Actively cooled coil

Description

[0001] The invention relates to a coil system comprising a first coil with a plurality of stacked planar coils. Furthermore, the invention encompasses a method for manufacturing such a coil system. Such a coil system can be used, for example, for compact and lightweight electric motors, such as those required in the field of servo drives. These can be linear motors as well as rotary motors.

[0002] The term "planar coil" generally refers to a winding that extends only in one plane. Several planar coils arranged vertically one above the other can be electrically connected to form a type of cylindrical coil. The term "flat coil" is also used below as a synonym for the term "planar coil."

[0003] A coil system with a coil consisting of a plurality of planar coils arranged in layers one above the other is known, for example, from DE102008062575A1. The coil system disclosed in this document is implemented in the form of a multilayer circuit board and forms the primary part of a linear motor. The various layers of this multilayer circuit board are largely filled with energizable windings. The windings arranged in layers one above the other are electrically connected vertically with so-called vias, thus each forming a solenoid coil for a phase of the linear motor. In this way, a particularly lightweight and compact primary part for a linear motor can be realized, which is particularly suitable as a rotor for highly dynamic applications.

[0004] Figure 1shows, in a cross-section perpendicular to the surface, a multilayer circuit board with an arrangement of planar coils 1 - 6 known from the prior art, which are stacked layer by layer and connected to form a type of solenoid coil. In each level of this multilayer circuit board there is, for example, a planar coil 1-6 with three turns each. The turns run either from the inside out or from the outside in. For example, the winding of a first planar coil 1 is wound from the outside in and electrically connected via an electrical via to an underlying second winding of a second planar coil 2. This second planar coil 2 is in turn wound from the inside out and is in turn connected via a further electrical via (not shown here) to a third planar coil 3 in the third level of the multilayer circuit board shown. In this way, a cylindrical coil ora solenoid was created that extends over six levels of the multilayer board.

[0005] Multilayer board technology is particularly well-suited for implementing applications with high electrical power in a compact and lightweight design. One example is the aforementioned primary part of the linear motor from DE102008062575A1, which is implemented as a multilayer printed circuit board. Due to the high currents in such applications, heat dissipation is a particular challenge. The higher the energy density of the multilayer board, the more compact the design can be, but the greater the demands on the heat dissipation of the multilayer board. As described in Figure 1As can be seen, in order to cool the multilayer board, the heat generated in an inner winding of a planar coil must be dissipated laterally to the outer edge of the multilayer board, where it can then be conducted to the surface of the board. An insulation distance is required between the individual windings of each planar coil, which for technological reasons must be in the order of a few hundred micrometers. Neither the board material made of fiber-reinforced plastic nor the prepreg layers typically used to insulate the various layers possess good thermal conductivity. Accordingly, lateral heat transfer within such a board stack presents a particular challenge.

[0006] Improved lateral heat dissipation in such a layered coil system in the form of a multilayer circuit board is disclosed in OE102015222400A1. This document teaches a coil system with the features according to the preamble of the present patent claim 1 and represents the closest prior art. Layers of flat coils arranged vertically one above the other are each arranged with a lateral offset from one another, so that, in a cross-section perpendicular to the surface of the multilayer circuit board, conductor track sections of a flat coil are always arranged vertically in partial overlap with two conductor track sections of another flat coil located vertically adjacent to said flat coil.

[0007] The partial overlap enables lateral heat transfer across layers. This means that the heat generated in one conductor section has the opportunity to reach the edge region laterally by transferring to a vertically adjacent conductor section of another planar coil, which, however, has a lateral offset. Such a shingle-like structure, which enables lateral heat transfer across layers, is Figure 2 The arrows illustrate how the heat transfer from a planar coil 3 to an overlying planar coil 2, which has a lateral offset from the planar coil 3, thus creating a kind of shingling.

[0008] The two planar coils 2, 3 are separated from each other only by a very thin prepreg layer of approximately 50 µm to 200 µm. The lateral distance between two turns of a planar coil in one plane cannot be arbitrarily minimized for process-related reasons. Laterally, the distance between the turns is at least 200 µm. (These distances are not shown to scale in the figures.)

[0009] A typical conductor track, for example, has a lateral width of 1 mm, while the thickness of the conductor tracks is, for example, 100 µm. Without the lateral offset of the conductor tracks, the thermal conductivity in the lateral direction is determined by the spacing of the turns in the lateral direction and the thickness of the conductor tracks. Due to the shingling, another conductivity is connected in parallel to this thermal conductivity, which includes cross-layer heat transfer in the vertical direction. The thermal resistance relevant for this depends primarily on the spacing of the turns of vertically adjacent planar coils that partially overlap, and the portion of the conductor track width that represents the overlap area.For example, if both the lateral spacing of the windings and the vertical spacing of the stacked planar coils are 200 µm, and the area of ​​a 1 mm wide conductor track that is in vertical overlap with a conductor track of an adjacent planar coil extends over 400 µm of the total conductor track width, the thermal conductivity in the vertical direction is four times greater than in the lateral direction if the thickness of the conductor tracks is 100 µm. This results in a shingled arrangement of the stacked planar coils resulting in more than a fourfold increase in the thermal conductivity compared to a fully overlapped arrangement of the planar coils, i.e., without shingling.

[0010] Therefore, the shingling enables cross-layer lateral heat transport with a significantly better thermal conductivity, since the vertical insulation distance is less than one-fifth of the lateral insulation distance between the turns.

[0011] DE102015222400A1 further discloses a passive conductor track structure 7, which engages comb-like into the outer conductor track sections of the stacked and shingled planar coils 1-6. This conductor track structure 7 is not powered. It is galvanically isolated from all current-carrying elements of the multilayer board. The passive conductor track structure 7 has the task of transporting the heat, which is conducted laterally through the multilayer board in the manner already described, vertically to one or both surfaces of the multilayer board. The superimposed conductors of the passive conductor track structure 7 are connected to one another by a so-called thermal via 8 to enable heat exchange between the passive conductor tracks in the vertical direction and thus heat transport to the surface(s). A heat sink can then be provided on the surface(s) to further dissipate the heat.

[0012] The invention is based on the object of enabling a further increase in the energy density in such a coil system consisting of planar coils arranged one above the other in a shingle-like manner.

[0013] This object is achieved by a coil system having the features according to patent claim 1. Furthermore, the object is achieved by a method having the features according to patent claim 16.

[0014] Advantageous embodiments of the invention can be found in the dependent patent claims.

[0015] The coil system according to the invention comprises a first coil with a plurality of planar coils stacked one above the other. To improve lateral heat transfer, the shingling described above, known from the prior art, is provided. In this context, the term shingling refers to an arrangement in which two planar coils directly above one another are stacked vertically with a lateral offset such that, at least in sections, one turn of a planar coil and two turns of a second planar coil arranged directly above the first planar coil are arranged in partial overlap. A conductor track section of a planar coil is therefore partially covered by conductor track sections of two turns of an overlying planar coil.The exception to this is, of course, the uppermost of the planar coils, which are particularly spirally arranged and stacked on top of each other, as well as the outermost turns of the planar coils. The inventive shingling of the conductor tracks of the coils also allows for individual conductor track sections—for example, supply line sections—that do not partially overlap vertically with two conductor track sections of a vertically adjacent coil. However, the majority of the conductor track associated with a coil complies with the shingling principle described above and thus enables lateral heat transport with comparatively low thermal resistance through cross-layer heat transport.

[0016] The lateral offset of the stacked planar coils results in the first coil exhibiting a comb-like structure in the area of ​​the outermost turns. This comb structure is created by the vertical offset of two stacked outer turns.

[0017] The coil system according to the invention further comprises a passive conductor track structure that is galvanically isolated from all current-carrying windings of the coil system. This passive conductor track structure also comprises a plurality of stacked conductor tracks. These conductor tracks are stacked on top of each other in such a way that they also form a comb-like structure. The first comb-like structure of the passive conductor track structure engages with the second comb-like structure, which is formed by the outer turns of the stacked windings. The two comb-like structures are galvanically isolated from each other. The first comb-like structure is thus electrically insulated from the second comb-like structure.

[0018] The inventive concept is based on implementing basic insulation of the current-carrying, spiral-shaped, stacked windings from the passive conductor structure. In particular, no further insulation of the passive conductor structure is necessary to meet the basic insulation requirements of DIN EN 60664-1. In accordance with the cited DIN EN 60664-1, basic insulation is understood in this document as insulation for the basic protection of parts carrying dangerous voltages. Basic insulation is therefore crucial for direct contact protection and differs from functional insulation. Functional insulation merely ensures insulation between conductive parts that are necessary for the intended function of the equipment.

[0019] To achieve this, the lateral distance between the outer turn of each winding and the passive conductor structure must be sufficiently large. For example, a lateral distance of at least 1.2 mm is required to withstand a test voltage of 4 kV. Such test voltages are used, for example, to test printed circuit board motors designed for a three-phase input supply voltage of 400 V. For example, when fed via conventional B6 bridge circuits with a voltage intermediate circuit, this results in intermediate circuit voltages of 730 V. In the vertical direction, however, only a 200 µm thick PrePreg layer is required between the interlocking conductor tracks of the passive conductor structure and the outer turns of the coil to ensure basic protection of the passive conductor structure.

[0020] Because the passive conductor structure partially overlaps vertically with the outer windings of the stacked planar coils, heat can still be transferred from the current-carrying windings to the passive conductor structure. As explained above, a thin, insulating prepreg layer between the comb-like interlocking elements of the passive conductor structure and the outer windings is sufficient to ensure basic insulation in the vertical direction. This small insulation distance enables good heat transfer from the first coil to the passive conductor structure.

[0021] More critical, as explained above, is the insulation distance in the lateral direction. This distance can be selected to be sufficiently large without significantly impairing heat transfer to the passive conductor structure. For example, the lateral insulation distance of the passive conductor structure relative to the outer turns of the first coil can be selected such that at no point is it less than 6 times, and in particular even 10 times, the vertical distance between the planar coils directly above one another. In this way, basic insulation is achieved in the edge region of the coil system by means of the passive conductor structure, which is excellently thermally connected to the current-carrying coil. Nevertheless, the passive conductor structure can be basicly insulated from the voltage-carrying elements and thus also be touched in particular.Sufficient vertical overlap between the conductors of the passive conductor structure and the outer turns of the planar coils reduces the thermal resistance for heat transfer within a plane, which is largely determined by the lateral distance of the passive conductor structure from the outer turns of the planar coils and must be relatively large to ensure basic insulation. Heat transfer primarily occurs across layers. This is because, on the one hand, a significantly smaller insulation distance has to be overcome vertically, and, on the other hand, sufficient overlap of the conductors within the comb-like structure provides a larger surface area for heat transfer through the insulation layer.

[0022] The heat dissipation of the coil system is further improved by the fact that the coil system includes a cooling channel for a liquid cooling medium. This liquid cooling medium can be brought particularly close to the current-carrying first coil because the cooling channel runs along the edge region of the first coil and is electrically insulated from the first coil by the passive conductor track structure. Because the passive conductor track structure is already basically insulated from the first coil, yet is excellently thermally connected to the first coil, effective cooling of the passive conductor track structure by the liquid cooling medium also results in efficient cooling of the first coil. This is further achieved because a side of the passive structure facing away from the outer turns of the first coil represents a side wall of the cooling channel.This allows the liquid cooling medium to come into direct contact with the passive conductor structure, resulting in very low heat transfer to the first coil.

[0023] By implementing basic protection through the comb-like passive conductor structure that engages the outer windings of the coil, it is possible to combine high electrical insulation strength with good thermal conductivity between the coil and the passive conductor structure. The connection of the cooling channel to the active, heat-generating part of the coil system is correspondingly efficient.

[0024] Heat transfer is further improved by copper-plating the surface of the cooling channel facing the liquid coolant. The copper-plated surface of the cooling channel is galvanically connected to the numerous stacked conductor tracks of the passive conductor track structure. This further optimizes the heat transfer resistance between the liquid coolant and the passive conductor track structure. This is achieved while complying with current regulations on touch protection, in particular DIN EN 60664-1, by insulating the passive conductor track structure from the first coil.

[0025] The magnetic flux density generated by the first coil can be increased by interspersing the numerous stacked planar coils with an iron core. This can be made of an SMC material, for example. The vertically stacked windings can be insulated from each other by a thin prepreg layer.

[0026] If a PrePreg cover layer is provided on the top and bottom sides of the stack of layered planar coils, this can achieve basic insulation of the coil system on the respective surfaces. If the first coil is also interspersed with an iron core, particularly made of SMC material, a PrePreg layer on the top and bottom of the stack can ensure that the insulation distance between the iron core and the innermost turn of the planar coil can be selected smaller than would be necessary to achieve basic insulation. This is because the basic insulation of the entire stack is already ensured by the top and bottom PrePreg layers. Reducing the distance between the iron core and the innermost turn of each planar coil further increases the maximum possible flux density that can be generated with the proposed coil system.In particular, if a cooling channel is provided in the edge area of ​​the first coil, which is separated from the first coil by the passive conductor track structure, the top and bottom PrePreg layers have no negative influence on the cooling of the coil system, since this does not occur primarily on the top and bottom but on at least one end face, on which the at least one cooling channel runs.

[0027] The coil system can be designed as a multilayer board, with the windings and the conductor tracks of the passive conductor track structure of each layer arranged on a common individual board of the multilayer board. In a first step, individual boards are manufactured and metallized. The desired conductor tracks to form the respective planar coils and passive conductor track structure of each individual layer are then carved out by etching. The space for a cooling channel to guide a liquid coolant can also be provided on each individual board. The individual boards are then stacked on top of each other in such a way that the desired lateral offset is achieved between the stacked planar coils, thus forming the shingled structure.The passive conductor tracks of each individual board are also layered laterally offset in such a way that the first comb structure can form.

[0028] For insulation purposes, pre-preg layers are placed between the individual boards. By baking the resulting board stack together, the pre-preg layers serve as both an insulation and an adhesive layer between the conductor tracks.

[0029] Electrical vias are then inserted to electrically connect the vertically adjacent planar coils. The cooling channel can then be milled into the multilayer board. This occurs on the side of the passive conductor track structure facing away from the first coil. After milling the cooling channel, the cooling channel can be metallized, in particular copper-plated, on its inside. Such a copper layer lining the cooling channel is advantageously galvanically connected to the previously applied conductor tracks of the passive conductor track structure. The thermal resistance between the passive conductor track structure and the inner lining of the cooling channel created in this way is thus minimized.An alternative embodiment of the coil system provides that the windings and the conductor tracks of the passive conductor track structure of several layers are produced from the same metal sheet, in particular a copper sheet, by a separation process and that an insulation layer is arranged between each two windings lying directly one above the other.

[0030] The planar coils and the conductor tracks of the passive conductor structure of each layer are punched from sheet metal. Using punched coils instead of a multilayer PCB design can significantly reduce costs. Prepreg can be used as an insulation and adhesive layer between the individual punched coils. The windings, which are stacked directly on top of each other, can be electrically connected to each other by pins made of electrically conductive material that penetrate the insulation layers, particularly the prepreg layers, between the windings.

[0031] A particularly advantageous and simple way of manufacturing a coil system from punched coils is when the lamination pattern of the individual coils that are placed on top of each other is always the same. For example, an embodiment is conceivable in which the windings and the conductor tracks of the passive conductor track structure of four superimposed layers have the same lamination pattern. Said lamination pattern within the four superimposed layers is arranged in a second layer as a mirror image of the first layer. In a third layer, the lamination pattern of the first layer is rotated 180 degrees. In a fourth layer, the lamination pattern of the first layer is mirrored and rotated 180 degrees. This creates a stack of four layers that creates the desired shingle. This arrangement of four layers can be repeated as often as required. The sequence described here is not mandatory.

[0032] Of course, the coil system can also comprise more than one coil. If, for example, a second coil is provided in addition to the first coil, it is arranged laterally offset from the first coil. This second coil also comprises stacked and laterally offset planar coils; it therefore also complies with the shingling principle. Heat transport in the lateral direction between the first and second coils is ensured by the outer windings of the first coil and the outer windings of the second coil interlocking like a comb and thus overlapping each other vertically. The heat is thus transferred from the outer windings of the first coil to the outer windings of the second coil, again in a vertical direction between superimposed conductor track sections, where it can then be transported further laterally.

[0033] In this way, for example, a primary part of an electric motor can be realized using such a coil system. This electric motor can be, for example, a linear motor, which, in addition to the aforementioned primary part, also has a secondary part spaced from the primary part by an air gap, which is particularly equipped with permanent magnets.

[0034] In a method for manufacturing a coil system according to some previously described embodiments, individual layers are first produced, each comprising a planar coil and a passive conductor track laterally offset in the respective layer from an outer turn of the planar coil, which is electrically insulated from the planar coil by a lateral insulation distance. This layer can, for example, be a printed circuit board that is appropriately metallized and etched. However, it is also conceivable that the described structure was stamped, for example, from a copper sheet.

[0035] Such individual layers are then stacked one above the other to form a stack. This arrangement creates the shingled structure that ensures lateral heat transfer within the stack. An insulation layer is applied between each layer. Furthermore, the stacked passive conductor tracks form a first comb-like structure, which, at an edge region of the first coil, engages a second comb-like structure created by the lateral offset of the outer turns of the stacked windings.

[0036] According to the invention, care must be taken to ensure a lateral distance is maintained between the passive conductor structure and the outer turns of each winding, ensuring basic insulation of the first coil in the edge area where the two comb-like structures interlock. Of course, basic insulation must also be ensured vertically across the intermediate prepreg layers.

[0037] Two stacked layers can be separated by an insulating layer, such as a prepreg layer. It is also conceivable, especially in connection with punched coils, for the sheet metal cuts used for this purpose to be powder-coated. However, after the individual layers have been stacked, electrical connections must still be made between the individual planar coils. For this purpose, an electrically conductive pin can be used, for example, which is driven into corresponding holes that penetrate the insulating layer.

[0038] In the following, the invention is explained in more detail with reference to the embodiments shown in the figures.

[0039] They show: Figure 1: A coil known from the prior art with vertically stacked planar coils, Figure 2: A coil known from the prior art with vertically stacked planar coils, in which a lateral offset of vertically adjacent conductor track sections is provided, Figure 3: An embodiment of the invention with a coil system in the form of two stacked multilayer boards with a base-insulated cooling channel, Figure 4: A coil system with vertically stacked, punched planar coils, Figure 5: A sectional view of the coil system from Figure 4 with vertically stacked, punched planar coils, Figure 6: a sheet metal section of a coil system according to the Figures 4 and 5 , Figure 7: the sheet metal cut after Figure 6 after rotation of 180° around an axis perpendicular to the plane of the drawing, Figure 8: the sheet metal section after Figure 6 after reflection around the vertical center axis, Figure 9: the sheet metal section after Figure 7after reflection around the vertical center axis, Figure 10: a section through a coil system designed as a printed circuit board with an iron core and top and bottom PrePreg layers, Figure 11: a cross-section of another coil system designed as a printed circuit board with a plurality of laterally adjacent coils with vertically stacked planar coils and Figure 12: a linear motor with a primary part designed as a multilayer board according to an embodiment of the invention.

[0040] Figure 1shows a coil known from the prior art with vertically stacked planar coils 1-6. The multilayer board consists of three individual boards stacked on top of each other, which are separated from each other by two prepreg layers 9. A first board of this board stack is metallized on its top side with a first planar coil 1 and on its bottom side with a second planar coil 2. Below this first board is a second board with a third planar coil 3 on its top side and a fourth planar coil 4 on its bottom side. At the bottom is a third board with a fifth planar coil 5 on its top side and a sixth planar coil 6 on its bottom side. These three boards are manufactured using the manufacturing technology known from the prior art. They are structurally identical boards.These are then stacked on top of each other and separated from each other by prepreg 9, which has electrically insulating properties. The resulting board stack is then baked, so that the prepreg layers 9 mechanically connect the three individual boards and electrically insulate them from each other. The prepreg layers 9 are only penetrated at a few points by vias (not shown here), which connect the vertically stacked planar coils 1-6 in series.

[0041] As already mentioned at the beginning, the lateral thermal conductivity of this multilayer board design, or rather the coil system implemented with it, is relatively low, since, for manufacturing reasons, a relatively large insulation distance must be maintained between the laterally adjacent turns of the windings in each layer. The thickness of the conductor track, which also determines the lateral thermal conductivity within a layer of the multilayer board, is in the range of approximately 100 µm. This electrical insulation distance results in a relatively high thermal resistance.

[0042] To improve lateral heat transfer, the Figure 2The coil shown in Figure 1, which is also known from the prior art, is advantageous, in which planar coils 1-6 are also arranged vertically one above the other. To improve heat transfer, however, a lateral offset of the vertically adjacent conductor track sections is provided. This allows heat from the interior of the board to be transported much more easily in a lateral direction, since cross-layer heat transfer between the individual boards is now possible, the thermal resistance of which is determined by the vertical insulation distance between the planar coils and the overlap area of ​​the individual conductor track sections of the vertically adjacent planar coils.This thermal resistance is significantly lower than that within a single layer of the circuit board. This is due to the fact that the prepreg layers 9 are relatively thin compared to the lateral spacing of the individual turns, and the overlap area of ​​the conductor tracks is comparatively large compared to the vertical thickness of the conductor tracks. Accordingly, heat transfer from a conductor track section of one layer to a vertically adjacent conductor track section through the prepreg layer 9 is associated with a significantly lower thermal transfer resistance than heat transfer from one turn to a laterally adjacent turn of the same layer of the multilayer circuit board. This heat transfer is shown in . Figure 2 illustrated by arrows.

[0043] At the lateral edge of the Figure 2The multilayer board shown contains a passive conductor track structure 7. This engages in a comb-like manner with the outer turns of the windings 2, 4, 6. The passive conductor track structure 7 is electrically insulated from all current-carrying conductor tracks of the multilayer board. Due to the comb-like arrangement of the passive conductor track structure 7, heat transfer can take place in a vertical direction from the outer turns of the planar coils 2, 4, 6 to the conductor tracks of the passive conductor track structure 7, whereby even with this heat transfer, only the comparatively low thermal resistance in the vertical direction caused by the prepreg layer 9 has to be overcome. The multilayer board is penetrated by a passive via 8, which is in contact with a heat sink 10 located on the top side of the multilayer board.Accordingly, the heat is conducted from the individual conductor tracks of the passive conductor track structure 7 through the thermal via 8 in a vertical direction to the heat sink 10.

[0044] If the heat sink 10, which is only shown schematically here, can be touched by a user during operation or, for example, is in contact with a liquid cooling medium, a basic insulation must be provided between the heat sink 10 and the passive conductor structure 7 or the thermal via 8 in order to ensure appropriate contact protection. Figure 2 However, the basic insulation (not shown) results in a high thermal resistance, which prevents the heat from being dissipated from the passive conductor structure 7 to the cooling medium.

[0045] Figure 3shows an embodiment of the invention with a coil system in the form of two stacked multilayer boards 11, 12, each with a base-insulated cooling channel 13. The two multilayer boards 11, 12 are constructed identically. An upper multilayer board 12 of the same design, rotated 180°, is placed on a lower multilayer board 11. An insulation layer made of prepreg 9 is located between the two multilayer boards 11, 12.

[0046] The planar coils 1-6 have the same shingled arrangement as already described in connection with Figure 2explained. The outer windings of the spiral-shaped, stacked windings 1-6 also engage comb-like in a passive conductor track structure 7. Laterally adjacent to this passive conductor track structure 7 there is a cooling channel 13 which was milled into the multilayer boards 11, 12 and metallized on its inside before the multilayer boards 11, 12 were stacked on top of one another. A metallization 14 applied to the inside of the respective cooling channel 13 is galvanically connected to the passive conductor track structure 7, so that the conductor track structure 7 is excellently thermally connected to the inner wall of the respective cooling channel 13. A liquid cooling medium flows through the cooling channel 13, so that the heat introduced via the passive conductor structure 7 is efficiently dissipated.

[0047] Crucial for this highly effective heat transfer is that the passive conductor structure 7 is base-insulated from the live windings 1-6 of the coil system. This enables the low-resistance connection of the passive conductor structure 7 to the metallization 14 of the inner wall of the cooling channel 13. In this example, the base insulation is ensured by ensuring that the lateral insulation distance 15 between the passive conductor structure 7 and the outer windings of the first coil is at no point less than six times the vertical distance between the directly superimposed windings 1-6. This, of course, presupposes that the vertical insulation distance, which is ensured by the prepreg layers 9, also meets the base insulation requirements, i.e., is thick enough to ensure the base insulation and the resulting contact protection.

[0048] Figure 4shows a coil system with vertically stacked, punched, planar coils 17. Each planar coil 17 is punched from a metal sheet, in particular a copper sheet, together with a passive conductor track 16. The stacked, passive, punched conductor tracks 16 engage, like a comb, in the outer windings of the punched coils 17. The stacked sheet metal sections with the resulting punched windings 17 and the punched passive conductor tracks 16 are designed such that a cooling channel 13 can be formed at one end. The arrangement shown, which forms the cooling channel 13, is also located at the opposite end of the coil system (not shown here).

[0049] Here, too, there is a prepreg layer between each individual punched winding 17. The prepreg layers are placed between the punched windings before these windings 17 are stacked on top of each other. The entire stack is then baked in the oven, creating a mechanical bond of electrically insulated, punched windings 17.

[0050] An important criterion when dimensioning the distances between the turns of the stamped winding and between the stamped windings 17 and the stamped passive conductor tracks 16 is again to ensure basic insulation from the cooling channel 13.

[0051] To increase the magnetic flux density that can be generated with the coil system shown, the spiral-shaped, punched windings 17 are axially penetrated by iron cores 18 made of SMC material.

[0052] In order to create a coil system in the manner of a solenoid coil from the individual, stacked, punched windings 17, the stacked, punched windings 17 must be electrically connected to each other. This is done by the targeted introduction of electrical vias 19 between the vertically adjacent, punched windings 17. These electrical vias 19 are in Figure 5 more clearly, which shows a sectional view of the coil system from Figure 4The electrical vias 19 are metal pins, particularly copper pins, which are inserted into corresponding holes. After the winding stack is drilled through at the appropriate locations, electrically conductive pins are first driven into the holes, penetrating the entire winding stack. To create the illustrated, targeted electrical connections between two vertically adjacent, punched windings 17, the unwanted portion of each electrically conductive pin is subsequently drilled out, leaving the electrical via 19 only at the desired location.

[0053] The Figures 6-9 show a sheet metal cut 20, on the basis of which the Figures 4 and 5 The coil system shown is constructed. The same sheet metal section 20 is shown in all figures. Figure 7 shows the sheet metal cut after Figure 6after a rotation of 180° around a rotation axis perpendicular to the drawing plane. Figure 8 shows the sheet metal cut after Figure 6 after it has been mirrored about the vertical center axis, the Y-axis. The sheet metal section in Figure 9 corresponds to the sheet metal cut from Figure 7 , but also mirrored along the vertical center axis. The representation in Figure 6 related corresponds to the Figure 9 shown sheet metal section of a rotation of the sheet metal section according Figure 6 by 180° around the rotation axis orthogonal to the x and y planes and subsequent reflection on the vertical central axis, the y axis.

[0054] The Figures 4 and 5 The coil system shown can now be constructed very easily by inserting sheet metal sections 20 into the Figures 6-9 shown layers are stacked successively on top of each other. This means that a sheet metal cut according to Figure 6 followed by a sheet metal cut according to Figure 7, on which a sheet metal cut is placed according to Figure 8 and finally a sheet metal cut according to Figure 9 The resulting stack is then sealed at the top. A prepreg layer is placed between each of the 20 sheet metal sections for insulation.

[0055] Since the lamination sections 20 do not have any axial symmetry with respect to their longitudinal axis Y or their transverse axis X, the desired shingling is created when the lamination sections 20 are stacked on top of each other, which is responsible for the advantageous lateral heat transport within the coil system.

[0056] The position of the cooling channel is marked by a dashed line at the front ends of the sheet metal section 20. This cooling channel is milled into the resulting stack after the individual sheet metal sections 20 have been stacked on top of each other and then metallized.

[0057] Of course, the coil system can consist of more than four punched planar coils. The order of the arrangement of the sheet metal cuts 20 then continues successively as in connection with the Figures 6-9 This means that the sheet metal cut according to Figure 9 followed by another sheet metal cut according to Figure 6 , which in turn is made from a sheet metal cut according to Figure 7 covered, and so on. The order of the layers can also be changed as long as the desired shingle pattern is maintained.

[0058] The reference number 21 in the Figures 6-9 the positions of the sheet metal sections 20 are marked, into which holes 21 are drilled after the sheet metal sections 20 are stacked. These holes separate the electrical contact to the cooling channel after the layer bonding.

[0059] In the Fig. 101 shows a sectional view through a printed circuit board 22 according to an exemplary embodiment of the invention. The sectional plane runs parallel to the plane of the printed circuit board 22 through an inner layer of the printed circuit board 22. The inner layer of the printed circuit board 22 has a plurality of conductor tracks 23 which are designed to run in a spiral shape, so that a plurality of windings 1 are formed within this layer. By means of each winding 1, a magnetic field can be generated which is oriented perpendicular to the plane of the printed circuit board 22—here the sectional plane. The magnetic field has its maximum in the center of the respective spiral formed by the conductor track 23.

[0060] The conductor track 23 is formed from a metallic material, preferably a copper-containing material, particularly preferably copper. The conductor track 23 is surrounded by a dielectric material 24, which electrically insulates the individual sections of the spiral-shaped conductor track 23 from one another. The dielectric material 24 is preferably an FR4 material.

[0061] In addition to the Fig. 10In addition to the layer of the printed circuit board 22 shown, the printed circuit board 22 has further layers. In this respect, the printed circuit board 22 is a multi-layer printed circuit board, also referred to as a multi-layer board. The printed circuit board 22 can have four, eight, ten, twelve, fourteen or more layers, with conductor tracks arranged in each layer. The conductor tracks of the other layers also have a spiral structure, so that planar coils are also formed in these layers. The conductor tracks 23 of adjacent layers are connected to one another via so-called vias 19, electrically conductive connections perpendicular to the board plane. Fig. 10 In the layer shown, for example, vias 19 are provided which connect the conductor tracks 3 with the conductor tracks of the adjacent layers, so that windings 1 are formed which extend in a direction perpendicular to the plane of the plate.

[0062] Within the circuit board 22, several separate iron cores 18 made of a ferromagnetic or ferrimagnetic material are also arranged. Each iron core 18 extends in a direction perpendicular to the layers of the circuit board 22. The iron core 18 is formed from sheets and / or layers of pressed powder material. The material of the iron core 18 is iron, a ferromagnetic alloy, or a ferrite. The iron core 18 is provided within the spiral conductor track 23, which forms a winding 1. The iron core 18 concentrates the magnetic flux generated by the winding 1 and increases the magnetic flux density.

[0063] The iron cores 18 are provided entirely within the circuit board 22 and are electrically insulated from the environment of the circuit board 22. The iron cores 18 are insulated by a first dielectric layer arranged parallel to the layers of the circuit board 22, for example, a dielectric cover layer of the circuit board 22. The respective iron core 18 can be insulated from the environment on a first surface of the circuit board 22 via the first dielectric layer. Furthermore, the circuit board 22 has a second dielectric layer, which is also arranged parallel to the layers of the circuit board 22. The iron cores 18 are arranged within the circuit board 22 between the first and second dielectric layers.In this respect, each iron core 18 is insulated from the environment by the first dielectric layer on a first surface of the circuit board 22 and by the second dielectric layer on a second surface opposite the first surface.

[0064] The first and second dielectric layers are formed from an FR4 material. The thermal conductivity of the FR4 material is preferably at least 0.5 W / (mK), particularly preferably at least 1 W / (mK), so that the ohmic heat loss generated during operation of the coil can be dissipated to the outside more effectively through the first and second dielectric layers.

[0065] The first and second dielectric layers provide basic insulation of the iron core 18 from the surroundings of the printed circuit board 22. The arrangement of the iron cores 18 entirely within the printed circuit board 22 enables, for example, a compact design of an electric motor. Furthermore, it also allows the insulation provided inside the printed circuit board 22 between the respective iron core 18 and the associated winding 1 to be designed to be weaker, thus increasing the performance of the winding 1 and the resulting coil from the layered windings or of the electric motor in which the printed circuit board 22 is used. These advantages will be explained below with reference to the illustration in Fig. 11 be explained in more detail.

[0066] The Fig. 11 shows a second embodiment of a circuit board 22 for an electric motor. In contrast to the Fig. 10 The embodiment shown is in Fig. 11Only one iron core 18 is shown. The circuit board 22 of this further exemplary embodiment, like the circuit board according to Fig. 110, can have several separate iron cores 18 made of a ferromagnetic or ferrimagnetic material. A first dielectric layer 25 is provided on a first surface of the circuit board 22, which is referred to below as the top side. A second dielectric layer 26 is arranged on a second surface of the circuit board 1 opposite the first surface, referred to below as the bottom side. The iron core 18 is thus arranged within the circuit board 22 between the first dielectric layer 25 and the second dielectric layer 26. The first dielectric layer 25 forms a cover layer on the top side of the circuit board 22, and the second dielectric layer 26 forms a cover layer on the bottom side of the circuit board 22.

[0067] The representation in Fig. 11further shows a layer of the circuit board 22, which has a spiral-shaped conductor track 23. In addition to the layer shown, further layers, in particular with spiral-shaped conductor tracks 23, can be present, which are electrically connected to the conductor track 23 of the layer shown. For electrically insulating the conductor track 23 from the iron core 18, an insulating region 27 of the layer is provided. The insulating region 27 is formed from a dielectric material, for example from an FR4 material. The material of the insulating region 27 and / or the dimensioning of the insulating region 27 is selected such that the first dielectric layer 25 and the second dielectric layer 26 have a higher breakdown voltage and / or a higher insulation resistance than the insulating region.Thus, the basic insulation of the coil and iron core from the environment can be achieved via the first dielectric layer 25 and the second dielectric layer 26. The insulation between the conductor track 23 of the winding and the iron core 18 only needs to meet the lower requirements of functional insulation. Optionally, it can be provided that the insulating region 27 and the first dielectric layer 25 and the second dielectric layer 26 are formed from the same dielectric material, and a first thickness D1 of the insulating region 27 is less than a second thickness D2 of the first dielectric layer 25 and less than a third thickness D3 of the second dielectric layer 26.Alternatively, it is possible for the insulating region 27 to be formed from a different dielectric material than the first dielectric layer 25 and the second dielectric layer 26, wherein the first thickness D1 of the insulating region 27 is greater than the second thickness D2 of the first dielectric layer 25 and greater than the third thickness D3 of the second dielectric layer 26. For example, the first thickness D1 of the insulating region 27 can be in the range from 200 µm to 300 µm, and the second thickness D2 of the first dielectric layer 25 and the third thickness D3 of the second dielectric layer 26 can be in the range from 110 µm to 190 µm, preferably in the range from 140 µm to 160 µm, particularly preferably 150 µm.

[0068] Figure 12shows a schematic diagram of a linear motor with a primary part 28, which can be constructed as a multilayer circuit board. Such a primary part 28 is very compact and lightweight, making it particularly suitable for highly dynamic applications. This primary part 28 interacts electromagnetically with a secondary part 29. The secondary part 29 comprises permanent magnets 30 embedded in a soft iron bed. The primary part 28 and the secondary part 29 are separated from each other by an air gap 31. By appropriately energizing the solenoid coils present in the primary part 28, a translational, highly dynamic movement of the primary part 28 can be realized. List of reference symbols

[0069] 1-6 Planar coils 7 Passive conductor track structure 8 Thermal via 9 Prepreg layer 10 Heat sink 11 Lower multilayer board 12 Upper multilayer board 13 Cooling channel 14 Metallization 15 Lateral insulation distance 16 Punched passive conductor track 17 Punched winding 18 Iron core 19 Electrical vias 20 Sheet metal cut 21 Drill holes 22 Circuit board 23 Conductor track 24 Dielectric material 25 First dielectric layer 26 Second dielectric layer 27 Insulating area 28 Primary part 29 Secondary part 30 Permanent magnets 31 Air gap

Claims

1. A coil system comprising a first coil with a plurality of stacked planar coils (1-6), • wherein in each case two planar coils (1-6) lying directly above one another are stacked vertically with a lateral offset such that at least in sections in each case one turn of a first planar coil (1) and two turns of a second planar coil (2) arranged directly above the first planar coil are arranged in partial overlap, • wherein the coil system comprises a passive conductor track structure (7) which is galvanically separated from all current-carrying planar coils (1-6) of the coil system and has a plurality of conductor tracks (23) that are stacked on top of one another and form a first comb-like structure, • wherein the first comb-like structure engages at at least one edge region of the first coil in a second comb-like structure that is formed by the lateral offset of the outer turns of the planar coils (1-6) lying above one another, characterised in that the lateral insulation distance (15) of the outer turn of each planar coil (1-6) from the passive conductor track structure (7) is dimensioned such that it effects a basic insulation of the first coil with respect to the passive conductor track structure (7), and wherein the coil system comprises a cooling channel (13) for a liquid cooling medium, which is located laterally adjoining the passive conductor track structure (7) and extends along the edge region of the first coil and is electrically base-insulated from the first coil via the lateral insulation distance (15) between the passive conductor track structure (7) and the outer turns of the planar coils (1-6).

2. The coil system according to claim 1, wherein the two comb-like structures are arranged relative to one another such that the lateral insulation distance (15) between the passive conductor track structure (7) and the outer turns of the first coil is at no point less than 6 times the vertical distance between the planar coils (1-6) lying directly above one another.

3. The coil system according to claim 1 or 2, wherein a side of the passive conductor track structure (7) facing away from the outer turns of the first coil forms a side wall of the cooling channel (13).

4. The coil system according to claim 3, wherein the surface of the cooling channel (13) facing the liquid cooling medium is copper-plated, wherein the copper-plated surface of the cooling channel (13) is galvanically connected to the plurality of conductor tracks of the passive conductor track structure (7) stacked on top of one another.

5. The coil system according to any one of the preceding claims, wherein the plurality of stacked planar coils (1-6) is penetrated by an iron core (18).

6. The coil system according to claim 5, wherein the iron core (18) consists of an SMC material.

7. The coil system according to any one of the preceding claims, wherein a prepreg layer (9) is arranged between two planar coils (1-6) lying directly above one another in each case.

8. The coil system according to any one of the preceding claims, each with a prepreg cover layer (25, 26) on an upper and a lower side of the stack of stacked planar coils (1-6), which effect a basic insulation of the coil system.

9. The coil system according to any one of the preceding claims, wherein the coil system is designed as a multi-layer board (11, 12, 22) and wherein the planar coils (1-6) and the conductor tracks of the passive conductor track structure (7) of each layer are arranged on a common single board of the multi-layer board (11, 12, 22).

10. The coil system according to any one of claims 1 to 8, wherein the planar coils (1-6) and the conductor tracks of the passive conductor track structure (7) of multiple layers are produced from the same metal sheet, in particular a copper sheet, by means of a separation method, and wherein an insulating layer (9) is arranged between two planar coils (1-6) lying directly above one another in each case.

11. The coil system according to claim 10, wherein the planar coils (1-6) and the conductor tracks of the passive conductor track structure (7) of each layer are punched out of the metal sheet.

12. The coil system according to claim 10 or 11, wherein the planar coils (1-6) and the conductor tracks of the passive conductor track structure (7) of four layers lying above one another have the same sheet metal cut (20), wherein said sheet metal cut (20) within the four layers lying above one another is arranged • in a second layer as a mirrored sheet metal cut (20) of the first layer, • in a third layer as a sheet metal cut (20) of the first layer rotated through 180°, and • in a fourth layer as a sheet metal cut (20) of the first layer mirrored and rotated through 180°.

13. The coil system according to any one of claims 10 to 12, wherein the planar coils (1-6) stacked directly on top of one another are electrically connected by pins (19) made of electrically conductive material, which pass through the insulating layers (9) present between the planar coils (1-6).

14. The coil system according to any one of the preceding claims, with a second coil arranged laterally offset from the first coil and also comprises planar coils (1-6) stacked on top of one another and laterally offset from one another, wherein outer turns of the first coil and outer turns of the second coil engage with one another in a comb-like manner.

15. An electric motor with a primary part (28) comprising a coil system according to any one of the preceding claims and a secondary part (29) spaced apart from the primary part (28) by an air gap (31).

16. A method for producing a coil system having the following method steps: • producing individual layers, each with ∘ a planar coil (1-6) and ∘ a passive conductor track laterally offset in the respective layer relative to an outer turn of the respective planar coil (1-6), which is electrically insulated from the respective planar coil (1-6) by a lateral insulation distance (15), • stacking the individual layers on top of one another to form a stack in such a way that ∘ in each case two planar coils (1-6) lying directly above one another are stacked vertically with a lateral offset such that at least in sections in each case one turn of a first planar coil (1) and two turns of a second planar coil (2) arranged directly above the first planar coil (1) are arranged in partial overlap, ∘ and the passive conductor tracks lying above one another form a first comb-like structure, wherein the first comb-like structure engages at at least one edge region of the first coil in a second comb-like structure that is formed by the lateral offset of the outer turns of the planar coils (1-6) lying above one another, characterised in that the lateral distance of the outer turn of each planar coil (1-6) from the passive conductor track structure (7) is dimensioned such that it effects a basic insulation of the first coil with respect to the passive conductor track structure (7), and wherein a cooling channel (13) for a liquid cooling medium is milled into the stack, which is located laterally adjoining the passive conductor track structure (7) and extends along the edge region of the first coil and is electrically insulated from the first coil via the passive conductor track structure (7).

17. The method according to claim 16, wherein an insulating layer (9) is arranged between two layers stacked above one another in each case and planar coils (1-6) of layers lying above one another are connected to one another by means of an electrically conductive pin (19) which passes through the respective insulating layer (9).