EP3286428B1 - Fuel injector - Google Patents

Fuel injector Download PDF

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Publication number
EP3286428B1
EP3286428B1 EP16707116.6A EP16707116A EP3286428B1 EP 3286428 B1 EP3286428 B1 EP 3286428B1 EP 16707116 A EP16707116 A EP 16707116A EP 3286428 B1 EP3286428 B1 EP 3286428B1
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EP
European Patent Office
Prior art keywords
pressure
chamber
nozzle
measuring element
force measuring
Prior art date
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EP16707116.6A
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German (de)
French (fr)
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EP3286428A1 (en
Inventor
Martin Bernhaupt
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication of EP3286428A1 publication Critical patent/EP3286428A1/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
    • F02M57/00—Fuel-injectors combined or associated with other devices
    • F02M57/005—Fuel-injectors combined or associated with other devices the devices being sensors
    • 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
    • F02M2200/24—Fuel-injection apparatus with sensors
    • 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
    • F02M2200/24—Fuel-injection apparatus with sensors
    • F02M2200/244—Force sensors
    • 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
    • F02M2200/24—Fuel-injection apparatus with sensors
    • F02M2200/247—Pressure sensors

Definitions

  • the invention relates to a fuel injector, in particular a common rail injector, according to the preamble of claim 1.
  • a fuel injector is from the EP 1 042 603 B1 famous.
  • the known fuel injector has a sensor within its injector housing which is arranged in the area of a drain hole between a control chamber of the fuel injector and a low-pressure area.
  • the sensor surrounds the drain hole on a sleeve-shaped section of a component in which the drain hole is formed.
  • An end section of an injection member designed as a nozzle needle protrudes into the control chamber of the fuel injector. By influencing the pressure in the control chamber, the movement of the nozzle needle is controlled in a known manner in order to release injection holes formed in the injector housing for injecting fuel into the combustion chamber of an internal combustion engine.
  • the pressure in the control chamber is brought about by the outflow of fuel from the said control chamber into the low-pressure area via the outlet bore or outlet throttle, the outlet bore m * by means of a closing element in the low-pressure area of the injector housing, which in turn is equipped with an actuator, for example a magnetic actuator or a piezo actuator can be actuated, can be closed.
  • an actuator for example a magnetic actuator or a piezo actuator can be actuated
  • the known sensor is designed to measure the pressure or pressure fluctuations in the drain hole caused by the opening of the Closing member from the control room to detect, from which the position of the nozzle needle can be inferred.
  • the disadvantage of the known arrangement is that the sensor is arranged in the high pressure area of the injector housing and therefore has to be designed in a relatively complex manner.
  • the space available for such a sensor in the injector housing is limited, so that special constructive solutions, which are particularly critical with regard to the strength of the injector housing, have to be selected.
  • a fuel injector with a pressure sensor system is known, which is arranged in the low-pressure region.
  • a measuring channel or a tap hole is brought up to a membrane-like partition wall.
  • the pressure sensor system or the force measuring element is arranged on the back of the partition.
  • the pressure sensor system is preferably a less rigid measuring strip arrangement which measures the stresses or deformations in the partition. Due to the high pressures in the branch hole, however, strength problems can arise on the partition wall.
  • the fuel injector according to the invention has an increased fatigue strength in the area of the pressure sensor system, since the pressure is not measured via a tension or deformation of the partition.
  • the force is measured with a force measuring element which is as rigid as possible and which supports the partition so that the partition experiences almost no deformation.
  • the fuel injector comprises an injector housing in which a nozzle chamber is formed, which can be supplied with fuel under pressure via an inlet formed in the injector housing.
  • a longitudinally movable nozzle needle that releases or closes at least one injection hole is arranged in the nozzle space.
  • the fuel injector comprises a force measuring element for at least indirect detection of a pressure in a pressure chamber formed in the injector housing.
  • the pressure chamber can be hydraulically connected to the inlet.
  • the force measuring element is arranged in a measuring space formed in the injector housing, the measuring space being separated from the pressure space by a membrane-like partition. According to the invention, the force measuring element supports the partition.
  • the force measuring element is advantageously designed to be very rigid.
  • the partition wall is thus supported by the force measuring element against the effective direction of the pressure to be measured in the pressure chamber, so that the stresses and bends in the partition wall are minimized when the pressure is loaded.
  • the force measuring element is pretensioned by an oversize inside the injector housing.
  • the force measuring element is oversized in relation to the measuring space, so that the force measuring element is simultaneously pretensioned with the axial bracing of the injector housing during assembly.
  • the pressure chamber is hydraulically connected to the control chamber via a branch bore.
  • This determines the pressure in the control room, which has a decisive influence on the movement of the hydraulically controlled nozzle needle.
  • the branch bore is formed in the throttle plate of the injector housing, in which an outlet throttle from the control chamber to the pilot valve is also formed.
  • the pressure in the control chamber is subject to greater fluctuations than the pressure in the nozzle chamber. As a result, pressure differences in the control chamber can be determined more reliably than pressure differences in the nozzle chamber.
  • the force measuring element is pretensioned against the partition.
  • the high pressure present in the pressure chamber during operation of the fuel injector then counteracts the pretensioning or bending of the partition, so that the deformations and stresses - especially the tensile stresses - in the partition and in the surrounding areas are minimized.
  • On the high pressure side of the partition are those Changes in pressure are highly dynamic, so that a pretensioning of the partition wall by the force measuring element results in a significant increase in fatigue strength.
  • the inlet is connected to the pressure chamber.
  • the pressure drop between the nozzle space and a high pressure source is measured, that is to say approximately the pressure drop in the nozzle space.
  • This design can be made particularly inexpensive and has advantages in terms of the installation space required, since the measurement by the force measuring element can take place, for example, remote from the nozzle needle, i.e. in an area in which there is more free installation space than in an area close to the nozzle.
  • the injector housing further comprises a nozzle body, a throttle plate, a valve plate and a holding body, which are axially clamped to one another by a nozzle clamping nut.
  • a fuel injector in particular a fuel injector with a hydraulic pilot valve, which, for example, can in turn be controlled by an electromagnetic actuator.
  • Such fuel injectors are operated by changing hydraulic pressures. A determination of pressures or pressure differences is therefore of great advantage, particularly with such fuel injectors, in order to determine the injection characteristics on the one hand, but also to obtain the desired injection characteristics robustly over the service life on the other hand through targeted evaluation of the pressure curves.
  • the force measuring element is pretensioned by a screw element, for example a nut.
  • a screw element for example a nut.
  • the force measuring element is designed as a piezoelectric force measuring element.
  • Such an element has the advantage of a relatively high measurement sensitivity with a compact design and low manufacturing costs. Furthermore, such a force measuring element can be made particularly stiff and thereby support the partition wall very effectively.
  • the longitudinal movement of the nozzle needle is controlled by the pressure in a control chamber.
  • the pressure in the control chamber can in turn be controlled, for example, by a pilot valve.
  • a valve chamber is formed in the pilot valve and the control chamber is hydraulically connected to the valve chamber via an outlet throttle.
  • the nozzle needle is switched as a servo valve.
  • the pilot valve can be designed, for example, as a directly connected solenoid valve.
  • the pressure in the valve chamber is subject to even greater fluctuations than the pressure in the control chamber. In this embodiment too, the pressure differences can therefore be determined very reliably.
  • the measuring space is formed in the valve plate, a pilot valve seat of the pilot valve for controlling the nozzle needle being arranged on the valve plate.
  • the invention also includes the use of a fuel injector according to the invention in compression-ignition internal combustion engines.
  • the system pressure prevailing in the fuel injection system is preferably more than 2000 bar.
  • a fuel injector 1 according to the invention is shown, as it serves as part of a so-called common rail injection system for injecting fuel into the combustion chamber of an internal combustion engine, not shown.
  • the common rail injection system has a system pressure of more than 2000 bar.
  • the fuel injector 1 comprises an injector housing 10 which, in the exemplary embodiment shown, essentially comprises four components adjoining one another in the axial direction: On the side facing the combustion chamber (not shown) of the internal combustion engine, the injector housing 10 has a nozzle body 10a, to which a throttle plate 10b and 10b are attached these in turn connect a valve plate 10c and a holding body 10d on the side facing away from the nozzle body 10a. These components of the injector housing 10 are axially clamped to one another in a sealing manner by a nozzle clamping nut 10e.
  • a blind hole 31 is formed with at least one, but preferably a plurality of injection holes 9 for injecting the high pressure fuel into the combustion chamber of the internal combustion engine.
  • the nozzle body 10a forms a nozzle space 6 in a bore-shaped recess, which is hydraulically connected to a fuel source, for example a common rail, via an inlet 7.
  • An injection member in the form of a nozzle needle 2, which is arranged to be movable in a stroke, is arranged within the nozzle space 6.
  • the nozzle needle 2 is guided radially in the nozzle space 6 by the nozzle body 10a, the nozzle needle 2 being acted upon by force in the direction of the nozzle seat 8 by a closing spring 35.
  • the nozzle needle 2 delimits a control chamber 4 with an end face.
  • the control chamber 4 is formed in the injector housing 10 between the nozzle needle 2, the throttle plate 10b and a sleeve 36.
  • the control chamber 4 is connected to the inlet 7 by an inlet throttle 11 formed in the throttle plate 10b.
  • the sleeve 36 is tensioned by the closing spring 35 against the throttle plate 10b and guides the nozzle needle 2 in a longitudinally movable manner or the nozzle needle 2 positions the sleeve 36 in the radial direction.
  • the pressure in the control chamber 4 acts on the nozzle needle 2 with a hydraulic force in the direction of the nozzle seat 8, that is, in the closing direction.
  • the pressure in the control chamber 4 is controlled by a pilot valve 3 arranged in the injector housing 10.
  • the pilot valve 3 comprises a closing body 40 which cooperates with a pilot valve seat 21 formed on the valve plate 10c, an actuator 41 and a valve chamber 20.
  • the actuator 41 is in the exemplary embodiment from FIG Fig. 1 shown as an electromagnetic actuator, but can be any actuator, for example also a piezo actuator.
  • the valve chamber 20 is connected to the control chamber 4 via an outlet throttle 5 formed in the throttle plate 10b.
  • the closing body 40 opens and closes a connection between the valve chamber 20 and a low-pressure chamber 42 formed in the injector housing 10 by interacting with the pilot valve seat 21.
  • the valve chamber 20 comprises essentially two bores, one each formed in the valve plate 10c and one in the throttle plate 10b. In alternative embodiments, however, the valve chamber 20 can have any shape.
  • a force measuring element 17 is arranged in the injector housing 10 in order to measure a pressure of a pressure chamber 14 under high pressure.
  • Two electrical lines 17a lead from the force measuring element 17 through the injector housing 10 to a control unit (not shown). From the force or pressure measurement, conclusions can be drawn directly about the stroke movement of the nozzle needle 2 and thus about the injection characteristics of the fuel injector 1.
  • the control of the pilot valve 3 can then, for example, be changed by the control unit as a function of the injection characteristics.
  • the pressure chamber 14 is hydraulically connected to the inlet 7, the nozzle chamber 6, the control chamber 4 or the valve chamber 20.
  • the pressure chamber 14 is formed by a recess in the valve plate 10c and is connected to the control chamber 4 via a tap bore 12 formed in the throttle plate 10b.
  • a measuring chamber 16 is also formed opposite the pressure chamber 14 and separated from it by a membrane-like intermediate wall 13.
  • the force measuring element 17 is arranged in the measuring space 16 in such a way that it supports the partition 13.
  • the measuring space 16 has the shape of a blind hole opening towards the holding body 10d.
  • the force measuring element 17 can either be oversized relative to the holding body 10d or, as in the exemplary embodiment in FIG Fig. 1 , be clamped against the intermediate wall 13 by a screw element 18 screwed into the measuring space 16.
  • the measuring chamber 16 is in the low pressure range, the pressure chamber 14 is acted upon by high pressure. This means that the partition 13 is hydraulically loaded on one side. The bias of the intermediate wall 13 by the force measuring element 17 compensates for this one-sided load. The maximum stresses, in particular tensile stresses, in the intermediate wall 13 are thereby reduced and thus the service life of the entire fuel injector 1 is increased.
  • the pressure chamber 14 is designed as a recess in the valve plate 10c and is delimited by the valve plate 10c and the throttle plate 10b.
  • the pressure chamber 14 is connected to the valve chamber 20 via a groove 15 also formed in the valve plate 10c, so that the pressure prevailing in the valve chamber 20 also prevails in the pressure chamber 14.
  • the pressure chamber 14 and the groove 15 can also be designed as a single recess. Furthermore, the pressure chamber 14 and / or the groove 15 can also be formed in the throttle plate 10b.
  • FIG. 3 shows the force measuring element 17 in a further arrangement, namely for measuring the pressure of the nozzle space 6.
  • the force measuring element 17 is braced in the measuring space 16 by an oversize between the holding body 10d and the intermediate wall 13.
  • a connecting bore 32 is formed in the throttle plate 10b and connects the nozzle space 6 with the pressure space 14, so that the pressure prevailing in the nozzle space 6 also prevails in the pressure space 14.
  • the pressure chamber 14 is designed as a recess or blind hole in the valve plate 10c, but in alternative designs it can also be designed in the throttle plate 10b.
  • Fig. 4 shows a tensioning concept according to the invention of the force measuring element 17 in the measuring space 16.
  • the force measuring element 17 is provided with an oversize 19 compared to the measuring space 16 ( Fig. 4 above ). If the force measuring element 17 is now clamped between the holding body 10d and the partition 13, the diaphragm-like partition 13 is bent in the direction of the pressure chamber 14 ( Fig. 4 below ). The high pressure in the pressure chamber 14 during operation then counteracts the deflection of the partition 13, so that the tensile stresses in the partition 13 and in the surrounding areas are minimized when the fuel injector 1 is in operation.
  • the measuring space 16 in the throttle plate 10b, so that the force measuring element 17 is arranged within the throttle plate 10b.
  • the force measuring element 17 can then be clamped between the throttle plate 10b and the valve plate 10c, or between the throttle plate 10b and the holding body 10d if the measuring space 16 is designed, for example, as a through hole in the valve plate 10c.
  • the mode of operation of the fuel injector 1 is as follows: The opening and closing of the nozzle needle 2 of the fuel injector 1 is controlled by means of the pilot valve 3.
  • the pilot valve 3 by the actuator 41 is controlled and opened, that is, the closing body 40 lifts off the pilot valve seat 21, the valve chamber 20 is connected to the low-pressure chamber 42.
  • the pressure above the nozzle needle 2 in the control chamber 4 is lowered via the outlet throttle 5 and the pilot valve seat 21.
  • the nozzle needle 2 is thus moved upwards from the nozzle seat 8 by the pressure in the nozzle chamber 6, which remains the same as the system pressure, and the injection quantity reaches the inlet 7, the nozzle chamber 6, the nozzle seat 8, the blind hole 31 and the injection holes 9 in the combustion chamber of the internal combustion engine.
  • the pressure in the control chamber 4 has a characteristic curve during this cycle:
  • the pressure in the control chamber 4 corresponds to the pressure in the nozzle chamber 6, and this corresponds to the system pressure.
  • the pilot valve 3 opens, the pressure in the control chamber 4 drops, since more fuel flows out of the control chamber 4 through the outlet throttle 5 than flows in through the inlet throttle 11.
  • the nozzle needle 2 then moves in the opening direction, i.e. away from the nozzle seat 8. As long as the nozzle needle 2 is in motion, the pressure in the control chamber 4 is based on the balance of forces on the nozzle needle 2.
  • the pressure in the control chamber 4 can, for example, be passed on to a suitable location for the pressure chamber 14 via the branch bore 12.
  • the pressure chamber 14 is advantageously located in the area of a flat sealing surface within the injector housing 10.
  • the pressure in the valve chamber 20 between the outlet throttle 5 and the pilot valve seat 21 behaves in a similar way to the pressure in the control chamber 4. This means that the pressure in the valve chamber 20 can also be used to assess the movement of the pilot valve 3 and / or nozzle needle 2 .
  • the pressure in the valve chamber 20 can be guided to the pressure chamber 14 via the groove 15, for example.
  • the pressure in the nozzle chamber 6 can also be measured and used to assess the movement of the nozzle needle 2.
  • the pressure in the nozzle chamber 6 can be conducted through the connecting bore 32 to the pressure chamber 14.
  • the membrane-like intermediate wall 13 can be implemented through the bottom of the blind hole or the measuring space 16 in the valve plate 10c or in the throttle plate 10b.
  • the force measuring element 17 can be, for example, a piezo force transducer which is braced against the partition 13 by the screw element 18 or by an oversize.
  • the diaphragm-like intermediate wall 13 is loaded by the bias against the effective direction of the pressure to be measured in the pressure chamber 14, so that when the pressure is loaded, the stresses in the intermediate wall 13 are minimized during operation of the fuel injector 1.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)

Description

Stand der TechnikState of the art

Die Erfindung betrifft einen Kraftstoffinjektor, insbesondere einen Common-Rail-Injektor, nach dem Oberbegriff des Anspruchs 1.The invention relates to a fuel injector, in particular a common rail injector, according to the preamble of claim 1.

Ein Kraftstoffinjektor ist aus der EP 1 042 603 B1 bekannt. Der bekannte Kraftstoffinjektor weist innerhalb seines Injektorgehäuses einen Sensor auf, der im Bereich einer Ablaufbohrung zwischen einem Steuerraum des Kraftstoffinjektors und einem Niederdruckbereich angeordnet ist. Insbesondere umgibt der Sensor die Ablaufbohrung an einem hülsenförmigen Abschnitt eines Bauteils, in dem die Ablaufbohrung ausgebildet ist. In den Steuerraum des Kraftstoffinjektors ragt ein Endabschnitt eines als Düsennadel ausgebildeten Einspritzglieds hinein. Über eine Beeinflussung des Drucks in dem Steuerraum wird in bekannter Art und Weise die Bewegung der Düsennadel gesteuert, um zum Einspritzen von Kraftstoff in den Brennraum einer Brennkraftmaschine im Injektorgehäuse ausgebildete Spritzlöcher freizugeben. Der Druck im Steuerraum wird über den Abfluss von Kraftstoff aus dem besagten Steuerraum in den Niederdruckbereich über die Ablaufbohrung bzw. Ablaufdrossel bewirkt, wobei die Ablaufbohrung m*mittels eines Schließglieds im Niederdruckbereich des Injektorgehäuses, welches wiederum mit einem Aktor, beispielsweise einem Magnetaktor oder einem Piezoaktor betätigbar ist, verschlossen werden kann. In der abgesenkten Position der Düsennadel herrscht in dem Steuerraum und somit auch in der Ablaufbohrung ein relativ hoher (hydraulischer) Druck. Beim Entlasten des Steuerraums fließt hingegen Kraftstoff aus dem Steuerraum in den Niederdruckbereich ab, wobei sich der hydraulische Druck in der Ablaufbohrung verringert. Der bekannte Sensor ist dazu ausgebildet, den Druck bzw. Druckschwankungen in der Ablaufbohrung, verursacht durch das Öffnen des Schließglieds aus dem Steuerraum, zu erfassen, woraus auf die Stellung der Düsennadel geschlossen werden kann. Nachteilig bei der bekannten Anordnung ist es, dass der Sensor im Hochdruckbereich des Injektorgehäuses angeordnet ist und somit konstruktiv relativ aufwendig gestaltet sein muss. Darüber hinaus ist der zur Verfügung stehende Bauraum für einen derartigen Sensor im Injektorgehäuse eingeschränkt, so dass spezielle konstruktive Lösungen, die insbesondere auch mit Blick auf die Festigkeit des Injektorgehäuses kritisch sind, gewählt werden müssen.A fuel injector is from the EP 1 042 603 B1 famous. The known fuel injector has a sensor within its injector housing which is arranged in the area of a drain hole between a control chamber of the fuel injector and a low-pressure area. In particular, the sensor surrounds the drain hole on a sleeve-shaped section of a component in which the drain hole is formed. An end section of an injection member designed as a nozzle needle protrudes into the control chamber of the fuel injector. By influencing the pressure in the control chamber, the movement of the nozzle needle is controlled in a known manner in order to release injection holes formed in the injector housing for injecting fuel into the combustion chamber of an internal combustion engine. The pressure in the control chamber is brought about by the outflow of fuel from the said control chamber into the low-pressure area via the outlet bore or outlet throttle, the outlet bore m * by means of a closing element in the low-pressure area of the injector housing, which in turn is equipped with an actuator, for example a magnetic actuator or a piezo actuator can be actuated, can be closed. In the lowered position of the nozzle needle, there is a relatively high (hydraulic) pressure in the control chamber and thus also in the drain hole. When the control chamber is relieved, however, fuel flows out of the control chamber into the low-pressure area, with the hydraulic pressure in the drain hole being reduced. The known sensor is designed to measure the pressure or pressure fluctuations in the drain hole caused by the opening of the Closing member from the control room to detect, from which the position of the nozzle needle can be inferred. The disadvantage of the known arrangement is that the sensor is arranged in the high pressure area of the injector housing and therefore has to be designed in a relatively complex manner. In addition, the space available for such a sensor in the injector housing is limited, so that special constructive solutions, which are particularly critical with regard to the strength of the injector housing, have to be selected.

Aus der DE 10 2011 051 765 A1 ist ein Kraftstoffinjektor mit einer Drucksensorik bekannt, welche im Niederdruckbereich angeordnet ist. Dabei wird ein Messkanal bzw. eine Stichbohrung an eine membranartige Zwischenwand herangeführt. Die Drucksensorik bzw. das Kraftmesselement ist auf der Rückseite der Zwischenwand angeordnet. Die Drucksensorik ist dabei vorzugsweise eine wenig steife Messstreifenanordnung, welche die Spannungen bzw. Verformungen in der Zwischenwand misst. Aufgrund der hohen Drücke in der Stichbohrung kann es jedoch zu Festigkeitsproblemen an der Zwischenwand kommen.From the DE 10 2011 051 765 A1 a fuel injector with a pressure sensor system is known, which is arranged in the low-pressure region. A measuring channel or a tap hole is brought up to a membrane-like partition wall. The pressure sensor system or the force measuring element is arranged on the back of the partition. The pressure sensor system is preferably a less rigid measuring strip arrangement which measures the stresses or deformations in the partition. Due to the high pressures in the branch hole, however, strength problems can arise on the partition wall.

Aus der DE 198 13 756 A1 ist darüber hinaus ein Verfahren zur Messung des Drucks eines Fluids bekannt, wobei ein Messobjekt mit einem Fluid druckbeaufschlagt und durch den Druck ein mechanischer Messaufnehmer ausgelenkt wird. Aus der DE 10 2011 051 765 A1 ist weiterhin ein Einspritzinjektor bekannt, bei dem in Abhängigkeit vom Druck in einem Steuerraum die Einspritzparameter erfasst und/oder gesteuert werden.From the DE 198 13 756 A1 In addition, a method for measuring the pressure of a fluid is known, a measurement object being pressurized with a fluid and a mechanical measuring transducer being deflected by the pressure. From the DE 10 2011 051 765 A1 an injection injector is also known in which the injection parameters are recorded and / or controlled as a function of the pressure in a control chamber.

Offenbarung der ErfindungDisclosure of the invention

Demgegenüber hat der erfindungsgemäße Kraftstoffinjektor im Bereich der Drucksensorik eine erhöhte Dauerfestigkeit, da der Druck nicht über eine Spannung oder Verformung der Zwischenwand gemessen wird. Die Kraft wird erfindungsgemäß mit einem möglichst steifen Kraftmesselement gemessen, welches die Zwischenwand abstützt, so dass die Zwischenwand nahezu keine Verformung erfährt.In contrast, the fuel injector according to the invention has an increased fatigue strength in the area of the pressure sensor system, since the pressure is not measured via a tension or deformation of the partition. According to the invention, the force is measured with a force measuring element which is as rigid as possible and which supports the partition so that the partition experiences almost no deformation.

Dazu umfasst der Kraftstoffinjektor ein Injektorgehäuse, in dem ein Düsenraum ausgebildet ist, der über einen im Injektorgehäuse ausgebildeten Zulauf mit unter Druck stehendem Kraftstoff versorgbar ist. Eine wenigstens ein Spritzloch freigebende oder verschließende längsbewegliche Düsennadel ist im Düsenraum angeordnet. Weiterhin umfasst der Kraftstoffinjektor ein Kraftmesselement zur zumindest mittelbaren Erfassung eines Drucks in einem im Injektorgehäuse ausgebildeten Druckraum. Der Druckraum ist mit dem Zulauf hydraulisch verbindbar. Das Kraftmesselement ist in einem im Injektorgehäuse ausgebildeten Messraum angeordnet, wobei der Messraum durch eine membranartige Zwischenwand vom Druckraum getrennt ist. Erfindungsgemäß stützt das Kraftmesselement die Zwischenwand ab. Vorteilhafterweise ist das Kraftmesselement dabei sehr steif ausgeführt. Die Zwischenwand wird somit durch die Abstützung durch das Kraftmesselement gegen die Wirkrichtung des zu messenden Drucks im Druckraum unterstützt, so dass bei Belastung durch den Druck die Spannungen und Biegungen in der Zwischenwand minimiert sind. Das Kraftmesselement ist durch ein Übermaß innerhalb des Injektorgehäuses vorgespannt. Das Kraftmesselement weist gegenüber dem Messraum ein Übermaß auf, so dass das Kraftmesselement mit der axialen Verspannung des Injektorgehäuses während der Montage gleichzeitig mit vorgespannt wird.For this purpose, the fuel injector comprises an injector housing in which a nozzle chamber is formed, which can be supplied with fuel under pressure via an inlet formed in the injector housing. A longitudinally movable nozzle needle that releases or closes at least one injection hole is arranged in the nozzle space. Furthermore, the fuel injector comprises a force measuring element for at least indirect detection of a pressure in a pressure chamber formed in the injector housing. The pressure chamber can be hydraulically connected to the inlet. The force measuring element is arranged in a measuring space formed in the injector housing, the measuring space being separated from the pressure space by a membrane-like partition. According to the invention, the force measuring element supports the partition. The force measuring element is advantageously designed to be very rigid. The partition wall is thus supported by the force measuring element against the effective direction of the pressure to be measured in the pressure chamber, so that the stresses and bends in the partition wall are minimized when the pressure is loaded. The force measuring element is pretensioned by an oversize inside the injector housing. The force measuring element is oversized in relation to the measuring space, so that the force measuring element is simultaneously pretensioned with the axial bracing of the injector housing during assembly.

Erfindungsgemäß ist der Druckraum über eine Stichbohrung mit dem Steuerraum hydraulisch verbunden. Dadurch wird der Druck im Steuerraum ermittelt, welcher maßgeblich die Bewegung der hydraulisch angesteuerten Düsennadel beeinflusst. Dabei ist die Stichbohrung in der Drosselplatte des Injektorgehäuses ausgebildet, in welcher auch eine Ablaufdrossel aus dem Steuerraum zum Pilotventil ausgebildet ist. Der Druck im Steuerraum ist größeren Schwankungen unterworfen als der Druck im Düsenraum. Dadurch können Druckunterschiede im Steuerraum zuverlässiger ermittelt werden als Druckunterschiede im Düsenraum.According to the invention, the pressure chamber is hydraulically connected to the control chamber via a branch bore. This determines the pressure in the control room, which has a decisive influence on the movement of the hydraulically controlled nozzle needle. The branch bore is formed in the throttle plate of the injector housing, in which an outlet throttle from the control chamber to the pilot valve is also formed. The pressure in the control chamber is subject to greater fluctuations than the pressure in the nozzle chamber. As a result, pressure differences in the control chamber can be determined more reliably than pressure differences in the nozzle chamber.

Weiterhin ist erfindungsgemäß das Kraftmesselement gegen die Zwischenwand vorgespannt. Der im Betrieb des Kraftstoffinjektors im Druckraum anliegende Hochdruck wirkt dann der Vorspannung bzw. Durchbiegung der Zwischenwand entgegen, so dass die Verformungen und Spannungen - speziell die Zugspannungen - in der Zwischenwand und in den umgebenden Bereichen minimiert werden. Auf der Hochdruckseite der Zwischenwand sind die Druckänderungen hochdynamisch, so dass eine Vorspannung der Zwischenwand durch das Kraftmesselement eine deutliche Erhöhung der Dauerfestigkeit zur Folge hat.Furthermore, according to the invention, the force measuring element is pretensioned against the partition. The high pressure present in the pressure chamber during operation of the fuel injector then counteracts the pretensioning or bending of the partition, so that the deformations and stresses - especially the tensile stresses - in the partition and in the surrounding areas are minimized. On the high pressure side of the partition are those Changes in pressure are highly dynamic, so that a pretensioning of the partition wall by the force measuring element results in a significant increase in fatigue strength.

Erfindungsgemäß ist der Zulauf mit dem Druckraum verbunden. Dadurch wird der Druckabfall zwischen Düsenraum und einer Hochdruckquelle gemessen, also annähernd der Druckabfall des Düsenraums. Diese Ausführung kann besonders kostengünstig ausgeführt werden und hat Vorteile bezüglich des benötigten Bauraums, da die Messung durch das Kraftmesselement beispielsweise düsennadelfern erfolgen kann, also in einem Bereich, in welchem mehr freier Bauraum vorhanden ist als in einem düsennahen Bereich.According to the invention, the inlet is connected to the pressure chamber. As a result, the pressure drop between the nozzle space and a high pressure source is measured, that is to say approximately the pressure drop in the nozzle space. This design can be made particularly inexpensive and has advantages in terms of the installation space required, since the measurement by the force measuring element can take place, for example, remote from the nozzle needle, i.e. in an area in which there is more free installation space than in an area close to the nozzle.

Weiter umfasst erfindungsgemäß das Injektorgehäuse einen Düsenkörper, eine Drosselplatte, eine Ventilplatte und einen Haltekörper, welche durch eine Düsenspannmutter axial miteinander verspannt sind. Dies ist ein sehr vorteilhafter Aufbau eines Kraftstoffinjektors, insbesondere eines Kraftstoffinjektors mit einem hydraulischen Pilotventil, welches beispielsweise wiederum durch einen elektromagnetischen Aktor angesteuert werden kann. Derartige Kraftstoffinjektoren werden durch Änderung von hydraulischen Drücken betrieben. Eine Ermittlung von Drücken bzw. Druckunterschieden ist daher besonders bei derartigen Kraftstoffinjektoren von großem Vorteil, um die Einspritzcharakteristik einerseits zu ermitteln aber auch andererseits durch gezielte Auswertung der Druckverläufe die gewünschte Einspritzcharakteristik robust über die Lebensdauer zu erhalten.According to the invention, the injector housing further comprises a nozzle body, a throttle plate, a valve plate and a holding body, which are axially clamped to one another by a nozzle clamping nut. This is a very advantageous structure of a fuel injector, in particular a fuel injector with a hydraulic pilot valve, which, for example, can in turn be controlled by an electromagnetic actuator. Such fuel injectors are operated by changing hydraulic pressures. A determination of pressures or pressure differences is therefore of great advantage, particularly with such fuel injectors, in order to determine the injection characteristics on the one hand, but also to obtain the desired injection characteristics robustly over the service life on the other hand through targeted evaluation of the pressure curves.

In einer vorteilhaften Ausführung ist das Kraftmesselement durch ein Schraubelement, beispielsweise eine Mutter, vorgespannt. Dadurch kann die Vorspannung des Kraftmesselements und somit der Zwischenwand während der Montage des Kraftstoffinjektors sehr genau eingestellt werden.In an advantageous embodiment, the force measuring element is pretensioned by a screw element, for example a nut. As a result, the pretensioning of the force measuring element and thus of the partition wall can be set very precisely during the assembly of the fuel injector.

In bevorzugter Ausgestaltung des Kraftmesselements ist dieses als piezoelektrisches Kraftmesselement ausgebildet. Ein derartiges Element hat den Vorteil einer relativ hohen Messempfindlichkeit bei kompaktem Aufbau und geringen Herstellkosten. Weiterhin kann ein derartiges Kraftmesselement besonders steif ausgeführt werden und dadurch die Zwischenwand sehr effektiv abstützen.In a preferred embodiment of the force measuring element, it is designed as a piezoelectric force measuring element. Such an element has the advantage of a relatively high measurement sensitivity with a compact design and low manufacturing costs. Furthermore, such a force measuring element can be made particularly stiff and thereby support the partition wall very effectively.

In einer Weiterbildung der Erfindung wird die Längsbewegung der Düsennadel durch den Druck in einem Steuerraum gesteuert. Der Druck im Steuerraum wiederum kann dabei beispielsweise von einem Pilotventil gesteuert werden.In a further development of the invention, the longitudinal movement of the nozzle needle is controlled by the pressure in a control chamber. The pressure in the control chamber can in turn be controlled, for example, by a pilot valve.

In vorteilhaften Ausführungen ist im Pilotventil ein Ventilraum ausgebildet und der Steuerraum über eine Ablaufdrossel mit dem Ventilraum hydraulisch verbunden. Dadurch ist die Düsennadel als Servoventil geschaltet. Das Pilotventil kann beispielsweise als ein direktgeschaltetes Magnetventil ausgeführt sein. Der Druck im Ventilraum ist noch größeren Schwankungen unterworfen als der Druck im Steuerraum. Auch in dieser Ausführung können die Druckunterschiede demzufolge sehr zuverlässig ermittelt werden.In advantageous embodiments, a valve chamber is formed in the pilot valve and the control chamber is hydraulically connected to the valve chamber via an outlet throttle. As a result, the nozzle needle is switched as a servo valve. The pilot valve can be designed, for example, as a directly connected solenoid valve. The pressure in the valve chamber is subject to even greater fluctuations than the pressure in the control chamber. In this embodiment too, the pressure differences can therefore be determined very reliably.

In einer Weiterbildung der Erfindung ist der Messraum in der Ventilplatte ausgebildet, wobei an der Ventilplatte ein Pilotventilsitz des Pilotventils zur Steuerung der Düsennadel angeordnet ist. Dadurch sind das Kraftmesselement und zumindest Teile des hydraulischen Pilotventils bauraumsparend in einem Bauteil des Injektorgehäuses angeordnet, nämlich in der Ventilplatte.In a further development of the invention, the measuring space is formed in the valve plate, a pilot valve seat of the pilot valve for controlling the nozzle needle being arranged on the valve plate. As a result, the force measuring element and at least parts of the hydraulic pilot valve are arranged in a structural space-saving component of the injector housing, namely in the valve plate.

Die Erfindung umfasst auch die Verwendung eines erfindungsgemäßen Kraftstoffinjektors bei selbstzündenden Brennkraftmaschinen. Hierbei beträgt der in dem Kraftstoffeinspritzsystem herrschende Systemdruck bevorzugt mehr als 2000 bar.The invention also includes the use of a fuel injector according to the invention in compression-ignition internal combustion engines. In this case, the system pressure prevailing in the fuel injection system is preferably more than 2000 bar.

Weitere Vorteile, Merkmale und Einzelheiten der Erfindung ergeben sich aus der nachfolgenden Beschreibung bevorzugter Ausführungsbeispiele sowie anhand der Zeichnungen.Further advantages, features and details of the invention emerge from the following description of preferred exemplary embodiments and on the basis of the drawings.

Diese zeigen in:

Fig. 1
einen Längsschnitt durch einen erfindungsgemäßen Kraftstoffinjektor mit einem Kraftmesselement zur Erfassung eines Drucks bzw. zur Erfassung von Druckschwankungen, wobei nur die wesentlichen Bereiche dargestellt sind,
Fig. 2
einen Ausschnitt eines weiteren Ausführungsbeispiels des Kraftstoffinjektors im Längsschnitt, wobei nur die wesentlichen Bereiche dargestellt sind,
Fig. 3
einen Ausschnitt eines noch weiteren Ausführungsbeispiels des Kraftstoffinjektors im Längsschnitt, wobei nur die wesentlichen Bereiche dargestellt sind,
Fig. 4
ein Verspannungskonzept des Kraftmesselements innerhalb des Kraftstoffinjektors.
These show in:
Fig. 1
a longitudinal section through a fuel injector according to the invention with a force measuring element for detecting a pressure or for detecting pressure fluctuations, only the essential areas being shown,
Fig. 2
a section of a further embodiment of the fuel injector in longitudinal section, only the essential areas being shown,
Fig. 3
a section of yet another embodiment of the fuel injector in longitudinal section, only the essential areas being shown,
Fig. 4
a tension concept of the force measuring element within the fuel injector.

Gleiche Elemente bzw. Elemente mit gleicher Funktion sind in den Figuren mit den gleichen Bezugsziffern versehen.The same elements or elements with the same function are provided with the same reference numbers in the figures.

In der Fig.1 ist ein erfindungsgemäßer Kraftstoffinjektor 1 dargestellt, wie er als Bestandteil eines sogenannten Common-Rail-Einspritzsystems zum Einspritzen von Kraftstoff in den Brennraum einer nicht dargestellten Brennkraftmaschine dient. Insbesondere weist das Common-Rail-Einspritzsystem hierbei einen Systemdruck von mehr als 2000 bar auf.In the Fig. 1 a fuel injector 1 according to the invention is shown, as it serves as part of a so-called common rail injection system for injecting fuel into the combustion chamber of an internal combustion engine, not shown. In particular, the common rail injection system has a system pressure of more than 2000 bar.

Der Kraftstoffinjektor 1 umfasst ein Injektorgehäuse 10, das im dargestellten Ausführungsbeispiel im Wesentlichen vier in Axialrichtung aneinander anschließende Bauteile umfasst: Auf der dem nicht gezeigten Brennraum der Brennkraftmaschine zugewandten Seite weist das Injektorgehäuse 10 einen Düsenkörper 10a auf, an den sich eine Drosselplatte 10b, und an diese wiederum auf der dem Düsenkörper 10a abgewandten Seite eine Ventilplatte 10c und ein Haltekörper 10d anschließen. Diese Bauteile des Injektorgehäuses 10 sind durch eine Düsenspannmutter 10e axial miteinander dichtend verspannt.The fuel injector 1 comprises an injector housing 10 which, in the exemplary embodiment shown, essentially comprises four components adjoining one another in the axial direction: On the side facing the combustion chamber (not shown) of the internal combustion engine, the injector housing 10 has a nozzle body 10a, to which a throttle plate 10b and 10b are attached these in turn connect a valve plate 10c and a holding body 10d on the side facing away from the nozzle body 10a. These components of the injector housing 10 are axially clamped to one another in a sealing manner by a nozzle clamping nut 10e.

In dem Düsenkörper 10a ist ein Sackloch 31 mit wenigstens einem, vorzugsweise jedoch mehreren Spritzlöchern 9 zum Einspritzen des unter Hochdruck stehenden Kraftstoffs in den Brennraum der Brennkraftmaschine ausgebildet. Der Düsenkörper 10a bildet in einer bohrungsförmigen Ausnehmung einen Düsenraum 6 aus, der über einen Zulauf 7 hydraulisch mit einer Kraftstoffquelle, beispielsweise einem Common Rail verbunden ist. Innerhalb des Düsenraums 6 ist ein hubbeweglich angeordnetes Einspritzglied in Form einer Düsennadel 2 angeordnet.In the nozzle body 10a, a blind hole 31 is formed with at least one, but preferably a plurality of injection holes 9 for injecting the high pressure fuel into the combustion chamber of the internal combustion engine. The nozzle body 10a forms a nozzle space 6 in a bore-shaped recess, which is hydraulically connected to a fuel source, for example a common rail, via an inlet 7. An injection member in the form of a nozzle needle 2, which is arranged to be movable in a stroke, is arranged within the nozzle space 6.

Am Düsenkörper 10a ist ein Düsensitz 8 angeordnet, mit dem die Düsennadel 2 zum Öffnen und Schließen der Spritzlöcher 9 zusammenwirkt.A nozzle seat 8, with which the nozzle needle 2 interacts to open and close the injection holes 9, is arranged on the nozzle body 10a.

Die Düsennadel 2 ist im Düsenraum 6 vom Düsenkörper 10a radial geführt, wobei die Düsennadel 2 durch eine Schließfeder 35 in Richtung des Düsensitzes 8 kraftbeaufschlagt ist. An ihrem dem Düsensitz 8 abgewandten Ende begrenzt die Düsennadel 2 mit einer Stirnfläche einen Steuerraum 4. Der Steuerraum 4 ist im Injektorgehäuse 10 zwischen der Düsennadel 2, der Drosselplatte 10b und einer Hülse 36 ausgebildet. Der Steuerraum 4 ist doch eine in der Drosselplatte 10b ausgebildete Zulaufdrossel 11 mit dem Zulauf 7 verbunden. Die Hülse 36 ist von der Schließfeder 35 gegen die Drosselplatte 10b gespannt und führt die Düsennadel 2 längsbeweglich bzw. die Düsennadel 2 positioniert die Hülse 36 in radialer Richtung. Der Druck im Steuerraum 4 beaufschlagt die Düsennadel 2 mit einer hydraulischen Kraft in Richtung des Düsensitzes 8, also in Schließrichtung.The nozzle needle 2 is guided radially in the nozzle space 6 by the nozzle body 10a, the nozzle needle 2 being acted upon by force in the direction of the nozzle seat 8 by a closing spring 35. At its end facing away from the nozzle seat 8, the nozzle needle 2 delimits a control chamber 4 with an end face. The control chamber 4 is formed in the injector housing 10 between the nozzle needle 2, the throttle plate 10b and a sleeve 36. The control chamber 4 is connected to the inlet 7 by an inlet throttle 11 formed in the throttle plate 10b. The sleeve 36 is tensioned by the closing spring 35 against the throttle plate 10b and guides the nozzle needle 2 in a longitudinally movable manner or the nozzle needle 2 positions the sleeve 36 in the radial direction. The pressure in the control chamber 4 acts on the nozzle needle 2 with a hydraulic force in the direction of the nozzle seat 8, that is, in the closing direction.

Der Druck im Steuerraum 4 wird durch ein im Injektorgehäuse 10 angeordnetes Pilotventil 3 gesteuert. Das Pilotventil 3 umfasst einen Schließkörper 40, der mit einem an der Ventilplatte 10c ausgebildetem Pilotventilsitz 21 zusammenwirkt, einen Aktor 41 und einen Ventilraum 20. Der Aktor 41 ist im Ausführungsbeispiel der Fig.1 als elektromagnetischer Aktor dargestellt, kann aber ein beliebiger Aktor, beispielsweise auch ein Piezoaktor sein. Der Ventilraum 20 ist über eine in der Drosselplatte 10b ausgebildete Ablaufdrossel 5 mit dem Steuerraum 4 verbunden. Der Schließkörper 40 öffnet und schließt eine Verbindung des Ventilraums 20 zu einem im Injektorgehäuse 10 ausgebildeten Niederdruckraum 42, indem er mit dem Pilotventilsitz 21 zusammenwirkt. Im Ausführungsbeispiel der Fig.1 umfasst der Ventilraum 20 im Wesentlichen zwei Bohrungen, je eine in der Ventilplatte 10c und in der Drosselplatte 10b ausgebildet. In alternativen Ausführungen kann der Ventilraum 20 jedoch beliebige Formen aufweisen.The pressure in the control chamber 4 is controlled by a pilot valve 3 arranged in the injector housing 10. The pilot valve 3 comprises a closing body 40 which cooperates with a pilot valve seat 21 formed on the valve plate 10c, an actuator 41 and a valve chamber 20. The actuator 41 is in the exemplary embodiment from FIG Fig. 1 shown as an electromagnetic actuator, but can be any actuator, for example also a piezo actuator. The valve chamber 20 is connected to the control chamber 4 via an outlet throttle 5 formed in the throttle plate 10b. The closing body 40 opens and closes a connection between the valve chamber 20 and a low-pressure chamber 42 formed in the injector housing 10 by interacting with the pilot valve seat 21. In the embodiment of Fig. 1 the valve chamber 20 comprises essentially two bores, one each formed in the valve plate 10c and one in the throttle plate 10b. In alternative embodiments, however, the valve chamber 20 can have any shape.

Erfindungsgemäß ist im Injektorgehäuse 10 ein Kraftmesselement 17 angeordnet, um einen Druck eines unter Hochdruck stehenden Druckraums 14 zu messen. Vom Kraftmesselement 17 führen zwei elektrische Leitungen 17a durch das Injektorgehäuse 10 zu einem nicht dargestellten Steuergerät. Aus der Kraft- bzw. Druckmessung kann direkt auf die Hubbewegung der Düsennadel 2 geschlossen werden und damit auf die Einspritzcharakteristik des Kraftstoffinjektors 1. Die Ansteuerung des Pilotventils 3 kann dann beispielsweise von dem Steuergerät in Abhängigkeit der Einspritzcharakteristik geändert werden.According to the invention, a force measuring element 17 is arranged in the injector housing 10 in order to measure a pressure of a pressure chamber 14 under high pressure. Two electrical lines 17a lead from the force measuring element 17 through the injector housing 10 to a control unit (not shown). From the force or pressure measurement, conclusions can be drawn directly about the stroke movement of the nozzle needle 2 and thus about the injection characteristics of the fuel injector 1. The control of the pilot valve 3 can then, for example, be changed by the control unit as a function of the injection characteristics.

Der Druckraum 14 ist hydraulisch mit dem Zulauf 7, dem Düsenraum 6, dem Steuerraum 4 oder dem Ventilraum 20 verbunden. Im Ausführungsbeispiel der Fig.1 ist der Druckraum 14 durch eine Ausnehmung in der Ventilplatte 10c gebildet und über eine in der Drosselplatte 10b ausgebildete Stichbohrung 12 mit dem Steuerraum 4 verbunden.The pressure chamber 14 is hydraulically connected to the inlet 7, the nozzle chamber 6, the control chamber 4 or the valve chamber 20. In the embodiment of Fig. 1 the pressure chamber 14 is formed by a recess in the valve plate 10c and is connected to the control chamber 4 via a tap bore 12 formed in the throttle plate 10b.

In der Ventilplatte 10c ist weiterhin gegenüberliegend zum Druckraum 14 ein Messraum 16 ausgebildet und von diesem durch eine membranartige Zwischenwand 13 getrennt. Das Kraftmesselement 17 ist im Messraum 16 angeordnet und zwar derart, dass es die Zwischenwand 13 abstützt.In the valve plate 10c, a measuring chamber 16 is also formed opposite the pressure chamber 14 and separated from it by a membrane-like intermediate wall 13. The force measuring element 17 is arranged in the measuring space 16 in such a way that it supports the partition 13.

Der Messraum 16 hat die Form einer zum Haltekörper 10d hin geöffneten Sacklochbohrung. Dadurch kann das Kraftmesselement 17 entweder durch ein Übermaß zum Haltekörper 10d oder, wie im Ausführungsbeispiel der Fig.1 , durch ein in den Messraum 16 eingeschraubtes Schraubelement 18 gegen die Zwischenwand 13 gespannt werden.The measuring space 16 has the shape of a blind hole opening towards the holding body 10d. As a result, the force measuring element 17 can either be oversized relative to the holding body 10d or, as in the exemplary embodiment in FIG Fig. 1 , be clamped against the intermediate wall 13 by a screw element 18 screwed into the measuring space 16.

Der Messraum 16 liegt im Niederdruckbereich, der Druckraum 14 ist mit Hochdruck beaufschlagt. Dies führt dazu, dass die Zwischenwand 13 hydraulisch einseitig belastet ist. Die Vorspannung der Zwischenwand 13 durch das Kraftmesselement 17 kompensiert diese einseitige Belastung. Die maximalen Spannungen, insbesondere Zugspannungen in der Zwischenwand 13 werden dadurch verringert und somit die Lebensdauer des gesamten Kraftstoffinjektors 1 erhöht.The measuring chamber 16 is in the low pressure range, the pressure chamber 14 is acted upon by high pressure. This means that the partition 13 is hydraulically loaded on one side. The bias of the intermediate wall 13 by the force measuring element 17 compensates for this one-sided load. The maximum stresses, in particular tensile stresses, in the intermediate wall 13 are thereby reduced and thus the service life of the entire fuel injector 1 is increased.

Im Folgenden werden weitere Ausführungsformen des erfindungsgemäßen Kraftstoffinjektors 1 beschrieben. Nicht näher beschriebene Bereiche sind dabei so ausgeführt wie im Ausführungsbeispiel der Fig.1 . Further embodiments of the fuel injector 1 according to the invention are described below. Areas not described in more detail are designed as in the exemplary embodiment in FIG Fig. 1 .

Fig.2 zeigt das Kraftmesselement 17 in einer alternativen Anordnung, nämlich zur Druckmessung des Ventilraums 20. Der Messraum 16 ist analog zur Ausführung der Fig.1 als Sacklochbohrung in der Ventilplatte 10c ausgebildet, wobei die Sacklochbohrung zum Haltekörper 10d geöffnet ist. Das Kraftmesselement 17 weist in Längsrichtung des Kraftstoffinjektors 1 ein Übermaß gegenüber dem Messraum 16 auf. Bei der Montage des Kraftstoffinjektors 1 wird dadurch beim Anziehen der Düsenspannmutter 10e das Kraftmesselement 17 zwischen dem Haltekörper 10d und der Zwischenwand 13 vorgespannt. Fig. 2 shows the force measuring element 17 in an alternative arrangement, namely for measuring the pressure of the valve chamber 20. The measuring chamber 16 is analogous to the embodiment of FIG Fig. 1 designed as a blind hole in the valve plate 10c, the blind hole being open to the holding body 10d. The force measuring element 17 has an oversize in the longitudinal direction of the fuel injector 1 compared to the measuring space 16. During the assembly of the fuel injector 1, when the nozzle clamping nut 10e is tightened, the force measuring element 17 is pretensioned between the holding body 10d and the partition 13.

Auf der dem Messraum 16 gegenüberliegenden Seite der Zwischenwand 13 ist der Druckraum 14 als Ausnehmung in der Ventilplatte 10c ausgebildet und wird von der Ventilplatte 10c und der Drosselplatte 10b begrenzt. Der Druckraum 14 ist über eine ebenfalls in der Ventilplatte 10c ausgebildete Nut 15 mit dem Ventilraum 20 verbunden, so dass der im Ventilraum 20 herrschende Druck auch im Druckraum 14 herrscht.On the side of the partition 13 opposite the measuring chamber 16, the pressure chamber 14 is designed as a recess in the valve plate 10c and is delimited by the valve plate 10c and the throttle plate 10b. The pressure chamber 14 is connected to the valve chamber 20 via a groove 15 also formed in the valve plate 10c, so that the pressure prevailing in the valve chamber 20 also prevails in the pressure chamber 14.

In alternativen Ausführungen können der Druckraum 14 und die Nut 15 auch als eine einzige Ausnehmung ausgeführt sein. Weiterhin können der Druckraum 14 und/oder die Nut 15 auch in der Drosselplatte 10b ausgebildet sein.In alternative embodiments, the pressure chamber 14 and the groove 15 can also be designed as a single recess. Furthermore, the pressure chamber 14 and / or the groove 15 can also be formed in the throttle plate 10b.

Fig.3 zeigt das Kraftmesselement 17 in einer weiteren Anordnung, nämlich zur Druckmessung des Düsenraums 6. Analog zum Ausführungsbeispiel der Fig.2 ist das Kraftmesselement 17 dabei im Messraum 16 durch ein Übermaß zwischen dem Haltekörper 10d und der Zwischenwand 13 verspannt. Eine Verbindungsbohrung 32 ist in der Drosselplatte 10b ausgebildet und verbindet den Düsenraum 6 mit dem Druckraum 14, so dass der im Düsenraum 6 herrschende Druck auch im Druckraum 14 herrscht. Der Druckraum 14 ist als Ausnehmung bzw. Sacklochbohrung in der Ventilplatte 10c ausgebildet, kann in alternativen Ausführungen jedoch auch in der Drosselplatte 10b ausgebildet sein. Fig. 3 FIG. 3 shows the force measuring element 17 in a further arrangement, namely for measuring the pressure of the nozzle space 6. Analogous to the exemplary embodiment of FIG Fig. 2 the force measuring element 17 is braced in the measuring space 16 by an oversize between the holding body 10d and the intermediate wall 13. A connecting bore 32 is formed in the throttle plate 10b and connects the nozzle space 6 with the pressure space 14, so that the pressure prevailing in the nozzle space 6 also prevails in the pressure space 14. The pressure chamber 14 is designed as a recess or blind hole in the valve plate 10c, but in alternative designs it can also be designed in the throttle plate 10b.

Fig.4 zeigt ein erfindungsgemäßes Verspannungskonzept des Kraftmesselements 17 im Messraum 16. Das Kraftmesselement 17 ist gegenüber dem Messraum 16 mit einem Übermaß 19 versehen ( Fig.4 oben). Wird das Kraftmesselement 17 nun zwischen dem Haltekörper 10d und der Zwischenwand 13 verspannt, so ergibt sich eine Durchbiegung der membranartigen Zwischenwand 13 in Richtung des Druckraums 14 ( Fig.4 unten). Der im Betrieb anliegende Hochdruck im Druckraum 14 wirkt dann der Durchbiegung der Zwischenwand 13 entgegen, so dass die Zugspannungen in der Zwischenwand 13 und in den umgebenden Bereichen im Betrieb des Kraftstoffinjektors 1 minimiert sind. Fig. 4 shows a tensioning concept according to the invention of the force measuring element 17 in the measuring space 16. The force measuring element 17 is provided with an oversize 19 compared to the measuring space 16 ( Fig. 4 above ). If the force measuring element 17 is now clamped between the holding body 10d and the partition 13, the diaphragm-like partition 13 is bent in the direction of the pressure chamber 14 ( Fig. 4 below ). The high pressure in the pressure chamber 14 during operation then counteracts the deflection of the partition 13, so that the tensile stresses in the partition 13 and in the surrounding areas are minimized when the fuel injector 1 is in operation.

Alternativ ist es auch möglich die Verspannung des Kraftmesselements 17 im Messraum 13 durch eine Schraubverbindung, wie in der Ausführung der Fig.1 gezeigt, zu realisieren.Alternatively, it is also possible to brace the force measuring element 17 in the measuring space 13 by means of a screw connection, as in the embodiment of FIG Fig. 1 shown to realize.

Weiterhin ist es alternativ auch möglich, den Messraum 16 in der Drosselplatte 10b auszubilden, so dass das Kraftmesselement 17 innerhalb der Drosselplatte 10b angeordnet ist. Das Kraftmesselement 17 kann dann zwischen der Drosselplatte 10b und der Ventilplatte 10c verspannt werden, oder auch zwischen der Drosselplatte 10b und dem Haltekörper 10d, falls der Messraum 16 beispielsweise als Durchgangsbohrung in der Ventilplatte 10c ausgebildet ist.Furthermore, it is alternatively also possible to form the measuring space 16 in the throttle plate 10b, so that the force measuring element 17 is arranged within the throttle plate 10b. The force measuring element 17 can then be clamped between the throttle plate 10b and the valve plate 10c, or between the throttle plate 10b and the holding body 10d if the measuring space 16 is designed, for example, as a through hole in the valve plate 10c.

Die Funktionsweise des erfindungsgemäßen Kraftstoffinjektors 1 ist wie folgt:
Das Öffnen und Schließen der Düsennadel 2 des Kraftstoffinjektors 1 wird mittels des Pilotventils 3 gesteuert. Wenn das Pilotventil 3 durch den Aktor 41 angesteuert und geöffnet wird, also der Schließkörper 40 vom Pilotventilsitz 21 abhebt, wird der Ventilraum 20 mit dem Niederdruckraum 42 verbunden. Dadurch wird der Druck über der Düsennadel 2 im Steuerraum 4 über die Ablaufdrossel 5 und den Pilotventilsitz 21 abgesenkt. Die Düsennadel 2 wird so durch den Druck im Düsenraum 6, welcher gleich dem Systemdruck bleibt, vom Düsensitz 8 nach oben bewegt, und die Einspritzmenge gelangt über den Zulauf 7, den Düsenraum 6, den Düsensitz 8, das Sackloch 31 und die Spritzlöcher 9 in den Brennraum der Brennkraftmaschine.The mode of operation of the fuel injector 1 according to the invention is as follows:
The opening and closing of the nozzle needle 2 of the fuel injector 1 is controlled by means of the pilot valve 3. When the pilot valve 3 by the actuator 41 is controlled and opened, that is, the closing body 40 lifts off the pilot valve seat 21, the valve chamber 20 is connected to the low-pressure chamber 42. As a result, the pressure above the nozzle needle 2 in the control chamber 4 is lowered via the outlet throttle 5 and the pilot valve seat 21. The nozzle needle 2 is thus moved upwards from the nozzle seat 8 by the pressure in the nozzle chamber 6, which remains the same as the system pressure, and the injection quantity reaches the inlet 7, the nozzle chamber 6, the nozzle seat 8, the blind hole 31 and the injection holes 9 in the combustion chamber of the internal combustion engine.

Wenn das Pilotventil 3 wieder geschlossen wird, baut sich über die Zulaufdrossel 11 der Druck im Steuerraum 4 wieder auf, die Düsennadel 2 wird wieder nach unten gegen den Düsensitz 8 gedrückt, und die Einspritzung wird beendet.When the pilot valve 3 is closed again, the pressure in the control chamber 4 builds up again via the inlet throttle 11, the nozzle needle 2 is pressed down again against the nozzle seat 8, and the injection is terminated.

Der Druck im Steuerraum 4 hat während dieses Zyklus einen charakteristischen Verlauf: Bei unbetätigtem, also geschlossenem Pilotventil 3 entspricht der Druck im Steuerraum 4 dem Druck im Düsenraum 6, und dieser entspricht dem Systemdruck. Wenn das Pilotventil 3 öffnet, fällt der Druck im Steuerraum 4 ab, da mehr Kraftstoff durch die Ablaufdrossel 5 aus dem Steuerraum 4 abströmt als durch die Zulaufdrossel 11 nachströmt. Daraufhin bewegt sich die Düsennadel 2 in Öffnungsrichtung, also weg vom Düsensitz 8. Solange die Düsennadel 2 in Bewegung ist, ergibt sich der Druck im Steuerraum 4 auf Basis der Kräftebilanz an der Düsennadel 2. Das heißt der Druck steigt im Steuerraum 4 aufgrund des steigenden Drucks im Sackloch 31 und der daraus wirksamen Kraft auf die Düsennadel 2 nach oben, also vom Düsensitz 8 weg gerichtet. Wenn die Düsennadel 2 den maximalen Hub erreicht und am oberen Hubanschlag ansteht, ergibt sich ein Abfall des Drucks im Steuerraum 4 entsprechend der Durchflüsse durch Ablaufdrossel 5 und Zulaufdrossel 11.The pressure in the control chamber 4 has a characteristic curve during this cycle: When the pilot valve 3 is not actuated, i.e. closed, the pressure in the control chamber 4 corresponds to the pressure in the nozzle chamber 6, and this corresponds to the system pressure. When the pilot valve 3 opens, the pressure in the control chamber 4 drops, since more fuel flows out of the control chamber 4 through the outlet throttle 5 than flows in through the inlet throttle 11. The nozzle needle 2 then moves in the opening direction, i.e. away from the nozzle seat 8. As long as the nozzle needle 2 is in motion, the pressure in the control chamber 4 is based on the balance of forces on the nozzle needle 2. That is, the pressure rises in the control chamber 4 due to the rising pressure Pressure in the blind hole 31 and the force acting therefrom on the nozzle needle 2 upwards, that is, directed away from the nozzle seat 8. When the nozzle needle 2 reaches the maximum stroke and is present at the upper stroke stop, there is a drop in the pressure in the control chamber 4 corresponding to the flow rates through the outlet throttle 5 and inlet throttle 11.

Wenn das Pilotventil 3 wieder geschlossen wird, steigt der Druck im Steuerraum 4 solange an bis Kräftegleichgewicht an der Düsennadel 2 herrscht und die Düsennadel 2 sich wieder in Richtung des Düsensitzes 8 bewegt. Wenn die Düsennadel 2 im Düsensitz 8 auftrifft, steigt schließlich der Druck im Steuerraum 4 wieder auf den Systemdruck an. Auch im ballistischen Betrieb der Düsennadel 2, das heißt wenn die Einspritzdauer so kurz ist, dass die Düsennadel 2 nicht den Hubanschlag erreicht, gelten diese Zusammenhänge zwischen dem Druck im Steuerraum 4 und den Hüben von Pilotventil 3 und Düsennadel 2.When the pilot valve 3 is closed again, the pressure in the control chamber 4 rises until there is an equilibrium of forces at the nozzle needle 2 and the nozzle needle 2 moves again in the direction of the nozzle seat 8. When the nozzle needle 2 hits the nozzle seat 8, the pressure in the control chamber 4 finally rises again to the system pressure. Even in ballistic operation of the nozzle needle 2, that is, when the injection duration is so short that the nozzle needle 2 does not When the stroke stop is reached, these relationships apply between the pressure in the control chamber 4 and the strokes of the pilot valve 3 and the nozzle needle 2.

Der Druck im Steuerraum 4 kann beispielsweise über die Stichbohrung 12 zu einem geeigneten Ort für den Druckraum 14 weitergeleitet werden. Vorteilhaft liegt der Druckraum 14 im Bereich einer Plandichtfläche innerhalb des Injektorgehäuses 10.The pressure in the control chamber 4 can, for example, be passed on to a suitable location for the pressure chamber 14 via the branch bore 12. The pressure chamber 14 is advantageously located in the area of a flat sealing surface within the injector housing 10.

Auch der Druck im Ventilraum 20 zwischen der Ablaufdrossel 5 und dem Pilotventilsitz 21 verhält sich in ähnlicher Weise wie der Druck im Steuerraum 4. Das heißt auch der Druck im Ventilraum 20 kann für eine Beurteilung der Bewegung von Pilotventil 3 und/oder Düsennadel 2 herangezogen werden. Der Druck im Ventilraum 20 kann beispielweise über die Nut 15 zum Druckraum 14 geführt werden.The pressure in the valve chamber 20 between the outlet throttle 5 and the pilot valve seat 21 behaves in a similar way to the pressure in the control chamber 4. This means that the pressure in the valve chamber 20 can also be used to assess the movement of the pilot valve 3 and / or nozzle needle 2 . The pressure in the valve chamber 20 can be guided to the pressure chamber 14 via the groove 15, for example.

Weiterhin kann auch der Druck im Düsenraum 6 gemessen und zur Beurteilung der Bewegung der Düsennadel 2 verwendet werden. Beispielsweise kann dazu der Druck im Düsenraum 6 durch die Verbindungsbohrung 32 zum Druckraum 14 geführt werden.Furthermore, the pressure in the nozzle chamber 6 can also be measured and used to assess the movement of the nozzle needle 2. For this purpose, for example, the pressure in the nozzle chamber 6 can be conducted through the connecting bore 32 to the pressure chamber 14.

Die membranartige Zwischenwand 13 kann durch den Boden der Sacklochbohrung bzw. des Messraums 16 in der Ventilplatte 10c oder in der Drosselplatte 10b ausgeführt werden. Im Messraum 16 ist das in Längsrichtung sehr steife Kraftmesselement 17 eingesetzt, das den Druck bzw. die Druckschwankungen im Druckraum 14 mittelbar ermittelt. Maßgeblich ist eine starke Abstützung gegen Durchbiegen der Zwischenwand 13 durch das Kraftmesselement 17. Das Kraftmesselement 17 kann beispielsweise ein Piezo-Kraftaufnehmer sein, welcher durch das Schraubelement 18 oder durch ein Übermaß gegen die Zwischenwand 13 verspannt wird. Die membranartige Zwischenwand 13 wird durch die Vorspannung gegen die Wirkrichtung des zu messenden Drucks im Druckraum 14 belastet, so dass bei Belastung durch den Druck die Spannungen in der Zwischenwand 13 im Betrieb des Kraftstoffinjektors 1 minimiert werden.The membrane-like intermediate wall 13 can be implemented through the bottom of the blind hole or the measuring space 16 in the valve plate 10c or in the throttle plate 10b. The force measuring element 17, which is very stiff in the longitudinal direction and indirectly determines the pressure or the pressure fluctuations in the pressure chamber 14, is inserted in the measuring space 16. A strong support against bending of the partition 13 by the force measuring element 17 is decisive. The force measuring element 17 can be, for example, a piezo force transducer which is braced against the partition 13 by the screw element 18 or by an oversize. The diaphragm-like intermediate wall 13 is loaded by the bias against the effective direction of the pressure to be measured in the pressure chamber 14, so that when the pressure is loaded, the stresses in the intermediate wall 13 are minimized during operation of the fuel injector 1.

Claims (4)

  1. Fuel injector (1) with an injector housing (10) in which there is formed a nozzle chamber (6) which can be supplied with pressurized fuel via a feed line (7) formed in the injector housing (10), the injector housing (10) including a nozzle body (10a), a throttle plate (10b), a valve plate (10c) and a retaining body (10d), which are braced together axially by means of a nozzle clamping nut (10e), and with a longitudinally movable nozzle needle (2) which opens or closes at least one spray hole (9) and which is arranged in the nozzle chamber (6), and with a force measuring element (17) for at least indirectly detecting a pressure in a pressure chamber (14) formed in the injector housing (10), the pressure chamber (14) being hydraulically connectable to the feed line (7), the force measuring element (17) being arranged in a measuring chamber (16) formed in the injector housing (10), the measuring chamber (16) being separated from the pressure chamber (14) by a diaphragm-like intermediate wall (13), the force measuring element (17) supporting the intermediate wall (13), the force measuring element (17) being preloaded against the intermediate wall (13), and the longitudinal movement of the nozzle needle (2) being controlled by the pressure in a control chamber (4), and the pressure chamber (14) being connected to the control chamber (4) via a tap bore (12),
    characterized
    in that the force measuring element (17) is preloaded by means of an oversize (19) inside the injector housing (10), and the pressure chamber (14) and the measuring chamber (16) separated therefrom by a diaphragm-like intermediate wall (13) are formed in the valve plate (10c), and the tap bore (12) is formed in the throttle plate (10b).
  2. Fuel injector (1) according to Claim 1,
    characterized
    in that the force measuring element (17) is a piezoelectric force measuring element.
  3. Fuel injector (1) according to Claim 1,
    characterized
    in that a pilot valve seat (21) of a pilot valve (3) for controlling the nozzle needle (2) is arranged on the valve plate (10c).
  4. Fuel injector (1) according to Claim 3,
    characterized
    in that the measuring chamber (16) is formed in the throttle plate (10b), the throttle plate (10b) delimiting the nozzle chamber (6).
EP16707116.6A 2015-04-22 2016-03-01 Fuel injector Active EP3286428B1 (en)

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DE102015207307.6A DE102015207307A1 (en) 2015-04-22 2015-04-22 fuel injector
PCT/EP2016/054285 WO2016169682A1 (en) 2015-04-22 2016-03-01 Fuel injector

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DE102015207307A1 (en) 2016-10-27
JP6636043B2 (en) 2020-01-29
JP2018517867A (en) 2018-07-05
US10330063B2 (en) 2019-06-25
WO2016169682A1 (en) 2016-10-27
US20180087480A1 (en) 2018-03-29
EP3286428A1 (en) 2018-02-28

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