JP2024053164A - Bonded magnet manufacturing apparatus and method - Google Patents

Abstract

To provide a technique capable of making a strong magnetic field act to a bond magnet with a simple structure.SOLUTION: A manufacturing apparatus of a bond magnet comprises: a ring-shaped holding member; a plurality of permanent magnets which are arranged in a circumferential direction at an inner side in a radial direction of the holding member and are disposed annularly; and a housing part which is present at an inner side in a radial direction of the plurality of permanent magnets and forms a space filled with a material of the bond magnet. In the plurality of permanent magnets, a first permanent magnet, a second permanent magnet, a third permanent magnet and a fourth permanent magnet are arranged over a round adjacently to one another in the circumferential direction. A direction of magnetization of the first permanent magnet faces the inner side in the radial direction of the plurality of permanent magnets. Directions of magnetization of the second permanent magnet and the fourth permanent magnet face the first permanent magnet. A direction of magnetization of the third permanent magnet faces an outer side in a radial direction of the plurality of permanent magnets.SELECTED DRAWING: Figure 1

Description

The present invention relates to a manufacturing device and method for bonded magnets.

Conventionally, a technique for manufacturing bonded magnets is known in which materials such as magnet powder and binder resin are injection molded using a mold. When manufacturing anisotropic bonded magnets using this manufacturing method, a magnetic field is applied to the material in the mold by a field device. Patent Document 1 discloses a configuration in which a yoke that induces a radial magnetic field to the magnetic substrate and a permanent magnet are arranged in the circumferential direction on the outer peripheral surface side of a container that houses the magnetic substrate. Patent Document 2 discloses a configuration in which an oriented magnetic body made of a ferromagnetic material is arranged opposite the magnetic pole center of the bonded magnet, and a pair of permanent magnets are arranged symmetrically with the oriented magnetic body in between, arranged in the circumferential direction. Patent Document 2 states that if the oriented magnetic body is made of a permanent magnet, the effect of the oriented magnetic field is too strong and it is not possible to manufacture a magnet with the desired characteristics (Patent Document 2, paragraph 0018).

JP 2020-156203 A JP 2018-148041 A

In conventional technology, the magnetic field induced by the permanent magnet acts on the material of the bonded magnet via a yoke or oriented magnetic body, and the magnetic poles of the bonded magnet are formed at the positions where the magnetic field from the yoke or oriented magnetic body acts directly. Although the yoke and oriented magnetic body are materials with low magnetic permeability, in conventional technology the magnetic field induced by the permanent magnet acts on the bonded magnet via the yoke or oriented magnetic body. Therefore, it was difficult to apply a strong magnetic field to a bonded magnet. Bonded magnets are given magnetic anisotropy by the magnetic field applied during molding, but if the magnetic field is weak, the orientation of the magnetic powder becomes insufficient, and the magnetic properties may be lost or the desired magnetic properties may not be obtained.

The present invention was made in consideration of the above problems, and aims to provide a technology that can apply a strong magnetic field to a bonded magnet with a simple configuration.

To achieve the above object, the bond magnet manufacturing device includes a circular holding member, a plurality of permanent magnets arranged in a circular ring on the radial inside of the holding member, and a storage section that is located radially inside the plurality of permanent magnets and forms a space filled with material of the bond magnet, and the plurality of permanent magnets include a set formed by a first permanent magnet, a second permanent magnet adjacent to the first permanent magnet in the circumferential direction, a third permanent magnet adjacent to the second permanent magnet in the circumferential direction, and a fourth permanent magnet adjacent to the third permanent magnet in the circumferential direction, and the plurality of sets are arranged adjacent to each other in the circumferential direction over one revolution, the direction of magnetization of the first permanent magnet faces the radial inside of the plurality of permanent magnets, the directions of magnetization of the second permanent magnet and the fourth permanent magnet face the first permanent magnet, and the direction of magnetization of the third permanent magnet faces the radial outside of the plurality of permanent magnets.

In other words, in the bonded magnet manufacturing device, multiple permanent magnets are arranged radially outside the housing portion in which the bonded magnet material is filled to form a field device, and a first permanent magnet and a third permanent magnet are arranged at positions corresponding to the magnetic poles of the bonded magnet. Therefore, the magnetic field lines passing through the magnetic pole portions of the bonded magnet are magnetic field lines extending directly from the permanent magnet. Therefore, it is possible to form the magnetic poles of the bonded magnet with the magnetic field of the permanent magnet acting directly on the bonded magnet material.

FIG. 1A is a diagram showing a manufacturing apparatus for a bonded magnet, and FIG. 1B is a diagram showing an injection molding apparatus including the manufacturing apparatus for a bonded magnet. 4 is a flowchart of a method for manufacturing a bonded magnet. FIG. 2 is an enlarged view of a bonded magnet manufacturing device. FIG. 13 is a diagram showing the simulation results of magnetic field lines. 5A shows the magnetization directions of adjacent permanent magnets, FIG. 5B shows the reversal of the magnetization directions, FIG. 5C shows the inner product of unit vectors indicating the magnetization directions, and FIG. 5D shows the forces acting on the boundary surface. 6A and 6B are diagrams for explaining forces acting on a boundary surface. FIG. 7A is a diagram showing the relationship between the intrinsic coercive force of a permanent magnet and the magnetic flux density in a molding region, and FIG. 7B is a diagram showing modified examples of the configuration of the permanent magnet. 8A and 8B are diagrams showing modified examples of the configuration of the permanent magnet.

Here, the embodiments of the present invention will be described in the following order.
(1) Configuration of bonded magnet manufacturing equipment:
(2) Manufacturing method of bonded magnet:
(3-1) Characteristics of bonded magnets:
(3-2) Ease of installation of permanent magnets:
(3-2) Intrinsic coercivity of permanent magnet:
(4) Other embodiments:

(1) Configuration of bonded magnet manufacturing equipment:
Figure 1A shows a bonded magnet manufacturing apparatus 1 according to one embodiment of the invention, and Figure 1B is a cross-sectional view showing an injection molding apparatus 2 including the bonded magnet manufacturing apparatus. Figure 1B is a cross-sectional view of the injection molding apparatus cut at a position corresponding to the A-A cross section in Figure 1A.

The bonded magnet manufacturing apparatus 1 includes a holding member 10, a plurality of permanent magnets 20, and a storage section 30. The bonded magnet manufacturing apparatus 1 is a cylindrical device, and FIG. 1B shows the thickness t and diameter d of the bonded magnet manufacturing apparatus 1.

The holding member 10 is an annular member centered on the axis Ax. In FIG. 1A, the axis Ax is perpendicular to the drawing, and in FIG. 1B, the axis Ax extends in the left-right direction of the drawing. In this specification, the direction parallel to the axis Ax is called the axis Ax direction. Furthermore, the direction along the circumference of a circle centered on the axis Ax is called the circumferential direction, and the direction parallel to the radius of the circle is called the radial direction. In FIG. 1A, the circumferential direction Dc and the radial direction Dr are shown superimposed on a certain permanent magnet 20. Furthermore, here, the direction closer to the axis Ax in the radial direction Dr as viewed from a certain member is called the radial inner side, and the direction opposite the axis Ax is called the radial outer side.

When the bonded magnet manufacturing apparatus 1 is viewed in the direction of axis Ax as shown in FIG. 1A, the outer periphery of the holding member 10 is a circle centered on axis Ax, and the inner periphery of the holding member 10 is a polygon centered on axis Ax (a dodecagon in the example of FIG. 1A). The thickness of the holding member 10 along the direction of axis Ax is thickness t shown in FIG. 1B, and there is no change in shape along the direction of axis Ax. In this embodiment, the holding member 10 is made of a soft magnetic material.

A number of permanent magnets 20 are arranged radially inside the holding member 10. When the bonded magnet manufacturing apparatus 1 is viewed in the direction of the axis Ax, the number of permanent magnets 20 are an isosceles trapezoid. The thickness of each permanent magnet 20 in the direction of the axis Ax is thickness t shown in FIG. 1B, and there is no change in shape in the direction of the axis Ax. In this embodiment, the shapes of the number of permanent magnets 20 are identical to each other. Each permanent magnet 20 is arranged so that the larger base side of the isosceles trapezoid faces radially outward, and adjacent to each other on the sides corresponding to the legs of the isosceles trapezoid, and goes around the axis Ax.

That is, the larger base of the isosceles trapezoid of the permanent magnets 20 is the same length as one side of the polygon formed on the inner circumferential surface of the holding member 10, and multiple permanent magnets 20 are arranged in the circumferential direction with the larger base in contact with the inner circumferential surface of the holding member 10. As a result, the permanent magnets 20 are arranged in a circular ring shape, going around the axis Ax and adjacent to each other in the circumferential direction.

In this embodiment, the multiple permanent magnets 20 are sintered magnets. In this embodiment, each permanent magnet is obtained by cutting out a block of sintered magnet larger than each permanent magnet 20 by wire cutting. In this embodiment, the multiple permanent magnets 20 all have the same shape, but there are four different magnetization directions. Here, the multiple permanent magnets 20 are classified into four types based on the difference in magnetization direction, and are called the first permanent magnet 21 to the fourth permanent magnet 24.

The first permanent magnet 21 is adjacent to the second permanent magnet 22 and the fourth permanent magnet 24 in the circumferential direction. The direction of magnetization in the first permanent magnet 21 is perpendicular to the base of the isosceles trapezoid of the first permanent magnet 21, and is directed from the larger base to the smaller base of the isosceles trapezoid. In FIG. 1A, the direction of magnetization is indicated by overlapping dashed arrows on each of the multiple permanent magnets 20. When the first permanent magnet 21 is disposed radially inside the holding member 10, the direction of magnetization faces the radially inside of the multiple permanent magnets 20 (for example, the direction D ₁ indicated by the dashed arrow in FIG. 1A). That is, the direction of magnetization in the center of the circumferential direction of the first permanent magnet 21 is parallel to the radial direction passing through the axis Ax, which is the center of the ring, and faces the axis Ax side.

The second permanent magnet 22 is adjacent to the first permanent magnet 21 and the third permanent magnet 23 in the circumferential direction. The direction of magnetization in the second permanent magnet 22 is parallel to the base of the isosceles trapezoid of the second permanent magnet 22, and faces left when the larger base of the isosceles trapezoid is placed at the bottom and the smaller base is placed at the top. When the second permanent magnet 22 is placed radially inside the holding member 10, the direction of magnetization faces the adjacent first permanent magnet 21 (for example, the direction D ₂ shown by the dashed arrow in FIG. 1A). That is, the direction of magnetization in the second permanent magnet 22 is perpendicular to a radial line (for example, the line L ₁ shown in FIG. 1A) that divides the second permanent magnet 22 in half in the circumferential direction, and faces the direction of the adjacent first permanent magnet 21.

The third permanent magnet 23 is adjacent to the second permanent magnet 22 and the fourth permanent magnet 24 in the circumferential direction. The direction of magnetization in the third permanent magnet 23 is perpendicular to the base of the isosceles trapezoid of the third permanent magnet 23, and is directed from the smaller base to the larger base of the isosceles trapezoid. When the third permanent magnet 23 is disposed radially inside the holding member 10, the direction of magnetization faces the radially outer side of the multiple permanent magnets 20 (for example, the direction D ₃ indicated by the dashed arrow in FIG. 1A ). That is, the direction of magnetization in the center of the circumferential direction of the third permanent magnet 23 is parallel to the radial direction passing through the axis Ax, which is the center of the ring, and faces the opposite side of the axis Ax.

The fourth permanent magnet 24 is adjacent to the first permanent magnet 21 and the third permanent magnet 23 in the circumferential direction. The direction of magnetization in the fourth permanent magnet 24 is parallel to the base of the isosceles trapezoid of the fourth permanent magnet 24, and faces to the right when the larger base of the isosceles trapezoid is placed on the bottom and the smaller base is placed on the top. When the fourth permanent magnet 24 is placed radially inside the holding member 10, the direction of magnetization faces the opposite direction to the direction pointing to the adjacent third permanent magnet 23 (for example, the direction D ₄ shown by the dashed arrow in FIG. 1A). That is, the direction of magnetization in the fourth permanent magnet 24 is perpendicular to a radial line (for example, the line L ₂ shown in FIG. 1A ) that divides the fourth permanent magnet 24 in half in the circumferential direction, and faces the opposite direction to the direction pointing to the adjacent third permanent magnet 23. As the first permanent magnet 21 to the fourth permanent magnet 24 complete one revolution in the circumferential direction, the fourth permanent magnet 24 is also adjacent to the first permanent magnet 21. Therefore, it can be said that the direction of magnetization in the fourth permanent magnet 24 is oriented toward the first permanent magnet 21 adjacent to the fourth permanent magnet 24.

In this embodiment, the legs of the isosceles trapezoid of each of the multiple permanent magnets 20 are parallel to the radial direction. In this embodiment, the multiple permanent magnets 20 are arranged at equal intervals in the circumferential direction, and each permanent magnet 20 occupies a range of 30° in terms of the angle centered on the axis Ax. As a result, in this embodiment, a total of 12 multiple permanent magnets 20 are arranged in the circumferential direction. In the example shown in FIG. 1A, the first permanent magnet 21, the second permanent magnet 22, the third permanent magnet 23, and the fourth permanent magnet 24 are arranged in this order in the circumferential direction. In addition, if the first permanent magnet 21, the second permanent magnet 22, the third permanent magnet 23, and the fourth permanent magnet 24 are considered as one set, the multiple sets are adjacent to each other in the circumferential direction, and multiple sets are arranged around one circumference. In FIG. 1A, each set of the first permanent magnet 21 to the fourth permanent magnet 24 is indicated by a reference symbol.

In the above configuration, the total number of the first permanent magnets 21 and the third permanent magnets 23 is six. The configuration is such that the magnetization direction rotates by (6-2)×720° in one revolution of the multiple permanent magnets 20 including these permanent magnets. For example, when considering the rotation direction based on the first permanent magnet 21 with the magnetization direction D ₁ written in FIG. 1A, the magnetization direction D ₂ of the second permanent magnet 22 adjacent in the counterclockwise direction is a direction rotated 240° clockwise from the magnetization direction D ₁ of the first permanent magnet 21. Similarly, the magnetization direction D ₃ of the third permanent magnet 23 adjacent in the counterclockwise direction to the second permanent magnet 22 is a direction rotated 240° clockwise from the magnetization direction D ₂ of the second permanent magnet 22.

Thus, in this embodiment, when the positions of the permanent magnets 20 are shifted to the next position in the counterclockwise direction, the magnetization direction rotates 240° clockwise. In this embodiment, since there are 12 permanent magnets 20, they rotate 12 x 240° in one revolution. When the number of permanent magnets 20 changes, the angle that each permanent magnet occupies in the circumferential direction (30° in FIG. 1A) changes, and the rotation angle of the magnetization direction also changes. In these various cases, if the total number of first permanent magnets and third permanent magnets is P, the magnetization direction is determined so that the magnetization direction rotates (P-2) x 720° in one revolution of the permanent magnets, as shown in FIG. 1A, and multiple permanent magnets 20 can be configured to be evenly arranged in the circumferential direction.

A storage section 30 is located radially inside the permanent magnets 20, forming a space in which the bond magnet material is filled. In this embodiment, the storage section 30 includes a partition member 31 and a cylindrical section 32. The partition member 31 is a thin member located radially inside the permanent magnets 20. The outer periphery of the partition member 31 is polygonal, and the smaller base of the isosceles trapezoid of the permanent magnets 20 is the same length as one side of the polygon. With this configuration, the outer periphery of the partition member 31 is in contact with the inner periphery of the permanent magnets 20. The inner periphery of the partition member 31 is circular, and a cylindrical space is formed radially inside the partition member 31. The partition member 31 is made of, for example, a non-magnetic material, a soft magnetic material, etc.

The cylindrical portion 32 is disposed radially inside the partition member 31 and has a cylindrical shape centered on the axis Ax. The cylindrical portion 32 is made of, for example, a non-magnetic material, a soft magnetic material, etc. The outer diameter of the cylindrical portion 32 is smaller than the inner diameter of the partition member 31, and a space is formed between the outer peripheral surface of the cylindrical portion 32 and the inner peripheral surface of the partition member 31 to fill with the material of the bond magnet. The bond magnet is molded by the injection molding device 2 and is magnetized by a plurality of permanent magnets 20 during injection molding. For this reason, the material of the bond magnet may be injection moldable and magnetizable during injection molding. Examples of the material of the bond magnet include a material containing magnet powder and a binder resin. Of course, additives such as a reinforcing agent, a plasticizer, and a lubricant may be included. The magnet powder may be selected according to the specifications of the bond magnet, and examples of the magnet powder include rare earth magnet powder and ferrite magnet powder. The binder resin may also be selected according to the specifications of the bonded magnet, and examples include polyamide resin and polyphenylene sulfide resin.

The injection molding device 2 is a device for performing injection molding using the bonded magnet manufacturing device 1. The injection molding device 2 is equipped with a first mold 41 and a second mold 42 that accommodate the bonded magnet manufacturing device 1. The first mold 41 is a mold in which a cavity is formed for accommodating the bonded magnet manufacturing device 1, and a cavity having an inner peripheral surface that contacts the outer peripheral surface of the holding member 10 is formed. The bonded magnet manufacturing device 1 is accommodated in the cavity. However, in this embodiment, the cylindrical portion 32 is also a part of the first mold 41. That is, the first mold 41 has a cavity that accommodates the bonded magnet manufacturing device 1, but the center of the cavity protrudes in a cylindrical shape. And, when the bonded magnet manufacturing device 1 is accommodated in the first mold 41, the cylindrical protrusion is located radially inside the partition member 31, and is designed to become the cylindrical portion 32. The first mold 41 is made of a non-magnetic material or the like. The cylindrical portion 32 may be a separate member from the first mold 41 or may be an integral member.

The second mold 42 is combined with the first mold 41 when the bonded magnet manufacturing device 1 is housed in the first mold 41, and is a member that covers the bonded magnet manufacturing device 1 so that it is not exposed to the outside. The second mold 42 is formed with a supply path 221 that connects to the cavity between the partition member 31 and the cylindrical portion 32. The supply path 221 is formed at a position that includes the axis Ax. The supply path 221 is a through hole that has a circular cross section perpendicular to the axis Ax, and has a portion with a constant cross-sectional radius and a portion with a gradually changing radius. In the portion with the gradually changing cross-sectional radius, the radius gradually increases with increasing distance from the first mold 41 side. The second mold 42 is made of a non-magnetic material, etc.

A cylinder 50 is connected to the second mold 42 at a position corresponding to the opening of the supply path 221. The cylinder 50 is a roughly cylindrical member, and the diameter gradually decreases at the tip portion connected to the second mold 42. A rod 51 is provided within the cylinder 50 so that it can move back and forth in the direction of the axis Ax and rotate. The outer diameter of the rod 51 is smaller than the inner diameter of the cylinder 50, and a space exists between the rod 51 and the cylinder 50 into which the bond magnet material M is filled.

The rod 51 can rotate and move, and can move the molten material present in the space between the rod 51 and the cylinder 50 to the supply path 221. In the injection molding device 2 shown in FIG. 1B, some of the known configurations are omitted or simplified, such as the accumulation section for accumulating the material, the supply path for the material from the accumulation section to the cylinder 50, the material passage for injection, the mechanism for separating the first mold 41 and the second mold 42 after injection molding, and the ejection pin for removing the bonded magnet after injection molding from the storage section 30. The above-mentioned configuration of the injection molding device 2 is one example, and various known configurations may be adopted for the parts of the injection molding device 2 other than the bonded magnet manufacturing device 1.

(2) Manufacturing method of bonded magnet:
Next, a method for manufacturing a bonded magnet using an injection molding apparatus 2 equipped with the bonded magnet manufacturing apparatus 1 will be described. Figure 2 is a flow chart showing the method for manufacturing a bonded magnet. When manufacturing a bonded magnet, first, the user prepares the material for the bonded magnet and stores the material in a storage unit equipped in the injection molding apparatus 2.

With the material stored, the user executes the filling process (step S100). In the filling process, the user operates a heater (not shown) to heat the first mold 41 and the second mold 42. Various conditions can be set for the temperature when heating. For example, the temperature is adjusted so that the bond magnet material M is about 300°C, and the first mold 41 and the second mold 42 are about 130°C. The heating time, etc. are adjusted appropriately depending on the bond magnet material, etc. At these temperatures, it is assumed that the multiple permanent magnets 20 in the bond magnet manufacturing device 1 will be about 140°C to 170°C. Of course, the temperature conditions, etc. are just examples, and other temperatures, etc. may be used.

In either case, when the bonded magnet material M reaches the target temperature, the user operates the rod of the injection molding device 2 to move the molten material M present inside the cylinder 50 from inside the cylinder 50 toward the supply path 221. As a result, the material M is supplied to the storage section 30 of the bonded magnet manufacturing device 1 via the supply path 221. In other words, the molten material M fills the space between the inner surface of the partition member 31 and the outer surface of the cylindrical section 32.

Next, the user executes the forming process (step S110). That is, the user adjusts the temperature of the bond magnet material M, the first mold 41, and the second mold 42 so that they are at a preset temperature. The user also holds the bond magnet material M at the preset temperature for a preset time, hardening the bond magnet material M. The temperature and time may be various values, may change during the forming process, or may change the temperature to create a predetermined temperature gradient.

When the material M has hardened through the forming process, the user executes the removal process (step S120). That is, the user operates a mechanism (not shown) to separate the first mold 41 and the second mold 42. Furthermore, the user operates an ejection pin (not shown) to remove the bonded magnet from the bonded magnet manufacturing device 1. With the above configuration, a bonded magnet magnetized by a plurality of permanent magnets 20 can be manufactured.

(3-1) Characteristics of bonded magnets:
When injection molding of a bonded magnet is performed using the injection molding device 2 as described above, the material of the bonded magnet hardens in the magnetic field induced in the housing section 30 by the multiple permanent magnets 20. As a result, the magnetization easy axis of the magnetic powder is aligned along the magnetic field lines, resulting in an anisotropic magnet. In other words, the magnetization easy axis is oriented so that the position corresponding to the first permanent magnet 21 is the S pole and the position corresponding to the third permanent magnet 23 is the N pole. Figure 3 is an enlarged view of a portion of Figure 1A, and shows a schematic diagram of the magnetic poles induced by the multiple permanent magnets 20.

In FIG. 3, the magnetic field lines of the magnetic field induced by the first permanent magnet 21 to the fourth permanent magnet 24 are shown as dashed lines. The dashed lines showing the magnetic field are intended to qualitatively explain the induced magnetic field and do not necessarily exactly match the magnetic field actually induced. In this embodiment, the magnetic flux density of the magnetic field induced by the first permanent magnet 21 to the fourth permanent magnet 24 is large on the radial inside of the multiple permanent magnets 20 (e.g., part Zb shown in FIG. 3). On the other hand, the magnetic flux density of the magnetic field formed inside the holding member 10 located radially outside the multiple permanent magnets 20 (e.g., part Zp shown in FIG. 3) is smaller than that of the radially inner part.

The main reason why there is a difference in the magnetic flux density of the magnetic field induced by the multiple permanent magnets 20 between the radial inside and the radial outside of the multiple permanent magnets 20 is that the magnetization directions of the first permanent magnets 21 to the fourth permanent magnets 24 have been designed. Specifically, the magnetization direction of the first permanent magnet 21 faces radially inward, and the magnetization direction of the third permanent magnet 23 faces radially outward. Therefore, the magnetic field lines formed radially inward of the first permanent magnet 21 make a circuit, passing through the inside of the second permanent magnet 22, the inside of the first permanent magnet 21, the outside of the first permanent magnet, the molding region B of the bond magnet, the inside of the third permanent magnet 23, and the inside of the second permanent magnet 22, as shown by the dashed line Ld in FIG. 3, for example.

In the magnetic field lines shown by the dashed line Ld, the magnetic field lines point in the direction Ab on the radial inside of the second permanent magnet 22, but the direction of magnetization Am of the second permanent magnet 22 is opposite to the direction Ab of the magnetic field lines. Therefore, the second permanent magnet 22 blocks the magnetic field lines in the molding region B of the bond magnet from entering the interior of the second permanent magnet 22, and contributes to increasing the magnetic flux density in the space radially inside the multiple permanent magnets 20. In other words, according to this embodiment, the magnetic flux density of the magnetic field induced radially inside the multiple permanent magnets 20 can be increased compared to when the second permanent magnet 22 is not present.

In addition, since the direction of magnetization of the third permanent magnet 23 faces radially outward from the multiple permanent magnets 20, a magnetic field can be induced radially outward from the third permanent magnet 23 outside the third permanent magnet 23, i.e., inside the holding member 10. In order for the magnetic field induced inside the holding member 10 to loop without becoming small, it is preferable that the holding member 10 be a soft magnetic material with low magnetic permeability. Furthermore, even if a magnetic field is induced outside the third permanent magnet 23, the direction of the induced magnetic field is similar to the direction of magnetization of the second permanent magnet 22, so that the magnetic field lines can pass through the inside of the second permanent magnet 22.

Figure 4 shows the results of a simulation showing the magnetic field lines of the magnetic field formed by multiple permanent magnets 20. The simulation was performed using JMAG-Designer, an electromagnetic analysis software. In the simulation, the first permanent magnet 21 and the third permanent magnet 23 are assumed to be permanent magnets with a residual magnetic flux density Br of 13.9 kG and an intrinsic coercivity Hcj of 18 kOe. The second permanent magnet 22 and the fourth permanent magnet 24 are assumed to be permanent magnets with a residual magnetic flux density Br of 11.3 kG and an intrinsic coercivity Hcj of 35 kOe. The material parameters of the holding member 10 are assumed to be S10C, and the molding region B of the bonded magnet is assumed to be hollow. In Figure 4, the magnetic flux density of the magnetic field formed in the molding region B of the bonded magnet is colored, and parts of the same magnetic flux density are shown in the same color. According to the simulation, the magnetic flux density is generally greater the further radially outward from the molded region B of the bonded magnet, and is generally smaller the further radially inward.

According to the magnetic field lines shown in FIG. 4, many magnetic field lines are present outside the second permanent magnet 22 on the radial inner side of the second permanent magnet 22, but inside the second permanent magnet 22 (for example, the part surrounded by a white line in FIG. 4), there are almost no magnetic field lines extending from the first permanent magnet 21 to reach the third permanent magnet 23. Therefore, it can be confirmed that the second permanent magnet 22 blocks the magnetic field lines in the molding region B of the bond magnet from entering the inside of the second permanent magnet 22, and as a result, prevents the magnetic flux density of the magnetic field from decreasing in the space radially inside the multiple permanent magnets 20. In FIG. 3 and FIG. 4, the explanation is mainly given using the second permanent magnet 22, but in the fourth permanent magnet 24, the same principle as the second permanent magnet 22 is used to prevent the magnetic field from entering the inside of the fourth permanent magnet 24 on the radial inner side of the fourth permanent magnet 24. As a result, the magnetic flux density of the magnetic field induced outside the fourth permanent magnet 24 can be increased radially inward of the fourth permanent magnet 24 compared to when the fourth permanent magnet 24 is not present.

As described above, in this embodiment, the magnetic flux density is higher on the radial inside of the multiple permanent magnets 20 than on the radial outside due to the presence of the second permanent magnet 22 and the fourth permanent magnet 24, compared to when they are not present (when the first permanent magnet 21 and the third permanent magnet 23 are adjacent to each other). As a result, it is possible to easily improve the magnetic performance of the bonded magnet molded by the injection molding device 2. For example, if the residual magnetic flux density in a state in which the magnetization easy axis is aligned with the tangent direction of the magnetic field lines is 100%, the residual magnetic flux density in the manufactured bonded magnet will be 100% or less, and the closer it is to 100%, the higher the magnetic performance of the bonded magnet will be. Here, the ratio at which the magnetization easy axis is aligned with the tangent direction of the magnetic field lines is the orientation rate. The higher the magnetic flux density of the magnetic field induced in the molding region B of the bonded magnet, the higher the orientation rate becomes, so according to this embodiment, it is possible to easily improve the orientation rate of the bonded magnet.

Furthermore, in this embodiment, the first permanent magnet 21 and the third permanent magnet 23 face the molding area B of the bonded magnet, and the magnetic poles of the N and S poles are formed directly below these permanent magnets. Therefore, compared to the above-mentioned conventional technology in which an oriented magnetic body other than a yoke or a permanent magnet faces the molding area B of the bonded magnet, the magnetic field of the permanent magnet can be directly applied to the magnetic pole portion. In this embodiment, a partition member 31 exists between the first permanent magnet 21 and the third permanent magnet 23 and the molding area B of the bonded magnet, but since the partition member 31 is very thin, it can be considered that the magnetic field of the first permanent magnet 21 and the third permanent magnet 23 directly acts on the magnetic pole portion. With this configuration, it is possible to directly apply the magnetic field of the first permanent magnet 21 and the third permanent magnet 23 to the molding area B of the bonded magnet, and it is possible to easily improve the magnetic performance of the bonded magnet.

Furthermore, in a bonded magnet, it is preferable that the surface magnetic flux density of the outer peripheral surface of the bonded magnet changes in the circumferential direction in a manner similar to a sine wave. For example, it is known that when a bonded magnet is used in a motor, the closer the change in surface magnetic flux density in the circumferential direction is to a sine wave, the smaller the cogging torque. The inventor of this embodiment measured the surface magnetic flux density in each of the cases where the second permanent magnet 22 and the fourth permanent magnet 24 were used as the multiple permanent magnets 20, and where the first permanent magnet 21 and the third permanent magnet 23 were adjacent to each other without using the second permanent magnet 22 and the fourth permanent magnet 24. As a result, it was confirmed that when the second permanent magnet 22 and the fourth permanent magnet 24 were used, the change in the surface magnetic flux density in the circumferential direction was closer to a sine wave than when the second permanent magnet 22 and the fourth permanent magnet 24 were not used. Therefore, according to this embodiment, it is possible to manufacture a bonded magnet that has a smaller cogging torque than when the second permanent magnet 22 and the fourth permanent magnet 24 are not used.

(3-2) Ease of installation of permanent magnets:
When permanent magnets are placed adjacent to each other, depending on the direction of magnetization of the permanent magnets, a repulsive force may be generated between the permanent magnets, an attractive force may be generated, or a neutral state may occur in which neither repulsive nor attractive forces are generated. In the bonded magnet manufacturing apparatus 1 according to this embodiment, the multiple permanent magnets 20 are arranged around one circumferential turn while being adjacent to each other. Therefore, unless the magnetization direction is adjusted so that no repulsive force is generated between the permanent magnets, it becomes difficult to configure the bonded magnet manufacturing apparatus 1 by placing the multiple permanent magnets 20 adjacent to each other.

Therefore, in this embodiment, the magnetization direction is determined so that no repulsive force is generated between adjacent permanent magnets. First, a method for determining whether or not a repulsive force is generated at the boundary when planes of bulk permanent magnets with one magnetization direction are placed adjacent to each other will be described. Fig. 5A shows a schematic diagram of the boundary Lb when permanent magnets _M1 and _M2 are placed adjacent to each other. The dashed vectors _V1 and _V2 shown on the left and right of the boundary in Fig. 5A are unit vectors indicating the magnetization directions of the permanent magnets _M1 and _M2 .

In order to determine the force acting on the boundary of the permanent magnets _M1 and _M2 magnetized as shown in Fig. 5A, the unit vector indicating the magnetization direction of one of the adjacent permanent magnets _M1 and _M2 is inverted around the boundary between the adjacent permanent magnets. Fig. 5B shows an example of the case where the unit vector is inverted in the example shown in Fig. 5A. That is, when the unit vector _V1 indicating the magnetization direction of the permanent magnet _M1 is inverted around the boundary Lb, it becomes the unit vector _V3 shown in Fig. 5B.

In addition, when the unit vector of one of the adjacent permanent magnets is reversed, if the inner product of the reversed vector and the unit vector of the other adjacent permanent magnet is 0 or less, no repulsive force is generated between the adjacent permanent magnets. FIG. 5C is a diagram showing the unit vector _V3 shown in FIG. 5B and the unit vector _V2 of the permanent magnet _M2 with the same starting point. In the example shown in FIG. 5C, the smaller angle α of the unit vectors _V2 and _V3 with the same starting point is an obtuse angle, so the inner product of both unit vectors _V2 and _V3 is 0 or less. Therefore, in the example shown in FIG. 5A, no repulsive force acts on the boundary between the permanent magnets _M1 and _M2 . Therefore, when the relationship between the magnetization direction of the adjacent permanent magnets and the orientation of the boundary is as shown in FIG. 5A, no repulsive force acts on the permanent magnets _M1 and _M2 , and they can be easily combined.

Fig. 5D is an explanatory diagram for explaining the relationship between the intersection angle of unit vectors and the force acting between adjacent permanent magnets. In Fig. 5D, examples of unit vectors after inversion are shown by dashed arrows as unit vectors _V31 , _V32 , and _V33 , and an example of a unit vector of a permanent magnet after inversion is shown as unit vector _V21 . These unit vectors are written so that their starting points coincide. When the unit vector after inversion is orthogonal to the unit vector after inversion _V21 , for example, in the case of unit vectors _V31 and _V33 , the inner product is 0, and no repulsive or attractive force acts between the permanent magnets, resulting in neutrality.

On the other hand, when the smaller angle of the angles formed when the starting points of the inverted unit vector _V21 and the inverted unit vector are aligned is an acute angle (0° or more and less than 90°), the inner product is greater than 0, and a repulsive force acts between the permanent magnets. Furthermore, when the smaller angle of the angles formed when the starting points of the inverted unit vector _V21 and the inverted unit vector are aligned is an obtuse angle (90° or more and 180° or less), the inner product is greater than 0, and an attractive force acts between the permanent magnets. In order to easily assemble multiple permanent magnets 20 adjacent to each other when manufacturing the bonded magnet manufacturing device 1 and to prevent them from separating after manufacturing, it is sufficient to determine the magnetization direction of each permanent magnet so that no repulsive force acts at the boundaries between the multiple permanent magnets 20.

In this embodiment, the first permanent magnet 21 to the fourth permanent magnet 24 constituting the multiple permanent magnets 20 all have the same shape, and there are a total of 12 of them. Therefore, as shown in Fig. 6A, each permanent magnet occupies an area of 30° in the circumferential direction. Note that Fig. 6A is an enlarged view of the first permanent magnet 21, the second permanent magnet 22, and the cylindrical portion 32 extracted from Fig. 1A. In this embodiment, the magnetization direction of each of the first permanent magnet 21 and the third permanent magnet 23 is parallel to the radial direction, and in the example shown in Fig. 6A, the straight line _L2 parallel to the radial direction and the magnetization direction _D1 of the first permanent magnet 21 are parallel to each other.

The magnetization direction of each of the second permanent magnet 22 and the fourth permanent magnet 24 is perpendicular to a radial line that bisects each of the second permanent magnet 22 and the fourth permanent magnet 24 in the circumferential direction. In the example shown in Fig. 6A, the magnetization direction _D2 of the second permanent magnet 22 is perpendicular to the radial line _L1 that bisects the second permanent magnet 22 in the circumferential direction. In this configuration, for example, when the magnetization direction of the second permanent magnet 22 or the fourth permanent magnet 24 is reversed toward the first permanent magnet 21 or the third permanent magnet 23, the unit vectors before and after the reversal are orthogonal to each other.

For example, in the example shown in Fig. 6A, if the magnetization direction _D2 of the second permanent magnet ₂₂ is reversed about the boundary L3 between the first permanent magnet 21 and the second permanent magnet 22, the direction becomes direction Di. Therefore, no force acts on the boundary between the first permanent magnet 21 and the second permanent magnet 22, and the boundary is neutral. The relationship between the magnetization directions of the first permanent magnet 21 to the fourth permanent magnet 24 according to this embodiment is all the same, and no force acts on the boundary between the first permanent magnet 21 to the fourth permanent magnet 24, and the boundary is neutral. Therefore, when manufacturing the bonded magnet manufacturing device 1, it is easy to assemble multiple permanent magnets 20 adjacent to each other, and it is possible to prevent them from being separated after manufacturing.

The magnetization direction of the first permanent magnet 21 to the fourth permanent magnet 24 may be adjusted more freely. For example, when at least one of the first permanent magnet 21 to the fourth permanent magnet 24 is made to have a different shape from the other permanent magnets, the magnetization direction can be configured to face a different direction from that of this embodiment. FIG. 6B is a diagram showing a configuration in which the size of the first permanent magnet 21 to the fourth permanent magnet 24 is changed from the configuration shown in FIG. 1A. In the configuration shown in FIG. 6B, the circumferential size of the second permanent magnet 22 and the fourth permanent magnet 24 shown in FIG. 1A is increased to form the second permanent magnet 220 and the fourth permanent magnet 240. In addition, the circumferential size of the first permanent magnet 21 and the third permanent magnet 23 shown in FIG. 1A is reduced to form the first permanent magnet 210 and the third permanent magnet 230. In FIG. 6B, a part of the first permanent magnet 210 to the fourth permanent magnet 240 constituting the multiple permanent magnets 20 and the cylindrical portion 32 are extracted and shown. In the configuration shown in FIG. 6B, the first permanent magnet 210 to the fourth permanent magnet 240 are arranged in the circumferential direction, and the configuration of the holding member 10 and other components not shown is the same as in FIG. 1A.

In the example shown in Fig. 6B, the magnetization direction of each of the second permanent magnet 220 and the fourth permanent magnet 240 is perpendicular to a radial line that bisects each of the second permanent magnet 220 and the fourth permanent magnet 240 in the circumferential direction. For example, in Fig. 6B, the magnetization direction _D2 of the second permanent magnet 220 is perpendicular to the radial line _L1 that bisects the second permanent magnet 220 in the circumferential direction. In Fig. 6B, the direction of the magnetization direction _D2 of the second permanent magnet 220 when reversed with respect to the boundary _L3 is shown as direction _Di1 . Also, the direction of the magnetization direction _D2 of the second permanent magnet 220 when reversed with respect to the boundary _L4 is shown as direction _Di2 .

Among the angles formed by matching the start points of the unit vectors indicating the magnetization direction _D1 and the reversed direction _Di1 , the smaller angle is greater than 90°, and among the angles formed by matching the start points of the unit vectors indicating the magnetization direction _D3 and the reversed direction _Di2 , the smaller angle is greater than 90°. Therefore, the inner product of both unit vectors is less than 0, and an attractive force acts on the boundary. Therefore, even in the example shown in FIG. 6B, the first permanent magnet 210 to the fourth permanent magnet 240 can be easily assembled.

Furthermore, in the configuration shown in FIG. 6B, the crossing angle between the magnetization direction D ₁ and the direction after reversal Di ₁ and the crossing angle between the magnetization direction D ₃ and the direction after reversal Di ₂ are not right angles but are greater than 90°. Therefore, there is a degree of freedom in the direction of magnetization. In FIG. 6B, the line segments perpendicular to the magnetization directions D ₁ and D ₃ are shown by dashed lines Lp ₁ and Lp _2. The dashed lines Lp ₁ and Lp ₂ do not coincide with the directions after reversal Di ₁ and Di ₂ , and a gap Gp is generated. Therefore, even if the magnetization direction D ₂ is rotated at least by the angle of the gap Gp, the force acting between the second permanent magnet 220 and the first permanent magnet 210 or the third permanent magnet 230 can be made neutral or attractive. As described above, by giving the multiple permanent magnets 20 different shapes, a degree of freedom is given to the magnetization direction, and by adjusting the magnetization direction within the range of this degree of freedom, it is possible to prevent the force acting on the boundaries of the permanent magnets from becoming a repulsive force. Therefore, the shapes and magnetization directions of the multiple permanent magnets 20 may be adjusted within this range.

(3-2) Intrinsic coercivity of permanent magnet:
The specifications of the multiple permanent magnets 20, such as the residual magnetic flux density Br and the intrinsic coercivity Hcj, are not limited and may be selected from various combinations, and the specifications may be determined for various purposes. For example, the specifications of the permanent magnets may be selected for the purpose of suppressing the effects of demagnetization of the permanent magnets and maintaining the magnetic properties of the bonded magnets manufactured by the bonded magnet manufacturing apparatus 1 over the long term.

More specifically, the specifications of the permanent magnets may be selected so that the intrinsic coercivity of the second permanent magnet 22 and the fourth permanent magnet 24 is equal to or greater than the intrinsic coercivity of the first permanent magnet 21 and the third permanent magnet 23. In the example shown in FIG. 3, the direction of the magnetic field in part Zb, which is located radially inside the second permanent magnet 22 within the molding region B of the bonded magnet, is mainly oriented in the same direction as direction Ab, and is almost opposite to the magnetization direction Am of the second permanent magnet 22.

Therefore, the second permanent magnet 22 is easily demagnetized by the magnetic field in portion Zb. The same situation applies to the fourth permanent magnet 24. On the other hand, around the first permanent magnet 21 and the third permanent magnet 23, particularly in the molding region B of the bond magnet, there is no magnetic field in the direction opposite to the magnetization direction of the first permanent magnet 21 and the third permanent magnet 23. Therefore, the first permanent magnet 21 and the third permanent magnet 23 are less likely to be demagnetized than the second permanent magnet 22 and the fourth permanent magnet 24.

When the second permanent magnet 22 and the fourth permanent magnet 24 are demagnetized, the magnetic field lines easily enter the inside of the permanent magnet 20 on the radial inside of the second permanent magnet 22 and the fourth permanent magnet 24. When the magnetic field lines enter the inside of the second permanent magnet 22 and the fourth permanent magnet 24, the magnetic flux density in the molding region B of the bonded magnet decreases compared to when they do not enter. Therefore, it is possible to adopt a configuration in which the specifications of the permanent magnet 20 are selected so that the intrinsic coercive force of the second permanent magnet 22 and the fourth permanent magnet 24 is equal to or greater than the intrinsic coercive force of the first permanent magnet 21 and the third permanent magnet 23. With this configuration, the second permanent magnet 22 and the fourth permanent magnet 24 can be made less susceptible to the effects of demagnetization. In other words, when the specifications of the permanent magnet 20 are selected so that the intrinsic coercive force of the second permanent magnet 22 and the fourth permanent magnet 24 is large, the magnetic flux density in the molding region B of the bonded magnet is larger compared to when not selected. In addition, the high magnetic flux density in the molding region B of the bonded magnet can be maintained for a long period of time.

Figure 7A shows the change in magnetic flux density of the magnetic field induced in the molding region B of the bonded magnet when the residual magnetic flux density Br of the permanent magnet is fixed and the intrinsic coercivity Hcj is changed. The magnetic flux density was performed using the same software as the simulation shown in Figure 4. In addition, in the simulation, the residual magnetic flux density Br of the multiple permanent magnets 20 was fixed to 12 kG. S10C is assumed as the holding member 10, and the molding region B of the bonded magnet is assumed to be hollow. The simulation results when the intrinsic coercivity of the first permanent magnet 21 and the third permanent magnet 23 is fixed and the intrinsic coercivity of the second permanent magnet 22 and the fourth permanent magnet 24 is adjusted are plotted with square markers. The simulation results when the intrinsic coercivity of the first permanent magnet 21 and the third permanent magnet 23 is adjusted and the intrinsic coercivity of the second permanent magnet 22 and the fourth permanent magnet 24 is fixed are plotted with circular markers. In addition, in FIG. 7A, the black markers indicate the maximum value of the magnetic flux density in the forming region B, and the white markers indicate the minimum value of the magnetic flux density in the forming region B.

The intrinsic coercivity of the permanent magnets to be adjusted was varied in the range of 12.5 kOe to 35.0 kOe, as shown by the values plotted in Figure 7A. The intrinsic coercivity of the permanent magnets not to be adjusted was fixed at 35.0 kOe. When the intrinsic coercivity of the second permanent magnet 22 and the fourth permanent magnet 24 was adjusted, the magnetic flux density in the molding region B increased with increasing intrinsic coercivity, as shown by the square markers in Figure 7A. That is, in the second permanent magnet 22 and the fourth permanent magnet 24, which are positioned in positions that are easily demagnetized, the magnetic flux density in the molding region B increases as the intrinsic coercivity is increased.

On the other hand, when the intrinsic coercivity of the first permanent magnet 21 and the third permanent magnet 23 is adjusted, as shown by the circular markers in FIG. 7A, changing the intrinsic coercivity does not significantly change the magnetic flux density in the molding region B. In other words, because the first permanent magnet 21 and the third permanent magnet 23 are positioned in a way that makes them difficult to demagnetize, changing the intrinsic coercivity does not significantly change the magnetic flux density in the molding region B.

From the above, the intrinsic coercivity of the first permanent magnet 21 and the third permanent magnet 23 does not need to be excessively large, but it is preferable that the intrinsic coercivity of the second permanent magnet 22 and the fourth permanent magnet 24 is as large as possible. Therefore, if the specifications of the permanent magnets are set so that the intrinsic coercivity of the second permanent magnet 22 and the fourth permanent magnet 24 is equal to or greater than the intrinsic coercivity of the first permanent magnet 21 and the third permanent magnet 23, it is possible to suppress the effects of demagnetization. Furthermore, with this configuration, it is possible to increase the magnetic flux density of the molding region B of the bond magnet compared to when the intrinsic coercivity of the second permanent magnet 22 and the fourth permanent magnet 24 is smaller than the intrinsic coercivity of the first permanent magnet 21 and the third permanent magnet 23.

Furthermore, there is often a trade-off between the intrinsic coercivity Hcj and the residual magnetic flux density Br. Therefore, if a permanent magnet with a large intrinsic coercivity Hcj is selected, the residual magnetic flux density Br will be small. Since the first permanent magnet 21 and the third permanent magnet 23 are located in positions corresponding to the magnetic poles of the bonded magnet, it is preferable that the first permanent magnet 21 and the third permanent magnet 23 have a large residual magnetic flux density Br rather than a large intrinsic coercivity. In this embodiment, the intrinsic coercivity of the first permanent magnet 21 and the third permanent magnet 23 does not need to be excessively large, making it easier to select magnets with a large residual magnetic flux density Br.

(4) Other embodiments:
The above embodiment is an example for implementing the present invention, and various other embodiments can be adopted. For example, in the embodiment shown in FIG. 1A, the boundaries between the multiple permanent magnets 20 are parallel to the radial direction, but in at least some of the permanent magnets, the orientation of the boundaries does not have to be parallel to the radial direction. FIG. 7B shows a configuration in which the boundaries are parallel to each other. That is, in the example shown in FIG. 7B, the first permanent magnet 211 and the third permanent magnet 231 are rectangular in shape when viewed from a direction parallel to the axis Ax. Of course, the present invention is not limited to such an example, and may be configured such that the width of the permanent magnet 20 narrows toward the radial outside.

Furthermore, the multiple permanent magnets 20 may have curved surfaces. Figure 8A shows an example of a bonded magnet manufacturing device configured with the first permanent magnets 212 to 242, the inner and outer circumferential surfaces of which are curved, of the first permanent magnets 21 to 24 shown in Figure 1A. In other words, the inner and outer circumferential surfaces formed by the first permanent magnets 212 to 242 being adjacent to each other in the circumferential direction are circular when viewed from a direction parallel to the axis Ax. Of course, one of the inner and outer circumferential surfaces may be curved and the other may be flat.

Furthermore, the multiple permanent magnets 20 only need to be adjacent to each other, and may not be adjacent to each other. FIG. 8B is a diagram showing an example in which the first permanent magnet 213 to the fourth permanent magnet 243 are made up of permanent magnets that have a rectangular shape when viewed from a direction parallel to the axis Ax. In the configuration shown in FIG. 8B, members 213a to 243a made of soft magnetic material or non-magnetic material are present between the first permanent magnet 213 to the fourth permanent magnet 243. Members 213a to 243a are in the shape of a triangular prism, and have a triangular shape when viewed from a direction parallel to the axis Ax. In this way, it is possible to manufacture a bonded magnet within the storage section 30 even if the boundaries between the multiple permanent magnets 20 are not in contact with each other.

In a configuration in which the boundaries between permanent magnets 20 are not in contact as in FIG. 8B, the force acting on the boundary can be either attractive or neutral depending on the direction of magnetization formed in the member adjacent to permanent magnet 20 and the relationship with the boundary surface. For example, when first permanent magnet 213 to fourth permanent magnet 243 are adjacent to members 213a to 243a, a unit vector indicating the direction of magnetization induced in members 213a to 243a is identified, and this unit vector is reversed around the boundary as its axis. The magnetization direction of the permanent magnets can then be adjusted so that the dot product of the unit vector after the reversal and the unit vector indicating the magnetization direction of the permanent magnet after the reversal is 0 or less.

The annular holding member only needs to be able to hold multiple permanent magnets. In other words, the multiple permanent magnets need only be arranged on the radial inside of the annular holding member, so that the multiple permanent magnets do not move and are held in the mold when the bonded magnet is manufactured. The shape of the holding member is annular, and it is only necessary that the multiple permanent magnets can be arranged in an annular shape at least on the radial inside of the holding member. Therefore, the shapes of the radially inner surface and the radially outer surface of the holding member are not limited, and various configurations can be adopted other than the configuration in which the inner peripheral surface is polygonal and the outer peripheral surface is circular, as in the above-mentioned embodiment. For example, the inner peripheral surface may be circular and the outer peripheral surface may be polygonal, or both the inner peripheral surface and the outer peripheral surface may be circular, or both may be polygonal.

The multiple permanent magnets are arranged in a circumferential direction on the radial inside of the holding member, in a circular ring shape. That is, the multiple permanent magnets may be arranged continuously or discretely around one circumference on the radial inside of the holding member to form a ring. The radial inside of the holding member is the radial inside of the ring formed by the holding member, and in order for the multiple permanent magnets to be held by the holding member, it is preferable that the multiple permanent magnets are in contact with the inner peripheral surface of the holding member, or indirectly in contact with the inner peripheral surface via another member.

The ring formed by the multiple permanent magnets may have any shape as long as the multiple permanent magnets are lined up in the circumferential direction to complete one revolution, and no permanent magnets are present radially inward of the multiple permanent magnets. Therefore, the shapes of the surfaces formed on the radially inner side and the surfaces formed on the radially outer side of the multiple permanent magnets are not limited. For example, each of the radially inner surface and the radially outer surface may be circular or polygonal.

The storage section is located radially inside the multiple permanent magnets and forms a space into which the bonded magnet material is filled. In other words, the storage section is configured so that the bonded magnet material is filled radially inside the ring formed by the multiple permanent magnets, and the bonded magnet is magnetized during the process of molding the bonded magnet. Since the storage section is formed radially inside the multiple permanent magnets, it has a shape that follows the inner circumferential surface of the multiple permanent magnets, but to this extent, the shape is not limited. For example, the radial thickness of the space for filling the bonded magnet material is not limited, and it may have various shapes depending on the specifications of the bonded magnet to be manufactured. In addition, the shape of the storage section may be variable, such as by configuring the central cylindrical portion of the storage section to be replaceable.

The multiple permanent magnets are configured by groups formed by a first permanent magnet, a second permanent magnet, a third permanent magnet, and a fourth permanent magnet, and the groups are adjacent to each other in the circumferential direction of the circle, and multiple groups are lined up around one circumference. In other words, the multiple permanent magnets are configured by having one or more groups (an integer number) formed by the first permanent magnet, the second permanent magnet, the third permanent magnet, and the fourth permanent magnet. In addition, since the groups are adjacent to each other and exist around one circumference, the multiple permanent magnets are lined up in the circumferential direction in the order of the first permanent magnet, the second permanent magnet, the third permanent magnet, and the fourth permanent magnet. As a result, in the bonded magnet, an integer number (one or more) of groups of south poles and north poles induced in the bonded magnet by the first permanent magnet and the third permanent magnet are formed.

The magnetization direction of the first permanent magnet needs only to face radially inward of the multiple permanent magnets. In the above embodiment, the straight line extending from the magnetization direction at the circumferential center of the first permanent magnet passes through the center of the ring, but this configuration is not limited to this. In other words, the magnetization direction needs only to face radially inward of the multiple permanent magnets and the pole of the bond magnet needs only to be formed at a position corresponding to the first permanent magnet, and the extension line of the magnetization direction may not pass through the center of the ring. The radial direction may not pass through the center of the ring. Note that since the permanent magnets make one revolution in a ring shape, the first permanent magnet is adjacent to the second permanent magnet and the fourth permanent magnet.

The second permanent magnet is adjacent to the first permanent magnet, and the direction of magnetization should face the direction of the first permanent magnet. This state is also the state in which the second permanent magnet is adjacent to the third permanent magnet, and the direction of magnetization faces the opposite direction to the direction pointing to the third permanent magnet. In other words, the second permanent magnet faces in the opposite direction to the magnetic field lines formed on the bond magnet side by the first permanent magnet and the third permanent magnet, so that the magnetic field lines formed on the bond magnet side are blocked from penetrating into the second permanent magnet side. The direction of magnetization of the second permanent magnet may or may not coincide with the direction perpendicular to the radial line (the radial line passing through the center in the circumferential direction) that divides the second permanent magnet in half in the circumferential direction. In any case, it is preferable that the direction of magnetization of the second permanent magnet is in a direction that does not repel (attract or neutralize) the first permanent magnet and the third permanent magnet adjacent to the second permanent magnet. In addition, since the permanent magnets rotate in a circular pattern, the second permanent magnet is adjacent to the first and third permanent magnets.

The third permanent magnet is adjacent to the second permanent magnet, and the direction of magnetization needs to face radially outward from the multiple permanent magnets. In the above embodiment, the straight line extending from the direction of magnetization at the circumferential center of the third permanent magnet passes through the center of the ring, but this configuration is not limited to this. In other words, the direction of magnetization needs to face radially outward from the multiple permanent magnets, and the pole of the bond magnet needs to be formed at a position corresponding to the third permanent magnet, so long as this is the case, the extension of the direction of magnetization may not pass through the center of the ring. Note that since the permanent magnets make one revolution in a ring shape, the third permanent magnet is adjacent to the second permanent magnet and the fourth permanent magnet.

The fourth permanent magnet is adjacent to the first permanent magnet, and the direction of magnetization should face the first permanent magnet. This state is also the state in which the fourth permanent magnet is adjacent to the third permanent magnet, and the direction of magnetization faces the opposite direction to the direction pointing to the third permanent magnet. In other words, the fourth permanent magnet faces in the opposite direction to the magnetic field lines formed on the bond magnet side by the first permanent magnet and the third permanent magnet, so that the magnetic field lines formed on the bond magnet side are blocked from penetrating into the fourth permanent magnet side. The direction of magnetization of the fourth permanent magnet may or may not coincide with a direction perpendicular to a radial line (a radial line passing through the center in the circumferential direction) that divides the fourth permanent magnet in half in the circumferential direction. In any case, it is preferable that the direction of magnetization of the fourth permanent magnet is in a direction that does not repel (attract or neutralize) the first permanent magnet and the third permanent magnet adjacent to the fourth permanent magnet. In addition, since the permanent magnets rotate in a circular pattern, the fourth permanent magnet is adjacent to the first and third permanent magnets.

1... manufacturing device, 2... injection molding device, 10... holding member, 20... permanent magnet, 21... first permanent magnet, 22... second permanent magnet, 23... third permanent magnet, 24... fourth permanent magnet, 30... storage section, 31... partition member, 32... cylindrical section, 41... first mold, 42... second mold, 50... cylinder, 51... rod

Claims (6)

An annular holding member;
A plurality of permanent magnets arranged in a circular ring in a circumferential direction on the radially inner side of the holding member;
a housing portion that is located radially inside the plurality of permanent magnets and that forms a space into which a material for the bonded magnet is filled,
The plurality of permanent magnets include
a set formed of a first permanent magnet, a second permanent magnet adjacent to the first permanent magnet in the circumferential direction, a third permanent magnet adjacent to the second permanent magnet in the circumferential direction, and a fourth permanent magnet adjacent to the third permanent magnet in the circumferential direction, a plurality of the sets being arranged adjacent to each other in the circumferential direction over one revolution,
The magnetization direction of the first permanent magnet faces radially inward of the plurality of permanent magnets,
The magnetization directions of the second permanent magnet and the fourth permanent magnet are oriented toward the first permanent magnet,
The magnetization direction of the third permanent magnet faces radially outward of the plurality of permanent magnets.
Bonded magnet manufacturing equipment. The intrinsic coercivity of the second permanent magnet and the fourth permanent magnet is equal to or greater than the intrinsic coercivity of the first permanent magnet and the third permanent magnet.
2. An apparatus for manufacturing the bonded magnet according to claim 1. the direction of magnetization of each of the first permanent magnet and the third permanent magnet at a circumferential center is parallel to a radial direction passing through a center of a ring formed by the plurality of the permanent magnets;
The magnetization direction of each of the second permanent magnet and the fourth permanent magnet is perpendicular to a radial line that divides each of the second permanent magnet and the fourth permanent magnet into two equal parts in the circumferential direction of a ring formed by the multiple permanent magnets.
2. An apparatus for manufacturing the bonded magnet according to claim 1. The permanent magnets are adjacent to each other, and the inner product of a unit vector indicating the direction of magnetization in one of the adjacent permanent magnets, which is inverted around the boundary between the adjacent permanent magnets, and a unit vector indicating the direction of magnetization in the other adjacent permanent magnet is equal to or less than 0.
3. An apparatus for manufacturing a bonded magnet according to claim 1 or 2. When the total number of the first permanent magnets and the third permanent magnets is P, the magnetization direction rotates by (P-2) x 720° in one revolution of the multiple permanent magnets.
An apparatus for manufacturing a bonded magnet according to any one of claims 1 to 3. A method for manufacturing a bonded magnet using the bonded magnet manufacturing apparatus according to any one of claims 1 to 3,
a filling step of filling the material into the container;
a forming step of magnetizing and hardening the material filled in the container;
a removal step of removing the material from the container;
A method for producing a bonded magnet comprising the steps of:

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