Patent Application
20130257184
1. Field of the Invention
The present invention relates to a rotor unit, a rotating electrical machine, and a method for manufacturing a rotor unit.
2. Description of the Related Art
In the related art, an inner rotor type motor that rotates a rotor unit having magnets inside a coil is known. For example, WO-A 2006-008964 discloses a brushless motor including a stator, and a rotor arranged inside the stator.
The rotor of WO-A 2006-008964 includes a rotor shaft, a rotor core, a magnet holder, and six rotor magnets. Paragraph 0026 of WO-A 2006-008964 discloses that the rotor core is fixed to the rotor shaft, and the six rotor magnets are attached to an outer periphery of the rotor core. Additionally, Paragraph 0027 of WO-A 2006-008964 discloses that the magnet holder is fixed to the rotor shaft.
Additionally, Paragraph 0029 of WO-A 2006-008964 descloses that a fitting projection of the magnet holder is fitted into an electrode holder attachment groove formed at an outer peripheral portion of the rotor core. In WO-A 2006-008964, such fitting prevents a holder arm of the magnet holder from slipping out of the rotor core in a radial direction.
However, WO-A 2006-008964 does not disclose how to obtain the axial fixing strength between the rotor core and the magnet holder. Particularly, if the rotor core and the magnet holder are not firmly fixed in an axial direction when the magnets are press-fitted to the magnet holder in the axial direction, there is a concern that the rotor core and the magnet holder may be separated from each other due to the load at the time of press-fitting.
An object of the invention is to provide the technique of improving the fixing strength between a rotor core and a holder in a rotor unit of a rotating electrical machine.
A rotor unit for a rotating electrical machine that is a first exemplary invention of the present application includes an annular rotor core made of laminated steel sheets that are vertically laminated; a plurality of magnets arranged in a circumferential direction around the rotor core; and a holder made of resin that holds the magnets. The holder has a plurality of partitioning portions that extends vertically along an outer peripheral surface of the rotor core, and a coupling portion that connects the plurality of partitioning portions. The rotor core and the holder are fixed by insert molding. In the outer peripheral surface of the rotor core, a portion of resin that constitutes the holder is present between the plurality of steel sheets that constitutes the rotor core. The magnet is press-fitted into a pair of partitioning portions that is mutually adjacent.
A second exemplary invention of the present application is a method for manufacturing a rotor unit for a rotating electrical machine including an annular rotor core made of laminated steel sheets that are vertically laminated, a plurality of magnets arranged in a circumferential direction around the rotor core, and a holder made of resin that holds the magnets. The manufacturing method includes the following steps. One is a) arranging the rotor core inside a mold, injecting resin in a fluidized state into the mold, and insert-molding the holder in a shape having a plurality of partitioning portions that extends vertically along an outer peripheral surface of the rotor core, and a coupling portion that connects the partitioning portions. Another is b) press-fitting the magnet to the pair of partitioning portions that are mutually adjacent after step a).
According to the first exemplary invention of the present application, in the outer peripheral surface of the rotor core, a portion of resin that constitutes the holder is present between the plurality of steel sheets that constitutes the rotor core. This improves the fixing strength of the rotor core and the holder.
According to the second exemplary invention of the present application, the manufacturing process of the rotor core and the holder is shortened by the insert molding. Additionally, a portion of resin that constitutes the holder is present between the plurality of steel sheets that constitutes the rotor core. This improves the fixing strength of the rotor core and the holder. Additionally, since the separation between the rotor core and the holder is suppressed, the magnets can be easily press-fitted.
The present invention is arranged to achieve an improvement in perpendicularity of the upper end surface of the thrust portion with respect to the outside surface of the shaft.
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 of the present invention with reference to the attached drawings.
Exemplary embodiments of the invention will be described below, referring to the drawings. In addition, the shapes and positional relationship of respective portions will be described with a direction along the central axis of a rotating electrical machine being a vertical direction. However, this merely defines the vertical direction for the convenience of description, and does not limit the posture of a rotor unit and a rotating electrical machine related to the invention when being used.
The rotor core 41A is an annular member made of laminated steel sheets that are vertically laminated. The holder 42A is a member made of resin, which holds the magnets 43A. The holder 42A has a plurality of partitioning portions 60A and a coupling portion 70A. The plurality of partitioning portions 60A extends vertically along the outer peripheral surface of the rotor core 41A, respectively. The coupling portion 70A connects the plurality of partitioning portions 60A. The plurality of magnets 43A is arranged in the circumferential direction around the rotor core 41A. Each magnet 43A is press-fitted into a pair of partitioning portions 60 that is mutually adjacent.
When the rotor unit 32A is manufactured, first, the rotor core 41A is arranged inside a mold. Then, resin in a fluidized state is injected into the mold. By injecting resin, the holder 42A is insert-molded in a shape having the plurality of partitioning portions 60A and a coupling portion 70A. Thereafter, the magnet 43A is press-fitted between a pair of partitioning portions 60A that is mutually adjacent.
As such, in the present embodiment, the rotor core 41A and the holder 42A are fixed by insert molding. For this reason, the process of manufacturing the rotor core 41A and the holder 42A is shortened.
Subsequently, a more specific embodiment of the invention will be described.
The stationary portion 2 of the present embodiment has a housing 21, a lid portion 22, an armature 23, a lower bearing 24, and an upper bearing 25.
The housing 21 is a bottomed, substantially cylindrical housing that accommodates the armature 23, the lower bearing 24, and the rotating portion 3 therein. A recess 211 that holds the lower bearing 24 is formed at the center of the bottom of the housing 21. The lid portion 22 is a plate-shaped member that closes an upper opening of the housing 21. A circular hole 221 that holds the upper bearing 25 is formed at the center of the lid portion 22.
The armature 23 generates magnetic flux according to a driving current. The armature 23 has a stator core 26 and a coil 27. The stator core 26 is made of laminated steel sheets in which a plurality of steel sheets is laminated in an axial direction (a direction along the central axis 9; this is the same in the following). The stator core 26 has an annular core back 261, and a plurality of teeth 262 that protrude toward the inside in a radial direction (a direction orthogonal to the central axis 9; this is the same in the following) from the core back 261. The core back 261 is fixed to the inner peripheral surface of the side wall of the housing 21. The coil 27 is constituted by conducting wires that are wound around each tooth 262 of the stator core 26.
The lower bearing 24 and the upper bearing 25 rotatably support a shaft 31 on the side of the rotating portion 3. Ball bearings that allow an outer ring and an inner ring to rotate relatively via balls are used for the lower bearing 24 and the upper bearing 25 of the present embodiment.
An outer ring 241 of the lower bearing 24 is fixed to the recess 211 of the housing 21. Additionally, an outer ring 251 of the upper bearing 25 is fixed to the edge of the circular hole 221 of the lid portion 22. On the other hand, inner rings 242 and 252 of the lower bearing 24 and the upper bearing 25 are fixed to the shaft 31. For this reason, the shaft 31 is rotatably supported with respect to the housing 21 and the lid portion 22.
The rotating portion 3 of the present embodiment has the shaft 31, a pair of rotor units 32 and 33, and a cover 34.
The shaft 31 is a substantially cylindrical member that extends in the vertical direction along the central axis 9. The shaft 31 rotates about the central axis 9, and is supported by the above-described lower bearing 24 and upper bearing 25. Additionally, the shaft 31 has a head 311 that protrudes upward from the lid portion 22. The head 311 is coupled to a power steering device of an automobile via a power transmission mechanism, such as a gear.
The pair of rotor units 32 and 33 and the cover 34 rotate along with the shaft 31 radially inside the armature 23. The pair of rotor units 32 and 33 has a rotor core 41, a magnet holder 42, and a plurality of magnets 43, respectively. The pair of rotor units 32 and 33 is arranged in the axial direction in a state where the units are turned upside down. The detailed structure of the rotor units 32 and 33 will be described below.
The cover 34 is a substantially cylindrical member that holds the pair of rotor units 32 and 33. The cover 34 covers the outer peripheral surface of the rotor units 32 and 33 and portions of upper and lower end surfaces of the rotor units. Thereby, the pair of rotor units 32 and 33 is maintained in a state where the units are brought close to each other or brought into contact with each other.
In such a motor 1, if a driving current is applied to the coil 27 of the stationary portion 2, radial magnetic flux is generated in the plurality of teeth 262 of the stator core 26. Then, circumferential torque is generated by the action of the magnetic flux between the teeth 262 and the magnet 43, and the rotating portion 3 rotates about the central axis 9 with respect to the stationary portion 2. If the rotating portion 3 rotates, a driving force is transmitted to the power steering device coupled to the shaft 31.
As described above, the motor 1 of the present embodiment has the pair of rotor units 32 and 33. The detailed structure of the rotor unit 32 arranged on the lower side will be described below. Although the rotor unit 33 arranged on the upper side is arranged in a state where the rotor unit 32 arranged on the lower side is vertically reversed, since the structure itself thereof is equivalent to that of the lower rotor unit 32, duplicate description thereof will be omitted.
The rotor core 41 is an annular member fixed to the shaft 31. The rotor core 41 is made of laminated steel sheets in which electromagnetic steel sheets are vertically laminated. The rotor core 41 of the present embodiment has a regular polygonal columnar appearance. A through hole 51 that allows the shaft 31 to be inserted therethrough is provided at the center of the rotor core 41. Additionally, the outer peripheral surface of the rotor core 41 is provided with a plurality of groove portions 52 that extends in the axial direction. The groove portions 52 are depressed radially inward at boundary portions of a plurality of planes that constitutes the outer peripheral surface of the rotor core 41.
The magnet holder 42 is a member that holds the magnets 43 made of resin. The magnet holder 42 has a plurality of partitioning portions 60, and a coupling portion 70 that connects lower ends of the plurality of partitioning portions 60. The plurality of partitioning portions 60 is arranged at equal intervals in the circumferential direction. Each partitioning portion 60 extends in the axial direction along the lateral face of the rotor core 41 in the vicinity of each groove portion 52 of the rotor core 41. The coupling portion 70 is a circular portion located below the plurality of partitioning portions 60. A radial inside portion of the coupling portion 70 comes in contact with the lower surface of the rotor core 41.
In
As for the rotor core 41 and the magnet holder 42 of the present embodiment, both the members slightly bite into each other at the boundary portion thereof. Thereby, the rotor core 41 and the magnet holder 42 are firmly fixed. Particularly, resin is present in an axial gap formed between a steel sheet 411 and a steel sheet 411. For this reason, the axial relative movement between the rotor core 41 and the magnet holder 42 is suppressed.
The plurality of steel sheets 411 that constitutes the rotor core 41 is obtained by punching, respectively. For this reason, as shown in the enlarged view in
Additionally, as shown in
Particularly, in the present embodiment, the engaging portion 61 of which the dimension in a width direction increases toward the inside in the radial direction engages the groove portion 52 of which the dimension in the width direction decreases toward the outside in the radial direction. This further suppresses the radial separation of the rotor core 41 and the magnet holder 42.
The plurality of magnets 43 is arranged around the rotor core 41. Each magnet 43A is substantially arcuate on the external diameter side thereof and substantially linear on the internal diameter side thereof, and is press-fitted into a pair of partitioning portions 60 that is mutually adjacent. The radial outside surface of the magnet 43 is a magnetic polar surface that faces the armature 23. The plurality of magnets 43 is arranged at equal intervals so that an N magnetic polar surface and an S magnetic polar surface are alternately arranged in the circumferential direction. In addition, for example, an Nd—Fe—B alloy based sintered magnet can be used for a magnet 43.
The partitioning portion 60 of the magnet holder 42 has the columnar portion 62 and a wall portion 63. The columnar portion 62 is a portion that extends in the axial direction between the magnets 43 that are mutually adjacent. The wall portion 63 is a portion that spreads toward one side or the other side in the circumferential direction from the columnar portion 62. The radial outside surface of the magnet 43 is partially covered with the wall portion 63.
An upper end of the wall portion 63 is located lower than an upper end of the rotor core 41. For this reason, when a magnet 43 is attached, the lower end of the magnet 43 is brought into contact with the lateral face of the rotor core 41, so that the magnet 43 can be positioned in the radial direction. The magnet 43 positioned in the radial direction can be press-fitted radially inward of the wall portion 63.
Additionally, the upper end of the wall portion 63 is located lower than an upper end of the columnar portion 62. For this reason, when a magnet 43 is attached, the lower end of the magnet 43 can be easily inserted between the pair of columnar portions 62 that is mutually adjacent. Additionally, the magnet 43 can be positioned in the radial direction by the pair of columnar portions 62, and then, the magnet 43 can then be press-fitted radially inward of the wall portion 63.
If the magnet 43 is positioned in the radial direction and the circumferential direction in this way, the bias of the load at the time of press-fitting can be suppressed. Accordingly, it is possible to suppress the magnet 43 from shaving off the partitioning portions 60 of the magnet holder 42 and generating dust at the time of press-fitting.
Additionally, in the present embodiment, an inclined surface 631 is provided in the vicinity of an upper end of the radial inside surface of the wall portion 63. The inclined surface 631 gradually approaches the outer peripheral surface of the rotor core 41 downward from an upper end. The inclined surface 631 guides the magnet 43 radially inward of the wall portion 63 at the time of the press-fitting of the magnet 43. This facilitates the press-fitting work of the magnet 43. Additionally, as the magnet 43 is guided to a proper position, the bias of the load at the time of press-fitting is further suppressed. As a result, generation of dust accompanying the press-fitting is further suppressed.
Additionally, if such an inclined surface 631 is provided, the vicinity of the upper end of the wall portion 63 can be easily separated from a mold at the time of insert molding. In this way, the inclined surface 631 has technical value at the time of both press-fitting and insert molding.
The coupling portion 70 has a bottom 71 located below the magnet 43. That is, the bottom 71 is also arranged at a circumferential position between the partitioning portions 60 that are mutually adjacent. The lower surface of the magnet 43 after press-fitting faces the upper surface of the bottom 71 in the axial direction, and the lower surface of the magnet 43 and the upper surface of the bottom 71 separate from or come into contact with each other. Additionally, the bottom 71 has a recess 72 below both ends the magnet 43 in the circumferential direction. The recess 72 of the present embodiment is provided at a position surrounded by the lateral face of the rotor core 41, the columnar portion 62, and the wall portion 63.
Even if the magnet 43 contacts the columnar portion 62 or the wall portion 63 to generate dust at the time of the press-fitting of the magnet 43, the dust is received in the recess 72. For this reason, it is possible to suppress a problem of the dust being caught between the upper surface of the bottom 71 and the lower surface of the magnet 43, whereby the axial position of the magnet 43 deviates. Additionally, the recess 72 is sealed by the lower surface of the magnet 43 after press-fitting, and becomes a closed space. For this reason, scattering of the dust received in the recess 72 to the outside is prevented.
In addition, at the time of the press-fitting of the magnet 43, the columnar portion 62 receives a stronger load from the magnet 43 than the wall portion 63. Accordingly, the columnar portion 62 becomes a source of dust more easily than the wall portion 63. If this point is taken into consideration, it is preferable that the recess 72 be provided at least at a position adjacent to the lower end of the columnar portion 62.
Subsequently, an example of a method for manufacturing the rotor unit 32 will be described, referring to
When the rotor unit 32 is manufactured, first, a pair of molds 81 and 82 and the rotor core 41 made in advance are prepared (Step S1). The pair of molds 81 and 82 form a cavity 83 inside the pair of molds 81 and 82 by bringing mutually opposed surfaces into contact with each other. The cavity 83 corresponds to the shape of the rotor core 41 and the magnet holder 42. The rotor core 41 is made of laminated steel sheets in which steel sheets subjected to punching are laminated in the axial direction.
Next, the rotor core 41 is arranged inside the pair of molds 81 and 82 (Step S2). Here, first, the rotor core 41 is set inside one mold 81. Then, the upper portion of the mold 81 is closed by the other mold 82. Thereby, the cavity 83 is formed inside molds 81 and 82, bringing a state where the rotor core 41 is arranged in the cavity 83.
Thereafter, resin 421 in a fluidized state is injected into the cavity 83 (Step S3). Here, as shown in
If the resin 421 in the fluidized state spreads in the cavity 83, the resin 421 in the mold 81 and 82 is cooled and solidified (Step S4). The resin 421 in the mold 81 and 82 is solidified into the magnet holder 42. The magnet holder 42 is molded in a shape having the plurality of partitioning portions 60 and the coupling portion 70, including the above engaging portion 61, the columnar portion 62, the wall portion 63, the inclined surface 631, the bottom 71, and the recess 72.
Additionally, the rotor core 41 and the magnet holder 42 are fixed along with the solidification of the resin. Thereby, in the lateral face of the rotor core 41, a portion of the resin that constitutes the magnet holder 42 is present among the plurality of steel sheets 411 that constitutes the rotor core 41. Thereby, the rotor core 41 and the magnet holder 42 are firmly fixed.
Thereafter, the pair of molds 81 and 82 are opened, and the rotor core 41 and the magnet holder 42 are separated from the molds 81 and 82 (Step S5). The inclined surface 631 is formed at the upper end of the wall portion 63 of the magnet holder 42. For this reason, the wall portion 63 can be easily separated from the mold 82.
The above Steps S1 to S5 are the procedure that becomes an example of the insert molding. Thereby, the rotor core 41 and the magnet holder 42 of
Subsequently, a magnet 43 is prepared, and the magnet 43 is positioned at a position to be inserted with respect to the rotor core 41 and the magnet holder 42 (Step S6). Here, first, a lower end of the magnet 43 is brought close to the lateral face of the rotor core 41 above the wall portion 63 as indicated by an arrow 84 in
Next, the magnet 43 is moved downward as indicated by an arrow 85 in
Thereafter, the magnet 43 is press-fitted to the pair of columnar portions 62 that is mutually adjacent and the wall portion 63 (Step S7). In the above step S6, the magnet 43 is positioned in the radial direction and in the circumferential direction. For this reason, the bias of load at the time of press-fitting is suppressed. As a result, generation of dust accompanying the press-fitting is suppressed.
Additionally, the magnet holder 42 of the present embodiment has the recess 72 below both ends the magnet 43 in the circumferential direction. For this reason, even if the magnet 43 shaves off the partitioning portion 60 generating dust 86 at the time of press-fitting, as shown in
Additionally, the rotor core 41 and the magnet holder 42 are firmly fixed by insert molding. For this reason, the load at the time of the press-fitting of the magnet 43 suppresses the rotor core 41 and the magnet 42 from being separated from each other. Accordingly, the magnet 43 can be easily press-fitted.
If a plurality of magnets is intended to be arranged inside the mold at the time of the above insert molding, it is necessary to fix the magnets to the surface of the rotor core by adhesion or the like. In contrast, in the present embodiment, the magnet 43 is press-fitted into the magnet holder 42 after insert molding is completed and hardening is made. For this reason, the time and effort to adhere the magnet 43 to the rotor core 41 can be saved. Additionally, a plurality of magnets 43 can be easily positioned with high precision.
Features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises.
While preferred embodiments of the present invention have been described above, it is to 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.
The inclined surface 631 of the magnet holder 42 may be a curved surface as shown in
The number of the partitioning portions 60 of the magnet holder 42 and the number of the magnets 43 may be different numbers from those of the above embodiment. Additionally the coupling portion 70 of the magnet holder 42 may connect portions other than the lower ends of the plurality of partitioning portions 60.
Additionally, the number of the rotor units 32 included in the rotating portion 3 of the motor 1 may be one, or may be three or more.
Additionally, the rotating electrical machine of the invention may be the above motor 1 for power steering, or may be motors used for other portions of an automobile. For example, the rotating electrical machine of the invention may be a motor for generating the driving force of an electric motorcar. Additionally, the rotating electrical machine of the invention may be a motor used for an electric power-assisted bicycle, an electric motorcycle, home electronics, OA equipment, a medical instrument, or the like.
Additionally, a generator can also be configured with the structure equivalent to the motor of the above embodiment or modification. The rotating electrical machine of the invention may be a generator used for an automobile, an electric power-assisted bicycle, wind power generation, or the like.
Additionally, the respective elements appeared in the above embodiment or modification may be appropriately combined together within a range where inconsistency does not occur.
The invention can be used for a rotor unit, a rotating electrical machine, and a method for manufacturing a rotor unit.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-082322 | Apr 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/002273 | 4/2/2012 | WO | 00 | 5/30/2013 |
