US20110168361A1

US20110168361A1 - Heat dissipation device and airflow generator thereof

Info

Publication number: US20110168361A1
Application number: US12/820,078
Authority: US
Inventors: Chien-Yu Chao; Yen-Chih Chen
Original assignee: Foxconn Technology Co Ltd
Current assignee: Foxconn Technology Co Ltd
Priority date: 2010-01-11
Filing date: 2010-06-21
Publication date: 2011-07-14
Also published as: TW201125479A

Abstract

An exemplary heat dissipation device includes a heat sink defining a plurality of air passages therein, and an airflow generator disposed at a side of the heat sink. The airflow generator includes airflow-generating units stacked together. Each airflow-generating unit includes a casing in which two spaced vibration diaphragms are received, and a nozzle connected to the casing. A chamber is defined between the two vibration diaphragms within the casing. The nozzle defines an air channel therein for communicating the chamber with an exterior of the casing. Two piezoelectric elements are respectively attached to the two vibration diaphragms. When the two piezoelectric elements drive the two vibration diaphragms towards each other, the two vibration diaphragms compress the air in the chamber and drive the air towards the air channel of the nozzle, thereby generating an airflow from the nozzle towards the air passages of the heat sink.

Description

BACKGROUND

1. Technical Field
The disclosure generally relates to heat dissipation; and more particularly to a heat dissipation device incorporating an airflow generator.
2. Description of Related Art
With developments in electronic components such as central processing units (CPUs), such components are nowadays capable of operating at very high speeds. The amount of heat generated by such components during normal operation is commensurately large. If not quickly removed from a CPU, this generated heat may cause the CPU to become overheated and finally affect its workability and stability.
In order to remove the heat from a CPU and hence enable normal operation, a heat dissipation device is usually provided. A frequently used heat dissipation device includes a fan with a heat sink arranged at an outlet thereof, with the heat sink thermally connected to the CPU via a heat pipe. Heat generated by the CPU is transferred to fins on the heat sink via the heat pipe. Airflow from the fan crosses the fins of the heat sink and removes the heat from the fins to the exterior of the system.
However, when running at high speeds, the fan generates noise. In addition, an impeller of the fan usually increases the size of the heat dissipation device, compromising efforts to limit the size of the corresponding electronic product.
What is needed, therefore, is a means to overcome the described limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is an isometric, assembled view of a heat dissipation device in accordance with an exemplary embodiment of the present disclosure.

FIG. 2 is an exploded view of the heat dissipation device of FIG. 1.

FIG. 3 is similar to FIG. 2, but viewed from a different aspect.

FIG. 4 is a cross-section of the heat dissipation device of FIG. 1, taken along a line IV-IV thereof.

FIG. 5 is a schematic view corresponding to FIG. 4, showing a first stage of operation of one airflow-generating unit of the heat dissipation device of FIG. 1.

FIG. 6 is similar to FIG. 5, but showing a second stage of operation of the airflow-generating unit of the heat dissipation device of FIG. 1.

FIG. 7 is similar to FIG. 6, but showing a third stage of operation of the airflow-generating unit of the heat dissipation device of FIG. 1.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, a heat dissipation device 100 according to an exemplary embodiment of the present disclosure is shown. The heat dissipation device 100 includes an airflow generator 10 and a heat sink 20. In a typical application, a heat-generating electronic component (not shown) generates heat, and such heat is transferred from the heat-generating electronic component to the heat sink 20.
Referring also to FIG. 4, the airflow generator 10 includes a shell 11 and a plurality of airflow-generating units 12. The airflow-generating units 12 are arranged in the shell 11, and are stacked together horizontally. Each airflow-generating unit 12 includes a casing 121, two vibration diaphragms 122 received in the casing 121, and a nozzle 123 arranged at an end of the casing 121.
The casing 121 is cuboid. The two vibration diaphragms 122 are horizontally mounted in the casing 121 at different levels. The two vibration diaphragms 122 are spaced from and parallel to each other. An inner space of the casing 121 is divided by the two vibration diaphragms 122 into a first chamber 124 between the two vibration diaphragms 122, a second chamber 125 located above the first chamber 124 and isolated from the first chamber 124 via a top one of the vibration diaphragms 122, and a third chamber 126 located below the first chamber 124 and isolated from the first chamber 124 via a bottom one of the vibration diaphragms 122. Each vibration diaphragm 122 is elastic material, such as rubber, flexible resin or a thin metal sheet.
Two piezoelectric elements 127 are received in the second chamber 125 and the third chamber 126 of the casing 121, respectively. The two piezoelectric elements 127 are respectively attached to middle portions of the two vibration diaphragms 122, so as to vibrate substantially perpendicularly to the two vibration diaphragms 122 when an alternating voltage is applied to the piezoelectric elements 127. Each piezoelectric element 127 is made of piezoelectric ceramic. Through holes (not labeled) are defined in a sidewall of the casing 121 for extension of wires 128 therethrough to electrically connect the piezoelectric elements 127 on the two vibration diaphragms 122 with an external power supply (not shown).
The nozzle 123 is disposed at the end of the casing 121 which faces the heat sink 20. The nozzle 123 is connected to a middle portion of the sidewall of the casing 121 at the end of the casing 121, and corresponds to the first chamber 124. The nozzle 123 defines a tapered air channel 1231 therein. A large end of the air channel 1231 communicates with the first chamber 124, and a small end of the air channel 1231 is adjacent to the heat sink 20.
The shell 11 defines a receiving space (not labeled) therein, with an opening 111 of the receiving space adjacent to the heat sink 20. The stacked airflow-generating units 12 are arranged into the shell 11 via the opening 111. The shell 11 fixes the stacked airflow-generating units 12 together. In other embodiments, the stacked airflow-generating units 12 can be fixed together by adhesive or glue.
The heat sink 20 includes a plurality of spaced fins 21, with a plurality of air passages 22 defined between the fins 21. The airflow generator 10 is arranged at a lateral side of the heat sink 20, with the nozzles 123 of the airflow-generating units 12 facing the air passages 22 of the heat sink 20. The small end of the nozzle 123 of each airflow-generating unit 12 is spaced a predetermined distance from an entrance of a corresponding air passage 22 of the heat sink 20.
In operation, the external power supply provides an alternating voltage to the two piezoelectric elements 127 of each airflow-generating unit 12 via the wires 128. As a result of the reverse piezoelectric effect, the two piezoelectric elements 127 produce alternating expansion and retraction, driving the two vibration diaphragms 122 up and down. In particular, the two vibration diaphragms 122 bend towards each other simultaneously or bend away from each other simultaneously. When the two piezoelectric elements 127 drive the two vibration diaphragms 122 towards each other, the two vibration diaphragms 122 compress the air in the first chamber 124 towards the air channel 1231 of the nozzle 123, generating airflow towards the air passages 22 of the heat sink 20 from the small end of the nozzle 123. The airflow along the air passages 22 of the heat sink 20 removes heat present in the fins 21.
Referring to FIGS. 5-7, an airflow-generating process of each airflow-generating unit 12 in one vibrating period is as follows:
The airflow-generating process is divided into a first stage, a second stage, and a third stage. In the first stage, the external power supply provides a negative/positive voltage to the two piezoelectric elements 127 via the wires 128, and the two piezoelectric elements 127 drive the two vibration diaphragms 122 towards each other. The air in the first chamber 124 is compressed by the two vibration diaphragms 122 and flows towards the air channel 1231 of the nozzle 123. Referring to FIG. 5, when the two vibration diaphragms 122 move from originally horizontal positions to curved positions indicated by broken lines 122 a, a first airflow 31 is generated towards the air passages 22 of the heat sink 20 from the outer end of the nozzle 123. The first airflow 31 along the air passages 22 of the heat sink 20 results in heat exchange from the fins 21 to the air, and the heat of the fins 21 is thereby removed.
In the second stage of the airflow-generating process, the negative/positive voltage supplied to the two piezoelectric elements 127 is inverted to a positive/negative voltage, such that the two piezoelectric elements 127 drive the two vibration diaphragms 122 away from each other. Referring to FIG. 6, when the two vibration diaphragms 122 return from the curved positions indicated by broken lines 122 b (see in FIG. 5) back to the horizontal positions, the air outside and around the nozzle 123 is drawn into the air passages 22 of the heat sink 20, generating a second airflow 32 along the air passages 22 of the heat sink 20, at a flow rate about ten times that of the first airflow 31.
In the third stage of the airflow-generating process, the two vibration diaphragms 122, as shown in FIG. 7, continue to move farther way from each other until they reach the curved positions indicated by broken lines 122 b. During this stage, the volume of the first chamber 124 is expanded, such that cool air (indicated by arrows 33) outside and around the nozzle 123 is drawn into the first chamber 124 of the casing 121. Then the positive/negative voltage supplied to the two piezoelectric elements 127 is inverted to the negative/positive voltage, and the first stage of the airflow-generating process begins again.
In each airflow-generating unit 12, under the alternating voltage, the two piezoelectric elements 127 drive the two vibration diaphragms 122 to periodically compress the air in the first chamber 124 of the casing 121, generating airflow towards the air passages 22 of the heat sink 20 from the outer end of the nozzle 123. In addition, by supplying alternating voltages of different frequencies, the flow rate of the airflow generated by the airflow-generating unit 12 can be adjusted to meet different cooling requirements.
In the heat dissipation device 100, the heat transferred to the fins 21 of the heat sink 20 is dissipated from the fins 21 by the airflow generator 10. The number of airflow-generating units 12 of the airflow generator 10 can be chosen to meet the cooling requirements of a particular application. Further, no motor or impeller is used in the heat dissipation device 100. Thus the heat dissipation device 100 can have a small size and quiet operation.
It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. An airflow generator, comprising:

at least one airflow-generating unit, comprising:

a casing;

two spaced vibration diaphragms received in the casing, with a chamber defined between the two vibration diaphragms;

a nozzle connected to a sidewall of the casing in a position corresponding to the chamber, an air channel defined in the nozzle and communicating the chamber with an exterior of the casing; and

two piezoelectric elements respectively attached to the two vibration diaphragms, the two piezoelectric elements capable of vibrating substantially perpendicularly to the two vibration diaphragms when voltage is applied to the two piezoelectric elements and thereby driving the two vibration diaphragms to vibrate, whereby when the two piezoelectric elements drive the two vibration diaphragms towards each other, the two vibration diaphragms compress the air in the chamber of the casing and drive the air towards the air channel of the nozzle, generating an airflow from the nozzle to the exterior of the casing.

2. The airflow generator of claim 1, wherein the air channel of the nozzle is tapered from an inner end of the nozzle adjacent to the chamber towards an opposite outer end of the nozzle.

3. The airflow generator of claim 1, wherein the two vibration diaphragms are parallel to each other.

4. The airflow generator of claim 1, wherein the casing is cuboid.

5. The airflow generator of claim 1, wherein the piezoelectric elements are attached to middle portions of the two vibration diaphragms, respectively.

6. The airflow generator of claim 1, further comprising a shell in which the at least one airflow-generating unit is mounted.

7. A heat dissipation device, comprising:

a heat sink defining a plurality of air passages therein; and

an airflow generator disposed at a side of the heat sink, the airflow generator comprising:

a plurality of airflow-generating units stacked together, each of the airflow-generating units comprising:

a casing;

two spaced vibration diaphragms received in the casing, between which a chamber is defined;

a nozzle disposed at a lateral side of the casing facing the heat sink and connected to a sidewall of the casing, an air channel defined in the nozzle and communicating the chamber with an exterior of the casing; and

two piezoelectric elements respectively attached to the two vibration diaphragms, the two piezoelectric elements capable of vibrating substantially perpendicularly to the two vibration diaphragms when voltage is applied to the two piezoelectric elements and thereby driving the two vibration diaphragms to vibrate, whereby when the two piezoelectric elements drive the two vibration diaphragms towards each other, the two vibration diaphragms compress the air in the chamber of the casing and drive the air towards the air channel of the nozzle, generating an airflow from the nozzle to at least one of the air passages of the heat sink.

8. The heat dissipation device of claim 7, wherein the air channel of the nozzle is tapered from an inner end of the nozzle adjacent to the chamber towards an opposite outer end of the nozzle.

9. The heat dissipation device of claim 7, wherein the two vibration diaphragms are parallel to each other.

10. The heat dissipation device of claim 7, wherein the casing is cuboid.

11. The heat dissipation device of claim 7, wherein the piezoelectric elements are attached to middle portions of the two vibration diaphragms, respectively.

12. The heat dissipation device of claim 7, wherein the airflow generator further comprises a shell in which the airflow-generating units are mounted.

13. The heat dissipation device of claim 7, wherein the heat sink comprises a plurality of stacked fins, the air passages are defined between adjacent fins, and the air passages are aligned with the airflow-generating units.

14. A heat dissipation device, comprising:

a heat sink defining a plurality of air passages therein; and

an airflow generator disposed at a side of the heat sink, the airflow generator comprising a plurality of airflow-generating units stacked together, each airflow-generating unit comprising:

a casing;

two vibration diaphragms received in the casing, the diaphragms defining a chamber therebetween;

a nozzle extending from a sidewall of the casing at a position corresponding to the chamber, the nozzle defining an air channel therein, the air channel communicating the chamber with an exterior of the casing; and

two piezoelectric elements received in the casing and attached to the diaphragms, respectively, the piezoelectric elements configured for driving the diaphragms to vibrate such that when the piezoelectric elements drive the diaphragms towards each other simultaneously, the diaphragms compress the air in the chamber and drive the air into the air channel of the nozzle, thereby generating an airflow from the nozzle to at least one of the air passages of the heat sink.

15. The heat dissipation device of claim 14, wherein the piezoelectric elements are further configured for driving the diaphragms to vibrate such that when the piezoelectric elements drive the diaphragms away from each other simultaneously, air outside and around the nozzle is drawn into the at least one air passage of the heat sink, generating an airflow along the at least one air passage.

16. The heat dissipation device of claim 15, wherein the piezoelectric elements are further configured for driving the diaphragms to vibrate such that when the piezoelectric elements drive the diaphragms away from each other simultaneously, the volume of the chamber is eventually expanded and air outside and around the nozzle is drawn into the chamber.

17. The heat dissipation device of claim 15, wherein when the diaphragms move towards each other simultaneously and thereby generate an airflow from the nozzle to the at least one air passage of the heat sink, resulting airflow along the at least one air passage has a first flow rate; when the diaphragms move away from each other simultaneously and air outside and around the nozzle is drawn into the at least one air passage of the heat sink and generates an airflow along the at least one air passage, such airflow has a second flow rate; and the second flow rate is greater than the first flow rate.

18. The heat dissipation device of claim 17, wherein the second flow rate is about ten times the first flow rate.