Piezoelectric Cooling Fan

Abstract

A piezoelectric cooling fan comprises a support frame and two piezoelectric actuators. Each piezoelectric actuator includes an electrical-conductive plate and a piezoelectric plate attached to the electrical-conductive plate, wherein an edge portion of the electrical-conductive plate is fixedly attached to a base of the support frame and approximately aligned with an edge portion of the piezoelectric plate attached thereto. The two piezoelectric actuators are symmetrically arranged with respect to the base of the support frame to define a cavity therebetween and are electrically connected with an AC power source, so that the piezoelectric actuators can be driven to flex towards and away from each other with respect to the edge portions of the piezoelectric actuators, so that air pulses can be induced from the cavity between the piezoelectric actuators for heat dissipation. The piezoelectric cooling fan is light, compact, low noise, low power, and free of electromagnetic interference.

Description

(a) TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a piezoelectric cooling fan and, more particular, to a cooling fan which does not employ a rotary motor and can achieve a design that is light, compact, low noise, low power, and free of electromagnetic interference.

(b) DESCRIPTION OF THE PRIOR ART

[0002] FIGS. 1 and 1A show a conventional cooling fan 2, which is driven by a motor. For example, U.S. Pat. No. 7,165,938 B2 and US. Publication Number 2008/0130226 A1 belong to this type of cooling fan. Since portable electronic products, such as notebook or tablet pc, become smaller and smaller, the conventional cooling fan 2 has been challenged by space issues. To effectively reduce the thickness of a cooling fan is an important task that all manufacturers of cooling fan should face.

[0003] Based on long-term experience of related works and constant test and innovation, the applicant has contrived a piezoelectric cooling fan that is light, compact, low noise, low power, and free of electromagnetic interference.

SUMMARY OF THE INVENTION

[0004] The primary object of the present invention is to provide a piezoelectric cooling fan that employs slim piezoelectric actuators and can achieve a design that is light, compact, low noise, low power, and free of electromagnetic interference.

[0005] To achieve the above object, the piezoelectric cooling fan may comprise a support frame and two piezoelectric actuators. Each piezoelectric actuator includes an electrical-conductive plate and a piezoelectric plate attached to the electrical-conductive plate, wherein an edge portion of the electrical-conductive plate is fixedly attached to a base of the support frame and approximately aligned with an edge portion of the piezoelectric plate attached thereto. The two piezoelectric actuators are symmetrically arranged with respect to the base of the support frame to define a cavity therebetween and are electrically connected with an AC power source, so that the piezoelectric actuators can be driven to flex towards and away from each other with respect to the edge portions of the electrical-conductive plates and the piezoelectric plates, so that air pulses can be induced from the cavity between the piezoelectric actuators for heat dissipation.

[0006] According to one aspect of the present invention, the piezoelectric cooling fan may further comprise two protective covers being respectively placed over the piezoelectric plates and mounted to the support frame.

[0007] In operation, when the piezoelectric actuators are energized with an AC power source, the remaining portions other than the edge portions of the electrical-conductive plates and the piezoelectric plate can be driven to flex towards and away from each other with respect to the edge portions of the electrical-conductive plates and the piezoelectric plates, so that air pulses can be induced from the cavity between the piezoelectric actuators for heat dissipation. The piezoelectric cooling fan can achieve a design that is light, compact, low noise, low power, and free of electromagnetic interference.

[0008] Other objects, advantages, and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 shows a 3-dimensional view of a conventional cooling fan.

[0010] FIG 1A shows a sectional view of the conventional cooling fan taken along line A-A in FIG. 1.

[0011] FIG. 2 shows a 3-dimensional view of a piezoelectric cooling fan according to one embodiment of the present invention.

[0012] FIG. 3 shows an exploded view of the embodiment of the present invention.

[0013] FIG. 4 shows a top view of the embodiment of the present invention.

[0014] FIG. 5 shows various sectional views of the embodiment of the present invention, wherein one view illustrates that the piezoelectric actuators thereof are flexed away from each other for sucking in airflow whereas another view illustrates that the piezoelectric actuators thereof are flexed towards each other for forcing out airflow.

[0015] FIG. 6 shows an exploded view of one of the piezoelectric actuators used in the present invention.

[0016] FIG. 7 shows a 3-dimensional view of one of the piezoelectric actuators used in the present invention.

[0017] FIG. 8 shows a 3-dimensional view of the embodiment of the present invention that further includes two protective covers.

[0018] FIG. 9 shows an exploded view of the embodiment of the present invention that further includes two protective covers.

[0019] FIG. 10 shows a top view of the embodiment of the present invention that further includes two protective covers.

[0020] FIG. 11 shows a sectional view (taken along line A-A in FIG. 10) of the embodiment of the present invention that further includes two protective covers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] To allow the features and advantages of the present invention to be fully understood, one embodiment of the present invention is illustrated in the following paragraphs with reference to the accompanying drawings.

[0022] FIGS. 2 through 7 show a piezoelectric cooling fan according to one embodiment of the present. As shown, the piezoelectric cooling fan generally comprises a support frame 11 and two piezoelectric actuators 12. Each piezoelectric actuator 12 includes an electrical-conductive plate 121 and a piezoelectric plate 122 attached to the electrical-conductive plate 121, wherein an edge portion of the electrical-conductive plate 121 is fixedly attached to a base of the support frame 11 and approximately aligned with an edge portion of the piezoelectric plate 122 attached thereto. The two piezoelectric actuators 12 are symmetrically arranged with respect to the base of the support frame 11 to define a cavity therebetween. Furthermore, the two piezoelectric actuators 12 are electrically connected with an AC power source (not shown) through a pair of electrical wires, so that the piezoelectric actuators 12 can be driven to flex towards and away from each other with respect to the edge portions of the electrical-conductive plates 121 and the piezoelectric plates 122, so that air pulses can be induced from the cavity between the piezoelectric actuators 12 for heat dissipation. One of the electrical wires can be a neutral wire that are electrically connected to the electrical-conductive plates 121 whereas the other one of the electrical wires can be a live wire that are electrically connected to the piezoelectric plates 122 on the electrical-conductive plates 121.

[0023] As shown in FIG. 6, the electrical-conductive plates 121 and the piezoelectric plates 122 are rectangular. Because the edge portions of the plates 121, 122 are fixed to the base of the support frame 11, the effective length (or the remaining length) of the electrical-conductive plates 121 and the piezoelectric plates 122 is less than their original length. As shown, each electrical-conductive plate 121 has a length of Lm, an effective length of Lme, and an effective width of Wme; each piezoelectric plate 122 has a length of Lc, an effective length of Lce, and an effective width of Wce; wherein the ratio of Lce to Lme is less than or equal to 1.0 and is greater than or equal to 0.1; the ratio of Wce to Wme is less than or equal to 1.0 and is greater than or equal to 0.5. Preferably, the above ratios can be further limited to allow the piezoelectric cooling fan to have an optimal performance, wherein the ratio of Lce to Lme is less than or equal to 0.6 and is greater than or equal to 0.4; the ratio of Wce to Wme is less than or equal to 1.0 and is greater than or equal to 0.96. Furthermore, the support frame 11 can be made of metal, plastic, engineering plastic, ceramic, or composite material. The electrical-conductive plates 121 can be made of metal or composite material with electrical conductivity.

[0024] In operation, when the piezoelectric actuators 12 are energized with an AC power source, the remaining portions other than the edge portions of the electrical-conductive plates 121 and the piezoelectric plates 122 will be driven to flex towards and away from each other with respect to the edge portions of the electrical-conductive plates 121 and the piezoelectric plates 122, so that air pulses can be induced from the cavity between the electrical-conductive plates 122 for heat dissipation. As shown in FIG. 5, when the piezoelectric actuators 12 are flexed away from each other, airflow can be sucked into the cavity between the piezoelectric actuators 12 (see right figure). On the other hand, when the piezoelectric actuators 12 are flexed towards each other, airflow can be forced out from the cavity (see left figure). To design a piezoelectric cooling fan with a proper flow rate and a reduced noise level is determined by the dimension of the cavity between the two piezoelectric actuators 12. In an experiment, a piezoelectric cooling fan according to the embodiment of the present invention is investigated, wherein the cooling fan has an outside dimension of 40 mm (length)×40 mm (width)×3 mm (thickness), the area of the cavity exit of the cooling fan is about 35 mm×1.3 mm=45.5 square-mm, and the AC power source for the cooling fan is an electrical power of 30 volts at 200 HZ. The measurement of the flow rate of the airflow from the cavity can reach 1.0 cubic-meter per minute. This amount of the airflow induced from the cavity is adequate for dissipating the heat generated from a CPU. The noise level measured at a distance of 30 cm from the cooling fan is about 30 dB. In the experiment, the associated parameters of the electrical-conductive plate 121 is: Lm=34 mm, Lme=28 mm; the associated parameters of the piezoelectric plate 122 is: Lc=18 mm; the ratio of Lce to Lme is 0.5 (14:28); the ratio of Wce to Wme is 0.96. The electrical current required for the cooling fan is about 7 mA, and thus the power consumption is about 30 volts×7 mA, which is equal to 0.21W, and thus the fan is a power-saving device.

[0025] FIGS. 8 through 11 show the embodiment of the present invention that further includes two protective covers 13a being respectively placed over the two piezoelectric actuators 12a and mounted to the support frame 11a. Specifically, the two protective covers 13a are placed over the piezoelectric plates of the piezoelectric actuators 12a respectively. The protective covers 13a, which can be made of resin, paper, or composite material, are used to protect the piezoelectric plates of the piezoelectric actuators 12a from being touched.

[0026] As a summary, the piezoelectric cooling fan of the present invention can achieve a design that is light, compact, low noise, low power, and free of electromagnetic interference. Therefore, the present invention is a useful creation.

[0027] Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure is made by way of example only and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention hereinafter claimed.

Claims

1. A piezoelectric cooling fan, comprising: a support frame, and two piezoelectric actuators each including an electrical-conductive plate and a piezoelectric plate attached to the electrical-conductive plate, wherein an edge portion of the electrical-conductive plate is fixedly attached to a base of the support frame and approximately aligned with an edge portion of the piezoelectric plate attached thereto, the two piezoelectric actuators being symmetrically arranged with respect to the base of the support frame to define a cavity therebetween and being electrically connected with an AC power source, so that the piezoelectric actuators can be driven to flex towards and away from each other with respect to the edge portions of the electrical-conductive plates and the piezoelectric plates, so that air pulses can be induced from the cavity between the piezoelectric actuators for heat dissipation.

2. The piezoelectric cooling fan of claim 1, further comprising two protective covers being respectively placed over the piezoelectric plates and mounted to the support frame

3. The piezoelectric cooling fan of claim 2, wherein the protective covers are made of resin, paper, or composite material.

4. The piezoelectric cooling fan of claim 1, wherein each electrical-conductive plate is rectangular and has a length of Lm, an effective length of Lme, and an effective width of Wme; each piezoelectric plate is rectangular and has a length of Lc, an effective length of Lce, and an effective width of Wee; wherein the ratio of Lce to Lme is less than or equal to 1.0 and is greater than or equal to 0.1; the ratio of Wce to Wme is less than or equal to 1.0 and is greater than or equal to 0.5., and wherein all the ratios are further limited such that the ratio of Lee to Lme is less than or equal to 0.6 and is greater than or equal to 0.4; the ratio of Wce to Wme is less than or equal to 1.0 and is greater than or equal to 0.96.

5. The piezoelectric cooling fan of claim 1, wherein the support frame is made of metal, plastic, engineering plastic, ceramic, or composite material.

6. The piezoelectric cooling fan of claim 1, wherein the electrical-conductive plates are made of metal or composite material with electrical conductivity

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