JP2015185819A - Driver of bimorph piezoelectric element and portable terminal including the same, acoustic generator, acoustic generation device, electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driver of a bimorph piezoelectric element which allows for a large amount of displacement and a large generation force in the bimorph piezoelectric element, and to provide a portable terminal including the same, an acoustic generator, an acoustic generation device, and an electronic apparatus.SOLUTION: A driver of a bimorph piezoelectric element includes a bimorph piezoelectric element 1 having a laminate 15 of a plurality of piezoelectric layers 11 and a plurality of electrode layers 12, and consisting of a first region 13 located on one side in the lamination direction, and a second region 14 located on the other side in the lamination direction, and a drive circuit 17 for driving the bimorph piezoelectric element 1. A drive voltage is applied, respectively, to the first region 13 and second region 14, while offsetting a reverse potential.

Description

  The present invention relates to a driving device for a bimorph piezoelectric element that can be used for a portable terminal, a speaker, an acoustic device, an electronic device, and the like, and a portable terminal, an acoustic generator, an acoustic generator, and an electronic device that include the driving device.

  Conventionally, a piezoelectric body layer and an electrode layer are laminated, and has a laminated body including a first region located on one side in the laminating direction and a second region located on the other side in the laminating direction of the laminated body. A bimorph type piezoelectric element is known (see, for example, Patent Document 1).

  When this bimorph type piezoelectric element is driven, when an electric field in the same direction as the direction of polarization is applied to the piezoelectric layer constituting the first region (a forward voltage is applied), the piezoelectric material constituting the second region When an electric field in the direction opposite to the direction of polarization is applied to the layer (a reverse voltage is applied) and a reverse voltage is applied to the first region, a forward voltage is applied to the second region. With this structure, when the piezoelectric layer in the first region contracts in the in-plane direction perpendicular to the stacking direction, the piezoelectric layer in the second region extends in the in-plane direction and is bent as a whole. Vibrate.

JP 61-30974 A

  Here, the bimorph type piezoelectric element is previously polarized. However, when a voltage exceeding the polarization degradation voltage Vec corresponding to the coercive electric field is applied in a direction opposite to the polarization direction of the bimorph type piezoelectric element, the polarization direction P is changed. Inverted and unusable. Therefore, it cannot be driven by applying a high voltage in the direction opposite to the polarization direction. Therefore, since it must be driven with a voltage equal to or lower than the polarization deterioration voltage Vec, a large amount of displacement and generated force cannot be extracted.

  The present invention has been made in view of the above circumstances, and a driving device for a bimorph piezoelectric element capable of obtaining a large displacement and generating force in a bimorph piezoelectric element, and a portable terminal, an acoustic generator, and an acoustic device including the same. It aims at providing a generator and an electronic device.

  A driving device for a bimorph piezoelectric element of the present invention includes a plurality of piezoelectric layers and a plurality of electrode layers stacked, a first region positioned on one side in the stacking direction, and a second positioned on the other side in the stacking direction. A bimorph type piezoelectric element drive device, comprising: a bimorph type piezoelectric element having a laminated body composed of a plurality of regions; and a drive circuit for driving the bimorph type piezoelectric element, wherein the first region and the second region A drive voltage is applied to each of the regions by applying an offset of a reverse potential.

  The drive device for a bimorph piezoelectric element according to the present invention has the above-described configuration, wherein the plurality of electrode layers are provided in the first region provided in the first region and in the second region. A second electrode layer; and a common electrode layer provided opposite to the first electrode layer and the second electrode layer with the piezoelectric layer interposed therebetween, and the common electrode layer is used as a reference. As described above, an AC signal is input to each of the first electrode layer and the second electrode layer.

  The piezoelectric vibration device of the present invention is characterized in that the bimorph type piezoelectric element in the above-described bimorph type piezoelectric element driving device is joined to a vibration plate.

  A portable terminal of the present invention includes the above-described bimorph piezoelectric element driving device, an electronic circuit, a display, and a casing, and the bimorph piezoelectric element is joined to the display or the casing. It is characterized by.

  The portable terminal according to the present invention is characterized in that, in the above-described configuration, the display or the casing generates a vibration for transmitting sound information through an ear cartilage or air conduction.

  An acoustic generator according to the present invention includes the above-described drive device for the bimorph piezoelectric element, a diaphragm to which the bimorph piezoelectric element is bonded, and a support body that supports a peripheral portion of the diaphragm. It is characterized by.

  According to another aspect of the present invention, there is provided a sound generator comprising: the above-described sound generator; and a housing that houses the sound generator.

  According to another aspect of the invention, there is provided an electronic device including the above-described acoustic generator, an electronic circuit connected to the acoustic generator, and a housing that houses the electronic circuit and the acoustic generator. It has the function to generate | occur | produce.

  According to the present invention, the displacement amount and generated force of the bimorph piezoelectric element can be increased. Moreover, in an acoustic generator in which a bimorph piezoelectric element is attached to a diaphragm, the amplitude of the diaphragm can be increased, and the sound pressure of the generated sound can be improved.

It is a block diagram which shows an example of embodiment of the drive device of the bimorph type piezoelectric element of this invention. It is a graph which shows the applied voltage in the 1st area | region and 2nd area | region of the drive device of the bimorph type piezoelectric element of this invention. 1 is a schematic perspective view schematically showing an embodiment of a piezoelectric vibration device of the present invention. It is a schematic perspective view which shows typically embodiment of the portable terminal of this invention. It is the schematic sectional drawing cut | disconnected by the AA line shown in FIG. It is the schematic sectional drawing cut | disconnected by the BB line shown in FIG. (A) is a typical top view which shows schematic structure of embodiment of the acoustic generator of this invention, (b) is a schematic sectional drawing of an example cut | disconnected by the AA line of (a), ( (c) is a schematic sectional drawing of the other example cut | disconnected by the AA line of (a). It is a figure which shows the structure which concerns on embodiment of the sound generator of this invention. It is a figure which shows the structure which concerns on embodiment of the electronic device of this invention.

  One example of an embodiment of a driving device for a bimorph piezoelectric element of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an example of an embodiment of a drive device for a bimorph piezoelectric element of the present invention. The driving device for the bimorph piezoelectric element of the example shown in FIG. 1 includes a plurality of piezoelectric layers 11 and a plurality of electrode layers 12 stacked, and a first region 13 located on one side in the stacking direction and the other in the stacking direction. Bimorph piezoelectric element 1 having a laminate 15 composed of a second region 14 located on the side
And a drive circuit 17 for driving the bimorph type piezoelectric element 1, and a drive voltage is applied to each of the first region 13 and the second region 14 by applying a reverse potential offset.

  The driving device of the bimorph type piezoelectric element of this example has a bimorph type piezoelectric element 1, and a laminated body 15 constituting the bimorph type piezoelectric element 1 is formed by laminating a plurality of piezoelectric layers 11 and a plurality of electrode layers 12. It is formed in a plate shape. The bimorph piezoelectric element 1 has an active portion in which a plurality of electrode layers 12 overlap in the stacking direction and an inactive portion other than the active portion, and is formed in a long shape, for example. When the bimorph piezoelectric element 1 is used by being attached to a display or casing of a mobile terminal, the length of the laminate 15 is preferably, for example, 18 mm to 28 mm, and more preferably 22 mm to 25 mm. The width of the laminate 15 is preferably 1 mm to 6 mm, for example, and more preferably 3 mm to 4 mm. The thickness of the laminated body 15 is preferably 0.2 mm to 1.0 mm, for example, and more preferably 0.4 mm to 0.8 mm.

The plurality of piezoelectric layers 11 constituting the multilayer body 15 are formed of ceramics having piezoelectric characteristics. As such ceramics, for example, perovskite type oxidation made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ) is used. For example, lithium niobate (LiNbO ₃ ) or lithium tantalate (LiTaO ₃ ) can be used. The thickness of one layer of the piezoelectric layer 11 is preferably set to, for example, 0.01 to 0.1 mm in order to drive at a low voltage. In order to obtain a large bending vibration, it is preferable to have a piezoelectric constant d31 of 200 pm / V or more.

  The plurality of electrode layers 12 constituting the multilayer body 15 are formed by simultaneous firing with ceramics forming the piezoelectric body layer 11, and are alternately stacked with the piezoelectric body layers 11 so as to sandwich the piezoelectric body layers 11 from above and below. The drive voltage is applied to the piezoelectric layer 11 sandwiched between them. As this forming material, for example, a conductor mainly composed of silver or silver-palladium alloy having low reactivity with piezoelectric ceramics, or a conductor containing copper, platinum or the like can be used. You may make it contain.

  In the example shown in FIG. 1, the stacked body 15 includes a first region 13 positioned on one side (upper side) in the stacking direction and a second region 14 positioned on the other side (lower side) in the stacking direction. ing. The electrode layer 12 constituting the stacked body 15 includes a common electrode layer 120, a first electrode layer 121, and a second electrode layer 122, and the common electrode layer 120 and the first electrode layer 121 are included in the first region 13. And the common electrode layer 120 and the second electrode layer 122 are disposed in the second region 14. The common electrode layer 120 is led out on one side surface of the pair of side surfaces of the stacked body 15, and the first electrode layer 121 and the second electrode layer 122 are led out on the other side surface. In the case of a piezoelectric actuator attached to a display or casing of a mobile terminal, the length of the electrode layer 12 is preferably, for example, 17 mm to 25 mm, and more preferably 21 mm to 24 mm. For example, the width of the electrode layer 12 is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The thickness of the electrode layer 12 is preferably 0.1 μm to 5 μm, for example.

  A common side surface electrode 160 is provided on one side surface of the multilayer body 15, and the common side surface electrode 160 is electrically connected to the common electrode layer 120. Further, a first side electrode 161 and a second side electrode 162 are provided on the other side surface of the multilayer body 15, and the first side electrode 161 is electrically connected to the first electrode layer 121, The second side electrode 162 is electrically connected to the second electrode layer 122.

The bimorph piezoelectric element 1 applies a voltage in the opposite direction between the common electrode layer 120 and the first electrode layer 121 and between the common electrode layer 120 and the second electrode layer 122, The direction of polarization of the piezoelectric layer 11 constituting one region 13 is directed from the common electrode layer 120 to the first electrode layer 121, whereas the direction of polarization of the piezoelectric layer 11 constituting the second region 14 is directed. Is manufactured so as to face from the second electrode layer 122 to the common electrode layer 120. For example, such a polarization direction can be obtained by applying a voltage of +75 V to the first electrode layer 121 and −75 V to the second electrode layer 122 with the common electrode layer 120 as the ground.

  The common electrode layer 120, the first electrode layer 121, and the second electrode layer 122 of the bimorph type piezoelectric element 1 are the common side electrode 160, the first side electrode 161, the second side electrode 162, or other not shown. A drive device for the bimorph piezoelectric element is configured by being electrically connected to the drive circuit 17 through electrodes or the like.

  At the time of driving, as shown in FIG. 2, a driving voltage is applied to each of the first region 13 and the second region 14 by applying a reverse potential offset to drive the region. FIG. 2 shows applied voltages in the first region 13 and the second region 14 of the driving device for the bimorph piezoelectric element of the present invention.

  That is, a drive voltage is applied to the first region 13 with an offset applied to the polarization direction and the forward direction of the piezoelectric layer 11 constituting the first region 13. On the other hand, a drive voltage is applied to the second region 14 by applying an offset to the polarization direction and the forward direction of the piezoelectric layer 11 constituting the second region 14. The first region 13 and the second region 14 include a direction in which the polarization direction of the piezoelectric layer 11 is directed from the first electrode layer 121 to the common electrode layer 120, and from the common electrode layer 120 to the second electrode. Since the arrangement of the piezoelectric layers 11 having different polarization directions is symmetric with respect to the direction toward the layer 122, the drive voltage is applied by applying a reverse potential offset by applying a drive voltage by applying an offset in the forward direction. Is applied. Here, if the direction of polarization is positive when the direction from the common electrode layer 120 toward the opposite electrode is positive, since the polarization direction of the first region 13 is positive, the applied voltage is applied with an offset in the forward direction. Will be offset in the positive direction. On the other hand, since the polarization direction of the second region 14 is negative, when the applied voltage is applied with an offset in the forward direction, the second region 14 is offset in the negative direction.

  Thereby, the displacement amount and generated force of the bimorph piezoelectric element 1 can be increased.

  When the polarization degradation voltage is 20 V and the dielectric breakdown voltage is 50 V, in the conventional driving method, for example, a voltage of −15 to +15 V is applied as a voltage that does not cause polarization degradation in both the first region 13 and the second region 14. Had to drive. On the other hand, according to the present invention, it is possible to apply a voltage not higher than the polarization degradation voltage in the direction opposite to the polarization direction and to apply a voltage not higher than the dielectric breakdown voltage in the polarization direction and the forward direction. When the polarization degradation voltage is 20 V and the dielectric breakdown voltage is 50 V, for example, a voltage of −15 to +45 V is applied to the first region 13, and a voltage of −45 to +15 V is applied to the second region 14. be able to. Therefore, it is possible to obtain a larger displacement and generated force than in the past. In an acoustic generator in which a bimorph piezoelectric element is attached to a diaphragm, the amplitude of the diaphragm can be increased, and the sound pressure of the generated sound can be increased.

  By applying a driving voltage to each of the first region 13 and the second region 14 while simultaneously applying a reverse potential offset, both the first region 13 and the second region 14 are flexibly vibrated. In addition, since a large amount of displacement and generated force can be obtained, it is not necessary to increase the number of stacked bimorph type piezoelectric elements 1, and it can be manufactured at low cost.

Here, in the driving device for the bimorph piezoelectric element 1, the plurality of electrode layers 12 includes the first electrode layer 121 provided in the first region 13 and the second electrode provided in the second region 14. 2 and a common electrode layer 120 provided to face the first electrode layer 121 and the second electrode layer 122 with the piezoelectric layer 11 in between, and as shown in FIG. It is preferable that an AC signal is input to each of the first electrode layer 121 and the second electrode layer 122 with the electrode layer 120 as a reference, and an offset driving voltage is applied. Here, using the common electrode layer 120 as a reference means that the common electrode layer 120 is grounded, for example, to be a ground electrode (0 V).

  By providing the common electrode layer 120 so as to face the first electrode layer 121 and the second electrode layer 122, the bimorph piezoelectric element 1 can be manufactured at low cost, and the common electrode layer 120 is used as a reference. Since the drive of the first region 13 and the second region 14 can be synchronized by inputting an AC signal to each of the first electrode layer 121 and the second electrode layer 122, vibration can be efficiently performed. Can be made.

  In a configuration in which an AC signal is input to the common electrode layer 120 and a bias voltage is applied to each of the first electrode layer 121 and the second electrode layer 122, the bimorph piezoelectric element 1 is attached to the diaphragm as will be described later. When a voltage is generated from a bimorph type piezoelectric element due to stress and the bias voltage fluctuates and the applied voltage becomes unstable, the applied voltage becomes unstable while using the common electrode layer 120 as a reference. An AC signal is input to each of the layer 121 and the second electrode layer 122 so that an offset driving voltage is applied, whereby a voltage is generated from the bimorph piezoelectric element due to stress. A high-performance bimorph type piezoelectric element drive device that is less susceptible to fluctuations in applied voltage can be obtained.

  As shown in FIG. 3, the piezoelectric vibration device of this embodiment is obtained by joining the bimorph piezoelectric element 1 in the above-described bimorph piezoelectric element driving device to a vibration plate 81. In other words, the driving device for the bimorph piezoelectric element 1 described above and the vibration plate 81 bonded to the main surface of the laminate 15 constituting the bimorph piezoelectric element 1 are provided. In FIG. 3, the drive circuit 17 is omitted.

  The diaphragm 81 is, for example, a rectangular thin plate. The diaphragm 81 can be preferably formed using a material having high rigidity and elasticity, such as acrylic resin or glass. Moreover, the thickness of the diaphragm 81 is set to 0.4 mm to 1.5 mm, for example.

  The diaphragm 81 is joined to one main surface of the multilayer body 15 constituting the bimorph piezoelectric element 1 via a joining member 82. The entire main surface of the laminate 15 constituting the bimorph piezoelectric element 1 may be bonded to the vibration plate 81 via the bonding member 82, or the substantially entire surface may be bonded.

  The joining member 82 has a film shape. Further, the joining member 82 is formed of a material that is softer and more easily deformed than the vibration plate 81, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk elastic modulus than the vibration plate 81. That is, the joining member 82 can be deformed when the vibration plate 81 is vibrated by driving the bimorph type piezoelectric element 1, and is deformed more greatly than the vibration plate 81 when the same force is applied. Then, one main surface (main surface on the −z direction side in the drawing) of the laminate 15 is entirely fixed to one main surface (main surface on the + z direction side in the drawing) of the bonding member 82. A part of one main surface (main surface on the + z direction side in the drawing) of the diaphragm 81 is fixed to the other main surface (main surface on the −z direction side in the drawing).

  By joining the laminate 15 and the vibration plate 81 with the deformable joining member 82, when the vibration is transmitted from the bimorph piezoelectric element 1, the deformable joining member 82 is deformed more greatly than the vibration plate 81.

At this time, since the anti-phase vibration reflected from the vibration plate 81 can be reduced by the deformable joining member 82, the bimorph type piezoelectric element 1 is not affected by the surrounding vibration and the vibration plate 81.
Strong vibrations can be transmitted.

  In particular, since at least a part of the bonding member 82 is formed of a viscoelastic body, strong vibration from the bimorph piezoelectric element 1 is transmitted to the vibration plate 81, while weak vibration reflected from the vibration plate 81 is transmitted to the bonding member. 82 is preferable in that it can be absorbed. For example, it is possible to use a double-sided tape in which an adhesive is attached to both surfaces of a base material made of nonwoven fabric or the like, or a joining member including an adhesive having elasticity, and the thickness thereof is, for example, 10 μm to 2000 μm. Can be used.

  The joining member 82 may be a single member or a composite made up of several members. As such a joining member 82, for example, a double-sided tape in which a pressure-sensitive adhesive is attached to both surfaces of a base material made of a nonwoven fabric or the like, various elastic adhesives that are adhesives having elasticity, and the like can be suitably used. In addition, the thickness of the bonding member 82 is desirably larger than the amplitude of the bending vibration of the bimorph piezoelectric element 1, but if it is too thick, the vibration is attenuated, so that the thickness is set to 0.1 mm to 0.6 mm, for example. . However, in the piezoelectric vibration device of the present invention, the material of the bonding member 82 is not limited, and the bonding member 82 may be formed of a material that is harder and more difficult to deform than the vibration plate 81. Moreover, depending on the case, the structure which does not have the joining member 82 may be sufficient.

  The piezoelectric vibration device of this example having such a configuration functions as a piezoelectric vibration device that flexures and vibrates the bimorph piezoelectric element 1 by applying an electrical signal, thereby vibrating the vibration plate 81. Note that the other end of the diaphragm 81 in the length direction (the end in the −y direction in the figure, the peripheral edge of the diaphragm 81, etc.) may be supported by a support member (not shown).

  Further, in the piezoelectric vibration device of this example, a vibration plate 81 is bonded to one flat main surface of the bimorph piezoelectric element 1. As a result, a piezoelectric vibration device in which the bimorph piezoelectric element 1 (laminated body 15) and the vibration plate 81 are firmly bonded can be obtained.

  Since the piezoelectric vibration device of this example is configured by using the bimorph type piezoelectric element 1 having a large displacement and generating force, it can be a high-performance piezoelectric vibration device.

  As shown in FIGS. 4 to 6, the portable terminal of the present embodiment includes a driving device for the bimorph piezoelectric element 1, an electronic circuit (not shown), a display 91, and a housing 92. The main surface of the laminate 15 constituting the bimorph piezoelectric element 1 is bonded to the housing 92. 4 is a schematic perspective view schematically showing the portable terminal of the present invention, FIG. 5 is a schematic cross-sectional view taken along line AA shown in FIG. 4, and FIG. 6 is a line BB shown in FIG. It is the schematic sectional drawing cut | disconnected by. 4 to 6, the drive circuit 17 is omitted.

  Here, it is preferable that the laminated body 15 and the housing | casing 92 are joined using the deformable joining member. That is, in FIG. 5 and FIG. 6, the joining member 82 is a deformable joining member.

  By joining the laminate 15 and the housing 92 with the deformable joining member 82, when vibration is transmitted from the bimorph piezoelectric element 1, the deformable joining member 82 is deformed to a greater extent than the housing 92.

  At this time, the anti-phase vibration reflected from the casing 92 can be mitigated by the deformable joining member 82, so that the bimorph type piezoelectric element 1 is strongly influenced by the casing 92 without being influenced by the surrounding vibration. Can be transmitted.

  In particular, since at least a part of the joining member 82 is formed of a viscoelastic body, strong vibration from the bimorph piezoelectric element 1 is transmitted to the housing 92, while weak vibration reflected from the housing 92 is transmitted to the joining member. 82 is preferable in that it can be absorbed. For example, it is possible to use a double-sided tape in which an adhesive is attached to both surfaces of a base material made of nonwoven fabric or the like, or a joining member including an adhesive having elasticity, and the thickness thereof is, for example, 10 μm to 2000 μm. Can be used.

  In this example, the laminated body 15 is attached to a part of the casing 92 that serves as a cover for the display 91, and a part of the casing 92 functions as the diaphragm 922.

  In this example, the laminated body 15 is bonded to the housing 92, but the laminated body 15 may be bonded to the display 91.

  The housing 92 includes a box-shaped housing main body 921 having one surface opened, and a diaphragm 922 that closes the opening of the housing main body 921. The casing 92 (the casing main body 921 and the diaphragm 922) can be formed preferably using a material such as a synthetic resin having high rigidity and elastic modulus.

  A peripheral edge portion of the vibration plate 922 is attached to the housing main body 921 via a bonding material 93 so as to vibrate. The bonding material 93 is formed of a material that is softer and easier to deform than the diaphragm 922, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk modulus than the diaphragm 922. That is, the bonding material 93 can be deformed, and deforms more greatly than the diaphragm 922 when the same force is applied.

  The bonding material 93 may be a single material or a composite material composed of several members. As such a bonding material 93, for example, a double-sided tape in which an adhesive is attached to both surfaces of a base material made of a nonwoven fabric or the like can be suitably used. The thickness of the bonding material 93 is set so that vibration is not attenuated due to being too thick, and is set to, for example, 0.1 mm to 0.6 mm. However, in the mobile terminal of the present invention, the material of the bonding material 93 is not limited, and the bonding material 93 may be formed of a material that is harder than the vibration plate 922 and hardly deforms. Moreover, depending on the case, the structure which does not have the joining material 93 may be sufficient.

  Examples of the electronic circuit (not shown) include a circuit that processes image information displayed on the display 91 and audio information transmitted by the mobile terminal, a communication circuit, and the like. At least one of these circuits may be included, or all the circuits may be included. Further, it may be a circuit having other functions. Furthermore, you may have a some electronic circuit. The electronic circuit and the drive circuit for the bimorph piezoelectric element 1 are connected by a connection wiring (not shown).

  The display 91 is a display device having a function of displaying image information. For example, a known display such as a liquid crystal display and an organic EL display can be suitably used. The display 91 may have an input device such as a touch panel. Moreover, the cover (diaphragm 922) of the display 91 may have an input device such as a touch panel. Further, the entire display 91 or a part of the display 91 may function as a diaphragm.

  Since the mobile terminal of this example is configured using the bimorph piezoelectric element 1 having a large displacement and generated force, it can be a high-performance mobile terminal.

In addition, the mobile terminal according to the present embodiment is characterized in that the display 91 or the casing 92 generates vibration that transmits sound information through the ear cartilage or air conduction. The portable terminal of this example can transmit sound information by transmitting a vibration to the cartilage of the ear by bringing the diaphragm (display 91 or housing 92) into contact with the ear directly or via another object. That is, sound information can be transmitted by bringing a vibration plate (display 91 or housing 92) into direct or indirect contact with the ear and transmitting vibration to the cartilage of the ear. Thereby, for example, even when the surroundings are noisy, sound information can be transmitted clearly, and a portable terminal capable of recognizing voice even by a hearing impaired person can be obtained. Note that the object interposed between the diaphragm (display 91 or housing 92) and the ear may be, for example, a cover of a mobile terminal, a headphone or an earphone, and any object that can transmit vibration. Anything can be used. Further, it may be a portable terminal that transmits sound information by propagating sound generated from the diaphragm (display 91 or housing 92) in the air. Furthermore, it may be a portable terminal that transmits sound information via a plurality of routes.

  Further, as shown in FIG. 7, the acoustic generator 10 of the present embodiment includes a driving device for the above-described bimorph piezoelectric element, a diaphragm 20 to which the bimorph piezoelectric element 1 is bonded, and a peripheral portion of the diaphragm 20. And a frame body 30 as a support body for supporting In FIG. 7, the drive circuit 17 is omitted.

  The bimorph piezoelectric element 1 is an exciter that excites the diaphragm 20 by vibrating under application of a voltage. One main surface of the bimorph type piezoelectric element 1 and the main surface of the diaphragm 20 are joined by an adhesive such as an epoxy resin, and the bimorph type piezoelectric element 1 is flexibly vibrated, so that the bimorph type piezoelectric element 1 is moved to the diaphragm 20. A sound can be generated by applying a certain vibration to the.

  The periphery of the diaphragm 20 is fixed to the frame 30 in a state where tension is applied, and the diaphragm 20 vibrates together with the bimorph piezoelectric element 1 by the vibration of the bimorph piezoelectric element 1. The diaphragm 20 can be formed using various materials such as resin and metal. For example, the diaphragm 20 can be formed of a resin film such as polyethylene, polyimide, or polypropylene having a thickness of 10 to 200 μm. Since the resin film is a material having a lower elastic modulus and mechanical Q value than a metal plate or the like, the diaphragm 20 is made of a resin film, so that the diaphragm 20 bends and vibrates with a large amplitude, thereby reducing the sound pressure. It is possible to reduce the difference between the resonance peak and the dip by widening the width of the resonance peak and reducing the height in the frequency characteristics.

  The frame body 30 functions as a support body that supports the diaphragm 20 at the periphery of the diaphragm 20, and can be formed using various materials such as metals such as stainless steel and resins. The frame 30 may be composed of one frame member (upper frame member 301) as shown in FIG. 7 (b), and two frame members (upper frame member 301 and upper frame member 301 and The lower frame member 302) may be used. In this case, the tension of the diaphragm 20 can be stabilized by sandwiching the diaphragm 20 between the two frame members. The upper frame member 301 and the lower frame member 302 have a thickness of, for example, 100 to 5000 μm.

  In the acoustic generator 10 of this example, as shown in FIGS. 7B and 7C, at least part of the surface of the diaphragm 20 from the bimorph piezoelectric element 1 (for example, the periphery of the bimorph piezoelectric element 1) It is preferable to further have a resin layer 40 provided so as to cover up to the portion). As the resin layer 40, for example, an acrylic resin can be used. By embedding the bimorph type piezoelectric element 1 in the resin layer 40, an appropriate damper effect can be induced, so that the resonance phenomenon can be suppressed and the peak or dip in the frequency characteristic of the sound pressure can be reduced. 7B and 7C, the resin layer 40 may be formed to be the same height as the upper frame member 301.

Since the sound generator 10 of this example is configured using the bimorph piezoelectric element 1 having a large displacement and generating force, it can be a high-performance sound generator.

  Next, an example of an embodiment of the sound generator of the present invention will be described.

  The sound generation device 80 is a sound generation device such as a so-called speaker, and includes, for example, a sound generator 10 and a housing 70 that houses the sound generator 10 as illustrated in FIG. 8. In FIG. 8, the drive circuit 17 is omitted.

  The housing 70 resonates the sound generated by the sound generator 10 and radiates sound to the outside from an opening (not shown) formed in the housing 70. By having such a housing | casing 70, the sound pressure in a low frequency band can be raised, for example.

  Such a sound generator 80 can be used alone as a speaker, and can be suitably incorporated into a portable terminal, a thin television, a tablet terminal, or the like, as will be described later. Moreover, it can also be incorporated into home appliances that have not been prioritized in terms of sound quality, such as refrigerators, microwave ovens, vacuum cleaners, and washing machines.

  Since the sound generator 80 of the present invention is configured using the bimorph piezoelectric element 1 having a large displacement and generating force, a high-performance sound generator can be obtained.

  Next, an electronic device equipped with an acoustic generator will be described with reference to FIG. FIG. 9 is a diagram illustrating a configuration of the electronic device 50 according to the embodiment. In the figure, only components necessary for explanation are shown, and descriptions of general components are omitted. In FIG. 9, the drive circuit 17 is omitted.

  As shown in FIG. 9, the electronic device 50 of this example includes an acoustic generator 10, an electronic circuit 60 connected to the acoustic generator 10, and a housing 70 that houses the electronic circuit 60 and the acoustic generator 10. And having a function of generating sound from the sound generator 10.

  The electronic device 50 includes an electronic circuit 60. The electronic circuit 60 includes, for example, a controller 50a, a transmission / reception unit 50b, a key input unit 50c, and a microphone input unit 50d. The electronic circuit 60 is connected to the sound generator 10 and has a function of outputting an audio signal to the sound generator 10. The sound generator 10 generates sound based on the sound signal input from the electronic circuit 60.

  The electronic device 50 includes a display unit 50e, an antenna 50f, and the sound generator 10. Further, the electronic device 50 includes a housing 70 that accommodates these devices. Although FIG. 9 shows a state in which each device including the controller 50a is accommodated in one casing 70, the accommodation form of each device is not limited. In the present embodiment, it is only necessary that at least the electronic circuit 60 and the sound generator 10 are accommodated in one housing 70.

  The controller 50 a is a control unit of the electronic device 50. The transmission / reception unit 50b transmits / receives data via the antenna 50f based on the control of the controller 50a. The key input unit 50c is an input device of the electronic device 50 and accepts a key input operation by an operator. The microphone input unit 50d is also an input device of the electronic device 50, and accepts a voice input operation by an operator. The display unit 50e is a display output device of the electronic device 50, and outputs display information based on the control of the controller 50a.

The sound generator 10 operates as a sound output device in the electronic device 50.
The sound generator 10 is connected to the controller 50a of the electronic circuit 60, and emits sound upon application of a voltage controlled by the controller 50a.

  In FIG. 9, the electronic device 50 is described as a portable terminal device. However, the electronic device 50 is not limited to the type of the electronic device 50, and 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 50 is configured using the bimorph type piezoelectric element 1 having a large displacement and generating force, it can be a high-performance electronic device. In addition, by providing the housing 70, it is possible to increase the low-frequency sound pressure.

1: Bimorph type piezoelectric element 11: Piezoelectric layer 12: Electrode layer 13: First region body layer 14: Second region 15: Laminate 16: Side electrode 17: Drive circuit 81: Diaphragm 82: Bonding member 91 : Display 92: Housing 921: Housing body 922: Diaphragm 93: Bonding material 10: Sound generator 20: Diaphragm 30: Frame body 301: Upper frame member 302: Lower frame member 40: Resin layer 50: Electronic device 60: Electronic circuit 70: Housing 80: Sound generator

Claims (8)

A bimorph type piezoelectric device having a laminated body in which a plurality of piezoelectric layers and a plurality of electrode layers are laminated, and which includes a first region located on one side in the laminating direction and a second region located on the other side in the laminating direction Elements,
A drive device for a bimorph piezoelectric element including a drive circuit for driving the bimorph piezoelectric element,
A driving device for a bimorph piezoelectric element, wherein a driving voltage is applied to each of the first region and the second region by applying an offset of a reverse potential. The plurality of electrode layers include the first electrode layer provided in the first region, the second electrode layer provided in the second region, and the first piezoelectric layer through the piezoelectric layer. A common electrode layer provided opposite to the electrode layer and the second electrode layer,
An AC signal is input to each of the first electrode layer and the second electrode layer with the common electrode layer as a reference, and an offset driving voltage is applied. The drive device for a bimorph piezoelectric element according to claim 1.   3. The piezoelectric vibration device according to claim 1, wherein the bimorph piezoelectric device in the bimorph piezoelectric device driving device is bonded to a diaphragm.   A drive device for a bimorph piezoelectric element according to claim 1, an electronic circuit, a display, and a housing, wherein the bimorph piezoelectric element is bonded to the display or the housing. A mobile terminal characterized by   The mobile terminal according to claim 4, wherein the display or the casing generates vibrations that transmit sound information through ear cartilage or air conduction.   A driving device for a bimorph piezoelectric element according to claim 1, a diaphragm to which the bimorph piezoelectric element is bonded, and a support body that supports a peripheral portion of the diaphragm. A featured sound generator. An acoustic generator according to claim 6;
A sound generator comprising: a housing for housing the sound generator. A function of generating sound from the sound generator, comprising: the sound generator according to claim 6; an electronic circuit connected to the sound generator; and a housing that houses the electronic circuit and the sound generator. An electronic device comprising: