WO2009143858A1

WO2009143858A1 - Method for controlling an injection process of an internal combustion engine, control device for an internal combustion engine and an internal combustion engine

Info

Publication number: WO2009143858A1
Application number: PCT/EP2008/004175
Authority: WO
Inventors: Thorsten Schnorbus
Original assignee: Fev Motorentechnik Gmbh
Priority date: 2008-05-26
Filing date: 2008-05-26
Publication date: 2009-12-03
Also published as: DE112008003841A5

Abstract

The invention relates to a method for controlling an injection process of a direct-injection internal combustion engine (33) of a vehicle (34). In the method in which a fuel is injected into a combustion chamber of the internal combustion engine (33), a start of injection (9), an injection quantity (7) and an injection profile (12) are identified using combustion position control and taking into account the combustion duration of the fuel. In this context, at least one state variable (3, 5, 15) which is assigned to the combustion chamber and which describes the combustion position is used for the combustion position control. In addition, the pilot control system (30, 31, 32) which can be switched on and off and which is brought about by means of a mathematical model which is based on at least one state variable (3, 5, 15) of the combustion chamber is used for controlling the injection process. The ignition delay is estimated using a model. Furthermore, the invention relates to a control device in which the method is stored, and in addition to a direct-injection internal combustion engine (33) of a vehicle (34), having the control device.

Description

Method for controlling an injection process of an internal combustion engine,

Control unit for an internal combustion engine and an internal combustion engine

The invention relates to a method for controlling an injection process of an internal combustion engine of a vehicle, in particular a directly injecting internal combustion engine. The invention further relates to a control unit, in which the method is stored, and also to an internal combustion engine of a vehicle with the control unit.

Direct injection internal combustion engines are becoming more and more popular in the motor vehicle field because of their potential in connection with fuel consumption, exhaust emission and combustion noise. The increasingly stricter exhaust emission limits and the continuously rising fuel costs are driving the further development of such internal combustion engines, by means of which the increasing demands on the said criteria using so-called engine measures and measures for exhaust aftertreatment is met.

Various fuel injections are known in the art. In addition to a map controlled fuel injection, in which a fuel depends on the

Engine speed and engine load is injected into a combustion chamber, it is known for example from DE 197 498 17 A1, the beginning of the fuel injection and the

Determine combustion position from a difference between a measured pressure profile and a calculated pressure profile. Furthermore, it is known, for example from WO 2005/005813 A2, to set the beginning of the fuel injection and / or the inert gas fraction in the combustion chamber from a state variable assigned to a combustion chamber.

Furthermore, from WO 2005/005813 A2 a control of a fuel injection is known, in which the beginning and the duration of the fuel injection is adjusted combustion chamber selectively taking into account the last working cycle using a combustion position controller.

Furthermore, a regulation of a fuel injection is known from WO 2007/115630 A2, in which a change in the temporal injection curve of the injection process is set taking into account the respectively last working cycle.

BESTATIGUNGSKOPIE The object of the invention is to improve the combustion process on which an internal combustion engine is based.

This object is achieved by a method having the features of claim 1, with a control device having the features of claim 22 and with a vehicle having the features of claim 27. The features specified in the subclaims are the subject of preferred embodiments of the solution. Other features contained in the description can be linked to other features contained in the disclosure for additional developments.

A method for combustion control is proposed, which is used in a direct-injection internal combustion engine. The method provides for estimating an ignition delay in at least one cylinder of the direct injection internal combustion engine using a model. Ignition delay is the time that elapses from the start of injection into the cylinder of the internal combustion engine until the actual start of combustion of an air-fuel mixture in the cylinder. The estimation of the ignition delay allows, for example, to be able to achieve an improved control quality of a control, in particular a combustion position control, with which the estimation is preferably coupled. In addition, the model estimate of the ignition delay allows a check to be made as to whether a pilot injection is being executed or not. This can be done depending on boundary conditions such as emission behavior, torque development as well as combustion noise or independently.

A further development provides that, based on the estimation, at least one control of a time of commencement of injection takes place. In this way, for example, a controller for injection can be executed. If, for example, an injection control is carried out, the estimation in the context of the combustion control can serve as pilot control for this control.

The ignition delay is preferably estimated taking into account a combustion chamber pressure in the cylinder. The combustion chamber pressure can be detected for this purpose according to an embodiment via a sensor. According to another embodiment, the combustion chamber pressure is determined via a calculation, taken from a characteristic map or determined in other non-direct manner. When using the model, a mathematical modeling is preferably used, which is based on data from test bench tests, with one or more state variables in the cylinder as input variables in the model. In this case, it can be provided, for example, that at least part of the input variables are themselves determined based on models.

A further embodiment, which can also be carried out independently of the one described above, provides a self-learning model of the ignition delay based on at least one neural network, for which model a measurement of a combustion chamber pressure is provided, which is processed in the model. An example of a self-learning model integrated in a control unit can be found for example in DE 10 2004 030 782 A1, to which reference is made in its entirety within the scope of the disclosure. There are various procedures specified how a self-learning model can be constructed and executed.

The model is based, for example, directly or indirectly on a combination of different sizes, which preferably describes a tendency to ignite the fuel, for example by a cetane number or octane number, a temperature in the combustion chamber, a pressure in the combustion chamber, a type of mixture formation, for example through the nozzle, For example, distribution of the droplet size in the fuel jet, or by an air duct, for example umbrella valves in the inlet, tangential flow channels, shape of the piston crown, can be influenced. The model can also resort to the results of other models, for example a model with regard to fluid flows, as can be seen for example from DE 10 2005 007 057 A1, which is also referred to in the context of the disclosure. For example, the quantities can be determined directly or indirectly via corresponding sensors or also calculated. Furthermore, variables such as an oxygen concentration, an injection quantity or even a rail pressure can be included.

Preferably, the method is carried out on a supercharged internal combustion engine, which operates on the diesel principle.

A further development provides that a precontrol takes place on the basis of the estimated ignition delay for a combustion position control. A combustion position control is disclosed, for example, in WO 2005/005813 A2, to which reference is made in this regard, as well as with regard to the design of the control device, data transmission and sensor system in the context of this disclosure. Outflow of the model-based control or regulation may for example also be that a pilot injection is omitted. Thus, for example, at least in a low load range, an injection without pre-injection take place, with an extension of the ignition delay takes place.

Furthermore, a further method for controlling an injection process of an internal combustion engine of a vehicle, in particular a direct-injection internal combustion engine, is proposed, which can also be executed independently of the above method or linked thereto. In the method, a fuel is injected into a combustion chamber of the internal combustion engine, wherein a start of injection, an injection amount and an injection curve are determined using a combustion position control and taking into account a burning time of the fuel. For the combustion position control, at least one state variable assigned to the combustion chamber is used to describe the combustion position. For the control of the injection process while a switchable and disconnectable pilot control is used, which is effected by means of a model based on at least one state variable of the combustion chamber.

According to an additional aspect of the invention, a method is proposed which can be combined with the methods proposed above as well as operated independently thereof. It is a method for controlling an injection process of an internal combustion engine of a vehicle, in particular a direct-injection internal combustion engine proposed, in which a fuel is injected into a combustion chamber of the internal combustion engine, taking into account a Zündverzugs, preferably taking into account a burning time of the fuel, at least one At the beginning of injection, preferably additionally an injection quantity and / or an injection curve is determined, wherein at least one of the combustion chamber associated state variable used to determine a Zündverzugszeit and wherein for the determination of the injection timing or the control of the injection process, a controller, preferably a switchable and disconnectable pilot control, is used , which is effected by means of a model based on at least one state variable of the combustion chamber.

The feedforward is based on the consideration to set a desired operating point for the injection process, then to reach a regulation. The pilot control relieves the control of the injection process while improving their Dynamics. Furthermore, the relief also contributes to the stabilization of the control process, especially as the regulation becomes more responsive and faster due to the relief.

In a transient operation of an internal combustion engine, conditions can arise in which the actual combustion position of the individual combustion chambers of the

Internal combustion engine deviates greatly from the desired combustion position.

Such deviations can have a negative influence on the torque and the

Have combustion noise. Furthermore, by such deviations also

Combustion misfires develop which impair the smooth running of the internal combustion engine.

The pilot control counteracts these deviations and thus makes it possible to make the transient operation of the internal combustion engine more manageable by contributing to an improvement in a desired homogenization of the combustion in the individual combustion chambers. As a result, an emission characteristic and / or a noise characteristic of the internal combustion engine also improves.

Furthermore, the improved homogenization of the combustion causes an improvement in the control quality of the combustion position control.

As a state variable for use both for the combustion position control and the pilot control for the regulation of an injection process, the combustion chamber pressure associated with the respective combustion chambers of the internal combustion engine is preferably used. As an alternative or in addition to the combustion chamber pressure, the parameters "temperature, ion current or signal of an optical measurement principle" can also be used as state variables that can be assigned to the respective combustion chambers. The course of the state variables is preferably detected as a function of the crankshaft angle. Alternatively or additionally, the course of the state variables can be detected as a function of time. The state variables can be measured and / or calculated.

According to a preferred embodiment, the feedforward control for the start of injection, the injection quantity and / or the course of injection can be effected.

In a combustion engine comprising several combustion chambers, the pilot control can be effected in various ways. On the one hand, the feedforward control can globally effect all combustion chambers comprehensively. In this case, from a consideration of the combustion positions assigned to the individual combustion chambers, a plurality of combustion an average value for the start of injection, the injection amount and / or the injection curve determined in order to then use the individual average values as global precontrol values for the following combustion cycles according to the firing order of the internal combustion engine. The number of contemplated combustion cycles can be arbitrarily selected or predetermined. Preferably, all combustion cycles of the last three cycles are considered for consideration.

A combustion cycle is to be understood as the period in which an injection of fuel into a combustion chamber begins and an injection following combustion in the combustion chamber is completed. Accordingly, a combustion cycle is within a work cycle, which is to be understood as the time period which denotes the passage of the four strokes of an internal combustion engine. In a 4-stroke engine, this is known to extend over a crankshaft angle of 720 degrees and in a 2-stroke engine is known to have a crankshaft angle of 360 °.

On the other hand, as an alternative or in addition to the global precontrol, a combustion chamber-selective precontrol can be effected by determining an average value for the start of injection, the injection quantity and / or the injection profile over a period of time comprising several combustion cycles relative to the individual combustion chambers of the internal combustion engine. in order then to be able to use the individual mean values as pre-control values for the subsequent combustion cycles of the associated combustion chambers. Preferably, the last three combustion cycles of the associated combustion chambers are used to determine the mean values.

Furthermore, it can be provided to take over the combustion chamber-selective pilot control of only a few combustion chambers or at least one combustion chamber for all other combustion chambers in order on the one hand to simplify the technical implementation of the combustion chamber-selective pilot control and, on the other hand, to claim the least possible computing power of at least one control unit. Preferably, two to six combustion chambers of an internal combustion engine are considered over a period comprising a plurality of combustion cycles and their pre-control values are taken over for the remaining combustion chambers, whereby preferably the last three combustion cycles are used to determine the average values for the start of injection, the injection quantity and / or the injection curve become. In the case of a combination of a global and combustion chamber-selective pilot control, a parallel implementation of the two Vorsteuerungsarten be provided, it being possible to switch between the two Vorsteuerungsarten depending on an operating point of the internal combustion engine. The switching can be initiated by means of a characteristic and / or a map, wherein as Betriebsbzw. Switching point, a load / speed state and / or emission can be provided. Preferably, the global Vorsteuerungsart is first made and then optionally switched to the combustion chamber selective pilot control if necessary. The switching can, as already stated above, take place in such a way that the combustion chamber-selective pilot control of only a few combustion chambers or at least one combustion chamber of the internal combustion engine is adopted for all other combustion chambers. Preferably, it is switched to a combustion chamber-selective pilot control of all combustion chambers.

Alternatively, a linear or cascaded implementation of the two Vorsteuerungsarten be provided, starting with one of the two Vorsteuerungsarten. Preferably, the global Vorsteuerungsart is started.

According to a further embodiment, it is proposed that the precontrol be adaptive, i. self-learning to effect, with the objective that the adaptation of the trend development of the possible manipulated variables "injection start, injection course and injection quantity" better follows.

A further embodiment provides that the feedforward control operating mode dependent switched by means of a map or a characteristic switched on and off to take into account the actually given to an internal combustion engine control needs. This connection and disconnection can be made depending on a load / speed state and / or an emission output.

The model on which the precontrol is based can be designed as a mathematical and / or physical model that has to be validated by means of test bench measurements. A mathematical model is a model that is based on input and output variables of the respective combustion chamber, while a physical model is a model that describes the relationships between the input and output variables. According to a further embodiment, the fuel is injected into the combustion chamber while switching off a pilot injection. In this case, an ignition delay in the combustion chamber that occurs as a result of the deactivation of the pilot injection is predicted by means of a model. Corresponding to the ignition delay, an injection start, an injection quantity and an injection profile are determined using the combustion position control and taking into account the burning time of the fuel.

This measure also contributes to improving the homogenization of the combustion and thus to improving the control quality of the combustion position control, in addition to the shutdown of the pilot injection, especially in the range of low and medium engine loads, a significant extension of the ignition delay is achieved. Usually, the ignition delay is about 2000 to 1000 microseconds and at higher loads at about 800 to 500 microseconds. The time associated with the shutdown of the pilot injection time can be advantageously provided for the mixture preparation, so that the mixture preparation can be improved in favor of emission reduction.

Both the pilot control to the control of the injection process and the shutdown of the pilot injection help to reduce the application costs for an internal combustion engine of a vehicle. The correction factors stored in a control unit, which act on the start of injection, the injection quantity and the course of injection, preferably those representing the altitude, cold and / or a cold engine, may be associated with monitoring of the combustion noise and / or the combustion emissions be compensated and therefore omitted.

The prediction of the ignition delay can be effected by means of a mathematical and / or physical model based on at least one state variable of the combustion chamber, which is to be validated by means of test bench measurements. In this case, a mathematical and / or physical model is to be understood as already described above for such a statement.

Additionally or alternatively, the prediction of the ignition delay can be effected by means of neural networks.

According to a further preferred embodiment, at least the combustion chamber pressure is used as a state variable both for the combustion position control, the pilot control and the model for predicting the ignition delay. It can also be provided according to a further, preferred embodiment, both for the combustion position control, the pilot control and the model for predicting the ignition delay to use a plurality of state variables, which may include or exclude the combustion chamber pressure. In addition to the combustion chamber pressure, the parameters "temperature, ion current or signal of an optical measuring principle" are preferably considered state variables, the course of which can preferably be detected as a function of the crankshaft angle. Alternatively or additionally, the course of the state variables can also be detected as a function of time. The state variables can be measured and / or calculated.

The pilot injection can be switched on or off depending on the operating point by means of a characteristic map or a characteristic curve, in order to take into account the actual control requirement of an internal combustion engine. In this case, reference is also preferably made to the result of an estimate of the ignition delay and the consequences resulting therefrom, for example, the combustion process, the mixture formation or another. This connection and disconnection can be made depending on a load / speed state and / or an emission output.

Furthermore, according to a further embodiment, it is possible to regulate a change over time of the course of the injection with respect to a combustion chamber during at least one operating cycle by means of at least one state variable of the same combustion chamber detected during the same operating cycle. For further details in this context, reference is made at this point to the already acknowledged at the beginning of the prior art document WO 2007/115630 A2, from which such a configuration of a method for controlling a fuel injection is known and is hereby made the disclosure of the present invention ,

Furthermore, a control unit for at least one directly injecting internal combustion engine of a vehicle is proposed. The control unit comprises at least one control unit for controlling an injection process of the internal combustion engine, wherein in the control unit a model for determining a Zündverzugs and a switchable and disconnectable feedforward for the control of the injection process is deposited, and at least one arithmetic unit for processing of the injection process underlying control algorithm. As far as the model is concerned, this is to be understood previously for such a statement. In the model, at least one switch for the connection and disconnection of the pilot control is stored, so that a global all combustion chambers of the internal combustion engine comprehensive connection and shutdown of the pilot control can be effected.

According to a further development, a number of control units corresponding to the number of combustion chambers is stored in the control unit, wherein a changeover switch is provided in each of the control units for connection and deactivation of the pilot control. Alternatively, preferably two to six control units may also be provided in the control unit, each of which enables the combustion chamber-selective connection and disconnection of the pilot control of the associated combustion chamber via an associated changeover switch. In this case, the pilot control values obtained for the associated combustion chambers can be used in accordance with what has already been described above for the remaining combustion chambers.

The switch is in each case preferably designed as a characteristic map or a characteristic, so that an operating point-dependent connection and disconnection of the pilot control can take place, which takes into account the actually given to an internal combustion engine control needs.

The model for the pilot control is preferably designed as an adaptive model for the reasons already mentioned above.

Furthermore, a further model can be stored in the control unit, which serves to predict a Zündverzuges in a combustion chamber, wherein adjusts the ignition delay due to a shutdown of a pilot injection in the combustion chamber. Furthermore, at least one further changeover switch for switching on and switching off the pre-injection is deposited in the control unit, so that a global connection of all combustion chambers of the internal combustion engine and shutdown of the pilot injection can be effected.

Furthermore, in the control unit a number of combustion chambers corresponding number of switches for the combustion chamber selective connection and shutdown of the pilot injection can be deposited.

Here too, with regard to the model and the changeover switch, what has already been said must be understood. It can therefore be an operating point-dependent connection and shutdown of the pilot injection. To process the control algorithm underlying the injection process, more than one arithmetic unit is proposed, but at least two arithmetic units in order to increase the computing power of the control unit. Preferably, a number of arithmetic units corresponding to the number of combustion chambers is proposed.

Furthermore, a directly injecting, at least one combustion chamber having internal combustion engine of a vehicle is proposed. The internal combustion engine comprises an injection device for injecting fuel into the combustion chamber, at least one control device having at least one control unit for controlling the injection process, and at least one sensor which is assigned to the combustion chamber and detects a state variable that coincides with the combustion process in the combustion chamber is related. The sensor, which is preferably designed as a spark plug comprising a pressure sensor, is connected to the control unit. In the control unit, a model for a determination of an ignition delay and a switchable and switchable pilot control for controlling the injection process is also provided.

According to a preferred embodiment, it is proposed to deposit in the control unit one of the number of combustion chambers corresponding number of control units.

Such a vehicle has the advantage that a combustion position control is not mandatory. By using the model, this can for example also be omitted, for example in case of failure of the combustion chamber associated sensor. This also allows a redundant design of the engine control, since the vehicle can continue to operate, even if it should come to a fault.

In the following, embodiments of the invention will be explained in detail with reference to the drawings, wherein the embodiments are not to be interpreted as limiting. Rather, the features resulting from the drawings and the descriptions referring to the drawings are not limited to the respective exemplary embodiments. Therefore, the individual features with regard to possible developments with each other as well as with features from the above description are to be regarded as combinable.

Show it:

1 shows a first signal flow diagram 1, 2 shows a second signal flow diagram 13,

3 shows a third signal flow diagram 18 and

Fig. 4 is a schematic representation of an injection course.

The first signal flow diagram 1 shown in FIG. 1 shows a control unit 2, which is stored in a control unit and serves to regulate an injection process for an injection device of a direct injection internal combustion engine. The control unit 2 has various inputs, which are not fully shown in detail. Among other things, the inputs are a pressure curve 3, an output 4, a boost pressure 5, a Saugrohrtemperatur 6, an injection quantity 7, an injection characteristic 8, an injection start 9, a rail pressure 10 and an angle sensor signal 11. From these inputs calculates the Control unit 2, a control signal 12 for controlling an output voltage of an output stage for an injector. The desired injection quantity 7 and the desired start of injection 9 are obtained, for example, from a map (not shown here) which takes into account a driver's request. The adjustment quantities injection quantity 7, injection characteristic 8 and start of injection 9 are pre-controlled here and supplied to the control unit 2 as pilot control variables 30, 31, 32.

The core of the control unit is a microprocessor or a computing unit, which can or make a corresponding control and regulation of the injection process via stored in a memory of the control unit control and regulation instructions.

As a reference point for the pressure curve 3, a crankshaft angle α is preferably used. This is transmitted to the control unit 2 by means of an angle sensor or crank angle sensor. Alternatively or additionally, it can also be provided to relate the pressure curve 3 to the time.

By means of the input injection characteristic 8, for example, it is predetermined whether it is intended to be a plurality of injection pulses or else a continuous course of injection. In this case, 8 different classes of injection curves can be specified by means of the injection characteristic. The classes describe different parameters to which the injection, and here the controlled injection curve refers. For example, the course of injection can be applied over the crankshaft angle α. Alternatively or additionally, the course can also be applied over an ignition delay. The second signal flow diagram 13 shown in FIG. 2 shows a control unit 14, which can be stored in the same control unit and which regulates an injection start 9 and an injection characteristic 8 for the injection device. The control unit 14 has various inputs, which are in detail a combustion focal point position 15, a lambda value 16, which is determined in a suction pipe, a boost pressure 5, a Saugrohrtemperatur 6, a rail pressure 10 and an operating mode 17 , The combustion center of gravity 15 is determined by means of a sensor, which detects, for example, the combustion chamber pressure, in conjunction with an angle sensor. By way of the operating mode 17, it is possible, for example, to specify how the internal combustion engine or in which state it is to be operated, for example in a regeneration mode for a diesel particulate filter. Furthermore, as an operating mode, for example, a rich or a lean combustion can be provided. The specification of the operating mode 17, for example, by means of a map in conjunction with a driver's request.

The second control unit 14 calculates as starting values an injection start 9, an injection characteristic 8 and a pilot control variable 31 for the injection start 9 and a pilot control variable 30 for the injection characteristic 8. These four output variables can be fed, for example, into the first control unit 2 from the first signal flow diagram 1 , The injection characteristic is preferably adapted to the operating mode. For example, it is provided in the combustion in a high-load operating point to make an increase in the injection rate in the direct connection to a start injection at the start of combustion and finally end the injection abruptly. In the case of a transient operation of an internal combustion engine with short-term high exhaust gas recirculation rates, on the other hand, it may be provided to shift a main injection in the direction of late and, if appropriate, additionally to provide a pilot injection. Furthermore, for example, in a regeneration mode of operation for a diesel soot particulate filter, one or more post-injections may be provided.

The third signal flow diagram 13 shown in FIG. 3 shows a further control unit 19, which can be stored in the same control unit and on which the regulation of the injection quantity 7 is based. The control unit 19, an average combustion chamber pressure 20 and a driver request 21 are supplied as input variables. The driver request 21 is determined, for example, from an accelerator pedal position or accelerator pedal acceleration. In particular, a selected gear of a transmission is taken into account in determining the driver's request. As an output, the third control unit 19 calculates the injection quantity 7 and a pilot value 32 for the injection quantity 7. These two Outputs can for example be supplied to the first control unit 2 according to the first signal flow scheme 1. When calculating the injection quantity, it is preferably taken into account that, depending on the operating mode, in particular depending on the exhaust gas recirculation rate or boost pressure, a different average combustion chamber pressure is set depending on the injection quantity. Additionally or alternatively, different adjusting combustion chamber pressures can also be taken into account. Preferably, by means of the regulation of the injection quantity, the mean combustion chamber pressure can be maintained at a desired value, despite a variation of the other operating parameters, such as the exhaust gas recirculation rate or the boost pressure.

The signal flow diagrams 1, 13, 18 described with reference to FIGS. 1 to 3 are preferably used in a combustion chamber-selective manner, so that one of the units 2, 14, 19 can be assigned to each individual combustion chamber of an internal combustion engine. The control signal 12 is used to control the injector assigned to the combustion chamber.

According to an alternative embodiment, the signal flow schemes 1, 13, 18 can also be used globally in all combustion chambers of the internal combustion engine. In this case, each of the control units 2, 14, 19 deposited in a control unit only once. Therefore, the individual combustion chambers associated input variables of a common control unit are supplied. In this case, those input variables which do not differ from one another for the regulation of the injection process are preferably supplied only once as input variables of the common control unit. These variables which are common to the regulation of all combustion chambers are, in particular, the rail pressure, the boost pressure, the intake manifold temperature, the lambda value and the operating mode. The common control unit supplies a control signal for the assigned injector for each of the combustion chambers.

The control units 2, 14, 19 are each preferably based on an adaptive pilot control, which can be switched on or off by means of a changeover switch. In this case, in each of the units 2, 14, 19, a mathematical and / or physical model serving for precontrol of the corresponding output variables can be stored, which is based, for example, at least on the combustion chamber pressure 3. The combustion chamber pressure is detected by means of a spark plug, which comprises a pressure sensor which is connected to the control unit 2. The mathematical and / or physical model may be understood to be a mathematical model based on input and output variables of the combustion chamber, and / or a physical model that includes the between the input and output variables describes existing relationships. The state variables can be measured and / or calculated.

The switching on and off of the precontrol effecting - not shown here - Umstellschalter, which can be stored in each of the control units 2, 14, 19, can be configured as a map or a characteristic for operating point-dependent connection and disconnection. This connection and disconnection can be made depending on a load / speed state and / or an emission output.

All control units 2, 14, 19 have in common that the fuel can be injected with shutdown of a pilot injection into the combustion chamber. Here too, another switch (not shown here) is used, which is deposited in the control unit 2 and can be designed as a characteristic map or a characteristic curve for operating point-dependent connection and disconnection of the pilot injection. Again, the connection and disconnection can be made depending on a load / speed condition and / or an emission. The ignition delay occurring as a result of the deactivation of the pilot injection in the combustion chamber is predicted by means of a further model which can be stored in the control unit 2. The model used here is a mathematical / and / or physical model which is based at least on the combustion chamber pressure 3. The mathematical and / or physical model is to be understood as meaning what has previously been said about such a statement. By means of this model, a start of injection 9, injection course 12 and an injection quantity 7 corresponding to the ignition delay are determined using the combustion position control and a burning time of the fuel. The state variables can be measured and / or calculated.

In addition or as an alternative to the mathematical and / or physical model, the prediction of the ignition delay can be effected by means of neural networks.

The injection curve 22 illustrated in FIG. 4 - or the injection characteristic 22 - illustrates an injection rate 23 that varies over a crankshaft angle α. Also shown is the pressure curve 24, 29 corresponding to the course of the injection rate 23 with respect to the crankshaft angle α. At the beginning of the injection process, a start injection 25 is provided, which provides a constant injection rate extending over a first crankshaft angle section 26. This start injection 25 is closed at a point in time at which combustion commences - this point in time corresponds to the crankshaft angle oti - a linear or ramp feed. mig increasing injection rate 27, which extends over a second crankshaft angle section and shortly before the end of the injection transiently in a constant injection rate 28 and then drops abruptly to zero.

The increase in the injection rate at the onset of combustion advantageously increases the turbulence in the combustion chamber. Due to the abrupt end of the injection, post-oxidation of the fuel can advantageously be effected as a result of a hot end of the combustion.

The injection rate profile 23 corresponds to the pressure profile 24. As a result of the ramp-shaped increasing injection rate 27 of the pressure profile 24 is continued in a second pressure curve 29. This second pressure profile 29 is shifted in the "late" direction relative to the first pressure profile 24.

For further details in connection with the temporal variability of the injection rate curve, reference is again made at this point to the document WO 2007/115630 A2 cited at the outset in the introductory part of the specification, from which a method for regulating a time-variable injection rate profile is known and which is hereby incorporated by reference The disclosure of the present invention is made.

Claims

claims

1. A method for controlling combustion in a direct injection internal combustion engine by estimating an ignition delay in at least one cylinder of the direct injection internal combustion engine using a

Model.

2. The method according to claim 1, characterized in that on the basis of the estimate at least a control of an injection start takes place.

3. The method according to claim 1 or 2, characterized in that, taking into account a combustion chamber pressure in the cylinder of the ignition delay is estimated.

4. The method of claim 1, 2 or 3, characterized in that when using the model, a mathematical modeling is used, which is based on data from test bench tests, with one or more state variables in the cylinder as input variables in the model.

5. The method according to claim 4, characterized in that at least a part of the input variables are determined even model-based.

6. The method of claim 1, 2 or 3, characterized in that a self-learning model of the ignition delay is used, which is based on at least one neural network, wherein a measurement of a combustion chamber pressure takes place and is processed in the model.

7. The method according to any one of the preceding claims, characterized in that a precontrol takes place on the basis of the estimated ignition delay for a combustion position control.

8. The method according to any one of the preceding claims, characterized in that in at least one low load range injection takes place without pre-injection, wherein an extension of the ignition delay takes place.

9. Method preferably according to one of the preceding claims, for determining or regulating an injection process of a direct-injection internal combustion engine (33) of a vehicle (34), wherein a fuel in a Combustion chamber of the internal combustion engine (33) is injected, taking into account a Zündverzugs, preferably also taking into account a burning time of the fuel, at least one injection start (9), preferably additionally an injection quantity (7) and / or an injection curve (12) is determined, wherein at least one state variable (3, 5,

15) is used to determine an ignition delay time and wherein at least one control, preferably a switchable and switchable control, in particular feedforward control (30, 31, 32), is used for the definition or regulation of the injection process, which by means of at least one of the state large (3, 5, 15) of the combustion chamber based model is effected.

10. The method according to any one of the preceding claims, characterized in that a pilot control (30, 31, 32), for the start of injection (9), the injection quantity (7) and / or the injection profile (8) is effected.

11. The method according to any one of the preceding claims, characterized in that in a combustion chamber comprising a plurality of combustion engines (33) a pilot control (30, 31, 32), globally all combustion chambers is effected in a comprehensive manner.

12. The method according to any one of the preceding claims, characterized in that in a combustion chamber comprising a plurality of combustion engines (33) a pilot control (30, 31, 32) is effected combustion chamber selectively.

13. The method according to any one of the preceding claims, characterized in that a feedforward control (30, 31, 32) is effected adaptively.

14. The method according to any one of the preceding claims, characterized in that the feedforward control (30, 31, 32) is switched on or off depending on operating point by means of a Kennfel- des or a characteristic.

15. The method according to any one of the preceding claims, characterized in that as a model on which the feedforward control (30, 31, 32) is based, a mathematical and / or a physical model is used.

16. The method according to any one of the preceding claims, characterized in that a fuel with shutdown of a pilot injection into the combustion chamber a is injected, wherein an adjusting due to the shutdown of the pilot injection ignition delay in the combustion chamber is predicted by means of a model.

17. The method according to claim 16, characterized in that using a combustion position control and taking into account a burning time of the fuel corresponding to the ignition delay, an injection start (9), an injection quantity (7) and an injection curve (12) are determined.

18. The method according to any one of the preceding claims, characterized in that both for a combustion position control, a pilot control (30, 31, 32) and for the model for predicting the ignition delay at least the combustion chamber pressure (3) is used as a state variable.

19. The method according to any one of the preceding claims, characterized in that both for a combustion position control, a feedforward control (30, 31, 32) as well as for the model for the ignition delay prediction several state variables (5, 15) are used, the Exclude combustion chamber pressure (3).

20. The method according to any one of the preceding claims, characterized in that the pilot injection is switched on or off depending on the operating point by means of a map or a characteristic.

21. The method according to any one of the preceding claims, characterized in that a temporal change of the injection profile with respect to a combustion chamber during at least one operating cycle by means of at least one detected during the same cycle state variable (3, 5, 15) of the same combustion chamber is controlled.

22. Control unit for at least one directly injecting internal combustion engine (33) of a vehicle (34), with at least one control unit (2, 14, 19) for controlling an injection process of the internal combustion engine (33), wherein in the control unit (2, 14, 19) a model for a determination of an ignition delay and an activatable and deactivatable pilot control (30, 31, 32) is stored for controlling the injection process, and with at least one arithmetic unit for processing the control algorithm underlying the injection process.

23. Control device according to claim 22, characterized in that in the control unit at least one switch for connection and disconnection of the pilot control

(30, 31, 32) is deposited.

24. Control unit according to claims 22 and 23, characterized in that in the control unit one of the number of combustion chambers corresponding number of control units (2, 14, 19) are deposited, wherein in each of the control units (2, 14,

19) a switch for the combustion chamber selective connection and shutdown of the pilot control (30, 31, 32) is provided.

25. Control device according to one of claims 22 to 24, characterized in that the switch as a characteristic map or a characteristic for operating point-dependent

Connection and disconnection of the pilot control (30, 31, 32) is configured.

26. Control device according to one of claims 22 to 25, characterized in that the model to the feedforward control (30, 31, 32) is designed as an adaptive model.

27. Direct injection, at least one combustion chamber having internal combustion engine (33) of a vehicle (34), with an injection device for injection of fuel into the combustion chamber, at least one control unit, the at least one control unit (2, 14, 19) for

Control of the injection process, wherein in the control unit (2, 14, 19) a model for a determination of an ignition delay and a switchable and switchable pilot control (30, 31, 32) is provided for the control of the injection process, and with at least one sensor, which is assigned to the combustion chamber and detects a state variable (3, 5, 15) which is related to the combustion process in the combustion chamber, the sensor being connected to the control unit (2, 14, 19).

28. Internal combustion engine according to claim 27, characterized in that in the control unit one of the number of combustion chambers corresponding number of control units (2, 14, 19) is deposited.

29. Internal combustion engine according to claim 27 or 28, characterized in that the sensor is designed as a spark plug comprising a pressure sensor.