EP0233190B1 - Fuel injection nozzle for internal combustion engines - Google Patents

Fuel injection nozzle for internal combustion engines Download PDF

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Publication number
EP0233190B1
EP0233190B1 EP86902328A EP86902328A EP0233190B1 EP 0233190 B1 EP0233190 B1 EP 0233190B1 EP 86902328 A EP86902328 A EP 86902328A EP 86902328 A EP86902328 A EP 86902328A EP 0233190 B1 EP0233190 B1 EP 0233190B1
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EP
European Patent Office
Prior art keywords
wall area
hardness
end dome
valve seat
injection nozzle
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
EP86902328A
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German (de)
French (fr)
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EP0233190A1 (en
Inventor
Werner Banzhaf
Ewald Eblen
Heinrich Faber
Rolf Jürgen GIERSCH
Karl Hofmann
Dieter Liedtke
Helmut Norberg
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication date
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Publication of EP0233190A1 publication Critical patent/EP0233190A1/en
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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
    • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
    • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
    • F02M61/18—Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
    • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
    • F02M61/166—Selection of particular materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
    • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
    • F02M61/168—Assembling; Disassembling; Manufacturing; Adjusting
    • 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
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49229—Prime mover or fluid pump making
    • Y10T29/49298—Poppet or I.C. engine valve or valve seat making
    • Y10T29/49306—Valve seat making
    • 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
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49428—Gas and water specific plumbing component making
    • Y10T29/49432—Nozzle making

Definitions

  • the invention relates to a fuel injector for internal combustion engines according to the preamble of the main claim.
  • the end cap of the nozzle body is hardened so that the inside valve seat surface withstands the impact stress caused by the valve needle and the outside wall area is protected against abrasive wear caused by the gas flow in the combustion chamber.
  • the breaking strength of the end cap of the nozzle body is reduced as a result of this and by the presence of the spray holes in the region of the valve seat surface or in the region of a blind hole adjoining the valve seat surface.
  • This disadvantage can only be partially countered by appropriate dimensioning of the wall thickness of the forehead cap, because it also decisively influences the length of the spray holes and thereby the spray jet formation.
  • the cross section and the length of the spray holes are defined within narrow limits by injection parameters, such as the injection quantity, fuel atomization and the like.
  • the inventive arrangement with the characterizing features of the main claim is easier to manufacture and has the further advantage that the strength of the forehead can be increased particularly effectively without any impairment of its other properties.
  • the nozzle bodies of injection nozzles are generally made of case hardening steel, which is carburized for the purpose of high hardness.
  • the reduced hardness of the outer wall area of the end cap opposite the valve seat surface or the blind hole surface can be achieved in that the end cap is not or only slightly carburized on the outside, so that in the case-hardened state on the outside of the tip a sufficient elastic deformation capacity is achieved. Comparative studies have shown that this can significantly increase the strength behavior of the forehead.
  • nitriding or nitrocarburizing is used instead of case hardening, for which purpose steels other than case hardening steels, preferably alloyed tempering steels or hot working steels are used. In this case, it is advisable to temper the nozzle before nitriding or nitrocarburizing.
  • the additional reduction in hardness in the central region of the forehead can be achieved in the manner known per se from FR-A-2 328 854 in that the wall thickness of the forehead is initially chosen to be greater than the finished size and that only after carburizing or Nitriding or nitrocarburizing the inner and outer wall areas of the forehead, the finished dimension is produced by removing a partial layer of the carburized or nitrided or nitrocarburized outer wall area and only then hardening or, in the case of nitriding or nitrocarburizing, nitriding or nitrocarburizing, if necessary, a second time.
  • the breaking strength of the forehead can be further increased if the spray holes are drilled only after carburizing or nitriding or nitrocarburizing or only after hardening, and if the leading edges of the spray holes are rounded off more.
  • FIG. 1 shows a longitudinal section through the end section of the first exemplary embodiment on the injection side, approximately on a scale of 1:10
  • FIG. 2 shows the hardness profile across the dome wall of the nozzle body of the injection nozzle according to FIG. 1
  • FIG. 3 shows the second exemplary embodiment in a representation corresponding to FIG. 1.
  • the injection nozzle according to Figure 1 has a nozzle body 10, in which a valve needle 12 is slidably mounted. This has a conical sealing surface 14, which cooperates with a conical valve seat surface 16, which is formed on an inner wall region 18 of an end cap 20 of the nozzle body 10. From the valve seat surface 16 there are a number of spray holes 22 which penetrate the wall of the end cap 20 at an angle to the nozzle axis.
  • An annular space 24 is formed between the valve needle 12 and a cylindrical inner wall of the nozzle body 10, into which an unillustrated fuel supply line opens.
  • the valve needle 12 is pressed against the valve seat surface 16 by a closing spring, also not shown.
  • a closing spring also not shown.
  • the cone angle of the sealing surface 14 on the valve needle 12 can be chosen to be somewhat larger than the angle of the valve seat surface 16, so that the highest sealing press force results initially at the upper edge 26 of the sealing surface 14.
  • valve seat surface 16 is subjected to very high loads.
  • the inner wall region 18 of the end cap 20 which has the valve seat surface 16 is therefore, as usual, treated by a suitable method in such a way that it has a hardness of approximately 750 HV1 (Vickers hardness, load 9.8 N).
  • HV1 Vanickers hardness, load 9.8 N.
  • FIG. 2 shows the course of hardness along a cross-sectional line through the end cap 20 with a full line a, the distance from the valve seat surface 16 being plotted on the abscissa and the hardness in HV1 being plotted on the ordinate.
  • the hardness curve in a conventional injection nozzle is also shown in FIG. 2 by a dashed line b.
  • the hardness in the central wall region 28 drops to approximately 470 HV1 and rises again in the outer wall region 30 to approximately 600 HV 1.
  • a nozzle body made of case-hardening steel was used, which had not yet been provided with the spray holes 22 and whose end cap 20 had a wall thickness which exceeded the finished dimension by a certain amount.
  • the spray holes 22 were machined into the end cap 20, and by removing the excess on the outer lateral surface to the prescribed wall thickness of the remaining outer wall area 30, this is less than the hardness of the inner wall area 18.
  • Another manufacturing option is to drill the spray holes with an increased wall thickness and, after carburizing or nitriding or nitrocarburizing, to twist off or grind off the outside of the tip and thus the insert layer or nitriding or nitrocarburizing layer. In this process, the spray holes are hardened throughout.
  • the exemplary embodiment according to FIG. 3 differs from that according to FIG. 1 in that the spray holes 22 do not start from the valve seat surface, but from a blind hole 32 formed in the end cap 20a.
  • the nozzle body 10a has a transition section 34 which is delimited on the outside by a conical outer surface 36. At a throat radius 38, this merges into an outer wall region 40 of the end cap 20a, which lies opposite an inner wall region 42 surrounding the blind hole 32.
  • the outer wall area 44 delimited by the conical surface area 36 and the fillet radius 38 and the outer wall area 40 of the end cap 20a opposite the blind hole 32 have a lower hardness than the inner wall area 18a forming the valve seat area 16a and the inner wall area 42 surrounding the blind hole 32 .
  • the central wall region 28a of the end cap 20a can advantageously have a lower hardness than the outer wall regions 40, 44.

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

Abstract

Fuel injection nozzle for internal combustion engines with a tapered valve seat surface (16 or 16a) located in an end-cup (20 or 20a) of the nozzle body (10), in which at least one spray orifice (22) is provided. The outer wall region (30 or 44) of the end-cup (20 or 20a) which lies opposite the valve seating surface (16 or 16a) is of a lesser hardness than that of the inner wall region (18 or 18a) which forms the valve seating surface (16 or 16a). If the spray orifice (22) emerges from a blind hole (32), the outer wall region (40) of the end cup (20a) which surrounds the blind hole (32) should preferably also have a lesser hardness than that of the opposed inner wall region (42). The central wall region (28 or 28a) which lies between these should preferably have an even lesser hardness than that of the outer wall region (30 or 40, 44). In this way it is ensured that the end cup (20 or 20a) of the nozzle body (10 or 10a) can be provided altogether with a greater strength than with a known design, without the valve seat surface losing any of its heardness and without any marked decrease in the protection afforded to the outer wall region (30 or 40, 44) of the end cup (20 or 20a) against abrasive wear and tear.

Description

Stand der TechnikState of the art

Die Erfindung geht aus von einer Kraftstoff-Einspritzdüse für Brennkraftmaschinen nach der Gattung des Hauptanspruchs. Bei diesen Einspritzdüsen ist die Stirnkuppe des Düsenkörpers gehärtet, damit die innenliegende Ventilsitzfläche der Schlagbeanspruchung durch die Ventilnadel standhält und der außenliegende Wandbereich gegen abrasiven Verschleiß durch die Gasströmung in der Brennkammer geschützt ist. Nachteilig ist jedoch, daß dadurch und durch das Vorhandensein der Spritzlöcher im Bereich der Ventilsitzfläche oder im Bereich eines an die Ventilsitzfläche anschließenden Sacklochs die Bruchfestigkeit der Stirnkuppe des Düsenkörpers verringert wird. Diesem Nachteil kann durch eine entsprechende Bemessung der Wandstärke der Stirnkuppe nur teilweise begegnet werden, weil dadurch auch die Länge der Spritzlöcher und dadurch die Spritzstrahlausbildung entscheidend beeinflußt wird. Der Querschnitt und die Länge der Spritzlöcher sind durch Einspritzkenngrößen, wie Einspritzmenge, Kraftstoffzerstäubung und dergleichen in engen Grenzen festgelegt.The invention relates to a fuel injector for internal combustion engines according to the preamble of the main claim. In the case of these injection nozzles, the end cap of the nozzle body is hardened so that the inside valve seat surface withstands the impact stress caused by the valve needle and the outside wall area is protected against abrasive wear caused by the gas flow in the combustion chamber. However, it is disadvantageous that the breaking strength of the end cap of the nozzle body is reduced as a result of this and by the presence of the spray holes in the region of the valve seat surface or in the region of a blind hole adjoining the valve seat surface. This disadvantage can only be partially countered by appropriate dimensioning of the wall thickness of the forehead cap, because it also decisively influences the length of the spray holes and thereby the spray jet formation. The cross section and the length of the spray holes are defined within narrow limits by injection parameters, such as the injection quantity, fuel atomization and the like.

Zur Behebung des geschilderten Nachteils ist es Einspritzdüsen der gattungsmäßigen Art gemäß der JP-A-5 888 459 auch schon bekannt, den Ventilsitz an einem in den Düsenkörper nachträglich eingebauten Hartmetallkörper auszubilden. Diese Ausführung ist aufwendig, weil der Düsenkörperzunächst aufgeschnitten und nach dem Einbringen des Hartmetalls wieder zusammengeschweißt wird. Danach muß in das Hartmetall durch mehrere Arbeitsgänge erst die Form des konischen Ventilsitzes eingearbeitet werden. Diese Arbeitsgänge verteuern die Herstellung der Einspritzdüse wesentlich und sind für eine Massenfertigung nicht geeignet.In order to remedy the described disadvantage, it is also known to inject nozzles of the generic type according to JP-A-5 888 459 to design the valve seat on a hard metal body subsequently installed in the nozzle body. This design is expensive because the nozzle body is first cut open and welded together again after the hard metal has been introduced. After that, the shape of the conical valve seat has to be worked into the carbide through several operations. These operations make the injection nozzle significantly more expensive and are not suitable for mass production.

Vorteile der ErfindungAdvantages of the invention

Die erfidnungsgemäße Anordnung mit den kennzeichnenden Merkmalen des Hauptanspruchs ist einfacher herzustellen und hat den weiteren Vorteil, daß sich die Festigkeit der Stirnkuppe ohne jede Beeinträchtigung ihrer übrigen Eigenschaften besonders wirksam erhöhen läßt.The inventive arrangement with the characterizing features of the main claim is easier to manufacture and has the further advantage that the strength of the forehead can be increased particularly effectively without any impairment of its other properties.

Durch die in den Unteransprüchen aufgeführten Maßnahmen sind vorteilhafte Weiterbildungen der Anordnung nach dem Hauptanspruch möglich.Advantageous further developments of the arrangement according to the main claim are possible through the measures listed in the subclaims.

Durch Versuche hat sich eine Ausführung als besonders zweckmässig herausgestellt, bei weicher die Härte eines Außenwandbereichs der Stirnkuppe um mindestens 100 HV1, vorzugsweise um 150 HV1, geringer ist als die Härte des die Ventilsitzfläche bildenden Innenwandbereichs.Experiments have shown an embodiment to be particularly expedient in which the hardness of an outer wall area of the end cap is at least 100 HV1, preferably 150 HV1, less than the hardness of the inner wall area forming the valve seat surface.

Besonders gute Ergebnisse wurden erzielt mit Einspritzdüsen, bei welchen die Härte des mittleren Wandbereichs um mindestens 100 HV1 geringer ist als die Härte des Außenwandbereichs. Als optimal hat es sich herausgestellt, wenn die Härte des mittleren Wandbereiches zwischen 400 HV1 und 550 HV1 liegt.Particularly good results have been achieved with injection nozzles in which the hardness of the central wall area is at least 100 HV1 lower than the hardness of the outer wall area. It has proven to be optimal if the hardness of the middle wall area is between 400 HV1 and 550 HV1.

Die Düsenkörper von Einspritzdüsen werden im allgemeinen aus Einsatzstahl herausgestellt, der zum Zweck hoher Härte aufgekohlt wird. Die verminderte Härte des der Ventilsitzfläche bzw. der Sacklochoberfläche gegenüberliegenden Außenwandbereichs der Stirnkuppe kann dadurch erreicht werden, daß die Stirnkuppe außen nicht oder nur wenig aufgekohlt wird, so daß im einsatzgehärteten Zustand an der Kuppenaußenseite ein ausreichendes elastisches Formänderungsvermögen erreicht wird. Vergleichsuntersuchungen haben gezeigt, daß bereits dadurch das Festigkeitsverhalten der Stirnkuppe deutlich erhöht werden kann. Derselbe Erfolg läßt sich erzielen, wenn statt des Einsatzhärtens nitriert oder nitrocarburiert wird, wozu auch andere Stähle als Einsatzstähle, vorzugsweise legierte Vergütungsstähle oder Warmarbeitungsstähle verwendet werden. In diesem Fall ist es zweckmäßig, vor dem Nitrieren oder Nitrocarburieren die Düse zu vergüten.The nozzle bodies of injection nozzles are generally made of case hardening steel, which is carburized for the purpose of high hardness. The reduced hardness of the outer wall area of the end cap opposite the valve seat surface or the blind hole surface can be achieved in that the end cap is not or only slightly carburized on the outside, so that in the case-hardened state on the outside of the tip a sufficient elastic deformation capacity is achieved. Comparative studies have shown that this can significantly increase the strength behavior of the forehead. The same success can be achieved if nitriding or nitrocarburizing is used instead of case hardening, for which purpose steels other than case hardening steels, preferably alloyed tempering steels or hot working steels are used. In this case, it is advisable to temper the nozzle before nitriding or nitrocarburizing.

Die zusätzliche Absenkung der Härte im mittleren Bereich der Stirnkuppe kann in der an sich aus der FR-A-2 328 854 bekannten Weise dadurch erreicht werden, daß die Wandstärke der Stirnkuppe zunächst größer als das Fertigmaß gewählt wird und daß erst nach dem Aufkohlen bzw. Nitrieren oder Nitrocarburieren der inneren und äußeren Wandbereiche der Stirnkuppe das Fertigmaß durch Abtragen einer Teilschicht des aufgekohlten bzw. nitrierten oder nitrocarburierten äußeren Wandbereichs hergestellt und dann erst gehärtet bzw. im Falle des Nitrierens oder Nitrocarburierens gegebenenfalls ein zweites Mal nitriert oder nitrocarburiert wird.The additional reduction in hardness in the central region of the forehead can be achieved in the manner known per se from FR-A-2 328 854 in that the wall thickness of the forehead is initially chosen to be greater than the finished size and that only after carburizing or Nitriding or nitrocarburizing the inner and outer wall areas of the forehead, the finished dimension is produced by removing a partial layer of the carburized or nitrided or nitrocarburized outer wall area and only then hardening or, in the case of nitriding or nitrocarburizing, nitriding or nitrocarburizing, if necessary, a second time.

Die Bruchfestigkeit der Stirnkuppe läßt sich weiter erhöhen, wenn die Spritzlöcher erst nach dem Aufkohlen bzw. Nitrieren bzw. Nitrocarburieren oder überhaupt erst nach dem Härten gebohrt werden, und wenn die Einlaufkanten der Spritzlöcher stärker abgerundet werden.The breaking strength of the forehead can be further increased if the spray holes are drilled only after carburizing or nitriding or nitrocarburizing or only after hardening, and if the leading edges of the spray holes are rounded off more.

Zeichnungdrawing

Zwei Ausführungsbeispiele der Erfindung sind in der Zeichnung dargestellt und in der nachfolgenden Beschreibung näher erläutert. Es zeigen Figur 1 einen Längsschnitt durch den einspritzseitigen Endabschnitt des ersten Ausführungsbeispiels etwa im Maßstab 1:10, Figur 2 den Härteverlauf quer durch die Kuppenwand des Düsenkörpers der Einspritzdüse nach Figur 1, und Figur 3 das zweite Ausführungsbeispiel in einer der Figur 1 entsprechenden Darstellung.Two embodiments of the invention are shown in the drawing and explained in more detail in the following description. 1 shows a longitudinal section through the end section of the first exemplary embodiment on the injection side, approximately on a scale of 1:10, FIG. 2 shows the hardness profile across the dome wall of the nozzle body of the injection nozzle according to FIG. 1, and FIG. 3 shows the second exemplary embodiment in a representation corresponding to FIG. 1.

Beschreibung der AusführungsbeispieleDescription of the embodiments

Die Einspritzdüse nach Figur 1 hat einen Düsenkörper 10, in welchem eine Ventilnadel 12 verschiebbar gelagert ist. Diese hat eine kegelige Dichtfläche 14, die mit einer konischen Ventilsitzfläche 16 zusammenarbeitet, welche an einem Innenwandbereich 18 einer Stirnkuppe 20 des Düsenkörpers 10 gebildet ist. Von der Ventilsitzfläche 16 gehen mehrere Spritzlöcher 22 aus, welche die Wand der Stirnkuppe 20 in einem Winkel zur Düsenachse durchstoßen.The injection nozzle according to Figure 1 has a nozzle body 10, in which a valve needle 12 is slidably mounted. This has a conical sealing surface 14, which cooperates with a conical valve seat surface 16, which is formed on an inner wall region 18 of an end cap 20 of the nozzle body 10. From the valve seat surface 16 there are a number of spray holes 22 which penetrate the wall of the end cap 20 at an angle to the nozzle axis.

Zwischen der Ventilnadel 12 und einer zylindrischen Innenwand des Düsenkörpers 10 ist ein Ringraum 24 gebildet, in welchen eine nicht dargestellte Kraftstoffzuleitung einmündet. Die Ventilnadel 12 ist von einer ebenfalls nicht dargestellten Schließfeder gegen die Ventilsitzfläche 16 gepreßt. Wenn der Kraftstoffdruck im Ringraum 24 auf einen vorgegebenen Wert angestiegen ist, wird die Ventilnadel 12 entgegen der Kraft der Schließfeder angehoben und der Kraftstoff durch die Spritzlöcher 22 ausgespritzt. Der Kegelwinkel der Dichtfläche 14 an der Ventilnadel 12 kann etwas größer gewählt sein als der Winkel der Ventilsitzfläche 16, so daß sich anfangs an der oberen Kante 26 der Dichtfläche 14 die höchste Dichtpreßkraft ergibt.An annular space 24 is formed between the valve needle 12 and a cylindrical inner wall of the nozzle body 10, into which an unillustrated fuel supply line opens. The valve needle 12 is pressed against the valve seat surface 16 by a closing spring, also not shown. When the fuel pressure in the annular space 24 is predetermined benen value has increased, the valve needle 12 is raised against the force of the closing spring and the fuel is sprayed out through the spray holes 22. The cone angle of the sealing surface 14 on the valve needle 12 can be chosen to be somewhat larger than the angle of the valve seat surface 16, so that the highest sealing press force results initially at the upper edge 26 of the sealing surface 14.

Im Betrieb der Einspritzdüse wird die Ventilsitzfläche 16 sehr hoch beansprucht. Der die Ventilsitzfläche 16 aufweisende Innenwandbereich 18 der Stirnkuppe 20 ist daher wie üblich durch ein geeignetes Verfahren so behandelt, daß er eine Härte von etwa 750 HV1 (Vickershärte, Belastung 9,8 N) aufweist. Beim Aufschlagen der Ventilnadel 12 auf die Stirnkuppe 20 treten jedoch auch erhebliche Radialkräfte auf, welche eine Sprengwirkung auf die Stirnkuppe 20 ausüben. Diesen Kräften kann durch eine entsprechende Bemessung der Wandstärke der Stirnkuppe 20 nur begrenzt Rechnung getragen werden, weil dadurch auch die Länge der Spritzlöcher 22 beeinflußt wird, die wiederum auf andere Kenngrößen des Einspritzverlaufes, wie Strahlform, Einspritzdruck, Einspritzmenge usw. abgestimmt werden muß.During operation of the injection nozzle, the valve seat surface 16 is subjected to very high loads. The inner wall region 18 of the end cap 20 which has the valve seat surface 16 is therefore, as usual, treated by a suitable method in such a way that it has a hardness of approximately 750 HV1 (Vickers hardness, load 9.8 N). When the valve needle 12 strikes the forehead 20, however, considerable radial forces also occur which exert an explosive effect on the forehead 20. These forces can only be taken into account to a limited extent by appropriate dimensioning of the wall thickness of the end cap 20, because this also influences the length of the spray holes 22, which in turn has to be matched to other parameters of the course of the injection, such as jet shape, injection pressure, injection quantity, etc.

Um die Bruchfestigkeit der Stirnkuppe 20 zu erhöhen, sind erfindungsgemäß der mittlere Wandbereich 28 und der Außenwandbereich 30 der Stirnkuppe 20 mit einer geringeren Härte als der Innenwandbereich 18 versehen. In Figur 2 ist mit einem vollen Linienzug a der Härteverlauf entlang einer Querschnittslinie durch die Stirnkuppe 20 dargestellt, wobei auf der Abszisse die Entfernung von der Ventilsitzfläche 16 und auf der Ordinate die Härte in HV1 aufgetragen ist. Zum Vergleich mit dem erfindungsgemäßen Härteverlauf a ist in Figur 2 durch einen gestrichelten Linienzug b auch der Härteverlauf bei einer herkömmlichen Einspritzdüse dargestellt.In order to increase the breaking strength of the end cap 20, the middle wall region 28 and the outer wall region 30 of the end cap 20 are provided with a lower hardness than the inner wall region 18. FIG. 2 shows the course of hardness along a cross-sectional line through the end cap 20 with a full line a, the distance from the valve seat surface 16 being plotted on the abscissa and the hardness in HV1 being plotted on the ordinate. For comparison with the hardness curve a according to the invention, the hardness curve in a conventional injection nozzle is also shown in FIG. 2 by a dashed line b.

Beim Ausführungsbeispiel nach Figur 1 sinkt die Härte im mittleren Wandbereich 28 bis auf ca. 470 HV1 ab und steigt im Außenwandbereich 30 wieder bis auf ca. 600 HV 1 an. Als Ausgangsteil für das Härten wurde beispielsweise ein aus Einsatzstahl bestehender Düsenkörper verwendet, der noch nicht mit den Spritzlöchern 22 versehen war und dessen Stirnkuppe 20 eine das Fertigmaß um einen bestimmten Betrag übersteigende Wandstärke hatte. Nach dem Aufkohlen und Härten wurden die Spritzlöcher 22 in die Stirnkuppe 20 eingearbeitet und diese durch Abtragen des Übermaßes an der äußeren Mantelfläche auf die vorgeschriebene Wandstärke des verbleibenden Außenwandbereiches 30 geringer als die Härte des Innenwandbereiches 18 ist.In the exemplary embodiment according to FIG. 1, the hardness in the central wall region 28 drops to approximately 470 HV1 and rises again in the outer wall region 30 to approximately 600 HV 1. As the starting part for hardening, for example, a nozzle body made of case-hardening steel was used, which had not yet been provided with the spray holes 22 and whose end cap 20 had a wall thickness which exceeded the finished dimension by a certain amount. After carburizing and hardening, the spray holes 22 were machined into the end cap 20, and by removing the excess on the outer lateral surface to the prescribed wall thickness of the remaining outer wall area 30, this is less than the hardness of the inner wall area 18.

Eine weitere Fertigungsmöglichkeit besteht darin, die Spritzlöcher bei vergrößerter Wandstärke zu bohren und nach dem Aufkohlen bzw. Nitrieren oder Nitrocarburieren die Kuppenaußenseite und damit die Einsatzschicht bzw. Nitrier- oder Nitrocarburierschicht abzudrehen bzw. abzuschleifen. Bei diesem Verfahren sind die Spritzlöcher durchgehend gehärtet.Another manufacturing option is to drill the spray holes with an increased wall thickness and, after carburizing or nitriding or nitrocarburizing, to twist off or grind off the outside of the tip and thus the insert layer or nitriding or nitrocarburizing layer. In this process, the spray holes are hardened throughout.

Eine andere Möglichkeit, die Härte des Außenwandbereichs 30 der Stirnkuppe 20 gegenüber dem Innenwandbereich 18 zu vermindern, besteht wie schon erwähnt darin, daß die Stirnkuppe beim Aufkohlen bzw. Nitrieren oder Nitrocarburieren und Härten bereits das Fertigmaß hat, daßjedoch der Außenwandbereich 30 nicht oder nur geringfügig aufgekohlt bzw. nitriert oder nitrocarburiert wird. Dabei kann sich ein Härteverlauf ergeben, der von innen nach außen betrachtet zunächst in etwa dem herkömmlichen Verlauf b und danach den strichpunktierten Linie c in Figur 2 folgt.Another possibility of reducing the hardness of the outer wall region 30 of the end cap 20 compared to the inner wall region 18 is, as already mentioned, that the end cap already has the finished dimensions when carburizing or nitriding or nitrocarburizing and hardening, but that the outer wall region 30 does not or only slightly carburized or nitrided or nitrocarburized. This can result in a hardness curve which, viewed from the inside out, initially follows approximately the conventional curve b and then the dash-dotted line c in FIG. 2.

Das Ausführungsbeispiel nach Figur 3 unterscheidet sich von jenem nach Figur 1 dadurch, daß die Spritzlöcher 22 nicht von der Ventilsitzfläche, sondern von einem in der Stirnkuppe 20a gebildeten Sackloch 32 ausgehen. Zwischen der Stirnkuppe 20a und dem Schaft weist der Düsenkörper 10a einen Übergangsabschnitt 34 auf, der außen durch eine Kegelmantelfläche 36 begrenzt ist. Diese geht an einem Kehlenradius 38 in einen Außenwandbereich 40 der Stirnkuppe 20a über, welcher einem das Sackloch 32 umschließenden Innenwandbereich 42 gegenüberliegt.The exemplary embodiment according to FIG. 3 differs from that according to FIG. 1 in that the spray holes 22 do not start from the valve seat surface, but from a blind hole 32 formed in the end cap 20a. Between the end cap 20a and the shaft, the nozzle body 10a has a transition section 34 which is delimited on the outside by a conical outer surface 36. At a throat radius 38, this merges into an outer wall region 40 of the end cap 20a, which lies opposite an inner wall region 42 surrounding the blind hole 32.

Bei der Ausführung nach Figur 3 weist der durch die Kegelmantelfläche 36 und den Kehlenradius 38 begrenzte Außenwandbereich 44 und der dem Sackloch 32 gegenüberliegende Außenwandbereich 40 der Stirnkuppe 20a eine geringere Härte als der die Ventilsitzfläche 16a bildende Innenwandbereich 18a und der das Sackloch 32 umgebende Innenwandbereich 42 auf. Der mittlere Wandbereich 28a der Stirnkuppe 20a kann wie beim ersten Ausführungsbeispiel vorteilhaft eine geringere Härte als die Außenwandbereiche 40, 44 haben.In the embodiment according to FIG. 3, the outer wall area 44 delimited by the conical surface area 36 and the fillet radius 38 and the outer wall area 40 of the end cap 20a opposite the blind hole 32 have a lower hardness than the inner wall area 18a forming the valve seat area 16a and the inner wall area 42 surrounding the blind hole 32 . As in the first exemplary embodiment, the central wall region 28a of the end cap 20a can advantageously have a lower hardness than the outer wall regions 40, 44.

Claims (10)

1. Fuel injection nozzle for internal combustion engines, having a nozzle body (10, 10a) in which a valve needle (12) having a conical sealing face is displaceably supported which operates in conjunction with a conical valve seat face (16, 16a) which is formed at an inside wall area (18, 18a) of an end dome (20, 20a) of the nozzle body, in which at least one spray hole (22) is provided and which has at least one outside wall area which has less hardness than the inside wall area of the end dome provided with the valve seat face, characterized in that the greater hardness of the inside wall area (18, 18a) of the end dome (20, 20a) provided with the valve seat face (16, 16a) is created by skin-hardening of this inside wall area (18, 18a) and in that the centre wall area (28, 28a), located between the valve seat face (16, 16a) and the opposite outside wall area (30, 44), of the end dome (20, 20a) exhibits less hardness than the outside wall area (30, 40, 44).
2. Injection nozzle according to Claim 1, characterized in that the hardness of one outside wall area (30 and 40, 44) of the end dome (20 and 20a, respectively) is less than the hardness of the inside wall area (18 and 18a, respectively) forming the valve seat face (16 and 16a, respectively) by at least 100 HV1, preferably by 150 HV1.
3. Injection nozzle according to Claim 1, characterized in that the hardness of the centre wall area (28 and 28a) of the end dome (20 and 20a) is less than the hardness of the outside wall area (30 and 40, 44) by at least 100 HV 1.
4. Injection nozzle according to Claim 1, characterized in that the hardness of the centre wall area (28 and 28a) of the end dome (20 and 20a) is between 400 HV1 and 550 HV1.
5. Injection nozzle according to Claim 1, having a blind hole adjoining the valve seat face, from which at least one spray hole originates, characterized in that the inside wall area (18a, 42) of the end dome (20a) surrounding the blind hole (32) is also skin- hardened and the centre wall area (28a) of the end dome (20a) located between the blind hole (32) and the opposite outside wall area (40) exhibits less hardness than the outside wall area (40, 44).
6. Method for fabricating an injection nozzle according to one of the preceding claims, characterized in that the skin hardening is produced by the so- called case hardening in which the wall areas of the nozzle body (10) are carburized before annealing.
7. Method for fabricating an injection nozzle according to one of Claims 1 to 5, characterized in that the skin-hardening is effected by nitriding or nitro-carburizing.
8. Method according to Claim 6 or 7, characterized in that the finished dimension of the wall thickness of the end dome (20 and 20a) is produced by removing the material layer corresponding to an outside excess dimension, after the carburizing but before the hardening or after the tempering and nitriding or nitro-carburizing.
9. Method according to one of Claims 6 to 8, characterized in that the spray hole or spray holes (22) are only machined into the end dome (20 and 20a) after the skin-hardening.
10. Method according to one of Claims 6 to 9, characterized in that the spray hole or spray holes (22) are machined into the end dome after the carburizing but before the hardening or after the nitriding or nitro-carburizing of the end dome (20 and 20a).
EP86902328A 1985-08-10 1986-04-11 Fuel injection nozzle for internal combustion engines Expired EP0233190B1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE3528792 1985-08-10
DE3528792 1985-08-10
DE3536452 1985-10-12
DE19863536452 DE3536452A1 (en) 1985-08-10 1986-10-12 FUEL INJECTION NOZZLE FOR INTERNAL COMBUSTION ENGINES

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EP0233190A1 EP0233190A1 (en) 1987-08-26
EP0233190B1 true EP0233190B1 (en) 1989-12-20

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US (1) US4801095A (en)
EP (1) EP0233190B1 (en)
JP (1) JP2545520B2 (en)
DE (2) DE3667704D1 (en)
WO (1) WO1987000889A1 (en)

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Also Published As

Publication number Publication date
US4801095A (en) 1989-01-31
WO1987000889A1 (en) 1987-02-12
EP0233190A1 (en) 1987-08-26
JPS63500669A (en) 1988-03-10
JP2545520B2 (en) 1996-10-23
DE3667704D1 (en) 1990-01-25
DE3536452A1 (en) 1987-02-19

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