DE102015206286B4 - Method and device for operating an injector - Google Patents

Abstract

Method for operating a fuel injector, which has a displaceable closure element for releasing and closing at least one injection opening of the injector and an actuator (22), which is designed to actuate the closure element depending on a predetermined electrical control, depending on a predetermined target Injection mass flow for the injector and / or depending on a predetermined target injection volume flow for the injector and / or dependent on a predetermined desired speed change of the closure element when opening and / or closing the injector and depending on a current fuel pressure in the injector and depending on A reference position for a Hubverlauf of the closure element are determined and determined depending on the determined reference reference coordinates one or more electrical control variables for controlling the actuator (22) and bereitgest Become.

Description

The invention relates to a method and a corresponding device for operating an injector. The invention further relates to a computer program and a computer program product for operating an injector and to a system for operating an internal combustion engine.

Increasingly stringent statutory regulations regarding permissible pollutant emissions of internal combustion engines for motor vehicles make it necessary to achieve improved mixture preparation in the cylinders of internal combustion engines by means of fuel injectors. In current fuel injectors, fuel injection is controlled by means of a nozzle needle which is slidably mounted in the fuel injector and releases or closes an opening cross section or one or a plurality of spray holes of a nozzle assembly of the fuel injector depending on its stroke. A control of the nozzle needle, for example, by means of a piezoelectric actuator, which actuates the nozzle needle mechanically or hydraulically.

For fuel injectors, very high demands are placed on the accuracy and robustness of the injection quantity under all operating conditions and over the entire service life of the fuel injector. A deviation of an actual injection quantity from a desired injection quantity of a fuel injector always has negative effects on combustion with regard to the resulting pollutant emissions and consumption of the internal combustion engine.

Reference coordinates for the control of fuel injectors are nowadays mostly determined via characteristic diagrams for activation duration and activation energies (time setpoints, energy, current and / or voltage setpoints). Thus, certain reference coordinates are rigid with respect to an injection course and do not allow dynamic operating point-dependent specifications of needle strokes.

DE 10 2011 007 393 B3 discloses a method for detecting a nozzle space pressure in an injector, which comprises a closure element for opening and closing an injection opening, at least one actuator directly actuating the closure element, and at least one sensor for measuring a state of the closure element that is dependent on the nozzle space pressure, wherein at least one measured value with the sensor at least one of the state-dependent measured variable is detected and wherein a deviation of the measured value is determined by a predetermined value.

DE 103 17 684 B4 discloses a method for operating an internal combustion engine, wherein a control of at least one injection valve of the internal combustion engine is carried out in accordance with a by the individual behavior of the injection valve used representing flow-to-charge quantity characteristic during operation. For calculating the flow-to-charge amount characteristic, a slope of the characteristic curve for the individual injection valve is detected by changing a charge with which the individual injection valve is driven from a reference charge by a predetermined amount, and a change resulting from the change in charge Lambda value is detected in the internal combustion engine, and the slope of the characteristic curve for the individual injection valve from the change in the charge and the change in the lambda value is calculated. DE 10 2012 109 655 A1 discloses a method for determining the injection rate of a fuel injector. The injection rate is calculated from a pressure in an antechamber, an outside pressure of the nozzle area of the fuel injector, and a density of the fuel. The pressure is calculated using a calculation model for the transport of fuel in the fuel injector from a pressure detected at the inlet area of the fuel injector.

In the US 2014 0346244 A1 a control method for an injection valve for injecting fuel into an internal combustion engine, and an injection system is described. In recurrent injection cycles and as a function of a desired lifting height of a closure element of the injection valve, at least one control signal is generated in each case for driving a drive of the injection valve. The drive is driven by the control signal for lifting the closure element to the desired lifting height and raised the closure element by means of the drive to an actual lifting height. At least one measured variable correlated with the actual lifting height is detected and the actual lifting height is determined as a function of this at least one measured variable. The control signal is generated in at least one of the subsequent injection cycles in response to a deviation of the actual lifting height of the desired lifting height.

In the DE 10 2005 054 239 A1 is an injector for injecting fuel into combustion chambers of internal combustion engines, in particular a piezoactuator-controlled common rail injector described. The injector has a arranged in an injector control means, a nozzle body at the combustion chamber end of which a nozzle outlet is formed and further comprises a nozzle needle which is axially movable or actuated in a longitudinal recess of the nozzle body. At this time, the fuel injection amount and rate become over a detection and control of the Düsennadelhubes closed controlled, the Düsennadelhub is preferably detected by an optical measuring method.

The object underlying the invention is to provide a method and a corresponding device for operating an injector, which enable a precise and / or variable mass flow control of a fluid to be injected by the injector.

The object is solved by the features of the independent claims. Advantageous developments of the invention are characterized in the subclaims.

The invention is characterized according to a first and second aspect by a method and a corresponding device for operating an injector. The injector has a displaceable closure element for releasing and closing at least one injection opening of the injector. Furthermore, the injector has an actuator which is designed to actuate the closure element as a function of a predetermined electrical activation. Depending on a predetermined target injection mass flow for the injector and / or depending on a predetermined target injection volume flow and / or dependent on a predetermined desired speed change of the closure element when opening and / or closing the injector and depending on a current fuel pressure in the injector and Depending on a backpressure of combustion, nominal reference coordinates for a stroke course of the closure element are determined. Furthermore, depending on the determined reference reference coordinates, one or more electrical control variables for controlling the actuator are determined and provided.

This allows a dynamic determination of desired reference coordinates for a stroke course of the closure element. Depending on injector-inherent volume and mass flows, which can be determined as a function of predetermined models, the reference reference coordinates for the stroke profile of the closure element can be determined.

In this case, it is useful that an injection quantity is dependent on an injection duration, an injection pressure, a stroke of the closure element and a geometry of the fuel injector. By presetting the desired injection mass flow for the injector and / or the desired injection volume flow and / or the desired speed change of the closure element when opening and / or closing the injector, it is possible to determine desired reference coordinates for the stroke of the closure element. The change in speed of the closure element is also referred to as the gradient of the closure element.

The desired injection mass flow for the injector and / or the nominal injection volume flow for the injector and / or the desired speed change of the closure element during opening and / or closing of the injector can be set variably. This allows a freely definable injection rate shaping. This allows a fully variable control of the injection mass flow through a continuous adjustment of the stroke of the nozzle needle or a nozzle opening cross-section. Internal operating point-dependent states, such as the temperature of the fuel and an injector-inherent pressure state, can already be taken into account when determining the desired reference coordinates.

Advantageously, thereby complex map structures can be greatly simplified and / or a calibration effort can be significantly reduced. Compared to concepts that use signals from a piezo actuator to identify individual points of a nozzle needle position during an injection event, an improved control of an absolute position of the closure element taking into account a variety of disturbances is possible. The feedback signals from the piezo actuator are subject to a high disturbance variable influence, since the piezo injector is used at the same time as an actuator and sensor. Furthermore, these signal-based approaches do not allow any statement about the dynamic behavior of the closure element, that is, it is not possible to characterize the course of movement of the needle stroke, whereby a generation of absolute position values is not sufficiently possible.

Taking into account the actual fuel pressure in the injector when determining the desired reference coordinates for a stroke of the closure element allows a precise derivation of control variables to an improved control of the injector, so that an improved mixture preparation in the cylinders can be achieved.

The thus corrected fuel pressure is also referred to as inherent injector pressure. The combustion back pressure is the pressure prevailing in the combustion chamber of the cylinder. The combustion pressure is also referred to as the combustion chamber pressure. The combustion pressure can be determined as a function of a given combustion chamber pressure model. This can advantageously contribute to improving the activation of the injector, so that improved mixture preparation in the cylinders can be achieved.

In a further advantageous embodiment according to the first and second aspects of the fuel pressure in the injector is determined depending on a predetermined model for a pressure propagation in the injector. Since the fuel pressure in the injector can not be measured or can not be measured with sufficient accuracy, it is estimated using the given model. This allows a sufficiently accurate provision of this operating size. The injector preferably comprises a nozzle space, which is connected via a fuel line with a high-pressure accumulator. Alternatively, it is possible that the fuel line is connected to an injection pump. The fuel pressure in the injector may be determined depending on a fuel pressure in the fuel line and / or a fuel temperature in the fuel line and / or a cylinder pressure.

In a further advantageous embodiment according to the first and second aspects, the reference reference coordinates for the stroke profile of the closure element are determined depending on a substance property of the fuel in the injector and / or a fuel temperature in the injector. The material property of the fuel preferably comprises a density and / or viscosity of the fuel. Preferably, the material property of the fuel in the injector is determined depending on a fuel pressure in the injector and a fuel temperature in the injector. Considering the substance property of the fuel and / or the fuel temperature in the injector when determining the desired reference coordinates for the stroke of the closure element makes it possible to further improve the derivation of manipulated variables for controlling the injector.

In a further advantageous embodiment according to the first and second aspects, the injector comprises an injection nozzle with a nozzle body in which the closure element is mounted at least partially displaceable, and the desired reference coordinates for the stroke profile of the closure element are determined depending on a predetermined permeable opening cross section of the injection nozzle which forms when opening the injection nozzle between the opening closure element and the nozzle body. The flow-through opening cross-section is preferably fully variable predetermined.

In a further advantageous embodiment according to the first and second aspects, the at least one control variable is determined depending on provided correction values, which are determined depending on a comparison of the determined reference reference coordinates with currently determined and / or detected actual coordinates for the stroke profile of the closure element. This advantageously allows a state control via a feedback circuit.

According to a third aspect, the invention is characterized by a computer program for operating an injector, wherein the computer program is designed to perform the method for operating an injector and / or an advantageous embodiment of the method for operating an injector on a data processing device.

According to a fourth aspect, the invention is characterized by a computer program product comprising executable program code, the program code, when executed by a data processing device, executing the method for operating an injector and / or an advantageous embodiment of the method for operating an injector.

In particular, the computer program comprises a medium which can be read by the data processing device and on which the program code is stored.

According to a fifth aspect, the invention is characterized by a system for operating an internal combustion engine comprising a pre-control module, a characterization module and a state control module. The pilot module is designed to carry out a method for operating an injector and / or an advantageous embodiment of the method for operating an injector. The characterization module comprises at least one predetermined model and is designed to determine predetermined state variables of the injector as a function of predetermined input variables and to provide them for the pilot control module. The state control module is designed to determine correction values dependent on a comparison of the setpoint reference coordinates determined by the pilot control module with actual coordinates for the stroke of the closure element currently determined and / or detected by the characterization module and to provide the correction values for the pilot control module.

In an advantageous embodiment according to the fifth aspect, the characterization module is designed to determine a current fuel injection pressure as a function of the fuel pressure in the injector and a combustion back pressure and / or a fuel mass flow in the injector and / or a fuel mass in the injector and / or to determine a compression modulus depending on a current rail pressure and / or a fuel temperature in a fuel supply line and / or a cylinder pressure. Alternatively or additionally, the characterization module is formed, the current stroke of the closure element and / or a deflection of the actuator and / or a closing and opening speed of the closure element and / or a deflection speed of the Actuator to determine depending on a current current and Spannungsbeaufschlagung the actuator.

Embodiments of the invention are explained below with reference to the schematic drawings.

• 1 ein beispielhaftes Blockdiagramm für ein Programmsystem zum Betreiben einer Brennkraftmaschine,
• 2 eine Schnittansicht eines beispielhaften Kraftstoffinjektors,
• 3 ein beispielhaftes Blockdiagramm für ein Vorsteuer-Programmmodul eines Vorsteuer-Funktionsblocks,
• 4 ein beispielhaftes Ablaufdiagramm des Steuer-Programmmoduls,
• 5 einen beispielhaften, näherungsweisen Verlauf eines Öffnungsquerschnitts des Injektors abhängig von einem Hub eines Verschlusselements,
• 6 einen beispielhaften Verlauf eines Volumenstroms und eines Massenstroms abhängig von dem Hub des Verschlusselements,
• 7 einen beispielhaften Verlauf des Massenstroms abhängig von einem Raildruck,
• 8 einen beispielhaften Verlauf des Massenstroms abhängig von einer hydraulischen Einspritzzeit,
• 9 beispielhafte Referenztrajektorien für den Hub des Verschlusselements und
• 10 einen beispielhaften Verlauf des approximierten Soll-Massenstroms und des Soll-Hubverlaufs des Verschlusselements im Vergleich zu realen Messwerten.

Show it:

• 1 an exemplary block diagram for a program system for operating an internal combustion engine,
• 2 a sectional view of an exemplary fuel injector,
• 3 an exemplary block diagram for a pre-control program module of a pre-control function block,
• 4 an exemplary flow chart of the control program module,
• 5 an exemplary, approximately course of an opening cross-section of the injector depending on a stroke of a closure element,
• 6 an exemplary profile of a volume flow and a mass flow depending on the stroke of the closure element,
• 7 an exemplary course of the mass flow as a function of a rail pressure,
• 8th an exemplary course of the mass flow as a function of a hydraulic injection time,
• 9 exemplary reference trajectories for the stroke of the closure element and
• 10 an exemplary course of the approximated desired mass flow and the desired stroke profile of the closure element in comparison to real measured values.

Elements of the same construction or function are provided across the figures with the same reference numerals.

1 shows an exemplary block diagram for a program system 1 for operating an internal combustion engine, in which a variable, in particular fully variable, specification of a fluid mass flow and / or fluid volume flow for an injector of the internal combustion engine is possible.

The program system 1 includes a characterization function block 5 , a pre-control function block 7 and a state control function block 9 ,

The injector is preferably as a fuel injector 10 designed for an internal combustion engine. Alternatively, the injector may be configured to inject another fluid, such as water, oil, a gas, or another process fluid.

2 shows an example of a fuel injector 10 ,

The fuel injector 10 includes a drive module 12 and an injection module 14 , The drive module 12 and the injection module 14 are for example by means of a clamping nut 30 coupled fluid-tight. The drive module 12 has an injector housing 20 in which an actuator 22 is provided, which is preferably designed as a piezo actuator. An electromagnetic actuator (not shown) is alternatively applicable.

The fuel injector 10 includes a closure element 42 that from the actuator 22 is pressed. The closure element 42 is preferably directly from the actuator 22 actuated.

The closure element 42 can be materially integral or integrally formed. The closure element 42 is in a recess 44 an injection body 40 slidably and partially stored.

In the present case is the closure element 42 an outwardly opening nozzle needle; an inwardly opening nozzle needle is alternatively applicable (not shown). Furthermore, the closure element 42 a register or vario injection needle (not shown).

The in 1 Characterization function block shown 5 of the program system 1 includes, for example, models for estimating state variables of the injector that are not or only very inaccurately measurable, for example a fuel temperature in the injector and / or a fuel pressure in the injector and / or a current course of the stroke H the closure element.

The pre-control function block 7 is configured to carry out a method for operating an injector, wherein the reference reference coordinates for the stroke H of the closure element are determined and at least one electrical control variable for controlling the actuator 22 the injector is provided.

Preferably, the electrical control variable comprises a current with which the actuator 22 is charged. The pilot control function block 7 includes, for example, an adaptive pilot control structure.

The state control function block 9 For example, this is formed by the pre-tax function block 7 determined reference reference coordinates for the stroke H of the closure element with associated internal state coordinates and correction values for the at least one control variable for controlling the actuator 22 provide. The associated internal state coordinates, in particular a current stroke of the closure element and / or a deflection of the actuator 22 and / or a closing and opening speed and a deflection speed of the actuator 22 for example, from the characterization function block 5 provided.

The pre-control function block 7 preferably comprises a control program module 100 , which is designed, when executed on a data processing unit, for example on a computer unit of a motor controller, to carry out the method for operating an injector.

The control program module 100 from 1 is formed, depending on a predetermined target injection mass flow for the injector and / or dependent on a desired injection volume flow for the injector and / or depending on a predetermined desired speed change of the closure element when opening and / or closing the injector, the reference reference coordinates for the hub H determine the closure element and depending on the determined reference reference coordinates, the at least one electrical control variable for controlling the actuator 22 to determine and make available.

Preferably, for the control program module 100 of the pilot control function block 7 one or more further input variables provided.

The further input variables for the first program module of the pre-control function block 7 and for example for the state control function block 9 are specified for example via an application interface. The input variables are provided, for example, by the motor controller.

The further input variables include, for example, one or more desired specifications, for example a desired injection mass and / or a desired injection angle and / or a nominal injection pressure.

Alternatively or additionally, the further input variables may comprise, for example, one or more metrologically recorded state variables, for example a rotational speed of the internal combustion engine and / or a rail pressure and / or a combustion chamber pressure and / or a fuel temperature in a return line.

The further input variables include, for example, one or more estimated state variables which are estimated by means of predefined models, since these can not be measured or only with very high technical outlay. Such estimated input variables are, for example, a current stroke profile of the closure element, a fuel temperature in the injector and / or an inherent injector pressure.

Determining the reference reference coordinates for the hub H Depending on the metrologically detected and / or estimated input variables, the closure element makes it possible for current, operating point-dependent states of the internal combustion engine and / or of the injector to be taken into account when determining the desired reference coordinates.

The estimated inputs are, for example, from the characterization function block 5 provided. This includes the characterization function block 5 for example, a pressure characterization program module 101 and an optional stroke characterization program module 102 and optional temperature characterization program module 103 ,

The pressure characterization program module 101 For example, it is configured to determine a current fuel injection pressure as a function of the fuel pressure in the injector and a combustion back pressure and / or a fuel mass flow in the injector and / or a fuel mass in the injector and / or to determine a compression modulus depending on a current rail pressure and / or a fuel temperature in a fuel supply line and / or a cylinder pressure. Preferably, to determine the actual fuel injection pressure, the fuel pressure in the injector is corrected with the combustion back pressure.

One possible method for determining the inherent injector pressure is in DE 10 2011 007 393 B3 disclosed.

The stroke characterization program module 102 is formed, for example, a current stroke of the closure element and / or a deflection of the actuator 22 and / or a closing and opening speed and / or a deflection speed of the actuator 22 to determine depending on a current current and voltage of the actuator 22 ,

The temperature characterization program module 103 For example, it is designed to determine a fuel temperature in the injector.

The fuel temperature in the injector is preferably based on a predetermined determined thermal resistance model. The fuel temperature in the injector is determined, for example, as a function of the fuel pressure in the injector and / or the fuel temperature in the injector and / or a coolant temperature in the internal combustion engine and / or an oil temperature in the internal combustion engine and / or a drive frequency of the injector.

3 shows an example of a block diagram for the control program module 100 of the pilot control function block 7 ,

The control program module 100 has for example two functional units 110 . 120 on.

A first functional unit 110 is formed, for example, depending on at least a predetermined desired injection mass flow for the injector and / or a desired injection volume flow for the injector and / or dependent on a desired speed change of the closure element when opening and / or closing the injector reference reference coordinates for the stroke H to determine the closure element.

In particular, the first functional unit 110 designed to determine and provide a reference movement sequence, also called reference trajectory, for the closure element.

The second functional unit 120 is formed, depending on the determined reference reference coordinates one or more electrical control variables for controlling the actuator 22 to investigate.

For example, depending on the determined reference trajectories, drive quantities in the form of current and / or charge polygon data for the actuator 22 determined.

In injectors having an electrically driven actuator, a transformation of the electrical control variables into mechanical manipulated variables is usually carried out by means of a predetermined electromechanical system model for the injector.

In the second functional unit 120 By means of an inverse consideration of the electromechanical system model (inverted model), a mechanical stroke is transformed into an electrical energy and a hydraulic opening and closing time is transformed into an electrical current application time.

4 shows an exemplary flowchart of the control program module 100 ,

The control program module 100 gets in one step S1 started.

In one step S2 For example, input variables provided by the engine control unit are read in. The provided input variables include, for example, one or more desired specifications, for example a desired injection mass and / or a desired injection angle and / or a nominal injection pressure. The provided input variables include, for example, one or more metrologically detected state variables, for example a rotational speed of the internal combustion engine and / or a rail pressure. The provided input variables include, for example, one or more estimated state variables, for example a fuel temperature in the injector and / or a fuel pressure in the injector.

The injection quantity is correlated with an injection duration, which in turn is dependent on an injection pressure, a stroke H the closure element and a geometry of the fuel injector 10 ,

In one step S3 Therefore, an opening cross section of the injector depends on the stroke H the closure element determined. In the case of an injector with an outwardly opening nozzle, the opening cross section can be approximately calculated, for example, by means of a lateral surface of a truncated cone.

The lateral surface can, for example, according to Eq. 1 to be determined: $$M=\left(\frac{1}{2}{D}_{NS}+\left(\frac{1}{2}{D}_{NS}-r\right)\right)\cdot \pi \cdot m$$

Here, M is the lateral surface, D _NS the diameter of the base of the truncated cone, r the radius of the top surface and m is a length of a surface line.

5 shows an example of an idealized course of the opening cross-section A depending on the hub H the closure element.

In the in 4 shown flow diagram for the control program module 100 gets in one step S5 depending on the determined opening cross section, a volume flow Q determined. $$Q=A\cdot \nu$$

wird beispielsweise gemäß Gl. 3 ermittelt.

The mass flow

For example, according to Eq. 3 determined.

der Massenstrom und ρ die Dichte. Die Dichte kann ermittelt werden abhängig von dem Raildruck P_rail und der Temperatur T des Kraftstoffes. Q is the volume flow, A the cross-sectional area and ν the mean flow velocity,

the mass flow and ρ the density. The density may be determined depending on the rail pressure P _rail and the temperature T of the fuel.

abhängig von dem Hub H des Verschlusselements bei einem konstanten Druck von 20 MPa. 6 shows an example of the course of the volume flow Q and the mass flow

depending on the hub H the closure element at a constant pressure of 20 MPa.

abhängig von dem Raildruck ermittelt.In the in 4 shown flow diagram for the control program module 100 gets in one step S7 based on the continuity equation for incompressible fluids and the regularity Bernulli's for constant densities of mass flow

determined depending on the rail pressure.

The course of the mass m depending on the rail pressure is exemplary in 7 shown for different needle strokes.

und die Geschwindigkeitsänderung des Verschlusselements beim Öffnen und/oder Schließen des Injektors

In one step S9 becomes the injection mass m depending on a hydraulic injection time thyI determined with the aid of Eq. 4 and taking into account nominal values for the mass flow

and the speed change of the shutter member when opening and / or closing the injector

The course of the mass m depending on the hydraulic injection time thyI is exemplary in 8th shown for different pressures in the injector.

In one step S11 each becomes a reference trajectory for the hub H the closure element determined. Taking into account the respective desired mass flows and the desired gradient, it is possible to set the reference reference coordinates for the stroke H of the shutter element (time and amplitude). Target injection profiles are approximated, for example, via parabolas (ballistic injection forms) and / or trapezoids (partial strokes) and / or sigmoidal and / or s-shaped profiles. By a concatenation of the approximation forms quasi arbitrary course forms can be given, for example boat course shapes.

In 9 are exemplary 3 reference trajectories R1 . R2 . R3 shown. The dashed line represents the stroke H of the shutter member and the solid line represents the injection time of the shutter member. The injected fuel mass is the same in all three cases. The courses differ in each case in the amplitudes.

10 shows an example of a course of the approximated target injection mass flow and the desired stroke profile of the closure element in comparison to real measured values.

In one step S13 the determined reference reference coordinates are transferred into electrical coordinates depending on internal state variables. This step can be carried out, for example, in a subroutine.

The steps S2 to S13 For example, are repeatedly executed repeatedly during an operating time of the injector.

After completion of the operating time of the injector, the program is in one step S15 completed.

LIST OF REFERENCE NUMBERS

1

program system

5

Characterization function block

7

Pre-function block

9

State control function block

10

fuel injector

12

drive module

14

Injection Module

20

injector

22

actuator

30

locknut

40

Injector body

42

closure element

44

recess

100

Control program module

101

Pressure characterization program module

102

Hubcharakterisierungs program module

103

Temperature characterization program module

110

first functional unit

120

second functional unit

A

Opening cross-section

H

stroke

m

Injection mass

m

Injection mass flow

Q

flow

R1, R2, R3

reference trajectory

S1 ... S15

program steps

thyI

Hydraulic injection time

Claims (10)

A method of operating a fuel injector comprising a slidable closure member for releasing and closing at least one injection port of the injector and an actuator (22) configured to actuate the closure member in response to a predetermined electrical drive, wherein - Depending on a predetermined target injection mass flow for the injector and / or depending on a predetermined target injection volume flow for the injector and / or dependent on a predetermined desired speed change of the closure element when opening and / or closing the injector and depending on a current fuel pressure be determined in the injector and depending on a combustion back pressure setpoint reference coordinates for a stroke course of the closure element and - Depending on the determined reference reference coordinates one or more electrical control variables for controlling the actuator (22) are determined and provided. Method according to Claim 1 in which the fuel pressure in the injector is determined depending on a given model for pressure propagation in the injector. Method according to one of Claims 1 to 2 in which the reference reference coordinates for the stroke profile of the closure element are determined depending on a substance property of the fuel in the injector and / or a fuel temperature in the injector. Method according to one of Claims 1 to 3 in which the injector comprises an injection nozzle with a nozzle body, in which the closure element is mounted at least partially displaceable, and the desired reference coordinates for the stroke profile of the closure element are determined depending on a predetermined permeable opening cross-section of the injection nozzle, which opens when opening the injector between forms the opening closure element and the nozzle body. Method according to one of Claims 1 to 4 in which the at least one control variable is determined as a function of provided correction values which are determined as a function of a comparison of the determined reference reference coordinates with currently determined and / or detected actual coordinates for the stroke profile of the closure element. A device for operating a fuel injector, which has a closing element for injecting a fluid displaceable in the injector and which has an actuator (22) which is designed to actuate the closure element in dependence on a predetermined electrical activation, the device being designed to Method according to one of Claims 1 to 5 perform. A computer program for operating a fuel injector, wherein the computer program is designed, a method according to one of Claims 1 to 5 when executed on a data processing device. Computer program product comprising executable program code, wherein the program code when executed by a data processing device, the method according to one of Claims 1 to 5 performs. System for operating an internal combustion engine comprising a pre-control module (7), a characterization module (5) and a state control module (9), wherein - the pre-control module (7) is formed a method according to one of Claims 1 to 5 The characterization module (5) comprises at least one predefined model and is designed to determine predefined state variables of the fuel injector and to provide them to the precontrol module (7) and - the state control module (9) is designed to determine correction values depending on one Comparison of the reference reference coordinates determined by the pre-control module (7) with actual coordinates for the stroke profile of the closure element and the correction values for the pre-control module (7) currently determined and / or detected by the characterization module (5). System after Claim 9 wherein the characterization module (5) is configured to determine a current fuel injection pressure depending on the fuel pressure in the fuel injector and a combustion backpressure and / or fuel mass flow in the fuel injector and / or a fuel mass in the fuel injector and / or a compression modulus to be determined depending on a current one Rail pressure and / or a fuel temperature in a fuel supply line and / or a cylinder pressure and / or - the current stroke of the closure element and / or a deflection of the actuator (22) and / or a closing and opening speed of the Closing element and / or a deflection speed of the actuator (22) to determine depending on a current current and voltage of the actuator (22).

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