Note: Descriptions are shown in the official language in which they were submitted.
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WAVE WINDING ARMATURE
Cross-Reference to Related Application
[0001] This application claims priority to US provisional application Serial
No. 60/744,096, filed on March 31, 2006, entitled "Armature for an
Electromotive
Device," the contents of which are incorporated herein by reference.
Field
[0002] The present disclosure relates to electric machines and, more
particularly, to
DC and brushless electric motors.
Background
[0003] DC and brushless motors constructed with commutator and coil winding
structures typically include a plurality of interconnection components between
the coil
windings. This is because of how the coil windings must be arranged in order
for the
motor to operate. Electronic commutation for a DC or brushless motor requires
that
each magnet in the moving rotor be pushed and pulled around a centerline. To
accomplish this, coil sets of conductors are phase-spaced around the diameter
of the
coil assembly and connected in series by electrical interconnections.
Specifically, a
plurality of lap-wound coil conductors is arranged in series such that one
coil set
conductor is oriented adjacent to each of the motor's magnets. A coil assembly
for a
brush motor is often called an armature. The coil assembly for a brushless
motor is
often called a stator. Since the coil set conductors are arranged around the
diameter of
the armature, the interconnections are required between them in order to place
them in
series. These interconnections represent separate parts in the construction of
a motor,
which increases the complexity of the motor as well as the complexity, time
and cost of
manufacturing.
[0004] Accordingly, there is a need in the art of DC and brushless motors for
a coil
and commutator arrangement without the electrical interconnections used in the
past. If
these electrical interconnections between phase-spaced coil conductors could
be
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eliminated, it could reduce the complexity of the motor armature, improve the
reliability
of the armature (and thus the motor), and reduce the cost of manufacture.
SUMMARY
[0005] In one aspect of the teachings disclosed herein, an inductive coil for
an
electromotive device includes a pair of concentric inner and outer sheet metal
winding
portions. Each of the winding portions comprises a plurality of parallel
linear conductive
bands with each of the conductive bands of one of the winding portions being
coupled
to one of the conductive bands of the other winding portion to form a
continuous coil.
[0006] In another aspect of the teachings disclosed herein, an electromotive
device
includes an armature having a plurality of inductive coils wherein each
inductive coil
comprises a pair of concentric inner and outer sheet metal winding portions.
Each of the
winding portions comprises a plurality of parallel linear conductive bands
with each of
the conductive bands of one of the winding portions being coupled to one of
the
conductive bands of the other winding portion to form a continuous coil. Each
of the
plurality of inductive coils comprises a first end and a second end, wherein
each first
end is electrically connected to a power source and each second is
electrically
connected to every other second end.
[0007] In a further aspect of the teachings disclosed herein, an inductive
coil for an
electromotive device includes a pair of concentric inner and outer sheet metal
winding
portions. Each of the winding portions comprises a plurality of conductive
bands each
having a first end and a second end offset from the first end by a radial
distance about
the coil. Each of the conductive bands of one of the winding portions is
coupled to one
of the conductive bands of the other winding portion.
[0008] In yet a further aspect of the teachings disclosed herein, an inductive
coil for
an electromotive device includes a pair of concentric inner and outer sheet
metal
winding portions. Each of the winding portions includes a plurality of
conductive bands
each extending from a first end to a second end in a single radial direction,
with each of
the conductive bands of one of the winding portions being coupled to one of
the
conductive bands of the other winding portion.
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[0009] It is understood that other embodiments of the teachings disclosed
herein will
become readily apparent to those skilled in the art from the following
detailed
description, wherein various embodiments are shown and described by way of
illustration. As will be realized, the teachings disclosed herein may be
applied to other
and different embodiments and its several details are capable of modification
in various
other respects, all without departing from the spirit and scope of the present
teachings.
Accordingly, the drawings and detailed description are to be regarded as
illustrative in
nature and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Aspects of the teachings disclosed herein are illustrated by way of
example,
and not by way of limitation, in the accompanying drawings in which like
reference
numerals refer to similar elements wherein:
[0011] FIGS. 1 A and 1 B are graphical illustrations exhibiting a plan view of
a pair of
copper plates, precision cut for use in a brushless motor;
[0012] FIG. 2 is a graphical illustration of an elevation perspective view of
the copper
plate of FIG. 1A rolled into a hollow cylinder for use in a motor;
[0013] FIG. 3 is a graphical illustration of an elevation perspective view of
the copper
plate of FIG. 1 B rolled into a hollow cylinder for use in a motor;
[0014] FIG. 4 is a graphical illustration of an elevation perspective view of
the
cylinder of FIG. 2 being inserted into the cylinder of FIG. 3 to form a
cylindrical
conductive coil for use in a motor;
[0015] FIG. 4A is a graphical illustration of an enlargement of a portion of
FIG. 4
illustrating detail of a wound glass fiber layer;
[0016] FIG. 5 is a schematic illustration of a conductive lap winding to form
a
continuous cylindrical conductive coil for use in a motor;
[0017] FIG. 5A is a graphical illustration of a conductive wave winding to
form one
phase of a continuous cylindrical conductive coil for use in a motor;
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[0018] FIG. 5B illustrates a series of connection pads in a portion of a
conductive
wave winding;
[0019] FIG. 5C illustrates connection features in a portion of a conductive
wave
winding;
[0020] FIG. 5D illustrates additional connection features in a portion of a
conductive
wave winding;
[0021] FIG. 5E illustrates a series of lap windings forming spaced phase loops
in a
prior art conductive coil;
[0022] FIG. 6 is a plan view of a commutator;
[0023] FIG. 6A is a plan view of an alternative commutator;
[0024] FIG. 7 is an exploded perspective view of an ironless core armature
with
flywheel inserted and a commutator electrically connected to the conductive
coil;
[0025] FIG. 7A is an exploded perspective view of an ironless core armature
with
drive shaft and flywheel inserted and an alternative commutator electrically
connected
to the conductive coil;
[0026] FIG. 8 is a perspective view of an assembled ironless core armature
with
drive shaft and flywheel inserted and a commutator electrically connected to
the
conductive coil; and
[0027] FIG. 8A is a perspective view of an assembled ironless core armature
with
drive shaft and flywheel inserted and an alternative commutator electrically
connected
to the conductive coil.
DETAILED DESCRIPTION
[0028] The detailed description set forth below in connection with the
appended
drawings is intended as a description of various embodiments of the teachings
disclosed herein and is not intended to represent the only embodiments to
which the
present teachings may be applied. The detailed description includes specific
details for
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the purpose of providing a thorough understanding of the present teachings.
However,
it will be apparent to those skilled in the art that the teachings disclosed
herein may be
practiced without these specific details. In some instances, well-known
structures and
devices are shown in block diagram form in order to avoid obscuring the
concepts of the
present invention. Acronyms and other descriptive terminology may be used
merely for
convenience and clarity and are not intended to limit the scope of the
teachings
disclosed herein.
[0029] The teachings herein relate to an ironless core armature for an
electric
commutated DC or brushless motor. The armature may have a conductive coil
constructed from a thin pair of nearly mirror image, electrically conductive
and precision-
machined pieces of bare sheet metal such as sheets or plates 10 and 12 shown
in
FIGS. 1 A and 1 B, respectively. Plates 10 and 12 may comprise tempered copper
grade
110 with each plate precision cut in a pattern to produce a series of
generally parallel
and linear conductive bands, 18 and 22. Each conductive band may have a first
end
and a second end, such as ends 17 and 19 of conductive band 18, for example.
The
first and second end of each linear conductive band may define a line that is
diagonal
with respect to the edges of the metal plates 10 and 12 such that when the
metal plate
is rolled to form a tube, which will be explained in further detail below, the
first and
second ends are radially offset from one another. For example, when the metal
plate is
rolled, the first end may be offset by a radial distance of about 90 from the
second end.
Each band may be separated from the other by an elongated cutout such as
cutout 14
of plate 10 and cutout 16 of plate 12 as shown in FIGS. 1 A and 1 B. The
cutouts may be
identical and subsequently electrically insulated to prevent electrical
contact between
neighboring bands such as bands 18 and 20 of plate 12 and bands 22 and 24 of
plate
10. The width of a cutout may, for example, be about 1-1.5 times the conductor
thickness. The cutout width may be chosen to optimize the current flow and the
number
of conductive bands that can be precision machined on a copper plate.
[0030] Each copper plate may be, though is not limited to, 2 inch by 3 inch
(approximately 5 cm by 7.5 cm) and have a thickness of about 0.005 inch (0.12
mm).
Those skilled in the art will recognize that the length, width and material
thickness can
vary depending on the desired motor size. For example, an armature can be
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manufactured with plates that are 5 inches wide, 30 inches long and 1/2 mm
thick.
Other dimensions and materials may be used to manufacture conductive plates 10
and
12 provided that such materials and dimensions are consistent with the
intended
purpose of the teachings disclosed herein.
[0031] The desired plate pattern for creating a conductive coil in a wave
winding
pattern may be achieved by precision cutting the plates by chemical machining
to create
the pattern of FIGS. 1A and 1B. The pattern may include, for example, a
plurality of
conductive bands each extending in a substantially linear fashion such that
when the
plate is rolled as described below, each conductive band extends from a first
end to a
second in a single radial direction. In other words, when the plate is rolled
into a tube
shape, each conductive band extends in only one radial direction and does not
reverse
radial direction between its first and second end. The result, when the plate
is rolled into
a tube, is that the conductive bands form at least a partial spiral in one
radial direction.
The desired pattern can be machined by alternate techniques such as water jet
cutting,
laser cutting, electron beam cutting, fine blanking or conventional machining
methods.
Each plate may include a carrier strip on each edge, such as carrier strips 26
and 28 of
plate 10 and carrier strips 30 and 32 of plate 12. The carrier strips may
support the
conductive bands at each end during a portion of the manufacturing process and
may
subsequently be removed, as explained below. The wave winding pattern may also
include a series of relatively small holes such as holes 34 and 36 of plate 10
and holes
38 and 40 of plate 12, one on each end of a conductive band. The diameter of
each
hole may be about 0.25 mm, for example. The total number of holes on each side
may
equal the number of conductive bands. The total number of holes matches on
each side
may equal the total number of conductive bands on each plate. Those skilled in
the art
will recognize that armature coils of this type may be constructed from plates
having
less or more conductive bands/holes depending on various DC motor operational
requirements.
[0032] Plate 10 may be rolled into a thin-walled hollow cylindrical shape such
as
cylinder 42, of FIG. 2. Plate 12 may also be rolled into a thin-walled hollow
cylindrical
shape such as cylinder 44, of FIG. 3, but with its pattern of conductive bands
and
cutouts specifically oriented to create a near mirror image of the pattern of
conductive
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bands and cutouts of plate 10. The diameter of cylinder 42 may be about 0.510
inch
(approximately 2 cm) and the diameter of cylinder 44 may be about 0.520 inch
(approximately 2 cm). Of course, motor requirements may necessitate a variety
of
different diameters such that an appropriate diameter can exceed 15 inches,
for
example.
[0033] Cylinder 42 may be formed with a slightly smaller diameter to allow
subsequent telescoping of the same into cylinder 44 to form a conductive coil.
For this
reason, cylinder 44 will hereafter be referred to as outer cylinder 44 and
cylinder 42 will
respectively be referred to as inner cylinder 42. Other size cylinder
diameters may be
utilized provided that they do not deviate from the intended purpose of the
teachings
disclosed herein.
[0034] Next, inner cylinder 42 may be placed on a mandrel and four to five
layers of
fine industrial grade fiberglass strands may be tightly wrapped over the
entire outer
surface, or any portion of the surface where separation of the conductors is
required. In
a multilayer coil having more than two layers, fiberglass strands may be
wrapped over
each of the layers. Fiberglass strand 46, shown in FIG. 4, may have a
thickness of
between 0.00015 and 0.00075 inch, for example. This fiberglass layer insulates
and, at
the same time, avoids the interconnect areas of inner cylinder 42. Tightly
wrapping
multiple layers of fiberglass strands over outer surface of inner cylinder 42
also provides
structural support for the tubular structure, and a certain degree of
electrical insulation
between inner cylinder 42 and outer cylinder 44. For motors requiring higher
voltage
breakdown resistance, the fiberglass layer thickness may be increased
proportional to
the voltage requirement.
[0035] After wrapping, the fiberglass-wrapped inner cylinder 42 may be
inserted all
the way into outer cylinder 44 (i.e. inner cylinder 42 and outer cylinder 44
are of equal
length) with the insertion carried out so as to ensure concentric and axial
alignment of
both cylinders and matching of respective holes on each side of inner cylinder
42 with
the corresponding holes on each side of outer cylinder 44 (FIG. 4). The next
step may
be to tightly wrap four to five layers of industrial grade fiberglass strands
over the outer
surface of outer cylinder 44 in the same way as was done with inner cylinder
42. This
fiberglass layer may provide additional structural support. The thickness of
the outer
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cylinder fiberglass layers may be about 0.00075 inch, but can vary. Those
skilled in the
art will recognize that electrical insulation and armature structural strength
required will
depend on the application of the DC motor being manufactured. For example, the
0.00075 inch material thickness along with the subsequent encapsulation
material
(described below) is sufficiently strong to withstand the centrifugal forces
of rotational
speeds in excess of 30,000 RPM. Voltage breakdown resistance requirements for
low
voltage DC motors is also met with the .00075 inch material. For voltage
breakdown
resistance of 500V, a total thickness of .001 inches or more, may be required
between
the fiberglass thread and the encapsulation material.
[0036] After this outer wrapping, the matched holes may be utilized to provide
solder
flow paths to interconnect pads of each coil segment using, for example, a
lead-silver-
tin solder material which can withstand operational temperatures as high as
450 F. The
solder material may be in the form of a solder paste, comprising a slurry of
flux and
solder. Solder paste may allow for easy placement of the solder with a
pressurized
syringe and needle applicator. Alternatively, welding may be used instead of
soldering
to create an interconnect with copper, which would withstand even higher
armature
temperatures. Alternative methods of joining the matched hoies may be used,
such as
crimping, spot welding or laser welding. If welding is used, the armature
operational
temperature may rise to about 650 F, which is the utilization temperature of
the current
embodiment of the encapsulation material. The matched solder holes (See FIGS.
1A
and 1 B) e.g., 34, 36, and 40, 38, respectively, may not be required if solder
is not the
selected bonding material.
[0037] The soldered joints may electrically interconnect all outer cylinder 44
conductive bands with respective inner cylinder 42 conductive bands so as to
form a
continuous, inductive wave winding structure as shown in FIG. 5A. Because the
first
end of each linear conductive band may be offset by a radial distance of about
90 from
the second end of the linear conductive band, the soldered joints may comprise
three
connection points so that the continuous, inductive wave winding structure has
four
sections as illustrated in FIG. 5A, each section spanning about 90 to cover
the entire
360 radial distance about the cylinder. The inductive wave winding structure
may form
a substantially cylindrical conductive coil having one start point and one end
point, and
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winding through 3600, without requiring an interconnect to another conductive
coil. This
is different from other windings that require electrical interconnects between
them to
traverse the 360 circumference of the armature. This difference is
illustrated, for
example, in FIG. 5E, which depicts a series of lap windings forming four
spaced phase
loops 524, 526, 528, 530 in a prior art conductive coil. The lap windings
require
interconnections 532, 534, 536 to place the phase spaced loops in series about
the
360 circumference of the armature. In a continuous wave winding, on the other
hand,
interconnections may be eliminated or reduced. A continuous wave winding
indexes
one conductor width only after the conductor path has progressed 360 . In
other words,
the wave winding is "continuous" about 360 without having interconnections to
other
loops. All the necessary electrical connections may therefore be placed within
the first
90 degrees.
[0038] Referring once more to the continuous wave winding disclosed herein,
FIG. 5
illustrates in detail how a portion of the wave winding structure is
accomplished. For
example, inner cylinder 42 conductive band 23 is electrically connected at one
end (hole
33) with outer cylinder 44 conductive band 19 and at the other end (hole 41)
with outer
cylinder conductive band 21. The rest of the inner cylinder 42 conductive
bands are
similarly interconnected with respective outer cylinder 44 conductive bands
with the total
number of interconnections at each end being the same. Essentially, the inner
cylinder
42 conductive bands provide one half of the electric circuit and the outer
cylinder 44
conductive bands provide the other half of the circuit. Joining the two halves
completes
the electric circuit.
[0039] This arrangement is different from coil winding structures having lap-
wound
coil conductors because the resulting arrangement of coil conductors formed by
the
wave winding techniques disclosed herein requires significantly fewer
interconnections.
FIG. 5A illustrates a conductive wave winding that forms one phase of a
continuous
cylindrical conductive coil. For illustrative purposes, only one of three
phases for a
three-phase layout is shown in FIG. 5A. Those skilled in the art will
recognize that a
three-phase layout may be applied in a four pole motor, but that other layouts
may be
achieved in accordance with the teachings herein as well.
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[0040] The conductive wave winding 500 may comprise four sections 502, 504,
506
and 508 that, together, form the shape of a "W". Sections 502 and 506 may be
formed
on inner cylinder 42 shown in FIG. 2. Sections 504 and 508 may be formed on
outer
cylinder 44 shown in FIG. 3. When the two cylinders are joined at the solder
points as
described above, the cylindrical conductive coil illustrated in FIG. 5A is
formed. The
cylindrical conductive coil has a start point, and winds through 360 to
complete one
winding at point 512. The coil may then be indexed one wire width, to begin
its next
winding at point 514. This pattern may continue through a plurality of
windings until the
end point 516 of the conductive coil. Accordingly, the conductive coil formed
by the
wave winding process disclosed herein has one start point 510 and one finish
point 516.
In the example shown in FIG. 5A, the conductive coil is indexed four times so
that it
includes five complete windings. However, those skilled in the art will
recognize that
different numbers of windings may be used to create each conductive coil. In a
three
phase layout, two more conductive coils (not shown) may be added, each having
its
start point between 0 and 90 . The resulting set of conductive coils wi(I
cover the entire
circumference of the armature, from 0 to 360 . Accordingly, the wave winding
armature
may comprise three separate conductive coils, "A," "B," and "C," each one
having one
start point and one finish point. The start and finish points may be used to
connect the
conductive coils to one another (at a neutral connection) and to input power,
as will be
described in further detail below. Accordingly, only three interconnections
are required
for the inductive coils when assembled in an electromotive device.
[0041] At each end of the conductive bands on the copper plates that
eventually
form the inner and outer cylinders, a solder, or connection pad, may be
provided. FIG.
5B illustrates a series of connection pads 518 within a solder zone 502. The
connection
pads may be used as solder points to join the two cylinders together as
described
above. Although only a small amount of space is required for electrical
connection,
illustrated in FIG. 5C as the solder zone 502, the connection pads may
extended away
from each conductor for a distance 504 that allows for bonding to a mounting
surface.
This extension of the solder pad beyond useful electrical distance provides a
surface
that the two combined sheet metal pieces may be attached to, i.e. a mounting
surface
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506. The distance 504 may be selected as any length of exposed conductive band
sufficient to create a sturdy bond with the mounting surface 506.
[0042] Figure 5A shows a coil start 510 and a coil finish 512. As illustrated
in
FIG. 5C, solder pads may extend beyond the mounting surface (506 in FIG. 5B),
and
may be connected to power connections, other coil segments or, alternatively,
to the
neutral to form a "Y" connection as illustrated in FIG. 5D. In the event the
connection
must be electrically isolated from the coil conductor under the top conductor,
for
example in a BLDC motor, insulation may be applied between the those
conductors.
This configuration can also be wired as a Delta connection.
[0043] In addition to serving as a supporting member, the mounting surface 506
may
operate as a heat sink. During motor operation, electrical current may create
heat in the
conductors formed by the conductive bands. This heat may limit the power
output
capability of the motor. Removing the heat may allow for a higher power output
from the
motor. Therefore, the extended copper connection pads 500 not only provide for
a
mounting technique but also provide a path for the removal of heat from the
motor.
Because copper thermal conductivity is very high, those skilled in the art
will recognize
that the copper used for the conductive bands is also a suitable material for
the
connection pads 500. Heat generated by the motor may easily transfer through
the
extended connection pads 500 to the mounting and heat sink surface 506. The
mounting surface may be formed of high thermal transfer material aluminum, for
example. Other materials are suitable as well, and those skilled in the art
will recognize
that any high thermal transfer material will allow for a higher power output
motor.
[0044] FIG. 5C illustrates connection features in a portion of a conductive
wave
winding. The start and end points of each phase (A, B and C as described
above) may
overlap one another in the solder connection zone. Radial space may therefore
be
required on the several conductors that overlap but cannot be in electrical
contact. An
insulation material, such as polyimide film, may be used as a spacer 508 when
placed
in the radial space between the overlapping conductors in the solder zone.
Then, the
conductive coils may be connected to each other and to input power. To connect
to
each other, the inner portion 510 of a conductive coil may be connected at
what is
considered the "neutral." To connect to power, the outer portion 512 of a
conductive coil
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may be used. As illustrated in FIG. 5C, these connection points are extensions
of the
conductors themselves. The extended inner conductors may be bent inward to
connect
multiple conductive coils to each other at the "neutral," and the outside
conductors may
be bent outward to connect each of the conductive coils to input power. FIG.
5D
illustrates the "Y" configuration 514 that results from the "neutral"
connection 516
between the three inner conductors. The outer end point of each conductor,
518, 520
and 522, may be used to connect to input power as described above.
[0045] FIG. 6 illustrates a commutator 50 which may be constructed by
precision
machining a thin metal sheet plate, such as tempered copper alloy like
Beryllium/Copper or Silver Copper, in the pattern shown. Commutator 50 may
have a
carrier ring 52 that may support a plurality of segments such as segments 54,
56, etc.
The commutator segments may be soldered to matching solder points on the
outside of
outer cylinder 44. Commutator 50 may collect current from DC motor brushes and
provide power (or distribute current) to the coil circuit of the telescoped
cylinder
assembly via its current conducting segments. A plurality of tabs at opening
571 and the
plurality of segments 54,56, etc., may be bent at 90 degree to the commutating
surface
using a cold forming tool. This step prepares the commutator ring for solder
attachment
to the completed armature coil 62 of FIG. 8. Before the commutator mounted,
carrier
ring 30 from outer cylinder 44 (FIG. 3) and carrier ring 26 from inner
cylinder 42 (FIG. 2)
may be removed by cold forming in preparation for attaching the commutator
ring 50.
After soldering or welding the commutator ring 50 to the armature coil 48, the
carrier
ring 52 (FIG. 6) may be removed from the commutator 50 by cold forming.
[0046] FIG. 6A illustrates an alternative commutator design. A commutator 600
may
comprise a plurality of connection legs 602 and 604, for example. The
connection legs
602 and 604 extend from a commutation ring 606 and may be attached to
extending
portions of the conductive coils on an armature as will be described below
with
reference to FIG. 7A.
[0047] Those skilled in the art will recognize that these teachings apply to
BLDC
motors as well as to DC Brush motors. A BLDC motor differs from the DC Brush
motor
in that the coil remains stationary during operation, i.e., it is called a
stator, while the
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magnets attached to an output shaft rotate. The BLDC motor does not require a
commutator but is commutated electronically. Terminals may therefore be
provided at
the coil phase attachment points of the coil.
[0048] FIG. 7 illustrates an ironless core armature being assembled from a
coil 48
(which is the telescoped cylinder assembly described above), a commutator 50
and a
disk-shaped flywheel 57. Flywheel 57 may be provided with a circular central
opening
60 for fitting a shaft, such as shaft 700 illustrated in FIG. 7A, and may be
constructed of
high-strength aluminum. Flywheel 57 may be anodized on its exterior surface to
create
a consistent insulation layer over the outer surface. Flywheel 57 is capable
of current
and voltage isolation via a non-conductive anodized coating and yet has high
thermal
mass, thermal conductivity and stiffness to transmit torque and securely fix
shaft 700
shown in FIG. 7A. The diameter of flywheel 57 may be slightly smaller than the
diameter
of the inner cylinder 42 to allow snug fit of the flywheel inside inner
cylinder 42 when the
flywheel is subsequently pressed into one end of inner cylinder 42. Other
materials such
as ceramic, high-strength glass and the like may be employed to manufacture
the
flywheel as long as said materials do not depart from the intended purpose of
the
teachings disclosed herein.
[0049] Those skilled in the art will recognize that the flywheel 57 is
applicable to a
BLDC stationary coil as well. With the BLDC stationary coil, the flywheel does
not turn
but becomes the mounting surface of the coil. The mounting surface may be
placed at
the end of the mandrel used for coil making, which eliminates the need to
place the
mounting surface into the coil late in the building process. Instead, the
mounting surface
may be formed at the beginning of the manufacturing process, with the coils
being
layered over the disc which will subsequently be bonded in place.
[0050] As described above, the order of assembly may include first press-
fitting
flywheel 57 into one of the open ends of coil 48 (FIG. 7). Then flywheel 57
may be
inserted inside inner cylinder 42 of coil 48, where it may be held by friction
alone. Next,
the commutator 50 tabs may be soldered (using the type of solder material as
previously described) over the electrically joined interconnections of the
telescoped
cylinder assembly 48. As determined by the total number of commutator segments
and
the total number of soldered holes, one segment may service two solder holes
(or
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electrical interconnections) on the telescoped cylinder assembly. Other
multiples are
also possible. This type of commutator construction allows for a relatively
large number
of segments to be utilized which results in a reduced number of coils at each
switch of
the commutator, thereby reducing commutator sparking.
[0051] The assembled shaftless armature may then be subjected to encapsulation
to
provide additionai structural stability. Encapsulation may permanently secure
all
components and provide complete electrical insulation of the armature.
Specifically, the
shaftless armature may be dipped into a polyimide solution comprised of 25%
solid/solute (polyimide) and 75% solvent (NMP). Polyimides are known for their
high
thermal resistance and are also non-flammable due to their aromatic, halogen-
free
structure that manifests itself in a very high limited oxygen index (about
38%). When
subjected to flame, polyimide has a very low level of smoke formation and
toxic gas
formation, which makes it a preferred bonding agent for this armature.
Polyimide is also
chemically resistant to organic solvents such as alcohol, ketones, chlorinated
hydrocarbons, and has low moisture absorption.
[0052] The dipped armature may then be centrifuged to remove air and replace
air
voids with the polyimide solution. Centrifugal force may push the air out of
the structure
and, at the same time, push the polyimide deeper into the crevices and cracks
of the
telescoped tubular structure, allowing permanent bonding and insulation of the
components.
[0053] Alternatively, the polymide may be inserted into the coil structure
with a rolling
technique. While spinning the mandrel and coil structure in parallel with, and
touching,
another metal (or structural material) round surface, the polyimide material
is introduced
between the rollers. This forces the material into the openings of the coil
structure. This
technique is call "milling" material. This milling technique may be used to
apply a
specific amount of material into the coil.
[0054] The polyimide-dipped armature may be heat-cured at about 4500 F to
remove
solvents and to yield a hardened, cured polyimide encapsulation of the
armature. The
limitation to the curing temperature may be the 550 F solder flow
temperature;
however, using non-solder welding techniques may allow polyimide curing at 700
F
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and armature operating temperatures of 6500 F. Other potting materials may be
used
such as ceramic, glass, silicates, silicones, epoxies and the like. After the
shaftless
armature has been heat-cured, it may be cooled to room temperature. Upon
inserting a
shaft, the end product is a strong, stiff and fully insulated armature that
can be used in
any DC or brushiess motor application.
[0055] FIG. 7A is a perspective view of an ironless core armature with drive
shaft
and flywheel inserted and an alternative commutator, as depicted in FIG. 6A,
electrically
connected to the conductive coil. In this alternative design, the commutation
ring 606
may attach to the axis 700 of the armature 702. The connection legs, such as
connection leg 602, may then be attached to extended portions of the
conductive coils,
such as extension 704.
[0056] FIG. 8 Illustrates a fully assembled freestanding ironless core
armature 62 for
a DC motor with brushes. Armature 62 may include an axially inserted shaft
(not shown)
with portions 59 and 61 protruding from each end (also shown as shaft 700 in
Fig 8A).
Before shaft 58 can be mounted, carrier rings 28 from inner cylinder 42 and
carrier ring
32 from outer cylinder 44 (FIGS. 2&3, respectively) may be cut off by cold
forming. This
removal of the carrier rings 28 and 32 completes the isolation of the
individual helical
segments thereby creating a continuous coil loop around the armature. Shaft 58
may be
constructed from hardened stainless steel grade 17-4PH, and may be press-fit
axially
inside inner cylinder 42, passing through opening 60 of already mounted
flywheel 57
and through opening 571 of already mounted commutator 50. An example of
dimensions for shaft 58 are 1/8" diameter by 21/2" length. Other materials and
dimensions may be used to manufacture the shaft 58 if said materials do not
depart
from the intended purpose of the teachings herein. Moreover, those skilled in
the art will
recognize that a BLDC coil assembly does not require a shaft.
[0057] FIG. 8A is a perspective view of an assembled ironless core armature
with
drive shaft and flywheel inserted and an alternative commutator, as depicted
in FIG. 6A,
electrically connected to the conductive coil. In this alternative design, the
commutation
ring 606 attaches to the axis of the armature 702. The connection legs, such
as
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connection leg 602, may then be attached to extended portions of the
conductive coils,
such as extension 704.
[0058] While particular embodiments of the teachings disclosed herein have
been
illustrated and described, it would be apparent to those skilled in the art
that various
other changes and modifications can be made without departing from the spirit
and
scope of the invention. For example, the brushless motor in alternative
embodiments
may be configured to provide electrical generation when the shaft is rotated
by
mechanical means. Thus, the teachings disclosed herein are not intended to be
limited
to the embodiments shown herein but are to be accorded the widest scope
consistent
with the principles and novel features related by them.
[0059] The previous description is provided to enable any person skilled in
the art to
practice the various embodiments described herein. Various modifications to
these
embodiments will be readily apparent to those skilled in the art, and the
generic
principles defined herein may be applied to other embodiments. Thus, the
claims are
not intended to be limited to the embodiments shown herein, but are to be
accorded the
full scope consistent with the language of the claims, wherein reference to an
element in
the singular is not intended to mean "one and only one" unless specifically so
stated,
but rather "one or more." All structural and functional equivalents to the
elements of the
various embodiments described throughout this disclosure that are known or
later come
to be known to those of ordinary skill in the art are expressly incorporated
herein by
reference and are intended to be encompassed by the claims. Moreover, nothing
disclosed herein is intended to be dedicated to the public regardless of
whether such
disclosure is explicitly recited in the claims. No claim element is to be
construed under
the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is
expressly
recited using the phrase "means for" or, in the case of a method claim, the
element is
recited using the phrase "step for."
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