JP2012029111A - Oscillation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a new demodulation system in a parametric speaker.SOLUTION: An oscillation device has: a sheet-like vibration member 10; a vibrator 20 attached to one side of the vibration member 10; a supporting part 40 that supports an edge of the vibration member 10; and a reflection part 30 opposed to the vibration member 10, and that reflects a sonic wave. The oscillation device further has a sound releasing hole 32 formed to at least one of the reflection part 30 and the supporting part 40.

Description

  The present invention relates to an oscillation device.

  In recent years, the demand for mobile terminals such as mobile phones and laptop computers has been increasing. In particular, the development of thin mobile terminals with commercial functions such as videophones, video playback, and hands-free phone functions is underway. In these developments, there is an increasing demand for electroacoustic transducers that are small in size and large in output. Conventionally, an electrodynamic electroacoustic transducer is used as an electroacoustic transducer in an electronic device such as a mobile phone. This electrodynamic electroacoustic transducer has a permanent magnet, a voice coil, and a diaphragm. However, the electrodynamic electroacoustic transducer is limited in thickness because of its operation principle and structure. Therefore, for example, as described in Patent Documents 1 and 2, a parametric speaker having a piezoelectric vibrator is expected as a new electroacoustic transducer.

  Patent Document 3 describes a parametric speaker having a plurality of ultrasonic transducers and a reflecting plate corresponding to each ultrasonic transducer. In this parametric speaker, the ultrasonic waves radiated from the individual ultrasonic transducers are reflected by the corresponding reflection plates, and the ultrasonic waves reflected from the plurality of reflection plates are synthesized to obtain reproduced audible sounds.

JP 2000-005454 A JP 2005-101749 A JP 2009-290357 A

  A parametric speaker reproduces sound in the audible range by demodulating a modulated audio signal after oscillation. Here, if a new demodulation method is created, it may become a clue to further improve the characteristics of the parametric speaker.

  An object of the present invention is to provide an oscillation device that can realize a new demodulation method in a parametric speaker.

According to the present invention, a sheet-like vibration member;
A vibrator attached to one surface of the vibrating member;
A support portion for supporting an edge of the vibration member;
A reflecting portion facing the vibrating member and reflecting sound waves;
A sound emitting hole formed in at least one of the reflecting portion and the supporting portion;
An oscillating device is provided.

  According to the present invention, a new demodulation method can be realized in a parametric speaker.

It is sectional drawing of the oscillation apparatus which concerns on 1st Embodiment. It is sectional drawing which shows the layer structure of a vibrator | oscillator. It is a schematic diagram for demonstrating an example of the mechanism of a demodulation. It is sectional drawing of the oscillation apparatus which concerns on 2nd Embodiment. It is sectional drawing of the oscillation apparatus which concerns on 3rd Embodiment. It is a disassembled perspective view which shows the structure of the vibrator | oscillator of the oscillation apparatus which concerns on 4th Embodiment. It is sectional drawing of the oscillation apparatus which concerns on 5th Embodiment. It is sectional drawing of the oscillation apparatus which concerns on 6th Embodiment. It is sectional drawing of the oscillation apparatus which concerns on 7th Embodiment. It is a disassembled perspective view which shows the structure of the MEMS actuator used as a vibrator | oscillator of the oscillation apparatus which concerns on 8th Embodiment. It is a top view which shows the structure of the portable communication terminal which has an oscillation apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

[First Embodiment]
FIG. 1 is a cross-sectional view illustrating the configuration of the oscillation device according to the first embodiment. The oscillation device includes a sheet-like vibration member 10, a vibrator 20, a support part 40, and a reflection part 30. The vibrator 20 is a piezoelectric vibrator, for example, and is attached to one surface of the vibration member 10. The support unit 40 supports the edge of the vibration member 10. The reflection unit 30 faces the vibration member 10 and reflects sound waves oscillated from the vibrator 20 and the vibration member 10. Furthermore, a sound emitting hole 32 is formed in at least one of the reflecting portion 30 and the support portion 40. This oscillation device is used as an oscillation source of a parametric speaker, for example. The parametric speaker is used as a sound source of an electronic device (for example, a mobile phone, a laptop personal computer, a small game device, etc.). Details will be described below.

  The vibration member 10 vibrates due to vibration generated from the vibrator 20, and oscillates a sound wave having a frequency of 20 kHz or more, for example. The vibrator 20 also oscillates, for example, a sound wave having a frequency of 20 kHz or more when vibrated. The vibrating member 10 adjusts the basic resonance frequency of the vibrator 20. The fundamental resonance frequency of the mechanical vibrator depends on the load weight and compliance. Since the compliance is the mechanical rigidity of the vibrator, the basic resonance frequency of the vibrator 20 can be controlled by controlling the rigidity of the vibration member 10. The thickness of the vibration member 10 is preferably 5 μm or more and 500 μm or less. In addition, the vibration member 10 preferably has a longitudinal elastic modulus, which is an index indicating rigidity, of 1 GPa or more and 500 GPa or less. When the rigidity of the vibration member 10 is too low or too high, there is a possibility that the characteristics and reliability of the mechanical vibrator are impaired. The material constituting the vibration member 10 is not particularly limited as long as it is a material having a high elastic modulus with respect to the vibrator 20 that is a brittle material, such as metal or resin, but phosphor bronze or the like from the viewpoint of workability and cost. Stainless steel or the like is preferable.

  In the present embodiment, the planar shape of the vibrator 20 is a circle. However, the planar shape of the vibrator 20 is not limited to a circle. For example, the entire surface of the vibrator 20 facing the vibration member 10 is fixed to the vibration member 10 with an adhesive. Thereby, the entire surface of one surface of the vibrator 20 is restrained by the vibration member 10.

  The oscillation device further includes a signal generation unit 54 and a control unit 50. The signal generation unit 54 and the control unit 50 constitute an oscillation circuit (input unit) that oscillates the transducer 20 by inputting an oscillation signal to the transducer 20 and oscillates a sound wave from the transducer 20 and the vibrating member 10. ing. The signal generation unit 54 generates an electrical signal input to the vibrator 20, for example, a modulation signal in a parametric speaker. The transport wave of the modulation signal is, for example, an ultrasonic wave having a frequency of 20 kHz or higher, and specifically, an ultrasonic wave having a frequency of 100 kHz, for example. The control unit 50 controls the signal generation unit 54 in accordance with information input from the outside. When the oscillation device is used as a speaker, information input to the control unit 50 is an audio signal.

  As described above, the reflection unit 30 faces the vibration member 10 and reflects sound waves oscillated from the vibrator 20 and the vibration member 10. Although the material which comprises the reflection part 30 will not be specifically limited if it is a material which can reflect an ultrasonic wave, From a viewpoint of workability and cost, it is preferable that it is a metal, and aluminum or stainless steel is especially preferable, for example. The reflection unit 30 is formed in a flat plate shape, for example.

  In the case of the present embodiment, for example, the reflection portion 30 and the support portion 40 are integrally formed to constitute the case 4. The case 4 surrounds the vibrator 20 with a space between the case 20 and the case 20. In addition, when integrally forming the reflection part 30 and the support part 40 in this way, the reflection part 30 and the support part 40 can be comprised with the same kind of metal.

  The case 4 is formed in, for example, a semi-housing shape with one end open. More specifically, the case 4 is formed in a flat cylindrical shape with one end open and the other end closed. The other end of the case 4 is closed by the reflecting portion 30, and the support portion 40 constitutes a cylindrical side wall of the case 4. The vibration member 10 is attached to the case 4 so as to close the open end side of the case 4.

  Moreover, the sound emission hole 32 is formed in the side surface (namely, support part 40) which cross | intersects with respect to the surface (namely, reflection part 30) facing the open end in the case 4, for example. In addition, the number of the sound emission holes 32 is arbitrary. There may be one or more sound emitting holes 32.

  Here, the thickness of the reflecting portion 30 is preferably 100 μm or more, and more preferably 200 μm or more, from the viewpoint of making the mechanical strength sufficiently large. In addition, from the viewpoint of downsizing the oscillation device, it is preferable that the reflecting portion 30 is thin.

  In the present embodiment, the vibrator 20 is located on the same side as the reflection unit 30 with respect to the vibration member 10. However, the vibrator 20 may be located on the opposite side of the reflecting member 30 with respect to the vibration member 10.

  FIG. 2 is a cross-sectional view showing the layer structure of the vibrator 20 in the thickness direction. The vibrator 20 includes a piezoelectric body 22, an upper surface electrode 24, and a lower surface electrode 26.

  The piezoelectric body 22 is polarized in the thickness direction. The material constituting the piezoelectric body 22 may be either an inorganic material or an organic material as long as it has a piezoelectric effect. However, a material having high electromechanical conversion efficiency, for example, zirconate titanate (PZT) or barium titanate (BaTiO3) is preferable. The thickness h1 of the piezoelectric body 22 is, for example, not less than 10 μm and not more than 1 mm. When the thickness h1 is less than 10 μm, there is a possibility that the vibrator 20 is damaged during the manufacture of the oscillation device. On the other hand, if the thickness h1 is more than 1 mm, the electromechanical conversion efficiency becomes too low, and there is a possibility that a sufficiently large vibration cannot be obtained. The reason is that as the thickness of the vibrator 20 increases, the electric field strength in the piezoelectric vibrator decreases in inverse proportion.

  Although the material which comprises the upper surface electrode 24 and the lower surface electrode 26 is not specifically limited, For example, silver and silver / palladium can be used. Since silver is used as a general-purpose electrode material with low resistance, it has advantages in manufacturing process and cost. Since silver / palladium is a low-resistance material excellent in oxidation resistance, there is an advantage from the viewpoint of reliability. The thickness h2 of the upper surface electrode 24 and the lower surface electrode 26 is not particularly limited, but the thickness h2 is preferably 1 μm or more and 50 μm or less. When the thickness h2 is less than 1 μm, it is difficult to uniformly mold the upper surface electrode 24 and the lower surface electrode 26, and as a result, the electromechanical conversion efficiency may be reduced. Moreover, when the film thickness of the upper surface electrode 24 and the lower surface electrode 26 exceeds 100 μm, the upper surface electrode 24 and the lower surface electrode 26 serve as constraining surfaces with respect to the piezoelectric body 22, and there is a possibility that energy conversion efficiency is reduced.

  Next, a method for manufacturing the oscillation device will be described. First, the vibrator 20 is processed into a predetermined planar shape. Further, the vibrating member 10 is processed into a predetermined shape. At this stage, the piezoelectric body 22 of the vibrator 20 has already been polarized. Next, the vibrator 20 is fixed to the vibration member 10 using an adhesive such as an epoxy resin. The timing for fixing the vibration member 10 to the support portion 40 (case 4) may be after the vibrator 20 is fixed to the vibration member 10 or before the vibration member 10 is fixed. When the reflection unit 30 is separate from the support unit 40, the vibrator 20 is fixed to the vibration member 10, and after the vibration member 10 is fixed to the support unit 40, the reflection unit 30 is attached to the support unit 40. .

  Here, the vibrator 20 can have an outer diameter = φ18 mm, an inner diameter = φ12 mm, and a thickness = 100 μm. Further, as the upper surface electrode 24 and the lower surface electrode 26, for example, a silver / palladium alloy having a thickness of 8 μm (weight ratio is, for example, 7: 3) can be used. The vibrating member 10 may be made of phosphor bronze having an outer diameter = φ20 mm and a thickness = 50 μm (0.3 mm). The case 4 is formed in a cylindrical shape (for example, a cylindrical shape) with an outer diameter = φ22 mm and an inner diameter = φ20 mm, for example.

  Next, a case where the oscillation device according to the present embodiment is used as a parametric speaker will be described.

  First, the principle of a general parametric speaker will be described. A parametric speaker emits ultrasonic waves (transport waves) subjected to AM modulation, DSB modulation, SSB modulation, and FM modulation from each of a plurality of oscillation sources into the air, and due to nonlinear characteristics when the ultrasonic waves propagate into the air , To make an audible sound appear. Non-linear here means that the flow changes from laminar flow to turbulent flow when the Reynolds number indicated by the ratio between the inertial action and the viscous action of the flow increases. Since the sound wave is slightly disturbed in the fluid, the sound wave propagates nonlinearly. In particular, in the ultrasonic frequency band, the nonlinearity of sound waves can be easily observed. And when an ultrasonic wave is radiated in the air, harmonics accompanying the nonlinearity of the sound wave are remarkably generated. The sound wave is a dense state where the density of the molecular density is generated in the air. When it takes time for air molecules to recover from compression, air that cannot be recovered after compression collides with air molecules that continuously propagate, and a shock wave is generated. An audible sound is generated by this shock wave.

  Next, the principle when the oscillation device of this embodiment is used as a parametric speaker will be described. In this embodiment, when a modulation signal is input to the vibrator 20, ultrasonic waves according to the modulation signal are emitted from the vibrator 20 and the vibration member 10.

  FIG. 3 is a schematic diagram showing an example of a mechanism for demodulating the emitted ultrasonic wave, and corresponds to the cross-sectional view of FIG. As shown in FIG. 3, a part 1 of the emitted ultrasonic wave travels straight from the transducer 20 toward the reflection unit 30 and is reflected by the reflection unit 30. The other part 2 of the emitted ultrasonic wave interferes with the part 1 in the interference region 3 shown in FIG. Here, when the ultrasonic wave part 1 is reflected by the reflecting unit 30, the phase is inverted, that is, the phase is shifted by 1/2 of the wavelength. Part 1 reaches the interference region 3 after being reflected by the reflection unit 30. On the other hand, a part 2 of the ultrasonic wave goes straight to the interference region 3. That is, the part 1 of the ultrasonic wave reaches the interference region 3 via a longer distance than the other part 2. For this reason, a phase difference of (1/2 of wavelength) + α is generated between part 1 and part 2 of the ultrasonic wave before reaching the interference region 3. An audible sound is generated (demodulated) by overlapping part 1 and part 2 of ultrasonic waves having a phase difference of (1/2 of wavelength) + α. The audible sound is radiated to the outside of the case 4 through the sound emission hole 32.

  If α is ½ of the wavelength, there is no phase difference between the part 1 and part 2 of the ultrasonic wave in the interference region 3, making it difficult to perform demodulation appropriately. . For this reason, in order to suppress that said (alpha) becomes 1/2 of a wavelength, it is preferable to set the distance of the vibrating member 10 and the reflection part 30 to 1/4 or less of the wavelength of a sound wave.

  Thus, according to the present embodiment, a new demodulation method can be realized in the parametric speaker.

[Second Embodiment]
FIG. 4 is a cross-sectional view of the oscillation device according to the second embodiment. In the oscillation device according to the present embodiment, the angle formed by the vibration member 10 and the surface (that is, the reflection portion 30) facing the open end in the case 4 is an angle that spreads toward the sound emission hole 32 side. . That is, the vibration member 10 and the surface (the reflecting portion 30) facing the open end in the case 4 are arranged to be inclined with respect to each other. Thereby, the directivity to the sound emission hole 32 side of the audible sound demodulated in the interference area | region 3 improves. Therefore, an audible sound can be efficiently output from the sound emission hole 32 to the outside. The oscillation device according to the present embodiment is configured in the same manner as the oscillation device according to the first embodiment in other points. In the example of FIG. 4, an example in which the vibration member 10 is arranged to be inclined is illustrated. However, the relative arrangement of the vibration member 10 and the support portion 40 is the same as that of the first embodiment, and the relative arrangement of the reflection portion 30 and the support portion 40 is different from that of the first embodiment. The vibrating member 10 and the reflecting portion 30 may be inclined with respect to each other.

[Third Embodiment]
FIG. 5 is a cross-sectional view of the oscillation device according to the third embodiment. The oscillation device according to the present embodiment is configured in the same manner as the oscillation device according to the first or second embodiment, except that the sound emission hole 32 is formed in the reflection unit 30. That is, in the present embodiment, the sound emitting hole 32 is formed on the surface of the case 4 that faces the open end. Also in this embodiment, the same effect as the first or second embodiment can be obtained.

[Fourth Embodiment]
FIG. 6 is an exploded perspective view showing the configuration of the vibrator 20 of the oscillation device according to the fourth embodiment. The oscillation device according to the present embodiment is the same as the oscillation device according to the first embodiment, except that the vibrator 20 has a structure in which a plurality of piezoelectric bodies 22 and electrodes 24 are alternately stacked. It is a configuration. FIG. 6 shows an example in which the piezoelectric body 22 and the electrode 24 each have four layers, for a total of eight layers. The polarization direction of the piezoelectric body 22 is changed every layer and is alternated.

  Also in this embodiment, the same effects as those in the first to third embodiments can be obtained. Further, since the vibrator 20 has a structure in which a plurality of piezoelectric bodies 22 and electrodes 24 are alternately laminated, the amount of expansion and contraction of the vibrator 20 increases. Therefore, the output of the oscillation device can be increased.

[Fifth Embodiment]
FIG. 7 is a cross-sectional view of the oscillation device according to the fifth embodiment. In the oscillation device according to the present embodiment, a plurality of the oscillation devices according to the first to fourth embodiments are provided side by side in the surface direction of the vibration member 10.
Also according to this embodiment, the same effects as those of the first to fourth embodiments can be obtained. In addition, since a plurality of oscillation devices are provided, the output can be increased.

[Sixth Embodiment]
FIG. 8 is a cross-sectional view of the oscillation device according to the sixth embodiment. This oscillator has the same configuration as that of the oscillator according to the first to fifth embodiments, except that the vibrator 20 is provided on each side of the vibration member 10. That is, in this embodiment, the oscillation device has a bimorph structure in which both surfaces of the vibration member 10 are constrained by the vibrator 20. An oscillation signal is input to each transducer 20 from the signal generation unit 54. The two vibrators 20 may have the same shape or different shapes.

  According to this embodiment, the same effects as those of the first to fifth embodiments can be obtained. Further, since the vibrator 20 has a bimorph structure, a larger vibration can be obtained.

[Seventh Embodiment]
FIG. 9 is a cross-sectional view of the oscillation device according to the seventh embodiment. This oscillating device has the same configuration as that of the first to sixth embodiments except that the vibrating member 10 is attached to the support portion 40 via the second vibrating member 60. FIG. 9 shows a case similar to that of the first embodiment except for this point.

  The second vibration member 60 is formed so as to have lower rigidity than the vibration member 10. The second vibrating member 60 is formed of a resin material such as urethane, PET, and polyethylene. Although the thickness of the 2nd vibration member 60 is not specifically limited, The value is determined so that the ease of a movement of the edge part of the vibration member 10 can be ensured, and durability satisfy | fills a reference | standard.

  Also according to this embodiment, the same effects as those of the first to sixth embodiments can be obtained. Further, since the vibration member 10 is attached to the support portion 40 via the second vibration member 60, the end portion of the vibration member 10 can be brought closer to the free end. Therefore, the volume exclusion amount in the vibration of the vibration member 10 is increased, and the output of the oscillation device can be increased. Further, the impact resistance of the vibrating member 10 and the vibrator 20 can be increased.

[Eighth Embodiment]
The oscillating device according to the present embodiment relates to the first to seventh embodiments except that the resonator 20 includes a MEMS (Micro Electro Mechanical Systems) actuator 70 shown in FIG. The configuration is the same as that of the oscillation device.

  In the example shown in FIG. 10, the driving method of the MEMS actuator 70 is a piezoelectric method, and has a structure in which a piezoelectric thin film layer 72 is sandwiched between an upper movable electrode layer 74 and a lower movable electrode layer 76. The MEMS actuator 70 operates when a signal is input from the signal generation unit 54 to the upper movable electrode layer 74 and the lower movable electrode layer 76. For example, an aerosol deposition method is used for manufacturing the MEMS actuator 70, but the method is not limited to this method. However, it is preferable to use the aerosol deposition method because the piezoelectric thin film layer 72, the upper movable electrode layer 74, and the lower movable electrode layer 76 can be formed on curved surfaces. The driving method of the MEMS actuator 70 may be an electrostatic method, an electromagnetic method, or a heat conduction method.

  Also according to this embodiment, the same effects as those of the first to seventh embodiments can be obtained.

  Here, the oscillation device according to each of the above embodiments can be used as the speaker 102 of the mobile communication terminal 100, for example, as shown in FIG. The mobile communication terminal 100 has, for example, at least one flat rectangular parallelepiped casing 101. For example, the sound emission hole 32 of the speaker 102 (oscillator) is located on the side surface of the housing 101, and the output direction of the audible sound from the speaker 102 is the direction indicated by the arrow A in FIG. It is a preferable example that the direction is orthogonal. In addition, it is also preferable that the sound emission hole 32 is disposed on the front side of the housing 101.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

DESCRIPTION OF SYMBOLS 1 Part of ultrasonic wave 2 Other part of ultrasonic wave 3 Interference area 4 Case 10 Vibrating member 20 Piezoelectric vibrator 22 Piezoelectric body 24 Upper surface electrode 26 Lower surface electrode 30 Reflection part 32 Sound emitting hole 40 Support part 50 Control part 54 Signal Generation unit 60 Second vibrating member 70 MEMS actuator 72 Piezoelectric thin film layer 74 Upper movable electrode layer 76 Lower movable electrode layer 100 Portable communication terminal 101 Case 102 Speaker A Arrow

Claims (10)

A sheet-like vibrating member;
A vibrator attached to one surface of the vibrating member;
A support portion for supporting an edge of the vibration member;
A reflecting portion facing the vibrating member and reflecting sound waves;
A sound emitting hole formed in at least one of the reflecting portion and the supporting portion;
An oscillation device comprising:   The oscillation device according to claim 1, wherein the reflection portion is made of metal. An input unit that oscillates the vibrator by inputting an oscillation signal to the vibrator and oscillates a sound wave from the vibrator and the vibration member;
3. The oscillation according to claim 1, wherein the input unit oscillates the vibrator at a frequency of 20 kHz or more to oscillate a sound wave having a frequency of 20 kHz or more from the vibrator and the vibration member. apparatus.   The oscillation device according to claim 3, wherein a distance between the vibrating member and the reflecting portion is ¼ or less of a wavelength of the sound wave.   5. The reflection part and the support part are integrally formed with each other to form a case, and surround the vibrator with a space from the vibrator. The oscillation device described in 1. The case is formed in a semi-casing shape with one end open,
The vibration member is attached to the case so as to close the open end side of the case,
The oscillating device according to claim 5, wherein the sound emitting hole is formed on a side surface of the case that intersects the surface facing the open end.   The oscillation device according to claim 6, wherein an angle formed by the vibration member and a surface of the case facing the open end is an angle that spreads toward the sound emitting hole side. The case is formed in a semi-casing shape with one end open,
The vibration member is attached to the case so as to close the open end side of the case,
The oscillation device according to claim 5, wherein the sound emitting hole is formed in a surface of the case that faces the open end.   The oscillation device according to claim 1, wherein the vibrator is a piezoelectric vibrator.   The said vibrator | oscillator is MEMS (Micro Electro Mechanical Systems), The drive system is a piezoelectric system, an electrostatic system, an electromagnetic system, or a heat conduction system, It is any one of Claim 1 thru | or 8 characterized by the above-mentioned. Oscillation device.

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