HK1225888B - Electroacoustic transducer - Google Patents

Description

Electroacoustic conversion device

Technical Field

The present invention relates to an electroacoustic conversion device that can be applied to, for example, earphones, headphones, portable information terminals, etc.

Background Art

Piezoelectric sounding bodies are widely used as simple electroacoustic transducers, for example, in audio equipment such as earphones and headphones, and also in speakers for portable information terminals. Piezoelectric sounding bodies are typically constructed by laminating a piezoelectric element to a vibrating plate (see, for example, Patent Document 1).

[Background Art Literature]

[Patent Document]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2013-150305

Summary of the Invention

[Problems to be solved by the invention]

In recent years, there has been a growing demand for improved sound quality in audio devices such as earphones and headphones. Therefore, improving the electroacoustic conversion characteristics of piezoelectric sounding bodies is essential. For example, when playing music, high-frequency vocal sibilance can sometimes degrade sound quality. In such cases, electroacoustic conversion functions with high-frequency characteristics that can reduce the peak sound pressure of these sibilance sounds are required.

In view of the above circumstances, an object of the present invention is to provide an electroacoustic transducer having excellent high-frequency characteristics.

[Technical means to solve the problem]

To achieve the above-mentioned object, an electroacoustic transducer according to one aspect of the present invention includes a housing, a piezoelectric sounding body, an electromagnetic sounding body, and a supporting member.

The piezoelectric sound-generating body includes: a vibration plate having a first surface and a second surface opposite to the first surface; and a piezoelectric element bonded to at least one of the first surface and the second surface; and the piezoelectric sound-generating body divides the interior of the shell into a first space portion facing the first surface and a second space portion facing the second surface.

The electromagnetic sounding body is arranged in the first space portion.

The supporting member is formed by a part of the housing or a member different from the housing, has a supporting portion facing the first surface or the second surface, and supports the peripheral edge of the first surface or the second surface with the supporting portion.

In the electroacoustic transducer, the support member supports the peripheral edge of any one surface of the diaphragm. This allows the peripheral edge of the diaphragm to vibrate more freely when the piezoelectric element is driven, compared to a case where the peripheral edge of each surface of the diaphragm is securely fixed to the support member. This allows the desired high-frequency characteristics to be achieved.

[Effects of the Invention]

As described above, according to the present invention, it is possible to provide an electroacoustic transducer having excellent high-frequency characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

1A and 1B are schematic configuration diagrams of a speaker unit according to a reference example of an embodiment of the present invention, wherein A is a side sectional view and B is a top view.

FIG. 2 is an experimental result showing the frequency characteristics of the speaker unit of the reference example.

FIG3 is an overall perspective view of the speaker unit in the electroacoustic transducer according to the first embodiment of the present invention.

FIG. 4 is an exploded perspective view of the speaker unit shown in FIG. 3 .

FIG5 is a schematic side sectional view of the speaker unit shown in FIG3 .

FIG. 6 is an experimental result showing the frequency characteristics of the speaker unit shown in FIG. 3 .

FIG7 is a schematic side sectional view showing the structure of the electroacoustic transducer according to the first embodiment of the present invention.

FIG8 is a schematic side sectional view of an electroacoustic transducer according to a second embodiment of the present invention.

FIG. 9 shows an experimental result showing the frequency characteristics of the speaker unit in the electroacoustic transducer according to the second embodiment of the present invention.

FIG. 10 is a diagram showing a comparison of frequency characteristics of the speaker unit in the electroacoustic transducer according to the first embodiment of the present invention and the speaker unit in the electroacoustic transducer according to the second embodiment of the present invention.

11A and 11B are schematic structural diagrams of an electroacoustic transducer according to a third embodiment of the present invention, where A is a side sectional view and B is a top view.

12A and 12B are schematic structural diagrams of an electroacoustic transducer according to a fourth embodiment of the present invention, where A is a side sectional view and B is a top view.

FIG13 is a schematic side sectional view of an electroacoustic transducer according to a fifth embodiment of the present invention.

FIG14 is an overall perspective view of the speaker unit in the electroacoustic transducer shown in FIG13.

FIG15 is a schematic side sectional view showing a modified example of the structure of the electroacoustic transducer of the present invention.

FIG16 is an overall perspective view showing a modified example of the structure of the speaker unit shown in FIG3 .

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

＜Basic structure (reference example)＞

First, the basic structure of a speaker unit according to a reference example of the present embodiment will be described.

1A and 1B are respectively a side sectional view and a top view schematically showing a reference example speaker unit 1. In the figure, the X, Y, and Z axes represent three mutually orthogonal axial directions (the same applies to the following figures).

Speaker unit 1 includes a piezoelectric sounding body 10 having a diaphragm 11 and a piezoelectric element 12, and a support member 13 that supports piezoelectric sounding body 10. Piezoelectric sounding body 10 generates sound waves having a peak sound pressure level around 8 kHz, for example, and is supported by support member 13. Speaker unit 1 is housed within a housing (not shown), thereby forming an electroacoustic transducer such as an earphone or headphone.

As shown in Figure 1B , diaphragm 11 is made of a conductive material such as metal (e.g., 42 alloy) or an insulating material such as resin (e.g., liquid crystal polymer), and has a circular planar shape. The outer diameter and thickness of diaphragm 11 are not particularly limited and are appropriately set based on factors such as the frequency band of the sound waves being reproduced. In this example, a disc-shaped diaphragm with a diameter of approximately 12 mm and a thickness of approximately 0.2 mm is used.

The piezoelectric element 12 functions as an actuator that vibrates the vibration plate 11. The piezoelectric element 12 is integrally bonded to at least one of the first surface 112 and the second surface 113 opposite the first surface of the vibration plate 11. In this example, the piezoelectric sounding body 10 has a single-layer structure in which the piezoelectric element 12 is bonded to one surface of the vibration plate 11.

The surface of the vibration plate 11 to which the piezoelectric element 12 is bonded may be any surface; in the illustrated example, the piezoelectric element 12 is bonded to the second surface 113. The piezoelectric element 12 is disposed approximately in the center of the vibration plate 11. This allows isotropic oscillation driving over the entire in-plane region of the vibration plate 11.

The planar shape of the piezoelectric element 12 is polygonal, and in this example, is a rectangle. However, it may be a square, a parallelogram, a trapezoid, or other quadrilateral, or a polygon other than a quadrilateral, or a circle, an ellipse, an oblong, etc. The thickness of the piezoelectric element 12 is not particularly limited, and is, for example, approximately 50 μm.

The piezoelectric element 12 has a structure in which a plurality of piezoelectric layers and a plurality of electrode layers are alternately stacked. Typically, the piezoelectric element 12 is manufactured by the following method: a plurality of ceramic sheets having piezoelectric properties, such as lead zirconate titanate (PZT) and niobium oxide containing alkali metals, are stacked on each other with electrode layers therebetween, and then fired at a specific temperature. One end of each electrode layer is alternately led out to the two end faces in the long side direction of the dielectric layer. The electrode layer exposed at one end face is connected to the first lead electrode layer, and the electrode layer exposed at the other end face is connected to the second lead electrode layer. The piezoelectric element 12 expands and contracts at a specific frequency by applying a specific AC voltage between the first and second lead electrode layers, and causes the vibration plate 11 to vibrate at a specific frequency. There is no particular limitation on the number of layers of the piezoelectric layer and the electrode layer, and each is set to an appropriate number of layers that can obtain the required sound pressure.

The support member 13 is formed into an annular shape, and in this example, has a cylindrical shape with an axis in the Z-axis direction. The support member 13 has a first end 131 and a second end 132 opposite the first end 131. The vibration plate 11 is supported around the entire periphery 111 of the first and second surfaces 112 and 113 by a retaining portion 133 provided at the first end 131. The support member 13 is formed from an injection-molded body of a synthetic resin material. Typically, the peripheral portion 111 of the vibration plate 11 is securely fixed to the retaining portion 133 by insert molding.

Fig. 2 shows the oscillation frequency characteristics of the speaker unit 1 having the above configuration. In Fig. 2 , the horizontal axis represents frequency [Hz] (logarithmic scale), the left vertical axis represents sound pressure level (SPL) [dB], and the right vertical axis represents total harmonic distortion (THD) [%].

The measurements were conducted in accordance with the Japan Electronics and Information Technology Industries Association standard for headphones and earphones (JEITA RC-8140A), and the characteristics were evaluated using an earphone coupler.

As shown in Figure 2, the speaker unit 1 of the reference example exhibits a first sound pressure peak around 8 kHz. Meanwhile, a similar second sound pressure peak is observed around 9 to 10 kHz, as indicated by the elliptical region A in the figure. This second sound pressure peak generally contributes to the prominent sibilance of vocal sounds in music, and therefore, it is desirable to minimize this second sound pressure peak.

On the other hand, the second sound pressure peak appears because the Q value (sharpness of resonance) of the speaker unit 1 is relatively high around 9-10 kHz. Therefore, it is believed that if the Q value of the speaker unit around 9-10 kHz can be reduced, the second sound pressure peak can be eliminated.

Therefore, in the present invention, in order to suppress the sound pressure peak level that may appear in an undesired frequency band and obtain desired high-frequency characteristics, the support structure of the vibration plate 11 is designed as described in detail below.

<First embodiment>

3 is an overall perspective view of a speaker unit in the electroacoustic transducer according to the first embodiment of the present invention, FIG. 4 is an exploded perspective view thereof, and FIG. 5 is a schematic side sectional view thereof.

The speaker unit 2 of this embodiment includes a piezoelectric sounding body 20 and a support member 23. The speaker unit 2 is housed in a housing (not shown), thereby constituting an electroacoustic transducer such as an earphone or a headphone.

The piezoelectric sounding body 20 includes a diaphragm 21 and a piezoelectric element 22. The diaphragm 21 has a first surface 212 and a second surface 213 opposite the first surface. The piezoelectric element 22 is integrally bonded to at least one of the first surface 212 and the second surface 213 of the diaphragm 21. In the illustrated example, the piezoelectric element 22 is bonded to the second surface 213. The configuration of the diaphragm 21 and the piezoelectric element 22 is identical to that of the diaphragm 11 and the piezoelectric element 12 in the speaker unit 1 of the reference example, and therefore, a description thereof will be omitted here.

The support member 23 includes a support portion (a plurality of protrusions 233) facing the first surface 212 of the vibration plate 21, and supports the peripheral portion 211 of the vibration plate 21 with this support portion. The support member 23 may be formed as part of the housing or as a separate component from the housing. Furthermore, the peripheral portion 211 of the vibration plate 21 includes the peripheral portion of the first surface 212, the peripheral portion of the second surface, and the side surface of the vibration plate 21. However, as described below, the peripheral portion 211 supported by the support portion corresponds to the peripheral portion of the first surface 212.

In this embodiment, the support member 23 includes an annular body 230 and a plurality of protrusions 233 that support the peripheral edge 211 of the first surface 212 of the vibration plate 21. The plurality of protrusions 233 serve as the "support portion" that supports the vibration plate 21. The support member 23 is formed of an injection-molded body of a synthetic resin material, but is not limited thereto and may also be formed of a metal material.

The annular body 230 is formed of an annular or cylindrical member having an outer diameter substantially the same as that of the diaphragm 21. It has a first end 231 located on the first surface 212 side of the diaphragm 21, and a second end 232 opposite the first end 231. The thickness (height) of the annular body 230 along the Z-axis direction is not particularly limited, as long as it is a size sufficient to ensure stable strength of the piezoelectric sounding body 20.

The plurality of protrusions 233 are arranged in the following manner: opposite to the first surface 212 of the vibration plate 21, they protrude from the first end portion 231 of the annular body 230 along the axial direction (Z-axis direction) toward the first surface 212 of the vibration plate 21. The plurality of protrusions 233 have the same height, respectively, and are respectively arranged at equal angle intervals or unequal angle intervals. Thus, the peripheral portion 211 of the vibration plate 21 is supported at multiple points by the plurality of protrusions 233. In this embodiment, the number of protrusions 233 is three, but is not limited to this, and may be four or more. By providing three or more protrusions 233, the vibration plate 21 can be stably supported in the XY plane.

The peripheral edge portion 211 of the vibration plate 21 is supported at multiple points by the plurality of protrusions 233. The peripheral edge portion 211 of the vibration plate 21 is bonded to the upper surface of each protrusion 233 by an adhesive or an adhesive material.

In the speaker unit constructed as described above, the piezoelectric element 22 is driven to vibrate the diaphragm 21 at a specific frequency, thereby generating sound waves with a peak sound pressure level around 8 kHz, for example. In this embodiment, multiple regions of the peripheral edge 211 of the first surface 212 of the diaphragm 21 are partially supported by multiple protrusions 233 of the support member 23. This leaves the second surface 213 of the diaphragm 21 free, allowing for more vibration of the peripheral edge 211 than in the case of the reference example where the peripheral edges of each surface of the diaphragm are securely fixed throughout their entire circumference. As a result, the desired high-frequency characteristics can be achieved.

FIG6 shows the oscillation frequency characteristics of the speaker unit 2 constructed as described above. The measurement was performed using the same method as that used for measuring the frequency characteristics of the reference example ( FIG2 ). Furthermore, in the speaker unit 2 used for the measurement, each protrusion 233 was bonded to the peripheral edge 211 of the vibration plate 21 using an adhesive or pressure-sensitive adhesive.

As shown in FIG6 , according to the speaker unit 2 of the above structure, it is possible to maintain the peak sound pressure level near 8 kHz and reduce or eliminate the second sound pressure peak (see FIG2 ) that originally existed near 9 to 10 kHz. The reason for this is believed to be that since the support member 23 supports only the first surface 212 of the vibration plate 21, the support strength and symmetry of the peripheral portion 211 are relaxed compared to the structure in which the peripheral portions of each surface of the vibration plate are firmly fixed as in the reference example. The relaxation of the support strength and symmetry of the peripheral portion 211 of the vibration plate 21 means that the fixation of the peripheral portion 211 becomes loose, thereby increasing the degree of freedom of vibration of the peripheral portion 211 and, as a result, reducing the Q value of the resonance. In this way, by optimizing the support structure of the vibration plate 21 in such a way that the sound pressure peak in the target frequency band (9 to 10 kHz in this embodiment) is reduced or eliminated, the desired high-frequency characteristics can be easily achieved.

Furthermore, it was confirmed that the sound pressure level in the high-frequency range above 10kHz was higher than that of the reference example. This is believed to be because the peripheral portion is not firmly fixed and is supported with low symmetry, thereby exciting higher-order resonances of the piezoelectric sounding element. Experiments conducted by the present inventors have confirmed that this effect is greater when the number of supports is as small as three, five, or seven, and the symmetry is low.

In order to optimize the vibration mode or vibration form of the peripheral portion 211 of the diaphragm 21, the peripheral portion 211 of the diaphragm 21 can also be configured to elastically support the peripheral portion 211 of the diaphragm 21. In this case, the peripheral portion 211 of the diaphragm 21 can be bonded to the plurality of protrusions 233 of the support member 23 via an elastically deformable adhesive material (first adhesive layer 26 in FIG. 7 ). Alternatively, the speaker unit 2 can further include an elastically deformable adhesive layer that fills the gaps V1 (see FIG. 3 ) formed between the plurality of protrusions 233 (the gaps formed between the first end portion 231 of the annular body 230 and the peripheral portion 211 of the diaphragm 21).

7 is a schematic side sectional view of an electroacoustic transducer 200 including the speaker unit 2 having the above-described configuration. Hereinafter, the electroacoustic transducer 200 of this embodiment will be described.

The electroacoustic transducer 200 of this embodiment includes a housing 24 and a speaker unit 2 having an electromagnetic sounding body 25. The electroacoustic transducer 200 can be used as headphones, for example, by attaching the earpiece 120 to the sound channel 241. However, the present invention is not limited thereto.

The housing 24 has a cover 240 that is detachable in the Z-axis direction. The interior of the housing 24 is partitioned by the piezoelectric sounding body 20 into a first space S1 facing the first surface 212 and a second space S2 facing the second surface 213 .

The peripheral edge 211 of the vibration plate 21 is bonded to the plurality of protrusions 233 of the support member 23 via an elastically deformable first adhesive layer 26. The first adhesive layer 26 is provided between the peripheral edge 211 of the vibration plate 21 and the plurality of protrusions 233. Thus, the peripheral edge 211 of the vibration plate 21 is elastically supported by the support member 23, thereby optimizing the vibration mode or vibration form of the peripheral edge 211 of the vibration plate 21.

Furthermore, an elastically deformable second adhesive layer 27 is provided between the housing 24 and the support member 23. Second adhesive layer 27 can be provided in a ring-shaped manner in a specific area around the annular body 230, or it can be provided locally at multiple locations around the annular body 230. Second adhesive layer 27 has the same configuration as first adhesive layer 26. This improves the vibration insulation between the housing 24 and the speaker unit 6, thereby enabling, for example, the diaphragm 21 to vibrate stably with desired vibration characteristics.

The first adhesive layer 26 and the second adhesive layer 27 are not particularly limited as long as they are elastic after curing. Typically, they are made of elastically deformable resin materials such as silicone resin or urethane resin. Alternatively, these adhesive layers can be made of double-sided tape (double-sided adhesive tape). By making the adhesive layers of double-sided tape, the thickness can be easily controlled.

Furthermore, these adhesive layers may also contain spherical insulating fillers with uniform particle sizes. By constructing each adhesive layer from an adhesive material dispersed with such insulating fillers, the thickness of each adhesive layer can be precisely adjusted. This allows for highly precise control of the vibration damping function of diaphragm 21 using each adhesive layer, enabling stable realization of desired high-frequency characteristics.

The electromagnetic sounding body 25 is arranged in the first space S1 so as to face the piezoelectric sounding body 20 (vibrating plate 21) in the Z-axis direction. In this embodiment, the electromagnetic sounding body 25 is housed in the annular body 230 formed of a cylindrical member. However, this is not limiting, and the electromagnetic sounding body 25 may be supported by a member different from the support member 23.

The electromagnetic sounding body 25 includes a vibrating body such as a voice coil motor (electromagnetic coil) and is configured as a speaker unit (woofer) that primarily generates sound waves in the low frequency range below 7kHz. The electromagnetic sounding body 25 of this embodiment includes a housing 250, a vibration plate 251 supported by the housing 250 so as to be vibrated, a permanent magnet 252, a voice coil 253, and a yoke 254 that supports the permanent magnet 252. The voice coil 253 is formed by winding a conductive wire around a bobbin that serves as a winding core and is joined to the center of the vibration plate 251. The voice coil 253 is arranged perpendicular to the direction of the magnetic flux of the permanent magnet 252 (along the Y-axis in the figure). When an alternating current (sound signal) flows into the voice coil, an electromagnetic force acts on the voice coil 253, causing the voice coil 253 to vibrate along the Z-axis in the figure in accordance with the signal waveform. This vibration is transmitted to the diaphragm 251 connected to the voice coil 253 , causing the air in the first space S1 to vibrate, thereby generating sound waves in the bass range.

In contrast, the piezoelectric sounding body 20 is configured as a speaker unit (tweeter) that primarily produces high-frequency sound waves above 7 kHz, for example. The piezoelectric sounding body 20 vibrates the diaphragm 21 by inputting an audio signal into the piezoelectric element 22, generating these high-frequency sound waves in the sound channel 241 via the second space S2. This allows the electroacoustic transducer to be configured as a hybrid speaker comprising both a low-frequency sounding body and a high-frequency sounding body.

Hybrid speakers are generally known to produce sibilance in the high-frequency range around 9-10kHz. Specifically, sound pressure peaks that are insignificant when using a tweeter alone often become pronounced when combined with a woofer, causing the sibilance to become undeniable. The present invention is particularly effective in this type of hybrid speaker, significantly reducing sibilance by improving the support structure of the piezoelectric sounding element.

Furthermore, in this embodiment, the gaps V1 formed between the plurality of protrusions 233 serve as passages for the sound generated by the electromagnetic sounding body 25 (see FIG3 ). This facilitates adjustment of the frequency characteristics of the low-frequency sound waves generated by the electromagnetic sounding body 25 and reaching the sound channel 241. Furthermore, the frequency characteristics at the intersection (intersection point) between the characteristic curve for the high-frequency sound generated by the piezoelectric sounding body 20 and the characteristic curve for the low-frequency sound generated by the electromagnetic sounding body 25 can be optimized.

<Second embodiment>

8 is a schematic side sectional view showing the structure of an electroacoustic transducer 300 according to a second embodiment of the present invention. Hereinafter, the structures different from the first embodiment will be mainly described. The same structures as the first embodiment are denoted by the same reference numerals and their description will be omitted or simplified.

As shown in Fig. 8 , the electroacoustic transducer 300 of the present embodiment includes a speaker unit 3 having an electromagnetic sounding body 25, and a housing 24. The internal structure of the electromagnetic sounding body 25 is omitted from illustration.

In this embodiment, the support member 33 includes a support portion (annular protrusion 333) facing the first surface 212 of the vibration plate 21, and supports the peripheral edge 211 of the vibration plate 21 with this support portion. The support member 33 may be formed as part of the housing or as a separate member from the housing.

The support member 33 includes an annular body 330 and an annular protrusion 333 that supports the peripheral edge 211 of the vibration plate 21. The annular protrusion 333 serves as the "support portion" that supports the vibration plate 21. The support member 33 is formed of an injection-molded body of a synthetic resin material, but is not limited thereto and may also be formed of a metal material.

Ring body 330 is formed of an annular or cylindrical member having an outer diameter larger than that of vibration plate 21 , and has a first end 331 located on the first surface 212 side of vibration plate 21 and a second end 332 opposite to first end 331 .

The annular projection 333 is provided so as to face the first surface 212 of the vibration plate 21 and protrude radially inward from the inner circumference of the first end portion 331 of the annular body 330. The outer diameter of the annular projection 333 is equal to or greater than the outer diameter of the vibration plate 21, and is configured to support the entire circumference of the peripheral edge 211 of the first surface 212 of the vibration plate 21. Alternatively, the annular projection 333 may be composed of a plurality of arcuate projections arranged at equal or unequal intervals on the same circumference. In this case, the vibration plate 21 is supported at multiple regions of the peripheral edge 211 of the first surface 212.

Furthermore, the peripheral edge 211 of the vibration plate 21 is bonded to the upper surface of the annular protrusion 333 via an elastically deformable first adhesive layer 36. The first adhesive layer 36 is configured similarly to the first adhesive layer 26 (see FIG7 ) described in the first embodiment. Thus, the peripheral edge 211 of the vibration plate 21 is elastically supported by the support member 33, enabling optimization of the vibration mode or vibration form of the peripheral edge 211 of the vibration plate 21.

Furthermore, the electromagnetic sounding body 25 is positioned within the support member 33 so as to face the piezoelectric sounding body 20 (vibrating plate 21) in the Z-axis direction. In this embodiment, the annular body 330 is formed of a cylindrical member, and the outer circumference of the electromagnetic sounding body 25 is bonded and fixed to the inner circumference of the second end portion 332 of the annular body 330. However, this is not limiting, and the electromagnetic sounding body 25 may be supported by a member separate from the support member 33.

In this embodiment, an elastically deformable second adhesive layer 37 is provided between the support member 33 and the housing 24. The second adhesive layer 37 is configured similarly to the second adhesive layer 27 (see FIG. 7 ) described in the first embodiment. This improves the vibration insulation effect between the housing 24 and the speaker unit 6.

Fig. 9 shows an experimental result showing the oscillation frequency characteristics of the speaker unit 3 according to the present embodiment. The measurement was performed using the same method as that used for measuring the frequency characteristics of the reference example (Fig. 2).

As shown in Figure 9, the speaker unit 3 of this embodiment maintains the peak sound pressure level near 8 kHz, similar to the first embodiment, while reducing or eliminating the second sound pressure peak (see Figure 2) that previously existed near 9 to 10 kHz. This is believed to be because only the peripheral edge 211 of the first surface 212 of the diaphragm 21 is elastically supported by the support member 33 via the first adhesive layer 36. This reduces the support strength of the peripheral edge 211 compared to a structure where the peripheral edge of the diaphragm is firmly fixed, as in the reference example. This reduced support strength of the peripheral edge 211 means that the fixation of the peripheral edge 211 becomes looser, thereby increasing the degree of freedom of vibration of the peripheral edge 211 and, as a result, reducing the Q value of the resonance. Thus, by optimizing the support structure of the diaphragm 21 so that the sound pressure peak in the target frequency band (9 to 10 kHz in this embodiment) is reduced or eliminated, the desired high-frequency characteristics can be easily achieved. Furthermore, in this embodiment, THD is reduced. This is considered to be because the nonlinearity is suppressed by softening the support of the peripheral edge portion 211 .

Figure 10 shows the experimental results of the high-frequency characteristics of the speaker unit 3 of this embodiment and the speaker unit 2 of the first embodiment described above. For comparison, the high-frequency characteristics of a commercially available ear canal earphone are also shown. In the figure, the solid line, dashed line, and dashed-dotted line respectively represent the high-frequency characteristics of the speaker unit 3 of this embodiment, the speaker unit 2 of the first embodiment, and the commercially available ear canal earphone.

<Third embodiment>

Figures 11A and 11B are schematic side and cross-sectional views, respectively, showing the configuration of an electroacoustic transducer 400, which is an electroacoustic transducer according to a third embodiment of the present invention. The following description will focus on configurations that differ from the first embodiment. Configurations identical to those of the first embodiment are denoted by the same reference numerals, and their descriptions will be omitted or simplified.

11A , the electroacoustic transducer 400 of the present embodiment includes a speaker unit 4 having an electromagnetic sounding body 25, and a housing 24. The internal structure of the electromagnetic sounding body 25 is omitted from illustration.

In this embodiment, the support member 43 includes a support portion (a plurality of protrusions 433) facing the first surface 212 of the vibration plate 21, and uses this support portion to support the peripheral edge 211 of the vibration plate 21. The support member 43 may be formed as part of the housing or as a separate member from the housing.

The support member 43 includes an annular body 430 and a plurality of protrusions 433 that support the peripheral edge 211 of the vibration plate 21. The plurality of protrusions 433 serve as the "support portion" that supports the vibration plate 21. The support member 43 is formed of an injection-molded body of a synthetic resin material, but is not limited thereto and may also be formed of a metal material.

Ring body 430 is formed of an annular or cylindrical member having an inner diameter equal to or larger than the outer diameter of vibration plate 21 , and has a first end 431 located on the peripheral edge 211 side of vibration plate 21 and a second end 432 opposite to first end 431 .

The multiple protrusions 433 are arranged to project radially inward from the inner circumference of the first end portion 431 of the annular body 430, facing the first surface 212 of the vibration plate 21. These protrusions 433 are configured to partially support the peripheral edge 211 of the first surface 212 of the vibration plate 21. The multiple protrusions 433 each have the same width (protrusion amount) and are spaced at equal or unequal angular intervals. The protrusion amount of each protrusion 433 is not particularly limited, as long as it is sufficient to support the peripheral edge 211 of the vibration plate 21.

Furthermore, the peripheral edge 211 of the vibration plate 21 is bonded to the upper surface of each protrusion 433 via an elastically deformable first adhesive layer 46. The first adhesive layer 46 is configured similarly to the first adhesive layer 26 (see FIG7 ) described in the first embodiment. Thus, the peripheral edge 211 of the vibration plate 21 is elastically supported by the support member 43, and the vibration mode or vibration form of the peripheral edge 211 of the vibration plate 21 can be optimized.

The electromagnetic sounding body 25 is positioned within the support member 43 so as to face the piezoelectric sounding body 20 (vibrating plate 21) in the Z-axis direction. In this embodiment, the annular body 430 is formed of a cylindrical member, and the outer circumference of the electromagnetic sounding body 25 is bonded and fixed to the inner circumference of the second end 432 of the annular body 430. This is not limiting; the electromagnetic sounding body 25 may also be supported by a member separate from the support member 43.

In this embodiment, an elastically deformable second adhesive layer 47 is provided between the support member 43 and the housing 24. The second adhesive layer 47 can be configured similarly to the second adhesive layer 27 (see FIG. 7 ) described in the first embodiment. This improves the vibration insulation between the housing 24 and the speaker unit 6.

As described above, the electroacoustic converter 400 of this embodiment is constructed as follows: the second surface 213 of the vibration plate 21 is set as a free surface, and only the peripheral edge portion 211 of the first surface 212 is supported by the support member 43. This achieves the same functional effects as the first embodiment described above. Furthermore, according to this embodiment, the support portion supporting the vibration plate 21 is composed of a plurality of protrusions 433 that protrude radially inward of the annular body 430. Therefore, even if the inner diameter of the annular body 430 is larger than the outer diameter of the vibration plate 21, the vibration plate 21 can be stably supported with the target high-frequency characteristics.

<Fourth embodiment>

12A and 12B are schematic side and cross-sectional views, respectively, showing the structure of an electroacoustic transducer 500 according to a fourth embodiment of the present invention. Hereinafter, the structures different from those of the first embodiment will be mainly described. Structures identical to those of the first embodiment will be denoted by the same reference numerals, and their description will be omitted or simplified.

12A , an electroacoustic transducer 500 of this embodiment includes a speaker unit 5 having a piezoelectric sounding body 50 and an electromagnetic sounding body 25, and a housing 24. The internal structure of the electromagnetic sounding body 25 is omitted from illustration.

The piezoelectric sounding body 50 includes a vibration plate 51 and a piezoelectric element 22 .

The vibration plate 51 is formed into a roughly disc-shaped shape made of a conductive material or a resin material, and has a first surface 512 facing the electromagnetic sounding body 25, and a second surface 513 on the opposite side of the first surface 512, and a plurality of protrusions 511 protruding radially toward the periphery are provided on its peripheral portion. The plurality of protrusions 511 are typically formed at equal angular intervals, but are not limited to this and can also be formed at unequal intervals. The plurality of protrusions 511 are formed, for example, by providing a plurality of cutouts 511h on the peripheral portion of the vibration plate 51. The amount of protrusion of the protrusion 511 is adjusted by the cutout depth of the cutout 511h. The number of protrusions 511 is three in the example shown in the figure, but it can also be four or more. In this way, the vibration plate 21 can be stably supported in the XY plane.

Meanwhile, the support member 53 includes a support portion (first end portion 531) facing the first surface 512 of the vibration plate 51. This support portion supports the peripheral edge portion (plural protruding pieces 511) of the vibration plate 51. In this embodiment, the support member 53 supports each protruding piece 511 of the vibration plate 51. The support member 53 may be formed as part of the housing or as a separate component from the housing.

The support member 53 includes an annular body 530, which is formed from an annular or cylindrical member having an outer diameter approximately the same as that of the vibration plate 51. The annular body 530 has a first end 531 located toward the periphery of the vibration plate 51 (the plurality of protruding pieces 511), and a second end 532 opposite the first end 531. The first end 531 serves as the "support portion" that supports the vibration plate 21. As shown in FIG12B , the first end 531 is configured to partially support the tip of each protruding piece 511. The support member 53 is formed from an injection-molded synthetic resin material, but this is not limited to this and may also be formed from a metal material.

An elastically deformable first adhesive layer 56 is provided between each protruding piece 511 and the upper surface of the first end portion 531. The first adhesive layer 56 can be configured similarly to the first adhesive layer 26 (see FIG7 ) described in the first embodiment. Thus, each protruding piece 511 of the vibration plate 51 is elastically supported by the support member 53, thereby optimizing the vibration mode or vibration form of the peripheral portion of the vibration plate 51.

Furthermore, the electromagnetic sounding body 25 is positioned within the support member 53 so as to face the piezoelectric sounding body 50 (vibrating plate 51) in the Z-axis direction. In this embodiment, the annular body 530 is formed of a cylindrical member, and the outer circumference of the electromagnetic sounding body 25 is bonded and fixed to the inner circumference of the second end 532 of the annular body 530. This is not limiting; the electromagnetic sounding body 25 may be supported by a member separate from the support member 53.

In this embodiment, an elastically deformable second adhesive layer 57 is provided between the support member 53 and the housing 24. The second adhesive layer 57 can be configured similarly to the second adhesive layer 27 (see FIG. 7 ) described in the first embodiment. This improves the vibration insulation effect between the housing 24 and the speaker unit 6.

In the electroacoustic transducer 500 of this embodiment constructed as described above, the diaphragm 51 is configured such that the second surface 513 is free via a plurality of protruding pieces 511 formed on the periphery of the diaphragm 51, and only the first surface 512 is supported by the first end 531 of the support member 53. This relaxes the constraints on the periphery of the diaphragm 51. This achieves the same operational advantages as the first embodiment.

Furthermore, according to this embodiment, the gaps V2 (notches 511h) formed between the plurality of protruding pieces 511 can be configured as passages for the sound generated by the electromagnetic sounding body 25. This allows the frequency characteristics of the sound waves emitted by the electromagnetic sounding body 25 to be adjusted. Furthermore, the frequency characteristics at the intersection (intersection point) between the characteristic curve for the high-frequency sound emitted by the piezoelectric sounding body 50 and the characteristic curve for the low-frequency sound emitted by the electromagnetic sounding body 25 can be optimized.

<Fifth embodiment>

13 is a schematic side sectional view showing the structure of an electroacoustic transducer 600 according to a fifth embodiment of the present invention. Hereinafter, the structures different from the first embodiment will be mainly described. The same structures as the first embodiment are denoted by the same reference numerals and their description will be omitted or simplified.

As shown in Fig. 13, an electroacoustic transducer 600 of the present embodiment includes a speaker unit 6 having an electromagnetic sounding body 25, and a housing 24. The internal structure of the electromagnetic sounding body 25 is omitted from illustration.

In this embodiment, the support member 63 includes a support portion (first end portion 631) facing the first surface 212 of the vibration plate 21, and supports the peripheral edge portion 211 of the vibration plate 21 with this support portion. The support member 63 may be formed as part of the housing or as a separate member from the housing.

The support member 63 includes an annular body 630. The annular body 630 is formed of an annular or cylindrical member having an outer diameter substantially the same as that of the vibration plate 21. The annular body 630 has a first end 631 located on the side of the peripheral edge 211 of the vibration plate 21, and a second end 632 opposite the first end 631. The first end 631 serves as the "support portion" that supports the vibration plate 21, supporting the peripheral edge 211 of the first surface 212 of the vibration plate 21 over its entire circumference. The support member 63 is formed of an injection-molded synthetic resin material, but is not limited thereto and may also be formed of a metal material.

Furthermore, a first adhesive layer 66 is provided between the first end portion 631 of the support member 63 and the peripheral portion 211 of the vibration plate 21. The first adhesive layer 66 is configured similarly to the first adhesive layer 26 (see FIG7 ) described in the first embodiment. This allows the peripheral portion 211 of the vibration plate 21 to be elastically supported by the support member 63, thereby optimizing the vibration mode or vibration form of the peripheral portion 211 of the vibration plate 21.

Furthermore, the electromagnetic sounding body 25 is positioned within the support member 63 so as to face the piezoelectric sounding body 20 (vibrating plate 21) in the Z-axis direction. In this embodiment, the annular body 630 is formed of a cylindrical member, and the outer circumference of the electromagnetic sounding body 25 is bonded and fixed to the inner circumference of the second end portion 632 of the annular body 630. This is not limiting; the electromagnetic sounding body 25 may be supported by a member separate from the support member 63.

In this embodiment, an elastically deformable second adhesive layer 67 is provided between the support member 63 and the housing 24. The second adhesive layer 67 is configured similarly to the second adhesive layer 27 (see FIG. 7 ) described in the first embodiment. This improves the vibration insulation between the housing 24 and the speaker unit 6.

In this embodiment, a passage portion P1 that communicates between the first space portion S1 and the second space portion S2 is provided in the diaphragm 21 of the piezoelectric sounding body 20. FIG14 is a schematic perspective view showing the structure of the speaker unit 6. As shown in FIG14 , the speaker unit 6 is provided with a passage portion P1 that communicates between the first space portion S1 and the second space portion S2.

Passageway P1 is provided along the thickness direction of the vibration plate 21. In this embodiment, passageway P1 is formed by multiple through-holes provided in the vibration plate 21. As shown in Figure 14, multiple passageways P1 are formed around the piezoelectric element 22 (the area between any side of the piezoelectric element 22 and the peripheral edge of the vibration plate 21). In this embodiment, because the piezoelectric element 22 has a rectangular planar shape, the area for forming passageway P1 can be ensured without further restrictions on the size of the piezoelectric element 22.

The passageway P1 is used to pass a portion of the sound waves generated in the electromagnetic sounding body 25 from the first space S1 to the second space S2. Therefore, the frequency characteristics of the low-pitched sound can be adjusted or tuned by adjusting the number and size of the passageways P1. The number and size of the passageways P1 can be determined based on the desired frequency characteristics of the low-pitched sound. Therefore, the number and size of the passageways P1 are not limited to the example shown in FIG14 ; for example, a single passageway P1 may be provided.

Furthermore, when multiple through-holes are provided as passages P1 in the diaphragm 21, the rigidity of the diaphragm 21 tends to decrease in the areas where the through-holes are provided. Therefore, by optimizing the position, number, and size of passages P1, undesirable high-frequency resonances in the peripheral portion 211 can be mitigated, thereby enabling the diaphragm 21 to achieve desired high-frequency characteristics. In this case, as described above, the passages P1 can also be designed to balance the frequency characteristics of the low-frequency sound waves generated by the electromagnetic sounding body 25.

On the other hand, by forming the passage portion P1 with a through hole penetrating the thickness direction of the vibration plate 21, the sound wave propagation path from the first space portion S1 to the second space portion S2 can be minimized (shortest), thereby facilitating setting the sound pressure peak in a specific low frequency range.

As mentioned above, although embodiment of this invention was demonstrated, this invention is not limited only to the said embodiment, Of course, various changes can be added.

For example, in each of the above embodiments, the peripheral edge of the surface (first surface) of the piezoelectric sounding body's diaphragm that faces the electromagnetic sounding body is supported by a support member. However, a configuration in which the peripheral edge of the surface (second surface) that does not face the electromagnetic sounding body is also supported by a support member may also be employed. For example, the electroacoustic transducer 800 schematically shown in FIG15 is configured as follows: an electromagnetic sounding body U1 and a piezoelectric sounding body U2 are housed within a housing B, respectively. The sound waves generated by each sounding body U1 and U2 are guided to a sound channel B2 formed in the bottom B1 of the housing B. Furthermore, the electroacoustic transducer 800 is configured as follows: multiple regions of the peripheral edge of the diaphragm that constitutes the piezoelectric sounding body U2 are supported by multiple pillars B3 formed in the bottom B1 of the housing B.

Furthermore, while the above embodiments describe an example in which the support member supporting the diaphragm of the piezoelectric sounding element is formed from a separate component from the housing, the support member may also be formed as part of the housing. For example, in the electroacoustic transducer 800 shown in Figure 15 , a plurality of pillars B3 form a portion of the housing B. The peripheral edge of the diaphragm is bonded to the upper surface of each pillar B3 via, for example, an adhesive or elastically deformable adhesive material. In this case, each pillar B3 corresponds to, for example, the plurality of protrusions 233 of the support member 23 described in the first embodiment.

In the electroacoustic transducer 800, an annular gap is formed between the outer periphery of the piezoelectric sounding body U2 and the sidewall of the housing B. Therefore, low-frequency sound waves generated by the electromagnetic sounding body U1 are guided toward the sound channel B2 through the passage T formed by the annular space between the piezoelectric sounding body U2 and the sidewall of the housing B, and the spaces formed between the multiple pillars B3.

Furthermore, in the fifth embodiment ( FIG. 14 ), a configuration example in which passage portion P1 is formed in diaphragm 21 is described. However, this passage portion P1 can also be provided in the diaphragm described in the first to fourth embodiments. FIG. 16 is a perspective view of a speaker unit 9 showing an example of an application in which passage portion P1 is applied to the first embodiment.

In FIG16 , the sound waves generated by the electromagnetic sounding body pass through a plurality of passages P1 formed by through-holes formed in the vibration plate 21. In this case, the gaps V1 formed between the plurality of protrusions 233 supporting the peripheral portion of the vibration plate 21 can also function as passages for the sound waves. Furthermore, although not shown, the passages can be formed by forming a cutout of a specific shape in the peripheral portion of the vibration plate, without forming the passage P1. The cutout may be single or multiple, and in the case of multiple cutouts, the shapes of the cutouts may be the same or different.

A vibrating plate with a partially cutout portion formed in the circular periphery in this manner is also included in the "disc-shaped vibrating plate." The cutout is not limited to the passage portion. In other words, a "disc-shaped vibrating plate" may have a cutout portion, such as a concave portion or a slit portion, recessed from the outer periphery toward the inner periphery, as needed. Furthermore, as long as the planar shape of the vibrating plate is generally circular, even if it is not strictly circular due to the formation of a cutout portion, it is still considered "disc-shaped."

[Explanation of Symbols]

2, 3, 4, 5, 6 speaker units

20, 50 piezoelectric sounder

21, 51 vibration plate

22 Piezoelectric element

23, 33, 43, 53, 63 support parts

24 Shell

25 Electromagnetic sounder

26, 36, 46, 56, 66 First adhesive layer

27, 37, 47, 57, 67 Second adhesive layer

200, 300, 400, 500, 600, 800 electroacoustic conversion devices

211 (peripheral portion of the vibration plate)

230, 330, 430, 530, 630 rings

233, 433 protrusions

333 annular convex part

511 protruding piece

Claims (10)

1. An electroacoustic conversion device, comprising: case; A piezoelectric sound generator includes a planar vibrating plate having a first surface and a second surface opposite to the first surface, and a piezoelectric element engaged with at least one of the first surface and the second surface, and the interior of the housing is divided into a first space facing the first surface and a second space facing the second surface. A support member, comprising a portion of the housing or a component different from the housing, has an annular body and a support portion. The annular body has a first end located on the vibrating plate side and a second end opposite to the first end. The support portion has a plurality of protrusions disposed at the first end and supporting only the peripheral portion of the first surface. An electromagnetic sound generator is disposed in the first space and housed within the annular body; The annular body has an outer diameter approximately the same as that of the vibrating plate, and The plurality of protrusions extend from the first end toward the axis of the annulus. 2. An electroacoustic conversion device, comprising: case; A piezoelectric sound generator includes a planar vibrating plate having a first surface and a second surface opposite to the first surface, and a piezoelectric element engaged with at least one of the first surface and the second surface, and the interior of the housing is divided into a first space facing the first surface and a second space facing the second surface. A support member, comprising a portion of the housing or a component different from the housing, has an annular body and a support portion. The annular body has a first end located on the vibrating plate side and a second end opposite to the first end. The support portion has a plurality of protrusions disposed at the first end and supporting only the peripheral portion of the first surface. An electromagnetic sound generator is disposed in the first space and housed within the annular body; The annular body has an inner diameter that is the same as or larger than the outer diameter of the vibrating plate, and The plurality of protrusions protrude from the first end toward the inner side of the diameter. 3. The electroacoustic conversion device according to claim 1 or 2, wherein... It also has a first adhesive layer disposed between the peripheral portion and the first end portion, and is capable of elastic deformation. 4. The electroacoustic conversion device according to claim 1 or 2, wherein... The support component is composed of a component different from the housing, and The electroacoustic conversion device also includes a second adhesive layer disposed between the support member and the housing, and is capable of elastic deformation. 5. The electroacoustic conversion device according to claim 3, wherein... The support component is composed of a component different from the housing, and The electroacoustic conversion device also includes a second adhesive layer disposed between the support member and the housing, and is capable of elastic deformation. 6. The electroacoustic conversion device according to claim 1 or 2, wherein... The gaps between the plurality of protrusions constitute a passage for the sound generated by the electromagnetic sound generator to pass through. 7. The electroacoustic conversion device according to claim 1 or 2, wherein... It also has a passage section, which is provided on the vibrating plate to allow the sound generated by the electromagnetic sound generator to pass through. 8. The electroacoustic conversion device according to claim 3, wherein... It also has a passage section, which is provided on the vibrating plate to allow the sound generated by the electromagnetic sound generator to pass through. 9. The electroacoustic conversion device according to claim 1 or 2, wherein... The piezoelectric element has a structure formed by alternately stacking multiple piezoelectric layers and multiple electrode layers. 10. The electroacoustic conversion device according to claim 3, wherein... The piezoelectric element has a structure formed by alternately stacking multiple piezoelectric layers and multiple electrode layers.