Audio equipment

Abstract

To provide an acoustic device with improved sound quality.SOLUTION: An acoustic device includes a plurality of vibrating elements 10a, 10b, and 10c that vibrate in response to a common audio signal, and a vibrating member 20 in which the plurality of vibrating elements are connected to the same main surface. The plurality of vibrating elements include a first vibrating element 10a and a second vibrating element 10b, and the first vibrating element and the second vibrating element transmit vibrations having different phases to the vibrating member.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an audio device. [Background technology]

[0002] Patent Document 1 discloses a display device including a display panel and an actuator. The display device of Patent Document 1 has a function of vibrating the display panel by controlling the actuator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Korean Patent Publication No. 10-2018-0077582 Summary of the Invention [Problem to be solved by the invention]

[0004] The structure described in Patent Document 1 can also be applied to audio devices. However, audio devices with the structure described in Patent Document 1 may not have sufficient sound quality.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide an audio device with improved sound quality. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided an acoustic device comprising a plurality of vibration elements that vibrate in response to a common audio signal, and a vibration member having the plurality of vibration elements connected to the same main surface, wherein the plurality of vibration elements include a first vibration element and a second vibration element, and the first vibration element and the second vibration element transmit vibrations of different phases to the vibration member. Effect of the Invention

[0007] According to the present invention, it is possible to provide an audio device with improved sound quality. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a schematic configuration of an audio device according to a first embodiment. [Diagram 2] FIG. 2 is a plan view showing an arrangement of piezoelectric elements according to the first embodiment. [Diagram 3] 2 is a cross-sectional view showing the arrangement of piezoelectric elements according to the first embodiment. FIG. [Figure 4] 2 is a cross-sectional view showing the arrangement of piezoelectric elements according to the first embodiment. FIG. [Diagram 5] 2 is a cross-sectional view showing the structure of the piezoelectric element according to the first embodiment in more detail. FIG. [Figure 6] 3A to 3C are schematic diagrams showing deformation when a voltage is applied to the piezoelectric element according to the first embodiment. [Figure 7] 3A to 3C are schematic diagrams showing deformation when a voltage is applied to the piezoelectric element according to the first embodiment. [Figure 8] 3A to 3C are schematic diagrams showing in more detail a method of inputting an audio signal to a piezoelectric element according to the first embodiment. [Figure 9] 3A to 3C are schematic diagrams illustrating the effects of the acoustic device according to the first embodiment. [Figure 10] 4 is a graph illustrating the effect of the audio device according to the first embodiment. [Figure 11] FIG. 11 is a plan view showing an arrangement of piezoelectric elements according to a second embodiment. [Figure 12] FIG. 11 is a cross-sectional view showing the arrangement of piezoelectric elements according to a second embodiment. [Figure 13] 6 is a cross-sectional view showing the structure of the piezoelectric element according to the second embodiment in more detail. FIG. [Figure 14] 6A to 6C are schematic diagrams showing deformation when a voltage is applied to a piezoelectric element according to a second embodiment. [Figure 15] 6A to 6C are schematic diagrams showing deformation when a voltage is applied to a piezoelectric element according to a second embodiment. [Figure 16]13A to 13C are schematic diagrams showing in more detail a method of inputting an audio signal to a piezoelectric element according to a second embodiment. [Figure 17] 11 is a cross-sectional view showing the structure of a piezoelectric element according to a third embodiment in more detail. FIG. [Figure 18] 13A to 13C are schematic diagrams showing in more detail a method of inputting an audio signal to a piezoelectric element according to a third embodiment. [Figure 19] FIG. 13 is a block diagram showing a schematic configuration of a display device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Elements having common functions are designated by the same reference numerals throughout the drawings, and duplicated descriptions may be omitted or simplified.

[0010] [First embodiment] FIG. 1 is a schematic diagram of an audio device 1 according to a first embodiment. The audio device 1 of this embodiment may be used as a speaker by itself, or may be built into another device. For example, the audio device 1 may be built into a signage such as an advertising billboard, poster, or guide board. In this case, a voice such as guidance can be emitted from the signage. The audio device 1 may also be built into a display device, a computer, a television receiver, or the like. However, the use of the audio device 1 of this embodiment is not particularly limited.

[0011] 1, the acoustic device 1 includes a plurality of piezoelectric elements 10a, 10b, and 10c, a vibrating member 20, and a control unit 40. The acoustic device 1 is a device that produces sound based on an input audio signal or the like.

[0012] The piezoelectric elements 10a, 10b, and 10c are elements that are displaced by the inverse piezoelectric effect when a voltage based on an input audio signal is applied. The piezoelectric elements 10a, 10b, and 10c may be, for example, bimorph, unimorph, or other elements that are displaced by bending in response to a voltage. Since the input audio signal is usually an AC voltage, the piezoelectric elements 10a, 10b, and 10c function as vibration elements that vibrate in response to the input audio signal.

[0013] The vibrating member 20 is a member that vibrates to emit a sound based on a common audio signal input to the piezoelectric elements 10a, 10b, and 10c. Each of the piezoelectric elements 10a, 10b, and 10c is mechanically connected to the vibrating member 20 via an elastic member. The material of the vibrating member 20 is not limited to a specific material. However, it is preferable that the material of the vibrating member 20 is glass, resin, hard paper, compressed paper, or the like that has material properties suitable for transmitting the vibrations transmitted from the piezoelectric elements 10a, 10b, and 10c.

[0014] The host system 2 is a device or a system including multiple devices that controls the audio device 1 by supplying audio signals. However, the host system 2 may also supply other signals such as image signals (e.g., RGB data) and timing signals (vertical synchronization signal, horizontal synchronization signal, data enable signal, etc.) depending on the application of the audio device 1. The host system 2 may be, for example, a sound source playback device, a public address device, a radio broadcast playback system, a television system, a set-top box, a navigation system, an optical disc player, a computer, a home theater system, a video telephone system, etc. The audio device 1 and the host system 2 may be an integrated device or separate devices.

[0015] The control unit 40 supplies a voltage based on a common audio signal to the piezoelectric elements 10a, 10b, and 10c. The control unit 40 may be configured with a plurality of semiconductor integrated circuits. More specifically, the control unit 40 may include an amplifier circuit such as a preamplifier and a power amplifier.

[0016] FIG. 2 is a plan view showing the arrangement of the piezoelectric elements 10a, 10b, and 10c according to the first embodiment. FIG. 3 and FIG. 4 are cross-sectional views showing the arrangement of the piezoelectric elements 10a, 10b, and 10c according to the first embodiment. The arrangement of the piezoelectric elements 10a, 10b, and 10c will be described with reference to FIG. 2 to FIG. 4. The rectangular outer frame of the vibration member 20 in FIG. 2 shows the outline of the vibration member 20. As shown in FIG. 2, the vibration member 20 is flat and rectangular in plan view from a direction perpendicular to the main surface.

[0017] As shown in FIG. 3, the surface of the vibration member 20 corresponding to the planar sound source is the sound source surface 20a, and the surface opposite to the sound source surface 20a is the back surface 20b. In this case, FIG. 2 is illustrated as a perspective plan view of the vibration member 20 seen from the back surface 20b side. In FIG. 2, coordinate axes are shown in which the horizontal direction of the sound source surface 20a is the x-axis, the vertical direction of the sound source surface 20a is the z-axis, and the depth direction of the sound source surface 20a is the y-axis. In addition, the direction from the back surface 20b toward the sound source surface 20a is the positive direction of the y-axis. FIG. 3 is a cross-sectional view taken along the line A-A' in FIG. 2, and FIG. 4 is a cross-sectional view taken along the line B-B' in FIG. 2.

[0018] 2 to 4, one surface of a frame 22 having a rectangular frame shape in a plan view is connected to the outer periphery of the back surface 20b of the vibrating member 20. A back cover 24 is connected to the surface of the frame 22 opposite to the side to which the vibrating member 20 is connected. The vibrating member 20 and the back cover 24 face each other with a gap therebetween. As a result, the vibrating member 20, the frame 22 and the back cover 24 form a housing for the acoustic device 1. The piezoelectric elements 10a, 10b and 10c are arranged inside this housing.

[0019] The back cover 24 shields the internal space of the housing so that the sound generated by the vibration of the piezoelectric elements 10a, 10b, and 10c does not leak out from the rear direction of the housing. The back cover 24 also has a protective function to prevent objects from contacting the piezoelectric elements 10a, 10b, and 10c from the outside. The vibration member 20 and the back cover 24 can be connected to the frame 22 by, for example, a pressure-bonding resin material, an adhesive, an adhesive tape, or the like (not shown). The frame 22 can be made of, for example, a material such as metal or resin. The back cover 24 can be made of, for example, a material such as metal, resin, glass, or hard paper. However, the material of the frame 22 and the back cover 24 is not limited to a specific material.

[0020] In the case where the vibrating member 20 has a signage function in addition to a sound generation function, the contents of the signage, such as text, pictures, and symbols, are arranged so as to be visible from the sound source surface 20a side of the vibrating member 20. That is, the sound source surface 20a also has a function as a content arrangement surface. The contents may be directly attached to the sound source surface 20a, or a medium such as paper on which the contents are attached by printing or the like may be attached to the sound source surface 20a. The contents may be attached to a place other than the sound source surface 20a of the vibrating member. For example, the contents may be arranged on the outer surface of the back cover 24 (the surface opposite to the surface facing the vibrating member 20). In this case, the outer surface of the back cover 24 may also have a function as a content arrangement surface. The contents may be attached to both the sound source surface 20a and the outer surface of the back cover 24. In this case, both the sound source surface 20a and the outer surface of the back cover 24 are content arrangement surfaces, and signage that can be viewed from both sides is realized.

[0021] Each of the piezoelectric elements 10a, 10b, and 10c has a flat plate shape. As shown in Fig. 2, the piezoelectric elements 10a, 10b, and 10c have a rectangular shape with a longitudinal direction (x direction in the figure) and a lateral direction (z direction in the figure) in a plan view. As a result, when a voltage is applied, the piezoelectric elements 10a, 10b, and 10c are deformed so as to bend when viewed from a cross section (line A-A') along the longitudinal direction. The piezoelectric elements 10a, 10b, and 10c are arranged so that the longitudinal direction is perpendicular to the end of the vibration member 20.

[0022] Each of the piezoelectric elements 10a, 10b, and 10c is connected to the rear surface 20b of the vibrating member 20 via two elastic members 30. That is, each of the piezoelectric elements 10a, 10b, and 10c is connected to the same main surface of the vibrating member 20.

[0023] The elastic member 30 is a member made of a material having elasticity. The material of the elastic member 30 is typically a material such as rubber having a smaller elastic modulus than the piezoelectric elements 10a, 10b, 10c and the vibration member 20. Both ends of the piezoelectric element 10a in the longitudinal direction and a part of the vibration member 20 are connected by the elastic member 30. Similarly, both ends of the piezoelectric elements 10b, 10c in the longitudinal direction and a part of the vibration member 20 are connected by the elastic member 30. As a result, the vibration of the piezoelectric elements 10a, 10b, 10c is transmitted to the vibration member 20, and the vibration member 20 generates a sound based on the input audio signal. Both ends of the piezoelectric elements 10a, 10b, 10c in the longitudinal direction are portions that become antinodes of the bending vibration. Therefore, the elastic member 30 is connected near both ends of the piezoelectric elements 10a, 10b, 10c in the longitudinal direction, so that the vibration is efficiently transmitted to the vibration member 20.

[0024] Fig. 5 is a cross-sectional view showing the structure of the piezoelectric element 10a according to the first embodiment in more detail. Fig. 5 is oriented in a different direction from Fig. 3, but shows a cross-sectional view taken along the line A-A' in Fig. 2, similar to Fig. 3. Fig. 5 shows an enlarged view of only the vicinity of the piezoelectric element 10a, but the other piezoelectric elements 10b and 10c have the same structure. Fig. 5 also shows a schematic circuit diagram of the connection relationship of the electrodes included in the piezoelectric element 10a to explain a method of inputting an audio signal to the piezoelectric element 10a.

[0025] The piezoelectric element 10a shown in FIG. 5 has a structure called a bimorph in which two piezoelectric layers are laminated. The piezoelectric element 10a includes electrodes 101, 103, 105 and piezoelectric layers 102, 104. The electrode 101 provided on the side closest to the vibration member 20 is connected to the elastic member 30. The electrodes 101 and 103 are arranged to sandwich the piezoelectric layer 102 in the thickness direction. The electrodes 103 and 105 are arranged to sandwich the piezoelectric layer 104 in the thickness direction. The arrows shown inside the piezoelectric layers 102 and 104 indicate the polarization directions of the piezoelectric layers 102 and 104. In other words, the polarization directions of the piezoelectric layers 102 and 104 are the same. Wiring for applying a voltage to each electrode can be connected to the electrodes 101, 103, and 105 by soldering or the like, but the wiring is omitted in FIG. 5.

[0026] The voltage applied to the piezoelectric element 10a is based on an audio signal, and can therefore be considered as an AC voltage corresponding to the frequency of the audio to be generated. In FIG. 5, this AC voltage is indicated by the circuit symbol of an AC power source V. One terminal of the AC power source V is connected to the electrodes 101 and 105, and the other terminal is connected to the electrode 103. In other words, voltages of the same phase are applied to the electrodes 101 and 105, voltages of opposite phases are applied to the electrodes 101 and 103, and voltages of opposite phases are also applied to the electrodes 103 and 105. As a result, voltages of opposite directions are applied to the piezoelectric layers 102 and 104.

[0027] The material of the piezoelectric layers 102 and 104 is not particularly limited, but it is preferable that the material has good piezoelectric properties, such as lead zirconate titanate, in order to increase the amount of displacement. Although not shown in the configuration of Fig. 5, the outer periphery of the piezoelectric element 10a may be covered with an insulator such as resin to prevent shorting with other members.

[0028] 6 and 7 are schematic diagrams showing deformation when a voltage is applied to the piezoelectric element 10a according to the first embodiment. As shown in Fig. 5, the polarization directions of the piezoelectric layers 102 and 104 are the same, and the voltages applied to the piezoelectric layers 102 and 104 are opposite. As a result, the piezoelectric layers 102 and 104 expand and contract in opposite directions.

[0029] 6, at the timing when the piezoelectric layer 102 deforms so as to contract laterally, the piezoelectric layer 104 deforms so as to expand laterally. This causes the end of the piezoelectric element 10a to bend in a direction approaching the vibration member 20. At this time, the vibration member 20 is deformed by receiving a stress in a direction away from the piezoelectric element 10a.

[0030] 7, at the timing when the piezoelectric layer 102 deforms so as to expand in the lateral direction, the piezoelectric layer 104 deforms so as to contract in the lateral direction. This causes the end of the piezoelectric element 10a to bend in a direction away from the vibration member 20. At this time, the vibration member 20 is deformed by receiving a stress toward the piezoelectric element 10a.

[0031] When an AC voltage based on an audio signal is applied to the piezoelectric element 10a, the state of FIG. 6 and the state of FIG. 7 are alternately repeated at the frequency of the audio. In this manner, the vibration of the piezoelectric element 10a is transmitted to the vibrating member 20, which vibrates. Therefore, the vibrating member 20 generates a sound based on the audio signal, and thus functions as a driving unit of the speaker. Note that, since sounds of various frequencies in the audible range are superimposed in an actual audio, the actual vibration state may be more complicated than that shown in the figure.

[0032] In this embodiment, some of the piezoelectric elements 10a, 10b, and 10c are configured to vibrate in a phase different from that of the other piezoelectric elements. As a specific example, a configuration in which an audio signal is input so that the piezoelectric element 10b (second vibration element) vibrates in an opposite phase to the piezoelectric element 10a (first vibration element) and the piezoelectric element 10c (third vibration element) will be described with reference to FIG. 8.

[0033] FIG. 8 is a schematic diagram showing in more detail a method of inputting an audio signal to the piezoelectric elements 10a, 10b, and 10c according to the first embodiment. The control unit 40 outputs an AC voltage based on the audio signal from a terminal t1 (first terminal) and a terminal t2 (second terminal) of a signal source. The output potentials of the terminals t1 and t2 are in opposite phase to each other. The terminal t1 is connected to the electrodes 101 and 105 (first electrode) of the piezoelectric element 10a, the electrode 103 (second electrode) of the piezoelectric element 10b, and the electrodes 101 and 105 of the piezoelectric element 10c. The terminal t2 is connected to the electrode 103 (second electrode) of the piezoelectric element 10a, the electrodes 101 and 105 (first electrode) of the piezoelectric element 10b, and the electrode 103 of the piezoelectric element 10c.

[0034] Due to this connection relationship, the voltage applied between the electrodes of the piezoelectric element 10a and the voltage applied between the electrodes of the piezoelectric element 10b are in opposite phases. Also, the voltage applied between the electrodes of the piezoelectric element 10a and the voltage applied between the electrodes of the piezoelectric element 10c are in the same phase. As a result, for example, when the piezoelectric elements 10a and 10c are displaced to the state shown in FIG. 6, the piezoelectric element 10b is displaced to the state shown in FIG. 7, and when the piezoelectric elements 10a and 10c are displaced to the state shown in FIG. 7, the piezoelectric element 10b is displaced to the state shown in FIG. 6. In this way, the piezoelectric elements 10a and 10c and the piezoelectric element 10b transmit vibrations of opposite phases to the vibration member 20.

[0035] The effect of vibrating the piezoelectric elements 10a, 10c and the piezoelectric element 10b in opposite phases will be described with reference to Figs. 9 and 10. Fig. 9 is a schematic diagram for explaining the effect of the acoustic device 1 according to the first embodiment. In general, in a speaker that generates sound by vibrating a diaphragm, the natural frequency of the diaphragm and the vibration state of the diaphragm according to the frequency have a large effect on the frequency characteristic of the sound pressure level. In particular, when a divided vibration occurs in a vibration form in which the diaphragm vibrates finely due to a high-order natural vibration mode, sound quality deterioration such as a decrease in sound pressure level and the occurrence of peaks and dips in the frequency characteristic may occur.

[0036] In the rectangular flat plate-shaped vibration member 20 of this embodiment, a natural vibration mode occurs in which resonances in the vertical and horizontal directions are two-dimensionally combined, so strictly speaking, it is necessary to conduct an examination using a two-dimensional or three-dimensional model. However, in order to simplify the model, a one-dimensional model will be described here. In FIG. 9, the vibration form in a model considering only one dimension in the longitudinal direction (x direction) of the vibration member 20 is illustrated for five natural vibration modes from the first order (n=1) to the fifth order (n=5). The natural frequency of each of these natural vibration modes is higher as the order increases. Note that this natural vibration mode is based on the boundary condition that the end of the vibration member 20 is supported by the frame 22 as shown in FIG. 2 to FIG. 4.

[0037] 9, the positions of the nodes and antinodes of the vibration change according to the order of the natural vibration mode, and the position dependency of the phase of the displacement also changes. For example, in the first natural vibration mode, the sign of the phase is the same throughout the vibrating member 20, whereas in the second natural vibration mode, the sign of the phase is opposite across the center of the vibrating member 20.

[0038] Here, in the third natural vibration mode, the phase is the same near both ends of the vibration member 20, and the phase is opposite near the center of the vibration member 20. This phase relationship is consistent with the phase relationship in which the vibrations of the piezoelectric elements 10a, 10c and the piezoelectric element 10b are in opposite phase as described in the description of FIG. 8. Also, as shown in FIG. 9, the positions of the piezoelectric elements 10a, 10b, and 10c correspond to the positions of the antinodes of the third natural vibration mode. Therefore, the phase relationship of the piezoelectric elements in this embodiment is such that the third natural vibration mode is more likely to be excited than other natural vibration modes. On the other hand, the second and fourth or higher natural vibration modes are not easily excited because the phase relationship does not match the piezoelectric elements 10a, 10b, and 10c.

[0039] In this manner, as in the present embodiment, by vibrating some of the piezoelectric elements in the opposite phase, it is possible to easily excite a relatively low-order natural vibration mode while controlling so that a higher-order natural vibration mode is less likely to be excited. Therefore, it is difficult for a split vibration, such as a fine wavy vibration of the diaphragm, to occur due to a high-order natural vibration mode, etc. Therefore, according to the present embodiment, the deterioration of sound quality caused by such split vibration can be reduced.

[0040] FIG. 10 is a graph illustrating the effect of the acoustic device 1 according to the first embodiment. FIG. 10 shows the frequency characteristics of the sound pressure level of the configuration of this embodiment and two comparative examples (first comparative example and second comparative example). The vertical axis of FIG. 10 shows the sound pressure, in arbitrary units, generated from the acoustic device 1 when a predetermined voltage is applied to the acoustic device 1. The horizontal axis of FIG. 10 shows the frequency of the voltage applied to the piezoelectric element. Here, the unit of frequency is Hertz (Hz). Note that FIG. 10 is a double logarithmic graph.

[0041] In the first comparative example, no voltage is applied to the piezoelectric element 10b, so that only the piezoelectric elements 10a and 10c are vibrated in the same phase, and the piezoelectric element 10b is not vibrated. In the second comparative example, voltages in the same phase are applied to the three piezoelectric elements so that the piezoelectric elements 10a, 10b, and 10c are all vibrated in the same phase.

[0042] First, in Fig. 10, when comparing the characteristics of the first embodiment and the characteristics of the first comparative example, it is found that the sound pressure of the first embodiment is significantly improved in the low to mid ranges around 100 Hz to 500 Hz and around 600 Hz to 1500 Hz. Therefore, it is found that the effect of improving the sound pressure is obtained by adding the piezoelectric element 10b that vibrates in the opposite phase.

[0043] Moreover, when comparing the characteristics of the first embodiment with those of the second comparative example, it is found that the characteristics of the first embodiment provide higher sound pressure in the frequency range from low to mid range. Therefore, it is found that it is preferable that the phase of the piezoelectric element 10b is not the same phase as the piezoelectric elements 10a and 10c but is the opposite phase. As described above, according to the graph of FIG. 10, it is found that the acoustic device 1 according to the first embodiment provides an effect of improving sound pressure in the frequency range from low to mid range by providing the piezoelectric element 10b that vibrates in the opposite phase to the piezoelectric elements 10a and 10c. Thus, according to this embodiment, the frequency characteristic of the sound pressure in the audible range approaches flat, and an acoustic device 1 with improved sound quality is provided.

[0044] The sound pressure in the low to mid range of the second comparative example is lower than that of the first comparative example. That is, when the piezoelectric element 10b that vibrates in the same phase as the piezoelectric elements 10a and 10c is added, the sound pressure decreases even though the number of operating piezoelectric elements is increased. By comparing the graphs of the first comparative example and the second comparative example in this way, it can be seen that the sound quality may not be improved or may be deteriorated by simply providing the piezoelectric element 10b in the same phase without considering the phase relationship and increasing the number of piezoelectric elements. By comparing the graphs of the first embodiment and the second comparative example, it can be seen that appropriately setting the phase relationship between the piezoelectric element 10b and the piezoelectric elements 10a and 10c to control the natural vibration mode is an important factor that contributes to improving the sound pressure. In this embodiment, the phase relationship between the piezoelectric elements 10a, 10b, and 10c is set based on these findings, thereby improving the sound quality of the audio device 1.

[0045] [Second embodiment] In this embodiment, a modified example of the acoustic device 1 according to the first embodiment will be described. Descriptions of elements common to the first embodiment may be omitted or simplified.

[0046] FIG. 11 is a plan view showing the arrangement of piezoelectric elements 10a, 10b, and 10c according to the second embodiment. FIG. 12 is a cross-sectional view showing the arrangement of piezoelectric elements 10a, 10b, and 10c according to the second embodiment. The arrangement of piezoelectric elements 10a, 10b, and 10c will be described with mutual reference to FIG. 11 and FIG. 12. FIG. 12 is a cross-sectional view taken along line A-A' in FIG. 11. The cross-sectional view taken along line B-B' in FIG. 11 is similar to FIG. 4, and therefore will not be shown or described.

[0047] As shown in Figs. 11 and 12, each of the piezoelectric elements 10a and 10c has a structure similar to that of the first embodiment, and is connected to the vibration member 20 via an elastic member 30 at both ends (first connection portion) in the longitudinal direction of the piezoelectric element. In contrast, the piezoelectric element 10b is connected to the vibration member 20 via an elastic member 30 near the center of the piezoelectric element 10b (second connection portion). This is a difference between the present embodiment and the first embodiment. The vicinity of the center of the piezoelectric element 10b is also a portion that becomes the antinode of the bending vibration. Therefore, by connecting the elastic member 30 near the center of the piezoelectric element 10b, the vibration is efficiently transmitted to the vibration member 20.

[0048] FIG. 13 is a cross-sectional view showing the structure of the piezoelectric element 10b according to the second embodiment in more detail. Although the orientation of FIG. 13 is different from that of FIG. 12, FIG. 13 shows a cross-sectional view taken along the line A-A' in FIG. 11, similar to FIG. 12. FIG. 13 also shows an enlarged view of only the vicinity of the piezoelectric element 10b. The other piezoelectric elements 10a and 10c have the same structure as that of FIG. 5 of the first embodiment. FIG. 13 also shows the connection relationship of each electrode included in the piezoelectric element 10b in a schematic circuit diagram in order to explain the method of inputting an audio signal to the piezoelectric element 10b. In FIG. 13, the structure other than the arrangement of the elastic member 30 connecting the piezoelectric element 10b and the vibration member 20, the voltage application direction, and the like are the same as those shown in FIG. 5, and therefore will not be described.

[0049] 14 and 15 are schematic diagrams showing deformation when a voltage is applied to the piezoelectric element 10b according to the second embodiment. As shown in Fig. 5, the polarization directions of the piezoelectric layers 102 and 104 are the same, and the voltages applied to the piezoelectric layers 102 and 104 are opposite. As a result, the piezoelectric layers 102 and 104 expand and contract in opposite directions.

[0050] 14, at the timing when the piezoelectric layer 102 deforms so as to contract laterally, the piezoelectric layer 104 deforms so as to expand laterally. This causes the end of the piezoelectric element 10b to bend in a direction approaching the vibration member 20. At this time, the vibration member 20 is deformed by receiving a stress directed toward the piezoelectric element 10b.

[0051] 15, at the timing when the piezoelectric layer 102 deforms so as to expand in the lateral direction, the piezoelectric layer 104 deforms so as to contract in the lateral direction. This causes the end of the piezoelectric element 10b to bend in a direction away from the vibration member 20. At this time, the vibration member 20 is deformed by receiving a stress in a direction away from the piezoelectric element 10b.

[0052] A structure in which elastic members 30 are disposed on both ends of the piezoelectric element 10b in FIG. 14 is compared with a structure in which elastic members 30 are disposed near the center of the piezoelectric element 10a in FIG. 6. In FIG. 6 and FIG. 14, the displacements of the piezoelectric elements 10a, 10b are the same in that the ends are bent in a direction approaching the vibration member 20. On the other hand, focusing on the vibration member 20, the vibration member 20 in FIG. 6 is deformed by receiving a stress in a direction away from the piezoelectric element 10a, whereas the vibration member 20 in FIG. 14 is deformed by receiving a stress toward the piezoelectric element 10b. In other words, the displacements of the piezoelectric element 10a in FIG. 6 and the piezoelectric element 10b in FIG. 14 are in phase, whereas the displacements of the vibration member 20 in FIG. 6 and the vibration member 20 in FIG. 14 are in opposite phase.

[0053] Also, when Fig. 7 is compared with Fig. 15, the same phase relationship as described above is found. That is, the displacements of the piezoelectric element 10a in Fig. 7 and the piezoelectric element 10b in Fig. 15 are in phase, whereas the displacements of the vibrating member 20 in Fig. 7 and the vibrating member 20 in Fig. 15 are in opposite phase.

[0054] 16 is a schematic diagram showing in more detail a method of inputting an audio signal to the piezoelectric elements 10a, 10b, and 10c according to the second embodiment. The control unit 40 outputs an AC voltage based on the audio signal from terminals t1 and t2. The terminal t1 is connected to the electrodes 101 and 105 of the piezoelectric elements 10a, 10b, and 10c, respectively. The terminal t2 is connected to the electrodes 103 of the piezoelectric elements 10a, 10b, and 10c, respectively.

[0055] Due to this connection relationship, the phases of the voltages applied between the electrodes of the piezoelectric elements 10a, 10b, and 10c are all in the same phase. At this time, as described above, the stress applied to the vibration member 20 by the piezoelectric elements 10a and 10c and the stress applied to the vibration member 20 by the piezoelectric element 10b are in opposite phase. In other words, the piezoelectric elements 10a and 10c and the piezoelectric element 10b transmit vibrations to the vibration member 20 that are in opposite phase to each other.

[0056] Thus, in this embodiment, the configuration of the acoustic device 1 is different from that of the first embodiment, and the phase of the applied voltage is also different, but the phase relationship of the vibrations that the piezoelectric elements 10a, 10b, and 10c impart to the vibrating member 20 is the same as in the first embodiment. Therefore, the same effects as in the first embodiment can be obtained in this embodiment.

[0057] [Third embodiment] In this embodiment, a modified example of the acoustic device 1 according to the first embodiment will be described. Descriptions of elements common to the first embodiment may be omitted or simplified.

[0058] FIG. 17 is a cross-sectional view showing the structure of the piezoelectric element 10b according to the third embodiment in more detail. FIG. 17 shows a cross-sectional view taken along the line A-A' in FIG. 2, similar to FIG. 5. FIG. 17 shows only the vicinity of the piezoelectric element 10b in an enlarged manner. The other piezoelectric elements 10a and 10c have the same structure as FIG. 5 of the first embodiment. FIG. 17 also shows the connection relationship of each electrode included in the piezoelectric element 10b in a schematic circuit diagram in order to explain the method of inputting an audio signal to the piezoelectric element 10b. The arrows inside the piezoelectric layers 102 and 104 indicate the polarization directions of the piezoelectric layers 102 and 104. In this embodiment, the piezoelectric elements 10a and 10c shown in FIG. 5 have an upward polarization direction (negative direction of the y-axis), whereas the piezoelectric element 10b shown in FIG. 17 has a downward polarization direction (positive direction of the y-axis). That is, the piezoelectric element 10b has a polarization direction opposite to that of the piezoelectric elements 10a and 10c. In addition, in FIG. 17, other than the polarization direction of the piezoelectric element 10b, the configuration is the same as that shown in FIG. 5, and therefore the description will be omitted.

[0059] 18 is a schematic diagram showing in more detail a method of inputting an audio signal to the piezoelectric elements 10a, 10b, and 10c according to the third embodiment. The control unit 40 outputs an AC voltage based on the audio signal from terminals t1 and t2. The terminal t1 is connected to the electrodes 101 and 105 of the piezoelectric elements 10a, 10b, and 10c, respectively. The terminal t2 is connected to the electrodes 103 of the piezoelectric elements 10a, 10b, and 10c, respectively.

[0060] Due to this connection relationship, the voltages applied between the electrodes of the piezoelectric elements 10a, 10b, and 10c are all in phase. The direction of the displacement generated in the piezoelectric element is determined by the voltage application direction and the polarization direction. In two piezoelectric elements of the same structure, if the voltage application direction is the same and the polarization direction of the piezoelectric body is opposite, the direction of the force generated by the voltage will be opposite, and the direction of the displacement generated in the piezoelectric element will also be opposite. Therefore, in the configuration of FIG. 18, the stress applied to the vibration member 20 by the piezoelectric elements 10a and 10c and the stress applied to the vibration member 20 by the piezoelectric element 10b are in opposite phase. In other words, the piezoelectric elements 10a and 10c and the piezoelectric element 10b transmit vibrations of opposite phases to the vibration member 20.

[0061] Thus, in this embodiment, the configuration of the acoustic device 1 is different from that of the first embodiment, and the phase of the applied voltage is also different, but the phase relationship of the vibrations that the piezoelectric elements 10a, 10b, and 10c impart to the vibrating member 20 is the same as in the first embodiment. Therefore, the same effects as in the first embodiment can be obtained in this embodiment.

[0062] [Fourth embodiment] In this embodiment, a specific configuration example will be described in which the acoustic device 1 according to the first to third embodiments is a display device, and the vibrating member 20 also functions as a display panel of the display device. Descriptions of elements common to the first to third embodiments may be omitted or simplified.

[0063] 19 is a schematic diagram of a display device 3 according to a fourth embodiment. The display device 3 of this embodiment can be used, for example, as an electronic poster, a digital bulletin board, an electronic billboard, a computer screen, a television receiver, etc. The structures of the host system 2, the piezoelectric elements 10a, 10b, and 10c, and the control unit 40 are similar to those of any of the first to third embodiments, and therefore will not be described.

[0064] 19, the display device 3 has piezoelectric elements 10a, 10b, 10c, a control unit 40, a panel control unit 60, a data driving circuit 70, a gate driving circuit 80, and a display panel 90. The display device 3 is a device that displays an image on the display panel 90 based on input RGB data, etc., and generates sound based on input audio signals, etc.

[0065] The panel control unit 60 controls the data drive circuit 70 and the gate drive circuit 80 based on image data and timing signals input from the host system 2. The data drive circuit 70 supplies data voltages and the like to the pixels P via drive lines 71 arranged for each column of the pixels P. The gate drive circuit 80 supplies control signals to the pixels P via drive lines 81 arranged for each row of the pixels P. Each of the drive lines 71 and 81 may be composed of multiple wirings.

[0066] The display panel 90 includes a plurality of pixels P arranged in a plurality of rows and a plurality of columns. The display device 3 may be, for example, an OLED display using a display panel 90 in which organic light-emitting diodes (OLEDs) are arranged as light-emitting elements of the pixels P. Alternatively, the display device 3 may be a liquid crystal display (LCD) using a liquid crystal panel including a liquid crystal material, a polarizing plate, etc. as the display panel 90. These structures allow the display panel 90 to be thin, which is suitable for making the display device 3 thinner. When the display device 3 is capable of displaying a color image, the pixel P may be a sub-pixel that displays one of a plurality of colors (e.g., RGB) that constitute the color image.

[0067] Each of the control unit 40, the panel control unit 60, the data drive circuit 70, and the gate drive circuit 80 may be configured by one or more semiconductor integrated circuits. In addition, some or all of the control unit 40, the panel control unit 60, the data drive circuit 70, and the gate drive circuit 80 may be integrated into one semiconductor integrated circuit.

[0068] The display device 3 of this embodiment displays an image and generates a sound by receiving an image signal (e.g., RGB data), an audio signal, and a timing signal (vertical synchronization signal, horizontal synchronization signal, data enable signal, etc.) from the host system 2. The display panel 90 has an image display surface for displaying an image, and a back surface facing the image display surface. Piezoelectric elements 10a, 10b, and 10c are connected to the back surface of the display panel 90 via an elastic member 30. This allows the display panel 90 to have a function of image display and the function of the vibration member 20 in the first to third embodiments. Therefore, in this embodiment, a display device 3 having an acoustic effect in which sound is generated from an image displayed on the display panel 90 can be provided.

[0069] [Other embodiments] The above-mentioned embodiments merely exemplify some aspects to which the present invention can be applied, and the technical scope of the present invention should not be interpreted as being limited by the above-mentioned embodiments. Furthermore, the present invention can be implemented in various aspects by appropriately modifying or modifying it without departing from the spirit of the present invention. For example, it should be understood that an embodiment in which a part of the configuration of any of the embodiments is added to another embodiment, or an embodiment in which a part of the configuration of any of the embodiments is replaced with a part of the configuration of another embodiment, is also an embodiment to which the present invention can be applied. Below, modified examples that can be applied to the above-mentioned embodiments are listed.

[0070] In the above-mentioned embodiment, a bimorph in which two piezoelectric layers 102 and 104 are laminated is exemplified as an example of the structure of the piezoelectric elements 10a, 10b, and 10c, but the present invention is not limited to this. For example, the piezoelectric elements 10a, 10b, and 10c may be unimorphs including one piezoelectric layer and two layers of electrodes sandwiching the piezoelectric layer. In this case, there is an advantage that the element structure is simplified compared to a bimorph. Furthermore, the piezoelectric elements 10a, 10b, and 10c may be multimorphs including three or more piezoelectric layers and four or more electrodes sandwiching each piezoelectric layer. In this case, the displacement for the same applied voltage is larger and the sound pressure is improved compared to a unimorph and a bimorph.

[0071] Furthermore, the piezoelectric elements 10a, 10b, and 10c may have a structure in which a plurality of unimorphs, bimorphs, or multimorphs are stacked together. In this structure, the displacements generated by the plurality of elements are superimposed, thereby improving the sound pressure.

[0072] In the above embodiment, the planar shape of the piezoelectric elements 10a, 10b, and 10c is a rectangle with different aspect ratios from the viewpoint of facilitating bending displacement, but is not limited thereto. For example, the planar shape of the piezoelectric elements 10a, 10b, and 10c may be a shape having symmetry, such as a circle or a regular polygon. In this case, the distribution of vibration is likely to be two-dimensionally uniform, and an effect of making it difficult for resonance to occur in the vibrating member 20 is obtained. In addition, the planar shape of the piezoelectric elements 10a, 10b, and 10c may be a polygon with sides of non-uniform length, or may be a figure including curves.

[0073] In the above embodiment, an example is shown in which three piezoelectric elements 10a, 10b, and 10c are provided, but the number can be changed as appropriate as long as vibrations of different phases can be transmitted to the vibration member. For example, there may be only two piezoelectric elements 10a and 10b, or there may be four or more. In the case of four or more, it is desirable that a piezoelectric element having a configuration similar to that of the piezoelectric element 10a and a piezoelectric element having a configuration similar to that of the piezoelectric element 10b are alternately provided in order to effectively excite the natural vibration mode of the corresponding order.

[0074] In the above embodiment, the displacements between the piezoelectric elements 10a, 10c and the piezoelectric element 10b are in opposite phase, but the phase difference does not necessarily have to be strictly opposite (i.e., the phase difference is 180°). The phase difference between the piezoelectric elements 10a, 10c and the piezoelectric element 10b may be slightly different from 180°, and even in this case, the effect of improving sound quality can be obtained.

[0075] In the above embodiment, the piezoelectric elements 10a, 10b, and 10c are given as examples of the vibration element that vibrates the vibration member 20, but the driving method of the vibration element is not limited to the piezoelectric type as long as it can transmit vibration corresponding to sound vibration to the vibration member 20. For example, instead of the piezoelectric elements 10a, 10b, and 10c, vibration elements of other types such as dynamic type and electrostatic type may be used. However, since piezoelectric elements can be made thinner than vibration elements of other types, they are more suitable for applications requiring thinness such as signage and display devices. [Explanation of symbols]

[0076] 1 Sound equipment 10a, 10b, 10c Piezoelectric element 20 Vibration member 30 Elastic member 40 Control section

Claims

1. A plurality of vibration elements including a first vibration element and a second vibration element, the vibration elements vibrating in response to a common audio signal; a vibration member having the plurality of vibration elements connected to the same main surface; a first connecting member that connects the first vibration element and the vibration member; a plurality of second connection members that connect the second vibration element and the vibration member; Equipped with The first vibration element and the second vibration element transmit vibrations having different phases to the vibration member, the first vibration element and the second vibration element are rectangular flat plates, the first connecting member directly connects the center of the flat plate and the vibration member; The plurality of second connection members directly connect both longitudinal ends of the flat plate to the vibration member.

1. An acoustic device comprising:

2. The first vibration element and the second vibration element transmit vibrations of opposite phases to the vibration member.

2. The acoustic device according to claim 1.

3. The audio signals are input to the first vibration element and the second vibration element in phase with each other.

3. The acoustic device according to claim 1 or 2.

4. Each of the first vibration element and the second vibration element has a first electrode and a second electrode, the signal source for outputting the audio signal has a first terminal and a second terminal for outputting signals in opposite phases to each other; the first terminal is connected to the first electrode of the first vibration element and the first electrode of the second vibration element; The second terminal is connected to the second electrode of the first vibration element and the second electrode of the second vibration element.

4. The acoustic device according to claim 3.

5. A position of a first connection portion on the first vibration element where the first vibration element and the vibration member are connected is different from a position of a second connection portion on the second vibration element where the second vibration element and the vibration member are connected.

3. The acoustic device according to claim 1 or 2.

6. The vibration elements are rectangular flat plates, The first connection portion includes a center of the flat plate, and the second connection portion includes a position spaced apart from the center of the flat plate in a longitudinal direction of the flat plate.

6. The acoustic device according to claim 5.

7. Each of the plurality of vibration elements is a piezoelectric element.

7. An acoustic device according to claim 1, wherein the first and second acoustic components are arranged in a first direction.

8. Each of the plurality of vibration elements is a piezoelectric element, The polarization direction of the piezoelectric body of the first vibration element and the polarization direction of the piezoelectric body of the second vibration element are the same.

3. The acoustic device according to claim 1 or 2.

9. The audio signals are input to the first vibration element and the second vibration element in phase with each other.

9. An acoustic device according to claim 5, 6 or 8.

10. The plurality of vibration elements further includes a third vibration element, The first vibration element and the third vibration element transmit vibrations in phase with each other to the vibration member.

10. An acoustic device according to claim 1, wherein the first and second acoustic components are arranged in a first direction.

11. The second vibration element is disposed between the first vibration element and the third vibration element in a plan view with respect to the main surface.

11. The acoustic device according to claim 10.

12. The vibration member is a rectangular flat plate, The first vibration element, the second vibration element, and the third vibration element are arranged side by side in the longitudinal direction of the vibration member.

12. An acoustic device according to claim 11.

13. the vibration member is a display panel of a display device, the vibration member has an image display surface on which an image is displayed and the main surface facing the image display surface, Vibrations of the first vibration element and the second vibration element are transmitted to the main surface of the display panel.

13. An acoustic device according to any one of the preceding claims.

14. The display panel includes an organic light-emitting diode (OLED).

14. An acoustic device according to claim 13.

15. The display panel includes a liquid crystal panel.

14. An acoustic device according to claim 13.

16. The vibrating member is a signage, the vibration member has a content placement surface on which the content of the signage is visibly arranged, and the main surface facing the content placement surface; The vibration of the first vibration element and the second vibration element is transmitted to the main surface of the signage.

13. An acoustic device according to any one of the preceding claims.

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