JP2018170638A - Electroacoustic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroacoustic transducer capable of improving acoustic properties of a piezoelectric sounder.SOLUTION: An electroacoustic transducer includes a piezoelectric sounder, and an enclosure. The piezoelectric sounder has a first diaphragm having a peripheral portion, a piezoelectric element placed on at least one side of the first diaphragm, and multiple openings provided around the piezoelectric element and penetrating the first diaphragm in a first axial direction, i.e., the thickness direction thereof. The enclosure has a support for supporting the peripheral portion directly or indirectly, and a sound guide facing the piezoelectric sounder in the first axial direction. The sound guide is provided at a position not overlapping a first opening, having the largest opening area out of the multiple openings, in the first axial direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electroacoustic transducer applicable to, for example, an earphone or a headphone, a portable information terminal, or the like.

  Piezoelectric sound generating elements are widely used as simple electroacoustic conversion means, and are frequently used, for example, as acoustic devices such as earphones or headphones, and also as speakers of portable information terminals. A piezoelectric sounding element typically has a configuration in which a piezoelectric element is bonded to one or both surfaces of a diaphragm (see, for example, Patent Document 1).

  On the other hand, Patent Document 2 describes a headphone that is provided with a dynamic driver and a piezoelectric driver, and that enables reproduction with a wide bandwidth by driving these two drivers in parallel. The piezoelectric driver is provided at the center of the inner surface of the front cover that closes the front surface of the dynamic driver and functions as a diaphragm, and is configured to function as a driver for the high frequency range.

JP2013-150305A Japanese Utility Model Publication No. 62-68400

  In recent years, for example, acoustic devices such as earphones and headphones have been required to further improve sound quality. For this reason, in the piezoelectric sound generating element, it is essential to improve the characteristics of the electroacoustic conversion function. Further, it is desired to increase the sound pressure in the high sound range when combined with a dynamic speaker.

  In view of the circumstances as described above, an object of the present invention is to provide an electroacoustic transducer capable of improving the acoustic characteristics of a piezoelectric sounding body.

In order to achieve the above object, an electroacoustic transducer according to one embodiment of the present invention includes a piezoelectric sounding body and a housing.
The piezoelectric sounding body includes a first diaphragm having a peripheral portion, a piezoelectric element disposed on at least one surface of the first diaphragm, and the first vibration provided around the piezoelectric element. And a plurality of openings penetrating the plate in the first axial direction, which is the thickness direction thereof.
The housing includes a support portion that directly or indirectly supports the peripheral edge portion, the piezoelectric sounding body, and a sound guide opening facing the first axial direction. The sound introduction port is provided at a position where the first opening having the largest opening area among the plurality of openings does not overlap in the first axial direction.

  According to the electroacoustic transducer, since the sound guide port is provided at a position that does not overlap the first opening in the first axial direction, the sound pressure characteristics of the piezoelectric sounding body can be improved. it can.

The first opening may be partially covered on the peripheral edge of the piezoelectric element.
In this case, the first opening may be formed of a pair of openings that face each other in a second axial direction orthogonal to the first axial direction.
The plurality of openings may include a second opening that overlaps the sound guide opening in the first axial direction.

  Alternatively, the plurality of openings may include a second opening that faces the first opening in a second axial direction orthogonal to the first axial direction.

  The electroacoustic transducer may further include an electromagnetic sounding body including a second diaphragm. In this case, the housing has a second space that communicates the first space portion in which the electromagnetic sounding body is disposed, and the first space portion and the sound inlet through the plurality of openings. And a space portion.

An electroacoustic transducer according to another embodiment of the present invention includes a piezoelectric sounding body and a housing.
The piezoelectric sounding body includes a first diaphragm having a peripheral portion, a piezoelectric element disposed on at least one surface of the first diaphragm, the first diaphragm and the piezoelectric element. And an opening penetrating in the first axial direction which is the thickness direction.
The housing includes a support portion that supports the peripheral edge portion, the piezoelectric sounding body, and a guide provided at a position that faces the first axial direction and does not overlap the opening portion and the first axial direction. And a sound outlet.

  As described above, according to the present invention, the acoustic characteristics of the piezoelectric sounding body can be improved.

It is a schematic sectional side view which shows the structure of the electroacoustic transducer concerning the 1st Embodiment of this invention. It is sectional drawing of the principal part which shows one structural example of the electromagnetic sounding body in the said electroacoustic transducer. It is a schematic plan view of the piezoelectric sounding body in the electroacoustic transducer. It is a schematic sectional drawing which shows the internal structure of the piezoelectric element in the said piezoelectric type sounding body. It is a schematic plan view of the support member in the electroacoustic transducer. It is a decomposition | disassembly side sectional view of the sound generation unit containing the said piezoelectric sounding body. It is an experimental result which shows an example of the sound pressure characteristic of the said piezoelectric type sounding body. It is a schematic plan view explaining the relative position of a piezoelectric sounding body and a sound guide port. It is a schematic plan view of the piezoelectric sounding body in the electroacoustic transducer according to the second embodiment of the present invention. It is an experimental result which shows an example of the sound pressure characteristic of the said piezoelectric type sounding body. It is a schematic plan view explaining the relative position of a piezoelectric sounding body and a sound guide port. It is a schematic plan view of the piezoelectric sounding body in the electroacoustic transducer according to the third embodiment of the present invention. It is a schematic plan view which shows the modification of a structure of the said piezoelectric sounding body.

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

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

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

  The earphone main body 10 includes a sound generation unit 30 and a housing 40 that houses the sound generation unit 30. The sounding unit 30 includes an electromagnetic sounding body 31 and a piezoelectric sounding body 32.

[Case]
The housing 40 has an internal space that accommodates the sound generation unit 30 and has a two-part structure that can be separated in the Z-axis direction.

  The housing 40 is configured by a combination of a first housing portion 401 and a second housing portion 402. The first housing unit 401 has a housing space for housing the sound generation unit 30 therein. The second housing unit 402 has a sound guide path 41 that guides the sound wave generated by the sounding unit 30 to the outside. The second housing unit 402 is combined with the first housing unit 401 in the Z-axis direction, thereby Cover.

  The sound guide path 41 has a sound guide port 41a at a base end portion thereof (an end portion opposite to a tip portion to which the earpiece 20 is attached). The sound guide port 41a corresponds to the entrance of the sound guide path 41, and has a circular opening shape parallel to the XY plane. The sound guide port 41a is provided at a position deviated from the center of the housing 40 in the X-axis direction, and is opposed to the piezoelectric sounding body 32 in the Z-axis direction. The sound guide path 41 is inclined by a predetermined angle in the X-axis direction with respect to the Z-axis direction from the sound guide port 41 a and protrudes outwardly from the bottom portion 410 of the second housing portion 42.

  The internal space of the housing 40 is partitioned by the piezoelectric sounding body 32 into a first space portion S1 and a second space portion S2. An electromagnetic sounding body 31 is disposed in the first space S1. The second space portion S <b> 2 is a space portion that communicates with the sound guide path 41, and is formed between the piezoelectric sounding body 32 and the bottom portion 410 of the second housing portion 402. The first space portion S1 and the second space portion S2 communicate with each other via a passage portion 330 (see FIG. 3) of the piezoelectric sounding body 32.

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

  The structure of the mechanism part 311 of the electromagnetic sounding body 31 is not particularly limited. FIG. 2 is a cross-sectional view of a main part showing one configuration example of the mechanism unit 311. The mechanism 311 includes a diaphragm E1 (second diaphragm) supported by the pedestal 312 so as to vibrate, a permanent magnet E2, a voice coil E3, and a yoke E4 that supports the permanent magnet E2. The diaphragm E1 is supported by the pedestal portion 312 by sandwiching the peripheral edge portion between the bottom portion of the pedestal portion 312 and the annular fixture 310 assembled integrally therewith.

  The voice coil E3 is formed by winding a conductive wire around a bobbin serving as a winding core, and is joined to the central portion of the diaphragm E1. The voice coil E3 is disposed 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 drawing according to the signal waveform. This vibration is transmitted to the diaphragm E1 connected to the voice coil E3, and the sound in the low frequency range is generated by vibrating the air in the first space S1 (FIG. 1).

  The electromagnetic sounding body 31 is fixed inside the housing 40 by an appropriate method. A circuit board 33 constituting an electric circuit of the sounding unit 30 is fixed on 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 electrical signal to the electromagnetic sounding body 31 and the piezoelectric sounding body 32 via a wiring member (not shown). 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 this embodiment, for example, the oscillation frequency is set so as to mainly generate sound waves of 7 kHz or higher. The piezoelectric sounding body 32 includes a diaphragm 321 (first diaphragm) and a piezoelectric element 322.

  The vibration plate 321 is made of a conductive material such as metal (for example, 42 alloy) or an insulating material such as resin (for example, liquid crystal polymer), and its planar shape is formed in a substantially circular shape. The “substantially circular” means not only a circular shape but also a substantially circular shape as described later. 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 may have a notch formed in a concave shape or a slit shape that is recessed from the outer periphery toward the inner periphery as necessary. Note that the planar shape of the diaphragm 321 is substantially circular if the rough shape is circular, even if it is not strictly circular due to the formation of the notch.

The diaphragm 321 has a first main surface 32 a that faces the sound guide path 41 and a second main surface 32 b that faces 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 32 a of the diaphragm 321.
The piezoelectric element 322 may be bonded to the second main surface 32b of the diaphragm 321 without being limited thereto. The piezoelectric sounding body 32 may have a bimorph structure in which piezoelectric elements are joined to both main surfaces 32 a and 32 b of the diaphragm 321.

  FIG. 3 is a plan view of the piezoelectric sounding body 32.

  As shown in FIG. 3, the planar shape of the piezoelectric element 322 is rectangular, and the central axis of the piezoelectric element 322 is typically arranged coaxially with the central axis C <b> 1 of the diaphragm 321. The center axis of the piezoelectric element 322 may be displaced by a predetermined amount, for example, in the X-axis direction from the center axis C1 of the diaphragm 321. That is, the piezoelectric element 322 may be disposed at a position eccentric with respect to the diaphragm 321. As a result, the vibration center of the diaphragm 321 is shifted to a position different from the center axis C 1, so that the vibration mode of the piezoelectric sounding body 32 is asymmetric with respect to the center axis C 1 of the diaphragm 321. Therefore, for example, by bringing the vibration center of the diaphragm 321 closer to the sound guide path 41, the sound pressure characteristics in the high sound range can be further improved.

  The diaphragm 321 has a plurality of passage portions 330 in its plane. These passage portions 330 constitute passage portions that penetrate the diaphragm 321 in the thickness direction (Z-axis direction), and include a first opening portion 331 and a second opening portion 332. The passage portion 330 allows the first space portion S1 and the second space portion S2 to communicate with each other inside the housing 40.

  The first opening 331 is provided between the peripheral edge 321c and the piezoelectric element 322, and is formed in a rectangular shape having a long side in the X-axis direction. The first opening 331 is formed along the peripheral edge of the piezoelectric element 322, and a part of the first opening 331 is partially covered by the peripheral edge of the piezoelectric element 322. The first opening 331 has a function of preventing a short circuit between two external electrodes of the piezoelectric element 322, as described later, in addition to a function as a passage penetrating the front and back of the diaphragm 321.

  The first opening 331 is an opening having the largest opening area among the plurality of openings constituting the passage portion 330. The number of the first openings 331 is not particularly limited, and may be one or two or more. In the present embodiment, an opening shape having a long side in the X-axis direction, which is provided directly below a pair of opposite sides facing the Y-axis direction of the piezoelectric element 322, is configured by a rectangular opening. .

  The second opening 332 includes a plurality of circular holes provided in a region between the peripheral edge 321 c of the diaphragm 321 and the piezoelectric element 322. These second openings 332 are respectively provided at positions symmetrical with respect to the central axis C1 (a total of four) on the central line CL (a line parallel to the X-axis direction passing through the center of the diaphragm 321). Each of the second openings 332 is formed by a round hole having the same diameter (for example, a diameter of about 1 mm), but is not limited thereto.

  In the present embodiment, as shown in FIG. 3, arc-shaped or rectangular recesses 321 a and 321 b are provided on the peripheral edge of the diaphragm 321 at intervals of 90 degrees. These recesses 321a and 321b may be used as a reference point to be referred to when the diaphragm 321 is joined to the housing 40 or the support member 50, or referred to for positioning the piezoelectric element 322 to the diaphragm 321. It may be used as a reference point. In particular, as shown in the drawing, one of the four recesses 321b has a shape different from that of the other three recesses 321a, so that a guide indicating the direction of the diaphragm 321 can be obtained. There is an advantage that assembly can be prevented.

  In the present embodiment, the sound guide port 41a is provided at a position that does not overlap (does not face) the first opening 331 in the Z-axis direction. In other words, the piezoelectric sounding body 32 is attached to the housing 40 so that the first opening 331 does not overlap the sound guide path 41a in the Z-axis direction. Thereby, as will be described later, the acoustic characteristics of the piezoelectric sounding body 32 can be improved. FIG. 3 shows an example in which the sound introduction port 41a is provided at a position where it overlaps (opposes) one of the second openings 332 in the Z-axis direction.

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

  The piezoelectric element 322 includes an element body 328 and a first external electrode 326a and a second external electrode 326b that face each other in the XY axis direction. In addition, the piezoelectric element 322 has a first main surface 322a and a second main surface 322b that are perpendicular to the Z-axis and face each other. The second main surface 322 b of the piezoelectric element 322 is configured as a mounting surface that faces the first main surface 32 a of the diaphragm 321.

  The element body 328 has a structure in which a ceramic sheet 323 and internal electrode layers 324a and 324b are stacked in the Z-axis direction. That is, the internal electrode layers 324a and 324b are alternately stacked with the ceramic sheet 323 interposed therebetween. The ceramic sheet 323 is made of, for example, 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 conductive materials such as various metal materials.

  The first internal electrode layer 324 a of the element body 328 is connected to the first external electrode 326 a and is insulated from the second external electrode 326 b by the margin portion of the ceramic sheet 323. The second internal electrode layer 324b of the element body 328 is connected to the second external electrode 326b and 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 of the element body 328 (the upper surface in FIG. 4), and the second internal electrode layer The lowermost 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 is interposed via an appropriate bonding material. It is electrically and mechanically connected to the first main surface 32a of the diaphragm 321. When the vibration plate 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 electrode is connected to the vibration plate. 321 can be provided.

  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 surfaces of the element body 328 in the X-axis direction. 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 connected to the second internal electrode layer 324b and the second extraction electrode It is electrically connected to the electrode layer 325b.

  With this configuration, when an AC voltage is applied between the external electrodes 326a and 326b, the ceramic sheets 323 between the internal electrode layers 324a and 324b expand and contract at a predetermined frequency. Thereby, the piezoelectric element 322 can generate vibration applied to the diaphragm 321.

  Here, as shown in FIG. 4, the first and second external electrodes 326 a and 326 b protrude from the both end surfaces of the element body 328, respectively. 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 first opening 331 described above is formed in a size that can accommodate the raised portions 329a and 329b. This prevents 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.

  The earphone 100 includes a support member 50 (support portion) that supports the piezoelectric sounding body 32 so as to vibrate inside the housing 40. FIG. 5 is a schematic plan view of the support member 50, and FIG. 6 is an exploded side sectional view of the sound generation unit 30 including the support member 50.

  The support member 50 is configured by a ring-shaped (annular) block body as shown in FIG. The support member 50 includes a support surface 51 that supports the peripheral portion 321c of the diaphragm 321 of the piezoelectric sounding body 32, an outer peripheral surface 52 that faces the inner wall surface of the housing 40, and an inner periphery that faces the first space S1. It has the surface 53, the front end surface 54 joined to the housing | casing 40 (2nd housing | casing part 402), and the bottom face 55 joined to the peripheral part of the electromagnetic sounding body 31. As shown in FIG.

  The support surface 51 is joined to the peripheral portion 321c of the vibration plate 321 via an annular adhesive material layer 61 (first adhesive material layer). Thereby, since the diaphragm 321 is elastically supported with respect to the support member 50, the vibration of the vibration of the diaphragm 321 is suppressed, and the stable resonance operation of the diaphragm 321 is ensured.

  Further, the front end surface 54 is joined to the inner peripheral edge of the second casing portion 402 via an annular pressure-sensitive adhesive layer 62 (second pressure-sensitive adhesive layer). The bottom surface 55 is joined to the electromagnetic sound producing body 31 via an annular adhesive material layer 63 (third adhesive material layer). Accordingly, since the support member 50 can be elastically sandwiched between the first housing portion 401 and the second housing portion 402, the piezoelectric sounding body 32 is stably supported by the support member 50. be able to.

  The pressure-sensitive adhesive layers 61 to 63 are made of a material having moderate elasticity, and are typically made of double-sided pressure-sensitive adhesive tapes each cut with a predetermined diameter. In addition to this, the pressure-sensitive adhesive layers 61 to 63 may be composed of a cured viscoelastic resin, a pressure-adhesive viscoelastic film, or the like. Further, the pressure-sensitive adhesive layers 61 to 63 are formed of an annular body, so that the airtightness between the electromagnetic sounding body 31 and the support member 50, the airtightness between the support member 50 and the diaphragm 321, and The airtightness between the support member 50 and the housing 40 is enhanced, and sound waves generated in the first and second space portions S1 and S2 can be efficiently guided to the sound guide path 41.

  The support member 50 is made of a material having a Young's modulus (longitudinal elastic modulus) of 3 GPa or more, for example. Since the support member 50 made of such a material can ensure a relatively high rigidity, the piezoelectric sounding body 31 (the diaphragm 321) that vibrates in a relatively high frequency band of 7 kHz or more can be stably supported. can do.

  The upper limit of the Young's modulus of the material constituting the support member 50 is not particularly limited. However, for example, a material alone of 5 GPa or more is almost limited to inorganic materials such as metals and ceramics. Can be set as appropriate, for example, 500 GPa or less. On the other hand, the support member 50 made of a synthetic resin material is advantageous in terms of weight reduction and productivity.

Examples of the material having a Young's modulus of 3 GPa or more include metal materials, ceramics, synthetic resin materials, and composite materials mainly composed of synthetic resin materials. As the metal material, in addition to ferrous materials such as rolled steel, stainless steel, and cast iron, non-ferrous materials such as aluminum and brass can be used without particular limitation. As the ceramic, an appropriate material such as SiC or Al ₂ O ₃ is applicable.

  Examples of the synthetic resin material include polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), polyacetal (POM), hard vinyl chloride, methyl methacrylate / styrene copolymer (MS), and the like. Even if it is a resin material such as polycarbonate (PC) or styrene / butadiene / acrylonitrile copolymer (ABS) that does not have a Young's modulus of 3 GPa or more, it can be made of fibers and inorganic particles such as glass fibers. It is possible to employ a composite material (reinforced plastic) having a Young's modulus (longitudinal elastic modulus) of 3 GPa or more to which a filler (filler) made of fine particles such as the above is added.

  The support member 50 may not be a simple plate material but may be formed in a three-dimensional shape having a different thickness depending on the region. Thereby, the cross-sectional secondary moment can be increased, and even if the material has the same Young's modulus, the rigidity (bending rigidity) can be further increased.

  For example, the support member 50 in the present embodiment is provided with an annular piece 56 (first annular piece) that protrudes upward along the outer peripheral edge of the support surface 51 and surrounds the peripheral edge 321 c of the diaphragm 321. (Refer to FIG. 6), and the tip surface 54 described above is formed on the top thereof. Thereby, since the outer peripheral side of the support member 50 is thicker than the inner peripheral side, the rigidity against twisting and bending is enhanced.

[Earphone operation]
Subsequently, a 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, a reproduction signal is input to the circuit board 33 of the sound generation unit 30 via the cable 50. The reproduction signal is input to the electromagnetic sounding body 31 and the piezoelectric sounding body 32 via the circuit board 33. Thereby, the electromagnetic sounding body 31 is driven, and a sound wave in a low frequency range of 7 kHz or less is mainly generated. On the other hand, in the piezoelectric sounding body 32, the diaphragm 321 vibrates due to the expansion / contraction operation of the piezoelectric element 322, and mainly high-frequency sound waves of 7 kHz or higher are generated. The generated sound wave of each band is 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 low-frequency sounding body and a high-frequency sounding body.

  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 portion S2 and the second space portion via the passage portion 330. It is formed by a synthesized wave with a sound wave component propagating to S2. Therefore, by optimizing the size and number of the passage portions 330, the low frequency sound wave output from the piezoelectric sounding body 32 has a frequency characteristic such that a sound pressure peak can be obtained in a predetermined low frequency band, for example. Adjustment or tuning is possible.

  According to the present embodiment, since the sound guide port 41a is provided at a position that does not overlap the first opening 331 of the piezoelectric sounding body 32 in the Z-axis direction, the sound pressure characteristics of the piezoelectric sounding body 32 are reduced. Improvements can be made.

  FIGS. 7 and 8 are experimental results showing the change in the sound pressure characteristics due to the difference in the relative position of the sound guide port 41 a with respect to the piezoelectric sounding body 32. In this experiment, the piezoelectric sounding body 32 shown in FIG. 3 was manufactured, and the relative position with respect to the sound inlet 41a was changed while rotating at a 15 ° pitch around the central axis C1 in the housing 40. An average sound pressure level (SPL: Sound Pressure Level) of 8 kHz to 20 kHz was measured. Here, the rotation position of the piezoelectric sounding body 32 shown in FIG. 8A was set to 0 °, and rotated clockwise 180 ° therefrom. In FIG. 7, the sound pressure level at each rotational position is shown as a difference from the average sound pressure level at 0 °.

The dimensions of each part of the piezoelectric sounding body 32 were as follows.
Diaphragm 321 diameter: 12 mm
Size of piezoelectric element 322: vertical (Y-axis direction dimension) 7 mm, horizontal (X-axis direction dimension) 7 mm
Size of first opening 331: length (dimension in the X-axis direction) 3.6 mm, width (dimension in the Y-axis direction) 0.5 mm
Diameter of second opening 332: 1 mm
Diameter of sound guide port 41a: 4.1 mm

  As shown in FIG. 7, it was confirmed that an average sound pressure level higher than 0 degrees can be obtained at all rotational positions other than 0 °. Since the piezoelectric sounding body 32 is symmetric with respect to the X axis (see FIG. 3), the sound pressure level at 180 ° is evaluated at the same value when it is substantially 0 degrees.

  In addition, the angle range indicated by R1 in FIG. 7 indicates a region where the overlap between the sound guide port 41a and the first opening 331 is not maximized, and the sound pressure level varies according to the rotational position in the angle range. I understand that In particular, the angle range (60 ° to 120 °) indicated by R2 corresponds to a region where the sound guide port 41a and the first opening 331 do not overlap in the Z-axis direction, and is higher than other angle ranges. It can be seen that the sound pressure level can be obtained.

  As described above, according to the present embodiment, since the sound introduction port 41a is disposed at a position that does not face the first opening 331, the electromagnetic sounding body 31 and the piezoelectric sounding body 32 as in the present embodiment. In the electroacoustic transducer 100 having the above, the sound generated by the electromagnetic sounding body 31 does not easily reach the sound guide path 41 directly. Thereby, the sound pressure level in the high sound range caused by the piezoelectric sounding body 32 can be relatively increased.

<Second Embodiment>
FIG. 9 is a plan view of a piezoelectric sounding body in the electroacoustic transducer according to the second embodiment of the present invention. Hereinafter, the configuration different from the first embodiment will be mainly described, and the same configuration as the first embodiment will be denoted by the same reference numeral, and the description thereof will be omitted or simplified.

  The piezoelectric sounding body 72 of this embodiment has two openings, a first opening 731 and a second opening 732 as a passage provided in the plane of the circular diaphragm 721. The first and second openings 731 and 732 also have a function as an opening for preventing a short circuit. The first opening 731 is formed with a larger opening area than the second opening 732.

  The first opening 731 is formed in a substantially semicircular or semilunar shape in a region between the peripheral edge 721 c of the diaphragm 721 and one side of the piezoelectric element 322. In this embodiment, as shown in FIG. 9, the piezoelectric sounding body 72 is assembled to the housing 40 so that the first opening 731 does not face the sound guide port 41a in the Z-axis direction. The second opening 732 is formed in a rectangular shape similar to the first opening 331 in the first embodiment.

  Four concave portions 721a and 721b are provided in the peripheral portion 721c of the diaphragm 721 at intervals of 90 °. These recesses 721 a and 721 b are used for positioning with respect to the housing 40. In particular, as shown in the drawing, one of the four recesses 721b has a shape different from that of the other three recesses 721a, so that a guide indicating the direction of the diaphragm 721 can be obtained. There is an advantage that assembly can be prevented.

  According to the electroacoustic transducer of the present embodiment configured as described above, the sound guide port 41a is provided at a position that does not overlap the first opening 331 of the piezoelectric sounding body 32 in the Z-axis direction. Therefore, the sound pressure characteristics of the piezoelectric sounding body 72 can be improved as in the first embodiment.

  10 and 11 are experimental results showing changes in sound pressure characteristics due to differences in the relative position of the sound guide port 41a with respect to the piezoelectric sounding body 72. FIG. In this experiment, the piezoelectric sounding body 72 shown in FIG. 9 was produced, and the relative position with respect to the sound inlet 41a was changed while rotating around the central axis C1 within the housing 40 at a pitch of 15 °. An average sound pressure level (SPL: Sound Pressure Level) of 8 kHz to 20 kHz was measured. Here, the rotation position of the piezoelectric sounding body 32 shown in FIG. 11A was set to 0 °, and was rotated 360 ° (one rotation) clockwise from here. In FIG. 10, the sound pressure level at each rotational position is shown as a difference from the average sound pressure level at 0 °.

The dimensions of each part of the piezoelectric sounding body 72 were as follows.
Diaphragm 721 diameter: 12 mm
Size of piezoelectric element 322: vertical (Y-axis direction dimension) 7 mm, horizontal (X-axis direction dimension) 7 mm
Size of first opening 731: length (maximum dimension in the X-axis direction) 6.1 mm, width (maximum dimension in the Y-axis direction) 1.6 mm
Diameter of second opening 332: 1 mm
Diameter of sound guide port 41a: 4.1 mm

  As shown in FIG. 10, it was confirmed that an average sound pressure level higher than 0 ° was obtained at all rotational positions other than 0 ° and 180 °.

  In addition, the angle range indicated by R1 in FIG. 10 indicates a region where the overlap between the sound guide port 41a and the first opening 731 is not maximized, and the sound pressure level varies in accordance with the rotational position in the angle range. I understand that In particular, the angle range (60 ° to 300 °) indicated by R2 corresponds to a region where the sound guide port 41a and the first opening 331 do not overlap in the Z-axis direction, and a relatively high sound pressure level is obtained. I understand that. In particular, it can be seen that the angle range indicated by R3 (about 100 ° to about 230 °) provides a higher sound pressure level than other angle ranges.

<Third Embodiment>
FIG. 12 is a plan view of a piezoelectric sounding body in an electroacoustic transducer according to the third embodiment of the present invention. Hereinafter, the configuration different from the first embodiment will be mainly described, and the same configuration as the first embodiment will be denoted by the same reference numeral, and the description thereof will be omitted or simplified.

  The piezoelectric sounding body 82 of this embodiment is different from the first embodiment in the configuration of the opening 831 constituting the passage portion 330. That is, the opening 831 is configured by a single through hole that penetrates the diaphragm 321 and the piezoelectric element 322 in the thickness direction (Z-axis direction). The opening 831 is provided at the center of the diaphragm 321 (piezoelectric sounding body 82). The opening shape of the opening 831 is not limited to the circular shape shown in the figure, and may be an ellipse, a rectangle, or other shapes.

  Also in the electroacoustic transducer of the present embodiment, the sound introduction port 41a is provided at a position that does not overlap the opening 831 of the piezoelectric sounding body 32 in the Z-axis direction. The opening 831 is formed in an appropriate size that does not overlap the sound guide port 41a in the Z-axis direction. Thereby, the effect similar to 1st Embodiment can be acquired.

  According to the present embodiment, since the opening 831 is formed in the central portion of the diaphragm 321 so as not to overlap the sound guide port 41a in the Z-axis direction, the relative position of the piezoelectric sounding body 82 with respect to the housing 40 Acoustic characteristics independent of (rotational position) can be obtained.

  Note that the opening 831 is not limited to being provided at the center of the diaphragm 321, and may be provided at a position other than the center of the diaphragm 321 as shown in FIG. 13, for example. In addition to the opening 831, another opening may be provided in the plane of the piezoelectric element 322, or as shown in FIG. 13, an opening 331 that also serves to prevent a short circuit of the external electrode of the piezoelectric element 322, and vibration An opening 332 (see FIG. 3) provided between the peripheral edge 321c of the plate 321 and the piezoelectric element 322 may be further provided in the diaphragm 321 (the same applies to FIG. 12).

  As mentioned above, although embodiment of this invention was described, this invention is not limited only to the above-mentioned embodiment, Of course, a various change can be added.

  For example, in the above embodiment, the electroacoustic transducer including both the electromagnetic sounding body 31 and the piezoelectric sounding bodies 32 and 72 has been described as an example. However, the electroacoustic conversion composed only of the piezoelectric sounding body is described. The present invention can also be applied to an apparatus.

  In the above embodiment, the earphone has been described as an example of the electroacoustic conversion device. However, the present invention is not limited to this, and the present invention can also be applied to headphones, stationary speakers, speakers built in portable information terminals, and the like. is there.

  Further, in the above embodiment, the support member 50 is provided as a support portion that supports the piezoelectric sounding body 32, but the support member 50 may be configured as a part of the housing 40 or the electromagnetic sounding body 31.

31 ... Electromagnetic sound generator 32, 72, 82 ... Piezoelectric sound generator 40 ... Housing 41a ... Sound inlet 100, 200 ... Earphone 321, 721 ... Diaphragm 322 ... Piezoelectric element 331, 731 ... First opening 332 732 ... second opening 831 ... opening 401 ... first casing 402 ... second casing

Claims (7)

A first diaphragm having a peripheral edge; a piezoelectric element disposed on at least one surface of the first diaphragm; and the first diaphragm provided around the piezoelectric element in a thickness direction thereof. A piezoelectric sounding body having a plurality of openings penetrating in the first axial direction;
The first opening and the first shaft, which are opposed to the supporting portion for supporting the peripheral portion, the piezoelectric sounding body in the first axial direction, and have the largest opening area among the plurality of openings. An electroacoustic transducer comprising: a sound guide opening provided at a position that does not overlap in the direction. The electroacoustic transducer according to claim 1,
The first opening is an electroacoustic transducer in which a part of the periphery of the piezoelectric element is covered. The electroacoustic transducer according to claim 2,
The first opening is an electroacoustic transducer including a pair of openings facing each other in a second axial direction orthogonal to the first axial direction. The electroacoustic transducer according to claim 3,
The plurality of openings include an electroacoustic transducer including a second opening that overlaps the sound guide opening in the first axial direction. The electroacoustic transducer according to claim 2,
The plurality of openings include an electroacoustic transducer including a second opening facing the first opening in a second axial direction orthogonal to the first axial direction. The electroacoustic transducer according to any one of claims 1 to 5,
An electromagnetic sounding body including a second diaphragm;
The housing is
A first space in which the electromagnetic sounding body is disposed;
An electroacoustic transducer comprising: a second space portion that communicates the first space portion with the sound guide port through the plurality of openings. A first diaphragm having a peripheral edge; a piezoelectric element disposed on at least one surface of the first diaphragm; and the first diaphragm and the piezoelectric element in the thickness direction thereof. A piezoelectric sounding body having an opening that penetrates in the axial direction;
A support portion for supporting the peripheral edge portion, and a sound guide port provided at a position facing the piezoelectric sounding body and the first axial direction so as not to overlap the opening portion and the first axial direction. An electroacoustic transducer comprising a housing having the same.

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