Cylindrical magnetic body, outer rotor, and motor

Abstract

The invention provides an outer rotor capable of improving the torque of a motor, and a cylindrical magnetic body capable of providing a motor having the outer rotor. A cylindrical magnetic body having a multilayer structure comprising a transition metal layer, an intermediate layer, and a rare earth magnet layer in the stated order from the outer peripheral surface side toward the inner peripheral surface side, the intermediate layer and the rare earth magnet layer each containing a transition metal element and a rare earth element.

Description

Technical Field

[0001] The present disclosure relates to a cylindrical magnetic body, an outer rotor having the cylindrical magnetic body, and a motor having the outer rotor. Background Art

[0002] In outer rotor motors, bonded magnets or sintered magnets are generally incorporated into the inner peripheral wall of the rotor. For example, Patent Document 1 discloses an outer rotor having cylindrical bonded magnets disposed on the inner peripheral surface of a rotor core.

[0003] In conventional outer rotor type motors, if the diameter of the outer rotor including bonded magnets or sintered magnets is reduced, it becomes practically difficult to obtain sufficient motor torque.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-111738 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] An object of exemplary embodiments of the present disclosure is to provide an outer rotor capable of achieving an improvement in motor torque, a cylindrical magnetic body that can be used for the outer rotor, and a motor having the outer rotor.

[0009] Technical means to solve the problem

[0010] To achieve the above-mentioned object, the cylindrical magnetic body of the present disclosure has a multilayer structure comprising a transition metal layer, an intermediate layer, and a rare earth magnet layer in the order described from the outer peripheral surface toward the inner peripheral surface, wherein both the intermediate layer and the rare earth magnet layer contain a transition metal element and a rare earth element.

[0011] Since the cylindrical magnetic body has the multilayer structure described above, it can be used as a part of the outer rotor of a motor, for example, thereby improving the motor torque and reducing the size of the motor.

[0012] Preferably, the average thickness of the rare earth magnet layer is not less than 10 μm and not more than 300 μm.

[0013] Preferably, in the multilayer structure, no intervening layer exists between the transition metal layer and the intermediate layer, and between the intermediate layer and the rare earth magnet layer.

[0014] Preferably, the rare earth element contained in the intermediate layer is a rare earth element diffused from the rare earth magnet layer, and the transition metal contained in the intermediate layer is the same as the metal contained in the transition metal layer.

[0015] Preferably, the intermediate layer covers the entire circumference of the inner circumferential surface of the transition metal layer.

[0016] The rare earth magnet layer covers the entire circumferential direction of the inner peripheral surface of the intermediate layer.

[0017] Preferably, the easy magnetization axis of the rare earth magnet layer is oriented radially.

[0018] The orientation degree of the easy magnetization axis with respect to the radial direction is 90% or more.

[0019] Preferably, the transition metal layer is a Co layer, and the intermediate layer is Sm2Co 17 layer, and the rare earth magnet layer is a SmCo5 layer.

[0020] The cylindrical magnetic body disclosed herein can be used in motors for various applications, such as medical and watch applications, for controlling magnetic fluids placed within the outer rotor or the inner portion of the barrel, protecting piping from the effects of plasma, and other applications. For example, the magnet layer can have a multipolar magnetization pattern in the circumferential or axial directions, or it can be located only within a portion of the barrel. Furthermore, the motor with an outer rotor disclosed herein can also have a stator inserted inside the outer rotor. Furthermore, the stator in the motor with an outer rotor disclosed herein can also include a magnetic sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a cross-sectional view showing an outer rotor having a cylindrical magnetic body according to one embodiment of the present disclosure, and shows a cross section perpendicular to the rotation axis of the outer rotor.

[0022] Figure 2 (a) and (b) represent the direction along Figure 1 An example of a cross section along line II-II.

[0023] Figure 3 Yes Figure 1 Schematic diagram of an example of the arrangement of magnetization (magnetic poles) of the outer rotor shown.

[0024] Figure 4 Yes means having Figure 1 The cross-sectional view of the outer rotor motor shown shows a cross section perpendicular to the rotation axis of the motor.

[0025] Figure 5 It means along Figure 4 A simplified diagram of the cross section along line V-V is shown.

[0026] Figure 6 It is a cross-sectional view showing a modified example of the outer rotor having a cylindrical magnetic body.

[0027] Figure 7 This is a cross-sectional view showing still another modified example of the outer rotor having a cylindrical magnetic body. DETAILED DESCRIPTION

[0028] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. Furthermore, the shapes and the like shown in the drawings of the present disclosure may not necessarily correspond to the actual shapes and the like. This is because the shapes and the like may be modified for the purpose of explanation in the drawings.

[0029] like Figure 1 As shown, the outer rotor 2 of this embodiment includes a cylindrical magnetic body 10 having a multilayer structure. In addition to the magnetic body 10, the outer rotor 2 may also include a rotor housing that supports the magnetic body 10, a coupling member for connecting the outer rotor 2 to the shaft, and other accessories such as a fan and gears.

[0030] like Figure 1 As shown, the magnetic body 10 has an outer peripheral surface 10a and an inner peripheral surface 10b, and preferably has an integral structure without any adhesive layer or gaps or other joints along the circumferential direction. Figure 1 The magnetic body 10 shown has a cylindrical shape. However, the shape of the magnetic body 10 is not necessarily limited as long as the magnetic body 10 has at least a cylindrical portion.

[0031] Figure 1 The central axis AX shown is an imaginary line extending along the inner circumferential surface 10a and passing through the center of the region surrounded by the inner circumferential surface 10a. The central axis AX of the magnetic body 10 coincides with the rotation axis of the outer rotor 2. Furthermore, the Z axis in each drawing is parallel to the central axis AX, and the X axis, Y axis, and Z axis are perpendicular to each other.

[0032] The dimensions of the magnetic body 10 are not necessarily limited. For example, the outer diameter d1 of the magnetic body 10 is preferably 1 mm to 6 mm, and the inner diameter d2 of the magnetic body 10 is preferably 0.5 mm to 5 mm. The thickness of the magnetic body 10 is represented by (d1 - d2) / 2 and is, for example, preferably 0.1 mm to 2 mm. Furthermore, the length L of the magnetic body 10 in the Z-axis direction may be, for example, 1 mm to 20 mm.

[0033] The magnetic body 10 has a multilayer structure including a transition metal layer 11, an intermediate layer 12, and a rare earth magnet layer 13 in the order listed from the outer peripheral surface side toward the inner peripheral surface side. In the multilayer magnetic body 10, the transition metal layer 11 is a matrix, and the intermediate layer 12 and the rare earth magnet layer 13 are stacked in the order listed on the inner peripheral surface side of the transition metal layer 11. Figure 1 As shown, each layer (11 to 13) of the magnetic body 10 is a continuous layer without any joints or cuts in the circumferential direction.

[0034] In the multilayer structure of magnetic material 10, the inner circumferential surface of transition metal layer 11 and the outer circumferential surface of intermediate layer 12 are preferably in direct contact, and the inner circumferential surface of intermediate layer 12 and the outer circumferential surface of rare earth magnet layer 13 are preferably in direct contact. Specifically, while layers thinner than the 0.5-4 nm resolution observable by a scanning electron microscope (SEM) may exist between transition metal layer 11 and intermediate layer 12, and between intermediate layer 12 and rare earth magnet layer 13 (between layers of the multilayer structure), intervening layers made of non-magnetic materials, such as oxide layers, resin layers, and adhesive layers, that are thicker than the 0.5-4 nm resolution observable by an SEM are preferably absent. In this embodiment, "no intervening layers" between the layers of the multilayer structure means that the intervening layers cannot be identified at the resolution observable by an SEM, as described above.

[0035] Figure 2 (a) and (b) are examples of cross sections of the magnetic body 10 along the central axis AX. Figure 2 As shown in (a), the intermediate layer 12 preferably covers the entire circumferential direction of the inner peripheral surface of the transition metal layer 11, and the rare earth magnet layer 13 preferably covers the entire circumferential direction of the inner peripheral surface of the intermediate layer 12. However, the multilayer structure of the magnetic body 10 is not limited to Figure 2 In the embodiment shown in (a), a portion of the inner peripheral surface of the transition metal layer 11 may also have a non-stacked region where the intermediate layer 12 and the rare earth magnet layer 13 are not stacked. Figure 2 In (b), the inner peripheral surface of the transition metal layer 11 has non-laminated regions 11b at both ends in the Z-axis direction that are not covered by the intermediate layer 12 and the rare earth magnet layer 13, and a multilayer structure is formed between the non-laminated regions 11b.

[0036] like Figure 1 and Figure 2 As shown, the outer peripheral surface 11a of the transition metal layer 11 can also form the outer peripheral surface 10a of the magnetic body 10. Alternatively, a part or all of the outer peripheral surface 11a of the transition metal layer 11 can also be covered by other layers. As other layers located on the outer peripheral surface side of the transition metal layer 11, for example, a layer containing a high melting point non-magnetic material such as W, Ta, Nb or Mo can be mentioned. In addition, when a layer of a high melting point non-magnetic material is present on the outer peripheral surface side of the transition metal layer 11, the average thickness of the layer of the high melting point non-magnetic material is not particularly limited, and for example, it is preferably not less than 0.5 μm and not more than 25 μm, and more preferably not less than 5 μm and not more than 25 μm.

[0037] A part or the whole of the inner peripheral surface 13b of the rare earth magnet layer 13 may be covered with a layer containing Sm2O3 or / and a protective layer containing Ni, Cu or Sn. Figure 1 and Figure 2As shown, it is preferable that the inner peripheral surface 13b of the rare-earth magnet layer 13 is exposed at the inner peripheral surface 10b of the magnetic body 10 to form the inner peripheral surface 10b.

[0038] The characteristics of each layer (11-13) that constitutes the multilayer structure of the magnetic body 10 will be described in detail below. The composition of each layer can be analyzed using, for example, inductively coupled plasma atomic emission spectrometry (ICP-AES), fluorescence X-ray analysis (XRF), energy dispersive X-ray analysis (EDS), or wavelength dispersive X-ray analysis (WDS), while the crystalline structure of each layer can be analyzed using, for example, X-ray diffraction (XRD), electron beam diffraction, or electron backscatter diffraction (EBSD). Furthermore, when measuring the thickness of each layer, the magnetic body 10 is preferably divided equally and analyzed in at least three cross sections approximately perpendicular to the central axis AX. In each cross section, the thickness is preferably measured at at least four points at equal intervals along the circumference. Specifically, the thickness of each layer is preferably measured at at least 12 points uniformly distributed in three-dimensional space, and the average thickness and standard deviation of the thickness are calculated.

[0039] In this embodiment, the transition metal layer 11 is a soft magnetic layer primarily composed of Co and serves as the base material of the magnetic body 10. "Primarily composed of Co" means that the Co content in this layer is the highest. The transition metal layer 11 may also contain other metal elements such as Cr, Mn, Fe, Ni, Cu, Pb, and Mo. The Co content in the transition metal layer 11 is preferably 95 wt% or greater, and more preferably 99 wt% or greater, for example.

[0040] The average thickness t1 of the transition metal layer 11 is not particularly limited and can be appropriately selected depending on the application of the motor. For example, it is preferably not less than 0.1 mm and not more than 1.8 mm.

[0041] In this embodiment, the intermediate layer 12 comprises Sm2Co 17 As the main phase layer. Main phase Sm2Co 17 Is Th2Zn 17 The alloy of Sm and Co with a crystal structure of type 1 is a soft magnetic material with a higher saturation magnetization than the following SmCo5. 17 With Th2Zn 17 Type of crystal structure, then Sm2Co 17 The ratio of Sm atoms to Co atoms in the intermediate layer 12 may deviate slightly from the stoichiometric ratio. For example, in order to improve the magnetic properties, other elements such as Ti, Zr, Nb, Ta, Cu, Ce, and Fe may be added. When other elements are added, the ratio of Sm atoms to Co atoms may deviate from the stoichiometric ratio.

[0042] In addition, in this embodiment, the "main phase" refers to the phase with the highest content in a predetermined layer. The intermediate layer 12 may also contain a composition and / or a crystal structure different from that of Sm2Co. 17 Different phases (heterophases) and grain boundaries are equal. Sm2Co in the intermediate layer 12 17 The content of may be, for example, 70 wt % or more, preferably 80 wt % or more, more preferably 90 wt % or more, and further preferably 95 wt % or more.

[0043] The average thickness t2 of the intermediate layer 12 is not particularly limited, but is preferably, for example, not less than 1 μm and not more than 100 μm. The coefficient of variation of the thickness of the intermediate layer 12 is preferably, for example, not more than 50%. The "coefficient of variation" is a factor indicating thickness variation and is expressed as the ratio of the standard deviation of the thickness to the average thickness (standard deviation / average thickness).

[0044] In this embodiment, the rare earth magnet layer 13 is a hard magnetic layer containing SmCo5 as its main phase. The SmCo5 main phase is an alloy of Sm and Co with a CaCu5-type crystal structure. If the SmCo5 main phase has a CaCu5-type crystal structure, the ratio of Sm atoms to Co atoms in the SmCo5 may deviate slightly from the stoichiometric ratio. For example, to improve magnetic properties, other elements such as Ti, Zr, Nb, Ta, Cu, Ce, and Fe may be added to the rare earth magnet layer 13. When these other elements are added, the ratio of Sm atoms to Co atoms may deviate from the stoichiometric ratio.

[0045] The rare earth magnet layer 13 may contain a phase (heterophase) having a different composition and / or crystal structure from that of SmCo5, as well as a grain boundary phase. The SmCo5 content in the rare earth magnet layer 13 may be, for example, 70 wt% or greater, preferably 80 wt% or greater, more preferably 90 wt% or greater, and even more preferably 95 wt% or greater. Examples of heterophases in the rare earth magnet layer 13 include an Sm-rich phase having a higher Sm ratio than SmCo5.

[0046] The average thickness t3 of the rare-earth magnet layer 13 is preferably not less than 10 μm and not more than 300 μm. The coefficient of variation (standard deviation / average thickness) of the thickness of the rare-earth magnet layer 13 is preferably not more than 50%, for example. By reducing the coefficient of variation, the distance between the outer rotor 2 and the stator can be minimized at a constant interval when the outer rotor 2 is incorporated into the motor, thereby contributing to improved motor torque.

[0047] Furthermore, the ratio of the average thickness t3 of the rare-earth magnet layer 13 to the average thickness t2 of the intermediate layer 12 (t3 / t2) is preferably 1 or more and 100 or less, and more preferably 5 or more and 100 or less. If the sum of the average thicknesses t1, t2, and t3 is defined as T0, the ratio of t3 to T0 (t3 / T0) may be 0.01 or more and less than 1. By controlling t3 / t2 and / or t3 / T0 within the above ranges, the magnetic properties of the cylindrical magnetic body can be further improved.

[0048] The Rz (maximum height difference) of the roughness curve of the inner circumferential surface 13b of the rare-earth magnet layer 13 is preferably 20 μm or less. When calculating Rz, it is preferable to obtain the roughness curve of the inner circumferential surface 13b based on the contour line in both a cross section perpendicular to the central axis AX and a cross section along the central axis AX. By setting the Rz of the inner circumferential surface 13b to 20 μm or less, the distance between the outer rotor 2 and the stator can be minimized at a certain distance when the outer rotor 2, which has a cylindrical magnetic body, is installed in the motor, thereby contributing to improved motor torque.

[0049] The multilayered magnetic body 10 is a rotor and an element constituting the magnetic circuit of the motor. The rare earth magnet layer 13, a hard magnetic layer, is a magnet, while the transition metal layer 11 and the intermediate layer 12, soft magnetic layers, function as a back yoke that collects magnetic flux.

[0050] The easy magnetization axis of the rare earth magnet layer 13 is preferably oriented radially. Here, "radial" refers to a direction perpendicular to the central axis AX of the magnetic body 10, and "oriented radially" means that the easy magnetization axes are arranged radially around the central axis AX when viewed from the direction of the central axis AX. Furthermore, the easy magnetization axis of the rare earth magnet layer 13 is preferably the crystal orientation [00L] of SmCo5, and the crystal orientation [00L] of SmCo5 is oriented radially. L in the crystal orientation is an arbitrary natural number, and when L is an arbitrary natural number, [00L] always indicates the same direction. For example, L is 2.

[0051] In outer rotor 2, the easy magnetization axis of rare-earth magnet layer 13, serving as the magnet, is radially oriented, thereby achieving a high surface magnetic flux density. Furthermore, because outer rotor 2's magnetic body 10 has a multilayer structure comprising a transition metal layer 11, an intermediate layer 12, and rare-earth magnet layer 13, the orientation of rare-earth magnet layer 13 can be improved compared to conventional sintered or bonded magnets.

[0052] In conventional outer rotors using sintered or bonded magnets, the degree of orientation in the radial direction of easy magnetization is only about 80% at best, making it difficult to achieve an orientation of 90% or higher. On the other hand, in the outer rotor 2 having a cylindrical magnetic body according to this embodiment, the transition metal layer 11, the intermediate layer 12, and the rare earth magnet layer 13 are stacked in the order described from the outer circumference to the inner circumference. This allows the degree of orientation in the radial direction of easy magnetization in the rare earth magnet layer 13 to be 90% or higher. While the reason is unclear, it is speculated that the intermediate layer 12 penetrates between the transition metal layer 11 and the rare earth magnet layer 13, resulting in radial anisotropy with an orientation of 90% or higher. In other words, the degree of orientation in the radial direction of easy magnetization in the rare earth magnet layer 13 is preferably 90% or higher, more preferably exceeding 90%, and even more preferably 95% or higher.

[0053] By setting the radial orientation degree to 90% or more, the surface magnetic flux density can be increased compared to conventional methods, and a sufficiently large motor torque can be obtained even if the outer rotor is reduced in diameter (for example, the outer diameter d1 is 6 mm or less).

[0054] The orientation direction of the easy magnetization axis and the degree of orientation in the radial direction of the easy magnetization axis can be calculated by crystal orientation analysis using EBSD. In EBSD, the degree of orientation at each location in the rare earth magnet layer 13 is calculated and averaged over the entire rare earth magnet layer 13 to calculate the degree of orientation.

[0055] The rare earth magnet layer 13 as a magnet is magnetized radially along the easy magnetization axis and has two or more magnetic poles on the inner peripheral surface 13b. Figure 3 In FIG. 1 , arrows indicate the arrangement of magnetic poles in the rare-earth magnet layer 13, and the inner peripheral surface 13b of the rare-earth magnet layer 13 has eight poles. The number of magnetic poles in the inner peripheral surface 13b of the rare-earth magnet layer 13 is not particularly limited.

[0056] An example of a method for manufacturing the outer rotor 2 having a cylindrical magnetic body will be described below.

[0057] The magnetic body 10 is preferably manufactured by a method applying a molten salt impregnation method. First, a cylindrical Co substrate and a reaction solution containing an Sm source and a molten salt are prepared.

[0058] When preparing the reaction solution, first, a predetermined inorganic salt is dried to dehydrate it. Examples of the inorganic salt include KCl (potassium chloride), LiCl (lithium chloride), and NaCl (sodium chloride). One inorganic salt may be used, or two or more inorganic salts may be used in combination. The dehydrated inorganic salt is heated to a predetermined temperature to melt the inorganic salt (molten salt). The temperature at which the inorganic salt is melted can be appropriately determined according to the type of inorganic salt used, and is, for example, preferably 400° C. or more, more preferably 500° C. or more, and even more preferably 600° C. or more.

[0059] An Sm source is added to the molten salt (molten inorganic salt) to obtain a reaction solution. Examples of the Sm source include metallic Sm and Sm alloys. A single Sm source or two or more Sm sources may be used. If the total number of moles of the Sm source and the number of moles of the inorganic salt in the reaction solution is 100 mol%, the proportion of the Sm source in the reaction solution is preferably, for example, not less than 0.2 mol% and not more than 6 mol%. Furthermore, when adding an additive element to the intermediate layer 12 and / or the rare earth magnet layer 13, a raw material containing the desired additive element and the Sm source are simply added to the molten salt.

[0060] Next, the above-mentioned reaction solution is brought into contact with the surface of the Co matrix, and a magnetic film containing Sm is formed on the inner peripheral surface of the Co matrix by the reaction diffusion of the Sm source in the molten salt relative to the surface of the Co matrix. This process is called a reaction diffusion process. In this reaction diffusion process, if the Co matrix is ​​directly immersed in the reaction solution, a magnetic film containing Sm is formed not only on the inner peripheral surface of the Co matrix, but also on the outer peripheral surface and the end surface (the surface perpendicular to the Z axis). Therefore, it is necessary to make the Sm source react and diffuse only on the inner peripheral surface of the Co matrix, and suppress the reaction diffusion at the outer peripheral surface and the end surface.

[0061] For example, it is preferred to form a mask of a high melting point material on the outer peripheral surface and end surface of the Co substrate. Examples of the high melting point material include W, Ta, Nb, Mo, or an alloy containing at least one of these elements. The mask of the high melting point material can be formed, for example, by a vapor deposition method. After forming a mask of the high melting point material on the outer peripheral surface and end surface, the Co substrate is immersed in the reaction solution, whereby the Sm source reacts and diffuses only on the inner peripheral surface of the Co substrate, and a magnetic film containing Sm can be formed on the inner peripheral surface. Alternatively, it is also possible to form no mask, and the Sm source reacts and diffuses on the inner peripheral surface and outer peripheral surface of the Co substrate, forming a magnetic film containing Sm on the inner peripheral surface and outer peripheral surface.

[0062] Instead of forming a mask of a high melting point material, a method for making the reaction solution flow into an area (inner peripheral area) surrounded by the inner peripheral surface of the Co substrate can also be adopted. For example, an introduction tube is connected at both ends of the Co substrate, and a pump or a mass flow controller is used to make the reaction solution flow into the inner peripheral area of ​​the Co substrate at a constant flow rate. It is preferred to circulate the reaction solution so that the reaction solution flowing out from one end of the Co substrate flows into the inner peripheral area again. In the method of making the reaction solution flow into the inner peripheral area, the uniformity of the thickness of the magnetic coating can be improved compared to the case where the Co substrate is immersed in the reaction solution.

[0063] During the reaction-diffusion step, the reaction solution is maintained at a temperature at which the inorganic salt remains molten. To effectively form a magnetic film, the reaction solution temperature is preferably between 500°C and 900°C, and more preferably between 650°C and 800°C. The reaction time can be appropriately set based on the reaction temperature and the proportion of the Sm source in the reaction solution to form a magnetic film of the desired thickness. For example, the reaction time can be between 1 hour and 48 hours.

[0064] The magnetic coating formed on the inner surface of the Co matrix during the reaction-diffusion process is a precursor to the intermediate layer 12 and the rare-earth magnet layer 13. Specifically, the magnetic coating after the reaction-diffusion process preferably contains SmCo2 as the main phase. SmCo2 is an alloy of Sm and Co with a MgCu2-type crystal structure. If the main phase of SmCo2 has a MgCu2-type crystal structure, the ratio of Sm atoms to Co atoms in the SmCo2 may deviate slightly from the stoichiometric ratio. For example, when additive elements are added to improve magnetic properties, the ratio of Sm atoms to Co atoms may deviate from the stoichiometric ratio.

[0065] In addition to the main phase, the magnetic coating may further include a different phase such as an Sm-rich phase having a higher Sm ratio than SmCo2, and a grain boundary phase. The SmCo2 content in the magnetic coating may be 50 wt% or more, preferably 70 wt% or more, and more preferably 90 wt% or more.

[0066] Furthermore, after the reaction diffusion step, the Co substrate on which the magnetic film is formed may be cleaned using an organic solvent such as ethanol or pure water.

[0067] Next, the Co substrate on which the magnetic film containing SmCo2 is formed is heated at a predetermined temperature for a predetermined time (heating step). In this heating step, the reaction between SmCo2 and the Co of the substrate proceeds further, and a magnetic film containing SmCo2 is generated from the inner surface of the Co substrate and the magnetic film. 17 The intermediate layer 12 and the rare earth magnet layer 13 having SmCo5.

[0068] The heating rate in the heating process is not particularly limited, and is preferably, for example, 1°C / min or more and 20°C / min or less. The holding temperature (reaching temperature) is preferably 800°C or more and 1200°C or less, more preferably 850°C or more and 1150°C or less, and further preferably 900°C or more and 1100°C or less. The holding time at the above-mentioned holding temperature is, for example, preferably 2 hours or more and 48 hours or less. In addition, the cooling rate during cooling after heating is preferably 5°C / min or more, more preferably 10°C / min or more, and further preferably 20°C / min or more.

[0069] The atmosphere in the heating step is not particularly limited, but an inert gas atmosphere is preferred from the viewpoint of suppressing oxidation of the rare earth magnet layer 13. As the inert gas, for example, Ar gas and N2 gas may be used.

[0070] Through the above-described steps, the intermediate layer 12 and the rare-earth magnet layer 13 are formed on the inner circumference of the Co substrate in the order described, resulting in a magnetic body 10 having a multilayer structure. In particular, the above-described method provides a multilayer structure in which no non-magnetic layer, such as an adhesive layer, is interposed between the transition metal layer 11 (Co substrate) and the intermediate layer 12, or between the intermediate layer 12 and the rare-earth magnet layer 13. Furthermore, when a mask of a high-melting-point material is formed on the outer circumference and end faces of the Co substrate, the mask of the high-melting-point material can be removed after the heating step, or the mask of the high-melting-point material can remain. Furthermore, when a mask of a high-melting-point material is not formed on the outer circumference and end faces of the Co substrate, a structure in which the intermediate layer and the rare-earth magnet layer are also formed on the outer circumference of the Co substrate is obtained.

[0071] Next, an example of a motor using the outer rotor 2 having the cylindrical magnetic body according to this embodiment will be described. Figure 4 Schematic diagram showing a cross section perpendicular to the rotation axis of the motor 100 according to one embodiment. Figure 5 Schematic diagram showing a cross section along the rotation axis of the motor 100. Figure 4 and Figure 5 As shown, the motor 100 includes an outer rotor 2 , a stator 50 inserted into the inner side of the outer rotor 2 , and a shaft 60 .

[0072] like Figure 4 As shown in FIG. 5 , the stator 50 is composed of a stator core 51 and a coil 52. The stator core 51 includes a cylindrical portion 51a and teeth 51b protruding outward from the cylindrical portion 51a. A coil 52 is formed on each tooth 51b. Figure 4 In the embodiment, the stator core 51 has six teeth 51b, but the number of teeth 51b is not particularly limited. The coil 52 can be formed by winding a conductive wire with an insulating coating around the teeth 51b. Furthermore, the material of the stator core 51 is not particularly limited; for example, electromagnetic steel sheets, SPCC (cold-rolled steel sheets), amorphous alloys, or magnetic powders can be used. Powdered amorphous alloys and magnetic powders can be formed into the stator core through compression molding.

[0073] like Figure 5 As shown, stator 50 is inserted into the area surrounded by inner circumferential surface 10b of magnetic body 10, and the multilayer structure of magnetic body 10 surrounds outer circumferential surface 50a of stator 50. In other words, inner circumferential surface 13b of rare earth magnet layer 13 located on the innermost side of the multilayer structure faces outer circumferential surface 50a of stator 50.

[0074] In the motor 100, the shaft 60 is arranged to pass through the inner side of the cylindrical portion 51a of the stator core 51. Figure 5 Although omitted, the shaft 60 and the outer rotor 2 may be connected so that they rotate synchronously. For example, a rotor housing containing the outer rotor 2 formed of the magnetic body 10 may be connected to the shaft 60 via a bearing such as a sleeve or a bearing. Furthermore, the motor 100 may include a container as an exterior, and this container may be connected to the stator 50.

[0075] The motor 100 can be used in various applications such as medical equipment and watches.

[0076] The structure of the motor using the outer rotor 2 is not limited to Figure 4 and Figure 5 The motor 100 shown in FIG. For example, the outer rotor 2 can also be applied to a coreless motor or a frameless motor. In the case of a coreless motor, the stator can be constructed using coils made of cylindrical coreless wiring or coils made of a flexible printed circuit board with printed coil wiring, rather than a stator core.

[0077] (Summary of Implementation Methods)

[0078] The cylindrical magnetic body of the present embodiment has a multilayer structure including a transition metal layer 11 , an intermediate layer 12 , and a rare earth magnet layer 13 in the order listed from the outer peripheral surface side toward the inner peripheral surface side.

[0079] The multilayered structure of the cylindrical magnetic body 10 described above allows the easy magnetization axis of the rare-earth magnet layer 13 to be radially oriented, resulting in a higher degree of radial orientation of the easy magnetization axis than in conventional sintered or bonded magnets. Consequently, the outer rotor 2 having the cylindrical magnetic body 10 of this embodiment can achieve a high surface magnetic flux density. As a result, even when the outer diameter of the outer rotor 2 is reduced to 6 mm or less, a sufficiently high motor torque can be achieved for practical purposes. Furthermore, the degree of radial orientation of the easy magnetization axis of the rare-earth magnet layer 13 is preferably 90% or greater.

[0080] The average thickness t3 of the rare earth magnet layer 13 is preferably not less than 10 μm and not more than 300 μm. By controlling t3 within the above range, the magnetic properties of the cylindrical magnetic body can be further improved.

[0081] In the multilayer structure, it is preferable that no intervening layers, such as adhesive layers, exist between the layers (i.e., between the transition metal layer 11 and the intermediate layer 12, and between the intermediate layer 12 and the rare earth magnet layer 13). By eliminating intervening protective layers or adhesive layers, the proportion of non-magnetic layers in the cylindrical magnetic body can be reduced, increasing the proportion of magnets, thereby further improving motor torque.

[0082] As mentioned above, although embodiment of this disclosure was described, this disclosure is not limited to the said embodiment, Various changes are possible within the range which does not deviate from the summary of this disclosure.

[0083] For example, the shape of the cylindrical magnetic body 10 is not limited to Figure 1 and Figure 2 The cylindrical shape shown in FIG. 1 may also be formed into a shape other than a circle when viewed from above as defined by the outer peripheral surface 11a. For example, Figure 6 As shown, the outer peripheral surface 10a of the magnetic body 10 (ie, the outer peripheral surface 11a of the transition metal layer 11) may also have a gear structure. In this case, the shape of the tip of the gear, the number of teeth, and the pitch interval between gears are not particularly limited.

[0084] In addition, as Figure 5 or Figure 6 A modification of the motor 100 shown in FIG. Figure 7 As shown, the stator 50 may also include a magnetic sensor 70. In this case, the magnetic sensor detects the magnetic field generated by the relative rare earth magnet layer 13. Figure 3 As shown, the stator 50 is multi-polarly magnetized, so the direction of the magnetic field detected by the magnetic sensor 70 changes periodically when the outer rotor 2 rotates. Therefore, by providing the magnetic sensor 70 on the stator 50, the rotation angle and rotation speed (rotational speed) of the outer rotor 2 can be detected.

[0085] The magnetic sensor 70 is preferably positioned in a location where it is less affected by the magnetic field generated by the coil 52. A protrusion may be provided on the transition metal layer 11 to reduce the distance between the rare-earth magnet layer 13 and the magnetic sensor 70. Providing the protrusion on the transition metal layer 11 reduces the distance between the magnetic sensor 70 and the rare-earth magnet layer 13. This makes it easier for the magnetic field detected by the magnetic sensor 70 from the rare-earth magnet layer 13 to be larger than the magnetic field generated by the coil 52. This improves the accuracy of detecting the rotation angle and rotation speed.

[0086] In addition, the composition of the transition metal layer 11, the intermediate layer 12, and the rare earth magnet layer 13 constituting the magnetic body 10 is not limited to the above-mentioned combination. For example, in the above-mentioned embodiment, the intermediate layer 12 and the rare earth magnet layer 13 both contain Co as a transition metal element and Sm as a rare earth element, but the intermediate layer 12 and the rare earth magnet layer 13 may contain at least one or more transition metals such as Fe and Ni in addition to Co, and may contain at least one or more rare earth elements such as Nd, Pr, Dy, and Tb in addition to Sm. Specifically, the intermediate layer 12 may be Sm2Fe 17 layer, Nd2Fe 17 layer, Pr2Fe 17 layer, particularly preferably Sm2Co 17In addition, the rare earth magnet layer 13 can be Sm2Fe 17 N3 layer, SmFe 12 layer, NdFe 12 layer, PrFe 12 The transition metal layer 11 preferably contains at least one transition metal element that is repeated in the intermediate layer 12, and more preferably contains the same transition metal element as that contained in the intermediate layer 12. The rare earth element contained in the intermediate layer 12 is a rare earth element diffused from the rare earth magnet layer 13, and the transition metal contained in the intermediate layer 12 is preferably the same as that contained in the transition metal layer 11.

[0087] The cylindrical magnetic body disclosed herein can be used not only as an outer rotor or motor, but can also be applied to controlling magnetic fluids placed within the cylinder, protecting piping from plasma, and other applications. In this case, the magnet layer can have a multipolar magnetization pattern in the circumferential or axial direction, or can be located only on a portion of the cylinder.

[0088] (Example)

[0089] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[0090] Example 1

[0091] A cylindrical Co substrate (outer diameter: 6.0 mm, thickness: 0.3 mm) was prepared. A Mo mask was formed on the outer surface of the Co substrate using a known method. The inner surface of the Co substrate was then polished with #120 polishing paper for 5 minutes and then washed with acetone.

[0092] Prepare LiCl and dehydrate it by drying. Heat the dehydrated LiCl to 600°C in a metal Mo container using an external heater to melt it. Add Sm metal powder as a Sm source to the molten LiCl. Add the Sm source so that the molar ratio of LiCl and Sm becomes LiCl:Sm=100:3. Next, immerse the ground cylindrical Co substrate in the molten LiCl. The reaction diffusion temperature is 700 degrees and the reaction diffusion time is 30 hours. Through the reaction diffusion process, a stacked body having a SmCo2 film formed on the Co substrate is obtained.

[0093] The resulting laminate was heated to 1050°C. Next, the laminate was heated for 24 hours at 1050°C without applying a magnetic field. Afterward, the laminate was cooled without applying a magnetic field, yielding a cylindrical magnetic body. The heating rate was 0.15°C / second, and the cooling rate was 50°C / second. The atmosphere during the heating step was Ar. Finally, the Mo mask was removed.

[0094] The structure of the obtained cylindrical magnetic body was confirmed by an X-ray diffraction measuring device and an energy dispersive X-ray analyzing device to be that Sm2Co 17 The structures of the film and the SmCo5 film. In addition, crystal orientation analysis using EBSD revealed that the cylindrical magnetic body was oriented in the radial direction, and the orientation degree of the rare earth magnet layer was 90%.

[0095] The motor torque was calculated by simulation (JMAG) for a motor using the obtained cylindrical magnetic body as an outer rotor. Specifically, the cylindrical magnetic body has a transition metal layer composed of a Co substrate with a diameter of 6.0 mm and a thickness of 0.3 mm. As an intermediate layer, a Sm2Co 17 The layer is in contact with the inner circumference of the Co substrate. The SmCo5 layer with a thickness of 0.2 mm, which is the rare earth magnet layer, is in contact with the inner circumference of the intermediate layer. The rare earth magnet layer is magnetized in a radial direction with four poles and an orientation degree of 90%.

[0096] Example 2

[0097] A cylindrical magnetic body was produced in the same manner as in Example 1 except that the type of the grinding paper was changed to a finer #4000. The structure of the obtained cylindrical magnetic body was confirmed by an X-ray diffraction measuring device and an energy dispersive X-ray analyzing device to be a structure in which Sm2Co 17 The structures of the film and the SmCo5 film. In addition, crystal orientation analysis using EBSD revealed that the cylindrical magnetic body was oriented in the radial direction, and the orientation degree of the rare earth magnet layer was 98%.

[0098] The motor torque was obtained by simulation under the same conditions as in Example 1 except that the above-mentioned cylindrical magnetic body was used, that is, except that the orientation degree of the rare earth magnet layer was 98%.

[0099] Example 3

[0100] Compared with Example 2, the motor torque was calculated by simulation under the same conditions as Example 2 except that the thickness of the intermediate layer was set to 0.025 mm and an intervening layer composed of an adhesive (epoxy resin) with a thickness of 0.025 mm was arranged between the rare earth magnet layer.

[0101] Comparative Example 1

[0102] Compared to Example 1, the intermediate layer was a 0.05 mm thick adhesive layer made of epoxy resin, and the rare earth magnet layer was magnetized in a parallel direction. The motor torque was determined by simulation. The orientation degree of the rare earth magnet layer was 100%.

[0103] Comparative Example 2

[0104] Compared with Example 1, the motor torque was obtained by simulation in the same manner as in Example 1 except that the intermediate layer was an adhesive layer made of epoxy resin with a thickness of 0.05 mm and the orientation degree of the rare earth magnet layer was set to 80%.

[0105] Table 1 shows the simulation results of Examples 1 to 3 and Comparative Examples 1 and 2.

[0106] [Table 1]

[0107]

[0108] The results shown in Table 1 show that the use of the cylindrical magnetic body disclosed herein can improve the motor torque compared to the comparative example corresponding to the conventional art.

[0109] Example 10

[0110] A cylindrical magnetic body was produced in the same manner as in Example 2 except that a mask made of Mo was not formed. The structure of the obtained cylindrical magnetic body was confirmed by an X-ray diffraction measuring device and an energy dispersive X-ray analyzing device to be that Sm2Co 17 In addition to the film and SmCo5 film, Sm2Co 17 The structures of the film and the SmCo5 film. In addition, crystal orientation analysis using EBSD revealed that the cylindrical magnetic body was oriented in the radial direction, and the orientation degree of the rare earth magnet layer was 98%.

[0111] Explanation of symbols

[0112] 2…Outer rotor

[0113] 10…Magnetic material

[0114] 11…Transition metal layer

[0115] 12…Middle layer

[0116] 13…Rare earth magnet layer

[0117] 10a…outer surface

[0118] 10b…Inner circumference

[0119] 100...Motor

[0120] 50…stator

[0121] 51… stator core

[0122] 51a…cylindrical part

[0123] 51b…tooth

[0124] 52…Coil

[0125] 60…Axis

[0126] 70…Magnetic sensor.

Claims

1. A cylindrical magnetic body, wherein: It has a multilayer structure comprising a transition metal layer, an intermediate layer, and a rare earth magnet layer in the order listed from the outer peripheral surface side toward the inner peripheral surface side. The intermediate layer and the rare earth magnet layer both contain transition metal elements and rare earth elements.

2. The cylindrical magnetic body according to claim 1, wherein The average thickness of the rare earth magnet layer is not less than 10 μm and not more than 300 μm.

3. The cylindrical magnetic body according to claim 1, wherein In the multilayer structure, no intervening layer exists between the transition metal layer and the intermediate layer, and between the intermediate layer and the rare earth magnet layer.

4. The cylindrical magnetic body according to claim 1, wherein The rare earth element contained in the intermediate layer is a rare earth element diffused from the rare earth magnet layer, and the transition metal contained in the intermediate layer is the same as the metal contained in the transition metal layer.

5. The cylindrical magnetic body according to claim 1, wherein The intermediate layer covers the entire circumference of the inner circumferential surface of the transition metal layer. The rare earth magnet layer covers the entire circumferential direction of the inner peripheral surface of the intermediate layer.

6. The cylindrical magnetic body according to claim 1, wherein The easy magnetization axis of the rare earth magnet layer is oriented in the radial direction. The orientation degree of the easy magnetization axis with respect to the radial direction is 90% or more.

7. The cylindrical magnetic body according to claim 1, wherein The transition metal layer is a Co layer, The intermediate layer is Sm2Co 17 layer, The rare earth magnet layer is a SmCo5 layer.

8. An outer rotor, wherein: A cylindrical magnetic body according to any one of claims 1 to 7 is provided.

9. A motor, wherein: A stator is provided which comprises the outer rotor according to claim 8 and is inserted into the inner side of the outer rotor.

10. The motor according to claim 9, wherein The stator has a magnetic sensor.

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