Magnet unit and manufacturing method thereof

Abstract

A magnet unit can be easily obtained. A method for manufacturing a magnet unit includes: disposing a holding member provided with a plurality of holes penetrating from a first end surface to a second end surface in a mold provided with one or more gas discharge grooves such that the second end surface faces the one or more gas discharge grooves; injection-molding a magnet material from one side of the first end face toward the plurality of holes; and removing the holding member from the mold, and connecting two or more of the plurality of holes by means of the one or more gas discharge grooves in the step of disposing the holding member in the mold.

Description

Technical Field

[0001] The present disclosure relates to a magnet unit and a method for manufacturing the same. Background Art

[0002] Patent Document 1 describes an embedded magnet type motor including a rotor and a magnet embedded in a hole of the rotor. The magnet is formed by filling the hole of the rotor with a bonded magnet by injection molding. During injection molding, the rotor is placed in a mold, and an air exhaust structure for exhausting air in the hole is provided in the mold.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-61430 Summary of the invention

[0006] Problems that the invention will solve

[0007] There is room for improvement in the structure of the mold when injection molding a magnet.

[0008] Means for solving problems

[0009] A manufacturing method for a magnet unit according to one embodiment of the present disclosure includes the following steps: placing a retaining component having a plurality of holes extending from a first end face to a second end face in a mold having one or more gas discharge grooves so that the second end face is opposite to the one or more gas discharge grooves; injection molding a magnet material from one side of the first end face toward the plurality of holes; and removing the retaining component from the mold, and in the step of placing the retaining component in the mold, connecting two or more of the plurality of holes using the one or more gas discharge grooves.

[0010] A magnet unit in one embodiment of the present disclosure comprises: a retaining component, which is provided with a plurality of holes extending from a first end face to a second end face; and a plurality of magnets, which are respectively arranged in the plurality of holes, have a gate mark on one side of the first end face, and have a groove mark connecting two or more of the plurality of holes on one side of the second end face.

[0011] Effects of the Invention

[0012] According to the above-described magnet unit and the method for manufacturing the same, the magnet unit can be obtained easily. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a flowchart showing a method for manufacturing a magnet unit according to an embodiment.

[0014] Figure 2This is a schematic cross-sectional view for explaining one step of the method for manufacturing the magnet unit according to the embodiment.

[0015] Figure 3 It is a schematic cross-sectional view showing a cross section at a position where there is no gas discharge groove.

[0016] Figure 4 This is a schematic cross-sectional view for explaining one step of the method for manufacturing the magnet unit according to the embodiment.

[0017] Figure 5 It is a schematic cross-sectional view showing a magnet unit according to the embodiment.

[0018] Figure 6 It is a schematic plan view showing an example of arrangement of a plurality of holes and gas discharge grooves.

[0019] Figure 7 It is a schematic plan view showing a first modification of the arrangement of a plurality of holes and gas discharge grooves.

[0020] Figure 8 This is a schematic cross-sectional view for explaining the gas discharge groove in Modification Example 1.

[0021] Fig. 9 It is a schematic plan view showing a second modification of the arrangement of a plurality of holes and gas discharge grooves.

[0022] Fig.10 It is a schematic plan view showing a third modification of the arrangement of a plurality of holes and gas discharge grooves.

[0023] Fig.11 It is a schematic plan view showing the magnet unit according to the embodiment. DETAILED DESCRIPTION

[0024] The following is a detailed description of the embodiments of the present disclosure. However, the embodiments shown below are examples for concretizing the technical ideas of the present invention, and do not limit the present invention to the following. In addition, the term "process" in this specification is not only an independent process, but also is included in this term as long as the intended purpose of the process is achieved, even if it cannot be clearly distinguished from other processes.

[0025] use Figure 1 to Figure 6 , a method for manufacturing a magnet unit according to an embodiment of the present invention is described. Figure 1 This is a flowchart showing a method for manufacturing a magnet unit according to an embodiment. Figure 2 This is a schematic cross-sectional view for explaining one step of the method for manufacturing the magnet unit according to the embodiment. Figure 3 It is a schematic cross-sectional view showing a cross section at a position where there is no gas discharge groove. Figure 4This is a schematic cross-sectional view for explaining one step of the method for manufacturing the magnet unit according to the embodiment. Figure 5 It is a schematic cross-sectional view showing a magnet unit according to the embodiment. Figure 6 It is a schematic plan view showing an example of arrangement of a plurality of holes and gas discharge grooves. Figure 6 This is a top view from one side of the first end surface 11. Figure 6 In FIG. 1 , the holding member 10 provided with the plurality of holes 13 is indicated by solid lines, and the gas discharge grooves 21 and 22 at the portion overlapping with the holding member 10 are indicated by dotted lines.

[0026] The manufacturing method of the magnet unit 100 of the embodiment includes a step S101 of arranging the holding member 10 in the mold 20, a step S102 of injection molding, and a step S103 of removing the holding member 10 from the mold 20. In the step S101, the holding member 10 having a plurality of holes 13 penetrating from the first end face 11 to the second end face 12 is arranged in the mold 20 having one or more gas discharge grooves 21 so that the second end face 12 is opposed to the one or more gas discharge grooves 21. In the step S101, two or more of the plurality of holes 13 are connected by using the one or more gas discharge grooves 21. In the step S102, the magnet material 30 is injection molded from one side of the first end face 11 to the plurality of holes 13. In the step S103, the holding member 10 is removed from the mold 20.

[0027] In the method of injection molding the magnet material 30 into the plurality of holes 13 provided in the holding member 10, by configuring the configuration in which two or more of the plurality of holes 13 are connected by the gas discharge groove 21, it is possible to easily design the mold compared to the case in which one gas discharge groove is connected to only one hole. Therefore, the magnet unit 100 can be easily obtained.

[0028] In addition, if a gas discharge groove is connected to only one hole, it is necessary to avoid other holes to configure the gas discharge groove, so there is a risk that the gas discharge groove is complicatedly bent and hinders the discharge of gas. If the gas discharge groove 21 is connected to more than two holes 13, it is not necessary to avoid the hole 13, so the gas discharge groove 21 can be designed considering the gas discharge efficiency. In addition, it can also be, as Figure 6As shown, the mold 20 is provided with not only a gas discharge groove 21 connecting two or more holes 13, but also a gas discharge groove 22 connected to only one hole 13. By improving the gas discharge efficiency of the gas discharge groove 21, the filling pressure during injection molding can be reduced. As a result, the strength required for the holding component 10 can be reduced, and the degree of freedom in the design of the multiple holes 13 provided in the holding component 10 is increased, so that the magnetic properties of the obtained magnet unit 100 can be improved. The strength required for the holding component 10 is reduced, so that the total volume of the multiple holes 13 provided in the holding component 10 can be increased. The strength required for the holding component 10 is reduced, so that the thickness of the wall of the holding component 10, that is, the distance from the side of the holding component 10 (the outer side when the holding component 10 is cylindrical) to the hole 13 can be reduced.

[0029] In addition, in the case of injection molding into multiple holes 13, the time until the filling is completed may vary depending on the hole 13. The gas discharge groove 21 can be directly or indirectly connected to a device for discharging gas, such as a suction device, to discharge the gas present in the hole 13 to the outside, but in the case where only one hole is connected to one gas discharge groove, if suction is continued when one hole has been filled but the other hole is still in the middle of filling, there is a possibility that the magnetic material in the filled hole overflows into the gas discharge groove. If it is a gas discharge groove 21 connecting more than two holes 13, even if one of the more than two holes 13 connected to one gas discharge groove 21 is filled first, as long as the other hole 13 is in the middle of filling, the possibility of the magnetic material 30 overflowing from the filled hole 13 to the gas discharge groove 21 can be reduced.

[0030] (Process of placing the holding member in the mold)

[0031] In the step S101 of arranging the holding member 10 on the mold 20, the holding member 10 and the mold 20 are arranged so that the second end surface 12 faces one or more gas discharge grooves 21. Two or more of the plurality of holes 13 are connected by the one or more gas discharge grooves 21. When viewed from one side of the first end surface 11, a part of one gas discharge groove 21 overlaps a part or all of the two or more holes 13.

[0032] The gas discharge groove 21 is designed to discharge the gas present in the hole 13 to the outside. For example, the gas discharge groove 21 is connected to the suction device directly or via other grooves or holes. When the magnetic material 30 is ejected, the gas discharge groove 21 and the hole 13 can be depressurized by the suction device. In this way, the gas present in the hole 13 can be discharged from the hole 13 to the outside. The gas present in the hole 13 is, for example, air, and when the gas is released from the magnetic material 30, the released gas is also included. Figure 2As shown, another groove may be provided in the mold 20 continuously from the gas discharge groove 21. In this case, the gas discharge groove 21 refers to a portion of the groove provided in the mold 20 that faces the second end surface 12 of the holding member 10. The same applies to the gas discharge groove 22.

[0033] The width of the gas discharge groove 21 can be large enough to discharge the gas present in the hole 13, and small enough that the gas discharge groove 21 will not be crushed by the force of the clamping mold 20. The width of the gas discharge groove 21 refers to the length in the direction perpendicular to the extension direction of the gas discharge groove 21 when viewed from above. In the case where the length in this direction is not constant, the smallest length is set as the width of the gas discharge groove 21. In the case where the gas discharge groove 21 overlaps only a portion of the hole 13 when viewed from above, the width of the gas discharge groove 21 can be set to 0.5 mm or more, preferably 2 mm or more. Thus, the gas discharge efficiency can be improved. The width of the gas discharge groove 21 can be set to 12 mm or less, preferably 5 mm or less. Thus, the possibility of the gas discharge groove 21 being crushed by the clamping force can be reduced. The width of the gas discharge groove 21 is preferably 2 mm or more and 5 mm or less. The width of the gas discharge groove 22 can be selected from the same numerical range as the width of the gas discharge groove 21. In the case where a plurality of gas discharge grooves 21 are provided in the mold 20, their widths can all be the same. The same width includes an error within ±1 mm.

[0034] The one or more gas discharge grooves 21 may be linear in shape when viewed from the first end surface 11. This can improve the discharge efficiency of the gas in the hole 13. Figure 6 As shown, the one or more gas discharge grooves 21 may include a plurality of grooves extending radially in a plan view. This can improve the discharge efficiency of the gas present in the hole 13. The plurality of grooves extending radially are a plurality of straight grooves extending from the central portion toward the outer edge of the holding member 10 in a plan view. Figure 6 In the example shown, the width of the plurality of grooves is constant from one end to the other end. The width of the plurality of grooves may not be constant. The plurality of grooves may also be shaped so that the width increases from the central portion of the holding member 10 toward the outer edge. The one or more gas discharge grooves 22 may also include a plurality of grooves that expand radially when viewed from above.

[0035] The edge of one or more gas discharge grooves 21 may be located at the same position as or closer to the outside of the edges of the plurality of holes 13. In this way, a configuration in which the plurality of holes 13 are not blocked by the mold 20 can be formed, and the discharge efficiency of the gas present in the holes 13 can be improved. In this case, the top view shape of the gas discharge groove 21 may not be a straight line. Figure 7 as well as Figure 8 , a modification 1 of the arrangement of the plurality of holes 13 and the gas discharge grooves 21 will be described. Figure 7 It is a schematic plan view showing a first modification of the arrangement of the plurality of holes 13 and the gas discharge grooves 21 . Figure 7 This is a top view from one side of the first end surface 11. Figure 7 In FIG. 1 , the holding member 10 provided with the plurality of holes 13 is indicated by solid lines, and the gas discharge grooves 21 and 22 at the portion overlapping with the holding member 10 are indicated by dotted lines. Figure 8 This is a schematic cross-sectional view for explaining the gas discharge groove 21 in Modification Example 1.

[0036] exist Figure 7 as well as Figure 8 In the illustrated variation 1, the edge of one or more gas discharge grooves 21 is located outside the edge of the plurality of holes 13. Therefore, the gas present in the hole 13 can be discharged to the gas discharge groove 21 without being blocked by the mold 20. In variation 1, the one or more gas discharge grooves 21 are shaped to include the plurality of holes 13 when viewed from above. The gas discharge groove 21 has a shape connected to the outer edge of the retaining member 10 when viewed from above. With such a shape, it is easy to ensure a path for discharging the gas to the outside. In variation 1, the mold 20 is not provided with a gas discharge groove connected to only one hole 13, and only a gas discharge groove 21 is provided.

[0037] In the case where the gas discharge groove 21 is provided in such a manner that the plurality of holes 13 are not blocked by the mold 20, the edge of the hole 13 may coincide with the edge of the gas discharge groove 21 when viewed from above, but it is preferred that the edge of the gas discharge groove 21 is located outside the edge of the hole 13 when viewed from above. In this case, it can be said that the edge of the gas discharge groove 21 is located away from the edge of the hole 13 when viewed from above. Thus, even if the magnetic material 30 reaches the gas discharge groove 21 during injection molding, the possibility that the gas discharge groove 21 is completely blocked by the magnetic material 30 can be reduced. The shortest distance from the edge of the hole 13 to the edge of the gas discharge groove 21 when viewed from above is preferably greater than 0.1 mm, and more preferably greater than 0.2 mm. Thus, the possibility that the gas discharge groove 21 is completely blocked by the magnetic material 30 can be further reduced. The shortest distance from the edge of the hole 13 to the edge of the gas discharge groove 21 when viewed from above is preferably less than 5 mm, and more preferably less than 2 mm. Thus, the possibility that the gas discharge groove 21 is crushed by the clamping force can be reduced. The shortest distance from the edge of the hole 13 to the edge of the gas discharge groove 21 when viewed from above is preferably 0.2 mm or more and 2 mm or less. It is preferred that, when viewed from above, the edge of the gas discharge groove 21 is located outside the edge of the hole 13 over the entire circumference of the gas discharge groove 21. This can further reduce the possibility that the gas discharge groove 21 is completely blocked by the magnetic material 30.

[0038] The shapes, sizes, and numbers of the multiple holes 13 can be set according to the target values ​​of the magnetic properties of the magnet unit 100. The multiple holes 13 can all be of the same shape or different. The areas of the openings on one side of the second end faces 12 of the multiple holes 13 can all be the same or different. The number of multiple holes 13 provided in a retaining component 10 is more than two, can be more than 8, or can be more than 30. The larger the number of holes 13, the easier it is to obtain the simplified effect of the design brought about by connecting more than two holes 13 with a gas discharge groove 21, and the possibility of differences in the time until the filling is completed increases, so it is easy to obtain the effect as a countermeasure. The number of multiple holes 13 provided in a retaining component 10 also depends on the size of the retaining component 10, but can be set to less than 100, less than 80, or less than 60.

[0039] The plurality of holes 13 may include a plurality of first holes 13A whose opening area on one side of the second end face 12 is a first area and a plurality of second holes 13B whose opening area on one side of the second end face 12 is a second area smaller than the first area. If different types of holes 13 are arranged in this way, the possibility of a difference in the time until the filling is completed is increased compared with a case where this is not the case, so the effect brought about by the provision of the gas discharge groove 21 can be further obtained. One or more gas discharge grooves 21 may also include a first groove 21A. It is preferred that at least one of the plurality of first holes 13A and at least one of the plurality of second holes 13B are connected by the first groove 21A. Since the first holes 13A and the second holes 13B having different areas tend to have a difference in the time until the filling is completed, the possibility of the filled magnetic material 30 overflowing into the first groove 21A can be further reduced by connecting the first groove 21A to both parties. The second area of ​​the second hole 13B may be less than 90% of the first area of ​​the first hole 13A, or less than 80%. The second area of ​​the second hole 13B may be 20% or more of the first area of ​​the first hole 13A, or 40% or more. For example, the second area of ​​the second hole 13B may be 40% or more and 80% or less of the first area of ​​the first hole 13A.

[0040] In the case of providing a gas discharge groove 22 connected to only one hole 13, the hole 13 connected to the gas discharge groove 22 is preferably a hole 13 in which the time until filling is completed is relatively long. Thus, the possibility of the magnetic material 30 overflowing into the gas discharge groove 22 can be reduced. For example, among the first hole 13A and the second hole 13B, the first hole 13A having a large opening area tends to have a longer time until filling is completed, so it is preferred that the gas discharge groove 22 is connected to the first hole 13A.

[0041] use Fig. 9 as well as Fig.10, Modifications 2 and 3 of the arrangement of the plurality of holes 13 and the gas discharge grooves 21 are described. Fig. 9 It is a schematic plan view showing a second modification of the arrangement of the plurality of holes 13 and the gas discharge grooves 21 . Fig.10 It is a schematic plan view showing a third modification of the arrangement of the plurality of holes 13 and the gas discharge grooves 21 . Fig. 9 as well as Fig.10 This is a top view from one side of the first end surface 11. Fig. 9 as well as Fig.10 In FIG. 1 , the holding member 10 provided with the plurality of holes 13 is indicated by solid lines, and the gas discharge grooves 21 and 22 at the portion overlapping with the holding member 10 are indicated by dotted lines. Fig. 9 as well as Fig.10 The modified examples 2 and 3 shown are Figure 6 as well as Figure 7 Compared with the example shown in the figure, the shape and arrangement of the hole 13 are different. Even when such a hole 13 is provided, the same effect as the above-mentioned example can be obtained by providing the gas discharge groove 21.

[0042] like Fig.10 As shown, two or more of the plurality of first holes 13A may be connected through a gas discharge groove 21 (first groove 21A). Two or more of the plurality of second holes 13B may be connected through the first groove 21A. Two or more first holes 13A may be connected to two or more second holes 13B through the first groove 21A. Thus, the possibility of the filled magnetic material 30 overflowing into the first groove 21A can be further reduced.

[0043] The holding member 10 is, for example, a rotor core. The shape of the holding member 10 is, for example, a cylindrical shape. When the holding member 10 is a rotor core, the holding member 10 is a magnetic body. When the holding member 10 is a rotor core, the holding member 10 is a laminated steel plate. The laminated steel plate is composed of a plurality of steel plates laminated in a direction from the second end face 12 toward the first end face 11. The laminated steel plate is, for example, an electromagnetic steel plate.

[0044] The mold 20 may also be composed of a plurality of parts. The mold 20 is composed of a plurality of parts, so that the holding component 10 can be easily fixed by the mold 20, and the holding component 10 can be easily removed from the mold 20. A gate 23 may also be provided in the mold 20. The gate 23 is connected to the hole 13 on one side of the first end surface 11. In the example shown in the figure, a plurality of gas discharge grooves 21 are provided independently, but they may also be partially connected. In the case where all the gas discharge grooves 21 are connected, it can be said that only one gas discharge groove 21 is provided in the mold 20.

[0045] (Injection molding process)

[0046] In the injection molding step S102, the magnetic material 30 is injection molded from one side of the first end surface 11 toward the plurality of holes 13. Figure 4 As shown, the magnet material 30 reaches the hole 13 through the gate 23 of the mold 20. The magnet material 30 is Figure 4 The injection molding can be performed, for example, until the hole 13 is completely filled with the magnetic material 30. The degree of filling to terminate the injection molding can be appropriately set according to the magnetic properties of the target magnet unit.

[0047] The magnetic material 30 includes a resin and magnetic powder. The resin may be a thermoplastic resin or a thermosetting resin. The resin may include both a thermosetting resin and a thermoplastic resin. The resin is, for example, a thermoplastic resin.

[0048] Examples of thermoplastic resins include nylon resin (polyamide resin); polyolefins such as polypropylene (PP) and polyethylene (PE); polyester; polycarbonate (PC); polyphenylene sulfide resin (PPS); polyetheretherketone (PEEK); polyoxymethylene (POM); liquid crystal polymer (LCP); and the like. Examples of nylon resins include polylactams such as 6 nylon, 11 nylon, and 12 nylon; condensates of dicarboxylic acids and diamines such as 6,6 nylon, 6,10 nylon, and 6,12 nylon; 6 / 6,6 nylon, 6 / 6,10 nylon, 6 / 12 nylon, 6 / 6,12 nylon, 6 / 6,10 / 6,10 nylon, 6 / 6,6 / 6,12 nylon; copolymer polyamides such as 6-nylon / polyether; nylon 6T, nylon 9T, nylon MXD6, aromatic nylon, and amorphous nylon. Examples of thermoplastic resins include 12 nylon.

[0049] The magnetic powder may be, for example, rare earth magnetic powders such as SmFeN, NdFeB, and SmCo. The magnetic powder may also be SmFeN magnetic powder. In this case, the magnetic material 30 includes a resin and SmFeN magnetic powder. Examples of SmFeN magnetic powder include: x Fe 100－x－y N y The nitride is composed of rare earth metal Sm, iron Fe and nitrogen N. Preferably, x is 8.1 atomic % or more and 10 atomic % or less, y is 13.5 atomic % or more and 13.9 atomic % or less, and the remainder is mainly Fe. The magnetic powder can also be Th2Zn 17 The magnetic powder may be an SmFeN-based anisotropic magnetic powder. The SmFeN-based magnetic powder may be produced, for example, by the method disclosed in Japanese Patent Publication No. 11-189811. The magnetic powder may also have a SmFeN-based core and a covering portion containing P and O. The magnetic powder may also be surface treated with a silane coupling agent or the like.

[0050] The average particle size of the magnetic powder is preferably 10 μm or less. Thus, the crystal particle size can be reduced and the coercive force of the magnetic powder can be increased. The smaller the average particle size of the magnetic powder, the lower the fluidity of the magnetic material 30 tends to be. If the fluidity decreases, the filling pressure increases. Therefore, when using magnetic powder with an average particle size of 10 μm or less, it is easier to obtain the effect brought about by setting a gas discharge groove 21 connecting two or more holes 13. In addition, since the fluidity of the magnetic material 30 is reduced, the possibility of the magnetic material 30 overflowing into the gas discharge groove 21 can be reduced. The average particle size of the magnetic powder is preferably 6 μm or less, and further preferably 4 μm or less. Thus, the coercive force of the magnetic powder can be further increased. The average particle size of the magnetic powder is preferably 1 μm or more. Thus, the filling rate of the magnetic powder in the magnetic material 30 can be increased. The average particle size of the magnetic powder is preferably 2 μm or more, and further preferably 2.5 μm or more. The average particle size of the magnetic powder is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 10 μm or less, and further preferably 2 μm or more and 4 μm or less. The average particle size is measured as a particle size corresponding to 50% of the volume accumulation from the small particle size side in the particle size distribution, and can be measured, for example, by a laser diffraction particle size distribution measuring device (HELOS & RODOS of Japan Laser Co., Ltd.).

[0051] The span of the magnetic powder is defined as follows: span = (D90-D10) / D50 (here, the particle diameters D90, D10, and D50 refer to the particle diameters corresponding to the cumulative values ​​of the particle size distribution of 90%, 10%, and 50%). It can be set to 2 or less, preferably 1.5 or less. If it exceeds 2, the proportion of fine magnetic powder with small coercive force increases, so there is a tendency for the coercive force to decrease.

[0052] The filling rate of the magnetic powder in the magnetic material 30 is preferably 50% by volume or more, and more preferably 60% by volume or more. As a result, the residual magnetic flux density of the obtained magnet 40 can be increased. In addition, there is a trend that the fluidity of the magnetic material 30 decreases as the filling rate of the magnetic powder in the magnetic material 30 increases, so it is easier to obtain the effect brought about by providing the gas discharge groove 21 connecting two or more holes 13. In addition, since the fluidity of the magnetic material 30 is reduced, the possibility of the magnetic material 30 overflowing into the gas discharge groove 21 can be reduced.

[0053] In the case of obtaining a magnet 40 in which the magnetic powder is oriented, in the injection molding step S102, an orientation magnetic field is applied to the magnetic material 30. The application of the orientation magnetic field begins at least before the resin is completely solidified. By applying a magnetic field to the magnetic material 30, the easy magnetization axis of the magnetic powder contained in the magnetic material 30 can be aligned. In order to apply a magnetic field to the magnetic material 30, an orientation magnet can be set in the mold 20. As an orientation magnet, an electromagnet or a permanent magnet can be used. When a permanent magnet is used as an orientation magnet, injection molding and application of a magnetic field are performed simultaneously. The size of the orientation magnetic field can be set to, for example, 637 kA / m (8 kOe) or more, and can be set to 1511 kA / m (19 kOe) or less.

[0054] (Step of removing the holding component from the mold)

[0055] In the step S103 of removing the holding member 10 from the mold 20, the holding member 10 is removed from the mold 20. Thus, the magnet unit 100 can be obtained. The magnet material 30 in the injection molding step S102 is Figure 5 The magnet unit 100 shown is a magnet 40. The magnet 40 is provided in the hole 13 of the holding member 10 removed from the mold 20. The magnetic material 30 remaining in the gate 23 is cut off from the magnetic material 30 filled in the hole 13 in the step S103 of removing the holding member 10 from the mold 20 or thereafter.

[0056] The magnetizing step may also be performed after the step S103 of removing the holding component 10 from the mold 20. In the case of performing the magnetizing step, the magnet unit 100 having the magnet 40 is obtained after the magnetizing step. In the magnetizing step, a magnetic field for magnetization is applied to the holding component 10 provided with the magnetic material 30. As a magnetizing method, a pulse magnetic field generation method or a static magnetic field generation method may be listed. The magnitude of the magnetic field for magnetization in the magnetizing step may be set to, for example, 1990 kA / m (25 kOe) or more, or may be set to 4777 kA / m (60 kOe) or less. The magnetic field for magnetization in the magnetizing step may be larger than the magnetic field for orientation in the injection molding step S102.

[0057] (Magnet unit)

[0058] use Figure 5 as well as Fig.11 , the magnet unit 100 according to the embodiment will be described. Fig.11 It is a schematic plan view showing the magnet unit 100 according to the embodiment. Fig.11 This is a top view from one side of the first end surface 11. Fig.11 In FIG. 1 , a trace 60 of a groove provided on one side of the second end surface 12 is indicated by a dotted line.

[0059] The magnet unit 100 has a holding component 10 and a plurality of magnets 40. The holding component 10 is provided with a plurality of holes 13 penetrating from the first end face 11 to the second end face 12. The plurality of magnets 40 are respectively arranged in the plurality of holes 13. The magnet unit 100 has a gate mark 50 on one side of the first end face 11. The magnet unit 100 has a groove mark 60 connecting two or more of the plurality of magnets 40 on one side of the second end face 12. The magnet unit 100 has a groove mark 60 connecting two or more of the plurality of holes 13 on one side of the second end face 12.

[0060] The magnet unit 100 is, for example, a rotor. The holding member 10 is a member having the hole 13 in which the magnet 40 is arranged. In the magnet unit 100 of the embodiment, the magnet 40 is filled in the hole 13. As described above, the holding member 10 is, for example, a rotor core.

[0061] The magnet 40 has a resin and a magnetic powder. The resin can use the material described as the resin constituting the magnet material 30. The magnetic powder can use the material described as the magnetic powder constituting the magnet material 30. The magnet 40 can have a resin and a SmFeN-based magnetic powder. The filling rate of the magnetic powder in the magnet 40 is preferably 50% by volume or more, and more preferably 60% by volume or more. Thereby, the residual magnetic flux density of the magnet 40 can be improved. The volume ratio of the filling rate of the magnetic powder in the magnet 40 can also be calculated based on a cross-section of a portion of the magnet 40. For example, a scanning electron microscope (SEM) image of a cross-section of a portion of the magnet 40 can be taken, and the ratio of the area of ​​the magnetic powder in the SEM image to the area of ​​the magnet 40 can be regarded as the volume ratio of the filling rate of the magnetic powder in the magnet 40.

[0062] The gate mark 50 is formed on the magnet 40. The gate mark 50 appears as a convex shape on the surface of the first end surface 11 of the magnet 40. The top view shape of the gate mark 50 is, for example, circular or elliptical. One or more gate marks 50 are provided on one magnet 40.

[0063] The groove trace 60 is formed on at least one of the retaining member 10 and the magnet 40. The groove trace 60 is observed as a continuous line or a discontinuous line. The groove trace 60 can also be observed, for example, by irradiating a light source from an oblique direction relative to the second end face 12. The groove trace 60 provided in the retaining member 10 is formed by pressing the mold 20 provided with the gas discharge groove 21 against the retaining member 10. The groove trace 60 provided in the magnet 40 is formed by pressing the magnet material 30 with the mold 20 provided with the gas discharge groove 21. The groove trace 60 is formed at the position where the edge of the gas discharge groove 21 is located. The step or concave-convex formed on the second end face 12 of the retaining member 10 can be observed as the groove trace 60. In the case where the magnetic material 30 is pushed out to the gas discharge groove 21 and remains as the magnet 40 attached to the groove trace 60, the magnet 40 remaining in the groove trace 60 does not extend from the hole 13 on one side connected by the groove trace 60 to the hole 13 on the other side. That is, the magnet 40 provided in the hole 13 on one side connected by the groove trace 60 is not connected to the magnet 40 provided in the hole 13 on the other side. At least a part of the groove trace 60 is not covered by the magnet 40 but exposed. The magnet 40 may not remain in the groove trace 60. It is also possible that the groove trace 60 is not covered by the magnet 40 but exposed. The position and shape of the groove trace 60 may be the same as the position and shape of the gas discharge groove 21 described above. On one side of the second end face 12 of the magnet unit 100, in addition to the groove trace 60, a groove trace having the same position and shape as the gas discharge groove 22 may also be formed.

[0064] exist Fig.11 In the embodiment, the groove trace 60 is the same position and shape as the gas discharge groove 21. The groove trace 60 may be only a trace of a part of the gas discharge groove 21. The groove trace 60 tends to be formed on the magnet 40 more easily than the retaining member 10. The groove trace 60 may also be formed only on the magnet 40. It is also possible to judge that they are traces formed by a continuous groove based on the fact that the extension line of one groove trace 60 is consistent with the extension line of another groove trace 60. If an inferred shape formed by two or more groove traces 60 and their extension lines is the position and shape that connects two or more of the multiple holes 13, it can also be judged that it is a groove trace 60 that connects two or more of the multiple holes 13. If an inferred shape formed by two or more groove traces 60 and their extension lines is the position and shape that connects two or more of the multiple magnets 40, it can also be judged that it is a groove trace 60 that connects two or more of the multiple magnets 40. For example, when the extension line of the groove trace 60 formed in one magnet 40 coincides with the extension line of the groove trace 60 formed in another magnet 40 , it can be determined that they are groove traces 60 connecting two or more of the plurality of magnets 40 . Fig.11 The example shown is similar to Figure 6The example shown corresponds to Figure 7 When the edge of the gas discharge groove 21 does not overlap with the hole 13 as in the illustrated example, the groove trace 60 is formed only on the holding member 10 .

[0065] The following technical matters are disclosed through the contents described so far in this specification.

[0066] (Item 1)

[0067] A method for manufacturing a magnet unit comprises the following steps:

[0068] Arrange a holding member having a plurality of holes extending from a first end surface to a second end surface in a mold having one or more gas discharge grooves so that the second end surface faces the one or more gas discharge grooves;

[0069] injection molding a magnet material from one side of the first end surface toward the plurality of holes; and

[0070] removing the retaining member from the mold,

[0071] In the step of arranging in the mold, two or more of the plurality of holes are connected by the one or more gas discharge grooves.

[0072] (Item 2)

[0073] According to the method for manufacturing a magnet unit as described in item 1, in the step of arranging in the mold, the edges of the one or more gas discharge grooves coincide with the edges of the plurality of holes or are located outside the edges of the plurality of holes.

[0074] (Item 3)

[0075] According to the method for manufacturing a magnet unit as described in Item 1, the one or more gas discharge grooves include a plurality of grooves extending radially in a plan view.

[0076] (Item 4)

[0077] According to the method for manufacturing a magnet unit described in any one of items 1 to 3, the plurality of holes include a plurality of first holes whose opening area on one side of the second end surface is a first area and a plurality of second holes whose opening area on one side of the second end surface is a second area smaller than the first area.

[0078] (Item 5)

[0079] According to the method for manufacturing a magnet unit as described in item 4, in the step of configuring the mold, the one or more gas exhaust grooves have a first groove, and at least one of the plurality of first holes and at least one of the plurality of second holes are connected by the first groove.

[0080] (Item 6)

[0081] The method for producing a magnet unit according to any one of items 1 to 5, wherein the magnet material includes a resin and a SmFeN-based magnetic powder.

[0082] (Item 7)

[0083] According to the method for manufacturing a magnet unit according to any one of items 1 to 6, the holding member is a rotor core.

[0084] (Item 8)

[0085] A magnet unit, comprising:

[0086] a retaining member having a plurality of holes extending from the first end surface to the second end surface; and

[0087] a plurality of magnets, which are respectively arranged in the plurality of holes,

[0088] A gate mark is provided on one side of the first end surface,

[0089] A trace of a groove connecting two or more of the plurality of holes is provided on one side of the second end surface.

[0090] Description of Reference Numerals

[0091] 10. Retaining parts

[0092] 11 First end face

[0093] 12 Second end face

[0094] 13 holes

[0095] 13A First hole

[0096] 13B Second hole

[0097] 14 Side

[0098] 20 Mould

[0099] 21, 22 Gas discharge slot

[0100] 21A Slot 1

[0101] 23. Gate

[0102] 30 Magnet material

[0103] 40 Magnet

[0104] 50 Gate traces

[0105] 60 groove marks

[0106] 100 Magnet Units

Claims

1. A method for manufacturing a magnet unit, characterized in that: The process is as follows: Arrange a holding member having a plurality of holes extending from a first end surface to a second end surface in a mold having one or more gas discharge grooves so that the second end surface faces the one or more gas discharge grooves; injection molding a magnet material from one side of the first end surface toward the plurality of holes; as well as removing the retaining member from the mold, In the step of arranging in the mold, two or more of the plurality of holes are connected by the one or more gas discharge grooves.

2. The method for manufacturing a magnet unit according to claim 1, characterized in that: In the step of arranging in the mold, edges of the one or more gas discharge grooves coincide with edges of the plurality of holes or are located outside the edges of the plurality of holes.

3. The method for manufacturing a magnet unit according to claim 1, characterized in that: The one or more gas discharge grooves include a plurality of grooves extending radially in a plan view.

4. The method for manufacturing a magnet unit according to claim 1, characterized in that: The plurality of holes include a plurality of first holes whose opening area on one side of the second end surface is a first area and a plurality of second holes whose opening area on one side of the second end surface is a second area smaller than the first area.

5. The method for manufacturing a magnet unit according to claim 4, characterized in that: In the step of arranging in the mold, the one or more gas exhaust grooves include a first groove, and at least one of the plurality of first holes and at least one of the plurality of second holes are connected by the first groove.

6. The method for manufacturing a magnet unit according to any one of claims 1 to 5, characterized in that: The magnetic material includes resin and SmFeN-based magnetic powder.

7. The method for manufacturing a magnet unit according to claim 6, characterized in that: The holding member is a rotor core.

8. A magnet unit, characterized in that: have: a retaining member having a plurality of holes extending from the first end surface to the second end surface; and a plurality of magnets, which are respectively arranged in the plurality of holes, A gate mark is provided on one side of the first end surface, A trace of a groove connecting two or more of the plurality of holes is provided on one side of the second end surface.

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