the voltage applied to the electric fuel pump (102) is reduced to a minimum value when the measured value (62) of the current falls below the maximum limit value (64), the minimum value for the voltage being maintained. [9] Control unit for operating an electric fuel pump (102) of an injection system (100), wherein a maximum limit value (48) is provided for a voltage for regulating a pressure of fuel to be delivered, which voltage is applied to the electric fuel pump (102), and a maximum limit value (64) is provided for a current flowing through the electric fuel pump (102), wherein the control unit (106) is designed to measure a current required by the electric fuel pump (102), and wherein the control unit (106) is designed to reduce the maximum limit value (48), which is provided for the voltage applied to the electric fuel pump (102), in the event that the measured value (62) of the current exceeds the provided maximum limit value (64), depending on the measured value (62) of the current. [10] Control device according to claim 9, which has an integrator (54) which is designed to reduce the maximum limit value (48) for the voltage until the measured value (62) of the current has fallen below the permissible maximum limit value (64).

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