Rotor manufacturing method

Abstract

To provide a simple method for manufacturing a rotor.SOLUTION: A rotor is manufactured by a manufacturing method including a temporary magnetization step of temporarily magnetizing a magnet member which is a magnetic material, an attraction step of attracting the temporarily magnetized magnet member to a holding portion of the magnet member formed in a rotor core, and a molding step of insert-molding the rotor core together with the magnet member attracted to the holding portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a rotor. [Background technology]

[0002] Conventionally, when manufacturing an IPM (Interior Permanent Magnet) type rotor, a manufacturing method is known in which a magnetized magnet is inserted into a hole formed in a rotor core and resin is injected into the hole to manufacture the rotor (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-20379 Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional technology is applied to IPM rotors, and magnets are fixed inside the holes by injecting resin into the holes. However, in the case of SPM (Surface Permanent Magnet) rotors, there are no holes into which magnets can be inserted, so the same method as the conventional technology cannot be used. The present invention has been made in view of the above-mentioned problems, and has an object to provide a simple method for manufacturing a rotor that can also be applied to an SPM type rotor. [Means for solving the problem]

[0005] In order to achieve the above-mentioned objective, the manufacturing method of the rotor includes a temporary magnetization process in which a magnetic material, that is, a magnetic member, is temporarily magnetized; an adsorption process in which the temporarily magnetized magnetic member is attracted to a holding portion of the magnetic member formed on the rotor core; and a molding process in which the rotor core is insert-molded together with the magnetic member attracted to the holding portion.

[0006] That is, in the rotor manufacturing method, the magnetic members are temporarily magnetized so that they are attracted to the holding portion of the rotor core. By insert-molding the rotor core together with the magnetic members in this state, a rotor can be manufactured in which the magnetic members and the rotor core are integrated with resin. In the above manufacturing method, because the magnetic members are insert-molded together with the rotor core, even if the magnetic members are attracted to the rotor core without being covered by the holes, the magnetic members can be integrated with the rotor core without falling off. Therefore, even SPM-type rotors can be easily manufactured. [Brief explanation of the drawings]

[0007] [Figure 1] Fig. 1A is a perspective view of a water pump, and Fig. 1B is a cross-sectional view showing the water pump in a cut-away state. [Figure 2] FIG. 2A is an exploded perspective view of the rotor core, and FIG. 2B is a view showing the rotor as viewed in a direction parallel to the rotation axis. [Figure 3] 10 is a flowchart showing a method for manufacturing a rotor. [Figure 4] FIG. 4A is a view showing a rotor according to a comparative example as viewed in a direction parallel to the rotation axis, FIG. 4B is an enlarged view of a rotor core according to the comparative example, and FIG. 4C is an enlarged view of a rotor core according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Here, the embodiments of the present invention will be described in the following order. (1) Rotor configuration: (2) Rotor manufacturing method: (3) Other embodiments:

[0009] (1) Rotor configuration: Fig. 1A is a perspective view of a water pump 1 using a motor including a rotor 10 according to this embodiment. Fig. 1B is a cross-sectional view showing the water pump 1 cut along a plane including the rotation axis Ax of the rotor 10. In these figures, parts around the rotor are extracted from the water pump 1 and shown. In Fig. 1B, only parts obtained by insert molding are shown with hatching to indicate a cross section.

[0010] In this specification, the direction parallel to the rotation axis Ax is referred to as the axial direction. The direction along the circumference of a circle centered on the rotation axis Ax is referred to as the circumferential direction, and the direction parallel to the radius of the circle is referred to as the radial direction. Furthermore, in this specification, the direction toward the rotation axis Ax in the radial direction as seen from a certain component is referred to as the radially inner direction, and the direction opposite the rotation axis Ax is referred to as the radially outer direction.

[0011] The water pump 1 includes a rotor 10. The rotor 10 is an annular component that includes a magnet member 20, a rotor core 30, and a resin that integrates these together. A stator (not shown) is disposed radially outward of the rotor 10. The magnetic field generated by the stator causes the rotor 10 to rotate about a rotation axis Ax.

[0012] The rotor 10 rotates integrally with a portion including the impeller 11 around a rotation axis Ax. The water pump 1 is a device that, by the rotation of the impeller 11, draws water present on the IN side shown in FIG. 1B into the impeller 11 portion and discharges it to the OUT side.

[0013] As described above, the rotor 10 according to this embodiment constitutes part of a motor and is formed by attaching permanent magnets to a rotor core. FIG. 2A is an exploded perspective view of the rotor core 30, and FIG. 2B is a view showing the rotor 10 as viewed from a direction parallel to the rotation axis Ax. In this embodiment, the rotor core 30 is formed by stacking identically shaped plate-shaped electromagnetic steel sheets in the direction of the rotation axis Ax. A substantially hexagonal hole is formed radially inside the rotor core 30, but the shape of the hole is arbitrary.

[0014] Retaining portions 30a for retaining the magnet members 20 are formed at six locations on the radially outer surface of the rotor core 30. The retaining portions 30a are recesses formed by recessing the surface of the outermost peripheral portion of the rotor core 30 radially inward. That is, in this embodiment, the retaining portions 30a are recesses formed so that a plurality of them are lined up in the circumferential direction on the outer periphery of the annular rotor core 30 radially outward. Furthermore, the retaining portions 30a form recesses by extending in the axial direction with a constant circumferential width.

[0015] Between adjacent holding portions 30a in the circumferential direction, protrusions 31 are formed that protrude radially outward. Between the protrusions 31, the holding portions 30a have rectangular planes that extend in the axial direction and in a direction perpendicular to the axial direction. The planes are the portions to which the magnetic member 20 is attracted. Because the protrusions 31 protrude radially outward, the circumferential ends of the protrusions 31 can be said to be the circumferential ends of the recesses formed by the holding portions 30a. In other words, the holding portions 30a are recesses formed by the planes to which the magnetic member 20 is attracted and wall surfaces that extend radially outward at the circumferential ends of the planes.

[0016] In this embodiment, when attached to the holding portion 30a, the magnet member 20 is a substantially hexahedron whose axial length is longer than its circumferential length and whose radial length is shorter than its circumferential length. When attached to the holding portion 30a, the radially inner surface of the magnet member 20 is a rectangular flat surface, and the radially outer surface opposite the rectangular flat surface is a substantially rectangular curved surface. Due to this curved surface, the radial thickness of the magnet member 20 is smallest at both circumferential ends and gradually increases from both ends toward the center.

[0017] The circumferential width of the retaining portions 30a is slightly larger than the circumferential width of the magnet members 20, and the axial length of the retaining portions 30a is the same as the axial length of the magnet members 20. Therefore, the magnet members 20 are sized to fit into the recesses formed by the retaining portions 30a, and the rotor 10 is formed by fitting the magnet members 20 into all six retaining portions 30a formed on the outer periphery of the rotor core 30.

[0018] (2) Rotor manufacturing method: Next, a method for manufacturing the rotor 10 shown in FIGS. 2A and 2B will be described. FIG. 3 is a flowchart showing a method for manufacturing a rotor. In this embodiment, first, the rotor core 30 is manufactured (step S100). As shown in FIGS. 2A and 2B, the rotor core 30 is formed by stacking plate-shaped members. Here, the plate-shaped members are manufactured by forming protrusions 31 and holding portions 30a in six locations on an electromagnetic steel plate. A plurality of such plate-shaped members are manufactured and stacked to manufacture the rotor core 30.

[0019] Next, an unmagnetized magnet member 20 is manufactured (step S105). The magnet member 20 is obtained, for example, by molding a hard magnetic body, which is a magnetic material, into a shape designed for the magnet member 20. In this embodiment, six magnet members 20 of the same shape are manufactured. In this embodiment, the magnet members 20 are unmagnetized. Therefore, in the stage of step S105, no action that may magnetize the magnet members 20, such as bringing them close to a permanent magnet, is performed.

[0020] Next, the rotor core 30 is temporarily magnetized to a strength that allows demagnetization by insert molding (step S110). Specifically, the rotor core 30 is manufactured by insert molding in step S120, which will be described later. Insert molding is a molding method in which the rotor core 30 and magnet members 20 to be molded are placed in a predetermined mold, and resin is injected into the mold to integrally mold the rotor core 30 and magnet members 20. The temperatures of the mold and resin are predetermined so that the predetermined resin can be appropriately injected into the mold, solidified, and the molded rotor 10 can be obtained. The length of time that the temperature is maintained in the mold is also known.

[0021] On the other hand, since the magnet member 20 is a hard magnetic material, it can be magnetized by bringing a permanent magnet close to it, but it can also be demagnetized by applying heat (thermal demagnetization). That is, the magnetized magnet member 20 is demagnetized when maintained at a temperature equal to or higher than the Curie temperature. In this embodiment, the strength of magnetization that will be demagnetized when maintained at the mold temperature and resin temperature for the molding time in insert molding is specified in advance. Therefore, in this embodiment, the magnet member 20 is magnetized to a strength that can be demagnetized by insert molding and that will attract to the holding portion 30a of the rotor core 30.

[0022] The temporary magnetization may be performed by various methods, such as bringing a permanent magnet close to the surface where the magnet member 20 contacts the holding portion 30a and moving the permanent magnet in a certain direction a predetermined number of times.

[0023] Next, the magnet members 20 are attracted to the holding portions 30a (step S115). That is, the flat surface of the magnet members 20 is aligned with the flat surface of the holding portions 30a, and the magnet members 20 are attracted to the holding portions 30a. At this time, the positions in the axial and circumferential directions are finely adjusted, and each of the six magnet members 20 is positioned inside each of the six holding portions 30a.

[0024] As described above, in this embodiment, the magnet members 20 are temporarily magnetized, so that the magnet members 20 attracted to the holding portions 30a do not move and do not fall off from the holding portions 30a. Therefore, after the magnet members 20 are positioned in the holding portions 30a, it becomes possible to very easily perform tasks such as moving the rotor core 30 integrated with the magnet members 20 to a mold for insert molding.

[0025] Next, insert molding is performed at a predetermined mold temperature and resin temperature (step S120). That is, a pre-fabricated mold is heated by a heater or the like and maintained at a predetermined temperature. The resin is also heated by a heater or the like and maintained at a predetermined temperature. Then, the rotor core 30 with the magnet members 20 attached thereto is placed in the mold, and the resin is injected into the mold to perform insert molding.

[0026] Insert molding is a molding method in which the magnet members 20 are integrated into the holding portions 30a of the rotor core 30 while they are disposed therein. Insert molding may be performed in various ways as long as it can integrate the magnet members 20 with the rotor core 30. In this embodiment, as shown in FIG. 1B , a configuration is adopted in which the resin after molding extends radially outward from the magnet members 20 and the rotor core 30, and the outermost radial portion is covered with resin, thereby maintaining the magnet members 20 within the holding portions 30a of the rotor core 30. With this configuration, even if the rotor 10 rotates during operation after manufacture and a centrifugal force acts on the magnet members 20 in a radially outward direction, the magnet members 20 will not fall off the holding portions 30a of the rotor core 30.

[0027] Once insert molding is performed and the temperature drops below a predetermined value, the molded rotor 10 is removed from the mold. According to the insert molding described above, the magnet members 20 are demagnetized by the heat generated during molding. That is, in step S110, temporary magnetization is performed to a strength that allows demagnetization by the heat generated during the insert molding. Therefore, after insert molding, the magnetization strength of the magnet members 20 becomes zero, and they are no longer in a state where they can be attracted to the rotor core 30 by magnetic force. However, since the magnet members 20 and the rotor core 30 are integrated by the resin after molding, the rotor 10 is formed with the magnet members 20 still positioned in the holding portions 30a of the rotor core 30.

[0028] Next, the magnet members 20 are magnetized (step S125). That is, the magnet members 20 are members that apply torque to the rotor 10 by interacting with the magnetic field generated by the stator. For this reason, the magnet members 20 need to be magnetized with a predetermined magnetic pole and a predetermined strength. Therefore, in this embodiment, the rotor 10 including the magnet members 20 is placed in a magnetization device to magnetize the magnet members 20.

[0029] The magnetization device may be a device of various types, such as a device that generates a magnetic field from a coil arranged radially outside each of the magnet members 20 to magnetize each magnet member 20. A plurality of magnet members 20 are arranged in the circumferential direction, and adjacent magnet members 20 in the circumferential direction are magnetized with opposite polarities. In FIG. 2B, the magnetic poles of the magnet members 20 after magnetization are indicated by the letters N or S. As shown in FIG. 2B, if the radially inner magnetic pole of a certain magnet member 20 is N and the radially outer magnetic pole is S, the radially inner magnetic pole of the circumferentially adjacent magnet members 20 is S and the radially outer magnetic pole is N.

[0030] Furthermore, the magnetization strength is the same for each of the multiple magnet members 20. Therefore, in the magnetization device, the polarities of the magnetic fields applied to adjacent magnet members 20 are opposite to each other, and the magnitudes of the magnetic fields are the same. With the above configuration, it is possible to manufacture a rotor 10 in which the circumferentially adjacent magnet members 20 have opposite polarities to each other and the magnetic field strength is the same.

[0031] In this embodiment, the magnet member 20 that has been temporarily magnetized in step S110 is demagnetized by insert molding in step S120, and then magnetized again in step S125. Therefore, in step S125, the unmagnetized magnet member 20 only needs to be magnetized.

[0032] For this reason, in this embodiment, it is possible to easily adjust the magnetization strength of each magnet member 20. If magnetization in step S125 is started when the magnet members 20 have not been demagnetized, it is necessary to further magnetize each magnet member 20 in accordance with the state of magnetization remaining in each magnet member 20. In this case, the strength of additional magnetization to be performed for each magnet member 20 may differ. Furthermore, when adjacent magnet members 20 are magnetized with opposite polarities, the strength of additional magnetization to be performed for each magnet member 20 may differ in a complex manner.

[0033] However, in this embodiment, the magnetization of step S125 can be performed from a state in which the magnetization strength of the magnet members 20 is 0. Therefore, the magnetization device only needs to apply magnetic fields of opposite polarity and the same magnitude to adjacent magnet members 20 to magnetize them, and the magnet members 20 can be magnetized very easily to the desired characteristics.

[0034] As described above, the rotor 10 according to this embodiment is manufactured through a process of attracting the magnet members 20. Therefore, there is no need to provide the rotor core 30 with a structure for holding the magnet members 20 in the holding portions 30a. FIG. 4A is a diagram showing a structure that can be employed for holding an unmagnetized magnet member in the rotor core without attracting it. FIG. 4A shows the rotor 100 as viewed from a direction parallel to the rotation axis Ax. The rotor 100 includes the magnet members 200 and the rotor core 300. The rotor 100 has the same external shape as the rotor 10, but the magnet members 200 and 20 have different shapes, and the protruding portions 310 of the rotor core 300 and the protruding portions 31 of the rotor core 30 have different shapes.

[0035] Specifically, in rotor core 300, the recesses that hold magnet members 200 are called holding portions 300a. Rotor core 30 has holding portions 30a formed therein, and rotor core 300 has holding portions 300a formed therein, and both have specific shapes at the ends in the circumferential direction, and extend axially to form recesses, but the shapes of the ends in the circumferential direction are different between holding portions 30a and 300a.

[0036] 4B is an enlarged view showing the vicinity of protruding portion 310 of rotor core 300. Protruding portion 310 has protruding portions 310a that protrude from both ends in the circumferential direction. That is, protruding portion 310 protrudes radially outward from rotor core 300 and also protrudes circumferentially at the outermost periphery to form protruding portion 310a. Protruding portion 310a is part of the wall surface that constitutes the circumferential end of the recess that serves as retaining portion 300a, and it can be said that the wall surface that constitutes the circumferential end of retaining portion 300a protrudes toward retaining portion 300a at the outermost periphery on the radially outer side.

[0037] The magnet members 200 and 20 are formed by extending in the axial direction, and have the same cross-sectional shape when cut in a direction perpendicular to the axial direction, but the cross-sectional shapes of the two are different. As shown in Fig. 4B, the magnet member 200 has protrusions 200a formed on both circumferential ends thereof, which extend in the circumferential direction and enter radially inward of the protrusions 310a.

[0038] In this way, in this example, the protrusion 310a constituting the inner wall of the holding portion 300a extends radially outward in one circumferential direction, and the protrusion 200a formed on the magnet member 200 extends radially inward in the other circumferential direction. By using this configuration, even without temporarily magnetizing the magnet member 200, when the magnet member 200 is inserted into the holding portion 300a, the magnet member 200 can be held so as not to fall out radially outward.

[0039] As described above, in the rotor core 300, the protruding portion 310a, which is the circumferential end of the retaining portion 300a, and the protruding portion 200a, which is the circumferential end of the magnet member 200 retained by the retaining portion 300a, overlap in the circumferential direction. When such a configuration is adopted, waste may occur in the magnetic flux generated from one of the adjacent magnet members 200 to the other. Specifically, it is preferable that the adjacent magnet members 200 are magnetized to have opposite polarities, and that all of the magnetic field lines extending from one magnet member 200 are directed toward the adjacent magnet member 200. The more magnetic flux that enters the adjacent magnet member 200 out of the magnetic flux emitted from the magnet member 200, the more efficiently the magnetic field from the magnet member 200 can be converted into torque.

[0040] As in the rotor core 300 shown in Fig. 4B, when the protruding portion 310a, which is the circumferential end of the retaining portion 300a, and the protruding portion 200a, which is the circumferential end of the magnet member 200 held by the retaining portion 300a, overlap in the circumferential direction, the greater the amount of overlap, the greater the leakage of magnetic flux that is not used for torque conversion. In Fig. 4B, the magnetic field lines passing through the protruding portion 310a and the protruding portion 200a are schematically shown by dashed arrows.

[0041] Because the rotor core 300 is a soft magnetic material with high magnetic permeability, if a structure such as the protrusion 310 is located at a position different from the magnetic field lines connecting the magnet members 200 (for example, the magnetic field lines indicated by the dashed lines), magnetic flux will leak toward the protrusion 310. The dashed arrows indicate magnetic field lines that show examples of leaked magnetic flux. The larger the protrusion 310a, which faces the protrusion 200a of the magnet member 200, which is a permanent magnet and has high magnetic permeability, the more efficiently the magnetic flux will leak via the protrusion 310a.

[0042] However, in the rotor 10 according to this embodiment, the magnet members 20 are temporarily magnetized and attracted to the holders 30a, so there is no need to form circumferentially extending portions such as the protruding portions 310a and 200a on the rotor core 30 and the magnet members 20. Fig. 4C is an enlarged view showing the vicinity of the protruding portion 31 of the rotor core 30. As shown in Fig. 4C, the protruding portion 31 does not have a portion that protrudes in the circumferential direction, unlike the protruding portion 310a.

[0043] In this embodiment, the wall surface 31a of the holding portion 30a formed by the circumferential end of the protrusion 31 is parallel to a perpendicular line Lv (see FIG. 2B) extending from the rotation axis Ax to the attracting surface of the magnet member 20 to the holding portion 30a. In other words, when each magnet member 20 is moved along the perpendicular line Lv and brought closer to the holding portion 30a, the magnet member 20 is configured to fit into the holding portion 30a without interfering with the wall surface 31a of the holding portion 30a.

[0044] As configured as described above, the radial height of the protrusion 31 is configured to be lower than that of the magnet member 20, so in this embodiment, the circumferential end of the holding portion 30a and the circumferential end of the magnet member 20 attracted to the holding portion 30a are configured not to overlap in the circumferential direction.

[0045] This situation in which the circumferential end of the holding portion 30a and the circumferential end of the magnet member 20 attracted to the holding portion 30a do not overlap in the circumferential direction can also be confirmed by looking at the straight lines extending from the rotation axis Ax to the circumferential end of the holding portion 30a. In Fig. 2B, one of the straight lines extending from the rotation axis Ax to the circumferential end of the holding portion 30a is shown as line Le. This line Le is also shown in Fig. 4C.

[0046] As shown in FIGS. 2B and 4C , the line Le extends from the rotation axis Ax so as to be tangent to the circumferential end of the holding portion 30a (the circumferential end of the protrusion 31). The line Le is also tangent to the circumferential end of the magnet member 20. Therefore, the line Le is tangent to both the circumferential end of the holding portion 30a and the circumferential end of the magnet member 20. If the line Le rotates even slightly clockwise around the rotation axis Ax, the line Le intersects only with the circumferential end of the magnet member 20, but does not intersect with the circumferential end of the holding portion 30a. If the line Le rotates even slightly counterclockwise around the rotation axis Ax, the line Le intersects only with the circumferential end of the holding portion 30a, but does not intersect with the circumferential end of the magnet member 20. As described above, in this embodiment, the circumferential end of the holding portion 30a and the circumferential end of the magnet member 20 attracted to the holding portion 30a do not overlap in the circumferential direction.

[0047] This configuration reduces the leakage of magnetic flux from one magnet member 20 to an adjacent magnet member 20 compared to the configuration shown in FIG. 4B . Specifically, because the protruding portion 31 does not have a structure such as the protruding portion 310a that protrudes in the circumferential direction, the area where the rotor core 30 with high magnetic permeability and the magnet member 20 face each other is smaller compared to the configuration shown in FIG. 4B . Therefore, even if magnetic flux from one magnet member 20 to an adjacent magnet member 20 leaks toward the protruding portion 31 as indicated by the dashed arrow, the amount of leakage is smaller compared to the configuration shown in FIG. 4B . As a result, if the magnetization strength of the magnet members 20 and 200 is the same, the configuration shown in FIG. 4C makes it easier to manufacture a motor with higher torque compared to the configuration shown in FIG. 4B . Furthermore, if a motor with the same torque is to be manufactured, the configuration shown in FIG. 4C makes it easier to miniaturize the motor compared to the configuration shown in FIG. 4B .

[0048] Furthermore, in this embodiment, the circumferential end of the holding portion 30a and the circumferential end of the magnet member 20 attracted to the holding portion 30a do not overlap in the circumferential direction, so the shape of the magnet member 20 can be simplified. Specifically, in a cross section of the magnet member 20 attracted to the holding portion 30a cut in a direction perpendicular to the axial direction, no recesses are formed on the outer periphery of the magnet member 20. For example, the outer periphery of the magnet member 20 shown in FIG. 2B is the same as the outer periphery of the magnet member 20 in that cross section. As shown in FIG. 2B, the outer periphery of the magnet member 20 is composed of straight lines and curves, and is either convex toward the outer periphery or does not protrude toward the outer periphery at any position.

[0049] 4A and 4B, in a cross section of the magnet member 200 held by the holder 300a taken in a direction perpendicular to the axial direction, a recess 201 is formed on the outer periphery of the magnet member 200 (see FIG. 4B). That is, in the magnet member 200, in order to form the protruding portion 200a that enters the radially inner side of the protruding portion 310a, the recess 201 is formed on the outer periphery of the magnet member 200, and the radial thickness of the magnet member 200 is changed at the circumferential end beyond the recess 201 so that the protruding portion 200a extends toward the circumferential end.

[0050] The protrusions 200a enable the magnet member 200 to be held by the holder 300a without being attracted, but in such a structure, unless the radial thickness of the protrusions 200a is made large to a certain extent, problems such as cracking of the magnet member 200 may occur. For this reason, in the configuration shown in Figures 4A and 4B, it is necessary to ensure that the radial thickness of the magnet member 200 is large enough to prevent cracking even when the protrusions 200a are provided.

[0051] However, since the magnet member 20 according to this embodiment is attracted to the holder 30a by temporary magnetization, there is no need to provide a structure such as the protrusion 200a, and there is no need to form a recess on the outer periphery of the cross section as shown in Fig. 2B. This allows the magnet member 20 to be configured with a very simple shape, and the radial thickness of the magnet member 20 can be made thinner than the configuration shown in Figs. 4A and 4B.

[0052] (3) Other embodiments: The above embodiment is one example for carrying out the present invention, and various other embodiments are also possible. For example, the number of magnet members 20 and holders 30a is not limited to six, and other numbers may be used. Furthermore, the shape and size of the magnet members 20 and holders 30a may also be various. Furthermore, the application of the motor using the rotor is not limited to a water pump. Furthermore, the order of the replaceable steps in the rotor manufacturing method may be changed. For example, the order of S100 and S105 may be changed in the manufacturing method shown in FIG. 3.

[0053] The temporary magnetization process only needs to be able to temporarily magnetize the magnetic member, which is a magnetic material. Therefore, various magnetizable magnetic materials can be used as the magnetic member. However, as described above, it is preferable that the magnetic material be various hard magnetic materials so that it can be temporarily magnetized, demagnetized, and then further magnetized to become a permanent magnet. Various methods for temporary magnetization other than the above-described method may be adopted. For example, the magnetic material may be magnetized by a magnetic field generated by a coil. Furthermore, the number of magnetic members to be magnetized is not limited, and multiple magnetic members may be magnetized at once. Furthermore, the direction of the magnetic field generated by the magnetized magnetic members is not limited. In other words, the temporary magnetization only needs to magnetize the magnetic member so that it is attracted to the holding portion of the rotor core so that insert molding can be performed, and demagnetization may be performed during the insert molding process.

[0054] The attraction process only needs to be able to attract the temporarily magnetized magnet member to the magnet member holding portion formed on the rotor core. That is, the rotor core needs to have a portion for holding the magnet member, and the magnetic field of the temporarily magnetized magnet member needs to be able to attract the magnet member to the holding portion. The holding portion is the portion that attracts the magnet member, and is preferably shaped to hold the magnet member so that it does not shift when insert molding is performed with the magnet member attracted. For this reason, as in the above-described embodiment, it is preferable that the shape be such that the magnet member is held in the recess. Furthermore, to be applicable to SPM-type rotors, the holding portion is preferably formed at the outermost radial portion of the rotor core.

[0055] The molding process may be performed by insert molding the rotor core together with the magnetic members attached to the holding portion. In other words, the molding process may be performed by integrally molding the rotor core and the magnetic members. To prevent the magnetic members from separating from the rotor core when the rotor core rotates, the integral molding is preferably performed in such a manner that the integrally molded resin is present radially outside the magnetic members, and the resin covers the magnetic members in the circumferential and axial directions at the radially outermost peripheral portion of the magnetic members. Note that the range of integral molding is not limited, and any portion may be integrally molded. [Explanation of symbols]

[0056] 1...water pump, 10...rotor, 11...impeller, 20...magnetic member, 30...rotor core, 30a...holding portion, 31...protruding portion, 31a...wall surface, 100...rotor, 200...magnetic member, 200a...protruding portion, 201...recess, 300...rotor core, 300a...holding portion, 310...protruding portion, 310a...protruding portion

Claims

1. a temporary magnetization step of temporarily magnetizing a magnetic member that is a magnetic material; an attracting step of attracting the temporarily magnetized magnet members to a magnet member holder formed on a rotor core; a molding step of insert-molding the rotor core together with the magnet members attracted to the holding portion; A method for manufacturing a rotor comprising:

2. The molding step includes: demagnetizing the magnetic member by heat generated during molding; A method for manufacturing the rotor according to claim 1 .

3. The holding portion is a plurality of recesses extending in the axial direction formed on the outer periphery of the annular rotor core at the radially outer side; a circumferential end of the holding portion and a circumferential end of the magnet member attracted to the holding portion do not overlap in the circumferential direction; The method for manufacturing a rotor according to claim 1 or 2.

4. In a cross section of the magnet member attracted to the holding portion taken in a direction perpendicular to the axial direction of the rotor core, no recess is formed on the outer periphery of the magnet member. The method for manufacturing a rotor according to claim 1 or 2.

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