JP2019146108A - Acoustic generator and electronic apparatus - Google Patents

Abstract

To provide an acoustic generator that has improved sound pressure, and an electronic apparatus.SOLUTION: An acoustic generator 1 of the present disclosure comprises: a diaphragm 2; a rectangular piezo electric element 3 mounted on the diaphragm 2 and having a longitudinal direction; and a first columnar part 41 provided between the diaphragm 2 and piezo electric element 3. The first columnar part 41 has an area in a plane perspective smaller than the area of an under surface of the piezo electric element 3 and is at a position not protruding from the outer periphery of the piezo electric element 3 in a plane perspective.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an acoustic generator and an electronic device using, for example, a piezoelectric element.

  A small-sized, low-current drive acoustic generator using a piezoelectric element as a drive source is known (see, for example, Patent Document 1). The piezoelectric element is incorporated in a small electronic device such as a mobile computing device by being attached to an inner surface of a panel constituting the housing, for example.

JP 2013-232874 A

  Sound generators that use a piezoelectric element as the drive source and the panel that makes up the casing as a diaphragm will have low sound pressure due to the increase in size of the panel due to the increase in size of the casing and the reduction in panel vibration due to waterproof structures. It has become. Therefore, the sound generator is required to further improve the sound pressure.

  The present disclosure has been made in view of the above circumstances, and an object thereof is to provide an acoustic generator and an electronic device with improved sound pressure.

  The acoustic generator according to the present disclosure includes a diaphragm, a rectangular plate-shaped piezoelectric element having a longitudinal direction mounted on the diaphragm, and a first columnar shape provided between the diaphragm and the piezoelectric element. And the first columnar part has a smaller area when viewed through the plane than the area of the lower surface of the piezoelectric element, and is in a position that does not protrude from the outer periphery of the piezoelectric element when viewed through the plane. It is what.

  Further, the acoustic generator of the present disclosure includes a diaphragm, a rectangular plate-like piezoelectric element having a longitudinal direction mounted on the diaphragm, and two pieces provided between the diaphragm and the piezoelectric element. And the two or more columnar portions have a smaller area when viewed through the plane than the area of the lower surface of the piezoelectric element and do not protrude from the outer periphery of the piezoelectric element when viewed through the plane. It is characterized by that.

  In addition, an electronic device according to the present disclosure contains the acoustic generator according to any one of the above, an electronic circuit connected to the piezoelectric element constituting the acoustic generator, the piezoelectric element, and the electronic circuit. And a housing to be provided.

  According to the acoustic generator of the present disclosure, since the displacement of the piezoelectric element is difficult to be restrained, the amplitude of the bending vibration can be increased, and the vibration energy is concentrated on the columnar portion and easily transmitted to the diaphragm. Can be improved.

  Furthermore, according to the electronic device of the present disclosure, since the sound generator with improved sound pressure is provided, a high sound quality electronic device can be realized.

It is a schematic perspective view which shows an example of embodiment of an acoustic generator. It is a schematic sectional drawing of the piezoelectric element shown in FIG. It is a schematic perspective view which shows the other example of embodiment of an acoustic generator. It is a schematic perspective view which shows the other example of embodiment of an acoustic generator. It is a schematic perspective view which shows the other example of embodiment of an acoustic generator. It is a block diagram which shows an example of embodiment of an electronic device.

  Hereinafter, an embodiment of a sound generator will be described with reference to the drawings.

  The acoustic generator 1 shown in FIG. 1 is provided between a diaphragm 2, a rectangular plate-like piezoelectric element 3 having a longitudinal direction mounted on the diaphragm 2, and the diaphragm 2 and the piezoelectric element 3. The first columnar portion 41 is provided.

  The diaphragm 2 constituting the sound generator 1 is, for example, a rectangular thin plate. The diaphragm 2 can be made of a material having high rigidity and elasticity such as acrylic resin or glass. Moreover, the thickness of the diaphragm 2 is set to, for example, 0.3 mm to 1.5 mm. As will be described later, the first columnar portion 41 may be formed integrally with the diaphragm 2 or may be formed separately. The protruding portion protruding from () is defined as a first columnar portion 41.

  A piezoelectric element 3 is mounted on the diaphragm 2. The piezoelectric element 3 has a rectangular plate shape having a longitudinal direction.

  As shown in FIG. 2, the piezoelectric element 3 includes a laminate 33 in which a piezoelectric layer 31 and an internal electrode layer 32 are laminated, a surface electrode 34 provided on the upper surface of the laminate 33, and a side surface of the laminate 33. A so-called laminated type including the provided side electrode 35 can be used.

  The stacked body 33 has a stacked structure in which a plurality of piezoelectric layers 31 and internal electrode layers 32 are stacked in a direction perpendicular to the diaphragm 2, for example. By applying an electrical signal to the piezoelectric element 3 mounted on the diaphragm 2, the piezoelectric element 3 is flexibly vibrated to vibrate the diaphragm 2.

  For example, in the case of the laminated piezoelectric element 3 used by being attached to a part of the casing of the portable terminal or the display, the length of the laminated body 33 in the longitudinal direction is, for example, 18 mm to 28 mm. The width of the stacked body 33 is, for example, 1 mm to 6 mm. The thickness of the stacked body 33 is, for example, 0.2 mm to 2.0 mm.

The piezoelectric layer 31 constituting the multilayer body 33 is formed of ceramics having piezoelectric characteristics. As such ceramics, for example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), Lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), or the like can be used. The thickness of one layer of the piezoelectric layer 31 is set to, for example, 0.01 to 0.1 mm in order to drive with a low voltage. Moreover, in order to obtain a large flexural vibration, it can have a piezoelectric d31 constant of 200 pm / V or more.

  The internal electrode layer 32 constituting the multilayer body 33 is formed by, for example, simultaneous firing with ceramics that form the piezoelectric layer 31. The internal electrode layers 32 are alternately drawn out to a pair of opposing side surfaces. As this forming material, for example, a conductor containing silver or a silver-palladium alloy as a main component, or a conductor containing copper, platinum, or the like can be used. However, a ceramic component or a glass component may be contained therein.

  A surface electrode 34 is provided on the upper surface of the stacked body 33. The surface electrode 34 is electrically connected to an external circuit (external power source) by connecting a lead member.

  Side electrodes 35 are provided on the side surfaces of the stacked body 33. The side electrode 35 electrically connects the internal electrode layer 32 and the surface electrode 34.

  The surface electrode 34 and the side electrode 35 can be formed by, for example, applying and baking a silver glass-containing conductive paste.

  The piezoelectric element 3 is not limited to the laminated type, and may be a so-called single plate type including a single-layer piezoelectric body and a surface electrode provided on the surface of the piezoelectric body.

  There is a first columnar portion 41 between the diaphragm 2 and the piezoelectric element 3. The area of the first columnar portion 41 when viewed through the plane is smaller than the area of the lower surface of the piezoelectric element 3 and is in a position that does not protrude from the outer periphery of the piezoelectric element 3 when viewed through the plane.

  Examples of the material of the first columnar section 41 include ABS resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyetheretherketone (PEEK), and glass. The first columnar portion 41 may be made of the same material as that of the diaphragm 2, and in this case, the first columnar section 41 may be made integrally with the diaphragm 2 or may be made separately.

  When the 1st columnar part 41 is made integrally with the diaphragm 2, let the protrusion part which protruded from the diaphragm 2 (flat part) be a columnar part. Here, the width | variety of the 1st columnar part 41 shall be 1-5 mm, for example, and height shall be 1-5 mm, for example. The width of the first columnar portion 41 means both the width along the longitudinal direction of the piezoelectric element 3 and the width along the width direction of the piezoelectric element 3.

  In the case where the first columnar part 41 and the diaphragm 2 are separate, the bonding material that joins the first columnar part 41 and the diaphragm 2 is, for example, an epoxy resin or an acrylic resin, and has a thickness of 1 μm to 10 μm, for example. It is said. Moreover, for example, an epoxy resin or an acrylic resin is used as a bonding material between the first columnar portion 41 and the piezoelectric element 3, and the thickness is set to 1 μm to 10 μm, for example.

  According to the acoustic generator 1 of the present disclosure, since the displacement of the piezoelectric element 3 is difficult to be restrained, the amplitude of the bending vibration can be increased, and the vibration energy is concentrated on the first columnar portion 41 and thus the diaphragm 2. Sound pressure can be improved.

  Here, the first columnar portion 41 has a size (width) that is smaller than the area of the lower surface of the piezoelectric element 3 when viewed through the plane and is not protruded from the outer periphery of the piezoelectric element 3 when viewed through the plane. If it is, there will be no limitation in particular, For example, the following forms can be taken.

  As shown in FIG. 3, the first columnar portion 41 may be joined to one end portion in the longitudinal direction on the lower surface of the piezoelectric element 3. According to this configuration, one end in the longitudinal direction on the lower surface of the piezoelectric element 3 is fixed by one columnar portion, and the portion other than the one end in the longitudinal direction on the lower surface of the piezoelectric element 3 is not restrained. The amplitude of flexural vibration can be increased by increasing the mechanical moment applied to one fixed end, and in particular, the sound pressure in the low frequency portion can be improved.

In addition to the first columnar portion 41, a second columnar portion 42 may be further provided between the diaphragm 2 and the piezoelectric element 3 as shown in FIG. The area of the second columnar portion 42 when viewed through the plane is smaller than the area of the lower surface of the piezoelectric element 3 and is in a position that does not protrude from the outer periphery of the piezoelectric element 3 when viewed through the plane. When the first columnar portion 41 is joined to one end portion in the longitudinal direction on the lower surface of the piezoelectric element 3, the second columnar portion 42 is the other end portion in the longitudinal direction on the lower surface of the piezoelectric element 3. It may be joined to. The one end portion and the other end portion of the piezoelectric element 3 are the respective end portions on both sides when the entire longitudinal direction is divided into five equal parts as viewed in a cross section obtained by cutting the piezoelectric element 3 along the longitudinal direction. means. In addition, being bonded to one end means to be bonded to a part or all of the range of the end of one end, and being bonded to the other end is to be bonded to the other end. It means that it is joined to a part or all of the ends.

  Even with such a configuration, since the displacement of the piezoelectric element 3 is difficult to be restrained, vibration energy is easily transmitted to the diaphragm 2, that is, the transmission efficiency of bending vibration is improved. In addition, the amplitude of the bending vibration increases, and it is possible to make a single vibration instead of a divided vibration in a vibration mode of a specific frequency, thereby improving the sound pressure.

  As described above, there may be two columnar portions between the diaphragm 2 and the piezoelectric element 3, or there may be more columnar portions. For example, as shown in FIG. 5, there are a first columnar portion 41 and a second columnar portion 42 below both ends of the piezoelectric element 3, and a third columnar portion below the center portion of the piezoelectric element 3. The structure with 43 may be sufficient. The two or more columnar portions are all in a position where the area when viewed through the plane is smaller than the area of the lower surface of the piezoelectric element 3 and does not protrude from the outer periphery of the piezoelectric element 3 when viewed through the plane. Even with such a configuration, the piezoelectric element 3 is less constrained, the amplitude of flexural vibration can be increased, and the vibration energy is concentrated on the columnar portion and easily transmitted to the diaphragm 2, thereby improving sound pressure. it can.

  The diaphragm 2 may be a part of a casing (case) of a portable terminal or a display. Moreover, the peripheral part of the diaphragm 2 may be fixed by a frame-like support made of, for example, a metal such as stainless steel or a resin.

  Next, a method for manufacturing the acoustic generator 1 will be described.

First, a ceramic green sheet to be the piezoelectric layer 31 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced using this ceramic slurry by using tape molding methods, such as a doctor blade method and a calender roll method. As the piezoelectric ceramic, any material having piezoelectric characteristics may be used. For example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ) can be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.

  Next, a conductive paste to be the internal electrode layer 32 is produced. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is applied on the above ceramic green sheet in a pattern of internal electrodes using a screen printing method. Furthermore, after laminating a plurality of ceramic green sheets printed with this conductive paste and performing a binder removal treatment at a predetermined temperature, firing at a temperature of 900 to 1200 ° C., using a surface grinder or the like By performing a grinding process so as to obtain a shape, a laminated body 33 including piezoelectric body layers 31 and internal electrode layers 32 that are alternately laminated is manufactured.

  The laminate 33 is not limited to the one produced by the above production method, and any production method can be used as long as the laminate 33 formed by laminating a plurality of piezoelectric layers 31 and internal electrode layers 32 can be produced. May be produced.

  Thereafter, a silver glass-containing conductive paste prepared by adding a binder, a plasticizer, and a solvent to a mixture of conductive particles mainly composed of silver and glass is used to form a main surface of the laminate 33 in the pattern of the surface electrode 34. In addition to printing by a screen printing method or the like, after printing on the side surface of the laminate 33 with the pattern of the side electrode 35 and drying, a baking process is performed at a temperature of 650 to 750 ° C. Then, the piezoelectric element 3 is manufactured.

  Next, the diaphragm 2 is prepared.

  Here, when the first columnar portion 41 (the second columnar portion 42 and other columnar portions) is formed integrally with the diaphragm 2, the diaphragm 2 is manufactured with an integral thickness, What is necessary is just to perform additional processes, such as cutting, and to remove an unnecessary part.

On the other hand, when the first columnar part 41 (the second columnar part 42 and other columnar parts) is formed separately from the diaphragm 2, the columnar part having a desired size is formed by resin molding using a mold. And the columnar portion may be joined to the diaphragm 2 using an adhesive or an adhesive tape.
Then, the piezoelectric element 3 is mounted on the diaphragm 2.

  Finally, the columnar part and the piezoelectric element 1 are joined using an adhesive or an adhesive tape.

  The sound generator 1 of this embodiment can be produced by the above method.

  Next, the electronic apparatus of this embodiment will be described.

  As shown in FIG. 6, the electronic device 10 according to the present disclosure includes the above-described acoustic generator 1, the electronic circuit 5 connected to the piezoelectric element 3 constituting the acoustic generator 1, the piezoelectric element 3, and the electronic circuit 5. And a housing 6 for housing the container. Note that FIG. 6 shows only components necessary for the description, and description of general components is omitted. Further, although the acoustic generator 1 is not shown in FIG. 6, a part of the housing 6 becomes a diaphragm, and becomes the acoustic generator 1 in combination with the piezoelectric element 3.

  The electronic device 10 includes an electronic circuit 5. The electronic circuit 5 includes, for example, a controller 51, a transmission / reception unit 52, a key input unit 53, and a microphone input unit 54. The electronic circuit 5 is connected to the piezoelectric element 3 and has a function of outputting an audio signal to the piezoelectric element 3.

  The controller 51 is a control unit of the electronic device 10. The transmission / reception unit 52 transmits / receives data via the antenna 62 based on the control of the controller 51. The key input unit 53 is an input device of the electronic device 10 and accepts a key input operation by an operator. The microphone input unit 54 is also an input device of the electronic device 10 and accepts a voice input operation by an operator. The display unit is a display output device of the electronic device 10 and outputs display information based on the control of the controller.

  The piezoelectric element 3 operates as an acoustic output device in the electronic device 10. Note that the piezoelectric element 3 is connected to the controller 51 of the electronic circuit 5 and vibrates in response to application of a voltage controlled by the controller 51 to emit sound.

In addition, the electronic device 10 includes a display unit 61 and an antenna 62. The display unit 61 has a display having a function of displaying image information. For example, known displays such as a liquid crystal display, a plasma display, and an organic EL display can be suitably used. Note that the display may have an input device such as a touch panel. Further, the display cover may be the diaphragm 2, and this may have an input device such as a touch panel. Further, the entire display or a part of the display may function as the diaphragm 2.

  The electronic apparatus 10 includes a housing 6 that accommodates or constitutes each of these devices. In the figure, all devices including the controller 51 are accommodated or constituted as one component in one housing 6. Although the state is shown, this form is not limited.

  Here, the description has been made assuming that the electronic device 10 is a portable terminal, but the type of the electronic device 10 is not questioned, and the present invention may be applied to various consumer devices having a function of emitting sound. For example, flat-screen televisions and car audio devices can of course be used for products having a function of generating sound, for example, various products such as vacuum cleaners, washing machines, refrigerators, microwave ovens, and the like.

  Since such an electronic device 10 includes the sound generator 1 with improved sound pressure, a high-quality electronic device can be realized.

DESCRIPTION OF SYMBOLS 1 Sound generator 2 Diaphragm 3 Piezoelectric element 31 Piezoelectric layer 32 Internal electrode layer 33 Laminated body 34 Surface electrode 35 Side electrode 41 1st columnar part 42 2nd columnar part 10 Electronic device 5 Electronic circuit 51 Controller 52 Transmission / reception part 53 Key Input Unit 54 Microphone Input Unit 6 Case 61 Display Unit 62 Antenna

Claims (5)

A vibration plate, a rectangular plate-shaped piezoelectric element having a longitudinal direction mounted on the vibration plate, and a first columnar portion provided between the vibration plate and the piezoelectric element,
The first columnar portion has an area when viewed through the plane that is smaller than an area of the lower surface of the piezoelectric element, and is located at a position that does not protrude from the outer periphery of the piezoelectric element when viewed through the plane. .   The sound generator according to claim 1, wherein the first columnar portion is joined to one end portion in the longitudinal direction on the lower surface of the piezoelectric element. A second columnar portion provided between the diaphragm and the piezoelectric element;
The area of the second columnar portion when viewed through the plane is smaller than the area of the lower surface of the piezoelectric element, and the second columnar portion does not protrude from the outer periphery of the piezoelectric element when viewed through the plane. The sound generator according to claim 2, wherein the sound generator is joined to the other end portion in the longitudinal direction. A vibration plate, a rectangular plate-shaped piezoelectric element having a longitudinal direction mounted on the vibration plate, and two or more columnar portions provided between the vibration plate and the piezoelectric element,
The two or more columnar portions have an area when viewed through the plane that is smaller than the area of the lower surface of the piezoelectric element, and are in a position that does not protrude from the outer periphery of the piezoelectric element when viewed through the plane. Generator.   The acoustic generator according to any one of claims 1 to 4, an electronic circuit connected to the piezoelectric element constituting the acoustic generator, and a housing for housing the piezoelectric element and the electronic circuit An electronic device comprising:

Images