Magnet unit and manufacturing method thereof

Abstract

To make it possible to easily obtain a magnet unit.SOLUTION: A manufacturing method of a magnet unit includes a step of placing a holding member having a plurality of holes penetrating from a first end face to a second end face in a mold having one or more gas vent grooves such that the second end face faces the one or more gas vent grooves, a step of injection-molding a magnetic material into the plurality of holes from the first end face side, and a step of removing the holding member from the mold. In the step of placing the holding member in the mold, two or more of the plurality of holes are connected to each other by the one or more gas vent grooves.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a magnet unit and a manufacturing method thereof. [Background technology]

[0002] Patent Document 1 describes an embedded magnet motor that includes a rotor and magnets embedded in its holes. The magnets are formed by filling the holes in the rotor with bonded magnets by injection molding. During injection molding, the rotor is placed in a mold, and the mold is provided with an air vent structure to vent air from the holes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-61430 A Summary of the Invention [Problem to be solved by the invention]

[0004] There is room for improvement in the structure of the mold used for injection molding magnets. [Means for solving the problem]

[0005] A manufacturing method of a magnet unit according to one embodiment of the present disclosure includes the steps of: placing a retaining member having a plurality of holes penetrating from a first end face to a second end face in a mold having one or more gas vent grooves such that the second end face faces the one or more gas vent grooves; injection molding a magnetic material into the plurality of holes from the side of the first end face; and removing the retaining member from the mold, wherein in the step of placing in the mold, two or more of the plurality of holes are connected by the one or more gas vent grooves.

[0006] A magnet unit according to one embodiment of the present disclosure has a retaining member having a plurality of holes penetrating from a first end face to a second end face, and a plurality of magnets respectively arranged in the plurality of holes, with a gate mark on the first end face side and a groove mark connecting two or more of the plurality of holes on the second end face side. Effect of the Invention

[0007] According to the above-described magnet unit and manufacturing method thereof, the magnet unit can be obtained easily. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a flowchart showing a method for manufacturing a magnet unit according to an embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view for explaining one step of the manufacturing method of the magnet unit of the embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing a cross section at a position where there is no gas release groove. [Figure 4] FIG. 4 is a schematic cross-sectional view for explaining one step of the manufacturing method of the magnet unit of the embodiment. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing a magnet unit according to the embodiment. [Figure 6] FIG. 6 is a schematic plan view showing an example of the arrangement of a plurality of holes and gas vent grooves. [Figure 7] FIG. 7 is a schematic plan view showing a first modified example of the arrangement of a plurality of holes and gas vent grooves. [Figure 8] FIG. 8 is a schematic cross-sectional view for illustrating the gas vent groove in the first modification. [Figure 9] FIG. 9 is a schematic plan view showing a second modified example of the arrangement of the plurality of holes and gas vent grooves. [Figure 10] FIG. 10 is a schematic plan view showing a third modified example of the arrangement of a plurality of holes and gas vent grooves. [Figure 11] FIG. 11 is a schematic plan view showing the magnet unit of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present disclosure will be described in detail. However, the embodiments shown below are examples for embodying the technical idea of ​​the present invention, and the present invention is not limited to the following. In this specification, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0010] A method for manufacturing a magnet unit according to an embodiment will be described with reference to Figs. 1 to 6. Fig. 1 is a flow chart showing a method for manufacturing a magnet unit according to an embodiment. Fig. 2 is a schematic cross-sectional view for explaining one step of a method for manufacturing a magnet unit according to an embodiment. Fig. 3 is a schematic cross-sectional view showing a cross section at a position where there is no gas vent groove. Fig. 4 is a schematic cross-sectional view for explaining one step of a method for manufacturing a magnet unit according to an embodiment. Fig. 5 is a schematic cross-sectional view showing a magnet unit according to an embodiment. Fig. 6 is a schematic plan view showing an example of an arrangement of a plurality of holes and gas vent grooves. Fig. 6 is a plan view seen from the side of a first end face 11. In Fig. 6, a holding member 10 provided with a plurality of holes 13 is shown by a solid line, and gas vent grooves 21, 22 in a portion overlapping with the holding member 10 are shown by a dashed line.

[0011] The manufacturing method of the magnet unit 100 of the embodiment includes a step S101 of placing the holding member 10 in a mold 20, a step S102 of injection molding, and a step S103 of removing the holding member 10 from the mold 20. In 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 placed in a mold 20 having one or more gas vent grooves 21 so that the second end face 12 faces the one or more gas vent grooves 21. In step S101, two or more of the plurality of holes 13 are connected by the one or more gas vent grooves 21. In step S102, the magnet material 30 is injection molded into the plurality of holes 13 from the side of the first end face 11. In step S103, the holding member 10 is removed from the mold 20.

[0012] In a method of injection molding the magnet material 30 into the multiple holes 13 provided in the holding member 10, by arranging two or more of the multiple holes 13 to be connected by the gas vent groove 21, the mold can be designed more easily than in a case where one gas vent groove is arranged to be connected to only one hole. Therefore, the magnet unit 100 can be obtained easily.

[0013] In addition, if one gas vent groove is connected to only one hole, the gas vent groove needs to be arranged to avoid other holes, so the gas vent groove may be bent in a complex manner, which may hinder the discharge of gas. If the gas vent groove 21 is arranged to connect two or more holes 13, the holes 13 do not need to be avoided, so the gas vent groove 21 can be designed taking into consideration the gas discharge efficiency. As shown in FIG. 6, the mold 20 may be provided with not only the gas vent groove 21 connecting two or more holes 13, but also a gas vent groove 22 connected to only one hole 13. By improving the gas discharge efficiency by the gas vent groove 21, the filling pressure during injection molding can be reduced. This allows the strength required for the holding member 10 to be reduced, and the degree of freedom in designing the multiple holes 13 provided in the holding member 10 to be increased, thereby improving the magnetic properties of the resulting magnet unit 100. By reducing the strength required for the holding member 10, the total volume of the multiple holes 13 provided in the holding member 10 can be increased. By reducing the strength required for the retaining member 10, the wall thickness of the retaining member 10, i.e., the distance from the side surface of the retaining member 10 (the outer surface if the retaining member 10 is cylindrical) to the hole 13, can be reduced.

[0014] In addition, when injection molding is performed on multiple holes 13, the time until the filling is completed may differ depending on the hole 13. The gas vent 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 if only one hole is connected to one gas vent groove, and suction is continued in a state where one hole is filled but another hole is still in the middle of filling, the magnet material in the filled hole may overflow into the gas vent groove. If the gas vent groove 21 connects two or more holes 13, even if only one of the two or more holes 13 connected to one gas vent groove 21 is filled first, the possibility of the magnet material 30 overflowing from the filled hole 13 into the gas vent groove 21 can be reduced if another hole 13 is in the middle of filling.

[0015] (Process of placing the holding member in the mold) In step S101 of placing the holding member 10 in the mold 20, the holding member 10 and the mold 20 are placed so that the second end face 12 faces one or more gas vent grooves 21. Two or more of the multiple holes 13 are connected by one or more gas vent grooves 21. When viewed through from the first end face 11 side, a portion of one gas vent groove 21 overlaps with some or all of the two or more holes 13.

[0016] The gas vent groove 21 is designed so that the gas present in the hole 13 can be discharged to the outside. For example, the gas vent groove 21 is connected to a suction device directly or via another groove or hole. When the magnet material 30 is injected, the gas vent groove 21 and the hole 13 can be decompressed by the suction device. This allows the gas present in the hole 13 to be discharged to the outside from the hole 13. The gas present in the hole 13 is, for example, air, and in the case where gas is released from the magnet material 30, the gas released is also included. As shown in FIG. 2, the mold 20 may be provided with an additional groove continuing from the gas vent groove 21. In this case, the gas vent 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 vent groove 22.

[0017] The width of the gas vent groove 21 can be large enough to discharge the gas present in the hole 13, and can be small enough to prevent the gas vent groove 21 from being crushed by the force of clamping the mold 20. The width of the gas vent groove 21 refers to the length in a direction perpendicular to the extension direction of the gas vent groove 21 in a plan view. If the length in such a direction is not constant, the minimum length among them is defined as the width of the gas vent groove 21. When the gas vent groove 21 overlaps only a part of the hole 13 in a plan view, the width of the gas vent groove 21 can be 0.5 mm or more, and preferably 2 mm or more. This can improve the gas discharge efficiency. The width of the gas vent groove 21 can be 12 mm or less, and preferably 5 mm or less. This can reduce the possibility that the gas vent groove 21 will be crushed by the clamping force. The width of the gas vent groove 21 is preferably 2 mm or more and 5 mm or less. The width of the gas vent groove 22 can be selected from the same numerical range as the width of the gas vent groove 21. When multiple gas release grooves 21 are provided in the mold 20, they may all have the same width. The "same width" includes an error of ±1 mm.

[0018] The one or more gas vent grooves 21 may have a linear shape in a plan view seen from the first end face 11 side. This can improve the efficiency of discharging the gas present in the hole 13. As shown in FIG. 6, the one or more gas vent grooves 21 may include a plurality of grooves that spread radially in a plan view. This can improve the efficiency of discharging the gas present in the hole 13. The radially spreading grooves are linear grooves that extend from the center of the holding member 10 toward the outer edge in a plan view. In the example shown in FIG. 6, the width of each of the plurality of grooves is constant from one end to the other end. The width of the plurality of grooves does not have to be constant. Each of the plurality of grooves may have a shape in which the width increases from the center of the holding member 10 toward the outer edge. The one or more gas vent grooves 22 may also include a plurality of grooves that spread radially in a plan view.

[0019] The edge of one or more gas vent grooves 21 may be aligned with or positioned outside the edge of the holes 13. This allows the holes 13 to be arranged so that they are not blocked by the mold 20, and the efficiency of discharging the gas present in the holes 13 can be improved. In this case, the shape of the gas vent groove 21 in plan view does not have to be linear. A first modified example of the arrangement of the holes 13 and the gas vent groove 21 will be described with reference to Figs. 7 and 8. Fig. 7 is a schematic plan view showing a first modified example of the arrangement of the holes 13 and the gas vent groove 21. Fig. 7 is a plan view seen from the first end face 11 side. In Fig. 7, the holding member 10 provided with the holes 13 is shown by a solid line, and the gas vent grooves 21 and 22 in the portions overlapping with the holding member 10 are shown by a dashed line. Fig. 8 is a schematic cross-sectional view for explaining the gas vent groove 21 in the first modified example.

[0020] In Modification 1 shown in Figures 7 and 8, the edges of one or more gas vent grooves 21 are located outside the edges of the multiple holes 13. Therefore, gas present in the holes 13 can be discharged to the gas vent grooves 21 without being blocked by the mold 20. In Modification 1, the one or more gas vent grooves 21 have a shape that encompasses the multiple holes 13 in a plan view. The gas vent grooves 21 have a shape that connects to the outer edge of the holding member 10 in a plan view. This shape makes it easy to ensure a path for discharging gas to the outside. In Modification 1, the mold 20 does not have a gas vent groove that connects to only one hole 13, and only has the gas vent groove 21.

[0021] In the case where the gas vent groove 21 is provided so that the holes 13 are not blocked by the mold 20, the edge of the hole 13 and the edge of the gas vent groove 21 may coincide in plan view, but it is preferable that the edge of the gas vent groove 21 is located outside the edge of the hole 13 in plan view. In this case, it can be said that the edge of the gas vent groove 21 is located at a position away from the edge of the hole 13 in plan view. This can reduce the possibility that the gas vent groove 21 will be completely blocked by the magnet material 30 even if the magnet material 30 reaches the gas vent groove 21 during injection molding. The shortest distance from the edge of the hole 13 to the edge of the gas vent groove 21 in plan view is preferably 0.1 mm or more, more preferably 0.2 mm or more. This can further reduce the possibility that the gas vent groove 21 will be completely blocked by the magnet material 30. The shortest distance from the edge of the hole 13 to the edge of the gas vent groove 21 in plan view is preferably 5 mm or less, more preferably 2 mm or less. This can reduce the possibility that the gas vent groove 21 will be crushed by the clamping force. The shortest distance from the edge of the hole 13 to the edge of the gas vent groove 21 in a plan view is preferably 0.2 mm or more and 2 mm or less. In a plan view, it is preferable that the edge of the gas vent groove 21 is located outside the edge of the hole 13 over the entire circumference of the gas vent groove 21. This can further reduce the possibility that the gas vent groove 21 will be completely blocked by the magnet material 30.

[0022] The shape, size, number, etc. of the multiple holes 13 can be set according to the target value of the magnetic properties of the magnet unit 100. The multiple holes 13 may all be the same shape or may be different. The multiple holes 13 may all have the same opening area on the second end face 12 side or may be different. The number of multiple holes 13 provided in one holding member 10 is 2 or more, may be 8 or more, or may be 30 or more. The larger the number of holes 13, the easier it is to obtain the effect of simplifying the design by connecting two or more holes 13 with one gas vent groove 21, and also to obtain the effect of countermeasures against the increased possibility of differences in the time until the completion of filling. The number of multiple holes 13 provided in one holding member 10 can be 100 or less, may be 80 or less, or may be 60 or less, depending on the size of the holding member 10.

[0023] The holes 13 may have a plurality of first holes 13A whose opening area on the second end face 12 side is a first area, and a plurality of second holes 13B whose opening area on the second end face 12 side is a second area smaller than the first area. When different types of holes 13 are arranged in this way, the possibility that the time until filling is completed is different increases compared to when not arranged, so the effect of providing the gas vent groove 21 can be further obtained. One or more gas vent grooves 21 may have a first groove 21A. It is preferable that the first groove 21A connects at least one of the plurality of first holes 13A and at least one of the plurality of second holes 13B. Since the first hole 13A and the second hole 13B, which have different areas, tend to have a difference in the time until filling is completed, the first groove 21A connecting them to both of them can further reduce the possibility that the filled magnet material 30 overflows into the first groove 21A. The second area of ​​the second hole 13B may be 90% or less, or 80% or less, of the first area of ​​the first hole 13A. The second area of ​​the second hole 13B may be 20% or more, or 40% or more, of the first area of ​​the first hole 13A. 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.

[0024] When providing a gas vent groove 22 connected to only one hole 13, it is preferable that the hole 13 connected to the gas vent groove 22 is a hole 13 that takes a relatively long time to complete filling. This can reduce the possibility of the magnet material 30 overflowing into the gas vent groove 22. For example, between the first hole 13A and the second hole 13B, the first hole 13A, which has a larger opening area, tends to take a longer time to complete filling, so it is preferable that the gas vent groove 22 is connected to the first hole 13A.

[0025] 9 and 10, modified example 2 and modified example 3 of the arrangement of the holes 13 and the gas vent grooves 21 will be described. FIG. 9 is a schematic plan view showing modified example 2 of the arrangement of the holes 13 and the gas vent grooves 21. FIG. 10 is a schematic plan view showing modified example 3 of the arrangement of the holes 13 and the gas vent grooves 21. FIGS. 9 and 10 are plan views seen from the first end face 11 side. In FIGS. 9 and 10, the holding member 10 provided with the holes 13 is shown by solid lines, and the gas vent grooves 21 and 22 in the portion overlapping with the holding member 10 are shown by dashed lines. Modified examples 2 and 3 shown in FIGS. 9 and 10 differ from the examples shown in FIGS. 6 and 7 in the shape and arrangement of the holes 13. Even when such holes 13 are provided, the same effect as the above-mentioned example can be obtained by providing the gas vent grooves 21.

[0026] As shown in Fig. 10, two or more of the multiple first holes 13A may be connected by one gas vent groove 21 (first groove 21A). Two or more of the multiple second holes 13B may be connected by the first groove 21A. Two or more first holes 13A and two or more second holes 13B may be connected by the first groove 21A. This can further reduce the possibility that the filled magnet material 30 will overflow into the first groove 21A.

[0027] The holding member 10 is, for example, a rotor core. The shape of the holding member 10 is, for example, cylindrical. 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 the direction from the second end face 12 to the first end face 11. The laminated steel plate is, for example, an electromagnetic steel plate.

[0028] The mold 20 may be composed of a plurality of parts. By having the mold 20 composed of a plurality of parts, the holding member 10 can be easily fixed by the mold 20, and the holding member 10 can be easily removed from the mold 20. The mold 20 may be provided with a gate 23. The gate 23 is connected to the hole 13 on the side of the first end face 11. In each of the examples shown in the figures, a plurality of gas vent grooves 21 are provided independently, but these may be partially connected. When all the gas vent grooves 21 are connected, it can be said that the mold 20 is provided with only one gas vent groove 21.

[0029] (Injection molding process) In the injection molding step S102, the magnetic material 30 is injection molded into the multiple holes 13 from the side of the first end face 11. As shown in FIG. 4, the magnetic material 30 passes through the gate 23 of the mold 20 and reaches the holes 13. The magnetic material 30 is injected from above in FIG. 4. The injection molding can be performed, for example, until the holes 13 are completely filled with the magnetic material 30. The degree to which the holes 13 are filled before the injection molding is terminated can be appropriately set according to the magnetic properties of the target magnet unit.

[0030] The magnet material 30 includes a resin and a 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.

[0031] Examples of the thermoplastic resin include nylon resin (polyamide resin), polyolefins such as polypropylene (PP) and polyethylene (PE), polyesters, polycarbonates (PC), polyphenylene sulfide resins (PPS), polyether ether ketones (PEEK), polyacetals (POM), and liquid crystal polymers (LCP). Examples of the nylon resin include polylactams such as nylon 6, nylon 11, and nylon 12, condensates of dicarboxylic acids and diamines such as nylon 6,6, nylon 6,10, and nylon 6,12, copolymer polyamides such as 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, and nylon 6-nylon / polyether, nylon 6T, nylon 9T, nylon MXD6, aromatic nylon, and amorphous nylon. Examples of the thermoplastic resin include nylon 12.

[0032] The magnetic powder may be, for example, a rare earth magnetic powder such as SmFeN, NdFeB, or SmCo. The magnetic powder may be a SmFeN magnetic powder. In this case, the magnet material 30 includes a resin and a SmFeN magnetic powder. The SmFeN magnetic powder has a general formula of Sm x Fe 100-x-y N y The nitrides are made of rare earth metal Sm, iron Fe, and nitrogen N, and are preferably represented by the formula: 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 is preferably represented by the formula: Th2Zn 17 The magnetic powder may be an SmFeN magnetic powder having a crystal structure of the type. The magnetic powder may be an SmFeN anisotropic magnetic powder. The SmFeN magnetic powder can be produced, for example, by the method disclosed in JP-A-11-189811. The magnetic powder may have a SmFeN core and a coating containing P and O. The magnetic powder may be surface-treated with a silane coupling agent or the like.

[0033] The average particle size of the magnetic powder is preferably 10 μm or less. This allows the crystal grain size to be reduced, and the coercive force of the magnetic powder to 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 is reduced, the filling pressure increases, so when using magnetic powder with an average particle size of 10 μm or less, the effect of providing the gas vent groove 21 connecting two or more holes 13 is more likely to be obtained. In addition, the reduced fluidity of the magnetic material 30 reduces the possibility that the magnetic material 30 will overflow into the gas vent groove 21. The average particle size of the magnetic powder is more preferably 6 μm or less, and even more preferably 4 μm or less. This allows the coercive force of the magnetic powder to be further increased. The average particle size of the magnetic powder is preferably 1 μm or more. This allows the filling rate of the magnetic powder in the magnetic material 30 to be increased. The average particle size of the magnetic powder is more preferably 2 μm or more, and even more 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 even more preferably 2 μm or more and 4 μm or less. The average particle size is measured as the particle size corresponding to 50% of the cumulative volume 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 by Nippon Laser Co., Ltd.).

[0034] The span of the magnetic powder is defined as follows: Span = (D90-D10) / D50 (Here, particle sizes D90, D10, and D50 are particle sizes corresponding to 90%, 10%, and 50% of the integrated value of the particle size distribution.) can be 2 or less, and preferably 1.5 or less. If it exceeds 2, the proportion of fine magnetic powder with low coercivity increases, so the coercivity tends to decrease.

[0035] The filling rate of the magnetic powder in the magnet material 30 is preferably 50% by volume or more, and more preferably 60% by volume or more. This can improve the residual magnetic flux density of the resulting magnet 40. In addition, since the fluidity of the magnet material 30 tends to decrease as the filling rate of the magnetic powder in the magnet material 30 increases, the effect of providing the gas vent groove 21 connecting two or more holes 13 can be more easily obtained. In addition, the decrease in the fluidity of the magnet material 30 can reduce the possibility of the magnet material 30 overflowing into the gas vent groove 21.

[0036] When obtaining a magnet 40 in which the magnetic powder is oriented, an orientation magnetic field is applied to the magnet material 30 in the injection molding step S102. The application of the orientation magnetic field is started at least before the resin is completely solidified. By applying a magnetic field to the magnet material 30, the magnetization easy axis of the magnetic powder contained in the magnet material 30 can be aligned. In order to apply a magnetic field to the magnet material 30, an orientation magnet can be provided in the mold 20. An electromagnet or a permanent magnet can be used as the orientation magnet. When a permanent magnet is used as the orientation magnet, the injection molding and the application of the magnetic field are performed simultaneously. The magnitude of the orientation magnetic field can be, for example, 637 kA / m (8 kOe) or more and 1511 kA / m (19 kOe) or less.

[0037] (Process of removing the holding member from the mold) In step S103 of removing the holding member 10 from the mold 20, the holding member 10 is removed from the mold 20. This results in a magnet unit 100. The magnetic material 30 in the injection molding step S102 becomes magnets 40 in the magnet unit 100 shown in FIG. 5. The magnets 40 are provided in the holes 13 of the holding member 10 removed from the mold 20. The magnetic material 30 remaining in the gate 23 is separated from the magnetic material 30 filled in the holes 13 in or after step S103 of removing the holding member 10 from the mold 20.

[0038] A magnetizing step may be performed after the step S103 of removing the holding member 10 from the mold 20. When the magnetizing step is performed, the magnet unit 100 having the magnet 40 is obtained by going through the magnetizing step. In the magnetizing step, a magnetic field for magnetization is applied to the holding member 10 provided with the magnetic material 30. Examples of the magnetizing method include a pulse magnetic field generation method and a static magnetic field generation method. The magnitude of the magnetic field for magnetization in the magnetizing step can be, for example, 1990 kA / m (25 kOe) or more and 4777 kA / m (60 kOe) or less. The magnetic field for magnetization in the magnetizing step can be larger than the magnetic field for orientation in the injection molding step S102.

[0039] (Magnet unit) The magnet unit 100 of the embodiment will be described with reference to Fig. 5 and Fig. 11. Fig. 11 is a schematic plan view showing the magnet unit 100 of the embodiment. Fig. 11 is a plan view seen from the first end face 11 side. In Fig. 11, the groove trace 60 provided on the second end face 12 side is indicated by a dashed line.

[0040] The magnet unit 100 has a holding member 10 and a plurality of magnets 40. The holding member 10 is provided with a plurality of holes 13 penetrating from a first end face 11 to a 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 the first end face 11 side. The magnet unit 100 has a groove mark 60 connecting two or more of the plurality of magnets 40 on the second end face 12 side. The magnet unit 100 has a groove mark 60 connecting two or more of the plurality of holes 13 on the second end face 12 side.

[0041] The magnet unit 100 is, for example, a rotor. The holding member 10 is a member having holes 13 in which the magnets 40 are arranged. In the magnet unit 100 of the embodiment, the magnets 40 are filled in the holes 13. As described above, the holding member 10 is, for example, a rotor core.

[0042] The magnet 40 has a resin and a magnetic powder. The resin may be any of the materials described above as the resin constituting the magnet material 30. The magnetic powder may be any of the materials described above as the magnetic powder constituting the magnet material 30. The magnet 40 may have a resin and a SmFeN magnetic powder. The filling rate of the magnetic powder in the magnet 40 is preferably 50% by volume or more, more preferably 60% by volume or more. This can improve the residual magnetic flux density of the magnet 40. The volumetric ratio of the filling rate of the magnetic powder in the magnet 40 may be calculated from 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 is taken, and the ratio of the area of ​​the magnetic powder to the area of ​​the magnet 40 in the SEM image can be regarded as the volumetric ratio of the filling rate of the magnetic powder in the magnet 40.

[0043] The gate mark 50 is formed on the magnet 40. The gate mark 50 appears, for example, as a convex shape on the surface of the magnet 40 on the side of the first end face 11. The shape of the gate mark 50 in a plan view is, for example, circular or elliptical. One or more gate marks 50 are provided on one magnet 40.

[0044] The groove mark 60 is formed on at least one of the holding member 10 and the magnet 40. The groove mark 60 is observed as a continuous line or a fragmented line. The groove mark 60 may be observed, for example, by irradiating the second end face 12 with a light source from an oblique direction. The groove mark 60 on the holding member 10 is formed by pressing the mold 20 provided with the gas release groove 21 against the holding member 10. The groove mark 60 on the magnet 40 is formed by pressing the magnet material 30 with the mold 20 provided with the gas release groove 21. The groove mark 60 is formed at the location where the edge of the gas release groove 21 was. A step or unevenness formed on the second end face 12 of the holding member 10 may be observed as the groove mark 60. When the magnet material 30 is pushed out into the gas vent groove 21 and adheres to the groove trace 60 to remain as the magnet 40, the magnet 40 remaining in the groove trace 60 is not continuous from one hole 13 to the other hole 13 connected by the groove trace 60. That is, the magnet 40 provided in one hole 13 connected by the groove trace 60 is not connected to the magnet 40 provided in the other hole 13. At least a part of the groove trace 60 is exposed and not covered by the magnet 40. The magnet 40 may not remain in the groove trace 60. The entire groove trace 60 may be exposed and not covered by the magnet 40. The position and shape of the groove trace 60 can be the same as the position and shape of the gas vent groove 21 described above. In addition to the groove trace 60, a groove trace having the same position and shape as the gas vent groove 22 may be formed on the second end surface 12 side of the magnet unit 100.

[0045] In FIG. 11, the groove trace 60 is in the same position and shape as the gas release groove 21. The groove trace 60 may be a trace of only a part of the gas release groove 21. The groove trace 60 tends to be formed more easily on the magnet 40 than on the holding member 10. The groove trace 60 may be formed only on the magnet 40. When an extension line of one groove trace 60 coincides with an extension line of another groove trace 60, it may be determined that these are traces formed by one continuous groove. If an estimated shape formed by two or more groove traces 60 and their extension lines is in a position and shape connecting two or more of the multiple holes 13, it may be determined that it is a groove trace 60 connecting two or more of the multiple holes 13. If an estimated shape formed by two or more groove traces 60 and their extension lines is in a position and shape connecting two or more of the multiple magnets 40, it may be determined that it is a groove trace 60 connecting two or more of the multiple magnets 40. For example, if an extension line of a groove mark 60 formed on one magnet 40 coincides with an extension line of a groove mark 60 formed on another magnet 40, it can be determined that these are groove marks 60 connecting two or more of the multiple magnets 40. The example shown in Figure 11 corresponds to the example shown in Figure 6. When the edge of the gas vent groove 21 does not overlap with the hole 13 as in the example shown in Figure 7, the groove mark 60 is formed only on the holding member 10.

[0046] Through the contents described so far in this specification, the following technical matters are disclosed. (Section 1) a step of disposing a holding member having a plurality of holes penetrating from a first end surface to a second end surface in a mold having one or more gas vent grooves so that the second end surface faces the one or more gas vent grooves; injection molding a magnetic material into the holes from the first end surface side; and removing the holding member from the mold. A method for manufacturing a magnet unit, wherein in the step of placing the magnet unit in the mold, two or more of the plurality of holes are connected by the one or more gas vent grooves. (Section 2) Item 2. A method for manufacturing a magnet unit according to item 1, wherein in the step of placing the magnet in the mold, edges of the one or more gas vent grooves coincide with edges of the plurality of holes or are positioned outside edges of the plurality of holes. (Section 3) 2. The method for manufacturing a magnet unit according to item 1, wherein the one or more gas vent grooves include a plurality of grooves that extend radially in a plan view. (Section 4) The method for manufacturing a magnet unit described in any one of items 1 to 3, wherein the plurality of holes include a plurality of first holes whose opening area on the second end face side is a first area, and a plurality of second holes whose opening area on the second end face side is a second area smaller than the first area. (Section 5) 5. The method for manufacturing a magnet unit according to item 4, wherein in the step of placing in the mold, the one or more gas vent grooves have a first groove, and the first groove connects at least one of the plurality of first holes and at least one of the plurality of second holes. (Section 6) 6. The method for producing a magnet unit according to any one of items 1 to 5, wherein the magnet material contains a resin and an SmFeN-based magnetic powder. (Section 7) 7. The method for producing a magnet unit according to any one of Items 1 to 6, wherein the holding member is a rotor core. (Section 8) a holding member having a plurality of holes extending from the first end surface to the second end surface; a plurality of magnets disposed in the plurality of holes, There is a gate mark on the side of the first end surface, A magnet unit having a groove trace connecting two or more of the plurality of holes on the second end face side. [Explanation of symbols]

[0047] 10 Retaining member 11 First end surface 12 Second end face 13 holes 13A 1st hole 13B 2nd hole 14 Side 20 Mold 21, 22 Gas vent groove 21A 1st groove Gate 23 30 Magnetic Materials 40 Magnet 50 Gate Mark 60 Groove marks 100 magnet units

Claims

1. a step of placing a holding member having a plurality of holes penetrating from a first end surface to a second end surface in a mold having one or more gas vent grooves such that the second end surface faces the one or more gas vent grooves; injection molding a magnetic material into the holes from the first end surface side; and removing the holding member from the mold. A method for manufacturing a magnet unit, wherein in the step of placing the magnet in the mold, two or more of the plurality of holes are connected by the one or more gas vent grooves.

2. The method for manufacturing a magnet unit according to claim 1 , wherein in the step of placing in the mold, the edges of the one or more gas vent grooves coincide with the 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 , wherein the one or more gas vent grooves include a plurality of grooves that extend radially in a plan view.

4. 2. A method for manufacturing a magnet unit as described in claim 1, wherein the plurality of holes include a plurality of first holes whose opening area on the second end face side is a first area, and a plurality of second holes whose opening area on the second end face side is a second area smaller than the first area.

5. The method for manufacturing a magnet unit according to claim 4, wherein in the step of placing in the mold, the one or more gas vent grooves have a first groove, and the first groove connects at least one of the plurality of first holes and at least one of the plurality of second holes.

6. The method for manufacturing a magnet unit according to any one of claims 1 to 5, wherein the magnetic material includes a resin and an SmFeN magnetic powder.

7. The method for manufacturing a magnet unit according to claim 6 , wherein the holding member is a rotor core.

8. a holding member having a plurality of holes extending from the first end surface to the second end surface; a plurality of magnets disposed in the plurality of holes, A gate mark is present on the first end surface side, A magnet unit having a groove trace connecting two or more of the plurality of holes on the second end face side.

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