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EP1094908A1 - Method for the production of a steel camshaft and camshaft produced according to said method - Google Patents

Method for the production of a steel camshaft and camshaft produced according to said method

Info

Publication number
EP1094908A1
EP1094908A1 EP99947245A EP99947245A EP1094908A1 EP 1094908 A1 EP1094908 A1 EP 1094908A1 EP 99947245 A EP99947245 A EP 99947245A EP 99947245 A EP99947245 A EP 99947245A EP 1094908 A1 EP1094908 A1 EP 1094908A1
Authority
EP
European Patent Office
Prior art keywords
camshaft
steel
casting
pouring
molds
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
EP99947245A
Other languages
German (de)
French (fr)
Other versions
EP1094908B1 (en
Inventor
Martin Basler
Ulrich Engelhart
Peter Grahle
Volker Korte
Jürgen Schmid
Matthias Vogelsang
Jens WIESENMÜLLER
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.)
Mahle Ventiltrieb GmbH
Original Assignee
Mahle Ventiltrieb 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
Application filed by Mahle Ventiltrieb GmbH filed Critical Mahle Ventiltrieb GmbH
Publication of EP1094908A1 publication Critical patent/EP1094908A1/en
Application granted granted Critical
Publication of EP1094908B1 publication Critical patent/EP1094908B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • B22C9/04—Use of lost patterns
    • B22C9/046—Use of patterns which are eliminated by the liquid metal in the mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
    • B22C7/02—Lost patterns
    • B22C7/023—Patterns made from expanded plastic materials
    • B22C7/026—Patterns made from expanded plastic materials by assembling preformed parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F7/00—Casings, e.g. crankcases or frames
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F2200/00—Manufacturing
    • F02F2200/06—Casting
    • F02F2200/08—Casting using a lost model, e.g. foam casting

Definitions

  • the invention relates to a method for producing a one-piece, profiled hollow camshaft made of steel.
  • Profiled means that the camshaft is tubular with a profiled inner surface that corresponds to the contours of the cams and the bearing areas on the camshaft in a certain sense.
  • Steel camshafts are known, for example, from JP 02 102 302 A.
  • camshafts are suitable and intended for valve drives of internal combustion engines in which the valve is actuated in particular via a roller contact to the camshaft.
  • camshafts are required that can withstand Hertzian surface pressures of up to 2,500 MPa throughout the engine life without damaging the tread.
  • the design as a hollow camshaft has the advantage, on the one hand, of saving weight and, on the other hand, of being able to lubricate through the camshaft. From JP 61 115 660 A and JP 62 296 935 A it is known to manufacture metal cam shafts in a lost foam casting process.
  • the invention is concerned with the problem of being able to produce a generic camshaft as efficiently as possible.
  • a gate system according to claim 2 is of particular importance for casting production.
  • the casting molds are based on the principle of the lost foam casting system. This means that the camshaft is created and used as a lost form from, for example, a polymer blank with an external small amount of material for the finishing. This blank, which dissolves when pouring the cast steel, is placed in a sand form inserted, the hollow interior also being filled with sand.
  • the polymer used is one that has a special chemical composition that prevents harmful carburizing processes when pouring the molten steel. As a result, the high geometric requirements for the casting mold required when carrying out the teaching according to the invention are met.
  • a special sprue system according to the subclaims is used according to the invention, by means of which it is possible to cast a large number of camshafts, for example more than 50, at the same time.
  • the plug-in system shown in the subclaims is used.
  • the use of adhesive can be dispensed with, which has an advantageous effect on the casting quality.
  • Fig. 1 shows a sand mold box without sand with a mold consisting of a large number of individual, interconnected molds.
  • the mold device shown consists of a central, vertically aligned filling channel 1 for liquid casting material to be filled into the device, which is connected at its lower end via horizontally star-shaped connecting channels 2 with pouring channels 3 for the camshaft molds 4.
  • All of the above-mentioned parts consist of material that melts under the casting material, such as, for example, a polymer known from lost foam casting processes. However, it can be expedient to design the filler channel 1 from a non-melting material.
  • the camshaft molds 4 are arranged axially parallel to the respective pouring channel 3, around which they are distributed, and are connected to the latter via its height via a plurality of gate connections 5.
  • the individual pouring channels 3, of which a large number may be present, are each closed at their upper ends with a ceramic stopper 6 as a throttle valve.
  • the parts 1, 2, 3, 4 and possibly also 5 of the casting device which melt during the execution of the casting process are each coated on their surfaces with a size-acting size.
  • the material of this size also ensures sufficient permeability of the gases formed when the lost molded parts, ie the polymer parts, are dissolved. This simple ensures, in particular, a high surface quality of the camshafts produced according to the invention.
  • a molding box 7 is filled with sand in such a way that all meltable molded parts are completely enclosed by sand.
  • Fully enclosed in the case of the camshaft casting molds means that they are also completely filled with sand in their inner, profiled cavity.
  • the sand surrounding the molded parts is merely poured into the molding box 7 as loose sand and is not pressed there in any particular way.
  • the molding box 7 vibrates to achieve a good molding sand distribution.
  • the individual parts of the pouring device are simply non-positively inserted into one another.
  • the filling channel 1 is plugged into a composite part formed from the connecting channels 2 and the pouring channels 3 into the connecting channels 2.
  • the camshaft casting molds 4 are also only plugged into the respective pouring channel 3, specifically via the gate connections 5. Even the camshaft casting shapes 4 can be built up from individual parts in the axial direction and put together.
  • the sequence of filling a pouring device molded in sand inside a molding box 7 is as follows.
  • Liquid casting material is introduced into the filler channel 1 and passes through the connecting channels 2 from below into the pouring channels 3. From there, the casting material penetrates through the gate connections 5 into the individual camshaft casting molds 4, the casting material being uniform in the respective pouring channel 3 and with it connected camshaft molds 4 rises.
  • the ceramic plug 6 creates a certain casting pressure above atmospheric pressure when the casting material penetrates into the pouring channels 3. Under the heat of the casting material, the individual molded parts of the casting device dissolve in a manner which is customary in the lost foam casting process known per se. In order to achieve good casting quality and to ensure sufficient dimensional stability of the casting device during the casting process, the size coating on the individual molded parts is of particular importance.
  • the casting material in the form of the casting device can simply be pulled out of the sand bed of the molding box 7 and completely removed from the casting sand by shaking.
  • This provides an extremely efficient manufacturing process.
  • more than 50 camshafts can be produced in a single system arrangement in a single casting process.
  • the individual camshafts must of course still be mechanically freed from the respective sprues or sprue channels after their manufacture in the casting process described.
  • this is possible in a simple, customary manner.
  • a particularly favorable material for a camshaft that can be produced according to the invention has the following composition in% by weight:
  • camshafts are mechanically pre-processed at the bearing points and the cam running points, solidified at the edge layer by, for example, inductive hardening, case hardening, carbonitriding or other comparable processes and then finished. Finishing is expediently carried out by grinding.
  • camshafts according to the invention have a typical surface relief which is known from styrofoam parts at locations which are not machined. The cavity of the camshaft is not machined. In places of the camshaft that are not specially hardened at the surface, the surface hardness is 150 to 400 HB.
  • the size of the casting defects is limited to 0.1 mm by the method according to the invention in a range of 1 mm below the cam surfaces.
  • the hardness of the cam surface is between 35 and 70 HRC, depending on the surface pressure required.
  • the cam surface typically has residual stresses between 50 and 600 MPa.
  • the structure of the camshaft according to the invention is ferritic-pearlitic or ledeburitic. In the area of surface hardening, there are typically martensitic or bainitic structures.
  • C, N or B contents increased by 0.1 to 3% can also be present in this area.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Gears, Cams (AREA)
  • Valve-Gear Or Valve Arrangements (AREA)

Abstract

The invention relates to a camshaft made of cast steel having an inner cavity with a cylindrical inner shape, especially a profiled cylindrical inner shape produced rationally according to a lost-foam casting method known per se. A steel camshaft thus produced exhibits a long service life and can withstand extremely high hertzian surface pressures on its bearing surfaces without any damages.

Description

VERFAHREN ZUR HERSTELLUNG EINER NOCKENWELLE AUS STAHL UND NACH DIESEM VERFAHREN HERGESTELLTE NOCKENWELLEMETHOD FOR PRODUCING A STEEL CAMSHAFT AND CAMSHAFT PRODUCED BY THIS METHOD
Die Erfindung betrifft ein Verfahren zu Herstellung einer einstückigen, profiliert hohlen Nockenwelle aus Stahl. Profiliert bedeutet, daß die Nockenwelle rohrförmig ausgeführt ist mit einer profilierten Innenmantelfläche, die den Konturen der Nocken und der Lagerbereiche auf der Nockenwelle in gewissem Sinne entspricht.The invention relates to a method for producing a one-piece, profiled hollow camshaft made of steel. Profiled means that the camshaft is tubular with a profiled inner surface that corresponds to the contours of the cams and the bearing areas on the camshaft in a certain sense.
Nockenwellen aus Stahl sind beispielsweise bekannt aus JP 02 102 302 A.Steel camshafts are known, for example, from JP 02 102 302 A.
Gattungsgemäße Nockenwellen sind geeignet und bestimmt für Ventiltriebe von Verbrennungsmotoren, bei denen die Ventilbetätigung insbesondere über einen Rollenkontakt zur Nockenwelle erfolgt. In diesen Fällen werden Nockenwellen benötigt, die Hertzsche Flächenpressungen von bis zu 2.500 MPa während der gesamten Motorlebensdauer ohne Laufflächenbe- schädigungen ertragen können. Die Ausführung als hohle Nokkenwelle besitzt den Vorteil, einerseits Gewicht einzusparen und andererseits durch die Nockenwelle hindurch schmieren zu können. Aus JP 61 115 660 A und JP 62 296 935 A ist es bekannt, Nokkenwellen aus Metall in einem Lost Foam-Gießverfahren herzustellen.Generic camshafts are suitable and intended for valve drives of internal combustion engines in which the valve is actuated in particular via a roller contact to the camshaft. In these cases, camshafts are required that can withstand Hertzian surface pressures of up to 2,500 MPa throughout the engine life without damaging the tread. The design as a hollow camshaft has the advantage, on the one hand, of saving weight and, on the other hand, of being able to lubricate through the camshaft. From JP 61 115 660 A and JP 62 296 935 A it is known to manufacture metal cam shafts in a lost foam casting process.
Die Erfindung beschäftigt sich mit dem Problem, eine gattungsgemäße Nockenwelle möglichst rationell herstellen zu können.The invention is concerned with the problem of being able to produce a generic camshaft as efficiently as possible.
Gelöst wird dieses Problem durch ein Herstellungsverfahren mit den Merkmalen des Patentanspruchs 1.This problem is solved by a manufacturing method with the features of claim 1.
Zweckmäßige Ausgestaltungen des erfindungsgemäßen Herstellungsverfahrens sind Gegenstand der Unteransprüche.Appropriate embodiments of the manufacturing method according to the invention are the subject of the dependent claims.
Der letzte Patentanspruch zeigt eine nach dem erfindungsgemäßen Verfahren hergestellte gattungsgemäße Nockenwelle mit einer besonders vorteilhaften Materialzusammensetzung auf.The last patent claim shows a generic camshaft produced by the method according to the invention with a particularly advantageous material composition.
Für die Gußherstellung ist ein Anschnittsystem nach dem Patentanspruch 2 von besonderer Bedeutung.A gate system according to claim 2 is of particular importance for casting production.
Die Gießformen sind nach dem Prinzip des Lost Foam- Gießsystems aufgebaut. Dies bedeutet, daß die Nockenwelle mit einer äußeren geringen Materialzugabe für die Endbearbeitung als verlorene Form aus beispielsweise einem Polymer- Rohling erstellt und eingesetzt wird. Dieser sich beim Einfüllen des Stahlgusses auflösende Rohling wird in eine Sand- form eingelegt, wobei auch der hohle Innenraum mit Sand ausgefüllt wird.The casting molds are based on the principle of the lost foam casting system. This means that the camshaft is created and used as a lost form from, for example, a polymer blank with an external small amount of material for the finishing. This blank, which dissolves when pouring the cast steel, is placed in a sand form inserted, the hollow interior also being filled with sand.
Als Polymer wird ein solches eingesetzt, das eine spezielle chemische Zusammensetzung aufweist, durch die schädliche Aufkohlungsprozesse beim Eingießen des flüssigen Stahls verhindert werden. Hierdurch werden die bei der Durchführung der erfindungsgemäßem Lehre erforderlichen hohen geometrischen Anforderungen an die Gießform erfüllt.The polymer used is one that has a special chemical composition that prevents harmful carburizing processes when pouring the molten steel. As a result, the high geometric requirements for the casting mold required when carrying out the teaching according to the invention are met.
Zur Verhinderung von Gießfehlstellen und auch aus wirtschaftlichen Gründen wird erfindungsgemäß ein spezielles Angußsystem entsprechend den Unteransprüchen eingesetzt, durch das es möglich ist, eine Vielzahl von Nockenwellen, beispielsweise mehr als 50, gleichzeitig abzugießen. Zur Gewährleistung der Stabilität einer sogenannten Traube aus mehr als 50 Nockenwellenrohlingen mit Angußsystem dient das in den Unteransprüchen aufgezeigte Stecksystem. Dabei kann auf die Verwendung von Klebstoff verzichtet werden, was sich vorteilhaft auf die Gußqualität auswirkt.To prevent casting defects and also for economic reasons, a special sprue system according to the subclaims is used according to the invention, by means of which it is possible to cast a large number of camshafts, for example more than 50, at the same time. To ensure the stability of a so-called grape made of more than 50 camshaft blanks with sprue system, the plug-in system shown in the subclaims is used. The use of adhesive can be dispensed with, which has an advantageous effect on the casting quality.
Ein Ausführungsbeispiel für das erfindungsgemäße Verfahren ist in der Zeichnung dargestellt.An embodiment of the method according to the invention is shown in the drawing.
In dieser zeigt in schematischer Darstellung die einzigeThis shows the only one in a schematic representation
Fig. 1 einen Sandformkasten ohne Sand mit einer aus einer Vielzahl einzelner, untereinander verbundener Gießformen bestehenden Gießform-Einrichtung. Die dargestellte Gießform-Einrichtung besteht aus einem zentralen, lotrecht ausgerichteten Einfüllkanal 1 für in die Einrichtung einzufüllendes flüssiges Gußmaterial, der an seinem unteren Ende über horizontal sternförmig abzweigende Verbindungskanäle 2 mit Eingießkanälen 3 für die Nockenwelle-Gießformen 4 verbunden ist. Sämtliche vorgenannten Teile bestehen aus unter dem Gußmaterial aufschmelzendem Material wie beispielsweise einem bei Lost Foam-Gießverfahren bekannten Polymer. Allerdings kann es zweckmäßig sein, den Einfüllkanal 1 aus einem nicht schmelzendem Material auszubilden.Fig. 1 shows a sand mold box without sand with a mold consisting of a large number of individual, interconnected molds. The mold device shown consists of a central, vertically aligned filling channel 1 for liquid casting material to be filled into the device, which is connected at its lower end via horizontally star-shaped connecting channels 2 with pouring channels 3 for the camshaft molds 4. All of the above-mentioned parts consist of material that melts under the casting material, such as, for example, a polymer known from lost foam casting processes. However, it can be expedient to design the filler channel 1 from a non-melting material.
Die Nockenwellengießformen 4 sind achsparallel zu dem jeweiligen Eingießkanal 3, um den sie verteilt sind, angeordnet und mit diesem über dessen Höhe über mehrere Anschnitt- Verbindungen 5 verbunden.The camshaft molds 4 are arranged axially parallel to the respective pouring channel 3, around which they are distributed, and are connected to the latter via its height via a plurality of gate connections 5.
Die einzelnen Eingießkanäle 3, von denen eine Vielzahl vorhanden sein kann, sind an ihren oberen Enden jeweils mit einem Keramikstopfen 6 als Drosselventil verschlossen.The individual pouring channels 3, of which a large number may be present, are each closed at their upper ends with a ceramic stopper 6 as a throttle valve.
Die während der Durchführung des Gießverfahrens aufschmelzenden Teile 1, 2, 3, 4, und gegebenenfalls auch 5 der Gießeinrichtung sind an ihren Oberflächen jeweils mit einer formstabil wirkenden Schlichte überzogen. Das Material dieser Schlichte sorgt im übrigen für eine ausreichende Permeabilität der beim Auflösen der verlorenen Formteile, das heißt der Polymerteile, sich bildenden Gase. Diese Schlichte sorgt insbesondere für eine hohe Oberflächengüte der erfindungsgemäß erzeugten Nockenwellen.The parts 1, 2, 3, 4 and possibly also 5 of the casting device which melt during the execution of the casting process are each coated on their surfaces with a size-acting size. The material of this size also ensures sufficient permeability of the gases formed when the lost molded parts, ie the polymer parts, are dissolved. This simple ensures, in particular, a high surface quality of the camshafts produced according to the invention.
Vor dem Füllen der Gießeinrichtung mit flüssigem Gußmaterial wird ein Formkasten 7 mit Sand derart aufgefüllt, daß sämtliche ausschmelzbaren Formteile vollständig von Sand eingeschlossen sind. Vollständig eingeschlossen bedeutet bei den Nockenwellengießformen, daß diese jeweils auch in ihrem inneren, profilierten Hohlraum vollständig mit Sand ausgefüllt sind. Der die Formteile umschließende Sand wird lediglich als loser Sand in den Formkasten 7 eingefüllt und dort in keiner besonderen Weise verpreßt. Während des Einfüllens des Formsandes vibriert der Formkasten 7 zur Erzielung einer guten Formsandverteilung.Before the pouring device is filled with liquid casting material, a molding box 7 is filled with sand in such a way that all meltable molded parts are completely enclosed by sand. Fully enclosed in the case of the camshaft casting molds means that they are also completely filled with sand in their inner, profiled cavity. The sand surrounding the molded parts is merely poured into the molding box 7 as loose sand and is not pressed there in any particular way. During the filling of the molding sand, the molding box 7 vibrates to achieve a good molding sand distribution.
Bei für das Einfüllen des Gießmaterials vorbereitetem Zustand des Formkastens mit darin befindlicher Gießeinrichtung ragen lediglich die, die Eingießkanäle 3 verschließenden Keramikstopfen 6 und ein Einfülltrichter des zentralen Ein- füllkanales 1 aus dem eingefüllten Sand heraus.When the mold box with the casting device located therein is prepared for the pouring of the casting material, only the ceramic plugs 6 closing the pouring channels 3 and a filling funnel of the central filling channel 1 protrude from the filled sand.
Die einzelnen Teile der Gießeinrichtung sind, soweit sie nicht einstückig hergestellt sind, einfach kraftschlüssig ineinandergesteckt . Ineinandergesteckt sind insbesondere der Einfüllkanal 1 in ein aus den Verbindungskanälen 2 gebildetes Verbundteil sowie die Eingießkanäle 3 in die Verbindungskanäle 2. Auch die Nockenwellengießformen 4 sind an den jeweiligen Eingießkanal 3 lediglich angesteckt und zwar über die Anschnitt-Verbindungen 5. Selbst die Nockenwellengieß- formen 4 können aus Einzelteilen in axialer Richtung aufgebaut und zusammengesteckt sein.Unless they are made in one piece, the individual parts of the pouring device are simply non-positively inserted into one another. In particular, the filling channel 1 is plugged into a composite part formed from the connecting channels 2 and the pouring channels 3 into the connecting channels 2. The camshaft casting molds 4 are also only plugged into the respective pouring channel 3, specifically via the gate connections 5. Even the camshaft casting shapes 4 can be built up from individual parts in the axial direction and put together.
Der Ablauf des Befüllens einer innerhalb eines Formkastens 7 in Sand eingeformten Gießeinrichtung stellt sich wie folgt dar.The sequence of filling a pouring device molded in sand inside a molding box 7 is as follows.
Flüssiges Gießmaterial wird in den Einfüllkanal 1 eingeführt und gelangt über die Verbindungskanäle 2 von unten in die Eingießkanäle 3. Von dort dringt das Gießmaterial durch die Anschnittverbindungen 5 in die einzelnen Nockenwellengießformen 4 ein, wobei das Gießmaterial gleichmäßig in dem jeweiligen Eingießkanal 3 und den mit diesem verbundenen Nok- kenwellengießformen 4 aufsteigt. Durch die Keramikstopfen 6 entsteht beim Eindringen des Gießmaterials in die Eingießkanäle 3 in diesen ein gewisser oberhalb Atmosphärendruck liegender Gießdruck. Unter der Hitze des Gießmaterials lösen sich die einzelnen Formteile der Gießeinrichtung in einer Art auf, wie es bei dem an sich bekannten Lost Foam- Gießverfahren an sich üblich ist. Für die Erzielung einer guten Gußqualität sowie die Gewährleistung einer ausreichenden Formstabilität der Gießeinrichtung während des Gießvorganges ist der Schlichten-Überzug auf den einzelnen Formteilen von besonderer Bedeutung.Liquid casting material is introduced into the filler channel 1 and passes through the connecting channels 2 from below into the pouring channels 3. From there, the casting material penetrates through the gate connections 5 into the individual camshaft casting molds 4, the casting material being uniform in the respective pouring channel 3 and with it connected camshaft molds 4 rises. The ceramic plug 6 creates a certain casting pressure above atmospheric pressure when the casting material penetrates into the pouring channels 3. Under the heat of the casting material, the individual molded parts of the casting device dissolve in a manner which is customary in the lost foam casting process known per se. In order to achieve good casting quality and to ensure sufficient dimensional stability of the casting device during the casting process, the size coating on the individual molded parts is of particular importance.
Nach Abschluß des Gießvorganges und Erstarren des Gießmate- riales kann das Gußmaterial in der Form der Gießeinrichtung einfach aus dem Sandbett des Formkastens 7 herausgezogen und durch Rütteln vollständig von dem Gießsand befreit werden. Damit ist ein äußerst rationelles Herstellungsverfahren gegeben. Es können beispielsweise mehr als 50 Nockenwellen in einer einzigen System-Anordnung in einem einzigen Gießvorgang erzeugt werden. Die einzelnen Nockenwellen müssen nach ihrer Herstellung in dem beschriebenen Gießverfahren selbstverständlich noch von den jeweiligen Angüssen bzw. Angußkanälen mechanisch befreit werden. Dies ist jedoch auf einfache, fachübliche Weise möglich.After the casting process has been completed and the casting material has solidified, the casting material in the form of the casting device can simply be pulled out of the sand bed of the molding box 7 and completely removed from the casting sand by shaking. This provides an extremely efficient manufacturing process. For example, more than 50 camshafts can be produced in a single system arrangement in a single casting process. The individual camshafts must of course still be mechanically freed from the respective sprues or sprue channels after their manufacture in the casting process described. However, this is possible in a simple, customary manner.
Ein besonders günstiger Werkstoff für eine erfindungsgemäß herstellbare Nockenwelle besitzt folgende Zusammensetzung in Gewichts-% :A particularly favorable material for a camshaft that can be produced according to the invention has the following composition in% by weight:
Kohlenstoff 0,5 bis 2, 5 %Carbon 0.5 to 2.5%
Chrom 1 bis 18 %Chrome 1 to 18%
Silicium 0,1 bis 1 %Silicon 0.1 to 1%
Mangan 0, 1 bis 1 %Manganese 0.1 to 1%
Molybdän 0,1 bis 2 %Molybdenum 0.1 to 2%
Vanadium 0,1 bis 2 %Vanadium 0.1 to 2%
Wolfram 0,1 bis 2 % sonstige Elemente bis zu 4 %Tungsten 0.1 to 2% other elements up to 4%
Nach dem Gußvorgang werden die Nockenwellen an den Lagerstellen und den Nockenlaufstellen mechanisch vorbearbeitet, randschichtverfestigt durch beispielsweise induktives Härten, Einsatzhärten, Karbonitrieren oder andere vergleichbare Verfahren und sodann fertig bearbeitet. Die Fertigbearbeitung erfolgt zweckmäßigerweise durch Schleifen. Als typisches Merkmal weisen erfindungsgemäße Nockenwellen an Stellen, die nicht mechanisch bearbeitet werden, ein von Styroporteilen her bekanntes, typisches Oberflächenrelief auf. Der Hohlraum der Nockenwelle wird mechanisch nicht bearbeitet. An Stellen der Nockenwelle, die nicht speziell randschichtverfestigt werden, beträgt die Oberflächenhärte 150 bis 400 HB. Die Größe der Gußfehlstellen ist durch das erfindungsgemäße Verfahren in einem Bereich von 1 mm unterhalb der Nockenoberflächen auf 0,1 mm begrenzt. Die Härte der Nockenoberfläche beträgt dort, abhängig von der geforderten Flächenpressung, zwischen 35 und 70 HRC. Die Nokkenoberfläche weist typischerweise Eigenspannungen zwischen 50 und 600 MPa auf. Das Gefüge der erfindungsgemäßen Nockenwelle ist ferritisch-perlitisch oder ledeburitisch. Im Bereich der Randschichtverfestigung liegen typischerweise mar- tensitische oder bainitische Gefüge vor.After the casting process, the camshafts are mechanically pre-processed at the bearing points and the cam running points, solidified at the edge layer by, for example, inductive hardening, case hardening, carbonitriding or other comparable processes and then finished. Finishing is expediently carried out by grinding. As a typical feature, camshafts according to the invention have a typical surface relief which is known from styrofoam parts at locations which are not machined. The cavity of the camshaft is not machined. In places of the camshaft that are not specially hardened at the surface, the surface hardness is 150 to 400 HB. The size of the casting defects is limited to 0.1 mm by the method according to the invention in a range of 1 mm below the cam surfaces. The hardness of the cam surface is between 35 and 70 HRC, depending on the surface pressure required. The cam surface typically has residual stresses between 50 and 600 MPa. The structure of the camshaft according to the invention is ferritic-pearlitic or ledeburitic. In the area of surface hardening, there are typically martensitic or bainitic structures.
Bei speziellen erfindungsgemäßen Ausführungen der Randschichtverfestigung können in diesem Bereich auch um 0,1 bis 3 % erhöhte C-, N- oder B-Gehalte vorliegen. In the case of special embodiments of the surface layer consolidation according to the invention, C, N or B contents increased by 0.1 to 3% can also be present in this area.

Claims

Ansprüche Expectations
1. Verfahren zur Herstellung einer Nockenwelle aus Stahlguß mit einem inneren Hohlraum mit einer insbesondere profilierten, zylindrischen Innenform in einem an sich bekannten „Lost Foam"-Gießverfahren.1. Process for producing a camshaft from cast steel with an inner cavity with a particularly profiled, cylindrical inner shape in a “lost foam” casting process known per se.
2. Verfahren nach Anspruch 1, dadurch geken zeichnet, daß die Nockenwelle in einer innerhalb Formsand stehenden und von dem Formsand um- und ausgefüllten Gießform (4) gegossen wird, wobei der Stahlguß von unten in die Gießform (4) eingeführt wird und wobei ferner über die Höhe der Gießform (4) Anschnitte zu einem achsparallel hierzu verlaufenden Stahl-Eingußkanal (3) vorgesehen sind.2. The method according to claim 1, characterized in that the camshaft is poured into a mold (4) standing inside the molding sand and filled and filled by the molding sand, the steel casting being introduced from below into the casting mold (4) and furthermore Through the height of the casting mold (4), gates to a steel sprue (3) running parallel to it are provided.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Stahl-Eingußkanal (3) von unten mit Stahlguß beaufschlagt wird.3. The method according to claim 1 or 2, characterized in that the steel sprue (3) is acted upon from below with cast steel.
4. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichne , daß der Stahl-Eingußkanal (3) an seinem oberen Ende mit einem Drosselventil zur Erzeugung eines Atmosphärendruck über- steigenden Druckes innerhalb dieses Kanales während des Gießvorganges versehen ist.4. The method according to any one of the preceding claims, characterized in that the steel sprue (3) at its upper end with a throttle valve for generating an atmospheric pressure. increasing pressure within this channel is provided during the casting process.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, daß das Drosselventil ein Keramikstopfen (6) ist.5. The method according to claim 4, characterized in that the throttle valve is a ceramic plug (6).
6. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß über den Umfang eines Stahl-Eingußkanales (3) verteilt mehrere Nockenwellen-Gießformen (4) angeschlossen sind.6. The method according to any one of the preceding claims, characterized in that several camshaft casting molds (4) are connected distributed over the circumference of a steel pouring channel (3).
7. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß mehrere Stahl-Eingußkanäle (4) von einem gemeinsamen, etwa achsparallel zu den Stahl-Eingußkanälen (3) verlaufendem Einfüllkanal (1) versorgt werden.7. The method according to any one of the preceding claims, characterized in that a plurality of steel pouring channels (4) from a common, approximately axially parallel to the steel pouring channels (3) extending filler channel (1) are supplied.
8. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Nockenwellen-Gießformen (4) und die Gießkanäle (1, 2, 3, 5) zumindest teilweise durch lediglich kraftschlüssige Steckverbindungen miteinander verbunden sind.8. The method according to any one of the preceding claims, characterized in that the camshaft molds (4) and the pouring channels (1, 2, 3, 5) are at least partially connected to one another by only non-positive plug connections.
9. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Nockenwellen-Gießformen (4) aus einzelnen, lediglich ineinandergesteckten Einzelteilen bestehen. 9. The method according to any one of the preceding claims, characterized in that the camshaft molds (4) consist of individual, only nested items.
10. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß sämtliche Nockenwellen-Gießformen (4) sowie Gießkanäle (1, 2, 3, 5) lediglich in einem Formkasten mit lose eingebrachtem Gießsand um- und ausgefüllt werden.10. The method according to any one of the preceding claims, characterized in that all the camshaft casting molds (4) and pouring channels (1, 2, 3, 5) are filled and filled only in a molding box with loosely poured pouring sand.
11. Nach dem Verfahren einer der vorhergehenden Ansprüche hergestellte Nockenwelle, gekennzeichnet durch die folgende Legierungzusammensetzung in Gewichts-%:11. Camshaft produced by the method of one of the preceding claims, characterized by the following alloy composition in% by weight:
Kohlenstoff 0,5 bis 2,5 %Carbon 0.5 to 2.5%
Chrom 1 bis 18 %Chrome 1 to 18%
Silicium 0,1 bis 1 %Silicon 0.1 to 1%
Mangan 0, 1 bis 1 %Manganese 0.1 to 1%
Molybdän 0,1 bis 2 %Molybdenum 0.1 to 2%
Vanadium 0,1 bis 2 %Vanadium 0.1 to 2%
Wolfram 0,1 bis 2 % sonstige Elemente bis zu 4 % Tungsten 0.1 to 2% other elements up to 4%
EP99947245A 1998-07-25 1999-07-21 Method for the production of a steel camshaft and camshaft produced according to said method Expired - Lifetime EP1094908B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19833594A DE19833594A1 (en) 1998-07-25 1998-07-25 Cast steel camshaft, especially an i.c. engine camshaft for rolling contact valve operation, has an internal cavity and is produced by a lost foam casting technique
DE19833594 1998-07-25
PCT/DE1999/002244 WO2000006320A1 (en) 1998-07-25 1999-07-21 Method for the production of a steel camshaft and camshaft produced according to said method

Publications (2)

Publication Number Publication Date
EP1094908A1 true EP1094908A1 (en) 2001-05-02
EP1094908B1 EP1094908B1 (en) 2005-09-21

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EP (1) EP1094908B1 (en)
BR (1) BR9912441A (en)
DE (3) DE19833594A1 (en)
WO (1) WO2000006320A1 (en)

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Publication number Publication date
US6478074B1 (en) 2002-11-12
EP1094908B1 (en) 2005-09-21
DE19833594A1 (en) 2000-01-27
DE59912583D1 (en) 2006-02-02
BR9912441A (en) 2001-04-17
DE19981402D2 (en) 2001-07-12
WO2000006320A1 (en) 2000-02-10

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