EP0590262A1 - Explosion assisted hydromechanical deep drawing - Google Patents

Explosion assisted hydromechanical deep drawing Download PDF

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Publication number
EP0590262A1
EP0590262A1 EP93111956A EP93111956A EP0590262A1 EP 0590262 A1 EP0590262 A1 EP 0590262A1 EP 93111956 A EP93111956 A EP 93111956A EP 93111956 A EP93111956 A EP 93111956A EP 0590262 A1 EP0590262 A1 EP 0590262A1
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EP
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Prior art keywords
punch
press
shape
tool
pressure
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Granted
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EP93111956A
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German (de)
French (fr)
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EP0590262B1 (en
Inventor
Volker Dr. Thoms
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Daimler Benz AG
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Daimler Benz AG
Mercedes Benz AG
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Publication of EP0590262A1 publication Critical patent/EP0590262A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • B21D22/205—Hydro-mechanical deep-drawing

Definitions

  • the invention is based on a method for hydromechanical deep-drawing of sheet metal into a shape specified by only one of the two tool parts, preferably the punch, using a press, according to the preamble of claim 1, as is known, for example, from DE-OS 37 09 181 emerges.
  • hydromechanical deep drawing part of the drawing tool, preferably the die, is relatively simple and only needs to be adapted to the opposite tool part with respect to its contact surface, which considerably reduces tool costs.
  • very high pressures in the range from 600 to 1000 bar have to act in order to be able to press the sheet into the engraving of the punch true to shape. After these high pressures are effective over the entire surface of the workpiece, this results in very high forces that are considerably higher than the press loads that occur between the forming punch and the die in purely mechanical deep drawing, because there the load is essentially due to the material cross section in the drawing area and the yield stress of the material is determined.
  • Pressing times of two minutes can easily occur, which are much too long compared to the cycle times of four to six seconds that can be achieved with conventional body presses.
  • a disadvantage of the hydromechanical deep drawing of larger sheet metal parts in presses is that the presses are disproportionately expensive and still not rigid enough and that the process is not productive enough.
  • the object of the invention is to improve the generic method for hydromechanical deep-drawing of sheet metal by means of a press in such a way that the process is significantly increased in productivity and in this respect is approximated to purely mechanical deep-drawing and that the press is relieved of the high forces and is therefore much cheaper to manufacture with reasonable rigidity.
  • the method according to the invention not only represents a combination of the known hydromechanical deep drawing with the known explosion forming, whereby short cycle times and thus high productivity are achieved.
  • the inertial locking of the Stamp and the tool chamber by a correspondingly generous mass allocation, whereby the high, but only briefly acting forming forces are limited to these parts and are kept away from the press construction.
  • the press 1 shown is essentially formed with respect to its static part by a press frame 2 which contains lateral press stands, a press head at the top and a press foot at the bottom.
  • a press frame 2 which contains lateral press stands, a press head at the top and a press foot at the bottom.
  • a die 6 with a large mass is arranged on the press foot as the lower part of the tool. This mass assignment will be discussed in more detail below.
  • a die 7 which can be driven in a stroke direction 24 is required for shaping.
  • the shape with which the sheet 8 introduced into the press 1 is to be deep-drawn is predetermined by the stamp 7.
  • the die 6 arranged opposite the punch is designed in the form of an open tool chamber 9, which can be applied to the inserted sheet 8 in a liquid-tight and gas-tight manner with its upper end-face contact surface. Accordingly, seals are let into the contact surface of the die 6 that comes into contact with the sheet metal 8.
  • the sheet 8 inserted into the press is on its outer edge between this contact surface on the one hand and a correspondingly shaped counter-contact surface of a hold-down frame 5 on the front side of the hold-down bar 4, on the other hand, can be clamped.
  • the hold-down bear 4 is also covered with a very large mass, which will be discussed in more detail below.
  • the hold-down frame 5 is interchangeably screwed to the hold-down bear.
  • the hold-down bar with the hold-down frame is lowered onto the inserted sheet metal and pressed there in a liquid-tight manner and with sustained force.
  • the separately drivable plunger bear 3 is attached with the aforementioned stamp 7, which can be moved up and down within the hold-down bear 4 in the manner of the plunger of a double-acting deep-drawing press.
  • the holding-down frame 5 In order to be able to carry out a hydromechanical deep-drawing process with such a press, the holding-down frame 5 must be brought into sealing contact by lowering the holding-down bear 4 after inserting the sheet 8 into the press or onto the die 6.
  • the tool chamber 9, which is initially largely filled with liquid, must contain a certain residual volume of fuel or air.
  • a filling and emptying pump 19 which can be controlled by a control device 20 is connected to the tool chamber 9 via a filling and emptying line 25; the control unit for the pump 19 receives from the angle sensor 11 a timed trigger signal for the filling and emptying processes.
  • the valve 16 Before and during the descent of the plunger 7, an increasing pressure in the liquid and in the gas is generated in the tool chamber 9 in accordance with the plunger movement and the plunger force.
  • the valve 16 On the part of a control unit 18, which receives a timed trigger signal from an angle transmitter 11, the valve 16 is switched on at a suitable point in time during the pressing cycle for feeding a gaseous propellant charge into the tool chamber.
  • the possibility of feeding the propellant charge into the tool chamber 9 during the filling process is through a gas supply line opening into the tool chamber 17 with check valve 21 and created by the controllable gas supply valve 16.
  • the gaseous propellant charge can be supplied from the gas bottle 14 and - if and / or as far as necessary - from the oxygen bottle 15, in which the gases mentioned are stored in a high-tension form, so that they can be raised without pressure into the tool chamber, which is initially still under relatively low pressure 9 can be fed.
  • Both the liquid filling and the feeding of the gaseous propellant charge should be largely completed before the pusher bear 3 has approximately reached the reversal point of its stroke. It is thereby achieved that the tool chamber can be filled with gas or liquid at a relatively low pressure but at high speed. It may well be that during the filling, which of course takes place with increasing pressure, the sheet metal protrudes toward the descending stamp and - as far as the sheet metal touches the stamp - bulges into its engraving.
  • a control device 13 for the ignition device which also receives a timed ignition signal from the angle transmitter 11.
  • the ignition device 12 can be, for example, an electrical ignition device in the manner of a spark plug, as is known from the technology of internal combustion engines. A short current surge at high voltage can trigger a powerful spark at the electrodes of the spark plug, which ignites the propellant charge and causes an explosive build-up of pressure in the tool chamber, which is already under a relatively high pressure.
  • the pressure rises very quickly to a high peak value; this powerful pressure peak brings about the final shaping of the sheet in the engraving of the stamp.
  • the check valves 21 and 22 arranged in the gas supply line 17 and in the filling and emptying line 25 for the liquid, an outflow of the introduced media is prevented. Due to a vent hole 23 on the stamp, a resistance-free outflow of the air enclosed between the plate and the engraving of the stamp is ensured, so that the engraving can be formed cleanly and accurately through the plate.
  • a cooling of the burned propellants leads to a relatively rapid drop in pressure, which is, however, desirable in order to relieve the press construction from high forces.
  • the high pressure peaks of the exploding propellant charge and the resulting high forces exerted on the walls of the tool chamber 9 or the plunger 7 are kept away from the press construction or the press frame 2 by an inertial locking of these parts. This inertia locking is due to the generous mass allocation already mentioned above the die 6 or by a very large dimensioning of the ram bear 3 and the hold-down bear 4. Since the very high pressure peak is only effective for a very short time in the range of a few milliseconds, but which is sufficient to ensure that the sheet is completely formed, the masses involved cannot be moved out of the rest position.
  • the check valve 22 arranged in the filling and emptying line 25 for the liquid is designed to be controllable, so that the closing action can be canceled, if necessary, and emptying of the tool chamber 9 can be initiated if necessary.
  • the controllable check valve 22 receives a corresponding opening signal from the control device 20 for the pump, so that an outflow of a corresponding part of the enclosed liquid can be initiated at a suitable time within the pressing cycle, for example before the propellant charge is fed in. Not only is the pump 19 driven in the outflow direction, but the residual pressure of the propellant charge that is present inside the tool chamber 9 also acts.
  • the advantage of the invention is that the advantages of a simple tool for hydromechanical deep drawing are fully retained, but that the disadvantages of this method are avoided, that relatively short press cycle times in the range of a few seconds can be achieved and that the press construction is subject to the high pressure forces is relieved.
  • propellant charge can also be introduced into the tool chamber in a defined position in the form of an explosive tablet with an integrated ignition device, but this is more complex than letting a gas flow into it.
  • the propellant charge can also be introduced into the tool chamber in a defined position in the form of an explosive tablet with an integrated ignition device, but this is more complex than letting a gas flow into it.

Abstract

The invention relates to a method for the hydromechanical deep drawing of sheet metal (8) into a shape predetermined by a punch (7) by means of a press (1) which contains the punch and a die chamber (9) that can be supplied with pressurised fluid and is open towards the punch, one of the two parts being drivable in a reciprocating manner. The sheet is clamped fluid-tightly and with a sustained force at its outer rim, between a contact surface (5) at the front end of the punch and a correspondingly shaped counter-contact surface (5) at the front end of the die chamber. The die chamber is very largely filled with a fluid under rising pressure, the yielding sheet being drawn by the fluid pressure, the rim of the sheet sliding out of the rim clamping (5) as it is drawn, and being pressed exactly into the shape of the punch. In order to shorten the pressure build-up to the required final pressure and to relieve the press of the very high forces, a metered explosive charge, preferably in the form of a combustible gas (14) mixed with oxygen (15) is introduced into the die chamber and ignited at a defined instant shortly before the lower point of reversal is reached, i.e. before the completion of the drawing operation. The forces caused by the explosion of the explosive charge, which act for a brief time on the punch (7) and on the die chamber (9) in the direction (24) of motion of the die chamber, are isolated from the press structure (2) by means of an appropriate distribution of the mass of these parts. <IMAGE>

Description

Die Erfindung geht aus von einem Verfahren zum hydromechanischen Tiefziehen von Blech in eine durch nur einen der beiden Werkzeugteile, vorzugsweise den Stempel vorgegebene Form mittels einer Presse, nach dem Oberbegriff von Anspruch 1, wie es beispielsweise durch die DE-OS 37 09 181 als bekannt hervorgeht.The invention is based on a method for hydromechanical deep-drawing of sheet metal into a shape specified by only one of the two tool parts, preferably the punch, using a press, according to the preamble of claim 1, as is known, for example, from DE-OS 37 09 181 emerges.

Der Vorteil des hydromechanischen Tiefziehens liegt darin, daß ein Teil des Ziehwerkzeuges, vorzugsweise die Matrize relativ einfach gestaltet ist und nur bezüglich seiner Anlagefläche an den gegenüberliegende Werkzeugteil angepaßt zu sein braucht, was die Werkzeugkosten erheblich verbilligt. Jedoch müssen beim hydromechanischen Tiefziehen zumindest gegen Ende des Formvorganges sehr hohe, im Bereich von 600 bis 1000 bar liegende Drücke wirken, um das Blech formgetreu in die Gravur des Stempels einpressen zu können. Nachdem diese hohen Drücke über die gesamte Fläche des Werkstückes wirksam sind, resultieren daraus sehr hohe Kräfte, die wesentlich höher sind, als die beim rein mechanischen Tiefziehen zwischen formgebendem Stempel und Matrize auftretenden Pressenbelastungen, weil dort die Belastung im wesentlichen lediglich durch den Materialquerschnitt im Ziehbereich und die Fließspannung des Werkstoffes bestimmt ist. Sollen beispielsweise Karosserieteile mit einer Flächenerstreckung von etwa einem Quadratmeter hydromechanisch tiefgezogen werden, so treten je nach erforderlichem Ausformdruck Kräfte in der Größe von 0,6 bis 1 Giganewton auf. Abgesehen von den dazu erforderlichen schweren, voluminösen und dementsprechend teuren Pressenkonstruktionen treten unter diesen Belastungen unvermeidlicherweise Verformungen der Presse auf, die in ihrer Größe nicht mehr tolerierbar sind, um einwandfreie Ziehergebnisse und vertretbare Werkzeugstandzeiten erzielen zu können. Darüber hinaus ist auch zu berücksichtigen, daß das gesamte, vom fertig gezogenen Blech eingenommene Volumen unter Druck mit Flüssigkeit aufgefüllt werden muß, was relativ lange dauert, weil dazu in der Druckhöhe zwar leistungsstarke, aber im Förderstrom nur schwache Druckpumpen verwendet werden. Preßzeiten von zwei Minuten können ohne weiteres vorkommen, die im Vergleich zu den mit herkömmlichen Karosserie-Pressen erzielbaren Zykluszeiten von vier bis sechs Sekunden viel zu lang sind. Nachteilig beim hydromechanischen Tiefziehen von größeren Blechteilen in Pressen ist also, daß die Pressen unverhältnismäßig teuer und trotzdem noch zu wenig steif sind und daß das Verfahren zu wenig produktiv ist.The advantage of hydromechanical deep drawing is that part of the drawing tool, preferably the die, is relatively simple and only needs to be adapted to the opposite tool part with respect to its contact surface, which considerably reduces tool costs. However, in hydromechanical deep drawing, at least towards the end of the molding process, very high pressures in the range from 600 to 1000 bar have to act in order to be able to press the sheet into the engraving of the punch true to shape. After these high pressures are effective over the entire surface of the workpiece, this results in very high forces that are considerably higher than the press loads that occur between the forming punch and the die in purely mechanical deep drawing, because there the load is essentially due to the material cross section in the drawing area and the yield stress of the material is determined. If, for example, body parts with a surface extension of approximately one square meter are to be deep-drawn hydromechanically, this depends on required molding pressure forces in the size of 0.6 to 1 Giganewton. Apart from the heavy, voluminous and correspondingly expensive press designs required for this, deformations of the press inevitably occur under these loads, the size of which can no longer be tolerated in order to achieve flawless drawing results and acceptable tool life. In addition, it must also be taken into account that the entire volume occupied by the finished sheet must be filled with liquid under pressure, which takes a relatively long time because powerful pressure pumps are used in the pressure head, but only weak in the flow rate. Pressing times of two minutes can easily occur, which are much too long compared to the cycle times of four to six seconds that can be achieved with conventional body presses. A disadvantage of the hydromechanical deep drawing of larger sheet metal parts in presses is that the presses are disproportionately expensive and still not rigid enough and that the process is not productive enough.

Aufgabe der Erfindung ist es, das gattungsgemäß zugrundegelegte Verfahren zum hydromechanischen Tiefziehen von Blech mittels einer Presse dahingehend zu verbessern, daß das Verfahren in der Produktivität erheblich gesteigert und diesbezüglich dem rein mechanischen Tiefziehen angenähert wird und daß zugleich die Presse von den hohen Kräften entlastet wird und somit bei vertretbarer Steifigkeit wesentlich kostengünstiger herstellbar ist.The object of the invention is to improve the generic method for hydromechanical deep-drawing of sheet metal by means of a press in such a way that the process is significantly increased in productivity and in this respect is approximated to purely mechanical deep-drawing and that the press is relieved of the high forces and is therefore much cheaper to manufacture with reasonable rigidity.

Diese Aufgabe wird bei Zugrundelegung des gattungsgemäßen Verfahrens erfindungsgemäß durch die kennzeichnenden Merkmale von Anspruch 1 gelöst. Das erfindungsgemäße Verfahren stellt nicht nur eine Vereinigung des bekannten hydromechanischen Tiefziehens mit dem für sich bekannten Explosionsumformen dar, wodurch kurze Zykluszeiten und somit eine hohe Produktivität erreicht wird. Als weiterer Erfindungsschritt kommt die Trägheitsverriegelung des Stempels und der Werkzeugkammer durch eine entsprechend großzügige Massenbelegung hinzu, wodurch die hohen, jedoch nur kurzzeitig wirkenden Umformkräfte auf diese Teile beschränkt bleiben und von der Pressenkonstruktion ferngehalten werden.This object is achieved on the basis of the generic method according to the invention by the characterizing features of claim 1. The method according to the invention not only represents a combination of the known hydromechanical deep drawing with the known explosion forming, whereby short cycle times and thus high productivity are achieved. As a further step of the invention comes the inertial locking of the Stamp and the tool chamber by a correspondingly generous mass allocation, whereby the high, but only briefly acting forming forces are limited to these parts and are kept away from the press construction.

Die Erfindung ist anhand eines in der Zeichnung dargestellten Ausführungsbeispieles nachfolgend noch erläutert; dabei zeigt die einzige Figur eine Presse zum hydromechanischen Tiefziehen von Blechen mit starker Massebelegung der am Ziehvorgang beteiligten Werkzeugteile und mit der Möglichkeit zur Einspeisung einer gasförmigen Treibladung.The invention is explained below with reference to an embodiment shown in the drawing; the single figure shows a press for hydromechanical deep-drawing of sheet metal with a high mass of the tool parts involved in the drawing process and with the possibility of feeding a gaseous propellant charge.

Die dargestellte Presse 1 ist bezüglich ihres statischen Teiles im wesentlichen durch einen Preßrahmen 2 gebildet, der seitliche Pressenständer, oben ein Pressenhaupt und unten einen Pressenfuß enthält. Für die Darstellung ist das Beispiel einer doppeltwirkenden Presse gewählt, wenngleich dieses nicht für die vorliegende Erfindung Voraussetzung ist; vielmehr läßt sich diese auch an anderen Pressentypen realisieren. Auf dem Pressenfuß ist als unterer Teil des Werkzeuges eine Matrize 6 mit großer Masse angeordnet. Auf diese Massenbelegung sei weiter unten noch näher eingegangen. Zur Formgebung wird beim dargestellten Ausführungsbeispiel - wie beim konventionellen Tiefziehen - ein in Bewegungsrichtung 24 hubbeweglich antreibbarer Stempel 7 benötigt. Durch den Stempel 7 ist die Form, mit welcher das in die Presse 1 eingebrachte Blech 8 tiefgezogen werden soll, vorgegeben. Die gegenüberliegend zum Stempel angeordnete Matrize 6 ist in Form einer offenen Werkzeugkammer 9 ausgebildet, die mit ihrer oberen stirnseitigen Anlagefläche flüssigkeits- und gasdicht an das eingelegte Blech 8 anlegbar ist. In die mit dem Blech 8 in Berührung gelangende Anlagefläche der Matrize 6 sind dementsprechend Dichtungen eingelassen. Das in die Presse eingebrachte Blech 8 ist an seinem Außenrand zwischen dieser Anlagefläche einerseits und einer entsprechend geformten Gegen-Anlagefläche eines Niederhalter-Rahmens 5 an der Stirnseite des Niederhalter-Bärs 4 andererseits einklemmbar. Der Niederhalterbär 4 ist ebenfalls mit einer sehr großen Masse belegt, worauf weiter unten noch näher eingegangen werden soll. Der Niederhalterrahmen 5 ist auswechselbar mit dem Niederhalterbär verschraubt. Bei Ausführung eines Pressenhubes wird der Niederhalterbär mit dem Niederhalterrahmen auf das eingelegte Blech abgesenkt und dort flüssigkeitsdicht und mit anhaltender Kraft angedrückt. Innerhalb des Niederhalterbärs ist der gesondert antreibbarer Stößelbär 3 mit dem bereits erwähnten Stempel 7 angebracht, der innerhalb des Niederhalterbäres 4 nach Art des Stößels einer doppeltwirkenden Tiefziehpresse auf- und abbeweglich ist.The press 1 shown is essentially formed with respect to its static part by a press frame 2 which contains lateral press stands, a press head at the top and a press foot at the bottom. The example of a double-acting press is chosen for the illustration, although this is not a prerequisite for the present invention; rather, this can also be realized on other types of press. A die 6 with a large mass is arranged on the press foot as the lower part of the tool. This mass assignment will be discussed in more detail below. In the illustrated embodiment, as in conventional deep drawing, a die 7 which can be driven in a stroke direction 24 is required for shaping. The shape with which the sheet 8 introduced into the press 1 is to be deep-drawn is predetermined by the stamp 7. The die 6 arranged opposite the punch is designed in the form of an open tool chamber 9, which can be applied to the inserted sheet 8 in a liquid-tight and gas-tight manner with its upper end-face contact surface. Accordingly, seals are let into the contact surface of the die 6 that comes into contact with the sheet metal 8. The sheet 8 inserted into the press is on its outer edge between this contact surface on the one hand and a correspondingly shaped counter-contact surface of a hold-down frame 5 on the front side of the hold-down bar 4, on the other hand, can be clamped. The hold-down bear 4 is also covered with a very large mass, which will be discussed in more detail below. The hold-down frame 5 is interchangeably screwed to the hold-down bear. When a press stroke is carried out, the hold-down bar with the hold-down frame is lowered onto the inserted sheet metal and pressed there in a liquid-tight manner and with sustained force. Inside the hold-down bear, the separately drivable plunger bear 3 is attached with the aforementioned stamp 7, which can be moved up and down within the hold-down bear 4 in the manner of the plunger of a double-acting deep-drawing press.

Um mit einer solchen Presse einen hydromechanischen Tiefziehvorgang ausüben zu können, muß - nach dem Einlegen des Bleches 8 in die Presse bzw. auf die Matrize 6 - der Niederhalterrahmen 5 durch Absenken des Niederhalterbäres 4 dichtend zur Anlage gebracht werden. Die zunächst weitestgehend mit Flüssigkeit gefüllte Werkzeugkammer 9 muß ein gewisses Restvolumen von Stauerstoff oder Luft enthalten. Zu diesem Zweck ist eine durch ein Steuergerät 20 ansteuerbare Füll- und Entleerungspumpe 19 an die Werkzeugkammer 9 über eine Füll- und Entleerungsleitung 25 angeschlossen; das Steuergerät für die Pumpe 19 erhält seitens des Winkelgebers 11 ein zeitlich abgstimmtes Triggersignal für die Füll- bzw. Entleerungsvorgänge. Vor und während des Niedergehens des Stempels 7 wird in der Werkzeugkammer 9 ein ansteigender Druck in der Flüssigkeit und im Gas entsprechend der Stößelbewegung und der Stößelkraft erzeugt. Seitens eines Steuergerätes 18, welches von einem Winkelgeber 11 ein zeitlich abgestimmtes Triggersignal erhält, wird das Ventil 16 zum Einspeisen einer gasförmigen Treibladung in die Werkzeugkammer zu einem geeigneten Zeitpunkt innerhalb des Preßzyklus' eingeschaltet. Die Möglichkeit zum Einspeisen der Treibladung in die Werkzeugkammer 9 während des Befüllvorganges ist durch eine in die Werkzeugkammer einmündende Gaszufuhrleitung 17 mit Rückschlagventil 21 und durch das steuerbare Gaszufuhrventil 16 geschaffen. Die gasförmige Treibladung kann aus der Gasflasche 14 und - sofern und/oder soweit notwendig - aus der Sauerstoffflasche 15 zugeführt werden, in denen die erwähnten Gase in hochgespannter Form bevorratet sind, so daß sie ohne Druckanhebung in die anfänglich noch unter relativ niedrigem Druck stehende Werkzeugkammer 9 eingespeist werden können.In order to be able to carry out a hydromechanical deep-drawing process with such a press, the holding-down frame 5 must be brought into sealing contact by lowering the holding-down bear 4 after inserting the sheet 8 into the press or onto the die 6. The tool chamber 9, which is initially largely filled with liquid, must contain a certain residual volume of fuel or air. For this purpose, a filling and emptying pump 19 which can be controlled by a control device 20 is connected to the tool chamber 9 via a filling and emptying line 25; the control unit for the pump 19 receives from the angle sensor 11 a timed trigger signal for the filling and emptying processes. Before and during the descent of the plunger 7, an increasing pressure in the liquid and in the gas is generated in the tool chamber 9 in accordance with the plunger movement and the plunger force. On the part of a control unit 18, which receives a timed trigger signal from an angle transmitter 11, the valve 16 is switched on at a suitable point in time during the pressing cycle for feeding a gaseous propellant charge into the tool chamber. The possibility of feeding the propellant charge into the tool chamber 9 during the filling process is through a gas supply line opening into the tool chamber 17 with check valve 21 and created by the controllable gas supply valve 16. The gaseous propellant charge can be supplied from the gas bottle 14 and - if and / or as far as necessary - from the oxygen bottle 15, in which the gases mentioned are stored in a high-tension form, so that they can be raised without pressure into the tool chamber, which is initially still under relatively low pressure 9 can be fed.

Sowohl die Flüssigkeitsbefüllung als auch die Einspeisung der gasförmigen Treibladung sollten weitgehend abgeschlossen sein, bevor der Stößelbär 3 etwa den Umkehrpunkt seines Hubes erreicht hat. Dadurch wird erreicht, daß die Befüllung der Werkzeugkammer mit Gas bzw. mit Flüssigkeit bei relativ niedrigem Druck aber mit hoher Geschwindigkeit vorgenommen werden kann. Es kann durchaus sein, daß während der Befüllung, die selbstverständlich mit ansteigendem Druck erfolgt, das Blech sich dem niedergehenden Stempel entgegen- und - soweit das Blech den Stempel berührt - in seine Gravur hineinwölbt.Both the liquid filling and the feeding of the gaseous propellant charge should be largely completed before the pusher bear 3 has approximately reached the reversal point of its stroke. It is thereby achieved that the tool chamber can be filled with gas or liquid at a relatively low pressure but at high speed. It may well be that during the filling, which of course takes place with increasing pressure, the sheet metal protrudes toward the descending stamp and - as far as the sheet metal touches the stamp - bulges into its engraving.

Nach Abschluß der flüssigkeitsseitigen und der gasseitigen Befüllung der Werkzeugkammer 9 erfolgt ein weiterer Druckaufbau darin aufgrund des niedergehenden Stempels 7, der die in der Werkzeugkammer 9 eingeschlossenen Medien unter gleichzeitiger Kompression des eingeschlossenen Gases vor sich herschiebt, wobei das Blech 8 durch den Druck zunehmend in die Gravur des Stempels hineingewölbt wird und wobei das randseitig eingeklemmte Blech aus dieser Randeinklemmung herausgleitet. Mit zunehmendem Verformungsgrad und Vollendung der Blechausformung nimmt der Druck in der eingegebenen Flüssigkeit bzw. in dem eingegebenen Gas mehr und mehr zu. Kurz vor Erreichen des unteren Umkehrpunktes des Stempels 7 wird mittels der am oberen Bereich des Stößelkolbens eingelassenen Zündeinrichtung 12 die eingebrachte, komprimierte gasförmige Treibladung gezündet. Zu diesem Zweck ist ein Steuergerät 13 für die Zündeinrichtung vorgesehen, die ebenfalls von dem Winkelgeber 11 ein zeitlich abgestimmtes Zündsignal erhält. Mit Rücksicht auf die Tatsache, daß sich die gasförmige Treibladung stets an der höchsten Stelle der weitgehend mit Flüssigkeit gefüllten Zündkammer hält, muß auch dort oben die Zündeinrichtung 12 angebracht sein. Es kann sich dabei bspw. um eine elektrische Zündeinrichtung nach Art einer Zündkerze handeln, wie sie aus der Technik der Verbrennungsmotoren bekannt ist. Durch einen kurzen Stromstoß bei hoher Spannung kann ein leistungsfähiger Zündfunke an den Elektroden der Zündkerze ausgelöst werden, der die Treibladung zur Entzündung bringt und einen explosionsartigen Druckaufbau in der ohnehin bereits unter einem relativ hohen Druck stehenden Werkzeugkammer hervorruft. Dank der Vorkompression der Treibladung kommt es zu einem sehr raschen Druckanstieg auf einen hohen Spitzenwert; diese leistungsstarke Druckspitze bewerkstelligt die Endausformung des Bleches in die Gravur des Stempels. Dank der in die Gaszufuhrleitung 17 und in die Füll- und Entleerungsleitung 25 für die Flüssigkeit angeordneten Rückschlagventile 21 bzw. 22 wird ein Abströmen der eingebrachten Medien verhindert. Aufgrund einer Entlüftungsbohrung 23 am Stempel wird auch ein widerstandsfreies Abströmen der zwischen Blech und Gravur des Stempels eingeschlossenen Luft sichergestellt, so daß die Gravur sauber und formgetreu durch das Blech ausgeformt werden kann.After completion of the liquid-side and gas-side filling of the tool chamber 9, there is a further pressure build-up in it due to the descending stamp 7, which pushes the media enclosed in the tool chamber 9 with simultaneous compression of the enclosed gas, the sheet 8 increasing in pressure due to the pressure Engraving of the stamp is arched in and the sheet metal clamped in on the edge slides out of this edge clamp. With increasing degree of deformation and completion of the sheet metal forming, the pressure in the liquid or gas entered increases more and more. Shortly before the lower reversal point of the plunger 7 is reached, the introduced, compressed gaseous propellant charge is ignited by means of the ignition device 12 embedded in the upper region of the plunger piston. For this purpose, a control device 13 for the ignition device is provided, which also receives a timed ignition signal from the angle transmitter 11. In view of the fact that the gaseous propellant charge always remains at the highest point of the ignition chamber, which is largely filled with liquid, the ignition device 12 must also be attached there. It can be, for example, an electrical ignition device in the manner of a spark plug, as is known from the technology of internal combustion engines. A short current surge at high voltage can trigger a powerful spark at the electrodes of the spark plug, which ignites the propellant charge and causes an explosive build-up of pressure in the tool chamber, which is already under a relatively high pressure. Thanks to the pre-compression of the propellant charge, the pressure rises very quickly to a high peak value; this powerful pressure peak brings about the final shaping of the sheet in the engraving of the stamp. Thanks to the check valves 21 and 22 arranged in the gas supply line 17 and in the filling and emptying line 25 for the liquid, an outflow of the introduced media is prevented. Due to a vent hole 23 on the stamp, a resistance-free outflow of the air enclosed between the plate and the engraving of the stamp is ensured, so that the engraving can be formed cleanly and accurately through the plate.

Zwar kommt es aufgrund einer Abkühlung der verbrannten Treibgase zu einem relativ raschen Druckabfall, der jedoch durchaus erwünscht ist, um die Pressenkonstruktion von hohen Kräften zu entlasten. Die hohen Druckspitzen der explodierenden Treibladung und die damit ausgelösten hohen, auf die Wandungen der Werkzeugkammer 9 bzw. des Stempels 7 ausgeübten Kräfte werden durch eine Trägheitsverriegelung dieser Teile von der Pressenkonstruktion bzw. dem Pressenrahmen 2 ferngehalten. Diese Trägheitsverriegelung kommt durch die bereits weiter oben erwähnte großzügige Massenbelegung der Matrize 6 bzw. durch eine sehr große massenmäßige Dimensionierung des Stößelbäres 3 und des Niederhalterbäres 4 zustande. Da die sehr hohe Druckspitze nur während einer sehr geringen Zeit im Bereich weniger Millisekunden wirksam ist, die jedoch ausreicht, um eine vollständige Ausformung des Bleches sicherzustellen, können die beteiligten Massen nicht aus der Ruhelage herausbewegt werden. Die auf die sehr stark massebelegte Werkzeugkammer 9 bzw. der Matrize 6 einerseits und auf den Stempel 7 bzw. Stößelbär 3 und Niederhalterbär 4 andererseits einwirkenden fluidischen Kräfte bleiben also in der sehr kurzen Zeit der Druckspitze auf die erwähnten Massen beschränkt; der Pressenrahmen 2 wird durch diese Kräfte nicht belastet.A cooling of the burned propellants leads to a relatively rapid drop in pressure, which is, however, desirable in order to relieve the press construction from high forces. The high pressure peaks of the exploding propellant charge and the resulting high forces exerted on the walls of the tool chamber 9 or the plunger 7 are kept away from the press construction or the press frame 2 by an inertial locking of these parts. This inertia locking is due to the generous mass allocation already mentioned above the die 6 or by a very large dimensioning of the ram bear 3 and the hold-down bear 4. Since the very high pressure peak is only effective for a very short time in the range of a few milliseconds, but which is sufficient to ensure that the sheet is completely formed, the masses involved cannot be moved out of the rest position. The fluidic forces acting on the very strongly mass-loaded tool chamber 9 or the die 6 on the one hand and on the plunger 7 or plunger bear 3 and hold-down bear 4 on the other hand are thus limited to the masses mentioned in the very short time of the pressure peak; the press frame 2 is not burdened by these forces.

Das in der Füll- und Entleerungsleitung 25 für die Flüssigkeit angeordnete Rückschlagventil 22 ist steuerbar ausgebildet, so daß die Schließwirkung ggf. aufhebbar ist und zu einem geeigneten Zeitpunkt eine Entleerung der Werkzeugkammer 9 erforderlichenfalls eingeleitet werden kann. Hierbei erhält das steuerbare Rückschlagventil 22 von dem Steuergerät 20 für die Pumpe ein entsprechendes Öffnungssignal, so daß zu einem geeigneten Zeitpunkt innerhalb des Preßzyklus', beispielsweise vor dem Einspeisen der Treibladung, eine Abströmung eines entsprechenden Teiles der eingeschlossenen Flüssigkeit eingeleitet werden kann. Hierbei wird nicht nur die Pumpe 19 in Abströmrichtung angetrieben, sondern es wirkt außerdem noch der im Innern der Werkzeugkammer 9 anstehender Restdruck der Treibladung.The check valve 22 arranged in the filling and emptying line 25 for the liquid is designed to be controllable, so that the closing action can be canceled, if necessary, and emptying of the tool chamber 9 can be initiated if necessary. In this case, the controllable check valve 22 receives a corresponding opening signal from the control device 20 for the pump, so that an outflow of a corresponding part of the enclosed liquid can be initiated at a suitable time within the pressing cycle, for example before the propellant charge is fed in. Not only is the pump 19 driven in the outflow direction, but the residual pressure of the propellant charge that is present inside the tool chamber 9 also acts.

Der Vorteil der Erfindung liegt darin, daß die Vorteile eines einfachen Werkzeuges für das hydromechanische Tiefziehen voll erhalten bleiben, daß aber die Nachteile dieses Verfahrens vermieden werden, daß also relativ kurze Preßzykluszeiten im Bereich von wenigen Sekunden erreichbar sind und daß die Pressenkonstruktion von den hohen Druckkräften entlastet ist.The advantage of the invention is that the advantages of a simple tool for hydromechanical deep drawing are fully retained, but that the disadvantages of this method are avoided, that relatively short press cycle times in the range of a few seconds can be achieved and that the press construction is subject to the high pressure forces is relieved.

Der Vollständigkeit halber sei erwähnt, daß auch andere Möglichkeiten der Treibladungseinbringung möglich sind. Bspw. kann die Treibladung auch in Form einer Sprengstofftablette mit integrierter Zündeinrichtung lagedefiniert in die Werkzeugkammer eingebracht werden, was jedoch aufwendiger ist als das Einströmenlassen eines Gases. Ferner ist es auch denkbar, während des Befüllens lediglich Sauerstoff oder unter Umständen sogar Luft in die Werkzeugkammer einzuspeisen und diese adiabatisch nach Art eines Dieselmotores zu verdichten und den Brennstoff der Treibladung erst zum Zeitpunkt der Zündung in Form eines vernebelten flüssigen Kraftstoffes einzuspritzen, dessen Zündtemperatur unterhalb der Verdichtungstemperatur der komprimierten Luft bzw. des komprimierten Sauerstoffes liegt. Nachdem jedoch die Kompressionsvorgänge im Vergleich zu motorischen Anwendungen vorliegend relativ langsam ablaufen und die beteiligten Medien vergleichsweise kühl sind, wird es schwierig sein, eine annähernd adiabatische Verdichtung zu erreichen. Die eingespritzte Kraftstoffflüssigkeit müßte demgemäß eine vergleichsweise sehr niedrige Zündtemperatur aufweisen. Als Gas für die gasförmige Treibladung wäre Wasserstoff geeignet, zumal es keine schädlichen Verbrennungsgase bildet und die Verbrennungsprodukte sich ohne weiteres mit der im wesentlichen durch Wasser gebildeten Druckflüssigkeit vertragen; die Verbrennungsgase kondensieren selber sehr schnell zu Wasser. Außerdem bilden Wasserstoff und Sauerstoff eine hochbrisante Mischung, die in sehr weiten Mischungsgrenzen zündfähig ist. Um allerdings sicherzustellen, daß sich im Bereich der Presse kein Wasserstoff ansammeln kann, um andererseits sicherzustellen, daß kein übermäßiger Überschuß an Sauerstoff innerhalb der Presse entsteht, was ebenfalls ein Gefahrenpunkt sein kann, sollte annähernd stöchiometrisch mit leichtem Sauerstoffüberschuß gefahren werden, um eine vollständige Verbrennung des Treibgases sicherzustellen.For the sake of completeness, it should be mentioned that other options for introducing propellant charge are also possible. E.g. the propellant charge can also be introduced into the tool chamber in a defined position in the form of an explosive tablet with an integrated ignition device, but this is more complex than letting a gas flow into it. Furthermore, it is also conceivable to feed only oxygen or possibly even air into the tool chamber during filling and to compress it adiabatically in the manner of a diesel engine and to inject the fuel of the propellant charge in the form of a nebulized liquid fuel at the time of ignition, the ignition temperature of which is below the compression temperature of the compressed air or oxygen. However, since the compression processes here are relatively slow compared to motor applications and the media involved are comparatively cool, it will be difficult to achieve an almost adiabatic compression. The injected fuel liquid should accordingly have a comparatively very low ignition temperature. Hydrogen would be suitable as the gas for the gaseous propellant charge, especially since it does not form any harmful combustion gases and the combustion products are readily compatible with the hydraulic fluid essentially formed by water; the combustion gases themselves very quickly condense into water. In addition, hydrogen and oxygen form a highly explosive mixture that is ignitable within very wide mixing limits. However, in order to ensure that no hydrogen can accumulate in the area of the press, and on the other hand to ensure that there is no excessive excess of oxygen within the press, which can also be a danger point, it should be operated approximately stoichiometrically with a slight excess of oxygen in order to ensure complete combustion of the propellant gas.

Claims (2)

Verfahren zum hydromechanischen Tiefziehen von Blech in eine durch nur eines der beiden Werkzeugteile, vorzugsweise den Stempel, vorgegebene Form mittels einer Presse, die den formbestimmenden Werkzeugteil, vorzugsweise den Stempel und eine mit Druckflüssigkeit beaufschlagbare, zum formbestimmenden Werkzeugteil hin offene Werkzeugkammer enthält, wobei eines der beiden Teile hubbeweglich antreibbar ist, - bei dem das Blech an seinem Außenrand zwischen einer Anlagefläche an der Stirnseite des formbestimmenden Werkzeugteiles, vorzugsweise des Stempels bzw. Niederhalters und einer entsprechend geformten Gegen-Anlagefläche an der Stirnseite der Werkzeugkammer flüssigkeits- und gasdicht und mit anhaltender Kraft eingeklemmt wird, - bei dem ferner die flüssigkeitsgefüllte Werkzeugkammer zunehmend unter Druck gesetzt wird, wobei das nachgebende Blech unter Nachgleiten des Blechrandes aus der Randeinklemmung durch den Flüssigkeitsdruck gezogen und formgetreu in die Gravur des formbestimmenden Werkzeugteiles hineingedrückt wird, dadurch gekennzeichnet,
daß vor dem oder während des Füllen(s) der Werkzeugkammer (9) mit Flüssigkeit in diese eine abgemessene Treibladung eingebracht, die Werkzeugkammer (9) bei relativ geringem Druck zügig mit Druckflüssigkeit gefüllt und die Treibladung zu einem bestimmten Zeitpunkt vor Vollendung des Ziehvorganges gezündet wird und daß die durch die Explosion der Treibladung auf den formbestimmenden Werkzeugteil, vorzugsweise den Stempel (7) und auf die Werkzeugkammer (9) kurzzeitig in Bewegungsrichtung (24) des hubbeweglichen Werkzeugteiles (7) einwirkenden Kräfte durch eine entsprechend dimensionierte Massenbelegung dieser Teile von der Pressenkonstruktion (2) ferngehalten werden.Process for the hydromechanical deep-drawing of sheet metal into a shape predetermined by only one of the two tool parts, preferably the stamp, by means of a press which contains the shape-determining tool part, preferably the stamp and a tool chamber which can be acted upon by hydraulic fluid and is open towards the shape-determining tool part, one of the both parts are drivable, in which the sheet metal is clamped on its outer edge between a contact surface on the end face of the shape-determining tool part, preferably the punch or hold-down device, and a correspondingly shaped counter-contact surface on the end face of the tool chamber in a liquid-tight and gas-tight manner and with lasting force, in which the liquid-filled tool chamber is also increasingly put under pressure, the yielding sheet being pulled out of the edge clamping by the liquid pressure while the sheet edge is sliding and being pressed into the engraving of the shape-determining tool part in a true-to-shape manner, characterized by
that before or during the filling (s) of the tool chamber (9) with liquid, a measured propellant charge is introduced into it, the tool chamber (9) is rapidly filled with pressurized liquid at relatively low pressure, and the propellant charge is ignited at a certain time before the drawing process is completed and that by the explosion of the propellant charge on the shape-determining Tool part, preferably the punch (7) and forces acting on the tool chamber (9) briefly in the direction of movement (24) of the movable tool part (7) are kept away from the press construction (2) by an appropriately dimensioned mass assignment of these parts. Verfahren nach Anspruch 1,
dadurch gekennzeichnet,
daß die Treibladung in Form eines brennbaren, mit Sauerstoff gemischten Gases in die Druckflüssigkeit eingebracht wird.Method according to claim 1,
characterized by
that the propellant charge is introduced into the pressure fluid in the form of a combustible gas mixed with oxygen.
EP93111956A 1992-10-01 1993-07-27 Explosion assisted hydromechanical deep drawing Expired - Lifetime EP0590262B1 (en)

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DE4232913 1992-10-01
DE4232913A DE4232913C2 (en) 1992-10-01 1992-10-01 Two-stage process for hydromechanical explosion-assisted deep-drawing of sheet metal and a deep-drawing press for carrying out the process

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EP0590262A1 true EP0590262A1 (en) 1994-04-06
EP0590262B1 EP0590262B1 (en) 1996-04-17

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Also Published As

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DE59302247D1 (en) 1996-05-23
EP0590262B1 (en) 1996-04-17
ES2087621T3 (en) 1996-07-16
DE4232913C2 (en) 1995-04-27
DE4232913A1 (en) 1994-04-07

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