Rotor unit, rotating electric machine and method for manufacturing a rotor unit

Abstract

A rotor unit for a rotating electric machine, which has the following features: a plurality of rotating bodies arranged along a central axis; wherein Each of the plural rotating bodies comprises the following characteristics: a ring-shaped rotor core that surrounds the central axis; a plurality of magnets arranged in a circumferential direction around the rotor core; and a holder arranged to hold the majority of magnets; wherein the holder comprises a plurality of partitioning sections, each extending axially between the respective plurality of magnets; wherein an axial dimension of the plurality of partitioning sections is longer than an axial dimension of the plurality of magnets held by the plurality of partitioning sections; and the majority of rotating bodies are arranged in a state in which the circumferential positions of the majority of magnets of the respective majority of rotating bodies are not in alignment. wherein the plurality of rotating bodies comprises a first rotating body and a second rotating body arranged along the central axis in a state in which first surfaces face each other and second surfaces face away from each other; a holder of both the first rotating body and the second rotating body further comprising a connecting section that connects the majority of partitioning sections; the connecting section comprises a contact surface that comes into contact with an end section on the side of a second surface of the plurality of magnets; and an axial dimension from the contact surface to an end section on the side of a first surface of the plurality of partitioning sections is longer than the axial dimension of the plurality of magnets; wherein the partitioning sections of each of the plurality of rotating bodies are connected only on one side by a connecting section that connects end sections of the partitioning sections.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to a rotor unit, a rotating electrical machine and a method for manufacturing a rotor unit. 2. Description of related technology

[0002] An internal rotor type of motor is known from the past, in which a rotor unit rotates with magnets inside a coil. For example, WO 2006 / 008964 A1 describes a brushless motor provided with a stator and a rotor arranged inside the stator.

[0003] The rotor described in WO 2006 / 008964 A1 comprises a rotor shaft, a rotor core, a magnet holder and six rotor magnets. Furthermore, in paragraphs

[0048] to

[0051] and Fig. 8 of WO 2006 / 008 964 A1 describes a rotor in a step-offset form, in which the rotor magnet on the front side and the rotor magnet on the back side are mounted in such a way that they are shifted in a step shape.

[0004] In the example shown in Fig. However, as shown in Figure 8 of WO 2006 / 008964 A1, contact between the front-side magnet and the back-side magnet is not prevented. Therefore, the magnets come into contact with each other due to impact during manufacturing, transportation, or use, resulting in a problem that cracking or chipping may occur in the magnets on one or both sides. Cracking or chipping of the magnet causes a deterioration in the magnetic properties of a motor and also becomes a noise factor.

[0005] JP 2011-67057 A relates to a magnet unit comprising a rotor core externally mounted and fixed to a rotating shaft; a plurality of magnets arranged side by side along a circumferential direction on an outer peripheral surface of the rotor core; and a magnet holder for circumferentially positioning the plurality of magnets. The magnet holder includes a plurality of arm units arranged between the plurality of magnets; and a base unit provided at one end of the plurality of arm units and connecting the respective arm units 36.

[0006] JP 2002-34188 A further relates to a rotor for a permanent magnet motor comprising a permanent magnet, a yoke made of a ferromagnetic body provided near the permanent magnet, and a clamping element used for tightening against a rotating shaft. The permanent magnet, the yoke, and the clamping element are integrally bonded together by a resin in a mold. SUMMARY OF THE INVENTION

[0007] Preferred embodiments of the present invention provide a technique that reduces or prevents damage to magnets by preventing contact between the magnets in a rotor unit of a rotating electrical machine.

[0008] A first preferred embodiment of the present invention relates to a rotor unit arranged to rotate an electric machine. The rotor unit arranged to rotate an electric machine includes a plurality of rotating bodies arranged along a central axis. Each of the plurality of rotating bodies includes an annular rotor core surrounding the central axis, a plurality of magnets arranged in the circumferential direction around the rotor core, and a holder that holds the plurality of magnets. The holder includes a plurality of partitioning portions each extending axially between the plurality of magnets. The axial dimension of the plurality of partitioning portions is longer than the axial dimension of the plurality of magnets held by the plurality of partitioning portions.The plurality of rotating bodies are arranged in a state where the circumferential positions of the plurality of magnets are not in alignment.

[0009] A second preferred embodiment of the present invention relates to a method for manufacturing a rotor unit for a rotating electrical machine. The rotor unit for a rotating electrical machine includes a plurality of rotating bodies. Each of the plurality of rotating bodies includes an annular rotor core surrounding a central axis, a plurality of magnets arranged circumferentially around the rotor core, and a holder made of resin that holds the plurality of magnets.The method for manufacturing a rotor unit includes the following steps: (a) insert-molding the holder by placing the rotor core inside a mold and injecting resin into the mold (the holder is molded into a shape having a plurality of partitioning portions extending axially along the outer peripheral surface of the rotor core); (b) arranging the plurality of magnets each between a pair of adjacent ones of the plurality of partitioning portions after step (a); and (c) axially arranging the plurality of rotating bodies manufactured by steps (a) and (b). In step (a), the holder is molded such that the axial dimension of the plurality of partitioning portions becomes longer than the axial dimension of the plurality of magnets.In step (c), the plurality of rotating bodies are arranged in a state in which the circumferential positions of the plurality of magnets are not in alignment.

[0010] According to the first preferred embodiment of the present invention, contact between the plurality of magnets is prevented. Accordingly, damage to each magnet can be significantly reduced or prevented.

[0011] According to the second preferred embodiment of the present invention, contact between the plurality of magnets is prevented. Accordingly, damage to each magnet can be significantly reduced or prevented. Furthermore, the molding process shortens the manufacturing process of the rotor core and the holder. Furthermore, compared to a case where the molding is performed including the magnets, a plurality of magnets can be easily and accurately positioned.

[0012] The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE CHARACTERS Fig. 1 is a perspective view of a rotor unit according to a preferred embodiment of the present invention. Fig. 2 is a longitudinal sectional view of an engine according to a preferred embodiment of the present invention. Fig. 3 is a perspective view of a first rotating body according to a preferred embodiment of the present invention. Fig. 4 is a plan view of the first rotating body according to a preferred embodiment of the present invention. Fig. 5 is a perspective view of the first rotating body and a second rotating body according to a preferred embodiment of the present invention. Fig. 6 is a partial side view of the first rotating body and the second rotating body according to a preferred embodiment of the present invention. Fig. 7 is a partial longitudinal sectional view of the rotor unit according to a preferred embodiment of the present invention. Fig. 8 is a flowchart showing a manufacturing process of the rotor unit according to a preferred embodiment of the present invention. Fig. 9 is a side view of a first rotating body, a second rotating body, and a rotating center body according to a preferred embodiment of the present invention. Fig. 10 is a partial side view of the first rotating body, the second rotating body, and the rotating center body according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, exemplary preferred embodiments of the present invention will be described with reference to the drawings. In addition, the shape or positional relationship of each part will be described hereinafter such that each of the surfaces facing each other of a first rotating body and a second rotating body is regarded as an "upper surface" and each of the surfaces facing away from each other is regarded as a "lower surface." However, these conditions are defined merely for convenience of explanation. These conditions are not intended to limit the positions when using a rotor unit and a rotating electrical machine related to the various preferred embodiments of the present invention.

[0014] Fig. 1 is a perspective view of a rotor unit 32A for a rotating electric machine according to a preferred embodiment of the present invention.

[0015] As in Fig. 1, the rotor unit 32A preferably comprises two rotating bodies 41A and 42A. The two rotating bodies 41A and 42A are arranged along a central axis 9A. In addition, Fig. 1 some hidden lines of the rotating body 41A are shown by dashed lines.

[0016] Each of the two rotating bodies 41A and 42A preferably includes a rotor core 51A, a holder 52A, and a plurality of magnets 53A. The rotor core 51A is an annular member surrounding the central axis 9A. The plurality of magnets 53A are arranged circumferentially around the rotor core 51A and are held by the holder 52A.

[0017] The holder 52A preferably includes a plurality of partitioning sections 60A, each extending axially between the magnets 53A. As shown in Fig. 1, the axial dimension of each partitioning portion 60A is made longer than the axial dimension of the magnet 53A held by the partitioning portions 60A.

[0018] Furthermore, the two rotating bodies 41A and 42A are arranged in a state where the circumferential positions of the plurality of magnets 53A are not aligned. For this reason, the partitioning portion 60A restricts the axial movement of the magnet 53A. Thus, contact between the magnet 53A of the rotating body 41A on one side and the magnet 53A of the rotating body 42A on the other side is prevented. Therefore, damage to each magnet 53A is significantly reduced or prevented.

[0019] In manufacturing the rotor unit 32A, preferably, the rotor core 51A is first placed inside a mold. Then, resin is injected into the mold. In this way, the holder 52A is cast into a mold having the plurality of partitioning portions 60A. Here, the holder 52A is molded such that the axial dimension of the partitioning portion 60A becomes longer than the axial dimension of the magnet 53A. In the casting manufacturing process, both the molding of the holder 52A and the fixing of the rotor core 51A to the holder 52A are performed. For this reason, the process of manufacturing the rotor core 51A and the holder 52A is shortened.

[0020] Thereafter, the magnet 53A is arranged between a pair of adjacent partition portions 60A. When attempting to mold the magnets, it is necessary to fix the magnets to the rotor core at least once with an adhesive or the like before molding. In contrast, in this preferred embodiment, the magnets 53A are positioned using the holder 52A after molding is completed, and then hardening is performed. For this reason, compared with the case of performing the molding including the magnets 53A, the plurality of magnets 53A can be easily and accurately positioned.

[0021] Thereafter, the two rotating bodies 41A and 42A manufactured through the above process are arranged in the axial direction. At this time, the plurality of rotating bodies 41A and 42A are arranged in a state where the circumferential positions of the plurality of magnets 53A are not aligned.

[0022] A more specific preferred embodiment of the present invention will be described below.

[0023] Fig. Fig. 2 is a longitudinal sectional view of a motor 1, which is an example of a rotating electrical machine according to a preferred embodiment of the present invention. The motor 1 relating to this preferred embodiment is preferably mounted on an automobile and generates, for example, the driving force of a power steering system. As shown in Fig. 2, the motor 1 comprises a fixed part 2 and a rotating part 3. The rotating part 3 is mounted so that it can rotate with respect to the fixed part 2.

[0024] The fixed part 2 in this preferred embodiment preferably comprises a housing 21, a cover part 22, an armature 23, a lower bearing part 24 and an upper bearing part 25.

[0025] The housing 21 is preferably a bottomed and cylindrical or approximately cylindrical casing that accommodates the armature 23, the lower bearing part 24, and the rotating part 3 inside it. A concave portion 211, which is arranged to hold the lower bearing part 24, is preferably defined in the center of the lower surface of the housing 21. The cover part 22 is preferably a flat or substantially flat plate-shaped member that blocks an opening of an upper portion of the housing 21. A circular hole 221, which is arranged to hold the upper bearing part 25, is preferably provided in the center or approximately in the center of the cover part.

[0026] The armature 23 generates a magnetic flux depending on a drive current. The armature 23 preferably includes a stator core 26 and a coil 27. The stator core 26 is preferably defined by laminated steel plates, with a plurality of steel plates being laminated in the axial direction (i.e., a direction along a central axis 9). The stator core 26 includes an annular core back 261 and a plurality of tooth portions 262 protruding inward from the core back 261 in the radial direction (i.e., a direction perpendicular or substantially perpendicular to the central axis 9). The core back 261 is fixed to the inner peripheral surface of a side wall of the housing 21. The coil 27 is preferably defined by a conductive wire wound around each tooth portion 262 of the stator core 26.

[0027] The lower bearing part 24 and the upper bearing part 25 are mechanisms that rotatably support a shaft 31 on the side of the rotating part 3. In both the lower bearing part 24 and the upper bearing part 25 in this preferred embodiment, a ball bearing is preferably used in which an outer spherical shell and an inner spherical shell are rotated relative to each other by a spherical body. However, instead of the ball bearing, another type of bearing could also be used, such as a plain bearing, a fluid bearing, etc.

[0028] An outer spherical shell 241 of the lower bearing part 24 is preferably fixed to the concave portion 211 of the housing 21. Further, an outer spherical shell 251 of the upper bearing part 25 is preferably fixed to an edge of the circular hole 221 of the cover part 22. On the other hand, inner spherical shells 242 and 252 of the lower bearing part 24 and the upper bearing part 25 are preferably fixed to the shaft 31. For this reason, the shaft 31 is supported so that it can rotate with respect to the housing 21 and the cover part 22.

[0029] The rotating part 3 in this preferred embodiment preferably comprises the shaft 31 and a rotor unit 32.

[0030] The shaft 31 is a roughly columnar member extending in the up-and-down direction along the central axis 9. The shaft 31 rotates around the central axis 9 while being supported by the lower bearing part 24 and the upper bearing part 25, as described above. Furthermore, the shaft 31 preferably includes a head portion 311 protruding from the cover part 22. The head portion 311 is preferably connected to, for example, a steering gear of an automobile through a power transmission mechanism such as a gear.

[0031] The rotor unit 32 is a unit that rotates radially inside the armature 23 together with the shaft 31. The rotor unit 32 preferably comprises a first rotating body 41, a second rotating body 42, and a cover 43.

[0032] Each of the first rotating body 41 and the second rotating body 42 in this preferred embodiment preferably includes a rotor core 51, a magnet holder 52, and a plurality of magnets 53. The first rotating body 41 and the second rotating body 42 are arranged along the central axis 9 in a state where first surfaces where the magnets 53 are exposed face each other and second surfaces, which are the other end surfaces, face away from each other.

[0033] The cover 43 is a cylindrical or approximately cylindrical member that supports the rotor unit 32. The cover 43 is arranged to cover the outer periphery and a portion of each of the two axial end surfaces of the rotor unit 32. In this way, the first rotating body 41 and the second rotating body 42 are maintained in contact with each other.

[0034] In the motor 1, when a drive current is supplied to the coil 27 of the fixed part 2, a radial magnetic flux is generated in a plurality of tooth portions 262 of the stator core 26. Then, a circumferential torque is generated by the action of the magnetic flux between each tooth portion 262 and each magnet 53. Consequently, the rotating part 3 rotates around the central axis 9 with respect to the fixed part 2. When the rotating part 3 rotates, a drive force is preferably transmitted to, for example, the steering gear connected to the shaft 31.

[0035] The following describes the more detailed structure of the rotor unit 32. As described above, the rotor unit 32 in this preferred embodiment preferably includes the first rotating body 41, the second rotating body 42, and the cover 43. The following describes the structures of the first rotating body 41 and the second rotating body 42 first.

[0036] Fig. 3 is a perspective view of the first rotating body 41 according to a preferred embodiment of the present invention. Fig. Figure 4 is a diagram showing the first rotating body 41 as viewed from the side of the upper surface. As shown in the Fig. 3 and Fig. 4, the first rotating body 41 preferably includes the rotor core 51, the magnet holder 52, and the plurality of magnets 53.

[0037] The rotor core 51 is an annular member surrounding the central axis 9. A through hole 511, into which the shaft 31 is inserted, is preferably provided in the center of the rotor core 51. The rotor core 51 is preferably defined by laminated steel plates, with electromagnetic steel plates laminated in the axial direction. The rotor core 51 in this preferred embodiment has an outer peripheral surface with an approximately regular polygonal column shape. A plurality of groove portions 512 extending in the axial direction are preferably provided in the outer peripheral surface of the rotor core 51. Each groove portion 512 is recessed radially inward at a boundary portion between the flat surfaces defining the outer peripheral surface of the rotor core 51.

[0038] The magnet holder 52 is preferably a resin-made component that holds the magnets 53. The magnet holder 52 preferably includes a plurality of partitioning sections 60 and an annular connecting section 70 connecting end portions on the lower surface side of the plurality of partitioning sections 60. The plurality of partitioning sections 60 are arranged at regular or approximately regular intervals in the circumferential direction. Each partitioning section 60 extends axially along the side surface of the rotor core 51 in the vicinity of the groove portion 512 of the rotor core 51.

[0039] The partitioning portion 60 preferably includes an inner columnar portion 61 and an outer columnar portion 62. The inner columnar portion 61 extends axially within the groove portion 512, i.e., further toward the inside in the radial direction than the outer peripheral surface of the rotor core 51. In this preferred embodiment, an end portion on the upper surface side of the inner columnar portion 61 is disposed at an axial position equal to or approximately equal to the upper surface of the rotor core 51. The outer columnar portion 62 extends axially further toward the outside in the radial direction than the outer peripheral surface of the rotor core 51.A convex portion 63, which protrudes further to the second rotating body 42 side than the upper surface of the rotor core 51, is provided at an end portion on the upper surface side of the outer columnar portion 62.

[0040] The plurality of magnets 53 are arranged around the rotor core 51. Each magnet 53 preferably has a flat or approximately flat plate-like outer configuration and is press-fitted between a pair of adjacent partitioning portions 60. An end portion on the lower surface side of the magnet 53 comes into contact with the connecting portion 70 of the magnet holder 52. This means that the connecting portion 70 of the magnet holder 52 preferably includes a contact surface 71 that contacts the end portion on the lower surface side of the magnet 53.

[0041] The radially outer surface of the magnet 53 defines a magnetic pole surface facing the armature 23. The plurality of magnets 53 are arranged at regular intervals in the circumferential direction in such a manner that an N-pole magnetic pole surface and an S-pole magnetic pole surface are alternately arranged. In addition, a sintered magnet based on an Nd-Fe-B alloy, for example, can preferably be used as the magnet 53.

[0042] The second rotating body 42 in this preferred embodiment is arranged in a state where the upper surface and the lower surface are reversed. However, a structure itself is approximately the same as that of the first rotating body 41. This means that the second rotating body 42 preferably includes the rotor core 51, the magnet holder 52, and the plurality of magnets 53, which are the same as those of the first rotating body 41. Regarding the details of each part of the second rotating body 42, overlapping explanation will be omitted.

[0043] Fig. 5 is a perspective view of the first rotating body 41 and the second rotating body 42 arranged inside the cover 43. As shown in Fig. 5, the first rotating body 41 and the second rotating body 42 are axially arranged in a state where the first surfaces face each other and the second surfaces face away from each other. Furthermore, preferably, the first rotating body 41 and the second rotating body 42 are arranged in a state where the circumferential positions of the plurality of magnets 53 are not aligned. In this way, the circumferential positions of the plurality of magnets 53 being not aligned reduces sticking or torque ripple of the motor 1.

[0044] As described above, the end portion on the upper surface side of the inner columnar portion 61 is arranged at an axial position equal to or approximately equal to the upper surface of the rotor core 51. Then, the convex portion 63 (refer to Fig. 3) provided at a position farther outward in the radial direction than the outer peripheral surface of the rotor core 51. For this reason, in this preferred embodiment, the circumferential positions of the first rotating body 41 and the second rotating body 42 can be positioned out of alignment with each other while the rotor cores 51 are brought into contact with each other. In addition, the end portion on the upper surface side of the inner columnar portion 61 can also be arranged farther toward the lower surface side than the upper surface of the rotor core 51.

[0045] Fig. 6 is a partial side view of the first rotating body 41 and the second rotating body 42. As in Fig. 6, in each of the rotating bodies 41 and 42, the axial dimension d1 from the contact surface 71 of the connecting portion 70 to an end portion on the upper surface side of the convex portion 63 is preferably longer than the axial dimension d2 of the magnet 53. For this reason, even if the axial position of the magnet 53 is shifted before the magnets 53 come into contact with each other, an end portion on the upper surface side of the magnet 53 comes into contact with the convex portion 63 of the rotating body on the other side. This means that the convex portion 63 of the partitioning portion 60 restricts axial movement of the magnet 53. In this way, contact between the magnets 53 is prevented. As a result, damage to the magnet 53 can be significantly reduced or prevented.

[0046] Specifically, in this preferred embodiment, the rotor core 51 preferably has an outer shape of an approximately regular polygonal columnar shape. Then, the rotor cores 51 of the two rotating bodies 41 and 42 are arranged in a state where their circumferential positions are not aligned. For this reason, corner portions of the rotor core 51 of the rotating body on one side protrude outward in the radial direction from the rotor core 51 on the other side and axially face the magnets 53 of the rotating body on the other side. Therefore, if an axial movement of the magnet 53 is not restricted, contact may occur between the corner portion of the rotor core 51 and the magnet 53.

[0047] In this regard, in this preferred embodiment, the convex portions 63 of each rotating body preferably protrude further toward the other rotating body side than the upper surface of the rotor core 51. This means that the axial dimension d1 from the contact surface 71 and the end portion on the upper surface side of the convex portion 63 is longer than the axial dimension d3 from the contact surface 71 to the upper surface of the rotor core 51. Furthermore, the axial dimension d2 of the magnet 53 is shorter than the axial dimension d3 from the contact surface 71 to the upper surface of the rotor core 51.

[0048] For this reason, even if the axial position of the magnet 53 is shifted, the magnet 53 comes into contact with the convex portion 63 of the rotating body on the other side before coming into contact with the corner portion of the rotor core 51. In this way, the partitioning portion 60 in this preferred embodiment preferably prevents not only contact between the magnets 53, but also contact between the rotor core 51 and the magnet 53. In this way, damage to the magnet 53 is further reduced or prevented.

[0049] Furthermore, in this preferred embodiment, the axial dimension d3 from the contact surface 71 to the upper surface of the rotor core 51 is preferably larger than the sum of the axial dimension d2 of the magnet 53 and the axial dimension d4 from the upper surface of the rotor core 51 to the end portion on the upper surface side of the convex portion 63. For this reason, a clearance is provided between the magnet 53 of the rotating body on one side and the convex portion 63 of the rotating body on the other side. This clearance allows dimensional errors of each component to be absorbed.

[0050] In particular, in this preferred embodiment, the rotor core 51 is preferably defined by laminated steel plates. For this reason, the axial dimension of the rotor core 51 is susceptible to variations. Therefore, proximity of the magnets 53 to each other or proximity of the rotor core 51 to the magnet 53 may occur. However, if the above-described dimensional relationship is satisfied, contact between the magnets 53 and contact between the rotor core 51 and the magnet 53 can be prevented.

[0051] Next, a fixing structure of the cover 43 to the first rotating body 41 and the second rotating body 42 will be described. The cover 43 is preferably made of a non-magnetic metal such as aluminum, an aluminum alloy, stainless steel, etc. The cover 43 is preferably formed, for example, by press working or the like. Fig. 7 is a partial longitudinal sectional view of the rotor unit 32. As in Fig. 7, the cover 43 preferably includes a cylindrical portion 431, a first annular depressed portion 432, and a second annular depressed portion 433. The cylindrical portion 431 surrounds the outer peripheral surfaces of the first rotating body 41 and the second rotating body 42. In addition, the cover 43 is not limited to a non-magnetic metal and may also be formed of non-magnetic resin or the like.

[0052] The first annular countersunk portion 432 is an annular portion folded radially inward along the lower surface of the first rotating body 41. The first annular countersunk portion 432 comes into contact with the lower surface of the magnet holder 52 of the first rotating body 41. Here, in the lower surface of the connecting portion 70, a plurality of cutouts 72 and 73 are formed. Fig. 5. A radially inner end portion of the first annular depressed portion 432 is preferably further depressed so as to fit into the cutouts 72 and 73. In this way, relative circumferential rotation about the central axis 9 of the first rotating body 41 and the cover 43 is prevented.

[0053] In addition, the plurality of cutouts 72 and 73 are provided at circumferential positions corresponding to the plurality of magnets 53, as shown in Fig. 5. Furthermore, in this preferred embodiment, the plurality of cutouts 72 and 73 preferably include a rectangular cutout 72 and a semicircular cutout 73, and the cutouts 72 and 73, which are therefore distinguishable in appearance, are arranged alternately in the circumferential direction. Even after the cover 43 is attached, the cutouts 72 and 73 are visible from the outside of the rotor unit 32. Therefore, the positions of an N pole and an S pole of the rotor unit 32 can be confirmed based on the cutouts 72 and 73.

[0054] The second annular depressed portion 433 is preferably folded radially inward along an edge of the lower surface on the side of the second rotating body 42. The second annular depressed portion 433 comes into contact with the lower surface of the magnet holder 52 of the second rotating body 42. The radial dimension of the second annular depressed portion 433 is preferably smaller than the radial dimension of the first annular depressed portion 432. In this way, the occurrence of wrinkles in the second annular depressed portion 433 is substantially reduced or prevented.

[0055] The first rotating body 41 and the second rotating body 42 are sandwiched between the first annular depressed portion 432 and the second annular depressed portion 433 in a state where the first rotating body 41 and the second rotating body 42 come into contact with the first annular depressed portion 432 and the second annular depressed portion 433, respectively. In this way, the first rotating body 41 and the second rotating body 42 are held in a state where they contact each other. In this way, the cover 43 in this preferred embodiment easily and reliably fixes the first rotating body 41 and the second rotating body 42 by depressing both end portions.The structure of the cover 43 can be widely applied to fixing a plurality of rotating bodies arranged axially without being limited to the first rotating body 41 and the second rotating body 42 in this preferred embodiment.

[0056] An example of a method for manufacturing the rotor unit 32 will be described below with reference to the flowchart of Fig. 8 described.

[0057] In manufacturing the rotor unit 32, a pair of molds and the prefabricated rotor core 51 are first prepared (step S1). The rotor core 51 is preferably manufactured, for example, by axially laminating steel plates processed by stamping. The pair of molds defines a cavity corresponding to the shapes of the rotor core 51 and the magnet holder 52 inside the rotor core by bringing their opposing surfaces into contact with each other.

[0058] Next, the rotor core 51 is placed inside the pair of molds (step S2). Here, the rotor core 51 is first placed inside the mold on one side. Then, an upper portion of the above mold is blocked by the mold on the other side. In this way, a state is created in which a cavity is defined inside the molds and the rotor core 51 is placed in the cavity.

[0059] Next, resin in a fluid state is injected into the cavity defined inside the mold (step S3). Here, resin in a fluid state is preferably injected into the cavity in the mold through a gate provided on the mold.

[0060] Once the resin has completely spread throughout the entire cavity in the mold, the resin in the mold is subsequently cooled and solidified (step S4). The resin in the mold is solidified to form the magnet holder 52. Further, the rotor core 51 and the magnet holder 52 are fixed together with the solidification of the resin. The magnet holder 52 is molded to have the plurality of partitioning portions 60 and the connecting portion 70 and to have the above-described dimensional relationship in Fig. 6 to be fulfilled.

[0061] Thereafter, the pair of molds is opened and the rotor core 51 and the magnet holder 52 are then released from the molds (step S5).

[0062] The above steps S1 to S5 are an example of molding. At the time of molding, both the molding of the magnet holder 52 and the fixing of the rotor core 51 to the magnet holder 52 are performed. For this reason, compared to a case where the rotor core 51 and the magnet holder 52 are manufactured separately and fixed to each other, the process of manufacturing the rotor core 51 and the magnet holder 52 can be shortened.

[0063] At the time of pouring, it is preferable to position the rotor core 51 by bringing the upper surface of the rotor core 51 into contact with the mold on one side. This means that it is preferable to position the rotor core 51 axially inside the pair of molds with the upper surface side as the standard. When the rotor core 51 is positioned with the upper surface side as the standard, even if there is a variation in the axial dimension of the rotor core 51, the thickness of the connecting portion 70 of the magnet holder 52 is increased or decreased depending on the variation. Therefore, the dimensional relationship of d1 to d4 described above can be realized regardless of the variation in the axial dimension of the rotor core 51.

[0064] Once the molding is completed, the magnet 53 is subsequently provided and press-fitted between a pair of adjacent outer columnar portions 62 (step S6). Then, preferably, the bottom surface of the magnet 53 is brought into contact with the contact surface 71 of the connecting portion 70. The axial and circumferential positions of the magnet 53 are determined by the contact surface 71 and the outer columnar portion 62 of the magnet holder 52.

[0065] If one attempts to arrange a plurality of magnets inside the mold during pouring, the structure of the mold inevitably becomes much more complicated in order to perform positioning of the magnets with respect to the rotor core. Or, it is necessary to fix the magnets to the rotor core once before pouring using adhesive or the like. In contrast, in this preferred embodiment, the magnet 53 is positioned using the magnet holder 52 after pouring is completed and solidification is performed. For this reason, it is possible to easily and accurately position a plurality of magnets 53.

[0066] Each of the first rotating body 41 and the second rotating body 42 is manufactured through the above steps S1 to S6. In this preferred embodiment, the magnet holder 52 of the first rotating body 41 and the magnet holder 52 of the second rotating body 42 have approximately the same shape. For this reason, during molding, it is possible to manufacture the magnet holder 52 of both rotating bodies 41 and 42 using the same mold.

[0067] Next, the first rotating body 41 and the second rotating body 42 are axially arranged (step S7). Here, the first rotating body 41 and the second rotating body 42 are arranged in a state where the upper surfaces of both rotating bodies 41 and 42 face each other, the lower surfaces of both rotating bodies 41 and 42 face away from each other, and the circumferential positions of the plurality of magnets 53 are not aligned.

[0068] Next, the cover 43 is attached to the first rotating body 41 and the second rotating body 42 (step S8). Here, after the first rotating body 41 and the second rotating body 42 are inserted into the cylindrical cover 43, both end portions of the cover 43 are depressed to form the first depressed portion 432 and the second depressed portion 433. In this way, the first rotating body 41 and the second rotating body 42 are fixed to each other in a state of contacting each other.

[0069] Next, another preferred embodiment of the present invention will be described, focusing on differences between it and the preferred embodiment described above. Fig. 9 is a side view of a rotor unit 32B relating to another preferred embodiment. In Fig. 9, a representation of the cover is omitted. As in Fig. 9, the rotor unit 32B preferably includes a first rotating body 41B, a second rotating body 42B, and a rotating center body 44B.

[0070] The structures of the first rotating body 41B and the second rotating body 42B are preferably the same as those of the first rotating body 41 and the second rotating body 42 in the above-described preferred embodiment. That is, each of the first rotating body 41B and the second rotating body 42B preferably includes a rotor core 51B, a magnet holder 52B, and a plurality of magnets 53B similar to those in the above-described preferred embodiments. Regarding the details of each part, overlapping explanation will be omitted.

[0071] The rotating center body 44B preferably includes a center rotor core 54B, a center magnet holder 55B, and a plurality of center magnets 56B. As the center rotor core 54B in this preferred embodiment, a rotor core similar to the rotor core 51B of the first rotating body 41B and the second rotating body 42B is preferably used. The center rotor core 54B is fixed to a shaft between a pair of rotor cores 51B.

[0072] Furthermore, in this preferred embodiment, a magnet similar to the magnet 53B of both the first rotating body 41B and the second rotating body 42B is preferably used as the center magnet 56B. The plurality of center magnets 56B are arranged at regular intervals around the center rotor core 54B. The number of center magnets 56B included in the center rotating body 44B is preferably made equal to the number of magnets 53B included in the first rotating body 41B and the second rotating body 42B.

[0073] The center magnet holder 55B is preferably a resin-made member that holds the center magnets 56B. The center magnet holder 55B differs from the magnet holders 52B of the first rotating body 41B and the second rotating body 42B in that the center magnet holder 55B does not include a connecting portion 70B. The center magnet holder 55B preferably includes a plurality of center partitioning portions 90B. Each center partitioning portion 90B extends axially between the center magnets 56B that are adjacent to each other.

[0074] A first convex portion 93B is preferably provided at an end portion on the first rotating body 41B side of each center partitioning portion 90B. The first convex portion 93B protrudes further toward the first rotating body 41B side than an end portion on the first rotating body 41B side of the center rotor core 54B. Further, a second convex portion 94B is preferably provided at an end portion on the second rotating body 42B side of each center partitioning portion 90B. The second convex portion 94B protrudes further toward the second rotating body 42B side than an end portion on the second rotating body 42B side of the center rotor core 54B.

[0075] As in Fig. 9, the first rotating body 41B and the second rotating body 42B are preferably axially arranged in a state where the first surfaces face each other and the second surfaces face away from each other. Further, the center rotating body 44B is arranged between the first rotating body 41B and the second rotating body 42B. The first rotating body 41B, the center rotating body 44B, and the second rotating body 42B are preferably arranged in a state where the circumferential positions of the plurality of magnets 53B and 56B are not in alignment. In this way, by having the circumferential positions of the plurality of magnets 53B and 56B not in alignment, sticking or torque ripple of a motor is preferably reduced.

[0076] Fig. 10 is a partial side view of the first rotating body 41B, the second rotating body 42B, and the rotating center body 44B. As shown in Fig. 10, the axial dimension d5 of the center partitioning portion 90B, that is, the axial dimension d5 from an end portion on the first rotating body 41B side of the first convex portion 93B to an end portion on the second rotating body 42B side of the second convex portion 94B is preferably longer than the axial dimension d6 of the center rotor core 54B. Further, the axial dimension d7 of the center magnet 56B is preferably shorter than the axial dimension d6 of the center rotor core 54B. Then, the center magnet 56B is arranged between a convex portion 63B provided at a partitioning portion 60B of the first rotating body 41B and a convex portion 63B provided at a partitioning portion 60B of the second rotating body 42B.

[0077] For this reason, even if the axial position of the center magnet 56B is shifted before the center magnet 56B comes into contact with another magnet 53B or the rotor core 51B, the end surface of the center magnet 56B comes into contact with the convex portion 63B of the first rotating body 41B or the second rotating body 42B. In this way, the convex portions 63B of the partitioning portions 60B of the first rotating body 41B and the second rotating body 42B restrict axial movement of the center magnet 56B. In this way, damage to the center magnet 56B is significantly reduced or prevented.

[0078] Further, in each of the first rotating body 41B and the second rotating body 42B, the axial dimension d8 from a contact surface 71B to an end portion on the upper surface side of the convex portion 63B is preferably longer than the axial dimension d9 from the contact surface 71B to the upper surface of the rotor core 51B. Further, the axial dimension d10 of the magnet 53B is preferably shorter than the axial dimension d9 from the contact surface 71B to the upper surface of the rotor core 51B. Then, the magnet 53B is arranged between the contact surface 71B and the first convex portion 93B or the second convex portion 94B provided at the center partitioning portion 90B.

[0079] In the Fig.In the example shown in Figure 10, a clearance is provided between the first convex portion 93B and the upper surface of the magnet 53B of the first rotating body 41B. This clearance allows for dimensional errors of each component. Furthermore, even if the axial position of the magnet 53B of the first rotating body 41B shifts, the end surface of the magnet 53B preferably comes into contact with the first convex portion 93B before the magnet 53B comes into contact with the center magnet 56B or the center rotor core 54B. In this way, the first convex portion 93B of the center partitioning portions 90B restricts axial movement of the magnet 53B of the first rotating body 41B. In this way, damage to the magnet 53B is significantly reduced or prevented.

[0080] On the other hand, the second convex portion 94B comes into contact with the upper surface of the magnet 53B of the second rotating body 42B. This means that in this preferred embodiment, the magnet 53B of the second rotating body 42B preferably comes into contact with both the contact surface 71B of the second rotating body 42B and the second convex portion 94B. In this way, the displacement of the axial position of the magnet 53B of the second rotating body 42B is prevented.

[0081] The rotating center body 44B is preferably manufactured by a manufacturing method based on the method for manufacturing the first rotating body 41B or the second rotating body 42B in the preferred embodiments described above. The center magnet holder 55B is preferably cast after the center rotor core 54B is placed inside a mold.

[0082] At the time of pouring, for example, the end surface on the first rotating body 41B side of the center rotor core 54B is brought into contact with a mold on one side. This means that the center rotor core 54B is axially positioned inside a pair of molds with the end surface on the first rotating body 41B side as the standard. Therefore, it is possible to cause the first convex portion 93B to protrude from the end surface on the first rotating body 41B side of the center rotor core 54B, regardless of a variation in the axial dimension of the center rotor core 54B.

[0083] However, when the center rotor core 54B is positioned with the end surface on the first rotating body 41B side as a standard, a positional relationship between the end surface on the second rotating body 42B side of the center rotor core 54B and the end portion on the second rotating body 42B side of the second convex portion 94B is varied by a variation in the axial dimension of the center rotor core 54B. For this reason, in this preferred embodiment, the second convex portion 94B is preferably formed longer than the first convex portion 93B, so that the second convex portion 94B is forced to protrude from the end surface on the second rotating body 42B side of the center rotor core 54B.Then, when the second rotating body 42B and the rotating center body 44B are arranged, a leading end portion of the second convex portion 94B is pressed against the magnet 53B of the second rotating body 42B while being squeezed, thereby adjusting the dimension of the second convex portion 94B.

[0084] Furthermore, in this preferred embodiment, the dimensions of the center rotor core 54B and the center magnet holder 55B are set such that the end surface on the second rotating body 42B side of the center rotor core 54B is preferably located further toward the second rotating body 42B side than a base end portion of the second convex portion 94B, regardless of a variation in the axial dimension of the center rotor core 54B. In this way, the end surface on the second rotating body 42B side of the center rotor core 54B and the upper surface of the rotor core 51B of the second rotating body 42B are caused to contact each other.

[0085] Features of the above-described preferred embodiments and modifications thereof may be appropriately combined as long as no conflict arises.

[0086] For example, the outer peripheral surface of the rotor core may also have a polygonal column shape as described above, and a cylindrical shape is also acceptable as another example. Furthermore, the number of partitioning sections of the magnet holder or the number of magnets may also be a number different from that in the preferred embodiments described above.

[0087] The partitioning portion may also protrude further to the side of the rotating body on the other side than the upper surface of the rotor core without the convex portion as described above.

[0088] The magnet holder may also be manufactured by casting as described above, and may also be molded independently separately from the rotor core.

[0089] The plurality of rotating bodies relating to the various preferred embodiments of the present invention may also have structures that differ from one another, and the rotor unit according to various preferred embodiments of the present invention may also include four or more rotating bodies. For example, two or more of the rotating center bodies may also be arranged between the first rotating body and the second rotating body.

[0090] Furthermore, the rotating electric machine according to various preferred embodiments of the present invention may also be a motor for power steering as described above, and may also be, for example, a motor used elsewhere in an automobile. For example, the rotating electric machine according to various preferred embodiments of the present invention may also be a motor for generating the driving force of an electric automobile. Furthermore, the rotating electric machine according to various preferred embodiments of the present invention may also be a motor used in, for example, an electric power-assisted bicycle, an electric motorcycle, a household electrical appliance, office equipment, medical equipment, or the like.

[0091] Furthermore, it is also possible to provide an electric generator using a structure similar to that of the motors related to the above-described preferred embodiments or modified examples thereof. The rotating electric machine according to various preferred embodiments of the present invention and modifications thereof can also be an electric generator used, for example, in an automobile, an electric power-assisted bicycle, wind power generation, or the like.

[0092] Furthermore, the respective elements included in the above-described preferred embodiments or modified examples may also be appropriately combined within a range where no inconsistency occurs.

[0093] The preferred embodiments of the present invention and modifications thereof can be used in a rotor unit, a rotating electrical machine, and a method of manufacturing a rotor unit.

[0094] While preferred embodiments of the present invention have been described above, it should be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.

Claims

[1] A rotor unit for a rotating electrical machine having the following features: a plurality of rotating bodies arranged along a central axis; wherein each of the plurality of rotating bodies includes the following features: an annular rotor core surrounding the central axis; a plurality of magnets arranged in a circumferential direction around the rotor core; and a holder arranged to hold the plurality of magnets; wherein the holder comprises a plurality of partitioning portions each extending axially between respective ones of the plurality of magnets; wherein an axial dimension of the plurality of partitioning sections is longer than an axial dimension of the plurality of magnets held by the plurality of partitioning sections; and the plurality of rotating bodies are arranged in a state in which circumferential positions of the plurality of magnets of respective ones of the plurality of rotating bodies are not in alignment. wherein the plurality of rotating bodies comprises a first rotating body and a second rotating body arranged along the central axis in a state where first surfaces face each other and second surfaces face away from each other; a holder of each of the first rotating body and the second rotating body further comprises a connecting portion connecting the plurality of partitioning portions; the connecting portion includes a contact surface that comes into contact with an end portion on the side of a second surface of the plurality of magnets; and an axial dimension from the contact surface to an end portion on the first surface side of the plurality of partitioning portions is longer than the axial dimension of the plurality of magnets; wherein the partitioning portions of each of the plurality of rotating bodies are connected only at one side by a connecting portion connecting end portions of the partitioning portions. [2] The rotor unit according to claim 1, wherein an axial dimension from the contact surface to an end portion on the first surface side of the rotor core is shorter than an axial dimension from the contact surface to the end portion on the first surface side of the plurality of partitioning portions and longer than the axial dimension of the plurality of magnets. [3] The rotor unit according to claim 2, wherein the rotor core includes an outer peripheral surface having a regular polygonal column shape. [4] The rotor unit according to claim 2, wherein the plurality of partitioning sections comprises the following features: an inner columnar portion located further toward an inner side in a radial direction than an outer peripheral surface of the rotor core; and an outer columnar portion located further toward an outer side in the radial direction than the outer peripheral surface of the rotor core; wherein an end portion on the first surface side of the inner columnar portion is arranged at an axial position equal to or farther from that of the second surface side than the end portion on the first surface side of the rotor core; and wherein an end portion on the first surface side of the outer columnar portion is disposed further toward the first surface side than the end portion on the first surface side of the rotor core. [5] The rotor unit according to claim 1, wherein an axial dimension from the contact surface to the end portion on the first surface side of the rotor core is larger than a sum of an axial dimension from the end portion on the first surface side of the rotor core to the end portion on the first surface side of the plurality of partitioning portions and the axial dimension of the plurality of magnets. [6] The rotor unit according to claim 1, wherein the plurality of partitioning portions includes a convex portion provided at an end portion thereof on the first surface side. [7] The rotor unit according to claim 1, wherein the holder of the first rotating body and the holder of the second rotating body have a shape identical to each other. [8] The rotor unit according to claim 1, wherein the holder is a resin component; and the holder is made of a cast-in material to be fixed to the surface of the rotor core. [9] The rotor unit according to claim 1, wherein the plurality of rotating bodies further comprises a rotating center body disposed between the first rotating body and the second rotating body; wherein a magnet of the first rotating body is arranged between a contact surface of the first rotating body and a partitioning portion of the rotating center body; wherein a magnet of the rotating center body is arranged between a partitioning portion of the first rotating body and a partitioning portion of the second rotating body; and wherein a magnet of the second rotating body is arranged between a contact surface of the second rotating body and the partitioning portion of the rotating center body. [10] The rotor unit according to claim 9, wherein the partitioning section of the rotating center body comprises the following features: a first convex portion provided at an end portion thereof on the side of a first rotating body; and a second convex portion provided at an end portion thereof on the side of a second rotating body. [11] The rotor unit according to claim 10, wherein the first convex portion protrudes further toward the first rotating body side than an end portion on the first rotating body side of a rotor core of the rotating center body; the second convex portion protrudes further toward the second rotating body side than an end portion on the second rotating body side of the rotor core of the rotating center body; and the magnet of the second rotating body comes into contact with both the contact surface of the second rotating body and the second convex portion. [12] The rotor unit according to claim 11, wherein the end portion on the second rotating body side of the rotor core of the rotating center body is arranged further toward the second rotating body side than a base end portion of the second convex portion. [13] A rotating electrical machine having the following characteristics: a fixed part; and a rotating part mounted to rotate relative to the fixed part, wherein the rotating part includes the following features: the rotor unit according to claim 1; and a shaft inserted into the rotor core; and the fixed part includes the following features: Bearing parts that support the shaft in a rotatable manner; and an armature arranged in a radial direction outwardly from the rotor unit. [14] A method of manufacturing a rotor unit for a rotating electrical machine comprising a plurality of rotating bodies each comprising an annular rotor core surrounding a central axis, a plurality of magnets arranged in a circumferential direction around the rotor core, and a holder made of resin and arranged to hold the magnets, the method comprising the steps of: (a) molding the holder into a mold having a plurality of partitioning portions extending axially along an outer peripheral surface of the rotor core by disposing the rotor core inside a mold and injecting resin into an interior of the mold; (b) disposing a respective one of the plurality of magnets between a pair of adjacent ones of the plurality of partitioning sections after step (a); and (c) axially arranging the plurality of rotating bodies manufactured by steps (a) and (b); wherein in step (a), the holder is formed such that an axial dimension of the pair of adjacent ones of the plurality of partitioning portions becomes longer than an axial dimension of the respective one of the plurality of magnets; and in step (c), the plurality of rotating bodies are arranged in a state in which circumferential positions of the plurality of magnets of respective ones of the plurality of rotating bodies are not in alignment; such that the plurality of rotating bodies includes a first rotating body and a second rotating body arranged along the central axis in a state where first surfaces face each other and second surfaces face away from each other; such that a holder of each of the first rotating body and the second rotating body further comprises a connecting portion connecting the plurality of partitioning portions; so that the connecting portion includes a contact surface that comes into contact with an end portion on the side of a second surface of the plurality of magnets; and such that an axial dimension from the contact surface to an end portion on the first surface side of the plurality of partitioning portions is longer than the axial dimension of the plurality of magnets; such that the partitioning portions of each of the plurality of rotating bodies are connected only at one side by a connecting portion connecting end portions of the partitioning portions.

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