DE102016212945B4 - Method and device for controlling an internal combustion engine with an exhaust gas turbocharger - Google Patents

Abstract

Method for controlling an internal combustion engine (1) having a plurality of cylinders (11) and an exhaust gas turbocharger (2), wherein when the power demand on the internal combustion engine (1) increases, the speed of the turbocharger (2) is increased by increasing the exhaust gas temperature is supported, characterized in that- depending on the power requirement and the respective current operating point of the exhaust gas turbocharger (2), a current setpoint exhaust gas temperature (AT_S) is determined by means of an exhaust gas turbocharger calculation model,- starting from the determined setpoint exhaust gas temperature (AT_S ) by means of an exhaust gas temperature calculation model, the setpoint control value (StW_S) required to achieve the setpoint exhaust gas temperature (AT_S) of at least one control parameter influencing the exhaust gas temperature is determined and from the setpoint control value (StW S) including at least one limit control value ( StW_GR, StW_GR_BG, StW GR TQ) determine a default tax value (StW_VG). and the determined default control value (StW_VG) of the at least one control parameter influencing the exhaust gas temperature is used to control the internal combustion engine (1) in order to increase the exhaust gas temperature, the combustion center position being used as the control parameter and the combustion center position only for a partial number of the total existing cylinder (11) of the internal combustion engine (1) is shifted to a later point in time with respect to the combustion center of gravity at the point in time before the power requirement is increased.

Description

The invention relates to a method and a device for controlling an internal combustion engine that is equipped with an exhaust gas turbocharger to increase output.

Internal combustion engines, in particular for motor vehicles, are in the majority designed as reciprocating piston internal combustion engines, to which particular reference is made in the present invention. However, rotary piston internal combustion engines (Wankel principle) are also covered by this generic term and the scope of the invention.

Reciprocating internal combustion engines have at least one reciprocating cylinder, hereinafter referred to as cylinder for short, but often have at least three or more cylinders. A reciprocating piston is provided for each cylinder, which delimits a combustion chamber with the cylinder and can move up and down in the cylinder over a distance referred to as the piston stroke. The reciprocating piston is driven by filling the combustion chamber with a fuel-air mixture and the subsequent combustion of the fuel, and the movement of the reciprocating piston is transmitted via a connecting rod to the crankshaft of the internal combustion engine, which is thereby set in rotation and generates the torque required to drive a motor vehicle gives. A distinction is made between so-called Otto engines and diesel engines, with Otto engines using normal or premium gasoline with external ignition by means of at least one ignition device, e.g. B. spark plug, per cylinder and diesel engines are operated with diesel fuel with self-ignition.

Due to the increasingly strict legislation with regard to the exhaust gas behavior of combustion engines and the increased performance expectations of the users, ever higher demands are placed on the design, control and regulation of the combustion process of the fuel in the combustion chamber and the exhaust gas aftertreatment. In order to meet these requirements, modern internal combustion engines are equipped with electronically controlled systems for fuel and air metering, ignition, valve opening, exhaust gas recirculation and exhaust gas aftertreatment, usually by means of a central control unit, the so-called ECU (Electronic Control Unit).

Direct fuel injection systems are used for fuel metering, in which the fuel is provided under high pressure, for example in a so-called common rail, and metered with high precision using electronically controlled injectors depending on the current performance requirement, with high pressure, often in several parts -Injection quantities are divided up and injected into the combustion chamber at exactly the desired time.

The oxygen required for combustion is also metered into the combustion chamber of the respective cylinder in the form of ambient air, if necessary under increased pressure, by a charging system, for example an exhaust gas turbocharger, as required via throttle valves and inlet valves.

The fuel-air mixture in the combustion chamber is also ignited, depending on the current operating point of the combustion engine, with precise timing in relation to the reciprocating piston position correlating with the current crankshaft rotation angle, this current crankshaft rotation angle also being referred to as the so-called ignition angle. In the case of Otto engines, the ignition is specified via an ignition device controlled by the central control device, and in the case of diesel engines, it is specified by the point in time at which the fuel is injected.

Another way of influencing the combustion process is with internal combustion engines that are equipped with a so-called variable valve train, i.e. a system for variable adjustment of the valve opening intervals. With such a system, the opening cross-sections and the opening times of the intake valves, through which the intake air from the intake system enters the combustion chamber, and the exhaust valves, through which the exhaust gas enters the exhaust system from the combustion chamber after combustion, can be variably controlled within certain limits . This allows the so-called gas exchange in the combustion chamber, i.e. the exchange of exhaust gas for a fuel-air mixture, and thus the power output to be significantly influenced.

Another unit that significantly influences the combustion process and thus the performance of the internal combustion engine is charging systems, in particular exhaust gas turbochargers, which are used particularly in diesel engines, but increasingly also in Otto engines. This is happening more and more frequently with the aim of reducing the size and weight of the internal combustion engine with the same or even increased performance and at the same time reducing consumption and thus CO ₂ emissions in view of the increasingly strict legal requirements in this regard. The operating principle is to use the energy contained in the exhaust gas flow to increase the pressure in the intake system in front of the cylinders of the combustion engine and thus to achieve better filling of the combustion chamber with air-oxygen and thus more fuel, petrol or diesel, per combustion process to be able to implement, i.e. to increase the power of the internal combustion engine.

For this purpose, the exhaust gas turbocharger has an exhaust gas turbine arranged in the exhaust system of the internal combustion engine, a fresh air compressor arranged in the intake system and a rotor bearing arranged between them. The exhaust gas turbine has a turbine housing and a turbine impeller which is arranged therein and is driven by the exhaust gas mass flow. The fresh air compressor has a compressor housing and a compressor impeller which is arranged therein and builds up boost pressure. The turbine impeller and the compressor impeller are arranged in a rotationally fixed manner on the opposite ends of a common shaft, the so-called rotor shaft, and thus form the so-called turbocharger rotor. The rotor shaft extends axially between the turbine rotor and the compressor rotor through the rotor bearing arranged between the exhaust gas turbine and the fresh air compressor and is rotatably mounted in it radially and axially with respect to the rotor shaft axis. According to this design, the turbine impeller driven by the exhaust gas mass flow drives the compressor impeller via the rotor shaft, whereby the pressure in the intake system of the combustion engine, related to the fresh air mass flow behind the fresh air compressor, is increased and this causes better filling of the combustion chamber with air-oxygen.

In the event of a sudden load increase, for example in connection with an acceleration process of a motor vehicle, the turbocharger rotor is only accelerated with a delay due to the increasing exhaust gas pressure have poor efficiencies. For this reason and reinforced by the inertial mass of the turbocharger rotor, the pressure build-up in the intake system is delayed, which in turn results in a delayed response of the combustion engine, which is generally referred to as so-called turbo lag. As a rule, this turbo lag is not only perceived as unpleasant by the vehicle driver, since the vehicle only reacts with a delay to a dynamic performance requirement, for example when overtaking, but also represents a safety risk that should not be underestimated, for example if overtaking is due to the "turbo lag delay" cannot be completed in time.

This undesirable effect is countered with different approaches, such as the parallel or sequential arrangement of several turbochargers of different size, power and response. Another solution is the additional arrangement of a compressor unit in the intake system that can be operated independently of the exhaust gas flow, which is used as a supplement to an exhaust gas turbocharger, specifically in transient operating phases of the combustion engine, for rapid pressure build-up in the intake system, i.e. to eliminate turbo lag. However, these solutions are structurally and conceptually very complex and correspondingly expensive.

Another approach to at least reducing the aforementioned turbo lag is, for example in combustion engines equipped with a variable valve train, to change the opening times of the intake and exhaust valves of the respective cylinder in relation to the crankshaft angle so that there is an overlap the opening times of the intake and exhaust valves, i.e. the intake and exhaust valves open simultaneously for a certain period of time. This leads to what is known as scavenging, which is also known under the term "scavening", whereby the gas exchange in the cylinder is promoted by the pressure drop between the intake system and the exhaust system and a better filling of the combustion chamber with air can be achieved. Thus, a larger amount of fuel can be metered, resulting in an immediate increase in power output. The disadvantage of this method is worse exhaust gas behavior, since in this operating mode you have to drive with an excess of oxygen (lambda >1), i.e. with a so-called lean fuel-air mixture, for example to limit the catalyst temperature, but this leads to increased NOx emissions, As a result, the limit values specified in existing or at least in future exhaust gas legislation can no longer be observed.

Another way to reduce turbo lag is to increase the exhaust gas temperature in front of the turbine of the exhaust gas turbocharger. This results in greater exhaust gas enthalpy, which results in faster acceleration of the turbocharger rotor and thus faster pressure build-up by the compressor in the intake system.

Such a method is for example in the document DE 10 2011 081 844 A1 disclosed. This relates to a method for operating a supercharged internal combustion engine with at least one exhaust gas turbocharger, the response behavior of the exhaust gas turbocharging or of the internal combustion engine charged by means of exhaust gas turbocharging being improved in the event of a sudden change in load. This is achieved by a process which is characterized in that, in the event of a sudden change in load, the ignition point is retarded, starting from an ignition point that has been optimized in terms of efficiency, specifically beyond an ignition point required to avoid knocking combustion.

Also the document DE 101 40 120 A1 discloses a method for operating an internal combustion engine with an exhaust gas turbocharger, in which the response behavior of the internal combustion engine is improved by increasing the exhaust gas enthalpy. For this purpose, when the opening angles of the intake and exhaust valves of a cylinder overlap, fuel is post-injected, which leads to an air-fuel mixture in the exhaust system that is combustible and is ignited and burned by controlling an additional ignition agent in the exhaust system in front of the turbine of the exhaust gas turbocharger.

Similarly, the one in the document DE 199 44 190 A1 disclosed method an increase in the efficiency of the exhaust gas turbocharger and thus the torque in an internal combustion engine operated with direct fuel injection is achieved in that, in addition to a primary injection, a post-injection is caused into one or more cylinders of the internal combustion engine, which leads to an increase in the exhaust gas temperature in front of the turbine of the exhaust gas turbocharger leads.

However, the methods mentioned for increasing the exhaust gas enthalpy have the disadvantage that the exhaust gas temperature can increase in an uncontrolled manner and there is a risk of thermal damage to the exhaust gas turbine or the downstream components in the exhaust system, such as soot particle filters and catalytic converters, particularly in the case of Otto engines. Furthermore, there is a risk that the control interventions, which are only oriented towards optimizing the exhaust gas enthalpy, will have a negative effect on the overall operating behavior of the internal combustion engine. This can result in increased emission values or even an additional reduction in torque, for example if the ignition point is shifted too far back or the exhaust valves are opened too early.

In the DE 199 51 096 C2 describes an engine control system for a diesel engine charged by means of an exhaust gas turbocharger, which regulates the operation of the diesel engine as a function of characteristic diagrams and enables a change between two operating modes of the diesel engine. The system has a computer which, depending on predetermined switching criteria, causes the diesel engine to switch to one or the other mode of operation. A sensor system that communicates with the computer is provided, which monitors the parameters required for switching criteria, and a memory that communicates with the computer, in which separate characteristic maps for the operation of the diesel engine are stored for one operating mode and for the other operating mode. In order to reduce the turbo lag in such a diesel engine, it is proposed to implement one operating mode through normal operation and the other operating mode through a special operation serving to increase the output of the exhaust gas turbocharger, in which the exhaust gas temperature and/or the exhaust gas pressure upstream of the exhaust gas turbocharger is increased relative to normal operation are.

the DE 10 2005 048 692 A1 shows a turbine temperature control system for regulating the operation of an engine that controls the temperature of an air charging device. The system includes a sensor that is responsive to exhaust gas temperature and generates a signal. A control module uses the temperature signal to determine a temperature and compares it to a threshold temperature. The control module regulates the operation of the engine and lowers the temperature if it exceeds the threshold temperature.

From the DE 102 32 326 A1 a method for operating an internal combustion engine with a turbocharger is known, with a current engine torque setpoint being determined from a maximum engine torque setpoint and an original engine torque setpoint and with the maximum engine torque setpoint being determined from a precalculated fuel consumption. The precalculated fuel consumption is determined from a fuel mass flow target value and a current engine torque value.

Furthermore is off DE 10 2013 208 962 A1 a method and system for increasing the exhaust gas temperature of an internal combustion engine is known, which serves to spin up a turbocharger turbine and reduce turbo lag. To do this, pressurized air is delivered from a boost reservoir to an intake manifold while increasing spark retard to accelerate exhaust gas heating while also increasing net combustion torque.

Finally it's over DE 697 16 205 T2 An exhaust gas heating system for an internal combustion engine with fuel injection directly into a combustion chamber of the internal combustion engine is known, in which the exhaust gas temperature is increased by controlling the fuel injection amount and the injection start time to activate the exhaust gas purification device.

The object of the present invention is therefore to provide a method and a device for controlling at least one exhaust gas turbocharger having internal combustion engine, specify through or in which the torque weakness is safely and significantly reduced in a sudden performance requirement from low speeds of the internal combustion engine, while at the same time safely avoiding thermal overload of the system components and an excessively increased pollutant emissions.

This object is achieved by a method and a device for controlling an internal combustion engine with the features of the independent patent claims. Advantageous training and further developments, which can be used individually or, provided they are not mutually exclusive alternatives, can be used in combination with one another, are the subject matter of the dependent claims.

In the method according to the invention for controlling an internal combustion engine which has a plurality of cylinders and has an exhaust gas turbocharger, when there is an increase, in particular in the event of a sudden increase, in the power requirement of the internal combustion engine, the speed of the turbocharger is increased and thus the torque that can be called up is increased supported by the exhaust gas temperature. The method according to the invention is characterized in that initially a current target exhaust gas temperature is determined as a function of the power requirement and the respective current operating point of the exhaust gas turbocharger by means of an exhaust gas turbocharger calculation model. Based on the determined setpoint exhaust gas temperature, the setpoint control value required to achieve the setpoint exhaust gas temperature is then determined using an exhaust gas temperature calculation model of at least one control parameter influencing the exhaust gas temperature. A default control value is then determined from the setpoint control value, including at least one limit control value, and the determined default control value of the at least one control parameter influencing the exhaust gas temperature is used to control the internal combustion engine in order to increase the exhaust gas temperature, the combustion center of gravity being the control parameter is used and the combustion center position is shifted to a later point in time only for a partial number of the total number of cylinders of the internal combustion engine with respect to the combustion center position at the point in time before the increase in the power requirement.

The calculation models used in the method according to the invention and the further versions of the method, the exhaust gas turbocharger calculation model, the exhaust gas temperature calculation model, the combustion limit calculation model and the torque calculation model are mathematical calculation models based on the physical laws of the internal combustion engine or the exhaust gas turbocharger, which are described in The form of appropriate program algorithms are stored, for example, in the central control unit. These calculation models can calculate in advance the sought-after variable manipulated variables or control values for controlling the subsystems on the basis of or as a function of sensor-determined, constructively specified, available in characteristic diagrams or operationally predetermined system parameters. Such models can be designed and programmed in such a way that, depending on which variables are specified, the respective other variable can be determined as the result variable. For example, the calculation method can also be reversed.

In this case, the exhaust gas turbocharger calculation model is intended to calculate the torque or power required from the combustion engine, which is specified by the vehicle driver using the gas pedal, for example, and taking into account the current operating variables, for example determined by sensors, such as For example, engine speed, charge pressure in the intake system, rotor speed of the turbocharger, exhaust gas enthalpy (pressure and temperature) before and after the exhaust gas turbine, etc., to calculate the increase in exhaust gas enthalpy required for a desired rapid increase in speed of the turbocharger rotor, i.e. also the target exhaust gas temperature before the turbine.

The exhaust gas temperature calculation model, on the other hand, is provided for determining at least one setpoint control value of at least one control parameter influencing the exhaust gas temperature, based on the required target exhaust gas temperature determined using the exhaust gas turbocharger calculation model. Parameters that can be included in this calculation are, for example, the mass and temperature of the intake air and the metered fuel mass. The setpoint control value to be calculated can then be, for example, the ignition point or the injection point in time of the fuel, or also the opening times or opening angles of the intake and exhaust valves. A combined adjustment of the control values of several of the control parameters mentioned can also be provided.

An essential point of the method according to the invention is that a default control value is determined from the setpoint control value, including at least one limit control value. As a rule, there are limits for the setpoint control values to be determined for the control parameters influencing the exhaust gas temperature, and if these are exceeded, the operating behavior is affected of the internal combustion engine as a whole or in relation to individual characteristics, such as emission behavior or engine torque, is undesirably negatively altered. In order to avoid this, corresponding limit control values can now be specified in a fixed manner or also as a function of the operating point and used when determining the default control values ultimately used for the temperature increase. This happens in the sense that, for example, if the determined setpoint control value exceeds the limit control value, the default control value is set to the value of the limit control value, whereas if the limit control value is undershot by the determined setpoint control value, the default control value is set to the value of the target control value.

Compared to the previously known methods, this method has the significant advantage that the intervention in the control of the internal combustion engine to increase the exhaust gas temperature is limited in such a way that an optimal increase in torque can be achieved without any other negative effects on the operating behavior of the internal combustion engine being accepted Need to become.

If the combustion center position is used as a control parameter and the combustion center position is only shifted for a subset of the total number of cylinders of the internal combustion engine with respect to the combustion center position at the point in time before the increase in the power requirement to a later point in time, the result is not only an advantageous increase in the exhaust gas temperature and thus a Enthalpy increase, but it is also achieved an exhaust pulse increase. The exhaust impulse is significantly increased with the same increase in enthalpy, which in turn leads to an acceleration of the turbine of the exhaust gas turbocharger.

If the internal combustion engine has an even number of cylinders, it is expedient to shift the center of combustion in half of the total number of cylinders present. The cylinders in which the combustion center of gravity is shifted can also be selected in alternation. It should only be noted that a shift does not take place for all existing cylinders at the same time.

In this context, the combustion center of gravity is referred to as the temporal position during the combustion process at which a certain proportion (e.g. 50%) of fuel introduced into the combustion chamber has been completely burned.

A development of the method according to the invention is characterized in that the at least one limit control value is determined by means of a combustion limit calculation model for the current operating point of the internal combustion engine. The so-called combustion limit represents a maximum value for retarding the ignition angle or the ignition point. The retarded ignition angle must not exceed a maximum latest value, the combustion limit, otherwise a permissible exhaust gas temperature or a limit value for emissions will be exceeded. According to the state of the art, the burn limit is often determined on the basis of the limit value for the emission of hydrocarbons and the limit value for the manifold temperature. The combustion limit is also dependent to a certain extent on the current operating point and can be determined for the respective current operating point using the combustion limit calculation model mentioned. This in turn results in a maximum ignition angle that can be specified as a limit control value or also a latest injection time. This has the advantage that the exhaust gas temperature can always be increased to an optimum at the respective operating point and does not have to be reduced prematurely for safety reasons or kept too low overall.

A further embodiment of the method according to the invention is characterized in that the at least one limit control value is determined using a torque calculation model for the current operating point of the internal combustion engine. The torque calculation model determines the torque to be expected at the crankshaft of the combustion engine on the basis of current operating and control variables. As already mentioned above, an undesired drop in torque can occur as certain control parameters continue to change after an initial torque increase due to the rise in exhaust gas temperature when a respective limit control value is exceeded. The advantage of this embodiment of the method is that the maximum torque possible at the respective operating point can be determined using the torque calculation model and a respective limit control value correlating thereto can be defined for the respective control parameter. In this way, the maximum possible torque can be generated at every operating point.

In another embodiment of the method according to the invention, the target exhaust gas temperature determined is limited to a predefined limit exhaust gas temperature. The exhaust gas temperature limit is selected in such a way that it is ensured that no thermal damage is caused to the components of the exhaust gas turbocharger and the other components in the exhaust gas system is to be feared. This is a relatively simple way of preventing the system from overheating.

In a further advantageous embodiment of the method according to the invention, the at least one control parameter influencing the exhaust gas temperature is an ignition point of at least one cylinder of the internal combustion engine, which in order to increase the exhaust gas temperature is shifted to a point in time that is later than a normal ignition point, i.e. retarded. By retarding the ignition point, the so-called center of combustion is retarded, i.e. closer to the opening of the exhaust gas outlet valve. As a result, the exhaust gas has a higher temperature when it exits the combustion chamber of the cylinder. In Otto engines, the ignition timing can be controlled by time-controlled spark ignition and in diesel engines by time-controlled injection of diesel fuel into the combustion chamber. The advantage of this design can be seen in the relatively simple implementation without the need for additional system components.

A further embodiment of the method according to the invention provides that the internal combustion engine is equipped with a direct injection system for direct fuel injection into the combustion chambers of the plurality of cylinders and that the center of combustion is adjusted by changing the injection point and/or the injection mass. This also makes it possible, for example, to divide the injected fuel quantity into a number of sub-quantities and to late inject a fuel sub-quantity whose late combustion results in a temperature increase in the exhaust gas. In this way, the center of combustion can also be shifted to a later point in diesel engines.

In a particularly advantageous embodiment, the method is carried out repeatedly until a target boost pressure is reached in the intake system or the internal combustion engine has reached a required performance level or the increased performance requirement is withdrawn. This ensures that the method is optimized and adapted to the current and dynamically changing operating conditions in the transient operation of the internal combustion engine and is carried out for as long as necessary. The higher the repetition rate of the execution of the method, the more precisely the execution takes place in direct dependence on the current operating point.

Particularly advantageous exemplary embodiments, details or developments of the invention are explained in more detail below with reference to the figures.

• 1 ein vereinfachtes Ablaufdiagramm eines erfindungsgemäßen Verfahrens zur Steuerung eines Verbrennungsmotors und
• 2 eine schematisch vereinfachte Darstellung eines erfindungsgemäßen Verbrennungsmotors mit einem Abgasturbolader.

Show it:

• 1 a simplified flowchart of a method according to the invention for controlling an internal combustion engine and
• 2 a schematically simplified representation of an internal combustion engine according to the invention with an exhaust gas turbocharger.

The flow chart in 1 shows in rough steps the sequence of the method for controlling an internal combustion engine with an exhaust gas turbocharger, in which, when the power demand on the internal combustion engine increases, an increase in the speed of the turbocharger is supported by an increase in the exhaust gas temperature. The process sequence for increasing the exhaust gas temperature is embedded in a higher-level process for controlling the internal combustion engine, which is executed, for example, in the form of an executable sequence program in the central control unit ECU, with instantaneous state variables of the internal combustion engine detected by sensors being read in via inputs of the control unit ECU and according to the program are processed and, on the other hand, control values of various control parameters are output to corresponding actuators that determine the operation.

From an upstream method step SX of the higher-level method for controlling the internal combustion engine, in a branch VX it is monitored whether there is an abrupt power demand, i.e. a torque difference between the momentarily present and the suddenly demanded increased torque, also referred to as a load step TQ_D. This is the case, for example, when, starting from an operating point with a low load, at a low speed of the internal combustion engine and the turbocharger rotor, a greatly increased power is suddenly requested, and a so-called load step TQ_D is therefore present. This is the case, for example, when starting a vehicle quickly from idling speed or when starting an overtaking manoeuvre, when the driver suddenly requests a greatly increased output or even the maximum output of the combustion engine, for example by a so-called "kickdown" of the accelerator pedal. As long as such a sudden increase in the power requirement is not detected, the higher-level method is continued according to the program in a method step SY.

However, as soon as a load jump TQ_D is detected in branch VX, in a subsequent method step SX1, depending on the power requirement and the current operating point of the exhaust gas turbocharger, i.e. depending on the magnitude of the load jump TQ_D a current setpoint exhaust gas temperature AT_S is determined using an exhaust gas turbocharger calculation model. Depending on the execution of the method, as shown in the flowchart, the determined setpoint exhaust gas temperature AT_S can already be limited here by means of a predefined limit exhaust gas temperature AT_GR, which provides initial protection against overheating of subsequent system components in the exhaust gas flow.

Then, in the subsequent method step SX2, based on the determined target exhaust gas temperature AT_S using an exhaust gas temperature calculation model, the target control value StW S required to achieve the target exhaust gas temperature AT_S is determined for at least one control parameter influencing the exhaust gas temperature. Corresponding control parameters are, for example, the ignition times or the injection times of the fuel in the individual cylinders, the injected fuel mass or the opening times of the exhaust valves.

In the subsequent method step SX3, a default control value StW VG is determined from the target control value StW_S, including at least one limit control value StW GR. The corresponding respective limit control value StW_GR can be specified in characteristic maps, for example, as a fixed value or as a function of the operating point of the internal combustion engine. In addition or instead, at least one limit control value StW_GR_BG can be determined using a combustion limit calculation model for the current operating point of the internal combustion engine, or a limit control value StW GR TQ can also be determined using a torque calculation model for the current operating point of the internal combustion engine and used to determine the default tax value StW VG. The default control value determined in this way for the at least one control parameter influencing the exhaust gas temperature for controlling the internal combustion engine is then output and used when controlling the internal combustion engine in order to increase the exhaust gas temperature.

After the determination of the default control value StW VG in method step SX3 and the application of the default control value StW_VG, branching VX1 monitors the torque that has already been achieved or the load step TQ_D that is still present at the moment between the requested and the delivered torque or the power. Likewise, the boost pressure P_L present in the fresh air distributor 71 can also be monitored.

If there is still a relevant load jump TQ_D or a torque difference, or the pending boost pressure P_L has not yet reached the desired value, a target boost pressure, a return to method step SX1 takes place and the now current target exhaust gas temperature is determined again. In this way, the method is repeatedly carried out until the sudden change in load has been overcome, or a target boost pressure has been reached in the intake system, or the internal combustion engine has reached the required performance level, or the increased performance requirement is withdrawn.

2 shows a schematic representation of an internal combustion engine 1, which has four cylinders 11, a direct fuel injection system 3, an intake system 7, an exhaust system 8 and at least one exhaust gas turbocharger 2 with an exhaust gas turbine 22 arranged in the exhaust system 8 and a compressor 21 arranged in the intake system 7 . Each cylinder 11 has an ignition device 4 , an injection valve 32 , an intake valve 51 and an exhaust gas outlet valve 52 . For better clarity of 1 the aforementioned components per cylinder 11 are only marked with reference symbols on the first cylinder 11 . Furthermore, the internal combustion engine in this example has a variable valve train 5, which is shown here symbolically with a camshaft adjuster 53 and a camshaft 54.

The intake system 7 has a fresh air distributor 71 with a supply line for each cylinder 11 and a throttle valve 72 arranged upstream with respect to the flow of fresh air, see arrows drawn, for controlling the mass of fresh air supplied. The compressor 21 of the exhaust gas turbocharger 2 is arranged in the intake system 7 upstream of the throttle flap 72 . An air filter system 73 for cleaning the outside air sucked in by the compressor 21 is arranged in the intake system 7 upstream of the compressor 21 . Furthermore, a charge air pressure sensor 74 for measuring the charge pressure in front of the cylinders and upstream of the compressor 21 an air mass sensor 75 for detecting the supplied air mass is arranged in the intake system 7 in the fresh air distributor 71 . The charge-air pressure sensor 74 and the air-mass sensor 75 are connected to the electronic control device ECU via electrical connections and thus feed the measured values recorded into the ECU.

The exhaust system 8 has an exhaust manifold 81 with a connection to each of the cylinders 11 . The exhaust gas turbine 22 of the exhaust gas turbocharger is arranged in the exhaust gas system in the flow direction of the exhaust gas, see arrows drawn in, downstream of the exhaust gas manifold 81 . The exhaust gas aftertreatment system 82 then follows downstream of the exhaust gas turbine 22, which is shown here as a single component for the sake of simplicity, but can have several components, such as a catalytic converter and a soot filter. An exhaust gas pressure sensor 83 and an exhaust gas temperature sensor 84 and downstream of the exhaust gas turbine 22 a further exhaust gas pressure sensor 85 and, for example, a catalytic converter temperature sensor 86 are arranged in the exhaust gas system 8, which are also connected to the ECU via electrical connections and thus feed the measured values into the ECU.

The direct fuel injection system 3 has a fuel pressure accumulator, also referred to as a common rail 31, which is fed via a fuel feed line 33 by a high-pressure fuel pump (not shown). The injectors 32 of the individual cylinders 11, which are hydraulically connected to the common rail 31, also belong to the direct fuel injection system 3. The injectors 32 are also electrically connected to the ECU, which activates the injectors 32 according to the values determined for the injection point and Controls injection mass and so the fuel in the individual combustion chambers of the cylinder 11 meters. A fuel pressure sensor 34 is arranged on the common rail 31, which is also electrically connected to the ECU and records the fuel pressure in the common rail and transmits corresponding values to the ECU. As a rule, direct fuel injection systems 3 also have different valve units, such as a pressure control valve or a volume flow control valve for controlling the fuel pressure in the common rail. For the sake of clarity, the representation of these components has been omitted 2 waived. It goes without saying, however, that within the scope of the present invention, all configurations of direct fuel injection systems that are customary or known to those skilled in the art can be used. In Otto engines, other injection systems, such as intake manifold injection systems, can also be used, since the ignition point can be specified by the ECU using a separate ignition device and the exhaust gas temperature can be increased in this way.

The variable valve drive 5 has a camshaft adjuster 53 which is electrically connected to the electronic control unit ECU and is controlled by it for variable adjustment of the valve opening intervals. Of course, all systems known to those skilled in the art for variable adjustment of the valve opening intervals can be used within the scope of the invention.

In the example shown, each cylinder 11 of the internal combustion engine 1 is equipped with an ignition device 4, for example a spark plug, which is electrically connected to the ECU and used by the ECU to ignite the fuel mixture in the combustion chamber of the respective cylinder 11, according to the determined control values for the ignition timing, is controlled directly or indirectly. In the case of diesel engines, such a device can be omitted and the ignition point or the center of combustion is adjusted by means of high-pressure injection of the diesel fuel.

To control the operation of the internal combustion engine 1, an electronic control device ECU is provided, which is electrically connected via electrical connections to sensors and control systems of the internal combustion engine, as already described above. Furthermore, the ECU is electrically connected to a turbocharger rotor speed sensor 23 and a crankshaft speed sensor 12 as well as a vehicle driver interface 15, for example an accelerator pedal or gas pedal for specifying the power or torque requirement.

The current operating parameters of the internal combustion engine 1 and the driver's request are recorded via the various sensors and the vehicle driver interface 15 and fed into the ECU. The process sequences and algorithms required to control the internal combustion engine 1 or the subsystems assigned to the internal combustion engine 1 are stored in sequence programs in the ECU, as well as corresponding default values and characteristic diagrams, which are used to calculate or determine the respective control values of the control parameters that determine the operation, depending on the driver's request , are used. The corresponding control values are then output by the ECU directly or via corresponding so-called power output stages to the control units in order to set the corresponding control parameters.

In particular, the electronic control unit ECU is set up in terms of programming and system technology to control internal combustion engine 1 in normal operation according to a respective embodiment of the aforementioned control method, with an increase in the power demand on internal combustion engine 1 supporting an increase in speed of turbocharger 2 by increasing the exhaust gas temperature will.

Finally, it should be pointed out once again that the in 2 illustrated internal combustion engine 1 according to the invention is merely an example, so to speak, with maximum equipment in relation to the different versions of the method according to the invention. So no separate ignition devices are required for example in a diesel engine. A variable valve train is also only required if the exhaust gas temperature is to be influenced by means of the valve opening intervals.

Furthermore, the invention was explained using an internal combustion engine that has 4 cylinders. However, the method and device described can also be used for internal combustion engines with a different number of cylinders, provided they have at least 2 cylinders.

Furthermore, the configuration of the combustion engine shown, which is greatly simplified compared to a real combustion engine of modern design, should not have a restrictive effect with regard to the configuration and function of the subsystems such as the fuel direct injection system, the variable valve train, the ignition device, the exhaust gas turbocharger and the intake system and the exhaust system.

reference list

1

combustion engine

2

exhaust gas turbocharger

3

Direct fuel injection system

4

ignition device

5

Variable valve train

6

Electronic control device

7

intake system

8th

exhaust system

11

cylinder

12

Crankshaft speed sensor

15

Driver Interface

21

compressor

22

exhaust turbine

23

Turbocharger rotor speed sensor

31

common rail

32

injector

33

fuel line

34

Fuel pressure sensor

51

intake valve

52

Exhaust outlet valve

53

camshaft adjuster

54

camshaft

71

fresh air diffuser

72

throttle

73

air filter system

74

Charge air pressure sensor

75

air mass sensor

81

exhaust manifold

82

exhaust aftertreatment system

83

Exhaust gas pressure sensor

84

Exhaust gas temperature sensor

85

Exhaust gas pressure sensor

86

Catalyst temperature sensor

ECU

electronic control device

Claims (9)

Method for controlling an internal combustion engine (1) having a plurality of cylinders (11) and an exhaust gas turbocharger (2), wherein when the power demand on the internal combustion engine (1) increases, the speed of the turbocharger (2) is increased by increasing the exhaust gas temperature is supported, characterized in that - depending on the power requirement and the respective current operating point of the exhaust gas turbocharger (2), a current setpoint exhaust gas temperature (AT_S) is determined by means of an exhaust gas turbocharger calculation model, - based on the determined setpoint exhaust gas temperature (AT_S ) by means of an exhaust gas temperature calculation model, the setpoint control value (StW_S) required to achieve the setpoint exhaust gas temperature (AT_S) of at least one control parameter influencing the exhaust gas temperature is determined and from the setpoint control value (StW S) including at least one limit control value ( StW_GR, StW_GR_BG, StW GR TQ) a default tax value (StW_VG) e is determined and the determined default control value (StW_VG) of the at least one control parameter influencing the exhaust gas temperature is used to control the internal combustion engine (1) in order to increase the exhaust gas temperature, the combustion center position being used as the control parameter and the combustion center position only for a partial number of the total existing cylinder (11) of the internal combustion engine (1) is shifted to a later point in time with respect to the combustion center of gravity at the point in time before the power requirement is increased. Method for controlling an internal combustion engine (1). claim 1 , characterized in that in an internal combustion engine (11) with an even number of cylinders, the combustion center of gravity is shifted at half the number of cylinders. Method for controlling an internal combustion engine (1). claim 1 or 2 , characterized in that the at least one limit control value (StW_GR_BG) is determined by means of a combustion limit calculation model for the current operating point of the internal combustion engine (1). Method for controlling an internal combustion engine (1) according to one of Claims 1 until 3 , characterized in that the at least one limit control value (StW_GR_TQ) is determined by means of a torque calculation model for the current operating point of the internal combustion engine (1). Method for controlling an internal combustion engine (1) according to one of Claims 1 until 4 , characterized in that the determined target exhaust gas temperature (AT_S) is limited to a predetermined limit exhaust gas temperature (AT_GR). Method for controlling an internal combustion engine (1) according to one of Claims 1 until 5 , characterized in that the combustion center of gravity is carried out by shifting the ignition point to a later point in time than a normal ignition point. Method for controlling an internal combustion engine (1) according to one of Claims 1 until 6 , characterized in that the internal combustion engine (1) is equipped with a direct injection system (3) for direct fuel injection into the combustion chambers of the plurality of cylinders (11) and the combustion center position is carried out by changing the injection point and/or the injection mass. Method for controlling an internal combustion engine according to one of Claims 1 until 6 , characterized in that the method is carried out repeatedly until a target boost pressure in the intake system (7) is reached or the internal combustion engine (1) has reached a required performance level or the increased performance requirement is withdrawn. Device for controlling an internal combustion engine (1) having a plurality of cylinders (11) and an exhaust gas turbocharger (2), wherein when the power demand on the internal combustion engine (1) increases, the speed of the turbocharger (2) increases due to an increase in the exhaust gas temperature is supported, wherein the device is set up a method according to one of Claims 1 - 8th to perform.

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