Manufacturing method of magnet unit and magnet unit

Abstract

Provided are a method for manufacturing a magnet unit and a magnet unit capable of suppressing deformation of a holding member. Provided is a method for manufacturing a magnet unit having a holding member provided with a plurality of grooves and bonded magnets disposed inside each of the plurality of grooves. The manufacturing method includes the steps of: injecting a magnet material through a plurality of gates from an opening on one end side of each of the plurality of grooves; and cutting the magnet material in the plurality of gates, the cross-sectional area of each of the plurality of gates being set so that the internal pressure of the magnet material does not exceed a threshold value at which the holding member is plastically deformed inside each of the plurality of grooves, and the threshold value being calculated on the basis of the shape of the holding member.

Description

Technical Field

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

[0002] Patent Document 1 describes an embedded magnet type motor including a magnet embedded in a hole of a rotor core. In the hole of the rotor core, a bonded magnet is formed by injection molding.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015 - 61430

[0004] When injecting a material of a bonded magnet into a hole of a magnet unit such as a rotor core, due to the internal pressure generated inside the hole, there may sometimes occur a problem that a holding member of the magnet unit is deformed. Summary of the Invention

[0005] Technical Problem to be Solved by the Invention

[0006] Embodiments of the present disclosure are achieved in view of the above problems, and an object thereof is to provide a method for manufacturing a magnet unit and a magnet unit capable of suppressing deformation of a holding member.

[0007] Technical Solution for Solving the Technical Problem

[0008] In one aspect of the present disclosure, there is provided a method for manufacturing a magnet unit having a holding member provided with a plurality of grooves and a bonded magnet disposed inside each of the plurality of grooves. The manufacturing method includes the following steps: injecting a magnet material through a plurality of gates respectively from openings on one end side of each of the plurality of grooves; and cutting the magnet material in the plurality of gates, and a cross-sectional area of each of the plurality of gates is set such that an internal pressure of the magnet material does not exceed a threshold value of plastic deformation of the holding member inside each of the plurality of grooves, and the threshold value is calculated based on the shape of the holding member.

[0009] A magnet unit according to one aspect of the present disclosure has a holding member provided with a plurality of grooves and a bonded magnet disposed inside each of the plurality of grooves. The magnet unit includes a pair of end faces formed with a plurality of grooves penetrating therethrough along a central axis, and the bonded magnet has gate marks formed when the magnet material is injected into the inside of the grooves from one side of the pair of end faces, and areas of the gate marks having different radial distances from the central axis are different from each other.

[0010] Advantageous Effects of the Invention

[0011] According to embodiments of the present disclosure, there can be provided a method for manufacturing a magnet unit and a magnet unit capable of suppressing deformation of a holding member. Brief Description of the Drawings

[0012] Figure 1Is a perspective view of the magnet unit 1 of the embodiment.

[0013] Figure 2 Is a top view of the magnet unit 1.

[0014] Figure 3 Is a flowchart for explaining the manufacturing process of the magnet unit 1.

[0015] Figure 4 Is a schematic diagram for explaining the intensity simulation in the threshold calculation process (S100).

[0016] Figure 5 Is a chart for explaining the threshold of the internal pressure in the threshold calculation process (S100).

[0017] Figure 6 Is a sectional view for explaining the arrangement in the mold in the arrangement process (S300).

[0018] Figure 7 Is a perspective view schematically showing a plurality of flow paths 21 provided in the mold 20.

[0019] Figure 8 Is a top view schematically showing a plurality of flow paths 21 provided in the mold 20.

[0020] Figure 9 Is a sectional view for explaining the injection process (S400).

[0021] Figure 10 Is a perspective view of the magnet unit 2 of the modified example.

[0022] Figure 11 Is a top view of the magnet unit 2.

[0023] Figure 12 Is a top view schematically showing a plurality of flow paths 21 provided in the mold 20 in the modified example. Specific embodiments

[0024] Hereinafter, with reference to the accompanying drawings, the magnet unit and the manufacturing method of the magnet unit of the embodiment of the present disclosure are described. The method shown below illustrates the magnet unit and the manufacturing method of the magnet unit for concretizing the technical idea of ​​the present embodiment, and is not limited to the following. In addition, the size, material, shape, relative configuration, etc. of the constituent parts described in the embodiment are not the purpose of limiting the scope of the present disclosure to this only, as long as there is no specific description, but are only simple illustrative examples. In addition, the size, positional relationship, etc. of the components shown in the various drawings are sometimes exaggerated for clear explanation. In the following description, for the components with the same name and figure mark representing the same or the same nature, detailed description is appropriately omitted. In the following description, "area" refers to the "area" when viewed from above unless otherwise specified. In addition, "shape" is used as a concept that includes size. For example, when two shapes are similar to each other but different in size, the two shapes are different.

[0025] <1. First embodiment>

[0026] (1.1. Magnet unit 1)

[0027] use Figure 1 as well as Figure 2 , a magnet unit 1 according to a first embodiment will be described. The magnet unit 1 is a rotor core as an example, and includes a holding member 10 and a plurality of bonded magnets 40. The holding member 10 is Figure 1 As shown, as an example, it is formed into a cylindrical shape and has an outer side surface 13 along the central axis A of the holding member 10 and a pair of end surfaces orthogonal to the central axis A, namely, a first end surface 11 and a second end surface 12. The holding member 10 is provided with a plurality of grooves 14 as holes that pass from the first end surface 11 to the second end surface 12 along the central axis A. A plurality of bonded magnets 40 are respectively arranged inside each of the plurality of grooves 14. A gate mark 50 is formed on an exposed surface 41 of the bonded magnet 40 exposed on the first end surface 11 side.

[0028] The holding member 10 may be a magnetic body, and as an example, the holding member 10 may be a laminated steel plate composed of a plurality of steel plates laminated in a direction from the second end surface 12 toward the first end surface 11. The laminated steel plate may be, for example, an electromagnetic steel plate.

[0029] The bonded magnet 40 includes a resin and magnetic powder. As the resin constituting the magnet material 30, the materials described later can be used. As the magnetic powder constituting the magnet material 30, the materials described later can be used. As an example, the bonded magnet 40 can have a resin and SmFeN-based magnetic powder. The content rate of the magnetic powder in the bonded magnet 40 is preferably 50% by volume or more, more preferably 60% by volume or more. Thereby, the residual magnetic flux density of the bonded magnet 40 can be increased. The volume ratio of the filling rate of the magnetic powder in the bonded magnet 40 can also be calculated based on the cross-section of a part of the bonded magnet 40. For example, a scanning electron microscope (SEM) image of the cross-section of a part of the bonded magnet 40 can be taken, and the ratio of the area of the magnetic powder in the SEM image to the area of the bonded magnet 40 can be regarded as the volume ratio of the filling rate of the magnetic powder in the bonded magnet 40.

[0030] The shape, size, number, etc. of the plurality of grooves 14 provided in the holding member 10 are set according to the target values of the magnetic characteristics of the magnet unit 1. As an example, the number of the plurality of grooves 14 is 2 or more, and can also be 8 or more, or 30 or more.

[0031] Preferably, the magnet unit 1 has rotational symmetry with respect to the central axis A. In the present embodiment, as an example, the grooves 14 are provided in the holding member 10 with 4-fold symmetry with respect to the central axis A. That is, as Figure 2 shown, in a plan view, with respect to the central axis A, the grooves 14 are formed in a manner having rotational symmetry every 90°. The groove 14 includes: an outer groove 14a that is curved in an arc shape in a direction opposite to the outer side surface 13 of the holding member 10 in a plan view; and an inner groove 14b that is disposed closer to the central axis A side than the outer groove 14a and is curved in an arc shape in the same direction as the outer groove 14a. The inner groove 14b is divided into three, including a central portion 14b1 and two end portions 14b2.

[0032] In addition, the shapes of the plurality of grooves 14 in a plan view can all be similar shapes to each other (that is, shapes that are substantially the same when one is enlarged or reduced and the other is compared), or a part of them can be set to be similar shapes to each other, and the other parts can be set to be different shapes. In this case, in the region having rotational symmetry with respect to the central axis A, it can also be a manner in which a plurality of grooves 14 having similar shapes and one or more grooves 14 having different shapes are mixedly present.

[0033] The ratio of the width W to the depth H in the plurality of grooves 14 preferably satisfies the relationship of 1 / 10 ≤ W / H ≤ 1 / 50, and more preferably satisfies the relationship of 1 / 20 ≤ W / H ≤ 1 / 50. Thus, the larger the depth H is relative to the width W, the more difficult it is to fill the plurality of grooves 14 simultaneously, and thus the effect of the technical idea of the present disclosure is easily obtained. In addition, when viewed from above, when the area of the largest groove 14 is set as Smax and the area of the smallest groove 14 is set as Smin, it is preferably to satisfy the relationship of 1 / 1 ≤ Smin / Smax ≤ 1 / 10. Thus, the larger the difference in area between the plurality of grooves 14 when viewed from above, the more difficult it is to fill the plurality of grooves 14 simultaneously, and thus the effect of the technical idea of the present disclosure is easily obtained.

[0034] The gate mark 50 formed on the exposed surface 41 of the bonded magnet 40 is formed when injecting the magnet material 30 from the first end face 11 side into the inside of the groove 14. As an example, the gate mark 50 has, for example, a convex shape on the exposed surface 41. The shape of the gate mark 50 when viewed from above is, for example, circular, elliptical, or doubloon-shaped. One or more gate marks 50 are provided on one bonded magnet 40.

[0035] The gate mark 50 includes a first gate mark 50a and a second gate mark 50b. The area of the gate mark 50 is different when the distances from the central axis A are different. The first gate mark 50a is located at a position where the distance (hereinafter, also simply referred to as the distance) when viewed from above is longer than that of the second gate mark 50b with respect to the central axis A, and the area of the first gate mark 50a is larger than the area of the second gate mark 50b. As Figure 2 shown, the central portion 14b1 of the inner groove 14b has the second gate mark 50b, and the end portion 14b2 of the inner groove 14b and the outer groove 14a have the first gate mark 50a.

[0036] (1.2. Manufacturing method of the magnet unit 1)

[0037] Hereinafter, using Figures 3 to 9 , the manufacturing method of the magnet unit 1 in the present disclosure will be described in detail. In addition, in this specification, the term "process" not only includes an independent process, but also includes this term even when it cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0038] As Figure 3 shown, the manufacturing process of the magnet unit 1 of the embodiment has a threshold calculation process S100, a gate area setting process S200, an arrangement process S300, an injection process S400, and a removal process S500. Hereinafter, each process will be described in detail.

[0039] (1.2.1. Threshold calculation process)

[0040] In the threshold calculation process (S100), a threshold of the internal pressure generated when injecting the magnet material 30 into the inside of the groove 14 in the subsequent injection process (S400) is calculated. As an example, this threshold can be obtained as the pressure of plastic deformation of the magnet unit 1 through strength analysis simulation based on the shape of the holding member 10.

[0041] Specifically, for example, a well-known finite element analysis software is used to perform strength analysis simulation. In this simulation, three-dimensional model data representing the shape of the holding member 10 and information related to the material of the holding member 10 are used as input parameters for strength analysis. As information related to the material of the holding member 10, for example, materials, material qualities (specifications), manufacturers, Young's modulus, Poisson's ratio, yield stress (F1), tensile strength, coefficient of linear expansion, etc. can be cited.

[0042] As an example, in the case of performing strength analysis simulation on the holding member 10 with the Figure 4 shown shape, as the parts that may cause plastic deformation due to the internal pressure in the groove 14, parts B1 between the end 14b2 of the inner groove 14b and the outer side surface 13, part B2 between the central part 14b1 and the end 14b2 of the inner groove 14b, part B3 between the outer groove 14a and the outer side surface 13, etc. can be cited. Therefore, if strength analysis simulation is performed on these parts, for example, a Figure 5 shown graph can be obtained as the analysis result.

[0043] In the Figure 5 shown graph, the equivalent stress that may be generated at parts B1 to B3 when increasing the internal pressure in the injection process is shown. If the equivalent stress exceeds the yield stress F1 of the holding member 10, plastic deformation occurs. According to the Figure 5 shown analysis result, it can be read that plastic deformation may occur at part B3 when the internal pressure is P1. Thus, the threshold of the internal pressure when injecting the magnet material 30 into the groove 14 of the holding member 10 is calculated as P1.

[0044] (1.2.2. Gate area setting process)

[0045] In the gate area setting process (S200), the cross-sectional area of the gate 24 (refer to Figure 6 ) when injecting the magnet material 30 into the inside of the groove 14 in the subsequent injection process (S400) is set. In addition, in the present disclosure, the cross-sectional area of the gate 24 refers to the cross-sectional area of the opening of the gate 24. This cross-sectional area is set through flow analysis simulation.

[0046] Specifically, for example, a flow analysis simulation related to the filling of the magnet material 30 into the groove 14 is performed using known flow analysis software. In this simulation, three-dimensional model data representing the shape of the holding member 10, information related to the material of the magnet material 30 injected into the groove 14 in the injection process, information related to the molding conditions during the injection process, and information related to the cross-sectional area of the gate 24 are input as input parameters into the flow analysis software. As information related to the material of the magnet material 30, the material name, the mixing ratio of the materials, etc. can be cited. As information related to the molding conditions, the resin temperature, the mold temperature, the injection speed (or injection pressure), etc. can be cited.

[0047] If the flow analysis simulation is executed, it is possible to analyze how the magnet material 30 is filled in each groove 14 of the holding member 10 having the input shape. For example, when the cross-sectional area of the gate 24 for injecting the magnet material into each groove 14 of the holding member 10 is set to be constant, at the timing when the filling of the central portion 14b1 of the inner groove 14b is completed, an analysis result that the filling of the other grooves 14 (that is, the end portion 14b2 of the inner groove 14b and the outer groove 14a) is not completed is output. Thus, if there is a deviation in the filling timing of each groove 14, the internal pressure inside the groove 14 with a fast filling speed rises sharply, which may cause plastic deformation in the holding member 10. Therefore, in the present embodiment, the cross-sectional areas of the plurality of gates 24 are set so that the filling is performed at substantially the same timing in the plurality of grooves 14. In addition, in the present disclosure, "filling at substantially the same timing" means that at a certain moment, the filling rate of the plurality of grooves 14 becomes 90% to 100%, and more preferably means that the filling rate of the plurality of grooves 14 becomes 95% to 100%.

[0048] Specifically, for example, the cross-sectional areas of the plurality of gates 24 are set such that the farther the gate 24 is from the sprue 22 (refer to Figure 7 , Figure 8 ), when viewed from above, the larger the cross-sectional area of the gate 24 is. That is, by reducing the cross-sectional area of the gate 24 facing the central portion 14b1, it is possible to adjust to fill the magnet material 30 at the same timing as the other grooves 14 (the end portion 14b2 of the inner groove 14b and the outer groove 14a). In addition, when the cross-sectional shape of the gate 24 is circular, the cross-sectional area of the gate 24 can also be set by setting the diameter of the gate 24. In addition, the diameter of the gate 24 refers to the diameter of the opening of the gate 24.

[0049] In addition, in the flow analysis simulation, the pressure generated inside the groove 14 is also analyzed in coordination with the timing of filling the groove 14. In this way, the cross-sectional area of each of the plurality of gates 24 is set such that the internal pressure generated by the bonded magnet material does not exceed the threshold value for plastic deformation of the holding member 10 calculated in the threshold calculation step (S100) inside each of the plurality of grooves 14.

[0050] (1.2.3. Arrangement step)

[0051] In the arrangement step (S300), the holding member 10 is arranged in the mold 20. As Figure 6 shown, the mold 20 is composed of a plurality of components. Since the mold 20 is composed of a plurality of components, it is easy to fix the holding member 10 using the mold 20, and in addition, the holding member 10 can be easily removed from the mold 20. A plurality of flow paths 21 for the magnet material 30 to flow through are provided in the mold 20.

[0052] Figure 7 And Figure 8 Schematically shows the plurality of flow paths 21 provided in the mold 20. As Figure 7 And Figure 8 shown, the plurality of flow paths 21 have a sprue 22 extending in the vertical direction, a plurality of runners 23 extending horizontally from the sprue, and a plurality of gates 24 extending from the plurality of runners 23 toward the holding member 10 side. As an example, the sprue 22 is arranged on the extension line of the central axis A of the holding member 10. The gate 24 is provided at the end of the plurality of runners 23 and is arranged opposite to the opening of the groove 14 on the first end face 11.

[0053] A pressure sensor 25 is also provided in the mold 20. As an example, as Figure 6 shown, the pressure sensor 25 is arranged opposite to the opening on the second end face side of the groove 14. Thereby, the internal pressure of the magnet material 30 filled in the groove 14 can be accurately measured.

[0054] As Figure 8 shown, in a plan view, the flow path 21 has rotational symmetry of 90° with respect to the central axis A of the holding member 10. The runner 23 has an extension portion 23a extending radially from the sprue 22 and a branch portion 23b branched from the extension portion 23a. In this way, by arranging the sprue 22 on the extension line of the central axis A of the holding member 10 and arranging the plurality of runners 23 extending horizontally from the sprue 22 and the plurality of gates 24 extending from the plurality of runners 23 symmetrically with respect to the central axis A, it is easy to evenly fill the magnet material 30 into each groove 14.

[0055] In addition, as described above, the cross-sectional areas of the plurality of gates 24 are set such that the gate 24 that is farther from the sprue 22 from which the magnet material 30 flows out has a larger cross-sectional area. As Figure 8 shown, the gate 24 includes a first gate 24a and a second gate 24b. The first gate 24a is farther from the sprue 22 than the second gate 24b, and the cross-sectional area of the first gate 24a is larger than the cross-sectional area of the second gate 24b.

[0056] (1.2.4. Injection process)

[0057] In the injection process (S400), the magnet material 30 is injected into the plurality of grooves 14 by injection molding, and the magnet material 30 is filled in the grooves 14. As Figure 9 shown, the magnet material 30 is injected into the mold 20 from the sprue 22, and reaches the groove 14 via the runner 23 and the gate 24. The injection process can be performed, for example, until the groove 14 is filled with the magnet material 30. The state at which injection molding ends in terms of the degree of filling can be appropriately set according to the magnetic characteristics of the target magnet unit.

[0058] The magnet material 30 has a resin and magnetic powder. The resin may be a thermoplastic resin or a thermosetting resin. The resin may also include both a thermosetting resin and a thermoplastic resin. The resin is, for example, a thermoplastic resin, but even if a thermosetting resin is used, the technical idea in the present disclosure can be appropriately implemented.

[0059] Examples of the thermoplastic resin 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), etc. Examples of the nylon resin include polycaprolactams such as nylon 6, nylon 11, and nylon 12; condensates of dicarboxylic acids and diamines such as 6,6 nylon, 6,10 nylon, and 6,12 nylon; copolyamides such as 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, 6-nylon / polyether; nylon 6T, nylon 9T, nylon MXD6, aromatic nylon, amorphous nylon, etc. As the thermoplastic resin, for example, 12 nylon can be used.

[0060] Examples of the magnetic powder include rare earth magnetic powders such as SmFeN-based, NdFeB-based, and SmCo-based magnetic powders. The magnetic powder may also be a SmFeN-based magnetic powder. In this case, the magnet material 30 has a resin and a SmFeN-based magnetic powder. As the SmFeN-based magnetic powder, those having a general formula of Sm x Fe 100－x－y Ny A nitride composed of rare earth metal Sm, iron Fe, and nitrogen N is shown. 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 a SmFeN-based magnetic powder having a Th2Zn17-type crystal structure. The magnetic powder can also be a SmFeN-based anisotropic magnetic powder. The SmFeN-based magnetic powder can be manufactured, for example, by the method disclosed in Japanese Patent Laid-Open No. 11-189811. The magnetic powder can also have a core portion containing SmFeN and a covering portion of P and O. The magnetic powder can also be surface-treated using a silane coupling agent or the like.

[0061] The average particle size of the magnetic powder is preferably 10 μm or less. Thereby, the crystal grain 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 more likely the fluidity of the magnet material 30 is to decrease. The average particle size of the magnetic powder is more preferably 6 μm or less, and further preferably 4 μm or less. Thereby, 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. Thereby, the filling rate of the magnetic powder in the magnet material 30 can be increased. The average particle size of the magnetic powder is more 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 the particle size corresponding to 50% of the volume cumulative from the small particle size side in the particle size distribution, and can be measured, for example, by a laser diffraction type particle size distribution measuring device (HELOS&RODOS of Nippon Laser Co., Ltd.).

[0062] The span of the magnetic powder defined as follows:

[0063] Span = (D90 - D10) / D50

[0064] (Here, the particle sizes D90, D10, and D50 refer to the particle sizes corresponding to 90%, 10%, and 50% of the cumulative value of the particle size distribution.) can be set to 2 or less, preferably 1.5 or less. If it exceeds 2, the proportion of fine magnetic powder with a small coercive force increases, and thus there is a tendency for the coercive force to decrease.

[0065] The filling rate of the magnetic powder in the magnet material 30 is preferably 50% by volume or more, more preferably 60% by volume or more. Thereby, the residual magnetic flux density of the obtained bonded magnet 40 can be improved.

[0066] In order to obtain a bonded magnet 40 in which magnetic powder is oriented, in the injection step (S400), a step of magnetizing the magnet material 30 by applying an orientation magnetic field may also be performed. The application of the orientation magnetic field starts at least before the resin is completely solidified. By applying a magnetic field to the magnet material 30, the easy magnetization axes of the magnetic powder contained in the magnet material 30 can be made to coincide. In order to apply a magnetic field to the magnet material 30, an orientation magnet may be provided in the mold 20. As the orientation magnet, an electromagnet or a permanent magnet can be used. In the case where a permanent magnet is used as the orientation magnet, injection molding and the application of the magnetic field are performed simultaneously. The magnitude of the orientation magnetic field can be set, for example, to 637 kA / m (8 kOe) or more and can be set to 1511 kA / m (19 kOe) or less.

[0067] (1.2.5. Removal step)

[0068] In the removal step (S500), the holding member 10 is removed from the mold 20. Thereby, the magnet unit 1 can be obtained. In the case where the magnetization step is performed in the injection step (S400), the magnet material 30 injected into the inside of the groove 14 becomes the bonded magnet 40 in the removed magnet unit 1. The magnet material 30 remaining in the gate 24 is cut off at the opening of the gate 24 and is cut off from the bonded magnet 40 in the groove 14. Thereby, a gate mark 50 is formed on the exposed surface 41 of the bonded magnet 40, and the area of the gate mark 50 is substantially equal to the cross-sectional area of the gate diameter.

[0069] After the removal step (S500), a step of magnetizing the magnet material 30 twice may also be performed. In this case, a magnetic field for secondary magnetization is applied to the holding member 10 that holds the magnet material 30 in the groove 14. As the magnetization method, a pulsed magnetic field generation method, a static magnetic field generation method, etc. can be cited. The magnitude of the magnetic field for magnetization in the magnetization step can be set, for example, to 1990 kA / m (25 kOe) or more and can also be set to 4777 kA / m (60 kOe) or less. The magnetic field for magnetization in the step of magnetizing twice can be larger than the orientation magnetic field in the injection step (S400). Thereby, the magnet unit 1 that can maximize the magnetic force of the bonded magnet 40 in the groove 14 can be obtained.

[0070] After the removal step (S500), in S600, it is determined whether there is a defect in the magnet unit 1. As a defect, for example, it can be cited that the magnet unit 1 has undergone plastic deformation, the measured value of the pressure sensor 25 provided in the mold 20 exceeds a predetermined threshold value, etc.

[0071] In the case where there is a defect in the magnet unit 1 (Yes in S600), the molding conditions are changed and injection molding is performed again. For example, if the injection speed into the mold 20 is slow, it is easy to preferentially inject into the groove 14 close to the sprue 22. In addition, if the resin temperature is high, the fluidity of the magnet material 30 becomes high, so even under a lower injection pressure, it is easy to inject into the groove 14 at a long distance from the center. In the case where the defect cannot be eliminated even after changing the molding conditions in this way, the gate area setting process (S200) is performed again. On the other hand, in the case where there is no defect in the magnet unit 1 or the defect has been eliminated (No in S600), the manufacturing process is terminated.

[0072] (1.3. Summary)

[0073] As described above, the magnet unit 1 in the present disclosure includes: a holding member 10 provided with a plurality of grooves 14; and bonded magnets 40 disposed inside each of the plurality of grooves 14. The manufacturing method of the magnet unit 1 includes the following steps: injecting the magnet material 30 through the openings on one end side of each of the plurality of grooves 14 via a plurality of gates 24 respectively; and cutting off the magnet material 30 in the plurality of gates. The cross-sectional area of each of the plurality of gates 24 is set such that the internal pressure of the magnet material 30 does not exceed the threshold value of plastic deformation of the holding member 10 inside each of the plurality of grooves 14, and this threshold value is calculated based on the shape of the holding member 10.

[0074] By adopting such a configuration, the internal pressure generated in the groove 14 can be suppressed, and the deformation of the holding member 10 can be prevented.

[0075] In addition, the cross-sectional area of each of the plurality of gates 24 can also be set so as to be filled at the same timing in the plurality of grooves 14. By adopting such a configuration, it is possible to prevent the internal pressure in the groove 14 from rising sharply due to the premature filling of the magnet material 30 in a part of the plurality of grooves 14.

[0076] In addition, it may be that in the step of injecting the magnet material 30, the magnet material 30 is injected into the groove 14 through a sprue 22 disposed on the extension line of the central axis of the holding member 10, a plurality of runners 23 branched radially of the magnet unit 1 from the sprue 22, and a plurality of gates 24 that are the terminals of the plurality of runners 23. The cross-sectional area of the plurality of gates 24 is set such that the gate 24 at a longer distance from the sprue 22 has a larger cross-sectional area. By adopting such a configuration, the flow rate of the magnet material 30 flowing through the gate 24 that is difficult to fill due to the long distance from the sprue 22 can be increased, and it is easy to fill the plurality of gates 24 at substantially the same timing.

[0077] Alternatively, the cross-sectional shape of the gate can be made circular, and the diameter of the gate can be set to thereby set the cross-sectional area of the gate. By adopting such a configuration, it is easy to set the cross-sectional area of the gate 24 provided in the mold 20 to an optimal value.

[0078] (1.4. Modification Example)

[0079] Refer to Figures 10 to 12 , and the magnet unit 2 of the modification example of the present embodiment will be described centering on the differences from the above-described embodiment. In addition, for the same configurations as those in the above-described embodiment, the same reference numerals are given and will not be described repeatedly.

[0080] As Figure 10 and Figure 11 shown, the shape and number of the grooves 14 of the magnet unit 2 of the modification example are different from those of the above-described magnet unit 1. Specifically, the inner groove 14b in the magnet unit 2 is not divided into three, but is connected into an arc shape in the direction opposite to the outer side surface 13 of the holding member 10. In addition, the area of the first gate mark 50a provided in the outer groove 14a is smaller than the area of the second gate mark 50b provided in the inner groove 14b.

[0081] In addition, regarding the size relationship between the cross-sectional area of the gate 24a opposed to the outer groove 14a and the cross-sectional area of the gate 24b opposed to the inner groove 14b, it can also be appropriately changed according to the volume of the groove 14 and the molding conditions. As an example, when the diameter of the gate 24a is set to B, the volume of the outer groove 14a is set to D, the diameter of the gate 24b is set to A, and the volume of the inner groove 14b is set to C, when C / D ≤ 0.4, it is preferable that A ≤ B, and when 2.5 ≤ C / D, it is preferable that B ≤ A.

[0082] As Figure 12 shown, in the flow path 21 in the mold 20 used when manufacturing the magnet unit 2, the runner 23 only has an extension portion 23a extending radially from the sprue 22. In addition, the first gate 24a is longer in distance from the sprue 22 than the second gate 24b, and the cross-sectional area of the first gate 24a is smaller than the cross-sectional area of the second gate 24b. Thus, in the modification example, the inner groove 14b is connected and the volume becomes larger, so it is set such that the cross-sectional area of the second gate 24b opposed to the inner groove 14b is larger than the cross-sectional area of the first gate 24a opposed to the outer groove 14a to allow more magnet material 30 to flow. Even for the magnet unit 2 in this manner, the technical idea of the present disclosure can be applied to obtain the same effects as those in the above-described embodiment.

[0083] <2. Other Embodiments>

[0084] As described above, the embodiments of the present disclosure have been explained, but are not limited to the above. For example, in the above embodiment, the holding member 10 is formed in a cylindrical shape, but it may be other shapes. Further, in the above embodiment, the groove 14 includes an outer groove 14a and an inner groove 14b and has rotational symmetry with four-fold symmetry in a plan view, but is not limited to this example. That is, the outer groove 14a and the inner groove 14b may be connected, or may have n-fold symmetry different from four-fold symmetry. Specifically, it may be rotational symmetry with an even number such as n = 2, 6, 8, etc., or rotational symmetry with an odd number such as n = 3, 5, 7, etc. Alternatively, it may not have rotational symmetry.

[0085] Further, in the above embodiment, the presence or absence of defects is confirmed after the taking-out step (S500), but it may be that once the cross-sectional area of the appropriate gate 24 and the molding conditions are determined, the presence or absence of such defects is not confirmed, and instead, the threshold calculation step (S100) to the taking-out step (S500) are performed to manufacture the magnet unit 1.

[0086] Further, in the above embodiment, as an example of the magnet unit, a rotor core is disclosed, but is not limited to this embodiment. That is, the technical idea of the present disclosure can also be applied to magnet units other than the rotor core having a holding member and a bonded magnet, and the same effects as those of the above embodiment can be obtained.

[0087] The present disclosure includes the following aspects.

[0088] (Supplementary Note 1)

[0089] A method for manufacturing a magnet unit, the magnet unit having a holding member provided with a plurality of grooves and bonded magnets disposed inside each of the plurality of grooves, the method for manufacturing the magnet unit including the following steps: injecting a magnet material through a plurality of gates respectively from openings on one end side of each of the plurality of grooves; and cutting the magnet material in the plurality of gates, the cross-sectional area of each of the plurality of gates being set such that the internal pressure of the magnet material does not exceed a threshold value of plastic deformation of the holding member inside each of the plurality of grooves, the threshold value being calculated based on the shape of the holding member.

[0090] (Supplementary Note 2)

[0091] According to the method for manufacturing a magnet unit described in Supplementary Note 1, the cross-sectional area of each of the plurality of gates is set so as to fill the plurality of grooves at substantially the same timing.

[0092] (Supplementary Note 3)

[0093] According to the method for manufacturing a magnet unit described in Supplementary Note 1, in the injection step, the magnet material is injected into the groove through a sprue arranged in the direction along the central axis of the holding member, a plurality of runners branched in the radial direction of the magnet unit from the sprue, and the plurality of gates that are the terminals of the plurality of runners. The cross-sectional area of the plurality of gates is set such that the gate farther away from the sprue in a top view has a larger cross-sectional area.

[0094] (Supplementary Note 4)

[0095] According to the method for manufacturing a magnet unit described in Supplementary Note 3, the sprue is arranged on the extension line of the central axis.

[0096] (Supplementary Note 5)

[0097] According to the method for manufacturing a magnet unit described in Supplementary Note 3, the cross-sectional shape of the gate is circular.

[0098] (Supplementary Note 6)

[0099] According to the method for manufacturing a magnet unit described in Supplementary Note 1, the following step is included: a pressure sensor is provided so as to face the opening on the side opposite to the gate of the groove, and the internal pressure generated in the groove is measured.

[0100] (Supplementary Note 7)

[0101] A magnet unit includes a holding member provided with a plurality of grooves and bonded magnets arranged inside each of the plurality of grooves. The bonded magnets have gate marks on one end face side, and the areas of the gate marks at different radial distances with respect to the central axis of the holding member are different.

[0102] (Supplementary Note 8)

[0103] According to the magnet unit described in Supplementary Note 7, the gate mark at a position farther away from the central axis in a top view has a larger area.

[0104] As described above, the embodiments of the present disclosure have been described with reference to specific examples. However, the present disclosure is not limited to these specific examples. All modes that those skilled in the art can appropriately design and implement based on the above embodiments of the present disclosure as long as they include the gist of the present disclosure are within the scope of the present disclosure. In addition, as long as they are those skilled in the art, various modification examples and correction examples that can be conceived within the scope of the idea of the present disclosure also belong to the scope of the present disclosure.

[0105] Explanation of reference numerals

[0106] 1, 2: Magnet units, 10: Holding member, 11: First end face, 12: Second end face, 13: Outer side face, 14: Groove, 14a: Outer groove, 14b: Inner groove, 14b1: Central portion, 14b2: End portion, 20: Mold, 21: Flow path, 22: Sprue, 23: Runner, 24: Gate, 25: Pressure sensor, 30: Magnet material, 40: Bonded magnet, 41: Exposed surface, 50: Gate mark, 50a: First gate mark, 50b: Second gate mark.

Claims

1. A method for manufacturing a magnet unit, characterized in that: The magnet unit includes a holding member having a plurality of grooves and a bonded magnet disposed inside each of the plurality of grooves. The manufacturing method of the magnet unit includes the following steps: injecting the magnet material from the openings at one end of each of the plurality of grooves through the plurality of gates; as well as cutting off the magnet material in the plurality of gates, The cross-sectional area of ​​each of the plurality of gates is set so that the internal pressure of the magnetic material in each of the plurality of grooves does not exceed a threshold value of plastic deformation of the holding member. The threshold value is calculated based on the shape of the holding member.

2. The method for manufacturing a magnet unit according to claim 1, characterized in that: The cross-sectional area of ​​each of the plurality of gates is set so that the plurality of grooves are filled at substantially the same timing.

3. The method for manufacturing a magnet unit according to claim 1, characterized in that: In the injection process, the magnet material is injected into the groove through a sprue arranged in the direction along the central axis of the retaining member, a plurality of runners arranged to branch from the sprue in the radial direction of the magnet unit, and the plurality of gates serving as the terminals of the plurality of runners. The cross-sectional areas of the plurality of gates are set so that the gate that is farther away from the sprue in a plan view has a larger cross-sectional area.

4. The method for manufacturing a magnet unit according to claim 3, characterized in that: The sprue is arranged on an extension line of the central axis.

5. The method for manufacturing a magnet unit according to claim 4, characterized in that: The cross-sectional shape of the gate is circular.

6. The method for manufacturing a magnet unit according to claim 1, characterized in that: The following processes are available: A pressure sensor is provided so as to face the opening of the groove on the opposite side to the gate, and the internal pressure generated in the groove is measured.

7. A magnet unit, characterized in that: A holding member having a plurality of grooves and a bonded magnet disposed inside each of the plurality of grooves. The bonded magnet has a gate mark on one end surface side. The gate marks having different radial distances with respect to the central axis of the holding member have different areas.

8. The magnet unit according to claim 7, characterized in that The gate mark has a larger area at a position that is farther away from the central axis in a plan view.

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