Acoustic Devices

Abstract

To provide an acoustic device that can improve acoustic characteristics.SOLUTION: An acoustic device 1 has a piezoelectric element 4 and a piezoelectric element 5 arranged opposite to each other in the first direction D1, and a connecting member 6 connecting the piezoelectric element 4 and the piezoelectric element 5 to each other. The piezoelectric element 4 has an end 4c and an end 4d in the second direction D2. The piezoelectric element 5 has an end 5c and an end 5d in the second direction D2. The connecting member 6 is fixed to the end 4c and the end 5c.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to acoustic devices. [Background technology]

[0002] An example of a conventional acoustic device is a transparent speaker described in Patent Document 1. This conventional acoustic device is configured by fixing a piezoelectric element to a diaphragm. In this acoustic device, the vibration of the piezoelectric element is amplified by the diaphragm, and a bending vibration is generated in the diaphragm, thereby obtaining a desired acoustic output. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-70100 Summary of the Invention [Problem to be solved by the invention]

[0004] In an acoustic device using a piezoelectric element as described in Patent Document 1, the sound pressure in the low frequency range is insufficient.

[0005] One aspect of the present disclosure provides an acoustic device that can improve acoustic characteristics. [Means for solving the problem]

[0006] An acoustic device according to one aspect of the present disclosure comprises a first piezoelectric element and a second piezoelectric element arranged opposite each other in a first direction, and a connecting member connecting the first piezoelectric element and the second piezoelectric element to each other, wherein the first piezoelectric element has first and second ends in a second direction intersecting the first direction, the second piezoelectric element has third and fourth ends in the second direction, and the connecting member is fixed to the first end and the third end.

[0007] In this acoustic device, for example, when the first piezoelectric element is cantilevered by a fixing member such that the first end is a free end and the second end is a fixed end, the second piezoelectric element is cantilevered by a connecting member such that the third end is a fixed end and the fourth end is a free end. This increases the amount of displacement of the fourth end. As a result, the sound pressure in the low frequency range can be increased, and the acoustic characteristics can be improved.

[0008] The first piezoelectric element may have a first main surface and a second main surface facing each other, the second piezoelectric element may have a third main surface and a fourth main surface facing each other, the first piezoelectric element and the second piezoelectric element may be arranged such that the first main surface and the third main surface face each other in the first direction, and the connecting member may be fixed to the first main surface and the third main surface. In this case, the distance between the first piezoelectric element and the second piezoelectric element can be easily set by the connecting member.

[0009] The first piezoelectric element and the second piezoelectric element may have the same shape, in which case individual differences between the first piezoelectric element and the second piezoelectric element can be reduced.

[0010] The first piezoelectric element may have a first external electrode disposed on the second end side of the connection member when viewed from the first direction, whereby an electrical short circuit between the first external electrode and the connection member can be suppressed.

[0011] The acoustic device may further include a strip-shaped first wiring member connected to the first external electrode, which can prevent the vibration of the first piezoelectric element from being hindered compared to a case in which a lead wire is connected to the first external electrode.

[0012] The second piezoelectric element may have a second external electrode disposed on a fourth end side of the connecting member when viewed from the first direction. In this case, an electrical short circuit between the second external electrode and the connecting member can be suppressed.

[0013] The acoustic device may further include a strip-shaped second wiring member connected to the second external electrode. In this case, it is possible to suppress the vibration of the second piezoelectric element from being inhibited, compared to a case in which a lead wire is connected to the second external electrode.

[0014] The first and second piezoelectric elements may be arranged such that their longitudinal directions coincide with the second direction, in which case the displacement is further increased, thereby further improving the acoustic characteristics.

[0015] A vibration device according to another aspect of the present disclosure comprises a first piezoelectric element and a second piezoelectric element arranged opposite each other in a first direction, and a connecting member connecting the first piezoelectric element and the second piezoelectric element to each other, wherein the first piezoelectric element has first and second ends in a second direction intersecting the first direction, the second piezoelectric element has third and fourth ends in the second direction, and the connecting member is fixed to the first end and the third end.

[0016] In this vibration device, for example, when the first piezoelectric element is cantilevered by a fixing member so that the first end side is a free end and the second end side is a fixed end, the second piezoelectric element is cantilevered by a connecting member so that the third end side is a fixed end and the fourth end side is a free end. Therefore, the displacement amount of the fourth end increases. .child As a result, the amount of displacement can be improved. Effect of the Invention

[0017] According to one aspect of the present disclosure, it is possible to improve acoustic characteristics. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view showing an acoustic device according to a first embodiment. [Diagram 2] FIG. 2 is a side view showing the acoustic device of FIG. [Diagram 3] FIG. 3 is a bottom view showing the acoustic device of FIG. [Figure 4]FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is an exploded perspective view showing a piezoelectric element. [Figure 6] FIG. 6 is a cross-sectional view showing a piezoelectric element. [Figure 7] FIG. 7 is a perspective view showing a state in which the vibrating portion is attached to a jig. [Figure 8] FIG. 8 is a perspective view showing the base of the jig. [Figure 9] FIG. 9 is an explanatory diagram showing the operation of the vibration section. [Figure 10] FIG. 10 is a graph showing sound pressure waveforms of the acoustic devices according to the example and the comparative example. [Figure 11] FIG. 11 is a side view showing an acoustic device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same functions will be denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0020] 1 to 4, an acoustic device 1 according to an embodiment is used, for example, as a speaker or a buzzer. The acoustic device 1 is provided in, for example, an electronic device such as a television or a smartphone. The acoustic device 1 includes a vibration section 2 and an acoustic section 3. The acoustic device 1 is also a vibration device.

[0021] First, the vibration section 2 will be described.

[0022] The vibration section 2 includes a piezoelectric element 4, a piezoelectric element 5, a connection member 6, a fixing member 7, a wiring member 8, and a wiring member 9. The piezoelectric elements 4, 5 are arranged to face each other. The piezoelectric elements 4, 5 have, for example, the same shape. The piezoelectric elements 4, 5 are arranged so that their longitudinal directions coincide with each other. In the following, the facing direction of the piezoelectric elements 4, 5 is referred to as a first direction D1, and the longitudinal direction of the piezoelectric elements 4, 5 is referred to as a second direction D2. The first direction D1 and the second direction D2 intersect with each other (here, perpendicularly). The piezoelectric elements 4, 5 are arranged so that they overlap each other when viewed from the first direction D1.

[0023] The piezoelectric element 4 has main surfaces 4a, 4b that face each other in the first direction D1. The piezoelectric element 5 has main surfaces 5a, 5b that face each other in the first direction D1. The piezoelectric elements 4, 5 are arranged such that the main surfaces 4a and 5b face each other in the first direction D1. The piezoelectric element 4 has an end portion 4c and an end portion 4d in the second direction D2. The piezoelectric element 5 has an end portion 5c and an end portion 5d in the second direction D2. The end portions 4c, 5c face each other in the first direction D1. The end portions 4d, 5d face each other in the first direction D1.

[0024] Each of the piezoelectric elements 4, 5 is, for example, a bimorph type piezoelectric element. Each of the piezoelectric elements 4, 5 has a piezoelectric body 11 and a plurality of (here, three) external electrodes 13, 14, 15 as shown in FIG.

[0025] The piezoelectric element 11 has a rectangular parallelepiped shape. The rectangular parallelepiped shape includes, for example, a rectangular parallelepiped shape with chamfered corners and ridges, and a rectangular parallelepiped shape with rounded corners and ridges. The piezoelectric element 11 has a pair of principal surfaces 11a, 11b facing each other, and four side surfaces 11c connecting the pair of principal surfaces 11a, 11b to each other. In the piezoelectric element 4, the principal surface 11a constitutes the principal surface 4a, and the principal surface 11b constitutes the principal surface 4b. In the piezoelectric element 5, the principal surface 11a constitutes the principal surface 5a, and the principal surface 11b constitutes the principal surface 5b.

[0026] Each of the principal surfaces 11a, 11b has a rectangular shape having a pair of long sides and a pair of short sides. That is, the length of the piezoelectric element 11 (the length of the piezoelectric element 11 in the direction of the long sides of the principal surface 11a) is, for example, 20 mm or more and 70 mm or less. The width of the piezoelectric element 11 (the length of the piezoelectric element 11 in the direction of the short sides of the principal surface 11a) is, for example, 10 mm or more and 35 mm or less. The thickness of the piezoelectric element 11 (the length of the piezoelectric element 11 in the opposing direction of the pair of principal surfaces 11a, 11b) is, for example, 0.2 mm or more and 1 mm or less.

[0027] The piezoelectric element 11 includes a plurality of stacked piezoelectric layers 12a, 12b, 12c, and 12d. The plurality of piezoelectric layers 12a, 12b, 12c, and 12d are stacked in this order. The stacking direction (hereinafter also simply referred to as the "stacking direction") of the plurality of piezoelectric layers 12a, 12b, 12c, and 12d coincides with the opposing direction of the pair of principal surfaces 11a and 11b. The stacking direction is along the first direction D1. The piezoelectric layer 12a has a principal surface 11a. The piezoelectric layer 12d has a principal surface 11b. The piezoelectric layers 12b and 12c are located between the piezoelectric layer 12a and the piezoelectric layer 12d. In this embodiment, the thicknesses of the piezoelectric layers 12a, 12b, 12c, and 12d are equal. The "equal" includes the range of manufacturing error.

[0028] Each of the piezoelectric layers 12a, 12b, 12c, and 12d is made of a piezoelectric material. In this embodiment, each of the piezoelectric layers 12a, 12b, 12c, and 12d is made of a piezoelectric ceramic material. For example, PZT [Pb(Zr, Ti)O3], PT (PbTiO3), PLZT [(Pb, La) (Zr, Ti)O3], or barium titanate (BaTiO3) is used as the piezoelectric ceramic material. Each of the piezoelectric layers 12a, 12b, 12c, and 12d is made of a sintered ceramic green sheet containing the above-mentioned piezoelectric ceramic material, for example. In the actual piezoelectric element 11, each of the piezoelectric layers 12a, 12b, 12c, and 12d is integrated to such an extent that the boundaries between the piezoelectric layers 12a, 12b, 12c, and 12d are not recognizable.

[0029] The external electrodes 13, 14, and 15 are disposed closer to the end 4c in the piezoelectric element 4, and closer to the end 5c in the piezoelectric element 5. In each of the piezoelectric elements 4 and 5, the external electrodes 13, 14, and 15 are disposed on the main surface 11a. The external electrodes 13, 14, and 15 are arranged along one short side of the main surface 11a in the order of the external electrode 13, the external electrode 14, and the external electrode 15. The external electrodes 13 and 14 are adjacent to each other in the short side direction of the main surface 11a. The external electrodes 14 and 15 are adjacent to each other in the short side direction of the main surface 11a. In the short side direction of the main surface 11a, the distance (shortest distance) between the external electrodes 14 and 15 is longer than the distance (shortest distance) between the external electrodes 13 and 14. When viewed from the stacking direction, each of the external electrodes 13, 14, and 15 is spaced apart from all edges (four sides) of the main surface 11a.

[0030] Each of the external electrodes 13, 14 has a rectangular shape when viewed from the stacking direction. In this embodiment, each corner of the rectangular shape is rounded. The external electrode 15 has a square shape when viewed from the stacking direction. The square shape includes, for example, a shape in which each corner is chamfered and a shape in which each corner is rounded. In this embodiment, each corner of the square shape is rounded. Each of the external electrodes 13, 14, 15 is made of a conductive material. For example, Ag, Pd, Pt, or an Ag-Pd alloy is used as the conductive material. Each of the external electrodes 13, 14, 15 is configured as a sintered body of a conductive paste containing the conductive material.

[0031] Each of the piezoelectric elements 4, 5 includes a plurality of internal electrodes 16, 17, 18 arranged in the piezoelectric body 11. Each of the internal electrodes 16, 17, 18 is made of a conductive material. For example, Ag, Pd, Pt, or an Ag-Pd alloy is used as the conductive material. Each of the internal electrodes 16, 17, 18 is configured as a sintered body of a conductive paste containing the conductive material. In this embodiment, the external shape of each of the internal electrodes 16, 17, 18 is rectangular.

[0032] The internal electrodes 16, 17, 18 are disposed at different positions (layers) in the stacking direction. The internal electrodes 16, 17, 18 face each other with a gap in the stacking direction. The internal electrodes 16, 17, 18 are not exposed on the surface of the piezoelectric element 11. That is, the internal electrodes 16, 17, 18 are not exposed on the side surfaces 11c. The internal electrodes 16, 17, 18 are spaced apart from all edges (four sides) of the main surfaces 11a, 11b when viewed from the stacking direction.

[0033] The internal electrode 16 is located between the piezoelectric layer 12a and the piezoelectric layer 12b. The internal electrode 17 is located between the piezoelectric layer 12b and the piezoelectric layer 12c. The internal electrode 18 is located between the piezoelectric layer 12c and the piezoelectric layer 12d.

[0034] The external electrode 13 is electrically connected to the internal electrode 16 and the multiple connecting conductors 21 through multiple via conductors 24. The multiple connecting conductors 21 are located in the same layer as the internal electrodes 17, 18. Specifically, each connecting conductor 21 is located in an opening formed in each internal electrode 17, 18. Each opening is formed at a position corresponding to the external electrode 13 when viewed from the stacking direction. That is, each connecting conductor 21 is surrounded by each internal electrode 17, 18 when viewed from the stacking direction. Each connecting conductor 21 is spaced apart from each internal electrode 17, 18.

[0035] Each connecting conductor 21 faces the external electrode 13 in the stacking direction, and is arranged at a position overlapping with the external electrode 13 when viewed from the stacking direction. Each connecting conductor 21 faces the internal electrode 16 in the stacking direction, and is arranged at a position overlapping with the internal electrode 16 when viewed from the stacking direction. Each of the multiple via conductors 24 is located between the external electrode 13, the internal electrode 16, and the multiple connecting conductors 21, and is arranged at a position overlapping with the external electrode 13 when viewed from the stacking direction. Each of the multiple via conductors 24 penetrates the corresponding piezoelectric layers 12a, 12b, and 12c in the stacking direction.

[0036] The external electrode 14 is electrically connected to the internal electrode 18 and the multiple connection conductors 22 through multiple via conductors 25. The multiple connection conductors 22 are located in the same layer as the internal electrodes 16 and 17. Specifically, each connection conductor 22 is located in an opening formed in each internal electrode 16 and 17. Each opening is formed at a position corresponding to the external electrode 14 when viewed from the stacking direction. That is, each connection conductor 22 is surrounded by each internal electrode 16 and 17 when viewed from the stacking direction. Each connection conductor 22 is spaced from each internal electrode 16 and 17. The connection conductors 21 and 22 located in the same layer as the internal electrode 17 are arranged adjacent to each other in the same opening and are spaced from each other.

[0037] Each connecting conductor 22 faces the external electrode 14 in the stacking direction, and is arranged at a position overlapping with the external electrode 14 when viewed from the stacking direction. Each connecting conductor 22 faces the internal electrode 18 in the stacking direction, and is arranged at a position overlapping with the internal electrode 18 when viewed from the stacking direction. Each of the multiple via conductors 25 is located between the external electrode 14, the internal electrode 18, and the multiple connecting conductors 22, and is arranged at a position overlapping with the external electrode 14 when viewed from the stacking direction. Each of the multiple via conductors 25 penetrates the corresponding piezoelectric layers 12a, 12b, and 12c in the stacking direction.

[0038] The external electrode 15 is electrically connected to the internal electrode 17 and the multiple connecting conductors 23 through multiple via conductors 26. The multiple connecting conductors 23 are located in the same layer as the internal electrodes 16, 18. Specifically, each connecting conductor 23 is located in an opening formed in each internal electrode 16, 18. Each opening is formed at a position corresponding to the external electrode 15 when viewed from the stacking direction. In other words, the entire edge of each connecting conductor 23 is surrounded by each internal electrode 16, 18 when viewed from the stacking direction. Each opening is formed at a position corresponding to the external electrode 15 when viewed from the stacking direction.

[0039] Each connecting conductor 23 faces the external electrode 15 in the stacking direction, and is arranged at a position overlapping with the external electrode 15 when viewed from the stacking direction. Each connecting conductor 23 faces the internal electrode 17 in the stacking direction, and is arranged at a position overlapping with the internal electrode 17 when viewed from the stacking direction. Each of the multiple via conductors 26 is located between the external electrode 15, the internal electrode 17, and the multiple connecting conductors 23, and is arranged at a position overlapping with the external electrode 15 when viewed from the stacking direction. Each of the multiple via conductors 26 penetrates the corresponding piezoelectric layers 12a, 12b, and 12c in the stacking direction.

[0040] Each of the connecting conductors 21 and 22 has a rectangular shape when viewed from the stacking direction. In this embodiment, each corner of the rectangular shape is rounded. Each of the connecting conductors 23 has a square shape when viewed from the stacking direction. In this embodiment, each corner of the square shape is rounded.

[0041] The connection conductors 21, 22, 23 and the via conductors 24, 25, 26 are made of a conductive material. For example, Ag, Pd, Pt, or an Ag-Pd alloy is used as the conductive material. The connection conductors 21, 22, 23 and the via conductors 24, 25, 26 are formed as a sintered body of a conductive paste containing the conductive material. The via conductors 24, 25, 26 are formed by sintering a conductive paste filled in a through hole formed in a ceramic green sheet for forming the corresponding piezoelectric layers 12a, 12b, 12c.

[0042] No conductor electrically connected to the internal electrodes 16, 17, 18 is disposed on the principal surface 11b of the piezoelectric element 11. In this embodiment, when the principal surface 11b is viewed from the stacking direction, the entire principal surface 11b is exposed. The principal surfaces 11a and 11b are natural surfaces. The natural surfaces are surfaces formed by the surfaces of crystal grains grown by firing.

[0043] No conductor electrically connected to the internal electrodes 16, 17, 18 is disposed on each side surface 11c of the piezoelectric element 11. In this embodiment, when each side surface 11c is viewed from a direction intersecting the stacking direction, the entire side surface 11c is exposed. In this embodiment, each side surface 11c is also a natural surface.

[0044] In the piezoelectric layer 12b, a region sandwiched between the internal electrode 16 connected to the external electrode 13 and the internal electrode 17 connected to the external electrode 15 constitutes a first piezoelectric active region 19. In the piezoelectric layer 12c, a region sandwiched between the internal electrode 18 connected to the external electrode 14 and the internal electrode 17 connected to the external electrode 15 constitutes a second piezoelectric active region 20.

[0045] The first active region 19 and the second active region 20 are polarized in the same direction by applying voltages of different polarities to the external electrodes 13 and 14, for example, with the external electrode 15 connected to the ground. The first active region 19 is polarized in a direction from the internal electrode 16 to the internal electrode 17, and the second active region 20 is polarized in a direction from the internal electrode 17 to the internal electrode 18. When the piezoelectric elements 4 and 5 are driven, for example, voltages of the same polarity are applied to the external electrodes 13 and 14, and a voltage of a different polarity from the external electrodes 13 and 14 is applied to the external electrode 15. As a result, one of the first active region 19 and the second active region 20 is applied with a voltage in the same direction as the polarization direction (forward direction) to expand, and the other is applied with a voltage in the opposite direction (reverse direction) to the polarization direction to contract. As a result, the piezoelectric element flexurally vibrates in the stacking direction.

[0046] As shown in Figs. 1 to 4, the connection member 6 connects the piezoelectric elements 4 and 5 to each other. The connection member 6 is a vibration transmission member that transmits the vibration of the piezoelectric element 4 to the piezoelectric element 5. The connection member 6 is made of a metal such as aluminum. The connection member 6 is fixed to the end 4c and the end 5c. The connection member 6 is fixed to the main surface 4a (the main surface 11a of the piezoelectric element 4) and the main surface 5b (the main surface 11b of the piezoelectric element 5). The connection member 6 has a rectangular parallelepiped shape. The connection member 6 is provided such that its longitudinal direction is along the short sides of the piezoelectric elements 4 and 5 when viewed from the first direction D1. The connection member 6 has side surfaces 6a and 6b that face each other in the first direction D1 and a pair of side surfaces 6c that face each other in the second direction D2.

[0047] The side surface 6a is fixed to the main surface 5b. The side surface 6b is fixed to the main surface 4a. The connection member 6 is joined to the piezoelectric elements 4, 5 by an insulating joining member 31. The joining member 31 is, for example, a double-sided tape or an adhesive. When viewed from the first direction D1, the entire connection member 6 overlaps with the piezoelectric elements 4, 5. When viewed from the first direction D1, the connection member 6 is arranged so as to contact the short sides of the piezoelectric elements 4, 5, but may be arranged inside the short sides of the piezoelectric elements 4, 5 (closer to the ends 4d, 5d). The connection member 6 is provided over the entire short sides of the piezoelectric elements 4, 5.

[0048] The length of the connection member 6 in the longitudinal direction is equal to the width of the piezoelectric body 11 (the length of the piezoelectric body 11 in the short side direction of the main surface 11a), and is, for example, 10 mm or more and 50 mm or less. The thickness of the connection member 6 (the length in the first direction D1) is set so that the piezoelectric elements 4, 5 do not interfere with each other even when they vibrate. The thickness of the connection member 6 is at least twice the maximum displacement when the piezoelectric elements 4, 5 are bent individually so that the main surface 11a is curved outward, and is, for example, 1 mm or more and 20 mm or less. The distance between the piezoelectric elements 4, 5 is set by the thickness of the connection member 6. The length of the connection member 6 in the second direction D2 is, for example, 1 mm or more and 30 mm or less.

[0049] The fixing member 7 is a member for fixing the acoustic device 1 to a housing (not shown). The fixing member 7 is made of a metal such as aluminum. The fixing member 7 is fixed to the end 4d of the piezoelectric element 4. The fixing member 7 is fixed to the main surface 4b (main surface 11b of the piezoelectric element 4). The fixing member 7 has a rectangular parallelepiped shape. The fixing member 7 is provided such that its longitudinal direction is aligned with the short side of the piezoelectric element 4 when viewed from the first direction D1. The fixing member 7 has side surfaces 7a and 7b facing each other in the first direction D1, and a pair of side surfaces 7c facing each other in the second direction D2.

[0050] The side surface 7a is fixed to the main surface 4b. The fixing member 7 is joined to the piezoelectric element 4 by an insulating joining member 32. The joining member 32 is, for example, a double-sided tape or a joining member. When viewed from the first direction D1, the fixing member 7 entirely overlaps the piezoelectric element 4. When viewed from the first direction D1, the fixing member 7 is disposed so as to contact the short side of the piezoelectric element 4, but may be disposed inside the short side of the piezoelectric element 4 (closer to the end 4c).

[0051] The length of the fixing member 7 in the longitudinal direction is longer than the length of the short side of the piezoelectric element 4. A pair of longitudinal ends 7d of the fixing member 7 protrude from the piezoelectric element 4 when viewed from the first direction D1. The length of the fixing member 7 in the longitudinal direction is, for example, 10 mm or more and 50 mm or less. The thickness of the fixing member 7 (length in the first direction D1) may be greater than or equal to the maximum displacement amount when the piezoelectric element 4 is bent alone so that the main surface 11a is curved outward. The thickness of the fixing member 7 is, for example, 1 mm or more and 20 mm or less. The length of the fixing member 7 in the second direction D2 is, for example, 1 mm or more and 30 mm or less.

[0052] 3, the external electrodes 13, 14, and 15 of the piezoelectric element 4 are disposed between the connecting member 6 and the fixing member 7 when viewed from the first direction D1, and are spaced apart in the second direction D2 from the connecting member 6 and the fixing member 7. In other words, the external electrodes 13, 14, and 15 of the piezoelectric element 4 are disposed on the end 4d side of the connecting member 6 and the end 4c side of the fixing member 7 when viewed from the first direction D1.

[0053] 3, the external electrodes 13, 14, and 15 of the piezoelectric element 5 are disposed between the connecting member 6 and the fixing member 7 when viewed from the first direction D1, and are spaced apart in the second direction D2 from the connecting member 6 and the fixing member 7. In other words, the external electrodes 13, 14, and 15 of the piezoelectric element 5 are disposed on the end 5d side of the connecting member 6 and the end 5c side of the fixing member 7 when viewed from the first direction D1.

[0054] The wiring member 8 has a strip shape and is electrically connected to the external electrodes 13, 14, and 15 of the piezoelectric element 4. The wiring member 8 is drawn out from the end 4d side of the piezoelectric element 4 along the second direction D2. The wiring member 9 has a strip shape and is electrically connected to the external electrodes 13, 14, and 15 of the piezoelectric element 5. The wiring member 9 is drawn out from the end 5c side of the piezoelectric element 5 along the second direction D2.

[0055] Each of the wiring members 8, 9 is, for example, a flexible printed circuit board (FPC) or a flexible flat cable (FFC). One end of each of the wiring members 8, 9 is disposed on the external electrodes 13, 14, 15 and connected to the external electrodes 13, 14, 15. Each of the wiring members 8, 9 is disposed so that the thickness direction coincides with the first direction D1. Each of the wiring members 8, 9 has, for example, a first conductor layer (not shown) connected to the external electrodes 13, 14 and a second conductor layer (not shown) connected to the external electrode 15. The external electrodes 13, 14 are short-circuited by the first conductor layer.

[0056] The acoustic device 1 includes a control circuit (not shown). The control circuit includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). In this case, the control circuit loads a program stored in the ROM into the RAM and executes the program with the CPU to perform various processes. The control circuit is connected to the other end of each of the wiring members 8 and 9. The control circuit inputs a drive signal for driving the piezoelectric element 4 via the wiring member 8, and inputs a drive signal for driving the piezoelectric element 5 via the wiring member 9.

[0057] Next, the audio section 3 will be described.

[0058] As shown in FIGS. 1 to 4, the acoustic unit 3 has a base 41, a center pole 42, a center cap 44, a diaphragm 45, an edge 46, a frame 47, a gasket 48, and a damper 49.

[0059] The base 41 is provided at the lower end of the acoustic device 1 and is connected to the vibration section 2. The base 41 is connected to the end 5d of the piezoelectric element 5. The base 41 is joined to the end 5d of the piezoelectric element 5 by an insulating joining member 33. The joining member 33 is, for example, a double-sided tape or an adhesive. The base 41 is fixed to the main surface 5a of the piezoelectric element 5 by the joining member 33.

[0060] The center pole 42 is, for example, a rod-shaped member with a circular cross section, and protrudes in the first direction D1 from the center of the base 41. An outer flange portion 42a having a circular shape in a plan view is provided in the center of the first direction D1 on the outer circumferential surface of the center pole 42.

[0061] The center cap 44 is a cylindrical member whose axial direction is the first direction D1. The center cap 44 covers the center pole 42 from the upper end to the outer flange portion 42a. The center cap 44 has a dome-shaped tip portion 44a attached to the upper end of the center pole 42. The outer flange portion 42a is attached to the lower end of the center cap 44. The opening at the lower end of the center cap 44 is closed by the outer flange portion 42a.

[0062] The diaphragm 45 generates sound by vibration. The diaphragm 45 is, for example, cone-shaped and has a circular ring shape in a plan view. The axial direction of the diaphragm 45 coincides with the first direction D1. The diaphragm 45 may be, for example, dome-shaped or flat. The diaphragm 45 is curved so as to bulge outward. This allows vibration to be transmitted efficiently. The diaphragm 45 is formed of, for example, resin, paper, or metal. The inner edge of the diaphragm 45 is joined to the outer circumferential surface of the center cap 44.

[0063] When viewed from the first direction D1, the edge 46 has a circular ring shape surrounding the diaphragm 45. The inner edge of the edge 46 is joined to the outer edge of the diaphragm 45. The outer edge of the edge 46 is joined to the inner edge of the gasket 48. In a radial cross section, the edge 46 is formed in an arc shape whose center is convex toward the outside of the acoustic device 1. The edge 46 is formed from an elastic member such as rubber. The edge 46 suppresses the vibration of the diaphragm 45 from being transmitted to the frame 47.

[0064] The frame 47 is a substantially cylindrical member whose axial direction is the first direction D1. The frame 47 is formed of, for example, metal or resin. The frame 47 is disposed so as to surround the base 41 and the center pole 42. The frame 47 supports the diaphragm 45 via a gasket 48 and an edge 46. An inner flange portion 47a is provided on the inner peripheral surface of the frame 47. The frame 47 is inclined with respect to the first direction D1 so that the outer diameter and the inner diameter gradually increase from the inner flange portion 47a toward the gasket 48.

[0065] Gasket 48 is a member for fixing diaphragm 45 to frame 47 via edge 46. Gasket 48 has an annular inner flange portion 48a joined to the outer edge portion of edge 46, and a cylindrical portion 48b surrounding the outer edge of frame 47 when viewed from first direction D1.

[0066] The damper 49 has an annular shape when viewed from the first direction D1. An outer edge of the damper 49 is attached to an inner peripheral surface of the frame 47, and an inner edge of the damper 49 is attached to an outer peripheral surface of the center cap 44. The damper 49 is formed, for example, so that a cross section in the radial direction shows a wave shape. The damper 49 suppresses the vibration of the diaphragm 45 from being transmitted to the frame 47.

[0067] The vibration from the vibration unit 2 is transmitted to the diaphragm 45 through the base 41, the center pole 42, and the center cap 44, causing the diaphragm 45 to vibrate. This causes the acoustic unit 3 to generate sound.

[0068] Next, a method for attaching the acoustic device 1 to a housing will be described with reference to Fig. 7 and Fig. 8. Fig. 7 shows a state in which only the vibration section 2 is attached to a jig 50, with the acoustic section 3 not shown. The jig 50 is a member used for attaching the acoustic device 1 to a housing (not shown). The acoustic device 1 is supported by the jig 50 so that the portions other than the fixing member 7 (see Fig. 1) are floating above the housing.

[0069] The jig 50 includes a base 51. The base 51 is made of, for example, metal. The base 51 has side portions 52, 53 arranged opposite each other in the second direction D2, and a side portion 54 extending in the second direction D2 and connecting one end of the side portions 52, 53 to each other. When viewed from the first direction D1, the side portion 52 is arranged along one short side of the piezoelectric elements 4, 5, the side portion 53 is arranged along the other short side of the piezoelectric elements 4, 5, and the side portion 54 is arranged along one long side of the piezoelectric elements 4, 5. When viewed from the first direction D1, the side portion 52 is arranged so as to overlap the ends 4d, 5d of the piezoelectric elements 4, 5, and the side portions 53, 54 are arranged apart from the piezoelectric elements 4, 5.

[0070] The side portion 52 is a support portion that supports the acoustic device 1. The side portion 52 is provided with a step portion 55 on which the fixing member 7 is placed. The height of the step portion 55 is set to match the height of the fixing member 7. The height of the step portion 55 is set so that the upper surface of the side portion 52 and the upper surface of the fixing member 7 are at the same height position when the fixing member 7 is placed on the step portion 55. The fixing member 7 is fixed to the step portion 55 by, for example, an insulating bonding member. The bonding member is, for example, double-sided tape or an adhesive.

[0071] A pressing plate 56 is disposed on the side portion 52 so as to cover the end portion 7d of the fixing member 7 disposed on the step portion 55. The pressing plate 56 is fastened to the side portion 52 with a bolt 57, thereby fixing the fixing member 7 to the side portion 52. Of the vibration portion 2, only the fixing member 7 is in contact with the jig 50. The jig 50 holds the vibration portion 2 with the fixing member 7 as a fixed end so as to be vibrable in the first direction D1. The base 51 is provided with a plurality of mounting holes 58 for mounting the jig 50 to a housing.

[0072] The effects of the acoustic device 1 will now be described.

[0073] The acoustic device 1 includes piezoelectric elements 4 and 5 arranged opposite to each other in a first direction D1, and a connecting member 6 connecting the piezoelectric elements 4 and 5 to each other. The piezoelectric element 4 has ends 4c and 4d in a second direction D2, and the piezoelectric element 5 has ends 5c and 5d in the second direction D2. The connecting member 6 is fixed to the ends 4c and 5c. In the acoustic device 1, the piezoelectric element 4 is cantilevered by a fixing member 7 so that the end 4c side is a free end and the end 4d side is a fixed end. The piezoelectric element 5 is cantilevered by the connecting member 6 so that the end 5c side is a fixed end and the end 5d side is a free end. The acoustic unit 3 is arranged at the end 5d. Therefore, the amount of displacement of the acoustic unit 3 caused by the vibration unit 2 is the amount of displacement of the end 5d.

[0074] When the piezoelectric elements 4 and 5 are flexurally vibrated in the same direction, as shown in FIG. 9, the displacement of the vibration part 2 becomes larger than the displacement when the piezoelectric elements 4 and 5 are vibrated independently. In the central diagram of FIG. 9, both of the piezoelectric elements 4 and 5 are bent so that the main surface 11a (see FIG. 2) side is the curved outer side. In the right diagram of FIG. 9, both of the piezoelectric elements 4 and 5 are bent so that the main surface 11b (see FIG. 2) side is the curved outer side. The direction of the flexural vibration of the piezoelectric elements 4 and 5 can be controlled by a signal input from a control circuit. The control circuit applies voltages of the same phase to the piezoelectric elements 4 and 5, thereby flexurally vibrating the piezoelectric elements 4 and 5 in the same direction.

[0075] In order to confirm the effect of the acoustic device 1, acoustic devices according to an embodiment and a comparative example were prepared. In the acoustic device according to the comparative example, one piezoelectric element was supported at both ends in the longitudinal direction, and an acoustic section was placed in the center in the longitudinal direction. The horizontal axis of FIG. 10 indicates frequency, and the vertical axis indicates sound pressure level. As shown in FIG. 10, it was confirmed that the sound pressure in the low frequency range (around 100 Hz) was improved in the acoustic device according to the embodiment, compared to the acoustic device according to the comparative example.

[0076] The piezoelectric elements 4 and 5 are arranged such that the principal surface 11a of the piezoelectric element 4 and the principal surface 11b of the piezoelectric element 5 face each other in the first direction D1. The connecting member 6 is fixed to the principal surface 11a of the piezoelectric element 4 and the principal surface 11b of the piezoelectric element 5. For this reason, the distance between the piezoelectric elements 4 and 5 can be easily set by the connecting member 6.

[0077] The piezoelectric elements 4 and 5 have the same shape, so that the individual differences between the piezoelectric elements 4 and 5 can be reduced.

[0078] When viewed from the first direction D1, the piezoelectric element 4 has external electrodes 13, 14, and 15 arranged on the end 4d side of the connection member 6. This makes it possible to prevent electrical short circuits between the external electrodes 13, 14, and 15 of the piezoelectric element 4 and the connection member 6.

[0079] A strip-shaped wiring member 8 is connected to the external electrodes 13, 14, and 15 of the piezoelectric element 4. This makes it possible to prevent the vibration of the piezoelectric element 4 from being hindered, compared to a case in which lead wires are connected to the external electrodes 13, 14, and 15 of the piezoelectric element 4. In addition, since the wiring member 8 is fixed closer to the end 4d, which is the fixed end of the piezoelectric element 4, it makes it possible to prevent the vibration of the piezoelectric element 4 from being hindered, compared to a case in which the wiring member 8 is fixed closer to the end 4c, which is the free end.

[0080] When viewed from the first direction D1, the piezoelectric element 5 has external electrodes 13, 14, and 15 arranged on the end 5d side of the connection member 6. This makes it possible to prevent electrical short circuits between the external electrodes 13, 14, and 15 of the piezoelectric element 5 and the connection member 6.

[0081] A strip-shaped wiring member 9 is connected to the external electrodes 13, 14, and 15 of the piezoelectric element 5. Therefore, it is possible to suppress the vibration of the piezoelectric element 5 from being hindered, compared to a case where lead wires are connected to the external electrodes 13, 14, and 15 of the piezoelectric element 5. In addition, since the wiring member 9 is fixed closer to the end 5c, which is the fixed end of the piezoelectric element 5, it is possible to suppress the vibration of the piezoelectric element 5 from being hindered, compared to a case where the wiring member 9 is fixed closer to the end 5d, which is the free end. Although the end 5c is a fixed end, it is joined to the end 4c, which is the free end of the piezoelectric element 4, by the connection member 6 and vibrates. For this reason, it is particularly effective to use the strip-shaped wiring member 9.

[0082] The piezoelectric elements 4 and 5 are arranged such that their longitudinal directions coincide with the second direction D2, which further increases the displacement, thereby further improving the acoustic characteristics.

[0083] The piezoelectric elements 4 and 5 do not have a diaphragm. Therefore, no distortion components originating from a diaphragm are generated in the piezoelectric elements 4 and 5. In addition, the piezoelectric elements 4 and 5 can be made lighter.

[0084] The piezoelectric elements 4 and 5 are joined to the connection member 6 by an insulating joining member 31. This prevents an electrical short circuit from occurring between the piezoelectric elements 4 and 5 and the connection member 6. The piezoelectric element 4 is joined to the fixing member 7 by an insulating joining member 32. This prevents an electrical short circuit from occurring between the piezoelectric element 4 and the fixing member 7. The piezoelectric element 5 is joined to the base 51 of the acoustic unit 3 by an insulating joining member 33. This prevents an electrical short circuit from occurring between the piezoelectric element 5 and the base 51.

[0085] The present invention is not necessarily limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

[0086] The acoustic device 1 includes two piezoelectric elements 4 and 5, but may include three or more piezoelectric elements. The piezoelectric elements 4 and 5 may have different shapes. The piezoelectric elements 4 and 5 may be monomorph types.

[0087] The bonding member 31 may be conductive. Even in this case, the internal electrodes 16, 17, and 18 are not exposed on the surfaces of the piezoelectric elements 4 and 5, so that the occurrence of an electrical short circuit between the piezoelectric elements 4 and 5 and the connecting member 6 is suppressed. The bonding member 32 may be conductive. Even in this case, the internal electrodes 16, 17, and 18 are not exposed on the surfaces of the piezoelectric element 4, so that the occurrence of an electrical short circuit between the piezoelectric element 4 and the fixing member 7 is suppressed. The bonding member 33 may be conductive. Even in this case, the internal electrodes 16, 17, and 18 are not exposed on the surfaces of the piezoelectric element 5, so that the occurrence of an electrical short circuit between the piezoelectric element 5 and the base 51 is suppressed.

[0088] 11, in the acoustic device 1A according to the modified example, the connection members 6 are disposed at the ends 4c and 5c so as to be spaced apart from the short sides of the piezoelectric elements 4 and 5 and to be on the inside of the short sides (closer to the ends 4d and 5d) when viewed from the first direction D1. Moreover, the fixing member 7 is disposed at the end 4d so as to be spaced apart from the short sides of the piezoelectric element 4 and to be on the inside of the short sides (closer to the end 4c) when viewed from the first direction D1. Moreover, the base 41 of the acoustic section 3 is disposed at the end 5d so as to be spaced apart from the short sides of the piezoelectric element 5 and to be on the inside of the short sides (closer to the end 5c) when viewed from the first direction D1. [Explanation of symbols]

[0089] 1, 1A...acoustic device, 2...vibration portion, 3...acoustic portion, 4...piezoelectric element, 4a, 4b...main surface, 4c, 4d...end portion, 5...piezoelectric element, 5a, 5b...main surface, 5c, 5d...end portion, 6...connecting member, 8, 9...wiring member, 11a...main surface, 11b...main surface, 13, 14, 15...external electrode, D1...first direction, D2...second direction.

Claims

1. a first piezoelectric element and a second piezoelectric element arranged opposite to each other in a first direction; a connection member connecting the first piezoelectric element and the second piezoelectric element to each other, a piezoelectric body of the first piezoelectric element having a first end portion and a second end portion in a second direction intersecting the first direction, a piezoelectric body of the second piezoelectric element having a third end and a fourth end in the second direction, the connecting member is fixed to the first end portion and the third end portion so as to overlap with a piezoelectric body of the first piezoelectric element and a piezoelectric body of the second piezoelectric element when viewed from the first direction, the first piezoelectric element is cantilever-supported by a fixing member such that the first end side is a free end and the second end side is a fixed end, the second piezoelectric element is cantilever-supported by the connecting member such that the third end side is a fixed end and the fourth end side is a free end. Acoustic device.

2. the first piezoelectric element has a first principal surface and a second principal surface opposed to each other; the second piezoelectric element has a third principal surface and a fourth principal surface opposed to each other, the first piezoelectric element and the second piezoelectric element are arranged such that the first principal surface and the third principal surface face each other in the first direction, The connection member is fixed to the first main surface and the third main surface.

2. The acoustic device of claim 1.

3. The first piezoelectric element and the second piezoelectric element have the same shape.

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

4. the first piezoelectric element has a first external electrode disposed on the second end side of the connection member when viewed from the first direction; An acoustic device according to any one of claims 1 to 3.

5. The first wiring member is connected to the first external electrode.

5. The acoustic device according to claim 4.

6. the second piezoelectric element has a second external electrode disposed on the third end side of the connection member when viewed from the first direction. An acoustic device according to any one of claims 1 to 5.

7. The second wiring member is connected to the second external electrode.

7. The acoustic device of claim 6.

8. The first piezoelectric element and the second piezoelectric element are arranged such that their longitudinal directions coincide with the second direction. An acoustic device according to any one of claims 1 to 7.

9. a first piezoelectric element and a second piezoelectric element arranged opposite to each other in a first direction; a connection member connecting the first piezoelectric element and the second piezoelectric element to each other, a piezoelectric body of the first piezoelectric element having a first end portion and a second end portion in a second direction intersecting the first direction, a piezoelectric body of the second piezoelectric element having a third end and a fourth end in the second direction, the connecting member is fixed to the first end portion and the third end portion so as to overlap with a piezoelectric body of the first piezoelectric element and a piezoelectric body of the second piezoelectric element when viewed from the first direction, the first piezoelectric element is cantilever-supported by a fixing member such that the first end side is a free end and the second end side is a fixed end, the second piezoelectric element is cantilever-supported by the connecting member such that the third end side is a fixed end and the fourth end side is a free end. Vibration devices.

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