JP2012015765A - Oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillator which realizes a high sound pressure level while reducing the size.SOLUTION: An oscillator includes a piezoelectric vibrator 10, a vibrating member 20 restricting one surface of the piezoelectric vibrator 10, an elastic member 24 supporting an edge of the vibrating member 20, and a supporting member 30 located around the elastic member 24. The vibrating member 20 is not restricted by the supporting member 30, and the supporting member 30 has a protruding portion 32 on the side where the elastic member 24 is located. The elastic member 24 is supported by one surface of the protruding portion 32 and an edge of the vibrating member 20 overlaps with the protruding portion 32 in a plan view.

Description

  The present invention relates to an oscillation device using a piezoelectric vibrator.

  There is an electrodynamic electroacoustic transducer as an electroacoustic transducer for a portable device or the like. The electrodynamic electroacoustic transducer generates a vibration amplitude by using an action of a magnetic circuit. However, since the magnetic circuit is composed of a large number of members such as a permanent magnet and a voice coil, the electrodynamic electroacoustic transducer has a limit in thinning.

  As an electroacoustic transducer that replaces the electrodynamic electroacoustic transducer, there is a piezoelectric electroacoustic transducer. Piezoelectric electroacoustic transducers generate vibration amplitude by utilizing the expansion and contraction generated by applying an electric field to a piezoelectric vibrator. Piezoelectric electroacoustic transducers are advantageous for thinning because they do not require a large number of members in order to generate vibration amplitude.

  As technologies related to acoustic equipment using a piezoelectric vibrator, there are those described in Patent Documents 1 to 3. Patent Document 1 discloses a light receiving type piezoelectric element in which a piezoelectric vibrator is sandwiched between a pair of rigid members. The technique described in Patent Document 2 is to provide a quality factor reducing means in a piezoelectric sounding body including a piezoelectric sounding element. Patent Document 3 discloses a piezoelectric horn speaker in which a piezoelectric speaker element is bent or arranged in a folding screen.

JP-A-6-269092 JP 2002-108346 A Japanese Utility Model Publication No. 60-155300

  Electroacoustic transducers mounted on portable communication terminals and the like are required to be downsized. On the other hand, it is desired for the electroacoustic transducer to ensure a sound pressure level above a certain level to enable sound reproduction.

  An object of the present invention is to provide an oscillation device capable of realizing a high sound pressure level while achieving downsizing.

According to the present invention, a piezoelectric vibrator;
A first vibrating member that restrains one surface of the piezoelectric vibrator;
A first elastic member that supports an edge of the first vibrating member;
A support member positioned around the first elastic member;
With
The first vibration member is not restrained by the support member,
The support member has a protrusion on the side where the first elastic member is located,
The first elastic member is supported by one surface of the protrusion,
An oscillation device is provided in which an edge of the first vibration member overlaps the protrusion in a plan view.

  ADVANTAGE OF THE INVENTION According to this invention, the oscillation apparatus which can implement | achieve a high sound pressure level can be provided, aiming at size reduction.

It is sectional drawing which shows the oscillation apparatus which concerns on 1st Embodiment. It is sectional drawing which shows the piezoelectric vibrator shown in FIG. It is sectional drawing which shows the oscillation apparatus which concerns on 2nd Embodiment. It is sectional drawing which shows the piezoelectric vibrator which concerns on 3rd Embodiment.

  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 oscillation device 100 according to the first embodiment. The oscillation device 100 includes a piezoelectric vibrator 10, a vibration member 20, an elastic member 24, and a support member 30. The oscillation device 100 is used as an oscillation source of a speaker or a sound wave sensor, for example. It can also function as a temperature sensor by utilizing the pyroelectric effect of the piezoelectric body. When the oscillation device 100 is used as a speaker, for example, it is used as a sound source of an electronic device (a mobile phone, a laptop computer, a small game device, etc.).

  The vibration member 20 restrains one surface of the piezoelectric vibrator 10. Further, the vibration member 20 is not restrained by the support member 30. The support member 30 is located around the elastic member 24. The support member 30 has a protrusion 32 on the side where the elastic member 24 is located. The elastic member 24 supports the edge of the vibration member 20. The elastic member 24 is supported by one surface of the protruding portion 32. The edge of the vibration member 20 overlaps the protrusion 32 in plan view. Hereinafter, the configuration of the oscillation device 100 will be described in detail with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the oscillation device 100 further includes a control unit 90 and a signal generation unit 92. The signal generation unit 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 the signal generation unit 92 based on information input from the outside. When the oscillation device 100 is used as a speaker, information input to the control unit 90 is an audio signal. When the oscillation device 100 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 100 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.

  Further, when a plurality of sets of the piezoelectric vibrator 10, the vibration member 20, and the elastic member 24 are provided, the oscillation device 100 can be used as a parametric speaker. In this case, the control unit 90 inputs a modulation signal as a parametric speaker via the signal generation unit 92. When used as a parametric speaker, the piezoelectric vibrator 10 uses a sound wave of 20 kHz or more, for example, 100 kHz, as a signal transport wave.

  As shown in FIG. 1, the oscillation device 100 further includes a vibration member 22 and an elastic member 26. In the oscillation device 100, the structure constituted by the piezoelectric vibrator 10, the vibrating members 20 and 22, the elastic members 24 and 26, and the protruding portion 32 is a surface based on the center plane in the thickness direction of the protruding portion 32. Symmetric. The vibration member 22 is not restrained by the support member 30. The elastic member 26 is supported by the other surface of the protrusion 32. The edge of the vibration member 22 overlaps the protrusion 32 in plan view.

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 an upper electrode 40, a lower electrode 45, and a piezoelectric body 50. The piezoelectric vibrator 10 has, for example, a circle, an ellipse, or a rectangle. For example, the piezoelectric vibrator 10 has a thickness obtained by combining the thickness of the elastic member 24, the thickness of the protruding portion 32, and the thickness of the elastic member 26. The piezoelectric body 50 is sandwiched between the upper electrode 40 and the lower electrode 45. The piezoelectric body 50 is made of a material having a piezoelectric effect, and is made of, for example, lead zirconate titanate (PZT), barium titanate (BaTiO ₃ ), or the like. The thickness of the piezoelectric body 50 is preferably 10 um to 1 mm. When the thickness is less than 10 μm, the piezoelectric body 50 is made of a brittle material, and thus is easily damaged. On the other hand, when the thickness exceeds 1 mm, the electric field strength of the piezoelectric body 50 is reduced. Therefore, the energy conversion efficiency is reduced.

  The upper electrode 40 and the lower electrode 45 are made of, for example, silver or a silver / palladium alloy. The thicknesses of the upper electrode 40 and the lower electrode 45 are preferably 1 to 50 um. When the thickness is less than 1 μm, it becomes difficult to form the film uniformly. On the other hand, when it exceeds 50 um, the upper electrode 40 or the lower electrode 45 becomes a constraining surface with respect to the piezoelectric body 50 and causes a decrease in energy conversion efficiency.

  A gap is provided between the vibration members 20 and 22 and the support member 30. The vibrating members 20 and 22 are made of a material having a high elastic modulus with respect to the ceramic material, and are made of, for example, phosphor bronze or stainless steel. The thickness of the vibrating members 20 and 22 is preferably 5 to 500 μm. The longitudinal elastic modulus of the vibrating members 20 and 22 is preferably 1 to 500 GPa. When the longitudinal elastic modulus of the vibration members 20 and 22 is excessively low or high, the characteristics and reliability as a mechanical vibrator may be impaired.

  The elastic members 24 and 26 are made of a material that performs elastic motion, for example, a resin material. The vibration members 20 and 22 are supported by the support member 30 via the elastic members 24 and 26. Further, the vibration members 20 and 22 are not restrained by the support member 30. Therefore, the elastic members 24 and 26 have a function of forming a free end at the vibration end of the oscillation device 100. Part of the elastic members 24 and 26 is sandwiched between the vibration members 20 and 22 and the support member 30. For this reason, when vibrating, the inertia and restoring force of the elastic members 24 and 26 act on the vibrating members 20 and 22. Further, by selecting a material having a large internal loss as the elastic members 24 and 26, it has a function of reducing the mechanical quality factor (Q value) of the oscillation device 100.

  The protrusion 32 of the support member 30 is formed from the entire circumference of the support member 30 toward the inside (not shown). In addition, one surface and the other surface of the protrusion 32 are parallel to each other. Furthermore, one surface and the other surface of the protrusion 32 are each perpendicular to the support member 30.

  Next, a method for manufacturing the oscillation device 100 according to this embodiment will be described. First, the piezoelectric body 50 is manufactured. The piezoelectric body 50 is manufactured by the green sheet method and baked at 1100 ° C. for 2 hours in the air. Next, the upper electrode 40 and the lower electrode 45 are formed on the piezoelectric body 50. The piezoelectric body 50 is subjected to polarization processing in the thickness direction. The piezoelectric vibrator 10 thus obtained is bonded to the vibration member 20 fixed to the support member 30 through the elastic member 24 using an epoxy resin or the like. Thereafter, the vibration member 22 is bonded to the support member 30 via the elastic member 26. Thereby, the oscillation device 100 is formed.

  Next, a sound reproduction method using a piezoelectric electroacoustic transducer using the oscillation device 100 according to the present embodiment will be described. In the present embodiment, for example, sound reproduction can be performed using the operating principle of a parametric speaker. In this case, the control unit 90 inputs a modulation signal as a parametric speaker to the piezoelectric vibrator 10 via the signal generation unit 92. When used as a parametric speaker, the piezoelectric vibrator 10 uses a sound wave of 20 kHz or more, for example, 100 kHz, as a signal transport wave.

  Here, the operation principle of the parametric speaker will be described. 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.

  Next, the effect of this embodiment will be described. In the oscillation device 100 according to the present embodiment, the vibration member 20 is supported by one surface of the protrusion 32 provided on the support member 30 via the elastic member 24. For this reason, the inertia and restoring force of the elastic member 24 act on the vibration member 20, and the amplitude increases. Further, since the vibration end is a free end, the amplitude sweep volume is increased. Furthermore, since the vibration member 20, the elastic member 24, and the protrusion 32 overlap in plan view, an increase in the area of the oscillation device 100 can be suppressed. Therefore, a high sound pressure level can be realized while downsizing.

  The piezoelectric vibrator 10 is supported by the support member 30 via the elastic members 24 and 26. Therefore, the mechanical strength of the oscillation device 100 can be improved. Further, when the elastic members 24 and 26 are made of a material having a large internal loss, the Q value of the oscillation device 100 is reduced. Therefore, a flat sound pressure level frequency characteristic can be realized. Furthermore, the Q value in the specific frequency band can be controlled by selecting the material constituting the elastic members 24 and 26. Therefore, when the Q value is reduced in the low frequency band and the Q value is adjusted to be high in the high frequency band, an electroacoustic transducer operable as an audible sound speaker or a parametric speaker can be realized.

  FIG. 3 is a cross-sectional view showing the oscillation device 102 according to the second embodiment, and corresponds to FIG. 1 in the first embodiment. The oscillation device 102 according to the present embodiment is the same as the oscillation device 100 according to the first embodiment except that the elastic members 24 and 26 are configured by springs.

  Also in this embodiment, the vibration member 20 is supported by one surface of the protruding portion 32 provided on the support member 30 via the elastic member 24. Moreover, the vibration member 20, the elastic member 24, and the protrusion part 32 have overlapped with planar view. Therefore, a high sound pressure level can be realized while downsizing.

  FIG. 4 is a perspective view showing the piezoelectric vibrator 110 according to the third embodiment. The oscillation device according to the present embodiment is the same as the oscillation device 100 according to the first embodiment except for the configuration of the piezoelectric vibrator. The piezoelectric vibrator 110 according to the present embodiment is the same as the piezoelectric vibrator 10 according to the first embodiment except that it has a laminated structure.

  As shown in FIG. 4, the piezoelectric vibrator 110 is configured by alternately laminating a plurality of piezoelectric bodies and a plurality of electrodes. Between the piezoelectric bodies 60, 61, 62, 63 and 64, electrodes 70, 71, 72 and 73 are formed one by one. The electrode 70 and the electrode 72, and the electrode 71 and the electrode 73 are connected to each other. The polarization direction of each piezoelectric body is reverse for each layer. In addition, the direction of the electric field generated between the electrodes is alternately reversed.

  Also in this embodiment, the same effect as that of the first embodiment can be obtained. In addition, since the piezoelectric vibrator 110 has a laminated structure, the electric field strength generated between the electrode layers is high. Thereby, the driving force of the piezoelectric vibrator 110 can be improved. Note that the number of stacked piezoelectric vibrators 110 can be arbitrarily increased or decreased.

  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 Vibration member 22 Vibration member 24 Elastic member 26 Elastic member 30 Support member 32 Projection part 40 Upper electrode 45 Lower electrode 50 Piezoelectric body 60-64 Piezoelectric body 70-73 Electrode 90 Control part 92 Signal generation part 100 Oscillator 102 Oscillator 110 Piezoelectric Vibrator

Claims (6)

A piezoelectric vibrator;
A first vibrating member that restrains one surface of the piezoelectric vibrator;
A first elastic member that supports an edge of the first vibrating member;
A support member positioned around the first elastic member;
With
The first vibration member is not restrained by the support member,
The support member has a protrusion on the side where the first elastic member is located,
The first elastic member is supported by one surface of the protrusion,
An oscillation device in which an edge of the first vibration member overlaps the protrusion in a plan view. The oscillation device according to claim 1,
A second vibrating member that restrains the other surface of the piezoelectric vibrator;
A second elastic member that supports an edge of the second vibrating member;
Further comprising
The second vibration member is not restrained by the support member,
The second elastic member is supported by the other surface of the protrusion,
An oscillation device in which an edge of the second vibration member overlaps the protrusion in a plan view. The oscillation device according to claim 1 or 2,
The first elastic member is an oscillation device made of a resin material. The oscillation device according to claim 1 or 2,
The first elastic member is an oscillation device configured by a spring. The oscillation device according to any one of claims 1 to 4,
The oscillation device is an oscillation device that is a transmission source of a sound wave sensor. The oscillation device according to any one of claims 1 to 4,
The oscillation device is an oscillation device which is a speaker.

Images