Note: Descriptions are shown in the official language in which they were submitted.
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STATOR AND ROTOR DESIGN FOR PERIODIC TORQUE REQUIREMENTS
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. 119(e) of U.S.
Provisional Application Serial No. 62/754,051, entitled PLANAR STATOR AND
ROTOR DESIGN FOR PERIODIC TORQUE REQUIREMENTS, filed November 1,
2018. This application is also a continuation-in-part and claims the benefit
under 35
U.S.C. 120 to U.S. Patent Application Serial No. 16/378,294, entitled
STRUCTURES
AND METHODS FOR CONTROLLING LOSSES IN PRINTED CIRCUIT BOARDS,
filed April 8, 2019, which is a continuation of and claims the benefit under
35 U.S.C.
120 to U.S. Patent Application Ser. No. 16/165,745, entitled STRUCTURES AND
METHODS FOR CONTROLLING LOSSES IN PRINTED CIRCUIT BOARDS, filed
October 19, 2018, and now U.S. Patent No. 10,256,690, which is a continuation
of and
claims the benefit under 35 U.S.C. 120 to U.S. Patent Application Serial No.
15/852,972, entitled PLANAR COMPOSITE STRUCTURES AND ASSEMBLIES FOR
AXIAL FLUX MOTORS AND GENERATORS, filed December 22, 2017, and now
U.S. Patent No. 10,170,953, which claims the benefit under 35 U.S.C. 119(e)
of U.S.
Provisional Application Serial No. 62/530,552, entitled STRUCTURES AND
METHODS OF STACKING SUBASSEMBLIES IN PLANAR COMPOSITE
STATORS TO OBTAIN HIGHER WORKING VOLTAGES, filed July 10, 2017, and
which is also a continuation-in-part of and claims the benefit under 35 U.S.C.
120 to
U.S. Patent Application Serial No. 15/611,359, entitled STRUCTURES AND
METHODS FOR CONTROLLING LOSSES IN PRINTED CIRCUIT BOARDS, filed
June 1, 2017, and now U.S. Patent No. 9,859,763, which (A) is a continuation-
in-part of
and claims the benefit under 35 U.S.C. 120 to U.S. Patent Application Serial
No.
15/283,088, entitled STRUCTURES AND METHODS FOR CONTROLLING LOSSES
IN PRINTED CIRCUIT BOARDS, filed September 30, 2016, and now U.S. Patent No.
9,800,109, which is a continuation-in-part and claims the benefit under 35
U.S.C. 120
to U.S. Patent Application Serial No. 15/199,527, entitled STRUCTURES AND
METHODS FOR THERMAL MANAGEMENT IN PRINTED CIRCUIT BOARD
STATORS, filed June 30, 2016, and now U.S. Patent No. 9,673,684, and which
also
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claims the benefit under 35 U.S.C. 119(e) to each of (1) U.S. Provisional
Patent
Application Serial No. 62/236,407, entitled STRUCTURES TO REDUCE LOSSES IN
PRINTED CIRCUIT BOARD WINDINGS, filed October 2, 2015, and (2) U.S.
Provisional Patent Application Serial No. 62/236,422, entitled STRUCTURES FOR
THERMAL MANAGEMENT IN PRINTED CIRCUIT BOARD STATORS, filed
October 2, 2015, and (B) is a continuation-in-part of and claims the benefit
under 35
U.S.C. 120 to U.S. Patent Application Serial No. 15/208,452, entitled
APPARATUS
AND METHOD FOR FORMING A MAGNET ASSEMBLY, filed July 12, 2016, and
now U.S. Patent No. 9,673,688, which claims the benefit under 35 U.S.C.
119(e) to
U.S. Provisional Patent Application Serial No. 62/275,653, entitled ALIGNMNET
OF
MAGNETIC COMPONENTS IN AXIAL FLUX MACHINES WITH GENERALLY
PLANAR WINDINGS, filed January 6, 2016. This application is also a
continuation-in-
part and claims the benefit under 35 U.S.C. 120 to U.S. Patent Application
Serial No.
15/983,985, entitled PRE-WARPED ROTORS FOR CONTROL OF MAGNET-
STATOR GAP IN AXIAL FLUX MACHINES, filed May 18, 2018, and published as
U.S. Patent Application Pub. No. US 2018/0351441, which claims the benefit
under 35
U.S.C. 119(e) to each of (1) U.S. Provisional Patent Application Serial No.
62/515,251,
entitled PRE-WARPED ROTORS FOR CONTROL OF MAGNET-STATOR GAP IN
AXIAL FLUX MACHINES, filed June 5, 2017, and (2) U.S. Provisional Patent
Application Serial No. 62/515,256, entitled AIR CIRCULATION IN AXIAL FLUX
MACHINES, filed June 5, 2017. The contents of each of the foregoing
applications,
publications, and patents are hereby incorporated herein, by reference, in
their entireties,
for all purposes.
BACKGROUND
[0002] Permanent magnet axial flux motors and generators described by
several
patents, including U.S. Patent No. 7,109,625 ("the '625 patent"), feature a
generally
planar printed circuit board stator (PCS) interposed between magnets featuring
alternating north-south poles. These printed circuit board stators, when
supported to the
fixed frame from the outside edge of the stator, have a hole through which the
shaft
linking the rotors passes. An alternate embodiment is to interchange roles of
the inner
and outer radius, resulting in a situation where the inner radius of the
stator is supported,
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and the rotor envelopes the stator. The shaft is effectively moved to the
outer radius in
this configuration, sometimes called an "out-runner."
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Objects, aspects, features, and advantages of embodiments disclosed
herein
will become more fully apparent from the following detailed description, the
appended
claims, and the accompanying figures in which like reference numerals identify
similar or
identical elements. Reference numerals that are introduced in the
specification in
association with a figure may be repeated in one or more subsequent figures
without
additional description in the specification in order to provide context for
other features,
and not every element may be labeled in every figure. The drawings are not
necessarily
to scale, emphasis instead being placed upon illustrating embodiments,
principles and
concepts. The drawings are not intended to limit the scope of the claims
included
herewith.
[0004] FIG. 1A shows an example of an axial flux motor or generator with
which
some aspects of this disclosure may be employed;
[0005] FIG. 1B is an expanded view showing the components of the axial flux
motor
or generator shown in FIG. 1A and a means for assembling such components;
[0006] FIG. 2 is a conceptual diagram showing three printed circuit board
stators
having equal areas but different configurations;
[0007] FIG. 3 is a diagram showing how multiple stator segments may be
arranged
for manufacture on a printed circuit board panel of standard dimensions;
[0008] FIG. 4 is a diagram showing how a subset of the stator segments
shown in
FIG. 3 would appear if they were arranged edge to edge on the circuit board
panel shown
in FIG. 3;
[0009] FIG. 5 shows an example arrangement of a stator segment with respect
to
magnets on a rotor in accordance with some aspects of the present disclosure;
[0010] FIG. 6 shows the same arrangement as FIG. 5, but where the rotor is
shown at
an angle where the stator segment overlaps with a magnet section that provides
peak
torque;
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[0011] FIG. 7 shows an example arrangement of multiple stator segments with
respect to magnets on a rotor in accordance with some aspects of the present
disclosure;
and
[0012] FIG. 8 illustrates a cross section of an example embodiment of an
axial flux
motor that is configured and integrated with a washing machine load in
accordance with
some aspects of the present disclosure.
SUMMARY
[0013] This Summary is provided to introduce a selection of concepts in a
simplified
form that are further described below in the Detailed Description. This
Summary is not
intended to identify key features or essential features, nor is it intended to
limit the scope
of the claims included herewith.
In some of the disclosed embodiments, a motor or generator comprises a
rotor and a stator, wherein the rotor has an axis of rotation and is
configured to
generate first magnetic flux parallel to the axis of rotation, the stator is
configured to
generate second magnetic flux parallel to the axis of rotation, and at least
one of the
rotor or the stator is configured to generate a magnetic flux profile that is
non-
uniformly distributed about the axis of rotation.
In other disclosed embodiments, a method involves arranging one or more
magnetic flux producing windings of a stator non-uniformly about an axis of
rotation of a rotor of an axial flux motor or generator.
In yet other disclosed embodiments, a rotor for use in a motor or generator
comprises a support structure and one or more magnet segments that are
supported by the support structure and that generate first magnetic flux
parallel to
an axis of rotation about which the support structure rotates when assembled
with
a stator that generates second magnetic flux parallel to the axis of rotation,
wherein
the one or more magnet segments are configured and arranged to generate a
magnetic flux profile that is non-uniformly distributed about the axis of
rotation.
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DETAILED DESCRIPTION
[0014] In existing axial flux motors or generators, such as those disclosed
in U.S.
Patent Nos. 7,109,625; 9,673,688; 9,800,109; 9,673,684; and 10,170,953, as
well as U.S.
Patent Application Publication No. 2018-0351441 Al ("the '441 Publication"),
the entire
contents of each of which are incorporated herein by reference, the magnetic
flux
generating components of the stator, whether comprised of a single continuous
printed
circuit board or multiple printed circuit board segments, are arranged such
that, at any
given time when the windings of the stator are energized with current, the
locations of
peak magnetic flux generated by the stator are distributed uniformly with
respect to the
angle about the rotor's axis of rotation. Similarly, in such machines, the
magnetic flux
generating components of the rotor, whether comprised of a ring magnet or
individual
magnets disposed in pockets, are also arranged such that, at any given point
in time, the
locations of peak magnetic flux generated by the rotor are likewise
distributed uniformly
with respect to angle about the rotor's axis of rotation. Accordingly, in all
such
machines, at any given time the machine is in operation, the locations of peak
magnetic
flux generated by each of the rotor and the stator are uniformly distributed
as a function
of angle about the machine's axis of rotation. In other words, for each of the
rotor and
the stator in such machines, the same angle separates each location of peak
magnetic flux
from the next adjacent location of peak magnetic flux about the axis of
rotation so that
that the magnetic flux profile of each of the rotor and the stator are
uniformly distributed
about the axis of rotation.
[0015] Disclosed herein are alternate designs, with advantages in cost
relative to
conventional designs for certain loads and machine configurations, in which
the stator
and/or the rotor may instead be configured to have a magnetic flux profile
that is non-
uniformly distributed about the rotor's axis of rotation. In some embodiments,
for
example, a stator can be configured so that it describes a fraction an arc
surrounding the
principle axis of the machine. If such a stator segment can be located, due to
the
integration of the machine with the attached load, at a large radius compared
to a stator of
equal area distributed uniformly about the same axis, the torque produced may
be
proportional to the increase in radius at which the stator segment is
disposed, assuming
equivalent flux in the gap and current density limits in the stator. However,
the cost of
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maintaining equivalent flux in the gap for an "off center" stator segment is
an increase in
magnet volume inversely proportional to the angle subtended by that segment.
This is
not a desirable tradeoff in most cases. However, in an application where peak
torque is
desired at a particular angle or range of shaft angles, the magnet material
may be
distributed non-uniformly with respect to the rotor, so that the stator is
exposed to peak
magnetic flux density at the shaft angles where peak torque is desired. For
generator
applications where the source has periodic torque production capacity, a
machine
designed according to this principle may offer similar advantages.
[0016] The
design of the stator and magnet system to produce peak torque at specific
angles is not limited to one stator segment and/or one concentration of
magnetic material
on the rotor, although this is the simplest embodiment. Embodiments including
one or
more non-uniformly distributed stator segments and/or one or more non-
uniformly
distributed magnet segments may provide useful combinations of torque
capability as a
function of angle. It should be appreciated that the same or similar torque
capability as a
function of angle can be achieved using different combinations of one or more
non-
uniformly distributed stator segments and one or more non-uniformly
distributed magnet
segments. For example, the same or similar torque capability as a function of
angle can
be achieved by interchanging the distribution of stator segments versus rotor
magnet
locations. This may allow designers to effect tradeoffs in the cost of magnet
material and
stator area while achieving the same or similar torque capability as a
function of angle.
[0017] The
design of a machine to produce peak torque at a particular angle does not
preclude continuous rotation. When continuous rotation is desired, a machine
designed
according to the principles disclosed here can supply torque in a series of
pulses (at the
peak torque angles) that are smoothed by the moment of inertia of the attached
load to
provide approximately constant speed. An advantage of this design is that the
losses in
the stator due to eddy currents may be zero when the stator does not overlap
the magnets.
Another possibility for continuous rotation is to distribute magnets so that
the stator
segment always sees magnet flux, but at smaller magnitude than the "peak
torque"
angles.
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[0018] Some embodiments described herein may be particularly advantageous
for
applications where the machine radius can be significantly increased, relative
to a
conventional design. In these applications, a planar circuit board stator (PC
S) segment
disposed at a larger radius than a uniform planar circuit board stator may
achieve higher
peak torque per unit area of stator. Further, in comparison to a thin annular
stator at a
large radius, stator segments can be "tiled" or arranged on a printed circuit
board "panel"
of standard size. This may allow a more efficient utilization of printed
circuit board
material and reduce the cost of the associated machine.
[0019] Examples of application areas include reciprocating piston or
diaphragm type
pumps, which may have a periodic torque requirement. Also, for purposes of
balance,
these machines frequently include an off-center mass that can potentially be
replaced by
an asymmetrically designed rotor. Similarly, generators coupled to single
piston engines
may benefit from co-design of balancing masses with the magnetic materials in
a stator-
segment type generator. Other potential applications include washing machines
or other
applications where the motor or generator moves through a limited angle, and
periodic or
"reversing" type loads.
[0020] A basic observation of the novel concepts disclosed herein can be
reduced to a
"scaling" argument for otherwise equivalent stators or stator segments,
independent of
the internal organization and connection of the stator, based on fundamental
considerations of the design. In a conventional annular PCS, conforming to the
description in the '625 patent, the torque can be expressed as follows
T = fr2 127 r dr dO r
arl a 0 f dens (r) =
[0021] The components of this expression include integration from a first
radius rl to
a second radius r2, comprising the active area of the stator. The integral
covers a
complete annulus by the limits of integration on 0. The term r dr dO is a
differential area
element, and rfdens is the torque density magnitude corresponding to the
equation T =
rxF . The force density is 0-directed due to the axial flux and radial current
density, i.e.,
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fdens = J(r)XB
[0022] Here, the force density is the product of the current density
supported by the
stator, and magnetic flux density resulting from the rotor magnet circuit and
stator
reaction at that current density. For illustration, B is assumed to be radial.
In stators
designed according to the '625 patent, diverging radial traces effectively
introduce a 1/r
decrease in current density from the inner radius rl . A model capturing this
effect is
J(r) = Jo r/r
[0023] where Jo is the maximum supported current density based on the
interference
of features at a given copper weight, via size and clearance requirements at
the inner
radius. With this model,
Tpeak = JoBAri
the current density supported by the stator depends on the number of inner
vias that can
be disposed at rl, which is dependent on feature sizes and associated
clearances, as well
as the circumference at rl, and whether that circumference accommodates
features at a
spacing that approaches the fabrication limits. Thus, it is not strictly
correct to regard Jo
as constant. For rl = 0, for example, no vias can be accommodated, and Jo = 0.
However, for motors of practical interest, Jo will approach a value dependent
primarily
on thermal considerations and clearance requirements. Taking Jo as a constant
for
purposes of comparison between otherwise equivalent stators tends to make a
conventional stator located around the central shaft, with a smaller rl,
appear more
competitive than a stator segment at a larger radius.
[0024] The area A of the stator or stator segment with angular extent 6 is
6
A = ¨2ff7r (7-1 ¨r)
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[0025] For a stator of conventional design, 6 = 27r. For a stator segment,
6 ideally
corresponds to a whole number of pole pairs. For purposes of comparison
between stator
segments and conventional designs on the basis of cost, it is reasonable to
compare equal-
area stators and magnet assemblies. Multiple solutions of 6 and r2 exist for
any rias the
inner radius riis increased, and considered here as the independent variable.
In
particular, when considering 6, the pole spacing over a segment need not also
conform to
the usual constraint of disposing poles uniformly over 27r rad, as in a
conventional stator.
This suggests considerable design flexibility for the segment that is not
enjoyed by the
conventional stator, as well as the ability to achieve equal area A. Examples
of
advantages of displacing stator area to larger 71 with compact 6, include: (1)
stator
segments with larger r1 offer higher peak torque per unit area, (2) when
stator segments
and magnetic material overlap fully at specific rotor angles (or angle
ranges), peak torque
is available, (3) there is no eddy current loss in the machine when the
magnetic material
and stator do not overlap, (4) stator segments can be obtained where 71, r2,
and 6 are such
that the segments can "nest" on a printed circuit board panel, minimizing
wasted material
and cost, and (5) peak torque per unit area (or per unit cost) increases with
the radius of
stator segment.
[0026] Given a design procedure for a prototype conventional stator with 6
= 27r
meeting a specific torque Tp, designs for stator segments subtending a subset
of the poles
in the prototype design spanning an angle 6 can be inferred to produce a peak
torque of
over the range of angles where the segment fully overlaps the magnetic
material.
Thus, a practical design procedure for segments is to design conventional
stator
prototypes, where the torque requirement is increased by the ratio of the
poles in the
conventional stator relative to the poles intended to be preserved in the
segment. This
procedure, while expedient, does not exploit the freedom in the segmented
design,
because the pole spacing is simultaneously constrained to the angular extent
of the
segment, and to the 27r extent of the conventional design. The segment angle 6
does not
need to be a divisor of 27r and can thus be optimized to meet the design
constraints.
[0027] Combinations of stator segments and magnetic material, concentrated
at
particular angles on the fixed frame and rotor, can achieve various torque
capabilities as a
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function of angle. One or more areas on the rotor may carry magnetic materials
comprising different flux densities, one or more pole pairs, and may be
distributed at
various angles. There may be one or more stator segments, in the fixed frame,
positioned at various angles.
[0028] Examples of motor and/or generator designs in which non-uniformly
distributed stators and/or rotors, such as those disclosed herein, may be
employed are
described in U.S. Patent Nos. 7,109,625; 9,673,688; 9,800,109; 9,673,684; and
10,170,953, as well as U.S. Patent Application Publication No. 2018-0351441 Al
("the
'441 Publication"), which are incorporated by reference above. Illustrative
examples of
such machines will initially be described in connection with FIGS. lA and 1B.
Examples
of stators and rotors having magnetic flux profiles that are non-uniformly
distributed
about a rotor's axis of rotation, and which may be employed in such machines,
will then
be described in connection with FIGS. 2-8.
[0029] FIG. lA shows an example of a system 100 employing a planar
composite
stator 110 in an assembly with rotor components 104a and 104b, shaft 108,
wires 114,
and controller 112. An expanded view showing these components and a means for
their
assembly is shown in FIG. 1B. The pattern of magnetic poles in the permanently
magnetized portions 106a, 106b of the rotor assembly is also evident in the
expanded
view of FIG. 1B. FIG.1A is an example of an embodiment where the electrical
connections 114 are taken at the outer radius of the PCS 110, and the stator
is mounted to
a frame or case at the outer periphery. Another useful configuration, the "out-
runner"
configuration, involves mounting the stator at the inner radius, making
electrical
connections 114 at the inner radius, and replacing the shaft 108 with an
annular ring
separating the rotor halves. It is also possible to configure the system with
just one
magnet, either 106a or 106b, or to interpose multiple stators between
successive magnet
assemblies. Wires 114 may also convey information about the position of the
rotor
based on the readings of Hall-effect or similar sensors mounted on the stator.
Not shown,
but similar in purpose, an encoder attached to the shaft 108 may provide
position
information to the controller 112.
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[0030] The system 100 in FIGS. 1 A and 1B can function either as a motor,
or a
generator, depending on the operation of the controller 112 and components
connected to
the shaft 108. As a motor system, the controller 112 operates switches so that
the
currents in the stator 110 create a torque about the shaft, due to the
magnetic flux in the
gap originating from the magnets 104a, 104b connected to the shaft 108.
Depending on
the design of the controller 112, the magnetic flux in the gap and/or the
position of the
rotor may be measured or estimated to operate the switches to achieve torque
output at
the shaft 108. As a generator system, a source of mechanical rotational power
connected
to the shaft 108 creates voltage waveforms at the terminals 112 of the stator.
These
voltages can either be directly applied to a load, or they can be rectified
with a three-
phase (or poly phase) rectifier within the controller 112. The rectifier
implementation
112 can be "self-commutated" using diodes in generator mode, or can be
constructed
using the controlled switches of the motor controller, but operated such that
the shaft
torque opposes the torque provided by the mechanical source, and mechanical
energy is
converted to electrical energy. Thus, an identical configuration in Figure 1A
may
function as both a generator and motor, depending on how the controller 112 is
operated.
Additionally, the controller 112 may include filter components that mitigate
switching
effects, reduce EMI/RFI from the wires 114, reduce losses, and provide
additional
flexibility in the power supplied to or delivered from the controller.
[0031] FIG. 2 shows geometries of three stators 202, 204, 206 with
different angular
and radial extent, but of equal area. Stators 204 and 206 differ by the inner
radius. Stator
206 shows relative dimensions typical of stators as described by the '625
patent. Stator
204 is a thin annular design. In stator 204, the inner radius is increased,
but a stator with
these relative dimensions does not make efficient use of a "panel" of printed
circuit board
material. Stator 202 shows a stator segment 208, as proposed herein, of equal
area and
equivalent radius to stator 204. All else equal, at the larger radii, stators
202 and 204
would produce a higher peak torque than stator 206 as the radius increases the
torque
arm.
[0032] FIG. 3 shows the "panelization," or packing, of stator segments like
the
segment 208 shown in FIG. 1, on a standard sized printed circuit board panel
302. The
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effective utilization of the panel 302 is high with the illustrated
arrangement. Cost of the
stator segments 208 is inversely proportional to the utilization of the panel
302.
[0033] FIG. 4 shows an ineffective arrangement of segments 208 of the same
size as
in FIG. 3 on the panel 302. While this arrangement is not practical, it shows
the effective
panel utilization that would be achieved for a conventional stator with the
same inner and
outer radii as achieved by the segments 208.
[0034] FIG. 5 shows an example arrangement of a stator segment 208 with
respect to
magnets 502 on a rotor 504. In the illustrated example, a dense angular extent
506 of the
magnets 502, also referred to herein as a "dense magnet area," on the rotor
504 is
provided to achieve peak torque at the angle of overlap with the stator
segment 208. Less
dense angular extents 508 of the magnets 502, also referred to herein as "less
dense
magnet areas," are arranged to provide a lower torque capability independent
of angle.
Although not illustrated, it should be appreciated that, in some embodiments,
non-
magnetic elements may be added in the vicinity or the less dense magnet areas
508 to
balance the weight of the rotor 504 as a whole. Further, it should be
appreciated that, in
some embodiments, an additional rotor portion (not shown) having a
corresponding,
though opposite polarity, magnet arrangement may be positioned above the
illustrated
portion of the rotor 504 such that the stator segment 208 may be positioned
within a gap
between the two rotor portions, with lines of magnetic flux extending in a
direction
parallel to the axis of rotation of the rotor between pairs of opposing,
opposite polarity
magnets. In addition, although not illustrated in FIG. 5, it should be
appreciated that the
stator segment 208 may include conductive traces and/or vias, e.g., disposed
on one or
more dielectric layers, that are configured to form windings that, when
energized with
current, generate magnetic flux in a direction parallel to the axis of
rotation of the rotor.
Such windings may be configured to receive one or more phases of current from
a power
supply (not shown in FIG. 5), and may be arranged in one or more spirals, one
or more
serpentine patterns, or otherwise, so as to generate such magnetic flux.
[0035] As shown in FIG. 5, in some embodiments, the stator segment 208 may
be
held in place via an arcuate attachment member 510 to which the stator segment
208 may
be attached using one or more fasteners 512, and the one or more windings (not
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illustrated) of the stator segment 208 may be connected to terminals 514
associated with
the attachment member 510, which terminals may be connected to a controller
(not
shown in FIG. 5), such as the controller 112 discussed above in connection
with FIGS.
1A and 1B, so as to supply energizing current(s) to the winding(s).
[0036] FIG. 6 shows the same configuration as FIG. 5, but with the rotor
504
positioned at an angle where the stator segment 208 overlaps with the dense
magnet
section 506 that provides peak torque.
[0037] FIG. 7 shows an alternate arrangement to FIGS. 4 and 5. As shown,
in
addition to or in lieu of employing less dense magnet regions 508 (not shown
in FIG. 7)
together with a dense angular extent 506, stator segments 502a-g may be
arranged so that
they fully or nearly describe an annular stator with constant available torque
at any angle.
In some embodiments, a subset of the stator segments 502a-g may be made
smaller, may
be arranged with a coarser pitch, may contain fewer winding "turns," and/or
may be
supplied with less power than one or more other stator segments 502, so that a
machine
with concentrated magnets can offer angle-specific peak torque, while still
providing
torque capability at any angle. For example, in some embodiments, the stator
segment
502a may be configured, arranged and/or energized differently than the other
stator
segments 502b-g for such a purpose.
[0038] No matter the particular arrangement of magnet(s) 502 and stator
segment(s)
208 that is employed, in at least some circumstances, care may be taken to
ensure that at
least one stator segment 208 at least partially overlaps at least one magnet
502 at each
position during a revolution of the rotor 504, so that the rotor 504 does not
become
"stuck" at a position where no magnetic flux from a stator segments 208
interacts with
magnetic flux from a magnet 502.
[0039] In each of the above-described example configurations, the stator
segment(s)
208 and/or the magnet(s) 502 of the rotor 504 are configured to have a
magnetic flux
profile that is non-uniformly distributed about the machine's principle axis
of rotation. In
particular, the stator segment(s) 208 are arranged such that, at any given
point in time
when the windings of the stator 504 are energized with current, the locations
of peak
magnetic flux generated by the stator are non-uniformly distributed with
respect to angle
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about the rotor's axis of rotation. Similarly, in such machines, the magnets
502 of a rotor
504 are also arranged such that, at any given point in time, the locations of
peak magnetic
flux generated by the rotor are likewise non-uniformly distributed with
respect to angle
about the rotor's axis of rotation. Accordingly, for each of the rotor and the
stator in such
machines, different angles separate at least some locations of peak magnetic
flux from
adjacent locations of peak magnetic flux about the axis of rotation so that
that magnetic
flux profile generated by such component is non-uniformly distributed about
the axis of
rotation.
[0040] FIG. 8 illustrates a cross section of an example embodiment of an
axial flux
motor 802 that is configured with components like those shown in FIGS. 5 and 6
and that
is integrated with a washing machine load 804 in accordance with some aspects
of the
present disclosure. As shown, a stator segment 208 of the motor 802 may be
secured to a
housing 806 containing a washing machine tub 808 via an attachment member 510
and
one or more fasteners 512, and the washing machine tub 808 may be rotatably
couple to
the housing 806 via bearing elements 810. A rotor 504 of the motor 802 may
directly
drive the washing machine tub 808 via a shaft 812 that may extend from and/or
be
fixedly attached to the washing machine tub 808. With the illustrated
configuration,
continuous rotation at relatively high speed and low torque in "spin" mode may
be
achieved using the stator segment 208 and a collection of magnets 502 arranged
into a
dense magnet region 506 and one or more less dense magnet regions 508, as
described
above in connection with FIGS. 5 and 6. During such a spin mode, due to the
non-
uniform distribution of the magnetic flux profiles of the rotor and the stator
about the
rotor's axis of rotation, as the rotor 504 rotates though a range of angles
with respect to
the stator segment 208 at a substantially constant speed, the periodicity of
the torque
produced due to interaction between the magnetic flux generated by the rotor
and the
stator is irregular. The reversing action needed for "wash" mode may be a
relatively low
speed, high-torque mode of operation where torque can be supplied at specific
angles. In
this case, the interaction of the stator segment 208 with the dense magnet
region 506 may
provide the peak torque requirement.
EXAMPLES IMPLEMENTATIONS OF APPARATUSES AND METHODS IN
ACCORDANCE WITH THE PRESENT DISCLOSURE
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[0041] The following paragraphs (Al) through (A14) describe examples of
apparatuses that may be implemented in accordance with the present disclosure.
[0042] (Al) A motor or generator may comprise a rotor having an axis of
rotation
and configured to generate first magnetic flux parallel to the axis of
rotation, and a stator
configured to generate second magnetic flux parallel to the axis of rotation,
wherein at
least one of the rotor or the stator is configured to generate a magnetic flux
profile that is
non-uniformly distributed about the axis of rotation.
[0043] (A2) A motor or generator may be configured as described in
paragraph (Al),
and the rotor may be further configured to generate a first magnetic flux
profile that is
non-uniformly distributed about the axis of rotation.
[0044] (A3) A motor or generator may be configured as described in
paragraph (A2),
and the rotor may further comprise one or more magnet segments non-uniformly
distributed about the axis of rotation.
[0045] (A4) A motor or generator may be configured as described in
paragraph (A3),
and each of the one or more magnet segments may further have a respective
surface
location at which the first magnetic flux has a maximum density, and the
respective
surface locations may be non-uniformly distributed about the axis of rotation.
[0046] (A5) A motor or generator may be configured as described in any of
paragraphs (A2) through (A4), and the rotor may be further configured such
that, as the
rotor rotates though a range of angles with respect to the stator at a
substantially constant
speed, a periodicity of torque produced due to interaction of the first
magnetic flux and
the second magnetic flux is irregular.
[0047] (A6) A motor or generator may be configured as described in any of
paragraphs (A2) through (A5), and the stator may be further configured to
generate a
second magnetic flux profile that is non-uniformly distributed about the axis
of rotation.
[0048] (A7) A motor or generator may be configured as described in
paragraph (Al),
and the stator may be further configured to generate a magnetic flux profile
that is non-
uniformly distributed about the axis of rotation.
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[0049] (A8) A motor or generator may be configured as described in any of
paragraphs (A2) through (A7), and the stator may further comprise one or more
printed
circuit board segments non-uniformly distributed about the axis of rotation.
[0050] (A9) A motor or generator may be configured as described in any of
paragraphs (A2) through (A8), and the stator may further comprises conductive
traces
arranged on at least one dielectric layer to generate the second magnetic flux
when
energized with current.
[0051] (A10) A motor or generator may be configured as described in any of
paragraphs (A2) through (A9), and the stator may be further configured such
that, at any
given time when the conductive traces are energized with current, one or more
locations
of maximum density of the second magnetic flux are non-uniformly distributed
about the
axis of rotation.
[0052] (A11) A motor or generator may be configured as described in
paragraph (A9)
or paragraph (A10), the conductive traces are arranged on the at least one
dielectric layer
and coupled to a power source to generate three phases of the second magnetic
flux
corresponding to three phases of current output by the power source.
[0053] (Al2) A motor or generator may be configured as described in any of
paragraphs (Al) through (A11), and the stator may be further configured such
that, as the
rotor rotates though a range of angles with respect to the stator at a
constant speed, a
periodicity of torque produced due to interaction of the first magnetic flux
and the second
magnetic flux is irregular.
[0054] (A13) A rotor for use in a motor or generator may comprise a support
structure, and one or more magnet segments that are supported by the support
structure
and that generate first magnetic flux parallel to an axis of rotation about
which the
support structure rotates when assembled with a stator that generates second
magnetic
flux parallel to the axis of rotation, wherein the one or more magnet segments
are
configured and arranged to generate a magnetic flux profile that is non-
uniformly
distributed about the axis of rotation.
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[0055] (A14) A rotor may be configured as described in paragraph A13, and
the one
or more magnet segments may further include at least a first magnet segment
and a
second magnet segment spaced apart from the first magnet segment, and the
first magnet
segment may include a larger number of adjacent magnets than the second magnet
segment.
[0056] The following paragraphs (M1) through (M5) describe examples of
methods
that may be implemented in accordance with the present disclosure.
[0057] (M1) A method may comprise arranging one or more magnetic flux
producing
windings of a stator non-uniformly about an axis of rotation of a rotor of an
axial flux
motor or generator.
[0058] (M2) A method may be performed as described in paragraph (M1),
wherein
arranging the one or more magnetic flux producing windings further comprises
arranging
one or more printed circuit board segments including the windings non-
uniformly about
the axis of rotation.
[0059] (M3) A method may be performed as described in paragraph (M1) or
paragraph (M2), wherein arranging the one or more printed circuit board
segments may
further comprise arranging the one or more printed circuit board segments such
that, at
any given time when the windings are energized with current, one or more
locations of
maximum density of the second magnetic flux are non-uniformly distributed
about the
axis of rotation.
[0060] (M4) A method may be performed as described in any of paragraphs
(M1)
through (M3), wherein the rotor may comprise magnets arranged non-uniformly
about
the axis of rotation.
[0061] (M5) A method may be performed as described in any of paragraphs
(M1)
through (M4), wherein arranging the one or more magnetic flux producing
windings may
further comprise arranging the one or more magnetic flux producing windings
such that,
as the rotor rotates though a range of angles with respect to the stator at a
constant speed,
a periodicity of torque produced due to interaction of magnetic flux generated
by the
rotor and the stator is irregular.
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[0062] Having thus described several aspects of at least one embodiment, it
is to be
appreciated that various alterations, modifications, and improvements will
readily occur
to those skilled in the art. Such alterations, modifications, and improvements
are
intended to be part of this disclosure, and are intended to be within the
spirit and scope of
the disclosure. Accordingly, the foregoing description and drawings are by way
of
example only.
[0063] Various aspects of the present disclosure may be used alone, in
combination,
or in a variety of arrangements not specifically discussed in the embodiments
described
in the foregoing and is therefore not limited in this application to the
details and
arrangement of components set forth in the foregoing description or
illustrated in the
drawings. For example, aspects described in one embodiment may be combined in
any
manner with aspects described in other embodiments.
[0064] Also, the disclosed aspects may be embodied as a method, of which an
example has been provided. The acts performed as part of the method may be
ordered in
any suitable way. Accordingly, embodiments may be constructed in which acts
are
performed in an order different than illustrated, which may include performing
some acts
simultaneously, even though shown as sequential acts in illustrative
embodiments.
[0065] Use of ordinal terms such as "first," "second," "third," etc., in
the claims to
modify a claim element does not by itself connote any priority, precedence or
order of
one claim element over another or the temporal order in which acts of a method
are
performed, but are used merely as labels to distinguish one claimed element
having a
certain name from another element having a same name (but for use of the
ordinal term)
to distinguish the claim elements.
[0066] Also, the phraseology and terminology used herein is used for the
purpose of
description and should not be regarded as limiting. The use of "including,"
"comprising," or "having," "containing," "involving," and variations thereof
herein, is
meant to encompass the items listed thereafter and equivalents thereof as well
as
additional items.
What is claimed is:
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