U.S. patent application number 17/212145 was filed with the patent office on 2022-09-29 for rotor with arcuate magnets.
This patent application is currently assigned to Nidec Motor Corporation. The applicant listed for this patent is Nidec Motor Corporation. Invention is credited to Ryan M. Bastien.
Application Number | 20220311294 17/212145 |
Document ID | / |
Family ID | 1000005489097 |
Filed Date | 2022-09-29 |
United States Patent
Application |
20220311294 |
Kind Code |
A1 |
Bastien; Ryan M. |
September 29, 2022 |
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
arcuately about the axis. The rotor includes a plurality of
arcuately arranged magnets alternating arcuately with the pole
segments, such that each of the magnets is at least in part
interposed between a pair of adjacent pole segments. Each of the
magnets includes a curved section extending arcuately between
radially inner and outer curved section ends. An effective rotor
pole location is defined on each of the pole segments. Each of the
pole segments has an end opposite the effective rotor pole
location. A center point is defined at the pole segment end. Each
of the effective rotor pole locations is arcuately offset from a
corresponding one of the center points by between about five tenths
(0.5) rotor poles and about two (2.0) rotor poles.
Inventors: |
Bastien; Ryan M.; (St.
Charles, MO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nidec Motor Corporation |
St. Louis |
MO |
US |
|
|
Assignee: |
Nidec Motor Corporation
St. Louis
MO
|
Family ID: |
1000005489097 |
Appl. No.: |
17/212145 |
Filed: |
March 25, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K 1/2773 20130101;
H02K 2213/03 20130101; H02K 1/28 20130101 |
International
Class: |
H02K 1/27 20060101
H02K001/27; H02K 1/28 20060101 H02K001/28 |
Claims
1. A spoked rotor rotatable about an axis, said rotor comprising: a
core including a plurality of pole segments arranged arcuately
about the axis; and a plurality of arcuately arranged magnets
alternating arcuately with said pole segments, such that each of
the magnets is at least in part interposed between a pair of
adjacent pole segments, each of said magnets including a curved
section extending arcuately between radially inner and outer
ends.
2. The rotor as claimed in claim 1, said curved section presenting
opposite axially extending curved faces, each extending arcuately
between the inner and outer ends.
3. The rotor as claimed in claim 1, said curved section presenting
opposite axially extending curved faces, each having a constant
radius of curvature between the inner and outer ends, with spacing
between the curved faces being constant the full length of the
curved section.
4. The rotor as claimed in claim 1, said curved section presenting
opposite axially extending curved faces, each extending arcuately
between the inner and outer ends, one of said curved faces facing
generally radially inward, another of said curved faces facing
generally radially outward.
5. The rotor as claimed in claim 1, each of said magnets further
including a straight section adjacent the curved section
thereof.
6. The rotor as claimed in claim 5, said curved section presenting
opposite axially extending curved faces, each extending arcuately
between the inner and outer ends, said straight section presenting
opposite axially extending straight faces, each extending from a
corresponding one of the curved faces at the outer end.
7. The rotor as claimed in claim 6, each of said straight faces
extending tangentially from the corresponding one of the curved
faces at the outer end.
8. The rotor as claimed in claim 5, said curved section presenting
opposite axially extending curved faces, each extending arcuately
between the inner and outer ends, with spacing between the curved
faces being constant the full length of the curved section, said
straight section presenting opposite, parallel, axially extending
straight faces.
9. The rotor as claimed in claim 5, said curved section extending
along a curved section centerline and having a curved section
length defined along the curved section centerline, said straight
section extending along a straight section centerline and having a
straight section length defined along the straight section
centerline, said magnet having a total length equal to the sum of
the curved section length and the straight section length, said
curved section length being at least 50% of the total length.
10. The rotor as claimed in claim 9, said curved section length
being between about 60% and about 90% of the total length.
11. The rotor as claimed in claim 5, said straight section
presenting a non-rectangular axial face.
12. The rotor as claimed in claim 1, each of said pairs of adjacent
pole segments defining a slot therebetween, each of said slots
including a magnet-receiving portion and a gap portion, said gap
portion being at least substantially disposed radially outwardly of
said magnet-receiving portion, each of said magnets being at least
in part received within a corresponding one of said
magnet-receiving portions, with each of the corresponding gap
portions being devoid of the magnet.
13. The rotor as claimed in claim 1, said curved section having an
arc length between about 45 degrees and about 95 degrees.
14. The rotor as claimed in claim 13, said arc length being between
about 60 degrees and about 80 degrees.
15. A rotor rotatable about an axis, said rotor comprising: a core
including a plurality of pole segments arranged arcuately about the
axis; and a plurality of arcuately arranged magnets alternating
arcuately with said pole segments, such that each of the magnets is
at least in part interposed between a pair of adjacent pole
segments, wherein an effective rotor pole location is defined on
each of said pole segments, each of said pole segments having an
end opposite the effective rotor pole location, wherein a center
point is defined at said end, each of said effective rotor pole
locations being arcuately offset from a corresponding one of the
center points by between about 0.5 rotor poles and about 2.0 rotor
poles.
16. The rotor of claim 15, each of said rotor poles being arcuately
offset from the corresponding ones of the center points by between
about 1.25 rotor poles and about 1.5 rotor poles.
17. The rotor of claim 15, said rotor core defining a radially
outermost circumferential margin, each of said center points being
spaced from said margin by a radial distance, each of said magnets
extending along a magnet centerline having a total length, each of
said total magnet lengths being at least 10% greater than a
corresponding one of said radial distances.
18. The rotor of claim 15, each of said magnets including a curved
section and a straight section adjacent the curved section.
19. The rotor of claim 18, said curved section extending along a
curved section centerline and having a curved section length
defined along the curved section centerline, said straight section
extending along a straight section centerline and having a straight
section length defined along the straight section centerline, said
magnet having a total length equal to the sum of the curved section
length and the straight section length, said curved section length
being at least 50% of the total length.
20. The rotor of claim 19, said curved section extending arcuately
between radially inner and outer ends, said curved section having
an arc length between about 45 degrees and about 95 degrees.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates generally to an electric
motor. More particularly, the motor includes a plurality of
arcuately arranged magnets configured and arranged to provide
improved magnetic flux.
2. Discussion of the Prior Art
[0002] Electric motors conventionally comprise a stator and a
rotatable rotor. Such motors may be inner rotor motors, outer rotor
motors, or dual rotor motors. Furthermore, a variety of rotor and
stator configurations are permissible. Among other alternatives,
for instance, the rotor might comprise a rotor can supporting a
plurality of arcuately arranged magnets, a plurality of arcuately
arranged magnets alternating with a plurality of arcuately arranged
pole segments, or a rotor core with a plurality of magnets arranged
arcuately around a perimeter thereof. Pole segment, magnet, and
stator tooth geometry may vary according to desired performance
characteristics, space constraints, and cost considerations.
SUMMARY
[0003] According to one aspect of the present invention a spoked
rotor is rotatable about an axis. The rotor includes a core
including a plurality of pole segments arranged arcuately about the
axis. The rotor further includes a plurality of arcuately arranged
magnets alternating arcuately with the pole segments, such that
each of the magnets is at least in part interposed between a pair
of adjacent pole segments. Each of the magnets includes a curved
section extending arcuately between radially inner and outer
ends.
[0004] According to another aspect of the present invention, a
rotor is rotatable about an axis. The rotor includes a core
including a plurality of pole segments arranged arcuately about the
axis. The rotor further includes a plurality of arcuately arranged
magnets alternating arcuately with the pole segments, such that
each of the magnets is at least in part interposed between a pair
of adjacent pole segments. An effective rotor pole location is
defined on each of the pole segments. Each of the pole segments has
an end opposite the effective rotor pole location. A center point
is defined at the end. Each of the effective rotor pole locations
is arcuately offset from a corresponding one of the center points
by between about five tenths (0.5) rotor poles and about two (2.0)
rotor poles.
[0005] Among other things, provision of (1) rotor magnets each
having a curved section having first and second ends, wherein the
second end is disposed radially outward of the first end, and/or
(2) a core and magnets configured such that each of a plurality of
effective rotor pole locations is arcuately offset by between about
five tenths (0.5) rotor poles and about two (2.0) rotor poles from
a corresponding one of a plurality of center points enables
improved motor performance (e.g., via excellent flux concentration)
to be achieved within a given motor envelope in comparison to a
conventional spoked motor configuration. It is particularly noted
that the inventive aspects of the present invention facilitate
excellent cost vs. efficiency outcomes in some circumstances that
would otherwise require costly upgrades to magnet material (e.g.,
rare earth magnets rather than ferrite magnets) and/or the addition
of expensive additional active material (copper, steel, etc.).
[0006] This summary is provided to introduce a selection of
concepts in a simplified form. These concepts are further described
below in the detailed description of the preferred embodiments.
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.
[0007] Various other aspects and advantages of the present
invention will be apparent from the following detailed description
of the preferred embodiments and the accompanying drawing
figures.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0008] Preferred embodiments of the present invention are described
in detail below with reference to the attached drawing figures,
wherein:
[0009] FIG. 1 is a front perspective view of a motor in accordance
with a preferred embodiment of the present invention;
[0010] FIG. 2 is a partially sectioned perspective view of the
motor of FIG. 1;
[0011] FIG. 3 is a front perspective view of the rotor core and
magnets of the motor of FIGS. 1 and 2;
[0012] FIG. 4 is a front view of the rotor core and magnets of FIG.
3;
[0013] FIG. 5 is an enlarged front view of a portion of the rotor
core and magnets as shown in FIG. 4, particularly illustrating the
skew of the effective rotor pole locations relative to the
corresponding pole segment bridges;
[0014] FIG. 6 is an enlarged, outer perspective view of a magnet of
the rotor of FIGS. 1-5;
[0015] FIG. 7 is an inner perspective view of the magnet of FIG. 6;
and
[0016] FIG. 8 a front view of the magnet of FIGS. 6 and 7,
particularly illustrating the relative proportions and general
geometries of the curved and straight portions thereof.
[0017] The drawing figures do not limit the present invention to
the specific embodiments disclosed and described herein. While the
drawings do not necessarily provide exact dimensions or tolerances
for the illustrated structures or components, the drawings are to
scale with respect to the relationships between the components of
the structures illustrated in the drawings.
DETAILED DESCRIPTION
[0018] The present invention is susceptible of embodiment in many
different forms. While the drawings illustrate, and the
specification describes, certain preferred embodiments of the
invention, it is to be understood that such disclosure is by way of
example only. There is no intent to limit the principles of the
present invention to the particular disclosed embodiments.
[0019] Furthermore, unless specified or made clear, the directional
references made herein with regard to the present invention and/or
associated components (e.g., top, bottom, upper, lower, inner,
outer, etc.) are used solely for the sake of convenience and should
be understood only in relation to each other. For instance, a
component might in practice be oriented such that faces referred to
as "top" and "bottom" are sideways, angled, inverted, etc. relative
to the chosen frame of reference.
[0020] With initial reference to FIGS. 1 and 2, an electric motor
10 is provided. The motor 10 includes a rotor 12 rotatable about an
axis. The motor 10 further includes a stator 14. The stator 14
preferably at least substantially circumscribes 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.
[0021] The motor 10 further preferably includes a housing 16
including a cylindrical shell 18 extending between and
interconnecting a pair of axially opposed endshields 20 and 22.
[0022] The stator 14 preferably includes a stator core 24 and a
plurality of coil assemblies 26 mounted to the stator core 24. Each
coil assembly 26 preferably includes a bobbin 28 and a plurality of
coils 30. The coils 30 comprise electrically conductive wiring 32
wound about the respective bobbins 28.
[0023] 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 instance,
the stator might be provided with full length endcaps, overmolding,
or insulative inserts or wraps (e.g., Mylar papers).
[0024] Furthermore, although the illustrated stator 14 is formed
from punched linear bar laminations that are thereafter formed into
curves, the stator might be alternatively formed without departing
from the scope of the present invention. For instance, the stator
might be a full round stator (i.e., comprising laminations punched
in a full circle), be solidly constructed, be arcuately segmented,
etc.
[0025] The rotor 12 preferably includes a rotor core 34, a
plurality of magnets 36, and a shaft 38 defining a rotational axis
for the rotor 12. The rotor core 34 includes a plurality of pole
segments 40 arranged arcuately about the axis. The magnets 36 are
arranged arcuately so as to alternate arcuately with the pole
segments 40. Each of the magnets 36 is thus at least in part
interposed between a pair of adjacent pole segments 40.
[0026] The rotor core 34 preferably comprises steel, although other
materials may alternatively be used without departing from the
scope of the present invention. The magnets 36 are preferably
permanent magnets comprising ferrite, although other suitable
magnet materials, such as neodymium, may be used according to
certain aspects of the present invention.
[0027] The rotor core 34 further preferably includes a hub 42 and a
plurality of bridges 44 extending between and interconnecting
respective ones of the pole segments 40 to the hub 42. The shaft 38
preferably extends through an opening 46 defined by the hub.
[0028] Preferably, as illustrated, the hub 42 is at least
substantially toroidal in form to present inner and outer
cylindrical faces centered about the rotor axis. The hub might be
alternatively configured without departing from some aspects of the
present invention, however. For instance, the hub might
alternatively present a faceted or polygonal outer surface
comprising a plurality of flat faces, or the inner opening defined
by the hub might be non-circular in keeping with an alternative
shaft formation.
[0029] In a preferred embodiment, each of the bridges 44 connects
with a corresponding one of the pole segments 40. Furthermore, each
pole segment 40 is connected to the hub 42 via a corresponding
bridge 44. That is, the number of pole segments 40 is preferably
equal to the number of bridges 44. It is permissible according to
some aspects of the present invention, however, for the rotor core
to include differing numbers of bridges and pole segments.
[0030] In the illustrated embodiment, each bridge 44 is at least
substantially rectangular in form and extends radially outward from
the hub 42, although alternate shapes and/or directions of
extension for some or all of the bridges are permissible according
to some aspects of the present invention.
[0031] Preferably, each bridge 44 engages a corresponding one of
the pole segments 40 at tangential or arcuate bridge interface 48.
The bridge interface 48 has a generally tangential or arcuate
center point 48a.
[0032] The center points 48a may alternatively be characterized in
relation to the pole segments 40 themselves, rather than in
relation to the bridge interfaces 48. More particularly, each pole
segment 40 may be understood to present a radially inner end 48
(which coincides with the respective bridge interface 48 in the
illustrated embodiment). Each radially inner end 48 preferably has
a generally tangential or arcuate center point 48a.
[0033] The rotor core 34 further preferably includes a plurality of
nubs 50 extending radially outward from the hub 42. The nubs 50
preferably alternate arcuately with the bridges 44, with even
spacing being provided from each bridge 44 to adjacent ones of the
nubs 50 and vice versa. Each nub 50 preferably engages a
corresponding one of the magnets 36 to restrict shifting thereof in
a radially inward direction.
[0034] The nubs 50 each preferably include a rounded radially outer
end, although alternative geometries are permissible. Furthermore,
the nubs might be omitted in lieu of alternative magnet retention
means such as overmolding, other structural components, etc. Such
retention means might also be provided in addition to nubs.
[0035] Although the rotor core 34 of the present invention is
preferably formed of axially stacked punched laminations (each of
which includes at least pole segment, hub, bridge, and nub
components), it is permissible for alternative manufacturing and/or
assembly techniques to be utilized. For instance, fully formed pole
segments might be press-fit into the hub using a dovetail joint or
other suitable connection. (In such an instance, the hub is
preferably but not necessarily formed of a different material than
the pole segments.) In another alternative, pole segments might be
molded into position in such a manner that "direct" connections
between the pole segments and the hub, whether via bridges,
jointing, or another technique, are not present. Molding might also
be provided supplementarily to another connection or positioning
technique. Still further, varying lamination designs might be
provided, perhaps in an axially alternating or staggered manner. In
summary, provided operability of the motor in a broad sense is
maintained, it is permissible for varying or alternative bridge
types or pole segment-to-hub connection configurations to be
provided, for bridges or direct connections to be omitted entirely,
and/or for other variations in rotor core design to occur without
departing from the scope of some aspects of the present
invention.
[0036] In a broad sense, each magnet 36 preferably defines a
radially inner end 52 and a radially outer end 54. Furthermore,
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 a radially outer curved section end 60
disposed intermediately between the inner and outer ends 52 and 54.
The straight section 58 preferably extends straight and, most
preferably non-radially, from the outer curved section end 60 to
the radially outer end 54 of the magnet 36.
[0037] In the illustrated embodiment, the radially inner end 52
presents a radially inner end face 52a of the magnet 36. Similarly,
the radially outer end 54 presents a radially outer end face 54a of
the magnet 36.
[0038] Furthermore, in a preferred embodiment, the curved section
end 60 can alternatively be characterized with reference to the
magnet 36 as a whole as presenting a transition interface 60a
between the curved and straight sections 56 and 58. That is, the
transition interface 60a is preferably disposed intermediately
between the inner and outer ends 52 and 54 of the magnet, where the
curved and straight sections 56 and 58 abut each other.
[0039] The curved and straight sections 56 and 58, respectively,
are preferably continuously formed with one another such that each
magnet 36 comprises a unitary body. However, it is permissible
according to some aspects of the present invention for the sections
to be separate or discrete pieces.
[0040] The curved section 56 preferably presents a front curved
face 56a, a back curved face 56b, and opposite axially extending
inner and outer curved faces 56a and 56b extending between and
interconnecting the front curved face 56a and the back curved face
56b. The inner and outer curved faces 56c and 56d each also
preferably extend continuously (i.e., without gaps, obstructions,
or other irregularities) between the radially inner end 52 and the
outer curved section end 60.
[0041] The inner curved face 56c preferably faces generally
radially inward. The outer curved face 56d preferably faces
generally radially outward.
[0042] Most preferably, the inner curved face 56c has a constant
curvature or, alternatively stated, presents a constant radius of
curvature R1 so as to extend along a circular arc. Likewise, the
outer curved face 56d preferably has a constant curvature or,
alternatively stated, presents a constant radius of curvature R2 so
as to extend along a circular arc.
[0043] In a preferred embodiment, the inner and outer curved faces
56c and 56d are centered on a common center of curvature C. That
is, the hypothetical circles along which the inner and outer curved
faces 56c and 56d extend are concentric.
[0044] Thus, it will also be understood by those of ordinary skill
in the art that the curved section 56 preferably presents a
constant width W1 between the inner and outer curved faces 56c and
56d.
[0045] Although concentric, constant-radius extension of both the
inner and outer curved faces 56c and 56d is preferred, it is
permissible according to some aspects of the present invention for
variations to occur. For instance, the curved section might
alternatively include multiple portions each having distinct
geometries (e.g., varying radii of curvature, centers of curvature,
etc.). Such variations might apply similarly to both the inner and
outer curved faces, or the variations might be irregularly applied
such that the width of the curved section varies along its
length.
[0046] In both a preferred embodiment and in the above-described
alternative magnet configurations, despite potential variations in
radii of curvature, centers of curvature, and so on, the magnets
remain in a general sense continuously curved (i.e., smoothly
curved). That is, vertices are not present. However, it is also
permissible according to some aspects of the present invention for
the curved section to comprise a plurality of straight sections
positioned relative to one another in such a manner that a curve is
broadly formed thereby. That is, each of the inner and outer curved
faces might be understood to be faceted yet still curved in a
general sense.
[0047] In a preferred embodiment, the radius of curvature R1 of the
inner curved face 56c is between about five tenths (0.5) inches and
about one and twenty-five hundredths (1.25) inches. Most
preferably, the radius of curvature R1 of the inner curved face 56c
is about eight hundred thirty six thousandths (0.836) inches.
[0048] The radius of curvature R2 of the outer curved face 56d is
preferably between about seventy-five hundredths (0.75) inches and
about one and five tenths (1.5) inches. Most preferably, the radius
of curvature R2 of the outer curved face 56d is about one and one
hundred twenty-three thousandths (1.123) inches.
[0049] Preferably, the width W1 of the curved section 56 is between
about fifteen hundredths (0.15) inches and about one (1) inch. Most
preferably, the width W of the curved section 56 is about two
hundred eighty-seven thousandths (0.287) inches.
[0050] As shown in FIG. 8, a hypothetical magnet centerline 62
comprising a curved section centerline 62a and a straight section
centerline 62b preferably extends through the magnet 36. More
particularly, the curved section centerline 62a preferably extends
arcuately through the curved section 56 from the radially inner end
52 of the magnet 36 to the radially outer curved section end or
transition interface 60 so as to be equally spaced from each of the
inner and outer curved faces 56c and 56d. That is, the curved
section 56 preferably extends along the curved section centerline
62a.
[0051] Furthermore, the curved section 56 preferably has a curved
section length L1 along the curved section centerline 62a. The
preferred curved section length L1 is between about five tenths
(0.5) inches and about one and five tenths (1.5) inches. Most
preferably, the curved section length L1 is about one thousand, six
hundred ninety-eight ten thousandths (1.1698) inches.
[0052] Alternatively characterized, the curved section 56
preferably extends along the curved section centerline 62a for an
angular arc length .theta.1 of between about forty-five (45)
degrees and about ninety-five (95) degrees. More preferably, the
curved section 56 has an arc length .theta.1 along the curved
section centerline 62a of between about sixty (60) degrees and
about eighty (80) degrees. Most preferably, the arc length .theta.1
of the curved section 56 along the curved section centerline 62a is
about sixty eight (68) degrees.
[0053] The end face 52a and the transition interface 60a are
preferably angled relative to each other by an angle .PHI.1 of
between about seventy (70) degrees and about one hundred ten (110)
degrees. More preferably, .PHI.1 is between about eighty (80)
degrees and about one hundred (100) degrees. Most preferably, the
angle .PHI.1 of the face 52 relative to the interface 60 is about
eighty-seven (87) degrees.
[0054] As noted previously, the straight section 58 of each magnet
36 preferably extends straight and, most preferably non-radially,
from the outer curved section end 60 to the radially outer end 54
of the magnet 36. More particularly, each straight section 58
preferably presents a front straight face 58a, a back straight face
58b, and opposite axially extending inner and outer straight faces
58c and 58d extending between and interconnecting the front
straight face 58a and the back straight face 58b. The inner and
outer straight faces 58c and 58d each 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.
[0055] The inner straight face 58c preferably faces generally
radially inward. The outer straight face 58d preferably faces
generally radially outward.
[0056] 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.
[0057] The straight section 58 preferably presents a constant width
W2 between the inner and outer straight faces 58c and 58d.
(Alternatively stated, the inner and outer straight faces 58c and
58d are preferably parallel to one another.) The width W2 of the
straight section 58 is most preferably equal to the width W1 of the
curved section 56. It is permissible according to some aspects of
the present invention for the straight section to instead be
variable in width (e.g., tapered or flared), to extend
non-tangentially from the curved section, to present a different
width than that of the curved section (or a portion thereof),
etc.
[0058] Preferably, the width W2 of the straight section 58 is
between about fifteen hundredths (0.15) inches and about one (1)
inch. Most preferably, the width W2 of the straight section 58 is
about two hundred eighty-seven thousandths (0.287) inches.
[0059] The aforementioned hypothetical straight section centerline
62b (see FIG. 8) preferably extends linearly through the straight
section 58 from the transition interface 60 to the radially outer
end 54 of the magnet 36 so as to be equally spaced from each of the
inner and outer curved straight faces 58c and 58d. That is, the
straight section 58 preferably extends along the straight section
centerline 62b.
[0060] As will be apparent from the above descriptions, the curved
section centerline 62a preferably interconnects smoothly with the
straight section centerline 62b. That is, the centerlines 62a and
62b (and, in turn, the curved and straight sections 56 and 58) are
not offset or angled relative to one another.
[0061] The straight section 58 preferably has a straight section
length L2 along the straight section centerline 62b. Preferably,
the straight section length L2 is between about twenty-five
hundredths (0.25) inches and about seventy-five hundredths (0.75)
inches. Most preferably, the straight section length L2 is about
three thousand, eight hundred one ten thousandths (0.3801)
inches.
[0062] Each magnet 36 preferably has a total length L3 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 about
sixty percent (60%) and about ninety percent (90%) of the total
length L3, and most preferably about seventy-five and forty-eight
hundredths percent (75.48%) of the total length L3.
[0063] Nominally, as will be apparent from the above described
preferred lengths L1 and L2 of the curved and straight sections 56
and 58, respectively, the total magnet length L3 is preferably
between about seventy-five hundredths (0.75) inches and about two
and twenty-five hundredths (2.25) inches. Most preferably, the
total magnet length L3 is about one and five thousand, four hundred
ninety-nine ten thousandths (1.5499) inches.
[0064] As shown in FIG. 5, a radial distance D may be defined from
each bridge interface 48 to a radially outermost circumferential
margin 64 of the rotor core 34. In a preferred embodiment, the
distance D is between about (0.75) inches and (1.75) inches. More
preferably, the distance D is between about one (1) inch and about
one and five tenths (1.5) inches. Most preferably, the distance D
is about one and three thousand, one hundred ninety-eight ten
thousandths (1.3198) inches.
[0065] Due to provision of the curved section 56 and the non-radial
orientation of the straight section 58, the total magnet lengths L3
are preferably significantly greater than the radial distances D.
For instance, it is preferred that each total magnet length L3 is
at least five percent (5%), more preferably at least ten percent
(10%), and most preferably at least fifteen percent (15%) greater
than corresponding ones of the radial distances D. In the
illustrated embodiment, for instance, each total magnet length L3
is about seventeen and forty-three hundredths percent (17.43%)
greater than the radial distance D.
[0066] In a practical sense, the increased relative length
facilitates a greater magnet pole face area for each magnet 36
compared to that conventionally achieved in the same motor
envelope. In turn, an increased magnet pole face area facilitates
improved flux concentration. For instance, in comparison to a
conventional spoked rotor, the present invention preferably
achieves at least a ten percent (10%) increase, more preferably at
least a twenty-five percent (25%) increase, and most preferably a
greater than thirty percent (30%) increase in magnet pole face
area.
[0067] As will be apparent to those of ordinary skill in the art,
the magnet pole face area in the preferred, illustrated embodiment
can be understood to be the combined area of the inner and outer
faces 56c and 56d of the curved section 56 and the inner and outer
faces 58c and 58d of the straight section 58. (As will be discussed
in greater detail below, these faces 56c, 56d, 58c, and 58d are
tangential to the local magnetizing direction.)
[0068] Each magnet 36 also preferably has a total arcuate span
.theta.2 along the centerline 62 from the radially inner end 52 to
the radially outer end 54, and measured relative to the center of
curvature C, of between about seventy (70) degrees and about one
hundred ten (110) degrees, more preferably between about eighty
(80) degrees and about one hundred (100) degrees, and most
preferably of about ninety (90) degrees.
[0069] The end faces 52a and 54a of each magnet 36 are preferably
angled relative to each other by an angle .PHI.2 of between about
forty (40) degrees and about ninety (90) degrees. More preferably,
.PHI.2 is between about fifty (50) degrees and about eighty (80)
degrees. Most preferably, the angle .PHI.2 of the face 52a relative
to the face 54a is about sixty-four (64) degrees.
[0070] In a preferred embodiment, the straight section 58 presents
non-rectangular front and back straight faces 58a and 58b. More
particularly, the inner straight section face 58c is preferably
longer than the outer straight section face 58d, such that the
front and back straight faces 58a and 58b are generally
trapezoidal. Still more particularly, the front and back straight
faces 58a and 58b are preferably at least substantially right
trapezoidal such that the magnet 36 defines an acute apex 66 at the
outer end 54 and adjacent the inner straight section face 58c.
[0071] In the illustrated embodiment, various surfaces of the
magnets 36 are chamfered. However, it is permissible according to
some aspects of the present invention for some or all of the
illustrated chamfers to be omitted, for some or all of the chamfers
to be replaced with rounds or other transitions, etc.
[0072] 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. The magnets 36 are each at least
in part received in the magnet-receiving portion 70 of a
corresponding one of the slots 68, with the corresponding gap
portion 72 being devoid of the corresponding magnet 36.
[0073] As noted previously, the rotor core 34 preferably presents a
circumferential radially outermost margin 64. The slots 68 each
preferably extend to the radially outermost margin 64 of the rotor
core 34 except for the presence of a corresponding plurality of
tangential (or, alternatively, arcuate) connectors 74 extending
between and interconnecting adjacent ones of the pole segments 40.
The previously described shape of the magnets 36 is such that the
gap portion 72 is defined between each radially outer magnet end 54
and the corresponding connector 74.
[0074] The geometry of the slots 68 and the magnets 36 (including
the straight sections 58 thereof) is such that the gap portions 72
are preferably generally triangular in form. Most preferably, the
gap portions 72 are generally right triangular in form. However,
alternative gap portion shapes are permissible according to some
aspects of the present invention.
[0075] The gap portions 72 may be naturally or environmentally
filled (i.e., with ambient air), be filled with a non-magnetically
conductive material (e.g., an epoxy), etc. without departing from
the scope of the present invention. It is also permissible
according to some aspects of the present invention for the magnets
and slots to be configured in such a manner that the magnets fill
the slots entirely. The gap portions in such an embodiment would
therefore be omitted.
[0076] It is noted that some or all of the connectors may be
omitted according to some aspects of the present invention,
particularly if the gap portions are filled with a structural
material (e.g., an epoxy, etc. as noted above).
[0077] The magnets 36 are each preferably magnetized at least
substantially radially. That is, the direction of magnetization is
radially from the inner curved face 56c to the outer curved face
56d and orthogonally or straight from the inner straight face 58c
to the outer straight face 58d. Thus, each magnet 36 has a first
polarity along its inner curved and straight faces 56c and 58c and
a second, opposite polarity along its outer curved and straight
faces 56d and 58d.
[0078] Minor deviations from such magnetization (e.g., parallel
magnetization within the curved section, radial magnetization
within the straight section, etc.) are permissible according to
some aspects of the present invention, although performance
outcomes may suffer.
[0079] The directionality or polarity of the magnets 36 preferably
alternates arcuately. That is, outer faces 56d and 58d presenting a
north polarity will be opposed to inner faces 56c and 58e of a
different magnet 36 also presenting a north polarity, and so on,
with corresponding "like-polarity" faces being separated from one
another by one of the pole segments 40.
[0080] Alternatively stated, a magnet 36 for which the outer faces
56d and 58d present a first polarity (e.g., a north polarity) will
be disposed arcuately between a pair of magnets 36 for which the
outer faces 56d and 58d present a second, opposite polarity (e.g.,
a south polarity). (Pole segments 40 will, of course, be interposed
between the magnets 36 as described above.)
[0081] Each pole segment 40 includes a generally radially extending
body 76 and a pair of circumferentially extending ears 78
projecting outward from the body 76. The body 76 connects to a
corresponding one of the bridges 44 at the corresponding bridge
interface 48. The ears 78 each are connected to corresponding ears
78 of adjacent ones of the pole segments 40 by corresponding ones
of the connectors 74.
[0082] Each body 76 is preferably generally shaped in a curved or
"swept" triangular manner. More particularly, each body 76 includes
a curved inner body face 76a that abuts the outer curved face of an
adjacent magnet 36 and a curved outer body face 76b that abuts the
inner curved face 56c of another adjacent magnet 36. This geometry
in turn dictates a general arcuate widening or flaring of each pole
segment 40 as it expands radially outwardly.
[0083] Although it is preferred that the rotor core 34 include
solid pole segment bodies 76 disposed between adjacent magnets 36,
as described above, it is noted that alternative rotor core designs
that omit such pole bodies fall within the scope of some aspects of
the present invention. Among other things, for instance, the core
or a comparable component might alternatively be at least in part
in the form of a latticed, spoked, or cylindrical framework
supporting the magnets. That is, use of curved magnets as described
above in broadly differing rotor (or rotor core) designs is
permissible according to some aspects of the present invention.
[0084] Each pole segment body 76 (or, more broadly, each pole
segment 40) includes a radially outer face 76c that at least in
part defines the previously mentioned radially outermost margin 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
pole location P is defined on each of the pole segments 40,
centered arcuately along the radially outer face 76c of the
corresponding pole segment 40.
[0085] As noted previously, each bridge interface 48 or,
alternatively, inner end 48 of a pole segment 40, has a center
point 48a. For each pole segment 40, the effective rotor pole
location P is arcuately offset from (i.e., skewed from) the center
point 48a by a skew angle .alpha.. That is, in contrast to a
conventional spoked rotor, the effective rotor pole locations P are
not disposed directly radially outward of the associated bridges
or, alternatively stated, the centers of the inner ends of the pole
segments.
[0086] Preferably, each rotor pole location P is arcuately offset
from the corresponding one of the center points 48a by a skew angle
.alpha. between about five tenths (0.5) rotor poles and about two
(2.0) rotor poles. More preferably, the skew angle .alpha. is
between about one and twenty-five hundredths (1.25) rotor poles and
about one and five tenths (1.5) rotor poles. Most preferably, the
rotor pole locations P are arcuately offset from the corresponding
center points 48a by a skew angle .alpha. of about one and
thirty-seven hundredths (1.37) poles.
[0087] In a preferred embodiment, the motor 10 is a ten (10) pole
motor 10. Thus, as will be understood by those of ordinary skill in
the art, the rotor pole locations P might alternatively be
understood to most preferably be arcuately offset from the
corresponding ones of center points 48a by a skew angle .alpha. of
about forty-nine and two tenths (49.2) degrees.
[0088] As will be apparent from the above, it is preferred that the
rotor pole locations P are disposed radially outward from the
center points 48a. More particularly, the rotor pole locations P
are preferably disposed at radially outer ends (and, more
specifically at the radially outer faces 76c) of the pole segments
40. The center points 48a are disposed opposite the rotor pole
locations P and, more specifically, at the radially inner ends 48
of the pole segments 40. It is permissible according to some
aspects of the present invention, however, for the rotor pole
locations to instead be radially inward of the center points (e.g.,
as in an outer rotor motor) or to be otherwise positioned relative
thereto and/or relative to the respective pole segment bodies in a
broad sense.
[0089] The above-described design is highly advantageous, achieving
significant flux concentration without increasing the motor
envelope (e.g., via a greater stack height), requiring the use of
upgraded materials (e.g., neodymium magnets, aluminum stator
wiring, etc.), and/or utilizing added active materials (e.g.,
copper, steel, etc.). For instance, in comparison to an otherwise
similarly configured and sized conventional spoked rotor motor, and
in addition to the previously described performance
characteristics, the motor 10 of the illustrated embodiment enables
improved stator tooth flux density (e.g., at least a ten percent
(10%) increase and most preferably a fifteen percent (15%) increase
or greater). The motor 10 also enables significantly increased
maximum rotor pole face flux density (e.g., at least a twenty
percent (20%) increase compared to a comparable conventional spoked
rotor motor, more preferably at least a thirty percent (30%)
increase, and most preferably a forty percent (40%) increase or
greater).
[0090] The motor 10 also maintains equivalent performance in both
rotational directions despite being a non-symmetrical design.
[0091] Still further, it is noted that the motor 10 achieves an
increase of at least ten percent (10%) and most preferably fifteen
percent (15%) or more in back electromotive force (BEMF) compared
to an equivalent stator paired with a conventional spoked
rotor.
[0092] The preferred forms of the invention described above are to
be used as illustration only and should not be utilized in a
limiting sense in interpreting the scope of the present invention.
Obvious modifications to the exemplary embodiments, as hereinabove
set forth, could be readily made by those skilled in the art
without departing from the spirit of the present invention.
[0093] Although the above description presents features of
preferred embodiments of the present invention, other preferred
embodiments may also be created in keeping with the principles of
the invention. Furthermore, as noted previously, these other
preferred embodiments may in some instances be realized through a
combination of features compatible for use together despite having
been presented independently as part of separate embodiments in the
above description.
[0094] The inventor hereby states his intent to rely on the
Doctrine of Equivalents to determine and access the reasonably fair
scope of the present invention as pertains to any apparatus not
materially departing from but outside the literal scope of the
invention set forth in the following claims.
* * * * *