JP2010177867A - Piezoelectric speaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric speaker obtaining high sound pressure with a simple structure without specially providing a diaphragm. <P>SOLUTION: A bimorph type vibrating body 1 equipped with: a laminate 13 formed by laminating a piezoelectric material layer 7 and an internal electrode layer 9 alternately; and a pair of external electrode layers 17 and 19 connected to the internal electrode layer 9, is held between a pair of resin films 3 and 4 from a thickness direction (y) of the bimorph type vibrating body 1, and fixed to a fixed frame member 5 in the state where tension is applied to at least one of the pair of resin films 3 and 4. A diaphragm is not provided separately from the resin films 3 and 4, and the resin film 3 to which the tension is applied, serves as a diaphragm to provide the simple structure. The bimorph type vibrating body 1 is used, so the high sound pressure is maintained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric speaker, and more particularly to a piezoelectric speaker used in a computer, a mobile phone, a small terminal device, an acoustic device, or the like.

  Conventionally, a piezoelectric speaker is known as a small low current drive acoustic device using a piezoelectric body as an electroacoustic transducer, and is used as an acoustic output device of a small device. In general, a piezoelectric speaker has a structure in which a piezoelectric element in which an electrode made of a silver thin film or the like is formed on a metal diaphragm is provided. The sound generation mechanism of a piezoelectric speaker is generated by applying an alternating current to both sides of the piezoelectric element to cause shape distortion in the piezoelectric element and vibrating a metal diaphragm.

  A conventional piezoelectric speaker is known in which a bimorph type vibrating body is formed by providing piezoelectric elements on the upper and lower surfaces of a metal diaphragm, and the outer periphery of the metal vibrating body is fixed by a fixed frame (see Patent Document 1). . In the piezoelectric speaker described in Patent Document 1, it is described that a bimorph-type vibrating body is sandwiched between polymer films from the upper and lower surfaces and laminated. In this bimorph type vibrator, when a piezoelectric element on both sides of the metal vibrator is applied with an electric current so that the other contracts when the other is extended, the vibration of the metal diaphragm protruding or dented on the piezoelectric element forming side is repeated. become.

  Conventionally, it is also known to produce a bimorph type vibrator with only one piezoelectric element (see, for example, Patent Document 2). In Patent Document 2, the bimorph type vibrator is accommodated in a case and supported and fixed. The bimorph type vibrator has an internal electrode layer formed between two piezoelectric layers, and surface electrode layers formed on upper and lower surfaces. When one piezoelectric layer extends, the other piezoelectric layer shrinks. By applying an electric current, the bimorph-type vibrator is repeatedly vibrated to be deformed.

  Patent Document 2 describes that a reinforcing sheet such as a resin sheet may be attached to one side of a bimorph type vibrating body in order to prevent cracking of the piezoelectric layer.

JP 2001-285994 A JP 2001-95094 A

  However, in the conventional vibrator described in Patent Document 1, piezoelectric elements using thin piezoelectric layers are formed on the upper and lower surfaces of a metal diaphragm, and a reinforcing sheet such as a resin sheet is attached to one side of the piezoelectric element. In addition, there is a problem that it is necessary to provide a reinforcing sheet in addition to the metal diaphragm, and the structure is complicated.

  Further, in Patent Document 2, since the bimorph type vibrator itself is supported and fixed in the case, there is a problem that the amplitude of the bimorph type vibrator is small and the sound pressure of the piezoelectric speaker cannot be improved.

  An object of this invention is to provide the piezoelectric speaker which can obtain a high sound pressure with a simple structure, without providing a diaphragm separately.

  A piezoelectric speaker according to the present invention includes a bimorph type vibration body including a laminated body in which piezoelectric layers and internal electrode layers are alternately stacked, and a pair of external electrode layers connected to the internal electrode layer. It is characterized in that it is sandwiched by a pair of resin films from the thickness direction of the mold vibrating body, and at least one outer peripheral portion of the pair of resin films is fixed to a fixed frame member.

  The piezoelectric speaker according to the present invention is not a conventional bimorph type vibrator configured by providing a laminate in which piezoelectric layers and internal electrode layers are alternately laminated on both surfaces of a diaphragm, but a piezoelectric layer. A bimorph type vibrating body is constituted by a single laminated body in which an internal electrode layer and an internal electrode layer are alternately laminated, and the bimorph type vibrating body is sandwiched between a pair of resin films, and at least one outer peripheral portion of the pair of resin films is formed. Without being provided with a diaphragm separately from the resin film and fixed to the fixed frame member, a tensioned resin film can be used as a diaphragm, and a simple structure can be obtained. Therefore, a high sound pressure can be maintained.

  Further, in the piezoelectric speaker of the present invention, the resin film having an outer peripheral portion fixed to the fixed frame member has a concave portion in the central portion, and a part of the bimorph type vibrator in the thickness direction is formed in the concave portion. It is housed. In such a piezoelectric speaker, the center of vibration in the thickness direction of the bimorph type vibrating body can be brought close to the position where the supporting resin film is fixed to the fixed frame member, and the supporting resin film is fixed to the fixed frame member. It is possible to stably vibrate the bimorph-type vibrating body around the position where it is located. Thereby, the amplitude of the supporting resin film can be increased, and the sound pressure of the piezoelectric speaker can be improved.

  Furthermore, in the piezoelectric speaker of the present invention, the bimorph type vibrating body is covered with the pair of resin films from both sides in the thickness direction of the bimorph type vibrating body, and the bimorph type is between the pair of resin films. The vibrating body is filled with resin. In such a piezoelectric speaker, the bimorph type vibrating body is securely fixed between the pair of resin films, the bimorph type vibrating body and the pair of resin films can be integrated, and the amplitude of the supporting resin film can be increased. The sound pressure of the piezoelectric speaker can be improved.

  In the piezoelectric speaker of the present invention, the bimorph-type vibrating body is sandwiched between a pair of resin films, and at least one outer peripheral portion of the pair of resin films is fixed to a fixed frame member, and a diaphragm is provided separately from the resin film. Without any problem, at least one of the pair of resin films can be used as a diaphragm, and a simple structure can be obtained, and a high sound pressure can be maintained because a bimorph type vibrator is used.

The piezoelectric speaker of this invention is shown, (a) is a longitudinal cross-sectional view, (b) is sectional drawing along the AA line of (a). It is a longitudinal cross-sectional view which shows the state which also fixed the resin sheet which coat | covers a bimorph type vibrating body to the fixed frame member. It is a longitudinal cross-sectional view which shows the state by which resin is filled between the resin sheets which pinch | interpose a bimorph type vibration body, and the circumference | surroundings of a bimorph type vibration body. The piezoelectric speaker which accommodated and fixed the bimorph type | mold vibrating body in the recessed part formed in the resin film for support is shown, (a) is a longitudinal cross-sectional view, (b) is along the BB line of (a). FIG. It is a longitudinal cross-sectional view which shows the state which also fixed the resin sheet which coat | covers the bimorph type vibrating body of FIG. 4 to the fixed frame member. It is a longitudinal cross-sectional view which shows the state which clamped the bimorph type vibration body with the resin film of the same thickness, and was filled with resin around the bimorph type vibration body between the resin sheets. It is a longitudinal cross-sectional view which shows the state which accommodated and fixed the bimorph type vibration body in the recessed part formed in a pair of resin film of the same thickness.

  Hereinafter, an embodiment of a piezoelectric speaker according to the present invention will be described with reference to FIG. FIG. 1 shows a piezoelectric speaker of the present invention, and in order to facilitate understanding, the thickness direction y of the bimorph type vibrator is enlarged and shown.

  As shown in FIG. 1, the piezoelectric speaker of the present invention is a fixed frame member in which a bimorph-type vibrating body 1 is sandwiched between a pair of resin films 3 and 4 from the thickness direction y and the resin film 3 is tensioned. 5a and 5b are sandwiched and fixed.

  The bimorph vibrator 1 includes a laminated body 13 in which piezoelectric layers 7 made of four ceramic layers and three internal electrode layers 9 are alternately laminated, and surfaces formed on both upper and lower surfaces of the laminated body 13. Electrode layers 15 a and 15 b and a pair of external electrodes 17 and 19 provided at both ends in the longitudinal direction x of the laminate 13 are provided.

  The external electrode layer 17 is connected to the surface electrode layers 15a and 15b and one internal electrode layer 9b, and the external electrode layer 19 is connected to the two internal electrode layers 9a and 9c. The piezoelectric layers 7 are alternately polarized as indicated by arrows in FIG. 1, and when the piezoelectric layers 7a and 7b contract, the external electrode layers 17 and 19 are extended so that the piezoelectric layers 7c and 7d extend. It is comprised so that a voltage may be applied to.

  As the piezoelectric layer 7, conventionally used piezoelectric ceramics such as PZ, PZT, Bi layered compounds, lead-free piezoelectric materials such as tungsten bronze structure compounds, and the like 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 preferably contains a metal component composed of silver and palladium and a material component constituting the piezoelectric layer 7. By containing the ceramic component constituting the piezoelectric layer 7 in the internal electrode layer 9, the stress due to the thermal expansion difference between the piezoelectric layer 7 and the internal electrode layer 9 can be reduced, and bimorph type vibration without stacking failure. The body 1 can be obtained. The internal electrode layer 9 is not particularly limited to a metal component composed of silver and palladium, and is not limited to a material component constituting the piezoelectric layer 7 as a ceramic component. It may be.

  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, it is possible to obtain a strong adhesion 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 fixed frame member 5 has a rectangular shape, and is formed by bonding two rectangular frame-shaped fixed frame members 5a and 5b, and the fixed frame members 5a and 5b. The outer periphery of the resin film 3 is sandwiched between and fixed. The fixed frame members 5a and 5b are made of, for example, 100 to 1000 μm stainless steel. In the present invention, the thickness, material, and the like of the fixed frame members 5a and 5b are not particularly limited.

  As shown in FIG. 1A, the resin film 3 is formed thicker than the resin film 4, and the resin film 3 is surfaced by sandwiching the outer periphery of the resin film 3 between the fixed frame members 5a and 5b. In a state where tension is applied in the direction, the resin film 3 is fixed to the fixed frame members 5a and 5b, and the resin film 3 serves as a diaphragm. The thickness of the resin film 3 is, for example, 10 to 100 μm, the thickness of the resin film 4 is, for example, 5 to 50 μm, and the resin films 3 and 4 are made of a resin such as polyethylene or polyimide, for example. . In the present invention, the thickness, material and the like of the resin films 3 and 4 are not particularly limited.

  As shown in FIG. 1A, the resin film 4 is made of a material that is thinner than the resin film 3 and can be easily deformed to some extent, and the resin film 4 is a bimorph type vibrator 1 disposed on the resin film 3. The bimorph vibrator 1 is laminated with the resin films 3 and 4.

  As shown in FIG. 1B, lead wires 21a and 21b are connected to the external electrodes 17 and 19, respectively, and are drawn to the outside. These lead wires 21a and 21b are sandwiched between the resin film 3 and the fixed frame member 5a.

  A method for manufacturing the piezoelectric speaker of the present invention will be described. First, the bimorph type vibrator 1 is prepared. In the bimorph vibrator 1, first, a binder, a dispersing agent, 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 obtained slurry can be formed into a sheet 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 Three sheets are laminated, and only a green sheet is laminated on the uppermost layer to produce a laminated molded body.

  Next, the laminate 13 can be obtained by degreasing, firing, and cutting the laminate compact 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 vibrator 1 shown in FIG. 1 can be obtained by printing the paste of the external electrodes 17 and 19 on both sides of x and baking the electrodes at a predetermined temperature.

  Next, in order to impart piezoelectricity to the bimorph type vibrator 1, a DC voltage is applied through the surface electrode layers 15 a and 15 b or the external electrodes 17 and 19 to polarize the piezoelectric layer 7 of the bimorph type vibrator 1. . For example, the external electrode 19 is cut while the internal electrode 9 a and the internal electrode 9 c are connected so that the polarization is in the direction indicated by the arrow in FIG. 1, and between the upper portion of the external electrode 19 and the external electrode 17. After a voltage is applied to, a voltage having a polarity different from this voltage is applied between the lower portion of the external electrode 19 and the external electrode 17. After the polarization is completed, the upper part and the lower part of the external electrode 19 are electrically connected.

  Next, the resin film 3 is prepared, the outer peripheral portion of the resin film 3 is sandwiched between the fixing frame members 5a and 5b, and is fixed in a state where tension is applied to the resin film 3. Thereafter, an adhesive is applied to the resin film 3, the surface electrode 15a side of the bimorph type vibrator 1 is pressed onto the resin film 3, and then the adhesive is cured by irradiation with heat or ultraviolet rays. . And the resin film 4 is coat | covered to the upper surface of the bimorph type vibration body 1 and the fixed frame member 5a, and the air between the resin film 3 and the resin film 4 is extracted by heat-sealing, and the resin film 4 is removed. The piezoelectric speaker of the present invention can be obtained by closely contacting the mold vibrator 1 and the resin film 3.

  In the piezoelectric speaker configured as described above, the bimorph type vibrator 1 is constituted by a single laminated body 13 in which the piezoelectric layers 7 and the internal electrode layers 9 are alternately laminated. The resin film 3 is sandwiched between the resin films 3 and 4, and the resin film 3 is fixed to the fixed frame 5 in a tensioned state, and the tensioned resin film 3 is provided without providing a diaphragm separately from the resin films 3 and 4. Since the bimorph type vibrator 1 is used, a high sound pressure can be maintained.

  Further, even if the piezoelectric layer 7 is thin, the bimorph type vibrator 1 as a whole is thick, so that cracks and the like are less likely to occur, reliability is improved, and handling is facilitated.

  In the piezoelectric speaker of FIG. 1, the number of stacked piezoelectric layers 7 in the bimorph type vibrator 1 is four. However, in the piezoelectric speaker of the present invention, the number of stacked piezoelectric layers 7 in the bimorph type vibrator 1 is as follows. It is not specifically limited, For example, two layers may be sufficient.

  FIG. 2 shows another embodiment of the present invention, in which the resin film 4 of FIG. 1 is sandwiched and fixed between the resin film 3 and the fixed frame member 5a. In such a piezoelectric speaker, not only the resin film 3 but also the resin film 4 serves as a diaphragm, and the bimorph type vibrator 1 can be reliably fixed between the resin films 3 and 4, and the resin films 3 and 4 functioning as diaphragms. The amplitude can be improved. In this case, the step of adhering the bimorph vibrator 1 to the resin film can be omitted.

  FIG. 3 shows still another embodiment of the present invention. Between the resin film 4 and the resin film 3 in FIG. 2, the periphery of the bimorph type vibrator 1 is filled with the resin P, and the bimorph type vibration is shown. The body 1 is joined and fixed. In such a piezoelectric speaker, not only the resin film 3 but also the resin film 4 can be a diaphragm, and the bimorph type vibrator 1 can be reliably bonded and fixed between the resin films 3 and 4 and functions as a diaphragm. The amplitude of the resin films 3 and 4 can be further improved.

  FIG. 4 shows still another embodiment of the present invention. In this embodiment, the resin film 3 has a recess 33 formed therein, and the bimorph type vibrator 1 is accommodated in the recess 33. The depth of the concave portion 33 of the resin film 3 is about ½ of the thickness of the bimorph type vibrator 1. The resin film 4 covers the surface of the bimorph vibrator 1 and the upper surface of the fixed frame member 5a.

  In such a piezoelectric speaker, the resin film 3 is fixed to the fixed frame 5 at a position about ½ of the thickness of the bimorph type vibrator 1, and the bimorph type vibrator 1 is stably centered on the resin film 3. It can vibrate up and down, and the sound pressure of the piezoelectric speaker can be improved.

  In FIG. 5, the resin film 4 of FIG. 4 is sandwiched and fixed between the resin film 3 and the fixed frame member 5a. In such a piezoelectric speaker, not only the resin film 3 but also the resin film 4 can be a diaphragm, and the bimorph type vibrator 1 can vibrate up and down stably around the resin film 3, and the bimorph type vibrator. 1 can be fixed between the resin films 3 and 4, and the sound pressure of the piezoelectric speaker can be improved.

  FIG. 6 shows still another embodiment of the present invention. In this embodiment, the resin films 3 and 4 have the same thickness, and the outer peripheral portions of these resin films 3 and 4 are sandwiched between the fixed frame members 5a and 5b. It is fixed. In such a piezoelectric speaker, the bimorph type vibrating body 1 can be fixed between the resin films 3 and 4, and the sound pressure of the piezoelectric speaker can be improved.

  In this case, it is desirable that the resin P is filled between the resin films 3 and 4 and the periphery of the bimorph vibrator 1 is filled, and the bimorph vibrator 1 is bonded and fixed between the resin films 3 and 4.

  FIG. 7 shows still another embodiment of the present invention. In this embodiment, the resin films 3 and 4 have the same thickness, and the resin films 3 and 4 are formed with recesses 33, respectively. The bimorph type vibrator 1 is accommodated in the recess 33. The depth of the recess 33 of the resin films 3 and 4 is about ½ of the thickness of the bimorph type vibrator 1. The outer peripheral portions of these resin films 3 and 4 are sandwiched and fixed between the fixed frame members 5a and 5b. A resin P is filled between the resin films 3 and 4 and around the bimorph type vibrator 1.

  In such a piezoelectric speaker, the bimorph type vibrator 1 can be fixed between the resin films 3 and 4, and the bimorph type vibrator 1 can vibrate up and down stably around the resin films 3 and 4, and the sound of the piezoelectric speaker can be obtained. The pressure can be improved.

DESCRIPTION OF SYMBOLS 1 ... Bimorph type vibrating body 3, 4 ... Resin film 5, 5a, 5b ... Fixed frame member 7, 7a, 7b, 7c, 7d ... Piezoelectric layer 9, 9a, 9b, 9c. .... Internal electrode layer 13 ... Laminated bodies 15a, 15b ... Surface electrode layers 17, 19 ... External electrode layer x ... Longitudinal direction y of laminated body ... Thickness direction of bimorph type vibrator

Claims (3)

  A bimorph type vibrator comprising a laminate formed by alternately laminating piezoelectric layers and internal electrode layers and a pair of external electrode layers connected to the internal electrode layer is formed from the thickness direction of the bimorph type vibrator. A piezoelectric speaker characterized by being sandwiched between a pair of resin films and having at least one outer peripheral portion of the pair of resin films fixed to a fixed frame member.   The resin film having an outer peripheral portion fixed to the fixed frame member has a concave portion in a central portion, and a portion in the thickness direction of the bimorph type vibrator is accommodated in the concave portion. The piezoelectric speaker according to claim 1.   The bimorph type vibrating body is covered with the pair of resin films from both sides in the thickness direction of the bimorph type vibrating body, and a resin is filled between the pair of resin films and around the bimorph type vibrating body. The piezoelectric speaker according to claim 1, wherein the piezoelectric speaker is provided.

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