EP0133470B1 - Fuel injection nozzle for internal-combustion engines - Google Patents

Fuel injection nozzle for internal-combustion engines Download PDF

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Publication number
EP0133470B1
EP0133470B1 EP19840107559 EP84107559A EP0133470B1 EP 0133470 B1 EP0133470 B1 EP 0133470B1 EP 19840107559 EP19840107559 EP 19840107559 EP 84107559 A EP84107559 A EP 84107559A EP 0133470 B1 EP0133470 B1 EP 0133470B1
Authority
EP
European Patent Office
Prior art keywords
valve needle
piston
fuel
accumulator
pressure
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.)
Expired
Application number
EP19840107559
Other languages
German (de)
French (fr)
Other versions
EP0133470A1 (en
Inventor
Dietrich Dipl.-Ing. Trachte
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
Original Assignee
Robert Bosch GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from DE19833328824 external-priority patent/DE3328824A1/en
Priority claimed from DE19833344396 external-priority patent/DE3344396A1/en
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP0133470A1 publication Critical patent/EP0133470A1/en
Application granted granted Critical
Publication of EP0133470B1 publication Critical patent/EP0133470B1/en
Expired legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M45/00—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship
    • F02M45/02—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts
    • F02M45/04—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts with a small initial part, e.g. initial part for partial load and initial and main part for full load
    • F02M45/08—Injectors peculiar thereto
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/7722—Line condition change responsive valves
    • Y10T137/7781—With separate connected fluid reactor surface
    • Y10T137/7832—Plural valves biased closed
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/877—With flow control means for branched passages
    • Y10T137/87708—With common valve operator
    • Y10T137/87764—Having fluid actuator

Definitions

  • the invention relates to a fuel injection nozzle according to the preamble of the main claim.
  • injection nozzles of this type in order to end the pre-injection phase, a certain volume of the supplied fuel is swallowed by the evasive accumulator piston, so that the valve needle is braked temporarily or, if appropriately designed, is even returned to the valve seat.
  • the effective pressure area on the valve needle is reduced by the size of the second pressure shoulder, so that a noticeably higher fuel pressure is required to move the valve needle further or to reopen the valve, and the majority of the fuel is injected at this higher pressure.
  • the reduced effective pressure area is maintained until the end of the injection process, resulting in an exact end of injection with high closing pressure.
  • the storage piston is arranged displaceably in a cylinder bore in the interior of the valve needle.
  • the confluence of the auxiliary fuel channel lies at one end of the cylinder bore, which forms the second pressure shoulder of the valve needle.
  • the accumulator piston has a valve pin shoulder with a diameter which is pressed by the return spring against the mouth of the auxiliary channel and monitors the mouth.
  • the opening of the auxiliary channel at the end of the pre-injection phase is dependent on the fuel pressure, which propagates almost unthrottled into the auxiliary channel and there acts on the valve surface of the valve pin extension on the accumulator piston.
  • the fuel pressure in the cylinder bore acts on the entire cross-sectional area of the accumulator piston and quickly leads it to its end position, in which it is supported on the housing and remains approximately until the end of injection.
  • the pressure-dependent introduction of the main injection phase has the disadvantage that if the opening pressures for the valve needle and the evasive piston change, the evasive piston can be opened without a pre-injection taking place.
  • fuel injection nozzles for pre-injection and main injection are known, in which a storage space opened at the end of a pre-injection stroke of the valve needle is formed between two guide sections of the valve needle arranged at an axial distance from one another in the bore in the nozzle housing that guides the valve needle (DE-B 1 751 080 ).
  • the swallowing capacity of the storage space which is based solely on the compressibility of the fuel, is low and, moreover, the forces exerted by the fuel in the storage space on the valve needle cancel each other out, so that a fuel pressure jump does not occur at the transition to the main injection phase.
  • fuel injection nozzles are known in which, for the initial throttling of the fuel throughput, a fuel storage space is arranged between the valve needle and closing spring and is continuously connected to the fuel supply line via a throttle (DE-A 2032484).
  • the closing spring engages a piston member delimiting the storage space on one end face, which, in the closed position of the valve needle with an axial extension ensuring a minimum size of the storage space, rests on a piston member rigidly connected to the valve needle, which delimits the storage space on the other end face.
  • fuel flows into the storage space via the throttle and lifts both piston members apart, after which the closing spring force is transferred hydraulically to the valve needle via the fuel cushion in the storage space.
  • This version requires careful coordination of the parts and, if necessary, speed-dependent control of the throttle if the desired effect is to occur in the entire working area of the machine.
  • fuel injection nozzles with storage pistons acted upon by the fuel from the start of the injection are known, which are arranged coaxially to the valve needle or are displaceably mounted in the form of a sleeve on the valve needle and acted upon in the same direction as the fuel.
  • the accumulator pistons act on the valve needle in the direction of opening and are intercepted at stops fixed to the housing after a preliminary stroke, after which the valve needle alone continues to move into the fully open position.
  • a fuel pressure jump occurs at the transition to the main injection phase, because the effective pressure area suddenly decreases after the piston of the accumulator is caught by the piston surfaces acted upon by the fuel.
  • the pressure increase-inhibiting swallowing effect of the accumulator pistons is present from the start of the injection process and is therefore not available for the formation of a clearly pronounced transition between the pre-injection and the main injection.
  • a simple construction results if the storage piston is mounted in a cylinder bore of the nozzle housing so as to be displaceable coaxially with the valve needle and is pressed against the second pressure shoulder of the valve needle by its own return spring during the pre-injection phase.
  • the injection nozzle can have a nozzle body and a valve needle of a conventional design if the cylinder bore receiving the storage piston is formed in the nozzle holder and opens into the closing spring chamber, and the valve needle acts on the storage piston via a plunger, which extends into the cylinder bore and there the junction the cylinder bore in the closing spring chamber seals the piston shoulder.
  • the storage piston is designed as an annular body and is mounted in an annular chamber, which is formed between the wall of the cylinder bore in the nozzle body leading the valve needle and a valve needle section with a diameter and at which an end face is bounded by the annular shoulder serving as the second pressure shoulder at the transition to the stepped valve needle section.
  • the annular chamber receiving the accumulator piston can advantageously be formed by an intermediate disk between the nozzle body and the nozzle holder that limits the valve needle stroke.
  • the storage piston be coupled to the valve needle via a stroke-converting fuel cushion. It is thereby achieved that the overlap of the auxiliary channel in the closed position of the valve needle can be dimensioned greater than the valve needle stroke approximately in the ratio of the stroke ratio of the fuel cushion, as a result of which the tightness of the overlap is increased. Furthermore, the opening speed of the auxiliary channel is increased accordingly.
  • a simple design results if the stroke-changing fuel cushion is enclosed in a cylinder bore with a graduated diameter, the further bore section of which guides a piston which is fixedly connected to the valve needle, and the narrower bore section of which is delimited by the control piston.
  • the cylinder bore receiving the fuel cushion can advantageously serve as a storage space and the control piston itself can form a storage piston.
  • FIG. 1 shows the first exemplary embodiment, partly in longitudinal section and partly in side view
  • FIGS. 2 to 4 each show a partial longitudinal section through the second, third and fourth exemplary embodiments.
  • the injection nozzle according to FIG. 1 has a nozzle body 10, in which an only indicated valve needle 12 is slidably mounted.
  • the nozzle body 10 is only shown in a side view, because the special design of the actual nozzle area with the spray openings is of only minor importance in the present context.
  • the nozzle body 10 is clamped by a union nut 14 to a nozzle holder 16 which has a threaded connector 18 at the upper end for the connection of a leakage oil line.
  • an intermediate disk 20 is stretched, which limits the opening stroke of the valve needle 12 (total stroke hg).
  • the valve needle 12 has an annular shoulder at the transition to a needle section 22 weakened in diameter, which comes to rest on the lower end face of the intermediate disk 20 at the end of the opening stroke.
  • a pressure piece 24 is attached to the needle section 22, on which a closing spring 26 engages, which is arranged in a closing spring chamber 28 in the nozzle holder 16.
  • the closing spring 26 is supported by a spring plate 30 on the bottom of the closing spring chamber 28.
  • a cylinder bore 32 for a storage piston 34 is provided coaxially with the closing spring chamber 28, which starts from the threaded connector 18 and opens into the closing spring chamber 28.
  • a storage spring 36 acts on the accumulator piston 34 and is supported on a screw piece 38 which is screwed into an outer threaded section of the cylinder bore 32 and contains a central bore 39 for the drainage of leakage oil.
  • a plunger 40 which, with a piston-shaped extension 42, projects sealingly into the cylinder bore 32. At the transition to the neck 42 an annular shoulder is formed, which rests on the spring plate 30 at the top in the position of the plunger 40 shown.
  • the lower end 50 of the plunger 40 extends to a central shoulder surface of the pressure piece 24.
  • the accumulator piston 34 is provided on its end facing the plunger 40 with an elevation 52 which ensures a free space between the accumulator piston 34 and the piston-shaped extension 42 of the plunger 40.
  • the storage spring 36 presses the storage piston 34 against the shoulder 42 of the plunger 40.
  • the accumulator piston 34 covers a small lifting dimension h, an annular groove 54, which is connected via an auxiliary channel 56 to a connecting piece 58 for a fuel supply line. From the connecting piece 58 leads Main channel 60 into a pressure chamber in the nozzle body 10, in which, as is known, the valve needle 12 has a first pressure shoulder and which is connected to the spray openings via a valve seat monitored by the valve needle 12.
  • the injector shown works as follows: At the beginning of an injection process, the fuel supplied acts only on the first pressure shoulder of the valve needle 12 located in the nozzle body 10, as a result of which the valve needle 12 is displaced. At the same time, the valve needle 12 moves the accumulator piston 34 upward by the stroke dimension h 1 via the tappet 40, so that the latter opens the annular groove 54. From this moment on, fuel reaches the area of the cylinder bore 32 between the storage piston 34 and shoulder 42 via the auxiliary channel 56. The storage piston 34 deflects upwards and swallows a certain volume of the supplied fuel, so that the fuel pressure temporarily drops. At the same time, the fuel pressure exerts a closing force on the end face of the extension 42. As a result, the valve needle 12 is quickly returned to the valve seat. Until then, a pre-injection quantity of the fuel has emerged from the injection nozzle at a moderate pre-injection pressure.
  • the injection nozzle according to FIG. 2 has a valve needle 64, which is displaceably mounted in a nozzle body 66 and has a first pressure shoulder 70 in the area of a pressure chamber 68.
  • the nozzle body 66 and an intermediate disk 72 are clamped to a nozzle holder 74 with the aid of a screw nut (not shown).
  • a chamber 76 is provided for a closing spring, which acts on the valve needle 64 via a pressure piece 78.
  • the pressure chamber 68 is connected to a fuel connection piece on the nozzle holder 74 via a main channel 80 formed by bores and annular grooves in the individual housing parts.
  • a cylinder bore 82 is provided in the nozzle body 66, in which the valve needle 64 is guided axially with a small amount of play, shown enlarged in the drawing.
  • the intermediate disk 72 has a central through-hole 84, the diameter of which is smaller than that of the cylinder bore 82, so that an annular shoulder 86 results in the parting plane of the parts 66, 72.
  • the valve needle 64 has a reduced-diameter section 88 which extends within the cylinder bore 82 and merges into an end pin 89 which passes through the through bore 84 and carries the pressure piece 78.
  • a second pressure shoulder 90 is formed on the valve needle 64, which is directed opposite the first pressure shoulder 70 and whose area is smaller than the overall surface area of the fuel acting on the valve needle 64 in the opening direction.
  • annular chamber 92 is formed, which is delimited in the axial direction by the annular shoulder 86 fixed to the housing and the pressure shoulder 90 on the valve needle 64.
  • a storage piston 94 designed as an annular body is plugged onto the section 88, which has only a slight radial play in relation to the attachment 88 as well as the wall of the cylinder bore 82 and which is shorter by the total stroke hg of the valve needle 64 than the annular chamber 92 when the valve needle 64 is in the closed position.
  • the storage piston 94 is provided at its upper edge with three evenly distributed recesses 96 for receiving coil springs 97, which are supported on the annular shoulder 86 and press the storage piston 94 against the pressure shoulder 90 of the valve needle 64.
  • An annular groove 98 is provided in the cylinder bore 82 and is connected to the main channel 80 via an auxiliary channel 100.
  • the lower flank of the annular groove 94 is offset by the length hy of a pre-injection stroke with respect to the pressure shoulder 90 when the valve needle 64 is in the closed position.
  • the chamber 76 in the nozzle holder 74 is provided with a leakage oil connection, as is known.
  • the pressure shoulder 90 reaches the area of the annular groove 98. From this moment on, the fuel pressure acts via the auxiliary channel 100 in the gap between the annular piston 94 and the pressure shoulder 90 and leads the storage piston 94 upwards until he strikes the washer 72.
  • the storage piston 94 swallows a certain volume of the fuel and at the same time the fuel pressure exerts a closing force on the pressure shoulder 90, so that the valve needle 64 closes again. Due to the action of the fuel pressure on the pressure shoulder 90, the effective area of the fuel acting in the opening direction is reduced by the area of the pressure shoulder 90.
  • the fuel pressure must now rise to a noticeably higher value, as in the example described above, until the valve needle 64 is again lifted from the valve seat and transferred to its full open position, in which it is supported on the intermediate disk 72 via the storage piston 94.
  • the higher closing pressure remains until the valve needle has returned to its closed position.
  • the injection nozzle according to Figure 3 has one Accumulator piston 110, which is guided in a cylinder bore 112 of a valve needle 114 with little movement play.
  • a transverse bore 116 opens into the cylinder bore 112, the upper edge of which, in the closed position of the valve needle 114, is a length of a preliminary stroke hy away from the lower flank of an annular groove 118, which is connected to a main channel 122 via an auxiliary channel 120.
  • An annular shoulder 128 is formed in the cylinder bore 112, against which the storage piston 110 is pressed by a coil spring 130. This is supported on a plate 132 which is fixedly connected to the valve needle 114 and serves as a pressure piece for a closing spring 134 which acts on the valve needle 114 in the closing direction.
  • the closing spring 134 is arranged in a chamber 136, on the bottom 138 of which it is supported.
  • a stop bolt 140 is also fastened to the bottom 138 and, in cooperation with the plate 132, limits the valve needle stroke to the dimension hg.
  • a pin 142 is formed on the accumulator piston 110 and, in cooperation with the stop pin 140, limits the entire stroke of the accumulator piston 110 to the dimension h.
  • the chamber 136 is connected to a leak oil line 144.
  • the transverse bores 116 and the annular groove 118 overlap, so that the fuel pressure also builds up in the cylinder bore 112 below the accumulator piston 110 and leads the accumulator piston up to the stop on the stop pin 140.
  • the accumulator piston 110 swallows a certain volume of fuel and the fuel pressure acts on the bottom surface 146 of the cylinder bore 112, so that the valve needle 114 is returned to the valve seat. If the fuel pressure then rises to a correspondingly higher value, the valve needle is moved again in the opening direction until the plate 132 strikes the stop bolt 140 after covering the entire stroke hg. The increased closing pressure is then maintained until the valve needle is completely closed.
  • the storage piston 110 which returns to its illustrated starting position under the influence of the helical spring 130, displaces the previously absorbed fuel volume into the main channel 122 as long as the transverse bore 116 and the annular groove 118 overlap. Thereafter, the fuel volume that may still need to be displaced can reach the leakage oil line 144 via the radial play between the storage piston 110 and the wall of the cylinder bore 112, and via the chamber 136.
  • the injection nozzle according to FIG. 4 corresponds in principle to the injection nozzle according to FIG. 1.
  • the difference is that the means for opening the auxiliary channel 56, namely a storage piston 150, are coupled to the valve needle via a stroke-converting fuel cushion 152.
  • the fuel cushion 152 is enclosed in a cylinder bore 154 which has two bore sections 156, 158 of different sizes in diameter.
  • a piston 160 is tightly guided in the larger bore section 156 and is mechanically coupled to the valve needle via the tappet 40.
  • the accumulator piston 150 is tightly guided, which has an annular collar 162 which, in the closed position of the valve needle, is pressed by a return spring 164 against a shoulder 166 fixed to the housing.
  • the auxiliary channel 56 opens into an annular groove 54 which surrounds the narrower bore section 158 of the cylinder bore 154, which at the same time forms the storage space.
  • the storage piston 150 is dimensioned such that it covers the annular groove 54 by the dimension h 2 in the starting position shown.
  • the dimension h 2 can or must be dimensioned larger than the dimension h in FIG. 1 because the storage piston 150 travels a larger distance than the valve needle or the piston 160 by the diameter ratio d j / d 2 of the pistons.
  • the stroke of the accumulator piston 150 is limited by an inserted socket 168.

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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)

Description

Stand der TechnikState of the art

Die Erfindung geht aus von einer Kraftstoff-Einspritzdüse nach der Gattung des Hauptanspruchs. Bei Einspritzdüsen dieser Gattung wird um die Voreinspritzphase zu beenden, ein bestimmtes Volumen des zugeführten Kraftstoffs durch den ausweichenden Speicherkolben geschluckt, so dass die Ventilnadel vorübergehend abgebremst oder bei entsprechender Auslegung sogar auf den Ventilsitz zurückgeführt wird. Ausserdem wird die wirksame Druckfläche an der Ventilnadel um die Grösse der zweiten Druckschulter verringert, so dass zum Weiterbewegen der Ventilnadel bzw. zum Wiederöffnen des Ventils ein merklich höherer Kraftstoffdruck erforderlich ist und die Hauptmenge des Kraftstoffs bei diesem höheren Druck eingespritzt wird. Die verringerte wirksame Druckfläche wird bis zum Ende des Einspritzvorganges beibehalten, wodurch sich ein exaktes Spritzende mit hohem Schliessdruck ergibt.The invention relates to a fuel injection nozzle according to the preamble of the main claim. In the case of injection nozzles of this type, in order to end the pre-injection phase, a certain volume of the supplied fuel is swallowed by the evasive accumulator piston, so that the valve needle is braked temporarily or, if appropriately designed, is even returned to the valve seat. In addition, the effective pressure area on the valve needle is reduced by the size of the second pressure shoulder, so that a noticeably higher fuel pressure is required to move the valve needle further or to reopen the valve, and the majority of the fuel is injected at this higher pressure. The reduced effective pressure area is maintained until the end of the injection process, resulting in an exact end of injection with high closing pressure.

Bei einer bekannten Einspritzdüse der eingangs genannten Gattung (US-A 2558148) ist der Speicherkolben in einer Zylinderbohrung im Inneren der Ventilnadel verschiebbar angeordnet. Die Einmündung des Kraftstoff-Hilfskanals liegt an der einen Stirnseite der Zylinderbohrung, welche die zweite Druckschulter der Ventilnadel bildet. Der Speicherkolben hat einen im Durchmesser abgesetzten Ventilzapfenansatz, welcher von der Rückführfeder gegen die Einmündung des Hilfskanals gedrückt ist und die Einmündung überwacht. Das Aufsteuern des Hilfskanals am Ende der Voreinspritzphase erfolgt abhängig vom Kraftstoffdruck, der sich annähernd ungedrosselt in den Hilfskanal fortpflanzt und dort auf die Ventilfläche des Ventilzapfenansatzes am Speicherkolben einwirkt. Sobald dieser die Einmündung des Hilfskanals freigegeben hat, wirkt der Kraftstoffdruck in der Zylinderbohrung auf die gesamte Querschnittsfläche des Speicherkolbens ein und führt diesen rasch in seine Endstellung, in welcher er sich am Gehäuse abstützt und etwa bis zum Einspritzende verbleibt. Die druckabhängige Einleitung der Haupteinspritzphase hat den Nachteil, dass bei einer Veränderung der Öffnungsdrücke für Ventilnadel und Ausweichkolben eine Öffnung des Ausweichkolbens möglich wird, ohne dass eine Voreinspritzung stattgefunden hat.In a known injection nozzle of the type mentioned at the beginning (US-A 2558148), the storage piston is arranged displaceably in a cylinder bore in the interior of the valve needle. The confluence of the auxiliary fuel channel lies at one end of the cylinder bore, which forms the second pressure shoulder of the valve needle. The accumulator piston has a valve pin shoulder with a diameter which is pressed by the return spring against the mouth of the auxiliary channel and monitors the mouth. The opening of the auxiliary channel at the end of the pre-injection phase is dependent on the fuel pressure, which propagates almost unthrottled into the auxiliary channel and there acts on the valve surface of the valve pin extension on the accumulator piston. As soon as this has released the opening of the auxiliary channel, the fuel pressure in the cylinder bore acts on the entire cross-sectional area of the accumulator piston and quickly leads it to its end position, in which it is supported on the housing and remains approximately until the end of injection. The pressure-dependent introduction of the main injection phase has the disadvantage that if the opening pressures for the valve needle and the evasive piston change, the evasive piston can be opened without a pre-injection taking place.

Ferner sind Kraftstoff-Einspritzdüsen für Vor-und Haupteinspritzung bekannt, bei denen ein am Ende eines Voreinspritzhubs der Ventilnadel aufgesteuerter Speicherraum zwischen zwei im axialen Abstand zueinander angeordneten Führungsabschnitten der Ventilnadel in der die Ventilnadel führenden Bohrung im Düsengehäuse gebildet ist (DE-B 1 751 080). Bei dieser Anordnung ist die lediglich auf der Zusammendrückbarkeit des Kraftstoffs beruhende Schluckfähigkeit des Speicherraumes gering und ausserdem heben sich die vom Kraftstoff im Speicherraum auf die Ventilnadel ausgeübten Kräfte gegenseitig auf, so dass sich auch ein Kraftstoff-Drucksprung am Übergang zur Haupteinspritzphase nicht einstellt.Furthermore, fuel injection nozzles for pre-injection and main injection are known, in which a storage space opened at the end of a pre-injection stroke of the valve needle is formed between two guide sections of the valve needle arranged at an axial distance from one another in the bore in the nozzle housing that guides the valve needle (DE-B 1 751 080 ). With this arrangement, the swallowing capacity of the storage space, which is based solely on the compressibility of the fuel, is low and, moreover, the forces exerted by the fuel in the storage space on the valve needle cancel each other out, so that a fuel pressure jump does not occur at the transition to the main injection phase.

Ausserdem sind Kraftstoff-Einspritzdüsen bekannt, bei denen zur anfänglichen Drosselung des Kraftstoffdurchsatzes ein Kraftstoff-Speicherraum zwischen Ventilnadel und Schliessfeder angeordnet und über eine Drossel ständig mit der Kraftstoff-Zuleitung verbunden ist (DE-A 2032484). Die Schliessfeder greift an einem den Speicherraum auf der einen Stirnseite begrenzenden Kolbenglied an, das in Schliessstellung der Ventilnadel mit einem eine Mindestgrösse des Speicherraumes sicherstellenden axialen Ansatz auf einem mit der Ventilnadel starr verbundenen Kolbenglied aufliegt, das den Speicherraum auf der anderen Stirnseite begrenzt. Über die Drossel strömt bereits zu Beginn eines Einspritzhubes Kraftstoff in den Speicherraum und hebt beide Kolbenglieder voneinander ab, wonach die Schliessfederkraft über das Kraftstoffpolster im Speicherraum hydraulisch auf die Ventilnadel übertragen wird. Diese Ausführung erfordert eine sorgfältige Abstimmung der Teile und gegebenenfalls eine von der Drehzahl abhängige Steuerung der Drossel, wenn die angestrebte Wirkung im gesamten Arbeitsbereich der Maschine eintreten soll.In addition, fuel injection nozzles are known in which, for the initial throttling of the fuel throughput, a fuel storage space is arranged between the valve needle and closing spring and is continuously connected to the fuel supply line via a throttle (DE-A 2032484). The closing spring engages a piston member delimiting the storage space on one end face, which, in the closed position of the valve needle with an axial extension ensuring a minimum size of the storage space, rests on a piston member rigidly connected to the valve needle, which delimits the storage space on the other end face. At the beginning of an injection stroke, fuel flows into the storage space via the throttle and lifts both piston members apart, after which the closing spring force is transferred hydraulically to the valve needle via the fuel cushion in the storage space. This version requires careful coordination of the parts and, if necessary, speed-dependent control of the throttle if the desired effect is to occur in the entire working area of the machine.

Ferner sind Kraftstoff-Einspritzdüsen mit vom Beginn der Einspritzung an vom Kraftstoff beaufschlagten Speicherkolben bekannt (DE-A 2555019), die koaxial zur Ventilnadel angeordnet oder in Form einer Hülse verschiebbar auf der Ventilnadel gelagert und gleichsinnig wie diese vom Kraftstoff beaufschlagt sind. Die Speicherkolben wirken im Öffnungssinn auf die Ventilnadel ein und werden nach einem Vorhub an gehäusefesten Anschlägen abgefangen, wonach sich die Ventilnadel allein weiter in die volle Offenstellung bewegt. Bei dieser Anordnung tritt am Übergang zur Haupteinspritzphase zwar ein Kraftstoff-Drucksprung auf, weil sich die wirksame Druckfläche nach dem Abfangen der Speicherkolben schlagartig um die vom Kraftstoff beaufschlagten Kolbenflächen verkleinert. Jedoch ist auch bei dieser Ausführung die druckanstiegshemmende Schluckwirkung der Speicherkolben schon vom Beginn des Einspritzvorgangs an vorhanden und somit für die Bildung eines deutlich ausgeprägten Übergangs zwischen Vor- und Haupteinspritzung nicht verfügbar.Furthermore, fuel injection nozzles with storage pistons acted upon by the fuel from the start of the injection (DE-A 2555019) are known, which are arranged coaxially to the valve needle or are displaceably mounted in the form of a sleeve on the valve needle and acted upon in the same direction as the fuel. The accumulator pistons act on the valve needle in the direction of opening and are intercepted at stops fixed to the housing after a preliminary stroke, after which the valve needle alone continues to move into the fully open position. In this arrangement, a fuel pressure jump occurs at the transition to the main injection phase, because the effective pressure area suddenly decreases after the piston of the accumulator is caught by the piston surfaces acted upon by the fuel. However, even in this version, the pressure increase-inhibiting swallowing effect of the accumulator pistons is present from the start of the injection process and is therefore not available for the formation of a clearly pronounced transition between the pre-injection and the main injection.

Vorteile der ErfindungAdvantages of the invention

Die erfindungsgemässen Anordnungen mit den kennzeichnenden Merkmalen der Patentansprüche 1 und 9 haben demgegenüber den Vorteil, dass die Haupteinspritzphase in Abhängigkeit vom zurückgelegten Hub der Ventilnadel eingeleitet wird und dass zur Bildung eines ausgeprägten Übergangs zwischen Vor- und Haupteinspritzphase gleichzeitig sowohl ein gegen Federkraft erweiterbarer Speicher zugeschaltet als auch die im Öffnungssinn wirksame Druckfläche an der Ventilnadel reduziert wird.The arrangements according to the invention with the characterizing features of claims 1 and 9 have the advantage, in contrast, that the main injection phase is initiated as a function of the stroke of the valve needle and that, in order to form a pronounced transition between the pre-injection and main injection phases, an accumulator which can be expanded against spring force is simultaneously activated as well the pressure area on the valve needle that is effective in the opening direction is also reduced.

Durch die in den Unteransprüchen aufgeführten Massnahmen sind vorteilhafte Weiterbildungen der im Patentanspruch 1 angegebenen Anordnung möglich.The measures listed in the subclaims allow advantageous developments of the arrangement specified in claim 1.

Ein einfacher Aufbau ergibt sich, wenn der Speicherkolben in einer Zylinderbohrung des Düsengehäuses gleichachsig zur Ventilnadel verschiebbar gelagert und während der Voreinspritzphase von seiner eigenen Rückführfeder gegen die zweite Druckschulter der Ventilnadel gedrückt ist.A simple construction results if the storage piston is mounted in a cylinder bore of the nozzle housing so as to be displaceable coaxially with the valve needle and is pressed against the second pressure shoulder of the valve needle by its own return spring during the pre-injection phase.

Die Einspritzdüse kann einen Düsenkörper und eine Ventilnadel herkömmlicher Bauart haben, wenn die den Speicherkolben aufnehmende Zylinderbohrung im Düsenhalter gebildet ist und in die Schliessfederkammer mündet, und die Ventilnadel über einen Stössel auf den Speicherkolben einwirkt, der sich in die Zylinderbohrung hineinerstreckt und dort einen die Einmündung der Zylinderbohrung in die Schliessfederkammer dichtenden Kolbenabsatz trägt.The injection nozzle can have a nozzle body and a valve needle of a conventional design if the cylinder bore receiving the storage piston is formed in the nozzle holder and opens into the closing spring chamber, and the valve needle acts on the storage piston via a plunger, which extends into the cylinder bore and there the junction the cylinder bore in the closing spring chamber seals the piston shoulder.

Eine gegenüber herkömmlichen Bauarten nicht oder nur geringfügig verlängerte Ausführung einer Einspritzdüse ergibt sich, wenn der Speicherkolben als Ringkörper ausgebildet und in einer Ringkammer gelagert ist, welche zwischen der Wand der die Ventilnadel führenden Zylinderbohrung im Düsenkörper und einem im Durchmesser abgesetzten Ventilnadelabschnitt gebildet ist und an der einen Stirnseite von der als zweite Druckschulter dienenden Ringschulter am Übergang zum abgesetzten Ventilnadelabschnitt begrenzt ist. An der anderen Stirnseite kann die den Speicherkolben aufnehmende Ringkammer vorteilhaft durch eine den Ventilnadelhub begrenzende Zwischenscheibe zwischen Düsenkörper und Düsenhalter gebildet sein.A version of an injection nozzle that is not or only slightly extended compared to conventional designs is obtained if the storage piston is designed as an annular body and is mounted in an annular chamber, which is formed between the wall of the cylinder bore in the nozzle body leading the valve needle and a valve needle section with a diameter and at which an end face is bounded by the annular shoulder serving as the second pressure shoulder at the transition to the stepped valve needle section. On the other end face, the annular chamber receiving the accumulator piston can advantageously be formed by an intermediate disk between the nozzle body and the nozzle holder that limits the valve needle stroke.

In Weiterbildung der Erfindung wird vorgeschlagen, dass der Speicherkolben über ein hubwandelndes Kraftstoffpolster mit der Ventilnadel gekoppelt ist. Dadurch ist erreicht, dass die Überdeckung des Hilfskanals in Schliessstellung der Ventilnadel etwa im Verhältnis der Hubübersetzung des Kraftstoffpolsters grösser als der Ventilnadelhub bemessen werden kann, wodurch die Dichtheit der Überdeckung erhöht wird. Ferner wird auch die Aufsteuerungsgeschwindigkeit des Hilfskanals entsprechend erhöht.In a development of the invention, it is proposed that the storage piston be coupled to the valve needle via a stroke-converting fuel cushion. It is thereby achieved that the overlap of the auxiliary channel in the closed position of the valve needle can be dimensioned greater than the valve needle stroke approximately in the ratio of the stroke ratio of the fuel cushion, as a result of which the tightness of the overlap is increased. Furthermore, the opening speed of the auxiliary channel is increased accordingly.

Eine einfache Ausführung ergibt sich, wenn das hubwandelnde Kraftstoffpolster in einer im Durchmesser abgestuften Zylinderbohrung eingeschlossen ist, deren weiterer Bohrungsabschnitt einen mit der Ventilnadel fest verbundenen Kolben führt und deren engerer Bohrungsabschnitt vom Steuerkolben begrenzt ist. Dabei kann vorteilhaft die das Kraftstoffpolster aufnehmende Zylinderbohrung als Speicherraum dienen und der Steuerkolben selbst einen Speicherkolben bilden.A simple design results if the stroke-changing fuel cushion is enclosed in a cylinder bore with a graduated diameter, the further bore section of which guides a piston which is fixedly connected to the valve needle, and the narrower bore section of which is delimited by the control piston. The cylinder bore receiving the fuel cushion can advantageously serve as a storage space and the control piston itself can form a storage piston.

Zeichnungdrawing

Vier Ausführungsbeispiele der Erfindung sind in der Zeichnung dargestellt und in der nachfolgenden Beschreibung näher erläutert. Es zeigen Figur 1 das erste Ausführungsbeispiel, teilweise im Längsschnitt und teilweise in Seitenansicht, und die Figuren 2 bis 4 je einen Teil-Längsschnitt durch das zweite, das dritte und das vierte Ausführungsbeispiel.Four embodiments of the invention are shown in the drawing and explained in more detail in the following description. 1 shows the first exemplary embodiment, partly in longitudinal section and partly in side view, and FIGS. 2 to 4 each show a partial longitudinal section through the second, third and fourth exemplary embodiments.

Beschreibung der AusführungsbeispieleDescription of the embodiments

Die Einspritzdüse nach Figur 1 hat einen Düsenkörper 10, in welchem eine nur angedeutete Ventilnadel 12 verschiebbar gelagert ist. Der Düsenkörper 10 ist nur in Seitenansicht dargestellt, weil die spezielle Ausbildung des eigentlichen Düsenbereichs mit den Spritzöffnungen im vorliegenden Zusammenhang nur von untergeordneter Bedeutung ist. Der Düsenkörper 10 ist durch eine Überwurfmutter 14 an einem Düsenhalter 16 festgespannt, der am oberen Stirnende einen Gewindestutzen 18 für den Anschluss einer Leckölleitung hat.The injection nozzle according to FIG. 1 has a nozzle body 10, in which an only indicated valve needle 12 is slidably mounted. The nozzle body 10 is only shown in a side view, because the special design of the actual nozzle area with the spray openings is of only minor importance in the present context. The nozzle body 10 is clamped by a union nut 14 to a nozzle holder 16 which has a threaded connector 18 at the upper end for the connection of a leakage oil line.

Zwischen dem Düsenkörper 10 und dem Düsenhalter 16 ist eine Zwischenscheibe 20 gespannt, welche den Öffnungshub der Ventilnadel 12 begrenzt (Gesamthub hg). Die Ventilnadel 12 hat zu diesem Zweck am Übergang zu einem im Durchmesser geschwächten Nadelabschnitt 22 eine Ringschulter, die am Ende des Öffnungshubes zur Anlage an die untere Stirnseite der Zwischenscheibe 20 kommt. Auf den Nadelabschnitt 22 ist ein Druckstück 24 aufgesteckt, an welchem eine Schliessfeder 26 angreift, die in einer Schliessfederkammer 28 im Düsenhalter 16 angeordnet ist. Die Schliessfeder 26 stützt sich über einen Federteller 30 am Boden der Schliessfederkammer 28 ab.Between the nozzle body 10 and the nozzle holder 16, an intermediate disk 20 is stretched, which limits the opening stroke of the valve needle 12 (total stroke hg). For this purpose, the valve needle 12 has an annular shoulder at the transition to a needle section 22 weakened in diameter, which comes to rest on the lower end face of the intermediate disk 20 at the end of the opening stroke. A pressure piece 24 is attached to the needle section 22, on which a closing spring 26 engages, which is arranged in a closing spring chamber 28 in the nozzle holder 16. The closing spring 26 is supported by a spring plate 30 on the bottom of the closing spring chamber 28.

Im Düsenhalter 16 ist koaxial zur Schliessfederkammer 28 eine Zylinderbohrung 32 für einen Speicherkolben 34 vorgesehen, welche vom Gewindestutzen 18 ausgeht und in die Schliessfederkammer 28 mündet. Auf den Speicherkolben 34 wirkt eine Speicherfeder 36 ein, die sich an einem Schraubstück 38 abstützt, welches in einen äusseren Gewindeabschnitt der Zylinderbohrung 32 eingeschraubt ist und eine zentrale Bohrung 39 zur Leckölabführung enthält. Innerhalb der Schliessfeder 26 ist ein Stössel 40 angeordnet, der mit einem kolbenförmigen Ansatz 42 dichtend in die Zylinderbohrung 32 hineinragt. Am Übergang zum Ansatz 42 ist eine Ringschulter gebildet, die in der dargestellten Lage des Stössels 40 auf dem Federteller 30 oben aufliegt. Dabei reicht das untere Ende 50 des Stössels 40 bis an eine zentrale Schulterfläche des Druckstückes 24 heran.In the nozzle holder 16, a cylinder bore 32 for a storage piston 34 is provided coaxially with the closing spring chamber 28, which starts from the threaded connector 18 and opens into the closing spring chamber 28. A storage spring 36 acts on the accumulator piston 34 and is supported on a screw piece 38 which is screwed into an outer threaded section of the cylinder bore 32 and contains a central bore 39 for the drainage of leakage oil. Arranged within the closing spring 26 is a plunger 40 which, with a piston-shaped extension 42, projects sealingly into the cylinder bore 32. At the transition to the neck 42 an annular shoulder is formed, which rests on the spring plate 30 at the top in the position of the plunger 40 shown. The lower end 50 of the plunger 40 extends to a central shoulder surface of the pressure piece 24.

Der Speicherkolben 34 ist an seiner dem Stössel 40 zugekehrten Stirnseite mit einer Erhebung 52 versehen, welche einen freien Zwischenraum zwischen dem Speicherkolben 34 und dem kolbenförmigen Ansatz 42 des Stössels 40 sicherstellt. In der dargestellten Schliessstellung der Ventilnadel 12 drückt die Speicherfeder 36 den Speicherkolben 34 an den Ansatz 42 des Stössels 40 an. In dieser Stellung überdeckt der Speicherkolben 34 um ein geringes Hubmass h, eine Ringnut 54, welche über einen Hilfskanal 56 mit einem Anschlussstutzen 58 für eine Kraftstoffzuleitung verbunden ist. Vom Anschlussstutzen 58 führt ein Hauptkanal 60 in einen Druckraum im Düsenkörper 10, in welchem die Ventilnadel 12 wie bekannt eine erste Druckschulter aufweist und welcher über einen von der Ventilnadel 12 überwachten Ventilsitz mit den Spritzöffnungen verbunden ist.The accumulator piston 34 is provided on its end facing the plunger 40 with an elevation 52 which ensures a free space between the accumulator piston 34 and the piston-shaped extension 42 of the plunger 40. In the illustrated closed position of the valve needle 12, the storage spring 36 presses the storage piston 34 against the shoulder 42 of the plunger 40. In this position, the accumulator piston 34 covers a small lifting dimension h, an annular groove 54, which is connected via an auxiliary channel 56 to a connecting piece 58 for a fuel supply line. From the connecting piece 58 leads Main channel 60 into a pressure chamber in the nozzle body 10, in which, as is known, the valve needle 12 has a first pressure shoulder and which is connected to the spray openings via a valve seat monitored by the valve needle 12.

Die dargestellte Einspritzdüse arbeitet wie folgt: Zum Beginn eines Einspritzvorganges wirkt der zugeführte Kraftstoff nur auf die im Düsenkörper 10 liegende erste Druckschulter der Ventilnadel 12 ein, wodurch die Ventilnadel 12 verschoben wird. Gleichzeitig verschiebt die Ventilnadel 12 über den Stössel 40 den Speicherkolben 34 um das Hubmass h1 nach oben, so dass dieser die Ringnut 54 aufsteuert. Von diesem Augenblick an gelangt Kraftstoff über den Hilfskanal 56 in den zwischen Speicherkolben 34 und Ansatz 42 liegenden Bereich der Zylinderbohrung 32. Der Speicherkolben 34 weicht nach oben aus und schluckt dabei ein bestimmtes Volumen des zugeführten Kraftstoffs, so dass der Kraftstoffdruck vorübergehend sinkt. Gleichzeitig übt der Kraftstoffdruck eine Schliesskraft auf die Stirnfläche des Ansatzes 42 aus. Dadurch wird die Ventilnadel 12 rasch auf den Ventilsitz zurückgeführt. Bis dahin ist eine Voreinspritzmenge des Kraftstoffs bei einem mässigen Voreinspritzdruck aus der Einspritzdüse ausgetreten.The injector shown works as follows: At the beginning of an injection process, the fuel supplied acts only on the first pressure shoulder of the valve needle 12 located in the nozzle body 10, as a result of which the valve needle 12 is displaced. At the same time, the valve needle 12 moves the accumulator piston 34 upward by the stroke dimension h 1 via the tappet 40, so that the latter opens the annular groove 54. From this moment on, fuel reaches the area of the cylinder bore 32 between the storage piston 34 and shoulder 42 via the auxiliary channel 56. The storage piston 34 deflects upwards and swallows a certain volume of the supplied fuel, so that the fuel pressure temporarily drops. At the same time, the fuel pressure exerts a closing force on the end face of the extension 42. As a result, the valve needle 12 is quickly returned to the valve seat. Until then, a pre-injection quantity of the fuel has emerged from the injection nozzle at a moderate pre-injection pressure.

Durch die Einwirkung des Kraftstoffdrucks auf die Stirnfläche des kolbenförmigen Ansatzes 42 wird im Ergebnis die in Öffnungsrichtung wirksame Angriffsfläche des Kraftstoffs an der Ventilnadel 12 um die Querschnittsfläche des Ansatzes 42 verringert, so dass die Ventilnadel 12 vom Ventilsitz erst wieder abgehoben wird, wenn der Kraftstoffdruck auf einen merklichen höheren Wert angestiegen ist. Danach wird in einer zweiten Phase des Einspritzvorganges die Hauptmenge des Kraftstoffs bei dem höheren Druck eingespritzt. Der höhere Öffnungs- bzw. Schliessdruck bleibt jetzt unabhängig vom Nadelhub bis zum vollständigen Ende des Einspritzvorganges erhalten, so dass sich ein scharfes Spritzende mit schnellem Nadelschliessen ergibt.As a result of the action of the fuel pressure on the end face of the piston-shaped attachment 42, the area of action of the fuel on the valve needle 12 that is effective in the opening direction is reduced by the cross-sectional area of the attachment 42, so that the valve needle 12 is only lifted off the valve seat again when the fuel pressure increases has increased significantly. The main amount of fuel is then injected at the higher pressure in a second phase of the injection process. The higher opening or closing pressure is now maintained regardless of the needle stroke until the end of the injection process, so that there is a sharp spray end with quick needle closing.

Die Einspritzdüse nach Figur 2 hat eine Ventilnadel 64, die in einem Düsenkörper 66 verschiebbar gelagert ist und im Bereich eines Druckraums 68 eine erste Druckschulter 70 hat. Der Düsenkörper 66 und eine Zwischenscheibe 72 sind mit Hilfe einer nicht dargestellten Schraubmutter an einem Düsenhalter 74 festgespannt. In diesem ist wie üblich eine Kammer 76 für eine Schliessfeder vorgesehen, die über ein Druckstück 78 auf die Ventilnadel 64 einwirkt. Der Druckraum 68 ist über einen durch Bohrungen und Ringnuten in den einzelnen Gehäuseteilen gebildeten Hauptkanal 80 mit einem Kraftstoff-Anschlussstutzen am Düsenhalter 74 verbunden.The injection nozzle according to FIG. 2 has a valve needle 64, which is displaceably mounted in a nozzle body 66 and has a first pressure shoulder 70 in the area of a pressure chamber 68. The nozzle body 66 and an intermediate disk 72 are clamped to a nozzle holder 74 with the aid of a screw nut (not shown). In this, as usual, a chamber 76 is provided for a closing spring, which acts on the valve needle 64 via a pressure piece 78. The pressure chamber 68 is connected to a fuel connection piece on the nozzle holder 74 via a main channel 80 formed by bores and annular grooves in the individual housing parts.

Im Düsenkörper 66 ist eine Zylinderbohrung 82 vorgesehen, in welcher die Ventilnadel 64 mit geringem, in der Zeichnung vergrössert dargestellten Bewegungsspiel axial geführt ist. Die Zwischenscheibe 72 hat eine zentrale Durchgangsbohrung 84, deren Durchmesser kleiner als jener der Zylinderbohrung 82 ist, so dass sich in der Trennebene der Teile 66, 72 eine Ringschulter 86 ergibt. Die Ventilnadel 64 hat einen im Durchmesser verkleinerten Abschnitt 88, der sich innerhalb der Zylinderbohrung 82 erstreckt und in einen Endzapfen 89 übergeht, der die Durchgangsbohrung 84 durchsetzt und das Druckstück 78 trägt. Am Übergang zum Abschnitt 88 ist an der Ventilnadel 64 eine zweite Druckschulter 90 gebildet, welche der ersten Druckschulter 70 entgegengerichtet ist und deren Fläche kleiner ist als die in Öffnungsrichtung insgesamt wirkende Angriffsfläche des Kraftstoffs an der Ventilnadel 64.A cylinder bore 82 is provided in the nozzle body 66, in which the valve needle 64 is guided axially with a small amount of play, shown enlarged in the drawing. The intermediate disk 72 has a central through-hole 84, the diameter of which is smaller than that of the cylinder bore 82, so that an annular shoulder 86 results in the parting plane of the parts 66, 72. The valve needle 64 has a reduced-diameter section 88 which extends within the cylinder bore 82 and merges into an end pin 89 which passes through the through bore 84 and carries the pressure piece 78. At the transition to section 88, a second pressure shoulder 90 is formed on the valve needle 64, which is directed opposite the first pressure shoulder 70 and whose area is smaller than the overall surface area of the fuel acting on the valve needle 64 in the opening direction.

Zwischen dem Abschnitt 88 der Ventilnadel 64 und der Wand der Zylinderbohrung 82 ist eine Ringkammer 92 gebildet, die in axialer Richtung von der gehäusefesten Ringschulter 86 und der Druckschulter 90 an der Ventilnadel 64 begrenzt ist. Auf den Abschnitt 88 ist ein als Ringkörper ausgebildeter Speicherkolben 94 aufgesteckt, der sowohl gegenüber dem Ansatz 88 als auch gegenüber der Wand der Zylinderbohrung 82 nur ein geringes radiales Bewegungsspiel hat und der um den Gesamthub hg der Ventilnadel 64 kürzer ist als die Ringkammer 92, wenn sich die Ventilnadel 64 in Schliessstellung befindet. Der Speicherkolben 94 ist an seinem oberen Rand mit drei gleichmässig über den Umfang verteilten Ausnehmungen 96 zur Aufnahme von Schraubenfedern 97 versehen, die sich an der Ringschulter 86 abstützen und den Speicherkolben 94 gegen die Druckschulter 90 der Ventilnadel 64 drücken.Between the section 88 of the valve needle 64 and the wall of the cylinder bore 82, an annular chamber 92 is formed, which is delimited in the axial direction by the annular shoulder 86 fixed to the housing and the pressure shoulder 90 on the valve needle 64. A storage piston 94 designed as an annular body is plugged onto the section 88, which has only a slight radial play in relation to the attachment 88 as well as the wall of the cylinder bore 82 and which is shorter by the total stroke hg of the valve needle 64 than the annular chamber 92 when the valve needle 64 is in the closed position. The storage piston 94 is provided at its upper edge with three evenly distributed recesses 96 for receiving coil springs 97, which are supported on the annular shoulder 86 and press the storage piston 94 against the pressure shoulder 90 of the valve needle 64.

In der Zylinderbohrung 82 ist eine Ringnut 98 vorgesehen, die über einen Hilfskanal 100 an den Hauptkanal 80 angeschlossen ist. Die untere Flanke der Ringnut 94 ist um die Länge hy eines Voreinspritzhubes gegenüber der Druckschulter 90 versetzt, wenn sich die Ventilnadel 64 in Schliessstellung befindet. Die Kammer 76 im Düsenhalter 74 ist wie bekannt mit einem Leckölanschluss versehen.An annular groove 98 is provided in the cylinder bore 82 and is connected to the main channel 80 via an auxiliary channel 100. The lower flank of the annular groove 94 is offset by the length hy of a pre-injection stroke with respect to the pressure shoulder 90 when the valve needle 64 is in the closed position. The chamber 76 in the nozzle holder 74 is provided with a leakage oil connection, as is known.

Wenn die Ventilnadel 64 den Vorhub hy zurückgelegt hat, gelangt die Druckschulter 90 in den Bereich der Ringnut 98. Von diesem Augenblick an wirkt der Kraftstoffdruck über den Hilfskanal 100 in den Spalt zwischen Ringkolben 94 und Druckschulter 90 und führt den Speicherkolben 94 nach oben, bis er an der Zwischenscheibe 72 anschlägt. Der Speicherkolben 94 schluckt dabei ein gewisses Volumen des Kraftstoffs und gleichzeitig übt der Kraftstoffdruck eine Schliesskraft auf die Druckschulter 90 aus, so dass die Ventilnadel 64 wieder schliesst. Durch die Einwirkung des Kraftstoffdrucks auf die Druckschulter 90 wird die in Öffnungsrichtung wirksame Angriffsfläche des Kraftstoffs um die Fläche der Druckschulter 90 verkleinert. Der Kraftstoffdruck muss jetzt wie im vorbeschriebenen Beispiel auf einen merklich höheren Wert ansteigen, bis die Ventilnadel 64 wieder vom Ventilsitz abgehoben und in ihre volle Offenstellung überführt wird, in der sie sich über den Speicherkolben 94 an der Zwischenscheibe 72 abstützt. Der höhere Schliessdruck bleibt erhalten, bis die Ventilnadel in ihre Schliessstellung zurückgekehrt ist.When the valve needle 64 has completed the preliminary stroke hy, the pressure shoulder 90 reaches the area of the annular groove 98. From this moment on, the fuel pressure acts via the auxiliary channel 100 in the gap between the annular piston 94 and the pressure shoulder 90 and leads the storage piston 94 upwards until he strikes the washer 72. The storage piston 94 swallows a certain volume of the fuel and at the same time the fuel pressure exerts a closing force on the pressure shoulder 90, so that the valve needle 64 closes again. Due to the action of the fuel pressure on the pressure shoulder 90, the effective area of the fuel acting in the opening direction is reduced by the area of the pressure shoulder 90. The fuel pressure must now rise to a noticeably higher value, as in the example described above, until the valve needle 64 is again lifted from the valve seat and transferred to its full open position, in which it is supported on the intermediate disk 72 via the storage piston 94. The higher closing pressure remains until the valve needle has returned to its closed position.

Die Einspritzdüse nach Figur 3 hat einen Speicherkolben 110, der in einer Zylinderbohrung 112 einer Ventilnadel 114 mit geringem Bewegungsspiel geführt ist. In die Zylinderbohrung 112 mündet eine Querbohrung 116 ein, deren obere Kante in der Schliessstellung der Ventilnadel 114 um die Länge eines Vorhubes hy von der unteren Flanke einer Ringnut 118 entfernt ist, welche über einen Hilfskanal 120 mit einem Hauptkanal 122 verbunden ist. Dieser führt in einen Druckraum 124, innerhalb welchem die Ventilnadel 114 eine erste Druckschulter 126 hat.The injection nozzle according to Figure 3 has one Accumulator piston 110, which is guided in a cylinder bore 112 of a valve needle 114 with little movement play. A transverse bore 116 opens into the cylinder bore 112, the upper edge of which, in the closed position of the valve needle 114, is a length of a preliminary stroke hy away from the lower flank of an annular groove 118, which is connected to a main channel 122 via an auxiliary channel 120. This leads into a pressure chamber 124, within which the valve needle 114 has a first pressure shoulder 126.

In der Zylinderbohrung 112 ist eine Ringschulter 128 gebildet, gegen welche der Speicherkolben 110 durch eine Schraubenfeder 130 gedrückt ist. Diese stützt sich an einer Platte 132 ab, welche mit der Ventilnadel 114 fest verbunden ist und als Druckstück für eine Schliessfeder 134 dient, welche im Schliesssinn auf die Ventilnadel 114 einwirkt. Die Schliessfeder 134 ist in einer Kammer 136 angeordnet, an deren Boden 138 sie sich abstützt. Am Boden 138 ist ferner ein Anschlagbolzen 140 befestigt, welcher im Zusammenwirken mit der Platte 132 den Ventilnadelhub auf das Mass hg begrenzt. Am Speicherkolben 110 ist ein Zapfen 142 angeformt, welcher im Zusammenwirken mit dem Anschlagbolzen 140 den gesamten Hub des Speicherkolbens 110 auf das Mass h., begrenzt. Die Kammer 136 ist mit einer Leckölleitung 144 verbunden.An annular shoulder 128 is formed in the cylinder bore 112, against which the storage piston 110 is pressed by a coil spring 130. This is supported on a plate 132 which is fixedly connected to the valve needle 114 and serves as a pressure piece for a closing spring 134 which acts on the valve needle 114 in the closing direction. The closing spring 134 is arranged in a chamber 136, on the bottom 138 of which it is supported. A stop bolt 140 is also fastened to the bottom 138 and, in cooperation with the plate 132, limits the valve needle stroke to the dimension hg. A pin 142 is formed on the accumulator piston 110 and, in cooperation with the stop pin 140, limits the entire stroke of the accumulator piston 110 to the dimension h. The chamber 136 is connected to a leak oil line 144.

Wenn die Ventilnadel 114 den Vorhub hy zurückgelegt hat, kommen die Querbohrungen 116 und die Ringnut 118 zur Überdeckung, so dass sich der Kraftstoffdruck auch in der Zylinderbohrung 112 unterhalb des Speicherkolbens 110 aufbaut und den Speicherkolben nach oben bis zum Anschlag an dem Anschlagbolzen 140 führt. Dabei schluckt der Speicherkolben 110 ein gewisses Kraftstoffvolumen und der Kraftstoffdruck wirkt auf die Bodenfläche 146 der Zylinderbohrung 112 ein, so dass die Ventilnadel 114 wieder auf den Ventilsitz zurückgeführt wird. Wenn der Kraftstoffdruck danach auf einen entsprechend höheren Wert angestiegen ist, wird die Ventilnadel wieder in Öffnungsrichtung verschoben, bis die Platte 132 nach Zurücklegung des gesamten Hubes hg an den Anschlagbolzen 140 anschlägt. Der erhöhte Schliessdruck bleibt danach bis zum völligen Schliessen der Ventilnadel erhalten.When the valve needle 114 has completed the preliminary stroke hy, the transverse bores 116 and the annular groove 118 overlap, so that the fuel pressure also builds up in the cylinder bore 112 below the accumulator piston 110 and leads the accumulator piston up to the stop on the stop pin 140. The accumulator piston 110 swallows a certain volume of fuel and the fuel pressure acts on the bottom surface 146 of the cylinder bore 112, so that the valve needle 114 is returned to the valve seat. If the fuel pressure then rises to a correspondingly higher value, the valve needle is moved again in the opening direction until the plate 132 strikes the stop bolt 140 after covering the entire stroke hg. The increased closing pressure is then maintained until the valve needle is completely closed.

Der unter dem Einfluss der Schraubenfeder 130 in seine dargestellte Ausgangslage zurückkehrende Speicherkolben 110 verdrängt das vorher aufgenommene Kraftstoffvolumen in den Hauptkanal 122, solange sich die Querbohrung 116 und die Ringnut 118 überdecken. Danach kann das gegebenenfalls noch zu verdrängende Kraftstoffvolumen über das Radialspiel zwischen Speicherkolben 110 und der Wand der Zylinderbohrung 112, sowie über die Kammer 136 und von dort in die Leckölleitung 144 gelangen.The storage piston 110, which returns to its illustrated starting position under the influence of the helical spring 130, displaces the previously absorbed fuel volume into the main channel 122 as long as the transverse bore 116 and the annular groove 118 overlap. Thereafter, the fuel volume that may still need to be displaced can reach the leakage oil line 144 via the radial play between the storage piston 110 and the wall of the cylinder bore 112, and via the chamber 136.

Die Einspritzdüse nach Figur 4 stimmt im Prinzip mit der Einspritzdüse nach Figur 1 überein. Unterschiedlich ist, dass die Mittel zum Aufsteuern des Hilfskanals 56, nämlich ein Speicherkolben 150, über ein hubwandelndes Kraftstoffpolster 152 mit der Ventilnadel gekoppelt sind. Das Kraftstoffpolster 152 ist in einer Zylinderbohrung 154 eingeschlossen, die zwei im Durchmesser unterschiedlich grosse Bohrungsabschnitte 156,158 hat. Im grösseren Bohrungsabschnitt 156 ist ein Kolben 160 dicht geführt, der mit der Ventilnadel über den Stössel 40 mechanisch gekoppelt ist. Im engeren Bohrungsabschnitt 158 der Zylinderbohrung 154 ist der Speicherkolben 150 dicht geführt, welcher einen Ringbund 162 hat, der in der Schliessstellung der Ventilnadel von einer Rückführfeder 164 gegen eine gehäusefeste Schulter 166 gedrückt ist.The injection nozzle according to FIG. 4 corresponds in principle to the injection nozzle according to FIG. 1. The difference is that the means for opening the auxiliary channel 56, namely a storage piston 150, are coupled to the valve needle via a stroke-converting fuel cushion 152. The fuel cushion 152 is enclosed in a cylinder bore 154 which has two bore sections 156, 158 of different sizes in diameter. A piston 160 is tightly guided in the larger bore section 156 and is mechanically coupled to the valve needle via the tappet 40. In the narrower bore section 158 of the cylinder bore 154, the accumulator piston 150 is tightly guided, which has an annular collar 162 which, in the closed position of the valve needle, is pressed by a return spring 164 against a shoulder 166 fixed to the housing.

Der Hilfskanal 56 mündet wie beim Ausführungsbeispiel nach Figur 1 in eine Ringnut 54 ein, die den engeren Bohrungsabschnitt 158 der Zylinderbohrung 154 umgibt, welche gleichzeitig den Speicherraum bildet. Der Speicherkolben 150 ist so bemessen, dass er in der dargestellten Ausgangslage die Ringnut 54 um das Mass h2 überdeckt. Das Mass h2 kann bzw. muss grösser als das Mass h, in Figur 1 bemessen werden, weil der Speicherkolben 150 einen um das Durchmesserverhältnis dj/d2 der Kolben grösseren Weg als die Ventilnadel bzw. der Kolben 160 zurücklegt. Dadurch wird die Dichtheit der Überdeckung des Hilfskanals 56 bzw. der Ringnut 54 verbessert. Im übrigen laufen die Vorgänge wie bei der Ausführung nach Figur 1 ab. Der Hub des Speicherkolbens 150 wird durch eine eingesetzte Buchse 168 begrenzt.As in the exemplary embodiment according to FIG. 1, the auxiliary channel 56 opens into an annular groove 54 which surrounds the narrower bore section 158 of the cylinder bore 154, which at the same time forms the storage space. The storage piston 150 is dimensioned such that it covers the annular groove 54 by the dimension h 2 in the starting position shown. The dimension h 2 can or must be dimensioned larger than the dimension h in FIG. 1 because the storage piston 150 travels a larger distance than the valve needle or the piston 160 by the diameter ratio d j / d 2 of the pistons. As a result, the tightness of the overlap of the auxiliary channel 56 or the annular groove 54 is improved. Otherwise, the processes take place as in the embodiment according to FIG. 1. The stroke of the accumulator piston 150 is limited by an inserted socket 168.

Claims (9)

1. Fuel injection nozzle for internal-combustion engines, having a valve needle (12) which is loaded by a closing spring (26) and possesses a first pressure shoulder which is engaged permanently in the opening sense by the fuel pressure, and also having means to open an auxiliary fuel duct (56, 100) at the end of a pre-injection phase, through which the fuel passes into an accumulator chamber (32, 82, 158) which is delimited by a second pressure shoulder (42, 90,160) connected to the valve needle (12) and by an accumulator piston (34, 94, 150) constructed as a separate component and subject to the influence of a particular return spring (36, 97, 164) and executes a movement derived from the valve needle movement in the pre-injection phase and there after executes a yielding movement independent of the valve needle movement under the influence of the fuel pressure in the accumulator chamber (32, 82, 158) whereby the accumulator chamber (32, 82, 158) is enlarged by a prescribed value, characterized by the following features:
a) the auxiliary fuel duct (56, 100) leads from the side into a cylindrical bore (32, 82, 158) forming the accumulator chamber in a nozzle housing comprising nozzle element (10, 66) and nozzle holder (16, 74) at a point which is located outside the second pressure shoulder (42, 90, 160) when the valve needle (12) is closed and in which the accumulator piston (34, 94, 150) is slidably guided,
b) the accumulator piston (34, 94,150) masks, in its initial position corresponding to the closed position of the valve needle (12) and through a first partial stroke, the orifice of the auxiliary fuel duct (56, 100) into the cylindrical bore (32, 82, 158) forming the accumulator chamber and opens this orifice as a function of the stroke at the end of the first partial stroke.
2. Injection nozzle according to Claim 1, characterized in that the accumulator piston (34,94) is mounted slidably coaxially to the valve needle in a cylindrical bore (32, 82) of the nozzle housing and is urged by its particular return spring (36, 97) against the second pressure shoulder (42,90) of the valve needle during the first partial stroke.
3. Injection nozzle according to Claim 1, characterized in that the cylindrical bore (32) accommodating the accumulator piston (34) is formed in the nozzle holder (16) and leads into a closing spring chamber (28), and that the valve needle (12) influences through a push rod (40) the accumulator piston (34) which extends into the cylindrical bore (32) and carries there a piston at- tachement (42) sealing the orifice of the cylindrical bore (32) into the closing spring chamber (28).
4. Injection nozzle according to Claim 2, characterized in that the accumulator piston (94) is constructed as an annular element and is mounted in an annular chamber (92) which is formed between the wall of the cylindrical bore (82) carrying the valve needle (64) in the nozzle element (66) and a valve needle section (88) shouldered in diameter and is delimited on one end face by the annular shoulder (90), serving as the second pressure shoulder, at the transition to the shouldered valve needle section (88).
5. Injection nozzle according to Claim 4, characterized in that the annular chamber (92) ac- comodating the accumulator piston (94) is delimited directly on the other end face by an intermediate disc (72) between nozzle element (66) and nozzle holder (74) which limits the valve needle stroke, and the accumulator piston (94) is provided on its end section facing the intermediate disc (72) with a plurality of recesses (96) to accommodate individual return springs (97) which are braced against the intermediate disc (72).
6. Injection nozzle according to Claim 1, characterized in that the accumulator piston (150) is coupled to the valve needle (12) by a stroke- changing fuel cushion (152).
7. Injection nozzle according to Claim 6, characterized in that the fuel cushion (152) is enclosed in a cylindrical bore (154) of stepped diameter, the larger bore section (156) of which carries a piston (160) coupled mechanically to the valve needle (12) and the narrower bore section (158) of which is delimited by a control piston (150) monitoring the auxiliary duct (56).
8. Injection nozzle according to Claim 7, characterized in that the control piston (150) is urged by a return spring (164) against a stop (166) integral with the housing in the closed position of the valve needle (12).
9. Fuel injection nozzle for internal-combustion engines, having a valve needle which is loaded by a closing spring (134) and has a first pressure shoulder which is engaged permanently in the opening direction by the fuel pressure, and also with means to open at the end of a pre-injection phase an auxiliary fuel duct (120) through which the fuel passes into an accumulator chamber (112) which is delimited by a second pressure shoulder (146) of the valve needle an by an accumulator piston (110) constructed as a separate component and subject to the influence of a particular return spring (130), which executes a movement derived from the valve needle movement in the pre-injection phase an thereafter executes a yielding movement independent of the valve needle movement under the influence of the fuel pressure in the accumulator chamber (112), whereby the accumulator chamber (112) is enlarged by a prescribed value, characterized by the following features:
a) the valve needle has a piston-like attachment (114) which projects into a cylindrical bore of a nozzle housing comprising nozzle element and nozzle holder and is provided with a blind bore (112), the base (146) of which forms the second pressure shoulder of the valve needle and which is connected by a transverse duct (116) starting in proximity of the base (146) to the cylindrical bore in the nozzle housing,
b) the auxiliary fuel duct (120) leads from the side into the cylindrical bore in the nozzle housing at a point which is located outside the second pressure shoulder (146) of the valve needle in the closed position of the valve needle (114),
c) an accumulator piston (110) which is mounted slidably in the blind bore (112) of the valve needle (114) delimits, with the second pressure shoulder (146) of the valve needle (114), an accumulator chamber in the blind bore (112),
d) the transverse bore (116) in the piston-like attachment of the valve needle (114) comes into communication with the auxiliary fuel duct (120) after a prescribed partial stroke of the valve needle (114).
EP19840107559 1983-08-10 1984-06-29 Fuel injection nozzle for internal-combustion engines Expired EP0133470B1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE19833328824 DE3328824A1 (en) 1983-08-10 1983-08-10 Fuel injection nozzle for internal combustion engines
DE3328824 1983-08-10
DE3344396 1983-12-08
DE19833344396 DE3344396A1 (en) 1983-12-08 1983-12-08 Fuel injection nozzle for internal combustion engines

Publications (2)

Publication Number Publication Date
EP0133470A1 EP0133470A1 (en) 1985-02-27
EP0133470B1 true EP0133470B1 (en) 1988-05-11

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EP19840107559 Expired EP0133470B1 (en) 1983-08-10 1984-06-29 Fuel injection nozzle for internal-combustion engines

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US (1) US4566635A (en)
EP (1) EP0133470B1 (en)
DE (1) DE3471134D1 (en)

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Also Published As

Publication number Publication date
EP0133470A1 (en) 1985-02-27
US4566635A (en) 1986-01-28
DE3471134D1 (en) 1988-06-16

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