Method for controlling an internal combustion engine, computing unit and computer program

Abstract

The invention relates to a method for controlling an injection valve (4) for an internal combustion engine, comprising specifying a center of gravity position of the injection; determining a duration of injection by the injection valve (4); calculating an injection timing of the injection valve (4) depending on the center of gravity position and the duration of injection; and controlling the injection valve (4) to inject the fuel based on the calculated injection timing and the determined injection duration.

Description

[0001] The present invention relates to a method for controlling an injection valve for an internal combustion engine, an internal combustion engine, a computing unit and a computer program for carrying out the method. Background of the invention

[0002] To control fuel injection into an internal combustion engine, the engine control unit can specify target values ​​for the start of energization (SOE), the end of energization (EOE), and the duration of electrical actuation (ti) of one or more injection valves. The start of injection (SOI) occurs a specific time after the start of actuation, depending on the characteristics of the injection valve. The same applies to the end of injection (EOI), which occurs a specific time after the end of actuation.

[0003] The start and end points of the injection valve activation, as well as the activation duration, can be set independently of each other, so that a change in the activation duration does not necessarily result in a change in the start or end points. However, to ensure the required amount of fuel is supplied to the cylinder under varying operating conditions, the activation duration is adjusted, for example, based on a measured fuel pressure. Disclosure of the invention

[0004] According to the invention, a method for controlling an injection valve for an internal combustion engine, an internal combustion engine, a computing unit, and a computer program for carrying out the method are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0005] The internal combustion engine can be operated, in particular, with a gaseous fuel, especially hydrogen, and can be equipped with port fuel injection. The internal combustion engine can, in particular, include one injection valve per cylinder, arranged upstream of an intake valve of the respective cylinder. It is also possible for the injection valve to introduce the gaseous fuel directly into the cylinder. The injection valve can, in particular, be a solenoid valve.

[0006] The invention makes it possible to control the injection of fuel through an injection valve into an internal combustion engine in such a way that the center of gravity of the injection is not affected by a change in the injection duration.

[0007] Studies have shown that, particularly with hydrogen injection, the injection point, rather than its start or end time, is crucial for optimizing exhaust emissions (e.g., nitrogen oxide emissions). The injection point (center of injection - COI) can be, for example, the point in time when half of the fuel to be injected has entered the cylinder. If the injection duration is shortened or lengthened depending on the fuel pressure, the injection point shifts, even with a constant start or end time, which can result in a deterioration of exhaust emissions.

[0008] In the method according to the invention, a center of gravity position for the injection is first specified. This can be done, for example, by means of a center of gravity position map in which a target center of gravity position for the injection is stored for a multitude of operating points of the internal combustion engine, e.g., via load and speed. The center of gravity position map can be determined on an engine test bench and / or vehicle test bench and stored in a processing unit, which can in particular be an engine control unit (ECU) of the internal combustion engine. The target center of gravity position for the injection can be determined in such a way that exhaust emissions from the internal combustion engine, in particular nitrogen oxide emissions, are minimized.

[0009] In addition to specifying the center of gravity, the duration of an injection through the injection valve is determined in this process.

[0010] According to one embodiment, the duration of the injection process can be determined by the actuation time of the injection valve. The actuation time can, in particular, be the period between the start and end of the injection valve's actuation, during which the injection valve or its solenoid coil is energized. The actuation time is used to set the opening duration and thus the injection quantity of the injection valve.

[0011] The injection duration can be determined, for example, from an injection duration map stored in the engine control unit to supply the combustion engine with the required amount of fuel at each operating point. The injection duration map can also be determined on an engine test bench and / or vehicle test bench for the numerous operating points of the combustion engine. A target fuel pressure can be specified for each operating point to determine the injection duration.

[0012] According to one embodiment, the injection duration can also be determined depending on the fuel pressure. For example, a correction value can be calculated in the engine control unit based on the fuel pressure. This value can then be used to correct, for instance, the injection duration from the injection duration map if the actual fuel pressure does not correspond to the target fuel pressure. The correction value can be calculated, for example, using the flow formula according to Saint-Vernant and Wantzel, or determined experimentally on a component test bench, an engine test bench, and / or a vehicle test bench and stored in the engine control unit. Correcting the injection duration may be particularly necessary during the transient operation of the internal combustion engine, when the actual fuel pressure has not yet reached the target fuel pressure.

[0013] Depending on the center of gravity and the duration of the injection, an injection time for the injection valve is then calculated.

[0014] According to one embodiment, the center of energizing (COE) of the injection valve can be predetermined at a point in time when half of the electrical activation time of the injection valve has elapsed. In this case, a COE of the electrical activation of the injection valve is predetermined, which may have a specific distance from the actual COI of the injection.

[0015] The injection timing, whether COI or COE, can be specified in relation to a specific crankshaft angle of the internal combustion engine. Consequently, the injection timing can also be calculated based on the crankshaft angle. It follows that the injection duration, particularly the actuation time of the injection valve, can also be converted into degrees of crankshaft angle (°CA). A top dead center (TDC) in the combustion engine's power stroke (ignition TDC) can be chosen as the reference point (0°CA). Times before TDC can be counted as positive, and times after TDC as negative.

[0016] According to one embodiment, the injection point can be determined as the start of actuation (SOE) or the end of actuation (EOE) of the injection valve. For example, an end of actuation (EOE) as the injection point can be calculated based on the center of gravity of the electrical actuation (COE) and the actuation duration (ti) as follows: EOE=COE−ti2

[0017] The start of operation (SOE) of the injection valve can be calculated below based on the end of operation (EOE) and the duration of operation (ti): SOE=EOE+ti

[0018] If, for example, at a transient operating point of the internal combustion engine, the actual fuel pressure does not correspond to the target fuel pressure, the control duration (ti) can be adjusted to the prevailing fuel pressure using the correction value (Δti). In this case, the control end time (EOEt) can be calculated according to the following formula: EOEt=COE−(ti2±Δti2)

[0019] The correction value (Δti) can have a positive value if the actual fuel pressure is lower than the target fuel pressure, and a positive value if the actual fuel pressure is higher than the target fuel pressure.

[0020] The start of the approach (SOE) t ) can then be calculated as follows: SOEt=EOE+(ti±Δti)

[0021] If the start of the approach (SOE, SOE t ) as the injection time is calculated based on the center of gravity of the electrical control (COE) and the control duration (ti), then the following applies: SOE=COE+ti2 SOEt=COE+(ti2±Δti2)

[0022] It becomes clear that by specifying the center of gravity of the electrical control (COE), both the control end (EOE, EOEt) and the control start (SOE, SOE) are determined. t) of the injection valve can be adjusted depending on the required control duration (ti ± Δti), which means that even if the fuel pressure deviates from its target value, the center of gravity of the injection (COI) can be kept constant and an increase in the exhaust emissions of the combustion engine can be avoided in transient operation.

[0023] According to an alternative embodiment, the injection center of gravity can be set at a point in time when half the opening time of the injection valve has elapsed. In this case, a center of gravity position can be specified that approximately corresponds to the actual center of gravity (COI) of the injection at which half of the fuel to be injected into the combustion engine has been introduced. The point in time when half the opening time of the injection valve has elapsed can be determined, for example, by measuring the needle lift on the injection valve. To calculate the end or start of the control sequence based on the center of gravity of the injection (COI), a delay time between the center of gravity of the injection (COI) and the center of gravity of the electrical control (COE) can be determined and taken into account in formulas (1) to (6).

[0024] According to one embodiment, the injection timing can be limited by at least one predetermined injection point. In particular, the start and / or end of the control can be limited to the earliest possible time or crank angle before top dead center (TDC) and the latest possible time or crank angle after TDC. For direct injection, the earliest possible time for the start of the control can be limited, for example, to 180° crank angle before TDC (+180° crank angle) and the latest possible time for the end of the control can be limited, for example, to 180° crank angle after TDC (-180° crank angle). For port injection, the earliest possible time for the start of the control can be limited, for example, to 360° crank angle before TDC and the latest possible time for the end of the control can be limited, for example, to 180° crank angle, if necessary minus a buffer time to prevent incomplete intake of the hydrogen quantity, which essentially corresponds to the intake valve opening time.

[0025] Based on the calculated injection timing and the determined injection duration, the injection valve is then controlled. For example, in transient operation of the internal combustion engine, the injection valve can be controlled at the start of operation (SOE) calculated according to formula (4) or (6). t ) are powered for the control duration (ti ± Δti) in order to introduce the required amount of fuel into the combustion engine.

[0026] A computing unit according to the invention, which may preferably be an engine control unit, is, in particular in terms of programming, equipped to carry out a method according to the invention as described above.

[0027] Implementing a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous. Finally, a machine-readable storage medium is provided with a computer program stored on it as described above. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical, and electrical storage devices, such as hard drives, flash memory, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, intranet, etc.) is also possible. Such a download can be wired or wireless (e.g., via a WLAN network, a 3G, 4G, 5G, or 6G connection, etc.).

[0028] Further advantages and embodiments of the invention will become apparent from the description of the accompanying drawing.

[0029] The invention is schematically illustrated with reference to exemplary embodiments in the drawings and is described below with reference to the drawings. Brief description of the drawing Fig. Figure 1 shows a schematic and partial view of an internal combustion engine according to an embodiment of the invention. Fig. Figure 2 schematically and exemplarily shows a flow path and a valve needle lift of an injection valve that is used in the internal combustion engine made of Fig. 1 can be used. embodiment(s) of the invention

[0030] Fig. Figure 1 shows a schematic and partial view of an internal combustion engine according to an embodiment of the invention.

[0031] The depicted internal combustion engine has an intake port 2, a cylinder 1, and an exhaust port 9. An intake valve 5 and an exhaust valve 7 are arranged in cylinder 1, closing off cylinder 1 from the intake port 2 and exhaust port 9. A throttle valve 6 and an injection valve 4 are arranged in the intake port 2. The injection valve 4 can, in particular, be a solenoid valve. A fuel pressure sensor 10 is located in a fuel line (not specified) upstream of the injection valve 4. Gaseous fuel, e.g., natural gas or, in particular, hydrogen, is introduced into the intake port 2 upstream of the intake valve 5 by means of the injection valve 4, where it mixes with fresh air supplied via the throttle valve 6.A lambda sensor 8 is installed in the exhaust channel 9 of the combustion engine shown, which measures the residual oxygen in the exhaust gas of the combustion engine in order to determine the air-fuel ratio of the air-fuel mixture burned in cylinder 1.

[0032] Furthermore, the internal combustion engine includes a control unit 3, which can be, for example, the engine control unit, and is connected to the throttle valve 6, the injection valve 4, the lambda sensor 8, and the fuel pressure sensor 10. The control unit 3 can receive signals from the internal combustion engine's sensors (e.g., the lambda sensor 8 and the fuel pressure sensor 10) and control the internal combustion engine's actuators (e.g., the throttle valve 6 and the injection valve 4). For example, the control unit 3 can receive a signal from the lambda sensor 8 and adjust the fresh air supply via the throttle valve 6 based on this signal. Furthermore, the control unit 3 can receive a signal from the fuel pressure sensor 10 and adjust the duration of an electrical actuation of the injection valve 4 if the measured actual fuel pressure does not match a predetermined target fuel pressure.

[0033] The actuation duration ti of the injection valve (see Fig. 2) can be stored in a control duration map in the processing unit 3 and adjusted to the measured actual fuel pressure by means of a correction value. The correction value can be calculated by the processing unit 3 or, for example, taken from a characteristic curve in which the correction value is stored, for example, as a function of the actual fuel pressure.

[0034] To prevent a concentration of COI from developing in such a case (see Fig. 2) if the amount of fuel to be introduced into the combustion engine changes, a center of gravity position map can be stored in the processing unit 3, which contains a preset value for the center of gravity position of the injection, based on which an injection timing of the injection valve 4, e.g. its start of control SOE and / or end of control EOE, can be calculated (see Fig. 2) In the center of gravity position characteristic field, for example, a center of gravity position of the electrical control COE can be determined (see Fig. 2) be stored and the control end EOE and the control start SOE of the injection valve 4 can be calculated in the computing unit 3 according to the above formulas (1) to (6).

[0035] Fig. Figure 2 shows a diagram in which a flow path 10 and a valve needle stroke 20 of the injection valve 4 are schematically and exemplarily represented. Fig. 1 is shown.

[0036] The diagram clearly shows a relationship between the electrical control and the opening behavior of the injection valve 4.

[0037] At the start of the electrical actuation (SOE), the current 10 in a solenoid coil (not shown) of the injection valve 4 rises sharply, thereby building up a magnetic field within it. As a result, a valve needle (not shown) opens after a delay time t. antotThe valve is lifted from its seat and the injection valve 4 is opened at time SOI. The current 10 remains essentially constant during the actuation period ti, with the exception of an overshoot after activation, and drops sharply again after the electrical actuation is switched off (actuation end EOE). When the actuation is switched off, the magnetic field at the solenoid coil drops and the valve needle closes the injection valve 4 after a closing delay time t. ab at the time of EOL.

[0038] An opening duration t open The operating time of the injection valve 4 is therefore related to the control duration ti by the opening and closing delay times t antot and t abThis is shifted in time, resulting in an earlier center of gravity for the electrical control (COE) compared to the actual center of gravity for the injection (COl). The center of gravity for the electrical control (COE) refers to a point in time or crank angle at which half of the control duration (ti) has elapsed, while the center of gravity for the injection indicates a point in time or crank angle at which half of the opening duration (t) has elapsed. open of the injection valve. Due to the symmetrical valve needle stroke profile 20 during the opening and closing of the injection valve, this corresponds approximately to the time at which half of the fuel quantity has been introduced into cylinder 1.

[0039] Both center of gravity positions COE and COI can be used to control the injection. If the center of gravity position COI is specified, a delay time between COE and COI can be taken into account to calculate the control end EOE and / or the control start SOE, e.g., according to formulas (1) to (6), which is based, for example, on the opening and closing delay times t. antot , t ab This can be determined if the needle stroke pattern is sufficiently symmetrical, which is not always the case.

Claims

[1] Method for controlling an injection valve (4) for an internal combustion engine comprising the steps: - Specifying a focus area for the injection; - Determining the duration of an injection through the injection valve (4); - Calculating an injection time of the injection valve (4) depending on the center of gravity position and the duration of the injection; and - Controlling the injection valve (4) to inject the fuel based on the calculated injection time and the determined injection duration. [2] Method according to claim 1, wherein the duration of the injection is determined depending on a fuel pressure. [3] Method according to claim 1 or 2, wherein the duration of the injection is determined as the actuation duration of the injection valve (4). [4] Method according to one of the preceding claims, wherein the injection time is determined as a start or end of the control of the injection valve (4). [5] Method according to one of the preceding claims, wherein the main point of injection is specified as a time at which half of the actuation time of the injection valve (4) has elapsed. [6] Method according to one of claims 1 to 4, wherein the center of gravity of the injection is specified as a time at which half of the opening time of the injection valve (4) has elapsed. [7] Method according to one of the preceding claims, wherein the injection time is limited by at least one predetermined injection time. [8] Computing unit (3) which is configured to perform all the process steps of a process according to any of the preceding claims. [9] Internal combustion engine which is operated with a gaseous fuel and has at least one injection valve (4) and the computing unit (3) according to claim 8. [10] Computer program that causes a computing unit (3) to perform all the process steps of a method according to any one of claims 1 to 7 when executed on the computing unit (3). [11] Machine-readable storage medium with a computer program stored thereon according to claim 10.

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