EP2513490B1 - Method for operating a hydraulic working machine - Google Patents

Description

The present invention relates to a method for operating a hydraulic working machine, in particular a machine tool, according to the preamble of patent claim 1 and a corresponding hydraulic machine.

State of the art

A method for operating a hydraulic working machine according to the preamble of claim 1 and a corresponding hydraulic working machine according to the preamble of claim 7 is made US 5,762,973 known.

Although hereinafter mainly reference is made to processing machines, in particular machine tools, the invention is not limited to these, but rather can be used in all types of working machines in which a, in particular time-variable, i. with time changing fluid pressure and / or volume flow (also referred to more generally below as fluid requirement) is needed. With particular advantage, the invention can be realized in hydraulic systems.

In mechanical engineering, conventional hydraulic systems with a pump and a standard electric motor, on the one hand, and purely electromechanical solutions, on the other hand, are used to provide power for drives.

Hydraulic systems are known to have greater dynamics and higher power and power density over electromechanical systems, but at the same time consume more energy. Electromechanical systems can therefore be more energy efficient; However, flexible processes with high process forces and a high power density can be realized less electromechanically.

To solve this conflict, a hybrid approach can be followed using, for example, Variable Speed Pump Drives (DvP). For this purpose, a pump is used with a standard asynchronous motor or a synchronous servo motor and a fixed displacement pump, wherein the energy is supplied depending on the energy demand in the machine cycle and the respective motor is driven accordingly. The speed of the motor and thus the performance of the constant pump can, for example by a drive controller, be adapted to the needs.

Certain advantages can already be achieved by hybrid methods, but there is still a need for an improved provision of a demand-adapted fluid pressure and / or volume flow for working machines.

Disclosure of the invention

According to the invention for this purpose, a method for operating a hydraulic machine, in particular a machine tool, and a corresponding hydraulic machine with the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

Advantages of the invention

By the proposed measures, a particularly advantageous, demand-dependent and demand-oriented adaptation of a fluid system, in particular a hydraulic pump system, to the fluid requirements of a working machine is made possible. The inventive solution includes a control of the fluid device by a control device of the working machine, in particular by a programmable logic controller, make.

As a result, as explained below, the fluid requirements of a working machine can be served by smaller, more energy-efficient and less powerful pumps. Such less powerful pumps can be driving without overload for a short time in overload mode to meet peak demands. As a consequence, for example, by the solution according to the invention Reduced noise emissions and an electrical energy saving potential can be realized. Furthermore, for example, cooling devices that naturally have to correlate their conductivity directly with the performance of the fluid device can be made smaller and less powerful. Optionally, can be completely dispensed with an additional cooling. With particular advantage can be realized with the inventive measures compared to conventional, valve-controlled hydraulic systems, a significantly lower heat input into the hydraulic oil and thus less wear.

Outside the actual processing time in a corresponding machine, or in other times lower fluid requirements, a variable-speed pump can be operated in partial load operation. In this case, for example, a drive controller reduces the speed of the electric motor and the pump. As a result, for example in a hydraulic system, the energy consumption, the hydraulic loss line introduced into the oil and the noise emissions decrease. As soon as the hydraulic system requires more power again, the drive controller adjusts the speed as needed.

The method according to the invention can involve the use of highly dynamic servomotors which provide the required torque at a very short acceleration time at all times. In a drive controller, which is assigned to this highly dynamic servomotor, decentralized setpoints and actual values are processed and analyzed. A pressure cell can report the actual values to the inverter, which regulates the requested speed accordingly and forwards it to a constant pump. Parameterized software can take hydraulic-specific control strategies into account. For example, the software can compensate for non-linearity typical of hydraulics.

Alternatively, a standard asynchronous motor can be provided to provide the drive function. A dynamic inverter can be used to control the speed of this motor. Both the control or activation of the servomotors and those of the asynchronous motors are carried out according to the invention by means of a control already provided in the working machine, in particular a programmable logic controller.

With particular advantage, a solution according to the invention can also be retrofitted in existing machines, whereby the said energy-saving potentials, together with the further advantages mentioned, can also be implemented in already existing equipment.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and the following still to be explained not only in the particular combination specified but also in other combinations or alone, without departing from the scope of the present invention.

The invention is illustrated schematically by means of exemplary embodiments in the drawing and will be described in detail below with reference to the drawing.

Figur 1

zeigt ein Diagramm zur Veranschaulichung zeitvariabler Fluidanforderungen sowie der Bereitstellung zeitvariabler Fluiddrücke und/oder -volumenströme im Stand der Technik.

Figur 2

zeigt eine schematische Darstellung einer Arbeitsmaschine gemäß einer besonders bevorzugten Ausführungsform der Erfindung.

Figur 3

zeigt ein Diagramm zur Veranschaulichung zeitvariabler Fluidanforderungen sowie der Bereitstellung zeitvariabler Fluiddrücke und/oder -volumenströme gemäß einer besonders bevorzugten Ausführungsform der Erfindung.

figure description

FIG. 1

FIG. 12 is a diagram illustrating time varying fluid requirements and providing time varying fluid pressures and / or flow rates in the prior art. FIG.

FIG. 2

shows a schematic representation of a working machine according to a particularly preferred embodiment of the invention.

FIG. 3

FIG. 12 is a diagram illustrating time-varying fluid requirements and providing time-varying fluid pressures and / or flows in accordance with a particularly preferred embodiment of the invention. FIG.

In FIG. 1 FIG. 2 is a diagram illustrating the operation of fluid requirements in the prior art by providing a time-varying fluid volume flow 30 at time-constant fluid pressure 40. In the diagram 100 is on an x-axis 10th a time in seconds, a fluid volume flow in liters / minute on a first y-axis 20 and a fluid pressure in bar on a second y-axis 21.

Diagram 100 illustrates a processing cycle completed within 60 seconds. The machine cycle illustrated in diagram 100 includes, for example, three hydraulic functions 51, 52 and 53, each with a different fluid requirement.

A first function 51, which is to be executed three times, is, for example, a tool clamping function with a pressure requirement of 100 bar at a flow rate of 15 l / min. Operation of function 51 results in the last three peaks 32 of one second each in fluid flow 30.

In a second function 52, a clamping pressure for a workpiece in a chuck of the working machine is maintained with a pressure requirement of 50 bar at a continuous flow rate of 5 l / min. The operation of the function 52 leads to a base value 31 in the fluid volume flow 30.

In a third function 53 is a two-time clamping (open / close) of a workpiece with a pressure requirement of 50 bar at a flow rate of 15 l / min done. The operation of function 53 results in the first two peak values 32 of one second each in fluid flow 30.

As a result, the working machine in the prior art is controlled so that the maximum necessary pressure of 100 bar is maintained (line 40), the volume flows being between 5 l / min (denoted by 31) and 5 + 15 = 20 l / min (denoted by 32). The beginning of the respective peak values is denoted by 33, their end by 34. Thus, although the peak demand of 100 bar at 20 l / min is required only for relatively short periods of time 32, in conventional fluid devices, constant operation of a corresponding pump to service the potentially maximum retrievable maximum demand is common. In other words, when using non-variable speed pumps, the power of a corresponding hydraulic unit should always be designed for the maximum pressure / flow rate in order to meet the peak requirements, in the present case 100 bar at 20 l / min.

In FIG. 2 is a total of 200, a work machine shown having a hydraulic consumer 202, in particular a consumer with time-varying fluid requirements as explained above, a fluid device 201 and a control device 203.

Although only one hydraulic consumer 202 is illustrated in FIG. 200, it should be understood that the present invention may be implemented particularly in systems having multiple hydraulic consumers 202.

The control device 203 is assigned to the working machine and controls the functions of this working machine (sequence control). The control device 203 therefore has detailed information about the program running in the work machine and thus about the sequence and times of the individual fluid requirements and their temporal variability. With particular advantage, therefore, the control device 203, for example via control means 242, also be used for a regulation or control of the fluid device 201.

The fluid device 201 has a control system 220. The control system 220 interacts with a pump 230, such as a fixed displacement pump 230. The pump 230 is connected via a clutch 233 to a controllable electric motor 231 which, as previously explained, may be provided as an asynchronous motor or servomotor. The control of the electric motor 231 via other control means 243. on. Optionally, a cooling device 232 is provided. It should be emphasized that, in particular due to the measures according to the invention, this cooling device 232 may also be dispensed with.

The control or regulation of the electric motor 231 and thus the pump 230 via a designed as a frequency converter 240 drive controller. The frequency converter 240 has an input 241, via which an actual value of a pressure cell 250 can be provided. The fluid device 201 further has a pressure control system 270, which is designed for example in a conventional manner.

The pump 230 delivers fluid, for example hydraulic oil, via a line 262 from a fluid reservoir 260 and provides this after passing through the pump 230 to the hydraulic consumer 202 at a pressure ready. In a pressure line P, a check valve 263 is provided. Excess fluid is returned to the fluid reservoir 260 via a return line 261.

In FIG. 3 the time-variable fluid pressure 40 resulting from the operation of time-variable fluid requirements of one or more hydraulic consumers in accordance with an embodiment of the invention is shown in a diagram 300 with a time-variable fluid volume flow 30. The machine cycle on which the diagram 300 is based also contains the three hydraulic functions 51, 52 and 53, each with a different fluid requirement. In the FIGS. 1 and 3 are the same elements designated by the same reference numerals and will not be explained again at this point.

The time profile of the volume flow 30 corresponds in diagram 300 to that of the diagram 100, ie there is a temporal change between a basic requirement 31 and a peak requirement 32 FIG. 3 Furthermore, it is illustrated how, with the use of the measures according to the invention, a demand-oriented adaptation to fluid requirements of a working machine by means of activation of a hydraulic unit by a control device, such as eg the control device 203 of FIG FIG. 2 that can be done by working machine.

By a corresponding hydraulic pump or fluid device, a fluid pressure of 50 bar is provided in the periods designated 41, to both the basic requirement according to the function 51, as well as FIG. 1 as well as being able to serve the fluid requirements of the third function 53 of 50 bar and a flow rate of 15 l / min. By a correspondingly controlled pressure increase to 100 bar, preferably at a time 43, which is before the time 33, the fluid device will be able to deliver the then necessary pressure of 100 bar at time 33. By means of such activation for the advance provision of a fluid pressure and / or volume flow, the maximum fluid requirement can be served directly at the time 33. At the end of the maximum requirement 32, ie at the time 34, a corresponding signal is given by the control device, so that after time 34 the fluid device again provides only the base pressure 41 of 50 bar again.

A leading provision 45 of a time-variable fluid pressure 40 at the times 43 illustrated in diagram 300 is made possible in particular by the control device as part of the work machine having precise information about the impending fluid requirements, so that a corresponding fluid device advantageously leads to a fluid requirement can be adjusted.

Through the in FIG. 3 or diagram 300, which is illustrated, for example, by using the in FIG. 2 can be realized, significant advantages can be achieved. Compared to a power of a hydraulic power unit of 4 kW, as in FIG. 1 permanent provision of 100 bar is to be provided under the FIG. 3 only one hydraulic unit with a power consumption of about 2.2 kW required. This weaker hydraulic unit can be driven during the request peaks 32, in particular in the context of function 51, briefly in overload operation, without any damage to be feared.

As a result, a noise emission, an energy consumption and / or a thermal load by such a hydraulic unit or fluid device are significantly reduced.

Claims (9)

1. Method for operating a hydraulic working machine, in particular a machine tool, having an associated control device (203) for the sequential control of the working machine, a hydraulic system with at least one hydraulic load (202) with time-variable fluid requirements (51, 52, 53), and at least one fluid device (201) for providing a fluid pressure (40, 40') and a fluid volume flow (30) for meeting the time-variable fluid requirements (51, 52, 53), the at least one fluid device (201) comprising a variable-speed pump (230), a time-variable fluid pressure (40') for meeting the time-variable fluid requirements (51, 52, 53) being provided as specified by the control device (203) by means of time-variable setting of the rotational speed of the variable-speed pump (230), characterized in that, as specified by the control device (203), a fluid pressure (40') is provided in advance (45) of the time-variable fluid requirements (51, 52, 53).
2. Method according to Claim 1, wherein the fluid pressure (40') is provided in advance (45) in such a way that the fluid requirements (51, 52, 53) are met with the correct fluid pressure.
3. Method according to one of the preceding claims, wherein use is made of a control device (203) which has a programmable logic controller, a numerical controller or a motion controller.
4. Method according to one of the preceding claims,
   wherein at least one pressure setpoint of a closed-loop and/or open loop control device (220) of the variable-speed pump (230) is predefined by the control device (203) for the purpose of setting the rotational speed.
5. Method according to one of the preceding claims,
   wherein different parameter sets and/or predefined values, each assigned to a pressure, of a drive control unit (240) of the variable-speed pump (230) are predefined or activated by the control device (203) for the purpose of setting the rotational speed.
6. Method according to one of the preceding claims, wherein each fluid requirement is assigned to a machine function (51, 52, 53) to be carried out during the operation.
7. Hydraulic working machine which is configured so as to carry out a method according to one of the preceding claims, having an associated control device (203) for sequential control, a hydraulic system with at least one hydraulic load (202) with time-variable fluid requirements (51, 52, 53) and at least one fluid device (201) for providing a fluid pressure (40, 40') and a fluid volume flow (30) for meeting the time-variable fluid requirements (51, 52, 53), wherein the at least one fluid device (201) comprises a variable-speed pump (230), having means (240-243) for predefining a time-variable rotational speed of the variable-speed pump (230) as specified by the control device (203) for providing a time-variable fluid pressure (40') for meeting the time-variable fluid requirements (51, 52, 53), characterized in that the control device (203) has means for providing of the fluid pressure (40') in advance (45) of the time-variable fluid requirements (51, 52, 53).
8. Working machine according to Claim 7, which is constructed as a stationary or mobile processing machine, in particular as a press, machine tool, pressure die-casting machine, pipe bending machine, wood processing machine and/or plastic processing machine.
9. Working machine according to Claim 7 or 8, wherein the fluid device (201) has a drive control unit (240), an electric motor (231), a fixed displacement pump, a pressure measuring device (250), a pressure regulating device (270) a pressure controller and/or a cooling device (232).

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