Method for manufacturing motor rotor and motor rotor

Abstract

Provided is a method for manufacturing a motor rotor in which: a protective tube is installed in a mold, the protective tube being arranged so as to surround a shaft between a first ring part and a second ring part; a gap allowing the protective tube to expand in a radial direction is formed between the protective tube and the mold; a bond magnet in a molten state is, from a filling hole of the first ring part, injected and filled into a magnet region surrounded by the shaft, the first ring part, the second ring part and the protective tube; the protective tube is expanded in the radial direction; the bond magnet is left in the filling hole; and the mold is released after the bond magnet in the magnet region is cured.

Description

Motor rotor manufacturing method and motor rotor

[0001] The present disclosure relates to a method for manufacturing a motor rotor, and a motor rotor.

[0002] Motor rotors with bonded magnets and methods for manufacturing motor rotors are known. Patent Document 1 discloses a motor rotor in which a bonded magnet is disposed within a sleeve. Patent Document 2 discloses a motor rotor in which a bonded magnet is fixed to a shaft. Patent Document 2 also discloses a method for manufacturing a motor rotor by placing a shaft with a rotor yoke in a mold and supplying a magnetic material into the mold. Patent Document 3 discloses a method for manufacturing a motor rotor in which a resin-bonded permanent magnet is molded onto the inner surface of the yoke. Patent Document 4 discloses a method for manufacturing a motor rotor using rare earth bonded magnets and ferrite bonded magnets as permanent magnets. Patent Document 5 discloses a method for manufacturing a plastic magnet rotor.

[0003] Japanese Patent Application Laid-Open No. 2012-100526 Japanese Patent No. 6296514 Japanese Patent Application Laid-Open No. 2020-48292 International Publication No. 2021 / 192236 Japanese Patent Application Laid-Open No. 2002-252940

[0004] In motor rotors with bonded magnets attached to shafts, centrifugal force can cause the bonded magnets to lift up, and differences in linear expansion can create gaps between the bonded magnets and their support members. Such lifting or gaps can reduce the torque transmission performance between the bonded magnets and the shaft.

[0005] The present disclosure describes a motor rotor and a manufacturing method thereof that can improve torque transmission performance between a shaft and a bonded magnet.

[0006] One example of the present disclosure is a method for manufacturing a motor rotor including a first ring portion extending radially from a shaft and having a bonded magnet filling hole, and a second ring portion extending radially from the shaft and positioned opposite the first ring portion along the shaft's rotational axis. This motor rotor manufacturing method includes: placing a protective tube in a molding die, the protective tube being disposed between the first and second ring portions and surrounding the shaft; forming a gap between the protective tube and the molding die to allow radial expansion of the protective tube; injecting a molten bonded magnet through the filling hole into a magnet region surrounded by the shaft, the first and second ring portions, and the protective tube to expand radially while leaving the bonded magnet in the filling hole; and releasing the molding die after the bonded magnet in the magnet region has hardened.

[0007] In the motor rotor manufacturing method described above, a molten bonded magnet is injected and filled to expand the protective tube radially. Therefore, even when the bonded magnet cools and shrinks radially, the protective tube follows the bonded magnet. As a result, the bonded magnet and the protective tube are less likely to separate, making it easier to ensure a stable, tight fit without gaps. Furthermore, the first ring portion is a component that protrudes radially from the shaft, and when the bonded magnet hardens, the bonded magnet remains in the filling hole of the first ring portion. As a result, the bonded magnet and the first ring portion are engaged, improving torque transmission performance between the bonded magnet and the shaft via the first ring portion.

[0008] In some examples, the protective tube may be made of carbon fiber reinforced resin. The resin contained in the bonded magnet is, for example, a high-resistivity material, and by making the protective tube out of carbon fiber reinforced resin, eddy current loss can be reduced.

[0009] In some cases, the protective tube may be expanded radially by injecting a molten bonded magnet through a filling hole so that the radial expansion of the protective tube remains even after the bonded magnet has hardened. This allows the protective tube and the bonded magnet to be tightly attached with no gaps even after the bonded magnet has hardened, and centrifugal force makes it difficult for gaps to form between them.

[0010] In some examples, the expansion rate of the protective tube, which remains radially expanded even after the bonded magnet has hardened, may be 0.1% or more compared to the diameter of the protective tube before the bonded magnet is filled in. This makes it easier to adjust the pressure when injecting and filling the bonded magnet so that the protective tube and the bonded magnet are in close contact with each other without any gaps after the bonded magnet has hardened.

[0011] A motor rotor according to an example of the present disclosure includes a shaft rotatable about a rotation axis, a first ring portion extending radially from the shaft, a second ring portion extending radially from the shaft and positioned opposite the first ring portion in a direction along the rotation axis, a bonded magnet positioned between the first and second ring portions, and a cylindrical protective tube covering the bonded magnet. The first ring portion has a through hole, and the bonded magnet is positioned within the through hole and has an engaging portion that is in close contact with the first ring portion within the through hole.

[0012] The first ring portion of the motor rotor projects radially from the shaft, and the bonded magnet is disposed within the through-hole of the first ring portion and has an engaging portion that is in close contact with the first ring portion within the through-hole. Therefore, the bonded magnet and the first ring portion are engaged, and torque transmission performance between the bonded magnet and the shaft via the first ring portion can be improved.

[0013] In some examples, the protective tube may have a first end abutting the first ring portion and a second end abutting the second ring portion, the first ring portion having a first positioning portion for positioning the first end, and the second ring portion having a second positioning portion for positioning the second end. The protective tube is sandwiched between the first positioning portion of the first ring portion and the second positioning portion of the second ring portion, and is positioned in a stable state.

[0014] In some examples, the first positioning portion includes a first protrusion that fits into the first end to position the first end, the second positioning portion includes a second protrusion that fits into the second end to position the second end, and the bonded magnet may include a first adhesion layer that is disposed between the inner circumferential surface of the protective tube and the outer circumferential surface of the first protrusion and is in close contact with the protective tube and the first protrusion, and a second adhesion layer that is disposed between the inner circumferential surface of the protective tube and the outer circumferential surface of the second protrusion and is in close contact with the protective tube and the second protrusion. The first adhesion layer and the second adhesion layer strengthen the bond between the protective tube and the first and second ring portions, improving the torque transmission performance between the bonded magnet and the shaft.

[0015] In some examples, the first ring portion has a first inner circumferential portion fixed to the shaft and a first outer circumferential portion opposite the first inner circumferential portion in the radial direction of the shaft, and the second ring portion has a second inner circumferential portion fixed to the shaft and a second outer circumferential portion opposite the second inner circumferential portion in the radial direction of the shaft, and a step may be formed in the radial direction of the shaft between at least one of the first outer circumferential portion and the second outer circumferential portion and the outer surface of the protective tube.

[0016] In some examples, the bonded magnet may include a first contact portion disposed between the protective tube and the first ring portion and in tight contact with the protective tube and the first ring portion, and a second contact portion disposed between the protective tube and the second ring portion and in tight contact with the protective tube and the second ring portion. The first contact portion and the second contact portion strengthen the bond between the protective tube and the first and second ring portions, improving the torque transmission performance between the bonded magnet and the shaft.

[0017] According to various examples of the present disclosure, it is possible to improve the torque transmission performance between the shaft and the bonded magnet.

[0018] FIG. 1 is a cross-sectional view showing the schematic configuration of an electric motor, which is an example of a rotary machine. FIG. 2 is a side view showing an example of a first ring portion. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is an enlarged cross-sectional view showing a portion of a motor rotor. FIG. 5 is a side view showing an example of a first ring portion. FIG. 6 is a flowchart showing each step of a method for manufacturing a motor rotor. FIG. 7 is a diagram showing a method for manufacturing a motor rotor, with (a) showing an assembly step, (b) showing an installation step of placing a precursor in a mold, (c) showing a bonded magnet filling step, and (d) showing a demolding step of removing the motor rotor from the mold.

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and redundant description will be omitted.

[0020] The rotating machine (e.g., electric motor 1) shown in FIG. 1 functions as a drive source for various electric devices. The electric motor 1 includes a motor rotor 2 and a stator 3 arranged to surround the motor rotor 2. The motor rotor 2 includes a shaft 10 that can rotate about a rotation axis L, and a bonded magnet 13 provided on the outer circumferential surface 10a of the shaft 10. In the following description, the rotation axis direction Ld refers to the direction along the rotation axis L. The circumferential direction refers to the direction along a circle centered on the rotation axis L, and means, for example, the circumferential direction of the shaft 10 or the circumferential direction of a protective tube 14 described below. The radial direction Rd refers to the direction perpendicular to the rotation axis L, and means, for example, the radial direction of the shaft 10 or the radial direction of the protective tube 14.

[0021] The stator 3 includes a core 30 disposed to surround the bond magnet 13 of the motor rotor 2, and a coil 31 formed by winding a conductor around the core 30. The core 30 is cylindrical with the rotation axis L as its central axis. The motor rotor 2 is disposed inside the core 30. The core 30 faces the motor rotor 2 in the radial direction. When an alternating current is supplied to the coil 31 of the stator 3 through the conductor, the stator 3 generates a rotating magnetic field inside the core 30. This rotating magnetic field generates torque in the motor rotor 2. As a result, the motor rotor 2 rotates around the rotation axis L.

[0022] In addition to the shaft 10 and bond magnet 13, the motor rotor 2 further includes a first ring portion 11, a second ring portion 12, and a protective tube 14. The first ring portion 11 and the second ring portion 12 each protrude outward in the radial direction Rd from the outer circumferential surface 10a of the shaft 10. The first ring portion 11 and the second ring portion 12 are disposed to face each other in the rotational axis direction La. The first ring portion 11 and the second ring portion 12 are disposed at a predetermined interval from each other in the rotational axis direction La to form a magnet region MR (see FIG. 7 ) in which the bond magnet 13 is filled.

[0023] Bond magnet 13 is provided between first ring portion 11 and second ring portion 12. Bond magnet 13 has a cylindrical shape that covers outer peripheral surface 10a of shaft 10. Protective tube 14 has a cylindrical shape that covers outer peripheral surface 13f of bond magnet 13. Protective tube 14 is disposed between first ring portion 11 and second ring portion 12. Protective tube 14 is formed, for example, from a non-magnetic material with high electrical resistance. For example, protective tube 14 is made of fiber reinforced resin, for example, carbon fiber reinforced plastic (CFRP).

[0024] The area surrounded by the shaft 10, first ring portion 11, second ring portion 12, and protective tube 14 is the magnet region MR. The bond magnet 13 is disposed within the magnet region MR. The first ring portion 11 is formed with a filling hole 11a that is used when the molten bond magnet 13 is filled into the magnet region MR. The second ring portion 12 is formed with a vent hole 12a that is used for venting. The bond magnet 13 disposed within the magnet region MR remains and hardens within the filling hole 11a and the vent hole 12a. The bond magnet 13 remaining within the filling hole 11a forms a first engaging portion 13a that is in close contact with the first ring portion 11 within the filling hole 11a. The bond magnet 13 remaining within the vent hole 12a forms a second engaging portion 13b that is in close contact with the second ring portion 12 within the vent hole 12a.

[0025] 2 and 3 , the first ring portion 11 has a first inner surface 11b facing the second ring portion 12 and a first outer surface 11c opposite the first inner surface 11b in the rotational axis direction La. The filling hole 11a of the first ring portion 11 has a first through hole 111 penetrating from the first outer surface 11c to the first inner surface 11b. The filling hole 11a has a plurality of first through holes 111 arranged along the circumferential direction of the first ring portion 11. The plurality of first through holes 111 are arranged, for example, at equal intervals in the circumferential direction of the first ring portion 11. The bond magnet 13 has one or more first engaging portions 13a that are in close contact with the first ring portion 11 in some or all of the plurality of first through holes 111 (see FIG. 1 ). In addition, the filling hole 11a may have a single first through hole 111, in which case the bond magnet 13 may have a single first engaging portion 13a that is in close contact with the first ring portion 11 within the single first through hole 111.

[0026] As shown in FIG. 4 , the second ring portion 12 has a second inner surface 12b facing the first ring portion 11 and a second outer surface 12c opposite the second inner surface 12b in the rotational axis direction La. The gas vent holes 12a of the second ring portion 12 have second through holes 121 penetrating from the second inner surface 12b to the second outer surface 12c. The gas vent holes 12a have, for example, one or more second through holes 121. The second through holes 121 are arranged in positions that allow appropriate gas venting, taking into consideration the positions of the first through holes 111. The bonded magnet 13 may have one or more second engaging portions 13b that are in close contact with the second ring portion 12 in some or all of the one or more second through holes 121. In addition, the gas vent hole 12a may have a single second through hole 121, in which case the bond magnet 13 may have a single second engaging portion 13b that is in close contact with the second ring portion 12 within the single second through hole 121.

[0027] The protective tube 14 is arranged so as to be sandwiched between the first ring portion 11 and the second ring portion 12. The protective tube 14 is positioned so as to be arranged substantially concentrically with the shaft 10. The positioning structure of the protective tube 14 will be described.

[0028] 1 and 4 , the protective tube 14 has one end (first end 14 a) in the rotation axis direction La and the other end (second end 14 b) opposite the first end 14 a. The first end 14 a abuts against the first ring portion 11, and the second end 14 b abuts against the second ring portion 12.

[0029] The first ring portion 11 includes a first positioning portion 11d that positions the first end portion 14a. The first positioning portion 11d includes a first protrusion 112 that is annular (see FIG. 2 ) and protrudes from the first inner surface 11b of the first ring portion 11. The first protrusion 112 has a cylindrical shape that is concentric with the rotation axis L. The first protrusion 112 includes an outer peripheral surface 113 that is disposed radially outward from the rotation axis L in the radial direction Rd. The outer diameter of the outer peripheral surface 113 corresponds to the inner diameter of the first end portion 14a. For example, the shape and outer diameter of the outer peripheral surface 113 are shaped and sized so that the first end portion 14a can be inserted into the protective tube 14 and can abut against the inner peripheral surface 14c of the protective tube 14. The first end portion 14a is positioned at a predetermined position by the first protrusion 112 of the first ring portion 11 being inserted therein. The first protrusion 112 may be a ring-shaped portion that is closed in the circumferential direction, or may be a divided portion such that the ring shape is interrupted midway.

[0030] The second ring portion 12 includes a second positioning portion 12d that positions the second end portion 14b. The second positioning portion 12d includes a second annular protrusion 122 that protrudes from the second inner surface 12b of the second ring portion 12. The second protrusion 122 has a cylindrical shape that is concentric with the rotation axis L. The second protrusion 122 includes an outer peripheral surface 123 that is disposed outward in the radial direction Rd relative to the rotation axis L. The outer diameter of the outer peripheral surface 123 corresponds to the inner diameter of the second end portion 14b. For example, the shape and outer diameter of the outer peripheral surface 123 are shaped and sized so that the second end portion 14b can be inserted into the protective tube 14 and can abut against the inner peripheral surface 14c of the protective tube 14. The second end portion 14b is positioned at a predetermined position by the second protrusion 122 of the second ring portion 12 being inserted therein. The second protrusion 122 may be a ring-shaped portion that is closed in the circumferential direction, or may be a divided portion such that the ring shape is interrupted midway.

[0031] Bonded magnet 13 includes a first contact portion 13x disposed between protective tube 14 and first ring portion 11, and a second contact portion 13y disposed between protective tube 14 and second ring portion 12. First contact portion 13x is in close contact with protective tube 14 and first ring portion 11, and second contact portion 13y is in close contact with protective tube 14 and second ring portion 12. Although first contact portion 13x is interposed between protective tube 14 and first ring portion 11, first contact portion 13x is thin, so protective tube 14 and first ring portion 11 are substantially in contact. Furthermore, second contact portion 13y is interposed between protective tube 14 and second ring portion 12, but since second contact portion 13y is thin, protective tube 14 and second ring portion 12 are substantially in contact.

[0032] The first contact portion 13x includes a first contact layer 131 disposed between the inner peripheral surface 14c of the protective tube 14 and the outer peripheral surface 113 of the first convex portion 112, and a first extension layer 132 disposed between the first end portion 14a and the inner surface of the first ring portion 11. The first contact layer 131 is in close contact with the inner peripheral surface 14c of the protective tube 14 and the outer peripheral surface 113 of the first convex portion 112, and the first extension layer 132 is in close contact with the first end portion 14a and the first inner surface 11b of the first ring portion 11.

[0033] The second contact portion 13y includes a second contact layer 133 disposed between the inner peripheral surface 14c of the protective tube 14 and the outer peripheral surface 123 of the second convex portion 122, and a second extension layer 134 disposed between the second end portion 14b and the inner surface of the second ring portion 12. The second contact layer 133 is in close contact with the inner peripheral surface 14c of the protective tube 14 and the outer peripheral surface 123 of the second convex portion 122, and the second extension layer 134 is in close contact with the second end portion 14b and the second inner surface 12b of the second ring portion 12.

[0034] The first ring portion 11 includes a first inner peripheral portion 114 fixed to the shaft 10 and a first outer peripheral portion 115 opposite the first inner peripheral portion 114 in the radial direction Rd of the shaft 10. The second ring portion 12 includes a second inner peripheral portion 124 fixed to the shaft 10 and a second outer peripheral portion 125 opposite the second inner peripheral portion 124 in the radial direction Rd of the shaft 10. Steps St are formed between the outer peripheral surface 14d of the protective tube 14 and the first outer peripheral portion 115, and between the outer peripheral surface 14d of the protective tube 14 and the second outer peripheral portion 125. The steps St may be formed only either between the outer peripheral surface 14d of the protective tube 14 and the first outer peripheral portion 115 or between the outer peripheral surface 14d of the protective tube 14 and the second outer peripheral portion 125. In addition, there may be no step St between the outer peripheral surface 14d of the protective tube 14 and the first outer peripheral portion 115, and between the outer peripheral surface 14d of the protective tube 14 and the first outer peripheral portion 115, and the shapes may be flush with each other.

[0035] The first inner circumferential portion 114 is provided with a plurality of first through holes 111 that form the filling holes 11a (see FIG. 2 ). Here, the arrangement of the filling holes 11a is not limited to the first inner circumferential portion 114, and the filling holes 11a may also be provided in the first convex portion 112 (see FIG. 5 ). For example, some or all of one or more first through holes 111 that form the filling holes 11a may be provided so as to penetrate the first convex portion 112. Furthermore, some of the plurality of first through holes 111 may be provided in the first inner circumferential portion 114, and the rest may be provided in the first convex portion 112.

[0036] 6 and 7, a manufacturing method for the motor rotor 2 will be described. The motor rotor 2 is formed by injection molding of a bonded magnet 13. This manufacturing method includes an assembly process in which a protective tube 14 is arranged between the first ring portion 11 and the second ring portion 12 to surround the shaft 10 to form a precursor 2A, an installation process in which the precursor 2A is placed in a molding die (e.g., a metal mold 50), a filling process in which molten bonded magnets 13 are injected and filled into the magnet region MR of the precursor 2A, and a demolding process in which the metal mold 50 is released from the motor rotor 2.

[0037] As shown in FIG. 7A , in the assembly process, each component is assembled to the shaft 10 to form a precursor 2A of the motor rotor 2. In the assembly process, the first ring portion 11 and the second ring portion 12 are arranged to sandwich the protective tube 14, and the first ring portion 11 and the second ring portion 12 are each fixed to the shaft 10. Fixing the first ring portion 11 to the shaft 10 and fixing the second ring portion 12 to the shaft 10 can be performed using various methods that ensure appropriate torque transmission, such as press-fitting or engagement. By fixing the first ring portion 11 and the second ring portion 12 to the shaft 10 in predetermined positions, a magnet region MR is formed, surrounded by the shaft 10, the first ring portion 11, the second ring portion 12, and the protective tube 14. The precursor 2A of the motor rotor 2 refers to a state in which the magnet region MR is empty, i.e., a state before the bond magnets 13 are filled into the magnet region MR. In the following description, the reference diameter of the protective tube 14 refers to the outer diameter when no load is applied to the protective tube 14, for example, when the magnet region MR is empty.

[0038] In the precursor 2A of the motor rotor 2, the first protrusion 112 of the first ring portion 11 is fitted into the first end 14a of the protective tube 14, and the second protrusion 122 of the second ring portion 12 is fitted into the second end 14b. The protective tube 14 is supported by the inner peripheral surface 14c, not the outer peripheral surface 14d, interfering with the first protrusion 112 and the second protrusion 122 (see FIG. 4). Therefore, the protective tube 14 is allowed to expand outward in the radial direction Rd, and is positioned by the first ring portion 11 and the second ring portion 12 in this state.

[0039] As shown in (b) of Figure 7, in the installation step, a precursor 2A of the motor rotor 2 is installed in a mold 50. When the precursor 2A is installed in the mold 50, a gap S is formed between the protective tube 14 and the mold 50 to allow expansion of the protective tube 14 in the radial direction Rd. The gap S can be set to a dimension that allows expansion of, for example, 0.1% or more with respect to the outer diameter (reference diameter) of the protective tube 14 when the magnet region MR is empty. Furthermore, this gap S can be set to a dimension that allows expansion of 0.1% or more and 0.5% or less.

[0040] In the filling process, injection device 60 is driven to inject and fill molten bond magnet 13 into magnet region MR. First ring portion 11 is provided with filling hole 11a, and second ring portion 12 is provided with vent hole 12a. Bond magnet 13 is filled into magnet region MR through filling hole 11a. When bond magnet 13 is filled, gas within magnet region MR is discharged through vent hole 12a.

[0041] In the filling step, injection device 60 fills bond magnet 13 so that protective tube 14 expands in radial direction Rd. For example, injection device 60 is set to a filling pressure that can fill bond magnet 13 until the expansion rate of protective tube 14 reaches a predetermined value. Injection device 60 continues filling even after bond magnet 13 reaches inner circumferential surface 14c of protective tube 14, and fills bond magnet 13 until the expansion rate of protective tube 14 reaches the predetermined value. Note that the filling of bond magnet 13 by injection device 60 may be controlled by the filling amount of bond magnet 13, filling time, etc.

[0042] The technical significance of expanding protective tube 14 and the rate of expansion of protective tube 14 will now be explained. Bond magnet 13 filled in magnet region MR shrinks as it cools and hardens. In contrast, protective tube 14 expands in radial direction Rd compared to the unloaded state before bond magnet 13 was filled. Therefore, when bond magnet 13 shrinks, the inner diameter of protective tube 14 shrinks in response to this shrinkage. As a result, even if bond magnet 13 shrinks as it hardens, a gap is unlikely to form between inner circumferential surface 14c of protective tube 14 and bond magnet 13.

[0043] The expansion rate of protective tube 14 is the ratio of the outer diameter (diameter) after expansion in radial direction Rd to the reference diameter of protective tube 14. The outer diameter of protective tube 14 after expansion in radial direction Rd can be determined, for example, by measuring the outer diameters of first end 14a and second end 14b of protective tube 14 after being filled with bonded magnet 13 and averaging the measured values.

[0044] The predetermined value for the expansion rate of protective tube 14 can be determined by taking into consideration the linear expansion coefficient of bonded magnet 13 or the difference in linear expansion between bonded magnet 13 and protective tube 14. For example, the reference diameter of protective tube 14 and the diameter of bonded magnet 13 after hardening can be determined by simulation, and the predetermined value for the expansion rate of protective tube 14 can be set to an expansion rate that can absorb this difference.

[0045] Alternatively, a value that causes protective tube 14 to bulge in the radial direction Rd even after bond magnet 13 has hardened may be used as the predetermined value for the expansion rate of protective tube 14. For example, the outer diameter (cured diameter) of protective tube 14 after bond magnet 13 has hardened may be compared with a reference diameter of protective tube 14, and the predetermined value for the expansion rate may be determined so that the hardened diameter is larger than the reference diameter. If the hardened diameter is made larger than the reference diameter, the tight contact between bond magnet 13 and inner surface 14c of protective tube 14 can be stably maintained. In this case, the predetermined value (set value) can be, for example, 0.1% or more. Furthermore, taking into consideration shape stability, the possibility of breakage, and the like, the predetermined value can be 0.5% or less.

[0046] In the filling process, bond magnet 13 is filled into magnet region MR so that it remains in filling hole 11a. A state in which bond magnet 13 remains in filling hole 11a means a state in which bond magnet 13 and first ring portion 11 can maintain close contact within filling hole 11a even after bond magnet 13 hardens. For example, a state in which bond magnet 13 remains in filling hole 11a includes not only a state in which bond magnet 13 completely fills filling hole 11a, but also a state in which bond magnet 13 at least partially fills filling hole 11a. Furthermore, filling hole 11a has one or more first through holes 111 (see FIG. 4). Bond magnet 13 is filled so that it remains in one or more first through holes 111. Alternatively, bond magnet 13 may be filled so that it remains in all of first through holes 111.

[0047] Furthermore, bond magnet 13 may be filled in magnet region MR so as to remain in vent hole 12a. A state in which bond magnet 13 remains in vent hole 12a refers to a state in which bond magnet 13 and second ring portion 12 can maintain close contact within vent hole 12a even after bond magnet 13 hardens. A state in which bond magnet 13 remains in vent hole 12a includes, for example, not only a state in which bond magnet 13 completely fills vent hole 12a, but also a state in which bond magnet 13 at least partially fills vent hole 12a. Furthermore, vent hole 12a has one or more second through holes 121. Bond magnet 13 may be filled so as to remain in one or more second through holes 121. Furthermore, bond magnet 13 may be filled so as to remain in all second through holes 121. Furthermore, bond magnet 13 may be filled so as to remain in all first through holes 111 and all second through holes 121.

[0048] 7(d), in the demolding process, bond magnet 13 is held in magnet region MR for a certain period of time at a temperature lower than that at the time of filling, and hardens. Bond magnet 13 shrinks during the hardening process, and protective tube 14 shrinks inward in radial direction Rd to follow this shrinkage. For example, the post-hardening diameter of protective tube 14 is larger than the reference diameter, and close contact between protective tube 14 and bond magnet 13 is maintained. After bond magnet 13 has hardened, mold 50 is removed from motor rotor 2, and mold 50 is demolded.

[0049] Next, the effects of the method for manufacturing the rotor motor according to the embodiment will be described.

[0050] In the manufacturing method of motor rotor 2 described above, molten bond magnet 13 is injected and filled, causing protective tube 14 to expand in radial direction Rd. Therefore, even when bond magnet 13 cools and shrinks in the radial direction, protective tube 14 follows bond magnet 13, and as a result, bond magnet 13 and protective tube 14 are unlikely to separate, making it easy to ensure a stable, tight contact state without any gaps.

[0051] Furthermore, when bond magnet 13 hardens, bond magnet 13 remains in filling hole 11a of first ring portion 11. As a result, bond magnet 13 and first ring portion 11 are engaged with each other, and the torque transmission performance between bond magnet 13 and shaft 10 via first ring portion 11 can be improved. Furthermore, when bond magnet 13 hardens, bond magnet 13 can also remain in gas vent hole 12a of second ring portion 12. As a result, bond magnet 13 and second ring portion 12 are engaged with each other, and the torque transmission performance between bond magnet 13 and shaft 10 via second ring portion 12 can be improved.

[0052] Furthermore, protective tube 14 can be made of fiber-reinforced resin, for example, carbon fiber-reinforced resin. The resin contained in bonded magnet 13 is, for example, a high-resistance material, and by making protective tube 14 out of fiber-reinforced resin, for example, carbon fiber-reinforced plastic (CFRP), it is possible to reduce eddy current loss.

[0053] Furthermore, bond magnet 13 in a molten state is injected and filled so that a bulge in the radial direction Rd of protective tube 14 remains even after bond magnet 13 has hardened. As a result, even after bond magnet 13 has hardened, a state of close contact with protective tube 14 and bond magnet 13 can be formed with no gaps between them, and even if centrifugal force acts when motor rotor 2 is in use, gaps are unlikely to form between protective tube 14 and bond magnet 13, and torque transmission performance can be maintained.

[0054] Furthermore, the predetermined value for the expansion rate that leaves protective tube 14 bulging in radial direction Rd even after bond magnet 13 has hardened can be set to 0.1% or more relative to the reference diameter of protective tube 14. Although this depends on the material of bond magnet 13, a state in which protective tube 14 bulges in radial direction Rd even after bond magnet 13 has hardened can usually be created by setting the predetermined value to 0.1% or more. Therefore, it becomes easier to adjust the pressure when injecting and filling bond magnet 13 so that protective tube 14 and bond magnet 13 are in close contact with each other with no gaps after bond magnet 13 has hardened.

[0055] Next, the operation and effects of the rotor motor according to the embodiment will be described.

[0056] First ring portion 11 of motor rotor 2 protrudes from shaft 10 in radial direction Rd, and bond magnet 13 is disposed within first through-hole 111 of first ring portion 11 and has first engaging portion 13a that is in close contact with first ring portion 11 within first through-hole 111. Therefore, bond magnet 13 and first ring portion 11 are engaged with each other, and the torque transmission performance between bond magnet 13 and shaft 10 via first ring portion 11 can be improved.

[0057] Furthermore, second ring portion 12 of motor rotor 2 protrudes from shaft 10 in radial direction Rd, and bond magnet 13 is disposed within second through-hole 121 of second ring portion 12 and includes second engaging portion 13b that is in close contact with second ring portion 12 within second through-hole 121. Therefore, bond magnet 13 and second ring portion 12 are engaged with each other, and the torque transmission performance between bond magnet 13 and shaft 10 via second ring portion 12 can be improved.

[0058] The first ring portion 11 has a first positioning portion 11d that positions the first end portion 14a of the protective tube 14, and the second ring portion 12 has a second positioning portion 12d that positions the second end portion 14b. The protective tube 14 is sandwiched between the first positioning portion 11d of the first ring portion 11 and the second positioning portion 12d of the second ring portion 12, and is positioned in a stable state.

[0059] Bonded magnet 13 is provided with a first contact portion 13x that is disposed between protective tube 14 and first ring portion 11 and that is in close contact with protective tube 14 and first ring portion 11, and a second contact portion 13y that is disposed between protective tube 14 and second ring portion 12 and that is in close contact with protective tube 14 and second ring portion 12. First contact portion 13x and second contact portion 13y strengthen the bond between protective tube 14 and first ring portion 11 and second ring portion 12, improving the torque transmission performance between bonded magnet 13 and shaft 10.

[0060] Bond magnet 13 also includes first adhesion layer 131 that is in close contact with protective tube 14 and first convex portion 112. Bond magnet 13 may also include second adhesion layer 133 that is in close contact with protective tube 14 and second convex portion 122. First adhesion layer 131 and second adhesion layer 133 strengthen the bond between protective tube 14 and first ring portion 11 and second ring portion 12, improving the torque transmission performance between bond magnet 13 and shaft 10.

[0061] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. For example, it is also possible to form an engagement portion by leaving the bond magnet only in the filling hole, without leaving the bond magnet in the gas vent hole. Also, in the above embodiment,

[0062] The gist of the present disclosure is as follows: [1] A method for manufacturing a motor rotor, wherein the motor rotor includes a first ring portion extending radially from a shaft and having a filling hole for a bonded magnet, and a second ring portion extending radially from the shaft and positioned opposite the first ring portion in the direction of the shaft's rotation axis, the method comprising: placing a protective tube in a molding die, the protective tube being positioned between the first ring portion and the second ring portion so as to surround the shaft, and forming a gap between the protective tube and the molding die that allows radial expansion of the protective tube; injecting a molten bonded magnet through the filling hole into a magnet region surrounded by the shaft, the first ring portion, the second ring portion, and the protective tube to expand the protective tube radially and leave the bonded magnet in the filling hole; and releasing the molding die after the bonded magnet in the magnet region has hardened. [2] The method for manufacturing a motor rotor according to [1], wherein the protective tube is made of carbon fiber resin. Alternatively, the method for manufacturing a motor rotor according to [1], wherein the protective tube is made of carbon fiber reinforced resin. [3] The method for manufacturing a motor rotor according to [1] or [2], wherein a molten bonded magnet is injected and filled through the filling hole to expand the protective tube in the radial direction so that the radial bulge of the protective tube remains even after the bonded magnet has hardened. [4] The method for manufacturing a motor rotor according to [3], wherein the expansion rate of the protective tube so that the radial bulge of the protective tube remains even after the bonded magnet has hardened is 0.1% or more compared to the diameter of the protective tube before the bonded magnet is filled. [5] A motor rotor comprising: a shaft rotatable around a rotation axis; a first ring portion extending radially from the shaft; a second ring portion extending radially from the shaft and positioned opposite the first ring portion in a direction along the rotation axis; a bonded magnet positioned between the first ring portion and the second ring portion; and a cylindrical protective tube covering the bonded magnet, wherein the first ring portion has a through hole, and the bonded magnet is positioned within the through hole and has an engaging portion that is in close contact with the first ring portion within the through hole.[6] The motor rotor according to [5], wherein the protective tube has a first end abutting the first ring portion and a second end abutting the second ring portion, the first ring portion has a first positioning portion that positions the first end, and the second ring portion has a second positioning portion that positions the second end. [7] The motor rotor according to [6], wherein the first positioning portion has a first convex portion that fits into the first end to position the first end, and the second positioning portion has a second convex portion that fits into the second end to position the second end, and the bonded magnet has a first adhesion layer that is arranged between the inner circumferential surface of the protective tube and the outer circumferential surface of the first convex portion and is in close contact with the protective tube and the first convex portion, and a second adhesion layer that is arranged between the inner circumferential surface of the protective tube and the outer circumferential surface of the second convex portion and is in close contact with the protective tube and the second convex portion. [8] The motor rotor according to any one of [5] to [7], wherein the first ring portion comprises a first inner circumferential portion fixed to the shaft and a first outer circumferential portion opposite the first inner circumferential portion in the radial direction of the shaft, the second ring portion comprises a second inner circumferential portion fixed to the shaft and a second outer circumferential portion opposite the second inner circumferential portion in the radial direction of the shaft, and a step is formed between at least one of the first outer circumferential portion and the outer circumferential surface of the protective tube in the radial direction of the shaft. [9] The motor rotor according to any one of [5] to [8], wherein the bonded magnet comprises a first contact portion disposed between the protective tube and the first ring portion and in close contact with the protective tube and the first ring portion, and a second contact portion disposed between the protective tube and the second ring portion and in close contact with the protective tube and the second ring portion.

[0063] 2 Motor rotor 10 Shaft 11 First ring portion 11a Filling hole 11d First positioning portion 12 Second ring portion 12d Second positioning portion 13 Bond magnet 13a First engaging portion (engaging portion) 13x First contact portion 13y Second contact portion 14 Protective tube 14a First end portion 14b Second end portion 14d Outer circumferential surface of protective tube 50 Mold (molding die) 111 First through hole (through hole) 112 First convex portion 114 First inner circumferential portion 115 First outer circumferential portion 122 Second convex portion 124 Second inner circumferential portion 125 Second outer circumferential portion 131 First contact layer Rd Radial direction La Rotation axis direction MR Magnet region St Step S Gap

Claims

1. A method for manufacturing a motor rotor, wherein the motor rotor comprises a first ring portion that protrudes radially from a shaft and has a filling hole for a bonded magnet, and a second ring portion that protrudes radially from the shaft and is positioned opposite the first ring portion in the direction of the shaft's rotational axis, the manufacturing method comprising: installing a protective tube that is positioned between the first ring portion and the second ring portion so as to surround the shaft in a molding die, and forming a gap between the protective tube and the molding die that allows for radial expansion of the protective tube; injecting a molten bonded magnet through the filling hole to fill a magnet region surrounded by the shaft, the first ring portion, the second ring portion, and the protective tube, causing the protective tube to expand radially and leaving the bonded magnet in the filling hole; and releasing the molding die after the bonded magnet in the magnet region has hardened.

2. The method for manufacturing a motor rotor according to claim 1, wherein the protective tube is made of carbon fiber reinforced resin.

3. A method for manufacturing a motor rotor as described in claim 1, wherein a molten bonded magnet is injected and filled through the filling hole to expand the protective tube in the radial direction so that the radial bulge of the protective tube remains even after the bonded magnet has hardened.

4. A method for manufacturing a motor rotor as described in claim 3, wherein the expansion rate of the protective tube, such that the radial bulge of the protective tube remains even after the bonded magnet has hardened, is 0.1% or more of the diameter of the protective tube before the bonded magnet is filled.

5. A motor rotor comprising: a shaft rotatable around a rotation axis; a first ring portion extending radially from the shaft; a second ring portion extending radially from the shaft and positioned opposite the first ring portion in a direction along the rotation axis; a bonded magnet positioned between the first and second ring portions; and a cylindrical protective tube covering the bonded magnet, wherein the first ring portion has a through hole, and the bonded magnet is positioned within the through hole and has an engaging portion that is in close contact with the first ring portion within the through hole.

6. A motor rotor according to claim 5, wherein the protective tube has a first end abutting against the first ring portion and a second end abutting against the second ring portion, the first ring portion has a first positioning portion that positions the first end, and the second ring portion has a second positioning portion that positions the second end.

7. A motor rotor as described in claim 6, wherein the first positioning portion comprises a first convex portion that fits into the first end portion to position the first end portion, the second positioning portion comprises a second convex portion that fits into the second end portion to position the second end portion, and the bonded magnet comprises a first adhesion layer that is arranged between the inner surface of the protective tube and the outer surface of the first convex portion and is in close contact with the protective tube and the first convex portion, and a second adhesion layer that is arranged between the inner surface of the protective tube and the outer surface of the second convex portion and is in close contact with the protective tube and the second convex portion.

8. A motor rotor as claimed in claim 5, wherein the first ring portion comprises a first inner peripheral portion fixed to the shaft and a first outer peripheral portion on the opposite side of the shaft from the first inner peripheral portion in the radial direction of the shaft, the second ring portion comprises a second inner peripheral portion fixed to the shaft and a second outer peripheral portion on the opposite side of the shaft from the second inner peripheral portion in the radial direction of the shaft, and a step is formed in the radial direction of the shaft between at least one of the first outer peripheral portion and the second outer peripheral portion and the outer surface of the protective tube.

9. A motor rotor as described in claim 5, wherein the bonded magnet has a first contact portion that is arranged between the protective tube and the first ring portion and is in close contact with the protective tube and the first ring portion, and a second contact portion that is arranged between the protective tube and the second ring portion and is in close contact with the protective tube and the second ring portion.

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