Using varying magnetization to create flux-focusing magnets

Abstract

An apparatus (460) and a method for manufacturing a permanent magnet (250, 350) are described. The apparatus (460) includes (a) a mold (470); (b) a first magnetic device (461) and a second magnetic device (464); (c) a mold; and (d) a magnetic element (480) for spatially guiding and / or changing magnetic flux. The magnetic element is located in a region extending between the first magnetic device and the second magnetic device and is movably supported in the region so that in a first position (480a), a first spatial magnetic flux distribution is provided, and in a second position (480b), a second spatial magnetic flux distribution different from the first spatial magnetic flux distribution is provided. A magnet (350) manufactured using the method, an electromechanical transducer (140) including such a magnet (350), and a wind turbine (100) are further described.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for producing a permanent magnet. Furthermore, the present invention relates to a magnet produced using said method, as well as an electromechanical transducer and a wind turbine comprising at least one such magnet. Background Art

[0002] Permanent magnetic materials are used in a wide variety of applications. Perhaps the most technically and economically important application area is in electromechanical transducers, namely electric motors and generators. Electric motors, equipped with at least one permanent magnet (PM), convert electrical energy into mechanical energy by generating a temporarily varying magnetic field through windings or coils. This temporarily varying magnetic field interacts with the PM's magnetic field, generated, for example, by the rotational motion of the motor's rotor assembly relative to its stator assembly. Generators convert mechanical energy into electrical energy in a physically complementary manner.

[0003] A generator is the core component of any power plant used to generate electrical energy. This applies to power plants that directly capture mechanical energy, such as hydroelectric power plants, tidal power plants, and wind power plants, also known as wind turbines. However, this also applies to power plants that (i) first use chemical energy, such as from burning fossil fuels or from nuclear energy, to generate thermal energy, and (ii) secondly convert the generated thermal energy into mechanical energy by means of appropriate thermodynamic processes.

[0004] Generator efficiency is perhaps the most important factor in optimizing electrical energy production. For PM generators, a strong magnetic flux generated by the permanent magnets (PMs) is essential. This can be best achieved using sintered rare-earth magnets, for example, using an FeNdB material composition. However, the spatial magnetic field distribution generated by the PM device or PM workpiece also has an impact on generator efficiency. In the latter case, it is often advantageous to use a PM device with a nonuniform magnetic domain pattern, resulting in an intentionally nonuniform magnetic field strength or flux density, particularly in the air gap between the rotor and stator assemblies.

[0005] It is known to configure non-uniform magnetic domain patterns in PM devices to achieve so-called "flux focusing." WO 2012 / 141932 A2 discloses a PM magnet arrangement in which PM devices with different magnetizations are combined to achieve "magnetic focusing." EP 3 276 642 A1 discloses a sintered rare earth PM with a focused magnetic domain pattern, which has a single-piece PM body. EP 2 762 838 A2 discloses an apparatus and method for manufacturing PMs, in which a non-uniform external magnetic field is applied during the sintering process to magnetize different regions of the PM in different directions.

[0006] Magnetic flux provides a substantial increase in the air gap flux density, which results in higher torque / power for electromechanical transducers, such as generators for direct-drive wind turbines. Consequently, the demand for flux-focusing permanent magnet (FFPM) workpieces / devices will increase in the near future. However, the desired strength or degree of magnetic focusing, which can be characterized by the so-called (magnetic) focal length, similar to optical devices, depends on the specific application. Consequently, manufacturing different types of FFPM workpieces is expensive, as different equipment for compacting, magnetizing, and sintering the magnetic powder is required for FFPM workpieces with different focal lengths.

[0007] There may be a need to facilitate the fabrication of flux focusing permanent magnet (FFPM) workpieces. Summary of the Invention

[0008] The subject matter of the present invention satisfies this need. Advantageous embodiments of the invention are described.

[0009] According to a first aspect of the present invention, there is provided an apparatus for manufacturing permanent magnets, in particular sintered permanent magnets. The apparatus provided comprises (a) a mold having a mold cavity for receiving permanent magnet material powder; (b) a first magnetic device and a second magnetic device for generating a magnetic flux for magnetizing the powder contained in the mold cavity; (c) a mold for compacting the powder contained in the mold cavity; and (d) a magnetic element for spatially guiding and / or changing the magnetic flux. The magnetic element is located in an area extending between the first magnetic device and the second magnetic device and is movably supported in the area, so that in a first position of the magnetic element, a first spatial magnetic flux distribution is given at least in the mold cavity, and in a second position of the magnetic element, a second spatial magnetic flux distribution is given at least in the mold cavity. The second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution.

[0010] The described apparatus is based on the concept that, when a magnetic element is placed in at least two different positions during the powder compaction and magnetization steps, the spatial magnetic flux distribution changes during these processes. Specifically, the spatial magnetic flux distribution changes in such a way that the powder is subjected to at least one spatially non-uniform or uneven distribution of magnetic flux lines. This means that the magnetized compact resulting from the magnetization and compaction steps will not exhibit a uniform magnetization with parallel orientation of the magnetic domain alignment directions. Instead, a spread angular distribution of the magnetic domain alignment directions is generated, at least within some regions of the magnetized compact. This spread angular distribution can produce a focused magnetization of the (sintered) permanent magnet (PM) workpiece, which can be obtained from the magnetized compact using a known sintering process in a suitable sintering furnace or chamber. Therefore, the degree of focusing of the (sintered) PM (workpiece), and in particular the position of the focus or focus area, depends on the position to which the magnetic element is brought during the compaction and magnetization steps. This means that by appropriately selecting the position to which the magnetic element is brought, the magnetic focusing properties of the resulting (sintered) and magnetized block can be adjusted.

[0011] Using the described apparatus, different types of flux focusing permanent magnet (FFPM) workpieces can be manufactured. Specifically, to manufacture a first type of FFPM having a first flux focusing characteristic, the magnetic element is brought to a first set of at least two locations, and to manufacture a second type of FFPM workpiece having a second flux focusing characteristic, the magnetic element is brought to a second set of at least two locations that are spatially different from the first set of locations.

[0012] It is worth noting that the magnetic flux focusing characteristics can be defined not only by the location of the magnetic element, but also by the duration of the magnetic element's presence within the respective location. Furthermore, the magnetic flux focusing characteristics can also be determined by taking into account the relative timing between these locations and the progression of the magnetization and compaction processes.

[0013] It should be further mentioned that the magnetic flux focusing properties of the magnetized compact generally correspond at least partially to the magnetic focusing properties of a sintered permanent magnet (PM) workpiece to be produced from the sintered magnetized compact by means of known post-processing steps. These steps may include, for example, appropriate shaping, for example by removing sintered magnetic material and / or surface finishing.

[0014] Furthermore, it is mentioned that the steps of magnetization and compaction are usually carried out simultaneously or at least overlap for a certain period of time.

[0015] Furthermore, it is mentioned that the magnetization of the powder by means of a magnetic flux can be coupled with an alignment of magnetic domains.

[0016] According to another embodiment of the invention, the device further comprises an actuator mechanism for changing the position of the magnetic element. This may provide the advantage that the position of the magnetic element may be controlled accurately and in an automated manner.

[0017] The actuator mechanism can be configured to move the magnetic element in a continuous manner. However, in certain applications, the actuator mechanism can drive the magnetic element to and from discrete positions in a stepwise manner.

[0018] According to another embodiment of the present invention, the first and second magnetic devices are configured to generate a magnetic flux pattern in the substantial absence of the magnetic element, the magnetic flux pattern comprising a diffuse angular distribution of magnetic flux lines at least within the mold cavity. This can provide the advantage that, even in the absence of the magnetic element, a FFPM and a corresponding magnetized compact having a focused pattern of magnetic alignment directions can be produced. This means that the (presence of) the movable magnetic element will (only) modify the focused magnetic flux pattern.

[0019] In the case where the spread angular distribution of the magnetic flux lines generated by only (at least) two magnetic devices is stationary in time, it can be considered to represent the basic magnetic flux pattern. Therefore, the time-varying magnetic flux generated by the moving magnetic element can be considered to represent a deviation from the basic magnetic flux pattern.

[0020] According to another embodiment of the invention, at least one of the two magnetic devices comprises (a) an electromagnetic coil for generating a magnetic flux and (b) a magnetic yoke for guiding and / or for shaping the magnetic flux generated by the electromagnetic coil.

[0021] Providing a suitable magnetic yoke to support the electromagnetic coils generating the magnetic flux can provide the advantage that the magnetic flux (density) can be significantly increased, at least in selected areas of the mold cavity. Furthermore, by designing the shape and / or geometry of the magnetic yoke in a suitable manner, a desired (base) spread angular distribution of the magnetic flux lines can be generated, which results in a desired focused flux base magnetization design.

[0022] The magnetic yoke, which can also be called a pole piece, can be made of a ferromagnetic material, in particular iron or cobalt iron, to achieve a high magnetic saturation. In contrast, the mold can be made of a non-magnetic material, in particular a non-ferromagnetic material. Stainless steel is currently the preferred material. However, other mold materials that provide mechanical rigidity can also be used.

[0023] According to an embodiment of the present invention, the magnetic element is supported in such a way that it can be continuously moved along a predefined trajectory. This can provide the advantage that the position to which the magnetic element can be brought and to which it is brought can be spatially defined with high precision. This can result in a high degree of precision in the resulting magnetic focusing properties.

[0024] The trajectory may be predefined by any mechanical guiding structure, including, for example, guide rods or guide rails. Preferably, the guiding structure is made of a non-magnetic material, such as, for example, stainless steel, so as not to disturb the magnetic flux.

[0025] It is worth mentioning that in the "quasi-continuous consideration", continuous movement corresponds to continuous movement to multiple locations with small distances between adjacent locations. Continuous movement can even be considered as discrete movement to and from an infinite number of locations, where the distance between two adjacent locations is zero.

[0026] According to another embodiment of the invention, the length of the predefined track determines the magnetic focal length of the permanent magnet.

[0027] By moving the magnet along a relatively long trajectory, an angular distribution of magnetic domain alignment directions will be generated that has a relatively large or wide spread. Consequently, the magnetic focusing will be relatively strong, and therefore, the focal length will be relatively small.

[0028] It is to be mentioned that magnetic focusing can be considered as analogous to optical focusing. This means that an angular expansion of the magnetic domain arrangement direction along one direction, which is sufficient for most applications of FFPM, results in a one-dimensional (1D) flux focusing, resulting in a linearly extending focusing region. This magnetic focusing corresponds to optical focusing with the aid of a cylindrical optical lens. Alternatively, the magnetic flux within the cavity (in the time average) can have an angular expansion along two directions perpendicular to each other (and both parallel to the main surface of the PM). This results in a two-dimensional (2D) flux focusing, which results in a magnetic focus or a location where the (small) magnetic flux density is focused. This magnetic focusing corresponds to optical focusing with the aid of a spherical optical lens.

[0029] It is important to note that the length may not necessarily be the maximum possible length allowed by, for example, the guide structure determined above. Rather, the length can be the actual length traveled by the magnetic element during a given magnetization and compaction step. This means that the flux focusing characteristics can be appropriately adjusted based on the actual length relative to the maximum possible length. Therefore, different types of FFPMs can be manufactured simply by varying the actual length of the path traveled by the magnetic element.

[0030] According to another embodiment of the present invention, the predefined trajectory is a path along a curved shape, particularly a path along a circular arc. This offers the advantage of allowing the magnetic element to follow a geometrically simple path. Consequently, the resulting magnetic flux focusing characteristics can be predicted in a simple and accurate manner. This facilitates the magnetic design of FFPM workpieces.

[0031] According to another embodiment of the present invention, the first magnetic device includes a first magnetic yoke, and the second magnetic device includes a second magnetic yoke. The first magnetic yoke and the second magnetic yoke are located on opposite sides of the mold cavity. Furthermore, the first magnetic yoke has a first outer yoke surface facing the mold cavity, and the second magnetic yoke has a second outer yoke surface facing the mold cavity. Furthermore, the first outer yoke surface is concave, and the second outer yoke surface is convex or flat.

[0032] The described spatial design of the two yokes offers the advantage that a suitable and well-defined extended angular distribution of magnetic flux lines can be generated within the mold cavity in a simple and effective manner. Depending on the specific application, the curvature of the outer yoke surface can be regular, i.e. without any corners and edges ("bumps and bumps"), or can be irregular.

[0033] According to another embodiment of the present invention, the first outer yoke surface has a first radius, and the second outer yoke surface has a second radius different from the first radius. This may provide the advantage that a higher alignment angle of the magnetic domains at and relative to the side edges of the magnetized compact can be achieved.

[0034] In some embodiments, the (at least one) magnetic element comprises or is made of a magnetic material, in particular a ferromagnetic material. This can provide the following advantages: the (desired) temporary magnetic perturbation caused by the moving magnetic element will be strong relative to the underlying magnetic flux pattern caused (only) by the magnetic device. As a result, higher alignment angles of the magnetic domains at and relative to the side edges of the magnetized compact can be achieved.

[0035] The ferromagnetic material may be iron or a combination of iron and cobalt. It is mentioned that in embodiments comprising (at least) two magnetic elements, all magnetic elements may of course comprise or be made of such a magnetic material.

[0036] According to another embodiment of the present invention, the device further comprises a further magnetic element, which is supported so that it can be continuously moved along another predefined trajectory. This can provide the advantage that the magnetization process can be more efficient in terms of magnetization intensity. Alternatively or in combination, the magnetization process can be accelerated because (at least) two magnetic elements are "operating" simultaneously.

[0037] According to another embodiment of the invention, the predefined track and the further predefined track are symmetrical relative to each other with respect to the magnetic symmetry axis of the device. This can provide the following advantage: FFPMs with a symmetrically spread angular distribution of the magnetic domain alignment direction can be manufactured in a simple and reliable manner.

[0038] In this document, the term "magnetic symmetry axis" of a device may particularly refer to the spatial distribution of magnetic field lines generated by means of two magnetic devices. This applies to operating conditions of the device in which (a) two magnetic elements are substantially absent or (b) the two magnetic elements are equidistant from the magnetic symmetry axis.

[0039] According to another embodiment of the present invention, the predefined trajectory is a path along a curved or linear shape, and the other predefined trajectory is another path along another curved or linear shape. To move at least one of the two magnetic elements, the corresponding curved shape can be a circular arc. This offers the advantage of allowing the two magnetic elements to travel along a geometrically simple path. Consequently, the resulting magnetic flux focusing characteristics can be predicted in a simple and accurate manner. This facilitates the magnetic design of FFPM workpieces.

[0040] According to another embodiment of the present invention, the first magnetic device includes a first magnetic yoke, and the second magnetic device includes a second magnetic yoke. Furthermore, the first magnetic yoke and the second magnetic yoke are located on opposite sides of the mold cavity. Furthermore, the first magnetic yoke has a first outer yoke surface facing the mold cavity, and the second magnetic yoke has a second outer yoke surface facing the mold cavity. The first outer yoke surface is flat, and the second outer yoke surface is convex.

[0041] Also for the above-described embodiment with at least two magnetic elements, the described spatial design of the two magnetic yokes can provide the following advantages: a suitable and well-defined extended angular distribution of magnetic flux lines can be generated in the mold cavity in a simple and effective manner. Depending on the specific application, the curvature of the convex second outer yoke surface can be regular, i.e. without any corners and edges ("bumps and bumps"), or can be irregular.

[0042] According to another aspect of the present invention, a method for manufacturing a permanent magnet, in particular a sintered permanent magnet, is provided. The provided method comprises (a) filling a mold cavity of a mold with a powder of a permanent magnet material; (b) generating a magnetic flux for magnetizing the powder contained in the mold cavity by means of a first magnetic device and a second magnetic device; (c) compacting the powder contained in the mold cavity by means of a mold; and (d) moving at least one magnetic element in an area extending between the first magnetic device and the second magnetic device, the magnetic element spatially guiding and / or modifying the generated magnetic flux from a first position to at least a second position. Thus, in the first position of the at least one magnetic element, a first spatial magnetic flux distribution is given at least in the mold cavity, and in the second position of the at least one magnetic element, a second spatial magnetic flux distribution is given at least in the mold cavity. The second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution.

[0043] Furthermore, the described method is based on the idea that by moving at least one magnetic element, the spatial magnetic flux distribution can be modified in such a way that FFPMs can be manufactured in an efficient and flexible manner. In this context, flexible means that, depending on the spatial movement of the at least one magnetic element, different patterns of magnetic domain alignment directions within the magnetized compact can be achieved.

[0044] According to an embodiment of the present invention, moving the at least one magnetic element comprises (a) a first movement along a predefined trajectory in a first direction and (b) a second movement along a predefined trajectory in a second direction opposite to the first direction. This means, in descriptive terms, that during the magnetization and compaction process, there is a back-and-forth movement of the at least one magnetic element. This can provide the advantage that not only one but multiple magnetization cycles can be achieved using the at least one magnetic element. This can improve the precision and strength of the flux focusing characteristics of the PM that can be generated by the magnetized compaction block.

[0045] In a preferred application of the method, the permanent magnet material comprises a rare earth material, in particular NdFeB. This can offer the advantage that very strong FFPMs can be produced.

[0046] In this regard, other components mentioned as permanent magnet materials may include ferrite and / or SmCo.

[0047] According to another aspect of the present invention, a permanent magnet, in particular a sintered permanent magnet, manufactured by implementing the above method is provided.

[0048] According to another aspect of the present invention, an electromechanical transducer, particularly a generator, is provided. The provided electromechanical transducer includes (a) a stator assembly and (b) a rotor assembly. The rotor assembly includes (b1) a support structure and (b2) at least one permanent magnet as described above. The permanent magnet is mounted to the support structure.

[0049] The electromechanical converter provided is based on the concept that it can be constructed with a rotor assembly comprising at least one (sintered) FFPM that exhibits appropriate flux focusing. Due to appropriate flux focusing, the efficiency of the generator can be improved relative to the amount of electrical power that can be generated with a given amount of available "mechanical" power.

[0050] According to another aspect of the present invention, a wind turbine for generating electric power is provided. The provided wind turbine includes (a) a tower, (b) a wind rotor disposed at a top portion of the tower and including at least one blade, and (c) an electromechanical transducer as described above. The electromechanical transducer is mechanically coupled to the wind rotor.

[0051] The proposed wind turbine, also known as a wind energy device, is based on the concept that the electromechanical transducer allows for an increase in the energy conversion efficiency of the wind turbine. This can help to increase the attractiveness of wind turbine technology for renewable electricity production compared to other technologies such as solar power plants.

[0052] It has to be noted that embodiments of the invention have been described with reference to different subject matters.

[0053] The aspects defined above and further aspects of the invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment.The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A wind turbine according to an embodiment of the invention is shown.

[0055] Figure 2 The schematic diagram shows Figure 1 generators of wind turbines.

[0056] Figure 3 A flux focusing permanent magnet (FFPM) made according to an embodiment of the present invention is shown.

[0057] Figure 4 An apparatus for producing a sintered permanent magnet having one movable magnetic element is shown.

[0058] Figure 5An apparatus for producing a sintered permanent magnet having two movable magnetic elements is shown. DETAILED DESCRIPTION

[0059] The illustrations in the accompanying drawings are schematic. It should be noted that in different drawings, similar or identical elements or features are provided with the same reference numerals or reference numerals that differ from the corresponding reference numerals only within the first digit. To avoid unnecessary repetition, elements or features already described with respect to previously described embodiments are not described again later in this specification.

[0060] Figure 1 A wind turbine 100 according to an embodiment of the present invention is shown, comprising a tower 120 mounted on a foundation, not shown. A nacelle 122 is arranged on top of tower 120. Furthermore, a yaw angle adjustment device 121 is provided, which enables nacelle 122 to be rotated about a vertical axis, not shown, that is aligned with the longitudinal extension of tower 120. By appropriately controlling yaw angle adjustment device 121, it is possible to ensure that nacelle 122 is always properly aligned with the wind direction during normal operation of wind turbine 100.

[0061] The wind turbine 100 further includes a wind rotor 110 having three blades 114. Figure 1 In the perspective view of FIG, only two blades 114 are visible. The rotor 110 is rotatable about an axis of rotation 110a. The blades 114 mounted on the hub 112 extend radially relative to the axis of rotation 110a.

[0062] A blade angle adjustment device 116 is provided between the hub 112 and the blades 114, respectively, to adjust the pitch angle of each blade 114 by rotating the corresponding blade 114 about an axis (not shown) that is aligned substantially parallel to the longitudinal extension of the corresponding blade 114. By controlling the blade angle adjustment device 116, the pitch angle of the corresponding blade 114 can be adjusted so that the maximum wind force can be extracted from the available mechanical power of the wind-driven wind rotor 110.

[0063] As from Figure 1 As can be seen in FIG, an optional gearbox 124 is arranged in the nacelle 122. The gearbox 124 is used to convert the rotational speed of the rotor 110 into a higher rotational speed of a shaft 125, which is coupled to an electromechanical transducer 130 in a known manner. The electromechanical transducer is a generator 130. Wind turbines without a gearbox are called direct drive (DD) wind turbines.

[0064] Furthermore, a brake 126 is provided in order to stop the operation of the wind turbine 100 or in order to reduce the rotational speed of the rotor 110 , for example in an emergency situation.

[0065] The wind turbine 100 further comprises a control system 143 for operating the wind turbine 100 in an efficient manner. In addition to controlling eg the yaw angle adjustment device 121, the depicted control system 153 is also used for adjusting the blade pitch angles of the rotor blades 114 in an optimized manner.

[0066] Generator 130 includes a stator assembly 135 and a rotor assembly 140. In the embodiment described herein, generator 130 is implemented in a so-called "inner stator-outer rotor" configuration. This means that rotor assembly 140 surrounds stator assembly 135 and a non-illustrated permanent magnet or PM assembly of rotor assembly 140 travels around an arrangement of multiple non-illustrated coils of inner stator assembly 135, which generate induced currents generated by picking up time-varying magnetic flux from the traveling permanent magnets.

[0067] According to the embodiments described herein, each permanent magnet (PM) assembly includes at least three sintered PM workpieces made of a NdFeB material composition.

[0068] Figure 2 A schematic diagram of a generator 130 is shown in cross-section. The generator 130 includes a stator assembly 135. The stator assembly 135 includes a stator support structure 237, which includes a stack of multiple laminates, and a plurality of stator windings 239 housed within the stator support structure 237. The windings 239 are interconnected in a known manner by means of electrical connections, not shown.

[0069] The rotor assembly 140 of the generator 130 is separated from the stator assembly 135 by an air gap ag, and the rotor assembly 140 includes a rotor support structure 242 that provides a mechanical base for mounting a plurality of sintered permanent magnets 250. The sintered magnets are flux focusing permanent magnets (FFPMs) that, when designed with an appropriate magnetic focal length, allow for an increase in the magnetic flux density within the air gap ag. Figure 2 , the rotation axis of the rotor assembly 140 is indicated by reference numeral 230a.

[0070] In the exemplary embodiment described here, three sintered FFPMs are arranged adjacent to each other at each angular position of the rotor assembly 140. Figure 2 , for ease of illustration, only three sintered FFPMs 250 (assigned to one angular position) are depicted. In practice, depending on the size of the generator 130, multiple FFPMs 250 are mounted to the rotor support structure 242. The FFPMs 250 are preferably arranged in a matrix-like configuration around a curved surface area of the support structure 242 having a substantially cylindrical geometry around the generator axis 240a.

[0071] from Figure 2 As can be seen in FIG, the sintered FFPM 250 is not mounted directly to the rotor support structure 242. Instead, a backing plate 244 made of a ferromagnetic material, such as iron, is provided. The backing plate 244 is provided to ensure proper magnetic flux guidance. This significantly reduces the intensity of the magnetic stray fields in an advantageous manner.

[0072] Figure 3 A FFPM 350 made in accordance with an embodiment of the present invention is shown. The FFPM 350 is magnetized in a manner that imparts an extended angular distribution of magnetic domain alignment directions 352. According to the embodiments described herein, each magnetic domain alignment direction 352 follows a straight magnetization line. The straight lines are angled or tilted relative to each other in a fan-shaped manner. Specifically, the extended angular distribution of the straight magnetization lines produces a focus 354 in a region above the major surface 350a of the FFPM 350 that is characterized by a local maximum of the magnetic field and corresponding magnetic flux density generated by the FFPM 350. The distance between the front surface of the FFPM 350 and the focus 354 is the magnetic focal length fd.

[0073] According to the exemplary embodiment described herein, the depicted magnetic domain arrangement pattern is symmetrical about an axis of symmetry 354a, which is also referred to in this document as the magnetic axis. The magnetic axis 354a is the normal axis of the major surface 350a, which passes through the focal point 354.

[0074] Figure 4 An apparatus 460 is shown for producing blocks in the form of pressed magnet powder that can be sintered in a furnace to form sintered permanent magnets. Specifically, the apparatus 460 is used to compact and magnetize magnetic material powder 495. The resulting magnetized compacted blocks are then sintered in a sintering furnace (not shown).

[0075] The apparatus 460 comprises a die 470 in which a cavity 472 is formed. The cavity 472 may be closed by at least one die element (not shown) which also serves to compact the powder 495. The movement of the at least one die element is in a direction perpendicular to the plane of the drawing.

[0076] The apparatus 460 further comprises means for generating magnetic flux, which is applied to the compacted powder 495. These magnetic flux generating means comprise first magnetic means 461 and second magnetic means 464. Figure 4In the embodiment shown in FIG, the first magnetic device 461 generates a magnetic north pole N, and the second magnetic device 464 generates a magnetic south pole S. According to known equipment, the first magnetic device 461 includes (i) a first electromagnetic coil 462 for generating magnetic flux, and (ii) a first magnetic yoke 463 for guiding and / or shaping the magnetic flux (line) present in the mold cavity 472. Correspondingly, the second magnetic device 464 includes (i) a second electromagnetic coil 465 and (ii) a second magnetic yoke 466.

[0077] According to the exemplary embodiment described herein, the first magnetic yoke 463 assigned to the north pole and the second magnetic yoke 466 assigned to the south pole have different geometric shapes. Specifically, the bending radii of the outer surfaces of the two magnetic yokes 463, 466 are different from each other. The first magnetic yoke 463 has a first outer yoke surface 463a facing the mold cavity 472. The first outer yoke surface 463a is a convex surface with a bending radius R1 relative to the position of the mold cavity 472. The second magnetic yoke 466 has a second outer yoke surface 466a facing the mold cavity 472. The second outer yoke surface 466a is a concave surface with a bending radius R2 relative to the position of the mold cavity 472. As shown from Figure 4 It can be seen that R1 is significantly larger than R2.

[0078] The difference in the geometry of the yokes 463, 466 has the effect of providing an inhomogeneous magnetic field and corresponding magnetic flux within the die cavity 472, which results in an inhomogeneous magnetization of the compacted powder 495 agglomerate. Figure 3 As shown in , this non-uniform magnetization can produce an extended angular distribution of magnetic domain alignment directions 352.

[0079] However, the apparatus 460 further comprises means for increasing the non-uniformity of the magnetic flux within the mold cavity. Thus, a FFPM with a short focal length can be produced.

[0080] Specifically, the device 460 further includes a magnetic element 480 that can travel along a predefined trajectory 481. The spatial path of the trajectory 481 is defined by a guide structure (not shown). According to the exemplary embodiment described here, the predefined trajectory is an arc-shaped curved path 481 that runs parallel to the concave surface 463a of the first magnetic yoke 463.

[0081] from Figure 4 As can be seen in FIG, during the compaction and magnetization process, the magnetic element 480 can be moved back and forth between a first position 480a and a second position 480b. The corresponding movement is actuated by means of an actuator mechanism 482, which is shown schematically.

[0082] It will be appreciated that by varying the (bent) distance between the two locations 480a, 480b, and the corresponding spacing, the inhomogeneity of the magnetic flux pattern within the mold cavity 472 changes. This has an impact on the focal length of (a) the FFPM produced using the apparatus 460 and (b) the focal length of the FFPM produced in the sintering furnace, where the magnetized compact produced using the apparatus 460 is further processed. Specifically, the greater the spacing between the two locations 480a, 480b, the greater the inhomogeneity and the smaller the focal length.

[0083] Figure 5 An apparatus 560 for manufacturing sintered permanent magnets according to another embodiment of the present invention is shown. Apparatus 560 has significant structural similarities to apparatus 460. Specifically, the second magnetic device and mold 470 for producing the magnetic south pole for magnetic powder 495 in this embodiment are identical to those in apparatus 460.

[0084] and Figure 4 Compared to the device 460 shown in FIG, the device 560 includes not only one but two magnetic elements, a first magnetic element 580 and another or second magnetic element 590. During operation of the device 560, the two magnetic elements 580, 590 move in a linear direction. Specifically, a first trajectory 581 is assigned to the first magnetic element 580, while the other or second trajectory 591 is assigned to the second magnetic element 590. The first trajectory 581 extends between a first position 580a of the first magnetic element 580 (depicted with a solid line) and a second position 580b of the first magnetic element 580 (depicted with a dotted line). Accordingly, the second trajectory 591 extends between the first position 590a of the second magnetic element 590 (depicted with a solid line) and the second position 590b of the second magnetic element 590 (depicted with a dotted line).

[0085] from Figure 5 It can be seen that the first magnetic device 561 that generates the north pole (for the magnetic powder 495) includes a first electromagnetic coil 562 and a first magnetic yoke 563. Figure 4 Compared to the device 460 shown in FIG. 4 , the first yoke 563 includes a flat first outer yoke surface 563 a .

[0086] According to the exemplary embodiment described herein, the device 560 operates in a symmetrical manner. Thus, "symmetry" relates to the magnetic field (line) pattern imparted between the two magnetic devices 561 and 464. Specifically, the pattern exhibits axisymmetry relative to the magnetic symmetry axis 560a. Although the magnetic field pattern changes as the two magnetic elements 580, 590 move, the symmetry about the axis 560a is always imparted. "Conservation of symmetry" is imparted because, in this embodiment, the movement of the two magnetic elements 580, 590 is always symmetrical. This means that at any moment, the first distance between the first magnetic element 580 and the axis of symmetry 560a is the same as the second distance between the second magnetic element 590 and the axis of symmetry 560a. Therefore, not only is the magnetic field line pattern generated by the two magnetic devices 561 and 464 symmetrical, but the "perturbations" to the magnetic field line pattern caused by the magnetic elements 580, 590 move in a spatially symmetrical manner.

[0087] It is mentioned that in other embodiments, the two magnetic elements move along a non-linear path. Such a non-linear path may have any other curved shape, such as Figure 4 Furthermore, the shape of the yokes 563, 466, particularly in the region near the mold cavity 472, may have any shape.

[0088] The process of magnetizing and compacting or compressing the powder 495 using the apparatus 560 may be as follows:

[0089] (1) Powder 495 is filled into the mold cavity 472 .

[0090] (2) Two mold parts (not shown) are moved into the plane of the drawing as a pressing tool. This forms the cover.

[0091] (3) A magnetic field is generated with the aid of two magnetic devices 561 and 464 .

[0092] (4) The two magnetic elements 580 and 590 move outward.

[0093] (5) When a desired pressure is applied to the magnetic powder 495 , the lower portion or the upper portion of the pressing tool will press out a magnet block consisting of the compacted powder 495 .

[0094] (6) The magnet block is now ready for optional isostatic pressing and undergoes a conventional sintering process.

[0095] Although the above embodiments are generally used for the production of sintered magnets, it is mentioned that with the described apparatus it is also possible to produce bonded magnets or other magnets made from powder without sintering.

[0096] It should be noted that the term "comprising" does not exclude other elements or steps, and the use of the article "a" or "an" does not exclude a plurality. Elements described in connection with different embodiments may also be combined.

Claims

1. A device (460; 560) for manufacturing a permanent magnet (250; 350), the device (460; 560) comprising: a mold (470) having a mold cavity (472) for receiving permanent magnet material powder (495); a first magnetic device (461; 561) and a second magnetic device (464), each for generating a magnetic flux for magnetizing a powder (495) contained in the mold cavity (472); a mold member for compacting the powder (495) contained in the mold cavity (472); as well as a magnetic element (480; 580, 590) for spatially guiding and / or modifying the magnetic flux; wherein The magnetic element (480; 580, 590) is located in a region extending between the first magnetic device (461; 561) and the second magnetic device (464) and is movably supported in the region such that In a first position (480a; 580a, 590a) of the magnetic element (480; 580, 590), a first spatial magnetic flux distribution is provided at least within the mold cavity (472); and in a second position (480b; 580b, 590b) of the magnetic element (480; 580, 590), a second spatial magnetic flux distribution is provided at least within the mold cavity (472), wherein the second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution; At least one of the two magnetic devices (461, 464; 561) comprises an electromagnetic coil (462, 465; 562) for generating said magnetic flux, and a magnetic yoke (463, 466; 563) for guiding and / or for shaping the magnetic flux generated by the electromagnetic coil (462, 465; 562); The magnetic element (480; 580, 590) is supported in such a manner that it can be continuously moved along a predefined trajectory (481; 581, 591), the predefined trajectory (481; 581, 591) being a path along a curved or linear shape; The first magnetic device (461; 561) has a first magnetic yoke (463; 563), and the second magnetic device (464) has a second magnetic yoke (466), With respect to the mold cavity (472), the first magnetic yoke (463; 563) and the second magnetic yoke (466) are located on opposite sides, The first magnetic yoke (463; 563) has a first outer yoke surface (463a; 563a) facing the mold cavity (472), and the second magnetic yoke (466) has a second outer yoke surface (466a) facing the mold cavity (472), and, The first outer yoke surface (463a) is concave and the second outer yoke surface (466a) is convex or flat; or the first outer yoke surface (563a) is flat and the second outer yoke surface (466a) is convex.

2. The device (460; 560) according to claim 1, further comprising: An actuator mechanism (482) for changing the position of the magnetic element (480).

3. The device (460; 560) according to claim 1 or 2, wherein The first magnetic arrangement (461; 561) and the second magnetic arrangement (464) are configured to produce a magnetic flux pattern in the substantial absence of the magnetic element (480; 580, 590), the magnetic flux pattern comprising an extended angular distribution of magnetic flux lines at least within the mold cavity (472).

4. The device (460; 560) according to claim 1 or 2, wherein The permanent magnet (250; 350) is a sintered permanent magnet (250; 350).

5. The device (460; 560) according to claim 1 or 2, wherein The length of the predefined trajectory (481; 581, 591) determines the magnetic focal length (fd) of the permanent magnet (250, 350).

6. The apparatus (460) according to claim 1 or 2, wherein The predefined trajectory (481) is a path along a circular arc.

7. The apparatus (460) according to claim 1 or 2, wherein The first outer yoke surface (463a) has a first radius (R1), and the second outer yoke surface (466a) has a second radius (R2) different from the first radius (R1).

8. The apparatus (560) according to claim 1 or 2, further comprising: Another magnetic element (590) is supported in such a way that it can be moved continuously along another predefined trajectory (591).

9. The apparatus (560) of claim 8, wherein The predefined trajectory (581) and the further predefined trajectory (591) are symmetrical with respect to each other relative to an axis of magnetic symmetry (560a) of the device (560).

10. The apparatus (560) of claim 8, wherein: The another predefined trajectory (591) is another path along another curved or linear shape.

11. A method for manufacturing a permanent magnet (250, 350), the method comprising: Filling the permanent magnet material powder (495) into the mold cavity (472) of the mold (470); generating a magnetic flux for magnetizing the powder (495) contained in the mold cavity (472) by means of a first magnetic device (461) and a second magnetic device (464); compacting the powder (495) contained in the mold cavity (472) by means of a mold; At least one magnetic element (480) for spatially directing and / or modifying the generated magnetic flux is moved from a first position (480a) to at least a second position (480b) in an area extending between the first magnetic device (461) and the second magnetic device (464), wherein In a first position (480a) of the at least one magnetic element (480), a first spatial magnetic flux distribution is provided at least within the mold cavity (472), and in a second position (480b) of the at least one magnetic element (480), a second spatial magnetic flux distribution is provided at least within the mold cavity (472), wherein the second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution; At least one of the two magnetic devices (461, 464) includes electromagnetic coils (462, 465) for generating said magnetic flux, and a magnetic yoke (463, 466) for guiding and / or shaping the magnetic flux generated by the electromagnetic coil (462, 465); The at least one magnetic element (480) is supported in such a manner that it can be continuously moved along a predefined trajectory (481), the predefined trajectory (481) being a path along a curved or linear shape; The first magnetic device (461) has a first magnetic yoke (463), and the second magnetic device (464) has a second magnetic yoke (466), With respect to the mold cavity (472), the first magnetic yoke (463) and the second magnetic yoke (466) are located on opposite sides, The first magnetic yoke (463) has a first outer yoke surface (463a) facing the mold cavity (472), and the second magnetic yoke (466) has a second outer yoke surface (466a) facing the mold cavity (472), and, The first outer yoke surface (463a) is concave and the second outer yoke surface (466a) is convex or flat; or the first outer yoke surface (463a) is flat and the second outer yoke surface (466a) is convex.

12. The method according to claim 11, wherein The permanent magnet (250, 350) is a sintered permanent magnet (250, 350).

13. The method according to claim 11 or 12, wherein: Moving the at least one magnetic element (480) includes a first movement along a predefined trajectory (481) in a first direction, and A second movement along a predefined trajectory (481) in a second direction opposite to the first direction.

14. A permanent magnet (250, 350) manufactured by implementing the method according to any one of claims 11 to 13.

15. The permanent magnet (250, 350) according to claim 14, wherein The permanent magnet (250, 350) is a sintered permanent magnet (250, 350).

16. An electromechanical transducer (130), comprising: a stator assembly (135), and A rotor assembly (140) comprising Support structure (242) and At least one permanent magnet (250, 350) according to claim 14 or 15, wherein the permanent magnet (250, 350) is mounted to the support structure (242).

17. The electromechanical transducer (130) according to claim 16, wherein The electromechanical transducer (130) is a generator.

18. A wind turbine (100) for generating electrical power, the wind turbine (100) comprising: Tower (120), a wind rotor (110) disposed at a top portion of the tower (120) and comprising at least one blade (114); as well as The electromechanical transducer (130) according to claim 16 or 17, wherein the electromechanical transducer (130) is mechanically coupled to the wind rotor (110).

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