Rotor with arcuate magnets

Abstract

A spoked rotor is rotatable about an axis. The rotor includes a core. The core includes a plurality of pole segments arranged in an arc direction about the axis. The rotor includes a plurality of magnets arranged in the arc direction, the magnets being alternately arranged with the pole segments in the arc direction such that each magnet is at least partially interposed between a pair of adjacent pole segments. Each magnet includes a curved section extending in an arcuate shape between a curved section radially outer end and a curved section radially inner end. An effective rotor pole position is defined on each pole segment. Each pole segment has an end opposite an effective rotor pole position. A center point is defined at the end of the pole segment. Each effective rotor pole position is offset in the arc direction from a respective center point by about one tenth (0.5) to about two (2.0) rotor poles.

Description

[0001] Cross - Reference to Related Applications

[0002] 1. Prior Application

[0003] This application is a partial continuation of U.S. Patent Application No. 17 / 212,145, filed on March 25, 2021, the entire disclosure of which is incorporated herein by reference. Background of the Invention 1. Technical Field

[0004] The present invention generally relates to an electric motor. More specifically, the electric motor includes a plurality of arc - arranged magnets configured and arranged to provide improved magnetic flux.

[0005] 2. Discussion of the Related Art

[0006] An electric motor typically includes a stator and a rotatable rotor. Such a motor can be an inner - rotor motor, an outer - rotor motor, or a dual - rotor motor. Additionally, a variety of rotor and stator configurations are allowed. In other alternatives, for example, the rotor can include a rotor shroud for supporting a plurality of arc - arranged magnets, a plurality of arc - arranged magnets alternating with a plurality of arc - arranged pole segments, or a rotor core having a plurality of arc - arranged magnets around its periphery. The geometries of the pole segments, magnets, and stator teeth can vary according to desired performance characteristics, space limitations, and cost considerations. Summary of the Invention

[0007] According to one aspect of the present invention, a spoke - type rotor is rotatable about an axis. The rotor includes a core that includes a plurality of pole segments arranged in an arc around the axis. The rotor further includes a plurality of magnets arranged in an arc, which are arranged in an arc - alternating manner with the pole segments such that each magnet is at least partially interposed between a pair of adjacent pole segments. Each magnet includes a curved section that extends arcuately between its radially inner end and its radially outer end.

[0008] According to another aspect of the present invention, a rotor is rotatable about an axis. The rotor includes a core that includes a plurality of pole segments arranged in an arc around the axis. The rotor further includes a plurality of magnets arranged in an arc, which are arranged in an arc - alternating manner with the pole segments such that each magnet is at least partially interposed between a pair of adjacent pole segments. An effective rotor magnetic - pole position is defined on each pole segment. Each pole segment has an end opposite the effective rotor magnetic - pole position. A center point is defined at the end. Each effective rotor magnetic - pole position is offset arc - wise from the corresponding center point by approximately five - tenths (0.5) to approximately two (2.0) rotor magnetic poles.

[0009] In particular, there is provided (1) a rotor magnet, each rotor magnet having a curved section with a first end and a second end, where the second end is disposed radially outward of the first end, and / or (2) a core and magnet configured such that each of a plurality of effective rotor pole positions is offset arcwise from a respective one of a plurality of center points by approximately five-tenths (0.5) to approximately two (2.0) rotor poles, which enables improved motor performance (e.g., through good flux concentration) to be achieved within a given motor housing as compared to conventional spoke-type motor configurations. It should be noted in particular that the inventive aspects of the present invention contribute in some cases to obtaining excellent cost-benefit ratio results that would otherwise require expensive upgrades to magnet materials (e.g., rare-earth magnets instead of ferrite magnets) and / or the addition of expensive additional active materials (copper, steel, etc.).

[0010] This summary is provided to introduce some concepts in a simplified form. These concepts are further described in the detailed description of the preferred embodiments below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0011] From the following detailed description of the preferred embodiments and the drawings, various other aspects and advantages of the present invention will become apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the drawings, in which:

[0013] Figure 1 is a front perspective view of a motor according to a first preferred embodiment of the present invention;

[0014] Figure 2 is Figure 1 a partially cut-away perspective view of the motor;

[0015] Figure 3 is Figure 1 and Figure 2 a front perspective view of the rotor core and magnet of the motor;

[0016] Figure 4 is Figure 3 a front view of the rotor core and magnet;

[0017] Figure 5 is as Figure 4 shown, an enlarged front view of a portion of the rotor core and magnet, particularly showing the skew of the effective rotor pole positions relative to the respective pole segment bridges;

[0018] Figure 6 is Figures 1 - 5 an enlarged external perspective view of the magnet of the rotor;

[0019] Figure 7 is Figure 6 an internal perspective view of the magnet; and

[0020] Figure 8 is Figure 6 and 7 a front view of the magnet, particularly showing the relative proportions and overall geometry of its curved and straight portions;

[0021] Figure 9 is a front view of the rotor core and magnet according to a second preferred embodiment of the present invention;

[0022] Figure 10 is Figure 9 an enlarged front view of a portion of the rotor core and magnet;

[0023] Figure 11 is Figure 9 and 10 a front view of one of the magnets, particularly showing its proportions and overall geometry;

[0024] Figure 12 is a front view of the rotor core and magnet according to a third preferred embodiment of the present invention;

[0025] Figure 13 is Figure 12 an enlarged front view of a portion of the rotor core and magnet; and

[0026] Figure 14 is Figure 12 and 13 a front view of one of the magnets, particularly showing its proportions and overall geometry.

[0027] The drawings do not limit the present invention to the specific embodiments disclosed and described herein. Although the drawings may not necessarily provide the exact dimensions or tolerances of the structures or components shown, the drawings are drawn to scale with respect to the relationships between the components of the structures shown. Detailed Description

[0028] The present invention admits of many different forms of embodiments. Although the drawings illustrate and the specification describes certain preferred embodiments of the present invention, it should be understood that such disclosure is merely exemplary. There is no intention to limit the principles of the present invention to the specifically disclosed embodiments.

[0029] In addition, unless otherwise specified or clear, directional references in this document regarding the present invention and / or related components (e.g., top, bottom, upper, lower, inner, outer, etc.) are used merely for convenience and should be understood to be only relative to each other. For example, in practice, a component may be oriented such that the surfaces referred to as the "top surface" and "bottom surface" are lateral, angled, inverted, etc. with respect to a selected reference system.

[0030] Referring first to Figure 1 and Figure 2 , an electric motor 10 is provided. The motor 10 includes a rotor 12 that is rotatable about an axis. The motor 10 also includes a stator 14. The stator 14 preferably at least substantially surrounds the rotor 12 such that the motor 10 is an inner rotor motor. However, at least some of the inventive features described herein are equally applicable to outer rotor motors and / or dual rotor motors.

[0031] The motor 10 also preferably includes a housing 16 that includes a cylindrical outer shell 18 that extends between a pair of axially opposed end caps 20 and 22 and interconnects the end caps.

[0032] The stator 14 preferably includes a stator core 24 and a plurality of coil assemblies 26 mounted on the stator core 24. Each coil assembly 26 preferably includes a bobbin 28 and a plurality of coils 30. The coils 30 include conductive windings 32 wound around the respective bobbins 28.

[0033] Although the stator 14 is provided with bobbins 28, the stator may be insulated in any manner known in the art without departing from the scope of the present invention. For example, the stator may be provided with full-length end caps, overmolds, or insulating inserts or wraps (e.g., Mylar paper).

[0034] In addition, although the illustrated stator 14 is formed from stamped linear bar laminations that are subsequently formed into curved pieces, the stator may be formed in alternative ways without departing from the scope of the present invention. For example, the stator may be a complete circular stator (i.e., including laminations stamped into a complete circle), may be a solid structure, may be arc-segmented, etc.

[0035] The rotor 12 preferably includes a rotor core 34, a plurality of magnets 36, and a shaft 38 that defines the axis of rotation of the rotor 12. The rotor core 34 includes a plurality of pole segments 40 arranged circumferentially about the axis. The magnets 36 are arranged circumferentially so as to be circumferentially alternating with the pole segments 40. Thus, each magnet 36 is at least partially interposed between a pair of adjacent pole segments 40.

[0036] The rotor core 34 preferably comprises steel, although other materials may alternatively be used without departing from the scope of the invention. The magnet 36 is preferably a permanent magnet comprising ferrite, although other suitable magnet materials, such as neodymium, may be used in accordance with certain aspects of the invention.

[0037] The rotor core 34 also preferably includes a hub 42 and a plurality of bridges 44 that extend between respective pole segments 40 and the hub 42 and interconnect them. The shaft 38 preferably extends through an opening 46 defined by the hub.

[0038] Preferably, as shown, the hub 42 is at least substantially toroidal in shape to have inner and outer cylindrical surfaces centered on the rotor axis. However, the hub can be constructed in an alternative manner without departing from some aspects of the invention. For example, the hub may alternatively have a polyhedral or polygonal outer surface including a plurality of planes, or the internal opening defined by the hub may be non-circular to conform to an alternative shaft structure.

[0039] In a preferred embodiment, each bridge 44 is connected to a respective one of the pole segments 40. Additionally, each pole segment 40 is connected to the hub 42 by a respective bridge 44. That is, the number of pole segments 40 is preferably equal to the number of bridges 44. However, in accordance with some aspects of the invention, the rotor core is allowed to include different numbers of bridges and pole segments.

[0040] In the illustrated embodiment, each bridge 44 is at least substantially rectangular and extends radially outward from the hub 42, although alternative shapes and / or directions of extension are allowed for some or all of the bridges in accordance with some aspects of the invention.

[0041] Preferably, each bridge 44 engages a respective one of the pole segments 40 at a tangential or arcuate bridging interface 48. The bridging interface 48 has a generally tangential or arcuate center point 48a.

[0042] Alternatively, the center point 48a may be characterized relative to the pole segment 40 itself rather than relative to the bridging interface 48. More specifically, each pole segment 40 can be understood to have a radially inner end 48 (which coincides with the respective bridging interface 48 in the illustrated embodiment). Each radially inner end 48 preferably has a generally tangential or arcuate center point 48a.

[0043] The rotor core 34 also preferably includes a plurality of protrusions 50 that extend radially outward from the hub 42. The protrusions 50 preferably alternate with the bridges 44 in the arc direction, with a uniform spacing provided between each bridge 44 and an adjacent protrusion 50, and vice versa. Each protrusion 50 preferably engages a respective one of the magnets 36 to limit movement of the magnet in the radially inward direction.

[0044] Each projection 50 preferably includes a rounded outer radial end, although alternative geometries are permitted. Additionally, the projections may be omitted and replaced with alternative magnet retention means, such as by overmolding, other structural components, etc. Such retention means may also be provided as an additional arrangement to the projections.

[0045] Although the rotor core 34 of the present invention is preferably formed of axially stacked stamped laminations (each lamination including at least a pole segment, a hub, a bridge, and a projection member), alternative manufacturing and / or assembly techniques are permitted. For example, fully formed pole segments may be press-fitted into the hub using dovetail joints or other suitable connection means (in which case, the hub is preferably but not necessarily made of a different material than the pole segments). In another alternative, the pole segments may be molded in place such that there is no "direct" connection (whether by bridging, joining, or other techniques) between the pole segments and the hub. Molding may also be supplementary to another connection or positioning technique. Additionally, varying lamination designs may be provided, possibly in an axially alternating or staggered manner, or a single lamination design may be provided, but the axially adjacent laminations or groups of laminations are rotationally angled or circumferentially deflected relative to each other (clocked). In summary, as long as the general operability of the electric machine is maintained, varying or alternative bridge types or pole segment-hub connection structures are permitted, thereby allowing the bridge to be completely omitted or directly connected, and / or allowing other variations in the rotor core design without departing from the scope of some aspects of the present invention.

[0046] In general, each magnet 36 preferably defines a radially inner end 52 and a radially outer end 54. Additionally, in Figures 1 - 8 the illustrated embodiment, each magnet 36 includes a curved section 56 and a straight section 58. The curved section 56 preferably extends arcuately from the radially inner end 52 to an outer end 60 of the curved section, which is disposed between the inner end 52 and the outer end 54. The straight section 58 preferably extends linearly from the outer end 60 of the curved section of the magnet 36 to the radially outer end 54, most preferably non-radially (as will be discussed below with respect to the second and third embodiments of the present invention, according to some aspects of the present invention, the straight section may be completely omitted).

[0047] In the illustrated embodiment, the radially inner end 52 has a radially inner end face 52a of the magnet 36. Similarly, the radially outer end 54 has a radially outer end face 54a of the magnet 36.

[0048] Additionally, in a preferred embodiment, the outer end 60 of the curved section may alternatively be characterized with respect to the magnet 36 as a whole as presenting a transition interface 60a between the curved section 56 and the straight section 58. That is, the transition interface 60a is preferably disposed at an intermediate position between the inner end 52 and the outer end 54 of the magnet, where the curved section 56 and the straight section 58 are adjacent to each other.

[0049] The curved section 56 and the straight section 58 are preferably formed continuously with each other such that each magnet 36 includes a single body. However, in some aspects of the present invention, it is allowed that these sections are separate or discontinuous parts.

[0050] The curved section 56 preferably has a front curved surface 56a, a rear curved surface 56b, and axially extending opposite inner and outer curved surfaces 56c and 56d that extend between and connect the front curved surface 56a and the rear curved surface 56b to each other. The inner curved surface 56c and the outer curved surface 56d each also preferably extend continuously (i.e., without gaps, obstructions, or other irregularities) between the radially inner end 52 and the outer end 60 of the curved section.

[0051] The inner curved surface 56c preferably faces generally radially inward. The outer curved surface 56d preferably faces generally radially outward.

[0052] Most preferably, the inner curved surface 56c has a constant curvature, or in other words, a constant radius of curvature R1, so as to extend along an arc. Similarly, the outer curved surface 56d preferably has a constant curvature, or in other words, a constant radius of curvature R2, so as to extend along an arc.

[0053] In a preferred embodiment, the inner curved surface 56c and the outer curved surface 56d are centered about a common center of curvature C. That is, the imaginary circles in which the inner curved surface 56c and the outer curved surface 56d extend are concentric.

[0054] Thus, one of ordinary skill in the art will also understand that the curved section 56 preferably has a constant width W1 between the inner curved surface 56c and the outer curved surface 56d.

[0055] Although it is preferred that both the inner curved surface 56c and the outer curved surface 56d each extend concentrically with a constant radius, in some aspects of the present invention, variations are allowed. For example, the curved section may alternatively include multiple parts, each having a different geometry (e.g., varying radius of curvature, center of curvature, etc.). Such variations can similarly be applied to the inner and outer curved surfaces, or the variations can be applied irregularly such that the width of the curved section varies along its length.

[0056] In Figures 1 - 8In the preferred embodiments shown and the alternative magnet configurations described above, although the radius of curvature, center of curvature, etc. may vary, the curved segments of the magnet preferably maintain a generally continuous curvature (i.e., a smooth curvature) in the general sense. That is, there are no vertices. However, in some aspects of the present invention, it is also permitted for the curved segments to include a plurality of straight portions that are positioned relative to each other such that a curvature is formed in the general sense. That is, each of the inner and outer surfaces can be understood as being polyhedral, but still curved in the general sense.

[0057] Note that the transition at the transition interface 60a is likewise preferably substantially smooth and has no sharp angles or vertices.

[0058] In the preferred embodiment, the radius of curvature R1 of the inner surface 56c is between approximately five-tenths (0.5) inch and approximately one and twenty-five hundredths (1.25) inches. Most preferably, the radius of curvature R1 of the inner surface 56c is approximately eight hundred thirty-six thousandths (0.836) inch.

[0059] The radius of curvature R2 of the outer surface 56d is preferably between approximately seventy-five hundredths (0.75) inch and approximately one and five-tenths (1.5) inches. Most preferably, the radius of curvature R2 of the outer surface 56d is approximately one and one hundred twenty-three thousandths (1.123) inches.

[0060] Preferably, the width W1 of the curved segment 56 is between approximately fifteen hundredths (0.15) inch and approximately one (1) inch. Most preferably, the width W1 of the curved segment 56 is approximately two hundred eighty-seven thousandths (0.287) inch.

[0061] As Figure 8 shown, the imaginary magnet centerline 62, which includes the curved segment centerline 62a and the straight segment centerline 62b, preferably extends through the magnet 36. More specifically, the curved segment centerline 62a preferably extends arcuately through the curved segment 56 from the radially inner end 52 of the magnet 36 to the radially outer end or transition interface 60 of the curved segment so as to be equidistant from each of the inner surface 56c and the outer surface 56d. That is, the curved segment 56 preferably extends along the curved segment centerline 62a.

[0062] In addition, the curved segment 56 preferably has a curved segment length L1 along the curved segment centerline 62a. The preferred curved segment length L1 is between approximately five-tenths (0.5) inch and approximately one and five-tenths (1.5) inches. Most preferably, the curved segment length L1 is approximately one and sixteen thousand six hundred ninety-eight ten-thousandths (1.1698) inches.

[0063] As an alternative representation, the bent section 56 preferably extends along the centerline 62a of the bent section by an angular arc length θ1 between approximately forty-five (45) degrees and approximately ninety-five (95) degrees. More preferably, the bent section 56 has an arc length θ1 between approximately sixty (60) degrees and approximately eighty (80) degrees along the centerline 62a of the bent section. Most preferably, the arc length θ1 of the bent section 56 along the centerline 62a of the bent section is approximately sixty-eight (68) degrees.

[0064] The end face 52a and the transition interface 60a are preferably at an angle φ1 between approximately seventy (70) degrees and approximately one hundred and ten (110) degrees relative to each other. More preferably, φ1 is between approximately eighty (80) degrees and approximately one hundred (100) degrees. Most preferably, the angle φ1 of the face 52 relative to the interface 60 is approximately eighty-seven (87) degrees.

[0065] As previously described, the straight section 58 of each magnet 36 preferably extends linearly, most preferably non-radially, from the outer end 60 of the bent section of the magnet 36 to the radially outer end 54. More specifically, each straight section 58 preferably has a front straight face 58a, a rear straight face 58b, and axially extending opposite inner straight faces 58c and outer straight faces 58d that extend between and connect the front straight face 58a and the rear straight face 58b to each other. The inner straight face 58c and the outer straight face 58d also preferably extend continuously (i.e., without gaps, obstructions, or other irregularities) between the transition interface 60 and the radially outer end 54 of the magnet 36.

[0066] The inner straight face 58c preferably faces generally radially inward. The outer straight face 58d preferably faces generally radially outward.

[0067] The inner straight face 58c preferably extends tangentially from the inner curved face 56c at the transition interface 60. Similarly, the outer straight face 58d preferably extends tangentially from the outer curved face 56d at the transition interface 60.

[0068] The straight section 58 preferably has a constant width W2 between the inner straight face 58c and the outer straight face 58d (in other words, the inner straight face 58c and the outer straight face 58d are preferably parallel to each other). The width W2 of the straight section 58 is most preferably equal to the width W1 of the bent section 56. According to some aspects of the present invention, it is allowed to design the straight section to have a variable width (e.g., tapered or flared) such that it extends non-tangentially from the bent section to have a different width from the bent section (or a part thereof), and so on.

[0069] Preferably, the width W2 of the straight section 58 is between approximately fifteen (0.15) hundredths of an inch and approximately one (1) inch. Most preferably, the width W2 of the straight section 58 is approximately two hundred and eighty-seven (0.287) thousandths of an inch.

[0070] The centerline 62b of the aforementioned assumed straight section preferably extends linearly from the transition interface 60 to the radially outer end 54 of the magnet 36 through the straight section 58 so as to be equidistant from each of the inner straight surface 58c and the outer straight surface 58d. That is to say, the straight section 58 preferably extends along the centerline 62b of the straight section. Figure 8 ) Preferably, it extends linearly from the transition interface 60 to the radially outer end 54 of the magnet 36 through the straight section 58 so as to be equidistant from each of the inner straight surface 58c and the outer straight surface 58d. That is to say, the straight section 58 preferably extends along the centerline 62b of the straight section.

[0071] It is obvious from the above description that the centerline 62a of the curved section is preferably smoothly interconnected with the centerline 62b of the straight section. That is to say, the centerlines 62a and 62b (and thus the curved section 56 and the straight section 58) are not offset or angled relative to each other.

[0072] The straight section 58 preferably has a straight section length L2 along the centerline 62b of the straight section. Preferably, the straight section length L2 is between approximately twenty-five percent (0.25) inches and approximately seventy-five percent (0.75) inches. Most preferably, the straight section length L2 is approximately three thousand eight hundred and one ten-thousandths (0.3801) inches.

[0073] Each magnet 36 preferably has a total length L3, which is equal to the sum of the curved section length L1 and the straight section length L2. The curved section length L1 is preferably at least fifty percent (50%) of the total length L3, more preferably between approximately sixty percent (60%) and approximately ninety percent (90%) of the total length L3, and most preferably approximately seventy-five point four eight percent (75.48%) of the total length L3.

[0074] Similarly, as mentioned above, according to some aspects of the present invention, it is allowed to completely omit the straight section. Although two (2) such embodiments are described in detail below, it should be noted here that in this case, the curved section length L1 will be equal to the total length L3. Therefore, considering such an embodiment, the curved section length L1 can alternatively be described as most preferably between approximately sixty percent (60%) and approximately one hundred percent (100%) of the total length L3, and most preferably one hundred percent (100%) of the total length L3.

[0075] Nominal, it can be clearly seen from the preferred lengths L1 and L2 of the above-mentioned curved section 56 and straight section 58 that the total magnet length L3 is preferably between approximately seventy-five percent (0.75) inches and approximately two and twenty-five percent (2.25) inches. Most preferably, the total magnet length L3 is approximately one and five thousand four hundred and ninety-nine ten-thousandths (1.5499) inches.

[0076] As Figure 5As shown, the radial distance D can be defined as the circumferentially outermost radial edge 64 from each bridging interface 48 to the rotor core 34. In a preferred embodiment, the distance D is between approximately (0.75) inches and (1.75) inches. More preferably, the distance D is between approximately one (1) inch and approximately one and five-tenths (1.5) inches. Most preferably, the distance D is approximately one and three thousand one hundred ninety-eight ten-thousandths (1.3198) inches.

[0077] Due to the non-radial orientation of the curved section 56 and the straight section 58, the total magnet length L3 is preferably significantly greater than the radial distance D. For example, preferably, each total magnet length L3 is at least five (5%) greater than the corresponding radial distance D, more preferably at least ten (10%) greater, and most preferably at least fifteen (15%) greater. For example, in the illustrated embodiment, each total magnet length L3 is approximately seventeen point four three (17.43%) greater than the radial distance D.

[0078] In practical terms, the increase in relative length enables each magnet 36 to have a larger pole face area compared to the pole face area achieved by a conventional design within the same motor package space. In turn, the increase in pole face area helps to enhance flux concentration. For example, compared to a conventional spoke-type rotor, the present invention preferably achieves an increase in pole face area of at least ten (10%), more preferably at least twenty-five (25%), and most preferably greater than thirty (30%).

[0079] It will be apparent to those of ordinary skill in the art that in the illustrated preferred embodiment, the pole face area can be understood as the combined area of the inner surface 56c and the outer surface 56d of the curved section 56 and the inner surface 58c and the outer surface 58d of the straight section 58 (as will be discussed in more detail below, these surfaces 56c, 56d, 58c, and 58d are tangent to the local magnetization direction).

[0080] Each magnet 36 also preferably has a total arc span θ2 measured along the centerline 62 from the radially inner end 52 to the radially outer end 54 and relative to the center of curvature C, which is between approximately seventy (70) degrees and approximately one hundred ten (110) degrees, more preferably between approximately eighty (80) degrees and approximately one hundred (100) degrees, and most preferably approximately ninety (90) degrees.

[0081] The end faces 52a and 54a of each magnet 36 are preferably at an angle φ2 between approximately forty (40) degrees and approximately ninety (90) degrees relative to each other. More preferably, φ2 is between approximately fifty (50) degrees and approximately eighty (80) degrees. Most preferably, the angle φ2 of face 52a relative to face 54a is approximately sixty-four (64) degrees.

[0082] In a preferred embodiment, the straight section 58 has a non-rectangular front straight face 58a and a rear straight face 58b. More specifically, the inner straight face 58c of the straight section is preferably longer than the outer straight face 58d of the straight section, such that the front straight face 58a and the rear straight face 58b are generally trapezoidal. More specifically, the front straight face 58a and the rear straight face 58b are preferably at least substantially right trapezoidal, such that the magnet 36 defines an acute vertex 66 at the outer end 54 and adjacent to the inner straight face 58c of the straight section.

[0083] In the illustrated embodiment, the respective surfaces of the magnet 36 are chamfered. However, according to some aspects of the present invention, it is allowed to omit some or all of the illustrated chamfers, and to replace some or all of the chamfers with rounded corners or other transitional structures, etc.

[0084] Preferably, each pair of adjacent pole segments 40 defines a slot 68 therebetween. Each slot 68 includes a magnet receiving portion 70 and a gap portion 72. Each magnet 36 is at least partially received in the magnet receiving portion 70 of a corresponding one of the slots 68, and there is no corresponding magnet 36 in the corresponding gap portion 72.

[0085] As previously mentioned, the rotor core 34 preferably has a radially outermost edge 64 extending circumferentially. Each slot 68 preferably extends to the radially outermost edge 64 of the rotor core 34, except for the presence of a corresponding plurality of tangential (or optionally arcuate) connecting portions 74 that extend between adjacent pole segments 40 and interconnect the adjacent pole segments 40. The aforementioned shape of the magnet 36 causes the gap portion 72 to be defined between the radially outer end 54 of each magnet and the corresponding connecting portion 74.

[0086] In Figures 1 - 8 the illustrated embodiment, the connecting portions 74 are provided between each pair of adjacent pole segments 40. However, according to some aspects of the present invention, it is allowed to completely omit the connecting portions or to provide the connecting portions only between some pole segments / a subset of pole segments. Such partial pole segments may include multiple pairs of pole segments (and thus include multiple connecting portions) or even only one pair of pole segments (and thus only one connecting portion). As Figures 9 - 11 shown and discussed in more detail below, the second preferred embodiment of the present invention is characterized by such a design based on partial pole segments / a subset of pole segments.

[0087] The geometry of the slots 68 and the magnets 36 (including their straight sections 58) causes the gap portion 72 to preferably be generally triangular. Most preferably, the gap portion 72 is generally a right triangle. However, according to some aspects of the present invention, alternative shapes of the gap portion are allowed.

[0088] The gap portion 72 can be filled naturally or environmentally (i.e., with ambient air), filled with a non-magnetic material (e.g., epoxy resin), etc., without departing from the scope of the present invention. According to some aspects of the present invention, it is also allowed that the magnet and the slot are configured such that the magnet completely fills the slot. Thus, the gap portion in such an embodiment will be omitted.

[0089] Note that filling the gap portion with a structural material (e.g., epoxy resin as described above, etc.) may be particularly advantageous in embodiments where some or all of the connecting portions are omitted.

[0090] Each magnet 36 is preferably at least substantially radially magnetized. That is, the magnetization direction is along the radial direction from the inner curved surface 56c to the outer curved surface 56d, and in an orthogonal manner or linearly from the inner straight surface 58c to the outer straight surface 58d. Thus, each magnet 36 has a first polarity along its inner curved surface 56c and inner straight surface 58c, and an opposite second polarity along its outer curved surface 56d and outer straight surface 58d.

[0091] According to some aspects of the present invention, small deviations from these magnetization modes are allowed (e.g., parallel magnetization within a bent section, radial magnetization within a straight section, circumferential or toroidal magnetization, etc.), although the performance results may be affected.

[0092] The directionality or polarity of the magnets 36 preferably alternates in the arc direction. That is, the outer surfaces 56d and 58d presenting the north pole polarity will face the inner surfaces 56c and 58c of different magnets 36 that also present the north pole polarity, and so on, where the corresponding "like-polarity" surfaces are separated from each other by a pole segment 40.

[0093] In other words, the magnets 36 whose outer surfaces 56d and 58d present a first polarity (e.g., north pole polarity) will be arranged in the arc direction between a pair of magnets 36 whose outer surfaces 56d and 58d present an opposite second polarity (e.g., south pole polarity) (as described above, the pole segments 40 will of course be interposed between the magnets 36).

[0094] Each pole segment 40 includes a body 76 extending substantially radially and a pair of circumferentially extending ears 78 protruding outward from the body 76. The body 76 is connected to a corresponding one of the bridges 44 at a corresponding bridging interface 48. Each ear 78 is connected to the corresponding ear 78 of an adjacent pole segment 40 through a corresponding connecting portion 74.

[0095] According to some aspects of the present invention, it is also allowed to omit some or all of the ears and / or omit some or all of the connecting portions (in embodiments where the ears are omitted, the connecting portions can be directly provided between adjacent pole segment bodies).

[0096] Each body 76 is typically preferably formed as a curved or "swept" triangular structure. More specifically, each body 76 includes an inner body surface 76a adjacent to the outer curved surface of an adjacent magnet 36 and an outer body surface 76b adjacent to the inner curved surface 56c of another adjacent magnet 36. This geometry in turn determines the generally arcuate widening or spreading of each pole segment 40 as it expands radially outward.

[0097] Although as described above, the rotor core 34 preferably includes solid pole segment bodies 76 disposed between adjacent magnets 36, it should be noted that alternative rotor core designs that omit such pole bodies fall within the scope of some aspects of the present invention. In particular, for example, the core or a similar component may optionally be at least partially in the form of a grid-like, spoke-like, or cylindrical frame for supporting the magnets. That is, according to some aspects of the present invention, the curved magnets described above are allowed to be used in rotor (or rotor core) designs that are generally different.

[0098] Each pole segment body 76 (or more generally, each pole segment 40) includes a radially outer surface 76c that at least partially defines the aforementioned radially outermost edge 64 of the rotor core 34. In a preferred embodiment, as a result of the above-described magnet and pole segment designs, an effective rotor magnetic pole position P is defined on each pole segment 40 and is centered in the arc direction along the radially outer surface 76c of the corresponding pole segment 40.

[0099] As previously described, each bridging interface 48 or the inner end 48 of the pole segment 40 has a center point 48a. For each pole segment 40, the effective rotor magnetic pole position P is offset (i.e., skewed) in the arc direction by a skew angle α relative to the center point 48a. That is, compared to a conventional spoke-type rotor, the effective rotor magnetic pole position P is not disposed directly radially outside the associated bridge, or in other words, does not coincide with the center of the inner end of the pole segment.

[0100] Preferably, each rotor magnetic pole position P is offset in the arc direction relative to a corresponding center point 48a by a skew angle α between approximately five-tenths (0.5) of a rotor magnetic pole and approximately two (2.0) rotor magnetic poles. More preferably, the skew angle α is between approximately one and twenty-five hundredths (1.25) rotor magnetic poles and approximately one and five-tenths (1.5) rotor magnetic poles. Most preferably, the rotor magnetic pole position P is offset in the arc direction relative to the corresponding center point 48a by a skew angle α of approximately one and thirty-seven hundredths (1.37) magnetic poles.

[0101] In a preferred embodiment, the electric machine 10 is a ten (10)-pole electric machine 10. Thus, as will be understood by those of ordinary skill in the art, the rotor magnetic pole position P can alternatively be understood as being most preferably offset in the arc direction relative to the corresponding center point 48a by a skew angle α of approximately forty-nine and two-tenths (49.2) degrees.

[0102] As can be clearly seen from above, the rotor magnetic pole position P is preferably set radially outside the center point 48a. More specifically, the rotor magnetic pole position P is preferably set at the radially outer end of the pole segment 40 (more specifically, on the radially outer surface 76c). The center point 48a is set opposite to the rotor magnetic pole position P, more specifically, at the radially inner end 48 of the pole segment 40. However, according to some aspects of the present invention, it is allowed that the rotor magnetic pole position is alternatively located radially inside the center point (e.g., in an outer rotor motor), or otherwise positioned relative to the center point and / or relative to the corresponding pole segment body in a broad sense.

[0103] The above design is very advantageous, achieving significant flux concentration without increasing the motor housing (e.g., by a greater stack height), without the need to use upgraded materials (e.g., neodymium magnets, aluminum stator windings, etc.) and / or without utilizing added active materials (e.g., copper, steel, etc.). For example, compared with other conventional spoke rotor motors of similar configurations and size designs, in addition to the aforementioned performance characteristics, the motor 10 of the illustrated embodiment is also capable of increasing the stator tooth flux density (e.g., by at least ten percent (10%), most preferably by fifteen percent (15%) or more). The motor 10 is also capable of significantly increasing the maximum rotor pole face flux density (e.g., compared with a comparable conventional spoke rotor motor, by at least twenty percent (20%), more preferably by at least thirty percent (30%), most preferably by forty percent (40%) or more).

[0104] Despite being an asymmetric design, the motor 10 also maintains the same performance in both rotational directions.

[0105] Furthermore, it is noted that the motor 10 achieves an increase in back electromotive force (BEMF) of at least ten percent (10%) and most preferably fifteen percent (15%) or more compared with an equivalent stator paired with a conventional spoke rotor.

[0106] Figures 9 - 11 A second preferred embodiment of the present invention is shown. First, it is noted that many elements of the rotor 110 of the second embodiment are the same as or very similar to those elements described in detail above with respect to the motor 10 (especially its rotor 12) of the first embodiment, except for certain exceptions that will be discussed in detail below. Therefore, for the sake of brevity and clarity, redundant descriptions and numbering will generally be avoided here. Unless otherwise specified, the detailed descriptions of the elements given above with respect to the first embodiment should be understood to apply at least generally also to the second embodiment.

[0107] Similar to rotor 12, rotor 110 of the second preferred embodiment preferably includes a rotor core 112 and a plurality of magnets 114. The rotor core 112 preferably includes a plurality of pole segments 116 spaced apart circumferentially, each pole segment including a body 118. The magnets 114 are disposed circumferentially between adjacent pole segments 116.

[0108] The rotor core 112 preferably includes a plurality of rotor laminations 120 stacked axially. Each lamination 120 defines a part 116a or a "slice" of each pole segment 116.

[0109] Each lamination 120 also includes a plurality of ears 122, each ear 122 extending respectively from a corresponding part of the body 118 of the circumferentially alternating pole segment parts 116a.

[0110] The lamination 120 also includes a connecting portion 124 that extends between every other pair of adjacent pole segment parts 116a and connects them to each other. As Figure 10 best shown, the ears 122 are most preferably arranged to be associated with the pole segment parts 116a that are not connected to each other by the connecting portion 124.

[0111] The laminations 120 are preferably identical to each other, but are rotated or "clocked" relative to each other by the arcuate span of a single pole segment 116 such that the connecting portions 124 are spaced axially along the axial length of the rotor core 112 (i.e., alternating with gaps).

[0112] Configurations of various connecting portions, including but not limited to providing connecting portions between each pair of pole segment parts, circumferentially deflecting an axially stacked set of laminations (rather than each lamination individually) relative to another, circumferential deflection achieved by rotating at a greater or smaller angle, etc., fall within the scope of some aspects of the present invention. However, generally, structural robustness and magnetic properties are preferably considered.

[0113] Similar to the rotor core 34 of the first preferred embodiment, the rotor core 112 also includes a hub 126 and a bridge 128 that extends between the corresponding pole segments 116 and the hub 126 and connects them to each other. A plurality of protrusions 130 also extend from the hub 126 towards the corresponding magnets 114. However, compared to the rounded protrusions 50 of the first preferred embodiment, the protrusions 130 are generally rectangular.

[0114] Compared to the partially arcuate and partially linear magnets 36 of the first preferred embodiment, the magnets 114 of the second preferred embodiment are curved as a whole. More specifically, each magnet 114 preferably defines a radially inner end 132 and a radially outer end 134 and is continuously curved between the ends 132 and 134.

[0115] Relative to magnet 36 of the first preferred embodiment, the continuous bend between ends 132 and 134 of magnet 114 can improve ease of manufacture in some cases.

[0116] Each magnet 114 preferably has an inner surface 136 and an outer surface 138 respectively, each surface having a respective constant radius of curvature R1 or R2, and thus extending along a circular arc. The inner surface 136 and the outer surface 138 also preferably share a common center of curvature C.

[0117] A constant width W is defined between the inner surface 136 and the outer surface 138. In addition, each magnet 114 has an arc length L defined between a radially inner end 132 and a radially outer end 134 and along the magnet center line. In other words, each magnet 114 extends an angular arc length θ along the center line.

[0118] In a preferred embodiment, the radius of curvature R1 of the inner surface 136 is between approximately five-tenths (0.5) of an inch and approximately one and twenty-five hundredths (1.25) inches. Most preferably, the radius of curvature R1 of the inner surface 136 is approximately eight hundred and forty-eight thousandths (0.848) of an inch.

[0119] The radius of curvature R2 of the outer surface 138 is preferably between approximately seventy-five hundredths (0.75) of an inch and approximately one and five-tenths (1.5) inches. Most preferably, the radius of curvature R2 of the outer surface 138 is approximately one and ninety-three thousandths (1.093) inches.

[0120] Preferably, the width W is between approximately fifteen hundredths (0.15) of an inch and approximately one (1) inch. Most preferably, the width W is approximately two hundred and forty-four thousandths (0.244) of an inch.

[0121] The preferred length L is between approximately five-tenths (0.5) of an inch and approximately two (2) inches. Most preferably, the length L is approximately one and three hundred and fifty-nine thousandths (1.359) inches.

[0122] The arc length θ is preferably between approximately sixty (60) degrees and approximately one hundred (100) degrees. More preferably, the arc length θ is between approximately seventy (70) degrees and approximately ninety (90) degrees. Most preferably, the arc length θ is approximately eighty (80) degrees.

[0123] Preferably, the length L is related to the radii of curvature R1 and R2. That is, an increase in the length L will be associated with an increase in the radii of curvature R1 and R2. For example, preferably, the length L is approximately five-tenths (0.5) times to approximately three (3) times the radius R1, more preferably approximately one (1) time to approximately two (2) times the radius R1, and most preferably approximately one and six-tenths (1.6) times the radius R1.

[0124] Similarly, the length L is preferably from about five-tenths (0.5) times to about three (3) times the radius R2, more preferably from about one (1) time to about two (2) times the radius R2, and most preferably about one and twenty-four hundredths (1.24) times the radius R2.

[0125] In addition, the length L is preferably from about three (3) times to about eight (8) times the width W, more preferably from about four (4) times to about seven (7) times the width W, and most preferably about five and fifty-seven hundredths (5.57) times the width W.

[0126] The radially inner end 132 of each magnet has the radially inner end face 140 of the magnet 114. The radially outer end 134 of each magnet 114 has the radially outer end face 142 of the magnet 114.

[0127] The radially inner end faces 140 each include a main straight face 140a and a secondary straight face 140b.

[0128] The radially outer end face 142 preferably includes a straight portion 142a and a rounded portion 142b. This is different from the simple flat or straight end face 54 of the first preferred embodiment.

[0129] The rounded portion 142b preferably has a radius of curvature R3 between about five-tenths (0.5) inches and about two (2) inches. Most preferably, the radius of curvature R3 is about nine hundred and eighty-four thousandths (0.984) inches.

[0130] It is obvious to those of ordinary skill in the art that the rounded portion 142b with a relatively large radius can be easily distinguished from a simple small-radius rounded or chamfered edge (which may be provided purely for manufacturing convenience or clearance).

[0131] Proportionally, the radius of curvature R3 of the rounded portion 142b is preferably from about five-tenths (0.5) times to about two (2) times the radius of curvature R1 of the inner curved surface 120. More preferably, the radius of curvature R3 is from about seventy-five hundredths (0.75) times to about one and five-tenths (1.5) times the radius of curvature R1. Most preferably, the radius of curvature R3 is about one and sixteen hundredths (1.16) times the radius of curvature R1.

[0132] The provision of the rounded portion 142b helps to improve the back electromotive force characteristics, as well as other advantages in terms of motor performance and manufacturing.

[0133] The main straight surface 140a of the radially inner end face 140 and the straight portion 142a of the radially outer end face 142 are preferably at an angle φ of between approximately forty (40) degrees and approximately eighty (80) degrees with respect to each other. More preferably, the angle φ is between approximately fifty (50) degrees and approximately seventy (70) degrees. Most preferably, the angle φ is approximately sixty (60) degrees.

[0134] Figures 12 - 14 A third preferred embodiment of the present invention is shown. First, it is noted that, with certain exceptions to be discussed in detail below, many elements of the rotor 210 of the third embodiment are the same as or very similar to those described in detail above with respect to the motor 10 (especially its rotor 12) of the first embodiment and the rotor 110 of the second embodiment. Therefore, for the sake of brevity and clarity, redundant descriptions and numbering will generally be avoided here. Unless otherwise stated, the detailed descriptions of the elements given above with respect to the first and second embodiments should be understood to apply at least generally also to the third embodiment.

[0135] Similar to the rotor 12 and the rotor 110, the rotor 210 of the third preferred embodiment preferably includes a rotor core 212 and a plurality of magnets 214. The rotor core 212 preferably includes a plurality of pole segments 216 spaced apart in the circumferential direction. The magnets 214 are circumferentially disposed between adjacent pole segments 216.

[0136] The rotor core 212 is preferably a laminated rotor core, and each pole segment 216 includes a plurality of pole segment portions 216a stacked axially.

[0137] The connecting portion 218 preferably extends between each pair of adjacent pole segments 216 and connects them to each other.

[0138] The rotor core 212 also preferably includes a plurality of holding protrusions 220. In the illustrated embodiment, the holding protrusions 220 extend from the circumferentially alternating pole segment portions 216a to engage or nearly engage the corresponding magnets 214, wherein the laminations of the rotor core 212 are rotated relative to each other such that each magnet 214 is engaged or nearly engaged by a plurality of holding protrusions 220.

[0139] Similar to the magnet 114 of the second preferred embodiment, the magnet 214 of the third preferred embodiment is curved as a whole. However, the magnet 214 of the third preferred embodiment includes a radially outer end face 222, and the radially outer end face 222 includes a main straight portion 222a and a secondary straight portion 222b. This is different from the simple flat or straight end face 54a of the first preferred embodiment and the straight portion 142a and the rounded portion 142b of the second preferred embodiment, respectively.

[0140] The preferred forms of the invention described above are for illustrative purposes only and should not be used in a limiting sense when interpreting the scope of the invention. As described above, those skilled in the art can readily make obvious modifications to the exemplary embodiments without departing from the spirit of the invention.

[0141] Although the above description presents the features of the preferred embodiments of the invention, other preferred embodiments can also be created in accordance with the principles of the invention. In addition, as mentioned above, these other preferred embodiments can in some cases be achieved by combinations of features that are compatible and used together, although they have been presented separately as part of the individual embodiments in the above description.

[0142] The inventors hereby state their intention to rely on the doctrine of equivalents to determine and access the fair and reasonable scope of the invention, which relates to any device that does not substantially depart from but falls within the literal scope of the invention as set forth in the appended claims.

Claims

1. A spoke-type rotor capable of rotating about an axis, the rotor comprising: a core including a plurality of pole segments arranged in an arc around the axis; and a plurality of magnets arranged in an arc, the magnets and the pole segments being arranged alternately in an arc such that each magnet is at least partially interposed between a pair of adjacent pole segments; each magnet includes a curved section that extends in an arc between a radially inner end and a radially outer end.

2. The rotor according to claim 1, the curved section has two axially extending surfaces that are opposite to each other, and each surface extends in an arc between the inner end and the outer end.

3. The rotor according to claim 1, the curved section has two axially extending surfaces that are opposite to each other, each surface having a constant radius of curvature between the inner end and the outer end, and the spacing between the surfaces is constant along the entire length of the curved section.

4. The rotor according to claim 1, the curved section has two axially extending surfaces that are opposite to each other, and each surface extends in an arc between the inner end and the outer end, one of the two surfaces faces substantially radially inwards, the other of the two surfaces faces substantially radially outwards.

5. The rotor according to claim 1, each magnet further includes a straight section adjacent to its curved section.

6. The rotor according to claim 5, the curved section has two axially extending surfaces that are opposite to each other, and each surface extends in an arc between the inner end and the outer end, the straight section has two axially extending flat surfaces that are opposite to each other, and each flat surface extends from a corresponding one of the surfaces at the outer end.

7. The rotor according to claim 6, each flat surface extends tangentially from a corresponding one of the surfaces at the outer end.

8. The rotor according to claim 5, the curved section has two axially extending surfaces that are opposite to each other, and each surface extends in an arc between the inner end and the outer end, and the spacing between the two surfaces is constant along the entire length of the curved section, the straight section has two axially extending flat surfaces that are opposite and parallel to each other.

9. The rotor according to claim 5, the curved section extends along a curved section center line and has a curved section length defined along the curved section center line, the straight section extends along a straight section center line and has a straight section length defined along the straight section center line, the total length of the magnet is equal to the sum of the curved section length and the straight section length, the curved section length is at least 50% of the total length.

10. The rotor according to claim 9, the curved section length is in the range of about 60% to about 90% of the total length.

11. The rotor according to claim 1, the magnet has a total length, the curved section extends along a curved section center line and has a curved section length defined along the curved section center line, the curved section length is at least substantially equal to the total length.

12. The rotor according to claim 1, a slot is defined between each pair of adjacent pole segments, each slot includes a magnet receiving portion and a gap portion, The clearance portion is disposed at least substantially radially outside the magnet receiving portion. Each magnet is at least partially received within a respective one of the magnet receiving portions, with no magnet in each respective clearance portion.

13. The rotor according to claim 1, The curved section has an arc length in the range of approximately 60 degrees to approximately 100 degrees.

14. The rotor according to claim 13, The arc length is in the range of approximately 70 degrees to approximately 90 degrees.

15. A rotor capable of rotating about an axis, the rotor comprising: a core including a plurality of pole segments arranged in an arc around the axis ； and a plurality of magnets arranged in an arc, the magnets being arranged alternately with the pole segments in an arc such that each magnet is at least partially interposed between a pair of adjacent pole segments; wherein an effective rotor magnetic pole position is defined on each pole segment; each pole segment has an end opposite the effective rotor magnetic pole position; wherein a center point is defined at the end; each effective rotor magnetic pole position is offset arcwise from the corresponding center point by approximately 0.5 rotor magnetic poles to approximately 2.0 rotor magnetic poles.

16. The rotor according to claim 15, each rotor magnetic pole is offset arcwise from the corresponding center point by approximately 1.25 rotor magnetic poles to approximately 1.5 rotor magnetic poles.

17. The rotor according to claim 15, The core of the rotor defines a radially outermost edge in the circumferential direction, each center point is spaced from the edge by a radial distance, each magnet extending along a magnet center line has a total length, the total length of each magnet is at least 10% greater than the corresponding radial distance.

18. The rotor according to claim 15, each magnet includes a curved section extending in an arc.

19. The rotor according to claim 18, each magnet further includes a straight section adjacent to the curved section, the curved section extends along a curved section center line and has a curved section length defined along the curved section center line, the straight section extends along a straight section center line and has a straight section length defined along the straight section center line, the total length of the magnet is equal to the sum of the curved section length and the straight section length, the curved section length is at least 50% of the total length.

20. The rotor according to claim 19, the curved section extends in an arc between a radially inner end and a radially outer end, the curved section has an arc length in the range of approximately 45 degrees to approximately 95 degrees.

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