Rotor for an axial flux permanent magnet synchronous machine and axial flux permanent magnet synchronous machine

Abstract

Rotor (24) for an axial flux permanent magnet synchronous machine (20), - wherein the rotor (24) is rotatable about an axis (A) in a direction of rotation (u); - wherein the rotor (24) has a carrier disk (28) made of a soft magnetic material (40) which, at least with respect to an axial disk part of the carrier disk (28), is divided in the direction of rotation (u) into several magnetic sectors (28a, 28b) which are divided in the direction of rotation (u) into first and second magnetic sectors (28a, 28b) arranged alternately with respect to each other; - wherein the rotor (24) has several permanent magnets (30, 34), each having a north pole and a south pole and each having a magnetic direction (m) directed from its south pole to the north pole; - wherein at least two of the multiple permanent magnets (30, 34) are arranged in each magnetic sector (28a, 28b), and the at least two permanent magnets (30, 34) arranged in one of the respective magnetic sectors (28a, 28b) comprise two first permanent magnets (30); - wherein the permanent magnets (30, 34) arranged in the first magnetic sectors (28a) are arranged such that their magnetic direction (m) points partly in a first direction (a) which is parallel to an axial direction (a), and wherein the permanent magnets (30, 34) arranged in the second magnetic sectors (28b) are arranged such that their magnetic direction (m) points partly opposite to the first direction (a); - wherein the magnetic direction (m) of the respective first permanent magnets (30) is not parallel to the first direction (a) and is inclined in the direction of rotation (u) by a respective angle to the first direction (a); - for at least one of the magnetic sectors (28a, 28b) a common first magnetic pocket (26) is assigned to the two first permanent magnets (30) arranged in the magnetic sector (28a, 28b), which is free of the soft magnetic material, and which is directly adjacent to first ends (30a) of the two first permanent magnets (30) facing each other in the direction of rotation (u) and fills a first intermediate area (26a) in the direction of rotation (u) between the first ends (30a) of the two first permanent magnets (30); where - the first magnetic pocket (26) fills a second area (26b) which is many times larger than the first intermediate area (26a) and which lies behind the two first permanent magnets (30) with respect to the axial direction (a) and which adjoins the first intermediate area (26a) with respect to the axial direction (a), - wherein the first magnetic pocket (26) widens with respect to the axial direction (a) with increasing distance from the first permanent magnets (30).

Description

[0001] The invention relates to a rotor for an axial-flux permanent-magnet synchronous machine, wherein the rotor is rotatable about an axis in a rotational direction and has a carrier disk made of a soft magnetic material, which, at least with respect to an axial disk portion of the carrier disk, is divided in the rotational direction into a plurality of magnetic sectors, which are divided in the rotational direction into alternating first and second magnetic sectors. Furthermore, the rotor comprises a plurality of permanent magnets, each having a north pole and a south pole, and each of which is assigned a magnetic direction directed from its south pole to the north pole. At least two of the plurality of permanent magnets are arranged in each magnetic sector, and the at least two permanent magnets arranged in one of the respective magnetic sectors comprise two first permanent magnets.The permanent magnets arranged in the first magnetic sectors are arranged such that their magnetic direction partially points in a first direction parallel to an axial direction, while the permanent magnets arranged in the second magnetic sectors are arranged such that their magnetic direction partially points opposite the first direction. The magnetic direction of the respective permanent magnets is not parallel to the first direction and is inclined in the direction of rotation by a respective angle relative to the first direction.Furthermore, for at least one of the magnet sectors, a common first magnet pocket is assigned to the two first permanent magnets arranged in the magnet sector, which first magnet pocket is free of the soft magnetic material and which directly adjoins first ends of the two first permanent magnets facing one another in the direction of rotation and fills a first intermediate region in the direction of rotation between the first ends of the two first permanent magnets facing one another.

[0002] The present invention is located in the field of axial-flux permanent-magnet synchronous machines, such as those used, for example, as electric motors for motor vehicles. An axial-flux permanent-magnet synchronous machine is a permanently excited synchronous machine from the group of axial-flux synchronous machines. Permanent-magnet synchronous machines have permanent magnets as part of the stator or rotor, in this case as part of the rotor. These permanent magnets are sometimes simply referred to as magnets below. In permanently excited synchronous machines, which are designed as axial-flux synchronous machines, which are also simply called axial-flux machines, the magnets are aligned with their magnetic direction, as defined above, essentially parallel to the axial direction.The magnetic field generated by these magnets is accordingly also aligned in the axial direction, at least in the immediate vicinity of the magnets. In axial flux machines, the stator and rotor are arranged next to each other in the axial direction, whereas in radial flux machines, for example, the stator and rotor are arranged radially to each other. In order to be able to provide a sufficiently large torque, the magnets typically have to be a certain size. In radial flux machines, the magnets extend relatively far in the axial direction, whereas in axial flux machines the magnets extend mainly in the radial direction. In other words, the dimension of the magnets in the radial direction typically represents the largest dimension of the magnets in axial flux machines. Overall, this means that axial flux machines can be designed to be significantly more compact in the axial direction than radial flux machines.Accordingly, axial flux machines have a higher power density, particularly in terms of kilowatts per kilogram and kilowatts per cubic meter, and torque density, particularly in terms of newton meters per kilogram and newton meters per cubic meter, than radial flux machines. The axial length and weight of the electric motor are also significantly smaller in axial flux machines than in radial flux machines of the same power class. For comparison, an axial flux machine typically has an axial length in the range of 70 mm to 140 mm, while a radial flux machine, for example, has an axial length in the range of 150 mm to 250 mm. The average weight of an axial flux machine is approximately 15 kg to 35 kg, while a radial flux machine weighs between 30 kg and 50 kg.

[0003] Most axial flux machine rotors have surface magnets, meaning magnets arranged on the surface of a soft magnetic carrier, particularly a soft magnetic carrier disk. The surface magnets are arranged parallel to the direction of rotation, so that their magnetic direction is perpendicular to the surface of the carrier disk and therefore parallel to the axis of rotation. As described, this has the advantage that the rotor is relatively short in the axial direction. However, it has the disadvantage that this orientation of the magnets prevents the generation of reluctance torque. Therefore, a larger number of magnets and correspondingly more magnet weight and volume are required than with axial flux machines with so-called "V-arranged" magnets, i.e., per power or per torque. The increased number of magnets causes additional costs and high prices for axial flux machines.

[0004] A permanent-magnet axial flux machine with V-oriented magnets is also described, for example, in US 2020 / 0 106 351 A1. This machine is designed as a double-stator, single-rotor axial flux machine. Due to their "V-arrangement," the magnets are not aligned exactly parallel to the axial direction, but are slightly inclined alternately in and against the direction of rotation, forming a V-shaped structure when viewed from the radial direction.

[0005] Such a V-shaped arrangement of magnets generates additional reluctance torque, which therefore offers significant advantages. Consequently, more torque can be achieved with the same number of magnets, so these machines have a higher power density and a higher torque density than machines with rotors with surface magnets—that is, with magnets arranged parallel to the direction of rotation and whose magnetic directions are aligned parallel to the axial direction. The V-shaped arrangement of the magnets also has the advantage that the magnets are buried in the iron sheet stack that provides the carrier disk, thus providing better protection against damaging mechanical impacts.

[0006] Furthermore, it is known from the prior art to provide so-called magnetic pockets. These are areas that are free of soft magnetic material. These can, for example, simply be provided as holes or through-openings in the carrier disk. These are typically located at the ends of the permanent magnets, which delimit the permanent magnets in their extension direction perpendicular to the magnet direction. Such enlarged magnetic pockets between two V-arranged magnets can generate a reluctance torque, which leads to an increase in power density without increasing magnet costs. Especially in radial flux machines, a web is usually always provided between the two V-shaped magnets made of electrical steel, which also separates the magnetic pockets assigned to the respective magnets. This web absorbs tensile forces resulting from the centrifugal forces during rotor rotation.However, the bridge creates a magnetic leakage flux, which reduces the achievable torque.

[0007] In the aforementioned US 2020 / 0 106 351 A1, such magnetic pockets can also be connected to the V-arranged magnets. These can also be designed as a single magnetic pocket between two magnets. Accordingly, these pockets are arranged primarily in an intermediate region between two magnets of a magnet pair in the direction of rotation and extend only slightly in the axial direction. This allows the installation space in the axial direction to be kept small.

[0008] Particularly in connection with radial flux machines, there are numerous different designs and shapes of such magnetic pockets, as described, for example, in EP 1 942 572 A1 and WO 2019 / 215 853 A1. Since the magnets in radial flux machines extend essentially in the axial direction, there is sufficient space available in the radial direction for a corresponding design of these magnetic pockets. However, this is not the case with axial flux machines, since the magnets here extend essentially in the radial direction. However, even here there is still a need to be able to increase the power density and torque density of such a machine in the simplest, most cost-effective, and most space-saving way possible.

[0009] CN 1 12 039 236 A describes an axial rotor of a rotary motor.

[0010] DE 10 2019 117 686 A1 describes a rotor device for an electrical machine, wherein the rotor poles each have an inner recess serving as a flux barrier.

[0011] Further prior art can be found in DE 199 41 107 A1, CN 2 11 930 361 U, CN 1 11 756 145 A, WO 2018 / 235 145 A1 and CN 1 04 638 863 A.

[0012] The object of the present invention is therefore to provide a rotor and an axial flux permanent magnet synchronous machine which allow the highest possible power and energy density while at the same time being as compact, simple and cost-effective as possible.

[0013] This object is achieved by a rotor and an axial-flux permanent-magnet synchronous machine having the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description, and the figures.

[0014] A rotor according to the invention for an axial-flux permanent-magnet synchronous machine is rotatable about an axis in a rotational direction and has a carrier disk made of a soft magnetic material, which, at least with respect to an axial disk portion of the carrier disk, is divided in the rotational direction into a plurality of magnetic sectors. These sectors are divided in the rotational direction into alternating first and second magnetic sectors. Furthermore, the rotor has a plurality of permanent magnets, each having a north pole and a south pole, each associated with a magnetic direction directed from its south pole to the north pole. At least two of the plurality of permanent magnets are arranged in each magnetic sector, and the at least two permanent magnets arranged in one of the respective magnetic sectors comprise two first permanent magnets.The permanent magnets arranged in the first magnet sectors are arranged such that their magnetic direction partly points in a first direction which is parallel to an axial direction, and the permanent magnets arranged in the second magnet sectors are arranged such that their magnetic direction partly points opposite to the first direction.Furthermore, the magnetic direction of the respective first permanent magnets is not parallel to the first direction and is inclined in the direction of rotation by a respective angle with respect to the first direction, wherein for at least one of the magnetic sectors, the two first permanent magnets arranged in the magnetic sector are assigned a common first magnetic pocket which is free of the soft magnetic material and which directly adjoins first ends of the two first permanent magnets facing one another in the direction of rotation and fills a first intermediate region in the direction of rotation between the first ends of the two first permanent magnets facing one another.The first magnetic pocket fills a second region which is many times larger than the first intermediate region and which lies behind the two first permanent magnets in the axial direction and which directly adjoins the first intermediate region in the axial direction, the first magnetic pocket widening in the axial direction with increasing distance from the first permanent magnets.

[0015] It has been shown that with the same number of magnets, a significantly higher energy density and power density can be provided if the magnetic pockets are made as large as possible and are arranged mainly behind the permanent magnets in the axial direction. The shared magnetic pocket of the two first permanent magnets can therefore be divided into the first intermediate region and the second region, which is arranged behind the two first permanent magnets in the axial direction. The second region is many times larger than the intermediate region, which means that the second region is at least twice as large in terms of volume as the first intermediate region, preferably even larger. Moreover, there is advantageously sufficient space behind the permanent magnets, particularly in or against the axial direction, to be able to provide very large magnetic pockets.This does increase the installation space of the axial flux machine somewhat in the axial direction, but due to its already very small extension in the axial direction this only plays a very minor role. The shared magnetic pocket can, for example, take up a volume within the carrier disk that is at least as large as the volume of one of the first permanent magnets, preferably even larger. In the direction of rotation, however, there is usually only little installation space between two first permanent magnets, depending on the design of the permanent magnets. It is precisely by designing the first magnetic pocket in such a way that it extends largely into an area that is positioned behind the permanent magnets in the axial direction that such a large first magnetic pocket can be realized in the first place.At the same time, this can be achieved in a particularly simple and cost-effective way, since no additional magnets are required for such an increase in power density and energy density, and larger magnetic pockets also lead to a reduced weight of the rotor, since these can, for example, be designed simply as holes or openings in the carrier disk, as described above. Optionally, the magnetic pockets can also be filled with an electrically and magnetically non-conductive material, such as a plastic, which also offers weight advantages over the soft magnetic material of the carrier disk. The design of the first magnetic pocket as a common magnetic pocket for the first two permanent magnets also has the advantage, particularly in contrast to the design of two magnetic pockets separated by a web, that flux leakage caused by the web can be avoided.This, in turn, contributes to increasing the efficiency of the rotor and, in particular, of the permanent-magnet axial flux machine in which the rotor is used. Unlike radial flux machines, such a web is not required in axial flux machines due to the different arrangement of the magnets and magnet pockets to absorb tensile forces resulting from the centrifugal forces during rotor rotation. Overall, this enables an increase in power and energy density in a simple, compact, and cost-effective manner.

[0016] The permanent magnets are preferably formed with at least two flat sides that lie opposite one another, one of which represents a north pole and the other the south pole. As defined above, the direction from the south pole to the north pole is referred to as the magnetic direction. The magnetic field lines outside the permanent magnets, in contrast, run from the north pole to the south pole. The magnetic direction thus corresponds to the magnetic field direction in the immediate vicinity of the north pole and south pole. A respective first permanent magnet can, for example, have a length in the radial direction, a height in the magnetic direction, and a width in a second direction that is perpendicular to the first and radial directions, wherein the first ends of the first permanent magnets then delimit these with respect to the second direction.As defined above, the magnetic direction is not aligned exactly parallel to the axial direction, but is inclined in or against the direction of rotation relative to the axial direction. The permanent magnets are, so to speak, rotated by a specific angle around an axis running in the radial direction, so that their magnetic direction encloses this specific angle with the axial direction. One of the two first permanent magnets of a same magnetic sector is preferably inclined by the specific angle in the direction of rotation with respect to the plane of rotation perpendicular to the axial direction, and the other of the second permanent magnets is inclined by the same specific angle but against the direction of rotation. In other words, the two permanent magnets of the same magnetic segment are inclined by the same angle with respect to the plane of rotation but in opposite directions.This makes it possible to generate a reluctance torque, as described at the beginning, which in turn brings with it the advantages also described at the beginning. This arrangement therefore preferably corresponds to the V-arrangement of the magnets mentioned at the beginning. The two first permanent magnets of a magnetic sector of the carrier disk can be understood as a magnet pair. Each magnetic sector therefore has such a magnet pair, which are arranged circumferentially in the direction of rotation with alternating directions of their magnetic directions. The fact that the magnetic direction points partly in or opposite to the first direction should be understood to mean that the magnetic direction is not parallel to the first direction, but has a directional component that points in or opposite to the first direction.

[0017] If, for example, the rotor is used in a double-stator single-rotor axial flux machine, the rotor can have two magnetic layers arranged next to each other in the axial direction. In this case, the rotor is arranged axially between two stators, with one of the magnetic layers assigned to and facing one of the stators, and the other of the magnetic layers facing the other stator. In this case, the rotor can have a carrier disk that is divided axially into two disk sections. This subdivision is intended to represent only an imaginary subdivision and not a spatially structured subdivision. Each of these disk sections can then be divided into a corresponding number of magnetic sectors. This division, too, should be understood as an imaginary division and not as a structural subdivision of the carrier disk itself.The magnetic sectors of a first disk part of the carrier disk can then also be arranged offset from one another in the direction of rotation with respect to the magnetic sectors of the second disk part of the carrier disk, for example by half the width of such a magnetic sector in the direction of rotation. The definition of the magnetic sectors and the orientation of the permanent magnets they comprise should apply accordingly to at least one such disk part of the carrier disk. If the carrier disk therefore optionally has several such disk parts, for example two disk parts, these can also differ in the arrangement of the magnetic sectors. However, it can also be provided, in particular if the rotor is used as a rotor for a single-stator single-rotor axial flux machine or for a double-rotor single-stator axial flux machine, that the carrier disk has only one disk part.In this case, the carrier disk does not contain two magnetic layers assigned to different stators. This is also the preferred variant. Nevertheless, the carrier disk can have multiple axial magnet rows assigned to the same stator, as will be explained in more detail later. In this case, the multiple magnet rows are then provided within the same magnet sector.

[0018] Furthermore, the permanent magnets can be embedded in the carrier disc, as also described above. In other words, the permanent magnets are not arranged on a surface of the carrier disc; instead, the carrier disc is provided with corresponding recesses in the axial direction, in which the permanent magnets are arranged and encapsulated, for example, using plastic, resin, or adhesive. However, the permanent magnets can also be attached in other ways, for example, purely mechanically. A combination of these attachment options is also conceivable.

[0019] Furthermore, each magnet sector can be designed as described for at least one magnet sector. Preferably, each first permanent magnet pair consisting of the two first permanent magnets of a respective magnet sector is assigned such a common first magnet pocket. Such a configuration is also conceivable, for example, for only every second magnet sector or the like. However, it is most efficient if all magnet sectors are designed identically. The further descriptions relating to the at least one magnet sector and in particular to the design of the permanent magnets and magnet pockets arranged in this magnet sector can thus be applied analogously to all other magnet sectors.

[0020] In a further particularly advantageous embodiment of the invention, at least one second permanent magnet is arranged in front of the first magnetic pocket for at least one of the magnetic sectors with respect to the axial direction. This is based on the knowledge that the energy density and power density can be increased enormously by means of an additional row of magnets in the axial direction within the same magnetic sector. In particular, the ratio of torque density to magnet costs can be optimized in this way. The magnet pair of the two first permanent magnets, which are then assigned to an identical first magnet row, forms a V in a plan view in the radial direction, wherein the first magnetic pocket is arranged in the region of the V tip, in such a way that it is arranged behind the permanent magnets in the direction in which the V tip points.In the axial region opposite the first magnet pocket, so to speak between the V-shaped legs of the first permanent magnets, there is still sufficient installation space available to integrate at least one further permanent magnet as part of a second magnet row, which can in particular be smaller than the two first permanent magnets. The integration of such a second permanent magnet therefore does not require any additional installation space. For example, two such second permanent magnets can also be arranged in this region. These can also be arranged in a V-shape to one another, corresponding to the first permanent magnets, and for example also have a common second magnet pocket, which is located in the direction of rotation in an intermediate region between the two second permanent magnets and partly also extends behind these two second permanent magnets in the axial direction.This can also be designed to be smaller than the first magnetic pocket. Magnetic pockets can also be attached to the opposite ends of both the first and second permanent magnets.

[0021] However, it has proven particularly efficient to use only one such second permanent magnet. It is precisely this single second permanent magnet that maximizes the ratio of torque density to magnet cost.

[0022] Therefore, it represents a further very advantageous embodiment of the invention if, for at least one of the magnet sectors, precisely one second permanent magnet is arranged in front of the first magnet pocket with respect to the axial direction, the magnetic direction of which is parallel to the axial direction and which is arranged partly between the two first permanent magnets, in particular in the direction of rotation. This enables a particularly space-efficient arrangement of such a second permanent magnet and permits a particularly efficient increase in energy density with only minor additional costs due to the additional magnet. This second permanent magnet is then arranged on the side of the first permanent magnets facing the stator, while the first magnet pocket is arranged at least for the most part on the side of the first permanent magnets facing away from the stator.This allows both the first and second permanent magnets to be positioned closer to the stator, allowing for more efficient operation.

[0023] If only one such second permanent magnet is provided per magnetic sector, it is also preferred that its magnetic direction is aligned parallel to the axial direction and thus to the first direction.

[0024] In a further advantageous embodiment of the invention, the first magnetic pocket extends directly adjacent to the first ends over at least a large part of their length, preferably over their entire length in the radial direction. This allows for maximum efficient use of the available space in the radial direction for forming the first magnetic pocket. The first magnetic pocket can completely penetrate the carrier disk in the radial direction, which also allows for particularly simple production.

[0025] It is further advantageous if the first magnetic pocket has a width in the direction of rotation that increases with increasing distance from the first permanent magnets over a large portion of the height of the first magnetic pocket in the axial direction. In other words, the first magnetic pocket can widen in or against the axial direction with increasing distance from the first permanent magnets. Since the magnetic pocket is therefore arranged mainly behind the first permanent magnets in the axial direction, sufficient installation space is also provided here to enable such a widening. This widening, in turn, allows the first magnetic pockets to be as large as possible, which in turn serves to increase efficiency.

[0026] In a further advantageous embodiment of the invention, the first magnetic pocket has a width in the direction of rotation that tapers conically toward the axis. This also allows for maximum efficient use of the available installation space. The first magnetic pocket can thus widen in the direction of rotation with increasing distance from the axis.

[0027] In principle, it is also conceivable for the permanent magnets to widen with increasing distance from the axis in the direction of rotation, so that they have a quasi-triangular shape when viewed from above in the axial direction. However, it is preferred for the magnets to be cuboid-shaped. Cuboid-shaped magnets can be manufactured significantly more cost-effectively than special geometric shapes. The option of making the first magnet pockets particularly large as described, in particular in the shape described, advantageously makes it possible to provide an extremely high torque density and energy density even without special shaping of the magnets. This, in turn, makes it possible to maximize the ratio of torque density to magnet costs. The length of the magnets in the radial direction preferably represents their largest dimension.Their height and width, as defined above, can, for example, be approximately equal, or the width can be slightly larger than their height in the magnetic direction. The distance between the two first permanent magnets in the direction of rotation thus increases with increasing distance from the rotation axis. The intermediate region, which represents part of the first magnetic pocket, is arranged within this distance range.

[0028] In a further very advantageous embodiment of the invention, the soft magnetic material is provided by a soft magnetic composite material. This is also referred to as an SMC (soft magnetic composite) material. Such a soft magnetic composite material can be provided from powder-like iron particles that are coated on all sides with an electrically insulating material, in particular a plastic, i.e., enclosed in such a material. Such a soft magnetic composite material can be formed into any desired shape, for example, by sintering, which enables the formation of complex three-dimensional structures within such a material.Similar to the use of laminated iron sheets, but in a significantly improved form, such a soft magnetic composite material also prevents or reduces eddy currents within the soft magnetic material through the electrical insulation surrounding the individual iron particles. While with laminated iron sheets such eddy currents can generally only be prevented in one direction, namely perpendicular to the iron sheets, such a soft magnetic composite material can prevent eddy currents isotropically in all directions. This allows the energy and torque density to be further increased, as there are significantly fewer losses through the carrier disc. At the same time, this enables the complex structure of the first magnetic pockets to be integrated into the carrier disc in a particularly simple manner. The integration of the permanent magnets is also particularly straightforward.

[0029] Since the use of such a soft magnetic composite material makes it particularly easy to create holes and apertures of any geometry in the carrier disc, the carrier disc can also have additional holes or apertures that are not directly adjacent to the permanent magnets integrated into the carrier disc. These then serve solely to reduce the weight of the rotor. This also allows for savings in soft magnetic material for the carrier disc.

[0030] Furthermore, the invention also relates to an axial-flux permanent-magnet synchronous machine with a rotor according to the invention or one of its embodiments. The advantages described for the rotor according to the invention and its embodiments apply equally to the axial-flux permanent-magnet synchronous machine.

[0031] According to a further advantageous embodiment of the invention, the axial flux permanent magnet synchronous machine is designed as a single-stator double-rotor axial flux machine having a stator and two rotors according to the invention or two rotors according to embodiments of the invention, wherein the stator is arranged in the axial direction between the two rotors.

[0032] In principle, it is also possible for the axial-flux permanent magnet synchronous machine to be designed as a single-stator, single-rotor axial-flux machine or a double-stator, single-rotor axial-flux machine. In both cases, it would then comprise only a single rotor and one or two stators, respectively. From a power density perspective, however, a double-stator, single-rotor arrangement is less efficient because the stator yoke of the two stators requires additional installation space and is very heavy due to the iron. This allows a single-stator, double-rotor axial-flux machine to be designed significantly more efficiently in terms of installation space and weight. However, significantly higher values ​​can also be achieved with a single-stator, double-rotor axial-flux machine in terms of power density and torque density than with single-stator, single-rotor axial-flux machines or double-stator, single-rotor axial-flux machines.

[0033] In this case, the stator is arranged between the two rotors. The rotors are each designed so that the first magnetic pockets face away from the stator, while the first permanent magnets face toward the stator. The first permanent magnets are therefore arranged closer to the stator than the first magnetic pockets. There is an air gap between the stator and the respective rotor. The first magnetic pockets are therefore located on the side of the first permanent magnets facing away from the air gap.

[0034] Furthermore, a motor vehicle with an axial-flux permanent magnet synchronous machine according to the invention or one of its embodiments is also considered to be part of the invention. This can represent a drive device of the motor vehicle.

[0035] The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.

[0036] The invention also encompasses combinations of the features of the described embodiments. The invention therefore also encompasses implementations that each comprise a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.

[0037] Exemplary embodiments of the invention are described below. Shown are: Fig. 1 is a schematic representation of an axial flux synchronous machine with V-shaped magnets according to an example not belonging to the invention; Fig. 2 a graphical representation of the composition of the total torque from magnetic component and reluctance component according to an embodiment of the invention; Fig. 3 is a schematic representation of an axial flux permanent magnet synchronous machine designed as a double rotor single stator axial flux machine according to an embodiment of the invention; Fig. 4 a schematic representation of a rotor for an axial flow machine according to an embodiment of the invention; Fig. 5 a schematic representation of the rotor from Fig. 4 as a transparent representation, according to an embodiment of the invention; Fig. 6 a schematic representation of a magnet segment of the rotor from Fig. 4 in a plan view of the radial direction; Fig. 7 a schematic and perspective as well as transparent representation of the magnet segment of the rotor from Fig. 4; Fig. 8 a schematic and transparent representation of a magnet segment with an additional permanent magnet for a rotor according to an embodiment of the invention; Fig. 9 a schematic and perspective view of the magnet segment from Fig. 8; Fig. 10 a schematic, perspective and transparent representation of the magnet segment from Fig. 8; Fig. 11 is a schematic and perspective view of a rotor according to a further embodiment of the invention; Fig. 12 is a schematic representation of a magnet segment for a rotor according to another embodiment of the invention; Fig. 13 a schematic, perspective and transparent representation of the magnet segment from Fig. 12; Fig. 14 is a schematic diagram showing the structure of a soft magnetic composite material for use in a rotor according to an embodiment of the invention; Fig. 15 is a further schematic representation of a soft magnetic composite material for use in a rotor according to an embodiment of the invention; Fig. 16 is a further schematic and perspective view of a rotor according to a further embodiment of the invention, in which additional openings are now provided in the carrier disk; and Fig. 17 a further schematic and perspective representation of a rotor according to a further embodiment of the invention, in which the magnets and the other openings in the carrier disk are now cast with a non-soft magnetic material.

[0038] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0039] In the figures, the same reference symbols designate elements with the same function.

[0040] Fig. Figure 1 shows a schematic representation of a permanent-magnet axial flux machine 10 according to an example not belonging to the invention. In principle, such axial flux machines 10 can take on numerous forms. Fig. 1 shows a variant according to which the axial flux machine 10 is designed as a single-rotor, double-stator axial flux machine. The rotor 12 is located in the axial direction a between two stators 14a and 14b. The rotor 12 is rotatable about a rotation axis A. The rotor 12 further comprises a plurality of magnets 16, which are arranged in the axial direction in two layers, namely an upper layer and a lower layer, based on the illustration in Fig. 1. The upper layer in the axial direction a is assigned to the upper stator 14a, and the lower layer to the lower stator 14b. The magnets 16 are further embedded in a carrier 18, which is disk-shaped. The special feature of this arrangement of the magnets 16 is in particular that they are arranged in a V-shape to one another. In order to be able to describe this better, a magnetic direction m is defined which is directed from the side of a magnet 16 with the magnetic south pole to the magnetic north pole. In conventional axial flux machines, the magnetic directions m of the permanent magnets 16 are typically aligned parallel to the axis of rotation A. However, due to the V-shape of the magnets 16 illustrated here, the respective magnetic directions m are inclined by an angle to the axial direction a, in particular in or against the direction of rotation u.This allows a reluctance torque to be generated, which has the great advantage of providing a significantly higher overall power density and torque density. This is illustrated graphically using . Fig. 2 illustrates. Fig. Figure 2 shows a graphical representation of the torque M as a function of the electrical angle α in degrees. The electrical angle α is the product of the number of pole pairs and the geometric angle α', so that, for example, the electrical angle α is equal to the geometric angle α' if the number of pole pairs is 1, e.g. for a two-pole electric machine. The torque M plotted on the ordinate is plotted in unit values. Curve M1 illustrates the total torque, which is made up of a purely magnetic component, illustrated by curve M2, and a reluctance torque component, illustrated by curve M3. In rotors with only surface magnets, no reluctance torque is generated, but only a torque originating from the magnets, as illustrated by curve M2.In synchronous reluctance machines, only a reluctance torque is generated, as illustrated by curve M3, but no magnetic torque. A synchronous reluctance machine does not contain a permanent magnet in the rotor. In rotors where the magnets are arranged in a V-shape, such as in . Fig. As shown in Figure 1, both a magnetic torque and a reluctance torque are generated, resulting in the overall torque curve M1. Therefore, such machines can generate more torque and power with the same number of magnets than, for example, machines with only surface magnets, which do not generate reluctance torque.

[0041] Accordingly, the invention and its embodiments also relate to rotors whose permanent magnets are arranged in such a V-shape, because this allows the aforementioned significant advantages to be achieved. In addition, the invention now makes it possible to further increase the torque density and power density, as will be explained in more detail below.

[0042] Fig. 3 shows a schematic representation of an axial flux permanent magnet synchronous machine 20 according to an embodiment of the invention. In this example, it is designed as a single-stator, double-rotor axial flux machine 20. The synchronous machine 20 thus has a single stator 22 and two rotors 24. The stator 22 is arranged in the axial direction a between the two rotors 24. The rotors 24 are rotatable about the axis A. In principle, the invention and its embodiments explained in more detail below can also be used in the same way for a single-stator, single-rotor axial flux machine, according to which one of the two rotors 24 would then be omitted, or for a double-stator, single-rotor axial flux machine, as shown, for example, in Fig. 1. In this case, one of the two rotors 24 could also be formed with two magnetic layers, which are assigned to the respective outer stators. Fig. In this case, the single rotor 24 shown in Figure 3 could then represent half of a rotor as would be designed for such a double-stator, single-rotor axial flux machine. The other half would simply be obtained by mirroring the rotor 24 on a mirror plane perpendicular to the axis A. The two rotor halves could then also be arranged offset from one another in the direction of rotation u, and the first magnetic pockets 26, explained in more detail later, could also be arranged overlapping in the direction of rotation u and meshing with one another like a gear. However, single-stator, double-rotor axial flux machines 20 in particular have particularly great advantages over the other alternatives mentioned, since they can achieve a greater power density or torque density.They also have advantages in terms of installation space and weight, since, for example, a double-stator single-rotor axial flux machine requires an additional iron yoke, which in turn requires a lot of installation space and is very heavy.

[0043] A rotor 24 for such a synchronous machine 20 is again separately in Fig. 4 in a perspective view and in Fig. 5 in a transparent representation. The rotor 24 comprises, on the one hand, a carrier disk 28 made of soft magnetic material, in particular of soft magnetic composite material, as will be explained in more detail later. Embedded in this carrier disk 28 are, on the one hand, several permanent magnets 30, which are also referred to below as first permanent magnets 30. In principle, the carrier disk 28 can initially be divided into several magnet segments 28a, 28b, as indicated by the dashed lines in Fig. 4. These magnet segments 28a, 28b can in turn be grouped into first magnet segments 28a and second magnet segments 28b. These alternate in their arrangement in the direction of rotation u. Accordingly, there are just as many first as second magnet segments 28a, 28b. In this example, the rotor 24 comprises ten magnet segments 28a, 28b, which accordingly form five pole pairs. Two first permanent magnets 30 are arranged in each of the magnet segments 28a, 28b. The magnetic direction m, which points from the magnetic south pole to the magnetic north pole of a respective magnet 30, is then illustrated by arrows, whereby not all of these arrows are provided with a reference symbol for reasons of clarity. The dimension of the permanent magnets 30 in the magnetic direction m can, for example, define a height of the respective permanent magnets 30, while their extension in the radial direction r has a length l (cf. Fig. 5) and an extension of the permanent magnets 30 perpendicular to the radial direction r and perpendicular to the magnetic direction m has a width b (cf. also Fig. 5). Here, too, the magnets 30 are advantageously arranged such that their magnetic direction m is not parallel to the rotation axis A, but is inclined relative to it by a certain angle in or against the rotation direction u, so that in this way, too, a reluctance torque can advantageously be generated in addition to the magnetic moment, which in turn makes it possible to provide a significantly higher torque density or power density overall.

[0044] This torque density or power density can now advantageously be further increased by assigning a common first magnetic pocket 26 to the two first permanent magnets 30 of a magnetic sector 28a, 28b. This first magnetic pocket 26 represents an area within the carrier disk 28 that is free of soft magnetic material and in which no magnets 30 are arranged. The first magnetic pocket 26 thus forms a reluctance cavity, in particular in the center between the magnets 30, for generating a high reluctance torque. These first magnetic pockets 26 can, for example, be designed as openings in the radial direction r in the carrier disk 28, i.e., they can completely penetrate the carrier disk 28 in the radial direction r. Preferably, one such common first magnetic pocket 26 is provided for each magnet pair consisting of two permanent magnets 30 per magnetic sector 28a, 28b.

[0045] The magnets 30 in a respective first magnet sector 28a are oriented such that their magnetic direction m partially points in the axial direction a, while the magnets 30 in the second magnet sectors 28b are oriented such that their magnetic direction m has a portion directed opposite to the axial direction a. The exact geometry of these first magnet pockets 26 is now described with reference to Fig. 6 and Fig. 7, each of which shows a schematic representation of a single magnet segment 28a of the rotor 24 from Fig. 4 and Fig. 5 illustrate. Fig. 6 shows such a magnet segment 28a in a plan view of the radial direction r in a transparent representation, and Fig. 7 in a perspective and transparent representation. The permanent magnets 30 of the magnet sector 28a each have an end 30a, which in this example defines the side of the permanent magnets 30 that delimits the permanent magnets 30 in the direction of their width b and which face each other in the direction of rotation u. The first magnet pocket 26 can now be divided into two regions, namely a first intermediate region 26a, which is arranged between the two first ends 30a of the two first permanent magnets 30 in the direction of rotation u, and a second region 26b, which is arranged behind the permanent magnets 30 with respect to the axial direction a. The second region 26b is many times larger than the intermediate region 26a.This means that more than the majority of the first magnetic pocket 26 lies behind the permanent magnets 30 in the axial direction a and thus on a side of the permanent magnets 30 facing away from the air gap to the stator arranged adjacent in the axial direction a. This first magnetic pocket 26 consequently serves as a reluctance cavity for both permanent magnets 30. This first magnetic pocket 26 is therefore advantageously not separated into two separate pockets, for example by a web, which in turn would lead to flux leakage. Furthermore, the knowledge is used here that sufficient installation space is available in the axial direction a to be able to integrate such a large first magnetic pocket 26 into the carrier disk 28. Since axial flux machines can already be designed very compactly in the axial direction a, this additional installation space in the axial direction a hardly plays a role. The magnets 30 can also be designed as simple cuboid-shaped magnets 30.Accordingly, a distance between the two magnets 30 also increases with increasing distance from the rotation axis A, as can be seen particularly in . Fig. 7 can be clearly seen. Accordingly, the first magnetic pocket 26 also widens with increasing distance from the axis A. In other words, the geometry of the first magnetic pocket 26 tapers conically in the direction of the axis of rotation A. For example, a width B of the magnetic pocket 26 can be defined in the direction of rotation u, which width does not, of course, have to be constant across the entire first magnetic pocket 26. This width B of the first magnetic pocket 26 therefore increases opposite to the axial direction a with increasing distance from the permanent magnets 30, at least across a large part of the first magnetic pocket 26 in the axial direction a, and likewise in the radial direction with increasing distance from the axis of rotation A.

[0046] In the axial direction between the first intermediate region 26a and the second region 26b of the first magnetic pocket 26, in the region of the first ends 30a of the permanent magnets 30, there is a holding projection 28c of the carrier disk 28. This serves to mechanically fix and hold the magnets 30 in their receiving regions. This can advantageously provide additional stabilization of the magnets 30, particularly in the direction of rotation u. These projections 28c can run along the edge of the permanent magnets 30 that borders the respective first ends 30a. Furthermore, further magnetic pockets 32, e.g. second magnetic pockets 32, can also be arranged at the ends 30b of the magnets 30 opposite the first ends 30a. However, these are significantly smaller than the first magnetic pocket 26.

[0047] The two first magnets 30 cannot be the only magnets arranged in a same magnet sector 28a, 28b. In particular, it has proven particularly advantageous if at least one additional magnet row is arranged in the axial direction a, which comprises at least one further second permanent magnet 34, as shown in Fig. 8. This further second permanent magnet 34 has a magnetic direction m which is aligned parallel to the axis of rotation A and is also aligned centrally with respect to the two first permanent magnets 30. In the direction of the width of this second magnet 34, which in this case is aligned parallel to the circumferential direction or direction of rotation u, two respective magnetic pockets 36, e.g. third magnetic pockets 36, are in turn adjacent to the second magnet 34. This second magnet 34 is also arranged directly opposite the first magnetic pocket 26 in the axial direction, that is to say in front of the permanent magnets 30. The remaining arrangement, however, can be designed as previously described.

[0048] Fig. 9 and Fig. 10 show the magnet segment 28a again with these now three permanent magnets 30, 34, namely the two first permanent magnets 30, as well as the additional second smaller permanent magnet 34. This can extend in the radial direction r as far as the two first permanent magnets 30, but can be somewhat smaller with regard to its height in the magnetic direction m, and optionally also with regard to its width in the direction of rotation u.

[0049] Fig. 11 shows a schematic representation of another example of a rotor 24 as a whole, which now has the further second magnet 34 in each magnet segment 28a, 28b in addition to the two first magnets 30. Otherwise, the rotor 24 can be designed as previously described.

[0050] This arrangement, with just one additional second magnet 34, has proven to be the most efficient in terms of optimizing the ratio of torque density to magnet costs. Nevertheless, other configurations are also conceivable. For example, this additional axial magnet row can also comprise multiple magnets, for example, two second magnets 34, as shown in Fig. 12 and Fig. 13 is illustrated.

[0051] Fig. 12 shows in particular a schematic representation of a magnet segment 28a in a plan view of the radial direction relative to the air gap 39 to the stator 22 (cf. Fig. 3) and Fig. 13 shows a schematic perspective and transparent representation of this magnet segment 28a. In this example, the two second magnets 34 are also arranged in a V-shape relative to one another and have a common fourth magnet pocket 38, as well as two separate third magnet pockets 36 at the opposite ends. However, this common fourth magnet pocket 38 is significantly smaller than the first magnet pocket 26 and, in the direction of rotation u, is located essentially only between the second permanent magnets 34 and does not protrude beyond them or protrudes only slightly in the axial direction a.

[0052] Due to the V-shaped arrangement of the first magnets 30, it is therefore advantageously possible to use the previously unused area provided by this V-shape to provide a further row of magnets with at least one second magnet 34 in order to be able to further increase the torque density and power density in an efficient manner.

[0053] As already mentioned, it is preferred that the carrier disc 28 is formed from a soft magnetic composite material 40, which is shown schematically in Fig. 14 and Fig. 15. Such a soft magnetic composite material 40 comprises powdered iron particles 42. As shown in Fig. 14, these iron particles 42 are completely surrounded by an electrically insulating coating 44. According to Fig. 15, the iron particles 42 are embedded in such an electrically insulating matrix 44. By sintering, such a soft magnetic composite material 40 can be formed into any complex three-dimensional geometry. Accordingly, such a soft magnetic composite material 40 is particularly suitable for forming a carrier disk 28 for a rotor 24 according to the invention or one of its embodiments. This material can also be used for the stator 22 as a carrier for the coil windings. As shown in Fig. As shown in Figure 15, this composite material 40 has the effect of effectively preventing eddy currents 46, which is achieved by the electrically insulating matrix 44 or the electrically insulating coating 44 around the iron particles 42. In contrast to laminated iron sheets, this eddy current suppressing effect is isotropic in the case of such a composite material 40. This composite material 40 allows the special three-dimensional rotor shapes of the rotor 24 to be manufactured in a particularly simple, cost-effective, and efficient manner, which would be very difficult or expensive to achieve with conventional laminated electrical sheets.

[0054] Such a composite material 40 therefore has the following properties: It is magnetically conductive and consists of two or more materials, namely a soft magnetic material, in particular metal powder, and a composite material such as plastic. Such a composite material 40 represents a composite material. Metal buffer particles are embedded in the composite material, whereby two adjacent metal powder particles 42 do not touch each other and therefore have no metallic, electrically conductive interface. Accordingly, there is no electron traffic between two adjacent metal buffer particles 42 and, accordingly, no or only minimal eddy currents 46, resulting in very low iron losses. Due to the low iron losses, it is very advantageous to use this composite material 40 in electric motors as a stator or rotor material, or both.

[0055] Fig. Figure 16 shows a further schematic and perspective view of a rotor 24 according to a further embodiment of the invention, in which the magnets as well as the various other openings in the carrier disk 28, such as the magnet pockets 26, 32, 36, are now cast with a non-soft magnetic material, for example, plastic or epoxy resin. It is particularly advantageous to fill the reluctance openings, i.e., the magnet pockets, for example, by means of transfer molding, epoxy resin, or plastic injection molding. This creates a good magnet fixation in the rotor 24. The casting material is electrically and magnetically non-conductive, and the magnetic properties are similar to those of vacuum or air (µ r=1). Such a spout can be realized for all variants of the rotors 24 shown, i.e., with only two first magnets 30 without second magnets 26, with one second magnet 26, or with two second magnets 26, as well as optional additional magnets not shown, and any number of magnetic pockets.

[0056] In addition, additional openings or recesses or holes can be provided in the rotor 24, which do not represent magnetic pockets or reluctance cavities, and which can also be filled with such a casting compound 48. Such additional openings are, for example, in Fig. 17 illustrated.

[0057] In particular, Fig.17 again shows a schematic and perspective illustration of a rotor 24 according to a further exemplary embodiment of the invention, which can be designed as described above except for the differences described below. Here, on the one hand, groove-shaped depressions 50 which run in the radial direction r are formed in the carrier disk 28 on one of its surfaces 28d. In this example, such a depression 50 is arranged in each of the magnet segments 28a, 28b. In this example, this surface 28d represents the surface of the rotor 24 facing the stator 22. In addition, further through-openings 52 are arranged in the carrier disk 28, which can have a circular base perpendicular to the radial direction and, for example, can also taper conically in the radial direction in the direction of the axis of rotation A, i.e. can have a truncated cone-shaped basic shape.In principle, such openings 52 can also be of any desired geometric shape. In this example, one such opening 52 is provided in the boundary area between each two magnet segments 28a, 28b. Such openings 52 and the grooves 50 can achieve additional weight savings. At the same time, such openings 52 can be realized particularly easily by using a composite material 40. Any number of additional openings, openings, or recesses can be provided in addition or alternatively, in any desired geometry and arrangement relative to one another, in the still free area of ​​the carrier disk 28.

[0058] Overall, the examples show how the invention can be used to provide rotor cores, i.e. rotors, for axial flux permanent magnet synchronous machines with enlarged magnetic pockets for generating a reluctance torque.

Claims

[1] Rotor (24) for an axial flux permanent magnet synchronous machine (20), - wherein the rotor (24) is rotatable about an axis (A) in a direction of rotation (u); - wherein the rotor (24) has a carrier disc (28) made of a soft magnetic material (40) which is divided into a plurality of magnetic sectors (28a, 28b) in the direction of rotation (u) at least with respect to an axial disc part of the carrier disc (28), which magnetic sectors are divided into first and second magnetic sectors (28a, 28b) arranged alternately with one another in the direction of rotation (u); - wherein the rotor (24) has a plurality of permanent magnets (30, 34), each having a north pole and a south pole, each of which is assigned a magnetic direction (m) directed from its south pole to the north pole; - wherein at least two of the plurality of permanent magnets (30, 34) are arranged in each magnet sector (28a, 28b), and the at least two permanent magnets (30, 34) arranged in one of the respective magnet sectors (28a, 28b) comprise two first permanent magnets (30); - wherein the permanent magnets (30, 34) arranged in the first magnet sectors (28a) are arranged such that their magnetic direction (m) points partly in a first direction (a) which is parallel to an axial direction (a), and wherein the permanent magnets (30, 34) arranged in the second magnet sectors (28b) are arranged such that their magnetic direction (m) points partly opposite to the first direction (a); - wherein the magnetic direction (m) of the respective first permanent magnets (30) is not parallel to the first direction (a) and is inclined in the direction of rotation (u) by a respective angle relative to the first direction (a); - for at least one of the magnet sectors (28a, 28b), a common first magnet pocket (26) is assigned to the two first permanent magnets (30) arranged in the magnet sector (28a, 28b), which first magnet pocket is free of the soft magnetic material and which directly adjoins first ends (30a) of the two first permanent magnets (30) facing one another in the direction of rotation (u) and fills a first intermediate region (26a) in the direction of rotation (u) between the first ends (30a) of the two first permanent magnets (30) facing one another; where - the first magnet pocket (26) fills a second region (26b) which is many times larger than the first intermediate region (26a) and which lies behind the two first permanent magnets (30) with respect to the axial direction (a) and which directly adjoins the first intermediate region (26a) with respect to the axial direction (a), - wherein the first magnet pocket (26) widens with respect to the axial direction (a) with increasing distance from the first permanent magnets (30). [2] Rotor (24) according to claim 1, characterized by that for the at least one of the magnet sectors (28a, 28b) at least one second permanent magnet (34) is arranged in the axial direction (a) in front of the first magnet pocket (26). [3] Rotor (24) according to claim 2, characterized by that for the at least one of the magnet sectors (28a, 28b) in the axial direction (a) in front of the first magnet pocket (26) there is arranged exactly one second permanent magnet (34), the magnetic direction (m) of which is parallel to the axial direction (a) and which is arranged in particular in the direction of rotation (u) partly between the two first permanent magnets (30). [4] Rotor (24) according to one of the preceding claims, characterized bythat the first magnetic pocket (26) extends directly adjacent to the first ends (30a) over at least a large part of their length (l), preferably over their entire length (l) in the radial direction (r). [5] Rotor (24) according to one of the preceding claims, characterized by in that the first magnetic pocket (26) has a width (B) in the direction of rotation (u) which increases with respect to the axial direction (a) with increasing distance from the first permanent magnets (30) over a large part of a height of the first magnetic pocket (26) in the axial direction (a). [6] Rotor (24) according to one of the preceding claims, characterized by that the first magnetic pocket (26) has a width (B) in the direction of rotation (u) which tapers conically in the direction of the axis (A). [7] Rotor (24) according to one of the preceding claims, characterized by that the permanent magnets (30, 34) are cuboid-shaped. [8] Rotor (24) according to one of the preceding claims, characterized by that the soft magnetic material (40) is provided by a soft magnetic composite material (40). [9] Axial flux permanent magnet synchronous machine (20) with a rotor (24) according to one of the preceding claims. [10] Axial flux permanent magnet synchronous machine (20) according to claim 9, characterized by that the axial flux permanent magnet synchronous machine (20) is designed as a single-stator double-rotor axial flux machine (20) having a stator (22) and two rotors (24) according to one of claims 1 to 7, wherein the stator (22) is arranged in the axial direction (a) between the two rotors (24).

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