Method for manufacturing a multipole magnet

Abstract

A method for manufacturing a multipole magnet includes: a first step of changing a distribution of a rare earth material in a hot worked magnet (10) having a plurality of magnetic powders containing the rare earth material; and a second step of magnetizing the hot worked magnet (10) subjected to the first step to obtain a multipole magnet (20) having a plurality of magnetic pole portions. It is preferable that, in the first step, the distribution of the rare earth material in the hot worked magnet (10) be changed by increasing an amount of the rare earth material interposed between the plurality of magnetic powders. It is more preferable that, in the first step, the distribution of the rare earth material in the hot worked magnet (10) be changed by heating the hot worked magnet (10) at a prescribed temperature.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a multipole magnet. Background Technology

[0002] Patent Document 1 discloses a method for manufacturing a permanent magnet rotor, which involves heating and then magnetizing the permanent magnet rotor. The permanent magnet rotor has a rotating shaft at the center of an iron core and a magnet before magnetization is provided in the iron core. The magnet before magnetization is a neodymium magnet composed of fine crystal grains with an average crystal grain size of 0.1 μm to 3.5 μm. The method for manufacturing the permanent magnet rotor includes: a heating step, in which the permanent magnet rotor is heated within a range above a specific temperature (Ta °C) that can achieve complete magnetization and below a specific temperature (Tb °C) that will cause irreversible demagnetization, to obtain a heated permanent magnet; and a magnetization step, in which the heated permanent magnet is magnetized to achieve a magnetization rate of 98% or higher.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-083288 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, the magnetization method in Patent Document 1 cannot produce a multipole magnet with a narrow pitch and strong magnetization.

[0008] Therefore, the object of the present invention is to provide a method for manufacturing a multipole magnet that can obtain a narrow-pitch multipole magnet that is strongly magnetized.

[0009] Solution for solving the problem

[0010] To solve the above problems and achieve the objective, one embodiment of the present invention provides a method for manufacturing a multipole magnet comprising: a first step of changing the distribution of the rare earth material in a hot-processed magnet having a plurality of magnetic powders containing rare earth materials; and a second step of magnetizing the hot-processed magnet that has undergone the first step to obtain a multipole magnet having a plurality of magnetic poles.

[0011] According to one aspect of the present invention, a method for manufacturing a multipole magnet can obtain a narrow-pitch multipole magnet that is strongly magnetized. Attached Figure Description

[0012] Figure 1 This diagram illustrates the magnetization process in the second step of the manufacturing method of the multipole magnet in Embodiment 1.

[0013] Figure 2This is a diagram used to illustrate the multipole magnet obtained through the second step of the manufacturing method of the multipole magnet in Embodiment 1.

[0014] Figure 3 This diagram illustrates the magnetization process in the second step of a method for manufacturing a multipole magnet in other embodiments.

[0015] Figure 4 This diagram illustrates the magnetization process in the second step of a method for manufacturing a multipole magnet in other embodiments.

[0016] Figure 5 This is a graph showing the measurement results of the surface magnetic flux of the multipole magnet obtained in Example 1.

[0017] Figure 6 This is a graph showing the measurement results of the surface magnetic flux of the multipole magnet obtained in Example 2. Detailed Implementation

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to these embodiments. Furthermore, the constituent elements in the following embodiments include constituent elements that can be substituted and easily replaced by those skilled in the art, or substantially the same constituent elements.

[0019] <Implementation Method 1>

[0020] The manufacturing method of the multipole magnet in Embodiment 1 includes: a first step of changing the distribution of rare earth materials in a hot-processed magnet having a plurality of rare earth material-containing magnetic powders; and a second step of magnetizing the hot-processed magnet that has undergone the first step to obtain a multipole magnet having a plurality of magnetic poles.

[0021] [First Process]

[0022] In the first step, a hot-worked magnet with an annular shape and its easily magnetized axis oriented radially is used. The radial thickness of the hot-worked magnet is preferably 4 mm or less.

[0023] Hot-working magnets are made from magnetic powder containing rare-earth materials. Magnetic powder is obtained, for example, by crushing magnetically isotropic thin strips produced by ultraquenching. Examples of rare-earth materials contained in magnetic powder include praseodymium (Pr). Other rare-earth materials besides praseodymium (Pr) include neodymium (Nd), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Rare-earth elements other than Pr can be used alone or in combination of two or more.

[0024] Specifically, in Embodiment 1, from the viewpoint of obtaining a narrow-pitch, strongly magnetized multipole magnet, the magnetic powder is preferably Nd-Fe-B magnet powder containing Pr. Furthermore, in Embodiment 1, from the viewpoint of obtaining a narrow-pitch, strongly magnetized multipole magnet, the Nd-Fe-B magnet powder preferably contains Co by substituting a portion of Fe (typically less than 50 atomic percent). In addition, the Nd-Fe-B magnet powder may also contain other elements. These other elements include titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), tungsten (W), copper (Cu), gallium (Ga), and oxygen (O). Other elements may be used individually or in combination of two or more.

[0025] The hot-worked magnet can be made using the aforementioned magnetic powder and by, for example, the method described in HIOKI, "Development of High-Performance Hot-Worked Nd-Fe-B Magnets," J. Jpn. Soc. Powder Powder Metallurgy, 69 (2022) S3-S13 https: / / dōi.org / 10.2497 / jjspm.69.S3. Specifically, the aforementioned magnetic powder is cold-formed at room temperature and then hot-formed at approximately 800°C to produce a cylindrical molded body with approximately true density. Next, the molded body is thermoplasticized at approximately 800°C. During thermoplasticization, it is extruded backward to obtain a hot-worked magnet with an anisotropic ring shape.

[0026] In the first step, the hot-working magnet is heated, for example, from room temperature, to a specified temperature (i.e., above the Curie temperature of the magnetic powder). Specifically, in this first step, the amount of rare-earth material interposed between multiple magnetic powders is increased to change the distribution of the rare-earth material in the hot-working magnet. More specifically, the amount of rare-earth material Pr interposed between multiple magnetic powders is increased to change the distribution of the rare-earth material in the hot-working magnet. By performing this first step in advance, a narrow-pitch, strongly magnetized multipole magnet is finally obtained. Pr is used as an example of the rare-earth material interposed between multiple magnetic powders, but it is not limited to this. Specifically, it can be La, Ce, Pr, Nd, PrNd (neodymium praseodymium), and multiple materials can also be mixed together.

[0027] [Second Process]

[0028] In the second process, the heat-processed magnet from the first process is multipole magnetized radially to obtain a multipole magnet. Like the heat-processed magnet, the multipole magnet has a ring shape and multiple magnetic poles in the circumferential direction. Specifically, it has 20 or more magnetic poles.

[0029] Magnetization can be performed, for example, by the UHM magnetization disclosed in Japanese Patent Application Publication No. 2021-093521. That is, it can be performed by heating a hot-working magnet, which is the object to be magnetized, to a temperature above the Curie temperature of the magnetic powder contained therein (e.g., above 250°C and below 500°C), and while cooling to a temperature below the Curie temperature, continuously applying a magnetizing magnetic field to the object to be magnetized using a permanent magnet as an excitation source.

[0030] Figure 1 This diagram illustrates the magnetization process in the second step of the manufacturing method of the multipole magnet in Embodiment 1. Figure 2 This diagram illustrates the multipole magnet obtained in the second step of the manufacturing method of the multipole magnet according to Embodiment 1. The magnetization of the heat-worked magnet 10 utilizes an outer peripheral jig 110 and an inner peripheral jig 120. The outer peripheral jig 110 is made of a non-magnetic metal material and is formed in a cylindrical shape. The outer peripheral jig 110 has an insertion hole 112 for inserting the heat-worked magnet 10. A permanent magnet 114 is radially embedded in the insertion hole 112 side of the outer peripheral jig 110 to generate a magnetic field on the heat-worked magnet 10; for example, it is a rectangular SmCo magnet. When viewed from above, the permanent magnets 114 are formed in concentric circles centered on the center of the outer peripheral jig 110, and multiple (e.g., more than 20) are arranged at equal intervals in the circumferential direction. Figure 1 (As an example, there are 28).

[0031] Furthermore, the inner peripheral jig 120 is made of a non-magnetic metallic material and is cylindrical in shape. The permanent magnet 124, for example a rectangular SmCo magnet, is radially embedded on the outer periphery of the inner peripheral jig 120, generating a magnetic field on the heat-processed magnet 10. Viewed from above, the permanent magnets 124 are arranged in concentric circles around the center of the inner peripheral jig 120, with multiple (e.g., more than 20) evenly spaced circumferentially. Figure 1 (As an example, there are 28).

[0032] During magnetization, the heat-processed magnet 10, which has undergone the first process, is positioned between the outer peripheral fixture 110 and the inner peripheral fixture 120. Specifically, for the heat-processed magnet 10 heated to above the Curie temperature of the magnetic powder in the first process, the outer peripheral fixture 110 is positioned on the outer peripheral side of the heat-processed magnet 10, and the inner peripheral fixture 120 is positioned on the inner peripheral side. Then, a magnetizing magnetic field is applied by the permanent magnets 114 and 124, which serve as excitation sources. It should be noted that the permanent magnets 114 and 124 of the outer peripheral fixture 110 and the inner peripheral fixture 120 are positioned to... Figure 1The permanent magnets 114 and 124 are arranged in the direction indicated by the arrows, applying magnetizing magnetic fields in opposite directions. In this state, while the hot-worked magnet 10 is cooled to below the Curie temperature (e.g., room temperature), the permanent magnets 114 and 124, acting as excitation sources, continuously apply magnetizing magnetic fields to magnetize the hot-worked magnet 10. This results in a multipole magnet 20 serving as the magnetized hot-worked magnet 10. It should be noted that... Figure 2 In this embodiment, the multipole magnet 20 has 28 magnetic poles in the circumferential direction. Thus, in Embodiment 1, by performing a second process on the heat-processed magnet that has undergone the first process, a multipole magnet with a narrow pitch and strong magnetization can be obtained.

[0033] <Implementation Method 2>

[0034] In Embodiment 1, the second step is performed after the first step. In contrast, in Embodiment 2, the first and second steps can be performed simultaneously. Specifically, the heat-working magnet 10 is positioned between the outer peripheral fixture 110 and the inner peripheral fixture 120, and a magnetizing magnetic field is initially applied by permanent magnets 114 and 124, which serve as excitation sources. Then, the heat-working magnet is heated, for example, from room temperature, at a predetermined temperature (i.e., a temperature above the Curie temperature of the magnetic powder). Next, while the heat-working magnet 10 is cooled to below the Curie temperature (e.g., room temperature), a magnetizing magnetic field is continuously applied by the permanent magnets 114 and 124, which serve as excitation sources, to magnetize the heat-working magnet 10. In this case, a multipole magnet 20 can also be obtained as the magnetized heat-working magnet 10.

[0035] <Other Implementation Methods>

[0036] In Embodiments 1 and 2, the number of permanent magnets 114 in the outer peripheral jig 110 is the same as the number of permanent magnets 124 in the inner peripheral jig 120. Alternatively, the number of permanent magnets 114 in the outer peripheral jig 110 may differ from the number of permanent magnets 124 in the inner peripheral jig 120. That is, a multipole magnet 20 with a different number of inner and outer magnetic pole portions can also be manufactured using the manufacturing method of the multipole magnets described in the embodiments.

[0037] also, Figure 3 and Figure 4 This diagram illustrates the magnetization process in the second step of a method for manufacturing a multipole magnet according to other embodiments. In Embodiments 1 and 2, an outer peripheral jig 110 and an inner peripheral jig 120 are used in the second step. Alternatively, as... Figure 3 As shown, using only the peripheral jig 110, it is also possible to... Figure 4The diagram shows the use of only the inner circumferential jig 120. In these cases, also along... Figure 3 and Figure 4 A magnetizing magnetic field is applied in the direction indicated by the arrow, and a multipole magnet is obtained in the same manner as in Embodiment 1 and Embodiment 2.

[0038] The multipole magnets obtained through the above embodiments are suitable for use in servo motors, low-frequency generators, magnetic gears, etc.

[0039] The present invention will now be described in more detail with reference to embodiments, but the present invention is not limited to these embodiments.

[0040] [Example]

[0041] [Example 1]

[0042] In the first process, a hot-worked magnet with a ring shape and its easily magnetized axis oriented radially is used. The radial thickness of the hot-worked magnet is less than 4 mm.

[0043] The hot-working magnet uses a magnet obtained from magnetic powder containing rare-earth materials. That is, the magnetic powder is an Nd-Fe (iron)-B (boron) based magnetic powder containing Pr. In addition, a portion of the Fe (usually less than 50 atomic percent) is replaced by Co, thus containing Co. The hot-working magnet uses the above-mentioned magnetic powder and is manufactured by the method described in Hioki, "Development of High-Performance Hot-Working Nd-Fe-B Magnets", J. Jpn. Soc. Powder Powder Metallurgy, 69 (2022) S3-S13 https: / / dōi.org / 10.2497 / jjspm.69.S3. That is, the hot-working magnet is obtained by the following method. After the above-mentioned magnetic powder is cold-formed at room temperature, it is thermoformed at about 800°C to produce a cylindrical molded body with approximately true density. Then, the molded body is thermoplasticized at about 800°C. During thermoplasticization, it is extruded backward to obtain a hot-working magnet with an anisotropic ring shape.

[0044] In the first step, the heat-processed magnet is heated from room temperature to a temperature above the Curie temperature of the magnetic powder (370°C) (400°C). This heating state is maintained before starting the second step. That is, as... Figure 1As shown, for the hot-worked magnet 10 heated at 400°C in the first process, an outer peripheral jig 110 is disposed on the outer peripheral side of the hot-worked magnet 10 and an inner peripheral jig 120 is disposed on the inner peripheral side. Then, a magnetizing magnetic field is applied by permanent magnets 114 and 124 as excitation sources. In this state, while the hot-worked magnet 10 is cooled to room temperature, a magnetizing magnetic field is continuously applied by permanent magnets 114 and 124 as excitation sources to magnetize the hot-worked magnet 10. However, in Embodiment 1, compared with Figure 1 Unlike other methods, when viewed from above, the permanent magnets 114 are arranged in concentric circles around the center of the outer peripheral fixture 110, with 24 magnets evenly spaced in the circumferential direction. Similarly, when viewed from above, the permanent magnets 124 are arranged in concentric circles around the center of the inner peripheral fixture 120, with 24 magnets evenly spaced in the circumferential direction. This results in a multipole magnet 20 used as the magnet for heat treatment after magnetization. The multipole magnet 20 has 24 magnetic poles in the circumferential direction.

[0045] [Example 2]

[0046] In the first step, a heat-worked magnet with a ring shape and its easily magnetized axis oriented radially is used. The radial thickness of the heat-worked magnet is 4 mm or less. The heat-worked magnet is the same as that used in Example 1.

[0047] In the first step, the heat-processed magnet is heated from room temperature to a temperature above the Curie temperature of the magnetic powder (370°C) (400°C). This heating state is maintained before starting the second step. That is, as... Figure 1 As shown, for the hot-worked magnet 10 heated at 400°C in the first process, an outer peripheral jig 110 is disposed on the outer peripheral side of the hot-worked magnet 10 and an inner peripheral jig 120 is disposed on the inner peripheral side. Then, a magnetizing magnetic field is applied by permanent magnets 114 and 124 as excitation sources. In this state, while the hot-worked magnet 10 is cooled to room temperature, a magnetizing magnetic field is continuously applied by permanent magnets 114 and 124 as excitation sources to magnetize the hot-worked magnet 10. However, in Embodiment 2, with Figure 1 Unlike other methods, when viewed from above, the permanent magnets 114 are arranged in concentric circles around the center of the outer peripheral fixture 110, with 100 of them evenly spaced in the circumferential direction. Similarly, when viewed from above, the permanent magnets 124 are arranged in concentric circles around the center of the inner peripheral fixture 120, with 100 of them evenly spaced in the circumferential direction. This results in a multipole magnet 20, which serves as the magnet for heat treatment after magnetization. The multipole magnet 20 has 100 magnetic poles in the circumferential direction.

[0048] [Distribution of rare earth materials]

[0049] In the first process, it was confirmed that the distribution of rare earth materials in the hot-worked magnet containing multiple rare earth-containing magnetic powders changed. In Example 1, the amount of rare earth materials interspersed among the multiple magnetic powders was investigated for the hot-worked magnet before (before heating) and after (after heating). First, the hot-worked magnet before (before heating) was divided in half along the axial direction. Elemental analysis was performed on the divided cross-section using an electron probe microanalysis (EPMA). Specifically, analysis was performed on the magnetic powder between magnetic powders on the inner circumference side (near the inner circumference) and between magnetic powders in the center (the portion located at equidistant from the inner and outer circumferences of the divided hot-worked magnet). Next, the hot-worked magnet after (after heating) was divided along the axial direction in the same manner as above. Elemental analysis was performed on the divided cross-section using an electron probe microanalysis (EPMA). Specifically, analyses were performed on the magnetic powder between particles on the inner circumference side (near the inner circumference) and between particles in the central part (located at equidistant from the inner and outer circumferences of the split, heat-processed magnet). Table 1 summarizes the detected elements and their amounts (wt%). It should be noted that the amounts of the elements are the average values ​​of measurements taken at ten locations between the magnetic powder particles.

[0050] [Table 1]

[0051]

[0052] It was confirmed on both the inner circumference and the center that the amount of Pr contained between the magnetic powders increased after the heating in the first process.

[0053] [Surface magnetic flux]

[0054] The surface magnetic flux (Flux (mT)) of the multipole magnets obtained in Example 1 and Example 2 was measured. Specifically, the evaluation was carried out using an extremely fine probe (manufactured by DMT Co., Ltd.) with a Hall element size of 50 μm and a magnet-element distance of 0.14 mm. Figure 5 This is a graph showing the measurement results of the surface magnetic flux of the multipole magnet obtained in Example 1. Furthermore, Figure 6 This is a graph showing the measurement results of the surface magnetic flux of the multipole magnets obtained in Example 2. It was confirmed that the multipole magnets obtained in Examples 1 and 2 have a narrow pitch and are strongly magnetized.

[0055] Explanation of reference numerals in the attached figures

[0056] 10: Heat-processed magnet; 110: Outer peripheral jig; 112: Insertion hole; 114: Permanent magnet; 120: Inner peripheral jig; 124: Permanent magnet; 20: Multipole magnet.

Claims

1. A method for manufacturing a multipole magnet, comprising: The first step involves changing the distribution of the rare earth materials in a hot-processed magnet containing multiple rare earth-containing magnetic powders; and The second step involves magnetizing the magnet that has undergone the heat treatment in the first step to obtain a multipole magnet with multiple magnetic poles.

2. The method for manufacturing a multipole magnet according to claim 1, In the first step, the amount of rare earth material contained between the plurality of magnetic powders is increased to change the distribution of the rare earth material in the hot-processed magnet.

3. The method for manufacturing a multipole magnet according to claim 1 or 2, In the first step, the hot-working magnet is heated at a specified temperature to change the distribution of the rare earth material in the hot-working magnet.

4. The method for manufacturing a multipole magnet according to claim 3, In the first step, the hot-working magnet is heated at a temperature above the Curie temperature of the magnetic powder, which is the specified temperature, to change the distribution of the rare earth material in the hot-working magnet.

5. The method for manufacturing a multipole magnet according to claim 4, In the first step, the distribution of the rare earth material in the hot-working magnet, which has a ring shape and whose easily magnetized axis is oriented radially, is changed. In the second step, the hot-processed magnet from the first step is multipole magnetized in the radial direction to obtain a multipole magnet having more than 20 magnetic poles in the circumferential direction as the plurality of magnetic poles.

6. The method for manufacturing a multipole magnet according to claim 5, In the first step, the distribution of the rare earth material in the hot-processed magnet with a radial thickness of less than 4 mm is changed.

7. The method for manufacturing a multipole magnet according to claim 2, In the first step, the distribution of the rare earth materials in the hot-working magnet is changed by increasing the amount of any one or more of the rare earth materials Pr, La, Ce, Nd, and PrNd that are present between the plurality of magnetic powders.

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