U.S. patent application number 10/317589 was filed with the patent office on 2004-06-17 for micro-beam friction liner and method of transferring energy.
Invention is credited to Mentesana, Charles.
Application Number | 20040113519 10/317589 |
Document ID | / |
Family ID | 32506165 |
Filed Date | 2004-06-17 |
United States Patent
Application |
20040113519 |
Kind Code |
A1 |
Mentesana, Charles |
June 17, 2004 |
Micro-beam friction liner and method of transferring energy
Abstract
A micro-beam friction liner adapted to increase performance and
efficiency and reduce wear in a piezoelectric motor or actuator or
other device using a traveling or standing wave to transfer energy
in the form of torque and momentum. The micro-beam friction liner
comprises a dense array of micro-beam projections having first ends
fixed relative to a rotor and second ends projecting substantially
toward a plurality of teeth of a stator, wherein the micro-beam
projections are compressed and bent during piezoelectric movement
of the stator teeth, thereby storing the energy, and then react
against the stator teeth to convert the stored energy stored to
rotational energy in the rotor.
Inventors: |
Mentesana, Charles;
(Leawood, KS) |
Correspondence
Address: |
THOMAS B. LUEBBERING
HOVEY WILLIAMS LLP
Suite 400
2405 Grand Boulevard
Kansas City
MO
64108
US
|
Family ID: |
32506165 |
Appl. No.: |
10/317589 |
Filed: |
December 12, 2002 |
Current U.S.
Class: |
310/323.09 |
Current CPC
Class: |
H02N 2/0065 20130101;
H02N 2/163 20130101 |
Class at
Publication: |
310/323.09 |
International
Class: |
H02N 002/00; H01L
041/04 |
Goverment Interests
[0001] The present invention was developed with support from the
U.S. government under Contract No. DE-AC04-01AL66850 with the U.S.
Department of Energy. Accordingly, the U.S. government has certain
rights in the present invention.
Claims
1. A friction liner adapted to facilitate a transfer of energy from
a driver component to a movable component, the friction liner
comprising: a plurality of projections, with each of the
projections having a first end fixed to the movable component and a
second end oriented substantially toward the driver component, and
each of the projections being bendable such that action by the
driver against the second ends of some or all of the plurality of
projections bends the some or all of the plurality of projections
and thereby stores energy which is released to the movable
component when the some or all of the plurality of projections
react by unbending against the driver component.
2. The friction liner as set forth in claim 1, wherein the friction
liner is incorporated into a piezoelectric device and the driver
component is a stator and the movable component is a rotor.
3. The friction liner as set forth in claim 1, wherein the friction
liner is coupled with a surface of the movable component so as to
be interposed between the driver component and the movable
component.
4. The friction liner as set forth in claim 1, wherein the friction
liner is adapted to facilitate transferring momentum and torque
from the driver component to the movable component.
5. The friction liner as set forth in claim 1, wherein the
plurality of projections are oriented to project perpendicularly
from the movable component toward the driver component.
6. The friction liner as set forth in claim 1, wherein the
plurality of projections are oriented to project
non-perpendicularly from the movable component toward the driver
component.
7. A piezoelectric device comprising: a driver component having
piezoelectric properties; a movable component adapted to move
relative to the driver component; and a friction liner interposed
between the driver component and the movable component and having a
plurality of projections oriented such that a wave moving through
the driver component acts against some or all of the plurality of
projections to thereby cause the movable component to move.
8. The piezoelectric device as set forth in claim 7, wherein the
driver component is a stator and the movable component is a
rotor.
9. The piezoelectric device as set forth in claim 7, wherein the
friction liner is coupled with a surface of the movable
component.
10. The piezoelectric device as set forth in claim 7, wherein the
friction liner is adapted to facilitate transferring momentum and
torque from the driver component to the movable component.
11. The piezoelectric device as set forth in claim 7, wherein the
some or all of the plurality of projections are adapted to bend in
response to the wave in the driver component, thereby storing
energy for transfer to the movable component.
12. The piezoelectric device as set forth in claim 7, wherein the
plurality of projections are oriented to project perpendicularly
from the movable component toward the driver component.
13. The piezoelectric device as set forth in claim 7, wherein the
plurality of projections are oriented to project
non-perpendicularly from the movable component toward the driver
component.
14. The piezoelectric device as set forth in claim 7, wherein the
wave is a traveling wave.
15. The piezoelectric device as set forth in claim 7, wherein the
wave is a standing wave.
16. A piezoelectric device comprising: a stator having
piezoelectric properties; a rotor adapted to move relative to the
first component; and a friction liner interposed between the stator
and the rotor having a plurality of projections oriented such that
a wave moving through the stator acts against some or all of the
plurality of projections, and wherein the plurality of projections
are adapted to receive, store, and release to the rotor an energy
associated with the wave, thereby facilitating a transfer of
momentum and torque from the stator to the rotor.
17. The piezoelectric device as set forth in claim 16, wherein the
friction liner is coupled with a surface of the rotor.
18. The piezoelectric device as set forth in claim 16, wherein the
plurality of projections are oriented to project perpendicularly
from the rotor toward the stator.
19. The piezoelectric device as set forth in claim 16, wherein the
plurality of projections are oriented to project
non-perpendicularly from the rotor toward the stator.
20. A method of facilitating a transfer of energy between a driver
component and a movable component in a piezoelectric device, the
method comprising the steps of: generating a wave in the driver
component, wherein the wave has an energy; receiving the energy at
a plurality of projections, wherein each of the projections are
bendable; storing the energy by bending some or all of the
plurality of projections; and releasing and transferring the energy
to the movable component by allowing the some or all of the
plurality of projections to unbend and react against the driver
component.
21. The method as set forth in claim 20, wherein the piezoelectric
device is a piezoelectric motor.
22. The method as set forth in claim 20, wherein the driver
component is a stator and the movable component is a rotor.
23. The method as set forth in claim 20, wherein the wave is a
traveling wave.
24. The method as set forth in claim 20, wherein the wave is a
standing wave.
Description
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates broadly to friction liners and
other mechanisms for enhancing a transfer of energy, in the form
of, for example, torque and momentum, between a stator or other
driver component and a rotor or other movable component. More
particularly, the present invention concerns a micro-beam friction
liner comprising a dense array of micro-beam projections having
first ends substantially fixed relative to a rotor and second ends
projecting substantially toward a plurality of teeth of a stator,
wherein the micro-beam projections compress and bend to store
energy during movement of the stator teeth and then react against
the stator teeth to convert the stored energy to rotational energy
in the rotor.
[0004] 2. Description of the Prior Art
[0005] Generally, a piezoelectric material expands and contracts
when an alternating voltage is applied across two opposing
surfaces. In a rotary embodiment, a piezoelectric motor comprises a
stator and a rotor, with the stator having a plurality of teeth
that, due to a traveling wave developed in the stator by
piezoelectric action, drives the rotor using elliptic motion of the
stator teeth to transfer torque and momentum. Commonly, a friction
liner is bonded to the rotor and the rotor and the friction liner
are spring-loaded against the stator in order to maximize the
transfer of torque and momentum therebetween.
[0006] Unfortunately, prior art friction liners are constructed of
such materials as hard metals or metal oxides or soft organic
polymers, and often experience slippage resulting in significant
energy loss and reduced torque transfer. Furthermore, because the
tangential velocity of each stator tooth varies at each point on
its elliptical path, and because the rotor's velocity can be
considered constant during one traversal of the ellipse, the
tangential velocity of each stator tooth can only match the rotor
velocity at one or two points along the elliptical path. Thus, the
majority of contact between the stator tooth and the rotor or the
friction liner involves slippage. Additionally, prior art friction
liners typically have low Q, or little dynamic action. Such dynamic
reaction force/impulse is thought to be one of the mechanisms
whereby torque is transferred between the stator and the rotor.
[0007] Due to the above-identified and other problems and
disadvantages in the art, a need exists for an improved friction
liner.
SUMMARY OF THE INVENTION
[0008] The present invention overcomes the above-described and
other problems and disadvantages in the prior art with a micro-beam
friction liner adapted to increase performance and efficiency and
reduce wear in a piezoelectric motor or actuator or other device
involving a transfer of energy in the form of, for example, torque
and momentum. The micro-beam friction liner of the present
invention can be incorporated, for example, into an otherwise
substantially conventional piezoelectric motor having a stator and
a rotor, with the stator including a plurality of teeth. A
traveling wave generated in the stator causes each stator tooth to
execute a circular or elliptical motion which is to be transferred
to the rotor.
[0009] In a preferred embodiment, the micro-beam friction liner of
the present invention is bonded to or otherwise coupled with the
rotor, so as to be interposed between the rotor and the stator
teeth. The micro-beam friction liner broadly comprises a dense
plurality or array of micro-beam projections, each having a first
end fixed relative to the rotor and a second end projecting
therefrom substantially toward the stator teeth.
[0010] In operation, the second ends of some or all of the
plurality of micro-beam projections make contact with the stator
teeth moving relative to the rotor during an elliptic traversal. As
each stator tooth moves up and tangentially ahead of the rotor, a
number of the micro-beam projections contact the stator tooth and
are compressed and bent in the direction of rotation. As the stator
tooth completes the elliptic path traversal, the micro-beam
projections react against the stator tooth to convert energy stored
in compression and bending to rotational energy in the rotor.
[0011] It will be appreciated that the concept of the micro-beam
friction liner can also be expressed as a method of facilitating a
transfer of momentum and torque from the stator to the rotor. First
the traveling wave is generated through piezoelectric action, with
the wave having a certain energy. This energy is then transferred
to the micro-beam projections and stored in the form of compression
and bending. Lastly, the micro-beam projections react against the
stator teeth as they decompress and unbend and thereby transfer the
stored energy to the rotor.
[0012] Thus, it will be appreciated that the micro-beam friction
liner of the present invention provides a number of substantial
advantages over the prior art, including, for example, increased
performance and efficiency through improved torque transfer, and
reduced wear through decreased slippage. Furthermore, the
micro-beam friction liner allows for replacement of organic and
polymer friction materials used in prior art friction liners with
inorganic materials, primarily metals, to further increase friction
and wearability. Additionally, the micro-beam friction liner has a
high Q, or increased reaction forces, which is believed to play an
important role in transferring torque and momentum.
[0013] These and other important features of the present invention
are more fully described in the section titled DETAILED DESCRIPTION
OF A PREFERRED EMBODIMENT, below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] A preferred embodiment of the present invention is described
in detail below with reference to the attached drawing figures,
wherein:
[0015] FIG. 1 is an exploded view of a piezoelectric motor
incorporating a preferred embodiment of the micro-beam friction
liner of the present invention;
[0016] FIG. 2 is a fractional magnified view of a surface of the
micro-beam friction liner of FIG. 1 showing a plurality of
micro-beam projections; and
[0017] FIG. 3 is a block diagram of preferred steps in the
operation of the micro-beam friction liner of FIG. 1.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0018] Referring to FIG. 1, a micro-beam friction liner 10 is shown
constructed in accordance with a preferred first embodiment of the
present invention. The micro-beam friction liner 10 is adapted to
increase performance and efficiency and reduce wear in a
piezoelectric motor 12 or actuator or other device involving a
transfer of energy, in the form of, for example, torque and
momentum, between a stator 14 or other driver component and a rotor
16 or other movable component.
[0019] As illustrated, the piezoelectric motor 12 is substantially
conventional in both form and function, and includes the
aforementioned stator 14 and rotor 16. The stator 14 includes a
piezoelectric ceramic element 18 bonded to a metal ring 20, with
the metal ring 20 having a plurality of projecting teeth 22. The
rotor 16 may be spring-loaded to enhance contact with the stator
14. Broadly, the piezoelectric element 18 expands and contracts
when an alternating voltage is applied across two opposing
surfaces. A thin metal electrode is deposited on the piezoelectric
element 18 in sections, and each such section is conditioned
(poled) such that when the alternating voltage is applied across
the entire piezoelectric element 18, one section will expand or
contract while adjacent sections correspondingly contract or
expand. This results in alternating expansions and contractions
that give rise to two standing waves that combine to form a
traveling wave. As the wave travels through the stator 14, each
stator tooth 22 executes a circular or elliptical motion. It is
desirable to transfer to the rotor 16 as much as possible of the
energy associated with this circular or elliptical motion. When the
applied alternating voltage is at the natural resonant frequency of
the metal ring 20, which is typically approximately between 30 kHz
and 120 kHz, the elliptical motion movements will be approximately
between 50 micro-inches and 400 micro-inches.
[0020] In a preferred embodiment, referring also to FIG. 2, the
micro-beam friction liner 10 of the present invention is interposed
between the rotor 16 and the stator teeth 22 to enhance the
transfer of energy therebetween. The micro-beam friction liner 10
may be fabricated using polymer materials, including, for example,
Teflon, PTFE, PBT, PEEK, and PPS, and may be fiber-reinforced as
necessary or desirable. Furthermore, the micro-beam friction liner
10 may be fabricated as a discrete component and then coupled with
the rotor 16, such as, for example, by chemical bonding or
mechanical fastening, or may be fabricated directly on the rotor
16, such as, for example, by application thereto as a liquid
coating.
[0021] The micro-beam friction liner 10 broadly comprises a dense
plurality or array of micro-beam projections 24, each having a
first end 26 substantially fixed relative to the rotor 16 and a
second end 28 projecting therefrom substantially toward the stator
teeth 22. The second end 28 may be coated with an appropriate
friction-enhancing material, such as, for example, a metal oxide
(e.g., TiN, Al.sub.2O.sub.3, NiP, alumite) or a polymer. Such
coating may be accomplished using any suitable process, including,
for example, sputtering or plasma spraying.
[0022] Design considerations for the micro-beam projections 24
include various material properties, such as, for example, modulus
of elasticity and density; physical dimensions and cross-section
geometry; stiffness; spacing; number per unit area or ratio to
stator tooth area; and array pattern. These considerations may be
greatly dependent on application and use. In an 8 mm piezoelectric
motor, for example, the micro-beam projections 24 can be fabricated
using a LiGA process to have a cross-section of 0.001 inch by
0.0026 inch, a length of 0.0065 inch, and a spacing of 0.001 inch.
This results in approximately thirty-six of the micro-beam
projections 24 contacting a stator tooth 22 during a contact event.
Regardless, however, of the actual design parameters used, it may
be preferable that the stator teeth 22 contact an approximately
equal number of the micro-beam projections 24 during each contact
event so as to avoid a variable torque output.
[0023] Another important design consideration is the angle at which
the micro-beam projections 24 project toward the stator 14. In a
bi-directional motor, the angle of projection is preferably
approximately 90.degree. so as to accommodate traveling waves from
both forward and reverse directions. In a uni-directional motor,
however, wherein the traveling waves move in only one direction,
performance may be improved with an angle of projection that is
greater or less than 90.degree. in the direction of the traveling
waves.
[0024] Another important design consideration is resonant
frequency. If the resonant frequency of the micro-beam projections
24 is large compared to the stator drive frequency, then the
micro-beam projections 24 will respond without lag to movement of
the stator teeth 22 and will return to their rest positions prior
to the next elliptic traversal. If, however, the resonant frequency
of the micro-beam projections 24 is adjusted to synchronize their
movements with that of the stator teeth 22, then the micro-beam
projections 24 will be optimally positioned for the next elliptic
traversal.
[0025] Techniques for fabricating the micro-beam projections 24 may
depend on the size of the piezoelectric motor 12 into which the
micro-beam friction liner 10 is to be incorporated. In large
piezoelectric motors, the micro-beam projections 24 may be
manufactured using traditional machining methods, such as, for
example, mechanical milling, chemical milling/etching, or
electrical discharge machining (EDM). In extremely small
piezoelectric motors, the micro-beam projections 24 may be
manufactured using LiGA or MEMS-type photolithographic processing
and micro-EDM processing.
[0026] It will be appreciated that the concept of the micro-beam
friction liner 10 can also be characterized and expressed as a
method of facilitating a transfer of energy, in the form of, for
example, momentum and torque, from the stator 14 to the rotor 16.
Referring to FIG. 3, first the wave is generated through
piezoelectric action, as depicted in box 50, wherein the wave has a
certain energy. Next, the energy of the wave is transferred to and
stored in the micro-beam projections 24 in the form of compression
and bending, as depicted in box 52. This occurs as the second ends
28 of the plurality of micro-beam projections 24 make contact with
the stator teeth 22 moving relative to the rotor 16 during an
elliptic traversal, and, as each stator tooth 22 moves up and
tangentially ahead of the rotor 16, a number of the micro-beam
projections 24 are compressed and bent in the direction of
rotation. Lastly, as the stator tooth 22 completes the elliptic
path traversal, the micro-beam projections 24 react against the
stator tooth 22 as they decompress and unbend and thereby transfer
the stored energy to the rotor 16 in the form of momentum and
torque, as depicted in box 54.
[0027] It will also be appreciated that, although described herein
in the context of facilitating the transfer of torque and momentum
from elliptical motion caused by traveling waves, the micro-beam
friction liner 10 of the present invention may also be used to
facilitate a transfer of energy in non-elliptic contact motors,
such as, for example, standing wave motors which rely more on
impact rather than contact along an elliptical path.
[0028] From the preceding description, it will be appreciated that
the micro-beam friction liner 10 of the present invention provides
a number of substantial advantages over the prior art, including,
for example, increased performance and efficiency through improved
torque transfer, and reduced wear through decreased slippage.
Furthermore, the micro-beam friction liner 10 allows for
replacement of organic and polymer friction materials used in prior
art friction liners with inorganic materials, primarily metals, to
further increase friction and wearability. Additionally, the
micro-beam friction liner 10 has a high Q, or increased reaction
forces, which is believed to play an important role in transferring
torque and momentum.
[0029] Although the invention has been described with reference to
the preferred embodiments illustrated in the attached drawings, it
is noted that equivalents may be employed and substitutions made
herein without departing from the scope of the invention as recited
in the claims. It will be appreciated, for example, that the
micro-beam friction liner of the present invention can be adapted
for use in substantially any device that uses traveling or standing
waves to transfer energy from a driver to a movable element,
including, for example, both linear and rotary piezoelectric motors
and actuators.
[0030] Having thus described the preferred embodiment of the
invention, what is claimed as new and desired to be protected by
Letters Patent includes the following:
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