Method for operating a spark ignition internal combustion engine and control device for carrying out said method

Abstract

A method for operating a spark ignition internal combustion engine, the internal combustion engine being operated using hydrogen as fuel, and the lambda injection value being a fuel injection amount (F 噴射 ) and the amount of air (L) supplied to the combustion chamber from outside the internal combustion engine, Here, the injected fuel amount (F 噴射 ) is determined independently of the lambda target value, at least within some ranges. To ensure proper operation of the hydrogen engine, the amount of injected fuel (F 噴射 ) is determined, at least within some ranges, based at least on the amount of air (L).

Description

[Technical Field]

[0001] The present invention relates to a method for operating a spark-ignition internal combustion engine and a control device for carrying out this method. [Background technology]

[0002] In spark-ignition gasoline engines, it is known to determine the amount of fuel supplied to the combustion chamber based on a controlled amount of air. In particular, to increase the performance of gasoline engines, the flow area is enlarged by a throttle valve. In this case, the amount of fuel is determined depending on the amount of air flowing through the flow area to achieve a constant, typically stoichiometric air / fuel mixture (lambda = 1).

[0003] When such a gasoline engine is operated using hydrogen as fuel, the above-described control of the fuel amount is not appropriate, since the combustion behavior of hydrogen is significantly different from the combustion behavior of fuels such as gasoline that are typically used in gasoline engines.

[0004] EP 1 754 874 A1 and DE 10 2019 213 132 A1 show methods for operating a spark-ignition internal combustion engine in which the amount of exhaust gas recirculation is increased to burn a richer mixture. US Pat. No. 7,421,330 shows how an internal combustion engine has several combustion chambers and knock monitoring is performed for specific combustion chambers. International Publication No. 2021 / 005344 The number is 1 shows a spark-ignition internal combustion engine operated with hydrogen. Engine performance is controlled solely by fuel quantity. However, such fuel-only control can lead to combustion anomalies that adversely affect engine behavior. Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for determining the amount of fuel required to meet the requirements of an internal combustion engine operated on hydrogen. [Means for solving the problem]

[0006] The object according to the present invention is met by a method according to claim 1.

[0007] According to a first independent aspect, there is provided a method for operating a spark-ignition internal combustion engine, the method comprising: operating the internal combustion engine using hydrogen as fuel; and a lambda injection value indicative of mixture formation based on an amount of injected fuel supplied to a combustion chamber of the internal combustion engine and an amount of air supplied to the combustion chamber from outside the internal combustion engine, the injected fuel amount being determined, at least within some ranges, independently of the lambda target value, preferably based on at least a predetermined fuel amount, and particularly preferably equal to the predetermined fuel amount. Additionally, the injected fuel amount is determined, at least within some ranges, based on the air amount.

[0008] According to the first aspect, the fuel quantity can be a controlled variable. More precisely, the injected fuel quantity is determined, at least within certain limits, independently of a predetermined lambda target value. Therefore, for example, if a fluctuation occurs in the amount of air supplied to the engine, the fuel quantity can be freely determined based on a predetermined fuel quantity, without being bound by the amount of air supplied, as in conventional gasoline systems. The determination of the fuel quantity thus follows a diesel system. The injected fuel quantity is determined and injected independently of a fixed lambda target value, at least within certain limits. The internal combustion engine is operated according to a quality control system, at least within certain limits. This increases the flexibility of the internal combustion engine. However, if the air quantity is not taken into account, the internal combustion engine may be operated with a combustion mixture that causes combustion abnormalities, such as knocking. Therefore, according to the present invention, the injected fuel quantity is determined, at least within certain limits, based on the air quantity. This makes it possible to limit the lambda injection value, for example, to prevent knocking.

[0009] The amount of air is preferably measured and / or obtained by modelling, which allows conclusions to be drawn regarding the amount of air supplied to the combustion chamber.

[0010] The amount of fuel injected is preferably determined to be equal to a predetermined amount of fuel, at least within some ranges, which means that the desired predetermined amount of fuel can be set and injected independently of the amount of air supplied.

[0011] The present invention According to the method, the injected fuel amount is determined based on a lambda target range, at least within some ranges, such that the lambda injection value is within a lambda target range of lambda target values ​​limited at least on one side by a first lambda target limit value. And do.

[0012] It may be necessary to limit the hydrogen / air mixture (lambda injection value) within a certain range to prevent combustion abnormalities. The fuel amount can be determined so that the hydrogen / air mixture falls within a range in which combustion abnormalities do not occur, taking into account the amount of air supplied to the internal combustion engine. This range includes multiple possible lambda target values ​​and is limited on at least one side by a lambda target limit value. Therefore, according to this aspect, the air amount is taken into account when determining the fuel amount.

[0013] The first lambda target limit is preferably the lower limit of the range of lambda target values, preferably ≧1.2 and ≦2.5, particularly preferably ≧1.2 and ≦1.8, and even more preferably it corresponds to 1.2.

[0014] This makes it possible to ensure that an excessively rich hydrogen / air mixture is not subjected to combustion. Hydrogen-fueled internal combustion engines are preferably operated in the lean range (lambda > 1). For example, depending on the performance range, the limit value can be taken from the aforementioned value range. The lambda target limit value is therefore preferably variable across the performance range.

[0015] According to yet another aspect, the injected fuel amount can be preferably determined such that the lambda injection value corresponds to the target lambda limit value when the lambda preset value, which indicates the formation of a mixture based on the preset fuel and air amounts, is outside the lambda target range.

[0016] This allows the fuel amount to be adjusted up to the limit of an acceptable combustion mixture. The fuel amount is therefore determined to provide a suitable acceptable combustion mixture from the amount of air supplied. In particular, because the lambda target limit is the next value in the lambda target range relative to the lambda default value, the correction of the default fuel amount can be relatively small.

[0017] According to yet another aspect, the lambda target range, and in particular the first lambda target limit, can be variable.

[0018] This aspect increases the flexibility of the internal combustion engine: depending on the boundary conditions, the restriction can be made stronger or weaker.

[0019] According to yet another aspect, the internal combustion engine may further include an exhaust gas recirculation system for recirculating exhaust gases to the combustion chamber, at least in some areas.

[0020] By providing exhaust gas recirculation, it is possible to stabilize the combustion in the combustion chamber, for example to prevent knocking of the internal combustion engine due to misfires. Particularly in the case of lean combustion, the recirculated exhaust gas contains a significant proportion of unburned oxygen (residual gas), which helps to stabilize the combustion. The recirculated exhaust gas is preferably inert to combustion.

[0021] Alternatively or additionally, the internal combustion engine may comprise an inert medium supply device arranged to supply an inert medium that does not participate in the combustion, preferably water, to the combustion chamber.

[0022] By providing an inert medium, it is also possible to stabilize the combustion by lowering the combustion temperature. In particular, the inert medium can be liquid or gaseous water, which is particularly inert when burning hydrogen and therefore makes it possible to lower the temperature. Furthermore, it is possible to prevent additional emissions.

[0023] According to the present invention The amount of injected fuel is determined, at least to some extent, based on the amount of exhaust gas recirculation and / or the amount of inert medium supplied.

[0024] It is therefore possible to take into account the combustion behavior, which is influenced by the amount of exhaust gas recirculation and / or the amount of inert medium supplied, when determining the amount of injected fuel.

[0025] The present invention According to the present invention, the lambda target range, in particular the first lambda target limit value, is dependent on the exhaust gas recirculation amount and / or the inert medium supply amount. Crate Preferably, the first lambda target range is decreaseable with increasing required exhaust gas recirculation and / or inert medium supply.

[0026] The exhaust gas recirculation amount and / or the inert medium supply amount can influence combustion. Therefore, a limitation can be made by a lambda target range depending on the exhaust gas recirculation amount and / or the inert medium supply amount. Since the exhaust gas recirculation and the inert medium supply stabilize combustion, the range of permissible lambda target values ​​can be expanded. This can be achieved, in particular, by reducing the first lambda target limit value as a lower limit value.

[0027] According to yet another aspect, exhaust gas recirculation and / or inert medium supply may be required if the lambda preset value, which indicates the formation of a mixture based on the preset fuel and air amounts, is outside the lambda target range and / or exceeds the limits of performance requirements.

[0028] By stabilizing combustion with the exhaust gas recirculation amount and / or the inert medium supply amount, the lambda target range can be accurately expanded if the lambda default value is outside the lambda target range without exhaust gas recirculation or inert medium supply. As performance requirements increase, the demand for fuel increases, which is why the lambda default value may be outside the acceptable range. Therefore, the exhaust gas recirculation amount and / or the inert medium supply amount may also be required beyond the performance requirement limit. During a temporary increase in the load of an internal combustion engine, such as during an acceleration process in a vehicle, the required performance can be provided by requesting the exhaust gas recirculation amount and / or the inert medium supply amount. Without the exhaust gas recirculation amount and / or the inert medium supply amount, the lambda target range would be more limited and would not be able to provide the required performance. The exhaust gas recirculation amount and / or the inert medium supply amount are preferably required at least over the entire load range.

[0029] Alternatively, or additionally, if the lambda default value is outside the lambda target range, i.e., if it reaches or falls below / exceeds a limit value, in particular if it falls below a lower limit value and / or exceeds a limit value beyond the performance requirement, the required exhaust gas recirculation amount and / or inert medium supply amount can be increased.

[0030] Therefore, the first lambda target limit can be reduced accordingly and a lambda default can be set, allowing for proper control of exhaust gas recirculation and mixing on demand.

[0031] According to yet another aspect, the required exhaust gas recirculation rate and / or the inert medium supply rate can be increased as performance demands on the internal combustion engine increase.

[0032] This allows for a richer mixture, i.e., a lower lambda injection value, as desired for higher performance requirements, since exhaust gas recirculation and / or inert medium supply stabilize combustion, and it is possible to prevent knocking of the internal combustion engine even at low lambda injection values. Therefore, an increase in the amount of exhaust gas recirculation and / or inert medium supply can be used to improve performance, which is advantageous for temporary processes. According to yet another aspect, the predetermined fuel amount can be determined based at least on the performance requirements for the internal combustion engine.

[0033] Thus, performance requirements can be used as the basis for determining the predetermined fuel quantity and therefore the amount of fuel injected.

[0034] Preferably, the predetermined fuel amount increases as performance demands increase, and vice versa. The heating value of the hydrogen / air mixture is related to the percentage of fuel in the mixture. Therefore, higher performance can be achieved by increasing the fuel amount.

[0035] According to yet another aspect, the amount of fuel injected can be determined, at least within certain ranges, based on the value of the knock signal.

[0036] According to this aspect, the knock signal value, and therefore the value indicative of a combustion anomaly, can be taken into account in determining the fuel quantity. Information about the tendency of a relevant cylinder of an internal combustion engine to knock can be obtained based on the knock signal value, for example, from a previous combustion cycle. The tendency to knock depends on factors such as the temperature of the combustion chamber walls, compression, and manufacturing tolerances. These factors can be used in determining the injected fuel quantity for the current cycle based on 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 indicative of stronger knocking can provide information about a low oxygen content in the exhaust gas, which makes stabilizing combustion more difficult.

[0037] The first lambda target limit is preferably increased as the knock signal value increases.

[0038] This can reduce knocking in an internal combustion engine, since increasing the lambda target limit can make the mixture leaner and reduce the tendency towards knocking.

[0039] According to yet another aspect of the present invention, there is provided a method of operating a spark ignition internal combustion engine, wherein the internal combustion engine is operated using hydrogen as fuel, and the internal combustion engine has a plurality of combustion chambers, and wherein: a) determining a fuel injection amount for at least one combustion chamber and a fuel injection amount for at least one other combustion chamber based on a knock signal value associated with at least one combustion chamber; ,child The amount of fuel injected into one combustion chamber is determined so that the knock signal value of that combustion chamber is reduced. ,child One combustion chamber is operated with a lean hydrogen / air mixture, and in at least one other combustion chamber of the plurality of combustion chambers, the injected fuel amount is determined, and again preferably achieved, to approximate as closely as possible an overall predetermined fuel amount, which is a predetermined amount of fuel supplied to all combustion chambers.

[0040] Because quality control is performed within at least some ranges in each combustion chamber, according to this aspect of the invention, the fuel quantity in at least one other cylinder can be adapted based on the knock signal value of at least one combustion chamber. In particular, the adjustment of the fuel quantity in at least one combustion chamber can be compensated for individually. Preferably, the knock signal value in at least one combustion chamber is higher than that in at least one other combustion chamber. This aspect can be provided as a second independent aspect, which can be collectively defined as fuel quantity redistribution, or can be provided in combination with the preceding aspects according to the first independent aspect. This aspect also reduces the occurrence of combustion anomalies, thus providing a method that takes into account the needs of internal combustion engines operated with hydrogen.

[0041] 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, this performance can be achieved or at least approached by adapting the fuel amount in the other cylinders accordingly, regardless of knocking in the combustion chamber of a certain cylinder.

[0042] In a), the modification compared to the predetermined fuel quantity of at least one combustion chamber is preferably added at least partially, preferably entirely, to the fuel quantity of at least one other combustion chamber associated with a lower knock signal value, and particularly preferably to the fuel quantities of a plurality of other combustion chambers respectively. According to a further embodiment, the modification can be added to the fuel quantity of each combustion chamber depending on the respective knock signal value of the other combustion chambers.

[0043] The amount of fuel can then be reduced in at least one combustion chamber, for example by increasing the lower lambda target limit, and the amount of fuel can be increased by this reduction, preferably in at least one other combustion chamber, thereby maintaining the overall performance output of the internal combustion engine.

[0044] In a second independent embodiment, in addition to a): b) increasing the amount of exhaust gas recirculation in at least one combustion chamber; c) shifting the ignition timing in at least one combustion chamber to a later time; and d) Reducing performance requirements for the internal combustion engine It is possible to implement at least one of the following.

[0045] As already described in relation to the first independent aspect above, combustion can be stabilized by b). The exhaust gas recirculation amount is increased at least in one combustion chamber associated with a critical (highest) knock signal value, for example, by a valve or throttle in the supply line to the respective combustion chamber. However, this can also be advantageously performed globally for each of several combustion chambers, where a valve or throttle does not need to be provided in each supply line, and control can be performed by a central valve. This simplifies the system and ensures that combustion is stabilized in each of all cylinders or combustion chambers. For this reason, the fuel amount can be increased in at least one other combustion chamber. The change in at least one combustion chamber can therefore be better absorbed in at least one other combustion chamber.

[0046] Knocking in at least one combustion chamber can be reduced by c), since retarding the ignition position prevents premature and uncontrolled combustion. In particular, the spark plug can be activated at a later time. The shift of the ignition timing to a later time means, for example, that it is related to the piston position or crank angle of the piston defining the combustion chamber and is based on a reference value for the ignition point. The reference value can, for example, be the ignition point from the previous cycle or another reference value related to the combustion lambda of one combustion chamber, preferably the optimal ignition point for the respective lambda. In particular, the mixture can be ignited at a time when the piston is closer to top dead center than the reference time.

[0047] The predetermined fuel quantity in at least one combustion chamber, which is the critical knock signal value, can be reduced by d), which makes it possible to make the mixture leaner and thus reduce the tendency towards knocking.

[0048] For example, if it is determined that the knock signal value limit is still exceeded, steps b), c), and d) are preferably performed in the order mentioned above. For example, if it is determined that too high a knock signal value continues to occur in one combustion chamber despite the redistribution according to a), b) can be performed. The same applies to steps c) and d). This means that engine-friendly steps such as redistribution and exhaust gas recirculation can be performed first.

[0049] It is further preferred that at least in a second independent aspect a verification is performed as to whether a fuel quantity redistribution is possible, for example whether the knock signal value in at least one of the combustion chambers is below a limit value of the knock signal value, in which case fuel can be redistributed from at least one combustion chamber to the combustion chamber with the lower knock signal value, in which case fuel redistribution can be performed, otherwise one of steps b), c) and d) can be performed.

[0050] According to yet another aspect, the amount of fuel injected may be determined, at least within some ranges, based on lambda sensor measurements in the exhaust section of the internal combustion engine.

[0051] This allows the residual gas content in the exhaust gas to be determined, providing information about the mixture ratio from the previous combustion cycle. If exhaust gas recirculation is required, this information can be of double relevance, since it also provides information about the residual gas content of the exhaust gas returned to the combustion chamber via exhaust gas recirculation. Therefore, the lambda target limit value can also be determined based on the lambda sensor measurement value.

[0052] According to a further aspect, The present invention There is provided a control device for carrying out the method according to one of the above aspects.

[0053] Then, for example, when this control device is provided in a motor vehicle equipped with a hydrogen combustion engine, it is possible to carry out the method according to the above aspects.

[0054] According to a further aspect of the present invention, when executed on a computer connected to an internal combustion engine, the computer The present invention A program for causing the method according to the above aspect to be performed is provided.

[0055] According to yet another aspect of the present invention, there is provided a computer-readable storage medium having the above program stored thereon.

[0056] The invention will now be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0057] [Figure 1] FIG. 1 shows a flow chart illustrating the method according to the present invention. [Figure 2] Figure 2 compares the performance profile versus rotational speed and the exhaust gas recirculation rate versus rotational speed. [Figure 3a] FIG. 3a shows a schematic representation of the external formation of the mixture in a hydrogen-fueled internal combustion engine. [Figure 3b] Figure 3b shows the internal formation of the mixture. DETAILED DESCRIPTION OF THE INVENTION

[0058] The flow chart shown in Figure 1 illustrates a method that can be used, for example, to control the amount of fuel in a hydrogen-fueled internal combustion engine. In particular, it is possible to determine the amount of hydrogen for the next combustion cycle that is metered into each combustion chamber by an injector. The internal combustion engine has a spark plug in the cylinder head of each combustion chamber. For the purposes of the present invention, these are spark-ignition internal combustion engines. The internal combustion engine has at least one combustion chamber that can be defined by a cylinder, a cylinder head, and a piston connected to a crankshaft. The method controls the fuel of the combustion cycle for this combustion chamber, in which a hydrogen / air mixture is combusted.

[0059] According to this method, first, a predetermined fuel amount F def is preferably determined according to the required load. def is adjusted according to the calorific value of the fuel. Similarly, the amount of ambient air L entering the combustion chamber from outside the internal combustion engine, measured for example by an air mass sensor, can be determined. From these two values, a predetermined fuel amount F def and the default lambda value λ coming from the ambient air L 既定 can be calculated in step S1.

[0060] Then, the lambda default value λ 既定 is the lower limit λ 標的-l and upper limit λ 標的-u Lambda target range [λ 標的-l ;λ 標的-u In this case, it can be verified in step S3 whether the injected fuel amount F 噴射 is the default fuel amount F def is set equal to

[0061] In step S2, the lambda default value λ 空気-既定 is the lambda target range [λ 標的-l ;λ 標的-u If it is outside the range, in step S41, the injection fuel amount F 噴射 is the initial lambda value, lambda λ 既定 The limit value λ is close to標的-l or λ 標的-u The injected fuel amount F 噴射 is therefore corrected in the case of step S41. 標的-l ;λ 標的-u ] can be determined in advance for a particular internal combustion engine. According to the present invention, the lambda target range [λ 標的-l ;λ 標的-u ] is the lambda target range, where the exhaust gas recirculation amount is not recirculated to the combustion chamber. In these cases, the lower limit value λ 標的-l is preferably 2.0 or more and 4.5 or less, more preferably 2.0 or more and 4 or less, and particularly preferably 2.2 to 3.8.

[0062] In step S2, the lambda default value λ 空気-既定 is within the lambda target range [λ 標的-l ;λ 標的-u ], it is possible to request an exhaust gas recirculation amount instead in step S42 if the internal combustion engine is additionally equipped with an exhaust gas recirculation device. act can be determined or modeled, for example, by an air mass sensor. Preferably, at least one of the air mass and the exhaust gas recirculation mass is detected based on the interaction between the air mass and the exhaust gas recirculation mass. For example, the exhaust gas recirculation mass R act can be obtained from the difference between the combustion chamber charge and the air amount. Instead of or in addition to an exhaust gas recirculation device, the internal combustion engine can also be equipped with an inert medium supply device. The inert medium supply device can supply an inert medium, such as water, directly or indirectly to the combustion chamber. The inert medium does not participate in combustion and preferably has a specific heat capacity of at least 900 J / (kg×K), preferably at least 1500 J / (kg×K), and even more preferably at least 4000 J / (kg×K).

[0063] Exhaust gas recirculation and inert medium supply ensure a stable combustion in the combustion chamber of the internal combustion engine, and for example, knocking of the internal combustion engine due to misfires can be at least reduced or even completely prevented.

[0064] Exhaust gas recirculation rate R act Considering different lambda target ranges [λ 標的-l ;λ 標的-u ] R is the required exhaust gas recirculation amount R act This lambda target range [λ 標的-l ;λ 標的-u ] R In particular, the lower limit λ 標的-l is reduced compared to that in step S2. This means that a richer hydrogen / air mixture can be burned without combustion abnormalities. The lambda target range [λ 標的-l ;λ 標的-u ] R depends on the amount of exhaust gas recirculation available. If the amount of exhaust gas recirculation is high, the lambda lower limit can be reduced, preferably to a value of 1.2.

[0065] In step S44, a comparison similar to that in step S2 is again made. 既定 However, the exhaust gas recirculation amount R act The lower limit λ 標的-l and upper limit λ 標的-u Lambda target range [λ 標的-i ;λ 標的-u ] R In this case, it is specifically verified whether the injected fuel amount F 噴射 is the default fuel amount F def is set equal to

[0066] Otherwise, the injected fuel amount F 噴射 In step S46, the exhaust gas recirculation amount R act While taking into account the default lambda value λ 既定 The limit value λ of the lambda target range close to 標的-lor λ 標的-u Therefore, in the case of step S46, the injected fuel amount F 噴射 is corrected.

[0067] Instead, the lambda default value λ 既定 is outside the lambda target range, i.e., the limit values, especially the lower limit λ 標的-l Note that if the exhaust gas recirculation rate is determined to be above or below 0.001, the exhaust gas recirculation rate can be increased. This can occur in step S42, where the increase is associated with the initial request. However, this can occur after step S44 if the current exhaust gas recirculation rate is not sufficient.

[0068] Similarly, the exhaust gas recirculation amount may already exist in step S2, and an increase in the exhaust gas recirculation amount may be requested in step S42.

[0069] The advantageous effects of the present invention will now be described.

[0070] According to the method illustrated with reference to Figure 1, the fuel quantity can be the controlled variable. More precisely, the injected fuel quantity is determined independently of the predetermined lambda target value, at least within some ranges. In particular, the injected fuel quantity is determined independently of the predetermined lambda target value, within the lambda target range [λ 標的-l ;λ 標的-u ] can be determined independently of a predetermined lambda target value. For example, if there is a change in the amount of air supplied to the engine, the amount of fuel is not bound by the amount of air supplied, as in a conventional gasoline system, but is instead determined by a predetermined fuel amount F def The injected fuel amount can be freely determined based on the lambda target range [λ] in the above embodiments, at least within some ranges. 標的-l ;λ 標的-u ] is determined independently of the fixed lambda target value. This allows for increased flexibility of the internal combustion engine. In addition, the air amount L is determined independently of the lambda default value λ 既定or lambda injection value, respectively. The amount of fuel to be injected is then determined based on the air amount. Preferably, here the amount of fuel is determined based on the air amount and the lambda target range.

[0071] The injected fuel quantity is determined to be at least within the lambda target range and equal to the predetermined fuel quantity F def This means that a desired predetermined fuel amount can be set and injected regardless of a constant lambda target value. The term "lambda target range" refers to the lambda target range [λ] without exhaust gas recirculation, as explained above. 標的-l ;λ 標的-u ] and the lambda target range with exhaust gas recirculation [λ 標的-l ;λ 標的-u ] R It is possible to include multiple lambda target ranges with

[0072] Injected fuel amount F 噴射 In steps S41 and S46, the lambda injection value is determined to be greater than or equal to the first lambda target limit value λ 標的-l The amount of fuel injected is determined so as to be within a lambda target range of lambda target values ​​limited by the increment ΔF in steps S41 and S46. def The lower limit λ is determined to be added to 標的-l , the increment is negative and therefore the lambda injection value is increased by reducing the fuel quantity. Conversely, above the upper limit the increment is positive. Note that the air quantity in this case is fixed, i.e. not controlled, but is the actual air quantity L determined by measurements in the intake section, and therefore the lambda injection value is set by controlling the fuel quantity.

[0073] The increment ΔF, and therefore the injected fuel amount, can be determined so that the lambda injection value corresponds to the lambda target limit. This allows the fuel amount to be adjusted up to the limit of an acceptable combustion mixture. The fuel amount is therefore determined so that an appropriate acceptable combustion mixture is obtained from the actual amount of air supplied. In particular, because the lambda target limit is the next value in the lambda target range relative to the lambda default value, the correction of the default fuel amount can be relatively small.

[0074] In the above embodiment, the lower limit of the range of lambda target values ​​depends on the amount of exhaust gas recirculation and is preferably ≧1.2 and ≦2.5, particularly preferably ≧1.2 and ≦1.8, and even more preferably this corresponds to 1.2.

[0075] This makes it possible to ensure that an excessively rich hydrogen / air mixture is not subjected to combustion. The hydrogen-fueled internal combustion engine is therefore operated within the lean range (lambda > 1). Depending on the performance range, the limit value can be taken from the above value range. The lambda target limit value is therefore preferably variable across the performance range.

[0076] As mentioned above, the lambda target range [λ 標的-l ;λ 標的-u ] R depends on the amount of exhaust gas recirculation available, and the lambda target range can be variable.

[0077] As described above, the internal combustion engine of this embodiment further includes an exhaust gas recirculation device that recirculates exhaust gas to the combustion chamber, at least in some areas. Exhaust gas recirculation can stabilize combustion in the combustion chamber. For example, it can prevent knocking of the internal combustion engine due to misfires. In particular, in the case of lean combustion, the recirculated exhaust gas contains a significant proportion of unburned oxygen (residual gas), which helps stabilize combustion.

[0078] Lambda target range [λ 標的-l ;λ 標的-u ]R depends not only on the amount of exhaust gas recirculation available, but also, in an embodiment, on the lower limit λ 標的-l is adjusted depending on the exhaust gas recirculation amount. Therefore, the exhaust gas recirculation amount is taken into account when determining the injected fuel amount, at least in some ranges where exhaust gas recirculation is effective. In particular, the first lambda target limit value can be decreased as the required exhaust gas recirculation amount increases. Note that, as indicated by the arrow in FIG. 1, the exhaust gas recirculation amount not only affects the limit value of the lambda target range, but also the supplied ambient air amount L. This is because as the exhaust gas recirculation amount increases, the amount of air to be supplied to the combustion chamber decreases. If the default fuel amount remains the same, the default lambda value that must be taken into account in step S44 decreases. Note that in FIG. 1, the air amount L for step S2 can be a measured air amount L (stored), such as from the previous cycle, while the currently measured air amount is reduced to take into account the actual exhaust gas recirculation amount and can be used for step S44. In other words, to determine whether a request for exhaust gas recirculation is necessary, a reference value for air mass can be used, preferably obtained from a current measurement from the previous cycle, but also determined in advance for a given internal combustion engine. Note that a request for exhaust gas recirculation does not necessarily have to precede the comparison from step S2. Instead, exhaust gas recirculation can also be requested at any time or for a certain performance range.

[0079] As shown in Figure 1, the exhaust gas recirculation rate R act is the lambda target range [λ], which indicates the formation of a mixture based on a predetermined amount of fuel and air. 標的-l ;λ 標的-u ] R If exhaust gas recirculation is already present when out, it is requested or increased.

[0080] By stabilizing combustion with the exhaust gas recirculation amount, the lambda target range can be expanded precisely if the lambda default value is outside the lambda target range without exhaust gas recirculation. As performance requirements increase, the demand for fuel increases, which is why the lambda default value may be outside the acceptable range. Therefore, the exhaust gas recirculation amount may also be requested beyond the performance requirement limit (i.e., if it is determined that the performance requirement limit will be exceeded). During a temporary increase in load on an internal combustion engine, such as during an acceleration process in a vehicle, the required performance can be provided by requesting an exhaust gas recirculation amount. Without exhaust gas recirculation, the lambda target range would be more limited and would not be able to provide the required performance.

[0081] In the embodiment, the predetermined fuel amount F def As the amount of required exhaust gas recirculation increases, the amount of required exhaust gas recirculation also increases. def The lambda target range [λ] without exhaust gas recirculation cannot be achieved by 標的-l ;λ 標的-u ] is derived from the measured air volume L. The exhaust gas recirculation volume is determined, for example, by a valve in the exhaust gas recirculation section, within the lambda target range [λ 標的-l ;λ 標的-u ] is the air amount and the specified fuel amount F def Advantageously, the predetermined fuel quantity F def is increased as performance demands increase, the required amount of exhaust gas recirculation is also increased. Therefore, the required amount of exhaust gas recirculation is advantageously increased as performance demands on the internal combustion engine increase.

[0082] This allows for a richer mixture, i.e. a lower lambda injection value, as desired for higher performance requirements, since the exhaust gas recirculation stabilizes the combustion, and it is possible to prevent knocking of the internal combustion engine even at low lambda injection values. An increase in the amount of exhaust gas recirculation can therefore be used to improve performance, which is particularly advantageous in transient processes and at full load. This effect is shown in Figure 2. In the upper part of Figure 2, the profile of the exhaust gas recirculation rate EGR is shown over the rotational speed. As can be seen, the exhaust gas recirculation rate is increased at the rotational speed limit n 限界 , and increases continuously from there. On the other hand, the performance profile is shown in the lower part of Figure 2, where it is shown that even an increase in the amount of exhaust gas recirculation can provide higher performance. The solid line shows the performance profile when exhaust gas recirculation is provided. The dashed line profile is without exhaust gas recirculation. Without exhaust gas recirculation, increasing the fuel amount no longer allows a significant increase in performance.

[0083] This effect does not occur in conventional gasoline engines, as they are controlled to a fixed lambda value. Therefore, when exhaust gas recirculation is increased in a conventional gasoline engine, the amount of air must be reduced, which also results in a reduction in fuel.

[0084] The heat value of the combustion mixture correlates with the output performance. def is determined based at least on the performance requirements for the internal combustion engine.

[0085] Thus, performance requirements can be used as the basis for determining the default fuel amount and therefore the amount of fuel injected.

[0086] As performance requirements increase, the predetermined fuel amount is preferably increased, and vice versa. The heating value of a hydrogen / air mixture is related to the percentage of fuel in the mixture. This means that higher performance requirements can be met by increasing the fuel amount.

[0087] In the above embodiments, it is possible to use, at least within some ranges, the knock signal value to determine the amount of fuel injected.

[0088] According to this aspect, the knock signal value, and therefore the value indicative of a combustion abnormality, can be taken into account when determining the fuel quantity. Information about the tendency of each cylinder of an internal combustion engine to knock can be obtained, for example, from the previous combustion cycle based on the knock signal value. The tendency to knock depends on factors such as the temperature of the combustion chamber walls, compression, and manufacturing tolerances. These factors can be used to determine the injected fuel quantity for the current cycle based on 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 indicative of stronger knock can provide information about a low oxygen content in the exhaust gas, which makes stabilizing combustion more difficult. The knock signal value can also provide information about the actual available exhaust gas recirculation amount, which may differ from the required exhaust gas recirculation amount. Errors in the air mass measurement can also be taken into account and compensated for.

[0089] The lambda target range is preferably determined based on the knock signal value, and particularly preferably the first lambda target limit value is increased with increasing knock signal value.

[0090] This can reduce knocking in an internal combustion engine, since increasing the lambda target limit can make the mixture leaner and reduce the tendency towards knocking.

[0091] The knock signal value can also be taken into account as follows: For example, if in step S2 of the above embodiment the lambda target range is adjusted based on the knock signal value, the fuel amount is changed by an increment ΔF in step S41.

[0092] However, if multiple combustion chambers are provided, the negative value of the increment ΔF resulting from 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 increment ΔF can be divided among the multiple combustion chambers.

[0093] This means that the fuel injection quantity for at least one combustion chamber and the fuel injection quantity for at least one other combustion chamber can both be determined based on the (measured) knock signal value associated with at least one combustion chamber. By determining the lambda target range based on the knock signal value in step S41 and subsequently correcting the fuel quantity, the knock signal value for one combustion chamber can be reduced, while in at least one other combustion chamber of the plurality of combustion chambers, the fuel quantity is determined, and again preferably achieved, so as to approximate as closely as possible to an overall default fuel quantity, which is a predetermined fuel quantity supplied to all combustion chambers. One combustion chamber can continue to operate with a leaner mixture than would result from a default fuel quantity achievable with a smaller injected fuel quantity compared to the default fuel quantity.

[0094] In particular, the adjustment of the fuel amount in at least one combustion chamber can be compensated for in the individual combustion chambers, preferably such that the knock signal value in at least one combustion chamber is higher than in at least one other combustion chamber.

[0095] The total predetermined fuel amount can be a fuel amount determined based on performance requirements. The predetermined fuel amount for each individual combustion chamber can be determined from the total predetermined fuel amount by, for example, dividing the total predetermined fuel amount by the number of combustion chambers if the combustion chambers are identical.

[0096] Preferably, in a), as described above, the amount of the change compared to the default fuel quantity of one combustion chamber is at least partly, preferably entirely, compensated by the fuel quantity of at least one other combustion chamber.

[0097] The aforementioned fuel quantity redistribution can be made dependent on the respective knock signal values ​​of the other combustion chambers, and combustion chambers with lower associated knock signal values ​​can be compensated proportionally with a larger percentage of the change.

[0098] If the overall predetermined fuel amount or performance requirement can be achieved by redistribution, steps S42 to S46 can be omitted.

[0099] However, redistribution and exhaust gas recirculation can be combined. For example, if it is determined that the total predetermined fuel amount cannot be achieved by compensation in the other combustion chambers, the exhaust gas recirculation amount can be increased in at least one of the combustion chambers. This corresponds to step b) above. As already explained above, combustion can be stabilized by b). The exhaust gas recirculation amount is increased at least in one combustion chamber associated with a critical (highest) knock signal value, for example, by a valve or throttle in the supply line to the respective combustion chamber. However, this can also be done globally for each of several combustion chambers. In this case, there is no need to provide a valve or throttle in each supply line, and control can be performed by a central valve. This simplifies the system and ensures stable combustion in each of all cylinders or combustion chambers. Therefore, the fuel amount can be increased in at least one other combustion chamber. The change in at least one combustion chamber can therefore be better absorbed in at least one other combustion chamber.

[0100] Alternatively or additionally to increasing the amount of exhaust gas recirculation, it is also possible to shift the ignition timing in at least one combustion chamber to a later time (step c)) and / or reduce the performance demands on the internal combustion engine (step d)).

[0101] Retarding the ignition point prevents premature and uncontrolled combustion. In particular, the spark plug can be activated at a later time. Shifting the ignition point to a later time means that it is related to, for example, the piston position or crank angle of the piston defining the combustion chamber and is based on a reference value for the ignition point. The reference value can be, for example, the ignition point from the previous cycle or another reference value, preferably the optimum ignition point, related to the combustion lambda of one combustion chamber. In particular, the mixture can be ignited at an ignition point when the piston is located closer to top dead center than at the reference time.

[0102] Reducing performance requirements means that the overall prescribed fuel quantity can be reduced, particularly by reducing the prescribed fuel quantity in at least one combustion chamber, thereby reducing performance requirements.

[0103] For example, if it is determined that the knock signal value is higher than an acceptable limit despite the redistribution, it may be advantageous to activate exhaust gas recirculation control after the redistribution.

[0104] Steps b), c) and d) are then carried out in that order, which means that engine-friendly steps such as redistribution and exhaust gas recirculation can be carried out first.

[0105] It is also possible to verify whether fuel quantity redistribution is possible, if so, fuel redistribution can be performed, otherwise one of steps b), c) and d) can be performed.

[0106] The redistribution feature does not necessarily need to be combined with the feature of determining the injected fuel amount based on the air amount, but can be applied independently, and therefore there is no need to measure the air amount for this purpose.

[0107] Regardless of the number of combustion chambers, the fuel amount 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 determined based on the knock signal value. For example, the lambda target range in step S2 of the above embodiment can be adapted based on the knock signal value. Increasing the exhaust gas recirculation amount can increase the lambda target range. Thus, the exhaust gas recirculation amount is advantageously increased as the knock signal value increases.

[0108] Similarly, in this embodiment, a lambda sensor can be provided in the exhaust section, and the signal value from the lambda sensor can then be used to determine the amount of fuel injected.

[0109] This allows the residual gas content in the exhaust gas to be determined, providing information about the mixture ratio from the previous combustion cycle. If exhaust gas recirculation is required, this information can be of double relevance, since it also provides information about the residual gas content of the exhaust gas returned to the combustion chamber via exhaust gas recirculation. Therefore, the lambda target limit value can also be determined based on the lambda sensor measurement value.

[0110] In the above embodiment, the air amount (air mass) is measured, for example, using an air mass meter. However, the air amount can also be modeled, for example, using parameters. Figures 3a and 3b show the composition of the cylinder charge in the combustion chamber, i.e. the mixture of fuel, air and recirculated exhaust gases. In the external formation of the mixture according to Figure 3a, the air mass flow rate m 空気 and the mass flow rate of the recirculated exhaust gas m EGR Further downstream, the hydrogen mass flow rate m H2 is fed into the supply passage to the cylinder. In the mixing zone of the supply passage, the mass flow of air from the air inlet passage, the mass flow of recirculated exhaust gas from the exhaust gas inlet passage, and the mass flow of hydrogen from the fuel inlet passage are mixed, resulting in a mixture mass flow m 混合By integrating the time over which the mixture mass flow enters the cylinder, we obtain the cylinder charge mass m 混合気 It is possible to place air mass meters in both the air inlet and the exhaust gas inlet, measuring the mass flow rate in each inlet. By integrating over time, the mixture m 混合気 The air mass L and exhaust gas R present in act However, it is also possible to measure only one of these values, or even none of them, and to omit at least one air mass sensor. For example, if the maximum cylinder volume and / or the cross-sectional area of ​​the inlet passages are known, each of the gas quantities (masses) can be modeled, for example, by a pressure sensor in the respective inlet passage.

[0111] In contrast to Figure 3a, Figure 3b shows the case of internal mixture formation, where fuel is supplied to the cylinder, preferably when the combustion chamber is closed. Therefore, in the mixing zone, only the mass flow of air and the mass flow of recirculated exhaust gas are mixed. Here too, the air amount and the exhaust gas recirculation amount can be measured or modeled.

[0112] The air amount and / or the exhaust gas recirculation amount are preferably known actual variables of the combustion cycle being performed, which can be determined, for example, based on sensors or modeling. The fuel amount can be controlled, for example, by opening the injection nozzles. In both types of mixture, the fuel amount can be adapted using known variables.

[0113] The above method is suitable for use in both types of internal combustion engines.

[0114] The above steps do not necessarily have to be provided in their entirety, nor do they necessarily have to be performed in this order. To the extent that exhaust gas recirculation is not activated, steps S42 to S46 can be omitted, for example. However, steps S3 to S41 can also be omitted if the control device directly requests the amount of exhaust gas recirculation, for example due to specific performance requirements.

[0115] In the above description, wherever reference is made to exhaust gas recirculation, an inert medium supply can also be used instead or in combination.

[0116] The invention is particularly suitable for internal combustion engines with an unrestricted air flow, but it is also possible, for example, to provide a throttle valve in the supply line to the combustion chamber, which restricts the cross section of the supply line in the partial load range and completely opens the cross section in the full load range.

[0117] Preferably, hydrogen alone is used as the fuel.

[0118] The lambda target range may also include only one lambda target value, so that the fuel amount can always be adjusted relative to the target lambda value, which is a variable that depends, for example, on the amount of exhaust gas recirculation.

[0119] In this disclosure, the term "within certain ranges" preferably refers to a performance range and / or a lambda range. For example, within a lambda target range, the fuel amount is determined independently of the lambda target value. For example, the air amount can only be determined within certain performance ranges. For example, in the part load range, decisions based on the air amount cannot be made because there is no risk of the engine knocking.

[0120] Unless otherwise specified, the term "at least" also includes the whole.

[0121] The term "performance" includes torque and / or rotational speed of an internal combustion engine.

[0122] The term "amount" particularly includes mass, but can also include, for example, number or volume of particles.

[0123] "Injection" in this disclosure includes any type of fuel supply for the formation of a combustion mixture.

Claims

1. A method for operating a spark ignition internal combustion engine, comprising: The internal combustion engine is operated using hydrogen as fuel, and the internal combustion engine further comprises, at least in some areas, an exhaust gas recirculation device for recirculating exhaust gas to a combustion chamber of the internal combustion engine, and / or an inert medium supply device for supplying an inert medium that does not participate in combustion to the combustion chamber; the lambda injection value is a value indicating the formation of an air-fuel mixture based on an injected fuel amount (F injection) supplied to the combustion chamber of the internal combustion engine and an air amount (L) supplied to the combustion chamber from outside the internal combustion engine; The injected fuel amount (F injected) is determined, at least within some performance ranges, independently of the lambda target value, based on at least a default fuel amount (F def ), and based on the exhaust gas recirculation amount (R) and / or the inert medium supply amount; and the injected fuel amount is determined based on the air amount within at least some performance ranges; the injected fuel quantity is determined based on at least a lambda target range ([λ target-l; λ target-u]) and within the lambda target range ([λ target-l; λ target-u]) independently of the lambda target value, the injected fuel quantity being determined so that the lambda injection value is within the lambda target range of lambda target values ​​limited at least on one side by a first lambda target limit value, the lambda target range ([λ target-l; λ target-u]) depending on the exhaust gas recirculation amount (R) and / or the inert medium supply amount, The method of claim 1, wherein the first lambda target limit value is the lower limit value of the range of lambda target values ​​(λ target - 1) and decreases with increasing exhaust gas recirculation amount (R) and / or inert medium supply amount.

2. The method of claim 1 , wherein the injected fuel amount is determined such that the lambda injection value corresponds to the first lambda target limit value.

3. 2. The method of claim 1, wherein the exhaust gas recirculation amount and / or the inert medium supply amount are requested or increased when a lambda preset value (λ preset) indicating the formation of a mixture based on the preset fuel amount and the preset air amount is outside the lambda target range and / or exceeds a limit value of a performance requirement.

4. 2. The method of claim 1, wherein the required exhaust gas recirculation amount and / or the inert medium supply amount are increased as performance demands on the internal combustion engine increase.

5. The method of claim 1 , wherein the default fuel quantity (Fdef) is determined based at least on performance requirements for the internal combustion engine.

6. The method of claim 1 , wherein the amount of injected fuel is determined, at least in some ranges, based on a knock signal value.

7. A control device for carrying out the method of claim 1.

8. A program that, when executed on a computer coupled to an internal combustion engine, causes the computer to perform the method of claim 1.

9. A computer-readable storage medium on which the program described in claim 8 is stored.

Images