DE102017200837A1 - Method and apparatus for operating a supercharged fuel-fired internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating a fuel-driven internal combustion engine (2) with exhaust-driven charging device (7), wherein fuel in cylinder (3) of the internal combustion engine (2) in a main injection quantity during a main injection and in a Nacheinspritzmenge is metered during a post-injection, with the following Steps: providing (S1) a target torque representing an increase in torque and requiring boosted engine operation; and when the target torque can not be provided without exceeding a rich limit by metering an amount of fuel for the main injection (S5), providing a main injection amount and a post-injection amount so as to increase an exhaust enthalpy by the post injection, to charge the supercharger (7) Increase the air filling in the cylinders (3) to operate.

Description

Technical area

The invention relates to fuel-driven internal combustion engines with exhaust-driven charging device and in particular measures for increasing the dynamics of such internal combustion engines with positive load jumps.

Technical background

Fuel-controlled internal combustion engines, in particular diesel engines, are operated in stationary operation with an excess of oxygen. With a positive load dynamics, the excess oxygen can be used by a Mehreinspritzung of fuel to increase the power of the engine up to the required target torque. However, if the target torque of the internal combustion engine is at an operating point that requires a larger oxygen content of the cylinder and can only be achieved by a charged operating mode, this approach only leads to a gradually expanding cylinder filling. The structure of the cylinder filling is determined by the transient charging behavior of the charger and can be up to several seconds. This process takes a long time and causes a torque build-up, which is noticeably delayed compared to the specification of the setpoint torque.

The publication DE10029502 A1 describes a method for operating a diesel engine, wherein the combustion of the first post-combustion amount introduced after the main combustion leads to an increase in the exhaust gas enthalpy before a turbine connected downstream of the engine. The start of injection of the first post-injection is designed so that a combustion of this Nacheinspritzmenge takes place in the combustion chamber, which on the one hand contributes to the output engine load and on the other hand causes the very high exhaust gas temperatures. By means of post-injection, the combustion can be designed either superstoichiometrically or substoichiometrically.

The publication DE 199 51 096 A1 relates to an engine control system for a supercharged by an exhaust gas turbocharger diesel engine, which controls the function of maps the operation of the diesel engine and allows a change between two modes of operation of the diesel engine. In a special mode, the exhaust gas temperature and / or the exhaust gas pressure upstream of the exhaust gas turbocharger are increased relative to the normal operation.

Disclosure of the invention

According to the invention, a method for operating a fuel-guided internal combustion engine with an exhaust gas-driven charging device according to claim 1 and a device and an engine system according to the independent claims are provided.

Further embodiments are specified in the dependent claims.

• - Bereitstellen eines Solldrehmoments, das von dem Verbrennungsmotor nur durch einen aufgeladenen Betrieb bereitstellbar ist;
• - Wenn das Solldrehmoment nicht ohne Überschreiten der Fettgrenze durch Zumessen einer Kraftstoffmenge für die Haupteinspritzung bereitstellbar ist, Bereitstellen einer Haupteinspritzmenge und einer Nacheinspritzmenge, die so verlaufen, dass durch die Nacheinspritzung eine Abgasenthalpie erhöht wird, um die Aufladeeinrichtung zum Erhöhen der Luftfüllung in den Zylindern zu betreiben.

According to a first aspect, there is provided a method of operating a fuel-injected internal combustion engine having an exhaust gas driven supercharger, wherein fuel is metered into a cylinder of the internal combustion engine in a main injection amount during a main injection and in a post-injection amount during a post injection, comprising the steps of:

• - Providing a target torque that can be provided by the internal combustion engine only by a charged operation;
• When the target torque can not be provided without exceeding the rich limit by metering a fuel amount for the main injection, providing a main injection amount and a post injection amount that are increased by the post injection, an exhaust enthalpy is increased to the charging device for increasing the air charge in the cylinders operate.

With common rail diesel injection available today, multiple injections per combustion stroke are possible and widely used. An introduction of a part of the fuel to be injected at the end of the expansion phase of the combustion cycle into the exhaust stroke is called post-injection and serves mainly to increase the exhaust gas enthalpy, since the fuel is introduced into the exhaust system, which responds there exothermically with the unburned atmospheric oxygen. The post-injection of the fuel has an indirect torque-forming effect and is currently used predominantly for the regeneration of the soot particle filter.

According to the above method is now provided to provide the post-injection of the fuel and the associated increase in exhaust enthalpy to support the torque build-up in a positive load step. As a result of the increased thermal energy of the exhaust gas stream, the exhaust gas-driven charging device (exhaust gas turbocharger) is accelerated more strongly, whereby the charging and thus the fresh air supply of the cylinders of the internal combustion engine are supported. The air charge in the cylinders therefore increases the faster the exhaust enthalpy increases.

The maximum allowable amount of fuel that can be injected into the cylinders depends on the air charge in the cylinders, as combustion with excess fuel is not allowed due to high soot emissions (soot limit). Thus, a higher air charge allows an increase in the amount of fuel that can be injected per combustion stroke, since the soot limit accordingly shifts absolutely but relatively, i. expressed as the fuel air ratio (lambda) remains the same. Overall, increased air charge in the cylinders increases the amount of fuel that can be metered for the main injection, which eventually determines the torque provided by the engine.

By the above method, the disadvantage is avoided in conventional modes for fuel-fired internal combustion engines, in which a rapid increase in the required load torque is followed with a correspondingly rapid increase in the main injection quantity often up to the soot limit. This provides an immediate reaction of the internal combustion engine, which is limited in the further course by the delayed charge pressure build-up. On the other hand, delaying the construction of the torque-generating main injection amount at a positive load step allows an allocation of a post-injection post-injection amount to a level which is e.g. is limited by the soot limit in the exhaust system. As a result, the residual oxygen content in the exhaust gas in the exhaust system can be post-combusted, so that thereby the exhaust gas enthalpy flow increases and the boost pressure can be increased rapidly by the exhaust-driven charging device. The earlier increase in the boost pressure thus achieved leads to a marked increase in the increase of the air charge in the cylinders, so that subsequently the main injection quantity for reaching the target torque can be increased more quickly.

The delay of increasing the main injection amount also allows damping of a load shock, especially when the driver dictates the positive load jump from a coasting operation out. Overall, a dead time behavior of the torque build-up can be used in order to make a stop change of the drive train steady and also to achieve a pleasant start of the torque build-up of the internal combustion engine.

It can be provided that the additional provision of the post-injection quantity is carried out in conjunction with a main injection quantity in mutually dependent relationship if the setpoint torque can only be achieved by a supercharged operation of the internal combustion engine.

Further, when the target torque is provided during a coasting operation of the engine, the main injection amount for a predetermined period of time may be limited to a predetermined load shock damping amount.

According to one embodiment, the main injection quantity and the post-injection quantity may be so dimensioned that an excess of oxygen in an exhaust system of the engine system is burned to a rich limit by the post-injection amount, the rich limit of the main injection corresponding to a limit on the amount of fuel from which a critical engine condition is reached in particular, a limit above which a given soot emission limit is exceeded (soot limit), a temperature limit, a pollutant emission limit, a mechanical load limit or a limit determined by a combination of the aforementioned limits.

The fat limit of the post-injection may be defined by component temperature limits in the exhaust system, a maximum permissible rotor speed of the exhaust gas turbocharger, a maximum allowable lubricating oil dilution, a maximum allowable boost pressure and / or a maximum permissible carbon black emission limit.

Furthermore, the main injection amount may be set according to a low-pass filter behavior depending on a difference between a current engine torque and the target torque. In place of the torque, equivalently, the fuel mass injected per combustion cycle, i. the difference between a current fuel mass and a given desired fuel mass.

In particular, a time constant of the low-pass filter behavior can be specified as fixed or operating point-dependent.

• - das Sollmoment wurde erreicht,
• - es wird ein begrenzendes Drehmoment vorgegeben, und
• - es liegt eine Bremspedalbetätigung vor.

Furthermore, the process can be aborted if one of the following termination conditions is present:

• - the target torque has been reached,
• - It is given a limiting torque, and
• - There is a brake pedal operation.

• - ein Solldrehmoment bereitzustellen, das eine Erhöhung des Drehmoments darstellt und einen aufgeladenen Motorbetrieb erfordert.
• - wenn das Solldrehmoment nicht ohne Überschreiten einer Fettgrenze durch Zumessen einer Kraftstoffmenge für die Haupteinspritzung bereitstellbar ist, eine Haupteinspritzmenge und einer Nacheinspritzmenge bereitzustellen, die so verlaufen, dass durch die Nacheinspritzung eine Abgasenthalpie erhöht wird, um die Aufladeeinrichtung zum Erhöhen der Luftfüllung in den Zylindern zu betreiben.

According to a further aspect, there is provided an apparatus for operating a fuel-injected internal combustion engine with an exhaust gas driven supercharger, wherein fuel in cylinders of the internal combustion engine is susceptible to a main injection amount during a main injection and an after injection amount during a post-injection, the apparatus being configured to:

• to provide a setpoint torque that represents an increase in torque and requires boosted engine operation.
• if the target torque can not be provided without exceeding a rich limit by metering an amount of fuel for the main injection to provide a main injection amount and a post injection amount that are increased by the post injection, an exhaust enthalpy is increased to the charging device for increasing the air charge in the cylinders operate.

list of figures

• 1 eine schematische Darstellung eines Motorsystems mit einem kraftstoffgeführten Verbrennungsmotor und einer abgasgetriebenen Aufladeeinrichtung;
• 2 ein Flussdiagramm zur Veranschaulichung eines Verfahrens zum Betreiben des kraftstoffgeführten aufgeladenen Verbrennungsmotors der 1.

Embodiments are explained below with reference to the accompanying drawings. Show it:

• 1 a schematic representation of an engine system with a fuel-fueled internal combustion engine and an exhaust gas driven charging device;
• 2 a flowchart for illustrating a method for operating the fuel-guided supercharged internal combustion engine of 1 ,

Description of embodiments

1 shows a schematic representation of an engine system 1 with an internal combustion engine 2 , The internal combustion engine 2 has a number (four in the present embodiment) cylinder 3 on, in which movable pistons are arranged, the torque on a crankshaft 4 of the internal combustion engine 2 provide.

The cylinders 3 are formed in a conventional manner with inlet and outlet valves 31, 32 for the supply of fresh air and the discharge of combustion exhaust gases. Furthermore, the cylinders 3 Injectors 33 on, over which a predetermined amount of fuel enters the cylinders 3 can be injected to carry out a combustion.

Fresh air is the internal combustion engine 2 via an air supply system 5 supplied, and combustion exhaust gases are via an exhaust system 6 dissipated.

It is an exhaust gas driven charging device 7 , a so-called turbocharger, which provided an exhaust gas turbine 71 that is in the exhaust system 6 is arranged and a compressor 72 that in the air supply system 5 is arranged. The exhaust gas turbine 71 is driven by combustion exhaust gas and converts exhaust enthalpy provided therein into mechanical energy (rotational energy). Through a mechanical coupling between the exhaust gas turbine 71 and the compressor 72 can the mechanical energy of the compressor 72 be supplied, which uses these for the compression of fresh air from the environment and fresh air under a boost pressure to the engine 2 provides.

It is a control unit 10 provided the engine system 1 according to a specification V operates. The default V may be a target torque that the engine 2 to provide, display or specify this. For example, the target torque can be specified by a position of an accelerator pedal. Alternatively, equivalent control variables such as load or fuel mass can be used as nominal values.

The operation of the internal combustion engine 1 takes place by engagement in suitable position sensors, in particular depending on operating state variables, which are detected by a suitable sensor. For example, in a manner known per se, information about a rotational speed of the internal combustion engine 2 , are provided via the ambient pressure, a boost pressure and the like. In essence, the control unit controls 10 in the cylinders 3 each amount of fuel to be injected, which is usually determined by a corresponding operating model depending on the target torque and the operating state variables. The injection quantities / masses described here are to be understood in each case as the injection quantities / masses to be injected for a combustion cycle.

The fuel is usually injected by a common rail system in which diesel fuel is stored under a high pressure and injected by opening the injectors accordingly. It is intended to inject the fuel during a combustion cycle in several injections. In particular, the fuel injection may be injected in a main injection immediately before or at the beginning of the combustion cycle, and a post-injection injected into the exhaust stroke towards the end of the combustion cycle. Post-injection is the term for any injected fuel quantity that follows the main injection in the same engine cycle over time. It begins significantly after reaching the upper combustion dead point and may occur before or after the lower combustion dead point, i. in the Ausschiebetakt, end. Because of this phase relationship, the post-injection - depending on the specific injection position - only partially effective torque. The main injection serves only for the generation of torque, while the post-injection mainly serves to increase the exhaust gas enthalpy, i. the exhaust gas temperature and the exhaust gas pressure, is used.

In stationary operation at low and medium load ranges, where no charging by the charging device 7 takes place, finds the combustion in the cylinders 3 of the internal combustion engine 2 under excess oxygen instead. Now, a positive load step is specified or requested, which defines a target torque in an operating range in which the internal combustion engine 2 has to be operated in the charged state, so the amount of fuel in the main injection can indeed be increased up to the soot limit, but not beyond, otherwise the soot emissions would assume unacceptable levels. The soot limit corresponds to an amount of fuel or air-fuel ratio (λ value) at which fuel and oxygen content of the fresh air in a cylinder during the combustion cycle form approximately a stoichiometric balance.

However, if the requested target torque is higher than the torque that can be achieved by increasing the amount of fuel up to the soot limit, it is necessary that until the final attainment of the requested target torque, the air filling in the cylinders 3 is increased accordingly. However, since with complete implementation of an increased to the soot limit fuel quantity in a main injection high torque but only a small or slow increase in exhaust enthalpy, the boost pressure that is necessary to build up the required air charge for reaching the target torque, only build up slowly. According to the soot limit listed here, other fat limits for the combustion chamber fuel air mixture can be limiting effect.

It is therefore intended to use the internal combustion engine 2 according to the following with reference to the flowchart of 2 operate described method.

In step S1 it is checked whether there is a change in the engine load, eg due to a corresponding actuation of an accelerator pedal, in particular a change in the engine load, by which the internal combustion engine 2 from a non-supercharged operation to a supercharged operation case and whether the self-ignition conditions in the exhaust system for post-injected fuel are reached. This criterion is given above a local minimum thermal level, which can be modeled based on the exhaust gas temperature, the ambient temperature, the engine temperature and current engine control variables.

If this is the case (alternative: yes), the method is continued with step S3, otherwise (alternative: no), the method continues with step S2.

In step S2, the fuel injection amount is conventionally calculated, and subsequently jumped back to step S1.

In step S3, it is checked whether there was a coasting operation at the time of the request of increasing the engine load. If this is the case (alternative: yes), the method is continued with step S4. Otherwise (alternative: no), the method is continued with step S5.

In step S4, a load shock absorption is activated and then the process proceeds to step S5.

In step S5, it is checked whether the air filling in the cylinders 3 or the available oxygen content in the cylinders 3 sufficient to achieve the required setpoint torque with a metering of the thus determined amount of fuel in a main injection, without the fat limit is exceeded in the combustion chamber. If this is the case (alternative: yes), the method is continued with step S2 and the amount of fuel corresponding to the load torque is assigned as the main injection quantity.

wobei M einem Solldrehmoment, T einer bereitgestellten Filterzeitkonstanten, C einem Konvertierungsfaktor zwischen der Kraftstoffmenge zu einem Drehmoment mit M = C · m entsprechen. ,i' ist ein laufender Index der Zylinderzählung. Der Konvertierungsfaktor C kann gemäß einer realen Drehmomenterzeugung appliziert werden und zudem von Motorbetriebsbedingungen abhängig modelliert werden. Die obige Formel entspricht einer Diskretisierung eines Tiefpassfilters erster Ordnung, wobei t ein diskreter Zeitschritt als eine feste Zeiteinheit oder als eine mit der Motordrehzahl variable Segmentzeit mit t = 2/(n·z), wobei n der Motordrehzahl und z der Zylinderanzahl entsprechen, bestimmt sein kann. Insbesondere kann die Segmentzeit t dem zeitlichen Abstand zwischen zwei aufeinanderfolgenden gleichartigen Motortakten im Zündabstand aufeinanderfolgender Zylinder- bzw. aufeinanderfolgender Verbrennungsereignisse entsprechen.If the air charge in the cylinders is insufficient to reach the required load torque (alternative: no), fuel quantities for the main injections and for the post-injections during the dynamic operation of the load jump are then determined in step S6. In general, the main injection quantity and the post injection quantity in the combustion strokes are set such that the combustion taking place during the main injection is performed under an oxygen excess, with the oxygen excess being responsible for subsequent combustion cycles, ie the smaller the distance between the torque provided by the internal combustion engine and the target torque the combustion is performed in the combustion cycle decreases. Likewise, at the beginning of the load step, the fuel not injected at the main injection amount becomes in the cylinder 3 burned oxygen in the exhaust system 5 burned by the post-injection amount of the fuel. The one in the exhaust system 5 burned oxygen decreases accordingly with increasing approach of the torque to the target torque. An exemplary configuration of the characteristics of the main injection quantity m (i) of fuel as a result of a load jump can be determined as follows: $$\left(\right)\mathrm{=}\left(\mathrm{-}\right)\mathrm{+}\left(/\right)\text{*}\left(M/C\mathrm{-}\left(\mathrm{-}\right)\right)$$

where M is a set torque, T is a provided filter time constant, C is a conversion factor between the amount of fuel to a torque with M = C · m. 'i' is a running index of the cylinder count. The conversion factor C can be applied according to a real torque generation and also modeled depending on engine operating conditions. The above formula corresponds to a discretization of a first order low-pass filter, where t defines a discrete time step as a fixed time unit or as an engine speed variable segment time with t = 2 / (n * z), where n is the engine speed and z is the cylinder number can be. In particular, the segment time t may correspond to the time interval between two consecutive identical engine cycles in the firing interval of successive cylinder or successive combustion events.

The filter time constant T is empirically optimized or derived from model calculations and determines accordingly the response of the internal combustion engine 2 on a load jump.

In accordance with a driver's request from the selected position of a so-called driving experience switch, the currently effective value for the filter time constant T can be specified individually within the scope of an admissible interval. However, if there is no such option, then the filter time constant T can be calibrated so that a compromise between comfort and driving performance is desired. It basically depends on design parameters such as engine size, turbocharger and compressor design of the supercharger, and the design of gas paths in the internal combustion engine 2 from.

With the definition of the main injection quantity m (i) in accordance with the above formula, the time profile of the post-injection quantity p (i) implicitly results as the proportion of fuel that can be used for the complete conversion of the residual oxygen content in the combustion exhaust gas.

This benefit is in increasing the exhaust enthalpy flow for the turbine drive of the supercharger 7 , This early exhaust enthalpy flow is mechanically transferred to the compressor side and used to boost the charge. Thus, an increased amount of fresh air is introduced early into the cylinders 3 so that overall there is a higher potential for increasing the main injection quantity.

wobei I der Luftmasse, L_min der stöchiometrischen Mindestluftmenge und m der Kraftstoffmasse entspricht. Es kann zwischen dem Kraftstoff-Luftverhältnis im Brennraum der Zylinder λ_B, das der Haupteinspritzung zugeordnet ist, und dem Kraftstoff-Luftverhältnis im Verbrennungsabgas λ_A, das der Nacheinspritzung zugeordnet ist, sowie ihren jeweiligen Fettgrenzen λ_Bmin und λ_Amin unterschieden werden. Die Fettgrenzen λ_Bmin und λ_Amin können jeweils Grenzen entsprechen, ab denen ein unzulässiger Schadstoffanstieg - wie z.B. der Rußemisssion - auftreten. Die Fettgrenze für den Brennraum ergibt sich aus einer Maximalauswahl von spezifischen relevanten Kriterien, wie z.B. der Rußgrenze im Brennraum, dem maximal gewünschten Drehmoment, der maximal zulässigem thermischen/mechanischen Motor- bzw. Getriebebelastung. Die Fettgrenze für das Abgassystem ergibt sich aus einer Maximalauswahl von spezifischen relevanten Kriterien, wie z.B. der Rußgrenze im Abgassystem 6, der höchsten zulässigen Abgasbauteiltemperatur, der Limitierung der Laufzeugdrehzahl der Aufladeeinrichtung 7, der maximal zulässigen Aufladung und der höchstens zulässigen Schmierölverdünnung und dergleichen und ist betriebspunktabhängig. Die Haupteinspritzmenge wird damit nach oben limitiert: $$m<=I/\left(Lmin\text{*}{\mathrm{\lambda }}_{Bmin}\right)$$

The post-injection of fuel may be provided as single or multiple timed rate feeds. The time courses may result from the following equations. Overall, the fuel-air ratio λ corresponds to: $$\mathrm{\lambda \; =}I/\left(m\text{*}Lmin\right)$$

where I corresponds to the air mass, L _{min to} the stoichiometric minimum air quantity and m the fuel mass. It can be made between the air-fuel ratio in the combustion chamber of the cylinders λ _B, which is assigned to the main injection, and the air-fuel ratio in the combustion exhaust gas λ _A, which is associated with the post-injection, as well as their respective fat limits λ _Bmin and λ _amine. The fat limits λ _Bmin and λ _Amin can each correspond to limits above which an impermissible increase in pollutants, such as, for example, soot emission, occurs. The fat limit for the combustion chamber results from a maximum selection of specific relevant criteria, such as the soot limit in the combustion chamber, the maximum desired torque, the maximum permissible thermal / mechanical engine or transmission load. The fat limit for the exhaust system results from a maximum selection of specific relevant criteria, such as the soot limit in the exhaust system 6 , the highest permissible exhaust gas component temperature, the limitation of the supercharger speed of the supercharger 7 , the maximum allowable charge and the maximum allowable lubricating oil dilution and the like and is operating point dependent. The main injection quantity is thus limited upwards: $$m<=I/\left(Lmin\text{*}{\mathrm{\lambda }}_{Bmin}\right)$$

For the post-injection amount p, the rest of the fresh air portion is decisive, which was not burned during the main combustion. The total amount of fresh air I is composed of a completely, that is stoichiometrically burned portion I _V with a completely unburned portion lu, which can be used for afterburning. $$I=Iv+Iu$$

This results in the stoichiometrically burned air fraction with the main injection quantity: $$Iv=m\text{*}Lmin$$

wobei λ_Amin noch mit einer Zumessungstoleranz versehen werden kann. Die diskreten Nacheinspritzmengen ergeben sich analog zu obiger Formel: $$p\left(i\right)=\left(\left(I\left(i\right)/Lmin\right)-m\left(i-1\right)-\left(t/T\right)\text{*}\left(\left(M/C\right)-m\left(i-1\right)\right)\right)/{\mathrm{\lambda }}_{\text{Amin}}$$

The post-injection quantity, which is the maximum fuel quantity, is calculated as: $$p=\left(I/Lmin-m\right)/{\mathrm{\lambda }}_{\text{Amin}}$$

where λ _{amine can} still be provided with a metering tolerance. The discrete post-injection quantities result analogously to the above formula: $$p\left(i\right)=\left(\left(I\left(i\right)/Lmin\right)-m\left(i-1\right)-\left(t/T\right)\text{*}\left(\left(M/C\right)-m\left(i-1\right)\right)\right)/{\mathrm{\lambda }}_{\text{Amin}}$$

In step S7, the internal combustion engine 2 with the main injection amount m (i) and the post-injection amount p (i) operated.

• - Erreichen des Sollmomentes (z.B. auch bei Rücknahme des Fahrerwunschs),
• - Eingriff eines extern vorgegebenen begrenzenden Drehmoments (automatisiertes Fahren, Steuergeräteüberwachungsfunktion),
• - Bremspedalbetätigung.

In step S8, an abort condition is checked. The abort of the above method may be accomplished by the occurrence of at least one of the following criteria:

• - reaching the target torque (eg even when the driver request is withdrawn),
• - intervention of an externally given limiting torque (automated driving, ECU monitoring function),
• - Brake pedal operation.

If an abort condition exists, the method is continued with step S2. Otherwise, it returns to step S6.

It may additionally be provided that the main injection quantity is limited during the first combustion cycles after the request for the load jump, so that a load impact, in particular when the load jump originates from a coasting operation, is so braked that a load impact is avoided. The limitation of the main injection quantity as well as the time duration or the number of combustion cycles required by the torque increase during which the main injection quantity is limited can be determined by application. This puts the drive train after overcoming the game ("Triebstranglose") gentler to the Zuganschlag, which comfort-enhancing and wear-limiting acts.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10029502 A1 [0003]
• DE 19951096 A1 [0004]

Claims (13)

Method for operating a fuel-controlled internal combustion engine (2) with an exhaust-gas-charged charging device (7), wherein fuel in cylinder (3) of the internal combustion engine (2) can be measured in a main injection quantity during a main injection and in a post-injection quantity during a post-injection, with the following steps: - providing (S1) a target torque representing an increase in torque and requiring supercharged engine operation; and When the target torque can not be provided without exceeding a predetermined rich limit by metering an amount of fuel for the main injection (S5), providing a main injection amount and a post injection amount so as to increase an exhaust enthalpy by the post injection, to charge the supercharger (7) Increase the air filling in the cylinders (3) to operate. Method according to Claim 1 wherein the providing of the main injection amount and the post injection quantity is performed only when the target torque can be provided only by a supercharged operation of the internal combustion engine (2), in particular when the exhaust gas temperature exceeds a threshold temperature allowing post-combustion. Method according to Claim 1 or 2 wherein, when the increased target torque is provided during a coasting operation of the internal combustion engine (2), the main injection amount is limited to a predetermined amount of impact impact damping for a predetermined period of time. Method according to one of Claims 1 to 3 in which the main injection quantity and the post-injection quantity are so dimensioned that an excess of oxygen in an exhaust system (6) of the engine system (1) is burned through the post-injection amount up to a rich limit, the additional limit to be observed for the main injection corresponding to a limit for the amount of fuel from which a critical engine condition is reached, in particular by exceeding a predefined soot emission limit value, a temperature limit, a pollutant emission limit value or a mechanical load limit. Method according to Claim 4 wherein the exhaust limit for the exhaust system (6) valid by component temperature limits in the exhaust system (6), a maximum permitted engine speed of the exhaust gas supercharger (7), a maximum lubricating oil dilution, a maximum allowable boost pressure and / or a limit on the maximum allowable soot emissions or combinations is determined by this. Method according to one of Claims 4 to 5 wherein the post-injection amount is determined depending on a respective oxygen excess of the combustion exhaust gas and the rich limit of combustion in the exhaust system (6), wherein in particular the post-injection amount is chosen such that the combustion takes place in the exhaust system (7) at the rich limit. Method according to one of Claims 1 to 6 wherein the main injection amount is set according to a low-pass filter behavior depending on a difference between an indication of a current torque of the engine (2) and an indication of the target torque, or a difference between a target injection amount and a current injection amount. Method according to Claim 7 , wherein a time constant of the low-pass filter behavior is given fixed or operating point-dependent or according to a driver's request. Method according to one of Claims 1 to 8th wherein the process is terminated when one of the following termination conditions is present: - the target torque has been reached, - a limiting torque is specified, - there is a brake pedal actuation. An apparatus for operating a fuel-guided internal combustion engine (2) with an exhaust gas-driven charging device (7), wherein fuel can be metered into cylinders (3) of the internal combustion engine (2) with a main injection quantity during a main injection and with a post-injection quantity during a post-injection, the device being designed to: provide a setpoint torque that is an increase in torque and requires boosted engine operation. - when the target torque can not be provided without exceeding a rich limit by metering an amount of fuel for the main injection to provide a main injection amount and a post injection quantity that are increased by the post injection, an exhaust enthalpy is increased to the charging device for increasing the air charge in the cylinders (3 ) to operate. Engine system (1) comprising: - an internal combustion engine (2); - a device after Claim 10 , Computer program adapted to perform all steps of a procedure according to one of Claims 1 to 9 perform. Machine-readable storage medium on which a computer program is based Claim 12 is stored.

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