CONTROL DEVICE AND METHOD FOR CONTROLLING AN INJECTOR - Patent application

Abstract

A control device is provided that reduces deviations in fuel quantity between different injectors / different injections during ballistic operation. [Solution] The control device includes a control parameter calculation unit, an injection pulse calculation unit, an injection pulse compensation unit, and a memory, wherein the control parameter calculation unit determines a target closing time based on an amount of fuel to be injected into the internal combustion engine, and if the target closing time is greater than a maximum closing time of the fuel injector in ballistic operation, the injection pulse calculation unit calculates a pulse duration for the injector based on a characteristic curve of the fuel injector and outputs the pulse duration to the fuel injector, and if the target closing time is less than or equal to the maximum closing time, the injection pulse compensation unit receives a set of parameters from the memory, calculates a pulse duration for the fuel injector based on the set of parameters, and outputs the pulse duration to the fuel injector.

Description

[Technical field]

[0001] The subject matter particularly relates to a control device and method for controlling a fuel injector mounted on an internal combustion engine, as well as a method for adapting the pulse duration of a fuel injector and a learning unit for carrying out said method. [Background technology]

[0002] To comply with current stringent emission regulations, it is necessary to prevent the fuel injected into the cylinder of an internal combustion engine from reaching the cylinder wall. To achieve this goal, splitting the amount of fuel to be injected into multiple small injections is a promising approach. However, to accurately meter small amounts of fuel, the so-called ballistic operating range of the fuel injector must be precisely controlled. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent Application No. 2018 / 0209373 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent document 1 describes a control device for controlling fuel injection in an internal combustion engine, in which the closing time of a fuel injector is determined based on the drive voltage of the fuel injector, and the period between a specified reference time and the closing time of the fuel injector is taken into account in a number of characteristic curves for each injection pulse width in the internal combustion engine and for each fuel injector. [Means for solving the problem]

[0005] The subject matter described herein addresses the technical objective of improving the accuracy of small amounts of fuel to be injected into an internal combustion engine with reduced calibration effort while maintaining improved accuracy over the life of the engine. This objective is achieved by the subject matter of the accompanying claims.

[0006] According to the claimed subject matter, a control device is proposed for controlling a fuel injector mounted on an internal combustion engine. The control unit may preferably include an engine control unit (ECU) and a drive circuit for driving the fuel injector. The control device comprises a control parameter calculation unit, an injection pulse calculation unit, an injection pulse compensation unit and at least one memory. The at least one memory may be capable of storing data permanently and / or non-permanently. It may also be envisaged that the at least one memory comprises a non-volatile memory and / or a volatile memory. Preferably, the at least one memory may comprise a read-only memory (ROM) and a random access memory (RAM).

[0007] The fuel injector may preferably be a solenoid injector capable of directly injecting fuel into a combustion chamber of an internal combustion engine. The fuel injector may be electrically connected to a control device and may include a fuel supply unit disposed at an upper end of the fuel injector, a fuel injection port and a valve seat disposed at a lower end of the fuel injector, and a valve body disposed between the fuel supply source and the valve seat.

[0008] A fuel passage may be provided within the fuel injector for allowing fuel to flow from a fuel supply unit to a fuel injection hole. An injector coil may be disposed between the stationary core and a housing of the fuel injector. The stationary core, the injector coil, and the housing may form an electromagnet.

[0009] In a valve-closed state in which the injector coil is not energized, the valve disc may be biased against the valve seat by the spring force of at least one spring that may bias the valve disc in a valve-closing direction (towards the bottom end of the fuel injector). To energize the injector coil, an injection pulse may be output from the controller, which may apply a drive current / drive voltage to the injection coil.

[0010] When the injection coil is energized, the valve body is displaced away from the valve seat in a valve opening direction (toward the top end of the fuel injector), thereby opening the fuel passage and allowing fuel to be injected into the internal combustion engine through the fuel injection hole.

[0011] A detailed description of the components and functions of a fuel injector that can be controlled in accordance with the subject matter described herein can be found below in connection with FIG.

[0012] The control parameter calculation unit of the control device determines a target closing time for the fuel injector based on the amount of fuel to be injected into the internal combustion engine. The term "closing time for / of a fuel injector" is to be understood as the period between a reference time and the time when the fuel injector is fully closed, i.e. when the valve disc of the fuel injector is fully seated on its valve seat. The reference time may for example be the rising edge of an injection pulse signal output by the control unit to open the fuel injector. It may also be envisaged to define as the reference time the time when the valve disc is displaced from its valve seat. Any other suitable time corresponding to the opening of the fuel injector may be selected as the reference time. It has been found that the closing time is linearly correlated with the amount of fuel injected, regardless of the operating range of the fuel injector.

[0013] The amount of fuel to be injected may depend on the operating conditions of the internal combustion engine, such as engine load, engine speed, air-fuel ratio, fuel pressure, etc. These operating conditions may be determined by a number of sensors that may be connected to the control device, enabling the control parameter calculation unit to determine the required amount of fuel for a given operating condition.

[0014] If the determined target closing time is greater than the maximum closing time of the fuel injector in ballistic operation, the injection pulse calculation unit calculates a pulse duration for the injector based on a characteristic curve of the fuel injector and outputs the calculated pulse duration to the fuel injector for injecting a quantity of fuel into the internal combustion engine.

[0015] "Pulse duration of / for a fuel injector" may be the duration / width of a control pulse (injection pulse) that can control the amount of fuel to be injected. "Ballistic operation of a fuel injector" shall be understood as an operation in which the injection pulse output to the fuel injector is stopped before the valve disc of the fuel injector achieves its full lift.

[0016] The maximum closing time of the fuel injector in ballistic operation can be correlated with the pulse duration that brings the valve body closer to its full lift. This means that the injector is operated at full lift of the valve body if the determined target closing time is greater than the maximum closing time of the injector in ballistic operation. In this case, the pulse duration required to deliver the fuel quantity to be injected into the internal combustion engine is determined by the injection pulse calculation unit from a characteristic curve of the fuel injector. The characteristic curve can represent a relationship between the pulse duration of the fuel injector and the associated fuel quantity delivered by the injector. The characteristic curve can be given to a specific type of fuel injector that is to be installed in the internal combustion engine and may be permanently stored in at least one memory. However, the characteristic curve of the fuel injector only shows a defined linear relationship between the pulse duration and the injected fuel quantity when the fuel injector is operated at full lift of the valve body.

[0017] Therefore, if the determined target closing time is less than or equal to the maximum closing time in ballistic operation, the injection pulse compensation unit receives a set of parameters from at least one memory and calculates a pulse duration for the fuel injector based on the determined target closing time and the received set of parameters.

[0018] According to a preferred example, the set of parameters may include a slope and an intercept of a first correlation between a pulse duration and a closing time of the fuel injector.The set of parameters may be stored in at least one memory.

[0019] In other words, when the fuel injectors are operated in ballistic operation, the pulse duration for injecting a required amount of fuel is calculated by the injection pulse compensation unit based on the determined target closing time, which is linearly related to the amount of fuel to be injected, and the slope and intercept of a first correlation representing the relationship between the pulse duration and the closing time of the respective fuel injector, and then the injection pulse compensation unit outputs the calculated pulse duration to the fuel injector for injecting the amount of fuel into the internal combustion engine.

[0020] By calculating the pulse duration as described above, deviations in the injected fuel quantity between different injectors in ballistic operation and between different injections of a single fuel injector can be avoided without increasing the calibration effort.

[0021] According to one example, the control parameter calculation unit determines the target closing times for the fuel injectors based on a second correlation between the closing times and the fuel quantities of the plurality of fuel injectors, For example, the second correlation may be pre-determined at a test bench for all fuel injectors installed in the internal combustion engine and may be persistently stored in the at least one memory.

[0022] According to an example, the control unit may further comprise an injector closing time calculation unit and an injection pulse learning unit, where in a learning mode of the internal combustion engine, the injection pulse learning unit may increase the pulse duration of the fuel injector stepwise, and the injector closing time calculation unit may determine a closing time for each pulse duration and may send the determined closing time back to the injection pulse learning unit. The injection pulse learning unit may then receive the determined closing time for each pulse duration from the injector closing time calculation unit and may determine a first correlation between the pulse duration and the closing time of the fuel injector. The injector closing time calculation unit may be configured to perform mathematical calculations on the drive signal (drive current, drive voltage) of the fuel injector, such as signal filtering and signal derivation.

[0023] According to one example, the injection pulse learning unit can calculate a slope and an intercept of a first correlation between the pulse duration and the closing time of the fuel injector for each pulse duration and can store the calculated slope and intercept in at least one memory. Since the first correlation may not exhibit a linear behavior, the first correlation is preferably approximated by calculating the slope and intercept of the first correlation for subsequent pulse durations. Preferably, the calculated slope and intercept at each pulse duration may be non-persistently stored in the memory. This means that the learning procedure can be repeated periodically to constantly adapt the first correlation to the fuel injector conditions.

[0024] According to an example, the injection pulse learning unit may determine the closing time for which the calculated slope is less than or equal to a predefined slope value as the maximum closing time of the fuel injector in ballistic operation and store the determined maximum closing time in at least one memory. In other words, if the closing time is determined over a pulse duration for which the calculated slope a0 is less than or equal to a predefined slope value, said closing time may be determined as the maximum closing time of the fuel injector in ballistic operation. Since the first correlation may show a significant decrease in slope during the transition from ballistic operation to full stroke operation, the end of the ballistic operation range may be reliably determined by setting the predefined slope value as a threshold. This may limit the calculation effort of the control unit as well as the time required for the learning mode. For example, the predefined slope value may be predefined on a test bench and may be permanently stored in at least one memory.

[0025] According to one example, the injection pulse learning unit may stop the learning mode of the internal combustion engine when the maximum closing time of the fuel injector in ballistic operation is determined, in this way the learning mode takes only a short time and does not affect the operating comfort, since only a limited number of relevant slopes and intercepts are calculated.

[0026] According to one example, the injection pulse learn unit may initiate the learn mode when the internal combustion engine is operated in a predefined operating mode. For example, the learning mode may be initiated after each start of the combustion engine, when the engine is at idle. During this time, for example, the control unit may prevent the engine from absorbing load until the first correlation and its slope and intercept have been determined. This means that the first correlation is constantly adjusted during the operating time of the engine, so that aging effects of the fuel injectors and environmental conditions that affect the opening and closing behavior of the fuel injectors may be permanently taken into account.

[0027] According to one example, the injector closing time calculation unit can determine the closing time of the fuel injector based on the drive voltage curve of the fuel injector. When the injection pulse is turned off to close the fuel injector, a reverse drive voltage can be applied to the injector coil and the current supply to the injector coil can be cut off. Since there is no magnetic attraction force, the valve body can be pushed back to a closed position, which can be biased against the valve seat by the load of at least one spring.

[0028] When the valve disc strikes the valve seat, the slope of the drive voltage changes and an inflection point may be created. This inflection point can be used to determine the time when the valve is completely closed. For example, by forming the second derivative of the control voltage curve, the inflection point can be precisely determined as a maximum or minimum.

[0029] The subject matter disclosed herein further includes an internal combustion engine including at least one fuel injector and the aforementioned control system.

[0030] Furthermore, a method for controlling a fuel injector mounted on an internal combustion engine is claimed. Each configuration of the control device as claimed is also intended to be encompassed by the method, which may be claimed by itself and / or by a computer program product claim.

[0031] Further claimed is a method for adapting a pulse duration of a fuel injector mounted on an internal combustion engine by an injection pulse learning unit in a learn mode of the engine, the method comprising the steps of: increasing the pulse duration of the fuel injector stepwise, detecting a closing time for each pulse duration, calculating a slope and an intercept between the pulse duration and the closing time of the fuel injector for each pulse duration, determining as a maximum closing time of the fuel injector in ballistic operation a closing time for which the calculated slope is less than or equal to a predetermined slope value and / or a closing time for which the calculated slope has a negative slope value, stopping the learn mode after determining the maximum closing time of the fuel injector in ballistic operation, and storing the calculated slope and intercept and the maximum closing time of the fuel injector in ballistic operation as a set of parameters in at least one memory.

[0032] The method for adapting a fuel injector pulse duration is intended to be carried out by a computer program product storable in a memory and / or by an injection pulse learning unit for a controller. Effect of the Invention

[0033] In summary, the disclosed subject matter allows to significantly reduce the deviation of the fuel quantity between different injectors / different injections in ballistic operation. This can be achieved by calculating the pulse duration of the individual fuel injectors based on a general linear relationship (second correlation) between the closing time and the injected fuel quantity Q, which can be adapted to the individual behavior of the respective fuel injector via a first correlation between the pulse duration and the closing time for each fuel injector. The described calculation requires little calibration effort and ensures a continuous adjustment of the calculated pulse duration during the operating time of the engine, so that the aging effects of the fuel injectors and the environmental conditions affecting the opening and closing behavior of the fuel injectors can be permanently taken into account. [Brief description of the drawings]

[0034] The claimed subject matter will now be further described on the basis of at least one preferred embodiment with reference to the accompanying drawings. [Figure 1] 1 illustrates a schematic diagram of an example of a fuel injection system for an internal combustion engine. [Diagram 2] 1 shows a cross-sectional view of an exemplary fuel injector connected to a control system including a drive circuit and an engine control unit (ECU). [Diagram 3] Figure 3 shows, in schematic form, an injection pulse for operating the fuel injector shown in Figure 2 in a fully open condition, b shows the associated drive voltage supplied to the fuel injector, c shows the associated drive current supplied to the fuel injector, and d shows the resulting valve displacement. [Figure 4] Figure 3 shows, in schematic form, an injection pulse for operating the fuel injector shown in Figure 2 under ballistic conditions, b shows, in schematic form, the associated drive voltage supplied to the fuel injector, c shows, in schematic form, the associated drive current supplied to the fuel injector, and d shows, in schematic form, the resulting valve displacement. [Diagram 5] 3 shows an example of a hardware configuration of the control device shown in FIGS. 1 and 2. [Figure 6] 3 is a schematic diagram showing a functional configuration of the control device shown in FIG. 1 and FIG. 2 according to a preferred embodiment of the subject matter disclosed in this specification; [Figure 7] 1A and 1B show schematic diagrams of the relationship between pulse duration and injection volume for different fuel injectors not controlled in accordance with the subject matter disclosed herein, and FIG. [Figure 8] a shows an example of a first correlation between pulse duration and closing time determined for any fuel injector, b shows the slope of the exemplary first correlation shown in Fig. 8a determined per pulse duration, and c shows the intercept of the exemplary first correlation shown in Fig. 8a determined per pulse duration. [Figure 9]a shows an exemplary second correlation that can determine a target closing time for a fuel injector based on the amount of fuel to be injected into an internal combustion engine, b shows the target closing time tEOI_tar and the corresponding slope a0, and c shows the target closing time tEOI_tar and the corresponding intercept b0. [Figure 10] 1 shows a flow chart illustrating a preferred example of the method according to the subject matter disclosed herein. [Figure 11] 1 shows a flow chart illustrating a further preferred example of the method according to the subject matter disclosed herein. [Figure 12] 4 illustrates generally the relationship between pulse duration and injection volume for a fuel injector controlled in accordance with the subject matter disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] 1 shows diagrammatically an example of a fuel injection system for an internal combustion engine comprising a fuel pump 106, a fuel rail 105 having a pressure sensor 102, four fuel injectors 101, and a controller 150. The number of fuel injectors is not limited to four and may range, for example, from 1 to 12.

[0036] In the illustrated example, each cylinder 108 of the internal combustion engine (not shown) is provided with one fuel injector 101 for injecting fuel directly into the combustion chamber 107 of the cylinder 108. It may also be possible to provide multiple injectors for each cylinder. The fuel to be injected may be pressurized by a fuel pump 106 and delivered to the fuel injector 101 via a fuel line 105. The fuel pressure may vary depending on the balance between the flow rate of fuel discharged by the fuel pump 106 and the injection amount of fuel injected by the fuel injector 101 into the combustion chamber 107. However, based on information from the pressure sensor 102, the control device 150 may control the amount of fuel discharged from the fuel pump 106 so that the pressure in the fuel line 105 becomes a predetermined pressure.

[0037] Fuel injection of each fuel injector 101 may be controlled by the width (pulse duration) of an injection pulse sent from an engine control unit (ECU) 109 to a drive circuit 127. The drive circuit 127 may calculate a drive current curve based on the injection pulse received from the ECU 109. The calculated drive current curve may then be provided to each fuel injector 101. The drive circuit 127 may be an integral part of the ECU 109 or may be a separate device. The drive circuit 127 and the ECU 109 may be included in a control device 150.

[0038] FIG. 2 shows a cross-sectional view of an exemplary fuel injector connected to a controller 150 already shown in FIG.

[0039] The illustrated fuel injector 101 includes a fuel supply unit 212 arranged at an upper end of the fuel injector 101, a fuel injection hole 215 and a valve seat 202 arranged at a lower end of the fuel injector 101, and a valve body 201 having an intermediate member 214 and a movable iron core 206 arranged between the fuel supply unit 212 and the valve seat 202.

[0040] A fuel passage is provided within the fuel injector 101 to allow fuel to flow along a central axis 200a of the fuel injector 101 from a fuel supply unit 212 to a fuel injection hole 215. An injector coil 208 is disposed between a fixed core (stator) 207 and a housing 209 of the fuel injector 101. The fixed core 207, the injector coil 208 and the housing 209 form an electromagnet.

[0041] In a valve closed state in which the injector coil 208 is not energized, the valve body 201 is urged toward the inside of the valve seat 202 by the spring forces of the first spring 210 and the second spring 216 which urge the valve body 201 in the valve closing direction (toward the lower end of the fuel injector 101). The spring forces of the first spring 210 and the second spring 216 act against the spring force of the third spring 217 which urges the movable core 206 in the valve opening direction (toward the upper end of the fuel injector 101) so as to abut against the intermediate member 214. Because the spring force of the second spring 216 is greater than the spring force of the third spring 217, a gap 250 is formed between the valve body 201 and the movable core 206.

[0042] The drive circuit 127 and the ECU 109 are connected to the fuel injector 101. The ECU 109 can receive a number of sensor signals indicative of the operating state of the internal combustion engine (not shown) from various kinds of sensors, such as a pressure sensor 102 attached to a fuel pipe upstream of the fuel injector 101 (see FIG. 1), and can calculate a required fuel quantity Q according to the operating state of the internal combustion engine, and can calculate a pulse duration and an injection timing of the fuel injector 101 based on the calculated fuel quantity Q. The injection pulse output from the ECU 109 may be input to the drive circuit 127 via a signal line 223.

[0043] The drive circuit 127 may include circuitry for receiving injection pulses from the ECU 109 and energizing the injector coil 208 of the fuel injector 101 with a drive current / drive voltage to perform fuel injection. The ECU 109 may communicate / receive with the drive circuit 127 via communication line 222 and may switch the drive current generated by the drive circuit 127 depending on the fuel pressure and operating conditions of the internal combustion engine.

[0044] When the ejection coil 208 is energized, a magnetic driving force can be generated by an electromagnet including a solid core 207, a coil 208, and a housing 209. This magnetic driving force can cause magnetic flux to circulate in a magnetic path passing through the coil 208, the fixed core 207, the movable core 206, the housing 209, and the movable core 206. As a result, a magnetic attraction force acts between the movable core 206 and the fixed core 207, and the movable core 206 and the intermediate member 214 are displaced toward the fixed core 207.

[0045] The movable core 206 can be displaced until the transmission surface 219 of the valve body 201 and the transmission surface 218 of the movable core 206 come into contact with each other. During this time, the valve body 201 can still be in contact with the valve seat 202. Only when the movable core 206 is displaced by a gap 250 generated between the valve body 201 and the movable core 206 and the transmission surface 219 of the valve body 201 collides with the transmission surface 218 of the movable core 206, can the valve body 201 be separated from the valve seat 202 by the kinetic energy of the movable core 206. This allows the fuel passage to be opened and fuel to be injected from the fuel injection hole 215 into the internal combustion engine.

[0046] When the movable core 206 comes into contact with the fixed core 207 during displacement, the valve element 201 may be displaced in the valve opening direction, and the movable core 206 may be displaced in the valve closing direction. This means that when the fixed core 207 and the movable core 206 collide, the valve element 201 and the movable core 206 may separate, and the movable core 206 may be displaced in the valve closing direction and come to rest at the target lift position (stable open valve state).

[0047] Thereafter, when the power supply to the injection coil 208 is turned off to release the magnetic attraction force, the movable iron core 206 is pushed back by the spring force of the first spring 210 and the force due to the fuel pressure, and the valve body 201 may assume a closed position in which it is urged toward the valve seat 202. The spring force of the first spring 210 acting on the valve body 201 can be transmitted to the movable iron core 206 via a transmission surface 219 on the valve body 201 side and a transmission surface 218 on the movable iron core 206 side.

[0048] After the required valve closing time, the valve disc 201 impacts the valve seat 202 and the transmission surface 218 of the armature 206 may be separated from the transmission surface 219 of the valve disc 201 .

[0049] During closing of the fuel injector 101, the third spring 217 may go from extension to compression and the direction of movement of the armature 206 may be reversed when the valve disc 201 strikes the valve seat 202. This may change the acceleration of the armature 206 and therefore the inductance of the injector core 208. This effect may be used to detect the closing time of the fuel injector, as described below in connection with Figures 3a-3d.

[0050] Figures 3a-3d show diagrammatically the injection pulse ti for operating the fuel injector 101 shown in Figure 2 in a fully open condition (Figure 3a), the associated drive voltages 304, 305 (Figure 3b) and associated drive currents 308, 331, 332 (Figure 3c) supplied to the fuel injector 101, and the resulting displacement curves of the valve body 201 (dotted displacement curve 334 in Figure 3d) and the armature core 206 (solid displacement curve 335 in Figure 3d).

[0051] In Figures 3a-c it can be seen that when an injection pulse ti is sent to the fuel injector 101 at time ts, a high voltage 304 is applied to it, starting to power the injection coil 208. The high voltage may be a voltage having a value of 50V or more. As a result, the armature 206 is displaced in the valve opening direction (see solid displacement curve 335 in Figure 3d). The armature 206 abuts against the valve body 201 after passing the gap 250 at delay time t0. Both elements are then displaced until the full lift of the valve body 201 is reached (see displacement curves 334, 335 in Figure 3d).

[0052] As shown in the current curve 308, after the application of the high voltage 304 causes the current value to rise sharply to a predetermined peak current value Ip, in order to achieve a fully open state of the fuel injector 101, the application of the high voltage 304 is stopped / reduced at time t31, and the current value is reduced to a first holding current value Ih1 according to a first current profile 331. Then, a pulse-width modulated low voltage 305 is applied to the fuel injector 101 to obtain the first holding current value Ih1. The low voltage may be a battery voltage having a value in the range of 12V to 14V. In a next step, the current is reduced to a second holding current value Ih2 according to a second current profile 332 by decreasing the pulse width of the low voltage 305 (see FIG. 3b and FIG. 3c). By passing the holding currents Ih1 and Ih2 through the fuel injector 101, a stable open state can be maintained.

[0053] Subsequently, when the injection pulse ti is turned off at time te, the drive circuit 127 applies a reverse drive voltage to the injector coil 208 (see FIG. 3b). As a result, the current supply to the injector coil 208 is cut off (see FIG. 3c), and the magnetic flux generated in the magnetic circuit is removed, so that the magnetic attraction force is also removed. As a result, the movable iron core 206, which has lost the magnetic attraction force, can be pushed back to the closed position where the valve body 201 can collide with the valve seat 202 by the load of the first spring 210 and the force due to the fuel pressure (see FIG. 3d).

[0054] Time t EOI At time t , the valves 201, 202 are completely closed, and the valve disc 201 is again fully seated on the valve seat 202. When the valve disc 201 collides with the valve seat 202, the transmission surface 218 of the movable core 206 separates from the transmission surface 219 of the valve disc 201, and continues to move in the valve closing direction. At this time, the slope of the drive voltage changes, and an inflection point 330 (see FIG. 3b) occurs. This inflection point 330 occurs at time t EOI can be used to determine

[0055] That is, when the fuel injector 101 closes, the drive current flowing through the injector coil 208 is cut off and a back electromotive force is applied to the injector coil 208. After the drive current is completely dissipated, the back electromotive force gradually decreases, and an inflection point 330 occurs in the drive voltage by changing the inductance when the valve disc 201 hits the valve seat 202 (see Figures 3b to 3d). For example, by deriving the drive voltage curve applied to the fuel injector twice, the inflection point 330 can be accurately determined as a maximum or minimum value.

[0056] Figures 4a-4d show diagrammatically the injection pulse ti for operating the fuel injector shown in Figure 2 under ballistic conditions (Figure 4a), the associated drive voltage 304 (Figure 4b) and associated drive current 308 (Figure 4c) supplied to the fuel injector 101, and the resulting displacement curves of the valve body 201 (dotted displacement curves 334a,b in Figure 4d) and the armature core 206 (solid displacement curves 335a,b in Figure 4d).

[0057] 3a-3d, an injection pulse ti is also sent to the fuel injector 101 at time ts, high voltage 304 is applied, power supply to the injection coil 208 begins, and the movable core 206 is displaced in the valve opening direction (see solid displacement curve 335 in FIG. 3d). As in FIG. 3d, the movable core 206 passes through the gap 250 at delay time t0 and abuts against the valve disc 201, displacing both elements.

[0058] Unlike the fuel injector operation shown in Figures 3a-3d, at a time te just after the current curve 308 reaches a predetermined peak current value Ip, the injection pulse ti is turned off and a reverse voltage is applied to the fuel injector 101 (see Figures 4b and 4c), so that the valve disc 201 does not achieve its full lift and is pushed back to the closed position at about ⅔ of the lift (see dotted displacement curves 334a,b in Figure 4d).

[0059] Stopping the injection pulse before the valve disc achieves its full lift (ballistic operation / state of the fuel injector) leads to different displacements of the iron core 206 (see displacement curves 335a, b in FIG. 4d) and the valve disc 201 (see displacement curves 335a, b in FIG. 4d) and therefore to a different closing time t EOI_a , t EOI_b It is clear from Figure 4d that this can result in fluctuations in the amount of injected fuel. This means that when operating a fuel injector in ballistic operation, a stable opening condition cannot be achieved, and as a result, high deviations in the amount of injected fuel can occur without additional measures.

[0060] In order to solve the above problem, the closing time t EOI can be determined using the inflection points 330a,b derived from the driving voltage (see FIG. 4b). EOI Due to the defined correlation between t and the amount of fuel injected, it is possible to compensate for fuel deviations in ballistic operation by individually adjusting the injection pulse ti of each fuel injector 101. A preferred example of the implementation of such compensation according to the subject matter disclosed herein is described below in conjunction with Figures 6 through 12.

[0061] Fig. 5 shows an example of a hardware configuration of the control device 150 shown in Fig. 1 and Fig. 2. In the example shown, the hardware configuration includes a CPU 501 connected to a driving IC 502 via a communication line 222 and a signal line 223. For example, the CPU may be included in the ECU 109, and the driving IC 502 may be included in the driving circuit 127.

[0062] Furthermore, the illustrated hardware configuration includes a boost circuit 514 for providing a high voltage VH to a high voltage source 560, and the high voltage VH is generated by boosting a battery voltage VB input to the boost circuit 514. The boost circuit 514 may be a DC / DC converter. In the illustrated example, the boost circuit 514 includes a coil 530, a transistor 531, a diode 532, and a capacitor 533. The transistor 531 is connected to the CPU 501 via the driving IC 502, and the boosted voltage VH output from the boost circuit 514 can be detected by the driving IC 502 or the CPU 501.

[0063] Furthermore, according to the illustrated example, a switching element 505 is arranged between a high voltage source 516 of the voltage boost circuit 514 and a high voltage side terminal 590 of the fuel injector 101. Furthermore, a switching element 507 is arranged between a low voltage source 517 and the high voltage side terminal 590 of the fuel injector 101, and a further switching element 506 is arranged between a low voltage side terminal 591 of the fuel injector 101 and ground potential 515. The switching elements 505, 506, 507 may be transistors, preferably field effect transistors (FETs), and are capable of switching the fuel injector 101 on and off.

[0064] In the illustrated example, a diode 535 is arranged between the high voltage terminal 590 of the injector coil 208 and the switching element 505 to pass current from the high voltage source 516 to the injector coil 208 and ground potential 515. Also, a diode 511 is arranged between the high voltage terminal 590 of the coil 208 and the switching element 507 to pass current from a low voltage source 517 to the injector coil 208 and ground potential 515. The low voltage source 517 may be a battery providing a voltage VB which may be in the range of, for example, 12 to 14 V.

[0065] Additionally, the illustrated hardware configuration includes diodes 509 and 510 for applying a reverse drive voltage to the injector coil 208. Current detection resistors 508, 512, and 513 are also connected to the driver IC 502 to detect the current values ​​flowing from the respective power supplies to the fuel injector 101.

[0066] The CPU 501 can receive multiple sensor signals indicating the operating state of the internal combustion engine (not shown) from various types of sensors, such as a pressure sensor 102 attached to a fuel pipe upstream of the fuel injector 101 (see FIG. 1), and can calculate a required fuel quantity Q according to the operating state of the internal combustion engine, and based on that, can calculate a pulse duration and injection timing of the fuel injector 101.

[0067] CPU 501 may then output the calculated pulse durations for each timing to drive IC 502 of fuel injector 101 via signal line 223. Drive IC 502 may switch switching elements 505, 506, and 507 to generate a desired drive current based on the detected current value. In other words, switching elements 505, 506, and 507 may be switched between energized and de-energized by drive IC 502 to provide drive current to fuel injector 101.

[0068] Figure 6 shows a schematic functional configuration of the control device 150 shown in Figures 1 and 2 according to a preferred embodiment of the subject matter disclosed herein. As already shown in Figures 1 and 2, the control device 150 is connected to the injector 101 and comprises an ECU 109 and a drive circuit 127. According to a preferred embodiment of the subject matter disclosed herein, the ECU 109 comprises a control parameter calculation unit 603, an injection pulse calculation unit 604, an injection pulse compensation unit 605, an injection pulse learning unit and a current profile calculation unit 609. The ECU 109 also comprises a read only memory (ROM) 607 and a random access memory (RAM) 608. The drive circuit 127 of the control device 150 comprises a current profile generation unit 601 and an injector closing time calculation unit 602.

[0069] The control parameter calculation unit 603 calculates the amount of fuel Q injected into an internal combustion engine (not shown). tar Based on this, a target closing time t for the fuel injector 101 is determined. EOI_tar Determine the fuel quantity Q tar may depend on the operating conditions of the internal combustion engine, such as engine load, engine speed, air-fuel ratio, etc. These operating conditions are connected to the ECU 109, which determines the required amount of fuel Q for the given operating conditions. tar This may be determined by a number of sensors (not shown) that may enable the ECU 109 to determine.

[0070] The control parameter calculation unit 603 calculates the closing time t EOI and the fuel quantity Q of the plurality of fuel injectors 101 based on a predetermined correlation between tar The corresponding target closing time t EOI_tar For example, this predetermined correlation (second correlation) may be determined in advance on a test bench for all fuel injectors 101 attached to the internal combustion engine and stored in the ROM 607 of the ECU 109.

[0071] Furthermore, the control parameter calculation unit 603 calculates the determined target closing time t EOI_tar is the maximum closing time t of the fuel injector 101 during ballistic operation. EOI_max In this case, the control parameter calculation unit 603 may cause the injection pulse calculation 604 unit to calculate the pulse duration ti for the fuel injector 101 based on the characteristic curve.

[0072] A fuel injector characteristic curve may represent the relationship between the pulse duration ti of the fuel injector 101 and the associated fuel quantity Q delivered by the injector 101 (see FIG. 7a). The characteristic curve may be provided for a particular type of fuel injector 101 installed in the internal combustion engine and may be stored in the ROM 607 of the ECU 109. The injection pulse calculation unit 604 may output the calculated pulse duration ti to a current profile calculation unit 609, which may calculate a current profile (start of injection SOI, end of injection EOI, peak current Ip, holding current Ih, etc.) based on the calculated pulse duration ti and send the calculated current profile to a current profile generation unit 601 of the drive circuit 127 via signal line 223. The current profile generation unit 601 may generate a required drive current / drive voltage and deliver a required fuel quantity Q to the internal combustion engine. tar can be supplied to the injector 101 which injects the

[0073] The control parameter calculation unit 603 calculates the determined target closing time t EOI_tar is the maximum closing time t of the fuel injector 101 during ballistic operation. EOI_max If so, the injection pulse compensation unit 605 reads the pulse duration ti and closing time t of the fuel injector 101 from the RAM 608. EOI Receive the slope a0 and intercept b0 of the first correlation with the determined target closing time t EOI_tar and the received slope a0 and intercept b0, a pulse duration ti for the fuel injector 101 may be calculated.

[0074] This means that for each injector 101, an individual pulse duration ti is determined by the pulse duration ti and closing time t EOI The target closing time t is adapted by a first correlation between EOI_tar The injected fuel quantity Q is calculated by the injection pulse compensation unit 605 based on tar Target closure time t as a function of EOI_tarmay be the same for each fuel injector 101, but the pulse duration ti and closing time t EOI may be determined for each fuel injector 101 individually by the injection pulse learning unit 606 and stored in the RAM 608. After the injection pulse compensation unit 605 calculates the individual pulse duration ti for each fuel injector 101, it may output each pulse duration ti to the current profile calculation unit 609, which may calculate a current profile for each fuel injector 101 based on the calculated pulse duration ti and send it to the current profile generation unit 601 of the drive circuit 127 via signal line 223.

[0075] The injection pulse learning unit 605 learns the pulse duration ti and closing time t of the fuel injector 101 during a learning mode of the internal combustion engine. EOI During the learning mode, the injection pulse learning unit 605 may incrementally increase the pulse duration ti of the internal combustion engine fuel injector 101 and transmit each pulse duration ti to the injector closing time calculation unit 602 of the drive circuit 127, which in turn may determine a first correlation between the closing time t EOI can be determined and sent back to the injector pulse learn unit 605.

[0076] The injector closing time calculation unit 602 of the drive circuit 127 calculates the closing time t of the fuel injector based on the drive current curve of the fuel injector 101. EOI As discussed above in relation to Figures 3b and 4b, when the disc 201 impacts the seat 202, the slope of the actuation voltage changes, creating an inflection point 330 in the actuation voltage (see Figures 3b and 4b). This inflection point 330, 330a,b can be determined by, for example, forming the second derivative of the control voltage curve, to determine the closing time t EOI can be used to determine

[0077] The injection pulse learning unit 606 calculates the closing time tEOI Based on this, the pulse duration ti and closing time t of each fuel injector 101 are determined. EOI and storing in the RAM 608. The injection pulse learning unit 605 may also determine a first correlation between the pulse duration t i and the closing time t EOI The slope a0 and intercept b0 of the first correlation with may be calculated, and the calculated slope a0 and intercept b0 may also be stored in the RAM 608.

[0078] Calculating the slope a0 and intercept b0 for each pulse duration may mean that the slope a0 of the closing time and the corresponding intercept b0 between two adjacent pulse durations ti are determined. The slope a0 and intercept b0 of the first pulse duration ti1 sent to the injector closing time calculation unit 602 may be, for example, EOI = 0 as the preceding pulse duration ti0 of the first pulse duration ti1.

[0079] In the learning mode, the injection pulse learning unit 606 gradually increases the pulse duration ti while checking whether the calculated slope a0 is equal to or smaller than a predetermined slope value a 0_thr The closing time t is smaller than EOI The closing time t EOI is the maximum closing time t of the fuel injector 101 during ballistic operation. EOI_max The maximum closing time t EOI_max may be stored in RAM 608. This procedure may be repeated for all fuel injectors 101 installed in the internal combustion engine.

[0080] Note that the injection pulse learning unit 606 determines the maximum closing time t EOI_max The learn mode of the internal combustion engine may be stopped when the learn unit 606 has determined and stored in RAM the closing time t ...EOI and may cause the control parameter calculation unit 603 to stepwise increase the pulse duration ti of the first fuel injector 101 to determine a θ and calculate the slope a0 and intercept b0 of the first correlation, respectively.

[0081] The learning mode may be initiated every time the combustion engine is started, for example when the engine is at idle. During this time, for example, the ECU 109 may prevent the engine from absorbing a load until the first correlation and its slope a0 and intercept b0 have been determined for all fuel injectors 101. This means that the first correlation is constantly adjusted during the operating time of the engine so as to permanently take into account the effects of aging of the fuel injectors 101 and the environmental conditions that affect the opening and closing behavior of the fuel injectors 101. The learning mode is initiated by determining the maximum closing time t in the ballistic operation of each fuel injector 101. EOI_max Since it ends when it reaches, it can only last for a short time and does not affect the operating comfort.

[0082] FIG. 7a shows a schematic representation of the relationship between the pulse duration ti and the injected quantity Q of different fuel injectors 101 that are not controlled according to the subject matter disclosed herein. The relationship shown as a dashed line may be a typical curve for the type of fuel injector shown and may be stored as a characteristic curve in the ECU 109. From FIG. 7a it becomes clear that the same pulse duration ti may result in different fuel quantities Q for different injectors 101 when the fuel injectors 101 are operating in ballistic conditions, i.e. when the injection pulse ti ends before reaching the full lift of the valve body 201. In other words, if the characteristic curve of the fuel injector 101 is used for metering the fuel quantity Q in ballistic operation, large deviations of the injected fuel quantity Q are expected. Even when a single injector 101 operates in ballistic operation, large deviations of the injected fuel quantity Q may occur between different injections at the same pulse duration ti.

[0083] Therefore, in accordance with the subject matter disclosed herein, the characteristic curve of the fuel injector 101 is determined based on the closing time t EOIis the maximum closing time t of the fuel injector 101 during ballistic operation. EOI_max In other words, the characteristic curve of the fuel injector 101 is only used when the fuel injector 101 is operated in a stable / fully open condition where the valve disc 201 reaches its full lift. Figure 7a shows that in this case the characteristic curve has a slope a over the pulse duration ti. full and intercept b full , indicating that only small deviations in the injected fuel quantity Q between different fuel injectors / different injections are expected.

[0084] FIG. 7b shows the closing time t EOI FIG. 7b shows a schematic diagram of the relationship between the closing time t EOI It is shown that there is a linear relationship between the target closing time t and the fuel quantity Q. This relationship is valid for the entire operating range of the fuel injector 101, i.e., ballistic operation as well as operation at the full lift of the valve disc 201. Therefore, the target closing time t EOI_tar can be determined using the slope a1 and intercept b1 of a single correlation (the second correlation) that is valid for all fuel injectors 101 installed in the internal combustion engine, which may be determined once and stored in the ROM 607 of the ECU 109.

[0085] 8a-8c are schematic diagrams illustrating a preferred example for calculating the slope and intercept of a first correlation for each pulse duration according to the subject matter disclosed herein. In particular, FIG. 8a illustrates a relationship between the pulse duration t and the closing time t determined for a given fuel injector 101. EOI 1 shows an example of a first correlation between the closing time t EOI 7a (see FIG. 7b), since the fuel quantity Q and the fuel quantity Q are linearly dependent on each other. As mentioned above, the first correlation is performed by gradually increasing the pulse duration ti applied to the fuel injector 101 during a learn mode of the internal combustion engine, and by gradually increasing the closing time t for each pulse duration ti. EOIThe variation in pulse duration may begin at a delay time t0 for each fuel injector 101 and is determined by determining a preliminary maximum pulse duration t i_max is the closing time t EOI may be preset as the final pulse duration to be determined.

[0086] Figures 8b and 8c show the slope a0 and intercept b0 of the exemplary first correlation shown in Figure 8a determined for each pulse duration ti, meaning that the slope a0 shown in Figure 8b and the corresponding intercept b0 shown in Figure 8c are determined between two adjacent pulse durations ti of the exemplary first correlation shown in Figure 8a.

[0087] The calculated slope a0 is the specified slope value a 0_thr A pulse duration t i_e Regarding closing time t EOI When the closing time t EOI is the maximum closing time t of the fuel injector 101 during ballistic operation. EOI_max The first correlation shows a significant decrease in slope during the transition from ballistic to full stroke operation (see FIG. 8a), so the ballistic operating range t i_e The end of the slope is a given value a 0_thr This can be reliably determined by setting a threshold value a . This makes it possible to limit not only the calculation effort of the control unit 150 but also the time required for the learning mode. For example, a given slope value a 0_thr may be determined in advance on a test bench for all fuel injectors 101 mounted on an internal combustion engine and stored in the ROM 607 of the ECU 109. i_e The determined slope a0 and intercept b0 for pulse durations up to may be stored in RAM 608.

[0088] 9a-9c show target closure times t EOI_tar9a shows a schematic diagram of a preferred embodiment for determining the pulse duration of an individual fuel injector based on the corresponding slope a0 and intercept b0. In particular, FIG. 9a shows a schematic diagram of a fuel quantity Q injected into an internal combustion engine based on the corresponding slope a0 and intercept b0. tar The target closing time t of the fuel injector 101 is set based on EOI_tar 4 shows an exemplary second correlation that can determine the target closure time t EOI_tar After is determined, the associated slope a0 and intercept b0 determined in the learn mode for each fuel injector 101 can be read from the RAM 608 (see Figures 9b and 9c). The required pulse duration t of the individual fuel injector 101 during ballistic operation can then be i_bal can be calculated using the following format: TIFF2025508259000002.tif14170 According to FIG. 9a the following applies: TIFF2025508259000003.tif14170

[0089] This means that the pulse duration t i_bal But the closing time t EOI and the injected fuel quantity Q, which means that the pulse duration ti and closing time t of each fuel injector 101 can be determined based on a general linear relationship (second correlation) between the EOI Through a first correlation between the fuel injection amount and the fuel injection amount, the individual behavior of each fuel injector 101 can be adapted. The individual steps of the procedure described in Figures 8a-8c and 9a-9c are explained below using the flow charts shown in Figures 10 and 11.

[0090] 10 shows a flow chart illustrating a preferred embodiment of a method according to the subject matter disclosed herein. In particular, FIG. 10 illustrates a method for determining the required pulse duration t i_bal Or t i_full But the required fuel amount Q tar In the first step S1001 after starting the method, the amount of fuel to be injected Q tarmay be determined according to the operating conditions of the internal combustion engine. EOI_tar can be determined from a second correlation stored in ROM 607 of ECU 109 according to equation (2) above (see also FIG. 9a).

[0091] Determined target closing time t EOI_tar is the maximum closing time in ballistic operation t EOI_max If so, the method proceeds to step S1004, where the target closing time t EOI_tar The slope a0 and intercept b0 of the fuel injector that correlates with the determined target closing time t EOI_tar and based on the slope a0 and intercept a0 read from the RAM 608, the required pulse duration t i_bal may be calculated in step S1005 according to equation (1), and a resulting injection pulse may be output to the fuel injector 101 (S1006). After outputting the injection pulse in step S1006, the method may end.

[0092] Determined target closing time t EOI_tar is the maximum closing time in ballistic operation t EOI_max If so, the method proceeds to step S1003, where the pulse duration t is calculated from the characteristic curve of the fuel injector 101. i_full may then be determined (see FIG. 7a). The resulting injection pulse may then be output to the fuel injector 101 (S1006) before terminating the method.

[0093] 11 shows a flow chart illustrating a further preferred example of a method according to the subject matter disclosed herein. In particular, FIG. 11 shows, by way of example, how a first correlation and its slope a0 and intercept b0 may be determined during a learn mode for an individual injector 101. After starting the method, an initial pulse duration ti1 may be set in step S1101, and an injection pulse resulting from the initial pulse duration ti1 may be output to the fuel injector 101 in step S1102. Subsequently, a closing time t corresponding to the initial pulse duration ti1 is determined in step S1103. EOI1 It is possible to detect the closing time t EOI Using the delay time t0, where =0, as the starting point for the calculation, the slope a 01 and intercept b 01 In the next step S1105, the determined closing time t EOI1 and the calculated slope a for the initial pulse duration ti1 01 and intercept b 01 and may be stored in the RAM 608 of the ECU 109. Next, in step S1106, the initial pulse duration ti1 may be increased by a period t to a second pulse duration ti2. The period t may be in the range of 0.001 ms to 0.4 ms.

[0094] Either the second pulse duration ti2 or the following pulse duration ti is equal to or greater than the preliminary maximum pulse duration t i_max If the second pulse duration ti2 is already greater than the preliminary maximum pulse duration t i_max If the required pulse duration t i_bal To calculate the slope, we use only one 01 and intercept b 01 However, if either the second pulse duration ti2 or the subsequent pulse duration ti is greater than the preliminary maximum pulse duration t i_maxIf so, the method proceeds to step S1107, where an injection pulse resulting from pulse duration ti2 (or a subsequent pulse duration ti) may be output to the fuel injector 101. Then, in step S1108, the closing time t corresponding to each pulse duration ti is calculated. EOIi can be detected, and its slope a 0i and intercept b 0i can be calculated (S1109).

[0095] In other words, the closing time t EOI The slope of a 0i and the corresponding intercept b between two subsequent pulse durations ti 0i may be determined in step S1109. 0i is the given slope value a 0_thr In step S1113, the determined closing time t EOIi and the calculated slope a for each pulse duration ti 0i and intercept b 0i The calculated slope a may be stored in the RAM 608 of the ECU 109. Next, in step S1114, the pulse duration ti may be increased again by a period ?t. 0i is the given slope value a 0_thr If it is less than or equal to the determined closing time t EOIi The maximum closing time t EOI_max Then, the required pulse duration t i_bal The method can be completed for each fuel injector 101 since all the relevant parameters needed to calculate

[0096] 12 shows a schematic diagram of the relationship between the pulse duration t i and the injection quantity Q of a different fuel injector 101 controlled in accordance with the subject matter disclosed herein. Comparing the characteristic curve of the different fuel injector 101 shown in FIG. 12 with the characteristic curve shown in FIG. 7a, it can be seen that the required pulse duration t i in ballistic operation as described above is smaller than the injection quantity Q. i_balIt becomes clear that the deviation in fuel quantity can be significantly reduced by calculating the pulse duration ti and closing time t of each fuel injector 101. In particular, the subject matter disclosed herein allows the deviation in fuel quantity between different injectors / different injections in ballistic operation to be reduced to the level of full lift operation. This is achieved by calculating the pulse duration ti and closing time t of each fuel injector 101. EOI , which can be adapted to the individual behavior of each fuel injector 101 through a first correlation between EOI The pulse duration t of each fuel injector 101 is calculated based on a general linear relationship (second correlation) between the fuel injection amount Q and the i_bal The described calculation requires little calibration effort and ensures a continuous adjustment of the calculated pulse duration during the engine's operating time so as to permanently take into account the effects of aging of the fuel injector 101 and environmental conditions that affect the opening / closing behavior of the fuel injector 101. [Explanation of symbols]

[0097] 101 Fuel injector 150 Control device 602 Injector Closing Time Calculation Unit 603 Control Parameter Calculation Unit 604 Injection Pulse Calculation Unit 605 Injection Pulse Compensation Unit 606 Injection Pulse Learning Unit 607 Read-only memory (ROM) 608 Random Access Memory (RAM)

Claims

1. A control device for controlling a fuel injector mounted on an internal combustion engine, the control device comprising: a control parameter calculation unit; an injection pulse calculation unit; an injection pulse compensation unit; and at least one memory; the control parameter calculation unit is configured to determine a target closing time for the fuel injector based on an amount of fuel to be injected into the internal combustion engine; if the determined target closing time is greater than a maximum closing time of the fuel injector in ballistic operation; the injection pulse calculation unit is configured to calculate a pulse duration for the injector based on a characteristic curve of the fuel injector and output the calculated pulse duration to the fuel injector for injecting the amount of fuel into the internal combustion engine, and if the determined target closing time is less than or equal to the maximum closing time during the ballistic operation, the injection pulse compensation unit is configured to receive from the at least one memory a set of parameters correlating to the determined target closing time, calculate a pulse duration for the fuel injector based on the received set of parameters, and output the calculated pulse duration to the fuel injector for injecting the amount of fuel into the internal combustion engine. Control device.

2. 2. The control system of claim 1, wherein the set of parameters includes a slope and an intercept of a first correlation between pulse duration and closing time of the fuel injector, the set of parameters being stored in the at least one memory.

3. The control system of claim 1 , wherein the control parameter calculation unit is configured to determine the target closing time for the fuel injector based on a second correlation between closing time and fuel quantity for a plurality of fuel injectors.

4. The injector closing time calculation unit and the injection pulse learning unit are further included. In a learning mode of the internal combustion engine, the injection pulse learn unit is configured to incrementally increase the pulse duration of the fuel injector; the injector closing time calculation unit is configured to determine a closing time for each pulse duration and to send the determined closing time to the injection pulse learning unit; the injection pulse learning unit is configured to receive the determined closing times from the injector closing time calculation unit for each pulse duration and to determine the first correlation between the pulse duration and the closing time of the fuel injector. The control device according to claim 1 .

5. 5. The control device of claim 4, wherein the injection pulse learning unit is configured to calculate a slope and an intercept of the first correlation between the pulse duration and the closing time of the fuel injector for each pulse duration and to store the calculated slope and intercept in the at least one memory.

6. 6. The control device of claim 5, wherein the injection pulse learning unit is configured to determine a closing time at which a calculated slope is less than or equal to a predetermined slope value as the maximum closing time of the fuel injector in ballistic operation, and to store the determined maximum closing time in the at least one memory.

7. The control system of claim 6 , wherein the injection pulse learn unit is configured to stop the learn mode of the internal combustion engine when the maximum closing time of the fuel injector in ballistic operation is determined.

8. The control system of claim 4 , wherein the injection pulse learn unit is configured to initiate the learn mode when the internal combustion engine is operated in a predetermined operating mode.

9. The control system of claim 1 , wherein the injector closing time calculation unit is configured to determine the closing time of the fuel injector based on a drive current curve of the fuel injector.

10. An internal combustion engine including at least one fuel injector and the control system of claim 1.

11. A method for controlling a fuel injector mounted on an internal combustion engine by means of a control device, the control device comprising a control parameter calculation unit, an injection pulse calculation unit, an injection pulse compensation unit and at least one memory, the method comprising: determining, by the control parameter calculation unit, a target closing time for the fuel injector based on the amount of fuel to be injected into the internal combustion engine. Including, if the determined target closing time is greater than a maximum closing time of the fuel injector in ballistic operation; calculating, by the injection pulse calculation unit, a pulse duration of the fuel injector based on a characteristic curve of the fuel injector; outputting, by the injection pulse calculation unit, the calculated pulse duration to the fuel injector for injecting the quantity of fuel into the internal combustion engine; Including, When the determined target closing time is equal to or less than a maximum closing time in the ballistic operation, receiving, by the injection pulse compensation unit, a set of parameters from the at least one memory that correlates to the determined target close time; calculating, by the injection pulse compensation unit, a pulse duration for the fuel injector based on the received set of parameters; outputting, by the injection pulse compensation unit, the calculated pulse duration to the fuel injector for injecting the quantity of fuel into the internal combustion engine; A method comprising:

12. 12. The method of claim 11, wherein the set of parameters includes a slope and an intercept of a first correlation between pulse duration and closing time of the fuel injector from the at least one memory, the set of parameters being stored in the at least one memory.

13. The method of claim 11 , wherein the target closing time for the fuel injector is determined by the control parameter calculation unit based on a second correlation of closing time and fuel quantity for a plurality of fuel injectors.

14. The control unit further comprises an injector closing time calculation unit and an injection pulse learning unit; In a learning mode of the internal combustion engine, the pulse duration of the fuel injector is increased in stages by the injection pulse learn unit; a closing time per pulse duration is determined by the injector closing time calculation unit and sent to the injection pulse learning unit; the determined closing time per pulse duration is received by the injection pulse learning unit, and the first correlation between the pulse duration and the closing time of the fuel injector is determined by the injection pulse learning unit. The method of claim 11.

15. 15. The method of claim 14, wherein a slope and an intercept of the determined first correlation between pulse duration and closing time of the fuel injector are calculated by the injection pulse learning unit for each pulse duration and stored in the at least one memory.

16. 16. The method of claim 15, wherein a closing time at which the calculated slope is less than or equal to a predetermined slope value is determined by the injection pulse learn unit as the maximum closing time for the fuel injector in ballistic operation and stored in the at least one memory.

17. 17. The method of claim 16, wherein the learn mode of the internal combustion engine is stopped by the injection pulse learn unit when the maximum closing time of the fuel injector in ballistic operation is determined.

18. The method of claim 14 , wherein the learn mode is initiated by the injection pulse learn unit when the internal combustion engine is operated in a predetermined operating mode.

19. The method of claim 11 , wherein the closing time of the fuel injector is determined based on a drive current curve of the fuel injector.

20. A computer program product storable in a memory comprising instructions which, when executed by a computer, cause the computer to carry out the method of claim 11.

21. 1. A method for adapting a pulse duration of a fuel injector fitted to an internal combustion engine by an injection pulse learn unit in a learn mode of the engine, the method comprising: incrementally increasing a pulse duration of the fuel injector; detecting a closure time for each pulse duration; calculating a slope and an intercept between the pulse duration and the closing time of the fuel injector for each pulse duration; determining a closing time at which the calculated slope is less than or equal to a predetermined slope value and / or a closing time at which the calculated slope is a negative slope value as a maximum closing time for said fuel injector in ballistic operation; stopping the learn mode after determining the maximum closing time of the fuel injector in ballistic operation; storing the calculated slope and intercept and the maximum closing time of the fuel injector under ballistic operation as a set of parameters in at least one memory; A method comprising:

22. 22. The method of claim 21, wherein the learn mode is initiated by the injection pulse learn unit when the internal combustion engine is operated in a predetermined operating mode.

23. 22. The method of claim 21, wherein the closing time of the fuel injector is determined based on a drive current curve of the fuel injector.

24. 22. A computer program product storable in a memory comprising instructions which, when executed by a computer, cause the computer to carry out the method of claim 21.

25. 22. An injection pulse learn unit for a control device configured to carry out the method of claim 21.

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