Method for manufacturing Halbach magnet array body and Halbach magnet array body

Abstract

Provided is a method for easily manufacturing a Halbach magnet array body having a large ratio of magnetic flux density between the surface and the back surface. A method for manufacturing a Halbach magnet array body, comprising, in sequence: (a) a step of magnetizing at least one first magnetic sheet and at least one second magnetic sheet in a direction parallel to a first direction; and (b) a step of magnetizing a third magnetic sheet in a direction parallel to a second direction perpendicular to the first direction. The first magnetic sheet and the second magnetic sheet are alternately arranged in the second direction with the third magnetic sheet sandwiched therebetween. Each of the first magnetic sheets is bonded to the adjacent third magnetic sheet via a non-magnetic layer of thickness t1, and each of the second magnetic sheets is bonded to the adjacent third magnetic sheet via a non-magnetic layer of thickness t2, and t1 and t2 satisfy t1. <t2。

Description

Technical Field

[0001] The invention relates to a method for manufacturing a Halbach magnet array body and the Halbach magnet array body. Background Art

[0002] Patent Document 1 describes a Halbach magnetic circuit including a plurality of permanent magnets having a plurality of regions magnetized in mutually different directions.

[0003] like Figure 1 As shown, the Halbach magnetic circuit 120 generally includes multiple permanent magnets arranged in a single direction, with the magnetization directions of adjacent permanent magnets 101 forming a predetermined angle (e.g., 90°). This arrangement allows one side (front) of the Halbach magnetic circuit 120 to have a high surface flux density, while the opposite side (back) has a low surface flux density or, ideally, zero surface flux density.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-092988 Summary of the Invention

[0007] When a Halbach magnetic circuit is manufactured by joining multiple magnetized magnets, accurate position control is difficult due to the repulsion between the magnets, and a large external force is required. Therefore, such a manufacturing method is not suitable for mass production. On the other hand, when a Halbach magnetic circuit is manufactured by joining multiple unmagnetized magnetic bodies and then magnetizing each magnetic body in a predetermined direction, or when a Halbach magnetic circuit is manufactured by forming multiple regions magnetized in different directions in a single permanent magnet as in Patent Document 1, the ratio of the magnetic flux density on the front and back surfaces of the Halbach magnetic circuit tends to be small.

[0008] Therefore, a method for easily manufacturing a Halbach magnet array body having a large ratio of magnetic flux density between the front surface and the back surface, and a Halbach magnet array body manufactured by the method are provided.

[0009] According to one embodiment of the present invention, a method for manufacturing a Halbach magnet array is provided, the method comprising:

[0010] a) magnetizing at least one first magnetic sheet and at least one second magnetic sheet in a direction parallel to the first direction,

[0011] wherein the at least one first magnetic sheet and the at least one second magnetic sheet are alternately arranged in a second direction perpendicular to the first direction with the third magnetic sheet interposed therebetween;

[0012] Each of the at least one first magnetic sheet is bonded to the adjacent third magnetic sheet via a non-magnetic layer having a thickness t1.

[0013] The at least one second magnetic sheet is bonded to the adjacent third magnetic sheet via a non-magnetic layer having a thickness of t2.

[0014] The thickness t1 and the thickness t2 satisfy t1 <t2,

[0015] The at least one first magnetic sheet and the at least one second magnetic sheet have easy magnetization axes parallel to the first direction.

[0016] The third magnetic sheet has an easy magnetization axis parallel to the second direction.

[0017] The magnetization direction of the at least one first magnetic piece and the magnetization direction of the at least one second magnetic piece differ by 180°; and

[0018] b) magnetizing the third magnetic piece in a direction parallel to the second direction so that the third magnetic piece has an S pole facing the adjacent first magnetic piece and an N pole facing the adjacent second magnetic piece.

[0019] According to one embodiment of the present invention, a Halbach magnet array is provided, wherein the Halbach magnet array comprises:

[0020] at least one first magnetic piece having magnetization parallel to a first direction;

[0021] at least one second magnetic sheet having a magnetization direction that is 180° different from the magnetization direction of the first magnetic sheet; and

[0022] at least one third magnetic piece having a magnetization parallel to a second direction perpendicular to the first direction,

[0023] The at least one first magnetic sheet and the at least one second magnetic sheet are alternately arranged in the second direction with the third magnetic sheet interposed therebetween.

[0024] The third magnetic piece has an S pole facing the adjacent first magnetic piece and an N pole facing the adjacent second magnetic piece.

[0025] Each of the at least one first magnetic sheet is bonded to the adjacent third magnetic sheet via a non-magnetic layer having a thickness t1.

[0026] The at least one second magnetic sheet is bonded to the adjacent third magnetic sheet via a non-magnetic layer having a thickness of t2.

[0027] The thickness t1 and the thickness t2 satisfy t1 <t2。

[0028] According to the manufacturing method of the present invention, a Halbach magnet array body having a large ratio of magnetic flux density between the front surface and the back surface can be easily manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a diagram schematically showing an example of a conventional Halbach magnetic circuit.

[0030] Figure 2 It is a flowchart of the manufacturing method involved in embodiment.

[0031] Figure 3 This is a diagram schematically showing an example of an array body provided for the step of magnetizing the first magnetic sheet.

[0032] Figure 4 This is a diagram schematically showing an example of a Halbach magnet array body manufactured by the manufacturing method according to the embodiment.

[0033] Figure 5 The graph shows the ratio of the magnetic flux on the surface to the sum of the magnetic flux on the surface and back surface, and the ratio of the magnetic flux on the back surface to the sum of the magnetic flux on the surface and back surface of the test bodies of Examples 1 and 2 and Comparative Examples 1 to 4.

[0034] Description of Reference Numerals

[0035] 1: first magnetic sheet; 2: second magnetic sheet; 3: third magnetic sheet; 5: non-magnetic layer; 10: array; 20: Halbach magnet array. DETAILED DESCRIPTION

[0036] Hereinafter, the embodiments will be described with reference to the accompanying drawings as appropriate. The present invention is not limited to the following embodiments, and various design changes can be made within the scope of the spirit of the present invention as described in the claims. Furthermore, in the drawings referred to in the following description, the same components or components having the same functions are marked with the same symbols, and repeated descriptions are sometimes omitted. In addition, for the sake of convenience of explanation, the dimensional ratios of the drawings are sometimes different from the actual ratios, part of the components are omitted in the drawings, and so on. In addition, in this application, the numerical range represented by the symbol "~" includes the numerical values recorded before and after the symbol "~" as the lower limit and upper limit, respectively. In this application, the so-called vertical means substantially vertical, and the so-called parallel means substantially parallel.

[0037] The manufacturing method of Halbach magnet array body, such as Figure 2 As shown, the method includes a step (S1) of magnetizing the first magnetic sheet and the second magnetic sheet, and a step (S2) of magnetizing the third magnetic sheet.

[0038] a) Magnetization of the first magnetic sheet and the second magnetic sheet

[0039] First, prepare at least one unmagnetized first magnetic sheet, at least one unmagnetized second magnetic sheet, and at least one unmagnetized third magnetic sheet. The first magnetic sheet, the second magnetic sheet, and the third magnetic sheet contain permanent magnet materials. Examples of permanent magnet materials include Nd-Fe-B magnet materials, Sm-Co magnet materials, Sm-Fe-N magnet materials, ferrite magnet materials, and Al-Ni-Co magnet materials. The first magnetic sheet, the second magnetic sheet, and the third magnetic sheet have magnetic anisotropy. That is, the first magnetic sheet, the second magnetic sheet, and the third magnetic sheet each have an easy magnetization axis and a hard magnetization axis. The first magnetic sheet, the second magnetic sheet, and the third magnetic sheet can have any shape. For example, each magnetic sheet can have a columnar shape with a roughly rectangular shape (especially a roughly square shape) or a roughly partially circular bottom surface. Furthermore, the first, second, and third magnetic sheets may have the same shape and size. If the first, second, and third magnetic sheets have a columnar (i.e., cuboid) shape with a substantially rectangular bottom surface and the same size, the easy magnetization axes of the first and second magnetic sheets may be perpendicular to a set of mutually parallel faces perpendicular to the bottom surface, and the easy magnetization axis of the third magnetic sheet may be perpendicular to another set of mutually parallel faces perpendicular to the bottom surface. Furthermore, if the first, second, and third magnetic sheets have a columnar shape with a substantially partially circular bottom surface and the same size, the easy magnetization axes of the first and second magnetic sheets may be parallel to the radial direction of the partial circular ring, and the easy magnetization axis of the third magnetic sheet may be parallel to the circumferential direction of the partial circular ring. The first, second, and third magnetic sheets can be manufactured using generally known manufacturing methods. Commercially available magnetic sheets may be used as the first magnetic sheet 1 , the second magnetic sheet, and the third magnetic sheet.

[0040] like Figure 3 As shown, the first magnetic sheet 1, the second magnetic sheet 2 and the third magnetic sheet 3 are arranged in a predetermined direction ( Figure 3 In the X direction) to obtain the array body 10. Figure 3A linear array body 10 is shown, but when the first magnetic body sheet 1, the second magnetic body sheet 2, and the third magnetic body sheet 3 have a columnar shape with a substantially partial circular bottom surface, a circular array body 10 can be formed by arranging a specified number of the first magnetic body sheets 1, the second magnetic body sheets 2, and the third magnetic body sheets 3 in their circumferential directions. In the array body 10, the first magnetic body sheets 1 and the second magnetic body sheets 2 are alternately arranged sandwiching the third magnetic body sheet 3. Each of the first magnetic body sheets 1 is joined to an adjacent third magnetic body sheet 3 via a non-magnetic layer 5 with a thickness t1, and the second magnetic body sheets 2 are joined to adjacent third magnetic body sheets 3 via a non-magnetic layer 5 with a thickness t2, where t1 < t2. The non-magnetic layer 5 may contain an adhesive (e.g., an epoxy resin-based adhesive, an acrylic resin-based adhesive).

[0041] The non-magnetic layer 5 may have a thermal conductivity of 0.5 W / m·K or less, particularly 0.2 W / m·K or less. Thus, when magnetizing the first magnetic body sheets 1 and the second magnetic body sheets 2 under the condition that the first magnetic body sheets 1 and the second magnetic body sheets 2 have a higher temperature than the third magnetic body sheet 3, heat transfer from the first magnetic body sheets 1 and the second magnetic body sheets 2 to the third magnetic body sheet 3 is suppressed. As a result, magnetization of the third magnetic body sheet 3 by the magnetic field used to magnetize the first magnetic body sheets and the second magnetic body sheets can be effectively suppressed. Similarly, in a subsequent step of magnetizing the third magnetic body sheet, when magnetizing the third magnetic body sheet 3 under the condition that the third magnetic body sheet 3 has a higher temperature than the first magnetic body sheets 1 and the second magnetic body sheets 2, heat transfer from the third magnetic body sheet 3 to the first magnetic body sheets 1 and the second magnetic body sheets 2 is suppressed. As a result, in the magnetization of the third magnetic body sheet 3, the influence of the magnetic field used to magnetize the third magnetic body sheet 3 on the residual magnetization of the first magnetic body sheets 1 and the second magnetic body sheets 2 can be effectively suppressed. Additionally, the non-magnetic layer 5 generally has a thermal conductivity of 0.01 W / m·K or more, but is not limited thereto.

[0042] In Figure 3 two first magnetic body sheets 1 and one second magnetic body sheet 2 are alternately arranged sandwiching the third magnetic body sheet 3, but if the first magnetic body sheets 1 and the second magnetic body sheets 2 can be alternately arranged, the array body 10 may also contain more or less than two first magnetic body sheets 1, may contain more than one second magnetic body sheet 2, and may contain more or less than two third magnetic body sheets 3.

[0043] In the array body 10, the easy magnetization axes of the first magnetic body sheets 1 and the second magnetic body sheets 2 (shown by blank arrows in Figure 3 ) are parallel to the first direction ( Figure 3 the Z direction of Figure 3, indicated by blank arrows) and the second direction ( Figure 3 Here, the first direction and the second direction are perpendicular to each other. In addition, the second direction is parallel to the arrangement direction of the first magnetic sheet 1, the second magnetic sheet 2, and the third magnetic sheet 3.

[0044] Next, the first magnetic sheet 1 and the second magnetic sheet 2 of the array body 10 are magnetized in a direction parallel to the first direction. The magnetization directions of the first magnetic sheet 1 and the second magnetic sheet 2 differ by 180 degrees.

[0045] The first magnetic sheet 1 and the second magnetic sheet 2 can be magnetized using any magnetizer. For example, the first magnetic sheet 1 and the second magnetic sheet 2 can be magnetized by placing them in a magnetic field (external magnetic field) generated by a magnetizing yoke.

[0046] Alternatively, the first and second magnetic sheets 1 and 2 can be magnetized while maintaining a higher temperature than the third magnetic sheet 3. This prevents the third magnetic sheet 3 from being magnetized by the magnetic field used to magnetize the first and second magnetic sheets 1 and 2, while imparting a sufficiently large residual magnetization to the first and second magnetic sheets 1 and 2. This is because the higher the temperature of the magnetic sheet during magnetization, the higher the residual susceptibility (i.e., the ratio of residual magnetization to saturation residual magnetization) of the magnetic sheet. Furthermore, the temperature dependence of the residual susceptibility of a magnetic sheet generally depends on the type of magnetic material used as the main component of the magnetic sheet, the presence or absence of element substitution in the magnetic material and the type of the substitutional element, and the structure of the magnetic sheet (e.g., grain size).

[0047] For example, the first magnetic sheet 1 and the second magnetic sheet 2 can be magnetized while being heated. Alternatively or in addition to this, the first magnetic sheet 1 and the second magnetic sheet 2 can be magnetized while being cooled. The first magnetic sheet 1 and the second magnetic sheet 2 can be heated using any heating means (e.g., a hot plate resistance heater or a rubber heater). A magnetizing yoke with a heater can also be used to heat and magnetize the first magnetic sheet 1 and the second magnetic sheet 2. The third magnetic sheet 3 can be cooled using any cooling means (e.g., a water cooling block).

[0048] b) Magnetization of the third magnetic sheet

[0049] Next, the third magnetic sheet 3 is magnetized so that the third magnetic sheet 3 has an S pole facing the adjacent first magnetic sheet 1 and an N pole facing the adjacent second magnetic sheet 2 .

[0050] The third magnetic sheet 3 can be magnetized using any magnetizer. For example, the third magnetic sheet 3 can be magnetized by placing it in a magnetic field (external magnetic field) generated by a magnetizing yoke.

[0051] The third magnetic sheet 3 can also be magnetized while being at a higher temperature than the first and second magnetic sheets 1 and 2. This prevents the magnetic field used to magnetize the third magnetic sheet 3 from affecting the residual magnetization of the first and second magnetic sheets 1 and 2, and allows the third magnetic sheet 3 to have a sufficiently large residual magnetization. For example, the third magnetic sheet 3 can be magnetized while being heated. Alternatively or in addition to this, the third magnetic sheet 3 can be magnetized while being cooled. The third magnetic sheet 3 can be heated using any heating means (e.g., a hot plate resistance heater or a rubber heater). A magnetizing yoke with a heater can also be used to heat and magnetize the third magnetic sheet 3. The first and second magnetic sheets 1 and 2 can be cooled using any cooling means (e.g., a water cooling block).

[0052] In this way, the Figure 4 The Halbach magnet array body 20 shown. The Halbach magnet array body 20 has: Figure 4 The first magnetic sheet 1 is magnetized in a direction parallel to the Z direction of the first magnetic sheet 1, the second magnetic sheet 2 is magnetized in a direction 180° different from the magnetization direction of the first magnetic sheet 1, and the second magnetic sheet 2 is magnetized in a direction perpendicular to the first direction ( Figure 4 The first magnetic sheet 1 and the second magnetic sheet 2 are alternately arranged in the second direction with the third magnetic sheet 3 sandwiched therebetween. The third magnetic sheet 3 has an S pole facing the adjacent first magnetic sheet 1 and an N pole facing the adjacent second magnetic sheet 2. Each of the first magnetic sheets 1 is bonded to the adjacent third magnetic sheet 3 via a non-magnetic layer 5 of thickness t1, and the second magnetic sheet 2 is bonded to the adjacent third magnetic sheet 3 via a non-magnetic layer 5 of thickness t2, and the thickness t1 and the thickness t2 satisfy t1. <t2。

[0053] In the Halbach magnet array body 20 obtained by the manufacturing method according to the embodiment, the thickness t2 of the non-magnetic layer 5 between the adjacent second magnetic sheet 2 and third magnetic sheet 3 is greater than the thickness t1 of the non-magnetic layer 5 between the adjacent first magnetic sheet 1 and third magnetic sheet 3. As a result, as shown in the embodiments described below, the ratio of the magnetic flux density between the surface and back surfaces of the Halbach magnet array body 20 becomes larger. In addition, in the manufacturing method according to the embodiment, since each magnetic sheet is magnetized in a predetermined direction after joining a plurality of unmagnetized magnetic sheets, no repulsive force is generated between the magnetic sheets when joining the magnetic sheets. Therefore, when joining the magnetic sheets, a large external force is not required to counteract the repulsive force between the magnetic sheets, and accurate position control of the magnetic sheets is also easy.

[0054] Example

[0055] Hereinafter, the present invention will be specifically described using examples, but the present invention is not limited to these examples.

[0056] Examples 1, 2 and Comparative Examples 1 to 3

[0057] Five 5mm×5mm×7mm rectangular magnetic pieces (neodymium magnet sintered bodies) with easy magnetization axes perpendicular to the 5mm×7mm surface were prepared. Two of the magnetic pieces were designated as the first magnetic piece, one as the second magnetic piece, and two as the third magnetic pieces.

[0058] The first magnetic sheet and the second magnetic sheet are alternately arranged in the second direction perpendicular to the first direction in such a manner that the easy magnetization axes of the first magnetic sheet and the second magnetic sheet are parallel to the first direction. The third magnetic sheet is arranged between the first magnetic sheet and the second magnetic sheet adjacent to each other in such a manner that the easy magnetization axis of the third magnetic sheet is parallel to the second direction. Furthermore, the first magnetic sheet, the second magnetic sheet and the third magnetic sheet are arranged in such a manner that the respective 5 mm × 5 mm surfaces are parallel to both the first direction and the second direction. The first magnetic sheet and the third magnetic sheet adjacent to each other, and the second magnetic sheet and the third magnetic sheet adjacent to each other are bonded using a non-magnetic bonding agent (with a thermal conductivity of 0.2 W / m·K). The layer thickness t1 of the bonding agent between the first magnetic sheet and the third magnetic sheet and the layer thickness t2 of the bonding agent between the second magnetic sheet and the third magnetic sheet are recorded in Table 1. In Table 1, S <M<L。

[0059] While heating the first and second magnetic sheets to 65° C., the first and second magnetic sheets were magnetized using an external magnetic field parallel to the first direction. The magnetization direction of the first magnetic sheet was set to be 180° different from the magnetization direction of the second magnetic sheet.

[0060] Next, while heating the third magnetic body piece to 65°C, the third magnetic body piece was magnetized by an external magnetic field parallel to the second direction such that the third magnetic body piece has an S pole facing the adjacent first magnetic body piece and an N pole facing the adjacent second magnetic body piece.

[0061] Thus, a test body having a Figure 4 Halbach array as shown was obtained.

[0062] Comparative Example 4

[0063] Five magnetically anisotropic magnetic body pieces (neodymium magnet sintered bodies) similar to those in Example 1 were prepared. Each magnetic body piece was magnetized in the direction of its easy magnetization axis. Next, two of the magnetic body pieces were used as the first magnetic body pieces, one as the second magnetic body piece, and two as the third magnetic body pieces, and they were arranged in the same manner as in Example 1. The first magnetic body piece and the third magnetic body piece adjacent to each other, and the second magnetic body piece and the third magnetic body piece adjacent to each other were joined using a non-magnetic bonding agent. The layer thickness t1 of the bonding agent between the first magnetic body piece and the third magnetic body piece and the layer thickness t2 of the bonding agent between the second magnetic body piece and the third magnetic body piece are shown in Table 1. Thus, a test body having a Figure 4 Halbach array as shown was obtained.

[0064] Table 1

[0065] t1 t2 Comparative Example 1 S S Example 1 S M Example 2 S L Comparative Example 2 M S Comparative Example 3 L L Comparative Example 4 S S

[0066] Evaluation

[0067] The magnetic flux in two faces perpendicular to the first direction of each test body was measured using a fluxmeter. The face with the larger magnetic flux among the two faces was taken as the front surface, and the face with the smaller magnetic flux was taken as the back surface. The ratio of the magnetic flux of each face to the sum of the magnetic fluxes of the front surface and the back surface was calculated. The results are shown in Figure 5 .

[0068] As Figure 5 shown, for the test bodies of Examples 1 and 2 where t1 < t2, the magnetic flux ratio of the front surface is larger than that of any of the test bodies of Comparative Examples 1 and 3 where t1 = t2 and Comparative Example 2 where t1 > t2.

[0069] Furthermore, the magnetic flux ratio of the front surface of the test bodies of Examples 1 and 2 is smaller than that of the test body of Comparative Example 4. However, the test body of Comparative Example 4 was made by joining magnetized magnetic body pieces, and this manufacturing method is not suitable for mass production.

Claims

1. A method for manufacturing a Halbach magnet array, comprising steps a and b in sequence. The step a is a step of magnetizing at least one first magnetic sheet and at least one second magnetic sheet in a direction parallel to the first direction. in, The at least one first magnetic sheet and the at least one second magnetic sheet are alternately arranged in a second direction perpendicular to the first direction with a third magnetic sheet interposed therebetween. Each of the at least one first magnetic sheet is bonded to the adjacent third magnetic sheet via a non-magnetic layer having a thickness t1. The at least one second magnetic sheet is bonded to the adjacent third magnetic sheet via a non-magnetic layer having a thickness of t2. The thickness t1 and the thickness t2 satisfy t1 <t2, The at least one first magnetic sheet and the at least one second magnetic sheet have easy magnetization axes parallel to the first direction. The third magnetic sheet has an easy magnetization axis parallel to the second direction. The magnetization direction of the at least one first magnetic sheet and the magnetization direction of the at least one second magnetic sheet differ by 180°. The step b is a step of magnetizing the third magnetic piece in a direction parallel to the second direction so that the third magnetic piece has an S pole facing the adjacent first magnetic piece and an N pole facing the adjacent second magnetic piece.

2. The method for manufacturing a Halbach magnet array according to claim 1, The non-magnetic layer has a thermal conductivity of 0.5 W / m·K or less.

3. The method for manufacturing a Halbach magnet array according to claim 1 or 2, The non-magnetic layer includes a binder.

4. A Halbach magnet array having: at least one first magnetic piece having magnetization parallel to a first direction; at least one second magnetic sheet having a magnetization direction that is 180° different from the magnetization direction of the first magnetic sheet; and at least one third magnetic piece having a magnetization parallel to a second direction perpendicular to the first direction, The at least one first magnetic sheet and the at least one second magnetic sheet are alternately arranged in the second direction with the third magnetic sheet interposed therebetween. The third magnetic piece has an S pole facing the adjacent first magnetic piece and an N pole facing the adjacent second magnetic piece. Each of the at least one first magnetic sheet is bonded to the adjacent third magnetic sheet via a non-magnetic layer having a thickness t1. The at least one second magnetic sheet is bonded to the adjacent third magnetic sheet via a non-magnetic layer having a thickness of t2. The thickness t1 and the thickness t2 satisfy t1 <t2。 5. The Halbach magnet array according to claim 4, The non-magnetic layer has a thermal conductivity of 0.5 W / m·K or less.

6. The Halbach magnet array according to claim 4 or 5, The non-magnetic layer includes a binder.

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