JP4564879B2 - Piezoelectric vibration element and voice conversion device including the piezoelectric vibration element - Google Patents

Description

  The present invention relates to a piezoelectric vibration element, and more particularly, to a piezoelectric vibration element that can be used as a material such as a speaker, a receiver, or a microphone, and a sound conversion device including the piezoelectric vibration element.

  In small electronic devices such as mobile phones, PDAs, notebook computers, etc., it is small and lightweight as a material for speakers, receivers or microphones for voice input / output, energy saving, and magnetostriction when used in conjunction with liquid crystal display devices. The piezoelectric vibration element is used from the feature that does not occur.

  A piezoelectric speaker made of a piezoelectric vibration element is one in which a piezoelectric ceramic plate as a piezoelectric element is attached to a vibration plate, and a voltage is applied to the piezoelectric ceramic plate to generate vibration and generate sound.

  The conventional piezoelectric speaker has a structure in which the peripheral portion of the diaphragm is fixed to the frame, and the diaphragm is constrained by the frame. There was a problem that sufficient sound pressure could not be obtained in the region.

  In order to solve the above problem, a piezoelectric speaker having a configuration in which a diaphragm is supported by adhering a resin sheet to the periphery of the diaphragm and sandwiching the resin sheet between frames is proposed (for example, Patent Document 1).

In this technique, since the diaphragm is not pressed by the frame, vibration is not suppressed by the frame. For this reason, the degree to which the vibration of the diaphragm is suppressed becomes small, and it becomes possible to obtain a wide-band vibration.
JP 11-113094 A

  The present inventor conducted various experiments for the purpose of improving the sound pressure and sound quality in a wide band, and as a result, by changing the shape of the resin sheet and the piezoelectric vibration element, the sound pressure in the wide band was secured and the flatness was improved. As a result, it has been found that an excellent frequency characteristic can be obtained, and the present invention has been achieved.

  An object of the present invention is to provide a piezoelectric vibration element with improved sound pressure and sound quality in a wide band, and a sound conversion device including the piezoelectric vibration element.

  A piezoelectric vibration element according to claim 1 of the present invention includes a vibration plate and a piezoelectric element attached to the vibration plate. In the piezoelectric vibration element held by a frame, a resin sheet is provided on the vibration plate. The vibration plate is bonded and held by the frame body through the resin sheet, and the resin sheet is provided with a mounting hole in which the piezoelectric vibration element is exposed and is installed in the mounting hole. A covering portion that covers and holds a part of the piezoelectric vibration element is provided.

In this way, by adopting a configuration in which the piezoelectric vibration element is held on the frame body via the resin sheet, the piezoelectric vibration element can be supported without being constrained, so that the piezoelectric vibration element is easily vibrated and has a low frequency. It is possible to obtain vibration in a wide band including the band.
In addition, by adopting a configuration in which a part of the piezoelectric vibration element is covered with a resin sheet and held, it is possible to control the exposure of the piezoelectric vibration element, thereby obtaining flat acoustic characteristics over a wide band.

  The specific configuration of the resin sheet is as follows. The covering portion is located substantially at the center of the piezoelectric vibration element, and is formed in a shape having an arcuate outer edge on the outer peripheral portion. Of the outer edges, the opposing outer edges are formed from arcs of the same shape, and these arcs constitute a part of a virtual circle having a center point on the same virtual line.

The radius length of the virtual circle forming the arc is changed according to the size of the piezoelectric vibration element.
A connecting portion is provided between a portion of the resin sheet that covers the peripheral portion of the diaphragm and the covering portion.

  By being covered with the resin sheet having the above shape, two sets of symmetrical exposed surfaces are formed on the piezoelectric vibration element with the resin sheet interposed therebetween.

The resin sheet is preferably made of foamed silicon.

  As described above, according to the piezoelectric vibration element of the present invention, it is possible to obtain flat acoustic characteristics over a wide band. Therefore, when the piezoelectric vibration element is used in a sound conversion device such as a speaker, a receiver, or a microphone, it is possible to improve sound pressure and sound quality in these sound conversion devices.

According to the piezoelectric vibration element of the present invention, it is possible to cope with the reproduction of a wideband sound, obtain a higher sound pressure in each sound range than before, and obtain flat acoustic characteristics over a wide band.
Therefore, if the piezoelectric vibration element of the present invention is used in a sound conversion device such as a piezoelectric speaker, it is possible to generate high-quality sound.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The members, arrangements, and the like described below are not intended to limit the present invention and can be variously modified within the scope of the gist of the present invention.

  1 to 4 relate to an embodiment of the present invention. FIG. 1 is a front view of a piezoelectric speaker using the piezoelectric vibration element of the present invention. FIG. 2 is an exploded perspective view of the piezoelectric speaker of FIG. 3 is an explanatory diagram of a covering portion of the piezoelectric speaker of FIG. 1, and FIG. 4 is a graph showing frequency characteristics of the piezoelectric speaker of FIG.

  FIG. 1 shows a piezoelectric speaker 1 manufactured by using the piezoelectric vibration element of the present invention. The piezoelectric speaker 1 includes a frame body 10 and a piezoelectric vibration element 20 held by the frame body 10. ing.

  As shown in FIG. 2, the frame body 10 includes an upper frame 11 and a lower frame 12, and the upper frame 11 and the lower frame 12 are fixed by bolts 13 or the like. Although only one bolt 13 is shown in FIG. 2, the upper frame 11 and the lower frame 12 are fixed by a plurality of bolts. The frame 10 is configured so that the constituent members of the piezoelectric vibration element 20 are sandwiched between the upper frame 11 and the lower frame 12.

The piezoelectric vibration element 20 includes a vibration plate 21 and a piezoelectric ceramic plate 22 as a piezoelectric element. The diaphragm 21 is made of a metal plate such as aluminum having a thickness of about 0.2 mm.
In addition, when making the diaphragm 21 thinner, a metal plate such as 42 alloy may be used.
The material of the diaphragm 21 is not limited to the above and may be other metals. Moreover, even if it is not a metal, another material may be used as long as vibration and conduction can be ensured. For example, a thin and hard resin plate with a conductive foil attached thereto may be used.

As shown in FIGS. 1 and 2, the diaphragm 21 is formed in a polygonal shape having no circumscribed circle. The diaphragm 21 of this example is formed in an elongated octagonal shape.
The piezoelectric ceramic plate 22 is formed to a thickness of about 0.1 mm and is attached to the central portion of the vibration plate 21.

  The piezoelectric ceramic plate 22 of this example is formed in a rectangular shape. The piezoelectric ceramic plate 22 is attached to one side or both sides of the vibration plate 21. In this example, the piezoelectric ceramic plate 22 is attached to one side of the vibration plate 21.

By making the diaphragm 21 have the above shape, a frequency characteristic close to flat with a wider band than before can be obtained.
The reason for this is that the vibration energy transmitted from the piezoelectric ceramic plate 22 to the vibration plate 21 is generated in various types due to the difference in the distance from the center to the peripheral edge as compared with the conventional circular or rectangular vibration plate 21. This is because the peak and dip of the image are corrected.

  In addition, the shape of the diaphragm 21 is not limited to the shape shown in the present embodiment, and has a shape having at least two opposite corners, such as a lemon shape, and connecting the corners with a curve. Also good. Even in such a shape, since the distance from the center point of the diaphragm 21 to the periphery varies, it is possible to obtain a frequency characteristic close to flat in a wide band.

  Electrodes of silver or the like are formed on both surfaces of the piezoelectric ceramic plate 22. A lead wire 24 connected to the drive circuit is attached to this electrode. In addition, when the diaphragm 21 is a metal, the diaphragm 21 can also be used as one electrode of the piezoelectric ceramic plate 22, and in this example, such a configuration is adopted.

A resin sheet 30 made of foamed silicon is bonded to the vibration plate 21, and is attached to the frame body 10 via the resin sheet 30.
The resin sheet 30 includes an attachment hole 31 for the vibration plate 21, and is configured to sandwich the peripheral edge portion 21 a of the vibration plate 21 with a holding portion 32 around the attachment hole 31.
The resin sheet 30 holds the four corners of the piezoelectric ceramic plate 22. In this way, the piezoelectric vibration element 20 is held on the resin sheet 30.
In addition, when producing the small and thin piezoelectric vibration element 20, it is good to use the synthetic paper (for example, a carre etc.) which uses a synthetic resin as the main raw material as the resin sheet 30. FIG.

In this example, the vibration plate 21 and the piezoelectric ceramic plate 22 are sandwiched between two resin sheets 30 and attached.
The two resin sheets 30 sandwich the vibration plate 21 and the piezoelectric ceramic plate 22 and are attached to each other with an adhesive or the like, thereby holding the piezoelectric vibration element 20.

The resin sheet 30 is formed to have a size slightly larger than the inner dimension of the frame body 10, that is, a size that can be held in the frame body 10.
This resin sheet 30 is sandwiched and held by the frame body 10 so that the piezoelectric vibration element 20 is supported by the frame body 10. That is, the piezoelectric vibration element 20 is held by the frame body 10 via the resin sheet 30 without the diaphragm 21 having a contact point with the frame body 10.

  With the above configuration, the vibration plate 21 is not pressed by the frame body 10, and the vibration is not suppressed by the frame body 10. Therefore, vibration inherent to the diaphragm 21 occurs in a wide frequency band, and can be prevented from being attenuated by being pressed by the frame body 10.

Furthermore, in the piezoelectric speaker 1 of this example, a part of the surface of the piezoelectric vibration element 20 is covered with the resin sheet 30.
As shown in FIG. 1 and FIG. 3, portions (hereinafter referred to as “cover portions 33”) that cover a part of the surface of the piezoelectric vibration element 20 of the resin sheet 30 are arcuate outer edges 33 a, 33 b, 33 c, It is formed in a shape with 33d.

As a result, the piezoelectric ceramic plate 22 is covered with the covering portion 33 at the center. The piezoelectric ceramic plate 22 is held by the covering portion 33 of the resin sheet 30 while exposing the exposed surfaces 22c, 22d, 22e, and 22f.
In this example, since the piezoelectric ceramic plate 22 is not provided on the back side of the piezoelectric speaker 1, the covering portion 33 covers the surface of the diaphragm 21 on the back side of the piezoelectric speaker 1.

The outer edges 33a and 33c and the outer edges 33b and 33d are formed from arcs having the same size.
The arcs forming the outer edges 33a and 33c constitute part of virtual circles C1 and C3 having a center point on the virtual line L1 orthogonal to the side 22a of the piezoelectric ceramic plate 22, respectively.
Similarly, the arcs forming the outer edges 33b and 33d constitute part of virtual circles C2 and C4 each having a center point on a virtual line L2 orthogonal to the side 22b of the piezoelectric ceramic plate 22.

  With the above configuration, the exposed surfaces 22c and 22e and the exposed surfaces 22d and 22f appear symmetrically on the piezoelectric ceramic plate 22 with the resin sheet 30 in between.

The radius lengths of the virtual circles C1, C3 and C2, C4 are changed corresponding to the size of the piezoelectric vibration element 20.
That is, the radius lengths of the virtual circles C1 to C4 are changed in proportion to the size of the piezoelectric vibration element 20 so that the covering portion 33 generally maintains the shape shown in FIG.

  As shown in FIG. 1, the covering portion 33 is connected to another portion of the resin sheet 30 via a connecting portion 34. That is, the covering portion 33 is connected to the holding portion 32 that covers the peripheral portion of the diaphragm 21.

  In this example, the covering portion 33 is formed integrally with the other portions of the resin sheet 30. However, the present invention is not limited to this, and the covering portion 33 is formed as a separate body and attached to the mounting hole 31 of the resin sheet 30 as a retrofit. May be.

  In the piezoelectric speaker 1 having the above configuration, the lead wire 24 is connected to a drive circuit (not shown). When an audio signal is input from the drive circuit to the piezoelectric ceramic plate 22, the piezoelectric ceramic plate 22 vibrates, whereby the vibration plate 21 vibrates and sounds are reproduced.

As the piezoelectric speaker 1 having the above-described configuration, a speaker having the following size was created and the sound pressure was measured. The size of the piezoelectric speaker 1 is the inner dimension of the frame 10, that is, the exposed surface of the piezoelectric vibration element 20 is 96 mm × 153 mm, the size of the piezoelectric ceramic plate 22 is 60 mm wide × 110 mm long × 0.1 mm thick, and the vibration plate 21. The radius of the virtual circles C1 and C3 constituting the outer edges 33a and 33c in the covering portion 33 of the resin sheet 30 is 30 mm, the radius of the virtual circles C2 and C4 constituting the outer edges 33b and 33d is 85 mm, The width of the connecting portion 34 is 2 mm.
The graph of FIG. 4 represents the frequency characteristics of the piezoelectric speaker 1.

The graphs of FIGS. 5 to 7 represent the frequency characteristics of the piezoelectric speakers according to Comparative Examples 1 to 3.
The piezoelectric speaker of Comparative Example 1 has a configuration in which the entire surface of the diaphragm 21 and the piezoelectric ceramic plate 22 is covered with the resin sheet 30 in the piezoelectric speaker 1.

The piezoelectric speakers of Comparative Examples 2 and 3 have a configuration in which the covering portion 33 is not provided in the piezoelectric speaker 1, and only the peripheral portion 21a of the diaphragm 21 is covered with the resin sheet 30.
The comparative example 2 has a configuration in which the peripheral portion 3 mm of the diaphragm 21 is covered, and the comparative example 3 has a configuration in which the peripheral portion 5 mm of the diaphragm 21 is covered.

  The frequency characteristics were measured by a method in which a voltage of 9 V was input to the piezoelectric ceramic plate 22 and the sound reproduced at a position 10 cm away was measured.

The vertical axis of the graph represents the sound pressure. The upper limit is 105 dB and the lower limit is 65 dB with 85 dB as a reference value.
The horizontal axis of the graph represents frequency, and the frequency band range is from 200 Hz to 20 KHz.
As can be seen from the graphs of FIGS. 5 to 7, the piezoelectric speaker of Comparative Example 1 has a low sound pressure as a whole and does not sufficiently reproduce sound. This is presumably because the resin sheet 30 covers the entire surface of the vibration plate 21 and the piezoelectric ceramic plate 22, so that vibration is suppressed and sound is not sufficiently transmitted.

  Further, the piezoelectric speakers of Comparative Example 2 and Comparative Example 3 have higher sound pressure than the piezoelectric speaker of Comparative Example 1, but when looking at the frequency characteristics, they have a plurality of large peaks and a large dip. Playback sound quality is not uniform. This is considered to be because the piezoelectric vibration element 20 is largely exposed because the piezoelectric vibration element 20 is held only by the peripheral portion 21a of the vibration plate 21 when the piezoelectric vibration element 20 is held by the resin sheet 30.

On the other hand, in the piezoelectric speaker 1 of this example, since the piezoelectric vibration element 20 includes the exposed surfaces 22c, 22d, 22e, and 22f, an appropriate sound pressure level is obtained.
In addition, since the piezoelectric vibration element 20 is held by the holding portion 32 of the resin sheet 30, the piezoelectric vibration element 20 is controlled without being blown, and the difference between the peak and the dip is small in the sound pressure characteristics. As described above, according to the piezoelectric speaker 1 of the present example, as a whole, the band is wider and the sound pressure is higher, and the variation in reproduced sound quality is reduced.

The diaphragm 21 and the piezoelectric ceramic plate 22 are not limited to the above shapes, and may be other shapes such as a circle and a rectangle.
Further, the covering portion 33 of the resin sheet 30 is not limited to the above-described shape, and is installed in the mounting hole 31 so as to cover a part of the piezoelectric vibration element 20, and the sound pressure and the vibration of the piezoelectric vibration element 20 are suppressed. Any shape may be used as long as it functions to improve sound quality, and any shape may be used.

FIG. 8 is an explanatory view showing another embodiment of the present invention , and FIG. 9 is an explanatory view showing a reference example . In other examples and reference examples, the same reference numerals are given to the same members as those in the previous example, and the description thereof is omitted.
In the piezoelectric speaker 1 of FIG. 8, the shape of the piezoelectric ceramic plate 22 is the same as that of the diaphragm 21, that is, a polygonal shape having no circumscribed circle. The piezoelectric ceramic plate 22 is formed in a size slightly smaller than the vibration plate 21.
A resin sheet 30 made of foamed silicon is bonded to the diaphragm, and is attached to the frame body 10 via the resin sheet 30, and a part of the surface of the piezoelectric vibration element 20 is covered with the covering portion 33 of the resin sheet 30. It is covered with.

  In the piezoelectric speaker 1 of FIG. 9, the shape of the piezoelectric ceramic plate 22 is formed in a polygon having the same shape as that of the vibration plate 21, as in the embodiment of FIG. It is set as the structure which does not have.

That is, the piezoelectric vibration element 20 in FIG. 9 includes a polygonal vibration plate 21 having no circumscribed circle and a polygonal piezoelectric ceramic plate 22 having no circumscribed circle. The piezoelectric vibration element 20 is a resin. It is held by a holding portion 32 around the mounting hole 31 of the sheet 30 and is configured so that substantially the entire surface is exposed from the mounting hole 31 of the resin sheet 30.
In the embodiment of FIG. 8 and the reference example of FIG. 9 , both the vibration plate 21 and the piezoelectric ceramic plate 22 are formed in a polygon having no circumscribed circle. The distance from the center point to the periphery is varied, so that various types of vibration energy can be generated, and a flatter sound pressure characteristic can be obtained .

  In the present embodiment, the structure in which the piezoelectric vibration element is supported by the frame 10 is shown, but the present invention can also be applied to a piezoelectric speaker having a structure in which the piezoelectric vibration element is directly supported by the case.

  In this embodiment, the piezoelectric vibration element is applied to the piezoelectric speaker. However, the present invention is not limited to this, and the piezoelectric vibration element can be used for other sound conversion devices such as a piezoelectric receiver and a microphone.

It is a front view of the piezoelectric speaker using the piezoelectric vibration element of this invention. It is a disassembled perspective view of the piezoelectric speaker of FIG. It is explanatory drawing of the coating | coated part of the piezoelectric speaker of FIG. It is a graph which shows the frequency characteristic of the piezoelectric speaker of FIG. It is a graph which shows the frequency characteristic of the piezoelectric speaker of a comparative example. It is a graph which shows the frequency characteristic of the piezoelectric speaker of a comparative example. It is a graph which shows the frequency characteristic of the piezoelectric speaker of a comparative example. It is explanatory drawing which shows another Example. It is explanatory drawing which shows a reference example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric speaker 10 Frame body 11 Upper frame 12 Lower frame 13 Bolt 20 Piezoelectric vibration element 21 Diaphragm 21a Peripheral part 22 Piezoelectric ceramic board (piezoelectric element)
22a, 22b Sides 22c, 22d, 22e, 22f Exposed surface 24 Lead wire 30 Resin sheet 31 Mounting hole 32 Holding portion (portion covering the peripheral portion of the diaphragm)
33 coating | cover part 33a-33d outer edge 34 connection part C1-C4 virtual circle L1, L2 virtual line

Claims (9)

In the piezoelectric vibration element that includes a diaphragm and a piezoelectric element attached to the diaphragm, and is held by a frame, a resin sheet is bonded to the diaphragm, and the diaphragm is interposed through the resin sheet. Held by the frame,
The resin sheet is provided with a mounting hole in which the piezoelectric vibration element is exposed and disposed,
A piezoelectric vibration element, characterized in that a covering portion is provided to cover and hold a part of the piezoelectric vibration element that is installed in the mounting hole.   The piezoelectric vibration element according to claim 1, wherein the covering portion is located at a substantially center of the piezoelectric vibration element.   The piezoelectric vibrating element according to claim 1, wherein the covering portion is formed in a shape having an arcuate outer edge on an outer peripheral portion.   4. The outer edges of the outer edges are formed from arcs having the same shape, and the arcs constitute a part of a virtual circle having a center point on the same virtual line. The piezoelectric vibration element as described.   The piezoelectric vibration element according to claim 4, wherein a radius length of a virtual circle forming the arc is changed in accordance with a size of the piezoelectric vibration element.   2. The piezoelectric vibration element according to claim 1, wherein a connecting portion is provided between a portion of the resin sheet that covers a peripheral portion of the vibration plate and the covering portion.   2. The piezoelectric vibration element according to claim 1, wherein two sets of symmetrical exposed surfaces are formed on the piezoelectric vibration element with the resin sheet interposed therebetween. The resin sheet is a piezoelectric vibrating element according to claim 1, characterized in that it consists of silicone foam. Speech conversion system having a piezoelectric vibrating element according to any one of claims 1 to 8.

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