Hydraulic forming machine for forming workpieces, hydraulic control unit and method for controlling a hydraulic cylinder of a hydraulic forming machine

Abstract

The underlying invention relates in particular to a hydraulic forming machine (1), especially a forging hammer, for workpiece forming, comprising a hydraulic cylinder (2) with a piston (29) guided in a cylinder tube (25), which divides the cylinder tube (25) into a first cylinder chamber (44) through which a piston rod (30) coupled to a ram (3) passes and into a second cylinder chamber (45), wherein the first cylinder chamber (44) has a first hydraulic connection (37) and the second cylinder chamber has a second hydraulic connection (38), a hydraulic circuit (7) with a control unit (6) for controlling and / or regulating the operation of the hydraulic cylinder (2), wherein the hydraulic circuit (7) comprises a first hydraulic valve (13) coupled to the control unit (6) for control purposes, which is preferably designed as a proportional valve, and is connected to the second cylinder chamber (45) via the second hydraulic connection (38).The control unit (8) is designed to regulate and / or control the opening width of the first hydraulic valve (13) during the execution of a working stroke intended for forming a workpiece, such that in a first phase the first hydraulic valve (13) is open and the ram (3) is accelerated to a target speed in the first phase, in a second phase following the first phase the opening width of the first hydraulic valve (13) is reduced to a post-flow opening width, and the first hydraulic valve (13) is closed during a return stroke running opposite to the working stroke.

Description

[0001] The underlying invention relates to a hydraulic forming machine for workpiece forming, a hydraulic control unit and a method for controlling a hydraulic cylinder of a hydraulic forming machine.

[0002] Various forming machines are known for pressing or forming workpieces during cold forming, particularly sheet metal forming, or during hot forming, particularly forging metallic, malleable materials (see, for example, the VDI Lexicon volume "Production Technology Process Engineering," published by Hiersig, VDI-Verlag, 1995, pages 1107 to 1113). At least one ram or ram with an upper forming tool of the forming machine is driven by a drive and moved relative to a lower forming tool of the forming machine, so that the workpiece can be formed between the forming tools using forming forces.

[0003] Known hydraulic forming machines utilize a hydraulic drive via a hydraulic medium or hydraulic fluid, such as oil or water. The pressure energy of the hydraulic medium or fluid is initially converted into kinetic energy by pistons running in hydraulic cylinders, particularly in forging hammers, and finally, during the forming process, into mechanical forming work. The hydraulic drive of the piston can be a pump drive with a pump and an electrically controllable pump motor (see, for example, DE 196 80 008 C1) or a hydraulic accumulator drive with a pressure accumulator and a motor-driven pump for generating pressure in the pressure accumulator (see, for example, WO 2013 / 167610 A1).

[0004] DE 10 2015 105 400 A1 discloses a forging hammer with a striking tool coupled to a hydraulic differential cylinder for performing a working stroke from top to bottom and a return stroke from bottom to top. A hydraulic pump is provided to drive the differential cylinder, which is connected to the cylinder chambers of the differential cylinder via a simple directional valve.

[0005] DE 10 2014 002 888 B4 discloses a forging hammer comprising a hydraulic cylinder coupled to a ram for workpiece forming. The hydraulic cylinder comprises an upper, a middle, and a lower hydraulic connection. During a working stroke, a lifting chamber of the hydraulic cylinder associated with the working stroke is supplied with hydraulic fluid via the upper hydraulic connection. During a return stroke, the upper hydraulic connection is closed, and the hydraulic fluid displaced from the lifting chamber is directed into a return tank via the middle connection. The operation of the forging hammer is configured such that during the return stroke, the upper hydraulic connection is closed, and the piston of the hydraulic cylinder is decelerated by the hydraulic fluid remaining in the hydraulic cylinder when it passes over the middle hydraulic connection.The disadvantage of the known forging hammer is its complex construction with four hydraulic connections and furthermore that a top dead center, which serves as the starting point for triggering a forging blow, is firmly linked to the position of the middle hydraulic connection.

[0006] In the case of known forming machines, in particular forging hammers, there is still potential for simplifying the structure, for safe operation of the hydraulic circuit, and for improving the movement sequences of the ram or the associated tools, for example with regard to the adjustability of the target speed of the ram for forming, with regard to the reproducibility of the movement of the ram and / or with regard to safe operation, for example in the event of a failure of the control electronics.

[0007] The object of the invention is to provide a new or improved hydraulic forming machine, in particular a forging hammer.

[0008] In particular, such a forming machine is to be provided that has a comparatively simple design, enables improved motion control and / or regulation of the ram with the coupled impact tool for forming, and / or enables motion control with increased safety and / or reduced or minimized cavitation formation in the hydraulic medium or hydraulic fluid. Furthermore, a hydraulic control unit for operating a hydraulic forming machine and a method for operating a hydraulic cylinder of a hydraulic forming machine, in particular a forging hammer, are to be provided.

[0009] This object is achieved by the features of the independent claims. Further developments emerge in particular from the dependent claims and from the following description of exemplary embodiments and developments.

[0010] According to one embodiment, a hydraulic forming machine, in particular a percussive forming machine, preferably a forging hammer, is provided for forming a workpiece. The forming machine comprises a hydraulic cylinder with a piston guided in a cylinder tube.

[0011] The piston divides the cylinder tube into a first cylinder chamber, through which a piston rod coupled to a ram passes, which is designed as an annular chamber due to the piston rod passing through, and into a second cylinder chamber, which is arranged on the side of the piston facing away from the first cylinder chamber and is also referred to as the piston chamber. The first cylinder chamber has a first hydraulic connection and the second cylinder chamber has a second hydraulic connection. If the hydraulic cylinder is arranged vertically, the first hydraulic connection can be referred to as a lower connection and the second hydraulic connection as an upper connection. Accordingly, the first cylinder chamber can be referred to as a lower cylinder chamber and the second cylinder chamber as an upper cylinder chamber.

[0012] The hydraulic forming machine further comprises a hydraulic circuit that includes at least one control unit, also referred to herein as a hydraulic control unit. The control unit is configured to control and / or regulate the operation of the hydraulic cylinder. In addition to the control unit, other components can be added to the hydraulic circuit, such as hydraulic lines, pressure sensors, etc.

[0013] The hydraulic cylinder is connected to the hydraulic circuit via the first and second hydraulic connections, or the hydraulic circuit is connected to the hydraulic cylinder via the first and second hydraulic connections.

[0014] The hydraulic circuit comprises a first hydraulic valve that is control-linked to the control unit. The first hydraulic valve is preferably designed as a proportional valve.

[0015] The first hydraulic valve is connected to the second cylinder chamber via the second hydraulic connection.

[0016] If the hydraulic cylinder is arranged vertically and the ram is positioned below the hydraulic cylinder, applying pressure to the second cylinder chamber causes a working stroke—in the case of a forging hammer, a forging blow or impact. The first hydraulic valve can therefore be referred to as a "percussion valve."

[0017] A working stroke is understood as an operation or operating phase of the hydraulic cylinder in which the second cylinder chamber is pressurized with hydraulic fluid and the ram can be moved away from the cylinder barrel toward a workpiece for forming. In the operation of a forming machine designed as a forging hammer, such a working stroke is also referred to as a blow or forming stroke. A movement opposite to the working stroke is referred to herein as a return stroke. A complete working cycle of the hydraulic cylinder can thus be understood as a successive movement cycle consisting of a working stroke and a return stroke.

[0018] According to one aspect of the invention, the control unit is designed to regulate and / or control an opening width of the first hydraulic valve when carrying out a working stroke intended for forming a workpiece in such a way that ▪ in a first phase of the working stroke, the first hydraulic valve is opened and the ram is accelerated to a target speed in the first phase, ▪ in a second phase of the working stroke following the first phase, in particular after the target speed has been reached, the opening width of the first hydraulic valve is reduced or decreased to a post-flow opening width, and ▪ the first hydraulic valve is closed during a return stroke running in the opposite direction to the working stroke.

[0019] It is particularly advantageous to adjust the afterflow opening width so that the hydraulic pressure in the hydraulic system is above the cavitation pressure. In particular, the control unit can be configured so that the hydraulic pressure in the second cylinder chamber is above 3 bar, but at least above 1 bar. Since air only releases from hydraulic oil at 1 bar, for example, harmful cavitation can be avoided or prevented.

[0020] Preferably, the control unit is configured to adjust the afterflow opening width according to a predetermined or predeterminable opening width.

[0021] Particularly advantageously, the hydraulic valve is designed as a proportional valve, in particular as a so-called cartridge valve.

[0022] In particular, it is provided, and the control unit is configured accordingly, that in the second phase, the first hydraulic valve is not completely closed, but rather that the opening width is closed down to a remaining opening gap, for example a minimum opening gap. Hydraulic fluid can flow into the second cylinder chamber via the remaining opening gap, in particular in such a way that the ram is no longer accelerated by the hydraulic fluid, so that the ram essentially maintains the achieved target speed. The term "follow-up flow" is to be understood in particular as a substantially pressureless filling of the second cylinder chamber with hydraulic fluid, in particular in such a way that the ram or piston is no longer accelerated by the inflowing hydraulic fluid, and the achieved target speed is at least essentially maintained or can be maintained.In particular or alternatively, "afterflow" should mean that the pressure at the hydraulic cylinder is approximately 3 bar or at least not below 1 bar - so that cavitations in the hydraulic fluid, especially hydraulic oil, can be avoided.

[0023] The system pressure of the hydraulic circuit, with which in particular the first hydraulic connection is or is acted upon, is preferably approximately 200 bar, e.g. in the range between 190 and 210 bar, or between 197 bar and 203 bar.

[0024] During a working stroke of the hydraulic cylinder for forming a workpiece, the ram continues to move after reaching the target speed, increasing the volume of the second cylinder chamber and filling it accordingly with hydraulic fluid, i.e., with the inflowing hydraulic fluid. This filling or inflow is achieved by adjusting the first hydraulic valve to the inflow opening width. The inflow opening width can, for example, be between 3 and 20%, preferably between 5 and 15%, or 10 and 15%, of the hydraulic valve opening width.

[0025] Overall, the proposed forming machine results in a comparatively simple, precise and reproducible control and / or regulation of the hydraulic cylinder for executing a working stroke for forming a workpiece.

[0026] According to embodiments, the hydraulic circuit further comprises a second hydraulic valve connected to the second hydraulic connection. The control unit is configured to control the opening width of the second hydraulic valve, which is preferably designed as a proportional valve, such that, during a return stroke opposite to the working stroke, a starting position of the ram for a subsequent working stroke can be variably adjusted. In a vertically arranged hydraulic cylinder, in which the working stroke is downward, the second hydraulic valve can also be referred to as a "rising valve." Thus, in a corresponding forming machine with a vertical structure, the first hydraulic valve can be referred to as a percussion valve and the second hydraulic valve as a rising valve.

[0027] By using proportional valves, comparatively precise control of the ram's movement can be achieved. In particular, advantageous and precise control of the ram's speed can be achieved. Furthermore, it is comparatively easy to control and / or regulate the ram's movement, for example, to different, respectively desired target speeds and / or to different and / or varying starting positions for executing a working stroke or impact.

[0028] According to embodiments, the forming machine can further comprise a measuring unit for determining the position and / or speed of the ram. The control unit can be configured to determine one or more operating parameters, for example for a subsequent, in particular immediately following, working stroke, on the basis of a forming position determined by the measuring unit for a previous working stroke and / or further recorded operating parameters. The following are particularly suitable operating parameters: starting position for executing a working stroke, a target speed reached after the first phase, an impact energy of the ram for forming the workpiece, a position of the ram, in particular the forming position of the ram. The forming position of the ram should be understood in particular as the position of the ram at which the forming of the workpiece takes place or begins during a working stroke.Advantageously, the control unit is configured to determine the operating parameter(s) for a subsequent working stroke, ie for a further working stroke immediately following a working stroke, for example.

[0029] In advantageous embodiments, the control unit can be configured to execute an initial working stroke during a forming operation on a workpiece as a straightening stroke performed with minimal impact energy. Such a straightening stroke makes it possible, in particular, to determine the forming position, i.e., the position of the ram at which it strikes the workpiece to be formed, or the position of the side of the workpiece facing the ram.

[0030] If the control unit is further configured to determine not only the forming position of the ram but also the starting position of the ram for executing a working stroke, or if the starting position is available, the stroke range available for a working stroke between the starting position and the forming position, and thus the required range or the available path length for accelerating the ram, can be determined and used to set operating parameters for accelerating the ram to the target speed. A corresponding operating parameter can be the opening width of the first hydraulic valve or the temporal progression of the opening width of the first hydraulic cylinder.

[0031] According to embodiments, it is further possible for the determined operating parameters such as starting position, forming position, impact energy, etc. to be used to control and / or regulate the second hydraulic valve during a return stroke. For example, the control unit can be configured to use corresponding operating parameters, for example the starting position for a subsequent working stroke, to control the second hydraulic valve during the return stroke. According to embodiments, the control unit can in particular be configured to control and / or regulate the opening width of the second hydraulic valve or to control and / or regulate the closing behavior of the second hydraulic valve such that the ram reaches the respectively desired starting position for the next working stroke during the return stroke.

[0032] With the proposed control unit and the hydraulic valves, especially with proportional valves, it is possible to dynamically adjust the starting position for executing a working stroke, for example, so that working strokes can be executed from different starting positions. This enables comparatively flexible operating cycles and forming operations while simultaneously allowing precise and reliable adjustment of the forming parameters.

[0033] According to embodiments, the control unit can be configured to control the opening width of the first hydraulic valve on the basis of a variably predeterminable and / or ascertainable starting position and / or a variable forming position (or: reversal position, rest position), in particular a variably predeterminable and / or ascertainable forming position, in particular such that the working stroke, in particular a forming impact, can be carried out with a respectively suitable, preferably predetermined, in particular a respectively maximum available, impact energy.

[0034] According to embodiments, the control unit can be configured to variably or dynamically variably set a starting position for executing a working stroke, in particular depending on at least one operating parameter of the hydraulic cylinder with respect to one or more preceding working strokes, wherein the operating parameter is preferably an operating parameter detected by one or more sensor units. For example, the forming position during a preceding working stroke when forming a workpiece with multiple strokes can be used to set the starting position for a subsequent working stroke for the workpiece and / or to set the opening width for accelerating the ram during the subsequent working stroke, for example according to a predetermined or desired forming energy and / or target speed.

[0035] According to embodiments, the control unit can be configured to determine a starting position for a working stroke for a predetermined forming energy and to set it by controlling and / or regulating the second hydraulic valve during a return stroke, wherein the control unit is preferably configured to variably, in particular dynamically variably, set the starting position on the basis of a free path length of the ram between the starting position and the forming position of a previous working stroke.

[0036] In the proposed forming machine, proportional valves can be used particularly advantageously for the first and second hydraulic valves. The two valves can be constructed identically, with one of them being used to trigger the impact, the other as a riser valve. The valves can be designed in a so-called cartridge design, with control and logic elements installed in a vibration-proof manner on the control cover. An integrated safety stage can be used to ensure the readiness of the first hydraulic valve, particularly an impact valve.

[0037] The proposed forming machine has the particular advantage that the hydraulic cylinder requires only two (in particular, exactly two) hydraulic connections, one for the working stroke and one for the return stroke. Compared to state-of-the-art forming machines with four functionally different hydraulic connections on the hydraulic cylinder, the design can thus be simplified.

[0038] As mentioned, the hydraulic cylinder can have a lower connection (first hydraulic connection) which is provided for the return stroke. The lower connection permanently and always provides hydraulic fluid, for example hydraulic oil, or operating pressure (e.g. in the range between 197 bar and 203 bar, preferably at approximately 200 bar). Therefore, in advantageous embodiments, it is provided that the lower or first hydraulic connection does not include direct control via a hydraulic valve. If the lower or first hydraulic connection is subjected to system pressure (e.g. approximately 200 bar), the return stroke can take place via the riser valve (second hydraulic valve) at the second or upper hydraulic connection.

[0039] The first and second hydraulic valves (impact valve and riser valve) are connected to the upper hydraulic port (second hydraulic port) and the second cylinder chamber, respectively. The hydraulic cylinder is controlled / regulated at the upper and second hydraulic ports, respectively.

[0040] Proportional valves for impact and rise are advantageously used for the hydraulic valves.

[0041] In embodiments, for example in large forming machines, several valves for each function (hitting / rising) can be connected in parallel as hydraulic valves or valve units.

[0042] The use of a proportional valve for the ascent or return stroke opens up the possibility of operating the forming machine with a variable starting position or impact starting position instead of with a fixed top dead center, since the braking process can essentially be started at any position, for example at any height, or the ram can be brought to a standstill at any height.

[0043] In particular, according to embodiments, it is possible for the hydraulic valve to be continuously closed during the return stroke according to a predetermined characteristic curve, for example, to achieve a gentle stop initially, but a precise stop towards the end of the return stroke. For the operation of the forming machine, it can advantageously be provided that the ram is only brought to a standstill when it has at least reached the initial height required to accelerate the ram for the next impact.

[0044] In particular, the proposed control of the hydraulic valves can ensure that, especially in the case of rebound impacts, the high volume flow generated by the rebound can be safely reduced during the subsequent braking phase or during the return stroke.

[0045] For operational safety, e.g. in the event of failure of the electronics of the riser valve, a rod extension above the piston can be provided, which dips into a bore and thus forms a hydraulic brake cushion, which is described in more detail below.

[0046] Using a proportional valve to accelerate the ram provides several control variables for controlling the acceleration phase. These include, for example, adjustable characteristics for opening and closing the first hydraulic valve or impact valve, the actual opening and thus the controllable volume flow that can flow through it, and the duration for which the hydraulic valve remains open. This can improve both the absolute accuracy and the repeatability of the machine.

[0047] With the proposed forming machine and the associated operating method, it is particularly possible that, when operating the forming machine with proportional valves, the impacts or working strokes can always be executed from an individually suitable or necessary height. In particular, it is not necessary for the hydraulic cylinder to move to the absolute upper end position after each impact or working stroke. Furthermore, the variability offered by a proportional valve as an impact valve can achieve improved impact accuracy.

[0048] In practical operation of a forming machine, for example, in an automated forging line, it may be necessary to provide a certain amount of clearance between the upper and lower tools for die maintenance, handling tasks, etc. This can be provided by using proportional devices because the top dead center or reversal point of the ram is variable.

[0049] The following operating modes represent procedural embodiments of the invention or functional embodiments of the control unit or the hydraulic control unit.

[0050] In one embodiment, forming, in particular forging, can be provided with automatic energy adjustment. After a blank or workpiece has been placed in the lower die of the forming machine, a straightening blow with low energy can first be carried out. A straightening blow is to be understood, for example, as a blow in which the upper die is lowered onto the workpiece, whereby the ram is moved onto the workpiece with low energy, for example so that essentially no or only negligible deformation occurs on the workpiece. The control system determines the available stroke. A subsequent blow can then be carried out automatically with a maximum achievable energy for this determined stroke, whereby the blow and the acceleration of the ram are automatically controlled or regulated by the control system based on the determined stroke.

[0051] Due to the deformation of the workpiece or forging, a longer stroke is now available for the subsequent working stroke or impact, which in turn can be automatically determined and converted into an increase in the impact energy. The process can be identical for all subsequent impacts. Depending on the design, it is also possible to set a limit value before the start of an impact sequence such that, for example, when a predetermined nominal energy of the forming energy is reached, for example 80% of the nominal energy of the forming machine, and / or when a selectable or predeterminable lower reversal point is reached, which can correspond, for example, to the final component height, no further automatic increase in the impact energy takes place. The limit value can, for example, be set by a user. Appropriate operation with a limitation of the, for example, maximum, energy and / or the criterion of the lower reversal point, e.g.the final component height, is particularly useful for upsetting and stretching operations in which the component height changes significantly during forging.

[0052] According to embodiments, an operating mode can be provided in which forming or forging takes place from a preselected height with adjustable energy.

[0053] For this purpose, a largely freely selectable starting position for executing a working stroke, as well as a die height and a blank or workpiece height, can be specified automatically or by an operator. The control system then determines the achievable maximum energy. Individual impacts or individual working strokes, or a sequence of working strokes or impacts with energies between 1% of the maximum impact energy of the forming machine and the previously determined maximum achievable energy, can then be programmed or set.

[0054] In certain embodiments, the control system can be configured to continuously perform plausibility checks between the entered or specified data and the actual working strokes or return strokes, and to stop the operation of the forming machine if limit values ​​for the automatically determined operating parameters are exceeded or undershot. As an alternative to data input by a user, this operating mode can be used to determine the initially available working stroke with an initial, low-energy directional blow.

[0055] According to embodiments, an operating mode can be provided in which forging is carried out with constant energy from an optimal height.

[0056] Here, it is possible to fix or specify a freely selectable energy level. Additionally, the die and component height can be entered or determined, for example, by performing a straightening blow and continuously determining the position of the ram at the reversal point. The control system can use the corresponding data to determine an optimal height or starting point for a sequence of working strokes or a sequence of impacts and execute a corresponding sequence of working strokes, e.g., with the same energy each time.

[0057] According to embodiments, it can be provided that during operation of the forming machine, all impacts, regardless of whether in continuous impact or single-impact mode, are always executed from the uppermost end position with the energy specified, e.g., by the operator. This corresponds in particular to the operation of a conventional forging hammer with four hydraulic connections and demonstrates that the proposed forming machine can be operated flexibly.

[0058] In addition to the advantages already mentioned, a number of other positive aspects arise from the use of proportional valves. While with a conventional drive, the proportion of the braking distance to the total stroke increases with decreasing energy, with proportional valves, impacts can be made from a reduced height. On the one hand, this saves acceleration work, and on the other hand, the impact frequency can be increased. The cartridge design of the proportional valves also increases ease of installation and maintenance, as they can be installed and connected in a few simple steps. The structure of the proven block hydraulics is also simpler, as fewer oil-carrying channels need to be manufactured. It is particularly noteworthy that the new hammer drive with proportional valve technology no longer requires a post-suction phase via a separate post-suction valve in the usual sense.The anti-cavitation valve, anti-cavitation reservoir, and all the disadvantages associated with the anti-cavitation phase can be eliminated. The main advantage here is that no unbalanced oil, possibly containing air pockets, enters the piston chamber, thus eliminating the associated risk of cavitation.

[0059] In the proposed forming machine with proportional valves, it is particularly advantageous if the acceleration phase of the ram is completed before the forming process begins. This prevents the piston chamber from still being connected to the accumulator via the proportional valve for impact at the moment of impact, while the ram simultaneously generates an opposing volume flow due to the rebound, which can cause uncontrollably high pressure peaks in the hydraulic system and potentially damage the system. Furthermore, it should be noted that by ending the acceleration phase before the forming process begins, which corresponds to "releasing" the ram—technically speaking, it is removed from the control system—it also shapes the character of the impact machine.

[0060] On the one hand, the flow of hydraulic fluid into the second cylinder chamber or piston chamber must not end until the ram reverses its direction; on the other hand, the acceleration phase must be completed before the forming process begins. This can be achieved by cleverly controlling the two proportional valves. A design-specific overlap phase, in which both valves are open to a certain degree, can ensure that, after the acceleration phase has ended, oil can both flow into and out of the piston chamber until the ram reverses.

[0061] Fluid power simulations and practical tests have shown that the forming machine and hydraulic control system proposed here, particularly when using proportional valves, can be configured so that pressures below 3 bar do not develop in the hydraulic system, especially in the hydraulic cylinder. Since air only releases from oil at pressures below 1 bar, harmful cavitation cannot occur. To prevent excessive pressures, the hydraulic system can be equipped with additional safety valves that function independently of the electronics. In certain embodiments, pressure sensors can be provided, which can be used to check the proper functioning and adjustment of the system.

[0062] One advantage of eliminating the post-suction phase and the associated air exchange is that only small, low-maintenance tank ventilation filters are required, rather than large hood filters. The associated piping is also eliminated. Filter and cooling units no longer need to be designed based on the required oil volume in the post-suction tank, but can be designed based on the actual heat development in the system.

[0063] According to a further embodiment of the invention, which can in particular be claimed independently, a hydraulic forming machine, in particular a forging hammer, is provided for workpiece forming.

[0064] The hydraulic forming machine, hereinafter also referred to as forming machine for short, comprises a hydraulic circuit with a unit for generating a predetermined system pressure (for example in the range between 190 bar and 210 bar, in particular 197 bar to 203 bar, preferably at approximately 200 bar) for the hydraulic fluid (or: the hydraulic fluid), for example a pressure accumulator and / or a pump unit, and at least one, in particular pressureless, reservoir, for example a return and / or suction tank, for hydraulic fluid. With a pressure accumulator and / or the pump unit, hydraulic fluid can be made available according to a predetermined system pressure. The reservoir is preferably pressureless, i.e. not subjected to system pressure. The return and suction tanks can be separate tanks. However, it is also possible for the return and suction tanks to be the same tank.

[0065] The forming machine further comprises a hydraulic cylinder comprising a cylinder tube with a piston movable therein between a first and a second end. The piston is coupled to a piston rod extending toward the first end and coupled or capable of being coupled to a ram.

[0066] On the side facing away from the piston rod, the piston has a particularly cylindrical rod extension (or piston extension) extending toward the second end. The rod extension can be designed as a separate component or be formed by a terminal section of the piston rod. In the latter case, the piston rod can, for example, extend axially through the center of the piston, so that the piston rod projects beyond the piston on the side facing away from the ram side and forms the rod extension. The rod extension has an outer diameter that is smaller than that of the piston.

[0067] At the second end or in the region of the second end, the hydraulic cylinder has a bore which is coaxial with the rod extension and open towards the piston and whose inner diameter essentially corresponds to the outer diameter of the rod extension or is slightly smaller. The said diameters are selected such that the rod extension can penetrate into the bore, in particular such that hydraulic fluid located in the bore acts as a brake cushion. Advantageously, the depth of the bore measured coaxially with the rod extension is greater than the length of the rod extension which can penetrate into the bore. In particular, the depth of the bore is preferably selected such that when the rod extension penetrates into the bore, it does not touch the bottom of the bore, i.e. is spaced from the bottom.Regarding the diameter of the bore, this can have a flat diameter, for example, 45 mm, and the rod extension can have a slightly smaller diameter, for example, 44.6 mm. The diameter of the bore or rod extension is preferably selected depending on the size of the forming machine, e.g., depending on the diameter of the piston of the hydraulic cylinder.

[0068] In embodiments, the outer diameter of the piston extension substantially corresponds to the outer diameter of the piston rod, or is the same as the outer diameter of the piston rod.

[0069] The hydraulic cylinder or cylinder tube has a first hydraulic connection in the region of the first end and a second hydraulic connection in the region of the second end.

[0070] A hydraulic connection is to be understood as a connection of the hydraulic cylinder which is intended to supply hydraulic fluid to or from an associated cylinder space (or: a cylinder chamber) of the hydraulic cylinder during hydraulic operation of the hydraulic cylinder.

[0071] In particular, there are no additional hydraulic connections in the aforementioned sense and with the aforementioned function between the first and second hydraulic connections. This allows the hydraulic cylinder and, correspondingly, the forming machine to be constructed with a comparatively simple design.

[0072] The second hydraulic connection is arranged and configured such that the piston closes the second hydraulic connection upon movement toward the second end when the rod extension reaches the bore, in particular when the rod extension reaches the opening of the bore. Preferably, the second hydraulic connection, the rod extension, and the opening are arranged and configured such that the second hydraulic connection is closed by the piston at approximately the same time as the opening through the distal end of the rod extension. A volume of hydraulic fluid enclosed in the bore and in the annular space around the rod extension can then act as a brake cushion.

[0073] The advantage of the combined effect of the rod extension and bore on the one hand, and the closure of the second hydraulic connection on the other, lies in the resulting brake for the unit comprising the piston, the piston rod, and the hammer with tools attached to it. If the rod extension closes the opening of the bore, for example when the rod extension dips into the bore, the hydraulic fluid in the bore exerts a braking effect. Furthermore, the hydraulic fluid present in the annular space surrounding the rod extension when the second hydraulic connection is closed also creates a braking effect. This means that the piston and associated components, such as the piston rod, hammer, tools, etc., can be braked efficiently, in particular even if, for example, electronics, hydraulic control or regulation provided for controlling the hydraulic cylinder via the first and second hydraulic valve with associated hydraulic valves fails or is defective. The bore with rod extension therefore forms a brake that works independently of other hydraulic components, in particular control or regulating units. In this respect, the bore can be described as a type of brake bushing. Since the brake works in particular independently of other hydraulic components, ie is defined solely by the structure of the bore, the rod extension and the position of the second hydraulic connection, these components, in particular the bore with rod extension, can also be used as an emergency or safety braking system.However, the components can be used not only in the event of emergency braking in the event of a system failure, but also in regular operation to slow down the movement of the piston towards the second end.

[0074] In some embodiments it can be provided that the volume of the bore formed when the opening is closed by the rod extension and the annular space of the second cylinder chamber formed around the rod extension are connected to one another with the interposition of a throttle, e.g. via a line. For example, a connecting line containing the throttle can run between the bottom of the bore and the annular bottom of the second cylinder chamber formed around the opening of the bore. If the rod extension closes the opening and the piston closes the second hydraulic connection, pressure equalization between the volume of the bore and the volume of the annular space can take place via the throttle. This can, for example, result in comparatively gentle and efficient braking.

[0075] The rod extension is preferably arranged coaxially to the piston, whereby tilting moments during braking can be essentially avoided.

[0076] In embodiments, the radius of the rod extension can be between 1 / 3 and 2 / 3 of the radius of the piston, in particular, for example, ½ times the radius of the piston.

[0077] The axial length of the rod extension and / or the outer diameter of the rod extension can vary depending on the size of the forming machine and / or depending on the diameter of the piston of the hydraulic cylinder.

[0078] In some embodiments, the piston rod and the rod extension are manufactured as a single piece. For example, the piston rod can extend through the piston and protrude beyond the piston toward the second end, wherein the projection or the projecting part, or a part projecting beyond the piston, can form the rod extension. However, it is also possible for the piston rod and rod extension to be two separate components that are attached or fixed to opposite ends of the piston. The piston rod, whether with or without the rod extension, can be manufactured as a whole, e.g., from a forged blank, which can achieve advantageous mechanical stability.

[0079] According to embodiments, the respective annular area of ​​the piston, i.e. the area formed by the end face of the piston less the cross-sectional area of ​​the piston rod or rod extension, is essentially or approximately the same size (e.g. within the scope of deviations of up to 5% or 10%) as the cross-sectional area of ​​the piston rod or rod extension. For example, if the diameter of the piston rod or rod extension is 45 mm, which corresponds to an area of ​​approximately 15.9 cm 2<, and the diameter of the piston is 63 mm, for example, which corresponds to an area of ​​approximately 31.2 cm 2<, the annular area is: 31.2 cm 2< - 15.9 cm 2< = 15.3 cm 2< for a piston rod area of ​​15.9 cm 2<. In this example, the ring area essentially corresponds to the piston rod area or the rod extension area, in particular within a deviation of between 3.5% and 4%.

[0080] According to embodiments, the first hydraulic connection can be or can be connected to the hydraulic circuit in such a way that a first cylinder chamber of the hydraulic cylinder, which is connected to the first hydraulic connection and downstream thereof, is or can be subjected to a predetermined system pressure, in particular to the pressure generated by the unit for generating the system pressure, for example a pressure accumulator and / or a pump unit. During operation of the hydraulic cylinder, the first cylinder chamber is preferably always subjected to system pressure. The system pressure is therefore present in the first cylinder chamber, which is designed as an annular chamber due to the piston rod running through the first cylinder chamber. The second cylinder chamber facing away from the piston rod is, apart from the annular volume formed around the rod extension, hollow cylindrical, i.e. not entirely designed as an annular chamber.If the system pressure is also present in the second cylinder chamber during an operating phase, a force is generated which accelerates the piston towards the first end.

[0081] A movement or acceleration of the piston towards the first end is preferably used for a working stroke, during which the ram coupled to the piston is accelerated to a target speed intended for the forming process or for an impact. The movement during the working stroke preferably occurs from top to bottom. During a working stroke, the second cylinder chamber is filled with hydraulic fluid, preferably at least temporarily by applying system pressure. The second cylinder chamber can therefore also be referred to as a displacement chamber. Correspondingly, a movement of the piston towards the second end can be used for a return stroke, preferably a movement from bottom to top, during which the piston or ram is moved into a starting position intended for executing a subsequent working stroke or impact.Therefore, the first cylinder chamber, which is designed in particular as an annular chamber, can be referred to as a return stroke chamber of the hydraulic cylinder.

[0082] Preferably, the hydraulic cylinder in the ready-to-use forming machine is arranged essentially vertically, i.e. the piston moves along a vertical axis, with the first end at the bottom and the second end at the top. A forming cycle can be carried out by pressurising the return stroke chamber and the displacement chamber when the working stroke is triggered, resulting in a force acting downwards towards the first end which, together with the weight of the piston, piston rod and ram and possibly other components such as tools on the ram, causes the ram to accelerate downwards. After a forming operation or an impact has been carried out, the displacement chamber can be connected, for example without pressure, to a reservoir, for example a return tank, so that the system pressure acting in the return stroke chamber causes a return stroke upwards.By appropriately controlling or regulating the hydraulic flows into and out of the cylinder chambers, the ram can be accelerated to a desired speed during the working stroke and positioned at a desired starting position for a subsequent forming operation during the return stroke. Suitable hydraulic controls and associated system configurations are described in more detail below. What all designs have in common, however, is that the rod extension and the bore at the second end act as a brake to decelerate the return stroke movement if necessary.

[0083] According to an advantageous embodiment, the hydraulic circuit comprises a valve unit connected or connectable to the second hydraulic connection. The hydraulic circuit and the valve unit are preferably configured such that a second cylinder chamber of the hydraulic cylinder, or the second cylinder chamber connected to the second hydraulic connection, can be selectively pressurized at least temporarily with hydraulic pressure, in particular at least temporarily with the system pressure, for example by connecting it to the pressure accumulator, via the valve unit when executing a working stroke, or can be connected at least temporarily without pressure to the reservoir, e.g. a return tank. For example, in an acceleration phase after triggering a working stroke to accelerate the ram to the target speed, the valve unit can be controlled or regulated such that the second cylinder chamber is pressurized with system pressure, for example by connecting it to the pressure accumulator.After reaching the target speed and / or during the return stroke, the valve unit can be controlled or regulated in such a way that the second cylinder chamber is connected, for example, without pressure to the return tank.

[0084] After the target speed has been reached, the second cylinder chamber can be connected to a suction tank during the working stroke, for example, so that hydraulic fluid can be sucked into the second cylinder chamber essentially without pressure, in line with the increase in volume of the second cylinder chamber as a result of the movement of the piston towards the first end. The suction after the target speed has been reached or a corresponding suction volume flow is preferably regulated or controlled by the valve unit such that the target speed is essentially maintained and / or that a predetermined forming speed is achieved. For example, the suction volume flow can be regulated or controlled such that a force equilibrium prevails between weight forces and compressive forces in the second cylinder chamber on the one hand and compressive forces in the first cylinder chamber on the other.If a force equilibrium cannot be achieved, the suction flow rate is preferably regulated and / or controlled such that the ram reaches a predetermined forming speed. Advantageously, the acceleration phase and / or the suction phase are regulated or controlled such that the hydraulic pressure in the parts of the hydraulic circuit affected by the suction is above the cavitation pressure of the hydraulic fluid.

[0085] After the forming process has been completed, the second cylinder chamber can be connected to a pressure-free reservoir, e.g. a return tank, via the valve unit so that the system pressure prevailing in the first cylinder chamber causes the return stroke movement. During the return stroke, a return stroke volume flow resulting from the second cylinder chamber into the reservoir or return tank can be controlled or regulated, for example, by controlling or regulating the valve unit in such a way that the return stroke movement ends at a predetermined starting or starting position for a subsequent working stroke. This makes it possible, for example, to select the starting or starting position of the piston in the cylinder tube essentially arbitrarily. This means that by suitable control or regulation of the return stroke by the valve unit, the starting position is not necessarily located at the second end or is not determined exclusively by the brake defined by the rod extension and bore.Further details are described in more detail below.

[0086] According to a preferred embodiment, the valve unit comprises a controllable or regulatable first hydraulic valve, for example a shock valve for triggering a forming impact or a working stroke, which is connected or connectable to the second hydraulic connection, and a controllable or regulatable second hydraulic valve, for example a rising valve for executing a return stroke, which is connected or connectable to the second hydraulic connection.

[0087] The first hydraulic valve is designed to, in a switching position or control or regulating position, at least temporarily pressurise the second cylinder chamber via the second hydraulic connection during execution of the working stroke with hydraulic pressure, in particular system pressure, for example by connecting it to the pressure accumulator. The second hydraulic valve is designed to, in a switching position or control or regulating position, at least temporarily connect the second cylinder chamber via the second hydraulic connection without pressure to the reservoir, in particular a suction tank, during execution of the working stroke. Consequently, a control or regulating system for the working stroke can be provided or designed by which the first hydraulic valve is controlled, e.g. opened, in such a way that the second cylinder chamber is pressurised with system pressure to trigger a working stroke and to accelerate the ram to the target speed.The opening width of the first hydraulic valve can, for example, be controlled or regulated such that the pressure forces acting on the piston from the second cylinder chamber are greater than the pressure forces resulting from the first cylinder chamber, for example, from the system pressure. In particular, it is possible to regulate or control the acceleration or acceleration process, for example, according to a predetermined target curve for the movement or acceleration and / or depending on the desired target speed or forming speed.

[0088] Once the target speed has been reached, the control or regulation can provide that the first hydraulic valve is closed, for example, and the second hydraulic valve is opened, so that hydraulic fluid is sucked into the second cylinder chamber, for example without pressure from the reservoir, e.g. the suction tank. Preferably, the opening or opening width of the second hydraulic valve and thus the suction volume flow are controlled or regulated such that the piston continues to move essentially at the target speed, or that the forming speed is reached and / or the pressure is above the cavitation pressure, i.e. that a pressure so low that the air dissolved in the oil is released (cavitation) is not reached.

[0089] The described operation of the forming machine with only two hydraulic connections and the proposed brake unit consisting of a cylinder extension and a bore enable, in particular, a precise adjustment of the target speed or forming speed of the ram while simultaneously ensuring safe operation, for example in the event of a failure of the control or regulation of the hydraulic valves.

[0090] Depending on the configuration, the valves or hydraulic valves can have an integrated safety stage. Specifically, an integrated safety stage can be implemented such that a safety valve associated with or integrated into the hydraulic valve must be pressurized before the actual hydraulic valve, e.g., a piston of a cartridge valve, can be controlled or regulated, or is enabled for control or regulation by the safety stage.

[0091] Depending on the design, a corresponding safety level can be assigned to the impact valve, for example. This safety level can be used to determine, for example, the readiness of the forming machine or hammer to accept a blow. If, for example, the safety level is pressurized, this corresponds to an operating state in which the execution of an impact is permitted.

[0092] Advantageously, the hydraulic valves are electrically controlled and closed when de-energized. This prevents uncontrollable movements of the ram or hydraulic cylinder, for example, in the event of a power failure, since pressure or the system pressure is maintained in the hydraulic system, e.g., in the accumulator, even when the valves are de-energized.

[0093] According to one embodiment, the first hydraulic valve is designed or is controlled or regulated such that it assumes a closed position at least temporarily during the working stroke, for example during the acceleration phase of the ram, and / or at least temporarily during a return stroke, preferably substantially during the entire return stroke. During a working stroke, the first hydraulic valve is preferably controlled or regulated into the closed position when the target speed is reached and the second cylinder chamber is connected to the reservoir or suction tank via the second hydraulic valve. In particular, the second hydraulic valve can be designed or is controlled or regulated such that the second cylinder chamber is connected to the reservoir or suction tank in a pressureless manner when the first hydraulic valve is in the closed position, for example after the target speed has been reached.For this purpose, the second hydraulic valve can be controlled or regulated into the open position.

[0094] According to one embodiment, the forming machine further comprises a hydraulic control unit, in particular a control unit or control unit, for controlling and / or regulating the hydraulic circuit, in particular the hydraulic valves, wherein the hydraulic control unit is configured, in particular programmed, for operating, in particular for controlling or regulating, a hydraulic forming machine according to one of the embodiments of the invention described herein.

[0095] The hydraulic control unit comprises a processor and / or control electronics or regulating electronics which are designed to control or regulate the opening width of the first hydraulic valve when executing a working stroke intended for forming a workpiece in such a way that ▪ in a first phase, the first hydraulic valve is opened and the ram is accelerated to a target speed in the first phase, ▪ in a second phase following the first phase, in particular after the target speed has been reached, the opening width is or will be reduced to a predetermined afterflow opening width, and ▪ the first hydraulic valve is or will be closed in the area of ​​the forming position of the ram and during a return stroke running opposite to the working stroke.

[0096] For further embodiments of the hydraulic control unit and with regard to advantages and advantageous effects of the hydraulic control unit, reference is made to the explanations regarding the hydraulic forming machine, which are correspondingly applicable to the hydraulic control unit.

[0097] All operating modes of the hydraulic forming machine and the control unit or hydraulic control unit can also be claimed as operating methods within the scope of the invention, with corresponding functional features being understood as method steps. A corresponding method can provide the following method steps for the aforementioned hydraulic control unit or for a corresponding forming machine: ▪ in a first phase of the working stroke, opening the first hydraulic valve and accelerating the ram to a target speed, ▪ in a second phase following the first phase, in particular after reaching the target speed, reducing the opening width to a predetermined afterflow opening width, and ▪ closing the first hydraulic valve in the area of ​​the forming position of the ram and during a return stroke running opposite to the working stroke.

[0098] According to embodiments of the hydraulic control unit, it can be provided that the hydraulic circuit further comprises a second hydraulic valve which is connected to the hydraulic connection, and wherein the hydraulic control unit is configured to control an opening width of the second hydraulic valve, which is preferably designed as a proportional valve, such that, in the case of a return stroke occurring opposite to the working stroke, a starting position of the ram for a subsequent working stroke can be variably adjusted and / or the forming machine further comprises a measuring unit for determining the position of the ram, wherein the hydraulic control unit is configured to determine one or more operating parameters, such as a starting position and / or a target speed and / or an impact energy of the ram, for a subsequent working stroke on the basis of a forming position determined by the measuring unit for a previous working stroke, wherein, preferably,an initial working stroke is configured as a directional blow executed with minimal impact energy, and / or the hydraulic control unit is configured to control the opening width of the first hydraulic valve based on a variably predeterminable and / or determinable starting position and a variable forming position (reversal position / rest position), in particular a variably predeterminable and / or determinable forming position, in particular such that the working stroke, in particular a forming blow, can be executed with a respective suitable, preferably predetermined, in particular a respective maximum achievable, impact energy, and / or the hydraulic control unit is configured to variably set a starting position for executing a working stroke, in particular depending on at least one operating parameter of the hydraulic cylinder with respect to one or more preceding working strokes,wherein the operating parameter is preferably an operating parameter detected by one or more sensor units, and / or the hydraulic control unit is configured to determine a starting position for a working stroke at a predetermined forming energy and to set it by controlling and / or regulating the second hydraulic valve during a return stroke, wherein the hydraulic control unit is preferably configured to variably set the starting position on the basis of a free path length of the ram between the starting position and the forming position of a previous working stroke.

[0099] According to an embodiment which can be claimed independently, the forming machine further comprises a control unit or control unit (or: hydraulic control unit) for controlling and / or regulating the hydraulic circuit, in particular the hydraulic valves, wherein the control unit is configured, in particular programmed, to: during a working stroke and in order to accelerate the ram to a target speed, to pressurise the second cylinder chamber with hydraulic pressure, for example with system pressure; during the working stroke and after reaching the target speed, to essentially depressurise the second cylinder chamber or to pressurise it with hydraulic pressure which is reduced compared to the system pressure, for example in such a way that there is an equilibrium of forces on the piston and / or the target speed is essentially maintained; and during a return stroke, to depressurise the second cylinder chamber; wherein the first cylinder chamber is pressurised with system pressure during the working stroke and return stroke.

[0100] According to an advantageous embodiment, the control unit is configured, in particular programmed: a) during the working stroke, to control or regulate the first hydraulic valve into an open position, in which the second cylinder chamber is or will be pressurised with hydraulic pressure via the first hydraulic valve, for example at least temporarily with the (full) system pressure, until a predetermined target speed of the ram is reached, and simultaneously to control or regulate the second hydraulic valve into a closed position, b) during the working stroke and after or upon reaching the target speed b1) to control or regulate the first hydraulic valve into a closed position, and by controlling or regulating the second hydraulic valve into an open position, to connect the second cylinder chamber via the second hydraulic valve and / or via a suction valve to the reservoir, in particular a suction tank, and to generate a suction volume flow in the second cylinder chamber,with which the target speed is essentially maintained and / or with which a predetermined forming speed is achieved at the time of forming; or b2) by controlling or regulating the open position of the first hydraulic valve via the first hydraulic valve and / or via a suction valve, to generate a post-flow volume flow into the second cylinder chamber, with which the target speed is essentially maintained and / or with which a predetermined forming speed is achieved at the time of forming, wherein the second hydraulic valve is preferably controlled or regulated into the closed position; c) during a return stroke following the working stroke, to control or regulate the second hydraulic valve connected to the second hydraulic connection into the open position and the first hydraulic valve connected to the second hydraulic connection into the closed position.

[0101] In short, the control unit according to a) effects an operation in which the ram is accelerated by controlled or regulated application of hydraulic pressure to the second cylinder chamber, for example to a target speed which, for example, essentially corresponds to a predetermined forming speed or with which the forming speed is reached at the time of forming.

[0102] The target speed for the impact forming machine is reached before the tool hits the workpiece or forged part. This means that the acceleration process is completed before the tool hits the workpiece or forged part. In any case, the first hydraulic valve or impact valve is actually closed at the latest when forming begins or the ram changes direction, i.e. moves in the return stroke direction. Since the hydraulic system has a certain reaction time, the first hydraulic valve or impact valve can be controlled accordingly so that it is reliably closed when forming begins or the ram changes direction. Otherwise, there would still be system pressure in the piston chamber and the reversing ram would push hydraulic fluid upwards, which would result in uncontrollably high pressure peaks and could damage the hydraulic system and / or hydraulic cylinder.

[0103] According to embodiments, the acceleration phase a) and in particular phases b1) and b2) are configured such that no cavitation occurs in the hydraulic fluid. In particular, the acceleration phase and the subsequent phase with the afterflow volume flow can be coordinated such that the pressure in the hydraulic fluid is above the cavitation pressure.

[0104] The process sequence of the percussive forming machine is designed so that the second hydraulic valve or riser valve is safely open or switched to the reservoir before the ram changes direction, i.e. moves in the return stroke direction. To take the system's reaction times into account, the second hydraulic valve or riser valve can be controlled so that it is safely open when the ram changes direction. For example, the riser valve or second hydraulic valve can be opened as soon as the acceleration phase has ended or is about to end. If the riser valve were not open, there would be no path for the hydraulic fluid that the ram displaces during this change of direction, which would lead to damage due to high pressure.

[0105] Thus, at the end of the acceleration phase, an overlap of "end of impact" and "beginning of rise" can occur, for example, if the first hydraulic valve or impact valve and the second hydraulic valve or rise valve are open simultaneously in an overlap phase. In this state or overlap phase, the ram is essentially removed from control (the ram is "released") and can then form the workpiece by impact. In particular, it can be provided that the ram is removed from control at least during the forming process, advantageously – taking into account the reaction times of the hydraulic system – even before the forming process.

[0106] According to steps b1) and b2, the re-cavitation volume flow can be generated at least partially via a re-cavitation valve. In this operating mode, the re-cavitation volume flow can be generated either entirely via the re-cavitation valve or via the re-cavitation valve and the first / second hydraulic valve. As explained in steps b1) and b2, it is possible, in particular, for the re-cavitation volume flow to be generated via the first / second hydraulic valve, so that a re-cavitation valve is not absolutely necessary.

[0107] For example, after reaching the target speed, there are the following two alternatives for the further working stroke.

[0108] In a mode of operation according to b1), the first hydraulic valve can be closed and the second hydraulic valve can be opened. This results in a system-side pressureless suction volume flow into the second cylinder chamber, which compensates or equalizes the volume increase of the second cylinder chamber by sucked-in hydraulic fluid. The open position of the second hydraulic valve can be regulated or controlled, if necessary, to maintain the target speed and / or achieve the forming speed. The suction volume flow can be provided alternatively or at least partially via a separate suction valve.

[0109] In the alternative mode of operation according to b2), it can be provided that the first hydraulic valve is not completely closed, with the second hydraulic valve preferably remaining closed. For example, the first hydraulic valve can be only partially regulated or controlled into the closed position, so that a pressure-based afterflow volume flow is established which generates a pressure in the second cylinder chamber that is lower than the system pressure. The afterflow volume flow can be regulated or controlled in such a way that the ram is not accelerated any further and the target speed is essentially maintained. The control and / or regulation of the valves can, for example, be based on predetermined control and / or regulation curves which can be determined, for example, from a test operation of the forming machine and / or by simulation.Even in this mode of operation, a suction volume flow via a suction valve is possible, which can be carried out via the suction valve and / or the first hydraulic valve.

[0110] If the first hydraulic valve or the impact valve is closed at the end of the acceleration phase, either completely, which would result in a suction effect, or only partially, which would result in a flow effect, the system pressure applied to the ring side of the hydraulic cylinder will have a braking effect on the ram. In this respect, the wording according to which "the target speed is essentially maintained" or "a predetermined forming speed is reached at the time of forming" is to be understood as meaning that the acceleration phase is set up in such a way that, despite any braking forces that may occur, the speed of the ram intended for forming is maintained after the time at which the acceleration phase is ended by at least partially closing the first hydraulic valve. For example, if an impact of 5 m / s, which e.g.100% energy preselection on the forming machine, and the acceleration phase extends over a stroke of 450 mm, with a maximum available stroke of 500 mm until the tool hits the workpiece or forged part, there is a remaining path of 50 mm. If braking forces act on this path, i.e. forces directed against the lifting movement, i.e. there is no equilibrium of forces, the speed of the ram is slightly higher (e.g. 0.2 m / s) for a stroke of 450 mm than for 500 mm. Corresponding braking forces or braking effects can, insofar as they are relevant for the forming and the target speed, be taken into account when controlling the first hydraulic valve or impact valve, or when controlling or regulating the acceleration phase.

[0111] During the post-suction or post-flow phase, a certain force counteracting the movement of the ram may be desirable, e.g., a vertically upward force during a downward movement of the ram during the stroke. Such a force can at least amplify the initial acceleration of the return stroke caused by the rebound. This can ensure that the tool, especially the upper tool, separates from the workpiece, especially the lower tool, in a shorter or very short time (e.g., a few milliseconds). Short pressure contact times are advantageous for long tool service life.

[0112] A rebound always occurs when the bear brings more kinetic energy than can be converted into forming work during a deformation or impact.

[0113] A particular advantage of the proposed forming machine and the forming method is that the braking phase following the acceleration phase (open impact valve) can be optimized so that optimal forming impacts can be set up or achieved.

[0114] As mentioned, the forming machine can be configured so that the ram moves downward during acceleration and upward during the return stroke. The ram moves vertically with a moving upper tool.

[0115] In the operating mode according to c), which corresponds to the return stroke, the first hydraulic valve is closed and the second hydraulic valve is regulated or controlled into an open position, whereby the second cylinder chamber is connected to the reservoir or return tank without pressure. The system pressure present in the first cylinder chamber causes the return stroke movement. By controlling or regulating the open position of the second hydraulic valve during the return stroke, the effectively acting return stroke force can be controlled or controlled in a targeted manner, in particular in such a way that the piston comes to a stop at a starting position desired for the next working stroke. The starting position can essentially be regulated or controlled to any point between the first and second hydraulic connection or between the two reversal points at the first and second end. This results in particular in optimized movement control, whereby the piston, for example, does not have to return to the reversal point or return point on every return stroke.Dead center at the second end must be moved. For example, wear can be reduced and precisely reproducible working strokes and target speeds can be set or achieved.

[0116] Another advantage of the proposed forming machine and method is that the second hydraulic valve or riser valve can be opened and closed in a targeted or controlled manner, for example by means of a suitable function or ramp. A corresponding control / regulation can provide that the second hydraulic valve or riser valve is initially wide open (a lot of hydraulic fluid can flow out) to compensate for the rebound, then the second hydraulic valve or riser valve can be closed continuously, for example, to initially generate gentle braking on the return stroke, followed by faster closing to finally achieve a targeted stop, for example at a predetermined position with little overrun (beyond the desired starting position for a subsequent impact) and high repeatability.

[0117] According to embodiments, at least at the beginning or in the initial phase and / or acceleration phase of a further working stroke following the return stroke, the first and second hydraulic valves can be redirected or regulated such that the first hydraulic valve is in the open position and the second hydraulic valve is in the closed position.

[0118] Preferably, during the working stroke and the return stroke, the first cylinder chamber is pressurized with the system pressure via the first hydraulic connection, preferably from the pressure accumulator.

[0119] According to one embodiment, a hydraulic forming machine according to one of the embodiments described herein is provided, which further comprises a position measuring system or a position measuring unit for detecting the position and / or speed of the piston, the piston rod and / or the ram. Position and / or speed data from the position measuring unit can be or are preferably used to control or regulate the hydraulic valves during the working stroke, e.g. during acceleration to the target speed, and / or during the return stroke, e.g. during positioning the piston or ram in the initial position or start position for a subsequent working stroke. Within the scope of a control system, the target speed, for example the reference variable, and the respectively determined position or speed can be used as the actual value to control the hydraulic valves.

[0120] According to one embodiment, the hydraulic circuit can further comprise at least one, preferably two, pressure sensors. For example, a first pressure sensor can be configured to detect the hydraulic pressure in the first cylinder chamber, and a second pressure sensor can be configured to detect the hydraulic pressure in the second cylinder chamber. Preferably, the pressure sensor(s) are connected in a hydraulic line adjoining the first or second hydraulic connection. Pressure values ​​of the pressure sensor(s) can be used, for example, to control or regulate the hydraulic circuit, in particular the valve unit or the hydraulic valves, such that the hydraulic pressure in the hydraulic system, in particular in the cylinder chambers, is always or substantially always above the cavitation pressure of the hydraulic fluid.The pressure values ​​can also be used, or alternatively, to control and / or regulate the hydraulic valves to achieve the target speed and forming speed. For this purpose, predefined pressure curves can be provided to the control and / or regulation system, for example, and the control unit can be configured or programmed such that the measured hydraulic pressures follow the pressure curve.

[0121] In particular, it is possible for the control unit to be set up or programmed in such a way that the determined position, speed, and / or pressure values ​​are used to control or regulate the hydraulic circuit according to predetermined position, speed, and / or pressure curves. For example, it is possible to control or regulate the working stroke and / or return stroke based on a predetermined position, speed, and / or pressure curve, such that the respectively determined actual values ​​follow the position, speed, and / or pressure curve. Position, speed, and / or pressure curves can, for example, be given in the form of value tables or other specified data. In particular, position, speed, and / or pressure can be given as setpoints as a function of time.It is also possible, for example, to use a position-speed profile and / or a position-pressure profile and / or a pressure-speed profile as a target profile for controlling or regulating the working stroke and / or return stroke.

[0122] According to one embodiment, as already indicated above, the volume of the bore can be connected to the volume of the second cylinder chamber via a throttle, so that the bore is connected to the second cylinder chamber via the throttle, in particular when the second hydraulic connection is closed by the piston and the opening is closed by the rod extension. The throttle can achieve pressure equalization between the volume of the bore and the annular volume around the rod extension, in particular when the rod extension closes the opening of the bore at the second end.

[0123] According to one embodiment, a hydraulic control unit is provided for operating, in particular for controlling or regulating, a hydraulic forming machine according to one of the embodiments described herein. The hydraulic control unit comprises a processor and / or control electronics or regulating electronics, which is / are configured, in particular programmed, to control or regulating the hydraulic circuit in such a way that it carries out the steps explained below during operation. In particular, the processor, the control electronics and / or the regulating electronics can have programming and / or computer-readable or electronically readable instructions can be stored on an associated electronic storage unit, which, when executed by the processor, the control electronics and / or the regulating electronics, bring about the steps described below.The hydraulic control unit is connected in terms of control and / or regulation technology at least to the hydraulic valves for their control / regulation, preferably furthermore to the position measuring unit and / or the pressure sensors.

[0124] The aforementioned control and / or regulation steps can be set up so that: a) in order to accelerate the ram to a target speed, the second cylinder chamber is pressurised with hydraulic pressure, in particular with system pressure, in a controlled or regulated manner via a first hydraulic valve connected thereto; b) after or upon reaching the target speed b1) via the second hydraulic connection (38) a follow-up volume flow is generated into the second cylinder chamber (45) via a suction valve and / or via the second hydraulic connection a follow-up volume flow, in particular a pressure-based follow-up volume flow, is controlled or regulated into the second cylinder chamber via the first hydraulic valve in such a way that the target speed is essentially maintained and / or a predetermined forming speed is reached at the time of forming, or b2) the first hydraulic valve is closed, and via a suction valve a follow-up volume flow and / or via the second hydraulic connection a follow-up volume flow, in particular a pressure-free one,The suction volume flow is controlled or regulated via a second hydraulic valve connected to the second cylinder chamber on the one hand and to the reservoir, in particular the suction tank, on the other hand, in such a way that the target speed is essentially maintained and / or a predetermined forming speed is achieved at the time of forming.

[0125] For the steps a), b) and b1) or b2) mentioned above, reference is made to the corresponding explanations above, which apply here accordingly.

[0126] In particular, a post-flow volume flow or post-flow is understood to be a pressure-based supply of hydraulic fluid, and a post-suction volume flow or post-suction is understood to be a pressureless suction of hydraulic fluid. During post-flow, the hydraulic fluid is supplied under pressure that can be less than or equal to the system pressure, and during post-suction, the hydraulic fluid is supplied through the system without active pressurization, i.e., it is sucked in.

[0127] According to embodiments, the hydraulic control unit is further configured to determine a position and / or speed of the piston, the piston rod and / or the ram via a position measuring unit of the forming machine, and to control or regulate the first and / or second hydraulic valve depending on the determined position and / or speed, preferably according to a predetermined or predeterminable position or speed curve or profile.For example, based on the determined position and / or speed, the afterflow volume flow and / or the after-suction volume flow during a working stroke and / or the volume flow from the second cylinder chamber during a return stroke can be regulated or controlled based on position and / or speed data, in particular to the effect that the target speed and / or the forming speed is reached and / or that a predetermined starting or starting position for a subsequent working stroke is reached.

[0128] According to embodiments, the hydraulic control unit is further configured to determine the hydraulic pressure prevailing in the first and / or second cylinder chamber by means of a first or second pressure sensor of the forming machine, and to control and / or regulate the first and / or second hydraulic valve as a function of the determined hydraulic pressure, in particular according to a predetermined pressure curve and / or such that the hydraulic pressure in the hydraulic circuit, in particular in the cylinder chambers, preferably in the second cylinder chamber, is substantially above the cavitation pressure of the hydraulic fluid.

[0129] According to embodiments, a hydraulic forming machine according to one of the embodiments described herein is provided, which comprises a hydraulic control unit according to one of the embodiments described herein.

[0130] According to embodiments, a method for operating, in particular for controlling or regulating a working stroke and return stroke, of a hydraulic cylinder of a hydraulic forming machine, in particular according to an embodiment described herein, or a method for operating a hydraulic forming machine, in particular according to an embodiment described herein, is further provided.

[0131] The hydraulic cylinder comprises a cylinder tube with a stroke chamber, i.e. a cylinder chamber or a cylinder space to which hydraulic fluid is supplied during a working stroke, and a return stroke chamber, i.e. a cylinder chamber or a cylinder space to which hydraulic fluid is supplied during a return stroke.

[0132] The stroke chamber and return stroke chamber are separated from each other by a piston that can be moved in a cylinder tube of the hydraulic piston. The hydraulic cylinder further comprises a piston rod that runs on the return stroke chamber side and is connected or coupled to the piston on the one hand and a ram on the other, a rod extension formed on the piston on the stroke chamber side, and a bore formed at the end of the cylinder tube on the stroke chamber side. The inner diameter of the bore essentially corresponds to the outer diameter of the rod extension, in particular such that the rod extension can penetrate into the bore. The bore is preferably designed like a blind hole and has an opening oriented towards the rod extension. The bore and the rod extension are arranged and formed coaxially to each other, wherein the rod extension is preferably further formed coaxially to the piston and the piston rod.

[0133] The return stroke chamber has a first hydraulic connection, and the lifting chamber has a second hydraulic connection. Apart from the two hydraulic connections, preferably no further hydraulic connections are present in the axial direction between the two hydraulic connections. A hydraulic connection is understood to be a connection through which hydraulic fluid is supplied to or removed from the respective associated chamber or cylinder chamber, i.e., the lifting chamber or return stroke chamber, for the purpose of actively operating the hydraulic cylinder, for executing the working stroke or return stroke.

[0134] In one embodiment of the method, the second hydraulic port is closed by the piston during a return stroke when the rod extension reaches an opening in the bore facing the rod extension. This allows the piston to be decelerated at the second end of the cylinder tube during the return stroke.

[0135] The method comprises the following steps in embodiments, in which: a) when triggering a working stroke, in particular an impact, and at least temporarily during the working stroke to accelerate the ram from a starting position to a desired speed, the lifting chamber is pressurised with hydraulic fluid via the second hydraulic connection, wherein the pressurisation is controlled or regulated by a first hydraulic valve connected to the second hydraulic connection, and wherein a second hydraulic valve connected to the second hydraulic connection is controlled into the closed position, ieclosed, b) when the target speed is reached during the working stroke b1) a post-flow volume flow is generated via a suction valve and / or the pressurisation and a post-flow volume flow of hydraulic fluid generated thereby are controlled or regulated via the first hydraulic valve in such a way that the target speed is essentially maintained and / or a predetermined forming speed is reached at the forming time; or b2) the first hydraulic valve is controlled or closed into the closed position and the stroke chamber or the second hydraulic connection is connected, in particular without pressure, to a reservoir, e.g.a re-cavitation tank, via a re-cavitation valve and / or via a second hydraulic valve, wherein a re-cavitation volume flow resulting from the reservoir via the second hydraulic valve and the second hydraulic connection into the stroke chamber is regulated or controlled by actuating or regulating the second hydraulic valve, in particular the opening state of the second hydraulic valve, such that the target speed is substantially maintained and / or a predetermined forming speed is reached at the time of forming. c) during a return stroke the first hydraulic valve is or remains closed, the second hydraulic valve is opened and the second hydraulic connection is connected to the (pressurised) reservoir, e.g. a return tank, wherein the piston, which is subjected to system pressure via the return stroke chamber, displaces hydraulic fluid of the stroke chamber via the second hydraulic connection and the second hydraulic valve into the reservoir.

[0136] With regard to advantages and configurations of the method, reference is made to the corresponding explanations on the control or regulation of the stroke or return stroke of the forming machine.

[0137] With regard to the formulations "that the target speed (v(target)) is essentially maintained" and "a predetermined forming speed is achieved at the time of forming", reference is made to the above statements, which are applicable to all embodiments proposed herein. In particular, it is possible, for example, that the speed reached at the end of the acceleration phase is greater than the speed during forming, for example if the ram is decelerated after the end of the acceleration phase with the first hydraulic valve open, e.g., by applied system pressure. Decelerations can occur, for example, in the last 5% to 15%, in particular 10%, of the working stroke or the stroke of the hydraulic cylinder, immediately before forming, and can be, for example, in the range of 0.1 m / s to 0.5 m / s, in particular around 0.2 m / s.

[0138] According to procedural embodiments, the method further comprises one or more of the following steps or features: Determining the position and / or speed of the ram using a position measuring unit of the forming machine, and controlling or regulating the pressurization in step a) based on the position and / or speed and the target speed or forming speed and / or controlling or regulating the pressurization in step a) based on the determined position and / or speed and a predetermined position and / or speed profile. Determining the position of the ram using a position measuring device and controlling or regulating the second hydraulic valve, in particular the opening state of the second hydraulic valve, during the return stroke such that the ram or piston is positioned in a predetermined or predeterminable, preferably variably predeterminable or variably selectable, starting position for executing a subsequent working stroke at the end of the return stroke.Detecting the hydraulic pressure in the displacement volume by means of a pressure sensor of the forming machine and controlling or regulating the first and / or second hydraulic valve during a working stroke, in particular after the target speed has been reached, on the basis of the detected hydraulic pressure, in particular in such a way that the hydraulic pressure in the hydraulic fluid is essentially always above the cavitation pressure of the hydraulic fluid. During the return stroke, the piston closes the second hydraulic connection when or as soon as the free or distal end of the rod extension reaches the opening of the bore facing the rod extension, so that the piston with piston rod and moving components is braked by the hydraulic fluid remaining between the piston and the bottom of the bore. Setting, in particular regulating or controlling, the return stroke movement of the piston to the starting position as the starting point for a further orsubsequent working stroke in such a way that the distance traveled by the piston from the starting position to reach the target speed is optimized, in particular maximized or minimized, and / or . that a post-flow phase according to b1) or post-suction phase according to b2) following the target speed has been reached is optimized, in particular minimized. To execute a return stroke, the first hydraulic valve is closed or remains closed, and the lifting chamber is connected to a reservoir, in particular a return tank, via the second hydraulic connection and the second hydraulic valve, wherein a return volume flow resulting from the lifting chamber into the reservoir is preferably regulated or controlled by actuating or regulating the intermediate second hydraulic valve such that the ram or the piston is positioned at a predetermined position during the return stroke, in particular a starting position suitable or desired for executing a subsequent working stroke, in particular a predetermined starting position. During the return stroke, the piston is braked in a controlled or regulated manner by controlling or regulating the opening state of the second hydraulic valve.Controlling or regulating the opening state of the second hydraulic valve when the first hydraulic valve is closed during a return stroke in such a way that the piston is positioned in a controlled or regulated manner at a predetermined or predeterminable position, in particular a starting position for triggering a subsequent working stroke, based on a detected position of the piston, the piston rod or the ram during the return stroke, wherein the starting position is preferably selected as a function of the target speed to be achieved, and, further preferably, the starting position corresponds to a position of the piston that is selectable or predeterminable, in particular essentially variably selectable or predeterminable, between the first hydraulic connection and the second hydraulic connection. The rod extension and the bore act as a type of emergency brake, in particular in the event of a failure of the hydraulic control, for example of the. second hydraulic valve during a return stroke. The braking effect of the rod extension and the bore can, of course, also be used during regular operation, for example, if the starting point for a working stroke corresponds to a position of the piston in the area of ​​the second end. The first hydraulic valve and the second hydraulic valve are controlled or regulated in method step b2) such that both hydraulic valves are temporarily at least partially open simultaneously in an overlap phase around the time the target speed is reached, so that a substantially uninterrupted flow of hydraulic fluid to the lifting chamber is achieved. A post-flow in step b1) comprises a supply of hydraulic fluid to the lifting chamber under hydraulic pressure, and a post-suction in step b2) comprises a pressureless supply of hydraulic fluid from the reservoir, in particular the post-suction tank. During the post-flow, the pressure or hydraulic pressure is preferably lower than the system pressure, wherein the respectively prevailing or applied hydraulic pressure can be regulated or controlled essentially as desired, in particular in the range from very low pressures up to the system pressure, in particular from pressureless up to the system pressure.By controlling or regulating the first and / or second hydraulic valve, the volume flow of the hydraulic fluid from or to the lifting chamber is controlled or regulated, and, based on the controlled or regulated volume flow, the speed and / or position of the ram during the working stroke or return stroke is adjusted, in particular controlled or regulated. The first and / or second hydraulic valves are controlled or regulated and / or the starting position is selected such that the ram continues to move at a substantially constant speed after reaching the target speed until the start of a forming process and / or that the forming speed is reached at the time of forming. A controllable hydraulic valve is used as the first and / or second hydraulic valve, preferably a continuous directional control valve, a proportional directional control valve, a servo directional control valve and / or a control directional control valve.The first and / or second hydraulic valve is / are regulated or controlled in a movement phase or lifting phase after reaching the target speed such that the hydraulic pressure in the lifting chamber corresponds to a predetermined or predeterminable hydraulic pressure or pressure range, wherein the predetermined or predeterminable pressure or pressure range is preferably between 2 and 6 bar, more preferably between 3 and 4 bar. By appropriate control and / or regulation, the hydraulic pressure can be adjusted so that it is essentially always above the cavitation pressure of the hydraulic fluid in the hydraulic system.The first and / or second hydraulic valve is / are dynamically controlled or regulated based on a value table for the positions, speeds, and / or target speeds of the ram, and / or for pressure profiles in the lifting chamber, and / or based on determined position and / or speed data of the ram. Determined position and / or speed data or profiles of the ram and / or pressure profiles of the hydraulic pressure in the lifting chamber and / or return stroke chamber are monitored and / or stored in a memory unit.The first and / or second hydraulic valve and a resulting volume flow of hydraulic fluid are regulated or controlled in such a way that the time until the target speed is reached is maximized while simultaneously minimizing the time duration of the movement phase after the target speed is reached, wherein, optionally, the movement phase covers between 5% to 15%, preferably approximately 10% of the stroke of the hydraulic cylinder.

[0139] The process-related designs provide similar advantages to those of the forming machine and the hydraulic control unit. In particular, a comparatively simple design can be achieved while simultaneously ensuring reliable operation.

[0140] During operation of the forming machine, specific tools are usually coupled to the ram or ram for the respective forming task, which, when acting on a workpiece to be formed at the end of a working stroke or press stroke, form the workpiece.

[0141] The hydraulic cylinder can in particular be a double-acting hydraulic cylinder, such as a differential cylinder.

[0142] A working stroke is understood in particular to be an operation of the hydraulic cylinder that results in a forming operation. A return stroke is understood in particular to be an operation of the hydraulic cylinder in which the piston or ram is moved back, for example, to a starting position intended for the execution of a subsequent working stroke. The starting positions of successive working strokes can, but do not have to, be identical. The working stroke and return stroke can be performed cyclically, with the hydraulic valves being controlled cyclically accordingly.

[0143] The term "hydraulic circuit" as used herein is to be understood in a particularly general sense. In particular, the term "hydraulic circuit" should encompass not only hydraulic lines, but also, depending on the context, additional components such as control units, regulating units, valves, pumps, pressure transducers, hydraulic cylinders, control blocks, etc., that are present or required for the hydraulic operation of the hydraulic cylinder.

[0144] The hydraulic valves referred to here are, in particular, valves with an adjustable, variable volume flow, i.e. in which the volume flow is adjustable, in particular controllable or regulatable. Such a valve differs from a conventional on-off valve with only two selectable switching positions in that several, for example a multitude of switching positions can be specifically set in a controllable or regulatable manner. In particular, the hydraulic valves referred to here can be designed such that the volume flow is essentially continuously or continuously adjustable, and that the opening state of the valve, in particular the opening width and / or the opening time, is specifically adjustable, in particular controllable or regulatable, e.g. over time according to a function of time or as a function of other variables.In particular, controllable valves are suitable, which allow the volume flow or the opening width and / or opening time to be adjusted using control and / or regulation technology.

[0145] The hydraulic circuit can in particular be designed to adjust and vary, in particular to control or regulate, the volume flow of the hydraulic valve(s) depending on a target speed of the ram to be achieved in an acceleration phase of the working stroke. For example, the hydraulic circuit can be designed to adjust the volume flow, for example the opening width and / or the opening duration of the hydraulic valve(s) over time such that the target speed is reached within a predetermined or predeterminable stroke range of the piston. For adjusting and varying, in particular controlling or regulating the volume flow, a corresponding control unit, in particular a control unit or regulating unit, can use data stored in a value table, for example, which is suitable for the respective operating conditions and operating parameters, such asForming machine, ram type, ram weight, tool height, tool weight, type of forming, type of material, etc., specify the volume flows and / or hydraulic pressures to be set over time to achieve the desired target speed, and / or from which the control unit can determine the volume flows to be set and / or dynamically regulate or control them.

[0146] The suction tank or return tank is preferably a pressureless reservoir for hydraulic fluid.

[0147] In a vertically operated ram, where the working stroke occurs vertically downwards, the weight of the piston, the piston rod, the ram and any components attached to it, such as tools, have an accelerating effect. The forming machine or the hydraulic control unit in such vertically operating forming machines can therefore be set up to reverse the hydraulic valves once the target speed has been reached, so that the speed desired for forming is achieved. The piston is acted upon on the one hand by the restoring forces generated by the system pressure in the first cylinder chamber or the lifting chamber and on the other hand by the weight of the piston, piston rod, ram, etc. and the lifting forces resulting from the pressurization of the second cylinder chamber or the lifting chamber.

[0148] If the second cylinder chamber is depressurized after the target speed has been reached, the piston is essentially subjected to the restoring force of the first cylinder chamber and the force of gravity. For a return stroke to occur, the restoring force must be greater than the force of gravity. If, in an operating mode with the second cylinder chamber depressurized after the target speed has been reached, a restoring force results, the target speed can be set higher than the forming speed to achieve a predetermined forming speed at the time of forming, so that the forming speed is reached in the movement phase resulting after the target speed has been reached.The force counteracting the movement resulting from the restoring force and the weight force can be taken into account when setting the target speed, in particular in that the target speed is set to the forming speed by the counteracting force from the pressure release when the forming position is reached.

[0149] Preferably, the forming machine is operated in such a way that the target speed is reached shortly before or immediately before the forming position or the forming point, so that any reduction in speed caused by depressurization is negligible, ie that the target speed is essentially maintained.

[0150] Setpoint tables or (setpoint) functions can be determined for position, speed, and / or hydraulic pressure under given boundary conditions, including, for example, the mass of the ram and the components moving with it, the stroke of the hydraulic cylinder, the type of hydraulic fluid (viscosity, etc.), etc., through test or trial runs and / or simulation. The setpoint tables or (setpoint) functions can be stored, for example, in an electronic memory of the forming machine and made available to a control unit or regulating unit for the timing or regulation of the hydraulic valves.

[0151] The pressure accumulator can, for example, be fed by a pump unit that applies the system pressure to the hydraulic circuit and the pressure accumulator.

[0152] The hydraulic valves represent actuators that can be configured, for example, in the form of controllable or adjustable valves and / or pumps with a controllable or adjustable motor, as a controllable or adjustable unit. The actuators can be selected, for example, from the group comprising continuous directional control valves, proportional directional control valves, servo directional control valves, control directional control valves, and servo pumps. The use of these actuators enables the implementation of advantageous, particularly relatively short, actuation times for positioning and varying the volume flows, and in particular, a comparatively precise and / or repeatable execution of a movement cycle consisting of a working stroke, forming, and return stroke for workpiece forming.With such actuators, comparatively short actuating times and comparatively fast reaction and response times can be achieved, whereby cavitations can be avoided, at least to a large extent or even completely.

[0153] A control system can be based on a specified or specifiable hydraulic pressure, hydraulic pressure interval, and / or a specified or specifiable temporal or spatial hydraulic pressure profile as a reference variable. For example, the hydraulic pressure or its profile can be specified or specifiable for the duration of a working stroke or return stroke, or for the position of the ram or the piston of the hydraulic cylinder during a working stroke or return stroke.

[0154] Corresponding hydraulic pressures and / or curves can be obtained, for example, from a test operation of the forming machine and / or from simulations.

[0155] An optimization of the movement sequence of the hydraulic cylinder during a working stroke can, for example, provide that the post-suction phase or post-flow phase corresponds to the range of 5% to 15%, preferably 10% of the stroke of the hydraulic cylinder. In particular, the volume flow for accelerating the ram can be set and varied such that the time period remaining after the acceleration phase until immediately before the forming process is longer than the actuating, response and / or switching times of the hydraulic valves, or generally of the actuator. By appropriately setting and varying, i.e. controlling and / or regulating, the volume flows in the acceleration phase, the length of the acceleration phase and accordingly the length of the post-suction or post-flow phase or their ratio can be set, e.g. also depending on the respective target speed or forming speed to be achieved.

[0156] For example, at low setpoint speeds the volume flow can be increased or set more slowly and with a smaller increase or smaller rate of change so that the setpoint speed is reached in a late phase of the working stroke, e.g. in the last third of the working stroke. At high setpoint speeds the volume flow can be increased accordingly more quickly, for example in such a way that the setpoint speed is also reached in a late phase of the working stroke. It is also possible for the starting position of the piston for executing a working stroke to be set depending on the setpoint speed. For example, for lower setpoint speeds or forming speeds starting positions can be selected that are closer to the first end, and for higher setpoint speeds or forming speeds starting positions can be used that are closer to the second end.

[0157] With the proposed forming machine and hydraulic control system, it is particularly possible to use only a partial stroke of the hydraulic cylinder for a working stroke to accelerate the ram, starting from a reversal point in the ram's movement sequence with zero ram speed, up to the target speed. Accordingly, it is possible to shift the starting position of the working stroke toward the first end or to shorten the return stroke. The starting positions suitable for given target speeds can be obtained, for example, from test or trial runs and / or through simulation, and provided, for example, in the form of a value table in a database of a control or regulating unit of the forming machine or the hydraulic circuit.

[0158] By shortening the return stroke, for example at comparatively low target speeds, it is possible to increase the frequency of forming operations on the forming machine and / or to save energy by shortening the return stroke.

[0159] In the proposed operation using the two hydraulic connections, by adjusting and varying, in particular by controlling or regulating, the volume flow to and from the cylinder chambers, e.g., depending on the target speed to be achieved, it is possible to shorten the post-suction or post-flow phase. This can, for example, calm the hydraulic fluid in the reservoir, e.g., in the post-suction tank or return tank, so that smaller reservoirs can be used. Furthermore, the risk of cavitation in the phase after the target speed is reached can be reduced.

[0160] By adjusting and varying, in particular controlling or regulating, the volume flow into the second cylinder chamber or stroke chamber, it is particularly possible to adjust, in particular to control or regulate, the volume of hydraulic fluid flowing into the second cylinder chamber per unit of time and / or the time interval in which hydraulic fluid flows into the second cylinder chamber. It is therefore possible, for example, to specifically and variably adjust the opening width of the hydraulic valves and their opening duration, in particular the filling time. The volume flow can be adjusted and / or varied, for example, by controlling or regulating the opening state of the hydraulic valves according to a function of time and / or a function of the stroke or stroke position. This makes it possible, for example, to adjust the duration of the acceleration phase for reaching the target speed, in particular depending on the target speed.In particular, it is possible to control or regulate the hydraulic valves, both at low and high target speeds, so that the target speed is reached shortly before or immediately before the forming process, preferably in such a way that the duration of the post-flow or post-suction phase is reduced to a minimum. Since cavitation can occur particularly during the post-suction phase, more reliable operation can be achieved by minimizing the post-suction phase.

[0161] Embodiments of the invention are described in more detail below with reference to the attached figures. They show: FIG. 1 schematically shows a forming machine, which may be a forging hammer, for example; FIG. 2 an enlarged view of a hydraulic cylinder of the forming machine; FIG. 3 an enlarged view of an upper end of the hydraulic cylinder; FIG. 4 a process sequence of a first variant of a forming cycle for the forming machine; FIG. 5 an exemplary flow diagram for a working cycle with a pressurized post-flow phase; FIG. 6 a process sequence of a second variant of a forming cycle for the forming machine; and FIG. 7 an exemplary flow diagram for a working cycle with a pressure-free post-suction phase.

[0162] FIG. 1 shows a schematic diagram of a forming machine 1, which may be, for example, a forging hammer.

[0163] The forming machine 1 comprises a hydraulic cylinder 2, a ram 3 with an upper die 4, a lower die 6 attached to a scraper 5 and a hydraulic circuit 7. The forming machine 1 further comprises a control unit 8, for example a hydraulic control or regulation, with e.g. a processor and / or a programmable or programmed electronic unit.

[0164] The control unit 8 is connected via control lines and / or data lines 9 to a position measuring unit 10, which comprises, for example, a measuring sensor and an associated scale, to a first pressure sensor 11 and a second pressure sensor 12, to a first hydraulic valve 13 and a second hydraulic valve 14.

[0165] The hydraulic circuit 7 comprises, apart from hydraulic lines 15, in addition to the pressure sensors 11, 12 and the hydraulic valves 13, 14, a pump unit 16, a pressure accumulator 17 and a first safety valve 18 and a second safety valve 19. Furthermore, at least one reservoir 20 for hydraulic fluid, in particular in the form of a suction tank and / or return tank, is provided.

[0166] The hydraulic forming machine 1 is intended for forming workpieces 21, with the forming being performed by the upper die 4 and lower die 6. Specifically, the forming is performed by moving the ram 3 with the attached upper die 4 in a working stroke 22 from a starting position 24 downwards to the lower die 6. During operation of the forming machine 1, the working stroke 22 is followed by a return stroke 23, during which the ram 3 is moved to a starting or initial position 24. The working stroke 22 and return stroke 23, with intermediate forming, form a working cycle that can be repeated cyclically.

[0167] The hydraulic cylinder 2, which is in FIG. 2 is shown enlarged, comprises a cylinder tube 25 with a piston 29 movable therein along a longitudinal axis 26 between a first end 27 and a second end 28, which is coupled to a piston rod 30 which extends in the direction of the first end 27 and is coupled or can be coupled to the bear 3.

[0168] The piston 29 has, on the side 31 facing away from the piston rod 30, a cylindrical rod extension 32 extending towards the second end 28, the outer diameter 33 of which is smaller than that of the piston 29. The rod extension 32 is coaxial with the piston 29 and the piston rod 30 with respect to the longitudinal axis 26.

[0169] The hydraulic cylinder 2 has a bore 34 at its second end 28 that is coaxial with the rod extension 32 with respect to the longitudinal axis 25 and open toward the piston 29 or rod extension 32. The inner diameter 35 of the bore 34 essentially corresponds to the outer diameter 33 of the rod extension 32, so that the rod extension 32 can penetrate into the bore 34. The bore 34 is designed like a blind hole, with an opening 36 oriented toward the cylinder extension 32.

[0170] The hydraulic cylinder 2 or the cylinder tube 25 has a first hydraulic connection 37 in the region of the first end 27 and a second hydraulic connection 38 in the region of the second end 28.

[0171] The second hydraulic connection 38 is arranged or positioned such that the piston 29 closes the second hydraulic connection 38 when it moves towards the second end 28 when the rod extension 32 reaches the bore 34 or closes it, which in FIG. 3 is shown enlarged.

[0172] The bore 34 is, in the operating state according to FIG. 3 connected to an annular space 39 formed around the rod extension 32 via a throttle 40, wherein the throttle 40 is connected in the present case into a channel 43 running between the bottom 41 of the bore 34 and a bottom-like shoulder 42 or annular shoulder at the second end 28 of the cylinder tube 25.

[0173] On the side of the piston rod 26 or in the region of the first end 27, the hydraulic cylinder 2 has a first cylinder chamber 44, and on the side of the rod extension 32 or in the region of the second end 28, the hydraulic cylinder 2 has a second cylinder chamber 45.

[0174] As from FIG. 2 As can be seen, the first cylinder chamber 44 is designed as an annular chamber, and as can be seen from the overview of the FIG. 2 und 3 As can be seen, the second cylinder space 45 is only an annular space when the distal end 46 of the rod extension 32 closes or reaches the opening 36.

[0175] When the hydraulic cylinder 2 is operated for a forming operation of the workpiece 21, the second cylinder chamber 39 is pressurized with hydraulic fluid or hydraulic pressure during the working stroke 22, whereby the piston 29 is accelerated towards the first end 27. After the forming operation, the piston 29 is moved towards the second end 28 during the return stroke 23. If the moving mass formed by the piston 29, the piston rod 26, the rod extension 32, the ram 3 and the upper die 4, and any other components coupled thereto, is not decelerated during the return stroke 23, deceleration occurs at the latest when the distal end 46 of the rod extension 32 reaches the opening 36 of the bore 34.

[0176] When the distal end 46 of the rod extension 32 reaches the opening 36, the second hydraulic connection 38 is closed, and the hydraulic fluid in the bore 34 and the annular space 39 acts as a brake cushion for the moving mass. The throttle 40 thereby equalizes the pressure between the hydraulic fluid in the bore 34 and the hydraulic fluid in the annular space 39, thereby improving the damping and braking characteristics.

[0177] However, the braking of the piston 29 or the moving mass by the interaction of the rod extension 32 and the bore 34 is not mandatory, because according to the invention the control unit 8 can be configured such that braking of the piston 29 or the moving masses can be effected by controlling or regulating the hydraulic valves 13 and 14, which will be explained below using an exemplary forming cycle.

[0178] This shows FIG. 4 a process sequence of a first variant of a forming cycle. FIG. 6 shows a process flow of a second variant of a forming cycle for the forming machine. The process sequences are regulated or controlled by control unit 8.

[0179] According to the variant according to FIG. 4 the piston 29 or ram 3 is in the starting position or initial position 24 at the beginning of a working stroke 22, in FIG. 4 designated initial position i. When the working stroke 22 is triggered, for example a blow, the second cylinder chamber 45, or the lifting chamber, is pressurized with hydraulic fluid via the second hydraulic connection 38. The hydraulic pressure can correspond to the system pressure provided by the pump unit 16 or the pressure accumulator 17. For this purpose, the first hydraulic valve 13 is controlled or regulated by the control unit into an open position, for example (fully) open. In the direction of the working stroke 22, the hydraulic pressure generated by the first hydraulic valve 13, preferably the system pressure, and the weight of the mass to be moved (piston 29, rod extension 23, piston rod 26, ram 3, upper die 4) less any friction losses act. During this phase, the ram 3, or more precisely the mass to be moved, is accelerated. The acceleration serves to accelerate the ram 3 to a target speed v(target).As long as the target speed v(target) is not reached, the pressurization continues. The second hydraulic valve 14 is closed or controlled or regulated to the closed position.

[0180] If the target speed v(soll) is or will be reached, the control unit 8 intervenes in a control or regulation manner and controls or regulates the pressurisation via the second hydraulic connection 38, specifically the open position of the first hydraulic valve 13, in such a way that the piston 29 continues to move at a substantially constant speed, i.e. the target speed, and / or that the forming speed is reached. The determination as to whether the target speed has been reached or whether the piston 29 or ram 3 continues to move at the target speed can be made, for example, using speed or position data from the travel measuring unit 10. In particular, the first hydraulic valve 13 can be closed further compared to the acceleration phase in order to reach the target speed v(soll), so that the hydraulic pressure present in the second cylinder chamber 45 is reduced compared to the system pressure. In this case, the first hydraulic valve 13 orA pressurized afterflow volume flow is generated at the second hydraulic connection 38. This counteracts the system pressure prevailing in the first cylinder chamber 44 with the weight of the moving mass. For this purpose, and throughout the entire forming cycle, the first hydraulic connection 37 is pressurized with the system pressure, e.g., from the pressure accumulator 17.

[0181] When the workpiece 21 is reached, the forming operation takes place, which is followed by the return stroke 23 after the lower reversal point or bottom dead center of the hydraulic cylinder 2 is reached.

[0182] After the forming operation, which can be determined, for example, via speed and / or position data from the position measuring unit 10, the return stroke 23 takes place. During this, the hydraulic valves 13 and 14 are reversed or regulated accordingly. Specifically, the first hydraulic valve 13 is closed and the second hydraulic valve 14 is opened. This connects the second hydraulic connection 38 to the reservoir 20, a return tank, without pressure, so that there is no system-related hydraulic pressure in the second cylinder chamber 39. The system pressure present in the first cylinder chamber 44 accelerates the moving mass, in particular the ram 3, upwards, as a result of which the return stroke 23 takes place. As described above, since forming and the start of the return stroke follow one another in a comparatively short time (in the range of milliseconds) and / or due to system inertia, it is advantageous if the hydraulic valves are reversed before the forming operation or that the ram orThe hydraulic cylinder is removed from control shortly before the forming process, so that pressure peaks in the forming area during rebound are avoided. Please refer to the explanations above.

[0183] If the return stroke 23 extends to the second end 28, the piston 29 can be braked by the braking effect of the rod extension 32 and the bore 34. However, the piston 29 can also be braked by throttling the return flow of the hydraulic fluid via the second hydraulic connection 38 and the second hydraulic valve 14 by controlling or regulating the opening state of the second hydraulic valve 14 accordingly. In particular, the second hydraulic valve 14 can be increasingly closed so that the force required to displace the hydraulic fluid from the second cylinder chamber 39 increases. This creates a braking force that brakes the return stroke movement 23 of the piston 29. With suitable control orBy controlling the opening state of the second hydraulic valve 14, it can be achieved that the return stroke movement ends at a desired starting position for carrying out a subsequent working stroke 22, this starting position, in . FIG. 4 is designated i+1 and can, but does not have to, correspond to the initial position i upon initiation of the preceding working stroke 22. Depending on the forming requirements, it is possible, for example, that the two initial positions i and i+1 differ from each other. Due to the possibility of controlling or regulating the return stroke 23 via the second hydraulic valve 14, the initial position i+1 reached after the return stroke 23 can be determined from the reversal point or dead center at the second end 28 (see illustration of the FIG. 3 ) and lie at a substantially arbitrary position between the first end 27 and the second end 28.

[0184] In particular, the starting position 24 can be selected depending on the target speed to be achieved. This is possible in particular because the pressurization of the second cylinder chamber 45 can be controlled or regulated via the first hydraulic valve 13. For example, the starting position 24 can be selected or set such that the target speed v(soll) is reached with the respectively selected pressurization, for example with system pressure, on the piston stroke remaining from the starting position 24, preferably in such a way that the time period remaining from reaching the target speed v(soll) until forming is optimized, in particular minimized. For example, the starting position 24 and the pressurization in the acceleration phase can be set such that the target speed v(soll) is reached immediately before forming.

[0185] FIG. 5 shows an example curve diagram for a working cycle A with a pressurized post-flow phase via the first hydraulic valve 13 after the target speed has been reached. The time t is plotted on the abscissa and the hydraulic pressure P supplied to the first cylinder chamber 45 via the second hydraulic connection 38 and the first hydraulic valve 13 is plotted on the ordinate. At the start of the working cycle A at t 0 , the first hydraulic valve 13 is controlled or regulated into the open position so that the system pressure PS is present in the first cylinder chamber 45. This system pressure PS is maintained until the ram 3 has reached the target speed v(soll) at a time tv(soll).At time tv(soll) the forming point has not yet been reached and the opening state of the first hydraulic valve 13 is controlled or regulated in such a way that the first cylinder chamber 45 is pressurised with a post-flow pressure PN to generate a post-flow volume flow, wherein the post-flow pressure PN is less than the system pressure PS . The post-flow pressure PN is set or controlled or regulated, for example, in such a way that the piston 29 is in force equilibrium, ie that the achieved target speed v(soll) is maintained. At or shortly before the forming time tu the first hydraulic valve 13 is closed. Up to this point in time the second hydraulic valve 14 is in the process variant according to . FIG. 4 closed, and the system pressure PS is present in the first cylinder chamber 44.

[0186] For the return stroke R, or even during the forming process, the second hydraulic valve 14 is controlled or regulated to the open position, so that the second cylinder chamber 45 is connected to the return tank without pressure. The system pressure PS present in the first cylinder chamber 44 results in a restoring force after the forming process, which causes the return stroke 23.

[0187] During the return stroke 23, the second hydraulic valve 14 can initially be fully open and then controlled or regulated into the closed position over time, such that the piston 29 is positioned at a predetermined starting position for a subsequent working stroke 22. If the second hydraulic valve 14 is not controlled or regulated, the moving mass is decelerated by the rod extension 32 and bore 34 as well as by the annular space 39 at the latest after the piston 29 closes the second hydraulic connection 38.

[0188] In contrast to the FIG. 5 The curve of the hydraulic pressure P provided via the first hydraulic valve 13 can be different from the curve shown; for example, it can decrease continuously or gradually. Due to the controllable or regulatable first hydraulic valve 13, the curve of the hydraulic pressure P can be set essentially as desired, preferably in such a way that cavitation is avoided and the target speed v(target) is reliably reached. The control or regulation can be based, for example, on a predetermined pressure curve, which can be determined, for example, from test runs and / or simulation.

[0189] FIG. 6 shows a process flow of a second variant of a forming cycle for the forming machine 1.

[0190] According to the variant according to FIG. 6 the piston 29 or ram 3 is in the starting position or initial position 24 at the beginning of a working stroke 22, in FIG. 6 designated initial position i. When the working stroke 22 is triggered, for example an impact, the second cylinder chamber 45, or stroke chamber, is pressurized with hydraulic fluid via the second hydraulic connection 38. The hydraulic pressure P can correspond to the system pressure PS provided by the pump unit 16 or the pressure accumulator 17. For this purpose, the first hydraulic valve 13 is controlled or regulated into an open position by the control unit 8. In the direction of the working stroke 22, the hydraulic pressure P, in particular the system pressure PS and the weight of the mass to be moved (piston 29, rod extension 23, piston rod 26, ram 3, upper die 4) less any friction losses act. During this phase, the ram 3, or more precisely the mass to be moved, is accelerated. The acceleration serves to accelerate the ram 3 to a target speed v(target).As long as the target speed v(target) is not reached, the pressurization continues. The second hydraulic valve 14 is closed or controlled or regulated to the closed position.

[0191] If the target speed v(target) is or will be reached, the control unit 8 intervenes with control or regulation technology and controls or regulates the first hydraulic valve 13 to the closed position and the second hydraulic valve to an open position. This connects the second cylinder chamber 45, without pressure, to the reservoir 20, a suction tank, from which hydraulic fluid is drawn via the second hydraulic valve 14 and the second hydraulic connection 38. The determination of whether the target speed v(target) has been reached can be carried out analogously to the first variant.

[0192] Due to the pressureless suction, the moving mass can continue to move at the achieved target speed v(soll), so that this is essentially maintained. If the system-related suction causes the moving mass to decelerate, this reduction is generally negligible, so that the target speed v(soll) is essentially maintained and / or the desired forming speed is achieved. For this purpose, it is particularly advantageous if the acceleration phase is set so that the target speed v(soll) is only reached shortly before or immediately before forming, so that any decelerations of the moving mass (e.g. by 0.2 m / s, see above) are negligible. It is also possible to include any decelerations, in particular by increasing the target speed by the deceleration value, so that the desired forming speed is achieved at the forming point.

[0193] The first hydraulic connection 37 is, and also during the entire forming cycle, in particular during the return stroke 23, subjected to the system pressure PS, e.g. from the pressure accumulator 17.

[0194] When the workpiece 21 is reached, the forming operation takes place, which is followed by the return stroke 23 after the lower reversal point or bottom dead center of the hydraulic cylinder 2 is reached.

[0195] After the forming operation, which can be determined, for example, via speed and / or position data from the position measuring unit 10, the return stroke 23 occurs. The first hydraulic valve 13 remains in the closed position, and the second hydraulic valve 14 is controlled and / or regulated to the open position or remains in the open position. As a result, the second hydraulic connection 38 is connected without pressure to the reservoir 20, in particular a return tank, so that no system-related hydraulic pressure P is present in the second cylinder chamber 39. The system pressure PS present in the first cylinder chamber 44 accelerates the moving mass, in particular the ram 3, upwards, and causes the return stroke 23.

[0196] The braking of the ram 3 or the moving mass and the setting of a starting position i+1 or starting position for a subsequent working stroke 22 can be carried out analogously to the variant according to FIG. 4 Please refer to the above comments.

[0197] It may be advantageous in this variant that the transfer of the first hydraulic valve 13 into the closed position and the transfer of the second hydraulic valve 14 into an open position for suction overlap, in particular to avoid flow separation in the hydraulic fluid.

[0198] FIG. 7 shows an example curve diagram for a working cycle A with a pressure-free suction phase via the second hydraulic valve 14 after the target speed v(soll) has been reached. The time t is plotted on the abscissa and the hydraulic pressure P supplied to the first cylinder chamber 45 via the second hydraulic connection 38 and the first hydraulic valve 13 is plotted on the ordinate. At the start of the working cycle A at t 0 , the first hydraulic valve 13 is controlled or regulated into the open position so that the system pressure PS is present in the first cylinder chamber 45, which causes the ram 3 to accelerate. This system pressure PS is maintained until the ram 3 has reached the target speed v(soll) at a time tv(soll). At time tv(soll), the deformation point has not yet been reached, and the first hydraulic valve 13 is controlled and / or regulated into the closed position.Furthermore, the second hydraulic valve 14 is opened, so that the second cylinder chamber 45 is connected, without pressure, to the reservoir 20, in particular a suction tank. The continued movement of the piston 29 creates a pressureless suction volume flow via the second hydraulic connection 38 and the second hydraulic valve 14, allowing the moving mass to continue moving essentially at the desired speed reached. The system pressure PS is present throughout the first cylinder chamber 44.

[0199] The FIG. 7 The dashed line shown at tv(setpoint) corresponds to a variant in which the opening state of the first hydraulic valve 13 and that of the second hydraulic valve 14 overlap when reversing or regulating the hydraulic valves at tv(setpoint). Such an overlap, as already mentioned, is advantageous for preventing flow separation.

[0200] The return stroke is carried out as in the variant after FIG. 5 , where the first hydraulic valve 13 is already closed and the second hydraulic valve 14 is already open. The system pressure P s in the first cylinder chamber 44 counteracts the weight of the moving mass and thus causes the return stroke 23. For the return stroke 23, please refer to the explanations to FIG. 5 which apply analogously here.

[0201] By minimizing the time between reaching the target speed v(target) and the forming process, the post-flow phase or post-suction phase is shortened or minimized. Since the transition from the acceleration phase to reaching the target speed to the post-flow phase or post-suction phase, as well as the post-flow or post-suction phases, are particularly susceptible to cavitation, the probability of cavitation can be at least reduced by minimizing the post-flow phases or post-suction phases. With suitable control or regulation, cavitation can even be avoided entirely, or at least largely avoided.

[0202] To avoid cavitations, it is possible for the control unit 8 to detect the hydraulic pressure P in the hydraulic circuit 7 via the pressure sensors 11 and 12 and to control or regulate the hydraulic valves 13, 14 in such a way that the hydraulic pressure P prevailing in the hydraulic circuit, in particular in the second cylinder chamber 45, is always above the cavitation pressure of the hydraulic fluid.

[0203] The acceleration phase to reach the target speed v(target) and the subsequent post-flow phase or post-suction phase can be set up so that the hydraulic pressure in the hydraulic circuit is always above the cavitation pressure of the hydraulic fluid. For this purpose, the control or regulation of the volume flows makes it possible to set these, for example on the basis of test runs and / or simulation, so that the working stroke and / or return stroke can be carried out without cavitation. Parameters for setting the working stroke and / or return stroke include, in particular, the level of the hydraulic pressure during acceleration, the temporal progression of the hydraulic pressure P for acceleration, the duration of the acceleration phase until the target speed v(target) is reached, the post-flow volume flow and the post-suction volume flow. These parameters can be controlled or regulated via the first and second hydraulic valves 13, 14.

[0204] Overall, it can be seen that the problem underlying the invention is solved.

[0205] The underlying invention also has the following advantages and advantageous effects: Only two hydraulic connections are required on the hydraulic cylinder to carry out a work cycle, i.e. the lower first hydraulic connection and the upper second hydraulic connection. The upper or second hydraulic connection is used for both the working stroke and the return stroke. The lower or first hydraulic connection can be pressurised with system pressure PS throughout, so that no control or regulation is required in this respect. The rod extension, which can be part of the piston rod if this passes through the piston, for example, and the bore at the first end, in particular at the upper end of the cylinder tube above the piston, can be used to brake the moving mass, in particular as an emergency brake, e.g. in the event of a failure of the control or regulating electronics. The moving mass can advantageously be braked during the return stroke via the rod extension and the bore, or alternatively by controlling or regulating the second hydraulic valve, i.e.i.e. the return flow into the return tank. No additional brake throttles are required, as is the case with conventional forming machines or forging hammers, through which the hydraulic fluid remaining in the upper cylinder chamber must be discharged to achieve a braking effect. The proposed forming machine or hydraulic control system enables flexibly adjustable starting positions for the working stroke and is therefore not limited to just one top dead center. The proposed forming machine or hydraulic control system enables correct approach to the variable top dead center, i.e. the starting position for the next impact, if, for example, the position measuring unit or a position measuring system is used for position monitoring. The hydraulic valves can also be controlled based on speed data orControl or regulate pressure data so that the acceleration phase can be optimized and / or controlled or regulated according to specified position, speed and / or pressure curves or profiles. The proposed forming machine or hydraulic control system does not require a separate suction valve like conventional forming machines or forging hammers. The proposed forming machine or hydraulic control system allows a certain degree of flexibility with regard to the control or regulation of the hydraulic valves for the working stroke phase after the target speed has been reached. In particular, on the one hand, operation is possible in which, after the target speed has been reached, hydraulic fluid is sucked in without pressure via the second hydraulic valve, and on the other hand, operation in which, after the target speed has been reached, hydraulic fluid flows in based on pressure via the first hydraulic valve.Depending on the requirements for the working stroke, one or the other variant can be selected, which is particularly advantageous with regard to different forming operations and / or avoiding flow stalls and / or cavitations. It is possible to optimize the acceleration phase and / or the post-suction phase or post-flow phase, particularly with regard to their timing and duration. For optimization, the acceleration phase can be variably controlled or regulated via the first hydraulic valve and the subsequent post-suction phase or post-flow phase can be variably controlled or regulated via the second or first hydraulic valve. In particular, as already mentioned, no separate post-suction valve is required for the post-suction phase. The first hydraulic valve can be used as a check valve, and the second hydraulic valve, in the variant with post-suction, can be used both as a post-suction valve and as a riser valve for the return stroke.The forming machine or hydraulic control system in particular enables a work cycle in which the work cycle is initiated by opening the first hydraulic valve. Once the desired target speed has been reached, the first hydraulic valve can be closed and the second hydraulic valve opened, whereby an overlap phase can be integrated between the opening of the second hydraulic valve and the closing of the first hydraulic valve due to the control or regulation, so that the flow of hydraulic fluid does not interrupt. The re-suction can take place via the second hydraulic valve up to the forming stage, with a subsequent return stroke via the second hydraulic valve. The different variants regarding re-suction, e.g. from a re-suction tank or container, and the re-flow, e.g. from the pressure accumulator, enable operating modes in which hydraulic oil comes out of the re-suction tank without pressure (re-suction phase) oris sucked from it, and in which hydraulic oil is supplied in a pressure-based, controlled or regulated manner via the first hydraulic valve. The hydraulic oil for the follow-up flow can be supplied based on the hydraulic pressure provided by the pressure accumulator.

[0206] Overall, the proposed forming machine, the proposed hydraulic control system and the proposed method enable a comparatively simple design with flexible control or regulation of the working cycle, whereby safe operation can be provided by the rod extension and the bore. Bezugszeichenliste

[0207] 1 Forming machine 2 Hydraulic cylinder 3 Bear 4 Upper die 5 Shabot 6 Lower die 7 Hydraulic circuit 8 Control unit 9 Control / data line 10 Position measuring unit 11, 12 First and second pressure transducers 13, 14 First and second hydraulic valves 15 Hydraulic line 16 Pump unit 17 Pressure accumulator 18, 19 Safety valve 20 Reservoir 21 Workpiece 22 Working stroke 23 Return stroke 24 Initial position 25 Cylinder tube 26 Longitudinal axis 27 First end 28 Second end 29 Piston 30 Piston rod 31 Side facing away from the piston rod 32 Rod extension 33 Outer diameter 34 Bore 35 Inner diameter 36 Opening 37 First hydraulic connection 38 Second hydraulic connection 39 Annular space 40 Throttle 41 Bottom 42 Shoulder 43 Channel 44 First cylinder chamber 45 Second cylinder chamber 46 Distal end AWorking cycle v(target)Target speed tTime PS System pressure PN Afterflow pressure

Claims

1. A hydraulic forming machine (1), in particular a percussive forming machine, preferably a forging hammer, for forming a workpiece (21), comprising - a hydraulic cylinder (2) with a piston (29) guided in a cylinder tube (25), which divides the cylinder tube (25) into a first cylinder chamber (44) through which a piston rod (30) coupled to a ram (3) passes, and into a second cylinder chamber (45), wherein the first cylinder chamber (44) has a first hydraulic connection (37) and the second cylinder chamber has a second hydraulic connection (38) - a hydraulic circuit (7) with a control unit (6) for controlling and / or regulating the operation of the hydraulic cylinder (2), wherein the hydraulic circuit (7) comprises a first hydraulic valve (13) which is control-technically coupled to the control unit (6), which is preferably designed as a proportional valve, and is connected to the second cylinder chamber (45) via the second hydraulic connection (38), characterized in that- the control unit (8) is designed to regulate and / or control an opening width of the first hydraulic valve (13) when carrying out a working stroke intended for forming a workpiece in such a way that ▪ in a first phase the first hydraulic valve (13) is opened and the ram (3) is accelerated to a desired speed in the first phase, ▪ in a second phase following the first phase the opening width of the first hydraulic valve (13) is reduced to a post-flow opening width, and ▪ the first hydraulic valve (13) is closed during a return stroke running opposite to the working stroke.

2. Hydraulic forming machine (1) according to claim 1, wherein the hydraulic circuit (7) further comprises a second hydraulic valve (14) which is connected to the second hydraulic connection (38), and wherein the control unit (8) is configured to control an opening width of the second hydraulic valve (14), which is preferably designed as a proportional valve, such that, in the case of a return stroke which is opposite to the working stroke, a starting position of the ram (3) for a subsequent working stroke can be variably adjusted.

3. Hydraulic forming machine (1) according to one of the preceding claims, further comprising a measuring unit for determining the position of the ram (3), wherein the control unit (8) is configured to determine one or more operating parameters, such as a starting position and / or a target speed and / or an impact energy of the ram (3) for a subsequent working stroke on the basis of a forming position determined by the measuring unit for a previous working stroke, wherein, preferably, an initial working stroke is configured as a directional impact carried out with minimal impact energy.

4. Hydraulic forming machine (1) according to one of the preceding claims, wherein the control unit (8) is configured to control the opening width of the first hydraulic valve (13) on the basis of a variably predeterminable and / or ascertainable starting position and / or a variable forming position, in particular a variably predeterminable and / or ascertainable forming position, in particular in such a way that the working stroke, in particular a forming impact, can be carried out with a respectively suitable, preferably predetermined, in particular respectively maximum available, impact energy.

5. Hydraulic forming machine (1) according to one of the preceding claims, wherein the control unit (8) is configured to variably set a starting position for executing a working stroke, in particular depending on at least one operating parameter of the hydraulic cylinder (2) with respect to one or more preceding working strokes, wherein the operating parameter is preferably an operating parameter detected by one or more sensor units.

6. Hydraulic forming machine (1) according to one of the preceding claims, wherein the control unit (8) is configured to determine a starting position for a working stroke at a predetermined forming energy and to set it by controlling and / or regulating the second hydraulic valve (14) during a return stroke, wherein the control unit (8) is preferably configured to variably set the starting position on the basis of a free path length of the ram (3) between the starting position and the forming position of a previous working stroke.

7. Hydraulic forming machine (1), in particular according to one of claims 1 to 6, preferably a forging hammer, designed for workpiece forming, comprising a hydraulic circuit (7) with a unit for generating a predetermined system pressure (P S) for the hydraulic fluid and at least one reservoir (20) for hydraulic fluid and comprising a hydraulic cylinder (2) with a cylinder tube (25) with a piston (29) which can be moved therein between a first and a second end (27, 28), which is coupled to a piston rod (30) which extends in the direction of the first end (27) and is coupled or can be coupled to a ram (3), wherein the piston (29) divides the cylinder tube into a first and a second cylinder chamber and has, on the side (31) facing away from the piston rod (30), a rod extension (32) which extends towards the second end (28), the outer diameter (33) of which is smaller than that of the piston (29), wherein the hydraulic cylinder (2) has, at the second end (28), a bore (34) which is coaxial with the rod extension (32) and open towards the piston (29), the inner diameter (35) of which bore substantially corresponds to the outer diameter (33) of the rod process (32),so that the rod extension (32) can dip into the bore (34), and wherein the hydraulic cylinder (2) or the cylinder tube (25) comprises a first hydraulic connection (37) in the region of the first end (27) and a second hydraulic connection (38) in the region of the second end (28), which is arranged such that the piston (29) closes the second hydraulic connection (38) when moving towards the second end (28) when the rod extension (32) reaches the bore (34).

8. Hydraulic forming machine (1) according to one of the preceding claims, wherein - the first hydraulic connection (37) is connected or connectable to the hydraulic circuit (7), so that the first cylinder chamber (44) of the hydraulic cylinder (2) connected to the first hydraulic connection (37) and arranged downstream thereof is supplied with system pressure (P S), in particular a pressure accumulator, and / or - wherein the hydraulic circuit (7) comprises a valve unit (13, 14) connected or connectable to the second hydraulic connection (38), wherein the hydraulic circuit (7) and the valve unit (13, 14) are designed such that the second cylinder chamber (45) of the hydraulic cylinder (2), which is connected to the second hydraulic connection (38), can optionally be at least temporarily pressurised with hydraulic pressure (P) via the valve unit (13, 14) or can be connected to the reservoir (20) at least temporarily without pressure when a working stroke (22) is carried out.

9. Hydraulic forming machine (1) according to one of the preceding claims, wherein the first hydraulic valve (13) is designed to assume a closed position at least temporarily during the working stroke (22) and / or at least temporarily during a return stroke (23), preferably substantially during the entire return stroke (23), and wherein the second hydraulic valve (14) is designed to connect the second cylinder chamber (45) to the reservoir (20) in a pressureless manner when the first hydraulic valve (13) is in the closed position.

10. Hydraulic forming machine (1) at least according to claim 7, wherein the control unit (8) is configured, in particular programmed: a) during the working stroke, to control or regulate the first hydraulic valve (13) into an open position, in which the second cylinder chamber (45) is or is pressurized with hydraulic pressure (P) via the first hydraulic valve (13) until a predetermined target speed (v(target)) of the ram (3) is reached, and simultaneously to control or regulate the second hydraulic valve (14) into a closed position, b) during the working stroke (22) and after or upon reaching the target speed (v(target)) b1) to control or regulate the first hydraulic valve (13) into a closed position, and by controlling or regulating the second hydraulic valve (14) into an open position, to connect the second cylinder chamber (45) via the second hydraulic valve (14) and / or via a suction valve to the reservoir (20), in particular a suction tank,to connect and to generate a suction volume flow into the second cylinder chamber (45), with which the target speed (v(soll)) is essentially maintained and / or a predetermined forming speed is reached at the forming time (tu); or b2) by controlling or regulating the open position of the first hydraulic valve (13) via the first hydraulic valve (13) and / or via a suction valve, to generate a suction volume flow into the second cylinder chamber (45), with which the target speed (v(soll)) is essentially maintained and / or with which a predetermined forming speed is reached at the forming time (tu),wherein the second hydraulic valve (14) is preferably controlled or regulated into the closed position; c) during a return stroke (23) following the working stroke (22), the second hydraulic valve (14) connected to the second hydraulic connection (38) is controlled or regulated into the open position and the first hydraulic valve (13) connected to the second hydraulic connection (38) is controlled or regulated into the closed position; and, optionally, d) at least at the beginning of a further working stroke (22) following the return stroke (23), the first and second hydraulic valves (13, 14) are reversed or regulated such that the first hydraulic valve (13) is in an open position and the second hydraulic valve (14) is in the closed position, wherein e) during the working stroke (22) and the return stroke (23), the first cylinder chamber (44) is supplied with the system pressure (P, S ) is applied.

11. Hydraulic forming machine (1) according to one of the preceding claims, wherein - the forming machine further comprises a travel measuring unit (10) for detecting the position and / or speed of the piston (29), the piston rod (30) and / or the ram (3) and / or - wherein the hydraulic circuit (7) further comprises at least one, preferably two pressure sensors (11, 12), wherein a first pressure sensor (11) is configured to detect the hydraulic pressure (P) in the first cylinder chamber (44) and a second pressure sensor (12) is configured to detect the hydraulic pressure (P) in the second cylinder chamber (45).

12. Hydraulic forming machine (1) at least according to claim 7, wherein - the volume of the bore (34) is connected to the volume of the second cylinder chamber (45) via a throttle (40), so that the bore (34) is connected to the second cylinder chamber (45) via the throttle (40), in particular when the second hydraulic connection (38) is closed by the piston (29) and / or - a diameter of the bore is larger than a diameter of the rod extension, such that an annular gap formed by a diameter difference between the bore and the rod extension acts as a throttle for braking the piston.

13. Hydraulic control unit (8) for operating, in particular for controlling or regulating, a hydraulic forming machine (1) according to one of claims 1 to 12, comprising a processor and / or control electronics or regulating electronics which is or are set up to control or regulating the opening width of the first hydraulic valve (13) when carrying out a working stroke intended for forming a workpiece (21), in particular in such a way that ▪ in a first phase the first hydraulic valve (13) is opened and the ram (3) is accelerated to a desired speed in the first phase, ▪ in a second phase following the first phase the opening width of the first hydraulic valve (13) is reduced to a predetermined afterflow opening width, and ▪ the first hydraulic valve (13) is closed during a return stroke running opposite to the working stroke.

14. Hydraulic control unit (8) according to claim 13, wherein - the hydraulic circuit further comprises a second hydraulic valve (14) connected to the second hydraulic connection (38), and wherein the hydraulic control unit (8) is configured to control an opening width of the second hydraulic valve (14), which is preferably designed as a proportional valve, such that, in the case of a return stroke occurring opposite to the working stroke, a starting position of the ram (3) for a subsequent working stroke can be variably adjusted and / or - the forming machine (1) further comprises a measuring unit for determining the position of the ram (3), wherein the hydraulic control unit is configured to determine one or more operating parameters, such as a starting position and / or a target speed and / or an impact energy of the ram (3), based on a forming position determined by the measuring unit for a previous working stroke,for a subsequent working stroke, wherein, preferably, an initial working stroke is configured as a directional blow executed with minimal impact energy, and / or - the hydraulic control unit (8) is configured to control the opening width of the first hydraulic valve (13) on the basis of a variably predeterminable and / or determinable starting position and a variable forming position, in particular a variably predeterminable and / or determinable forming position, in particular such that the working stroke, in particular a forming blow, can be executed with a respectively suitable, preferably predetermined, in particular respectively maximum available, impact energy and / or - the hydraulic control unit (8) is configured to variably set a starting position for executing a working stroke, in particular depending on at least one operating parameter of the hydraulic cylinder (2) with respect to one or more preceding working strokes,wherein the operating parameter is preferably an operating parameter detected by one or more sensor units, and / or - the hydraulic control unit is configured to determine a starting position for a working stroke at a predetermined forming energy and to set it by controlling and / or regulating the second hydraulic valve (14) during a return stroke, wherein the hydraulic control unit is preferably configured to variably set the starting position on the basis of a free path length of the ram (3) between the starting position and the forming position of a previous working stroke.

15. Hydraulic control unit (8) according to one of claims 13 or 14, wherein the hydraulic control unit (8) is further configured to determine a position and / or speed of the piston (29), the piston rod (30) and / or the ram (3) via a path measuring unit (10), and to control or regulate the first and / or second hydraulic valve (13, 14) as a function of the determined position and / or speed, preferably according to a predetermined or predeterminable position and / or speed profile.

16. Hydraulic control unit (8) according to one of claims 13 to 15, wherein the hydraulic control unit (8) is further configured to determine the hydraulic pressure (P) prevailing in the first and / or second cylinder chamber (44, 45) by means of a first or second pressure sensor (11, 12), and to control and / or regulate the first and / or second hydraulic valve (13, 14) as a function of the determined hydraulic pressure (P), in particular according to a predetermined pressure curve and / or in such a way that the hydraulic pressure (P) in the hydraulic circuit (7), in particular in the second cylinder chamber (45), is substantially above the cavitation pressure of the hydraulic fluid.

17. Method for operating, in particular for controlling or regulating, a hydraulic cylinder (2) of a hydraulic forming machine (1), in particular according to one of claims 1 to 12, - controlling and / or regulating the opening width of the first hydraulic valve (13) by the control unit (8) when carrying out a working stroke intended for forming a workpiece (21) in such a way that ▪ in a first phase the first hydraulic valve (13) is opened and the ram (3) is accelerated to a desired speed in the first phase, ▪ in a second phase following the first phase the opening width of the first hydraulic valve (13) is reduced to a predetermined afterflow opening width, and ▪ the first hydraulic valve (13) is closed during a return stroke running opposite to the working stroke.

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