JP2012029078A - Oscillation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variation in oscillation characteristics of an oscillation device.SOLUTION: The oscillation device includes: two vibrating members 10; a piezoelectric vibrator 20; and a support 40. The two vibrating members 10 each have a sheet shape. The support 40 has a frame-shape and the inner surface thereof supports edges of the vibrating members 10. The piezoelectric vibrator 20 is sandwiched between the two vibrating members 10. In each of the two vibrating members 10, a surface in contact with at least the piezoelectric vibrator 20 has conductivity.

Description

  The present invention relates to an oscillation device.

  In recent years, 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 is composed of 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 Document 1, it is expected to use a piezoelectric vibrator as an electroacoustic transducer.

  As a use of the piezoelectric vibrator, there is a sound wave sensor. The sound wave sensor is a sensor that detects a distance to an object using a sound wave oscillated from a piezoelectric vibrator.

International Publication No. 2007/026736 Pamphlet

  In order to use the piezoelectric vibrator as an oscillation device, it is necessary to provide electrodes and lead terminals on both sides of the piezoelectric vibrator and to apply a voltage to the piezoelectric vibrator through the electrodes. Soldering is necessary to connect the lead terminal to the electrode. If the amount of solder varies, the oscillation characteristics of the oscillation device may vary.

  An object of the present invention is to provide an oscillation device that can suppress variation in oscillation characteristics.

According to the present invention, a piezoelectric vibrator;
A sheet-like first vibrating member in contact with the first surface of the piezoelectric vibrator;
A sheet-like second vibrating member in contact with the second surface of the piezoelectric vibrator;
A support that supports edges of the first vibrating member and the second vibrating member;
With
The piezoelectric vibrator is sandwiched between the first vibrating member and the second vibrating member,
The first vibration member and the second vibration member are provided with an oscillation device in which at least a surface in contact with the piezoelectric vibrator has conductivity.

  According to the present invention, it is possible to suppress variations in characteristics of the piezoelectric vibrator.

It is sectional drawing which shows the structure of the oscillation apparatus which concerns on 1st Embodiment also including a peripheral circuit. It is a top view of the oscillation apparatus shown in FIG. It is sectional drawing which shows the structure of the thickness direction of a piezoelectric vibrator. It is a perspective exploded view which shows the structure of the piezoelectric vibrator of the transmitter which concerns on 2nd Embodiment. It is a top view of the oscillation apparatus which concerns on 3rd Embodiment. It is a top view of the oscillation device concerning a 4th embodiment. It is sectional drawing which shows the structure of the oscillation apparatus which concerns on 5th Embodiment also including a peripheral circuit. FIG. 8 is a plan view of the oscillation device illustrated in FIG. 7. It is a top view which shows the modification of FIG. It is sectional drawing which shows the structure of the oscillation apparatus which concerns on 6th Embodiment also including a peripheral circuit. It is a top view of the oscillation apparatus shown in FIG. It is a top view which shows the structure of the portable communication terminal used in an Example.

  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.

(First embodiment)
FIG. 1 is a cross-sectional view showing the configuration of the oscillation device according to the first embodiment, including peripheral circuits. FIG. 2 is a plan view of the oscillation device shown in FIG. The oscillation device includes two vibration members 10, a piezoelectric vibrator 20, and a support body 40. The two vibration members 10 have a sheet shape. The support body 40 is a frame-like member, and the inner side surface supports the edge of the vibration member 10. The piezoelectric vibrator 20 is sandwiched between two vibration members 10. The two vibrating members 10 have conductivity at least on the surface in contact with the piezoelectric vibrator 20. This oscillation device is used as an oscillation source of a speaker or a sound wave sensor, for example. When the oscillation device is used as a speaker, the oscillation device is used as a sound source of an electronic device (for example, a mobile phone, a laptop personal computer, a small game device, or the like). Details will be described below.

  The vibration member 10 vibrates due to vibration generated from the piezoelectric vibrator 20. The vibrating member 10 adjusts the basic resonance frequency of the piezoelectric 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 piezoelectric 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 piezoelectric vibrator 20 which is a brittle material such as metal or resin, but phosphor bronze from the viewpoint of workability and cost Or stainless steel is preferred.

  In the present embodiment, the piezoelectric vibrator 20 is rectangular, for example, square. The outer edge of the piezoelectric vibrator 20 is located inside the portion of the vibration member 10 supported by the support body 40. Solder is not provided at the interface between the two vibrating members 10 and the piezoelectric vibrator 20.

  Further, at least one of the two vibrating members 10 is provided with an opening 12 penetrating vertically. A part of the opening 12 does not overlap the piezoelectric vibrator 20 in plan view. In the present embodiment, the opening 12 is formed by removing a portion corresponding to each of the four corners of the support body 40 that is a rectangular frame in the vibration member 10 into a rectangular shape. That is, the vibration member 10 is a substantially cross-shaped beam, and four ends thereof are connected to the centers of the four sides of the support body 40. A piezoelectric vibrator 20 is held at the center of the vibration member 10.

  The oscillation device has a control unit 50 and a signal generation unit 54 as an oscillation circuit. The signal generator 54 generates an electrical signal that is input to the piezoelectric vibrator 20. The control unit 50 controls the signal generation unit 54 based on 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. When the oscillation device is used as a sound wave sensor, the signal input to the control unit 50 is a command signal indicating that a sound wave is transmitted. When the oscillation device is used as a sound wave sensor, the signal generation unit 54 causes the piezoelectric vibrator 20 to generate a sound wave having a resonance frequency of the piezoelectric vibrator 20.

FIG. 3 is a cross-sectional view illustrating the configuration of the piezoelectric vibrator 20 in the thickness direction. The piezoelectric 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 such as zirconate titanate (PZT) or barium titanate (BaTiO ₃ ) is preferable. The thickness h of the piezoelectric body 22 is, for example, not less than 10 μm and not more than 1 mm. When the thickness h ₁ is less than 10 μm, there is a possibility that the piezoelectric vibrator 20 is damaged when the oscillation device is manufactured. Further if the thickness h ₁ of 1mm greater than the electro-mechanical conversion efficiency is too low, not obtained vibration large enough. The reason is that as the thickness of the piezoelectric vibrator 20 increases, the electric field strength in the piezoelectric vibrator decreases in inverse proportion. The thickness of the piezoelectric body 22 may be equal to or different from each other.

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 h ₂ of the upper surface electrode 24 and the lower surface electrode 26 is not particularly limited, but the thickness h ₂ is preferably 1 μm or more and 50 μm or less. The thickness h ₂ is less than 1 [mu] m, it becomes difficult to uniformly mold the upper electrode 24 and the lower electrode 26, as a result, the electromechanical conversion efficiency may be lowered. 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 become restraining surfaces with respect to the piezoelectric body 22, and there is a possibility that the energy conversion efficiency is lowered. come.

  Next, a method for manufacturing the oscillation device will be described. First, the piezoelectric vibrator 20 is processed into a predetermined planar shape. Further, the vibrating member 10 is processed into a predetermined shape. At this point, the piezoelectric vibrator 20 has already been polarized. Next, the vibration member 10 is fixed to the support body 40 while the piezoelectric vibrator 20 is held between the vibration members 10. The support 40 is made of a metal such as stainless steel.

  Here, the piezoelectric 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 40 is, for example, a hollow case having an outer diameter = φ22 mm and an inner diameter = φ20 mm.

  A plurality of sets of the vibration member 10 and the piezoelectric vibrator 20 may be provided. In this case, the oscillation device can be used as a parametric speaker. When used as a parametric speaker, the piezoelectric vibrator 20 uses a sound wave of 20 kHz or more, for example, 100 kHz, as a signal transport wave.

  In general, a piezoelectric vibrator has a high mechanical quality factor Q. For this reason, since energy concentrates in the vicinity of the fundamental resonance frequency, the sound wave is large near the resonance frequency, but the sound wave is remarkably attenuated in other bands. On the other hand, the parametric speaker may oscillate a single frequency. For this reason, it is preferable to use the piezoelectric vibrator 20 as a parametric speaker from the viewpoint of increasing the efficiency of the speaker.

  Here, the principle of the parametric speaker will be described. Parametric loudspeakers emit AM, DSB, SSB, and FM-modulated ultrasonic waves from each of a plurality of oscillation sources into the air. It is something that appears. 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 operation and effect of this embodiment will be described. In the present embodiment, the piezoelectric vibrator 20 is sandwiched between two vibration members 10. The surface of the vibrating member 10 that is in contact with the piezoelectric vibrator has conductivity. Therefore, a drive signal can be transmitted to the electrodes 24 and 26 of the piezoelectric vibrator 20 via the vibrating member 10 without soldering lead wires to the electrodes 24 and 26 of the piezoelectric vibrator 20. Therefore, since it is not necessary to use solder, it is possible to suppress variation in oscillation characteristics of the oscillation device due to variation in the amount of solder.

  In addition, the outer edge of the piezoelectric vibrator 20 is located inside the portion of the vibration member 10 supported by the support body 40 in plan view. For this reason, compared with the case where the outer edge of the piezoelectric vibrator 20 is fixed to the support body 40, the amplitude of the vibration member 10 can be increased and the output of the oscillation device can be increased.

  The vibration member 10 has an opening 12. For this reason, the oscillation mode (natural vibration mode) of the oscillation device can be adjusted by adjusting the position and shape of the opening 12.

(Second Embodiment)
FIG. 4 is an exploded perspective view illustrating the configuration of the piezoelectric vibrator 20 of the transmission device according to the second embodiment. The oscillation device according to the present embodiment is the oscillation device according to the first embodiment except that the piezoelectric vibrator 20 has a structure in which a plurality of piezoelectric bodies 22 and electrodes 24 are alternately stacked. It is the same composition as. 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. In addition, since the piezoelectric vibrator 20 has a structure in which a plurality of piezoelectric bodies 22 and electrodes 24 are alternately stacked, the amount of expansion and contraction of the piezoelectric vibrator 20 increases. Therefore, the output of the oscillation device can be increased.

(Third embodiment)
FIG. 5 is a plan view of the oscillation device according to the third embodiment. The oscillation device according to the present embodiment has the same configuration as that of the oscillation device according to the first embodiment except that the planar shape of the piezoelectric vibrator 20 is circular.
Also according to this embodiment, the same effect as that of the first embodiment can be obtained.

(Fourth embodiment)
FIG. 6 is a plan view of the oscillation device according to the fourth embodiment. The oscillation device according to the present embodiment has the same configuration as that of the oscillation device according to the third embodiment except for the planar shape of the vibration member 10.

  In this embodiment, the vibration member 10 has a shape in which an additional beam 14 that connects the central portion of the vibration member 10 and the four corners of the support 40 is added to the shape shown in the first embodiment. ing. The widths of these additional beams 14 may be equal to or different from the width of the crossed portion.

  Also according to this embodiment, the same effect as that of the first embodiment can be obtained. Further, the length of the cross portion of the vibration member 10 and the length of the additional beam 14 are different from each other. Therefore, since the types of natural frequencies of the vibration member 10 increase, the vibration mode of the oscillation device can be increased.

(Fifth embodiment)
FIG. 7 is a cross-sectional view illustrating the configuration of the oscillation device according to the fifth embodiment including peripheral circuits. FIG. 8 is a plan view of the oscillation device shown in FIG. The oscillation device according to the present embodiment has the same configuration as that of the oscillation device according to the first embodiment except for the planar shape of the vibration member 10.

  In the oscillation device according to the present embodiment, a plurality of openings 12 of the vibration member 10 are provided at positions overlapping the piezoelectric vibrator 20. The outer shape of the vibration member 10 and the shape of the inner peripheral portion of the support body 40 are substantially the same, and the entire outer periphery of the vibration member 10 is fixed to the support body 40.

  Also according to this embodiment, the same effect as that of the first embodiment can be obtained.

  In the present embodiment, the planar shapes of the piezoelectric vibrator 20 and the vibration member 10 are arbitrary. For example, as shown in FIG. 9, the piezoelectric vibrator 20 and the vibration member 10 may be circular.

(Sixth embodiment)
FIG. 10 is a cross-sectional view illustrating the configuration of the oscillation device according to the sixth embodiment, including peripheral circuits. FIG. 11 is a plan view of the oscillation device shown in FIG. The oscillation device according to the present embodiment has the same configuration as that of the oscillation device according to the first embodiment, except that the two vibration members 10 are fixed to the support body 40 via the elastic member 30.

  In the example shown in the drawing, the end portions of the two vibrating members 10 sandwich the elastic member 30 and are fixed to the elastic member 30. The elastic member 30 is made of a material having a higher elastic modulus than that of the vibration member 10, for example, a resin material such as urethane, PET, and polyethylene.

  Also according to this embodiment, the same effect as that of the first embodiment can be obtained. Further, the two vibrating members 10 are fixed to the support body 40 via the elastic member 30. Since the elastic modulus of the elastic member 30 is higher than the elastic modulus of the vibration member 10, the amplitude of the vibration member 10 can be increased as compared with the case where the vibration member 10 is directly fixed to the support body 40. Therefore, the output of the oscillation device can be increased.

(Example)
The oscillation devices shown in FIGS. 1, 4, 5, 6, 8, and 9 were produced, and the characteristics of the oscillation devices were examined (Examples 1 to 6). Further, in the oscillation device shown in FIG. 8, the piezoelectric vibrator 20 having a circular planar shape was created and the characteristics were examined (Example 7). Further, in the oscillation device shown in FIG. 8, a piezoelectric vibrator 20 having the structure shown in FIG. 4 was prepared, and the characteristics were examined (Example 8). In this embodiment, the oscillation device functions as a parametric speaker. In addition, as a comparative example, an electrodynamic oscillation device having the same plane area as in Examples 1 to 8 was created, and the characteristics were examined. The results are shown in Table 1.

  From this table, it was shown that the transmitting device according to each example had a large output, a flat frequency characteristic, and a strong resistance to impact when dropped, compared with the oscillation device according to the comparative example.

  Also, as shown in FIG. 12, the oscillation devices according to Examples 1 to 8 were used as the speaker 102 of the mobile communication terminal 100. The speaker 102 was attached to the inner surface of the casing of the mobile communication terminal 100. Table 2 shows the characteristics of the speaker 102 when each example is used.

  From this table, it was shown that the speaker 102 according to each example has a flat frequency characteristic and is strong against an impact when dropped.

  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 Vibration member 12 Opening 14 Additional beam 20 Piezoelectric vibrator 22 Piezoelectric body 24 Upper surface electrode 26 Lower surface electrode 30 Elastic member 40 Support body 50 Control part 54 Signal generation part 100 Portable communication terminal 102 Speaker

Claims (9)

A piezoelectric vibrator;
A sheet-like first vibrating member in contact with the first surface of the piezoelectric vibrator;
A sheet-like second vibrating member in contact with the second surface of the piezoelectric vibrator;
A support that supports edges of the first vibrating member and the second vibrating member;
With
The piezoelectric vibrator is sandwiched between the first vibrating member and the second vibrating member,
The first vibration member and the second vibration member are oscillation devices in which at least a surface in contact with the piezoelectric vibrator has conductivity. The oscillation device according to claim 1,
The oscillation device in which an outer edge of the piezoelectric vibrator is located inside a portion of the first vibrating member and the second vibrating member supported by the support body in a plan view. The oscillation device according to claim 1 or 2,
An oscillation device in which no solder is provided at an interface between the first vibrating member and the piezoelectric vibrator and an interface between the second vibrating member and the piezoelectric vibrator. In the oscillation device according to any one of claims 1 to 3,
An oscillation device in which at least one of the first vibration member and the second vibration member has an opening penetrating vertically. The oscillation device according to claim 4,
An oscillation device in which a part of the opening does not overlap the piezoelectric vibrator in plan view. The oscillation device according to claim 4,
The oscillation device in which the opening overlaps the piezoelectric vibrator in plan view. In the oscillation device according to any one of claims 1 to 6,
The oscillation device in which the first vibration member and the second vibration member are both fixed to the support via an elastic member having a higher elastic modulus than the first vibration member and the second vibration member. In the oscillation device according to any one of claims 1 to 7,
The oscillation device is an oscillation device that is an oscillation source of a sound wave sensor. In the oscillation device according to any one of claims 1 to 7,
The oscillation device is a speaker.

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