Gas injector control method

Abstract

The present invention relates to a method for controlling a gas injector which injects a gaseous medium, in particular a gaseous fuel, into a combustion chamber of an internal combustion engine. The gas injector comprises a closing element for opening and closing at least one passage opening at a sealing seat, and an actuator for actuating the closing element on the basis of a control characteristic curve, the actuator being designed to open the closing element at the beginning of actuation and to close it at the end of actuation. The gas injector also comprises a stroke stop which limits the maximum stroke of the closing element. The method comprises the steps of: determining the control characteristic curve; determining a critical operating range, the critical operating range being present if the position of the closing element is undefined after reaching the stroke stop due to an opening bounce; determining whether the end of actuation is within the critical operating range; and adapting the control characteristic of the actuator so that the end of actuation is outside the critical operating range.

Description

[0001] Description

[0002] title

[0003] Control method of a gas injector

[0004] State of the art

[0005] The present invention relates to a method for controlling a gas injector to avoid critical working areas and a device for controlling a gas-powered internal combustion engine.

[0006] A large number of gas injectors are known from the prior art which inject a gaseous medium (e.g. H2 or methane) into a combustion chamber. Some of these gas injectors have closing elements with very long opening strokes in order to enable the injection of large quantities of the gaseous medium. The long opening stroke leads to high kinetic energy when the closing element opens. As a result, the closing element reaches a stroke stop at high speed and a strong opening bounce occurs. If the current supply to the closing element ends at the time of the stroke stop or shortly thereafter, the opening bounce has not yet completely subsided. Because the closing element recoils due to the opening bounce, the closing element has an undefined opening position at this time, which leads to difficult dispersion of the gas injector in this characteristic map range.

[0007] It would be desirable to have a method for controlling a gas injector that avoids opening bounce and enables precise introduction of a gas in any operating range.

[0008] Disclosure of the invention

[0009] The method according to the invention for controlling a gas injector has the advantage that a critical operating range of the gas injector is detected early on, and a control characteristic of a closing element is adjusted in such a way that precise introduction of a gaseous medium is enabled. This is achieved by a method for controlling a gas injector having the features of claim 1.

[0010] The gas injector is designed to inject a gaseous medium, in particular a gaseous fuel, into a combustion chamber of an internal combustion engine. The gas injector comprises a closing element for opening and closing at least one passage opening on a sealing seat. The sealing seat is preferably opened by a stroke movement of the closing element. An actuator actuates the closing element based on a control characteristic. The closing element is opened at the start of actuation of the actuator and closed at the end of actuation of the actuator. The gas injector further comprises a stroke stop which limits the maximum stroke of the closing element during opening. The method for controlling a gas injector comprises the step of determining the control characteristic and the end of actuation. The control characteristic is determined, for example, based on the load requirement, the quantity of fuel to be injected, the engine speed, or other parameters.The control characteristic describes, for example, a current supply characteristic of the actuator for one working cycle of the internal combustion engine. In a further step of the process, a critical operating range is determined. The critical operating range exists when the position of the closing element is undefined after reaching the stroke stop due to an opening bounce. The impact of the closing element on impact with the stroke stop is partially elastic, so that the closing element experiences an impulse in the direction of the sealing seat, which is called opening bounce. The opening bounce results in a short-term reduction in the volume flow through the gas injector and thus makes it more difficult to control the injection quantity. By continuing to supply current to the actuator, it continues to exert a force on the closing element in the direction of the stroke stop, so that the closing element is brought into a defined position at the stroke stop.To prevent the control of a precise gas injection quantity by the gas injector from being hampered due to an opening bounce, a further step of the invention determines whether the actuation end lies within the critical operating range. If the determined actuation end falls within the determined critical range, the actuator's actuation characteristic is adjusted so that the actuation end lies outside the critical operating range. However, if the determined actuation end does not fall within the determined critical range, the injection process can be carried out based on the previously determined actuation characteristic. The inventive method thus enables control of the gas injector, which enables precise gas injection in any operating range.

[0011] The subclaims show preferred developments of the invention.

[0012] Preferably, the start of the actuator's control characteristic is shifted in time when the end of the control is in the critical range. An internal combustion engine experiences changing conditions over the duration of a working cycle, which influence the occurrence of the critical operating range. By shifting the start of the control characteristic, these conditions can be deliberately exploited to ensure that the end of the control of the gas injector lies outside the critical range.

[0013] Particularly preferably, the start of the control characteristic curve is shifted backward in time if the determined end of the control lies in the determined critical operating range. The introduction of a gaseous fuel into a combustion chamber of an internal combustion engine preferably takes place during a compression stroke. During the combustion stroke, the pressure in the combustion chamber increases continuously. A higher backpressure in the combustion chamber reduces the speed with which the closing element opens the through-opening of the gas injector. This reduces the intensity of a possible opening bounce and consequently also the duration during which the position of the closing element is undefined. Consequently, by shifting the start of the control backward in time, it is possible to prevent the end of the control from falling into the critical range.

[0014] Preferably, the actuator's activation duration is extended by shifting the activation start point of the activation characteristic curve back in time. By shifting the activation start point back in time, the backpressure in the combustion chamber increases and the opening speed of the closing element decreases, thereby reducing the volume flow injected into the combustion chamber by the gas injector. Extending the actuator's activation duration compensates for the reduced volume flow caused by the delayed activation start point, so that the introduced gas mass remains constant.

[0015] The method preferably includes a step for determining a cylinder pressure in the combustion chamber, particularly as the first step of the method, in order to determine the critical operating range. The characteristics of the critical operating range can be significantly influenced by the cylinder pressure. The cylinder pressure depends on a variety of parameters, such as temperature, the time in the operating cycle, or boost pressure. By determining the cylinder pressure, the critical operating range can be determined more precisely, thus enabling more precise control of the gas injector.

[0016] In a preferred embodiment, the gas injector's injection rate is controlled exclusively by the actuator's activation duration. Controlling the gas injector's injection rate via a parameter reduces the complexity of the control system. The method according to the invention eliminates the need for any additional measures to control the opening or closing speed, such as reducing the supply pressure or adjusting the flow profile.

[0017] Further preferably, the gas injector is configured to inject the gaseous medium directly into the combustion chamber. Thus, the control characteristic and / or the start of control can preferably be adapted to the duty cycle and cylinder pressure to prevent the end of control from falling into the critical operating range.

[0018] The maximum opening stroke of the closing element is preferably 0.2 mm to 0.7 mm. This stroke range enables efficient injection of the gaseous medium at maximum opening speeds of the closing element, allowing precise control of the injection volume.

[0019] The method for controlling the gas injector preferably determines the switching dynamics of the closing element. A relevant parameter of the switching dynamics is the opening speed of the closing element, in particular shortly before reaching the stroke stop, which has a significant influence on the extent of the opening bounce. The switching dynamics can change during operation, for example due to temperature influences. Furthermore, the switching dynamics can change with the progressive aging of the gas injector. Thus, the determination of the switching dynamics can be incorporated into the determination of the critical operating range and can improve this. When operating multiple gas injectors, the determination of the switching dynamics is preferably carried out individually for each gas injector in order to adapt the control of the gas injectors to their individual switching behavior.

[0020] Furthermore, the invention relates to a device for controlling a gas-powered internal combustion engine, which comprises data acquisition means for detecting current operating parameters, such as cylinder pressure. Furthermore, the device comprises a gas injector and a controller for implementing one of the previously described methods.

[0021] Short description of the drawings

[0022] An embodiment of the invention will be described in detail below with reference to the accompanying drawings. In the drawing:

[0023] Figure 1 shows a device for controlling a gas-powered

[0024] Internal combustion engine according to a preferred embodiment,

[0025] Figure 2 shows a flow diagram of a method for controlling a

[0026] Gas injector according to a preferred embodiment,

[0027] Figure 3 is a line diagram for graphically representing a

[0028] Valve lift VH of a closing element as a function of a control duration t and the cylinder pressure, and

[0029] Figure 4 is a line diagram for graphically representing a

[0030] Injection quantity mg / VH depending on the control duration t of the closing element and the cylinder pressure.

[0031] Embodiment of the invention A device and a method for controlling a gas injector 1 according to a preferred embodiment will be described below with reference to Figures 1 to 4.

[0032] Figure 1 schematically shows an embodiment of a device for controlling a gas-powered internal combustion engine 4. The device comprises a gas injector 1, which is configured to inject a gaseous medium 2 directly into a combustion chamber 3 of an internal combustion engine 4. The gas injector 1 is arranged in a cylinder head 16 of the internal combustion engine 4.

[0033] The gas injector 1 comprises a closing element 5 for opening and closing at least one through-opening at a sealing seat 6. Furthermore, the gas injector 1 comprises an actuator 7 for actuating the closing element 5 based on a control characteristic 8.

[0034] In the exemplary embodiment, the actuator 7 has an armature 71, which is actuated electromechanically. With the aid of the armature 71, the actuator 7 is configured to open the closing element 5 at a control start 11 and to close it at a control end 12. A housing 15 of the gas injector 1 has a stroke stop 9 at the injection-side end 17 near the closing element 5, which limits a maximum stroke H of the closing element 5. Alternatively, the stroke stop 9 could also be arranged in the actuator and limit the movement of the armature 71 in the actuator 7.

[0035] The device further comprises a data acquisition means 13. The data acquisition means 13 is configured to acquire operating parameters of the internal combustion engine 4. The operating parameters include data from the gas injector 1, such as its switching dynamics, as well as data from the cylinder head and combustion chamber 3. The data acquisition means 13 is configured, for example, to acquire the cylinder pressure, temperatures, and / or the position data of the closing element 5. Alternatively, the data acquisition means 13 can also be divided into several individual data acquisition means 13.

[0036] The device further comprises a control unit 14 configured to receive the information from the data acquisition means 13. Based on the required injection quantity for operating the internal combustion engine 4 and the operating data of the internal combustion engine 4, the control unit 14 controls the actuator 7 of the gas injector 1. The control unit 14 is configured to carry out the previously described method for controlling a gas injector 1.

[0037] Figure 2 describes a preferred embodiment of a method for controlling a gas injector 1.

[0038] In a first step S1, a control characteristic curve 8 of the actuator 7 is determined for a defined injection quantity of a gaseous medium 2 into an internal combustion engine 4 in order to control the closing element 5 of the gas injector 1. The closing element 5 is designed to open and close the through-opening at the sealing seat 6. The control characteristic curve 8 comprises a control start 11 and a control end 12. The actuator 7 preferably has an armature 71 which is electromechanically actuated and is mechanically connected to the closing element 5. The actuator 7 is preferably constantly energized between the control start 11 and the control end 12, whereby the closing element 5 is opened up to the stroke stop 9 and is held open at the stroke stop 9 until the control end 12. The stroke stop 9 can be designed in different ways. With a short control duration, the energization end can occur before the closing element 5 has reached the stroke stop 9.

[0039] In a second step S2, a critical operating range 10 is determined. The critical operating range 10 exists when the position of the closing element 5 is undefined after reaching the stroke stop 9 due to an opening bounce. The position of the closing element 5 is undefined if the closing element 5 or the armature 71 does not rest against the stroke stop 9 due to the opening bounce.

[0040] Alternatively, it is also possible to first determine the critical operating range and then determine the control characteristic, or to run both steps in parallel.

[0041] Due to the high flow requirements, gas injectors 1 have a large stroke of the closing element 5. Depending on the desired flow requirement, the stroke of the closing element 5 is, for example, between 0.2 mm and 0.7 mm. As a result, the armature 71 or the closing element 5 reaches the stroke stop 9 at a high speed. Upon reaching the stroke stop 9, an impact with an elastic component occurs, resulting in an opening bounce, in which the closing element 5 briefly springs in the closing direction and reduces the through opening.

[0042] The intensity of the opening bounce depends in particular on the speed of the armature 71 or closing element 5 when reaching the stroke stop 9. Other influencing factors can be, for example, the temperature of the gas injector 1 or the aging state of the gas injector 1. The speed of the armature 71 and closing element 5 depends, among other things, on the pressure ratio between the pressure of the gaseous medium 2 to be injected and the pressure on the injection side of the gas injector 1, such as in a combustion chamber 3. The higher the pressure on the injection side and the lower the pressure of the gaseous medium 2 to be injected, the lower the speed of the armature 71 and closing element 5 at the stroke stop 9.

[0043] In a third step S3, it is determined whether the previously determined control end 12 lies within the critical operating range 10. Due to the undefined position of the closing element 5, precise control of the injection quantity of the gaseous medium 2 is difficult.

[0044] If the determined control end 12 is not in the critical working range 10, no adjustment of the control characteristic 8 follows in step S42 and the actuator 7 of the gas injector 1 is actuated with the previously determined control characteristic 8.

[0045] If the determined control end 12 lies in the critical working range 10, the control characteristic curve 8 is adapted in step S41 so that the control end 12 lies outside the critical working range 10.

[0046] The gas injectors 1 according to the invention can be used in particular in internal combustion engines 4 and inject a gaseous fuel directly into the combustion chamber 3. The injection takes place particularly during the compression cycle. By shifting the control characteristic curve 8 to a later point in time during the compression cycle, the closing element 5 opens at a higher pressure in the combustion chamber 3, thereby reducing the speed upon reaching the stroke stop 9 and reducing or avoiding the opening bounce.

[0047] Alternatively, the actuation current of the actuator 7 and / or the pressure of the gas to be injected can be reduced in order to reduce the opening bounce and thus ensure that the actuation end 12 does not fall into the critical working range 10.

[0048] Figure 3 shows the valve lift VH of the closing element 5 as a function of a control duration t of three identical control characteristic curves 8 at different cylinder pressures p1, p2 and p3 at the time of the start of control 11. Here, p1 describes a cylinder pressure of 1.2 bar, p2 a cylinder pressure of 3 bar and p3 a cylinder pressure of 5 bar.

[0049] As can be seen in Figure 3, at cylinder pressure p1 the closing element 5 opens more quickly after the start of control 11 than at a higher cylinder pressure p2 or p3. The maximum valve lift VHmax is therefore reached first at p1. The kinetic energy of the closing element 5 means that the valve lift VH of the closing element is briefly higher than the maximum valve lift VHmax. Due to the higher speed of the closing element 5 at the lift stop 9 at pressure p1 than at a pressure p2 or p3, the opening bounce, after which the valve lift VH is briefly reduced, is greater at p1 than at p2 or p3. After the opening bounce, the closing element 5 has an undefined position during operation until it reaches the maximum valve lift VHmax again at a lower speed. The area in which the position of the closing element 5 is undefined is marked in Figure 3 by the critical operating range 10.

[0050] After the critical operating range 10, the closing element 5 is in a defined position at the maximum valve lift VHmax until the control end 12. After the control end 12, the closing element 5 moves back toward the sealing seat 6.

[0051] Figure 4 shows the injection quantity mg / VH of a stroke as a function of the control duration t for different cylinder pressures p1, p2 and p3 at the time of start of control 11. After a short, sharp increase at the beginning of start of control 11, the injection quantity increases progressively as a function of the control duration until the closing element 5 has reached the maximum valve lift at the stroke stop 9. After reaching the stroke stop 9, there is a strong characteristic map ripple in the critical operating range 10, which makes precise control of the injection quantity difficult. After the critical operating range 10, the injection quantity increases proportionally to the control duration. At a low cylinder pressure p1, the injection quantity is higher for the same control duration than at a higher cylinder pressure p2 or p3.

[0052] For a defined injection quantity mg1 / VH, the first control end t1 for a cylinder pressure p1 falls within the critical operating range 10, making precise control of the injection quantity more difficult. By shifting the start of control 11 to a time with a higher cylinder pressure p3, a longer control duration is required to achieve the same injection quantity, so that the second control end t2 lies outside the critical operating range 10, enabling precise control of the injection quantity. By shifting the control time to a time with a higher cylinder pressure, the opening bounce is also reduced, which improves injection accuracy.

[0053] For an injection quantity mg2 / VH, the first control end t1 for a cylinder pressure p2 falls within the critical operating range 10, making precise control of the injection quantity more difficult. By shifting the start of control 11 to a time with a lower cylinder pressure p1, a shorter control duration is required to achieve the same injection quantity, so that the third control end t3 can occur before the closing element 5 reaches its maximum stroke. Thus, no opening bounce occurs during the injection process, enabling precise control of the injection quantity.

Claims

Claims 1. A method for controlling a gas injector (1) which injects a gaseous medium (2), in particular a gaseous fuel, into a combustion chamber (3) of an internal combustion engine (4), and which comprises a closing element (5) for opening and closing at least one through-opening on a sealing seat (6), an actuator (7) for actuating the closing element (5) on the basis of a control characteristic curve (8), wherein the actuator (7) is configured to open the closing element (5) at a control start (11) and to close it at a control end (12), and a stroke stop (9) which limits a maximum stroke (H) of the closing element (5), comprising the steps: Determine the control characteristic (8), Determining a critical working area (10), wherein the critical working area (10) exists when the position of the closing element (5) is undefined after reaching the stroke stop (9) due to an opening bounce, Determine whether the control end (12) is in the critical working area (10), and Adjusting the control characteristic (8) of the actuator (7) so that the control end (12) lies outside the critical working range (10).

2. Method for controlling a gas injector (1) according to claim 1, wherein the start of control (11) of the control characteristic (8) is shifted in time when the end of control (12) lies in the critical operating range (10).

3. Method for controlling a gas injector (1) according to claim 2, wherein the start of control (11) of the control characteristic (8) is shifted backward in time when the end of control (12) lies in the critical operating range (10).

4. Method for controlling a gas injector (1) according to claim 3, wherein the control duration of the actuator (7) is extended in time if the start of control (11) of the control characteristic curve (8) is shifted backward in time.

5. Method for controlling a gas injector (1) according to one of the preceding claims, comprising a step for determining a cylinder pressure in order to determine the critical working range (10).

6. Method for controlling a gas injector (1) according to one of the preceding claims, wherein an injection quantity of the gas injector (1) is controlled exclusively by a control duration of the actuator (7).

7. Method for controlling a gas injector (1) according to one of the preceding claims, wherein the gas injector (1) is designed to inject the gaseous medium (2) directly into the combustion chamber (3).

8. Method for controlling a gas injector (1) according to one of the preceding claims, wherein a maximum opening stroke (H) of the closing element (5) is 0.2 mm to 0.7 mm.

9. Method for controlling a gas injector (1) according to one of the preceding claims, comprising a step for determining a switching dynamics of the closing element, wherein the determined switching dynamics are incorporated into the determination of the critical operating range.

10. Device for controlling a gas-powered internal combustion engine (4), comprising data acquisition means (13) for detecting current operating parameters of the internal combustion engine (4), a control unit (14) and at least one gas injector (1), which are configured to carry out a method according to one of the preceding claims.

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