JP2007049473A - Piezoelectric vibration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric vibration device which can be downsized, can gain a large amplitude even when the thinning is achieved, is hard to cause deformation when used and dealt with, and is hard to cause sound pressure variations and deterioration in the sound quality. <P>SOLUTION: In the piezoelectric vibration device 1, a piezoelectric diaphragm 3 is laminated against a first surface 2a of a metal plate 2 via adhesive 7, at least one of recesses 2c to 2e is formed on the first surface 2a of the metal plate 2, and materials lower in Young's modulus than the metal plate 2 are replenished in the recesses 2c to 2e. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piezoelectric vibration device used for a piezoelectric buzzer, a piezoelectric speaker, and the like, and more particularly to a piezoelectric vibration device having a structure in which a piezoelectric vibration plate is bonded to a metal plate.

  Conventionally, a piezoelectric vibration device in which a piezoelectric vibration plate is attached to a metal plate is widely used for a speaker, a buzzer, or the like. In addition, there is a strong demand for miniaturization of this type of piezoelectric vibration device for use in OA equipment, mobile phone equipment, and the like. Therefore, there is a demand for a piezoelectric vibration device that can obtain a large sound pressure while being small.

  The following Patent Document 1 discloses a piezoelectric vibration device shown in a schematic front sectional view in FIG. In the piezoelectric vibration device 101, a piezoelectric vibration plate 103 in which electrodes are formed on both surfaces of a piezoelectric ceramic plate is bonded to a metal plate 102. The outer peripheral edge portion of the metal plate 102 is sandwiched and supported by the fixing plates 104 and 105.

  On the outer side of the portion of the metal plate 102 that is bonded to the piezoelectric vibration plate 103, a recess 102a is provided on the surface of the metal plate 102, and a recess 102b is provided on the back surface. Providing the recesses 102a and 102b facilitates vibration and lowers the frequency.

  In addition, in the piezoelectric vibration device 101, a groove 102 c is also provided in a portion where the metal plate 102 is bonded to the piezoelectric vibration plate 103. In the portion where the groove 102 c is provided, the metal plate 102 is not bonded to the piezoelectric vibration plate 103. That is, the metal plate 102 is bonded to the piezoelectric vibration plate 103 with an adhesive at the center portion 102d inside the groove 102c and the outer peripheral portion 102e outside the groove 102c. By using such partial adhesion, the piezoelectric diaphragm 103 and the metal plate 102 can be reduced in thickness, and even if the frequency is lowered, a decrease in sound pressure level can be prevented. ing.

  On the other hand, the following Patent Document 2 discloses a piezoelectric vibration device 111 shown in a schematic exploded plan view in FIG. In the piezoelectric vibration device 111, the piezoelectric vibration plate 113 is bonded to the metal plate 112. A plurality of arc-shaped empty grooves 112 a are formed in the metal plate 112 so as to form a plurality of concentric circles centered on the center of the metal plate 112 by punching. It is said that the sound pressure at a low frequency can be increased by forming the air groove 112a.

Patent Document 3 listed below discloses a configuration in which a groove and a long hole are provided in a piezoelectric plate in which a piezoelectric plate is bonded to a metal plate that allows the metal plate to expand and contract in the circumferential direction. Yes. Also here, as in the case of Patent Document 1, the piezoelectric vibration plate is bonded at a portion other than the groove, that is, by using partial bonding, the displacement during vibration of the metal plate is facilitated.
JP-A-2-84900 JP 63-316999 A JP-A-2-266799

  As described above, in a conventional piezoelectric vibration device in which a metal plate is bonded to a piezoelectric vibration plate, in order to reduce the frequency without lowering the sound pressure level even when the size is reduced. In addition, there has been known a structure in which an empty groove or a long hole made of a through hole formed by a groove or punching is formed on a metal plate.

  However, the stress based on the displacement when the piezoelectric vibration device as described above is driven concentrates on the groove of the metal plate. In some cases, stress concentrated on the groove or the like acts on the piezoelectric ceramic plate constituting the piezoelectric diaphragm, and cracks are generated in the piezoelectric ceramic plate. In particular, when the thickness of the piezoelectric diaphragm is reduced in order to reduce the size and the frequency, the above-described cracks tend to be further generated.

  In addition, in order to reduce the size, when the size of the piezoelectric diaphragm and the metal plate is reduced and the thickness is reduced, a fine groove is formed in the metal plate, and the fine groove is shaped as designed. It was very difficult to keep. That is, it is very difficult to process a fine groove with high accuracy in a thin metal plate and to keep the shape as designed during and after assembly. For this reason, in the obtained piezoelectric vibration device, there is a possibility that variations in sound pressure occur or sound quality deteriorates.

  Further, when the metal plate or the piezoelectric plate becomes thin, deformation and cracking are likely to occur during handling and processing. Therefore, great care must be taken in the manufacturing process, and productivity tends to decrease.

  The object of the present invention is to solve the above-mentioned drawbacks of the prior art, to promote downsizing, and to obtain sufficient amplitude, that is, sound pressure, even when the thickness of the piezoelectric diaphragm or metal plate is reduced, In addition, an object of the present invention is to provide a piezoelectric vibration device in which the metal plate and the piezoelectric vibration plate are hardly deformed during handling, and the piezoelectric vibration plate is hardly cracked during driving.

  A piezoelectric vibration device according to the present invention includes a metal plate having first and second surfaces facing each other and an adhesive bonded to the first surface of the metal plate, and is configured using a piezoelectric ceramic plate. At least one recess is formed in a region where the piezoelectric diaphragm is bonded to the first surface of the metal plate, and the recess has a Young's modulus lower than that of the metal plate. It is characterized by being filled with material.

  In a specific aspect of the piezoelectric vibration device according to the present invention, a case material fixed to the metal plate is further provided in order to support a laminate including the metal plate and the piezoelectric vibration plate.

  In another specific aspect of the piezoelectric vibration device according to the present invention, the concave portion is provided at a position parallel to the displacement contour when the piezoelectric vibration plate of the piezoelectric vibration device is vibrated.

  In a more specific aspect of the piezoelectric vibration device according to the present invention, the material filled in the concave portion is an adhesive.

  In still another specific aspect of the piezoelectric vibration device according to the present invention, the adhesive is the same material as the adhesive used to bond the piezoelectric vibration plate to the metal plate.

  In still another specific aspect of the piezoelectric vibration device according to the present invention, the concave portion is also formed on the second surface of the metal plate.

  In the piezoelectric vibration device according to the present invention, the shape of the concave portion can be variously modified. However, in a specific aspect of the present invention, the concave portion is constituted by a groove.

  In a specific aspect of the piezoelectric vibration device according to the present invention, the recess is formed by a groove.

  In another specific aspect of the piezoelectric vibration device according to the present invention, a plurality of dot-shaped recesses are provided as the recesses.

  In the piezoelectric vibration device according to the present invention, a piezoelectric vibration plate configured using a piezoelectric ceramic plate is bonded to the first surface of the metal plate using an adhesive, and in the first surface of the metal plate, At least one recess is formed in a region where the piezoelectric vibration plate is bonded, and the recess is filled with a material having a Young's modulus lower than that of the metal plate. Therefore, a recess is provided in the metal plate, and the recess is filled with a material having a lower Young's modulus than the metal plate. Therefore, compared to the case where a corresponding metal plate having no recess is provided in the metal plate. Therefore, the metal plate is easily bent. Therefore, a sufficiently large amplitude, that is, a sound pressure can be obtained.

  Moreover, even when the thickness of the piezoelectric vibration plate or the metal plate is reduced in order to reduce the size and the frequency, the concave portion of the metal plate is filled with the material having the low Young's modulus. Even if the stress is concentrated in the recess, the stress is relaxed. Accordingly, it is difficult for stress to be applied to the piezoelectric ceramic plate constituting the piezoelectric diaphragm, and therefore cracks of the piezoelectric ceramic plate are difficult to occur. Also, in the manufacturing process, since the recess is filled with a material having a low Young's modulus, deformation of the metal plate is difficult to occur, and after filling the recess with a material having a low Young's modulus, the metal plate is not easily handled. You can handle metal plates without worrying. Therefore, productivity can be increased.

  Further, since the recess is filled with a material having a low Young's modulus, the recess is hardly deformed. Therefore, variations in sound pressure and sound quality can be suppressed.

  In the case where a case material fixed to the metal plate is further provided to support the laminate composed of the metal plate and the piezoelectric diaphragm, the case material is used for OA equipment, cellular phone equipment, etc. The piezoelectric vibration device can be easily attached.

  Further, when the concave portion is provided at a position parallel to the displacement amount contour line when the piezoelectric diaphragm of the piezoelectric vibration device is vibrated, the amplitude can be further increased.

  If the material filled in the concave portion is a material having a Young's modulus lower than that of the metal plate, the portion where the concave portion is provided can be easily deformed, but is preferably filled with an adhesive. In this case, when the adhesive is cured, the metal plate can be reliably bonded to the piezoelectric vibration plate even in the recess, and the bonding strength can be increased. Moreover, since it is difficult to separate the cured adhesive filled in the recesses from the recesses during deformation, variations in sound pressure and sound quality can be suppressed.

  When the adhesive filled in the recess is the same material as the adhesive used to bond the piezoelectric diaphragm to the metal plate, a single adhesive is used and the metal plate is used as the piezoelectric diaphragm. In addition, the material filled in the concave portion of the metal plate can be configured, and the work process and the manufacturing cost can be reduced.

  In addition, since the bonding strength by the adhesive filled in the concave portion and the bonding strength by the adhesive at the portion where the metal plate outside the concave portion and the piezoelectric vibration plate are bonded are substantially equal, the entire area of the piezoelectric vibration plate In addition, it can be uniformly bonded to the metal plate with the same degree of bonding strength.

  In the case where the concave portion is also formed on the second surface of the metal plate, the metal plate is thereby more easily displaced, and a larger amplitude can be obtained.

  The recess may be a groove or a dot-like recess, and the shape is not particularly limited. However, when the concave portion is a groove, an arc-shaped, circular, or linear concave portion can be formed by forming an arc-shaped or linear groove.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1A is a perspective view showing a main part of a piezoelectric vibration device according to a first embodiment of the present invention, FIG. 1B is a front sectional view thereof, and FIG. It is a partial notch front sectional drawing shown.

  The piezoelectric vibration device 1 includes a metal plate 2 and a piezoelectric vibration plate 3. The piezoelectric diaphragm 3 is illustrated as a single plate-like member in FIGS. 1A and 1B, but as shown in an enlarged view in FIG. The electrodes 5 and 6 are laminated on both main surfaces. In this embodiment, the piezoelectric ceramic plate 4 is polarized in the thickness direction. Therefore, when an AC voltage is applied between the electrodes 5 and 6, as shown schematically in FIG. 2, it vibrates so as to be displaced between the vibration state indicated by the alternate long and short dash line A and the vibration state indicated by B. . The sound pressure based on this vibration is taken out and used, for example, as a piezoelectric buzzer or a piezoelectric speaker.

  The ceramic material constituting the piezoelectric ceramic plate 4 is not particularly limited, and examples thereof include lead titanate ceramics and lead zirconate titanate ceramics. Further, the metal plate 2 is bonded to the piezoelectric vibration plate 3 by using an adhesive 7, and the material constituting the metal plate 2 may be an appropriate material such as Ni, Ni—Fe alloy, copper, or copper alloy. Metal can be used.

  The adhesive 7 can be configured using an appropriate adhesive as long as the piezoelectric diaphragm 3 can be bonded to the metal plate 2. In this embodiment, an epoxy resin adhesive is used as these adhesives, but an insulating adhesive such as a silicon adhesive may be used.

  In the present embodiment, the metal plate 2 is made of a Ni alloy, and the piezoelectric ceramic plate 4 is made of a lead zirconate titanate ceramic. In the piezoelectric diaphragm 3, the lower electrode 6 may not be provided. In this case, the metal plate 2 is used in place of the lower electrode 6 by using the adhesive 6 as a conductive adhesive. Also good.

  A plurality of grooves 2c to 2e, 2g are formed on the upper surface 2a as the first surface of the metal plate 2 and the lower surface 2b, which is the second surface opposite to the first surface 2a of the metal plate 2, respectively. , 2h are formed. A circular dot-shaped recess 2f is formed at the center of the lower surface 2b.

  FIG. 3 is a plan view of the metal plate 2 and shows the grooves 2c to 2e. The grooves 2c to 2e are circular grooves arranged so as to be concentric with the metal plate 2 in the disk-shaped metal plate 2, respectively. The grooves 2 g and 2 h are also concentric circular grooves arranged concentrically with the metal plate 2.

  However, the grooves 2c to 2e and the grooves 2g and 2h are arranged so as not to overlap with each other via the metal plate 2, that is, shifted.

  In the present embodiment, the grooves 2 c to 2 e are filled with an adhesive 8 made of the same epoxy adhesive as the adhesive 7 as a material having a Young's modulus lower than that of the metal plate 2. The dot-shaped recess 2f and the grooves 2g and 2h are filled with the adhesive 9 made of the same epoxy adhesive.

  The piezoelectric vibration device 1 has a case material 10 shown in FIG. The case material 10 has a substantially cylindrical shape, and includes a cylindrical portion 10a and a top plate portion 10b provided at one end of the cylindrical portion 10a. A through hole 10c is provided in the center of the top plate portion 10b. An opening 10d is provided on the opposite side of the cylindrical portion 10a from the top plate portion 10b. At an intermediate height position of the cylindrical portion 10a, a step portion 10e is provided on the inner peripheral surface. The metal plate 2 of the piezoelectric vibration device 1 is fixed to and supported by the step portion 10e from the second surface 2b side by an adhesive (not shown). When supported by the case material 10, when a laminate composed of the metal plate 2 and the piezoelectric diaphragm 3 is laminated, the vibration displacement amount contour line has the same center as the centers of the metal plate 2 and the piezoelectric diaphragm 3. Appears concentrically.

  Note that the displacement amount contour line indicates a line drawn when the displacement amount during vibration connects the same position when the metal plate 2 and the piezoelectric diaphragm 3 vibrate. In the present invention, the phrase “parallel to the displacement amount contour line” is not limited to the case where the displacement amount contour line is linear. That is, when the displacement amount contour line is a straight line, “parallel to the displacement amount contour line” broadly includes the displacement amount contour line and the straight line parallel to the displacement amount contour line. Further, as in this embodiment, the displacement amount contour line may be a curve like a circle. In this case, the parallel to the displacement amount contour line means that the displacement amount contour line maintains a constant width with the displacement amount contour line. And widely include both the curve that translates and the amount of displacement on the contour line. That is, in the present invention, the phrase “parallel to the displacement amount contour line” includes the displacement amount contour line, and further includes a wide straight line or curved line that maintains a certain width with the displacement amount contour line.

  4B shows a schematic plan view of the metal plate 2 supported by the case material 10, and the positions of the displacement contour lines of vibration appearing on the metal plate 2 are schematically shown by arrows CE. As is apparent from FIG. 4B, the displacement contour lines C to E appear in the concentric regions having different diameters on the metal plate 2.

  The circular grooves 2c to 2e are provided at positions where displacement contour lines C to E appear.

  In the piezoelectric vibration device 1 of the present embodiment, as described above, the grooves 2 c to 2 e are provided in the metal plate 2, and an epoxy-based material that is a material having a lower Young's modulus than the metal plate 2 is provided in the grooves 2 c to 2 e. Since the adhesive 8 is filled, it is easier to bend when driving compared to a structure in which the metal plate 2 is not provided. Therefore, a large displacement can be obtained, and the amplitude and thus the sound pressure can be increased.

  In addition, since the adhesive 8 is filled, even when stress concentrates on the portion where the grooves 2c to 2e are provided during vibration, the stress is relieved. Therefore, it is difficult for stress to be transmitted to the piezoelectric ceramic plate 4 constituting the piezoelectric vibration plate 3, and cracks of the piezoelectric ceramic plate 4 are hardly generated.

  In addition, when the adhesive is filled in the grooves 2c to 2e and cured in advance, the metal plate 2 is less likely to be deformed than when the grooves 2c to 2e are not filled with anything. Even when the piezoelectric diaphragm 3 is bonded to the metal plate 2 via the adhesive 8 and cured, the shape of the grooves 2c to 2e is maintained by the cured product of the adhesive 8 after curing. Therefore, deformation of the grooves 2c to 2e is difficult to occur. Therefore, variations in sound pressure and sound quality hardly occur.

  Further, as will be apparent from the experimental examples described later, in this embodiment, since the grooves 2c to 2e are located at positions corresponding to the displacement amount contours C to E, in other words, a portion parallel to the displacement amount contour line is present. Since it is hard to be restrained, the fall of an amplitude, ie, the fall of sound pressure, can be suppressed further, and it becomes possible to make sound pressure still higher.

  Furthermore, in the present embodiment, since the dot-like recesses 2f and the grooves 2g and 2h are provided on the lower surface 2b of the metal plate 2, the metal plate 2 is also easily deformed, and a large sound pressure can be obtained. it can. In addition, since the dot-shaped recess 2f and the grooves 2g and 2h are also filled with the adhesive 9, the deformation of the metal plate 2 is suppressed.

  Further, since the grooves 2c to 2e and the dot-shaped concave portions 2f and the grooves 2g and 2h are arranged to be shifted, the grooves 2c to 2e and the dot-shaped concave portions 2f and the grooves 2g and 2h are arranged to overlap each other. Compared to the existing structure, it is possible to suppress undesired deformation of the metal plate 2.

  However, in the present invention, it is not always necessary to provide the dot-shaped recess 2f and the grooves 2g and 2h on the lower surface 2b which is the second surface. Further, it is not always necessary to fill the adhesive 9 in the dot-like recesses 2f and the grooves 2g and 2h.

  Next, in the present embodiment, the grooves 2c to 2e are filled with the same epoxy adhesive 8 as the adhesive 7. However, other adhesives may be used for the grooves 2c to 2e, rather than the metal plate 2. A material other than an adhesive having a low Young's modulus may be filled in the grooves 2c to 2e.

  However, preferably, as described above, by filling the grooves 2c to 2e with the adhesive, the deformation of the grooves 2c to 2e can be suppressed by curing the adhesive. Further, by forming the adhesive 8 with the same adhesive as the adhesive 7, it is possible to reduce the type of the adhesive, and by using the same adhesive, the metal plate is spread over the entire area of the piezoelectric diaphragm 3. 2 can be bonded to the piezoelectric diaphragm 3 with uniform bonding strength.

  5A and 5B are a perspective view of a piezoelectric vibration device according to a second embodiment of the present invention and a perspective view showing a metal plate used in the second embodiment. The piezoelectric vibration device 21 includes a rectangular metal plate 22 and a piezoelectric vibration plate 23. The metal plate 22 and the piezoelectric diaphragm 23 are configured similarly to the metal plate 2 and the piezoelectric diaphragm 3 of the first embodiment, respectively, except that the planar shape is rectangular. Therefore, only different parts will be described.

  As illustrated in FIG. 5B, a plurality of grooves 22 c to 22 h are formed on the upper surface 22 a as the first surface of the rectangular metal plate 22. A plurality of grooves 22i to 22m are formed on the lower surface 22b as the second surface. These grooves 22c to 22h and 22i to 22m are filled with adhesives 8 and 9, respectively.

  The adhesives 8 and 9 are made of the same epoxy adhesive as the adhesive 7 that joins the piezoelectric diaphragm 23 to the metal plate 22.

  As shown in FIG. 6A, the piezoelectric vibration device 21 includes a case material 30. In the case material 30, a laminated body formed by bonding the piezoelectric vibration plate 23 to the metal plate 22 is accommodated. The case material 30 is configured in the same manner as the case material 10 shown in FIG. 4A except that it has a rectangular tube shape. That is, the top plate portion 30b is provided at one end of the cylindrical portion 30a, and the through hole 30c is provided at the center of the top plate portion 30b. An opening 30d is provided at the end of the cylindrical portion 30a opposite to the top plate portion 30b. Further, a stepped portion 30e is provided on the inner side surface of the cylindrical portion 30a, and the metal plate 22 is joined from the second surface 22b using an adhesive (not shown) at the stepped portion 30e, It is supported.

  In the piezoelectric vibration device 21, when an AC voltage is applied to both surfaces of the piezoelectric vibration plate 23, bending mode vibration is generated, and displacement contour lines of the vibration appear in a plurality of linear regions parallel to the support portion. That is, as shown in the bottom view of FIG. 6B, the metal plate 22 has a rectangular plate shape having a pair of opposing sides and another pair of opposing sides. The pair of sides 22n and 22o are fixed to and supported by the case material 30. At the time of driving, vibration displacement amount contour lines appear in a plurality of regions parallel to the sides 22n and 22o. In the present embodiment, a plurality of grooves 22c to 22h provided on the upper surface 22a of the first surface of the metal plate 22 are provided so as to be parallel to the vibration displacement contour lines.

  Also in this embodiment, the grooves 22 c to 22 h provided on the upper surface and the grooves 22 i to 22 m provided on the lower surface are provided at positions that do not overlap with each other with the metal plate 22 interposed therebetween. Therefore, it is possible to prevent undesired deformation and distortion of the metal plate 22.

  Also in the present embodiment, since the adhesive 9 is filled in the grooves 22c to 22h, the grooves 22c to 22h are provided so as to be parallel to the vibration displacement contour lines. Vibration is not suppressed, and therefore a large sound pressure can be obtained. Therefore, even if stress is applied to the groove by filling the adhesive 8, stress concentration on the piezoelectric ceramic plate side is alleviated and cracks in the piezoelectric ceramic plate can be suppressed. This will be clarified by a specific experimental example.

As the metal plate 22, a metal plate made of 42Ni-Fe alloy of 9.9mm x 10mm x 0.05mm thickness is prepared, and on one side 22n side in the length direction 10mm, as shown in FIG. It was clamped by the devices 31 and 31. A piezoelectric diaphragm 23 was bonded to one side of the metal plate 22. As this piezoelectric diaphragm 23, a piezoelectric ceramic plate having electrodes 10 mm × 8 mm × thickness 0.055 mm on which electrodes are formed is prepared. The electrodes on both main surfaces are made of a Ni—Cu alloy and have a thickness of 0.2 μm. The electrodes on both main surfaces are formed on the entire surface of the piezoelectric ceramic plate. The epoxy adhesive is made such that the side of the piezoelectric plate 23 having the dimension of 10 mm corresponds to the side of the metal plate 22 having the dimension of 10 mm, and the center of the piezoelectric ceramic plate 23 and the center of the metal plate 22 are matched. Was pasted together. The metal plate 22 was formed with a plurality of grooves as grooves each having a width of 0.04 mm and a depth of 0.02 mm and a semicircular cross section. Then, an epoxy adhesive having a Young's modulus of 1 × 10 ⁸ Pa was filled in the groove and cured. The Young's modulus of the metal plate 22 made of the 42Ni—Fe alloy is 1 × 10 ¹¹ Pa.

  On the other hand, a plurality of grooves were also formed on the lower surface side of the metal plate 22 in the same manner, filled with an epoxy adhesive, and cured.

  As shown in FIG. 8, the pitches P1 and P2 of the plurality of grooves on the upper surface and the lower surface are both 0.2 mm, and 32 grooves are formed on the upper surface of the metal plate 22, and 38 grooves are formed on the lower surface. The grooves on the front and back sides were arranged with a shift of D = 0.1 mm in the direction perpendicular to the grooves.

  The laminated body composed of the metal plate 22 and the piezoelectric vibration plate 23 of the piezoelectric vibration device thus prepared is sandwiched over the length portion S of 1.0 mm at one end by the clamps 31 and 31 as shown in FIG. Then, an alternating voltage was applied and vibrated. And the amplitude T at the time of vibrating was measured so that the edge part on the opposite side to the side supported is shown by the continuous line and the dashed-two dotted line in FIG. The amplitude T refers to a dimension along the direction perpendicular to the first surface of the metal plate 22 between the vibration state indicated by the solid line and the vibration state indicated by the two-dot chain line and the position of each tip in the maximum displacement state. And The driving voltage was 3V. As a result, the amplitude was 1.56 mm and the frequency was 630 Hz.

  On the other hand, the amplitude was measured in the same manner as in the above experimental example, except that no groove was provided on the lower surface of the metal plate 22, and it was 1.5 mm and the frequency was 670 Hz.

  Further, for comparison, the amplitude was measured in the same manner as described above except that the grooves were not provided on both sides of the metal plate. As a result, the amplitude remained at 0.65 mm and the frequency was 630 Hz. .

  Therefore, as is clear from the above experimental example, in the piezoelectric vibration device corresponding to the second embodiment, the amplitude can be greatly increased from 0.65 mm to 1.65 mm as compared with the comparative example having no groove, Therefore, it can be seen that the sound pressure can be significantly increased.

  Further, it can be seen that the frequency can be increased and the sound pressure can be further increased by providing the grooves on both sides as compared with the experimental example in which the grooves are provided on one side.

  Next, in the above experimental example, the groove pitch was changed from 0.2 mm to 0.4 mm, and 19 grooves were formed on the upper surface and the lower surface of the metal plate 22, respectively. A modified piezoelectric vibration device was produced. When the amplitude was measured in the same manner with the piezoelectric vibration device of this modification, it was 1.27 mm. Therefore, the amplitude can be changed by changing the position of the groove provided on the bonding surface of the piezoelectric plate of the metal plate, and the pitch of the groove is reduced as in the above experimental example. It can be seen that a larger amplitude can be obtained because the cross-sectional area of the metal plate is reduced when forming.

  However, if the number of grooves increases too much, the strength of the metal plate may be reduced. Therefore, it is desirable to increase the number of the grooves within a range where the strength of the metal plate and undesired deformation hardly occur.

  As is clear from the experimental example of the modification of the second embodiment, it can be seen that the amplitude can be changed by changing the number and pitch of the grooves provided in the metal plate in the present invention.

  Further, when the thickness of the metal plate is T1 and the thickness of the piezoelectric diaphragm is T2, the total thickness T = T1 + T2 of the laminated structure is changed by changing the thickness T1 of the metal plate. On the other hand, in the present invention, by providing a plurality of grooves on the first surface of the metal plate to which the piezoelectric diaphragm is bonded, the substantial thickness of the metal plate can be reduced. It can be seen that the amplitude can be increased.

  In this type of piezoelectric vibration device, it is known that the sound pressure can be increased by increasing the number of piezoelectric ceramic layers. For example, in the first embodiment and the second embodiment, one piezoelectric ceramic plate is used, but when one piezoelectric ceramic plate is further laminated, one piezoelectric ceramic plate is increased. As a result, the sound pressure can be increased by about 6 dB. In the present invention, the sound pressure cannot be increased as much as the case where the piezoelectric ceramic layer is increased, but it can be increased without increasing the piezoelectric ceramic layer by about 3 dB, which is about 1/2 of that.

  Further, the shape of the groove provided in the metal plate in the present invention is not limited to the shape shown in the first and second embodiments. For example, the rectangular metal plate 41 shown in FIG. 9 is a case where the four sides around the metal plate 4 are supported and fixed, and the first surface 41a has a plurality of concentric circular grooves with different diameters. 41b to 41d are formed. As described above, the circular grooves 41 b to 41 d may be formed in the rectangular metal plate 41.

  That is, the shape of the recesses in the present invention, such as the grooves and the dot-like recesses described later, can be appropriately changed according to the node position and shape of vibration when the piezoelectric vibration device is driven. In addition, the vibration node position also changes depending on the support structure when the laminated body including the piezoelectric vibration plate and the metal plate is supported, and the position of the displacement contour line also changes. Therefore, it is desirable to provide a recess in parallel to the displacement contour line appearing at a specific position on the metal plate. In this case, at least some of the plurality of recesses may be provided in parallel to the displacement amount contour line, and in that case, the amplitude can be increased more effectively according to the present invention. Most preferably, it is desirable that all the concave portions are arranged in parallel to the displacement amount contour lines.

  In the modification shown in FIGS. 10A and 10B, a plurality of grooves 42c to 42k are formed on the first surface 42a of the rectangular metal plate 42 in parallel with each other. On the other hand, a plurality of linear grooves 42l to 42t are also formed on the lower surface 42b. But 42c-42k and the groove | channels 42l-42t of a lower surface are extended in the direction orthogonal to each other. That is, the grooves 42c to 42k formed on the first surface and the grooves 42l to 42t formed on the second surface may be arranged to intersect each other.

  10A and 10B show a state in which the groove 42c to 42k is filled with the adhesive 8, and the grooves 42l to 42t are filled with the adhesive 9.

  In the metal plate 43 shown in FIGS. 11A and 11B, a lattice-shaped groove 43c is provided on the upper surface 43a, and no groove is provided on the lower surface 43b. As described above, the grooves provided on the first surface 43a may be lattice-shaped grooves 43c.

  In the metal plate 44 shown in FIGS. 12A and 12B, a plurality of dot-like recesses 44c, a plurality of second dot-like recesses 44d, and a plurality of third dot-like recesses 44e on the first surface 44a. Is formed. The plurality of first dot-shaped recesses 44c are arranged along the circumferential direction so as to form a circle. The plurality of second dot-shaped recesses 44d are also arranged in the circumferential direction so as to form a circle. Similarly, the plurality of third dot-shaped recesses 44e are also arranged in the circumferential direction so as to form one circle. A plurality of circles composed of these are concentric circles having different diameters. Thus, in this invention, a recessed part does not need to be a groove | channel and may be a some dot-shaped recessed part. In the metal plate 44, a plurality of dot-shaped recesses 44f are also provided on the lower surface 44b.

(A) is a perspective view which shows the principal part of the piezoelectric vibration apparatus which concerns on the 1st Embodiment of this invention, (b) is the front sectional drawing, (c) is the principal part of the piezoelectric vibration apparatus of 1st Embodiment. The partial notch front sectional drawing which expands and shows. The typical front view for demonstrating the vibration mode of the piezoelectric vibration apparatus shown in FIG. The top view of the metal plate used in 1st Embodiment. (A) is front sectional drawing of the piezoelectric vibration apparatus of 1st Embodiment with which the case material is provided, (b) is a typical top view which shows the displacement amount contour line in a metal plate. (A) is a perspective view which shows the principal part of a 2nd piezoelectric vibration apparatus, (b) is a perspective view which shows the metal plate used in 2nd Embodiment. (A) is front sectional drawing of the piezoelectric vibration apparatus of 2nd Embodiment, (b) is a bottom view. The typical front view for demonstrating the method to measure an amplitude in the piezoelectric vibration apparatus of 2nd Embodiment. The partial notch front sectional drawing for demonstrating pitch arrangement | positioning of the groove | channel in the piezoelectric vibration apparatus of 2nd Embodiment. The typical top view of the metal plate of the piezoelectric vibration apparatus which concerns on the modification of this invention. (A) And (b) is a top view which shows the metal plate used for the piezoelectric vibration apparatus which concerns on the other modification of this invention, and sectional drawing which follows the XX line in (a). (A) And (b) is a top view of the metal plate used with the piezoelectric vibration apparatus which concerns on the further another modification of this invention, and sectional drawing which follows the YY line in (a). (A) And (b) is the top view and front sectional drawing of a metal plate which are used for the piezoelectric vibration apparatus which concerns on another modification of this invention. The typical front sectional view for explaining an example of the conventional piezoelectric vibration device. The exploded plan view for demonstrating the other example of the conventional piezoelectric vibration apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric vibration apparatus 2 ... Metal plate 2a ... Upper surface (1st surface)
2b ... lower surface (second surface)
2c to 2e ... groove 2f to 2h ... groove 3 ... piezoelectric diaphragm 4 ... piezoelectric ceramic plate 5,6 ... electrode 7 ... adhesive 8 ... adhesive 9 ... adhesive 10 ... case material 10a ... cylindrical part 10b ... top plate part DESCRIPTION OF SYMBOLS 10c ... Through-hole 10d ... Opening 10e ... Step part 21 ... Piezoelectric vibration device 22 ... Metal plate 22a ... Upper surface (1st surface)
22b ... lower surface (second surface)
22c-22h ... groove 22i-22m ... groove 23 ... piezoelectric diaphragm 30 ... case material 30a ... cylindrical portion 30b ... top plate portion 30c ... through hole 30d ... opening 30e ... stepped portion 31 ... clamp device 41 ... metal plate 41a ... 1st surface 41b-41d ... groove | channel 42 ... metal plate 42a ... 1st surface 42b ... 2nd surface 42c-42k ... groove | channel 42l-42t ... groove | channel 43 ... metal plate 43a ... 1st surface 43b ... 2nd surface Surface 43c ... Groove 44 ... Metal plate 44a ... First surface 44b ... Second surface 44c-44e ... Dot-shaped recess 44f ... Dot-shaped recess

Claims (8)

A metal plate having first and second surfaces facing each other;
A piezoelectric diaphragm that is bonded to the first surface of the metal plate with an adhesive and is configured using a piezoelectric ceramic plate;
In the first surface of the metal plate, at least one recess is formed in a region where the piezoelectric vibration plate is bonded, and the recess is filled with a material having a Young's modulus lower than that of the metal plate. A piezoelectric vibration device.   The piezoelectric vibration device according to claim 1, further comprising a case member fixed to the metal plate in order to support a laminate including the metal plate and the piezoelectric vibration plate.   The piezoelectric vibration device according to claim 1, wherein the concave portion is provided at a position parallel to a displacement amount contour line when the piezoelectric vibration plate of the piezoelectric vibration device is vibrated.   The piezoelectric vibration device according to any one of claims 1 to 3, wherein the material filled in the recess is an adhesive.   The piezoelectric vibration device according to claim 4, wherein the adhesive is made of the same material as the adhesive used to bond the piezoelectric vibration plate to the metal plate.   The piezoelectric vibration device according to claim 1, wherein the concave portion is also formed on the second surface of the metal plate.   The piezoelectric vibration device according to claim 1, wherein the recess is a groove. The piezoelectric vibration device according to claim 1, wherein a plurality of dot-like recesses are provided as the recesses.

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