EP1419314A1 - Fuel injection valve for internal combustion engines and a method for hardening said valve - Google Patents

Fuel injection valve for internal combustion engines and a method for hardening said valve

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Publication number
EP1419314A1
EP1419314A1 EP02748600A EP02748600A EP1419314A1 EP 1419314 A1 EP1419314 A1 EP 1419314A1 EP 02748600 A EP02748600 A EP 02748600A EP 02748600 A EP02748600 A EP 02748600A EP 1419314 A1 EP1419314 A1 EP 1419314A1
Authority
EP
European Patent Office
Prior art keywords
valve
valve body
fuel injection
internal combustion
steel
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.)
Granted
Application number
EP02748600A
Other languages
German (de)
French (fr)
Other versions
EP1419314B1 (en
Inventor
Dieter Liedtke
Alfred Hoch
Franz Wolf
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
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Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP1419314A1 publication Critical patent/EP1419314A1/en
Application granted granted Critical
Publication of EP1419314B1 publication Critical patent/EP1419314B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20—Carburising
    • C23C8/22—Carburising of ferrous surfaces
    • 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
    • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/90—Selection of particular materials
    • F02M2200/9053—Metals
    • F02M2200/9061—Special treatments for modifying the properties of metals used for fuel injection apparatus, e.g. modifying mechanical or electromagnetic properties

Definitions

  • the temperature load on the fuel injection valves and thus on the needle seat in the valve body will continue to increase due to an increase in performance or an increase in braking power, particularly in commercial vehicles.
  • the case-hardened steels previously used and the hardening methods used for them are no longer sufficient for these applications.
  • the fuel injection valve according to the invention for internal combustion engines according to the preamble of claim 1 has the advantage that the valve body is dimensionally and wear-resistant up to high temperatures and is therefore suitable for use at all operating points of an internal combustion engine.
  • the valve body of the fuel injector consists of a high-alloy hot-work steel that has been hardened by a carburizing process. By combining the high-alloy hot-work steel with a suitable carburizing process, the advantages of material and hardening process add up positively.
  • a significant increase in the fatigue strength of the high-alloy steel is obtained through a reduced notch effect during use, a reduction in stock removal during the subsequent grinding work on the functional geometries and a reduction in the necessary initial hardness of the valve body and thus improved machinability and a reduction in the cavitation sensitivity in the valve body, in particular in the area of the valve seat.
  • the hot-work steel is dimensionally and wear-resistant up to a temperature of 450 ° C.
  • the fuel injection valve is suitable for use at all possible operating points of the internal combustion engine.
  • the high-alloy hot-work steel consists at least approximately of 0.4% carbon, 5% chromium, 1% molybdenum and other metallic and non-metallic elements in traces of less than 1% overall, the 100% missing iron is.
  • Such steels, such as X 40 CrMo V 51, are commercially available and can be used without further effort.
  • the carburizing process is a gas carburizing process. Carburizing eliminates the need for time-consuming post-processing.
  • the method according to the invention for hardening a valve body which is part of a fuel injection valve for internal combustion engines, has the advantage that the treatment has the necessary heat resistance for use in the combustion chamber of an internal combustion engine.
  • the valve body is carburized in a gas atmosphere that contains a hydrocarbon and then heat-treated at a temperature of about 900 ° C. in vacuo, but at most at a pressure of 100 Pa.
  • the carburizing will take place at a pressure of less than 100 kPa.
  • This vacuum carburizing process in particular results in a reduction in the formation of edge oxidations which reduce the strength.
  • a fuel injection valve is shown in longitudinal section as an example of a hardened valve body.
  • the fuel injection valve shown in FIG. 1 has a valve body 1, in which a valve needle 5 is arranged to be longitudinally displaceable in a bore 3.
  • a valve needle 5 is arranged to be longitudinally displaceable in a bore 3.
  • an essentially conical valve seat 9 is formed, in which at least one injection opening 11 is formed, which connects the bore 3 with the combustion chamber of the internal combustion engine.
  • the valve needle 5 has a guide section 15 with which it is sealingly guided in a leading section 23 of the bore 3. In the direction of the valve seat 9, the valve needle 5 tapers to form a pressure shoulder 13 and merges into a shaft section 17 with a reduced diameter.
  • an essentially conical valve sealing surface 7 is formed on the valve needle 5, which cooperates with the valve seat 9 and thus closes the at least one injection opening 11 with respect to the bore 3 when it contacts the valve seat 9.
  • a radial expansion of the bore 3 forms a pressure chamber 19 which can be filled with fuel under high pressure via an inlet channel 25.
  • the pressure chamber 19 continues to the valve seat 9 as an annular channel 21 which surrounds the shaft section 17 of the valve needle 3. In this way, the fuel flows from the inlet channel 25 through the pressure chamber 19 and the annular channel 21 to the valve seat 9 and, if the valve sealing surface 7 is lifted off the valve seat 9, through the injection openings 11 into the combustion chamber of the internal combustion engine.
  • the valve needle 5 is controlled by the ratio of the hydraulic forces on the pressure shoulder 13 and the valve sealing surface 7 on the one hand and a closing force on the other hand, which acts on the end of the valve needle 5 facing away from the combustion chamber and acts on the valve needle 5 in the direction of the valve seat 9.
  • One possible operating state of the fuel injection valve is that the closing force on the valve needle 5 remains constant, while the fuel pressure in the pressure chamber 19 and in the annular channel 21 changes due to fuel being supplied from the inlet channel 25. Due to the fuel pressure in the pressure chamber 19 and in the region of the valve seat 9, the valve needle 5 experiences a hydraulic force which is directed away from the valve seat 9.
  • this hydraulic force is greater than the closing force on the valve needle 5, it moves away from the valve seat 9 and thus lifts off from the valve seat 9 with the valve sealing surface 7. If the pressure in the pressure chamber 19 falls below a certain threshold pressure, the closing force on the valve needle 5 predominates and it moves again in the direction of the valve seat 9 until the valve sealing surface 7 closes the at least one injection opening 11 again.
  • valve needle 5 The longitudinal movement of the valve needle 5 and the relatively hard placement of the valve needle 5 on the valve seat 9 result in high forces on the valve body 1 in the region of the valve 9.
  • longitudinal movement of the valve needle 5 in the leading section 23 of the bore 3 results in friction losses between the valve needle 5 and the wall of the bore 3, which can lead to an impermissibly high wear with a soft material of the valve body 1.
  • a so-called hot working steel which belongs to the tool steels, is used for the valve body 1.
  • high-alloy hot-work steels such as X 40 steel, has proven to be particularly advantageous CrMoV 51.
  • This high-alloy hot-work steel can be exposed to working temperatures of up to 450 ° C without losing hardness and therefore wear resistance.
  • the surface of the valve body 1 must be additionally hardened.
  • carbon is introduced into the layers of the valve body 1 near the surface in a so-called carburizing process, as a result of which the surface becomes hardenable.
  • a possible carburizing process is the gas carburizing process, in which the steel is exposed to an atmosphere of hydrocarbons and chemically inert gases, such as nitrogen (2), at a temperature of 900 ° C. to 1000 ° C. The carbon diffuses into the layers of the valve body 1 near the surface, so that the carbon content increases there.
  • the hardening depths are 0.3 to 4 mm.
  • the carburizing makes the material hardenable, which is carried out by subsequent heating in a vacuum furnace.
  • the workpiece in this case the valve body 1, is heated to approximately 800 ° C., the vacuum largely prevailing in the hardening furnace, in any case a pressure of less than 100 Pa.
  • the advantage of this hardening method of the valve body 1 consists in the combination of a high-alloy hot-work steel with a gas carburizing method that works with negative pressure, that is to say at a pressure of less than 100 kPa. This adds the advantages of hot-work steel to those of the carburizing and hardening process. A significant increase in the fatigue strength of the high-alloy steel is achieved through a reduced notch effect when using the vacuum carburizing process, since edge oxidation is avoided. At the same time, there is a reduction in the stock removal during the subsequent grinding on the functional geometries, since the injection opening 11 is reworked by hydroerosive grinding. Another advantage is the reduction in the necessary initial hardness of the fuel injection valve and thus an improved machinability after the heat treatment of the valve body 1. A reduction in the cavitation sensitivity of the surfaces is also obtained, especially in the inlet bore and needle seat area of the valve body 1.
  • high-alloy hot-work steel X 40 CrMoV 51 In addition to the high-alloy hot-work steel X 40 CrMoV 51, other high-alloy hot-work steels with a carbon content of 0.3 to 0.5% can also be used.

Abstract

The invention relates to a fuel injection valve for internal combustion engines, comprising a valve body (1) and at least one injection opening (11), provided therein. Fuel can be injected through said opening into the combustion chamber of the internal combustion engine in a controlled manner by a valve needle (5) which cooperates with a valve seat (9), provided in the valve body (1). Said valve body (1) is composed of a high-alloy hot-work steel, hardened by a carburizing method.

Description

Kraftstoffeinspritzventil für Brennkraftmaschinen und ein Verfahren zur Härtuncr desselbenFuel injection valve for internal combustion engines and a method for hardening the same
Stand der TechnikState of the art
Aus dem Stand der Technik sind verschiedene Verfahren zum Härten von Stahl bekannt. Hierdurch soll die Verschleißfestigkeit und die Beständigkeit des Werkstoffs und seine Bear- beitbarkeit beeinflusst werden. Ein Beispiel hierfür ist das sogenannte Aufkohlen, bei dem Kohlenstoff in die oberflächennahen Schichten des Werkstücks eingebracht wird. Ein diesbezügliches Verfahren wird beispielsweise in der Schrift US 4 836 864 beschrieben. Weitere Möglichkeiten sind das Nitrieren von Stählen, bei dem Stickstoff in die oberflächennahen Schichten des Werkstücks eingebracht wird. Auch bei Kraf stoffeinspritzventilen, wie sie vorzugsweise für selbstzündende Brennkraftmaschinen verwendet werden und beispielsweise in der DE 196 18 650 AI beschrieben sind, ist der Einsatz solch gehärteter und behandelter Stähle bekannt, um die Lebensdauer der Stähle zu verlängern. Im Rahmen der Weiterentwicklung der Motoren wird durch Leistungssteigerung oder Erhöhung der Bremsleistung insbesondere bei Nutzfahrzeugen die Temperaturbelastung der Kraftstoffeinspritzventi- le und damit des Nadelsitzes im Ventilkörper weiter zunehmen. Die bisher verwendeten Einsatzstähle und die dafür verwendeten Härtungsmethoden reichen für diese Anwendungen nicht mehr aus . Vorteile der ErfindungVarious methods for hardening steel are known from the prior art. This is intended to influence the wear resistance and the durability of the material and its machinability. An example of this is the so-called carburizing, in which carbon is introduced into the near-surface layers of the workpiece. A method in this regard is described, for example, in US Pat. No. 4,836,864. Another option is the nitriding of steels, in which nitrogen is introduced into the near-surface layers of the workpiece. Even with Kraf fuel injection valves, such as are preferably used for self-igniting internal combustion engines and are described for example in DE 196 18 650 AI, the use of such hardened and treated steels is known to extend the life of the steels. As part of the further development of the engines, the temperature load on the fuel injection valves and thus on the needle seat in the valve body will continue to increase due to an increase in performance or an increase in braking power, particularly in commercial vehicles. The case-hardened steels previously used and the hardening methods used for them are no longer sufficient for these applications. Advantages of the invention
Das erfindungsgemäße Kraftstoffeinspritzventil für Brennkraftmaschinen nach der Gattung des Patentanspruchs 1 weist demgegenüber den Vorteil auf, dass der Ventilkörper bis zu hohen Temperaturen form- und verschleißbeständig ist und so für die Anwendung bei allen Betriebspunkten einer Brennkraftmaschine geeignet ist. Der Ventilkörper des Kraftstoff- einspritzventils besteht aus einem hochlegierten Warmar- beitsstahl, der durch ein Aufkohlverfahren gehärtet worden ist. Durch die Kombination des hochlegierten Warmarbeits- stahls mit einem geeigneten Aufkohlverfahren addieren sich die Vorteile von Material und Härtverfahren positiv. Man erhält eine deutliche Steigerung der Schwingfestigkeit des hochlegierten Stahls durch eine reduzierte Kerbwirkung beim Einsatz, eine Reduzierung der Abträge bei der anschließenden Schleifbearbeitung an den Funktionsgeometrien und eine Reduzierung der notwendigen Ausgangshärte des Ventilkörpers und damit eine verbesserte Bearbeitbarkeit sowie eine Reduzierung der Kavitationsempfindlichkeit im Ventilkörper, insbesondere im Bereich des Ventilsitzes .The fuel injection valve according to the invention for internal combustion engines according to the preamble of claim 1 has the advantage that the valve body is dimensionally and wear-resistant up to high temperatures and is therefore suitable for use at all operating points of an internal combustion engine. The valve body of the fuel injector consists of a high-alloy hot-work steel that has been hardened by a carburizing process. By combining the high-alloy hot-work steel with a suitable carburizing process, the advantages of material and hardening process add up positively. A significant increase in the fatigue strength of the high-alloy steel is obtained through a reduced notch effect during use, a reduction in stock removal during the subsequent grinding work on the functional geometries and a reduction in the necessary initial hardness of the valve body and thus improved machinability and a reduction in the cavitation sensitivity in the valve body, in particular in the area of the valve seat.
In einer vorteilhaften Ausgestaltung des Gegenstandes der Erfindung ist der Warmarbeitsstahl bis zu einer Temperatur von 450 °C form- und verschleißbeständig. Hierdurch ist das Kraftstoffeinspritzventil für den einen Einsatz bei allen möglichen Betriebspunkten der Brennkraftmaschine geeignet.In an advantageous embodiment of the object of the invention, the hot-work steel is dimensionally and wear-resistant up to a temperature of 450 ° C. As a result, the fuel injection valve is suitable for use at all possible operating points of the internal combustion engine.
In einer vorteilhaften Ausgestaltung der Erfindung besteht der hochlegierte Warmarbeitsstahl zumindest näherungsweise aus 0,4 % Kohlenstoff, 5 % Chrom, 1 % Molybdän und sonstigen metallischen und nicht metallischen Elementen in Spuren von insgesamt weniger als 1 %, wobei der zu 100 % fehlende Anteil Eisen ist. Derartige Stähle, wie z.B. X 40 CrMo V 51, sind handelsüblich und können ohne weiteren Aufwand zum Einsatz kommen.In an advantageous embodiment of the invention, the high-alloy hot-work steel consists at least approximately of 0.4% carbon, 5% chromium, 1% molybdenum and other metallic and non-metallic elements in traces of less than 1% overall, the 100% missing iron is. Such steels, such as X 40 CrMo V 51, are commercially available and can be used without further effort.
In einer weiteren vorteilhaften Ausgestaltung ist das Aufkohlverfahren ein Gasaufkohlverfahren. Durch das Aufkohlen wird eine sonst nötige aufwendige Nachbearbeitung überflüssig.In a further advantageous embodiment, the carburizing process is a gas carburizing process. Carburizing eliminates the need for time-consuming post-processing.
Das erfindungsgemäße Verfahren zur Härtung eines Ventilkörpers, der Teil eines Kraftstoffeinspritzventils für Brennkraftmaschinen ist, weist den Vorteil auf, dass der Ventilkörper durch die Behandlung für den Einsatz im Brennraum einer Brennkraftmaschine die notwendige Warmfestigkeit aufweist. Hierzu wird der Ventilkörper in einer Gasatmosphäre, die einen Kohlenwasserstoff enthält, aufgekohlt und anschließend bei einer Temperatur von etwa 900 °C im Vakuum, höchstens jedoch bei einem Druck von 100 Pa, wärmebehandelt. Durch die Kombination dieser beiden Verfahrensschritte bei einem hochlegierten Warmarbeitsstahl kann eine optimale Härtung und Verschleißfestigkeit des hochlegierten Warmarbeitsstahl erreicht werden, so dass dieser auch bei Temperaturen, wie sie unter extremen Belastungen im Brennraum einer selbstzündenden Brennkraftmaschine auftreten, verwendbar bleibt.The method according to the invention for hardening a valve body, which is part of a fuel injection valve for internal combustion engines, has the advantage that the treatment has the necessary heat resistance for use in the combustion chamber of an internal combustion engine. For this purpose, the valve body is carburized in a gas atmosphere that contains a hydrocarbon and then heat-treated at a temperature of about 900 ° C. in vacuo, but at most at a pressure of 100 Pa. By combining these two process steps in a high-alloy hot-work steel, optimal hardening and wear resistance of the high-alloy hot-work steel can be achieved, so that it can also be used at temperatures such as those which occur under extreme loads in the combustion chamber of a self-igniting internal combustion engine.
In einer vorteilhaften Ausgestaltung des Verfahren wird das Aufkohlen bei einem Druck von weniger als 100 kPa stattfinden. Durch dieses Unterdruckaufkohlverfahren erhält man insbesondere eine Verminderung der Bildung von Randoxidationen, die festigkeitsvermindernd sind. ZeichnungIn an advantageous embodiment of the method, the carburizing will take place at a pressure of less than 100 kPa. This vacuum carburizing process in particular results in a reduction in the formation of edge oxidations which reduce the strength. drawing
In der Zeichnung ist ein Kraftstoffeinspritzventil im Längsschnitt als Beispiel für einen gehärteten Ventilkörper dargestellt.In the drawing, a fuel injection valve is shown in longitudinal section as an example of a hardened valve body.
Beschreibung des AusführungsbeispielsDescription of the embodiment
Das in Figur 1 dargestellte Kraftstoffeinspritzventil weist einen Ventilkörper 1 auf , in dem in einer Bohrung 3 eine Ventilnadel 5 längsverschiebbar angeordnet ist. Am brenn- raumseitigen Ende der Bohrung 3 ist ein im wesentlichen konischer Ventilsitz 9 ausgebildet, in dem wenigstens eine Einspritzöffnung 11 ausgebildet ist, die die Bohrung 3 mit dem Brennraum der Brennkraftmaschine verbindet. Die Ventilnadel 5 weist einen Führungsabschnitt 15 auf, mit dem sie in einen führenden Abschnitt 23 der Bohrung 3 dichtend geführt ist. In Richtung des Ventilsitzes 9 verjüngt sich die Ventilnadel 5 unter Bildung einer Druckschulter 13 und geht in einen im Durchmesser verminderten Schaftabschnitt 17 über. An ihrem Ende ist an der Ventilnadel 5 eine im wesentlichen konische Ventildichtfläche 7 ausgebildet, die mit dem Ventilsitz 9 zusammenwirkt und so bei Anlage am Ventilsitz 9 die wenigstens eine Einspritzöffnung 11 gegenüber der Bohrung 3 verschließt.The fuel injection valve shown in FIG. 1 has a valve body 1, in which a valve needle 5 is arranged to be longitudinally displaceable in a bore 3. At the end of the bore 3 on the combustion chamber side, an essentially conical valve seat 9 is formed, in which at least one injection opening 11 is formed, which connects the bore 3 with the combustion chamber of the internal combustion engine. The valve needle 5 has a guide section 15 with which it is sealingly guided in a leading section 23 of the bore 3. In the direction of the valve seat 9, the valve needle 5 tapers to form a pressure shoulder 13 and merges into a shaft section 17 with a reduced diameter. At its end, an essentially conical valve sealing surface 7 is formed on the valve needle 5, which cooperates with the valve seat 9 and thus closes the at least one injection opening 11 with respect to the bore 3 when it contacts the valve seat 9.
Auf Höhe der Druckschulter 13 ist durch eine radiale Erweiterung der Bohrung 3 ein Druckraum 19 ausgebildet, der über einen Zulaufkanal 25 mit Kraftstoff unter hohem Druck befüllt werden kann. Der Druckraum 19 setzt sich dem Ventilsitz 9 zu als Ringkanal 21 fort, der den Schaftabschnitt 17 der Ventilnadel 3 umgibt. Auf diese Weise fließt der Kraftstoff aus dem Zulaufkanal 25 durch den Druckraum 19 und den Ringkanal 21 bis zum Ventilsitz 9 und, falls die Ventildichtfläche 7 vom Ventilsitz 9 abgehoben ist, durch die Ein- spritzöffnungen 11 in den Brennraum der Brennkraftmaschine. Die Ventilnadel 5 wird durch das Verhältnis der hydraulischen Kräfte auf die Druckschulter 13 und die Ventildichtfläche 7 einerseits und einer Schließkraft andererseits gesteuert, welche auf das brennraumabgewandte Ende der Ventilnadel 5 einwirkt und die Ventilnadel 5 in Richtung des Ventilsitzes 9 beaufschlagt. Ein möglicher Betriebszustand des Kraftstoffeinspritzventils ist der, dass die Schließkraft auf die Ventilnadel 5 konstant bleibt, während sich der Kraftstoffdruck im Druckraum 19 und im Ringkanal 21 durch nachgeführten Kraftstoff aus dem Zulaufkanal 25 ändert. Durch den Kraftstoffdruck im Druckraum 19 und im Bereich des Ventilsitzes 9 erfährt die Ventilnadel 5 eine hydraulische Kraft, die vom Ventilsitz 9 weggerichtet ist. Ist diese hydraulische Kraft größer als die Schließkraft auf die Ventilnadel 5, so bewegt sich diese vom Ventilsitz 9 weg und hebt somit mit der Ventildichtfläche 7 vom Ventilsitz 9 ab. Unterschreitet der Druck im Druckraum 19 einen bestimmten Schwelldruck, so überwiegt die Schließkraft auf die Ventilnadel 5 und sie bewegt sich wieder in Richtung des Ventilsitzes 9, bis die Ventildichtfläche 7 die wenigstens eine Einspritzöffnung 11 erneut verschließt.At the level of the pressure shoulder 13, a radial expansion of the bore 3 forms a pressure chamber 19 which can be filled with fuel under high pressure via an inlet channel 25. The pressure chamber 19 continues to the valve seat 9 as an annular channel 21 which surrounds the shaft section 17 of the valve needle 3. In this way, the fuel flows from the inlet channel 25 through the pressure chamber 19 and the annular channel 21 to the valve seat 9 and, if the valve sealing surface 7 is lifted off the valve seat 9, through the injection openings 11 into the combustion chamber of the internal combustion engine. The valve needle 5 is controlled by the ratio of the hydraulic forces on the pressure shoulder 13 and the valve sealing surface 7 on the one hand and a closing force on the other hand, which acts on the end of the valve needle 5 facing away from the combustion chamber and acts on the valve needle 5 in the direction of the valve seat 9. One possible operating state of the fuel injection valve is that the closing force on the valve needle 5 remains constant, while the fuel pressure in the pressure chamber 19 and in the annular channel 21 changes due to fuel being supplied from the inlet channel 25. Due to the fuel pressure in the pressure chamber 19 and in the region of the valve seat 9, the valve needle 5 experiences a hydraulic force which is directed away from the valve seat 9. If this hydraulic force is greater than the closing force on the valve needle 5, it moves away from the valve seat 9 and thus lifts off from the valve seat 9 with the valve sealing surface 7. If the pressure in the pressure chamber 19 falls below a certain threshold pressure, the closing force on the valve needle 5 predominates and it moves again in the direction of the valve seat 9 until the valve sealing surface 7 closes the at least one injection opening 11 again.
Durch die Längsbewegung der Ventilnadel 5 und das relativ harte Aufsetzen der Ventilnadel 5 auf den Ventilsitz 9 ergeben sich im Bereich des Ventils 9 hohe Kräfte auf den Ventilkörper 1. Darüber hinaus ergibt sich durch die Längsbewegung der Ventilnadel 5 im führenden Abschnitt 23 der Bohrung 3 Reibungsverluste zwischen der Ventilnadel 5 und der Wand der Bohrung 3 , was bei einem weichen Material des Ventilkörpers 1 zu einem unzulässig hohen Verschleiß führen kann. Um die Härte und damit die Verschleißfestigkeit zu erhöhen, verwendet man für den Ventilkörper 1 einen sogenannten Warm- arbeitsstahl, der zu den Werkzeugstählen gehört. Besonders vorteilhaft hat sich die Verwendung von hochlegierten Warm- arbeitsstählen erwiesen, wie beispielsweise des Stahls X 40 CrMoV 51. Dieser hochlegierte Warmarbeitsstahl kann Arbeitstemperaturen von bis zu 450 °C ausgesetzt werden, ohne dabei an Härte und damit an Verschleißfestigkeit zu verlieren. Um jedoch die erforderlichen Qualitätsanforderungen für Kraftstoffeinspritzventile zu erreichen, muss die Oberfläche des Ventilkörpers 1 zusätzlich gehärtet werden. Hierzu wird in die oberflächennahen Schichten des Ventilkörpers 1 Kohlenstoff in einem sogenannten Aufkohlverfahren eingebracht, wodurch die Oberfläche härtbar wird. Ein mögliches Aufkohlverfahren ist das Gasaufkohlverfahren, bei dem der Stahl bei einer Temperatur von 900 °C bis 1000 °C einer Atmosphäre aus Kohlenwasserstoffen und chemisch inerten Gasen, wie beispielsweise Stickstoff ( 2), ausgesetzt wird. Dabei diffundiert der Kohlenstoff in die oberflächennahen Schichten des Ventilkörpers 1 ein, so dass dort der Kohlenstoffgehalt ansteigt. Die Einhärtungstiefen betragen hierbei 0,3 bis 4 mm. Durch das Aufkohlen wird der Werkstoff härtbar, was durch ein anschließendes Heizen im Vakuumofen durchgeführt wird. Hierbei wird das Werkstück, in diesem Fall der Ventilkörper 1, auf ca. 800 °C erwärmt, wobei in dem Härtungsofen weitgehend Vakuum herrscht, auf jeden Fall ein Druck von weniger als 100 Pa.The longitudinal movement of the valve needle 5 and the relatively hard placement of the valve needle 5 on the valve seat 9 result in high forces on the valve body 1 in the region of the valve 9. In addition, the longitudinal movement of the valve needle 5 in the leading section 23 of the bore 3 results in friction losses between the valve needle 5 and the wall of the bore 3, which can lead to an impermissibly high wear with a soft material of the valve body 1. In order to increase the hardness and thus the wear resistance, a so-called hot working steel, which belongs to the tool steels, is used for the valve body 1. The use of high-alloy hot-work steels, such as X 40 steel, has proven to be particularly advantageous CrMoV 51. This high-alloy hot-work steel can be exposed to working temperatures of up to 450 ° C without losing hardness and therefore wear resistance. However, in order to achieve the required quality requirements for fuel injection valves, the surface of the valve body 1 must be additionally hardened. For this purpose, carbon is introduced into the layers of the valve body 1 near the surface in a so-called carburizing process, as a result of which the surface becomes hardenable. A possible carburizing process is the gas carburizing process, in which the steel is exposed to an atmosphere of hydrocarbons and chemically inert gases, such as nitrogen (2), at a temperature of 900 ° C. to 1000 ° C. The carbon diffuses into the layers of the valve body 1 near the surface, so that the carbon content increases there. The hardening depths are 0.3 to 4 mm. The carburizing makes the material hardenable, which is carried out by subsequent heating in a vacuum furnace. In this case, the workpiece, in this case the valve body 1, is heated to approximately 800 ° C., the vacuum largely prevailing in the hardening furnace, in any case a pressure of less than 100 Pa.
Der Vorteil dieses Härtungsverfahrens des Ventilkörpers 1 besteht in der Kombination eines hochlegierten Warmarbeits- stahls mit einem Gasaufkohlverfahren, das mit Unterdruck arbeitet, also bei einem Druck von weniger als 100 kPa. Hierdurch addieren sich die Vorteile des Warmarbeitsstahls mit denen des Aufkohl- und Härtverfahrens. Man erhält eine deutliche Steigerung der Schwingfestigkeit des hochlegierten Stahls durch reduzierte Kerbwirkung beim Einsatz des UnterdruckaufkohlVerfahrens , da Randoxidationen vermieden werden. Gleichzeitig erhält man eine Reduzierung der Abträge bei der anschließenden Schleifbearbeitung an den Funktionsgeometrien, da die Einspritzöffnung 11 durch hydroerosives Schleifen nachbearbeitet wird. Ein weiterer Vorteil ist die Reduzierung der notwendigen Ausgangshärte des Kraftstoffeinspritzventils und damit eine verbesserte Bearbeitbarkeit nach der Wärmebehandlung des Ventilkörpers 1. Man erhält auch eine Reduzierung der Kavitationsempfindlichkeit der Oberflächen speziell im Zulauf- bohrungs- und Nadelsitzbereich des Ventilkörpers 1.The advantage of this hardening method of the valve body 1 consists in the combination of a high-alloy hot-work steel with a gas carburizing method that works with negative pressure, that is to say at a pressure of less than 100 kPa. This adds the advantages of hot-work steel to those of the carburizing and hardening process. A significant increase in the fatigue strength of the high-alloy steel is achieved through a reduced notch effect when using the vacuum carburizing process, since edge oxidation is avoided. At the same time, there is a reduction in the stock removal during the subsequent grinding on the functional geometries, since the injection opening 11 is reworked by hydroerosive grinding. Another advantage is the reduction in the necessary initial hardness of the fuel injection valve and thus an improved machinability after the heat treatment of the valve body 1. A reduction in the cavitation sensitivity of the surfaces is also obtained, especially in the inlet bore and needle seat area of the valve body 1.
Neben dem hochlegierten Warmarbeitsstahl X 40 CrMoV 51 können auch andere hochlegierte Warmarbeitsstähle verwendet werden, die einen Kohlenstoffgehalt von 0,3 bis 0,5 % aufweisen. In addition to the high-alloy hot-work steel X 40 CrMoV 51, other high-alloy hot-work steels with a carbon content of 0.3 to 0.5% can also be used.

Claims

Patentansprüche claims
1. Kraftstoffeinspritzventil für Brennkraftmaschinen mit einem Ventilkörper (1) und wenigstens einer darin ausgebildeten Einspritzöffnung (11) , durch die gesteuert durch eine Ventilnadel (5) , die mit einem im Ventilkörper (1) ausgebildeten Ventilsitz (9) zusammenwirkt, Kraftstoff in den Brennraum der Brennkra tmaschine eingespritzt werden kann, wobei der Ventilkörper (1) aus einem Stahl besteht, dadurch gekennzeichnet, dass der Stahl ein hochlegierter Warmarbeitsstahl ist, der durch ein Aufkohlverfahren gehärtet worden ist.1. Fuel injection valve for internal combustion engines with a valve body (1) and at least one injection opening (11) formed therein, controlled by a valve needle (5) which cooperates with a valve seat (9) formed in the valve body (1), fuel into the combustion chamber the internal combustion engine can be injected, the valve body (1) consisting of a steel, characterized in that the steel is a high-alloy hot-work steel which has been hardened by a carburizing process.
2. Kraftstoffeinspritzventil nach Anspruch 1, dadurch gekennzeichnet, dass der Warmarbeitsstahl bis zu einer Temperatur von 450 °C form- und verschleißbeständig ist.2. Fuel injection valve according to claim 1, characterized in that the hot-work steel is dimensionally and wear-resistant up to a temperature of 450 ° C.
3. Kraftstoffeinspritzventil nach Anspruch 2, dadurch gekennzeichnet, dass der Warmarbeitsstahl zumindest näherungsweise 0,4 % Kohlenstoff, 5 % Chrom, 1 % Molybdän und sonstige metallische und nicht metallische Elemente in Spuren von insgesamt weniger als 1 % enthält, wobei der zu 100 % fehlende Anteil Eisen ist.3. Fuel injection valve according to claim 2, characterized in that the hot working steel contains at least approximately 0.4% carbon, 5% chromium, 1% molybdenum and other metallic and non-metallic elements in traces of less than 1% in total, the 100% iron is missing.
4. Kraftstoffeinspritzventil nach Anspruch 1, dadurch gekennzeichnet, dass das Aufkohlverfahren ein Gasaufkohlverfahren ist.4. Fuel injection valve according to claim 1, characterized in that the carburizing process is a gas carburizing process.
5. Verfahren zur Härtung eines Ventilkörpers (1), der Teil eines Kraftstoffeinspritzventils für Brennkraftmaschinen ist und aus einem hochlegierten Warmarbeitsstahl gefertigt ist, gekennzeichnet durch folgende Verfahrensschritte: Aufkohlen des Ventilkörpers in einer Gasatmosphäre, die einen Kohlenwasserstoff enthält,5. A method for hardening a valve body (1) which is part of a fuel injection valve for internal combustion engines and is made from a high-alloy hot-work steel, characterized by the following method steps: Carburizing the valve body in a gas atmosphere containing a hydrocarbon,
Wärmebehandlung des Ventilkörpers bei einer Temperatur von 900 bis 1000 °C bei einem Druck von weniger alsHeat treatment of the valve body at a temperature of 900 to 1000 ° C at a pressure of less than
100 Pa. Verfahren nach Anspruch 7, dadurch gekennzeichnet, dass das Aufkohlen bei einem Druck von weniger als 100 kPa stattfindet. 100 Pa. A method according to claim 7, characterized in that the carburizing takes place at a pressure of less than 100 kPa.
EP02748600A 2001-08-11 2002-06-19 Fuel injection valve for internal combustion engines and a method for manufacturing said valve Expired - Lifetime EP1419314B1 (en)

Applications Claiming Priority (3)

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DE10139620 2001-08-11
DE10139620A DE10139620A1 (en) 2001-08-11 2001-08-11 Fuel injection valve for internal combustion engines and a method for hardening the same
PCT/DE2002/002239 WO2003016708A1 (en) 2001-08-11 2002-06-19 Fuel injection valve for internal combustion engines and a method for hardening said valve

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JP (1) JP2004538423A (en)
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EP1419314B1 (en) 2007-06-06
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CN100365268C (en) 2008-01-30
CN1464942A (en) 2003-12-31
BR0205866A (en) 2003-10-21
US7419553B2 (en) 2008-09-02
JP2004538423A (en) 2004-12-24
BR0205866B1 (en) 2011-02-08
US20040050456A1 (en) 2004-03-18
WO2003016708A1 (en) 2003-02-27

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