Patent Application
20090026881
The disclosed embodiments of the invention relate generally to the thermal management of microelectronic devices, and relate more particularly to piezoelectric fans.
Piezoelectric materials are capable of generating a voltage when subjected to a mechanical strain according to what is known as the piezoelectric effect. The piezoelectric effect also works in reverse, such that a piezoelectric material may be made to change shape slightly when subjected to an externally-applied voltage. Piezoelectric materials have been used as components in piezoelectric cooling fans, where a blade attached to a piezoelectric patch is made to oscillate in order to generate airflow. However, the performance of piezoelectric fans is significantly affected by operating conditions such as altitude, any background airflow, and manufacturing variabilities. The microelectronics industry has thus far not developed a low cost, small size active feedback controller for piezoelectric fans in order to achieve desired deflection and performance at different system boundary conditions and varying operating conditions.
The disclosed embodiments will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying figures in the drawings in which:
For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the discussion of the described embodiments of the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different figures denote the same elements.
The terms “first,”. “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Similarly, if a method is described herein as comprising a series of steps, the order of such steps as presented herein is not necessarily the only order in which such steps may be performed, and certain of the stated steps may possibly be omitted and/or certain other steps not described herein may possibly be added to the method. Furthermore, the terms “comprise,” “include,” “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. The term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical or non-electrical manner. Objects described herein as being “adjacent to” each other may be in physical contact with each other, in close proximity to each other, or in the same general region or area as each other, as appropriate for the context in which the phrase is used. Occurrences of the phrase “in one embodiment” herein do not necessarily all refer to the same embodiment.
In one embodiment of the invention, a piezoelectric fan comprises a blade, a piezoelectric actuator patch adjacent to the blade, and a piezoelectric sensor patch adjacent to either the piezoelectric actuator patch or the blade. The piezoelectric sensor patch measures a voltage proportional to a strain caused by a deflection in a system due to the operation of the piezoelectric actuator patch and uses that voltage to generate an input signal to an active feedback controller that in turn adjusts the oscillation amplitude of the blade to satisfy desired cooling specifications. Operation of the piezoelectric fan within the airflow of an axial fan or the like may cause changes in the blade oscillation amplitude. The piezoelectric sensor patch measures these changes and, in conjunction with the active feedback controller, enables adjustments to the piezoelectric fan system that maintain that system within the desired cooling specifications.
Referring now to the drawings,
In at least one embodiment, piezoelectric sensor patch 130 is capable of generating an electrical signal containing information relating to the operation of piezoelectric fan 100. As an example, piezoelectric actuator patch 120 can cause a deflection that generates a voltage created by a corresponding strain in piezoelectric sensor patch 130, and a voltage pattern supplied to piezoelectric fan 100 can then be adjusted according to this generated voltage in order to achieve certain performance criteria, as further discussed below.
Piezoelectric actuator patch 120 comprises a piezoelectric layer 121 located between electrodes 122 and 123. An adhesive layer 124 is located between electrode 122 and blade 110. Similarly, piezoelectric sensor patch 130 comprises a piezoelectric ceramic layer 131 located between an electrode 132 and an electrode 133. In the illustrated embodiment, an adhesive layer 134 is located between electrode 132 and electrode 123. As an example, adhesive layer 124 and, where present, adhesive layer 134, can be an epoxy layer or the like that can both physically attach components of piezoelectric fan 100 to each other and electrically insulate components of piezoelectric fan 100 from each other or from some other object.
In a different embodiment, adhesive layer 134 is omitted from piezoelectric fan 100, in which case the last electrode layer (i.e., the electrode layer farthest from the blade) would be wired separately in order to capture the measured voltage from piezoelectric sensor patch 130. In this latter embodiment the various layers may all be cofired together, eliminating the need for adhesive layer 134 and possibly leading to an increase in performance. Various piezoelectric fan embodiments illustrated herein have a piezoelectric actuator patch located between a blade and a piezoelectric sensor patch. Although each of these embodiments show an adhesive layer (corresponding to adhesive layer 134) between the piezoelectric actuator patch and the piezoelectric actuator patch, each embodiment could also have a (non-illustrated) variation in which such adhesive layer is omitted, just as adhesive layer 134 may be omitted from piezoelectric fan 100 as was just discussed. In those (non-illustrated) embodiments lacking such adhesive layer, outermost electrodes of the adjacent piezoelectric actuator patch and piezoelectric sensor patch may be in physical contact with each other.
As an example, blade 110 can be made of mylar, plastic, steel or another metal, or the like. As another example, electrodes 122, 123, 132, and 133 can be made of a highly electrically conductive material such as nickel, silver palladium, or the like. In one embodiment, electrodes 122, 123, 132, and 133 have a thickness of between approximately three and approximately eight micrometers. As yet another example, piezoelectric layers 121 and 131 can be made of lead zirconium titanate (PZT) or a lead-free piezoelectric material such as bismuth titanate or the like. Alternatively, piezoelectric layers 121 and 131 can be made of another piezoelectric material, including piezoelectric ceramic and piezoelectric polymers. In one embodiment, piezoelectric layers 121 and 131 each have a thickness no greater than approximately 30 micrometers. In general, piezoelectric sensor patch should be made as thin as possible.
In one embodiment, piezoelectric fan 100 (like piezoelectric fans according to other embodiments of the invention) can include a plurality of blades, including blade 110, that may all be made to oscillate in order to further enhance the piezoelectric fan's thermal management capabilities. In the same or another embodiment, the piezoelectric fans may be made to be compatible with multiple systems, thus reducing costs and increasing efficiency.
As mentioned,
As an example, blade 210, piezoelectric actuator patch 220, piezoelectric layer 221, electrode 222, electrode 223, adhesive layer 224, piezoelectric sensor patch 230, piezoelectric layer 231, electrode 232, electrode 233, and adhesive layer 234 can be similar to, respectively, blade 110, piezoelectric actuator patch 120, piezoelectric layer 121, electrode 122, electrode 123, adhesive layer 124, piezoelectric sensor patch 130, piezoelectric layer 131, electrode 132, electrode 133, and adhesive layer 134, all of which are shown in
Piezoelectric sensor patch 330 comprises a piezoelectric layer 331 located between an electrode 332 and an electrode 333. An adhesive layer 334 is located between electrode 332 of piezoelectric sensor patch 330 and one of plurality 350 of electrodes in piezoelectric actuator patch 320. As illustrated, piezoelectric sensor patch 330 and piezoelectric actuator patch 320 are both located on a first side of blade 310. It should be understood that piezoelectric sensor patch 330 and piezoelectric actuator patch 320 could, in a non-illustrated embodiment, be located instead on a different side of blade 310.
As an example, blade 310, piezoelectric actuator patch 320, piezoelectric layer 321, electrode 322, electrode 323, adhesive layer 324, piezoelectric sensor patch 330, piezoelectric layer 331, electrode 332, electrode 333, and adhesive layer 334 can be similar to, respectively, blade 110, piezoelectric actuator patch 120, piezoelectric layer 121, electrode 122, electrode 123, adhesive layer 124, piezoelectric sensor patch 130, piezoelectric layer 131, electrode 132, electrode 133, and adhesive layer 134, all of which are shown in
Piezoelectric sensor patch 430 comprises a piezoelectric layer 431 located between an electrode 432 and an electrode 433. An adhesive layer 434 is located between electrode 432 and blade 410. As illustrated, piezoelectric sensor patch 430 is located on a first side of blade 410 and piezoelectric actuator patch 420 is located on a second side of blade 410 opposite the first side. It should be understood that in a non-illustrated embodiment, piezoelectric sensor patch 430 can be located on the side of blade 410 that in the illustrated embodiment is occupied by piezoelectric actuator patch 420, and vice versa.
As an example, blade 410, piezoelectric actuator patch 420, piezoelectric layer 421, electrode 422, electrode 423, adhesive layer 424, piezoelectric sensor patch 430, piezoelectric layer 431, electrode 432, electrode 433, and adhesive layer 434 can be similar to, respectively, blade 110, piezoelectric actuator patch 120, piezoelectric layer 121, electrode 122, electrode 123, adhesive layer 124, piezoelectric sensor patch 130, piezoelectric layer 131, electrode 132, electrode 133, and adhesive layer 134, all of which are shown in
Section 525 of piezoelectric actuator patch 520 comprises a piezoelectric layer 521 located between an electrode 522 and an electrode 523. An adhesive layer 524 is located between electrode 523 and blade 510. Section 526 of piezoelectric actuator patch 520 comprises a piezoelectric layer 527 located between an electrode 528 and an electrode 529. An adhesive layer 544 is located between electrode 528 and blade 510. Similarly, piezoelectric sensor patch 530 comprises a piezoelectric layer 531 located between an electrode 532 and an electrode 533. An adhesive layer 534 is located between electrode 532 and electrode 529. As an example, piezoelectric layer 527 can be similar to piezoelectric layer 521, and electrodes 528 and 529 can be similar to electrodes 522 and 523. As another example, adhesive layer 544 can be similar to adhesive layer 524.
As illustrated, piezoelectric sensor patch 530 is located on a first side of blade 510 with section 526 of piezoelectric actuator patch 520, with section 525 of piezoelectric actuator patch 520 located on a second side of blade 510 opposite the first side. It should be understood that in a non-illustrated embodiment, piezoelectric sensor patch 530 can be located on the side of blade 510 that in the illustrated embodiment is occupied by section 525 of piezoelectric actuator patch 520, and vice versa. Similarly, in a non-illustrated embodiment, section 525 of piezoelectric actuator patch 520 can be located on the side of blade 510 that in the illustrated embodiment is occupied by section 526 of piezoelectric actuator patch 520, and vice versa.
As an example, blade 510, piezoelectric actuator patch 520, piezoelectric layer 521, electrode 522, electrode 523, adhesive layer 524, piezoelectric sensor patch 530, piezoelectric layer 531, electrode 532, electrode 533, and adhesive layer 534 can be similar to, respectively, blade 110, piezoelectric actuator patch 120, piezoelectric layer 121, electrode 122, electrode 123, adhesive layer 124, piezoelectric sensor patch 130, piezoelectric layer 131, electrode 132, electrode 133, and adhesive layer 134, all of which are shown in
Section 625 of piezoelectric actuator patch 620 comprises a piezoelectric layer 621 located between an electrode 622 and an electrode 623. An adhesive layer 624 is located between electrode 622 and blade 610. Piezoelectric layer 621 is one of a plurality 640 of piezoelectric layers that form a part of section 625 of piezoelectric actuator patch 620. Piezoelectric actuator patch 620 further comprises a plurality 650 of electrodes (a plurality that includes electrodes 622 and 623), and, as depicted in
Section 626 of piezoelectric actuator patch 620 comprises a piezoelectric layer 627 located between an electrode 628 and an electrode 629. An adhesive layer 644 is located between electrode 628 and blade 610. As an example, piezoelectric layer 627 can be similar to piezoelectric layer 621, and electrodes 628 and 629 can be similar to electrodes 622 and 623. As another example, adhesive layer 644 can be similar to adhesive layer 624. Piezoelectric layer 627 is one of a plurality 660 of piezoelectric layers that form a part of section 626 of piezoelectric actuator patch 620. Piezoelectric actuator patch 620 further comprises a plurality 670 of electrodes (a plurality that includes electrodes 628 and 629), and, as depicted in
Piezoelectric sensor patch 630 comprises a piezoelectric layer 631 located between an electrode 632 and an electrode 633. An adhesive layer 634 is located between electrode 632 and one of plurality 670 of electrodes of section 626. As illustrated, piezoelectric sensor patch 630 is located on a first side of blade 610 with section 626 of piezoelectric actuator patch 620, with section 625 of piezoelectric actuator patch 620 located on a second side of blade 610 opposite the first side. It should be understood that in a non-illustrated embodiment, piezoelectric sensor patch 630 can be located on the side of blade 610 that in the illustrated embodiment is occupied by section 625 of piezoelectric actuator patch 620, and vice versa. Similarly, in a non-illustrated embodiment, section 625 of piezoelectric actuator patch 620 can be located on the side of blade 610 that in the illustrated embodiment is occupied by section 626 of piezoelectric actuator patch 620, and vice versa.
As an example, blade 610, piezoelectric actuator patch 620, piezoelectric layer 621, electrode 622, electrode 623, adhesive layer 624, piezoelectric sensor patch 630, piezoelectric layer 631, electrode 632, electrode 633, and adhesive layer 634 can be similar to, respectively, blade 110, piezoelectric actuator patch 120, piezoelectric layer 121, electrode 122, electrode 123, adhesive layer 124, piezoelectric sensor patch 130, piezoelectric layer 131, electrode 132, electrode 133, and adhesive layer 134, all of which are shown in
A step 720 of method 700 is to supply an alternating current with a pattern, an input voltage amplitude, and an input frequency to the piezoelectric actuator patch in order to cause a tip of the blade to oscillate with an oscillation amplitude.
A step 730 of method 700 is to measure an output voltage corresponding to the oscillation amplitude. The measured output voltage is due to the strain on the piezoelectric sensor patch resulting from the deformation of the piezoelectric actuator patch, but such voltage can be correlated to the oscillation amplitude of the blade tip according to methods known in the art.
A step 740 of method 700 is to adjust one or both of the input voltage amplitude and the input frequency such that the oscillation amplitude is substantially equal (a phrase that herein encompasses identically equal) to a target amplitude for the blade. In one embodiment, step 740 comprises adjusting the input frequency such that it is substantially equal to a resonance frequency for the blade, and, after adjusting the input frequency, adjusting the input voltage amplitude such that the oscillation amplitude is substantially equal to the target amplitude for the blade. As known in the art, once the input frequency is set identical to the resonance frequency of the blade, the oscillation amplitude becomes largest for a given voltage amplitude. As an example, the target amplitude can be a specified amplitude that achieves a targeted cooling performance. This target amplitude may be, but is not necessarily, the maximum amplitude for the given voltage amplitude.
In one embodiment, step 740 further comprises adjusting one or both of the input voltage amplitude and the input frequency using an active feedback controller. As an example, the active feedback controller may adjust one or both of the input frequency and the input voltage amplitude based on an input signal generated by the piezoelectric sensor patch. As another example, the active feedback controller may adjust one or both of the input frequency and the input voltage amplitude using a voltage and frequency controller card.
As an example, piezoelectric fan 810 can be similar to one of piezoelectric fans 100, 200, 300, 400, 500, and 600, shown, respectively, in
Power supply 820 is capable of supplying an alternating voltage with a pattern, an input voltage amplitude, and an input frequency to piezoelectric actuator patch 811. Active feedback controller 840 is electrically coupled to piezoelectric fan 810 and is capable of receiving an input signal from piezoelectric sensor patch 812 and adjusting at least one of the input voltage amplitude and the input frequency in response to the input signal.
The amplitude of the piezoelectric fan is very dependent on the frequency of the electrical wave (i.e., the voltage pattern) applied to it, and that amplitude is maximized when the frequency of the applied voltage pattern equals the resonance frequency for the blade of the piezoelectric fan. In order for maximum performance to be achieved, the piezoelectric fan should be operated at resonance frequency at all times. However, the resonance frequency and blade tip amplitude are highly dependent on the conditions in which the fan operates, as mentioned above.
One environment in which embodiments of the piezoelectric fan may be used to advantage is an environment where the piezoelectric fan is used to enhance the forced convection supplied by axial fans. To this end a rake piezoelectric system, for example, may be used in conjunction with a parallel fin heat sink (and the axial fans) to provide more effective cooling. As mentioned, however, the piezoelectric fan's natural frequency and amplitude change as the flow rate provided by the axial fans changes. Thus, in order to achieve optimal performance, the frequency applied to the piezoelectric fan should be altered along with (and in response to) the changing flow rate. This is done using the active feedback controller to adjust the voltage pattern in response to the input signal from the piezoelectric sensor patch such that the frequency of the voltage pattern matches the resonance frequency. The amplitude of the voltage pattern may also be adjusted, if needed, to achieve desired performance parameters.
Although the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made without departing from the spirit or scope of the invention. Accordingly, the disclosure of embodiments of the invention is intended to be illustrative of the scope of the invention and is not intended to be limiting. It is intended that the scope of the invention shall be limited only to the extent required by the appended claims. For example, to one of ordinary skill in the art, it will be readily apparent that the piezoelectric fans and associated methods and systems discussed herein may be implemented in a variety of embodiments, and that the foregoing discussion of certain of these embodiments does not necessarily represent a complete description of all possible embodiments.
Additionally, benefits, other advantages, and solutions to problems have been described with regard to specific embodiments. The benefits, advantages, solutions to problems, and any element or elements that may cause any benefit, advantage, or solution to occur or become more pronounced, however, are not to be construed as critical, required, or essential features or elements of any or all of the claims.
Moreover, embodiments and limitations disclosed herein are not dedicated to the public under the doctrine of dedication if the embodiments and/or limitations: (1) are not expressly claimed in the claims; and (2) are or are potentially equivalents of express elements and/or limitations in the claims under the doctrine of equivalents.
