Patent Application
20060281398
The present invention contains subject matter related to Japanese Patent Application JP 2005-134302 filed in the Japanese Patent Office on May 2, 2005, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to jet generators for generating gas jets and electronic devices including the jet generators.
2. Description of the Related Art
Increased performance of personal computers (PCs) has posed the problem of increased amounts of heat generated from heat sources such as integrated circuits (ICs). Accordingly, a wide variety of heat dissipation techniques have been proposed or commercialized. For example, radiation fins formed of a metal such as aluminum are brought into contact with an IC to transmit heat from the IC to the fins and dissipate it. In addition, a fan is used to forcibly eject warm air in a PC casing and introduce ambient cool air to the vicinity of a heat source. Furthermore, a fan and radiation fins are used in combination to forcibly eject warm air around the radiation fins with increased contact area between the air and a heat source.
The forced convection of air using a fan, however, causes a thermal boundary layer at the surfaces of radiation fins on the downstream side thereof. The thermal boundary layer undesirably makes it difficult to draw heat away from the radiation fins effectively. One of the possible solutions to this problem is to increase the air velocity of the fan to reduce the thickness of the thermal boundary layer. However, increasing the number of revolutions of the fan for increased air velocity undesirably causes noise, such as noise from a fan bearing and wind noise due to wind from the fan.
Japanese Unexamined Patent Application Publication Nos. 2000-223871, 2000-114760, 2-213200, and 3-116961, for example, disclose methods for efficiently dissipating heat from radiation fins to the outside air by breaking the thermal boundary layer without using a fan as an air blower. These methods involve the use of a diaphragm that reciprocates periodically. In particular, Japanese Unexamined Patent Application Publication Nos. 2-213200 and 3-116961 disclose devices including a diaphragm that separates the space in a chamber substantially in half, an elastic member disposed in the chamber so as to support the diaphragm, and means for vibrating the diaphragm. The diaphragm, when displaced upward, decreases the volume of the upper space of the chamber to increase the pressure therein. The increased pressure in the upper space forces part of the air contained therein into the outside air. The upper space communicates with the outside air through inlet/outlet openings. At the same time, the diaphragm increases the volume of the lower space, opposite the upper space across the diaphragm, to decrease the pressure therein. The decreased pressure in the lower space forces part of the outside air into the lower space. The lower space communicates with the outside air through inlet/outlet openings. When displaced downward, on the other hand, the diaphragm increases the volume of the upper space of the chamber to decrease the pressure therein. The decreased pressure in the upper space forces part of the outside air into the upper space through the inlet/outlet openings. At the same time, the diaphragm decreases the volume of the lower space to increase the pressure therein. The increased pressure in the lower space forces part of the air contained therein into the outside air through the inlet/outlet openings. The diaphragm is, for example, electromagnetically actuated. The diaphragm thus reciprocates and periodically repeats the ejection of the air contained in the chamber to the outside air and the suction of the outside air into the chamber. The periodic reciprocating motion induces a pulsating air jet which impinges on a heat source such as radiation fins (heatsink). The pulsating air jet efficiently breaks a thermal boundary layer on the surface of the heat source, thus efficiently cooling the heat source.
In recent years, the amounts of heat generated from ICs have been rising with increasing clock speed. Accordingly, for example, a larger amount of air supply is demanded for ICs and radiation fins to break a thermal boundary layer caused near the fins after heat generation. In air ejection techniques using a diaphragm that reciprocates periodically as disclosed in the above publications, the amount of air ejected can be increased by increasing the amplitude of vibration of the diaphragm. If the amplitude of vibration is increased, however, the vibration of the diaphragm is undesirably transmitted through, for example, a casing of a jet generator and a casing of an electronic device including the jet generator.
This problem arises from a vibrational force produced by the reciprocating motion of the diaphragm, which has weight, and an actuator that actuates the diaphragm. The transmission of vibration can be reduced by, for example, decreasing the weight or amplitude of vibration of the diaphragm or the frequency used. However, there are trade-offs between the reduction in the weight of the diaphragm and the maintenance of the strength thereof and between the reduction in amplitude of vibration and frequency and the increase in the amount of air ejected for increased cooling efficiency (the amount of air ejected is proportional to the product of the amplitude of vibration, the effective cross-sectional area, and the frequency).
Accordingly, it is desirable to provide a jet generator that can inhibit the transmission of vibration to the outside thereof without decreasing the amount of gas ejected or cooling capability and also provide an electronic device including the jet generator.
A jet generator according to an embodiment of the present invention includes a casing containing a gas and having an opening, vibrators attached to the casing, and actuators for actuating the vibrators. The vibrators vibrate with the vibrational forces thereof being synthesized so as to attenuate each other, thereby vibrating the gas to eject a pulsating jet thereof through the opening.
This jet generator can inhibit the transmission of vibration to the outside of the casing or the jet generator because the vibrators vibrate with the vibrational forces thereof being synthesized so as to attenuate each other. In addition, the jet generator can avoid a decrease in the amount of gas ejected, or rather can increase it, because the vibrational forces attenuate each other even for increased amplitudes of vibration.
For example, at least one of the mass, structure, amplitude of vibration, and phase of the vibrators may be adjusted so that the vibrational forces attenuate each other. Alternatively, the vibrators may be arranged in such a manner that the vibrational forces attenuate each other, as described later.
The vibrators may be arranged in any manner that allows the vibrational forces thereof to attenuate each other after synthesis. For example, the vibrators may be arranged in the vibration direction or perpendicularly thereto. In addition, the vibrators may be arranged in three dimensions. For example, three vibrators may be arranged with the vibration directions thereof tilted 120° from each other (such that they define, for example, a triangular prism), or four vibrators may be arranged with the vibration directions thereof tilted 90° from each other (such that they define, for example, a rectangular parallelepiped). The term “vibration direction” herein is unrelated to phase; this term represents the direction of reciprocating motion, namely vibration, and is hereinafter used with this meaning.
Although the gas used is typically air, other gases may also be used, including nitrogen gas, helium gas, and argon gas.
The actuators may actuate the vibrators with, for example, an electromagnetic effect, a piezoelectric effect, or an electrostatic effect.
The vibrators may have a three-dimensional structure, rather than a flat structure. Such vibrators are exemplified by those having side plates or ribs for increasing rigidity, although any three-dimensional structure may be used for any purpose. Examples of the shape of the vibrators in a plane perpendicular to the vibration direction include a circle, an ellipse, and a rectangle.
In this embodiment, two of the vibrators may face each other and be actuated by the actuators so as to move toward and away from each other. This allows the vibrational forces to attenuate each other. In this case, the vibrators may, for example, have different sizes, have different shapes, or be formed of different materials.
In this embodiment, preferably, the vibrators have the same size and shape, are formed of the same material, and vibrate with the same frequency, and the actuators actuate the vibrators with a phase difference of substantially 360/n° from each other where n is the number of the vibrators. This allows the vibrational forces to attenuate each other. The same size, shape, and material described above mean sizes, shapes, and materials, respectively, that are sufficiently similar to achieve the embodiment of the present invention, that is, that can be construed as being substantially identical in terms of mass production, rather than as being physically completely identical.
This embodiment preferably meets the following conditions: the number of the vibrators is at least three; the vibrators have the same size and shape, are formed of the same material, and vibrate with the same frequency; a first vibrator group including at least two of the vibrators is actuated to vibrate at a first phase; the sum of the amplitudes of vibration of the first vibrator group is a first amplitude of vibration; at least one of the vibrators other than the first vibrator group is actuated to vibrate at a second phase opposite the first phase; and the sum of the amplitude of vibration of the at least one vibrator is a second amplitude of vibration equal to the first amplitude of vibration. The vibration of the vibrators may thus be controlled so that the vibrational forces thereof attenuate each other after synthesis.
In this embodiment, at least two of the vibrators may differ in at least one of size, shape, and material. Even if the jet generator includes two or more different types of vibrators, the amplitudes of vibration or phases thereof, for example, may be controlled so that the vibrational forces thereof attenuate each other after synthesis.
A jet generator according to another embodiment of the present invention includes casings that contain a gas and each have an opening, vibrators attached to the individual casings, and actuators disposed in the individual casings to actuate the vibrators. The vibrators vibrate with the vibrational forces thereof being synthesized so as to attenuate each other, thereby vibrating the gas to eject a pulsating jet thereof through the openings.
This jet generator can inhibit the transmission of vibration to the outside of the casings or the jet generator because the vibrators vibrate with the vibrational forces thereof being synthesized so as to attenuate each other. Each of the casings may have a single opening or a plurality of openings.
In this embodiment, preferably, the number of the vibrators is at least three, a first vibrator group including at least two of the vibrators is actuated to vibrate at a first phase in a first direction, and at least one of the vibrators other than the first vibrator group is actuated to vibrate at a second phase opposite the first phase in the first direction. The vibrators do not necessarily have to have the same size and shape or be formed of the same material, and may be arranged and actuated by the actuators 5 so that the vibrational forces thereof attenuate each other.
In this embodiment, preferably, the vibrators vibrate in the same direction, and the casings are arranged in the vibration direction. In this case, at least two of the vibrators vibrate at different phases in the same direction. This allows effective ejection of the gas toward objects, such as heat sources, arranged in one or two dimensions in a plane including the vibration direction. Alternatively, preferably, the vibrators vibrate in the same direction, and the casings are arranged in a plane substantially perpendicular to the vibration direction. This allows the ejection of the gas toward objects, such as heat sources, arranged in one or two dimensions in the plane substantially perpendicular to the vibration direction.
In this embodiment, the casings may have engaging portions that engage with each other. These engaging portions allow the casings to be stacked on top of each other or to be arranged in a plane according to the shapes and positions of objects of interest, such as heat sources, to achieve, for example, effective heat dissipation.
An electronic device according to another embodiment of the present invention includes a heat source, a jet generator casing containing a gas and having an opening, vibrators attached to the casing, and actuators for actuating the vibrators. The vibrators vibrate with the vibrational forces thereof being synthesized so as to attenuate each other, thereby vibrating the gas to eject a pulsating jet thereof through the opening toward the heat source.
An electronic device according to another embodiment of the present invention includes a heat source, jet generator casings that contain a gas and each have an opening, vibrators attached to the individual casings, and actuators disposed in the individual jet generator casings to actuate the vibrators. The vibrators vibrate with the vibrational forces thereof being synthesized so as to attenuate each other, thereby vibrating the gas to eject a pulsating jet thereof through the openings toward the heat source.
Examples of the electronic devices include computers (such as laptop PCs and desktop PCs), personal digital assistants (PDAs), electronic dictionaries, cameras, displays, audio/video equipment, cellular phones, game machines, and other electrical appliances. The heat source may be any object that releases heat. Examples of the heat source include, though not limited to, electronic components such as ICs and resistors and radiation fins (heatsinks).
The jet generators and the electronic devices according to the embodiments described above can inhibit the transmission of vibration to the outside of the jet generators without decreasing the amount of gas ejected or cooling capability.
Embodiments of the present invention will now be described with reference to the drawings.
A jet generator 10 includes a casing 1 containing air. This casing 1 has, for example, a rectangular parallelepiped shape. The casing 1 includes, for example, two opposing diaphragms 3a and 3b and actuators 5a and 5b for actuating the diaphragms 3a and 3b, respectively. For example, the actuator 5a is disposed on the top side of the casing 1, and the actuator 5b is disposed on the bottom side of the casing 1. Elastic supports 6a and 6b are attached to the peripheries of the diaphragms 3a and 3b, respectively. The elastic supports 6a and 6b are also attached to ribs 7 protruding from the inner walls of the casing 1. That is, the diaphragms 3a and 3b are attached to the elastic supports 6a and 6b so as to be vibratable with respect to the casing 1. The diaphragms 3a and 3b and the elastic supports 6a and 6b separate the space in the casing 1 into three chambers 11a, 11b, and 11c.
The chamber 11b has a larger volume than the chambers 11a and 11c. This structure, however, does not necessarily have to be employed, and the chambers 11a, 11b, and 11c may all have identical or different volumes.
Arrays of openings 1a to id are provided in a side surface 12 of the casing 1. The openings 1a communicate with the chamber 11a. The openings 1b and 1c communicate with the chamber 11b. The openings id communicate with the chamber 11c. The air contained in the chambers 11a, 11b, and 11c is ejected through the openings 1a to id toward a heat source (not shown) such as a heatsink.
The two actuators 5a and 5b, which have the same structure, each include, for example, a cylindrical yoke 8, a magnet 14 accommodated in the yoke 8 and magnetized in the vibration direction R of the diaphragms 3a and 3b, and a disc-shaped yoke 18 attached to the magnet 14. The magnet 14 and the yokes 8 and 18 constitute a magnetic circuit. A coil bobbin 9 having a coil 17 wound therearound moves into and out of the space between the magnet 14 and the yoke 8. That is, the actuators 5a and 5b are composed of voice coil motors. The actuators 5a and 5b are connected to drive ICs (not shown) through feed lines (not shown) connected to the coils 17. The drive ICs supply electrical signals to the actuators 5a and 5b through the feed lines to vibrate the diaphragms 3a and 3b in the vibration direction R.
The casing 1 is formed of, for example, resin, rubber, metal, or ceramic. In particular, resin and rubber are suitable for mass production because of their formability. In addition, resin and rubber can inhibit, for example, noise from the actuators 5a and 5b and jet noise due to the vibration of the diaphragms 3a and 3b. That is, if the casing 1 is formed of resin or rubber, it can inhibit the noise with high attenuation. Furthermore, these materials allow for reductions in weight and cost. Among metals, copper and aluminum are preferred for their high thermal conductivity in view of heat dissipation from the casing 1. The elastic supports 6a and 6b are formed of, for example, resin or rubber.
The diaphragms 3a and 3b are formed of, for example, resin, paper, rubber, or metal. The diaphragms 3a and 3b do not necessarily have to have a flat shape as shown in the drawings and may also have a three-dimensional shape such as a conical shape like diaphragms for loudspeakers. The planar shape (the shape in a plane substantially perpendicular to the vibration direction R) of the diaphragms 3a and 3b is not limited to the rectangular shape shown in
The operation of the jet generator 10 is then described below.
The actuators 5a and 5b are supplied with, for example, a sinusoidal AC voltage to induce the sinusoidal vibration of the diaphragms 3a and 3b. Specifically, the actuators 5a and 5b actuate the diaphragms 3a and 3b, respectively, so that they move toward and away from each other to increase or decrease the volumes of the chambers 11a, 11b, and 11c. The changes in the volumes thereof vary the pressures therein to produce a pulsating air jet through the openings 1a to 1d. If, for example, the diaphragms 3a and 3b are displaced in such directions as to increase the volumes of the chambers 11a and 11c, respectively, the pressures in the chambers 11a and 11c decrease and the pressure in the chamber 11b increases. As a result, the air outside the casing 1 flows into the chambers 11a and 11c through the openings 1a and 1d, respectively, while the air contained in the chamber 11b is ejected to the outside of the casing 1 through the openings 1b and 1c. If, on the other hand, the diaphragms 3a and 3b are displaced in such directions as to decrease the volumes of the chambers 11a and 11c, respectively, the pressures in the chambers 11a and 11c increase so that the air contained in the chambers 11a and 11c is ejected to the outside through the openings 1a and 1d.
When the air is ejected through the openings 1a to id, the atmospheric pressure outside the casing 1 decreases around the openings 1a to 1d. As a result, the ambient air is drawn to the air ejected through the openings 1a to id to produce a synthetic jet. The synthetic jet is allowed to impinge on a heat source, such as a heatsink, and cool it.
Sound waves occur in the vicinities of the openings 1a to id when the air is ejected to the outside through the openings 1a to id. These sound waves attenuate each other and result in reduced noise because the vibration of the diaphragm 3a is out of phase with that of the diaphragm 3b and thus the timing when the air is ejected through the openings 1b and 1c is out of phase with the timing when the air is ejected through the openings 1a and 1d.
The jet generator 10, as described above, can inhibit the transmission of the vibration of the diaphragms 3a and 3b to the outside of the casing 1 or the jet generator 10 because the diaphragms 3a and 3b vibrate so that the vibrational forces thereof attenuate each other. In addition, the jet generator 10 can avoid a decrease in the amount of air ejected, or rather can increase it, because the vibrational forces of the diaphragms 3a and 3b attenuate each other even for increased amplitudes of vibration.
A jet generator 20 includes a first jet-generating unit 120 and a second jet-generating unit 220 that are stacked on top of each other. The first jet-generating unit 120 includes a casing 121 accommodating a diaphragm 3 and an elastic support 6 which separate the space in the casing 121 into a first chamber 131a and a second chamber 131b. The second jet-generating unit 220 includes a casing 221 having the same structure as the casing 121 of the first jet-generating unit 120. The second jet-generating unit 220 is disposed upside down with respect to the position of the first jet-generating unit 120 with the diaphragms 3 thereof facing each other.
Actuators 5 actuate the diaphragms 3 so as to decrease the volumes of the chambers 131b and 231a while increasing the volumes of the chambers 131a and 231b. On the other hand, the actuators 5 actuate the diaphragms 3 so as to increase the volumes of the chambers 131b and 231a while decreasing the volumes of the chambers 131a and 231b. These operations eject a pulsating air jet through openings 121a, 121b, 221a, and 221b.
The two jet-generating units 120 and 220 can allow the vibrational forces of the diaphragms 3 to attenuate each other. The jet generator 20 thus has the same advantages as the jet generator 10 shown in
Even if the diaphragms 33a and 33b have different sizes, have different shapes, or are formed of different materials, for example, the diaphragms 33a and 33b may be allowed to move toward or away from each other so that the vibrational forces thereof attenuate each other after synthesis. A residual force may be left after the attenuation of the vibrational forces by synthesis. The vibrational forces may also be substantially eliminated by, for example, increasing the amplitude of vibration of the diaphragm 33a to larger than that of the diaphragm 33b, which has a larger mass than the diaphragm 33a.
The three diaphragms 3a, 3b, and 3c may also vibrate as shown in
The diaphragms 3a, 3b, and 3c preferably have the same size and shape and be formed of the same material, for example, to achieve waveforms as shown in
The occurrence of the moment may be inhibited by arranging at least three jet-generating units 120 longitudinally, as shown in
Jet generators shown in
The jet-generating units 60 and 70 (and other jet-generating units 80 and 90) are in contact with each other in
Although the four bumps 121c and the four recesses 121d are disposed on each casing 121 in
The sizes and shapes of the bumps 121c and the recesses 121d are not limited to those in
Alternatively, in
In
Which structure has the best effect of attenuating the vibration of an electronic device among the structures shown in
The present invention is not limited to the embodiments described above, and various modifications are permitted.
Although the simple openings 1a to id are provided on the casing 1 in
At least two of the features of the embodiments shown in the drawings may be used in any combination.
The jet generators described above may also be used to supply fuel to fuel cells. Specifically, the nozzles (or openings) of the jet generators according to the embodiments described above may be disposed opposite oxygen (air) inlets of fuel cell bodies. The jet generators can thus inject a jet into the inlets as an oxygen fuel.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2005-134302 | May 2005 | JP | national |
