Method for operating a spark-ignition internal combustion engine and control unit for implementing the method

Abstract

A method for operating a spark-ignition internal combustion engine, wherein the internal combustion engine is operated using hydrogen as fuel, and the λ injection value is a value indicating the composition of the mixture based on the amount of injected fuel (F injection ) to be supplied to the combustion chamber of the internal combustion engine and the amount of air (L) to be supplied from outside the internal combustion engine to the combustion chamber, wherein the amount of injected fuel (F injection ) is determined independently of the λ target value at least in some ranges. To ensure the proper operation of the hydrogen engine, the amount of injected fuel (F injection ) is determined at least in some ranges based at least on the amount of air (L).

Description

Technical Field

[0001] The invention relates to a method for operating a spark-ignition internal combustion engine and to a control unit for carrying out the method. Background Art

[0002] In spark-ignition gasoline engines, it is known to determine the amount of fuel to be supplied to the combustion chamber based on the controlled air quantity. In particular, if the performance of a gasoline engine is to be increased, the flow cross section is increased via a throttle. The amount of fuel is then determined as a function of the amount of air flowing through the flow cross section, so that a constant, usually stoichiometric air / fuel mixture (λ=1) is produced.

[0003] If such a gasoline engine is operated using hydrogen as fuel, the previously described control of the fuel quantity is not sufficient, since the combustion behavior of hydrogen differs greatly from the combustion behavior of fuels commonly used in gasoline engines, such as gasoline.

[0004] EP 1 754 874 A1 and DE 10 2019 213 132 A1 show a method for operating a spark-ignition internal combustion engine, in which the exhaust gas recirculation amount is increased in order to burn a richer mixture.

[0005] US7421330B2 shows a method in which an internal combustion engine comprises a plurality of combustion chambers and a specific combustion chamber is monitored for knock.

[0006] WO 2021 / 050344A1 shows a hydrogen-driven spark-ignition internal combustion engine. The engine performance is controlled only by the amount of fuel. However, under this fuel-only control, combustion anomalies may occur that have a negative impact on the engine behavior. Summary of the invention

[0007] It is therefore an object of the present invention to provide a method for determining the amount of fuel required to meet the needs of a hydrogen driven internal combustion engine.

[0008] The object according to the invention is met by a method according to a first aspect.

[0009] According to a first independent aspect, a method for operating a spark-ignition internal combustion engine is provided, wherein the internal combustion engine is operated using hydrogen as fuel, and a lambda (lambda) injection value is a value indicating the composition of the mixture based on an injected fuel amount to be supplied to a combustion chamber of the internal combustion engine and an air amount to be supplied to the combustion chamber from outside the internal combustion engine, wherein the injected fuel amount is determined independently of a lambda target value at least within some ranges, preferably at least based on a default fuel amount, and particularly preferably equal to the default fuel amount. In addition, at least within some ranges, the injected fuel amount is determined based on the air amount.

[0010] According to a first aspect, the amount of fuel can be a controlled variable. More precisely, at least within some ranges, the amount of injected fuel to be injected is determined independently of a predetermined lambda target value. Thus, for example, in the case of fluctuations in the amount of air supplied to the engine, the amount of fuel can be freely determined based on a default fuel amount, without having to be linked to the amount of air supplied as in conventional gasoline methods. Thus, the determination of the amount of fuel follows the diesel method. At least within some ranges, the amount of injected fuel is determined and injected independently of a fixed lambda target value. At least within some ranges, the internal combustion engine is operated according to a quality control system. Thus, the flexibility of the internal combustion engine can be increased. However, if the amount of air is not taken into account, there is a risk that the internal combustion engine will operate with a combustion mixture that causes combustion anomalies (such as knocking). Therefore, according to the present invention, at least within some ranges, the amount of injected fuel is determined based on the amount of air. This allows, for example, limiting the lambda injection value to prevent knocking.

[0011] The air quantity is preferably measured and / or obtained by modeling. This enables conclusions to be drawn about the air quantity supplied to the combustion chamber.

[0012] At least in some ranges, the injected fuel amount is preferably determined to be equal to a default fuel amount. This means that a desired default fuel amount can be set and injected independently of the supplied air amount.

[0013] According to the invention, at least in some ranges, the injected fuel quantity is determined based on a lambda target range such that the lambda injection value is within a lambda target range of lambda target values ​​limited on at least one side by a first lambda target limiting value.

[0014] In order to suppress the occurrence of combustion abnormality within a certain range, the hydrogen / air mixture (λ injection value) must be limited. The fuel amount can be determined so that the hydrogen / air mixture is obtained within a range where combustion abnormality does not occur when considering the amount of air to be supplied to the internal combustion engine. The range includes a plurality of possible λ target values ​​and is limited to a λ target limit value at least on one side. Therefore, according to this aspect, the air amount is taken into account when determining the fuel amount.

[0015] The first λ target limit value is preferably the lower limit value of the range of the λ target value, preferably greater than or equal to 1.2 and less than or equal to 2.5, particularly preferably greater than or equal to 1.2 and less than or equal to 1.8, and even more preferably corresponds to 1.2.

[0016] This can ensure that no too rich hydrogen / air mixture is provided for combustion. The hydrogen powered internal combustion engine is preferably operated in the lean range (λ>1). For example, depending on the performance range, the limit value can be taken from the range of values ​​mentioned above. Therefore, the λ target limit value is preferably variable within the performance range.

[0017] According to yet another aspect, preferably, when a λ default value indicating a composition of a mixture based on a default fuel amount and the air amount is outside a λ target range, the injected fuel amount can be determined such that the λ injection value corresponds to the target λ limit value.

[0018] This allows the fuel quantity to be adjusted to the limit of the permissible combustion mixture. The fuel quantity is thus determined such that a sufficient permissible combustion mixture is produced by the amount of air to be supplied. In particular, since the lambda target limit value is the next value of the lambda target range relative to the lambda default value, a relatively small correction to the default fuel quantity can be obtained.

[0019] According to yet another aspect, the lambda target range, in particular the first lambda target limit value, can be variable.

[0020] According to this aspect, the flexibility of the internal combustion engine is increased. Depending on the boundary conditions, the restriction can be stronger or weaker.

[0021] According to yet another aspect, the internal combustion engine can further comprise an exhaust gas recirculation device which recirculates exhaust gas into the combustion chamber at least to some extent.

[0022] By providing exhaust gas recirculation, the combustion in the combustion chamber can be stabilized. For example, knocking of the internal combustion engine due to misfires can be prevented. In particular in the case of lean combustion, the recirculated exhaust gas contains a large proportion of unburned oxygen (residual gas), which helps to stabilize the combustion. The recirculated exhaust gas is preferably inert with respect to combustion.

[0023] Alternatively or additionally, the internal combustion engine can comprise an inert medium supply device which is configured to supply an inert medium which does not participate in the combustion, preferably water, into the combustion chamber.

[0024] By supplying an inert medium, the combustion can also be stabilized by reducing the combustion temperature. In particular, the inert medium can be liquid water or gaseous water. It is particularly inert when burning hydrogen and can therefore reduce the temperature. In addition, additional emissions can be prevented.

[0025] According to the invention, at least within certain limits, the injected fuel quantity is determined based on the exhaust gas recirculation quantity and / or the inert medium supply quantity.

[0026] Thus, the combustion behavior which is influenced by the exhaust gas recirculation amount and / or the inert medium supply amount can be taken into account when determining the injected fuel amount.

[0027] According to the present invention, the lambda target range, in particular the first lambda target limit value, depends on the exhaust gas recirculation amount and / or the inert medium supply amount. Preferably, the first lambda target limit value can be reduced as the required exhaust gas recirculation amount and / or the inert medium supply amount increases.

[0028] The exhaust gas recirculation amount and / or the inert medium supply amount can influence the combustion. Therefore, it can be limited by a lambda target range that depends on the exhaust gas recirculation amount and / or the inert medium supply amount. Since the exhaust gas recirculation and the inert medium supply stabilize the combustion, the range of the permissible lambda target value can be increased. This can be achieved in particular by reducing the first lambda target limit value as a lower limit value.

[0029] According to yet another aspect, an exhaust gas recirculation amount and / or an inert medium supply amount can be requested if the lambda default value indicating a composition of the mixture based on the default fuel amount and the air amount is outside a lambda target range and / or above a limit value of a performance requirement.

[0030] By utilizing the exhaust gas recirculation amount and / or the inert medium supply amount to stabilize combustion, the lambda target range can be precisely increased when the lambda default value is outside the lambda target range without considering the exhaust gas recirculation or the inert medium supply. As the performance requirements increase, the demand for fuel also increases, which is why the lambda default value can exceed the permissible range. Therefore, the exhaust gas recirculation amount and / or the inert medium supply amount can be required above the limit value of the performance requirement. In the case of a transient increase in the load of the internal combustion engine, for example during acceleration in a motor vehicle, the necessary performance can be provided by requiring the exhaust gas recirculation amount and / or the inert medium supply amount. Because without the exhaust gas recirculation amount and / or the inert medium supply amount, the lambda target range will be more limited and cannot provide the necessary performance. Preferably, the exhaust gas recirculation amount and / or the inert medium supply amount are required at least in the full load range.

[0031] Alternatively or additionally, the required exhaust gas recirculation amount and / or the inert medium supply amount can be increased if the lambda default value is outside the lambda target range, i.e. when a limit value is reached or falls below / exceeded, in particular below a lower limit value of a performance requirement and / or above a limit value of a performance requirement.

[0032] Therefore, the first lambda target limit value can be reduced accordingly and a lambda default value can be set. This allows for appropriate control of the exhaust gas recirculation amount and demand-based mixing.

[0033] According to yet another aspect, the required exhaust gas recirculation amount and / or the inert medium supply amount can be increased as the performance requirements of the internal combustion engine increase.

[0034] This allows setting a richer mixture, i.e. a lower lambda injection value, which is desirable for higher performance requirements, since exhaust gas recirculation and / or the inert medium supply stabilizes the combustion and thus prevents knocking of the internal combustion engine even at low lambda injection values. Thus, an increase in the exhaust gas recirculation amount and / or the inert medium supply amount can be used to increase performance. This is particularly advantageous for transient processes. According to a further aspect, the default fuel amount can be determined at least based on the performance requirements of the internal combustion engine.

[0035] Therefore, the performance requirement can be used as a basis for determining a default fuel amount and can be used as a basis for determining the amount of injected fuel.

[0036] Preferably, the default fuel amount increases as the performance demand increases, and vice versa. The calorific value of a hydrogen / air mixture is related to the proportion of fuel in the mixture. Therefore, higher performance can be achieved by increasing the fuel amount.

[0037] According to yet another aspect, at least within some ranges, the amount of injected fuel can be determined based on the knock signal value.

[0038] According to this aspect, the knock signal value and therefore the value indicating combustion anomalies can be taken into account when determining the fuel amount. Information about the knock tendency of the relevant cylinder of the internal combustion engine can be obtained based on, for example, the knock signal value from a previous combustion cycle. The tendency to knock depends on factors such as the temperature of the combustion chamber wall, compression and manufacturing tolerances. These factors can be used to determine the amount of injected fuel for the current cycle by the knock signal value. The knock signal value can also provide information about the composition of the recirculated exhaust gas. For example, a knock signal value indicating a stronger knock can provide information about a low oxygen content in the exhaust gas, which makes it more difficult to stabilize combustion.

[0039] The first lambda target limit value preferably increases as the knock signal value increases.

[0040] This can reduce knocking in the internal combustion engine because, by increasing the lambda target limit value, the mixture can be made leaner, thereby reducing the tendency to knock.

[0041] According to yet another aspect of the present invention, a method for operating a spark-ignition internal combustion engine is provided, wherein the internal combustion engine is operated using hydrogen as fuel and the internal combustion engine includes a plurality of combustion chambers, wherein a) based on a knock signal value corresponding to at least one combustion chamber, an amount of injected fuel into the at least one fuel chamber and an amount of injected fuel into at least one other combustion chamber are determined, the amount of injected fuel into the one combustion chamber is determined so that the knock signal value of the one combustion chamber is reduced, the one combustion chamber is operated with a leaner hydrogen / air mixture, and the amount of injected fuel is determined at at least one other combustion chamber of the plurality of combustion chambers so that the total default fuel amount as a predetermined amount of fuel supplied to all combustion chambers is again preferably as close as possible.

[0042] Since mass control is performed in each combustion chamber at least within some ranges, according to this aspect of the invention, the amount of fuel at at least one other cylinder can be adjusted based on the knock signal value of at least one combustion chamber. In particular, the adjustment of the amount of fuel at at least one combustion chamber can be compensated at each combustion chamber. The knock signal value of the at least one combustion chamber is preferably higher than the knock signal value of the at least one other combustion chamber. This aspect can be provided as a second independent aspect, which can be collectively referred to as redistribution of fuel amount, or this aspect can be provided in combination with the aforementioned aspects of the first independent aspect. This aspect also reduces the occurrence of combustion anomalies and therefore provides a method in which the needs of a hydrogen-driven internal combustion engine are taken into account.

[0043] The total default fuel amount can be a fuel amount determined based on performance requirements. For example, if a certain performance is to be achieved, the performance can be achieved or at least approximated by adjusting the fuel amounts at other cylinders accordingly, even if knocking occurs in the combustion chambers of some cylinders.

[0044] In a), the variation compared to the default fuel quantity of the at least one combustion chamber is preferably added at least partially, preferably completely, to the fuel quantity of at least one other combustion chamber with an associated lower knock signal value, particularly preferably to the fuel quantities of a plurality of other combustion chambers, respectively. According to another aspect, the variation can be added to the fuel quantity of the respective combustion chamber depending on the respective knock signal value of the further combustion chamber.

[0045] The fuel quantity can then be reduced at at least one combustion chamber, for example by increasing the lower lambda target limit value, and the fuel quantity can preferably be increased by this reduction at at least one other combustion chamber, such that the overall performance output of the internal combustion engine can be maintained.

[0046] In a second independent aspect, in addition to a), at least one of the following is included:

[0047] b) increasing the amount of exhaust gas recirculation of the at least one combustion chamber;

[0048] c) delaying ignition timing at the at least one combustion chamber to a later point in time; and

[0049] d) A reduction in the performance requirements of the internal combustion engine can be achieved.

[0050] As already described with respect to the above-mentioned first independent aspect, the combustion can be stabilized by means of b). For example, by means of a valve or a throttle in the supply channel to each combustion chamber, the increase in the exhaust gas recirculation amount occurs at least in one combustion chamber associated with the critical (highest) knock signal value. However, it is advantageous if the increase in the exhaust gas recirculation amount occurs globally in each of the multiple combustion chambers, in which case it is not necessary to provide a valve or a throttle in each supply channel, but control can be achieved by means of a central valve. This simplifies the system and ensures combustion stabilization in all cylinders or combustion chambers, respectively. As a result, the amount of fuel can be increased in at least one other combustion chamber. As a result, the amount of change at at least one combustion chamber can be better absorbed at at least one other combustion chamber.

[0051] Knock at least at one combustion chamber can be reduced by c) because the delayed position of the ignition prevents premature uncontrolled combustion. In particular, the spark plug can be activated at a later point in time. Delaying the ignition timing to a later point in time is, for example, related to the piston position or crank angle of the piston defining the combustion chamber, and means a reference value relative to the ignition time point. The reference value can be, for example, the ignition time point from the previous cycle, or another reference value associated with the combustion lambda of one combustion chamber, preferably the optimal ignition time point for the corresponding lambda. In particular, the mixture can be ignited at a time point when the piston is closer to the top dead center than the reference time point.

[0052] d) The default fuel quantity at the at least one combustion chamber having a critical knock signal value can be reduced, whereby the mixture can be leaned and the tendency to knock can be reduced.

[0053] For example, if it is determined that the limit value of the knock signal value is still exceeded, steps b), c) and d) are preferably carried out in the above order. For example, if it is determined that a knock signal value that is too high still occurs at one combustion chamber despite the redistribution according to a), b) can be carried out. The same applies to steps c) and d). This means that engine-friendly steps such as redistribution and exhaust gas recirculation can be carried out first.

[0054] It is further preferred that at least in the second independent aspect, a verification is performed as to whether redistribution of the fuel amount is possible, for example, whether the knock signal value at at least one combustion chamber is below a limit value of the knock signal value, in which case the fuel can be redistributed from at least one combustion chamber to the combustion chamber with the low knock signal value. If yes, fuel redistribution can be performed, otherwise one of steps b), c) and d) can be performed.

[0055] According to yet another aspect, at least within certain limits, the injected fuel quantity can be determined based on a measurement value of a lambda sensor in an exhaust section of the internal combustion engine.

[0056] This allows the residual gas content in the exhaust gas to be determined, which can provide information about the mixing ratio from the previous combustion cycle. In the case of a requirement for exhaust gas recirculation, this information can have a doubly relevant relevance, since it also provides information about the residual gas content of the exhaust gas which is fed back into the combustion chamber via exhaust gas recirculation. Thus, a lambda target limit value can also be determined based on the measured value of the lambda sensor.

[0057] According to a further aspect, a controller is provided, which is configured to perform the method according to any one of the preceding aspects of the invention.

[0058] The method according to the above aspect can be performed if the controller is installed in, for example, a motor vehicle having a hydrogen combustion engine.

[0059] According to another aspect of the present invention, there is provided a program which, when executed on a computer connected to an internal combustion engine, causes the computer to execute the method according to the above aspect of the present invention.

[0060] According to another aspect of the present invention, there is provided a computer-readable storage medium on which the above-mentioned program is stored. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The present invention will be described below with reference to the accompanying drawings.

[0062] Figure 1 A flow chart illustrating the method according to the invention is shown.

[0063] Figure 2 The speed-dependent performance curves are compared with the speed-dependent exhaust gas recirculation rate.

[0064] Figure 3a Schematic diagram of the external formation of the mixture in a hydrogen powered internal combustion engine. Figure 3b The internal formation of the mixture is shown. DETAILED DESCRIPTION

[0065] Figure 1The flow chart shown shows a method that can be used, for example, to control the amount of fuel in a hydrogen-powered internal combustion engine. In particular, the amount of hydrogen for the next combustion cycle that is metered into the corresponding combustion chamber by an injector can be determined. The internal combustion engine includes a spark plug in its cylinder head for each combustion chamber. For the purposes of the present invention, these are spark-ignition internal combustion engines. The internal combustion engine includes at least one combustion chamber that can be defined by a cylinder, a cylinder head, and a piston connected to a crankshaft. The method is used to control the fuel of the combustion cycle of the combustion chamber, wherein a hydrogen / air mixture is burned in the combustion chamber.

[0066] According to the method, preferably according to the load demand, a default fuel quantity F is first specified. def Default fuel quantity F def Corresponds to the calorific value of the fuel. Likewise, the amount of ambient air L, which is measured, for example, by an air mass sensor and flows from outside the internal combustion engine into the combustion chamber, can be determined. Based on these two values, the default fuel amount F can be calculated in step S1. def The default value of λ obtained by the ambient air L is default .

[0067] Then, the default value λ can be verified in step S2 default Is it in the lower limit value λ target-l and the upper limit λ target-u The target range of λ[λ target-l ; target-u If this is the case, then in step S3 the amount of fuel F injection Set to equal the default fuel quantity F def .

[0068] If in step S2 the default value λ air-default In the λ target range [λ target-l ; target-u ], then in step S41 the injected fuel amount F injection Set to be equal to the default value λ which is closer to λ default The limit value λ target-1 or target-u Therefore, in the case of step S41, the injected fuel amount F is corrected. injection The lambda target range [λ can be predetermined for a specific internal combustion engine target-l ; target-u According to the present invention, the λ target range [λ target-l ; target-u ] is the lambda target range within which no exhaust gas recirculation quantity is recirculated to the combustion chamber. In these cases, the lower limit value lambda target-lIt is preferably greater than or equal to 2.0 and less than or equal to 4.5, more preferably greater than or equal to 2.0 and less than or equal to 4, and particularly preferably between 2.2 and 3.8.

[0069] If in step S2, without exhaust gas recirculation, λ default value λ air-default In the λ target range [λ target-l ; target-u ], in the case where the internal combustion engine additionally includes an exhaust gas recirculation device, the exhaust gas recirculation amount may alternatively be requested in step S42. The exhaust gas recirculation amount R actually supplied to the combustion chamber is determined according to the request. act It can also be determined or modeled, for example, by an air mass sensor. Preferably, at least one of the air quantity and the exhaust gas recirculation quantity is detected based on the interaction between the air quantity and the exhaust gas recirculation quantity. For example, the exhaust gas recirculation quantity R act It can be obtained from the difference between the filling amount of the combustion chamber and the air amount. Instead of the exhaust gas recirculation device or in addition to the exhaust gas recirculation device, an inert medium supply device can also be provided in the internal combustion engine. The inert medium supply device can directly or indirectly supply an inert medium such as water into the combustion chamber. The inert medium does not participate in the combustion and preferably has a specific heat capacity of at least 900 J / (kg*K), preferably a specific heat capacity of at least 1500 J / (kg*K), and further more preferably a specific heat capacity of at least 4000 J / (kg*K).

[0070] Exhaust gas recirculation and inert medium supply ensure combustion stability in the combustion chamber of the internal combustion engine. For example, knocking of the internal combustion engine caused by misfire can be at least reduced or even completely prevented.

[0071] Based on the required exhaust gas recirculation amount R act To determine the exhaust gas recirculation amount R act Different λ target ranges [λ target-l ; target-u ] R In the λ target range [λ target-l ; target-u ] R In particular, compared with the lower limit value in step S2, the lower limit value λ target-l This means that a richer hydrogen / air mixture can be burned without combustion anomalies. λ Target Range [λ target-l ; target-u ] R Depending on the available exhaust gas recirculation amount, in the case of high exhaust gas recirculation amounts, the lambda lower value can preferably be reduced to a value of 1.2.

[0072] In step S44, a comparison similar to that in step S2 is again performed. In particular, the default value λ is verified. default Is the exhaust gas recirculation (R) taken into account? act and has a lower limit λ target-l and the upper limit λ target-u The λ target range [λtarget-i; λ target-u ] R If this is the case, then in step S45 the amount of fuel injected F injection Set to equal the default fuel quantity F def .

[0073] Otherwise, in step S46, taking into account the exhaust gas recirculation amount R act At the same time, the fuel amount F injection Set to be equal to the limit value λ of the target range target-l or target-u , which is closer to the default value of λ default Therefore, in the case of step S46, the injected fuel amount F is corrected. injection .

[0074] Note that, if the default value λ is determined, default Outside the lambda target range, i.e. exceeding or falling below a limit value, in particular the lower limit lambda target-l , the exhaust gas recirculation amount can be increased. This can occur in step S42, in which case the increase is associated with the initial request. However, if the current exhaust gas recirculation amount is not sufficient, this can also occur after step S44.

[0075] Likewise, in step S2 an exhaust gas recirculation quantity may already be present and subsequently in step S42 an increase in the exhaust gas recirculation quantity may be requested.

[0076] The advantageous effects of the present invention will now be described.

[0077] according to Figure 1 In the method shown, the fuel quantity can be the controlled variable. More precisely, at least in some ranges, the injected fuel quantity to be injected can be determined independently of the predetermined lambda target value. In particular, it is possible to determine the injected fuel quantity independently of the predetermined lambda target value within the lambda target range [λ target-l ; target-u ] to determine the amount of injected fuel. For example, in the case where the amount of air supplied to the engine fluctuates, it is possible to determine the amount of injected fuel based on the default fuel amount F def The amount of fuel can be freely determined without being linked to the amount of air supplied as is the case with conventional gasoline methods. In the above embodiments, at least in some ranges, the λ target range [λ target-l ; target-u] to determine the amount of injected fuel. Therefore, the flexibility of the internal combustion engine can be increased. In addition, the air volume L is determined to be used to determine the default value λ default Or lambda injection value. Then the injected fuel amount is determined based on the air amount. Preferably, as described herein, the fuel amount is determined based on the air amount and lambda target range.

[0078] The injected fuel amount is determined to be equal to the default fuel amount F at least within the lambda target range. def This means that, regardless of a certain lambda target value, a desired default fuel quantity can be set and injected. The term “lambda target range” can include a plurality of lambda target ranges, such as the lambda target range [λ target-l ; target-u ] and the lambda target range [λ with exhaust gas recirculation target-1 ; target-u ] R .

[0079] In steps S41 and S46, the injected fuel amount F is determined. injection , so that the λ injection value falls within a λ target range of the λ target value, which λ target range is at least on one side limited by a first λ target limit value λ target-l In steps S41 and S46, the amount of injected fuel is determined so that the increment ΔF increases to the default fuel amount F def If it is below the lower limit λ target-l , then the increment is negative, so the lambda injection value is increased by reducing the fuel amount. In the opposite case, if the upper limit value is exceeded, the increment is positive. It should be noted that the air amount in the present case is fixed, i.e. not controlled, but the actual air amount L is determined by measurement in the intake section, and the lambda injection value is therefore set by controlling the fuel amount.

[0080] The increment ΔF and therefore the injected fuel quantity can be determined so that the lambda injection value corresponds to the lambda target limit value. This allows the fuel quantity to be adjusted to the limit of the permissible combustion mixture. Thus, the fuel quantity is determined so that a sufficient permissible combustion mixture is produced by the actual amount of air to be supplied. In particular, since the lambda target limit value is the next value of the lambda target range relative to the lambda default value, a relatively small correction to the default fuel quantity can be obtained.

[0081] In the above embodiment, the lower limit of the range of the lambda target value depends on the exhaust gas recirculation amount, and is preferably greater than or equal to 1.2 and less than or equal to 2.5, particularly preferably greater than or equal to 1.2 and less than or equal to 1.8, and even more preferably corresponds to 1.2.

[0082] This can ensure that no too rich hydrogen / air mixture is provided for combustion. The hydrogen powered internal combustion engine is therefore operated in the lean range (λ>1). Depending on the performance range, the limit value can be taken from the range of values ​​mentioned above. Therefore, the λ target limit value is preferably variable within the performance range.

[0083] As mentioned above, the λ target range [λ target-l ; target-u ] R The lambda target range can be variable depending on the available exhaust gas recirculation amount.

[0084] As described above, the internal combustion engine of the embodiment further includes an exhaust gas recirculation device that recirculates the exhaust gas into the combustion chamber at least to some extent. The combustion in the combustion chamber can be stabilized by providing the exhaust gas recirculation. For example, knocking of the internal combustion engine due to misfire can be prevented. Especially in the case of lean combustion, the recirculated exhaust gas contains a large proportion of unburned oxygen (residual gas), which helps to stabilize the combustion.

[0085] Not only the target range [λ target-l ; target-u ] R Depending on the available exhaust gas recirculation amount, in this embodiment the lower limit value λ is also adjusted according to the exhaust gas recirculation amount target-l . Therefore, when determining the amount of injected fuel, the exhaust gas recirculation amount is taken into account, at least in some ranges in which exhaust gas recirculation is effective. In particular, the first lambda target limit value can be reduced as the required exhaust gas recirculation amount increases. It should be noted that the exhaust gas recirculation amount not only affects the limit value of the lambda target range, but also affects the amount of ambient air L to be supplied, such as Figure 1 As shown by the arrow in . Because, as the exhaust gas recirculation amount increases, the amount of air supplied to the combustion chamber decreases. If the default fuel amount remains unchanged, the default value of λ that must be considered in step S44 decreases. It should be noted that Figure 1 In step S2, the air quantity L can be, for example, the air quantity last measured (stored) from the previous cycle, while the currently measured air quantity can be used for step S44, which is reduced taking into account the actual exhaust gas recirculation quantity. In other words, in order to determine whether an exhaust gas recirculation quantity must be requested, a reference value for the air quantity can be used, which reference value is preferably derived from the currently measured value of the previous cycle, but can also be predetermined for a given internal combustion engine. It should be noted that the request for the exhaust gas recirculation quantity does not necessarily have to precede the comparison in step S2. On the contrary, it is also possible to request an exhaust gas recirculation quantity at any time or for a specific performance range.

[0086] like Figure 1 As shown, when the λ default value indicating the composition of the mixture based on the default fuel amount and the default air amount is within the λ target range [λtarget-l ; target-u ] R If the exhaust gas recirculation rate R act Or if there is already an exhaust gas recirculation amount, increase the exhaust gas recirculation amount R act .

[0087] By utilizing the exhaust gas recirculation amount to stabilize combustion, the lambda target range can be precisely increased when the lambda default value is outside the lambda target range without exhaust gas recirculation. As the performance demand increases, the demand for fuel also increases, which is why the lambda default value can exceed the permissible range. Therefore, even when it is determined that the limit value of the performance demand is exceeded, the exhaust gas recirculation amount can also be requested to be higher than the limit value of the performance demand. In the case of a transient increase in the load on the internal combustion engine, such as an acceleration process in a motor vehicle, the necessary performance can be provided by requesting the exhaust gas recirculation amount. Because without the exhaust gas recirculation amount, the lambda target range will be more limited and cannot provide the necessary performance.

[0088] In this embodiment, the default fuel quantity F def In particular, if the default fuel quantity F obtained from the measured air quantity L cannot be used, def The target range of lambda without exhaust gas recirculation [λ target-l ; target-u ], then the exhaust gas recirculation amount is required. Advantageously, the exhaust gas recirculation amount is adjusted, for example, by a valve in the exhaust gas recirculation section, so that a flow rate consisting of the air amount and the default fuel amount F is generated. def The obtained λ target range of λ injection value [λ target-l ; target-u ]. Since the default fuel quantity F def As performance demands increase, the required exhaust gas recirculation amount therefore also increases. Thus, advantageously, as performance demands on the internal combustion engine increase, the required exhaust gas recirculation amount also increases.

[0089] This allows richer mixtures to be set, i.e. lower lambda injection values, as desired for higher performance requirements, since exhaust gas recirculation stabilizes combustion and prevents knocking of the internal combustion engine even at low lambda injection values. Thus, an increase in the amount of exhaust gas recirculation can be used to increase performance. This is particularly advantageous for transient processes and at full load. This effect is shown in Figure 1. Figure 2 As shown. Figure 2 The above figure shows the curve of exhaust gas recirculation rate EGR relative to speed. It can be seen from the figure that exhaust gas recirculation is above the speed limit value n limit On the other hand, performance curves such as Figure 2The results show that higher performance can be provided by increasing the amount of exhaust gas recirculation. The solid line shows the performance curve when exhaust gas recirculation is provided. The dashed line curve appears without exhaust gas recirculation. Therefore, without exhaust gas recirculation, the performance can no longer be significantly improved even if the amount of fuel is increased.

[0090] This effect does not occur in conventional gasoline engines because they are controlled at a fixed lambda value. Therefore, when increasing the amount of exhaust gas recirculation in a conventional gasoline engine, the amount of air must be reduced, which also results in a reduction in the amount of fuel.

[0091] The calorific value of the combustion mixture is related to the performance of the output. Therefore, the default fuel quantity F is determined based at least on the performance requirements of the internal combustion engine. def .

[0092] The performance requirement can therefore serve as a basis for determining a default fuel quantity and thus also as a basis for determining an injected fuel quantity.

[0093] As performance requirements increase, the default fuel quantity is preferably increased, and vice versa. The calorific value of a hydrogen / air mixture is related to the proportion of fuel in the mixture. This means that higher performance requirements can be met by increasing the fuel quantity.

[0094] In the above-described embodiments, at least within some ranges, the knock signal value can be used to determine the injected fuel amount.

[0095] According to this aspect, when determining the amount of fuel, the knock signal value and therefore the value indicating combustion abnormality can be taken into account. Information about the knock tendency of each cylinder of the internal combustion engine can be obtained based on, for example, the knock signal value from a previous combustion cycle. The tendency of knock depends on factors such as the temperature of the combustion chamber wall, compression and manufacturing tolerances. These factors can be used to determine the amount of injected fuel for the current cycle through the knock signal value. The knock signal value can also provide information about the composition of the recirculated exhaust gas. For example, a knock signal value indicating a stronger knock can provide information about the low oxygen content in the exhaust gas, which makes it more difficult to stabilize combustion. The knock signal value can also provide information about the actual available exhaust gas recirculation amount, which can be different from the required exhaust gas recirculation amount. It is also possible to take into account and compensate for errors in air quantity measurement.

[0096] The lambda target range is preferably determined based on the knock signal value, and particularly preferably the first lambda target limiting value is increased as the knock signal value increases.

[0097] This can reduce knocking in the internal combustion engine because, by increasing the lambda target limit value, the mixture can be made leaner, thereby reducing the tendency to knock.

[0098] The knock signal value can also be considered as follows. For example, if the lambda target range is adjusted based on the knock signal value in step S2 of the above embodiment, then the fuel amount is changed by an increment ΔF in step S41 .

[0099] However, if a plurality of combustion chambers are provided, the negative value of the increase ΔF resulting from the execution of step S41 can be added to the amount of fuel from at least one other combustion chamber in step a), or the negative value of the increase ΔF can be shared among the plurality of combustion chambers.

[0100] This means therefore that both the injected fuel amount of at least one combustion chamber and the injected fuel amount of at least one other combustion chamber can be determined based on the (measured) knock signal value associated with the at least one combustion chamber. By determining the lambda target range in step S41 based on the knock signal value and subsequently performing a fuel amount correction, the knock signal value of one combustion chamber can be reduced, while in at least one other combustion chamber of the plurality of combustion chambers the fuel amount is determined such that the total default fuel amount is as close as possible, which is a predetermined fuel amount supplied to all combustion chambers, and again preferably achieved. One combustion chamber can continue to operate with a lean mixture compared to the mixture obtained by the default fuel amount, which can be achieved by reducing the injected fuel amount compared to the default fuel amount.

[0101] In particular, the regulation of the fuel quantity at at least one combustion chamber can be compensated at the individual combustion chambers.Preferably, the knock signal value of at least one combustion chamber is higher than the knock signal value of at least one other combustion chamber.

[0102] The total default fuel amount can be a fuel amount determined based on performance requirements. The default fuel amount for each individual combustion chamber can be determined from the total default fuel amount, for example, by dividing the total default fuel amount by the number of combustion chambers if the combustion chambers are identical.

[0103] Preferably, in a), as described above, the amount of the variation compared to a default fuel amount of one combustion chamber is at least partially, preferably completely, compensated by the fuel amount of at least one other combustion chamber.

[0104] The previously described redistribution of the fuel quantity can be carried out as a function of the respective knock signal values ​​of the other combustion chambers. The combustion chamber with the lower associated knock signal value can then proportionally compensate for the greater proportion of the change.

[0105] If the total default fuel amount or performance requirement can be achieved by redistribution, steps S42 to S46 can be omitted.

[0106] However, it is possible to combine redistribution and exhaust gas recirculation. For example, if it is determined that the total default fuel amount cannot be achieved by compensation at other combustion chambers, the exhaust gas recirculation amount can be increased at at least one combustion chamber. This corresponds to step b) above. As mentioned above, combustion can be stabilized by b). For example, the increase in the exhaust gas recirculation amount occurs at least in one combustion chamber associated with a critical (highest) knock signal value through a valve or throttle in a supply channel leading to each combustion chamber. However, the increase in the exhaust gas recirculation amount can also occur globally in each of the multiple combustion chambers, in which case it is not necessary to provide a valve or throttle in each supply channel, but can be controlled by a central valve. This simplifies the system and ensures stable combustion in all cylinders or combustion chambers respectively. Therefore, the fuel amount can be increased in at least one other combustion chamber. Therefore, the change at at least one combustion chamber can be better absorbed at at least one other combustion chamber.

[0107] Alternatively or in addition to increasing the exhaust gas recirculation amount, the ignition timing in at least one combustion chamber can be delayed to a later point in time (step c)) and / or the performance requirements of the internal combustion engine can be reduced (step d)).

[0108] Delaying the ignition position prevents uncontrolled combustion from occurring too early. In particular, the spark plug can be activated at a later point in time. Delaying the ignition time to a later point in time is, for example, related to the piston position or crank angle of the piston defining the combustion chamber and means a reference value relative to the ignition time. The reference value can be, for example, an ignition time from a previous cycle, or another reference value associated with the combustion lambda of a combustion chamber, preferably an optimal ignition time. In particular, the mixture can be ignited at an ignition time at which the piston is arranged closer to top dead center than at a reference time.

[0109] Reducing the performance demand means that the total default fuel amount can be reduced. In particular, this is achieved by reducing the default fuel amount and thus reducing the performance demand of at least one combustion chamber.

[0110] Advantageously, the control of the exhaust gas recirculation is activated after the redistribution, if, for example, a knock signal value is detected that is above a permissible limit value despite the redistribution.

[0111] Steps b), c) and d) are then carried out in sequence. This means that engine-friendly steps such as redistribution and exhaust gas recirculation can be carried out first.

[0112] It is also possible to verify whether a redistribution of the fuel quantity is possible. If so, a fuel redistribution can be performed, otherwise one of steps b), c) and d) can be performed.

[0113] The aspect of redistribution does not have to be combined with the aspect of determining the injected fuel quantity based on the air quantity, but can also be applied independently. Therefore, it is not necessary to measure the air quantity for this purpose.

[0114] Regardless of the number of combustion chambers, the amount of fuel can be determined based on the knock signal value and / or the exhaust gas recirculation amount. In particular, the exhaust gas recirculation amount can be requested based on the knock signal value. For example, the lambda target range can be adjusted based on the knock signal value in step S2 of the above embodiment. By increasing the exhaust gas recirculation amount, the lambda target range can be increased in turn. Therefore, advantageously, the exhaust gas recirculation amount increases as the knock signal value increases.

[0115] Likewise, in this embodiment, a lambda sensor can be arranged in the exhaust section. The signal value from the lambda sensor can then also be used to determine the injected fuel quantity.

[0116] The residual gas content in the exhaust gas can be determined from this, which can provide information about the mixing ratio from the previous combustion cycle. In the case of a required exhaust gas recirculation, this information can have a doubly relevant relevance, since it also provides information about the residual gas content of the exhaust gas which is fed back into the combustion chamber via the exhaust gas recirculation. Thus, the lambda target limit value can also be determined based on the measured value of the lambda sensor.

[0117] In the above-described embodiment, the air quantity (air mass) is measured using, for example, an air mass meter. However, it is also possible to model the air quantity using, for example, a parameter. Figure 3a and 3b The composition of the cylinder charge, i.e. the mixture of fuel, air and recirculated exhaust gas in the combustion chamber, is shown. Figure 3a , in the case where the mixture is formed externally, the air mass flow and the mass flow of recirculated exhaust gas Then further downstream, the hydrogen mass flow In the mixing zone of the supply channel, the mass flow of air from the air inlet channel, the mass flow of recirculated exhaust gas from the exhaust gas inlet channel, and the mass flow of hydrogen from the fuel inlet channel are mixed. In this way, the mixture mass flow As the mixed mass flow flows into the cylinder over time, the cylinder filling mass m composed of fuel, air and EGR is generated. mixture The air mass meter for measuring the mass flow in each inflow channel can be arranged in the air inflow channel or in the exhaust gas inflow channel. mixture The air mass L and the exhaust gas recirculation volume R actHowever, only one or even none of these values ​​can be measured and at least one air mass sensor can be omitted. For example, if the maximum cylinder volume and / or the cross section of the inflow channel are known, the amount (mass) of the respective gas can be modeled, for example, by means of pressure sensors in the respective inflow channels.

[0118] and Figure 3a different, Figure 3b The mixture is shown to be formed internally, wherein the fuel is preferably supplied to the cylinder when the combustion chamber is closed. Therefore, the mixing zone only mixes the mass flows of air and recirculated exhaust gas. Here, the air quantity and the exhaust gas recirculation quantity can also be measured or modeled.

[0119] The amount of air and / or the amount of exhaust gas recirculation are preferably known actual variables of the combustion cycle to be performed, which can be determined, for example, based on sensors or modeling. The amount of fuel can be controlled, for example, by opening the nozzle. In both types of mixtures, the fuel amount can be adjusted using known variables.

[0120] The above method is applicable to two types of internal combustion engines.

[0121] The above steps are not necessarily provided, nor are they necessarily performed in this order. For example, steps S42 to S46 can be omitted within the range where exhaust gas recirculation is not activated. However, if, for example, the controller directly requires an exhaust gas recirculation amount for a specific performance requirement, steps S3 to S41 can also be omitted.

[0122] Insofar as exhaust gas recirculation was mentioned in the above description, an inert medium supply can also be used as an alternative or in combination.

[0123] The invention is particularly suitable for internal combustion engines with unregulated air volumes. However, for example, a throttle valve can also be set in the feed channel to the combustion chamber, which restricts the cross section of the feed channel in the partial load range and fully opens the cross section in the full load range.

[0124] Preferably, hydrogen is used only as fuel.

[0125] The lambda target range can also include only one lambda target value. Thus, the fuel quantity can always be adjusted relative to a target lambda value which is variable, for example, depending on the exhaust gas recirculation quantity.

[0126] In the present disclosure, the term "in some ranges" preferably refers to a performance range and / or a lambda range. For example, in a lambda target range, the fuel quantity is determined independently of the lambda target value. For example, the air quantity can only be determined in a certain performance range. For example, a determination based on the air quantity cannot be performed in a partial load range because there is no risk of the engine knocking.

[0127] Unless stated otherwise, the term "at least" shall also include the entirety.

[0128] The term "performance" includes the torque and / or speed of the internal combustion engine.

[0129] The term "amount" particularly includes mass, but can also include, for example, the number of particles or volume.

[0130] "Injection" in this disclosure includes any type of fuel supply used to make up the combustion mixture.

Claims

1. A method for operating a spark-ignition internal combustion engine, wherein: The internal combustion engine is operated using hydrogen as fuel, wherein the internal combustion engine further comprises an exhaust gas recirculation device and / or an inert medium supply device, wherein the exhaust gas recirculation device recirculates the exhaust gas into the combustion chamber at least within some performance ranges, and the inert medium supply device is configured to supply an inert medium that does not participate in combustion to the combustion chamber, The lambda injection value is based on the amount of injected fuel (F injection ) and the amount of air (L) to be supplied to the combustion chamber from outside the internal combustion engine to express the value of the composition of the mixture, Wherein, the injected fuel amount (F injection ) is independent of the lambda target value at least in some performance ranges, based at least on a default fuel quantity (F def ) and is determined based on the exhaust gas recirculation amount (R) and / or the inert medium supply amount, and determining the injected fuel amount based on the air amount in at least some performance ranges, It is characterized by at least based on the λ target range ([λ target-l ; target-u ]) and in the λ target range ([λ target-l ; target-u ]) to determine the injected fuel amount so that the λ injection value is within a λ target range of a λ target value, at least one side of the λ target range being limited by a first λ target limit value, wherein the λ target range ([λ target-l ; target-u ]) depends on the exhaust gas recirculation amount (R) and / or the inert medium supply amount.

2. The method according to claim 1, wherein: The first lambda target limit value is the lower limit value of the lambda target value range (λ target-l ).

3. The method according to claim 1 or 2, wherein: The injected fuel amount is determined so that the lambda injection value corresponds to the lambda target limit value (λ target-l ).

4. The method according to claim 1, wherein: If the λ default value (λ) representing the composition of the mixture based on the default fuel amount and the air amount default ) is outside the lambda target range and / or is above the limit value of the performance requirement, the exhaust gas recirculation amount and / or the inert medium supply amount are required or increased.

5. The method according to claim 1, wherein: The required exhaust gas recirculation amount and / or inert medium supply amount increases as the performance requirements of the internal combustion engine increase.

6. The method according to claim 1, wherein: The default fuel quantity (F def ) is determined based at least on the performance requirements of the internal combustion engine.

7. The method according to claim 1, wherein: At least in some performance ranges, the injected fuel amount is determined based on a knock signal value.

8. A controller configured to perform the method according to any one of the preceding claims.

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