Sot module

Abstract

To provide a SoT module capable of improving sound pressure of a specific frequency band by outputting a vibration of a plurality of piezoelectric elements after amplification in a specific area of a diaphragm.SOLUTION: A SoT module 100 includes: a plurality of plate-like piezoelectric elements 111-114 for generating a vibration by application of an AD voltage; and a first diaphragm 130 to which a vibration of the piezoelectric elements 111-114 is transmitted. The vibration of the piezoelectric elements 111-114 is amplified in a specific area of the first diaphragm 130.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an SoT module having a piezoelectric element formed on a rectangular flat plate. [Background technology]

[0002] In the field of acoustics, dynamic speakers using coils are generally used. Dynamic speakers can generate sufficient sound pressure even in the low frequency range, but their weight and volume are large, and their power consumption is high, limiting their applications. On the other hand, the application of piezoelectric speakers using piezoelectric elements is progressing (see Patent Document 1, for example). Piezoelectric speakers are not bulky, are light in weight, and consume little power, so they can be used in applications where it is difficult to apply dynamic speakers.

[0003] The acoustic generator described in Patent Document 1 has two bent piezoelectric elements superimposed with their longitudinal directions perpendicular to each other. An elastic support is provided at the end or center of the longitudinal direction of the piezoelectric element, and transmits vibration to a diaphragm. Patent Document 1 also discloses an application of the acoustic generator to a display panel itself functioning as a speaker. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-106029 A Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, various approaches are being considered for applying piezoelectric elements to speakers. However, because the piezoelectric element itself is made of a hard material, it is difficult to obtain sufficient sound pressure in the mid-low range, and the overall sound pressure is often low. If this weakness can be overcome, the application fields of piezoelectric modules will expand. Such piezoelectric modules have completely different possibilities from conventional piezoelectric modules, and should be called SoT (Sound of Things) modules (hereinafter, a piezoelectric module that can improve sound pressure in a specific range will be called an SoT module).

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide an SoT module that can improve sound pressure in a specific frequency band by amplifying and outputting the vibrations of multiple piezoelectric elements in a specific area of ​​the diaphragm. [Means for solving the problem]

[0007] (1) In order to achieve the above object, the present invention employs the following means: That is, the SoT module of the present invention comprises a plurality of flat piezoelectric elements that generate vibrations when an AC voltage is applied thereto, and a first diaphragm to which the vibrations of the piezoelectric elements are transmitted, and is characterized in that the vibrations of the plurality of piezoelectric elements are amplified in a specific region of the first diaphragm.

[0008] (2) Furthermore, in the SoT module described in (1) above, the vibration transmission path from one of the multiple piezoelectric elements to the first diaphragm is different from the vibration transmission path from the other piezoelectric elements to the first diaphragm.

[0009] (3) In the SoT module according to (1) or (2) above, the plurality of piezoelectric elements are arranged so as to overlap with the first diaphragm.

[0010] (4) In the SoT module described in (3) above, the piezoelectric elements are formed in a rectangular shape, and the central axes of the piezoelectric elements are aligned.

[0011] (5) In the SoT module described in (4) above, the plurality of piezoelectric elements are arranged in such a way that the directions along the sides of each rectangle are different.

[0012] (6) In the SoT module described in (4) above, the plurality of piezoelectric elements are arranged in a manner that they have regions that do not overlap with each other.

[0013] (7) Furthermore, in the SoT module described in any one of (1) to (6) above, the phase for driving the one piezoelectric element is different from the phase for driving the other piezoelectric element.

[0014] (8) Furthermore, in the SoT module described in any one of (1) to (7) above, the one piezoelectric element has a portion that is attached to the other piezoelectric element, and none of the attached portions is the center of gravity of a piezoelectric composite formed by connecting the piezoelectric elements.

[0015] (9) Furthermore, in the SoT module described in any one of (1) to (8) above, the one piezoelectric element is connected to the first vibration plate by an elastic body, and the other piezoelectric element is attached to the first vibration plate.

[0016] (10) Furthermore, in the SoT module described in any one of (1) to (9) above, the module further comprises a second vibration plate to which the other piezoelectric element is directly connected, and the second vibration plate is connected to the one piezoelectric element by an elastic body.

[0017] (11) Furthermore, in the SoT module described in (10) above, the one piezoelectric element is attached to the first vibration plate, and the other piezoelectric element is attached to the second vibration plate.

[0018] (12) In the SoT module described in (10) or (11) above, the second diaphragm is connected to the first diaphragm by an elastic body.

[0019] (13) Furthermore, the SoT module described in any one of (10) to (12) above is characterized in that it further comprises a cover plate provided on the opposite side of the first diaphragm with respect to the second diaphragm.

[0020] (14) Furthermore, the SoT module according to any one of (1) to (13) above is characterized in that it is used in one of the displays of a television, a tablet, a smartphone, or an automobile navigation system. [Brief description of the drawings]

[0021] [Figure 1] 1A to 1C are a plan view and a cross-sectional view showing an SoT module, and a schematic diagram showing a vibration area of ​​a diaphragm, respectively. [Diagram 2] 4A to 4C are cross-sectional views showing an example of the configuration and operation of a piezoelectric element. [Diagram 3] 1A and 1B are a plan view and a cross-sectional view, respectively, showing an SoT module in which an elastic body is provided between a piezoelectric element and a diaphragm. [Figure 4] 1A and 1B are a plan view and a cross-sectional view, respectively, showing an SoT module in which piezoelectric elements are connected by an elastic body. [Diagram 5] 1A and 1B are a plan view and a cross-sectional view, respectively, showing an SoT module having a circular plate-shaped elastic body. [Figure 6] 1A and 1B are a plan view and a cross-sectional view, respectively, showing an SoT module in which weights are attached to each piezoelectric element. [Figure 7] 1A to 1C are a perspective view and an exploded perspective view showing a fully attached piezoelectric module and a square supported piezoelectric module, respectively, and a graph showing their sound pressure frequency characteristics. [Figure 8] 13(a) to 13(c) are exploded perspective views showing upper and lower center-connected SoT modules, respectively, and graphs showing the sound pressure-frequency characteristics thereof. [Figure 9] 1A and 1B are exploded perspective views showing a center-connected and center-single-supported SoT module and graphs showing the sound pressure-frequency characteristics thereof, respectively. [Figure 10] 1A and 1B are exploded perspective views of a centrally connected and centrally double-supported SoT module and graphs showing the sound pressure-frequency characteristics thereof, respectively. [Figure 11] 1A and 1B are exploded perspective views showing a centrally connected SoT module with independent attached elements, and graphs showing the sound pressure vs. frequency characteristics thereof, respectively. [Figure 12] 1A and 1B are exploded perspective views showing a center-connected SoT module and a center-connected SoT module with attached elements, respectively, and a graph showing the sound pressure-frequency characteristics thereof. [Figure 13] 13(a) to 13(c) are exploded perspective views showing centrally connected and peripherally connected SoT modules with attached elements, respectively, and graphs showing the frequency characteristics of sound pressure in the cases of in-phase driving and out-of-phase driving. [Figure 14] 1A and 1B are exploded perspective views showing a fully supported and a multi-part supported stacked SoT module, respectively. [Figure 15] 1A and 1B are exploded perspective views showing a stacked SoT module having multiple overlapping parts. [Figure 16] 1A and 1B are exploded perspective views showing a stacked-type SoT module in which a diaphragm is disposed between elements. [Figure 17] 1A and 1B are exploded perspective views showing a superimposed type SoT module in which the reference axes of the elements are shifted, and graphs showing the sound pressure vs. frequency characteristics, respectively. [Figure 18]FIG. 1 is an exploded perspective view showing a stacked SoT module in which the element arrangement is shifted. [Figure 19] 1A and 1B are exploded perspective views showing a stacked-type SoT module in which multiple parts are stacked and the reference axes of the elements are shifted. [Figure 20] 13(a) and 13(b) are exploded perspective views showing a multi-part overlapping SoT module in which a large diaphragm is disposed between elements. [Figure 21] 1A to 1C are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, showing a thin display (using an intermediate plate) incorporating an SoT module. [Figure 22] 1A to 1C are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, showing a thin display (using an intermediate plate) incorporating an SoT module. [Diagram 23] 1A to 1C are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, showing a thin display (using an intermediate plate) incorporating an SoT module. [Figure 24] 1A to 1C are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, showing a thin display (using an intermediate plate) incorporating an SoT module. [Diagram 25] 1A to 1C are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, of a thin display (using a display panel and an intermediate plate) incorporating an SoT module. [Figure 26] 1A to 1C are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, of a thin display (using a display panel and an intermediate plate) incorporating an SoT module. [Figure 27] 1A to 1C are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, of a thin display (using a display panel and an intermediate plate) incorporating an SoT module. [Figure 28] 1A to 1C are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, of a thin display (using a display panel and an intermediate plate) incorporating an SoT module. [Figure 29]1A to 1C are a plan view and a cross-sectional view showing a piezoelectric module having a single piezoelectric element, respectively, and a diagram showing a vibration mode pattern thereof. [Diagram 30] 1A to 1C are a plan view and a cross-sectional view showing a piezoelectric module having piezoelectric elements connected by a single elastic body, and a diagram showing a vibration mode pattern thereof. [Diagram 31] 1A to 1C are plan views showing an SoT module having piezoelectric elements and elastic bodies arranged in a lattice pattern, and diagrams showing its vibration mode patterns. [Diagram 32] 1A to 1C are plan views showing an SoT module having piezoelectric elements and elastic bodies arranged in a circular ring shape, and diagrams showing its vibration mode patterns. [Diagram 33] 1A to 1C are plan views showing an SoT module having piezoelectric elements and elastic bodies arranged in point symmetry, and diagrams showing its vibration mode patterns. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the present invention, in order to improve the sound pressure in a specific frequency band, a single module is constructed by loosely connecting multiple piezoelectric elements with adhesives made of soft materials or elastic bodies so that each piezoelectric element can maintain its vibration band.

[0023] [First embodiment (windmill type)] In this embodiment, the piezoelectric elements are attached directly to the diaphragm in an arrangement with one end of the piezoelectric element gathered in the center like the blades of a windmill. The central longitudinal axes of the piezoelectric elements (so-called reference axes of the elements) do not coincide with each other. Since the piezoelectric elements are attached directly to the diaphragm, the displacement range can be made large, and the large displacement force can amplify the sound pressure in the low frequency range. Note that the reference axis of each element is the central longitudinal axis in the case of a rectangular plate, and is the central axis parallel to each side in the case of a square plate.

[0024] Regardless of whether the vibrator vibrates the vibration surface or the air, from the viewpoint of vibration generation, creating vibration in a circular shape is a highly efficient output method. The piezoelectric elements of this embodiment are preferably attached in a rotationally symmetrical manner so that the displacement force of each area is uniformly distributed. In this form, the piezoelectric elements are not attached in consideration of the surface displacement form, but the displacement of each area can be made different with the same drive, so that a specific sound pressure can be increased.

[0025] <Simple windmill type> (SoT module configuration) 1(a)-(c) are respectively a plan view and a cross-sectional view of the SoT module 100, and a schematic diagram showing the vibration region of the diaphragm 130 (first diaphragm). FIG. 1(b) shows the cross-section 1b shown in FIG. 1(a) (the relationship between the reference numerals of the cross-sections and the numbers of the cross-sections is similar in other figures). The SoT module 100 is composed of piezoelectric elements 111-114 and a diaphragm 130. Each of the piezoelectric elements 111-114 is formed as a bending type rectangular flat plate, and generates bending vibration when an AC voltage is applied.

[0026] The piezoelectric elements 111-114 are not connected to each other, and are arranged facing each other with their longitudinal ends almost in contact with the side faces of the adjacent piezoelectric elements 111-114 (windmill-shaped arrangement). One surface of each of the piezoelectric elements 111-114 is attached to the diaphragm 130. The attachment can be achieved by, for example, bonding using an epoxy-, acrylic-, or urethane-based adhesive, and either soft or hard adhesives can be used (hereinafter, the same applies to both attachments).

[0027] Fig. 1(c) shows each vibration region of the diaphragm 130 when viewed from the same perspective as Fig. 1(a). Region R1 is a region where vibrations from the piezoelectric elements 111-114 are transmitted and the region simply vibrates passively. Region R2 is a region where active vibrations from the piezoelectric elements 111-114 are transmitted. Region R3 is a region where the vibrations of the multiple piezoelectric elements 111-114 are combined and amplified.

[0028] By vibrating each of the piezoelectric elements 111-114 in the same phase or in opposite phase, the vibration is transmitted from each attachment portion to the center of the SoT module 100, and the vibration in the center can be amplified. In this way, the vibration of the multiple piezoelectric elements 111-114 transmitted through different vibration transmission paths can be amplified in a specific area of ​​the diaphragm. As a result, the sound pressure in a frequency band generated by a specific area of ​​the diaphragm can be improved by utilizing the interference between the vibrations transmitted through the different vibration transmission paths. Note that the vibration transmission path refers to a connection structure that indicates through what means the connection is made.

[0029] For example, when the region R3 in Fig. 1(c) vibrates in the low frequency range of 20 to 100 Hz, the sound pressure in that range can be increased. By using such a configuration, it is easy to obtain sufficient sound pressure in the mid-low frequency range, and the SoT module 100 can be applied to various applications. In the windmill-shaped arrangement of the piezoelectric elements 111 to 114, the position close to the symmetrical center of the arrangement is called the center, and the positions away from the symmetrical center are called the periphery.

[0030] (Piezoelectric element) A piezoelectric element is an element that utilizes the inverse piezoelectric effect and vibrates when an AC voltage is applied. Fig. 2 is a cross-sectional view showing an example of the configuration and operation of a piezoelectric element 111. The piezoelectric element 111 shown in Fig. 2 is an example of the configuration of a piezoelectric element used in the present invention, and piezoelectric elements other than the piezoelectric element 111 may have a similar configuration. The piezoelectric element 111 includes piezoelectric bodies 121 and 122, electrodes 123 and 124, and a shim plate 125. The shim plate 125 is made of metal and also functions as an electrode.

[0031] The piezoelectric bodies 121 and 122 are preferably made of a piezoelectric ceramic material. Examples of the piezoelectric material include zirconate titanate (Pb(Ti,Zr)O3, commonly known as PZT) and barium titanate (BaTiO3). Both are ferroelectrics, and PZT is preferable in terms of efficiency, while barium titanate is preferable from the perspective of lead-free. The piezoelectric bodies 121 and 122 may be made of a piezoelectric polymer. Examples of the piezoelectric polymer include polyvinylidene fluoride and its copolymers, polylactic acid, polyvinylidene cyanide, polyurea, and odd-numbered nylon. Thin sheets of materials having a piezoelectric effect can be manufactured as the piezoelectric bodies 121 and 122.

[0032] Piezoelectric body 121 is polarized in the direction from electrode 123 to shim plate 125, and piezoelectric body 122 is polarized in the direction from shim plate 125 to electrode 124. One electrode is connected to electrodes 123 and 124, and the other electrode is connected to shim plate 125. In this configuration, when an AC voltage is applied to piezoelectric bodies 121 and 122 from power source P1, one of them contracts and the other expands in a direction parallel to the surface due to the inverse piezoelectric effect, and they perform flexural vibration by repeating the movements of arrows S1 and S2 shown in FIG.

[0033] The above-mentioned piezoelectric element 111 has a parallel bimorph structure in which the polarization directions of the piezoelectric bodies 121 and 122 are the same, but may have a series bimorph structure in which the polarization directions are different. An insulator may be used for the central shim plate. The piezoelectric element 111 preferably has a bimorph structure, but may have a unimorph structure. The piezoelectric element 111 may also use a piezoelectric laminate instead of a single-plate piezoelectric body. In that case, an external electrode may be used or an electrode may be formed in a via structure. The piezoelectric element 111 may also be an expansion-and-contraction type piezoelectric element formed by laminating a piezoelectric layer and an electrode, and expanding and contracting in the lamination direction. The piezoelectric element 111 is preferably a laminate type, but may be a single plate. Such a piezoelectric element may also be used in other embodiments.

[0034] (diaphragm) The diaphragm 130 is formed in a flat plate shape, and outputs the vibration of the transmitted piezoelectric element as sound. The material of the diaphragm 130 varies depending on the application. For example, a styrene board can be used for the diaphragm 130. Also, an OLED panel can be used as the diaphragm 130 of a TV speaker. A resin board is often used, but a board with increased inelasticity using wood or fiber tissue can also be used.

[0035] The diaphragm 130 vibrates in the thickness direction due to the displacement force transmitted from the piezoelectric elements 111-114, vibrating the air and generating sound waves. The pitch of the sound generated from the diaphragm 130 and the magnitude of the sound pressure vary depending on the frequency of the signal and the strength of the current given to the piezoelectric elements 111-114. In order to generate a large sound pressure, it is effective to improve the vibration efficiency leading to the diaphragm. Such a diaphragm can also be used in other embodiments.

[0036] <Windmill type with elastic body> A structure in which an elastic body is provided in the SoT module may be adopted. Figures 3(a) and (b) are a plan view and a cross-sectional view, respectively, showing an SoT module 100a in which elastic bodies 151, 152 are provided between the piezoelectric elements 111-114 and the diaphragm 130. The SoT module 100a is composed of the piezoelectric elements 111-114, the diaphragm 130, and the elastic bodies 151, 152. The SoT module 100a is configured similarly to the SoT module 100, except that the SoT module 100a is connected to the diaphragm 130 by the elastic bodies 151, 152 on both sides in the longitudinal direction.

[0037] In the SoT module 100a, an elastic body 151 is attached to one side of the longitudinal direction of each of the piezoelectric elements 111-114 (the central side of the SoT module 100). Then, an elastic body 152 is attached to the other side of the longitudinal direction of each of the piezoelectric elements 111-114 (the peripheral side of the SoT module 100). The elastic bodies 151, 152 are also attached to the diaphragm 130, and connect the piezoelectric elements 111-114 and the diaphragm 130. This makes it possible to further amplify the sound pressure in the low frequency range, for example.

[0038] (Elastic body) The elastic bodies 151 and 152 are made of a soft material such as urethane, and support the vibrator on one side and transmit the vibration to the other side. In the example shown in FIG. 3, one side of the elastic bodies 151 and 152 is attached to the main surfaces of the piezoelectric elements 111-114, and the other side is attached to the main surface of the vibration plate 130. The attachment can be performed by adhesion using, for example, an epoxy-based, acrylic-based, or urethane-based adhesive. The displacement of the piezoelectric elements 111-114 is transmitted to the vibration plate 130 by the elastic bodies 151 and 152, and the vibration of the center part of the SoT module 100b is amplified. The amplified vibration is output as sound by the vibration plate 130.

[0039] The elastic bodies 151 and 152 are preferably made of a resin such as urethane. For example, a material having an elastic modulus of 70 MPa or more and 690 MPa or less can be used for the elastic bodies 151 and 152. This makes it easier to amplify vibrations in the low-frequency range.

[0040] The elastic bodies 151 and 152 are preferably formed in a disk shape. They may be formed in a rectangular shape. It is preferable that the elastic bodies 151 and 152 control the frequency to be amplified by the size and material. Such elastic bodies can be used in other embodiments.

[0041] <Windmill type connected with elastic body> 4(a) and (b) are a plan view and a cross-sectional view, respectively, showing an SoT module 100b in which piezoelectric elements 111-114 are connected by an elastic body 153. The SoT module 100b is composed of piezoelectric elements 111-114, a diaphragm 130, and an elastic body 153. The SoT module 100b is configured similarly to the SoT module 100a, except that the piezoelectric elements 111-114 are connected by the elastic body 153 at the center.

[0042] In the SoT module 100b, the piezoelectric elements 111-114 are connected via an elastic body 153 in a central region (region R3) where vibrations are amplified by the piezoelectric elements 111-114. The configuration of the elastic body 152 provided on the peripheral side of each of the piezoelectric elements 111-114 is the same as that of the SoT module 100a. Vibrations of a predetermined frequency are further amplified depending on the material of the elastic body 153, etc. For example, by using an elastic body 153 made of a soft material, the sound pressure in the low frequency range can be emphasized.

[0043] <Windmill type with annular elastic body> 5(a) and (b) are a plan view and a cross-sectional view, respectively, showing an SoT module having a circular plate-shaped elastic body. The SoT module 100c is composed of piezoelectric elements 111-114, a vibration plate 130, and elastic bodies 153 and 155. The SoT module 100c is composed similarly to the SoT module 100b, except that a circular plate-shaped elastic body 155 is attached in place of the elastic body 152 on the peripheral side of the piezoelectric elements 111-114.

[0044] With the above configuration, in the SoT module 100c, the piezoelectric elements 111-114 are connected at the center by a disk-shaped elastic body 153, and are connected at the periphery by an annular plate-shaped elastic body 155. This allows the SoT module 100c to have a centrally symmetrical shape, and it is possible to create vibration loops and nodes alternately from the center of the diaphragm 130 to the periphery. As a result, it is possible to further amplify the vibration of low frequencies.

[0045] <Windmill type with weights attached to each piezoelectric element> 6(a) and 6(b) are a plan view and a cross-sectional view, respectively, showing an SoT module 100d in which weights are attached to each piezoelectric element. The SoT module 100d is composed of piezoelectric elements 111-114, a diaphragm 130, and weights 141-144. The SoT module 100d is configured similarly to the SoT module 100, except that weights 141-144 are independently attached to the ends of the piezoelectric elements 111-114.

[0046] Since the piezoelectric elements 111-114 are arranged in a windmill shape, the area where each of the weights 141-144 is attached to each of the piezoelectric elements 111-114 corresponds to the peripheral area (area R2) of the SoT module 100d. As a result, the weights 141-144 can amplify the vibration specific to this area.

[0047] The weight may be formed by connecting the piezoelectric elements 111 to 114. In this case, various shapes are possible, but a plate shape is preferable from the viewpoint of vibration control, and a disk or annular plate is more preferable from the viewpoint of symmetry. If the shape is a disk, the diameter can be easily adjusted according to the frequency to be amplified, and the element is easy to handle.

[0048] [Second embodiment (center connection type)] The windmill-type SoT module described above has a trade-off relationship in that it can greatly amplify low-frequency sound pressure, but reduces mid- and high-frequency sound pressure. The center-connected SoT module of this embodiment has a structure that amplifies displacement, while minimizing the above trade-off and improving the level difference of peak-dip sound pressure.

[0049] <Simple form as premise> 7(a) to (c) are a perspective view and an exploded perspective view of the fully attached and square supported piezoelectric modules 200 and 200a, respectively, and a graph showing their sound pressure frequency characteristics.

[0050] 7(a), the piezoelectric module 200 is composed of a piezoelectric element 210 and a diaphragm 130. The piezoelectric element 210 is formed in a square plate shape, and one of its main surfaces is entirely attached to the diaphragm 130. When an AC voltage is applied to the piezoelectric module 200, the generated vibration is directly transmitted to the diaphragm 130 and output as sound. In this case, the diaphragm 130 has an area where the active vibration of the piezoelectric element 210 is transmitted and an area where the vibration is passively transmitted.

[0051] As shown in FIG. 7(b), the piezoelectric module 200a is composed of a piezoelectric element 211, a vibration plate 130, and elastic bodies 251-254. The piezoelectric element 211 is formed in a square plate shape, and is connected to the vibration plate 130 by elastic bodies 251-254 attached to its four corners. The multiple elastic bodies 251-254 are formed in a square plate shape, and support the lower surface of the piezoelectric element 211 parallel to the surface of the vibration plate 130. The multiple elastic bodies described below basically support the lower surface of the piezoelectric element parallel to the surface of the vibration plate. The multiple elastic bodies 251-254 are formed in a square plate shape, but the shape is not necessarily limited to a square, and may be a polygon or a circle. The same applies to the shapes of the multiple elastic bodies in other embodiments.

[0052] When an AC voltage is applied to the piezoelectric module 200a, the generated vibration is transmitted to the diaphragm 130 via the elastic bodies 251-254 and output as sound. In this case, there are four different vibration transmission paths via the four elastic bodies 251-254, and the vibrations transmitted through each path can be amplified in the center.

[0053] Curve P200 on the graph shown in Fig. 7(c) indicates the frequency characteristic of the sound pressure due to the piezoelectric module 200. Curve P200a indicates the frequency characteristic of the sound pressure due to the piezoelectric module 200a. The correspondence between the signs of these curves and the signs of the piezoelectric modules is the same in the figures described below. Comparing the two, the sound pressure of the piezoelectric module 200a is greater than that of the piezoelectric module 200 in the mid-range, and the sound pressure of the piezoelectric module 200a is less than that of the piezoelectric module 200 in the treble range.

[0054] <Simple center-linked type> 8(a)-(c) are exploded perspective views showing upper and lower centrally connected SoT modules 300a and 300b, respectively, and graphs showing the frequency characteristics of the sound pressure. The exploded perspective view is a representation in which what is originally connected is disassembled in order to easily show the shape and connection structure of each part, and each part is actually connected at a position along the dashed line in this representation. The SoT module 300a shown in FIG. 8(a) includes piezoelectric elements 311-314, 315, a vibration plate 130, and elastic bodies 351-354. Note that the part where the piezoelectric elements are attached to each other does not become the center of gravity of the piezoelectric composite formed by connecting the piezoelectric elements. As a result of such a configuration, a free vibration property with a high degree of freedom can be maintained except for the attached part, and the vibration is amplified and the force transmitted to the vibration plate is increased. Such an action is also generated in the similar configuration of the following embodiments.

[0055] The four piezoelectric elements 311-314 are each formed into a rectangular flat plate, and are arranged such that one end of each element faces each other at a distance in the center of the SoT module 300a. Elastic bodies 351-354 are attached to the lower surfaces of the other ends of the four piezoelectric elements 311-314. Meanwhile, the elastic bodies 351-354 are attached to the vibration plate 130 and support the piezoelectric elements 311-314.

[0056] In the center of the SoT module 300a, a single square flat piezoelectric element 315 is attached to the underside of the ends of the four piezoelectric elements 311-314 at positions along each side. In this case, "under" refers to the vibration plate 130 side as seen from the piezoelectric element 315. In this way, in the central region of the SoT module 300a, the piezoelectric elements 311-314 and the piezoelectric element 315 are connected to form a piezoelectric composite 310a. An AC voltage can be applied to the four peripheral piezoelectric elements 311-314 and the central piezoelectric element 315 in the same phase or in opposite phase.

[0057] The vibration generated in piezoelectric composite 310a is transmitted to diaphragm 130 via elastic bodies 351-354 and is output as sound. The vibration generated in the four peripheral piezoelectric elements 311-314 is transmitted to diaphragm 130 via elastic bodies 351-354, and the vibration generated in central piezoelectric element 315 is transmitted to diaphragm 130 via the four peripheral piezoelectric elements 311-314 and elastic bodies 351-354. In this way, the center-connected SoT module can amplify the vibration of a specific region of diaphragm 130 through different vibration transmission paths.

[0058] 8(b) includes piezoelectric elements 311-314, 316, a vibration plate 130, and elastic bodies 351-354. The SoT module 300b is configured similarly to the SoT module 300a, except that a single square, flat-plate-shaped piezoelectric element 316 is attached to the upper sides of the ends of the four piezoelectric elements 311-314 at positions along each side of the elements.

[0059] In this case, since the piezoelectric element 316 is provided above the piezoelectric elements 311-314, it is easy to utilize the space generated between the piezoelectric element 316 and the diaphragm 130. The piezoelectric elements 311-314 and the piezoelectric element 315 form a piezoelectric composite 310b. An AC voltage can be applied to the four peripheral piezoelectric elements 311-314 and the central piezoelectric element 316 in the same phase or in opposite phase. The generated vibration of the piezoelectric composite 310b is transmitted to the diaphragm 130 via the elastic bodies 351-354 and is output as sound.

[0060] 8(c) shows the frequency characteristics of the sound pressure of the SoT module 300b. In the mid-range, the sound pressure of the SoT module 300b is greater than that of the piezoelectric modules 200 and 200a. In the low-range, the sound pressure of the SoT module 300b is equivalent to that of the piezoelectric modules 200 and 200a.

[0061] <Central connection type and central single support> 9(a) and (b) are an exploded perspective view and a graph showing the sound pressure vs. frequency characteristics of a center-connected, center-single-supported SoT module 300c, respectively. The SoT module 300c includes piezoelectric elements 311-314, 316, a diaphragm 130, and elastic bodies 351-354, 355. The SoT module 300c is configured similarly to the SoT module 300b, except that the central square, flat-plate-shaped piezoelectric element 316 is supported by an elastic body 355.

[0062] In the SoT module 300c, an elastic body 355 is attached at its upper end surface to the center of the lower surface of the piezoelectric element 316. The elastic body 355 is formed in a rectangular column shape with the longitudinal direction perpendicular to the lower surface of the piezoelectric element 316, and its lower end surface is attached to the vibration plate 130 to support the piezoelectric element 316. The elastic body 355 has a thickness that keeps the lower surface of the piezoelectric element 316 connected on the piezoelectric elements 311 to 314 parallel to the surface of the vibration plate 130. In this way, in the central region of the SoT module 300c, the piezoelectric elements 311 to 314 and the piezoelectric element 316 are connected to each other to form a piezoelectric composite 310b. The piezoelectric element 316 transmits vibrations through a path via the piezoelectric elements 311 to 314. On the other hand, the piezoelectric element 316 is connected to the vibration plate 130 through the elastic body 355, and transmits vibrations to the vibration plate 130 through this path as well.

[0063] Vibrations of piezoelectric composite 310b caused by applying AC voltages in the same phase or in opposite phase to four piezoelectric elements 311-314 and piezoelectric element 316 are transmitted to diaphragm 130 via elastic bodies 351-354 and 355. In this manner, vibrations are transmitted through different types of vibration transmission paths.

[0064] 9(b) shows the frequency characteristics of the sound pressure of the SoT module 300c. In the low frequency range, the sound pressure of the SoT module 300c is greater than the sound pressure of the piezoelectric modules 200 and 200a, although it does not reach the sound pressure of the SoT module 300b.

[0065] <Central connection type with central double support> 10(a) and (b) are an exploded perspective view and a graph showing the sound pressure vs. frequency characteristics of a centrally connected and centrally supported SoT module 300d, respectively. The SoT module 300d includes piezoelectric elements 311-314, 316, a diaphragm 130, and elastic bodies 351-354, 356-359. The SoT module 300c is configured similarly to the SoT module 300c, except that the central square, flat-plate-shaped piezoelectric element 311 is supported by multiple elastic bodies 356-359.

[0066] In the SoT module 300d, multiple elastic bodies 356-359 have their upper surfaces attached to the lower surface of the piezoelectric element 316. Each of the multiple elastic bodies 356-359 is formed in a rectangular column shape with its longitudinal direction parallel to each side of the piezoelectric element 316. The multiple elastic bodies 356-359 have their lower surfaces attached to the vibration plate 130, and support the central piezoelectric element 316 at multiple positions.

[0067] In the central region of the SoT module 300d, the piezoelectric elements 311-314 and the piezoelectric element 316 are connected to each other to form a piezoelectric composite 310b. The piezoelectric element 316 transmits vibrations through a path that goes through the piezoelectric elements 311-314. On the other hand, the piezoelectric element 316 is connected to the diaphragm 130 through the elastic bodies 356-359, and transmits vibrations to the diaphragm 130 through this path as well. The vibrations of the piezoelectric composite 310b generated by applying AC voltages in the same phase or opposite phase to the four piezoelectric elements 311-314 and the piezoelectric element 316 are transmitted to the diaphragm 130 through the elastic bodies 351-354 and 355. In this way, the vibrations are transmitted through different types of vibration transmission paths.

[0068] 10(b), a curve P300d on the graph shows the frequency characteristics of the sound pressure of the SoT module 300d. In the low frequency range, the sound pressure of the SoT module 300d is greater than that of the piezoelectric module 200, although it does not reach that of the SoT module 300b.

[0069] <Central connection type with independent adhesive element> 11(a) and (b) are an exploded perspective view and a graph showing the sound pressure vs. frequency characteristics of a centrally-connected SoT module 300e having independent attached elements. The SoT module 300e includes piezoelectric elements 311-314, 316, and 318, a diaphragm 130, and elastic bodies 351-354.

[0070] SoT module 300e is configured similarly to SoT module 300b, except that in the center, square, flat-plate-shaped piezoelectric element 318 is attached to diaphragm 130. In the central region where piezoelectric element 318 is independently attached to diaphragm 130, diaphragm 130 can be vibrated in a frequency band different from the vibrations in the surrounding regions.

[0071] In SoT module 300e, vibrations in the center or periphery can be amplified by applying an AC voltage in the same phase or in opposite phase to any combination of four piezoelectric elements 311-314 and piezoelectric elements 316 and 318. The vibrations of piezoelectric composite 310b are transmitted to diaphragm 130 via elastic bodies 351-354, and the vibrations of piezoelectric element 318 are transmitted directly to the center of diaphragm 130. Vibrations transmitted via these different vibration transmission paths enable SoT module 300e to amplify vibrations in the center.

[0072] The curve P300e on the graph shown in Fig. 11(b) shows the frequency characteristics of the sound pressure of the SoT module 300e. In the low frequency range, the sound pressure of the SoT module 300e is greater than that of the piezoelectric modules 200 and 200a and is equivalent to that of the SoT module 300b. In the high frequency range, the sound pressure of the SoT module 300e is greater than that of the SoT module 300b.

[0073] <Central connection type and centrally connected adhesive element available> 12(a) and (b) are an exploded perspective view and a graph showing the frequency characteristics of sound pressure of a center-connected SoT module 300f having a center-connected attached element, respectively. The SoT module 300f includes piezoelectric elements 311-314, 316, and 318, a diaphragm 130, and elastic bodies 351-354 and 355f. The SoT module 300f is configured similarly to the SoT module 300e, except that the piezoelectric element 318 attached to the diaphragm 130 at the center is connected to the piezoelectric element 316 via the elastic body 355f.

[0074] In the SoT module 300f, the vibration in the center or the periphery can be amplified by applying an AC voltage in the same phase or in the opposite phase to any combination of the four piezoelectric elements 311-314 and the piezoelectric elements 316 and 318. The vibration of the piezoelectric composite 310b is transmitted to the diaphragm 130 via the elastic bodies 351-354, and is also transmitted to the center of the diaphragm 130 via the elastic body 355f and the piezoelectric element 318. The vibration of the piezoelectric element 318 is also transmitted directly to the center of the diaphragm 130. The vibration transmitted through these different vibration transmission paths allows the SoT module 300f to amplify the vibration in the center.

[0075] 12(b), a curve P300f indicates the frequency characteristics of the sound pressure of the SoT module 300f. In the low frequency range, the sound pressure of the SoT module 300f is greater than the sound pressure of the piezoelectric modules 200 and 200a, although it does not reach the sound pressure of the SoT module 300b.

[0076] <Available with both center-linked and peripheral-linked adhesive elements> 13(a)-(c) are exploded perspective views showing a centrally connected and peripherally connected SoT module 300g with attached elements, and graphs showing the frequency characteristics of sound pressure in the cases of in-phase driving and out-of-phase driving. SoT module 300g includes piezoelectric elements 311-314, 316, and 318, diaphragm 130, and elastic bodies 351-354, and 356g-359g. SoT module 300g is configured similarly to SoT module 300e, except that piezoelectric element 318 attached to diaphragm 130 at the center is connected to piezoelectric element 316 via elastic bodies 356g-359g.

[0077] Elastic bodies 356g-359g are formed in a rectangular column shape, and their bottom end surfaces are attached to the four corner positions of square plate-shaped piezoelectric element 318. On the other hand, elastic bodies 356g-359g have their top end surfaces attached to the lower surface of piezoelectric element 316. Vibrations of piezoelectric composite 310b are transmitted to piezoelectric element 318 via elastic bodies 356g-359g. This makes it possible to amplify vibrations in a specific region of SoT module 300g.

[0078] In the SoT module 300g, the vibration in the center or the periphery can be amplified by applying an AC voltage in the same phase or in the opposite phase to any combination of the four piezoelectric elements 311-314 and the piezoelectric elements 316 and 318. The vibration of the piezoelectric composite 310b is transmitted to the diaphragm 130 via the elastic bodies 351-354, and is also transmitted to the center of the diaphragm 130 via the elastic bodies 356g-359g and the piezoelectric element 318. The vibration of the piezoelectric element 318 is also transmitted directly to the center of the diaphragm 130. The vibration transmitted through these different vibration transmission paths allows the SoT module 300f to amplify the vibration in the center.

[0079] 13(b), curve P300g-1 shows the frequency characteristics of sound pressure when the SoT module 300g is driven in phase. In the low frequency range, the sound pressure of the SoT module 300g when driven in phase is greater than that of the piezoelectric modules 200 and 200a, although it does not reach that of the SoT modules 300b and 300e.

[0080] The curve P300g-2 in the graph shown in Fig. 13(c) shows the frequency characteristics of the sound pressure when the SoT module 300g is driven in opposite phase. In the low frequency range, the sound pressure of the SoT module 300g when driven in opposite phase is equivalent to the sound pressure of the SoT module 300g when driven in in phase. In the high frequency range, the sound pressure of the SoT module 300g when driven in opposite phase is greater than the sound pressure of the SoT module 300g when driven in in phase.

[0081] In the above measurements, in-phase driving refers to the phases of the voltages applied to piezoelectric composite 310b and piezoelectric element 318 being the same, and out-of-phase driving refers to the phases of the voltages applied to piezoelectric composite 310b and piezoelectric element 318 being opposite.

[0082] [Third embodiment (superimposed type)] If a thin piezoelectric element is used in a structure that amplifies low-frequency sound pressure as in the first embodiment, the element may be overloaded and cracked depending on the amount of displacement. In this embodiment, the strength of the module is improved by using an overlapping structure, while the sound pressure can be improved by adopting a partial connection or rotationally symmetric structure. Note that overlapping refers to stacking elements in the direction of the central axis of the main surface, regardless of whether they overlap partially. Note that the central axis of the main surface refers to the axis perpendicular to the main surface at the center of the main surface.

[0083] <Overlap type with full support and multiple part support> 14(a) and (b) are exploded perspective views showing fully supported and partially supported stacked SoT modules 400 and 400a, respectively. The SoT module 400 shown in FIG. 14(a) is composed of piezoelectric elements 410 and 411, a vibration plate 130, and an elastic body 450. The piezoelectric elements 410 and 411 are both formed in a square plate shape and are stacked on the vibration plate 130. This arrangement is also called an array, which improves the strength of the module.

[0084] Piezoelectric element 410 is directly attached to vibration plate 130. Square flat elastic body 450 is attached to piezoelectric element 410, and piezoelectric element 411 is further attached to elastic body 450. Piezoelectric element 410, elastic body 450, and piezoelectric element 411 all have the same shape and are attached to the entire surface. Elastic body 450 supports piezoelectric element 411 over the entire surface, and transmits the vibrations of the piezoelectric elements to vibration plate 130 by connecting the piezoelectric elements. With this structure, the force of some parts of piezoelectric element 410 attached to vibration plate 130 becomes strong, and the force of other parts becomes weak. In this case, the force transmitted through vibration plate 130, which serves as the surface that receives the vibrations, differs for each area.

[0085] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 410 and 411, the vibration of the piezoelectric element 411 is transmitted to the piezoelectric element 410 via the elastic body 450, and the vibration of the piezoelectric element 410 is transmitted directly to the diaphragm 130. In this way, the vibration of a plurality of completely overlapping piezoelectric elements can be transmitted through different vibration transmission paths, and the vibration of a specific region of the diaphragm 130 can be amplified. Note that overlap refers to the overlapping of the projections of the main surfaces in the direction of the central axis.

[0086] The SoT module 400a shown in FIG. 14(b) is composed of piezoelectric elements 410 and 411, a vibration plate 130, and an elastic body 451. The SoT module 400a is composed similarly to the SoT module 400, except that the piezoelectric elements are connected by multiple elastic bodies 451, not a single one. The multiple elastic bodies 451 are each formed in a square plate shape, and are arranged symmetrically on the piezoelectric element 410. The multiple elastic bodies 451 are attached to the piezoelectric element 410 at their lower surfaces, and are attached to the piezoelectric element 411 at their upper surfaces. Due to such connections, the multiple elastic bodies 451 support the piezoelectric element 411 at multiple portions.

[0087] The example of the multiple elastic bodies 451 shown in FIG. 14(b) has a shape obtained by dividing a square flat plate into nine parts. It is preferable that the multiple elastic bodies 451 have a shape obtained by symmetrically dividing a square flat plate, regardless of the number of divisions. The multiple elastic bodies 451 are arranged at the vertices of the square and the midpoints of the line segments connecting the vertices, and the main surfaces of the multiple elastic bodies 451 are parallel to the main surfaces of the piezoelectric elements 410 and 411 as the main surface of the arrangement formed by the group, and their central axes coincide with each other. The reference axis of the multiple elastic bodies 451 is the central axis in a direction parallel to the side of the square specified by the arrangement of the group. The main surfaces, central axes of the main surfaces, and reference axes of the multiple elastic bodies can be specified in the same manner in other embodiments.

[0088] By applying AC voltages in the same phase or in opposite phase to the piezoelectric elements 410 and 411, the vibration of the piezoelectric element 411 is transmitted to the piezoelectric element 410 via the multiple elastic bodies 451. Also, the vibration of the piezoelectric element 410 is transmitted directly to the diaphragm 130. This makes it possible to amplify the vibration of a specific region of the diaphragm 130.

[0089] <Multiple parts overlapping type> 15(a) and (b) are exploded perspective views showing overlapping-type SoT modules 400b and 400c in which multiple portions overlap. The SoT module 400b shown in FIG. 15(a) is composed of piezoelectric elements 410 and 412, a vibration plate 130, and an elastic body 451. The SoT module 400b is composed similarly to the SoT module 400a, except that the multiple piezoelectric elements 412 are connected to the piezoelectric element 410 by the multiple elastic bodies 451.

[0090] 15(a), nine piezoelectric elements 412 are each formed in a square plate shape, are arranged symmetrically like the nine elastic bodies 451, and are connected to the piezoelectric element 410. The piezoelectric elements 412 and the elastic bodies 451 are preferably formed in a square plate shape, but may be in other shapes such as a disk shape.

[0091] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 410 and 412, the vibration of each of the multiple piezoelectric elements 412 can be transmitted to the piezoelectric element 410 via the corresponding elastic body 451. Meanwhile, the vibration of the piezoelectric element 410 can be transmitted to the diaphragm 130. This makes it possible to amplify the vibration of a specific region of the diaphragm 130. It is possible to transmit the vibration of the multiple piezoelectric elements 412 and the piezoelectric element 410 through multiple different vibration transmission paths and amplify it in a specific region of the diaphragm 130.

[0092] 15(b) is composed of piezoelectric elements 410, 413, a vibration plate 130, and an elastic body 452. The SoT module 400c is composed similarly to the SoT module 400b, except that five piezoelectric elements 413 are connected to the piezoelectric element 410 by five elastic bodies 452. The five piezoelectric elements 413 are each formed in a square plate shape, and are arranged symmetrically like the five elastic bodies 452. The five piezoelectric elements 413 are each connected to the piezoelectric element 410 via the elastic body 452.

[0093] By applying an AC voltage in the same phase or in opposite phase to any combination of piezoelectric elements 410 and 413, the vibration of each of the multiple piezoelectric elements 413 can be transmitted to the piezoelectric element 410 via the corresponding elastic body 452. Meanwhile, the vibration of the piezoelectric element 410 can be transmitted to the diaphragm 130. This makes it possible to amplify the vibration in a specific region of the diaphragm 130. Depending on the number of piezoelectric elements and elastic bodies, it is possible to transmit the vibration from the multiple piezoelectric elements 413 through multiple different vibration transmission paths and amplify it in a specific region of the diaphragm 130.

[0094] <Stacked type with diaphragms placed between elements> 16(a) and (b) are exploded perspective views showing stacked SoT modules 400d and 400e in which a diaphragm is disposed between elements. The SoT module 400d shown in FIG. 16(a) is composed of piezoelectric elements 410 and 414, diaphragms 130 and 430, and an elastic body 451. The SoT module 400d is configured similarly to the SoT module 400a, except that an intermediate diaphragm 430 (second diaphragm) is provided between the piezoelectric element 414 and the elastic body 451.

[0095] The second diaphragm may be a stainless steel strength-reinforcing plate. The second diaphragm is provided basically for the purpose of reinforcing the strength, and if the piezoelectric element attached thereon is originally hard, there is little need to provide the second diaphragm. One piezoelectric element 414 is attached onto the middle diaphragm 430. The piezoelectric element 414 attached to the diaphragm 430 may be a thin film-type element. Meanwhile, a plurality of elastic bodies 451 are attached to the lower surface of the middle diaphragm 430.

[0096] By applying AC voltages in the same phase or in opposite phase to the piezoelectric elements 410 and 414, the vibration of the piezoelectric element 414 is transmitted to the diaphragm 430, and the vibration is further transmitted to the diaphragm 130 via the multiple elastic bodies 451. Meanwhile, the vibration of the piezoelectric element 410 is transmitted to the diaphragm 130. This makes it possible to amplify the vibration of a specific region of the diaphragm 130. In this case, multiple different vibration transmission paths exist via the multiple elastic bodies 451.

[0097] 16(b) is composed of piezoelectric elements 410, 415, diaphragms 130, 430, and an elastic body 451. The SoT module 400e is configured similarly to the SoT module 400a, except that a plurality of piezoelectric elements 415 are provided on the middle diaphragm 430. In the SoT module 400e, five square flat-plate-shaped piezoelectric elements 415 are symmetrically arranged and attached to the middle diaphragm 430.

[0098] By applying AC voltages in the same phase or in opposite phase to the piezoelectric elements 410 and 415, the vibration of the piezoelectric element 415 is transmitted to the diaphragm 430, and the vibration is further transmitted to the diaphragm 130 via the multiple elastic bodies 451. Meanwhile, the vibration of the piezoelectric element 410 is transmitted to the diaphragm 130. This makes it possible to amplify the vibration of a specific region of the diaphragm 130. In this case as well, multiple different vibration transmission paths exist via the multiple elastic bodies 451.

[0099] <Superposition type with the reference axis of the element shifted> 17(a) and (b) are an exploded perspective view showing a stacked-type SoT module 400f in which the reference axes of the elements are shifted, and a graph showing the frequency characteristics of the sound pressure. The SoT module 400f is composed of piezoelectric elements 410 and 416, diaphragms 130 and 431, and elastic bodies 453 and 454. The SoT module 400f is configured similarly to the SoT module 400a, except that the reference axes of the piezoelectric element 416, the intermediate diaphragm 431, and the multiple elastic bodies 453 and 454 are shifted from the reference axis of the piezoelectric element 410.

[0100] In the SoT module 400f, the piezoelectric element 416, the diaphragm 431 (second diaphragm), the elastic bodies 453 and 454, and the piezoelectric element 410 are attached in an overlapping manner with the central axes of the main surfaces aligned. This arrangement makes it easier to amplify the vibration.

[0101] However, the reference axis of the piezoelectric element 416 and the vibration plate 431 formed in a square plate shape is shifted by 45° from the reference axis of the piezoelectric element 410 formed in a square plate shape. That is, the piezoelectric elements 410 and 416 are arranged in an arrangement with a region where they do not overlap each other. The vibration plate 431 and the piezoelectric element 410 are connected in the overlapping region by an elastic body 453. The vibration plate 431 is connected to the vibration plate 130 via an elastic body 454 in the region where it does not overlap with the piezoelectric element 410. The thickness of the elastic body 454 is larger than the thickness of the elastic body 453, and the lower surface of the piezoelectric element 410 is maintained parallel to the surface of the vibration plate. Such shape adjustment is also performed for the elastic bodies of the other embodiments.

[0102] Each of the elastic bodies 453, 454 is formed in a square plate shape, but the shape is not limited to a square and may be a polygon or a circle. Since the reference axes of the overlapping piezoelectric element 410 and the piezoelectric element 416 are different from each other in this way, the vibration transmission paths are different, and the sound pressure characteristics are improved and the peak-dip is also improved.

[0103] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 410 and 412, the vibration of the piezoelectric element 416 and the diaphragm 431 can be transmitted to the diaphragm 130 via the elastic bodies 453 and 454. Also, the vibration of the piezoelectric element 410 can be transmitted directly to the diaphragm 130. Since the piezoelectric elements are superimposed with their positions shifted, the vibration of the diaphragm 431 is transmitted to the diaphragm 130 by a vibration transmission path via the elastic body 453 and a vibration transmission path via the elastic body 454. In this way, different vibration transmission paths are formed in the overlapping and non-overlapping regions, and a specific region in which the vibration is amplified can be created.

[0104] 17(b), curve P400f indicates the frequency characteristics of the sound pressure of the SoT module 400f. The sound pressure of the SoT module 400f exceeds the sound pressure of the SoT modules 300b and 300e in the low frequency range, and is approximately the same as the sound pressure of the piezoelectric module 200 in the high frequency range.

[0105] 18 is an exploded perspective view showing a superimposed type SoT module in which the element arrangement is shifted. The SoT module 400g is composed of piezoelectric elements 417, 418, diaphragms 130, 432, and elastic bodies 455, 456. The SoT module 400g is common to the SoT module 400f in that the reference axes of the piezoelectric element 418, the intermediate diaphragm 432 (second diaphragm), and the multiple elastic bodies 455, 456 are shifted from the reference axis of the piezoelectric element 417. In addition, the order of arrangement in the superimposed direction, etc. are also common.

[0106] In the SoT module 400g, the piezoelectric element 418, the vibration plate 433, the multiple elastic bodies 455 and 456, and the piezoelectric element 417 are attached in a superimposed manner with the central axes of their main surfaces aligned. However, what is different is that the reference axes of the piezoelectric element 418, the vibration plate 433, and the multiple elastic bodies 455 and 456, all of which are formed or arranged in a rectangular plate shape, are shifted by 90° from the reference axis of the piezoelectric element 417, which is formed in a rectangular plate shape.

[0107] The overlapping region of vibration plate 432 and piezoelectric element 417 is connected by elastic body 455. The region of vibration plate 432 that does not overlap with piezoelectric element 417 is connected to vibration plate 130 via elastic body 454. Each of the multiple elastic bodies 455, 456 is formed in a square plate shape, but the shape of the elastic bodies may be a polygon or a circle.

[0108] By applying an AC voltage in the same phase or in opposite phase to piezoelectric elements 417 and 418, the vibration of piezoelectric element 418 and diaphragm 432 is transmitted to diaphragm 130 via elastic bodies 455 and 456, and the vibration of piezoelectric element 417 is transmitted to diaphragm 130. Since the piezoelectric elements are superimposed with the reference axis shifted, it is possible to create an area on diaphragm 130 that vibrates due to diaphragm 432, an area that vibrates due to piezoelectric element 417, and an area where the vibration is amplified by diaphragm 432 and piezoelectric element 417.

[0109] <Overlapping type with multiple parts overlapping and shifted reference axes of elements> 19(a) and (b) are exploded perspective views showing a superimposed type SoT module 400h in which multiple parts are superimposed and the reference axes of the elements are shifted. The SoT module 400h shown in FIG. 19(a) is composed of piezoelectric elements 410 and 419, vibration plates 130 and 430, and elastic bodies 453 and 454. The SoT module 400h is configured similarly to the SoT module 400f, except that multiple piezoelectric elements 419 are provided on the intermediate vibration plate 430. Nine square flat plate-shaped piezoelectric elements 419 are symmetrically arranged at the vertices of the square and the midpoints of the line segments connecting the vertices, and are attached to the intermediate vibration plate 430. In addition, multiple elastic bodies 453 and 454 are provided at positions corresponding to the multiple piezoelectric elements 419.

[0110] The reference axes of the multiple piezoelectric elements 419, diaphragm 430, and elastic bodies 453 and 454 are shifted by 45° from the reference axis of piezoelectric element 410. Elastic body 453 connects diaphragm 430 and piezoelectric element 410 in their overlapping regions, and elastic body 454 connects diaphragm 430 and diaphragm 130 in a region where diaphragm 430 and piezoelectric element 410 do not overlap.

[0111] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 410 and 419, the vibration of the piezoelectric element 419 is transmitted to the diaphragm 430, and the vibration is further transmitted to the diaphragm 130 via the multiple elastic bodies 453 and 454. The vibration of the piezoelectric element 410 is also transmitted directly to the diaphragm 130. These vibrations can amplify the vibration of a specific region of the diaphragm 130. In this case, multiple different vibration transmission paths exist via the multiple elastic bodies 453 and 454.

[0112] 19(b) is composed of piezoelectric elements 410, 415, vibration plates 130, 430, and elastic bodies 453, 454. The SoT module 400i is composed similarly to the SoT module 400h, except that five piezoelectric elements 415 are provided on the intermediate vibration plate 430. In the SoT module 400i, five square flat plate-shaped piezoelectric elements 415 are arranged symmetrically at the vertices and the center of a square, and are attached to the intermediate vibration plate 430. In addition, a plurality of elastic bodies 453, 454 are provided at positions corresponding to the plurality of piezoelectric elements 415.

[0113] The reference axes of the multiple piezoelectric elements 415, diaphragm 430, and elastic bodies 453 and 454 are shifted by 45° from the reference axis of piezoelectric element 410. Elastic body 453 connects diaphragm 430 and piezoelectric element 410 in their overlapping regions, and elastic body 454 connects diaphragm 430 and diaphragm 130 in a region where diaphragm 430 and piezoelectric element 410 do not overlap.

[0114] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 410 and 415, the vibration of the piezoelectric element 415 is transmitted to the diaphragm 430, and the vibration is further transmitted to the diaphragm 130 via the multiple elastic bodies 453 and 454. The vibration of the piezoelectric element 410 is also transmitted directly to the diaphragm 130. These vibrations can amplify the vibration of a specific region of the diaphragm 130. In this case as well, multiple different vibration transmission paths exist via the multiple elastic bodies 453 and 454.

[0115] <Multiple overlapping types with large diaphragms placed between elements> 20(a) and (b) are exploded perspective views showing overlapping type SoT modules 400j and 400k of multiple overlapping parts in which a large vibration plate is arranged between elements. The SoT module 400j shown in FIG. 20(a) is composed of piezoelectric elements 410 and 415, vibration plates 130 and 435, and elastic bodies 453 and 454. The SoT module 400j is configured similarly to the SoT module 400h, except that the intermediate vibration plate 435 (second vibration plate) is large, and the arrangement of the five piezoelectric elements 415 and the elastic bodies 453 and 454 corresponds to the arrangement of the piezoelectric element 410.

[0116] Specifically, the piezoelectric element 415 and the elastic bodies 453 and 454 are symmetrically arranged at the vertices and center positions of the respective squares, and their reference axes coincide with the reference axis of the piezoelectric element 410 formed in a square plate shape. In addition, the multiple piezoelectric elements 415 are arranged so that their projection onto the vibration plate 130 covers a range wider than the range of the piezoelectric element 410, and the elastic bodies 453 and 454 are also arranged over this range. As a result of such an arrangement, the elastic body 453 connects the vibration plate 435 and the piezoelectric element 410 in their overlapping region, and the elastic body 454 connects the vibration plate 435 and the vibration plate 130 in a region where the vibration plate 435 and the piezoelectric element 410 do not overlap.

[0117] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 410 and 415, the vibration of the piezoelectric element 415 is transmitted to the diaphragm 435, and the vibration is further transmitted to the diaphragm 130 via the multiple elastic bodies 453 and 454. The vibration of the piezoelectric element 410 is also transmitted directly to the diaphragm 130. These vibrations can amplify the vibration of a specific region of the diaphragm 130. In this case, multiple different vibration transmission paths exist via the multiple elastic bodies 453 and 454.

[0118] 20(b) is composed of piezoelectric elements 410, 415, diaphragms 130, 435, and elastic bodies 453, 454. The SoT module 400k is configured similarly to the SoT module 400i, except that the reference axes of the five piezoelectric elements 415 and the elastic bodies 453, 454 are shifted from the reference axis of the piezoelectric element 410.

[0119] Specifically, piezoelectric element 415 and elastic bodies 453, 454 are symmetrically arranged at the vertices and center of a square, and their reference axes are shifted by 45° from the reference axis of piezoelectric element 410. That is, piezoelectric elements 410, 415 are arranged in an arrangement having regions where they do not overlap with each other. Elastic body 453 connects vibration plate 435 and piezoelectric element 410 in their overlapping region, and elastic body 454 connects vibration plate 435 and vibration plate 130 in a region where vibration plate 435 and piezoelectric element 410 do not overlap.

[0120] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 410 and 415, the vibration of the piezoelectric element 415 is transmitted to the diaphragm 435, and the vibration is further transmitted to the diaphragm 130 via the multiple elastic bodies 453 and 454. The vibration of the piezoelectric element 410 is also transmitted directly to the diaphragm 130. These vibrations can amplify the vibration of a specific region of the diaphragm 130. In this case, multiple different vibration transmission paths exist via the multiple elastic bodies 453 and 454.

[0121] [Fourth embodiment (application to a display)] The SoT module can be applied to a thin display with an internal cavity structure. In the thin display, the display panel and the back plate are separated by an intermediate plate, forming a first cavity and a second cavity. There are two types of thin displays with an SoT module: one that uses the intermediate plate as a diaphragm, and one that uses the display panel and the intermediate plate as a diaphragm. In these cases, the back plate can be used as a cover plate to protect the SoT module. The thin display with an SoT module can be applied to televisions, tablets, smartphones, or car navigation systems.

[0122] <Thin display incorporating the SoT module (using an intermediate plate)> FIGS. 21(a) to (c) are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, showing a thin display 800 incorporating the SoT module (using an intermediate plate). The thin display 800 includes a display panel 810, an SoT module 500, and a back plate 820.

[0123] The SoT module 500 is composed of piezoelectric elements 510, 511, an intermediate plate 830, and an elastic body 550. The piezoelectric elements 510, 511 are both formed in a square flat plate shape and are stacked on the intermediate plate 830. The SoT module 500 is configured in the same manner as the SoT module 400 and uses the intermediate plate 830 as a diaphragm (the first diaphragm).

[0124] The piezoelectric element 510 is directly attached to the intermediate plate 830. A square flat plate-shaped elastic body 550 is attached on the piezoelectric element 510, and the piezoelectric element 511 is attached on the elastic body 550. The piezoelectric element 510, the elastic body 550, and the piezoelectric element 511 are all of the same shape and are attached over the entire surface. The elastic body 550 supports the piezoelectric element 511 over the entire surface and transmits their vibrations to the intermediate plate 830 through the connection between the piezoelectric elements.

[0125] By applying an AC voltage to the piezoelectric elements 510, 511 in the same phase or in the opposite phase, the vibration of the piezoelectric element 511 is transmitted to the piezoelectric element 510 through the elastic body 550. Also, the vibration of the piezoelectric element 510 is directly transmitted to the intermediate plate 830. These vibrations can amplify the vibration of a specific region of the intermediate plate 830. Note that as the thickness d10 of the second cavity becomes thinner, the thickness d20 of the thin display becomes thinner, but there is a limit due to the stacking of the piezoelectric elements 510, 511.

[0126] 22(a) to (c) are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, of a thin display 800a (using an intermediate plate) incorporating an SoT module. The thin display 800a includes a display panel 810, an SoT module 500a, and a back plate 820.

[0127] The SoT module 500a is composed of piezoelectric elements 510 and 511, an intermediate plate 830, and an elastic body 551. The SoT module 500a is configured similarly to the SoT module 500, except that the piezoelectric elements are connected by multiple elastic bodies 551. The multiple elastic bodies 551 are each formed in a square plate shape, and are arranged symmetrically on the piezoelectric element 510 at the vertices of the square, and are connected to the piezoelectric element 511.

[0128] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 510 and 511, the vibration of the piezoelectric element 511 is transmitted to the piezoelectric element 510 via the multiple elastic bodies 551. Also, the vibration of the piezoelectric element 510 is transmitted directly to the intermediate plate 830. These vibrations can amplify the vibration of a specific region of the intermediate plate 830. In this case, there are multiple different vibration transmission paths via the multiple elastic bodies 551, and it is possible to amplify the vibration transmitted through each of them in a specific region. It is also possible to apply the SoT module 400d in which the second diaphragm is used to the SoT module 500a.

[0129] 23(a) to (c) are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, of a thin display 800b (using an intermediate plate) incorporating an SoT module. The thin display 800b includes a display panel 810, an SoT module 500b, and a back plate 820.

[0130] The SoT module 500b is composed of piezoelectric elements 510 and 516, an intermediate plate 830, and elastic bodies 553 and 554. The SoT module 500b differs from the SoT module 500a in that the reference axes of the piezoelectric element 516 and the multiple elastic bodies 553 and 554 are shifted from the reference axis of the piezoelectric element 510.

[0131] In the SoT module 500b, the piezoelectric element 516, the multiple elastic bodies 553, 554, and the piezoelectric element 510 are attached in an overlapping manner with the central axes of their main surfaces aligned. However, the reference axis of the piezoelectric element 516 formed in a square plate shape and the multiple elastic bodies 553, 554 arranged accordingly is shifted by 45° from the reference axis of the piezoelectric element 510 formed in a square plate shape. In other words, the piezoelectric elements 510, 516 are arranged in an arrangement having areas where they do not overlap each other.

[0132] The piezoelectric element 516 is connected to the piezoelectric element 510 in the overlapping region via an elastic body 553, and is connected to the intermediate plate 830 in the non-overlapping region via an elastic body 554. Each of the multiple elastic bodies 553, 554 is formed in a square plate shape.

[0133] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 510 and 516, the vibration of the piezoelectric element 516 can be transmitted to the intermediate plate 830 via the elastic bodies 553 and 554, and the vibration of the piezoelectric element 510 can be transmitted to the intermediate plate 830. Since the piezoelectric elements are superimposed with the reference axis shifted, it is possible to create an area on the intermediate plate 830 that vibrates due to the piezoelectric element 516, an area that vibrates due to the piezoelectric element 510, and an area where the vibration is amplified by the piezoelectric elements 510 and 516. Note that the SoT module 400d in which a second diaphragm is used can also be applied to the SoT module 500b.

[0134] 24(a) to (c) are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, of a thin display 800c (using an intermediate plate) incorporating an SoT module. The thin display 800c includes a display panel 810, an SoT module 500c, and a back plate 820.

[0135] The SoT module 500c is composed of piezoelectric elements 510 and 517, an intermediate plate 830, a diaphragm 531 (second diaphragm), and an elastic body 551. The SoT module 500c is configured in the same manner as the SoT module 500, except that the diaphragm 531 is provided between the piezoelectric element 517 and the elastic body 551. One piezoelectric element 517 is attached onto the diaphragm 531, while the diaphragm 531 is also attached to the elastic body 551.

[0136] By applying an AC voltage to the piezoelectric elements 510 and 517 in the same phase or in the opposite phase, the vibration of the piezoelectric element 517 is transmitted to the diaphragm 531, and further the vibration is transmitted to the intermediate plate 830 via the elastic body 551. Also, the vibration of the piezoelectric element 510 is directly transmitted to the intermediate plate 830. These vibrations can amplify the vibration of a specific region of the intermediate plate 830.

[0137] <Thin display incorporating the SoT module (using the display panel and the intermediate plate)> Figs. 25(a) to (c) are a perspective view, an exploded perspective view, and a cross-sectional view showing a thin display 900 (using the display panel and the intermediate plate) incorporating the SoT module, respectively. The thin display 900 includes the SoT module 600 and a back plate 920.

[0138] The SoT module 600 is composed of piezoelectric elements 610 and 615, a display panel 910, an intermediate plate 930, and an elastic body 652. The piezoelectric elements 610 and 615 in the SoT module 600 are both formed in a square flat plate shape. The piezoelectric element 610 is attached onto the display panel 910, and the piezoelectric element 615 is superimposed on the intermediate plate 930.

[0139] The SoT module 600 is configured similarly to a superimposed SoT module using two diaphragms, and uses the display panel 910 and the intermediate plate 930 as diaphragms (first and second diaphragms, respectively). In this application example, one of the superimposed piezoelectric elements 610, 615 is also disposed in the first cavity, so that the thickness d10 of the second cavity can be made thin, and the thickness d20 of the entire thin display can be made thin. The elastic body 652 is formed in a square flat plate shape, and the intermediate plate 930 and the piezoelectric element 610 are connected by the elastic body 652 in the overlapping region.

[0140] By applying AC voltages in the same phase or in opposite phase to the piezoelectric elements 610 and 615, the vibration of the intermediate plate 930 can be transmitted to the piezoelectric element 610 via the elastic body 652, and the vibration of the piezoelectric element 610 can be transmitted to the display panel 910. These vibrations can amplify the vibration of a specific area of ​​the display panel 910.

[0141] 26(a) to (c) are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, showing a thin display 900a (using a display panel and an intermediate plate) incorporating an SoT module. The thin display 900a includes an SoT module 600a and a back plate 920.

[0142] The SoT module 600a is composed of piezoelectric elements 610 and 615, a display panel 910, an intermediate plate 930, and an elastic body 653. The SoT module 600a is composed similarly to the SoT module 600, except that the SoT module 600a is provided with multiple elastic bodies 653 instead of a single one. The multiple elastic bodies 653 are each formed in a square flat plate shape, and are arranged symmetrically at the vertices of the square on the piezoelectric element 610, and are connected to the intermediate plate 930. In this case, the reference axes of the piezoelectric element 615 and the multiple elastic bodies 653 coincide with the reference axis of the piezoelectric element 610.

[0143] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 610 and 615, the vibration of the intermediate plate 930 is transmitted to the piezoelectric element 610 via the multiple elastic bodies 653. Also, the vibration of the piezoelectric element 610 is directly transmitted to the display panel 910. These vibrations can amplify the vibration of a specific region of the display panel 910. In this case, there are multiple different vibration transmission paths via the multiple elastic bodies 653, and it is possible to amplify the vibration transmitted through each of them in a specific region.

[0144] 27(a) to (c) are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, of a thin display 900b (using a display panel and an intermediate plate) incorporating an SoT module. The thin display 900b includes an SoT module 600b and a back plate 920.

[0145] The SoT module 600b is composed of piezoelectric elements 610, 616, a display panel 910, an intermediate plate 930, and elastic bodies 654, 655. The SoT module 600b is configured similarly to the SoT module 600a, except that the reference axes of the piezoelectric element 616 and the multiple elastic bodies 654, 655 are offset from the reference axis of the piezoelectric element 610, and eight elastic bodies 654, 655 are arranged.

[0146] In the SoT module 600b, the piezoelectric element 616, the multiple elastic bodies 654, 655, and the piezoelectric element 610 are attached in an overlapping manner with the central axes of their main surfaces aligned. However, the reference axis of the piezoelectric element 616 and the multiple elastic bodies 654, 655 formed in a square plate shape is shifted by 45° from the reference axis of the piezoelectric element 610 formed in a square plate shape. In other words, the piezoelectric elements 610, 616 are arranged in an arrangement with some areas that do not overlap each other.

[0147] The intermediate plate 930 is connected to the piezoelectric element 610 in an overlapping region thereof by an elastic body 654. The intermediate plate 930 is connected to the display panel 910 via an elastic body 655 in an area not overlapping with the piezoelectric element 410. Each of the multiple elastic bodies 654, 655 is formed in a square flat plate shape.

[0148] By applying AC voltages in the same phase or in opposite phase to the piezoelectric elements 610 and 616, the vibration of the intermediate plate 930 can be transmitted to the display panel 910 via the elastic bodies 654 and 655, and the vibration of the piezoelectric element 610 can also be transmitted to the display panel 910. Since the piezoelectric elements are superimposed with the reference axis shifted, it is possible to create on the display panel 910 an area vibrating due to the intermediate plate 930, an area vibrating due to the piezoelectric element 610, and an area where the vibration is amplified by the display panel 910 and the piezoelectric element 610.

[0149] 28(a) to (c) are a perspective view, an exploded perspective view, and a cross-sectional view, respectively, of a thin display 900c (using a display panel and an intermediate plate) incorporating an SoT module. The thin display 900c includes an SoT module 600c and a back plate 920.

[0150] The SoT module 600c is composed of piezoelectric elements 610 and 617, a display panel 910, an intermediate plate 930, and elastic bodies 656 and 657. The SoT module 600c is configured similarly to the SoT module 600b, except that nine piezoelectric elements 617 and nine elastic bodies 656 and 657 are provided.

[0151] Specifically, the piezoelectric element 617 and the elastic bodies 656, 657 are arranged symmetrically about the vertices of a square and the midpoints of the line segments connecting the vertices, and their reference axes are shifted by 45° from the reference axis of the piezoelectric element 610 formed in a square plate shape. That is, the piezoelectric elements 610, 617 are arranged in such a way that there are areas where they do not overlap each other. The elastic body 656 connects the intermediate plate 930 and the piezoelectric element 610, and the elastic body 657 connects the intermediate plate 930 and the display panel 910.

[0152] By applying an AC voltage in the same phase or in opposite phase to the piezoelectric elements 610 and 617, the vibration of the piezoelectric element 617 is transmitted to the intermediate plate 930, and the vibration is further transmitted to the display panel 910 via the multiple elastic bodies 656 and 657. In addition, the vibration of the piezoelectric element 610 is transmitted directly to the display panel 910. These vibrations can amplify the vibration of a specific area of ​​the display panel 910. In this case, multiple different vibration transmission paths exist via the multiple elastic bodies 656 and 657.

[0153] <Measurement of vibration area> The prepared piezoelectric modules and SoT modules were driven, and the vibration area of ​​the diaphragm was measured with a laser Doppler meter. Figures 29(a) to (c) are a plan view and a cross-sectional view of a piezoelectric module 1100 having a single piezoelectric element, and a diagram showing the vibration mode pattern. The piezoelectric module 1100 includes a piezoelectric element 1110 and a diaphragm 1130. The piezoelectric element 1110 is formed in a disk shape and is attached to the center of the square flat diaphragm 1130.

[0154] In Fig. 29(c), the distribution of amplitude on the diaphragm 1130 is shown as a vibration mode pattern, and the magnitude of the amplitude is displayed in shades of gray (similarly below). As shown in Fig. 29(c), the distribution of amplitude varies depending on the distance from the center of the diaphragm 1130. The center of the diaphragm 1130 is the region to which the active vibration of the piezoelectric element 1110 is transmitted, and the peripheral region is the region to which the vibration from the piezoelectric element 1110 is transmitted and which only passively vibrates.

[0155] 30(a) to (c) are a plan view, a cross-sectional view, and a diagram showing a vibration mode pattern of a piezoelectric module 1200 having piezoelectric elements 1210 connected by a single elastic body 1250. The piezoelectric module 1200 includes a piezoelectric element 1210, an elastic body 1250, and a vibration plate 1130. The piezoelectric element 1210 is formed in a square plate shape, and is connected to the center of the square plate-shaped vibration plate 1130 by a disk-shaped elastic body 1250.

[0156] 30(c), the distribution of amplitude magnitude differs depending on the distance from the center of diaphragm 1130. The distribution of vibration caused by piezoelectric module 1200 is the same as that of piezoelectric module 1100. The vibration is transmitted to areas within circles of the same shape where piezoelectric element 1110 and elastic body 1250 are bonded to diaphragm 1130, and therefore the distribution caused by them is also the same.

[0157] 31(a) to (c) are plan views showing SoT modules 1300 and 1400 having piezoelectric elements 1311 and 1312 and an elastic body 1450 arranged in a lattice pattern, respectively, and diagrams showing mode patterns of vibration thereof. The SoT module 1300 shown in FIG. 31(a) includes piezoelectric elements 1311 and 1312 and a vibration plate 1130. The piezoelectric elements 1311 and 1312 are formed in a disk shape and are arranged at each lattice point of a square lattice on the vibration plate 1130. The piezoelectric elements 1311 and 1312 are alternately arranged on a plane, and the piezoelectric element 1312 is driven in a phase opposite to the phase in which the piezoelectric element 1311 is driven. The piezoelectric elements 1311 and 1312 are attached to the vibration plate 1130, and their vibrations are transmitted to the vibration plate 1130. As a result, the vibration plate 1130 vibrates in a mode pattern shown in FIG. 31(c).

[0158] The SoT module 1400 shown in FIG. 31(b) includes piezoelectric elements 1411 and 1412, an elastic body 1450, and a vibration plate 1130. The piezoelectric elements 1411 and 1412 are formed in a square plate shape and are arranged at each lattice point of a square lattice on the vibration plate 1130. The piezoelectric elements 1411 and 1412 are connected to the vibration plate 1130 by an elastic body 1450 formed in a disk shape at each arrangement. The piezoelectric elements 1411 and 1412 are arranged alternately on a plane, and the piezoelectric element 1412 is driven in a phase opposite to the phase in which the piezoelectric element 1411 is driven. The piezoelectric elements 1411 and 1412 are connected to the vibration plate 1130 by the elastic body 1450, and their vibration is transmitted to the vibration plate 1130. As a result, in the SoT module 1400, the diaphragm 1130 vibrates in the mode pattern shown in FIG.

[0159] 32(a) to (c) are plan views showing an SoT module having piezoelectric elements and elastic bodies arranged in a circular ring shape, and diagrams showing mode patterns of the vibration of the module. The SoT module 1500 shown in FIG. 32(a) includes piezoelectric elements 1511 and 1512 and a vibration plate 1130. The piezoelectric elements 1511 and 1512 are formed in a circular plate shape and arranged at equal intervals (45° intervals in the illustrated example) on the circumference of the vibration plate 1130. The piezoelectric elements 1511 and 1512 are arranged alternately, and the piezoelectric element 1512 is driven in a phase opposite to the phase in which the piezoelectric element 1511 is driven. The piezoelectric elements 1511 and 1512 are attached to the vibration plate 1130, and their vibrations are transmitted to the vibration plate 1130. As a result, the vibration plate 1130 vibrates in the mode pattern shown in FIG. 32(c).

[0160] The SoT module 1600 shown in FIG. 32(b) includes piezoelectric elements 1611 and 1612, an elastic body 1650, and a vibration plate 1130. The piezoelectric elements 1611 and 1612 are formed in a square plate shape and are arranged on the circumference of the vibration plate 1130 at equal intervals (45° intervals in the illustrated example). The piezoelectric elements 1611 and 1612 are connected to the vibration plate 1130 by an elastic body 1650 formed in a disk shape at each arrangement. The piezoelectric elements 1611 and 1612 are arranged alternately, and the piezoelectric element 1612 is driven in a phase opposite to the phase in which the piezoelectric element 1611 is driven. The piezoelectric elements 1611 and 1612 are connected to the vibration plate 1130 by the elastic body 1650, and their vibrations are transmitted to the vibration plate 1130. As a result, in the SoT module 1600, the diaphragm 1130 vibrates in the mode pattern shown in FIG.

[0161] 33(a) to (c) are plan views showing an SoT module having piezoelectric elements and elastic bodies arranged in point symmetry, and diagrams showing mode patterns of the vibration thereof. The SoT module 1700 shown in FIG. 33(a) includes piezoelectric elements 1711 and 1712 and a vibration plate 1130. The piezoelectric elements 1711 and 1712 are formed in a disk shape and arranged in a point-symmetric figure on the vibration plate 1130. Specifically, the piezoelectric elements 1711 and 1712 are arranged alternately at a certain angular interval on a square drawn in two layers, large and small, centered on the center of the vibration plate 1130. The piezoelectric element 1712 is driven in a phase opposite to the phase in which the piezoelectric element 1711 is driven. The piezoelectric elements 1711 and 1712 are attached to the vibration plate 1130, and their vibrations are transmitted to the vibration plate 1130. As a result, the vibration plate 1130 vibrates in a mode pattern shown in FIG. 33(c).

[0162] An SoT module 1800 shown in FIG. 33(b) includes piezoelectric elements 1811-1814, an elastic body 1850, and a vibration plate 1130. Piezoelectric elements 1811 and 1812 are formed in a square plate shape, and piezoelectric elements 1813 and 1814 are formed in a rectangular plate shape. Elastic body 1850 formed in a disk shape is arranged on a point-symmetric figure of vibration plate 1130. Specifically, elastic bodies 1850 are arranged at regular angular intervals on a square drawn in two layers, large and small, centered on the center of vibration plate 1130.

[0163] Piezoelectric elements 1811, 1812 are connected to elastic body 1850 provided at the center of the sides of the outer square, and are arranged in a staggered manner. Piezoelectric elements 1813, 1814 are connected to elastic body 1850 provided at the corners of the inner square and outer square, and are arranged so that their longitudinal direction is from the center to the periphery of diaphragm 1130. Adjacent piezoelectric elements 1813, 1814 are arranged in parallel so that their longitudinal directions are parallel.

[0164] Piezoelectric elements 1811-1814 are connected to diaphragm 1130 by elastic body 1850. Piezoelectric element 1813 is driven in phase with piezoelectric element 1811, and piezoelectric elements 1812 and 1814 are driven in phase opposite to piezoelectric element 1811. Vibrations of piezoelectric elements 1811-1814 are transmitted to diaphragm 1130 via elastic body 1850. As a result, in SoT module 1800, diaphragm 1130 vibrates in the mode pattern shown in FIG. 33(c) similarly to SoT module 1700.

[0165] <Modification> In the above embodiment, the piezoelectric elements can be driven in different phases, but it is preferable to drive them in opposite phases. However, they may be driven in other phases than the same phase or opposite phases. This allows the amplification of vibration to be adjusted. Although nine or five piezoelectric elements or elastic bodies are used as the piezoelectric elements or elastic bodies, other numbers may be used. It is preferable to use a quantity that allows for symmetrical arrangement. [Explanation of symbols]

[0166] 100~100d SoT module 111~114 Piezoelectric elements 121, 122 Piezoelectric 123, 124 electrode 125 Shim plate 130, 430, 431, 432, 435 diaphragm 141~144 Weight 151, 152, 153, 155 Elastic body 200, 200a Piezoelectric Module 210, 211 Piezoelectric element 251~254 Elastic body 300a~300g SoT module 310a, 310b Piezoelectric composite 311~314, 315, 316, 318 Piezoelectric elements 351~354, 355, 355f, 356~359, 356g~359g Elastic body 400, 400a-400f, 400h-400k SoT modules 410~416, 419 Piezoelectric elements 430~431, 435 diaphragm 450~454 Elastic body 500, 500a~500c SoT modules 510, 511, 516, 517 Piezoelectric elements 531 Diaphragm 550, 551, 553, 554 Elastic body 600, 600a, 600b, 600c SoT Modules 610, 615, 616, 617 Piezoelectric elements 652~657 Elastic body 800, 800a800c~ Thin display 810 Display Panel 820 Back plate 830 Intermediate plate 900, 900a~900c Thin Display 910 Display Panel 920 Back plate 930 Intermediate plate 1100, 1200 Piezoelectric Module 1110, 1210 Piezoelectric element 1130 Vibration plate 1250 Elastic body 1300, 1400 SoT Modules 1311, 1312 Piezoelectric element 1411, 1412 Piezoelectric element 1450 Elastic body 1500, 1600 SoT Modules 1511, 1512 Piezoelectric element 1611, 1612 Piezoelectric element 1650 Elastic body 1700, 1800 SoT Modules 1711, 1712 Piezoelectric element 1811~1814 Piezoelectric elements 1850 Elastic body

Claims

1. Multiple flat-plate piezoelectric elements that generate vibrations when an AC voltage is applied, The device comprises a first diaphragm on which the vibrations of the piezoelectric element are transmitted, In a specific region of the first diaphragm, the vibrations of the plurality of piezoelectric elements are amplified. Of the plurality of piezoelectric elements, the vibration transmission path from one piezoelectric element to the first diaphragm is different from the vibration transmission path from the other piezoelectric elements to the first diaphragm. The SoT module is characterized in that one piezoelectric element has a portion attached to the other piezoelectric element, and when viewed along the central axis perpendicular to the main surface of the piezoelectric element, the attached portion does not become the center of gravity of the piezoelectric composite formed by the connection of the piezoelectric elements.

2. A plurality of flat-plate piezoelectric elements that generate vibration by applying an AC voltage, The device comprises a first diaphragm on which the vibrations of the piezoelectric element are transmitted, In a specific region of the first diaphragm, the vibrations of the plurality of piezoelectric elements are amplified. Of the plurality of piezoelectric elements, the vibration transmission path from one piezoelectric element to the first diaphragm is different from the vibration transmission path from the other piezoelectric elements to the first diaphragm. The SoT module is characterized in that the plurality of piezoelectric elements are not connected to each other and are arranged in a windmill shape facing each other at positions where their longitudinal ends are almost touching the side surfaces of adjacent piezoelectric elements.

3. A plurality of flat-plate piezoelectric elements that generate vibration by applying an AC voltage, The device comprises a first diaphragm on which the vibrations of the piezoelectric element are transmitted, In a specific region of the first diaphragm, the vibrations of the plurality of piezoelectric elements are amplified. Among the plurality of piezoelectric elements, the vibration transmission path from one piezoelectric element to the first diaphragm is different from the vibration transmission path from the other piezoelectric elements to the first diaphragm, and the one piezoelectric element is connected to the first diaphragm by an elastic body. The other piezoelectric element is attached to the first diaphragm. The SoT module is characterized in that one piezoelectric element and the other piezoelectric body are connected by an elastic body made of a material having an elastic modulus of 690 MPa or less.

4. A plurality of flat-plate piezoelectric elements that generate vibration by applying an AC voltage, The device comprises a first diaphragm on which the vibrations of the piezoelectric element are transmitted, In a specific region of the first diaphragm, the vibrations of the plurality of piezoelectric elements are amplified. Of the plurality of piezoelectric elements, the vibration transmission path from one piezoelectric element to the first diaphragm is different from the vibration transmission path from the other piezoelectric elements to the first diaphragm. The system further comprises a second diaphragm to which the other piezoelectric element is directly connected, The second diaphragm is connected by one piezoelectric element and a plurality of elastic bodies. The SoT module is characterized in that the plurality of elastic bodies are formed from a material having an elastic modulus of 690 MPa or less.

5. The one piezoelectric element is attached to the first diaphragm, The SoT module according to claim 4, characterized in that the other piezoelectric element is attached to the second diaphragm.

6. The SoT module according to claim 5, further comprising a cover plate provided on the opposite side of the first diaphragm to the second diaphragm.

7. The SoT module according to claim 4, characterized in that the second diaphragm is connected to the first diaphragm by an elastic body.

8. The SoT module according to claim 7, further comprising a cover plate provided on the opposite side of the first diaphragm to the second diaphragm.

9. A plurality of flat-plate piezoelectric elements that generate vibration by applying an AC voltage, The device comprises a first diaphragm on which the vibrations of the piezoelectric element are transmitted, In a specific region of the first diaphragm, the vibrations of the plurality of piezoelectric elements are amplified. Of the plurality of piezoelectric elements, the vibration transmission path from one piezoelectric element to the first diaphragm is different from the vibration transmission path from the other piezoelectric elements to the first diaphragm. The system further comprises a second diaphragm to which the other piezoelectric element is directly connected, The second diaphragm is connected to the one piezoelectric element by an elastic body, The SoT module is characterized in that the first diaphragm and the second diaphragm are connected by an elastic body made of a material having an elastic modulus of 690 MPa or less.

10. The one piezoelectric element is attached to the first diaphragm, The SoT module according to claim 9, characterized in that the other piezoelectric element is attached to the second diaphragm.

11. The SoT module according to claim 10, further comprising a cover plate provided on the opposite side of the first diaphragm to the second diaphragm.

12. The SoT module according to claim 9, characterized in that the second diaphragm is connected to the first diaphragm by an elastic body.

13. The SoT module according to claim 12, further comprising a cover plate provided on the opposite side of the first diaphragm to the second diaphragm.

14. The SoT module according to any one of claims 1 to 13, characterized in that the phase for driving one piezoelectric element and the phase for driving the other piezoelectric element are different.

15. The SoT module according to any one of claims 1 to 13, characterized in that it is used in a display of a television, tablet, smartphone, or car navigation system.

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