JP2002339900A - Piezoelectric fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the noise of a piezoelectric fan and to simplify the structure of intake/ventilation holes. SOLUTION: The piezoelectric fan has a wind generating vibrator 4 including a piezoelectric element 3, and the ventilation holes 7 and the intake 6 are disposed on the same plane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric fan for use in forced air cooling of, for example, electronic equipment, that is, a piezoelectric fan for discharging heat inside the equipment to the outside of the equipment.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller and more densely packed, measures against heat inside the devices have become more important. A typical example is a portable personal computer (hereinafter, referred to as a portable PC). Technological development for making the mobile PC lighter and thinner is progressing, while the speed of the CPU (central processing unit) is also progressing, and the performance and the miniaturization are being made simultaneously. C
An increase in the speed of the PU results in an increase in the power consumption of the CPU, that is, an increase in the amount of heat generated. When the mounting density increases, the amount of heat generated inside the device increases, and it becomes more difficult to release this heat to the outside of the device to suppress the temperature rise inside the device.

FIG. 23 shows an example of a cooling fan used as a measure against heat of electronic equipment. FIG. 23A shows an electromagnetic fan 102 configured to draw in air 101 from the back side and discharge it to the front side. FIG. 23B shows an electromagnetic fan 1 configured to draw in air 101 from the top side and discharge it to the front side.
03 is shown. FIG. 23C shows a piezoelectric fan 104 configured to suck air 101 from the back side and discharge it to the front side.
Is shown. The illustrated example is a typical intake / exhaust structure of an electromagnetic fan and a piezoelectric fan, and both the intake port and the exhaust port are formed on different surfaces.

[0004] As a typical heat countermeasure for a portable PC, a combination of an electromagnetic fan and a heat pipe is known. This is a system that uses a heat pipe having high heat transfer efficiency between a heat source (for example, a CPU or the like) and a heat radiation element (an electromagnetic fan or the like). The heat pipe has a function of transmitting heat, and the electromagnetic fan has a function of releasing the transmitted heat to the outside of the device. Electromagnetic fans are widely used not only for portable PCs but also as indispensable electronic devices that require measures against heat. Many portable PCs use a structure (see FIG. 23B) that sucks air from the upper part of the fan (the upper part of the propeller) and discharges the air in the horizontal direction (one direction) due to the limitation of the thickness of the device. . In general, an electromagnetic fan having such a structure tends to have a smaller blowing air volume and a maximum static pressure as the thickness of the fan becomes thinner.

As described above, as a means for releasing the heat inside the device to the outside of the device, a method of generating a flow of air and discharging the heated air inside to the outside has been widely used. An electromagnetic fan is used as a means for generating the noise. As a means for generating a flow of air other than the electromagnetic fan, there is a method of generating a distortion by applying an electric field to a piezoelectric body to reciprocate a blowing plate to blow air. This method has been introduced in literatures and gazettes, but has not been put to practical use. For example, "Piezoelectric fan"<Jiro Inoue / Katsumi Fujimoto> Handbook of Precision Control Actuator, JP-A-9-321360, "Piezoelectric fan", JP-B-6-56160, "Piezoelectric fan", JP-A-8-330488 “Heat sink with piezoelectric fan”, JP-B-6-4079, “Piezoelectric fan”, and JP-B-6-6960, “Piezoelectric fan-type blower” are known.

[0006]

The structure of the piezoelectric fan is as follows.
There are several structural examples as shown in the above publications.
The principle of operation is that a predetermined electric field is applied to the piezoelectric body to generate distortion, and the generated distortion causes the diaphragm to vibrate to generate wind. The principle of blowing air from a piezoelectric fan is to generate a flow of fluid by reciprocating motion of a plate having a predetermined area (precisely, it is not a full parallel reciprocating motion, but a swing motion). You can imagine a fan. In contrast to the "fan" of a piezoelectric fan, a general electromagnetic fan is a "fan" that generates a flow of fluid by rotational movement.

As described above, the piezoelectric fan utilizes the reciprocating motion of the plate. The higher the speed of the reciprocating motion of the plate, the larger the wind speed tends to be obtained.
A frequency of 0 Hz or more may be required. When the frequency of the plate reaches the audible frequency range, noise is generated by compression waves (sound waves) generated by the reciprocating motion of the plate. The noise of piezoelectric fans differs from the “wind noise” of general cooling fans, and has the characteristic that the noise level is high at a specific frequency. This is a big issue.

On the other hand, a cooling fan basically releases the heat inside a device to be cooled to the outside of the device. Like a CPU cooler, the cooling fan installed inside the equipment is C
The purpose is to diffuse the heat of the PU portion into the inside of the device, but also in this case, strictly speaking, the basic principle is the same in that the heat of the CPU is released outside the CPU. As described above, the cooling fan is a heat exchanger using air, and generally has a port for taking in air from the outside and a port for discharging air to the outside.

Therefore, equipment requiring a cooling fan is:
The cooling fan must have an “inlet” and an “outlet” for air, and the installation state of the inlet and the outlet greatly changes the cooling state inside the device. Thus, the design of the device is restricted due to the installation of the inlet and the outlet. That is, the design is restricted, and the hermeticity cannot be ensured. In the future, in particular, it is expected that various types of equipment will become smaller and thinner, and that the durability (waterproofness and dustproofness) for outdoor use will be required to be improved. It becomes noticeable.

The present invention has been made in view of the above circumstances, and provides a piezoelectric fan capable of solving the problems of the noise of the piezoelectric fan and the intake / exhaust port as a cooling fan.

[0011]

A piezoelectric fan according to the present invention has a wind vibrator including a piezoelectric element, and an exhaust port and an intake port are provided on the same surface.

In the piezoelectric fan according to the present invention, since the exhaust port and the intake port are provided on the same surface, the driving of the wind generating vibrator draws in outside air from one of the intake ports on the same surface and heats the inside. The discharged air is discharged to the outside from the other exhaust port, and cooling performance is ensured. On the other hand, sound waves having opposite phases emitted from the front and rear of the wind vibrator are emitted from the exhaust port and the other is emitted from the intake port, so that they interfere with each other and reduce the noise level.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a piezoelectric fan according to the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment which is a basic configuration of a piezoelectric fan according to the present invention. A piezoelectric fan (a so-called cooling fan) 1 according to the present embodiment has a fan case 2 formed in a flat box shape, a fan main body 5 including a piezoelectric element 3 and a blowing oscillator 4 built therein, and an intake port 6 [6A]. , 6B]
And the exhaust port 7 are formed on the same surface of the fan case 2. The fan case 2 has a bottom surface 8a, left and right side surfaces 8b and 8c, and a back surface 8d. The case body 8 is formed so that the front surface is open. And a flat cover member 9 to be formed. FIG. 1 shows a state in which the cover 9 is removed so that the inside of the piezoelectric fan can be seen.

A fan main body 5 is disposed substantially at the center of the case main body 8 so that the front end side of the wind vibrator 4 faces the front side, and an opening is formed only on the front side of the fan case 2.
An intake port 6 and an exhaust port 7 are formed facing this opening.
As will be described later, the intake port 6 and the exhaust port 7 are arranged close to each other at a position where they can interfere with each other in opposite phase sound waves generated from the fan body 5. In this example, an exhaust port 7 is formed at the center of the opening of the fan case 2, and intake ports 6 [6A, 6B] are formed on both sides of the exhaust port 7. For this reason, the case body 8 has a pair of partition walls 10 [10a, 10] extending inward from the opening so as to sandwich both sides of the wind vibrator 4.
b] are provided, and openings between the respective partition walls 10a, 10b and both sides 8a, 8b of the case body 8 are formed as intake ports 6A, 6B, and the two partition walls 10a, 10b are provided.
The opening interposed therebetween is formed as an exhaust port 7. The two partition walls 10a and 10b are connected to the fan case 2 as described later.
Is formed so as to extend inward from the opening portion to the intermediate position of the wind generator 4. The air is supplied from the outside to the intake ports 6 on both sides [6
A, 6B], and enters the fan case 2, goes around the base side of the vibrating vibrator 4, and is discharged to the outside from the front exhaust port 7. In the exhaust port 7, for example, the wind generator 4
A plurality of cooling fins 14 extending to near the tip are formed. The partition wall 10 [10a, 10b] and the cooling fin 11 can be formed integrally with the case body 8. The fan case 2 is made of, for example, aluminum die-cast.

FIG. 2 shows the basic structure of the wind generator 4 using the piezoelectric element 3, that is, the fan body 5. The fan body 5 fixes the base side of the piezoelectric element 3 and makes the front end side vibrable in a free state. The vibration plate 11 and the wind generating plate 12 By applying a voltage having a predetermined alternating waveform from the power supply circuit 13 to the piezoelectric element 3, the piezoelectric element 3
Is converted into bending displacement to vibrate the wind vibrator. In this example, a pair of piezoelectric plates 3
The two piezoelectric plates 3A, 3B are formed by using a bimorph-structured piezoelectric element 3 in which A and 3B are extended and contracted in opposite phases to each other.
B, the vibrator 11 is held between the two piezoelectric plates 3A, 3A.
The base portion of B is fixed to the fixing portion 15. Piezoelectric plate 3
A and 3B are connected to the power supply circuit 13 so as to expand and contract in opposite phases.
Connected to.

In the fan body 5, vibration is generated at the tip side of the piezoelectric element 3 by applying a voltage, and the frequency of the vibration is matched with the natural frequency of the wind vibrator 4, thereby causing the wind vibrator 4 to resonate. As a result, a large amplitude is generated at the tip of the blowing plate 12 to blow air.

The fan body 5 shown in FIG. 2 has a cantilever support structure in which one end of the wind vibrator 4 is fixed. In addition, as shown in FIG. 3, a fan provided with a vibrator having a tuning fork type elastic support structure. The main body 16 can also be applied. This fan body 1
6 is a pair of piezoelectric plates 3 having a bimorph structure similar to the above example.
a and 3b, and a dummy piezoelectric element 20 similarly composed of a pair of piezoelectric plates 3a and 3b having a bimorph structure.
Are assembled into a tuning fork type via a spacer 19, and the elastic plate 1 sandwiched between each of the piezoelectric elements 3 and the dummy piezoelectric element 20 is provided.
Blowers 18A are attached to the tips of 7A and 17A, respectively. 23 denotes an elastic leaf spring. In the fan body 16, by applying an AC waveform voltage to the piezoelectric element 3 and the dummy piezoelectric element 20, both the blowing plates 18 A, 1
8B has a large amplitude to generate wind.

As shown in FIG. 4, the piezoelectric fan 1 according to the present embodiment is installed inside a device 30 to be cooled, for example, an electronic device. In this case, the suction port 6 [6] of the piezoelectric fan 1 is provided on the same surface 31A of the housing 31 of the device 30 to be cooled.
A, 6B] and the exhaust port 7 are provided.

Next, the operation of the above-described piezoelectric fan 1 according to the present embodiment, that is, the cooling operation and the reduction of noise will be described. As described above, the piezoelectric fan 1 has a feature that the air is generated by the reciprocating motion of the blowing plate 12 of the blowing oscillator 4. That is, in FIG. 6, by applying a voltage having a predetermined AC waveform to the pair of piezoelectric plates 3a and 3b, the piezoelectric plate 3
Vibrations a and 3b are generated, and the frequency of the vibration is matched with the natural frequency of the baffle plate 12, whereby the baffle plate 12 vibrates greatly and a reciprocating motion is generated at the tip of the baffle plate 12. By this reciprocating motion, a blast as shown in the drawing is generated. Due to the generation of the wind, as shown in FIG. 5, air 33 is sucked into the piezoelectric fan 1 from the outside of the device 30 through the intake port 6 [6A, 6B], and travels around the rear and side of the blowing plate 12. Going forward, it is discharged from the exhaust port 7. The heat generated inside the device 30 due to the circulation of the air 33, that is, the piezoelectric fan 1
The heat transmitted to the inside of the device is released to cool the inside of the device.

Next, reduction of noise will be described. The air is generated by the reciprocating motion of the blowing plate 12, and the speed of the tip portion of the blowing plate 12 is proportional to the product of the reciprocating frequency and the reciprocating amplitude. The greater the speed of the tip, the greater the wind generated. On the other hand, compression waves (sound waves) 35 are generated around the blowing plate 12 as shown in FIG. 7 due to the reciprocating motion of the blowing plate 12. FIG. 7 shows an image of the compression wave 35 radiated before and after the wind oscillator 4, but is actually emitted from the wind oscillator 4 like a spherical wave in each direction. When the frequency of the compressional wave 35 reaches the audible region frequency, it is recognized as "sound" generated from the wind vibrator 4, and this becomes noise. The sound is originally a longitudinal wave, but will be described using a method of expressing a transverse wave in consideration of the legibility of the drawing.

The wind generating vibrator 4 as shown in FIG. 6 is actually installed inside an arbitrary finite space such as the fan case 2. For example, in the case of the piezoelectric fan 104 having the intake / exhaust port structure as shown in FIG. 23C described above, the fan body 5 including the wind vibrator 4 has front and rear openings as shown in FIG. It is installed in a fan case 37 having an opening 39. In the case of the structure shown in FIG. 8, the compression waves 35 radiated from the wind vibrator 4 are emitted from the intake port 39 and the exhaust port 38. As shown in FIG. 9, when the microphones 41 and 42 are placed in front of and behind the fan case 37 having openings 38 and 39 on the front and rear, and the sound wave waveform is observed, the waveform shown in FIG. 10 is obtained. Sound waves 35A and 35B received by the microphones 41 and 42
Have substantially the same waveform shape and opposite phases. This 2
When the waveforms of the two sound waves 35A and 35B are superimposed, the waveforms become smaller due to the cancellation of both.

In this embodiment, compression waves (sound waves) 35 of opposite phases radiated before and after the wind vibrator 4 are caused to interfere with each other to reduce the generated sound. That is, as shown in FIG. 11, the compression wave 35B radiated behind the wind vibrator 4 is radiated in front of the piezoelectric fan 1 and interferes with the compression wave 35A originally coming from the front to reduce the noise level. It is to let. The compression wave 35B emitted from the intake port 6 [6A, 6B] of the piezoelectric fan 1 and the compression wave 35A emitted from the exhaust port 7 interfere with each other, so that noise generated from the wind vibrator 4 can be reduced. Becomes Thus, as shown in FIG. 12, the piezoelectric fan 1 of the present embodiment
By providing [6A, 6B] and the exhaust port 7 on the same surface, the intake 33a and the exhaust 33b are performed on the same surface, and the noise generated from the wind vibrator 4 is reversed-phase sound waves 35A, 35B.
Can be suppressed by the interference action.

The present embodiment has a feature particularly in the intake / exhaust structure of the fan case structure, and the description of the configuration of the piezoelectric vibrator and the details of the materials used are omitted.

Next, a more detailed description will be given. An important point in the configuration of the present invention is to efficiently obtain two effects of an intake / exhaust structure and noise cancellation due to anti-phase sound wave interference.
Further, in the configuration of the piezoelectric fan of the present invention, since air inside the device to be cooled cannot be exhausted, it is necessary to efficiently cool the cooling fan at the airflow generating portion.

First, the intake / exhaust structure will be described.
FIG. 13 is a view of the inside of the piezoelectric fan 1 according to the present embodiment as viewed from above, and the cooling fins 11 are shown for easy understanding.
The structure from which is removed is shown. In FIG.
[6A, 6B] and the exhaust port 7 are two partition walls 10 [10
a, 10b]. Partition walls 10a, 10
The interval W 'between b must have an arbitrary gap with respect to the width W of the blowing plate 12, and W'> W. The interval W 'is the width of the exhaust port 7, and the interval W' and the partition walls 10a, 10
The width T of the intake port 6 [6A, 6B] is forcibly determined by the wall thickness t of b. In order to improve the intake and exhaust efficiency as much as possible, that is, to reduce the pressure loss in the intake and exhaust passages as much as possible, it is determined in consideration of the width of the fan body 5, the blowing capacity of the blowing plate 12, and the like. Need to do
Basically, it is desirable to make the width W of the blowing plate 12 as close as possible, that is, to make the interval W 'as small as possible.
Also, the length of the partition wall F + D [where F is the distance from the opening end of the fan case 2 to the tip of the blowing plate 12, and D is the rear end of the partition wall 10 [10, 10b] from the tip of the blowing plate 12. Distance), the distance D is the length L of the blowing plate 12
It is desirably smaller than the above. The distance F relating to the position of the blowing plate 12 can be set as appropriate, including the relationship of cooling fins described later.

In order to cause sound waves to interfere, it is necessary to take measures to minimize the reflection of sound waves emitted particularly backward. That is, as shown in FIG. 14, the sound wave radiated rearward is reflected on the rear and side walls of the fan body 5, and becomes a standing wave in which the incident wave 41 and the reflected wave 42 interfere.
Such a standing wave has a different waveform from the sound wave originally emitted backward. Forward radiation wave (sound wave) mentioned earlier
Is disturbed, and the canceling effect by interference is hindered. Therefore, it is effective to provide a reflected wave suppressing means for reducing the reflected wave as shown in the embodiment of FIG.

FIG. 15A shows the rear portion 8 d of the fan case 2.
In this case, the inner surface extending from the inner surface to the side surface portions 8b and 8c is configured as a wedge-shaped wavy wall surface 43 so as to suppress reflection. FIG. 15B shows a case in which a sound absorbing material 44 such as a sound absorbing sheet is attached to the inner surface of the fan case 2 from the rear surface 8d to the side surfaces 8b and 8c. FIG. 15C
This is a case where the fan case 2 is formed to have a wall shape, for example, an R-bend wall surface 45 for preventing standing waves from being generated and guiding sound waves forward from the rear surface 8d to the inner surfaces of both side surfaces 8b and 8c. These means for suppressing reflected waves are known techniques for suppressing sound and noise, and there are various other means, and these means can also be used. In addition, the shape and material of these means should be appropriately selected depending on the wavelength of the target sound wave, that is, they have a close relationship with the frequency of the wind vibrator.

A piezoelectric fan 1 according to an embodiment of the present invention
Is inhaling air from outside the device to the object to be cooled. Therefore, in order to efficiently discharge the heat inside the cooling target device, it is necessary to collect the heat in the piezoelectric fan 1 itself. For example, as shown in FIG. 16, the piezoelectric fan 1 disposed inside the device 30 and a heat generation source (heat source) 47 inside the device 30.
When the distances are large, a means for moving the heat of the heat source 47 to the piezoelectric fan 1 is required. This is possible by using a heat transfer means 48 such as a heat pipe which has already been put into practical use. The heat of the heat source 47 is transferred to the piezoelectric fan 1 by the heat transfer means, for example, the heat pipe 48, and The heat can be dissipated by the exhaust air. The principle of thermally connecting the heat source 47 and the piezoelectric fan 1 by, for example, a heat pipe 48 has already been put to practical use and will be briefly described below. Needless to say, a low connection is required.

The principle of the heat pipe is as follows. A liquid that is easily vaporized is sealed in the heat source side in the sealed pipe, the liquid is vaporized by the heat from the heat source, moves to the heat radiation side, cools and returns to the liquid there, and returns to the heat source side by capillary action.
This operation is repeated to release heat.

The arrangement of cooling fins is effective for causing high heat radiation due to the limited air flow of the piezoelectric fan. That is, as shown in the embodiment of FIG. 1, by providing the cooling fins 14 in the flow passage portion of the wind generator 4 for discharging the wind from the blowing plate, the heat radiation effect can be enhanced. Regarding the method of arranging the cooling fins 14, it is necessary to carry out an optimum design in consideration of the relationship between the wind speed and the air volume generated from the baffle plate, the thermal resistance of the cooling fin portion, the pressure loss of the cooling fin portion, and the like. There is. Also, as shown in FIG.
A, 6B] and other cooling fins 5 inside the piezoelectric fan.
It is also possible to provide 1, 52. In this case, the flow inside the piezoelectric fan can be grasped, and the flow can be determined appropriately in consideration of stagnation and pressure loss.

The characteristics of the piezoelectric fan of the present invention when implemented are summarized below. In order to make a comparison based on the difference in the intake method of the piezoelectric fans, a common fan body is used, and a fan body 16 having a tuning fork vibrator as shown in FIG. 3 is used. The fan body 16 of this tuning fork vibrator has a width of 30 mm and a length of 15 mm at the tip of a bimorph structure in which two 120 mm × 10 mm piezoelectric plates are bonded.
A vibrator to which a 2 mm air blower plate is attached is assembled into a tuning fork type via a 3 mm spacer.
And a voltage of 20 Vrms is applied to the two sets of piezoelectric bimorphs.

The vibration when 20 Vrms is applied resonates at about 350 Hz at the tip of the baffle plate, and the amplitude of the tip at that time is about 2.5 mmpp. The piezoelectric fan body 16 of the tuning fork type vibrator is incorporated in each of the conventional fan case and the fan case of the present invention, and the generated noise level is compared with the cooling performance when set in the simple cooling performance test box.

FIG. 18 shows a piezoelectric fan 64 incorporated in a conventional fan case 61. The conventional fan case 61 is 45 mm long × 45 mm wide × 10 height.
mm, the exhaust port 63 is provided at the front,
2 [62A, 62B, 62C] are formed. FIG. 19 shows the piezoelectric fan 1 incorporated in the fan case 2 of the present invention. The fan case 2 of the present invention
Has a length of 48.5 mm, a width of 50 mm, and a height of 10 mm, a width of the intake port 6 [6A, 6B] of 6 mm, and a width of the exhaust port 7 of 3 mm.
The configuration was 2 mm. The width of the blowing plate 12 was 30 mm. FIGS. 18 and 19 are views in which the cover is removed so that each piezoelectric fan 16 can be seen from above, but the cover is actually covered.

With respect to each of the piezoelectric fans 64 and 1, the noise when the above-mentioned driving conditions of 20 Vrms and 350 Hz are applied is measured. The measurement was performed as shown in FIG.
A piezoelectric fan or 1 is placed on a base 71 via an anti-vibration rubber 72, and an ordinary sound level meter 73 is used. The tip of a windproof cover 74 of the measuring device is in contact with the tip of an exhaust port of the piezoelectric fan 64 or 1. Went in position. The noise measurements for each piezoelectric fan are:
When the conventional piezoelectric fan 64 is 82 dB and the piezoelectric fan 1 of the present invention is 74 dB, and the same fan body is used,
It was confirmed that the noise level of the present invention was reduced by about 8 dB.

Further, the cooling performance was measured. FIG. 21 schematically shows a cooling performance evaluation jig 75. This jig 7
5 is, for example, width 80 mm, depth 100 mm, height 40
In a semi-closed box 76 mm, a heater plate with a thermocouple 77 attached thereto (for example, 45 m long × 45 mm wide × 9 m high)
m made of aluminum) 78. The box 76 includes a base 76b, a front plate 76a, and a back plate 76c formed of, for example, polyacetal, a cover 76d covering the base 76b formed of, for example, aluminum, and an exhaust port 78 of, for example, 45 mm × 10 mm formed in the front plate 76a. A plurality of air inlets 79 having a diameter of 6 mm in this example are formed on the upper surface of 76d. A piezoelectric fan to be evaluated is placed on a heater plate 78 in this box 76 via a heat conductive adhesive tape,
A predetermined electric power is supplied to the heater plate 78, the piezoelectric fan is turned on, and the heater plate temperature (hereinafter, referred to as heater temperature) is measured. In addition, since the heater temperature is not stabilized for a while after the start of heating, the heater temperature Th [° C.] when the temperature is stabilized after about one hour has elapsed since heating.
And the heater power P [W] applied at that time is measured.

FIG. 22 shows the result obtained by this measurement. Here, the room temperature Tr at a location where there is no influence of the heater at the time above is also measured, and the difference (Th-Tr) [° C.] from the heater temperature Th measured as described above is obtained. ] Is the thermal resistance. This figure 2
2, the thermal resistance of the piezoelectric fan 1 of the present invention is 6.5 ° C./W, and the conventional piezoelectric fan 64 is 7.5 ° C./W regardless of the magnitude of the heater power. The smaller the thermal resistance, the better the cooling performance. Therefore, according to the comparison result of FIG. 22, it is recognized that the piezoelectric fan of the present invention has better cooling performance.

The above-described piezoelectric fan 1 according to the present embodiment.
According to this configuration, sufficient cooling performance can be obtained with a configuration in which the intake port 6 and the exhaust port 7 are provided on the same surface. Therefore, it is not necessary to form an opening corresponding to the piezoelectric fan 1 on one surface and provide an opening on the other surface with respect to the device 30 to be cooled (however, it is not necessary to provide another opening for the purpose of natural air cooling or the like). An opening may be provided). Thereby, the design of the device 30 and the degree of freedom of the design are increased, and it is easy to ensure that the device 30 is sealed. Further, in the device to be cooled, the portion other than the present piezoelectric fan 1 can be made to have a completely sealed structure, and a device having excellent water resistance, dust resistance and the like can be designed. For example, even if the device is immersed in water, damage to the inside of the device is minimized, and repair can be performed only by replacing the submerged piezoelectric fan 1 alone.

Further, the structure of the present embodiment makes it possible to reduce noise. Further, by providing the cooling fins 14, it is possible to secure the same or better cooling performance. By providing means for suppressing the reflected wave of the sound wave generated from the wind vibrator 4 from the back surface portion to the both side surface portions of the fan case 2, it is possible to further reduce noise. Of course, with respect to noise, further reduction of noise can be expected by reducing noise generated from the wind vibrator 4 itself. The cooling performance can also be improved by optimizing the spacing between the cooling fins and the intake / exhaust passage.

In the above example, the exhaust port 7 is formed in the center and the intake ports 6 [6A, 6B] are formed on both sides. However, the intake port 6 is formed on one side on the same surface. ,
The exhaust port 7 may be formed on the other side to form a so-called U-shaped ventilation path.

Although the piezoelectric element is formed in a bimorph structure using two piezoelectric plates to obtain a large amplitude, basically any structure of the bimorph structure and the monomorph structure can be used.

[0042]

According to the piezoelectric fan of the present invention, sufficient cooling performance can be obtained, and noise during operation can be reduced. Since this piezoelectric fan has an intake port on the same plane as the exhaust port, the intake port and the exhaust port can be installed on the same surface and adjacent to each other. It is possible to increase the degree. Further, in the equipment to be cooled, parts other than the present piezoelectric fan can be made to have a completely sealed structure, and equipment having excellent water resistance, dust resistance and the like can be designed. For example, even if the device is immersed in water, the damage to the inside of the device is minimized, and repair can be performed only by replacing only the submerged piezoelectric fan.

[0043]

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a piezoelectric fan according to the present invention.

FIG. 2 is a schematic configuration diagram showing one embodiment of a fan main body including a piezoelectric element according to the present invention.

FIG. 3 is a schematic configuration diagram showing another embodiment of a fan main body including a piezoelectric element according to the present invention.

FIG. 4 is a perspective view showing an example in which a piezoelectric fan according to the present invention is mounted on a device to be cooled.

FIG. 5 is a cross-sectional view of the piezoelectric fan for explaining the operation of the piezoelectric fan according to the present invention, particularly the flow of air.

FIG. 6 is a perspective view showing the principle of air blowing of the fan body according to the present invention.

FIG. 7 shows compression waves (acoustic waves) generated by the fan body according to the present invention.
FIG. 4 is a perspective view showing the occurrence of the phenomenon.

FIG. 8 is an explanatory view showing a configuration in which a fan main body according to the present invention is housed in a conventional fan case.

FIG. 9 is an explanatory diagram provided for measurement of noise generated by the piezoelectric fan of FIG. 8;

FIG. 10 is a waveform diagram showing a noise waveform generated by the piezoelectric fan of FIG.

FIG. 11 is a perspective view for explaining a noise canceling effect according to the present invention.

FIG. 12 is a perspective view illustrating intake / exhaust and noise emission of the piezoelectric fan according to the present invention.

FIG. 13 is a top view showing a basic structure of the piezoelectric fan according to the present invention, with a cover removed.

FIG. 14 is an explanatory diagram illustrating reflection of a sound wave generated in a rear portion of a wind generator of a piezoelectric fan.

FIGS. 15A to 15C are configuration diagrams showing another embodiment of the piezoelectric fan according to the present invention, which is provided with a unit for preventing reflection of sound waves generated behind the wind vibrator of the piezoelectric fan.

FIG. 16 is a configuration diagram of a device showing heat dissipation measures when a heat source of a device to be cooled is located at a position different from that of a piezoelectric fan.

FIG. 17 is a configuration diagram showing another embodiment of the piezoelectric fan according to the present invention.

FIG. 18 is a configuration diagram of a conventional piezoelectric fan used for comparative measurement.

FIG. 19 is a configuration diagram of a piezoelectric fan of the present invention used for comparative measurement.

FIG. 20 is an explanatory diagram for explaining a noise measuring method.

FIG. 21 is a configuration diagram showing a jig for evaluating thermal resistance used for measuring cooling performance.

FIG. 22 is a table showing measurement results of cooling performance of the piezoelectric fan of the present invention and a conventional piezoelectric fan.

23A to 23C are schematic configuration diagrams illustrating examples of conventional cooling fans.

[Explanation of symbols]

1 ... piezoelectric fan, 2 ... fan case, 3 ...
Piezoelectric elements, 3A, 3B: piezoelectric plate, 4: wind generator, 5: fan body, 6 [6A, 6B]: intake port, 7: exhaust port, 8 ...・ Case body, 9 ・ ・ ・ Cover body, 11 ・ ・ ・ Vibration plate, 12 ・ ・ ・ Blow plate, 13 ・
..Power supply circuit, 14 cooling fin, 15 fixed part, 16 tuning fork-type fan body, 17 [17A, 1
7B] ··· elastic plate, 18 [18A, 18B] ··· blowing plate, 19 ··· spacer, 20 ··· dummy piezoelectric element, 43 ··· wedge-shaped corrugated wall surface, 44 ··· Sound absorbing member, 45 ... R curved wall, 47 ... Heat source, 48 ...
·heat pipe.

Claims (4)

[Claims] 1. A piezoelectric fan having a wind generating vibrator including a piezoelectric element, wherein an exhaust port and an intake port are provided on the same surface. 2. The piezoelectric fan according to claim 1, wherein the exhaust port and the intake port are arranged at positions where interference of opposite-phase sound waves generated from each other is possible. 3. The piezoelectric fan according to claim 2, wherein said intake ports are arranged on both sides of said exhaust port. 4. The piezoelectric fan according to claim 1, wherein parts other than the intake port and the exhaust port are sealed.