Forming machine and method and computer program product for monitoring a forming machine

Abstract

Forming machine, in particular injection molding machine, with a hydraulic drive unit comprising - a piston (4) arranged in a cylinder (3) so as to be linearly displaceable and a pressure chamber (5) delimited in the cylinder (3) by the piston (4), - at least one pressure sensor (6) which is designed to detect a signal characteristic of the pressure in the pressure chamber (5), and - a computing unit (7) which is signal-connected to the at least one pressure sensor (6) for receiving the characteristic signal, wherein the computing unit (7) is designed to determine a kinematic parameter, preferably a position and / or a change in position, of the piston (4) on the basis of the signal characteristic of the pressure in the pressure chamber (5), characterized in that the pressure chamber (5) cooperates with a constant pressure medium mass at least during the measurement of the characteristic signal.

Description

[0001] The present invention relates to a forming machine with a hydraulic drive unit having the features of the preamble of claim 1, a method for monitoring a forming machine with a hydraulic drive unit and a computer program product for monitoring a forming machine with a hydraulic drive unit.

[0002] Molding machines can include injection molding machines, transfer presses, presses, and the like. Molding machines in which the plasticized molding compound is fed into an open mold are also quite conceivable.

[0003] A wide variety of forming machines and / or methods and systems for monitoring a hydraulic drive unit are known from the prior art. For example, the paper "Research and experimental analysis of hydraulic cylinder position control mechanism based on pressure detection" by ZHOU, Rulin, et al. (Machines, 2021, Vol. 10, No. 1) discloses a forming machine with a piston displaceably arranged in a cylinder, a pressure sensor, and a computing unit connected to the pressure sensor. The computing unit is designed to use the input and output pressures obtained by the pressure sensor to calculate the flow required for the action of an individual hydraulic cylinder and the resulting stroke of the hydraulic cylinder.

[0004] Utility model DE 20 2021 103 086 U1 further describes the use of a pressure sensor in a fluid cylinder in which a piston can be moved linearly via a piston rod. The sensor is used to measure the fluid pressure in the cylinder chamber to control the dosage of the fluid.

[0005] The US document US 2016 / 0363441 A1 also describes a method for determining the position of a displacement component, in particular of a linearly movable cylinder piston, relative to a reference component, in particular a cylinder, using a correspondingly designed sensor.

[0006] The following will outline the state of the art in detail using an injection molding machine as an example. The same applies to forming machines in general.

[0007] Generic hydraulic drive units for an injection molding machine include - a piston arranged in a cylinder so as to be linearly displaceable and a pressure chamber in the cylinder delimited by the piston, - at least one pressure sensor which is designed to detect a signal characteristic of the pressure in the chamber and - a computing unit which is signal-connected to the at least one sensor for receiving the characteristic signal.

[0008] In injection molding machines, drive movements are often implemented by hydraulic drive units, which are usually realized via hydraulic cylinders.

[0009] For this purpose, it is almost always necessary to detect or know in some way the position of the injection molding machine part moved by the hydraulic drive unit.

[0010] For simple applications, it is usually sufficient to detect the end position of a movement axis via limit switches, whereby a limit switch detects exactly one position (usually the end position) of the injection molding machine part or the drive unit.

[0011] However, this only allows two functions to be implemented and monitored: on the one hand, it can be recorded whether the injection molding machine part has reached a certain position and, on the other hand, whether the injection molding machine part remains in this position during ongoing monitoring.

[0012] Such limit switches usually have to be mounted externally and are usually actuated by the moving part of the injection molding machine.

[0013] However, for many movements it is necessary to detect and monitor the constant and accurate knowledge of the absolute position, whereby various types of displacement sensors are usually known due to the state of the art.

[0014] The following feedback is provided to an injection molding machine control system and / or the following options are created for the injection molding machine using appropriate position sensors: - reaching a desired target position, - Monitoring of specific positions, - Speed ​​regulation and / or control depending on a position, and - Force regulation and / or control depending on the position.

[0015] Typically, clean acceleration and / or deceleration profiles as well as precise positions can be realized in such systems.

[0016] In most cases, linear position sensors require sensor elements to be arranged parallel to the moving injection molding machine part (or the drive unit) and over the entire length of movement in order to be able to detect the position.

[0017] However, corresponding position measuring systems are complex to install and involve high costs due to the high manufacturing effort and material expenditure.

[0018] A further disadvantage is that corresponding position measuring systems require space for corresponding hydraulic drive units and are therefore often difficult to access in even small installation spaces, making them difficult to assemble, disassemble and maintain.

[0019] In addition, these position measuring systems, which are arranged externally on the hydraulic drive units, are exposed to environmental influences, which means that the very precise measuring systems in particular are at an increased risk of damage.

[0020] The object of the present invention is to provide a hydraulic drive unit which enables simpler detection of a kinematic parameter of the hydraulic drive unit and / or has a smaller space requirement and / or less maintenance, installation or disassembly work and / or is easier to manufacture and / or enables kinematic parameter detection of the hydraulic drive unit by means of fewer components.

[0021] This object is achieved according to the invention by a forming machine with a hydraulic drive unit having the features of claim 1, a method for monitoring a forming machine with a hydraulic drive unit having the features of claim 15 and a computer program product for monitoring a forming machine with a hydraulic drive unit having the features of claim 16.

[0022] According to the invention, a shaping machine, in particular an injection molding machine, with a hydraulic drive unit comprises the following: - a piston arranged in a cylinder so as to be linearly displaceable and a piston chamber in the cylinder delimited by the piston, - at least one pressure sensor which is designed to detect a signal characteristic of the pressure in the pressure chamber and - a computing unit which is signal-connected to the at least one sensor for receiving the characteristic signal, wherein the computing unit is designed to determine a kinematic parameter, preferably a position and / or a change in position, of the piston on the basis of the signal characteristic of the pressure in the pressure chamber.

[0023] When the piston changes position, the volume of the pressure chamber formed by the piston and cylinder changes, resulting in a pressure change in the pressure medium mass, fluid, and / or hydraulic oil present in the pressure chamber. Based on this pressure change and the known behavior of the pressure medium mass, fluid, and / or hydraulic oil present in the pressure chamber (e.g., compressibility), the change in volume can be calculated from the pressure variation.

[0024] Since the piston and the cylinder have known geometric dimensions, a linear displacement of the piston can be calculated taking into account the change in volume, whereby the computing unit can determine the kinematic parameter, preferably a position and / or a change in position, of the piston.

[0025] It is therefore no longer necessary to provide position measuring systems, limit switches or similar sensors to record a kinematic parameter of the piston, since the kinematic parameter can be calculated simply by arranging a pressure sensor on or in the pressure chamber.

[0026] This has the enormous advantage that significantly fewer parts, components or modules of the sensor system are required to determine the kinematic parameter of the piston, which not only reduces costs but also the effort required for assembly, disassembly and / or maintenance.

[0027] Furthermore, an advantage is created in that the installation space can be significantly reduced, since no separate sensors need to be arranged on the hydraulic drive unit.

[0028] A pressure sensor can be integrated and / or screwed into the hydraulic drive unit, which also protects the pressure sensor from environmental influences and prevents it from being exposed to external damage.

[0029] The pressure in the pressure chamber is therefore preferably measured directly.

[0030] A hydraulic medium may be present in the pressure chamber, the pressure of which is measured by the pressure sensor. In other embodiments, a gas or other compressible fluid may be present in the pressure chamber, the pressure of which is detected by the pressure sensor (for example, in embodiments where the pressure chamber itself is an integrated hydraulic accumulator).

[0031] A device according to the invention and a method according to the invention can be used and subsequently installed by using them in already known embodiments of the prior art, as described, for example, in the introduction to the description.

[0032] Molding machines can include injection molding machines, transfer presses, presses, and the like. Molding machines in which the plasticized molding compound is fed into an open mold are also quite conceivable.

[0033] The computing unit can be physically part of the hydraulic drive unit or connected to the hydraulic drive unit via a remote data transmission connection.

[0034] In the latter case, the computing unit could be implemented by a computer server or a set of computers (distributed computing).

[0035] The same applies to a control or regulating device of a forming machine.

[0036] Advantageous embodiments are defined by the dependent claims.

[0037] The pressure chamber cooperates with a constant pressure medium mass, preferably hydraulic fluid mass and / or a gas, at least during the measurement of the characteristic signal.

[0038] It can be provided that a hydraulic fluid mass, preferably a hydraulic oil, or also a gas mass (for example nitrogen, air or other gases) is used as the pressure medium mass.

[0039] Preferably, it can be provided that at least during the measurement of the characteristic signal, the pressure chamber in the cylinder is closed and preferably encloses a constant pressure medium mass.

[0040] It can be provided that during the measurement of the characteristic signal the pressure chamber is connected to a hydraulic accumulator via a connecting line, preferably wherein a constant pressure medium mass is enclosed by the pressure chamber, the connecting line and the hydraulic accumulator.

[0041] Thus, it can preferably be provided that during the measurement of the characteristic signal, a pressure application or pressure relief of a precisely defined pressure medium mass is carried out, so that the volume variation of the pressure medium mass and thus a kinematic parameter of the piston can be determined in a simple manner via the pressure variation during the measurement by means of the pressure sensor.

[0042] It could of course also be provided that the pressure chamber cooperates with a non-constant pressure medium mass, whereby the kinematic parameter can still be determined by precise definition of the system, but the variations of the system can be determined by flow conditions for the pressure medium mass (for example, pressure variation taking into account passage cross sections and flow velocities) via complex processes.

[0043] Designs in which reference pressures for defined kinematic parameters are first determined and stored, whereby the computing unit uses the corresponding stored kinematic parameter when a pressure is measured, are also quite conceivable.

[0044] However, it can be particularly preferably provided that the pressure chamber is connected to a hydraulic accumulator, for example a bladder accumulator, wherein the pressure chamber and the hydraulic accumulator (naturally together with the connecting line thereto) inject a constant pressure medium mass, wherein in the event of a pressure variation of the pressure medium mass, taking into account a compression behavior of the pressure medium mass, a volume change and thus a kinematic parameter of the piston can be deduced in a simple manner.

[0045] By providing a hydraulic accumulator, in particular a bladder accumulator, the compression behavior of the system can be influenced, whereby, for example, when using hydraulic fluid, the limited compression capacity of the fluid can be expanded to the extent that larger volume changes in the pressure chamber are permitted by escaping into the hydraulic accumulator, so that the method according to the invention and / or the device according to the invention can also be used, for example, in hydraulic cylinders with high freedom of movement - drive movements.

[0046] It can be provided that the computing unit is designed to determine the kinematic parameter by means of a relationship with the pressure stored in the computing unit, preferably taking into account a stored compression behavior of the drive unit.

[0047] The compression behavior of the drive unit can affect the compressibility of the print media mass, alternatively or additionally take into account the geometric dimensions of the volumes in which the print media mass is enclosed.

[0048] If a hydraulic accumulator is provided, the compression behavior, the compression ratio of the system between two measurements and / or the back pressure of the hydraulic accumulator can also be taken into account in the compression behavior of the drive unit.

[0049] It can be provided that the drive unit has a hydraulic accumulator, preferably a bladder accumulator and / or diaphragm accumulator, particularly preferably with a variable compression ratio and / or variable back pressure.

[0050] It can be provided that the hydraulic accumulator is designed as a mechanical, preferably spring-actuated, and / or fluid-actuated hydraulic accumulator.

[0051] A fluid-actuated hydraulic accumulator (for example a bladder accumulator) can preferably have a gas (particularly preferably nitrogen, air or other gases) as the actuating medium.

[0052] Preferably, it can be provided that the piston divides the cylinder into the (first) pressure chamber and a second pressure chamber.

[0053] It can be provided that the drive unit has a pressure source, in particular at least one pump, preferably which pressure source is connected or connectable to the second pressure chamber in order to apply pressure to the second pressure chamber.

[0054] It can be provided that the pressure source is connected to the second pressure chamber via a valve, preferably which valve can be controlled or regulated by a control or regulating device.

[0055] It can be provided that the computing unit is signal-connected to a control or regulating device of the pressure source and / or is designed as an integral component of the control or regulating device, wherein the kinematic parameter can be used as an actual value by the control or regulating device for controlling or regulating the pressure source.

[0056] It can be provided that the cylinder with the piston arranged therein is designed as a double-acting piston-cylinder unit.

[0057] Preferably, it can be provided that the pressure chamber is designed as a rod-side chamber of a piston-cylinder unit.

[0058] It can be provided that the at least one drive unit is designed to drive a locking nut relative to a bar and / or as a pressure cushion for building up the closing force.

[0059] Furthermore, protection is sought for a method for monitoring a forming machine with a hydraulic drive unit, preferably a hydraulic drive unit according to the invention, which hydraulic drive unit comprises a piston arranged to be linearly displaceable in a cylinder and a pressure chamber delimited by the piston in the cylinder, wherein a pressure in the pressure chamber is measured and a kinematic parameter, in particular a position and / or a position change, of the piston is determined via the pressure, preferably a determined pressure change.

[0060] Protection is also sought for a computer program product for monitoring a forming machine with a hydraulic drive unit, preferably a hydraulic drive unit according to the invention, comprising instructions which cause a computer to carry out the following steps when executing the program: - Receiving a characteristic signal for a pressure in a pressure chamber and - Determining a kinematic parameter, preferably a position and / or a change in position, of a piston of the pressure chamber on the basis of the signal characteristic of the pressure in the pressure chamber.

[0061] Further advantages and details of the invention emerge from the figures and the associated description. Fig. 1 a first embodiment of a drive unit, Fig. 2 a second embodiment of a drive unit, Fig. 3 a third embodiment of a drive unit, Fig. 4 a fourth embodiment of a drive unit, Fig. 5 a fifth embodiment of a drive unit Fig. 6 an embodiment of a forming machine and Fig. 7 an embodiment of a locking unit.

[0062] The Fig. The embodiment of a hydraulic drive unit 1 shown in Figure 1 has a piston 4 arranged to be linearly displaceable in a cylinder 3, wherein the piston 4 divides the cylinder 3 into a pressure chamber 5 and a second pressure chamber 10.

[0063] Such a cylinder (3) - piston (4) arrangement is also called a double-acting piston-cylinder unit.

[0064] In order to supply the pressure chambers 5, 10 with a pressure medium mass, preferably a hydraulic fluid, these are connected to the valve 13 via the connecting lines.

[0065] The valve 13 is designed, for example, as a 4 / 3-way valve, which can be switched between the individual valve positions via a control or regulating device 14.

[0066] The valve 13 is designed to connect the pressure chambers 5, 10 selectively to the pressure source 11 or the tank 18 in order to selectively apply pressure to the pressure chamber 5 or the pressure chamber 10 and / or to discharge a pressure medium mass into the tank 18.

[0067] The pressure source 11 of this embodiment is formed by a pump 12 which is driven by a motor drive unit, wherein the drive unit can be controlled or regulated by the control or regulating device 14.

[0068] The control or regulating device 14 further comprises a computing unit 7, which is designed as an integral component of the control or regulating device 14 of the hydraulic drive unit 1.

[0069] The signal-conducting connections of the control or regulating device 14 with the individual components of the hydraulic drive unit 1 are in Fig. 1 shown as dashed lines.

[0070] The computing unit 7 is connected to the pressure sensor 6 in a signal-conducting manner (shown by the dashed line), wherein a characteristic signal for a pressure present in the pressure chamber 5 can be detected by the pressure sensor 6 and can be fed to the computing unit 7 via the signal-conducting connection.

[0071] Furthermore, a valve 17 is provided, which is designed as a shut-off valve and via which the pressure chamber 5 can be shut off.

[0072] In order to now carry out a measurement of a kinematic parameter of the piston 4, the pressure chamber 5 can be shut off via the valve 17 during the movement of the piston 4 and pressure medium mass can be supplied to the pressure chamber 10 via the valve 13 with the aid of the pressure source 11, whereby a higher pressure can be built up in the pressure chamber 10 than in the pressure chamber 5.

[0073] Alternatively or additionally, the piston 4 can of course also be moved via a machine part which is connected to the piston 4 via the piston rod.

[0074] As a result of the increasing pressure in the pressure chamber 10, the piston 4 is moved in the direction of the pressure chamber 5, whereby the closed pressure chamber 5 - more precisely: the constant pressure medium mass which is present in the pressure chamber 5 - is compressed and the pressure in the pressure chamber 5 increases.

[0075] This pressure increase in the pressure chamber 5 can be fed to the computing unit 7 as a characteristic signal via the pressure sensor 6, whereby the computing unit 7 can determine a kinematic parameter, preferably a position and / or a change in position, of the piston 4 on the basis of the signal characteristic of the pressure in the pressure chamber 5.

[0076] In the same way, a kinematic parameter for the piston 4 could of course also be determined in the event of a pressure drop.

[0077] This determination and / or calculation of the kinematic parameter of the piston 4 can be carried out by calculating the stroke volume, whereby the compression volume ΔV is determined by the following formula: K can be calculated via the pressure variation Δp and the initial volume V0 of the pressure chamber 5. ΔVK=1K⋅VO⋅Δp K Compression modulus of the printing media mass V0 output volume in the pressure chamber ΔV K Compression volume of the pressure chamber Δp pressure variation in the pressure chamber

[0078] The compression modulus K, which is also required in the formula, is a dependent quantity of the pressure medium mass and can be determined from tests and / or data sheets of the pressure medium mass (e.g. the hydraulic fluid).

[0079] Then the compression volume ΔV K and the known geometrical dimensions of the piston 4 and / or the cylinder 3 and / or the pressure chamber 5, a change in position of the piston 4 can be calculated, whereby an instantaneous position of the piston 4 can be determined taking into account the initial position of the piston 4.

[0080] It can be provided that the computing unit 7 transfers the determined kinematic parameter of the piston 4 to the control or regulating device 14, wherein the control or regulating device 14 uses the kinematic parameter of the piston 4 as the actual variable of the piston 4 in the control or regulating of the valve 13, the valve 17 and / or the pressure source 11, so that the piston 4 can be adjusted to a desired position.

[0081] Of course, this procedure can also be applied to a speed and / or acceleration of piston 4.

[0082] Alternatively or additionally, it can also be provided that the determination of the kinematic parameter of the piston 4 is carried out via a calibration process, wherein the position of the piston 4 is measured at different pressures in the pressure chamber 5 and, for example, a reference curve for the kinematic parameter of the piston 4 is created as a function of a pressure in the pressure chamber 5 (and an initial position of the piston 4).

[0083] Subsequently, as previously explained, a pressure can be measured via the pressure chamber 10 with the pressure chamber 5 closed and, taking into account the measured pressure in the pressure chamber 5, a kinematic parameter for the piston 4 can be determined via the calibrated reference curve.

[0084] Due to the limited compressibility of common pressure media masses, only limited changes in the position of the piston 4 are possible in the embodiment of the Fig. 1, whereby mostly only smaller strokes of the piston 4 can be detected via the pressure sensor 6 and the computing unit 7 due to the compression of the pressure chamber 5.

[0085] However, in order to be able to determine larger travel distances of the piston 4, the process can, for example, be carried out several times in succession, with several kinematic parameters of the piston 4 being measured and calculated one after the other, if necessary.

[0086] However, it can also be provided that the compressibility of the system is increased by connecting the pressure chamber 5 to a hydraulic accumulator 9, whereby significantly larger travel distances and strokes of the piston 4 can be determined.

[0087] Such embodiments are provided by the Fig. 2 and Fig. 3 shown.

[0088] In these embodiments, a pressure medium mass of a pressure source 11 can again be supplied to the second pressure chamber 10 via a valve 13, wherein the pressure chamber 5 can be shut off during this time and thus forms a constant pressure medium mass during the measurement with the hydraulic accumulator 9 and the connecting line 8.

[0089] A hydraulic accumulator 9 of this or a similar type may be provided in some embodiments anyway, for example to save energy through recuperation.

[0090] If the hydraulic accumulator 9 is used, for example, as a bladder accumulator (as Fig. 2 or Fig. 3), the compression behavior can be varied considerably by a suitable choice of the back pressure in the bladder accumulator, whereby even higher compression volumes ΔV K be made possible to detect larger changes in the position of the piston 4.

[0091] The one in the Fig. 2 and Fig. The hydraulic accumulator 9 shown in Figure 3 is designed as a fluid-actuated bladder accumulator which has a gas (for example nitrogen, air or other gases) as the actuating medium.

[0092] The determination of the kinematic parameter in the piston 4 by the computing unit 7 can again - as described above - be carried out via a previous calibration and determination of a reference curve or also by calculating the compression volume, whereby in the embodiments of the Fig. 2 and Fig. 3 The following formula can be used to take into account not only the compressibility of the print media mass, but of the entire system: ΔVK=V0[(p0p1)K1n−(p0p2)1n]Approx n polytropic exponent V0 effective gas volume of the hydraulic accumulator ΔV K Compression volume P0 Gas filling pressure of the hydraulic accumulator p1 Pressure at the start of the measurement in pressure chamber 5 p2 Pressure at the end of the measurement in the pressure chamber 5 C a Correction factor for adiabatic change of state

[0093] For the present case (in the case of adiabatic changes of state) the polytropic exponent = 1.4.

[0094] The compressibility of the hydraulic fluid is negligible due to its small size and was not taken into account in the calculation.

[0095] The Fig. The embodiments of a hydraulic drive unit 1 explained in Figures 1 to 3 can, for example, be used as a hydraulic drive unit 1 for individual movements in a shaping machine 2, preferably an injection molding machine.

[0096] Preferably, an embodiment of a hydraulic drive unit 1 according to the invention can be used to drive a locking nut 19 relative to a bar 15 and / or as a pressure cushion 20 for building up the closing force in a closing unit 16.

[0097] Fig. 4 shows a fourth embodiment of a hydraulic drive unit 1, which has a mechanically operated hydraulic accumulator 9, wherein the counterpressure can be varied and / or adjusted via the spring element 33 (suitable choice of the spring element 33).

[0098] The remaining features of the embodiment of the Fig. 4 essentially correspond to those of Fig. 2.

[0099] Fig. 5 shows a fifth embodiment of a hydraulic drive unit 1, wherein the pressure chamber 5 is integrated into the piston-cylinder unit and forms a hydraulic accumulator.

[0100] The pressure medium in the pressure chamber 5 can be implemented, for example, by nitrogen, air or another gas.

[0101] When the pressure medium in the pressure chamber 5 is compressed, a kinematic parameter of the piston 4 can be determined taking into account the compressibility of the pressure medium and the pressure in the pressure chamber 5 (which can be determined via the pressure sensor 6).

[0102] The remaining features essentially correspond to those of the Fig. 3.

[0103] The Fig. The molding machine 2 shown as an example in Figure 6 is an injection molding machine and has an injection unit 21 and a clamping unit 16, which are arranged together on a machine frame 22. The machine frame 22 could alternatively also be constructed in several parts.

[0104] The clamping unit 16 has a fixed mold clamping plate 23 and a movable mold clamping plate 24 which can be moved relative thereto.

[0105] Alternatively, versions with a front plate 21 are also possible. Such clamping units are also referred to as three-plate clamping units.

[0106] The movable mold clamping plate 24 is movable relative to the machine frame 22 via a clamping drive (not shown here). The clamping drive and the clamping unit 16 are shown in an exemplary embodiment in Fig. 6 is explained in more detail.

[0107] Mold halves of a mold 25 can be clamped or mounted on the fixed mold clamping plate 23 and the movable mold clamping plate 24 (shown in dashed lines).

[0108] The fixed mold clamping plate 23 and the movable mold clamping plate 24 are mounted and guided relative to each other by the bars 15.

[0109] The Fig. The mold 25, shown closed in Figure 6, has at least one cavity. An injection channel leads to the cavity, through which a plasticized mass can be fed to the plasticizing unit 26.

[0110] Fig. 6 shows a molding machine 2 with an injection unit 21, wherein the injection unit 21 shown in this embodiment has an injection screw, which is also used for plasticizing a material to be plasticized.

[0111] The injection screw is mounted in the mass cylinder 27 so that it can be moved axially along a longitudinal axis.

[0112] These movements are driven by a schematically illustrated drive unit 28.

[0113] Preferably, this drive unit 28 comprises a hydraulic rotary drive for the rotary movement and a linear hydraulic drive for the axial injection movement.

[0114] The plasticizing unit 26 (and thus the injection unit 21) is in signal connection with the central control or regulating device 14.

[0115] The central control or regulating device 14 can therefore simultaneously be the control or regulating device 14 of the hydraulic system 1.

[0116] In alternative embodiments, the control or regulating device 14 of the hydraulic system 1 and the forming machine is designed separately.

[0117] Analogously, the computing unit 7 can be designed separately or integrally with the control or regulating device 14.

[0118] Control commands are output from the central control or regulating device 14, for example, to the plasticizing unit 26, the injection unit 21 or to the clamping unit 16.

[0119] The central control or regulating device 14 can be connected to an operating unit 29 and / or a display device 30 via a signal-conducting connection or can be an integral part of such an operating unit 29.

[0120] The computing unit 7 can be signal-connected to the central control or regulating device 14 of the forming machine 2 and / or be designed as an integral component of the central control or regulating device 14.

[0121] In Fig. Figure 7 shows a side view of a clamping unit 16 of a molding machine 2 - in this case an injection molding machine.

[0122] The clamping unit 16 of the embodiment is again designed as a two-plate clamping unit, wherein a movable mold clamping plate 24 is linearly movable on the machine frame 22 relative to a fixed mold clamping plate 23.

[0123] To implement this linear movement of the movable mold clamping plate 24, the rapid stroke drive 31 and the pressure pads 20 are provided.

[0124] The following explains the typical movement sequence of such a locking unit 16 using a closing movement. The same applies in the opposite direction for the opening of the locking unit 16.

[0125] Thus, two mold halves of a mold 25 (not shown in this figure for reasons of clarity), which are arranged on the mold clamping plates 23, 24, are first brought closer to each other via the rapid stroke drive 31 designed as a piston-cylinder unit, until they rest against each other or are just about to touch each other.

[0126] Subsequently, the locking nuts 19 are locked with their inner profile to a corresponding outer profile of the bars 15, whereby the locking nuts 19 firmly connect the movable mold clamping plate 24 to the bars 15 by engaging the inner profile with the outer profile of the bars 15.

[0127] After locking the locking nuts 19, the movable mold clamping plate 24 is pulled towards the fixed mold clamping plate 23 via the bars 15 via the pressure cushions 20 until the mold halves of the molding tool 25 abut one another and then an additional pressure is built up between the movable mold clamping plate 24 and the fixed mold clamping plate 23 (via the molding tool 25 arranged therebetween), which pressure serves as the closing force of the clamping unit 26.

[0128] The actuation of the locking nuts 19 as well as the pressure pads 20 of this embodiment are implemented by embodiments of a hydraulic drive unit 1 according to the invention, whereby the kinematic parameter of the pistons 4 can be determined by a computing unit 7 and thus an actual position, a speed, an acceleration and / or a change in position of the locking nuts 19 and / or the pressure pads 20 can be determined.

Claims

[1] Shaping machine, in particular injection molding machine, with a hydraulic drive unit comprising - a piston (4) arranged in a cylinder (3) so as to be linearly displaceable and a pressure chamber (5) delimited in the cylinder (3) by the piston (4), - at least one pressure sensor (6) which is designed to detect a signal characteristic of the pressure in the pressure chamber (5), and - a computing unit (7) which is signal-connected to the at least one pressure sensor (6) for receiving the characteristic signal, wherein the computing unit (7) is designed to determine a kinematic parameter, preferably a position and / or a change in position, of the piston (4) on the basis of the signal characteristic of the pressure in the pressure chamber (5), characterized bythat the pressure chamber (5) cooperates with a constant pressure medium mass at least during the measurement of the characteristic signal. [2] Forming machine according to the preceding claim, wherein the pressure medium mass is a hydraulic fluid mass. [3] Shaping machine according to one of the preceding claims, wherein at least during the measurement of the characteristic signal the pressure chamber (5) in the cylinder (3) is closed and preferably encloses a constant pressure medium mass. [4] Shaping machine according to claim 1 or 2, wherein at least during the measurement of the characteristic signal, the pressure chamber (5) is connected to a hydraulic accumulator (9) via a connecting line (8), preferably wherein a constant pressure medium mass is enclosed by the pressure chamber (5), the connecting line (8) and the hydraulic accumulator (9). [5] Shaping machine according to at least one of the preceding claims, wherein the computing unit (7) is designed to determine the kinematic parameter by means of a relationship with the pressure stored in the computing unit (7), preferably taking into account a stored compression behavior of the drive unit. [6] Shaping machine according to at least one of the preceding claims, wherein the drive unit (1) has a hydraulic accumulator (9), preferably a bladder accumulator and / or diaphragm accumulator, particularly preferably with a variable compression ratio and / or variable back pressure. [7] Shaping machine according to the preceding claim, wherein the hydraulic accumulator (9) is designed as a mechanically, preferably spring-actuated, and / or fluid-actuated hydraulic accumulator (9). [8] Shaping machine according to at least one of the preceding claims, wherein the piston (4) divides the cylinder (3) into the (first) pressure chamber (5) and a second pressure chamber (10). [9] Shaping machine according to at least one of the preceding claims, preferably according to the preceding claim, wherein the drive unit (1) has a pressure source (11), in particular at least one pump, preferably which pressure source (11) is connected or connectable to the second pressure chamber (10) in order to apply a pressure to the second pressure chamber (10). [10] Shaping machine according to the preceding claim, wherein the pressure source (11) is connected to the second pressure chamber (10) via a valve (13), preferably which valve (13) is controllable or regulating by a control or regulating device (14). [11] Shaping machine according to one of the two preceding claims, wherein the computing unit (7) is signal-connected to a control or regulating device (14) of the pressure source (11) and / or is designed as an integral component of the control or regulating device (14), wherein the kinematic parameter can be used as an actual value by the control or regulating device (14) for controlling or regulating the pressure source (11). [12] Shaping machine according to at least one of the preceding claims, wherein the cylinder (3) with the piston (4) arranged therein is designed as a double-acting piston-cylinder unit. [13] Shaping machine according to at least one of the preceding claims, wherein the pressure chamber (5) is designed as a rod-side chamber of a piston-cylinder unit. [14] Shaping machine according to at least one of the preceding claims, wherein the at least one drive unit (1) is designed to drive a locking nut (19) relative to a spar (15) and / or as a pressure cushion (20) for building up the closing force. [15] Method for monitoring a forming machine (2) with a hydraulic drive unit (1), preferably a forming machine (2) with a hydraulic drive unit (1) according to one of claims 1 to 14, which hydraulic drive unit (1) comprises a piston (4) arranged to be linearly displaceable in a cylinder (3) and a pressure chamber (5) delimited in the cylinder (3) by the piston (4), wherein a pressure in the pressure chamber (5), which cooperates with a constant pressure medium mass during the measurement, is measured and a kinematic parameter, in particular a position and / or a position change, of the piston (4) is determined via the pressure, preferably a determined pressure change. [16] Computer program product for monitoring a forming machine (2) with a hydraulic drive unit (1), preferably a forming machine (2) with a hydraulic drive unit (1) according to one of claims 1 to 14, which hydraulic drive unit (1) comprises a piston (4) arranged in a cylinder (3) so as to be linearly displaceable and a pressure chamber (5) delimited in the cylinder (3) by the piston (4), which cooperates with a constant pressure medium mass during the measurement, comprising instructions which cause a computer to carry out the following steps when executing the program: - Receiving a characteristic signal for a pressure in the pressure chamber (5) and - Determining a kinematic parameter, preferably a position and / or a change in position, of the piston (4) of the pressure chamber (5) on the basis of the signal characteristic of the pressure in the pressure chamber (5).

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