Patent Grant
8272851
1) Field of Invention
This invention relates generally to apparatus and methods for conveying energy into a volume of fluid and more specifically to the field of linear pumps, linear compressors, synthetic jets, resonant acoustic systems and other fluidic devices.
2) Description of Related Art
For the purpose of conveying energy to fluids within a defined enclosure, prior technologies have employed a number of approaches, including positive displacement, agitation such as with mechanical stirring or the application of traveling or standing acoustic waves, the application of centrifugal forces and the addition of thermal energy. The transfer of mechanical energy to fluids by means of these various methods can be for a variety of applications, which could include for example, compressing, pumping, mixing, atomization, synthetic jets, fluid metering, sampling, air sampling for bio-warfare agents, ink jets, filtration, driving physical changes due to chemical reactions, or other material changes in suspended particulates such as comminution or agglomeration, or a combination of any of these processes, to name a few.
Within the category of positive displacement machines, diaphragms have found widespread use. The absence of frictional energy losses makes diaphragms especially useful in downsizing positive displacement machines while trying to maintain high energy efficiency. The interest in MESO and MEMS scale devices has lead to even further reliance on diaphragm type and diaphragm/piston (i.e. a piston with a flexible surround) type devices for conveying energy into fluids within small pumps or other fluidic devices. The term “pump” as used herein refers to devices designed for providing compression and/or flow for either liquids or gases. The term “fluid” used herein is understood to include both the liquid and the gaseous states of matter.
The actuators used to drive larger diaphragm pumps have proved problematic for MESO or MEMS machines since it is difficult to maintain their efficiency and low cost as they are scaled down in size. For example, the air gaps associated with electromagnetic and voice coil type actuators must be scaled down in order to maintain high transduction efficiency and this adds manufacturing complexity and cost. Also, motor laminations become magnetically saturated as motors are scaled down while seeking to maintain a constant mechanical power output. Within acceptable product cost targets, it is widely accepted that the electro-mechanical efficiency of these transducers will drop off significantly with size reduction.
These scaling challenges, associated with conventional magnetic actuators, have led to the widespread use of other technologies, such as electrostrictive actuators (e.g. piezoceramics), piezoceramic benders, electro-static and magnetostrictive actuators for MESO and MEMS applications. A piezo bender disk can naturally combine the fluid diaphragm and actuator into a single component.
The advantages of using the piezo as the fluidic diaphragm are offset by the piezo's inherent displacement limitations. Since ceramics are relatively brittle, piezoceramic diaphragms/disks can only provide a small fraction of the displacements provided by other materials such as metals, plastics, and elastomers, for example. The peak oscillatory displacements that a clamped circular piezoceramic disk can provide without failure are typically less than 1% of the disk's clamped diameter. Since diaphragm displacement is directly related to the fluidic energy transferred per stroke, piezo benders impose a significant limitation on the power density and overall performance of small fluidic devices such as MESO-sized pumps and compressors. These displacement-related energy limitations are especially true for gases.
Other types of piezo actuators that depend on the bulk flexing properties of the piezo material can provide high energy transfer to liquids by operating at very high frequencies, but at even smaller strokes. These small actuator strokes make the design of pumps impractical. Further, high-performance pumps employ passive valves that open and close each pumping cycle to provide optimal pumping efficiency. These pump valves may not provide the needed performance in the kHz-MHz frequency range that bulk-piezo actuators need to transfer sufficient energy.
Currently, the demand is increasing for ever smaller fluidic devices which may not be attainable or functionally consistently useful with current piezo pump technology. For example, pumps and compressors are needed that can provide higher power densities and specific flow rates (i.e. fluid volume flow rate divided by the pump's physical volume) at higher pressure heads and in ever smaller sized units. Examples of applications that require high performance MESO-sized pumps include the miniaturization of fuel cells for portable electronic devices such as portable computing devices, PDAs and cell phones; self-contained thermal management systems that can fit on a circuit card and provide cooling for microprocessors and other semi-conductor electronics and portable personal medical devices for ambulatory patients. Thus, there is a need for a compact economically viable piezo pump that remedies at least some of the deficiencies of current piezo pumps.
To satisfy these needs and overcome the limitations of previous efforts, the present invention is provided as a fluid energy-transfer device that uses new floating reaction-drive actuators for driving diaphragm and piston fluidic devices, such as pumps, compressors, synthetic jets and acoustic devices at a drive frequency and sometimes at or near their system resonance. To further satisfy these needs and overcome the limitations of previous efforts, the present invention is provided as a fluid energy-transfer device that enables the use of low-stroke high-force actuators for driving large diaphragm and piston strokes for fluidic devices, such as pumps, compressors and synthetic jets at a drive frequency and sometimes at or near their system resonance.
A fluidic energy transfer device according to one embodiment comprises a fluid chamber having an inner wall shaped so as to form a chamber volume with an opening and a fluidic diaphragm being rigidly attached to the perimeter of the opening and with a variable reluctance actuator being attachment to the fluidic diaphragm. The reaction-drive energy-transfer device according to some embodiments of the present invention provides a unique system for driving displacements of the fluidic diaphragm which can be an order of magnitude larger than the displacement of prior piezo diaphragms.
The reaction-drive system according to most embodiments of the present invention enables high-performance for devices such as MESO-sized pumps, compressors, synthetic jets and acoustic devices. The pumps and compressors according to some embodiments of the present invention may include tuned ports and valves that allow low-pressure fluid to enter and high-pressure fluid to exit a compression chamber in response to the cyclic compressions. The reaction-drive system may use a variety of actuators, such as bender actuator comprising uni-morph, bi-morph and multilayer PZT benders, piezo-polymer composites such as PVDF, crystalline materials, magnetostrictive materials, electroactive polymer transducers (EPTs), electrostrictive polymers and various “smart materials” such as shape memory alloys (SMA), radial field PZT diaphragm (RFD) actuators, as well as variable reluctance actuators and voice coil actuators.
The fluidic devices according to the present invention can be operated at a drive frequency that allows energy to be stored in the system's mechanical resonance, thereby providing diaphragm or piston displacements that can be larger and typically much larger that the actuator's displacements. The system resonance may be determined based on the effective moving mass of the diaphragm, actuator and related components and on the spring stiffness of the fluid, the fluidic diaphragm, and other optional mechanical springs; and or other components/environments that influence the resonant frequency.
The pumps according to some embodiments of the present invention may be utilized in a variety of applications including by way of example only the general compression of gases such as air, hydrocarbons, process gases, high-purity gases, hazardous and corrosive gases, with the compression of phase-change refrigerants for refrigeration, air-conditioning and heat pumps with liquids, and other specialty vapor-compression or phase-change heat transfer applications. The pumps according to some embodiments of the present invention may also pump liquids such as fuels, water, oils, lubricants, coolants, solvents, hydraulic fluid, toxic or reactive chemicals, depending on the particular pump design. The pumps of the present invention can also provide variable capacity for either gas or liquid operation.
More specifically, an exemplary embodiment of the present invention includes a fluid chamber having an inner wall shaped so as to form a chamber volume and having an opening. A fluidic diaphragm or piston is rigidly attached to the perimeter of the opening in the fluid chamber and the diaphragm or piston has a flexible portion capable of moving with respect to the outer perimeter between a plurality of first positions and a plurality of second positions, the first and second positions being of varying distances from the inner wall of the fluidic chamber. The chamber is filled with a fluid that comprises part of the load of the system. The fluid within the fluid chamber comprises a spring and the fluidic diaphragm also comprises a spring. An actuator having an attachment point is attached to the fluidic diaphragm. A mass-spring mechanical resonance frequency is determined by the combined effective moving masses of the actuator and diaphragm or piston and by the mechanical spring and the gas spring, and the actuator is operable over a range of drive frequencies with some frequencies resulting in energy being stored in the mass-spring mechanical resonance and providing displacements of the fluidic diaphragm or piston that are larger (and in many instances much larger) than the displacements of the actuator, such that increased energy is transferred to the fluidic load within the fluid chamber.
In another embodiment of the invention, there is a fluid energy transfer device comprising:
a chamber for receiving a fluid, at least a portion of the chamber comprising a movable portion relative to another portion of the chamber, the movable portion being adapted to change the volume of the chamber from a first volume to a second volume by movement of the movable portion; and
a variable reluctance actuator attached to the movable portion;
wherein the variable reluctance actuator is at least one of (i) connected directly to the movable portion and (ii) linked to the movable portion, to form a actuator-movable portion assembly;
wherein the variable reluctance actuator is effectively not connected and effectively not linked to any other component of the device other than the movable portion; and
wherein the actuator-movable portion assembly is adapted to move substantially only due to oscillation of the actuator at a drive frequency.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the actuator is driven at a frequency so as to store energy in the system resonance such that the displacements of the movable portion increase proportionately with the stored energy.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the actuator is resiliently connected to a component of the device that is separate from the movable portion.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein an air gap of the variable reluctance actuator is adapted to oscillate at a displacement amplitude and frequency such that the actuator and moving portion will move between a first position and a second position substantially only due to the displacement of the actuator, and wherein the distance between the first position and the second position is greater than the displacement amplitude of the actuator air gap.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the movable portion comprises a diaphragm.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the movable portion comprises a piston with a flexible surround.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the device further comprises;
a fluid inlet port in fluid communication with the chamber; and
a fluid outlet port in fluid communication with the chamber;
wherein the device is adapted to draw fluid into the chamber through the inlet port during movement of the movable portion in a manner that increases the volume of the chamber, and
wherein the device is adapted to expel fluid out of the chamber through the outlet port during movement of the movable portion in a manner that decreases the volume of the chamber.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein an opening in the chamber is provided that allows fluid to enter and exit the chamber, and wherein the oscillating flow through said opening creates a synthetic jet.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the chamber movable portion comprises a bellows.
In another embodiment of the invention, there is a fluid energy transfer device comprising:
a chamber for receiving a fluid, at least a portion of the chamber comprising a movable portion relative to another portion of the chamber, the movable portion being is adapted to change the volume of the chamber from a first volume to a second volume by movement of the movable portion; and
an electro-active actuator attached to the movable portion;
wherein the electro-active actuator is at least one of (i) connected directly to the movable portion and (ii) linked to the movable portion, to form a actuator-movable portion assembly;
wherein the electro-active actuator is effectively not connected and effectively not linked to any other component of the device other than the movable portion; and
wherein the actuator-movable portion assembly is adapted to move substantially only due to oscillation of the actuator at a drive frequency.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein a reaction mass is attached to the electro-active actuator
In another embodiment of the present invention, there is a fluid transfer device comprising:
a chamber for receiving a fluid, at least a portion of the chamber comprising a flexible portion being movable relative to another portion of the chamber such that a maximum deflection point on the flexible portion provides larger displacements than any other points on the flexible portion, the flexible portion being adapted to change the volume of the chamber from a first volume to a second volume by bending of the flexible portion; and
a force generating actuator being attached to the flexible portion at a point other than the maximum deflection point;
wherein the force generating actuator is at least one of (i) connected directly to the flexible portion and (ii) linked to the flexible portion, to form a actuator-movable portion assembly;
wherein the force generating actuator is effectively not connected and effectively not linked to any other component of the device other than the flexible portion; and
wherein the actuator-movable portion assembly is adapted to move substantially only due to oscillation of the actuator at a drive frequency.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the diaphragm further comprises a central piston section that becomes the maximum deflection point.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the flexible portion comprises a bellows having at least one bellows section.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the bellows further comprises a central piston section that becomes the maximum deflection point.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein said force generating actuator comprises a bender actuator.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein said force generating actuator comprises a variable reluctance actuator.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein said force generating actuator comprises a solid electro-active actuator.
In another embodiment of the present invention, there is a fluid transfer device comprising:
a chamber for receiving a fluid, at least a portion of the chamber comprising a flexible portion being movable relative to a second portion of the chamber, the flexible portion being adapted to change the volume of the chamber from a first volume to a second volume by bending of the flexible portion; and
a pivot clamp that clamps the flexible portion around a closed loop of the flexible portion thereby dividing the flexible portion into 2 sections comprising an inner section within the closed loop and an outer section outside of the closed loop, with the pivot clamp allowing the outer section and inner section to pivot about the pivot clamp such that the displacements of the inner and outer sections are in opposite directions, and
at least a single force-generating actuator having an attachment point to the outer section of the flexible portion;
wherein the force generating actuator is at least one of (i) connected directly to the outer section of the flexible portion and (ii) linked to the outer section of the flexible portion, to form a actuator-movable portion assembly;
wherein the force generating actuator is effectively not connected and effectively not linked to any other component of the device other than the outer section of the flexible portion; and
wherein the actuator-movable portion assembly is adapted to move substantially only due to oscillation of the actuator at a drive frequency.
In another embodiment of the present invention, there is a fluid transfer device comprising:
a chamber for receiving a fluid, at least a portion of the chamber comprising a first flexible portion being movable relative to a second portion of the chamber such that a maximum deflection point on the first flexible portion provides larger displacements than any other points on the first flexible portion, the first flexible portion being adapted to change the volume of the chamber from a first volume to a second volume by bending of the first flexible portion; and
at least a single force-generating actuator having an attachment point to the flexible portion at a point other than the maximum deflection point and an attachment point to the second portion of the chamber;
wherein the force-generating actuator exerts alternating forces between the flexible portion of the chamber and the second portion of the chamber with corresponding changes in the chamber volume; and
wherein the resulting peak displacement of the maximum deflection point is greater than the displacement of the force generating actuator.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein:
the second portion of the chamber comprises a second flexible portion of the chamber movable relative to the first flexible portion of the chamber, such that a maximum deflection point on the second flexible portion provides larger displacements than any other points on the second flexible portion, and
the force-generating actuator also having an attachment point to the second flexible portion at a point other than its maximum deflection point,
wherein the force-generating actuator exerts alternating forces between the first and second flexible portions of the chamber thereby resulting in peak displacements, between the maximum deflection points of the first and second flexible chamber portions, that are greater than the displacement of the force generating actuator.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein first flexible portion comprising a first piston with a flexible surround, and the second flexible portion comprising a second piston with a flexible surround.
In another embodiment of the present invention, there is a fluid transfer device comprising:
a chamber for receiving a fluid, at least a portion of the chamber comprising a first flexible portion being movable relative to a second portion of the chamber, the first flexible portion being adapted to change the volume of the chamber from a first volume to a second volume by bending of the first flexible portion; and
at least a single force-generating actuator having an attachment point to the first flexible portion at a point of zero flexing displacement and an attachment point to the second portion of the chamber and generating forces in the direction of the first flexible portion's flexing displacement;
wherein the force-generating actuator exerts alternating forces between the flexible portion of the chamber and the second portion of the chamber with changes in the chamber volume resulting from the instantaneous sum of the actuator displacement and the flexing displacement of the first flexible portion.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein
a fluid inlet port in fluid communication with the chamber; and
a fluid outlet port in fluid communication with the chamber;
wherein the device is adapted to draw fluid into the chamber through the inlet port during movement of the flexible portion in a manner that increases the volume of the chamber, and
wherein the device is adapted to expel fluid out of the chamber through the outlet port during movement of the flexible portion in a manner that decreases the volume of the chamber.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein:
the second portion of the chamber comprises a second flexible portion of the chamber movable relative to the first flexible portion of the chamber, and
the force-generating actuator also having an attachment point to the second flexible portion at a point of zero flexing displacement of the second flexible portion,
wherein the force-generating actuator exerts alternating forces between the first and second flexible portions of the chamber thereby resulting in peak displacements, between the maximum deflection points of the first and second flexible chamber portions, that are greater than the axial displacements of the force generating actuator.
In another embodiment of the present invention, there is a fluid transfer device comprising:
a chamber for receiving a fluid, at least a portion of the chamber comprising a first flexible portion being movable relative to a second portion of the chamber, the first flexible portion being adapted to change the volume of the chamber from a first volume to a second volume by bending of the first flexible portion; and
at least a single force-generating actuator having an attachment point to the first flexible portion at a point of zero flexing displacement and generating forces in a direction transverse to first flexible portion's flexing displacement;
wherein the force-generating actuator exerts alternating transverse forces on the first flexible portion of the chamber and with resulting changes in the chamber volume resulting from axial vibrations of the first flexible portion.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein:
the second portion of the chamber comprises a second flexible portion of the chamber movable relative to the first flexible portion of the chamber; and
the force-generating actuator also having an attachment point to the second flexible portion at a point of zero flexing displacement of the second flexible portion and generating forces in a direction transverse to the second flexible portion's flexing displacement;
wherein the force-generating actuator exerts alternating transverse forces on the first and second flexible portions of the chamber thereby resulting in with resulting changes in the chamber volume resulting from axial vibrations of the first and second flexible portions.
In another embodiment of the present invention, there is a fluid transfer device comprising:
a chamber for receiving a fluid, at least a portion of the chamber comprising a first flexible portion being movable relative to a second portion of the chamber, the first flexible portion being adapted to change the volume of the chamber from a first volume to a second volume by bending of the first flexible portion; and
a force-generating actuator having an attachment point to the center of first flexible portion and generating forces in a direction transverse to first flexible portion's axial flexing displacement;
wherein the force-generating actuator exerts alternating transverse forces on the first flexible portion of the chamber with resulting changes in the chamber volume resulting from axial vibrations of the first flexible portion.
In another embodiment of the present invention, there is a fluid transfer device comprising:
a chamber for receiving a fluid, at least a portion of the chamber comprising a flexible portion being movable relative to a second portion of the chamber, the flexible portion being adapted to change the volume of the chamber from a first volume to a second volume by bending of the flexible portion; and
a pivot clamp that clamps the flexible portion around a closed loop of the flexible portion thereby dividing the flexible portion into 2 sections comprising an inner section within the closed loop and an outer section outside of the closed loop, with the pivot clamp allowing the outer section and inner section to pivot about the pivot clamp such that the displacements of the inner and outer sections are in opposite directions, and
at least a single force-generating actuator having an attachment point to the outer section of the flexible portion and an attachment point to the pivot clamp and generating forces in the same direction as the flexible portion's flexing displacement;
wherein the force-generating actuator exerts alternating forces between the pivot clamp and the outer section of flexible portion with changes in the chamber volume resulting from the flexing of the flexible portion.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below for transferring energy to acoustic resonators.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the acoustic resonator comprises a resonant synthetic jet.
In another embodiment of the present invention, there is a fluid transfer device as described above and/or below, wherein the acoustic resonator comprises the resonator of an acoustic compressor.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the inventions. In the drawings:
In this section, descriptions of the embodiments of the present invention are organized under subheadings that describe the forces being applied to the diaphragms or pistons of the present invention. The force designations generally indicate the direction of the force with respect to the diaphragm/piston axis (i.e. axial or radial) and the point of application (e.g. on-center/axis, off-center, or at the clamp point).
Reaction-Drive Topologies
PCT patent application PCT/US2005/046557 describes reaction-drive devices with floating bender actuators (such as piezoceramics or any number of other electro-active actuators) the contents of which are incorporated herein by reference in their entirety. The floating-actuator dynamics of reaction-drive systems enables the use of high-force low-stroke actuators, thereby eliminating the expensive electric motors which drive conventional pumps and compressors. The present invention provides further actuators that can be used in reaction-drive systems. For the reaction-drive embodiments the forces are axially directed. The reaction-drive actuators are grouped into two different classes based on where their forces are applied to the fluidic system: (i) axial or piston driven and (ii) off-axis driven.
On-Axis and/or Piston Driving
The actuators discussed under this heading are used for either driving a diaphragm at its center or driving a piston.
Referring now to
In operation, an alternating voltage waveform of frequency f is applied to the coil of motor 20 creating a time varying force at frequency 2f which causes motor elements 24 and 26 to vibrate 180° out of phase with each other. The mass of component 24 will typically be smaller than the mass of component 26, thus causing the amplitude of component 24 to be larger than that of component 26. The motion of component 24 is directly transferred to diaphragm 16 via standoff 18, which in turn transfers energy to the fluid within fluid chamber 15. The reaction-drive fluidic system of
If a drive frequency f is chosen to be near or equal to the ½ the system's fundamental resonant frequency fo, then energy may be stored in the resonance in proportion to both the system's resonance quality factor Q and the proximity of the drive frequency f to the resonance frequency fo. As energy is stored in the system's resonance, the displacement of diaphragm 16 can exceed the actual air gap oscillation of motor 20. In this way, a low-displacement VR motor may be used to provide the higher diaphragm displacements required by current MESO and MEMS fluidics applications. Since the only substantial (or otherwise effective) mechanical connection to motor 20 of
Drive frequencies that result in stored energy and drive frequencies that do not result in stored energy are both considered within the scope of the present invention regardless of the particular embodiment.
The magnetic force generated by a VR motor can be approximated by Fmag=Li/2G, where L is the motor's inductance, i is the current and G is the air gap distance. Motor losses vary with i and the force generated for a given current will vary with the inverse of the air gap distance G. Consequently, the motor's efficiency will also vary inversely with G. As explained above, in a reaction-drive system the air gap need not oscillate at the same amplitude as the fluid diaphragm. Consequently, small air-gaps can be used which enables high transduction efficiencies in small VR motors. The combination of Reaction-Drive and variable reluctance actuators eliminates the need for high-cost conventional miniature electric motors. In
While motor 2 of
Many enhancements can be made to the reaction-drive device shown in
In operation, motor 76 drives bellows 82 resulting in a volume oscillation of compression chamber 84 and consequent fluid compression and flow, whereby fluid enters pump body 80 through port 88 and exits through port 86. Operating the device at or near its system resonant frequency will result in piston displacements becoming larger in proportion to the energy stored in the system. Although the pump in
In order to explain the operation of actuator 102, it is assumed that actuator 102 is made from a piezoceramic material. The orientation of actuator 102 is such that the application of an electric field of given polarity will cause the Z dimension of actuator 102 to contract. Upon reversing the field polarity, the Z dimension of actuator 102 will expand. When an electric field having a polarity that oscillates at frequency f is applied, then the actuator's Z dimension will oscillate at frequency f. It is intended that the electro-active actuator type will be chosen so that the principle vibrations of actuator 102 will be axial.
In operation, the Z axis vibrations of actuator 102 will cause diaphragm 100 to vibrate thereby transferring energy to the fluid within fluid chamber 105. In order to increase the diaphragm displacements and fluid energy transfer, an oscillating electric field is applied to actuator 102 having a frequency that is close enough to the system resonance frequency such that energy is stored in the system resonance resulting in diaphragm displacements that are proportional to the stored energy. The closer the drive frequency is to the instantaneous system resonance frequency, the greater the stored energy and the greater the fluid energy transfer. Drive frequencies that result in stored energy and drive frequencies that do not result in stored energy are both within the scope of the present invention regardless of the particular embodiment.
In
Many different electro-active actuators could be used within the scope of the embodiments of
It is understood for the embodiments of
The electro-active actuator embodiments of
For the sake of explanation, it is assumed that actuators 460 and 462 are solid electro-active actuators, such as piezoceramics, although any of the actuators discussed in connection with the present invention could alternatively be used. In operation, actuators 460 and 462 are energized with an alternating electric field of frequency f and the resulting cyclic displacement of actuators 460 and 462 cause the volume of bellows 450 to vary at frequency f. The resulting time varying pressure within bellows 450 will cause fluid to be drawn into port 472 and expelled from port 474. Optional reaction mass 464 and 466 can be used to tune the system's resonant frequency. Operating the pump of
Off Axis Driving
Off-axis driving provides a means to tune the impedance of the load to the impedance of the actuator in a reaction-drive system and can also be used to reduce the acceleration-related stresses on the actuator.
As is characteristic for Reaction-Drive systems, bender actuator 120 rides along with, or floats with, the displacements of diaphragm 122. Even though the bending displacements of bender actuator 120 can be much smaller than the bending displacements of diaphragm 122, actuator 120 can experience additional stresses related to riding along with the high accelerations of diaphragm 122. The off-axis driving system of
In the operation, bender actuators 148 and 146 would be energized so as to apply oscillating and opposing forces to bellows 140, which in turn causes pistons 144 and 142 to vibrate 180° out of phase with each other. If the frequency of the applied force is at or near to the system's resonant frequency, then large piston displacements will result with consequent fluid compression and flow, whereby fluid enters pump body 138 through port 162 and exits through port 164. In the embodiment of
In operation, the Z axis vibrations of actuator 166 will cause diaphragm 168 to vibrate thereby transferring energy to the fluid within fluid chamber 171. In order to increase the diaphragm displacements and fluid energy transfer, an oscillating electric field is applied to actuator 166 having a frequency that is close enough to the system resonance frequency such that energy is stored in the system resonance resulting in diaphragm displacements that are proportional to the stored energy.
If diaphragm 430 is excited by actuator 432 at a frequency f that is below the higher ordered resonant modes of diaphragm 430, then the diaphragm will respond by oscillating in its fundamental axial mode shape at frequency f. If diaphragm 430 is driven at a frequency f that is near or equal to the system fundamental resonance frequency, then energy will be stored in the system resonance and the displacements of diaphragm 430 will increase proportionately to the stored energy. The system resonance can be tuned using optional mass 442. Mass 442 and actuator for 432 are always moving in opposite directions, so by choosing the correct masses the forces that they exert on enclosure 434 can be reduced or canceled, thereby reducing enclosure vibrations and associated noise.
The embodiment of
Many improvements and modifications can be made to the Reaction-Drive embodiments of the present invention and will be obvious to those who are skilled in the art. For example, unsupported actuator wire leads may experience excessive stresses due to actuator vibration. A solution to this problem is illustrated by referring to
Mechanically Grounded Actuators
For the following embodiments of the present invention the actuator does not float but instead is mechanically grounded to the housing of the fluidic device.
Off-Axis Driving
The fluidic energy transfer system of
In operation, the Z axis vibrations of actuator 190 will cause diaphragm 196 to vibrate thereby transferring energy to the fluid within fluid chamber 200. In order to increase the diaphragm displacements and fluid energy transfer, an oscillating electric field is applied to actuator 190 having a frequency that is close enough to the system resonance frequency such that energy is stored in the system resonance resulting in diaphragm displacements that are proportional to the stored energy. The closer the drive frequency is to the instantaneous system resonance frequency, the greater the stored energy and the greater the fluid energy transfer. Drive frequencies that result in stored energy and drive frequencies that do not result in stored energy are both within the scope of the present invention regardless of the particular embodiment.
For the sake of explanation, it is assumed that actuators 260 and 262 are piezoceramic actuators although any of the actuators discussed in connection with the present invention could alternatively be used. In operation, actuators 260 and 262 are energized with an alternating electric field of frequency f and the resulting cyclic displacements of actuators 260 and 262 cause the volume of bellows 258 to vary at frequency f. The resulting time varying pressure within bellows 258 will cause fluid to be drawn into port 276 and dispelled from port 278. Optional reaction mass 280 and 282 can be used to tune the system's resonant frequency. Operating the device of
An alternative design for the pump of
Clamp Driving
In the previously described embodiments of the present invention, springs, bellows or other fluidic components are typically clamped to the housing body and a flexible portion of the spring or diaphragm is driven by an actuator. The characteristic difference of clamp driving is that the actuator drives the clamp point of the spring, diaphragm or other fluidic component. For sake of definition, the clamp-point or clamp-section of a bending member is the portion that cannot bend or flex due to the clamp, nevertheless the clamp point can usually move with respect to the device housing.
Axial Clamp Driving
The embodiment of the
Since the actuators of
Radial Clamp Driving
In the Following embodiments the forces exerted on the clamp point are in the radial direction.
If diaphragm 324 is excited at a frequency f that is below the higher ordered resonant modes of the diaphragm 324, then the diaphragm will respond by oscillating in its fundamental Z axis mode at frequency f. If diaphragm 324 is excited to axially oscillate at a frequency f that is near or equal to the system fundamental resonance frequency, then energy will be stored in the system resonance and the displacements of diaphragm 324 will increase proportionately to the stored energy. The system resonance can be tuned using optional mass 326.
The embodiments of
For the sake of explanation, it is assumed that actuators 352 and 354 are piezoceramic actuators although any of electro-active actuators capable of exerting radial forces could be used. In operation, actuators 352 and 354 are energized with an alternating electric field of frequency f and the resulting cyclic radial displacements of actuators 352 and 354 cause the volume of bellows 364 to vary at frequency f. The resulting time varying pressure within bellows 364 will cause fluid to be drawn into port 368 and discharged from port 370. Optional reaction masses could be added to the upper and lower bellows diaphragms to tune the system's resonant frequency.
In
Flex Radial Driving
In operation, an alternating voltage is applied to actuator 504. The resulting radial vibrational displacements of actuator 504 create oscillating radial tensile stresses within diaphragm 502 between actuator 504 and annular clamp 508. These oscillating tensile stresses are converted into Z axis vibrations of diaphragm 502, with actuator 504 of course traveling along with the Z axis vibrations of diaphragm 502. Initiation of this radial-to-axial conversion process is assisted by the fact that actuator 504 also vibrates in the direction of the diaphragm's axial displacement, although the actuator's axial displacement amplitude may be smaller than the radial displacement amplitude. Radial vibrational displacements of actuator 504 at frequency f can result in Z axis vibrational displacements of diaphragm 502 at frequency f or f/2 depending on the construction of diaphragm 502 (for example, flat diaphragm, pre-stressed bowed diaphragm, degree of axial and/or radial stiffness and/or nonlinearity, etc.). If the embodiment of
The bond between diaphragm 502 and actuator 504 can cause actuator 504 and diaphragm 502 to bend slightly over the area of the bond just like a typical uni-morph bender actuator, with the bending shape being either concave or convex depending on the polarity of the voltage applied. With respect to the Z axis displacements of diaphragm 502, actuator 504 will act like a piston, in a manner similar to the other embodiments of the present invention having pistons with flexible surrounds.
In operation, an alternating voltage is applied to actuator 510. The resulting radial vibrational displacements of actuator 510 create oscillating radial tensile stresses within diaphragm 512 between actuator 510 and annular clamp 514. These oscillating tensile stresses are converted into Z axis vibrations of diaphragm 512, with actuator 510 of course traveling along with the Z axis vibrations of diaphragm 512. Initiation of this radial-to-axial conversion process is assisted by the fact that actuator 510 also vibrates in the direction of the diaphragm's axial displacement, although the actuator's axial displacement amplitude may be smaller than the radial displacement amplitude. Radial vibrational displacements of actuator 510 at frequency f can result in Z axis vibrational displacements of diaphragm 502 at frequency f or f/2 depending on the construction of diaphragm 512 as discussed previously. The axial oscillations of diaphragm 112 and actuator 110 will cause fluid to be drawn into port 524 and discharged from port 526. If the embodiment of
Another embodiment of flex radial driving would be to sandwich flex radial diaphragm 556 or flex longitudinal spring 560 of
Edge Driving
If diaphragm 386 is excited by actuator 382 at a frequency f that is below the higher ordered resonant modes of the diaphragm 386, then the diaphragm will respond by oscillating in its fundamental axial mode at frequency f. If diaphragm 386 is driven at a frequency f that is near or equal to the system fundamental resonance frequency, then energy will be stored in the system resonance and the displacements of diaphragm 386 will increase proportionately to the stored energy. The system resonance can be tuned using optional mass 388.
The embodiment of
In
The embodiment of
The present invention can use piezoceramic uni-morph actuators that are pre-stressed such as the Thunder Actuators developed by NASA and covered by U.S. Pat. Nos. 5,632,841 and 6,734,603. The present invention can also use simple laminar uni-morph or poly-morph benders that are flat and have no pre-stress and in many cases these actuators are preferred since the present invention does not require large piezo displacements, but is instead designed to use high-force small-displacement actuators. (A uni-morph piezo bender is typically constructed from a slab of piezoceramic bonded to a metal sheet substrate). Simple laminar uni-morphs have the further advantaged that their manufacturing cost is quite low when compared to pre-stressed actuators. Another advantage of using low displacement piezo uni-morphs is that “harder” ceramics can be used that offer much higher electro-mechanical transduction efficiencies when compared to the softer ceramics that must be used in high-displacement benders. These harder ceramics are particularly more efficient than the softer ceramics above 100 Hz. Operating at higher frequencies is particularly desirable for small pumps and compressors to provide high flow rates in a small package, due to the large number of pumping cycles per second.
Driving of Resonant Acoustic Loads
The fluidic energy transfer devices of the present invention can also be used for driving high-power resonant acoustic loads, such as acoustic compressors and thermoacoustic engines. U.S. Pat. Nos. 5,515,684, 5,319,938, 5,579,399, 6,230,420 disclosure the principles of designing high energy density acoustic resonators, specific resonator shapes and the applications of high energy density acoustic resonators, the contents of which are all incorporated herein by reference in their entirety.
One of the challenges in miniaturizing acoustic compressors is the design of an actuator that can provide the power needed for practical applications. When adapted to driving small acoustic resonators, the present invention provides high-power low-cost actuators for miniaturized acoustic compressors and for the many other applications of small acoustic resonators.
Resonant Synthetic Jets
When driven by the present invention, or any of the embodiments of PCT Application NO. PCT/US2005/046557, acoustic resonators can be used to increase the flow performance of synthetic jets. For example,
A resonator, like that shown in
While the present invention enables miniaturization of fluidic energy transfer devices, the scope of the present invention is in no way limited to embodiments of any given size. The present invention can be scaled up beyond the mezzo size range and down into the MEMS size range. Various embodiments and enhancements of the present invention are disclosed herein and it will occur to those skilled in the art to use many different combinations of these embodiments and enhancements. All of the various combinations of these embodiments will be determined by the requirements of a given application and are considered within the scope of the present invention. For example, the number of valves used, whether or not added axial stability springs are required, the use of one or two diaphragms, actuators driving springs or diaphragms which in turn drive pistons, the number of actuators used in a single device, whether or not controls are needed, the types of methods used for joining components, the type of actuator used in a given embodiment, the types of seals used, and the use of pumps in series or parallel will all be determined by the performance and cost requirements of a given application.
Other examples of embodiments within the scope of the present invention that will occur to those skilled in the art would be to locate a single bender actuator (or other actuator) between two back-to-back fluidic diaphragms or pistons with each diaphragm or piston having its own compression chamber so as to drive the two diaphragms or pistons with the single actuator in a push-pull configuration. It will appear obvious to those skilled in the art to use both sides of a diaphragm or piston to form separate compression chambers and to stage those compression chambers by having valves on the diaphragm which allow fluid to pass from one chamber to the next. Also, the diaphragm reaction masses illustrated herein are shown as disks located at the center of the diaphragm, but could take many other forms and could be mounted off-center, such as in the case of an annular mass. In addition, many types of compressor and/or pump valves can be used in the present invention. For example, the moving piston or diaphragm of a given embodiment can be used to actuate inlet and outlet valves such as in the case of a sliding shaft valve, which would slide into a port and cyclically open and close an inlet or outlet port. Pumps of the present invention can be scaled up or down in size and can be used in closed cycle systems as well as open cycle systems as will be evident to those skilled in the art.
The present invention can use piezoceramic bimorph actuators that are pre-stressed such as the Thunder Actuators developed by NASA resulting in U.S. Pat. Nos. 5,632,841 and 6,734,603. The present invention can also use simple laminar bi-morphs that are flat and have no pre-stress and in many cases these actuators are preferred since the present invention does not require large actuator displacements, but is instead designed to use high-force small-displacement actuators. Simple laminar bi-morphs have the further advantaged that their manufacturing cost is quite low when compared to pre-stressed actuators.
All of the fluidic energy transfer embodiments of the present invention can also be used to drive conventional pistons with sliding seals and applied to pumps, compressors and the many other fluidic applications. However, care must be taken to assure that the fictional losses of the sliding seals are not excessive, since this would lower the device's energy efficiency.
The embodiments of the present invention can be driven at any frequency within the scope of the present invention. While performance advantages can be provided by operating the present invention at drive frequencies that are equal to or close to the system resonance, the scope of the present invention is not limited to the proximity of the drive frequency and the system resonance frequency. When drive frequencies are close enough to the system resonance that energy is stored in the resonance, then diaphragm and/or piston displacement amplitudes will increase in proportion to the stored energy. The closer the drive frequency is to the instantaneous system resonance frequency, the greater the stored energy, the greater the piston and/or diaphragm displacement and the greater the fluid energy transfer. Operation of the present invention, either with or without stored energy, is considered within the scope of the present invention.
It is also understood that the diaphragms of the present invention can be made of many different materials such as metals, plastics or elastomers. Whether diaphragms or piston surround materials behave as plates or membranes depends on the materials used and the deflections required by a given application and all of these materials and their behaviors are considered within the scope of the present invention. Further, various piston shapes could be used to provide different advantages. For example, in order to provide light weight pistons, conical piston shapes could be used to increase stiffness while using thinner lightweight materials. In this case, the compression chamber could also have a conical shape to receive the conical piston thereby avoiding excessive clearance volumes. Many other geometrical piston shapes could be used to provide similar advantages, all of which will be obvious to one skilled in the art. It is further understood that in many of the embodiments of the present invention diaphragms can be substituted for pistons and pistons can be substituted for diaphragms, which will be obvious to one skilled in the art.
The PCT Application No. PCT/US2005/046557, which has been incorporated by reference, discloses further embodiments, applications, controllers and control schemes and any combinations of these embodiments with the present invention will be obvious to one skilled in the art and are considered within the scope of the present invention.
Applications of the present invention for transferring kinetic energy, pressurization energy and acoustic energy to fluids could include for example, compressing, pumping, mixing, atomization, synthetic jets, fluid metering, sampling, air sampling for bio-warfare agents, ink jets, filtration, or driving physical changes due to chemical reactions, or other material changes in suspended particulates such as comminution or agglomeration, or a combination of any of these processes, to name a few. Applications for pump and compressor embodiments of the present invention include MEMs and MESO-sized pumps and compressors for micro fuel cells in portable electronic devices such as portable computing devices, PDAs and cell phones; self-contained thermal management systems that can fit on a circuit card and provide cooling for microprocessors and other semi-conductor electronics; and portable personal medical devices for ambulatory patients.
The foregoing description of some of the embodiments of the present invention have been presented for purposes of illustration and description. In the drawings provided, the subcomponents of individual embodiments provided herein are not necessarily drawn in proportion to each other, for the sake of functional clarity. In an actual product, the relative proportions of the individual components are determined by specific engineering designs. The embodiments provided herein are not intended to be exhaustive or to limit the invention to a precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Although the above description contains many specifications, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of alternative embodiments thereof.
This application claims priority to U.S. Provisional Patent Application No. 60/780,037, filed on Mar. 7, 2006, by Timothy S. Lucas of Providence Forge, Va., U.S.A., entitled “Fluidic Energy Transfer Devices,” the contents of which is incorporated herein by reference in their entirety. The PCT Patent Application PCT/US2005/046557, filed Dec. 22, 2005, entitled Reaction-Drive Energy Transfer Device, by Timothy S. Lucas, is hereby referenced, the contents of which are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2007/005713 | 3/7/2007 | WO | 00 | 1/22/2009 |
| Publishing Document | Publishing Date | Country | Kind |
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| WO2007/103384 | 9/13/2007 | WO | A |
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