ES2755813T3 - Electrohydraulic drive unit - Google Patents

Abstract

Electro-hydraulic drive unit, in particular for use in a mechanical press, comprising - a cylinder-piston arrangement (1) with a first hydraulic working space (10) associated with a first direction of movement (Y1) of the piston ( 9) and a second hydraulic working space (11) associated with a second direction of movement (Y2) of the piston (9) opposite to the first, - a tank (2; 2 ') that stores hydraulic fluid, - a hydraulic pump 2-quadrant (5), driven by an electric motor (4) in pump operation in an exactly predefined direction of rotation and with variable speed, with a tank connection leading directly into the tank ( 2; 2 ') and a pressure connection (29), - a valve arrangement installed between the pressure connection (29) of the hydraulic pump (5) and the cylinder-piston arrangement (1) comprising several valves of switching (S1-S6; S2'-S6 ', S7) co electrically controllable, - and a mechanical control (26) that acts on the switching valves (S1-S6; S2'-S6 ', S7) and the electric motor (4) and by means of which the switching valves (S1-S6; S2'-S6', S7) can be controlled by switching between a request from the first workspace hydraulic (10) and the second hydraulic work space (11) of the cylinder-piston arrangement (1) in the operation of the hydraulic pump (5) from its pressure connection (29), being able to switch the hydraulic pump (5) by means of the mechanical control (26) to a braking operation with a direction of rotation and current contrary to that of the pump operation.

Description

DESCRIPTION

Electrohydraulic drive unit

The present invention relates to an electrohydraulic drive unit, in particular for use in a mechanical press.

Electrohydraulic drive units as are appropriate and are determined in particular for use in mechanical presses (specifically for the up and down movement of the corresponding tool), are known in different embodiments and modes of construction. Typically, the drive units in question are designed so that the piston can be moved (in at least one of the two directions of movement) at different speeds, in particular, on the one hand, with a fast gear (with achievable pressing force relatively low) and, on the other hand, with a driving gear (with relatively high achievable pressing force). Two basically different concepts of the electro-hydraulic drive of mechanical presses differ in that, for rapid downward movement of the tool support unit / tool unit, either an active loading of the work space for lowering the unit or units is required cylinder-piston of the (respective) hydraulic group, specifically because the recovery force of a spring equipment must be exceeded, or the tool support unit / tool unit descends due to its own weight until the tool makes contact with the workpiece (braking) and is only requested for the subsequent driving of the working space for lowering the cylinder-piston unit or units from the (respective) hydraulic group. The current state of the art includes, for example, documents WO 2011/003506 A1, US 2010/0212521 A1, AT 8633 U1, DE 102012013098 A1, WO 2011/021986 A1, EP 103727 A1 and DE 102013000725 A1.

The present invention concerns electrohydraulic drive units which are suitable for mechanical presses according to the second of the above mentioned conceptions (rapid downward movement of the tool support unit / tool unit as a consequence of the weight itself). Typical electrohydraulic drive units of this type comprise a cylinder-piston arrangement with a first hydraulic working space associated with a first direction of piston movement and a second hydraulic working space associated with a second direction of piston movement opposite the first, a reservoir for storing hydraulic fluid, a hydraulic pump driven by means of an electric motor, a valve arrangement arranged between the hydraulic pump and the cylinder-piston arrangement comprising electrically controllable switching valves and a mechanical control acting on the switching valves and the electric motor by means of which the switching valves can be switched between a stress of the first hydraulic working space and the second hydraulic working space of the cylinder-piston arrangement in the pump operation of the pump hydraulics from your pressure connection.

In practice, electrohydraulic actuation equipment of the type in question must meet a number of partially contradictory requirements. Depending on the individual mounting situation, more or less marked demands are made, in particular, performance capacity, compact dimensions, long service life, reliability, low manufacturing costs, high energy efficiency, operational safety, high dynamics, performance stable operation also under very changing conditions and low noise emissions.

The present invention has for its object to provide an electrohydraulic drive unit that offers a balanced solution and particularly suitable for practice with respect to typical requirements such as those that arise in particular in applications for mechanical presses.

This objective has been achieved in accordance with the present invention, being carried out, as indicated in claim 1, in an electrohydraulic drive unit having the characteristics explained above, the hydraulic pump as a 2-quadrant hydraulic pump that is driven by of an electric motor (in particular carried out as a servo motor) in the pump operation (for an active movement of the piston in both directions of movement, that is, descending towards the press in the driving gear, as well as ascending to lift the unit tool holder / tool unit) in exactly a predefined direction of rotation with variable revolutions and which has a tank connection leading directly (i.e. normally without other control elements) into the tank and a pressure connection, being able to switching the hydraulic pump, in addition, by means of mechanical control, au n braking operation with the direction of rotation and current opposite to that of the pump operation. In this way, with a relatively small apparatus complexity, it is possible to provide a powerful, reliable and operationally safe electrohydraulic drive unit that also largely meets the other requirements mentioned above.

Particularly preferably, in the electrohydraulic drive unit according to the invention, the cylinder-piston arrangement is oriented with an axis of movement at least essentially perpendicular, the first direction of movement corresponding to a downward movement and the second direction of movement. movement, to an upward movement of the piston. And the hydraulic pump can be switched to braking operation both in a first phase of movement (fast downward travel), during which (by means of the valve arrangement) there is a flow connection of the second hydraulic working space of the cylinder-piston arrangement with the pressure connection of the hydraulic pump, as in a second phase of movement (upward decompression), in which there is a connection flow rate of the first hydraulic working space of the cylinder-piston arrangement with the pressure connection of the hydraulic pump, in the braking operation.

In a particularly preferred way, a throttle (for example, in the form of a nozzle) is provided which, in the braking operation in the second movement phase, is connected in series with the hydraulic pump. This discharges the hydraulic pump and limits its stress on the braking operation during the second phase of movement, in such a way that operating states (excessive rotation) are avoided, which may impair the safety of the process. In an alternative development which operates without such a throttle, in the decompression phase, that is, in the second movement phase during braking operation, a pressure-dependent control of the number of revolutions of the electric motor it operates is carried out, or -in this operating mode- brakes the hydraulic pump. In this case, a pressure sensor is provided that detects the prevailing pressure in the first hydraulic workspace and whose signal is connected to the mechanical control.

According to another preferred improvement of the invention, the hydraulic pump is arranged internally in the tank. This allows a development installed inside the reservoir of the pressure conductor that is attached to the pressure outlet of the hydraulic pump, which, from the point of view of operational safety, represents a considerable advantage and, in addition, is favorable to minimize the risk of external leakage. Furthermore, it is advantageous from the point of view of aspects relating to low noise emission and constant cooling of the hydraulic pump.

Another further preferred development of the electro-hydraulic drive unit according to the invention is characterized in that a flange block and connection with a first flange surface is provided for connection with a valve block housing the switching valves and a second Flange surface for connection to the cylinder of the cylinder-piston arrangement. The flange and connection block can be arranged in this respect in particular in a majority part of its volume in the tank and only protrude from it with greater or lesser amplitude with marginal areas adjacent to the two flange surfaces. According to an alternative preferred refinement, the flange and connection block is arranged outside the tank and, particularly, particularly preferably below its base. In the sense of the previous explanations, the hydraulic pump can be connected in this regard, in particular by means of a pressure conductor running inside the tank, with a pressure connection provided in the flange and connection block which, due to its part, it is connected by means of a channel with a pressure connection provided on the first flange surface; and, in both the first and the second flange surface, a hydraulic interface can be provided in each case, comprising two working connections that communicate with the two working spaces of the cylinder-piston arrangement.

In accordance with a further preferred development of the invention, the valve block is housed in a lateral recess in the tank. In particular, such a recess, which houses the valve block, can be arranged in one of the corner areas of the tank.

Another preferred development of the invention is characterized in that a hydraulically unlockable suction valve is arranged in the tank. In a particularly advantageous way, the arrangement of the suction valve is in a rupture of the flange and connection block described above arranged in a majority part of its volume in the tank; The suction valve may in this case have a connection flange for direct connection to the cylinder of the cylinder-piston arrangement. In an alternative preferred refinement, the suction valve is completely integrated in the flange and connection block, arranged outside the tank; only the latter is connected in this respect by means of its second flange surface directly with the cylinder of the cylinder-piston arrangement. And the suction valve can be connected by means of a control line with a control output provided in the flange and connection block. The control output of the flange and connection block is connected in this respect by means of a channel with a control fluid interface on the first flange surface.

From the foregoing explanations it follows that an electrohydraulic drive unit with outstanding advantages can be provided, applying the present invention (particularly in the case of use as a drive of a mechanical press). Among them, in particular, are the following: by means of units previously assembled at the factory that are equipped with a mechanical interface for the respective cylinder-piston arrangement and, therefore, can be easily connected to the latter, minimum times are obtained assembly and commissioning on the machine. The reduced design in tubular ducts and the consequent suppression of external pipes, results in great reliability and the reduction of the danger of external leaks. The drive unit is supplied with a reduced amount of hydraulic fluid. It has a very high energy efficiency with a reduced dependence on temperature, so that, as a general rule, it is not necessary to foresee an oil cooling time nor is an oil cooler required. In this way, the drive unit can have particularly small constructional dimensions. Noise development is minimal. By means of the valve control, a return stroke of the tool at the working speed is possible. In this way, particularly short cycle times are possible and, correspondingly, high productivity. Additional functions such as tool clamping and pumping can be effortlessly integrated into or attached to the drive unit. The drive unit is sufficient without pressure accumulator and without proportional rail valves. Pressure sensors are not necessarily required, however, these may be advantageously provided in certain designs of the drive unit according to the invention (see above). Nor is a regulator pump necessary. Very dynamic mechanical presses (for example, folding presses) can be made with a fast running speed of, for example, 200-230mm / sec.

The present invention is explained in more detail below with the help of two preferred embodiments illustrated in the drawing. In this regard, it shows

FIG. 1 in a perspective view, an electrohydraulic drive unit according to a first embodiment of the invention without the corresponding mechanical control,

Figure 2 the electrohydraulic drive unit according to figure 1 with partially cut side walls of the tank for illustration of its facilities, but without the cylinder-piston unit, Figure 3 the hydraulic diagram of the electrohydraulic drive unit according to the figures 1 and 2, Figure 4 in the form of a diagram, the control of the switching valves and the electric motor of the electrohydraulic drive unit according to Figures 1 to 3 and the resulting movement of the piston, Figure 5 in a view in perspective, an electrohydraulic drive unit according to a second embodiment of the invention without the corresponding mechanical control,

Figure 6 the hydraulic diagram of the electrohydraulic drive unit according to figure 5 (without the corresponding mechanical control) and

Figure 7 a functional diagram illustrating the control of the switching valves and the electric motor of the electrohydraulic drive unit according to Figures 5 and 6 and the resulting movement of the piston.

The electrohydraulic drive unit shown in Figures 1 and 2 according to a first embodiment of the invention, comprises as main components a cylinder-piston arrangement 1 with vertical movement axis Y, a tank 2 that stores hydraulic fluid, a group hydraulic 3 with an electric motor 4 and a hydraulic pump 5 driven by it and a valve block 6 with various active elements (in particular valves) housed in or within it, as well as a replaceable oil filter 20. The cylinder arrangement -Piston 1 comprises in a manner known per se a piston 9 linearly displaceable in a cylinder 7, connected with a piston rod 8 by means of which the interior space of cylinder 7 is divided into two working spaces, specifically, a first space of hydraulic work 10 that is associated with a first direction of movement Y1 of the piston in such a way that during this its volume increases, and a second is hydraulic working space 11 that is associated with a second direction of movement Y2 of the piston -opposed to the first direction of movement Y1- in such a way that during this increases its volume. In the existing mounting situation, the first direction of movement Y1 corresponds to the downward movement of piston 9 and piston rod 8 and the second direction of movement Y2, with its upward movement.

The tank 2, which is ventilated by means of a ventilation filter 12 in such a way that an ambient pressure prevails therein (called "open system"), has an L-shape. Thus, it has a side cutout 13 in the the valve block 6 is housed. On one of the side walls of the tank 2, a level sensor 34 is arranged.

The hydraulic pump 5 is arranged internally in the tank 2 ("under oil"). The electric motor 4 that serves to drive it is, however, outside of tank 2, flanged at its base 14. Also, in tank 2 there is a suction valve 15, as well as a flange and connection block 16 ( with a majority of its volume). The latter, however, protrudes through corresponding openings in the side wall 17 and the base 14 of the tank 2 outside it. In the section 18 of the flange and connection block 16 that protrudes through the lateral wall 17 of the tank, a first flange surface 19 is provided for the connection with the valve block 6; and in the section of the flange and connection block 16 that protrudes through the base 14 of the tank 2, there is a second flange surface 21 for the union with the cylinder 7 of the cylinder-piston arrangement 1. In the first As well as on the second flange surface 19, 21, a hydraulic interface is provided in each case, comprising two working connections A, B that communicate with the two working spaces 10, 11 of the cylinder-piston arrangement 1.

The flange and connection block 16 has a break 22 in which the suction valve 15 is inserted. This, for its part, has a connection flange for direct connection with cylinder 7 of cylinder-piston arrangement 1. The suction valve 15 can be hydraulically unlocked, for which it is connected by means of a control line 23 -installed inside the tank 2- with a control connection provided in the flange and connection block 16 and which, for its part, it communicates by means of a channel -through the flange and connection block 16- and a control fluid interface provided in the first flange surface 19 with a control outlet of the valve block 6. On the tank side of the Hydraulic pump 5, which during its operation as a pump constitutes the suction side, a suction nozzle 24 is provided which opens near the base. The pressure side of the pump 5, through which the required hydraulic fluid comes out during pump operation, is instead connected by means of a pressure tube 25 -installed inside the tank 2- with a pressure connection provided in the flange block and connection 16 which, for its part, communicates by means of a channel passing through the flange block and connection 16 and a control fluid interface provided on the first flange surface 19 with a pressure fluid connection of the valve block 6 .

The arrangement and connection of the switching valves and other components (suction valve, choke, pressure limiting valves, filters, etc.) of the hydraulic system is illustrated in figure 3. (To avoid misunderstandings it should be noted that in figure 3 the line symbolizing valve block 6 comprises the physical valve block 6 of Figures 1 and 2 together with the physical flange and connection block 16; these two components, according to Figures 1 and 2, constructively independent, could be also grouped into a unitary component.) In particular, they are important for the control of the movement developments of the drive unit, that is, for the downward and upward movement of piston 9 and piston rod 8, in this regard, the total of six switching valves S1 to S6 controlled by the mechanical control 26, as well as the electric motor 4 of the hydraulic group 3 also controlled by the Mechanical control 26 and performed as servo motor 27. Control of the switching valves S1 to S6, as well as the servo motor 27 in the individual partial sections and phases of a complete cycle is illustrated in this respect in the diagram according to figure 4.

And specifically, during the stop of the piston in the upper dead point (phase I) the servomotor 27 is in the stopped state (operating state "0"); and none of the six switching valves S1 to S6 is activated, in such a way that all the switching valves adopt the position shown in figure 3 (activation position "0"). In this activated state, the piston 9 is retained by the group of the closed switching valve S2 and the closed pressure limiting valve 30, as well as by the switching valve S3, also closed, in the sense that the weight of the components joined with the piston rod 8 (for example, tool holder and tool) of the corresponding machine with held by the hydraulic fluid retained in the second hydraulic workspace 11. (The safety valve 28, regulated to the maximum allowable system pressure including an increase, is in any case closed during normal operation.)

For the rapid downward movement of piston 9 and piston rod 8 (phase II), with the exception of the switching valve S4, all the switching valves, i.e. the switching valves S1, S2, S3, S5 and S6 (activation position "I"). The second working space 11 (lifting working space) of the cylinder-piston unit 7 is in connection by means of the switching valves S2 and S3 (open) and the switching valve S5 open according to bP, with the pressure connection 29 of the hydraulic pump 5. The servomotor 27 rotates in a counterclockwise direction (operating state L *), that is, in its braking operation to brake in a controlled way the induced downward movement of the piston 9 by means of the own weight of the mechanical components (tool holder plus tool) actuated by the drive unit, joined with the piston rod 8. By means of the suction valve 15, the first working space 10 is filled with the cylinder-piston arrangement 7 directly from the tank 2. This phase II extends to a switching point -saved in the mechanical control- that is freely programmable and conveniently close to the point of contact of the tool with the workpiece.

In the load change phase III, the servo motor 27 is stopped. The switching valves S2, S4 and S5 are switched, that is, the switching valves S2 and S5 are deactivated (activation position "0"), and the switching valve S4 is activated (activation position "I") . In this way, the first working space 10 of the cylinder-piston arrangement 7 is brought into flow connection by means of the switching valve s4 with the pressure side 29 of the hydraulic pump 5. The second working space 11 of the cylinder-piston arrangement 7, on the contrary, is brought into flow connection by means of the pressure limiting valve 30, the switching valve S3, the flow path bT of the switching valve S5 and the filter of oil 20 with the tank side.

For force pressing (phase IV), the servo motor 27 is started with its direction of rotation corresponding to the operation of the pump of the hydraulic pump 5 (clockwise according to operating state R *) . This operating state of the switching valves S1 to S6 and of the servomotor 27 is also maintained in the subsequent stop phase (phase V).

To decompress the hydraulic fluid (phase VI) found in the first working space 10, the servo motor 27 is switched. It now rotates counterclockwise, that is, in its braking operation L *, so that hydraulic fluid is transported in a controlled manner from the first working space 10 by means of the switching valve S4 and the choke 31 (made as a nozzle) to the tank 2.

At the end of the decompression phase, the switching valves S4, S5 and S6 are switched, that is, the switching valves S4 and S6 are deactivated (activation state "0") and the switching valve S5 is activated ( activation status "I"). As a consequence of its solicitation with control pressure by means of the switching valve S6 (path Pb), the suction valve 15 opens (unlocks). And the second working space 11 of the cylinder-piston arrangement 7 is connected by means of the pre-pressure valve 32 and the two switching valves S3 and S2 (in each case by means of a path secured by means of the valve non-return) with the pressure side 29 of the hydraulic pump 5. By switching the servomotor 27 clockwise, that is, in operation with the direction of rotation corresponding to the operation of the hydraulic pump pump ( operating state R *), piston 9 is raised in the fast stroke (phase VII). If necessary, the lift of the piston 9 can be divided into two partial phases, with a slow lift before a fast lift. During this first partial phase, with the suction valve 15 still not unlocked, displaced hydraulic fluid can flow into the first working space 10 by means of the switching valve S4 (path aT) and the oil filter 20 to the tank 2.

Upon reaching the top dead center (OT), the servo motor 27 enters the stopped state; and the switching valves S1 and S5 are switched in such a way that all the switching valves are again deactivated (stop phase VIII, analogously to stop phase I at the beginning of the cycle '; see above).

In stop phase I, VIII, the hydraulic pump 5 can be started if necessary to transport hydraulic fluid by means of the switching valve S1 (open) through the oil filter 20. Optionally, it can follow the filter of oil 20, connected to this in series, an oil cooler 33.

With respect to the control illustrated in Figures 3 and 4, to mention it only for the sake of completeness, various variations, modifications and adaptations are clearly possible within the framework of the present invention without abandoning the invention defined by the claims. One such modification consists, for example, in replacing normally open (NO) valves with normally closed (NG) valves and / or vice versa.

In figure 3 it is shown that the switching valves S1, S2, S3, S4 and S6 are equipped with an activation position control 34. This can be suppressed -in case of low safety requirements- if necessary, it can be suppressed in this case also the switching valve S3.

If, as mentioned above and shown in FIG. 3, an oil cooler 33 is provided, it is preferably arranged directly outside on one of the side walls of the tank 2. The oil supply to the oil cooler 33 is carried out in this regard by means of a conduit installed inside the tank 2 which is connected with a refrigerant flow connection provided in the flange block and connection 16 which, for its part, communicates by means of a channel that passes through the block flange and connection 16 and a refrigerant flow interface provided on the first flange surface 19 with a refrigerant flow connection of valve block 6.

The second preferred embodiment of the invention documented by Figures 5 to 7 is explained -due to the existing parallelisms and coincidences- in good part by the previous explanations relating to the first example of embodiment referred to in Figures 1 to 4 To avoid repetitions, therefore, we refer to this first example. In particular, reference will be made in the following to important divergences that are discussed below: The flange and connection block 16 'is not arranged in the tank, but on the contrary (entirely) outside the tank 2'. Specifically, it is below the tank 2 ', that is, below its base 14. Unlike the first embodiment, in which a suction valve with automatic functional capacity is used or is inserted in a recess or a breakage of the flange and connection block, in the second embodiment according to Figures 5-7, the suction valve 15 'is integrated in the flange and connection block 16' in the sense that this itself forms the Valve housing required for operation. This enables a particularly compact construction. Furthermore, the necessary double flange connection according to the first embodiment (on the one hand, of the flange and connection block 16 and, on the other hand, of the suction valve 15) is removed from the components in the cylinder arrangement- piston.

Furthermore, in figure 6 it can be seen that the active choke in the first embodiment in the decompression phase has been removed and connected in series with the hydraulic pump. Related to this is the pressure-dependent regulation (provided in the second example of embodiment) of the decompression by means of a corresponding activation of the hydraulic pump 5 in the braking operation by means of the control, for which purpose the signal from a pressure sensor 34 that detects the hydraulic pressure in the first hydraulic workspace is connected to the control.

In the second embodiment, the filtering of the hydraulic fluid is also configured differently. In this case, a filter unit 35 is provided in such a way that, in the operation of the pump of the hydraulic pump 5, all the hydraulic liquid transported by the latter is cleaned by the filter 20 '. Only in the event of filter 20 'clogging does hydraulic fluid flow by the hydraulic pump 5' flow through a "small" bypass 36 in which the non-return valve 37 acts as a pressure limiting valve and, in the event that the Filter 20 'becomes overloaded or clogged, opens to prevent filter breakage. In the braking operation of the hydraulic pump 5 ', the hydraulic fluid flows through the "large" bypass 38 in the filter unit 35.

As a consequence of the previously described embodiment of the filtering of the hydraulic liquid, the function of the switching valve S1 provided in the first embodiment has also been partially suppressed; since in the second exemplary embodiment, there is no longer a pure filter circulation operation. In this way, the second exemplary embodiment could operate with a switching valve less than the first example of realization. However, as Figure 6 shows, an S7 stop valve has been added for safety reasons. This locks the hydraulic pump 5 in position without flow passage with respect to the remaining valve arrangement and thus prevents an unintended build-up of pressure in the system.

Finally, it should be noted the suppression of a separate oil cooler; since it is not required in the second exemplary embodiment shown.

Claims (16)

1. Electro-hydraulic drive unit, in particular for use in a mechanical press, comprising - a cylinder-piston arrangement (1) with a first hydraulic working space (10) associated with a first direction of movement (Y1) of the piston (9) and a second hydraulic working space (11) associated with a second direction movement (Y2) of the piston (9) opposite to the first, - a tank (2; 2 ') that stores hydraulic fluid, - a 2-quadrant hydraulic pump (5), driven by an electric motor (4) in the operation of the pump in an exactly predefined direction of rotation and with variable number of revolutions, with a tank connection leading directly in the tank (2; 2 ') and a pressure connection (29), - a valve arrangement installed between the pressure connection (29) of the hydraulic pump (5) and the cylinder-piston arrangement (1) which it comprises several electrically controllable switching valves (S1-S6; S2'-S6 ', S7), - and a mechanical control (26) which acts on the switching valves (S1-S6; S2'-S6 ', S7) and the electric motor (4) and by means of which the switching valves (S1-S6; S2'-S6 ', S7) can be controlled by switching between a solicitation of the first hydraulic workspace (10) and the second hydraulic workspace (11) of the cylinder-piston arrangement (1) in the operation of the hydraulic pump (5) from its pressure connection (29), the hydraulic pump (5) being able to be switched by means of the mechanical control (26) to a braking operation with a direction of rotation and current contrary to that of the pump operation. Electro-hydraulic drive unit according to claim 1, characterized in that the cylinder-piston arrangement (1) is oriented with an axis of movement (Y) at least essentially perpendicular, the first direction of movement (Y1) corresponding to a movement down and the second direction of movement (Y2) to an upward movement of the piston (9). Electro-hydraulic drive unit according to claim 1 or claim 2, characterized in that the hydraulic pump (5) is switchable to the braking operation both in a first phase of movement, during which there is a flow connection of the second space of hydraulic work (11) of the cylinder-piston arrangement (1) with the pressure connection (29) of the hydraulic pump (5), as well as in a second phase of movement in which there is a flow connection of the first space hydraulic work (10) of the cylinder-piston arrangement (1) with the pressure connection (29) of the hydraulic pump (5). Electro-hydraulic drive unit according to claim 3, characterized in that a choke (31) is provided which is connected in the braking operation in the second phase of movement in series with the hydraulic pump (5). Electro-hydraulic drive unit according to one of claims 1 to 4, characterized in that the hydraulic pump (5) is arranged internally in the tank (2; 2 '). Electro-hydraulic drive unit according to one of claims 1 to 5, characterized in that a flange and connection block (16) with a first flange surface (19) is provided for connection to a valve block (6) which it houses the switching valves (S1-S6; S2'-S6 ', S7) and a second flange surface (21) for connection to the cylinder (7) of the cylinder-piston arrangement (1). 7. Electrohydraulic drive unit according to claim 6, characterized in that the flange and connection block (16) is arranged in a majority part of its volume in the tank (2). 8. Electro-hydraulic drive unit according to claim 6 or claim 7, characterized in that the valve block (6) is housed in a lateral recess (13) of the tank (2; 2 '). 9. Electro-hydraulic drive unit according to one of claims 6 to 8, characterized in that a hydraulic interface is provided on the second flange surface (21), comprising two working connections (A, B) that communicate with the two spaces (10, 11) of the cylinder-piston arrangement (1). 10. Electro-hydraulic drive unit according to one of claims 6 to 9, characterized in that the hydraulic pump (5) is connected, by means of a pressure conductor (25) running inside the tank (2), to the flange block and connection (16). 11. Electrohydraulic drive unit according to one of claims 1 to 10, characterized in that a suction valve (15) with a non-return valve that can be hydraulically unlocked is arranged in the tank (2). 12. Electrohydraulic drive unit according to claim 11, characterized in that the Suction (15) has a connection flange for direct connection to the cylinder ( 7) of the cylinder-piston arrangement (1). 13. Electro-hydraulic drive unit according to claim 11 or claim 12, characterized in that the suction valve (15) is connected by means of a control line (23) to a control outlet provided in the flange and connection block (16). 14. Electrohydraulic drive unit according to claim 6, characterized in that the flange and connection block (16 ') is arranged below the tank (2'). 15. Electrohydraulic drive unit according to claim 14, characterized in that a suction valve (15 ') with a hydraulically unlockable check valve is arranged in the flange and connection block (16'). 16. Electro-hydraulic drive unit according to one of claims 1 to 15, characterized in that it comprises a filter unit (35) with a filter (20 ') through which it passes, during the operation of the pump of the hydraulic pump (5 ), all the hydraulic fluid carried by the hydraulic pump (5).