Magnetic levitation device and electromagnetic rotary drive

Abstract

To provide a magnetic levitation device having a low eddy current loss, and concurrently securing an effective heat dissipation.SOLUTION: Provided is a magnetic levitation device for contactless magnetic levitation of a rotor 3. The magnetic levitation device has a stator 2 including a plurality of coil cores 25. At least one concentrated winding 61 is provided on a longitudinal leg 26 of each of the coil cores 25. The stator 2 further has a cup-shaped recess 211 into which the rotor 3 can be inserted. The cup-shaped recess 211 is arranged at an axial end of the stator 2. A transverse leg 27 is arranged around the cup-shaped recess 211. The stator 2 includes a shielding 4 that extends in a circumferential direction along the plurality of coil cores 25. The shielding 4 extends in the axial direction A from a first shielding end 41 to a second shielding end 42.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] In the biotechnology industry, such magnetic bearing devices are used, 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. In the semiconductor industry, such magnetic bearing devices are used to transport highly erosive or abrasive materials, but also in rotating devices to spin, for example, wafers.

[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 also includes a transverse leg, which is located at the second end of the longitudinal leg and extends radially, typically inward, perpendicular to the axial direction. The transverse leg therefore extends substantially perpendicular to the longitudinal leg. Each coil core has an L-shape, with the transverse leg forming the shorter leg of the L. The supported rotor is then placed 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 comprises, 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 comprises a magnetically effective core, such as a permanent magnetic disk or ring, disposed 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 axes of the concentrated windings extend 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 stator of a magnetic bearing device is enclosed in a stator housing so that it can withstand the harsh conditions of the aforementioned application fields. Stator housings known from the prior art are, for example, mostly made of aluminum to ensure good heat dissipation from the windings. Housings are known that include cooling fins to improve heat dissipation. It is also known to provide a more robust protection for the housing against external influences, such as aggressive chemicals, by means of a coating.

[0014] The use of aluminum as a stator housing is ideal due to its excellent thermal conductivity, allowing for good heat dissipation from the stator. However, the use of aluminum also has drawbacks. Aluminum housings are not only good thermal conductors, but also good electrical conductors. As a result, eddy currents are generated in the stator housing. The stator windings generate magnetic fields not only toward the inside of the stator, i.e., toward the stator's central axis for the bearing and rotor drive, but also toward the outside of the stator. These magnetic fields penetrate the highly conductive aluminum housing. During operation of the magnetic bearing device, eddy currents are then generated in the housing, which causes significant losses and heat generation in the housing, which in turn heats up the motor internally. Summary of the Invention [Problem to be solved by the invention]

[0015] The object of the present invention is therefore to depart from this state of the art and to propose a magnetic levitation device for contactless magnetic levitation of a rotor with a disk-shaped or ring-shaped magnetically effective core which has lower eddy current losses than previous techniques and at the same time ensures effective heat dissipation.

[0016] Furthermore, the object of the present invention is to propose an electromagnetic rotary drive comprising such a magnetic levitation device. [Means for solving the problem]

[0017] The subject matter of the invention which meets this object is characterized by the features of the independent patent claims.

[0018] According to the present invention, a magnetic levitation device is therefore proposed for contactless magnetic levitation of a rotor, the magnetic levitation device comprising a disk-shaped or ring-shaped magnetically active core, the magnetic levitation device comprising a stator comprising a stator housing, the stator comprising a plurality of coil cores, each coil core comprising a longitudinal leg extending axially from a first end to a second end, and a transverse leg arranged at the second end of the longitudinal leg and extending radially perpendicular to the axial direction, a back iron arranged at the first end, the back iron connecting the first ends of all the longitudinal legs, at least one concentrated winding provided on each longitudinal leg, the concentrated winding surrounding each longitudinal leg, the stator further comprising a cup-shaped recess into which the rotor can be inserted, the cup-shaped recess arranged at the axial end of the stator, and the transverse legs arranged around the cup-shaped recess. The stator includes shielding extending circumferentially along the plurality of coil cores, and the shielding extending axially from a first shielding end to a second shielding end.

[0019] The use of shielding prevents the magnetic field from being able to escape from the stator to the outside, i.e., the stator housing: the magnetic field no longer penetrates the stator housing but is conducted within it, which leads to a reduction in eddy current losses.

[0020] An additional advantage of using shielding inside the stator housing is that the stator housing can still be made from a material that is a good conductor of electricity, such as aluminum, thereby ensuring good dissipation of heat generated during operation of the stator.

[0021] The shielding extends radially outward in a circumferential direction along the coil cores. The shielding can be open in the circumferential direction, i.e., the shielding extends only along the coil cores, or closed, i.e., the shielding extends along all of the coil cores. In some embodiments, the shielding has cutouts. These cutouts can be provided for the passage of connectors, such as cables, through the shielding.

[0022] According to a preferred embodiment, the shielding is disposed radially outwardly around the coil core and extends circumferentially over an angle of at least 120 degrees, preferably at least 240 degrees.

[0023] According to a preferred embodiment, the shielding is designed in the shape of a ring.

[0024] Depending on the configuration of the stator, it may be advantageous to use a ring-shaped shielding. However, the shielding can also be designed in a polygonal shape, for example a hexagon or octagon. The design of the shielding can be individually adapted to the shape and / or arrangement of the corresponding stator or corresponding coil core.

[0025] In a preferred embodiment, the shielding includes at least two shielding segments, each shielding segment extending circumferentially from a first segment end to a second segment end.

[0026] Furthermore, it is preferred that the shielding segments are arranged adjacent to one another in the circumferential direction, although embodiments are also possible in which the shielding segments are arranged adjacent to one another in the axial direction.

[0027] In this regard, being disposed adjacent to one another includes having a distance between the shielding segments, the shielding segments abutting, and the shielding segments overlapping.

[0028] According to another preferred embodiment, the shielding is designed as a strip, which forms a plurality of strip windings which lie flat against one another in the radial direction and which are particularly preferably insulated from one another.

[0029] The strips can be made of electrical sheet metal, preferably grain-oriented electrical sheet metal. By general definition, electrical sheet metal is understood to be a flexible magnetic material for the magnetic core. There is also the possibility of using mu-metal as the material for the strips.

[0030] The advantage here is that such strips are frequently used in technology and are therefore cost-effective. It is also advantageous that the strips can be manufactured relatively easily and that it is possible to directly insulate the strip windings from one another during manufacture.

[0031] Furthermore, according to another preferred embodiment, the first shielding end is preferably arranged at the same height as the first winding end in the axial direction.

[0032] When exactly one winding is arranged on a longitudinal leg, the first winding end refers to the end of this winding that is axially closer to the first end of the longitudinal leg. The first winding end can also be considered the axially lower winding end if the second winding end is axially closer to the second end of the longitudinal leg and thus represents the axially upper winding end. When two or more windings are arranged on a longitudinal leg, the first winding end refers to the first winding end of the winding that is axially closer to the first end of the longitudinal leg. In other words, the first winding end is the axially lower end of the axially lowermost winding arranged on the longitudinal leg. Again, the definitions "lower" meaning closer to the first end of the longitudinal leg and "upper" meaning closer to the second end of the longitudinal leg apply.

[0033] It is advantageous to position the first shielding end at the same axial height as the first winding end, since the magnetic field is generated in the winding, which is the main source of stray magnetic fields. The shielding therefore ensures effective shielding of the magnetic field at the location where it is generated, thereby preventing the magnetic field from penetrating into the stator housing.

[0034] Of course, it is also possible for the first shielding end to be arranged axially below the first winding end, which may be advantageous, for example, for reasons of stability.

[0035] In another preferred embodiment, the first shielding end is axially disposed above the first winding end.

[0036] Stray magnetic fields are particularly strong in the upper region of the stator, i.e., the region axially closer to the second ends of the longitudinal legs. This is because the iron circuit is not closed here, and therefore the magnetically active core of the rotor only conducts its own magnetic field, not the magnetic field of the windings. On the other hand, in the lower region of the stator, i.e., the region axially closer to the first ends of the longitudinal legs, the magnetic field is sufficiently conducted by the back iron, and there is significantly less stray magnetic field. Therefore, it is advantageous to place the shielding in the upper region of the stator. A smaller extension of the shielding in the axial direction offers the possibility of constructing a more compact stator, which also has the advantage that less material is required, resulting in lower costs.

[0037] According to a preferred embodiment, the shielding extends axially to a housing cover of the stator, the housing cover being arranged at a first end of the stator.

[0038] Here, different housing cover designs are possible. Depending on the design, the shielding can extend to the housing cover so that contact between them is possible. If the housing cover is made of plastic, the shielding can come into contact with the housing cover because plastic housing covers are not conductive. If the housing cover is made of a conductive material, there should be a distance between the shielding and the housing cover. Otherwise, the effectiveness of reducing eddy current losses may be reduced. The shielding can also have a thinned region at the second shielding end over its entire circumferential extension, with the thinned region extending axially and made of a non-conductive material. Such an insulating layer can also be achieved by coating the shielding at the second shielding end.

[0039] It is advantageous for the shielding to extend as far as possible to the housing cover, since, as already explained, most of the stray magnetic fields occur at the axial upper end of the stator.

[0040] Additionally, it is preferred that the shielding be formed from a high magnetic permeability material, preferably a high magnetic permeability material that includes iron and silicon.

[0041] In the framework of this application, a high permeability material is understood to be a material with a relative permeability μ> 40. Further properties of such a material are, in particular, that it has a low electrical conductivity and low hysteresis losses.

[0042] According to a preferred embodiment, the shielding is designed as a coating, preferably applied to the radially inner side of the stator housing. The coating has the advantage that it can be applied to the existing stator housing by conventional coating methods known from the state of the art (e.g., PVD methods, thermal spraying). By doing so, no additional material (electrical sheet metal, etc.) is required for the shielding, and the shielding can be provided already during the manufacture of the stator housing, which saves additional processing steps. Preferably, the coating contains iron and / or plastic-bonded metal particles. Preferably, the coating thickness is greater than 50 micrometers.

[0043] According to a preferred embodiment, the shielding is designed as a metal sheet, which may contain iron and / or silicon. There is also the possibility of using mu-metal sheet and / or electrical metal sheet, preferably oriented-grain electrical metal sheet. The metal sheet can be bent into a ring shape and thus adapted to precisely fit the outer diameter of the coil core and the stator housing.

[0044] Furthermore, each coil core is preferably formed from elements of sheet metal, the elements being stacked in the circumferential direction of the stator.

[0045] This means that several metal sheets in the form of a coil core are stacked together and insulated from each other in the circumferential direction. The metal sheet design of the coil core prevents eddy currents due to the magnetic field extending in the direction of the metal sheets, i.e., the magnetic field following the longitudinal leg in the axial direction and the transverse leg in the radial direction. Here again, electric metal sheets or mu-metal sheets can be used as the preferred material.

[0046] According to a further preferred embodiment, two concentrated turns are provided on each longitudinal leg, each concentrated turn surrounding a respective longitudinal leg and arranged adjacent to one another in the axial direction.

[0047] According to a further preferred embodiment, the shielding comprises at least two shielding sections arranged adjacent to each other in the axial direction, which means that at least two shielding sections can be stacked in the axial direction, where the individual shielding sections can be made of different materials, and the individual shielding sections can be designed differently in terms of shape.

[0048] 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.

[0049] Furthermore, an electromagnetic rotary drive designed as a temple motor is proposed by the present invention, which comprises a magnetic levitation device according to the present invention and a rotor with a disk-shaped or ring-shaped magnetically effective core, the rotor being insertable into a cup-shaped recess, the rotor being designed as a rotor of an electromagnetic rotary drive.

[0050] Such electromagnetic rotary drives are also known as bearingless motors, the term referring to electromagnetic rotary drives in which the rotor is entirely magnetically levitated relative to the stator, with no separate magnetic bearings.

[0051] Further advantageous measures and embodiments of the invention are evident from the dependent claims.

[0052] 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]

[0053] [Figure 1] 1 is a perspective view of a first embodiment of a magnetic levitation device according to the present invention with a portion of the stator housing removed; [Figure 2] 2 is a cross-sectional view of the first embodiment of the magnetic levitation device of FIG. 1. [Figure 3] 2 is a cross-sectional view of a second embodiment of a magnetic levitation device according to the present invention. [Figure 4] FIG. 2 is a cross-sectional view of a third embodiment of a magnetic levitation device according to the present invention. [Figure 5] FIG. 10 is a cross-sectional view of a fourth embodiment of a magnetic levitation device according to the present invention. [Figure 6] FIG. 10 is a perspective view of a fifth embodiment of a magnetic levitation device according to the present invention with a portion of the stator housing removed. [Figure 7] FIG. 10 is a cross-sectional view of a sixth embodiment of a magnetic levitation device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] FIG. 1 shows a perspective view of a first embodiment of a magnetic levitation device according to the present invention, generally designated by reference numeral 1. The magnetic levitation device 1 is designed to magnetically levitate a rotor 3 having a disk-shaped or ring-shaped magnetically effective core 31 in a contactless manner. The magnetic levitation device 1 is designed according to a temple structure and includes a stator 2. The stator 2 includes a stator housing 21, a portion of which has been removed in FIG. 1 for clarity, and a housing cover 212 is disposed at a first end of the stator 22 and connected to the stator housing 21 to seal the stator housing 21 from entering any undesirable substances.

[0055] The stator housing 21 is typically made of metal, preferably aluminum, and the housing cover 212 is made of plastic, preferably polypropylene, in this case. The connection between the stator housing 21 and the housing cover 212 is preferably formed by welding or gluing. However, it is also possible to form the stator housing 21 and the housing cover 212 from the same material. For example, stainless steel can be used as the material for the stator housing 21 and the housing cover 212.

[0056] A cup-shaped recess 211 is provided in the housing cover 212, 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.

[0057] The stator 2 has a plurality of coil cores 25, six in this example, each having a longitudinal leg 26 and a transverse leg 27. In the illustration in FIG. 1 , only three coil cores 25 are visible, with the other three coil cores 25 hidden by the stator housing 21. Each longitudinal leg 26 extends from a first end 261 in the axial direction A to a second end 262, and the transverse leg 27 is disposed at the second end 262 and extends in a radial direction R perpendicular to the axial direction A. A back iron 28 is disposed at the first end 261 and connects the first ends 261 of all of the longitudinal legs 26.

[0058] The stator further has a cup-shaped recess 211 into which the rotor 3 can be inserted, the cup-shaped recess 211 being arranged at the first axial end 22 of the stator 2. The lateral legs 27 are arranged surrounding the cup-shaped recess 211.

[0059] At least one concentrated winding 61 is arranged on each longitudinal leg 26, surrounding the respective longitudinal leg 26. In a first embodiment, exactly one concentrated winding 61 is provided on each longitudinal leg 26. In other embodiments, multiple concentrated windings may be arranged on the longitudinal legs 26. For example, there is an embodiment (FIG. 4) in which exactly two concentrated windings 61 a, 61 b ​​are provided on each longitudinal leg 26, each concentrated winding 61 a, 61 b ​​surrounding the respective longitudinal leg 26, and 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.

[0060] The concentrated windings 61 act to generate an electromagnetic field that allows the rotor 3 to be magnetically levitated without contact in the cup-shaped recess 211 .

[0061] Furthermore, the stator 2 includes shielding 4 extending circumferentially along the multiple coil cores 25. The shielding 4 extends in the axial direction A from a first shielding end 41 to a second shielding end 42.

[0062] In this embodiment, the shielding 4 is disposed radially outwardly around the coil core 25 and extends circumferentially over an angle of 280 degrees.

[0063] However, embodiments are possible in which the shielding 4 extends over an angle of 360 degrees. However, embodiments are also possible in which the shielding 4 extends over an angle greater than 360 degrees. Ideally, the shielding 4 extends over an angle of at least 120 degrees, preferably at least 240 degrees.

[0064] Although the shielding 4 extends over an angle of 360 degrees, this does not directly mean that the shielding 4 is closed in the circumferential direction. There may be a distance between the first starting point 46 and the second starting point 47 of the shielding 4. However, it is also possible for the first starting point 46 and the second starting point 47 to be in contact or even overlap. In the latter case, a circumferential extension of the shielding 4 over an angle greater than 360 degrees is required. In some embodiments, the shielding 4 is provided with cutouts. These cutouts may be provided, for example, for the passage of connectors, such as cables, through the shielding.

[0065] For better understanding, FIG. 2 shows a cross-sectional view along an axial direction A of the first embodiment of the magnetic levitation device of FIG.

[0066] In this first embodiment, the shielding 4 is designed in the shape of a ring, and the first shielding end 41 is arranged in the axial direction A below the first end 261 of the longitudinal leg 26, i.e. closer to the first end 261 of the longitudinal leg 26, than the first winding end 611 of the winding 61.

[0067] In this case too, the definition that "lower" with respect to the axial direction A means closer to the first end 261 of the longitudinal leg 26 and "upper" with respect to the axial direction A means closer to the second end 262 of the longitudinal leg 26 applies.

[0068] If exactly one winding 61 is arranged on the longitudinal leg 26, the first winding end 611 refers to the end of the winding 61 that is arranged closer to the first end 261 of the longitudinal leg 26 in the axial direction A. If the second winding end 612 is arranged closer to the second end 262 of the longitudinal leg 26 with respect to the axial direction A and thus represents the axially upper winding end 612, the first winding end 611 can also be considered to be the axially lower winding end 611.

[0069] The first shielding end 41 can also be arranged at the same height as the first winding end 611 in the axial direction A (FIG. 3). This arrangement of the shielding 4 can often be sufficient, since the winding 61 is the main source of stray magnetic fields, since the magnetic field is generated at the winding's location. The shielding 4 therefore ensures effective shielding of the magnetic field at the location where it is generated, thereby preventing it from penetrating into the stator housing 21. For example, in the first embodiment, it can be advantageous for stability reasons to arrange the first shielding end 41 below the first winding end 611.

[0070] However, embodiments are also possible in which the first shielding end 41 is arranged above the first winding end 611 in the axial direction A, here preferably between the first winding end 611 and the second winding end 612.

[0071] The stray magnetic field is particularly strong in the upper region of the stator 2, i.e., in the region axially closer to the second ends 262 of the longitudinal legs 26. The reason for this is that the iron circuit is not closed here, and therefore the magnetically active core 31 of the rotor 3 conducts only its own magnetic field and not that of the windings 61. On the other hand, in the lower region of the stator 2, i.e., in the region axially closer to the first ends 261 of the longitudinal legs 26, the magnetic field is sufficiently conducted by the back iron 28, and significantly less stray magnetic field is present. It is therefore advantageous to arrange the shielding 4 at least in the upper region of the stator 2. A smaller extension of the shielding 4 in the axial direction offers the possibility of constructing the stator 2 more compactly, which also has the advantage that less material is required, resulting in lower costs.

[0072] In the first embodiment, the shielding 4 extends in the axial direction A up to the housing cover 212 of the stator 2 , which is arranged at the first end 22 of the stator 2 .

[0073] Here, the housing cover 212 is made of plastic, preferably polypropylene, and the shielding 4 is in contact with the housing cover 212 because the housing cover 212 is non-conductive. If the housing cover 212 were made of a conductive material, a distance should exist between the shielding 4 and the housing cover 212. Otherwise, the effect of reducing eddy current losses would be reduced. The shielding 4 can also have a thinned region at the second shielding end 42 over its entire circumferential extension, which extends in the axial direction A and is made of a non-conductive material as an insulating layer. Such an insulating layer can also be achieved by coating the shielding 4 at the second shielding end 42. In this case, contact between the shielding 4 and the housing cover 212 is possible even if the shielding 4 is made of a conductive material.

[0074] It is advantageous for the shielding 4 to extend as far as possible to the housing cover 212, since, as already explained, most of the stray magnetic fields occur at the axial upper end 22 of the stator 2.

[0075] The shielding 4 is preferably made of a high-permeability material. Here, it is preferred that this is a high-permeability material containing iron and / or silicon. A high-permeability material is understood to be a material with a relative permeability μ>40. Further properties of such a preferred material are, in particular, that it has low electrical conductivity and low hysteresis losses.

[0076] An embodiment is also possible in which the shielding 4 is designed as a metal sheet. The metal sheet can contain iron and / or silicon. There is also the possibility of using mu-metal sheets and / or electrical metal sheets, preferably oriented-grain electrical metal sheets, for the shielding 4.

[0077] In the first embodiment, the coil core 25 is preferably formed from sheet metal elements 253, which are stacked in the circumferential direction of the stator 2. The circumferential direction refers to a direction perpendicular to the radial direction R and perpendicular to the axial direction A. The elements 253 may be formed from electrical sheet metal, preferably non-oriented grain electrical sheet metal. The number of elements 253 in all embodiments and figures should be understood to be merely exemplary. The number may be greater or less than that shown.

[0078] In the first embodiment, the coil cores 25 each further include a radius at the axial upper end 252, which redirects the coil cores 25 from the axial direction A to the radial direction R.

[0079] According to a particularly preferred embodiment, the stator 2 is designed in such a way that, in addition to contactlessly magnetically levitating the rotor 3, it can also apply a torque to the rotor 3 or to the magnetically effective core 31 of the rotor 3, driving the rotor 3 to rotate about a desired axis of rotation. This means that in this preferred embodiment, the rotor 3 can be driven by the stator 2 to rotate about an axial direction A.

[0080] 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.

[0081] 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, or nine coil cores 25, or even an even greater number of coil cores 25.

[0082] 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, which lies 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.

[0083] The radial plane is indicated in Figure 1 by a line in the 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 in the operating state. When the rotor 3 is not tilted and not offset in the axial direction A, the magnetic center plane lies in the radial plane. The radial plane defines the xy plane of a Cartesian coordinate system whose z axis extends in the axial direction A.

[0084] The radial position of the magnetically effective core 31 or rotor 3 refers to the position of the rotor 3 in a radial plane.

[0085] Only the magnetically effective core 31 of the rotor 3 is shown in Figures 1 and 2, 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 for the magnetically effective core 31, preferably made from plastic, metal, alloy, or ceramic or ceramic material. The rotor 3 may also comprise vanes for mixing, stirring, or pumping fluids or other constituents.

[0086] When the rotor 3 is inserted into the cup-shaped recess 211, the rotor 3, and in particular its magnetically active core 31, 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.

[0087] When the magnetically effective core 31 of the rotor 3 is in a desired position during operation, the magnetically effective core 31 is centered between the end faces 272 of the lateral legs 27. The concentrated winding 61 is shown disposed below the radial plane E and aligned such that the coil axis of the concentrated winding extends in the axial direction A.

[0088] 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).

[0089] 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.

[0090] In operation, these electromagnetic rotating fields are generated by the concentrated windings 61 and can exert an arbitrarily adjustable radial transverse force on the rotor 3, thus making it possible to 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, these electromagnetic rotating fields can also produce a torque on the rotor 3.

[0091] 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.

[0092] 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.

[0093] These magnetically hard ferromagnetic or ferrimagnetic materials, i.e., with a high coercivity, are usually called permanent magnets. Coercivity refers to the magnetic field strength required to demagnetize a material. In the framework of this application, a permanent magnet is understood to be a component or material that has a coercivity, or more precisely, the coercivity of the magnetic polarization, greater than 10,000 A / m.

[0094] 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.

[0095] 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.

[0096] An embodiment is also possible in which the rotor is designed according to the squirrel cage rotor principle.

[0097] The ring-shaped back iron 28 can be formed from a soft magnetic material because the soft magnetic material acts as a flux conducting element for conducting magnetic flux.

[0098] Suitable soft magnetic materials for 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, in which the back irons 28 are designed as sheets of metal, i.e., the back irons 28 consist of a plurality of thin sheet metal elements stacked parallel to one another in the axial direction A. All elements are designed identically, i.e., in this case, substantially ring-shaped and each with the same thickness. Accordingly, the back irons 28 themselves are designed substantially ring-shaped and extend radially inward along the first ends 261 of the longitudinal legs 26 in the assembled state.

[0099] 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 2. In particular, such 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 in a powder metallurgy process.

[0100] An embodiment is also contemplated in which a so-called tape-wound toroidal core is used as the back iron 28. This is a coiled strip formed from electrical sheet metal. Preferably, oriented-grain electrical sheet metal is used here. In the state of the art, tape-wound toroidal cores are known for use primarily in transformers, transmitters, and inductors, but not for bearing devices, particularly electromagnetic rotary drives.

[0101] 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. Preferably, therefore, three degrees of freedom of the rotor 3, i.e., its position and rotation in the radial plane, can be actively adjusted. The magnetically active core 31 of the rotor 3 is passively stabilized by reluctance forces with respect to the axial offset of the core 31 from the radial plane in the axial direction A. That is, the axial offset of the core cannot be controlled. The magnetically active core 31 of the rotor 3 is also passively stabilized with respect to the remaining two degrees of freedom, i.e., tilt with respect to a radial plane perpendicular to the desired axis of rotation. The rotor 3 is therefore 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) by the interaction of the magnetically active core 31 with the coil core 25.

[0102] 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 passive magnetic stabilization is based on a reluctance force that returns the rotor 3 to the desired position again, for example if the rotor 3 is deviated from the desired position, i.e. if the rotor 3 is misaligned or offset in the axial direction A or if the rotor 3 is tilted.

[0103] In magnetic levitation device 1, magnetic levitation and selective 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.

[0104] 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, exactly two concentrated windings 61 a, 61 b ​​are arranged in each longitudinal leg 26 (see, for example, FIG. 4 ), 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.

[0105] 1, with just one concentrated winding 61 on each coil core 25, the current values ​​required for levitation and for torque generation, respectively determined in the control unit, are added or superimposed by calculation, for example using software, and the resulting total current is then applied to the respective concentrated winding 61.

[0106] 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. The magnetic levitation device 1 according to the invention is also 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.

[0107] 3 is a cross-sectional view of a second embodiment of a magnetic levitation device 1 according to the present invention. The cross-section is taken along the axial direction A. In the following description of the second embodiment, only the differences from the first embodiment of FIG. 1 are described in more detail. The description of the first embodiment applies in the same or similar manner to the second embodiment. The same reference numerals refer to the same features or functionally equivalent features described with respect to the first embodiment.

[0108] In the second embodiment, one difference is that the first shielding end 41 is arranged at the same height as the first winding end 611 in the axial direction A. The advantages of this have already been explained.

[0109] 4 is a cross-sectional view of a third embodiment of a magnetic levitation device 1 according to the present invention. The cross-section is taken along the axial direction A. In the following description of the third embodiment, only the differences from the previous embodiment are described in more detail. The descriptions of the previous embodiment also apply in the same or similar manner to the third embodiment. The same reference signs refer to the same features or functionally equivalent features described with respect to the previous embodiment.

[0110] In this embodiment, one difference is that the shielding 4 is designed as a coating 43, preferably applied to the radially inner side 213 of the stator housing 21. The coating 43 has the advantage that it can be applied to the existing stator housing 21 by conventional coating methods known from the state of the art (e.g., PVD methods, thermal spraying). By doing so, no additional material (such as electrical sheet metal) is required for the shielding 4; the shielding 4 can be provided already during the manufacture of the stator housing 21, which saves additional processing steps. Preferably, the coating 43 comprises iron and / or plastic-bonded metal particles. Preferably, the coating thickness is greater than 50 micrometers.

[0111] The coating 43 can extend over the entire radially inwardly disposed side 213 of the stator housing 21 in the axial direction A, or over only a portion of the extension of the radially inwardly disposed side 213 in the axial direction A. For example, the coating 43 is provided only on the radially inwardly disposed side 213 of the stator housing 21 in the region between the first winding end 611 and the second winding end 612. Preferably, the coating 43 extends over the entire circumference of the radially inwardly disposed side 213 of the stator housing 21.

[0112] 5 is a cross-sectional view of a fourth embodiment of a magnetic levitation device 1 according to the present invention. In this case, the cross-section is taken in a radial plane. In the following description of the fourth embodiment, only the differences from the previous embodiments are described in more detail. The descriptions of the previous embodiments apply in the same or similar manner to the fourth embodiment. The same reference symbols refer to the same features or functionally equivalent features described with respect to the previous embodiments.

[0113] In this embodiment, one difference is that the shielding 4 includes two shielding segments 45a, 45b, each extending circumferentially from a first segment end 451a, 451b to a second segment end 452a, 452b. It should be understood that the number of shielding segments 45a, 45b is merely exemplary. The shielding 4 includes at least two shielding segments 45a, 45b, but may include three or more, for example, three, four, five, or more, shielding segments 45a.

[0114] The shielding segments 45a, 45b can be formed from different materials.

[0115] In this embodiment, the shielding segments 45a, 45b are arranged adjacent to each other in the circumferential direction and have a predetermined distance from each other, i.e., the first and second segment ends 451a, 451b, 452a, 452b do not contact each other in this embodiment, however, it is also possible that all or only part of the segment ends 451a, 451b, 452a, 452b contact each other or that the shielding segments 45a, 45b overlap.

[0116] It is also possible to have an embodiment in which the shielding segments 45a, 45b are arranged adjacent to each other in the axial direction A. Such an embodiment is shown in FIG.

[0117] 6 is a perspective view of a fifth embodiment of a magnetic levitation device 1 according to the present invention, with a portion of the stator housing 21 removed. In the following description of the fifth embodiment, only the differences from the previous embodiments will be described in more detail. The descriptions of the previous embodiments apply in the same or similar manner to the fifth embodiment. The same reference numerals refer to the same features or functionally equivalent features described with respect to the previous embodiments.

[0118] One difference from the previous embodiment is that in this embodiment, the shielding 4 includes a plurality of, here three, shielding segments 45a, 45b, and 45c arranged adjacent to one another in the axial direction A. It should be understood that the number of shielding segments 45a, 45b, and 45c is merely exemplary. In this embodiment, the extensions of the individual shielding segments 45a, 45b, and 45c are different from one another. In other words, the widths of the individual shielding segments 45a, 45b, and 45c in the axial direction A are different. However, embodiments are also possible in which the shielding segments 45a, 45b, and 45c have the same width in the axial direction A. In this embodiment, all three shielding segments 45a, 45b, and 45c have the same shape. However, in other embodiments, the individual shielding segments 45a, 45b, and 45c may have different designs with respect to their shapes. It should be noted here that the shielding segments 45a, 45b, 45c are designed so that they can be positioned adjacent to each other at their respective first axial segment ends 41a, 41b, 41c with their corresponding respective second axial segment ends 42a, 42b, 42c.

[0119] A second difference is that the coil core 25 does not have a radius at the upper axial end 252. A further difference is that exactly two concentrated windings 61 a, 61 b ​​are now provided on each longitudinal leg 26, each surrounding the respective longitudinal leg 26 and arranged adjacent to one another in the axial direction A. In this case where two or more windings 61 a, 61 b ​​are arranged on each longitudinal leg 26, the first winding end 611 is the first winding end 611 of the winding 61 a that is arranged closer to the first end 261 of the longitudinal leg 26 in the axial direction A. In other words, the first winding end 611 is the axially lower end of the axially lowest winding 61 a arranged on the longitudinal leg 26. Again, the definitions apply that "lower" means closer to the first end 261 of the longitudinal leg 26 and "upper" means closer to the second end 262 of the longitudinal leg 26.

[0120] 7 shows a cross-sectional view of a sixth embodiment of a magnetic levitation device 1 according to the present invention. In this case, the cross-section is taken in a radial plane. In the following description of the sixth embodiment, only the differences from the previous embodiments are described in more detail. The descriptions of the previous embodiments apply in the same or similar manner to the sixth embodiment. The same reference signs refer to the same features or functionally equivalent features described with respect to the previous embodiments.

[0121] One difference is that here the shielding is designed as a strip 44, which forms a plurality of strip windings 441 lying flat to one another in the radial direction R. It is particularly preferred that the plurality of strip windings 441 are insulated from one another.

[0122] Here, the strips 44 can be made of electrical sheet metal, preferably grain-oriented electrical sheet metal. By common definition, electrical sheet metal is understood to be a flexible magnetic material for the magnetic core. There is also the possibility of using mu metal for the strips 44.

[0123] The advantage here is that such strips 44 are frequently used in technology and are therefore cost-effective. It is also advantageous that the strips 44 can be manufactured relatively easily and that the strip windings 441 can be directly insulated from each other during manufacturing.

[0124] It goes without saying that all embodiments having the respective characteristics shown in the description of the drawings can be combined with each other in any way.

[0125] Furthermore, all of the illustrated embodiments can be designed with a coil core 25 designed such that the available space for the rotor 3 in the magnetic levitation device 1 is increased. This is achieved by a special geometry of the coil core 25.

[0126] 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, the second distance being 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 increasing the distance between the magnetically effective core 31 of the rotor and the longitudinal legs 26, particularly also in the region of the axially upper section.

[0127] Such a coil core 25 as described above is designed similarly to such a coil core shown in FIG. 3 of EP-A-4084304.

Claims

1. A magnetic levitation device for contactless magnetic levitation of a rotor (3), the magnetic levitation device comprising a disk-shaped or ring-shaped magnetically effective core (31), the magnetic levitation device having a stator (2) comprising a stator housing (21), the stator including a plurality of coil cores (25), each of the coil cores including a longitudinal leg (26) extending from a first end (261) in an axial direction (A) to a second end (262), and a lateral leg (27) disposed at the second end (262) of the longitudinal leg and extending in a radial direction (R) perpendicular to the axial direction (A), and a back iron ( the back iron connects the first ends (261) of all the longitudinal legs (26), at least one concentrated winding (61; 61a, 61b) is provided on each longitudinal leg (26), the concentrated winding surrounds each of the longitudinal legs (26), the stator (2) further has a cup-shaped recess (211) into which a rotor (3) can be inserted, the cup-shaped recess (211) is arranged at the axial end of the stator (2), and the transverse legs (27) are arranged around the cup-shaped recess (211). A magnetic levitation device for contactless magnetic levitation of a rotor (3), comprising: The magnetic levitation device, characterized in that the stator (2) includes shielding (4) extending circumferentially along a plurality of coil cores (25), and the shielding (4) extends in the axial direction (A) from a first shielding end (41) to a second shielding end (42).

2. 2. The magnetic levitation device of claim 1, wherein the shielding (4) is disposed radially outwardly around the coil core (25) and extends circumferentially over an angle of at least 120 degrees, preferably at least 240 degrees.

3. 3. The magnetic levitation device according to claim 1 or 2, wherein the shielding (4) is designed in the shape of a ring.

4. 4. The magnetic levitation device of claim 1, wherein the shielding (4) includes at least two shielding segments (45a, 45b), each extending circumferentially from a first segment end (451a, 451b) to a second segment end (452a, 452b).

5. The magnetic levitation device according to claim 4, wherein the shielding segments (45a, 45b) are arranged adjacent to each other in the circumferential direction.

6. 4. A magnetic levitation device according to claim 1, wherein the shielding (4) is designed as a strip (44), the strip (44) forming a plurality of strip windings (441) lying flat relative to each other in the radial direction (R).

7. 7. A magnetic levitation device as claimed in any one of claims 1 to 6, wherein the first shielding end (41) is positioned at the same height as the first winding end (611) in the axial direction (A).

8. 6. The magnetic levitation device according to claim 1, wherein the first shielding end (41) is positioned higher than the first winding end (611) in the axial direction (A).

9. 9. The magnetic levitation device according to claim 1, wherein the shielding (4) extends in the axial direction to a housing cover (212) of the stator (2), and the housing cover (212) is disposed at a first end (22) of the stator (2).

10. 10. The magnetic levitation device according to any one of claims 1 to 9, wherein the shielding (4) is made of a high magnetic permeability material, preferably a high magnetic permeability material containing iron and silicon.

11. 10. A magnetic levitation device according to any one of claims 1 to 3 and 6 to 9, wherein the shielding (4) is preferably designed as a coating (43) applied to a radially inner side (213) of the stator housing (21).

12. 10. The magnetic levitation device according to any one of claims 1 to 9, wherein the shielding (4) is designed as a metal sheet.

13. 13. The magnetic levitation device of claim 1, wherein two concentrated windings (61 a, 61 b) are provided on each longitudinal leg (26), each concentrated winding surrounding a respective longitudinal leg (26) and arranged adjacent to each other in the axial direction (A).

14. 14. The magnetic levitation device according to any one of claims 1 to 13, wherein the stator (2) is designed to generate a torque that can magnetically drive the rotor (3) to rotate about the axial direction (A) without contact.

15. 15. 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 14 and a rotor (3) with a disk-shaped or ring-shaped magnetically effective core (31), the rotor (3) being insertable into the cup-shaped recess (211), the rotor (3) being designed as the rotor (3) of the electromagnetic rotary drive.

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