JPS5829676Y2 - piezoelectric speaker - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a piezoelectric speaker in which a diaphragm is driven by a piezoelectric element.

Dynamic speakers, which have been widely used in the past, are
Since the structure is such that the diaphragm (cone) is magnetically driven, the drive unit cannot be made smaller than a predetermined size.

In other words, it has been difficult to obtain a thin speaker by reducing the thickness of the speaker in the axial direction.

Therefore, a piezoelectric speaker in which the drive unit is replaced with a piezoelectric element has been proposed, but because the shape of the piezoelectric head used as the piezoelectric element is circular or quadrilateral, the lowest resonant frequency fO of the vibration system is high. For this reason, it has the defect that the sound pressure level in the low range is low.

For this reason, it is only used to some extent in tweeters, and speakers that cover a wide band have not been obtained.

The present invention was devised in view of these problems, and includes a piezoelectric speaker in which a diaphragm is driven by a piezoelectric element. The present invention relates to a piezoelectric speaker characterized in that the piezoelectric speaker has a shape having a piece, and the piezoelectric element is attached to the diaphragm made of a flexible sheet.

Therefore, it is possible to further lower the fo of the vibration system, and it is possible to provide a thin speaker that covers a wide band.

The present invention will be explained below using actual cases.

First, referring to the first embodiment, as shown in FIGS. 1 and 2, this piezoelectric speaker is composed of a cross-shaped piezoelectric ceramic 1, a metal plate 2, and a diaphragm 3. .

The piezoelectric ceramic 1 is made of barium titanate, titanium zirconate, etc., and converts an electric signal applied by a pair of lead wires 4 and 5 into mechanical displacement, and has electrodes 6 and 7 on both sides. It is formed.

Lead wire 4 is directly connected to electrode 6.

Further, a support body 8 is fixed to the lower surface of the piezoelectric ceramic 1, and the structure is such that it can be attached to an appropriate part by means of this support body 8.

The upper electrode 7 is bonded to the metal plate 2 via a silver paste layer 9 and an adhesive layer 10.

In this way, one surface of the piezoelectric ceramic 1 is connected to the metal plate 2.
, and is configured so that expansion and contraction in the plane direction of the piezoelectric ceramic 10 is converted into vibration in a direction perpendicular to the plane.

Therefore, the metal plate 2 and the piezoelectric ceramic 1 are bonded together using an adhesive such as an epoxy resin having a high Young's modulus, thereby forming the adhesive layer 10.

This increases the conversion efficiency in the vibration direction.

Note that this adhesive layer 10 made of epoxy resin is not conductive in itself, and by applying it thinly, many pinballs are generated, and the silver paste layer 9 and the metal plate 2 come into contact through these pinholes. are doing.

That is, the lead wire 5 is electrically connected to the electrode 7 via the metal plate 2 and the silver paste layer 9.

Note that this adhesive layer 10 may be made of a conductive adhesive.

In this case, the silver paste layer 9 can be omitted.

Further, in the configuration shown in FIG. 1, the electrode 7 and the silver paste layer 9 are provided respectively, but the silver paste layer 9 may also serve as an electrode.

A diaphragm 3 is further bonded to the upper surface of the metal plate 2 via an adhesive layer 11.

The adhesive layer 11 is made of, for example, a rubber-based adhesive having a low Young's modulus, and this adhesive layer 11 eliminates peak dips at the resonance point and provides flatter characteristics.

The diaphragm 3 is made of a flexible material other than metal, such as flat paper or plastic film, and has a shape other than a circular shape that is symmetrical with respect to the central axis 12, that is, an asymmetrical shape, such as a square shape. It is configured.

By making the shape asymmetrical with respect to the central axis 12 in this way, the diaphragm 3 is prevented from generating constant pressure waves, causing multiple resonances, many small peak dips are reported, and the diaphragm 3 is flat as a whole. A speaker with frequency characteristics can be obtained.

Note that in order for the diaphragm 3 to cause multiple resonance, it does not necessarily have to be square, but may have other shapes such as trapezoid, rectangle, etc.
It can be of various shapes, such as irregular polygons.

Furthermore, in this speaker, the shape of the piezoelectric ceramic 1, which is the drive source, is cross-shaped, as shown in FIG. It has 16.

By providing the four extension pieces 13, 14, 15, and 16 in this manner, the lowest resonance frequency fo of the vibration system is lowered, and therefore a lower frequency range is also covered.

In other words, it is possible to correct the defect of piezoelectric speakers that they can only cover high frequency ranges.

An example of experimental results that support this fact is that 30 fM
fO of a speaker with Lφ circular piezoelectric ceramic is 1
200H2S, but the fO of a speaker having a cross-shaped piezoelectric ceramic 1 inscribed in a circle of 30wnφ and each extension piece 13°, 14, 15, 16 having a width of 5wn is 820.
It's H7.

Note that, corresponding to the cross-shaped shape of the piezoelectric ceramic 1 as described above, the metal plate 2 has a similar and larger cross-shaped shape as shown in FIG.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. In this embodiment, instead of supporting the speaker at the center of the piezoelectric ceramic 1, I try to support it.

The support 17 for supporting the speaker is preferably made of a soft material such as urethane.

With such support, the diaphragm 3 vibrates so that its center portion has the largest amplitude.

Further, in this practical example of the speaker, the lengths and widths of the extension pieces 13, 14, 15, and 16 of the piezoelectric ceramic 1 are different from each other.

Therefore, the base pieces 13, 14, 15, and 16 each have a different minimum resonant frequency fo, resulting in a speaker having relatively flat characteristics as a whole.

Note that the shape of the piezoelectric ceramic □tsuku 1 is not necessarily limited to a cross shape, and the number of 200 extension pieces may be arbitrarily changed to 2, 3, 5, etc., as shown in Figures 5A to 5C. Is possible.

Further, the length and width of these extension pieces 20 can also be changed freely.

As described above, the present invention has a piezoelectric element shaped like a plurality of extension pieces extending in different directions from the center, and this piezoelectric element is attached to a diaphragm made of a flexible sheet. .

Therefore, the resonance frequency of the speaker's vibrations and the like is lowered, making it possible to provide a thin speaker that covers a wide range of sound.

[Brief Description of the Drawings] Fig. 1 is a vertical cross-sectional view of a speaker according to a first practical example of the present invention;
2 is a plan view of the same, FIG. 3 is a vertical sectional view of a speaker according to a second embodiment of the present invention, FIG. 4 is a plan view of the same, FIG.
FIG. B and FIG. 5C are plan views showing modified examples of the piezoelectric ceramic. In addition, in the symbols used in the drawings, 1...
・Piezoelectric ceramic, 3... Vibration plate, 13, 14
゜15.16...This is an extension piece.

Claims (1)

[Scope of utility model registration request] In a piezoelectric speaker in which a diaphragm is driven by a piezoelectric element, the piezoelectric element is formed into a shape having a plurality of extending pieces extending in different directions from a center part, and the piezoelectric element is made more compact than a flexible sheet. A piezoelectric speaker, characterized in that the piezoelectric speaker is attached to the diaphragm.