EP1423593B1 - Method for controlling a piezo-actuated fuel-injection valve - Google Patents

Method for controlling a piezo-actuated fuel-injection valve Download PDF

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Publication number
EP1423593B1
EP1423593B1 EP02760150A EP02760150A EP1423593B1 EP 1423593 B1 EP1423593 B1 EP 1423593B1 EP 02760150 A EP02760150 A EP 02760150A EP 02760150 A EP02760150 A EP 02760150A EP 1423593 B1 EP1423593 B1 EP 1423593B1
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EP
European Patent Office
Prior art keywords
injection
valve
timepoint
actuator
servo
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP02760150A
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German (de)
French (fr)
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EP1423593A1 (en
Inventor
Dirk Baranowski
Hellmut Freudenberg
Christian Hoffmann
Wolfgang Lingl
Lorand Ouvenou
Richard Pirkl
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Siemens AG
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Siemens AG
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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
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F02D2041/1413—Controller structures or design
    • F02D2041/143—Controller structures or design the control loop including a non-linear model or compensator
    • 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
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F02D2041/1433—Introducing closed-loop corrections characterised by the control or regulation method using a model or simulation of the system
    • 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
    • F02D2041/2055—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit with means for determining actual opening or closing time
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M45/00—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship
    • F02M45/02—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts
    • F02M45/04—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts with a small initial part, e.g. initial part for partial load and initial and main part for full load
    • F02M45/08—Injectors peculiar thereto
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M51/00—Fuel-injection apparatus characterised by being operated electrically
    • F02M51/06—Injectors peculiar thereto with means directly operating the valve needle
    • F02M51/0603—Injectors peculiar thereto with means directly operating the valve needle using piezoelectric or magnetostrictive operating means

Definitions

  • the invention relates to a method for driving a piezo-operated fuel injection valve according to the features of claim 1.
  • the fuel injection process in diesel engines is usually carried out in several stages, with one or more pre- or post-injections being assigned to achieve a smoother combustion process of each main injection, in which the injected fuel quantity is small compared to the main injection quantity.
  • the piezo actuator actuates a hydraulic servo valve, which then moves the main valve.
  • the electrical control of the piezoelectric actuator is made so that the desired amount of fuel is injected.
  • the electrical control signals are designed in the injection of small amounts of fuel in terms of driving time and amplitude so that a safe injection takes place. Because of security concerns with respect to pressure fluctuations in the fuel supply line, parameter tolerances of the system and the wide operating temperature range is thus, especially in pre and post injections, a fuel quantity overdose connected. For this purpose, it has hitherto been concluded from the charge or energy fed into the piezoelectric actuator to the piezoelectric deflection.
  • the method according to the invention is based on a detection and evaluation of the length changes or forces of the piezoactuator which are determined from the electrical signals (of the current supplied to the piezoactuator and the voltage that builds up on it) on the piezoelectric actuator, with the aid of a nonlinear actuator model and an adaptive Method for evaluating the length changes on the piezoelectric actuator or the forces occurring on it.
  • the actuator model contains the non-linear relationships between charge or voltage and mechanical deflection, as well as operating point-dependent parameters. Furthermore, the actuator model takes into account the dielectric hysteresis of the piezoelectric actuator. Thus, this actuator model allows the conclusion of the electrical to the mechanical parameters and the simulation of the piezoelectric actuator in the range of pulse-shaped deflection.
  • FIG. 1 shows the basic course of the piezo stroke, ie, the change in length s of a piezoelectric actuator over time t during a driving process of a fuel injection valve.
  • This change in length s is calculated by means of the measured data of the current supplied to the piezoelectric actuator and the voltage which subsequently builds up on it with the aid of an actuator model which simulates the properties of a piezoactuator.
  • the curve s 1 shows the basic course of the beginning of the change in length s (expansion) of a piezoelectric actuator in a correct injection process.
  • the curve rises from the beginning 0 of the Control on, has a kink at a time t A and then increases faster, until it reaches a maximum and then drops again.
  • the kink is explained by the fact that the piezoactuator travels a free path before it penetrates against the force of the rail pressure in the servo valve and opens the servo valve.
  • the dashed curve s 0 shows the difference from the curve s 1, the basic course of the beginning of the change in length (expansion) of a piezoelectric actuator in an incorrect injection process.
  • the curve rises flat without having a kink, reaches a maximum and then falls off again, ie, the free travel is not completely measured.
  • the maximum of the curve of the linear expansion of a piezoelectric actuator depends inter alia on the energy that is supplied to the piezoelectric actuator: the greater the energy amount, the greater the longitudinal expansion s.
  • the beginning of the opening of the servo valve is thus approximately at the time t A of the curve s. 1
  • This opening of the servo valve is a mandatory requirement for a subsequent injection.
  • the actual injection is significantly delayed, since with the opening of the servo valve, the pressure in the valve chamber is slowly reduced and only then opens the actual injection valve.
  • the presence of the "bend" in the path is an indication that there is enough energy in the piezo for the servo valve to open.
  • the inventive method for determining this opening timing t A of the servo valve will be explained below.
  • the time t A for example, varies with the energy supplied to the piezoelectric actuator E and counteracting him Fuel rail pressure p and the actuator temperature T etc. He is so empirically known.
  • the times t1 to t4 which are stored in the maps and which determine the time windows W1 and W2 are also stored, that is, adapted, as a function of the time t A determined in the preceding previous injection process.
  • a determination of the injection duration is only made if a correct injection with a defined start of injection has previously been determined.
  • the fuel injection duration D is determined by means of the force F acting on the piezoactuator.
  • This force F is - as the change in length s - determined from the electrical signals (from the current supplied to the piezoelectric actuator and the voltage built up on it) with the aid of the aforementioned non-linear actuator model.
  • FIG. 2 a shows the basic profile of the force F 1 acting on a piezoelectric actuator during a fuel injection process or during a faulty injection (F 0 , dashed).
  • the force F increases from the beginning of the driving process and reaches its maximum at about time t A , then goes into an approximately horizontal course (in a faulty injection, it decreases slowly) and makes when switching off first a dip in the negative and then a jump into Positive, before it becomes zero again.
  • the first time derivative dF 1 / dt of the force F is used according to the invention.
  • the course of the first derivative dF 1 / dt of the force F (FIG. 2 a ) is shown schematically in FIG. 2 b.
  • this derivative dF 1 / dt reaches its maximum where the force F 1 rises steepest, then becomes negative when the force drops and reaches a plateau around the value zero where the force F 1 is horizontal. before it turns off at first negative and then positive and finally to zero.
  • a tolerance band for the value of the first derivative is applied in the area of the abovementioned plateau, with an upper value g1 (for dF / dt positive) and a lower value g2 (for dF / dt negative). Both values are shown in dashed lines in FIG. 2b.
  • These values like the windows W1 and W2 in FIG. 1, can also be determined via characteristic maps as a function of supplied energy, rail pressure and so on. be varied.

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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

According to the invention, the current guided to the piezo actuator and the voltage which is consequently established thereon is used for calculating with the help of a non-linear actuator model, the characteristics of the longitudinal variations (s) and the force (F) exerted by the actuator (F), and variables therefrom or the derived variables (dF/dt) therefrom determine the beginning of the opening (tA) of a servovalve and the duration of injection (D).

Description

Die Erfindung betrifft ein Verfahren zum Ansteuern eines piezobetriebenen Kraftstoff-Einspritzventils gemäß den Merkmalen von Anspruch 1.The invention relates to a method for driving a piezo-operated fuel injection valve according to the features of claim 1.

Der Kraftstoff-Einspritzvorgang in Dieselmotoren wird üblicherweise in mehreren Abschnitten durchgeführt, wobei zur Erzielung eines sanfteren Verbrennungsverlaufs jeder Haupteinspritzung eine oder mehrere Vor- oder Nacheinspritzungen zugeordnet sind, bei denen die eingespritzte Kraftstoffmenge klein gegenüber der Haupteinspritzmenge ist.The fuel injection process in diesel engines is usually carried out in several stages, with one or more pre- or post-injections being assigned to achieve a smoother combustion process of each main injection, in which the injected fuel quantity is small compared to the main injection quantity.

Für eine präzise Dosierung der Kraftstoffmengen, insbesondere der Kleinmengen und zur Optimierung der Einspritz-Zeitpunkte, sind schnell schaltende Ventile erforderlich, wozu zunehmend piezobetriebene Einspritzventile eingesetzt werden.For a precise metering of the fuel quantities, in particular the small quantities and for the optimization of the injection times, fast switching valves are required, to which increasingly piezobetriebene injectors are used.

Wegen der geringen maximalen Längenänderung der eingesetzten Piezoelemente (stacks) betätigt der Piezoaktor ein hydraulisches Servoventil, welches dann das Hauptventil bewegt. Mittels einer Ansteuerelektronik wird die elektrische Ansteuerung des Piezoaktors so vorgenommen, daß die gewünschte Kraftstoffmenge eingespritzt wird.Because of the small maximum change in length of the piezo elements used (stacks), the piezo actuator actuates a hydraulic servo valve, which then moves the main valve. By means of a control electronics, the electrical control of the piezoelectric actuator is made so that the desired amount of fuel is injected.

Da es nicht möglich ist, Kraftstoffmengen oder mechanische Bewegungen im Einspritzventil zu erfassen, werden die elektrischen Steuersignale bei der Einspritzung kleiner Kraftstoffmengen hinsichtlich Ansteuerdauer und Amplitude so ausgelegt, daß ein sicheres Einspritzen erfolgt. Wegen der Sicherheitsvorbehalte gegenüber Druckschwankungen in der Kraftstoffzuleitung, Parametertoleranzen des Systems und des weiten Betriebstemperaturbereichs ist damit, insbesondere bei Vor- und Nacheinspritzungen, eine Kraftstoffmengen-Überdosierung verbunden. Dazu wurde bisher aus der in den Piezoaktor eingespeisten Ladung oder Energie auf die Piezoauslenkung geschlossen.Since it is not possible to detect fuel quantities or mechanical movements in the injection valve, the electrical control signals are designed in the injection of small amounts of fuel in terms of driving time and amplitude so that a safe injection takes place. Because of security concerns with respect to pressure fluctuations in the fuel supply line, parameter tolerances of the system and the wide operating temperature range is thus, especially in pre and post injections, a fuel quantity overdose connected. For this purpose, it has hitherto been concluded from the charge or energy fed into the piezoelectric actuator to the piezoelectric deflection.

Aus DE 196 44 521 A1 ist ein Verfahren zur Ansteuerung eines kapazitiven Stellgliedes eines Kraftstoffeinspritzventils bekannt, welchem zur Erzielung eines konstanten Hubs eine diesem Hub zugeordnete Energiemenge zugeführt wird.From DE 196 44 521 A1 a method for controlling a capacitive actuator of a fuel injection valve is known, which is supplied to achieve a constant stroke associated with this stroke amount of energy.

Es ist Aufgabe der Erfindung, ein Verfahren anzugeben, mit dessen Hilfe überwacht werden kann, ob Kraftstoff-Vor-, Haupt- oder Nach-Einspritzungen stattfinden oder nicht, und welches eine genauere Festlegung der Menge jeder Kraftstoff-Vor-, Haupt- oder Nach-Einspritzung ermöglicht.It is an object of the invention to provide a method by means of which it can be monitored whether fuel pre-, main- or post-injections take place or not, and which allows a more accurate determination of the amount of each fuel pre, main or post Injection allows.

Diese Aufgabe wird erfindungsgemäß durch die Merkmale des Anspruchs 1 gelöst.This object is achieved by the features of claim 1.

Das erfindungsgemäße Verfahren beruht auf einer Erfassung und Auswertung der am Piezoaktor bei einem Ansteuervorgang wirkenden, aus den elektrischen Signalen (des dem Piezoaktor zugeführten Stromes und der sich an ihm aufbauenden Spannung) ermittelten Längenänderungen oder Kräfte des Piezoaktors, unter Zuhilfenahme eines nichtlinearen Aktormodells und eines adaptiven Verfahrens zur Bewertung der Längenänderungen am Piezoaktor bzw. der an ihm auftretenden Kräfte.The method according to the invention is based on a detection and evaluation of the length changes or forces of the piezoactuator which are determined from the electrical signals (of the current supplied to the piezoactuator and the voltage that builds up on it) on the piezoelectric actuator, with the aid of a nonlinear actuator model and an adaptive Method for evaluating the length changes on the piezoelectric actuator or the forces occurring on it.

Das Aktormodell beinhaltet die nichtlinearen Zusammenhänge zwischen Ladung bzw. Spannung und mechanischer Auslenkung, sowie Arbeitspunkt-abhängigen Parametern. Ferner berücksichtigt das Aktormodell die dielektrische Hysterese des Piezoaktors. Damit erlaubt dieses Aktormodell den Rückschluß von den elektrischen auf die mechanischen Größen und die Simulation des Piezoaktors im Bereich pulsförmiger Auslenkung.The actuator model contains the non-linear relationships between charge or voltage and mechanical deflection, as well as operating point-dependent parameters. Furthermore, the actuator model takes into account the dielectric hysteresis of the piezoelectric actuator. Thus, this actuator model allows the conclusion of the electrical to the mechanical parameters and the simulation of the piezoelectric actuator in the range of pulse-shaped deflection.

Damit ist es möglich, eine fehlerhafte oder korrekte Einspritzfunktion sowie die Einspritzdauer (-menge) des Einspritzventils sicher festzustellen und die Ansteuersignale adaptiv so zu gestalten, daß die gewünschten minimalen Kraftstoffeinspritzungen ohne Überdosierung erfolgen.This makes it possible to reliably determine a faulty or correct injection function as well as the injection duration (quantity) of the injection valve and adaptively configure the control signals in such a way that the desired minimum fuel injections take place without overdosing.

Nachstehend wird ein Ausführungsbeispiel nach der Erfindung anhand einer schematischen Zeichnung näher erläutert.An embodiment of the invention will be explained in more detail with reference to a schematic drawing.

In der Zeichnung zeigen:

Figur 1
die Längenänderung s eines Piezoaktors bei einem Ansteuervorgang, und
Figur 2
die an einem Piezoaktor bei einem Öffnungsvorgang des Ventils mit oder ohne Kraftstoffeinspritzung wirkende Kraft F und die daraus abgeleiteten Größen.
In the drawing show:
FIG. 1
the change in length s of a piezoelectric actuator in a drive operation, and
FIG. 2
acting on a piezoelectric actuator in an opening operation of the valve with or without fuel injection force F and the variables derived therefrom.

Figur 1 zeigt den prinzipiellen Verlauf des Piezohubs, d.h., der Längenänderung s eines Piezoaktors über der Zeit t bei einem Ansteuervorgang eines Kraftstoffeinspritzventils. Diese Längenänderung s wird mittels der gemessenen Daten des dem Piezoaktor zugeführten Stromes und der sich daraufhin an ihm aufbauenden Spannung mit Hilfe eines Aktormodells, welches die Eigenschaften eines Piezoaktors nachbildet, errechnet. Die Kurve s1 zeigt den prinzipiellen Verlauf des Beginns der Längenänderung s (Ausdehnung) eines Piezoaktors bei einem korrekten Einspritzvorgang. Die Kurve steigt vom Beginn 0 der Ansteuerung an, weist zu einem Zeitpunkt tA einen Knick auf und steigt danach schneller an, bis sie ein Maximum erreicht und dann wieder abfällt. Der Knick erklärt sich daraus, dass der Piezoaktor einen Leerweg zurücklegt, bevor er sich gegen die Kraft des Raildrucks im Servoventil durchsetzt und das Servoventil öffnet.FIG. 1 shows the basic course of the piezo stroke, ie, the change in length s of a piezoelectric actuator over time t during a driving process of a fuel injection valve. This change in length s is calculated by means of the measured data of the current supplied to the piezoelectric actuator and the voltage which subsequently builds up on it with the aid of an actuator model which simulates the properties of a piezoactuator. The curve s 1 shows the basic course of the beginning of the change in length s (expansion) of a piezoelectric actuator in a correct injection process. The curve rises from the beginning 0 of the Control on, has a kink at a time t A and then increases faster, until it reaches a maximum and then drops again. The kink is explained by the fact that the piezoactuator travels a free path before it penetrates against the force of the rail pressure in the servo valve and opens the servo valve.

Die gestrichelt dargestellte Kurve s0 zeigt zum Unterschied von der Kurve s1 den prinzipiellen Verlauf des Beginns der Längenänderung (Ausdehnung) eines Piezoaktors bei einem nicht korrekten Einspritzvorgang. Die Kurve steigt flach an, ohne einen Knick aufzuweisen, erreicht ein Maximum und fällt dann wieder ab, d.h., der Leerweg wird nicht zur Gänze durchmessen. Das Maximum der Kurve der Längenausdehnung eines Piezoaktors hängt u.a. von der Energie ab, die dem Piezoaktor zugeführt wird: je größer der Energiebetrag, desto größer die Längenausdehnung s.The dashed curve s 0 shows the difference from the curve s 1, the basic course of the beginning of the change in length (expansion) of a piezoelectric actuator in an incorrect injection process. The curve rises flat without having a kink, reaches a maximum and then falls off again, ie, the free travel is not completely measured. The maximum of the curve of the linear expansion of a piezoelectric actuator depends inter alia on the energy that is supplied to the piezoelectric actuator: the greater the energy amount, the greater the longitudinal expansion s.

Der Beginn der Öffnung des Servoventils liegt also etwa im Zeitpunkt tA der Kurve s1. Diese Öffnung des Servoventils ist zwingende Voraussetzung für eine anschließende Einspritzung. Die eigentliche Einspritzung erfolgt deutlich verzögert, da mit dem Öffnen des Servoventils der Druck in der Ventilkammer langsam abgebaut wird und dann erst das eigentliche Einspritzventil öffnet. Das Vorhandensein des "Knicks" im Wegverlauf ist ein Indiz dafür, dass genügend Energie im Piezo vorhanden ist, damit das Servoventil öffnet.The beginning of the opening of the servo valve is thus approximately at the time t A of the curve s. 1 This opening of the servo valve is a mandatory requirement for a subsequent injection. The actual injection is significantly delayed, since with the opening of the servo valve, the pressure in the valve chamber is slowly reduced and only then opens the actual injection valve. The presence of the "bend" in the path is an indication that there is enough energy in the piezo for the servo valve to open.

Das erfindungsgemäße Verfahren zur Ermittlung dieses Öffnungszeitpunkts tA des Servoventils wird nachstehend erklärt. Der Zeitpunkt tA variiert beispielsweise mit der dem Piezoaktor zugeführten Energie E und dem ihm entgegenwirkenden Kraftstoff-Raildruck p sowie der Aktortemperatur T etc.. Er ist also empirisch bekannt.The inventive method for determining this opening timing t A of the servo valve will be explained below. The time t A , for example, varies with the energy supplied to the piezoelectric actuator E and counteracting him Fuel rail pressure p and the actuator temperature T etc. He is so empirically known.

Über Kennfelder, die diesen Zusammenhang berücksichtigen, werden ein erstes Zeitfenster W1 (festgelegt durch Zeitpunkte t1 und t2) kurz vor dem Zeitpunkt tA [tA=f(E, p, T ...)] und ein zweites Zeitfenster W2 (festgelegt durch Zeitpunkte t3 und t4) kurz nach diesem Zeitpunkt tA, definiert.Over maps which take into account this connection, a first time window W1 (defined by time points t 1 and t 2) shortly before the time t A [t A = f (E, p, T ...)] and a second time window W2 (defined by times t 3 and t 4 ) shortly after this time t A , defined.

Durch die Längenänderungen zu den Zeitpunkten t1 und t2 ist eine erste Gerade - Tangente T1 - bestimmt, und durch die Längenänderungen zu den Zeitpunkten t3 und t4 ist eine zweite Gerade - Tangente T1' - bestimmt. Diese beiden Tangenten, in Figur 1 fett hervorgehoben, schneiden sich in einem mittels einer einfachen trigonometrischen Rechnung ermittelbaren Zeitpunkt tA, der als Zeitpunkt der Öffnung des Servoventils gewertet wird. Für eine korrekte Einspritzung wird jedoch nur ein solcher Verlauf der Längenänderung s gewertet, bei dem die Tangente T1' einen definierbar steileren Winkel gegenüber der Abszisse aufweist als die Tangente T1. Andernfalls wird eine Fehleinspritzung angenommen (T0 - T0').By the length changes at the times t 1 and t 2 , a first straight line - tangent T 1 - is determined, and by the length changes at the times t 3 and t 4 , a second straight line - tangent T 1 '- determined. These two tangents, highlighted in bold in FIG. 1, intersect at a time t A , which can be determined by means of a simple trigonometric calculation, and which is evaluated as the time at which the servo valve opens. For a correct injection, however, only such a profile of the change in length s is evaluated, in which the tangent T 1 'has a definable steeper angle with respect to the abscissa than the tangent T 1 . Otherwise, a false injection is assumed (T 0 -T 0 ').

Aufgrund von Verschleißerscheinungen kann es langfristig vorkommen, dass sich die Lage des Zeitpunkts tA verschiebt. Deshalb ist vorgesehen, dass die in den Kennfeldern gespeicherten Zeitpunkte t1 bis t4, welche die Zeitfenster W1 und W2 bestimmen, auch von dem in dem jeweils vorhergehenden früheren Einspritzvorgang ermittelten Zeitpunkt tA abhängig gespeichert, d.h., adaptiert werden.Due to signs of wear, it can happen in the long term that the position of time t A shifts. It is therefore provided that the times t1 to t4 which are stored in the maps and which determine the time windows W1 and W2 are also stored, that is, adapted, as a function of the time t A determined in the preceding previous injection process.

Eine Ermittlung der Einspritzdauer wird nur dann vorgenommen, wenn zuvor eine korrekte Einspritzung mit definiertem Einspritzbeginn festgestellt wurde.A determination of the injection duration is only made if a correct injection with a defined start of injection has previously been determined.

Die Kraftstoff-Einspritzdauer D wird mittels der am Piezoaktor wirkenden Kraft F ermittelt. Diese Kraft F wird - wie die Längenänderung s -aus den elektrischen Signalen (aus dem dem Piezoaktor zugeführten Strom und der sich an ihm aufbauenden Spannung) unter Zuhilfenahme des bereits erwähnten, nichtlinearen Aktormodells ermittelt.The fuel injection duration D is determined by means of the force F acting on the piezoactuator. This force F is - as the change in length s - determined from the electrical signals (from the current supplied to the piezoelectric actuator and the voltage built up on it) with the aid of the aforementioned non-linear actuator model.

Figur 2a zeigt den prinzipiellen Verlauf der an einem Piezoaktor wirkenden Kraft F1 bei einem Kraftstoffeinspritzvorgang bzw. bei einer Fehleinspritzung (F0, strichliert).FIG. 2 a shows the basic profile of the force F 1 acting on a piezoelectric actuator during a fuel injection process or during a faulty injection (F 0 , dashed).

Die Kraft F steigt vom Beginn des Ansteuervorgangs an und erreicht etwa im Zeitpunkt tA ihr Maximum, geht anschließend in einen etwa horizontalen Verlauf über (bei einer Fehleinspritzung nimmt sie langsam ab) und macht beim Abschalten zunächst einen Sprung ins Negative und anschließend einen Sprung ins Positive, bevor sie wieder zu Null wird.The force F increases from the beginning of the driving process and reaches its maximum at about time t A , then goes into an approximately horizontal course (in a faulty injection, it decreases slowly) and makes when switching off first a dip in the negative and then a jump into Positive, before it becomes zero again.

Zur Ermittlung der Einspritzdauer D wird erfindungsgemäß die erste zeitliche Ableitung dF1/dt der Kraft F herangezogen. Der Verlauf der ersten Ableitung dF1/dt der Kraft F (Figur 2a) ist schematisch in Figur 2b dargestellt.In order to determine the injection duration D, the first time derivative dF 1 / dt of the force F is used according to the invention. The course of the first derivative dF 1 / dt of the force F (FIG. 2 a ) is shown schematically in FIG. 2 b.

Bei einem korrekten Einspritzvorgang erreicht diese Ableitung dF1/dt ihr Maximum da, wo die Kraft F1 am steilsten ansteigt, wird dann negativ, wenn die Kraft abfällt und erreicht ein Plateau um den Wert Null da, wo die Kraft F1 horizontal verläuft, bevor sie beim Abschalten zunächst negativ und dann positiv und schließlich zu Null wird.In a correct injection process, this derivative dF 1 / dt reaches its maximum where the force F 1 rises steepest, then becomes negative when the force drops and reaches a plateau around the value zero where the force F 1 is horizontal. before it turns off at first negative and then positive and finally to zero.

Bei einer Fehleinspritzung würde die Ableitung dF0/dt (in Figur 2b strichliert) ein geringeres Maximum erreichen und anschließend negativ werden, bevor sie beim Abschalten wieder zu Null würde.In the case of an incorrect injection, the derivative dF 0 / dt (dashed line in FIG. 2b) would reach a lower maximum and then become negative before it would become zero again when switching off.

Erfindungsgemäß wird im Bereich des oben genannten Plateaus ein Toleranzband für den Wert der ersten Ableitung gelegt, mit einem oberen Wert g1 (für dF/dt positiv) und einem unteren Wert g2 (für dF/dt negativ). Beide Werte sind in Figur 2b strichliert dargestellt. Auch diese Werte können, wie die Fenster W1 und W2 in Figur 1, über Kennfelder in Abhängigkeit von zugeführter Energie, Raildruck u.s.w. variiert werden.According to the invention, a tolerance band for the value of the first derivative is applied in the area of the abovementioned plateau, with an upper value g1 (for dF / dt positive) and a lower value g2 (for dF / dt negative). Both values are shown in dashed lines in FIG. 2b. These values, like the windows W1 and W2 in FIG. 1, can also be determined via characteristic maps as a function of supplied energy, rail pressure and so on. be varied.

Solange sich nun die erste Ableitung dF1/dt - nach dem Zeitpunkt tA - innerhalb dieses Toleranzbandes befindet, was zwischen den Zeitpunkten t5 und t6 in Figur 2b festgestellt wird, wird angenommen, dass die Kraftstoffeinspritzung, die allerdings erst zeitversetzt dazu erfolgt, eine Dauer D (D=t6-t5) aufweist.As long as now the first derivative dF 1 / dt - after the time t A - is within this tolerance band, which is determined between the times t 5 and t 6 in Figure 2b, it is assumed that the fuel injection, which, however, takes place only with a time delay , a duration D (D = t 6 -t 5 ).

Auf die beschriebene Weise kann für jede Ansteuerung eines Piezoaktors für eine Vor-, Haupt- oder Nacheinspritzung festgestellt werden, ob eine korrekte oder eine Fehl-Einspritzung stattfindet, wann die Einspritzung beginnt und wie lange sie dauert.In the described manner it can be determined for each actuation of a piezo actuator for a pre-injection, main injection or post-injection, whether a correct or a wrong injection takes place, when the injection begins and how long it lasts.

Claims (6)

  1. Method for control of a piezo-actuated fuel-injection valve during advanced, main or afterinjection, by means of a piezo actuator and a servo-valve actuated by same, to detect an opening of the servo-valve and determine the injection duration (D),
    characterised in that
    that during a control operation the current applied to the piezo actuator and the voltage which is consequently established therefrom is used for calculating, with the help of a non-linear actuator model, the characteristics of the longitudinal variations (s) and the force (F) exerted by the actuator, and these or variables (dF/dt) derived therefrom determine the beginning of the opening (tA) of the servo-valve and the duration of injection (D).
  2. Method in accordance with claim 1, characterised in that a first (W1) and second (W2) time window are provided,
    that the variations in longitude at the start (t1) and end (t2) of the first time window (W1) determine a first tangent (T1), and the variations in longitude at the start (t3) and at the end (t4) of the second time window (W2) determine a second tangent (T1') and
    that both tangents (T1, T1') intersect at a timepoint (tA) .
  3. Method in accordance with claim 2, characterised in that the timepoint (tA) is assessed as the opening point of the servo-valve if the tangent (T1') has a definably steeper angle compared
    with the abscissa than the tangent (T1), otherwise (T0, T0') is detected as a faulty injection.
  4. Method in accordance with claim 1, characterised in that at a timepoint (tA) assessed as the opening timepoint of the servo-valve, a tolerance band between an upper limit (g1) and a lower limit (g2) is specified for the first time derivation (dF1/dt) of force (F), and
    that the time (t5 to t6) in which the value of the first derivation (dF1/dt) moves within this tolerance band after timepoint (tA) is assessed as the injection duration (D).
  5. Method in accordance with claim 2 or 4, characterised in that the timepoints (t1 to t4) defining both time windows (W1, W2) or the limits (g1, g2) of the tolerance band are stored in maps as timepoints allocated at least to the energy applied to the piezo actuator, the fuel pressure in the rail or the actuator temperature.
  6. Method in accordance with claim 5, characterised in that the timepoints (t1 to t4), stored in the maps, that determine the time windows (W1, W2) are also adapted relative to the timepoint (tA) determined in the particular proceeding earlier injection operation.
EP02760150A 2001-09-05 2002-09-02 Method for controlling a piezo-actuated fuel-injection valve Expired - Lifetime EP1423593B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10143501A DE10143501C1 (en) 2001-09-05 2001-09-05 Method for controlling a piezo-operated fuel injection valve
DE10143501 2001-09-05
PCT/DE2002/003226 WO2003023212A1 (en) 2001-09-05 2002-09-02 Method for controlling a piezo-actuated fuel-injection valve

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EP1423593A1 EP1423593A1 (en) 2004-06-02
EP1423593B1 true EP1423593B1 (en) 2006-11-02

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EP1423593A1 (en) 2004-06-02
DE10143501C1 (en) 2003-05-28
US20050072854A1 (en) 2005-04-07
US7040297B2 (en) 2006-05-09
WO2003023212A1 (en) 2003-03-20
JP4047809B2 (en) 2008-02-13
DE50208611D1 (en) 2006-12-14
JP2005501999A (en) 2005-01-20

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