EP2229537B1 - Hydraulic drive device having two pressure chambers and method for operating a hydraulic drive device having two pressure chambers - Google Patents

Description

The invention relates to a hydraulic working device with a displaceably guided in a cylinder chamber along a working piston, which limits a hydraulic fluid pressurizable working pressure chamber, further comprising a guided at least partially in the piston between different control states control means for controlling the flow of hydraulic fluid from a high pressure supply in the working pressure chamber for moving the piston in the working direction and from the working pressure chamber to a return chamber. The invention also relates to a method for operating a hydraulic drive device, with a displaceably guided in a cylinder chamber piston which limits a working pressure chamber, wherein the working pressure chamber for moving the piston is pressurized in the working direction with hydraulic fluid.

Hydraulic drive devices and methods of the type mentioned are known in various designs. In that regard, the state of the art, for example, on the EP 0 296 104 B1 directed. A common feature in the prior art is that retraction and extension movements of the piston are effected by means of hydraulic fluid from a high-pressure supply. Such devices are used in particular in stamping, embossing, nibbling, bending or forming machines. In this typically highly dynamic working operation, inherently high volume flows of the hydraulic fluid from the high-pressure supply occur, and sufficient energy must be provided.

From the DE 37 20 266 C2 and the EP 0 296 104 B1 Further hydraulic drive have become known.

The invention has for its object to enable an energy-saving hydraulic working operation, especially for use in stamping, embossing, nibbling, bending or forming machines.

This object is achieved by a hydraulic drive device according to claim 1. It is therefore provided according to the invention that the working pressure chamber remote from the region of the piston defines a low pressure chamber which is pressurized during operation of the device by a low pressure supply for hydraulic fluid such that the piston is moved back against the working direction when the control means connects the working pressure chamber with the return chamber ,

Characterized in that the return movement of the piston is caused by hydraulic fluid from a low pressure supply, the energy requirement of the device is significantly reduced in a cycle of ancestors and return of the piston. In particular, when used in stamping, embossing, nibbling, bending or forming machines with inherently high repetition rates of the working cycles results in a large energy savings. In contrast, in the hydraulic drive devices known hitherto from the prior art, the return movement of the piston is connected to a volume flow of hydraulic fluid from a high-pressure supply, which entails a considerable loss of energy.

The piston advantageously limits not only the working pressure chamber and the return chamber, but also a high-pressure chamber and a low-pressure chamber. A pressurization of the working pressure chamber with hydraulic fluid causes a force on the piston in the working direction, while pressurization of the low-pressure chamber causes a force on the piston against the working direction. The return chamber is connected in particular via a tank connection with a tank and serves to discharge the hydraulic fluid from the working pressure chamber. The high-pressure chamber is connected in particular via a high-pressure connection to the high-pressure supply and serves to supply the working pressure chamber with hydraulic fluid. Separated from this, the low-pressure space is connected in particular via a low-pressure connection to the low-pressure supply. The high pressure chamber and the low pressure chamber are in particular so designed that when pressurized no resulting forces on the piston in or against the working direction

A further development of the invention provides that the low-pressure chamber is separated from the high-pressure supply independently of the control state of the control means. The high-pressure supply is thus removed only during the working step (i.e., during the pre-driving) hydraulic fluid in which the piston is moved in the working direction by filling the working pressure chamber with hydraulic fluid. When the piston is moved back, no hydraulic fluid flows from the high pressure supply.

As a preferred embodiment of the invention adjusting means are provided, by means of which the pressure of the high-pressure supply is adjustable depending on the travel of the piston and / or the working load of the piston. Thus, a further energy savings is possible because the full force of the piston is often required only for a fraction of the total piston movement. As a result, energy is not only saved during the return movement of the piston, as described above, but the energy requirement can also be reduced during the advancement of the piston.

Advantageously, the adjusting means are designed such that the pressure of the high pressure supply for moving the piston from its retracted end position in the working direction to or until just before recording a workload a value p1 and then, in particular during the workload, a value p2. Here p1 is smaller than p2.

Furthermore, the adjusting means are advantageously designed such that upon further movement of the piston in the working direction after overcoming the workload, the pressure of the high-pressure supply has a value p3, where p3 is less than p2 and / or p3 is equal to p1.

This ensures that an increased power requirement of the high pressure source occurs only in the range of workload, for example, during the forming of a workpiece by the piston movement. The ancestor of the piston to the onset of the workload is done with less energy.

As an advantageous development, a displacement measuring system is provided for determining the travel path (i.e., the position) of the piston and / or a load measuring system for determining the working load of the piston. In conjunction with the adjustment means for the pressure of the high-pressure supply, these measuring systems enable optimized high-pressure connection for further energy savings.

As a further embodiment of the invention it is provided that the control means in the region in which it is guided in the piston, along the working direction limits a pressure chamber which is pressure-connected to the low-pressure space.

A preferred embodiment of the invention results from the fact that the control means is designed as a control slide guided along the working axis, which is at least partially guided in the interior of the piston, and which has control edges, which are designed to cooperate with further control edges on the piston to the Control flow of hydraulic fluid in or out of the working pressure chamber. As described above, when the spool in the region where it is guided in the piston defines a pressure space along the working direction that is pressure-connected to the low-pressure space, the spool continuously receives a force against the working direction. For actuation of the spool must therefore only pushed in the direction of work, not pulled opposite. Alternatively, it is also conceivable to use a control means rotatable about its longitudinal axis.

The spool can be formed in one piece or in several parts, with individual parts of the spool can be connected to each other in particular via joints. As a result, in particular alignment errors can be compensated.

The spool can also on the one hand in the region adjacent to the low-pressure chamber of the piston in a cylindrical guide opening and on the other hand in the cylinder housing in a further cylindrical guide opening are guided, wherein the guide openings have the same diameter.

As a development of the invention, a coupling rod for actuating the control slide is provided such that the control slide can be pushed by means of the coupling rod in the working direction of the piston. If the spool as described above defines a pressure chamber in the piston, which is pressure-connected to the low-pressure chamber, thus acting on the spool uninterrupted a force counter to the working direction. The coupling rod therefore has to push this to actuate the spool this only in the working direction, but not pull the spool. It is therefore not necessary that control rod and spool are firmly connected. In particular, the coupling rod can rest only loosely on the spool.

Advantageously, the coupling rod is connected to an electromechanical transducer. In particular, it can be provided that the electromechanical transducer is designed as a linear direct motor and its longitudinal axis movable along the working rotor is firmly connected to the coupling rod.

To achieve the object set out above, a method with the features of claim 12 is also provided. In the method for operating a hydraulic working device with a displaceably guided in a cylinder chamber piston which limits a working pressure chamber, the working pressure chamber for moving the piston in the working direction with hydraulic fluid with a high pressure PH is applied. According to the invention, a low-pressure space, which is delimited by a region of the piston facing away from the working pressure chamber, is acted upon by a low-pressure PN to move the piston back against the working direction. Where PN <= PH. For carrying out the method, in particular a hydraulic drive device according to the invention is used. This ensures that the return movement of the piston counter to the working direction in an energy-saving manner by hydraulic fluid at low pressure is brought about. High pressure hydraulic fluid is only needed to move the piston in the direction of operation.

The method can be further configured in that the pressure of the hydraulic fluid pressurizing the working pressure chamber is set as a function of the travel of the piston and / or the working load of the piston.

As a further embodiment, the low-pressure space is continuously subjected to low pressure.

It is particularly preferred if the high pressure of the hydraulic fluid pressurizing the working pressure chamber has a value p1 for moving the piston from its retracted end position in the working direction until or shortly before a workload is received, and then, in particular during the workload, p1 is less than p2. In the event that a further movement of the piston is provided after overcoming the working load in the working direction, the high pressure has a value p3, where p3 is less than p2 and / or p3 is equal to p1.

Further details and advantageous embodiments of the invention will become apparent from the following description, with reference to which the embodiment of the invention shown in the figures is described and explained in more detail.

Show it:

FIG. 1 a longitudinal section through a hydraulic drive device according to the invention in the rest position,

FIG. 2 a part of the drive device according to FIG. 1 in the state for extending the piston as a longitudinal section,

FIG. 3 a part of the drive device according to FIG. 1 in the state for returning the piston as a longitudinal section,

FIG. 4 the time course of the travel of the piston and the set pressure of the high pressure supply.

The in the Figures 1-3 shown hydraulic working device has a cylinder 3 and a piston 5. The piston 5 is displaceable and sealing in a cylinder chamber 8 along a working axis 10 guided. The piston 5 is integrally connected to a piston rod 6, which projects beyond the cylinder 3 in a working direction 11. For example, the piston rod 6 may be connected to a punching tool (not shown) for forming a workpiece (not shown). The piston 5 defines a working pressure chamber 13, a return chamber 15, a high pressure chamber 17 and a low pressure chamber 19, which are filled with hydraulic fluid for operating the device in the manner described below. Pressurization of the working pressure chamber 13 with hydraulic fluid causes a force on the piston 5 in the working direction 11, while pressurization of the low-pressure chamber 19 causes a force on the piston 5 against the working direction 11. The return chamber 15 is connected via a tank connection 16 with a tank 22 and serves to discharge the hydraulic fluid. The high pressure chamber 17 is connected via a high pressure port 18 to a high pressure supply 24 for hydraulic fluid and serves to supply the working pressure chamber 13 with hydraulic fluid. Separated from this, the low-pressure space 19 is connected via a low-pressure connection 20 to a low-pressure supply 26 for hydraulic fluid.

The piston 5 has a coaxial cylindrical bore 28 in which a control means 29 in the form of a spool 30 along the working axis 10 is guided longitudinally displaceable and sealing. The axial end portions 32 and 34 of the spool 30 are formed like a piston. The piston-side end portion 32 is sealingly guided in a cylindrical guide bore 36 in the piston 5 and limited in the piston 5 a pressure chamber 38 which is pressure-connected to the low-pressure chamber 19. The piston 5 facing away from the end portion 34 of the spool 30 is sealingly guided in a cylindrical guide bore 40 in the cylinder 3. The diameters of the guide bores 36 and 40 are the same size.

The spool 30 has through windows 48 with control edges 42 and 43. These are designed to cooperate with control edges 45 and 46 on the piston to a hydraulic follow-up control for piston. 5 and spool 30 to provide. The return chamber 15 and the high pressure chamber 17 have flow openings 41 and 44, which connect the return chamber 15 and the high-pressure chamber with the axial bore 28 for the spool 30. The piston-side control edges 45 are in communication with the flow opening 41 and thus with the return chamber 15, the piston-side control edges 46 with the flow opening 44 and thus with the high pressure chamber 17. The control edges 42 and 43 on the spool 30 have the same or a slightly smaller distance from each other By shifting the spool 30 along the working axis 10, consequently, the working pressure space 13 can be pressure-connected either to the return space 15 or to the high-pressure space 17. The low-pressure chamber 19, regardless of the position of the spool 30 has no pressure connection to the high-pressure chamber 17 or to the return chamber 15.

For actuating the spool 30, a coupling rod 50 is provided, by means of which the spool 30 can be pushed in the direction of work 11. The coupling rod 50 is only loosely on the piston-like end portion 34 of the spool 30 at. The coupling rod 50 is on the other hand firmly connected to the rotor 52 of an electromechanical transducer 54, which is designed in particular as a linear direct motor.

To adjust the pressure of the high pressure supply 24 adjustment means 60 are provided. These set the pressure of the high pressure supply 24 dependent on the travel, i. the position of the piston 5 along the working direction 11 a. The position of the piston 5 along the working axis 10 is determined via a displacement measuring system 62. Furthermore, it can be provided that the adjusting means 60 adjust the pressure of the high pressure supply 24 as a function of the working load of the piston 5, which are determined by means of a load measuring system (not shown).

In operation, the hydraulic drive device 1 operates in the manner described below in the in FIG. 1 shown Rest position, the spool 30 is held by the coupling rod 50 in the rest position. In this case, the force acting on the spool 30 by the low pressure in the pressure chamber 38 is counteracted counter to the working direction 11 by the control rod 50. There is also force equilibrium between the force acting in the working direction 11 on the piston 5 through the hydraulic fluid in the working pressure chamber 13 and the working direction 11 counteracting force on the piston 5 through the low pressure chamber 19 located hydraulic fluid. A flow of hydraulic fluid from the high pressure chamber 17 in the working pressure chamber 13 or the working pressure chamber 13 in the return chamber 15 is prevented, since the flow openings 41 and 44 are sealingly covered by the spool 30.

If the coupling rod 50 is moved by the linear direct motor 54 in the working direction, the coupling rod 50 also pushes the control slide 30 in the working direction. As in FIG. 2 As a result, the high-pressure chamber 17 is pressure-connected to the working pressure chamber 13 and hydraulic fluid flows from the high-pressure supply 24 via the high-pressure chamber 17 through the through-windows 48 into the working pressure chamber 13. As a result, a force acts in the working direction 11 on the piston 5 and the piston 5 is moved in the working direction 11. The piston 5 follows the movement of the spool 30 until the control edges 43 and 46 again as in FIG. 1 illustrated close, so that a flow of hydraulic fluid from the high-pressure chamber 17 is prevented in the working pressure chamber 13 or the working pressure chamber 13 in the return chamber 15. It then turns back to a rest position similar to the one in FIG. 1 illustrated situation.

The high-pressure space 17, which is designed essentially as an annular space, extends so far in the axial direction that the high-pressure port 18 communicates with the flow opening 44 over the entire stroke. In operation, we also closed off by the spool 30 Flow opening 44 of the high-pressure chamber 17 is subjected to high pressure; however, a resultant force that moves the piston 5 in one direction does not result. Instead of the high-pressure chamber 17, a hose connection between the high-pressure connection 18 and the flow-through opening 44 could also be provided.

The same applies to the also formed as an annular space return chamber 15; it connects the flow opening 41 with the tank connection 16, without any force acting on the piston 5 acting. Again, a hose connection between the tank port 16 and the flow opening 41 may be provided.

To move back the piston against the working direction 11, the coupling rod 50 is moved by the linear direct motor 54 against the working direction of the end portion 34 of the spool 30 away. Due to the pressure prevailing in the pressure chamber 38 low pressure of the spool 30 is moved counter to the working direction 11. As in FIG. 3 illustrated, thereby opens a gap between the control edges 42 on the spool 30 and the control edges 45 on the piston 5, so that the working pressure chamber 13 is pressure-connected to the return chamber 15. Due to the low pressure prevailing in the low pressure chamber 19, a force counteracts the working direction 11 on the piston 5. The piston 5 can now move counter to the working direction 11, wherein the hydraulic fluid located in the working pressure chamber 13 through the passage window 48 in the return chamber 15 and there is displaced into the tank 22. The piston 5 and the spool 30 move so long against the working direction 11 until further movement of the spool 30 is prevented by abutment of the end portion 34 of the spool 30 to the coupling rod 50. Then, the spool shifts back into a position in which the gap between the control edges 42 and 45 is closed. It turns then again a rest position similar to the FIG. 1 illustrated rest position.

In typical use of the described hydraulic drive device in a punching machine for metal workpieces, the full working force of the piston 5 in the working direction 11 is not during the entire working cycle from forward and backward movement of the piston 5 is required. Rather, the full working force is only required when striking a piston rod 6 connected to the punching tool (not shown) on a workpiece (not shown) and during the penetration of the workpiece. In the described embodiment, it is therefore provided that the adjusting means 60 adjust the pressure of the high pressure supply 24 depending on the travel path, ie from the position of the piston 5.

In FIG. 4 the time course of the position of the piston 5 is shown together with the time course of the set by the adjusting means 60 pressure of the high-pressure supply 24. Starting from the retracted end position POSO of the piston 5, the piston 5 is moved in the working direction 11 up to the position POS1, in which the punching tool connected to the piston rod strikes the workpiece to be deformed. For this travel, the pressure of the high pressure supply 24 is set to a low value p1, which may be selected to be equal to that of the low pressure supply 26 in particular. The travel is detected by the displacement measuring system 62 and compared with a preset value, which corresponds for example to the distance of the punching tool in retracted end position of the piston 5 to the workpiece. If the piston has moved over the specified distance, then the punch meets the workpiece to be deformed. This happens at the in FIG. 4 POS1 position of the piston. Then, the adjusting means 60 increase the pressure of the high-pressure supply 24 to a value p2, which is significantly higher than p1 and typically corresponds to the maximum pressure of the high-pressure supply 24. This high pressure is maintained for the further movement of the piston 5 in the working direction 11 until the punching tool attached to the piston rod 6 has penetrated the workpiece (position POS2 of the piston 5 in FIG FIG. 4 ). Thus, the workload on the piston 5 decreases. If further movement of the piston 5 in the working direction 11 to the position POS3 is provided, the adjusting means 60 reduce the pressure of the high-pressure supply 24 to a value p3 which is less than the pressure p2 and in particular equal to the pressure of the low-pressure supply 26.

During the return movement of the piston 5 against the working direction 11, the spool 30 blocks a further flow of hydraulic fluid from the high-pressure supply 24 into the working pressure chamber 13. An energy-consuming volumetric flow of hydraulic fluid from the high-pressure supply 24 is therefore prevented. The return movement is effected only by a volume flow of hydraulic fluid from the low pressure supply 26.

The described embodiment of the invention reduces the energy consumption in typical use with repeated extension and retraction of the piston 5 considerably. This is done on the one hand in that the return movement of the piston 5 against the working direction 11 is basically caused by hydraulic fluid from an energy-saving low-pressure supply 26. On the other hand, the energy requirement is further reduced by the described, depending on the travel and / or the workload of the piston 5 high-pressure connection of the high-pressure supply 24.

Claims (15)

1. A hydraulic drive device (1), having a piston (5) guided in a cylinder chamber (8) along a work axis (10) and defining a working pressure chamber (13) that can be subjected to pressure by hydraulic fluid, and having a control means (29), guided in at least some portions in the piston (5) between various control states, for controlling the flow of hydraulic fluid from a high-pressure supply (24) into the working pressure chamber (13) for moving the piston in the working direction (11) and from the working pressure chamber (13) to a return chamber (15), characterized in that the region of the piston (5) remote from the working pressure chamber (13) defines a low-pressure chamber (19), which during the operation of the device is subjected to pressure by a low-pressure supply (26) for hydraulic fluid in such a manner that the piston (5) is moved back counter to the working direction (11) when the control means (29) connects the working pressure chamber (13) to the return chamber (15).
2. The drive device according to claim 1, characterized in that the low-pressure chamber (19) is separate from the high-pressure supply (24) regardless of the control state of the control means (29).
3. The drive device according to claim 1 or 2, characterized in that adjusting means (60) are provided, by means of which the pressure of the high-pressure supply (24) is adjustable as a function of the travel distance in the working direction (11) of the piston (5) and/or as a function of the workload of the piston (5).
4. The drive device according to claim 3, characterized in that the adjusting means (60) are embodied such that the pressure of the high-pressure supply (24) for moving the piston (5) in the working direction (11) from its returned terminal position to, or to shortly before, its taking up of a workload has a value p1 and after that, in particular during the workload, has a value p2, where p1 < p2.
5. The drive device according to claim 4, characterized in that the adjusting means (60) are embodied such that upon a further motion of the piston (5) in the working direction (11), after the workload has been overcome, the pressure of the high-pressure supply (24) has a value p3, where p3 < p2 and/or p3 = p1.
6. The drive device according to one of the foregoing claims, characterized in that a travel measurement system (62) for determining the travel distance of the piston (5) and/or a load measurement system for determining the workload of the piston (5) is provided.
7. The drive device according to one of the foregoing claims, characterized in that the control means (29), in the region in which it is guided in the piston (5), defines a pressure chamber (38) in the working direction (11), which chamber communicates in terms of pressure with the low-pressure chamber (19).
8. The drive device according to one of the foregoing claims, characterized in that the control means (29) is embodied as a control slide (30) that is guided in at least some portions in the interior of the piston (5) along the work axis (10), which slide has control edges (42, 43) which are embodied for cooperation with further control edges (45, 46) on the piston (5), in order to control the flow of the hydraulic fluid into or out of the working pressure chamber (13).
9. The drive device according to claim 8, characterized in that the control slide (30) is guided on the one hand, in the region of the piston (5) adjacent to the low-pressure chamber (19), in a cylindrical guide opening (36) and on the other hand, in the cylinder housing (3), in a further cylindrical guide opening (40), and the guide openings (36, 40) have the same diameter.
10. The drive device according to claim 8 or 9, characterized in that a coupling rod (50) for actuating the control slide (30) is provided in such a manner that the control slide (30) can be thrust in the working direction (11) of the piston by means of the coupling rod (50).
11. The hydraulic drive device according to claim 10, characterized in that the coupling rod (50) is connected to an electromechanical converter (54).
12. A method for operating a hydraulic drive device according to one of the foregoing claims, having a piston (5) guided displaceably in a cylinder chamber (8), which piston defines a working pressure chamber (13), and the working pressure chamber (13), for moving the piston (5) in the working direction (11), is subjected by hydraulic fluid to a high pressure PH, characterized in that for moving the piston (5) back counter to the working direction (11), a low-pressure chamber (19), which is defined by a region of the piston (5) remote from the working pressure chamber (13), is subjected to a low pressure PN, where PN <= PH.
13. The method according to claim 12, characterized in that the high pressure of the hydraulic fluid subjecting the working pressure chamber (13) to pressure is adjusted as a function of the travel distance of the piston (5) and/or as a function of the workload of the piston (5).
14. The method according to claim 12 or 13, characterized in that the low-pressure chamber (19) is subjected uninterruptedly to low pressure.
15. The method according to claim 12, 13 or 14, characterized in that the high pressure of the hydraulic fluid subjecting the working pressure chamber (13) to pressure for moving the piston (5) in the working direction (11) from its returned terminal position to, or to shortly before, its taking up of a workload has a value µl and after that, in particular during the workload, has a value p2, where µl < p2, and for the case that a further motion of the piston (5) in the working direction (11) after the workload has been overcome is contemplated, the high pressure has a value p3, where p3 < p2 and/or p3 = 1.

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