EP2657400B1 - Drive system and production assembly with such a drive system - Google Patents

Description

The invention relates to a drive system and a production plant with such a drive system.

Often, for example, industrial processes, various loads are synchronously positioned. An example would be so-called cross-cutters with two parallel rolls, on which knife blades are mounted. The rolls with the respective knife blades must be positioned very precisely to each other to obtain a respectively required dimensional accuracy of the crop. If this synchronous positioning can not be achieved with sufficient accuracy, the blades can collide with each other in extreme cases and thereby be damaged or destroyed. With a mechanical coupling of the rollers via gears, this problem can be avoided in principle. For such a coupling, however, a high mechanical bias of the coupling causing gears is required. But this high bias also leads to heavy wear in the field of teeth, so that such a solution is maintenance-prone. In addition, the rigid mechanical coupling requires space that is not always available.

However, if the rollers are driven mechanically separated from each other and synchronously positioned only by electronic means (control / regulation), this approach requires a very rigid connection of the motors to the rollers. However, such a rigid connection requires, for example, the use of torque supports on the stator of the motors in order to relieve the engine bearings. Torque supports require additional space and also require a higher design effort. A stiffening of the motor / load connection thus inevitably increases the moment of inertia of the system. Especially in a highly dynamic process, For example, a packaging process in which a web or multiple webs are processed and processed at high speeds, this is undesirable.

To couple each of a motor with the roller and to avoid bearing overdetermination, couplings and the like are used as connecting elements between a respective motor and a roller. If the space requirement of the motors is so great that, for example, mounting next to one another is not possible, it generally results that the connecting elements (shafts and couplings) between the motors and the load are different, in particular of different lengths. It follows in addition that during an acceleration process, the different connecting elements are clamped different degrees and therefore a synchronous positioning is impossible.

The DE 601 15 310 T2 mentions, inter alia, a drive system with two tool carrier shafts, each driven by a motor. To synchronize the angular positions of the two tool carrier shafts, one of the motors is controlled with respect to the other motor. The DE 10 2006 023 823 A deals with a possibility for error correction in the control of two axle drive devices and suggests that at least one axle drive device should be controllable by two independent control connections. The JP 2010 209746 A deals with a screw compressor, in which two worm rotors are engaged with each other, and suggests an increase in the natural frequencies of the motors driving the worm rotors directly or indirectly DE928073C discloses the features of the preamble of claim 1.

An object of the invention is correspondingly to provide a solution which avoids the disadvantages mentioned above or at least reduces their effects, in particular to provide a solution that allows for separately driven loads an exact and synchronous positioning.

This object is achieved with a drive system with the features of claim 1. For this purpose, in a drive system with at least two motors, each motor a rotating load, namely, for example, a roller drives, and wherein each of the at least two motors is coupled via a at least as part of its material properties dreelastisches connecting element with the respective driven rotating load provided in that a torsional rigidity of the connecting elements is in each case selected such that it leads, in relation to the inertia of the rotating loads, to equal natural frequencies of each oscillating load and of the oscillating system comprising the connecting element which couples the load to the respective motor.

The advantage of the invention is that with such a design (dimensioning) of the connecting elements and the same circumferential accelerations of the rotating loads, in particular rotating rollers as loads, the at least two of each motor driven drive trains behave synchronously. As a drive train here and below the rotating mass and the rotating mass coupling to the respective motor connecting element is called. Since the term "oscillatory system" has already been used above, the terms "drive train" and "oscillatory system" are used interchangeably here.

Overall, the waiver of the usual mechanical coupling of the driven loads is possible. Due to the approach proposed here, the mechanics of the system to be controlled are designed in such a way that a very precise but nevertheless highly dynamic positioning is possible through the use of modern control technology. It can be assumed that the performance of machines and systems with such a drive system is greater than in a design with purely mechanical connections between the rollers. Above all, greater performance means greater speeds, but also greater positioning accuracy and / or lower failure probabilities. The last two aspects arise not least because of manufacturing tolerances, as they are inevitable in a mechanical connection.

Advantageous embodiments of the invention are the subject of the dependent claims. This used backlinks point to the further development of the subject matter of the main claim by the features of the respective subclaim; they should not be construed as a waiver of obtaining independent, objective protection for the feature combinations of the dependent claims. Furthermore, with a view to an interpretation of the claims in a closer specification of a feature in a subordinate claim, it can be assumed that such a restriction is not present in the respective preceding claims.

In one embodiment of the drive system is provided that it comprises a control device and that the control device for synchronous positioning of each of the at least two motors is effective. Such a synchronous positioning of the at least two motors which can be achieved by means of a suitable regulation makes it possible to achieve equal circumferential accelerations of the respective rotating masses, in particular also to maintain such equal circumferential accelerations permanently. With the above-described design of the connecting elements, which initially only determines their dynamic behavior in the excited state, and the synchronous positioning achieved by the control and the consequent equal circumferential accelerations, this results in a total of the synchronous behavior of the at least two drive trains.

In a further embodiment of the drive system is provided that the control device dampens the decay of the at least two oscillatory systems. This damping takes account of the fact that it is often not possible to achieve absolutely identical natural frequencies of the at least two oscillatory systems. Such residual differences in the natural frequencies, however, result in positioning processes, for example, to a different decay behavior of the rotating masses. If this decay is not sufficiently damped, so if vibrations occurring during positioning do not decay fast enough, this can call into question the synchronicity of the at least two drive trains. When caused by the control device sufficiently strong damping of such decay processes, the problem does not occur and the synchronicity is maintained.

A particular embodiment of the drive system described here with at least two drive trains, so rotating Loads, is that it is at least one of the rotating loads to a roller with blades or a cutting blade, ie a knife roller, so that acts as a rotating load at least one knife roller. Such knife rollers, which cause separation of sections from the paper web, for example, in a running paper web or the like, must be positioned very accurately. The drive system described here and below ensures such a highly accurate positioning, especially when it comes to a highly accurate positioning in relation to a positioning of another rotating load (drive train). As such another rotating load, for example, a roller for applying adhesions or the like comes into consideration.

In a specific embodiment of the drive system described here having at least two drive trains, it is provided that two knife rollers act as rotating loads. Two such knife rollers are used, for example, to separate sections of a running track of exactly the same length or of a length which is at least equal within predetermined tolerances. For the two knife rollers so that a highly accurate synchronous positioning is required, which allows the drive system described here and below. The high-precision positioning also reliably prevents, for example, collisions of the blades / cutting blades of the two knife rollers. This avoids damage to the respective production facility, or at least standstill times, which are normally unavoidable if an exceptional situation occurs within the production facility, that is, for example, a collision between two tools.

The approach as described here and below is basically applicable to more than two drives / drive trains. Thus, the invention also relates to a drive system of the type described here and below with more than two motors and each driven rotating loads.

Finally, the invention also relates to a production plant, in particular an automatic or at least semi-automatic production plant, with at least one drive system with one or more features described herein.

As a production plant comes specifically a packaging system or generally a system that separates sections of a running web, into consideration.

The advantage of the invention and its embodiments is therefore in particular that a possibility is given to enable a synchronicity of the positioning of rotating loads, which was not previously attainable with a pure regulation. A need for such synchronicity is not necessarily limited to drive trains arranged close to one another, but can also be useful for further separate drive trains within one and the same production plant, for example by first applying alignment marks and then adhesive points to a running material web, and finally with at least one another drive train or two drive trains sections are separated from the material web. This example would require a synchronization of three or four drive trains, which is also readily feasible with the approach proposed here.

The above-mentioned object is also achieved with regard to the control characteristics with a control device for the synchronous positioning of each of the at least two motors and / or for damping the swinging out of the at least two oscillatory systems. This aspect of the invention is implemented in software or in hardware or a combination of software and hardware. Insofar as an implementation in software is envisaged, an embodiment of the invention thus also comprises, on the one hand, a computer program with program code instructions executable by a computer and, on the other hand, a storage medium with such a computer program, Thus, a computer program product with program code means, as well as finally a control device in the memory as a means for performing the method and its embodiments, such a computer program is loaded or loadable.

An embodiment of the invention will be explained in more detail with reference to the drawing. Corresponding objects or elements are provided in all figures with the same reference numerals.

The or each embodiment is not to be understood as limiting the invention. Rather, in the context of the present disclosure, modifications and modifications are possible, in particular those, for example, by combination or modification of individual in conjunction with the described in the general or specific description part and in the claims and / or drawings features or elements or method steps for the expert with regard to solving the problem can be removed and lead by combinable features to a new object or to new process steps or process steps.

FIG 1

eine Querschneider-Einheit mit zwei Schneidwalzen,

FIG 2

die Situation gemäß FIG 1 in einer schematisch vereinfachten Darstellung,

FIG 3

eine nochmals verallgemeinerte Darstellung der Situation gemäß FIG 2 und

FIG 4

sowie

FIG 5

Darstellungen von Simulationsergebnissen.

Show it

FIG. 1

a cross cutter unit with two cutting rollers,

FIG. 2

the situation according to FIG. 1 in a schematically simplified representation,

FIG. 3

a further generalized representation of the situation according to FIG. 2 and

FIG. 4

such as

FIG. 5

Representations of simulation results.

FIG. 1 shows an example of an application situation of the drive system described below, a cross-cutter unit 10. This includes driven, rotating loads 12, 14. These are in the situation illustrated around rollers, namely rollers with blades or a cutting blade (cutting rollers), so that the function can be met as a cross cutter. The further description is continued on the basis of the application of a cross cutter 10, so that in the following, but without renouncing any further generality, rotating loads of a general nature are accordingly also referred to as rollers 12, 14.

Each roller 12, 14 is driven by a motor 16, 18. Each motor 16, 18 is coupled to the respective driven roller 12, 14 via a torsionally elastic connecting element 20, 22, at least within the scope of its material properties.

The representation in FIG. 2 is a schematically simplified illustration of a detail of the situation in FIG. 1 , FIG. 2 specifically takes into account the situation that the respective space requirements of the motors 16, 18 prevents their attachment side by side, so that the connecting elements 20, 22 are different, in particular different lengths. Here a situation of different lengths is shown and the lengths of the connecting elements are symbolically entered as L1 and L2. Such and similar differences of the respective connecting elements 20, 22 cause them to be clamped differently in an acceleration process. This makes a synchronous positioning of the two rollers 12, 14 impossible. So far, one has essentially tried to address this problem by the fact that the rollers 12, 14 were mechanically coupled. Such a mechanical coupling can be realized, for example, with two toothed wheels which are in engagement and which are each assigned to a roller 12, 14 and are arranged between roller 12, 14 and connecting element 20, 22. However, such a mechanical coupling has the disadvantages outlined above, so that another possible solution is proposed here.

While in FIG. 2 nor the motors 16, 18 and the rollers 12, 14 are shown with the connecting elements 20, 22 therebetween, the connecting elements 20, 22 also in general, namely as a torsion spring, as in FIG. 3 is shown. It is irrelevant how the fasteners 20, 22 procured and executed in detail and whether they include, for example shaft sections and coupling elements. In a very abstract manner, these connecting elements 20, 22 have different lengths and in each case have a spring constant which has not yet been defined and which is also referred to below as torsional rigidity c1, c2.

Even if FIG. 3 shows an abstracted situation, nevertheless the reference numerals from the preceding figures are used to make the connections clear.

und kann nach dem gesuchten Aufspannwinkel ϕ_i umgeformt werden: $${\mathrm{\varphi }}_{\mathrm{i}}={\mathrm{J}}_{\mathrm{i},\mathrm{Last}}{\mathrm{\omega }}^{•}{}_{\mathrm{i},\mathrm{Last}}/{\mathrm{c}}_{\mathrm{i},\mathrm{Torsion}}={\mathrm{\omega }}^{•}{}_{\mathrm{i},\mathrm{Last}}/{\left(2{\mathrm{\pi f}}_{\mathrm{i},\mathrm{Tilger}}\right)}^2$$

In order to be able to make the optimum choice of these torsional stiffnesses c1, c2 on which the approach proposed here is based, the clamping of the motor / load connection is derived. In FIG. 3 the mechanical relationships that are important for this derivation are shown. In order to accelerate the respective load 12, 14, a moment J1, J2 acts which spans the respective torsion spring 20, 22 functioning as a connecting element. The spring tension is given by Hooke's law in conjunction with the third Newtonian axiom, according to which a force exerted on a body always counteracts a counterforce of the same magnitude, $${\mathrm{J}}_{\mathrm{i}.\mathrm{load}}{\mathrm{\omega }}^{•}{}_{\mathrm{i}.\mathrm{load}}={\mathrm{c}}_{\mathrm{i}.\mathrm{torsion}}{\mathrm{\phi }}_{\mathrm{i}}$$

and can be transformed according to the desired clamping angle φ _i : $${\mathrm{\phi }}_{\mathrm{i}}={\mathrm{J}}_{\mathrm{i}.\mathrm{load}}{\mathrm{\omega }}^{•}{}_{\mathrm{i}.\mathrm{load}}/{\mathrm{c}}_{\mathrm{i}.\mathrm{torsion}}={\mathrm{\omega }}^{•}{}_{\mathrm{i}.\mathrm{load}}/{\left(2{\mathrm{\pi f}}_{\mathrm{i}.\mathrm{<figure-callout\; id="2"\; label="absorber"\; filenames="imgf0002.png"\; state="\{\{state\}\}">absorber</figure-callout>}}\right)}^2$$

In this case, ω ^• = dω / dt denotes the change of the angular velocity ω over time.

empfehlenswert.If the accelerated rollers 12, 14, namely their effective load moments of inertia J1, J2, are to behave synchronously on the circumference, then the notation is correct $${\mathrm{s}}_{\mathrm{i}}={\mathrm{r}}_{\mathrm{i}}{\mathrm{\phi }}_{\mathrm{i}}={\mathrm{r}}_{\mathrm{i}}{\mathrm{\omega }}^{•}{}_{\mathrm{i}.\mathrm{load}}/{\left(2{\mathrm{\pi f}}_{\mathrm{i}.\mathrm{<figure-callout\; id="2"\; label="absorber"\; filenames="imgf0002.png"\; state="\{\{state\}\}">absorber</figure-callout>}}\right)}^2={\mathrm{a}}_{\mathrm{i}.\mathrm{load}}/{\left(2{\mathrm{\pi f}}_{\mathrm{i}.\mathrm{<figure-callout\; id="2"\; label="absorber"\; filenames="imgf0002.png"\; state="\{\{state\}\}">absorber</figure-callout>}}\right)}^2$$

recommended.

In this case, f _i, Tilger is the natural frequency of the respective oscillatory system _, which is also referred to below as the absorber frequency. The oscillatory system is the respective powertrain ( FIG. 1 . FIG. 2 The natural frequency occurs, for example, when the motor 16, 18 is stationary and the load 12, 14 oscillates with the torsion spring (the connecting element 20, 22): $${\mathrm{f}}_{\mathrm{i}.\mathrm{absorber}}=1/\left(2\mathrm{\pi }\right){\left({\mathrm{c}}_{\mathrm{i}.\mathrm{torsion}}/{\mathrm{J}}_{\mathrm{i}.\mathrm{<figure-callout\; id="1"\; label="load"\; filenames="imgf0002.png"\; state="\{\{state\}\}">load</figure-callout>}}\right)}^{1/2}$$

The circumferential error s _i (see above, equation 3) is thus correlated with the acceleration a _{i of} the load 12, 14 at the circumference of the radius r _i . If both load inertia J1, J2 are moved synchronously, so on both the same acceleration a _i must act on the periphery. So that both springs (connecting elements 20, 22) cause the same circumferential error s _i , they must have the same absorber frequency f _i, Tilger.

From f _{1, Tilger} = f _{2, Tilger} followed by the same circumferential acceleration a ₁ , a ₂ each have the same circumferential error s ₁ = s ₂ .

In relation to each other then no error occurs on the circumference of the rollers 12, 14. Both springs (connecting elements 20, 22) are indeed deflected, but in each case by the same amount and in the same direction. In addition, they also oscillate in sync with each other. A very precise positioning of the two rollers 12, 14 or even multiple rollers (not shown) is thus possible.

By a suitable regulator setting of a control device not shown separately for controlling the two motors 16, 18 should also be sought that the motors 16, 18 are synchronously positioned and that the control sufficiently dampens the decay of the two drive trains. The synchronous positioning causes the same or at least sufficiently equal circumferential accelerations a ₁ , a ₂ .

A high attenuation makes sense because it practically never succeeds in designing the connecting elements 20, 22 in such a way that really identical natural frequencies result. Accordingly, it is to be expected that always small differences in the absorber frequencies remain. If the vibrations do not turn off quickly enough during positioning, there is a risk that the synchronicity will be lost after a few oscillation periods. In a strongly damped decay of the vibrations, this problem does not occur.

When the load inertia J1, J2 are identical in each individual case which satisfies equating the torsional rigidities c1, c2 to the Tilgerfrequenzen f _{1, absorber,} f _2, adjust _absorber.

The exemplary application scenario of a cross cutter 10 (FIG. FIG. 1 ) illustrates the advantage of the mechanical balancing described here. Here, two rollers 12, 14 are driven with, for example, identical inertia (J = 4 kgm ² ) and are to be positioned synchronously on the circumference. Within about 0.2 s, the rollers 12, 14 starting from a standstill rotated by 180 ° and braked again to a standstill. Here are used as motors 16, 18, two torque motors per shaft. Both torque motors are mounted on one side of the roller 12, 14 via a coupling with a connecting sleeve and connected to the rollers 12, 14, so that the combination of coupling and connecting sleeve acts as a connecting element 20, 22.

The two connecting elements 20, 22 (coupling with connecting sleeve) are - as described above - designed so that they lead in the driven load 12, 14 to the same Tilgerfrequenz f _{1, Tilger} f _{2, Tilger} . Since both rollers 12, 14 in the assumed Example, the same inertia J = 4 kgm ² , so the two connecting elements 20, 22 are designed for the same torsional stiffness c1, c2.

A finite element model of such a drive system enables a computer-aided numerical simulation of the positioning process. The illustrations in FIG. 4 and FIG. 5 show the results of two different simulations.

In FIG. 4 be in a coordinate system in which the time t in seconds on the abscissa and the ordinate the clamping of the drive train, namely in particular the clamping of the respective connecting element 20, 22, is plotted in millimeters, the circumferential error s _i shown by the fixtures the connecting elements 20, 22 arise. Two different bills are compared. In a first calculation, it is assumed that the two rollers 12, 14 have different absorber frequencies f _{1, absorber} f _{2, absorbers} , since connecting sleeves of different lengths in the couplings lead to this detuning.

The result of this simulation is represented by a first and a second curve 30, 32. The first curve 30 shows the clamping error due to the greater length L2 (FIG. FIG. 2 The softer connection on the lower roller 14, the second curve 32, the error on the short coupling of the upper roller 12. The error caused by the clamping is temporarily even more than 0.5 mm at the periphery. It is striking that the curves deviate very clearly from each other. The softer connection coupling on the lower roller 14 leads to almost twice as large clamping.

In FIG. 5 the difference between the set stresses of the two drive trains, namely in particular a difference between the two setups of the respective connection elements 20, 22, is shown in seconds above the time plotted on the abscissa. The difference (curve 34), ie the mispositioning, is over 0.2 mm and stops only after a few periods.

This error can cause problems for many applications. With a cross cutter, this relative error can destroy the blades mounted on the rollers 12, 14.

In contrast, as the third curve 36 in FIG. 4 the result of another simulation presented. Here, a mechanical symmetrization was carried out according to the approach described here. In this case, the absorber frequencies f _{1, Tilger} , f _{2, Tilger} the two rollers 12, 14 were adapted by a suitable design / dimensioning of the connecting elements 20, 22 to each other. In the illustration in FIG. 4 It can be seen that there is still an error of 0.4 mm on the circumference. However, compared to the clearly spaced curves 30, 32, the resulting curves are now so close together that they are indistinguishable in appearance and appear as a curve, curve 34. Accordingly, the relative error (curve 38; FIG. 5 ) after such a mechanical symmetrization significantly smaller than in the previously considered simulation. This results even though the respective fixtures are still comparatively high. However, the stresses occurring in each drive train are the same. This is especially important for a sheeter and understandably affects the quality of cut.

While the invention has been further illustrated and described in detail by the exemplary embodiment, the invention is not limited by the disclosed or disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Individual aspects of the presently filed description may thus be briefly summarized as follows: A drive system with at least two motors 16, 18 is indicated, each motor 16, 18 driving a rotating load 12, 14 and each of the at least two Motors 16, 18 is coupled via a connecting element 20, 22 with the respective driven rotating load 12, 14.

It is provided with respect to the connecting elements 20, 22 or at least one connecting element 20, 22 that a torsional stiffness is chosen so that they in relation to an inertia of the rotating loads 12, 14 at the same natural frequencies each having a rotating load 12, 14 and the load 12, 14 leads to the respective motor 16, 18 coupling connecting element 20, 22 comprehensive oscillatory system.

Claims (8)

1. Drive system having at least two motors (16, 18), each motor (16, 18) driving a rotating load (12, 14), and each of the at least two motors (16, 18) being coupled via a connecting element (20, 22) to the respectively driven rotating load (12, 14), the connecting elements (20, 22) having different lengths, characterized in that a torsional rigidity of the connecting elements (20, 22) is chosen such that, in relation to an inertia of the rotating loads (12, 14), they lead to the same natural frequencies of each oscillating system, wherein each oscillating system respectively comprises a rotating load (12, 14) and the connecting element (20, 22) coupling the load (12, 14) to the respective motor (16, 18).
2. Drive system according to Claim 1, having a control device for the synchronous positioning of each of the at least two motors (16, 18).
3. Drive system according to Claim 2, wherein the control device damps the excursions of the at least two oscillating systems.
4. Drive system according to one of the preceding claims, wherein at least one knife roller functions as a rotating load (12, 14).
5. Drive system according to Claim 4, wherein two knife rollers function as rotating loads (12, 14).
6. Drive system according to one of the preceding claims, having more than two motors (16, 18) and rotating loads (12, 14) respectively driven thereby.
7. Production assembly having at least one drive system according to one of the preceding claims.
8. Packaging assembly having at least one drive system according to one of the preceding claims.

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