DE102008003106A1 - Method for energy-saving operation of a hydraulic press and an energy-saving and low-maintenance hydraulic press - Google Patents

Abstract

The invention relates to a hydraulic press and a method for operating a hydraulic press with a plunger (1) and a die cushion (2) for applying a blank holder force on the workpiece to be formed with a drive (11) for at least one hydraulic pump (10) for lifting and Lowering the plunger (1) and the die cushion (2). The following process steps are carried out when the plunger (1) and the die cushion (2) are in the upper reversal point: To lower the plunger (1), the release valve (9) is opened and the hydraulic medium from the plunger cylinder chamber (7) via the displacer unit (15 ), which drives suitable consumers. After encountering plunger (1) and die cushion (2) the release valve (9) is closed and the plunger cylinder chamber (5) with hydraulic medium via the control valve (19) from the hydraulic pump (10) acted upon. At the same time, the release valves (20) of the die cushion (2) are opened and the hydraulic medium is removed from the die cushion cylinder space (6) via the displacer unit (15), which drives suitable consumers. At the same time, the hydraulic pressure in the die cushion cylinder space (6) and thus the plate holding force are regulated by changing the swivel angle in the displacer unit (15) or via the delivered torque of the displacer unit (15). After completion of the forming, the plunger (1) and the die cushion (2) are moved to the upper reversal point.

Description

The The invention relates to a method for energy-saving operation of a hydraulic press according to the preamble of claim 1 and a Energy-saving and low-maintenance hydraulic press according to the generic term of claim 6.

Energy-saving Processes and manufacturing plants are in the present time and the accompanying climate discussion regularly an issue in sales negotiations and are rising energy prices and scarcer raw materials for energy in the future play a bigger role.

Nevertheless, energy-saving applications and presses have been the subject of patent literature for many years. For example, from the 1980s, the energy-saving drive for flywheel drives in hydraulic presses is from the DE 32 16 563 C1 or the DD 204 067 known. The flywheel drives for energy-saving or power peaks avoiding application are preferably charged continuously, the charging times are arranged opposite to cyclic to the load times of the press.

With DE 42 18 952 A1 is a hydraulic drive of a press, in particular for a sheet metal forming press has become known, in which the Rückhubzylinderkammer the plunger is connected to a hydraulic machine. It should be emphasized that the hydraulic circuit of the plunger and the plate holder or the lower table are basically separated and a first hydraulic machine is connected with its second output to a hydraulic accumulator. The hydraulic accumulator is charged in an energy-saving way and releases its charged energy when needed during the press play.

The same revealed DE 42 18 953 A1 shows a similar hydraulic drive of a press, wherein the kinetic energy of the downwardly moving plunger is used to support the pump drive, which supplies the pressing cylinder chamber with pressure. It is known to arrange one or more displacement units or hydraulic pumps and to control them differently depending on the needs. The circuit complexity and the necessary open and closed-loop control are very cumbersome and affect the availability of the press. Also here is in the foreground only to avoid the power peaks of energy intake, which is associated with high circuit and plant technical complexity.

All in all lacks the state of the art in an energy-saving application and at the same time simple construction of the entire hydraulic system. The possibilities of optimizing a press were in the time of departure from machine-controlled to electronically-controlled Systems on one side to other machine elements (pump / motor combinations, Power circuits, memory elements), which are Control and control technically easy to integrate in a press. On top of that, at that time, not the total power requirement the costly problem, but the peak performance, which consumes a press during operation.

In More recently, the problem of high electricity costs has been added now significantly the price of each workpiece produced to push up. The industry demands from the plant manufacturer not just an energy-saving and low-power plant, but also a low-maintenance and low-cost operating costs Plant for the production of mass and consumer goods. The worldwide Climate and environmental discussions also lead to massive inflation led the necessary hydraulic oil, so that The plant manufacturer is required to be similar to the car industry extend the maintenance intervals and wear of oils keep as low as possible.

meanwhile means the replacement of hydraulic oil in a hydraulic Press certainly a significant cost factor. At the same time the smallest possible number of switching elements in the hydraulics in short hydraulic paths (lines) are realized by pressure gradient in the hydraulic lines and to minimize the necessary valves. Of course, there are possible advantages as well as a favorable one Noise behavior by avoiding otherwise usual Control and regulating mechanism (valves, throttles, ...). Especially Throttling valves, so far regulating the downward movement in terms of acceleration, speed and braking behavior have taken over from drawing cushions or pestles, However, they are characterized by a high level of noise also by the resulting oil heating. The latter must be broken down again with high energy expenditure. Besides is the oil heating and hydraulic throttling chiefly responsible for the tribological wear of the Hydraulic medium.

Object of the present invention is to provide a method for energy-saving and low-maintenance operation of a hydraulic press, which is used in a simple manner, the kinetic energy of a plunger of a press during the forming process to provide the blank holder force of the counter-acting die cushion and adjustable to Shaping the excess kinetic energy during the Um Formvorganges can be used in an advantageous manner with the least possible load on the hydraulic medium. Next is an independent functioning and usable press to be created, which is also able to implement the method according to the invention and at the same time allows energy-saving and simplified control of the kinetic energy of the plunger and the force of the sheet metal holder at the same time significantly gentle use of the hydraulic medium, at the same time a reduced temperature increase of the hydraulic medium is associated.

The solution to the method consists in the course of the following process steps shown, when in the initial position of the plunger and the die cushion are in the upper reversal point:
to lower the plunger, the release valve is opened and the hydraulic medium discharged from the plunger ring cylinder space via the displacer unit which drives an asynchronous or DC motor or other suitable consumers via a torque clutch; after the ram and die cushion collide, the release valve is closed and the plunger cylinder chamber is acted upon by hydraulic fluid via the control valve from the hydraulic pump, while the release valves of the die cushion are opened and the hydraulic medium is removed from the die cushion cylinder space via the displacer unit, which via an torque clutch is an asynchronous or DC motor or other suitable consumers drives and at the same time is controlled by changing the pivot angle in the displacer unit or on the output torque to the displacer unit, the hydraulic pressure in Ziehkissenzylinderraum and thus the Blechhaltekraft, and after completion of the forming of the plunger and the die cushion by the supply via the Hydraulic pump moved back to the starting position, the upper reversal point.

The solution for an independently functioning press and also for a press for carrying out the method is that for lowering the plunger, the plunger ring cylinder space via a release valve with a displacer unit and / or for lowering the die cushion of Ziehkissenzylinderraum via at least one release valve with a displacer unit for Hydraulic medium is connectable,
wherein the displacer unit has a torque coupling to an asynchronous motor, a DC motor or another suitable consumer, and
No cited patent literature in the prior art treatise has suggested using the potential energy of the plunger to control the blank holder force with simple and direct introduction of energy into the die cushion via the effluent hydraulic medium with only one displacer unit, either a displacer unit with constant outflow Volume and a corresponding torque control or a displacer unit with variable outflowing volume is used.

Thereby the possibility arises, depending on the used displacement unit the speed of the departing ram or the blank holder force of the counteracting die cushion on a single machine element, the displacer unit and level. This is advantageously done in energy-saving or recovering manner. One goes that one Hydraulic medium gentle application, which extends the service life of the hydraulic medium Significantly extended and an otherwise energy-destroying Cooling of the hydraulic medium avoids.

• – Es werden keine Drosselelemente im regulären Betrieb der Presse verwendet und eine unnötige Belastung bzw. ein unnötiger tribologischer Verschleiß des Hydraulikmediums wird vermieden.
• – Einher gehen eine Verlängerung des möglichen Wartungsintervalls der Presse und eine Verlängerung der Lebensdauer des Hydraulikmediums.
• – Die Geschwindigkeit- bzw. Krafteinstellung erfolgt in einfacher Weise durch die Verstellung des Schwenkwinkels bzw. über die Drehzahl der Verdrängereinheit mit konstantem Verdrängungsvolumen,
• – es erfolgt eine Verringerung des Energiebedarfs und der Spitzenleistung der Presse und
• – eine Verringerung der notwendigen Kühlleistung für das Hydraulikmedium.
• – Zusätzlich zu den obigen Punkten erfolgt eine Verringerung der verbrauchten Energie und notwendiger Anlagenkosten je produziertes Werkstück und damit eine Verringerung der Herstellungskosten eines Werkstückes.

Unnecessary friction and heat losses via the hydraulic medium are avoided. This results in a clear overview of the following advantages:

• - No throttle elements are used in regular operation of the press and unnecessary stress or unnecessary tribological wear of the hydraulic medium is avoided.
• - Include an extension of the possible maintenance interval of the press and an extension of the service life of the hydraulic medium.
• - The speed or force adjustment takes place in a simple manner by the adjustment of the swivel angle or on the speed of the displacer unit with a constant displacement volume,
• - There is a reduction in energy consumption and peak performance of the press and
• - A reduction in the necessary cooling capacity for the hydraulic medium.
• - In addition to the above points, there is a reduction in the energy consumed and the necessary equipment costs per workpiece produced and thus a reduction in the manufacturing cost of a workpiece.

The relatively high cost of energy-saving or energy-recovering system components can be like at most energy saving investments over one amortize short period of time and ask for the decision investment as a secondary point of view. In addition are possibilities when purchasing or installing several presses given individual necessary plant parts (power supply, conversion) to be used by appropriate interconnections using multiple presses.

Even if the amortization costs are still too high for the energy despite rising energy prices are gierückspeisung, so it can still be driven by the displacer unit and the associated torque coupling in a simple manner other consumers, such as a cooling unit for the hydraulic cooling or the like.

The are described displacement units or hydraulic motors for those skilled in the well-known gear motors for one or both directions of rotation. One works on the shaft driven gear motor as a pump and can when fed of pressurized oil generate a torque on the shaft and in working as a motor in this condition. Axial piston pumps have the Possibility to adjust the volume from the outside, depending on the setting of the angle is more or less hydraulic medium promoted per shaft revolution or driven the shaft becomes.

Further advantageous measures and embodiments of the subject matter The invention will be apparent from the subclaims and the following Description with the drawing out.

It demonstrate:

1 a known prior art press drive for a press with known control of the kinetic energy of the plunger and the blank holder force by throttling the hydraulic medium in a schematic representation,

2 Press drive and press control for a press with control of the plunger kinetic energy and the blank holder force by directing the displaced hydraulic medium through a variable displacement displacer unit with coupled asynchronous motor for energy recovery,

3 Press drive and press control for a press with control of the plunger kinetic energy and the blankholder force by directing the displaced hydraulic medium through a constant displacement displaced volume unit and coupled asynchronous motor for energy recovery via a regenerative unit and frequency converter and

4 A press drive and press control for a press having kinetic energy control of the ram and the blank holder force by directing the displaced hydraulic medium through a constant displacement displacer unit and coupled DC motor for energy recovery via a 4-quadrant power converter.

In 1 the hitherto known state of the art is shown. In conventional hydraulic presses, for example for metal forming, in a press frame is a movable plunger 1 and a movable, usually executed as a counter-holder movable die cushion 2 arranged. tappet 1 is operated via a hydraulic cylinder system, which is divided systematically from a ram cylinder space 5 , a ram-ring cylinder space 7 and the two rooms separating plunger 3 consists. The drawing cushion 2 is symmetrical to a die cushion piston 4 , the die-cushion cylinder space 6 and the die cushion cylinder space 8th built up. To the pestle 1 The procedure is over the drive 11 driven hydraulic pump 10 either the ram cylinder space 5 or the ram-ring cylinder space 7 subjected to hydraulic medium. Similarly, the same applies again to the movement of the die cushion 2 , which usually has its own hydraulic pump 12 is used. It is not crucial so far, if any hydraulic pump 10 . 12 a separate drive 11 or this via a drive 11 as shown 11 are coupled.

Before the start of a forming process are the control valves 18 and 19 and the safety valves 17 closed. The pestle 1 and the drawing pillow 2 Both are at the upper reversal point and possess potential energy due to their respective mass and the arrangement at the upper reversal point.

At the beginning of the forming process, the safety valves 17 and the release valve 9 open. The pestle 1 accelerates due to the inherent potential energy and displaces the hydraulic medium from the ram ring cylinder space 7 , Through a controlled control on the release valve 9 becomes an inadmissible acceleration of the plunger 1 prevents and limits the downward speed to an appropriate level. By throttling, on the one hand kinetic energy is converted into heat, which in the further course has to be withdrawn again from the hydraulic medium and at the same time ensures high wear on the hydraulic medium. On the other hand, the remaining kinetic energy is simply released into the cooling and treatment tank (not shown) of the hydraulic medium. Reached the pestle 1 the drawing cushion 2 may be a damped deceleration of the plunger 1 take place and the forming process of the workpiece begins. To neatly fix the workpiece, as a sheet holding function, the hydraulic medium from the Ziehkissenzylinderraum 6 not suddenly displaced, but throttled over the drain valve 13 drained. Again, there is a loss of heat and potential energy, the heat in the hydraulic medium must be withdrawn consuming again later by means of cooling.

To further clarify a possible structure of a press are still the following STEU naming and control elements. The switching valve 31 closes the die cushion cylinder space 6 and the draw pillow ring cylinder space 8th short and allows a reduction of the volume flow. The switching valves 32 and 33 conduct volume flow to the cylinder of the die cushion 2 and have security-related features. The pressure transducer 34 and 35 detect the prevailing pressure in the cylinder of the plunger 1 or of the drawing cushion 2 and report this to the press control for the initiation of the necessary control and regulation measures during a press cycle. The pressure relief valve 38 secures the ram cylinder space 5 and the pressure relief valve 36 secures the ram-ring cylinder space 7 from. The pressure relief valve 37 acts after the end of the rapid traverse movement and supports the mass of the ram 1 ,

In 2 Now, a preferred embodiment of a press for metal forming is shown, can be used to save energy at a variable displacement volume.

For this purpose, the outlets of the release valve 9 and the die cushion cylinder space 6 with a hydraulic displacement unit 15 connected. Again in the starting position, the release valve 9 opened and the pestle 1 moves towards the drawing cushion 2 , The speed of the pestle 1 is determined by the adjustment of the swivel angle of the displacer unit 15 adjusted, which produces a torque in this time. The torque is via a torque coupling 16 an asynchronous motor 14 fed. Through the asynchronous motor 14 will now be either the hydraulic pump as needed 10 about a moment coupling 16 powered or the existing mechanical energy is converted into electrical energy and into the power grid 24 fed back. Of course, a correspondingly controlled combination is possible. Reached the pestle 1 the drawing cushion 2 The forming process begins and the ram is moved by the hydraulic pump 10 driven. The release valve 9 is closed and the asynchronous motor 14 removes electrical energy from the power grid when needed 24 around the hydraulic pump 10 drive.

During the forming process, the pressurized hydraulic medium is controlled from the die cushion cylinder space 4 over the now open release valves 20 drained and the displacer unit 15 fed, which in turn drives the hydraulic pump 10 or for the return of energy to the power grid 24 is being used. The blank holder force or the counterforce that the die cushion 2 on the pestle 1 exerts again on the adjustment of the swivel angle of the displacer unit 15 be controlled and regulated.

The exact arrangement of the circuit valves in the ram block 26 , executed as a steel block (not shown) with the necessary receiving bores or Anflanschflächen for the plunger valves shown in the drawing for plunger control is as follows: The pressure relief valve 27 secures the ram cylinder space 5 and the pressure relief valve 28 secures the ram-ring cylinder space 7 from. The pressure relief valve 29 acts after the end of the rapid traverse movement and supports the mass of the ram 1 from. Outside the ram block 26 Währe still to mention that on the ram 1 counteracting side of the switching valve 30 the die-cushion cylinder space 6 and the draw pillow ring cylinder space 8th if necessary short closes. The drawing cushion is moving 2 in differential circuit and there is a meaningful reduction of the required volume flow of the hydraulic medium.

In 3 Now, another preferred embodiment of a press for metal forming is shown, can be used to save energy at a constant displacement volume. In contrast to 2 now finds no double moment coupling 16 between displacer unit 15 and hydraulic pump 10 more instead. Instead, the pump points 10 a separate drive 11 on. This is the asynchronous motor 14 only via the torque coupling 16 with the displacer unit 15 coupled and feeds when lowering the plunger 1 or the draw cushion 2 the mechanical energy of the displaced hydraulic medium after conversion via a regenerative unit 22 and a frequency converter 21 in the power grid 24 one.

In 4 Now, a third preferred embodiment of a press for metal forming is shown, can be used to save energy at a constant displacement volume. In contrast to the previous embodiments, a DC motor now comes here to convert the mechanical energy 25 to use that power over a 4-quadrant power converter 23 in the power grid 24 feeds.

In the 3 and 4 be considered displacing units 15 Constant pumps / motors used, which regulate the flow through the speed. The released kinetic energy is converted into electrical energy and into the electric power grid 24 fed back. It is again pointed out that, compared with the known prior art, it should be emphasized that the plunger-side hydraulic circuit (plunger block 26 ) directly with the draw cushion side hydraulic circuit via the release valve 9 and an associated hydraulic line are connected.

Between the two hydraulic circuits or areas is the displacer unit 15 arranged, the be either as a motor or pump can be driven. Just this direct connection causes in their simplicity and effectiveness, a realization of the aforementioned advantages and avoiding the disadvantages. As already described, the hydraulic press according to the invention can be used for carrying out the method, but it can also be used independently of the prior art without the direct implementation of the method.

1

tappet

2

cushion

3

ram piston

4

Cushion plunger

5

Ram cylinder chamber

6

Die cushion cylinder chamber

7

Plunger ring cylinder space

8th

Cushion ring cylinder space

9

release valve

10

hydraulic pump

11

Drive for 10

12

Hydraulic pump ( 2 )

13

drain valve

14

asynchronous

15

displacement unit

16

moment coupling

17

Safety valves ( 1 )

18

Control valve on

19

Control valve from

20

Safety valves ( 2 )

21

frequency converter

22

Feedback unit

23

4-quadrant power converter

24

power grid

25

DC motor

26

follower block

27

Pressure relief valve (for 5 )

28

Pressure relief valve (for 7 )

29

Pressure relief valve (for 1 )

30

switching valve

31

switching valve

32

switching valve

33

switching valve

34

Pressure transducer

35

Pressure transducer

36

Pressure relief valve

37

Pressure relief valve

38

Pressure relief valve

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3216563 C1 [0003]
• - DD 204067 [0003]
• - DE 4218952 A1 [0004]
• - DE 4218953 A1 [0005]

Claims (10)

Method for energy-saving operation of a hydraulic press with a ram arranged at the top in a press frame ( 1 ) for the forming operation and lower die cushion ( 2 ) for applying a blank holder force to the workpiece to be formed with a drive ( 11 ) for at least one hydraulic pump ( 10 ) for raising and lowering the plunger ( 1 ) and the die cushion ( 2 ), characterized in that in the initial position of the plunger ( 1 ) and the die cushion ( 2 ) in the upper reversal point and the following process steps are carried out: 1.1 for lowering the plunger ( 1 ) the release valve ( 9 ) and the hydraulic medium from the ram ring cylinder space ( 7 ) via the displacer unit ( 15 ), which via a torque clutch ( 16 ) an asynchronous (14) or DC motor ( 25 ) or other suitable consumers, 1.2 after ram impact ( 1 ) and die cushions ( 2 ) the release valve ( 9 ) and the ram cylinder space ( 5 ) with hydraulic medium via the control valve ( 19 ) from the hydraulic pump ( 10 ) 1.3, at the same time the release valves ( 20 ) of the die cushion ( 2 ) and the hydraulic medium from the Ziehkissenzylinderraum ( 6 ) via the displacer unit ( 15 ), which via a torque clutch ( 16 ) an asynchronous ( 14 ) or DC motor ( 25 ) or other suitable consumers, 1.4 at the same time is about changing the swivel angle in the displacer unit ( 15 ) or via the delivered moment of the displacer unit ( 15 ) the hydraulic pressure in the die cushion cylinder space ( 6 ) and thus the sheet holding force is regulated, 1.5 after completion of the forming of the plunger ( 1 ) and the die cushion ( 2 ) by the supply via the hydraulic pump ( 10 ) return to the starting position, the upper reversal point. Method according to claim 1, characterized in that the displacer unit ( 15 ) via a moment coupling ( 16 ) with variable displacement volume an asynchronous motor ( 14 ), which via a torque coupling ( 16 ) if necessary, the hydraulic pump ( 10 ) and otherwise in generator mode electrical energy into the power grid ( 24 ) feeds. Method according to claim 1, characterized in that the displacer unit ( 15 ) via a moment coupling ( 16 ) with constant displacement volume an asynchronous motor ( 14 ) which, during generator operation, supplies electrical energy via a regenerative power unit ( 22 ) and a frequency converter ( 21 ) in the power grid ( 24 ) feeds Method according to claim 1, characterized in that the displacer unit ( 15 ) via a moment coupling ( 16 ) at constant displacement volume a DC motor ( 14 ) which, in generator mode, drives electrical energy through a 4-quadrant power converter ( 23 ) in the power grid ( 24 ) feeds. Method according to claim 1, characterized in that the displacer unit ( 15 ) as a consumer drives a cooling unit for cooling the hydraulic medium. Hydraulic press with an energy-saving and low-maintenance drive with a ram arranged at the top in a press frame ( 1 ) for the forming operation and underlying die cushion ( 2 ) for applying a blank holder force to the workpiece to be formed with a drive ( 11 ) for at least one hydraulic pump ( 10 ) for raising and lowering the plunger ( 1 ) and the die cushion ( 2 ), characterized in that for lowering the plunger ( 1 ) the ram ring cylinder space ( 7 ) via a release valve ( 9 ) with a displacer unit ( 15 ) and / or for lowering the die cushion ( 2 ) the die cushion cylinder space ( 6 ) via at least one release valve ( 20 ) with a displacer unit ( 15 ) is connectable to the hydraulic medium, wherein the displacer unit a torque coupling ( 16 ) to an asynchronous motor ( 14 ), a DC motor ( 25 ) or another suitable consumer, and Hydraulic press according to claim 6, characterized in that the asynchronous motor ( 14 ) another torque coupling for driving a hydraulic pump ( 10 ) and / or an electrically conductive connection to the power grid ( 24 ) having. Hydraulic press according to claim 6, characterized in that between asynchronous motor ( 14 ) and power grid ( 24 ) a frequency converter ( 21 ) and a parallel-connected feedback unit ( 22 ) is arranged. Hydraulic press according to claim 6, characterized in that between DC motor ( 25 ) and the power grid ( 24 ) a 4-quadrant power converter ( 23 ) is arranged. Hydraulic press according to claim 6, characterized that as other suitable consumers a refrigeration unit or similar heat exchangers are driven.