WO2014091813A1

WO2014091813A1 - Acoustic generator, acoustic generation device, and electronic device

Info

Publication number: WO2014091813A1
Application number: PCT/JP2013/076667
Authority: WO
Inventors: 稲垣　正祥
Original assignee: 京セラ株式会社
Priority date: 2012-12-12
Filing date: 2013-10-01
Publication date: 2014-06-19
Also published as: TW201436584A

Abstract

[Problem] To obtain a favorable frequency characteristic of acoustic pressure. [Solution] An acoustic generator pertaining to an embodiment of the present invention is provided with an exciter, a flat vibrating body, and a damping material. The exciter vibrates upon input of an electric signal. The vibrating body has the exciter attached thereto, so that as the attached exciter vibrates, the vibrating body vibrates along with the exciter. The damping material is attached to a principal surface of the vibrating body on the side opposite that to which the exciter is attached.

Description

SOUND GENERATOR, SOUND GENERATOR, AND ELECTRONIC DEVICE

The disclosed embodiment relates to a sound generator, a sound generation device, and an electronic apparatus.

Conventionally, an acoustic generator using a piezoelectric element is known (see, for example, Patent Document 1). Such an acoustic generator is configured to vibrate a diaphragm by applying a voltage to a piezoelectric element attached to the diaphragm to vibrate, and to output sound by actively utilizing resonance of the vibration.

In addition, since such a sound generator can use a thin film such as a resin film for the diaphragm, it can be configured to be thinner and lighter than a general electromagnetic speaker.

In addition, when using a thin film for a diaphragm, the thin film is supported in a state in which a uniform tension is applied, for example, by being sandwiched from a thickness direction by a pair of frame members so as to obtain excellent acoustic conversion efficiency. Is required.

JP 2004-023436 A

However, the conventional acoustic generator described above actively uses the resonance of the diaphragm that is uniformly tensioned, and therefore, in the frequency characteristics of the sound pressure, the peak (the portion where the sound pressure is higher than the surroundings) and the dip There is a problem that (a portion where the sound pressure is lower than the surroundings) easily occurs and it is difficult to obtain a good sound quality.

Also, the sound generator and the electronic device provided with the sound generator have a problem that it is difficult to obtain good sound quality.

One aspect of the embodiments has been made in view of the above, and an object thereof is to provide an acoustic generator, an acoustic generator, and an electronic apparatus that can obtain a favorable frequency characteristic of sound pressure.

The acoustic generator according to one aspect of the embodiment includes an exciter, a flat vibrating body, and a damping material. The exciter vibrates upon receiving an electrical signal. The vibrator is attached with the exciter, and vibrates with the exciter due to vibration of the exciter. The damping material is attached to the main surface of the vibrator opposite to the side on which the exciter is attached.

Further, a sound generation device according to one aspect of the embodiment includes the sound generator described above and a housing that houses the sound generator.

An electronic apparatus according to an aspect of the embodiment includes the above-described acoustic generator, an electronic circuit connected to the acoustic generator, and a housing that houses the electronic circuit and the acoustic generator. It has a function of generating sound from the sound generator.

According to one aspect of the embodiment, a favorable sound pressure frequency characteristic can be obtained.

FIG. 1A is a schematic plan view showing a schematic configuration of a basic sound generator. 1B is a cross-sectional view taken along line A-A ′ of FIG. 1A. FIG. 2 is a diagram illustrating an example of frequency characteristics of sound pressure. FIG. 3A is a schematic cross-sectional view showing the configuration of the sound generator according to the embodiment. FIG. 3B is a schematic plan perspective view corresponding to FIG. 3A. FIG. 4A is a schematic cross-sectional view illustrating an arrangement example of a damping material in an acoustic generator according to another embodiment. FIG. 4B is a schematic plan perspective view corresponding to FIG. 4A. FIG. 4C is another schematic plan perspective view corresponding to FIG. 4A. FIG. 5A is a schematic plan perspective view showing an arrangement region of a damping material. FIG. 5B is a schematic perspective plan view showing an example of arrangement of damping materials in a sound generator according to another embodiment. FIG. 5C is a schematic perspective plan view showing an example of arrangement of damping materials in an acoustic generator according to another embodiment. FIG. 5D is a schematic perspective plan view showing an example of arrangement of damping materials in a sound generator according to another embodiment. FIG. 5E is a schematic plan perspective view showing another arrangement region of the damping material. FIG. 5F is a schematic perspective plan view showing an example of arrangement of damping materials in a sound generator according to another embodiment. FIG. 5G is a schematic cross-sectional view illustrating an arrangement example of a damping material in an acoustic generator according to another embodiment. FIG. 6A is a diagram illustrating a configuration of the sound generation device according to the embodiment. FIG. 6B is a diagram illustrating a configuration of the electronic device according to the embodiment.

Hereinafter, embodiments of a sound generator, a sound generator, and an electronic device disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

First, prior to the description of the sound generator 1 according to the embodiment, a schematic configuration of a basic sound generator 1 ′ will be described with reference to FIGS. 1A and 1B. FIG. 1A is a schematic plan view showing a schematic configuration of the acoustic generator 1 ', and FIG. 1B is a cross-sectional view taken along line A-A' of FIG. 1A.

For easy understanding, FIGS. 1A and 1B show a three-dimensional orthogonal coordinate system including a Z-axis having a vertically upward direction as a positive direction and a vertically downward direction as a negative direction. Such an orthogonal coordinate system may also be shown in other drawings used in the following description.

Also, in the following, for a component composed of a plurality of components, only a part of the plurality of components may be provided with a reference numeral, and the provision of a reference numeral may be omitted for the others. In such a case, it is assumed that a part with the reference numeral and the other have the same configuration.

In FIG. 1A, the resin layer 7 (described later) is not shown. For easy understanding, FIG. 1B greatly exaggerates the sound generator 1 ′ in the thickness direction (Z-axis direction).

As shown in FIG. 1A, the sound generator 1 ′ includes a frame body 2, a diaphragm 3, and a piezoelectric element 5. As shown in FIG. 1A, in the following description, the case where there is one piezoelectric element 5 is illustrated, but the number of piezoelectric elements 5 is not limited.

The frame body 2 is composed of two frame members having a rectangular frame shape and the same shape, and sandwiches the peripheral edge portion of the diaphragm 3. Accordingly, the frame body 2 functions as a support body that supports a vibrating body 3a described later. The diaphragm 3 has a plate-like shape or a film-like shape, and its peripheral portion is sandwiched and fixed between two frame members constituting the frame body 2, and is uniformly tensioned within the frame of the frame body 2. It is supported substantially flat in a state where it is applied.

In addition, let the part inside the inner periphery of the frame 2 among the diaphragms 3, ie, the part which is not pinched | interposed into the frame 2 among the diaphragms 3, and can vibrate freely be the vibrating body 3a. That is, the vibrating body 3 a is a substantially rectangular portion in the frame 2 and is supported by the frame 2.

The diaphragm 3 can be formed using various materials such as resin and metal. For example, the diaphragm 3 can be made of a resin film such as polyethylene or polyimide having a thickness of 10 to 200 μm.

Further, the thickness and material of the frame member constituting the frame body 2 are not particularly limited, and can be formed using various materials such as metal and resin. For example, a stainless steel member having a thickness of 100 to 5000 μm can be suitably used as the frame member constituting the frame body 2 because of its excellent mechanical strength and corrosion resistance.

1A shows the frame 2 in which the shape of the inner region is substantially rectangular, but it may be a polygon such as a parallelogram, trapezoid, or regular n-gon. In the present embodiment, as shown in FIG.

Further, in the above description, the case where the frame body 2 is configured by two frame members and the peripheral portion of the diaphragm 3 is sandwiched and supported by the two frame members is described as an example. It is not a thing. For example, the frame body 2 may be constituted by a single frame member, and the peripheral edge portion of the diaphragm 3 may be bonded and supported to the frame body 2.

The piezoelectric element 5 is an exciter that is provided on the surface of the vibration plate 3 (vibration body 3a) or the like and excites the vibration plate 3 (vibration body 3a) by oscillating upon application of a voltage. .

As shown in FIG. 1B, the piezoelectric element 5 includes, for example, a laminate in which

piezoelectric layers

5a, 5b, 5c, and 5d made of four ceramic layers and three internal electrode layers 5e are alternately laminated,

Surface electrode layers

5f and 5g formed on the upper and lower surfaces of the laminate, and

external electrodes

5h and 5j formed on the side surfaces where the internal electrode layer 5e is exposed. The lead terminals 6a and 6b are connected to the

external electrodes

5h and 5j.

The piezoelectric element 5 has a plate shape, and the main surface on the upper surface side and the lower surface side has a polygonal shape such as a rectangular shape or a square shape. The

piezoelectric layers

5a, 5b, 5c, and 5d are polarized as shown by arrows in FIG. 1B. In other words, polarization is performed such that the direction of polarization with respect to the direction of the electric field applied at a certain moment is reversed between one side and the other side in the thickness direction (Z-axis direction in the figure). The piezoelectric element 5 here is a so-called bimorph type laminated piezoelectric element.

When a voltage is applied to the piezoelectric element 5 via the lead terminals 6a and 6b, for example, at a certain moment, the

piezoelectric layers

5c and 5d on the side bonded to the diaphragm 3 (vibrating body 3a) contract, The

piezoelectric layers

5a and 5b on the upper surface side of the piezoelectric element 5 are deformed so as to extend. Therefore, by applying an AC signal to the piezoelectric element 5, the piezoelectric element 5 can bend and vibrate, and the vibrating body 3a can be bent.

The main surface of the piezoelectric element 5 is joined to the main surface of the vibrating body 3a by an adhesive such as an epoxy resin.

In addition, the materials constituting the

piezoelectric layers

5a, 5b, 5c and 5d have conventionally been lead-free piezoelectric materials such as lead zirconate titanate, Bi layered compounds and tungsten bronze structure compounds. The used piezoelectric ceramics can be used.

Further, various metal materials can be used as the material of the internal electrode layer 5e. For example, when a metal component composed of silver and palladium and a ceramic component constituting the

piezoelectric layers

5a, 5b, 5c, and 5d are contained, the

piezoelectric layers

5a, 5b, 5c, and 5d and the internal electrode layer 5e Since the stress due to the difference in thermal expansion can be reduced, the piezoelectric element 5 free from stacking faults can be obtained.

Further, the lead terminals 6a and 6b can be formed using various metal materials. For example, if the lead terminals 6a and 6b are configured using flexible wiring in which a metal foil such as copper or aluminum is sandwiched between resin films, the height of the piezoelectric element 5 can be reduced.

Further, as shown in FIG. 1B, the sound generator 1 ′ is arranged so as to cover at least a part of the surface of the piezoelectric element 5 and the diaphragm 3 (vibrating body 3a) in the frame of the frame body 2 to vibrate. A resin layer 7 integrated with the plate 3 (vibrating body 3a) and the piezoelectric element 5 is further provided. That is, the piezoelectric element 5 is embedded in the resin layer 7.

The resin layer 7 is preferably formed using, for example, an acrylic resin so that the Young's modulus is about 1 MPa to 1 GPa. In addition, since the moderate damping effect can be induced by embedding the piezoelectric element 5 in the resin layer 7, the resonance phenomenon can be suppressed, and the peak and dip in the frequency characteristic of the sound pressure can be suppressed small.

FIG. 1B shows a state in which the resin layer 7 is formed so as to be the same height as the frame 2, but it is sufficient that the piezoelectric element 5 is embedded, for example, the resin layer 7 has a frame. It may be formed to be higher than the height of the body 2.

Incidentally, as shown in FIGS. 1A and 1B, the diaphragm 3 (vibrating body 3 a) is supported substantially flat in a state where tension is uniformly applied in the frame of the frame body 2. In such a case, since a peak dip or distortion due to resonance induced by vibration of the piezoelectric element 5 occurs, the sound pressure changes rapidly at a specific frequency, and it is difficult to flatten the frequency characteristic of the sound pressure.

This is illustrated in FIG. FIG. 2 is a diagram illustrating an example of frequency characteristics of sound pressure. As already described in the description of FIG. 1A, the vibrating body 3 a is supported substantially flat in a state where tension is uniformly applied within the frame of the frame body 2.

However, in such a case, since the peak concentrates and degenerates at a specific frequency due to resonance of the diaphragm 3 (vibrating body 3a), steep peaks and dips are scattered throughout the entire frequency region as shown in FIG. It is easy to occur.

As an example, attention is paid to a portion surrounded by a broken closed curve PD in FIG. When such a peak occurs, the sound pressure varies depending on the frequency, making it difficult to obtain good sound quality.

In such a case, as shown in FIG. 2, the height of the peak P is lowered (see the arrow 201 in the figure), the peak width is widened (see the arrow 202 in the figure), and the peak P or dip (not shown) is reduced. It is effective to take measures to make it smaller.

Therefore, in the present embodiment, first, the height of the peak P is lowered by giving mechanical vibration loss due to the damping material 8 (described later) to the vibrating body 3a.

Furthermore, in this embodiment, the damping material 8 is attached not to the side where the piezoelectric element 5 is attached but to the main surface of the vibrating body 3a on the opposite side. That is, the damping material 8 is directly attached to the vibrating body 3a having the largest distortion, not from the resin layer 7 on the side where the piezoelectric element 5 is attached, but directly from the opposite side. Thereby, a high damper effect can be obtained.

Thus, the resonance phenomenon is suppressed, the degeneration of the resonance mode is solved and dispersed, the height of the peak P is lowered, and the peak width is widened.

Hereinafter, the sound generator 1 according to the embodiment will be specifically described in order with reference to FIGS. 3A to 5G. First, FIG. 3A is a schematic cross-sectional view showing the configuration of the sound generator 1 according to the embodiment, and FIG. 3B is a schematic plan perspective view corresponding to FIG. 3A.

In addition, although there are cases where schematic cross-sectional views are shown below including FIG. 3A, both are schematic cross-sectional views taken along the line A-A ′ of FIG. 1A. In addition, a schematic plan view may be shown below including FIG. 3B, but the resin layer 7 is not shown in any case as in FIG. 1A.

As shown in FIG. 3A, the sound generator 1 includes a damping material 8 in addition to the sound generator 1 'shown in FIGS. 1A and 1B. Further, the damping material 8 is not over the resin layer 7 on the side where the piezoelectric element 5 is attached (see the damping material 8 ′ indicated by a two-dot chain line in the drawing), but on the opposite side of the vibrating body 3a. Can be attached directly to the main surface.

The damping material 8 may have any mechanical loss, but is preferably a member having a high mechanical loss factor, in other words, a low mechanical quality factor (so-called mechanical Q).

Such a damping material 8 can be formed to have a thickness 0.5 to 3 times the thickness of the diaphragm 3 (vibrating body 3a) using various elastic bodies, for example. For example, as the material of the damping material 8, rubbers such as urethane rubber, silicon rubber, fluorine rubber, chloroprene rubber, nitrile rubber, natural rubber, resins such as polyethylene resin, vinyl chloride resin, ABS resin, fluorine resin, , Polymer gels such as polyimide gel, polyvinylidene fluoride gel, polymethyl methacrylate gel, polyvinyl alcohol gel, and polyethylene terephthalate gel. Among them, urethane rubber that is soft and easily deformed and has stable elastic deformation for a long period of time is preferable in terms of a large damping effect. Further, among rubbers, resins, and polymer gels, it is preferable to have a void inside because a damping effect is further generated.

In particular, a porous rubber material such as urethane foam can be suitably used. Further, as shown in FIG. 3A, the damping material 8 is attached to the main surface of the vibrating body 3a opposite to the side on which the piezoelectric element 5 is attached, so that the vibrating body 3a, the piezoelectric element 5 and the resin layer 7 And integrated.

By providing the damping material 8 in this way, the interface between the diaphragm 3 (vibrating body 3a) and the damping material 8 receives vibration loss due to the damping material 8, and thereby the resonance phenomenon is suppressed. In particular, since the damping material 8 is directly attached to the main surface of the diaphragm 3 (vibrating body 3a), a high damper effect can be obtained and the resonance phenomenon can be more effectively suppressed.

This makes it possible to disperse the resonance mode degeneracy. In other words, it is possible to vary the sound pressure peak P at the resonance point and flatten the frequency characteristic of the sound pressure. That is, it is possible to obtain a favorable frequency characteristic of sound pressure.

One or a plurality of damping materials 8 may be attached to a region where the piezoelectric element 5 is present when the acoustic generator 1 is seen through the plane. Further, when seen through a plane as shown in FIG. 5A described later, the damping material 8 may be attached to an area along the contour of the piezoelectric element 5 so as to overlap at least a part of the area. Further, as shown in FIG. 3B, the damping material 8 may be attached so as to cover the entire region where the piezoelectric element 5 exists when the sound generator 1 is seen through the plane, and in this case, it is more effective. The resonance phenomenon can be suppressed.

Specifically, the piezoelectric element 5 as a vibration source and the vicinity thereof are covered with the damping material 8, so that the vibration material 3 a is mechanically formed by the damping material 8 at a portion where the distortion tends to increase when the vibrating body 3 a is flexibly vibrated. Vibration loss can be given efficiently.

That is, since the resonance phenomenon can be more effectively suppressed and the peak P and the dip can be reduced, the frequency characteristics of the sound pressure can be flattened and a good frequency characteristic of the sound pressure can be obtained.

FIGS. 3A and 3B show a configuration in which one piezoelectric element 5 and one damping material 8 are provided in correspondence therewith, but two or more piezoelectric elements 5 and this Correspondingly, two or more damping materials 8 may be provided. 3A and 3B illustrate the case where one damping material 8 is attached to one piezoelectric element 5, but the number of damping materials 8 is not limited. Next, a case where a plurality of such damping materials 8 are attached will be described.

FIG. 4A is a schematic cross-sectional view showing an example of arrangement of a damping material in an acoustic generator according to another embodiment, FIG. 4B is a schematic plan perspective view corresponding to FIG. 4A, and FIG. FIG. 4B is another schematic plan perspective view corresponding to FIG. 4A.

As shown in FIG. 4A, a plurality of damping materials 8 may be attached to the main surface of the vibrating body 3a opposite to the side on which the piezoelectric element 5 is attached. Since the damping material 8 can be dispersed and attached in this way, the natural vibration of the damping material 8 can be changed, so that the damping material can be effectively used for the natural vibration modes of the vibrating body 3a generated in a wide range of frequencies. The damper effect by 8 can be exhibited.

For example, as shown in FIG. 4B, a plurality (four in this case) of the damping material 8 may be attached to a region of the vibrating body 3a where the piezoelectric element 5 does not exist when viewed through a plane, and in particular, the entire region. It may be attached so as to cover.

In this case, since the damper effect by the damping material 8 can be given to a wide area of the vibrating body 3a excluding the portion where the piezoelectric element 5 exists, the resonance phenomenon is effectively suppressed and the peak P and dip are reduced. can do. That is, it is possible to flatten the frequency characteristic of sound pressure and obtain a good frequency characteristic of sound pressure.

Further, as shown in FIG. 4C, the damping material 8 is dispersed and attached to the region of the vibrating body 3a where the piezoelectric element 5 does not exist so as to leave a region where neither the damping material 8 nor the piezoelectric element 5 exists. May be. FIG. 4C shows a case where the damping members 8 are arranged in a distributed manner with the four corners of the vibrating body 3a and the vicinity thereof being spaced apart.

In such a case, since the region giving the damper effect by the damping material 8 can be scattered, the sound pressure peak P at the resonance point can be dispersed and the frequency characteristics of the sound pressure can be flattened. That is, it is possible to obtain a favorable frequency characteristic of sound pressure.

4A to 4C exemplify the case where the plurality of damping materials 8 are mainly attached to the region of the vibrating body 3a where the piezoelectric element 5 does not exist. However, the region where the piezoelectric element 5 exists and the existence thereof exist. It may be attached to both areas that are not.

Further, the damping material 8 may be attached so as to straddle both the region where the piezoelectric element 5 exists and the region where the piezoelectric element 5 does not exist. Such a case will be described with reference to FIGS. 5A to 5D.

FIG. 5A is a schematic plan perspective view showing an arrangement region of the damping material 8. 5B to 5D are schematic plan perspective views showing examples of arrangement of damping materials in the sound generator according to another embodiment. 5C and 5D, the symbols “8a” to “8d” are given to the four damping members 8 for easy understanding.

First, a plurality of damping materials 8 are attached, and may be attached across both the region where the piezoelectric element 5 exists and the region where the piezoelectric element 5 does not exist as described above. In particular, it is preferable that the damping material 8 is attached so that at least a part of the damping material 8 overlaps the region along the outline of the piezoelectric element 5 when viewed through.

In addition, the area | region along the outline of the piezoelectric element 5 said here is a part surrounding the outline of the piezoelectric element 5 at the time of seeing through the acoustic generator 1 shown as a hatched area filled with the oblique line in FIG. 5A.

When the damping material 8 is attached so that at least a part thereof overlaps with the hatched region, it is possible to suppress the propagation of vibration from the piezoelectric element 5 to the surroundings by the damper effect of the damping material 8. The peak P of the sound pressure at the resonance point can be made smooth.

That is, the sound pressure peak P at the resonance point can be varied to flatten the frequency characteristic of the sound pressure. Therefore, a favorable frequency characteristic of sound pressure can be obtained.

Specifically, for example, as shown in FIG. 5B, the damping material 8 is attached so as to straddle both the region where the piezoelectric element 5 exists and the region where the piezoelectric element 5 does not exist when seen in a plan view. At this time, it is preferable that the damping material 8 is attached so that at least a part thereof overlaps a region (see FIG. 5A) along the outline of the piezoelectric element 5 in the region where the piezoelectric element 5 exists.

Further, as shown in FIG. 5C, a plurality of damping materials 8 (8a to 8d) may be scattered on the basis of the region along the contour of the piezoelectric element 5.

For example, in FIG. 5C, the damping material 8c is in contact with the outline of the piezoelectric element 5 from the outside so that the damping material 8b is in contact with the outline of the piezoelectric element 5 from the inside so that the damping material 8a straddles the outline of the piezoelectric element 5. The example which attached to each is shown. Further, the damping material 8d is attached to be deviated from the region along the outline of the piezoelectric element 5.

By dispersing the damping material 8 in this manner, the symmetry of the composite vibration body integrally formed from the vibration body 3a, the piezoelectric element 5, the resin layer 7 (not shown) and the damping material 8 can be lowered. . And since it has symmetry, it can suppress that the peak P concentrates and degenerates to a specific resonant frequency, Therefore It can contribute to flattening of the frequency characteristic of sound pressure.

Of course, since the damping material 8 (8a to 8d) is attached based on the region along the contour of the piezoelectric element 5, the damper effect can be obtained more effectively, and the sound pressure peak P at the resonance point can be obtained. The frequency characteristics of sound pressure can be flattened. That is, it is possible to obtain a favorable frequency characteristic of sound pressure.

5B and 5C exemplify the case where a pair of damping materials 8 are arranged facing each other (for example, a combination of the damping

materials

8a and 8d in FIG. 5C, or the damping

materials

8b and 8c). ), And this may be diagonally opposite.

That is, as shown in FIG. 5D, the region along the contour of the piezoelectric element 5 is used as a base, and the combination of the damping

materials

8a and 8d or the combination of the damping

materials

8b and 8c are arranged so as to face each other diagonally. May be. Here, as shown in the combination of the damping

materials

8b and 8c, the length or the like of each of the damping materials 8 may be different.

Such an arrangement of the damping material 8 can also reduce the above-described symmetry and obtain a more effective damper effect. Therefore, the frequency characteristic of the sound pressure is also flattened, and a good sound pressure can be obtained. Frequency characteristics can be obtained.

5B to 5D show an example in which one damping material 8 is attached in association with each side forming the outline of the piezoelectric element 5; It is good also as attaching only to the edge.

Further, for example, one damping material 8 formed in a rectangular frame shape may be attached to the entire region along the outline of the piezoelectric element 5 (that is, the hatched region shown in FIG. 5A).

Further, the thickness of at least one damping material when a plurality of damping materials 8 are attached may be different from the thickness of other damping materials 8.

Incidentally, in order to effectively obtain the damper effect by the damping material 8, the damping material 8 may be attached to a region along the boundary between the frame body 2 and the vibrating body 3a. Next, such a case will be described with reference to FIGS. 5E and 5F.

FIG. 5E is a schematic plan perspective view showing another arrangement region of the damping material 8. FIG. 5F is a schematic perspective plan view showing an example of the arrangement of the damping material in the sound generator according to another embodiment.

The damping material 8 may be attached to a region along the boundary between the frame body 2 (support body) and the vibrating body 3a as described above. Note that the region along the boundary between the frame body 2 and the vibrating body 3a referred to here is a portion shown as a hatched region in FIG.

When the damping material 8 is attached to such a hatched region, the propagation of vibration around the frame 2 that becomes a vibration node can be suppressed by the damper effect of the damping material 8, so that the vibration from the piezoelectric element 5 is incident. It is possible to cause a difference between the speed and the reflection speed.

Therefore, since the sound pressure peak P at the resonance point can be varied on the surface and inside of the vibrating body 3a and the frequency characteristics of the sound pressure can be flattened, a favorable frequency characteristic can be obtained.

Incidentally, the point of reducing the symmetry of the above-described composite vibrator may be performed by making a difference in the thickness of the damping material 8.

Next, such a case will be described with reference to FIG. 5G.

FIG. 5G is a schematic cross-sectional view showing an arrangement example of the damping material 8 in the sound generator according to another embodiment. In FIG. 5G, the symbols “8e” and “8f” are given to the two damping members 8 for easy understanding.

As shown in FIG. 5G, the damping material 8 has a different thickness so that the thickness h1 of the damping material 8e and the thickness h2 of the damping material 8f have a relationship of “h1> h2,” for example. In addition, the symmetry of the above-described composite vibrator can be lowered.

As a result, the mass (and mass distribution) of the damping material 8e and the damping material 8f can be made different, and the vibration loss caused by the damping material 8e and the damping material 8f can be made different, so that the resonance mode degeneracy can be solved. And can be dispersed. And the sound generator 1 which has the frequency characteristic of a favorable sound pressure can be obtained.

Thus, by making the thickness of at least one damping material 8 different from the thicknesses of other damping materials 8, an acoustic generator having good sound pressure frequency characteristics can be obtained. At this time, the planar arrangement of the plurality of damping materials 8 may be symmetric or asymmetric.

Next, a sound generator and an electronic device equipped with the sound generator 1 according to the embodiment described so far will be described with reference to FIGS. 6A and 6B. FIG. 6A is a diagram illustrating a configuration of the sound generation device 20 according to the embodiment, and FIG. 6B is a diagram illustrating a configuration of the electronic device 50 according to the embodiment. In addition, in both figures, only the component required for description is shown and description about a general component is abbreviate | omitted.

The sound generator 20 is a sounding device such as a so-called speaker, and includes, for example, a sound generator 1 and a housing 30 that houses the sound generator 1 as shown in FIG. 6A. The housing 30 resonates the sound generated by the sound generator 1 and radiates the sound to the outside through an opening (not shown) formed in the housing 30. By having such a housing 30, for example, the sound pressure in a low frequency band can be increased.

Further, the sound generator 1 can be mounted on various electronic devices 50. For example, in FIG. 6B shown below, it is assumed that the electronic device 50 is a mobile terminal device such as a mobile phone or a tablet terminal.

As shown in FIG. 6B, the electronic device 50 includes an electronic circuit 60. The electronic circuit 60 includes, for example, a controller 50a, a transmission / reception unit 50b, a key input unit 50c, and a microphone input unit 50d. The electronic circuit 60 is connected to the sound generator 1 and has a function of outputting an audio signal to the sound generator 1. The sound generator 1 generates sound based on the sound signal input from the electronic circuit 60.

Moreover, the electronic device 50 includes a display unit 50e, an antenna 50f, and the sound generator 1. Further, the electronic device 50 includes a housing 40 that accommodates these devices.

6B shows a state in which each device including the controller 50a is accommodated in one housing 40, but the accommodation form of each device is not limited. In the present embodiment, it is sufficient that at least the electronic circuit 60 and the sound generator 1 are accommodated in one housing 40.

The controller 50 a is a control unit of the electronic device 50. The transmission / reception unit 50b transmits / receives data via the antenna 50f based on the control of the controller 50a.

The key input unit 50c is an input device of the electronic device 50 and accepts a key input operation by an operator. The microphone input unit 50d is also an input device of the electronic device 50, and accepts a voice input operation by an operator.

The display unit 50e is a display output device of the electronic device 50, and outputs display information based on the control of the controller 50a.

The sound generator 1 operates as a sound output device in the electronic device 50. The sound generator 1 is connected to the controller 50a of the electronic circuit 60, and emits sound upon application of a voltage controlled by the controller 50a.

In FIG. 6B, the electronic device 50 is described as a portable terminal device. However, the electronic device 50 is not limited to the type of the electronic device 50, and may be applied to various consumer devices having a function of emitting sound. . For example, flat-screen TVs and car audio devices can of course be used for products having a function of emitting sound such as "speak", for example, various products such as vacuum cleaners, washing machines, refrigerators, microwave ovens, etc. .

As described above, the sound generator according to the embodiment includes an exciter (piezoelectric element), a flat vibrating body, and a damping material. The exciter vibrates when an electric signal is input thereto. The vibrator is provided with the exciter, and vibrates with the exciter by the vibration of the exciter. The damping material is attached to the main surface of the vibrator on the side opposite to the side on which the exciter is attached.

Therefore, according to the sound generator according to the embodiment, it is possible to obtain a favorable frequency characteristic of sound pressure.

In the above-described embodiment, the case where the shape of the inner region of the frame is a substantially rectangular shape is taken as an example, and it may be a polygon, but is not limited thereto, and is not limited to a circle or an ellipse. It may be a shape.

Further, in the above-described embodiment, the case where the shape of the damping material when viewed in plan is an example of a substantially rectangular shape, but the shape of the damping material is not limited.

In the above-described embodiment, the case where the resin layer is formed so as to cover the piezoelectric element and the vibrating body in the frame of the frame has been described as an example. However, such a resin layer is not necessarily formed.

Further, in the above-described embodiment, the case where the diaphragm is configured by a thin film such as a resin film has been described as an example. However, the present invention is not limited to this. For example, the diaphragm may be configured by a plate-like member.

In the above-described embodiment, the case in which the support body that supports the vibrating body is a frame body and supports the periphery of the vibrating body has been described as an example, but the present invention is not limited thereto. For example, it is good also as supporting only the both ends of the longitudinal direction or a transversal direction of a vibrating body.

In the above-described embodiment, the case where the exciter is a piezoelectric element has been described as an example. However, the exciter is not limited to the piezoelectric element, and has a function of vibrating when an electric signal is input. What is necessary is just to have.

For example, an electrodynamic exciter, an electrostatic exciter, or an electromagnetic exciter well known as an exciter for vibrating a speaker may be used.

The electrodynamic exciter is such that an electric current is passed through a coil disposed between the magnetic poles of a permanent magnet to vibrate the coil. The electrostatic exciter is composed of two metals facing each other. A bias and an electric signal are passed through the plate to vibrate the metal plate, and an electromagnetic exciter is an electric signal that is passed through the coil to vibrate a thin iron plate.

Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1, 1 'Sound generator 2 Frame body 3 Diaphragm 3a Vibration body 5

Piezoelectric element

5a, 5b, 5c, 5d Piezoelectric layer 5e

Internal electrode layer

5f, 5g

Surface electrode layer

5h, 5j External electrode 6a, 6b Lead terminal 7

Resin layer

8, 8a to 8f Damping material 20 Sound generator 30, 40 Case 50 Electronic device 50a Controller 50b Transmission / reception unit 50c Key input unit 50d Microphone input unit 50e Display unit 50f Antenna 60 Electronic circuit P peak h1, h2 thickness

Claims

An exciter that vibrates upon receipt of an electrical signal;
A flat vibrator that is attached to the exciter and vibrates with the exciter by vibration of the exciter;
An acoustic generator, comprising: a damping material attached to a main surface of the vibrating body opposite to a side on which the exciter is attached.
The acoustic generator according to claim 1, wherein the damping material is attached to a region where the exciter exists when viewed through a plane.
The acoustic generator according to claim 2, wherein the damping material is attached so as to cover the entire region where the exciter is present when seen through a plane.
The acoustic generator according to claim 1, wherein the damping material is attached to a region where the exciter does not exist when seen through a plane.
The damping material according to claim 1, wherein a plurality of the damping materials are attached, and are attached to both a region where the exciter is present and a region where the exciter is not present when seen in a plan view. Sound generator.
The damping material is attached so that at least a part of the damping material overlaps a region along the outline of the exciter among regions where the exciter exists when seen through a plane. The sound generator according to claim 2 or 5.
2. The acoustic generator according to claim 1, wherein the damping material is attached so as to straddle both an area where the exciter exists and an area where the exciter does not exist when viewed through a plane.
A support for supporting the vibrating body;
The sound generator according to claim 4, wherein the damping material is attached to a region along a boundary between the support body and the vibrating body.
The acoustic generator according to any one of claims 2, 4, and 7, wherein a plurality of the damping materials are attached.
10. The sound generator according to claim 5, wherein the thickness of at least one of the damping materials is different from the thickness of the other damping materials.
11. The sound generator according to claim 1, wherein the vibrating body is made of a resin film.
The acoustic generator according to any one of claims 1 to 11, wherein the exciter is a bimorph multilayer piezoelectric element.
An acoustic generator according to any one of claims 1 to 12;
A sound generator comprising: a housing for housing the sound generator.
An acoustic generator according to any one of claims 1 to 12;
An electronic circuit connected to the acoustic generator;
A housing for housing the electronic circuit and the acoustic generator;
An electronic apparatus having a function of generating sound from the sound generator.