Magnetic levitation device and electromagnetic rotary drive

Abstract

To provide a magnetic levitation device with lower eddy current losses than the prior art, and an electromagnetic rotary drive with such a magnetic levitation device.SOLUTION: A magnetic levitation device for contactless magnetic levitation of a rotor 3 comprises: a stator 2 comprising a plurality of coil cores 25. Each coil core 25 is made of elements 253. The elements 253 are stacked in a circumferential direction of the stator 2. Each coil core 25 comprises a longitudinal leg 26 extending from a first end 261 in an axial direction A to a second end 262, and a transverse leg 27 arranged at the second end 262 of the longitudinal leg, and extending in a radial direction perpendicular to the axial direction A. At least one concentrated winding is provided on each longitudinal leg 26, and surrounds the longitudinal leg 26. The stator 2 further includes a cup-shaped recess into which the rotor 3 can be inserted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetic levitation device according to the preamble of the independent patent claim and to an electromagnetic rotary drive comprising such a magnetic levitation device. [Background technology]

[0002] Magnetic bearing devices that magnetically support a rotor without contact have the advantage of not requiring a mechanical bearing for the rotor. The rotor is supported or stabilized by the magnetic force generated by the stator of the magnetic bearing device. Because of the absence of a mechanical bearing, such magnetic bearing devices are particularly suitable for pumping, mixing, centrifuging, or stirring devices that convey highly sensitive substances, such as blood pumps, pumping, mixing, centrifuging, or stirring devices that make very high demands on purity, for example in the pharmaceutical or biotechnology industries, or pumps or mixers for slurries, sulfuric acid, phosphoric acid, or other chemicals, for example in the semiconductor industry, that convey highly abrasive or corrosive substances that would destroy mechanical bearings very quickly.

[0003] Such magnetic bearing devices are used in the biotechnology industry, for example with bioreactors, e.g. in centrifugal pumps to transport fluids into or out of bioreactors or in mixing devices to mix fluids within bioreactors, etc. Such magnetic bearing devices are used in the semiconductor industry to transport highly corrosive or abrasive materials, but also in rotating devices to rotate wafers, for example.

[0004] It is also known to use magnetic bearing devices in viscometers.

[0005] An advantageous, per se known design of a magnetic bearing device is that of a temple structure, to which the present invention also relates.

[0006] A unique feature of the temple structure is that the stator of the magnetic bearing device includes multiple coil cores, each with a longitudinal leg extending axially from a first end to a second end. The axial direction here refers to the direction defined by the desired axis of rotation of the rotor supported by the magnetic bearing device. The desired axis of rotation is the axis about which the rotor rotates when the rotor is in an operating, centered, and untilted position relative to the stator. In addition to the longitudinal legs, each coil core includes transverse legs, also called pole pieces, which are located at the second ends of the longitudinal legs and extend radially, usually inward, perpendicular to the axial direction. The transverse legs therefore extend substantially perpendicular to the longitudinal legs. Each coil core has an L-shape, with the transverse legs forming the shorter legs of the L. The supported rotor is therefore positioned between the transverse legs.

[0007] The structure gets its name from the fact that its axially extending longitudinal legs are reminiscent of temple columns.

[0008] In one design, the stator of a magnetic bearing device includes, for example, six coil cores arranged circularly and evenly spaced around a cup-shaped recess into which the rotor can be inserted. The first ends of the longitudinal legs are typically circumferentially connected by back irons, which act to conduct magnetic flux. The rotor to be supported includes a magnetically effective core, such as a permanent magnetic disk or ring, positioned between the radially inner ends of the transverse legs and rotates axially in an operating state, where the rotor is magnetically supported without contact with the stator.

[0009] In such magnetic bearing devices, it is not necessarily true that the magnetically effective core of the rotor must be designed in a permanent magnet manner. Designs are also known in which the magnetically effective core of the rotor is designed in a non-permanent magnet manner, i.e. without permanent magnets. The magnetically effective core of the rotor is in this case, for example, designed in a ferromagnetic manner and is made, for example, of iron, nickel-iron, cobalt-iron, silicon-iron, mu-metal or another ferromagnetic material.

[0010] Furthermore, designs are possible in which the magnetically effective core of the rotor includes both ferromagnetic and permanent magnetic materials. For example, permanent magnets can be disposed or inserted within a ferromagnetic substrate. Such designs are advantageous, for example, when it is desired to reduce the cost of large rotors by conserving permanent magnetic material.

[0011] The longitudinal legs carry the windings, which generate the electromagnetic fields necessary to magnetically support the rotor without contact. The windings are designed so that, for example, one concentrated winding is wound around each longitudinal leg, i.e., the coil axis of each concentrated winding extends in the axial direction. Here, in a typical temple design, the coil axis of the concentrated windings extends in the axial direction, and the concentrated windings are not located in the radial plane in which the rotor or its magnetically effective core is supported in operation.

[0012] In some designs, each longitudinal leg has exactly one concentrated winding. In other designs, each longitudinal leg has several, for example exactly two, concentrated windings. In other designs, windings are provided around two circumferentially adjacent longitudinal legs, so that both of these legs are located within the interior space of a concentrated winding.

[0013] The coil cores of magnetic bearing devices known from the prior art are usually designed in sheet metal. This means that several sheets of metal in the shape of the coil core are stacked circumferentially and insulated from each other. The sheet metal design of the coil core prevents eddy currents due to the magnetic field extending in the direction of the sheet metal, i.e., fields following the longitudinal legs in the axial direction and the transverse legs in the radial direction.

[0014] Due to the magnetic fields emanating laterally, i.e. circumferentially, from the sheet metal of the longitudinal and transverse legs, the sheet metal insulation is ineffective and therefore eddy currents still occur, since these fields pass through the sheet metal in orthogonal directions.

[0015] Particularly in the case of magnetic bearing devices with large magnetic gaps, where the magnetic gap is defined as the radial distance between the end faces of the lateral legs and the magnetically effective core of the rotor, the orthogonal magnetic field components cannot be neglected and result in significant eddy current losses.

[0016] In the context of this application, a large magnetic gap means a magnetic gap that is greater than 1% of the diameter of the magnetically effective core in the radial direction. In some cases, the magnetic gap may be 5% or greater of the diameter of the magnetically effective core in the radial direction. Summary of the Invention [Problem to be solved by the invention]

[0017] Therefore, starting from the prior art, the object of the present invention is to propose a magnetic levitation device for contactless magnetic levitation of a rotor with a disk-shaped or ring-shaped magnetically effective core, which magnetic levitation device has lower eddy current losses than the prior art.

[0018] Furthermore, the object of the invention is to propose an electromagnetic rotary drive comprising such a magnetic levitation device. [Means for solving the problem]

[0019] The subject matter of the invention which meets this object is characterized by the features of the independent patent claims.

[0020] Therefore, in accordance with the present invention, there is provided a magnetic levitation device for contactless magnetic levitation of a rotor including a disk-shaped or ring-shaped magnetically effective core, the magnetic levitation device having a stator including a plurality of coil cores, each coil core formed from elements of sheet metal, the elements being stacked circumferentially of the stator, each coil core having a first lateral boundary surface and a second lateral boundary surface, each coil core having a longitudinal leg extending axially from a first end to a second end, and a longitudinal leg extending axially from a first end to a second end. a stator having a first axial end, a second axial end, and a lateral leg disposed at a second end of the longitudinal leg and extending in a radial direction perpendicular to the axial direction, wherein at least one concentrated winding is provided on each longitudinal leg surrounding the longitudinal leg; the stator further has a cup-shaped recess into which a rotor can be inserted, the cup-shaped recess being disposed at an axial end of the stator, the lateral leg being disposed around the cup-shaped recess, and at least one of the first or second lateral boundary surfaces having at least one slot.

[0021] The provision of slots in at least one of the two lateral boundary surfaces of the coil core provides electrical insulation. This means that at least one slot ensures that the path of eddy currents in the coil core is interrupted and thus blocked. As a result, only small eddy currents remain in the coil core, and eddy current losses in the coil core are significantly reduced overall. Here, it is advantageous for at least one slot to extend parallel or at least approximately parallel to the course of the magnetic field in the coil core and not block the course of this magnetic field.

[0022] A number of different methods can be used to form the slots, including, among others, machining processes such as milling, punching or cutting, where cutting also includes the use of a laser or water jet cutter.

[0023] According to a preferred embodiment, the elements are made of electrical sheet metal, which by common definition is understood to be a flexible magnetic material for the magnetic core. There is also the possibility of using mu metal.

[0024] According to a preferred embodiment, at least one slot extends only in the lateral legs. For applications where the coil core must have high stability, it can be advantageous to have at least one slot extend only in the lateral legs. This embodiment also reduces eddy current losses to some extent, since most of the effects leading to eddy current losses occur in the region of the second end.

[0025] According to a preferred embodiment, the at least one slot extends in both the transverse legs and the longitudinal legs. This is advantageous for further reducing eddy current losses in the coil core. The extent to which the at least one slot extends in the longitudinal legs in the axial direction towards the first end of the longitudinal legs is variable. All lengths of the at least one slot are possible, from as little as 5% of the total length of the longitudinal legs in the axial direction to extending towards the first end of the longitudinal legs.

[0026] In a preferred embodiment, at least one slot has a radius that redirects the slot from a radial to an axial direction.

[0027] According to a preferred embodiment, at least one slot extends from the first lateral boundary surface to the second lateral boundary surface.

[0028] In a preferred embodiment, the extension of at least one slot is less than the distance of the first lateral boundary surface from the second lateral boundary surface when viewed in the circumferential direction of the stator.

[0029] In other words, at least one slot does not extend through the entire coil core in the circumferential direction of the stator. This means that at least one slot is not provided in every element of the sheet metal design of the coil core. This is advantageous because the majority of eddy currents occur in elements located directly at or near the two lateral boundaries. The path of eddy currents in the coil core is therefore interrupted by at least one slot where they occur most frequently. This ensures a significant reduction in eddy current losses. Furthermore, this embodiment is advantageous for the stability of the coil core.

[0030] According to a preferred embodiment, several slots are provided which are arranged parallel or at least approximately parallel to one another.

[0031] An arrangement of several slots parallel or at least approximately parallel to one another is advantageous because the slots do not interrupt the course of the magnetic field, since they also run parallel or at least approximately parallel to the course of the magnetic field in the coil core.

[0032] Furthermore, it is preferable that the coil core has a rounded portion at its upper axial end, and this rounded portion causes the coil core to change direction from the axial direction to the radial direction.

[0033] For example, in the case of an L-shaped coil core, in which the longer part of the "L" is formed by the longitudinal legs and the shorter part by the lateral legs, the edges extending circumferentially in the radial plane and located radially outward of the lateral legs when viewed from the cup-shaped recess are designed in a rounded manner. This embodiment has the advantage of having lower eddy current losses and is also easier to realize in terms of construction.

[0034] In a preferred embodiment, a back iron connecting the first ends of all the longitudinal legs is arranged at the first ends of the longitudinal legs, the back iron being designed in a ring-like form with a metal strip extending from a radially inner starting point to a radially outer end, the strip forming several strip turns lying flat relative to each other in the radial direction.

[0035] According to a preferred embodiment, two concentrated turns are provided on each longitudinal leg, each of the concentrated turns surrounding a respective longitudinal leg and arranged adjacent to each other in the axial direction.

[0036] Furthermore, it is preferred that at least one slot is provided in both the first and second lateral boundary surfaces, respectively.

[0037] This is particularly advantageous because the majority of eddy currents occur in the elements located directly at the two lateral boundaries. Therefore, the paths of the eddy currents in the coil core are interrupted by at least one slot each where they occur most frequently. This ensures a significant reduction in eddy current losses.

[0038] According to a particularly preferred embodiment, the stator of the magnetic levitation device is designed to generate a torque that can magnetically drive the rotor to rotate about an axial axis without contact.

[0039] Here, the stator is designed as a bearing and drive stator, both an electrically driven stator and a magnetically suspended stator. A magnetic rotating field can be generated by the electrical windings of the stator, which on the one hand exerts a torque on the rotor that causes the rotor to rotate about the desired axis of rotation, and on the other hand exerts an arbitrarily adjustable transverse force on the rotor, which allows the radial position of the rotor to be actively controlled or adjusted.

[0040] Furthermore, the present invention proposes an electromagnetic rotary drive designed as a temple motor, which comprises a magnetic levitation device according to the present invention and a rotor with a disk-shaped or ring-shaped magnetically effective core, which rotor can be inserted into a cup-shaped recess, and which rotor is designed as a rotor for an electromagnetic rotary drive.

[0041] Such electromagnetic rotary drives are also known as bearingless motors, the term bearingless motor meaning an electromagnetic rotary drive in which the rotor is entirely magnetically levitated with respect to the stator and no separate magnetic bearings are provided.

[0042] Further advantageous measures and embodiments of the invention are evident from the dependent claims.

[0043] In the following, the invention will be explained in more detail with reference to examples and with reference to the drawings. [Brief explanation of the drawings]

[0044] [Figure 1] 1 is a perspective view of a first embodiment of a magnetic levitation device according to the present invention; [Figure 2] FIG. 2 is a perspective view of a single coil core of the magnetic levitation device of FIG. [Figure 3] 10A-10C show different variations of coil core embodiments, each in a perspective view. [Figure 4] 10A-10C show different variations of coil core embodiments, each in a perspective view. [Figure 5] 10A-10C show different variations of coil core embodiments, each in a perspective view. [Figure 6] 10A-10C show different variations of coil core embodiments, each in a perspective view. [Figure 7] FIG. 2 is a perspective view of a second embodiment of a magnetic levitation device according to the present invention. [Figure 8] 2 is a schematic cross-sectional view of an embodiment of a stator housing. DETAILED DESCRIPTION OF THE INVENTION

[0045] FIG. 1 shows a perspective view of an embodiment of a magnetic levitation device 1 according to the present invention, generally designated by the reference numeral 1. The magnetic levitation device 1 is designed to magnetically levitate, without contact, a rotor 3 comprising a magnetically effective core 31 in the shape of a disk or a ring. The magnetic levitation device 1 is designed according to a temple structure and comprises a stator 2. The stator 2 typically comprises a stator housing 21 (FIG. 8), which is not shown in FIG. 1 for the sake of clarity. For this reason, FIG. 8 shows an embodiment of the stator housing 21 in a schematic cross-sectional view.

[0046] A cup-shaped recess 211 is provided at one axial end of the stator housing 21, into which the rotor 3 can be inserted. The rotor 3 is designed to rotate about a desired axis of rotation. This desired axis of rotation defines an axial direction A. Typically, the central axis of the stator 2 extending in the axial direction A coincides with the desired axis of rotation. The desired axis of rotation refers to the axis about which the rotor 3 rotates when the rotor 3 is in an operating state, centered relative to the stator 2, and not tilted, as shown in FIG. 1.

[0047] The stator 2 has a plurality of coil cores 25 (six coil cores in this example), each of which is formed from an element 253 as a sheet metal. The elements 253 are stacked in the circumferential direction of the stator 2, and each of the coil cores 25 has a first lateral boundary surface 255 and a second lateral boundary surface 256. The circumferential direction refers to a direction perpendicular to the radial direction R and perpendicular to the axial direction A. Furthermore, each of the coil cores 25 includes a longitudinal leg 26 extending from a first end 261 to a second end 262 in the axial direction A, and a lateral leg 27 disposed at the second end 262 of the longitudinal leg and extending in a radial direction perpendicular to the axial direction A.

[0048] For ease of understanding, a perspective view of a single coil core 25 of the magnetic levitation device 1 of FIG. 1 is shown in FIG.

[0049] The coil cores 25 of the stator 2 are equally spaced on a circular line so that when the rotor 3 is inserted into the cup-shaped recess 211, the lateral legs 27 surround the magnetically active core 31 of the rotor 3.

[0050] In this embodiment, the coil core 25 has a radius 257 at its upper axial end 252, which redirects the coil core 25 from the axial direction A to the radial direction R. The coil core 25 has a radius 257 at its outer edge 258 ( FIG. 4 ) at the upper axial end 252. This means that in this embodiment, the radially outer edge 258 at the upper axial end 252 of the coil core 25 is a broken or rounded edge, as represented by the radius 257. Depending on the embodiment of the coil core 25, the radius 257 can extend only in the region of the longitudinal legs 26, only in the region of the lateral legs 27, or in both the regions of the longitudinal legs 26 and the lateral legs 27. This has the advantage that this embodiment of the coil core 25 has low eddy current losses and is also easier to realize structurally.

[0051] At least one concentrated winding 61 is arranged on each longitudinal leg 26, surrounding the respective longitudinal leg 26. In other embodiments, two or more concentrated windings 61 may be arranged on the longitudinal legs 26. For example, as shown here in FIG. 1, there are embodiments in which each longitudinal leg 26 is provided with exactly two concentrated windings 61 a, 61 b, each of which surrounds the respective longitudinal leg 26, and in which the two windings 61 a, 61 b ​​arranged on the same longitudinal leg 26 are arranged adjacent to each other in the axial direction A.

[0052] The concentrated windings 61a, 61b serve to generate an electromagnetic field that allows the rotor 3 to be magnetically levitated without contact in the cup-shaped recess 211 (FIG. 8).

[0053] The element 253 can be made of electrical sheet metal, which by common definition is understood to be a flexible magnetic material for the magnetic core. There is also the possibility of using mu metal for the strips.

[0054] It should be understood that the number of elements 253 in all examples and figures is purely illustrative and may be greater or less than shown.

[0055] In the first embodiment of the magnetic levitation device 1 according to the present invention shown in FIG. 1, three slots 254 are arranged in each of the first and second lateral boundary surfaces 255, 256. The slots 254 extend in both the lateral leg 27 and the longitudinal leg 26. The insertion of the slots 254 in the two lateral boundary surfaces 255, 256 of the coil core 25 provides electrical insulation. This means that the slots 254 ensure that the path of eddy currents in the coil core 25 is interrupted and thus blocked. As a result, only small eddy currents remain in the coil core 25, and eddy current losses in the coil core 25 are significantly reduced overall.

[0056] In this embodiment, each slot 254 has a radius 2541 that redirects each slot 254 from the radial direction R to the axial direction A. The slots 254 are arranged parallel or at least approximately parallel to each other and parallel or at least approximately parallel to the course of the magnetic field in the coil core 25. This has the advantage that the slots 254 do not thereby obstruct and / or block the course of the magnetic field in the coil core 25.

[0057] Here, the slot 254 does not extend over the entire extension range of the longitudinal leg 26 in the axial direction A, but only partially, terminating before the axial upper end of the concentrated winding 61a.

[0058] Furthermore, however, embodiments are also possible in which at least one slot 254 has a longer extension in the longitudinal leg 26 than in the embodiment shown in Fig. 2. Such a possible embodiment is shown in Fig. 3. The perspective view there of a variant embodiment of the coil core 25 shows the maximum possible extension of the slot 254 in the coil core 25.

[0059] Of course, it is possible that the slot 254 can have any extension length in the longitudinal legs 26. It is also possible that the slot 254 extends only in the lateral legs 27.

[0060] In this embodiment, the extension of the slots 254, when viewed in the circumferential direction of the stator 2, is shorter than the distance between the first lateral boundary surface 255 and the second lateral boundary surface 256. In other words, the slots 254 do not penetrate all of the elements 253 of the coil core 25, but only a predetermined number of them. In a preferred embodiment, there are eight elements 253 per coil core 25, i.e., four elements 253 when viewed from each of the lateral boundary surfaces 255, 256.

[0061] This is advantageous, since the majority of eddy currents occur in elements 253 located directly at or close to the two lateral boundary surfaces 255, 256. The paths of eddy currents in the coil core 25 are therefore interrupted by the slots 254 where they occur most frequently. This ensures a significant reduction in eddy current losses. Furthermore, it is advantageous for the stability of the coil core 25 that the slots 254 do not completely penetrate all elements of the coil core 25.

[0062] However, embodiments in which the slot 254 extends from the first lateral boundary surface 255 to the second lateral boundary surface 256 are also possible.

[0063] According to a particularly preferred embodiment, the stator 2 is designed in such a way that, in addition to contactless magnetic levitation of the rotor 3, it can also apply a torque to the rotor 3 or to the magnetically active core 31 of the rotor 3, which torque drives the rotor 3 to rotate about a desired axis of rotation. This means that in a preferred embodiment, the rotor 3 can be driven for rotation about an axial direction A.

[0064] The concentrated windings 61 therefore generate an electromagnetic rotating field that in this embodiment can both magnetically levitate the rotor 3 without contact relative to the stator 2 and drive it to rotate without contact about the axial direction A.

[0065] It should be understood that the number of six coil cores 25, while preferred, should be understood as merely an example. Of course, embodiments are possible in which the stator 2 includes fewer than six coil cores 25, such as five, four, or three coil cores 25, or in which the stator 2 includes more than six coil cores 25, such as seven, eight, nine, or twelve coil cores, or even an even greater number of coil cores 25.

[0066] The rotor 3 comprises a magnetically effective core 31 designed in the shape of a ring or a disk. The magnetically effective core 31 is designed as a ring according to the illustration in FIG. 1 and defines a magnetic central plane. The magnetically effective core 31 can alternatively be designed as a disk. Typically, in the case of a disk- or ring-shaped magnetically effective core 31, the magnetic central plane is the geometrical central plane of the magnetically effective core 31 of the rotor 3, perpendicular to the axial direction A. In operation, the magnetically effective core 31 is suspended in a radial plane perpendicular to the axial direction A.

[0067] The radial plane is indicated in Figure 1 by the line of radial direction R perpendicular to the axial direction A. The radial plane is the plane perpendicular to the axial direction A and containing the radial direction R. The radial plane is the plane in which the magnetically active core 31 of the rotor 3 is actively magnetically levitated between the end faces 272 of the stator 2 in the operating state. When the rotor 3 is not tilted and not deflected in the axial direction A, the magnetic center plane lies in the radial plane E. The radial plane defines the xy plane of a Cartesian coordinate system whose z axis extends in the axial direction A.

[0068] The radial position of the magnetically effective core 31 or rotor 3 refers to the position of the rotor 3 in the radial plane E.

[0069] Only the magnetically effective core 31 of the rotor 3 is shown in Figure 1, as this is sufficient for understanding the invention. It should be understood that the rotor 3 may of course comprise further components such as a jacket or enclosure, preferably made of plastic, metal, alloy, or ceramic or ceramic material. The rotor 3 may also comprise vanes for mixing, stirring, or pumping fluids or other constituents.

[0070] When the rotor 3 is inserted into the cup-shaped recess 211 (FIG. 8), the rotor 3, and in particular the magnetically active core 31 of the rotor 3, is surrounded by the radially outwardly arranged end faces 272 of the lateral legs 27 of the coil core 25 of the stator 2. The lateral legs 27 therefore form a number of pronounced stator poles, in this case six stator poles.

[0071] When the magnetically active core 31 of the rotor 3 is in a desired position during operation, the magnetically active core 31 is centered between the end faces 272 of the lateral legs 27. According to the drawing, the concentrated windings 61 are arranged below the radial plane and are aligned such that the coil axes of the concentrated windings extend in the axial direction A.

[0072] All first ends 261 of the longitudinal legs 26, i.e., the lower ends 261 according to the illustration (FIG. 1), are connected to one another by the back iron 28. The back iron 28 is preferably designed in the shape of a ring. An embodiment is possible in which the back iron 28 extends radially inward along all first ends 261 of the longitudinal legs 26 (see, for example, FIG. 1).

[0073] In order to generate the electromagnetic fields necessary for magnetic levitation of the rotor 3 and, optionally, to generate torque on the rotor 3, the longitudinal legs 26 of the coil core 25 carry windings designed as concentrated windings 61.

[0074] In operation, such an electromagnetic rotating field is generated by the concentrated windings 61, which can exert an arbitrarily adjustable radial transverse force on the rotor 3, and thus can actively control or adjust the radial position of the rotor 3, i.e., the position of the rotor 3 in a radial plane perpendicular to the axial direction A. Optionally, such an electromagnetic rotating field can also generate a torque on the rotor 3.

[0075] The "magnetically active core 31" of the rotor 3 refers to that region of the rotor 3 that magnetically interacts with the stator 2 to generate a magnetic levitation force and, optionally, torque.

[0076] As already mentioned, in this embodiment the magnetically effective core 31 is designed in the shape of a ring. The magnetically effective core 31 is further designed to be permanently magnetic. For this purpose the magnetically effective core 31 can comprise at least one permanent magnet, but can also comprise several permanent magnets or, as in the embodiment described here, can be entirely made of permanent magnetic material, so that the magnetically effective core 31 is permanently magnetic. The magnetically effective core 31 is, for example, radially magnetized.

[0077] These ferromagnetic or ferrimagnetic materials that are magnetically hard, i.e. have a high coercivity, are usually called permanent magnets. The coercivity is the magnetic field strength required to demagnetize the material. Within the framework of this application, a permanent magnet is understood to be a component or material that has a coercivity, or more precisely, a coercivity of magnetic polarization, higher than 10,000 A / m.

[0078] An embodiment is also possible in which the magnetically active core 31 is designed without permanent magnets, i.e. without permanent magnets. The rotor 3 is then designed, for example, as a reluctance rotor. The magnetically active core 31 of the rotor 3 is then made, for example, of a soft magnetic material. Suitable soft magnetic materials for the magnetically active core 31 are, for example, ferromagnetic or ferrimagnetic materials, i.e. in particular iron, nickel-iron, cobalt-iron, silicon-iron, mu-metal.

[0079] Furthermore, embodiments are possible in which the magnetically effective core 31 of the rotor 3 comprises both ferromagnetic and permanent magnetic materials. For example, permanent magnets can be disposed or inserted within a ferromagnetic substrate. Such embodiments are advantageous, for example, when it is desired to reduce the cost of large rotors by saving on permanent magnetic material.

[0080] An embodiment is also possible in which the rotor is designed according to the squirrel cage rotor principle.

[0081] The ring-shaped back iron 28 can be made of a soft magnetic material because the back iron 28 acts as a flux conducting element for conducting magnetic flux. The coil core 25 of the stator 2 can also be made of a soft magnetic material.

[0082] Suitable soft magnetic materials for the coil core 25 and the back irons 28 are, for example, ferromagnetic or ferrimagnetic materials, i.e., in particular, iron, nickel-iron, cobalt-iron, silicon-iron, or mu-metal. In this case, a stator sheet-metal stack design is preferred for the stator 2, where the back irons 28 are designed in sheet metal, i.e., they consist of several thin sheet-metal elements stacked parallel to one another in the axial direction A. All magnetic flux-conducting elements are identically designed, i.e., in this case, substantially ring-shaped and each have the same thickness. Therefore, the back irons 28 themselves are substantially ring-shaped and extend radially inward along the first ends 261 of the longitudinal legs 26 in the assembled state.

[0083] An embodiment is also possible in which a so-called tape-wound toroidal core is used as the back iron 28. This is a coiled strip 29. Such a design is realized in the second embodiment shown in FIG.

[0084] Furthermore, the back iron 28 can consist of pressed and subsequently sintered grains of the aforementioned materials. The metal grains are preferably embedded in a plastic matrix so that they are at least partially insulated from one another, thereby minimizing eddy current losses. Therefore, soft magnetic composites consisting of electrically insulated, compressed metal particles are also suitable for the stator. In particular, these soft magnetic composites, also known as SMCs (Soft Magnetic Composites), can consist of iron powder grains coated with an electrically insulating layer. The SMC is then formed into the desired shape by a powder metallurgy process.

[0085] During operation of the magnetic levitation device 1, the magnetically active core 31 of the rotor 3 interacts with the stator 2 such that the rotor 3 can be magnetically levitated without contact with the stator 2 and, more preferably, magnetically rotated about the axial direction A without contact. In this case, it is particularly advantageous that the same windings 61 by which the rotor 3 is magnetically levitated also serve to generate torque on the rotor 3. In this case, it is preferable that three degrees of freedom of the rotor 3, namely, its position in the radial plane E and its rotation, can be actively adjusted. With respect to axial deviation from the radial plane E in the axial direction A, the magnetically active core 31 of the rotor 3 is passively magnetically stabilized by reluctance forces, i.e., cannot be controlled. The magnetically active core 31 of the rotor 3 is also passively magnetically stabilized with respect to the remaining two degrees of freedom, namely, tilt with respect to the radial plane E perpendicular to the desired axis of rotation. Thus, due to the interaction of the magnetically active core 31 with the coil core 25, the rotor 3 is passively magnetically levitated or passively magnetically stabilized in the axial direction A and against tilt (three degrees of freedom in total), and actively magnetically levitated in the radial plane (two degrees of freedom).

[0086] Active magnetic levitation is also, as is common practice, referred to in the framework of this application as magnetic levitation that can be actively controlled or regulated, for example by means of an electromagnetic field generated by concentrated windings 61. Passive magnetic levitation or passive magnetic stabilization is that which cannot be controlled or regulated. Passive magnetic levitation or stabilization is based, for example, on a reluctance force that returns the rotor 3 to the desired position again if the rotor 3 deviates from the desired position, i.e. if the rotor is misaligned or offset in the axial direction A or if the rotor is tilted.

[0087] In magnetic levitation device 1, magnetic levitation and optionally the generation of torque acting on the rotor are achieved by an electromagnetic rotating field, as opposed to conventional magnetic bearings. On the one hand, to generate a combined magnetic levitation force and torque that rotates rotor 3 about axial direction A, it is possible to place just one concentrated winding 61 on each longitudinal leg 26, as shown in FIG.

[0088] On the other hand, an embodiment is also possible in which two different winding systems are provided to generate a combined magnetic levitation force and a torque that rotates the rotor 3. For this purpose, for example, just two concentrated windings 61 a, 61 b ​​are arranged on each longitudinal leg 26, as shown in Fig. 1, with the concentrated windings 61 a, 61 b ​​being arranged adjacent to each other in the axial direction A. One of these two windings 61 a, 61 b ​​belongs to the first of the two winding systems, and the other belongs to the second of the two winding systems.

[0089] 7, which has just one concentrated winding 61 in each coil core 25, the values ​​of the current required for levitation and the current required for torque generation, each determined, for example, in a control unit, are added or superimposed by calculation, for example, using software, and the resulting total current is then applied to each concentrated winding 61.

[0090] If the stator 2 of the magnetic levitation device 1 according to the invention is designed to generate torque, the magnetic levitation device 1 is suitable for an electromagnetic rotary drive designed as a temple motor. It is also possible that the magnetic levitation device 1 according to the invention is suitable for other devices, such as a centrifugal pump, a mixing device for mixing flowable substances, e.g., a stirring device for mixing fluids in a tank, a fan, or a device for supporting and rotating wafers, e.g., in semiconductor manufacturing.

[0091] 4 shows a perspective view of a further variant of the embodiment of the coil core 25. In this variant, the coil core 25 is not rounded at the edges 258 but is designed rectangular. In this embodiment, only one slot 254 extends in the transverse leg 27, and no slot 254 extends in the longitudinal leg 26. The slot 254 extends from the first transverse boundary surface 255 to the second transverse boundary surface 256, i.e., it penetrates all elements 253 of the coil core 25.

[0092] Figure 5 shows a perspective view of a further variant for the embodiment of coil core 25. One difference from the variant in Figure 4 is that in this variant there are three slots 254, all of which extend from first lateral boundary surface 255 to second lateral boundary surface 256.

[0093] 6 shows a perspective view of a further variant of the embodiment of the coil core 25. Here, the difference with the variant of FIG. 4 is, on the one hand, that there are three slots 254, and, on the other hand, that the extension of the three slots 254 is shorter than the distance between the first and second lateral boundary surfaces when viewed in the circumferential direction of the stator 2. This means that the slots 254 do not penetrate all elements 253 of the coil core 25, but only a certain number of them. In a preferred embodiment, there are eight elements 253, i.e., four elements 253 when viewed from each lateral boundary surface 255, 256.

[0094] Of course, the described variants and embodiments of the coil core 25 of Figures 2 to 6 can be combined with one another in any way, and all statements apply equally or similarly to all variants.

[0095] 7 shows a perspective view of a second embodiment of a magnetic levitation device 1 according to the present invention. In the following description of the second embodiment of the magnetic levitation device 1, only the differences from the first embodiment of FIG. 1 will be described in more detail. The description of the first embodiment applies in the same or similar manner to the second embodiment. The same reference signs refer to the same features or functionally equivalent features described with reference to the first embodiment.

[0096] One difference between this embodiment of the magnetic levitation device 1 and the embodiment of FIG. 1 is that the back iron 28 has a different design. The back iron 28 is designed in a ring-like form with a metal strip 29 extending from a radially inner starting point 291 to a radially outer end 292. The strip 29 forms several strip turns 293 that lie flat against one another in the radial direction R. The longitudinal legs 26 are delimited at their first ends 261 by axial end faces 265 on which the back iron 28 rests. The back iron 28 forms a circular ring whose radial width is equal to the radial width of the end faces 265 of the longitudinal legs 26. This means that the radially inner starting point 291 is located in the same plane as the inner surface 266 arranged radially inward of the longitudinal leg 26 in the axial direction A, and the radially outer end 292 is located in the same plane as the outer surface 267 arranged radially outward of the longitudinal leg 26 in the axial direction A.

[0097] In particular, this has the advantage that there is more space inside the stator 2, which can be used to install other components therein. By doing so, the stator 2 together with the stator housing 21 can be made smaller and more compact, which increases the flexibility of use of the magnetic levitation device 1.

[0098] A further advantage of such an arrangement of the back iron 28 arises from the arrangement of the strip turns 293 of the strip 29 of the tape-wound toroidal core. Due to the arrangement of the strip turns 293 perpendicular to the radial direction R, the strip turns 293 have an orientation parallel to the magnetic field course in the longitudinal legs 26. As a result, the magnetic field in the longitudinal legs 26 enters the back iron 28 in the axial direction A, and thus parallel to the strip turns 293. This means that the magnetic field does not penetrate any of the strip turns 293 in the radial direction R, thereby avoiding eddy current losses.

[0099] A further difference with respect to the embodiment of Figure 1 is the longer extension of the slots 254 in the longitudinal legs 26. Depending on the field of application of the magnetic levitation device 1, this may be advantageous in order to achieve a greater reduction in eddy current losses.

[0100] Furthermore, the rotor 3 of this embodiment differs from that of the embodiment of Figure 1. The rotor 3 used here is designed as a so-called four-pole pair rotor.

[0101] However, it is of course possible to operate the magnetic levitation device 1 shown in this embodiment with any other rotor 3, some of which have already been described in the previous section.

[0102] It goes without saying that all embodiments with their respective characteristics shown in the description of the drawings can be combined with each other in any way.

[0103] Furthermore, all of the shown embodiments of the coil core 25 can be designed in such a way that the space available for the rotor 3 in the magnetic levitation device 1 is increased. This is achieved by a special geometry of the coil core 25.

[0104] In the process, the coil core 25 is divided into an axially lower section and an axially upper section, which are arranged adjacent to each other in the axial direction A. The transverse legs 27 are arranged in the axially upper section. For each coil core 25, the end face 272 of the transverse leg 27 has a first radial distance from the axially lower section of the associated longitudinal leg 26 and a second radial distance from the axially upper section, which is greater than the first distance. This means that each longitudinal leg 26 is designed such that the axially upper section is radially offset outward with respect to the axially lower section, thereby increasing the space available for the rotor 3 between the end faces 272 without the risk of direct transmission of magnetic flux between the longitudinal leg 26 and the magnetically effective core 31 of the rotor 3. Due to the axially upper section being radially offset radially outward relative to the axially lower section, the distance between the longitudinal legs 26 and the end faces 272, i.e. the second distance, is increased in the region of the axially upper section, thereby also increasing the distance between the magnetically effective core 31 of the rotor and the longitudinal legs 26, particularly in the region of the axially upper section.

[0105] Such a coil core 25 as just described is designed similarly to that shown in FIG. 3 of European Patent Application No. 4084304.

[0106] Figure 8 shows a schematic cross-sectional view of an embodiment of the stator housing 21. In the embodiments of Figures 1 and 7, this stator housing 21 is not shown for the sake of clarity. Figure 8 is intended only to serve as an example to show what the internal sealing of the stator 2 required for operation of the magnetic levitation device 1 looks like. For this reason, the other components of the stator 2 are shown only diagrammatically and should be understood to be purely illustrative.

[0107] An embodiment of the stator housing 21 is also possible in which the cup-shaped recess 211 is integrated into a bore extending centrally through the stator housing 21 in the axial direction A along the central axis of the stator 2 .

[0108] For example, during operation of the magnetic levitation device 1 in areas where chemically aggressive substances are used, it is important to ensure that the interior of the stator 2 is sealed and thereby protected from these substances. To ensure that the rotor 3 can still be used, the stator housing 21 has a cup-shaped recess 211 into which the rotor 3 can be inserted.

Claims

1. A magnetic levitation device for contactless magnetic levitation of a rotor (3) including a disk-shaped or ring-shaped magnetically effective core (31), the magnetic levitation device having a stator (2) including a plurality of coil cores (25), each of the coil cores (25) formed from elements (253) of sheet metal, the elements (253) being stacked in a circumferential direction of the stator (2), each of the coil cores (25) having a first lateral boundary surface (255) and a second lateral boundary surface (256), each of the coil cores (25) having a longitudinal leg (26) extending from a first end (261) to a second end (262) in an axial direction (A), and a magnetic field disposed at the second end (262) of the longitudinal leg. and lateral legs (27) positioned at the axial end of the stator (2) and extending in a radial direction perpendicular to the axial direction (A), wherein at least one concentrated winding (61) is provided on each of the longitudinal legs (26) surrounding the longitudinal legs (26), the stator (2) further having a cup-shaped recess (211) into which the rotor (3) can be inserted, the cup-shaped recess (211) being positioned at an axial end of the stator (2), and the lateral legs (27) being positioned around the cup-shaped recess (211), wherein at least one of the first and second lateral boundary surfaces (255, 256) has at least one slot (254).

2. The magnetic levitation device of claim 1 , wherein the element (253) is formed from electrical sheet metal.

3. 3. The magnetic levitation device of claim 1 or 2, wherein the at least one slot (254) extends only in the lateral leg (27).

4. 4. The magnetic levitation device of claim 1, wherein the at least one slot (254) extends in the lateral legs (27) and the longitudinal legs (26).

5. The magnetic levitation device of claim 4, wherein the at least one slot (254) has a radius (2541) that redirects the slot (254) from the radial direction (R) to the axial direction (A).

6. 6. The magnetic levitation device of claim 1, wherein the at least one slot extends from the first lateral boundary surface to the second lateral boundary surface.

7. 7. A magnetic levitation device as claimed in any one of claims 1 to 6, wherein the extension of the at least one slot (254) is shorter than the distance of the first lateral boundary surface from the second lateral boundary surface when viewed in the circumferential direction of the stator (2).

8. 8. A magnetic levitation device according to any one of the preceding claims, wherein there are provided several slots (254) arranged parallel or at least approximately parallel to one another.

9. 9. The magnetic levitation device of claim 1, wherein the coil core (25) has a radius (257) located at an upper axial end (252) that redirects the coil core from the axial direction (A) to the radial direction (R).

10. 10. A magnetic levitation device according to any one of claims 1 to 9, wherein a back iron (28) connecting the first ends (261) of all the longitudinal legs (26) is arranged at the first ends (261) of the longitudinal legs (26), the back iron (28) being designed in a ring-like form with a metal strip (29) extending from a radially inner starting point (291) to a radially outer end (292), the strip (29) forming several strip turns (293) lying flat to one another with respect to the radial direction (R).

11. 11. A magnetic levitation device as claimed in any one of claims 1 to 10, wherein each of the longitudinal legs (26) is provided with two concentrated windings (61a, 61b), each of the concentrated windings surrounding the respective longitudinal leg (26) and arranged adjacent to each other in the axial direction (A).

12. 12. The magnetic levitation device of claim 1, wherein both the first lateral boundary surface and the second lateral boundary surface each have at least one slot.

13. 13. The magnetic levitation device according to any one of claims 1 to 12, wherein the stator (2) is designed to generate a torque capable of magnetically driving the rotor (3) without contact for rotation about the axial direction (A).

14. 14. An electromagnetic rotary drive designed as a temple motor, characterized in that the electromagnetic rotary drive comprises a magnetic levitation device (1) according to claim 13 and a rotor (3) with a disk-shaped or ring-shaped magnetically effective core (31), the rotor (3) being insertable into a cup-shaped recess (211), the rotor (3) being designed as a rotor (3) of the electromagnetic rotary drive.

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