TRANSPORT DEVICE WITH REDUCED CREASING FOR BATTERY FOILS

Abstract

Proposed is a transport device for transporting a carrier in the form of a foil for producing electrodes for energy accumulators, in particular electrodes for lithium-ion batteries, having at least two rollers on which the carrier is able to be borne, and of which at least one roller is provided with a drive so as to transport the carrier from roller to roller. Provided for reducing creasing is a drive device for generating an additional force that facilitates transport, wherein the drive device for generating an alternating magnetic field has an alternating field generator which generates a temporally alternating magnetic field, the magnetic field being oriented such that, in addition to the effect of force in the transport direction, an effect of force perpendicular to the transport direction is initiated in the plane of the carrier.

Claims

1. A transport device for transporting a carrier in the form of a foil for producing electrodes for energy accumulators, having a least two rollers on which the carrier is able to be borne, and of which at least one of the rollers is provided with a drive so as to, by rotating the driven roller, move the carrier along the longitudinal extent thereof in a transport direction and to transport the carrier from roller to roller, further comprising a drive device for generating an alternating magnetic field that has an alternating field generator which, for generating eddy currents in the carrier, generates a temporally alternating magnetic field in order to exert a Lorentz force on the charges flowing in the carrier as a result of the eddy currents, said magnetic field being oriented such that, in addition to the effect of force in the transport direction, an effect of force perpendicular to the transport direction is initiated in the plane of the carrier.

2. The transport device according to claim 1, wherein the alternating field generator is disposed such that the latter is not in contact with the carrier during transport.

3. The transport device according to claim 1, wherein the drive device and/or the alternating field generator are/is configured for permitting forces to act on the carrier on at least two different points which lie along the transverse extent of said carrier perpendicular to the transport direction, said forces pointing in two mutually dissimilar directions.

4. The transport device according to claim 1, wherein the drive device and/or the alternating field generator are/is configured for permitting transverse forces to act on the carrier on the lateral peripheries of the carrier, said transverse forces in the carrier plane being directed perpendicularly to the transport direction and being greater than the forces acting in the center of the carrier and in the transverse extent in terms of the latter.

5. The transport device according to claim 1, wherein the alternating field generator is integrated in one of the rollers.

6. The transport device according to claim 1, wherein the alternating field generator is configured as a rotor, at least two permanent magnets being disposed along the circumference of said rotor.

7. The transport device according to claim 6, wherein the permanent magnets are disposed in a Halbach array along the circumference such that the fields in the interior of the permanent magnets are in each case oriented so as to be tangential or radial in relation to the path of rotation in the rotation plane.

8. The transport device according to claim 6, wherein at least one of the permanent magnets is in each case tilted about an axis running radially in relation to the rotation axis of the rotor.

9. The transport device according to claim 6, wherein the permanent magnets in the peripheral region of the rotor that is situated on the lateral region of the carrier are more intensely tilted about an axis running radially in relation to the rotation axis of the rotor than in the central region of the rotor.

10. The transport device according to claim 1, wherein the drive device and/or the alternating field generator are/is configured for permitting forces to act on the carrier, said forces running so as to be mirror-symmetrical in terms of a symmetry axis which is parallel to the transport direction and through which the center of the carrier runs.

11. The transport device according to claim 1, wherein the alternating field generator is configured as a stator of a linear motor which is disposed relative to the transport section of the carrier such that the carrier is driven as a rotor.

12. The transport device according to claim 11, wherein the stator of the linear motor has at least three coils which are disposed along the transport section of the carrier and through which a mutually phase-delayed alternating current flows.

13. The transport device according to claim 12, wherein the coils are disposed in the form of a matrix so as to be parallel to the carrier plane.

14. The transport device according to claim 1, wherein an orienting device is provided for orienting graphite particles as an electrode for lithium-ion batteries, in a coating with which the carrier is provided, said orienting device for orienting generating a magnetic field that is variable in terms of time and/or location.

15. The transport device according to claim 14, wherein the orienting device is configured for generating eddy currents in the carrier plane in the carrier, the preferred directions of said eddy currents in the center of the carrier, running transversely to the transport direction on the periphery of the carrier running in and/or obliquely to the transport direction.

Description

BRIEF DESCRIPTION OF THE INVENTION

[0022] Exemplary embodiments of the present invention are illustrated in the drawings and will be explained in more detail below with further details and advantages being set forth.

[0023] FIG. 1 shows a schematic illustration of a transport device according to the present invention, having a magnetic roller;

[0024] FIG. 2 shows a schematic illustration of a transport device according to the present invention, having a mirror-symmetrical disposal of the permanent magnets;

[0025] FIG. 3 shows a schematic illustration of the distribution of forces; and

[0026] FIG. 4 shows a schematic illustration of a transport device, having a stator of a linear motor.

DETAILED DESCRIPTION OF THE INVENTION

[0027] FIG. 1 shows a schematic of a transport device 1 having a carrier 2 which in the transport direction 3 is transported in a roller-to-roller process. The carrier 2 is coated with a layer which contains graphite particles. These graphite particles are subsequently oriented in a magnetic field which is variable in terms of time and/or location. This orienting device is also not illustrated in FIG. 1. As a result of magnetic induction as a consequence of the changing magnetic field, eddy currents are induced in the electrically conducting carrier (a copper foil, for example). These eddy currents generate magnetic fields which interact with the outer magnetic fields and cause a braking force. These braking forces can represent the cause for web warping.

[0028] Moreover, web tensions that act on the carrier can also be created in that the carrier web is very long and/or high transport speeds occur.

[0029] In order to counteract creasing as a result of these web tensions, an additional drive device 5, which is configured as a magnetic roller 13, is provided. Permanent magnets 12 are disposed along the circumference in a roller 11, the permanent magnets 12 in a Halbach array here being disposed in an alternating manner parallel to the surface of the roller 11 in the rotation direction (clockwise in FIG. 1), radially outward, parallel to the surface counter to the rotation direction, then radially inward, etc.

[0030] The magnetic roller 13 below the carrier 2 rotates clockwise at the rotating speed a), so as to generate a temporally variable magnetic field. To this end, the roller 11 per se is mounted on a static shaft and with roller bearings.

[0031] To be seen in FIG. 1 is also a lateral illustration of the magnetic roller 13, when viewed perpendicularly to the rotation axis D, and a perspective illustration of the magnetic roller 13, wherein the permanent magnets 12 along the circumference of the roller 11 are tilted by the angle α in relation to the transport direction 3, or in relation to an orientation perpendicular to the rotation axis D, respectively, so as to by magnetic induction generate forces that do not run parallel to the transport direction 3 but also comprise transverse forces in order to be able to avoid creasing even more effectively.

[0032] Creasing as a result of web tensions can typically be associated with bulging, the latter running toward the sides about an axis along the transport direction 3. FIG. 2 shows a transport device 1, wherein the carrier 2 to be transported is shown in a plan view from above. The additional drive device 5 is disposed below the carrier 2. The drive device 5 in the same view is shown once again beside the latter. The additional drive device 5 comprises a magnetic roller 13, permanent magnets 12 being disposed on the surface of the magnetic roller 13. The roller 13 rotates about the rotation axis D at the rotating speed a), so as to generate a temporally variable magnetic field. The envelope surface is divided into four regions, wherein the inner regions 14 show a disposal of the permanent magnets 12 in the rotation direction D. The permanent magnets 12 in the peripheral regions 15 are tilted in relation to the rotation axis D. The disposal of the permanent magnets 12 runs so as to be mirror-symmetrical in terms of an axis 3, the latter here coinciding with the transport direction. The drive device 5 is disposed below the carrier 2 such that the carrier in terms of the transverse extent thereof is completely engaged by the magnetic roller 13. The carrier 2 in the peripheral regions thereof is thereafter predominantly penetrated by the field lines of the magnetic fields of the permanent magnets 12 from the regions 15.

[0033] In this way, the direction of force in the peripheral regions 15 of the carrier 2 also deviates from the direction of force in the center 14 of the carrier 2. The effect of force in the center 14 is oriented so as to be parallel to the transport direction 3; the force acting on the carrier 2 in the peripheral regions 15 includes a component that in the carrier plane points away from the carrier 2, thus a transverse component.

[0034] FIG. 3 shows the illustration of the force vectors in the peripheral regions 15. The transport device 1 is again shown schematically when viewed toward the plane in which the carrier 2 is transported in the transport direction 3. The oblique position of the permanent magnets 12 of the drive device 5 is only schematically indicated. As a result of magnetic induction as a consequence of the magnetic fields being temporally changed by the rotation of the roller 13, eddy currents are created in the carrier 2. Lorentz forces act on the moving charges in the outer magnetic field, the Lorentz forces reducing undesirable braking forces parallel to the transport direction but also being able to counteract creasing all the more because transverse forces act on the peripheries.

[0035] The Lorentz forces substantially weaken the braking forces in the center 14. The Lorentz forces F are more intensely oriented outward in the peripheral regions 15. The acting force component F.sub.p in the transport direction 3 is smaller than the transverse force F.sub.s acting perpendicularly thereto. The closer to the periphery of the carrier 2, the greater the transverse forces that by lateral pulling can reduce bulging of the carrier 2, while the web tension in the center 15 of the carrier 2 is substantially reduced by reducing the braking forces.

[0036] The drive device 5 is preferably configured for not contacting the carrier 2, thus for operating in a non-contacting manner, so as not to damage the coating of the carrier 2, or disturb the orientation of the particles contained in the latter, respectively.

[0037] It is illustrated in FIG. 4 how such a drive device 5 can furthermore be implemented. For example, in order to exert high accelerations on the carrier 2 during the linear movement of the latter, the stator 20 of a linear motor can also be used as the additional drive device 5. Grooves 22, which in each case accommodate the coils 23, 24, 25, are incorporated in the iron core 21. The coils 23, 24, 25 are passed through by a phase-delayed 3-phase alternating current. The arrangement with a linear motor typically requires a high power consumption and produces a lot of heat.

[0038] In order to permit the transverse-force components in the peripheral regions 15 of the carrier 2 to become effective with respect to a parallel orientation in the center 14, the coils in the stator 20 are disposed in the form of a matrix in a plane parallel to the carrier plane, and are correspondingly tilted in the peripheral regions 15.

LIST OF REFERENCE SIGNS

[0039] 1 Transport device [0040] 2 Carrier [0041] 3 Transport direction [0042] 5 Additional drive device [0043] 11 Roller [0044] 12 Permanent magnets [0045] 13 Magnetic roller [0046] 14 Central region [0047] 15 Peripheral region [0048] 20 Stator of a linear motor [0049] 21 Iron core [0050] 22 Groove [0051] 23, 24, 25 Coils [0052] D Rotation axis [0053] F Force [0054] F.sub.p Force component parallel to the transport direction [0055] F.sub.s Force component perpendicular to the transport direction [0056] ω Rotating speed [0057] α Angle