Patent Application
20160365779
The present application claims priority under 35 U.S.C. §119 to Japanese Application No. 2015-117103 filed Jun. 10, 2015, the entire content of which is incorporated herein by reference.
The present disclosure relates to a rotor, a motor and a method of manufacturing the rotor.
In the past, a so-called inner rotor type motor has been known, in which a rotor is provided on a radially inner side of a stator. The rotor used in the inner rotor type motor may include, for example, a rotor yoke, a plurality of permanent magnets and a mold resin. Further, in the rotor, a method of pouring resin into an outer circumferential end portion of the permanent magnet and both axial end portions is used to fix the permanent magnets to a surface of the rotor yoke.
In the above-described structure of the past, only the vicinity of both circumferential end portions of the permanent magnets was covered by the resin. For this reason, when the motor is sped up and the centrifugal force applied to the permanent magnets is increased, there is a possibility that a known, conventional structure may not be able to prevent the permanent magnets from scattering.
In order to cope with a further speed-up of the motor, covering a wider region of a radially outer surface of the permanent magnets with the resin may be considered. However, when a radial distance between the permanent magnets and the stator is increased, efficiency of the motor is reduced. Accordingly, in terms of the efficiency of the motor, the thickness of the resin covering the permanent magnets needs to be reduced. To do so, when injection molding of the mold resin is performed, a gap between the radially outer surface of the permanent magnets and an inner circumferential surface of a mold needs to be narrowed.
However, it is difficult to pour the resin stably into such a narrow gap. Therefore, the gap may not be filled with the resin. Further, when there is air remaining in the narrow gap and the air is compressed to a high temperature, the resin provided around the narrow gap may be deteriorated. Further, due to the failure to fill the gap with the resin or the deteriorated resin, there is a possibility that the resin may be partially peeled off from the permanent magnets after manufacture.
A first exemplary embodiment according to the present disclosure is an inner rotor type motor and a rotor which rotates on a vertically extending center axis, the rotor comprising: a tube-shaped rotor core made of a magnetic material; a plurality of magnets which are provided on an outer circumferential surface of the rotor core; and a resin portion which holds the rotor core and the magnets, the resin portion including an outer cover portion which covers a radially outer side surface of the magnets, the outer cover portion including a groove portion which is concaved radially inward from a radially outer surface, and further, extends in an axial direction; and a wall portion adjacent to the groove portion in a circumferential direction.
A second exemplary embodiment according to the present disclosure is a method of manufacturing a rotor comprising a tube-shaped rotor core which is made of a magnetic material and has its center on a vertically extending center axis; a plurality of magnets which are provided on an outer circumferential surface of the rotor core; and a resin portion which holds the rotor core and the magnets, the method comprising the steps of: a) disposing the rotor core and the plurality of magnets in a cavity portion formed by a pair of upper and lower molds; b) pouring molten resin into the cavity portion; and c) forming the resin portion by solidifying the molten resin. At least one of the molds in the pair of the upper and lower molds includes a plurality of protrusions which protrude radially inward from an inner circumferential surface which defines the cavity portion, while extending in an axial direction, wherein, in step a), the plurality of protrusions contact or radially face each of the radially outer side surfaces of the plurality of magnets across a slight gap, and in step c), a groove portion is formed in the resin portion by the plurality of protrusions.
The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the embodiments with reference to the attached drawings.
Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which:
Herein, exemplary embodiments of the present disclosure will be explained with reference to the attached drawings. Further, herein, a direction parallel to a center axis of a rotor is referred to as “axial direction,” a direction orthogonal to the center axis of the rotor is referred to as “radial direction,” and a direction along a circular arc having its center on the center axis of the rotor is referred to as “circumferential direction.” Moreover, in the following embodiments, the shapes and positional relations of the elements will be explained by referring to the axial direction as upper and lower directions. It is to be understood that this definition of the upper and lower directions is not intended to define a particular direction when the rotor and the motor are actually manufactured or used.
As illustrated in
The resin portion 63A includes an outer cover portion 83A which covers a radially outer side surface of the magnets 62A. The outer cover portion 83A includes a groove portion 831A and a wall portion 832A. The groove portion 831A is concaved radially inward from a radially outer side surface of the outer cover portion 83A, and extends in the axial direction. The wall portion 832A is adjacent to the groove portion 831A in the circumferential direction. When the motor is driven, centrifugal force is applied to the magnets 62A; however, the wall portion 832A of the outer cover portion 83A prevents the magnets 62A from scattering out to a radially outer side.
As illustrated in
Further, in a space between an inner circumferential surface of the upper and lower molds 90A and the magnets 62A, a narrow space where it is difficult to pour molten resin into is made smaller by the protrusions 901A. When molten resin is poured into the cavity portion 93A inside the upper and lower molds 90A, air between an inner circumferential surface of the upper and lower molds 90A and the magnets 62A is discharged as illustrated with a dash-lined arrow in an enlarged view of
As illustrated in
The stationary portion 2 includes the stator 21, a stator housing 22, a cover member 23, a lower bearing portion 24 and an upper bearing portion 25.
The stator 21 is an armature which generates magnetic flux in response to a drive current. The stator 21 includes a stator core 211 and a conductive wire 212. The stator core 211 is made of a laminated steel plate, which is a magnetic material. The stator core 211 includes a core back 41 and a plurality of teeth 42. The core back 41 surrounds a center axis 9. The plurality of teeth protrudes radially inward from the core back 41. The core back 41 is disposed substantially coaxially with the center axis 9. The plurality of teeth 42 are arranged at substantially identical intervals in the circumferential direction. The conductive wire 212 is wound around the plurality of teeth 42. Further, a resin insulator 213 is interposed between the teeth 42 and the conductive wire 212.
The stator housing 22 is a resin member that holds the stator 21. The stator housing 22 is made of, for example, a thermosettable unsaturated polyester resin. The stator housing 22 is obtained by pouring resin into a cavity portion inside the mold in which the stator 21 is accommodated, and solidifying the resin. That is, the stator housing 22 is a resin-molded article having the stator 21 as an insert component. Accordingly, at least a portion of the stator core 211 and the conductive wires 212 is covered by the stator housing 22.
The stator housing 22 of this embodiment includes a cylindrical portion 51 and a bottom plate portion 52. The cylindrical portion 51 axially extends in a substantially cylindrical shape. The stator 21 is covered by the resin that forms the cylindrical portion 51. However, a portion of the stator 21 including a radially inner end surface of the teeth 42 may be exposed through the cylindrical portion 51. Further, the rotor 32, which will be described in detail in a subsequent section, is provided on a radially inner side of the cylindrical portion 51. The bottom plate portion 52 expands substantially perpendicularly to the center axis 9 on an axially lower side than the stator 21 and the rotor 32. An insertion hole 520, through which a shaft 31, which will be described in detail in a subsequent section, penetrates, is provided at the center of a lower surface of the bottom plate portion 52. The lower bearing portion 24 is provided around the insertion hole 520.
The cover member 23 is a disc-shaped member which closes an opening on a top portion of the stator housing 22. The cover member 23 expands substantially perpendicularly to the center axis 9 on an axially upper side than the stator 21 and the rotor 32. A bearing accommodation portion 230 having a concave shape is provided at the center of a lower surface of the cover member 23. The upper bearing portion 25 and the upper end portion of the shaft 31 are provided within the bearing accommodation portion 230.
The lower bearing portion 24 rotatably supports the shaft 31 from an axially lower side than the rotor 32. The upper bearing portion 25 rotatably supports the shaft 31 on an axially upper side than the rotor 32. A ball bearing having a plurality of spherical bodies between an outer ring and an inner ring is used in the lower bearing portion 24 and the upper bearing portion 25 of this embodiment. An outer ring of the lower bearing portion 24 is fixed to the bottom plate portion 52 of the stator housing 22. An outer ring of the upper bearing portion 25 is fixed to the cover member 23. Further, inner rings of the lower bearing portion 24 and the upper bearing portion 25 are fixed to an outer circumferential surface of the shaft 31. Also, instead of the ball bearing, other types of bearing, such as a sliding bearing, a liquid bearing, or the like, may be used.
The rotary portion 3 includes the shaft 31 and the rotor 32.
The shaft 31 is a columnar member provided along the center axis 9. The shaft 31 is supported by the lower bearing portion 24 and the upper bearing portion 25, and rotates on the center axis 9. The lower end of the shaft 31 protrudes below the lower bearing portion 24. A fan for an air conditioner, for example, is mounted on the lower end of the shaft 31. The shaft 31 may be connected to a drive unit other than the fan via a power transmission mechanism, such as a gear, or the like.
Further, although it has been described that the shaft 31 of this embodiment protrudes below the stator housing 22, the present disclosure is not limited thereto. The upper end of the shaft 31, which protrudes above the cover member 23, may be connected to the drive unit. Further, the upper end and the lower end of the shaft 31, which respectively protrude above the cover member 23 and below the stator housing 22, may both be connected to the drive unit.
The rotor 32 is fixed to the shaft 31, and rotates together with the shaft 31. An outer circumferential surface of the rotor 32 radially faces a radially inner end surface of the plurality of teeth 42 across a slight gap. The rotor 32 includes a tube-shaped rotor core 61, a plurality of magnets 62 and a resin portion 63.
An electromagnetic steel plate, which is a magnetic material, is used in the rotor core 61. The shaft 31 is press-fitted into a radially inner side of the rotor core 61, and vertically penetrates the rotor core 61. The plurality of magnets 62 are provided on an outer circumferential surface of the rotor core 61. A radially outer side surface of each of the magnets 62 is a magnetic pole surface of either an N pole or an S pole, and radially faces a radially inner end surface of the teeth 42. The plurality of magnets 62 are arranged at substantially identical intervals in the circumferential direction, such that the magnetic pole surface having an N pole and the magnetic pole surface having an S pole are alternately arranged. The resin portion 63 covers the rotor core 61 and the magnets 62, and is a so-called mold resin. By being covered with the resin portion 63, the rotor core 61 and the magnets 62 are supported without being misaligned from each other.
When the motor 1 is driven, driving voltage is supplied from an external power source to the conductive wire 212 of the stator 21 via a circuit board, which is not illustrated in the drawings. Then, magnetic flux is generated in the plurality of teeth 42 of the stator core 211. Then, a torque in the circumferential direction is generated by an action of the magnetic flux between the teeth 42 and the magnets 62. As a result, the rotary portion 3 rotates on the center axis 9.
Continuously, a further detailed structure of the rotor 32 will be explained.
As illustrated in
The plurality of magnets 62 are provided on an outer circumferential surface of the outer core 72. A radially inner side surface of each of the magnets 62 is formed of a substantially arc-shaped surface having its center on the center axis 9. Accordingly, a distance from the center axis 9 to the radially inner side surface of the magnets 62 is substantially constant, regardless of their circumferential position. Meanwhile, a radially outer side surface of each of the magnets 62 is formed of a substantially arc-shaped surface having a smaller radius of curvature than that of the radially inner side surface. A distance from the center axis 9 to the radially outer side surface of the magnets 62 gradually becomes shorter from the circumferential center toward both circumferential end portions. Accordingly, the magnets 62 of this embodiment have an apex portion 621, which has the farthest distance from the center axis 9, at the circumferential center of the radially outer side surface.
As illustrated in
The outer cover portion 83 expands in the axial direction between a radially outer edge portion of the upper cover portion 81 and a radially outer edge portion of the lower cover portion 82. A radially outer side surface of the plurality of magnets 62 is covered by the outer cover portion 83. As illustrated in
The wall portions 832 are arranged adjacent to both circumferential sides of each of the grove portions 831. Each of the wall portions 832 axially and circumferentially expands along a radially outer side surface of the magnets 62. When the motor 1 is driven, large centrifugal force is applied to the magnets 62. However, since the radially outer side surface of the magnets 62 is covered by the wall portion 832, the magnet 62 is prevented from scattering out to a radially outer side. Especially, in the rotor 32 of this exemplary embodiment, a circumferential width of the groove portions 831 is narrower than a circumferential width of the wall portions 832. By expanding the circumferential width of the wall portions 832 this way, it is possible to further prevent the magnets 62 from scattering out to a radially outer side.
Further, as illustrated as an enlarged view in
The core connection portion 84 is interposed between the inner core 71 and the outer core 72. The inner core 71 and the outer core 72 are connected by the core connection portion 84. In the rotor 31 of this embodiment, the inner core 71 is directly fixed to the shaft 31, not via the resin portion 63. For this reason, it is possible to increase a fixing strength between the shaft 31 and the rotor core 61 as compared to a case in which the rotor core 61 is fixed to the shaft 31 via the resin portion 63. Further, the core connection portion 84, which is an insulating material, is interposed between the inner core 71 and the outer core 72. Accordingly, a conductor group including the magnets 62 and the outer core 72 and a conductor group including the inner core 71, the shaft 31, the lower bearing portion 24 and the upper bearing portion 25 are electrically insulated. With this, when the motor 1 is driven, it is possible to suppress the damage which may occur in the lower bearing portion 24 and the upper bearing portion 25 due to electrolytic corrosion phenomenon.
Further, as illustrated in
Continuously, a manufacturing sequence of the rotor 32 will be described.
When manufacturing the rotor 32, first, the inner core 71, the outer core 72 and the plurality of magnets 62 are prepared. Then, the plurality of magnets 62 are fixed to an outer circumferential surface of the outer core 72 by the adhesive 64 (Step S1). It should be noted that, if it is possible to fix the outer core 72 and the plurality of magnets 62 in the next step S2, by the shape of a lower mold 91 or with a pin such that the outer core and the magnets are in contact with each other, then the fixing by the adhesive 64 in Step 1 may be omitted.
Next, the inner core 71, the outer core 72 and the plurality of magnets 62 are disposed inside upper and lower molds 90 to be used for resin molding (Step S2). The upper and lower molds 90 include the inner core 71, the outer core 72, a lower mold 91 and an upper mold 92. The lower mold 91 receives the plurality of magnets 62. The upper mold 92 closes an opening on the top portion of the lower mold 91. In this embodiment, the outer core 72 and the plurality of magnets 62 are adhered in advance during Step S1. For this reason, in Step S2, the outer core 72 and the plurality of magnets 62 can be easily disposed inside the lower mold 91.
After placing the rotor core 61 and the plurality of magnets 62 inside the lower mold 91, when a lower surface of the upper mold 92 is brought into contact with an upper surface of the lower mold 91, a cavity portion 93 is formed inside the upper and lower molds 90 as illustrated in
As illustrated in
Further, as illustrated in
Further, as illustrated as an enlarged view in
The outer core 72 includes a plurality of convex portions 721 protruding radially inward on an inner circumferential surface thereof. When disposing the outer core 72 in the lower mold 91, a positioning jig is brought into contact with the convex portions 721. With this, the outer core 72 is positioned in the circumferential direction. As a result, the apex portion 621 of each of the magnets 62 is arranged to face the protrusions 901 of the lower mold 91.
Further, as illustrated in
As illustrated in
Next, from a resin injection port 923 which is provided in the upper mold 92, molten resin is poured into the cavity portion 93 inside the upper and lower molds 90 (Step S3). In this embodiment, the resin injection port 923 is disposed in a position facing an upper end surface of the magnets 62. More specifically, the resin injection port 923 is disposed in a circumferential position substantially identical with the protrusions 901 of the lower mold 91 and the apex portion 621 of the magnet 62. Accordingly, the molten resin injected from the resin injection port 923 flows from a vicinity of a circumferential center of the magnets 62, which has a relatively narrow distance between the upper and lower molds 90, toward a vicinity of both circumferential end portions of the magnets 62, which has a relatively wide distance between the upper and lower molds 90. With this, it becomes easier to exhaust the air inside the upper and lower molds 90, and it thereby becomes easier to spread the molten resin in the entire cavity portion 93. Further, the resin injection port 923 may be provided in the lower mold 91.
As indicated with a dashed arrow in an enlarged view of
When the molten resin has spread out in the cavity portion 93 inside the upper and lower molds 90, the process is followed by a step of solidifying the molten resin (Step S4). With this, the resin portion 63 including the upper cover portion 81, the lower cover portion 82, the outer cover portion 83 and the core connection portion 84 is formed. Further, when the molten resin is solidified, the inner core 71, the outer core 72 and the plurality of magnets 62 are fixed together by the resin portion 63.
In Step S3, the groove portion 831 is formed on the outer cover portion 83 by the plurality of protrusions 901 of the lower mold 91. In this embodiment, the groove portion 831 is formed on a radially outer side of the apex portion 621 of the magnets 62. Further, the groove portion 831 of this embodiment extends from an upper end of the outer cover portion 83 to a lower end thereof in the axial direction. It should be noted that the groove portion 831 of this embodiment does not necessarily need to extend from the upper end of the outer cover portion 83 to the lower end thereof in the axial direction. However, in order to easily release the resin portion 63 from the upper and lower molds 90 after solidification, it is possible for the groove portion 831 to axially extend from at least one of the upper end and the lower end of the outer cover portion 83.
Further, as illustrated in the enlarged view of
Further, as illustrated in the enlarged view of
Further, the interface between the lower mold 91 and the upper mold 92 may be positioned on an axially lower side than the magnets 62 and the stator core 211. In this case, the parting line 833 is positioned on a further axially lower side than the magnets 62 and the stator core 211. For example, the parting line 833 is formed on a lower end of the outer cover portion 83.
Further, as illustrated in the enlarged view of
Further, as illustrated in the enlarged view of
Although the exemplary embodiments of the present disclosure have been described, the present disclosure is not limited thereto.
In the above-described exemplary embodiments, the radially outer side surface of the magnets has a curved surface bulging radially outward. For this reason, the apex portion thereof is positioned in a circumferential center of the radially outer side surface of the magnets. However, the radially outer side surface of the magnets may have a different shape as long as a distance from the center axis changes depending on a circumferential position. For example, the radially outer side surface of the magnets may have a curved surface which is concaved radially inward. That is, the apex portion may be provided on both circumferential end portions of the radially outer side surface of the magnets. In this case, it is possible for the resin portion to have the groove portions in a position radially overlapping with both circumferential end portions of the magnets.
Further, in the exemplary embodiments, the protrusions that define the groove portions are provided only in the lower mold. When the interface between the upper and lower molds is positioned on a lower side than the upper end portion of the magnets, the protrusions that define the groove portions may be provided in both of the lower mold and the upper mold, or only in the upper mold.
Features of the above-described embodiments and the modifications thereof may be combined appropriately as long as no conflict arises. While embodiments of the present disclosure 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 disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.
While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.
The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-117103 | Jun 2015 | JP | national |
