EP0773076A1 - Dispositif de commande de la pression dans des serre-flans hydrauliques des presses à emboutir - Google Patents

Dispositif de commande de la pression dans des serre-flans hydrauliques des presses à emboutir Download PDF

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Publication number
EP0773076A1
EP0773076A1 EP96117676A EP96117676A EP0773076A1 EP 0773076 A1 EP0773076 A1 EP 0773076A1 EP 96117676 A EP96117676 A EP 96117676A EP 96117676 A EP96117676 A EP 96117676A EP 0773076 A1 EP0773076 A1 EP 0773076A1
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EP
European Patent Office
Prior art keywords
pressure
cylinder
die cushion
valve
proportional valve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP96117676A
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German (de)
English (en)
Other versions
EP0773076B1 (fr
Inventor
Markus Dr. Müller
Axel Stange
Andreas Schlag
Eckhardt Menger
Gregor Geist
Steffen Schmidt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Umformtechnik Erfurt GmbH
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Umformtechnik Erfurt GmbH
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Publication date
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Application filed by Umformtechnik Erfurt GmbH filed Critical Umformtechnik Erfurt GmbH
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Classifications

    • 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
    • B21D24/00—Special deep-drawing arrangements in, or in connection with, presses
    • B21D24/10—Devices controlling or operating blank holders independently, or in conjunction with dies
    • B21D24/14—Devices controlling or operating blank holders independently, or in conjunction with dies pneumatically or hydraulically

Definitions

  • the invention relates to a device for controlling and regulating the pressure in hydraulic die cushions of presses according to the preamble of claims 1 and 2.
  • the displacement principle In hydraulic die cushions in presses, the displacement principle often occurs, in which the press ram drives the pistons of the die cushion cylinders and displaces the oil from the cylinder chambers.
  • a proportional valve arranged in the discharge line influences the discharge cross-section in such a way that the desired pressure profiles in the cylinder are established during the drawing process.
  • the current pressure in the die cushion cylinder is recorded by means of a pressure sensor and fed to a controller as an actual signal.
  • the controller forms a corresponding correction signal for controlling the proportional valve from the comparison of the nominal and actual signals.
  • the impact of the tappet on the extended pistons of the die cushion cylinders is regarded as a critical moment during the regulation, since the discharge volume flow suddenly changes from zero to its maximum value.
  • the main control piston of the proportional valve has to be moved into the open position at high speed in order to avoid undesirable pressure peaks.
  • the disturbing influences on the regulation of the die cushion pressure are comparatively low, so that generally simple control concepts (PI controllers) already ensure good results.
  • the ram speed is gradually reduced to zero.
  • the die cushion pressure should correspond to the specified courses. From EP 0 330 718 a circuit arrangement for regulating the holding force ... is known, which in a suitable manner Proportional valve actuated.
  • a number of coordinated control measures result in a reduction in the pressure peaks when the tappet hits the piston rods of the die cushion cylinders.
  • This circuit arrangement requires proportional valves with high control speeds.
  • Another assessment criterion is the effort required to commission the control loop and the options for influencing its behavior by the maintenance staff. In this case, special knowledge of maintenance personnel is required.
  • the pressure reducing valve is located in the inlet line and the pressure relief valve is located in the outlet line. Both valves are controlled by a controller using a specific procedure.
  • the object of the invention is therefore to design a device for controlling and regulating the pressure in such a way that the overshoot of the pressure when the tappet strikes is reduced using robust methods that can be traced by the operating personnel, and the pressure build-up path of the die cushion is also minimized.
  • the first, controlled mode of operation is the "pre-opening" of the proportional valve.
  • the main control piston Before the plunger hits the displacement piston, the main control piston is positioned on a predefined, defined opening gap.
  • the size of the pre-opening results from the speed of impact of the tappet on the die cushion and the specified pressure setpoint for the start of control.
  • This pre-opening value is determined once empirically or simulatively and stored, for example, in a table within a controller. With the help of this valve opening What is achieved is that the main piston of the proportional valve has already covered a certain distance in the opening direction and that only the difference to the maximum value has to be overcome when the tappet strikes.
  • the pre-opening value is generally smaller than the maximum required valve opening, which is necessary for setting the desired pressure in the volume flow caused by the impact speed, in order to enable the pressure in the cylinder to build up in a short time.
  • the rate of pressure rise is therefore dependent on the selected pre-opening value and the pressure setpoint.
  • a compromise between the shortest possible pressure build-up path and the maximum permissible overshoot can be regarded as the optimum.
  • the transition from the controlled mode of operation to the regulated mode takes place towards the end of the build-up of pressure.
  • the criterion for the switchover is derived from the process itself if no path measuring system is available for the detection of the die cushion path.
  • the switchover takes place when the difference between the pressure setpoint and actual pressure value falls below a predetermined amount. This ensures that the excitation of the control loop is reduced when switching.
  • Another method for the combination of control and regulation is described in the embodiment. After the tappet has hit the die cushion, the expected disturbances are relatively small, so that a generally known PID control algorithm is sufficient for pressure control. It is also advisable to make the D component of the controller switchable and to activate it only when larger control deviations are expected, i.e. when the controller is switched on or when the setpoint signal changes abruptly.
  • the press ram 1 strikes with the upper part 2 of the die 3, which rests on the sheet metal holder 4 of the lower part 5 of the tool.
  • the sheet metal holder 4 holds the circuit board 3 at a distance " ⁇ s", which corresponds to the pressure build-up path, above the lower part 5 of the die 4 applied and counteracts this in the downward movement of the plunger 1.
  • the die cushion cylinders 11 provided for the generation of force and a central cylinder 9 for controlling the position of the die cushion for its upward motion are fastened in the press table 6.
  • the hydraulic control 10 for generating pressure is each assigned to a die cushion cylinder 11 in the form of a control block.
  • FIG. 3 For external prestressing of the die cushion cylinder 11, its piston rod must be fixed in its upper working position by a stop 29, which is fixed or adjustable.
  • a stop 29 which is fixed or adjustable.
  • one or more drawing cushion cylinders 11 are respectively connected on the discharge side, in special cases not shown together, via a line 28 to a proportional valve 12.
  • the respective actual value of the die cushion pressure is recorded via pressure transducer 17 and fed to the cushion force regulator 23.
  • the proportional valve 12 is connected on the discharge side via the continued line 28 to the prestressed tank 13 which is pressurized with compressed air from the pressure source 14.
  • the hydraulic oil flows only then from the die cushion cylinder 11 via the opened proportional valve 12 into the prestressed tank 13 when the press ram 1 moves the pistons of the die cushion cylinder 11 downward.
  • Another check valve 18 separates the die cushion cylinder 11 from a switchable pressure source 20 in such a way that when the switching valve 19 is activated, hydraulic oil flows from the pressure source 20 into the die cushion cylinder 11 as long as there is a pressure difference.
  • the pressure in the pressure source 20 is adjusted by means of a pressure-controlled pump 22 to the target pressure of the die cushion in such a way that the storage pressure is slightly lower. Then the pressure rise caused by the impact of the press ram leads to the closing of the check valve 18.
  • the switching valve 19 is switched depending on the press ram path so that before the impact of the press ram the "active pressure build-up" begins in the die cushion cylinder and the apex of the pressure build-up curve at the point of impact of the pestle.
  • FIG. 1 The path-time profiles of the press ram and the die cushion can be seen in the diagram above. At point “A”, the point of impact of the ram 1 on the die cushion, both courses over the die area are identical.
  • the middle diagram shows the curves of the die cushion pressure over the drawing path "s z " at the maximum and minimum pressure setpoint. With a small pressure setpoint, the overshoot of the actual pressure is clearly pronounced in previous control concepts.
  • a higher-level controller 24 transfers the current actual values with respect to the cushion travel "s K ", the number of press strokes “n” and the crank angle “ ⁇ ” to the cushion force controller 23.
  • the cushion force controller 23 of the set pressure “p to” transmits a threshold pressure “p SW” the drawing depth "s Z” and.
  • the cushion force controller 23 contains a generally known PID controller with switchable I and D components and a resettable I component. The PID controller itself can also be switched. All switching functions of the cushion force controller 23 are triggered by an internal control unit 25 as a function of the cushion travel "s K ".
  • the cushion force controller 23 receives the actual pressure value "p ist " directly from a pressure sensor 17.
  • the pressure setpoint "p soll” is fed to the PID controller via a reference variable generator 26 to form the control deviation "x d ".
  • the command variable generator 26 changes the pressure value "p set” depending on the Kissenweg “s K” such that it is increased in the “passive” pressure build-up phase of a reduced proportion of more than a defined distance up to its original value.
  • the controller output is the Vorö réelleswert summed “to p” which in a module 27 in response to the Kissenweg “s K", the pad speed “ds K (t) / dt", the draw depth “s Z”, the pressure command value, the number of press “n” and the crank angle " ⁇ ” calculated the pre-opening value and activated during the pressure build-up.
  • a pressure threshold value "p SW” is transmitted to the module 27, which is used when the die cushion does not have its own measuring system.
  • the pre-opening value is then deactivated as a function of the pressure threshold "p SW ".
  • the command variable "w” and the pre-opening value are determined as a function of the number of press strokes.
  • the cushion force controller 23 delivers the switching signal to a valve 19 by comparing a reference angle " ⁇ ref " transferred by the control 24 with the current value of the crank angle " ⁇ ".

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Presses And Accessory Devices Thereof (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)
  • Braking Arrangements (AREA)
  • Paper (AREA)
EP96117676A 1995-11-09 1996-11-05 Dispositif de commande de la pression dans des serre-flans hydrauliques des presses à emboutir Expired - Lifetime EP0773076B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19541693 1995-11-09
DE19541693A DE19541693A1 (de) 1995-11-09 1995-11-09 Einrichtung zur Steuerung und Regelung des Druckes in hydraulischen Ziehkissen von Pressen

Publications (2)

Publication Number Publication Date
EP0773076A1 true EP0773076A1 (fr) 1997-05-14
EP0773076B1 EP0773076B1 (fr) 2000-04-05

Family

ID=7776963

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96117676A Expired - Lifetime EP0773076B1 (fr) 1995-11-09 1996-11-05 Dispositif de commande de la pression dans des serre-flans hydrauliques des presses à emboutir

Country Status (3)

Country Link
EP (1) EP0773076B1 (fr)
DE (2) DE19541693A1 (fr)
ES (1) ES2145362T3 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2377629A4 (fr) * 2008-11-18 2015-10-14 Aida Eng Ltd Dispositif coussin élastique pour presse
US10870251B2 (en) * 2016-04-06 2020-12-22 Schuler Pressen Gmbh Method and device for closed-loop control of ram movement and ram forces in multi-point servo hybrid presses

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102010019324B4 (de) 2010-05-03 2015-05-07 Schuler Pressen Gmbh Hydraulisches Ziehkissen
DE102015016773B4 (de) 2015-12-23 2024-12-24 Wieland Petter Verfahren zum Bearbeiten und zur Formgebung metallischer und anderer Werkstoffe

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3800527A1 (de) 1988-01-11 1989-07-20 Schnupp Gmbh & Co Hydraulik Kg Druckregelung
DE8905994U1 (de) * 1989-05-13 1989-07-20 Maschinenfabrik Müller-Weingarten AG, 7987 Weingarten Pneumatische Zieheinrichtung für Pressen
EP0330718A1 (fr) 1988-03-03 1989-09-06 MOOG GmbH Circuit de régulation de la force de serrage d'un serre-flan hydraulique dans une presse d'emboutissage
DE4031645A1 (de) 1990-10-05 1992-04-09 Dieffenbacher Gmbh Maschf Steuerung fuer eine hydroelastische tiefzieheinrichtung

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3800527A1 (de) 1988-01-11 1989-07-20 Schnupp Gmbh & Co Hydraulik Kg Druckregelung
EP0330718A1 (fr) 1988-03-03 1989-09-06 MOOG GmbH Circuit de régulation de la force de serrage d'un serre-flan hydraulique dans une presse d'emboutissage
DE8905994U1 (de) * 1989-05-13 1989-07-20 Maschinenfabrik Müller-Weingarten AG, 7987 Weingarten Pneumatische Zieheinrichtung für Pressen
DE4031645A1 (de) 1990-10-05 1992-04-09 Dieffenbacher Gmbh Maschf Steuerung fuer eine hydroelastische tiefzieheinrichtung

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2377629A4 (fr) * 2008-11-18 2015-10-14 Aida Eng Ltd Dispositif coussin élastique pour presse
US10870251B2 (en) * 2016-04-06 2020-12-22 Schuler Pressen Gmbh Method and device for closed-loop control of ram movement and ram forces in multi-point servo hybrid presses

Also Published As

Publication number Publication date
DE19541693A1 (de) 1997-05-15
EP0773076B1 (fr) 2000-04-05
DE59604877D1 (de) 2000-05-11
ES2145362T3 (es) 2000-07-01

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