Control unit for controlling the amount of hydrogen injected into an internal combustion engine

Abstract

Control unit (1) for a powertrain (2) comprising an internal combustion engine (3), wherein the internal combustion engine (3) is designed as a hydrogen engine and wherein the control unit (1) is designed and configured to perform the following steps: - Determining a required air-fuel ratio (S11, λ) erf ) based on a load requirement and a current air mass flow, - Determining a target combustion center (S12), - Determining a minimum air ratio (S13, λ) min ) at the determined target combustion center (S12) taking into account NOx emissions and / or a ratio of H2 / NOx emissions, - Comparing (S20) the required air ratio (S11, λ) erf ) and the minimum air ratio (S13, λ min ), - Determining a shift of the combustion center of gravity (S30) if the comparison (S20) shows that the required air-fuel ratio (S11, λ) erf ) smaller than the minimum air ratio (S13, λ min ) is, and - Control (S40) of an injection quantity of hydrogen based on the required air ratio (S11, λ erf ) or the specific shift of the combustion center of gravity (S30).

Description

[0001] The invention relates to a control unit for a powertrain comprising an internal combustion engine, for controlling an injection quantity of hydrogen.

[0002] From DE 43 44 715 A1 a system for controlling an air-fuel ratio for an engine powered by a gaseous fuel is known.

[0003] WO 2007 / 085 897 A1 discloses a gas engine and a method for controlling it, wherein it is provided to control the gas engine depending on the load range in which it is located, whereby operating modes with different air ratios and combustion types are selected.

[0004] The invention is based on the objective of providing an improved control unit for a powertrain with a hydrogen combustion engine, which limits pollutant emissions such as NOx in transient operating ranges of the engine, taking into account fuel consumption, engine power output and / or the integrity of components integrated into or downstream of the powertrain. This objective is achieved by the control unit according to the invention.

[0005] The control unit according to the invention for a powertrain comprising an internal combustion engine, wherein the internal combustion engine is designed as a hydrogen engine, is designed and configured to perform the following steps: - Determining a required air-fuel ratio based on a load requirement and a current air mass flow rate, - Determining a target combustion focus, - Determining a minimum air-fuel ratio at the determined target combustion center of gravity, taking into account NOx emissions and / or a ratio of H2 / NOx emissions, - Comparing the required air-fuel ratio and the minimum air-fuel ratio, - Determining a shift in the combustion center of gravity if comparison shows that the required air-fuel ratio is smaller than the minimum air-fuel ratio at the determined target combustion center of gravity and - Controlling the amount of hydrogen injected based on the required air-fuel ratio or the specific shift of the combustion center of gravity.

[0006] By controlling the amount of hydrogen injected based on the required air-fuel ratio or a specific shift in the combustion center of gravity, the invention enables the injection quantity to be adjusted taking into account NOx emissions and / or the H2 / NOx emission ratio. This has the advantage that the control unit can weigh the load requirement, an efficiency change resulting from the specific shift in the combustion center of gravity, and the NOx emissions and / or the H2 / NOx emission ratio when controlling the injection quantity.

[0007] The target combustion center of gravity is understood as a combustion center of gravity that enables efficient operation of the internal combustion engine. This depends on the current combustion mode. In efficiency-controlled operation, for example, the target combustion center of gravity is defined to achieve the highest possible efficiency. In heating operation, however, it might be defined to provide an advantageous exhaust gas temperature.

[0008] The minimum air-fuel ratio at the determined target combustion center is understood here as an air-fuel ratio for which, at the determined target combustion center, NOx emissions are lower than the target NOx emissions and / or the ratio of H2 / NOx emissions is higher than the target H2 / NOx ratio.

[0009] NOx emission, as used here, refers to raw NOx emissions, i.e., NOx emissions upstream of an exhaust aftertreatment system of the combustion engine. Similarly, the ratio of H2 / NOx emissions is understood here as the ratio of raw emissions of H2 and NOx.

[0010] The NOx target emission is defined here in such a way that legal requirements regarding NOx emissions downstream of an exhaust aftertreatment system of the powertrain can be met. The NOx target emission can be defined depending on the operating state of the powertrain.

[0011] The target H2 / NOx ratio is defined here such that a specific hydrogen content is present in the exhaust gas. This hydrogen can then be used, for example, for NOx reduction in the exhaust gas by an H2-SCR catalyst, so that an H2 injector is not needed in the exhaust system of the powertrain, or at least less H2 needs to be introduced into the exhaust system.

[0012] Here, "taxes" refers to both taxes with an open or temporarily closed course of action and regulations with a closed course of action.

[0013] To determine the required air-fuel ratio, the control unit preferably calculates the necessary amount of hydrogen to be injected based on the load demand. The load demand results, for example, from the position of the accelerator pedal in the powertrain. To calculate the required amount of injection, the control unit particularly preferably uses an efficiency model of the internal combustion engine, taking a combustion mode into account. A combustion mode can be, for example, efficiency-controlled operation, NOx-controlled operation, or heating operation of the internal combustion engine.

[0014] Furthermore, to determine the required air-fuel ratio, the control unit measures the current air mass flow in the intake manifold of the combustion engine. Based on the measured air mass flow and the calculated required injection quantity, the control unit determines the required air-fuel ratio.

[0015] Here, the target combustion center point is determined by the control unit program through the execution of the efficiency model. Alternatively or additionally, the control unit can use a characteristic map to determine the target combustion center point.

[0016] Determining the minimum air-fuel ratio at the calculated target combustion point is performed taking into account NOx emissions and / or the H2 / NOx emission ratio. Preferably, the control unit determines the minimum air-fuel ratio in such a way that the NOx target emission and / or the H2 / NOx target ratio can be met. This can be achieved, for example, by the control unit reading the minimum air-fuel ratio at the calculated target combustion point from a map. The map has been calibrated taking into account the NOx target emission and / or the H2 / NOx target ratio. The minimum air-fuel ratio can be stored in the map as a function of various parameters, such as a combustion mode, the state of an exhaust aftertreatment system, and / or an operating point of the powertrain.

[0017] Based on a comparison of the required and minimum air-fuel ratios, the control unit can initiate two different actions. If the required air-fuel ratio is greater than the minimum air-fuel ratio, it is possible to introduce the injection quantity required based on the load demand while maintaining the target combustion point. Since the control unit determines the minimum air-fuel ratio taking into account NOx emissions and / or an H2 / NOx emission ratio, a target NOx emission and / or an H2 / NOx ratio can also be met.

[0018] If the required air-fuel ratio is lower than the minimum air-fuel ratio at the target combustion center of gravity, the control unit determines a shift in the combustion center of gravity. This allows a lower air-fuel ratio to be used while still meeting the target NOx emissions and / or the target H2 / NOx ratio. The control unit then adjusts the injection quantity based on this determined shift in the combustion center of gravity.

[0019] Preferably, the control unit is designed and configured to take into account NOx emissions and / or a ratio of H2 / NOx emissions when determining the shift of the combustion center of gravity.

[0020] By having the control unit take into account NOx emissions and / or H2 / NOx emission ratios when determining the shift of the combustion center of gravity, the invention makes it possible to achieve the required air-fuel ratio by shifting the combustion center of gravity, while maintaining NOx emissions lower than the target NOx emissions and / or H2 / NOx emission ratios higher than the target H2 / NOx ratio.

[0021] To account for NOx emissions and / or the H2 / NOx ratio during the shift, the control unit can preferably access a map in which a shift of the combustion center of gravity is stored, depending on a difference between the required and the minimum air-fuel ratio. This allows the control unit to shift the combustion center of gravity so that the required air-fuel ratio is maintained. The map is calibrated so that the target NOx emissions and / or the target H2 / NOx ratio can be maintained for the stored shift of the combustion center of gravity.

[0022] Furthermore, it is preferred that the shift of the combustion center of gravity in the characteristic map is additionally dependent on an operating point of the combustion engine and / or a combustion mode. This allows the control unit to determine the shift of the combustion center of gravity depending on the operating conditions.

[0023] Preferably, the control unit includes a model for calculating NOx emissions and / or the H2 / NOx ratio depending on the air-fuel ratio and the combustion center point. Compared to using a map, using the model can reduce the calibration effort required for map creation, especially when transient conditions are represented.

[0024] The use of the model makes it possible in particular to take into account a change in NOx emission or a change in the ratio of H2 / NOx emissions in transient operation compared to steady-state operation.

[0025] The engine control unit (ECU) can determine a maximum NOx emission and / or a minimum H2 / NOx ratio under transient conditions, based on the target NOx emission and / or H2 / NOx ratio. To do this, it determines, for example, a steady-state NOx emission and / or H2 / NOx ratio from a characteristic map. By multiplying the steady-state NOx emission and / or H2 / NOx ratio by a factor, or by adding an offset to the steady-state NOx emission and / or H2 / NOx ratio, the ECU can determine the maximum transient NOx emission and / or the minimum transient H2 / NOx ratio. By inverting the model, the ECU can then determine the minimum air-fuel ratio at the determined target combustion center of gravity, taking into account the transient NOx target emission and / or H2 / NOx ratio.The factor is preferably greater than one to determine the transient NOx target emission and preferably less than one to determine the transient H2 / NOx target ratio. The offset is preferably greater than zero to determine the transient NOx target emission and preferably less than zero to determine the transient H2 / NOx target ratio.

[0026] If comparing the required air-fuel ratio and the minimum air-fuel ratio reveals that the required air-fuel ratio is lower than the minimum air-fuel ratio, the control unit can use the model to determine a change in the combustion center of gravity so that the required air-fuel ratio is met and compliance with the transient NOx target emission and / or the transient H2 / NOx target ratio is achieved. For this purpose, the control unit inverts the model so that, taking the required air-fuel ratio and the transient NOx target emission and / or the transient H2 / NOx target ratio into account as model input, the model can calculate the shift in the combustion center of gravity.

[0027] Preferably, the control unit is designed and configured to take into account a limitation of the specific shift of the combustion center of gravity, wherein the limitation depends on combustion stability and / or exhaust gas temperature.

[0028] By having the control unit take into account a limitation on the specific shift of the combustion center of gravity, the invention makes it possible to avoid unstable combustion or at least to minimize the likelihood of unstable combustion occurring and / or to provide a temperature advantageous for exhaust aftertreatment. An advantageous temperature is present when it is, on the one hand, high enough to enable sufficient conversion rates in an exhaust aftertreatment system of the powertrain, and, on the other hand, low enough to prevent component damage caused by excessively high exhaust gas temperatures or at least to reduce the likelihood thereof.

[0029] Here, "limitation" refers both to a limitation of the specific shift at later times and a limitation of the specific shift at earlier times. Combustion stability, for example, includes knocking combustion, pre-ignition, a maximum temperature, and / or misfires.

[0030] Preferably, the control unit is designed and configured to take into account a limitation of the injection quantity based on the limitation of the specific shift of the combustion center of gravity when controlling the injection quantity.

[0031] By having the control unit take into account a limitation of the injection quantity based on the limitation of the specific shift of the combustion center of gravity when controlling the injection quantity, the invention makes it possible to maintain a NOx target value and / or an H2 / NOx target ratio even if the shift of the combustion center of gravity is limited.

[0032] Preferably, the control unit is designed and configured to take combustion stability into account when determining the target combustion center of gravity.

[0033] By designing and configuring the control unit to take combustion stability into account when determining the target combustion center point, the invention enables the control unit to consider, for example, knocking, pre-ignition, a maximum temperature and / or a misfire when determining the target combustion center point.

[0034] Preferably, the powertrain includes an exhaust aftertreatment system and the control unit is designed and configured to determine the minimum air-fuel ratio based on a state of the exhaust aftertreatment system, based on a combustion mode, based on a change in NOx emissions and / or based on a change in the ratio of H2 / NOx emissions.

[0035] By having the control unit determine the minimum air-fuel ratio based on a state of the exhaust aftertreatment system, based on a combustion mode, based on a change in NOx emissions and / or based on a change in the ratio of H2 / NOx emissions, the invention enables the operation of the internal combustion engine with an air-fuel ratio advantageous for exhaust aftertreatment, combustion, NOx emissions and / or the ratio of H2 / NOx emissions.

[0036] The dependent claims describe further advantageous embodiments of the invention.

[0037] Preferred embodiments are explained in more detail with reference to the following figures. These show Fig. 1 an embodiment of a drive train with a control unit, Fig. 2 an embodiment of steps carried out by a control unit to control an injection quantity of hydrogen, Fig. 3 an alternative embodiment of steps carried out by a control unit for controlling an injection quantity of hydrogen, Fig. 4 an embodiment of steps carried out by a control unit to determine a displacement of a combustion center of gravity and Fig. 5 an alternative embodiment of steps carried out by a control unit to determine a shift of a combustion center of gravity.

[0038] Fig. Figure 1 shows a powertrain 2 for a vehicle. The powertrain 2 comprises an intake manifold 9, an internal combustion engine 3, an exhaust manifold 10, and a first 11 and a second 12 exhaust gas recirculation system. The intake manifold 9 is arranged upstream of the internal combustion engine 3. The exhaust manifold 10 is arranged downstream of the internal combustion engine 3 and includes an exhaust gas purification system 4.

[0039] The combustion engine 3 is designed as a turbocharged, direct-injection, and spark-ignition hydrogen engine with four cylinders 13. The combustion engine 3 also includes an exhaust gas turbocharger 14. The exhaust gas turbocharger 14 comprises a compressor 15 located in the intake manifold 9 and a turbine 16 located in the exhaust manifold 10. The turbine 16 and the compressor 15 are coupled together so that the energy absorbed from the exhaust gas by the turbine 16 can be used by the compressor 15 to compress the fresh gas to an increased pressure level.

[0040] To introduce hydrogen into the cylinders 13, the internal combustion engine 3 includes an injection device 30. The injection device 30 includes one injector per cylinder 13, supply lines and a fuel supply.

[0041] To ignite the hydrogen-air mixture, the internal combustion engine includes an ignition device 40. The ignition device 40 includes a spark plug for each cylinder 13 and an ignition system connected to the spark plugs.

[0042] The exhaust gas purification system 4 comprises an H2-SCR catalyst 5, an NH3-SCR system and an ammonia slip catalyst (ASK) 7. The H2-SCR catalyst 5 is designed to reduce nitrogen oxide emissions using H2.

[0043] The NH3-SCR system is arranged downstream of the H2-SCR catalyst 5 and comprises an NH3-SCR catalyst 6, a metering unit 19, and a mixer 20. The metering unit 19 is designed and configured to introduce ammonia (NH3) upstream of the NH3-SCR catalyst 6 into the exhaust gas section 10. In the mixer 20, located between the metering unit 19 and the NH3-SCR catalyst 6, the introduced ammonia and the exhaust gas are mixed. The NH3-SCR catalyst 6 is designed and configured to reduce NOx emissions using the ammonia.

[0044] To detect NOx emissions, a NOx sensor 22 is arranged downstream of the exhaust aftertreatment system 4.

[0045] The first exhaust gas recirculation section 11 is arranged upstream of the exhaust gas purification system 4 and is configured to discharge exhaust gas upstream of the turbine 16 of the exhaust gas turbocharger 14 from the exhaust gas section 10 and to supply it to the intake section 9 downstream of the compressor 15 of the exhaust gas turbocharger 14. The second exhaust gas recirculation section 12 is configured to discharge exhaust gas downstream of the H2-SCR catalyst 5 from the exhaust gas section 10 and to supply it upstream of the compressor 15 of the exhaust gas turbocharger 14 to the intake section 9. The first 11 and the second 12 exhaust gas recirculation sections enable the provision of preferred exhaust gas recirculation rates for the operation of the internal combustion engine 3 and ensure the most efficient operation of the internal combustion engine 3.

[0046] The powertrain 2 includes a control unit 1. The control unit 1 is designed and configured to execute a control program. The control program includes commands that are in Fig. to perform the 2 steps shown: - Determining a required air-fuel ratio (λ) erf ) S11 based on a load request and a current air mass flow, - Determining a target combustion center point S12, - Determining a minimum air-fuel ratio (λ) min ) S13 at the determined target combustion center S12 taking into account a NOx emission and / or a ratio of H2 / NOx emissions, - Compare S20 of the required air ratio (λ erf ) S11 and the minimum air ratio (λ min ) S13, - Determining a shift of the combustion center of gravity S30 if the comparison S20 shows that the required air-fuel ratio (λ) erf ) S11 smaller than the minimum air ratio (λ min ) S13 is and - S40 controls the amount of hydrogen injected based on the required air-fuel ratio (λ). erf) S11 or the specific shift of the combustion center of gravity S30.

[0047] Fig. Figure 3 shows an alternative embodiment of the steps performed by the control program to control the amount of hydrogen injected (S40). In a preliminary step 01, the control program first calculates the required amount of hydrogen injected (m) by executing an efficiency model of the combustion engine (3). H2,erf based on the load requirement M and a current combustion mode VM.

[0048] The control program includes commands, the required air-fuel ratio (λ) erf ) S11 based on the required injection quantity m H2,erf and a current air mass flow m L,akt to determine the current air mass flow m L,akt The control program determines this via an air path model in conjunction with information from the air mass meter 17.

[0049] By executing the efficiency model, the control program additionally calculates the target combustion center of gravity (S). α ) S12. This describes an advantageous combustion focus depending on the combustion mode VM and the load requirement M. Depending on the combustion mode VM, an advantageous aspect could be, for example, a desired efficiency, a desired emission level, or a desired exhaust gas temperature.

[0050] The control program includes commands that determine the minimum air-fuel ratio (λ). min ) S13 is determined taking into account the state of the exhaust aftertreatment system 4 and the combustion mode VM. For example, the control program can consider a heating requirement or a limit on raw emissions.

[0051] In the next step S20, the control program compares the required air-fuel ratio (λ). erf ) with the minimum air ratio (λ min). If comparing S20 shows that the required air ratio λ erf greater than the minimum air ratio λ min S13 is, S40 the control program controls the amount of hydrogen injected based on the required air-fuel ratio (λ). erf ) S11, by supplying the injection device 30 with the required injection quantity m H2,erf and the ignition device 40 with an ignition angle α ign Updated.

[0052] The ignition angle α ign The control program calculates this by executing a combustion model S41, which determines the ignition angle α. ign based on the target combustion center S α and a shift Δα of the combustion center of gravity. Since in the case that the required air-fuel ratio (λ erf ) greater than the minimum air ratio (λ min Since no shift Δα is required, the combustion model calculates the ignition angle α. ignbased on the target combustion center S α .

[0053] The NOx target emission S NOx The control program determines the NOx target emission S based on this target emission. NOx,st for a steady-state operating condition of the powertrain 2, where the NOx target emission S NOx,st The NOx target emission S is retrievable by the control program stored in the control unit. The control program multiplies this by a factor that is also defined depending on the operating point. NOx,st and thus determines a target NOx emission S NOx,tr for a transient operating state of the powertrain 2. The NOx target emission S NOx corresponds to the NOx target emission S NOx,tr By calibrating the NOx target emission S NOx,st and the factor is the NOx target emission S NOx defined in such a way that legal requirements for NOx emissions can be met. The NOx target emissions S NOx,st , S NOx,tr and S NOx are in Fig. 4 shown as examples.

[0054] The control program includes commands for shifting the center of combustion (S α ) to determine S30 if comparing S20 shows that the required air ratio (λ) erf ) S11 smaller than the minimum air ratio (λ min ) S13 is.

[0055] Fig. Figure 4 shows an embodiment for shifting the combustion center of gravity S30. Here, the required air-fuel ratio λ is erf smaller than the minimum air ratio λ min At the required air-fuel ratio λ erf Therefore, the NOx target emission S would be used for the target combustion focus. NOx be exceeded. That in Fig. 4 shown S NOx represents a maximum permissible NOx emission under transient conditions S NOx,tr To ensure compliance with the NOx target emission S NOx To achieve this, S30 shifts the combustion center of gravity in the control program.α Therefore, at a later time. The control program selects the specific shift Δα so that the NOx target emission S is reached. NOx adhered to and the required air ratio λ erf be fulfilled.

[0056] Based on the displacement Δα and the target combustion center S α In step S41, the control program calculates the ignition angle α. ign , with which it actuates the ignition device 40. Based on the displacement Δα, it calculates a change in the injection quantity of hydrogen Δ in step S42 by re-executing the efficiency model. m,H2 , so that the load requirement M is met even with the shifted combustion center of gravity and reduced combustion efficiency. The change in the injection quantity of hydrogen Δ m,H2 The control program calculates the required amount of hydrogen to be injected. H2,erf to a modified injection quantity of hydrogen m H2,mod .

[0057] The control program includes commands; when moving S30, a limitation L applies. α to take into account the specific displacement Δα of the combustion center of gravity. The limitation L α takes into account the combustion stability of the combustion engine 3 and is in Fig. 4 shown by the hatched area. One resulting from the limitation L α Resulting maximum displacement α lim The control program uses this in step S43 to set a limit λ. lim to calculate the air-fuel ratio. Based on the limitation λ lim for the air ratio and the current air mass flow m L,akt In step S44, the control program determines a maximum injection quantity of hydrogen. H2,max .

[0058] In step S45, the control program finally calculates the injection quantity m to be introduced into the combustion engine by the injection device 30. H2,injbased on the modified injection quantity m H2,mod and the maximum injection quantity of hydrogen m H2,max .

[0059] In another, alternative embodiment, the control program takes into account a ratio of H2 / NOx emissions in addition to NOx emissions. This allows a desired H2 content to be provided in the exhaust gas, enabling the conversion of raw NOx emissions by the H2-SCR catalyst 5 without the need to introduce H2 into the exhaust system.

[0060] The minimum air-fuel ratio λ min at the target combustion center S αThe control program determines this by taking into account the ratio of H2 / NOx emissions. To enable control even under transient conditions, the minimum air-fuel ratio is determined by running a model that calculates raw NOx and H2 emissions. In a later step (S30), this model is also used to determine the shift in the combustion center of gravity.

[0061] Additionally, the control program corrects the modified injection quantity if a shift S30 of the combustion center of gravity has occurred. For this purpose, the control program repeatedly executes steps S11, S30, S41, and S42 based on the modified injection quantity m. H2,mod The correction is complete when there is no difference between the required air-fuel ratio λ. erf and one resulting from the modified injection quantity m H2,modThe resulting air-fuel ratio is smaller than a predefined tolerance. The accuracy of the correction can be adjusted via the tolerance.

[0062] Fig. Figure 5 shows an alternative embodiment for shifting the combustion center of gravity S30. Here, the control program takes into account, in addition to the limitation L, the following when shifting S30: α a limitation L β the specific displacement Δα of the combustion center of mass. The limitation L β This takes into account in particular a combustion instability of the combustion engine 3 due to knocking or pre-ignition and is in Fig. 5 is indicated by the hatched area on the left. The maximum displacement α lim The tax program determines this based on the limitations L α and L β , whereby in the Fig. In the exemplary embodiment shown in section 5, the limitation L α and the NOx target emission SNOx the maximum displacement α lim define. For other operating points, a different maximum displacement α may apply. lim This results in further embodiments not shown. Alternatively or additionally, the control program includes commands to overcome the limitation L. β to take into account directly when determining the target combustion center point S12, so that it can take into account combustion stability as a result of knocking or pre-ignition when determining the target combustion center point S12.

[0063] In another, alternative embodiment, the control program includes commands to regulate the amount of hydrogen injected in a closed control loop. For this purpose, the powertrain includes cylinder pressure sensors arranged in the cylinders 13. The control program uses these cylinder pressure sensors to determine an indicated mean effective pressure and a combustion center point. The indicated mean effective pressure serves as an indicator of the load.

[0064] The combustion center of gravity determined via the cylinder pressure sensors is used by the control program to determine the displacement of the combustion center of gravity Δ. α , the determined indicated mean pressure for correcting the modified injection quantity m H2,mod This allows for more precise and robust control of the injection quantity (S40). H2,inj can be achieved.

Claims

[1] Control unit (1) for a powertrain (2) comprising an internal combustion engine (3), wherein the internal combustion engine (3) is designed as a hydrogen engine and wherein the control unit (1) is designed and configured to perform the following steps: - Determining a required air-fuel ratio (S11, λ) erf ) based on a load requirement and a current air mass flow, - Determining a target combustion center (S12), - Determining a minimum air ratio (S13, λ) min ) at the determined target combustion center (S12) taking into account NOx emissions and / or a ratio of H2 / NOx emissions, - Comparing (S20) the required air ratio (S11, λ) erf ) and the minimum air ratio (S13, λ min ), - Determining a shift of the combustion center of gravity (S30) if the comparison (S20) shows that the required air-fuel ratio (S11, λ) erf ) smaller than the minimum air ratio (S13, λ min ) is, and - Control (S40) of an injection quantity of hydrogen based on the required air ratio (S11, λ erf ) or the specific shift of the combustion center of gravity (S30). [2] Control unit (1) according to claim 1, wherein the control unit (1) is designed and configured to take into account NOx emissions and / or a ratio of H2 / NOx emissions when determining the displacement of the combustion center of gravity (S30). [3] Control unit (1) according to claim 1 or 2, wherein the control unit (1) is designed and configured to take into account a limitation of the specific displacement of the combustion center of gravity (S30) and wherein the limitation depends on a combustion stability and / or an exhaust gas temperature. [4] Control unit (1) according to claim 3, wherein the control unit (1) is designed and configured to take into account, when controlling (S40) the injection quantity, a limitation of the injection quantity based on the limitation of the specific displacement of the combustion center of gravity (S30). [5] Control unit (1) according to one of the preceding claims, wherein the control unit (1) is designed and configured to take combustion stability into account when determining the target combustion center of gravity (S12). [6] Control unit (1) according to one of the preceding claims, wherein the powertrain (2) comprises an exhaust aftertreatment system (4) and wherein the control unit (1) is designed and configured to determine the minimum air-fuel ratio (S13, λ). min ) based on a state of the exhaust aftertreatment system (4), based on a combustion mode, based on a change in NOx emissions and / or based on a change in the ratio of H2 / NOx emissions. [7] Control unit (1) according to one of the preceding claims, wherein the control unit (1) is designed and configured to implement a model for determining NOx and / or H2 emissions and to determine the minimum air-fuel ratio (S13, λ). min ) and / or to determine the shift of the combustion center of gravity (S30) based on a result of the model. [8] Control unit (1) according to one of the preceding claims, wherein the internal combustion engine (3) comprises an ignition device (40) and wherein the control unit (1) is designed and configured to determine an ignition timing based on the determined displacement of the combustion center of gravity (S30) and to actuate the ignition device (40) based on the determined ignition timing. [9] Control unit (1) according to one of the preceding claims, wherein the control unit (1) is designed and configured to perform a correction of the injection quantity when controlling (S40) the injection quantity.

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