JP2012077678A - Piezoelectric fan and heat radiator employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric fan that reduces, in a simple structure, vibration to be generated in a support by the drive of a piezoelectric element.SOLUTION: The piezoelectric fan 1 includes: a support 3; a vibration plate 2 having its one end in a length direction, fixed to and supported by the support, and the other end in the length direction, made as a free end; and the piezoelectric element 4 affixed at least on one side of both sides of fixed end side of the vibration plate, and the piezoelectric fan 1 generates an air flow by exciting in the plate thickness direction, the free end side of the vibration plate through the drive of the piezoelectric element. A vibration absorbing member 5 constituted of a vibration absorbing plate 2b and a weight 6, and having a natural vibration frequency the same as the drive frequency of the piezoelectric fan, or its neighborhood, is fixed to the support 3 so that it vibrates in the same direction as the vibration direction of the support by the reaction force of the vibration plate.

Description

  The present invention relates to an apparatus for reducing vibration in a piezoelectric fan that generates an air flow by vibrating a diaphragm with a piezoelectric element.

  In recent years, with miniaturization and high-density mounting of parts in portable electronic devices, measures to dissipate heat generated in the electronic devices have become issues. As means for efficiently radiating heat from such an electronic device, a heat radiating device using a piezoelectric fan has been proposed.

  In Patent Document 1, as shown in FIG. 14, one end in the length direction of a vibration plate 202 made of a thin metal plate is fixed to a support 201, and a piezoelectric element 204 is attached to both surfaces in the vicinity of the fixed end, and vibration is also performed. A piezoelectric fan 200 is disclosed in which a blade (air blowing part) 203 divided into a plurality of parts is formed at the other end in the longitudinal direction of the plate 202. The support 201 is fixed to both side surfaces of the heat sink 206 via a pair of arms 205. The blade 203 is inserted obliquely between the fins 207 of the heat sink 205, and driving the piezoelectric element 204 can excite the blade 203 and discharge warm air between the fins 207.

  In the piezoelectric fan 200 having the above-described structure, when the vibration plate 202 vibrates, the support 201 supporting the vibration plate 202 vibrates due to the reaction, and the vibration of the support 201 is transmitted to the heat sink 206 to cause noise. At the same time, there is a problem of causing malfunction of other devices. If the support 201 is fixed to the heat sink 206 via an elastic body such as rubber, it is possible to mitigate the influence of vibration on the heat sink 206, but the support rigidity of the support 201 is reduced. The amplitude of 203 becomes extremely small, and a desired air volume cannot be obtained.

  As a general vibration reducing method, there is a dynamic vibration absorber 300 as shown in FIG. That is, the main system 302 is supported on the base 301 via the spring K and the attenuator Z, and the dynamic vibration absorber 300 is disposed on the main system 302 via the spring k and the attenuator z. When the mass of the main system 302 is M, the displacement is X, the mass of the dynamic vibration absorber 300 is m, and the displacement is x, the main system 302 that vibrates in response to an external force is canceled by the positive vibration of the dynamic vibration absorber 300. Is. When such a dynamic vibration absorber 300 is attached to the piezoelectric fan device (the housing in which the piezoelectric fan and the piezoelectric fan are installed) as the main system 302 and the frequency is adjusted, the installation work becomes complicated, and the entire device However, there is a drawback that it is large and expensive.

  In Patent Document 2, as shown in FIG. 16, a plurality of piezoelectric fans 400 having the same vibration characteristics are supported in parallel on a support body 402, and these piezoelectric fans 400 are driven in opposite phases as indicated by arrows. Thus, an apparatus having a structure for canceling the vibration of the support 402 has been proposed. In this case, since the piezoelectric fans 400 themselves absorb vibrations, it is not necessary to provide another device such as a dynamic vibration absorber. However, in this case, since it is necessary to drive the plurality of fans 400 with the same frequency and inversion of the phase, the drive circuit and the individual piezoelectric fan structures become complicated, and there are disadvantages that increase the cost.

US2007 / 0037506A1 WO2009 / 119431A1

  SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric fan and a heat dissipation device using the piezoelectric fan that can reduce vibration generated in a support by driving a piezoelectric element with a simple structure.

  In order to achieve the above object, the present invention provides a support, a diaphragm having one end in the length direction fixedly supported by the support and the other end in the length direction being a free end, and a fixed end of the diaphragm A piezoelectric fan attached to at least one of the front and back sides of the side, wherein the piezoelectric element generates an air flow by exciting the free end side of the diaphragm in the thickness direction by driving the piezoelectric element. A vibration absorbing member having a natural frequency that is the same as or close to the drive frequency of the fan is fixed to the support so as to vibrate in the same direction as the vibration of the support due to the reaction force of the diaphragm. A piezoelectric fan is provided.

  The present invention cancels the vibration applied to the support when the fan is driven by resonating another component (vibration absorbing member) attached to the support to suppress the vibration of the support. In other words, when the support vibrates, the vibration absorbing member also vibrates accordingly, but since the natural frequency of the vibration absorbing member is the same as or close to the driving frequency of the piezoelectric fan, the vibration phase of the vibration absorbing member is automatically set. The phase of the vibration of the fan is almost opposite to that of the fan, and the vibration of the support can be canceled. The added vibration absorbing member does not vibrate actively using a piezoelectric element or the like, but simply vibrates at the natural frequency due to the reaction force of the fan drive, and thus has a simple structure. Moreover, since it is integrated with the fan, no adjustment is required when the fan is attached to a heat sink or the like. Therefore, an increase in size and an increase in cost can be suppressed to a minimum. Moreover, it is possible to suppress the vibration of the piezoelectric fan from spreading to the outside.

  The vibration absorbing member includes a leaf spring having one end fixed to the support and the other end extending in parallel with the diaphragm, and a natural frequency adjusting weight fixed to the other end of the leaf spring. It is good. Although the natural frequency can be adjusted only by the leaf spring, the leaf spring may be increased in size. On the other hand, if a weight is attached to the free end of the leaf spring, the natural frequency can be easily adjusted without increasing the size of the leaf spring. Since the vibration absorbing member is a leaf spring extending in parallel with the diaphragm, it can be vibrated in the same direction as the vibration direction of the support.

  The vibration absorbing member may be fixed to the opposite surface of the support to which the vibration plate is fixed so as to face the vibration plate. In this case, since the vibration absorbing member and the diaphragm extend in the same direction, an increase in the lengthwise dimension of the piezoelectric fan due to the vibration absorbing member can be suppressed.

  By forming a slit from the free end of the diaphragm toward the middle in the length direction, a plurality of divided blades are formed, and the piezoelectric element is an area on the fixed end side of the diaphragm from the root of the blade It is good also as a structure affixed on. In this case, a plurality of blades can be formed on one diaphragm, and these blades can be simultaneously driven by one piezoelectric element, and the air volume can be increased.

  A bending portion in the orthogonal direction is formed at the middle portion in the longitudinal direction of the diaphragm, and a blade divided into a plurality of parts is formed by forming a slit from the free end of the diaphragm toward the bending portion, A piezoelectric element is good also as a structure affixed on the fixed end side from the bending part. In this case, by bending the vibration plate in a U-shape, the tip of the blade can be vibrated in a direction orthogonal to the vibration direction of the piezoelectric element, and the degree of freedom in arranging the piezoelectric fan can be increased. it can.

  A heat dissipating device comprising a piezoelectric fan according to the present invention and a heat sink having a plurality of heat dissipating fins arranged in parallel at intervals, wherein the vibration plate of the piezoelectric fan is disposed between the heat dissipating fins of the heat sink. It is good also as a structure where it inserts so that the excitation direction of this may become parallel to the side surface of a radiation fin, and a support body is being fixed to the heat sink. In this case, since the positional relationship between the piezoelectric fan and the heat sink is stabilized, the diaphragm of the piezoelectric fan and the heat radiating fin do not come into contact with each other, and the warm air existing between the heat radiating fins can be efficiently discharged to the outside.

  A structure in which the diaphragm and the vibration absorbing member are fixed to the center portion in the length direction of the support and both ends in the length direction of the support are fixed to the heat sink may be employed. In this case, the central part of the support body vibrates most greatly by the excitation of the diaphragm, but since the vibration absorbing member is fixed to the vibration part, the vibration of the support body is suppressed while suppressing the spread of vibration to the heat sink. Vibration can be effectively canceled out.

  As described above, according to the present invention, the vibration absorbing member having the natural frequency that is the same as or close to the driving frequency of the fan is vibrated in the same direction as the vibration direction of the support. Therefore, it is possible to cancel the vibration of the support with a simple structure without requiring a special drive source such as a dynamic vibration absorber. Further, since the vibration absorbing member is integrated with the fan, no adjustment is required when the fan is attached to a heat sink or the like, and an increase in size and cost can be minimized.

1 is a side view of a first embodiment of a piezoelectric fan according to the present invention. It is a vibration model figure for demonstrating the operating principle of the piezoelectric fan shown in FIG. 3 is a graph showing a relationship between a frequency ω of an excitation force F of the piezoelectric fan shown in FIG. 1 and a support displacement X1. It is the top view and side view of 2nd Embodiment of the piezoelectric fan which concern on this invention. It is the top view and side view of 3rd Embodiment of the piezoelectric fan which concerns on this invention. It is the top view and side view of 4th Embodiment of the piezoelectric fan which concerns on this invention. It is a side view of 5th Embodiment of the piezoelectric fan which concerns on this invention. 1 is a side view of a heat dissipation device in which a first embodiment of a piezoelectric fan according to the present invention is combined with a heat sink and a substrate. It is a perspective view of the thermal radiation apparatus shown in FIG. It is a top view of the thermal radiation apparatus shown in FIG. It is a disassembled perspective view of the thermal radiation apparatus shown in FIG. It is a side view of the heat radiator using the piezoelectric fan which concerns on this invention, and the heat radiator of a comparative example. It is the perspective view which attached | subjected the dimension of each part of the piezoelectric fan shown in FIG. 12, a front view, a top view, and a side view. 10 is an exploded perspective view of an example of a piezoelectric fan disclosed in Patent Document 1. FIG. It is a principle figure of the example of application of a dynamic vibration absorber. It is a perspective view of the other example of the conventional piezoelectric fan.

[First Embodiment]
FIG. 1 shows a first embodiment of a piezoelectric fan according to the present invention. The piezoelectric fan 1 includes a diaphragm 2 that can be bent and displaced in a thickness direction, a support 3 that fixes and supports a middle portion in the length direction of the diaphragm 2, and piezoelectric elements 4 attached to the front and back surfaces of the diaphragm 2. 4. The method for fixing the diaphragm 2 to the support 3 is arbitrary, such as adhesion, welding, and screwing. The diaphragm 2 is made of, for example, a metal leaf spring, and a portion extending from the support 3 to one side in the length direction is a blower portion (blade) 2a. The piezoelectric element 4 is affixed to the base part (fixed end side) of the air blowing part 2a. In this example, the piezoelectric element 4 is attached to the front and back surfaces of the diaphragm 2 to form a bimorph type piezoelectric fan, but a unimorph structure may be attached to only one face of the diaphragm 2. The support 3 is fixed to a fixing portion (not shown) (for example, a heat sink or a case main body). The vibration absorbing portion 2b is extended in the opposite direction to the air blowing portion 2a of the diaphragm 2 with the support 3 interposed therebetween, and a weight 6 is fixed to the tip portion thereof. The vibration absorbing portion 2b and the weight 6 constitute a vibration suppressing portion 5. The vibration suppressing unit 5 can vibrate in the same vibration direction as that of the air blowing unit 2 a of the diaphragm 2, that is, in the vertical direction, and its natural frequency is set to be the same as or near the driving frequency of the piezoelectric element 4. Here, the air blowing portion 2a and the vibration absorbing portion 2b of the diaphragm 2 are integrally formed of the same member, but may be formed of different members and fixed to the support body 3, respectively.

  When a voltage having a frequency at which the diaphragm 2 is primarily resonated is applied to the piezoelectric elements 4 and 4, the blower portion 2 a of the diaphragm 2 greatly vibrates up and down as shown by a broken line to generate an air flow in the direction of arrow A. it can. When the fan 1 is driven, a vertical vibration B is applied to the support 3 as a reaction, and the vibration is transmitted to a heat sink or a case to which the support 3 is fixed. However, in the present invention, the vibration suppression unit 5 fixed to the support 3 resonates due to the vibration of the support 3, and the phase of the vibration is opposite to that of the fan 1. It is possible to cancel automatically, and to suppress the vibration spread to the heat sink and the case. Note that the addition of the vibration suppression unit 5 does not affect the original characteristics of the fan 1 (fan drive frequency, amplitude of the air blowing unit 2a).

Here, the operation principle of the vibration reduction of the piezoelectric fan in the present invention will be described with reference to FIG. In FIG. 2, M1 is the mass of the support, K1 is the mounting rigidity of the support, M2 and K2 are the mass and rigidity of the vibration suppression unit, X1 is the displacement of the support, and F (= F ₀ sin ω) is the fan blower Ω ₀ is the fan drive frequency, ω ₁ and ω ₂ are the natural frequency of the support and the natural frequency of the added vibration system (vibration suppression unit), and ω ₁ = √ (K1 / M1), ω ₂ = √ (K2 / M2).

In the two-degree-of-freedom vibration model as shown in FIG. 2, the relationship between the frequency ω of the excitation force F and the displacement X1 of the support is shown in a graph in FIG. That is, when ω = ω ₂ , X1 is minimum. Therefore, if the values of M2 and K2 are adjusted so that ω ₂ coincides with the fan drive frequency (ω ₀ ), the vibration of the support during driving of the fan can be reduced, and thus the fan support is attached. The ripple of vibration to the device can be suppressed. In FIG. 2, a system without attenuation is considered for the sake of simplicity, but a similar effect can be obtained even in a system including attenuation. In this case, the frequency at which X1 is minimized is considered to be slightly higher than ω ₂ due to the influence of attenuation. The maximum vibration reduction effect can be obtained by making the natural frequency of the vibration suppression unit slightly lower than the fan drive frequency.

[Second Embodiment]
FIG. 4 shows a second embodiment of the piezoelectric fan according to the present invention. The piezoelectric fan 10 is affixed to a diaphragm 11 that can be bent and displaced in the thickness direction, a support 12 that fixes and supports one end of the diaphragm 11 in the length direction, and the front and back surfaces of the diaphragm 11 on the fixed end side. Piezoelectric elements 13 and 13. A blower (blade) 11 a is provided at the free end of the diaphragm 11. One end of a vibration absorbing plate 14 extending in the opposite direction to the vibration plate 11 is fixed to the support 12. A weight 15 is fixed to the other end of the vibration absorbing plate 14, and the vibration absorbing plate 14 and the weight 15 constitute a vibration suppressing portion 16.

  In this embodiment, since the vibration absorbing plate 14 and the vibrating plate 11 are separate members, a material having arbitrary characteristics can be selected as the vibration absorbing plate 14. For example, by using a spring plate having a Young's modulus different from that of the vibration plate 11 or a spring plate having a different thickness, the natural frequency of the vibration suppressing unit 16 can be adjusted to the drive frequency of the piezoelectric element 13. Note that the diaphragm 11 and the vibration absorbing plate 14 do not have to be fixed in a row with respect to the support 12, and for example, the vibration absorbing plate 14 may be stacked on the diaphragm 11 and fixed to the support 12. .

[Third Embodiment]
FIG. 5 shows a third embodiment of a piezoelectric fan according to the present invention. The piezoelectric fan 20 is affixed to a diaphragm 21 that can be bent and displaced in the thickness direction, a support 22 that fixes and supports one end of the diaphragm 21 in the length direction, and the front and back surfaces of the diaphragm 21 on the fixed end side. Piezoelectric elements 23, 23. One end of a vibration absorbing plate 24 extending in the opposite direction to the vibration plate 21 is fixed to the support 22. A weight is not fixed to the other end portion of the vibration absorbing plate 24, and the vibration suppressing plate 24 alone constitutes a vibration suppressing portion.

  In this embodiment, since the vibration absorbing plate 24 is composed of a spring plate that is thinner than the vibration plate 21, the natural frequency can be adjusted to the drive frequency of the fan with a shorter length than the vibration plate 21. In this case, the number of parts can be reduced by the amount that does not require a weight.

[Fourth Embodiment]
FIG. 6 shows a fourth embodiment of the piezoelectric fan according to the present invention. The piezoelectric fan 30 is attached to the front and back surfaces of a diaphragm 31 that can be bent and displaced in the thickness direction, a support body 32 that fixes and supports an intermediate portion in the length direction of the diaphragm 31, and the vicinity of the support body 32 of the diaphragm 31. The piezoelectric elements 33 and 33 are attached. The diaphragm 31 is integrally formed with an air blowing part 31a extending from the support 32 to one side and a vibration absorbing part 31b extending in the opposite direction to the air blowing part 31a, and a wide part 31c at the free end of the vibration absorbing part 31b. Is formed. Compared with the first embodiment, this embodiment is characterized in that a wide portion 31c is formed instead of the weight.

  In this embodiment, since the wide part 31c of the vibration absorbing plate 31b acts as a weight, the natural frequency can be made close to the driving frequency of the fan with a shorter length than the air blowing part 31a. In this case, no weight is required, and the vibration absorbing portion 31b is formed integrally with the air blowing portion 31a, so that the number of components can be reduced. In addition, the vibration absorption part 31b may be configured separately from the air blowing part 31a and may be individually fixed to the support body 32.

[Fifth Embodiment]
FIG. 7 shows a fifth embodiment of a piezoelectric fan according to the present invention. The piezoelectric fan 40 includes a vibration plate 41 that can be bent and displaced in the thickness direction, a support body 42 that fixes and supports one end portion in the length direction of the vibration plate 41, and a fixed end side (a vicinity of the support body 42) of the vibration plate 41. The piezoelectric elements 43 and 43 are attached to the front and back surfaces. A blower (blade) 41 a is provided at the free end of the diaphragm 41. One end 44 a of the vibration absorbing plate 44 is fixed to the lower surface of the support 42, that is, the surface opposite to the upper surface to which the vibration plate 41 is fixed, and the other end of the vibration absorbing plate 44 is in the same direction as the vibration plate 41. The weight 45 is fixed to the free end. In this embodiment, the weight 45 is fixed to the upper surface of the free end of the vibration absorbing plate 44, that is, the position facing the piezoelectric element 43.

  Also in this embodiment, the vibration of the support 42 accompanying the driving of the fan 40 is achieved by setting the natural frequency of the vibration suppressing unit 46 constituted by the vibration absorbing plate 44 and the weight 45 in the vicinity of the driving frequency of the fan. Thus, the vibration suppressing unit 46 can resonate and the vibration of the support 42 can be canceled. In this embodiment, since the vibration absorbing plate 44 is fixed to the support 42 in the same direction as the vibration plate 41, the length dimension of the piezoelectric fan 40 can be suppressed and the vibration absorbing plate 44 is fixed to the vibration plate 41. Since the weight 45 is fixed to the upper surface of the vibration absorbing plate 44 and disposed on the opposite side of the support 42 in the thickness direction, the height of the piezoelectric fan 40 can also be suppressed.

[First embodiment]
FIG. 8 shows a first embodiment of a heat dissipation device using a piezoelectric fan according to the present invention. The heat dissipation device includes a substrate 100, a heating element 110 such as an IC fixed on the substrate 100, a heat sink 120 fixed on the heating element 110, and a piezoelectric fan 130 fixed on the heat sink 120. Has been. As the piezoelectric fan 130, as in the piezoelectric fan according to the fifth embodiment (FIG. 7), the vibration plate and the vibration absorbing plate are respectively fixed to the upper and lower surfaces of the support, and the air blowing portion of the vibration plate is bent at a right angle. It has a structure.

  As shown in FIGS. 9 to 11, the piezoelectric fan 130 includes a prismatic support 131, a diaphragm 132 having one end fixed to the upper surface of the intermediate portion in the longitudinal direction of the support 131, and the diaphragm 132. The piezoelectric element 133 is fixed to the front and back surfaces on the fixed end side. One end of the vibration absorbing plate 134 is fixed to the lower surface of the intermediate portion in the longitudinal direction of the support 131, and the weight 135 is fixed to the upper surface of the free end of the vibration absorbing plate 134. A vibration absorbing portion 136 is configured by the vibration absorbing plate 134 and the weight 135. The natural frequency of the vibration absorber 136 including the weight 135 is set in the vicinity of the drive frequency of the piezoelectric element 133. The diaphragm 132 is vertically bent at the middle in the longitudinal direction, and is divided into a plurality of blades (blowers) 132c by forming a slit 132b from the free end to a position near the bent portion 132a. ing. When the piezoelectric element 133 is driven, the bent portion 132a vibrates in the vertical direction, and the tip portion of the blade 132c vibrates in the horizontal direction with a larger amplitude than the bent portion 132a. The vibration absorbing plate 134 extends in the same direction as the vibration plate 132 with respect to the support 131, and the length thereof is shorter than the length from the fixed end of the vibration plate 132 to the bent portion 132a. Therefore, the free end of the vibration absorbing plate 134 does not come into contact with the blade 132c of the vibration plate 132. Further, since the weight 135 is thinner than the support 131, even if the vibration absorbing plate 134 resonates with the vibration of the vibration plate 132, the weight 135 may come into contact with the vibration plate 132 (piezoelectric element 133). Absent.

  The heat sink 120 has a plurality of heat dissipating fins 121 arranged in parallel at intervals, and the bottom surface of the heat sink 120 is attached in a state of being thermally coupled to the upper surface of the heating element 110. Therefore, the heat generated from the heating element 110 is conducted to the heat sink 120, and the air between the radiating fins 121 is heated. A pair of convex mounting seats 122 are formed on the upper surfaces of two adjacent corner portions of the heat sink 120, and a concave portion 124 is formed between the mounting seats 122. A screw hole 123 is formed in each mounting seat 122. The blade 132c is inserted between the heat radiating fins 121 so that the displacement direction thereof is parallel to the side surface of the heat radiating fin 121, and the mounting seat 122 is inserted through screw insertion holes 131a formed at both ends of the support 131. The piezoelectric fan 130 is fixed to the heat sink 120 by screws. Since the blades 132c inserted between the radiating fins 121 are displaced parallel to the side surfaces of the radiating fins 121, the warm air between the radiating fins 121 is scraped off by the blades 132c, and the warm air is discharged in the length direction of the blades 132c. . Also, in this embodiment, the blade 132c is inserted into the heat sink 120 in a direction perpendicular to its bottom surface, so that the air flow caused by the blade 132c hits the hottest bottom surface of the heat sink 120 in the vertical direction, The heat of the heat sink 120 can be discharged more effectively. As a result, it is possible to realize a heat dissipation device having an excellent heat dissipation effect.

  In this embodiment, the diaphragm 132 and the vibration absorbing plate 134 are respectively fixed to the upper and lower surfaces of the intermediate portion in the longitudinal direction of the support 131, and both ends of the support 131 in the longitudinal direction are screwed to the heat sink 120. The mounting seat 122 is fixed. Therefore, a gap in the height direction due to the recess 124 exists between the intermediate portion in the longitudinal direction of the support 131 and the heat sink 120. When the piezoelectric fan 130 vibrates by driving the piezoelectric element 133, the support 131 vibrates up and down due to the reaction. Since the vibration absorbing plate 134 resonates with the vibration of the support 131, the vibration of the support 131 is canceled and the propagation of vibration to the heat sink 120 is suppressed. Even if the vibration absorbing plate 134 resonates greatly in the vertical direction, there is a gap between the support 131 and the heat sink 120, so that the vibration absorbing plate 134 can be prevented from interfering with the heat sink 120.

  The structure for fixing the piezoelectric fan 130 to the heat sink 120 is not limited to the structure in which the support 131 is directly screwed to the mounting seat 122 of the heat sink 120 as in the above-described embodiment. In addition, the support may be fixed to both side surfaces of the heat sink via arms.

Here, the result of the vibration comparison experiment in the heat radiating device using the piezoelectric fan (with the vibration absorbing portion) in the present invention and the piezoelectric fan (without the vibration absorbing portion) of the comparative example is shown. Here, as the piezoelectric fan 130 ′ of the present invention, a vibration absorbing plate 134 fixed to the support 131 in the direction opposite to the vibration plate 132 was used. In the comparative example, the vibration absorbing plate 134 and the weight 135 are excluded from the present invention. As shown in FIG. 12, these piezoelectric fans were applied to a heat radiating device, and the vibration (vibration acceleration) of the substrate driven by the fan was measured. In the measurement, the vibration acceleration of the portion with the largest vibration of the substrate is measured. The dimensions of each part of the piezoelectric fan are as shown in FIG.
Diaphragm: SUS304 with thickness of 0.1mm
Vibration absorbing plate: SUS304 with a thickness of 0.1 mm
Weight: Resin with a weight of 3 g Support: Resin Substrate: Micro-ATX board (250 mm × 250 mm × 1.5 mm)
Plate heater (metal) instead of heating element: 10mm x 10mm x 1mm
Heat sink: 50mm x 50mm x 30mm

  As shown in Table 1, when the present invention and the comparative example are compared, when the fan is driven at the same frequency, the vibration transmitted to the substrate is 1/5 compared to the comparative example while the tip amplitude of the fan is substantially the same. It turns out that it was reduced to 2 or less. Therefore, the effectiveness of the piezoelectric fan having the vibration reducing function of the present invention was confirmed.

  In the first embodiment, the vibration absorbing plate 134 is fixed to the lower surface of the support 131 so as to extend in the same direction as the vibration plate 132, but the vibration absorbing plate 134 extends in the direction opposite to the vibration plate 132. It may be fixed to the lower surface. The structure of the support is not limited to a square bar shape as in the embodiment, and can have any shape. In addition, the vibration plate and the vibration absorbing plate are fixed to the support and the support is fixed to a heat sink so that the vibration of the support generated by the vibration plate can be canceled by the vibration absorbing plate without spreading to the outside. It is desirable that the fixed position to be separated is in the length direction.

1 Piezoelectric fan 2 Diaphragm 2a Air blower
2b Vibration absorber 3 Support body 4 Piezoelectric element 5 Vibration suppression section 6 Weight 100 Substrate 110 Heating element 120 Heat sink 130 Piezoelectric fan 131 Support body 132 Vibration plate 133 Piezoelectric element 134 Vibration absorption plate 135 Weight 136 Vibration absorption portion

Claims (7)

A support is attached to at least one surface of a diaphragm having one end in the length direction fixedly supported by the support and having a free end on the other end in the length direction, and the front and back surfaces of the fixed end side of the diaphragm. A piezoelectric fan that generates an air flow by exciting the free end of the diaphragm in the thickness direction by driving the piezoelectric element,
A vibration absorbing member having a natural frequency equal to or close to the driving frequency of the piezoelectric fan is fixed to the support so as to vibrate in the same direction as the vibration of the support due to the reaction force of the diaphragm. A piezoelectric fan characterized by The vibration absorbing member has a plate spring having one end fixed to the support and the other end extending parallel to the diaphragm, and a natural frequency adjusting weight fixed to the other end of the plate spring. The piezoelectric fan according to claim 1, comprising: 3. The piezoelectric fan according to claim 1, wherein the vibration absorbing member is fixed to an opposite surface of a support body to which the vibration plate is fixed so as to face the vibration plate. By forming a slit from the free end of the diaphragm toward the middle in the length direction, a blade divided into a plurality of parts is formed,
4. The piezoelectric fan according to claim 1, wherein the piezoelectric element is attached to a region on a fixed end side of the diaphragm from a root portion of the blade. 5. A bending portion in the orthogonal direction is formed at the middle portion in the longitudinal direction of the diaphragm,
By forming a slit from the free end of the diaphragm toward the bent portion, a plurality of blades are formed,
4. The piezoelectric fan according to claim 1, wherein the piezoelectric element is attached to a fixed end side with respect to the bent portion. 5. A heat dissipating device comprising the piezoelectric fan according to claim 1 and a heat sink having a plurality of heat dissipating fins arranged in parallel at intervals,
The diaphragm of the piezoelectric fan is inserted between the heat sink fins of the heat sink so that the excitation direction of the diaphragm is parallel to the side surface of the heat sink fin,
The heat dissipation device, wherein the support is fixed to the heat sink. The diaphragm and the vibration absorbing member are fixed to a central portion in the length direction of the support,
The heat dissipating apparatus according to claim 6, wherein both ends of the support in the length direction are fixed to the heat sink.

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