JP2007028469A - Acoustic vibration generating element, manufacturing method thereof, and acoustic vibration generating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acoustic vibration generating element which is simplified and small-sized in structure, rich in mass-productivity, improved in impulse resistance, robust and improved in acoustic characteristics, and to provide a manufacturing method thereof and an acoustic vibration generating apparatus using the element. <P>SOLUTION: An acoustic vibration generating element is comprised of a piezoelectric element 11 and a fixing member 21 for fixing the piezoelectric element 11 in a terminal portion, the piezoelectric element 11 is disposed on the fixing member 21 through an elastic member 22, and a piezoelectric element part 23 is thinner than the fixing member 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a speaker, an acoustic device, and a bone conduction application device that generate acoustic vibration, and more particularly to an acoustic vibration generating element using a piezoelectric element, a method for manufacturing the element, and an acoustic vibration generating apparatus using the same.

  Conventionally, an acoustic transducer for bone conduction, which is mainly used as a hearing aid, mainly transmits acoustic vibrations to the cochlear organ of the inner ear via the skull by contacting the head of the human body, for example, the cheekbone, Is configured to be heard. As a method of contacting the bone conduction acoustic transducer with the head, several methods have been put to practical use. For example, a system in which a speaker is mounted on the outside of a helmet, or a configuration similar to a headphone in which a bone-conducting speaker is installed at both ends of a headband has been widely put into practical use. Furthermore, an attachment for attaching a bone conduction speaker to a mobile phone has been proposed. Such acoustic vibration generating elements for the purpose of bone conduction are disclosed in Patent Documents 1 to 3.

  Conventionally, piezoelectric speakers, piezoelectric buzzers, and the like have been put to practical use as acoustic vibration generating elements using piezoelectric elements for transmitting electrical signals by converting them into mechanical vibrations. In particular, an acoustic vibration generating element mounted on a mobile phone or a portable terminal is required to be thin. On the other hand, a robust acoustic vibration generating element that does not break even when subjected to an impact caused by dropping is required. ing.

  However, the acoustic vibration generating element using a piezoelectric element has a problem that the mechanical strength decreases when the material becomes thin because the material used is ceramics. For this reason, many structures have been proposed that do not break even when subjected to impacts such as dropping.

  For example, FIGS. 1 and 2 are cross-sectional views of a conventional acoustic vibration generating element. In FIG. 1, a piezoelectric element 1 is fixed and accommodated inside a case 2, a lid 3 is disposed on the top, and a protrusion 4 is provided on the central bottom surface of the case 2. When the acoustic vibration generating element receives an impact due to dropping, the protrusion 4 serves as a stopper to prevent the piezoelectric element 1 from being destroyed so that the impact force does not cause the piezoelectric element 1 to be deformed exceeding the breaking stress. Yes. Such an acoustic vibration generating element is disclosed in Patent Document 4.

  In FIG. 2, shock absorbers 6 are arranged between two piezoelectric elements 1 and above and below and fixed by fixing members 7. Proposals have been made to prevent damage to the piezoelectric element 1 by reducing the impact from the outside with the shock absorber 6 with such a structure. Such an acoustic vibration generating element is disclosed in Patent Document 5.

JP 2001-333478 A JP-A-11-331970 JP 2002-164986 A Utility Model Registration No. 2599264 JP 2004-104327 A

  However, in the case of the structure shown in FIG. 1, the case 2 and the lid 3 provided with at least the protrusions 4 are required, and a process of incorporating the piezoelectric element 1 into the case 2 is required, resulting in a large number of parts and a large number of manufacturing processes. . Further, since the acoustic chamber 5 is necessary due to the structure, there is a problem that the height dimension is restricted and the thickness cannot be reduced. Further, the protrusion 4 serves as a stopper that suppresses deformation exceeding the breaking stress when the piezoelectric element 1 receives an impact. However, the impact force at which the piezoelectric element 1 and the protrusion 4 collide cannot be prevented. There is a problem that the piezoelectric element 1 is damaged such as generation of microcracks.

  Also in the structure shown in FIG. 2, there is a problem in that there are many manufacturing processes because a process of attaching the shock absorbing material 6 to both surfaces of the piezoelectric element 1 and further superimposing it is necessary. In addition, there is a problem that the vibration of the piezoelectric element 1 is constrained by the influence of the pasted shock absorbing material 6, the vibration amount is reduced, and the acoustic characteristics are lowered.

  Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art. Specifically, it is possible to provide an acoustic vibration generating element having a simple structure, a small size, high mass productivity, high impact resistance, robustness and improved acoustic characteristics, a method for manufacturing the same, and use of the element. It is an object of the present invention to provide an acoustic vibration generator.

  According to the present invention, there is provided an acoustic vibration generating element including a plate- or bar-shaped piezoelectric element and one or more fixing members that fix the piezoelectric element at an end, the piezoelectric element being interposed via an elastic member. Thus, an acoustic vibration generating element is obtained, wherein the piezoelectric element is disposed on the fixing member and the piezoelectric element is thinner than the fixing member.

  The piezoelectric element of the present invention has a plate shape or a rod shape. In the plate shape, there are a rectangular plate, a circular plate, a polygonal plate, and the like, all of which have a thickness. The rod-shaped member includes a cylinder, a prism, and the like, and has a thickness that becomes a maximum dimension portion in a direction perpendicular to a surface to be fixed in actual use in a cross section perpendicular to the longitudinal direction. The piezoelectric element of the present invention is fixed to the fixing member via an elastic member. The fixing member has a thickness that is a maximum dimension portion in a direction perpendicular to a surface to be fixed in actual use, but the thickness of the piezoelectric element is smaller than the thickness of the fixing member in the previous period. It is configured. With this configuration, for example, the impact when dropped is not directly transmitted to the piezoelectric element, but the impact is once transmitted to the fixing member and then propagated to the piezoelectric element via the elastic member. At this time, since the impact is absorbed by the first elastic member, an effect of drastically reducing the impact force transmitted to the piezoelectric element can be obtained. Furthermore, by changing the number and position of the elastic members, the frequency characteristics of the vibration amount of the piezoelectric element can be controlled, and the design of acoustic characteristics suitable for the application can be facilitated.

  In addition, according to the present invention, an acoustic vibration generating element is obtained in which the elastic member has the piezoelectric element gripping function.

  Furthermore, according to the present invention, there is obtained an acoustic vibration generating element characterized in that the elastic member has a substantially rectangular parallelepiped shape.

  Further, according to the present invention, there is obtained an acoustic vibration generating element characterized in that the elastic member is a convex portion formed by integrally molding the piezoelectric element with a flexible material.

  Further, according to the present invention, the fixing member has a shape capable of surrounding at least a part of the piezoelectric element or the piezoelectric element integrally molded with a flexible material. An element is obtained.

  Furthermore, according to the present invention, an acoustic vibration generating element is obtained in which the fixing member has a function of holding the elastic member.

  According to the above configuration of the present invention, the elastic member and the fixing member are made of the same flexible material, thereby providing a very simple structure with a small number of parts.

  Further, according to the present invention, there is obtained an acoustic vibration generating element, wherein the fixing member includes a terminal for inputting an electric signal to the piezoelectric element.

  Furthermore, according to the present invention, an acoustic vibration generating element is obtained, wherein the plate-like piezoelectric element is a piezoelectric bimorph element or a piezoelectric unimorph element.

  Furthermore, according to the present invention, an acoustic vibration generating element is obtained, wherein the plate or rod-shaped piezoelectric element uses a laminated piezoelectric element having an internal electrode inside.

  Furthermore, according to the present invention, there is a step of simultaneously molding both the step of covering the piezoelectric element with a flexible material and the step of molding the fixing member and the elastic member with a flexible material, and integrally molding them. Thus, a method for manufacturing an acoustic vibration generating element can be obtained.

  That is, it is not a conventional manufacturing process in which a number of parts are arranged and assembled in order. For example, a piezoelectric element is attached to a mold for molding a fixing member and an elastic member, and a liquid flexible substance is poured into the mold. Since it is a manufacturing method that molds and cures, it can be manufactured in one step.

  In addition, according to the present invention, there can be obtained an acoustic vibration generating device characterized in that the vibration generating element is attached to a panel or housed in a housing.

  Furthermore, according to the present invention, there is obtained an acoustic vibration generating apparatus characterized in that the vibration generating element is attached to a panel or a mounting part of a housing via a vibration absorbing member. This is because, for example, when a vibration generating element is attached to the casing of a mobile phone, the vibration absorbing member suppresses the propagation of the vibration of the vibration generating element, and the vibration of the vibration generating element is transmitted to the microphone to talk to the other party. Then, the effect of preventing the echo return phenomenon that one's voice comes back can be obtained.

  According to the present invention, it is possible to provide an acoustic vibration generating element having a simple structure, a small size, high mass productivity, high impact resistance, robustness, and improved acoustic characteristics. Furthermore, according to the present invention, it is possible to provide a method for manufacturing the acoustic vibration generating element and an acoustic vibration generating apparatus using the acoustic vibration generating element.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.
3 to 7 are perspective views showing an acoustic vibration generating element according to the present invention.

  The acoustic vibration generating element shown in FIG. 3 includes a plate-like piezoelectric element 11 and a fixing member 12, and the piezoelectric element 11 is arranged on the fixing member 12 via an elastic member 13. Further, the thickness t2 of the piezoelectric element 11 is smaller than the thickness t1 of the fixing member 12. The piezoelectric element 11 is an element that converts an acoustoelectric signal using an acoustic ceramic material into an acoustic vibration. When an acoustoelectric signal is input from the lead wire 14, vibration according to the frequency and voltage of the input acoustoelectric signal is generated. The elastic member 13 holds the two end portions in the longitudinal direction of the piezoelectric element 11 so as to hold it, and not only connects to the fixing member 12 but also buffers vibrations and shocks received by the fixing member 12, The piezoelectric element 11 has a function not to cause deformation beyond the breaking stress. Accordingly, the material used for the elastic member 13 is desirably a material having a large shock-absorbing effect against vibrations and shocks. For example, rubber, silicon, urethane, or the like is preferably used. Alternatively, an organic substance can be used in addition to a metal as long as it has elasticity.

  Furthermore, the elastic member 13 can control the vibration distribution of the acoustic vibration generated by the piezoelectric element 11 by changing the shape and the elastic material used. Therefore, it is possible to freely design the frequency characteristics of the acoustic vibration.

  For example, as shown in FIG. 4, the elastic member 15 has a substantially rectangular parallelepiped shape and is narrower than the width A of the piezoelectric element 11. In such an acoustic vibration generating element, the restraining force at both ends of the piezoelectric element 11 is smaller than that of the acoustic vibration generating element shown in FIG. 3, so that a larger vibration is generated and at the same time corners at both ends of the piezoelectric element 11. As a result, the frequency distribution of the acoustic vibration changes. In order to integrate the elastic member 15 with the piezoelectric element, a notch for insertion may be provided in advance, and the elastic member 15 may be assembled as a separate member. In order to improve production efficiency, when the piezoelectric element 11 is integrally molded with a flexible material, it is preferable to simultaneously mold a convex portion that protrudes from the end of the piezoelectric element.

  The acoustic vibration generating element shown in FIG. 5 includes a rod-shaped piezoelectric element 16 and a fixing member 12, and the piezoelectric element 16 is disposed on the fixing member 12 via an elastic member 17. Also in this configuration, since the thickness t2 of the piezoelectric element 16 is thinner than the thickness t1 of the fixing member 12, the same effect as the acoustic vibration generating element shown in FIG. 3 can be obtained.

  In the acoustic vibration generating element shown in FIG. 6, the fixing member 21 is formed in a shape that surrounds the entire circumference of the piezoelectric element portion 23 in which the piezoelectric element 11 is integrally molded with a flexible material, and the piezoelectric element portion 23 is formed at the end portion. It is fixed to the fixing member 21 via the elastic member 22 at four places. Further, the fixing member 21 and the elastic member 22 are formed of the same type of flexible material, and the piezoelectric element 11 is also covered with the same flexible material, so that the impact resistance is the same as that of the acoustic vibration generating element shown in FIG. And a robust acoustic vibration generating element. For example, rubber, silicon, urethane, epoxy resin, and the like are suitable as the flexible substance to be used. However, other materials may be used as long as they have flexibility. Further, the fixing member 21 does not surround the entire circumference of the piezoelectric element 11, but the U-shape lacking one side, the L-shape lacking two sides, the shape partially missing at one or more locations, or If the piezoelectric element is a disk, it has the same function as long as it is a C-shape or the like, and is not limited to the form shown in FIG.

  The fixing member shown in FIGS. 3 to 6 has a function of holding an elastic member, and is not particularly limited in material and shape as long as it can withstand impacts and vibrations, and considers acoustic characteristics and design. However, it may be selected as appropriate.

  The acoustic vibration generating element shown in FIG. 7 has a terminal 25 disposed on the surface of the fixing member 12 instead of the lead wire 14 in the acoustic vibration generating element shown in FIG. Thus, it is connected to the piezoelectric element 11 via the lead wire 24. Although FIG. 7 illustrates the connection state of only one of the two terminals 25, the other terminal 25 is also connected to the piezoelectric element 11 by a lead wire.

  The lead wire 14 shown in FIG. 3 can be easily routed for wiring on a circuit board to be driven. On the other hand, the provision of the terminal 25 eliminates the failure that the lead wire is broken due to vibration and impact, and the sound is more robust than the case where the lead wire is used against shock caused by vibration or dropping. It becomes a vibration generating element. Therefore, it is more preferable to use the terminal 25 as a connector from the viewpoint of easy handling.

  8 and 9 are perspective views showing the piezoelectric element 11. The piezoelectric element used for the acoustic vibration generating element is preferably a piezoelectric element having a large amount of vibration per unit voltage from the viewpoint of efficiency, and a piezoelectric ceramic plate 26 is attached only to one surface of the elastic plate 27 as shown in FIG. It is preferable to use an attached piezoelectric unimorph element or a piezoelectric bimorph element having a structure in which the piezoelectric ceramic plates 26 are attached to both surfaces of the elastic plate 27 as shown in FIG. 8 and 9 illustrate a rectangular piezoelectric element, the shape of the piezoelectric element is not limited to a rectangle, and may be appropriately selected in consideration of design and characteristics such as a circle or a polygon. In addition, the piezoelectric bimorph may be configured by directly bonding two piezoelectric ceramic plates without using an elastic plate. Furthermore, in addition to metals such as stainless steel and phosphor bronze, the elastic plate may be made of an inorganic material such as ceramics, carbon or glass, or an organic material containing an inorganic material.

  Furthermore, the piezoelectric element 11 is preferably a piezoelectric ceramic plate that reduces the power consumption by reducing the voltage of the acoustoelectric signal and also simplifies the acoustoelectric signal generation circuit. FIG. 10 is a cross-sectional view of the piezoelectric ceramic plate. The piezoelectric ceramic plate 26 shown in FIG. 10 has internal electrodes 28 and 29 inside, a laminated structure in which the internal electrode 28 is electrically connected to the external electrode 30 and the internal electrode 29 is electrically connected to the external electrode 31. Type piezoelectric ceramic plate. If such a laminated piezoelectric ceramic plate is used, the voltage of the acoustoelectric signal can be lowered. The structure, number, material, distance between electrodes, and the like of the internal electrodes may be appropriately selected in consideration of acoustic vibration characteristics.

  FIG. 11 is a perspective view showing a piezoelectric element. The piezoelectric element 16 is formed by laminating sheet-like piezoelectric ceramics 32 and internal electrodes 33 alternately in the longitudinal direction, integrally firing, and then arranging a pair of external electrodes 34 electrically connected to the internal electrodes 33. It is a laminated piezoelectric element. By using such a laminated piezoelectric element, the same effect as the acoustic vibration generating element shown in FIG. 5 can be obtained.

  Next, a method for manufacturing the acoustic vibration generating element shown in FIG. 6 will be described. A piezoelectric element such as a piezoelectric bimorph or a piezoelectric unimorph prepared in advance is fixed to a predetermined place of a mold engraved with a product shape, and then a flexible substance is filled into the mold. When the curing of the flexible material is completed, it is removed from the mold and the acoustic vibration generating element is completed. The curing of the flexible substance should be appropriately set according to the nature of the flexible substance used. Thus, since an acoustic vibration generating element can be obtained by a simple manufacturing method in one step, mass productivity is improved.

  Furthermore, FIG. 12 is a perspective view of an acoustic generator using the acoustic vibration generating element of the present invention. A single-sided portion of the fixing member 21 of the acoustic vibration generating element 20 according to the present invention shown in FIG. Even if an impact is applied to the panel portion of the acoustic generator, the impact transmitted to the fixing member 21 of the acoustic vibration generating element 20 is buffered by the elastic member 22 as described above, so that the piezoelectric element is not destroyed. Is obtained. This acoustic vibration generating element can be used not only for a panel speaker but also for various acoustic generators. For example, it can be used for a portable electronic device such as a pager, an IC card, or a mobile phone, or a headphone or a bone conduction application device.

  Hereinafter, the acoustic vibration generating element of the present invention will be described in more detail with specific examples. FIG. 13 is a diagram showing a first embodiment of an acoustic vibration generating element according to the present invention. 13 (a) is a perspective view, FIG. 13 (b) is a top view, FIG. 13 (c) is a cross-sectional view of (a)-(b) in FIG. 13 (b), and FIG. 13 (d) is a diagram. It is sectional drawing of (c)-(d) in 13 (b).

  The used piezoelectric element 11 is a piezoelectric bimorph element having the structure shown in FIG. Using NEC TOKIN piezoelectric ceramics (N10), two piezoelectric ceramic plates 26 having a length of 30 mm, a width of 8 mm and a thickness of 0.15 mm, and a brass elastic plate having a length of 32 mm, a width of 8 mm and a thickness of 50 μm 27 was bonded with an epoxy adhesive. This piezoelectric bimorph element was previously subjected to polarization treatment, and was bonded via an elastic plate 27 so that surfaces of different polarities face each other. When lead wires are provided on the outer surfaces of the elastic plate 27 and the piezoelectric ceramic plates 26 on both sides, and the lead wires provided on the piezoelectric ceramic plates are shared, and when the same electric field as the polarization direction is applied to one piezoelectric ceramic plate, the other The piezoelectric ceramic plate was connected so that a reverse electric field was applied.

  Next, the piezoelectric element 11 in which the terminal 25 is connected to the end of the lead wire in advance with solder is fixed to a brass mold, a polyurethane solution is poured, and a curing process at 100 ° C. is performed, as shown in FIG. An acoustic vibration generating element having a shape as shown in the perspective view was produced. As for the details of the shape, in the front view shown in FIG. 13B, the outer dimension of the fixing member 21 is 40 mm × 16 mm, which forms a frame shape. The inner dimension of the frame is 36 mm × 12 mm. The external dimensions of the piezoelectric element portion 23 are 34 mm × 10 mm. A 1 mm gap 36 was provided between the piezoelectric element portion 23 and the fixed member 21 on the entire circumference except for the portion where the elastic member 22 was disposed.

  Further, in the cross-sectional view including the elastic member 22 shown in FIG. 13C and the cross-sectional view not including the elastic member 22 shown in FIG. 13D, the dimension of t1 that is the thickness of the fixing member 21 is 5 mm, and the piezoelectric element. The dimension of t2, which is the thickness of the portion 23, was 2.5 mm. In the piezoelectric element portion 23, a polyurethane film having a thickness of 1 mm covers the entire piezoelectric element 11. The difference in thickness between the piezoelectric element portion 23 and the fixing member 21 is (t1−t2) /2=1.25 mm on both surfaces. Due to the difference in thickness, the piezoelectric element portion 23 has a structure that does not receive direct impact. The elastic member 22 has a width of 3 mm and a thickness of 2.5 mm, which is the same as that of the piezoelectric element portion 23, at the center of each side of the piezoelectric element portion 23, and is sandwiched and fixed to the fixing member 21.

  A drop test was performed using the acoustic vibration generating element of the present invention according to the above embodiment and 20 acoustic vibration generating elements each corresponding to a conventional product as a comparative example. In the drop test, a drop was made on a flat concrete from a height of 1 m, and the vibration output when an acoustic signal before and after the drop was input was compared. The results are shown in Table 1.

  As shown in Table 1, it can be seen that the impact resistance of the example is markedly improved compared to the comparative example.

  FIG. 14 is a perspective view showing a second embodiment of the acoustic vibration generating element according to the present invention. The piezoelectric element 11 used is a piezoelectric bimorph element having the structure shown in FIG. Using NEC TOKIN piezoelectric ceramics (N10), two piezoelectric ceramic plates 26 having a length of 30 mm, a width of 8 mm and a thickness of 0.15 mm, and a brass elastic plate having a length of 32 mm, a width of 8 mm and a thickness of 50 μm 27 was bonded with an epoxy adhesive. This piezoelectric bimorph element was previously subjected to polarization treatment, and was bonded via an elastic plate 27 so that surfaces of different polarities faced each other. When lead wires are provided on the outer surfaces of the elastic plate 27 and the piezoelectric ceramic plates 26 on both sides, and the lead wires provided on the piezoelectric ceramic plates are shared, and when the same electric field as the polarization direction is applied to one piezoelectric ceramic plate, the other The piezoelectric ceramic plate was connected so that a reverse electric field was applied.

  Next, the piezoelectric element 11 in which the terminal 25 is connected to the end of the lead wire with solder in advance is fixed to a brass mold, and a polyurethane solution is poured into the perspective view of FIG. An acoustic vibration generating element having a shape as shown was produced. The form of the fixing member 21 is a form in which a portion corresponding to a corner of a frame shape having an outer dimension of 40 mm × 16 mm is cut out and the length in the direction along the end of the piezoelectric element portion 23 is 10 mm. The external dimensions of the piezoelectric element portion 23 are 34 mm × 10 mm. A clearance of 1 mm was provided between the piezoelectric element portion 23 and the fixed member 21 on the entire circumference except for the portion where the elastic member 22 was disposed. The fixing member 21 has a thickness of 5 mm, and the piezoelectric element portion 23 has a thickness of 2.5 mm. The piezoelectric element portion 23 has a 1 mm thick polyurethane film covering the entire piezoelectric element 11. Accordingly, the height difference between the piezoelectric element portion 23 and the fixing member 21 is 1.25 mm on both side surfaces. The elastic member 22 has a width of 3 mm and a thickness of 2.5 mm, which is the same as that of the piezoelectric element portion 23, at the center of each side of the piezoelectric element portion 23, and is sandwiched and fixed to the fixing member 21.

  In Example 2 described above, even if the drop test is performed, there are no fixing members 21 at the four corners of the piezoelectric element portion 23, so that the portion directly hits concrete and damages the piezoelectric element 11. . However, if an actual use state is assumed, the acoustic vibration generating element according to the present invention is rarely used alone, and is usually used in a state of being attached to a panel, a casing, or the like. . Therefore, in the drop test in Example 2, an acrylic plate having an outer dimension of 45 mm × 20 mm and a thickness of 0.5 mm is attached to the surface opposite to the surface on which the terminals 25 of the fixing member 21 are disposed. And tested. As a result, the result that the output decreased by 5% or more before and after the test was 0 out of 20 units, and the effect of the present invention was confirmed as in Example 1.

  FIG. 15 is a perspective view showing a third embodiment of the acoustic vibration generating element according to the present invention. The used piezoelectric element 11 is a circular piezoelectric bimorph element. Using NEC TOKIN piezoelectric ceramics (N10), two piezoelectric ceramic plates with a diameter of 20 mm and a thickness of 0.15 mm and an elastic plate made of brass with a diameter of 25 mm and a thickness of 50 μm were bonded together with an epoxy adhesive. . This piezoelectric bimorph element was previously subjected to polarization treatment, and was bonded via an elastic plate so that different polar surfaces faced each other. When the lead wire is provided on the outer surface of the elastic plate and the piezoelectric ceramic plates on both sides and the lead wires provided on the piezoelectric ceramic plate are shared, and the same electric field as the polarization direction is applied to one piezoelectric ceramic plate, the other piezoelectric ceramic The plates were wired so that a reverse electric field was applied.

  Next, the piezoelectric element 11 whose terminal is connected to the end of the lead wire with solder in advance is fixed to a brass mold, and a polyurethane solution is poured into it, and a curing process at 100 ° C. is performed, as shown in the perspective view of FIG. Various types of acoustic vibration generating elements were produced. As for the details of the shape, the outer dimension of the fixing member 21 is 36 mm in diameter and forms an arcuate frame at four locations. The inner dimension of the frame is 30 mm in diameter. The external dimension of the piezoelectric element portion 23 is 27 mm in diameter. A gap of 1.5 mm was provided between the piezoelectric element portion 23 and the fixed member 21 on the entire circumference except for the portion where the elastic member 22 was disposed. The fixing member 21 has a thickness of 5 mm, and the piezoelectric element portion 23 has a thickness of 2.5 mm. The piezoelectric element portion 23 has a 1 mm thick polyurethane film covering the entire piezoelectric element 11. Therefore, the thickness difference between the piezoelectric element portion 23 and the fixing member 21 is 1.25 mm on both side surfaces. The elastic member 22 is sandwiched and fixed between the fixing member 21 and the piezoelectric element 11 with a width of 3 mm and a thickness of 2.5 mm at intervals of 90 degrees on the end portion circumference of the piezoelectric element portion 23. In the example described above, the same effect as in Example 1 was obtained.

  FIG. 16 is a perspective view showing a fourth embodiment of the acoustic vibration generator according to the present invention. The acoustic vibration generating element 20 produced in Example 1 is bonded to an acrylic panel 35 having a length of 45 mm, a width of 60 mm, and a thickness of 0.5 mm to obtain an acoustic vibration generator. By inputting an acoustoelectric signal to the terminal 25, the vibration generated by the acoustic vibration generating element 20 according to the present invention directly vibrates the surrounding air, and the sound that propagates and the acoustic vibration generating element 20 vibrate the panel 35. The air around the panel 35 vibrates and generates sound that propagates. For this reason, a larger sound pressure can be obtained than the sound pressure generated by the acoustic vibration generating element alone.

  FIG. 17 is a top view showing a fifth embodiment of the acoustic vibration generator according to the present invention. The state where the acoustic vibration generating element 20 shown in the first embodiment is fixed to the housing 37 is shown. In FIG. 17A, the acoustic vibration generating element 20 uses an acoustic vibration generating element in which a fixing member 21 and a piezoelectric element portion 23 are joined by elastic members 22 arranged at four locations. A fixed acoustic vibration generator is shown. In FIG. 17B, the acoustic vibration generating element 20 uses an acoustic vibration generating element in which a fixing member 21 and a piezoelectric element portion 23 are joined by elastic members 22 arranged at two locations. A fixed acoustic vibration generator is shown.

  FIG. 18 is a graph showing the vibration propagation characteristics of the acoustic vibration generator in FIGS. 17A and 17B shown in the fifth embodiment. In the graph, the horizontal axis indicates the amount of vibration propagation, and the horizontal axis indicates the drive frequency. As can be seen from the graph, the frequency characteristic of the propagation amount of vibration varies greatly depending on the number of the elastic members. That is, the frequency characteristics of the vibration propagation amount can be controlled by the number, location, and material of the elastic members, and the acoustic characteristics can be improved.

  FIG. 19 is a side view showing a sixth embodiment of the acoustic vibration generator according to the present invention. The acoustic vibration generating element 20 according to the first embodiment is fixed to the housing 37 via the vibration absorbing member 38. In Example 6, a sponge having a thickness of 5 mm was used for the vibration absorbing member 38. The result of measuring the amount of vibration propagation of the acoustic vibration generator according to Example 6 is shown in FIG. In the graph, the horizontal axis indicates the amount of vibration propagation, and the horizontal axis indicates the drive frequency. For comparison, the measurement result of the propagation amount of vibration in a state where the acoustic vibration generating element 20 is fixed to the casing 37 without using the vibration absorbing member 38 is also shown. As is apparent from the graph, in the acoustic vibration generating device according to the present invention, it is understood that the vibration propagation amount is suppressed by interposing the vibration absorbing member 38 between the acoustic vibration generating element 20 and the housing 37. . Therefore, the echo return phenomenon caused by the vibration of the acoustic vibration generating element propagating to the housing is prevented. The vibration absorbing member is not particularly limited as long as it is a material that absorbs vibration. For example, the same effect can be obtained with a flexible substance such as rubber or urethane.

  As described above, according to the present invention, an acoustic vibration generating element using a piezoelectric element has a simple structure, a small size, and an impact resistance. It is possible to provide a highly reliable and robust acoustic vibration generating element. In addition, the present invention provides a manufacturing method that is rich in mass productivity in the manufacturing method of the acoustic vibration generating element, and further provides an acoustic vibration generating device with improved acoustic characteristics.

  The acoustic vibration generating element according to the present invention can be used for an acoustic vibration generating element or speaker mounted on a mobile phone, a portable terminal or the like, a headphone as an acoustic device, an acoustic device using bone conduction, or the like.

Sectional drawing which shows the conventional acoustic vibration generating element. Sectional drawing which shows the conventional acoustic vibration generating element. The perspective view which shows the acoustic vibration generating element of this invention. The perspective view which shows the acoustic vibration generating element of this invention. The perspective view which shows the acoustic vibration generating element of this invention. The perspective view which shows the acoustic vibration generating element of this invention. The perspective view which shows the acoustic vibration generating element of this invention. The perspective view which shows the piezoelectric element provided to this invention. The perspective view which shows the piezoelectric element provided to this invention. Sectional drawing which shows the piezoelectric ceramic board provided to this invention. The perspective view which shows the piezoelectric element provided to this invention. The perspective view of the acoustic vibration generator of this invention. The figure which shows Example 1 of this invention. FIG. 13A is a perspective view. FIG. 13B is a top view. FIG. 13C is a cross-sectional view. FIG. 13D is a cross-sectional view. The perspective view which shows Example 2 of this invention. The perspective view which shows Example 3 of this invention. The perspective view which shows Example 4 of this invention. The top view which shows Example 5 of this invention. FIG. 17A is a top view showing Example 5 in which four elastic members are provided. FIG. 17B is a top view showing Example 5 in which two elastic members are provided. The graph which shows the propagation amount of the vibration by Example 5 of this invention. The side view which shows Example 6 of this invention. The graph which shows the propagation amount of the vibration by Example 6 of this invention.

Explanation of symbols

1, 11, 16 Piezoelectric element 2 Case 3 Lid
4 Projection 5 Acoustic chamber 6 Shock absorber 7, 12, 21 Fixing member 13, 15, 17, 22 Elastic member 14, 24 Lead wire 20 Acoustic vibration generating element 23 Piezoelectric element portion 25 Terminal 26 Piezoelectric ceramic plate 27 Elastic plate 28, 29, 33 Internal electrodes 30, 31, 34 External electrodes 32 Piezoelectric ceramics 35 Panel 36 Gap 37 Housing 38 Vibration absorbing member

Claims (12)

  An acoustic vibration generating element comprising a plate or rod-shaped piezoelectric element and one or more fixing members for fixing the piezoelectric element at an end thereof, wherein the piezoelectric element is arranged on the fixing member via an elastic member. The piezoelectric vibration generating element is characterized in that the piezoelectric element is thinner than the fixing member.   The acoustic vibration generating element according to claim 1, wherein the elastic member has the piezoelectric element gripping function.   The acoustic vibration generating element according to claim 1, wherein the elastic member has a substantially rectangular parallelepiped shape.   The acoustic vibration generating element according to any one of claims 1 to 3, wherein the elastic member is a convex portion formed by integrally molding the piezoelectric element with a flexible material.   5. The fixing member according to claim 1, wherein the fixing member has a shape capable of surrounding at least a part of the piezoelectric element or the piezoelectric element integrally formed of a flexible material. Acoustic vibration generating element.   The acoustic vibration generating element according to claim 1, wherein the fixing member has a function of holding the elastic member.   The acoustic vibration generating element according to claim 1, wherein the fixing member includes a terminal for inputting an electric signal to the piezoelectric element.   The acoustic vibration generating element according to any one of claims 1 to 7, wherein the plate-like piezoelectric element is a piezoelectric bimorph element or a piezoelectric unimorph element.   The acoustic vibration generating element according to any one of claims 1 to 8, wherein the plate or bar-shaped piezoelectric element is a stacked piezoelectric element having an internal electrode inside.   2. The method according to claim 1, further comprising the step of simultaneously molding both the step of covering the piezoelectric element with a flexible material and the step of molding the fixing member and the elastic member with a flexible material. A method for manufacturing the acoustic vibration generating element according to any one of claims 1 to 9.   An acoustic vibration generating device comprising the acoustic vibration generating element according to any one of claims 1 to 9 attached to a panel or housed in a housing.   An acoustic vibration generating device comprising: the acoustic vibration generating element according to any one of claims 1 to 9 attached to an attachment portion of a panel or a casing via a vibration absorbing member.

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