DE102014226236A1 - Hydraulic circuit and machine with a hydraulic circuit - Google Patents

Abstract

Disclosed is a hydraulic circuit in which a positive displacement control and a valve control are connected in parallel. The positive displacement control is connected with both connections to a consumer as in a closed circuit. The parallel valve control is operated as an open circuit. It is envisaged that the displacement control provides the majority of the hydraulic drive power and thus amount of fluid, while the valve timing compensates for deviations from a predetermined pressure, travel or speed control curve simultaneously.

Description

The invention is based on a hydraulic circuit, for controlling a hydraulically driven machine or for controlling a hydraulic consumer. Furthermore, the invention relates to a machine, with at least one hydraulic consumer, which is controllable via a hydraulic circuit.

From the post-published publication DE 10 2012 019 665 a hydraulic circuit for controlling a press is disclosed. This is, for example, a punching machine, a forming machine or a thermoforming machine for the production of workpieces having an upper and a lower tool to impart a pressing force on a workpiece. The hydraulic circuit in this case has a positive displacement control and a valve control.

Furthermore, from the prior art highly dynamic cylinder systems or actuators (Gleichgang or differential cylinder) for die cushion applications or punching / Nibbelapplikationen known with which a position and force control of at least one cylinder takes place. For this purpose, highly dynamic servo valves are used for control, which are designed for high flow rates and high pressures and which are provided in control plates. The control plates disadvantageously have an extremely large space requirement and have a high, heavyweight. The control plates can be arranged directly on a cylinder to be controlled. For pressure medium supply large hydraulic accumulator are provided, which are usually arranged directly on a control plates having the control block of the cylinder. To load the hydraulic accumulator supply units may be provided with pressure control pumps or constant displacement pumps with a pressure switch and a charging valve. The supply unit is fluidically and spatially spaced from the cylinder and control block. The supply unit is simply designed and has a large installation space engine pump drives with high performance (for example, with a power of 150 to 250kW in the die cushion application). For this purpose, then a large space having cooler filter circuits are used (for example, with a power of 300 to 500kW in the die cushion application) and tanks (for example, with a capacity of 6000 to 12000 liters in the die cushion application). The supply and control of the cylinder or cylinders is then via the servo-valves, which thus, as already explained above, regulate large volume flows (Qmax) and are designed for large pressure differences (delta-p-max). When rules occurs disadvantageously high power loss, which leads to the heating of the pressure medium or the oil and also causes rapid aging of the oil.

It is an object of the present invention to provide a hydraulic circuit, with the device-simple manner, a hydraulically driven machine is highly dynamic and controllable with high accuracy and eliminates the disadvantages mentioned. Furthermore, it is an object of the invention to provide a hydraulically driven machine with such a hydraulic circuit.

The object with regard to the hydraulic circuit is achieved according to the features of claim 1 and with regard to the hydraulically driven machine according to the features of claim 15.

Other advantageous developments of the invention are the subject of further subclaims.

According to the invention, a hydraulic circuit is provided for controlling a hydraulically driven machine, in particular a press, in particular a die cushion axis in a mechanical press, in particular a punch axis in a nibbling machine. The circuit has a positive displacement control and a valve control, which are arranged fluidically parallel to each other. The displacement control has a displacer, in particular a hydraulic machine - which is preferably used in four-quadrant operation -, with two terminals, via which preferably each pressure medium can be fed and discharged. A respective connection of the hydraulic machine is connected to the hydraulically operated machine in each case via a flow path, with which a closed hydraulic circuit can be formed. By contrast, the valve control can be connected to the machine in an open hydraulic circuit. Thus, the valve control is operated as an open circuit.

This solution enables highly dynamic energy-optimized control of the hydraulically driven machine. If, for example, the machine has a cylinder, it can be quickly extended and retracted via the displacement control. Due to the parallel valve control can then be an active accurate control of the cylinder via the open circuit (increase and decrease of volume / pressure). Since the valve control is usually made much more compact than the displacement control, this can be arranged in terms of device technology simple way closer to, for example, the cylinder of the hydraulically driven machine, whereby hydraulic flow paths are shortened and between the valve control and the hydraulically driven machine higher hydraulic stiffness is present, which in turn increases a quality of control. Thus, by the hydraulic control optimal control behavior by shortening the "hydraulic springs".

With the circuit according to the invention it is thus possible to operate highly dynamic cylinder systems, such as die-cushion applications or punching / nibbling applications, wherein in comparison to the prior art explained an extremely small valve control can be used, whereby power losses are significantly reduced. A speed of the applications can be, for example, between 500 and 1500 mm / s and / or a maximum speed of the applications can be achieved on the shortest paths, such as 5 to 10 mm, and / or a maximum speed of the applications can be reached in the shortest possible times. such as 5 to 10 ms, and / or reaching a maximum force of the applications can be done in the shortest times, such as 5 to 10ms, the maximum force may be, for example, 20, 50, 100, 150 or 200 tons.

With the circuit according to the invention can, as already stated above, be used for highly dynamic cylinder systems, such as die-cushion applications or punch / Nibbelapplikationen, a comparatively small space having valve control. In the prior art valves for such applications are usually used in the nominal sizes 25, 32, 50 or 63. These are now replaced according to the invention by the displacement control, which is preferably large, low in inertia and highly dynamic. As a hydraulic motor, for example, a motor of the company Hägglunds be used, which preferably promotes 1, 2 or 5 liters / revolution. Preferably, the displacement control is designed such that it has a large displacement at low speed, for example, about 500 revolutions / minute about 2500 liters / minute. Such comparatively low speeds, that is, for example, about 500 n / min, can be reached faster than previously conventional speeds of about 3000 n / min.

The solution according to the invention has the further advantage that the above-described large designed for high pressure hydraulic accumulator or supply storage, for example, have a capacity of 20 to 100 liters, can be replaced. As a substitute small hydraulic accumulator (high-pressure accumulator) can be used, for example, have between about 2 to 4 liters. A small hydraulic accumulator is sufficient to actively supply the valve control - which has, for example, a control / servo valve in the nominal size 6 or 10 - with pressure medium.

For the positive displacement control, a hydraulic accumulator (prestressing accumulator) for producing a basic supply, in particular on the low-pressure side, can be provided, which has, for example, 4 to 10 liters. In addition, a small pressure control pump or constant pump can be provided for the storage charge. Thus, in contrast to the prior art, only two relatively small hydraulic accumulator - one for the displacement control and one for the valve control - used. To control the hydraulic accumulator, in contrast to the prior art, only small pumps are necessary and thus only small pumps driving electric motors with comparatively low power.

Furthermore, in the solution according to the invention, it is advantageous that, compared to the prior art, significantly less energy is "destroyed" at a maximum volume flow (Qmax) and at a maximum pressure difference (delta-p-max) due to the comparatively small valve control , Thus, a cooler-filter circuit, for example, with a water supply, be made much smaller.

In addition, it is advantageous in the inventive solution that only a small tank is needed.

In a further embodiment of the invention is during the provision of a hydraulic drive power of the positive displacement simultaneously with the valve control, a deviation from a predetermined pressure control curve and / or a travel control curve and / or a speed control curve compensated. Thus, with the displacement control, for example, large adjustment speeds and thus large volume flows for controlling the hydraulically driven machine possible. At the same time can then be optimally fulfilled with the highly dynamic valve control in particular by short switching and control times control tasks.

The positive displacement control is preferably designed to provide a majority of the drive power for the hydraulic driven machine.

The valve control is preferably designed so that it can not provide the majority of the drive power for the hydraulic driven machine.

Preferably, the hydraulic machine is designed such that it has a comparatively low inertia and thus high dynamics and a relatively large displacement. Due to the large displacement this is advantageous drivable with a comparatively low speed. In a further embodiment of the invention, the hydraulic machine can be driven by an electric motor. This is preferably designed such that it is a comparatively low inertia and thus high dynamics and can be used with a comparatively low speed. The combination with the low-inertia and large-volume hydraulic machine leads to a displacement control that can control the hydraulically driven machine very quickly, with high dynamics (number of cycles) and at a high speed. Thus, for example, a cylinder of the machine with high dynamics and speed off or retracted. A change of a direction of rotation of the hydraulic machine can also be done very quickly here. The electric motor is, for example, a highly dynamic torque motor or servomotor. Such a hydraulic machine in combination with an electric motor, for example, from the post-published document DE 10 2013 221 410 known. In combination with the valve control, this allows a highly dynamic control of the hydraulically driven machine. For the electric motor, an "intelligent" regenerative drive can be provided (HCS).

Preferably, the electric motor is used for the main control and possibly also for the regulation of the hydraulically driven machine. The valve control can then have a (control / servo) valve, which can also control the machine highly dynamic active and which is designed so that it compensates for what the displacement control physically and technically can not cause. A nominal size of the valve is for example 6 or 10.

"Active control" means preferably that up to the maximum pressure active pressure medium supplied to the machine and discharged from the machine.

The valve control preferably has a control valve. This can then be used to control the open circuit. The control valve is in this case preferably designed such that it has a high dynamics and high accuracy with respect to a pressure medium quantity to be controlled. Thus, the valve control is advantageously used for precise control of the hydraulically driven machine. Furthermore, the control valve can be arranged fluidly very close to the hydraulically driven machine in a simple manner, since it has a small space requirement in comparison to the hydraulic machine and the electric motor and in comparison to the valves explained in the introduction. For example, the control valve is a servo control valve.

Advantageously, the control valve is arranged as close as possible to the hydraulically driven machine. Since the valve control has an extremely compact size and thus a small control disk or a small control block, it can be arranged fluidically and spatially closer to the hydraulic machine compared to the prior art. The "hydraulic spring" between the valve assembly and the machine is thereby extremely short.

In a further embodiment, the control valve preferably has two working connections, a pressure connection and a tank connection. The work connections can then be connected to the hydraulically driven machine, for example, in each case with a working space of a cylinder. Via a valve slide of the control valve, the first working connection with the tank connection and the second working connection with the pressure connection can be connectable in second switching positions, and in second switching positions, the second working connection can be connectable to the tank connection and the first working connection can be connectable to the pressure connection. It is conceivable that the control valve has third switching positions, which are preferably provided between the first and second switching positions. In the third switching positions, the valve spool, for example, all connections throttled connect with each other, so that the hydraulic driven machine or the cylinder can be pressure compensated as a safety measure. Preferably, the valve spool of the control valve is continuously adjustable.

In a further embodiment of the invention, a shut-off valve, which is preferably designed as a switching valve, is provided. With this, the control valve can be decoupled from the hydraulic machine. Preferably, the shut-off valve is arranged fluidically between the control valve and the machine.

The shut-off valve may have two input ports, with a respective input port connected to a respective working port of the regulator valve. Further, the shut-off valve may have two working ports which are connectable to the machine.

Advantageously, a hydraulic accumulator is connected to the pressure connection of the control valve. This can be designed such that a required working pressure for the hydraulic driven machine is available. The hydraulic accumulator is preferably a high-pressure accumulator. The hydraulic accumulator can be connected to a tank, for example via a drain valve and / or via a pressure relief valve. Of Furthermore, a pressure gauge for the high-pressure accumulator can be provided.

Alternatively or in addition to the hydraulic accumulator may be connected to the pressure port of the control valve, a hydraulic pump. The hydraulic pump is preferably a pressure-flow-controlled hydraulic pump. Preferably, a check valve between the hydraulic pump and the pressure port of the control valve is arranged, which opens in the pressure fluid flow direction to the control valve.

In a further embodiment of the invention, a biasing device is provided, with which one of the flow paths or both flow paths with a predetermined pressure is hydraulically prestressed or are. The biasing device may be connected to one of the flow paths via a check valve or may each be connected via a check valve to a respective flow path. The check valve opens in this case in a pressure medium flow direction towards the flow path. Preferably, the biasing device has a hydraulic accumulator connected to one or both flow paths. The connection is made via the check valve or the check valves. The hydraulic accumulator can be connected to a tank via a drain valve and / or via a pressure relief valve. In addition, a pressure gauge is preferably provided. The hydraulic accumulator is designed in a further embodiment of the invention such that a required biasing pressure is available, which is preferably a low pressure accumulator in the hydraulic accumulator. Alternatively or in addition to the hydraulic accumulator, a valve, in particular a pressure reducing valve, may be provided for biasing. For applying the biasing pressure this is connected to a hydraulic pump, in particular to a constant pump.

For flushing the hydraulic circuit, a flushing device is provided, which is connected to at least one flow path and can be discharged via the pressure medium from the at least one flow path. The flushing device may be designed such that an influence in a pressure control and / or path control and / or speed control of the machine is comparatively low or avoided. The control of the flushing device, ie a flushing process, for example, in a workpiece change during operation of the machine or when the cylinder should "stand still" in position control, which is disabled in the actual workpiece machining, the flushing device and does not adversely affect the scheme. The flushing device is connected to the flow path via an adjustable throttle. If it is connected to both flow paths, it is connected to it via an adjustable throttle. Furthermore, the flushing device has a flushing valve with which a pressure medium connection between one or both flow paths to a tank can be opened and closed. The throttles are preferably arranged between the flow paths and the flushing valve. The flush valve may be manually or electromagnetically or hydraulically actuated, for example. It is also conceivable to use the flushing valve as a safety valve for pressure relief.

Preferably, the displacement control and the valve control are each twofold secured and monitored. It may be arranged in one or both leading to the machine flow paths of the positive displacement control and the valve control one (or two) safety valve (s). In this case, the associated flow path can be blocked in a closed state of the safety valve and the associated flow path can be opened in an open state of the safety valve. If a safety valve is provided for a respective flow path, the hydraulically driven machine can be fluidically blocked when the flow paths are blocked by the safety valve. The safety valve or a respective safety valve can be opened and closed via a limit switching valve. Actually, here is generally intended that you also 2x times in a row ( 112 . 114 ) the safety valves, in both flow paths ( 68 . 70 ) can and must install depending on the required performance level or safety category!

The safety valves in combination with the shut-off valve and / or with the third switching position of the control valve can then form a double or triple protection for the valve control.

The safety valves in combination with an electrical protection circuit for the positive displacement control also lead to a double protection. The protection circuit may be provided in a drive of the hydraulic machine. The protection circuit provides, for example, a safe drive release of the drive of the hydraulic machine. Furthermore, for example with the protection circuit, a parking brake can be controlled on the electric motor which can be driven by the hydraulic machine.

Preferably, a valve element of a respective safety valve, which may be formed as a logic valve, in the closing direction via a first pressure chamber (cylinder chamber) acted upon with pressure medium and further acted upon in the opening direction via a second pressure chamber (annulus) with pressure medium. About the respective limit switching valve, the first pressure chamber and the second pressure chamber of a respective logic valve alternately with be connectable to a tank or a pressure medium source.

Furthermore, a shuttle valve may be provided having an output port and two input ports connecting the highest pressure input port to the output port. A respective limit switching valve may be connected to the output port to connect the output port to one of the pressure chambers of a respective logic valve. The biasing system may then be connected to the first input connection of the shuttle valve and one of the flow paths to the second input connection.

Advantageously, the flow paths can be connected to one another via at least one pressure limiting valve. The pressure relief valve is, for example, a pilot operated pressure relief valve with a discharge. The discharge is preferably carried out by a discharge valve. In the closing direction, a valve element of the pressure relief valve can be acted upon by the pressure medium of the hydraulic accumulator of the valve control. In a further embodiment of the invention, the flow paths are connectable via two pressure relief valves, which are formed in accordance with the above explained aspects. In this case, one pressure-limiting valve can be actuated by the pressure medium in the first flow path and the other pressure-limiting valve can be actuated by the pressure medium of the second flow path.

Advantageously, a further pressure limiting valve is provided, via which a flow path or both flow paths to the tank can be relieved. This may be configured according to one or more aspects of the above-described pressure relief valves. With a respective flow path, the pressure relief valve is connected via a check valve, which close in the direction of pressure fluid flow toward the flow path in each case.

According to the invention, a hydraulic driven machine has a hydraulic cylinder controlled by a circuit according to one of the preceding aspects. There may be provided a second hydraulic cylinder, which is also controlled by a circuit according to one of the preceding aspects.

The cylinder is, for example, a differential or synchronous cylinder, wherein in a synchronous cylinder advantageously no pressure medium volume compensation must be made.

Advantageously, the machine is a mechanical press and a cylinder forms a die cushion axis.

Alternatively, the machine may be a nibbling machine.

Several embodiments of a hydraulic circuit according to the invention and a hydraulically driven machine according to the invention are shown in the drawings. With reference to the figures of these drawings, the invention will now be explained in more detail.

Show it

1 a circuit diagram of a hydraulic circuit according to the invention according to a first embodiment,

2 a circuit diagram of a hydraulic circuit according to a second embodiment,

3a to 3c each a hydraulic circuit diagram of a part of a hydraulic circuit according to a third embodiment,

4 and 5 each a lift curve, a speed curve and a force curve, which are each plotted over a time and show an operation of the hydraulic circuit and

6 a circuit diagram of the hydraulic circuit according to the invention according to another embodiment.

According to 1 has a hydraulically driven machine 1 a first cylinder 2 and a second cylinder 4 , At the machine 1 it is for example a mechanical press, the cylinder 4 can form a die cushion axis. The first cylinder 2 is via a first hydraulic circuit 6 and the second cylinder 4 via a second substantially identical hydraulic circuit 8th controlled. The hydraulic circuits 6 and 8th each have a positive displacement control 10 respectively 12 and a valve control 14 respectively 16 on. The displacer control 10 . 12 and the valve control 14 . 16 a respective circuit 6 . 8th are arranged fluidically parallel to each other here.

The embodiment of the circuits 6 . 8th will now be described below with reference to the circuit 6 of the cylinder 2 explained in more detail. The displacer control 10 has a hydraulic machine 18 , which can be used in 4-quadrant operation. It is designed so that it has a large displacement and low inertia. Furthermore, the hydromachine 18 two connections A1, A2. It is at a low speed by a regulated electric motor 20 drivable. This is a torque motor with a low inertia. Furthermore, this is designed so that it can be used at a low speed. Due to the low inertia and the low speeds, the torque motor thus has a high dynamic. The combination of the electric motor 20 with the hydraulic machine 18 , which are designed according to the manner described above, leads to a displacement control with which high volume flows can be implemented within a very short time, which means a piston 22 of the cylinder 2 Removable and retractable at a high speed. Furthermore, rapid changes in direction of the piston can take place.

According to 1 is the piston 22 one-sided with a piston rod 24 connected. The piston 22 separates in the cylinder 2 a first cylinder space 26 from a second cylinder chamber 28 , The first cylinder room 26 is here via a flow path 30 to port A1 and via a second flow path 32 with the connection A2 of the hydraulic machine 18 connected. The displacer control 10 thus forms with the cylinder 2 a closed hydraulic circuit.

To the flow paths 30 . 32 is also the valve control 14 connected, thus the fluidic parallel to the displacement control 10 is arranged. The valve control 14 has a continuously adjustable control valve 34 (Servo-control valve). About a working port A is the control valve 34 with the flow path 30 and via a working port B with the flow path 32 connected. Furthermore, it is connected via a pressure connection P to a pressure medium source and via a tank connection T to a tank. In spring-centered basic positions 0 (third switching position) connects a valve spool of the control valve 34 the connections A, B, P and T with each other. Starting from the basic positions 0 can the valve spool of the control valve 34 be moved in the direction of the first switching positions a. In these, the pressure port P is connected to the working port B and the working port A to the tank port T. If the valve spool starts from the basic positions 0 shifted in the direction of the second switching positions b, the pressure port P is connected to the working port A and the working port B to the tank port T. The control valve 34 is here designed such that it has very short switching and control times. As the hydraulic machine 18 has a large displacement and thus for the main part of the drive power of the cylinder 2 is available, the control valve 34 be made comparatively small. It is thus highly dynamic actuated and has low switching and control times. Due to the small space requirement of the control valve 34 It can be flexible in terms of device technology to the cylinder 2 be arranged and thus also fluidly extremely close to the cylinder 2 be provided, resulting in a high hydraulic rigidity and thus to a high control quality of the cylinder 2 leads. The control valve 34 is hydraulically actuated, for example.

At the piston 22 of the cylinder 2 For example, it is an upper piston and a piston 36 of the cylinder 4 it can be a sub-piston, which cooperate to edit a workpiece.

According to 2 has a machine 38 a cylinder 40 , which is designed as a synchronous cylinder or upper piston-Gleichgangzylinder. Furthermore, she has a cylinder 42 , which is also designed as a Gleichgangzylinder or sub-piston Gleichgleichzylinder. The cylinders 40 . 42 are each controlled by a valve control, each in a control block 46 respectively 48 are arranged. Fluidic parallel to the valve control is for a respective cylinder 40 . 42 a displacement control 50 respectively 52 intended. The valve control of the control block 46 and the displacement control 50 are from a power electrical system 54 provided. The same applies to the valve control of the control block 48 and the displacement control 52 that have a power electrical system 56 are supplied. For the hydraulic supply of the valve controls in the control blocks 46 . 48 is a hydraulic supply unit 58 intended. For controlling the hydraulic supply unit 58 and the valve controls of the control blocks 46 and 48 is a control cabinet 60 provided with a logic and control unit. Above a respective cylinder 40 . 42 can each have a mass 62 respectively 64 be moved.

In 3a is a hydraulic circuit 65 an upper piston shown. The upper piston or cylinder 66 is designed as a synchronous cylinder. Via a first flow path 68 he is with a connection A1 of the hydraulic machine 18 and a second flow path 70 with connection A2 of the hydraulic machine 18 connected. The hydraulic machine 18 This is done by an electric motor 20 driven. Fluidic parallel is the valve control with the control valve 34 intended. At the pressure port P is in this case via a check valve 72 extending in the pressure fluid flow direction to the control valve 34 opens, an adjustable hydraulic pump 74 , please refer 3c , connected. Between the check valve 72 and the control valve 34 is a hydraulic accumulator 76 connected, which is a high-pressure accumulator. This is via a pressure relief valve 78 to a tank 80 , please refer 3c , secured. Of Further the hydraulic accumulator 76 a drain valve 82 for draining pressure medium to the tank 80 assigned.

The working connections A, B of the control valve 34 are via a designed as a switching valve shut-off valve 84 with the first and second flow paths, respectively 68 . 70 connected. The shut-off valve 84 has a port X, which communicates with the working port A of the control valve 34 is connected and a port Y connected to the working port B of the control valve 34 connected is. About a working port A is the shut-off valve 84 with the second flow path 70 and via a working port B to the first flow path 68 connected. In a first switching position of the shut-off valve 84 the connections A, B, X and Y are separated from each other. In a second switching position, the working port A is connected to the port X and the working port B to the port Y. In this switching position is thus the control valve 34 with its working ports A, B with the flow paths 70 respectively 68 connected.

Furthermore, the hydraulic circuit has 65 a hydraulic biasing device 86 , This has a pressure reducing valve 88 having a pressure port P, a tank port T and a working port A. At the pressure port P is a fixed displacement pump 90 , please refer 3c , connected. The tank connection T is with the tank 80 out 3c connected. Between the pressure connection P and the constant pump 90 is a way to the pressure reducing valve 88 opening check valve 92 arranged. About the working port A is the pressure reducing valve 88 with the first and second flow paths 68 . 70 connectable. The first flow path 68 Here is a check valve 94 with the working port A and the second flow path 70 via a check valve 96 connectable to the working connection A. The check valves 94 . 96 open in each case in a pressure fluid flow direction away from the pressure reducing valve 88 , Thus, via the constant pump 90 and the pressure reducing valve 88 the hydraulic circuit 65 with the cylinder 66 be preloaded with a low pressure. In addition, the working port A with a hydraulic accumulator 98 connected in the form of a low-pressure accumulator. This is via a pressure relief valve 100 and a drain valve 102 with the tank 80 out 3c connectable.

According to 3a has the hydraulic circuit 65 in addition a rinsing device 104 , This has a flush valve 106 on, over the two flow paths 68 . 70 with the tank 80 out 3c are connectable. The designed as a switching valve flush valve 106 has two working ports A, B, each with a respective flow path 70 respectively 68 are connected. Furthermore, the flushing device has 104 two tank connections T, with the tank 80 are connected. In a spring-biased first switching position of a valve spool of the purge valve 106 All connections are separated. In a second switching position, which can be actuated manually or electromagnetically, the valve spool connects the working port A with the first tank port T and the working port B with the second tank port T. The working port A is further via an adjustable throttle 108 with the flow path 70 connected. The same applies to the working port B, which has an adjustable throttle 110 with the first flow path 68 connected is.

To secure the hydraulic circuit 65 or the cylinder 66 are a first and second safety valve 112 respectively 114 intended. These are each a logic valve. With the safety valve 112 Here is the first flow path 68 taxable and registrable. With the safety valve 114 is then the second flow path 70 taxable and registrable. In the controlled state of the flow paths 68 . 70 are the control valve 34 , the hydraulic machine 18 , the pretensioner 86 and the flushing device 104 from the cylinder 66 separated. The safety valves 112 . 114 are designed identically, which is why in the following, for the sake of simplicity, only in the 3a upper safety valve 112 is explained in more detail. The safety valve designed as a logic valve 112 is designed in the usual way. A valve body 116 limits a cylinder space 118 , over which he in the closing direction of a spring force of a spring and a limit switching valve 120 can be acted upon with pressure medium. Furthermore, the valve body limits 116 an annulus 122 , over which he in the opening direction and against the spring force of the spring with pressure medium via the Endschaltventil 120 can be acted upon. The limit switching valve 120 has two working ports A, B, a tank port T and a pressure port P. The working port A is here with the cylinder chamber 118 and the working port B with the annulus 122 connected. The tank connection T is with the tank 80 out 3c connected. About the pressure port P is the limit switching valve 120 to an output terminal AW of a shuttle valve 124 connected. The shuttle valve 124 also has a first input terminal E1 and a second input terminal E2. The input terminal E2 is here with the biasing device 86 and the memory 98 hydraulically connected by fluidly between the check valves 94 and 96 connected to this. Alternatively, it is conceivable the input terminal E2 with the hydraulic accumulator 76 connect to. The other input terminal E1, on the other hand, is connected to the second flow path 70 connected. The input port E1 is thus preferably connected to a flow path, in this the load pressure or weight pressure the machine to be operated acts. The higher pressure port E1 or E2 then becomes the output port AW and thus the pressure port P of the end shift valve 120 connected. The limit switching valve 120 has a valve spool, which is spring-biased via a valve spring in a first switching position a. In this is the annulus 122 the safety valve 112 with the tank 80 and the cylinder space 118 with the pressure medium source, ie with the flow path 70 or the pretensioner 86 , connected. In this first switching position a is thus the safety valve 112 closed. Manually or electromagnetically, the valve slide of the limit switching valve 120 be moved to a second switching position b. In this is then the cylinder chamber 118 with the tank and the annulus 122 with the pressure medium source, ie with the flow path 70 or pretensioner 86 , connected, bringing the safety valve 120 is open.

The flow paths 86 and 70 are according to 3a via a first and second pressure relief valve 124 . 126 connectable with each other. The first pressure relief valve 124 is here by the pressure medium in the flow path 70 and the second pressure relief valve 126 from the pressure medium in the flow path 68 actuated. For the pressure relief valves 124 . 126 These are pilot-operated pressure relief valves with relief in the form of a directional control valve 128 , In the closing direction is a valve body of a respective pressure relief valve 124 . 126 via a control line with pressure medium from the hydraulic accumulator 76 or with pressure medium from the hydraulic pump 74 , please refer 3c , acted upon. About the respective way valve 128 the pressure medium can be discharged to the tank. Another pilot-operated pressure relief valve 132 with a discharge is via a first and second check valve 134 . 136 with the first flow path 68 or the second flow path 70 connected. The check valves 134 . 136 open in each case in a pressure fluid flow direction to the pressure relief valve 132 , This can be a pressure medium connection to the tank 80 to open. It is also in the closing direction via the control line 130 from the pressure medium of the hydraulic accumulator 76 or the hydraulic pump 74 , please refer 3c , acted upon and via the directional control valve 128 relieved.

The synchronous cylinder 66 in 3a has a position measuring system 138 on. Furthermore, at a respective cylinder space of the cylinder 66 a pressure gauge 140 connected.

According to 3b is a sub-piston or cylinder 142 shown. This will be according to the cylinder 66 out 3a with a corresponding to the hydraulic circuit 65 controlled hydraulic circuit controlled. The cylinders 66 and 142 act together and may be part of a mechanical press with a die cushion axis.

According to 3c is an aggregate 144 for pressure medium supply of the hydraulic circuits of the cylinder 66 and 142 from the 3a and 3b shown. The adjustable via a pressure-flow regulator hydraulic pump 74 is output side via a pump line 146 over the check valve 72 out 3a with the pressure port P of the control valve 34 connected. The hydraulic pump 74 is via an electric motor 184 drivable. Furthermore, the electric motor 148 with the constant pump 90 coupled via a pump line 150 over the check valve 92 on 3a with the pressure reducing valve 88 connected is. Both the pump line 146 as well as the pump line 150 are via a pressure relief valve 152 to the tank 80 relieved. Furthermore, there are two tank lines 154 . 156 and a leakage line 158 with the circuits 65 the cylinder 66 . 142 from the 3a and 3b connected. In the tank line 154 is a cooling and filtering device 160 intended. The tank line 154 is preferably with the flushing device 104 connected.

Below, in the 4 and 5 , Exemplary applications are explained with the hydraulic circuit according to the invention. As already explained, the hydraulic circuit should preferably be used for punch nibbling machines or die cushion systems having a force of 20, 30, 45, 67, 100, 150, 225 tons and so on. This may be, for example, a series. The hydraulic circuit can of course be used in other hydraulic cylinder axes, which are driven / driven with extremely large valves and large storage levels, with much energy wasted / destroyed and not optimally utilized.

According to the upper diagram in 4 is a stroke s mapped over a time t. The lower characteristic 162 shows here a course of the upper piston and the upper characteristic 164 a course of the lower piston. The stroke s of the upper piston in this case has approximately a sinusoidal course. He executes a stroke h of about 100 mm. A lifting force is then for example about 20 tons. For example, a diameter of a piston may be about 160 mm and a cylinder rod about 110 mm. The time periods z shown in the diagram are, for example, about 1.5 seconds. A stroke k of the sub-piston according to the characteristic 164 is about 100 mm, which is a pulling stroke. A diameter of the sub-piston may be about 125 mm and a diameter of the piston rod about 90 mm.

The middle diagram in 4 shows the course of a velocity v over the time t. The lower characteristic 166 in this case represents a course of the upper piston and the upper characteristic 168 a course of the lower piston. The time interval z is again 1.5 seconds. A maximum travel speed of the upper piston is for example about 600 mm / s (lower piston 10 tons). The displacement control for the upper piston can in this case for example be driven at about 400-450 revolutions / min and promote about 100 l / min. The maximum speed of the sub-piston may also be about 600 mm / s. The displacement control of the sub-piston, for example, then delivers about 220 l / min and is driven at about 200-250 revolutions / min.

In the lower diagram in 4 a force F is plotted over time t. The lower characteristic 170 shows here a course of the upper piston and the upper characteristic 172 a course of the lower piston. The time interval z is 1.5 sec. A drag 174 takes place in both the lower and the upper piston with a pressure difference between the terminals of the respective displacement control of about 200 bar. The top piston then has a force of about 20 tons and the bottom piston about a force of ten tons. The curve section 176 at the lower piston shows an ejection, which takes place with about 1 ton and a pressure difference of about 25 bar. The duration is about 200-300 ms. The section 178 during the course of the upper piston in the characteristic curve 170 represents the weight of the piston.

The diagrams according to 4 show a "draw-cushion-application" test. In this case, about 20 strokes / min are formed at a travel speed of about 600 mm / s and a delivery volume of about 15,000 cm ³ .

According to 5 is a "punch application" test shown. Here, an upper piston is provided which can apply a force of about 20 tons. The test is carried out at about 900 strokes / min and a travel speed of 600 mm / s and a delivery volume of up to 100 cm ³ . The upper diagram in 5 shows the course of the stroke s over the time t. A characteristic 180 shows here the Doppelhubzeit 182 which is about 30 ms at 4 mm, about 35 ms at 6 mm and about 50 ms at 10 mm. The cycle time 184 can then be about 60 ms, about 70 ms or about 110 ms.

According to the middle diagram in 5 , in which the speed v is plotted over the time t, the maximum speed 186 about 450 mm / s, about 600 mm / s or about 650 mm / s. The cylinder may in this case have a piston with a diameter of about 160 mm and a piston rod with a diameter of about 110 mm. A volumetric flow may then be about 290 l / min, about 380 l / min, or about 420 l / min, and a speed of about 300 revolutions / min, about 400 revolutions / min, and about 450 revolutions / min, respectively.

In the lower diagram in 5 then the force F over time t is shown. The maximum force can be 20 tons and in a time interval 188 be applied by about 5-10 ms. The time interval 190 may be about 60 ms, about 70 ms or about 100 ms. A pressure difference in the displacement control can be about 200 bar.

In 6 an alternative embodiment is shown with regard to an arrangement of safety valves. The remaining hydraulic arrangements are for simplicity in 6 Not shown. According to 6 is the synchronous cylinder 66 represented with sections of the flow paths 68 and 70 , Corresponding 3a are the pressure relief valves between the flow paths 124 and 126 arranged.

Unlike the embodiment in 3a are in the flow path 70 two safety valves 191 and 192 arranged. Furthermore, in the flow path 68 also two safety valves 194 . 196 intended. The safety valves 191 . 192 respectively. 194 . 196 a respective flow path 70 respectively. 68 are arranged fluidly in series. That is, the flow path 68 only then is opened, if both safety valves 194 and 196 are open. Is one of these safety valves 194 . 196 closed, so is the flow path 68 blocked. The same applies to the flow path 70 which is then open when both safety valves 191 . 192 are open. Is one of the safety valves 191 . 192 closed, so is the flow path 70 blocked. The safety valves 191 to 196 are according to the safety valves 112 and 114 of the 3a configured and can be connected hydraulically. By the arrangement of two safety valves 191 . 192 , respectively. 194 . 196 in a respective flow path 70 respectively. 68 is the safety of the hydraulic circuit 65 further improved.

Disclosed is a hydraulic circuit in which a positive displacement control and a valve control are connected in parallel. The positive displacement control is connected with both connections to a consumer as in a closed circuit. The parallel valve control is operated as an open circuit. It is envisaged that the displacement control provides the majority of the hydraulic drive power and thus fluid quantity, while the valve timing deviations simultaneously from a given pressure, travel or speed control curve.

LIST OF REFERENCE NUMBERS

1

machine

2

cylinder

4

cylinder

6

hydraulic circuit

8th

hydraulic circuit

10

displacer

12

displacer

14

valve control

16

valve control

18

hydromachine

20

electric motor

22

piston

24

piston rod

26

cylinder space

28

cylinder space

30

flow path

32

flow path

34

control valve

36

piston

38

machine

40

cylinder

42

cylinder

44

frame

46

control block

48

control block

50

displacer

52

displacer

54

Electrical power

56

Electrical power

58

supply unit

60

switch cabinet

62

Dimensions

64

Dimensions

65

hydraulic circuit

66

Rod cylinders

68

flow path

70

flow path

72

check valve

74

hydraulic pump

76

hydraulic accumulator

78

Pressure relief valve

80

tank

82

drain valve

84

shut-off valve

86

biasing device

88

Pressure reducing valve

90

fixed displacement pump

92

check valve

94

check valve

96

check valve

98

hydraulic accumulator

100

Pressure relief valve

102

drain valve

104

flushing

106

flush valve

108

throttle

110

throttle

112

safety valve

114

safety valve

116

valve body

118

cylinder space

120

Endschaltventil

122

annulus

124

Pressure relief valve

126

Pressure relief valve

128

way valve

130

control line

132

Pressure relief valve

134

check valve

136

check valve

138

displacement measuring system

140

pressure gauge

142

cylinder

144

aggregate

146

pump line

148

electric motor

150

pump line

152

Pressure relief valve

154

tank line

156

tank line

158

leakage line

160

Cooling and filtering device

162

 curve

164

curve

166

curve

168

curve

170

curve

172

curve

174

Pull

176

section

178

section

180

curve

182

Doppelhubzeit

184

cycle time

186

maximum speed

188

time interval

190

time interval

191

safety valve

192

safety valve

194

safety valve

196

Safety valve A1, A2, X, Y connection

A, B

working port

P

pressure connection

T

tank connection

0

Home positions

a

first switching positions

b

second switch positions

AW

output port

E1, E2

 input port

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102012019665 [0002]
• DE 102013221410 [0018]

Claims (15)

Hydraulic circuit for controlling a hydraulically driven machine ( 2 . 4 ), wherein a displacement control ( 10 ) and a valve control ( 14 ) are connected in fluidic parallel, characterized in that the displacement control ( 10 ) a hydraulic machine ( 18 ) with two connections (A1, A2) connected to the machine ( 2 ) each via a flow path ( 30 . 32 ) are connectable to form a closed hydraulic circuit, and wherein the valve control ( 14 ) with the machine ( 2 ) is connectable in an open hydraulic circuit. The circuit of claim 1, wherein when providing a hydraulic drive power of the positive displacement control ( 10 ) with the valve control ( 14 ) At the same time deviations from a predetermined pressure control curve and / or travel control curve and / or speed control curve are compensated. Circuit according to claim 1 or 2, wherein the valve control ( 14 ) during a start-up phase and / or a movement phase and / or a braking phase of the machine ( 2 . 4 ) and / or the displacement control ( 10 ) Adding or removing pressure medium. Circuit according to claim 1, 2 or 3, wherein the hydraulic machine ( 18 ) is designed such that it has a comparatively low inertia and a relatively large displacement. Circuit according to one of claims 1 to 4, wherein the hydraulic machine ( 18 ) of an electric motor ( 20 ), which is designed to have a comparatively low inertia and a comparatively low rotational speed. Circuit according to one of the preceding claims, wherein the valve control ( 14 ) a control valve ( 34 ) designed to have high dynamics and high accuracy. A circuit according to claim 6, wherein a shut-off valve ( 84 ) is provided so that the control valve ( 34 ) from the flow paths ( 68 . 70 ) is separable. Circuit according to claim 6 or 7, wherein the control valve ( 34 ) a hydraulic accumulator ( 76 ), which is designed such that a required working pressure for the machine ( 2 ) is available. Circuit according to one of claims 6 to 8, wherein the control valve ( 34 ) a hydraulic pump ( 74 ) connected. Circuit according to one of the preceding claims, wherein a pretensioning device ( 86 ) is provided to one or both flow paths ( 68 . 70 ) with a predetermined hydraulic pressure. Circuit according to one of the preceding claims, wherein a flushing device ( 104 ) provided on at least one flow path ( 68 . 70 ) is connected and via the pressure medium can be discharged, wherein the flushing device ( 104 ) is controlled such that an influence in a pressure control and / or path control and / or speed control of the machine ( 2 ) is comparatively low or avoided. Circuit according to one of the preceding claims, wherein the displacement control ( 10 ) and the valve control ( 34 ) are doubly secured and monitored. Circuit according to one of the preceding claims, wherein in one or both of the machine ( 2 ) leading flow paths ( 68 . 70 ) of the displacement control ( 10 ) and / or the valve control ( 14 ) a safety valve ( 112 . 114 ) or in each case a plurality of safety valves is or are arranged, wherein in a closed state of the safety valve ( 112 . 114 ) or the safety valves of the associated flow path ( 68 . 70 ) is locked and in an opened state of the safety valve ( 112 . 114 ) or the safety valves of the associated flow path is open. Circuit according to one of the preceding claims, wherein the displacement control ( 10 ) Is protected by an electrical protection circuit. Hydraulically driven machine with a hydraulic cylinder ( 2 ), which depends on a circuit ( 1 ) is controlled according to one of the preceding claims.

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