WO2020158173A1 - Electroacoustic transducer - Google Patents

Electroacoustic transducer Download PDF

Info

Publication number
WO2020158173A1
WO2020158173A1 PCT/JP2019/047186 JP2019047186W WO2020158173A1 WO 2020158173 A1 WO2020158173 A1 WO 2020158173A1 JP 2019047186 W JP2019047186 W JP 2019047186W WO 2020158173 A1 WO2020158173 A1 WO 2020158173A1
Authority
WO
WIPO (PCT)
Prior art keywords
piezoelectric
diaphragm
speaker
electroacoustic transducer
electromagnetic
Prior art date
Application number
PCT/JP2019/047186
Other languages
French (fr)
Japanese (ja)
Inventor
茂雄 石井
浜田　浩
幸弘 松井
富田　隆
Original Assignee
太陽誘電株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 太陽誘電株式会社 filed Critical 太陽誘電株式会社
Publication of WO2020158173A1 publication Critical patent/WO2020158173A1/en

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/24—Structural combinations of separate transducers or of two parts of the same transducer and responsive respectively to two or more frequency ranges
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/26—Spatial arrangements of separate transducers responsive to two or more frequency ranges
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R23/00—Transducers other than those covered by groups H04R9/00 - H04R21/00
    • H04R23/02—Transducers using more than one principle simultaneously

Definitions

  • the present invention relates to an electroacoustic transducer provided with an electromagnetic sounding body and a piezoelectric sounding body.
  • Piezoelectric sound element is widely used as a simple electro-acoustic conversion means, for example, it is often used as an acoustic device such as earphones or headphones, and as a speaker of a mobile information terminal.
  • the piezoelectric sounding element typically has a structure in which a piezoelectric element is attached to one side or both sides of a diaphragm (see, for example, Patent Document 1).
  • Patent Document 2 describes a headphone that includes a dynamic driver and a piezoelectric driver, and can drive 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 cause the piezoelectric driver to function as a driver for the high range.
  • Patent Document 3 describes an electroacoustic transducer that includes an electromagnetic sounding body and a piezoelectric sounding body, and uses the electromagnetic sounding body for a low sound range and the piezoelectric sounding body for a high sound range.
  • This electroacoustic transducer has a piezoelectric speaker or a passage around it, and adjusts the sound wave output from the piezoelectric speaker to a desired frequency characteristic by optimizing the size and number of the passages. Can be configured.
  • an object of the present invention is to provide an electroacoustic transducer that can improve the acoustic characteristics while reducing the size of the device.
  • an electroacoustic transducer includes an electromagnetic sounding body and a piezoelectric sounding body.
  • the piezoelectric sounding bodies are driven in mutually opposite phases with respect to the electromagnetic sounding body.
  • the electroacoustic transducer is configured so that the piezoelectric sounding body is driven in antiphase with respect to the electromagnetic sounding body. As a result, even if the piezoelectric speaker has a relatively small diameter, the sound pressure dip phenomenon near the crossover frequency can be suppressed, and the acoustic characteristics can be improved.
  • the piezoelectric speaker may have a circular diaphragm and a piezoelectric element arranged on at least one surface of the diaphragm.
  • the diaphragm is bonded to the piezoelectric element so as to be electrically connected to the negative electrode of the piezoelectric element.
  • the positive electrode of the electromagnetic speaker is electrically connected to the diaphragm, and the negative electrode of the electromagnetic speaker is electrically connected to the positive electrode of the piezoelectric element.
  • the diameter of the diaphragm is typically 8 mm or less.
  • the electroacoustic conversion device may further include a housing.
  • the housing has a sound guide and accommodates the sounding unit.
  • the piezoelectric speaker is arranged between the sound guide port and the electromagnetic speaker.
  • the casing may further include a support portion that supports a peripheral portion of the diaphragm.
  • the supporting area of the diaphragm in the supporting portion is 49% or less of the area of the diaphragm.
  • an earphone will be described as an example of the electroacoustic transducer.
  • the earphones have the same configuration on the right (R) side and the left (L) side, respectively.
  • the R side earphone will be described as an example.
  • FIG. 1 is a sectional view showing the configuration of the earphone 100.
  • FIG. 2 is an enlarged cross-sectional view of a part of FIG. 1
  • FIG. 3 is a cross-sectional view showing an exploded part of the structure of earphone 100.
  • the X direction, the Y direction, and the Z direction are three directions orthogonal to each other.
  • 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 is configured to be attached to the user's ear.
  • the earphone body 10 has a sounding unit 30 and a housing 40 that houses the sounding unit 30.
  • the sounding unit 30 has an electromagnetic sounding body 31 and a piezoelectric sounding body 32.
  • the housing 40 has an internal space for accommodating the sounding unit 30, and has a two-part structure that is separable in the Z-axis direction.
  • the housing 40 is composed of a combined body of a first housing portion 401 and a second housing portion 402.
  • the first housing portion 401 forms a housing space for housing the sounding unit 30 therein.
  • the first housing unit 401 also includes a sound guide path 41 that guides the sound waves generated by the sounding unit 30 to the outside.
  • the sound guide path 41 has a sound guide port 41a at its base end (the end opposite to the tip where the earpiece 20 is mounted).
  • the sound wave generated by the sounding unit 30 travels through the sound guide path 41 via the sound guide port 41a, passes through the earpiece 20, and is emitted.
  • the tubular lead portion 42 is provided on the second housing portion 402. Wires (not shown) for transmitting audio signals to the electromagnetic speaker 31 and the piezoelectric speaker 32 are inserted through the lead portion 42.
  • the electromagnetic speaker 31 is composed of a dynamic speaker unit that functions as a woofer that reproduces a low sound range.
  • a dynamic speaker that mainly generates sound waves of 7 kHz or less, and as shown in FIGS. 2 and 3, a mechanism unit 311 including a vibrating body such as a voice coil motor (electromagnetic coil), and a mechanism unit. And a pedestal portion 312 that supports the vibration element 311.
  • the mechanical unit 311 is composed of a diaphragm, a permanent magnet, a voice coil, and the like.
  • a current voice signal
  • an electromagnetic force acts on the voice coil and the voice coil vibrates according to the signal waveform. This vibration is transmitted to the diaphragm connected to the voice coil, and a sound wave is generated.
  • One end of the voice coil corresponds to the positive electrode of the electromagnetic speaker 31, and the other end of the voice coil corresponds to the negative electrode of the electromagnetic speaker 31.
  • the electromagnetic speaker 31 is labeled with a positive electrode and a negative electrode.
  • the positive electrode of the electromagnetic speaker 31 is electrically connected to the diaphragm 321 of the piezoelectric speaker 32, and the negative electrode of the electromagnetic speaker 31 is electrically connected to the positive electrode of the piezoelectric element 322 of the piezoelectric speaker 32. Connected to each other.
  • the piezoelectric speaker 32 is arranged between the sound guide port 41 a and the electromagnetic speaker 31.
  • the piezoelectric speaker 32 constitutes a speaker unit that functions as a tweeter that reproduces a high range.
  • the oscillation frequency is set so as to mainly generate a sound wave of, for example, 7 kHz or more.
  • the piezoelectric speaker 32 has a diaphragm 321 and a piezoelectric element 322.
  • the diaphragm 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 into a substantially circular shape.
  • the term “substantially circular” means not only a circular shape but also a substantially circular shape.
  • the outer diameter and the 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.
  • the vibration plate 321 is made of a conductive material and is joined to the piezoelectric element 322 so as to be electrically connected to the negative electrode of the piezoelectric element 322.
  • the diaphragm 321 has a diameter of 12 mm or less, preferably 8 mm or less. This makes it possible to reduce the size of the piezoelectric sounding body 32, and further reduce the size of the sounding unit 30 and the housing 40.
  • the lower limit of the thickness of the diaphragm 321 is not particularly limited as long as desired acoustic characteristics are obtained, and is, for example, 6 mm, but may be less than 6 mm.
  • the thickness of the diaphragm 321 is, for example, about 0.1 to 0.175 mm. In this embodiment, the diaphragm 321 has a diameter of 8 mm and a thickness of 0.05 to 0.1 mm.
  • the diaphragm 321 may have a notch formed in a concave shape or a slit shape that is recessed from the outer circumference toward the inner circumference side, if necessary. It should be noted that the planar shape of the diaphragm 321 is substantially circular even if it is not strictly circular due to the formation of the cutout portion and the like if the outline is circular. Further, the diaphragm 321 may be provided with a hole through which a sound wave generated by the electromagnetic speaker 31 passes.
  • the diaphragm 321 has a first main surface 32a that faces the sound guide port 41a and a second main surface 32b that faces the electromagnetic speaker 31.
  • the piezoelectric speaker 32 has a unimorph structure in which the piezoelectric element 322 is bonded only to the first main surface 32a of the vibration plate 321.
  • the piezoelectric element 322 is not limited to this, and may be joined to the second main surface 32b of the vibration plate 321.
  • the piezoelectric speaker 32 may have a bimorph structure in which piezoelectric elements are bonded to both main surfaces 32a and 32b of the vibration plate 321.
  • FIG. 4 is a plan view of the piezoelectric speaker 32.
  • the piezoelectric element 322 has a rectangular planar shape, and the central axis of the piezoelectric element 322 is typically arranged coaxially with the central axis C1 of the diaphragm 321.
  • the invention is not limited to this, and the central axis of the piezoelectric element 322 may be displaced from the central axis C1 of the vibration plate 321 by a predetermined amount in the X-axis direction, for example. That is, the piezoelectric element 322 may be arranged at a position eccentric to the vibration plate 321.
  • the diaphragm 321 has a plurality of passages 330 in its surface. These passages 330 penetrate the diaphragm 321 in the thickness direction and include a first opening 331 and a second opening 332.
  • the passage portion 330 is a sound passage that guides the sound generated by the electromagnetic speaker 31 to the sound guide 41.
  • the first opening 331 is composed of a plurality of circular holes provided in a region between the peripheral portion 321c of the vibration plate 321 and the piezoelectric element 322.
  • the first openings 331 are provided at positions symmetrical with respect to the central axis C1 on the central line CL (a line that passes through the center of the diaphragm 321 and is parallel to the Y-axis direction).
  • Each of the first openings 331 is formed of a round hole having the same diameter (for example, a diameter of about 1 mm), but it is not limited to this. Note that the opening 331 may not be formed if desired acoustic characteristics are obtained.
  • the second opening 332 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 Y-axis direction.
  • the second openings 332 are formed along the peripheral edge of the piezoelectric element 322, and a part of them is partially covered by the peripheral edge of the piezoelectric element 322.
  • the second opening 332 has a function as a passage that penetrates the front and back of the vibration plate 321, and also has a function of preventing a short circuit between two external electrodes of the piezoelectric element 322.
  • FIG. 5 is a schematic sectional view showing the internal structure of the piezoelectric element 322.
  • the piezoelectric element 322 has an element body 328, and a first external electrode 326a and a second external electrode 326b facing each other in the XY directions. Further, the piezoelectric element 322 has a first main surface 322a and a second main surface 322b which are opposed to each other and are perpendicular to the Z direction.
  • the second main surface 322b of the piezoelectric element 322 is configured as a mounting surface facing the first main surface 32a of the vibration plate 321.
  • the element body 328 has a structure in which a ceramic sheet 323 and internal electrode layers 324a and 324b are laminated in the Z direction. That is, the internal electrode layers 324a and 324b are alternately laminated with the ceramic sheets 323 sandwiched therebetween.
  • the ceramic sheet 323 is made of, for example, a piezoelectric material such as lead zirconate titanate (PZT) or 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 inner electrode layer 324a of the element body 328 is connected to the first outer electrode 326a and is insulated from the second outer electrode 326b by the margin portion of the ceramic sheet 323.
  • the second inner electrode layer 324b of the element body 328 is connected to the second outer electrode 326b and is insulated from the first outer electrode 326a by the margin portion of the ceramic sheet 323.
  • the uppermost layer of the first internal electrode layer 324a constitutes a first extraction electrode layer 325a that partially covers the surface (the upper surface in FIG. 5) of the element body 328, and the lowermost layer of the second internal electrode layer 324b. Form a second extraction electrode layer 325b that partially covers the back surface (lower surface in FIG. 5) of the element body 328.
  • the first extraction electrode layer 325a has a terminal portion 327a of one pole that is electrically connected to the wiring board 70 described later, and the second extraction electrode layer 325b is a diaphragm through an appropriate bonding material. It is electrically and mechanically connected to the first main surface 32a of 321.
  • a conductive bonding material such as a conductive adhesive or solder may be used as the bonding material.
  • the terminal portion of the other pole is used as the vibration plate. 321 can be provided.
  • the side to which a positive voltage is applied during polarization is the positive electrode
  • the side to which a negative voltage is applied during polarization is the negative electrode
  • the side joined to the vibration plate 321 is the negative electrode. Therefore, in the present embodiment, the first extraction electrode layer 325a corresponds to the positive electrode of the piezoelectric element 322, and the second extraction electrode layer 325b corresponds to the negative electrode of the piezoelectric element 322.
  • the terminal portion 327a corresponds to the positive electrode of the piezoelectric speaker 32, and the diaphragm 321 electrically connected to the second lead electrode layer 325a corresponds to the negative electrode of the piezoelectric speaker 32.
  • the first and second external electrodes 326a and 326b are formed of a conductive material such as various metal materials at approximately the center of both end surfaces of the element body 328 in the X direction.
  • the first outer electrode 326a is electrically connected to the first inner electrode layer 324a and the first lead electrode layer 325a
  • the second outer electrode 326b is the second inner electrode layer 324b and the second lead electrode layer 324b. It is electrically connected to the electrode layer 325b.
  • the piezoelectric element 322 can generate the vibration applied to the vibration plate 321.
  • the earphone body 10 includes a mount member 51 as shown in FIG. 3 in addition to the electromagnetic speaker 31 and the piezoelectric speaker 32.
  • the mount member 51 fixes the electromagnetic speaker 31 and the piezoelectric speaker 32 to the housing 40.
  • the mount member 51 is an annular member including a support portion 51a and a peripheral wall portion 51b, and is made of a material such as metal or synthetic resin.
  • the gap between the electromagnetic speaker 31 and the piezoelectric speaker 32 is not particularly limited and is 0.1 mm or more and 0.7 mm or less, preferably 0.2 mm or more and 0.3 mm or less. If the gap is too large, the sound pressure of both the electromagnetic sounding body 31 and the piezoelectric sounding body 32 tends to decrease.
  • the distance between the piezoelectric speaker 32 and the tip of the sound guide port 41a is not particularly limited, and is, for example, 5 mm or more and 7 mm or less in the present embodiment.
  • the peripheral portion of the second main surface 32b of the diaphragm 321 is joined to the surface of the support portion 51a on the sound guide port 41a side via the first support member 61.
  • the mechanism portion 311 is joined to the surface of the support portion 51a opposite to the sound guide port 41a via the second support member 62.
  • the first support member 61 and the second support member 62 are composed of, for example, an annular adhesive tape (double-sided tape) or an adhesive layer. Since the vibration plate 321 of the piezoelectric speaker 32 is joined to the mount member 51 via the first support member 61 having adhesiveness, the vibration plate 321 is elastically supported with respect to the mount member 51. The shake of the resonance of the diaphragm 321 is suppressed, and the stable resonance operation of the diaphragm 321 is secured.
  • the mount member 51 is made of, for example, a material having a Young's modulus (longitudinal elastic modulus) of 3 GPa or more. Since the mount member 51 made of such a material can secure a relatively high rigidity, it stably supports the piezoelectric speaker 32 (vibration plate 321) vibrating in a relatively high frequency band of 7 kHz or higher. can do.
  • the upper limit of the Young's modulus of the material forming the mount member 51 is not particularly limited, for example, a single material of 5 GPa or more is almost limited to an inorganic material such as metal or ceramics, and therefore the upper limit is taken into consideration in consideration of weight and production cost. Can be appropriately set, and can be set to, for example, 500 GPa or less. On the other hand, the mount member 51 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.
  • metal material iron-based materials such as rolled steel, stainless steel, cast iron, and non-ferrous materials such as aluminum and brass can be used without particular limitation.
  • ceramics an appropriate material such as SiC or Al 2 O 3 can be applied.
  • Examples of synthetic resin materials include polyphenylene sulfide (PPS), polymethylmethacrylate (PMMA), polyacetal (POM), rigid vinyl chloride, methylmethacrylate/styrene copolymer (MS), and the like.
  • 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 as a single substance may have a fiber material such as glass fiber or inorganic particles.
  • 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 is added, can be used.
  • the mount member 51 is not a simple plate material, but is formed of a three-dimensional shape having different thicknesses depending on regions as shown in the figure, so that the second moment of area can be increased and the material has the same Young's modulus. However, the rigidity (bending rigidity) can be further increased.
  • the peripheral wall portion 51b projects from the outer peripheral edge portion of the support portion 51a to the sound guide port 41a side, and the tip portion thereof is joined to the first housing portion 401.
  • the peripheral wall portion 51b is joined to the first housing portion 401, for example, by fitting into the groove provided in the first housing portion 401.
  • FIG. 6 is a schematic diagram showing a wiring structure of the earphone 100.
  • the earphone 100 includes a plug 80 connected to the jack 510 of the electronic device 500 that outputs a sound signal.
  • the plug 80 is electrically connected to the wiring board 70 via the wiring cable 72, and the wiring board 70 has a wiring circuit electrically connected to the sounding unit 30.
  • the wiring board 70 may be arranged at an appropriate position inside the housing 40, and is attached to the pedestal portion 312 of the electromagnetic speaker 31 in the present embodiment (see FIG. 1 ).
  • the wiring board 70 includes a first wiring 71a connected to the positive electrode 31p of the electromagnetic speaker 31 and the vibration plate 321 as the negative electrode of the piezoelectric speaker 32, the negative electrode 31n of the electromagnetic speaker 31, and the piezoelectric speaker 32.
  • the first wiring 71a and the second wiring 71b are composed of a wiring pattern on the wiring board 70 and wiring that connects the wiring pattern with the electromagnetic speaker 31 and the piezoelectric speaker 32.
  • the piezoelectric speaker 32 is configured to be driven in the opposite phase to the electromagnetic speaker 31.
  • the resistance element 73 connected between the positive electrode 31p of the electromagnetic speaker 31 and the negative electrode (vibration plate 321) of the piezoelectric speaker 32 is a protection resistor for preventing oscillation, and is omitted as necessary. May be.
  • the plug 80 has a first positive electrode portion 80p1 connected to the positive electrode of the R side earphone, a second positive electrode portion 80p2 connected to the positive electrode of the L side earphone (not shown), and a negative electrode of the R side and L side earphones. It has the negative electrode part 80n connected in common. The negative electrode portion 80n also serves as a ground terminal.
  • the wiring cable 72 includes a first cable 72p that electrically connects the first wiring 71a of the wiring board 70 and the first positive electrode portion 80p1 of the plug 80, a second wiring 71b of the wiring board 70, and the plug 80.
  • the second cable 72n that electrically connects the negative electrode portion 80n with the second cable 72n.
  • a reproduction signal is input to the sounding unit 30 via the wiring cable 72.
  • the reproduction signal is input to each of the electromagnetic speaker 31 and the piezoelectric speaker 32 via the wiring board 70.
  • the electromagnetic speaker 31 is driven to generate a sound wave mainly in the low frequency range of 7 kHz or less.
  • the piezoelectric speaker 32 the vibrating plate 321 vibrates due to the expansion and contraction operation of the piezoelectric element 322, and a sound wave in a high sound range of 7 kHz or higher is generated.
  • the generated sound waves of each band are transmitted to the user's ear via the sound guide port 41a.
  • the earphone 100 functions as a hybrid speaker having a sounding body for a low sound range and a sounding body for a high sound range.
  • FIG. 7 shows an example of acoustic characteristics of an electroacoustic transducer according to a comparative example.
  • This comparative example has the same configuration as the earphone 100 shown in FIG. 1, but is different from the present embodiment in that the piezoelectric sounding body is configured to be driven in the same phase as the electromagnetic sounding body. different. That is, in the comparative example, among the wiring cables 72 in FIG. 6, the first cable 72p on the positive electrode side is connected to the positive electrode 31p of the electromagnetic speaker 31 and the piezoelectric element 322 as the positive electrode of the piezoelectric speaker 32, and the negative electrode is connected to the negative electrode. The second cable 72n on the side is connected to the negative electrode 31n of the electromagnetic speaker 31 and the diaphragm 321 as the negative electrode of the piezoelectric speaker 32.
  • the horizontal axis represents frequency and the vertical axis represents sound pressure level.
  • the two-dot chain line shows sound pressure characteristics when only the electromagnetic sounding body is driven, and the broken line shows when only the piezoelectric sounding body is driven.
  • the sound pressure characteristic and the thick solid line respectively show the sound pressure characteristic when the electromagnetic sounding body and the piezoelectric sounding body are simultaneously driven.
  • the diameter of the diaphragm of the piezoelectric speaker was 8 mm, the thickness was 100 ⁇ m, and the material was 42 alloy alloy.
  • the electromagnetic speaker a dynamic speaker having a diaphragm diameter of 9 mm and a load impedance of 16 ⁇ was used.
  • the sound pressure is significantly reduced in the frequency band (10 kHz to 20 kHz) corresponding to the crossover frequency during simultaneous driving.
  • FIG. 8 shows an example of the acoustic characteristics of the earphone 100 of this embodiment.
  • the horizontal axis, the vertical axis, the alternate long and two short dashes line, the broken line, and the thick solid line in the figure are the same as those in FIG.
  • the vibration plate 321 of the piezoelectric speaker 32 has the same structure as that of the comparative example.
  • the decrease in sound pressure near the crossover frequency is significantly suppressed as compared with the comparative example.
  • phase matching between the electromagnetic sounding body 31 and the piezoelectric sounding body 32 can be achieved, and crossing can be achieved as compared with the case of the comparative example.
  • the decrease in sound pressure near the over frequency was alleviated.
  • the inventor has confirmed that the same effect can be obtained when the diameter of the diaphragm 321 of the piezoelectric speaker 32 is 6 mm.
  • the piezoelectric speaker 32 by driving the piezoelectric speaker 32 in the opposite phase with respect to the electromagnetic speaker 31, even in the case where the piezoelectric speaker 32 has a relatively small diameter, the piezoelectric speaker 32 is in the vicinity of the crossover frequency. It is possible to suppress the sound pressure dip phenomenon and improve the acoustic characteristics. This makes it possible to improve the acoustic characteristics while reducing the size of the device.
  • the supporting area of the diaphragm 321 in the supporting portion 51a of the mount member 51 is 49% or less of the area of the diaphragm 321.
  • the area ratio between the area of the diaphragm 321 and the supporting portion 51a is 2.4.
  • the piezoelectric speaker 32 has been described by taking the unimorph structure as an example, but a bimorph structure in which the piezoelectric elements 322A and 322B are arranged on both surfaces of the diaphragm 321 as shown in FIG. 9 is also applied. It is possible. In this case, a drive signal having a phase opposite to that of the electromagnetic speaker is input to each piezoelectric element 322A, 322B, and at this time, each piezoelectric element 322A, 322B has a vibration mode in which one expands and the other expands. The diaphragm 321 is vibrated by.
  • FIG. 10 is a result of an experiment showing the acoustic characteristics of the earphone including the piezoelectric speaker with the bimorph structure, and the solid line shows the sound pressure characteristics when the electromagnetic speaker and the piezoelectric speaker are driven in opposite phases. , The alternate long and short dash line shows the sound pressure characteristics when these are driven in the same phase.
  • the diameter of the diaphragm of the piezoelectric speaker is 8 mm.
  • earphones are taken as an example of the electroacoustic transducer, but the present invention is not limited to this, and the present invention is also applicable to headphones, stationary speakers, speakers incorporated in portable information terminals, and the like. is there.
  • Electromagnetic sounding body 32 Piezoelectric sounding body 40... Housing 41a... Sound inlet 51... Mounting member 70... Wiring board 72... Wiring cable 80... Plug 321... Vibration Plates 322, 322A, 322B... Piezoelectric element

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
  • Headphones And Earphones (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)

Abstract

An electroacoustic transducer according to one embodiment of the present invention comprises a magnetic sound generator and a piezoelectric sound generator. The piezoelectric sound generator is connected so as to be driven in an opposite phase to the magnetic sound generator. Thus, it is possible to suppress a sound pressure dip in the vicinity of a crossover frequency even when the piezoelectric sound generator is of a relatively small diameter and improve acoustic characteristics.

Description

電気音響変換装置Electro-acoustic transducer
　本発明は、電磁式発音体と圧電式発音体とを備えた電気音響変換装置に関する。 The present invention relates to an electroacoustic transducer provided with an electromagnetic sounding body and a piezoelectric sounding body.
　圧電発音素子は、簡易な電気音響変換手段として広く利用されており、例えば、イヤホンあるいはヘッドホンのような音響機器、さらには携帯情報端末のスピーカなどとして多用されている。圧電発音素子は、典型的には、振動板の片面あるいは両面に圧電素子を貼り合わせた構成を有する（例えば特許文献１参照）。 Piezoelectric sound element is widely used as a simple electro-acoustic conversion means, for example, it is often used as an acoustic device such as earphones or headphones, and as a speaker of a mobile information terminal. The piezoelectric sounding element typically has a structure in which a piezoelectric element is attached to one side or both sides of a diaphragm (see, for example, Patent Document 1).
　一方、特許文献２には、ダイナミック型ドライバと圧電型ドライバとを備え、これら２つのドライバを並列駆動させることで帯域幅の広い再生を可能としたヘッドホンが記載されている。上記圧電型ドライバは、ダイナミック型ドライバの前面を閉塞し振動板として機能するフロントカバーの内面中央部に設けられており、この圧電型ドライバを高音域用ドライバとして機能させるように構成されている。 On the other hand, Patent Document 2 describes a headphone that includes a dynamic driver and a piezoelectric driver, and can drive 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 cause the piezoelectric driver to function as a driver for the high range.
　特許文献３には、電磁式発音体と圧電式発音体を備え、電磁式発音体を低音域用に、圧電式発音体を高音域用に用いる電気音響変換装置が記載されている。この電気音響変換装置は、圧電式発音体又はその周囲に通路部を有し、通路部の大きさや個数を最適化することにより圧電式発音体から出力される音波を所望の周波数特性に調整することが可能に構成される。 Patent Document 3 describes an electroacoustic transducer that includes an electromagnetic sounding body and a piezoelectric sounding body, and uses the electromagnetic sounding body for a low sound range and the piezoelectric sounding body for a high sound range. This electroacoustic transducer has a piezoelectric speaker or a passage around it, and adjusts the sound wave output from the piezoelectric speaker to a desired frequency characteristic by optimizing the size and number of the passages. Can be configured.
特開２０１３－１５０３０５号公報JP, 2013-150305, A 実開昭６２－６８４００号公報Japanese Utility Model Publication No. 62-68400 特許第５７５９６４１号公報Japanese Patent No. 5759641
　近年、イヤホンやヘッドホン等の音響機器においては、小型化及び音質の更なる向上が求められている。しかしながら、機器の小型化は発音体の小型化を伴うため、特に圧電式発音体においては音圧特性が低下する傾向にある。このため、電磁式発音体と圧電式発音体とを備えた電気音響変換装置においては、電磁式発音体からの再生音の音圧レベルと圧電式発音体からの再生音の音圧レベルとが相互に交差する周波数（以下、クロスオーバ周波数ともいう）付近で、２つの再生音の合成音圧レベルが急激に低下する現象（ディップ）が生じやすいという問題がある。 In recent years, audio equipment such as earphones and headphones have been required to be smaller and have a higher sound quality. However, downsizing of the device accompanies downsizing of the sounding body, so that the sound pressure characteristic tends to deteriorate particularly in the piezoelectric sounding body. Therefore, in the electroacoustic transducer including the electromagnetic speaker and the piezoelectric speaker, the sound pressure level of the reproduced sound from the electromagnetic speaker and the sound pressure level of the reproduced sound from the piezoelectric speaker are different. There is a problem that a phenomenon (a dip) in which the synthesized sound pressure level of two reproduced sounds sharply decreases in the vicinity of a frequency (hereinafter, also referred to as a crossover frequency) crossing each other is likely to occur.
　以上のような事情に鑑み、本発明の目的は、機器の小型化を図りつつ、音響特性の改善を図ることができる電気音響変換装置を提供することにある。 In view of the above circumstances, an object of the present invention is to provide an electroacoustic transducer that can improve the acoustic characteristics while reducing the size of the device.
　上記目的を達成するため、本発明の一形態に係る電気音響変換装置は、電磁式発音体と、圧電式発音体とを具備する。
　前記圧電式発音体は、前記電磁式発音体に対して相互に逆位相で駆動する。 In order to achieve the above object, an electroacoustic transducer according to one aspect of the present invention includes an electromagnetic sounding body and a piezoelectric sounding body.
The piezoelectric sounding bodies are driven in mutually opposite phases with respect to the electromagnetic sounding body.
　上記電気音響変換装置は、圧電式発音体が電磁式発音体に対して逆位相で駆動するように構成されている。これにより、圧電式発音体が比較的小径の場合でもクロスオーバ周波数付近における音圧のディップ現象を抑制し、音響特性の改善を図ることができる。 The electroacoustic transducer is configured so that the piezoelectric sounding body is driven in antiphase with respect to the electromagnetic sounding body. As a result, even if the piezoelectric speaker has a relatively small diameter, the sound pressure dip phenomenon near the crossover frequency can be suppressed, and the acoustic characteristics can be improved.
　前記圧電式発音体は、円形の振動板と、前記振動板の少なくとも一方の面に配置された圧電素子とを有してもよい。この場合、前記振動板は、前記圧電素子の負極と電気的に接続されるように、前記圧電素子と接合される。前記電磁式発音体の正極は前記振動板に電気的に接続され、前記電磁式発音体の負極は前記圧電素子の正極に電気的に接続されている。 The piezoelectric speaker may have a circular diaphragm and a piezoelectric element arranged on at least one surface of the diaphragm. In this case, the diaphragm is bonded to the piezoelectric element so as to be electrically connected to the negative electrode of the piezoelectric element. The positive electrode of the electromagnetic speaker is electrically connected to the diaphragm, and the negative electrode of the electromagnetic speaker is electrically connected to the positive electrode of the piezoelectric element.
　前記振動板の直径は、典型的には、８ｍｍ以下である。 The diameter of the diaphragm is typically 8 mm or less.
　前記電気音響変換装置は、筐体をさらに具備してもよい。前記筐体は、導音口を有し、前記発音ユニットを収容する。前記圧電式発音体は、前記導音口と前記電磁式発音体との間に配置される。 The electroacoustic conversion device may further include a housing. The housing has a sound guide and accommodates the sounding unit. The piezoelectric speaker is arranged between the sound guide port and the electromagnetic speaker.
　前記筐体は、前記振動板の周縁部を支持する支持部をさらに有してもよい。前記支持部における前記振動板の支持面積は、前記振動板の面積の４９％以下である。 The casing may further include a support portion that supports a peripheral portion of the diaphragm. The supporting area of the diaphragm in the supporting portion is 49% or less of the area of the diaphragm.
　以上述べたように、本発明によれば、機器の小型化を図りつつ、音響特性の改善を図ることができる。 As described above, according to the present invention, it is possible to improve the acoustic characteristics while reducing the size of the device.
本発明の一実施形態に係る電気音響変換装置の断面図である。It is sectional drawing of the electroacoustic transducer which concerns on one Embodiment of this invention. 同電気音響変換装置の拡大断面図である。It is an expanded sectional view of the same electroacoustic transducer. 同電気音響変換装置の分解断面図である。It is an exploded sectional view of the same electroacoustic transducer. 同電気音響変換装置が備える圧電発音体の概略平面図である。It is a schematic plan view of a piezoelectric speaker provided in the same electroacoustic transducer. 同圧電発音体の断面図である。It is sectional drawing of the same piezoelectric sounding body. 同電気音響変換装置における発音ユニットの電気的接続関係の一例を示す図である。It is a figure which shows an example of the electrical connection relationship of the sound generation unit in the same electroacoustic converter. 比較例に係る電気音響変換装置の音響特性の一例を示す図である。It is a figure which shows an example of the acoustic characteristic of the electroacoustic converter which concerns on a comparative example. 本発明の一実施形態に係る電気音響変換装置の音響特性の一例を示す図である。It is a figure which shows an example of the acoustic characteristic of the electroacoustic transducer which concerns on one Embodiment of this invention. 本発明の他の実施形態に係る電気音響変換装置における圧電式発音体の構成を示す側断面図である。It is a sectional side view which shows the structure of the piezoelectric speaker in the electroacoustic transducer which concerns on other embodiment of this invention. 図８の電気音響変換装置の音響特性を比較例ととともに示す実験結果である。It is an experimental result which shows the acoustic characteristic of the electroacoustic transducer of FIG. 8 with a comparative example.
　以下、図面を参照しながら、本発明の実施形態を説明する。本実施形態では、電気音響変換装置としてイヤホンを例に挙げて説明する。イヤホンは、右（Ｒ）側及び左（Ｌ）側でそれぞれ同一の構成を有し、本実施形態ではＲ側のイヤホンを例に挙げて説明する。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an earphone will be described as an example of the electroacoustic transducer. The earphones have the same configuration on the right (R) side and the left (L) side, respectively. In the present embodiment, the R side earphone will be described as an example.
［イヤホンの全体構成］
　図１は、イヤホン１００の構成を示す断面図である。図２は図１の一部を拡大した断面図であり、図３は、イヤホン１００の一部の構成を分解して示す断面図である。なお、以下の各図においてＸ方向、Ｙ方向及びＺ方向を相互に直交する３方向とする。 [Overall configuration of earphones]
FIG. 1 is a sectional view showing the configuration of the earphone 100. FIG. 2 is an enlarged cross-sectional view of a part of FIG. 1, and FIG. 3 is a cross-sectional view showing an exploded part of the structure of earphone 100. In each of the following drawings, the X direction, the Y direction, and the Z direction are three directions orthogonal to each other.
　イヤホン１００は、イヤホン本体１０と、イヤピース２０とを有する。イヤピース２０は、イヤホン本体１０の導音路４１に取り付けられ、ユーザの耳に装着可能に構成されている。 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 is configured to be attached to the user's ear.
　イヤホン本体１０は、発音ユニット３０と、発音ユニット３０を収容する筐体４０とを有する。発音ユニット３０は、電磁式発音体３１と、圧電式発音体３２とを有する。 The earphone body 10 has a sounding unit 30 and a housing 40 that houses the sounding unit 30. The sounding unit 30 has an electromagnetic sounding body 31 and a piezoelectric sounding body 32.
　（筐体）
　筐体４０は、発音ユニット３０を収容する内部空間を有し、Ｚ軸方向に分離可能な２分割構造で構成される。 (Case)
The housing 40 has an internal space for accommodating the sounding unit 30, and has a two-part structure that is separable in the Z-axis direction.
　図１に示すように、筐体４０は、第１の筐体部４０１と第２の筐体部４０２との結合体で構成される。第１の筐体部４０１は、発音ユニット３０を内部に収容する収容空間を形成する。また、第１の筐体部４０１は、発音ユニット３０により生成される音波を外部へ導く導音路４１を備える。 As shown in FIG. 1, the housing 40 is composed of a combined body of a first housing portion 401 and a second housing portion 402. The first housing portion 401 forms a housing space for housing the sounding unit 30 therein. The first housing unit 401 also includes a sound guide path 41 that guides the sound waves generated by the sounding unit 30 to the outside.
　導音路４１は、その基端部（イヤピース２０が装着される先端部とは反対の端部）に導音口４１ａを有する。発音ユニット３０により生成された音波は、導音口４１ａを介して導音路４１を進行し、イヤピース２０を通過して放出される。 The sound guide path 41 has a sound guide port 41a at its base end (the end opposite to the tip where the earpiece 20 is mounted). The sound wave generated by the sounding unit 30 travels through the sound guide path 41 via the sound guide port 41a, passes through the earpiece 20, and is emitted.
　第２の筐体部４０２には、管状のリード部４２が設けられている。リード部４２には、電磁式発音体３１及び圧電式発音体３２に音声信号を伝達するための図示しない配線が挿通される。 The tubular lead portion 42 is provided on the second housing portion 402. Wires (not shown) for transmitting audio signals to the electromagnetic speaker 31 and the piezoelectric speaker 32 are inserted through the lead portion 42.
　（電磁式発音体）
　電磁式発音体３１は、低音域を再生するウーハ（Woofer）として機能するダイナミック型スピーカユニットで構成される。本実施形態では、例えば７ｋＨｚ以下の音波を主として生成するダイナミックスピーカで構成され、図２及び図３に示すように、ボイスコイルモータ（電磁コイル）等の振動体を含む機構部３１１と、機構部３１１を振動可能に支持する台座部３１２とを有する。 (Electromagnetic speaker)
The electromagnetic speaker 31 is composed of a dynamic speaker unit that functions as a woofer that reproduces a low sound range. In the present embodiment, for example, a dynamic speaker that mainly generates sound waves of 7 kHz or less, and as shown in FIGS. 2 and 3, a mechanism unit 311 including a vibrating body such as a voice coil motor (electromagnetic coil), and a mechanism unit. And a pedestal portion 312 that supports the vibration element 311.
　機構部３１１は振動板、永久磁石及びボイスコイル等から構成されている。ボイスコイルに電流（音声信号）を印加すると、ボイスコイルに電磁力が作用し、ボイスコイルは信号波形に合わせて振動する。この振動はボイスコイルに連結された振動板に伝達され、音波が発生する。ボイスコイルの一端は電磁式発音体３１の正極に相当し、ボイスコイルの他端は電磁式発音体３１の負極に相当する。電磁式発音体３１には、正極及び負極の表示がなされている。後述するように、電磁式発音体３１の正極は圧電式発音体３２の振動板３２１に電気的に接続され、電磁式発音体３１の負極は圧電式発音体３２の圧電素子３２２の正極に電気的に接続されている。 The mechanical unit 311 is composed of a diaphragm, a permanent magnet, a voice coil, and the like. When a current (voice signal) is applied to the voice coil, an electromagnetic force acts on the voice coil and the voice coil vibrates according to the signal waveform. This vibration is transmitted to the diaphragm connected to the voice coil, and a sound wave is generated. One end of the voice coil corresponds to the positive electrode of the electromagnetic speaker 31, and the other end of the voice coil corresponds to the negative electrode of the electromagnetic speaker 31. The electromagnetic speaker 31 is labeled with a positive electrode and a negative electrode. As will be described later, the positive electrode of the electromagnetic speaker 31 is electrically connected to the diaphragm 321 of the piezoelectric speaker 32, and the negative electrode of the electromagnetic speaker 31 is electrically connected to the positive electrode of the piezoelectric element 322 of the piezoelectric speaker 32. Connected to each other.
　（圧電式発音体）
　圧電式発音体３２は、導音口４１ａと電磁式発音体３１との間に配置される。圧電式発音体３２は、高音域を再生するツイータ（Tweeter）として機能するスピーカユニットを構成する。本実施形態では、例えば７ｋＨｚ以上の音波を主として生成するようにその発振周波数が設定される。図３に示すように圧電式発音体３２は、振動板３２１と、圧電素子３２２とを有する。 (Piezoelectric speaker)
The piezoelectric speaker 32 is arranged between the sound guide port 41 a and the electromagnetic speaker 31. The piezoelectric speaker 32 constitutes a speaker unit that functions as a tweeter that reproduces a high range. In the present embodiment, the oscillation frequency is set so as to mainly generate a sound wave of, for example, 7 kHz or more. As shown in FIG. 3, the piezoelectric speaker 32 has a diaphragm 321 and a piezoelectric element 322.
　振動板３２１は、金属（例えば４２アロイ）等の導電材料または樹脂（例えば液晶ポリマー）等の絶縁材料で構成され、その平面形状は略円形に形成される。「略円形」とは、円形だけでなく、実質的に円形のものも意味する。振動板３２１の外径や厚みは特に限定されず、筐体４０の大きさ、再生音波の周波数帯域などに応じて適宜設定される。本実施形態において振動板３２１は、導電材料で構成され、圧電素子３２２の負極と電気的に接続されるように圧電素子３２２と接合される。 The diaphragm 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 into a substantially circular shape. The term “substantially circular” means not only a circular shape but also a substantially circular shape. The outer diameter and the 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, the vibration plate 321 is made of a conductive material and is joined to the piezoelectric element 322 so as to be electrically connected to the negative electrode of the piezoelectric element 322.
　本実施形態では、振動板３２１の直径は１２ｍｍ以下、好ましくは８ｍｍ以下である。これにより、圧電式発音体３２の小型化、さらに発音ユニット３０及び筐体４０の小型化を図ることができる。振動板３２１の厚みの下限は、所望とする音響特性が得られる限りにおいて特に限定されず、例えば６ｍｍであるが、６ｍｍ未満であってもよい。振動板３２１の厚みとしては、例えば、約０．１～０．１７５ｍｍである。本実施形態では、振動板３２１の直径は８ｍｍ、厚みは０．０５～０．１ｍｍである。 In this embodiment, the diaphragm 321 has a diameter of 12 mm or less, preferably 8 mm or less. This makes it possible to reduce the size of the piezoelectric sounding body 32, and further reduce the size of the sounding unit 30 and the housing 40. The lower limit of the thickness of the diaphragm 321 is not particularly limited as long as desired acoustic characteristics are obtained, and is, for example, 6 mm, but may be less than 6 mm. The thickness of the diaphragm 321 is, for example, about 0.1 to 0.175 mm. In this embodiment, the diaphragm 321 has a diameter of 8 mm and a thickness of 0.05 to 0.1 mm.
　振動板３２１は、必要に応じ、その外周から内周側に向けてくぼむ凹状やスリット状などに形成された切欠き部を有していてもよい。なお、振動板３２１の平面形状は、概形が円形であれば、上記切欠き部が形成されることなどにより厳密には円形でない場合にも、実質的に円形として扱うものとする。また、振動板３２１には、電磁式発音体３１が生成した音波が通過する孔が設けられてもよい。 The diaphragm 321 may have a notch formed in a concave shape or a slit shape that is recessed from the outer circumference toward the inner circumference side, if necessary. It should be noted that the planar shape of the diaphragm 321 is substantially circular even if it is not strictly circular due to the formation of the cutout portion and the like if the outline is circular. Further, the diaphragm 321 may be provided with a hole through which a sound wave generated by the electromagnetic speaker 31 passes.
　振動板３２１は、導音口４１ａに臨む第１の主面３２ａと、電磁式発音体３１に臨む第２の主面３２ｂとを有する。本実施形態において圧電式発音体３２は、振動板３２１の第１の主面３２ａにのみ圧電素子３２２が接合されたユニモルフ構造を有する。なお、これに限られず、圧電素子３２２は、振動板３２１の第２の主面３２ｂに接合されてもよい。また、圧電式発音体３２は、振動板３２１の両主面３２ａ，３２ｂに圧電素子がそれぞれ接合されたバイモルフ構造で構成されてもよい。 The diaphragm 321 has a first main surface 32a that faces the sound guide port 41a and a second main surface 32b that faces the electromagnetic speaker 31. In the present embodiment, the piezoelectric speaker 32 has a unimorph structure in which the piezoelectric element 322 is bonded only to the first main surface 32a of the vibration plate 321. The piezoelectric element 322 is not limited to this, and may be joined to the second main surface 32b of the vibration plate 321. Further, the piezoelectric speaker 32 may have a bimorph structure in which piezoelectric elements are bonded to both main surfaces 32a and 32b of the vibration plate 321.
　図４は、圧電式発音体３２の平面図である。 FIG. 4 is a plan view of the piezoelectric speaker 32.
　図４に示すように、圧電素子３２２の平面形状は矩形状であり、圧電素子３２２の中心軸は、典型的には、振動板３２１の中心軸Ｃ１と同軸上に配置されている。これに限られず、圧電素子３２２の中心軸は、振動板３２１の中心軸Ｃ１よりも例えばＸ軸方向に所定量だけ変位してもよい。つまり、圧電素子３２２は、振動板３２１に対して偏心した位置に配置されてもよい。 As shown in FIG. 4, the piezoelectric element 322 has a rectangular planar shape, and the central axis of the piezoelectric element 322 is typically arranged coaxially with the central axis C1 of the diaphragm 321. The invention is not limited to this, and the central axis of the piezoelectric element 322 may be displaced from the central axis C1 of the vibration plate 321 by a predetermined amount in the X-axis direction, for example. That is, the piezoelectric element 322 may be arranged at a position eccentric to the vibration plate 321.
　振動板３２１は、その面内に複数の通路部３３０を有する。これら通路部３３０は、振動板３２１を厚み方向に貫通し、第１の開口部３３１と、第２の開口部３３２とを含む。通路部３３０は、電磁式発音体３１で発生した音を導音口４１へ導く通音口である。 The diaphragm 321 has a plurality of passages 330 in its surface. These passages 330 penetrate the diaphragm 321 in the thickness direction and include a first opening 331 and a second opening 332. The passage portion 330 is a sound passage that guides the sound generated by the electromagnetic speaker 31 to the sound guide 41.
　第１の開口部３３１は、振動板３２１の周縁部３２１ｃと圧電素子３２２との間の領域に設けられた複数の円形の孔で構成される。これら第１の開口部３３１は、中心線ＣＬ（振動板３２１の中心を通るＹ軸方向に平行な線）上の、中心軸Ｃ１に関して対称な位置にそれぞれ設けられる。第１の開口部３３１はそれぞれ同一径（例えば直径約１ｍｍ）の丸孔で形成されるが、勿論これに限られない。なお、所望とする音響特性が得られる場合には、開口部３３１を形成しなくてもよい。 The first opening 331 is composed of a plurality of circular holes provided in a region between the peripheral portion 321c of the vibration plate 321 and the piezoelectric element 322. The first openings 331 are provided at positions symmetrical with respect to the central axis C1 on the central line CL (a line that passes through the center of the diaphragm 321 and is parallel to the Y-axis direction). Each of the first openings 331 is formed of a round hole having the same diameter (for example, a diameter of about 1 mm), but it is not limited to this. Note that the opening 331 may not be formed if desired acoustic characteristics are obtained.
　第２の開口部３３２は、周縁部３２１ｃと圧電素子３２２との間にそれぞれ設けられ、Ｙ軸方向に長辺を有する矩形状に形成される。第２の開口部３３２は、圧電素子３２２の周縁部に沿って形成され、それらの一部は、圧電素子３２２の周縁部に部分的に被覆される。第２の開口部３３２は、振動板３２１の表裏を貫通する通路としての機能のほか、圧電素子３２２の有する２つの外部電極間の短絡防止の機能をも有する。 The second opening 332 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 Y-axis direction. The second openings 332 are formed along the peripheral edge of the piezoelectric element 322, and a part of them is partially covered by the peripheral edge of the piezoelectric element 322. The second opening 332 has a function as a passage that penetrates the front and back of the vibration plate 321, and also has a function of preventing a short circuit between two external electrodes of the piezoelectric element 322.
　図５は、圧電素子３２２の内部構造を示す概略断面図である。圧電素子３２２は、素体３２８と、Ｘ－Ｙ方向において対向する第１の外部電極３２６ａ及び第２の外部電極３２６ｂとを有する。また、圧電素子３２２は、相互に対向するＺ方向に垂直な第１の主面３２２ａ及び第２の主面３２２ｂを有する。圧電素子３２２の第２の主面３２２ｂは、振動板３２１の第１の主面３２ａに対向する実装面として構成される。 FIG. 5 is a schematic sectional view showing the internal structure of the piezoelectric element 322. The piezoelectric element 322 has an element body 328, and a first external electrode 326a and a second external electrode 326b facing each other in the XY directions. Further, the piezoelectric element 322 has a first main surface 322a and a second main surface 322b which are opposed to each other and are perpendicular to the Z direction. The second main surface 322b of the piezoelectric element 322 is configured as a mounting surface facing the first main surface 32a of the vibration plate 321.
　素体３２８は、セラミックシート３２３と、内部電極層３２４ａ，３２４ｂとがＺ方向に積層された構造を有する。つまり、内部電極層３２４ａ，３２４ｂは、セラミックシート３２３を挟んで交互に積層されている。セラミックシート３２３は、例えば、チタン酸ジルコン酸鉛（ＰＺＴ）、アルカリ金属含有ニオブ酸化物等の圧電材料によって形成されている。内部電極層３２４ａ，３２４ｂは各種金属材料などの導電性材料によって形成されている。 The element body 328 has a structure in which a ceramic sheet 323 and internal electrode layers 324a and 324b are laminated in the Z direction. That is, the internal electrode layers 324a and 324b are alternately laminated with the ceramic sheets 323 sandwiched therebetween. The ceramic sheet 323 is made of, for example, a piezoelectric material such as lead zirconate titanate (PZT) or alkali metal-containing niobium oxide. The internal electrode layers 324a and 324b are formed of a conductive material such as various metal materials.
　素体３２８の第１の内部電極層３２４ａは、第１の外部電極３２６ａに接続されるとともに、セラミックシート３２３のマージン部によって第２の外部電極３２６ｂから絶縁されている。また、素体３２８の第２の内部電極層３２４ｂは、第２の外部電極３２６ｂに接続されるとともに、セラミックシート３２３のマージン部によって第１の外部電極３２６ａから絶縁されている。 The first inner electrode layer 324a of the element body 328 is connected to the first outer electrode 326a and is insulated from the second outer electrode 326b by the margin portion of the ceramic sheet 323. The second inner electrode layer 324b of the element body 328 is connected to the second outer electrode 326b and is insulated from the first outer electrode 326a by the margin portion of the ceramic sheet 323.
　第１の内部電極層３２４ａの最上層は、素体３２８の表面（図５において上面）を部分的に被覆する第１の引出電極層３２５ａを構成し、第２の内部電極層３２４ｂの最下層は、素体３２８の裏面（図５において下面）を部分的に被覆する第２の引出電極層３２５ｂを構成する。 The uppermost layer of the first internal electrode layer 324a constitutes a first extraction electrode layer 325a that partially covers the surface (the upper surface in FIG. 5) of the element body 328, and the lowermost layer of the second internal electrode layer 324b. Form a second extraction electrode layer 325b that partially covers the back surface (lower surface in FIG. 5) of the element body 328.
　第１の引出電極層３２５ａは、後述する配線基板７０と電気的に接続される一方の極の端子部３２７ａを有し、第２の引出電極層３２５ｂは、適宜の接合材を介して振動板３２１の第１の主面３２ａに電気的かつ機械的に接続される。振動板３２１が導電性材料で構成される場合、接合材には、導電性接着剤、はんだ等の導電性接合材が用いられてもよく、この場合には他方の極の端子部を振動板３２１に設けることができる。 The first extraction electrode layer 325a has a terminal portion 327a of one pole that is electrically connected to the wiring board 70 described later, and the second extraction electrode layer 325b is a diaphragm through an appropriate bonding material. It is electrically and mechanically connected to the first main surface 32a of 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 pole is used as the vibration plate. 321 can be provided.
　圧電素子３２２の正極と負極については、分極時にプラスの電圧を印加した側を正極とし、分極時にマイナスの電圧を印加した側を負極としている。また、圧電式発音体３２については、振動板３２１に接合される側を負極としている。よって、本実施形態では、第１の引出電極層３２５ａが圧電素子３２２の正極に相当し、第２の引出電極層３２５ｂが圧電素子３２２の負極に相当する。また、端子部３２７ａが圧電式発音体３２の正極に相当し、第２の引出電極層３２５ａと電気的に接続される振動板３２１が圧電式発音体３２の負極に相当する。 Regarding the positive and negative electrodes of the piezoelectric element 322, the side to which a positive voltage is applied during polarization is the positive electrode, and the side to which a negative voltage is applied during polarization is the negative electrode. Further, regarding the piezoelectric speaker 32, the side joined to the vibration plate 321 is the negative electrode. Therefore, in the present embodiment, the first extraction electrode layer 325a corresponds to the positive electrode of the piezoelectric element 322, and the second extraction electrode layer 325b corresponds to the negative electrode of the piezoelectric element 322. The terminal portion 327a corresponds to the positive electrode of the piezoelectric speaker 32, and the diaphragm 321 electrically connected to the second lead electrode layer 325a corresponds to the negative electrode of the piezoelectric speaker 32.
　第１及び第２の外部電極３２６ａ，３２６ｂは、素体３２８のＸ方向の両端面の略中央部に各種金属材料などの導電性材料によって形成されている。第１の外部電極３２６ａは、第１の内部電極層３２４ａ及び第１の引出電極層３２５ａと電気的に接続され、第２の外部電極３２６ｂは、第２の内部電極層３２４ｂ及び第２の引出電極層３２５ｂと電気的に接続される。 The first and second external electrodes 326a and 326b are formed of a conductive material such as various metal materials at approximately the center of both end surfaces of the element body 328 in the X direction. The first outer electrode 326a is electrically connected to the first inner electrode layer 324a and the first lead electrode layer 325a, and the second outer electrode 326b is the second inner electrode layer 324b and the second lead electrode layer 324b. It is electrically connected to the electrode layer 325b.
　このような構成により、第１及び第２の外部電極３２６ａ、３２６ｂ間に交流電圧が印加されると、各内部電極層３２４ａ，３２４ｂ間にある各セラミックシート３２３が所定周波数で伸縮する。これにより、圧電素子３２２は振動板３２１に付与する振動を発生させることができる。 With such a configuration, when an AC voltage is applied between the first and second 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 the vibration applied to the vibration plate 321.
　（支持構造）
　イヤホン本体１０は、電磁式発音体３１及び圧電式発音体３２に加え、図３に示すようにマウント部材５１を備える。 (Support structure)
The earphone body 10 includes a mount member 51 as shown in FIG. 3 in addition to the electromagnetic speaker 31 and the piezoelectric speaker 32.
　マウント部材５１は、電磁式発音体３１及び圧電式発音体３２を筐体４０に固定する。マウント部材５１は、支持部５１ａと周壁部５１ｂを備える環状の部材であり、金属や合成樹脂等の材料からなる。 The mount member 51 fixes the electromagnetic speaker 31 and the piezoelectric speaker 32 to the housing 40. The mount member 51 is an annular member including a support portion 51a and a peripheral wall portion 51b, and is made of a material such as metal or synthetic resin.
　電磁式発音体３１と圧電式発音体３２との間の間隙は特に限定されず、０．１ｍｍ以上０．７ｍｍ以下、好ましくは、０．２ｍｍ以上０．３ｍｍ以下である。上記間隙が大きすぎると、電磁式発音体３１及び圧電式発音体３２のいずれについても音圧が低下する傾向にある。圧電式発音体３２と導音口４１ａの先端部までの距離も特に限定されず、例えば、本実施形態では５ｍｍ以上７ｍｍ以下である。 The gap between the electromagnetic speaker 31 and the piezoelectric speaker 32 is not particularly limited and is 0.1 mm or more and 0.7 mm or less, preferably 0.2 mm or more and 0.3 mm or less. If the gap is too large, the sound pressure of both the electromagnetic sounding body 31 and the piezoelectric sounding body 32 tends to decrease. The distance between the piezoelectric speaker 32 and the tip of the sound guide port 41a is not particularly limited, and is, for example, 5 mm or more and 7 mm or less in the present embodiment.
　図３に示すように、支持部５１ａの導音口４１ａ側の面には、第１支持部材６１を介して振動板３２１の第２の主面３２ｂの周縁部が接合される。支持部５１ａの導音口４１ａとは反対側の面には、第２支持部材６２を介して機構部３１１が接合されている。 As shown in FIG. 3, the peripheral portion of the second main surface 32b of the diaphragm 321 is joined to the surface of the support portion 51a on the sound guide port 41a side via the first support member 61. The mechanism portion 311 is joined to the surface of the support portion 51a opposite to the sound guide port 41a via the second support member 62.
　第１支持部材６１及び第２支持部材６２は例えば、円環状の粘着テープ（両面テープ）や粘着剤層などで構成される。圧電式発音体３２の振動板３２１が粘着性のある第１支持部材６１を介してマウント部材５１に接合されることにより、振動板３２１がマウント部材５１に対して弾性的に支持されるため、振動板３２１の共振のぶれが抑制され、振動板３２１の安定した共振動作が確保される。 The first support member 61 and the second support member 62 are composed of, for example, an annular adhesive tape (double-sided tape) or an adhesive layer. Since the vibration plate 321 of the piezoelectric speaker 32 is joined to the mount member 51 via the first support member 61 having adhesiveness, the vibration plate 321 is elastically supported with respect to the mount member 51. The shake of the resonance of the diaphragm 321 is suppressed, and the stable resonance operation of the diaphragm 321 is secured.
　マウント部材５１は、例えば、３ＧＰａ以上のヤング率（縦弾性係数）を有する材料で構成される。このような材料で構成されたマウント部材５１は、比較的高い剛性を確保することができるため、７ｋＨｚ以上の比較的高い周波数帯域で振動する圧電式発音体３２（振動板３２１）を安定に支持することができる。 The mount member 51 is made of, for example, a material having a Young's modulus (longitudinal elastic modulus) of 3 GPa or more. Since the mount member 51 made of such a material can secure a relatively high rigidity, it stably supports the piezoelectric speaker 32 (vibration plate 321) vibrating in a relatively high frequency band of 7 kHz or higher. can do.
　マウント部材５１を構成する材料のヤング率の上限は特に限定されないが、例えば５ＧＰａ以上の材料単体では、金属やセラミックス等の無機材料にほぼ限定されるため、重量や生産コスト等との兼ね合いで上限は適宜設定可能であり、例えば５００ＧＰａ以下とすることができる。一方、マウント部材５１を合成樹脂材料製とすることにより、軽量化、生産性の点で有利である。 Although the upper limit of the Young's modulus of the material forming the mount member 51 is not particularly limited, for example, a single material of 5 GPa or more is almost limited to an inorganic material such as metal or ceramics, and therefore the upper limit is taken into consideration in consideration of weight and production cost. Can be appropriately set, and can be set to, for example, 500 GPa or less. On the other hand, the mount member 51 made of a synthetic resin material is advantageous in terms of weight reduction and productivity.
　ヤング率が３ＧＰａ以上の材料としては、例えば、金属材料、セラミックス、合成樹脂材料、合成樹脂材料を主体とする複合材料が挙げられる。金属材料としては、圧延鋼、ステンレス鋼、鋳鉄等の鉄系材料のほか、アルミニウムや黄銅等の非鉄系材料など、特に制限なく採用可能である。セラミックスとしては、ＳｉＣやＡｌ２Ｏ３等の適宜の材料が適用可能である。 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, iron-based materials such as rolled steel, stainless steel, cast iron, and non-ferrous materials such as aluminum and brass can be used without particular limitation. As ceramics, an appropriate material such as SiC or Al 2 O 3 can be applied.
　合成樹脂材料としては、ポリフェニレンサルファイド（ＰＰＳ）、ポリメチルメタアクリレート（ＰＭＭＡ）、ポリアセタール（ＰＯＭ）、硬質塩化ビニル、メチルメタクリレート・スチレン共重合体（ＭＳ）等が挙げられる。また、ポリカーボネート（ＰＣ）やスチレン・ブタジエン・アクリロニトリル共重合体（ＡＢＳ）等のような単体で３ＧＰａ以上のヤング率を有しない樹脂材料であっても、これにガラス繊維等の繊維質や無機粒子等の微粒子からなるフィラー（充填材）が添加された、ヤング率（縦弾性係数）３ＧＰａ以上の複合材料（強化型プラスチック）が採用可能である。 Examples of synthetic resin materials include polyphenylene sulfide (PPS), polymethylmethacrylate (PMMA), polyacetal (POM), rigid vinyl chloride, methylmethacrylate/styrene copolymer (MS), and the like. In addition, even 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 as a single substance may have a fiber material such as glass fiber or inorganic particles. 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 is added, can be used.
　マウント部材５１は、単純な板材ではなく、図示するように領域によって厚みが異なる３次元形状に形成されることにより、断面二次モーメントが大きくすることができ、同一のヤング率を有する材料であっても剛性（曲げ剛性）をさらに高めることができる。 The mount member 51 is not a simple plate material, but is formed of a three-dimensional shape having different thicknesses depending on regions as shown in the figure, so that the second moment of area can be increased and the material has the same Young's modulus. However, the rigidity (bending rigidity) can be further increased.
　周壁部５１ｂは、支持部５１ａの外周縁部から導音口４１ａ側に突出し、その先端部が第１の筐体部４０１に接合される。周壁部５１ｂは例えば、第１の筐体部４０１に設けられた溝に嵌合することによって第１の筐体部４０１に接合される。 The peripheral wall portion 51b projects from the outer peripheral edge portion of the support portion 51a to the sound guide port 41a side, and the tip portion thereof is joined to the first housing portion 401. The peripheral wall portion 51b is joined to the first housing portion 401, for example, by fitting into the groove provided in the first housing portion 401.
　（配線構造）
　図６は、イヤホン１００の配線構造を示す模式図である。イヤホン１００は、音声信号を出力する電子機器５００のジャック５１０と接続されるプラグ８０を備える。プラグ８０は、配線ケーブル７２を介して配線基板７０と電気的に接続され、配線基板７０は発音ユニット３０と電気的に接続される配線回路を有する。配線基板７０は、筐体４０の内部の適宜の位置に配置されてもよく、本実施形態では電磁式発音体３１の台座部３１２に取り付けられる（図１参照）。 (Wiring structure)
FIG. 6 is a schematic diagram showing a wiring structure of the earphone 100. The earphone 100 includes a plug 80 connected to the jack 510 of the electronic device 500 that outputs a sound signal. The plug 80 is electrically connected to the wiring board 70 via the wiring cable 72, and the wiring board 70 has a wiring circuit electrically connected to the sounding unit 30. The wiring board 70 may be arranged at an appropriate position inside the housing 40, and is attached to the pedestal portion 312 of the electromagnetic speaker 31 in the present embodiment (see FIG. 1 ).
　配線基板７０は、電磁式発音体３１の正極３１ｐと圧電式発音体３２の負極としての振動板３２１と接続される第１配線７１ａと、電磁式発音体３１の負極３１ｎと圧電式発音体３２の正極としての圧電素子３２２に接続される第２配線７１ｂとを有する。第１配線７１ａ及び第２配線７１ｂは、配線基板７０上の配線パターンと、当該配線パターンと電磁式発音体３１及び圧電式発音体３２との間を接続する配線などにより構成される。このように本実施形態では、圧電式発音体３２は、電磁式発音体３１に対して逆位相で駆動するように構成される。なお、電磁式発音体３１の正極３１ｐと圧電式発音体３２の負極（振動板３２１）との間に接続される抵抗素子７３は、発振防止用の保護抵抗であり、必要に応じて省略されてもよい。 The wiring board 70 includes a first wiring 71a connected to the positive electrode 31p of the electromagnetic speaker 31 and the vibration plate 321 as the negative electrode of the piezoelectric speaker 32, the negative electrode 31n of the electromagnetic speaker 31, and the piezoelectric speaker 32. Second wiring 71b connected to the piezoelectric element 322 serving as the positive electrode of. The first wiring 71a and the second wiring 71b are composed of a wiring pattern on the wiring board 70 and wiring that connects the wiring pattern with the electromagnetic speaker 31 and the piezoelectric speaker 32. As described above, in the present embodiment, the piezoelectric speaker 32 is configured to be driven in the opposite phase to the electromagnetic speaker 31. The resistance element 73 connected between the positive electrode 31p of the electromagnetic speaker 31 and the negative electrode (vibration plate 321) of the piezoelectric speaker 32 is a protection resistor for preventing oscillation, and is omitted as necessary. May be.
　プラグ８０は、Ｒ側のイヤホンの正極に接続される第１正極部８０ｐ１と、図示しないＬ側のイヤホンの正極に接続される第２正極部８０ｐ２と、Ｒ側及びＬ側のイヤホンの負極に共通に接続される負極部８０ｎとを有する。負極部８０ｎは、グランド端子をも兼ねる。そして、配線ケーブル７２は、配線基板７０の第１配線７１ａとプラグ８０の第１正極部８０ｐ１との間を電気的に接続する第１ケーブル７２ｐと、配線基板７０の第２配線７１ｂとプラグ８０の負極部８０ｎとの間を電気的に接続する第２ケーブル７２ｎとを有する。 The plug 80 has a first positive electrode portion 80p1 connected to the positive electrode of the R side earphone, a second positive electrode portion 80p2 connected to the positive electrode of the L side earphone (not shown), and a negative electrode of the R side and L side earphones. It has the negative electrode part 80n connected in common. The negative electrode portion 80n also serves as a ground terminal. The wiring cable 72 includes a first cable 72p that electrically connects the first wiring 71a of the wiring board 70 and the first positive electrode portion 80p1 of the plug 80, a second wiring 71b of the wiring board 70, and the plug 80. The second cable 72n that electrically connects the negative electrode portion 80n with the second cable 72n.
［イヤホンの動作］
　続いて、以上のように構成される本実施形態のイヤホン１００の典型的な動作について
説明する。 [Earphone operation]
Next, a typical operation of the earphone 100 of the present embodiment configured as above will be described.
　本実施形態のイヤホン１００において、発音ユニット３０には、配線ケーブル７２を介して再生信号が入力される。再生信号は、配線基板７０を介して、電磁式発音体３１及び圧電式発音体３２にそれぞれ入力される。これにより、電磁式発音体３１が駆動されて、主として７ｋＨｚ以下の低音域の音波が生成される。一方、圧電式発音体３２においては、圧電素子３２２の伸縮動作により振動板３２１が振動し、主として７ｋＨｚ以上の高音域の音波が生成される。生成された各帯域の音波は、導音口４１ａを介してユーザの耳に伝達される。このようにイヤホン１００は、低音域用の発音体と高音域用の発音体とを有するハイブリッドスピーカとして機能する。 In the earphone 100 of this embodiment, a reproduction signal is input to the sounding unit 30 via the wiring cable 72. The reproduction signal is input to each of the electromagnetic speaker 31 and the piezoelectric speaker 32 via the wiring board 70. As a result, the electromagnetic speaker 31 is driven to generate a sound wave mainly in the low frequency range of 7 kHz or less. On the other hand, in the piezoelectric speaker 32, the vibrating plate 321 vibrates due to the expansion and contraction operation of the piezoelectric element 322, and a sound wave in a high sound range of 7 kHz or higher is generated. The generated sound waves of each band are transmitted to the user's ear via the sound guide port 41a. In this way, the earphone 100 functions as a hybrid speaker having a sounding body for a low sound range and a sounding body for a high sound range.
　ここで、近年、イヤホンやヘッドホン等の音響機器においては、小型化及び音質の更なる向上が求められている。しかしながら、機器の小型化は発音体の小型化を伴うため、特に圧電式発音体においては音圧特性が低下する傾向にある。このため、電磁式発音体と圧電式発音体とを備えた電気音響変換装置においては、電磁式発音体からの再生音の音圧レベルと圧電式発音体からの再生音の音圧レベルとが相互に交差する周波数（クロスオーバ周波数）付近で、２つの再生音の合成音圧レベルが急激に低下する現象（ディップ）が生じやすいという問題がある。 Here, in recent years, in audio equipment such as earphones and headphones, further miniaturization and further improvement of sound quality have been demanded. However, downsizing of the device accompanies downsizing of the sounding body, so that the sound pressure characteristic tends to deteriorate, particularly in the piezoelectric sounding body. Therefore, in the electroacoustic transducer including the electromagnetic speaker and the piezoelectric speaker, the sound pressure level of the reproduced sound from the electromagnetic speaker and the sound pressure level of the reproduced sound from the piezoelectric speaker are different. There is a problem that a phenomenon (dip) in which the synthesized sound pressure level of two reproduced sounds sharply decreases in the vicinity of frequencies (crossover frequencies) at which they intersect with each other is likely to occur.
　例えば図７に、比較例に係る電気音響変換装置の音響特性の一例を示す。この比較例は、図１に示したイヤホン１００と同様な構成を有するが、圧電式発音体が電磁式発音体に対して同位相で駆動するように構成されている点で、本実施形態と異なる。すなわち、比較例においては、図６における配線ケーブル７２のうち、正極側の第１ケーブル７２ｐが電磁式発音体３１の正極３１ｐと圧電式発音体３２の正極としての圧電素子３２２に接続され、負極側の第２ケーブル７２ｎが電磁式発音体３１の負極３１ｎと圧電式発音体３２の負極としての振動板３２１に接続される。 For example, FIG. 7 shows an example of acoustic characteristics of an electroacoustic transducer according to a comparative example. This comparative example has the same configuration as the earphone 100 shown in FIG. 1, but is different from the present embodiment in that the piezoelectric sounding body is configured to be driven in the same phase as the electromagnetic sounding body. different. That is, in the comparative example, among the wiring cables 72 in FIG. 6, the first cable 72p on the positive electrode side is connected to the positive electrode 31p of the electromagnetic speaker 31 and the piezoelectric element 322 as the positive electrode of the piezoelectric speaker 32, and the negative electrode is connected to the negative electrode. The second cable 72n on the side is connected to the negative electrode 31n of the electromagnetic speaker 31 and the diaphragm 321 as the negative electrode of the piezoelectric speaker 32.
　図７において、横軸は周波数、縦軸は音圧レベルをそれぞれ示し、二点鎖線は電磁式発音体のみ駆動させた場合の音圧特性を、破線は圧電式発音体のみ駆動させた場合の音圧特性を、そして太実線は、電磁式発音体及び圧電式発音体を同時に駆動させたときの音圧特性をそれぞれ示している。圧電式発音体の振動板の直径は８ｍｍ、厚みは１００μｍ、材質は４２アロイ合金とした。一方、電磁式発音体は、振動板の直径が９ｍｍ、負荷インピーダンスが１６Ωのダイナミックスピーカを用いた。 In FIG. 7, the horizontal axis represents frequency and the vertical axis represents sound pressure level. The two-dot chain line shows sound pressure characteristics when only the electromagnetic sounding body is driven, and the broken line shows when only the piezoelectric sounding body is driven. The sound pressure characteristic and the thick solid line respectively show the sound pressure characteristic when the electromagnetic sounding body and the piezoelectric sounding body are simultaneously driven. The diameter of the diaphragm of the piezoelectric speaker was 8 mm, the thickness was 100 μm, and the material was 42 alloy alloy. On the other hand, as the electromagnetic speaker, a dynamic speaker having a diaphragm diameter of 9 mm and a load impedance of 16Ω was used.
　同図において太実線で示すように、比較例に係る電気音響変換装置においては、同時駆動時におけるクロスオーバ周波数に相当する周波数帯域（１０ｋＨｚ～２０ｋＨｚ）での音圧の低下が著しい。 As shown by the thick solid line in the figure, in the electroacoustic transducer according to the comparative example, the sound pressure is significantly reduced in the frequency band (10 kHz to 20 kHz) corresponding to the crossover frequency during simultaneous driving.
　電磁式発音体及び圧電式発音体を備えた電気音響変換装置においては、これらの発音体は相互に同位相で駆動されるのが一般的であるが、機器の小型化に伴い、必要な音圧を確保することがより困難になる。また、圧電式発音体においては、振動板の周縁部を筐体部に弾性支持することで、圧電式発音体の振動の鋭さ（Ｑ値）を低減し、特定の周波数域での音圧ピークを抑制して比較的ブロードな音圧特性を得るようにしている。しかし、振動板の小径化に伴い、振動板の面積に対する筐体部との接合面積の比が低下し、振動板の所望とする振動モードが維持できず、かえって音圧特性の低下をもたらしていると考えられる。 In an electroacoustic transducer equipped with an electromagnetic sounding body and a piezoelectric sounding body, these sounding bodies are generally driven in the same phase with each other. It becomes more difficult to secure the pressure. Further, in the piezoelectric sounding body, the sharpness (Q value) of the vibration of the piezoelectric sounding body is reduced by elastically supporting the peripheral portion of the diaphragm to the case portion, and the sound pressure peak in a specific frequency range is reduced. Is suppressed to obtain a relatively broad sound pressure characteristic. However, as the diameter of the diaphragm becomes smaller, the ratio of the joint area of the housing to the area of the diaphragm decreases, and the desired vibration mode of the diaphragm cannot be maintained, which in turn causes a decrease in sound pressure characteristics. It is believed that
　そこで本発明者らは鋭意検討の結果、圧電式発音体３２を電磁式発音体３１とは逆位相で駆動することで、上記問題が解消されることを見出した。図８は、本実施形態のイヤホン１００の音響特性の一例を示す。図中の横軸、縦軸、二点鎖線、破線、太実線は図８と同様であるため説明を省略する。また、圧電式発音体３２の振動板３２１も比較例のそれと同様の構成とした。 Therefore, as a result of intensive studies, the present inventors have found that the above problem can be solved by driving the piezoelectric sounding body 32 in a phase opposite to that of the electromagnetic sounding body 31. FIG. 8 shows an example of the acoustic characteristics of the earphone 100 of this embodiment. The horizontal axis, the vertical axis, the alternate long and two short dashes line, the broken line, and the thick solid line in the figure are the same as those in FIG. Further, the vibration plate 321 of the piezoelectric speaker 32 has the same structure as that of the comparative example.
　図７と比較して明らかなように、本実施形態によれば、クロスオーバ周波数付近での音圧の低下が比較例よりも大幅に抑制されている。圧電式発音体３２を電磁式発音体３１とは逆位相で駆動することで、電磁式発音体３１と圧電式発音体３２との間の位相のマッチングが図られ、比較例の場合よりもクロスオーバ周波数付近での音圧の低下が緩和されたものと推察される。なお図示せずとも、圧電式発音体３２の振動板３２１の直径が６ｍｍの場合にも同様な効果が得られることが発明者によって確認されている。 As is clear from comparison with FIG. 7, according to the present embodiment, the decrease in sound pressure near the crossover frequency is significantly suppressed as compared with the comparative example. By driving the piezoelectric sounding body 32 in a phase opposite to that of the electromagnetic sounding body 31, phase matching between the electromagnetic sounding body 31 and the piezoelectric sounding body 32 can be achieved, and crossing can be achieved as compared with the case of the comparative example. It is inferred that the decrease in sound pressure near the over frequency was alleviated. Although not shown, the inventor has confirmed that the same effect can be obtained when the diameter of the diaphragm 321 of the piezoelectric speaker 32 is 6 mm.
　以上のように本実施形態によれば、圧電式発音体３２を電磁式発音体３１に対して逆位相で駆動することにより、圧電式発音体３２が比較的小径の場合でもクロスオーバ周波数付近における音圧のディップ現象を抑制し、音響特性の改善を図ることができる。これにより、機器の小型化を図りつつ、音響特性の改善を図ることができる。 As described above, according to the present embodiment, by driving the piezoelectric speaker 32 in the opposite phase with respect to the electromagnetic speaker 31, even in the case where the piezoelectric speaker 32 has a relatively small diameter, the piezoelectric speaker 32 is in the vicinity of the crossover frequency. It is possible to suppress the sound pressure dip phenomenon and improve the acoustic characteristics. This makes it possible to improve the acoustic characteristics while reducing the size of the device.
　また、マウント部材５１の支持部５１ａにおける振動板３２１の支持面積は、振動板３２１の面積の４９％以下であることが好ましい。本実施形態では、振動板３２１の直径が８ｍｍの場合、振動板３２１の面積と支持部５１ａとの面積比は、２．４である。振動板３２１の支持面積を上記のように設定することで、振動板３２１の共振状態をより安定に維持することができる。 Further, it is preferable that the supporting area of the diaphragm 321 in the supporting portion 51a of the mount member 51 is 49% or less of the area of the diaphragm 321. In the present embodiment, when the diameter of the diaphragm 321 is 8 mm, the area ratio between the area of the diaphragm 321 and the supporting portion 51a is 2.4. By setting the support area of the diaphragm 321 as described above, the resonance state of the diaphragm 321 can be maintained more stably.
　以上、本発明の実施形態について説明したが、本発明は上述の実施形態にのみ限定されるものではなく種々変更を加え得ることは勿論である。 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.
　例えば以上の実施形態では、圧電式発音体３２として、ユニモルフ構造を例に挙げて説明したが、図９に示すように振動板３２１の両面に圧電素子３２２Ａ，３２２Ｂが配置されるバイモルフ構造も適用可能である。この場合、各圧電素子３２２Ａ，３２２Ｂには、電磁式発音体とは逆位相の駆動信号が入力され、このとき各圧電素子３２２Ａ，３２２Ｂは、一方の伸長し他方が縮長するような振動モードで振動板３２１を振動させる。 For example, in the above embodiments, the piezoelectric speaker 32 has been described by taking the unimorph structure as an example, but a bimorph structure in which the piezoelectric elements 322A and 322B are arranged on both surfaces of the diaphragm 321 as shown in FIG. 9 is also applied. It is possible. In this case, a drive signal having a phase opposite to that of the electromagnetic speaker is input to each piezoelectric element 322A, 322B, and at this time, each piezoelectric element 322A, 322B has a vibration mode in which one expands and the other expands. The diaphragm 321 is vibrated by.
　図１０は、バイモルフ構造の圧電式発音体を備えたイヤホンの音響特性を示す一実験結果であり、実線は、電磁式発音体及び圧電式発音体を逆位相で駆動したときの音圧特性を、一点鎖線は、これらを同位相で駆動したときの音圧特性をそれぞれ示している。圧電式発音体の振動板の直径は８ｍｍである。同図に示すように、電磁式発音体及び圧電式発音体を相互に逆位相で駆動することにより、これらを同位相で駆動する場合と比較して、１０～２０ｋＨｚ付近の周波数帯域の低下（ディップ）を抑制することができる。 FIG. 10 is a result of an experiment showing the acoustic characteristics of the earphone including the piezoelectric speaker with the bimorph structure, and the solid line shows the sound pressure characteristics when the electromagnetic speaker and the piezoelectric speaker are driven in opposite phases. , The alternate long and short dash line shows the sound pressure characteristics when these are driven in the same phase. The diameter of the diaphragm of the piezoelectric speaker is 8 mm. As shown in the figure, by driving the electromagnetic sounding body and the piezoelectric sounding body in opposite phases to each other, the frequency band around 10 to 20 kHz is lowered as compared with the case where they are driven in the same phase ( Dip) can be suppressed.
　また以上の実施形態では、電気音響変換装置としてイヤホンを例に挙げて説明したが、これに限られず、ヘッドホン、据え置き型スピーカ、携帯情報端末に内蔵されるスピーカ等にも本発明は適用可能である。 In the above embodiments, earphones are taken as an example of the electroacoustic transducer, but the present invention is not limited to this, and the present invention is also applicable to headphones, stationary speakers, speakers incorporated in portable information terminals, and the like. is there.
　１０…イヤホン本体
　２０…イヤピース
　３０…発音ユニット
　３１…電磁式発音体
　３２…圧電式発音体
　４０…筐体
　４１ａ…導音口
　５１…マウント部材
　７０…配線基板
　７２…配線ケーブル
　８０…プラグ
　３２１…振動板
　３２２，３２２Ａ，３２２Ｂ…圧電素子 10... Earphone body 20... Earpiece 30... Sound generating unit 31... Electromagnetic sounding body 32... Piezoelectric sounding body 40... Housing 41a... Sound inlet 51... Mounting member 70... Wiring board 72... Wiring cable 80... Plug 321... Vibration Plates 322, 322A, 322B... Piezoelectric element

Claims (5)

  1. 　電磁式発音体と、
    　前記電磁式発音体に対して逆位相で駆動する圧電式発音体と
    　を具備する電気音響変換装置。     An electromagnetic speaker,
    An electroacoustic transducer comprising: a piezoelectric sounding body driven in a phase opposite to that of the electromagnetic sounding body.
  2. 　請求項１に記載の電気音響変換装置であって、
    　前記圧電式発音体は、円形の振動板と、前記振動板の少なくとも一方の面に配置された圧電素子とを有し、
    　前記振動板は、前記圧電素子の負極と電気的に接続されるように、前記圧電素子と接合され、
    　前記電磁式発音体の正極は前記振動板に電気的に接続され、前記電磁式発音体の負極は前記圧電素子の正極に電気的に接続されている
    　電気音響変換装置。     The electroacoustic transducer according to claim 1, wherein
    The piezoelectric speaker has a circular diaphragm and a piezoelectric element disposed on at least one surface of the diaphragm,
    The vibration plate is bonded to the piezoelectric element so as to be electrically connected to the negative electrode of the piezoelectric element,
    An electroacoustic transducer in which a positive electrode of the electromagnetic speaker is electrically connected to the diaphragm, and a negative electrode of the electromagnetic speaker is electrically connected to a positive electrode of the piezoelectric element.
  3. 　請求項２に記載の電気音響変換装置であって、
    　前記振動板の直径は、８ｍｍ以下である
    　電気音響変換装置。     The electroacoustic transducer according to claim 2, wherein
    An electroacoustic transducer in which the diaphragm has a diameter of 8 mm or less.
  4. 　請求項２又は３に記載の電気音響変換装置であって、
    　導音口を有し、前記発音ユニットを収容する筐体をさらに具備し、
    　前記圧電式発音体は、前記導音口と前記電磁式発音体との間に配置される
    　電気音響変換装置。     The electroacoustic transducer according to claim 2 or 3, wherein
    Further comprising a housing having a sound guide and housing the sound producing unit,
    The piezoelectric sounding body is an electroacoustic transducer arranged between the sound guide port and the electromagnetic sounding body.
  5. 　請求項４に記載の電気音響変換装置であって、
    　前記筐体は、前記振動板の周縁部を支持する支持部をさらに有し、
    　前記支持部における前記振動板の支持面積は、前記振動板の面積の４９％以下である
    　電気音響変換装置。     The electroacoustic transducer according to claim 4, wherein
    The casing further includes a support portion that supports a peripheral portion of the diaphragm,
    An electroacoustic transducer in which the supporting area of the diaphragm in the supporting portion is 49% or less of the area of the diaphragm.
PCT/JP2019/047186 2019-01-31 2019-12-03 Electroacoustic transducer WO2020158173A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2019-015910 2019-01-31
JP2019015910A JP2020123904A (en) 2019-01-31 2019-01-31 Electroacoustic conversion device

Publications (1)

Publication Number Publication Date
WO2020158173A1 true WO2020158173A1 (en) 2020-08-06

Family

ID=71841258

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2019/047186 WO2020158173A1 (en) 2019-01-31 2019-12-03 Electroacoustic transducer

Country Status (2)

Country Link
JP (1) JP2020123904A (en)
WO (1) WO2020158173A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0467894U (en) * 1990-10-23 1992-06-16
JP2016086402A (en) * 2014-10-24 2016-05-19 太陽誘電株式会社 Electroacoustic conversion device and electronic apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0467894U (en) * 1990-10-23 1992-06-16
JP2016086402A (en) * 2014-10-24 2016-05-19 太陽誘電株式会社 Electroacoustic conversion device and electronic apparatus

Also Published As

Publication number Publication date
JP2020123904A (en) 2020-08-13

Similar Documents

Publication Publication Date Title
JP6581792B2 (en) Electroacoustic transducer and electronic device
CN108513240B (en) Electroacoustic transducer
CN109309894B (en) Electroacoustic transducer
CN107615780B (en) Piezoelectric sounding body and electroacoustic conversion device
WO2020158173A1 (en) Electroacoustic transducer
JP6996853B2 (en) Electro-acoustic converter
JP5759642B1 (en) Electroacoustic transducer
CN107623888B (en) Electroacoustic transducer
JP7338962B2 (en) Electroacoustic converter
JP6875908B2 (en) Electro-acoustic converter
JP2021027506A (en) Electroacoustic conversion device
KR102021181B1 (en) Electroacoustic transducer
US20240048894A1 (en) Loudspeaker and electronic device
JP2021027511A (en) Electroacoustic conversion device
JP2021034994A (en) Electroacoustic conversion device
WO2016194425A1 (en) Piezoelectric sounder and electroacoustic conversion device

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 19913079

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 19913079

Country of ref document: EP

Kind code of ref document: A1