Method for controlling gas injectors in internal combustion engines

Abstract

The present invention relates to a method for controlling a gas injector of an internal combustion engine, wherein an injector valve needle (1) is moved to an open position by electromagnetic actuation to set the gas flow rate introduced into the internal combustion engine. The method is characterized in that, during the period when the power supply is cut off and the injector valve needle (1) returns to the closed position, the triggering time (t0) for generating a braking current pulse (23) to electromagnetically decelerate the injector valve needle (1) is determined by comparing an electromagnetically generated current (21) measured at each corresponding time and after eliminating the influence of electromagnetic self-induction with a predetermined comparison current value (I0).

Description

Technical Field

[0001] The present invention relates to a method for controlling a gas injector of an internal combustion engine, the method being of the type more specifically defined in the preamble of claim 1. Background Technology

[0002] A method for controlling a fuel injection valve is known from GB 2 552 516 A, wherein an actuator is provided for actuating a needle valve, and the needle valve is moved away from the valve seat to open the valve by an activation signal, the activation signal including a subsequent braking pulse, which is designed to slow the speed of the needle valve as it returns to the closed position when the valve subsequently closes.

[0003] DE 10 2014 203 538 A1 discloses a method for controlling a switchable valve in an internal combustion engine, wherein a braking pulse for valve movement is generated based on the supply voltage of the valve.

[0004] DE 10 2014 202 106 B3 discloses a method for operating an injection valve with closing speed control, which uses the actual closing speed of the valve needle derived from the time between the braking moment and the sensing signal as the control quantity.

[0005] DE 10 2009 000 132 A1 discloses a method for operating an injection valve, wherein the valve closing hysteresis time is measured and the braking pulse is adjusted accordingly.

[0006] A valve control method is known from WO 2016 / 062 494 A1, in which the length and timing of a braking pulse are adjusted by a specific event (such as a discontinuity in the second derivative of a voltage or current change, or a zero segment in its first derivative).

[0007] DE 10 2011 005 672 A1 discloses a method for operating an actuator, wherein a stop position is predetermined and the basis for determining the armature collision time is the time variation of current intensity.

[0008] Finally, DE 10 2010 063 009 A1 proposes to derive a braking pulse for the fuel injector based on a comparison between the hysteresis and a predetermined hysteresis. Summary of the Invention

[0009] The objective of this invention is to provide a method of the type described above, which can reduce wear on gas injectors and improve operational reliability during operation.

[0010] This task is achieved by the features of claim 1. Further advantageous and claimed embodiments can be derived from the dependent claims, the description, and the drawings.

[0011] Therefore, a method for controlling a gas injector in an internal combustion engine is proposed, wherein an injector valve needle is moved to an open position by electromagnetic actuation to set the gas flow rate introduced into the internal combustion engine. During the return of the injector valve needle to the closed position when power is cut off, a triggering moment for generating a braking current pulse to electromagnetically decelerate the injector valve needle is determined by comparing an electromagnetically generated current measured at each corresponding moment and after eliminating the influence of electromagnetic self-induction with a predetermined comparison current value.

[0012] In this way, targeted and reliable electromagnetic deceleration of the injector valve needle can be ensured in electromagnetically actuated gas injectors, thereby reliably avoiding mechanical wear or damage to the injector valve needle and / or valve seat when the injector valve needle contacts the valve seat.

[0013] Since the total current measured during the return period has been corrected for the self-induced current generated by the magnetic field decay when the power supply is cut off, this corrected current can be linearly mapped to a certain speed of the injector valve needle driven by the return. Furthermore, by comparing it with a predetermined comparison current value, the deceleration triggering time can be accurately determined in a simple manner. This reliably avoids both late triggering causing seating at high speeds and early triggering causing the injector valve needle to reverse its movement, resulting in seating at higher speeds and a longer closing time.

[0014] In a preferred embodiment, the current generated by electromagnetic self-induction at each corresponding moment is stored as a predetermined current value corresponding to that moment. Therefore, by subtracting this stored current value corresponding to the corresponding moment from the electromagnetically generated current measured at the corresponding moment during the return period, the correction current, after eliminating the influence of self-induction, can be calculated. In this way, the deceleration trigger moment can be determined very quickly after the injector valve needle begins to return, because the proposed method only requires performing a single subtraction calculation to obtain the correction current.

[0015] Preferably, the stored current value is predetermined by experiment and corresponds to the measured current generated by electromagnetic induction at each corresponding moment when the power supply is cut off.

[0016] Preferably, the current generated by electromagnetic self-induction at each corresponding moment is determined by a single experiment in a simple manner according to its type, and stored as a curve of current change over time. Other effects, especially eddy current effects, can also be considered here.

[0017] For example, a test can be conducted with the power supply to the electromagnetic actuation cut off and the electromagnetic actuation component (especially the armature of the electromagnet) fixed, and the self-induced current can be measured as a time curve.

[0018] Therefore, the proposed method can be implemented using a programmable control unit already equipped in the internal combustion engine, which in particular includes current measurement and a programmable integrated circuit (FPGA) that allows the implementation of digital circuits. Accordingly, the proposed method can be implemented as a pure software application in the internal combustion engine without the need for additional hardware.

[0019] In another preferred embodiment of the invention, the comparison current value used to determine the triggering time of the braking current pulse is pre-optimized through experimentation, particularly to minimize the impact velocity of the injector valve needle and its closing duration. Thus, the proposed method can execute the braking current pulse for electromagnetic deceleration of the injector valve needle with extremely high precision, thereby minimizing the closing duration and the impact velocity of the injector valve needle. This high precision allows deceleration to be performed with particularly high intensity and short duration, resulting in very short closing times and very high metering accuracy.

[0020] In a further improvement of the invention, a freewheeling diode is connected during the return period of the injector valve needle when the power supply is cut off. In this way, the electromagnetically generated current during the return period is attenuated only through an existing resistor (e.g., the electromagnetic coil of an electromagnet), thus the current change is no longer affected by other factors, especially the current controller. This facilitates continuous measurement of the electromagnetically generated current during the return period.

[0021] In a further improvement, a capacitor is connected to electromagnetically decelerate the injector valve needle, and the braking current pulse is amplified by the current from this capacitor. By connecting this capacitor, a strong and short deceleration of the injector valve needle can be achieved, ensuring its rapid return without delaying the closing process, while maintaining the high metering accuracy of the gas injector.

[0022] Braking can also be performed initially using only the capacitor current, and then, in order to achieve a gentle landing, braking can be performed using a current from the internal combustion engine's onboard electrical system, which is slightly lower than the holding current.

[0023] Preferably, before the injector valve needle returns to its original position and when the power supply is cut off, the capacitor is connected with opposite polarity to eliminate residual current. In this way, the closing process is accelerated.

[0024] Preferably, the same conditions are always established by means of a predetermined fixed voltage for the capacitor and a predetermined fixed duration for the discharge phase, at the end of the phase and at the start of each injection cycle return.

[0025] Preferably, at the end of the opening and holding phase, the current used to hold the injector valve needle in the open position is adjusted to a predetermined fixed value. Thus, in each injection cycle, the same conditions are always established before the start of the aforementioned discharge phase.

[0026] Furthermore, it is preferable to connect a capacitor, especially when the injector valve needle is electromagnetically actuated to move to the open position, to increase the voltage and accelerate the opening process.

[0027] Preferably, the braking current pulse used for electromagnetic deceleration of the injector valve needle occurs within 0.3 milliseconds after the injector valve needle begins to return to its original position. This allows for particularly rapid closure of the injector valve needle with exceptionally high metering accuracy.

[0028] Furthermore, advantageously, through electromagnetic deceleration, the injector valve needle is slowed to a speed of less than or equal to 0.5 m / s during return. This minimizes wear on the injector valve needle and seat during closure and reliably prevents damage.

[0029] Other claimed features of the invention will become apparent from the following description and the accompanying drawings, by which the invention will be further described. The drawings are as follows: Attached Figure Description

[0030] Figure 1 The graph shows the changes over time in the current, voltage, and the stroke and speed of the injector valve needle corresponding to the electromagnetic actuation during one injection cycle of a gas injector for an internal combustion engine. Figure 2 A cross-sectional view of a gas injector for an internal combustion engine; Figure 3 The electromagnetic current generated during the return of the injector valve needle varies with time and is related to the speed of the injector valve needle. Figure 4 The time variation of the self-induced current was determined by testing under the condition that the injector valve needle was fixed and the power supply was cut off; Figure 5 The electromagnetically generated, calculated correction current varies with time during the return of the injector valve needle and is related to the speed of the injector valve needle. Detailed Implementation

[0031] See Figure 1 The method for controlling a gas injector for an internal combustion engine according to the present invention is illustrated by way of example. The graph, starting from the left edge, shows the time variation of the entire injection cycle from opening the gas injector to introduce gas (preferably hydrogen) into the combustion chamber of the internal combustion engine to closing it and cutting off the gas supply to the combustion chamber.

[0032] like Figure 2The exemplary gas injector shown has a gas inlet 22 and an injector valve needle 1 for metering the gas introduced into the combustion chamber of an internal combustion engine. The injector valve needle 1 is longitudinally movable along a displacement axis 2 and is directly actuated by an electromagnet integrated within the gas injector. By powering the electromagnet's coil 3, the injector valve needle 1 can be moved by means of an actuating member (here, the electromagnet's armature 4) arranged coaxially with respect to the injector valve needle 1. Figure 2 The closed position shown is axially moved to the open position (not shown) to allow gas to be introduced into the combustion chamber. Figure 2 Move to the right within the plane.

[0033] The armature 4 can be fixedly connected to the injector valve needle 1 to actuate it. It is also conceivable that the armature 4 and the injector valve needle 1 can be arranged in a detachable manner.

[0034] like Figure 2 As shown, the injector valve needle 1 is longitudinally slidably supported within the multi-component housing 5 of the gas injector. It has a valve body 6 at its axial end facing the valve, which is arranged in a valve seat 7 formed on the housing 5 and is used to set the gas flow rate introduced into the combustion chamber of the internal combustion engine (not shown). Figure 2 The closed position of the gas injector is shown, in which the valve body 6 is sealed against the valve seat 7 of the housing 5 in an airtight manner.

[0035] By powering the electromagnet's coil 3, the injector valve needle 1 can be moved to an open position (not shown) using the electromagnet armature 4, which is movably arranged coaxially with respect to the injector valve needle 1. In this case, a return spring 8, which acts between the injector valve needle 1 and the housing 5 and is arranged coaxially with respect to the injector valve needle 1, is preloaded. This return spring 8 is made of a helical compression spring. In the open position, a flow gap is formed between the valve body 6 and the valve seat 7, through which gas can flow into the combustion chamber of the internal combustion engine.

[0036] After the power supply to the electromagnetic coil 3 of the electromagnet is cut off, the injector valve needle 1 returns to the closed position under the elastic force of the preloaded return spring 8. During the return of the injector valve needle 1 to the closed position, it is in contact with the valve seat 7.

[0037] To avoid wear and damage to the injector valve needle 1 and valve seat 7, an electromagnetic coil 3 of an electromagnet is used. Figure 1 A braking current pulse 23 is generated, which electromagnetically decelerates the injector valve needle 1 by the armature 4 during the closing process, so that it can gently contact the valve seat 7. Through the braking current pulse 23, a force is applied to the armature 4 in the opening direction, thereby braking its movement.

[0038] The electromagnetic coil 3 of the electromagnet is powered by a battery from an internal combustion engine (not shown).

[0039] exist Figure 1 In the graph, the change in current in electromagnetic coil 3 is represented by curve 9, the change in voltage in electromagnetic coil 3 is represented by curve 10, the change in axial stroke of armature 4 and injector valve needle 1 is represented by curve 11, and the change in velocity of injector valve needle 1 and armature 4 is represented by curve 12, all of which are functions of time t.

[0040] To open the gas injector, in the start-up phase 13, indicated by a double arrow parallel to the time axis, a capacitor (not shown) is connected to increase the voltage of the electromagnetic coil 3 relative to the battery voltage (curve 10) and accelerate the opening process. During this process, the current in the electromagnetic coil 3 (curve 9) rises sharply, and the injector valve needle 1 moves toward the open position along with the axial travel (curve 11). Figure 2 Within the plane, it moves to the right, and its velocity (curve 12) increases sharply.

[0041] In the opening and holding phase 14, indicated by another double arrow, the injector valve needle 1 moves to the open position with a further axial travel (curve 11) and a further increasing speed (curve 12), at which position the injector valve needle 1 stops and the speed (curve 12) is zero. In the open position, the injector valve needle 1 is held with a constant travel (curve 11). The current (curve 9) and voltage (curve 10) decrease and, relative to the starting phase 13, vary slightly at a lower level, maintaining the injector valve needle 1 in the open position through on / off control. During the holding period, a certain holding current I is maintained. H It flows over the average value, quickly switching between "hold" and "free run".

[0042] Before the injector valve needle 1 returns to the closed position, in discharge phase 15, indicated by another double arrow, the power supply to the solenoid coil 3 is cut off (curve 9), and a capacitor is connected with opposite polarity to eliminate residual current. The same conditions are always established at the end of this phase and at the beginning of the return phase of each injection cycle, i.e., at the start of detection phase 16, through a predetermined fixed voltage on the capacitor and a predetermined fixed duration of discharge phase 15. The same applies to the holding current I used to hold the injector valve needle 1 in the open position at the end of opening and holding phase 14 and the beginning of discharge phase 15. H .

[0043] Simultaneously with disconnecting the capacitor, a current controller cuts off the power supply from the battery. Current continues to flow through the solenoid coil 3 via a freewheeling diode. Subsequently, in detection phase 16, indicated by another double arrow, the process of the injector valve needle 1 returning to the closed position begins. The return is carried out by the elastic force of the return spring 8, the axial travel (curve 11) retracts to the closed position, and the speed of the armature 4 and the injector valve needle 1 (curve 12) increases. With the power supply cut off, the self-induced current (curve 9) caused by the attenuation of the magnetic field within the solenoid coil 3 and the movement of the armature 4 within the solenoid coil 3 is dissipated only through the resistance of the solenoid coil 3, so the changes in current and voltage (curves 9 and 10) are no longer affected by other factors, such as the current controller. During this process, the current generated during the return of the armature 4 (curve 9) is measured, which mainly includes the current component generated by self-induction.

[0044] During detection phase 16, the total current (curve 9) measured in the electromagnetic coil during the return phase (which does not exclude the current component generated by self-induction) and the simultaneously measured velocities of the injector valve needle 1 and armature 4 (curve 12) are plotted in separate graphs ( Figure 3 Its time variation is shown in the figure.

[0045] To determine the triggering time t0 for triggering the braking current pulse 23 to decelerate the injector valve needle 1, during the detection phase 16 ( Figure 1 In the process of the injector valve needle 1 and armature 4 returning to their original positions, the pre-stored current values ​​corresponding to each corresponding moment are used to... Figure 4 The corrected current value is calculated by subtracting the total current value (curve 9) measured at each corresponding time from curve 17. Figure 5 (Curve 21 in the text).

[0046] Among them, the storage current value corresponding to each corresponding time ( Figure 4 Curve 17 in the graph corresponds to the current generated at that corresponding moment by the electromagnetic self-induction caused by the decay of the magnetic field of the electromagnetic coil 3 when the power supply is cut off. The time variation of this stored current value is shown in a separate graph. Figure 4 Curve 17 is shown.

[0047] The corrected current value, calculated at each corresponding moment and after eliminating the current component generated by self-inductance, is expressed in the form of time variation. Figure 5 This is shown as curve 21 in a separate chart. Thus, the calculated corrected current value corresponds to the current generated at each corresponding moment during the return period due to the movement of armature 4, and this current varies over time substantially proportional to the velocity of armature 4 and injector valve needle 1. Figure 5 Therefore, each correction current value ( Figure 5Curve 21 in the figure) corresponds to a certain velocity of armature 4 and injector valve needle 1 at each corresponding moment. Figure 5 Corresponding to curve 12 in the text.

[0048] In the detection phase 16 ( Figure 1 In the calculation of the correction current value at each corresponding moment during the armature 4 return period, the correction current value is ( Figure 5 Curve 21 in the figure is compared with another pre-stored comparison current value I0, which corresponds to a predetermined speed of armature 4 and injector valve needle 1. Figure 5 (Curve 12 in the text).

[0049] Once the predetermined comparison current value I0 is identified as the correction current value ( Figure 5 Curve 21 in the figure shows that the deceleration trigger time t0 is reached, and in Figure 1 Braking phase 19 is indicated by another double arrow in the diagram. Figure 1 Within the ), a braking current pulse 23 is generated to electromagnetically decelerate the injector valve needle 1.

[0050] The corrected current value is calculated in this way ( Figure 5 The curve 21 in the figure and the pre-stored comparison current value I0 together determine the triggering time t0 for the braking current pulse 23. Preferably, the comparison current value I0 is determined experimentally, especially for the optimal triggering time t0 that minimizes the closing duration of the injector valve needle 1 at the valve seat 7 and minimizes the impact velocity v1, with an execution accuracy of ±0.05 milliseconds. High accuracy allows the deceleration of the injector valve needle 1 to be performed with particularly large intensity and particularly short duration, thereby obtaining a very short closing time and very high metering accuracy.

[0051] The braking current pulse 23 occurs within 0.3 milliseconds after the injector valve needle 1 begins to return to its original position.

[0052] At the beginning of braking phase 19, a capacitor is connected in enhancement phase 18, and the braking current pulse 23 (curve 9) is enhanced by the current from this capacitor. By connecting this capacitor, a strong and short deceleration of the injector valve needle 1 can be achieved. Therefore, at the closing moment t1, when the stroke (curve 11) is reduced to zero, the injector valve needle 1 contacts the valve seat 7 with a significantly reduced impact velocity v1 (less than or equal to 0.5 m / s) and is once again in a state of... Figure 2 The indicated closed position. This completes one injection cycle for the gas injector.

[0053] With the power supply cut off, the current generated by electromagnetic self-induction at corresponding moments due to the attenuation of the magnetic field of electromagnetic coil 3 is measured by a single test according to its type and stored as a time variation. This time variation is represented by the so-called static curve 17 ( Figure 4 As shown in the figure, the velocity 18 of the fixed armature 4 or the fixed injector valve needle 1 is marked as zero.

[0054] For this purpose, armature 4 is locked by a simple mechanical means, such as fixing the injector valve needle 1 in the open position once and executing the usual closing sequence. In this way, for the same type, the time variation of the current can be measured once and stored in the control device. All complex effects, especially self-inductance and eddy current effects, have been taken into account in this time variation.

[0055] During the homing period, the correction current value obtained by subtracting the values ​​at each corresponding moment varies over time. Figure 5 Another graph shows this as a correction curve 21, which is correlated with the velocity of the injector valve needle or armature (curve 12). Over the time interval t1 leading to closure, the velocity (curve 12) is substantially proportional to the change in the correction current value (curve 21).

[0056] Therefore, figuratively speaking, at any given moment, the correction current value ( Figure 5 Curve 21 in the middle can be obtained from the detection phase 16 ( Figure 1 The uncorrected original curves 9 (measured at each corresponding time) Figure 3 Subtract from Figure 4 The static curve 17 is obtained.

[0057] The proposed method can be implemented using a programmable control unit (FPGA) already integrated into the internal combustion engine. This control unit is programmable at multiple stages and includes current measurement and a programmable integrated circuit (FPGA) that allows for the implementation of digital circuitry. This enables the calculation of the trigger timing for deceleration to be performed simply and quickly using conventional computing power. Accordingly, the proposed method can be implemented as a pure software application in the internal combustion engine without the need for additional hardware.

[0058] Explanation of reference numerals in the attached figures 1. Injector valve needle 2. Displacement axis 3. Electromagnetic coil 4. Armature 5. Housing 6 Valve body 7 Valve seat 8. Return spring component, helical compression spring 9. Curve, time curve of electromagnetic coil current 10. Curve, time curve of electromagnetic coil voltage 11. Curve time curve of axial travel of injector valve needle / armature. 12. Time curve of injector valve needle / armature velocity. 13. Start-up Phase 14. Start-up and Maintenance Phase 15 Discharge Stage 16. Testing Phase 17. Stored "static" curves, current measurement time curves. 18. The calculated correction curve and the time curve for calculating the differential current value. 19. Braking Phase 20 Enhancement Phase Curve 21: Time curve of differential current value 22 Gas Interface 23 Braking current pulse t time t0 trigger time I0 is the predetermined comparison current value used to trigger the braking current pulse. I H Maintaining current t1 Closure time v1 Impact velocity of the injector valve needle

Claims

1. A method for controlling a gas injector in an internal combustion engine, wherein an injector valve needle (1) is moved to an open position by electromagnetic actuation to set the gas flow rate introduced into the internal combustion engine, characterized in that, When the power supply is cut off, during the period when the injector valve needle (1) returns to the closed position, the triggering time (t0) for generating braking current pulses (23) to electromagnetically decelerate the injector valve needle (1) is determined by comparing the electromagnetic generating current (21) measured at each corresponding time and after eliminating the influence of electromagnetic self-induction with a predetermined comparison current value (I0).

2. The method as described in claim 1, characterized in that, The current (17) generated by electromagnetic self-induction at each corresponding moment is stored as a predetermined current value corresponding to that moment, and the correction current (21) generated by electromagnetic self-induction at each corresponding moment is calculated by subtracting the current value (17) from the electromagnetic generated current (9) measured at each corresponding moment during the return period.

3. The method as described in claim 1 or 2, characterized in that, The comparison current value (I0) used to trigger the braking current pulse (23) is determined in advance through experimental optimization aimed at minimizing the impact velocity (v1) of the injector valve needle and its closing duration.

4. The method according to any one of claims 1 to 3, characterized in that, With the power supply cut off, a freewheeling diode is connected during the return of the injector valve needle (1), and the current (9) generated electromagnetically by the return is measured.

5. The method according to any one of claims 1 to 4, characterized in that, A capacitor is connected to electromagnetically decelerate the injector valve needle (1), and the current from the capacitor is used to enhance the braking current pulse (23).

6. The method according to any one of claims 1 to 5, characterized in that, Before the injector valve needle (1) returns to its original position and in the case of power cut-off, a capacitor is connected with opposite polarity to eliminate residual current, and a predetermined fixed voltage and a predetermined fixed time are used for the duration.

7. The method according to any one of claims 1 to 6, characterized in that, At the end of the holding phase (14), the current (I) used to hold the injector valve needle (1) in the open position will be applied. H Adjust to the predetermined fixed value.

8. The method according to any one of claims 1 to 7, characterized in that, When the injector valve needle (1) is electromagnetically actuated to move to the open position, a capacitor is connected to increase the voltage and accelerate the opening process.

9. The method according to any one of claims 1 to 8, characterized in that, The braking current pulse (23) used to electromagnetically decelerate the injector valve needle (1) occurs within 0.3 ms after the injector valve needle (1) begins to return to its original position.

10. The method according to any one of claims 1 to 9, characterized in that, The speed of the injector valve needle (1) is reduced to less than or equal to 0.5 m / s by electromagnetic deceleration.

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