Rotor for an electric axial flux machine

Abstract

The invention relates to a rotor (20) for an electric axial flux machine (10), wherein the rotor (20) is designed as a multipole magnet. Furthermore, the invention relates to an electric machine (10) comprising at least one stator (30) and at least one such rotor (20).

Description

[0001] The invention relates to a rotor for an electric axial flux machine, wherein the rotor is designed as a multipole magnet. The invention also relates to an electric machine comprising such a rotor.

[0002] Electric machines can be used as working machines for electrically powered motor vehicles, such as electric and hybrid vehicles. Electric machines of various designs can be used for this purpose, with an electric machine typically having a stator that is fixed in position and rotation and a rotor that is movable relative to the stator.

[0003] In electric machines, active components incorporate magnetic field-generating systems, for example, in the form of current-generating windings, to produce a magnetic flux that can be maximized by an iron core. The rotor can then rotate relative to the stationary stator, which is typically equipped with electromagnetic coils. A narrow air gap separates the coils. These coils generate an alternating magnetic field that interacts with the rotor's magnetic field, causing the rotor and thus the electric motor to rotate.

[0004] Electrical machines designed for a generated radial flux are largely researched and well-established. However, due to ever-increasing demands for torque and power densities, as well as further limitations on installation space, new approaches to electrical machine design are necessary. Axial flux machines, for example, offer a promising solution. These are already widely used in consumer electronics and automation technology.

[0005] Axial flux machines exhibit high power and torque density, but present a significant technical development challenge with regard to the rotor for such machines. Industrialization and / or cost reduction can also be demanding. Due to large diameters and high centrifugal forces, the design of such a rotor must, compared to conventional concepts, compromises between stiffness, lightweight construction, performance, and cost. Known solutions often use bands with carbon fibers, stainless steel, and / or titanium, and magnets bonded to a laminated core, which can lead to increased costs for raw materials and manufacturing processes.

[0006] Against this background, an object of the invention is to improve a rotor for an electric axial flux machine. In particular, a rotor for an electric axial flux machine is to be improved in such a way as to enable cost savings.

[0007] This problem is solved by a rotor for an electric axial flux machine with the features of claim 1 and an electric machine with the features of claim 9. The dependent claims relate to advantageous embodiments of the invention.

[0008] According to a first aspect, a rotor for an electric axial flux machine is specified, wherein the rotor, or at least one rotor core, is designed as a monolithic multipole magnet. The monolithic or one-piece design of such a multipole magnet improves the stiffness of the rotor. Furthermore, the resulting reduction or elimination of adhesive bonds can help to mitigate risks related to adhesive technology, operating temperatures, and quality control.

[0009] According to a further aspect, an electric machine, in particular an axial flux machine, is proposed, comprising at least one stator and at least one rotor, the rotor being configured as described herein. An electric axial flux machine is, in particular, an electric motor whose rotor, and especially also the stator, has a disk shape. Typically, the diameter of an axial flux machine is larger than its axial length, which can result in advantages with regard to space utilization. The axial flux machine comprises at least one stator and at least one rotor described herein, the rotor being able to be arranged between two stators. In some embodiments, a stator can also be arranged between two rotors, or other numbers and sequences of stators and rotors, such as a one-to-one ratio, can be provided.The respective design allows for improved space utilization.

[0010] A gap or air gap between the rotor and stator, and thus the direction of the magnetic flux between them, runs parallel to the axis of rotation of an axial flux machine, in contrast to the concentric cylindrical geometry of a radial flux motor, where the magnetic flux runs radially. The stator can have coils positioned via stator slots, which are configured to reverse their polarity, thereby setting the rotor in motion or rotation about its axis, or the axis of rotation of the electric machine. In an axial flux machine, the entire diameter of the rotor can be utilized, with the magnets or magnetic poles being, or potentially being, positioned further from the axis of rotation than in a radial flux machine. This results in a greater leverage effect and thus a higher torque, particularly with the same power input and current consumption.This can, for example, enable up to 30% higher torque density compared to a radial flux motor. Power density can also be increased by a factor of up to 2.5.

[0011] A monolithic multipole magnet is, in particular, an axially multipole magnetized magnet, wherein the multipole magnet has more than one pair of magnetic poles or more than two differently polarized magnetic poles along its geometric axis or axis of rotation and / or axial direction. The axial multipole magnetization can be circular, for example, depending on the arrangement of the magnetic poles, and can be, for example, a circular or ring-shaped ferrite magnet, a samarium-cobalt magnet, or a neodymium magnet.

[0012] Power losses, particularly in the form of iron losses in iron cores and / or eddy current losses in solid components, which can occur, for example, in the iron cores of conventional rotors and / or a steel rotor carrier, can be eliminated. This can improve the efficiency of the electric axial flux machine, especially over a wider speed range. By reducing such losses, the mass of other materials, such as copper and iron, required to generate the magnetic flux can also be reduced. In one embodiment, the rotor, or at least one rotor core, is made of a hard magnetic material. A hard magnetic material, or permanent magnet, has a high coercivity and can therefore offer high resistance to external magnetic fields.By using a hard magnetic material, magnetization and demagnetization can be avoided, as these can only be achieved through very strong external fields. This allows for a constant magnetic field, thereby improving the continuous performance of the rotor and / or the axial flux machine. A hard magnetic material could be, for example, neodymium-iron-boron (NdFeB) and / or an alloy of iron, cobalt, nickel, and / or at least one suitable ferrite.

[0013] In one embodiment, the rotor has a predetermined specific electrical resistance. This specific resistance is selected, in particular, such that eddy currents in the rotor, the gap, and / or the axial flux machine can be reduced, thereby improving the thermal stability of the axial flux machine. This reduces power losses, which in turn improves thermal properties and, for example, reduces heat generation, thus enabling a more geometrically compact design of the cooling system for the rotor and / or the axial flux machine.

[0014] In one embodiment, the rotor comprises a non-metallic permanent magnet material. Such non-metallic magnets are also known, in particular, as ceramic magnets based on iron oxide. In other embodiments, organic polymers with permanent magnetic properties can be used, which exhibit ferromagnetic properties, especially at a predetermined temperature. In other embodiments, the rotor can have a polymer matrix containing magnetic particles. This can result in improved corrosion resistance for the rotor.

[0015] In one embodiment, the rotor features a magnetized ferrite. Ferrite is, in particular, a poorly or non-conductive ferromagnetic ceramic material, which may, for example, contain iron oxide, magnetite, and / or metal oxides. This eliminates the need for a coating and thus the associated material and process costs. As a result, cost-effective magnets can be produced, for example, using a pressing process.

[0016] In one embodiment, the rotor is designed in the shape of an annular disk. The poles are arranged uniformly around the circumference of the annular disk. In some embodiments, the polarization on the two (flat) sides of the annular disk can be different, particularly opposite. The annular disk can be configured on its inner circumference to accommodate or be connected to a shaft or rotor shaft of the axial flux machine.

[0017] In one embodiment, the rotor, in its shaft connection area for connection with a rotor shaft, particularly of the axial flux machine, has a material different from the rotor material, in particular a non-magnetic material. This allows for improved connection properties or suitability in the area of ​​an inner circumference of the rotor or the multipole magnet, in order to provide a secure, rotationally and / or displacement-resistant connection between the rotor and, in particular, the driven shaft.

[0018] In one embodiment, the rotor has at least one cooling channel for a cooling fluid. The cooling channel can be arranged axially and / or radially within the multipole magnet to enable improved heat transfer. The cooling fluid can be used for cooling, heat exchange, and / or heat dissipation of the rotor by means of a hollow-shafted rotor shaft and / or a cooling device, in order to reduce thermal stress or prevent thermal overload.

[0019] In one embodiment, the axial distance between the at least one rotor and the at least one stator is adjustable. For example, increasing the axial distance between the rotor and stator can lead to a lower magnetic flux density in the stator or to a weakening of the field. This eliminates the need for additional currents to achieve electrically induced field weakening, thereby avoiding the ohmic losses associated with such currents. Furthermore, the reduced flux density in the stator can lead to reduced hysteresis and eddy current losses. Overall, the magnetic field strength, and thus the torque, can be adjusted to enable flexible use of the electric machine.

[0020] In one embodiment, the electric machine is configured to provide a cooling fluid for cooling the rotor. For this purpose, the electric machine can, in particular, have a cooling device that can utilize a cooling fluid and / or lubricant from the axial flux machine to cool the rotor and / or other components of the electric machine. The use of the monolithic multipole magnet can improve thermal degradation, which can be further enhanced by additional cooling of the rotor.

[0021] Further advantages and application possibilities of the invention will become apparent from the following description in conjunction with the figures. Fig. Figure 1 shows an embodiment of a rotor for an electric axial flux machine according to the present invention. Fig. Figures 2a - 2c show schematic sections of different embodiments of an electrical machine according to the present invention.

[0022] Fig. Figure 1 shows a rotor 20 for an electric axial flux machine according to a first embodiment of the present invention in a view along an axis of rotation of the rotor.

[0023] The rotor 20 is designed as a monolithic multipole magnet and, in the illustrated embodiment, has four magnetic poles 21a, 21b, which are arranged adjacent to each other in the circumferential direction on the ring-shaped rotor 20. In other embodiments, the multipole magnet can also have six, eight, or more poles 21a, 21b, which are arranged alternately in the circumferential direction on the rotor 20.

[0024] A monolithic multipole magnet 20 is a magnet with multiple poles 21a, 21b that consists of a single piece and / or is manufactured from a single piece, or is inseparably assembled and / or formed in one piece. For the purposes of the present invention, the term multipole magnet refers in particular to a magnet with multiples of two magnetic poles 21a, 21b, which are arranged symmetrically around an axis and with alternating polarity. The rotor 20 can be made of a hard magnetic material, in particular a non-metallic permanent magnet material or a magnetized ferrite, or be manufactured from such a material. This allows for permanent magnetization of the rotor 20 and thus, in particular, improves the continuous power output of an electric machine.

[0025] At a shaft connection area 22 of the rotor 20, which is designed and / or intended for connection with a rotor shaft of an electric machine, the rotor 20 may have a non-magnetic material in order to improve the connection with the rotor shaft.

[0026] In Fig. 2a is a first embodiment of an electric axial flux machine 10 or a rotor-stator arrangement of such an electric machine 10 shown in a schematic side view.

[0027] The rotor 20 is fixed against rotation and displacement on a rotor shaft 11 of the electric machine 10 and is rotatable about an axis of rotation D of the electric machine 10. The rotor 20 has multiple poles 21a, 21b and is formed in one piece. A stator 30 is associated with the rotor 20, arranged parallel to it and configured to provide a magnetic field. For this purpose, the stator can have radially extending slots 31, which can accommodate current-carrying windings (not shown here).

[0028] Fig. Figure 2b shows a second embodiment of an electric axial flux machine 10 or a rotor-stator arrangement of such an electric machine 10 in a schematic side view.

[0029] This electric machine 10 has a so-called I-arrangement, in which a rotor 20 is arranged axially between two stators 30. In the illustrated embodiment, the rotor 20 has polarization on both (flat) sides of the annular disk, which is opposite in direction; that is, the first poles 21a are arranged opposite the second poles 21b, which are polarized in the opposite direction. The poles 21a and 21b are arranged uniformly on the annular disk, particularly in the circumferential direction.

[0030] Fig. Figure 2c shows a third embodiment of an electric axial flux machine 10 or a rotor-stator arrangement of such an electric machine 10 in a schematic side view.

[0031] This electric machine 10 has a so-called H-arrangement, in which two rotors 20 are arranged on opposite axial sides of a stator 30. In the illustrated embodiment, an axial distance A between the at least one rotor 20 and the at least one stator 30 is adjustable. Here, a polarization similar to or corresponding to that of the rotor 20 or rotor core of the in Fig. as shown in the embodiment 2a. This allows the axial distance A to be changed or controlled, for example, depending on an applied torque. REFERENCE MARK LIST 10 electric axial flux machine 11 Rotor shaft 20 rotors 21a first pole 21b second pole 22 Shaft connection area 30 Stator A distance D Rotation or axis of rotation

Claims

[1] Rotor (20) for an electric axial flux machine (10), wherein the rotor (20) is designed as a monolithic multipole magnet. [2] Rotor (20) according to the preceding claim, wherein the rotor (20) comprises a hard magnetic material. [3] Rotor (20) according to one of the preceding claims, wherein the rotor (20) has a predetermined specific electrical resistance. [4] Rotor (20) according to one of the preceding claims, wherein the rotor (20) comprises a non-metallic permanent magnet material. [5] Rotor (20) according to the preceding claim, wherein the rotor (20) comprises a magnetized ferrite. [6] Rotor (20) according to one of the preceding claims, wherein the rotor (20) is formed in the shape of an annular disc. [7] Rotor (20) according to one of the preceding claims, wherein the rotor (20) has a material different from a material of the rotor (20) in its shaft connection region (22) for connection to a rotor shaft of an electrical machine (10). [8] Rotor (20) according to one of the preceding claims, wherein the rotor (20) has at least one cooling channel (23) for a cooling fluid. [9] Electrical machine (10), comprising at least one stator (30) and at least one rotor (20), wherein the rotor (20) is designed according to one of the preceding claims. [10] Electric machine (10) according to the preceding claim, wherein an axial distance (A) between the at least one rotor (20) and the at least one stator (30) is adjustable. [11] Electric machine (10) according to one of the two preceding claims, wherein the electric machine (10) is arranged to provide a cooling fluid for cooling the rotor (20).

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