EP1718854B1 - Method and device for determining the charging flanks of a piezoelectric actuator - Google Patents

Method and device for determining the charging flanks of a piezoelectric actuator Download PDF

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Publication number
EP1718854B1
EP1718854B1 EP05701432A EP05701432A EP1718854B1 EP 1718854 B1 EP1718854 B1 EP 1718854B1 EP 05701432 A EP05701432 A EP 05701432A EP 05701432 A EP05701432 A EP 05701432A EP 1718854 B1 EP1718854 B1 EP 1718854B1
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EP
European Patent Office
Prior art keywords
voltage
actuator
threshold
charging
switch
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EP05701432A
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German (de)
French (fr)
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EP1718854A1 (en
Inventor
Wolfgang Stoecklein
Holger Rapp
Kai Sutter
Andreas Rau
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Robert Bosch GmbH
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Robert Bosch GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/20—Output circuits, e.g. for controlling currents in command coils
    • F02D41/2096—Output circuits, e.g. for controlling currents in command coils for controlling piezoelectric injectors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/20—Output circuits, e.g. for controlling currents in command coils
    • F02D2041/202—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit
    • F02D2041/2051—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit using voltage control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/22—Safety or indicating devices for abnormal conditions
    • F02D41/221—Safety or indicating devices for abnormal conditions relating to the failure of actuators or electrically driven elements

Definitions

  • the invention relates to a method and a device for determining the charging flank of a piezoelectric actuator of at least one injector, with which an amount of liquid is injected under high pressure into a cavity, in particular a combustion chamber of an internal combustion engine.
  • From the DE 100 32 022 A1 shows a method for determining the drive voltage for a piezoelectric actuator of an injection valve, in which before the next injection initially the pressure in a hydraulic coupler is measured indirectly.
  • the pressure is measured by the fact that the piezoelectric actuator is mechanically coupled to the hydraulic coupler, so that the pressure induces a corresponding voltage in the piezo-actuator.
  • This induced voltage is used before the next injection process to correct the drive voltage for the actuator.
  • injectors are used for example in common rail systems.
  • the pressure in the hydraulic coupler also depends on the rail pressure, so that the drive voltage is varied as a function of the rail pressure.
  • the voltage requirement of a piezoelectric actuator depends primarily on the pressure in the valve chamber and on the linear expansion of the piezoelectric actuator.
  • the voltage necessary for the proper operation of the injector at an operating point is the so-called voltage requirement, that is to say the relationship between voltage and stroke at a certain force, which is proportional to the rail pressure.
  • the derivation of the current voltage requirement of an injector from the voltage difference between maximum actuator voltage and stationary end voltage is for example from DE 103 15 815.4 known.
  • the charging edge It is also known to measure the charging edge to measure the voltage of the actuator shortly before the start of the discharge and regulate it to a desired value.
  • the manipulated variable used for this purpose is the so-called switch-off voltage, that is to say the voltage at which the charging process is terminated.
  • the duration of the charging edge is set to a predetermined nominal value of typically 100 microseconds.
  • a method for adjusting the charging voltage in which the voltage of a piezo stack is compared with a voltage stored in a sample-and-hold circuit, is compared by means of a comparison circuit.
  • a control circuit terminates a charge phase of the piezo stack.
  • the energy charged in the piezo stack can be made equal to the energy charged before the discharge. Even if the piezo stack is switched to a store when unloading, the energy of the piezo stack can be kept constant in this way.
  • the invention is based on the object to set the charging edge at each injector so that the influence of parameter tolerances, which influence the valve movement, can be kept as low as possible and in particular can be reduced compared to known from the prior art methods.
  • This object is achieved by a method and a device for determining the charging edge of a piezoelectric actuator of the type described above in that the difference between a cut-off voltage threshold and a stationary end voltage is detected and regulated to a predefinable setpoint.
  • the basic idea of the invention is accordingly to keep constant the difference between the switch-off voltage threshold, that is to say the voltage at which the charging process is terminated, and the stationary end voltage, that is to say the voltage of the actuator shortly before the discharge process starts.
  • the difference between the switch-off voltage threshold and the voltage of the actuator shortly before the start of the discharge process is a measure of the change in length of the actuator after the end of the charging edge and is thus again a measure of the way the switching valve after the end of the charging edge until it reaches its Must cover the stroke stop. If this difference is adjusted to a constant value, the switching valves of all injectors at the end of the loading flank have a uniform distance from their respective stroke stop.
  • the difference between the switch-off voltage threshold and the voltage of the actuator shortly before the start of the discharge by varying the switch-off threshold voltage to regulate the specifiable setpoint.
  • This embodiment is particularly suitable when the specification of the charging current can not be sufficiently finely quantized or given injector-individual. It is also advantageous that a variation of an already known and therefore not additionally detected size takes place.
  • the charging time is preferably adjusted to its desired value by varying the charging current.
  • the duration of the charging process is therefore regulated by varying the current threshold to a desired value. In this case, only the accuracy of the set charging time depends on how exactly the current threshold can be specified, and whether this injector-individual and thus cylinder-individually possible.
  • Fig. 1 shows a schematic representation of a known from the prior art injection valve 1 with a central bore.
  • a control piston 3 introduced with a piezoelectric actuator 2 in the central bore, wherein the actuating piston 3 is fixedly connected to the actuator 2.
  • the actuating piston 3 closes upwards a hydraulic coupler 4, while at the bottom an opening with a connecting channel to a first seat 6 is provided, in which a piston 5 is arranged with a valve closing member 12.
  • the valve closing member 12 is formed in this embodiment as a double-closing control valve, but it can also be designed as a simple closing control valve. It closes the first seat 6 when the actuator 2 is at rest.
  • a nozzle needle 11 is arranged in a corresponding channel, which closes or opens the outlet in a high pressure channel (common rail pressure) 13, depending on which control voltage U is present.
  • the high pressure is supplied through the medium to be injected, for example fuel for an internal combustion engine, via an inlet 9, via an inlet throttle 8 and an outlet throttle 10, the inflow amount of the medium in the direction of the nozzle needle 11 and the hydraulic coupler 4 is controlled.
  • the hydraulic coupler 4 has the task on the one hand to increase the stroke of the piston 5 and on the other hand to decouple the control valve from the static temperature expansion of the actuator 2. The refilling of the coupler 4 is not shown here.
  • a high pressure which may be in the common rail system, for example, between 200 and 2000 bar. This pressure acts against the nozzle needle 11 and keeps it closed, so that no fuel can escape. If, as a result of the control voltage U, the actuator 2 is actuated, and thus the closure member 12 is moved in the direction of the second seat, the pressure in the high-pressure region is reduced and the nozzle needle 11 releases the injection channel.
  • P 1 is the so-called coupler pressure, as it is present in the hydraulic coupler 4. In the coupler 4 is set without control U, a stationary pressure P 1 . After discharging the actuator 2, the coupler pressure P 1 is approximately 0 and is raised again by refilling.
  • the stroke and the force of the actuator 2 now correlate with the voltage with which the actuator 2 is charged. Since the force is proportional to the rail pressure, the voltage for a required Aktorhub for safe reaching the seat 7 must be adjusted depending on the rail pressure.
  • the voltage necessary for the proper operation of the injection valve or injector 1 at an operating point is the so-called voltage requirement, that is to say the relationship between voltage and stroke at a certain force, which is proportional to the rail pressure. From the DE 103 158 15.4 shows how can be derived from the voltage difference between maximum actuator voltage and steady-state voltage of the individual, current voltage requirement of an injector.
  • a voltage U rule of the actuator 2 is measured shortly before the start of the discharge process and adjusted to a desired value.
  • the manipulated variable used for this purpose is the so-called switch-off voltage threshold U switch-off, that is to say the voltage at which the charging process is terminated.
  • the duration of the charging edge is set to a setpoint ⁇ t L of typically 100 microseconds. This setting is done either by control or by controlling a switching threshold I s for the charging current, which thus serves as a manipulated variable. To vary the charging time .DELTA.t L so the charging current I is varied.
  • the switching valves of all injectors at the end of the loading flank have a uniform distance from their stroke stop. Moreover, if the duration of the charging process is kept constant, it is ensured that this uniform distance is achieved in each case at a defined time after the start of control.
  • the lifting movement of the switching valve 12 is practically independent of parameters such as actuator idle stroke, actuator stiffness, stiffness of the transmission chain actuator valve, seat diameter of the valve, etc. Or, in other words, the switching valve movements of different injectors can be set to a same course, namely without these parameters need to be known.
  • a first embodiment shown in FIG Fig. 3 the difference between the cut-off voltage and the voltage of the actuator 2 is controlled shortly before the start of the discharge by changing the manipulated variable I s , the duration of the charging edge is fixed by stopping the charging after a predetermined period of time .DELTA.t L.
  • a circuit unit 310 is provided for a feedforward control for the manipulated variable I s , to which the rail pressure P rail is supplied as an input variable.
  • a circuit unit 320 is provided, which shut a controller for the difference of the cut-off voltage U and the Voltage of the actuator 2 shortly before the start of the discharge process U rule forms, which is fed to a predefinable setpoint input.
  • the outputs of the circuit units 310 and 320 are added and fed to a drive module 330, which in turn drives a piezo output stage 335, which supplies the actuator voltage U and the actuator current I of the actuator 2.
  • the piezo output stage 335 supplies the switch- off voltage U switch-off and the voltage of the actuator 2 shortly before the start of the discharge process U rule , the difference of which is formed in a switching point 340. This difference is supplied to the circuit unit 320.
  • the regulation is now carried out by varying the manipulated variable I s . If this manipulated variable of the current increases, then the voltage to which the actuator 2 is charged increases, the remaining path of the valve after the end of the charging process drops and thus also the voltage difference to be adjusted.
  • the in Fig. 4 shown in FIG Fig. 4 , the schematic unit to a controller for the charging time 410, to which a predetermined setpoint can be fed.
  • a circuit unit 420 is s provided for the pilot control of the threshold current I which is supplied as an input variable to the rail pressure p rail and a circuit unit 430, which shut a controller for the difference of the Abschaltschreibsschwelle U and the voltage of the actuator 2 just before the start the discharging U rule comprises further a circuit unit 440 for pilot control of the U Abschaltschreibsschwelle shutdown.
  • the controller 430 becomes outputted value and the output from the feedforward control for the switch-off voltage 440 value U abschalt added and this value of the switch- off threshold U disconnected a control module 460 which controls the actuator 2 via a piezo amplifier 465, that is, the actuator voltage U and the actuator current I is available ,
  • the piezo output stage 465 also outputs a signal for the duration of the charging process, which is supplied to the circuit unit 410, which forms the regulator for the charging time.
  • the control circuit for the difference U shutoff - U rule is only activated when a control condition is met, for example, that it is checked whether the activation duration exceeds a threshold value or whether the injection quantity setpoint exceeds an injection amount threshold. If the controller is inactive, the manipulated variables are "frozen" as a function of the prevailing rail pressure. This avoids that the control reacts to after the end of the charging several hundred microseconds lasting ringing of the actuator 2, which are reflected in the voltage curve of the actuator.
  • the respective manipulated variable can set the difference U Abtician - U rule to introduce a rail horrine diagnostic threshold, when they reach the associated injector is detected as defective.
  • This information can be read out via a diagnostic interface, for example during maintenance of the internal combustion engine, and this greatly simplifies troubleshooting.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Abstract

The invention relates to a method for determining the charging flank of a piezoelectric actuator (2) of at least one injector with which a quantity of liquid is injected under high pressure into a cavity, particularly into a combustion chamber of an internal combustion engine. The invention is characterized in that the difference between a cutoff voltage threshold (Ucutoff) and a voltage of the actuator (2) is adjusted to a predeterminable set value shortly before the start of the discharging process (Uadjust).

Description

Stand der TechnikState of the art

Die Erfindung betrifft ein Verfahren und eine Vorrichtung zum Bestimmen der Ladeflanke eines piezoelektrischen Aktors wenigstens eines Injektors, mit dem eine Flüssigkeitsmenge unter Hochdruck in einen Hohlraum, insbesondere einen Brennraum einer Brennkraftmaschine eingespritzt wird.The invention relates to a method and a device for determining the charging flank of a piezoelectric actuator of at least one injector, with which an amount of liquid is injected under high pressure into a cavity, in particular a combustion chamber of an internal combustion engine.

Aus der DE 100 32 022 A1 geht ein Verfahren zur Bestimmung der Ansteuerspannung für einen piezoelektrischen Aktor eines Einspritzventils hervor, bei dem vor dem nächsten Einspritzvorgang zunächst indirekt der Druck in einem hydraulischen Koppler gemessen wird. Der Druck wird dadurch gemessen, dass der piezoelektrische Aktor mechanisch mit dem hydraulischen Koppler gekoppelt ist, so dass der Druck eine entsprechende Spannung im Piezo-Aktor induziert. Diese induzierte Spannung wird vor dem nächsten Einpritzvorgang zur Korrektur der Ansteuerspannung für den Aktor verwendet. Derartige Injektoren werden beispielsweise in Common-Rail-Systemen verwendet. Der Druck in dem hydraulischen Koppler hängt dabei unter anderem auch von dem Raildruck ab, so dass die Ansteuerspannung in Abhängigkeit von dem Raildruck variiert wird. Der Spannungsbedarf eines piezoelektrischen Aktors hängt in erster Linie vom Druck im Ventilraum sowie von der Längenausdehnung des piezoelektrischen Aktors ab. Die zum ordnungsgemäßen Betrieb des Injektors an einem Arbeitspunkt notwendige Spannung ist der sogenannte Spannungsbedarf, das heißt der Zusammenhang zwischen Spannung und Hub bei einer bestimmten Kraft, die proportional zum Raildruck ist. Die Ableitung des aktuellen Spannungsbedarfs eines Injektors aus der Spannungsdifferenz zwischen maximaler Aktorspannung und stationärer Endspannung ist zum Beispiel aus der DE 103 15 815.4 bekannt.From the DE 100 32 022 A1 shows a method for determining the drive voltage for a piezoelectric actuator of an injection valve, in which before the next injection initially the pressure in a hydraulic coupler is measured indirectly. The pressure is measured by the fact that the piezoelectric actuator is mechanically coupled to the hydraulic coupler, so that the pressure induces a corresponding voltage in the piezo-actuator. This induced voltage is used before the next injection process to correct the drive voltage for the actuator. Such injectors are used for example in common rail systems. Among other things, the pressure in the hydraulic coupler also depends on the rail pressure, so that the drive voltage is varied as a function of the rail pressure. The voltage requirement of a piezoelectric actuator depends primarily on the pressure in the valve chamber and on the linear expansion of the piezoelectric actuator. The voltage necessary for the proper operation of the injector at an operating point is the so-called voltage requirement, that is to say the relationship between voltage and stroke at a certain force, which is proportional to the rail pressure. The derivation of the current voltage requirement of an injector from the voltage difference between maximum actuator voltage and stationary end voltage is for example from DE 103 15 815.4 known.

Bekannt ist auch, zum Bestimmen der Ladeflanke die Spannung des Aktors kurz vor Beginn des Entladevorgangs zu messen und auf einen Sollwert einzuregeln. Als Stellgröße hierfür dient die sogenannte Abschaltspannung, das heißt die Spannung, bei deren Erreichen der Ladevorgang abgebrochen wird. Dabei wird zusätzlich die Dauer der Ladeflanke auf einen vorgegebenen Sollwert von üblicherweise 100 Mikrosekunden eingestellt.It is also known to measure the charging edge to measure the voltage of the actuator shortly before the start of the discharge and regulate it to a desired value. The manipulated variable used for this purpose is the so-called switch-off voltage, that is to say the voltage at which the charging process is terminated. In addition, the duration of the charging edge is set to a predetermined nominal value of typically 100 microseconds.

Aus der nicht vorveröffentlichten DE 103 40 137.7 ist es ferner bekannt, den Sollwert für die Spannung des Aktors kurz vor Beginn des Entladevorgangs für jeden Injektor individuell an seinen Spannungsbedarf anzupassen.From the not pre-published DE 103 40 137.7 It is also known to adjust the target value for the voltage of the actuator just before the start of the discharge for each injector individually to its voltage requirements.

Aus der DE 103 03 975 A1 geht zur Minimierung des Einflusses von Toleranzen ein Verfahren zur Anpassung der Ladespannung hervor, bei dem die Spannung eines Piezostapels mit einer in einer Abtast-Halteschaltung gespeicherten Spannung mittels einer Vergleichsschaltung verglichen wird. Wenn die Spannung des Piezostapels die in der Abtast-Halte-Schaltung gespeicherte Spannung erreicht, beendet eine Steuerungsschaltung eine Ladephase des Piezostapels. Dadurch kann die in dem Piezostapel geladene Energie gleich zu der vor der Entladung geladenen Energie gemacht werden. Selbst wenn der Piezostapel beim Entladen auf ein Laden umgeschaltet wird, kann die Energie des Piezostapels auf diese Weise konstant gehalten werden.From the DE 103 03 975 A1 In order to minimize the influence of tolerances, a method for adjusting the charging voltage, in which the voltage of a piezo stack is compared with a voltage stored in a sample-and-hold circuit, is compared by means of a comparison circuit. When the voltage of the piezo stack reaches the voltage stored in the sample and hold circuit, a control circuit terminates a charge phase of the piezo stack. Thereby, the energy charged in the piezo stack can be made equal to the energy charged before the discharge. Even if the piezo stack is switched to a store when unloading, the energy of the piezo stack can be kept constant in this way.

Der Erfindung liegt nun die Aufgabe zugrunde, die Ladeflanke bei jedem Injektor so einzustellen, dass der Einfluss von Parametertoleranzen, welche die Ventilbewegung beeinflussen, so gering wie möglich gehalten werden kann und insbesondere gegenüber aus dem Stand der Technik bekannten Verfahren reduziert werden kann.The invention is based on the object to set the charging edge at each injector so that the influence of parameter tolerances, which influence the valve movement, can be kept as low as possible and in particular can be reduced compared to known from the prior art methods.

Vorteile der ErfindungAdvantages of the invention

Diese Aufgabe wird durch ein Verfahren und eine Vorrichtung zum Bestimmen der Ladeflanke eines piezoelektrischen Aktors der eingangs beschriebenen Art dadurch gelöst, dass die Differenz zwischen einer Abschaltspannungsschwelle und einer stationären Endspannung erfasst und auf einen vorgebbaren Sollwert geregelt wird. Grundidee der Erfindung ist es demnach, die Differenz zwischen der Abschaltspannungsschwelle, das heißt der Spannung, bei deren Erreichen der Ladevorgang abgebrochen wird, und der stationären Endspannung, das heißt der Spannung des Aktors kurz vor Beginn des Entladevorgangs durch einen Regelkreis konstant zu halten. Die Differenz zwischen der Abschaltspannungsschwelle und der Spannung des Aktors kurz vor Beginn des Entladevorgangs stellt ein Maß für die Längenänderung des Aktors nach Ende der Ladeflanke dar und ist damit wiederum ein Maß für den Weg, den das Schaltventil nach Ende der Ladeflanke noch bis zum Erreichen seines Hubanschlags zurücklegen muss. Wird diese Differenz auf einen konstanten Wert eingeregelt, so weisen die Schaltventile aller Injektoren am Ende der Ladeflanke einen einheitlichen Abstand von ihrem jeweiligen Hubanschlag auf.This object is achieved by a method and a device for determining the charging edge of a piezoelectric actuator of the type described above in that the difference between a cut-off voltage threshold and a stationary end voltage is detected and regulated to a predefinable setpoint. The basic idea of the invention is accordingly to keep constant the difference between the switch-off voltage threshold, that is to say the voltage at which the charging process is terminated, and the stationary end voltage, that is to say the voltage of the actuator shortly before the discharge process starts. The difference between the switch-off voltage threshold and the voltage of the actuator shortly before the start of the discharge process is a measure of the change in length of the actuator after the end of the charging edge and is thus again a measure of the way the switching valve after the end of the charging edge until it reaches its Must cover the stroke stop. If this difference is adjusted to a constant value, the switching valves of all injectors at the end of the loading flank have a uniform distance from their respective stroke stop.

Bei einer vorteilhaften Ausführungsform ist vorgesehen, die Differenz durch Variation des Ladestroms in einem vorgebbaren Intervall der Ladezeit auf einen vorgebbaren Sollwert zu regeln. Durch Konstanthalten der Dauer des Ladevorgangs ist sichergestellt, dass der einheitliche Abstand der Schaltventile von dem Hubanschlag jeweils zu einem definierten Zeitpunkt nach Ansteuerbeginn erreicht wird. Damit wird praktisch die Hubbewegung des Schaltventils unabhängig von Parametern wie Aktor-Leerlaufhub, Aktorsteifigkeit, Steifigkeit der Übertragungskette Aktor-Ventil, Sitzdurchmesser des Ventils usw. bei jedem Injektor auf einen gleichen Verlauf eingestellt, und zwar ohne, dass diese Parameter hierzu bekannt sein müssen. Hierdurch ist es auch möglich, den Injektor-Spannungsabgleich sowie die Nominal-Spannungskalibrierung implizit durchzuführen.In an advantageous embodiment, it is provided to regulate the difference by varying the charging current in a predefinable interval of the charging time to a predefinable desired value. By keeping the duration of the charging constant, it is ensured that the uniform distance of the switching valves from the stroke stop is reached at a defined point in time after the beginning of the activation. Thus, virtually the stroke movement of the switching valve regardless of parameters such as actuator idle stroke, actuator stiffness, stiffness of the transmission chain actuator valve, seat diameter of the valve, etc. set for each injector on a same course, and without that these parameters must be known for this purpose. This also makes it possible to implicitly perform the injector voltage balance as well as the nominal voltage calibration.

Bei einer wiederum anderen Ausführungsform ist vorgesehen, die Differenz zwischen der Abschaltspannungsschwelle und der Spannung des Aktors kurz vor Beginn des Entladevorgangs durch Variation der Abschaltspannungsschwelle auf den vorgebbaren Sollwert zu regeln. Diese Ausführungsform eignet sich insbesondere dann, wenn die Vorgabe des Ladestroms nicht ausreichend fein quantisiert oder nicht injektorindividuell vorgegeben werden kann. Vorteilhaft ist hierbei auch, dass eine Variation einer bereits bekannten und daher nicht zusätzlich zu erfassenden Größe erfolgt.In yet another embodiment is provided, the difference between the switch-off voltage threshold and the voltage of the actuator shortly before the start of the discharge by varying the switch-off threshold voltage to regulate the specifiable setpoint. This embodiment is particularly suitable when the specification of the charging current can not be sufficiently finely quantized or given injector-individual. It is also advantageous that a variation of an already known and therefore not additionally detected size takes place.

Bevorzugt wird dabei zusätzlich die Ladezeit durch Variation des Ladestroms auf ihren Sollwert eingeregelt. Die Dauer des Ladevorgangs wird demnach durch Variation der Stromschwelle auf einen Sollwert geregelt. In diesem Fall ist nur die Genauigkeit der eingestellten Ladedauer abhängig davon, wie genau die Stromschwelle vorgegeben werden kann, und ob dies Injektor-individuell und damit Zylinder-individuell möglich ist.In addition, the charging time is preferably adjusted to its desired value by varying the charging current. The duration of the charging process is therefore regulated by varying the current threshold to a desired value. In this case, only the accuracy of the set charging time depends on how exactly the current threshold can be specified, and whether this injector-individual and thus cylinder-individually possible.

Zeichnungdrawing

Weitere Vorteile und Merkmale sind Gegenstand der nachfolgenden Beschreibung sowie der zeichnerischen Darstellung von Ausführungsbeispielen der Erfindung.Further advantages and features are the subject of the following description and the drawings of embodiments of the invention.

In der Zeichnung zeigen:

Fig. 1
den schematischen Aufbau eines aus dem Stand der Technik bekannten Einspritzventils;
Fig. 2
schematisch ein Schaubild der Aktorspannung sowie des Aktorstroms über der Zeit während einer Ansteuerung;
Fig. 3
schematisch ein Blockschaltbild einer von dem erfindungsgemäßen Ver- fahren Gebrauch machenden Regeleinrichtung und
Fig.4
schematisch ein Blockschaltbild einer weiteren, von dem erfindungsge- mäßen Verfahren Gebrauch machenden Regeleinrichtung.
In the drawing show:
Fig. 1
the schematic structure of an injection valve known from the prior art;
Fig. 2
schematically a graph of the actuator voltage and the actuator current over time during a drive;
Fig. 3
1 is a schematic block diagram of a control device making use of the method according to the invention; and
Figure 4
schematically a block diagram of another, making use of the inventive method making control device.

Beschreibungdescription

Fig. 1 zeigt in schematischer Darstellung ein aus dem Stand der Technik bekanntes Einspritzventil 1 mit einer zentralen Bohrung. Im oberen Teil ist ein Stellkolben 3 mit einem piezoelektrischen Aktor 2 in die zentrale Bohrung eingebracht, wobei der Stellkolben 3 mit dem Aktor 2 fest verbunden ist. Der Stellkolben 3 schließt nach obenhin einen hydraulischen Koppler 4 ab, während nach unten eine Öffnung mit einem Verbindungskanal zu einem ersten Sitz 6 vorgesehen ist, in dem ein Kolben 5 mit einem Ventilschließglied 12 angeordnet ist. Das Ventilschließglied 12 ist in diesem Ausführungsbeispiel als doppelt schließendes Steuerventil ausgebildet, es kann aber auch als einfach schließendes Steuerventil ausgebildet sein. Es verschließt den ersten Sitz 6, wenn der Aktor 2 in Ruhephase ist. Bei Betätigung des Aktors 2, das heißt beim Anlegen einer Ansteuerspannung U an den Klemmen +, -, betätigt der Aktor 2 den Stellkolben 3 und drückt über den hydraulischen Koppler 4 den Kolben 5 mit dem Verschließglied 12 in Richtung auf einen zweiten Sitz 7. Unterhalb des zweiten Sitzes ist in einem entsprechenden Kanal eine Düsennadel 11 angeordnet, die den Auslauf in einem Hochdruckkanal (Common-Rail-Druck) 13 schließt oder öffnet, je nachdem, welche Ansteuerspannung U anliegt. Der Hochdruck wird durch das einzuspritzende Medium, beispielsweise Kraftstoff für einen Verbrennungsmotor, über einen Zulauf 9 zugeführt, über eine Zulaufdrossel 8 und eine Ablaufdrossel 10 wird die Zuflussmenge des Mediums in Richtung der Düsennadel 11 und des hydraulischen Kopplers 4 gesteuert. Der hydraulische Koppler 4 hat dabei die Aufgabe, einerseits den Hub des Kolbens 5 zu verstärken und andererseits das Steuerventil von der statischen Temperaturdehnung des Aktors 2 zu entkoppeln. Die Wiederbefüllung des Kopplers 4 ist hier nicht dargestellt. Fig. 1 shows a schematic representation of a known from the prior art injection valve 1 with a central bore. In the upper part is a control piston 3 introduced with a piezoelectric actuator 2 in the central bore, wherein the actuating piston 3 is fixedly connected to the actuator 2. The actuating piston 3 closes upwards a hydraulic coupler 4, while at the bottom an opening with a connecting channel to a first seat 6 is provided, in which a piston 5 is arranged with a valve closing member 12. The valve closing member 12 is formed in this embodiment as a double-closing control valve, but it can also be designed as a simple closing control valve. It closes the first seat 6 when the actuator 2 is at rest. Upon actuation of the actuator 2, that is, when applying a drive voltage U at the terminals +, -, the actuator 2 actuates the actuating piston 3 and presses the piston 5 with the closing member 12 in the direction of a second seat 7 via the hydraulic coupler 4 of the second seat, a nozzle needle 11 is arranged in a corresponding channel, which closes or opens the outlet in a high pressure channel (common rail pressure) 13, depending on which control voltage U is present. The high pressure is supplied through the medium to be injected, for example fuel for an internal combustion engine, via an inlet 9, via an inlet throttle 8 and an outlet throttle 10, the inflow amount of the medium in the direction of the nozzle needle 11 and the hydraulic coupler 4 is controlled. The hydraulic coupler 4 has the task on the one hand to increase the stroke of the piston 5 and on the other hand to decouple the control valve from the static temperature expansion of the actuator 2. The refilling of the coupler 4 is not shown here.

Nachfolgend wird die Funktionsweise dieses Einspritzventils näher erläutert. Bei jeder Ansteuerung des Aktors 2 wird der Stellkolben 3 in Richtung des hydraulischen Kopplers 4 bewegt. Dabei bewegt sich auch der Kolben 5 mit dem Verschließglied 12 in Richtung auf den zweiten Sitz 7 zu. Über Leckspalte wird dabei ein Teil des im hydraulischen Kopplers 4 befindlichen Mediums, beispielsweise der Kraftstoff, herausgedrückt. Zwischen zwei Einspritzungen muss daher der hydraulische Koppler 4 wiederbefüllt werden, um seine Funktionssicherheit zu erhalten.The operation of this injector will be explained in more detail below. Each time the actuator 2 is actuated, the actuating piston 3 is moved in the direction of the hydraulic coupler 4. In this case, the piston 5 also moves with the closing member 12 in the direction of the second seat 7. About leakage gaps while a part of the hydraulic coupler 4 located in the medium, for example, the fuel pushed out. Between two injections, therefore, the hydraulic coupler 4 must be refilled to maintain its functional reliability.

Über den Zulaufkanal 9 herrscht ein hoher Druck, der beim Common-Rail-System beispielsweise zwischen 200 und 2000 bar betragen kann. Dieser Druck wirkt gegen die Düsennadel 11 und hält sie geschlossen, so dass kein Kraftstoff austreten kann. Wird nun infolge der Ansteuerspannung U der Aktor 2 betätigt und damit das Verschlussglied 12 in Richtung des zweiten Sitzes bewegt, baut sich der Druck im Hochdruckbereich ab und die Düsennadel 11 gibt den Einspritzkanal frei. Mit P1 ist der sogenannte Kopplerdruck bezeichnet, wie er im hydraulischen Koppler 4 vorliegt. Im Koppler 4 stellt sich ohne Ansteuerung U ein stationärer Druck P1 ein. Nach dem Entladen des Aktors 2 ist der Kopplerdruck P1 näherungsweise 0 und wird durch Wiederbefüllung wieder angehoben.About the inlet channel 9, there is a high pressure, which may be in the common rail system, for example, between 200 and 2000 bar. This pressure acts against the nozzle needle 11 and keeps it closed, so that no fuel can escape. If, as a result of the control voltage U, the actuator 2 is actuated, and thus the closure member 12 is moved in the direction of the second seat, the pressure in the high-pressure region is reduced and the nozzle needle 11 releases the injection channel. P 1 is the so-called coupler pressure, as it is present in the hydraulic coupler 4. In the coupler 4 is set without control U, a stationary pressure P 1 . After discharging the actuator 2, the coupler pressure P 1 is approximately 0 and is raised again by refilling.

Der Hub und die Kraft des Aktors 2 korrelieren nun mit der Spannung, mit der der Aktor 2 aufgeladen wird. Da die Kraft proportional zum Raildruck ist, muss die Spannung für einen geforderten Aktorhub zum sicheren Erreichen des Sitzes 7 raildruckabhängig angepasst werden. Die zum ordnungsgemäßen Betrieb des Einspritzventils oder Injektors 1 an einem Arbeitspunkt notwendige Spannung ist der sogenannte Spannungsbedarf, das heißt der Zusammenhang zwischen Spannung und Hub bei einer bestimmten Kraft, die proportional zum Raildruck ist. Aus der DE 103 158 15.4 geht hervor, wie aus der Spannungsdifferenz zwischen maximaler Aktorspannung und stationärer Endspannung der individuelle, aktuelle Spannungsbedarfs eines Injektors abgeleitet werden kann.The stroke and the force of the actuator 2 now correlate with the voltage with which the actuator 2 is charged. Since the force is proportional to the rail pressure, the voltage for a required Aktorhub for safe reaching the seat 7 must be adjusted depending on the rail pressure. The voltage necessary for the proper operation of the injection valve or injector 1 at an operating point is the so-called voltage requirement, that is to say the relationship between voltage and stroke at a certain force, which is proportional to the rail pressure. From the DE 103 158 15.4 shows how can be derived from the voltage difference between maximum actuator voltage and steady-state voltage of the individual, current voltage requirement of an injector.

In Fig. 2 sind schematisch die Aktorspannung sowie der Aktorstrom über der Zeit aufgetragen.In Fig. 2 The actuator voltage and the actuator current are plotted over time.

Bei aus dem Stand der Technik bekannten Verfahren für die Bestimmung der Ladeflanke wird eine Spannung URegel des Aktors 2 kurz vor Beginn des Entladevorgangs gemessen und auf einen Sollwert eingeregelt. Als Stellgröße hierfür dient die sogenannte Abschaltspannungsschwelle Uabschalt, das heißt die Spannung, bei deren Erreichen der Ladevorgang abgebrochen wird. Zusätzlich wird die Dauer der Ladeflanke auf einen Sollwert ΔtL von üblicherweise 100 Mikrosekunden eingestellt. Diese Einstellung erfolgt entweder durch Steuerung oder durch Regelung einer Schaltschwelle Is für den Ladestrom, die somit als Stellgröße dient. Zur Variation der Ladezeit ΔtL wird also der Ladestrom I variiert.In known from the prior art method for the determination of the charging edge, a voltage U rule of the actuator 2 is measured shortly before the start of the discharge process and adjusted to a desired value. The manipulated variable used for this purpose is the so-called switch-off voltage threshold U switch-off, that is to say the voltage at which the charging process is terminated. In addition, the duration of the charging edge is set to a setpoint Δt L of typically 100 microseconds. This setting is done either by control or by controlling a switching threshold I s for the charging current, which thus serves as a manipulated variable. To vary the charging time .DELTA.t L so the charging current I is varied.

Die Grundidee der Erfindung ist es nun, anstelle der Spannung des Aktors 2 kurz vor Beginn des Entladevorgangs, die Differenz zwischen der Abschaltspannungsschwelle Uabschalt und der Spannung des Aktors 2 kurz vor Beginn des Entladevorgangs URegel durch einen Regelkreis konstant zu halten und zweitens die Dauer der Ladeflanke durch eine Steuerung oder eine Regelung konstant zu halten. Die Differenz zwischen der Abschaltspannungsschwelle Uabschalt und der Spannung des Aktors 2 kurz vor Beginn des Endladevorgangs URegel stellt ein Maß dafür dar, welche Längenänderung der Aktor 2 nach Ende der Ladeflanke noch ausführt und ist damit wiederum ein Maß dafür, welchen Weg das Schaltventil 12 nach Ende der Abschaltflanke noch bis zum Erreichen seines Hubanschlags zurücklegt. Wird diese Differenz auf einen konstanten Wert eingeregelt, so weisen die Schaltventile aller Injektoren am Ende der Ladeflanke einen einheitlichen Abstand von ihrem Hubanschlag auf. Wenn zudem auch die Dauer des Ladevorgangs konstant gehalten wird, ist sichergestellt, dass dieser einheitliche Abstand jeweils zu einem definierten Zeitpunkt nach Ansteuerbeginn erreicht wird. Damit wird die Hubbewegung des Schaltventils 12 praktisch unabhängig von Parametern wie Aktor-Leerlaufhub, Aktorsteifigkeit, Steifigkeit der Übertragungskette Aktor-Ventil, Sitzdurchmesser des Ventils usw.. Oder es können anders ausgedrückt die Schaltventilbewegungen unterschiedlicher Injektoren auf jeweils einen gleichen Verlauf eingestellt werden, und zwar ohne dass diese Parameter bekannt sein müssen.The basic idea of the invention it is now, instead of the voltage of the actuator 2 just before the start of the discharge process, the difference between the Abschaltspannungsschwelle shutdown U and to keep the voltage of the actuator 2 just before start of the discharge U control by a control loop constant, and secondly, the duration keep the charging edge constant by means of a control or regulation. The difference between the switch- off voltage threshold U turn off and the voltage of the actuator 2 shortly before the start of the discharge U rule represents a measure of what length change the actuator 2 is still running after the end of the charging edge and is thus again a measure of which way the switching valve 12th travels to the end of the cut-off edge until it reaches its stroke stop. If this difference is adjusted to a constant value, the switching valves of all injectors at the end of the loading flank have a uniform distance from their stroke stop. Moreover, if the duration of the charging process is kept constant, it is ensured that this uniform distance is achieved in each case at a defined time after the start of control. Thus, the lifting movement of the switching valve 12 is practically independent of parameters such as actuator idle stroke, actuator stiffness, stiffness of the transmission chain actuator valve, seat diameter of the valve, etc. Or, in other words, the switching valve movements of different injectors can be set to a same course, namely without these parameters need to be known.

Ein einer ersten Ausführungsform, dargestellt in Fig. 3, wird die Differenz zwischen der Abschaltspannung und der Spannung des Aktors 2 kurz vor Beginn des Entladevorgangs durch Änderung der Stellgröße Is geregelt, wobei die Dauer der Ladeflanke fest eingestellt wird durch Beenden des Ladevorgangs nach Ablauf einer vorgebbaren Zeitdauer ΔtL. Hierzu ist eine Schaltungseinheit 310 für eine Vorsteuerung für die Stellgröße Is vorgesehen, der der Raildruck PRail als Eingangsgröße zugeführt wird. Ferner ist eine Schaltungseinheit 320 vorgesehen, welche einen Regler für die Differenz der Abschaltspannung Uabschalt und der Spannung des Aktors 2 kurz vor Beginn des Entladevorgangs URegel bildet, der ein vorgebbarer Sollwert als Eingangsgröße zugeführt wird. Die Ausgänge der Schaltungseinheiten 310 und 320 werden addiert und einem Ansteuerbaustein 330 zugeführt, der wiederum eine Piezoendstufe 335 ansteuert, die die Aktorspannung U und den Aktorstrom I des Aktors 2 liefert. Die Piezoendstufe 335 liefert darüber hinaus die Abschaltspannung Uabschalt und die Spannung des Aktors 2 kurz vor Beginn des Entladevorgangs URegel, deren Differenz in einem Schaltpunkt 340 gebildet wird. Diese Differenz wird der Schaltungseinheit 320 zugeführt. Die Regelung erfolgt nun durch Variation der Stellgröße Is. Steigt diese Stellgröße des Stromes, so steigt die Spannung, auf die der Aktor 2 geladen wird, der verbleibende Weg des Ventils nach Ende des Ladevorgangs sinkt und damit auch die einzuregelnde Spannungsdifferenz. Da in diesem Falle die Abschaltspannung Uabschalt nicht von außen vorgegeben wird, sondern sich aufgrund des Ladestroms Is und der Ladezeit ΔtL einstellt, muss die Spannung zum Endzeitpunkt des Ladevorgangs gemessen werden und es muss dann dieser Messwert als Abschaltspannungsschwelle verwendet werden. Ferner ist Voraussetzung, dass die Regelung der Stellgröße Is ausreichend fein quantisiert und injektorindividuell und damit zylinderindividuell vorgegeben werden kann.A first embodiment shown in FIG Fig. 3 , the difference between the cut-off voltage and the voltage of the actuator 2 is controlled shortly before the start of the discharge by changing the manipulated variable I s , the duration of the charging edge is fixed by stopping the charging after a predetermined period of time .DELTA.t L. For this purpose, a circuit unit 310 is provided for a feedforward control for the manipulated variable I s , to which the rail pressure P rail is supplied as an input variable. Furthermore, a circuit unit 320 is provided, which shut a controller for the difference of the cut-off voltage U and the Voltage of the actuator 2 shortly before the start of the discharge process U rule forms, which is fed to a predefinable setpoint input. The outputs of the circuit units 310 and 320 are added and fed to a drive module 330, which in turn drives a piezo output stage 335, which supplies the actuator voltage U and the actuator current I of the actuator 2. In addition, the piezo output stage 335 supplies the switch- off voltage U switch-off and the voltage of the actuator 2 shortly before the start of the discharge process U rule , the difference of which is formed in a switching point 340. This difference is supplied to the circuit unit 320. The regulation is now carried out by varying the manipulated variable I s . If this manipulated variable of the current increases, then the voltage to which the actuator 2 is charged increases, the remaining path of the valve after the end of the charging process drops and thus also the voltage difference to be adjusted. Since in this case the cut- off voltage U cutoff is not specified from the outside, but due to the charging current I s and the charging time .DELTA.t L sets, the voltage at the end time of the charging must be measured and then this measurement must be used as shutdown voltage threshold. Furthermore, it is a prerequisite that the regulation of the manipulated variable I s can be sufficiently finely quantized and specified individually for the injector and thus for each cylinder.

Bei einer anderen Ausführungsform, dargestellt in Fig. 4, wird die einzuregelnde Spannungsdifferenz zwischen der Abschaltspannungsschwelle Uabschalt und der Spannung des Aktors 2 kurz vor Beginn des Entladevorgangs URegel durch Variation der bereits bekannten Abschaltspannungsschwelle Uabschalt selbst vorgenommen. Die Variation der Abschaltspannungsschwelle Uabschalt erfordert eine Variation des Ladevorgangs. Aus diesem Grunde weist die in Fig. 4 dargestellte Schaltungseinheit einen Regler für die Ladezeit 410 auf, der ein vorgebbarer Sollwert zuführbar ist. Dabei ist auch bei dieser Vorrichtung eine Schaltungseinheit 420 zur Vorsteuerung der Stromschwelle Is vorgesehen, die als Eingangsgröße dem Raildruck PRail zugeführt wird sowie eine Schaltungseinheit 430, welche einen Regler für die Differenz der Abschaltspannungsschwelle Uabschalt und der Spannung des Aktors 2 kurz vor Beginn des Entladevorgangs URegel umfasst, ferner eine Schaltungseinheit 440 zur Vorsteuerung der Abschaltspannungsschwelle Uabschalt. In einem Schaltungspunkt 450 werden der von dem Regler 430 ausgegebene Wert und der von der Vorsteuerung für die Abschaltspannung 440 ausgegebene Wert Uabschalt addiert und dieser Wert der Abschaltspannungsschwelle Uabschalt einem Ansteuerbaustein 460 zugeführt, der über eine Piezoendstufe 465 den Aktor 2 ansteuert, das heißt die Aktorspannung U und den Aktorstrom I zur Verfügung stellt. Die Piezoendstufe 465 gibt ferner ein Signal für die Dauer des Ladevorgangs aus, welches der Schaltungseinheit 410, die den Regler für die Ladezeit bildet, zugeführt wird. Ferner wird - wie bereits in Verbindung mit Fig. 3 beschrieben - die Abschaltspannungsschwelle Uabschalt sowie die Spannung des Aktors 2 kurz vor Beginn des Entladevorgangs URegel in einem Schaltungspunkt 470 voneinander subtrahiert und diese Differenz der Schaltungseinheit 430, welche den Regler für die Differenz der Abschaltspannungsschwelle und der Spannung kurz vor Beginn des Entladevorgangs URegel umfasst, zugeführt. Die Dauer des Ladevorgangs ΔtL wird nun auf einen vorgebbaren Sollwert durch die Schaltungseinheit 410 durch Variation der Stromschwelle Is geregelt. In diesem Falle ist nur die Genauigkeit der eingestellten Ladedauer abhängig davon, wie genau die Stromschwelle Is vorgegeben werden kann, und ob dies injektorindividuell und damit zylinderindividuell möglich ist. Die Genauigkeit des Regelkreises für die Spannungsdifferenz wird hierdurch jedoch nicht beeinträchtigt.In another embodiment, shown in FIG Fig. 4 , the einzuregelnde voltage difference between the switch-off threshold U shutdown and the voltage of the actuator 2 shortly before the start of the discharge process U rule by varying the already known cut-off voltage threshold U shutdown itself made. The variation of the turn-off voltage threshold U turn off requires a variation of the charging process. For this reason, the in Fig. 4 shown circuit unit to a controller for the charging time 410, to which a predetermined setpoint can be fed. Here, also in this apparatus, a circuit unit 420 is s provided for the pilot control of the threshold current I which is supplied as an input variable to the rail pressure p rail and a circuit unit 430, which shut a controller for the difference of the Abschaltspannungsschwelle U and the voltage of the actuator 2 just before the start the discharging U rule comprises further a circuit unit 440 for pilot control of the U Abschaltspannungsschwelle shutdown. At a node 450, the controller 430 becomes outputted value and the output from the feedforward control for the switch-off voltage 440 value U abschalt added and this value of the switch- off threshold U disconnected a control module 460 which controls the actuator 2 via a piezo amplifier 465, that is, the actuator voltage U and the actuator current I is available , The piezo output stage 465 also outputs a signal for the duration of the charging process, which is supplied to the circuit unit 410, which forms the regulator for the charging time. Furthermore - as already in connection with Fig. 3 described the switch- off voltage threshold U turn off and the voltage of the actuator 2 just before the start of the discharge U rule in a circuit point 470 subtracted from each other and this difference of the circuit unit 430, which controls the difference between the switch-off threshold and the voltage shortly before the start of the discharge U rule comprises, supplied. The duration of the charging process .DELTA.t L is now controlled to a predetermined desired value by the circuit unit 410 by varying the current threshold I s . In this case, only the accuracy of the set charging time depends on how exactly the current threshold I s can be specified, and whether this is injector-specific and thus cylinder-specific possible. However, the accuracy of the voltage difference control loop is not affected.

In einer Weiterbildung dieser in Fig. 3 und Fig. 4 dargestellten Ausführungsformen, wird der Regelkreis für die Differenz Uabschalt - URegel nur dann aktiv geschaltet, wenn eine Regelbedingung erfüllt ist, die beispielsweise darin bestehen, dass geprüft wird, ob die Ansteuerdauer einen Schwellwert überschreitet oder ob der Einspritzmengensollwert einen Einspritzmengenschwellwert überschreitet. Bei inaktivem Regler werden die Stellgrößen als Funktion des jeweils vorherrschenden Raildrucks "eingefroren". Dadurch wird vermieden, dass die Regelung auf nach Ende des Ladevorgangs einige hunderte Mikrosekunden andauernde Nachschwingungen des Aktors 2 reagiert, welche sich im Spannungsverlauf des Aktors widerspiegeln.In a further development this in Fig. 3 and Fig. 4 illustrated embodiments, the control circuit for the difference U shutoff - U rule is only activated when a control condition is met, for example, that it is checked whether the activation duration exceeds a threshold value or whether the injection quantity setpoint exceeds an injection amount threshold. If the controller is inactive, the manipulated variables are "frozen" as a function of the prevailing rail pressure. This avoids that the control reacts to after the end of the charging several hundred microseconds lasting ringing of the actuator 2, which are reflected in the voltage curve of the actuator.

Ferner kann vorgesehen sein, für die jeweilige Stellgröße zur Einstellung der Differenz Uabschaft - URegel eine raildruckabhängige Diagnoseschwelle einzuführen, bei deren Erreichen der zugehörige Injektor als defekt erkannt wird. Diese Information kann über eine Diagnoseschnittstelle, beispielsweise bei einer Wartung der Brennkraftmaschine ausgelesen und hierdurch die Fehlersuche stark vereinfacht werden.Furthermore, it can be provided for the respective manipulated variable to set the difference U Abschaft - U rule to introduce a raildruckabhängige diagnostic threshold, when they reach the associated injector is detected as defective. This information can be read out via a diagnostic interface, for example during maintenance of the internal combustion engine, and this greatly simplifies troubleshooting.

Claims (11)

  1. Method for determining the charging flank of a piezoelectric actuator (2) of at least one injector, by way of which a quantity of liquid is injected under high pressure into a hollow space, in particular into a combustion chamber of an internal combustion engine, characterized in that the difference between a switch-off voltage threshold (Uabschalt), that is to say the voltage, at the reaching of which the charging operation is terminated, and a voltage of the actuator (2) shortly before the beginning of the discharging operation (URegel) is regulated to a predefinable setpoint value.
  2. Method according to Claim 1, characterized in that the difference between the switch-off voltage threshold (Uabschalt) and the voltage of the actuator (2) shortly before the beginning of the discharging operation (URegel) is regulated to the predefinable setpoint value by variation of a charging current threshold (Is) at a predefinable interval of the charging time (ΔtL).
  3. Method according to Claim 1, characterized in that the difference between the switch-off voltage threshold (Uabschalt) and the voltage of the actuator (2) shortly before the beginning of the discharging operation (URegel) is regulated to the predefinable setpoint value by variation of the switch-off voltage threshold (Uabschalt).
  4. Method according to Claim 2, characterized in that the charging time (ΔtL) is varied or regulated to a setpoint value by variation of the charging current threshold (Is).
  5. Method according to one of the preceding claims, characterized in that the charging current threshold (Is) and/or the charging time (ΔtL) and/or the switch-off voltage threshold (Uabschalt) are/is compared with predefinable diagnosis threshold values, at the reaching of which the injector is detected to be defective.
  6. Method according to one of the preceding claims, characterized in that a regulating operation for the difference between the switch-off voltage and the voltage shortly before the beginning of the discharging operation takes place only when a regulating condition is met, and in that, if the regulating condition is not met, in each case the value of that actuating variable is used as actuating variables of the regulating circuits, which actuating variable was valid when the internal combustion engine was last operated in the current rail pressure range with the regulating condition met.
  7. Method according to Claim 6, characterized in that the result of a comparison of the actuation duration and an actuation duration threshold value is used as regulating condition.
  8. Method according to Claim 7, characterized in that the regulating condition is met when the actuation duration is greater than the actuation duration threshold value.
  9. Method according to Claim 6, characterized in that the result of a comparison of the injection quantity setpoint value and an injection quantity threshold value is used as regulating condition.
  10. Method according to Claim 9, characterized in that the regulating condition is met when the injection quantity setpoint value is greater than the injection quantity threshold value.
  11. Apparatus for determining the charging flank of a piezoelectric actuator (2) of at least one injector, by way of which a quantity of liquid can be injected under high pressure into a hollow space, in particular into a combustion chamber of an internal combustion engine, characterized by a switching unit for regulating the difference between a switch-off voltage threshold (Uabschalt), that is to say the voltage, at the reaching of which the charging operation is terminated, and a voltage of the actuator (2) shortly before the beginning of the discharging operation to a predefinable setpoint value.
EP05701432A 2004-02-18 2005-01-04 Method and device for determining the charging flanks of a piezoelectric actuator Expired - Fee Related EP1718854B1 (en)

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DE200410007798 DE102004007798A1 (en) 2004-02-18 2004-02-18 Method and device for determining the charging flanks of a piezoelectric actuator
PCT/EP2005/050017 WO2005080776A1 (en) 2004-02-18 2005-01-04 Method and device for determining the charging flanks of a piezoelectric actuator

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CN1922397A (en) 2007-02-28
JP2006525455A (en) 2006-11-09
WO2005080776A1 (en) 2005-09-01
JP4130840B2 (en) 2008-08-06

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