Radial-flux double-rotor electric machine

Description

AREA OF INVENTION

[0001] The present invention relates to a radial flux double rotor machine, in particular for a wheel hub drive. TECHNICAL BACKGROUND

[0002] Electric machines with one stator and two rotationally fixed rotors, so-called double-rotor machines (also referred to as multiple rotors, dual-rotor, etc.), can increase both the torque density and the efficiency of electric drives compared to conventional electric machines with only one rotor. This is because, particularly in the so-called "yokeless" design, no magnetic return path in the stator is required, thus significantly reducing remagnetization losses. Furthermore, with two rotors, there is generally more space available for the field-exciting magnets (in permanent magnet synchronous machines, PSM) or the conductor material (in induction machines, IM, or electrically excited synchronous machines, ESM).According to the orientation of the magnetic field lines in the air gap, such machines can be divided into two groups: axial flux-carrying (field lines parallel to the axis of rotation, so-called axial flux machines) on the one hand, and radial flux-carrying (field lines in a radial direction in the air gap, so-called radial flux machines) on the other.

[0003] Axial flux twin-rotor machines are described, for example, in DE 10 2015 226 105 A1 and DE 10 2013 206 593 A1. They are characterized by high torque and power density, but are complex to manufacture because very intricate geometries must be stamped or powder-metallurgically produced in the stator core. To date, such machines have therefore not made the leap into mass production and are only used in niche areas with high power density requirements, such as motorsports, aerospace, etc. Furthermore, the mechanical fastening concepts for the stator winding only allow the use of single-tooth windings, with corresponding disadvantages regarding noise excitation.

[0004] In contrast, established and mass-production-ready manufacturing processes can, in principle, be applied to the winding and stator core of radial flux twin-rotor machines. However, a major and largely unresolved technical challenge lies in supporting the torque generated in the stator core. Due to the rotating parts inside and outside, the stator stator core cannot be mounted in a stationary housing (e.g., pressed in, bolted, or glued) as is usually the case. The torque is therefore transmitted to the axial ends of the stator stator core and / or stator winding and supported there. Various approaches have been proposed in the prior art, but all of them are associated with significant disadvantages in terms of function and / or cost.

[0005] EP 1 879 283 B1 describes one possible design for the stator winding as a so-called yoke winding. The ring-shaped stator lamination stack has slots on its inner and outer diameters, between which a tangentially acting magnetic return path (also called the stator yoke) is located. The positive and negative conductors of each winding strand are guided in radially superimposed slots and wound around the yoke. The stator yoke is axially accessible between the winding strands and can be fixed to the housing, for example, by axial screws (e.g., described in JP 2018 082 600). The axial pressure of the screws ensures both torsional stiffness of the lamination stack and torque support at the axial end. The north and south poles of the rotor field are opposite each other.A disadvantage of this concept is that the magnetic flux must be guided entirely through the return yoke located between the stator slots. This leads to an increased weight of the stator lamination stack and significantly increases iron losses. The magnetic field lines of both rotor fluxes close via the magnetic return flux in the stator lamination stack, causing iron losses there. Furthermore, all individual coils of the yoke winding must be connected in parallel or in series in the area of ​​the winding head, which in turn leads to a space conflict with the torque support. However, the winding around the yoke allows for direct mechanical contact with the stator lamination stack.

[0006] Significant weight and loss savings can be achieved if the magnetization directions of the radially stacked magnets point in the same direction and the current directions of the conductors stacked in the slots are identical. In this case, the magnetic return path in the stator can be omitted, resulting in a so-called "yokeless" twin-rotor machine with distributed winding. The magnetic field lines close above the rotor. A magnetic return path in the stator is not required, which significantly reduces weight and iron losses in such machines. However, the distributed winding does not allow direct mechanical contact with the stator core for torque support. For example, WO 2004 / 004098 A1 describes a yokeless design with distributed winding.

[0007] Even in a so-called "yokeless" design, it can be advantageous to use a thin yoke for the mechanical connection of the stator teeth, although this is not necessary for electromagnetic purposes. The term "yokeless" refers to the electromagnetic flux flow, in which there is no flux in the tangential direction within the stator. However, the winding cannot be designed as a yoke winding because the forward and return conductors of the winding strands are radially distributed around the circumference, forming a distributed winding. This results in winding heads of distributed windings, which make axial access to the laminated core more difficult. Furthermore, the purely radial flux flow precludes the use of axial, metallic screw connections, as these create conductor loops with high levels of interconnected flux and significant additional heat losses.

[0008] For axial support, various auxiliary structures for torque support are proposed in the prior art, for example, as described in DE 10 2010 055 030 A1 or US 7,557,486 B2. A problem here is that electrically and / or magnetically conductive metals may not, or only to a very limited extent, protrude into the flow-carrying area, which severely restricts the material selection and geometric design. In contrast, plastic components, adhesives, and / or potting compounds can also be used in the flow-carrying area. However, it is very difficult to meet the high requirements regarding temperature stability and mechanical strength with such materials.

[0009] A twin-rotor aircraft is disclosed in US 2009 / 230808 A1 and in DE 197 04 652 C1.

[0010] In summary, it can be stated that no satisfactory solution for torque support in yokeless radial flux twin-rotor machines can be found in the current state of the art. This is a situation that needs to be improved. SUMMARY OF THE INVENTION

[0011] Against this background, the present invention aims to provide an improved radial flux twin-rotor machine.

[0012] According to the invention, this problem is solved by a radial flux double rotor machine with the features of claim 1.

[0013] Accordingly, the following is planned: A radial flux double rotor machine, in particular for a wheel hub drive, comprising: a mechanically fixed base; a stator according to the invention, wherein the support device for torque support is in positive engagement with at least one axial end of the winding and is supported at the base; a first rotor arranged radially inside the stator core; and a second rotor arranged radially outside the stator core.

[0014] The underlying insight of the present invention is that a winding of a radial flux twin-rotor machine can be designed to transmit force for torque support. The idea of ​​the present invention is to design the winding arranged in the stator core to be self-supporting for torque support and to engage it positively with a support device arranged axially offset from the stator core for torque support.

[0015] A self-supporting winding design means that the winding possesses sufficient stiffness and resistance to torsion around the machine axis to support the drive torque. The self-supporting winding is embedded in a soft magnetic stator core for magnetic flux guidance. This offers the particular advantage that the stator core itself does not require inherent torsional stiffness with respect to the machine axis, nor is any other auxiliary structure needed to fix the stator core in place. Instead, the torque is supported, in particular, entirely by the winding.

[0016] Thus, a previously unknown or technically unfeasible functional integration is created in the field of radial flux twin-rotor machines, by giving the winding a load-bearing function for supporting the torque in addition to conducting current, and by mechanically fixing the winding outside the stator core at an axial end.

[0017] In an embodiment not part of the invention, an integral manufacturing of the winding within the existing stator core is proposed for producing such a winding. For this purpose, the individual conductors of the winding are inserted through the radially inner and radially outer stator slots in the axial direction following the helical line of the stator slots and connected at the conductor ends. Preferably, a metallurgical connection is provided by welding or brazing. Thus, the winding is positively connected to the stator core.

[0018] The selected helix angle (also called twist angle) of the stator slots, or the helix lines they describe, ensures that conductor loops are formed by connecting the inserted conductor bars. The angle swept by the conductor loops within the machine, relative to the central axis, encloses each magnetic pole of the rotors. In this way, despite the functional integration, a very simple stator manufacturing process is possible, requiring very few components and comparatively simple conventional connection technology, and therefore also very few manufacturing steps.

[0019] The stator thus constructed can now be completed with various inner and outer rotors known to those skilled in the art to form an electric machine according to the invention. These include, for example, permanent magnet excited rotors with surface magnets and / or buried magnets, squirrel-cage rotors, or electrically excited rotors. Hybrid variants with different rotor types in the inner and outer rotors can also be provided. A particularly advantageous embodiment results when the rotors are made of solid soft magnetic material and with surface-mounted permanent magnets. The low upper magnetic field spectrum of the winding variants described here and the distance between the solid material and the air gap ensured by the magnets prevent the formation of unacceptably large losses due to eddy currents in the rotors.In this design, comparatively high efficiencies can be achieved to their advantage, and the rotors can still be manufactured very cost-effectively.

[0020] The support structure is firmly connected to the base, the stationary part of the electric machine, using a suitable method. One possible design provides recesses, such as through holes, for friction-fit fasteners like screws. However, alternatively or additionally, positive-locking fasteners and / or a material-bonded connection would also be conceivable.

[0021] In particular, the present invention is especially advantageous for use in a wheel hub motor, preferably for a motor vehicle. Due to the functional integration of the design according to the invention, the mass of a radial flux twin-rotor machine can be reduced and the torque density increased, which is particularly advantageous in wheel hub motors, resulting in a reduction of unsprung mass. Furthermore, according to the invention, a comparatively short axial length can be achieved with a comparatively large diameter, which is particularly advantageous inside the wheel with regard to torque support and installation space.

[0022] On the other hand, according to the invention, despite the extremely compact design, very high torques are also possible, which are particularly high enough to directly drive a wheel of a vehicle without a gearbox. In this way, gearbox losses are avoided, further weight is saved, and particularly high efficiency gains can be achieved.

[0023] Furthermore, this high torque, which is already well into four figures for wheel sizes comparable to those of standard vehicle rims, particularly exceeding 5000 Nm, and thus already approaches the grip limit of conventional road tires, even allows the wheel hub motor to replace a rear axle wheel brake. This enables unique synergies when used as a wheel hub motor.

[0024] Furthermore, according to one aspect, a vehicle axle, in particular for a motor vehicle, with a radial flux double rotor machine according to the invention, which is coupled without a gear to a drive wheel, is disclosed.

[0025] Furthermore, according to one aspect, a motor vehicle with such a vehicle axle is revealed.

[0026] Advantageous designs and further developments result from the further sub-claims as well as from the description with reference to the figures in the drawing.

[0027] According to one embodiment, the winding is designed to be so torsionally stiff that a torque acting on the stator core during the operation of a radial flux twin-rotor machine can be supported, in particular completely, by the torsionally stiff winding on the support element. In this way, all other types of force support devices, especially for the stator core, can advantageously be omitted.

[0028] According to one embodiment, the stator core is designed to guide a primarily radial magnetic flux. This is therefore a so-called "yokeless" design of the stator core, which in particular avoids guiding the magnetic flux in a circumferential or tangential direction. A magnetic return path within the stator core is not required, thereby reducing weight and iron losses.

[0029] According to one embodiment, the stator core has a radial yoke thickness that is less than 30%, preferably less than 20%, and particularly preferably less than 10% of the total radial stator core thickness. In a so-called "yokeless" design, this still provides a mechanical connection between the stator teeth, which is not electromagnetically necessary and through which no functionally relevant magnetic flux occurs. The term "yokeless" thus refers specifically to the electromagnetic flux guidance of the stator core.

[0030] According to one embodiment, the winding is formed from conductor bars connected to one another, in particular in a truss-like structure. In particular, the conductor bars can be joined by a material bond, for example by welding or soldering.

[0031] However, other connection techniques are also conceivable. Preferably, two conductor bars are connected at their ends, and all conductor bars together form a truss structure. The truss structure formed by the conductor bars is advantageously designed to be torsionally rigid and suitable for transmitting torque around the central axis of the stator. Furthermore, the conductor bars are designed with a sufficient thickness for power transmission. In a wheel hub motor, for example, the thickness of the conductor bars can be several millimeters. In particular, these can be square-profile bars with edge lengths of several millimeters.

[0032] According to one embodiment, the winding has a radially inner layer of helically arranged conductor bars and a radially outer layer of oppositely helically arranged conductor bars. In this way, the winding forms a truss structure exhibiting high torsional stiffness. The conductor bars of the inner layer and the conductor bars of the outer layer each describe a helix whose winding directions or pitches are opposite to each other. The angle swept by the helix between the beginning and end of a conductor bar, relative to the central axis of the stator, is particularly such that, in a radial flux twin-rotor machine, one conductor loop is formed per pole of the rotors. The required swept angle can thus be calculated from the quotient of one complete revolution (2π or 360°) and twice the number of pole pairs. p calculate.

[0033] According to one embodiment, the radially inner and radially outer layers of the winding each have the thickness of a single conductor bar. That is, each phase of the winding is formed with the cross-section of a single conductor bar. Such a winding configuration according to the invention is made possible, among other things, by the special design of the radial flux double-rotor machine, which, by means of its magnetic symmetry, prevents the current displacement to the surface that otherwise occurs in conductors. In this way, comparatively thick conductor cross-sections are possible, and a relatively uniform current distribution across the cross-section is still achieved. For example, the thickness of the conductor bars can be in the range of several millimeters. In particular, these can be square-profile bars with edge lengths of several millimeters, for example, in the range of 2 mm to 6 mm, and especially in the range of 3 mm to 5 mm.Other cross-sectional shapes are also possible.

[0034] According to one embodiment, the conductor bars are twisted in accordance with their helical shape such that the cross-section of each conductor bar, relative to a radial axis of the cross-section, is the same at every point along the conductor. Specifically, this involves a torsion of a conductor bar, particularly a non-circular one, around the central axis of the stator or machine. Depending on the helical shape, the conductor bars may also be bent. The inner and outer layers are interlocked with each other, meaning they are twisted, rotated, and optionally bent in opposite directions. In this way, the orientation of each conductor bar is ideally aligned with the stator core from a mechanical perspective, ensuring that the load is uniformly distributed along its length.In the resulting framework, the conductors advantageously absorb predominantly tensile and compressive stresses when subjected to tangential force. This avoids load peaks and deformations of the conductor bars. In particular, compared to a design with axially parallel, straight conductors, the mechanical stresses can thus be significantly reduced.

[0035] According to one embodiment, the conductor bars belonging to the same phase of the winding, in the radially inner and outer layers, are connected to each other at their ends, in particular via a radially arranged conductor bar section and / or by means of a material-bonded connection. This creates not only a conductor loop but also a torsionally rigid, truss-like structure, so that when an axially accessible winding end is fixed, the winding can absorb a high torque without causing excessively large deformations and / or stresses. Thus, the self-supporting design of the winding is made possible solely by the winding material, for example, copper, without additional support materials or elements.

[0036] According to one embodiment, the stator core contains a stator lamination stack with stator slots arranged helically according to the winding path, with a single conductor bar arranged in each stator slot of the stator lamination stack. The winding, or the self-supporting truss structure formed by it, is thus embedded in the stator lamination stack. Analogous to the conductor bars of the winding, the stator slots therefore change their tangential position depending on the axial position, resulting in the helical shape.

[0037] The direction of the change in position follows the conductor bars, i.e., the center line of the radially outer grooves and the radially inner grooves each describe a helix whose winding directions are opposite.

[0038] In further embodiments that are not part of the invention, other manufacturing methods known to the skilled person for producing the stator core geometry according to the invention with the oppositely helical radial inner and outer stator grooves would also be conceivable, in particular additive manufacturing methods such as sintering processes or the like.

[0039] According to one embodiment, only a single conductor bar is placed in each stator slot of the stator lamination stack. As already explained with regard to the winding, the conductor bars of the inner and outer stator slots are helically intertwined by torsion around the central axis of the machine, so that the conductor ends of the inner and outer layers are aligned. The conductor bars are conductively connected to each other at their ends, in particular via a radially arranged conductor bar section and / or by means of a metallurgical connection, for example by welding or brazing.

[0040] According to one embodiment, the conductively connected conductor bars of the inner and outer layers together form wave-shaped winding strands. These winding strands can be connected to form a rotating field-generating winding with a desired or adjustable number of strands by means of appropriate connections known to those skilled in the art. The voltage-holding number of strand turns is directly derived from the quotient of the number of slots in the counter and a product of the number of strands and the number of parallel branches in the counter. Advantageously, the number of parallel branches is chosen to be 1. In this case, the simplest possible winding connection is obtained.

[0041] According to one embodiment, the stator laminations of the stator lamination stack are identical, each with recesses designed to form the stator slots. The helical orientation of the stator slots is achieved by stacking the stator laminations at a twisted angle relative to one another. This allows for very economical manufacturing of the stator lamination stack, as the same die can be used for all parallel or stacked stator laminations. Accordingly, two adjacent stator laminations are slightly twisted relative to each other by a predetermined angle around the central axis, so that the recesses overlap, corresponding to the helical path.

[0042] According to an advantageous embodiment, the stator lamination stack comprises an inner sub-stack with radially inner stator slots and an outer sub-stack with radially outer stator slots. The stator laminations of the inner sub-stack and the stator laminations of the outer sub-stack each have the same geometry. The stator laminations of the inner sub-stack and the stator laminations of the outer sub-stack are stacked with opposite helical orientations. In this way, the opposing helical paths of the stator slots can be achieved with minimal manufacturing effort. Nevertheless, a very economical manufacturing method is still possible, since the same die can be used for all parallel stator laminations of the inner sub-stack and for all parallel stator laminations of the outer sub-stack.Accordingly, two adjacent stator laminations of the inner subpack are slightly rotated relative to each other in a first direction by a predetermined angle around the central axis, and two adjacent stator laminations of the outer subpack are slightly rotated relative to each other in a second, opposite direction by a predetermined angle around the central axis. In this way, the recesses of the stator laminations of the inner subpack and the recesses of the stator laminations of the outer subpack are arranged in an opposite overlap to each other, which corresponds to the opposite helix direction.

[0043] According to another embodiment, the stator laminations with recesses for forming the stator slots are each shaped differently. The helical orientation of the stator slots is achieved by varying the spacing of the recesses in the individual stator laminations. In this way, a custom-fit stator lamination shape is produced for each position of a stator lamination within the stack, and the individual geometries can also be repeated within the stack. In this case, production can be carried out, for example, using a beam cutting process, particularly laser beam cutting, which is more flexible with regard to shape compared to a stamping process. Flexible stamping dies with variable geometries would also be conceivable, or, for very high production volumes, several individual stamping dies for each of the different stator lamination shapes.

[0044] According to a further development, the recesses for radially inner and radially outer stator slots are each integrated into a common stator lamination, with the opposing helical orientation of the radially inner and radially outer stator slots being achieved by a continuous displacement of the inner and outer stator slots relative to each other from stator lamination to stator lamination. Here, too, a custom-fit stator lamination shape is produced for each position of a stator lamination within the stack, and the individual geometries can also be repeated within the stack. Flexible cutting processes, such as laser beam cutting, are used for manufacturing. The resulting single-piece production of the inner and outer recesses advantageously reduces the number of parts.

[0045] According to one embodiment, the stator laminations have straight, in particular stamped, edges. The width of the recesses provided for the stator slots is greater than the width of the conductor bars by an amount predetermined by the pitch of the helical shape of the stator slots and by the thickness of the stator laminations. The reduced clear width, or continuous width, of the stator slots, resulting from the offset between the recesses of the stator laminations, thus essentially corresponds to the width of a conductor bar. In practice, the continuous clear width of the stator slot is slightly larger than the width of the conductor bar to provide the necessary clearance for inserting the conductor bars. The edge of a stator slot therefore describes a stepped shape with the respective lamination thickness as steps, against which the conductor bar rests uniformly.In this way, the torque support is enabled to be distributed evenly across the entire thickness of the stator lamination stack or across the entire length of the conductor bars incorporated into the stator lamination stack.

[0046] According to one embodiment, the angle swept by each stator slot is smaller than the angle swept by each conductor bar. The swept angle refers to a rotation about the central axis of the stator. This difference in the swept angles arises because the conductor bars extend axially beyond the stator core and are therefore longer than the stator slots. Since the helical shape also continues, this results in a larger swept angle. This difference is designed to ensure sufficient accessibility to the winding ends for connecting, in particular welding, the conductor bar ends after insertion into the stator slots. Furthermore, this design allows the winding to engage with the support structure or its support element in an axially offset position relative to the stator core.

[0047] From the quotient of the swept angles, i.e., a ratio of the angle swept by the stator slots to the angle swept by the conductor bars, a so-called pole coverage ratio for the stator lamination stack can be defined.

[0048] According to one embodiment, the ratio of the angle swept by each stator slot to the angle swept by each conductor bar lies in a range between 0.6 and 0.8, in particular between 0.6 and 0.75, preferably between 0.6 and 0.7. This ratio (pole coverage ratio) provides an optimum in this range between losses caused by electrical heat and torque utilization.

[0049] According to one embodiment, the support structure comprises a support element in which support grooves corresponding to the helical arrangement of the conductor bars and engaging with the conductor bars are provided. In this way, a positive-locking embedding of the conductor bars in the support element is provided for torque support at the axial end. Preferably, there is engagement with all conductor bars, so that the torque support is distributed homogeneously or uniformly across the entire framework of the winding.

[0050] To transmit torque, the support element can be coupled to a mechanically fixed base of a radial flux twin-rotor machine. One possible design provides through-holes for friction-fit fasteners such as screws, but of course, positive-locking fasteners or a material-bonded connection would also be conceivable.

[0051] According to one embodiment, the support grooves at least partially follow the helical path of the twisted conductor bars. In particular, the support grooves have a twisted path that matches the conductor bars. For example, the support element is essentially ring-shaped and has recesses on its inner and / or outer circumference that are radially oriented and correspond to the path of the conductor bars.

[0052] According to one embodiment, the support structure comprises a radially inner support element for engaging with the radially inner layer of conductor bars and a radially outer support element for engaging with the radially outer layer of conductor bars. In this embodiment, the support elements can be ring-shaped, with the inner support element having grooves or teeth on its outer circumference corresponding to the path of the inner layer of conductor bars for the positive engagement of the radially inner conductor bars, and the outer support element having grooves or teeth on its inner circumference corresponding to the path of the outer layer of conductor bars for the positive engagement of the radially outer conductor bars. The grooves or teeth follow, in particular, the respective helical path. Due to their arrangement on the inner or outer circumference, the recessed grooves are easily accessible for machining, which simplifies the manufacture of the support elements.

[0053] According to one embodiment of a radial flux twin-rotor machine, the support elements are fixed to the base and thus transmit the torque to the stationary part of the electric machine. The support elements can be individually attached to the base, for example, a housing, of the machine. Alternatively or additionally, the inner and outer support elements can also be attached to each other.

[0054] According to one embodiment of a stator, the support structure contains a thermally conductive material, in particular a metal, preferably an aluminum alloy. In particular, both support elements can contain such a material. In this way, in addition to high mechanical strength, heat dissipation from the winding via the support structure is also enabled.

[0055] According to one embodiment of a corresponding radial flux twin-rotor machine with a support structure containing a thermally conductive material, the base additionally features a heat sink designed to absorb heat dissipated from the stator, particularly from the winding, via the support structure. This gives the support structure high mechanical strength while simultaneously ensuring good thermal contact between the winding and the heat sink. For example, the machine housing can serve as the heat sink. Alternatively or additionally, the support structure, preferably the inner and outer support elements, can be in thermal contact with an actively cooled heat sink of the machine. In this way, the heat losses arising in the winding or conductor bars can be effectively dissipated.

[0056] According to one embodiment of a radial flux twin-rotor machine, a predetermined number of pole pairs are provided on both the first and second rotors. The angle swept by the conductor bars is designed to form a conductor loop for each pole of the rotors. The required swept angle can thus be calculated as the quotient of one complete revolution (2π or 360°) and twice the number of pole pairs. p calculate.

[0057] According to one embodiment of the manufacturing process, which is not part of the invention, providing the stator core comprises manufacturing a stator lamination stack, wherein individual stator laminations, which have recesses for forming stator grooves, are stacked in a twisted orientation relative to one another. In this way, the stator lamination stack can be manufactured very economically, since the same die can be used for all parallel or stacked stator laminations. Accordingly, two adjacent stator laminations are slightly twisted relative to each other by a predetermined angle about the central axis, so that the recesses are arranged in an overlap corresponding to the helical path. The individual stator laminations with such a geometry are advantageously manufactured by stamping or laser cutting of individual laminations from electrical steel.

[0058] According to a further development of the method, the stator lamination stack comprises an inner sub-stack and an outer sub-stack, wherein all stator laminations of the inner sub-stack and all stator laminations of the outer sub-stack are formed with the same geometry, and wherein the stator laminations of the inner sub-stack are stacked with opposite twists to form the inner stator slots, and the stator laminations of the outer sub-stack are stacked with opposite twists to form the outer stator slots. In this case, all laminations of the inner and outer stacks can be manufactured with the same geometry, making the manufacturing process very economical. The same die can thus be used for all parallel stator laminations of the inner sub-stack and for all parallel stator laminations of the outer sub-stack.Two adjacent stator laminations of the inner subpack are slightly rotated relative to each other by a predetermined angle around their central axis in a first direction, and two adjacent stator laminations of the outer subpack are slightly rotated relative to each other by a predetermined angle around their central axis in a second direction. This results in the recesses of the stator laminations of the inner subpack and the recesses of the stator laminations of the outer subpack being arranged in opposite overlaps, corresponding to the opposite helix directions. In this way, the opposite helix directions of the stator slots can be achieved with minimal manufacturing effort.

[0059] According to a further embodiment of the method, the stator lamination stack comprises a plurality of differently shaped stator laminations, wherein the recesses for the inner and outer stator slots are each integrated into a common stator lamination, and wherein the pitch of the helix is ​​achieved by a continuous displacement of the inner and outer stator slots relative to each other from stator lamination to stator lamination, in particular with a flexible punching or laser beam cutting process. In this process, inner and outer stator slots are integrated into a single stator lamination (lamella), and the helical orientation of the stator slots is achieved in each individual lamination by a continuous displacement of the recesses relative to each other during the cutting process, for example, by means of a flexible punching process or a laser beam cutting process. This has the advantage that fewer parts mean fewer manufacturing steps are required, and the resulting stator lamination is therefore smaller.the entire stator core has a higher mechanical strength.

[0060] In a further embodiment, the method further includes the step of providing a support device which is designed for positive engagement with the conductor rod ends at at least one axial end for torque support, and the step of positively engaging the support device with the conductor rod ends at the at least one axial end in a position arranged axially offset to the stator core.

[0061] According to one aspect, a stator produced in this way can also be used to carry out a method for producing a radial flux double rotor machine, with the further steps of: providing a mechanically fixable base and a support device which is designed for positive engagement with the winding at at least one axial end for torque support, and fixing the support device to the base.

[0062] The above-mentioned designs and further training options can be combined with each other as appropriate. CONTENT OF THE DRAWING

[0063] The present invention will be explained in more detail below with reference to the exemplary embodiments shown in the schematic figures of the drawing. These figures show: Fig. 1 a schematic longitudinal sectional view of a stator; Fig. 2 a schematic longitudinal sectional view of a radial flux twin-rotor machine; Fig. 3 an exploded view of a stator according to one embodiment; Fig. 4 an exploded view of a radial flux twin-rotor machine according to one embodiment; Fig. 5 an exploded view of a radial flux twin-rotor machine according to a further embodiment; Fig. 6 a perspective view of the radial flux twin-rotor machine according to Fig. 5 in the assembled state; Fig. 7 a perspective longitudinal section of a radial flux twin-rotor machine according to a further embodiment; Fig. 8 an exploded view of a stator lamination stack of a stator core; Fig. 9 a schematic longitudinal section of a stator slot; Fig. 10 a perspective view of a winding; Fig. 11 a top view of a winding; Fig. 12 a perspective view of an FEM simulation of a winding under load; Fig. 13 a perspective view of an FEM simulation of a comparison winding with straight conductor bars under load; and Fig. 14 a flowchart. , which is not part of the invention, a method for manufacturing a stator.

[0064] The accompanying figures are intended to provide a further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain the principles and concepts of the invention. Other embodiments and many of the advantages mentioned will become apparent with reference to the drawings. The elements of the drawings are not necessarily shown to scale.

[0065] In the figures of the drawing, identical, functionally equivalent and similarly acting elements, features and components - unless otherwise stated - are each provided with the same reference symbols. DESCRIPTION OF EXAMPLES OF EXECUTION

[0066] Fig. 1 shows a schematic longitudinal section view of a stator 1.

[0067] This is a schematic diagram of a stator 1 for a radial flux double-rotor machine 10 (see also Fig. 2 ), particularly for a wheel hub motor. The stator comprises a stator core 2, a winding 3, and a support structure 5. The stator core 2, the winding 3, and the support structure 5 are rotationally symmetrical about the central axis M shown.

[0068] The winding 3 is designed to be self-supporting for torque support of the stator 1 and projects beyond the stator core 2 at at least one axial end 4. The support structure 5 is arranged axially offset from the stator core 2 and is positively connected to the winding 3 at at least one axial end 4 for torque support. In this way, a torque acting on the stator core 2 during the operation of a radial flux twin-rotor machine 10 can be supported by the self-supporting winding 3 on the support structure 4.

[0069] The winding contains a conductor material with low electrical resistance, preferably copper. The stator core 2 is preferably made of a soft magnetic material for magnetic flux guidance. The support structure preferably contains a thermally conductive material, for example, an aluminum alloy. Naturally, the winding 3 is electrically insulated.

[0070] Fig. 2 shows a schematic longitudinal section view of a radial flux twin-rotor machine 10.

[0071] This too is a purely illustrative schematic diagram. The radial flux double-rotor machine 10 therefore has, in addition to the stator 1 according to Fig. 1 a mechanically fixed base 11, a first rotor 12 and a second rotor 13. The stator core 2, the winding 3, the support structure 5, the base 11, the first rotor 12 and the second rotor 13 are also rotationally symmetrical about the central axis M shown.

[0072] The winding 3 is designed to be self-supporting for torque support of the stator 1 and projects beyond the stator core 2 at at least one axial end 4. It is supported at the base 11 by the support structure 5. The support structure 5 is arranged axially offset from the stator core 2 and is positively connected to the winding 3 at at least one axial end 4 for torque support. The support structure 5 is in turn attached to the base, so that the torque can be supported at the base 11 via the support structure 5.

[0073] The first rotor 12 is arranged radially inside the stator core 2, and the second rotor 13 is arranged radially outside the stator core 2. The base 11 can, for example, be designed as the housing of the machine and, for illustrative purposes, comprises an L-shaped structure shown here with two legs 7, 8. This illustration is not exhaustive; rather, the base can include further components and / or structural sections. The first leg 7 extends essentially radially, and the second leg 7 extends essentially axially at the greatest distance from the central axis M.

[0074] In purely schematic terms, the support structure 5 is shown as a single piece extending radially, but it can also be multi-part and / or have a different geometry designed for positive engagement with the winding 3. The depicted overlap of the winding 3 with the base 11 is purely for illustrative purposes and does not represent a direct connection. The winding 3 is preferably connected to the base 11 via the support element 5 for torque support.

[0075] Fig. 3 shows an exploded view of a stator 1 according to one embodiment.

[0076] The stator 1 has a winding 3, a stator core 2 and a support device 5, an advantageous exemplary embodiment of these components is shown in more detail in perspective.

[0077] The winding 3 consists of an inner and outer layer with several conductor bars 6 connected to each other in a truss-like arrangement. The conductor bars 6 in the inner and outer layers are arranged in opposite directions in a helical pattern and are connected at their ends to a radial conductor section 17 that connects the inner and outer layers.

[0078] The thickness of the inner and outer layers each corresponds to the thickness of a conductor rod 6. That is, the winding 3 is formed by a single conductor layer forming the conductor loop with a comparatively large cross-section in the form of a conductor rod 6.

[0079] The truss structure formed by the conductor bars makes the winding torsionally rigid and therefore self-supporting for torque support.

[0080] The conductor bars 6 accordingly form wave-shaped winding strands and can be connected to form a rotating field-generating winding of any number of strands by appropriate connections known to those skilled in the art and therefore not described further, such as delta connection, star connection or the like.

[0081] In the illustrated embodiment, the stator core 2 and the support structure 5 are each, by way of example, constructed from two components. For the assembly of the stator 1, the winding 3, the stator core 2, and the support structure 5 are arranged nested within one another. After assembly, the components are aligned coaxially with each other along the common central axis M. The support structure 5, shown here as an example in two parts, is arranged axially offset from the other components and forms the innermost and outermost components of the stator 1. It consists of an inner ring and an outer ring, each designed with grooves for positive engagement with the conductor bars.

[0082] The two-part stator core 2 shown here as an example is formed with two stator lamination stacks 18 twisted helically relative to each other, whereupon with respect to Fig. 8 will be discussed in more detail later.

[0083] In further embodiments, the stator core 2 and the support device 5 can each be made in one piece or with more than two parts.

[0084] Fig. 4 shows an exploded view of a radial flux twin-rotor machine 10 according to one embodiment.

[0085] The radial flux double-rotor machine 10 comprises, in addition to the components of the stator 1, a first rotor 12, a second rotor 13, and a base 11. The first rotor 12 is arranged radially inside and the second rotor 13 radially outside the stator core 2. The rotors 12 and 13 are preferably made of a soft magnetic solid material and are equipped with permanent magnets, so-called surface magnets, as poles on their respective surfaces facing the stator core. In further embodiments, other rotors known to those skilled in the art can also be used, for example, with buried magnets, squirrel-cage rotors, or electrically excited rotors.

[0086] Base 11 is shown here schematically for clarity only. As described in the description of Fig. 2 As already described, the base 11 is attached to the support device 5 in the assembled state. The base 11 is mechanically fixed relative to a reference system, for example, a support of a vehicle axle.

[0087] Fig. 5 shows an exploded view of a radial flux twin-rotor machine 10 according to a further embodiment.

[0088] The radial flux twin-rotor machine 10 has essentially the same components as in relation to Fig. 3 und 4 executed. On the left side of the figure, the stator core 2, the winding 3, the first rotor 12 and the second rotor 13 are shown in the assembled state.

[0089] The support structure 5 shown on the right is also designed in two parts and differs in the design of the respective ring-shaped inner support element 27 and outer support element 28. The support elements 27 and 28 are equipped with support grooves 26. These are provided for engagement with the conductor bars 6 of the winding 3 on the inner circumference of the outer support element 28 and on the outer circumference of the inner support element 27.

[0090] The support grooves 26 are axially angled according to the helical shape of the conductor bars or their pitch, so that they can engage with the conductor bars 6 of the winding 3.

[0091] The support elements 27, 28 are preferably made of a conductive metal, particularly preferably of an aluminum alloy. The two-part design of the support elements 27, 28 allows the support grooves 26 to be easily accessible for mechanical or machining during manufacturing.

[0092] The inner support element 27 and the outer support element 28 are each provided with several bores 9 around their circumference for fastening to the base 11. The bores 9 are shown here as an example, evenly distributed around the circumference along a pitch circle. The individual bores 9 are located slightly outside the main body of the support elements, and the support elements 27 and 28 therefore form a star shape on the circumference opposite the winding. Of course, other distributions of the bores 9, as well as other types of fasteners for connecting to the base 11, are conceivable.

[0093] Fig. 6 shows a perspective view of a radial flux twin-rotor machine 10 according to Fig. 5 in the assembled state.

[0094] The support structure 5 is attached via the bores 9, for example in a machine housing (not shown) as a base 11, and thus transmits the torque to the mechanically fixed part of the radial flux twin-rotor machine 10. In this way, the torque generated by the radial flux twin-rotor machine 10 can be effectively supported. The support structure 5 is attached using suitable fasteners (not shown), for example screws.

[0095] The conductor bars 6 of the winding 3 extend axially on both sides to outside the stator core 2 and the first and second rotors 12, 13. The helically arranged conductor bars 6 of the radially inner and outer positions are each connected to each other outside the stator core 2.

[0096] The support elements 27, 28 are shown here in engagement with the conductor bars 6 of the winding 3. It can be seen that a conductor bar 6 is placed in each support groove 26, so that all conductor bars are positively coupled to the support structure. Thus, a torque supported via the winding 3 can be supported via the support structure 5 on the base 11 attached to the bores 9.

[0097] Fig. 7 shows a perspective longitudinal section view of a radial flux twin-rotor machine 10 according to a further embodiment.

[0098] This embodiment essentially corresponds to the assembly of a radial flux twin-rotor machine 10 according to Fig. 4 , the components of which will be discussed in more detail below.

[0099] The stator core 2 has an inner sub-package 23 and an outer sub-package 24. The sub-packages 23, 24 run in a ring shape between the first and second rotors 12, 13. Due to the cross-sectional view, it is also possible to see the inner and outer layers 14, 15 of the conductor bars 6 running within the sub-packages 23, 24.

[0100] The illustrated radial flux twin-rotor machine 10 is a so-called "yokeless" design in which the yoke between two teeth is not located in the functionally relevant magnetic flux. A stator yoke 30 does run between the conductor bars 6, but it serves only to mechanically hold the stator lamination stack 18 together. Accordingly, the radial yoke thickness can be made very thin, which in the illustrated embodiment is, by way of example, approximately 10% of the total radial stator thickness. This comparatively small yoke thickness also reduces undesirable magnetic leakage flux in the yoke. In further embodiments, the radial yoke thickness can be less than 30%, preferably less than 20%, and particularly preferably less than 10% of the total radial stator thickness for this purpose.

[0101] The support structure 5 also has an inner support element 27 and an outer support element 28. The support elements 27, 28 are clearly arranged axially offset from the stator 5 and the rotors 12, 13. Furthermore, the positive engagement of the support elements 27, 28 with the conductor bars 6 of the inner and outer layers 14, 15 is at least partially visible.

[0102] Furthermore, it can be clearly seen here that the conductor bars 6 of the inner and outer layers 14, 15 are connected at the conductor bar ends 16 via a radially arranged conductor bar section 17. The connection is preferably realized as a material-bonded connection, for example by laser beam welding.

[0103] The cross-section also shows the surface magnets of rotors 12 and 13. The first rotor 12 has several permanent magnets mounted on its outer circumferential surface. The second rotor 13 has several permanent magnets mounted on its inner circumferential surface.

[0104] A particularly advantageous embodiment is achieved when the rotors are made of solid soft magnetic material and feature surface-mounted permanent magnets. In this design, the rotors can be manufactured very cost-effectively and a high efficiency can be achieved.

[0105] Fig. 8 shows an exploded view of the stator lamination stack 18 of the stator core 2.

[0106] As already mentioned, the stator lamination stack 18 of the stator core 2 has an inner sub-stack 23 and an outer sub-stack 24. This serves to simplify the production of the oppositely twisted stator slots 19 with identically twisted stacked inner and outer stator laminations 21, 22, which are provided with recesses at the same locations.

[0107] In further embodiments, the stator laminations can also be manufactured in one piece, so that a multitude of differently shaped stator laminations with differently arranged recesses are provided and stacked in the sequence necessary to form the stator slots. In still further embodiments, completely one-piece stator cores 2 are also conceivable, which can, for example, be additively manufactured.

[0108] In the illustrated two-part design, the inner diameter of the outer sub-package 24 is almost equal to the outer diameter of the inner sub-package 23. This makes it possible to arrange the inner sub-package 23 coaxially within the outer sub-package 24.

[0109] The sub-assemblies 23, 24 are constructed from individual, stacked, annular stator laminations 21, 22. The stator laminations 21 of the outer sub-assembly 24 are manufactured with recesses distributed around their outer circumference to form the outer stator grooves 19. The stator laminations 22 of the inner sub-assembly 23 are manufactured with recesses distributed around their inner circumference to form the inner stator grooves 20. For example, manufacturing such stator laminations by stamping is advantageous due to the edge quality and very low manufacturing costs.

[0110] The inner and outer stator slots 19, 20 describe oppositely oriented helical lines with the same pitch, which are characterized by the drawn sweep angle of the stator slots α. The sweep angle of the stator slots α can be defined from the angle between the position of the same stator slot on one axial side of the stator core 2 and on the other axial side of the stator core 2 with respect to the central axis M.

[0111] Stator slots 19 and 20 are shown here as examples of T-slots with a rectangular recess and a tapered opening. These are specifically designed for the positive-locking retention of conductor bars with a rectangular cross-section. Naturally, the geometry of the recesses or stator slots can be adapted to the conductor geometry. Other cross-sectional shapes are also conceivable.

[0112] Fig. 9 shows a schematic longitudinal section view of a stator slot 19, 20.

[0113] The usable or continuous clear width a of the stator slots 19,20 within the stator lamination stack 18 is essentially equal to the width of the conductor bars 6 accommodated within the stator core 2.

[0114] The stator laminations 21, 22 have straight, in particular stamped, edges. Due to the offset of the laminations relative to each other, the width b of the recesses provided for the stator slots 19, 20 is greater than the width d of the conductor bars 6 by an amount predetermined by the pitch δ of the helical shape of the profile and the lamination thickness t.

[0115] In Fig. 9 A conductor rod 6 is schematically shown with dashed lines in the stator groove 19, 20, wherein the continuous clear width a of the stator groove 19, 20 is slightly larger than the width d of the conductor rod 6 to provide a clearance fit, and the width a of the recess in the stator sheet 21, 22 is again significantly larger than the clear width b.

[0116] The sheet thickness t and the angle of inclination δ of the groove profile represent a significant influencing factor for the difference between the width b of the recess and the clear width a of the usable passage within the groove, especially with straight sheet metal edges, such as those produced by stamping. This difference arises because the angle of inclination on the one hand and the stepped structure of the sheet metal stack on the other must be compensated for.

[0117] A minimum size of the width a of the recess for the limiting case of infinitely thin sheets, that is, a pure consideration of the inclination angle δ of the conductor rod, would be b = 1 / cos δ * d .

[0118] In order to compensate for the actual sheet thickness on the one hand and to provide a clearance fit that allows the insertion of the conductor rods on the other, the width b of the recess is actually provided to be even larger.

[0119] The width b of the recesses according to Fig. 9 The stator slots 19, 20 are dimensioned such that the reduced clear width a of the slots, resulting from the offset between the recesses of the stator laminations, forms a predetermined clearance fit with the width d of a conductor bar 6 to be inserted into the stator slot. The contact is nevertheless tight enough to ensure evenly distributed power transmission and torque support between the stator core and the winding. This dimensioning is made possible, among other things, by ensuring that each stator lamination is manufactured with high edge quality and twisted with the same offset, and by placing only a single conductor bar 6, whose dimensions are constant, in each stator slot 19, 20.

[0120] In the illustrated embodiment, the conductor rod 6 is a rectangular rod with an edge length or width of several millimeters, for example in the range of 2 mm to 6 mm, and particularly in the range of 3 mm to 5 mm. Preferably, it can be a rectangular profile of 5 mm x 3 mm.

[0121] Fig. 10 shows a perspective view of a winding 3.

[0122] The winding 3 is constructed from the aforementioned conductor bars 6, which run helically along the central axis M. For this purpose, the conductor bars 6 are not only arranged in a correspondingly interlocked manner, but are also twisted along their helix path.

[0123] The swept angle β of the conductor bars 6 identifies the angle between the beginning and end of a conductor bar 6 relative to the central axis M. Since the pitch of the helix of the conductor bars 6 is equal to the pitch of the helix of the stator slots 19, 20, but the conductor bars 6 are longer than the stator slots, a ratio of the respective swept angles α and β can be established to characterize the geometric relationships, which is also referred to as the pole coverage ratio. To provide an optimum between magnetic losses and torque utilization of a radial flux twin-rotor machine, this ratio (pole coverage ratio) preferably lies in a range between 0.6 and 0.75.

[0124] The opposing twist and torsion of the inner and outer radial layers 14, 15 of the conductor bars 6 can also be seen here. The torsion is designed such that the cross-section with respect to a radial line through the center of the conductor bar is always the same at every point on the conductor bar, which is also referred to as 2.5D geometry. Thus, the conductor bar ends of the inner and outer layers 14, 15 are arranged one above the other in the same orientation. The conductor bars 6 of the radial inner and outer layers 14, 15 can therefore be easily conductively connected, here exemplified by a radially extending conductor bar section 17, which is welded to the conductor bars 6.

[0125] It should be noted that the winding shown here is not manufactured individually, but always in conjunction with the stator core 2, which is relevant in relation to Fig. 13 will be discussed in more detail.

[0126] Fig. 11 shows a top view of winding 3.

[0127] This view clearly shows the precise radial alignment of the conductor rods at every point along their helical path, which, in the depicted perspective, is aligned in the area of ​​the central axis M. The conductor rod ends 16 each form the connection point between the inner and outer radial layers 14, 15.

[0128] In the illustrated embodiment, the winding has, by way of example, a total of twelve connection contacts 31. With a three-phase connection, three-phase operation is preferably provided. However, the winding can be adapted to other connection configurations to a rotating field-generating winding of any number of phases in a manner known in the art.

[0129] Fig. 12 shows a perspective view of an FEM simulation of winding 3 under load.

[0130] With minor simplifications for simulation purposes, this essentially refers to the following: Fig. 10 The depicted winding geometry. The scale shown relates to the voltages within the winding, where, for example, in the case of a rectangular profile of conductor bars 6 measuring 5 mm x 3 mm, the scale can range from 0 MPa to 30 MPa.

[0131] In this example, the conductor rod ends are defined by a swept angle of the conductor rods β > 0, meaning they are arranged and formed helically or twisted accordingly. At the axial end where the support device engages, a maximum torque of the appropriately dimensioned radial flux double-rotor machine 10 is indicated by a thick arrow; for example, in the case of a rectangular profile of the conductor rods 6 measuring 5 mm x 3 mm, this torque could be approximately 5000 Nm.

[0132] The stresses within the winding are noticeably distributed very homogeneously due to the helical geometry.

[0133] Despite the significant camber setting, hardly any deformation is visible. This design significantly reduces stress peaks and therefore also deformation.

[0134] Due to the truss-like structure, a high torque can be absorbed by the winding 3 in a self-supporting manner when an axially accessible winding end is fixed, without causing excessively large deformations and / or stress states. This is primarily due to the fact that, when subjected to tangential force, the conductor bars 6 in the truss structure mainly absorb tensile and compressive stresses.

[0135] Compared to designs with axially parallel, straight conductors, the mechanical stresses can be significantly reduced.

[0136] Fig. 13 shows a perspective representation of a comparison model with a straight design and axial orientation of the conductor bars 6 under load.

[0137] Compared to Fig. 12 Due to the straight design and axial orientation of the conductor bars, a [missing word] is [missing word] directed at the [missing word]. Fig. 12 The side shown on the left shows a concentrated stress distribution and a strong deformation of the conductor bars resulting from the locally high stress, with a large deflection at the point where... Fig. 13 The right-hand side shows the same stress scale and the same exaggeration of deformation as in [the previous section]. Fig. 12 adjusted, which reveals the effect of the different structural arrangements on torsional stiffness.

[0138] Fig. 14 Figure 1.2 shows a flowchart of a process for manufacturing a stator. This manufacturing process is not part of the invention.

[0139] The method comprises a first step S1 of providing a stator core 2 with radially outer stator slots 19, each describing a helical path, and radially inner stator slots 20, each describing a helical path with the opposite winding direction. A further step S2 involves inserting individual conductor bars 6 through the inner and outer stator slots 19, 20, following the helical paths. The conductor bars are inserted primarily in the axial direction. A further step S3 involves connecting the conductor bars 6 inserted into the inner and outer stator slots at the conductor bar ends 16 to form conductor loops.

[0140] Although the present invention has been fully described above with reference to preferred embodiments, it is not limited thereto, but is defined by the attached claims. Reference symbol list

[0141] 1 Stator 2 Stator core 3 Winding 4 Axial end 5 Support assembly 6 Conductor bar 7 First leg 8 Second leg 9 Bore 10 Radial flux twin-rotor machine 11 Base 12 First rotor 13 Second rotor 14 Radial outer layer 15 Radial inner layer 16 Conductor bar ends 17 Conductor bar section 18 Stator lamination stack 19, 20 Stator slots 21, 22 Stator laminations 23 Inner sub-stack 24 Outer sub-stack 25 Support element 26 Support slots 27 Inner support element 28 Outer support element 29 Permanent magnet αSwept angle stator slots βSwept angle conductor bars δPitch aClear width bWidth of recess dBidity of a conductor bar MCenter axis tSheet thickness

Claims

1. Radial flux double-rotor machine (10), in particular for a wheel hub drive, comprising: a mechanically fixed base (11); a stator (1), having a stator core (2), a winding (3) placed in the stator core (2) and configured self-supporting for torque support of the stator (1), the winding (3) projecting beyond the stator core (2) at at least one axial end (4), and a carrier device (5) arranged axially offset from the stator core (2) and configured for positive engagement with the winding (3) at the at least one axial end (4) for torque support; wherein the carrier device (5) is in positive engagement with at least one axial end (4) of the winding (3) for torque support and is supported at the base (11); a first rotor (12) arranged radially inside the stator core (2); and a second rotor (13) arranged radially outside the stator core (2).

2. Radial flux double-rotor machine (10) according to claim 1, characterised in that the winding (3) is configured to be torsionally stiff in such a way that a torque acting on the stator core (2) during the operation of a radial flux double-rotor machine (10) can be supported, in particular completely, via the torsionally stiff winding (3) on the carrier element (5).

3. Radial flux double-rotor machine (10) according to either claim 1 or claim 2, characterised in that the stator core (2) is configured to guide a predominantly radial magnetic flux, and in particular has a radial yoke thickness which is less than 30%, preferably less than 20%, particularly preferably less than 10%, of a total radial stator core thickness.

4. Radial flux double-rotor machine (10) according to any of the preceding claims, characterised in that the winding (3) is formed from conductor bars (6) which are interconnected, in particular in the manner of a framework, the winding (3) having a radially inner layer (15) of helically arranged conductor bars (6) and a radially outer layer (14) of oppositely helically arranged conductor bars (6).

5. Radial flux double-rotor machine (10) according to claim 4, characterised in that the radially inner layer and the radially outer layer of the winding (3) each have the thickness of a single conductor bar (6), and / or in that the conductor bars (6) are each formed twisted in accordance with the helical path in such a way that a cross section of a conductor bar is the same at every point of the conductor (6) in terms of a radial axis of the cross section, and / or in that the conductor bars (6) of the radially inner and outer layers which are associated with the same phase of the winding (3) are interconnected at the conductor bar ends (16), in particular via a radially arranged conductor bar portion (17) and / or by a materially bonded connection.

6. Radial flux double-rotor machine (10) according to either claim 4 or claim 5, characterised in that the stator core (2) contains a stator lamination stack (18), having stator slots (19, 20) extending helically in accordance with the winding direction, a single conductor bar (6) being arranged in each stator slot (19, 20) of the stator lamination stack (18).

7. Radial flux double-rotor machine (10) according to claim 6, characterised in that the stator laminations (21, 22) of the stator lamination stack (18) are each identically formed with recesses provided to form the stator slots (19, 20), the helical path of the stator slots (19, 20) being provided by stacking the stator laminations (21, 22) twisted with respect to one another, the stator lamination stack (18) in particular comprising an inner sub-stack (23) having radially inner stator slots (20) and an outer sub-stack (24) having radially outer stator slots (19), the stator laminations (22) of the inner sub-stack (23) each being formed with the same geometry and the stator laminations (21) of the outer sub-stack (24) each being formed with the same geometry, and the stator laminations (22) of the inner sub-stack (23) and the stator laminations (21) of the outer sub-stack (24) being stacked twisted oppositely to one another.

8. Radial flux double-rotor machine (10) according to claim 6, characterised in that the stator laminations (21, 22), having recesses provided to form the stator slots (19, 20), are each configured differently, the helical path of the stator slots (19, 20) being provided by means of different spacings of the recesses in the individual stator laminations (21, 22), the recesses for radially inner and radially outer stator slots (19, 20) in particular being integrated into a common stator lamination (21, 22) in each case, the oppositely helical path of the radially inner and radially outer stator slots (19, 20) being provided by a progressive displacement of the inner and outer stator slots (19, 20) relative to each other from one stator lamination to the next stator lamination.

9. Radial flux double-rotor machine (10) according to either claim 7 or claim 8, characterised in that the stator laminations (21, 22) have straight, in particular punched, edges, a width (b) of the recesses provided for the stator slots (19, 20) being greater than the width (d) of the conductor bars (6), by an amount predetermined by the pitch (δ) of the helical shape of the path and by the sheet thickness (t), in such a way that a clear width (a) of the stator slots (19, 20), reduced by the offset between the recesses of the stator laminations, substantially corresponds to the width (d) of a conductor bar (6).

10. Radial flux double-rotor machine (10) according to any of claims 6 to 9, characterised in that an angle (α) swept by each of the stator slots (19, 20) is smaller than an angle (β) swept by each of the conductor bars (6), the ratio of the angle (α) swept by each of the stator slots (19, 20) to the angle (β) swept by each of the conductor bars (6) in particular being in a range between 0.6 and 0.8, preferably between 0.6 and 0.75.

11. Radial flux double-rotor machine (10) according to any of claims 4 to 10, characterised in that the carrier device (5) has a carrier element (25) in which carrier slots (26), corresponding to the helical arrangement of the conductor bars (6) and engaging with the conductor bars (6), are provided.

12. Radial flux double-rotor machine (10) according to claim 11, characterised in that the conductor bars (6) are each formed twisted in accordance with the helical path, in such a way that a cross section of a conductor bar is the same at every point of the conductor (6) in terms of a radial axis of the cross section and the carrier slots (26) follow the helical path of the twisted conductor bars (6) at least in portions, in particular having a similarly twisted path.

13. Radial flux double-rotor machine (10) according to either claim 11 or claim 12, characterised in that the carrier device (5) has a radially inner carrier element (27) for engagement with the radially inner layer (15) of the conductor bars (6) and a radially outer carrier element (28) for engagement with the radially outer layer (14) of the conductor bars (6).

14. Radial flux double-rotor machine (10) according to any of the preceding claims, characterised in that the carrier device (5) contains a thermally conductive material, in particular a metal, preferably an aluminium alloy, the base (11) having a heat sink configured to absorb heat dissipated via the carrier device (5) from the stator (1), in particular from the winding (3).

15. Radial flux double-rotor machine (10) according to any of the preceding claims, characterised in that a predetermined number of pole pairs are provided both on the first rotor (12) and on the second rotor (13), an angle (β) swept by each of the conductor bars (6) being configured to form one conductor loop per pole.