Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRIC DC MOTOR SYSTEM
FIELD OF THE INVENTION
[0001] The invention relates to electric direct current (DC) motor systems,
and, more
particularly, to cordless electric DC motor systems that may be used in
portable devices
such as vacuum cleaners and hand-controlled lawn equipment and power tools.
BACKGROUND OF THE INVENTION
[0002] Historically, battery operated brush-type DC motors have been around
and used
in a variety of applications for many years, including in small vacuum
cleaners. These
generally consist of a stator which includes some form of permanent magnets
and a
rotor having a winding energized through brush contacts. However, such
configurations
have been criticized for being inefficient and requiring maintenance mainly
due to the
replacement of the brushes. This has led to the advent of motors that do not
include any
brushes, commonly known as "brushless" motors. However, the present invention
may
provide increased efficiency in brush motors, while also reducing maintenance
issues.
The motor may provide high torque and efficiency while maintaining a small
size and
minimizing heat generation.
[0003] The term "cordless" is generally used to refer to electrical or
electronic devices
that are powered by a battery or a battery pack and can operate without a
power cord or
cable attached to a fixed electricity supply, such as an outlet, generator, or
other
centralized power source, thereby allowing greater mobility. The development
of more
powerful rechargeable batteries in recent years has allowed the production of
battery-
powered versions of power tools and appliances that once required a power
cord, and
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these are distinguished by the term "cordless," as in cordless drills,
cordless saws,
cordless irons, cordless vacuums and the like.
[0004] Numerous types of DC motors have been provided in the prior art in an
attempt
to address the shortcomings with the traditional design but each fails to
address them
like the present invention. For example, U.S. Pat. Nos. 4,873,463; 7,728,479;
8,324,775; U.S. Application 2013/0147311 and European Patent 106,002 are all
illustrative; however, these inventions are not as suitable for the purposes
of the present
invention described herein.
SUMMARY
[0005] The present invention relates to an Electric DC Motor System and method
of
manufacture. The Electric DC Motor System is accomplished by an improved
battery
management system, new stator design incorporating high permanent magnetism
(HPM) magnets and a unique controller, all of which are synchronized to
maximize
efficiency and lower operating temperature. The method of manufacture
discloses how
the present invention is made.
[0006] The invention provides a battery powered electric DC motor system and
method
of manufacture thereof. The present invention takes advantage of a novel
design for a
battery powered DC motor, which also incorporates improved battery management,
HPM magnets, and improved circuitry/controls, all of which increase efficiency
by,
among other things, eliminating wasted energy and optimizing motor and battery
performance, yielding a motor that can operate, at a minimum, very close to
the same
length of time in which the battery might be charged (e.g., 30 minutes of
charge time
yields nearly 30 minutes of use at full power). The motor of the present
invention, with
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its increased efficiency and size, provides an advancement in cordless
electric motor
technology. The present invention may make a variety of cordless devices and
machines more practical. In particular, the present invention is uniquely
suited for use
in a cordless upright vacuum cleaner and other portable power tools and
equipment.
[0007] In one embodiment, the present invention provides a battery operated
Electric
DC Motor System that features improved efficiency and reliability as a result
of the
novel arrangement of components noted herein. Unlike some improvements seen in
the
past, the present invention enables cooperation of all the components (e.g.,
motor,
battery, and controller) in such a way that all these components work together
more
efficiently than heretofore achieved in the art.
[0008] The invention comprises, in one form thereof, an electric DC motor
system for a
cordless vacuum cleaner, including a rotor and a stator having a plurality of
permanent
magnets. Each of the magnets includes six substantially flat and rectangular
faces.
[0009] The invention comprises, in another form thereof, an electric DC motor
system,
including a rotor, a stator having a plurality of permanent magnets, and a
housing
containing and supporting the magnets. The housing is formed of a non-magnetic
material.
[0010] The invention comprises, in yet another form thereof, an electric DC
motor
system for a cordless vacuum cleaner, including a rotor, a stator including at
least two
permanent magnets disposed opposite to each other relative to an axis of the
rotor, and
at least two brushes. Each of the brushes is disposed at angles relative to
each of the
magnets of approximately between eighty-five degrees and ninety-five degrees
in
circumferential directions defined by the axis of the rotor.
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100111
The invention comprises, in still another form thereof, an electric DC motor
system for a cordless device including a rotor and a stator including at least
two
permanent magnets disposed opposite to each other relative to an axis of the
rotor.
Each of the magnets spans less than forty-five degrees in a circumferential
direction
defined by the axis.
[0012] Yet other embodiments include the features described in any of the
three
previous paragraphs as combined with:
(i) one or more of the features described in one or more of the four previous
paragraphs,
(ii) one or more of the following aspects, or
(iii) one or more of the features described in one or more of the four
previous
paragraphs and one or more of the following aspects:
wherein each of the six faces is parallel to a respective other one of the six
faces;
wherein each of the six faces is oriented at an angle of about ninety degrees
relative to each of four other ones of the faces;
wherein a respective gap is defined between each of the magnets and the rotor
in a radial direction, each said gap being approximately between 0.025 inch
and 3
inches, preferably approximately between 0.035 inch and 2 inches, more
preferably
approximately between 0.05 inch and 0.1 inch, and, in one embodiment, about
0.078
inch;
wherein the system includes at least one brush, an angle between at least one
of
the magnets and at least one of the brushes being approximately between eighty
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degrees and one hundred degrees in a circumferential direction defined by an
axis of
the rotor;
wherein the angle is about ninety degrees;
wherein the plurality of permanent magnets comprises two permanent magnets
5 disposed opposite to each other relative to an axis of the rotor, the two
magnets being
oriented parallel to each other;
wherein the system further includes at least one brush and a battery pack
electrically coupled to the brush and configured to provide power thereto, the
battery
pack including at least two batteries connected to each other in parallel and
at least two
batteries connected to each other in series;
wherein the housing is formed of a plastic material;
wherein the housing is formed of a non-ferrous metal material;
wherein the housing contains and supports at least one brush and/or at least
one
magnet;
wherein the gap may be adjustable as a means of achieving a desired target
motor torque and/or a desired target rotational speed of the rotor;
wherein the system includes a battery pack electrically coupled to the brushes
and configured to provide power thereto, the battery pack including at least
two
batteries connected to each other in parallel and at least two other batteries
connected
to each other in series;
wherein the angles are each between a first centerline bisecting a
corresponding
brush and a second centerline bisecting a corresponding magnet;
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wherein the system includes a housing containing and supporting the magnets
and the brushes, the housing being formed of a non-magnetic material;
wherein the brushes are driven via pulse width modulation; and
wherein the system includes a processor coupled to the brushes and configured
to control the pulse width modulation.
[0013] Traditionally, upright vacuum cleaners, with their torque and storage
requirements, have primarily been "corded." However, the present invention
opens the
door to having a battery operated power tool, such as but not limited to an
upright
vacuum cleaner. The numerous advantages are, firstly, the fact that the user
need not
struggle with finding an outlet in which to plug the unit, and, secondly, when
the unit is
being used, a cordless unit avoids the troubles in dealing with the power
cord, not to
mention the issue of accidental unplugging of the unit, which sometimes
occurs. These
advantages are multiplied when considering cleaning (and/or groundskeeping) in
a
commercial environment, such as a hotel or commercial office setting and the
reduced
labor costs brought about by the present invention.
[0014] As used throughout this specification and claims, reference is made to
magnets
formed of one or more materials that display a "high permanent magnetism"
denoted as
"HPM" herein. These magnets, such as Neodymium magnets, are deemed to be those
which, when compared to typical ferrite magnets as commonly known in the art,
display
three (3x) or more times the magnetic flux density, and three (3x) or more
times the
coercive force, to give approximately ten (10x) times the total energy per
unit volume.
Further, when the term "Electric DC Motor System" is used in this
specification
(including as the title of this invention), it is understand that this
includes all components
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in which to make the invention operate, to wit: a motor, which may include a
stator and
rotor; a controller, which may be attached to the motor; and a battery, which
may be
attached to the controller. This term should not be confused with the more
generic use
of the term "motor," which includes only a stator, rotor and associated
hardware.
100151 An advantage of the invention is that it may provide a high level of
electromagnetic force and increased battery capacity, resulting in longer
operation
between battery re-charging than is known in the prior art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A better understanding of the present invention will be had upon
reference to the
following description in conjunction with the accompanying drawings.
[0016] FIG. 1 is a schematic view of one embodiment of the motor of the
present
invention in a configuration for use with an upright vacuum cleaner.
[0017] FIG. 2 is a schematic, expanded, partially cross-sectional view one
embodiment
of the stator and commutator of the motor.
[0018] FIG. 3 is a schematic diagram of one embodiment of the motor.
[0019] FIG. 4 is a schematic circuit diagram of one embodiment of the motor.
[0020] FIG. 5 is a schematic block diagram of another embodiment of an
electric DC
motor system provided by the present invention.
[0021] FIG. 6 is a schematic circuit diagram of one embodiment of the motor
and driver
circuit of the system of FIG. 5.
[0022] FIG. 7 is a schematic circuit diagram of one embodiment of the battery
pack of
the system of FIG. 5.
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[0023] FIG. 8 a schematic block diagram of yet another embodiment of an
electric DC
motor system provided by the present invention.
[0024] FIG. 9 is an exploded perspective view of one embodiment of a motor
suitable
for use in an electric DC motor system of the invention.
[0025] FIG. 10 is a perspective view of the motor of FIG. 9.
[0026] FIG. 11 is a side view of the motor of FIG. 9.
[0027] FIG. 12 is a schematic top view of the motor of FIG. 9.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] For the purpose of promoting an understanding of the principles of the
present
invention, reference will now be made to the embodiment illustrated in
specific language
contained herein. It will, nevertheless, be understood that no limitation of
the scope of
the invention is thereby intended; any alterations and further modifications
of the
described or illustrated embodiments, and any further applications of the
principles of
the invention as illustrated therein are contemplated as would normally occur
to one
skilled in the art to which the invention relates.
[0029] Battery system 1 (FIG. 1) may provide energy to the motor, and may be a
high-
capacity, high-use battery. Battery system 1 may be selected and tuned to meet
the
specific requirements of the motor itself in conjunction with the controller's
efforts to
minimize draw on the battery, while still maintaining the amount of energy
needed for
the motor to complete its appointed task. Battery system 1 may include
multiple
independent battery packs 2 (FIG. 3) each having its own circuitry 4 that
limits the rate
at which energy is discharged from each battery pack 2, thus limiting heat
generation,
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and also limiting the total amount of discharge allowed from any such battery
pack 2.
Limiting deep discharge from a battery pack may extend the useful life of the
battery
pack by virtue of the pack and the associated battery chemistry never being
stressed
outside the normal peak operating limits. In the illustrated embodiment of
FIG. 3, two
battery packs 2 with associated circuitry 4 are included.
[0030] The battery may be recharged from an outside source 5 dependent upon a
position of a switch 6. The switch 6 enables the device to be turned ON or
OFF, or may
enable the selection of a different setting of operation, e.g., high speed
versus low
speed. The switch 6 may be connected to a controller 7, which, in turn, is
connected to
the motor 8.
[0031] Controller 7 controls the flow of electricity from the battery to the
motor and
manages the energy used by the motor. Part of this management is an electrical
pulse
means 9 (FIG. 4). This pulse means operates intermittently and may maintain a
constant speed of the rotor, sending the pulse only when the rotor needs
additional
rotational velocity. In this way, only the minimally required amount of energy
is sent to
the motor in order to drive, in a pulsating manner, the motor. Further, the
controller also
includes a means 10 in which to recapture energy generated by the movement of
the
motor, and this energy is returned to the motor, as necessary. This
arrangement may
therefore minimize the energy that is drawn from the battery, thus increasing
battery
use-time.
[0032] The motor may include a stator 11 (FIG. 2) having magnets 12 and a
rotor 13
having a winding 14 energized through brush contacts 15 that touch a
commutator 16.
Unlike traditional DC motors, the motor of the present invention has a stator
exterior 11
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that is made of plastic versus metal. This helps reduce heat and eliminates
possible
distortion in the magnetic fields involved in the operation of the motor.
[0033] Also, unlike the arrangement of most magnets in a traditional DC motor,
which
are curved and extend around almost the entire circular interior of the
stator, the present
5 invention provides magnets arranged in a linear fashion taking up only
approximately
ten percent (10%) of the curved interior circumference of the stator or
housing. This
amount of coverage may vary depending upon the requirements of the motor, but
may
generally be less that the amount of coverage seen in traditionally built DC
motors.
Further, the magnets used are HPM magnets and in one embodiment may be
10 neodymium in nature.
[0034] The HPM magnets may be placed in the stator in linear fashion as shown
in FIG.
2. As noted above, these magnets are smaller than traditionally used and only
so many
are used as is necessary to facilitate continued movement of the rotor via the
relationship with the windings, which are fixedly attached to the rotor and
commutator.
The rotor, windings and commutators all move in a circular fashion around a
center
point of the rotor shaft 17. In this way, the magnetic field in the stator
created by the
HPM magnets is tuned specifically to that created by the rotor. This results
in increased
efficiency as the two magnetic fields do not end up fighting against each
other. In the
embodiment shown in FIG. 2, the number of HPM magnets is two, and they are
arranged such that they are not of curved design, to mimic the arc of a
circle, but are
rather linear.
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[0035] The invention also includes a method of manufacturing the Electric DC
Motor
System. This method begins with determining the requirements of the use for
the
Electric DC Motor System, which includes determining the amount of torque and
speed,
or speeds, which would be required from the motor. Once determined, then a
motor, of
the type disclosed in this invention, is made using the novel elements
disclosed herein,
such that the motor meets the necessary requirements. Thereafter, the
controller is
made, as disclosed herein, in light of the requirements of motor in
conjunction with the
energy needs (e.g., volts and amps) necessary to meet the requirements. Next,
a
battery system may be selected in light of the controller and consistent with
its energy
needs as determined by the requirements, which may include the amount of
battery
packs and their respective circuitry. A method of manufacture as indicated may
ensure
that all three components of the Electric DC Motor System work at maximum
efficiency,
which may result in significantly improved operating time, as well as lower
operating
temperature and a minimization of wasted energy.
[0036] Another embodiment of an electric DC motor system of the present
invention is
shown in FIG. 5, including a battery pack 502, a motor and driver circuit 504,
a plug-in
external battery charger 506, a diode 508, an ON/OFF switch 510 and a circuit
breaker
512. The detail of battery pack 502 is shown in FIG. 7, including charge
controllers
PMC1 and PMC2. Each of these charge controllers may be on its own dedicated
circuit
board. As shown, some of the batteries may be connected in series with each
other,
and some of the batteries may be connected in parallel with each other.
Parallel
combinations of batteries may be connected in series with other batteries or
with other
parallel combinations of batteries.
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[0037] The detail of motor and driver circuit 504 is shown in FIG. 6,
including a motor
602 and various electronic components including an LM555CN timer controller
604.
The general function of the motor driver circuit is to limit the total current
available to the
motor from the battery and improve overall system efficiencies by reducing
some
potential losses. By eliminating the field coil of the motor and adding
permanent
magnets as in this embodiment, the motor's magnetic field does not require AC
wall-
power in order to be present. This permanent-magnet motor may function as a
typical
DC motor, relying on the commutation of the rotor windings to move the aiding
and
opposing magnetic forces that spin the rotor with respect to the fixed
magnetic forces of
the stator. With DC current applied to the rotor, and with the magnetic field
fixed at the
stator, when voltage is applied to the rotor, through the commutator, the
current in the
selected rotor winding may rise as the magnetic field builds in that rotor
winding. Once
the rotor winding has reached its peak in magnetic field generation, or the
point of
magnetic saturation, the current in the winding may rapidly rise and approach
the limit
imposed by the rotor winding resistance. Commutation may also provide some
limit to
the maximum current possible, but at the risk of switching during a peak
current
condition in the rotor winding, which creates arcs, high electrical noise and
electromagnetic radiation, which can contribute to wear and reduced life for
the
commutator and rotor windings.
[0038] Because the rotor winding DC resistance is very low, nearly zero Ohms,
the
current can be extremely high and yet produce no work at the motor shaft, only
converting this energy to heat. The pulse width modulation (PWM) circuit,
including
LM555CN timer controller 604, allows the output of the battery to be current
limited by
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only applying DC power for 70-90% of the time, allowing the rotor-generated
magnetic
field to relax in the off-time, and keeping the rotor windings out of
saturation. This may
elevate the overall efficiency rating by reducing the potential losses of
applying power to
the rotor when it is potentially saturated. This percentage can be manually
adjusted for
best performance under nominal load conditions. It can also be improved such
that the
duty cycle could be made relative to commutation allowing the efficiency to
remain
optimized throughout motor startup, from low-speed to high-speed, and under
various
load conditions.
[0039] The LM555 timer controller 604 may be used to set the duty-cycle of its
output as
a function of the time constant created by R6, R9, and C8. The LM555 timer
controller
604 may generate a constant pulse width that may serve to extend battery life.
The
digital output of LM555 timer 604 may be level converted by U2 operational
amplifiers
606, 608 to create the appropriate switching levels for the gate of MOSFET
(Q1) 610 to
reach the fully-saturated on and off levels required for minimum switch
losses. MOSFET
01 (e.g., part no. IRF250) 610 may work as a sinking switch to the motor by
pulling one
of the motor rotor leads to BATTERY-MINUS, while the other rotor lead is
permanently
affixed to BATTERY-PLUS.
[0040] Illustrated in FIG. 8 is an embodiment of an electric DC motor system
in which
the PWM drive may be controlled by a microprocessor 802. In the illustrated
embodiment, microprocessor is a model PIC16C73 processor marketed by Microchip
Technology Inc., and its pinout is well known to those of skill in the art.
The
microprocessor can monitor motor current, battery voltage, and may
additionally monitor
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battery current and motor shaft rotation to improve the application of energy
to the
motor in a manner that further improves efficiency.
[0041] Microprocessor 802 may use firmware to control an on-chip timer that
creates a
pulse-width-modulated (PWM) drive signal. This PWM signal is amplified by Q1
(MOSFET) 804 and applied to the motor 806. Current flowing through the motor
windings is measured across a shunt resistance (R7) 808 and monitored by
amplifiers
810, 812 and 814. Amplifiers 812, 814 provide a shutdown signal to MOSFET 804
through transistor Q3 816 as the current in the motor winding approaches a
designated
maximum. Similarly, an interrupt is transmitted to microprocessor 802 to
signal to the
microprocessor that the maximum allowed current is being reached.
Microprocessor
802 also monitors the average current to the motor, which is represented as a
DC level
by amplifier 810.
[0042] In this diagram of FIG. 8 the battery voltage is monitored by
microprocessor 802
providing an ability to shut the drive off when the battery level becomes
critically low.
This same signal also enables evaluation of the discharge rate of the battery
over time
to better manage the current delivered by the PWM and transistor 804 and
achieve
better run times for the system while in use.
[0043] Illustrated in FIGS. 9-12 is an embodiment of a motor suitable for use
in an
electric DC motor system of the present invention. The motor includes brushes,
permanent magnetics and a rotor. A housing or casing 902 of the magnets and/or
a
housing or casing 904 of the motor may be formed of non-ferrous metal or some
non-
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metal material such as plastic. This helps reduce heat and eliminates possible
distortion
in the magnetic fields involved in the operation of the motor.
[0044] Magnets 906 may be linear in that they may have no curved surfaces, but
instead have six rectangular, flat faces and twelve line segment edges. In the
5
embodiment shown, each of the two magnets 906 may span less than 45 degrees of
the interior circumference of the magnetics housing 908. In another
embodiment, each
of the two magnets 906 may span less than 30 degrees of the interior
circumference of
the magnetics housing 908. In yet another embodiment, each of the two magnets
906
may span approximately between 10 degrees and 30 degrees of the interior
10
circumference of the magnetics housing 908. This relatively small
circumferential span
of the magnets may provide a narrower magnetic focus which allows the pulse to
push
past the point of magnetism and then better enable the magnets to do some
pushing
and pulling to better utilize their power. The result is greater efficiency
and more torque
in some applications. Magnets 906 may be aligned in that they are disposed
opposite
15 each
other (e.g., 180 degrees apart in a circumferential direction defined by the
axis of
the rotor) within housing 908.
[0045] FIG. 12 illustrates a 90-degree angular difference between the center
line of the
permanent magnets and the center line of the brushes. However, it is to be
understood
that this angle may vary from 90 degrees.
[0046] A gap between the permanent magnets and the rotor is shown in FIG. 12
to be
preferably about 0.078 inch. This relatively small gap may advantageously
produce a
high level of torque with the magnets being relatively close to the armature.
However, if
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more torque is needed for a particular application (e.g., a cordless chain
saw), then the
motor's rotational speed may be sacrificed (i.e., reduced) by further reducing
the gap.
Conversely, if more rotor speed is needed (e.g., for a cordless vacuum
cleaner), then
the motor's torque may be sacrificed (i.e., reduced) by increasing the gap.
Thus, this
invention provides a DC motor of variable design that affords the user to
custom design
and manufacture a DC motor depending on its intended field of use.
[0047] Another advantage of the above-described motor configuration is that it
may
enable magnetism to push the rotation of the rotor through the cycles rather
than
electricity providing the pushing force.
[0048] Although the invention has been described herein as being implemented
with
linear magnets, it is to be understood that it is within the scope of the
invention to use C-
shaped magnets, and particularly rare earth C-shaped magnets.
[0049] The foregoing detailed description is given primarily for clearness of
understanding and no unnecessary limitations are to be understood therefrom
for
modifications can be made by those skilled in the art upon reading this
disclosure and
may be made without departing from the spirit of the invention.
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