JP2014039093A - Acoustic generator, acoustic generating device, and electric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the variation in sound pressure on frequency characteristic of sound pressure.SOLUTION: An acoustic generator includes: a film 3; a frame member 5a provided in a peripheral part of the film 3; a piezoelectric element 1 provided in the film 3 within the frame member 5; and a resin layer 20 filled within the frame member 5 so that the piezoelectric element 1 is embedded. The frame member 5a is formed so that L/W ratio of length L and width W of an area, which is formed inside the frame member 5a, is 1.4-2.33.

Description

  The present invention relates to a sound generator, a sound generator, and an electronic apparatus.

  Conventionally, an acoustic generator typified by a piezoelectric speaker has been known as a small-sized, low-current driving acoustic device using a piezoelectric body as an electroacoustic transducer, for example, a small electronic device such as a mobile computing device. It is used as an integrated sound generator.

  In general, an acoustic generator using a piezoelectric body as an electroacoustic transducer has a structure in which a piezoelectric element in which an electrode made of a silver thin film or the like is attached to a metal diaphragm. The sound generation mechanism of an acoustic generator using a piezoelectric body as an electroacoustic transducer generates a shape distortion in the piezoelectric element by applying an AC voltage to both sides of the piezoelectric element, and the shape distortion of the piezoelectric element is made of a metal diaphragm. The sound is generated by transmitting to and vibrating.

  However, an acoustic generator having a structure in which a piezoelectric element is bonded to a metal diaphragm generates an area bending vibration by restraining a piezoelectric element that spreads and vibrates with a metal plate whose area does not change. It has been difficult to provide sound pressure characteristics with low conversion efficiency, small size, and low resonance frequency.

  In response to such a problem, the present applicant has proposed an acoustic generator in which a resin film is used as a diaphragm instead of a metal diaphragm (see, for example, Patent Document 1).

  In this acoustic generator, a bimorph-type laminated piezoelectric element is sandwiched between a pair of resin films in the thickness direction, and this resin film is fixed to a frame member in a tensioned state. Thereby, acoustic conversion efficiency is improved, and generation | occurrence | production of a high sound pressure is enabled.

JP 2010-177867 A

  However, the above-described acoustic generator is required to improve variation in sound pressure in the frequency characteristic of sound pressure.

  This invention is made | formed in view of the above, Comprising: It aims at providing the sound generator, sound generator, and electronic device which can reduce the dispersion | variation in the sound pressure in the frequency characteristic of a sound pressure.

  The acoustic generator of the present invention includes a film, a frame member provided on an outer peripheral portion of the film, a piezoelectric element provided on the film in a frame of the frame member, and the piezoelectric element embedded in the piezoelectric element. The frame member has a resin layer filled in the frame of the frame member, and the frame member is formed so that the ratio of the length and width of the region formed inside the frame member is 1.4 to 2.33 Is done.

  According to one aspect of the sound generator according to the present invention, there is an effect that variation in sound pressure in the frequency characteristic of sound pressure can be reduced.

FIG. 1A is a plan view showing a sound generator of a first form. FIG. 1B is a cross-sectional view illustrating a sound generator according to the first embodiment. FIG. 2 is a plan view showing a second type of sound generator. FIG. 3 is a plan view showing a third embodiment of the sound generator. FIG. 4 is a graph showing an example of frequency characteristics of sound pressure. FIG. 5 is a graph showing an example of frequency characteristics of sound pressure. FIG. 6 is a graph illustrating an example of frequency characteristics of sound pressure. FIG. 7 is a graph showing an example of frequency characteristics of sound pressure. FIG. 8 is a graph showing an example of frequency characteristics of sound pressure. FIG. 9 is a graph showing an example of frequency characteristics of sound pressure. FIG. 10 is a graph illustrating an example of frequency characteristics of sound pressure. FIG. 11 is a graph showing an example of frequency characteristics of sound pressure.

  Hereinafter, embodiments of a sound generator, a sound generator, and an electronic device according to the present invention will be described in detail with reference to the drawings. Note that this embodiment does not limit the present invention. And each form illustrated below as embodiment can be suitably combined in the range which does not contradict the shape and dimension of each member which comprise an acoustic generator.

(1) 1st form [structure of a sound generator]
First, the 1st form of an acoustic generator is demonstrated based on FIG. 1A and FIG. 1B. FIG. 1A is a plan view showing a sound generator of the first form, and FIG. 1B is a cross-sectional view showing the sound generator of the first form. FIG. 1B shows a cross-sectional view along the line AA shown in FIG. 1A. Moreover, in FIG. 1B, in order to facilitate understanding, the thickness direction (y direction) of the multilayer piezoelectric element 1 is shown enlarged.

  1A and 1B includes a laminated piezoelectric element 1 on the upper surface of a film 3 that serves as a support plate and is sandwiched between a pair of frame-shaped frame members 5. ing. In other words, as shown in FIG. 1B, the sound generator of the first form is configured such that the film 3 is held in the first and second frame members 5a and 5b by holding the film 3 in a tensioned state. The laminated piezoelectric element 1 is disposed on the upper surface of the film 3 and is fixed to the second frame members 5a and 5b.

  Among these, the piezoelectric element 1 is formed in a plate shape and the upper and lower main surfaces are formed in a rectangular shape. The piezoelectric element 1 includes a laminate 13 in which piezoelectric layers 7 made of four ceramic layers and three internal electrode layers 9 are alternately laminated, and surface electrodes formed on both upper and lower surfaces of the laminate 13. The layers 15a and 15b and a pair of external electrodes 17 and 19 provided at both ends in the longitudinal direction x of the laminate 13 are included.

  The external electrode 17 is connected to the surface electrode layers 15a and 15b and one internal electrode layer 9b. The external electrode 19 is connected to the two internal electrode layers 9a and 9c. The piezoelectric layer 7 is polarized as shown by an arrow in FIG. 1B. When the piezoelectric layers 7a and 7b contract, the piezoelectric layers 7c and 7d extend, or the piezoelectric layers 7a and 7b extend. In this case, a voltage is applied to the external electrodes 17 and 19 so that the piezoelectric layers 7c and 7d contract.

  Upper and lower end portions of the external electrode 19 are extended to the upper and lower surfaces of the multilayer body 13 to form folded external electrodes 19a, respectively. These folded external electrodes 19a are surface electrodes formed on the surface of the multilayer body 13. A predetermined distance is extended between the surface electrode layers 15a and 15b so as not to contact the layers 15a and 15b.

  The four piezoelectric layers 7 and the three internal electrode layers 9 are fired at the same time in a stacked state, and the surface electrode layers 15 a and 15 b are the stacked bodies 13. Thereafter, the paste is applied and baked.

  Further, in the piezoelectric element 1, the main surface on the film 3 side and the film 3 are joined by an adhesive layer 21. The thickness of the adhesive layer 21 between the piezoelectric element 1 and the film 3 is 20 μm or less. In particular, the thickness of the adhesive layer 21 is preferably other than 10 μm. Thus, when the thickness of the adhesive layer 21 is 20 μm or less, the vibration of the laminated body 13 is easily transmitted to the film 3.

  As the adhesive for forming the adhesive layer 21, known ones such as an epoxy resin, a silicon resin, and a polyester resin can be used. As a method for curing the resin used for the adhesive, the vibrating body can be produced by using any method such as thermosetting, photocuring or anaerobic curing.

  Furthermore, in the acoustic generator of the first form, the resin layer 20 is formed by filling the inside of the frame member 5a with the resin so that the piezoelectric element 1 is embedded. In FIG. 1A, the resin layer is not shown for easy understanding.

  For example, an epoxy resin, an acrylic resin, a silicon resin, rubber, or the like can be used for the resin layer 20. The resin layer 20 is preferably applied in a state of completely covering the piezoelectric element 1 from the viewpoint of suppressing spurious. Further, since the film 3 serving as a support plate also vibrates integrally with the piezoelectric element 1, the region of the film 3 that is not covered with the piezoelectric element 1 is similarly covered with the resin layer 20.

  As described above, in the acoustic generator of the first embodiment, by embedding the piezoelectric element 1 with the resin layer 20, it is possible to induce an appropriate damping effect against the peak dip associated with the resonance phenomenon of the piezoelectric element 1. Such a damping effect can suppress the resonance phenomenon and suppress the peak dip. As a result, the frequency dependence of the sound pressure can be reduced.

  As the piezoelectric layer 7, existing piezoelectric ceramics such as lead-free piezoelectric materials such as lead zirconate (PZ), lead zirconate titanate (PZT), Bi layered compounds, and tungsten bronze structure compounds can be used. . The thickness of the piezoelectric layer 7 is set to 10 to 100 μm from the viewpoint of low voltage driving.

  The internal electrode layer 9 desirably includes a metal component composed of silver and palladium and a material component constituting the piezoelectric layer 7. By including the ceramic component constituting the piezoelectric layer 7 in the internal electrode layer 9, the stress due to the difference in thermal expansion between the piezoelectric layer 7 and the internal electrode layer 9 can be reduced, and the piezoelectric element 1 without stacking failure can be obtained. Can do. The internal electrode layer 9 is not particularly limited to a metal component composed of silver and palladium, but may be another metal component, and is limited to a material component constituting the piezoelectric layer 7 as a ceramic component. It may be other ceramic components.

  The surface electrode layers 15a and 15b and the external electrodes 17 and 19 preferably contain a glass component in a metal component made of silver. By containing the glass component in this way, a strong adhesion can be obtained between the piezoelectric layer 7 and the internal electrode layer 9 and the surface electrode layer 15 or the external electrodes 17 and 19.

  As shown in FIG. 1B, the frame member 5 has a rectangular shape, and is formed by bonding two rectangular frame-shaped frame members 5a and 5b, and the film 3 is interposed between the frame members 5a and 5b. Are fixed in a state where a tension is applied. The frame members 5a and 5b are made of stainless steel having a thickness of 100 to 1000 μm, for example. The material of the frame members 5a and 5b is not limited to stainless steel and may be any material that is more difficult to deform than the resin layer 20. For example, hard resin, plastic, engineering plastic, ceramics, etc. can be used. In the form, the material and thickness of the frame members 5a and 5b are not particularly limited. Further, the frame shape is not limited to the rectangular shape, and a part of the inner peripheral portion or the outer peripheral portion may be curved or square.

  The film 3 is fixed to the frame members 5a and 5b in a state where the film 3 is tensioned in the surface direction by sandwiching the outer peripheral portion of the film 3 between the frame members 5a and 5b, and the film 3 serves as a diaphragm. Plays. The thickness of the film 3 is, for example, 10 to 200 μm, and the film 3 is made of, for example, a resin such as polyethylene, polyimide, polypropylene, polystyrene, or tenn, or paper made of pulp, fiber, or the like. The peak dip can be suppressed by using these materials.

[L / W ratio]
Next, the ratio between the length L and the width W of the region formed inside the frame member 5a included in the sound generator according to the first embodiment of the present embodiment will be described. In the present embodiment, a rectangle is illustrated as an example of the shape of the inner peripheral portion when the frame member 5a is viewed from the stacking direction. The part can be curved.

  Here, in the acoustic generator of the first embodiment, as shown in FIG. 1A, the ratio of the length L and the width W of the rectangular region formed inside the frame member 5a is 1.4 to 2.33. Thus, the inner peripheral portion of the frame member 5a is formed. Hereinafter, the ratio obtained by dividing the length L of the region formed in the inner peripheral portion of the frame member 5a by the width W may be referred to as “L / W ratio”.

  As described above, when the L / W ratio is 1.4 to 2.33, the L / W ratio is smaller than 1.4 or the L / W ratio is larger than 2.33. However, a large damping effect can be induced with respect to the peak dip associated with the resonance phenomenon of the piezoelectric element 1. Details will be described later with reference to FIGS. 4 to 9. In particular, when the L / W ratio is set to a value of about 1.8, a more remarkable damping effect can be obtained. With this damping effect, the acoustic generator of the first embodiment can suppress the resonance phenomenon and suppress the peak dip to a small value.

  Therefore, according to the sound generator of the first form, it is possible to reduce the variation of the sound pressure in the frequency characteristic of the sound pressure.

[Production method]
A method for producing the acoustic generator of the present invention will be described.

  First, the bimorph type piezoelectric element 1 is prepared. In the piezoelectric element 1, a binder, a dispersant, a plasticizer, and a solvent are kneaded with a piezoelectric material powder to produce a slurry. As the piezoelectric material, any of lead-based and non-lead-based materials can be used.

  Next, the slurry can be formed into a sheet shape to obtain a green sheet, and an internal electrode paste is printed on the green sheet to form an internal electrode pattern, and the green sheet on which the electrode pattern is formed 3 Laminated sheets are laminated, and only a green sheet is laminated on the uppermost layer to produce a laminated molded body.

  Next, the laminated body 13 can be obtained by degreasing and firing the laminated molded body and cutting it to a predetermined size. The laminated body 13 processes the outer peripheral part as necessary, prints the paste of the surface electrode layers 15a and 15b on the main surface in the lamination direction of the piezoelectric layer 7 of the laminated body 13, and then continues in the longitudinal direction of the laminated body 13 The bimorph piezoelectric element 1 shown in FIGS. 1A and 1B can be obtained by printing the external electrodes 17 and 19 on both end faces of x and baking the electrodes at a predetermined temperature.

  Next, in order to impart piezoelectricity to the bimorph type piezoelectric element 1, a DC voltage is applied through the surface electrode layers 15 a and 15 b or the external electrodes 17 and 19, so that the piezoelectric layer 7 of the bimorph type piezoelectric element 1 Perform polarization. Such polarization is performed by applying a DC voltage so as to be in the direction indicated by the arrow in FIG. 1B.

  Next, the film 3 which becomes a support is prepared, the outer peripheral portion of the film 3 is sandwiched between the frame members 5a and 5b, and the film 3 is fixed in a tensioned state. Thereafter, an adhesive is applied to the film 3, the surface electrode 15a side of the bimorph type piezoelectric element 1 is pressed onto the film 3, and then the adhesive is cured by irradiation with heat or ultraviolet rays. Then, the acoustic generator of the first form can be obtained by pouring resin inside the frame member 5a, completely embedding the bimorph type piezoelectric element 1, and curing the resin layer 20.

  The acoustic generator configured as described above has an inner peripheral portion of the frame member 5a so that the ratio of the length L and the width W of the region formed inside the frame member 5a is 1.4 to 2.33. Is formed. For this reason, the damping is larger with respect to the peak dip associated with the resonance phenomenon of the piezoelectric element 1 than the acoustic generator having an L / W ratio smaller than 1.4 or the acoustic generator having an L / W ratio larger than 2.33. Can induce effects. As a result of suppressing the resonance phenomenon and reducing the peak dip to a small extent by such a damping effect, it is possible to reduce variations in sound pressure in the frequency characteristics of sound pressure.

(2) Second form Next, a second form of the sound generator of the present embodiment will be described. FIG. 2 is a plan view showing a second type of sound generator. The acoustic generator of the second form shown in FIG. 2 is the length of the boundary line with the film 3 formed on the inner periphery of the frame member 5a, as compared with the acoustic generator of the first form shown in FIG. 1A. The difference is that the direction boundary is formed by a curve of a predetermined curvature. For example, as shown in FIG. 2, it is formed of a curved line that is concavely curved inside the frame member 5a.

  Here, the reason why the boundary line in the length direction is formed as a curve is that asymmetry can be increased as compared with the case where the inner peripheral portion of the frame member 5a is rectangular. That is, according to the shape of FIG. 2, by suppressing the degeneration of the resonance frequency and dispersing, the height of the resonance peak can be suppressed and the width can be widened. By increasing the asymmetry in this way, the resonance phenomenon can be suppressed and the peak dip can be suppressed smaller than in the case where only the L / W ratio is in the optimum range of 1.4 to 2.33. For this reason, according to the sound generator of the 2nd form, variation of sound pressure in the frequency characteristic of sound pressure can be reduced more effectively.

  Furthermore, as shown in FIG. 2, the boundary line in the length direction is curved so that the distance between the inner edge and the outer edge of the frame member 5a becomes closer as the distance from the corner to the center of the frame member 5a becomes closer. In this way, the boundary line in the length direction of the inner peripheral portion of the frame member 5a is curved to the outer peripheral portion side even if the area of the film 3 that vibrates integrally with the piezoelectric element 1 changes. This is because the width of the frequency region in which the sound pressure is obtained by the bending and bending vibration of the film 3, that is, the so-called reproduction frequency band, is maintained at the same bandwidth as when the inner peripheral portion of the frame member 5a is rectangular.

  The L / W ratio is 1.4 to 2.33 as in the first embodiment. Here, the length L and the width W represent the longest distance of the distance in the length direction or the distance in the width direction. In the example of FIG. 2, the distance between the line segments in the width direction is used as the value of the length L, and the distance between the central portions of the curve is used as the value of the width W.

(3) 3rd form Then, the acoustic generator of the 3rd form of this embodiment is demonstrated. FIG. 3 is a plan view showing a third embodiment of the sound generator. Compared with the acoustic generator of the first embodiment shown in FIG. 1A, the acoustic generator of the third embodiment shown in FIG. 3 applies a load to the film 3 by pressing the film 3 to a predetermined position on the surface of the resin layer 20. The difference is that the load member 30 to be applied is further bonded. The L / W ratio is 1.4 to 2.33 as in the first embodiment.

  The load member 30 desirably has a physical property that is soft and easily deformed. For example, a rubber material such as urethane rubber can be employed. In particular, a porous rubber material such as urethane foam can be suitably used.

  Here, the load member 30 is attached to a position on the surface of the resin layer 20 where the amplitude is maximized by a resonance phenomenon caused by the vibrating body including the film 3 and the resin layer 20 that vibrate integrally with the piezoelectric element 1. Is preferred. For example, the central portion of the film 3 has the maximum amplitude in a plurality of frequency bands included in a frequency region where a predetermined sound pressure can be obtained by vibration of the vibrating body. 30b are attached.

  In this way, by attaching the load members 30a and 30b to the position including the central portion of the film 3, the third sound generation is caused as compared with the case where only the L / W ratio is in the optimum range of 1.4 to 2.33. A sudden change in amplitude can be reduced in a plurality of frequency bands included in the reproduction frequency band of the device, and the amplitude in each frequency band can be flattened. For this reason, according to the sound generator of the 3rd form, variation of sound pressure in the frequency characteristic of sound pressure can be reduced more effectively. Here, the case where the load member 30 is provided at a position where the amplitude is maximum in a plurality of frequency bands included in the reproduction frequency band of the third sound generator is illustrated, but the amplitude is maximum in at least one frequency band. By attaching the load member 30 at a position to be, the amplitude of the frequency band can be flattened.

  Furthermore, the load members 30 a and 30 b are formed of a vibrating body that vibrates integrally with the piezoelectric element 1, that is, a material that is softer and more easily deformed than the film 3 and the resin layer 20. Here, “soft and easily deformed” means that the film 3 and the resin layer 20 are less elastic and rigid and easily deformed by an external force. As described above, the load member 30a, 30b is made of a material that is softer than the vibrator and easily deformed, and thus the vibrator including the piezoelectric element 1, the film 3, the resin layer 20, and the like in the portion to which the load member 30 is attached. It is possible to reduce the hindrance to the deformation and to smoothly deform the vibrating body. Thereby, the distortion of the sound generated by the vibration of the vibrating body can be reduced.

(4) Fourth Embodiment The embodiments of the present invention have been described so far, but the present invention may be implemented in various different forms other than the above-described embodiments. Therefore, other embodiments included in the present invention will be described below.

[Scope of application]
For example, in the first embodiment, the bimorph type piezoelectric element is exemplified, but the present invention is not limited to this. That is, the present invention is not limited to the case where the piezoelectric element is a bimorph type, and even if it is a unimorph type, the same effect can be obtained by employing the same L / W ratio as in the first embodiment. .

[Speaker device]
For example, the sound generator described in the first to third embodiments is configured as a sound generator, a so-called “speaker device”, by being housed in a housing that houses the sound generator, a so-called resonance box. You can also. For example, if it can be configured as a large-sized speaker device used for televisions, personal computers, etc., it can be a medium-sized or small-sized device mounted on mobile terminals such as smartphones, mobile phones, PHS (Personal Handyphone System), and PDA (Personal Digital Assistants). It can also be configured as a speaker device. In addition, a speaker apparatus is not limited to said use, It can comprise as a speaker apparatus mounted in arbitrary electronic devices, such as a vacuum cleaner, a washing machine, and a refrigerator.

[Electronics]
The acoustic generator described in the first to third embodiments includes at least an electronic circuit connected to the acoustic generator and a housing that houses the electronic circuit and the acoustic generator. The electronic device can also be configured as an electronic device having a function of generating sound from the sound generator. Examples of such electronic devices include televisions and personal computers, and various mobile terminals.

  In this embodiment, in order to clarify that the optimum range of the L / W ratio is 1.4 to 2.33, the frequency characteristics of sound pressure when various L / W ratios are employed will be described. To do. 4 to 9 are graphs showing examples of frequency characteristics of sound pressure. 4 to 9 show graphs of frequency characteristics of sound pressure related to the sound generator with the load member 30 shown in FIG.

  The graph of FIG. 4 indicates that of an acoustic generator with an L / W ratio of “1.33”, and the graph of FIG. 5 indicates that of an acoustic generator with an L / W ratio of “1.4”. The graph of FIG. 6 indicates that of an acoustic generator having an L / W ratio of “1.83”, and the graph of FIG. 7 illustrates an acoustic generator having an L / W ratio of “2.00”. The graph of FIG. 8 indicates that of an acoustic generator having an L / W ratio of “2.33”, and the graph of FIG. 9 has an L / W ratio of “2.5”. It refers to the sound generator. 4 to 9, the horizontal axis indicates the frequency [kHz], and the vertical axis of the graph indicates the sound pressure [dB].

  Of the six graphs shown in FIGS. 4 to 9, the L / W ratio of the sound generator is not in the optimum range of 1.4 to 2.33. The graphs of FIGS. The variation in sound pressure is larger than that in the graphs of FIGS. 5 to 8 included in the optimum range of the W ratio of 1.4 to 2.33.

  More specifically, as shown in FIG. 4, when the L / W ratio of the sound generator is 1.33, a peak dip reaching 30.6 dB at the maximum occurs. In the example shown in FIG. 4, it can be seen that a peak dip exceeding 25 dB occurs in the frequency band 41 before 1 kHz and the frequency band 42 of 2 kHz to 4 kHz. Furthermore, in the example shown in FIG. 4, in the frequency band 43 of 7 kHz to 10 kHz, the sound pressure is reduced to about 80 dB. Further, as shown in FIG. 9, when the L / W ratio of the sound generator is 2.5, a peak dip reaching 31.2 dB at maximum occurs. In the example shown in FIG. 9, it can be seen that a peak dip of about 30 dB occurs in the frequency band 91 before 1 kHz and the frequency band 92 of 2 kHz to 4 kHz. As shown in FIGS. 4 and 9, when the L / W ratio of the sound generator is not in the optimum range of 1.4 to 2.33, peak dip exceeding 25 dB occurs in a plurality of frequency bands. The resonance frequency due to the resonance phenomenon becomes peaky and the flatness of the frequency characteristics is also deteriorated.

  On the other hand, as shown in FIG. 5, when the L / W ratio of the acoustic generator is 1.4, only a peak dip of up to 16 dB occurs. In the example shown in FIG. 5, it can be seen that the peak dip in the frequency band 51 before 1 kHz and the frequency band 52 of 2 kHz to 4 kHz is improved to about 15 dB compared to the examples shown in FIGS. 4 and 9. Further, in the example shown in FIG. 5, it can be seen that a sound pressure of about 95 dB is obtained in the frequency band 53 of 7 kHz to 10 kHz as compared with the examples shown in FIGS. 4 and 9. Further, as shown in FIG. 7, even when the L / W ratio of the sound generator is 2.00, only a peak dip of up to 17.6 dB occurs. In the example shown in FIG. 7, it can be seen that the peak dip in the frequency band 71 before 1 kHz and the frequency band 72 of 2 kHz to 4 kHz is improved to about 15 dB compared to the examples shown in FIGS. 4 and 9. Furthermore, in the example shown in FIG. 7, it can be seen that a sound pressure of about 95 dB is obtained even in the frequency band 73 of 7 kHz to 10 kHz, compared to the examples shown in FIGS. Furthermore, as shown in FIG. 8, even when the L / W ratio of the sound generator is 2.33, only a peak dip of up to 20.2 dB occurs. In the example shown in FIG. 8, it can be seen that the peak dip in the frequency band 81 before 1 kHz and the frequency band 82 of 2 kHz to 4 kHz is improved to about 20 dB compared to the examples shown in FIGS. Furthermore, in the example shown in FIG. 8, it can be seen that a sound pressure of around 95 dB is obtained even in the frequency band 83 of 7 kHz to 10 kHz, compared to the examples shown in FIGS.

  In addition, as shown in FIG. 6, when the L / W ratio of the sound generator is 1.83, the peak dip can be suppressed to 4.6 dB at the maximum. In the example shown in FIG. 6, not only the examples shown in FIGS. 4 and 9 but also the frequency band 61 of 1 kHz before and the frequency band of 2 kHz to 4 kHz as compared with the examples shown in FIGS. 5, 7, and 8. It can be seen that the peak dip at 62 is dramatically improved to about 5 dB. Furthermore, in the example shown in FIG. 6, it can be seen that a sound pressure of about 95 dB is obtained in the frequency band 63 of 7 kHz to 10 kHz as compared with the examples shown in FIGS. 4 and 9.

  As described above, the sound generator with the L / W ratio of 1.4 to 2.33 shown in FIGS. 5 to 8 generates sound with the L / W ratio shown in FIG. 4 smaller than 1.4. 9 and the acoustic generator having an L / W ratio larger than 2.33 shown in FIG. 9, the flatness of the frequency characteristics is improved by suppressing the resonance phenomenon, and the peak dip can be suppressed to be small, and the frequency of the sound pressure is reduced. It can be said that it is possible to reduce variation in sound pressure in the characteristics.

  In addition, although the Example demonstrated the case where the load member 30 was provided in the sound generator here, L / W ratio is 1.4-2.33 also when the load member 30 is not provided. Of the sound pressure in the frequency characteristics of the sound pressure as compared with the sound generator having an L / W ratio smaller than 1.4 and the sound generator having an L / W ratio larger than 2.33. Needless to say, this can be reduced.

  By the way, in said Example 1, although the Example of the sound generator provided with the load member 30 was demonstrated, in a present Example, the boundary line with the film 3 formed in the inner peripheral part of the frame member 5a is demonstrated. The difference in the frequency characteristics of the sound pressure between the acoustic generator in which the boundary line in the length direction is formed by a curve with a predetermined curvature and the acoustic generator in which the inner peripheral portion of the frame member 5a is rectangular will be described.

  10 and 11 are graphs showing examples of frequency characteristics of sound pressure. FIG. 10 shows the frequency characteristics of sound pressure related to a sound generator whose inner periphery of the frame member 5a is rectangular, while in FIG. 11, the boundary line in the length direction is formed by a curve. The frequency characteristics of sound pressure for the sound generator are shown. 10 and 11, the frequency of the sound pressure measured by the sound generator having the frame member 5a having the L / W ratio “2.0” having the length L “60 mm” and the width W “30 mm” is shown. Characteristics are shown. The horizontal axis of the graph indicates frequency [kHz], and the vertical axis of the graph indicates sound pressure [dB].

  As shown in FIG. 10, in the case of the acoustic generator in which the inner periphery of the frame member 5a is rectangular, a peak dip exceeding 20 dB occurs in the frequency band 101 before 1 kHz, and the frequency band 102 of 2 kHz to 4 kHz. It can also be seen that a peak dip of about 15 dB occurs at. Furthermore, in the example shown in FIG. 10, the sound pressure is reduced to around 90 dB in the frequency band of 7 kHz to 10 kHz. On the other hand, as shown in FIG. 11, in the case of an acoustic generator in which the boundary line in the length direction is a curve, the peak dip in the frequency band 111 before 1 kHz and the frequency band 112 from 2 kHz to 4 kHz is up to about 5 dB. It can be seen that it has improved dramatically. Furthermore, in the example shown in FIG. 11, it can be seen that a sound pressure of about 95 dB is obtained even in the frequency band of 7 kHz to 10 kHz.

  As described above, the acoustic generator in which the boundary line in the length direction shown in FIG. 11 is formed in a curve is more resonant than the acoustic generator in which the inner peripheral portion of the frame member 5a shown in FIG. 10 is rectangular. It can be said that the suppression of the phenomenon improves the flatness of the frequency characteristics and can suppress the peak dip to be small, thereby reducing the variation of the sound pressure in the frequency characteristics of the sound pressure.

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 3 Film 5, 5a, 5b Frame member 7, 7a, 7b, 7c, 7d Piezoelectric layer 9, 9a, 9b, 9c Internal electrode layer 13 Laminated body 15a, 15b Surface electrode layer 17, 19 External electrode 20 Resin Layer 30, 30a, 30b Load member x Longitudinal direction of laminated body y Thickness direction of piezoelectric element

Claims (6)

With film,
A frame member provided on the outer periphery of the film;
A piezoelectric element provided on the film in the frame of the frame member;
A resin layer filled in the frame of the frame member so as to embed the piezoelectric element;
The sound generator, wherein the frame member is formed so that a ratio of a length and a width of a region formed inside the frame member is 1.4 to 2.33.   The acoustic generator according to claim 1, wherein a boundary line in a length direction among the boundary lines with the film formed in an inner region of the frame member is formed by a curve having a predetermined curvature.   3. The curve according to claim 2, wherein the boundary line in the length direction is formed such that the distance between the inner edge and the outer edge of the frame member becomes closer as the distance from the corner to the center of the frame member becomes closer. Sound generator.   The acoustic generator according to claim 1, wherein a load member that applies a load to the film by pressing the film to a predetermined position on the surface of the resin layer is further bonded. The sound generator according to any one of claims 1 to 4,
And a housing for housing the sound generator. The sound generator according to any one of claims 1 to 4,
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.

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