JP2012217030A - Electronic device, output control method of the electronic apparatus, and oscillation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smooth out frequency characteristics of a sound pressure level in an electronic device using an oscillation device having a piezoelectric vibrator.SOLUTION: An electronic device 100 includes: a piezoelectric vibrator 10; a vibration member 20 for restricting the piezoelectric vibrator 10 on one surface; a support member 30 for holding the vibration member 20; and a housing 32 for holding the support member 30 through an attenuation material 40. When the resonance frequency of a vibration system composed of the piezoelectric vibrator 10 and the vibration member 20 is indicated as f, the frequency that the internal loss of the attenuation material 40 reaches its maximum ranges from f×0.75 (Hz) or higher to f×1.25 (Hz) or lower.

Description

  The present invention relates to an electronic device having a piezoelectric vibrator, an output control method for the electronic device, and an oscillation device.

  Various studies have been made on technologies relating to an oscillation device that oscillates sound waves. For example, the technique described in Patent Document 1 is a technique related to an ultrasonic sensor, and describes that ultrasonic detection sensitivity is improved by an ultrasonic sensor including a vibration damping member. Moreover, for example, the techniques described in Patent Documents 2 to 5 are techniques related to electroacoustic transducers.

  The technique described in Patent Document 2 relates to an electrodynamic electroacoustic transducer using a voice coil or the like. The techniques described in Patent Documents 3 to 8 relate to a piezoelectric electroacoustic transducer using a piezoelectric vibrator. The technique described in Patent Document 9 is to control the frequency of a carrier wave signal in a super-directional speaker according to a demodulation distance. Furthermore, the technique described in Patent Document 10 is to fix one or a plurality of speakers to a balance member supported at the upper end of a support column.

JP 2009-20086 JP 2003-163981 A International Publication No. 2007/083497 Pamphlet JP 2006-303675 A Japanese Patent Laid-Open No. 9-271096 JP 2004-96629 A JP 2001-160999 A Japanese Utility Model Publication No. 63-165999 JP 2006-81117 A JP 2006-261909 A

In an oscillation device having a piezoelectric vibrator, vibration energy concentrates in the vicinity of the resonance frequency due to the high mechanical quality factor of the piezoelectric vibrator. For this reason, the vibration displacement amount becomes large at a specific frequency, and a valley occurs in the frequency characteristics of the sound pressure level.
Therefore, it is difficult to realize a frequency characteristic of a flat sound pressure level in an electronic device using an oscillation device having a piezoelectric vibrator.

  An object of the present invention is to flatten the frequency characteristic of sound pressure level in an electronic apparatus using an oscillation device having a piezoelectric vibrator.

According to the present invention, a piezoelectric vibrator;
A vibration member that restrains the piezoelectric vibrator on one surface;
A support member for holding the vibration member;
A housing holding the support member via a damping material;
With
When the resonance frequency of a vibration system constituted by the piezoelectric vibrator and the vibration member is f _n , the frequency at which the internal loss of the damping material is maximized is f _n × 0.75 (Hz) or more and f _n ×. An electronic device having a frequency of 1.25 (Hz) or less is provided.

  According to the present invention, there is provided the output control method for an electronic device described above, wherein the output control method for the electronic device controls the directivity of the sound wave by controlling the frequency of the sound wave output by the electronic device. The

  According to the present invention, a piezoelectric vibrator, a vibration member that restrains the piezoelectric vibrator on one surface, and an elastic member that holds one edge of the one surface of the vibration member or the other surface opposite to the one surface. And a support member that holds the elastic member.

  According to the present invention, an electronic device equipped with the above-described oscillation device is provided.

  According to the present invention, the frequency characteristic of the sound pressure level can be flattened in an electronic device using an oscillation device having a piezoelectric vibrator.

It is sectional drawing which shows the electronic device which concerns on 1st Embodiment. It is sectional drawing which shows the piezoelectric vibrator shown in FIG. It is a graph which shows the frequency characteristic of a dielectric loss tangent in the damping material shown in FIG. It is a graph which shows the frequency characteristic of the sound pressure level of the electronic device which concerns on 1st Embodiment and a comparative example. It is a schematic diagram which shows the output control method of the electronic device shown in FIG. It is sectional drawing which shows the electronic device which concerns on 2nd Embodiment. It is sectional drawing which shows the modification of the electronic device shown in FIG.

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

  FIG. 1 is a cross-sectional view showing an electronic device 100 according to the first embodiment. The electronic device 100 includes a piezoelectric vibrator 10, a vibration member 20, a support member 30, and a housing 32.

The vibration member 20 restrains the piezoelectric vibrator 10 on one surface. The support member 30 holds the vibration member 20. The housing 32 holds the support member 30 via the damping material 40. When the resonance frequency of the vibration system composed of the piezoelectric vibrator 10 and the vibration member 20 is fn, the frequency at which the internal loss of the damping material 40 is maximized is f _n × 0.75 (Hz) or more and f _n × 1. .25 (Hz) or less. Hereinafter, the configuration of the electronic device 100 will be described in detail.

  The electronic device 100 includes an oscillation device 200 and a housing 32. The oscillation device 200 includes the piezoelectric vibrator 10, the vibration member 20, and the support member 30. The electronic device 100 is a mobile terminal device such as a mobile phone.

  The vibration member 20 has, for example, a flat plate shape. The vibration member 20 is made of a material having a high elastic modulus with respect to a ceramic that is a brittle material, such as metal or resin, and is made of a general-purpose material such as phosphor bronze or stainless steel. The thickness of the vibration member 20 is preferably 5 to 500 μm. The longitudinal elastic modulus of the vibration member 20 is preferably 1 to 500 GPa. When the longitudinal elastic modulus of the vibration member 20 is excessively low or high, the vibration characteristics and reliability of the oscillation device may be impaired.

The damping material 40 is made of, for example, a urethane material or a polyester nonwoven fabric. In the drive oscillator 200, the frequency of internal loss is maximum damping material 40, _{f n} × 0.75 (Hz) or _{f n} × is at 1.25 (Hz) or less, preferably _{f n} × 0 .95 (Hz) or more and f _n × 1.05 (Hz) or less. When the oscillation device 200 is driven, that is, when the vibration system of the oscillation device 200 is oscillating, the temperature of the damping material 40 is, for example, 40 (° C.) or less.

As shown in FIG. 1, the housing 32 holds the support member 30 via a plurality of attenuation materials 42, 44, 46 that are different from each other when the oscillation device 200 is driven, for example, at the frequency at which the internal loss is maximum. Yes. The frequency at which the internal loss in the damping material 42, the damping material 44, and the damping material 46 is maximized corresponds to each of a plurality of resonance frequencies of the vibration system of the oscillation device 200, for example.
Note that the number of the plurality of attenuation materials having different frequencies at which the internal loss is maximized can be appropriately determined depending on the number of resonance frequencies and the like.

As shown in FIG. 1, the damping material 42, the damping material 44, and the damping material 46 are laminated on the housing 32, for example.
Moreover, the housing | casing 32 has the sound hole 50 for outputting the sound wave output from one surface of the vibration member 20, for example. As shown in FIG. 1, the sound hole 50 is composed of, for example, a plurality of openings provided in the support member 30 and separated from each other.

As shown in FIG. 1, the electronic device 100 includes a resin material 22. The support member 30 holds the vibration member 20 via the resin material 22. At this time, the vibration system of the oscillation device 200 is configured by the piezoelectric vibrator 10, the vibration member 20, and the resin material 22.
The resin material 22 is provided at the edge of the vibration member 20, for example. The resin material 22 may be integrally provided on the entire circumference of the vibration member 20 or may be constituted by a plurality separated from each other. The resin material 22 is made of, for example, a resin material such as urethane, PET, or polyethylene.

  As shown in FIG. 1, the electronic device 100 includes, for example, the piezoelectric vibrator 10 on both surfaces of the vibration member 20. In this case, the oscillation device 200 has a bimorph structure. Therefore, the vibration amplitude of the oscillation device can be increased.

  FIG. 2 is a cross-sectional view showing the piezoelectric vibrator 10 shown in FIG. As shown in FIG. 2, the piezoelectric vibrator 10 includes a piezoelectric body 70, an upper electrode 72, and a lower electrode 74. The piezoelectric body 70 is sandwiched between the upper electrode 72 and the lower electrode 74. The piezoelectric body 70 is polarized in the thickness direction (vertical direction in FIG. 2). The piezoelectric vibrator 10 has, for example, a circle or an ellipse in a plane direction parallel to one surface of the vibration member 20.

The piezoelectric body 70 is made of a material having a piezoelectric effect, for example, lead zirconate titanate (PZT) or barium titanate (BaTiO ₃ ) as a material having high electromechanical conversion efficiency. The thickness of the piezoelectric body 70 is preferably 10 μm to 1 mm. When the thickness is less than 10 μm, the piezoelectric body 70 is made of a brittle material, and thus is easily damaged during handling. On the other hand, when the thickness exceeds 1 mm, the electric field strength of the piezoelectric body 70 is reduced. For this reason, the energy conversion efficiency is reduced.

  The upper electrode 72 and the lower electrode 74 are made of a material having electrical conductivity, for example, silver or a silver / palladium alloy. Silver is a low-resistance general-purpose material and is advantageous from the viewpoint of manufacturing cost and manufacturing process. Further, the silver / palladium alloy is a low resistance material excellent in oxidation resistance and excellent in reliability. The thickness of the upper electrode 72 and the lower electrode 74 is preferably 1 to 50 μm. When the thickness is less than 1 μm, it becomes difficult to form the film uniformly. On the other hand, when the thickness exceeds 50 μm, the upper electrode 72 or the lower electrode 74 serves as a restraint surface with respect to the piezoelectric body 70 and causes a decrease in energy conversion efficiency.

  The electronic device 100 includes a control unit 90 and a signal generation unit 92. The signal generator 92 is connected to the piezoelectric vibrator 10 and generates an electric signal input to the piezoelectric vibrator 10. The control unit 90 is connected to the signal generation unit 92 and controls signal generation by the signal generation unit 92. The control unit 90 controls the generation of the signal of the signal generation unit 92 based on information input from the outside, whereby the output of the oscillation device 200 can be controlled.

When the oscillation device 200 is used as a parametric speaker, the control unit 90 inputs a modulation signal as a parametric speaker via the signal generation unit 92. In this case, the piezoelectric vibrator 10 uses a sound wave of 20 kHz or more, for example, 100 kHz, as a signal transport wave.
When the oscillation device 200 is used as a normal speaker, the control unit 90 may input the audio signal as it is to the piezoelectric vibrator 10 via the signal generation unit 92.
When the oscillation device 200 is used as a sound wave sensor, the signal input to the control unit 90 is a command signal for oscillating sound waves. When the oscillation device 200 is used as a sound wave sensor, the signal generation unit 92 causes the piezoelectric vibrator 10 to generate a sound wave having a resonance frequency of the piezoelectric vibrator 10.

  The principle of operation of the parametric speaker is as follows. The principle of operation of a parametric speaker is the principle that audible sound appears due to the non-linear characteristics when ultrasonic waves that have been subjected to AM modulation, DSB modulation, SSB modulation, and FM modulation are emitted into the air and the ultrasonic waves propagate into the air. The sound reproduction is performed with Non-linear here means transition from laminar flow to turbulent flow when the Reynolds number indicated by the ratio of the inertial action and viscous action of the flow increases. That is, since the sound wave is slightly disturbed in the fluid, the sound wave propagates nonlinearly. In particular, when ultrasonic waves are radiated into the air, harmonics accompanying non-linearity are prominently generated. The sound wave is a dense state in which molecular groups in the air are mixed. When it takes time for air molecules to recover from compression, air that cannot be recovered after compression collides with continuously propagating air molecules, generating shock waves and producing audible sound.

FIG. 5 is a schematic diagram illustrating an output control method of the electronic device 100 illustrated in FIG. 1. When the oscillation device 200 according to the present embodiment is used as a parametric speaker, the user can arbitrarily control the directivity angle of sound waves as shown in FIG. That is, the directivity of the ultrasonic wave can be changed by changing the frequency of the ultrasonic wave that carries the audio signal.
For example, by increasing the ultrasonic frequency, the ultrasonic directivity angle becomes narrower. In FIG. 5, the directivity angle of the ultrasonic wave is narrow in the order of the region 60, the region 62, and the region 64. At this time, the frequency of the ultrasonic wave output from the oscillation device 200 increases in the order of the region 60, the region 62, and the region 64.

Next, the operation and effect of this embodiment will be described. In the electronic device 100 according to the present embodiment, the housing 32 holds the support member 30 via the damping material 40. The support member 30 holds the vibration system of the oscillation device 200. Furthermore, when the resonance frequency of the vibration system constituted by the piezoelectric vibrator 10 and the vibration member 20 is f _n , the frequency at which the internal loss of the damping material 40 is maximum is f _n × 0.75 (Hz) or more f _n × 1.25 (Hz) or less.

  In an oscillating device using a piezoelectric vibrator, due to the high mechanical quality factor of the piezoelectric vibrator, a valley occurs in the frequency characteristics of the sound pressure level. In addition, in the vicinity of the resonance frequency where the vibration energy is concentrated, vibration from the vibration system of the oscillation device may be transmitted to the housing holding the vibration system. In this case, in the vicinity of the resonance frequency, acoustic radiation is generated from the vibration system and the casing, and the sound pressure level increases. Therefore, the peaks and valleys appearing in the frequency characteristics of the sound pressure level are further increased.

  According to the present embodiment, the resonance frequency of the vibration system is matched with the frequency at which the internal loss of the damping material 40 is maximized. This suppresses the transmission of vibration energy from the vibration system to the housing 32 in the vicinity of the resonance frequency of the vibration system. Compared with this, transmission of vibration energy from the vibration system to the housing 32 is not suppressed in a frequency region other than the vicinity of the resonance frequency of the vibration system. Therefore, in an electronic device using an oscillation device having a piezoelectric vibrator, it is possible to realize a flat sound pressure level frequency characteristic.

An oscillation device having a piezoelectric vibrator has a plurality of vibration modes due to, for example, the shape of the piezoelectric vibrator. These vibration modes may induce vibration of the casing connected to the vibration system depending on the shape and the like.
In the present embodiment, the housing 32 holds the support member 30 via the damping material 42, the damping material 44, and the damping material 46 having different frequencies at which the internal loss is maximized. The support member 30 holds the vibration system.
For this reason, it is possible to match a plurality of resonance frequencies at which each vibration mode is generated with a frequency at which the internal loss of the damping material is maximized. This suppresses the transmission of vibration energy from the vibration system to the support member in the vicinity of a plurality of resonance frequencies where each vibration mode occurs. Therefore, in an electronic device using an oscillation device having a piezoelectric vibrator, it is possible to realize a flat sound pressure level frequency characteristic.

  FIG. 3 is a graph showing an example of frequency characteristics of dielectric loss tangent of the damping material 40 according to the first embodiment. The plurality of damping materials (material A, material B, and material C) shown in FIG. 3 are different from each other in frequency at which the internal loss is maximum. FIG. 3 shows the frequency characteristics of each attenuation material at 25 (° C.).

FIG. 4 is a graph illustrating frequency characteristics of sound pressure levels of the electronic devices according to the first embodiment and the comparative example.
The electronic device according to the comparative example has the same configuration as that of the electronic device 100 according to the present embodiment (not shown) except that the electronic device does not have the attenuation material 40.
The electronic device 100 according to this embodiment shown in FIG. 4 uses the damping material 40 shown in FIG. At this time, the frequency at which the internal loss is maximum damping material 40 shown in Figure 3, the resonance frequency of the vibration system having the oscillation device 200 of the electronic device 100 shown in FIG. 4 is taken as f _n, f _n × is 0.75 (Hz) or _{f n} × 1.25 (Hz) or less.

  As shown in FIG. 4, the electronic device according to the comparative example has a sound pressure level peak near 1000 Hz, around 4000 Hz, and around 10000 Hz. On the other hand, the electronic device 100 according to the present embodiment exhibits a flat sound pressure level at 1000 to 10,000 Hz. Thus, according to the present embodiment, it can be seen that a frequency characteristic of a flat sound pressure level can be realized.

Further, according to the present embodiment, it is possible to realize the oscillation device 200 having a frequency characteristic of a flat sound pressure level. For this reason, for example, as shown in FIG. 5, even when the frequency of the ultrasonic wave is changed so as to have different directivity angles, it is possible to obtain a high sound pressure level at an arbitrary frequency.
Accordingly, it is possible to realize an electronic apparatus having an oscillation device that can easily control directivity.

  FIG. 6 is a cross-sectional view showing the electronic device 102 according to the second embodiment, and corresponds to FIG. 1 in the first embodiment. The electronic device 102 according to the present embodiment has the same configuration as the electronic device 100 according to the first embodiment except for the configuration described below. That is, the electronic device 102 includes the oscillation device 200.

As shown in FIG. 6, the damping material 40 is provided on the edge of the other surface opposite to the one surface of the vibration member 20 and holds the edge. The support member 30 holds the damping material 40. In the present embodiment, the damping material 40 functions as an elastic material.
In the present embodiment, the oscillation device 200 includes the piezoelectric vibrator 10, the vibration member 20, the damping material 40, and the support member 30.
The damping material 40 may be provided on one surface of the vibration member 20 (not shown).

  The support member 30 is directly fixed by the housing 32. As shown in FIG. 6, the damping material 40 is fixed on a protruding portion that protrudes from the support member 30, for example. At this time, the vibration member 20 is fixed on the damping material 40 fixed to the support member 30.

FIG. 7 is a cross-sectional view illustrating a modified example of the electronic device 102 illustrated in FIG. 6. As shown in FIG. 7, a resin material 22 may be provided on the other surface of the vibration member 20. In this case, the damping material 40 holds the vibration member 20 via the resin member 22.
The resin member 22 is provided on the entire other surface of the vibration member 20, for example. Further, the resin member 22 may be provided only on the edge of the vibration member 20 (not shown).

Also in this embodiment, the same effect as that of the first embodiment can be obtained.
Further, the damping material 40 that holds the other surface of the vibration member 20 functions as an elastic material. That is, the end portion of the vibration member 20 is a free end. For this reason, the vibration member 20 has a piston-type vibration state. Thereby, the volume exclusion amount of the vibration member 20 when the vibration member 20 vibrates increases. Therefore, the sound pressure level of the oscillation device can be improved. This effect can be obtained without depending on the frequency characteristics of the attenuation material included in the electronic device.

  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 10 Piezoelectric vibrator 20 Vibrating member 22 Resin member 30 Support member 32 Case 40 Attenuating material 42 Attenuating material 44 Attenuating material 46 Attenuating material 50 Sound hole 60 Area 62 Area 64 Area 70 Piezoelectric body 72 Upper electrode 74 Lower electrode 90 Control part 92 Signal generator 100 Electronic device 102 Electronic device 200 Oscillator

Claims (9)

A piezoelectric vibrator;
A vibration member that restrains the piezoelectric vibrator on one surface;
A support member for holding the vibration member;
A housing holding the support member via a damping material;
With
When the resonance frequency of a vibration system constituted by the piezoelectric vibrator and the vibration member is f _n , the frequency at which the internal loss of the damping material is maximized is f _n × 0.75 (Hz) or more and f _n ×. Electronic equipment that is 1.25 (Hz) or less. The electronic device according to claim 1,
The electronic device in which the casing holds the support member via a plurality of the attenuation materials having different frequencies at which internal loss is maximized. The electronic device according to claim 2,
The electronic device in which the plurality of damping materials are stacked on the casing. The electronic device according to any one of claims 1 to 3,
The support member holds the vibration member via a resin material,
The vibration system is an electronic device including the resin material. It is the output control method of the electronic device of any one of Claims 1 thru | or 4, Comprising:
An output control method for an electronic device that controls the directivity of the sound wave by controlling the frequency of the sound wave output by the electronic device. A piezoelectric vibrator;
A vibration member that restrains the piezoelectric vibrator on one surface;
An elastic member that holds an edge of either one surface of the vibration member or the other surface opposite to the one surface;
A support member for holding the elastic member;
An oscillation device comprising: The oscillation device according to claim 6,
The oscillation device wherein the elastic member holds the vibration member via a resin material. The oscillation device according to claim 6,
When the resonance frequency of a vibration system constituted by the piezoelectric vibrator and the vibration member is f _n , the frequency at which the internal loss of the elastic member is maximized is f _n × 0.75 (Hz) or more and f _n ×. An oscillation device that is 1.25 (Hz) or less.   An electronic device on which the oscillation device according to any one of claims 6 to 8 is mounted.

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