WO1996018823A1 - Metal enforced pvdf vibrational fan - Google Patents
Metal enforced pvdf vibrational fan Download PDFInfo
- Publication number
- WO1996018823A1 WO1996018823A1 PCT/US1995/013616 US9513616W WO9618823A1 WO 1996018823 A1 WO1996018823 A1 WO 1996018823A1 US 9513616 W US9513616 W US 9513616W WO 9618823 A1 WO9618823 A1 WO 9618823A1
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- WO
- WIPO (PCT)
- Prior art keywords
- vibrational
- fan
- layer
- piezoelectric
- core layer
- Prior art date
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D33/00—Non-positive-displacement pumps with other than pure rotation, e.g. of oscillating type
Abstract
The present invention is directed to a miniature vibrational fan composed of a piezoelectric material bonded to a metal reinforcing layer. An a.c. voltage is applied to the piezoelectric material with the frequency turned to the mechanical resonance of the fan, causing vibration of both the piezoelectric material and the metal reinforcing layer bonded thereto, and resulting in air-flow across the surface of the metal layer.
Description
METAL ENFORCED PVDF VIBRATIONAL FAN
The present invention is directed to a miniature vibrational fan composed of a piezoelectric material bonded to a metal reinforcing layer. An a.c. voltage is applied to the piezoelectric material with the frequency turned to the mechanical resonance of the fan, causing vibration of both the piezoelectric material and the metal reinforcing layer bonded thereto, and resulting in air-flow across the surface of the metal layer.
A piezoelectric multimorph vibrational fan was first reported to generate a considerable amount of air flow, when driven at mechanical resonant frequencies by M. Toda et al. , "Vibrational Fan Using Piezoelectric Polymer PVF2", Proc. IEEE, vol. 67, No. 8, p 1171 (1979) , and was investigated in more detail by M. Toda, "Theory of Air Flow Generation By A Resonant Type PVF2 Bimorph Cantilever Vibrator" Ferroelectronics. vol. 22, p 911 (1979) . These references disclose a structure with parallel connected multilayered PVDF, with one-half region of an electric field parallel to the direction of polarization, and another half region of the electric field anti-parallel to the polarization direction. The one half region expands in the length and another half shrinks leading to bending motion. Since the voltage is alternating with a frequency, the bending vibration shows a peak at the resonance and air flow is generated.
Other piezoelectric vibrational fans are known in the art. However, most known fan systems utilize piezoelectric ceramic bimorphs, e.g. lead-zirconium titanate (PZT) as the piezoelectric material, such as those fans disclosed in U.S. patent nos. 4,684,328 and 4,753,579, both to Murphy, 4,498,851 to Kolm et al. and 4,780,062 to Yamada et al.
Disadvantages to the use of piezoelectric ceramic materials in vibrational fans are high cost of manufacture, high power input and limitations on the ability to miniaturize such systems. While the use of piezoelectric polymer materials in vibrational fans and the like is known in the art, U.S. patent nos. 5,008,582 to Tanuma et al. and 4,342,936 to Marcus et al . , none have recognized the benefits of the combination of materials as disclosed herein. The above-cited references are hereby incorporated by reference.
The primary object of the present invention is to provide an improved vibrational fan which has an increased capacity for air movement across any particular device in need of air cooling.
The vibrational fan of the present invention comprises a metallic layer bonded to a layer of preferably piezoelectric polymer material however other piezoelectric materials to include composite and ceramic piezoelectric materials while less preferable will suffice, wherein the length of the metal layer exceeds the length of the polymer layer. Application of a.c. voltage to the piezoelectric polymer results in repetitive bending motion or vibration of the polymer, which causes bending of the metal layer and while the system vibrates showing a maximum at the resonance, resulting in the ability of the system to force air movement.
In a first embodiment, the vibrational fan comprises an aluminum core layer having two flat surfaces, defined by a length, 21; a width, w, and said core layer having a thickness, tA; a piezoelectric polymer film layer, comprising polyvinylidene fluoride, having a length, 12, a width, w, and a thickness, tp; and electrical means for electrically exciting the piezoelectric polymer film layer in order to induce a vibration in the vibrational fan, wherein said
piezoelectric film layer is bonded to one flat surface of said aluminum core layer and Iι>-- -
In a second embodiment, the vibrational fan comprises more than one piezoelectric polymer film layer. This embodiment may include the situation wherein a piezoelectric film layer is bonded to both flat surfaces of said aluminum core layer, one polymer layer on each side of said aluminum core layer.
Alternatively, two piezoelectric film layers may be bonded to one flat surface of said aluminum core layer or other thermally conductive material, both polymer layers on one side of the aluminum core layer.
Additionally, two piezoelectric film layers may be bonded to both flat surfaces of said aluminum core layer, that is, two layers of polymer on each side of the aluminum core layer.
A third embodiment of the present invention is wherein the basic piezoelectric fan is mounted on a conventional heat sink for cooling purposes in computer and other electronics assemblies.
The above and other objects, features and advantages of the present invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings, all of which are given by way of illustration only, and are not limitative of the present invention.
FIGURE 1 is a perspective view of the first embodiment of the piezoelectric vibrational fan of the present invention.
FIGURE 2 is a perspective view of the first embodiment of the piezoelectric vibrational fan of the present invention mounted as shown on a substrate. FIGURE 3 is a cross-sectional view of a second embodiment of the present invention.
FIGURE 4 is a perspective view of the second embodiment of the piezoelectric vibrational fan of the present invention mounted as shown on a substrate.
FIGURE 5 is a cross-sectional view of an alternative of the second embodiment of the present invention.
FIGURE 6 is a perspective view of an alternative of the second embodiment of the piezoelectric vibrational fan of the present invention mounted as shown on a substrate.
FIGURE 7 is an exploded view of a section of the piezo polymer of Figure 6.
FIGURE 8 is a cross-sectional view of another alternative of the second embodiment of the present invention.
FIGURE 9 is a perspective view of another alternative of the second embodiment of the present invention.
FIGURE 10 is an exploded view of a section of the fan of FIGURE 9.
FIGURE 11 is an exploded view of the fan assembly for the third embodiment.
FIGURES 12-14 are views of the fan assembly of Figure 11 mounted in heat sinks.
The following detailed description of the invention is provided to aid those skilled in the art in practicing the present invention. Even so, the following detailed description of the invention should not be construed to unduly limit the present invention, as modifications and variations in the embodiments herein discussed may be made by those of ordinary skill in the art without departing from the spirit or scope of the present inventive discovery. The vibrational fan of the present invention comprises a metallic layer and piezoelectric polymer layer bonded together wherein the length of the metal
layer exceeds the length of the polymer layer and other end is clamped. The polymer chain direction is chosen to be parallel to the direction from the clamped end to the moving edge. The a.c. voltage induces strain to the polymer so that that length towards the polymer chain repeats expansion and shrinkage. When the piezoelectric layer is at only one side surface of the metal (called asymmetric bimorph) . the vibration of the length is converted to deflectional motion due to the asymmetric layer structure. When he piezoelectric layer is at both side surfaces of the metal, both piezoelectric layers are so driven as to be our-of-phase strain and more effectively bending force is generated.
At the mechanical resonance condition of the drive frequency, the vibration becomes maximum and air flow becomes maximum.
More particularly, the subject of the present invention is a metal reinforced PVDF fan wherein an aluminum sheet doesn't "clamp" bonded to at least is clamped or bonded to at least one sheet of PVDF
(polyvinylidene fluoride) and wherein the length of the PVDF sheet is less than that of the aluminum sheet. The choice of aluminum for the core layer results in improved air movement by the inventive fan. The end opposite to the free moving edge (no PVDF) is securely clamped by a metallic structure.
PVDF film devices of the present invention have inherent advantages over those utilizing conventional piezoelectric materials, such as low excitation current, improved flexibility and low cost, due to the ability to mass produce PVDF materials in a continuous roll process. However, multilayer PVDF devices, especially thin film devices (less than 10 μm) , are difficult to produce at low cost due to difficulties in handling, bonding the layers together and attaching lead wires to each layer.
The inventors of the presently claimed devices propose a new structure which comprises a PVDF film clamped or bonded to an aluminum core layer, wherein the length of the aluminum core layer exceeds the length of the PVDF film.
Aluminum was chosen for the core layer because of its very high mechanical quality factor (Qm) , which is represented by its elastic loss term, η , wherein Qm = η' 1 » 2000 for aluminum. On the other hand, PVDF has Qm = 15. Therefore, aluminum is close to an ideal elastic material, even though its elastic constant is much larger than that of PVDF. The high elastic constant of aluminum means that it is elastically hard and applying a certain force produces very little bending. In the present system, upon excitation the expansion and shrinkage of the PVDF film generates a bending force, but the aluminum layer is too hard to bend. However, the situation is different at the resonance frequency, wherein the amplitude of the deflection due to the bending force increases by a factor of Qm of the system. This means that a high Qm material can be very easily bent at the resonance frequency.
FIGURE 1 illustrates a first embodiment of the present invention, wherein the vibrational fan comprises an aluminum core layer, 1, having two flat surfaces, defined by a length, 217 a width, w, and said core layer having a thickness, tA; a piezoelectric polymer film layer, 2, comprising polyvinylidene fluoride, having a length, 12 , a width, w, and a thickness, tp; and electrical means for electrically exciting the piezoelectric polymer film layer in order to induce a vibration in the vibrational fan, wherein said piezoelectric film layer is bonded to one flat surface of said aluminum core layer and 1 >12 - The polarization direction of the piezoelectric film are shown by the arrows 3 in Figures 4,6,7,9 and 10.
FIGURE 3 illustrates a second embodiment of the present invention, wherein the vibrational fan comprises more than one piezoelectric polymer film layer. This embodiment may include the situation wherein a piezoelectric film layer is bonded to both flat surfaces of said aluminum core layer, one polymer layer on each side of said aluminum core layer.
FIGURE 5 illustrates an alternative to the second embodiment of the present invention, wherein two piezoelectric film layers may be bonded to one flat surface of said aluminum core layer, both polymer layers on one side of the aluminum core layer. The two polymer layers may either be two distinct and separate layers with a suitable connection or two layers formed by folding the PVDF film over itself, as illustrated.
FIGURE 8 illustrates another alternative to the second embodiment of the present invention, wherein two piezoelectric film layers may be bonded to both flat surfaces of said aluminum core layer, that is, two layers of polymer on each side of the aluminum core layer. Again, the two polymer layers may either be two distinct and separate layers or two layers formed by folding the PVDF film over itself, as illustrated.
The third embodiment of the present invention can utilize any of the above embodiments for the fan
The following examples are provided to illustrate various configurations of the specific embodiments, described above, and are not intended to be limitative of the possible configurations of the invention within the scope of the claims.
Example 1
Various vibrational fans were designed according to the second embodiment, as illustrated in Fig. 2. The dimensions and performance characteristics are as follows :
Excitation conditions
100 V @ 1-4 mA Dimensions and performance tp = 28 microns; w = 10 cm; 12 = 1 cm
(microns) (cm) (m/s) (1/s) (Hz)
10 1.8 2.15 1.33 78.7
15 2.1 1.82 1.19 62.4
20 2.4 1.58 1.09 51.5
25 2.6 1.47 1.02 48.1,
Example 2
Various vibrational fans were designed according to the second embodiment, as illustrated in Fig. 2. The dimensions and performance characteristics are as follows:
Excitation conditions 100 V @ 1-4 mA Dimensions and performance tp = 28 microns; w = 10 cm; 12 = 2 cm
. tA 1. vair Flow Rate o
(microns) (cm) (m/s) (1/s) (Hz)
10 3.3 1.3 1.6 24.3
15 3.6 1.24 1.52 22.7
20 3.9 1.15 1.44 20.6
25 4.1 1.11 1.37 20.2
30 4.3 1.08 1.32 20.0
Example 3
Various vibrational fans were designed according to the second embodiment, as illustrated in Fig. 4. The dimensions and performance characteristics are as follows:
Excitation conditions
100 V @ 1-4 mA Dimensions and performance tp = 28 microns x 2; w = 10 cm; 12 = 1 cm
tA 1- Vvaι•r Flow Rate ft
(microns) (cm) (m/s) (1/s) (Hz)
10 1.5 4.7 2.52 191
15 1.8 3.7 2.30 137
20 2.0 3.3 2.08 117
25 2.3 2.8 1.91 89.9
30 2.6 2.4 1.80 72.4
Example 4 Various vibrational fans were designed according to the second embodiment, as illustrated in Fig. 4. The dimensions and performance characteristics are as follows:
Excitation conditions 100 V @ 1-4 mA
Dimensions and performance tP = 28 microns x 2; w = 10 cm; 12 = 2 cm
t* I. vair Flow Rate
(microns) (cm) (m/s) (1/s) iHzl
10 2.9 2 , .7 3, .0 54.4
15 3.3 2 , .4 2. .85 44.3
20 3.6 2 , .2 2. .7 39.1
25 3.9 2 , .0 2. .55 34.8
30 4.2 1. .8 2. ,42 29.4
50 5.3 1. .5 2.08 23.0
100 6.8 1.3 1.72 21.4
As is seen from the exemplary data, it is possible to optimize the air flow rate by optimizing the various dimensions of the PVDF and aluminum layers. For instance, when the aluminum layer is thicker, the layer may also be longer to give increased maximum flow rates. Additionally, increasing the length of the PVDF layer, 12 will provide for longer aluminum layers, l .
Comparative Example A comparative vibrational fan was designed comprising two layers of PVDF bonded together, without an intervening aluminum core layer. The dimensions and performance characteristics are as follows: Excitation conditions 100 V @ 1-4 mA
Dimensions and performance tp = 28 microns x 2; w = 10 cm; 12 = 1 cm
tA I-. Vaιr Flow Rate f0
(microns) (cm) (m/s) (1/s) (Hz) N/A N/A 1.6 0.36 155.
As is seen from the comparative data, the inclusion of an aluminum core layer, having a length exceeding the length of the PVDF layer, results in a great increase in the air moving capacity of piezoelectric vibrational fans.
The inventors believe that the presently disclosed fans may be made to any desired width, w, with an increase or decrease in air flow rate varying approximately linearly with the width. However, there are practical limitations on the lengths of the layers, 1-L and 12 , as well as the thicknesses of the layers, tP and tA, in order to preserve the low excitation current and efficiency of the presently claimed fans.
Accordingly, the relative lengths of the layers should be limited such that the ratio of 11/12 is greater than 1.4, and preferably such that the ratio of 1 ' 12 is between 1.45 and 3.4, with the maximum length of l being about 10 cm . Additionally, the maximum benefits of the present invention are obtained when the thickness, tp, is between about 7-55 microns and the thickness, tA, is between about 10 and 100 microns.
Turning to Figure 11, we see the fan assembly 110 for use in a heat sink system for use in a computer or other electronic equipment which requires heat dissipation. The fan 111 can be any of the above described assemblies. It is clamped by clamp 112 which is preferably metal or some other material capable of dissipating heat itself. The clamp is clamped to the fan via screws or other fasteners and there are electrical leads as at 113. This clamped fan assembly is then mounted preferably as is shown in heat sink assemblies of Figures 12-14. In any of the above assemblies, the clamp is mounted to the heat sinks 121, 141 preferably by thermally conductive material such as conductive gel, conductive epoxy, solder or mechanical fasteners such as rivets or screws. By having the assembly as shown in Figures 12-14, there is an increased surface area of heat dissipating material to cool the electronics. Furthermore, as it is common practice to mount a rotary fan on a heat sink having radially extending fins as opposed to the parallel fins anticipated by the instant invention. This design usually requires smaller fins to allow room for the bulky rotary fan. Because the heat sink is mounted on a microprocessor in computer systems, the present invention can effect airflow as does a rotary fan having a greater surface area of heat dissipating material through larger fins. The greater the rotary fan size, the less area that is available for heat sink material. Furthermore, the rotary fan is generally made of plastic
and itself cannot dissipate heat. Finally, the fan requires an electric motor that is generally integral and thus itself adds heat to the system. The instant invention however places the piezoelectric fans as described above in between the heat sink fins, thereby greatly increasing the available heat sink surface area. The fans placed in the fins maximizes the area of the heat sink causing the air to flow directly therebetween the fins. The efficiency of the design further uses the heat dissipative effects of the clamp to increase the heat dissipation of the heat sink fan assembly. Finally, turning to FIGURE 12, we see a version of the present invention that stacked heat sinks on top of one another. It is important that the heat sink assembly shown in FIGURE 14 is adaptable to be stacked vertically to accomplish the purpose described for the assembly shown in FIGURE 12. In a conventional design where a rotary fan is mounted on top of the heat sink, and the fins are radially extending therefrom, the only way to increase heat dissipation is to increase airflow and heat sink area is to have a larger fan and a larger heat sink. The design of the present invention anticipates the use of multiple fans in the stacked arrangement that does not intrude on the "real estate" area of the printed circuit board of the computer, and thus is a significant improvement over the conventional tack. Finally, it is important to note that this increased flow rate is effected by increasing the fan area through multiple fans as shown. While PVDF is a preferred piezoelectric material according to the present invention, copolymers of PVDF and other polymeric materials may be used. For example, a copolymer of PVDF and trifluoroethylene may be used to enhance the ability to bond the piezoelectric layer to the aluminum layer without an additional bonding substance, such as epoxy.
The presently claimed vibrational fans may be used in a variety of applications, such as for cooling a power transistor, a microprocessor or a large scale integration. A particular benefit of the present invention, when configured according to Figs. 1 and 5, is that the aluminum layer may contact the device to be cooled directly. In this case, the exceptional thermal conductivity of the aluminum core layer provides additional cooling to the heated device, by acting as a heat sink.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
Claims
1. A vibrational fan comprising: an aluminum core layer having two flat surfaces, defined by a length, ll t a width, w, and said core layer having a thickness, tA; a layer of piezoelectric material, comprising polyvinylidene fluoride, having a length, 12, a width, w, and a thickness, tp; and means for electrically exciting the piezoelectric polymer film layer in order to induce a vibration in the vibrational fan; and wherein said piezoelectric film layer is bonded to one flat surface of said aluminum core layer and 1 >12 .
2 . The vibrational fan according to claim 1, comprising more than one layer of piezoelectric material.
3. The vibrational fan according to claim 2, wherein a layer is bonded to each flat surface of said aluminum core layer.
4. The vibrational fan according to claim 2, wherein two piezoelectric film layers are bonded to one flat surface of said aluminum core layer.
5. The vibrational fan according to claim 2, wherein two piezoelectric film layers are bonded to each flat surface of said aluminum core layer.
6. The vibrational fan according to claim 1, wherein the ratio of 11/12 is greater than 1.4.
7. The vibrational fan according to claim 1, wherein the ratio of l / 12 is between 1.45 and 3.4.
8. The vibrational fan according to claim 1, wherein the thickness, tp, is between about 7-55 microns.
9. The vibrational fan according to claim 1, wherein the thickness, tA, is between about 10 and 100 microns.
10. The vibrational fan according to claim 1, wherein the length, I2, is between about 1 and 5 cm.
11. An integrated vibrational fan system comprising a plurality of vibrational fans according to claim 1.
12. The integrated vibrational fan system according to claim 11, wherein said piezoelectric polymer film layer comprises a copolymer of polyvinylidene fluoride and trifluoroethylene.
13. The vibrational fan according to claim 1, wherein said piezoelectric polymer film layer comprises a copolymer of polyvinylidene fluoride and trifluoroethylene.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US35609794A | 1994-12-15 | 1994-12-15 | |
| US08/356,097 | 1994-12-15 | ||
| US35996694A | 1994-12-20 | 1994-12-20 | |
| US08/359,966 | 1994-12-20 | ||
| US42637395A | 1995-04-21 | 1995-04-21 | |
| US08/426,373 | 1995-04-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1996018823A1 true WO1996018823A1 (en) | 1996-06-20 |
Family
ID=27408248
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US1995/013616 WO1996018823A1 (en) | 1994-12-15 | 1995-10-20 | Metal enforced pvdf vibrational fan |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO1996018823A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0995908A1 (en) * | 1998-10-20 | 2000-04-26 | vanden Brande, Pierre | Molecular pump |
| US20140341762A1 (en) * | 2012-02-13 | 2014-11-20 | Murata Manufacturing Co., Ltd. | Piezoelectric fan |
| JPWO2013157346A1 (en) * | 2012-04-17 | 2015-12-21 | 株式会社村田製作所 | Piezoelectric fan |
| WO2016032429A1 (en) * | 2014-08-25 | 2016-03-03 | Ge Aviation Systems Llc | Airflow generator and array of airflow generators |
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| US4780062A (en) * | 1985-10-09 | 1988-10-25 | Murata Manufacturing Co., Ltd. | Piezoelectric fan |
| US4834619A (en) * | 1987-11-10 | 1989-05-30 | The Boeing Company | Ducted oscillatory blade fan |
| GB2220485A (en) * | 1988-04-25 | 1990-01-10 | Pennwalt Piezo Film | Gas flow detector |
| EP0385090A1 (en) * | 1989-03-03 | 1990-09-05 | Microelectronics and Computer Technology Corporation | Heat exchanger having piezoelectric fan means |
| US5008582A (en) * | 1988-01-29 | 1991-04-16 | Kabushiki Kaisha Toshiba | Electronic device having a cooling element |
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| US4498851A (en) * | 1980-05-02 | 1985-02-12 | Piezo Electric Products, Inc. | Solid state blower |
| US4684328A (en) * | 1984-06-28 | 1987-08-04 | Piezo Electric Products, Inc. | Acoustic pump |
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0995908A1 (en) * | 1998-10-20 | 2000-04-26 | vanden Brande, Pierre | Molecular pump |
| WO2000023715A1 (en) * | 1998-10-20 | 2000-04-27 | Pierre Vanden Brande | Molecular pump |
| AU763828B2 (en) * | 1998-10-20 | 2003-07-31 | Pierre Vanden Brande | Molecular pump |
| US6612816B1 (en) | 1998-10-20 | 2003-09-02 | Pierre Vanden Brande | Molecular pump |
| US20140341762A1 (en) * | 2012-02-13 | 2014-11-20 | Murata Manufacturing Co., Ltd. | Piezoelectric fan |
| US9856868B2 (en) * | 2012-02-13 | 2018-01-02 | Murata Manufacturing Co., Ltd. | Piezoelectric fan |
| JPWO2013157346A1 (en) * | 2012-04-17 | 2015-12-21 | 株式会社村田製作所 | Piezoelectric fan |
| WO2016032429A1 (en) * | 2014-08-25 | 2016-03-03 | Ge Aviation Systems Llc | Airflow generator and array of airflow generators |
| CN106662122A (en) * | 2014-08-25 | 2017-05-10 | 通用电气航空系统有限责任公司 | Airflow generator and array of airflow generators |
| JP2017532477A (en) * | 2014-08-25 | 2017-11-02 | ジーイー・アビエイション・システムズ・エルエルシー | Airflow generator and arrangement of airflow generators |
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