Method for controlling an internal combustion engine, control device, internal combustion engine, and motor vehicle

Abstract

The invention relates to a method and a control device for controlling an internal combustion engine. The invention also relates to an internal combustion engine unit having the internal combustion engine and the control device, and to a motor vehicle having the internal combustion engine unit. According to the method, the internal combustion engine is ‒ operated in a first operating mode (B1), in which a closing of an inlet valve at the lower dead centre of the crankshaft (1) is stopped at a first crankshaft angle (KW1) when a first operating criterion is met, ‒ switched from the first to a second operating mode (B2), in which the closing of the inlet valve is stopped at a second crankshaft angle (KW2 < KW1), when a second operating criterion is met, ‒ is switched from the second to the third operating mode (B3), in which the closing of the inlet valve is stopped at a third crankshaft angle (KW3 < KW2 < KW1), when a third operating criterion is met.

Description

[0001] Method for controlling an internal combustion engine, control device, internal combustion engine and motor vehicle

[0002] The present invention relates to a method for controlling an internal combustion engine, a control device configured to carry out the method or to control the internal combustion engine, as well as an internal combustion engine having the control device and a motor vehicle having such an internal combustion engine.

[0003] There is a general need to keep pollutant emissions from internal combustion engines as low as possible throughout their entire operation, i.e. in all operating states, and to create means to operate internal combustion engines with ever lower emissions. To this end, the current aim is to ensure that the combustion process in the combustion chambers of the respective internal combustion engine always takes place with a combustion stoichiometric fuel-air ratio A = 1. Furthermore, it is known - for example from DE 44 80 333 T1, DE 603 ​​01 093 T2 or EP 3 620 635 A1 - to control an intake valve train in such a way that the corresponding intake valve is completely closed during a charging stroke (i.e. well before the corresponding connecting rod journal of a crankshaft of the internal combustion engine reaches its bottom dead center). This reduces the filling level of the corresponding combustion chamber for a structurally given compression ratio.The advantages of this include improved utilization of expansion energy during the power stroke and, consequently, increased thermodynamic efficiency, reduced knocking tendency, the ability to advance ignition timing at full load, and reduced exhaust gas temperature. To compensate for the performance disadvantage resulting from the application of this principle (known to internal combustion engine experts as the Miller cycle), charge air compressors (e.g., exhaust gas turbochargers, compressors, etc.) are used, which require higher charge air pressures to be provided compared to conventionally operated internal combustion engines with charge air charging.

[0004] The Miller cycle is already used in today's internal combustion engines when the engine speed and load, as well as the charge air pressure, allow the use of the Miller cycle or do not conflict with it. This allows the exhaust gas to be cooled early and efficiently, ensuring that specified temperature limits of components of the internal combustion engine that come into contact with the exhaust gas, or of its peripheral components and / or assemblies, are not exceeded. At the same time, however, such early use of the Miller cycle leads to increased component stress on components, particularly charge air compressors, of the internal combustion engine, even if the exhaust temperature would still be non-critical without the Miller exhaust cooling effect.Therefore, there is a conflict of objectives between the aim of achieving the advantages of the Miller principle and the increased component load on components, in particular on charge air compressors, of the internal combustion engine when the Miller principle is applied.

[0005] The object of the invention is to operate an internal combustion engine particularly efficiently and with low emissions.

[0006] This problem is solved by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the subclaims, the description, and the figures. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded, across categories and embodiments, at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0007] When an internal combustion engine is in operation, it emits exhaust gases. Temperature limits are specified to protect components of an internal combustion engine that come into contact with the exhaust gas, or its peripheral components and / or assemblies. The invention is based on the consideration that, during average overall use of the internal combustion engine—for example, when a motor vehicle containing the internal combustion engine is used by an end user—temperatures that exceed or approach the specified temperature limits are extremely rare.In order to at least mitigate the conflict of objectives described at the outset between the aim of being able to efficiently exploit the advantages of the Miller principle and the increased component load on the components, in particular a charge air compressor, of the internal combustion engine, the method according to the invention for controlling the internal combustion engine is proposed.

[0008] The invention further proposes a control device, for example an engine control unit, for an internal combustion engine, wherein the control device is configured to execute the method or to control the internal combustion engine according to the method. The invention further proposes an internal combustion engine unit comprising the internal combustion engine and the control device. The control device and the internal combustion engine are or can be coupled to one another in such a way that control signals provided by the control device result in an action of the internal combustion engine. The invention further proposes a motor vehicle comprising the internal combustion engine of the internal combustion engine unit as the drive motor.When installed as intended, the internal combustion engine forms a component of the motor vehicle, with a crankshaft of the internal combustion engine and a wheel of the motor vehicle being mechanically coupled or capable of being coupled to one another via one or more transmissions to transmit power / torque. Alternatively or additionally, the internal combustion engine forms a drive element for an electric generator that is coupled or capable of being coupled to an electric drive motor, with a rotor of the electric drive motor being coupled or capable of being coupled to the wheel directly or via one or more transmissions to transmit power / torque. Accordingly, the motor vehicle can be a purely internal combustion engine-powered motor vehicle or a hybrid-electric motor vehicle.

[0009] The method according to the invention for controlling the internal combustion engine can be a computer-implemented method. In this case, the control device is configured to execute the method. Furthermore, the invention proposes a computer program which, when its program instructions are executed by the control device, causes the control device to execute the method and consequently provide control signals for the internal combustion engine. The invention further proposes a computer-readable storage medium on which the computer program is / is stored.

[0010] The internal combustion engine is designed as a four-stroke reciprocating piston engine and has a crankshaft, a combustion chamber, and an intake valve associated with the combustion chamber. Furthermore, the internal combustion engine has a charge air compressor for pre-compressing charge air for the internal combustion engine. The charge air compressor has a charge air compressor unit. The charge air compressor unit is, in particular, an exhaust gas turbocharger or a compressor that can be driven mechanically by means of the crankshaft and / or electrically; combinations of two or more charge air compressors—particularly of different types—are conceivable. Further components required for a functional internal combustion engine, as well as possible designs—particularly with two or more combustion chambers, each combustion chamber with two or more intake valves, etc.- are familiar to those skilled in the art, which is why they are only discussed here to the extent necessary for the description. For the sake of simplicity of description, reference is made here only to a combustion chamber with an associated inlet valve. If it is stated herein that the inlet valve is completely closed, this means that an inlet valve seat of the combustion chamber is completely blocked off by an inlet valve body of the inlet valve against the flow of a fluid (for example air). If there are two or more inlet valves per combustion chamber, the statement that the inlet valve is completely closed is understood to mean that all inlet valve seats of the combustion chamber are completely blocked off against the flow of fluid.

[0011] In the method, an intake valve train of the internal combustion engine is controlled such that, during a charging stroke occurring every two full revolutions of the crankshaft, the intake valve is completely set to a closed position of the intake valve, depending on a currently active operating mode of the internal combustion engine at different crankshaft angles through which the crankshaft passes in the intended working direction of rotation. In other words: during the respective charging stroke, movement of the intake valve body towards the closed position is sooner or later no longer possible, depending on the operating mode, because the intake valve body is already fully seated in the intake valve seat at the corresponding crankshaft angle and completely blocks it against flow. The intake valve train can, for example, have a camshaft and / or a valve-specific linear drive.In any case, the intake valve train is designed to adjust the timing of the intake valve, i.e. to adjust an intake valve spread angle (described here in relation to a top dead center position of the crankshaft).

[0012] In a first of the operating modes, the intake valve is actuated by the intake valve train in such a way that, during a charging stroke of the internal combustion engine, closing of the intake valve is completely completed at a first crankshaft angle KW1 (measured from the top dead center position of the crankshaft in the working direction of rotation) at a bottom dead center position of the crankshaft. In the first operating mode, the adjustment of the intake valve in its closed position is completely completed at the bottom dead center position, i.e. closer to the bottom dead center position than in the other two operating modes. In a second of the operating modes, the intake valve is actuated by the intake valve train in such a way that, during the charging stroke, closing of the intake valve is completely completed at a second crankshaft angle KW2 (measured from the top dead center position of the crankshaft in the working direction of rotation).The second crankshaft angle KW2 is smaller than the first crankshaft angle KW1; the adjustment of the intake valve to its closed position is fully completed closer to the top dead center position (i.e. earlier) than in the first operating mode. In a third operating mode, the intake valve is actuated by the intake valve train in such a way that during the charging stroke the closing of the intake valve is fully completed at a third crankshaft angle KW3 (measured from the top dead center position of the crankshaft in the working direction of rotation). The third crankshaft angle KW3 is smaller than the second crankshaft angle KW2; the adjustment of the intake valve to its closed position is therefore fully completed even closer to the top dead center position (i.e. even earlier) than in the second operating mode.

[0013] The respective crankshaft angle KW1, KW2, KW3 is, in particular, an angle value that originates from a crankshaft angle range [KW1], [KW2], [KW3] associated with the corresponding operating mode. All angle values ​​of the first crankshaft angle range [KW1] are greater than all angle values ​​of the second and third crankshaft angle ranges [KW2], [KW3], whereby all angles of the second crankshaft angle range [KW2] are greater than all angle values ​​of the third crankshaft angle range [KW3]; the following applies:

[0014] KW1 > KW2 > KW3 or [KW1] > [KW2] > [KW3],

[0015] Thus, closing of the intake valve is completely completed in the first operating mode at the first crankshaft angle KW1 originating from the first crankshaft angle range [KW1], in the second operating mode at the second crankshaft angle KW2 originating from the second crankshaft angle range [KW2] and in the third operating mode at the third crankshaft angle KW3 originating from the third crankshaft angle range [KW3].

[0016] In the method, the internal combustion engine is further controlled such that it is operated in the first operating mode if or as long as a first operating criterion is met. The first operating criterion can be met, for example, if the charge air flowing into the combustion chamber during the charging stroke has a charge air pressure whose value originates from a first predetermined charge air pressure value range, which includes values ​​from zero up to and including a first predetermined limit charge air pressure value. Accordingly, the internal combustion engine is operated, for example, in the first operating mode if or as long as the charge air is compressed by the charge air compressor up to a maximum of the first predetermined limit charge air pressure.The current charge air pressure is determined, and if its value lies within the first predefined charge air pressure value range, the internal combustion engine continues to operate in the first operating mode—since the first sub-criterion relating to the charge air pressure is met. The first predefined limit charge air pressure characterizes, for example, a charge air pressure at which the greatest possible torque is provided to the internal combustion engine, for which the internal combustion engine is designed. This means that the internal combustion engine is operated according to the method in the first operating mode, in which the intake valve is fully closed at the first crankshaft angle KW1 until the internal combustion engine provides the greatest possible torque. This allows the full torque to be made available to the motor vehicle particularly quickly.The lower the charge air pressure, the better the response behavior, and therefore the more dynamic the driving experience of the motor vehicle is for a user or driver. Furthermore, the first operating criterion can be met, for example, if the current crankshaft speed has a value that comes from a first predetermined speed value range, which includes values ​​from zero, in particular from an idle speed value, up to and including a first predetermined limit speed value. The speed at which the crankshaft of the internal combustion engine is currently rotating is therefore determined. If the corresponding speed value lies within the first predetermined speed value range, the internal combustion engine continues to operate in the first operating mode, since the first sub-criterion relating to the crankshaft speed is met.

[0017] The first operating criterion can further be met if a current load of the internal combustion engine has a value that originates from a first predefined load value range, which includes values ​​from zero up to and including a first predefined limit load value. The internal combustion engine will therefore continue to operate in the first operating mode if the sub-criterion relating to the load is met. For this purpose, the current load is determined. If the corresponding load value lies within the first predefined load value range, the first sub-criterion relating to the load is met.

[0018] The first operating criterion can also be met if a current gear ratio of a gear change transmission coupled to the internal combustion engine has a value that originates from a first predefined gear ratio value range, which includes values ​​from zero up to and including a first predefined limit gear ratio value. Thus, the currently engaged and / or engaged gear ratio is determined, and if the corresponding gear ratio value lies within the first predefined gear ratio value range, the first subcriterion relating to the gear ratio is met, which is why the internal combustion engine continues to operate in the first operating mode.

[0019] Furthermore, the first operating criterion can be met if the current driving speed of a motor vehicle having the internal combustion engine as the prime mover has a value that originates from a first predefined speed value range, which includes values ​​from zero up to and including a first predefined limit speed value. Thus, the speed of the motor vehicle is determined. If the corresponding speed value lies within the first predefined speed value range, the internal combustion engine continues to operate in the first operating mode, since the first sub-criterion relating to the driving speed is met.

[0020] Furthermore, the first operating criterion can be met if a current operating time during which the internal combustion engine was last operated continuously in the first operating mode has a value that originates from a first predefined time value range, which includes values ​​from zero up to and including a first predefined limit operating time value. In other words, it is determined how long the internal combustion engine was last operated continuously in the first operating mode. If this time lies within the first predefined time value range, the first sub-criterion relating to the operating time is met, and the internal combustion engine continues to operate in the first operating mode.

[0021] The first operating criterion can also be met if an exhaust gas temperature is determined at an exhaust tract location of the internal combustion engine, the value of which originates from a first predefined exhaust gas temperature value range, which includes values ​​from zero up to and including a first predefined limit exhaust gas temperature value. The internal combustion engine will therefore continue to operate in the first operating mode if the first sub-criterion relating to the exhaust gas temperature is met. For this purpose, the current exhaust gas temperature at the corresponding exhaust tract location is determined. If the corresponding exhaust gas temperature value lies within the first predefined exhaust gas temperature value range, the first sub-criterion relating to the exhaust gas temperature is met.

[0022] One, some, or all of the values ​​described herein can be modeled, for example, by means of the control device of the internal combustion engine and / or by means of another control device (e.g., a transmission control unit, etc.). Alternatively or additionally, one, some, or all of said values ​​can be measured, for example, by means of an appropriately configured and arranged sensor. For example, the exhaust gas temperature value can be determined by modeling the exhaust gas temperature prevailing at the exhaust tract location or the corresponding exhaust gas temperature value, for example, by means of the control device of the internal combustion engine. Alternatively or additionally, the exhaust gas temperature value can be determined by measuring the exhaust gas temperature directly at the corresponding exhaust tract location, for example, by means of a temperature sensor. This applies analogously to the other values ​​determined for the method or an embodiment thereof.Measuring and modeling the same value to be determined is possible, for example for redundancy or operational safety reasons, for plausibility checks, etc.

[0023] In particular, two or more of the aforementioned first sub-criteria must be met in order for the first operating criterion to be considered fulfilled and for the internal combustion engine to be operated in the first operating mode.

[0024] If or as long as another, second operating criterion is met, the internal combustion engine is switched from the first to the second operating mode, in which the intake valve is fully closed at the second crankshaft angle KW2. The second operating criterion can be met, for example, if the charge air has a charge air pressure whose value originates from a second predetermined charge air pressure value range, which includes values ​​from the first predetermined limit charge air pressure value exclusively up to and including a second predetermined limit charge air pressure value. The current charge air pressure is therefore determined, and if its value lies within the second predetermined charge air pressure value range and consequently outside the first predetermined charge air pressure value range, the internal combustion engine is switched to the second operating mode - the second sub-criterion relating to the charge air pressure is met.

[0025] Furthermore, the second operating criterion can be met if the current crankshaft speed of the internal combustion engine has a value that originates from a second predefined speed value range, which includes values ​​from the first predefined limit speed value exclusively up to and including a second predefined limit speed value. Thus, the speed at which the crankshaft of the internal combustion engine is currently rotating is determined. If the corresponding speed value lies within the second predefined speed value range and consequently outside the first predefined speed value range, the internal combustion engine is switched to the second operating mode, since the second sub-criterion relating to the crankshaft speed is met.

[0026] The second operating criterion can also be met if the current load of the internal combustion engine has a value that originates from a second predefined load value range, which includes values ​​from the first predefined limit load value exclusively up to and including a second predefined limit load value. The internal combustion engine is consequently switched to the second operating mode if the second sub-criterion relating to the load is met. For this purpose, the current load is determined. If the corresponding load value lies within the second predefined load value range and thus outside the first predefined load value range, the second sub-criterion relating to the load is met.

[0027] Furthermore, the second operating criterion can be met if the current gear ratio of the gear change transmission has a value that originates from a second predefined gear ratio value range, which includes values ​​from the first predefined limit gear ratio value exclusively up to and including a second predefined limit gear ratio value. Thus, the currently engaged and / or engaged gear ratio is determined, and if the corresponding gear ratio value lies within the second predefined range of gear ratio values ​​and thus outside the first predefined range of gear ratio values, the second sub-criterion relating to the gear ratio is met, which is why the internal combustion engine is switched to the second operating mode.

[0028] Furthermore, it is conceivable that the second operating criterion is met if the current driving speed of the motor vehicle has a value that originates from a second predefined speed value range, which includes values ​​from the first predefined limit speed value exclusively up to and including a second predefined limit speed value. Thus, the speed of the motor vehicle is determined. If the corresponding speed value lies within the second predefined speed value range—and thus outside the first predefined speed value range—the internal combustion engine is switched to the second operating mode, since the second sub-criterion relating to the driving speed is met.

[0029] Furthermore, the second operating criterion can be met if a current operating time during which the internal combustion engine was last operated continuously in the first operating mode has a value that originates from a second predefined time value range, which includes values ​​from the first predefined limit operating time value exclusively up to and including a second predefined limit operating time value. In other words, it is determined how long the internal combustion engine was last operated continuously in the first operating mode. If this time lies within the second predefined time value range, i.e., outside the first predefined time value range, the second sub-criterion relating to the operating time is met, and the internal combustion engine is switched to the second operating mode.

[0030] Furthermore, the second operating criterion can be met if an exhaust gas temperature is determined at an exhaust tract point of the internal combustion engine, the value of which originates from a second predetermined exhaust gas temperature value range, which includes values ​​from the first predetermined limit exhaust gas temperature value exclusively up to and including a second predetermined limit exhaust gas temperature value. The internal combustion engine is therefore switched to the second operating mode if the second sub-criterion relating to the exhaust gas temperature is met. For this purpose, the current exhaust gas temperature at the corresponding exhaust tract point is determined. If the corresponding exhaust gas temperature value lies within the second predetermined exhaust gas temperature value range and therefore outside the first predetermined exhaust gas temperature value range, the second sub-criterion relating to the exhaust gas temperature is met.

[0031] In particular, two or more of the aforementioned second sub-criteria must be met in order for the second operating criterion to be considered fulfilled and for the internal combustion engine to be switched to the second operating mode or operated in the second operating mode.

[0032] The method specifically provides for the internal combustion engine to be switched to the second operating mode as early as possible, operating according to a Miller cycle with a first Miller intensity. This advantageously reduces the exhaust gas temperature particularly early. The Miller combustion process lowers the effective compression ratio by first expanding and then recompressing a portion of the charge air in the combustion chamber due to the premature closing of the intake valve. The resulting reduced effective compression ratio results in a lower knock tendency. This allows earlier ignition angles to be set. The earlier the fuel-air mixture is ignited in the combustion chamber, the earlier combustion starts and the more advanced combustion is at the time the exhaust valve opens. This results in a lower exhaust gas temperature.This ensures that the components interacting with the exhaust gas—for example, a charge air compressor turbine driven by the exhaust gas, an exhaust aftertreatment system, etc.—come into contact with particularly cool exhaust gas, effectively preventing undesirably high temperatures, particularly the reaching of specified temperature limits. Furthermore, switching from the first to the second operating mode is torque-neutral. This means that the intake valve spread angle and charge air pressure are adjusted while maintaining the current torque. Thus, vehicle occupants are unaware of the operating mode change.

[0033] Only when a third operating criterion is met, which is specified in particular to protect components of the internal combustion engine or its peripheral components and / or assemblies that come into contact with the exhaust gas and / or the charge air, is the internal combustion engine switched from the second to the third operating mode, in which the intake valve is fully closed at the third crankshaft angle KW3. In particular, the internal combustion engine is only operated in the third operating mode as long as the third operating criterion is met. The third operating criterion can be met, for example, if the charge air has a charge air pressure whose value originates from a third specified charge air pressure value range, which includes values ​​from the second specified limit charge air pressure value exclusively and higher charge air pressure values.The current charge air pressure is therefore determined, and if its value is within the third specified charge air pressure value range and consequently neither in the first nor in the second specified charge air pressure value range, the internal combustion engine is switched to the third operating mode - since the third sub-criterion relating to the charge air pressure is met.

[0034] Furthermore, the third operating criterion can be met if the current crankshaft speed of the internal combustion engine has a value that originates from a third predefined speed range, which includes values ​​exclusively from the second predefined limit speed value and higher speed values. Thus, the speed at which the crankshaft of the internal combustion engine is currently rotating is determined. If the corresponding speed value lies within the third predefined speed range and consequently neither in the first nor in the second predefined speed range, the internal combustion engine is switched to the third operating mode, since the third sub-criterion relating to the crankshaft speed is met.

[0035] The third operating criterion can also be met if the current load of the internal combustion engine has a value that originates from a third predefined load value range, which includes values ​​from the second first predefined limit load value exclusively and higher load values. The internal combustion engine is therefore switched to the third operating mode if the third sub-criterion relating to the load is met. For this purpose, the current load is determined. If the corresponding load value lies within the third predefined load value range, i.e., neither in the first nor in the second predefined load value range, the third sub-criterion relating to the load is met.

[0036] Furthermore, the third operating criterion can be met if the current gear ratio of the gear change transmission has a value that originates from a third predefined gear ratio value range, which includes values ​​exclusively from the second predefined gear ratio value range and higher gear ratio values. Thus, the currently engaged and / or engaged gear ratio is determined, and if the corresponding gear ratio value lies within the third predefined gear ratio value range—outside the first and second predefined gear ratio value ranges—the third sub-criterion relating to the gear ratio is met, which is why the internal combustion engine is switched to the third operating mode.

[0037] Furthermore, it is conceivable that the third operating criterion is met if the current driving speed of the motor vehicle has a value that originates from a third predefined speed range, which includes values ​​exclusively from the second predefined limit speed value and higher speed values. Thus, the speed of the motor vehicle is determined. If the corresponding speed value lies within the third predefined speed range—hence, neither within the first nor within the second predefined speed range—the internal combustion engine is switched to the third operating mode, since the third sub-criterion relating to the driving speed is met.

[0038] The third operating criterion can also be met if a current uninterrupted operating time, during which the internal combustion engine was last operated uninterruptedly in the second operating mode, has a value that originates from a third predefined time value range, which includes values ​​from the second predefined limit operating time value exclusively and higher operating time values. In other words, it is determined how long the internal combustion engine was last operated uninterruptedly in the second operating mode. If this time lies within the third predefined time value range, i.e., outside the first predefined time value range, the second sub-criterion relating to the operating time is met, and the internal combustion engine is switched to the second operating mode.

[0039] Furthermore, the third operating criterion can be met if an exhaust gas temperature is determined at an exhaust tract point of the internal combustion engine whose value originates from a third predetermined exhaust gas temperature value range, which includes values ​​from a second predetermined limit exhaust gas temperature value exclusively and higher exhaust gas temperature values. The internal combustion engine is therefore switched to the third operating mode if the third sub-criterion relating to the exhaust gas temperature is met. For this purpose, the current exhaust gas temperature at the corresponding exhaust tract point is determined. If the corresponding exhaust gas temperature value lies within the third predetermined exhaust gas temperature value range and therefore outside the first and second predetermined exhaust gas temperature value range, the third sub-criterion relating to the exhaust gas temperature is met.

[0040] In particular, two or more of the aforementioned third subcriteria must be met for the third operating criterion to be considered fulfilled and for the internal combustion engine to be switched to the third operating mode or operated in the third operating mode. It may further be provided that the internal combustion engine is operated in the second operating mode as long as the third operating criterion is met.

[0041] In particular, it is provided that the values ​​of the second predetermined charge air pressure value range are all greater than the largest value of the first predetermined charge air pressure value range, the values ​​of the second predetermined speed value range are all greater than the largest value of the first predetermined speed value range, the values ​​of the second predetermined load value range are all greater than the largest value of the first predetermined load value range, the values ​​of the second predetermined gear ratio value range are all greater than the largest value of the first predetermined gear ratio value range, the values ​​of the second predetermined speed value range are all greater than the largest value of the first predetermined speed value range,the values ​​of the second predefined time range are all greater than the largest value of the first predefined time range and / or the values ​​of the second predefined exhaust gas temperature range are all greater than the largest value of the first predefined exhaust gas temperature range. In the third operating mode, the internal combustion engine is operated according to a Miller cycle with a second Miller intensity, wherein the first Miller intensity of the second operating mode is lower than the second Miller intensity of the third operating mode. Compared to the second operating mode, the charge air compressor must provide a higher charge air pressure in the third operating mode, which places a greater load on the charge air compressor than in the second operating mode. However, this is accepted in order to sufficiently reduce the exhaust gas temperature in the third operating mode to maintain or not exceed a maximum permissible exhaust gas temperature.at which the intended function of the corresponding component is still guaranteed. This means that the maximum permissible exhaust gas temperature must be strictly observed during operation of the internal combustion engine for component protection reasons to prevent damage to the corresponding component.

[0042] In particular, the subcriteria are mutually exclusive. In other words, either the first subcriterion is met, or the second subcriterion is met, or the third subcriterion is met. The specified value ranges do not overlap.

[0043] The method particularly provides that the operating modes do not overlap one another. In other words, the first operating mode is active when neither the second nor the third operating mode is active. The second operating mode is active when neither the first nor the third operating mode is active. The third operating mode is active when neither the first nor the second operating mode is active. Furthermore, the method particularly provides that when the third operating mode is active, switching from the third to the second operating mode takes place as soon as possible. In other words, the third operating mode is only used to lower the exhaust gas temperature until the exhaust gas temperature is again lower than the limit exhaust gas temperature. In other words, switching from the third to the second operating mode takes place when the exhaust gas temperature is again lower than the limit exhaust gas temperature or falls below the limit exhaust gas temperature.In particular, for switching from the third to the second operating mode, a downshift limit temperature is specified which is lower than the limit exhaust gas temperature and which takes effect when switching from the third to the second operating mode instead of the limit exhaust gas temperature. This prevents jumping back and forth between the second and third operating modes. Only if the prerequisites for operating the internal combustion engine in the second operating mode are not yet or no longer met will the internal combustion engine be switched to the first operating mode according to the method, for example when the charge air pressure falls below the limit charge air pressure and / or a crankshaft speed and / or a load of the internal combustion engine prevent the use of the Miller cycle.

[0044] In particular, at least one intermediate operating mode for the operation of the internal combustion engine is conceivable. For example, the intake valve can close later in a first intermediate operating mode than in the second, but earlier than in the first operating mode. Furthermore, a second intermediate operating mode is conceivable in which the intake valve closes later than in the third, but earlier than in the second operating mode. Two or more different first or second intermediate operating modes (each with a different Miller intensity) can be provided between the first operating mode and the second operating mode and / or between the second operating mode and the third operating mode. This enables particularly finely graduated adjustment of the Miller intensity. The method is transferable to the intermediate operating mode(s).If the first operating criterion (or another / further first operating criterion, possibly with additional and / or different first sub-criteria) is met, the system can switch from the first operating mode to one of the first intermediate operating modes. From this mode, if the second operating criterion (or another / further second operating criterion, possibly with additional and / or different second sub-criteria) is met, the system can switch to another of the (first or second) intermediate operating stages or the third operating mode.

[0045] This process enables the internal combustion engine to be operated particularly efficiently and with low emissions, with the exhaust gas temperature being kept below the limit exhaust gas temperature while maintaining a combustion stoichiometric fuel or fuel-air ratio of A = 1. In particular, enrichment of the fuel-air mixture (A < 1) to cool the exhaust gas is dispensed with, as this leads to increased pollutant emissions from the internal combustion engine and to a low conversion rate of a catalyst connected to the exhaust side of the internal combustion engine. Furthermore, it is ensured that the thermal load on the components interacting with the exhaust gas does not exceed a permissible limit due to the third operating mode. Current legal requirements that prescribe low limits for pollutant emissions across the entire operating range of the internal combustion engine are met.In addition, higher performance is possible with a vehicle powered by an internal combustion engine. Thanks to the variable intake valve timing, higher performance can be achieved in the first and second operating modes than in the third.

[0046] According to a further possible embodiment, the first crankshaft angle KW1 or the first crankshaft angle range [KW1] and the second crankshaft angle KW2 or the second crankshaft angle range [KW2] are spaced apart from one another by a first angular distance, which is in particular more than 10° or more than 30°. Alternatively or additionally, the second crankshaft angle KW2 and the third crankshaft angle KW3 or the second crankshaft angle range [KW2] and the third crankshaft angle range [KW3] are spaced apart from one another by a second angular distance, which is in particular more than 5°. In particular, the first angular distance over which the crankshaft angles KW1, KW2 or the crankshaft angle ranges [KW1], [KW2] are spaced apart from one another is greater than the second angular distance over which the crankshaft angles KW2, KW3 or the crankshaft angle ranges [KW2], [KW3] are spaced apart from one another.

[0047] In a possible further development, switching between the first and second operating modes and / or between the second and third operating modes is provided for steplessly. This ensures a particularly smooth switching of the operating modes of the internal combustion engine. Alternatively or additionally, switching between the first and second operating modes and / or between the second and third operating modes can take place in discrete steps.

[0048] In a further possible embodiment of the method, determining the exhaust gas temperature comprises determining a first exhaust gas temperature at a first exhaust tract location. The first exhaust tract location is assigned to a turbine of an exhaust gas turbocharger of the internal combustion engine, in particular arranged in / on an inflow region of the turbine through which the exhaust gas flows during operation of the internal combustion engine in order to drive the turbine impeller of the turbine. Alternatively or additionally, determining the exhaust gas temperature comprises determining a second exhaust gas temperature at a second exhaust tract location, which is assigned to an inflow side of an exhaust gas aftertreatment device, for example a catalytic converter, of the internal combustion engine. The second exhaust tract location is arranged in particular in / on an inflow channel section of the exhaust gas aftertreatment device through which the exhaust gas flows during operation of the internal combustion engine.Alternatively or in addition to determining the first and / or second exhaust gas temperature at the first and / or second exhaust gas tract locations, respectively, it is further provided that determining the exhaust gas temperature comprises determining a third exhaust gas temperature at a third exhaust gas tract location. The third exhaust gas tract location is assigned to an aftertreatment chamber of the exhaust gas aftertreatment device through which the exhaust gas flows, for example a conversion chamber of the catalytic converter, for example arranged in the aftertreatment chamber. The respective exhaust gas temperature can be measured, for example by means of appropriately configured temperature sensors. Alternatively or additionally, one or more of the exhaust gas temperatures can be modeled, for example by means of the control device.

[0049] The first sub-criterion relating to the exhaust gas temperature is deemed to be met if the value of the first exhaust gas temperature originates from the first exhaust gas temperature value range and / or if the value of the second exhaust gas temperature originates from the first exhaust gas temperature value range and / or if the value of the third exhaust gas temperature originates from the first exhaust gas temperature value range. In particular, an individual first exhaust gas temperature value range is provided for each exhaust gas tract location. This means that, for example, a first exhaust gas temperature value range assigned to the first exhaust gas tract location can contain different exhaust gas temperature values ​​than a first exhaust gas temperature value range assigned to the second exhaust gas tract location.The second sub-criterion relating to the exhaust gas temperature is deemed to be met if the value of the first exhaust gas temperature originates from the second exhaust gas temperature value range and / or if the value of the second exhaust gas temperature originates from the second exhaust gas temperature value range and / or if the value of the third exhaust gas temperature originates from the second exhaust gas temperature value range. In particular, an individual first and / or an individual second exhaust gas temperature value range is / are provided for the respective exhaust tract point. This means that, for example, a first / second exhaust gas temperature value range assigned to the first exhaust tract point can contain different exhaust gas temperature values ​​than a first / second exhaust gas temperature value range assigned to the second exhaust tract point. This applies analogously to the other exhaust tract points.The third sub-criterion relating to the exhaust gas temperature is deemed to be met if the value of the first exhaust gas temperature originates from the third exhaust gas temperature value range and / or if the value of the second exhaust gas temperature originates from the third exhaust gas temperature value range and / or if the value of the third exhaust gas temperature originates from the third exhaust gas temperature value range. In particular, an individual third exhaust gas temperature value range is provided for each exhaust tract location. This means that, for example, a third exhaust gas temperature value range assigned to the first exhaust tract location can contain different exhaust gas temperature values ​​than a third exhaust gas temperature value range assigned to the second exhaust tract location. This applies analogously to the other exhaust tract locations.

[0050] This allows for particularly precise consideration of the exhaust gas temperatures at the various points of the internal combustion engine. Furthermore, a plausibility check can be provided. For example, if an implausibly high exhaust gas temperature is measured at the first exhaust tract point, which lies above the first exhaust gas temperature limit, switching from the second to the third operating mode can be omitted if a plausible exhaust gas temperature is measured at the second exhaust tract point and lies below the second exhaust gas temperature limit.

[0051] Further features of the invention may emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0052] The drawing shows:

[0053] Fig. 1 for an approximately 20-second fired acceleration of an internal combustion engine having a crankshaft, which is controlled by means of a method for controlling an internal combustion engine, over a common time axis a) a crankshaft speed curve of the internal combustion engine and a gear ratio curve of a gear change transmission coupled to the crankshaft, b) an active state curve of three operating modes of the internal combustion engine, c) a curve of an intake valve spread angle, which indicates at which angular position of the crankshaft relative to its top dead center position the intake valve is opened with a maximum lift, d) a charge air pressure curve and e) a charge air temperature curve, Fig.2 To illustrate the operating modes and the associated intake valve spread angles, the schematically illustrated crankshaft a) in a top dead center position, b) in a first angular position disengaged from the first dead center position by a first crankshaft angle, c) in a second angular position disengaged from the first dead center position by a second crankshaft angle, d) in a third angular position disengaged from the first dead center position by a third crankshaft angle.

[0054] The following provides a joint description of a method for controlling an internal combustion engine, a control device configured to carry out the method, an internal combustion engine unit comprising the internal combustion engine and the control device, and a motor vehicle comprising the internal combustion engine unit. In the figures, identical and functionally equivalent elements are provided with the same reference numerals.

[0055] The motor vehicle has the internal combustion engine unit, so that the internal combustion engine of the internal combustion engine unit forms a drive engine of the motor vehicle. In addition to the internal combustion engine, the internal combustion engine unit has a control device that has means for executing the method for controlling the internal combustion engine. The control device provides control signals for the internal combustion engine, in particular for an intake valve train of the internal combustion engine, wherein the internal combustion engine is configured to accept the control signals provided by the control device as input control signals. Accordingly, the internal combustion engine and the control device are or can be coupled to one another for control signal transmission.

[0056] The internal combustion engine is embodied as a four-stroke reciprocating piston engine and, in addition to the intake valve train, has a crankshaft 1, a combustion chamber, and an intake valve associated with the combustion chamber. Furthermore, the internal combustion engine has a charge air compressor, for example an exhaust gas turbocharger, for pre-compressing charge air to be supplied to the combustion chamber. During firing operation of the internal combustion engine, an outlet side of the combustion chamber is tightly closed by an exhaust valve to charge the combustion chamber with charge air or a fuel-air mixture during a charging stroke, whereas an inlet side of the combustion chamber is opened by an inlet valve that is at least partially open to allow fluid to flow into the combustion chamber.In order to move a reciprocating piston mounted so as to be translationally movable in the combustion chamber, the crankshaft 1 is rotated starting from its top dead center position TDC - shown at 0° in Fig. 2 - and in the intended working direction of rotation 2 (see Fig. 2 a)) towards a bottom dead center position BDC - shown at 180° in Fig. 2. The charging stroke is followed by a compression stroke, in which the crankshaft 1 is rotated in the working direction of rotation from the bottom dead center position BDC (180°) towards the top dead center position TDC (360°). In the subsequent full rotation of the crankshaft 1, an expansion stroke (from 360° to 540°) and an exhaust stroke (from 540° to 720° = 0°) follow and the four-stroke cycle begins again.

[0057] Fig. 1 a) shows a curve of a crankshaft speed n and a curve of gear ratios N of a gear change transmission coupled to the internal combustion engine over time t, with the internal combustion engine being accelerated under fire. The internal combustion engine is controlled according to the method.

[0058] Fig. 1 b) shows the time periods of the acceleration process in which the internal combustion engine is operated in a first operating mode B1, a second operating mode B2 and a third operating mode B3. It can be seen that the operating modes B1, B2 and B3 do not overlap. This means that the first operating mode B1 is only active when neither the second operating mode B2 nor the third operating mode B3 is active. The second operating mode B2 is active when neither the first operating mode B1 nor the third operating mode B3 is active. Consequently, the third operating mode B3 is only active when neither the first operating mode B1 nor the second operating mode B2 is active.

[0059] The operating modes B1, B2, B3 differ in particular in their respective intake valve spread angle ES, the curve of which over time t is shown in Fig. 1 c). Depending on the operating mode B1, B2, B3, the intake valve is maximally open at a different intake spread ES1, ES2, ES3, i.e. it is completely open. The intake valve spread angle ES is a crankshaft angle that is measured in the working direction of rotation 2 of the crankshaft 1 and starting from the top dead center position TDC of the crankshaft 1. It follows that the intake valve is completely closed at different crankshaft angles KW1, KW2, KW3 in relation to the respective charging stroke, depending on the operating mode B1, B2, B3.

[0060] Fig. 2 b), c) and d) show the intake valve spread angles ES1, ES2, ES3, at which the intake valve is open with maximum lift. It can be seen that in the first operating mode B1 the intake valve is maximally open at a first intake valve spread angle ES1. As a result, the intake valve is completely in the closed position at a first crankshaft angle KW1 of approximately 180°, i.e. approximately at the bottom dead center position UT. In other words: in the first operating mode B1, the closing movement of the intake valve is completely completed at the bottom dead center position UT or when the crankshaft has assumed the first crankshaft angle KW1. The flow of charge air into the combustion chamber is completely blocked at the first crankshaft angle KW1. It is known that (for tolerance reasons, such as valve clearance, and / or to utilize advantageous thermal or thermal properties)Due to fluid dynamic effects, the closing of the intake valve can be fully completed shortly before or shortly after the bottom dead center position, but in any case in a close range around the bottom dead center position UT, for example in a range of ± 10° around the bottom dead center position UT. Therefore, the first intake valve spread angle ES1 originates in particular from a first intake valve spread angle range [ES1], and consequently the first crankshaft angle KW1 originates in particular from a first crankshaft angle range [KW1].

[0061] In the second operating mode B2, the intake valve is fully open at a second intake valve spread angle ES2, whereby the intake valve closes earlier than in the first operating mode B1, i.e., at a second crankshaft angle KW2 and in any case before crankshaft 1 has reached the first crankshaft angle KW1. This completely blocks the flow of charge air into the combustion chamber during the charging stroke. The internal combustion engine thus operates in a Miller cycle of the first Miller intensity.

[0062] The second intake valve spread angle ES2 can originate from a second intake valve spread angle range [ES2], which means that the second crankshaft angle KW2 can originate from a second crankshaft angle range [KW2]. The first crankshaft angle KW1 or its angular range [KW1] and the second crankshaft angle KW2 or its angular range [KW2] are spaced apart from one another by a first angular distance. This means that the first intake valve spread angle ES1 or its angular range [ES1] and the second intake valve spread angle ES2 or its angular range [ES2] can be spaced apart from one another by the first angular distance. The first angular distance is more than 10°, in particular more than 30°. The closing of the intake valve is completed, for example, 40° earlier in the first Miller cycle or in the second operating mode B2 compared to the first operating mode B1.

[0063] In the third operating mode B3, the intake valve is fully open at a third intake valve spread angle ES3, whereby the closing of the intake valve is completed even earlier than in the second operating mode B2, namely at a third crankshaft angle KW3, whereby the internal combustion engine is then operated in a Miller cycle of second Miller intensity. The third crankshaft angle KW3 can originate from a third crankshaft angle range [KW3], and the third intake valve spread angle ES3 can originate from a third intake valve spread angle range [ES3]. The second crankshaft angle KW2 or its angular range [KW2] and the third crankshaft angle KW3 or its angular range [KW3] are spaced from each other by a second angular distance that is more than 5°. In this respect, the intake valve spread angle ranges [ES2], [ES3] can be spaced from each other by the second angular distance.Intake valve closing is completed earlier in the Miller cycle with the second Miller intensity, or in the third operating mode B3, than in the first operating mode B1, and even earlier than in the second operating mode B2. Thus, the effects associated with a Miller cycle are more pronounced in the Miller cycle with the second intensity, i.e., in the third operating mode B3, than in the second operating mode B2. The second operating mode B2 has the first, weak Miller intensity, and the third operating mode B3 has the second, strong Miller intensity.

[0064] The method determines the charge air pressure of the charge air. The curve of the charge air pressure p during the fired acceleration considered here is shown in Fig. 1 d) over time t. In particular, the crankshaft speed and load at which the internal combustion engine is operating are determined. Furthermore, the current gear ratio of a gear change transmission coupled to the internal combustion engine and the current driving speed of the vehicle are determined. Furthermore, the current operating time of the internal combustion engine and the exhaust gas temperature at an exhaust tract location are determined.One, some, or all of the values ​​determined here—in this case, a boost air pressure value, a crankshaft speed value (rpm value for short), a load value, a gear ratio value, a vehicle speed value (velocity value for short), a duration of operation value, and an exhaust gas temperature value—can be modeled, for example, by the control unit of the internal combustion engine. Alternatively or additionally, one, some, or all of the aforementioned values ​​can be measured, for example, by an appropriately configured and arranged sensor. For example, in this case, the exhaust gas temperature value is determined by modeling the exhaust gas temperature prevailing at the exhaust tract location or the corresponding exhaust gas temperature value using the control unit.

[0065] The internal combustion engine is operated in the first operating mode B1 if or as long as a first operating criterion is met. In this example, the first operating criterion is considered met if one of the first sub-criteria is met or if two or more of the first sub-criteria are met. The first sub-criteria are:

[0066] - The charge air currently has a charge air pressure p whose value originates from a first predefined charge air pressure value range, which includes values ​​from zero up to and including a first predefined limit charge air pressure value Gpi.

[0067] - The current crankshaft speed n has a value which originates from a first predetermined speed value range which includes values ​​from zero, in particular from an idle speed value, up to and including a first predetermined limit speed value.

[0068] - The current load has a value that comes from a first predetermined load value range, which includes values ​​from zero up to and including a first predetermined limit load value.

[0069] - The current gear ratio N of the gear ratio change transmission has a value which originates from a first predefined gear ratio value range which includes values ​​from zero up to and including a first predefined limit gear ratio value.

[0070] - The current vehicle speed has a value which comes from a first predetermined speed value range which includes values ​​from zero up to and including a first predetermined limit speed value.

[0071] - A current operating time during which the internal combustion engine was last operated continuously in the first operating mode has a value that originates from a first predetermined time value range that includes values ​​from zero up to and including a first predetermined limit operating time value.

[0072] - At the exhaust tract point of the internal combustion engine, the exhaust gas temperature is determined, the value of which originates from a first predetermined exhaust gas temperature value range, which includes values ​​from zero up to and including a first predetermined limit exhaust gas temperature value.

[0073] In the method, the internal combustion engine is switched from the first operating mode B1 to the second operating mode B2 if another, second operating criterion is met. In this example, the second operating criterion is considered to be met if one of the second sub-criteria is met or if two or more of the second sub-criteria are met. The second sub-criteria are:

[0074] - The charge air currently has a charge air pressure p whose value originates from a second predefined charge air pressure value range, which includes values ​​from the first predefined limit charge air pressure value Gpi exclusively up to and including a second predefined limit charge air pressure value.

[0075] - The current crankshaft speed has a value which originates from a second predetermined speed value range which includes values ​​from the first predetermined limit speed value exclusively up to and including a second predetermined limit speed value.

[0076] - The current load has a value that comes from a second specified load value range that includes values ​​from the first specified limit load value exclusively up to and including a second specified limit load value.

[0077] - The current gear ratio of the gear change transmission has a value that comes from a second predefined gear ratio value range, which includes values ​​from the first predefined limit gear ratio value exclusively up to a second predefined limit gear ratio value inclusive.

[0078] - The current driving speed has a value which comes from a second predefined speed value range which includes values ​​from the first predefined limit speed value exclusively up to and including a second predefined limit speed value.

[0079] - The current operating time during which the internal combustion engine was last operated continuously in the first operating mode has a value which originates from a second predefined time value range which includes values ​​from the first predefined limit operating time value exclusively up to and including a second predefined limit operating time value.

[0080] - At the exhaust tract point, an exhaust gas temperature is determined whose value originates from a second predetermined exhaust gas temperature value range, which includes values ​​from the first predetermined limit exhaust gas temperature value exclusively up to and including a second predetermined limit exhaust gas temperature value.

[0081] The internal combustion engine is therefore operated in the first operating mode B1 as long as one or more of the second sub-criteria are not met, for example as long as the charge air pressure PL is lower than the limit charge air pressure Gpi. The internal combustion engine is intended to be switched to the second operating mode B2 as early as possible and to be operated in the second operating mode B2 for as long as possible. It can be seen from Fig. 1 d) that in the second operating mode B2 the charge air compressor supplies a higher charge air pressure than in the first operating mode B1. The switching from the first operating mode B1 to the second operating mode B2 or vice versa is carried out continuously in the present case. Alternatively, it is conceivable that the switching from the first operating mode B1 to the second operating mode B2 or vice versa takes place via discrete steps.

[0082] According to the method, the internal combustion engine is switched from the second operating mode B2 to the third operating mode B3 only when necessary for component protection reasons. A third operating criterion is provided for this purpose, whereby the internal combustion engine is switched from the second operating mode B2 to the third operating mode B3 or is operated in the third operating mode B3 when the third operating criterion is met. In this example, the third operating criterion is considered to be met if one of the third sub-criteria is met or if two or more of the third sub-criteria are met. The third sub-criteria are:

[0083] - The charge air has a current charge air pressure p, the value of which originates from a third predefined charge air pressure value range, which includes values ​​from the second predefined limit charge air pressure value Gpi exclusively and higher.

[0084] - The current crankshaft speed has a value that comes from a third predetermined speed value range that includes values ​​from the second predetermined limit speed value exclusively and higher.

[0085] - The current load has a value that comes from a third predefined load value range, which includes values ​​from the second predefined limit load value exclusively and higher. - The current gear ratio of the gear change transmission has a value that comes from a third predefined gear ratio value range, which includes values ​​from the second predefined limit gear ratio value exclusively and higher.

[0086] - The current vehicle speed has a value that comes from a third predefined speed value range that includes values ​​from a second predefined limit speed value exclusively and higher.

[0087] - The current operating time during which the internal combustion engine was last operated continuously in the second operating mode has a value that originates from a third predetermined time value range that includes values ​​from the second predetermined limit operating time value exclusively and higher.

[0088] - At the exhaust tract point, an exhaust gas temperature is determined whose value comes from a third specified exhaust gas temperature value range, which includes values ​​from the second specified limit exhaust gas temperature value exclusively and higher.

[0089] If, for example, the determined exhaust gas temperature is / becomes higher than a predefined limit exhaust gas temperature, the internal combustion engine is switched to the third operating mode B3. In particular, as soon as the exhaust gas temperature permits it again, i.e. as soon as the determined exhaust gas temperature at the corresponding exhaust tract point falls or has fallen below a predefined limit exhaust gas temperature, the internal combustion engine is switched back to the second operating mode B2. In this case, a downshift limit temperature is specified for switching from the third operating mode B3 to the second operating mode B2. This limit temperature is lower than the limit exhaust gas temperature and comes into effect when switching from the third operating mode B2 to the second operating mode B3 instead of the limit exhaust gas temperature. In this case, switching from the second operating mode B2 to the third operating mode B3 and vice versa is stepless.Alternatively, it is conceivable that switching from the second operating mode B2 to the third operating mode B3 or vice versa takes place via discrete stages.

[0090] The internal combustion engine can further be operated in a first intermediate operating mode, which is characterized by an intake valve spread angle ES that is smaller than the first intake valve spread angle ES1 but greater than the second intake valve spread angle ES2. This means that in the first intermediate operating mode, the closing of the intake valve is completed at a crankshaft angle that is smaller than the first crankshaft angle KW1 and greater than the second crankshaft angle KW2. The internal combustion engine can further be operated in a second intermediate operating mode, which is characterized in particular by an intake valve spread angle ES that is smaller than the second intake valve spread angle ES2 and greater than the third intake valve spread angle ES3.In the respective second intermediate operating mode, the intake valve closes at a crankshaft angle that is smaller than the second crankshaft angle KW2 but greater than the third crankshaft angle KW3. Two or more first or two or more second intermediate operating modes are possible. By switching to one or more of the intermediate operating modes (e.g., first operating mode B1 - first intermediate operating mode - further first intermediate operating mode(s) - second operating mode B2 - second intermediate operating mode - further second intermediate operating mode(s) - third operating mode B3), the Miller intensity can be adjusted particularly precisely as required.

[0091] In the present case, a first exhaust gas temperature is determined at a first exhaust tract point, a second exhaust gas temperature at a second exhaust tract point, and a third exhaust gas temperature at a third exhaust tract point. The first exhaust tract point is assigned to a turbine of the exhaust gas turbocharger, for example, arranged in / on an inflow region of the turbine, and is specified for component protection for the turbine. The second exhaust tract point is assigned to an inflow side of an exhaust gas aftertreatment device, for example a catalytic converter, of the internal combustion engine and is arranged in particular in / on an inflow channel section of the exhaust gas aftertreatment device. A second limit exhaust gas temperature is specified for component protection for the exhaust gas aftertreatment device.The third exhaust tract location is assigned to an aftertreatment chamber of the exhaust gas aftertreatment system through which the exhaust gas flows, for example, a conversion chamber of the catalytic converter, and is located, for example, in the aftertreatment chamber. A third limit exhaust gas temperature is specified here to protect the aftertreatment chamber's components.

[0092] In this case, an individual first, an individual second, and an individual third exhaust gas temperature value range are assigned to the respective exhaust tract location. In this case, the first sub-criterion relating to the exhaust gas temperature is deemed to be met if the value of the first exhaust gas temperature and / or the value of the second exhaust gas temperature and / or the value of the third exhaust gas temperature originates from the correspondingly assigned one of the individual first exhaust gas temperature value ranges. The second sub-criterion relating to the exhaust gas temperature is deemed to be met if the value of the first exhaust gas temperature and / or the value of the individual second exhaust gas temperature and / or the value of the third exhaust gas temperature originates from the correspondingly assigned one of the second exhaust gas temperature value ranges.The third sub-criterion relating to the exhaust gas temperature is deemed to be met in this case if the value of the first exhaust gas temperature and / or the value of the second exhaust gas temperature and / or the value of the third exhaust gas temperature originates from the correspondingly assigned individual third exhaust gas temperature value ranges.

[0093] Fig. 1 e) shows the charge air temperature TL plotted against time t. It can be seen that the charge air temperature TL is higher in the second operating mode B2 than in the first operating mode B1. If necessary, measures may need to be taken to cool the charge air, such as a particularly efficient intercooler, etc.

[0094] From a joint review of Fig. 1 d) and e), it can be seen that components and peripheral components of the internal combustion engine that come into contact with or interact with the charge air and / or the exhaust gas are subject to greater stress in the second operating mode B2 than in the first operating mode B1. However, this is accepted in order to switch to the second operating mode as early as possible during fired operation of the internal combustion engine and to operate the internal combustion engine in the second operating mode as often and for as long as possible. This is because the second operating mode – i.e., the Miller cycle with first or weak Miller intensity – offers advantages in terms of exhaust gas temperature compared to the first operating mode B1. Thus, the components / peripheral components that interact with the exhaust gas – for example, the turbine of the charge air compressor, the exhaust gas aftertreatment device, in particular its aftertreatment chamber, etc.-in contact with advantageously cool exhaust gas. Undesirably high temperatures, in particular reaching the specified limit temperature(s), are therefore effectively avoided. By means of the method, the internal combustion engine is operated with a combustion stoichiometric fuel-air ratio A = 1, whereby enrichment of the fuel-air mixture (A < 1) to cool the exhaust gas is deliberately omitted. If, during operation of the internal combustion engine, exhaust gas temperatures are(are) hotter than the limit exhaust gas temperatures, enrichment of the fuel-air mixture (A < 1) to cool the exhaust gas is nevertheless omitted and instead the system switches to the third operating mode - i.e. the Miller cycle with second or strong Miller intensity.Thus, the internal combustion engine is operated with a fuel-air ratio A = 1 - even at high loads, especially at stationary full load - whereby the exhaust gas temperature or temperatures do not exceed the specified limit exhaust gas temperature or temperatures.

[0095] Current legal requirements, which stipulate particularly low limits for pollutant emissions across the entire operating range of the internal combustion engine, are met.

[0096] The method for controlling the internal combustion engine, the control device designed to carry out the method, the internal combustion engine and the motor vehicle having the internal combustion engine show a respective possibility of how an internal combustion engine can be operated particularly efficiently and with low emissions.

[0097] List of reference symbols

[0098] 1 crankshaft

[0099] 2 Working direction of rotation

[0100] KW1 first crankshaft angle

[0101] [KW1] first crankshaft angle range

[0102] KW2 second crankshaft angle

[0103] [KW2] second crankshaft angle range

[0104] KW3 third crankshaft angle

[0105] [KW3] third crankshaft angle range

[0106] TDC top dead center position of the crankshaft

[0107] UT bottom dead center position of the crankshaft

[0108] B1 first operating mode

[0109] B2 second operating mode or first Miller cycle

[0110] B3 third operating mode or second Miller cycle

[0111] ES1 first intake valve spread angle

[0112] ES2 second intake valve spread angle

[0113] ES3 third intake valve spread angle

[0114] PL charge air pressure

[0115] GPL Charge air pressure limit Charge air temperature

Claims

Patent claims 1. Method for controlling an internal combustion engine having a crankshaft (1), an intake valve and a charge air compressor for pre-compressing charge air, wherein during a charging stroke a closing of the intake valve starting from a top dead center position (OT, 0°) of the crankshaft (1) and in the working direction of rotation (2) of the crankshaft (1) is measured - in a first operating mode (B1) at a first crankshaft angle (KW1) at a bottom dead center position (UT, 180°) of the crankshaft (1) or - in a second operating mode (B2) at a second crankshaft angle (KW2) which is smaller than the first crankshaft angle (KW1), before the bottom dead center position (UT, 180°) or - in a third operating mode (B3) at a third crankshaft angle (KW3), which is smaller than the second crankshaft angle (KW2), before the bottom dead center position (UT, 180°), is completely completed, wherein the internal combustion engine - is operated in the first operating mode (B1) if a first operating criterion is met, - switching from the first operating mode (B1) to the second operating mode (B2) when a second operating criterion is met, - switching from the second operating mode (B2) to the third operating mode (B3) when a third operating criterion is met.

2. Method according to claim 1, characterized in that the first operating criterion is met if one or more of the following first sub-criteria is / are met: - The current charge air pressure (p ) has a value which originates from a first predetermined charge air pressure value range which includes values ​​from zero up to a first predetermined limit charge air pressure value (Gp inclusive); - A current crankshaft speed has a value which originates from a first predetermined speed value range which includes values ​​from zero, in particular from an idle speed value, up to and including a first predetermined limit speed value; - A current load of the internal combustion engine has a value which originates from a first predetermined load value range which includes values ​​from zero up to and including a first predetermined limit load value; - A current gear ratio of a gear change transmission coupled to the internal combustion engine has a value which originates from a first predetermined gear ratio value range which includes values ​​from zero up to and including a first predetermined limit gear ratio value; - A current driving speed of a motor vehicle having the internal combustion engine as the prime mover has a value which originates from a first predetermined speed value range which includes values ​​from zero up to and including a first predetermined limit speed value; - a current operating time during which the internal combustion engine was last operated continuously in the first operating mode has a value which originates from a first predetermined time value range which includes values ​​from zero up to and including a first predetermined limit operating time value; - At an exhaust tract point of the internal combustion engine, an exhaust gas temperature is determined, the value of which originates from a first predetermined exhaust gas temperature value range, which includes values ​​from zero up to and including a first predetermined limit exhaust gas temperature value.

3. Method according to claim 1 or 2, characterized in that the second operating criterion is met if one or more of the following second sub-criteria is / are met: - The current charge air pressure (pü) has a value which originates from a second predefined charge air pressure value range which comprises values ​​from a first predefined limit charge air pressure value (GpO) exclusively up to and including a second predefined limit charge air pressure value; - A current crankshaft speed has a value which originates from a second predetermined speed value range which includes values ​​from a first predetermined limit speed value exclusively up to and including a second predetermined limit speed value; - A current load of the internal combustion engine has a value which originates from a second predetermined load value range which includes values ​​from a first predetermined limit load value exclusively up to and including a second predetermined limit load value; - A current gear ratio of a gear change transmission coupled to the internal combustion engine has a value which originates from a second predetermined gear ratio value range which comprises values ​​from a first predetermined limit gear ratio value exclusively up to a second predetermined limit gear ratio value inclusive; - A current driving speed of a motor vehicle having the internal combustion engine as the prime mover has a value which originates from a second predetermined speed value range which includes values ​​from a first predetermined limit speed value exclusively up to a second predetermined limit speed value inclusive; - a current operating time during which the internal combustion engine was last operated continuously in the first operating mode has a value which originates from a second predetermined time value range which comprises values ​​from a first predetermined limit operating time value exclusively up to and including a second predetermined limit operating time value; - At an exhaust tract point of the internal combustion engine, an exhaust gas temperature is determined, the value of which originates from a second predetermined exhaust gas temperature value range, which comprises values ​​from a first predetermined limit exhaust gas temperature value exclusively up to and including a second predetermined limit exhaust gas temperature value.

4. Method according to one of the preceding claims, characterized in that the third operating criterion is met if one or more of the following third sub-criteria is / are met: - The current charge air pressure (p ) has a value which originates from a third predetermined charge air pressure value range which includes values ​​from a second predetermined limit charge air pressure value (GpO exclusive and higher); - A current crankshaft speed has a value that comes from a third predetermined speed value range that includes values ​​from a second predetermined limit speed value exclusively and higher; - A current load of the internal combustion engine has a value that comes from a third predetermined load value range that includes values ​​from the second first predetermined limit load value exclusively and higher; - A current gear ratio of a gear change transmission coupled to the internal combustion engine has a value which originates from a third predetermined gear ratio value range which includes values ​​from a second predetermined limit gear ratio value exclusively and higher; - A current driving speed of a motor vehicle having the internal combustion engine as the prime mover has a value which originates from a third predetermined speed value range which includes values ​​from a second predetermined limit speed value exclusively and higher; - a current operating time during which the internal combustion engine was last operated continuously in the second operating mode has a value which originates from a third predetermined time value range which includes values ​​from a second predetermined limit operating time value exclusively and higher; - At an exhaust tract point of the internal combustion engine, an exhaust gas temperature is determined, the value of which originates from a third predetermined exhaust gas temperature value range, which includes values ​​from a second predetermined limit exhaust gas temperature value exclusively and higher.

5. Method according to one of the preceding claims, characterized in that - the first crankshaft angle (KW1) and the second crankshaft angle (KW2) are spaced apart from each other by a first angular distance, which is in particular more than 10° or more than 30°, and / or - the second crankshaft angle (KW2) and the third crankshaft angle (KW3) are spaced apart from each other by a second angular distance which is in particular more than 5°.

6. The method according to any one of claims 2 to 5, characterized in that determining the exhaust gas temperature comprises determining a first exhaust gas temperature at a first exhaust tract location which is associated with a turbine of an exhaust gas turbocharger of the internal combustion engine.

7. The method according to any one of claims 2 to 6, characterized in that determining the exhaust gas temperature comprises determining a second exhaust gas temperature at a second exhaust tract location which is associated with an inflow side of an exhaust gas aftertreatment device of the internal combustion engine.

8. Method according to one of claims 2 to 7, characterized in that the measuring of the exhaust gas temperature comprises measuring a third exhaust gas temperature at a third exhaust tract location which is assigned to an aftertreatment chamber of the exhaust gas aftertreatment device through which the exhaust gas flows.

9. Control device for an internal combustion engine, wherein the control device is configured to carry out the method according to one of the preceding claims.

10. Internal combustion engine unit with an internal combustion engine and a control device designed according to claim 9, which is coupled or can be coupled to the internal combustion engine for controlling the internal combustion engine.

11. Motor vehicle with an internal combustion engine unit designed according to claim 10.

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