EP2328747A1

EP2328747A1 - Accumulator-free hydraulic drive system for a consumer and comprising the same, especially for hydraulic presses, and method for hydraulically driving a consumer without an accumulator

Info

Publication number: EP2328747A1
Application number: EP09778039A
Authority: EP
Inventors: Manfred Mitze
Original assignee: MAE MASCHINEN- und APPARATEBAU GOETZEN GMBH&CO KG; MAE Maschinen und Apparatebau Goetzen GmbH
Current assignee: MAE Maschinen und Apparatebau Goetzen GmbH
Priority date: 2008-08-21
Filing date: 2009-08-21
Publication date: 2011-06-08
Anticipated expiration: 2029-08-21
Also published as: DE102008039011A1; EP2732959A3; EP2328747B1; WO2010020427A1; EP2732959A2; DE102008039011B4; EP2732959B1; ES2693422T3; ES2541670T3

Abstract

The invention relates to an accumulator-free hydraulic drive system and to a method for hydraulically driving a consumer (1) without an accumulator. The drive system comprises a consumer (1) having two pressure compartments (K, R) which act in opposite directions, one of which can be supplied with a pressure medium via a first pressure conduit (D1) and a pump arrangement (20) and the other via a second pressure conduit (D2) and the pump arrangement (20). Said pump arrangement (20) consists of a main feed pump (P1) driven with variable torques for working strokes and of an auxiliary pump (P2) driven with variable torques for return strokes. The delivery direction of the auxiliary pump (P2) can be reversed and the auxiliary pump (P2) can be or is hydraulically connected via a directional valve (13) optionally to the first (K) and/or to the second (R) pressure compartment of the consumer (1).

Description

Accumulator-free hydraulic drive assembly for and with a

Consumer, especially for hydraulic

Presses, and methods for accumulatorless hydraulic driving a consumer

FIELD OF THE INVENTION

The invention relates to a pressure accumulator-free hydraulic drive assembly with the features of the preamble of claim 1. Accordingly, the drive arrangement a consumer with two oppositely acting pressure chambers, one of which via a first pressure line and a pump assembly and the other via a second pressure line and the Pump assembly can be supplied with pressure medium, for example, to actuate a consumer in the form of a piston / cylinder unit in a power stroke and retrieve in a return stroke to the starting position. The invention further relates to a method for accumulatorless hydraulic driving a consumer according to the features of the preamble of claim 12. TECHNICAL BACKGROUND

Circuits for the motion control of hydraulic consumers, such as differential cylinders, are today realized in the vast majority in such a way that a work pump is constantly driven by an asynchronous motor. The pumped hydraulic oil flows to a directional valve, in its rest position (closed state), the hydraulic oil, which conveys the pump, flows back to the storage tank without pressure. If the piston of the piston / cylinder unit extend, then the controlling directional valve is switched to a first working position, in which the hydraulic oil flows into the first pressure chamber (piston chamber) of the working cylinder, so that the piston rod extends. The oil displaced in the pressure space opposite the piston chamber with respect to the piston (annular space around the piston rod of the piston / cylinder unit) flows back into the tank via the directional control valve. To return the working piston, the directional control valve is transferred to a second working position, in which the hydraulic oil conveyed by the working pump is conveyed into the annular space of the piston / cylinder unit instead of into the piston space, while the piston space is now connected to the hydraulic oil tank via the return line. A pressure limiting valve limits the system pressure to the permissible level. If the limit pressure is exceeded, hydraulic oil can flow off into the tank without pressure.

Drive arrangements according to this concept have been implemented in large numbers and work reliably and safely. However, the controls also have significant disadvantages:

During rest periods of the system, the electrically driven drive motor continues to run and consumes energy;

If the working piston is to work, the system pressure increases and the hydraulic oil is compressed by about 1%. When reversing to the return stroke, the energy previously stored in the hydraulic oil is useless converted into heat, which heats the oil and can not be recovered; If a piston is to be precisely positioned with the system, normally infinitely controllable proportional valves or, more rarely, complex pumps with adjustable flow rate are used. In the former case, when throttling the oil flow, energy is again destroyed; in the second case, a considerable construction effort is required.

With the emergence of powerful, speed and direction variable to be controlled by appropriate inverter electric motors, the above-described basic concept was radically changed. The working pump is now connected switching valveless with the piston chamber of a piston / cylinder unit. The electric drive motor of the pump can be freely parameterized via a converter control in relation to speed and direction of rotation up to standstill. The oil flow delivered by the working pump behaves almost proportionally to the engine speed. In this way, the hydraulic oil flow and thus also the piston movement can be influenced freely. The annular space side of the piston is connected to an accumulator whose pressure is set slightly higher than the counterpressure required to overcome the frictional losses and the gravity of the piston and any appended masses. The actual position of the piston rod is transmitted via a travel sensor to the control device. At standstill phases of the consumer, the electric drive motor is stationary and there is no hydraulic oil conveyed and thus triggered no piston movement. If the working piston is to extend, the electric drive motor begins to rotate, the hydraulic oil flows into the piston chamber and the piston rod extends. The annular space side hydraulic oil volume flows into the accumulator and raises its pressure slightly. After reaching the desired piston position, the electric drive motor comes to a standstill via a corresponding control and the piston position is held. The ability of the system for precise angular control of the electric drive motor allows a very accurate positioning of the working piston. The setpoint positions are approached and held under full pressure with an accuracy of up to 1 μm without throttle losses. For the return stroke of the piston, the direction of rotation of the electric drive motor is now changed. The energy stored in the compressed hydraulic oil in the accumulator on the one hand supports the acceleration of the electric drive motor in the opposite direction, on the other hand, excess compression energy can be converted by the regenerative effect of the electric drive motor into electrical energy and electronically stored either in capacitors of the inverter or fed back into the electrical network. This pressure accumulator hydraulic drive arrangement has many advantages over accumulatorless hydraulic drive arrangements of the type described above, such as a high overall efficiency, a very simple system structure, very low thermal load of the hydraulic oil and less noise emission by the variable speed of the drive motor. Such an accumulator-hydraulic drive arrangement is known from DE 103 29 067 A1 or US 6,379,119 A.

Many applications have already been realized with this known hydraulic drive arrangement. On the one hand, the limits are reached when the loads or retraction forces arising from the process are so great that the inherently low pressures of the accumulator do not suffice for a return stroke of the piston or the cylinder diameter and / or the piston stroke are so great that the volume of the accumulator increases over an economically acceptable level. This is the case, for example, in hydraulic machines with forces above about 4000 kN and / or strokes over about 700mm. - Especially with large cylinders, however, the energy advantage would be particularly significant.

A hydraulic drive device, in which the accumulator or the passive pressure accumulator is replaced by an active pneumatic component, can be found in JP 2001-2 14 903 A. There is proposed to improve the controllability and the accuracy of the device to connect each pressure chamber of a piston / cylinder unit with its own, independently controlled motor / pump unit for pressurizing. In this way, the installation of valves in the pressure lines can be avoided. Also with two pumps operates a device for fall protection hydraulically lifted loads according to JP 08-0 14 208 A. The hydraulic controls the stroke and the return stroke of a piston / cylinder unit with a first pump and a conventional multi-way valve. The function of the directional valve is to switch between the lifting and the return stroke. When the load in the neutral position of the directional control valve slowly starts to decrease when the piston is stopped due to leakage or thermally assisted compression effects and concomitant pressure reduction in the pressure lines, the second pump is switched on to stabilize the load.

A hydraulically operated piston / cylinder unit, in which the piston chamber and the annular space are each supplied by a pump and a respective directional control valve, can be taken from DE 40 30 950 A1. In the control device described there can be changed by operating multi-way valves either between a lifting or Rückhubfunktion. In addition, for example, in addition to the function "return stroke" a lifting function can be superimposed targeted.

According to WO 02/04 820 A1 a drive device with two pumps is provided, which are operated by one or two variable speed and direction of rotation variable motors. The engine (s) do not operate continuously but only when the piston / cylinder unit is to be moved, whereby directional valves in the pressure lines for reversing the pressure direction are in principle not required. Only an arrangement of a plurality of conventional valves or, alternatively, a multiway valve can be provided only for limiting the pressure in the pressure lines.

In the whole of the prior art, however, complications arise in pressure-free hydraulic systems, especially in the case of large consumers, when, for example, long strokes or return strokes, in particular However, especially large volumes to be realized by large consumers in the shortest possible time.

PRESENTATION OF THE INVENTION

Based on this, the object of the invention is to make variable-speed and rotationally variable hydraulic drive arrangements usable for large consumers, in particular for hydraulic presses with a need for large delivery volumes, without pressure accumulators.

To solve this problem and to be able to operate particularly powerful and / or large consumers in pressure accumulator hydraulic drive assemblies quickly and accurately and still be able to realize reasonable costs, a pressure accumulator hydraulic drive assembly with the features of claim 1 is proposed. Accordingly, a pump assembly of a variable speed driven main working pump for working strokes and further provided from a variable speed driven auxiliary pump for return strokes, the conveying direction of the auxiliary pump reversible and the auxiliary pump via a directional control valve with either the first and / or the second pressure chamber of the consumer hydraulically connected or is connectable. With regard to a generic method, the object is achieved by the features of claim 12.

According to a further object of the invention, an accumulatorless hydraulic drive assembly with the features of claim 4 is proposed, which is also of independent inventive significance, so that the applicant reserves the right to make this solution the subject of a divisional application. This solution provides that in a generic accumulatorless hydraulic drive assembly, the pump assembly consists of a variable speed driven main working pump for working strokes and a variable speed driven auxiliary pump for return strokes, and that a control device is provided, which is to be established by the auxiliary pump, against the pressure in the Working space of the consumer acting back pressure in the auxiliary pump associated pressure chamber controls or regulates. It has been shown that the auxiliary pump at the same volume flow as the main working pump, for example, only 1/10 of the power of the main working pump needed and that the costs incurred by the additional and independently driven auxiliary pump effort is significantly lower than the cost of a suitably designed accumulator. In this case, more favorable space and weight ratios are possible than in a suitably large accumulator.

Optionally, or particularly preferably, it can be provided to realize switching-valveless direct connections between the main working pump and the first pressure chamber or the auxiliary pump and the second pressure chamber of the consumer and thus to avoid the potentially dangerous shocks in the system when using directional control valves in the pressure lines.

In order to achieve higher piston speeds of the consumer, it is also possible to realize the per se known concept of an additional rapid traverse pump, in which the electric drive motor of the main working pump simultaneously drives two hydraulic oil pumps whose combined flow allows the working piston to extend faster. Upon reaching a certain, transmitted via a pressure transducer to a converter limit pressure, the rapid traverse pump can be connected by switching a directional control valve with the return tank for hydraulic oil. Then only the second pump delivers. Thus, the required torque of the electric drive motor can be limited to an economically reasonable amount.

Another possible application of the accumulator-free hydraulic drive arrangement according to the invention is to combine the piston / cylinder unit of the consumer with a per se known rapid traverse piston and filling valves, as they are known from conventional hydraulic controls per se. However, the necessary filling valves with the necessarily large pipes so-called rapid traverse piston are relatively expensive. It may also be provided that a mechanical gear, in particular a transmission gear, is provided between the main working pump and a drive motor associated with the main work pump. As a result, the rotational speed of the main working pump can be changed with respect to the rotational speed of the drive motor assigned to the main working pump. Due to the interposed, mechanical transmission, which may have a constant ratio, it is possible to increase the usable speed range of the drive motor significantly. Thus, for example, a low-cost, lower-torque motor can be used, or alternatively, a higher-flow pump.

In the drive assembly according to the invention, it may also be useful if the pump assembly consists of a variable speed driven main working pump for working strokes and a variable speed driven auxiliary pump for return strokes, wherein the per revolution funded volume of the main working pump and / or the auxiliary pump is variable. The change in the volume delivered per revolution can preferably be regulated as a function of the pressure generated by the main working pump and / or the auxiliary pump. Because of the inherent inventive importance of this solution, the applicant reserves the right to make it the subject of a divisional application. Optionally, the main working pump and / or the auxiliary pump may be formed in this solution as per se known axial piston pump or vane pump with per revolution variable volume flow. The adjustment of the displacement of the pump can be done mechanically-hydraulically depending on the process pressure or a servo motor. The load-dependent change in the delivery volume per revolution or the Pumpenhubraums for controlling the flow rate - ie the delivery volume per time - has the advantage that at low load, a high flow rate is achieved. This is expedient in particular for large consumers connected to the drive arrangement, since these then reach long distances or strokes in a short time. Likewise, at high loads, the operation of the pump can be changed such that by reducing the Pumpenhubraums a lower torque of the drive motor is required, whereby the size of the drive motor can be reduced. At the same time, the possibility is given to achieve large volumes as needed.

If, according to a further embodiment, an electrical converter, in particular a frequency converter, is used as a replacement for a hydraulic control for the dangerous direction and speed control of the hydraulic pump, in particular if, in addition to the converter, a switchable brake between the electric drive motor of the pump arrangement Installation and the inverter are installed, easily higher-quality risk categories can be achieved with little effort. Because of the inherent inventive importance of this solution, the Applicant reserves the right to make that combination the subject of a divisional application. In the meantime, there are embodiments available as inverters which are certified according to the requirements of the second highest CE risk category 3. When such an inverter is combined with a hydraulic control of the type described above, i. with a hydraulic transmission without safety-relevant switching valves, and is designed to the rest of the electrical control accordingly safe, it can - virtually without in the field of hydraulics to operate a significant additional effort - a hydraulic drive assembly with category 3 classification can be realized. In this case, the hydraulic systems are used only as "hydraulic transmission" and the dangerous directional and speed control is realized exclusively by the inverter.A solution of this type is also feasible with hydraulic accumulator-operated hydraulic drive arrangements with variable-speed driven hydraulic pumps, as described, inter alia DE 103 59 067 A1 or as they are known using only a single driven by the electric drive motor hydraulic pump.

It is also possible to achieve the highest risk category 4 with only a small additional effort, in which, in addition to the converter with category 3 classification, a brake is installed between the electric drive motor and the work pump. This creates a redundant system. Brakes with a correspondingly safe design are known, for example, from elevator construction. In addition, the inverter can check the effectiveness of the brake at regular intervals by applying torque to the motor against the active brake, and the process controller checks to see if the rotor is moving improperly.

The abovementioned and the claimed components to be used according to the invention described in the exemplary embodiments are not subject to special exceptions in terms of their size, shape, material selection and technical design, so that the selection criteria known in the field of application can be used without restriction.

Further details, features and advantages of the subject matter of the invention will become apparent from the subclaims, as well as from the following description of the accompanying drawings, in which - by way of example - an embodiment of a pressure accumulator hydraulic drive assembly is shown. Also, individual features of the claims or of the embodiments may be combined with other features of other claims and embodiments.

BRIEF DESCRIPTION OF THE FIGURES

In the drawing show

FIG. 1 shows the block diagram of a first embodiment of a pressure-less hydraulic drive arrangement; FIG.

2 shows the block diagram of a second embodiment of a pressure accumulator-free hydraulic drive assembly.

3 A / B / C, the block diagram of a third embodiment of a pressure accumulator-free hydraulic drive assembly in three different valve positions. such as 4 shows the block diagram of a fourth embodiment of a pressure-saving hydraulic drive arrangement without pressure, an increased safety category being achieved.

DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 shows a pressure accumulator-free hydraulic drive assembly in which a driven by an electric variable speed drive motor M1 hydraulic see main pump P1 with the piston chamber K acting as a consumer 1 piston / cylinder unit via a pressure line D1 switching valveless directly connected. In addition, an auxiliary pump P2 driven by an electric variable-speed drive motor M2 is connected to the annular space R of the load 1 via a switch valve-free direct connection D2. The motor / pump unit M1 / P1 determines as a guide unit, the piston movement at least during its working stroke, as is customary even with accumulator-prone hydraulic drive assemblies. With the motor / pump unit M2 / P2, a back pressure is generated, which simulates the function of an accumulator, as it is used in the accumulator hydraulic drive assemblies. For this purpose, the torque of the motor M2 is controlled so that a certain, required for the process back pressure against the working pressure is generated and maintained. This back pressure can be arbitrarily controlled or regulated regardless of the position of the piston or the piston rod. Thus, it is possible to generate high stripping forces at the beginning of the return stroke, for example in the case of a forming process of a workpiece carried out by the consumer, e.g. are required to retrieve a forming die during the return stroke from the mold. Likewise, long return strokes, in particular with constant backpressure, can be realized. At a standstill or during downhill travel - i. in the initial range of the working stroke - the moment of the drive motor M1 can be reduced to save energy.

The motor / pump unit M2 / P2 requires only a low drive power, which is between 2% and 50% of the rated output, compared to the main work pump. tion, which is required by the main working pump. In many cases, about 1/10 of the rated power of the main working pump for the auxiliary pump is cheap and sufficient.

In such an arrangement, the same advantages as in a hydraulic accumulator-operated hydraulic drive arrangement with variable-speed driven hydraulic pump are achieved - even for applications in which long strokes and / or large forces from the consumer, i. the piston / cylinder unit are required. In addition, comparatively large delivery volumes can be realized, which are advantageously not limited by the volume of the pressure accumulator. Moreover, the invention not only achieves a more cost-effective construction, but above all very considerable advantages in the energy requirement of the arrangement. All the more so, as the drive arrangement can be optionally equipped with one or two axial piston pumps or vane cell pumps. Characterized in that these pumps are characterized by a variable with respect to the delivery volume per revolution pump stroke, the size and thus the energy and cost of the pump P1, P2 can be further reduced. When such pumps are used, it may be expedient to regulate, depending on the load or process pressure, variable delivery volumes per revolution. The function of the displacement reduction is approximately comparable to that of a (mechanical) gearbox: It causes a reduction of the required torque of the drive motor M1 and / or M2. Additionally or alternatively, the arrangement of a mechanical transmission or a gear transmission with a constant ratio between the drive motor M1 (M2) and the pump P1 (P2) may be useful. It allows to increase the usable speed range of the motor (s). This also reduces the cost and energy expenditure for the drive arrangement according to the invention.

In the arrangement of this first (and subsequent) embodiments, control lines 5A, 5B connect the controller 6 to the variable speed electric drive motors M1, M2. The variable speed motors M1 and M2 are via the control device 6, in particular in the form of a known converter, preferably in the form of a frequency converter, with respect to speed and direction of rotation - if desired, to a standstill - freely parameterized. By setting the setpoint to the inverter, the entire speed range can be traversed from standstill to the maximum permissible speed in both directions of rotation. The drives can work in all four quadrants of a speed-torque diagram. This means that the drives can either drive right-handed or left-handed (quadrants I and II or quadrants IM and IV) (quadrant I or IM) or brake (quadrant II or IV). Since the hydraulic oil flow conveyed by the pumps P1 and P2 behaves approximately proportionally to the engine speed, in this way the oil flow and thus also the piston movement can be influenced freely. Pressure relief valves 4A and 4B limit the system pressure to the permissible level, so that when the set pressure is exceeded, hydraulic oil flows back into the hydraulic oil tank T via the returns 2A and 2B, respectively. The actual position of the piston rod is transmitted via the encoder 8 to the inverter control 6.

A preferred mode of operation is the following: When the load is at a standstill, the motors M1 and M2 are generally approximately at rest, unless a leak or the like is to be compensated. When the engine is stopped, no oil is pumped and thus no piston movement is initiated.

If the piston rod S to be extended, so the motor M1 starts to rotate and the hydraulic oil flows into the piston chamber K (filling mode of the pump P1), so that the piston rod S extends. In this case, the torque of the motor M2 running in the discharge mode of the pump P2 can be limited to a relatively low value. The running in the emptying mode of the pump P2 motor M2 prevents, for example, that a hanging on the load load is lowered uncontrollably. The direction of rotation of the motor M2 thus corresponds to the emptying mode of the pump P2, ie hydraulic oil is withdrawn from the annulus controlled while maintaining a certain back pressure against the piston of the consumer or drained. The pump P2 is therefore from the hydraulic fluid flowing out on the annular space side. low-pressure rotation, that is, the motor M1 in turn drives the motor M2 and the motor M2 decelerates this driving force, since it runs slower than would correspond to the drive torque of the motor M1. The oil flows back to the tank T without pressure after flowing through the pump P2. By way of the control device 6 of the motor M2, the motor braking torque of the motor M2 can be varied and a predefinable counterpressure can thus be maintained. Since both electric motors M1 and M2 can be controlled with precision, this enables a very exact positioning of the piston rod, whose target positions can be approached and held under full pressure and without throttle losses with an accuracy of up to 1 μm. If necessary, a position of the piston can be approached exactly at a speed close to 0 with high or even full pressure.

For the return journey, the directions of rotation of the motors M1 and M2 are now changed, i. M1 / P1 operate in emptying mode and M2 / P2 operate in filling mode for the associated pressure chamber of the consumer 1. This makes it possible to decompress the pressurized cylinder by reversing the pump rotation direction. The stored energy in the compressed hydraulic oil on the one hand supports the acceleration of the motor M1 in the opposite direction. On the other hand, excess compression energy can be converted by the regenerative effect of the motor M1 into electrical energy and stored or fed back into the grid. During the return travel (return stroke of the piston), the speed of the motor M1, which is now reversed in the direction of rotation, further determines the position and speed of the piston rod S. The flow rate of the pump P2 generated by the limited drive torque of the motor M2 is just as high as that of the pump P2 is replaced by the reversed pump P1 from the piston chamber K funded amount of oil on the annular space side R. By stopping the motor M1, the piston comes to a precise stop position.

The embodiment of Figure 2 differs from that of Figure 1 by the use of a known so-called rapid traverse piston 3 'and a filling valve 9 and a third pressure line D3, which via an on / off Valve 11 can be connected in bypass to switch valve-free pressure line D1. The rapid traverse piston 3 'is inserted into the piston of the piston-cylinder unit 1. By closing the valve 11, the pump current of the main working pump P1 is not directed to the main piston but to the much smaller diameter piston in the diameter. The piston rod S extends so much faster. Hydraulic oil for filling the piston chamber K is sucked out of the tank T via a non-returnable, serving as a filling valve 9 check valve. After reaching an adjustable pressure, the main piston surface is switched with the valve 11, so that the full piston force can be achieved. During the return stroke, the filling valve 9 is also opened in order to drive at high speed here too.

The embodiment of Figures 3A to 3C differs from that of Figure 1 by the use of the switching valve 13 and the additional pressure line D4, with the annular space R of the piston rod S with the valve 13 and depending on the switching position of the valve 13 with the piston chamber K of the piston / cylinder unit 1 can be connected.

If the piston rod S is to be extended at rapid traverse speed, then the valve 13 is switched to the position "parallel arrows" shown in FIGURE 3 B. Both motors M1 and M2 are actuated by the control unit 6 with the same direction of rotation and speed the pressure line D1 also directly into the piston chamber K ₁ the pump P2 via the pressure line D4., Via the line D2, the annular space R is connected to the piston chamber K. The piston rod S moves because of the larger in relation to the surface of the annular space R surface of the piston The oil quantity displaced from the annular space R via the pressure line D2 also flows via the line and D4 into the piston space K. In this way, the combination of the flow rates of the pumps P1 and P2 and, in addition, the use of the amount of oil flowing out of the annular space side high extension speeds can be realized.

If, in the further course of the drive stroke, the actual work step begins, in which the cylinder works with a higher force, the valve 13 becomes in the picture 3A shown blocking position. Annulus R and piston chamber K are again separated from each other, the system works according to the principle shown in Figure 1. For this purpose, the control device 6, the mode of operation of the motor M2 to; Instead of running with the same speed and direction as the motor M1 in filling mode, M2 now again generates a specifiable, in particular constant braking torque, as described above for FIG. 1 (discharge mode). The direction of rotation of M2 is therefore reversed.

For the return stroke or idle stroke, the valve 13 can be switched to the "crossed arrows" position shown in FIGURE 3C. The piston chamber K is now directly connected to the tank T via the line 12. Thus, the usually quite high flow rate of the pump P2 is used for a high return speed, which is no longer limited by the relatively high resistance of the pump P1 permitting the draining of the piston space K according to the concept according to Figure 1. In this operating state, the motor M2 (filling mode) is set in relation to The direction of rotation and the speed are again operated synchronously with the motor M1 (discharge mode) Before reaching the upper end position both motors M1 and M2 are brought to a standstill, the valve 13 switches to the middle position according to Fig. 3A.

FIG. 4 shows a hydraulic control for a machine that corresponds to the highest CE risk category 4. The picture shows a control similar to that shown in FIG. 1; Controls of pictures 2 to 3 can be changed in the same way. The actual hydraulic control remains completely unchanged. The inverter controller 6, however, receives additional equipment to achieve the risk category 3, which includes, for example, redundant electrical circuits and specially certified software. Between the motor M1 and the pump P1, an electrically switchable brake B is installed. The braking torque is applied via springs, the ventilation is carried out by an electrically operated coil. For intentional movements of the piston S, the brake is released by switching on the coil, for safe standstill it remains closed. LIST OF REFERENCE NUMBERS

1 consumer 20 13 switching valve 2A return 20 pump arrangement

2B return B brake

3 cylinders D1 first pressure line

3 'rapid-action piston D2 second pressure line

4A pressure relief valve 25 D3 third pressure line 4B pressure relief valve D4 fourth pressure line

5A control line M1 first drive motor

5B control line M2 second drive motor

6 Control device P1 main working pump

7 Return / suction line 30 P2 Auxiliary pump 8 Position sensor K First pressure chamber

9 filling valve R second pressure chamber

10 drive arrangement S piston rod

11 valve T tank

12 line

Claims

claims:

1. Accumulator-free hydraulic drive arrangement for and with a consumer (1), in particular for presses, with two opposing We- kenden pressure chambers (K, R), one of which via a first pressure line

(D1) and a pump arrangement (20) and the other via a second pressure line (D2) and the pump assembly (20) are supplied with pressure medium,

characterized,

that the pump assembly (20) consists of a variable speed driven main working pump (P1) for working strokes and from a variable speed driven auxiliary pump (P2) for return strokes and

in that the conveying direction of the auxiliary pump (P2) is reversible and the auxiliary pump (P2) is hydraulically connected or connectable via a directional control valve (13) optionally to the first (K) and / or the second (R) pressure chamber of the consumer (1).

2. Arrangement according to claim 1, characterized in that the annular space (R) and the piston chamber (K) via a switchable pressure line (D2, D4) optionally hydraulically connected to each other and are separable again from each other.

3. Arrangement according to claim 1 or 2, characterized in that the piston chamber (K) via the directional control valve (13) optionally with an emptying pipe (12) is connectable.

4. pressure accumulatorless hydraulic drive assembly according to the preamble of claim 1, in particular according to one of claims 1 to 3, characterized that the pump assembly (20) consists of a variable speed driven main working pump (P1) for working strokes and a variable speed driven auxiliary pump (P2) for return strokes and

in that a control device (6) is provided with which a counter-pressure to be established by the auxiliary pump (P2) against the pressure in the working space of the consumer (1) can be controlled or regulated in the pressure space associated with the auxiliary pump.

5. Arrangement according to claim 4, characterized in that the first pressure line (D1) a switching valveless direct connection between the main working pump (P1) and the first pressure chamber (K) and the second pressure line (D2) a switching valveless direct connection between the auxiliary pump (P2) and the second pressure chamber (R) is.

6. Arrangement according to one of claims 1 to 5, characterized in that the rated power of the auxiliary pump (P2) is between 2% and 50% of the rated power, preferably about 10% of the rated power of the main working pump (P1).

7. Arrangement according to one of claims 1 to 6, characterized in that between the main working pump (P1) and one of the main working pump (P1) associated drive motor (M1), a mechanical transmission is provided whereby the speed of the main working pump (P1) with respect to the speed of the main working pump (P 1) associated drive motor (M 1) is variable.

8. accumulatorless hydraulic drive assembly according to the preamble of claim 1, in particular according to one of claims 1 to 7, characterized that the pump assembly (20) consists of a variable speed driven main working pump (P1) for working strokes and a variable speed driven auxiliary pump (P2) for return strokes and

the volume of the main working pump (P1) and / or the auxiliary pump (P2) conveyed per revolution is variable, the change in the volume delivered per revolution preferably being dependent on the pressure generated by the main working pump (P1) and / or the auxiliary pump (P2) is controllable.

9. Arrangement according to claim 8, characterized in that the main working pump (P1) and / or the auxiliary pump (P2) is formed as an axial piston pump or as a vane pump.

10. Accumulator hydraulic drive assembly according to the preamble of claim 1, in particular according to one of claims 1 to 9, characterized in that the pump assembly (20) at least one of a variable speed drivable electric drive motor driven pump for working strokes of the designed as a hydraulic transmission see hydraulic Having drive arrangement, in which the pressure lines (D1, D2) are free of safety-relevant switching valves, and that designed as a converter control device (6) has a known per se high risk category for the electric drive motor as a substitute for a hydraulic control.

11. Arrangement according to claim 10, characterized in that a brake (8) between the electric drive motor (M 1) and the working pump (P1) is effective.

12. A method for pressure accumulatorless hydraulic driving a consumer (1), with two oppositely acting pressure chambers (K, R) of which one via a first pressure line (D1) and a pump assembly (20) and the other via a second pressure line (D2) and the pump assembly (20) is supplied with pressure medium

characterized,

in that a variable speed driven main working pump (P1) for working strokes and a variable speed driven auxiliary pump (P2) is used for return strokes and by means of a control device (6) from the auxiliary pump (P2) a back pressure against the pressure in the working space of the consumer ( 1) is constructed or held.

13. The method according to claim 12, characterized in that the conveying direction of the auxiliary pump (P2) reversed during the working stroke of the consumer and the flow rate of the auxiliary pump (P2) from an initial connection to the piston chamber (K) of the consumer (1) to a connection to the annulus (R) of the consumer (1) is redirected.

14. The method according to claim 12 or 13, characterized in that the rotational speed of the main working pump (P1) relative to the rotational speed of the main working pump (P1) associated drive motor (M1) is changed, wherein the change in the rotational speed of the main working pump (P1) with respect to the rotational speed of the main working pump (P1) associated drive motor (M1) is preferably provided by a between the main working pump (P1) and the main working pump (P1) associated with the drive motor (M1) provided mechanical transmission.

15. The method according to any one of claims 12 to 14, characterized in that the per revolution funded volume of the main working pump (P1) and / or the auxiliary pump (P2) is changed, wherein the change in the volume delivered per revolution preferably in dependence of the Main working pump (P1) and / or the auxiliary pump (P2) pressure is controlled.

16. The method according to the preamble of claim 12, in particular according to one of claims 12 to 15, wherein the pump assembly (20) consists of at least one variable speed driven pump, characterized marked, that the pressure lines (D1, D2) without safety-relevant switching valves flowed through by the hydraulic oil and the at least one variable-speed pump drive motor is driven by an electrical converter of a high risk category.

17. The method according to claim 16, characterized in that between the electric drive motor (M 1) and the working pump (P1) effective brake (8) is used redundantly.