HYDRAULIC SWITCHING FOR ONE HYDRAULIC AXLE AND ONE HYDRAULIC AXLE

Description

[0001] The invention relates to a hydraulic circuit for a hydraulic axle and a hydraulic axle.

[0002] For the purposes of this application, a hydraulic axis is understood to mean a hydraulic actuator, e.g., a hydraulic cylinder, as well as the hydraulic or electro-hydraulic control arrangement or circuit that controls the actuator with fluid. Such hydraulic axes are compact, powerful, and high-performance drives. These can be used in a variety of industrial automation applications, e.g., presses, plastics processing machines, bending machines, etc. In particular, such drives are designed to implement at least two motion sequences: a rapid transfer movement—hereinafter referred to as rapid traverse or rapid stroke—and a force-applying working movement—hereinafter referred to as power traverse, working stroke, or pressing traverse.

[0003] A known hydraulic axis is shown in the applicant's application DE 10 2009 043 034. A master cylinder, a rapid-action cylinder, and a reversible hydraulic machine are interconnected in a preloaded hydraulic system. Valves can be used to change the interconnection of the components so that one of several hydromechanical transmission ratios, predetermined by factors such as piston areas, is selected. This allows the aforementioned rapid strokes or working strokes to be carried out efficiently.

[0004] EP 1 580 437 A1 discloses a hydraulic circuit for a multi-surface cylinder. A pressure control valve controls the supply of a pressure medium to the multi-surface cylinder depending on a pressure difference between two supply lines that are connectable to chambers of the multi-surface cylinder. The pressure control valve controls a pressure-controlled valve with three switching positions configured to connect / disconnect the supply lines to / from the chambers. According to one embodiment, of the four chambers of the multi-surface cylinder, the two chambers defined by a piston rod of the multi-surface cylinder are directly connected in a communicating manner.

[0005] WO 2007 / 083517 A1 also discloses a hydraulic circuit for a multi-surface cylinder, wherein several valves are configured to connect / disconnect the supply lines to / from the chambers.

[0006] FR 2 764 008 A1 discloses an electrohydrostatic servo drive comprising a multi-surface cylinder with three chambers, a first partial circuit and a second partial circuit. The second partial circuit comprises a pressure accumulator and a supply device and a regulating means for regulating pressure, and it acts on the third chamber. The first partial circuit has a bidirectional rotary machine that generates a differential pressure between the other two chambers to move a piston rod. The first partial circuit is supplied with pressure from the third chamber.

[0007] CA 2 279 435 A1 discloses a linear actuator with a bidirectional pump, a hydraulic circuit and a multi-surface cylinder, wherein a piston-side chamber is supplied with pressure medium from a bottom end via a transfer tube, a piston rod-internal chamber and a piston-internal line.

[0008] WO 2011 / 079333 A2 discloses a drive device for a bending press, comprising a closed hydraulic system having a hydraulic pump with a controllable drive motor, at least one control valve and at least one hydraulic linear actuator.

[0009] The disadvantage of this solution is that the hydraulic axis is comparatively complex in terms of device technology.

[0010] In contrast, the invention is based on the object of creating a hydraulic circuit for a hydraulic axle that results in a hydraulic axle with a relatively simple design in terms of device technology. A further object of the invention is to create a hydraulic axle with a simple design in terms of device technology.

[0011] This object is achieved with regard to the hydraulic circuit according to the features of patent claim 1 and with regard to the hydraulic axis according to the features of the independent patent claim.

[0012] Other advantageous developments of the invention are the subject of further subclaims.

[0013] According to the invention, a hydraulic circuit for a multi-surface cylinder is provided. A piston of the multi-surface cylinder has two retraction surfaces and one extension surface, each of which delimits a pressure chamber. The pressure chambers are supplied with and released with pressure medium via a reversible, in particular variable-speed, in particular pivotable hydraulic machine and via control valves. These are provided for switching between a rapid traverse and a power traverse of the multi-surface cylinder. For rapid traverse, the control valves switch a first retraction surface and the extension surface into regeneration, i.e. the surfaces or their pressure chambers are essentially pressure-balanced. The regeneration of the retraction surface and the extension surface is possible in both directions of travel of the piston of the multi-surface cylinder. For the power traverse, both retraction surfaces or the pressure chambers can be connected together via the control valves.

[0014] This solution has the advantage that the piston of the multi-surface cylinder can be easily extended and retracted at rapid traverse. When the piston extends at rapid traverse, pressure fluid can be released from the pressure chamber of the second retraction surface via the hydraulic machine and the control valves and supplied to the pressure chamber of the extension surface. Pressure fluid displaced from the pressure chamber of the first retraction surface by regeneration is also supplied to the pressure chamber of the extension surface. Conversely, when the piston retracts at rapid traverse, the pressure chamber of the second retraction surface is supplied with pressure fluid, while pressure fluid is released from the pressure chamber of the extension surface. Pressure fluid released by regeneration is also supplied to the pressure chamber of the first retraction surface.In power mode, when the piston extends, pressure fluid can be advantageously released from both pressure chambers of the retraction surfaces via the control valves via the hydraulic machine and supplied to the pressure chamber of the extension surface. Conversely, when the piston retracts in power mode, pressure fluid can be released from the pressure chamber of the extension surface via the hydraulic machine and supplied to the pressure chambers of the retraction surfaces via the control valves.

[0015] The circuit according to the invention thus enables the piston of the multi-surface cylinder to be moved in both directions of movement at high speed and low force, or at low speed and high force. Furthermore, the control valves can be used to shut off the pressure chamber of the extension surface from a high-pressure side of the hydraulic machine, at least in the power mode when the piston extends, in order to maintain the force of the multi-surface cylinder, thus eliminating the need for additional energy supply via the hydraulic machine.

[0016] In addition, a first pump connection of the hydraulic machine can be connected to a compensating reservoir via a first storage valve and a second pump connection of the hydraulic machine can be connected to a compensating reservoir via a second storage valve.

[0017] It is advantageous if the sum of the retraction areas corresponds approximately to the extension area.

[0018] In a further embodiment of the invention, a first control valve is provided as control valves in the pressure medium flow path between the hydraulic machine and the pressure chamber of the first retraction surface and a second control valve is provided fluidically in series with the first control valve between the latter and the pressure chamber of the extension surface.

[0019] In addition to the control valves, a shut-off valve is provided. This is located in the pressure medium flow path between the hydraulic machine and the pressure chamber of the extension surface. When the shut-off valve is closed, this advantageously prevents pressure medium from being released from the pressure chamber of the extension surface when the second control valve is simultaneously closed, thus allowing pressure to be essentially maintained at the extension surface without the use of the hydraulic machine.

[0020] Preferably, a switching valve is provided in the pressure medium flow path between the hydraulic machine and the second retraction surface. The switching valve, together with the control valves, can prevent the release of pressure medium from the pressure chambers of the retraction surfaces. If all valves except the second control valve are closed, the pressure chambers of the retraction surfaces and the extension surface can be fluidically shut off from the hydraulic machine. Thus, by preferably leak-free locking of the pressure medium in the pressure chambers, the piston can be held in any position without the need for pressure medium to be supplied via the hydraulic machine. The locking can occur, for example, after a desired pressing pressure has been reached. The locking stiffens the hydraulic axis.

[0021] According to the invention, the compensating accumulator, for example, a hydraulic accumulator with a preload, is provided. This accumulator is connected via the first accumulator valve to a pressure medium flow path between the hydraulic machine and the first control valve, and via the second accumulator valve to a pressure medium flow path between the hydraulic machine and the shut-off valve. The preload for the compensating accumulator can be, for example, approximately 1, approximately 2, approximately 3, or approximately 5 bar.

[0022] The compensating reservoir can serve to compensate for differential quantities and / or compression volumes. For example, a fluid displacement quantity of the pressure chamber of the extension surface less a fluid displacement quantity of the pressure chamber of the second retraction surface can correspond to at least 70, 80, 90, 95, or 99% of a fluid intake quantity of the pressure chamber of the first retraction surface. The compensating reservoir can then be provided to provide the differential quantity. It is also conceivable that the fluid displacement quantity of the pressure chamber of the extension surface less the fluid displacement quantity of the pressure chamber of the second retraction surface corresponds to at least 101, 110, 115, 120, or 130% of the fluid intake quantity of the pressure chamber of the first retraction surface, whereby in this case the compensating reservoir is provided to absorb the differential quantity. Of course, it is also conceivable that the differential quantity can also be zero.

[0023] The accumulator valves allow the hydraulic machine to charge the compensating accumulator by closing, for example, the control valves, the shut-off valve, and the switching valve, so that charging of the compensating accumulator occurs without affecting the multi-surface cylinder. If, for example, the switching valve and the control valves are open and the shut-off valve is closed, the hydraulic machine can, when an accumulator valve is open, pump pressure medium from the compensating accumulator to the pressure chambers of the retraction surfaces and the extension surface, thereby preloading the multi-surface cylinder and leading to a fixed position of its piston. The multi-surface cylinder can therefore be preloaded without the supply of external pressure medium. Furthermore, it is possible to move the piston of the multi-surface cylinder under a certain preload, which greatly accelerates the build-up of force at the end of a piston stroke.The compensating reservoir can also be used advantageously during decompression of the multi-surface cylinder, in which pressure medium is pumped from the pressure chambers of the retraction surfaces or the extension surface to be decompressed into them via the hydraulic machine.

[0024] According to the invention, a check valve is provided, fluidically parallel to each accumulator valve, that closes towards the equalizing accumulator. The check valves can then serve as anti-cavitation valves. Furthermore, the check valves eliminate the need to open one of the accumulator valves when preloading the multi-surface cylinder.

[0025] In a further embodiment of the hydraulic circuit, a control valve is provided. This valve allows the pressure chamber of the first retraction surface to be connected to the first compensating accumulator, and the pressure chamber of the extension surface to be connected to a second compensating accumulator. Furthermore, the control valve allows the pressure chamber of the first retraction surface to be connected to the pressure chamber of the second compensating accumulator, and the pressure chamber of the extension surface to be connected to the first compensating accumulator. The second compensating accumulator can also be, for example, a hydraulic accumulator with a preload. The control valve allows for fine positioning of the piston of the multi-surface cylinder, while the hydraulic machine can be inactive.

[0026] It is conceivable that the second compensating reservoir can be fluidically connected to the hydraulic machine via another accumulator valve, in particular for charging. Preferably, the second compensating reservoir is connected to the pressure medium flow path between the shut-off valve and the hydraulic machine via its accumulator valve.

[0027] The control valve can, for example, be a pulse width modulated control valve, which in particular has no leakage.

[0028] Preferably, the switching valve is arranged fluidically parallel to the first control valve.

[0029] To prevent overpressure in the hydraulic circuit, at least one pressure relief valve is provided. It is conceivable to protect the pressure chambers of the multi-surface cylinder with one or more pressure relief valves.

[0030] In the hydraulic machine, the speed and / or displacement are advantageously adjustable, which in turn allows the extension and retraction speed of the piston of the multi-surface cylinder to be adjusted. The hydraulic machine is advantageously driven by a drive unit in the form of an electric servomotor.

[0031] Preferably, the control valves, the shut-off valve, the switching valve and the storage valves are designed as directional seat valves.

[0032] The hydraulic axle is designed as a structural unit. The structural unit of the hydraulic axle comprises, in particular, the hydraulic circuit according to the invention, the multi-surface cylinder controllable via the circuit, and a control block containing the valves—in particular, the control valves, the shut-off valve, the switching valve, and the accumulator valves. Furthermore, the structural unit of the hydraulic axle comprises the hydraulic machine and a drive unit, which can be, in particular, the electric servomotor. Additionally, the structural unit can include the compensating volumes.

[0033] The design of the hydraulic axle as a modular unit makes it extremely compact and allows for flexible installation in a wide variety of positions. By arranging the hydraulic machine and drive unit within the modular unit, it is not necessary to provide the unit with any external power other than electrical power. The hydraulic axle can be designed as a modular unit with a closed hydraulic circuit, which can then be hermetically sealed from its environment.

[0034] Advantageously, at least two cylinder ports for the multi-surface cylinder are designed as connection surfaces or bores on the control block. This eliminates the need for piping for these two cylinder ports. The multi-surface cylinder can then be flanged directly to the control block, increasing the compactness of the hydraulic axis.

[0035] Furthermore, the compensating accumulators can be mounted directly on the control block to increase the compactness of the hydraulic axis.

[0036] In a further embodiment of the hydraulic axis, the control block serves as the machine housing for the hydraulic machine. This can be recessed into the control block, with an installation space for the hydraulic machine in the control block serving as a leakage oil collector.

[0037] A fluidic connection of the hydraulic machine in the control block is made simply, preferably via pipe nipples or pipe plug-in nipples.

[0038] It is conceivable that a displacement sensor for detecting the piston position of the multi-surface cylinder, for example, could be integrated into the cylinder, to control the multi-surface cylinder. It would also be conceivable to locate the displacement sensor outside the multi-surface cylinder. Pressure sensors can be provided to measure the pressures in the multi-surface cylinder.

[0039] Preferred embodiments of the invention are explained in more detail below with reference to the drawings. They show: Figure 1 in a hydraulic circuit diagram, a hydraulic axle according to the invention with a hydraulic circuit according to the invention according to a first embodiment, Figure 2 an enlarged section of Figure 1 in the area of ​​a multi-surface cylinder and Figure 3in a hydraulic circuit diagram, the hydraulic axle according to the invention with the hydraulic circuit according to the invention according to a second embodiment.

[0040] According to Figure 1 The hydraulic axis 1 according to the invention is shown. This has a multi-surface cylinder 2, which is used particularly for hydraulic presses. A hydraulic circuit 6 is provided for adjusting a piston 4 of the multi-surface cylinder 2. This circuit is arranged in a control block 8 and, together with the multi-surface cylinder 2 and a drive unit 10 in the form of an electric servomotor, forms a structural unit.

[0041] The drive unit 10 is connected to a hydraulic machine 14 via a drive shaft 12. The hydraulic machine 14 is installed in the hydraulic axis 1 as a pivotable hydraulic pump, allowing its delivery volume to be adjusted. The hydraulic machine 14 is advantageously configured within the control block 8, which forms a pump housing for the hydraulic machine 14. An installation space in the control block 8 for the hydraulic machine 14 then serves as a leakage oil collector. Pipe nipples are provided for easily connecting the hydraulic machine 14 in the installation space of the control block 8. The hydraulic machine 14 is reversible and can be driven by the drive unit 10 in both directions of rotation. The drive unit 10 is designed such that it can drive the hydraulic machine 14 at an adjustable speed.With the hydraulic machine 14, a first, second and third pressure chamber 16, 18 and 20 of the multi-surface cylinder 2 can be supplied with pressure medium and pressure medium can be released from the pressure chambers 16, 18 and 20 via the hydraulic machine 14.

[0042] The piston 4 of the multi-surface cylinder 2 is slidably guided in a cylinder housing 24 of the multi-surface cylinder 2. Based on the enlarged illustration in Figure 2 The multi-surface cylinder 2 is explained in more detail below.

[0043] According to Figure 2The piston 4 of the multi-surface cylinder 2 has a piston section 26 that separates the annular third pressure chamber 20 from an air chamber 28 in the cylinder housing 24. The air chamber 28 is preferably pressure-equalized with the surroundings of the hydraulic axis 1 via a cylinder vent 30. A rod section 32 of the piston 4 penetrates the cylinder housing 24 and thus the third pressure chamber 20 in a direction away from the air chamber 28. The piston 4 has a cylindrical interior into which a guide rod 34 projects. This extends approximately coaxially to the cylinder housing 24, starting from a bottom surface 36 of the cylinder housing 24 which delimits the air space 28, passes through the piston section 26 via a through opening 38 and opens into the cylinder chamber of the piston 4. At its end section arranged in the cylinder chamber of the piston 4, the guide rod 34 has a radial collar 40 whose outer diameter corresponds approximately to the inner diameter of the cylinder chamber of the piston 4.With this, the guide rod 34 in the piston 22 separates the first pressure chamber 16 from the second annular pressure chamber 18. Due to the guide rod 34, the air chamber 28 is also annular. The guide rod 34 is somewhat shorter in the axial direction than the cylinder housing 24 and ends approximately at the beginning of a through-opening 42 in the cylinder housing 24, through which the rod section 32 of the piston 22 is slidably guided.

[0044] The first pressure chamber 16 within the piston 22 is delimited by an extension surface A1 acting in the extension direction, which faces toward the guide rod 34. The third pressure chamber 20 is delimited by a first outer retraction surface A3 formed on the piston section 26 of the piston 22. The second pressure chamber 18 is delimited by a second inner retraction surface A2, which in turn is formed opposite the extension surface A1 within the piston 22. It extends in a ring around the guide rod 34. The retraction surfaces A2 and A3 act in a retraction direction of the piston 22. The sum of the retraction surfaces A2 and A3 approximately corresponds to the extension surface A1.

[0045] A first pressure channel 42 opens into the first pressure chamber 16, which extends axially through the guide rod 34 and is connected to a first pressure line 44 of the control block 8. The second pressure chamber 18 is fluidically connected to a second pressure channel 46, which is also formed in the guide rod 34 and extends from the control block 8 in the direction of the radial collar 40 and opens approximately radially into the second pressure chamber 18 in front of the radial collar 40. The second pressure channel 46 is connected to a second pressure line 48 of the control block 8. The third pressure chamber 20 is connected to a third pressure line 50, which is connected on the one hand to the cylinder housing 24 and on the other hand to the control block 8. At the control block 8, the third pressure line 50 is connected to a pressure line 52 formed in the control block 8. The first and second pressure lines 44, 48 open into an outer surface of the control block 8.The mouth area serves as a cylinder connection for the multi-surface cylinder 2 and is designed as a connection surface 53.

[0046] The hydraulic machine 14 is connected according to Figure 1 to the first pump connection A of which a first pump line 54 is connected and to the second pump connection B of which a second pump line 56 is connected. The first pump line 54 is connected to a pump connection P of a first control valve 58. This has, in addition to the pump connection P, a working connection X, which is connected to the pressure line 52, which in turn is fluidically connected to the third pressure chamber 20 of the multi-surface cylinder 2 from Figure 2is in pressure medium connection. The first control valve 58 is designed as a 2 / 2-way valve. A valve piston of the first control valve 58 is acted upon by a spring force via a valve spring 60 in the direction of a closed position, in which a pressure medium connection between the pump connection P and the working connection X is interrupted. In the direction of an open position, the valve spool of the control valve 58 can be acted upon by a force, in particular a magnetic force, via an actuator 62, which is, for example, an electric lifting magnet. In the open position, the pump connection P is in pressure medium connection with the working connection X.

[0047] A second control valve 64 is provided fluidically in series with the first control valve 58, which also has a working connection X and a pump connection P. The working connection X is connected to the pressure line 52 via a branch line 66. The pump connection P of the second control valve 64 is connected to the first pressure line 44 via a further branch line 68 and is thus connected to the first pressure chamber 16, see Figure 2, in pressure medium connection. The second control valve 64 is also a 2 / 2-way valve, but unlike the first control valve 58, its valve spool can be moved into an open position via the valve spring 60 and into a closed position via the actuator 62. The valve spool of the second control valve 64 is thus in the open position in the de-energized state, in which the pump connection P is fluidly connected to the working connection X and thus the third pressure chamber 20 is fluidly connected to the first pressure chamber 16.

[0048] The second pressure line 48, which is fluidically connected to the second pressure chamber 18, is connectable to the first pump line 54 via a switching valve 70. The switching valve 70 corresponds to the first control valve 58 and has a working port X and a pump port P. The second pressure line 48 is connected to the working port X, and the pump port P is connected to the first pump line 54 via a branch line 72.

[0049] The first pressure line 44 and thus also the branch line 68 are connected to the second pump line 56 via a shut-off valve 74. This is designed correspondingly to the first control valve 58 and has a working connection X, to which the first pressure line 44 is connected, and a pump connection P, to which a branch line 76 is connected, which is connected to the second pump line 56.

[0050] The pump lines 54 and 56 connected to the hydraulic machine 14 can further be connected to a compensating accumulator 78, which can be designed as a hydraulic accumulator and is preferably arranged or formed in the control block 8. It would also be conceivable to connect this to the control block 8. For the fluidic connection of the compensating accumulator 78, a first accumulator line 80 branches off from the first pump line 54 and a second accumulator line 82 branches off from the second pump line 56. The first accumulator line 80 is connected to a pump connection P of a first accumulator valve 84 and the second accumulator line 82 is connected to a pump connection P of a second accumulator valve 86. The accumulator valves 84 and 86 are designed correspondingly to the first control valve 58 and each have an accumulator connection S. These are connected to a common accumulator line 88, which in turn is connected to an accumulator connection S of the compensating accumulator 78.Hydraulically parallel to the first accumulator valve 84, a first suction line 90 is provided, which is arranged on the accumulator line 88 and on the first pump line 54. A first check valve 92, which closes in the direction of the equalizing accumulator 78, is arranged in the first suction line 90. The first suction line 90 with the first check valve 92 thus branches off from the first pump line 54 in the pressure medium flow path between the first control valve 58 and the hydraulic machine 14. A further second suction line 94 is arranged fluidically parallel to the second accumulator valve 86 between the equalizing accumulator 78 and the second pump line 56 and likewise has a second check valve 96 closing in the direction of the equalizing accumulator 78. The second suction line 94 is thus connected to the second pump line 56 in the pressure medium flow path between the hydraulic machine 14 and the shut-off valve 74.

[0051] The design of the hydraulic axis 1 as a structural unit makes it extremely compact. The control block 8 houses the hydraulic machine 14, the compensating reservoir 78, the control valves 58, 64, the switching valve 70, the shut-off valve 74, and the anti-cavitation valves 92, 96. The multi-surface cylinder 2 and the drive unit 10 are simply connected to the control block.

[0052] The functionality of hydraulic axis 1 is explained in more detail below. Extend rapid traverse:

[0053] When piston 4 is advanced in rapid motion, the valve spool of the switching valve 70 and the shut-off valve 74 are in their open position. The other valves 58, 64, 84, and 86 are de-energized. The hydraulic machine 14 conveys pressure medium from its pump connection A to its pump connection B. It thus conveys pressure medium from the second pressure chamber 18 via the switching valve 70, the first pump line 54 to the second pump line 56, and from there via the shut-off valve 74 into the first pressure chamber 16. The pressure chamber 16 is fluidly connected to the third pressure chamber 20 via the second control valve 64 and is pressure-balanced. The extension surface A1 of the piston 4, see Figure 2, is thus subjected to a higher pressure in the extension direction via the first pressure chamber 16 than the second retraction surface A2 of the piston 4 in the closing direction, which is why the piston 4 extends. The pressure medium displaced from the third pressure chamber 20 is supplied to the first pressure chamber 16 via the second control valve 64. By connecting the first pressure chamber 16 to the third pressure chamber 20, the extension surface A1 and the first retraction surface A3 are switched to regeneration. Extend power gear:

[0054] When the piston 4 of the hydraulic axis 1 is extended in the power mode, the first control valve 58, the switching valve 70, and the shut-off valve 74 are energized via their actuators, thus placing their valve spools in their open position. Furthermore, the second control valve 64 is energized, placing its valve spool in the closed position. The second and third pressure chambers 18, 20 are interconnected via the first control valve 58 and the switching valve 70. The hydraulic machine 14 conveys pressure fluid from its pump connection A to its pump connection B, thereby discharging pressure fluid from the second and third pressure chambers 18, 20 and supplying the first pressure chamber 16 with it via the shut-off valve 74. The piston 4 thus extends in the power mode. Decompression after power gear:

[0055] During decompression, the hydraulic machine 14 pumps pressure fluid from its pump connection B to its pump connection A. The shut-off valve 74 and the first accumulator valve 84 are energized, placing their valve spool in its open position. The second control valve 64 is also energized, placing its valve spool in its closed position. The first control valve 58, the switching valve 70, and the second accumulator valve 86 are de-energized, and their valve spool is in its closed position. The hydraulic machine 14 now pumps pressure fluid from the first pressure chamber 16 via the shut-off valve 74 into the first pump line 54 and from there via the first accumulator valve 84, the accumulator line 88 to the equalizing accumulator 78. Rapid traverse:

[0056] In rapid retraction, the hydraulic machine 14 delivers pressure medium from its pump connection B to its pump connection A. The shut-off valve 74 and the switching valve 70 are energized, whereby their valve spool is in its open position. The first and second control valves 58, 64 and the first and second accumulator valves 84, 86 are de-energized. The valve spool of the second control valve 64 is thus in its open position. The extension surface A1 and the first retraction surface A3 are connected via the second control valve 64, see Figure 2 , switched to regeneration. The hydraulic machine 14 now conveys pressure medium from the first pressure chamber 16 via the shut-off valve 74 and the switching valve 70 to the second pressure chamber 18, causing the piston 4 to move in the retraction direction. Pressure medium displaced from the first pressure chamber 16 is additionally supplied to the third pressure chamber 20 via the second control valve 64 due to the regeneration. Engage power gear:

[0057] The hydraulic machine pumps pressure medium from pump connection B to pump connection A. The first control valve 58, the second control valve 64, the switching valve 70, and the shut-off valve 74 are energized. The valve spool of the second control valve 64 is thus in its closed position, and the valve spools of the first control valve 58, the switching valve 70, and the shut-off valve 74 are in their open position. The accumulator valves 84 and 86 are de-energized, meaning their valve spools are in the closed position. The hydraulic machine 14 then pumps pressure medium from the first pressure chamber 16 via the shut-off valve 74 into the first pump line 54, and from there via the first control valve 58 to the third pressure chamber 20, and via the switching valve 70 to the second pressure chamber 18. Any missing compression volume is sucked in from the equalizing accumulator 78 via the second check valve 96. Piston 4 then retracts in power gear. Decompression after power gear:

[0058] The hydraulic machine 14 pumps pressure medium from pump connection A to pump connection B. The first and second control valves 58, 64, the switching valve 70 and the second storage valve 86 are energized. The valve spool of the second control valve 64 is thus in its closed position and the valve spools of the first control valve 58, the switching valve 70 and the second storage valve 86 are in their open position. The valve spool of the shut-off valve 74 and the first storage valve 84 are each de-energized in their closed position. The hydraulic machine 14 thus pumps pressure medium from the second and third pressure chambers 18, 20 into the second pump line 56 and from there via the second storage valve 86 and the storage line 88 to the equalizing accumulator 78, thereby charging the latter. Pressure holding phase:

[0059] During the pressure-holding phase, only the second control valve 64 is energized, causing the valve spools of the control valves 58, 64, the switching valve 70, the shut-off valve 74, and the accumulator valves 84, 86 to be in their closed position. The closed position of these valve spools fluidically decouples the pressure chambers 16 to 20 from the hydraulic machine 14, and the pressure medium cannot escape from them. The piston 4 is thus clamped in its position, preventing it from extending or retracting. Pressure build-up phase for preloading:

[0060] Here, the first control valve 58 and the switching valve 70 are energized, whereby their valve spools are in their open position. All other valves 74, 84, 86 and 64 are de-energized. The valve spool of the second control valve 64 is thus also in its open position. The hydraulic machine 14 conveys pressure medium from its pump connection B to its pump connection A. Pressure medium is thus conveyed from the equalizing reservoir 78 via the second check valve 96 into the first pump line 54 and from there via the switching valve 70, the first control valve 58 and the second control valve 64 into the pressure chambers 16 to 20. The open valves 58, 64 and 70 equalize the pressure. The retraction surfaces A2 and A3 and the extension surface A1, see Figure 2 , are thus preloaded with the same pressure.

[0061] In Figure 3According to a second embodiment, the hydraulic axis 98 additionally has a control valve 100 and a compensating accumulator 102 with a third accumulator valve 104.

[0062] The control valve 100 is designed as a 4 / 3-way valve and has a first accumulator port S1, a second accumulator port S2, a first working port X1, and a second working port X2. A valve spool of the control valve 100 is spring-centered by two valve springs 106 and 108 in its central closed position, in which the ports S1, S2, X1, and X2 are separated from one another. The valve spool can be displaced by an electric actuator 110 toward first open positions, in which the first working port X1 is connected to the first accumulator port S1 and the second working port X2 is connected to the second accumulator port S2.In the opposite direction, the valve spool can be moved by a further electric actuator 112, starting from its closed position, toward second open positions in which the first working port X1 is connected to the second accumulator port S2 and the second working port X2 is connected to the first accumulator port S1. The first working port X1 is connected via a branch line 114 to the branch line 66 and thus to the pressure line 52 connected to the third pressure chamber 20. The second working port X2 of the control valve 100 is connected to the first pressure line 44 via a branch line 116 and is thus in pressure communication with the first pressure chamber 16. The second accumulator port S2 is connected to the accumulator line 88 via a branch line 118 and is thus in pressure communication with the equalizing accumulator 78.The first storage terminal S1 is connected to a storage line 120, which in turn is connected to a storage terminal S of the equalization storage 102.

[0063] The storage line 120 is connected to the second pump line 56 via the third storage valve 104. The third storage valve 104 is configured similarly to the first control valve 58 and thus has a pump connection P and a working connection X. The pump connection P is connected to the second pump line 56 via a branch line 122, and the working connection X is connected to the storage line 120 via a branch line 124.

[0064] The control valve 100 is continuously adjustable and is used for the fine positioning of the piston 4 of the multi-surface cylinder 2.

[0065] The operation of the hydraulic axis 98 according to the second embodiment is explained below. Storage loading mode:

[0066] With the hydraulic axle 98 from Figure 3 can be used in addition to the hydraulic axis 1 Figure 1a storage charging mode can be executed. To charge the second equalizing accumulator 102, the third accumulator valve 104 is energized, whereby its valve spool is in its open position. All other valves except for the second control valve 64 are de-energized, whereby its valve spool is in its closed position, corresponding to the valve spools of the other valves 58, 70, 84, 86, 74, 100. The hydraulic machine 14 pumps pressure medium from pump connection A to pump connection B and thus from the first equalizing accumulator 78 via the first check valve 92 into the second pump line 56 and from there via the third accumulator valve 104 into the second equalizing accumulator 102. This continues until the desired pressure in the equalizing accumulator 102 is reached.After the desired pressure is reached, the current supply to the third storage valve 104 is interrupted and its valve slide is moved into its closed position, whereby the pressure medium remains in the equalizing reservoir 102. Regular operation:

[0067] During control operation of the hydraulic axis 98, the switching valve 70 and the second control valve 64 are energized. As a result, the valve spool of the switching valve 70 is in its open position and the valve spool of the control valve 64 is in its closed position. The valve spools of the first control valve 58, the shut-off valve 74 and the accumulator valves 84, 86 and 104 are also in their closed position. The hydraulic machine 14 is not driven in this case. Via the control valve 100, either the first pressure chamber 16 can be connected to the equalizing accumulator 102 or the third pressure chamber 20 can be connected to the equalizing accumulator 120. If the first pressure chamber 16 is connected to the equalizing accumulator 102, the valve spool of the control valve 100 is in the open positions in which the second working port X2 is connected to the first accumulator port S1.The third pressure chamber 20 is then connected to the second pressure chamber 18 via the control valve 100, the branch line 118, the first check valve 92, and the switching valve 70. This allows pressure medium to flow from the third pressure chamber 20 to the second pressure chamber 28.

[0068] If the third pressure chamber 20 is in pressure communication with the second compensating accumulator 102, the valve spool of the control valve 100 is in the open position, in which the first working port X1 is connected to the first accumulator port S1 and the second working port X2 is connected to the second accumulator port S2. The first pressure chamber 16 is then in pressure communication with the second pressure chamber 18 via the control valve 100, the branch line 118, the first check valve 92, and the switching valve 70, whereby pressure medium can then flow from the first pressure chamber 16 into the second pressure chamber 18.

[0069] The control valve thus enables position control of the piston 4 by alternately connecting the pressure chambers 16 and 20 to the second compensating accumulator 102. List of reference symbols

[0070] 1 hydraulic axis 2 multi-surface cylinder 4 piston 6 hydraulic circuit 8 control block 10 drive unit 12 drive shaft 14 hydraulic machine 16 first pressure chamber 18 second pressure chamber 20 third pressure chamber 24 cylinder housing 26 piston section 28 air chamber 30 cylinder opening 32 rod section 34 guide rod 36 base surface 38 through-hole 40 radial collar 42 first pressure channel 44 first pressure line 46 second pressure channel 48 second pressure line 50 third pressure line 52 pressure line 53 connection surface 54 first pump line 56 second pump line 58 first control valve 60 valve spring 62 actuator 64 second control valve 66 branch line 68 branch line 70 switching valve 72 branch line 74 Shut-off valve 76 Branch line 78 Compensation accumulator 80 First accumulator line 82 Second accumulator line 84 First accumulator valve 86 Second accumulator valve 88 Accumulator line 90 First suction line 92 First check valve 94 Second suction line 96 Second check valve 98 Hydraulic axis 100 Control valve 102 Compensation accumulator 104 ThirdAccumulator valve 106Valve spring 108Valve spring 110Actuator 112Actuator 114Branch line 116Branch line 118Branch line 120Accumulator line 122Branch line 124Branch line A1Extension surface A2Second retraction surface A3First retraction surface A, BPump connection PPump connection XWorking connection SStorage connection S1First storage connection S2Second storage connection X1First working connection X2Second working connection

Claims

1. Hydraulic circuit for a multi-surface cylinder (2), which has a piston (4) with two retraction surfaces (A2, A3) and a deployment surface (A1), wherein the circuit (6) has a hydraulic machine (14) and control valves (58, 64) for switching over between a rapid-traverse stroke and a force stroke of the piston (4), wherein the first retraction surface (A3) and the deployment surface (A1) can be switched to regeneration using the control valves (58, 64) for the rapid-traverse stroke, and wherein both retraction surfaces (A2, A3) can be interconnected using the control valves (58, 64) for the force stroke, wherein the hydraulic machine (14) is reversible, wherein a first control valve (58) of the control valves (58, 64) is provided in the pressure medium flow path between the hydraulic machine (14) and the first retraction surface (A3) and a second control valve (64) of the control valves (58, 64) is provided fluidically in series with the first control valve (58) in the pressure medium flow path between this first control valve and the deployment surface (A1), wherein a shut-off valve (74) is provided in the pressure medium flow path between the hydraulic machine (14) and the deployment surface (A1), and wherein a compensating accumulator (78) is provided, characterized in that the compensating accumulator (78) is connected via a first accumulator valve (84) to a pressure medium flow path between the hydraulic machine (14) and the first control valve (58) and via a second accumulator valve (86) to a pressure medium flow path between the hydraulic machine (14) and the shut-off valve (74), and in that a check valve (92, 96) which closes towards the compensating accumulator (78) is provided fluidically in parallel with respect to a respective accumulator valve (84, 86).

2. Hydraulic circuit according to Claim 1, wherein a switching valve (70) is provided in the pressure medium flow path between the hydraulic machine (14) and the second retraction surface (A2).

3. Hydraulic circuit according to Claim 1 or 2, wherein a control valve (100) is provided, by way of which the first retraction surface (A3) can be connected to the first compensating accumulator (78) and the deployment surface (A1) can be connected to a second compensating accumulator (102) and by way of which the first retraction surface (A3) can be connected to the second compensating accumulator (102) and the deployment surface (A1) can be connected to the first compensating accumulator (78).

4. Hydraulic circuit according to Claim 2 or 3, wherein the switching valve (70) is arranged fluidically in parallel with respect to the first control valve (58).

5. Hydraulic circuit according to any of the preceding claims, wherein a rotational speed and / or a swept volume of the hydraulic machine (14) are / is adjustable.

6. Hydraulic axle, which comprises, as one structural unit, a hydraulic circuit (6) according to any of the preceding claims, the multi-surface cylinder (2) which can be controlled via the circuit (6) and has two retraction surfaces (A2, A3) and a deployment surface (A1), a control block (8) comprising the valves (58, 64, 70, 74, 84, 86, 100), and a drive unit (10) for the hydraulic machine (14).

7. Hydraulic axle according to Claim 6, wherein at least two cylinder connections for the multi-surface cylinder (2) are formed on the control block (8) as connection surfaces (53) or bores.

8. Hydraulic axle according to Claim 6 or 7, wherein at least one compensating accumulator (78, 102) is mounted on the control block (8).

9. Hydraulic axle according to any of Claims 6 to 8, wherein the control block (8) is used as a machine housing for the hydraulic machine (14).

10. Hydraulic axle according to Claim 9, wherein the connection of the hydraulic machine (14) in the control block (8) is made via pipe nipples.