Method of operating an internal combustion engine having a plurality of cylinders with gaseous fuel, computer program product and control device

Abstract

In a method of operating an internal combustion engine (10) having a plurality of cylinders (11) with gaseous fuel, gaseous fuel is injected into an intake region (15) upstream of a combustion chamber (12) of a respective cylinder (11) by a fuel injector (14) during an intake stroke (50) of the respective cylinder (11). It is proposed that an ignition angle for each cylinder (F) is compared to an advance limit value, and that an action is triggered when the ignition angle reaches or exceeds the advance limit value, and preferably also at least one other condition is met; and / or it is ascertained whether an ignition command is being output to an ignition device (42) of a cylinder (11) that is still in an intake stroke, and that an action is triggered when the ascertaining indicates that an ignition command is being output to the ignition device (42) of a cylinder (11) that is still in an intake stroke, and preferably also at least one other condition is met.

Description

Technical Field

[0001] The present invention relates to a method for operating an internal combustion engine having multiple cylinders using gaseous fuel, as described in the preamble of the parallel claims, a computer program product, and a control device. Background Technology

[0002] DE102021210001A1 describes a method for operating an internal combustion engine that uses a gaseous fuel, such as hydrogen. Gaseous hydrogen is injected directly into the combustion chamber of the cylinder (direct injection or "DI"), or injected into the intake region upstream of the combustion chamber, such as the intake passage (intake manifold injection or "PI"). The hydrogen-air mixture is ignited in the combustion chamber by an ignition device. The hydrogen, in gaseous form, reaches the fuel rail via a pressure regulator, which functions similarly to the fuel rail of a gasoline or diesel direct injection internal combustion engine. Multiple fuel injectors are connected to the fuel rail, supplying the gaseous fuel to the combustion chamber. Summary of the Invention

[0003] The objective upon which this invention is based is solved by a method, control device, and computer program product having the features of the parallel claims. Advantageous improvements are given in the dependent claims.

[0004] The advantage of this invention is that it can identify so-called "backfiring" hazards or backfiring that has already occurred, and can implement corresponding actions to reduce or terminate the hazard, or prevent backfiring. This avoids damage to the internal combustion engine. This monitoring can be achieved through purely software measures, thus requiring no additional hardware costs.

[0005] "Backfire" refers to the abnormal combustion of the air-fuel mixture in an internal combustion engine. For example, this abnormal combustion occurs when the mixture is initially ignited in the combustion chamber, but the flame subsequently propagates to the upstream region of the cylinder combustion chamber through a still-open intake valve. Causes of backfire include, for example, ignition coordination errors, such as issuing an incorrectly timed ignition command to the cylinder's ignition device at the crankshaft angle just as injection is occurring. Backfire can also occur because an ignition command, although issued at the correct time for the intended cylinder, is output to the ignition device of the wrong cylinder—that is, the cylinder currently undergoing injection.

[0006] For internal combustion engines using gaseous hydrogen as fuel, backfire is particularly critical due to the relatively high reactivity of hydrogen. The flame velocity of an ignited air-hydrogen mixture is relatively fast. Therefore, the flame can spread relatively quickly to the intake area through an open intake valve. This can cause damage due to the pressure and heat waves generated by the flame. With the measures according to the invention described above, backfire hazards can be identified in advance or backfires that have already occurred can be detected, allowing for countermeasures to prevent backfire and protect the internal combustion engine from damage.

[0007] Specifically, this is achieved through a method of operating a multi-cylinder internal combustion engine using gaseous fuel, in which the gaseous fuel is injected via fuel injectors into the intake region upstream of the combustion chamber of the respective cylinder during the intake stroke of that cylinder. This internal combustion engine is a typical piston engine that operates on a four-stroke principle. Gaseous hydrogen is preferably used as the fuel. The fuel is injected via fuel injectors directly associated with the respective combustion chamber into the intake region (e.g., the intake manifold) located directly upstream of the respective combustion chamber. Therefore, the internal combustion engine considered here employs intake manifold injection, or PFI. The fuel injectors are then connected to a fuel rail, in which the gaseous fuel is stored at a relatively high pressure.

[0008] According to the invention, a first possible monitoring function proposes comparing the actual ignition angle for each cylinder with a pre-ignition limit (Früh-Grenzwert). This pre-ignition limit is typically located before the cylinder's top dead center (ZOT) and, for example, shortly after the crankshaft angle when the cylinder intake valve closes again after the intake stroke. Typically, the pre-ignition limit is in the range of approximately -160° to -30° ZOT, more preferably approximately -120° ZOT. In this first possible monitoring function, the action is triggered when, on the one hand, the actual ignition angle reaches or exceeds the pre-ignition limit, and on the other hand, and preferably, at least one other condition is also met. In this way, ignition commands that may lead to backfire timing errors can be reliably identified.

[0009] According to the invention, a second possible monitoring function is proposed: determining whether an ignition command has been output to the ignition device of the cylinder that is currently injecting (which is typically still in the intake stroke or with the intake valve open). (Strictly speaking, this situation often also occurs at the beginning of the compression stroke; therefore, this phase is also understood herein as falling within the conceptual scope of the "intake stroke"). In this second possible monitoring function, an action is triggered when, on the one hand, it is determined that an ignition command has been output to the ignition device of the cylinder that is currently injecting, and on the other hand, preferably, at least one other condition is also met. In this way, ignition commands that may lead to backfire can be reliably identified. For example, this includes issuing an ignition command to an "incorrect" cylinder.

[0010] The second monitoring function is based on the consideration that even if the ignition angle is reasonable for the cylinder that should be ignited, an incorrect allocation of the ignition command location can still occur. Every internal combustion engine has a specific ignition sequence. If this sequence is deviated from due to an error, ignition will occur in a cylinder that is in the wrong stroke (usually not at the end of the compression stroke). Ignition in a cylinder that is currently injecting fuel can lead to backfire. This "location" error can be detected by the second monitoring function.

[0011] One improved design specifies that the action includes cutting off the supply of gaseous fuel to the combustion chamber. This reliably prevents damage to the internal combustion engine. However, it is also possible to preemptively or alternatively switch to an emergency procedure, which performs the timing and location determination of the ignition command in a different manner and method, thereby preventing the ignition command from being output at the wrong time (e.g., while the intake valve is still open) or at the wrong location (a cylinder in the intake stroke).

[0012] In one improved embodiment, the other conditions are specified in the first monitoring function as follows: the occurrence of reaching or exceeding the advance limit value occurs at least with a defined frequency within a predetermined time period; or in the second monitoring function, the occurrence of ignition commands being output to the cylinder currently being injected occurs at least with a defined frequency within a predetermined time period. For example, the supply of gaseous fuel to the combustion chamber is cut off only if the timing or location error ignition command output occurs at least X times within its respective defined predetermined time period. Therefore, occasional or sporadic timing or location error ignition command outputs will not immediately trigger action.

[0013] One improved approach specifies that the presence of the ignition command is verified by a readback signal from the controlled hardware component. This improves the reliability of the first monitoring function.

[0014] One improved approach specifies that the presence of injection is verified by readback signals from controlled hardware components. This improves the reliability of the second monitoring function.

[0015] The present invention also includes a computer program product comprising instructions that, when executed by a microprocessor, cause the microprocessor to perform a method of the type described above.

[0016] The present invention also includes a control device having a processor and a memory, the memory storing a computer program product containing instructions that, when executed by the control device, cause the control device to perform the method of the type described above. Attached Figure Description

[0017] Embodiments of the present invention will now be explained with reference to the accompanying drawings. In the drawings: Figure 1 A schematic diagram of an eight-cylinder internal combustion engine is shown, which has multiple combustion chambers and intake valves and fuel injectors associated with these combustion chambers, with only five cylinders shown. Figure 2 It shows Figure 1 A bar graph showing the stroke of eight cylinders in an internal combustion engine during normal operation; Figure 3 It shows the relationship with Figure 2 A similar bar chart shows an incorrectly timed ignition command in one of the cylinders; Figure 4 It shows the relationship with Figure 2 A similar bar chart shows an incorrect ignition command in one of the cylinders; Figure 5 A block diagram is shown for two monitoring functions used to monitor ignition commands for timing and location errors; Figure 6 This shows the operation based on the first monitoring function (time error). Figure 1 A flowchart of a method for developing an internal combustion engine; and Figure 7 This demonstrates operation based on the second monitoring function (location error). Figure 1 The flowchart of the method for developing an internal combustion engine.

[0018] In the following text, functionally equivalent elements and regions in different figures and embodiments are given the same reference numerals. These are generally explained only upon first detailed reference. Furthermore, for simplicity, not all figures are labeled with all reference numerals. Detailed Implementation

[0019] Figure 1 The internal combustion engine is marked with reference numeral 10. It is a classic piston four-stroke internal combustion engine, which here exemplarily has eight cylinders 11 and eight combustion chambers 12, but... Figure 1 Only five cylinders 11a-e and their combustion chambers 12 are shown. The internal combustion engine 10 can drive, for example, a motor vehicle. Each combustion chamber 12 is assigned a fuel injector 14, which injects gaseous fuel (in this case, hydrogen) into an intake region 15 (e.g., an intake passage) located upstream of the respective combustion chamber 12. Thus, the outlet of the fuel injector 14 is located in the corresponding intake region 15 of the respective combustion chamber 12. The fuel injector 14 is connected to a fuel rail 16, which is supplied with gaseous fuel (e.g., hydrogen) by a fuel system not shown further. The pressure in the fuel rail 16 is detected by a pressure sensor 18.

[0020] Air enters each combustion chamber 12 through an intake valve 20 assigned to it (it should be understood that the following description applies both to an internal combustion engine 10 with multiple intake valves 20 per combustion chamber 12, as in this example, and to an internal combustion engine with only one intake valve per combustion chamber). An intake manifold 22 is arranged upstream of these intake valves 20 and their corresponding intake regions 15, and a throttle valve 24 is arranged upstream of it. A turbocharger air cooler 26 and the compressor 28 of the exhaust gas turbocharger 30 are arranged upstream of the throttle valve 24. Combustion exhaust gases travel from the combustion chamber 12 to the turbine 34 of the exhaust gas turbocharger 30 via an exhaust valve 31 and an exhaust manifold 32. A sensor 35 detects the rotational speed of the exhaust gas turbocharger 30. An exhaust gas recirculation line 36 branches off upstream of the turbine 34, leading to the intake manifold 22 via an exhaust gas recirculation valve 38 and an exhaust gas recirculation cooler 40.

[0021] The mixture of gaseous fuel and air present in combustion chamber 12 is ignited by ignition device 42. The piston of internal combustion engine 10 (not shown) acts on crankshaft 44 (illustrated only), the position and speed of which are detected by crankshaft sensor 46.

[0022] The operation of the internal combustion engine 10 is controlled and regulated by a control device, which in particular includes a control unit 48. The control unit receives signals from numerous sensors of the internal combustion engine 10, such as signals from the pressure sensor 18, speed sensor 35, and crankshaft sensor 46. The control unit 48 controls various actuators of the internal combustion engine 10, particularly the fuel injector 14 and the ignition device 42. For this purpose, the control unit 48 includes a processor and a memory. The memory stores a computer program product with program code, which contains instructions that, when executed by the control unit, cause the control unit to perform various methods, including those described below. Figure 2-5 Methods of explanation: Figure 2 The strokes of all eight cylinders 11a-11f within at least one complete working cycle are shown in bar graph form. The strokes of cylinders 11a-11f are distinguished from each other by different shading lines. The intake stroke is marked with reference numeral 50, the compression stroke with reference numeral 52, the power stroke with reference numeral 54, and the exhaust stroke with reference numeral 56. For simplicity, these reference numerals are only used for the stroke of cylinder 11a. Furthermore, Figure 2A timeline is plotted, representing the crankshaft angle KW of cylinder 11a. The top dead center (ZOT) for ignition is at 0° crankshaft angle. The intake stroke 50 is within the range of -360° to -180° ZOT, the compression stroke 52 is within the range of -180° to 0° ZOT, the power stroke 54 is within the range of 0° to +180° ZOT, and the exhaust stroke 56 is within the range of +180° to +360° ZOT. Dotted bars 58 indicate the injection of gaseous fuel through fuel injector 14 during the intake stroke 50, and black dots 60 indicate the output of an ignition command to the ignition device 42. The intake valve 20 is closed at the beginning of the compression stroke 52.

[0023] exist Figure 2 During normal operation, as shown, the ignition command 60 is always output to the corresponding ignition device 42 near the end of the compression stroke 52 in each cylinder 11a-11f. At this moment, the piston of the combustion chamber 12 is located not far before its top dead center (ZOT), and both the intake valve 20 and the exhaust valve 31 are closed.

[0024] Figure 3 A possible error is illustrated where the ignition command 60 for cylinder 11a is output incorrectly at the wrong time. For example, the ignition command 60 is advanced by approximately -180° of crankshaft angle, output at approximately -160° ZOT, meaning it is output at the end of intake stroke 50, still during injection 58, and while intake valve 20 is still open. In this case, the air-fuel mixture in combustion chamber 12 of cylinder 11a may be ignited, and the flame may spread from combustion chamber 12 of cylinder 11a into intake region 15 of cylinder 11a. This is referred to as "backfire."

[0025] To detect or monitor timing errors in the ignition command 60 output of cylinder 11, a first possible monitoring function is implemented in the control device 58 via corresponding software. This monitoring function compares the actual ignition angle at the actual output of the ignition command 60 with the advance limit value G. This advance limit value G is located before the top dead center (ZOT) of the ignition and after the crankshaft angle at the end of injection 58, and preferably after the crankshaft angle when the intake valve of cylinder 11 closes again after the intake stroke 50. For example, the advance limit value G is approximately -120°ZOT.

[0026] If control device 48 is determined, such as Figure 3As shown in the example, if the actual ignition angle of the ignition command 60 for cylinder 11a exceeds the advance limit G prematurely, it is stored in the control device 48 or a counter is incremented. If the number of times the actual ignition angle of the ignition command 60 reaches or exceeds the advance limit G (obtained by incrementing the counter) exceeds the frequency limit set in the counter, an action is triggered, for example, by cutting off the power supply to the power stage of, for example, fuel injection into the relevant cylinder 11.

[0027] Figure 4 Another possible error is shown: the ignition command 60 is incorrectly output to cylinder 11a. Instead of being output to the ignition device 42 of cylinder 11a, the ignition command 60 is output to the ignition device 42 of cylinder 11b, which is at the end of intake stroke 50 and injection 58, with intake valve 20 open. Similarly, if the ignition command 60 output to cylinder 11g is also incorrect, and cylinder 11g is at the middle of intake stroke 50 and injection 58, with intake valve 20 open, then the air-fuel mixture in the combustion chamber 12 of either cylinder 11b or cylinder 11g may be ignited, posing a risk of backfire.

[0028] To detect or monitor an erroneous output of the ignition command 60 to cylinder 11, a second possible monitoring function is implemented in the control device 58 via corresponding software. This monitoring function determines whether an ignition command 60 has been output to the ignition device 42 of cylinder 11, which is currently undergoing fuel injection 58, even though the cylinder is typically still in the intake stroke 50 or the intake valve 20 is open. Therefore, in Figure 4 In the example shown, the second monitoring function will detect that the ignition command 60 originally intended for cylinder 11a is incorrectly output to the ignition device 42 of cylinder 11b, which is currently injecting 58.

[0029] If control device 48 is determined, such as Figure 4 As shown in the example, if an ignition command 60 for cylinder 11a is incorrectly output to the ignition device 42 of cylinder 11b during the intake stroke 50, it is stored in the control device 48 or a counter is incremented. If the number of times the ignition command 60 is incorrectly output exceeds the frequency limit set in the counter, an action is triggered again, for example, by cutting off the power supply to the relevant cylinder 11 or all cylinders 11, such as the power stage of the fuel injector 14.

[0030] To improve the reliability of the first monitoring function, the presence of the ignition command can be verified by readback signals from the controlled hardware components. For example, the actual signal for controlling the power stage of the fuel injector 14 can be read back. Similarly, the actual signal for controlling the power stage of the ignition device 42 can be read.

[0031] The logic of the two monitoring functions is in Figure 5 The block diagram illustrates this: In function block 62, based on current operating conditions and load requirements, it determines when and in which cylinder 11 ignition should occur, i.e., which ignition device 42 should be driven and at what crankshaft angle. Function block 62 communicates with function block 64, which converts the requirements generated in function block 62 into specific signals 66 for the corresponding power stage 68 of the ignition device 42. Signal 66, along with the information it contains about the actual crankshaft angle and cylinder 11, is fed back to function block 64 via readback signal 70 for verification and further transmitted to read function block 72. This read function block also receives information about the crankshaft angle and cylinder 11 from function block 62.

[0032] In function block 74, based on factors such as the current operating state and load requirements, it is determined which cylinder 11 should be injected with how much fuel, i.e., for how long the fuel injector 14 should be driven. To this end, function block 74 generates a signal 76 for the power stage 78 of the fuel injector 14. The signal 76 and the information it contains about the cylinder to be injected are fed back to function block 74 for verification via readback signal 80, and further transmitted to verification block 82.

[0033] Reading block 72 transmits the actual cylinder 11 to which the controlled ignition device 42 belongs, and the actual crankshaft angle (actual crankshaft angle) when the ignition device 42 controls the cylinder 11, to verification block 84. Verification block 82 also transmits the actual cylinder 11 to which the controlled fuel injector 14 belongs. Now, the above monitoring function operates in this verification block. Therefore, the actual crankshaft angle of the cylinder 11 when the ignition device 42 is controlled is compared with the advance limit value G, and it is checked whether the ignition command (signal 66) has been output to the ignition device 42 of the cylinder 11 that is injecting 58 through the fuel injector 14.

[0034] Based on the results of the monitoring function in the verification block 84, a signal 88 is generated in the central block 86 for error handling as necessary and sent to the monitoring module 90. For example, the monitoring module 90 can cut off the power supply to the power stage 78, thereby preventing the supply of gaseous fuel to the combustion chamber 12.

[0035] Figure 5The system is divided into an upper region and a lower region by a dotted line. The upper region defines the first level of the monitoring logic, and the lower region defines the second level.

[0036] Now refer to it again Figure 6 and 7 Explain these two monitoring functions. Figure 6 Involves the first monitoring function, Figure 7 This involves a second monitoring function.

[0037] Figure 6 The method shown begins with the starting function block 92. In function block 94, the actual ignition angle of cylinder 11 is compared with the advance limit value G. If the actual ignition angle of cylinder 11 reaches or exceeds the advance limit value G, a counter is incremented in function block 96. In function block 98, the current value of the counter is compared with the counter limit value. If the current value of the counter reaches the counter limit value, the action described above is triggered in function block 100. The method terminates in the ending function block 102. If, in function block 94, the actual ignition angle of cylinder 11 does not reach or exceed the advance limit value G, the process jumps back to the entry point of function block 94. Similarly, if, in function block 98, the current value of the counter does not reach the limit value, the process also jumps back to the entry point of function block 94.

[0038] Figure 7 The method also begins with the starting function block 92. In function block 104, a check is performed to determine whether an ignition command 90 has been issued to the ignition device 42 of the cylinder 11 that is performing the injection operation. If so, the counter is incremented in function block 96. In function block 98, the current value of the counter is compared with the counter limit value. If the current value of the counter reaches the counter limit value, the action described above is triggered in function block 100. The method terminates at the ending function block 102. If the detection result in function block 104 is negative, the process jumps back to the entry point of function block 104. Similarly, if the current value of the counter in function block 98 has not reached the limit value, the process also jumps back to the entry point of function block 104.

[0039] Obviously, according to Figure 6 and Figure 7 The method can be executed selectively or cumulatively.

Claims

1. A method of operating an internal combustion engine (10) having a plurality of cylinders (11) using a gaseous fuel, in which method gaseous fuel is injected by means of a fuel injector (14) into an intake region (15) upstream of a combustion chamber (12) of a respective cylinder (11) during an intake stroke (50) of the respective cylinder (11), characterized in that, The actual ignition angle for each cylinder (F) is compared with the advance limit (G), and the action is triggered when the actual ignition angle reaches or exceeds the advance limit (G), and preferably when at least one other condition is also met; and / or it is known whether an ignition command (60) is output to the ignition device (42) of the cylinder (11) that is injecting (58), and the action is triggered when the knowing indicates that an ignition command (60) is output to the ignition device (42) of the cylinder (11) that is injecting (58), and preferably when at least one other condition is also met.

2. The method according to claim 1, characterized in that, The action includes cutting off the supply of gaseous fuel to the combustion chamber (12).

3. The method according to at least one of the preceding claims, characterized in that, The other conditions include: the occurrence of reaching or exceeding the advance limit value (G) at least at a certain frequency within a predetermined time period; or the occurrence of outputting an ignition command (60) to the cylinder (11) where injection (58) is taking place at least at a certain frequency within a predetermined time period.

4. The method according to at least one of the preceding claims, characterized in that, The presence of the ignition command (60) is verified by the readback signal (70) from the controlled hardware component (68).

5. The method according to at least one of the preceding claims, characterized in that, The presence of the jet (58) is verified by the readback signal (80) from the controlled hardware component (78).

6. A computer program product comprising instructions that, when executed by a computer, cause the computer to perform the method according to at least one of the preceding claims.

7. A control device (48) for controlling and / or regulating the operation of a fuel supply system, said control device comprising at least one processor, at least one memory, and at least one computer program product according to claim 6 stored in said memory.

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