EP1570165B1 - Method for adapting the characteristic curve of an injection valve - Google Patents

Abstract

The invention relates to a method for adapting an injection valve characteristic curve of a controlled fuel injection valve for an internal combustion engine, said curve reflecting the reference injection behaviour, to alterations in the actual injection behaviour caused by ageing. According to said method: during an operating mode of the internal combustion engine, which does not require an injection of fuel, the injection valve is intermittently controlled in accordance with a control period, said mode alternating with a period of no fuel injection, i.e. at least one working cycle with injection-valve control follows or precedes a working cycle without injection-valve control; at least one respective RPM value of the internal combustion engine is detected for the controlled working cycle and for at least one of the working cycles without control; a differential between the detected values is calculated and said differential is used to correct the characteristic curve.

Description

The present invention relates to a method for adapting a reference injection behavior reproducing injection valve characteristic of a controlled fuel injection valve of an internal combustion engine to age-related changes or production-related variations of an actual injection behavior.

For fuel allocation injection valves are controlled in internal combustion engines so that at each operating point an optimal amount of fuel enters the combustion chambers. For example, in direct fuel injection diesel engines, high pressure fuel is injected from a fuel reservoir into the combustion chambers. The metering of the amount of fuel introduced in the combustion chamber is done by suitable control of the injection valves, which are also referred to as injectors. The metering is usually time-controlled by the injection valve is opened for a specified time and then closed again. A control unit of the internal combustion engine specifies an opening time and an opening duration of the injection valve. In doing so one lays down e.g. to an electrically operated injection valve to a control signal, which specifies a drive time.

The control unit can make an association between the activation duration and the metered fuel mass; For this purpose, an injection valve characteristic is stored in the control unit, which establishes a relationship between the injected fuel quantity and the actuation duration of the injection valve, wherein also other conditions, such as fuel pressure or temperature are taken into account.

The injection valve characteristic is based on a standard fuel injector that meets certain specifications. However, since the injection behavior of each injection valve always differs slightly in principle, there are certain differences with regard to the amount of fuel delivered given a fixed control duration from injection valve to injection valve. This leads to non-round running of the internal combustion engine and especially to poorer exhaust gas values. Nevertheless, in order to be able to comply with strict emission standards, it is necessary to keep the permissible tolerances for the injection valves as low as possible, which is very costly.

But even then age-related signs of wear of the injector can cause deviations between the actual injection behavior and the reference injection behavior, as laid down in the injection valve characteristic, occur. In order to compensate for such deviations, it would in principle be conceivable to change the stored injection valve characteristic over the service life of the internal combustion engine in the direction of a reference injection behavior for an aged reference injection valve. However, such a purely controlled and thus very unspecific change could not take into account the individual properties of an injection valve. In addition, significant problems occur if an injector is replaced during the life of an internal combustion engine.

Alternatively, it would be conceivable to provide an additional knock sensor with which the combustion noise of the internal combustion engine is monitored. This would make it possible to determine the activation time required for the onset of a combustion noise. However, then only a minimum drive time can be determined at which the injection valve starts to deliver a fuel mass stable. Moreover, this procedure is relatively imprecise. In addition, it is It is very expensive, because it must be provided an additional sensor including the corresponding signal detection circuit.

The invention is therefore based on the object of specifying a method for adjusting a reference injection behavior reproducing injection valve characteristic of a controlled fuel injection valve of an internal combustion engine to age-related changes of an actual injection behavior, which makes it possible to make an individual adjustment for each injector.

This object is achieved by a method for adjusting a reference injection behavior reproducing injection valve characteristic of a controlled fuel injection valve of an internal combustion engine to age-related changes of an actual injection behavior, wherein during a fuel injection requiring operating state of the internal combustion engine, the injection valve is driven intermittently according to a drive time, while otherwise no fuel injection takes place, so that at least one working cycle with control follows or precedes at least one working cycle without activation of the injection valve, respectively a speed value or a value of a speed-dependent size of the internal combustion engine for the working cycle with control and for at least one of the working cycles without control is detected and formed a difference of the detected values and thus a correction of the injection characteristic v is taken.

According to the invention, therefore, during an operating state of the internal combustion engine, which actually required no fuel injection, the injection valve is driven intermittently according to a drive time. This alternates a working cycle with control of the injector with a working cycle, in which the injection valve is not activated, ie the internal combustion engine runs completely without fuel injection. This will turn on and off the injector, whose injection behavior is to be adapted caused. By comparing the speed value or the speed-dependent value according to the invention, a correction of the injection characteristic is effected. The speed information evaluated in this regard, either the speed directly or a speed-dependent variable, changes when a torque-generating injection occurs. The change is dependent on the injected fuel mass, so that not only the onset of injection above a certain Mindestansteuerdauer, but also the entire injection characteristic, ie the dependence of the output from the injector fuel mass of the drive time can be corrected.

Of course, in order to adapt the overall injection characteristic of the injection valve to the actual injection behavior, an injection must be carried out over the widest possible range of activation periods and other injection parameters, e.g. Fuel pressures are made. It is therefore preferred that the drive duration is increased in steps, the step size depending on the desired accuracy of the correction of the injection valve characteristic. In principle, e.g. two steps sufficient to check for a minimum and a maximum drive duration.

The fuel mass emitted by the injection valve causes the internal combustion engine to output a torque. Of course, this torque is reflected in the speed information. Conveniently, however, one will not evaluate the speed information directly, but previously calculate a torque value for a torque that was caused by the control of the injector with the drive time. The calculation of this torque value has the advantage that the finally sought value for the fuel mass can then be obtained by means of a simple conversion. The corresponding Relationships for this are usually deposited in the control unit of the internal combustion engine, since modern control units usually perform a so-called torque-based control, which determines a desired torque and from it a fuel mass is derived. Thus, if, as in the preferred embodiment, a torque value is determined, the implementation used anyway in the torque-based control need only be run in the reverse direction.

The determination of the torque value can be done by a suitable evaluation of the speed gradient. If an internal combustion engine is under overrun fuel cut, the engine speed will generally decrease. It shows a speed gradient of the working cycles, in which the injection valve, the injection valve characteristic is to be adapted, driven, precipitates differently than for cycles in which there is no injection valve actuation. An analysis of the speed gradient thus makes it possible to easily generate the mentioned torque value.

wobei F1 einen von einer Zylinderanzahl abhängigen Faktor, D den Drehmomentwert, M das Trägheitsmoment der Brennkraftmaschine, dN+ einen Drehzahlgradienten des Arbeitsspiels mit Ansteuerung des Einspritzventils, dN- einen Drehzahlgradienten eines der Arbeitsspiele ohne Ansteuerung des Einspritzventils und dJ ein Faktor für ein durch innere Reibung der Brennkraftmaschine bedingtes Bremsmoment bezeichnet, das drehzahlabhängig sein kann.In a preferred embodiment, therefore, the torque value is calculated according to the following formula: $$\mathrm{D}=\left(\mathrm{\pi }/\mathrm{F}1\right),\mathrm{M},\left(\mathrm{d}\mathrm{N}+-\mathrm{d}\mathrm{N}-\right)+\mathrm{d}\mathrm{J}.$$

where F1 is a factor dependent on a number of cylinders, D is the torque value, M is the moment of inertia of the internal combustion engine, dN + is a speed gradient of the operating cycle with control of the injection valve, dN is a speed gradient of one of the working cycles without activation of the injection valve and dJ is an internal friction factor of the Internal combustion engine refers conditional braking torque, which may be speed-dependent.

The difference in the speed gradient of the working cycle with control of the injector and one of the working cycles without control of the injection valve is thus a suitable size for the calculation of the torque in a preferred embodiment. The equation is applicable to internal combustion engines of any number of cylinders. Depending on the number of cylinders, another factor F will occur. For four cylinders, F1 = 30.

The moment of inertia M of the internal combustion engine is influenced by the flywheel mass of the piston, crankshaft, camshaft and possible flywheel masses and constitutes a fixed variable fixed for an internal combustion engine.

The braking torque of the internal combustion engine is due to internal friction and usually also a largely constant variable, which can be easily determined as the moment of inertia on a test bench. In order to make the effect caused by the speed gradient as large as possible, it is advantageous to minimize the braking torque. For this purpose, for example, a driven by the internal combustion engine drive train for the method for adjusting the injection valve characteristic can be decoupled, for example by actuation of a corresponding clutch.

Furthermore, in order to improve the signal-to-noise ratio, the method according to the invention, i. the intermittent control of the injector and the control of the speed information, are performed repeatedly with unchanged control period.

In multi-cylinder internal combustion engines usually driven by the internal combustion engine provided with a dividing segment wheel is scanned and detects the speed information in the form of segment times, which takes the passage of a particular segment of the segment wheel. As a rule, a segment is assigned to the working cycle of a cylinder of the multi-cylinder internal combustion engine. In such a speed detection, the difference between the Segment times for a cylinder without and with control of the injector particularly easily determined and used to adjust the injector characteristic.

wobei F2 einen von der Zylinderzahl abhängigen Faktor, D den Drehmomentwert, M das Trägheitsmoment der Brennkraftmaschine, dJ einen Faktor für ein durch innere Reibung der Brennkraftmaschine bedingtes Bremsmoment, Tx1 die Segmentzeit für den bestimmten Zylinder im ersten Arbeitsspiel, Tx2 die Segmentzeit für den bestimmten Zylinder im zweiten Arbeitsspiel, Tx3 die Segmentzeit für den Zylinder im dritten Arbeitsspiel, STdie mittlere Gesamtdauer des Durchlaufs aller Segmente während eines Arbeitsspiels ohne Ansteuerung des Einspritzventils und ST+ die mittlere Gesamtdauer des Durchlaufs aller Segmente während eines der Arbeitsspiele mit Ansteuerung des Einspritzventils bezeichnet.In this regard, therefore, a method is preferred in which a segment wheel driven by the internal combustion engine scanned and a first cycle without controlling the injector of a particular cylinder, then a second cycle with control of the injector of the particular cylinder and then a third cycle without controlling the injector of a particular Cylinder are performed, wherein at least in the first, second and third cycle for the particular cylinder, a segment time is determined, which takes the passage of a segment of the segment wheel during the working stroke of the cylinder, and wherein the torque is calculated according to the following equation: $$\mathrm{D}=\mathrm{F}\mathrm{Second}\mathrm{\pi },\mathrm{M}\left(\left(\mathrm{T}\mathrm{x}3-\mathrm{T}\mathrm{x}2\right)/{\left(\mathrm{S}\mathrm{T}-\right)}^3-\left(\mathrm{T}\mathrm{x}2-\mathrm{T}\mathrm{x}1\right)/{\left(\mathrm{S}\mathrm{T}+\right)}^3\right)+\mathrm{d}\mathrm{J}.$$

where F2 is a factor dependent on the number of cylinders, D is the torque value, M is the moment of inertia of the internal combustion engine, dJ is a factor for an internal friction of the internal combustion engine, Tx1 is the segment time for the particular cylinder in the first working cycle, Tx2 is the segment time for the particular cylinder Tx3 denotes the segment time for the cylinder in the third working cycle, ST the average total duration of the passage of all segments during a working cycle without control of the injection valve and ST + the average total duration of the passage of all segments during one of the working cycles with actuation of the injection valve.

In this embodiment, usually the average total duration of the run of all segments is used for the cycle, in which also indicated in the denominator of the equation Segment times were won. However, this is not absolutely necessary, depending on the speed detection and other total durations, for example, from more recent work cycles can be used.

Beyond the above equation, higher division orders of the segment times in the form of differential quotients can also be calculated and evaluated in order to increase the accuracy of the torque or injection quantity determination shown here. In addition, it is possible with the aid of signal analysis methods to evaluate the overall course of the speed drop over a larger number of working cycles with and without injection, in order to avoid disturbing influences, such as noise. Torsional vibrations of the drive train to identify and eliminate and thus increase the accuracy of the calculation of the torque or the injection quantity again.

In the listed embodiments for calculating the torque value D, a factor is used for a braking torque caused by internal friction of the internal combustion engine. A particularly accurate consideration of this in the equations additive incoming factor is obtained when the braking torque to the respective working cycle, in which the injection valve was activated or not driven zoom. Therefore, in this respect, a method is preferable in which a difference between two values is formed for determining the factor for the braking torque caused by the internal friction of the internal combustion engine, one value being one of the working cycles of the internal combustion engine without controlling the injector and the other the working cycle of the engine Internal combustion engine is associated with control of the working cycle.

In most cases, the injection valve characteristic, which is to be adapted to the actual injection behavior of an injection valve, in the form of a link between fuel mass and driving time before. For such In some cases, it is preferable for the adaptation that a fuel mass value for a fuel mass output from the injection valve is derived from the speed information or the torque value and is assigned to the value for the activation duration at which the fuel mass value was obtained. By means of this assignment, a simple correction of an injection valve characteristic is then possible, which includes the mentioned mapping between activation duration and fuel mass value.

Fig. 1

ein Diagramm, in dem eine von einem Einspritzventil abgegebene Kraftstoffmasse über der Ansteuerdauer des Einspritzventils aufgetragen ist,

Fig. 2

zwei Diagramme, in denen die Drehzahl der Brennkraftmaschine bzw. die Umlaufdauer eines mit der Kurbelwelle einer Brennkraftmaschine verbundenen Segmentrades als Zeitreihe aufgetragen ist, die sich bei der Ausführung des erfindungsgemäßen Verfahrens ergibt,

Fig. 3

ein detailliert dargestellter Ausschnitt der Darstellung der Fig. 2 und

Fig. 4

die von einem Einspritzventil abgegebene Kraftstoffmasse als Funktion der Ansteuerdauer des Einspritzventils zusammen mit zur Korrektur herangezogenen Messpunkten.

The invention will be explained in more detail with reference to the drawing by way of example. In the drawing show:

Fig. 1

a diagram in which a fuel mass discharged from an injection valve is plotted over the activation duration of the injection valve,

Fig. 2

two diagrams in which the rotational speed of the internal combustion engine or the circulation time of an associated with the crankshaft of an internal combustion engine segment wheel is plotted as a time series, resulting in the execution of the method according to the invention,

Fig. 3

a detailed section of the illustration of FIG. 2 and

Fig. 4

the fuel mass emitted by an injection valve as a function of the activation duration of the injection valve together with measuring points used for the correction.

1 shows the injection valve characteristic of an electrically controlled injection valve of an internal combustion engine (not shown). In this case, a fuel mass K is over a drive time TI applied. The injection valve is actuated by means of a corresponding electrical control signal for outputting a fuel mass, ie the control unit has to open the fuel injector fed by the fuel injector for the control period TI. However, due to mechanical and electrical input units, the injection valve will only follow above a certain minimum actuation duration, which is shown in FIG. 1 as start value TI_0. Shorter drive times are not feasible. If the starting value TI_0 is exceeded, the injection valve emits a fuel mass which, according to the characteristic shown in FIG. 1, depends on the activation duration. The dashed lines shown characteristic 1 of FIG. 1 is stored in a newly delivered internal combustion engine in the control unit of the internal combustion engine and is based on a reference injection behavior of a new injection valve, which meets certain specifications.

In addition, an exemplary characteristic 2 of an aged injection valve is shown in solid lines in FIG. As can be seen, the starting value TI_0, above which a control period TI must be in order for a fuel mass to be discharged from the injection valve, is above the starting value for the reference injection behavior according to characteristic 1. Due to manufacturing tolerances and / or changes occurring during the Lifetime of the injection valve due to wear or the like. occur, there is a shift dTI between the starting points. This shift has the consequence that a different activation duration TI is required in order to deliver the same fuel mass in the case of an injection valve having the characteristic 2, as in the case of a reference injection valve with the characteristic 1. The shift can indeed be longer or shorter after aging / production deviation Driving time available.

The deviation from the characteristic 1 used by the controller in the control leads to a deteriorated Performance and emission behavior of the internal combustion engine. In the adjustment described below, this deviation is remedied by correcting the reference characteristic 1 so as to be equal to the actual characteristic 2.

The illustration of FIG. 1 suggests that to adapt the actual injection behavior according to characteristic 2 to the reference injection behavior according to characteristic 1, it would be sufficient to determine the displacement dTI. Although this may be sufficient in most cases, however, wear-related aging phenomena on the injection valve can also lead to the characteristics 2 representing the injection behavior not being able to be obtained from the characteristic 1 of the reference injection behavior by a simple parallel displacement along the x-axis. As a result of aging, further deviations between the characteristics 1 and 2 may result. This is clear, for example, from the course of the characteristic 1 in the region of higher actuation durations TI; in this section, the shift between the characteristic 1 and the characteristic 2 is less than in the range of lower fuel masses K or in the region of the starting value TI_0.

In order to adapt the characteristic 1 used in the control unit of the internal combustion engine to the actual injection behavior according to characteristic 2, the fuel mass K emitted by the injection valve under consideration is determined as an function of the activation duration TI in an adaptation method.

For this purpose, a fuel cut-off phase of the internal combustion engine is utilized, in addition, in order to switch off external braking torques, the internal combustion engine is separated from a drive train of the motor vehicle driven by the engine by opening a clutch. In the fuel cut-off phase, the internal combustion engine is operated substantially without fuel, whereby the speed drops sharply until an idle controller engages the operation the internal combustion engine to idle speed to stabilize.

Operated under "substantially" without fuel supply is understood to mean that a fuel supply takes place only for the adaptation process, but in this operating state is actually not desired or is not required.

In order to adapt the characteristic of the injection valve, in the fuel cut-off phase, the injection valve is driven intermittently according to a drive duration, i. Working cycles of the internal combustion engine, in which the injection valve is driven to open for a certain driving time, alternate with working cycles, in which the injection valve is not actuated.

FIG. 2 shows, in each case in a time series, the profile of the rotational speed N of the internal combustion engine or of a revolution duration U of a segment wheel driven by the internal combustion engine, which is non-rotatably connected to the crankshaft of the internal combustion engine. In the left-hand time series of FIG. 2, the speed curve is shown together with a drive signal 4. The speed curve 3 is the time evolution of the speed of the engine again. The drive signal 4 is the signal with which an injection valve is activated during the overrun fuel cutoff of the internal combustion engine. The drive signal 4 is composed of drive pulses 5 and intervening rest pauses 6 together. During the duration of a drive pulse 5, the injection valve is driven according to a drive duration. If this is above the starting value TI-0, the injection valve opens, and a cylinder of the internal combustion engine fed by the injection valve carries out a power stroke because fuel is allocated. In the rest periods 6 lying working cycles of the cylinder take place without the injection valve is driven to open. So these are work cycles in which the corresponding cylinder is switched off.

The control signal 4 thus represents a binary signal which indicates whether the injection valve, whose characteristic is to be adjusted, is even activated. The width of the drive pulses 5 in Fig. 2 are not the Ansteuerdauer again, but only indicates whether in a working cycle, the injection valve is driven.

Since the internal combustion engine is in a fuel cut-off phase, the rotational speed N decreases. However, this decrease takes place with a varying gradient, since an injection valve is intermittently driven by the drive pulses 5.

The speed curve 3 shows in working cycles for which a drive pulse 5 is drawn, i. in which the injector opens, a lower slope than when the drive signal has a rest 6, i. the injection valve remains closed. The sections with a smaller pitch are marked with a "+" and provided with the reference numeral 7. The higher gradient portions, i. with a faster falling speed curve wear a "-" and are designated by the reference numeral 8.

The right-hand illustration of FIG. 2 shows, in addition to the drive signal 4, a passage duration curve which represents the time evolution of the cycle duration U of the segment wheel. The circulation time U is inversely proportional to the rotational speed N. In sections 7 of the passage duration curve 9, the circulation duration increases less than in sections 8, which in turn is caused by the activation of the injection valve, which has a drive pulse 5 during sections 7, while in sections 8 has a rest pause 6.

wobei F einen von einer Zylinderanzahl abhängigen Faktor, D den Drehmomentwert, M ein Trägheitsmoment der Brennkraftmaschine, dN+ einen Drehzahlgradienten des Arbeitsspiels mit Ansteuerung des Einspritzventils, dN- einen Drehzahlgradienten eines der Arbeitsspiele ohne Ansteuerung des Einspritzventils und dJ ein Faktor für ein durch innere Reibung der Brennkraftmaschine bedingtes Bremsmoment bezeichnet. Der Faktor F hat für eine Vierzylinderbrennkraftmaschine den Wert 30. Der Drehzahlgradient dN+ ist durch die Steigung des Drehzahlverlaufs 3 in den Abschnitt 7, der Drehzahlgradient dNdurch die Steigung der Abschnitte 8 des Drehzahlverlaufs 3 gegeben.The lower slope, the speed curve 3 in the phases 7, in which the injection valve is driven in accordance with the drive pulse 5 with a drive duration, therefore, that because of the fuel injection of the corresponding cylinder the internal combustion engine outputs a torque. This torque contribution depends on the activation duration, with which the injection valve is driven in the drive pulses, and is determined in a first embodiment according to the following equation: $$\mathrm{D}=\left(\mathrm{\pi }/\mathrm{F}\right),\mathrm{M},\left(\mathrm{d}\mathrm{N}+-\mathrm{d}\mathrm{N}-\right)+\mathrm{d}\mathrm{J}.$$

where F is a cylinder number dependent factor, D is the torque value, M is an inertia of the internal combustion engine, dN + is a speed gradient of the working cycle with injection control, dN is a speed gradient of one of the cycles without controlling the injector, and dJ is an internal friction factor Internal combustion engine referred conditional braking torque. The factor F has the value 30 for a four-cylinder internal combustion engine. The speed gradient dN + is given by the slope of the speed curve 3 in the section 7, the speed gradient dN by the slope of the sections 8 of the speed curve 3.

The factor dJ takes into account a braking torque caused by internal friction of the internal combustion engine. In the case of a disconnected drive train, this depends only on the design or operating parameters of the internal combustion engine itself and can be taken from a performance map, for example. The braking torque is dependent in particular on the speed, which is why, in an alternative embodiment, two values for the braking torque to the average speed in section 7 or section 8, which is pulled down for the calculation of the torque according to the above equation, and the difference is formed subtracting the braking torque at the time dN was determined from the braking torque at the time when dN + was determined to determine the factor dJ.

The torque value D calculated with the above equation represents the torque generated by the injection valve driving at the drive timing used for the adjustment. This torque can be converted into the desired fuel mass K in a manner known to those skilled in the art, for example by a characteristic map.

The described adaptation is now repeated for different drive durations, so that a set of value pairs is obtained, each of which consists of a torque value and a drive duration or a fuel mass value and a drive duration. 4 shows the plot of the value pairs obtained for an exemplary injection valve. The fuel mass K (in mg) is plotted over the activation time TI (in ms). At a drive time of just over 0.16 ms, a fuel mass of 1 mg is delivered.

Each measurement point corresponds to a performance of the method for adaptation with a specific activation duration, wherein the torque calculated as indicated above was additionally converted via a known relationship into a fuel mass which the injection valve delivered in the method for adaptation. As can be seen, the injection valve begins only above a certain drive time to deliver a fuel mass. This lower limit corresponds to the starting value TI_0 in Fig. 1. As the illustration of Fig. 4 further shows, the resolution in the adjustment is in the range of 0.1 to 0.2 mg.

The curve 14 shown in FIG. 4 can thus be used as characteristic 1 associated with the corresponding injection valve during operation of the internal combustion engine or serve for the correction of the characteristic 1 on the curve 14. FIG. 4 shows in this respect a small section of the characteristic 2 of FIG. 1 around the starting value TI_0.

FIG. 3 illustrates a second embodiment of the method with which an adaptation of the injection valve characteristic can be achieved. 3 shows a section of the passage duration curve 9 of the right-hand illustration of FIG. 2. Consecutive sections 7 and 8 are shown in a section of the passage duration curve 9 in FIG. 3, each section corresponding to a working cycle. In addition, a segment time signal 10 is shown representing the segment durations taken by the passage of a segment of the segmented wheel, each segment being associated with exactly one cylinder of a four-cylinder internal combustion engine. On the time axis, which shows the time t, the corresponding working order of the cylinders is additionally plotted with Roman numbers. The internal combustion engine considered in the example thus has the working game sequence IV, I, II and III. In this order, the cylinders of the four-cylinder internal combustion engine undergo their working cycles within a working cycle.

In the adaptation method described below, the characteristic of the injection valve of the cylinder I is adapted.

In three consecutive cycles 11 to 13, the injection valve of the cylinder I is first controlled in a first cycle 11 according to a drive duration. In the subsequent second cycle 12, no control of the injection valve of the cylinder I, ie the drive signal 4 has a rest 6 takes place. In the subsequent third work cycle 13, the drive signal 4 again has a drive pulse 5, ie the injection valve of the cylinder I is again driven according to a drive time, which is the same drive time as in the work cycle 11. Through the sequence of first cycle 11 to third cycle 13, the section 7, 8 and again 7 of the passage duration course 9 are effected.

In Fig. 3, the associated segment time T is plotted for each stroke of the cylinder I, II and III, with two additional Arabic numerals are added from suffix, of which the first digit for the cylinder number and the second digit for the working cycle is (1: first working game, 2: second working game, 3: third working game).

From Fig. 3 it can be seen clearly that by driving the injector of the first cylinder in the first cycle or the third cycle T11 or T13 is much shorter than the segment time T12 in the second cycle, in which the injection valve of the cylinder I is not is controlled. The shorter segment times T11 and T13 therefore arise because the cylinder I in the first working cycle 11 and in the third working cycle 13 outputs a torque. This is again due to the fact that the injection valve due to the control with a drive time a fuel mass in the combustion chamber of the cylinder I introduced.

wobei F2 einen von der Zylinderzahl abhängigen Faktor (16 bei einer Vierzylinderbrennkraftmaschine), D den Drehmomentwert, M das Trägheitsmoment der Brennkraftmaschine, dJ einen Faktor für ein durch innere Reibung der Brennkraftmaschine bedingtes Bremsmoment, Tx1 die Segmentzeit für den bestimmten Zylinder im ersten Arbeitsspiel, Tx2 die Segmentzeit für den bestimmten Zylinder im zweiten Arbeitsspiel, Tx3 die Segmentzeit für den Zylinder im dritten Arbeitsspiel, ST- die mittlere Gesamtdauer des Durchlaufs aller Segmente während eines Arbeitsspiels ohne Ansteuerung des Einspritzventils und ST+ die mittlere Gesamtdauer des Durchlaufs aller Segmente während eines der Arbeitsspiele mit Ansteuerung des Einspritzventils bezeichnet.The torque generated by this injection is now calculated according to the following equation: $$\mathrm{D}=\mathrm{F}\mathrm{Second}\mathrm{\pi },\mathrm{M}\left(\left(\mathrm{T}\mathrm{x}3-\mathrm{T}\mathrm{x}2\right)/{\left(\mathrm{S}\mathrm{T}-\right)}^3-\left(\mathrm{T}\mathrm{x}2-\mathrm{T}\mathrm{x}1\right)/{\left(\mathrm{S}\mathrm{T}+\right)}^3\right)+\mathrm{d}\mathrm{J}.$$

where F2 is a cylinder number dependent factor (16 for a four cylinder engine), D is the torque value, M is the inertia of the engine, dJ is an internal friction factor for the engine braking torque, Tx1 is the segment time for the particular cylinder in the first cycle, Tx2 the segment time for the particular cylinder in the second cycle, Tx3 the segment time for the cylinder in the third cycle, ST- the mean total duration of the passage of all segments during a cycle without actuation of the injector and ST + the average total duration of the passage of all segments during one of the working cycles referred to control of the injection valve.

ermittelt werden, wobei von einem Segmentrad mit 120 Teilsegmenten oder Zähnen ausgegangen wurde, und J das drehzahlabhängige Bremsmoment der Brennkraftmaschine bezeichnet. Dieser Wert ist zur Durchführung der Adaption im Steuergerät der Brennkraftmaschine abgelegt und stammt beispielsweise aus einer Prüfstandsvermessung.With respect to the moment of inertia of the internal combustion engine as well as the factor dJ, the statements made above for the first embodiment apply. The difference for the calculation of the factor dJ can, for example, with the equation $$\mathrm{d}\mathrm{J}=\mathrm{J}\left(120/\mathrm{S}\mathrm{T}-\right)-\mathrm{J}\left(120/\mathrm{S}\mathrm{T}+\right)$$

are determined, which was assumed by a segment wheel with 120 sub-segments or teeth, and J denotes the speed-dependent braking torque of the internal combustion engine. This value is stored to carry out the adaptation in the control unit of the internal combustion engine and comes for example from a test bench.

Analogous to the above first exemplary embodiment, a value pair is formed from the torque value and the associated activation duration. The value pairs for different activation periods then allow a correction of the reference injection valve characteristic, if necessary after conversion of the torque values into values for fuel masses.

Claims (11)

1. Method for adapting an injection valve characteristic, said characteristic representing a reference injection behaviour, of a triggered fuel injection valve of an internal combustion engine to aging-related changes or manufacturing-related variations of an actual injection behaviour, wherein

   a) during an operating state of the internal combustion engine, which operating state does not require a fuel injection, the injection valve is triggered intermittently in accordance with a trigger duration, while otherwise no fuel injection occurs, such that at least one work cycle with triggering follows or precedes at least one work cycle without triggering of the injection valve,

   b) a rotational-speed value or a value of a rotational-speed-dependent variable of the internal combustion engine is detected in each case for the work cycle with triggering and for at least one of the work cycles without triggering and

   c) a difference between the detected values is established and a correction of the injection characteristic is effected thereupon.
2. Method according to claim 1, in which a difference between the detected values is established and derivatives of a first and/or higher order are calculated therefrom.
3. Method according to claim 2, in which differences are calculated on the basis of measured segment times, difference quotients are calculated from said differences, and derivatives of a first and higher order are derived therefrom.
4. Method according to one of the preceding claims, in which an overall profile of the rotational-speed value or of the rotational-speed-dependent value is analysed using signal-analysis methods over a plurality of work cycles with and without triggering, and interference effects are identified and eliminated.
5. Method according to one of the preceding claims, in which the trigger duration is increased step-by-step.
6. Method according to one of the preceding claims, in which in step c) a turning-moment value is calculated for a turning moment which was produced by the triggering of the injection valve with the trigger duration.
7. Method according to claim 6, in which the turning-moment value is calculated in accordance with the following formula: $$\mathrm{D}=\left(\mathrm{\pi }/\mathrm{F}1\right).\mathrm{M}.\left(\mathrm{d}\mathrm{N}+-\mathrm{d}\mathrm{N}-\right)+\mathrm{d}\mathrm{J},$$

   

   
   where F1 is a factor that is dependent on a number of cylinders, D is the turning-moment value, M is a moment of inertia of the internal combustion engine, dN+ is a rotational-speed gradient of the work cycle with triggering of the injection valve, dN- is a rotational-speed gradient of one of the work cycles without triggering of the injection valve, and dJ is a factor for a braking moment which is caused by internal friction of the internal combustion engine.
8. Method according to one of the preceding claims, wherein the steps a) and b) are executed several times with an unchanged trigger duration for the purpose of noise suppression.
9. Method according to claim 6 concerning an internal combustion engine which is designed as a multi-cylinder internal combustion engine, in which a segment wheel that is driven by the internal combustion engine is sampled and a first work cycle without triggering of the injection valve of a specific cylinder, then a second work cycle with triggering of the injection valve of the specific cylinder, and then a third work cycle without triggering of the injection valve of a specific cylinder are executed, wherein a segment time is specified in at least the first, second and third work cycle for the specific cylinder, said segment time lasting for the passage of a segment of the segment wheel during the working stroke of the cylinder, and wherein the turning moment is calculated in accordance with the following equation: $$\mathrm{D}=\mathrm{F}2.\mathrm{\pi }.\mathrm{M}\left(\left(\mathrm{T}\mathrm{x}3-\mathrm{T}\mathrm{x}2\right)/{\left(\mathrm{S}\mathrm{T}-\right)}^3-\left(\mathrm{T}\mathrm{x}2-\mathrm{T}\mathrm{x}1\right)/{\left(\mathrm{S}\mathrm{T}+\right)}^3\right)+\mathrm{d}\mathrm{J},$$

   

   
   where F2 is a factor that is dependent on the number of cylinders, D is the turning-moment value, M is a moment of inertia of the internal combustion engine, dJ is a factor for a braking moment which is caused by internal friction of the internal combustion engine, Tx1 is the segment time for the specific cylinder in the first work cycle, Tx2 is the segment time for the specific cylinder in the second work cycle, Tx3 is the segment time for the cylinder in the third work cycle, ST- is the average total duration of the passage of all segments during a work cycle without triggering of the injection valve and ST+ is the average total duration of the passage of all segments during one of the work cycles with triggering of the injection valve.
10. Method according to claim 7 or 9, in which a difference between two values is established for the purpose of determining the factor for the braking moment which is caused by the internal friction of the internal combustion engine, wherein one value is assigned to one of the work cycles of the internal combustion engine without triggering of the injection valve and the other is assigned to the work cycle of the internal combustion engine with triggering of the work cycle.
11. Method according to claim 6, in which a fuel-mass value for a fuel mass that is delivered by the injection valve is derived from the turning-moment value, the fuel-mass value is assigned to the trigger duration and then used for correcting the injection valve characteristic.

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