EP0748662A1 - Method for controlling a tube bending machine - Google Patents

Method for controlling a tube bending machine Download PDF

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Publication number
EP0748662A1
EP0748662A1 EP96109222A EP96109222A EP0748662A1 EP 0748662 A1 EP0748662 A1 EP 0748662A1 EP 96109222 A EP96109222 A EP 96109222A EP 96109222 A EP96109222 A EP 96109222A EP 0748662 A1 EP0748662 A1 EP 0748662A1
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EP
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Prior art keywords
bending
feed force
pipe
actual value
cylinder
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EP96109222A
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German (de)
French (fr)
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EP0748662B1 (en
Inventor
Rigobert Dipl.-Ing. Schwarze
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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
    • B21D7/00—Bending rods, profiles, or tubes
    • B21D7/02—Bending rods, profiles, or tubes over a stationary forming member; by use of a swinging forming member or abutment
    • B21D7/024—Bending rods, profiles, or tubes over a stationary forming member; by use of a swinging forming member or abutment by a swinging forming member
    • B21D7/025—Bending rods, profiles, or tubes over a stationary forming member; by use of a swinging forming member or abutment by a swinging forming member and pulling or pushing the ends of the work

Definitions

  • the invention relates to a method for controlling a pipe bending machine and a pipe bending machine.
  • the pipe When bending pipes, the pipe is pressed laterally with a clamping jaw against a bending template, which is then rotated with the clamping jaw.
  • the tube When turning the bending template, the tube is bent around the bending template.
  • the unbent pipe section is supported on a slide rail.
  • a feed device acts on the slide rail, which pushes the slide rail forward during the bending process.
  • the mutual coordination between the rotary movement of the bending template and the feed movement of the slide rail is of particular importance. If the slide rail is advanced too quickly or too slowly, cracks, corrugations or oval deformations can occur on the tube. Areas of different wall thicknesses can also form.
  • DE 23 04 838 C2 describes a pipe bending process in which the angle of rotation of the bending template and the position of the slide rail are determined.
  • an actual value is determined, which is compared with a corresponding target value of the speed differences.
  • the comparison result is fed to a servo valve that influences one of the two hydraulic drives.
  • the feed speed and the bending speed are mutually coordinated, which are made equal to one another or adjusted to a specific ratio.
  • DE 41 29 478 A1 describes a method for controlling a pipe bending machine, which can be referred to as a synchronous feed.
  • the rotational position of the bending template and the feed position of the slide rail are determined.
  • the measured variables obtained in this way are compared with one another.
  • the difference value controls a pressure regulator that changes the pressure to be supplied to the feed device. If the actual position runs behind the target position in such a control method, in order to be able to drive synchronously again, the feed force acting must be constantly increased. Since no consideration is given to the flow behavior of the pipe material, there is a risk of wrinkles. There is also a risk that the slide rail slips on the pipe because the advancing force that occurs exceeds the frictional force of the slide rail on the pipe surface.
  • the invention has for its object to provide a control method with which it is possible to gently bend pipes with high accuracy and dimensional accuracy.
  • the method according to the invention provides a force control for the feed force with which the slide rail is advanced.
  • a setpoint value of the feed force is specified as a function of the angle of rotation of the bending template and the actual value of the feed force is regulated according to the setpoint value.
  • the feed force of the slide rail is changed depending on the current bending angle.
  • the system is particularly suitable for thick-walled pipes and especially for pressure bending technology, in which the unbent pipe section is pressed in the direction of the bending template during the bending process, as well as for extreme areas. As a result of the special pressure control, the force flow within the tube walls is influenced in a targeted manner.
  • the actual value of the feed force is preferably determined by detecting the pressures in the cylinder on both sides of the piston and determining the actual value of the feed force from the pressures, taking into account the sizes of the two piston surfaces. All that is required is pressure sensors on the hydraulic cylinder for the slide rail feed. Alternatively, it is possible to install a force sensor in the slide rail feed, but this reduces the stability of the slide rail feed.
  • the pressures in the cylinder on both sides of the piston are expediently changed in opposite directions to one another. This means that if the feed pressure increases, the back pressure is reduced. This makes it possible to fully utilize the maximum pump pressure for the feed.
  • the method according to the invention does not necessarily have to be carried out for a pipe bending process from start to finish. There is also the possibility of partially bending according to the synchronous method and only in the critical areas with the method according to the invention, i.e. through force control.
  • the invention further relates to a pipe bending machine.
  • a device for detecting the actual value of the feed force applied by the cylinder is provided and there is a controller which adjusts the actual value of the feed force in accordance with a desired value which is generated by a desired value generator as a function of the bending angle supplied by the position transmitter of the bending template.
  • the pipe bending machine shown schematically in FIG. 1 has a bending template 10 rotatably mounted on a machine table (not shown).
  • the bending template 10 arranged with the vertical axis of rotation 11 has essentially the shape of a cylindrical body, on the circumferential surface of which a bending groove 12 is formed, which takes up approximately half the cross section of the tube 13 to be bent.
  • a counter-clamping jaw 14 is fastened, with which a clamping jaw 15 cooperates in order to grip around the tube 13 together and clamp it tight for the bending process.
  • the clamping jaw 15 is attached to a pivot arm 16 which is pivotable about an axis which coincides with the axis of rotation 11 of the bending template 10.
  • the clamping jaw 15 can be moved radially on this swivel arm 16 in order to clamp or release the tube.
  • the unbent section 13a of the tube 13 is supported by a pressing device 17.
  • the pressing device has a slide 18 which can be moved in the direction of the double arrow 19 transversely to the pipe section 13.
  • the carriage 18 carries a lower carriage 20 which can be moved in the longitudinal direction to the unbent tube section 13a, that is to say in the direction of the double arrow 21, and a cylinder 22 for moving the lower carriage 20.
  • the cylinder 22 is fixedly arranged on the carriage 18 and in it the piston 23 is movable, the piston rod 24 of which engages the lower slide 20 in order to displace it.
  • the cylinder 22 has a working chamber 25 and a return stroke chamber 26, which are separated by the piston 23.
  • a position transmitter 30 is arranged on the bending template 10.
  • the position sensor 30 has, for example, a rotary angle encoder which indicates the rotary position of the bending template 10.
  • the bending template 10 is rotated by a (hydraulic) drive 31.
  • a slide rail 32 is attached to the lower slide 20 in the vicinity of the bending template 10 and presses against the tube 13 from the side facing away from the bending template and supports the unbent tube section 13a during the bending process. Furthermore, a thrust element 35 is attached to the lower slide 20, which engages on the rear part of the unbent pipe section 13a.
  • the thrust element 35 can have a clamping jaw 36 in order to firmly clamp the pipe section 13a. It is so trained that it acts on the pipe glelt free.
  • the thrust element 35 and the jaw 36 are required for the pressure bending. If no pressure bending is exerted, the feed force is transmitted exclusively from the slide rail 32 to the tube 13.
  • the straight tube is clamped between the clamping jaw 15 and the counter clamping jaw 14. Then the bending template 10 is rotated according to a predetermined program, whereby the tube is drawn around the bending template and at the same time the straight tube section 13a is moved forward. During the bending process, the lower slide 20 is advanced parallel to the pipe section 13a by the hydraulic cylinder 22.
  • the line 40 which is connected to the working chamber 25, and the line 41, which is connected to the return stroke chamber 26, are connected to a control valve 42 which can assume three different positions A, B and C.
  • the valve 42 connects the lines 40 and 41 to a switching valve 43, which is connected to a pump 44 and a sump 45 and can be switched between an open position and a blocking position.
  • the position B of the valve 42 is used for the rapid feed and the position C for the return stroke of the piston 23.
  • a pressure transducer 46 is connected to line 40 and generates a current signal which corresponds to the hydraulic pressure in line 40.
  • a pressure transducer 47 is connected to line 41 and generates a current signal which corresponds to the hydraulic pressure in line 41.
  • the outputs of the two pressure transducers 46 and 47 are connected to a controller 48, which supplies the control signal 39 for the control valve for the differential valve 42.
  • the controller 48 calculates the actual value Fi of the feed force that acts on the slide 20 from the pressures in the chambers 25 and 26 and the sizes of the two piston surfaces A1 and A2.
  • the controller 48 is also connected to a setpoint generator 49, which supplies a setpoint Fs of the feed force to the controller 48.
  • This target value Fs of the feed force varies depending on the angle of rotation ⁇ of the bending template 10, which is supplied by the position sensor 30.
  • Fig. 3 shows the control scheme.
  • the setpoint generator 49 contains several curves that indicate the setpoint Fs of the feed force as a function of the angle of rotation ⁇ of the bending template 10. Can on the setpoint generator the desired curve can be selected. Furthermore, the value ⁇ for the start and end of the tube processing can be entered on the setpoint generator. The setpoint generator 49 then supplies, depending on ⁇ , the respectively associated setpoint Fs, from which the actual value Fi is subtracted in a subtractor 50. The subtraction result is fed to controller 48, which is a PID controller, for example. This controller supplies a control signal to the control path 51 via the control line 39, which here consists of the differential valve 42 and the cylinder 22 (FIG. 2).
  • the pressure P1 in line 40 and the pressure P2 in line 41 are fed to the respective transducers 46 and 47, respectively.
  • the output signal of the converter 46 is multiplied in a multiplier 52 by a value which corresponds to the area A1 of the piston 23.
  • the output signal of the converter 47 is multiplied in a multiplier 53 by a value which corresponds to the size of the area A2 of the piston 23.
  • the multiplier 52 thus forms the product P1 x A1
  • the multiplier 53 forms the product P2 x A2.
  • Each of these products is a measure of one of the two forces acting in opposite directions on the piston 23.
  • a subtractor 54 subtracts the two products from one another, so that the actual value Fi of the feed force arises. This actual value is subtracted from the target value Fs in the subtractor 50 in order to form the input signal for the controller 48.
  • the output signals of the two converters 46 and 47 are fed to an error evaluation 55, which generates an alarm signal or stops the pipe bending machine when the pressures P1 and P2 show abnormalities. Total failures of the sensor can also be shown.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Bending Of Plates, Rods, And Pipes (AREA)

Abstract

The method involves measuring the bending angle of a bending former, generating a demand value (Fs) for the feed force from the measured bending angle (alpha), determining the actual value of the feed force and varying the pressure in a hydraulic cylinder (22) so that the actual value of the feed force follows the demand value. The actual value of the feed force is measured by determining the pressure (P1,P2) in the cylinder on both sides of a piston (23) and determining the force from the pressures taking into account the sizes of both piston surfaces.

Description

Die Erfindung betrifft ein Verfahren zur Steuerung einer Rohrbiegemaschine sowie eine Rohrbiegemaschine.The invention relates to a method for controlling a pipe bending machine and a pipe bending machine.

Beim Biegen von Rohren wird das Rohr mit einer Spannbacke seitlich gegen eine Biegeschablone gedrückt, die anschließend unter Mitnahme der Spannbacke gedreht wird. Beim Drehen der Biegeschablone wird das Rohr um die Biegeschablone herum gebogen. Der ungebogene Rohrabschnitt stützt sich dabei an einer Gleitschiene ab. Auf die Gleitschiene wirkt eine Vorschubvorrichtung ein, die die Gleitschiene während des Biegevorganges vorschiebt. Eine besondere Bedeutung kommt der gegenseitigen Abstimmung zwischen der Drehbewegung der Biegeschablone und der Vorschubbewegung der Gleitschiene zu. Wenn die Gleitschiene zu schnell oder zu langsam vorgeschoben wird, können an dem Rohr Risse, Wellungen oder ovale Verformungen entstehen. Ferner können sich Bereiche unterschiedlicher Wandstärke ausbilden.When bending pipes, the pipe is pressed laterally with a clamping jaw against a bending template, which is then rotated with the clamping jaw. When turning the bending template, the tube is bent around the bending template. The unbent pipe section is supported on a slide rail. A feed device acts on the slide rail, which pushes the slide rail forward during the bending process. The mutual coordination between the rotary movement of the bending template and the feed movement of the slide rail is of particular importance. If the slide rail is advanced too quickly or too slowly, cracks, corrugations or oval deformations can occur on the tube. Areas of different wall thicknesses can also form.

In DE 23 04 838 C2 ist ein Rohrbiegeverfahren beschrieben, bei dem der Drehwinkel der Biegeschablone und die Position der Gleitschiene ermittelt werden. Entsprechend der Differenz zwischen der Stauchgeschwindigkeit und der Umfangsgeschwindigkeit der Biegeschablone wird ein Istwert ermittelt, der mit einem entsprechenden Sollwert der Geschwindigkeitsdifferenzen verglichen wird. Das Vergleichsergebnis wird einem Servoventil zugeleitet, das einen der beiden hydraulischen Antriebe beeinflußt. Hierbei erfolgt eine gegenseitige Abstimmung von Vorschubgeschwindigkeit und Biegegeschwindigkeit, die einander gleichgemacht oder auf ein bestimmtes Verhältnis eingestellt werden.DE 23 04 838 C2 describes a pipe bending process in which the angle of rotation of the bending template and the position of the slide rail are determined. In accordance with the difference between the upsetting speed and the peripheral speed of the bending template, an actual value is determined, which is compared with a corresponding target value of the speed differences. The comparison result is fed to a servo valve that influences one of the two hydraulic drives. The feed speed and the bending speed are mutually coordinated, which are made equal to one another or adjusted to a specific ratio.

In DE 41 29 478 A1 ist ein Verfahren zur Steuerung einer Rohrbiegemaschine beschrieben, das als Synchronvorschub bezeichnet werden kann. Hierbei werden die Drehposition der Biegeschablone und die Vorschubposition der Gleitschiene ermittelt. Die so gewonnenen Meßgrößen werden miteinander vergleichen. Der Differenzwert steuert einen Druckregler, der den der Vorschubeinrichtung zuzuführenden Druck verändert. Wenn bei einem derartigen Steuerverfahren die Ist-Position einmal hinter der Soll-Position herläuft, muß, um wieder synchron fahren zu können, die einwirkende Vorschubkraft ständig erhöht werden. Da hierbei keine Rücksicht auf das Fließverhalten des Rohrmaterials genommen wird, besteht die Gefahr der Faltenbildung. Ferner besteht die Gefahr, daß die Gleitschiene an dem Rohr rutscht, weil die auftretende Vorschubkraft die Reibungskraft der Gleitschiene an der Rohroberfläche übersteigt.DE 41 29 478 A1 describes a method for controlling a pipe bending machine, which can be referred to as a synchronous feed. The rotational position of the bending template and the feed position of the slide rail are determined. The measured variables obtained in this way are compared with one another. The difference value controls a pressure regulator that changes the pressure to be supplied to the feed device. If the actual position runs behind the target position in such a control method, in order to be able to drive synchronously again, the feed force acting must be constantly increased. Since no consideration is given to the flow behavior of the pipe material, there is a risk of wrinkles. There is also a risk that the slide rail slips on the pipe because the advancing force that occurs exceeds the frictional force of the slide rail on the pipe surface.

Der Erfindung liegt die Aufgabe zugrunde, ein Steuerverfahren anzugeben, mit dem es möglich ist, Rohre mit hoher Genauigkeit und Maßhaltigkeit schonend zu biegen.The invention has for its object to provide a control method with which it is possible to gently bend pipes with high accuracy and dimensional accuracy.

Die Lösung dieser Aufgabe erfolgt erfindungsgemäß mit den Merkmalen des Patentanspruchs 1.This object is achieved according to the invention with the features of patent claim 1.

Das erfindungsgemäße Verfahren sieht eine Kraftregelung für die Vorschubkraft, mit der die Gleitschiene vorgeschoben wird, vor. Bei dieser Kraftregelung wird ein Sollwert der Vorschubkraft in Abhängigkeit von dem Drehwinkel der Biegeschablone vorgegeben und der Istwert der Vorschubkraft wird entsprechend dem Sollwert geregelt. Entsprechend dem programmierten Verlauf des Sollwerts wird in Abhängigkeit vom momentanen Biegewinkel die Vorschubkraft der Gleitschiene verändert. Das System eignet sich besonders für dickwandige Rohre und speziell für die Druckbiegetechnik, bei der der ungebogene Rohrabschnitt während des Biegevorganges in Richtung auf die Biegeschablone gedrückt wird, sowie für Extrembereiche. Infolge der speziellen Druckregelung wird der Kraftfluß innerhalb der Rohrwände gezielt beeinflußt. Schwankungen des Materials, seiner Homogenität und Festigkeit wirken sich auf das Endprodukt nur sehr gering aus. Daher sind Ovalität und Faltenbildung an dem gebogenen Rohr ebenfalls gering. Die Vorteile des erfindungsgemäßen Steuerverfahrens sind also geringe Wandstärkenverjüngung, geringe Ovalität und geringer Werkzeugverschleiß. Eine Folge hiervon ist die Möglichkeit der Verringerung der Rohrwandstärke, und damit eine Materialersparnis, bei gleicher Festigkeit des fertigen Rohres. Ferner eignen sich die nach dem Verfahren gebogenen Rohre ausgezeichnet für eine nachfolgende Hydroverformung, bei der es auf hohe Gleichmäßigkeit des Ausgangsprodukts ankommt.The method according to the invention provides a force control for the feed force with which the slide rail is advanced. With this force control, a setpoint value of the feed force is specified as a function of the angle of rotation of the bending template and the actual value of the feed force is regulated according to the setpoint value. Depending on the programmed course of the setpoint, the feed force of the slide rail is changed depending on the current bending angle. The system is particularly suitable for thick-walled pipes and especially for pressure bending technology, in which the unbent pipe section is pressed in the direction of the bending template during the bending process, as well as for extreme areas. As a result of the special pressure control, the force flow within the tube walls is influenced in a targeted manner. Fluctuations in the material, its homogeneity and strength only have a very minor effect on the end product. Therefore ovality and wrinkling on the bent tube are also low. The advantages of the control method according to the invention are thus a small tapering of the wall thickness, low ovality and low tool wear. One consequence of this is the possibility of reducing the tube wall thickness, and thus a material saving, with the same strength of the finished tube. Furthermore, the tubes bent according to the method are excellent for a subsequent one Hydroforming, which depends on high uniformity of the starting product.

Vorzugsweise wird der Istwert der Vorschubkraft dadurch ermittelt, daß die Drücke im Zylinder auf beiden Seiten des Kolbens erfaßt werden und aus den Drücken unter Berücksichtigung der Größen der beiden Kolbenflächen der Istwert der Vorschubkraft bestimmt wird. Hierzu sind lediglich Drucksensoren an dem hydraulischen Zylinder für den Gleitschienenvorschub erforderlich. Alternativ besteht die Möglichkeit, einen Kraftsensor in den Gleitschienenvorschub einzubauen, jedoch wird hierdurch die Stabilität des Gleitschienenvorschubes verringert.The actual value of the feed force is preferably determined by detecting the pressures in the cylinder on both sides of the piston and determining the actual value of the feed force from the pressures, taking into account the sizes of the two piston surfaces. All that is required is pressure sensors on the hydraulic cylinder for the slide rail feed. Alternatively, it is possible to install a force sensor in the slide rail feed, but this reduces the stability of the slide rail feed.

Zweckmäßigerweise werden die Drücke im Zylinder auf beiden Seiten des Kolbens gegenläufig zueinander verändert. Dies bedeutet, daß im Falle einer Erhöhung des Vorschubdruckes der Gegendruck verringert wird. Dadurch besteht die Möglichkeit, den maximalen Pumpendruck für den Vorschub vollständig auszunutzen.The pressures in the cylinder on both sides of the piston are expediently changed in opposite directions to one another. This means that if the feed pressure increases, the back pressure is reduced. This makes it possible to fully utilize the maximum pump pressure for the feed.

Das erfindungsgemäße Verfahren muß nicht notwendigerweise für einen Rohrbiegevorgang von Anfang bis Ende durchgeführt werden. Es besteht auch die Möglichkeit, das Biegeverfahren teilweise nach dem Synchronverfahren und nur in den kritischen Bereichen mit dem erfindungsgemäßen Verfahren, d.h. durch Kraftregelung, durchzuführen.The method according to the invention does not necessarily have to be carried out for a pipe bending process from start to finish. There is also the possibility of partially bending according to the synchronous method and only in the critical areas with the method according to the invention, i.e. through force control.

Die Erfindung betrifft ferner eine Rohrbiegemaschine. Hierbei ist eine Einrichtung zur Erfassung des Istwertes der von dem Zylinder aufgebrachten Vorschubkraft vorgesehen und es ist ein Regler vorhanden, der den Istwert der Vorschubkraft entsprechend einem Sollwert nachregelt, der von einem Sollwert-Generator in Abhängigkeit von dem vom Positionsgeber der Biegeschablone gelieferten Biegewinkel erzeugt wird.The invention further relates to a pipe bending machine. Here is a device for detecting the actual value of the feed force applied by the cylinder is provided and there is a controller which adjusts the actual value of the feed force in accordance with a desired value which is generated by a desired value generator as a function of the bending angle supplied by the position transmitter of the bending template.

Im folgenden wird unter Bezugnahme auf die Zeichnungen ein Ausführungsbeispiel der Erfindung näher erläutert.In the following an embodiment of the invention will be explained with reference to the drawings.

Es zeigen:

Fig. 1
eine schematische Darstellung einer Rohrbiegemaschine in Draufsicht,
Fig. 2
ein Blockschaltbild der Regelung des Gleitschienenvorschubes und
Fig. 3
das Regelschema des Gleitschienenvorschubes.
Show it:
Fig. 1
a schematic representation of a pipe bending machine in plan view,
Fig. 2
a block diagram of the control of the slide rail feed and
Fig. 3
the control scheme of the slide rail feed.

Die in Fig. 1 schematisch dargestellte Rohrbiegemaschine weist eine auf einem (nicht dargestellten) Maschinentisch drehbar montierte Biegeschablone 10 auf. Die mit vertikaler Drehachse 11 angeordnete Biegeschablone 10 hat im wesentlichen die Form ein zylindrischen Körpers, an dessen Umfangsfläche eine Biegerille 12 ausgebildet ist, die den Querschnitt des zu biegenden Rohres 13 etwa zur Hälfte aufnimmt. An der Biegeschablone 10 ist eine Gegenspannbacke 14 befestigt, mit der eine Spannbacke 15 zusammenwirkt, um gemeinsam das Rohr 13 zu umgreifen und für den Biegevorgang festzuspannen. Die Spannbacke 15 ist an einem Schwenkarm 16 angebracht, der um eine Achse schwenkbar ist, welche mit der Drehachse 11 der Biegeschablone 10 zusammenfällt.The pipe bending machine shown schematically in FIG. 1 has a bending template 10 rotatably mounted on a machine table (not shown). The bending template 10 arranged with the vertical axis of rotation 11 has essentially the shape of a cylindrical body, on the circumferential surface of which a bending groove 12 is formed, which takes up approximately half the cross section of the tube 13 to be bent. On the bending template 10, a counter-clamping jaw 14 is fastened, with which a clamping jaw 15 cooperates in order to grip around the tube 13 together and clamp it tight for the bending process. The clamping jaw 15 is attached to a pivot arm 16 which is pivotable about an axis which coincides with the axis of rotation 11 of the bending template 10.

An diesem Schwenkarm 16 ist die Spannbacke 15 radial bewegbar, um das Rohr einzuspannen oder freizugeben.The clamping jaw 15 can be moved radially on this swivel arm 16 in order to clamp or release the tube.

Der ungebogene Abschnitt 13a des Rohres 13 wird von einer Nachdrückvorrichtung 17 abgestützt. Die Nachdrückvorrichtung weist einen Schlitten 18 auf, der in Richtung des Doppelpfeiles 19 quer zu dem Rohrabschnitt 13 verfahrbar ist. Der Schlitten 18 trägt einen Unterschlitten 20, der in Längsrichtung zu dem ungebogenen Rohrabschnitt 13a, also in Richtung des Doppelpfeiles 21, verfahrbar ist, sowie einen Zylinder 22 zum Bewegen des Unterschlittens 20. Der Zylinder 22 ist an dem Schlitten 18 fest angeordnet und in ihm ist der Kolben 23 bewegbar, dessen Kolbenstange 24 an dem Unterschlitten 20 angreift, um diesen zu verschieben. Der Zylinder 22 weist eine Arbeitskammer 25 und eine Rückhubkammer 26 auf, die durch den Kolben 23 getrennt sind.The unbent section 13a of the tube 13 is supported by a pressing device 17. The pressing device has a slide 18 which can be moved in the direction of the double arrow 19 transversely to the pipe section 13. The carriage 18 carries a lower carriage 20 which can be moved in the longitudinal direction to the unbent tube section 13a, that is to say in the direction of the double arrow 21, and a cylinder 22 for moving the lower carriage 20. The cylinder 22 is fixedly arranged on the carriage 18 and in it the piston 23 is movable, the piston rod 24 of which engages the lower slide 20 in order to displace it. The cylinder 22 has a working chamber 25 and a return stroke chamber 26, which are separated by the piston 23.

An der Biegeschablone 10 ist ein Positionsgeber 30 angeordnet. Der Positionsgeber 30 weist beispielsweise einen Drehwinkelkodierer auf, der die Drehposition der Biegeschablone 10 angibt. Die Biegeschablone 10 wird von einem (hydraulischen) Antrieb 31 gedreht.A position transmitter 30 is arranged on the bending template 10. The position sensor 30 has, for example, a rotary angle encoder which indicates the rotary position of the bending template 10. The bending template 10 is rotated by a (hydraulic) drive 31.

An dem Unterschlitten 20 ist in der Nähe der Biegeschablone 10 eine Gleitschiene 32 angebracht, die von der der Biegeschablone abgewandten Seite her gegen das Rohr 13 drückt und den ungebogenen Rohrabschnitt 13a beim Biegevorgang abstützt. Ferner ist an dem Unterschlitten 20 ein Schubelement 35 angebracht, das an dem rückwärtigen Teil des ungebogenen Rohrabschnitts 13a angreift. Das Schubelement 35 kann eine Klemmbacke 36 aufweisen, um den Rohrabschnitt 13a fest einzuspannen. Es ist so ausgebildet, daß es an dem Rohr gleltfrei angreift. Das Schubelement 35 und die Klemmbacke 36 sind für das Druckbiegen erforderlich. Wenn kein Druckbiegen ausgeübt wird, wird die Vorschubkraft ausschließlich von der Gleitschiene 32 auf das Rohr 13 übertragen.A slide rail 32 is attached to the lower slide 20 in the vicinity of the bending template 10 and presses against the tube 13 from the side facing away from the bending template and supports the unbent tube section 13a during the bending process. Furthermore, a thrust element 35 is attached to the lower slide 20, which engages on the rear part of the unbent pipe section 13a. The thrust element 35 can have a clamping jaw 36 in order to firmly clamp the pipe section 13a. It is so trained that it acts on the pipe glelt free. The thrust element 35 and the jaw 36 are required for the pressure bending. If no pressure bending is exerted, the feed force is transmitted exclusively from the slide rail 32 to the tube 13.

Beim Biegevorgang wird das gerade Rohr zwischen Spannbacke 15 und Gegenspannbacke 14 eingespannt. Dann wird die Biegeschablone 10 nach einem vorgegebenen Programm gedreht, wobei das Rohr um die Biegeschablone herumgezogen wird und gleichzeitig der gerade Rohrabschnitt 13a nach vorne bewegt wird. Während des Biegevorganges wird der Unterschlitten 20 parallel zum Rohrabschnitt 13a durch den hydraulischen Zylinder 22 vorgeschoben.During the bending process, the straight tube is clamped between the clamping jaw 15 and the counter clamping jaw 14. Then the bending template 10 is rotated according to a predetermined program, whereby the tube is drawn around the bending template and at the same time the straight tube section 13a is moved forward. During the bending process, the lower slide 20 is advanced parallel to the pipe section 13a by the hydraulic cylinder 22.

Gemäß Fig. 2 sind die Leitung 40, die an die Arbeitskammer 25 angeschlossen ist, und die Leitung 41, die an die Rückhubkammer 26 angeschlossen ist, mit einem Regelventil 42 verbunden, das drei unterschiedliche Stellungen A, B und C einnehmen kann. In der dargestellten Stellung A verbindet das Ventil 42 die Leitungen 40 und 41 mit einem Schaltventil 43, das mit einer Pumpe 44 und einem Sumpf 45 verbunden ist und zwischen einer Durchlaßstellung und einer Sperrstellung umgeschaltet werden kann. Die Stellung B des Ventils 42 dient für den schnellen Vorschub und die Stellung C für den Rückhub des Kolbens 23.2, the line 40, which is connected to the working chamber 25, and the line 41, which is connected to the return stroke chamber 26, are connected to a control valve 42 which can assume three different positions A, B and C. In the position A shown, the valve 42 connects the lines 40 and 41 to a switching valve 43, which is connected to a pump 44 and a sump 45 and can be switched between an open position and a blocking position. The position B of the valve 42 is used for the rapid feed and the position C for the return stroke of the piston 23.

In der Stellung A des Regelventils 42 werden die Durchlässe zu den Leitungen 40 und 41 proportional zu dem Signal einer Steuerleitung 39 verändert. Wenn das Signal der Steuerleitung 39 klein ist, sind der zur Leitung 40 führende Drosselquerschnitt und der mit der Leitung 41 verbundene Drosselquerschnitt ebenfalls klein. Je größer das Signal der Steuerleitung 39 ist, um so größer wird der mit der Leitung 40 verbundene Drosselquerschnitt und um so größer wird der mit der Leitung 41 verbundene Drosselquerschnitt. Die Drosselquerschnitte in Zulauf und Ablauf sind stets gleich. Die Drücke zu beiden Seiten des Kolbens werden gegenläufig zueinander verändert.In position A of the control valve 42, the passages to the lines 40 and 41 are changed in proportion to the signal of a control line 39. If the signal of the control line 39 is small, the throttle cross section leading to the line 40 and that with the Line 41 connected throttle cross section also small. The larger the signal of the control line 39, the larger the throttle cross section connected to line 40 and the larger the throttle cross section connected to line 41. The throttle cross sections in the inlet and outlet are always the same. The pressures on both sides of the piston are changed in opposite directions to each other.

An die Leitung 40 ist ein Druckwandler 46 angeschlossen, der ein Stromsignal erzeugt, welches dem hydraulischen Druck in der Leitung 40 entspricht. An die Leitung 41 ist ein Druckwandler 47 angeschlossen, der ein Stromsignal erzeugt, das dem hydraulischen Druck in der Leitung 41 entspricht. Die Ausgänge der beiden Druckwandler 46 und 47 sind mit einem Regler 48 verbunden, der an die Steuerleitung 39 das Steuersignal für das Differentialventil 42 liefert. Der Regler 48 berechnet aus den Drücken in den Kammern 25 und 26 und den Größen der beiden Kolbenflächen A1 und A2 den Istwert Fi der Vorschubkraft, die auf den Schlitten 20 einwirkt.A pressure transducer 46 is connected to line 40 and generates a current signal which corresponds to the hydraulic pressure in line 40. A pressure transducer 47 is connected to line 41 and generates a current signal which corresponds to the hydraulic pressure in line 41. The outputs of the two pressure transducers 46 and 47 are connected to a controller 48, which supplies the control signal 39 for the control valve for the differential valve 42. The controller 48 calculates the actual value Fi of the feed force that acts on the slide 20 from the pressures in the chambers 25 and 26 and the sizes of the two piston surfaces A1 and A2.

Der Regler 48 ist ferner mit einem Sollwert-Generator 49 verbunden, welcher einen Sollwert Fs der Vorschubkraft an den Regler 48 liefert. Dieser Sollwert Fs der Vorschubkraft variiert in Abhängigkeit von dem Drehwinkel α der Biegeschablone 10, der vom Positionsgeber 30 geliefert wird.The controller 48 is also connected to a setpoint generator 49, which supplies a setpoint Fs of the feed force to the controller 48. This target value Fs of the feed force varies depending on the angle of rotation α of the bending template 10, which is supplied by the position sensor 30.

Fig. 3 zeigt das Regelschema. Der Sollwert-Generator 49 enthält mehrere Kurven, die den Sollwert Fs der Vorschubkraft in Abhängigkeit vom Drehwinkel α der Biegeschablone 10 angeben. An dem Sollwert-Generator kann die jeweils gewünschte Kurve ausgewählt werden. Ferner kann an dem Sollwert-Generator der Wert α für den Start und das Ende der Rohrbearbeitung eingegeben werden. Der Sollwert-Generator 49 liefert dann in Abhängigkeit von α den jeweils zugehörigen Sollwert Fs, von dem in einem Subtrahierer 50 der Istwert Fi subtrahiert wird. Das Subtraktionsergebnis wird dem Regler 48 zugeführt, der beispielsweise ein PID-Regler ist. Dieser Regler liefert über die Steuerleitung 39 ein Regelsignal an die Regelstrecke 51, die hier aus dem Differentialventil 42 und dem Zylinder 22 (Fig. 2) besteht.Fig. 3 shows the control scheme. The setpoint generator 49 contains several curves that indicate the setpoint Fs of the feed force as a function of the angle of rotation α of the bending template 10. Can on the setpoint generator the desired curve can be selected. Furthermore, the value α for the start and end of the tube processing can be entered on the setpoint generator. The setpoint generator 49 then supplies, depending on α, the respectively associated setpoint Fs, from which the actual value Fi is subtracted in a subtractor 50. The subtraction result is fed to controller 48, which is a PID controller, for example. This controller supplies a control signal to the control path 51 via the control line 39, which here consists of the differential valve 42 and the cylinder 22 (FIG. 2).

Der Druck P1 in der Leitung 40 und der Druck P2 in der Leitung 41 werden dem jeweiligen Wandler 46 bzw. 47 zugeführt. Das Ausgangssignal des Wandlers 46 wird in einem Multiplizierer 52 mit einem Wert multipliziert, der der Fläche A1 des Kolbens 23 entspricht. Das Ausgangssignal des Wandlers 47 wird in einem Multiplizierer 53 mit einem Wert multipliziert, der der Größe der Fläche A2 des Kolbens 23 entspricht. Der Multiplizierer 52 bildet also das Produkt P1 x A1 und der Multiplizierer 53 bildet das Produkt P2 x A2. Jedes dieser Produkte ist ein Maß für eine der beiden Kräfte, die gegensinnig zueinander auf den Kolben 23 einwirken. Ein Subtrahierer 54 subtrahiert die beiden Produkte voneinander, so daß der Istwert Fi der Vorschubkraft entsteht. Dieser Istwert wird in dem Subtrahierer 50 von dem Sollwert Fs subtrahiert, um das Eingangssignal für den Regler 48 zu bilden.The pressure P1 in line 40 and the pressure P2 in line 41 are fed to the respective transducers 46 and 47, respectively. The output signal of the converter 46 is multiplied in a multiplier 52 by a value which corresponds to the area A1 of the piston 23. The output signal of the converter 47 is multiplied in a multiplier 53 by a value which corresponds to the size of the area A2 of the piston 23. The multiplier 52 thus forms the product P1 x A1 and the multiplier 53 forms the product P2 x A2. Each of these products is a measure of one of the two forces acting in opposite directions on the piston 23. A subtractor 54 subtracts the two products from one another, so that the actual value Fi of the feed force arises. This actual value is subtracted from the target value Fs in the subtractor 50 in order to form the input signal for the controller 48.

Die Ausgangssignale der beiden Wandler 46 und 47 werden einer Fehlerauswertung 55 zugeführt, die ein Alarmsignal erzeugt oder die Rohrbiegemaschine stillsetzt, wenn die Drücke P1 und P2 Abnormalitäten zeigen. Es können auch z.B. Totalausfälle des Sensors aufgezeigt werden.The output signals of the two converters 46 and 47 are fed to an error evaluation 55, which generates an alarm signal or stops the pipe bending machine when the pressures P1 and P2 show abnormalities. Total failures of the sensor can also be shown.

Claims (6)

Verfahren zur Steuerung einer Rohrbiegemaschine, die eine drehbare Biegeschablone (10), eine das Rohr (13) gegen die Biegeschablone (10) drückende Spannbacke (15) und eine an dem ungebogenen Rohrabschnitt (13a) angreifende, von einem hydraulischen Zylinder (22) vorschiebbare Gleitschiene (32) aufweist, bei welchem der jeweilige Biegewinkel (α) der Biegeschablone (10) gemessen wird, aus einem Sollwert-Generator (49) entsprechend dem Biegewinkel (α) ein Sollwert (Fs) für die Vorschubkraft ausgegeben wird, der Istwert (Fi) der Vorschubkraft ermittelt wird, und die Drücke (P1,P2) im Zylinder (22) so verändert werden, daß der Istwert (Fi) dem Sollwert (Fs) der Vorschubkraft folgt. Method for controlling a pipe bending machine, which comprises a rotatable bending template (10), a clamping jaw (15) pressing the pipe (13) against the bending template (10) and a hydraulic cylinder (22) which can be pushed against the unbent pipe section (13a) Has slide rail (32), in which the respective bending angle (α) of the bending template (10) is measured, a setpoint (Fs) for the feed force is output from a setpoint generator (49) corresponding to the bending angle (α), the actual value (Fi) of the feed force is determined, and the pressures (P1, P2) in the cylinder (22) are changed so that the actual value (Fi) follows the target value (Fs) of the feed force. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Istwert (Fi) der Vorschubkraft dadurch ermittelt wird, daß die Drücke (P1,P2) im Zylinder (22) auf beiden Seiten des Kolbens (23) erfaßt werden und aus den Drücken unter Berücksichtigung der Größen der beiden Kolbenflächen (A1,A2) der Istwert (Fi) der Vorschubkraft bestimmt wird.Method according to Claim 1, characterized in that the actual value (Fi) of the feed force is determined in that the pressures (P1, P2) in the cylinder (22) on both sides of the piston (23) are recorded and from the pressures taking into account the Sizes of the two piston surfaces (A1, A2) the actual value (Fi) of the feed force is determined. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Drücke (P1,P2) im Zylinder (22) auf beiden Seiten des Kolbens (23) gegenläufig zueinander verändert werden.Method according to claim 1 or 2, characterized in that the pressures (P1, P2) in the cylinder (22) on both sides of the piston (23) are changed in opposite directions to one another. Rohrbiegemaschine zum Biegen eines Rohres (10), mit einer von einem Antrieb (33) drehbaren Biegeschablone (10), einer das Rohr (13) gegen die Biegeschablone (10) drückenden Spannbacke (15), einer an dem ungebogenen Rohrabschnitt (13a) angreifenden, von einem hydraulischen Zylinder (22) angetriebenen Gleitschiene (32), einem Positionsgeber (30) zur Ermittlung der Drehposition der Biegeschablone (10) und einer Einrichtung, die den Zylinder (22) für den Vorschub der Gleitschiene (32) in Abhängigkeit von dem Signal des Positionsgebers (30) verändert,
dadurch gekennzeichnet,
daß eine Einrichtung (46,47,52,53) zur Erfassung des Istwertes (Fi) der von dem Zylinder (22) aufgebrachten Vorschubkraft (F) vorgesehen ist, und daß ein Regler (48) den Istwert (Fi) der Vorschubkraft entsprechend einem Sollwert (Fs) nachregelt, der von einem Sollwert-Generator (49) in Abhängigkeit von dem vom Positionsgeber (30) gelieferten Biegewinkel (α) erzeugt wird.Pipe bending machine for bending a pipe (10), with a bending template (10) rotatable by a drive (33), a clamping jaw (15) pressing the pipe (13) against the bending template (10), and one which engages on the unbent pipe section (13a) , of a hydraulic cylinder (22) driven slide rail (32), a position sensor (30) for determining the rotational position of the bending template (10) and a device which the cylinder (22) for feeding the slide rail (32) depending on the Signal of the position transmitter (30) changed,
characterized,
that a device (46, 47, 52, 53) is provided for detecting the actual value (Fi) of the feed force (F) applied by the cylinder (22), and that a controller (48) adjusts the actual value (Fi) of the feed force in accordance with a Setpoint (Fs) readjusted, which is generated by a setpoint generator (49) as a function of the bending angle (α) supplied by the position transmitter (30). Rohrbiegemaschine nach Anspruch 4, dadurch gekennzeichnet, daß die Einrichtung (46,47,52,53) zur Erfassung des Istwertes (Fi) der Vorschubkraft (F) zwei Drucksensoren (46,47) aufweist, die die Drücke (P1,P2) zu beiden Seiten des Kolbens (23) erfassen.Pipe bending machine according to claim 4, characterized in that the device (46, 47, 52, 53) for detecting the actual value (Fi) of the feed force (F) has two pressure sensors (46, 47) which increase the pressures (P1, P2) grasp both sides of the piston (23). Rohrbiegemaschine nach Anspruch 4 oder 5, dadurch gekennzeichnet, daß der Regler (48) ein Regelventil (42) mit stetiger Drosselkennlinie steuert, welches die Drücke (P1,P2) zu beiden Seiten des Kolbens (23) gegenläufig zueinander verändert.Pipe bending machine according to claim 4 or 5, characterized in that the controller (48) controls a control valve (42) with a constant throttle characteristic which changes the pressures (P1, P2) on both sides of the piston (23) in opposite directions to one another.
EP96109222A 1995-06-17 1996-06-08 Method for controlling a tube bending machine Expired - Lifetime EP0748662B1 (en)

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DE19522062A DE19522062A1 (en) 1995-06-17 1995-06-17 Method for controlling a pipe bending machine
DE19522062 1995-06-17

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DE19522062A1 (en) 1996-12-19
EP0748662B1 (en) 2000-03-22
DE59604728D1 (en) 2000-04-27
CA2178985C (en) 2006-10-03
CA2178985A1 (en) 1996-12-18
US5682781A (en) 1997-11-04

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