JP5113689B2 - Piezo fan - Google Patents

Description

  The present invention relates to a piezo fan that drives a blower plate by expansion or contraction of a piezoelectric element made of a piezoelectric ceramic plate or the like, that is, vibration.

  Piezofans for cooling local heat sources of electronic devices have been proposed (Patent Document 1 and Patent Document 2). Since this piezo fan has advantages such as low power consumption, long life, compact size, and low noise, the piezo fan is not limited to electronic devices and has a possibility as a general blower.

  10 and 11 show the basic structure of the piezo fan 30. FIG. An elongated flat plate 31 and a rectangular or rectangular piezoelectric element 32 bonded to one surface of the blower plate 31 on the fixed end side (left end side in FIGS. 10 and 11) are provided. The piezoelectric element 32 expands and contracts in the length direction when a voltage is applied in the thickness direction. When the applied voltage is vibrated by repeating expansion and contraction, the blower plate 31 also resonates, and the free end of the blower plate 31 vibrates up and down greatly as shown by the dotted line in FIG. 11 to generate an air flow.

JP 59-224500 A JP 63-32975

  In the piezo fan as described above, the piezoelectric element and the blower plate are bonded with an adhesive. Here, since it is desirable that the adhesive can transmit the kinetic energy generated by the piezoelectric element to the blower plate as much as possible, an adhesive that is as thin as possible and capable of exhibiting a strong adhesive force is required. However, the deformation generated in the blower plate due to the vibration of the piezoelectric element is not only in the longitudinal direction connecting the fixed end and the free end, but also in the direction orthogonal to this, The stress accompanying complicated deformation acts as a force for separating the piezoelectric element and the blower plate. Therefore, if the thickness of the adhesive becomes thinner than a certain value, the adhesiveness and strength decrease, and it becomes unable to withstand vibration of the blower plate. Finally, the blower plate and the piezoelectric element are gradually peeled off, and the life as a piezo fan is shortened. . Further, when the coating thickness is increased, there is a problem that the kinetic energy transmitted from the piezoelectric element to the blower plate is reduced and the maximum displacement (amplitude) of the blower plate is reduced.

  In general, the adhesive strength of an adhesive tends to decrease at high temperatures. Therefore, when the adhesive is used in a high-temperature atmosphere, the adhesion between the piezoelectric element and the blower plate is peeled off at a speed higher than normal temperature. FIG. 12 shows the results of a performance investigation when a piezo fan whose performance does not change even if it is driven at room temperature for one month is used in a high temperature atmosphere. While driving the piezo fan at its resonance frequency, the ambient temperature is repeatedly changed between room temperature and 100 ° C. Each time the ambient temperature reached 100 ° C., it continued for 1 hour. The resonance frequency and amplitude shown in FIG. 12 are data measured when the ambient temperature reaches room temperature.

  As shown in FIG. 12, the resonance frequency gradually decreases, and at the time when 3 hours have elapsed from the start of measurement, both the resonance frequency and the maximum amplitude suddenly decrease, and the function as a fan is lost.

  Such a decrease in performance is caused by peeling of the adhesion between the piezoelectric element and the blower plate. In FIG. 11, when the free end of the blower plate 31 is displaced toward the position indicated by the dotted line on the upper side of the drawing, a pressing force acts on the piezoelectric element 32 from the blower plate 31. When it is displaced toward the indicated position, a peeling stress acts on the bonding portion between the blower plate 31 and the piezoelectric element 32. It can be explained that the adhesion between the blower plate 31 and the piezoelectric element 32 is gradually peeled off due to the peeling stress, and the performance as a fan changes as in the measurement result.

  As means for solving the problem of peeling of the adhesion between the blower plate and the piezoelectric element, there is means for changing the monomorph type piezofan shown in FIGS. 10 and 11 into the bimorph type piezofan shown in FIG. That is, the piezoelectric elements 32 and 32 are bonded to both the front and back surfaces of the blower plate 31 on the fixed end side. In such a bimorph type piezo fan, it is conceivable that one piezoelectric element relaxes the peeling stress acting on the bonded portion between the other piezoelectric element and the blower plate, and avoids performance degradation even when used in a high temperature atmosphere. The problem of requiring two piezoelectric elements and increasing the cost remains.

  The structure of the piezofan disclosed in Patent Document 1 is shown in FIG. In this piezo fan, the two piezoelectric elements 33, 33 sandwich the shim material 34, and the clip portion 36 formed at the fixed end of the blower plate 35 clips the two piezoelectric elements 33 and the tip of the shim material 34. It is said that. In this structure, it is recognized that the stress that peels off the adhesion between the piezoelectric element 33 and the shim member 34 due to the vibration of the blower plate 35 does not act. However, since the blower plate 35 includes the clip portion 36, it is necessary to use a synthetic resin molded product. In addition, there is a problem that the material and the manufacturing method are restricted, and the use efficiency of the kinetic energy generated by the piezoelectric element 33 is reduced because the blower plate 35 is connected to the piezoelectric element 33 via the clip portion 36. I can give you.

  The present invention has been made in view of the above-described problems of the prior art, and it is intended to provide a piezo fan that has a simple structure and avoids an increase in cost and that does not deteriorate in performance even when used in a high temperature atmosphere. It is aimed.

  The invention according to claim 1 that achieves the above object is characterized in that a thin plate-like air blowing plate is bonded to either one of the front and back surfaces of the plate-like piezoelectric element to which one end is fixed, and one of the air blowing plates. In the piezo fan configured to be further extended from the free end side of the piezoelectric element and vibrated by the piezoelectric element, the surface of the blower plate opposite to the surface bonded to the piezoelectric element In addition, a thick portion having a thickness greater than that of the other portion of the blower plate is provided in a portion facing the edge portion on the free end side of the piezoelectric element.

  According to a second aspect of the present invention, in the first aspect of the present invention, the thick portion is configured by a support block bonded to a surface of the blower plate opposite to the surface bonded to the piezoelectric element. It is a featured piezo fan.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the thick portion has the same length as the width of the piezoelectric element bonded to the surface of the blower plate opposite to the thick portion. The piezo fan is characterized in that the blower plate is sandwiched between the thick portion and the piezoelectric element.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the thick portion is configured by a narrow support ring having a rectangular or rectangular through hole, and an edge of the blower plate and the piezoelectric element is formed in the through hole. Is a piezo fan characterized in that the support ring surrounds the outer periphery of the piezoelectric element and the blower plate.

  According to a fifth aspect of the present invention, in the first aspect of the invention, the thick portion is constituted by a narrow support block having a concave cross section at the center back plate portion and the leg portions at both ends, and the support block. Is provided in parallel with the edge on the free end side of the piezoelectric element, the central back plate portion and the piezoelectric element sandwich the air blowing plate, and the leg portions on both ends are in contact with the side edge of the piezoelectric element and the air blowing plate. It is a piezo fan characterized by being comprised.

  According to a sixth aspect of the present invention, in the fifth aspect of the invention, the support block including the central back plate portion and the leg portions at both ends further includes a short protrusion on the central back plate portion. Is a piezo fan characterized by being fitted into an opening provided in advance in the blower plate.

  The invention according to claim 7 is the invention according to claim 5, wherein the support block having the central back plate portion and the leg portions at both ends has a plurality of short protrusions on the central back plate portion, The piezo fan is characterized in that the protrusion is fitted into a slit formed in advance at the free end of the blower plate.

  The invention of claim 8 is the invention according to any one of claims 1 to 7, wherein a plurality of the piezoelectric elements are laminated, and the laminated piezoelectric elements are bonded to at least one side surface of the blower plate. It is a piezo fan characterized by

  According to the piezo fan of the first aspect of the present invention, since the thick portion provided at the position facing the free end side edge portion of the piezoelectric element suppresses the relative deformation of the blower plate with respect to the piezoelectric element, The peeling stress acting on the bonding portion between the plate and the piezoelectric element is relaxed, and the problem of peeling off the bonding between the blower plate and the piezoelectric element can be eliminated. For this reason, it is possible to obtain a piezo fan that can suppress the increase in cost by using a single piezoelectric element and can continue to be driven stably without deterioration in performance even in a high temperature atmosphere.

  According to the invention of claim 2, since the thick part is constituted by the support block bonded to the blower plate, in addition to the effect of the invention of claim 1, the overall structure can be simplified. . If the support block has a narrow width, the effect on the driving or displacement of the piezoelectric element is small, the use efficiency of the kinetic energy of the piezoelectric element is improved, and the effect that the air blowing plate can be vibrated with a large amplitude is also obtained. It is done.

  According to the invention of claim 3, the relative displacement between the blower plate and the piezoelectric element is increased at the free end portion of the piezoelectric element, but the rigidity or thickness is provided on both the front and back sides of the blower plate at this portion. As a result, separation between the piezoelectric element and the air blowing plate can be prevented or suppressed.

  According to invention of Claim 4, since the said thick part is comprised by the narrow support ring which has a square or rectangular through-hole, in addition to the effect similar to the invention of Claim 1 or Claim 2 The mounting or positioning of the support ring can be easily performed, and an effect that the piezo fan can be easily manufactured can be obtained.

  According to the invention of claim 5, since the thick wall portion is constituted by a narrow support block having a concave cross section, in addition to the same effects as those of the invention of claim 1 or claim 2, It is easy to adapt to automation, and the effect of enabling high-speed and efficient production is obtained.

  According to the invention of claim 6, the short back is provided in the central back plate portion of the narrow support block having a concave cross section, and the short protrusion is fitted into the opening of the blower plate. The positioning of the support block in the longitudinal direction of the blower plate can be performed via the short protrusion. Therefore, in addition to the same effect as that of the invention of the fourth aspect, it is possible to obtain the effect of improving the positioning accuracy at the time of assembly automation.

  According to the invention of claim 7, since the plurality of short protrusions on the central back plate portion of the narrow support block having a concave cross section are fitted into the slit formed in the blower plate, the plurality of short protrusions Can be used as a reference plane when assembling the piezo fan and the cooling target component. Therefore, in addition to the effect of the invention of claim 5, it is possible to obtain an effect that can contribute to automation of mounting and improvement of accuracy.

  Furthermore, according to the invention of claim 8, it is possible to obtain the same operation and effect as the invention of claims 1 to 7, and in addition to this, it is easy to change the vibration characteristics in various ways. Moreover, the exciting force for vibrating the blower plate can be relatively increased.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view of a piezo fan 10 according to the first embodiment. A width substantially equal to the width W of the blower plate 11 and a length L of the blower plate 11 on the lower surface of the fixed end side (left side in the figure) of the elongated flat plate blower plate 11 having a length L longer than the width W. A rectangular piezoelectric element 12 having a half length is bonded so that the fixed edges are aligned. Further, on the upper surface of the blower plate 11, a support block 13 having a length l substantially equal to the width W of the blower plate 11 and a narrow width w is provided at a position substantially opposite to the free end side edge portion 12 a of the piezoelectric element 12. The piezoelectric element 12 is bonded substantially in parallel with the end edge portion 12a. For example, the width w is about 2 mm when the length of the piezoelectric element 12 is 41 mm. Therefore, the support block 13 forms a bead-shaped portion extending in the width direction of the blower plate 11.

  The air blowing plate 11 can be composed of a metal plate, resin, glass fiber, or a composite material of carbon fiber and resin. The piezoelectric element uses the d31 direction. In addition, the material of the support block 13 is not limited. However, if a heavy material is used, the piezo fan bends, so a light and strong material such as epoxy glass is desirable.

  When the piezoelectric element 12 is vibrated, the relative displacement between the piezoelectric element 12 and the blower plate 11 increases on the free end side of the piezoelectric element 12, but the support block 13 is placed on the free end of the piezoelectric element 12. It is bonded to one surface (surface opposite to the piezoelectric element 12) of the blower plate 11 at a corresponding position. Therefore, the rigidity (or cross-sectional second moment) of the blower plate 11 at this portion is larger than the other portions. That is, the support block 13 constitutes a thick portion in the present invention. Therefore, when the air blower plate 11 resonates with the piezoelectric element 12 and vibrates, the air blower plate 12 is curved along a line connecting the fixed end and the free end, and is orthogonal to the line (ie, the width direction). In addition, the support block 13 is provided to suppress the relative displacement of the blower plate 11 with respect to the piezoelectric element 12, although it tends to bend even slightly. Such an action is considered to be caused by the fact that the thickness or rigidity of the front and back sides of the blower plate 11 at the free end of the piezoelectric element 12 is approximated by the support block 13.

  As a result, according to the piezo fan 10 configured as described above, when the blower plate 11 is displaced upward in the figure by the support block 13 bonded to the upper surface of the blower plate 11, the blower plate 11 and the piezoelectric element 12. Peeling stress acting on the adhesive surface is relaxed, and performance degradation due to peeling of both can be prevented or suppressed. Further, since the width w of the support block 13 is narrow, there is no influence on the displacement of the free end of the piezoelectric element 12, and the driving energy of the piezoelectric element 12 is sufficiently transmitted to the blower plate 11 side and vibrates with a large amplitude. It is possible to make it.

  The maximum stress of the blower plate 11 was computer analyzed by a finite element method. According to this, the stress of the portion corresponding to the end edge portion 12a of the piezoelectric element 12 is higher than that in the case where the support block 13 is not provided (corresponding to the case of FIG. 10 and FIG. 11). It was found that the average could be 50%.

  In addition, a test in a high temperature atmosphere similar to the test that obtained the results of FIG. 12 was also attempted. That is, the piezo fan 10 was first driven at a resonance frequency in a room temperature atmosphere, and then the driving was continued at an ambient atmosphere temperature of 100 ° C. Then, the ambient temperature was lowered to room temperature, and changes in resonance frequency and maximum amplitude were measured. The result is shown in FIG. As apparent from the figure, the resonance frequency and the maximum amplitude were not changed before heating, and the effect of reducing the peeling stress on the bonded portion by installing the support block 13 could be confirmed.

  FIG. 3 shows a piezo fan 10 according to a second embodiment of the present invention. As in the first embodiment, a rectangular or rectangular piezoelectric element 12 is bonded to the lower surface of the elongated flat plate-like air blowing plate 11 on the fixed end side. A metal support ring 14 as shown in FIG. 4 is provided at a position substantially opposite to the free end side edge of the piezoelectric element 12 and fixed by adhesion. The support ring 14 has a narrow width like the support block 13, and is formed with a rectangular or rectangular through hole 15 through which the blower plate 11 and the piezoelectric element 12 bonded thereto can be inserted from the fixed end side. ing. Therefore, it can be easily attached only by inserting the blower plate 11 and the piezoelectric element 12 and setting the position so as to align with the edge of the piezoelectric element 12. When the support ring 14 is attached, the support ring 14 surrounds the outer periphery of the stacked air blowing plate 11 and the piezoelectric element 12. The manufacture of the piezo fan 10 can be simplified.

  FIG. 5 shows a piezo fan 10 according to a third embodiment of the present invention. Also in this example, the rectangular or rectangular piezoelectric element 12 is bonded to the lower surface on the fixed end side of the flat plate 11 as in the above embodiments. A thin support block 16 as shown in FIG. 6 is attached to the upper surface side of the blower plate 11 at a position substantially opposite to the free end side edge of the piezoelectric element 12 by bonding. The support block 16 has leg portions 18 and 18 at both ends of a narrow central back plate portion 17 and has a concave cross section. The internal dimensions of the leg portions 18 and 18 are substantially equal to the widths of the blower plate 11 and the piezoelectric element 12. As a result, by mounting the support block 16 from the upper surface side of the blower plate 11, the support block 16 is automatically positioned in the width direction of the blower plate 11. When the support block 16 is mounted, the edge portion of the central back plate portion 17 and the piezoelectric element 12 sandwiches the air blowing plate 11, and the leg portions 18 and 18 on both ends are side edges of the air blowing plate 11 and the piezoelectric element 12, respectively. It becomes the composition which touches. In the third embodiment configured as described above, a part of the positioning of the support block 16 can be automatically performed, so that it is easy to cope with the automation of the assembly of the piezo fan 10, and high-speed and efficient production is possible. Can be.

  Next, FIG. 7 is an exploded view of the piezo fan 10 according to the fourth embodiment of the present invention. In this embodiment, a short projection 19 is provided on the central back plate portion 17 of the narrow support block 16 having a concave cross section. Corresponding to the short protrusions 19, an opening 20 is provided in the blower plate 11 in advance. When the support block 16 is mounted, the short protrusion 19 is fitted into the opening 20. As a result, in the fourth embodiment, when the support block 16 is mounted, the support block 16 is positioned in the width direction of the blower plate 11 so that the leg portions 18 and 18 on both ends, the blower plate 11 and the side edges of the piezoelectric element 12 are positioned. Can be automatically performed by engaging the short projection 19 and the opening 20 so that the blower plate 11 can be positioned in the longitudinal direction automatically. Thus, since the positioning of the support block 16 is automatically performed in two directions, the assembly accuracy in the automatic assembly can be further improved.

  FIG. 8 is an exploded view of the piezo fan 10 according to the fifth embodiment of the present invention. In this embodiment, a plurality of short protrusions 19 provided on the narrow central back plate portion 17 are provided. This is provided with a plurality of slits 21 on the free end side of the blower plate 11, and the free end side of the blower plate 11 is divided into narrow fins 22, and each fin 22 is a heat radiating member, for example, a heat radiating block (not shown). The piezo fan 10 is used by inserting it between the radiating fins.

  The slit 21 is formed up to a position overlapping the free edge side edge portion of the piezoelectric element 12. When the support block 16 is mounted, the leg portions 18 on both sides are in contact with the side edges of the blower plate 11 and the piezoelectric element 12, and each of the plurality of short protrusions 19 is fitted into the corresponding slit 21. To be included. Also according to this embodiment, since the positioning of the support block 16 can be automatically performed in two orthogonal directions, the assembly accuracy of the automatic assembly can be improved. Furthermore, the plurality of short protrusions 19 can be used as a reference surface for positioning when the piezo fan 10 is mounted on an actual machine. For this reason, it contributes to the automatic mounting of the heat radiating member and the piezo fan 10, and the mounting accuracy can be improved.

  Furthermore, in the present invention, a plurality of piezoelectric elements may be laminated and disposed on one side surface or both surface sides of the blower plate. In that case, the structure which pinches | interposes a metal plate between piezoelectric elements is also employable. An example of this is shown in FIG. 9, in which two piezoelectric elements 12 and 12 are bonded together with a metal plate M sandwiching between the piezoelectric elements 12 and 12 sandwiched therebetween, resulting in a three-layer structure. A piezoelectric element unit 12A is configured. The blower plate 11 is bonded to one surface (lower surface in FIG. 9) of the piezoelectric element unit 12A, and the free end of the blower plate 11 extends from the free end of the piezoelectric element unit 12A. And it is comprised so that the free end part of the ventilation board 12 may vibrate by applying a voltage to the piezoelectric element unit 12A and vibrating this.

  In addition, the thick part in this invention is formed by building a bead on the blower plate, or by integrally forming it in the manufacturing process of the blower plate, in addition to the support block described above. It may be.

1 is a perspective view of a first embodiment of the present invention. It is a graph of the measurement result in the test of the high temperature atmosphere of 1st Embodiment. It is a perspective view of 2nd Embodiment of this invention. It is a top view of the support ring used in a 2nd embodiment. It is a perspective view of 3rd Embodiment of this invention. It is a perspective view of the support block used in 3rd Embodiment. It is a disassembled perspective view of 4th Embodiment of this invention. It is a disassembled perspective view of 5th Embodiment of this invention. It is a side view which shows the example which laminated | stacked the piezoelectric element. It is a perspective view of the conventional piezo fan. It is a front view explaining operation | movement of the conventional piezo fan similarly. It is a graph of the measurement result in the test of the high temperature atmosphere of the conventional piezo fan. It is a perspective view of the conventional bimorph type piezo fan. It is a perspective view of the conventional piezo fan of another structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Piezo fan, 11 ... Blower plate, 12 ... Piezoelectric element, 12a ... End edge part, 12A ... Piezoelectric element unit, 13 ... Support block, 14 ... Support ring, 15 ... Through-hole, 16 ... Support block, 17 ... Center Back plate part, 18 ... Leg part, 19 ... Short protrusion, 20 ... Opening part, 21 ... Slit, 22 ... Fin.

Claims (8)

A thin plate-like air blowing plate is bonded to either one of the front and back surfaces of the plate-like piezoelectric element to which one end is fixed, and one end portion of the air blowing plate further extends from the free end side of the piezoelectric element. In a piezo fan configured to extend and vibrate by the piezoelectric element,
The surface of the air blowing plate opposite to the surface bonded to the piezoelectric element and the portion facing the free end side edge of the piezoelectric element is thicker than the other portions of the air blowing plate. Piezofan characterized by a meat part.   2. The piezo fan according to claim 1, wherein the thick portion is configured by a support block adhered to a surface of the blower plate opposite to a surface adhered to the piezoelectric element.   The thick portion is a bead-shaped portion having the same length as the width of the piezoelectric element bonded to the surface of the blower plate opposite to the thick portion, and the blower plate is the thick portion. The piezoelectric fan according to claim 1, wherein the piezoelectric element is sandwiched between the piezoelectric element and the piezoelectric element.   The thick part is constituted by a narrow support ring having a rectangular or rectangular through hole, and the edge of the blower plate and the piezoelectric element is inserted into the through hole, and the support ring is formed between the piezoelectric element and the blower plate. The piezo fan according to claim 1, wherein the piezo fan is configured to surround an outer periphery.   The thick portion is composed of a narrow support block having a concave cross section at the center back plate portion and the leg portions at both ends, and the support block is parallel to the edge of the free end side of the piezoelectric element. 2. The structure according to claim 1, wherein the central back plate portion and the piezoelectric element sandwich the air blowing plate, and the leg portions at both ends are in contact with the side edges of the piezoelectric element and the air blowing plate. The piezo fan described.   The support block having the central back plate portion and the leg portions at both ends further has a short projection on the central back plate portion, and the short projection is fitted into an opening provided in advance on the blower plate. 6. The piezofan according to claim 5, wherein   The support block having the central back plate portion and the leg portions at both ends has a plurality of short protrusions on the central back plate portion, and each short protrusion is formed in a slit formed in advance on the free end of the blower plate. 6. The piezo fan according to claim 5, wherein the piezo fan is fitted.   The piezo fan according to any one of claims 1 to 7, wherein a plurality of the piezoelectric elements are laminated, and the laminated piezoelectric elements are bonded to at least one side surface of the blower plate.

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