JP5440422B2 - Oscillator - Google Patents

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 permanent magnets and voice coils, the electrodynamic electroacoustic transducer has a limit on miniaturization.

  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 miniaturization because they do not require a large number of members to generate vibration amplitude.

  As technologies related to piezoelectric electroacoustic transducers, there are those described in Patent Literature 1, Patent Literature 2, and Patent Literature 3. The technique described in Patent Document 3 is to provide a spring material as a damping means on one side or both sides of a piezoelectric diaphragm. The technique described in Patent Document 1 is to support the outer peripheral portion of the piezoelectric diaphragm via a thin flange and support the central portion of the piezoelectric diaphragm via an elastic body. According to this, it is described that an excellent frequency characteristic with less peak dip is realized along with improvement of the sound pressure level.

  The technique described in Patent Document 2 is to join a piezoelectric element and a vibration film via an elastic vibration transmission member. It is described that sufficient vibration amplitude can be obtained by utilizing the elastic restoring action of the vibration transmitting member.

JP 2002-135893 A Table WO2005 / 094121 Shokai 57-181198

  By using the piezoelectric vibrator, the electroacoustic transducer can be reduced in size. On the other hand, an electroacoustic transducer is required 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 vibrating member that restrains one surface of the piezoelectric vibrator;
A metal member attached to the other surface of the piezoelectric vibrator;
A first elastic member attached to the surface of the metal member opposite to the surface in contact with the piezoelectric vibrator;
A first support member for supporting an edge of the vibration member;
A second support member that supports the piezoelectric element via the metal member and the first elastic member;
An oscillation device is provided.

  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 oscillation apparatus which concerns on 3rd Embodiment. It is a perspective view which shows the piezoelectric vibrator which concerns on 4th Embodiment. It is the schematic which shows the structure of a portable communication terminal.

  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, a metal member 22, an elastic member 24, a support member 30, and a support member 35. 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. The metal member 22 is attached to the other surface of the piezoelectric vibrator 10. The elastic member 24 is attached to the surface of the metal member 22 opposite to the surface in contact with the piezoelectric vibrator 10. The support member 30 supports the edge of the vibration member 20. The support member 35 supports the piezoelectric vibrator 10 via the metal member 22 and the elastic member 24. 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 lead wire 26 and an external terminal 28. The external terminal 28 is embedded in the metal member 22. The external terminal 28 is connected to the piezoelectric vibrator 10. The lead wire 26 is connected to the external terminal 28 at one end, and extends to the outside of the oscillation device 100 at the other end.

  As shown in FIG. 1, the oscillation device 100 further includes a control unit 90 and a signal generation unit 95. The signal generator 95 generates an electrical signal that is input to the piezoelectric vibrator 10. The control unit 90 controls the signal generation unit 95 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 95 causes the piezoelectric vibrator 10 to generate a sound wave having a resonance frequency of the piezoelectric vibrator 10.

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. 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.

  The vibration member 20 is fixed by a support member 30. Therefore, it has a function of causing the oscillation device 100 to generate vibration by vibration generated from the piezoelectric vibrator 10. The vibration member 20 has a function of improving the mechanical strength of the oscillation device 100. The vibration member 20 is made of a material having a high elastic modulus with respect to the ceramic material, and is made of, for example, phosphor bronze or stainless steel. The thickness of the vibration member 20 is preferably 5 to 500 μm. The longitudinal elastic modulus of the vibrating member 20 is preferably 1 to 500 GPa. If the longitudinal elastic modulus of the vibration member 20 is excessively low or high, the characteristics and reliability as a mechanical vibrator may be impaired. The support member 30 is made of a metal film such as stainless steel.

  For example, the metal member 22 is attached to a position on the other surface of the piezoelectric vibrator 10 where the amount of vibration displacement is maximum. The elastic member 24 is made of, for example, a resin material. The Young's modulus of the metal member 22 is preferably 20 times or more that of the elastic member 24. When vibration is generated in the oscillation device 100, the elastic member 24 has an absorption / repulsion effect due to the restoring force. This absorption / repulsion effect is transmitted to the piezoelectric vibrator 10 and the vibration member 20 through the metal member 22. As a result, the amplitude of the oscillation device 100 increases. The support member 30 and the support member 35 are integrally provided, for example.

  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 using an epoxy resin or the like. Thereafter, the edge of the vibration member 20 is supported by the support member 30. The piezoelectric vibrator 10 is supported by the support member 35 through the metal member 22 and the elastic member 24. Thereby, the oscillation device 100 is formed.

  The piezoelectric body 50 can have an outer diameter = φ15 mm and a thickness = 100 μm. For the piezoelectric body 50, a lead zirconate titanate ceramic can be used. The upper electrode 40 and the lower electrode 45 can have a thickness = 8 μm. For the upper electrode 40 and the lower electrode 45, a silver / palladium alloy (weight ratio 70%: 30%) can be used. The vibration member 20 can have an outer diameter = φ17 mm and a thickness = 300 μm. The vibrating member 20 can use phosphor bronze. The support member 30 and the support member 35 can constitute a bathtub-shaped case having an outer diameter = φ19 mm and an inner diameter = φ18 mm. As the support member 30 and the support member 35, SUS304 can be used. The metal member 22 and the elastic member 24 can have an outer diameter = φ3 mm. Stainless steel can be used for the metal member 22. The elastic member 24 can use a PET material.

  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 95. 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. The inventor has found that the amplitude significantly increases in the oscillation device 100 having the configuration in the present embodiment. This is because the absorption / repulsion effect due to the restoring force generated by the elastic member 24 when vibration is generated in the oscillation device 100 is easily transmitted to the piezoelectric vibrator 10 and the vibration member 20 through the metal member 22. Is done. For this reason, according to the present embodiment, a high sound pressure level can be realized while downsizing.

  The inventor has also found that the amplitude of the oscillation device increases when the Young's modulus of the metal material 22 is 20 times or more the Young's modulus of the elastic member 24. Therefore, the sound pressure level can be further improved. Further, the piezoelectric vibrator 10 is supported by a support member 35 via an elastic member 24. For this reason, impact energy is absorbed by the elastic member 24 at the time of dropping or the like. Therefore, the mechanical strength of the oscillation device can be improved.

  The piezoelectric vibrator 10 is in contact with the metal member 22 in which the external terminal 28 is embedded. Therefore, the piezoelectric vibrator 10 can be connected to the outside through the external terminal 28 embedded in the metal member 22 without providing the piezoelectric vibrator 10 with an external terminal directly. Therefore, the manufacture of the oscillation device is facilitated.

  FIG. 3 is a cross-sectional view showing the oscillation device 102 according to the second embodiment, and corresponds to FIG. 1 according to 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 lead wire 26 is connected to the piezoelectric vibrator 10 via the metal member 22.

  The lead wire 26 is connected to the piezoelectric vibrator 10 via the metal member 22. A voltage is applied to the piezoelectric vibrator 10 via the metal member 22 and the lead wire 26. For this reason, it is not necessary to provide an external terminal directly on the piezoelectric vibrator 10. Therefore, also in this embodiment, the same effect as the first embodiment can be obtained.

  FIG. 4 is a cross-sectional view showing the oscillation device 104 according to the third embodiment, and corresponds to FIG. 1 according to the first embodiment. The oscillation device 104 according to the present embodiment is the same as the oscillation device 100 according to the first embodiment except that an elastic member 32 is provided.

  The elastic member 32 is provided on the outer peripheral portion of the vibration member 20. The vibration member 20 is supported by the support member 30 via the elastic member 32. The elastic member 32 is made of a resin material such as urethane, PET, or polyethylene, and has rigidity lower than that of the vibration member 20. The thickness of the elastic member 32 is not particularly limited, but the value is determined so that the ease of movement of the end of the vibration member 20 can be secured and the durability satisfies the standard.

  Also in this embodiment, the same effect as that of the first embodiment can be obtained. The vibration member 20 is supported by the support member 30 via an elastic member 32 provided on the edge of the outer peripheral portion. For this reason, the edge part of the vibration member 20 can be brought close to a free end. Therefore, the vibration sweep volume by the vibration member 20 is increased, and the sound pressure level of the oscillation device can be further improved. In addition, the impact energy is absorbed by the elastic member 32 when dropped. Therefore, the mechanical strength of the oscillation device can be further improved.

  FIG. 5 is a perspective view showing a piezoelectric vibrator 110 according to the fourth 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. 5, 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.

(Example)
The oscillators shown in FIGS. 1, 4 and 5 were prepared, and the characteristics of the oscillators were examined (Examples 1 to 3). In this embodiment, the oscillation device functions as a parametric speaker. Further, as Comparative Example 1, an electrodynamic oscillation device having the same plane area as that of Examples 1 to 3 was prepared, and the characteristics were examined. The results are shown in Table 1. In the measurement of the sound pressure level frequency characteristics, the sound pressure level when an AC voltage of 1 V was input was measured with a microphone placed at a position 10 cm away from the piezoelectric vibrator. The frequency measurement range was 10 Hz to 10 kHz. In the measurement of drop impact stability, a mobile communication terminal equipped with an electroacoustic transducer equipped with an oscillation device was naturally dropped five times from a height of 50 cm. Thereafter, the damage of the mobile communication terminal was visually confirmed. Furthermore, the sound pressure characteristic was measured, and when the sound pressure level difference before and after the test was within 3 dB, it was rated as “good”.

  From this table, it was shown that the oscillation device according to each example had a higher sound pressure level and a flat frequency characteristic than the comparative example. It was also shown that the drop impact stability was higher than that of the comparative example.

  As shown in FIG. 6, the oscillation devices according to Examples 1 to 3 were used as the speaker 122 of the mobile communication terminal 120. The speaker 122 was attached to the inner surface of the casing of the mobile communication terminal 120. Table 2 shows the characteristics of the speaker 122 when each embodiment is used. Measurement conditions are the same as in Table 1.

  From this table, it was shown that the frequency characteristics of the mobile communication terminal 120 according to each example are flat. It was also shown that the drop impact stability is high.

  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 Metal member 24 Elastic member 26 Lead wire 28 External terminal 30 Support member 32 Elastic member 35 Support member 40 Upper electrode 45 Lower electrode 50 Piezoelectric body 60-64 Piezoelectric body 70-73 Electrode 90 Control part 95 Signal generator 100 Oscillator 102 Oscillator 104 Oscillator 110 Piezoelectric vibrator 120 Mobile communication terminal 122 Speaker

Claims (8)

A piezoelectric vibrator;
A vibrating member that restrains one surface of the piezoelectric vibrator;
A metal member attached to the other surface of the piezoelectric vibrator;
A first elastic member attached to the surface of the metal member opposite to the surface in contact with the piezoelectric vibrator;
A first support member for supporting an edge of the vibration member;
A second support member that supports the piezoelectric element via the metal member and the first elastic member;
An oscillation device comprising: The oscillation device according to claim 1,
An oscillation device in which the Young's modulus of the metal member is 20 times or more that of the first elastic member. The oscillation device according to claim 1 or 2,
The first elastic member is an oscillation device made of resin. The oscillation device according to any one of claims 1 to 3,
The oscillation device in which the first support member and the second support member are integrally provided. The oscillation device according to any one of claims 1 to 4,
The piezoelectric vibrator is an oscillation device to which a voltage is applied via the metal member. The oscillation device according to any one of claims 1 to 5,
A second elastic member provided on an outer periphery of the vibration member;
The rigidity of the second elastic member is lower than the rigidity of the vibration member,
The oscillation device is supported by the first support member via the second elastic member. The oscillation device according to any one of claims 1 to 6,
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 6,
The oscillation device is an oscillation device which is a speaker.

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