Stator for radial flux dual-rotor electric machine, method for producing stator for radial flux dual-rotor electric machine, and radial flux dual-rotor electric machine

Abstract

The invention relates to a stator for a radial flux dual-rotor electric machine, in particular for a hub motor, comprising: a stator core; a winding disposed in the stator core, the winding configured to be self-supported to enable torque support of the stator, where the winding protrudes beyond the stator core at at least one axial end; a support device arranged axially offset with respect to the stator core, the support device configured for form-fitting engagement with the winding at at least one axial end for torque support; wherein the winding is formed from interconnected conductor bars and has a radially inner layer of conductor bars arranged in a spiral manner and a radially outer layer of conductor bars arranged in an opposite spiral manner, and wherein each conductor bar is configured to be bent at a first conductor bar end and not bent at a second conductor bar end, the first conductor bar ends of the conductor bars of the radially outer layer are arranged such that the bends are oriented radially inward in each case, and the first conductor bar ends of the conductor bars of the radially inner layer are arranged such that the bends are oriented radially outward in each case. The invention also relates to a method for producing a stator and to a radial flux dual-rotor electric machine.

Description

Technical Field

[0001] The invention relates to a stator for a radial flux twin-rotor electric machine, in particular for a wheel hub motor, a method for producing a stator for a radial flux twin-rotor electric machine, and a corresponding radial flux twin-rotor electric machine, in particular for a wheel hub drive. Background Art

[0002] Compared to conventional electric motors comprising only one rotor, electric motors comprising a stator and two rotationally fixed rotors, so-called dual-rotor motors (also called multi-rotor, twin-rotor, etc.), can increase both the torque density and the efficiency of electric drives. This is due to the fact that, in particular in the so-called "yokeless" design, no return magnetic circuit is required in the stator, and as a result, hysteresis losses can be significantly reduced. In addition, with two rotors, there is generally more space available for field excitation magnets (in permanent magnet synchronous motors (PSMs)) or conductor material (in induction motors (IMs) or electrically excited synchronous motors (ESMs). Depending on the orientation of the magnetic field lines in the air gap, such motors can be divided into two groups: axial flux-carrying motors (field lines parallel to the axis of rotation, so-called axial flux motors) on the one hand, and radial flux-carrying motors (field lines in the air gap are in a radial direction, so-called radial flux motors) on the other hand.

[0003] For example, DE 102015226105 A1 and DE 102013206593 A1 describe axial flux twin-rotor motors. These motors are characterized by high torque and power density, but they are expensive to manufacture because very complex geometries must be stamped or produced in the stator core using powder metallurgy. Consequently, these motors have not yet entered mass production and are used only in niche applications with high power density requirements, such as racing and aviation. Furthermore, the mechanical mounting concepts for the stator windings only allow the use of single-tooth windings, which have corresponding disadvantages in terms of noise excitation.

[0004] In contrast, in the case of radial flux twin-rotor motors, manufacturing methods that are established in principle for windings and stacked cores and are suitable for large-scale production can be used. However, in this case, there are major, largely unresolved technical challenges in supporting the torque generated in the stator core. Due to the internal and external rotating parts, the stator stacked core cannot be installed in a fixed housing as is usually the case (e.g., by pressing, screwing, or gluing). The torque is therefore directed to the axial ends of the stator stacked core or the stator winding and supported there. Various methods have been proposed in the prior art, but all of these methods are associated with significant disadvantages in terms of functionality and / or cost.

[0005] EP 1879283 B1 describes the possibility of designing the stator winding as a so-called yoke winding. In this case, the annular stator laminated core has slots on the inner and outer diameters, between which there is a return magnet (also called a stator yoke) that is effective in the tangential direction. Here, the forward conductor and the return conductor of each winding strand are guided in slots located radially above each other 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 an axial screw connection (for example, as described in JP 2018082600). The axial compression of the screw ensures both the torsional rigidity of the laminated core and the torque support at the axial ends. The north and south magnetic poles of the rotor field are positioned relative to each other. The disadvantage of this concept is that the magnetic flux must be guided entirely via the return yoke located between the stator slots. On the one hand, this leads to an increase in the weight of the stator laminated core and a significant increase in iron losses. The magnetic field lines of the two rotor fluxes are closed via the return magnetic flux in the stator core and cause iron losses there. In addition, all individual coils of the yoke winding must be interconnected in parallel or series in the region of the winding head, which in turn leads to installation space conflicts with the torque support. However, the winding wound around the yoke allows direct mechanical contact with the stacked stator core.

[0006] If the magnetization directions of the radially aligned magnets, which are positioned in the same direction, and the current directions of the conductors arranged in the slots, are identical, a significant reduction in weight and losses can be achieved. In this case, the return flux loop in the stator can be omitted, resulting in a so-called "yokeless" dual-rotor motor with distributed windings. The magnetic field lines are closed above the rotor. The return flux loop in the stator is unnecessary, resulting in very low weight and iron losses in this type of motor. However, distributed windings do not allow direct mechanical contact with the stator core for torque support. For example, WO2004 / 004098 A1 describes a yokeless design with distributed windings.

[0007] Even in the case of so-called "yokeless" designs, it may still make sense to use a thin yoke for the mechanical connection of the stator teeth, but this is not necessary for electromagnetic purposes. The term "yokeless" therefore refers to electromagnetic flux conduction in which there is no flux in the stator in the tangential direction. However, the winding cannot be designed as a yoke winding, because the forward and return conductors of the winding strands are distributed radially around the circumference and thus form a distributed winding. This results in winding heads with distributed windings, which makes it difficult to access the stacked core in the axial direction. Purely radial flux routing also prohibits the use of axial metal screw connections, because these form conductor loops with a lot of interconnected flux and high additional current heat losses.

[0008] For axial support, various auxiliary constructions for torque support are proposed in the prior art, such as those described in DE 102010055030 A1 or US 7,557,486 B2. The problem here is that electrically conductive and / or magnetically conductive metals are not permitted to protrude into the flux-carrying area, or only to a very limited extent. This severely restricts the choice of materials and geometric designs. In contrast, plastic components, adhesives, and / or potting materials can be used in the current-carrying area. However, it is difficult to achieve the high requirements for temperature stability and mechanical strength with such materials. Summary of the Invention

[0009] In view of the above background, a basic object of the present invention is to provide an improved stator for a radial flux dual-rotor motor, an improved method for producing a stator for a radial flux dual-rotor motor, and an improved radial flux dual-rotor motor.

[0010] According to the invention, this object is achieved by a stator having the features of patent claim 1 and / or by a method having the features of patent claim 8 and / or by a radial flux dual-rotor machine having the features of patent claim 10 .

[0011] Therefore, the present invention provides

[0012] - A stator for a radial flux dual-rotor electric machine, in particular for a hub motor, comprising: a stator core; a winding arranged in the stator core, the winding being configured to be self-supporting for torque support of the stator, wherein the winding protrudes beyond the stator core at at least one axial end; a support device, which is arranged axially offset relative to the stator core and is configured to engage with the winding at at least one axial end for torque support; wherein the winding is formed by interconnected conductor bars and has a radially inner layer of helically arranged conductor bars and a radially outer layer of oppositely helically arranged conductor bars, wherein each conductor bar is configured to be bent at a first conductor bar end and not bent at a second conductor bar end, wherein the first conductor bar ends of the conductor bars of the radially outer layer are arranged such that the bend is in each case directed radially inwards, and the first conductor bar ends of the conductor bars of the radially inner layer are arranged such that the bend is in each case directed radially outwards.

[0013] - A method for producing a stator for a radial flux dual-rotor electric machine, in particular a stator according to the present invention, comprising the following steps: providing a stator core with radially outer stator slots each describing a helix and radially inner stator slots each describing a helix having an opposite direction of rotation; providing individual conductor bars configured to be bent at a first conductor bar end and configured not to be bent at a second conductor bar end; introducing the individual conductor bars into the radially outer stator slots at a first axial end of the stator core such that the bend of the first conductor bar end of the radially outer conductor bar at the first axial end is directed radially inwards; The stator core further comprises a plurality of conductor rods, each of which is connected to the stator core by a plurality of conductor rods. The plurality of conductor rods are connected to each other by a plurality of conductor rods. The plurality of conductor rods are connected to each other by a plurality of conductor rods.

[0014] - A radial flux twin-rotor electric machine, in particular a radial flux twin-rotor electric machine for a wheel hub drive, comprising: a stator according to the invention or produced by a method according to the invention; a first rotor, which is arranged radially inside the stator core of the stator; and a second rotor, which is arranged radially outside the stator core of the stator.

[0015] The invention is based on the recognition that the joining of straight conductor rods can be greatly facilitated by shaping the conductor rod ends.

[0016] The present invention is based on the idea of ​​using bent conductor bars to facilitate joining. The bent conductor bars can thus be joined without any reshaping and without much effort in the assembled state of the winding. In particular, this advantageously avoids the need to first form the conductor bars in the assembled state, which would be highly mechanically stressful. Using bent conductor bar ends, a self-supporting winding can be provided in a very simple and particularly economical manner.

[0017] As a self-supporting design for the winding, it should be understood that the winding has sufficient rigidity and strength to resist torsion about the motor axis to support the drive torque. In particular, the self-supporting winding is embedded in the soft magnetic stator core for flux guidance. This has the particular advantage that the stator core itself does not require any inherent torsional rigidity relative to the motor axis, nor does it require any additional structure to secure the stator core. Torque is instead supported, and in particular, fully supported, via the winding.

[0018] This allows a functional integration that was previously unknown or technically impossible in the field of radial flux dual-rotor machines, since the winding is additionally provided with a load-bearing function for supporting the torque and is mechanically fixed at one axial end outside the stator core.

[0019] To produce such a winding, it is proposed to integrate it into the existing stator core. For this purpose, the individual rods of the winding are inserted through radially inner and outer stator slots in the axial direction, following the helical line of the stator slots, and connected at the conductor ends. Preferably, a material-locking connection is provided by welding or soldering. The winding is thus connected to the stator core in a form-fitting manner.

[0020] The bending of the conductor bars at one conductor bar end according to the present invention avoids mechanical deformation of the originally straight conductor bar end, particularly radially inward or radially outward, after the winding is installed in the stator. Rather, the bending is already provided before assembly and can be understood as a spatial projection, offset, and / or bend, particularly an angular bend, of the corresponding otherwise straight conductor bar end. In this way, to form the winding, the radial distance between the radially inner layer of the helically arranged conductor bars and the radially outer layer of the oppositely helically arranged conductor bars of the winding is spatially bridged by the bending of the respective first conductor bar end.

[0021] The opposite radial orientation of the bends of the conductor rod ends of the corresponding radial layers is therefore crucial for avoiding subsequent mechanical deformation of the conductor rods. Consequently, the stator is significantly easier to manufacture, advantageously avoiding the need for additional process steps. Furthermore, no additional parts, components, and / or connectors are required to bridge the radial distance between the radially inner and radially outer layers. This also reduces the overall number of stator parts and assembly complexity.

[0022] According to one embodiment, the curvature of the first conductor rod ends of the radially outer and inner conductor rods can also have an additional circumferential component, in particular a twist or torsion of the conductor rods or conductor rod ends. Thus, the curvature of the first conductor rod ends of the radially outer and inner conductor rods can be configured to bridge radial and circumferential spaces, in particular to achieve an overlap of conductor rods that spiral in opposite directions and form a loop. This overlap can then be directly joined in a simple manner, for example by welding (in particular by laser beam) or soldering.

[0023] The selected pitch angle (also called the set angle) of the stator slots or the helix described here ensures that conductor loops are formed by connecting the introduced conductor bars. The angle of the conductor loop in the electric machine, which is swept about the central axis, surrounds one magnetic pole per rotor. This makes it possible to produce the stator very simply, regardless of the functional integration, requiring very few components, relatively simple conventional connection techniques, and therefore also very few production steps.

[0024] A stator constructed in this manner can now be combined with various inner and outer rotors known to those skilled in the art to form the electric machine according to the invention. These include, for example, permanently excited rotors with surface and / or buried magnets, short-circuited rotors, or electrically excited rotors. Hybrid variants with different rotor variants in the inner and outer rotors can also be provided. A particularly advantageous embodiment results when the rotor is constructed from a soft-magnetic solid material and with surface-mounted permanent magnets. The low upper field spectrum of the winding variant described here and the distance between the solid material and the air gap ensured by the magnets prevent unacceptably high losses due to eddy currents in the rotor. In this embodiment, relatively high efficiencies can advantageously be achieved while still being very cost-effective to manufacture the rotor.

[0025] The support device is securely connected to the base, which is the fixed part of the motor, by suitable means. One possible embodiment provides recesses (e.g. through-holes) for non-positive fastening means such as screws. However, as an alternative or in addition, form-fitting connections and / or material-locked connections are of course also conceivable.

[0026] According to the invention, the winding is formed by interconnected conductor rods, in particular in the form of rods. In particular, the conductor rod ends can be connected by material joining, for example by welding or soldering. However, other connection techniques are also conceivable. Preferably, two conductor rods are connected at the conductor rod ends and all the conductor rods together form a rod structure. The rod structure formed with the conductor rods is advantageously torsionally rigid and is designed for torque transmission around the center axis of the stator. In addition, the conductor rod ends are designed to have sufficient thickness for power transmission. In the case of a hub motor, for example, the thickness of the conductor rods can be in the range of several millimeters. In particular, the rod can have a square profile with an edge length of several millimeters.

[0027] According to the present invention, the winding has a radially inner layer of helically arranged conductor bars and a radially outer layer of oppositely arranged conductor bars. In this way, the winding forms a rod structure with high torsional stiffness. The conductor bars of the inner layer and the conductor bars of the outer layer each describe a helix whose winding direction or pitch is opposite to one another. The angle of the helix between the start and end points of the conductor bars swept about the central axis of the stator is formed so that, in particular, a conductor loop is formed for each magnetic pole of the rotor in a radial flux dual-rotor motor. The sweep angle to be provided can therefore be calculated from the quotient of a full revolution (2π or 360°) and twice the number of magnetic pole pairs.

[0028] In particular, the present invention is particularly advantageously applicable to wheel hub motors, preferably for motor vehicles. Due to the functional integration, the design according to the present invention allows for a reduction in the mass of radial flux twin-rotor motors and an increase in torque density, which translates to a reduction in unsprung mass, particularly in wheel hub motors. Furthermore, the present invention enables a relatively short axial length with a relatively large diameter, which is particularly advantageous in terms of torque support and installation space within the wheel.

[0029] On the other hand, in addition to the extremely compact design, the invention also allows very high torques, in particular high enough to drive the wheels directly without a gearbox. This advantageously avoids transmission losses, further saves weight, and enables particularly high efficiency advantages to be achieved.

[0030] Furthermore, such high torques, which are possible within the dimensions of conventional vehicle rims and already reach the four-digit range (in particular, greater than 5000 Nm), and thus already reach the adhesion limits of conventional road tires, even allow the rear axle wheel brakes to be replaced with wheel hub motors. When using wheel hub motors, special synergistic effects are thus possible.

[0031] According to one aspect, an axle is therefore further disclosed, in particular for a motor vehicle, which has a radial flux twin-rotor electric machine according to the invention, which is coupled to drive wheels without a transmission.

[0032] According to one aspect, a motor vehicle comprising such an axle is further disclosed.

[0033] Advantageous embodiments and further configurations are apparent from the dependent claims and from the description of the figures with reference to the drawings.

[0034] According to one embodiment, the first conductor rod ends of the conductor rods of the radially outer layer are each joined to the second conductor rod ends of the conductor rods of the radially inner layer to form a conductor loop. Furthermore, the first conductor rod ends of the conductor rods of the radially inner layer are each joined to the second conductor rod ends of the conductor rods of the radially outer layer. In this way, the conductor rods of the radially inner layer and the conductor rods of the radially outer layer are guided toward each other to form a self-supporting winding so as to facilitate their joining. Furthermore, the joining of the conductor rod ends of the respective conductor rods provides improved stress and force distribution, resulting in a mechanically stable winding.

[0035] According to one embodiment, the conductor bars of the radially outer layer are accommodated in outer stator slots, with their first conductor bar ends arranged at a first axial end of the stator core, and the conductor bars of the radially inner layer are accommodated in inner stator slots, with their first conductor bar ends arranged at a second axial end of the stator core. Furthermore, to form the conductor loops, the first conductor bar ends of the conductor bars of the radially outer layer are joined at each first axial end to the second conductor bar ends of the conductor bars of the radially inner layer, and the first conductor bar ends of the conductor bars of the radially inner layer are joined at each second axial end to the second conductor bar ends of the conductor bars of the radially outer layer. In this way, the conductor bars of the radially inner and radially outer layers of the winding are embedded, in particular completely, in the respective inner and outer stator slots. Furthermore, a stator with high power density and small overall dimensions is thus provided.

[0036] According to one embodiment, the first conductor rod end is joined to the second conductor rod end at an overlapping abutment, in particular by laser beam welding. The overlapping abutment can be formed as an overlap of the respective surfaces of the first and second conductor rod ends, which are oriented radially inward and radially outward toward each other. In this way, a large surface area and / or a high material thickness are provided for joining the first and second conductor rod ends. Depending on the welding process, the weld joint can be configured as a fillet weld, a butt weld, or a combination of weld types. Furthermore, according to one embodiment, the overlapping abutment of the first and second conductor rod ends can be joined by electron beam welding.

[0037] According to one embodiment, the radial depth of the bend corresponds in each case to the radial distance between the radially inner and radially outer layers of the conductor bars within the stator core. In this way, the radial distance between the radially inner and radially outer layers of the conductor bars is bridged by the bend of the respective first conductor bar end. According to one embodiment, the radial distance between the radially inner and radially outer layers of the conductor bars can correspond to the radial thickness of the conductor bars. Other distances between the radially inner and radially outer layers are also conceivable and can be freely selected depending on the mechanical design, construction, and / or orientation of the bend. According to one embodiment, the radial distance between the radially inner and radially outer layers of the conductor bars can be selected as a function of the thickness of the stator yoke, in particular the thickness of the radial yoke.

[0038] According to one embodiment, each conductor bar is formed to be bent over a distance in the range of approximately 5% to approximately 25%, preferably approximately 10% to approximately 20%, and particularly preferably approximately 12% to approximately 18% of the total length of the respective conductor bar, starting from the first conductor bar end. In this way, a large portion of the length of the respective conductor bar remains unbent, which is particularly advantageous when handling the conductor bars.

[0039] According to one embodiment, the bend is configured as a double bend. In this way, the radial distance between the radially inner and radially outer layers of the conductor bars is bridged using a particularly cost-effective forming process. The bend can be configured as an opposite double bend. The respective angles of the conductor bars can reach between 20° and 70°, preferably between 30° and 60°, and particularly preferably between 40° and 50°.

[0040] According to an alternative embodiment, the bend of the respective conductor rod end can be formed as a double circular bend. The bend can be configured as an opposite double circular bend. In this way, a bend with a substantially S-shaped cross-section can be provided. The bend angle of the bend can be between 20° and 70°, preferably between 30° and 60°, and particularly preferably between 40° and 50°.

[0041] According to one embodiment of the method, after being introduced, the first conductor rod end, which is located in an overlapping position with the second conductor rod end, is joined at the overlapping abutment, in particular by laser beam welding. In this way, a large surface area and / or a high material thickness are provided for joining the first and second conductor rod ends. Depending in particular on the welding process, the weld joint can be configured as a fillet weld, a butt weld, or a combination of weld types. Furthermore, according to one embodiment, the overlapping abutment of the first and second conductor rod ends can be joined by electron beam welding. In this way, a welding process that is highly economical and flexible in use is provided.

[0042] [From this point on, the claims of P52372-DE are supported.]

[0043] According to one embodiment, the winding is designed to be torsionally rigid so that the torque acting on the stator core during operation of the radial flux dual-rotor electric machine can be supported on the carrier element via the torsionally rigid winding, in particular completely supported on the carrier element. In this way, all other types of force support devices, in particular force support devices for the stator core, can advantageously be omitted.

[0044] According to one embodiment, the stator core is designed to guide the main radial magnetic flux. This is a so-called "yokeless" design of the stator core, which specifically avoids flux guidance in the circumferential or tangential directions. A return field in the stator core is unnecessary, which reduces weight and iron losses.

[0045] 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 so-called "yokeless" designs, a mechanical connection of the stator teeth is still provided in this manner, but this is not electromagnetically necessary and no functionally relevant flux occurs. The term "yokeless" therefore refers specifically to the electromagnetic flux guidance of the stator core.

[0046] According to one embodiment, the radially inner layer and the radially outer layer of the winding each have the thickness of a single conductor rod end. This means that one phase of the winding is formed by the cross section of a single conductor rod end. Such a winding design according to the invention is made possible in particular by the special design of the radial flux twin-rotor motor, which, by virtue of its magnetic symmetry, prevents current displacements towards the surface that would otherwise occur in the conductor. In this way, relatively thick conductor cross sections are possible and still achieve a relatively uniform current distribution across the cross section. For example, the thickness of the conductor rod ends can be in the range of several millimeters. In particular, these can be rods with a square profile with an edge length of several millimeters, for example in the range of 2 mm to 6 mm, in particular in the range of 3 mm to 5 mm. Other cross-sectional shapes are also possible.

[0047] According to one embodiment, each conductor rod is twisted according to a helical shape, so that the cross-section of the conductor rod is the same at every point on the conductor, relative to the radial axis of the cross-section. This involves, in particular, twisting the conductor rod ends, especially non-circular ones, around the central axis of the stator or motor. Depending on the shape of the screw, the conductor rod ends can also be bent. The inner and outer layers interlock, twisting, twisting, and possibly bending in opposite directions. In this way, from a mechanical perspective at every point on the stator core, the conductor rods are ideally oriented for force transmission with the stator core, so that the respective conductor rods are subjected to forces evenly over their length. In the resulting rod structure, the conductors primarily absorb tensile and compressive stresses when tangential forces are applied. This avoids load peaks and deformations at the conductor rod ends. This significantly reduces mechanical stresses, particularly compared to configurations with straight conductors parallel to the axis.

[0048] According to one embodiment, the conductor bars of the radially inner and radially outer layers of the same phase of the winding are each interconnected at the conductor bar ends, in particular via radially arranged conductor bars and / or by means of a material connection. In addition to the conductor loops, this also creates a torsionally rigid rod-shaped structure, making it possible to accommodate high torques in the winding when the axially accessible winding ends are fixed without causing unacceptably large deformations and / or stress states. As a result, a self-supporting structure of the winding is made possible solely by the winding material (e.g., copper) without additional supporting devices or elements.

[0049] According to one embodiment, the stator core comprises stacked stator cores with spiral stator slots corresponding to the course of the windings, wherein a single conductor rod is arranged in each stator slot of the stacked stator cores. The windings, or the self-supporting rod system formed thereby, are thus embedded in the stacked stator cores. Similar to the conductor rods of the windings, the stator slots thus change their tangential position depending on their axial position, thereby creating a screw shape. The direction of the position change follows that of the conductor rods, i.e., the centerline of the radially outer slot and the centerline of the radially inner slot each describe a spiral with opposite directions.

[0050] In further embodiments, other manufacturing methods known to the skilled person for producing a stator core geometry according to the invention with radially inner and radially outer stator slots extending in opposite spiral directions would also be conceivable, in particular additive manufacturing methods such as sintering processes.

[0051] According to one embodiment, only a single conductor bar end is provided in each stator slot of the stacked stator core. As already described with respect to the windings, the conductor bars of the inner and outer stator slots are helically interlocked with one another by twisting about the central axis of the electric machine, such that the conductor ends of the inner and outer layers are directed toward one another. The conductor bars are electrically conductively connected to one another at the conductor bar ends, in particular via radially arranged conductor bar elements and / or by means of a material connection, for example, by welding or soldering.

[0052] According to one embodiment, the conductively connected conductor bars of the inner and outer layers together form a wavy winding strand. Using suitable interconnections known to those skilled in the art, the winding strands can be interconnected to form a rotating field generating winding with a desired or customizable number of strands. The number of winding strands capable of withstanding voltage is directly derived from the quotient of the number of slots in the numerator and the product of the number of strands in the numerator and the number of parallel branches. Advantageously, the number of parallel branches is selected to be 1. In this case, the simplest possible connection of the winding is achieved.

[0053] According to one embodiment, each stator lamination of a stacked stator core has identical recesses to form stator slots. The helical orientation of the stator slots is achieved by twisting the stator laminations relative to one another. This method allows for very economical manufacturing of the stacked stator core, as the same stamping die can be used for all parallel or stacked stator laminations. Therefore, two adjacent stator laminations are slightly rotated relative to one another by a predetermined angle about the central axis, so that the recesses are arranged so as to overlap one another, corresponding to the helical orientation.

[0054] According to an advantageous embodiment, the stacked stator core includes an inner partial enclosure having radially inner stator slots and an outer partial enclosure having radially outer stator slots. The stator laminations of the inner partial enclosure are each constructed to have the same geometric shape, and the stator laminations of the outer partial enclosure are each constructed to have the same geometric shape. The stator laminations of the inner partial enclosure and the stator laminations of the outer partial enclosure are stacked in a manner that is twisted in opposite directions relative to each other. In this way, it is possible to produce opposite spirals of the stator slots with minimal manufacturing effort. However, a very economical production method is still possible because the same stamping die can be used for all parallel or stacked stator laminations of the inner partial enclosure and the same stamping die can be used for all parallel or stacked stator laminations of the outer partial enclosure. As a result, two adjacent stator laminations of the inner partial enclosure 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 partial enclosure 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 partial encapsulation and the recesses of the stator laminations of the outer partial encapsulation are arranged in opposite overlaps relative to one another, corresponding to opposite helical runs.

[0055] According to another embodiment, the stator laminations with the recesses provided to form the stator slots are each designed differently. The spiral path of the stator slots is provided by means of different distances between the recesses in the individual stator laminations. In this respect, a stator lamination shape that is individually adapted is produced for each position of the stator lamination within the stack, wherein the individual geometries can also be repeated within the stack. In this case, production can be achieved using beam cutting processes, in particular laser beam cutting processes, which are more flexible in terms of shape compared to stamping processes. Also feasible would be a flexible stamping die with variable geometry or, in the case of very large quantities, of course, the production of several individual stamping dies for each different stator lamination shape.

[0056] According to a further development, the recesses for the radially inner and outer stator slots are each integrated into a common stator sheet, wherein the opposite spiral directions of the radially inner and outer stator slots are provided by a continuous displacement of the inner and outer stator slots relative to one another from stator sheet to stator sheet. Here, too, a uniquely adapted stator sheet shape is produced for each position of the stator sheet within the stack, wherein the individual geometries can also be repeated within the stack. In particular, flexible cutting processes such as laser cutting are also used for production here. The single-piece production of the inner and outer recesses made possible in this manner advantageously reduces the number of parts.

[0057] According to one embodiment, the stator laminations have straight edges, 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 spiral shape of the stator slots' course and by the sheet thickness of the stator laminations. The clear or continuous width of the stator slots, which is reduced by the curvature between the recesses of the stator laminations, thus corresponds essentially to the width of the conductor bar ends. In practice, the continuous clear width of the stator slots is slightly greater than the width of the conductor bar ends to provide the necessary clearance fit for introducing the conductor bars. The edges of the stator slots thus form a stepped shape with a corresponding sheet thickness, forming a step on which the conductor bar ends are evenly supported. In this way, torque support is provided evenly over the entire thickness of the stacked stator core or over the entire length of the conductor bars accommodated in the stacked stator cores.

[0058] According to one embodiment, the angle swept by each stator slot is smaller than the angle swept by each conductor rod end. The sweep angles are in each case related to a rotation about the central axis of the stator. The difference in sweep angles is due to the fact that the conductor rods protrude axially beyond the stator core and are therefore longer than the stator slots. This also results in a larger sweep angle as the spiral shape continues. This difference is provided to ensure sufficient accessibility of the winding ends in order to connect them, in particular by welding, after the conductor rod ends have been introduced into the stator slots. Furthermore, this allows the winding to be combined with a support device or its supporting elements that is axially offset relative to the stator core.

[0059] From the quotient of the sweep angles, ie the ratio of the angle swept by the stator slots to the angle swept by the conductor bars, a so-called pole cover ratio can be defined for the stacked stator cores.

[0060] According to one embodiment, the ratio of the angle swept by each stator slot to the angle swept by each conductor bar end is in a range between 0.6 and 0.8, in particular between 0.6 and 0.75, and preferably between 0.6 and 0.7. This ratio (pole coverage) within this range provides an optimum between losses caused by current heat and torque utilization.

[0061] According to one embodiment, the support device comprises a support element having support grooves therein that correspond to the helical arrangement of the conductor rod ends and are coupled to the conductor rods. This form-fitting insertion of the conductor rods in the support element is thus configured to support torque at the axial end. Preferably, this coupling is present with all conductor rods, so that the torque support is uniformly or evenly transmitted across the entire rod structure of the winding.

[0062] For transmitting torque the support element can be coupled to a mechanically fixed base of the radial flux dual rotor machine.One possible design provides through holes for force-fit fasteners such as screws, but of course form-fit fasteners or material-fit connections would also be possible.

[0063] According to one embodiment, the support groove at least partially follows the helical path of the twisted conductor rod end. In particular, the support groove has the same twisted shape as the conductor rod end. For example, the support element may be substantially annular in shape and have recesses on the inner and / or outer circumference, which are radially oriented and correspond to the path of the conductor rod end.

[0064] According to one embodiment, the support device comprises a radially inner support element for engaging with a radially inner layer of conductor bars, and a radially outer support element for engaging with a radially outer layer of conductor bars. In this embodiment, the support elements may be annular, with the inner support element having grooves or teeth on its outer circumference corresponding to the course of the inner layer of conductor bars, for form-fitting the radially inner conductor bars, and the outer support element having grooves or teeth on its inner circumference corresponding to the course of the radially outer layer of conductor bars, for form-fitting the radially outer conductor bars. In particular, the grooves or teeth follow corresponding helical courses. Due to their arrangement on the inner or outer circumference, the recessed grooves are easily accessible for machining, which simplifies the production of the support elements.

[0065] According to one embodiment of a radial flux dual-rotor motor, a support element is fixed to the base and thus directs torque to the stationary part of the motor. For this purpose, the support element can be separately attached to the motor's base, such as the housing. Alternatively or additionally, the inner and outer support elements can also be fastened together.

[0066] According to one embodiment of the stator, the support device comprises a thermally conductive material, in particular a metal, preferably an aluminum alloy. In particular, both support elements can comprise such a material. In addition to high mechanical strength, this also allows heat to be dissipated from the windings via the support device.

[0067] According to one embodiment of a corresponding radial flux dual-rotor electric machine with a support device comprising a thermally conductive material, the base also comprises a heat sink configured to absorb heat dissipated from the stator, in particular from the windings, via the support device. As a result, the support device exhibits high mechanical strength while simultaneously ensuring a good thermal connection between the windings and the heat sink. For example, the housing of the electric machine can serve as a heat sink. Alternatively or additionally, the support device, preferably the inner and outer support elements, can be in thermal contact with an actively cooled heat sink of the electric machine. This effectively dissipates heat losses from the current in the windings or at the conductor bar ends.

[0068] According to one embodiment of the radial flux dual-rotor motor, a predetermined number of magnetic pole pairs are provided on both the first and second rotors. The angle swept by the conductor rod ends is designed to form a conductor loop for each magnetic pole of the rotors. Therefore, the sweep angle to be set can be calculated from the quotient of a full revolution (2π, or 360°) and twice the number of magnetic pole pairs.

[0069] According to one embodiment of the production process, the stator core is provided by producing a stacked stator core in which individual stator laminations, each having recesses for forming stator slots, are stacked in an oppositely twisted manner relative to one another. This method allows for very economical production of the stacked stator core, as the same stamping die can be used for all parallel or stacked stator laminations. Thus, two adjacent stator laminations are slightly rotated relative to one another by a predetermined angle about the central axis, so that the recesses are arranged so as to overlap one another, corresponding to the course of the helical line. Individual stator laminations having this geometry are produced by stamping or laser cutting individual laminations from electrical steel.

[0070] According to a further development of the method, the stacked stator core comprises an inner partial package and an outer partial package, wherein all stator sheets of the inner partial package are each constructed with the same geometry and all stator sheets of the outer partial package are each constructed with the same geometry, and wherein the stator sheets of the inner partial package for forming the inner stator slots and the stator sheets of the outer partial package for forming the outer stator slots are stacked in a manner that is twisted in opposite directions relative to each other. In this case, all sheets of the inner package and the outer package can be constructed with the same geometry, making the manufacturing process very economical. The same stamping die can therefore be used for all parallel or stacked stator sheets of the inner partial package and the same stamping die can be used for all parallel or stacked stator sheets of the outer partial package. Two adjacent stator sheets of the inner partial package are slightly twisted around the central axis in a first direction at a predetermined angle and two adjacent stator sheets of the outer partial package are slightly twisted around the central axis toward each other in a second direction at a predetermined angle. In this way, the recesses of the stator laminations of the inner partial encapsulation and the recesses of the stator laminations of the outer partial encapsulation are arranged in opposite overlaps relative to each other, corresponding to opposite helical runs. In this way, opposite helices of the stator slots can be produced with little manufacturing effort.

[0071] According to another embodiment of the method, the stacked stator core has a plurality of differently shaped stator laminations, wherein the recesses for the inner and outer stator slots are each integrated in a common stator lamination, and wherein the pitch of the helix is ​​achieved by continuously shifting the inner and outer stator slots relative to each other from stator lamination to stator lamination, in particular using a flexible stamping or laser beam separation process. In this case, the inner and outer stator slots are integrated in a single stator lamination (laminate) and the helical shape of the stator slots is created in each individual lamination by continuously shifting the recesses relative to each other in a separation process, for example by means of a flexible stamping process or a laser beam separation process. This has the advantage that fewer production steps are required with fewer parts and the resulting stator lamination or the entire stator core has a higher mechanical strength.

[0072] In another embodiment, the method further comprises the steps of providing a support device configured for positive engagement with a conductor rod end at at least one axial end for torque support and the steps of positive engagement with the conductor rod end at at least one axial end at a position axially offset from the stator core.

[0073] According to one aspect, the stator produced in this way can furthermore be used to carry out a method for producing a radial flux dual-rotor electric machine, comprising the further steps of providing a mechanically fixable base and a support device configured for form-fitting engagement with the winding at at least one axial end for torque support, and fastening the support device to the base.

[0074] The above-described embodiments and modifications can be combined with one another in any practical manner. In particular, all features of the stator can be transferred to the method for producing the stator, and vice versa. Furthermore, all features of the stator can be transferred to a corresponding radial flux dual-rotor electric machine, as well as an axle having such a radial flux dual-rotor electric machine and / or a vehicle having such an axle.

[0075] Other possible embodiments of the present invention, other configurations and implementations are also included in the combinations (not explicitly mentioned) of the features of the present invention described above or below with respect to the exemplary embodiments. In this regard, the skilled person will also specifically add individual aspects as improvements or supplements to the corresponding basic forms of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] The invention will be explained in more detail below using exemplary embodiments shown in the schematic drawings in the accompanying drawings. The drawings show:

[0077] Figure 1 is an exploded view of a stator with an assembled stator core and support device according to the present invention;

[0078] Figure 2 is based on Figure 1 Exploded view of the stator;

[0079] Figure 3 is based on Figure 2 a side view of the stator with the assembled stator core and support assembly;

[0080] Figure 4 is a detailed view of a stator according to one embodiment;

[0081] Figure 5a and Figure 5b is a detailed view of a bent conductor rod according to one embodiment;

[0082] Figure 6 is a schematic longitudinal cross-sectional view of the stator;

[0083] Figure 7 is a schematic longitudinal cross-sectional view of a radial flux dual-rotor motor;

[0084] Figure 8 is an exploded view of a radial flux dual-rotor motor according to one embodiment;

[0085] Figure 9 is an exploded view of a stator according to one embodiment;

[0086] Figure 10 is an exploded view of a radial flux dual-rotor motor according to another embodiment;

[0087] Figure 11 is based on Figure 10 A perspective view of the radial flux dual-rotor motor in its assembled state;

[0088] Figure 12 is a perspective detail view of a longitudinal cross-section of a radial flux dual-rotor electric machine according to another embodiment;

[0089] Figure 13 It is an exploded view of the stacked stator core of the stator core;

[0090] Figure 14 is a schematic longitudinal cross-sectional view of a stator slot;

[0091] Figure 15 It is a perspective view of the winding;

[0092] Figure 16 is a plan view of the winding; and

[0093] Figure 17 is a flow chart of a method for producing a stator.

[0094] The accompanying drawings are intended to provide a further understanding of the embodiments of the present invention. They illustrate the embodiments and, in conjunction with the description, serve to illustrate the principles and concepts of the present invention. Other embodiments and many of the advantages mentioned will become apparent with reference to the accompanying drawings. The elements shown in the drawings are not necessarily shown to scale relative to each other.

[0095] In the figures of the drawings, like elements, features, and components that have the same function and function in the same manner are each identified by the same reference numeral unless otherwise stated. DETAILED DESCRIPTION

[0096] Figure 1 An exploded view of a stator 1 with an assembled stator core 2 and supporting means 5 according to the invention is shown.

[0097] A stator 1 for a radial flux dual-rotor electric machine 10, particularly a wheel hub motor, includes a stator core 2 and a winding 3 disposed in the stator core 2. The winding 3 is configured to be self-supporting to provide torque support for the stator 1, and the winding 3 protrudes beyond the stator core 2 at at least one axial end 4 (not shown).

[0098] The winding 3 is constructed from interconnected conductor bars 6 and has a radially inner layer 15 of helically arranged conductor bars 6 and a radially outer layer 14 of oppositely helically arranged conductor bars 6. The conductor bars 6 are each constructed to be bent at a first conductor bar end 6a and unbent at a second conductor bar end 6b.

[0099] Figure 1 The exploded view of the stator 1 is intended to show individual components of the stator 1 for the sake of improved clarity. In this respect, for example, the conductor bars 6 of the winding 3 are shown divided into a radially inner layer 15 and a radially outer layer 14.

[0100] The stator 1 also has a support device 5 axially offset from the stator core 2 , which is configured for form-fitting engagement with the winding 3 at at least one axial end 4 (not shown) for torque support.

[0101] like Figure 1 As shown, the first conductor bar ends 6a of the conductor bars 6 of the radially outer layer 14 are arranged so that the bends are in each case directed radially inwards. Furthermore, the first conductor bar ends 6a of the conductor bars 6 of the radially inner layer 15 are arranged so that the bends are in each case directed radially outwards.

[0102] The conductor bars 6 of the radially outer layer 14 are accommodated in the outer stator slots 19 and the first conductor bar ends 6a are arranged at the first axial end 2a of the stator core 2. The helical shape of the conductor bars 6 of the radially outer layer 14 corresponds to the helical shape of the outer stator slots 19.

[0103] The conductor bars 6 of the radially inner layer 15 are accommodated in the inner stator slots 20 and the first conductor bar ends 6 are arranged at the second axial end 2b of the stator core 2. The helical shape of the conductor bars 6 of the radially inner layer 15 corresponds to the helical shape of the inner stator slots 20.

[0104] Furthermore, the first axial end 2 a is arranged opposite to the second axial end 2 b with respect to the axial center of the stator core 2 .

[0105] In addition, in order to form a conductor loop, the first conductor rod end 6a of the conductor rod 6 of the radially outer layer 14 is joined to the second conductor rod end 6b of the conductor rod 6 of the radially inner layer 15 at the first axial end 2a, and the first conductor rod end 6a of the conductor rod 6 of the radially inner layer 15 is joined to the second conductor rod end 6b of the conductor rod 6 of the radially outer layer 14 at the second axial end 2b.

[0106] Figure 2 Shown as Figure 1 An exploded view of the stator 1 is shown.

[0107] Figure 2 Shown Figure 1 The stator 1 according to the invention is shown in the figure, in which the stator core 2 is divided into an inner partial encapsulation 23 and an outer partial encapsulation 24 of stator laminations. In this view, the conductor bars 6 of the radially inner layer 15 and the radially outer layer 14 and the corresponding spiral course of the stator slots 19, 20 are clearly shown. In addition, as shown in FIG. Figure 2 As shown, all components are coaxially arranged around a central axis M.

[0108] Figure 3 Shown according to Figure 1 Side view of the stator 1 with the assembled stator core 2 and support device 5.

[0109] The conductor bars 6 of the radially inner layer 15 and the conductor bars 6 of the radially outer layer 14 of the winding 3 are each shown axially offset in opposite directions towards the stator core 2 and the supporting device 5 .

[0110] With the help of Figure 3 , it is possible to illustrate a method for producing a stator 1 for a radial flux dual-rotor motor 10 .

[0111] The method comprises the steps of providing a stator core 2 with radially outer stator slots 19 each describing a helix and radially inner stator slots 20 each describing a helix having an opposite direction of rotation (not shown or hidden).

[0112] Furthermore, the method comprises the step of providing an individual conductor rod 6 which is bent at a first conductor rod end 6a and which is not bent at a second conductor rod end 6b.

[0113] Furthermore, the method comprises the step of introducing the individual conductor bars 6 of the radially outer layer 14 into the radially outer stator slots 19 at the first axial end 2a of the stator core 2 such that the bends of the first conductor bar ends 6a of the conductor bars 6 of the radially outer layer 14 at the first axial end 2a are directed radially inwards. In this respect, the introduction direction E1 indicates the axial direction in which the conductor bars 6 of the radially outer layer 14 are introduced into the stator slots 19 of the stator core 2.

[0114] Furthermore, the method includes the step of introducing the individual conductor bars 6 of the radially inner layer 15 into the radially inner stator slots 20 at the second axial end 2 b of the stator core 2 such that the bends of the first conductor bar ends 6 a of the conductor bars 6 of the radially inner layer 15 at the second axial end 2 b are directed radially outward. In this respect, the introduction direction E2 indicates the axial direction in which the conductor bars 6 of the radially inner layer 15 are introduced into the stator slots 20 of the stator core 2.

[0115] Furthermore, the method includes the step of joining the conductor rod ends 6a, 6b of the conductor rods 6 inserted into the outer stator slots 19 and the inner stator slots 20 to form a conductor loop. In this regard, the first conductor rod ends 6a of the conductor rods 6 of the radially outer layer 14 are joined to the second conductor rod ends 6b of the conductor rods 6 of the radially inner layer 15 at the first axial end 2a of the stator core 2, and the first conductor rod ends 6a of the conductor rods 6 of the radially inner layer 15 are joined to the second conductor rod ends 6b of the conductor rods 6 of the radially outer layer 14 at the second axial end 2b of the stator core 2.

[0116] Figure 4 A detailed view of a stator 1 according to one embodiment is shown.

[0117] To form a conductor loop, the first conductor rod ends 6a of the conductor rods 6 of the radially outer layer 14 are joined to the second conductor rod ends 6b of the conductor rods 6 of the radially inner layer 15. Figure 4 As shown, the first conductor rod ends 6a of the conductor rods 6 of the radially inner layer 15 are joined to the second conductor rod ends 6b of the conductor rods 6 of the radially outer layer 15, and the first conductor rod ends 6a of the conductor rods 6 of the radially outer layer 14 are joined to the second conductor rod ends 6b of the conductor rods 6 of the radially outer layer 15.

[0118] The respective first conductor shank end 6a is joined to the respective second conductor shank end 6b at an overlapping abutment. Figure 4 As shown, the conductor bars 6 of the radially inner layer 15 and the conductor bars 6 of the radially outer layer 14 each form an overlapping abutment at opposite axial ends 2a, 2b. The respective overlapping abutments can be joined, in particular, by laser beam welding.

[0119] Furthermore, it can be seen that the radial depth of the bend corresponds in each case to the radial distance between the radially inner layer 15 and the radially outer layer 14 of the conductor bars 6 within the stator core 2 .

[0120] Figure 5a and Figure 5b A detailed view of a bent conductor rod end 6 according to one embodiment is shown.

[0121] Starting from the first conductor bar end 6a, each conductor bar 6 is bent over a distance in the range of approximately 5% to approximately 25%, preferably approximately 10% to approximately 20%, particularly preferably approximately 12% to approximately 18% of the total length of the respective conductor bar 6. Starting from the first conductor bar end 6a, the conductor bar 6 shown in Figures 5A and 5B is bent over a distance of approximately 15% of the total length of the conductor bar 6.

[0122] The bend of the conductor rod end 6a of the conductor rod 6 is configured as a double circular bend. Furthermore, the respective conductor rod 6 shown is rotated, in particular twisted, along its longitudinal axis.

[0123] [Picture description of P52372-EN starts here]

[0124] Figure 6 A schematic longitudinal section through a stator 1 is shown.

[0125] In this respect, the subject matter here is a schematic diagram of a radial flux dual rotor motor 10 (see for example Figure 1 ) is a schematic diagram of a stator 1, in particular for a wheel hub motor. The stator has a stator core 2, a winding 3 and a support device 5. The stator core 2, the winding 3 and the support device 5 are rotationally symmetrical about the central axis M shown.

[0126] The winding 3 is configured to be self-supporting for torque support of the stator 1 and protrudes beyond the stator core 2 at at least one axial end 4. A support device 5 is arranged axially offset toward the stator core 2 and is connected to the winding 3 at at least one axial end 4 in a form-fitting manner for torque support. In this way, the torque applied to the stator core 2 during operation of the radial flux dual-rotor electric machine 10 can be supported by the self-supporting winding 3 on the support device 5.

[0127] The winding 3 comprises a conductor material with low electrical resistance, preferably copper. The stator core 2 is preferably made of a soft magnetic material for flux guidance. The support means 5 preferably comprises a thermally conductive material, such as an aluminum alloy. The winding 3 is obviously electrically insulating.

[0128] Figure 7 A schematic longitudinal cross-sectional view of a radial flux dual-rotor electric machine 10 is shown.

[0129] This is also a purely illustrative diagram. Figure 6 In addition to the stator 1 shown, the radial flux dual-rotor motor 10 also has a mechanically fixed base 11, a first rotor 12, and a second rotor 13. The stator core 2, the winding 3, the support device 5, the base 11, the first rotor 12, and the second rotor 13 are also rotationally symmetric around the central axis M shown.

[0130] The winding 3 is configured to be self-supporting to provide torque support for the stator 1 and protrudes beyond the stator core 2 at at least one axial end 4 and is supported on a base 11 via a support device 5. For this purpose, the support device 5 is arranged axially offset toward the stator core 2 and connected to the winding 3 in a form-fitting manner at at least one axial end 4 for torque support. The support device 5 is further attached to the base 11 so that torque can be supported on the base 11 via the support device 5.

[0131] 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 be configured, for example, as a housing for an electric machine and, for purely illustrative purposes, is shown as an L-shaped structure in longitudinal cross-section, including two limbs 7 and 8. This illustration should not be understood as definitive; the base 11 can have additional components and / or structural parts. The first limb 8 extends generally radially, and the second limb 7 extends generally axially at its greatest distance from the central axis M.

[0132] Purely schematically, the support device 5 is shown as extending radially in one piece, but it can also be provided in several pieces and / or with a different geometry configured to match the shape of the winding 3. The overlapping of the winding 3 with the base 11 is shown purely for illustrative purposes and does not indicate a direct connection. The winding 3 is preferably connected to the base 11 via the support device 5 for torque support.

[0133] Figure 8 An exploded view of a radial flux dual-rotor electric machine 10 is shown according to one embodiment.

[0134] In addition to the components of the stator 1, the radial flux dual-rotor motor 10 also includes a first rotor 12, a second rotor 13, and a base 11. 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 rotors 12, 13 are preferably made of a soft magnetic solid material and are equipped with permanent magnets (so-called surface magnets) as magnetic poles on the respective surfaces facing the stator core 2. In other embodiments, other rotors known to those skilled in the art can also be used, such as buried magnets, short-circuited rotors, or electrically excited rotors.

[0135] For the sake of clarity, the base 11 is only schematically shown here. Figure 7 As already described in the description of , the base 11 is attached to the support device 5 during installation. The base 11 is mechanically fixed with respect to a reference system, such as the carrier device of a vehicle axle.

[0136] Figure 9 An exploded view of a stator 1 according to one embodiment is shown.

[0137] The stator 1 has a winding 3 , a stator core 2 and a support device 5 , wherein an advantageous exemplary design of these components is shown in more detail here in a perspective view.

[0138] The winding 3 is composed of an inner layer and an outer layer having a plurality of conductor bars 6 connected together in a bar structure. The conductor bars 6 in the outer layer 14 and the inner layer 15 are conductor bars arranged in opposite spirals.

[0139] The thickness of the outer layer 14 and the inner layer 15 can each correspond to the thickness of the conductor bar 6. This means that the winding 3 is formed by a single conductor layer which in each case forms a conductor loop of relatively large cross section in the form of a conductor bar 6.

[0140] Due to the rod structure formed with the conductor rods 6 , the winding 3 is torsionally rigid and thus self-supporting for torque support.

[0141] The conductor bars 6 thus form wavy winding strands and can be interconnected to form a rotating field generating winding of any number of strands by means of corresponding interconnections known to the skilled person and therefore not further described, such as delta connection, star connection etc.

[0142] For example, in the illustrated embodiment, the stator core 2 and support device 5 each consist of two components. To assemble the stator 1, the windings 3, stator core 2, and support device 5 are nested within one another. After assembly, these components are coaxially positioned relative to one another about a common central axis M. The exemplary two-part support device 5 is arranged axially offset from the other components and forms the radially innermost and outermost components of the stator 1. It is composed of an inner ring and an outer ring, each of which is formed with slots for form-fitting engagement with the conductor rods 6.

[0143] The exemplary two-part stator core 2 is formed with two helically twisted stacked stator cores 18, which will be referred to as Figure 13 Discuss this in more detail.

[0144] In further exemplary embodiments, the stator core 2 and the supporting device 5 can each also be constructed in one piece or have more than two parts.

[0145] Figure 10 An exploded view of a stator 1 according to another embodiment is shown.

[0146] Stator 1 has here with reference Figure 9 The components of the construction are essentially the same components. Figure 10 On the left hand side of FIG, the stator core 2 and the winding 3 are shown in an assembled state. Furthermore, the first rotor 12 can be arranged radially inside the stator core 2 and the second rotor 13 can be arranged radially outside the stator core 2 (not shown).

[0147] The support device 5 shown on the right is also constructed in two parts and differs in the design of the respective annular inner support element 27 and outer support element 28. The support elements 27, 28 are here equipped with support grooves 26. These are provided on the inner circumference of the outer support element 28 and on the outer circumference of the inner support element 27 for coupling with the conductor bars of the winding 3.

[0148] For this purpose, the supporting grooves 26 are axially angled according to the helical shape of the conductor bars 6 or the pitch thereof, so that they can be combined with the conductor bars 6 of the winding 3 .

[0149] The support elements 27, 28 are preferably made of an electrically conductive metal, particularly preferably of an aluminum alloy.The two-part construction of the support elements 27, 28 makes it possible to easily access the support groove 26 for mechanical or machining processes during manufacture.

[0150] Each of the inner and outer support elements 27, 28 is provided with several holes 9 around its perimeter for fastening to the base 11. In this example, the holes 9 are arranged evenly distributed around the circumference along a bolt circle. The individual holes 9 are slightly outside the main body of the support element, and the support elements 27, 28 thus form a star-shaped structure that faces away from the windings. Other arrangements of the holes 9 and other types of fastening means for connection to the base 11 are readily possible.

[0151] Figure 11 Shown as Figure 10 A perspective view of the stator 1 is shown in the assembled state.

[0152] The support device 5 is fastened via corresponding holes 9 in a motor housing, for example, as a base 11 (not shown), and thus directs torque to a mechanically fixed portion (not shown) of the radial flux dual-rotor motor 10. In this way, the torque generated by the radial flux dual-rotor motor 10 can be effectively supported. The fastening of the support device 5 is achieved via corresponding fastening means (not shown), such as screws.

[0153] The conductor bars 6 of the winding 3 extend axially on both sides outside the stator core 2 and the first and second rotors 12 and 13. The helically arranged conductor bars 6 of the radially inner layer 15 and the radially outer layer 14 are each joined together outside the stator core 2.

[0154] The support elements 27, 28 are shown here in combination with the conductor bars 6 of the winding 3. Obviously, a conductor bar 6 is arranged in each support slot 26 so that all conductor bars 6 are positively coupled to the support device 5. Thus, the torque supported via the winding 3 can be supported via the support device 5 on the base 11 attached to the hole 9.

[0155] Figure 12 A perspective detail view of a longitudinal section of a radial flux dual-rotor electric machine 10 according to another embodiment is shown.

[0156] This embodiment basically corresponds to Figure 8 An assembly of a radial flux dual-rotor electric machine 10 , components of which are discussed in more detail below.

[0157] The stator core 2 has an inner partial enclosure 23 and an outer partial enclosure 24. The partial enclosures 23, 24 extend annularly between the first rotor 12 and the second rotor 13. The cross-sectional view also shows that the outer and inner layers 14, 15 of the conductor bars 6 extend within the partial enclosures 23, 24. Furthermore, it is also apparent that each conductor bar 6 is configured to be bent at a first conductor bar end 6a and unbent at a second conductor bar end 6b. In this regard, the first conductor bar ends 6a of the conductor bars 6 of the radially outer layer 14 are arranged so that the bend is directed radially inwards in each case, and the first conductor bar ends 6a of the conductor bars 6 of the radially inner layer 15 are arranged so that the bend is directed radially outwards in each case.

[0158] The radial flux dual-rotor motor 10 shown is a so-called "yokeless" design, in which the yoke between the two teeth is not in the functionally relevant magnetic flux. Although a stator yoke 30 is present between the conductor bars 6, this only serves to mechanically hold the stacked stator cores 18 together. The radial yoke thickness can be designed to be correspondingly thin, which in the shown embodiment is, for example, about 10% of the total radial stator thickness. The relatively low yoke thickness also reduces undesirable leakage flux in the yoke. In other embodiments, the radial yoke thickness can be less than 30% of the total radial stator thickness for this purpose, preferably less than 20%, and particularly preferably less than 10%.

[0159] The support device 5 here also has an inner support element 27 and an outer support element 28. The support elements 27, 28 are arranged here with a clearly recognizable axial offset relative to the stator 5 and the rotors 12, 13. Furthermore, the form-fitting engagement of the support elements 27, 28 with the conductor bars 6 of the outer layer 14 and the inner layer 15 is recognizable, at least in cross section.

[0160] Furthermore, it can be clearly seen in the embodiment shown that the first conductor shank end 6a is joined to the second conductor shank end 6b at an overlapping abutment.The connection is preferably realized as a material-locked connection, for example by laser beam welding.

[0161] The surface magnets 29 of the rotors 12, 13 can also be seen in cross section. The first rotor 12 has several permanent magnets 29 mounted on its outer circumferential surface. The second rotor 13 has several permanent magnets 29 mounted on its inner circumferential surface.

[0162] A particularly advantageous embodiment results if the rotor is constructed from a soft-magnetic solid material and with surface-mounted permanent magnets. In this design, the rotor can be manufactured very cost-effectively and a high degree of efficiency can be achieved.

[0163] Figure 13 An exploded view of the stacked stator cores 18 of the stator core 2 is shown.

[0164] As already mentioned, the stacked stator core 18 of the stator core 2 has an inner partial encapsulation 23 and an outer partial encapsulation 24. This serves to simplify the production of stator slots 19, 20 that are twisted in opposite directions relative to one another, and the inner stator sheets 21 and the outer stator sheets 22 are stacked in the same twist position and are provided with recesses at the same points.

[0165] In other embodiments, the stator laminations can also be constructed as one piece or a single piece, so that a plurality of differently shaped stator laminations with differently arranged recesses are provided and stacked in the order required to form the stator slots. In other embodiments, a completely one-piece stator core 2 that can be additively manufactured, for example, is also possible.

[0166] In the two-part design shown, the inner diameter of the outer partial encapsulation 24 is almost identical to the outer diameter of the inner partial encapsulation 23. This makes it possible to arrange the inner partial encapsulation 23 coaxially within the outer partial encapsulation 24.

[0167] The partial packages 23, 24 consist of individual annular stator laminations 21, 22 stacked on top of each other. The stator laminations 21 of the outer partial package 24 are produced with recesses distributed around the outer circumference to form the outer stator slots 19. The stator laminations 22 of the inner partial package 23 are produced with recesses distributed around the inner circumference to form the inner stator slots 20. For example, stamping is advantageous for producing such stator laminations due to the edge quality and very low manufacturing costs.

[0168] The inner stator slots 20 and the outer stator slots 19 describe opposing helices having the same pitch, which are characterized by the sweep angle α of the drawn stator slots. The sweep angle α of the stator slots can be defined based on 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.

[0169] Stator slots 19, 20 are exemplarily formed here as T-slots with rectangular recesses and tapered openings. These are particularly intended for form-fitting reception of conductor rod ends with a rectangular cross-section. The geometry of the recesses or stator slots can obviously be adapted to the conductor geometry. Other cross-sectional shapes are also possible.

[0170] Figure 14 A schematic longitudinal section through the stator slots 19 , 20 is shown.

[0171] The available or continuous clear width a of the stator slots 19 , 20 in the stacked stator core 18 is substantially equal to the width of the conductor bars 6 received in the stator core 2 .

[0172] The stator laminations 21, 22 have straight edges, in particular stamped edges. Due to the offset of the metal laminations relative to one another, 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 running thread shape and the lamination thickness t.

[0173] exist Figure 14 , the conductor bars 6 are schematically indicated by dashed lines in the stator slots 19 , 20 , wherein, in order to provide a clearance fit, the continuous clear width a of the stator slots 19 , 20 is slightly greater than the width d of the conductor bars 6 and the width a of the recesses in the stator laminations 21 , 22 is thus significantly greater than the clear width b.

[0174] The thickness of the sheet t and the set angle δ of the pitch of the slot run are significant factors affecting the difference between the width b of the recess and the clear width a of the available passage in the slot in the case of a straight (e.g. stamped) sheet edge. This difference occurs because the pitch angle on the one hand and the stepped nature of the stacked core on the other hand must be compensated.

[0175] In this case, the minimum dimension of the width a of the recess for a purely considered limit case of an infinitely thin sheet, ie a pitch angle δ of the conductor bars, would be

[0176] b=1 / cos(δ)*d.

[0177] In order to compensate for the actual sheet thickness on the one hand and to provide a clearance fit that allows the conductor rod to be introduced on the other hand, the width b of the recess is actually even greater.

[0178] according to Figure 9 The width b of the recesses is dimensioned so that the clear width a of the stator slots 19, 20, which reduces the offset between the recesses of the stator laminations, forms a predetermined clearance fit with the width d of the conductor bar 6 to be introduced into the stator slots, but the contact is still sufficiently close to achieve uniformly distributed power transmission or torque support between the stacked stator core and the winding. Such dimensioning is made possible in particular by the fact that, on the one hand, each stator lamination is formed with the same high edge quality and rotated with the same offset, and, on the other hand, only a single conductor bar 6 is arranged in the stator slots 19, 20 of constant size.

[0179] In particular, in the embodiment shown, the conductor rod 6 is a rectangular rod with an edge length or width of several millimeters, for example in the range of 2 to 6 mm, in particular in the range of 3 to 5 mm. Preferably, it may be a rectangular profile measuring 5 mm x 3 mm.

[0180] Figure 15 A perspective view of the winding 3 is shown.

[0181] The winding 3 is composed of said conductor bars 6 which extend helically along a central axis. For this purpose, the conductor bars 6 are not only arranged in an interlocking manner, but are also twisted according to the course of the helix.

[0182] The sweep angle β of the conductor bar 6 identifies the angle between the beginning and end of the conductor bar 6 relative to the central axis M. Since the pitch of the helix of the conductor bar 6 is equal to the pitch of the helix of the stator slots 19 and 20, but the conductor bar 6 is longer than the stator slots, the ratio of the corresponding sweep angles α and β can be formed to represent the geometric ratio, which is also called the magnetic pole coverage. In order to provide an optimal condition between magnetic losses and torque utilization of the radial flux dual-rotor motor, this ratio (magnetic pole coverage) is preferably in the range of between 0.6 and 0.75.

[0183] Here, too, the opposite rotation and twisting of the radially outer layer 14 and the radially inner layer 15 of the conductor bars 6 can be seen. The twisting is configured so that the cross-section about a radial line through the center of the conductor bar is always the same at every point on the conductor bar, which is also known as a 2.5D geometry. Consequently, the conductor bar ends of the outer layer 14 and the inner layer 15 are arranged one above the other in the same orientation. The conductor bars 6 of the radially outer layer 14 and the conductor bars 6 of the radially inner layer 15 can thus be connected in a simple manner, in this case, by way of example, by joining the first conductor bar end 6a and the second conductor bar end 6b.

[0184] It should be noted that the windings shown here are not manufactured separately, but are always manufactured in conjunction with the stator core 2, which will be referred to as Figure 17 Discuss this in more detail.

[0185] Figure 16 A plan view of the winding 3 is shown.

[0186] This view clearly shows the exact radial alignment of the conductor bars 6 at every point of their helical course, which in the perspective shown is aligned in the region of the central axis M. The first conductor bar end 6 a and the second conductor bar end 6 b each form a connection point between a radially outer layer 14 and a radially inner layer 15 .

[0187] In the embodiment shown, the winding 3 has, by way of example, a total of twelve connection contact points 31. In the case of a three-phase connection, preferably three-phase operation is provided. However, the winding 3 can be adapted to other connections in a manner known in the art to form a rotating field generating winding with any number of strands.

[0188] Winding 3 is essentially in the Figure 15 The FEM simulations for the winding geometry shown clearly show that the stresses within the winding 3 are very advantageously evenly distributed due to the spiral geometry.

[0189] In FEM simulations, the conductor rod ends 6a, 6b are defined by a sweep angle β > 0 for the conductor rods, i.e., a helical arrangement or a correspondingly twisted configuration. At the axial end where the support device is incorporated, the maximum torque of a correspondingly dimensioned radial flux dual-rotor motor 10 is applied. For example, with a rectangular profile of 5 mm x 3 mm for the conductor rods 6, this can be around 5000 Nm. Even under significantly exaggerated conditions, barely any deformation is visible. This configuration significantly reduces stress peaks and deformations.

[0190] Due to the rod-like structure, high torques can be accommodated in a self-supporting manner by the winding 3 while securing the axially accessible winding ends without causing unacceptably large deformations and / or stress states. This is due in particular to the fact that in the rod structure the conductor rods 6 absorb mainly tensile and compressive stresses when subjected to tangential forces.

[0191] Compared to designs with straight conductors parallel to the axis, mechanical stresses can thus be significantly reduced.

[0192] In the FEM comparison model with a straight design and purely axial orientation of the conductor rod 6 under load, it is possible to discern a stress profile concentrated on one side due to the straight design and axial orientation of the conductor rod 6, as well as strong deformations of the conductor rod 6 on the other side due to large deflections caused by localized high stresses. The deformations involved here are significantly greater than those in the case of a winding 3 with a spiral geometry, clearly demonstrating the influence of different structural arrangements on torsional stiffness.

[0193] Figure 17 A flow chart of a method for producing a stator 1 is shown.

[0194] The method comprises a first step S1 of providing a stator core 2 having radially outer stator slots 19 each describing a helix and radially inner stator slots 20 each describing a helix having an opposite direction of rotation.

[0195] Furthermore, the method comprises a second step S2 of providing an individual conductor rod 6 which is bent at a first conductor rod end 6a and which is not bent at a second conductor rod end 6b.

[0196] Another step involves step S3 of introducing individual conductor bars 6 into radially outer stator slots 19 at the first axial end 2a of the stator core 2 such that the bends of the first conductor bar ends 6a of the radially outer layer 14 of the conductor bars 6 at the first axial end 2a are directed radially inwards.

[0197] Another step involves step S4 of introducing individual conductor bars 6 into radially inner stator slots 20 at the second axial end 2b of the stator core 2 such that the bends of the first conductor bar ends 6a of the radially inner layer 15 of the conductor bars 6 at the second axial end 2b are directed radially outwards.

[0198] Furthermore, the method comprises a step S5 of joining the conductor rods 6 introduced at the conductor rod ends 6a, 6b into the outer stator slots 19 and the inner stator slots 20 to form conductor loops, wherein, at the first axial end 2a of the stator core 2, the first conductor rod ends 6a of the conductor rods 6 of the radially outer layer 14 are in each case joined to the second conductor rod ends 6b of the conductor rods 6 of the radially inner layer 15, and at the second axial end 2b of the stator core 2, the first conductor rod ends 6a of the conductor rods 6 of the radially inner layer 15 are in each case joined to the second conductor rod ends 6b of the conductor rods 6 of the radially outer layer 14.

[0199] Furthermore, the method may comprise a step after introduction, wherein the first conductor shank end 6a is overlapped with the second conductor shank end 6b and joined at the overlapping abutment during joining, in particular by laser beam welding.

[0200] Although the present invention has been fully described above based on the preferred exemplary embodiments, the present invention is not limited thereto but may be modified in various ways.

[0201] Reference Signs List

[0202] 1 stator

[0203] 2 stator core

[0204] 3 Winding

[0205] 4 Axial end

[0206] 5 Support device

[0207] 6 Conductive rods

[0208] 7 First limb

[0209] 8 Second limb

[0210] 9 holes

[0211] 10 Radial Flux Dual Rotor Motor

[0212] 11 Base

[0213] 12 First rotor

[0214] 13 Second rotor

[0215] 14 radial outer layer

[0216] 15 radial inner layer

[0217] 16 Conductive rod end

[0218] 17 Conductive rods

[0219] 18 stacked stator cores

[0220] 19, 20 stator slots

[0221] 21, 22 stator segments

[0222] 23 Inner local packaging

[0223] 24 External local packaging

[0224] 25 Support elements

[0225] 26 support slots

[0226] 27 Internal support elements

[0227] 28 External support elements

[0228] 29 Permanent Magnet

[0229] 30 stator yoke

[0230] 31 Connecting contact points

[0231] α is the sweep angle of the stator slots

[0232] β Sweep angle of the conductor rod

[0233] δ pitch

[0234] a Net width

[0235] b Width of the concave portion

[0236] d Width of the conductor rod

[0237] M Center axis

[0238] t sheet thickness

Claims

1. A stator (1) for a radial flux dual-rotor electric machine (10), in particular for a hub motor, comprising: stator core (2); a winding (3), the winding (3) being arranged in the stator core (2), the winding being configured to be self-supporting so as to achieve torque support for the stator (1), wherein the winding (3) protrudes beyond the stator core (2) at at least one axial end (4); A support device (5), the support device (5) being arranged to be axially offset relative to the stator core (2), the support device (5) being configured to be positively coupled to the winding (3) at the at least one axial end (4) for torque support; wherein the winding (3) is formed by interconnected conductor bars (6) and has a radially inner layer (15) of helically arranged conductor bars (6) and a radially outer layer (14) of oppositely helically arranged conductor bars (6), wherein each of the conductor rods (6) is configured to be bent at a first conductor rod end (6a) and not bent at a second conductor rod end (6b), wherein the first conductor rod ends (6a) of the conductor rods (6) of the radially outer layer (14) are arranged such that a bend is in each case directed radially inwards, and the first conductor rod ends (6a) of the conductor rods (6) of the radially inner layer (15) are arranged such that a bend is in each case directed radially outwards.

2. The stator (1) according to claim 1, wherein: To form a conductor loop, each of the first conductor rod ends (6a) of the conductor rods (6) of the radially outer layer (14) is joined to the second conductor rod ends (6b) of the conductor rods (6) of the radially inner layer (15), and each of the first conductor rod ends (6a) of the conductor rods (6) of the radially inner layer (15) is joined to the second conductor rod ends (6b) of the conductor rods (6) of the radially outer layer (14).

3. The stator (1) according to claim 1, in, The conductor bars (6) of the radially outer layer (14) are accommodated in outer stator slots (19) and are arranged with the first conductor bar ends (6a) at the first axial end (2a) of the stator core (2), The conductor bars (6) of the radially inner layer (15) are accommodated in inner stator slots (20) and are arranged with the first conductor bar ends (6a) at the second axial end (2b) of the stator core (2), wherein, in order to form the conductor loop (?) at the first axial end (2a), the first conductor rod ends (6a) of the conductor rods (6) of the radially outer layer (14) are each joined to the second conductor rod ends (6b) of the conductor rods (6) of the radially inner layer (15), and At the second axial end (2b), the first conductor rod ends (6a) of the conductor rods (6) of the radially inner layer (15) are each joined to the second conductor rod ends (6b) of the conductor rods (6) of the radially outer layer (14).

4. The stator (1) according to claim 2 or 3, characterized in that The first conductor shank end (6a) is joined to the second conductor shank end (6b) at an overlapping joint, in particular by laser beam welding.

5. The stator (1) according to any one of the preceding claims, wherein The radial depth of the bend corresponds to the radial distance between the radially inner layer (15) and the radially outer layer (14) of the conductor bars (6) in the stator core (2).

6. Stator (1) according to any one of the preceding claims, characterized in that The conductor bars (6) are each formed to be bent over a distance in the range of about 5% to about 25%, preferably about 10% to about 20%, particularly preferably about 12% to about 18% of the entire length of the corresponding conductor bar (6), starting from the first conductor bar end (6a).

7. A stator (1) according to any one of the preceding claims, wherein The bend is configured as a double bend head.

8. A method for producing a stator (1) for a radial flux dual-rotor electric machine (10), in particular a stator (1) according to claim 1, comprising the following steps: providing a stator core (2) having radially outer stator slots (19) each describing a helix and radially inner stator slots (20) each describing a helix having an opposite direction of rotation; providing a single conductor rod (6) configured to bend at a first conductor rod end (6a) and configured not to bend at a second conductor rod end (6b); introducing the individual conductor bars (6) into the radially outer stator slots (19) at a first axial end (2a) of the stator core (2) such that at the first axial end (2a) the bends of the first conductor bar ends (6a) of the conductor bars (6) of the radially outer layer (14) are directed radially inwards; introducing the individual conductor bars (6) into the radially inner stator slots (20) at a second axial end (2b) of the stator core (2) such that at the second axial end (2b) the bends of the first conductor bar ends (6a) of the conductor bars (6) of the radially inner layer (15) are directed radially outwards; as well as The conductor rods (6) introduced into the inner and outer stator slots (19, 20) are joined at the conductor rod ends (6a, 6b) to form a conductor loop (?), wherein the first conductor rod ends (6a) of the conductor rods (6) of the radially outer layer (14) are each joined to the second conductor rod ends (6b) of the conductor rods (6) of the radially inner layer (15) at the first axial end (2a) of the stator core (2), and the first conductor rod ends (6a) of the conductor rods (6) of the radially inner layer (15) are each joined to the second conductor rod ends (6b) of the conductor rods (6) of the radially outer layer (14) at the second axial end (2b) of the stator core (2).

9. The method according to claim 8, characterized in that After being introduced, the first conductor shank end (6a) is placed overlapping the second conductor shank end (6b) and during joining they are joined at the overlapping abutment, in particular by laser beam welding.

10. A radial flux dual-rotor motor (10), in particular a radial flux dual-rotor motor for a wheel hub drive, comprising: A stator (1) according to any one of claims 1 to 7 or produced by a method according to any one of claims 8 to 9; a first rotor (12), the first rotor (12) being radially arranged inside the stator core (2) of the stator (1); as well as A second rotor (13) is radially arranged outside the stator core (2) of the stator (1).

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