JP2012029105A - 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 member 40 that supports an edge of the vibration member 10; and a demodulation film 30 opposed to the vibration member 10, and that has at least one penetrating hole 32. The oscillation device has an input part that inputs an oscillation signal to the vibrator 20 to vibrate the vibrator 20 and makes a sonic wave be generated from the vibrator 20 and the vibration member 10. A film thickness of the demodulation film 30 is one-fourth or less of a wavelength of the sonic wave.

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.

  In Patent Document 3, the first and second electrodes having through holes, the vibrating film sandwiched between the first and second electrodes and having a conductive layer, and a voltage is applied to the conductive layer, An electrostatic ultrasonic transducer is described.

JP 2000-005454 A JP 2005-101749 A JP 2007-195150 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 member for supporting an edge of the vibration member;
A demodulating film facing the vibrating member and having at least one through hole formed thereon;
An input unit that vibrates the vibrator by inputting an oscillation signal to the vibrator and oscillates a sound wave from the vibrator and the vibrating member;
With
An oscillation device is provided in which the thickness of the demodulation film is ¼ or less of the wavelength of the sound wave.

  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. FIG. 2 is a plan view of a demodulation film of the oscillation device in FIG. 1. 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 a disassembled perspective view which shows the structure of the vibrator | oscillator of the oscillation apparatus which concerns on 2nd Embodiment. It is sectional drawing of the oscillation apparatus which concerns on 3rd Embodiment. It is sectional drawing of the oscillation apparatus which concerns on 4th Embodiment. It is sectional drawing of the oscillation apparatus which concerns on 5th 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 6th 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. FIG. 2 is a plan view of the demodulating film 30 of the oscillation device of FIG. The oscillation device includes a sheet-like vibration member 10, a vibrator 20, a demodulation film 30, a support member 40, a signal generation unit 54, and a control unit 50. The vibrator 20 is a piezoelectric vibrator, for example, and is attached to one surface of the vibration member 10. The support member 40 supports the edge of the vibration member 10. The demodulating film 30 faces the vibration member 10. At least one through hole 32 is formed in the demodulating film 30. 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 thickness of the demodulating film 30 is ¼ or less of the wavelength of the oscillating sound wave. 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. 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 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 thickness of the demodulating film 30 is ¼ or less of the wavelength of the sound wave oscillated by the vibrator 20 and the vibrating member 10.
Here, the signal generation unit 54 preferably inputs a predetermined modulation signal to the vibrator 20 so that a sound wave having a frequency within a predetermined range is oscillated from the vibrator 20 and the vibrating member 10. Even if the sound wave oscillated by the vibrator 20 and the vibration member 10 fluctuates with time, the film thickness of the demodulation film 30 is ¼ or less of the wavelength of the sound wave oscillated by the vibrator 20 and the vibration member 10. It is sufficient to satisfy the condition.

  The demodulating film 30 is made of, for example, a resin. The thickness of the demodulating film 30 is preferably 0.5 mm or less in order to damage the shape of the electroacoustic transducer. The resin material constituting the demodulating film 30 is not particularly limited, but in view of versatility and workability, PET (polyethylene terephthalate), urethane, polyethylene, or the like is preferable.

  In the present embodiment, the demodulating film 30 has a plurality of through holes 32 arranged in a distributed manner over the entire surface. Further, the edge of the demodulating film 30 is fixed to the support member 40. For example, the demodulating film 30 is located on the opposite side of the vibrating member 10 with the vibrator 20 interposed therebetween. However, the demodulating film 30 may be located on the side opposite to the vibrator 20 via the vibrating member 10.

  FIG. 3 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 member 40 may be after the vibrator 20 is fixed to the vibration member 10 or before the vibration member 10 is fixed. The support member 40 is made of a metal such as stainless steel. Then, after fixing the vibrator 20 to the vibration member 10 and fixing the vibration member 10 to the support member 40, the demodulating film 30 is attached to the support member 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 support member 40 functions as a case of the oscillation device, and is formed in a cylindrical shape (for example, a cylindrical shape) having 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. 4 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. 4, a part 1 of the emitted ultrasonic wave travels straight from the vibrator 20 toward the through hole 32, for example. The other part 2 of the emitted ultrasonic wave, for example, travels straight from the transducer 20 toward the back surface of the demodulating film 30 (the surface facing the transducer 20), and then passes through the through hole 32 along the back surface. Go to the side. Thus, the ultrasonic waves 1 and 2 interfere with each other in the interference region 3 near the through hole 32. Here, part 1 of the ultrasonic wave goes straight toward the interference region 3, while part 2 reaches the interference region 3 through a bent path. That is, the other part 2 of the ultrasonic wave reaches the interference region 3 via a distance longer than the part 1. For this reason, there is a phase difference between part 1 and part 2 of the ultrasonic wave before reaching the interference region 3. An audible sound is generated (demodulated) by overlapping a part 1 and a part 2 of the ultrasonic waves that are out of phase with each other.

Here, the operation when the film thickness of the demodulating film 30 exceeds ¼ of the wavelength of the oscillated sound wave will be described. The demodulating film 30 is considered to have a sound wave propagation speed different from that of air. Therefore, a phase difference is generated between the ultrasonic wave passing through the through hole 32 and the ultrasonic wave radiated from the demodulating film 30 after traveling through the demodulating film 30. Then, demodulation is caused by the superposition of these ultrasonic waves. When the thickness of the demodulating film 30 exceeds ¼ of the wavelength, demodulation by this mechanism is more likely to occur, and at the same time, demodulation by the mechanism described above with reference to FIG. 4 is less likely to occur.
On the other hand, in the present embodiment, since the thickness of the demodulating film 30 is ¼ or less of the wavelength of the oscillated sound wave, demodulation by the mechanism as described above with reference to FIG. 4 occurs preferentially. .
The demodulating film 30 is made of a material having a large internal loss, and the value thereof is larger than the internal loss of the vibration member 10. In the present embodiment, the audible sound obtained by demodulating part 1 and part 2 of the ultrasonic wave in the path as described above is more dominant than the audible sound obtained by demodulating the ultrasonic wave traveling through the demodulating film 30. Therefore, deterioration of sound quality can be suppressed.

The phase difference between the part 1 and the part 2 of the ultrasonic waves is preferably ¼ or less of the wavelength of the oscillated sound wave. If the phase difference between the part 1 and the part 2 of the ultrasonic wave is ½ of the wavelength, the part 1 and the part 2 cancel each other. Also, the closer the phase difference between part 1 and part 2 of the ultrasonic wave is to ½ of the wavelength, the higher the canceling ratio, and the lower the output of audible sound.
On the other hand, by setting the phase difference between the part 1 and the part 2 of the ultrasonic wave to ¼ or less, the output efficiency of the audible sound can be improved while the audible sound is reliably demodulated.
Then, by setting the radius of the through hole 32 to ¼ or less of the wavelength of the oscillated sound wave, the phase difference between the part 1 and part 2 of the ultrasonic wave is ¼ or less of the wavelength of the oscillated sound wave. It becomes easy to.

In addition, when the demodulating film 30 is made of a hard material such as a metal film, the other part 2 of the ultrasonic wave is easily reflected by the demodulating film 30, and thus it is difficult to travel on the ideal path as described above. .
On the other hand, in the present embodiment, the demodulating film 30 is made of a soft material such as a resin, so that the other part 2 of the ultrasonic wave is less likely to be reflected by the demodulating film 30, and as described above. It becomes easy to go on an ideal route. As a result, demodulation with the mechanism described with reference to FIG. 4 is likely to occur.

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

[Second Embodiment]
FIG. 5 is an exploded perspective view showing the configuration of the vibrator 20 of the oscillation device according to the second 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. 5 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.

  In this embodiment, the same effect as that of the first embodiment 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.

[Third Embodiment]
FIG. 6 is a cross-sectional view of the oscillation device according to the third embodiment. In the oscillation device according to the present embodiment, a plurality of the oscillation devices according to the first or second embodiment are provided side by side in the surface direction of the demodulation film 30 and the vibration member 10.
Also according to this embodiment, the same effect as that of the first embodiment can be obtained. In addition, since a plurality of oscillation devices are provided, the output can be increased.

[Fourth Embodiment]
FIG. 7 is a cross-sectional view of the oscillation device according to the fourth embodiment. This oscillation device has the same configuration as that of the oscillation device according to the first or second embodiment, except that the vibrator 20 is provided on both surfaces 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 effect as that of the first or second embodiment can be obtained. Further, since the vibrator 20 has a bimorph structure, a larger vibration can be obtained.

[Fifth Embodiment]
FIG. 8 is a cross-sectional view of the oscillation device according to the fifth embodiment. This oscillation device has the same configuration as that of any of the first to fourth embodiments, except that the vibration member 10 is attached to the support member 40 via the second vibration member 60. FIG. 8 illustrates 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 effect as that of the first embodiment can be obtained. Further, since the vibration member 10 is attached to the support member 40 via the second vibration member 60, the end 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.

[Sixth Embodiment]
The oscillating device according to the present embodiment relates to the first to fifth embodiments except that it has a MEMS (Micro Electro Mechanical Systems) actuator 70 shown in FIG. The configuration is the same as that of any of the oscillation devices.

  In the example shown in FIG. 9, 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 the present embodiment, the same effects as in any of the first to fifth embodiments can be obtained.

  Note that 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.

  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 10 Vibrating member 20 Vibrator 22 Piezoelectric body 24 Upper surface electrode 26 Lower surface electrode 30 Demodulating film 32 Through-hole 40 Support member 50 Control part 54 Signal generation part 60 1st 2 vibration member 70 MEMS actuator 72 Piezoelectric thin film layer 74 Upper movable electrode layer 76 Lower movable electrode layer 100 Portable communication terminal 102 Speaker

Claims (10)

A sheet-like vibrating member;
A vibrator attached to one surface of the vibrating member;
A support member for supporting an edge of the vibration member;
A demodulating film facing the vibrating member and having at least one through hole formed thereon;
An input unit that vibrates the vibrator by inputting an oscillation signal to the vibrator and oscillates a sound wave from the vibrator and the vibrating member;
With
An oscillation device, wherein the thickness of the demodulating film is ¼ or less of the wavelength of the sound wave.   2. The oscillation device according to claim 1, wherein the input unit oscillates a sound wave having a frequency of 20 kHz or more from the vibrator and the vibration member by vibrating the vibrator at a frequency of 20 kHz or more.   The oscillation device according to claim 1, wherein a radius of the through hole is equal to or less than ¼ of a wavelength of the sound wave.   The oscillation device according to claim 1, wherein the demodulation film is a resin film.   The oscillation device according to claim 1, wherein an edge of the demodulating film is fixed to the support member.   The oscillation device according to claim 1, wherein the vibrator is a piezoelectric vibrator.   The oscillation device according to claim 1, wherein the vibrator is a MEMS (Micro Electro Mechanical Systems) and a driving method thereof is a piezoelectric method.   The oscillation device according to claim 1, wherein the vibrator is a MEMS, and a driving method thereof is an electrostatic method.   The oscillation device according to claim 1, wherein the vibrator is a MEMS, and a driving method thereof is an electromagnetic method.   The oscillation device according to claim 1, wherein the vibrator is a MEMS, and a driving method thereof is a heat conduction method.

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