EP2133552B1 - Fuel injector - Google Patents

Fuel injector Download PDF

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Publication number
EP2133552B1
EP2133552B1 EP09100243A EP09100243A EP2133552B1 EP 2133552 B1 EP2133552 B1 EP 2133552B1 EP 09100243 A EP09100243 A EP 09100243A EP 09100243 A EP09100243 A EP 09100243A EP 2133552 B1 EP2133552 B1 EP 2133552B1
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EP
European Patent Office
Prior art keywords
chamber
pressure chamber
nozzle needle
fuel
plunger
Prior art date
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
Application number
EP09100243A
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German (de)
French (fr)
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EP2133552A1 (en
Inventor
Hans-Christoph Magel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
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Robert Bosch GmbH
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Publication date
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Publication of EP2133552A1 publication Critical patent/EP2133552A1/en
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Publication of EP2133552B1 publication Critical patent/EP2133552B1/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
    • 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
    • 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
    • F02M61/161—Means for adjusting injection-valve lift
    • 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.
  • the object of the invention is to provide a fuel injector according to the preamble of claim 1 for comparatively low design effort and reduced energy consumption for the actuator.
  • the low-pressure chamber arranged in a coupling space-side end face of the slave piston open blind bore of the slave piston and completed by a protruding into the blind bore relatively stationary plunger and a plunger passing through the axial bore with the relatively pressureless fuel reservoir in combination.
  • the actuating forces to be applied by the actuator during the opening stroke of the nozzle needle or the like can be comparatively low, so that comparatively little energy is required for the control stroke.
  • the degree of necessary force or energy during the opening stroke can be adjusted to the actuator.
  • additional measures are provided to keep the actuator forces required during the closing stroke of the nozzle needle or the like low.
  • a throttle is arranged within a flow path of the fuel connecting the high-pressure chamber with the inlet side of the nozzles.
  • a pressure difference occurs at this throttle, wherein the input side of the throttle is substantially an input pressure corresponding to the pressure in the high-pressure chamber and output side substantially an output pressure approximated to the comparatively low combustion chamber pressure, so that supportive hydraulic forces must occur in the closing stroke of the nozzle needle or the like ,
  • the flow path between the inner circumference of a subsequent to the high-pressure chamber nozzle needle chamber and the outer circumference of the nozzle needle or the like arranged and the throttle between a nozzle needle side flange or flange and the inner circumference formed or arranged.
  • the said throttle may be formed as an annular gap throttle between the inner circumference of the nozzle needle chamber and the outer periphery of a fixed to the nozzle needle or the like annular collar-shaped flange.
  • the plunger with an end piece which has a relation to the cross section of the blind bore and the plunger enlarged cross section, on one of the coupling chamber side end face of the slave piston axially opposed to the stationary surface on the injector housing and between the end piece and the stationary surface a substantially disc-shaped and communicating with the relatively pressureless fuel reservoir space with respect to the diameter of the blind bore or the plunger larger disc diameter may be formed.
  • the single FIGURE shows a schematic axial section of a particularly preferred embodiment of the fuel injector according to the invention.
  • the fuel injector 1 shown in the drawing has an injector body 2, which receives a first pressure chamber 3, a second pressure chamber 4 and an adjoining third pressure chamber 5.
  • the pressure chambers 3-5 are communicatively connected to each other by a between the first and second pressure chamber 4 arranged intermediate bottom 6 of the injector body 2 is penetrated by an axial bore 7 connecting the pressure chambers 3 and 4.
  • the pressure chamber 5 serves as an axial guide of a nozzle needle 8, which controls the arranged in the drawing lower end of the pressure chamber 5 injectors 9, via which the pressure chamber 5 is connected to a combustion chamber, not shown, of an internal combustion engine.
  • the nozzle needle 8 takes its nozzle 9 shut-off closing position in which the nozzle-side end of the nozzle needle 8 is seated with a nozzle-side annular edge tight on a the inputs of the nozzles 9 with radial spacing enclosing annular nozzle needle seat, so that within the pressure chamber 5 a Nozzle input space 10 is separated from a remaining between the axial inner wall of the pressure chamber 5 and the outer circumference of the nozzle needle 8 annular space.
  • This annular space communicates constantly with the pressure chamber 4.
  • the nozzle needle is guided in an axially adjacent to the pressure chamber 4 extended upper axial portion of the pressure chamber 5 with arranged on the nozzle needle axial webs or the like, between which the aforementioned annular space with the pressure chamber 4 connecting Free spaces remain.
  • the nozzle needle 8 assumes its lifted from the seat to the injectors 9 open position, the nozzle inlet chamber 10 via the pressure chambers 5 and 4 and the axial bore 7 in the intermediate bottom 6 and the pressure chamber 3 is connected to a high-pressure fuel reservoir 11, which typically as so-called Common Rail is formed and communicates via a connecting line 12 with the first pressure chamber 3. This can be under high pressure Fuel are injected via the injectors 9 in the combustion chamber of the internal combustion engine.
  • valve needle 8 To actuate the valve needle 8 is a trained in the example as a piezoelectric element actuator 13 which is connected via electrical lines 14 to an electrical voltage source and is hydraulically coupled to the valve needle 8.
  • This hydraulic coupling is effected by a positive displacement by means of the actuator 13 master piston 15 in a coupling chamber 16 which communicates via a the intermediate bottom 6 passing through line 17 with a coupling chamber 18, in which a arranged on the nozzle needle 8 slave piston 19 works displacer effective.
  • the master piston 15 performs a downward movement reducing the coupling space 16
  • fluid is expelled from the coupling space 16 via the conduit 17 into the coupling space 18, so that the slave piston 19 with the nozzle needle 8 performs a downward movement in the direction of the closed position of the nozzle needle 8.
  • the coupling space 16 receives fluid from the coupling space 18 during upward movement of the master piston 15, wherein the slave piston 19 with the valve needle 8 in the upward direction, i. moved in an open position of the valve needle 8. Since the displacement effective piston cross sections of the master and slave pistons 15 and 19 are different, a corresponding stroke ratio is effected, wherein the gear ratio is inverse to the ratio of the cross sections.
  • the coupling chamber 16 is separated from the pressure chamber 3 by a sealing sleeve 20 which is displaceably guided on the master piston 15 and by means of a helical compression spring 21 which is clamped between an annular collar arranged on the master piston 15 and the facing end edge of the sealing sleeve 20 against the master piston 15 facing Front side of the false floor 6 is stretched, the sealing sleeve 20 is tightly seated with a sharp annular edge on a ring line zone of the false floor.
  • the coupling space 18 is separated from the pressure chamber 4 by a sealing sleeve 22 which slidably guided on the slave piston 19 and by means of a clamped between an annular collar on the slave piston 19 and the facing end edge of the sealing sleeve 22 helical compression spring 23 against the slave piston 19 facing end side of the Intermediate tray 6 is tensioned, wherein the sealing sleeve 22 is tightly seated with a sharp edge of the ring on a corresponding ring line zone on the lower end face of the intermediate bottom 6 in the drawing.
  • axial blind bore 24 is arranged, which is shut off from the coupling space 18 by a protruding into the blind bore 24, stationary supported on the intermediate bottom 6 plunger 25.
  • the plunger 25 is penetrated by an axial bore, which is connected via a the intermediate bottom 6 passing through line 26 with a relatively pressureless fuel reservoir, such as a fuel tank (not shown). Accordingly, a low pressure space 27 remaining between the bottom of the blind bore 24 and the facing front end of the plunger 25 is constantly below the virtually vanishing pressure of the fuel reservoir or fuel tank.
  • the plunger 25 is held on the facing side of the intermediate bottom 6 by fluidic forces.
  • the intermediate bottom 6 facing the end of the plunger 25 has a relation to the cross section of the plunger 25 and the blind bore 24 significantly enlarged cross-section, within the intermediate bottom 6 facing side of said end piece a disc-shaped space 28 is recessed, the diameter clearly larger than the outer diameter of the plunger 25 and the inner diameter of the blind bore 24 is.
  • This disc-shaped space 28 is in communication with the line 26 to the relatively pressureless fuel reservoir or tank, so that the present in the coupling chamber 18, the pressure in the pressure chambers 3 and 4 corresponding pressure, which substantially corresponds to the pressure in the pressure accumulator 11, the End of the plunger 25 presses with a correspondingly large force against the facing end face of the intermediate bottom 6, wherein the end piece with a disk-shaped space 28 comprehensive sharp annular edge on a ring-shaped zone of the false bottom 6 is tightly seated.
  • said end piece of the plunger 25 is still tensioned against the intermediate bottom 6 by a helical compression spring 29 accommodated in the low-pressure space 27 and clamped between the bottom of the blind bore 24 and the facing front end of the plunger 25.
  • the helical compression spring 29 essentially serves only as a mounting aid and may be correspondingly weak dimensioned.
  • the helical compression spring 29 for the start of the end piece of the plunger 25 against the facing side of the intermediate bottom 6 is practically meaningless.
  • the illustrated fuel injector 1 functions as follows:
  • the coupling chambers 16 and 18 are filled with fuel during operation and are substantially under the same pressure as the fuel in the pressure accumulator 11.
  • the piezoelectric actuator 13 is subjected to an electrical voltage via the electrical leads 14, he holds the master piston 15 in the lower position shown in the drawing, and the nozzle needle 8 assumes the illustrated closed position.
  • the injection nozzles 9 are shut off from the pressure accumulator 11.
  • the piezoelectric actuator 13 pulls the master piston 15 in the direction of its top dead center position, ie the master piston 15 leads in the drawing Upstroke from which the slave piston 19 with the nozzle needle 8 with 19 by the ratio of the displacer cross sections of the master and slave piston 15, 19 given Hubüber ? That is, the nozzle needle 8 lifts from its nozzle-side seat, so that the nozzle input space 10 is connected to the pressure accumulator 11 and fuel is injected via the nozzles 9 in the adjacent combustion chamber. If subsequently the piezoelectric actuator 13 is acted upon again via the electrical connection lines 12 with an electrical voltage, the master piston 15 and the nozzle needle 8 are in turn pushed into the positions shown in the drawing.
  • the dimensioning of the cross-section of the low-pressure chamber 27 or the cross-section of the blind bore 24 and the plunger 25 displaceable therein is essential.
  • the forces which are necessary to bring the nozzle needle 8 located in the closed position in the open position are essentially determined by the difference between the cross section of the nozzle inlet chamber 10, that is, the cross section of the nozzle needle seat, and the cross section of the low pressure chamber 27.
  • the cross section of the low-pressure chamber 27 is about 60 - 80% of the cross-section of the nozzle input space 10.
  • a bypass throttle 30 is provided between the pressure chambers 4 and 5.
  • a flange 31 is arranged to form the bypass throttle 30 on the nozzle needle 8, which is dimensioned such that between its outer circumference and the inner circumference of the pressure chamber 5, a throttle-effective annular gap is formed.
  • the energy required for the closing stroke of the nozzle needle 8 and on the other hand, the energy requirements for the opening stroke of the nozzle needle 8 can be kept low, so that a correspondingly smaller cost-effective actuator 13 for the operation of the fuel injector 1 is sufficient.
  • the hydraulic coupling of the master and slave pistons 15, 19 described above also effects a compensation of thermal expansions without further design measures, so that no further measures for compensating fluctuations in the operating temperature of the injector 1 become necessary.
  • a throttle is preferably arranged, which exerts a damping effect on the piston strokes.
  • the upper end position of the nozzle needle should preferably be defined by a stop. This can for example be realized in that the intermediate bottom 6 facing end face of the slave piston 19 in the upper end position stop-like cooperates with the tail at the upper end of the plunger 25.
  • a nip is formed between the mutually facing surfaces of the slave piston 19 and said end piece, from the fluid is displaced during the upward stroke of the slave piston 19 under damping of the upward movement, so that the slave piston 19 and the nozzle needle 8 are braked damped shortly before taking their upper end position.

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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)

Abstract

The injector (1) has a low-pressure chamber (27) provided in a slave piston (19), where volume of the chamber is decreased during an opening stroke of a valve needle (8). The chamber is arranged in a blind hole (24) that is opened towards a coupling chamber sided front side of the slave piston. The chamber is closed by a plunger (25) extending into the blind hole. The chamber communicates with a relative depressurized fuel reservoir or tank via an axial bore hole penetrating the plunger. An actuator (13) i.e. piezoelectric element, is hydraulically coupled with the valve needle.

Description

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

Stand der TechnikState of the art

Es ist bekannt, zur Einbringung von Kraftstoff in direkteinspritzende Dieselmotoren hubgesteuerte Kraftstoffinjektoren zu verwenden. Damit wird der Vorteil geboten, dass der Einspritzdruck an Last und Drehzahl angepasst werden kann. Die Ansteuerung der Injektoren kann durch einen Piezoaktor direkt oder unter Zwischenschaltung eines Servo-Steuerraumes erfolgen.It is known to use stroke-controlled fuel injectors for introducing fuel into direct-injection diesel engines. This provides the advantage that the injection pressure can be adapted to load and speed. The actuation of the injectors can be done by a piezoelectric actuator directly or with the interposition of a servo control chamber.

Offenbarung der ErfindungDisclosure of the invention

Aufgabe der Erfindung ist es, einen Kraftstoffinjektor gemäß dem Oberbegriff des Anspruches 1 zu vergleichsweise geringem konstruktivem Aufwand und vermindertem Energiebedarf für den Aktor zu schaffen.The object of the invention is to provide a fuel injector according to the preamble of claim 1 for comparatively low design effort and reduced energy consumption for the actuator.

Zur Lösung dieser Aufgabe dient ein Kraftstoffinjektor mit

  • einem Injektorgehäuse sowie einem darin angeordneten Hochdruckraum, der ständig mit einer Hochdruckquelle (common rail) für Kraftstoff kommuniziert und über durch eine Düsennadel oder dergleichen gesteuerte Düsen zur Einspritzung von Kraftstoff mit einem Brennraum verbindbar ist,
  • einem Aktor, der mit der Düsennadel zu deren Betätigung hydraulisch gekoppelt ist, indem der Aktor mit einem Geberkolben, welcher in einem im Hochdruckraum abgetrennten Kopplungsraum arbeitet, und die Düsennadel oder dergleichen mit einem im Kopplungsraum arbeitenden Nehmerkolben antriebsverbunden ist, und
  • einem mit einem relativ drucklosem Kraftstoffreservoir (zum Beispiel Kraftstofftank) kommunizierenden Niederdruckraum am darin als Verdränger arbeitenden Nehmerkolben, wobei das Volumen des Niederdruckraumes beim Öffnungshub der Düsennadel oder dergleichen abnimmt.
To solve this problem is a fuel injector with
  • an injector housing and a high-pressure space arranged therein, which communicates constantly with a high-pressure source (common rail) for fuel and can be connected to a combustion chamber via nozzles which are controlled by a nozzle needle or the like for the injection of fuel,
  • an actuator which is hydraulically coupled to the nozzle needle for the actuation by the actuator with a master piston, which operates in a separated in the high-pressure chamber coupling space, and the nozzle needle or the like is drivingly connected to a slave piston working in the coupling space, and
  • a low-pressure space communicating with a relatively unpressurized fuel reservoir (for example fuel tank) on the slave piston operating therein as a displacer, the volume of the low-pressure space decreasing during the opening stroke of the nozzle needle or the like.

Zusätzlich zu diesem aus der nicht vorveröffentlichten DE 10 2006 062216.2 entnehmbaren Merkmalen ist erfindungsgemäß vorgesehen, dass der Niederdruckraum in einer zur kopplungsraumseitigen Stirnseite des Nehmerkolbens offenen Sackbohrung des Nehmerkolbens angeordnet und durch einen in die Sackbohrung hineinragenden relativ stationären Plunger abgeschlossen und über eine den Plunger durchsetzende Axialbohrung mit dem relativ drucklosen Kraftstoffreservoir in Verbindung steht.In addition to this from the not previously published DE 10 2006 062216.2 removable features is inventively provided that the low-pressure chamber arranged in a coupling space-side end face of the slave piston open blind bore of the slave piston and completed by a protruding into the blind bore relatively stationary plunger and a plunger passing through the axial bore with the relatively pressureless fuel reservoir in combination.

Aufgrund der besonderen Anordnung und Ausbildung des Niederdruckraumes wird in konstruktiv einfach zu verwirklichender Weise gewährleistet, dass im Schließzustand der Düsennadel oder dergleichen nur ein im Vergleich zum Querschnitt des Dichtsitzes der Düsennadel oder dergleichen an den Düsen verkleinerter Querschnitt der Düsennadel oder dergleichen von dem im Vergleich zum Brennraumdruck sehr hohen Druck im Hochdruckraum schließend belastet werden kann. Damit können die vom Aktor beim Öffnungshub der Düsennadel oder dergleichen aufzubringenden Stellkräfte vergleichsweise gering sein, so dass für den Stellhub vergleichsweise wenig Energie benötigt wird. Durch entsprechende Vorgabe des Durchmessers des stationären Plungers sowie der zugehörigen Sackbohrung im Nehmerkolben kann das Maß der notwendigen Stellkraft bzw. Energie beim Öffnungshub auf den Aktor eingestellt werden. Vorzugsweise sind zusätzliche Maßnahmen vorgesehen, um die beim Schließhub der Düsennadel oder dergleichen notwendigen Aktorkräfte gering zu halten.Due to the special arrangement and design of the low-pressure chamber is ensured structurally simple manner to be realized that in the closed state of the nozzle needle or the like only compared to the cross-section of the sealing seat of the nozzle needle or the like on the nozzle reduced cross-section of the nozzle needle or the like of the compared Brennraumdruck very high pressure in the high pressure chamber closing can be charged. Thus, the actuating forces to be applied by the actuator during the opening stroke of the nozzle needle or the like can be comparatively low, so that comparatively little energy is required for the control stroke. By appropriate specification of the diameter of the stationary plunger and the associated blind bore in the slave piston, the degree of necessary force or energy during the opening stroke can be adjusted to the actuator. Preferably, additional measures are provided to keep the actuator forces required during the closing stroke of the nozzle needle or the like low.

Dies kann gemäß einer bevorzugten Ausführungsform der Erfindung dadurch erreicht werden, dass innerhalb eines den Hochdruckraum mit der Eingangsseite der Düsen verbindenden Strömungspfades des Kraftstoffes eine Drossel angeordnet ist. Während der Einspritzphase tritt an dieser Drossel eine Druckdifferenz auf, wobei eingangsseitig der Drossel im Wesentlichen ein dem Druck im Hochdruckraum entsprechender Eingangsdruck und ausgangsseitig ein im Wesentlichen dem vergleichsweise geringem Brennraumdruck angenäherter Ausgangsdruck vorliegt, so dass im Schließhub der Düsennadel oder dergleichen unterstützende hydraulische Kräfte auftreten müssen. In konstruktiv besonders bevorzugter Weise kann der Strömungspfad zwischen dem Innenumfang eines an dem Hochdruckraum anschließenden Düsennadelraumes und dem Außenumfang der Düsennadel oder dergleichen angeordnet und die Drossel zwischen einem düsennadelseitigen Bund bzw. Flansch und dem Innenumfang ausgebildet oder angeordnet sein.This can be achieved according to a preferred embodiment of the invention in that a throttle is arranged within a flow path of the fuel connecting the high-pressure chamber with the inlet side of the nozzles. During the injection phase, a pressure difference occurs at this throttle, wherein the input side of the throttle is substantially an input pressure corresponding to the pressure in the high-pressure chamber and output side substantially an output pressure approximated to the comparatively low combustion chamber pressure, so that supportive hydraulic forces must occur in the closing stroke of the nozzle needle or the like , In a constructionally particularly preferred manner, the flow path between the inner circumference of a subsequent to the high-pressure chamber nozzle needle chamber and the outer circumference of the nozzle needle or the like arranged and the throttle between a nozzle needle side flange or flange and the inner circumference formed or arranged.

Insbesondere kann in zweckmäßiger Ausgestaltung der Erfindung die genannte Drossel als Ringspaltdrossel zwischen dem Innenumfang des Düsennadelraumes und dem Außenumfang eines an der Düsennadel oder dergleichen fest angeordneten ringbundförmigen Flansches ausgebildet sein.In particular, in an advantageous embodiment of the invention, the said throttle may be formed as an annular gap throttle between the inner circumference of the nozzle needle chamber and the outer periphery of a fixed to the nozzle needle or the like annular collar-shaped flange.

Für die stationäre Halterung des Plungers können hydraulische Kräfte ausgenutzt werden.For the stationary support of the plunger hydraulic forces can be utilized.

Zu diesem Zweck kann der Plunger mit einem Endstück, welches einen gegenüber dem Querschnitt der Sackbohrung bzw. des Plungers vergrößerten Querschnitt aufweist, auf einer der kopplungsraumseitigen Stirnseite des Nehmerkolbens gegenüberliegenden stationären Fläche am Injektorgehäuse axial abgestützt und zwischen dem Endstück und der stationären Fläche ein im Wesentlichen scheibenförmiger und mit dem relativ drucklosen Kraftstoffreservoir kommunizierender Raum mit gegenüber dem Durchmesser der Sackbohrung bzw. des Plungers größerem Scheibendurchmesser ausgebildet sein.For this purpose, the plunger with an end piece, which has a relation to the cross section of the blind bore and the plunger enlarged cross section, on one of the coupling chamber side end face of the slave piston axially opposed to the stationary surface on the injector housing and between the end piece and the stationary surface a substantially disc-shaped and communicating with the relatively pressureless fuel reservoir space with respect to the diameter of the blind bore or the plunger larger disc diameter may be formed.

Damit wird im Ergebnis eine der Differenz des Querschnittes von Plunger bzw. Sackbohrung und des Querschnittes des scheibenförmigen Raumes entsprechender Querschnitt am Plunger vom Hochdruck im Injektorgehäuse derart beaufschlagt, dass der Plunger entsprechender Kraft auf der stationären Wand aufsitzt.As a result, a difference of the cross section of plunger or blind bore and the cross section of the disk-shaped space corresponding cross section on the plunger from the high pressure in the injector is applied so that the plunger corresponding force is seated on the stationary wall.

Im Übrigen wird hinsichtlich bevorzugter Merkmale der Erfindung auf die Ansprüche und die nachfolgende Erläuterung der Zeichnung verwiesen, anhand der die Erfindung einschließlich besonders bevorzugter Merkmale näher beschrieben wird.Incidentally, with regard to preferred features of the invention, reference is made to the claims and the following explanation of the drawing, based on which the invention including particularly preferred features will be described in more detail.

Kurze Beschreibung der ZeichnungenBrief description of the drawings

Die einzige Figur zeigt einen schematisierten Axialschnitt einer besonders bevorzugten Ausführungsform des erfindungsgemäßen Kraftstoffinjektors.The single FIGURE shows a schematic axial section of a particularly preferred embodiment of the fuel injector according to the invention.

Ausführungsformen der ErfindungEmbodiments of the invention

Der in der Zeichnung dargestellte Kraftstoffinjektor 1 besitzt einen Injektorkörper 2, welcher einen ersten Druckraum 3, einen zweiten Druckraum 4 sowie einen daran anschließenden dritten Druckraum 5 aufnimmt. Die Druckräume 3-5 sind miteinander kommunizierend verbunden, indem ein zwischen dem ersten und zweiten Druckraum 4 angeordneter Zwischenboden 6 des Injektorkörpers 2 von einer die Druckräume 3 und 4 verbindenden Axialbohrung 7 durchsetzt wird. Der Druckraum 5 dient als Axialführung einer Düsennadel 8, die am in der Zeichnung unteren Ende des Druckraumes 5 angeordnete Einspritzdüsen 9 steuert, über die der Druckraum 5 mit einem nicht dargestellten Brennraum eines Verbrennungsmotors verbindbar ist. In der Zeichnung nimmt die Düsennadel 8 ihre die Düsen 9 absperrende Schließlage ein, in der das düsenseitige Ende der Düsennadel 8 mit einer düsenseitigen Ringkante dicht auf einem die Eingänge der Düsen 9 mit radialem Abstand umschließenden ringförmigen Düsennadelsitz aufsitzt, so dass innerhalb des Druckraumes 5 ein Düseneingangsraum 10 von einem zwischen der axialen Innenwand des Druckraumes 5 und dem Außenumfang der Düsennadel 8 verbleibenden Ringraum abgetrennt wird.The fuel injector 1 shown in the drawing has an injector body 2, which receives a first pressure chamber 3, a second pressure chamber 4 and an adjoining third pressure chamber 5. The pressure chambers 3-5 are communicatively connected to each other by a between the first and second pressure chamber 4 arranged intermediate bottom 6 of the injector body 2 is penetrated by an axial bore 7 connecting the pressure chambers 3 and 4. The pressure chamber 5 serves as an axial guide of a nozzle needle 8, which controls the arranged in the drawing lower end of the pressure chamber 5 injectors 9, via which the pressure chamber 5 is connected to a combustion chamber, not shown, of an internal combustion engine. In the drawing, the nozzle needle 8 takes its nozzle 9 shut-off closing position in which the nozzle-side end of the nozzle needle 8 is seated with a nozzle-side annular edge tight on a the inputs of the nozzles 9 with radial spacing enclosing annular nozzle needle seat, so that within the pressure chamber 5 a Nozzle input space 10 is separated from a remaining between the axial inner wall of the pressure chamber 5 and the outer circumference of the nozzle needle 8 annular space.

Dieser Ringraum kommuniziert ständig mit dem Druckraum 4. Zu diesem Zweck ist die Düsennadel in einem an den Druckraum 4 angrenzenden erweiterten oberen Axialabschnitt des Druckraumes 5 mit an der Düsennadel angeordneten Axialstegen oder dergleichen axial verschiebbar geführt, zwischen denen den vorgenannten Ringraum mit dem Druckraum 4 verbindende Freiräume verbleiben. Wenn die Düsennadel 8 ihre vom Sitz an den Einspritzdüsen 9 abgehobene Offenlage einnimmt, ist der Düseneingangsraum 10 über die Druckräume 5 und 4 sowie die Axialbohrung 7 im Zwischenboden 6 und den Druckraum 3 mit einem unter Hochdruck stehenden Kraftstoffspeicher 11 verbunden, der typischerweise als sogenanntes Common Rail ausgebildet ist und über eine Anschlußleitung 12 mit dem ersten Druckraum 3 kommuniziert. Damit kann unter Hochdruck stehender Kraftstoff über die Einspritzdüsen 9 in den Brennraum des Verbrennungsmotors eingespritzt werden.This annular space communicates constantly with the pressure chamber 4. For this purpose, the nozzle needle is guided in an axially adjacent to the pressure chamber 4 extended upper axial portion of the pressure chamber 5 with arranged on the nozzle needle axial webs or the like, between which the aforementioned annular space with the pressure chamber 4 connecting Free spaces remain. When the nozzle needle 8 assumes its lifted from the seat to the injectors 9 open position, the nozzle inlet chamber 10 via the pressure chambers 5 and 4 and the axial bore 7 in the intermediate bottom 6 and the pressure chamber 3 is connected to a high-pressure fuel reservoir 11, which typically as so-called Common Rail is formed and communicates via a connecting line 12 with the first pressure chamber 3. This can be under high pressure Fuel are injected via the injectors 9 in the combustion chamber of the internal combustion engine.

Zur Betätigung der Ventilnadel 8 dient ein im dargestellten Beispiel als piezoelektrisches Element ausgebildeter Aktor 13, der über elektrische Leitungen 14 mit einer elektrischen Spannungsquelle verbunden und mit der Ventilnadel 8 hydraulisch gekoppelt ist. Diese hydraulische Kopplung erfolgt dadurch, dass ein mittels des Aktors 13 hubbeweglicher Geberkolben 15 in einem Kopplungsraum 16 verdrängerwirksam arbeitet, der über eine den Zwischenboden 6 durchsetzende Leitung 17 mit einem Kopplungsraum 18 kommuniziert, in welchem ein an der Düsennadel 8 angeordneter Nehmerkolben 19 verdrängerwirksam arbeitet. Wenn also der Geberkolben 15 eine den Kopplungsraum 16 verkleinernde Abwärtsbewegung ausführt, wird Fluid aus dem Kopplungsraum 16 über die Leitung 17 in den Kopplungsraum 18 ausgeschoben, so dass der Nehmerkolben 19 mit der Düsennadel 8 eine Abwärtsbewegung in Richtung der Schließlage der Düsennadel 8 ausführt. Umgekehrt nimmt der Kopplungsraum 16 bei Aufwärtsbewegung des Geberkolbens 15 Fluid aus dem Kopplungsraum 18 auf, wobei sich der Nehmerkolben 19 mit der Ventilnadel 8 in Aufwärtsrichtung, d.h. in eine Offenlage der Ventilnadel 8 bewegt. Da die verdrängerwirksamen Kolbenquerschnitte von Geber- und Nehmerkolben 15 und 19 unterschiedlich sind, wird eine entsprechende Hubübersetzung bewirkt, wobei das Übersetzungsverhältnis invers zum Verhältnis der Querschnitte ist.To actuate the valve needle 8 is a trained in the example as a piezoelectric element actuator 13 which is connected via electrical lines 14 to an electrical voltage source and is hydraulically coupled to the valve needle 8. This hydraulic coupling is effected by a positive displacement by means of the actuator 13 master piston 15 in a coupling chamber 16 which communicates via a the intermediate bottom 6 passing through line 17 with a coupling chamber 18, in which a arranged on the nozzle needle 8 slave piston 19 works displacer effective. Thus, when the master piston 15 performs a downward movement reducing the coupling space 16, fluid is expelled from the coupling space 16 via the conduit 17 into the coupling space 18, so that the slave piston 19 with the nozzle needle 8 performs a downward movement in the direction of the closed position of the nozzle needle 8. Conversely, the coupling space 16 receives fluid from the coupling space 18 during upward movement of the master piston 15, wherein the slave piston 19 with the valve needle 8 in the upward direction, i. moved in an open position of the valve needle 8. Since the displacement effective piston cross sections of the master and slave pistons 15 and 19 are different, a corresponding stroke ratio is effected, wherein the gear ratio is inverse to the ratio of the cross sections.

Der Kopplungsraum 16 wird vom Druckraum 3 durch eine Dichthülse 20 abgetrennt, die auf dem Geberkolben 15 verschiebbar geführt und mittels einer Schraubendruckfeder 21, welche zwischen einem am Geberkolben 15 angeordneten Ringbund und dem zugewandten Stirnrand der Dichthülse 20 eingespannt ist, gegen die dem Geberkolben 15 zugewandte Stirnseite des Zwischenbodens 6 gespannt wird, wobei die Dichthülse 20 mit einer scharfen Ringkante auf einer Ringlinienzone des Zwischenbodens dicht aufsitzt.The coupling chamber 16 is separated from the pressure chamber 3 by a sealing sleeve 20 which is displaceably guided on the master piston 15 and by means of a helical compression spring 21 which is clamped between an annular collar arranged on the master piston 15 and the facing end edge of the sealing sleeve 20 against the master piston 15 facing Front side of the false floor 6 is stretched, the sealing sleeve 20 is tightly seated with a sharp annular edge on a ring line zone of the false floor.

In ähnlicher Weise wird der Kopplungsraum 18 vom Druckraum 4 durch eine Dichthülse 22 abgetrennt, die auf dem Nehmerkolben 19 verschiebbar geführt und mittels einer zwischen einem Ringbund am Nehmerkolben 19 und dem zugewandten Stirnrand der Dichthülse 22 eingespannten Schraubendruckfeder 23 gegen die dem Nehmerkolben 19 zugewandte Stirnseite des Zwischenbodens 6 gespannt wird, wobei die Dichthülse 22 mit einer scharfen Ringkante auf einer entsprechenden Ringlinienzone auf der in der Zeichnung unteren Stirnseite des Zwischenbodens 6 dicht aufsitzt.Similarly, the coupling space 18 is separated from the pressure chamber 4 by a sealing sleeve 22 which slidably guided on the slave piston 19 and by means of a clamped between an annular collar on the slave piston 19 and the facing end edge of the sealing sleeve 22 helical compression spring 23 against the slave piston 19 facing end side of the Intermediate tray 6 is tensioned, wherein the sealing sleeve 22 is tightly seated with a sharp edge of the ring on a corresponding ring line zone on the lower end face of the intermediate bottom 6 in the drawing.

Im Nehmerkolben 19 ist eine zum Kopplungsraum 18 offene axiale Sackbohrung 24 angeordnet, welche gegenüber dem Kopplungsraum 18 durch einen in die Sackbohrung 24 hineinragenden, stationär am Zwischenboden 6 abgestützten Plunger 25 abgesperrt wird. Der Plunger 25 wird von einer Axialbohrung durchsetzt, die über eine den Zwischenboden 6 durchsetzende Leitung 26 mit einem relativ drucklosen Kraftstoffreservoir, beispielsweise einem Kraftstofftank (nicht dargestellt), verbunden ist. Dementsprechend steht ein zwischen dem Boden der Sackbohrung 24 und dem zugewandten Stirnende des Plungers 25 verbleibender Niederdruckraum 27 ständig unter dem praktisch verschwindenden Druck des Kraftstoffreservoirs bzw. Kraftstofftanks.In the slave piston 19 is an open to the coupling space 18 axial blind bore 24 is arranged, which is shut off from the coupling space 18 by a protruding into the blind bore 24, stationary supported on the intermediate bottom 6 plunger 25. The plunger 25 is penetrated by an axial bore, which is connected via a the intermediate bottom 6 passing through line 26 with a relatively pressureless fuel reservoir, such as a fuel tank (not shown). Accordingly, a low pressure space 27 remaining between the bottom of the blind bore 24 and the facing front end of the plunger 25 is constantly below the virtually vanishing pressure of the fuel reservoir or fuel tank.

Der Plunger 25 wird an der zugewandten Seite des Zwischenbodens 6 durch fluidische Kräfte festgehalten. Zu diesem Zweck besitzt das dem Zwischenboden 6 zugewandte Endstück des Plungers 25 ein gegenüber dem Querschnitt des Plungers 25 bzw. der Sackbohrung 24 deutlich vergrößerten Querschnitt, wobei innerhalb der dem Zwischenboden 6 zugewandten Seite des genannten Endstückes ein scheibenförmiger Raum 28 ausgespart ist, dessen Durchmesser deutlich größer als der Außendurchmesser des Plungers 25 bzw. der Innendurchmesser der Sackbohrung 24 ist. Dieser scheibenförmige Raum 28 steht in Verbindung mit der Leitung 26 zum relativ drucklosen Kraftstoffreservoir bzw. -tank, so dass der im Kopplungsraum 18 vorliegende, dem Druck in den Druckräumen 3 und 4 entsprechende Druck, der im Wesentlichen dem Druck im Druckspeicher 11 entspricht, das Endstück des Plungers 25 mit entsprechend großer Kraft gegen die zugewandte Stirnseite des Zwischenbodens 6 andrückt, wobei das Endstück mit einer den scheibenförmigen Raum 28 umfassenden scharfen Ringkante auf einer ringlinienförmigen Zone des Zwischenbodens 6 dicht aufsitzt.The plunger 25 is held on the facing side of the intermediate bottom 6 by fluidic forces. For this purpose, the intermediate bottom 6 facing the end of the plunger 25 has a relation to the cross section of the plunger 25 and the blind bore 24 significantly enlarged cross-section, within the intermediate bottom 6 facing side of said end piece a disc-shaped space 28 is recessed, the diameter clearly larger than the outer diameter of the plunger 25 and the inner diameter of the blind bore 24 is. This disc-shaped space 28 is in communication with the line 26 to the relatively pressureless fuel reservoir or tank, so that the present in the coupling chamber 18, the pressure in the pressure chambers 3 and 4 corresponding pressure, which substantially corresponds to the pressure in the pressure accumulator 11, the End of the plunger 25 presses with a correspondingly large force against the facing end face of the intermediate bottom 6, wherein the end piece with a disk-shaped space 28 comprehensive sharp annular edge on a ring-shaped zone of the false bottom 6 is tightly seated.

Im Übrigen wird das genannte Endstück des Plungers 25 noch durch eine im Niederdruckraum 27 untergebrachte und zwischen dem Boden der Sackbohrung 24 und dem zugewandten Stirnende des Plungers 25 eingespannte Schraubendruckfeder 29 gegen den Zwischenboden 6 gespannt. Die Schraubendruckfeder 29 dient jedoch im Wesentlichen nur als Montagehilfsmittel und darf dementsprechend schwach dimensioniert sein. Während des Betriebes des Injektors 1 ist die Schraubendruckfeder 29 für den Anschub des Endstückes des Plungers 25 gegen die zugewandte Seite des Zwischenbodens 6 praktisch bedeutungslos.Incidentally, said end piece of the plunger 25 is still tensioned against the intermediate bottom 6 by a helical compression spring 29 accommodated in the low-pressure space 27 and clamped between the bottom of the blind bore 24 and the facing front end of the plunger 25. However, the helical compression spring 29 essentially serves only as a mounting aid and may be correspondingly weak dimensioned. During operation of the injector 1, the helical compression spring 29 for the start of the end piece of the plunger 25 against the facing side of the intermediate bottom 6 is practically meaningless.

Der dargestellte Kraftstoffinjektor 1 funktioniert wie folgt: Die Kopplungsräume 16 und 18 sind beim Betrieb mit Kraftstoff gefüllt und stehen im Wesentlichen unter gleichem Druck wie der Kraftstoff im Druckspeicher 11. Solange der piezoelektrische Aktor 13 über die elektrischen Leitungen 14 mit einer elektrischen Spannung beaufschlagt wird, hält er den Geberkolben 15 in der zeichnerisch dargestellten unteren Lage, und die Düsennadel 8 nimmt die dargestellte Schließlage ein. Damit sind die Einspritzdüsen 9 gegenüber dem Druckspeicher 11 abgesperrt. Wird die elektrische Spannung an den Leitungen 14 abgeschaltet, und der piezoelektrische Aktor 13 entladen, zieht er den Geberkolben 15 in Richtung von dessen oberer Totpunktlage, d.h. der Geberkolben 15 führt in der Zeichnung einen Aufwärtshub aus, dem der Nehmerkolben 19 mit der Düsennadel 8 mit durch das Verhältnis der verdrängerwirksamen Querschnitte des Geber- und des Nehmerkolbens 15, 19 vorgegebener Hubübersetzung folgt. Das heißt, die Düsennadel 8 hebt von ihrem düsenseitigen Sitz ab, so dass der Düseneingangsraum 10 mit dem Druckspeicher 11 verbunden und Kraftstoff über die Düsen 9 in den angrenzenden Brennraum eingespritzt wird. Wird nachfolgend der piezoelektrische Aktor 13 über die elektrischen Anschlussleitungen 12 wieder mit einer elektrischen Spannung beaufschlagt, werden der Geberkolben 15 und die Düsennadel 8 wiederum in die zeichnerisch dargestellten Lagen geschoben.The illustrated fuel injector 1 functions as follows: The coupling chambers 16 and 18 are filled with fuel during operation and are substantially under the same pressure as the fuel in the pressure accumulator 11. As long as the piezoelectric actuator 13 is subjected to an electrical voltage via the electrical leads 14, he holds the master piston 15 in the lower position shown in the drawing, and the nozzle needle 8 assumes the illustrated closed position. Thus, the injection nozzles 9 are shut off from the pressure accumulator 11. If the electrical voltage on the lines 14 is switched off and the piezoelectric actuator 13 is discharged, it pulls the master piston 15 in the direction of its top dead center position, ie the master piston 15 leads in the drawing Upstroke from which the slave piston 19 with the nozzle needle 8 with 19 by the ratio of the displacer cross sections of the master and slave piston 15, 19 given Hubübersetzung follows. That is, the nozzle needle 8 lifts from its nozzle-side seat, so that the nozzle input space 10 is connected to the pressure accumulator 11 and fuel is injected via the nozzles 9 in the adjacent combustion chamber. If subsequently the piezoelectric actuator 13 is acted upon again via the electrical connection lines 12 with an electrical voltage, the master piston 15 and the nozzle needle 8 are in turn pushed into the positions shown in the drawing.

Um zu gewährleisten, dass für den Öffnungshub der Düsennadel 8 vergleichsweise geringe Kräfte und dementsprechend vergleichsweise wenig Energie benötigt werden, ist die Bemessung des Querschnittes des Niederdruckraumes 27 bzw. des Querschnittes der Sackbohrung 24 und des darin verschiebbaren Plungers 25 wesentlich. Die Kräfte, welche notwendig sind, die in Schließlage befindliche Düsennadel 8 in die Offenlage zu bringen, werden im Wesentlichen bestimmt durch die Differenz zwischen dem Querschnitt des Düseneingangsraumes 10, das heißt dem Querschnitt des Düsennadelsitzes, und den Querschnitt des Niederdruckraumes 27. Gemäß einer bevorzugten Ausführungsform der Erfindung ist vorgesehen, dass der Querschnitt des Niederdruckraumes 27 bei etwa 60 - 80 % des Querschnittes des Düseneingangsraumes 10 liegt.In order to ensure that relatively small forces and comparatively little energy are required for the opening stroke of the nozzle needle 8, the dimensioning of the cross-section of the low-pressure chamber 27 or the cross-section of the blind bore 24 and the plunger 25 displaceable therein is essential. The forces which are necessary to bring the nozzle needle 8 located in the closed position in the open position, are essentially determined by the difference between the cross section of the nozzle inlet chamber 10, that is, the cross section of the nozzle needle seat, and the cross section of the low pressure chamber 27. According to a preferred Embodiment of the invention, it is provided that the cross section of the low-pressure chamber 27 is about 60 - 80% of the cross-section of the nozzle input space 10.

Um zu gewährleisten, dass die Düsennadel 8 aus ihrer Offenlage mit vergleichsweise geringen Stellkräften und entsprechend geringem Energiebedarf in ihre Schließlage gestellt werden kann, ist zwischen den Druckräumen 4 und 5 eine Bypassdrossel 30 vorgesehen. Im dargestellten Beispiel ist zur Ausbildung der Bypassdrossel 30 an der Düsennadel 8 ein Flansch 31 angeordnet, der so bemessen ist, dass zwischen seinem Außenumfang und dem Innenumfang des Druckraumes 5 ein drosselwirksamer Ringspalt gebildet wird. Wenn nun die Düsennadel 8 ihre Offenlage einnimmt und dementsprechend der Druckspeicher 11 mit dem Düseneingangsraum 10 kommuniziert, muss zwischen Eingangs- und Ausgangsseite der Bypassdrossel 30 aufgrund der Drosselwirkung des genannten Ringspaltes eine Druckdifferenz auftreten, mit der Folge, dass der im Düseneingangsraum 10 vorliegende Druck, welcher die Düsennadel 8 in Offenlage zu halten sucht, gegenüber dem Druck im Druckspeicher 11 vermindert ist und die Düsennadel 8 mit entsprechend geringen Kräften und geringem Energiebedarf in die Schließlage geschoben werden kann.In order to ensure that the nozzle needle 8 can be placed in its closed position from its open position with comparatively low actuating forces and correspondingly low energy requirement, a bypass throttle 30 is provided between the pressure chambers 4 and 5. In the example shown, a flange 31 is arranged to form the bypass throttle 30 on the nozzle needle 8, which is dimensioned such that between its outer circumference and the inner circumference of the pressure chamber 5, a throttle-effective annular gap is formed. If now the nozzle needle 8 assumes its open position and accordingly the pressure accumulator 11 communicates with the nozzle input space 10, a pressure difference must occur between the input and output side of the bypass throttle 30 due to the throttling effect of said annular gap, with the result that the pressure present in the nozzle inlet space 10, which the nozzle needle. 8 seeks to keep in open position, compared with the pressure in the accumulator 11 is reduced and the nozzle needle 8 can be pushed with correspondingly low forces and low energy consumption in the closed position.

Durch entsprechende Bemessung der Bypassdrossel 30 sowie des Querschnittes des Niederdruckraumes 27 können also einerseits der Energiebedarf für den Schließhub der Düsennadel 8 und andererseits der Energiebedarf für den Öffnungshub der Düsennadel 8 gering gehalten werden, so dass ein entsprechend kleiner kostengünstiger Aktor 13 für den Betrieb des Kraftstoffinjektors 1 ausreichend ist.By appropriate dimensioning of the bypass throttle 30 and the cross section of the low pressure chamber 27 so on the one hand, the energy required for the closing stroke of the nozzle needle 8 and on the other hand, the energy requirements for the opening stroke of the nozzle needle 8 can be kept low, so that a correspondingly smaller cost-effective actuator 13 for the operation of the fuel injector 1 is sufficient.

Die oben beschriebene hydraulische Kopplung von Geber- und Nehmerkolben 15, 19 bewirkt auch ohne weitere konstruktive Maßnahmen einen Ausgleich von Temperaturdehnungen, so dass keine weiteren Maßnahmen zur Kompensation von Schwankungen der Betriebstemperatur des Injektors 1 notwendig werden. In der die Kopplungsräume 16 und 18 verbindenden Leitung 17 ist vorzugsweise eine Drossel angeordnet, die eine dämpfende Wirkung auf die Kolbenhübe ausübt. Dadurch kann das Betriebsverhalten des Injektors 1 verbessert werden. Die obere Endlage der Düsennadel sollte vorzugsweise durch einen Anschlag definiert sein. Dieser kann beispielsweise dadurch realisiert werden, dass die dem Zwischenboden 6 zugewandte Stirnseite des Nehmerkolbens 19 in der oberen Endlage anschlagartig mit dem Endstück am oberen Ende des Plungers 25 zusammenwirkt. Dabei wird zwischen den einander zugewandten Flächen des Nehmerkolbens 19 und des genannten Endstückes ein Quetschspalt gebildet, aus dem beim Aufwärtshub des Nehmerkolbens 19 Fluid unter Dämpfung der Aufwärtsbewegung verdrängt wird, so dass der Nehmerkolben 19 und die Düsennadel 8 kurz vor Einnahme ihrer oberen Endlage gedämpft abgebremst werden. The hydraulic coupling of the master and slave pistons 15, 19 described above also effects a compensation of thermal expansions without further design measures, so that no further measures for compensating fluctuations in the operating temperature of the injector 1 become necessary. In the coupling spaces 16 and 18 connecting line 17, a throttle is preferably arranged, which exerts a damping effect on the piston strokes. As a result, the operating behavior of the injector 1 can be improved. The upper end position of the nozzle needle should preferably be defined by a stop. This can for example be realized in that the intermediate bottom 6 facing end face of the slave piston 19 in the upper end position stop-like cooperates with the tail at the upper end of the plunger 25. In this case, a nip is formed between the mutually facing surfaces of the slave piston 19 and said end piece, from the fluid is displaced during the upward stroke of the slave piston 19 under damping of the upward movement, so that the slave piston 19 and the nozzle needle 8 are braked damped shortly before taking their upper end position.

Claims (7)

  1. Fuel injector (1) having
    - an injector housing or body (2) and a high-pressure chamber (4, 5) which is arranged therein and which permanently communicates with a high-pressure source (11) for fuel and which can be connected to a combustion chamber via nozzles (9) for injecting fuel, which nozzles are controlled by means of a nozzle needle (8) or the like,
    - an actuator (13) which is hydraulically coupled to the nozzle needle (8) or the like, for the actuation of the latter, by virtue of the actuator being drive-connected to a master piston (15) which operates in a coupling chamber (16, 18) separate from the high-pressure chamber, and the nozzle needle (8) or the like being drive-connected to a slave piston (19) which operates in the coupling chamber, and
    - a low-pressure chamber (27) on the slave piston (19) which operates therein as a displacement body, with the volume of the low-pressure chamber decreasing during the opening stroke of the nozzle needle (8) or the like,
    characterized
    in that the low-pressure chamber (27) is arranged in a blind bore (24) which is open towards the coupling-chamber-side end side of the slave piston (19), and said low-pressure chamber (27) is closed off by means of a plunger (25) which projects into the blind bore, and said low-pressure chamber (27) communicates with the relatively unpressurized fuel reservoir via an axial bore extending through the plunger.
  2. Fuel injector according to Claim 1,
    characterized
    in that a throttle (30) is arranged within a flow path, which connects the high-pressure chamber to a nozzle inlet chamber (10), of the fuel.
  3. Fuel injector according to Claim 2,
    characterized
    in that the flow path is arranged between the inner circumference of a pressure chamber (5) adjoining the high-pressure chamber (3, 4) and the outer circumference of the nozzle needle (8) or the like, and the throttle (30) is arranged or formed between a nozzle-needle-side collar or flange (31) and the inner circumference.
  4. Fuel injector according to Claim 3,
    characterized
    in that the throttle (30) is formed as an annular gap throttle.
  5. Fuel injector according to one of Claims 1 to 4,
    characterized
    in that the plunger (25) is supported axially with an end piece, which has a larger cross section than the cross section of the blind bore (24), on a surface, which is situated opposite the coupling-chamber-side end side of the slave piston (19), of a part (6) of the injector housing or body (2) or of a coupler element or of the master piston (15), and a substantially disc-shaped chamber (28) which communicates with the relatively unpressurized fuel reservoir and which has a disc diameter larger than the diameter of the blind bore (24) is formed between the end piece and the surface.
  6. Fuel injector according to Claim 5,
    characterized
    in that the end piece is seated with a sealing edge, which is arranged on the end side and annularly surrounds the disc-shaped chamber (28), on the surface.
  7. Fuel injector according to one of Claims 1 to 6,
    characterized
    in that the cross section of the plunger (25) or of the blind bore (24) has a dimension which is approximately 60 - 80% of the cross section of a sealing seat of the nozzle needle (8) or the like at the injection nozzles (9).
EP09100243A 2008-06-13 2009-04-22 Fuel injector Not-in-force EP2133552B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE102008002419A DE102008002419A1 (en) 2008-06-13 2008-06-13 fuel injector

Publications (2)

Publication Number Publication Date
EP2133552A1 EP2133552A1 (en) 2009-12-16
EP2133552B1 true EP2133552B1 (en) 2010-10-27

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ID=41171200

Family Applications (1)

Application Number Title Priority Date Filing Date
EP09100243A Not-in-force EP2133552B1 (en) 2008-06-13 2009-04-22 Fuel injector

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Country Link
EP (1) EP2133552B1 (en)
AT (1) ATE486211T1 (en)
DE (2) DE102008002419A1 (en)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005012940A1 (en) * 2005-03-21 2006-09-28 Robert Bosch Gmbh Fuel injection device for an internal combustion engine
DE102005020597A1 (en) * 2005-05-03 2006-11-09 Robert Bosch Gmbh Fuel injector has temperature compensating element between actuator and mounting
DE102006022803A1 (en) * 2006-05-16 2007-11-22 Robert Bosch Gmbh Injection nozzle for internal combustion engine of motor vehicle, has preloading piston loaded with preloading force in preloading side, where preloading force actuates preloading piston against bypass plunger
DE102006062216A1 (en) 2006-12-22 2008-06-26 Robert Bosch Gmbh fuel injector

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Publication number Publication date
ATE486211T1 (en) 2010-11-15
EP2133552A1 (en) 2009-12-16
DE502009000146D1 (en) 2010-12-09
DE102008002419A1 (en) 2009-12-17

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