Note: Descriptions are shown in the official language in which they were submitted.
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SOFT-METAL ELECTROMECHANICAL COMPONENT
AND METHOD MAKING SAME
BACKGROUND OF THE INVENTION
Multi-pole rotating electro-mechanical devices, such as motors, generators, re-
gen motors, alternators, brakes and magnetic bearings are comprised of rotors
and electro-
mechanical components. AC motors rotate by producing a rotating magnetic field
pattern in
the electro-mechanical component that causes the rotor to follow the rotation
of this field
pattern. As the frequency varies, the speed of the rotor varies. To increase
the speed of the
motor, the frequency of the input source must be increased.
High frequency motors manufactured with the proper materials can be very
efficient. For certain applications, like electric or hybrid cars, highly
efficient electric motors
are desirable.
The construction of electromechanical components for high frequency
electric motors and generators is problematic. Iron or steel components are
quite common in
electric motors and generators. However, at high frequencies, such as those
greater than
400Hz, conventional iron or steel components are no longer practical. The high
frequency of
the AC source increases the core losses of the iron or steel components,
reducing the overall
efficiency of the motor. Additionally, at very high frequencies, the component
may become
extremely hot, cannot be cooled by any reasonably acceptable means and may
cause motor
failure.
For construction of electro-mechanical components used in high frequency
electric motors, ribbon made from soft magnetic material provides distinct
advantages.
Examples of soft magnetic ribbon materials would be either 1) conventional
material
typically defined as .008" and thicker, non grain oriented with a typical Si
content of 3%+/-
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1/2% or 2) alternate soft materials that are .007" or thinner with Si content
of 3% to 7%,
amorphous, or nanocrystalline alloys and other grain oriented or non grain
oriented alloys.
Some soft magnetic ribbon materials exhibit inherent characteristics that make
their use in
high frequency electro-mechanical rotating devices highly desirable. Some soft
magnetic
ribbons are easy to magnetize and demagnetize, which means an electro-
mechanical
component made with these metals would have low power loss, low temperature
rise at high
frequency, extremely fast magnetization and easy conversion of electrical to
mechanical
energy. An electro-mechanical component made of such an metal would generate
less core
losses and be able to operate at much higher frequencies, resulting in motors
and generators
of exceptional efficiency and power density.
Soft magnetic materials are commercially produced as ribbon or strip. A
preferred example of a soft magnetic metal ribbon is Metglas , which is an
amorphous
material, manufactured by Honeywell, Inc. Soft magnetic metal ribbons are very
thin and of
varying width. Manufacturing components of soft magnetic metal ribbon requires
winding
the soft magnetic ribbon into a shape and then heat processing the shape.
Simple three
dimensional shapes, such as toroids, can currently be constructed from soft
magnetic metal
ribbon.
However electro-mechanical components are often not simple three
dimensional shapes. The electro-mechanical component can have numerous slots
for
accommodating motor coils in a generally toroidal structure.
Attempts to create complex three dimensional configurations from soft
magnetic metal ribbon have heretofore been commercially unsuccessful. Various
manufacturing techniques have been attempted by industry such as but not
limited to: wire
electrical discharge machining, electrochemical creep grinding, conventional
electrical
discharge machining, cutting, stamping, acid etching and fine blanking. None
have proven
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satisfactory for reasons such as cost-effectiveness, manufacturing
repeatability, or process
cycle time.
This inability to fabricate complex three dimensional shapes from soft
magnetic ribbon has been the significant impediment to producing high
efficiency axial flux
motors and generators. A method to produce electro-mechanical components from
soft
magnetic ribbon in a cost effective, end use functional, high volume capable
method that will
also provide substantial design flexibility for end use requirements is highly
desirable.
SUMMARY OF THE INVENTION
A method for forming a three dimensional soft magnetic metal mass suitable
for milling consists of wrapping soft magnetic metal ribbon into a three
dimensional shape,
then applying adhesive to the three dimensional shape. The adhesive is then
cured and the
cured form is mechanically constrained in three dimensions. The method results
in aft soft
magnetic metal mass which can withstand the mechanical stresses of machining.
The three
dimensional soft magnetic metal form can be milled using a horizontal mill, a
vertical mill, a
computer numeric control (CNC) machine, or any other common milling equipment.
Thus,
complex three dimensional soft magnetic metal shapes can be created.
The ability to create three dimensional soft magnetic metal shapes allows the
use of soft magnetic metal for a variety of applications heretofore foreclosed
by the
mechanical characteristics of soft magnetic metal ribbon.
To manufacture an soft magnetic electro-mechanical component, soft
magnetic metal ribbon is wound into a toroid. The toroid is then placed in a
milling
assembly. Adhesive is applied to the toroid, and then cured. The toroid is
then milled into an
electro-mechanical component shape, and then thennally processed into a
electro-mechanical
component.
These and other objects, advantages and features of the invention will be more
readily understood and appreciated by reference to the detailed description of
the drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIG. I shows a soft magnetic metal ribbon being wound on an inner ring.
FIG. 2 shows an inner containment hat.
FIG. 3 shows an outer containment hat.
FIG. 4 shows a milling assembly.
FIG. 5 shows a milling assembly being milled.
FIG. 6 shows a soft magnetic metal electro-mechanical component.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 shows soft magnetic metal ribbon 10 being wound about a winding
axis 11 on an inner ring 14. Winding machine 13 contains soft magnetic metal
ribbon roll
12. Inner ring 14 is placed on winding plate 16. Soft magnetic metal ribbon 10
is wound on
inner ring 14, forming soft magnetic metal toroid 18. Soft magnetic metal
toroid 18 has an
inner side surface 15, an outer side surface 17, a top 19, and a bottom 21.
While FIG. 1 shows the formation of an soft magnetic metal toroid 18, it will
be appreciated that a three dimensional shape could be created with a geometry
distinctly
different from the soft magnetic metal toroid 18. For example, it would be
possible by
winding around four corners to create a rectangular prism.
Soft magnetic metal ribbon 10 can be wound using a variety of machines and
methods. Preferably, a consistent, firm toroid will have at least an 85% wind
density
compared to the inherent ribbon density. Soft magnetic metal toroid 18 is then
removed from
winding plate 16. Soft magnetic metal ribbon 10 can be wound around the inner
ring 14
while attached to the inner containment hat 20 as a single unit.
An adhesive is then applied to the soft magnetic ribbon toroid 18 in a manner
to permeate the soft magnetic metal toroid 18. Inner ring 14 is still
contained within the soft
magnetic ribbon toroid 18. A suitable adhesive is Scotch Cast adhesive by 3M,
diluted by
acetone so as to achieve about a 20% mix by volume. The adhesive is applied to
soft
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magnetic ribbon toroid 18 by an ambient atmospheric soak process. Soft
magnetic ribbon
toroid 18 is immersed in the adhesive until the adhesive infiltrates the
layers.
Alternatively, the adhesive could be applied by immersing soft magnetic
ribbon toroid 18 into the adhesive inside a vessel that is evacuated of air.
The vacuum
created would enhance the infiltration of the adhesive into the soft magnetic
ribbon toroid 18
layers. Adhesive could also be applied to the soft magnetic ribbon during the
winding
process utilizing a wet spray or dry electrolytic deposition process.
Alternative resins,
epoxies or adhesives may be used. Different brands as well as different types
of resins,
epoxies or adhesives may be used. Heat cured epoxies that require various
temperatures as
well a two stage epoxies that cure at room temperature would also be suitable.
After soft magnetic ribbon toroid 18 is sufficiently infiltrated with
adhesive,
soft magnetic ribbon toroid 18 is allowed to drain. Once dry, soft magnetic
ribbon toroid 18
is placed inside an oven for curing. Importantly, the temperature for heat
treating the
adhesive be a fraction of the temperature for heat processing soft magnetic
metal ribbon 10.
A preferable fraction is 1/2, although fractions of 1/4 and 3/4 might also be
satisfactory.
FIG. 2 shows inner containment hat 20. Inner containment hat 20 is a cylinder
comprised of a number of columns 22 extending upward from the inner
containment hat base
24. Fingers 26 extend outward from columns 22 at approximately a right angle.
Fingers 26
increase in width as they extend further from the columns 22. Fingers 26 are
arranged in a
circle, forming an annulus 28. The columns 22 and fingers 26 form a plurality
of inner
containment hat grooves 29. Columns 22 of inner containment hat 20 are placed
inside inner
ring 14.
The height of columns 22 is approximately equal to the height of the soft
magnetic metal toroid 18. The diameter of the soft magnetic metal toroid 18 is
about equal to
the diameter of the annulus 28.
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Following the placement of inner containment hat within soft magnetic metal
toroid 18, outer containment hat 30 shown in FIG. 3, is placed around soft
magnetic metal
toroid 18.
Outer containment hat 30 is cylindrical, with a base 32. Bars 34 extend
upward from base 32. At the top of each bar 34 is a lug 36 extending inward.
Lug 36 for
each bar 34 forms a flange for securing the amorphous metal toroid 18 within
outer
containment hat 30. Bars 34 and lugs 36 form a plurality of outer containment
hat grooves
38.
Milling assembly 40, shown in FIG. 4, is then formed. Soft magnetic metal
toroid 18, still containing inner ring 14, along with the inner containment
hat 20 is placed
within outer containment hat 30. Lugs 36 and fingers 26 are aligned. Milling
assembly 40
contains the soft magnetic metal toroid 18 within a toroidal geometry.
Alternatively, soft
magnetic metal toroid 18 could be placed within outer containment hat 30 and
inner
containment hat 20 prior to treatment with the adhesive.
After application of the adhesive and placement within the mechanical
constraints of the inner ring 14, inner containment hat 20, and outer
containment hat 30, the
soft magnetic metal toroid 18 has sufficient structural integrity to withstand
the stresses of
milling.
Milling plate 44 is placed on the bottom of the soft magnetic metal toroid 18.
Milling plate 44 could be the same as winding plate 16.
Soft magnetic metal toroid 18, having been treated with an adhesive, is thus
firmly contained within a structure, allowing soft magnetic metal toroid 18 to
be milled and
formed in three dimensions. Complex shapes can thus be constructed from the
metal ribbon
toroid 18, allowing structures such as electro-mechanical components to be
made from the
soft magnetic metal toroid 18.
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As illustrated by FIG. 5, milling assembly 40 is placed in mill 50. Mill 50
could be a horizontal mill, a vertical mill, a CNC machine, or any other type
of mill.
However, mill 50 should preferably have the axis of rotation of the mill tools
52
perpendicular to the axis of the soft magnetic metal toroid 18. By having the
axis of rotation
of the mill tool 52 perpendicular to the axis of the soft magnetic metal
toroid 18, the depth
and width of the slots milled into the soft magnetic metal toroid 18 can be
finely controlled.
Mill 50 cuts slots or other geometries into the soft magnetic metal toroid 18.
Inner ring 14, still contained within soft magnetic metal toroid 18, acts as a
positive
mechanical stop for the inside edge of soft magnetic metal toroid 18. Inner
ring 14, in
conjunction with the epoxy, does not allow strips of soft magnetic metal
ribbon 10 to separate
during machining, thereby producing clean and accurate cuts.
After the soft magnetic metal toroid 18 is milled into an electro-mechanical
component shape, milling assembly 40 is removed from mill 50. Milling assembly
50 is then
thermally processed in accordance with the recommendations of the manufacturer
of soft
magnetic metal ribbon 10 as required. If the amorphous metal ribbon 10 is
Metglas ,
thermal processing consists of placing milling assembly 50 into a vacuum
furnace at 695
degrees Fahrenheit for approximately sixty minutes. Some soft magnetic ribbon
materials
require thermal processing to achieve the desired magnetic properties while
others require
thermal processing to properly relieve the stresses in the milled electro-
mechanical
component shape as a result of the milling process. It is conceivable that,
given proper
mechanical containment during milling, some materials that do not require
thermal
processing for magnetic properties could forego the thermal processing.
Following thermal processing, the milling assembly 40 is disassembled by
removing retainer 42, outer containment 30, inner containment hat 20, and
inner ring 14.
Soft magnetic metal toroid 18 has thus been made into an soft magnetic metal
electro-
mechanical component 60, shown in FIG. 6.
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The method as described allows for the creation of three dimensional forms
from soft magnetic metal ribbon. The applications for such three dimensional
forms could be
as electro-mechanical components for a variety of machines.
The above description is of the preferred embodiment. Various alterations and
changes can be made without departing from the spirit and broader aspects of
the invention
as defined in the appended claims, which are to be interpreted in accordance
with the
principles of patent law including the doctrine of equivalents. Any references
to claim
elements in the singular, for example, using the articles "a," "an," "the," or
"said," is not to
be construed as limiting the element to the singular.
