Acoustic device

Abstract

In order to achieve the purpose, an acoustic device according to one embodiment of the present technology comprises: a housing having an opening and a bottom part respectively on one side and the other side in a first direction; a diaphragm supported in the housing; and a piezoelectric coil having a coil-shaped core material connecting the housing and the diaphragm, and a piezoelectric material spirally wound around the core material.

Description

audio equipment

[0001] The present technology relates to an acoustic device having a piezoelectric coil.

[0002] 2. Description of the Related Art Conventionally, a voice coil motor has been disclosed as an acoustic device, which includes a cylindrical case with a bottom, a permanent magnet disposed at the center bottom inside the case, and a coil portion.

[0003] Japanese Patent Application Laid-Open No. 2022-55903

[0004] In recent years, there has been a demand for lighter earphones and headphones. However, when a voice coil motor as described in Patent Document 1 is used, there is a problem that it is difficult to reduce the weight because a magnet is used.

[0005] In view of the above circumstances, an object of the present technology is to provide an acoustic device that can be made lighter.

[0006] According to one embodiment of the present technology, there is provided an acoustic device including a housing, a diaphragm, and a piezoelectric coil. The housing has an opening at one end in a first direction and a bottom at the other end in the first direction. The diaphragm is supported within the housing. The piezoelectric coil includes a coil-shaped core material connecting the housing and the diaphragm, and a piezoelectric material wound spirally around the core material.

[0007] The piezoelectric coil may be arranged along the first direction, with a first end portion on one end side of the first direction connected to a central portion of the diaphragm when viewed from the first direction, and a second end portion on the other end side of the first direction connected to the housing.

[0008] The first end and the second end may be the core.

[0009] The length of the core material in a second direction perpendicular to the first direction may be 40% or more and less than 100% of the length of the diaphragm in the second direction.

[0010] The length of the piezoelectric coil in the first direction may be 5% to 20% of the length of the diaphragm in a second direction perpendicular to the first direction.

[0011] The core may connect the bottom and the diaphragm.

[0012] The housing may further have a support portion facing the vibration plate in the first direction and provided on one end side in the first direction, and the piezoelectric coil may be provided between the support portion and the vibration plate.

[0013] FIG. 1 is a diagram showing an acoustic device according to a first embodiment of the present technology; FIG. 2 is a diagram showing a piezoelectric coil according to the first embodiment of the present technology as viewed from above; FIG. 3 is a diagram showing an acoustic device according to a second embodiment of the present technology; FIG. 4 is a diagram showing a piezoelectric coil according to the second embodiment of the present technology as viewed from above; FIG. 5 is a diagram showing a piezoelectric coil diameter and a displacement amount according to the second embodiment of the present technology; FIG. 6 is a diagram showing a piezoelectric coil length and a displacement amount according to the second embodiment of the present technology; FIG. 7 is a diagram showing an acoustic device according to a third embodiment of the present technology; FIG. 8 is a diagram showing a piezoelectric coil according to the third embodiment of the present technology as viewed from above.

[0014] Hereinafter, embodiments of the present technology will be described with reference to the drawings.

[0015] 1 is a diagram showing an acoustic device 1 according to a first embodiment of the present technology, and FIG. 2 is a diagram showing a piezoelectric coil 40 according to the first embodiment of the present technology as viewed from above. In the diagram, the X-axis, the Y-axis, and the Z-axis indicate three axial directions that are orthogonal to each other.

[0016] The acoustic device 1 includes a housing 10, a diaphragm 20, and a piezoelectric coil 40. In this embodiment, the acoustic device 1 is described as an earphone, but of course, the acoustic device 1 is not limited to this and can also be applied to headphones, speakers, etc.

[0017] (Housing) The housing 10 has an internal space W that houses the diaphragm 20 and the piezoelectric coil 40. As shown in Fig. 1, the housing 10 is cylindrical and has a bottom 10A that is open on the positive side (one end) of the Z axis (first direction) and a cylindrical side portion 10B that extends from the bottom 10A toward the positive side of the Z axis (the other end). The side portion 10B has an open end 101B that forms an opening on the positive side of the Z axis.

[0018] In this embodiment, the housing 10 is cylindrical, but of course, the shape is not limited to this.

[0019] (Vibration Plate) The diaphragm 20 is supported within the housing 10 by a flexible material 30, which will be described later. The diaphragm 20 (cone paper) is formed in a circular shape when viewed in the Z-axis direction. Here, "circular shape" refers not only to a circle but also to an approximately circular shape. The outer diameter and thickness of the diaphragm 20 are not particularly limited and are set appropriately depending on the size of the housing 10, the frequency band, etc.

[0020] In this embodiment, the vibration plate 20 has a concave (cone-shaped) shape that is recessed from its outer periphery toward its inner periphery. The cone-shaped vibration plate 20 has a bottom plate portion 20A, and the piezoelectric coil 40 is connected (adhered) to the bottom plate portion 20A.

[0021] In this embodiment, the diaphragm 20 is cone-shaped, but of course, the shape is not limited to this and may be disk-shaped.

[0022] In this embodiment, the flexible material 30 is made of an elastomer material such as polyurethane, but is not limited to this. The flexible material 30 is bonded to the open end 101B of the housing 10 and the diaphragm 20, as shown in FIG.

[0023] The flexible material 30, the housing 10 and the diaphragm 20 may be bonded together using, for example, an epoxy or silicone adhesive for elastomers, or if the flexible material 30 is a thermoplastic resin, they may be bonded together by thermocompression bonding, or of course they may be bonded together by other methods.

[0024] (Piezoelectric Coil) The piezoelectric coil 40 has a coil-shaped core material 40A that connects between the housing 10 and the diaphragm 20, and a piezoelectric material 40B that is spirally wound in the length direction (Z-axis direction) of the core material 40A. The piezoelectric coil 40 also has an electrode portion (not shown) that applies an electric field to the piezoelectric material 40B in the thickness direction of the piezoelectric material 40B.

[0025] The electrode portions are configured to be able to apply an electric field (DC or AC) to the piezoelectric material 40B in the thickness direction of the piezoelectric material 40B. In this embodiment, the electric field is applied in the thickness direction of the piezoelectric material 40B, but the electric field may also be applied in the length direction of the piezoelectric material 40B. When an electric field is applied by the electrode portions, the piezoelectric material 40B distorts, and at this time, the expansion and contraction of the piezoelectric material 40B in the length direction contributes to the deformation of the piezoelectric coil 40 in the Z-axis direction.

[0026] The electrode portion has a core material 40A and a surface electrode (not shown) that sandwiches the piezoelectric material 40B between the core material 40A and the surface electrode in the thickness direction of the piezoelectric material 40B. One of the core material 40A and the surface electrode is a positive electrode, and the other is a negative electrode.

[0027] The core material 40A is configured in a coil spring shape, and its cross section (cross section perpendicular to the longitudinal direction of the core material 40A) is circular. Note that the cross section of the core material 40A may be elliptical, polygonal, or the like, and the shape of this cross section is not particularly limited.

[0028] The core material 40A is made of at least one material selected from the group consisting of graphite, Mg alloy, Al, Ti, SUS, W, Au, Ag, Cu, Pt, and ceramics.

[0029] The piezoelectric material 40B is configured in a strip shape that is long in the length direction, short in the width direction, and thin in the thickness direction. The piezoelectric material 40B is wound around the core material 40A at a predetermined angle relative to the length direction.

[0030] The piezoelectric material 40B is, for example, Pb(Zr,Ti)O3[PZT], PbTiO3, Pb(Mg1 / 3Nb2 / 3)O3-PbTiO 3[PMN-PT], Pb(Zn1 / 3Nb2 / 3)O3-PbTiO3[PZN-PT], BaTiO3[BT], (K,Na ) NbO3 [KNN], KNbO3, NaNbO3, (K, Na, Li) NbO3, (K, Na, Li) (Nb, Ta, Sb) O 3. (Sr,Ba)Nb2O6, (Sr,Ca)NaNb5O15, (Na,K)Ba2NbO15, BiFeO3, Bi4Ti The piezoelectric material is constructed using at least one material selected from the group consisting of BaTiO3-(BiK1 / 2)TiO3, (BiNa1 / 2)TiO3, BaTiO3-(BiK1 / 2)TiO3, BaTiO3-(BiNa1 / 2)TiO3, AlN, LiNbO3, LiTaO3, alpha-SiO2, GaPO4, LiB4O7, LaGa5SiO14, LaTaO.5Ga5.5O14, MgSiO3, ZnO, polyvinylidene fluoride [PVDF], and halide perovskite-based piezoelectric materials as a base material.

[0031] As described above, core material 40A is connected between housing 10 and diaphragm 20. Core material 40A has a first end 401A connected to diaphragm 20 and a second end (not shown) connected to housing 10 (see FIG. 2).

[0032] The first end 401A of the core material 40A is not covered by the piezoelectric material 40B. As described above, the first end 401A is connected to the bottom plate portion 20A of the diaphragm 20 using an adhesive or the like. In this embodiment, the adhesive used may be, for example, an ultraviolet-curing or moisture-curing adhesive, but is not limited to these. Furthermore, by using an ultraviolet-curing resin, the bonding time can be shortened.

[0033] The second end of the core 40A is connected to the bottom 10A of the housing 10 using an adhesive, a jig, or the like. In this embodiment, the adhesive used may be, for example, an ultraviolet-curing or moisture-curing adhesive, but is not limited to these. Furthermore, the use of an ultraviolet-curing resin can shorten the bonding time.

[0034] This allows the acoustic device 1 to be made smaller and lighter. In other words, while conventionally, a magnet and a coil were used to drive the diaphragm, in this embodiment, there is no need to use a magnet, which takes up a large volume and weight in a voice coil motor, and the diaphragm 20 can be driven by the piezoelectric coil 40 alone. This simplifies the structure of the acoustic device 1 and allows for significant miniaturization and weight reduction. Furthermore, because the piezoelectric coil 40 exhibits a large displacement from low to high frequencies, when used in the acoustic device 1, high sound pressure can be obtained over a wide frequency range.

[0035] Furthermore, since the piezoelectric coil 40 (piezoelectric material 40B) is used, the drive current can be made smaller than that of a voice coil motor, thereby reducing power consumption.

[0036] Second Embodiment As described above, in the present technology, the connection position between the first end 401A of the core material 40A and the bottom plate portion 20A of the diaphragm 20 is not particularly limited. However, the first end 401A' of the core material 40A' may be connected to the center of the bottom plate portion 20A when viewed from the Z-axis direction. FIG. 3 is a diagram showing an acoustic device 1A according to a second embodiment of the present technology, and FIG. 4 is a top view of a piezoelectric coil 40' according to the second embodiment of the present technology. Furthermore, FIG. 5 is a diagram showing the diameter and displacement of a piezoelectric coil according to the second embodiment of the present technology, and FIG. 6 is a diagram showing the length and displacement of a piezoelectric coil according to the second embodiment of the present technology. Below, configurations different from the first embodiment will be mainly described, and configurations similar to those in the first embodiment will be denoted by the same reference numerals, and their description will be omitted or simplified.

[0037] In this embodiment, a first end 401A' of a piezoelectric coil 40' of an acoustic device 1A' is connected to a central portion of the diaphragm 20 (bottom plate portion 20A) when viewed from the Z-axis direction, and a second end 402A' is connected to the bottom portion 10A at a position overlapping the first end 401A' when viewed from the Z-axis direction. The piezoelectric coil 40' also has a fixed portion 40C. The fixed portion 40C has a first fixed portion 401C that connects the first end 401A' to the diaphragm 20 and a second fixed portion 402C that connects the second end 402A' to the housing 10 (bottom portion 10A).

[0038] As shown in Fig. 4, first end 401A' is core material 40A' and is provided so as to face the central portion of diaphragm 20 when viewed in the Z-axis direction. Here, the central portion is not limited to the strict center of diaphragm 20 but also includes the approximate center (substantially the center). In other words, as shown in Fig. 4, first end 401A', on which piezoelectric material 40B' is not wound, is bent from piezoelectric coil 40', which has a circular shape when viewed in the Z-axis direction, so as to face the central portion.

[0039] The first end 401A' is connected to the diaphragm 20 by the first fixing portion 401C described above. For the first fixing portion 401C, an ultraviolet-curing or moisture-curing adhesive is used, but the adhesive is not limited to this. Furthermore, by using an ultraviolet-curing resin, the time required for adhesion can be shortened.

[0040] Second end 402A' is core material 40A' and is provided so as to face the central portion of diaphragm 20 when viewed from the Z-axis direction. Furthermore, second fixed portion 402C is provided at a position overlapping first fixed portion 401C when viewed from the Z-axis direction, and second end 402A' is provided so as to face second fixed portion 402C. In other words, similar to first end 401A', second end 402A', on which piezoelectric material 40B' is not wound, is bent from piezoelectric coil 40', which has a circular shape when viewed from the Z-axis direction, so as to face the central portion described above.

[0041] The second end 402A' is connected to the housing 10 (bottom 10A) by the second fixing portion 402C described above. For example, an ultraviolet-curing or moisture-curing adhesive is used for the second fixing portion 402C, but the second fixing portion 402C is not limited to this and a jig or the like may also be used.

[0042] This allows the diaphragm 20 to vibrate smoothly. In other words, if the connection positions of the first end 401A' and the second end 402A' are offset from the center position of the diaphragm 20 as viewed in the Z-axis direction, the diaphragm 20 will not vibrate parallel to the Z-axis direction and will tilt. This causes tilting and asymmetric deformation of the diaphragm 20, particularly at high frequencies. However, in this embodiment, the first end 401A' of the piezoelectric coil 40' is connected to the center portion of the diaphragm 20 (bottom plate portion 20A) as viewed in the Z-axis direction, and the second end 402A' is connected to the bottom portion 10A at a position overlapping the first end 401A' as viewed in the Z-axis direction. This allows the diaphragm 20 to vibrate parallel (linearly) to the Z-axis direction even in the high-frequency band, thereby improving the sound quality in the high-frequency band.

[0043] Here, the relationship between the diameter of the piezoelectric coil 40' and its displacement will be explained using FIG. 5. The piezoelectric coil 40' shown in FIG. 5 has a core material 40A' made of a heat-resistant alloy, a piezoelectric material 40B made of PZT, and a coil length of 5 mm. The horizontal axis of FIG. 5 represents the ratio of the diameter of the piezoelectric coil 40' to the diameter of the diaphragm 20, and the vertical axis represents the displacement compared to a conventional product. The piezoelectric coil 40' shown in FIG. 4 is driven at 10 Hz.

[0044] Here, the diameter of the diaphragm 20 is the diameter including the flexible material 30, which is 30 mm in this embodiment and is also the diameter of the opening in the housing 10. The conventional product on the vertical axis is a voice coil motor, and the voice coil size is 30 mm in diameter and 5 mm in length.

[0045] In the piezoelectric coil 40', when the coil diameter (length along the X-axis direction (second direction)) is increased, the displacement rate of the coil length (length along the Z-axis direction) increases. In other words, by increasing the coil diameter, the piezoelectric coil 40' can vibrate the diaphragm 20 more greatly.

[0046] 5, when the ratio of the diameter of the piezoelectric coil 40' to the diameter of the diaphragm 20 is 40% or more, it becomes possible to vibrate the diaphragm 20 with a sufficient displacement compared to conventional voice coil motors, thereby increasing the sound pressure. Furthermore, it is preferable that the ratio of the diameter of the piezoelectric coil 40' to the diameter of the diaphragm 20 be 100% or less. The reason for this is that if the ratio exceeds 100%, the diameter (size) of the entire acoustic device 1 becomes large (for miniaturization).

[0047] The relationship between the length of the piezoelectric coil 40' and its displacement will be explained using Figure 6. The piezoelectric coil 40' shown in Figure 6 has a core material 40A' made of a heat-resistant alloy, a piezoelectric material 40B made of PZT, and a coil diameter of 20 mm. The horizontal axis of Figure 6 represents the ratio of the length of the piezoelectric coil 40' to the diameter of the diaphragm 20, and the vertical axis represents the displacement compared to a conventional product.

[0048] Here, the diameter of the diaphragm 20 is the diameter including the flexible material 30, which is 30 mm in this embodiment and is also the diameter of the opening in the housing 10. The conventional product on the vertical axis is a voice coil motor, and the voice coil size is 30 mm in diameter and 5 mm in length.

[0049] Increasing the coil length of the piezoelectric coil 40' increases the absolute value of the displacement of the coil length. In other words, by increasing the coil length of the piezoelectric coil 40', the vibration plate 20 can be vibrated more greatly.

[0050] 6, when the ratio of the length of the piezoelectric coil 40' to the diameter of the diaphragm 20 is 5% or more, it becomes possible to vibrate the diaphragm 20 with a sufficient displacement compared to conventional voice coil motors, thereby increasing the sound pressure. Furthermore, it is preferable that the ratio of the length of the piezoelectric coil 40' to the diameter of the diaphragm 20 be 20% or less. The reason for this is that if the ratio exceeds 20%, the overall length (size) of the acoustic device 1 becomes large (for miniaturization).

[0051] Third Embodiment As described above, in the present technology, the piezoelectric coil is provided between the diaphragm 20 and the bottom 10A of the housing 10, but it may also be provided between the diaphragm 20 and the open end 101B of the housing 10. Fig. 7 is a diagram showing an acoustic device 1B according to a third embodiment of the present technology, and Fig. 8 is a diagram showing the piezoelectric coil 1B according to the third embodiment of the present technology as viewed from above. Below, configurations different from the second embodiment will be mainly described, and configurations similar to those in the second embodiment will be assigned the same reference numerals, and descriptions thereof will be omitted or simplified.

[0052] In this embodiment, the housing 10' of the acoustic device 1B further includes a support portion 10C that faces the diaphragm 20 in the Z-axis direction and is provided on one end side in the Z-axis direction.

[0053] 7 and 8, the support portion 10C is columnar, and a plurality of support portions 10C are provided at the opening end 101B to divide the opening into a plurality of portions. In this embodiment, two support portions 10C are provided so as to intersect, but this is not limiting, and the number of support portions 10C may be one, three or more, or may be mesh-shaped.

[0054] In this embodiment, the support portion 10C is positioned so as to pass through the center of the diaphragm 20 when viewed in the Z-axis direction. The support portion 10C is made of, for example, a metal such as aluminum or SUS, or a resin such as acrylic or PC.

[0055] 7 and 8, the piezoelectric coil 40" is provided between the vibration plate 20 and the support portion 10C described above. A first end 401A" of the piezoelectric coil 40" is located at the center of the vibration plate 20 (bottom plate portion 20A) when viewed from the Z-axis direction and is connected to the support portion 10C, and a second end 402A" is connected to the support portion 10C of the bottom portion 10A and is provided at a position overlapping with the first end 401A" when viewed from the Z-axis direction.

[0056] As shown in FIGS. 7 and 8, the first end 401A'' is a core material 40A'' and is provided so as to face the center portion of the diaphragm 20 (the position where the support portion 10C intersects) when viewed in the Z-axis direction.

[0057] The first end 401A'' is connected to the support 10C by a first fixing portion 401C provided on the support 10C. For the first fixing portion 401C, for example, an ultraviolet-curing or moisture-curing adhesive is used, but the present invention is not limited to this. Furthermore, by using an ultraviolet-curing resin, the time required for bonding can be shortened. In this embodiment, the first fixing portion 401C is provided at an intersecting position of the support 10C, but the present invention is not limited to this.

[0058] Second end 402A'' is core material 40A'', and is arranged so as to face the central portion of diaphragm 20 when viewed from the Z-axis direction. Furthermore, second fixing portion 402C is arranged at a position overlapping first fixing portion 401C when viewed from the Z-axis direction, and second end 402A'' is arranged so as to face second fixing portion 402C.

[0059] Furthermore, second end 402A'' is connected to diaphragm 20 by second fixing portion 402C provided on the support portion 10C side of bottom plate portion 20A of diaphragm 20. For second fixing portion 402C, for example, an ultraviolet curing or moisture curing adhesive is used, but of course the present invention is not limited to this and a jig or the like may also be used.

[0060] This allows the diaphragm 20 to vibrate smoothly. In other words, if the connection positions of the first end 401A'' and the second end 402A'' are offset from the center position of the diaphragm 20 as viewed in the Z-axis direction, the diaphragm 20 will not vibrate parallel to the Z-axis direction and will tilt. This causes tilting and asymmetric deformation of the diaphragm 20, particularly at high frequencies. However, in this embodiment, the first end 401A'' of the piezoelectric coil 40'' is connected to the center of the diaphragm 20 (bottom plate portion 20A) of the support portion 10C as viewed in the Z-axis direction, and the second end 402A'' is connected to the bottom portion 10A at a position overlapping with the first end 401A'' as viewed in the Z-axis direction. This makes it possible to cause the diaphragm 20 to vibrate parallel to (linearly with) the Z-axis direction even in the high frequency band, thereby improving the sound quality in the high frequency band.

[0061] Furthermore, in this embodiment, the piezoelectric coil 40'' is provided in a recessed portion of the diaphragm 20, which allows the overall thickness of the acoustic device 1 to be reduced. In addition, the support portion 10C that supports the piezoelectric coil 40'' is shaped so as not to block the opening, which prevents the sound generated by the diaphragm 20 from being blocked.

[0062] While the present technology has been described above using an example of a piezoelectric coil made of one type of piezoelectric material, the present invention is not limited to this and multiple types of piezoelectric material may be wound around the core material. In other words, multiple piezoelectric materials are spirally wound around the core material so that they are alternately arranged along the core material. By using multiple piezoelectric materials in this way, it is possible to improve the energy conversion efficiency of the force that the piezoelectric material exerts on the core material in response to an electric field applied to the piezoelectric material.

[0063] The configurations of the acoustic devices described with reference to the drawings are merely exemplary embodiments, and may be modified as desired without departing from the spirit of the present technology. In other words, any other configuration for implementing the present technology may be adopted.

[0064] The present technology can also be configured as follows. (1) An acoustic device comprising: a housing having an open end in a first direction and a bottom end in the other direction; a diaphragm supported within the housing; and a piezoelectric coil having a coil-shaped core material connecting the housing and the diaphragm and a piezoelectric material wound spirally around the core material. (2) The acoustic device described in (1) above, wherein the piezoelectric coil is provided along the first direction, and a first end portion at one end in the first direction is connected to a central portion of the diaphragm when viewed from the first direction, and a second end portion at the other end in the first direction is connected to the housing. (3) The acoustic device described in (2) above, wherein the first end portion and the second end portion are the core material. (4) The acoustic device according to any one of (1) to (3) above, wherein the length of the core material in a second direction perpendicular to the first direction is 40% or more and less than 100% of the length of the diaphragm in the second direction. (5) The acoustic device according to any one of (1) to (4) above, wherein the length of the piezoelectric coil in the first direction is 5% or more and 20% or less of the length of the diaphragm in the second direction perpendicular to the first direction. (6) The acoustic device according to any one of (1) to (5) above, wherein the core material connects the bottom and the diaphragm. (7) The acoustic device according to any one of (1) to (6) above, wherein the housing further has a support part facing the diaphragm in the first direction and provided on one end side in the first direction, and the piezoelectric coil is provided between the support part and the diaphragm.

[0065] DESCRIPTION OF SYMBOLS 1... Acoustic device 10... Housing 20... Diaphragm 40... Piezoelectric coil 40A... Core material 40B... Piezoelectric material 40C... Fixing member

Claims

a housing having an opening at one end in a first direction and a bottom at the other end in the first direction; a diaphragm supported within the housing; a piezoelectric coil having a coil-shaped core material connecting the housing and the diaphragm, and a piezoelectric material wound spirally around the core material; Audio equipment equipped with:

2. The acoustic device according to claim 1, The piezoelectric coil is provided along the first direction, and a first end portion thereof, which is one end side in the first direction, is connected to a central portion of the vibration plate when viewed from the first direction, and a second end portion thereof, which is the other end side in the first direction, is connected to the housing. Sound equipment.

3. The acoustic device according to claim 2, The first end and the second end are the core material. Sound equipment.

2. The acoustic device according to claim 1, The length of the core material in a second direction perpendicular to the first direction is 40% or more and less than 100% of the length of the diaphragm in the second direction. Sound equipment.

2. The acoustic device according to claim 1, The length of the piezoelectric coil in the first direction is 5% to 20% of the length of the diaphragm in a second direction perpendicular to the first direction. Sound equipment.

2. The acoustic device according to claim 1, The core material connects the bottom and the diaphragm. Sound equipment.

2. The acoustic device according to claim 1, the housing further includes a support portion that faces the diaphragm in the first direction and is provided on one end side in the first direction, The piezoelectric coil is provided between the support portion and the vibration plate. Sound equipment.

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