DE102021116070B4 - Winding method for manufacturing a polygonal battery cell and device for manufacturing the polygonal battery cell - Google Patents

Abstract

The invention relates to a winding method for producing a polygonal battery cell (4), in which a polygonal core (6) is rotated about an axis of rotation (7, 30) and the winding tape (9) is wound around the core (6) so that the core (6) and the winding tape (9) form the battery cell (4) in a wound state, the cross section (8) of which has the polygonal contour. To reduce a pulsating force (11) on the winding tape (9), the core (6) is rolled over the winding tape (9) on an inverse cam track (27), which has the shape of an inverse curve (15) corresponding to the contour of the cross section (8). wherein the inverse curve (15) represents a catenary or a cycloid arc or an epicycloid arc or a sawtooth line interval. Additionally or alternatively, the winding tape (9) can be actively fed to the core (6) via a roller (25) by means of a freely suspended loop (26), the loop length corresponding to the length of at least one inverse curve (15).

Description

The invention relates to a winding method for producing a polygonal battery cell. The winding method is based on at least one core having a polygonal contour and at least one winding tape comprising at least one battery cell material, which is wound around the core. The invention also relates to a device for producing the polygonal battery cell, the device being set up to wind at least one winding tape as a so-called cell winding around the at least one core with the polygonal contour.

Winding processes for cylindrical coils have been known for a long time. In this case, rollers with a circular cross-section are used. If you want to produce polygon-shaped coils with this process, a pulsating force or jerks occur during application, which can affect the quality of the coil. For example, this pulsating force can tear a wrapping tape or reduce the uniformity of the application, although in certain cases such as battery cells it would be desirable. In electrically powered motor vehicles, the battery module consists of individual cells. If these cells are manufactured like the coils, then according to the prior art they are cylindrical. Square cells can also be produced using a different manufacturing technology. However, winding has great savings potential in production. Because of the cylindrical shape, however, the battery cell has a technical disadvantage in this case, since there is unused space within the battery module in this embodiment. The utilization of the installation space is therefore not optimal in the case of a cost-effective production of battery cells using a winding process. It is therefore desirable to produce square or hexagonal battery cells inexpensively, although theoretically perfect space filling in the battery module should still be possible. When using square or hexagonal battery cells for a battery module, about 10 percent better space utilization can be achieved compared to cylindrical battery cells, which ultimately leads to an increase in the energy density of the battery module.

That's it CN 210 384 729 U discloses a winding method for an electric resistance, in which a material layer of the resistance material is wound around a hexagonal core itself made of a magnetic material. Electromagnets are arranged on the resistance material at regular intervals so that the magnetic core runs on the material layer for winding and the material is evenly wound around the corners of the hexagonal core by means of electromagnetic attraction. The disadvantage of the known method is that the space within the resistor is not optimally used and a lower material density is achieved.

From the CN 111 478 474 A a manufacturing method for a polygon-shaped rotor of an electric motor is known, in which coil wire is wound around a polygon-shaped core in order to produce a coil with a polygon-shaped contour. The pulsating force that acts on the wire while it is being wound around the polygonal contour is kept within a specified tolerance range by controlling the voltage that occurs in the wire during winding, the speed of the coil during winding and the temperature of the wire, see above that the wire does not break.

From the U.S. 6,425,547 B1 a winding device and a winding method is known in which paper is circulated from a large carrier roll onto small, coreless rolls. In the device for circulating the paper from the carrier roll to the small, coreless rolls, the paper is guided through several stations along a hypocycloid, which means that the paper strips between the individual stations cannot get tangled with each other. The disadvantage of the known method is that pulsating fluctuations that occur when winding polygonal rolls are not reduced.

The object of the invention is to provide a winding method for manufacturing polygonal battery cells, in which a pulsating force during the application of the battery cell material around the core of the battery cell is reduced, the application of the battery cell material to the core being uniform despite the polygonal shape of the battery cell should take place.

The object is solved by the subject matter of the independent patent claims. Advantageous developments of the invention are described by the dependent patent claims, the following description and the figures.

The invention provides a winding method for producing a polygonal battery cell. The polygonal battery cell comprises at least one core, which has a polygonal contour in cross section (instead of the usual circular contour) and at least one winding tape, which comprises at least one battery cell material, which is wound around the core. For winding, the core is rotated about an axis of rotation and the winding tape around the Core wound, so that the core and the winding tape form the battery cell in a wound state, the cross-section continues to have the polygonal contour. The cross section is thus only thickened, in particular in comparison to the bare core, and blunted at the corners by the wound-up winding tape. The cross section of the battery cell includes the core and, in addition, at least one layer of the winding tape. In other words, the battery cell and the core have the polygonal contour. At least one winding strip is wound around the at least one core for winding the battery cell, so that overall the polygonal contour of the core is retained in the battery cell. The core can be provided as a rod with the polygonal cross section. A material of the core can be electrically insulating. For example, the core can be based on a plastic and/or a ceramic.

The winding method is characterized in that the winding tape is fed to the core during winding along an inverse curve path of at least one inverse curve, which corresponds to the geometric shape of a rotation of the polygonal contour of the cross section, the respective inverse curve being a chain line or a cycloid arc or an epicycloid arc or represents a sawtooth line interval or, in particular, an associated inverse thereof ("upside down"). The cycloid arc, the epicycloid arc and the sawtooth line interval each describe the geometric shape within a periodic interval of a cycloid, epicycloid or sawtooth line. The geometric shape of the periodic interval in the cycloid and the epicycloid can be an arc of a circle. For a sawtooth line, the geometric shape of the periodic interval can be a triangle. The inverse cam track is recessed or notched in such a way that an axis of rotation of the core remains stationary during the rotation of the core or moves along a straight line, with the winding tape resting or abutting on a surface of the inverse cam track for feeding, which corresponds to a series of inverse cam pieces, and the cross section of the battery cell on the winding tape is rolled along the surface of the inverse curved path for winding the battery cell.

Each inverse curve section of the inverse curve path comprises a series of inverse curves, i.e. individual geometric arcs or humps, with the number of inverse curves in the inverse curve section depending in particular on the number of sides of a polygon, in particular on the number of sides of the contour, which extends over the inverse curve section by at least one complete revolution, therefore should roll by a rotation angle of at least 360 degrees. For example, if the contour is a square, the inverse curve piece may comprise four inverse curves, hence four arcs or "humps" over which the sides of the square can roll for one revolution. If the contour is a pentagon, the inverse curve segment can comprise five inverse curves, for example. Each side of the contour therefore rolls once over an inverse curve. The number of inverse curves on the inverse curve piece can therefore be the number of inverse curves that the contour needs for one rotation of the core, ie one rotation of the core about its axis of rotation by an angle of 360 degrees, for rolling. Distances or gaps can be provided between the individual inverse curves, which will be explained in more detail below.

The inverse curve track comprises a series of inverse curve pieces, the number of inverse curve pieces on the inverse curve track depending on the number of revolutions of the polygon, hence the core and the intended number of winding layers to be applied to the core. In this way, in particular, contours that increase in size due to the application of wrapping tape can be taken into account by using inverse curve sections parameterized according to the contour. The inverse cam track can be made, for example, from a plastic that has been brought into the described geometric shape by means of a 3D printing process. In addition or as an alternative, the inverse cam track can include or be made of a metal. The inverse cam represents a surface on which the wrapping tape can rest while the core is unrolled onto the wrapping tape.

In other words, the winding process is based on the "rolling square wheel" method, in which a tricycle with wheels that have a square contour rolls evenly over a series of interconnected, inverted chain lines, i.e. a series of humps that the rotational axis of the wheels move in a straight line at the same height. The respective inverted chain line to the square can be a hump over which the sides of the square contour roll, the corners of the square dip into the indentations between the humps. When several of these humps are arranged in a row at a uniform distance, the square can thus roll over the respective humps having the form of an inverse catenary line, so that the axis of rotation of the square moves along a straight line in order to achieve uniform rolling. The inverse curve can be such a juxtaposition of inverted chain lines, so that the inverse curve forms a kind of road for the core or the cross-section, on which the contour of the core or the cross-section can roll, so that the axis of rotation of the contour moves along a straight line or during a relative movement of the road with respect to the rotating contour at the same point remains. The equation for calculating such a catenary is known from the prior art.

Depending on the geometric shape of the contour of the core (seen in cross-section), the sequence of inverse curves may alternatively be, for example, a sequence of inverse catenary lines when the contour is a square, or a sequence of sawtooth lines when the contour is a piecewise equiangular spiral . The polygonal contour can provide the geometric shapes of a square, a pentagon, a hexagon, a hexagon or a polygon with more than 6 corners. The geometric shape of the contour of the core and thus the contour of the battery cell and the associated inverse curve do not have to be limited to the examples mentioned. In the article "Roads and Wheels" by Hall and Wagon, 1992, various geometric shapes and their associated inverse curves were presented, so that when the contour of the geometric shape rolls over its associated inverse curve, the axis of rotation of the geometric shape always moves along a straight line moves or stays at the same point. For this purpose, the inverse curve can run along a straight line or along a circumference.

For winding, the winding tape is now guided along the inverse curve so that the winding tape is between the core or the partially wound battery cell and the surface of the inverse curve, so that the core or the battery cell rolls over the winding tape on the inverse curve and the winding tape unrolls applied to the core or battery cell. This can be realized in that the core is connected at its axis of rotation to a guide known from the prior art, which includes, for example, an electric drive, and the guide allows the core to roll over the inverse cam track. In addition or as an alternative, the inverse cam track can also be moved along the core in a transverse movement, for example by means of a linear drive, so that the core can roll on the inverse cam track. For this purpose, the winding tape can be placed on the inverse cam track in its entirety or in part. Alternatively, the winding tape can be actively fed to the core by means of a roller with a circumference corresponding to at least one inverse curve length.

The winding process has the advantage that a thin winding tape for a battery cell material, which is therefore prone to tearing, can be wound uniformly on a polygon-shaped core, with a pulsating force acting on the winding tape when applied via the corners of the polygon being avoided, so that the wrapping tape is not damaged during wrapping, in particular does not tear. At the same time, the winding process is based on the already established process for winding cylindrical battery cells, which has low production costs. A rotary drive from the prior art can thus be used to turn the core. Only the inverse cam track described must be provided. In this way, polygonal battery cells can be produced analogously with a low increase in costs, which at the same time enable better space filling in battery modules due to their polygonal cross section, so that gaps in the battery cells are avoided and energy density in battery modules can thus be increased. Furthermore, this results in the advantage that the need to check the tension in the winding tape by means of a control method can be avoided, since even tension is evened out by the rolling of the contour on the associated inverse curve.

The inverse curve track with the contour of the respective inverse curve can be produced, for example, by rolling the core over a smooth surface, the surface being made of a material that is soft and malleable at the time of rolling and has a higher resilience than the material of the core ( e.g. made of clay or kneaded rubber), whereby the axis of rotation of the core is moved along a straight line. This creates an impression of the inverse curve on the surface and thus the inverse curve path that corresponds to the inverse curve associated with the contour. The shape obtained in this way can be used as a template or model for producing further inverse curve paths with the shape of the at least one inverse curve.
The invention also includes embodiments that result in additional advantages.

One embodiment provides that the surface runs in particular on a plane or on a roller surface. In other words, the inverse curve can move along a straight line, in particular a straight line in the plane, so that the core or the battery cell with its respective geometric shape rolls on the surface whose contour corresponds to the inverse curve. The surface can be a 3D print, for example, which has the contour of the inverse curve and represents a kind of road on which the geomet ric shape of the core or the battery cell can roll, so that the axis of rotation of the geometric shape moves along a straight line.

As an alternative to this, the roller surface can be a lateral surface of the roller. The inverse curve can run along a circumference of the cross section of the roller, so that the contour rolls along the circumference, so that the axis of rotation of the core also moves parallel to the circumference during rolling on the circumference. The circle can be, for example, the contour of the cross section of a roller, on the lateral surface of which the inverse curve is embossed, on which the core or the battery cell roll during winding, interlocking with one another. The outer surface of the roller can be the surface that corresponds to the real image of the inverse curve. The axis of rotation of the roller can also remain on the same point. The core and roller can thus be gearedly engaged with one another, with the winding tape being guided between the core and the roller for winding around the core.

This results in the advantage that when using the level, the winding tape simply needs to be placed on the surface in order to then be evenly picked up by the core. Furthermore, an increasing cross-section of the core during winding and thus a changing contour, in particular an enlarging contour, can be taken into account by arranging different inverse curve pieces associated with the respective contour, which in particular correspond to one revolution of the respective contour. When using the roller, there is the advantage that the winding tape can be guided along the inverse curve in a small installation space.

The cross-section of the resulting battery cell increases while the winding tape is being wound around the core. This also increases the contour of the cross section. This can be taken into account in the winding process. One embodiment provides that a number of at least one inverse curve piece on the inverse curve path corresponds to the number of revolutions of the core for winding the battery cell, with the respective inverse curve piece corresponding to the geometric shape of a number of inverse curves that result when the polygonal contour of the cross section is rotated around an angle of 360 degrees. For a square contour (4 sides), a single inverse curve corresponds to an unrolling of 90 degrees each (quarter turn, a single arc or "hump") and 360 degrees (full revolution, four arcs or "humps") corresponds to 4 inverse curves according to the 4 sides of the square. It is based on the idea that after a complete rotation of the core, the winding tape is wound around the core with a thickness that corresponds to the tape thickness, and thus the outer dimension of the contour of the cross section increases by 2 tape thicknesses. For example, a square cross-section of the core can increase by one layer of the winding tape after it has been rolled over four inverse curves ("humps"). The number of revolutions can thus correspond to the number of inverse curve pieces associated with the respective contour on the inverse cam path. The inverse curve path can thus correspond to a series of at least one inverse curve piece. This results in the advantage that a changing contour of the cross section can be taken into account during the winding.

One embodiment provides that the respective inverse cam pieces on the inverse cam track have an increasing length corresponding to the number of revolutions of the core, with an increase in length corresponding to an increase in thickness of the wound cross section. In other words, with the increase in the outer dimensions of the contour, an inverse curve parameterized for the contour can also be longer or stretched (compared to previous inverse curves in the rolling sequence) and thus also the associated inverse curve segment, which is a series of inverse curves. The inverse cam track can be a series of at least two inverse cam sections that are successively designed to be longer and longer. For example, the first inverse curve portion may include a first inverse curve each associated with the contour of the core without a layer of wrapping tape during a first revolution, and the second inverse curve portion may include a second inverse curve each associated with the contour of the core with a layer of wrapping tape during belongs to a second revolution. This results in the advantage that changing cross sections of the winding can be taken into account, so that the winding tape can always be wound uniformly around the core, without a pulsating force occurring in the winding tape.

One embodiment provides that the inverse cam path has a gap between a first inverse cam piece, which is provided for a first rotation of the cross section through an angle of 360 degrees, and a second, subsequent inverse cam piece for a second, subsequent rotation of the core, with the respective Inverse curve piece in turn has a number of inverse curves, which are separated by gaps of the same gap size. In other words, the inverse cam sections of the inverse cam track can each be separated from one another by a gap, the respective gaps between the inverse cam sections of the inverse cam track differing in the gap dimension/in the gap width. The inverse curves within the respective inverse curve sections can be separated by gaps with the same gap dimension/with the same gap width. This gap width can correspond to the gap width of the gap to the previous inverse curve segment. As a result, the core, which increases during winding, can roll over an inverse curve piece per winding layer, which takes into account the thickness or the external dimensions of the contour. The respective gap can even out the rolling of the contour on the inverse curve compared to the mathematical ideal of the inverse curve.

Due to the size of the gap, the contour that increases during winding can be compensated for by an additional layer of the winding tape being wound around the contour after one rotation of the contour. So that the gap between the individual inverse curve pieces can compensate for the contour that increases with the number of layers of the wrapping tape, the size of the gap can correspond at least to a thickness of the wrapping tape or the respective layer. This results in the advantage that during the interlocking unrolling of the core, an increasing contour during winding can be taken into account and a tolerance for the unrolling during the transition from an inverse curve section to a following inverse curve section can be provided.

One embodiment provides that the respective gap between the respective inverse curve pieces on the inverse cam track has a respective size that, starting from an initial gap that the core touches on the inverse curve track first, is larger with the number of inverse curve pieces on the inverse curve track, wherein the size of the gap increases on successive inverse curves, the difference in size of the gap on successive inverse curves corresponding to the increase in the thickness of the wound cross-section after one revolution of the core on the preceding inverse curve. In other words, starting from an initial inverse curve piece over which the core rolls to receive a first layer of winding tape, the size of the gap in the following inverse curve pieces can correspondingly increase in accordance with the increase in the size of the contour, for example by a thickness of the layer of the Wrapping tape per revolution of the contour, so that the inverse cam path starting from an initial gap has a total of a series of increasing columns. This has the advantage that the edges of the contour of the rolling cross section can be corrected via the respective gap. In addition, a constantly increasing cross section can always roll evenly on the inverse cam path of the inverse curve.

Alternatively, the winding tape does not have to lie on the inverse curve for the winding process, but can be actively fed to the core by means of a freely hanging loop. One embodiment provides that the winding tape is actively fed to the core via at least one roller by means of at least one freely suspended loop, with a loop length of the respective freely suspended loop corresponding to the length of the respective inverse curve piece of the inverse curve that occurs when the polygonal contour of the cross section is rotated by an angle of at least 90 degrees. In other words, in order to feed the winding tape by means of at least the freely hanging loop, the roller can have a flat surface or a smooth surface, and the winding tape can be fed to the core in such a way that the winding tape has the length of the respective inverse curve piece, which belongs to the respective contour. sags. The length of the freely hanging loop can also correspond to the length of at least one or a series of at least two or more inverse curves. This results in the advantage that the changing length of the freely hanging loop does not create any pulling force in the winding tape. The roller for feeding in the winding tape can also rotate uniformly in the freely suspended loop, so that a tensile force in the winding tape for winding is evened out.

The invention also includes a device for producing a polygonal battery cell. The device is designed to wind at least one winding tape and at least one core with a polygonal contour, with the winding tape being wound around the core when the core is rotated, so that the core and the winding tape form the battery cell in a wound state, whose Cross-section having the polygonal contour. The cross section of the battery cell includes the core and additionally at least one layer of the winding tape.

The device is characterized in that the device is set up to move the winding tape during winding along at least one inverse curve, which corresponds to the geometric shape of a development or rotation of the polygonal contour of the cross section in space, the inverse curve being a chain line or a cycloid arc or a represents an epicycloid arc or a sawtooth line interval or, in particular, an associated inverse thereof, to be fed to the core.

The inverse curve is recessed in such a way that a rotation axis of the core remains stationary during the rotation of the core or moves along a straight line, with the winding tape being fed on at least one inverse curve path, which corresponds to a real image of the inverse curve, and the device being set up for this purpose is to unroll the core on the winding tape along the inverse curved path for winding the battery cell by the rotation. In other words, the device may have the inverse cam track moving in a plane or on a roller surface. The inverse curve path can comprise the described series or sequence of inverse curve sections or at least one inverse curve section. The device can have at least one rotating roller, the surface of which corresponds to a real image of the inverse cam path. The inverse cam track can therefore run on the lateral surface of the roller. The at least one roller can be set up in such a way that it touches the contour or rolls over one another on the contour in an interlocking manner. The roller and the contour can rotate in opposite directions about mutually parallel axes of rotation, so that the contour rolls on the roller in an interlocking manner. For winding, the winding tape can now be guided between the contour (the core) and the roller.

One embodiment of the device provides that the at least one inverse cam path is formed along a linear plane or on a circular surface, in particular on a roller surface. In other words, the inverse cam path can run in one plane or on a lateral surface of a roller. The lateral surface of the roller can correspond to the roller surface. The use of a roller surface as an inverse cam has the advantage that the device requires less installation space.

A further embodiment provides that the device comprises at least one roller, which is set up to actively feed the winding tape to the core by means of at least one freely suspended loop, with a loop length of the respective freely suspended loop corresponding to a length of at least one inverse curve that occurs when the polygonal contour of the cross section by at least an angle of 90 degrees. In other words, the loop length of the respective free-hanging loop can have a length of at least one inverse curve of an inverse curve piece, which arises when the polygonal contour of the cross section is rotated by an angle of at least 90 degrees. This results in the advantage that installation space can be saved by using a roller, since the winding tape does not have to rest completely on the inverse cam track.

The device also includes a control device which causes the device to carry out said winding process. The control device can have a data processing device or a processor device that is set up to carry out an embodiment of the winding method according to the invention. For this purpose, the processor device can have at least one microprocessor and/or at least one microcontroller and/or at least one FPGA (Field Programmable Gate Array) and/or at least one DSP (Digital Signal Processor). Furthermore, the processor device can have program code which is set up to carry out the embodiment of the winding method according to the invention when executed by the processor device. The program code can be stored in a data memory of the processor device.

The invention also includes a battery cell or a battery module comprising said battery cell, which has been manufactured or wound by means of said winding method or said device.

The invention also includes a motor vehicle which includes at least one of said battery cells.

The invention also includes developments of the method according to the invention, which have features as have already been described in connection with the developments of the device according to the invention. For this reason, the corresponding developments of the device according to the invention, the battery cell, the battery module or the motor vehicle are not described again here.

The invention also includes the combination of the features of the described embodiments. The invention also includes implementations that each have a combination of the features of several of the described embodiments, unless the embodiments were described as mutually exclusive.

The device also includes the developments of the method according to the invention and vice versa.

• 1 eine schematische Darstellung eines Batteriemoduls, welches aus zylinderförmigen Batteriezellen zusammengesetzt ist und zwei weiteren Batteriemodulen, welche aus polygonalen Batteriezellen zusammengesetzt sind;
• 2 eine schematische Darstellung eines Querschnitts des Kerns, um welchen ein Wickelband gewickelt wird;
• 3 eine schematische Darstellung des Prinzips des Abrollens der Kontur auf der zugehörigen inversen Kettenlinie;
• 4 eine allgemeine schematische Darstellung des Wickelverfahrens, wobei das Wickelband auf der Oberfläche in einer Ebene aufliegt;
• 5 eine schematische Darstellung des Wickelverfahrens in der Ebene unter Berücksichtigung einer beim Wickeln zunehmenden Kontur;
• 6 eine schematische Darstellung des Wickelverfahrens mittels eines aktiven Zuführens einer freihängenden Schlaufe zum Kern über eine Walze.

Exemplary embodiments of the invention are described below. For this shows:

• 1 a schematic representation of a battery module, which consists of cylindrical Bat tery cells and two other battery modules, which are composed of polygonal battery cells;
• 2 a schematic representation of a cross-section of the core around which a winding tape is wound;
• 3 a schematic representation of the principle of the rolling of the contour on the associated inverse chain line;
• 4 a general schematic representation of the winding process, wherein the winding tape rests on the surface in one plane;
• 5 a schematic representation of the winding process in the plane, taking into account an increasing contour during winding;
• 6 a schematic representation of the winding process by means of an active feeding of a freely hanging loop to the core via a roller.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another and that each also develop the invention independently of one another. Therefore, the disclosure is also intended to encompass combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.

In the figures, the same reference symbols designate elements with the same function.

1 shows a total of three different embodiments of a battery module 1, 2 and 3, which are each composed of different battery cells 4. The first embodiment of the battery module 1 comprises cylindrical battery cells 4. A property of the cylindrical battery cells 4 is that gaps 5 form between the individual battery cells 4, which require space and thus reduce an energy density of the first battery module 1. The battery cells 4 in the second battery module 2 are composed of square battery cells 4 . Due to the square cross section of the battery cells 4, the second battery module 2 has no gaps, so that an energy density of the second battery module 2 is increased. The third battery module 3 is composed of hexagonal battery cells 4, which also reduce the space required by the gaps 5 in the third battery module 3, so that an energy density of the third battery module 3 compared to the first battery module 1 can also be increased. It is therefore obviously advantageous to use battery cells 4 with a polygonal cross section.

2 shows the battery cell 4, which includes a core 6, the cross section of which has a square contour, and a winding tape 9. To wind the battery cell 4, the core 6 rotates about the axis of rotation 7 in a direction of rotation which is in 2 for example counterclockwise. By rotating the core 6 about the axis of rotation, the winding tape 9, which is fed to the core 6, is wound around the core. In order to produce the battery cell 4 , the winding tape 9 comprises at least one battery cell material that is wound around the core 6 to produce the battery cell 4 . As soon as the winding tape 9 is wound over an edge 10 of the contour, a pulsating force is created in the winding tape 9, which can lead to the winding tape 9 being damaged. Particularly in the case of a thin or generally sensitive wrapping tape 9, which can include a battery cell material, this can lead to the wrapping tape 9 tearing. The aim here is to reduce the pulsating force 11 when the winding tape 9 is being wrapped around the edge 10 of the core 6 . This can be achieved by rolling the core 6 over an inverse curve associated with the contour.

3 shows the geometric properties of a tangent 16 on an inverse curve 15, which is a cycloid of the circle 12, which rolls along the direction 14 on the straight line 13. The point P on the circle 12 draws the inverse curve 15 , which is a cycloidal curve of the circle 12 , while the circle 12 is rolling along the straight line 13 . At point P, where the circle 12 and the inverse curve 15 touch, a tangent 16 is drawn, which can be constructed from geometry using known methods. The tangent 16 on the inverse curve 15 has the property that it can smoothly and smoothly pass over the inverse curve 15 at the point P. This solves the problem that asks which trajectory a point mass can move from one point to another in the shortest possible time without friction. For this purpose, the point P as a mass point 5 can move in particular on the inverse curve 15, which is the cycloid of the circle 12. The inverse curve 15 enables the smooth rolling of an associated polygon, which is a square here, with the center of the polygon running uniformly on a straight line 13 at the axis of rotation 7 . The idea of the winding process is to use this geometric property of the inverse curve 15 to to realize uniform winding of the winding tape 9 onto the core 6.

4 shows a first embodiment of the winding method, wherein the core 6 in the device V provided for this purpose rolls on an inverse cam track 27 which has the geometric shape of the inverse cam 15. In 4 an inverse curve section 19 of the inverse cam path 27 is shown for this purpose, which comprises a total of four inverse curves 15, i.e. four humps 20 in the case of the square-shaped core, via which the core 6 can rotate for a complete revolution, i.e. a rotation about the axis of rotation 7 by an angle of 360 degrees, unrolls. The inverse cam path 27 is guided along a plane 18, with the inverse cam path 27 now having to be as long as the winding tape 9. The core 6 has, for example, a square cross section 8, with the cross section 8 also being able to have the shape of any polygon. Corresponding to the square, the inverse curve 15 is composed of several humps 20 in the individual inverse curve sections 19, which correspond to the inverse curve 15 of a rotation of the contour of the cross section 8 by an angle of 360 degrees around the axis of rotation 7. The core 6 rolls over the individual humps 20 of the inverse curve 15 . A winding tape 9 , which comprises a battery cell material, for example, rests on the inverse cam track 27 . The inverse cam track 27 can have the same length as the winding tape 9 so that the winding tape 9 rests completely on the inverse cam track 27 and the winding tape 9 is wound around the core 6 by the core 6 rolling over the inverse cam track 27 . As a result, the winding tape 9 can be evenly wound around the core 6, so that no pulsating force 11 is present in the winding tape 9 or is reduced. Alternatively, the inverse cam track 27 can also be arranged on a lateral surface of a roller.

5 shows the inverse cam track 27 in the device V, the inverse cam track 27 extending in the plane 18, therefore along a straight line. In 5 the inverse curve piece 19 is shown in the center comprising four humps 20 for a complete revolution of the square-shaped core 6 . To the left of the inverse curve piece 19, an attachment of the preceding inverse curve piece 19' can be seen, which is spaced apart from the inverse curve piece 19 by means of the first gap 21 with a first size 23. The individual inverse curves 15 of the in 5 Central inverse curve piece 19, so the individual humps 20 are each spaced from each other with the first gap 21 with the first size 23 from each other. To the right of the central inverse curve segment 19 is in 5 an approach of a subsequent inverse curve piece 19" can be seen, which is spaced from the inverse curve piece 19 by means of a second gap 22 with a second size 24. The second size 24 is larger than the first size 23, in particular by a thickness of the winding tape 9 larger, in order to take into account the contour of the core 6 which increases by one layer 28 of the winding tape 9 when it is wound.

For winding, the core rolls 6 in 5 from left to right from the preceding inverse curve piece 19' via the inverse curve piece 19, the core 6 receiving the winding tape 9 resting on the inverse cam track 27 and thus becoming thicker by an additional layer 28 of the winding tape 9. The increase in the thickness of the cross section by one thickness of the winding tape 9, than by an additional layer 28 after one revolution of the core 6, can now change the rolling behavior on the following inverse curve piece 19". This can be compensated for by the larger second gap 22 by the second gap 22 is greater than the first gap 21 by a thickness of the additional one layer 28.

In the longitudinal section, the inverse curves 15, in particular the respective arches or humps 20, of the central inverse curve piece 19 are parameterized or designed according to an external dimension of the core 6 including the layers 28, i.e. the cross section of the battery cell 4. The inverse curves of the central inverse curve piece 19 are separated from one another by gaps 21 with the same gap size, with the gap size corresponding to the first size 23 . In the case of the following inverse curve piece 19", the gap dimension corresponds to the second size 24 due to the additional layer 28 of winding tape 9 after the core 6 has rolled over the central inverse curve 15. This takes into account that during the winding of the battery cell 4 around the core 6 after a rotation an additional layer 28 of the winding tape 9 rests on it and thus the contour, i.e. the square, becomes larger ` and 19" can have different lengths. On the one hand, the different lengths come about as a result of the gap between the individual inverse curves, in the form of bumps 20, which becomes larger as the contour increases. On the other hand, the increasing length of the individual inverse curve sections is due to the fact that the individual inverse curves 15 of the respective inverse curve sections 19, 19' and 19" are newly parameterized for the respective geometric shape of the square with the layers 28, i.e. the respective inverse curves become longer as the square increases The gaps 21 and 22 thus allow the contour to roll off evenly on the inverse curve 15 in comparison to the ideal mathematical inverse curve.

6 shows a second aspect of the winding method, in which the winding tape 9 is actively fed to the core 6 by means of a freely hanging loop 26 . 6 shows the core 6 of the battery cell 4 with a square cross section, which rotates about the axis of rotation 7 and thereby rolls on the inverse curve path 27 with the impressed inverse curve 15 . The winding tape 9 does not initially lie on the inverse curve 15, but is actively fed to the core 6 by means of the roller 25, which rotates about the second rotation axis 7' in a direction of rotation opposite to the direction of rotation of the core 6.

The winding tape 9 no longer rests in its full length on the inverse cam track 27 with the inverse cams 15, which are shown as humps, but is actively applied to the core 6 in sections by the freely suspended loop 26 by the roller 25 by a corresponding number of revolutions Core 6 fed in such a way that the freely hanging loop 26 hangs freely between the core 6 and the roller 25 over a length of at least one inverse curve 15 . The roller 25 runs in front of the core 6, the core 6 rolling on the inverse cam track 27 along the inverse curve 15, so that the winding tape 9 is wound around the core 6 with a uniform pulling force.

Alternatively, the core 6 and the roller 25 can also rotate about a fixed axis of rotation 7 and 7`, with the inverse cam track 27 with the inverse cams 15 moving along the translation direction 29 with respect to the core 6, so that the core 6 is always evenly positioned above the Inverse curves 15 rolls. This can be accomplished, for example, by the plane 18 being directed along a circumference of a roll cross section. The inverse cam track 27 thus forms the lateral surface of another roller, which corresponds to an infinitely long series of inverse cams 15 .

The winding method of cylindrical winding has been known for a long time. Of course, circular rollers are used for this. If one wishes to produce polygon-shaped coils with this method, a pulsating force occurs during application, which can worsen the quality in that, for example, the pulsating force can tear a fine ribbon or reduce the uniformity of the application, although in certain cases it would be desirable such as battery cells. This exploits the geometric properties of the tangent lines of the cycloidal curves, which allow smooth and frictionless rolling of a polygon on the cycloidal curves, with the center of the polygon running smoothly.

The idea now is to use a surface that follows a mathematically correct cycloid curve. The tape or foil can be placed on this path or inserted in some other way between the surface and the core of the coil. The polygonal core, which can be practically square or hexagonal, then rolls off. This applies the tape to the polygon with normal force, smoothly and without traction. Since the dimension of the polygon increases after each revolution, the cycloidal curve must be parameterized appropriately for each revolution of the core. If necessary, the cycloidal curve must also be corrected at the edges of the polygon. These corrections can be carried out mathematically. The web can be produced, for example, by means of 3D printing, so that a web can be manufactured with great accuracy.

A possible application of this method is the production of so-called battery pack cells, with a battery pack in electrically driven motor vehicles consisting of several cells. When these cells are made with coils, according to the prior art they are cylindrical. Square cells can also be produced with other production technology, but winding (coils) has a large potential for savings in production. Due to the cylindrical shape, however, it has a technical disadvantage, since this design creates a significant unused space in the battery packs. As a result, the utilization of the installation space in the battery pack is not optimal. With the application of said idea one can produce practically square or hexagonal cells for the battery packs at low cost, whereby a theoretically perfect space filling is possible. According to calculations, the space in the battery pack can be used about 10 percent better than the cylindrical shape, which ultimately leads to an increase in the energy density of the battery pack.

The idea follows an even winding method on a polygonal coil core according to the thesis of the normals of the cycloids. In the even winding method, a polygonal coil core follows a surface that follows a mathematically correct cycloid curve. The tape can be placed on this track, for example, or introduced between the surfaces of the polygonal coil core and the track. The path must be corrected with the increasing polygon per revolution.

Overall, the example shows how a winding method and a device for producing a polygonal battery cell can be provided.

Claims (10)

Winding method for producing a polygonal battery cell (4), comprising: - at least one core (6) having a polygonal contour in cross section (8), - at least one winding strip (9) comprising at least one battery cell material, which is wound around the core (6), wherein the core (6) is rotated about an axis of rotation (7) and the winding tape (9) is wound around the core (6) so that the core (6) and the winding tape (9) in a wound-up state contain the battery cell (4 ) whose cross section (8) has the polygonal contour, the cross section (8) of the battery cell (4) comprising the core (6) and additionally at least one layer (28) of the winding tape (9), characterized in that the winding tape (9) is fed to the core (6) during winding along at least one inverse curve which corresponds to the geometric shape of a rotation of the polygonal contour of the cross section (8), the respective inverse curve (15) being a chain line or ei represents a cycloid arc or an epicycloid arc or a sawtooth line interval or a respective inverse thereof and wherein the inverse curve (15) is recessed in such a way that an axis of rotation (7) of the core (6) remains stationary during the rotation of the core (6) or moves along a Straight lines (13) are moved, with the winding tape (9) resting on an inverse cam track (27) for feeding, which corresponds to a real image of the at least one inverse curve (15) or being in contact with it, and the core (6) on the winding tape (9) along the inverse cam track (27) for winding the battery cell (4) is unrolled by the rotation. winding process claim 1 , wherein the inverse cam track (27) is formed on a plate or on a roller surface. Winding method according to one of the preceding claims, wherein a number of at least one inverse curve piece (19) on the inverse cam track (27) corresponds to the number of full revolutions of the core (6) for winding the battery cell (4), the respective inverse curve piece (19) being the corresponds to the geometric shape of the inverse curve (15) which arises when the polygonal contour of the cross section (8) is rotated through an angle of 360°. winding process claim 3 , wherein the respective inverse cam pieces (19) on the inverse cam path (27) have an increasing length corresponding to the number of revolutions of the core (6) completed until this inverse cam piece (19) is reached, with an increase in length corresponding to an increase in thickness of the wound cross section (8 ) is equivalent to. winding process claim 3 or 4 , wherein the inverse cam path (27) between a first inverse cam piece (19) after a first rotation of the cross section (8) by the angle of 360° and a second, following inverse cam piece (19) for a second, following rotation of the core (6). gap (21, 22), and/or wherein the respective inverse curve piece (19) has a number of inverse curves (15) which are separated from one another by gaps (21, 22) of the same gap size. winding process claim 5 , wherein the respective gap (21, 22) between the respective inverse cam pieces (19) on the inverse cam track (27) has a respective size (23, 24) which, starting from an initial gap that the core (6) has on the inverse cam track ( 27) touches first, is designed to be larger with the number of inverse curve sections (19) covered on the inverse curve path (27), the size of the gap increasing for successive inverse curve sections (19), the difference in size of the gaps (21, 22) for successive inverse curve pieces (19) corresponds to the increase in thickness of the wound section (8) after one revolution of the core (6) on the preceding inverse curve piece (19). Winding method according to one of the preceding claims, in which the winding tape (9) is actively fed to the core (6) via at least one roller (25) by means of at least one freely suspended loop (26), a loop length of the respective freely suspended loop (26) being at least the length corresponds to the inverse curve (15) which arises when the polygonal contour of the cross section (8) is rotated by an angle of at least 90°. Device (V) for producing a polygonal battery cell (4), the device being set up to wind at least one winding tape (9) around at least one core (6) with a polygonal contour, and the winding tape (9) thereby rotating when the Core (6) to be wound onto the core (6), so that the core (6) and the winding tape (9) form the battery cell (4) when wound up, the cross section (8) of which has the polygonal contour, the cross section (8 ) of the battery cell (4) comprises the core (6) and additionally at least one layer (28) of the winding tape (9), characterized in that the device (V) is set up to move the winding tape (9) during winding along at least one Inverse curve (15), the geometric shape of a rotation of the polygonal contour of the cross Section (8) corresponds to the core (6), wherein the inverse curve (15) represents a chain line or a cycloid arc or an epicycloid arc or a sawtooth line interval or a respective inverse thereof and the inverse curve (15) is recessed in such a way that a rotation axis (7) of the core (6) remains motionless during the rotation of the core (6) or moves along a straight line (13), with at least one inverse cam track (27) being provided in the device for feeding the winding tape (9) which corresponds to a real image of the inverse curve (15), and the device is set up to place the winding tape on the at least one inverse curved track (27) and the core (6) on the winding tape (9) along the inverse curved track (27) for winding the battery cell (4) unroll by the rotation. Device (V) after claim 8 , wherein the at least one inverse cam path (27) is formed along a linear plane (18) or on a circular surface, in particular on a roller surface. Device (V) after claim 8 or 9 , wherein the device comprises at least one roller which is set up to actively feed the winding tape (9) to the core (6) by means of at least one freely suspended loop (26), wherein a loop length of the respective freely suspended loop (26) has a length of at least one inverse curve (15) corresponds to a rotation of the polygonal contour of the cross section (8) by at least an angle of 90 °.

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