JP3771485B2 - Method for manufacturing piezoelectric diaphragm for use in piezoelectric speaker - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a piezoelectric diaphragm used for a piezoelectric speaker.
[0002]
[Prior art]
It is known to use a piezoelectric diaphragm as a sound source of an audio device such as a speaker. In this type of speaker, a piezoelectric diaphragm is attached to one side of an acoustic diaphragm made of a plastic material via a columnar mounting member, and an audio signal is applied to the piezoelectric diaphragm to vibrate the piezoelectric diaphragm. The vibration is transmitted to the acoustic diaphragm via the mounting member, and the generation of the sound corresponding to the audio signal is obtained. Piezoelectric diaphragms are made by bending a ceramic layer by attaching a ceramic layer to one or both sides of a thin metal plate and creating a potential difference across both sides of the ceramic layer. The piezoelectric diaphragm is vibrated. By changing the potential difference formed between both side surfaces of the ceramic layer according to the audio signal, the piezoelectric diaphragm vibrates according to the audio signal. Thus, in order to form a potential difference between both side surfaces of the piezoelectric diaphragm and cause the piezoelectric diaphragm to vibrate according to the audio signal, conductive layers are formed on both side surfaces of the piezoelectric diaphragm by silver plating or the like.
[0003]
[Problems to be solved by the invention]
Conventionally, there is a method of forming a center hole penetrating three layers with a punch after pasting a ceramic layer without a hole at the center on both surfaces of a metal plate without a hole at the center. . This method has an advantage that the relative positioning of the holes in each layer can be made perfect, compared to pasting after forming holes in the metal plate and ceramic layer in advance. However, when the punch penetrates the metal plate, the central region of the metal plate swells and deforms in the traveling direction of the punch, and the central region of the lower ceramic layer breaks larger than the desired dimension.
[0004]
In order to solve this, a punch having a central hole formed in a central portion of a thin metal plate molded into a predetermined shape, a ceramic layer attached to both surfaces of the thin metal plate, and having an outer diameter equal to or smaller than the inner diameter of the central hole. Is positioned with respect to the center hole on the surface of one ceramic layer affixed to the metal thin plate, and the punch is penetrated from the surface of the one ceramic layer to the other ceramic layer through the center hole. A method of forming a hole has been proposed. However, in this method, when a center hole is formed in the ceramic layer, a short circuit may occur between the conductive layers on both sides of the ceramic layer due to, for example, particles of the conductive layer adhering to the inner surface of the center hole of the ceramic layer. .
[0005]
An object of the present invention is to solve such problems of the prior art, and to provide a method for manufacturing a piezoelectric diaphragm that prevents or reduces short circuit accidents that occur in the center hole of a ceramic layer.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided the piezoelectric vibration used in a piezoelectric speaker in which a piezoelectric diaphragm having a ceramic layer attached to at least one side surface of a metal plate is supported at the center and attached to the acoustic diaphragm. In the manufacturing method of a board,
Forming a central hole in the center of the metal plate;
Attaching a ceramic layer having conductive layers on both sides to the metal plate;
Forming a center hole concentric with the center hole of the metal plate in the ceramic layer,
A piezoelectric diaphragm characterized in that the center hole of the ceramic layer is formed by a conical drilling tool converging in the tip direction, and the distance between the conductive layers along the inner surface of the center hole of the ceramic layer is increased. The manufacturing method is summarized.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
First, referring to FIG. 4, a piezoelectric speaker according to a preferred embodiment of the present invention includes a piezoelectric diaphragm 10, which is supported by a mounting member 18 in the center and is an acoustic diaphragm 20. Installed on. The piezoelectric vibration plate 10 includes a circular metal thin plate 12 made of a metal thin plate such as brass, and a circular ceramic layer 14 bonded to both side surfaces of the metal thin plate 12 with an appropriate adhesive.
[0008]
Referring to FIG. 3, the ceramic layer 14 can be formed into a circular thin plate with a ferroelectric ceramic material such as barium titanate or lead zirconate titanate, and the conductive layer is formed on both sides by a method such as silver plating. 16a and 16b are formed. The conductive layers 16a and 16b are formed in a circular shape having a smaller diameter than the ceramic layer 14 concentrically arranged with respect to the ceramic layer 14, and the outer conductive layer 16a facing the outside of the piezoelectric diaphragm 10 when assembled, The inner conductive layer 16b is in contact with the metal thin plate 12. In one embodiment, the ceramic layer 14 has a thickness of about 0.12 mm and the conductive layers 16a, 16b have a thickness of about 0.005 mm.
[0009]
In addition, an electric wire (not shown) is connected to each of the metal thin plate 12 and the outer conductive layer 16a of the ceramic layer 14, and the piezoelectric diaphragm 10 is connected to an amplifier (not shown) via the electric wire. ing. Then, by applying an audio signal between the metal thin plate 12 and the ceramic layer 14, the piezoelectric diaphragm vibrates or bends according to the audio signal.
[0010]
As described above, the piezoelectric diaphragm 10 is attached to the acoustic diaphragm 20 by being supported by the mounting member 18 including the rod 18a, the nut 18b, and the bracket 18c formed with external threads at the center thereof. The bracket 18c can be preferably attached to the acoustic diaphragm 20 with a suitable adhesive or double-sided tape. The acoustic diaphragm 20 is preferably made of a foamed polystyrene or a suitable plastic material, for example, a composite material formed by bending fibers of boron, silicon carbide, alumina, carbon, aramid, etc., with a plastic matrix such as nylon, polyester, or epoxy. . Further, an annular vibration control piece 22 may be attached to one side surface of the piezoelectric diaphragm. The vibration control piece 22 is made of an elastic material, preferably an elastomer material such as synthetic rubber, natural rubber, low density polyethylene, or soft vinyl chloride plastic. The vibration control piece 22 is not a single annular member, but a plurality of members formed in a rectangular, triangular, trapezoidal, etc. shape, preferably a pair of members arranged at point-symmetrical positions across the center of the piezoelectric diaphragm. Also good.
[0011]
By applying an audio signal to the piezoelectric diaphragm 10, the piezoelectric diaphragm repeatedly bends back and forth, and the vibration is transmitted from the center of the piezoelectric diaphragm to the acoustic diaphragm 20 via the mounting member 18. Then, the vibration is transmitted from the acoustic diaphragm 20 to the surrounding air. Since the piezoelectric diaphragm 10 does not use a heavier magnet than a dynamic type speaker, the piezoelectric diaphragm 10 has high followability with respect to an audio signal having a high frequency, and in particular, can obtain a high sound pressure without distortion in a high sound region. It becomes possible.
[0012]
The piezoelectric diaphragm 10 has center holes 10 a and 10 b for allowing the mounting member 18 to pass through the piezoelectric diaphragm 10 so as to be supported by the mounting member 18 at the center. This central hole is composed of a portion 10 a formed in the metal thin plate 12 and a portion 10 b formed in the ceramic layer 14. When the ceramic layer 14 is attached to the metal thin plate 12 after forming the central hole 10b in the ceramic layer 14, the positioning of the portion 10a formed in the metal thin plate 12 and the portion 10b formed in the ceramic layer 14 in the central hole is performed. Is a problem. Since the ceramic layer 14 is formed of a brittle material, care must be taken not to damage the ceramic layer 14 when assembling the piezoelectric diaphragm 10. However, if the above positioning is insufficient, the mounting member 18, particularly its When the rod 18a is inserted into the center holes 10a and 10b, the rod 18a may interfere with the inner peripheral surface of the portion 10b formed in the ceramic layer 14 in the center hole and damage the ceramic layer 14. In order to prevent this, according to the present embodiment, the center hole 10b is formed in the ceramic layer 14 by the drilling tool 50 after the ceramic layer 14 in which the center hole 10b is not formed is attached to the metal thin plate 12. Is done. Although it is difficult to position the ceramic layer 14 in which the center hole 10b is formed with respect to the thin metal plate 12, it is relatively easy to position the drilling tool 50 with respect to the central axis O of the thin metal plate 12. Therefore, it is possible to increase the concentricity of the central hole portions 10a and 10b by forming the central hole 10b after attaching the ceramic layer 14 without the central hole 10b to the metal thin plate 12. It becomes.
[0013]
Further, the drilling tool 50 used when forming the center hole 10b in the ceramic layer 14 is preferably a tool having a conical processing portion 54 that converges at one end of the shank 52 with a tip angle α, preferably a rotating grindstone. . As a result, the central hole portion 10b formed in the ceramic layer 14 has a mortar shape as shown in FIG. Thereby, the distance L between the conductive layers 16a and 16b along the inner surface of the center hole 10b can be increased, and the occurrence of a short circuit accident between the conductive layers 16a and 16b can be reduced. The tip angle α is preferably 90 degrees or 120 degrees.
[0014]
Further, when the ceramic layer 14 is bonded to the metal plate 12, the ceramic layer 14 is pressed against the metal plate 12 so as to extrude the adhesive from between the two, and the extruded adhesive causes the ceramic layer to be shown in FIG. It is further preferable to form an insulating protection portion 24 along the outer peripheral edge portion of the 14. Thereby, it is possible to prevent a short circuit at the outer peripheral portion of the ceramic layer 14.
[Brief description of the drawings]
FIG. 1 is a partially enlarged cross-sectional view of a piezoelectric diaphragm, showing a state in which a center hole is formed by a drilling tool.
FIG. 2 is a partial enlarged cross-sectional view of a piezoelectric diaphragm, showing an example of a protective portion formed along the outer peripheral edge of a ceramic layer.
3A is a cross-sectional view of a ceramic layer, and FIG. 3B is a front view of the ceramic layer.
FIG. 4 is a cross-sectional view of a piezoelectric speaker.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Piezoelectric diaphragm 12 ... Metal thin plate 14 ... Ceramic layer 16a ... Conductive layer 16b ... Conductive layer 18 ... Mounting member 20 ... Acoustic diaphragm 22 ... Vibration control piece

Claims (6)

In the method of manufacturing a piezoelectric diaphragm used for a piezoelectric speaker, wherein a piezoelectric diaphragm having a ceramic layer attached to at least one side surface of a metal plate is supported at the center and attached to the acoustic diaphragm.
Forming a central hole in the center of the metal plate;
Attaching a ceramic layer having conductive layers on both sides to the metal plate;
Forming a center hole concentric with the center hole of the metal plate in the ceramic layer,
A piezoelectric diaphragm characterized in that the center hole of the ceramic layer is formed by a conical drilling tool converging in the tip direction, and the distance between the conductive layers along the inner surface of the center hole of the ceramic layer is increased. Production method. The manufacturing method according to claim 1, wherein the drilling tool is a rotating grindstone. The manufacturing method according to claim 1, wherein the ceramic layer is bonded to a side surface of the metal plate with an adhesive. The metal plate is formed of a circular thin plate, the ceramic layer is formed in a circular shape having a smaller diameter than the metal plate, and a protective portion made of the insulating material is provided along an outer peripheral edge portion of the ceramic layer. 4. The production method according to any one of 1 to 3. When adhering the ceramic layer to the metal plate, the ceramic layer is pressed against the metal plate to extrude an adhesive from both sides, and the extruded adhesive insulates along the outer peripheral edge of the ceramic layer. The method according to claim 1, wherein the protective part is formed. In the method of manufacturing a piezoelectric diaphragm used for a piezoelectric speaker, wherein a piezoelectric diaphragm having a ceramic layer attached to at least one side surface of a metal plate is supported at the center and attached to the acoustic diaphragm.
Forming a central hole in the center of the metal plate;
Bonding a ceramic layer having a conductive layer on both sides to the metal plate using an adhesive;
Forming a center hole concentric with the center hole of the metal plate in the ceramic layer,
When adhering the ceramic layer to the metal plate, the ceramic layer is pressed against the metal plate to extrude an adhesive from both sides, and the extruded adhesive insulates along the outer peripheral edge of the ceramic layer. A method for manufacturing a piezoelectric diaphragm, wherein a protective part is formed.

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