Method for shifting time of gas injection in cylinders of direct-injection gas internal combustion engine having plurality of cylinders

Abstract

The invention relates to a method for shifting a gas injection time in a cylinder (6) of a direct-injection gas internal combustion engine (2) having a plurality of cylinders (6), in particular a hydrogen engine, from a first injection time (t1) to a second injection time (t2), the gas internal combustion engine (2) being first operated in a first operating mode, the gas internal combustion engine (2) is operated in a mode in which the gas is injected into each of the plurality of cylinders at a first injection time (t1) with the respective cylinder itself as a reference gas, the gas internal combustion engine (2) is subsequently operated in an offset operating mode, and the gas internal combustion engine (2) is ultimately operated in a second operating mode, in this mode, the gas is injected into each of the plurality of cylinders (6) at a second injection time (t2) using each cylinder itself as a reference gas. And in the offset operation mode, the interval between the offset starting moment of the first to-be-switched air cylinder in the multiple air cylinders and the offset ending moment of the last to-be-switched air cylinder in the multiple air cylinders is more than one working cycle by taking the first to-be-switched air cylinder as a reference.

Description

Technical Field

[0001] The present invention relates to a method for shifting the gas injection timing in the cylinders of a direct-injection gas internal combustion engine, particularly a hydrogen engine, having multiple cylinders from a first injection timing to a second injection timing, and also relates to a computing unit for performing the method and a computer program. Background Technology

[0002] To ensure combustion stability in hydrogen engines while limiting nitrogen oxide emissions, the injection timing can be selected based on operating conditions. For engines that inject hydrogen into the combustion chamber via a direct injection system, hydrogen can be injected either during open valve injection (OVI) or closed valve injection (CVI). In the first case, hydrogen displaces the intake air, while this effect is avoided in the second case. Therefore, during steady-state operation, condition-dependent optimizations can be performed to reduce nitrogen oxide emissions and provide advantages in achievable torque and power. In this case, the air displacement effect is taken into account in the steady-state target value of cylinder charge.

[0003] During transient engine operation, especially in the air system due to inertia, it is often impossible to adjust the boost pressure and the resulting cylinder charge to the target value in real time. Therefore, when switching from closed valve injection (CVI) to open valve injection (OVI) or vice versa, combustion instability may occur. Summary of the Invention

[0004] According to the present invention, a method for shifting the gas injection timing in the cylinders of a direct-injection gas internal combustion engine having multiple cylinders from a first injection timing to a second injection timing is proposed, along with a computing unit and a computer program for performing the method. Advantageous embodiments are the subject matter of the dependent claims and the following description.

[0005] This invention improves the offsetting or switching of injection timing in direct-injection gas internal combustion engines with multiple cylinders, particularly hydrogen engines. It enables offsetting from a first injection timing (especially during intake valve opening in gas internal combustion engines) to a second injection timing (especially during intake valve closing), or vice versa. In this process, feedback to the air system and supercharging system is significantly reduced, and the accuracy of fresh air quality detection is improved.

[0006] To address this, the present invention employs the following measure: taking the first cylinder to be switched as a reference, the interval between the start time of the offset of the first cylinder to be switched and the end time of the offset of the last cylinder to be switched exceeds one working cycle (e.g., for a four-stroke engine, the interval exceeds 720°KW). In embodiments of the present invention, the interval between the start time of the offset of the first cylinder to be switched and the end time of the offset of the last cylinder to be switched may exceed two working cycles.

[0007] Here, the injection timing is based on each specific cylinder, for example, it can be defined based on the cylinder's duty cycle and / or top dead center (ZOT). For example, the injection timing when the intake valve is open is during the intake stroke, that is, for a four-stroke engine, it is between 360°KW and 180°KW before ZOT. The injection timing when the intake valve is closed is during the compression stroke, that is, between 180°KW and 0°KW before ZOT. Global expressions related to the duty cycle or crankshaft angle (°KW), or expressions without a reference point, are conventionally referred to as "Cylinder 1", which, for convenience, is the first cylinder to be switched.

[0008] The start time of the offset of a certain cylinder refers to the moment when the cylinder stops injecting into the cylinder for the first time in the first operating mode; the end time of the offset of a certain cylinder refers to the moment when the cylinder starts injecting into the cylinder for the first time in the second operating mode in the second injection time.

[0009] In conventional technology, a rapid or digital transition is used between the two injection moments (or two injection modes, especially valve-open injection (OVI) and valve-closed injection (CVI)) of all cylinders, resulting in a complete air displacement effect occurring within a very short time. This causes the fresh air mass flow rate gradient to reach its maximum, and the air system must suppress this change, for example, through abrupt responses from the turbocharger regulator or throttle position. This invention provides a remedy because, from the air system's perspective, a significantly smoother transition is achieved, resulting in a significantly weaker response from the charge regulation. This reduces disruption to the air system during switching.

[0010] According to one embodiment, a respective offset start time is set for at least one of a plurality of cylinders, particularly for each cylinder, and the interval between this time and the offset start time of at least one other, preferably all other, cylinders is at least two ignition intervals, based on the first cylinder to be switched. Preferably, at least two ignition intervals exist between the offset start time of at least one cylinder and the offset start time of at least another cylinder. This is, for example, in... Figure 2 and Figure 5 As shown in the image.

[0011] Measurements on the engine test bench revealed that for direct-injection hydrogen engines, this zylinder-individuelle, time-sequential switching method between injection moments such as open-valve injection (OVI) and closed-valve injection (CVI) offers advantages in air quality measurement and combustion stability. By switching the injection moments of each cylinder non-synchronously, but at time intervals, transient feedback to the air system can be distributed over time, making it easier to track boost pressure and the resulting cylinder charge. Furthermore, it reduces unwanted feedback to the air system, such as pressure fluctuations within the intake manifold. Therefore, during the switching process, both charge regulation and combustion regulation are improved and stabilized.

[0012] During this process, the timing characteristics of the sequential switching injection times of the individual cylinders can be influenced by the engine control software. This allows for optimization of the time intervals between cylinder switching processes based on operating conditions. In particular, different parameters can be used depending on the switching direction and the corresponding operating conditions.

[0013] According to one embodiment, the time interval or crankshaft angle interval between the offset start time of at least one of the plurality of cylinders, particularly each cylinder, and the offset start time of at least one other, particularly all other cylinders, is determined according to at least one parameter selected from the operating condition, the number of cylinders, and the intake manifold geometry. The operating condition is given, for example, by torque and speed. The number of cylinders and the intake manifold geometry are known and can be stored in the controller performing the control.

[0014] According to one implementation, with the first cylinder to be switched as a reference, the interval between the start time of the offset of at least one cylinder and the start time of the offset of at least another cylinder is at least two ignition intervals, and / or at most a few seconds. These intervals are ideally suited to achieve the switching process in a manner that is "as fast as possible, but as slow as necessary".

[0015] According to one implementation, taking each cylinder as a reference, the start and end times of the offset of at least one of the multiple cylinders, particularly each cylinder, are the same. That is, at least one, preferably all, cylinders complete the switching directly or through a single operation; that is, the moment when a specific cylinder first stops injecting at the first injection moment in the first operating mode is the same moment when that cylinder first injects at the second injection moment in the second operating mode. However, it should be emphasized that even so, the start and end times of the offset of the first cylinder to be switched will still differ as described above. Therefore, the offset of each cylinder can be very easily completed through a single operation, while still achieving overall temporal dispersion. This situation is, for example, in... Figure 2 As shown in the image.

[0016] According to another implementation, taking the first cylinder to be switched as a reference, the interval between the start and end times of the offset for at least one of the multiple cylinders, particularly for each cylinder, is at least two ignition intervals. That is, at least one, preferably all, cylinders complete the switching gradually or in multiple steps. Specifically, between the moment when a particular cylinder first stops injecting at the first injection time in the first operating mode and the moment when that particular cylinder first injects at the second injection time in the second operating mode, there exists at least one third moment. At this third moment, the particular cylinder first injects gas into the cylinder at the third injection time (particularly between the first and second injection times). In this sense, the start and end times of the offset for one, particularly each, cylinder to be switched will have an interval as described above. Thus, the offset of all cylinders can be performed in the same way, particularly synchronously, while still achieving overall temporal dispersion. This situation is, for example, in... Figure 4 As shown in the diagram. However, it should be emphasized that even so, the starting moment of the offset can still differ between different cylinders. This can be seen, for example, in... Figure 5 As shown in the image.

[0017] For example, the injection timing can be offset along a ramp curve. Therefore, unlike (digital) switching, this process also includes a third injection moment located between the first and second injection moments. The advantage of this approach is that the crowding-out effect does not occur immediately but is completed within a set (applizierbare) time period. However, the disadvantage is that this approach inevitably manipulates the injection moments during the transition, which may trigger other undesirable effects.

[0018] According to one embodiment, the time interval or crankshaft angle interval between the start time of the offset of the first cylinder to be switched and the end time of the offset of the last cylinder to be switched is determined according to at least one parameter, which is selected from the operating condition, the number of cylinders, and the intake manifold geometry. The operating condition is given, for example, by torque and speed. The number of cylinders and the intake manifold geometry are known and can be stored in the controller performing the control.

[0019] The computing unit according to the invention, such as a controller of a motor vehicle, is configured, particularly by programming techniques, to execute the method according to the invention.

[0020] Similarly, it is advantageous to implement the method according to the invention in the form of a computer program or computer program product with program code to perform all method steps, because this approach is extremely low-cost, especially when the controller performing the control is also used to perform other tasks and therefore already exists. Finally, a machine-readable storage medium on which the aforementioned computer program is stored is also proposed. Suitable storage media or data carriers for providing computer programs include, in particular, magnetic, optical, and electrical memories, such as hard disks, flash memory, electrically erasable programmable read-only memory (EEPROM), digital universal optical discs (DVDs), etc. The program can also be downloaded via computer networks (such as the Internet, intranets, etc.), and this download process can be implemented via wired (cable connection) or wireless (e.g., via wireless local area network (WLAN), third-generation (3G), fourth-generation (4G), fifth-generation (5G), or sixth-generation (6G) mobile communication networks, etc.).

[0021] Other advantages and embodiments of the present invention can be seen from the specification and the accompanying drawings. Attached Figure Description

[0022] The present invention has been schematically illustrated by the embodiments shown in the accompanying drawings, and will be described below in conjunction with the drawings.

[0023] Figure 1 : This shows a schematic diagram of a hydrogen engine, based on modules.

[0024] Figure 2 : An embodiment of the method according to the present invention is illustrated in diagram form.

[0025] Figure 3 The turbocharger response is illustrated in graphical form when performing one embodiment of the method according to the invention.

[0026] Figure 4 Another embodiment of the method according to the present invention is illustrated schematically in diagram form.

[0027] Figure 5 Another embodiment of the method according to the present invention is illustrated schematically in diagram form. Detailed Implementation

[0028] Figure 1A hydrogen engine 2 is shown, having multiple cylinders 6. Gaseous hydrogen is injected into the cylinders through injection valves (or injectors) 5, where an air-hydrogen mixture is ignited by spark plugs 4. Therefore, this hydrogen engine is a direct injection engine. The hydrogen engine has an air inlet 8 and a hydrogen inlet 10. The air inlet 8 is connected to each cylinder 6 via a corresponding intake valve (not shown). The combusted air-hydrogen mixture is discharged from the cylinders through a corresponding exhaust valve (not shown) into the exhaust manifold.

[0029] A turbocharger 12 is provided, through which exhaust gas flows and exits from the exhaust outlet 14. The turbocharger 12 is coupled to a compressor 13, which compresses the air and delivers it to the air inlet 8. The diagram here is highly illustrative and can be supplemented with conventional piping and valve structures.

[0030] The control unit (or controller) 16 is coupled to the hydrogen engine 2 and specifically enables the injection of hydrogen into the cylinder 6 of the hydrogen engine 2 and the ignition of the spark plug 4, both of which are typically associated with the angular position of the engine shaft or crankshaft (not shown).

[0031] Multiple sensors (not shown here) are provided, which enable the control unit 16 to identify the current operating status of the hydrogen engine 2. These sensors may include temperature sensors, pressure sensors, and mass flow sensors, which may be arranged at different locations on the hydrogen engine 2.

[0032] Control unit 16 is configured to execute a method for shifting the injection timing of hydrogen (as a gas) into cylinder 6 of hydrogen engine 2 from a first injection timing to a second injection timing, wherein, as will be described below... Figures 2 to 5 Different implementation methods are described.

[0033] Figure 2 This illustration shows the variation of injection timing of different cylinders with time or crankshaft angle according to an embodiment of the present invention. The y-axis shows the injection timing of different cylinders (based on each cylinder itself), and the x-axis shows time or crankshaft angle (based on the first cylinder to be switched). (Unit: °KW).

[0034] Using each cylinder as a reference, the first injection time t1 and the second injection time t2 are marked on the y-axis. At injection time t1, the intake valve of the corresponding cylinder is in the open state (i.e., valve open injection OVI); at the second injection time t2, the intake valve of the corresponding cylinder is in the closed state (i.e., valve closed injection CVI). It should be noted that each cylinder has at least one intake valve.

[0035] The diagram illustrates the four injection timing variations 101, 102, 103, and 104 of cylinder 6 in an exemplary four-cylinder hydrogen engine 2.

[0036] Taking the first cylinder to be switched as a reference, each change process has an angle. … This angle represents the digital switching moment, at which the injection moment is shifted in a single operation. Therefore, in the illustrated embodiment, based on each cylinder itself or a local (lokal) reference, the start and end times of the shift for each of the four cylinders are the same. Specifically, the first cylinder... The second cylinder is constantly switching. The third cylinder is constantly switching. The fourth cylinder is constantly switching. Switching between different times.

[0037] At crankshaft angle Previously, the hydrogen engine 2 operated in a first operating mode, in which gas was injected into each of the multiple cylinders 6 at each first injection moment t1.

[0038] It needs to be clarified again that the injection timing of each cylinder refers to its working cycle. That is, if the different working cycles of a cylinder (conventionally) have different start times based on the first cylinder to be switched as the global reference, then although the injection timing is the same when using the cylinder itself or a local reference (e.g., referring to its own top dead center), the injection timing will differ when using the first cylinder to be switched or the "global" reference. When all cylinders are running in the first operating mode (i.e., injection timing is t1), the maximum difference in global injection timing is: for a two-cylinder four-stroke engine, the difference is at most two strokes (360°KW); for a four-cylinder four-stroke engine, the difference is at most one stroke (180°KW). For example, if all cylinders are running in the first operating mode, and the local injection timing is 150°KW before top dead center, then the global positions could be: first cylinder 210°KW, second cylinder 390°KW, third cylinder 570°KW, and fourth cylinder 750°KW. In this case, the first three injection moments are in the same working cycle based on the first cylinder to be switched, and the fourth injection moment is in the next working cycle based on the first cylinder to be switched.

[0039] At crankshaft angle Subsequently, the hydrogen engine 2 operates in a second operating mode, in which gas is injected into each of the multiple cylinders 6 at the second injection time t2.

[0040] At crankshaft angle and Between these points, hydrogen engine 2 operates in offset mode. In offset mode, taking the first cylinder to be switched as a reference, the start time of the offset of the first cylinder to be switched out of the four cylinders and the end time of the offset of the fourth cylinder to be switched out of the four cylinders are, here, […]. and They are spaced more than one work cycle apart.

[0041] As mentioned earlier, each cylinder is switched directly or through a single operation. Specifically, the moment a particular cylinder stops injecting fuel at the first injection time t1 in the first operating mode coincides with the moment it first injects fuel at the second injection time t2 in the second operating mode. Therefore, in the illustrated embodiment, each of the four cylinders has its own offset start time. Using the first cylinder to be switched as a reference, the interval between this offset start time and the offset start times of all other cylinders is at least two ignition intervals. For example, the offset start time of the i-th cylinder... The starting time of the offset from the (i+1)th cylinder There can be at least two ignition intervals between them. In other words, and The interval between (i=1, 2, 3) is at least two ignition intervals, which for a four-cylinder four-stroke engine is at least 360° KW. To minimize the duration of the offset operating mode, an upper limit can also be set for this interval.

[0042] For example, the control unit 16 is configured to: determine the interval between the offset start time of the i-th cylinder and the offset start time of the (i+1)-th cylinder based on at least one parameter. This parameter is selected from the operating condition, the number of cylinders, and the intake manifold geometry. The operating condition is given, for example, by torque and speed. The number of cylinders and the intake manifold geometry are known and can be stored in the control unit 16 (i.e., the controller).

[0043] Figure 3 The graph illustrates the change in air pressure in the turbocharger over time or crankshaft angle, where the y-axis represents the air pressure p inside the turbocharger, and the x-axis represents time or crankshaft angle. (Unit: °KW), this change process is for example... Figure 2 The response to the offset is compared with an offset not according to the invention. The air pressure response is equivalent to the response during turbocharger operation.

[0044] Here, in response to such Figure 2The air pressure change process during the described movement is labeled 201, while the air pressure change process in response to a non-inventional movement via a single operation is labeled 202. The corresponding switching processes are labeled 201' and 202', respectively. It is clearly evident that the gradient of the change process can be significantly reduced by the present invention; that is, in the case of the present invention, the turbocharger response is significantly "smoother," a characteristic that is easier to achieve and reduces the occurrence of turbulence, overshoot, and other phenomena.

[0045] Figure 4 This illustration shows the variation of injection timing of different cylinders with time or crankshaft angle according to another embodiment of the present invention. The y-axis shows the injection timing t of different cylinders, with each cylinder itself as a reference, and the x-axis shows time or crankshaft angle. (Unit: °KW), based on the first cylinder to be switched.

[0046] Figure 5 This diagram illustrates the variation of injection timing of different cylinders with time or crankshaft angle according to another embodiment of the present invention. The y-axis shows the injection timing t of different cylinders, with each cylinder itself as a reference, and the x-axis shows time or crankshaft angle. (Unit: °KW), based on the first cylinder to be switched.

[0047] The following will discuss the two mentioned above. Figure 1 The description begins, primarily focusing on its relationship with... Figure 2 The differences. With Figure 2 The difference is that the shift in the injection time from the first injection time t1 to the second injection time t2 is no longer completed in one step, but in multiple steps, and in particular, it will pass through multiple third injection times t3 during this period.

[0048] Therefore, the individual offset start time of each cylinder in the multiple cylinders and their respective offset end time Each of them is spaced more than one work cycle apart.

[0049] exist Figure 4 In the middle, each offsets the start time. … (On the one hand) and their respective offset end times … (On the other hand), based on the cylinder itself or a local part, the two are the same. Therefore, the offset of all cylinders can be performed in the same way, especially synchronously, while still achieving time dispersion overall.

[0050] exist Figure 5 In the middle, each offsets the start time. … (On the one hand) and their respective offset end times … (On the other hand), with Figure 2 Similarly, they are also different from each other. Therefore, a stronger time-dispersion effect can be achieved.

[0051] According to Figure 4 and Figure 5 In the offset operation mode shown, the start time of the offset of the first cylinder to be switched out of the four cylinders and the end time of the offset of the fourth cylinder to be switched out of the four cylinders are, here, […]. and Each of them is spaced more than one work cycle apart.

[0052] In all embodiments, for example, the control unit 16 is configured to determine the start and end times of the offset for all cylinders based on at least one parameter, which is selected from the operating condition, the number of cylinders, and the intake manifold geometry.

Claims

1. A method for shifting the gas injection timing within the cylinders (6) of a direct-injection gas internal combustion engine (2) having multiple cylinders (6), particularly a hydrogen engine, from a first injection timing (t1) to a second injection timing (t2), wherein, The gas internal combustion engine (2) first operates in a first operating mode. In the first operating mode, based on each cylinder itself, gas is injected into each of the multiple cylinders at the first injection moment (t1). The gas internal combustion engine (2) then operates in an offset operating mode. In this process, the gas internal combustion engine (2) ultimately operates in a second operating mode. In this second operating mode, based on each cylinder itself, gas is injected into each of the multiple cylinders (6) at the second injection time (t2). In the offset operation mode, taking the first cylinder to be switched as a reference, the interval between the offset start time of the first cylinder to be switched among the multiple cylinders and the offset end time of the last cylinder to be switched among the multiple cylinders exceeds one working cycle.

2. The method according to claim 1, in, During the first injection moment (t1), the intake valve of the gas internal combustion engine (2) is in the open state, and during the second injection moment (t2), the intake valve is in the closed state; or During the first injection moment (t1), the intake valve is in the closed state, and during the second injection moment (t2), the intake valve is in the open state.

3. The method according to claim 1 or 2, wherein, Based on the first cylinder to be switched, at least one of the multiple cylinders (6), especially the offset start time of each cylinder ( … ) and the offset start time of at least one of the multiple cylinders (6), especially all other cylinders ( … The difference between them is at least two ignition intervals, preferably more than two ignition intervals.

4. The method according to claim 3, wherein, At least one of the multiple cylinders (6), especially the offset start time of each cylinder ( … ) and the offset start time of at least one of the multiple cylinders (6), especially all other cylinders ( … The time interval or crankshaft angle interval between the two is determined according to at least one parameter, which is selected from the operating conditions, the number of cylinders, and the intake manifold geometry.

5. The method according to any one of the preceding claims, wherein, Based on each cylinder itself, at least one of the multiple cylinders (6), especially the respective offset start time of each cylinder ( … ) and their respective offset end times ( … )same.

6. The method according to any one of claims 1 to 4, wherein, Based on the first cylinder to be switched, at least one of the multiple cylinders (6), especially the respective offset start time of each cylinder ( … ) and their respective offset end times ( … The interval between them is at least two ignition intervals.

7. The method according to any one of the preceding claims, wherein, The offset start time of the first cylinder to be switched in a plurality of cylinders (6) ; The offset end time of the last cylinder to be switched in multiple cylinders (6) ; The time interval or crankshaft angle interval between the two is determined according to at least one parameter, which is selected from the operating conditions, the number of cylinders, and the intake manifold geometry.

8. A computing unit (16) configured to perform all the steps of the method according to any one of the preceding claims.

9. A computer program product, when run on a computing unit, causes the computing unit (16) to perform all the steps of the method according to any one of claims 1 to 8.

10. A machine-readable storage medium having stored thereon a computer program product according to claim 9.

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