EP2002111B1 - Fuel injector - Google Patents

Fuel injector Download PDF

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Publication number
EP2002111B1
EP2002111B1 EP07726342A EP07726342A EP2002111B1 EP 2002111 B1 EP2002111 B1 EP 2002111B1 EP 07726342 A EP07726342 A EP 07726342A EP 07726342 A EP07726342 A EP 07726342A EP 2002111 B1 EP2002111 B1 EP 2002111B1
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EP
European Patent Office
Prior art keywords
actuator
preload
pressure
fuel injector
coupler
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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.)
Not-in-force
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EP07726342A
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German (de)
French (fr)
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EP2002111A2 (en
Inventor
Thomas Pauer
Friedrich Boecking
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication of EP2002111A2 publication Critical patent/EP2002111A2/en
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    • 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
    • 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
    • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
    • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
    • F02M61/167—Means for compensating clearance or thermal expansion
    • 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
    • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/70—Linkage between actuator and actuated element, e.g. between piezoelectric actuator and needle valve or pump plunger
    • F02M2200/703—Linkage between actuator and actuated element, e.g. between piezoelectric actuator and needle valve or pump plunger hydraulic

Definitions

  • the invention relates to a fuel injector according to the preamble of claim 1.
  • Fuel injectors in which a piezoelectric actuator is coupled to the nozzle needle without the interposition of a control valve are known and are referred to as fuel injectors with directly controlled nozzle needle.
  • Such a fuel injector is out EP 1 111 230 A2 known, in which a piezoelectric actuator acts on a nozzle needle via a hydraulic coupler, wherein the piezoelectric actuator is biased by a tube spring. On the piezoelectric actuator acts another biasing element, which is formed by a compression spring and spring diaphragms.
  • WO 2005/050002 A1 is another fuel injector with a directly controlled nozzle needle known in which also acts the piezoelectric actuator via a hydraulic coupler on a nozzle needle.
  • the hydraulic coupler is limited by two sleeves, the one sleeve with a spring element at the same time biases the piezoelectric actuator.
  • a second spring element acts, which serves as a closing spring for the nozzle needle and thereby exerts no biasing force on the piezoelectric actuator.
  • the fuel injector is provided with an injector housing having a high fuel pressure inlet communicating with a central fuel high pressure source external to the injector housing and with a pressure space within the injector housing from which pressurized fuel is injected into a combustion chamber of an internal combustion engine when a nozzle needle opens which is coupled by a hydraulic coupler directly, without the interposition of a control valve, with an actuator, wherein the actuator is biased by a defined biasing force acting in the same direction as and greater than the compressive force, which at a relatively low operating pressure of the hydraulic coupler acts on the actuator.
  • the actuator is preferably a piezoactuator.
  • the hydraulic coupler serves to translate the stroke and / or force of the actuator.
  • the high pressure provided by the high-pressure fuel source operating can vary between a relatively high and a relatively low pressure level and is referred to as operating pressure.
  • the object of the invention is to improve the injection behavior of a fuel injector with respect to the response at low operating pressures.
  • At least one biasing element is biased parallel to the actuator, is applied by at least a portion of the biasing force to the actuator.
  • a coupler piston is provided, which is biased by a further biasing member against the actuator, is applied by the at least part of the biasing force to the actuator.
  • the further biasing element is clamped between the coupler piston and a sealing sleeve, which limits a coupler space.
  • the biasing forces of the biasing member and the further biasing member are coordinated so that the actuator is biased by a defined biasing force that is greater than the pressure force, which acts at a relatively low operating pressure from the hydraulic coupler to the actuator.
  • a preferred embodiment of the fuel injector is characterized in that the biasing force is 500 to 800 newtons. This biasing force range has proven to be particularly advantageous in the context of the present invention.
  • Another preferred embodiment of the fuel injector is characterized in that the actuator is disposed within a hollow biasing member. This has the advantage that only little space is required for the biasing element.
  • a further preferred embodiment of the fuel injector is characterized in that the biasing element comprises a spring sleeve.
  • the spring sleeve is preferably formed from spring steel and provided with a plurality of recesses.
  • Another preferred embodiment of the fuel injector is characterized in that the biasing element is biased between two cover plates of the actuator to train. Consequently, the actuator is stressed by the biasing element between the cover plates to pressure, so compressed.
  • the coupler piston defines on one side a coupler space which is bounded on the opposite side of the nozzle needle.
  • the coupler room can also be subdivided into several sub-coupling spaces, which are in communication with each other.
  • a further preferred embodiment of the fuel injector is characterized in that the further biasing element is biased to pressure parallel to the coupler piston.
  • This biasing elements is for example a helical compression spring.
  • Another preferred embodiment of the fuel injector is characterized in that the sealing sleeve is guided at one end of the coupler piston.
  • the attached figure shows a simplified representation of a fuel injector in longitudinal section.
  • FIG. 1 a fuel injector with an injector 1 is shown in longitudinal section.
  • the injector housing 1 comprises a nozzle body 2, which projects with its lower free end into a combustion chamber of an internal combustion engine to be supplied with fuel. With its upper end remote from the combustion chamber, the nozzle body 2 is clamped axially against an intermediate body 3 and an injector body 4 by means of a clamping nut (not shown).
  • the injector body 4 has substantially the shape of a circular-cylinder jacket-shaped sleeve, whose one end face is closed by the intermediate body 3.
  • an axial guide bore 6 is recessed, in which a nozzle needle 8 is guided axially displaceable.
  • a sealing edge 10 is formed, which cooperates with a sealing seat or a sealing surface 11 to selectively release or close two spray holes 13 and 14 depending on the position of the nozzle needle 8.
  • the nozzle needle 8 has a pressure chamber portion 15, followed by an expanding portion 16, which is also referred to as a pressure shoulder.
  • the pressure shoulder is arranged in a pressure chamber 17 which is formed between the nozzle needle 8 and the nozzle body 2.
  • On the pressure shoulder 16 is followed by a guide portion 18 which is guided in the guide bore 6 movable back and forth.
  • a fluid connection between the pressure chamber 17 and a nozzle spring chamber 22 is provided.
  • the nozzle spring chamber 22 communicates via a connecting channel (not shown) with an actuator chamber 25, which in turn is connected via an inlet channel or a feed line 26 to a high-pressure fuel source, which is also referred to as a common rail.
  • the fuel injector is actuated by a piezoelectric actuator 30.
  • the piezoelectric actuator 30 is coupled with the interposition of a compensation element 31, which is preferably made of ceramic, mechanically coupled to a coupler piston 32 whose combustion chamber near end face bounds a partial coupling space 34 in the axial direction.
  • partial coupling space 30 In the radial direction of the partial coupling space 30 is limited by a sealing sleeve 35, which is guided on the coupler piston 32 and biased by a compression spring 36 which is supported on a collar 37 of the coupler piston 32.
  • the partial coupling space 34 communicates with a further partial coupling space 40 via a connecting channel 38, which may be equipped with a throttle.
  • the guide portion 18 of the nozzle needle 8 is bounded away from the combustion chamber by a collar 44, from which the combustion chamber remote end 45 of the nozzle needle 8 goes out.
  • a sealing sleeve 48 is guided, which limits the partial coupling space 40 in the radial direction. Between the sealing sleeve 48 and the collar 44, a nozzle spring 60 is clamped.
  • the piezoelectric actuator 30 is disposed between two cover plates 71 and 72, which are held together by a biasing member 74 under bias. As a result, the piezoactuator 30 arranged therebetween is subjected to pressure, that is to say compressed.
  • the compression spring 36 which is also referred to as Aktor réellefeder is clamped under pretension between the collar 37 and the sealing sleeve 35 so that it acts alternatively or additionally as a biasing element for the piezoelectric actuator 30.
  • the high pressure acting in the fuel injector is also referred to as rail pressure.
  • the high pressure acts on the combustion chamber remote end face of the nozzle needle 8.
  • the piezoelectric actuator 30 is charged in the idle state of the fuel injector and has its maximum longitudinal extent. To actuate the fuel injector, the piezoelectric actuator 30 is discharged and retracts. The pressure in the sub-coupling spaces 34 and 40 drops off and the nozzle needle opens, that is, lifts off from its nozzle needle seat.
  • a needle stop is provided for limiting the stroke.

Abstract

The injector has a high pressure fuel inlet (26) connected with a central high pressure fuel source and a pressure chamber (17), where the fuel is injected from the inlet into a combustion chamber of an internal combustion engine, when a nozzle needle (8) opens. The needle is coupled with a piezo-actuator (30) by a hydraulic coupler. The actuator is preloaded by a defined preload force that acts in the same direction as a compressive force and is larger than the compressive force. The compressive force acts on the actuator with a relatively low operating pressure of the coupler.

Description

Die Erfindung betrifft einen Kraftstoffinjektor gemäß dem Oberbegriff des Anspruchs 1.The invention relates to a fuel injector according to the preamble of claim 1.

Stand der TechnikState of the art

Kraftstoffinjektoren, bei denen ein Piezoaktor ohne Zwischenschaltung eines Steuerventils mit der Düsennadel gekoppelt ist, sind bekannt und werden als Kraftstoffinjektoren mit direkt angesteuerter Düsennadel bezeichnet.Fuel injectors in which a piezoelectric actuator is coupled to the nozzle needle without the interposition of a control valve are known and are referred to as fuel injectors with directly controlled nozzle needle.

Ein derartiger Kraftstoffinjektor ist aus EP 1 111 230 A2 bekannt, bei dem ein Piezoaktor über einen hydraulischen Koppler auf eine Düsennadel einwirkt, wobei der Piezoaktor mittels einer Rohrfeder vorgespannt ist. Auf den Piezoaktor wirkt ein weiteres Vorspannelement ein, das von einer Druckfeder und von Federmembranen gebildet wird.Such a fuel injector is out EP 1 111 230 A2 known, in which a piezoelectric actuator acts on a nozzle needle via a hydraulic coupler, wherein the piezoelectric actuator is biased by a tube spring. On the piezoelectric actuator acts another biasing element, which is formed by a compression spring and spring diaphragms.

Aus WO 2005/050002 A1 ist ein weiterer Kraftstoffinjektor mit einer direkt angesteuerten Düsennadel bekannt, bei dem ebenfalls der Piezoaktor über einen hydraulischen Koppler auf eine Düsennadel einwirkt. Der hydraulische Koppler wird dabei von zwei Hülsen begrenzt, wobei die eine Hülse mit einem Federelement zugleich den Piezoaktor vorspannt. Auf die andere Hülse, die an einem Kolben der Düsennadel geführt ist, wirkt ein zweites Federelement ein, das als Schließfeder für die Düsennadel dient und dabei keine Vorspannkraft auf den Piezoaktor ausübt.Out WO 2005/050002 A1 is another fuel injector with a directly controlled nozzle needle known in which also acts the piezoelectric actuator via a hydraulic coupler on a nozzle needle. The hydraulic coupler is limited by two sleeves, the one sleeve with a spring element at the same time biases the piezoelectric actuator. On the other sleeve, which is guided on a piston of the nozzle needle, a second spring element acts, which serves as a closing spring for the nozzle needle and thereby exerts no biasing force on the piezoelectric actuator.

Weitere Kraftstoffinjektoren mit direkt angesteuerter Düsennadel, bei denen der Piezoaktor mittels eines Vorspannelements vorgespannt ist, sind aus WO 2002/14683 A1 und DE 199 12 666 A1 bekannt.Further fuel injectors with directly controlled nozzle needle, in which the piezoelectric actuator is biased by means of a biasing element, are out WO 2002/14683 A1 and DE 199 12 666 A1 known.

Offenbarung der ErfindungDisclosure of the invention

Der Kraftstoffinjektor ist mit einem Injektorgehäuse versehen, das einen Kraftstoffhochdruckzulauf aufweist, der mit einer zentralen Kraftstoffhochdruckquelle außerhalb des Injektorgehäuses und mit einem Druckraum innerhalb des Injektorgehäuses in Verbindung steht, aus dem mit Betriebsdruck beaufschlagter Kraftstoff in einen Brennraum einer Brennkraftmaschine eingespritzt wird, wenn eine Düsennadel öffnet, die durch einen hydraulischen Koppler direkt, ohne Zwischenschaltung eines Steuerventils, mit einem Aktor gekoppelt ist, wobei der Aktor durch eine definierte Vorspannkraft vorgespannt ist, die in die gleiche Richtung wirkt wie und größer ist als die Druckkraft, die bei einem relativ niedrigen Betriebsdruck von dem hydraulischen Koppler auf den Aktor wirkt. Bei dem Aktor handelt es sich vorzugsweise um einen Piezoaktor. Der hydraulische Koppler dient dazu, den Hub und/oder die Kraft des Aktors zu übersetzen. Der von der Kraftstoffhochdruckquelle bereitgestellte Hochdruck kann betriebsbedingt zwischen einem relativ hohen und einem relativ niedrigen Hochdruckniveau schwanken und wird als Betriebsdruck bezeichnet.The fuel injector is provided with an injector housing having a high fuel pressure inlet communicating with a central fuel high pressure source external to the injector housing and with a pressure space within the injector housing from which pressurized fuel is injected into a combustion chamber of an internal combustion engine when a nozzle needle opens which is coupled by a hydraulic coupler directly, without the interposition of a control valve, with an actuator, wherein the actuator is biased by a defined biasing force acting in the same direction as and greater than the compressive force, which at a relatively low operating pressure of the hydraulic coupler acts on the actuator. The actuator is preferably a piezoactuator. The hydraulic coupler serves to translate the stroke and / or force of the actuator. The high pressure provided by the high-pressure fuel source operating can vary between a relatively high and a relatively low pressure level and is referred to as operating pressure.

Aufgabe der Erfindung ist es, das Einspritzverhalten eines Kraftstoffinjektors bezüglich des Ansprechverhalten bei niedrigen Betriebsdrücken zu verbessern.The object of the invention is to improve the injection behavior of a fuel injector with respect to the response at low operating pressures.

Die Aufgabe der Erfindung wird mit den kennzeichnenden Merkmalen des Anspruchs 1 gelöst.The object of the invention is achieved with the characterizing features of claim 1.

Dazu ist parallel zu dem Aktor mindestens ein Vorspannelement vorgespannt, durch das zumindest ein Teil der Vorspannkraft auf den Aktor aufgebracht wird. Weiterhin ist ein Kopplerkolben vorgesehen, der durch ein weiteres Vorspannelement gegen den Aktor vorgespannt ist, durch das zumindest ein Teil der Vorspannkraft auf den Aktor aufgebracht wird. Das weitere Vorspannelement ist zwischen dem Kopplerkolben und einer Dichthülse eingespannt, die einen Kopplerraum begrenzt. Die Vorspannkräfte des Vorspannelements und des weiteren Vorspannelements sind dabei so aufeinander abgestimmt, dass der Aktor durch eine definierte Vorspannkraft vorgespannt ist, die größer als die Druckkraft ist, die bei einem relativ niedrigen Betriebsdruck von dem hydraulischen Koppler auf den Aktor wirkt.For this purpose, at least one biasing element is biased parallel to the actuator, is applied by at least a portion of the biasing force to the actuator. Furthermore, a coupler piston is provided, which is biased by a further biasing member against the actuator, is applied by the at least part of the biasing force to the actuator. The further biasing element is clamped between the coupler piston and a sealing sleeve, which limits a coupler space. The biasing forces of the biasing member and the further biasing member are coordinated so that the actuator is biased by a defined biasing force that is greater than the pressure force, which acts at a relatively low operating pressure from the hydraulic coupler to the actuator.

Durch die definierte Vorspannung des Aktors wird dessen Ansprechverhalten bei niedrigen Betriebsdrücken deutlich verbessert. Bei hohen Betriebsdrücken wird die Vorspannkraft durch die Druckkraft, die von dem hydraulischen Koppler auf den Aktor ausgeübt wird, kompensiert. Das liefert den Vorteil, dass sich die Vorspannung des Aktors nicht negativ auf die benötigte Aktorkraft und den benötigten Aktorhub auswirkt.Due to the defined bias of the actuator whose response at low operating pressures is significantly improved. At high operating pressures, the biasing force is compensated by the compressive force exerted by the hydraulic coupler on the actuator. This provides the advantage that the bias of the actuator does not adversely affect the required actuator force and the required Aktorhub.

Ein bevorzugtes Ausführungsbeispiel des Kraftstoffinjektors ist dadurch gekennzeichnet, dass die Vorspannkraft 500 bis 800 Newton beträgt. Dieser Vorspannkraftbereich hat sich im Rahmen der vorliegenden Erfindung als besonders vorteilhaft erwiesen.A preferred embodiment of the fuel injector is characterized in that the biasing force is 500 to 800 newtons. This biasing force range has proven to be particularly advantageous in the context of the present invention.

Ein weiteres bevorzugtes Ausführungsbeispiel des Kraftstoffinjektors ist dadurch gekennzeichnet, dass der Aktor innerhalb eines hohlen Vorspannelements angeordnet ist. Das hat den Vorteil, dass nur wenig Bauraum für das Vorspannelement benötigt wird.Another preferred embodiment of the fuel injector is characterized in that the actuator is disposed within a hollow biasing member. This has the advantage that only little space is required for the biasing element.

Ein weiteres bevorzugtes Ausführungsbeispiel des Kraftstoffinjektors ist dadurch gekennzeichnet, dass das Vorspannelement eine Federhülse umfasst. Die Federhülse ist vorzugsweise aus Federstahl gebildet und mit einer Vielzahl von Ausnehmungen versehen.A further preferred embodiment of the fuel injector is characterized in that the biasing element comprises a spring sleeve. The spring sleeve is preferably formed from spring steel and provided with a plurality of recesses.

Ein weiteres bevorzugtes Ausführungsbeispiel des Kraftstoffinjektors ist dadurch gekennzeichnet, dass das Vorspannelement zwischen zwei Abdeckplatten des Aktors auf Zug vorgespannt ist. Demzufolge wird der Aktor durch das Vorspannelement zwischen den Abdeckplatten auf Druck beansprucht, also zusammengedrückt.Another preferred embodiment of the fuel injector is characterized in that the biasing element is biased between two cover plates of the actuator to train. Consequently, the actuator is stressed by the biasing element between the cover plates to pressure, so compressed.

Der Kopplerkolben begrenzt auf einer Seite einen Kopplerraum, der auf der gegenüberliegenden Seite von der Düsennadel begrenzt wird. Der Kopplerraum kann auch in mehrere Teilkopplungsräume unterteilt sein, die miteinander in Verbindung stehen.The coupler piston defines on one side a coupler space which is bounded on the opposite side of the nozzle needle. The coupler room can also be subdivided into several sub-coupling spaces, which are in communication with each other.

Ein weiteres bevorzugtes Ausführungsbeispiel des Kraftstoffinjektors ist dadurch gekennzeichnet, dass das weitere Vorspannelement parallel zu dem Kopplerkolben auf Druck vorgespannt ist. Bei diesem Vorspannelemente handelt es sich zum Beispiel um eine Schraubendruckfeder.A further preferred embodiment of the fuel injector is characterized in that the further biasing element is biased to pressure parallel to the coupler piston. This biasing elements is for example a helical compression spring.

Ein weiteres bevorzugtes Ausführungsbeispiel des Kraftstoffinjektors ist dadurch gekennzeichnet, dass die Dichthülse an einem Ende des Kopplerkolbens geführt ist.Another preferred embodiment of the fuel injector is characterized in that the sealing sleeve is guided at one end of the coupler piston.

Kurze Beschreibung der ZeichnungShort description of the drawing

Die beiliegende Figur zeigt eine vereinfachte Darstellung eines Kraftstoffinjektors im Längsschnitt.The attached figure shows a simplified representation of a fuel injector in longitudinal section.

Ausführungsformen der ErfindungEmbodiments of the invention

In Figur 1 ist ein Kraftstoffinjektor mit einem Injektorgehäuse 1 im Längsschnitt dargestellt. Das Injektorgehäuse 1 umfasst einen Düsenkörper 2, der mit seinem unteren freien Ende in einen Brennraum einer mit Kraftstoff zu versorgenden Brennkraftmaschine ragt. Mit seiner oberen brennraumfernen Stirnfläche ist der Düsenkörper 2 mittels einer (nicht dargestellten) Spannmutter axial gegen einen Zwischenkörper 3 und einen Injektorkörper 4 verspannt. Der Injektorkörper 4 hat im Wesentlichen die Gestalt einer kreiszylindermantelförmigen Hülse, deren eine Stirnseite durch den Zwischenkörper 3 abgeschlossen ist.In FIG. 1 a fuel injector with an injector 1 is shown in longitudinal section. The injector housing 1 comprises a nozzle body 2, which projects with its lower free end into a combustion chamber of an internal combustion engine to be supplied with fuel. With its upper end remote from the combustion chamber, the nozzle body 2 is clamped axially against an intermediate body 3 and an injector body 4 by means of a clamping nut (not shown). The injector body 4 has substantially the shape of a circular-cylinder jacket-shaped sleeve, whose one end face is closed by the intermediate body 3.

In dem Düsenkörper 2 ist eine axiale Führungsbohrung 6 ausgespart, in der eine Düsennadel 8 axial verschiebbar geführt ist. An der Spitze 9 der Düsennadel 8 ist eine Dichtkante 10 ausgebildet, die mit einem Dichtsitz beziehungsweise einer Dichtfläche 11 zusammenwirkt, um zwei Spritzlöcher 13 und 14 in Abhängigkeit von der Stellung der Düsennadel 8 gezielt freizugeben oder zu verschließen. Wenn die Düsennadelspitze 9 mit der Dichtkante 10 von ihrem Dichtsitz abhebt, dann wird mit Hochdruck beaufschlagter Kraftstoff durch die Spritzlöcher 13 und 14 in den Brennraum der Brennkraftmaschine eingespritzt.In the nozzle body 2, an axial guide bore 6 is recessed, in which a nozzle needle 8 is guided axially displaceable. At the top 9 of the nozzle needle 8, a sealing edge 10 is formed, which cooperates with a sealing seat or a sealing surface 11 to selectively release or close two spray holes 13 and 14 depending on the position of the nozzle needle 8. When the nozzle needle tip 9 lifts off from its sealing seat with the sealing edge 10, high-pressure fuel is injected through the injection holes 13 and 14 into the combustion chamber of the internal combustion engine.

Ausgehend von der Spitze 9 weist die Düsennadel 8 einen Druckraumabschnitt 15 auf, auf den ein sich erweiternder Abschnitt 16 folgt, der auch als Druckschulter bezeichnet wird. Die Druckschulter ist in einem Druckraum 17 angeordnet, der zwischen der Düsennadel 8 und dem Düsenkörper 2 ausgebildet ist. Auf die Druckschulter 16 folgt ein Führungsabschnitt 18, der in der Führungsbohrung 6 hin und her bewegbar geführt ist. Durch mindestens eine Abflachung 19 an dem Führungsabschnitt 18 wird eine Fluidverbindung zwischen dem Druckraum 17 und einem Düsenfederraum 22 geschaffen.Starting from the tip 9, the nozzle needle 8 has a pressure chamber portion 15, followed by an expanding portion 16, which is also referred to as a pressure shoulder. The pressure shoulder is arranged in a pressure chamber 17 which is formed between the nozzle needle 8 and the nozzle body 2. On the pressure shoulder 16 is followed by a guide portion 18 which is guided in the guide bore 6 movable back and forth. By at least one flat 19 on the guide portion 18, a fluid connection between the pressure chamber 17 and a nozzle spring chamber 22 is provided.

Der Düsenfederraum 22 steht über einen (nicht dargestellten) Verbindungskanal mit einem Aktorraum 25 in Verbindung, der wiederum über einen Zulaufkanal oder eine Zulaufleitung 26 mit einer Kraftstoffhochdruckquelle in Verbindung steht, die auch als Common Rail bezeichnet wird. Der Kraftstoffinjektor wird durch einen Piezoaktor 30 betätigt. Der Piezoaktor 30 ist unter Zwischenschaltung eines Ausgleichselements 31, das vorzugsweise aus Keramik gebildet ist, mechanisch mit einem Kopplerkolben 32 gekoppelt, dessen brennraumnahe Stirnfläche einen Teilkopplungsraum 34 in axialer Richtung begrenzt. In radialer Richtung wird der Teilkopplungsraum 30 durch eine Dichthülse 35 begrenzt, die an dem Kopplerkolben 32 geführt und durch eine Druckfeder 36 vorgespannt ist, die sich an einem Bund 37 des Kopplerkolbens 32 abstützt. Der Teilkopplungsraum 34 steht über einen Verbindungskanal 38, der mit einer Drossel ausgestattet sein kann, mit einem weiteren Teilkopplungsraum 40 in Verbindung.The nozzle spring chamber 22 communicates via a connecting channel (not shown) with an actuator chamber 25, which in turn is connected via an inlet channel or a feed line 26 to a high-pressure fuel source, which is also referred to as a common rail. The fuel injector is actuated by a piezoelectric actuator 30. The piezoelectric actuator 30 is coupled with the interposition of a compensation element 31, which is preferably made of ceramic, mechanically coupled to a coupler piston 32 whose combustion chamber near end face bounds a partial coupling space 34 in the axial direction. In the radial direction of the partial coupling space 30 is limited by a sealing sleeve 35, which is guided on the coupler piston 32 and biased by a compression spring 36 which is supported on a collar 37 of the coupler piston 32. The partial coupling space 34 communicates with a further partial coupling space 40 via a connecting channel 38, which may be equipped with a throttle.

Der Führungsabschnitt 18 der Düsennadel 8 wird vom Brennraum weg durch einen Bund 44 begrenzt, von dem das brennraumferne Ende 45 der Düsennadel 8 ausgeht. An dem brennraumfernen Ende 45 der Düsennadel 8 ist eine Dichthülse 48 geführt, die den Teilkopplungsraum 40 in radialer Richtung begrenzt. Zwischen der Dichthülse 48 und dem Bund 44 ist eine Düsenfeder 60 eingespannt.The guide portion 18 of the nozzle needle 8 is bounded away from the combustion chamber by a collar 44, from which the combustion chamber remote end 45 of the nozzle needle 8 goes out. At the combustion chamber remote end 45 of the nozzle needle 8, a sealing sleeve 48 is guided, which limits the partial coupling space 40 in the radial direction. Between the sealing sleeve 48 and the collar 44, a nozzle spring 60 is clamped.

Der Piezoaktor 30 ist zwischen zwei Abdeckplatten 71 und 72 angeordnet, die durch ein Vorspannelement 74 unter Vorspannung zusammengehalten werden. Dadurch wird der dazwischen angeordnet Piezoaktor 30 auf Druck beansprucht, das heißt zusammengedrückt. Die Druckfeder 36, die auch als Aktordruckfeder bezeichnet wird, ist unter Vorspannung zwischen dem Bund 37 und der Dichthülse 35 eingespannt, so dass sie alternativ oder zusätzlich als Vorspannelement für den Piezoaktor 30 wirkt.The piezoelectric actuator 30 is disposed between two cover plates 71 and 72, which are held together by a biasing member 74 under bias. As a result, the piezoactuator 30 arranged therebetween is subjected to pressure, that is to say compressed. The compression spring 36, which is also referred to as Aktordruckfeder is clamped under pretension between the collar 37 and the sealing sleeve 35 so that it acts alternatively or additionally as a biasing element for the piezoelectric actuator 30.

Im Ruhezustand des Kraftstoffinjektors herrscht in den Teilkopplungsräumen 34 und 40 Hochdruck, der auch als Raildruck bezeichnet wird. Der Hochdruck hat nicht immer konstant das gleiche Niveau. Vielmehr schwankt der Hochdruck zwischen einem relativ hohen und einem relativ niedrigen Druckniveau. Daher wird der Hochdruck, der in dem Kraftstoffinjektor wirkt, auch als Betriebsdruck bezeichnet. Der Hochdruck wirkt auf die brennraumferne Stirnfläche der Düsennadel 8. Der Piezoaktor 30 ist im Ruhezustand des Kraftstoffinjektors aufgeladen und hat seine maximale Längsausdehnung. Zur Ansteuerung des Kraftstoffinjektors wird der Piezoaktor 30 entladen und zieht sich dabei zurück. Der Druck in den Teilkopplungsräumen 34 und 40 fällt ab und die Düsennadel öffnet, das heißt hebt von ihrem Düsennadelsitz ab. Vorteilhafterweise ist ein Nadelanschlag zur Hubbegrenzung vorgesehen.In the idle state of the fuel injector prevails in the partial coupling spaces 34 and 40 high pressure, which is also referred to as rail pressure. The high pressure does not always have the same level. Rather, the high pressure varies between a relatively high and a relatively low pressure level. Therefore, the high pressure acting in the fuel injector is also referred to as the operating pressure. The high pressure acts on the combustion chamber remote end face of the nozzle needle 8. The piezoelectric actuator 30 is charged in the idle state of the fuel injector and has its maximum longitudinal extent. To actuate the fuel injector, the piezoelectric actuator 30 is discharged and retracts. The pressure in the sub-coupling spaces 34 and 40 drops off and the nozzle needle opens, that is, lifts off from its nozzle needle seat. Advantageously, a needle stop is provided for limiting the stroke.

Claims (6)

  1. Fuel injector having an injector housing (1) which has a high-pressure fuel inlet (26) which is connected to a central high-pressure fuel source outside the injector housing (1) and to a pressure chamber (17) within the injector housing (1), from which pressure chamber (17) fuel at operating pressure is injected into a combustion chamber of an internal combustion engine when a nozzle needle (8) which is coupled by means of a hydraulic coupler to an actuator (30) is opened, with at least one preload element (74) being preloaded parallel to the actuator (30), which preload element (74) serves to impart at least a part of the preload force to the actuator (30), and with the hydraulic coupler comprising a coupler piston (32) which is preloaded against the actuator (30) by means of a further preload element (36) which serves to impart at least a part of the preload force to the actuator (30), characterized in that the further preload element (36) is clamped between the coupler piston (32) and a sealing sleeve (35) which delimits a coupler chamber (34), and in that the preload forces of the preload element (74) and of the further preload element (36) are coordinated with one another in such a way that the actuator (30) is preloaded by a defined preload force which is greater than the pressure force which is exerted by the hydraulic coupler on the actuator (30) at a relatively low operating pressure.
  2. Fuel injector according to Claim 1, characterized in that the preload force is 500 to 800 Newtons.
  3. Fuel injector according to Claim 1, characterized in that the actuator (30) is arranged within a hollow preload element (74).
  4. Fuel injector according to Claim 3, characterized in that the preload element (74) comprises a spring sleeve.
  5. Fuel injector according to Claim 1, characterized in that the preload element (74) is preloaded under tension between two cover plates (71, 72) of the actuator (30).
  6. Fuel injector according to Claim 1, characterized in that the preload element (36) or the further preload element (36) is preloaded under compression parallel to the coupler piston (32).
EP07726342A 2006-03-28 2007-02-12 Fuel injector Not-in-force EP2002111B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102006014251A DE102006014251A1 (en) 2006-03-28 2006-03-28 Fuel injector for internal combustion engine, has piezo-actuator coupled with nozzle needle and preloaded by defined preload force that acts in same direction as compressive force and is larger than compressive force
PCT/EP2007/051320 WO2007110267A2 (en) 2006-03-28 2007-02-12 Fuel injector

Publications (2)

Publication Number Publication Date
EP2002111A2 EP2002111A2 (en) 2008-12-17
EP2002111B1 true EP2002111B1 (en) 2010-05-12

Family

ID=38441577

Family Applications (1)

Application Number Title Priority Date Filing Date
EP07726342A Not-in-force EP2002111B1 (en) 2006-03-28 2007-02-12 Fuel injector

Country Status (4)

Country Link
EP (1) EP2002111B1 (en)
AT (1) ATE467759T1 (en)
DE (2) DE102006014251A1 (en)
WO (1) WO2007110267A2 (en)

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19843570A1 (en) * 1998-09-23 2000-03-30 Bosch Gmbh Robert Fuel injector
DE19905413A1 (en) * 1999-02-10 2000-08-24 Bosch Gmbh Robert Injector with piezo multilayer actuator for injection systems
DE19912666A1 (en) * 1999-03-20 2000-09-21 Bosch Gmbh Robert Fuel injector
DE19962177A1 (en) * 1999-12-22 2001-07-12 Siemens Ag Hydraulic device for transmitting an actuator movement
DE10039424A1 (en) * 2000-08-11 2002-02-28 Siemens Ag Dosing valve with a hydraulic transmission element
DE10352736A1 (en) * 2003-11-12 2005-07-07 Robert Bosch Gmbh Fuel injector with direct needle injection
DE102005046440B4 (en) * 2005-09-28 2007-07-19 Siemens Ag tension spring

Also Published As

Publication number Publication date
WO2007110267A3 (en) 2008-04-10
WO2007110267A2 (en) 2007-10-04
ATE467759T1 (en) 2010-05-15
EP2002111A2 (en) 2008-12-17
DE102006014251A1 (en) 2007-10-04
DE502007003736D1 (en) 2010-06-24

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