Bending machine with energy-saving drive

Abstract

The invention relates to a bending machine (1) for producing workpieces from sheet metal by means of forming in a bending operation or folding operation. Said bending machine comprises a machine frame (3) and a press beam (4) which can be moved relative to said machine frame and which can be moved by means of a first hydraulic cylinder (5) and by means of a second hydraulic cylinder (6) oriented substantially parallel to the first hydraulic cylinder (5), wherein the first hydraulic cylinder (5) and the second hydraulic cylinder (6) are operatively connected to a common hydraulic supply device (2). The common hydraulic supply device (2) comprises a single hydraulic pump (7) which can be driven by a servo motor (8), wherein the servo motor (8) can be controlled in an open- or closed-loop manner by a servo controller (9) capable of feedback.

Description

[0001] BENDING MACHINE WITH ENERGY-SAVING DRIVE

[0002] The invention relates to a bending machine comprising a machine frame and a press beam which can be displaced relative to the machine frame by means of two hydraulic cylinders, wherein the hydraulic cylinders are operatively connected or hydraulically coupled to a common hydraulic supply device.

[0003] In a classic drive system for bending machines, the two hydraulic cylinders are each controlled by a proportional directional control valve. The hydraulic drive energy is supplied by a central three-phase asynchronous motor, which typically provides the hydraulic pressure at a constant speed and thus runs continuously during the bending machine's operation. The constantly running three-phase asynchronous motor supplies significantly more energy than is required during the bending machine's operation. The unused energy is converted into heat, which, among other things, increases the oil temperature.

[0004] Another drive concept known from the prior art is one in which the motor speed of the three-phase asynchronous motor of a previously described drive system is adjusted to the respective requirements of the hydraulic cylinders using a frequency converter. This can save energy. However, this drive concept has the disadvantage that hydraulic energy or kinetic energy of the hydraulic cylinders is always converted into heat, even though some of this energy could be recovered.

[0005] Furthermore, it is already known from the state of the art that the hydraulic power for the hydraulic cylinders is provided by a servo motor for each hydraulic cylinder. This drive concept offers advantages over the previously mentioned ones. However, it also has the disadvantage of increasing the control engineering complexity and increasing the number of individual system components of the bending machine.

[0006] The object of the present invention was to overcome the disadvantages of the prior art and to provide a device by means of which the energy efficiency of a bending machine is improved without increasing the control and economic complexity. This object is achieved by a device according to the claims.

[0007] The bending machine according to the invention for producing workpieces from sheet metal by forming in a bending process or a folding process comprises a machine frame and a press beam which can be displaced relative to the machine frame, wherein the press beam can be displaced by means of a first hydraulic cylinder and by means of a second hydraulic cylinder which is aligned substantially parallel to the first hydraulic cylinder, wherein the first hydraulic cylinder and the second hydraulic cylinder are operatively connected to a common hydraulic supply device or are hydraulically coupled thereto, wherein the common hydraulic supply device comprises a single hydraulic pump, wherein the single hydraulic pump can be driven by a single servo motor and wherein the servo motor can be controlled or regulated by a servo controller.

[0008] In this context, operatively connected or hydraulically coupled means in particular that the hydraulic drive or kinetic energy for driving the hydraulic cylinders is provided by the hydraulic supply device.

[0009] The measure according to the invention not only enables precise control of the hydraulic cylinders, but also improves the energy efficiency of the bending machine compared to known drive systems from the prior art, while at the same time the complexity of the control and the number of individual components of a bending machine are not increased.

[0010] Furthermore, it may be expedient for the first hydraulic cylinder and the second hydraulic cylinder to be operatively connected to the common hydraulic supply device via a proportional directional control valve. This structural simplification allows hydraulic energy to be provided simultaneously and independently to both hydraulic cylinders via the hydraulic supply device.

[0011] Furthermore, it can be provided that the servo motor is demand-controlled and / or call-controlled by means of the servo controller in cooperation with a control or regulating device. This allows for simple energy savings, since the servo motor only provides hydraulic energy on demand by driving the hydraulic pump. The servo controller can be designed in such a way that, based on a signal conversion of the signals received from the control or regulating device, it drives the servo motor or initiates or causes corresponding control or regulation of the servo motor. This allows for precise control of the servo motor, and idle losses are minimized or even completely avoided.

[0012] Furthermore, the servo controller can be a regenerative servo controller, with the servo motor specifically being operable in a generator-like or regenerative mode. A regenerative servo controller, also called a regenerative servo controller, is a special type of servo controller that can, for example, feed the energy fed back by the servo motor back into a power grid or, if necessary, at least temporarily store the fed-back energy. In contrast to a conventional servo controller, which converts the excess energy into heat and thus allows it to be lost, a regenerative controller can, for example, reuse this energy. This saves energy and reduces operating costs.In particular, a regenerative servo controller can be used, for example, when the direction of movement of a servo motor changes frequently, as can occur in particular in a bending machine of the embodiment according to the invention and which will be referred to below.

[0013] Another advantageous embodiment is one in which the regenerative servo controller comprises at least one intermediate circuit capacitor for storing energy, wherein the at least one intermediate circuit capacitor is specifically operatively connected to a rectifier unit and / or an inverter unit of the regenerative servo controller for providing energy to the servo motor. This enables the servo controller to have storage capabilities, and energy recovered from the bending process can thus be temporarily stored and reused. During a bending process, the press beam is displaced relative to the machine frame and towards a press table by means of the hydraulic cylinders, wherein a workpiece is positioned between the press beam and the press table, which workpiece is plastically deformed by the pressing process.However, during such a pressing process, or similarly during a bending or press-bending process, the workpiece is also elastically deformed within certain limits. Thus, during such machining of a workpiece, machine components of the bending machine, such as the press table and the press beam, are also elastically deformed. These elastic deformations and also the pressure energy stored in the hydraulic oil can be at least partially recovered when the press beam is raised again after the workpiece has been deformed. For example, by temporarily storing the energy of the hydraulic oil flowing back through the hydraulic pump in at least one intermediate circuit capacitor through regenerative operation of the servo motor using the regenerative servo controller.

[0014] According to a further development, it can also be provided that the servo motor, in a generator mode, is operatively connected to the regenerative servo controller, specifically by means of the control or regulating device, is controllable or configured to control a speed ramp, in particular a continuous speed ramp. This allows the decompression phase, i.e., the phase of a pressing process when the workpiece is deformed and the press beam is lifted or raised again, to be designed to be continuous, so that a springback of the elastically deformed components of the bending machine as well as a continuous reduction of the hydraulic pressure can be advantageously fed back by means of the regenerative servo controller.Compared to a design in which the decompression phase is initiated purely via the proportional control valves, this has the further advantage that the decompression phase can be initiated more gently and steadily, thus also improving the operating safety of the bending machine.

[0015] Furthermore, it may be expedient for the servo controller to be operatively connected to auxiliary units of the bending machine, whereby the auxiliary units can be electrically supplied by energy stored in at least one intermediate circuit capacitor. This can further improve the energy efficiency of the bending machine.

[0016] Alternatively, or in addition to the measures described above, the hydraulic supply device can also include a hydraulic pressure accumulator for temporarily storing hydraulic pressure energy. This can further improve the energy efficiency of the bending machine.

[0017] Furthermore, it can be provided that more than two hydraulic cylinders are operatively connected via the common hydraulic supply device. Thus, the bending machine according to the invention is not limited to an embodiment with two hydraulic cylinders. Furthermore, an additional hydraulic cylinder can be advantageously positioned, for example, such that a high proportion of the elastic deformation of the press beam can be absorbed by this additional hydraulic cylinder during the decompression phase, and thus its energy can be temporarily stored by the regenerative servomotor. For this purpose, an additional hydraulic cylinder can be positioned, for example, essentially parallel to the other two hydraulic cylinders and centrally with respect to the press beam.

[0018] For a better understanding of the invention, it is explained in more detail using the following figures.

[0019] They show in a highly simplified, schematic representation:

[0020] Fig. 1 a bending machine;

[0021] Fig. 2 shows a possible embodiment of a hydraulic supply device.

[0022] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations. The disclosures contained throughout the description can be applied analogously to identical parts with identical reference symbols or component designations. Furthermore, the position information chosen in the description, such as top, bottom, side, etc., refer to the directly described and illustrated figure, and these position information must be applied analogously to the new position in the event of a change in position.

[0023] Fig. 1 shows a bending machine 1 in a highly simplified and schematic representation. Fig. 2 shows a possible and possibly independent embodiment of a hydraulic supply device 2 in a schematic representation, wherein the same reference numerals or component designations are used for the same parts as in the previous Fig. 1. To avoid unnecessary repetition, both representations are described below, whereby this description should be read and understood in conjunction with Fig. 1 and Fig. 2.

[0024] The bending machine 1 is designed to produce workpieces from sheet metal by forming in a bending or folding process. For this purpose, the bending machine 1 comprises at least one machine frame 3 and a press beam 4 that can be moved relative to the machine frame 3. The press beam 4 can be moved by means of a first hydraulic cylinder 5 and by means of a second hydraulic cylinder 6 that is aligned essentially parallel to the first hydraulic cylinder 5. The first hydraulic cylinder 5 and the second hydraulic cylinder 6 are operatively connected to a common hydraulic supply device 2. The common hydraulic supply device 2 comprises a single hydraulic pump 7, the single hydraulic pump 7 being drivable by a servomotor 8, and the servomotor 8 being controllable or regulated by a servo controller 9.It is not intended that each of the hydraulic cylinders 5, 6 be supplied by a respective servomotor and an associated hydraulic point. Rather, both hydraulic cylinders 5, 6 are coupled to the common hydraulic supply device 2, wherein the common hydraulic supply device 2 also includes a single hydraulic pump 7 and a single servomotor 8 coupled thereto. The servo controller 9 can be coupled to a supply network 11 for providing electrical energy.

[0025] It can also be provided that the first hydraulic cylinder 5 and the second hydraulic cylinder 6 are each operatively connected to the common hydraulic supply device 2 via a proportional directional control valve 10. In any case, the servo motor 8 can be demand-controlled and / or call-controlled by means of the servo controller 9 in cooperation with a control or regulating device 12.

[0026] During the bending process of a workpiece, elastic deformations can occur in the components of the bending machine 1. Furthermore, the hydraulic components of the hydraulic supply device 2 of the bending machine 1 have pressure energy stored during a bending process. In order to be able to recover at least parts of this energy, the servo controller 9 can be a regenerative servo controller 9, wherein the servo motor 8 can be operated in a generator or regenerative manner. In this context, or as an alternative extension thereto, it can be expedient for the regenerative servo controller 9 to comprise at least one intermediate circuit capacitor 13 for storing energy, wherein the at least one intermediate circuit capacitor 13 is operatively connected to a rectifier unit 14 and / or to an inverter unit 15 of the regenerative servo controller 9 for providing energy to the servo motor 8.To further improve energy recovery, it can alternatively be provided that the servomotor 8 is controllable or configured in a generator mode in operative connection with the regenerative servo controller 9 for controlling a speed ramp, in particular a continuous speed ramp. The energy that can be recovered and temporarily stored in this way can thus be further utilized. For example, it can alternatively also be provided that the servo controller 9 is operatively connected to auxiliary units 16 of the bending machine 1, wherein the auxiliary units 16 can be electrically supplied by energy stored in at least one intermediate circuit capacitor 13.

[0027] As a further useful alternative, it can also be provided that the hydraulic supply device 2 comprises a hydraulic pressure accumulator 17 for temporarily storing hydraulic pressure energy.

[0028] In any case, this possible embodiment of the invention is not limited to the provision of only two hydraulic cylinders 5, 6. Alternatively, it can also be provided that more than two hydraulic cylinders 6 are operatively connected via the common hydraulic supply device 2.

[0029] The embodiments show possible embodiments, whereby it should be noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but rather various combinations of the individual embodiments with each other are also possible and this possibility of variation lies within the skill of the person skilled in the art in this technical field due to the teaching of technical action by means of the objective invention.

[0030] The scope of protection is determined by the claims. However, the description and drawings must be used to interpret the claims. Individual features or combinations of features from the various embodiments shown and described may represent independent inventive solutions. The problem underlying these independent inventive solutions can be derived from the description.

[0031] All information on value ranges in this description is to be understood as including any and all sub-ranges thereof, e.g. the information 1 to 10 is to be understood as including all sub-ranges, starting from the lower limit of 1 and the upper limit of 10, ie all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10. For the sake of clarity, it should be pointed out that in order to improve understanding of the structure, some elements have been shown out of scale and / or enlarged and / or reduced.

[0032] Reference symbol list

[0033] Bending machine

[0034] Hydraulic supply device

[0035] Machine frame

[0036] Press beam

[0037] First hydraulic cylinder

[0038] Second hydraulic cylinder

[0039] hydraulic pump

[0040] Servo motor

[0041] Servo controller

[0042] Proportional directional control valve

[0043] supply network

[0044] Control or regulating device

[0045] DC link capacitor

[0046] Rectifier unit

[0047] Inverter unit

[0048] Auxiliary unit

[0049] Hydraulic pressure accumulator

Claims

Patent claims 1. Bending machine (1) for producing workpieces from sheet metal by forming in a bending process or a folding process, comprising a machine frame (3) and a press beam (4) which is displaceable relative to the machine frame (3), wherein the press beam (4) is displaceable by means of a first hydraulic cylinder (5) and by means of a second hydraulic cylinder (6) which is aligned substantially parallel to the first hydraulic cylinder (5), wherein the first hydraulic cylinder (5) and the second hydraulic cylinder (6) are operatively connected to a common hydraulic supply device (2), characterized in that the common hydraulic supply device (2) comprises a single hydraulic pump (7), wherein the single hydraulic pump (7) is drivable by a servomotor (8) and wherein the servomotor (8) is controllable or regulated by a servo controller (9).

2. Bending machine (1) according to claim 1, characterized in that the first hydraulic cylinder (5) and the second hydraulic cylinder (6) are each operatively connected to the common hydraulic supply device (2) via a proportional directional control valve (10).

3. Bending machine (1) according to one of the preceding claims, characterized in that the servo motor (8) is demand-controlled and / or call-controlled by means of the servo controller (9) in cooperation with a control or regulating device (12).

4. Bending machine (1) according to one of the preceding claims, characterized in that the servo controller (9) is a regenerative servo controller (9), wherein the servo motor (8) is specifically operable in a generator-like or regenerative manner.

5. Bending machine (1) according to claim 4, characterized in that the regenerative servo controller (9) comprises at least one intermediate circuit capacitor (13) for storing energy, wherein the at least one intermediate circuit capacitor (13) is specifically operatively connected to a rectifier unit (14) and / or to an inverter unit (15) of the regenerative servo controller (9) for providing energy to the servo motor (8).

6. Bending machine (1) according to one of claims 4 or 5, characterized in that the servo motor (8) is controllable or designed in a generator mode in operative connection with the regenerative servo controller (9) for controlling a speed ramp, in particular a continuous speed ramp.

7. Bending machine (1) according to claim 5, characterized in that the servo controller (9) is operatively connected to auxiliary units (16) of the bending machine (1), wherein the auxiliary units (16) can be electrically supplied by energy stored in at least one intermediate circuit capacitor (13).

8. Bending machine (1) according to one of the preceding claims, characterized in that the hydraulic supply device (2) comprises a hydraulic pressure accumulator (17) for temporarily storing hydraulic pressure energy.

9. Bending machine (1) according to one of the preceding claims, characterized in that more than two hydraulic cylinders (6) are operatively connected by means of the common hydraulic supply device (2).

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