JP6792979B2 - Electroacoustic converter - Google Patents

Description

The present invention relates to an electro-acoustic conversion device applicable to, for example, earphones or headphones, a personal digital assistant, and the like.

Piezoelectric sounding elements are widely used as simple electro-acoustic conversion means, and are often used, for example, as audio equipment such as earphones or headphones, and as speakers for mobile information terminals. The piezoelectric sounding element typically has a structure in which the piezoelectric element is bonded to one side or both sides of the diaphragm (see, for example, Patent Document 1).

On the other hand, Patent Document 2 describes headphones that include a dynamic type driver and a piezoelectric type driver, and enable reproduction with a wide bandwidth by driving these two drivers in parallel. The piezoelectric driver is provided in the center of the inner surface of a front cover that closes the front surface of the dynamic driver and functions as a diaphragm, and is configured to make the piezoelectric driver function as a treble driver.

Japanese Unexamined Patent Publication No. 2013-150305 Jikkai Sho 62-68400

In recent years, for example, in audio equipment such as earphones and headphones, further improvement in sound quality is required. Therefore, it is indispensable to improve the characteristics of the electroacoustic conversion function of the piezoelectric sounding element. Further, it is desired to increase the sound pressure in the high frequency range when combined with the dynamic speaker.

In view of the above circumstances, an object of the present invention is to provide an electro-acoustic conversion device capable of improving acoustic characteristics.

In order to achieve the above object, the electroacoustic conversion device according to one embodiment of the present invention includes a housing and a piezoelectric sounding body.
The piezoelectric sounding body includes a first diaphragm having a peripheral edge directly or indirectly supported by the housing, and a piezoelectric element arranged on at least one surface of the first diaphragm. However, the rigidity is asymmetrically configured with respect to the central axis of the first diaphragm.

In the electroacoustic conversion device, since the piezoelectric sounding body has a structure in which the rigidity is asymmetric with respect to the central axis of the first diaphragm, the vibration mode of the first diaphragm becomes non-uniform in the plane. As a result, the sound pressure level in the high frequency range becomes broad and the sound pressure characteristics are improved, so that good sound quality can be reproduced.

The piezoelectric element may be arranged at a position eccentric with respect to the first diaphragm.
As a result, the vibration mode of the first diaphragm can be made asymmetric with respect to the central axis.

The piezoelectric sounding body may further have a passage portion that penetrates the first diaphragm in the thickness direction.
The passage portion may include at least one opening provided in the plane of the first diaphragm, or may include at least one notch provided in the peripheral edge portion.

The electroacoustic converter may further include an electromagnetic sounding body including a second diaphragm. In this case, the housing has a first space portion and a second space portion.
The electromagnetic sounding body is arranged in the first space portion. The second space portion has a sound guide path that communicates with the first space portion via the passage portion and guides sound waves generated by the piezoelectric sounding body and the electromagnetic sounding body to the outside. ..

The passage portion may include a plurality of passage portions. In this case, the sound guide path is provided at a position facing the passage portion having the largest opening area among the plurality of passage portions. As a result, the sound waves generated from the electromagnetic sounding body can be efficiently guided to the sound guide path, so that the acoustic characteristics of the electromagnetic sounding body can be improved.

The planar shapes of the first diaphragm and the piezoelectric element are not particularly limited, and typically, the planar shape of the first diaphragm is circular, and the planar shape of the piezoelectric element is rectangular.

The piezoelectric sounding body may further have an annular member. The annular member is fixed to the housing and supports the peripheral edge of the first diaphragm.
As a result, the workability of assembling the piezoelectric sounding body to the housing is improved, and the distance between the first diaphragm and the second diaphragm can be easily adjusted.

The distance between the first diaphragm and the second diaphragm is not particularly limited, and can be appropriately set according to the size of each diaphragm, the target acoustic characteristics, and the like. For example, the ratio of the distance between the first diaphragm and the second diaphragm to the diameter of the second diaphragm can be 0.152 or more and 0.212 or less. This makes it possible to improve the drop in the sound pressure characteristic near 8 kHz.

The first diaphragm may be arranged at a position eccentric with respect to the second diaphragm. Even with such a configuration, it is possible to improve the acoustic characteristics.

As described above, according to the present invention, it is possible to improve the acoustic characteristics.

It is a schematic side sectional view which shows the electroacoustic conversion apparatus which concerns on one Embodiment of this invention. It is a schematic side sectional view which shows the electromagnetic sounding body in the said electro-acoustic converter. It is a schematic bottom view which shows the piezoelectric sounding body in the said electro-acoustic conversion apparatus. It is a schematic side sectional view of the piezoelectric element in the said piezoelectric sounding body. It is a schematic plan view explaining two piezoelectric sounding bodies having different configurations. This is a simulation result showing a comparison of the frequency characteristics of the above two piezoelectric sounding bodies. It is an experimental result which shows the frequency characteristic of the said electro-acoustic converter. It is a top view which shows one structural example of the piezoelectric sounding body described in the 2nd Embodiment of this invention. It is a top view which shows the other structural example of the said piezoelectric sounding body. It is a top view which shows the other structural example of the said piezoelectric sounding body. It is a top view which shows the other structural example of the said piezoelectric sounding body. It is a top view which shows the modification of the structure of FIG. It is a top view which shows the modification of the structure of FIG. It is a top view which shows the modification of the structure of FIG. It is an experimental result which compares and shows the frequency characteristic of the electromagnetic sounding body in the electroacoustic conversion apparatus provided with the piezoelectric sounding body shown in FIG. 10 and FIG. It is a schematic side sectional view which shows the structure of the electroacoustic conversion apparatus which concerns on 3rd Embodiment of this invention. This is an experimental result showing the sound pressure characteristics of the electroacoustic converter. An experimental result showing the relationship between the ratio of the distance (h) between the first and second diaphragms to the diameter (d) of the second diaphragm and the sound pressure in a predetermined frequency band in the electroacoustic converter. is there.

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

<First Embodiment>
FIG. 1 is a schematic side sectional view showing a configuration of an earphone 100 as an electroacoustic conversion device according to an embodiment of the present invention.
In the figure, the X-axis, the Y-axis, and the Z-axis indicate three axial directions orthogonal to each other.

[Overall configuration of earphones]
The earphone 100 has an earphone body 10 and an earpiece 20. The earpiece 20 is attached to the sound guide path 41 of the earphone body 10 and can be attached to the user's ear.

The earphone body 10 has a sounding unit 30 and a housing 40 for accommodating the sounding unit 30. The sounding unit 30 has an electromagnetic sounding body 31 and a piezoelectric sounding body 32.

[Case]
The housing 40 has an internal space for accommodating the sounding unit 30, and is composed of a two-divided structure that can be separated in the Z-axis direction. The bottom 410 of the housing 40 is provided with a sound guide path 41 that guides the sound waves generated by the sounding unit 30 to the outside.

The housing 40 has a support portion 411 that supports the peripheral edge portion of the piezoelectric sounding body 32. The support portion 411 is formed in an annular shape, and is provided so as to project upward from the peripheral edge portion of the bottom portion 410. In the figure, the upper surface of the support portion 411 is formed in a plane parallel to the XY plane, and directly or indirectly supports the peripheral portion of the piezoelectric sounding body 32 described later via another member.

The internal space of the housing 40 is divided into a first space portion S1 and a second space portion S2 by the piezoelectric sounding body 32. An electromagnetic sounding body 31 is arranged in the first space portion S1. The second space portion S2 is a space portion communicating with the sound guide path 41, and is formed between the piezoelectric sounding body 32 and the bottom portion 410 of the housing 40. The first space portion S1 and the second space portion S2 communicate with each other through openings 331 to 337 (see FIG. 3) of the piezoelectric sounding body 32.

[Electromagnetic sounding body]
The electromagnetic sounding body 31 is composed of a dynamic speaker unit that functions as a woofer that reproduces a low frequency range. In the present embodiment, for example, a mechanism unit 311 composed of a dynamic speaker that mainly generates sound waves of 7 kHz or less and including a vibrating body such as a voice coil motor (electromagnetic coil) and a pedestal unit 312 that vibrably supports the mechanism unit 311. And have.

The configuration of the mechanical unit 311 of the electromagnetic sounding body 31 is not particularly limited. FIG. 2 is a cross-sectional view of a main part showing a configuration example of the mechanism part 311. The mechanism portion 311 has a diaphragm E1 (second diaphragm) oscillatingly supported by the pedestal portion 312, a permanent magnet E2, a voice coil E3, and a yoke E4 supporting the permanent magnet E2. The diaphragm E1 is supported by the pedestal portion 312 by sandwiching the peripheral portion thereof between the bottom portion of the pedestal portion 312 and the annular fixture 310 integrally assembled to the bottom portion of the pedestal portion 312.

The voice coil E3 is formed by winding a lead wire around a bobbin serving as a winding core, and is joined to the central portion of the diaphragm E1. Further, the voice coil E3 is arranged perpendicular to the direction of the magnetic flux of the permanent magnet E2. When an alternating current (voice signal) is passed through the voice coil E3, an electromagnetic force acts on the voice coil E3, so that the voice coil E3 vibrates in the Z-axis direction in the figure according to the signal waveform. This vibration is transmitted to the diaphragm E1 connected to the voice coil E3, and the air in the first space S1 (FIG. 1) is vibrated to generate the sound wave in the low frequency range.

The electromagnetic sounding body 31 is fixed to the inside of the housing 40 by an appropriate method. A circuit board 33 constituting the electric circuit of the sounding unit 30 is fixed to the upper part of the electromagnetic sounding body 31. The circuit board 33 is electrically connected to the cable 50 introduced via the lead portion 42 of the housing 40, and sends an electric signal to the electromagnetic sounding body 31 and the piezoelectric sounding body 32 via a wiring member (not shown), respectively. Output.

[Piezoelectric sounding body]
The piezoelectric sounding body 32 constitutes a speaker unit that functions as a tweeter that reproduces a high frequency range. In the present embodiment, the oscillation frequency is set so as to mainly generate, for example, a sound wave of 7 kHz or higher. The piezoelectric sounding body 32 has a diaphragm 321 (first diaphragm) and a piezoelectric element 322.

The diaphragm 321 is made of a conductive material such as a metal (for example, 42 alloy) or an insulating material such as a resin (for example, a liquid crystal polymer), and its planar shape is formed in a circular shape. The outer diameter and thickness of the diaphragm 321 are not particularly limited, and are appropriately set according to the size of the housing 40, the frequency band of the reproduced sound wave, and the like. In this embodiment, a diaphragm having a diameter of about 8 to 12 mm and a thickness of about 0.2 mm is used.

The diaphragm 321 has a first main surface 32a facing the sound guide path 41 and a second main surface 32b facing the electromagnetic sounding body 31. In the present embodiment, the piezoelectric sounding body 32 has a unimorph structure in which the piezoelectric element 322 is bonded only to the first main surface 32a of the diaphragm 321.
Not limited to this, the piezoelectric element 322 may be joined to the second main surface 32b of the diaphragm 321. Further, the piezoelectric sounding body 32 may have a bimorph structure in which a piezoelectric element is bonded to both main surfaces 32a and 32b of the diaphragm 321.

The diaphragm 321 has a peripheral edge portion 321c supported by the support portion 411 of the housing 40. The peripheral edge portion 321c is elastically supported by the support portion 411 via an adhesive layer. The pressure-sensitive adhesive layer preferably has appropriate elasticity. As a result, the diaphragm 321 is elastically supported by the support portion 411, so that the resonance fluctuation of the diaphragm 321 is suppressed, and the stable resonance operation of the diaphragm 321 is ensured.

The diaphragm 321 may be fixed to the support portion 411 via an annular member that supports the peripheral edge portion 321c thereof. The annular member is preferably made of an elastic material such as rubber or resin, whereby the same action and effect as described above can be obtained. Alternatively, the annular member may be made of a material having relatively high rigidity and may be joined to the support portion 411 via the pressure-sensitive adhesive layer.

FIG. 3 is a plan view (or bottom view) of the piezoelectric sounding body 32. As shown in the figure, the piezoelectric sounding body 32 is configured to have asymmetric rigidity with respect to the central axis C1 of the diaphragm 321 (an axis parallel to the Z-axis direction passing through the center of the diaphragm 321).

Here, the rigidity asymmetric with respect to the central axis C1 means that the structure, shape, physical properties, etc. are asymmetric with respect to the central axis C1, and in particular, the vibration mode becomes asymmetric with respect to the central axis C1 when the diaphragm 321 oscillates. It refers to such a form.

In the present embodiment, the planar shape of the piezoelectric element 322 is rectangular, and the central axis C2 of the piezoelectric element 322 (the axis parallel to the Z axis passing through the center of the piezoelectric element 322) is larger than the central axis C1 of the vibrating plate 321. It is displaced by a predetermined amount in the X-axis direction. That is, the piezoelectric element 322 is arranged at a position eccentric with respect to the diaphragm 321. As a result, the vibration center of the diaphragm 321 shifts to a position different from that of the central axis C1, so that the vibration mode of the piezoelectric sounding body 32 becomes asymmetric with respect to the central axis C1.

Further, as shown in FIG. 3, the diaphragm 321 has a shape (morphology) in a right half region and a left half region with the center line CL (a line parallel to the Y-axis direction passing through the center of the diaphragm 321) as a boundary. ) Has anisotropy. That is, the piezoelectric sounding body 32 has a plurality of openings 331-337 (passage portions) penetrating the diaphragm 321 in the thickness direction, and each opening 331-337 is formed in the following manner. It is configured asymmetrically with respect to the center line CL.

The opening 331 is formed in a substantially semicircular or half-moon shape in the region between the peripheral edge portion 321c of the diaphragm 321 and one side portion of the piezoelectric element 322, and has the largest opening area of the openings 331 to 337. .. The piezoelectric sounding body 32 is assembled in the support portion 411 so that the opening 331 faces the entrance of the sound guide path 41 (see FIG. 1).

The openings 332 to 335 are composed of circular holes provided in the region between the peripheral edge portion 321c and the piezoelectric element 322. Among them, the openings 332 and 333 are provided at positions symmetrical with respect to the central axis C1 on the center line CL, and the openings 334 and 335 are provided between the openings 331 and the openings 332 and 333, respectively. The openings 332 to 335 are each formed of round holes having the same diameter (for example, about 1 mm in diameter), but are not limited to this, of course.

On the other hand, the openings 336 and 337 are provided between the openings 332 and 333 and the piezoelectric element 322, respectively, and are formed in a rectangular shape having a long side in the X-axis direction. The openings 336 and 337 are formed along the peripheral edge of the piezoelectric element 322, and a part of them is partially covered with the peripheral edge of the piezoelectric element 322. The openings 336 and 337 have a function as a passage penetrating the front and back surfaces of the diaphragm 321 and also have a function of preventing a short circuit between the two external electrodes of the piezoelectric element 322, as will be described later.

FIG. 4 is a schematic cross-sectional view showing the internal structure of the piezoelectric element 322.

The piezoelectric element 322 has a body 328 and a first external electrode 326a and a second external electrode 326b that face each other in the Y-axis direction. Further, the piezoelectric element 322 has a first main surface 322a and a second main surface 322b perpendicular to the Z axes facing each other. The second main surface 322b of the piezoelectric element 322 is configured as a mounting surface facing the first main surface 32a of the diaphragm 321.

The element body 328 has a structure in which the ceramic sheet 323 and the internal electrode layers 324a and 324b are laminated in the Z-axis direction. That is, the internal electrode layers 324a and 324b are alternately laminated with the ceramic sheet 323 interposed therebetween. The ceramic sheet 323 is formed of a piezoelectric material such as lead zirconate titanate (PZT) or an alkali metal-containing niobium oxide. The internal electrode layers 324a and 324b are formed of a conductive material such as various metal materials.

The first internal electrode layer 324a of the element body 328 is connected to the first external electrode 326a and is insulated from the second external electrode 326b by the margin portion of the ceramic sheet 323. Further, the second internal electrode layer 324b of the element body 328 is connected to the second external electrode 326b and is insulated from the first external electrode 326a by the margin portion of the ceramic sheet 323.

In FIG. 4, the uppermost layer of the first internal electrode layer 324a constitutes a first extraction electrode layer 325a that partially covers the surface (upper surface in FIG. 4) of the element body 328, and is a second internal electrode layer. The bottom layer of 324b constitutes a second extraction electrode layer 325b that partially covers the back surface (lower surface in FIG. 4) of the element body 328. The first extraction electrode layer 325a has a terminal portion 327a of one pole electrically connected to the circuit board 33 (FIG. 1), and the second extraction electrode layer 325b has an appropriate bonding material. It is electrically and mechanically connected to the first main surface 32a of the diaphragm 321. When the diaphragm 321 is made of a conductive material, a conductive bonding material such as a conductive adhesive or solder may be used as the bonding material. In this case, the terminal portion of the other pole is the diaphragm. It can be provided in 321.

The first and second external electrodes 326a and 326b are formed of conductive materials such as various metal materials at substantially central portions of both end faces in the Y-axis direction of the element body 328. The first external electrode 326a is electrically connected to the first internal electrode layer 324a and the first extraction electrode layer 325a, and the second external electrode 326b is the second internal electrode layer 324b and the second extraction. It is electrically connected to the electrode layer 325b.

With such a configuration, when an AC voltage is applied between the external electrodes 326a and 326b, each ceramic sheet 323 between the internal electrode layers 324a and 324b expands and contracts at a predetermined frequency. As a result, the piezoelectric element 322 can generate vibration applied to the diaphragm 321.

Here, the first and second external electrodes 326a and 326b project from each of the both end faces of the element body 328, respectively, as shown in FIG. At this time, the first and second external electrodes 326a and 326b may be formed with raised portions 329a and 329b protruding toward the first main surface 32a of the diaphragm 321. Therefore, the above-mentioned openings 336 and 337 are formed in a size capable of accommodating the raised portions 329a and 329b. As a result, an electrical short circuit between the external electrodes 326a and 326b due to contact between the raised portions 329a and 329b and the diaphragm 321 is prevented.

[Earphone operation]
Subsequently, the typical operation of the earphone 100 of the present embodiment configured as described above will be described.

In the earphone 100 of the present embodiment, the reproduction signal is input to the circuit board 33 of the sounding unit 30 via the cable 50. The reproduced signal is input to the electromagnetic sounding body 31 and the piezoelectric sounding body 32, respectively, via the circuit board 33. As a result, the electromagnetic sounding body 31 is driven, and mainly low-pitched sound waves of 7 kHz or less are generated. On the other hand, in the piezoelectric sounding body 32, the diaphragm 321 vibrates due to the expansion and contraction operation of the piezoelectric element 322, and mainly high-pitched sound waves of 7 kHz or more are generated. The generated sound waves in each band are transmitted to the user's ear via the sound guide path 41. As described above, the earphone 100 functions as a hybrid speaker having a sounding body for a low frequency range and a sounding body for a high frequency range.

On the other hand, the sound wave generated by the electromagnetic sounding body 31 vibrates the diaphragm 321 of the piezoelectric sounding body 32 and propagates to the second space S2, and the second sound wave component through the openings 331 to 337. It is formed by a combined wave with a sound wave component propagating to the space S2. Therefore, by optimizing the size, number, and the like of the openings 331 to 337, the sound wave in the bass range output from the piezoelectric sounding body 32 can be obtained, for example, at a frequency at which a sound pressure peak can be obtained in a predetermined bass band. It is possible to adjust or tune to the characteristics.

In the present embodiment, the piezoelectric sounding body 32 is configured to have asymmetric rigidity with respect to the central axis C1. Specifically, the piezoelectric element 322 is arranged at a position eccentric with respect to the diaphragm 321 and the shapes and numbers of the openings 331 to 337 are asymmetrically configured with respect to the Y-axis direction of the diaphragm 321. (See FIG. 3). Therefore, the vibration mode of the diaphragm 321 becomes non-uniform in the plane. As a result, the sound pressure level in the high frequency range becomes broad and the sound pressure characteristics are improved, so that good sound quality can be reproduced.

As an example, samples 11A and 11B of the two piezoelectric sounding bodies shown in FIGS. 5A and 5B were prepared, and as a result of comparing their frequency characteristics, simulation results as shown in FIGS. 6A and 6B were obtained.
Here, both the samples 11A and 11B have a circular diaphragm 12 and a rectangular piezoelectric element 13 arranged on the circular diaphragm 12, but in the sample 11A, the piezoelectric element 13 is arranged at the center of the diaphragm 12. On the other hand, in the sample 11B, the piezoelectric element 13 is arranged at an eccentric position from the diaphragm 12. A rectangular opening 14 wider than the piezoelectric element 13 is provided at the center of the diaphragm 12. The piezoelectric element 13 is arranged at the center of the opening 14 in the sample 11A, and the piezoelectric element 13 is arranged in the sample 11B. Is arranged at a position eccentric from the opening 14.

FIG. 6A shows the frequency characteristics of the samples 11A and 11B near the resonance frequency, and FIG. 6B shows the frequency characteristics in each higher-order mode. No significant difference was observed in the resonance frequencies (natural frequencies) of the samples 11A and 11B, and it was confirmed that the resonance frequencies of the samples 11B were slightly lowered (FIG. 6A). Since the symmetry of the sample 11B with respect to the central axis of the diaphragm 12 is broken as compared with the sample 11A, the resonance frequency is lowered due to multiple reasons such as a deviation of the maximum amplitude position and a decrease of the amplitude of the center position. It is presumed that it was. On the other hand, it was confirmed that when the resonance becomes higher order (for example, 30 kHz or more), the difference in frequency characteristics between the samples 11A and 11B begins to appear clearly (FIG. 6B).

As described above, when the symmetry with respect to the central axis C1 of the piezoelectric sounding body 32 is broken, the decrease of the resonance point in the higher-order mode becomes large. It is presumed that such a tendency becomes more remarkable as the degree of the asymmetry increases. Therefore, by arbitrarily adjusting the asymmetry of the piezoelectric sounding body 32, it is possible to realize a desired high frequency characteristic. Further, as the asymmetry of the piezoelectric sounding body becomes higher, the resistance element of vibration increases and the mechanical sharpness (Q value) of resonance decreases, so that the sound quality can be improved.

On the other hand, it was confirmed that the asymmetry of the piezoelectric sounding body 32 promotes an improvement in the sound pressure level especially in the high frequency range when combined with the electromagnetic sounding body 31. FIG. 7 is an experimental result showing the frequency characteristics of the reproduced sound of the earphone 100 of the present embodiment. As a comparative example, the frequency characteristics when the piezoelectric sounding body (sample 11A) shown in FIG. 5A is set in the housing 40 instead of the piezoelectric sounding body 32 of the present embodiment are shown by a solid line.

According to the present embodiment, as shown in FIG. 7, the sound pressure level can be raised in the high frequency range of 10 kHz or more as compared with the comparative example. This is because the maximum amplitude position of the diaphragm 321 is set to a position deviated from the center of the diaphragm 321 due to the asymmetry of the piezoelectric sounding body 32 in the present embodiment, so that the sound waves cancel each other out in the high frequency band. As a result of the relaxation, it is presumed that it led to the improvement of the sound pressure characteristics. Further, since the sound pressure level is increased in the band exceeding the audible range of 20 kHz or more, it is possible to reproduce a sound with a deeper feeling.

Further, according to the present embodiment, since the opening 331 of the piezoelectric sounding body 32 is arranged so as to face the sound guiding path 41, the reproduced sound in the electromagnetic sounding body 31 is efficiently guided to the sound guiding path 41. It becomes possible. As a result, as shown in FIG. 7, the sound pressure level in the low frequency range (7 kHz or less) is also improved, so that the sound pressure characteristics can be improved from the low frequency range to the high frequency range.

<Second embodiment>
8 to 15 are schematic plan views (or bottom views) showing the configuration of the pressure electron sounding body according to the second embodiment of the present embodiment. Hereinafter, configurations different from those of the first embodiment will be mainly described, and the same configurations as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted or simplified.

The piezoelectric sounding body of the present embodiment has a diaphragm structure different from that of the first embodiment described above as in each configuration example described below. In the following description, an example in which the piezoelectric element 322 is arranged at the center of the diaphragm will be described, but the present invention is not limited to this, and the position where the piezoelectric element 322 is eccentric with respect to the diaphragm as in the first embodiment is described. May be placed in.

(Configuration Example 1)
The piezoelectric sounding body 500 shown in FIG. 8 has a plurality of (four in this example) notches 522 to 525 as passage portions provided on the peripheral edge portion 521c of the circular diaphragm 521, and the surface of the diaphragm 521. It has two openings 526,527 formed within. The openings 526 and 527 are for preventing a short circuit between the external electrodes of the piezoelectric element 322, but also function as a sound passage hole (passage portion).

The notches 522 to 525 are provided at intervals of 90 ° and have a depth capable of forming a passage portion that allows the first space portion S1 and the second space portion S2 of the housing 40 to communicate with each other. , Each is formed at the same depth from the peripheral portion 521c toward the central axis C. Among them, the notch portion 522 is formed with an opening width larger than that of the other notch portions 523 to 525, and the other notch portions 523 to 525 are all formed with the same opening width. In this way, the diaphragm 521 is formed in a shape that is asymmetrical with respect to the center line CL parallel to the Y-axis direction.

Since the piezoelectric sounding body 500 having such a configuration has an asymmetrical structure with respect to the central axis C1, it is possible to obtain the same effects as those in the first embodiment described above. Further, in FIG. 8, by eccentricizing the piezoelectric element 322 to the right side of the center line CL, for example, the asymmetry of the piezoelectric sounding body 500 can be further enhanced.
In this example, the piezoelectric sounding body 500 is preferably installed in the housing 40 so that the notch 522 having the largest area of the passage portion faces the sound guide path 41 (FIG. 1).

(Configuration Example 2)
The piezoelectric sounding body 600 shown in FIG. 9 has a plurality of (five in this example) notches 622 to 626 as passages provided on the peripheral edge portion 621c of the circular diaphragm 621, and the above-mentioned opening 526. , 527 and.

The cutout portions 622-626 are provided at unequal angle intervals, and have a depth capable of forming a passage portion that allows the first space portion S1 and the second space portion S2 of the housing 40 to communicate with each other. The peripheral portion 621c is formed at an arbitrary depth toward the central axis C.

In this configuration example, the number and distribution of the notch portions 622-625 are set asymmetrically with respect to the center line CL parallel to the Y-axis direction. Since the piezoelectric sounding body 600 having such a configuration has an asymmetrical structure with respect to the central axis C1, it is possible to obtain the same effects as those in the first embodiment described above. Further, in FIG. 9, by eccentricizing the piezoelectric element 322 to the right side of the center line CL, for example, the asymmetry of the piezoelectric sounding body 600 can be further enhanced.
In this example, the piezoelectric sounding body 600 is installed in the housing 40 so that the formed portions of the cutout portions 625, 626, 622 in which the passage portions are densely arranged face the sound guide path 41 (FIG. 1). Is preferable.

(Configuration Example 3)
The piezoelectric sounding body 700 shown in FIG. 10 has an opening 722 as a passage portion provided in the plane of the circular diaphragm 721 and an opening 526,527 for preventing a short circuit.

The opening 722 is formed in a semicircular or semicircular shape similar to the opening 331 in the first embodiment. In this example, the opening 722 is formed continuously with one opening 526 for preventing a short circuit, but the present invention is not limited to this, and the opening may be an opening independent of the opening 526.

The peripheral edge portion 721c of the diaphragm 721 is provided with four recesses 731 and 732 at 90 ° intervals. These recesses 731 and 732 are used for positioning the housing 40 with respect to the support portion 411. In particular, as shown in the drawing, by making one of the four recesses 732 different in shape from the other three recesses 731, a guideline indicating the direction of the diaphragm 721 can be obtained, so that an error with respect to the housing 40 can be obtained. There is an advantage that assembly can be prevented.

In this configuration example, the position of the opening 722 is set asymmetrically with respect to the center line CL parallel to the Y-axis direction. Since the piezoelectric sounding body 700 having such a configuration has an asymmetrical structure with respect to the central axis C1, it is possible to obtain the same effect as that of the first embodiment described above. Further, in FIG. 10, by eccentricizing the piezoelectric element 322 to the right side of the center line CL, for example, the asymmetry of the piezoelectric sounding body 700 can be further enhanced.
In this example, the piezoelectric sounding body 700 is preferably installed in the housing 40 so that the opening 722 that functions as a passage portion faces the sound guide path 41 (FIG. 1).

(Configuration Example 4)
The piezoelectric sounding body 800 shown in FIG. 11 has a notch 822 as a passage portion provided in the peripheral edge portion 821c of the circular diaphragm 821, and openings 526 and 527 for preventing a short circuit.

In this configuration example, the notch portion 822 has a shape similar to that in which the peripheral edge portion 721c of the diaphragm 721 adjacent to the arc portion of the opening 722 in the configuration example 3 is notched. Even in such a configuration, the same effect as that of the configuration example 3 can be obtained.

In the present embodiment, for example, in the diaphragm 721 of the configuration example 3 (FIG. 10), the peripheral portions 721c are provided with the recesses 731 and 732 for positioning, respectively. As shown in FIG. 12, these recesses 731 are provided. , 732, a plurality of (four in this example) notches 741 may be further provided. Each notch 741 is a peripheral edge portion 321c of the diaphragm 321 and is provided at a position offset by 45 ° in the circumferential direction at 90 ° intervals, for example, from the recesses 731 and 732. These positions correspond to positions facing the four corners of the piezoelectric element 322 in the radial direction. Therefore, when the piezoelectric element 322 is joined onto the diaphragm 321, the relative position between the diaphragm 321 and the piezoelectric element 322 can be confirmed with reference to these notches 741.

(Configuration Example 5)
In the piezoelectric sounding bodies 700 and 800 according to the configuration example 3 (FIG. 10) and the configuration example 4 (FIG. 11), a plurality of openings may be further provided in the plane of the diaphragms 721 and 821. 13 and 14 show piezoelectric sounding bodies 710 and 810 in which a plurality of openings 528 are provided in the plane of the diaphragms 721 and 821, respectively. The opening 528 is a circular through hole, and is formed at a position symmetrical with respect to the center line CL of the diaphragms 721 and 821.

The number and size of the openings 528 are not particularly limited, and in the illustrated example, the openings 528 having a diameter of about 1 mm are provided at four positions symmetrical with respect to the center line CL and the piezoelectric element 322, respectively. Assuming that the diameters of the diaphragms 721 and 821 are 12 mm, the above four locations are, for example, positions where the facing distance perpendicular to the center line CL is 3.2 mm and the facing distance parallel to the center line CL is 8.6 mm. It is said that.

The same effects as those of the configuration examples 3 and 4 can be obtained in the piezoelectric sounding bodies 700 and 800 having such a configuration. Further, according to this configuration example, since each opening 528 effectively functions as a passage portion through which the sound wave generated from the electromagnetic sounding body passes, for example, as shown in FIG. 15, in the high frequency band of the electromagnetic sounding body. Sound pressure characteristics can be improved.

In FIG. 15, the white solid line shows the frequency characteristics when only the piezoelectric sounding body is driven in the earphone provided with the piezoelectric sounding body 710 shown in FIG. 13, and the white one-dot chain line is shown in FIG. It shows the frequency characteristic when only the piezoelectric sounding body in the earphone provided with the piezoelectric sounding body 700 is driven. As shown in the figure, according to the piezoelectric sounding body 710, the sound pressure characteristic can be improved at 10 to 20 kHz as compared with the piezoelectric sounding body 700.

<Third embodiment>
FIG. 16 is a schematic side sectional view showing a configuration of an electroacoustic conversion device according to a third embodiment of the present invention. Hereinafter, configurations different from those of the first embodiment will be mainly described, and the same configurations as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted or simplified.

The earphone 300 of the present embodiment includes a housing 340, a piezoelectric sounding body 350, and an electromagnetic sounding body 360, as in the first embodiment.

The housing 340 includes a first support 341 having an internal space for accommodating a sound guide path (not shown) and a piezoelectric sounding body 350, a second support 342 for supporting the electromagnetic sounding body 360, and a first support body 342. It has a third support 343 that joins the support 341 of the first support 341 and the second support 342 to each other, and constitutes a housing portion of the earphone. The third support 343 has a plate shape in which a through hole 343a is bored in the central portion, and prevents mutual contact between the diaphragm 351 of the piezoelectric sounding body 350 and the diaphragm 361 of the electromagnetic sounding body 360. It is configured as a protector. The second support 342 may be composed of a part of the electromagnetic sounding body 360.

The piezoelectric sounding body 350 has a diaphragm 351 (first diaphragm) and a piezoelectric element 352, and is configured to have asymmetric rigidity with respect to the central axis C1 of the diaphragm 351 as in the first embodiment. To. That is, the piezoelectric element 352 is arranged at a position eccentric with respect to the diaphragm 351. In the illustrated example, the central axis C2 of the piezoelectric element 352 is predetermined in the X-axis direction with respect to the central axis C1 of the diaphragm 351. The distance is only.

The diaphragm 351 is provided with a plurality of openings 353 and 354, respectively, as passage portions. One opening 353 corresponds to an opening 332-335 (see FIG. 3) in the first embodiment, and the other opening 354 corresponds to an opening 336,337 (see FIG. 3) in the first embodiment. Corresponds to.

In the present embodiment, the piezoelectric sounding body 350 further has a mount ring 353 (annular member). The mount ring 353 is fixed to the housing 340 (third support 343) via the bonding layer 356, and supports the peripheral edge of the diaphragm 351 of the piezoelectric sounding body 350. In the present embodiment, the mount ring 353 has a pedestal portion 353a that supports the diaphragm 351 on the upper surface, and a peripheral wall portion 353b that positions the peripheral edge portion of the diaphragm 351.

The support structure of the diaphragm 351 by the mount ring 353 is not particularly limited, and an adhesive, double-sided adhesive tape, or the like can be used. The bonding layer 356 is preferably made of an adhesive material having appropriate elasticity, whereby the piezoelectric sounding body 350 is elastically supported by the housing 340.

Since the piezoelectric sounding body 350 has the mount ring 353, the workability of assembling the piezoelectric sounding body 350 with respect to the housing 430 is improved, and the relative position of the piezoelectric sounding body 350 with respect to the electromagnetic sounding body 360 can be easily adjusted. It becomes. Typically, the diaphragm 351 is arranged concentrically with the diaphragm 361 of the electromagnetic sounding body 360, but the diaphragm 351 may be arranged at a position eccentric with respect to the diaphragm 361.

In the present embodiment, as shown in FIG. 16, the central axis C1 of the diaphragm 351 is arranged at a position separated by a predetermined distance in the X-axis direction from the central axis C3 of the diaphragm 361. By arranging the piezoelectric sounding body 350 asymmetrically with respect to the electromagnetic sounding body 360 in this way, it is possible to improve the acoustic characteristics of the piezoelectric sounding body 350. Such a configuration can be appropriately adopted depending on the shape and size of the housing 430, the position of the sound guide path, and the like.

Further, according to the present embodiment, the relative distance of the piezoelectric sounding body 350 to the electromagnetic sounding body 360 can be set by adjusting the thickness (height) of the pedestal portion 353a of the mount ring 353. The distance can be easily adjusted. Further, by optimizing the distance, it is possible to optimize the sound pressure characteristic in a predetermined frequency band.

For example, FIG. 17 shows the earphones shown in FIG. 16 using two mount rings 353 having different thicknesses of the pedestal portion 353a, and the experimental results of the frequency characteristics of the reproduced sound for each are compared and shown. In FIG. 17, the white solid line shows the sound pressure characteristic when the first mount ring in which the thickness of the pedestal portion 353a is 1.4 times the unit length (t) is applied, and the white two-dot chain line is It shows the sound pressure characteristics when the second mount ring, in which the thickness of the pedestal portion 353a is twice the unit length (t), is applied. The unit length (t) is 1 mm in this example.

As shown in FIG. 17, according to the electroacoustic converter to which the first mount ring is applied, the sound in the range of approximately 5 kHz to 9 kHz as compared with the electroacoustic converter to which the second mount ring is applied. The pressure improves. This occurs in the electromagnetic sounding body 360 because the volume of the space between them decreases as the distance between the diaphragm 351 of the piezoelectric sounding body 350 and the diaphragm 361 of the electromagnetic sounding body 360 decreases. It is considered that the sound wave is easily emitted to the outside through the piezoelectric sounding body 350.

The frequency band in which the sound pressure is improved at the distance between the piezoelectric sounding body 350 and the electromagnetic sounding body 360 is mainly determined by the size of the diameter (d) of the diaphragm 361 of the electromagnetic sounding body 360. For example, when the purpose is to improve the sound pressure at 6 kHz to 9 kHz, the diameter (d) of the diaphragm 361 is, for example, 7.5 mm to 13.5 mm. When the distance from the upper surface of the diaphragm 361 to the lower surface of the diaphragm 351 of the piezoelectric sounding body 350 is h, the smaller the ratio (h / d) of the distance (h) to the diameter (d), the more the predetermined value. It is possible to improve the sound pressure in the frequency band of.

18A and 18B are experimental results showing the relationship between the sound pressure of 7.5 kHz and the (h / d) value and the relationship between the average sound pressure of 5 to 9 kHz and the (h / d) value, respectively. Here, the value of the diameter d is 9.2 mm, and the diameter of the diaphragm 351 of the piezoelectric sounding body 350 is 8 mm. As shown in FIGS. 18A and 18B, the upper limit of the (h / d) value at which the sound pressure is improved as compared with the case where the second mount ring is applied (white two-dot chain line in FIG. 14) is 0.212 or less. (H = 1.908 mm or less).

The lower limit of the (h / d) value is not particularly limited, but can be set to an appropriate value at which the diaphragms 351 and 361 do not interfere with each other (or do not come into contact with the third support 343). In this example, the value is equal to or higher than the value (0.152 (h = 1.368 mm)) at the time of applying the first mount ring (white two-dot chain line in FIG. 14).

As described above, in the present embodiment, by selecting the thickness of the pedestal portion 353a of the mount ring 353 so that 0.152 ≦ (h / d) ≦ 0.212, the sound pressure observed in 5 kHz to 9 kHz is observed. It is possible to improve the dipping of the sound and obtain smooth sound pressure characteristics. Even if it is not shown, in the experiments of the present inventors, even when the diameter of the diaphragm 351 of the piezoelectric sounding body 350 is 12 mm, by adjusting the (h / d) value, 5 to 5 as described above It has been confirmed that the drop in sound pressure at 9 kHz can be improved.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

For example, in the above first and second embodiments, in order to realize the asymmetric structure of the piezoelectric sounding body, the shape of the diaphragm is made asymmetric with respect to the central axis, or in addition, the piezoelectric element is attached to the diaphragm. However, the present invention is not limited to this, and the same effect as described above can be obtained only by arranging the piezoelectric element at an eccentric position with respect to the diaphragm.

Further, in the above embodiment, the shape, position, size, and number of the openings or notches constituting the passage portion of the piezoelectric sounding unit are not particularly limited, and the openings or notches constituting the passage portion are not particularly limited. At least one is required.

10 ... Earphone body 20 ... Earpiece 30 ... Sounding unit 31,360 ... Electromagnetic sounding body 32,350,500,600,700,710,800,810 ... Piezoelectric sounding body 40,340 ... Housing 321,351,521 , 621, 721, 821 ... Diaphragm (first diaphragm)
322,352 ... Piezoelectric element 331-337, 354,353,526,527,528,722 ... Opening 522-525,622-626 ... Notch 100,300 ... Earphone (electroacoustic converter)
E1,361 ... Diaphragm (second diaphragm)

Claims (8)

With the housing
The thickness of the first diaphragm, the first diaphragm having a peripheral edge directly or indirectly supported by the housing, the piezoelectric element arranged on at least one surface of the first diaphragm, and the first diaphragm. A piezoelectric sounding body having a passage portion penetrating in the direction and having an asymmetric rigidity with respect to the central axis of the first diaphragm .
Equipped with an electromagnetic sounding body including a second diaphragm ,
The housing is
The first space where the electromagnetic sounding body is arranged and
A second space portion having a sound guide path that communicates with the first space portion via the passage portion and guides sound waves generated by the piezoelectric sounding body and the electromagnetic sounding body to the outside. Have and
When the distance between the first diaphragm and the second diaphragm is h and the diameter of the second diaphragm is d,
0.152 ≤ (h / d) ≤ 0.212
Electroacoustic converter that satisfies the relationship . The electroacoustic converter according to claim 1.
The piezoelectric element is an electroacoustic conversion device arranged at a position eccentric with respect to the first diaphragm. The electroacoustic converter according to claim 1 or 2 .
The passage portion is an electroacoustic conversion device including at least one opening provided in the plane of the first diaphragm. The electroacoustic conversion device according to any one of claims 1 to 3 .
The passage portion is an electroacoustic conversion device including at least one notch portion provided in the peripheral portion. The electroacoustic conversion device according to any one of claims 1 to 4 .
The passage portion includes a plurality of passage portions.
The sound guide path is an electroacoustic conversion device provided at a position facing the passage portion having the largest opening area among the plurality of passage portions. The electroacoustic converter according to any one of claims 1 to 5 .
The planar shape of the first diaphragm is circular,
An electroacoustic conversion device having a rectangular planar shape of the piezoelectric element. The electroacoustic conversion device according to any one of claims 1 to 6 .
The piezoelectric sounding body is an electroacoustic conversion device further comprising an annular member fixed to the housing and supporting the peripheral edge of the first diaphragm. The electroacoustic converter according to any one of claims 1 to 7 .
The first diaphragm is an electroacoustic conversion device arranged at a position eccentric with respect to the second diaphragm.

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