EP2796690A1 - Control for a common rail injection system - Google Patents

Abstract

The present invention relates to a control for a common rail injection system, which includes a plurality of fuel injectors, a common fuel supply line for the fuel injectors, a high pressure pump for supplying the common fuel supply line with fuel, and a pressure sensor for determining the pressure in the common fuel supply line comprising, with a determining unit, which evaluates data of the pressure sensor and determines from the caused by an injection pressure drop in the common rail fuel during this injection actually injected fuel amount or a value derived therefrom, and with an adaptation unit, which uses the results of the determination unit to to adjust the control of the fuel injectors. The determination unit carries out at least one test injection, by means of which the determination of the actually injected fuel quantity or a value derived therefrom takes place.

Description

The present invention relates to a controller for a common rail injection system, which includes a plurality of fuel injectors, a common fuel supply line for the fuel injectors, a high pressure pump for supplying the common fuel supply line with fuel, and a pressure sensor for determining the pressure in the common fuel supply line having. In particular, it is the control of a common rail injection system of a diesel engine.

When driving an engine, the precise metering of the amount of fuel injected plays an essential role in terms of the subsequent combustion and the resulting exhaust gases. Due to production-related component controls of the fuel injectors and aging phenomena during engine operation, these must therefore be calibrated during engine operation. This means that deviations or drifts in the actually injected fuel quantity must be detected, quantified and compensated for by a corresponding adaptation of the injector control.

For this it is for example from the publications DE19726100A1 . EP894965A1 such as DE69112355T2 It is known to calculate target injection quantities on the basis of the engine operating state and to carry out the control of the fuel injectors on the basis of these desired injection quantities. In this case, during the engine operation, the pressure drop caused by the injections is evaluated in the common fuel supply line of the common-rail injection system and from this the fuel quantity actually injected in the injections is determined. In this case, the difference is formed from the pressure before the injection made with a desired injection quantity and after the injection, and thus the pressure drop caused by the injection is determined, by means of which in turn the actually injected fuel quantity is determined. Based on the results for previous fuel injections, the control of the fuel injectors for subsequent fuel injections is adjusted.

The object of the present invention is to further improve such a system based on the pressure in the common fuel supply line.

This object is achieved by a control in accordance with claim 1.

The present invention includes a controller for a common rail injection system, which includes a plurality of fuel injectors, a common fuel supply line for the fuel injectors, a high pressure pump for supplying the common fuel supply line to the fuel, and a pressure sensor for determining the pressure in the common fuel supply line having. In this case, the control comprises a determination unit which evaluates data of the pressure sensor and determines the fuel quantity actually injected during this injection or a value derived therefrom from the pressure drop in the common fuel supply caused by an injection. The controller further comprises an adaptation unit which displays the results of the determination unit used to adjust the control of the fuel injectors. According to the invention, it is provided that the determination unit carries out at least one test injection based on which the determination of the actually injected fuel quantity or a value derived therefrom takes place.

Unlike in the prior art, this does not use the fuel injections that occur during normal operation of the injection system for this determination, but rather specific test injections. This allows greater flexibility and accuracy in determining the adaptation of the injection.

In a preferred embodiment, the determination unit determines a reference measurement signal of the pressure sensor without test injection and a test measurement signal of the pressure sensor in the event of a test injection. As a result, a significantly increased accuracy compared to methods known from the prior art, which operate without a reference signal can be achieved.

This procedure is only possible in that instead of an injection used during normal engine operation, a test injection is used, which thus can be omitted without a malfunction of the engine operation in subsequent engine cycles again.

Advantageously, the determination unit for determining the pressure drop caused by an injection forms the difference between the reference measurement signal and the test measurement signal.

It can be provided that the determination unit determines the reference measurement signal and the test measurement signal in the same time interval with respect to the motor cycle. Furthermore, it can be provided that the determination unit stores the reference measurement signal and the test measurement signal under injection and / or engine operating conditions determines which are identical except for the test injection. As a result, the influence of the test injection on the pressure signal can be determined exactly by the difference formation from the reference measurement signal and the test measurement signal.

According to a preferred embodiment of the present invention, the determination unit performs a plurality of test injections, and forms an average value for determining the actually injected fuel quantity or a value derived therefrom. As a result, the accuracy in the determination can be increased.

The determination unit preferably carries out the multiple test injections in the same time interval with regard to the engine cycle and / or under identical injection and / or engine operating conditions. Further preferably, the determination unit may perform the multiple test injections with identical drive periods of the fuel injector and / or injection quantities for the respective test injections. In particular, the activation in the individual test injections can take place with identical drive signals for the fuel injector.

In a particularly preferred embodiment, the determination unit determines both the test measurement signal and the reference measurement signal several times.

According to a preferred embodiment, the determination unit carries out the at least one test injection in a predetermined time interval of the engine cycle and / or with a predetermined drive duration and / or with a predetermined injection quantity of the fuel injector. In particular, a predetermined drive signal can be used.

In one possible embodiment, the predetermined time interval and / or the predetermined activation duration and / or injection quantity and in particular the predetermined activation signal can be stored in the controller.

Preferably, the predetermined time interval and / or the predetermined drive time and / or injection quantity of the fuel injector, and in particular the predetermined drive signal, regardless of the desired for normal engine operation injection time and / or injection quantity of the injection. As a result, a test routine adapted specifically to the adaptation can be used, whereby correspondingly better reproducibility and increased accuracy are achieved.

The determination made by the determining unit may be performed during normal operation of the engine by performing the test injections in addition to the normal engine-operating injections.

In particular, the test injection may be a pre-injection or post-injection before or after the main injection. Since the pressure signal used to determine the amount of fuel injected in a test injection is influenced by both the main injections and the test injections, some time interval between main and test injections is necessary. A test injection preferably takes place at a predetermined time interval from the preceding and the following main injection.

In order to influence the engine operation as little as possible and to avoid a too long injection time, which would lead to an excessive time proximity between main and test injection, the injection quantity of the test injection is preferably selected below 100 mg, more preferably below 50 mg.

Furthermore, the injection quantity of a test injection is preferably chosen over 2 mg, more preferably over 4 mg, since even smaller injection quantities of Pressure drop is so small that the corresponding signal can hardly be distinguished from interference signals.

A typical test injection quantity may be, for example, 20 mg.

Advantageously, the controller according to the invention has an activation unit, which causes the determination unit to start the evaluation operation and to initiate a test routine in which at least one test injection is performed. The activation of the determination unit can take place, for example, at predetermined intervals.

A preferred embodiment of the controller according to the invention comprises a monitoring unit for monitoring the engine operation, which is connected to the determination unit such that the determination of the actually injected fuel quantity or the value derived therefrom is carried out by the determination unit in operating states of the engine suitable for the determination. In particular, this transient operating conditions of the engine should be avoided, since they can reduce the accuracy of the determination.

For example, it can be provided that the determination is made at a constant desired pressure in the common fuel supply line, and / or at a constant temperature in the common fuel supply line and / or at constant engine speed, and / or at constant fuel injection quantities for the normal engine operation. This is particularly advantageous if, in addition to the test measurement signal, a reference measurement signal is determined, since this must necessarily be determined in a different engine cycle, and / or if several measurements and in particular multiple test injections are performed, so that changes in operating conditions would affect the measurement.

Furthermore, the determination of the actually injected fuel quantity or a value derived therefrom can be initiated by the determination unit upon a query as to whether the engine speed is operating below a certain speed threshold.

In particular, the monitoring unit can monitor the speed of the engine and only then initiate a test routine in which at least one test injection is performed when the speed is below a certain speed threshold. Since the rotational speed and the cycle length are inversely proportional to each other, the low rotational speed has the advantage that between two main injections of the normal engine operation a correspondingly long period of time remains in which the test injection can be carried out and a corresponding pressure measurement can be carried out. As a result, the important for the accuracy of the measurement distance between the main and test injection can be met.

Particularly preferably, the determination is carried out during idle operation of the internal combustion engine.

In a preferred embodiment, the determination unit determines the pressure drop caused by an injection based on at least one measured value determined within a predetermined evaluation interval. In particular, the evaluation interval may be a predetermined period of time or one or more predetermined times. According to the invention, at least one measuring time or at least one measuring interval is defined, in which the measurement of the pressure for determining the pressure drop through the test injection is made.

Advantageously, the evaluation interval is defined in relation to the time of the triggering of the fuel injector for the test injection. Since according to the invention it is a test injection with a predetermined duration and shape does not need to be monitored to determine the time of measurement, the pressure signal to a suitable time and in particular to a decrease in the pressure level out. Rather, such an evaluation interval or such a measurement time can be determined in advance, for example, in the experiment as a function of the timing of the control of the fuel injector for the test injection. Advantageously, therefore, the evaluation interval is stored in the controller. In particular, the triggering signal of the fuel injector for triggering the test injection may trigger a measured value recording over a predetermined period of time, the evaluation interval having a predetermined time interval at the beginning of the measured value recording.

Advantageously, the evaluation interval is after the end of the activation of the fuel injector for the test injection. Advantageously, at least one measured value is thus measured after the triggering of the fuel injector for the test injection has ended. Advantageously, a certain distance is provided at the time of the end of the activation of the fuel injector in order to take into account a delay between the activation of the fuel injector and the actual pressure drop.

Furthermore, the evaluation interval can be chosen such that the measurement signal corresponds as well as possible to the static portion of the pressure drop, which was caused by the outflow of fuel from the common rail system through the test injection.

In one possible embodiment, the evaluation interval may be selected such that it does not begin until after the first damped half oscillation of the pressure signal caused by the test injection. Advantageously, the evaluation interval can be selected such that it begins only after the first damped full oscillation of the pressure signal caused by the test injection.

In a further preferred embodiment of the present invention, a plurality of measured values are averaged within the evaluation interval in order to compensate for fluctuations in the signal.

Furthermore, the test injection is preferably carried out at a time which is after the first, caused by a main injection and / or the operation of the high-pressure pump damped half-wave. This takes into account that the operation of the high-pressure pump and the main injections also influence the pressure signal dynamically. This influence should have subsided as far as possible at the beginning of the test injection. The test injection preferably takes place at a point in time which lies after the first damped full oscillation of the pressure signal caused by a main injection and / or the operation of the high-pressure pump.

As described above, the difference between a test measurement signal and a reference measurement signal is particularly preferably used to determine the pressure drop. Advantageously, the reference measurement signal is also determined over the predetermined evaluation interval. Advantageously, the measured value recording is likewise started as a function of the time within the engine cycle at which the test injection would otherwise take place. Furthermore, the evaluation interval is advantageously also defined as described above as a function of this time. In this case, a very short drive pulse can be sent to the fuel injector to determine the reference measurement signal, which is not sufficient to open this, but sets the measured value recording as in the determination of the test measurement signal in motion.

By using a reference signal, superimpositions of the pressure curve caused by the test injection can be eliminated again with the pressure curves caused by other events such as the operation of the high-pressure pump or a main injection.

Alternatively, however, it would also be conceivable to determine the difference between a value of the test measurement signal at the measurement time described above or in the evaluation interval described above with a measured value determined before the injection in order to determine the pressure drop.

In a preferred embodiment, the determination and adaptation is done individually for each fuel injector. As a result, component tolerances and individual drifts of the properties of the fuel injectors can be taken into account.

According to a further preferred embodiment, the determination and adaptation by the determination unit for a plurality of different operating points of the injection system and / or the engine takes place. In particular, the determination can be made for several different pressures in the common pressure line. Alternatively, however, it is conceivable to carry out the test injections at only one pressure value and to extrapolate them for other pressure values.

According to a further preferred embodiment, the determination and adaptation by the determination unit takes place for a plurality of different drive times and / or injection quantities of the fuel injector during the test injection.

The injection quantity of the test injections may preferably be between 2 mg and 80 mg, more preferably between 5 mg and 50 mg. Furthermore, it can be provided that the test injections extend over a range of more than 10 mg, preferably more than 20 mg and furthermore more than 30 mg.

Furthermore, the number of different activation periods and / or injection quantities is preferably between 2 and 20, more preferably between 4 and 10.

Advantageously, the determination unit for this purpose comprises a test routine, which comprises a plurality of different test injections and / or a plurality of test injections under different operating conditions of the pressure line and / or the motor performs. This makes it possible to correct the map of the respective fuel injectors not only globally by a single correction factor, but separately for different input values.

In particular, the adaptation unit can determine a correction factor, which is dependent on one or more input values of the characteristic field, which is used to control the respective fuel injectors. In particular, the correction factor may depend on the pressure in the common rail and / or on the desired activation duration and / or injection quantity of the fuel injector.

In a further preferred embodiment of the present invention, the determination of the actually injected fuel quantity or a value derived therefrom is coordinated by the determination unit with the activation of the high-pressure pump. In particular, the coordination takes place in such a way that no operation takes place in the high-pressure pump between the beginning of a test injection and the end of the associated measurement phase. Advantageously, no operation of the high pressure pump is made even during the determination of a reference measurement signal. Furthermore, the time of the test injections is preferably chosen such that a certain period of time lies between the end of the operation of the high-pressure pump and the start of the test injection.

On the one hand, such coordination can take place in that the determination unit and the drive circuit of the high-pressure pump exchange data. Alternatively, the drive circuit may also be designed so that the pressure drop caused by the test injection in the common pressure line does not lead to a start of the high-pressure pump within the associated measurement phase. In particular, the drive circuit of the high-pressure pump can react with a certain delay to a pressure drop which is longer than the measurement phase. Further alternatively, the test injections and the operation of the High-pressure pump at predetermined, sufficiently spaced points in time, in particular at predetermined, mutually offended rotational angles of the crankshaft.

In one possible embodiment of the present invention, the operation of the high-pressure pump (2) and / or the initiation of the test injection takes place within an engine cycle at respectively predetermined times and / or crankshaft angles.

In this case, in an operating phase in which test injections are carried out, the operation of the high-pressure pump can be shifted to early or late, wherein the test injection in the thus extended interval between the operation of the high-pressure pump and the main injection or in the extended interval between the main injection and the Operation of the high pressure pump takes place.

In this case, the operation of the high-pressure pump can also take place simultaneously with the main injection, so that a maximum period of time is available for the test injection.

Furthermore, it can be provided that, in an operating phase in which test injections are carried out, individual main injections and / or operating phases of the high-pressure pump are dispensed with. As a result, the time available for the test injection is extended once again.

The present invention further includes a common rail injection system having a plurality of fuel injectors, a common rail for the fuel injectors, a high-pressure pump for supplying the common rail with fuel, and a pressure sensor for determining the pressure in the common rail. The common rail injection system according to the invention It still has a control, as described in more detail above, on.

Furthermore, the present invention comprises an engine with such a common rail injection system. In particular, it may be a diesel engine.

Furthermore, the present invention comprises a mobile working device with a motor according to the invention.

Also independently of the control according to the invention, the present invention comprises a method for controlling a common rail injection system comprising a plurality of fuel injectors, a common pressure line for the fuel injectors, a high-pressure pump for supplying the common pressure line with fuel, and a pressure sensor for determining the Having pressure in the common pressure line. In this case, according to the method according to the invention, data of the pressure sensor are evaluated and the fuel quantity actually injected during this injection or a value derived therefrom is determined from the pressure drop in the common fuel supply caused by an injection. Furthermore, the results of the evaluation are used to adjust the control of the fuel injectors. According to the invention, it is provided that the determination of the actually injected fuel quantity or of a value derived therefrom is based on at least one test injection.

The method according to the invention preferably takes place in the manner described above with regard to the embodiment of the controller according to the invention. In particular, the inventive method is carried out using a controller, as described in more detail above. Advantageously, the control according to the invention for the common-rail injection system is designed so that the controller carries out all activities and steps automatically. In particular, a corresponding computer program can be provided for this purpose, which is stored in a memory of the controller and includes instructions for carrying out the method according to the invention or for implementing the controller according to the invention.

Figur 1:

ein Ausführungsbeispiel eines erfindungsgemäßen Einspritzsystems mit einem Ausführungsbeispiel einer erfindungsgemäßen Steuerung,

Figur 2:

ein Ablaufdiagramm eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens, wie es in einer erfindungsgemäßen Steuerung abläuft,

Figur 3:

zwei Diagramme, welche den Zeitverlauf einer erfindungsgemäß eingesetzten Testeinspritzung sowie des hierdurch bewirkten Test-Druckverlaufs in der gemeinsamen Kraftstoffzuleitung im Vergleich zu einem Referenz-Druckverlauf ohne Testeinspritzung zeigen,

Figur 4:

eine Darstellung eines gemäß einer ersten Alternative gewählten Auswertungsintervalls für die in Figur 3 gezeigten Druckverläufe und

Figur 5:

eine Darstellung zweier alternativer Messzeitpunkte bzw. Auswertungsintervalle für die in Figur 3 gezeigten Druckverläufe.

The present invention will now be described in more detail with reference to an embodiment and drawings. Showing:

FIG. 1:

An embodiment of an injection system according to the invention with an embodiment of a controller according to the invention,

FIG. 2:

a flowchart of an embodiment of a method according to the invention, as it runs in a controller according to the invention,

FIG. 3:

two diagrams which show the time course of a test injection used according to the invention and of the test pressure curve in the common fuel supply line as a result compared to a reference pressure curve without test injection,

FIG. 4:

a representation of a selected according to a first alternative evaluation interval for in FIG. 3 shown pressure curves and

FIG. 5:

a representation of two alternative measurement times or evaluation intervals for the in FIG. 3 shown pressure curves.

FIG. 1 shows an embodiment of an injection system according to the invention with a controller according to the invention. The common rail injection system has a plurality of injectors 11, I2 to Li, which are supplied by a common fuel supply line 1 with pressurized fuel. there a high-pressure pump 2 is provided, which supplies the common fuel supply line 1 with high pressure. Furthermore, a pressure sensor 3 for measuring the pressure in the common fuel supply line 1 is provided.

FIG. 1 FIG. 2 also shows a block diagram of an engine control unit 4 according to the invention. This first contains a conventional control block 12 in which the activation duration for the respective injector is determined from the injection quantity requested for engine operation on the basis of characteristic maps. The requested injection quantity serving as input for the control block 12 is determined, for example, on the basis of engine operating conditions and / or control signals generated by the driver, in particular from the desired rotational speed and / or the desired torque of the engine. The control block 12 can either comprise a common map 11 for all injectors, or each injector-individual maps.

The engine control unit 4 further comprises a control 5 according to the invention, which determines the actually injected fuel quantity in a determination unit 6 from the fuel pressure determined by the sensor 3 during a test injection. In an adaptation unit 7, one or more correction factors are formed from a comparison of the desired injection quantity below the actual injection quantity during the test injection, by means of which the control period determined by the control block 12 is corrected. The corrected drive time is then supplied to the injector output stage 13, which generates the direct electrical drive signals for the injectors, which are transmitted to the latter via a control line 8.

This in Fig. 1 shown embodiment of the controller according to the invention will now be described in more detail below:

The precise metering of the amount of fuel injected plays an essential role in terms of the subsequent combustion and the resulting combustion Exhaust gases. Due to production-related component issues of the fuel injectors and aging phenomena during engine operation, these must be calibrated during engine operation.

Because fuel injectors are subject to production-related component scattering, which affect the dosing accuracy. The use of the fuel system with ever higher system pressures leads to additional component drivings, which have negative effects on the exhaust behavior and the efficiency of the engine. In order to counteract these deviations, a correction of the injector control is necessary to ensure a stable engine run.

This means that deviations or drifts in the actually injected fuel quantity must be detected, quantified and compensated for by a corresponding adaptation of the injector control.

To this end, the present invention provides a strategy and control for injector diagnostics and calibration. Since an additional amount of motor sensors, e.g. additional acceleration or pressure sensors, should be avoided if possible, in this case the recourse is made to the signal of the standard common-rail pressure sensor in the high-pressure pump. The control is thus based on the evaluation of the pressure sensor signal at the high-pressure pump.

• Eine Bestimmungseinheit (6) zur Schätzung der tatsächlich eingespritzten Kraftstoffmenge. Diese Einrichtung besteht aus einer Methode, die die tatsächlich eingespritzte Kraftstoffmenge je Injektor auf Basis des jeweiligen Druckabfalls in der Kraftstoffzuleitung schätzt. Der Druckabfall wird aus dem Drucksensorsignal der Kraftstoffzuleitung bestimmt.
• Eine Adaptionseinheit (7), die auf Basis der Einspritzmengenschätzung einen Soll-/Ist-Abgleich durchführt und auf Basis des Resultats die Injektoransteuerung adaptiert.

The control (5) according to the invention, which can be integrated in the engine control (4), consists essentially of two parts, see the in Fig. 1 shown embodiment:

• A determination unit (6) for estimating the amount of fuel actually injected. This device consists of a method that determines the actual injected fuel quantity per injector based on the respective fuel quantity Pressure drop in the fuel supply estimates. The pressure drop is determined from the pressure sensor signal of the fuel supply line.
• An adaptation unit (7), which performs a target / actual adjustment on the basis of the injection quantity estimation and adapts the injector control on the basis of the result.

• Ungenauigkeiten aufgrund von Fertigungstoleranzen
• Alterungserscheinungen bzw. Verschleiß
• Düsenverkokung

Deviations or inaccuracies in the injected fuel quantity can be compensated for by the control according to the invention, which results from the following reasons:

• Inaccuracies due to manufacturing tolerances
• Aging phenomena or wear
• nozzle carbonization

Fig. 2 shows the block diagram of the control for a single injector of the common rail system. This performs test injections (10) through which the injected fuel quantity can be estimated for the respective injector.

This occurs at a static operating point of the internal combustion engine, i. at constant injector drive duration and constant fuel pressure. On the basis of this estimation, an injector-individual correction of the actuation duration is determined, by means of which the actuation characteristic field is adapted. In this case, the actually injected fuel quantity can be determined in several predetermined static operating points of the engine in order to perform a setpoint / actual adjustment.

• Eine Überwachungseinheit (9) setzt ein ok_flag auf 1, sobald sich der Motor in einem zur Durchführung der Einspritzkorrektur günstigen Betriebszustand befindet. Ist dies der Fall, so wird in einem definierten, festen Zeitintervall eine Testeinspritzung (10) in Zylinder 1,2,... mit einer vorgegebenen Ansteuerdauer bei konstantem Kraftstoffdruck durchgeführt.
• Nach einer Datenqualitätsprüfung, vor allem einer Ausreißerbehandlung zur Identifizierung schlechter Messungen, wird der Signalverlauf in Buffer 1 zwischengespeichert.
• In direktem Anschluss wird der Drucksensorverlauf im selben Zeitintervall ohne Einspritzung aufgezeichnet. Dieser Signalverlauf dient als Referenz und wird in Buffer 2 abgelegt.
• Sind beide Buffer gefüllt, so wird die Schätzung der tatsächlich eingespritzten Kraftstoffmenge durchgeführt und das Ergebnis zwischengespeichert.
• Auf Basis der Schätzergebnisse zu unterschiedlichen Testeinspritzungen wird eine Injektor-individuelle Korrektur der Ansteuerdauer ermittelt.

The control works as follows:

• A monitoring unit (9) sets an ok_flag to 1 as soon as the engine is in a favorable operating condition for performing the injection correction located. If this is the case, then in a defined, fixed time interval, a test injection (10) is carried out in cylinders 1, 2,... With a predetermined activation duration at constant fuel pressure.
• After a data quality check, especially an outlier treatment to identify bad measurements, the waveform in buffer 1 is buffered.
• In direct connection, the pressure sensor profile is recorded in the same time interval without injection. This waveform serves as a reference and is stored in buffer 2.
• If both buffers are filled, then the estimate of the actually injected fuel quantity is carried out and the result is buffered.
• On the basis of the estimation results for different test injections, an injector-individual correction of the activation duration is determined.

Input variables of the monitoring unit (9) are the injection quantity for the normal engine operation and / or the temperature of the fuel. It is checked whether the change of these quantities is below a predetermined threshold, i. Whether engine operation is changing and / or the fuel injection system is in a steady state. The speed of the internal combustion engine serves as a further input variable. It is checked whether this is below a predetermined threshold, since at low speeds available for the test injection period is greater than at high speeds. The test operation therefore preferably takes place when the engine is idling.

The estimation of the injection amount is based on the determination of the pressure drop resulting from the fuel injection in the common rail. This can be determined from the two pressure curves from buffer 1 and buffer 2.

mit $$\mathrm{\Delta }p\left(t\right)=p_{\mathrm{ref}}\left(t\right)-p\left(t\right)$$

The approach for determining the actually injected fuel mass is given by GI. (1), $$\mathrm{\Delta }m=-{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="imgf0004.png"\; state="\{\{state\}\}">V</figure-callout>}}_0\cdot \beta \cdot \rho \cdot \mathrm{\Delta }p$$

With $$\mathrm{\Delta }p\left(t\right)=p_{\mathrm{ref}}\left(t\right)-p\left(t\right)$$

Here, V _{0 represents} the known raw volume of the high-pressure side of the injection system, β the compressibility coefficient and ρ the fuel density at the system pressure p and the temperature T.

The pressure difference Δ p can be determined by averaging from a plurality of measurements. In Fig. 3 is in a solid line as a test waveform (40) the share average from 10 measurements of the course of the pressure sensor signal at a constant test injection (10), here a pilot injection, each with a constant drive time shown. The dash mean value from 10 measurements of the signal profile in which no test injection (10) has been carried out is shown as a reference signal course (30) in a dashed line. From these measurements, the actual injected fuel mass can be determined.

In the exemplary embodiment, the measured value recording is triggered by the drive pulse of the fuel injector for triggering the test injection (10). This represents a hardware triggering, which triggers the acquisition of the measured value by the A / D converter provided for measuring value recording.

It is in Figure 3 even when generating the reference measurement signal to see a small rash in the drive signal. This is a very short actuation time of the fuel injector, in which there is no injection. This means that this short excitation is not enough to open the injector. This very short drive pulse is used to trigger the measured value recording to determine the reference measurement signal.

The pressure difference Δ p is then given as the difference between the test pressure signal 40 and the reference pressure signal 30, which difference in a previously defined evaluation interval 50 which is determined from the start of control, that is, energization of the injector depends.

The determination of the measured values takes place in a fixed time interval [t ₁ , t ₂ ] (evaluation interval), which in Fig. 4 is shown. The evaluation interval (50) depends on the activation time, for example on the start or end of the test injection (10), and takes into account the time delay (60) between this activation time and the pressure drop triggered by the test injection. Furthermore, the evaluation interval should be selected such that the pressure signal within the evaluation interval (50) does not depend on a start of the high-pressure pump or other injections, such as, for example, the main injection (20). Alternatively or additionally, a test injection could also take place after the main injection (20).

The evaluation interval may depend on the injection duration and / or quantity of the test injection (10). In this case, the evaluation interval in the exemplary embodiment has been selected such that it is used only after the first damped half oscillation of the pressure signal (40) and preferably after the first full oscillation of the pressure signal (40) in order to measure as far as possible only the static portion of the pressure drop.

In this case, the pressure signal represents a superimposition of the signals generated by the main injections, the operation of the high-pressure pump and the test injections. Therefore, a certain time interval between the test injection and the preceding operation of the high-pressure pump or the preceding main injection is necessary. Preferably, the test injection should take place only after one or two, caused by a main injection and / or the operation of the high-pressure pump, damped full vibrations.

In the exemplary embodiment, the operation of the high-pressure pump (2), the main injection (20) and the initiation of the test injection (10) in each case take place at predetermined times and / or crankshaft angles within the engine cycle. In this way it can be ensured that the test injection takes place with a sufficient time interval to the preceding and following events.

In order to avoid too short and too long injection times, which would lead to a high degree of inaccuracy in the measurement or to a large time proximity between main and test injection, the injection quantities of the test injections are chosen in the embodiment between 4 mg and 5 mg, continue preferably below 50mg.

It is at too high speeds and / or an engine with many cylinders only a very short time window between the operation of the high-pressure pump and the main injection for the test injection and the subsequent measurement phase available. To increase this amount of time, the operation of the high pressure pump may be advanced if the test injection is pilot injection, or late if the test injection is post injection. Such an adjustment can be made either only in the operating phases in which test injections are made, or generally. Possibly. In this case, the operation of the high-pressure pump and the main injection can even take place simultaneously, so that the time window for the test injection becomes maximum.

Alternatively or additionally, in an operating phase in which test injections are carried out, it is possible to dispense with individual main injections and / or operating phases of the high-pressure pump. This also extends the time available for the test injection.

According to the present invention, the actual injection quantity is now calculated from the pressure difference caused by the test injection. In the exemplary embodiment, the calculation of the pressure difference Δ p takes place from a discrete-time pressure curve p (n) and the reference pressure curve p _ref (n) , with n as a discrete time index, by an arithmetic mean value formation in a previously defined discrete time interval [ n ₁ , n ₂ ]. , which depends on the start of control, ie start of energization of the injector.

The signal evaluation corresponds to the calculation of the pressure drop according to GI (3). $$\mathit{\Delta }p=\frac{1}{n_2-{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_1+1}\cdot \underset{n=n_1}{\overset{n_2}{\Sigma }}\left(p_{\mathrm{ref}}\left(n\right)-p\left(n\right)\right)$$

On the basis of the determined pressure drop from equation (3), the actually injected fuel mass is determined on the basis of equation (1).

The process of estimating the actual injected fuel mass using the specified procedure is repeated for several drive times at a constant predetermined fuel pressure.

The estimated fuel quantities are buffered for each injector, see Fig. 2 , From these data, the injector-individual correction values α for the activation duration are then determined on the basis of a comparison with the desired fuel quantities.

und damit der Fläche zwischen den beiden Kurven entspricht, siehe Fig. 5.As an alternative to the averaging given in equation (3), the integral of the pressure profile drop A can also be determined, which in the discrete-time case is the sum $$A=\underset{n=n_1}{\overset{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_2}{\Sigma }}\mathrm{\Delta }p\left(n\right)$$

and thus corresponds to the area between the two curves, see Fig. 5 ,

Furthermore, the maximum Δ p _{max of} the pressure profile drop can also be determined, which is also shown in FIG Fig. 5 is shown.

In the latter two cases, the characterization of the actual state of the respective injector is not based on the injection quantity, but on the basis of the auxiliary quantities A and Δ p _max by which the injector drift is detected and compensated for by the injector individual correction values α for the actuation duration.

The corrected drive duration corresponds to a function from the respective drive duration TOC and the injector-individual correction α . $${\mathrm{TOC}}_{\mathrm{corrected}}=\mathrm{f}\left(\mathrm{TOC}\alpha \right)$$

If the injector-individual correction values α are determined as described above for a plurality of different activation periods of the test injection, then α can be a function of the activation duration α (TOC) .

Furthermore, the injector-individual correction values α can be determined in a plurality of predetermined static operating points of the engine, in particular at different system pressures p. In this case, the injector individual correction values α represent themselves as a characteristic diagram. Alternatively, a determination is possible with only one static operating point of the engine, in particular at a system pressure p, where the correction values for other static operating points of the engine, in particular other system pressures p, are possible so extrapolated certain correction values.

Alternatively, the correction values can also be used to correct the injector-specific characteristic maps (11) stored in the control for determining the activation period TOC from the desired injection quantity.

1. i. Die erfindungsgemäße Steuerung ermittelt in einem fixen Zeitintervall [t₁,t₂] (Auswertungsintervall) die tatsächlich eingespritzte Kraftstoffmenge aus dem Druckabfall in der Kraftstoffzuleitung.
2. ii. Erfindungsgemäß wird eine Testeinspritzung durchgeführt, falls sich das Aggregat in einem dazu günstigen Betriebspunkt befindet (hierzu kann der Motorlauf überwacht werden).
3. iii. Die Druckverläufe zu M Testeinspritzungen bei konstanter Ansteuerdauer und konstant vorgegebenen Kraftstoffdruck werden aufgezeichnet und gemittelt.
4. iv. Durch den Vergleich mit der Referenzaufzeichnung (M Druckverläufe ohne Testeinspritzung) wird der effektive Druckabfall Δ p bestimmt.
5. v. Anhand von GI.(1) und (2) wird aus den aufgezeichneten Druckverläufen die tatsächlich eingespritzte Kraftstoffmasse bestimmt (keine Hilfsgröße sondern die Kraftstoffmasse, welche direkt interpretiert werden kann).
6. vi. Zur Aufzeichnung der Drucksensorsignale ist kein zusätzlicher Sensor d.h. keine konstruktive Änderung am Einspritzsystem notwendig. Es sind keine zusätzlichen Sensoren, Drosseln oder Hydrospeicher zur Realisierung der Einspritzmengenschätzung notwendig. Die Einspritzmenge wird rein aus dem Sensorsignal ermittelt, welches der standardmäßig verbaute Drucksensor liefert.
7. vii. Anhand der ermittelten tatsächlichen Einspritzmengen in verschiedenen Arbeitspunkten wird eine Injektor-individuelle Ansteuerkorrektur bestimmt, welche für zukünftige Einspritzungen angewandt wird.
8. viii.Die Einspritzmenge wird für jeden der verbauten Injektoren einzeln und unabhängig voneinander ermittelt.
9. ix. Die Einspritzmengenschätzung wird auf Basis einer Testeinspritzung, d.h. einer Vor- oder Nacheinspritzung durchgeführt und lässt sich im normalen Motorlauf durchführen.
10. x. Die erfindungsgemäße Steuerung kann auf einem Motorsteuergerät integriert werden
    alternativ zu iv. kann das Integral des Druckverlaufabfalls A bestimmt werden, und/oder das Maximum Δ p _max des Druckverlaufabfalls.
11. xi. das falls wie in Punkt xi vorgegangen wird, erfolgt die Charakterisierung des Ist-Zustands des jeweiligen Injektors nicht anhand der Einspritzmenge, sondern anhand der Hilfsgrößen A bzw. Δ p _max durch die die Injektordrift erkannt und kompensiert wird.

The essential aspects of the control according to the invention for compensating deviations and drifts in the injection quantity for direct injection systems on the basis of the injection-related pressure drop in the fuel supply line are again shown below independently of the exemplary embodiment illustrated above:

1. i. The controller according to the invention determines the actually injected fuel quantity from the pressure drop in the fuel supply line in a fixed time interval [t ₁ , t ₂ ] (evaluation interval).
2. ii. According to the invention, a test injection is carried out if the unit is in a favorable operating point (this can be the engine running monitored).
3. iii. The pressure curves for M test injections at a constant activation duration and a constant preset fuel pressure are recorded and averaged.
4. iv. By comparison with the reference record (M pressure curves without test injection), the effective pressure drop Δ p is determined.
5. v. Based on GI. (1) and (2), the actually injected fuel mass is determined from the recorded pressure curves (no auxiliary variable but the fuel mass, which can be interpreted directly).
6. vi. For recording the pressure sensor signals no additional sensor, ie no structural change to the injection system is necessary. There are no additional sensors, throttles or hydraulic accumulator necessary to realize the injection quantity estimation. The injection quantity is determined purely from the sensor signal which the standard built-in pressure sensor supplies.
7. vii. On the basis of the determined actual injection quantities at different operating points, an injector-individual drive correction is determined, which is used for future injections.
8. viii.The injection quantity is determined individually and independently for each of the installed injectors.
9. ix. The injection amount estimation is performed on the basis of a test injection, ie, a pre-injection or a post-injection, and can be performed during normal engine running.
10. x. The control according to the invention can be integrated on an engine control unit
    alternatively to iv. the integral of the pressure gradient drop A can be determined, and / or the maximum Δ p _{max of} the pressure profile drop.
11. xi. if the procedure is as in point xi, the characterization of the actual state of the respective injector is not based on the injection quantity, but on the basis of the auxiliary quantities A and Δ p _max by which the injector drift is detected and compensated.

Particularly preferably, the essential aspects presented above are realized in this way, as was described at the beginning in general and above in more detail in the exemplary embodiment.

Claims (15)

Control for a common-rail injection system comprising a plurality of fuel injectors (I1, I2, ..Ii), a common fuel supply line (1) for the fuel injectors, a high-pressure pump (2) for supplying the common fuel supply line with fuel, and a pressure sensor (3) for determining the pressure in the common fuel supply line,
with a determination unit (6) which evaluates data of the pressure sensor (3) and determines the fuel quantity actually injected during this injection or a value derived therefrom from the pressure drop in the common fuel supply line caused by an injection, and with an adaptation unit (7) the results of the determination unit used to adjust the control of the fuel injectors, characterized
that the determination unit (6) performs at least one test injection (10), based on which the determination of the actually injected fuel quantity or a value derived therefrom is carried out. Control according to claim 1, wherein the determination unit (6) determines a reference measurement signal (30) of the pressure sensor (3) without test injection and a test measurement signal (40) of the pressure sensor upon successful test injection (10), wherein the determination unit (6) Determining the pressure drop caused by an injection (10) advantageously the difference from the reference measurement signal and the test measurement signal draws. Control according to claim 2, wherein the determination unit (6) determines the reference measurement signal (30) and the test measurement signal (40) in the same time interval with respect to the motor cycle, and / or wherein the determination unit (6) converts the reference measurement signal ( 30) and the test measurement signal (40) under injection and / or engine operating conditions, which are identical except for the test injection (10). Control according to one of the preceding claims, wherein the determination unit (6) performs a plurality of test injections (10) and an average value for determining the actually injected amount of fuel or a value derived therefrom, wherein the determination unit (6), the plurality of test injections (10) preferably in the same Time interval with respect to the engine cycle and / or under identical injection and / or engine operating conditions makes and / or with identical drive times and / or injection quantities of fuel injector, in particular with identical drive signals, wherein the determination unit (6) further preferably both the test measurement signal ( 40) and the reference measurement signal (30) determined several times. Control according to one of the preceding claims, wherein the determining unit (6) the at least one test injection (10) in a predetermined Time interval and / or with a predetermined drive time and / or injection quantity of the fuel injector, in particular with a predetermined drive signal, performs
wherein advantageously the predetermined time interval and / or the predetermined drive duration and / or injection quantity of the fuel injector, in particular the predetermined drive signal, is independent of the desired for normal engine operation injection time and / or injection quantity. Control according to one of the preceding claims, wherein the test injection (10) is a pre-injection or post-injection taking place before and after the main injection (20), respectively. Control according to one of the preceding claims, comprising a monitoring unit (9) for monitoring the engine operation, which is in communication with the determining unit (6) such that the determination of the actually injected fuel quantity or a value derived therefrom by the determining unit is suitable for the determination Operating conditions of the engine is performed, in particular at a constant pressure and / or constant temperature in the common fuel supply, constant speed and / or constant fuel injection amount for normal engine operation, the determination is carried out in particular over several engine cycles, and / or wherein the initiation of the determination actually injected fuel quantity or a value derived therefrom by the determination unit is based on a query whether the engine speed is below a certain speed threshold, the determination favors In idle mode of the internal combustion engine takes place. Control according to one of the preceding claims, wherein the determination unit (6) determines the pressure drop caused by an injection based on at least one within a predetermined evaluation interval (50). lying measured value of a test measurement signal (40) of the pressure sensor (3) when test injection (10) is determined, wherein the evaluation interval (50) is advantageously defined with respect to the timing of the control of the fuel injector for the test injection (10), wherein the evaluation interval (50) is advantageously after the end of the control of the fuel injector for the test injection, and / or wherein the evaluation interval is advantageously selected so that it begins after the first, caused by the test injection attenuated half and preferably full vibration of the pressure signal, preferably a plurality of measured values are averaged within the evaluation interval, and / or wherein the test injection takes place at a time which is after the first, caused by the main injection and / or operation of the pump damped half and preferably full vibration of the pressure signal. Control according to one of the preceding claims, wherein the determination and adaptation for each fuel injector (I1, I2, ..Ii) is done individually. Control according to one of the preceding claims, wherein the determination and adaptation takes place for a plurality of different operating points, in particular for a plurality of different pressures in the common fuel supply line (1) and / or for several different drive times and / or injection quantities of the fuel injector during the test injection, wherein the Injection amount of the test injections preferably between 2 mg and 80 mg, more preferably between 5 mg and 50 mg and / or wherein the number of different drive times and / or injection amounts between 2 and 20, preferably between 4 and 10. Control according to one of the preceding claims, wherein the determination of the actually injected fuel quantity or a derived value by the determining unit (6) with the drive circuit of the high-pressure pump (2) is coordinated, advantageously between the start of a test injection (10) and the end of the associated Measuring phase (50) no operation of the high-pressure pump takes place, wherein further, when determining a reference measuring signal (30) of the pressure sensor without test injection advantageously also during the corresponding reference period no operation of the high-pressure pump. Control according to one of the preceding claims, wherein the operation of the high pressure pump (2) and / or the initiation of the test injection takes place within an engine cycle at predetermined times and / or crankshaft angles, wherein advantageously in an operating phase in which test injections are made, the operation of High pressure pump is shifted to early or late, the test injection is in the thus extended interval between the operation of the high-pressure pump and the main injection and in the extended interval between main injection and the operation of the high-pressure pump, and / or wherein in an operating phase, in which Test injections are made, is dispensed to individual main injections and / or operating phases of the high-pressure pump. Common rail injection system, which has a plurality of fuel injectors (I1, I2, ..Ii), a common fuel supply line (1) for the fuel injectors, a high-pressure pump (2) for supplying the common fuel supply line with fuel, and a pressure sensor ( 3) for determining the pressure in the common fuel supply line, with a controller according to one of the preceding claims. Engine with a common rail injection system according to claim 13. Method for controlling a common-rail injection system, which comprises a plurality of fuel injectors (I1, I2,... Ii), a common fuel feed line (1) for the fuel injectors, a high-pressure pump (2) for supplying the common fuel feed line with fuel, and a pressure sensor (3) for determining the pressure in the common fuel supply line, in particular using a controller according to one of claims 1 to 12,
wherein data of the pressure sensor (3) is evaluated and determined from the pressure drop caused by an injection in the common fuel supply line (1) the actually injected during this injection amount of fuel or a value derived therefrom,
and wherein the results of the evaluation are used to adjust the control of the fuel injectors (I1, I2, ..Ii),
characterized,
in that the determination of the actually injected fuel quantity or of a value derived therefrom takes place on the basis of at least one test injection (10).

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