JP5527082B2 - Electroacoustic transducer - Google Patents

Description

  The present invention relates to an electroacoustic transducer using ultrasonic waves.

  As an electroacoustic transducer for a portable device or the like, 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 do not require a large number of members in order to generate vibration amplitude, and are advantageous for thinning.

  A piezoelectric electroacoustic transducer may be used as a parametric speaker using ultrasonic waves. A parametric speaker demodulates audible sound from modulated ultrasonic waves using the phenomenon of air density. Since ultrasonic waves are used, high directivity can be realized as compared with a normal speaker.

  In addition to the above, in order to improve the performance of the electroacoustic transducer, various techniques have been studied for its configuration. The technique described in Patent Document 1 is to equalize the additional mass of air applied to the front diaphragm and the rear diaphragm of the speaker. The technique described in Patent Document 2 is to efficiently use sound waves radiated from the back surface of the electrostatic ultrasonic transducer.

JP 7-177593 A JP 2006-86789 A

  By using ultrasonic waves, an electroacoustic transducer having high directivity can be realized. On the other hand, development of an electroacoustic transducer capable of controlling the direction of sound wave oscillation is required so that ultrasonic waves emitted from both sides of the oscillation device can be separated and used effectively within a practical range. It has been.

  An object of the present invention is to provide an electroacoustic transducer capable of controlling the oscillation direction of sound waves so that ultrasonic waves emitted from both surfaces of the oscillation device can be separated and effectively used within a practical range. It is to provide.

According to the present invention, an oscillation device;
A first waveguide provided on a first vibration surface of the oscillation device and having a first opening end;
A second waveguide provided on a second vibration surface constituted by a surface opposite to the first vibration surface of the oscillation device, and having a second opening end;
With
The oscillation device emits ultrasonic waves from the first vibration surface toward the first waveguide and from the second vibration surface toward the second waveguide,
The first waveguide is constituted by a first inner region constituting the oscillation device side and a first outer region constituting the first opening end side,
The second waveguide is composed of a second inner region constituting the oscillation device side and a second outer region constituting the second opening end side,
An electroacoustic transducer is provided in which an angle formed by the first outer region and the second outer region is not less than 60 ° and not more than 140 °.

  According to the present invention, there is provided an electroacoustic transducer capable of controlling the oscillation direction of sound waves so that ultrasonic waves emitted from both surfaces of the oscillation device can be separated and effectively used within a range suitable for practical use. Can be provided.

It is sectional drawing which shows the electroacoustic transducer which concerns on 1st Embodiment. It is sectional drawing which shows the modification of the electroacoustic transducer shown in FIG. It is sectional drawing which shows the oscillation apparatus shown in FIG. It is sectional drawing which shows the piezoelectric vibrator shown in FIG. It is sectional drawing which shows the electroacoustic transducer which concerns on 2nd Embodiment. It is sectional drawing which shows the electroacoustic transducer which concerns on 3rd Embodiment. It is sectional drawing which shows the electroacoustic transducer which concerns on 4th 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 electroacoustic transducer 100 according to the first embodiment. The electroacoustic transducer 100 includes an oscillation device 10, a waveguide 30, and a waveguide 32. The electroacoustic transducer 100 is used, for example, as a sound source of an electronic device (a mobile phone, a laptop computer, a small game device, etc.). FIG. 2 is a sectional view showing a modification of the electroacoustic transducer 100 shown in FIG.

  The waveguide 30 is provided on the first vibration surface of the oscillation device 10. The waveguide 30 has an open end 50. The waveguide 32 is provided on a second vibration surface constituted by a surface opposite to the first vibration surface. The waveguide 32 has an open end 52. The oscillation device 10 emits an ultrasonic wave from the first vibration surface toward the waveguide 30. The oscillation device 10 emits an ultrasonic wave from the second vibration surface toward the waveguide 32.

  The waveguide 30 includes an inner region 110 that forms the oscillation device 10 side and an outer region 120 that forms the opening end 50 side. The waveguide 32 includes an inner region 112 that constitutes the oscillation device 10 side and an outer region 122 that constitutes the opening end 52. An angle formed by the outer region 120 and the outer region 122 is configured to be 60 ° or more and 140 ° or less. Hereinafter, the configuration of the electroacoustic transducer 100 will be described in detail with reference to FIGS.

  As shown in FIG. 1, the electroacoustic transducer 100 further includes a housing 20. The housing 20 has the oscillation device 10 inside. The opening end 50 and the opening end 52 are provided on the surface of the housing 20. Note that the open ends 50 and 52 in this case indicate portions where at least a part of the waveguides 30 and 32 starts to be opened to the outside of the housing 20.

  As illustrated in FIG. 3, the oscillation device 10 includes a piezoelectric vibrator 60, a vibration member 80, and a support member 70. The vibration member 80 restrains the piezoelectric vibrator 60. The support member 70 supports the vibration member 80. The oscillation device 10 further includes a control unit 90 and a signal generation unit 92. The signal generation unit 92 is connected to the piezoelectric vibrator 60 and generates an electric signal input to the piezoelectric vibrator 60. The control unit 90 is connected to the signal generation unit 92 and controls signal generation by the signal generation unit 92 based on information input from the outside. Since the oscillation device 10 is used as a speaker, information input to the control unit 90 is an audio signal.

  In the present embodiment, the oscillation device 10 is used as a parametric speaker. Therefore, 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 60 uses a sound wave of 20 kHz or more, for example, 100 kHz, as a signal transport wave. In the oscillation device 10, for example, a plurality of piezoelectric vibrators 60 and vibration members 80 are provided in an array. Thereby, the directivity of the ultrasonic waves 40 and 45 emitted from the oscillation device 10 can be improved.

4 is a cross-sectional view showing the piezoelectric vibrator 60 shown in FIG. As shown in FIG. 4, the piezoelectric vibrator 60 includes a piezoelectric body 62, an upper electrode 64, and a lower electrode 66. The piezoelectric vibrator 60 has, for example, a circle, an ellipse, or a rectangle. The piezoelectric body 62 is sandwiched between the upper electrode 64 and the lower electrode 66. The piezoelectric body 62 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 62 is preferably 10 um to 1 mm. When the thickness is less than 10 μm, the piezoelectric body 62 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 62 is reduced. Therefore, the energy conversion efficiency is reduced.

  The upper electrode 64 and the lower electrode 66 are made of, for example, silver or a silver / palladium alloy. The thickness of the upper electrode 64 and the lower electrode 66 is 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 64 or the lower electrode 66 becomes a constraining surface with respect to the piezoelectric body 62 and causes a decrease in energy conversion efficiency.

  The vibration member 80 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 80 is preferably 5 to 500 μm. The longitudinal elastic modulus of the vibration member 80 is preferably 1 to 500 GPa. When the longitudinal elastic modulus of the vibration member 80 is excessively low or high, the characteristics and reliability as a mechanical vibrator may be impaired.

  As shown in FIG. 1, the waveguide 30 is bent at the junction between the inner region 110 and the outer region 120. In this case, the angle formed by the inner region 110 and the outer region 120 is not less than 120 ° and not more than 160 °. Moreover, the waveguide 30 can also be made into the shape curved in the whole which match | combined the inner side area | region 110 and the outer side area | region 120, as shown in FIG. As shown in FIG. 1, the waveguide 32 is bent at the junction between the inner region 112 and the outer region 122. In this case, the angle formed by the inner region 112 and the outer region 122 is not less than 120 ° and not more than 160 °. In addition, the waveguide 32 may have a curved shape as a whole in which the inner region 112 and the outer region 122 are combined as shown in FIG.

  Next, the principle of controlling the oscillation direction of sound waves using the electroacoustic transducer 100 will be described. The ultrasonic wave 40 is emitted from the open end 50 through the outer region 120. Further, the ultrasonic wave 45 is emitted from the opening end 52 through the outer region 122. The angle formed by the outer region 120 and the outer region 122 is not less than 60 ° and not more than 140 °. Therefore, the angle formed by the ultrasonic wave 40 and the ultrasonic wave 45 is also 60 ° or more and 140 ° or less. The ultrasonic wave 40 and the ultrasonic wave 45 travel with high directivity. For this reason, if the angle between the ultrasonic wave 40 and the ultrasonic wave 45 is 60 ° or more, the sound waves can be separated. The viewing angle of the liquid crystal display is about 160 °. For this reason, for example, even when sound is generated from both the left and right sides of the mobile phone, it is sufficient that the angle of the ultrasonic wave 40 and the ultrasonic wave 45 is 140 ° in order to hear the sound while watching the liquid crystal display.

  Next, the effect of this embodiment will be described. In the electroacoustic transducer 100 according to this embodiment, the ultrasonic wave 40 is radiated from the oscillation device 10 through the outer region 120 and the ultrasonic wave 45 is radiated through the outer region 122. The angle formed by the outer region 120 and the outer region 122 is not less than 60 ° and not more than 140 °. Therefore, it is possible to control the oscillating direction of the sound wave so that the ultrasonic waves emitted from both surfaces of the oscillation device can be separated and effectively used within a practical range.

  In addition, ultrasonic waves are superior in straightness compared to audible sound waves. For this reason, it is possible to suppress the sound wave from being disturbed in the waveguides 30 and 32 and being canceled. Therefore, it is possible to suppress a reduction in the sound pressure level.

  FIG. 5 is a sectional view showing the electroacoustic transducer 102 according to the second embodiment, and corresponds to FIG. 1 according to the first embodiment. The electroacoustic transducer 102 according to the present embodiment is the same as the electroacoustic transducer 100 according to the first embodiment except that the reflection members 54 and 56 are provided in the waveguides 30 and 32, respectively. .

  The waveguide 30 is bent at the junction between the inner region 110 and the outer region 120. The waveguide 32 is bent at the junction between the inner region 112 and the outer region 122. The reflecting member 54 is located at the junction between the inner region 110 and the outer region 120 and has a function of changing the traveling direction of the ultrasonic wave 40. The reflecting member 56 is located at the joint between the inner region 112 and the outer region 122 and has a function of changing the traveling direction of the ultrasonic wave 45.

  Also in this embodiment, the same effect as that of the first embodiment can be obtained. Reflecting members 54 and 56 that can change the traveling directions of the ultrasonic waves 40 and 45 are provided in the waveguides 30 and 32, respectively. For this reason, the canceling of the sound wave in the waveguides 30 and 32 can be suppressed more effectively. Therefore, it is possible to more effectively suppress the reduction of the sound pressure level.

  FIG. 6 is a cross-sectional view showing the electroacoustic transducer 104 according to the third embodiment, and corresponds to FIG. 5 according to the second embodiment. The electroacoustic transducer 104 according to the present embodiment relates to the second embodiment except that the electroacoustic transducer 104 includes a drive mechanism 98 that moves the reflecting members 54 and 56 and a control unit 96 that controls the drive mechanism 98. This is the same as the electroacoustic transducer 102.

  The drive mechanism 98 is connected to the reflecting member 54 and the reflecting member 56. The drive mechanism 98 is configured by, for example, MEMS. The control unit 96 is connected to the drive mechanism 98. The control unit 96 can control the angles of the reflecting members 54 and 56 via the drive mechanism 98. By changing the angles of the reflecting members 54 and 56, the radiation angles of the ultrasonic wave 40 and the ultrasonic wave 45 can be controlled. Note that the diameters of the opening end 50 and the opening end 52 may be increased in accordance with the range of radiation angles of the ultrasonic wave 40 and the ultrasonic wave 45.

  Also in this embodiment, the same effect as that of the first embodiment can be obtained. Further, by controlling the radiation angle of the ultrasonic waves 40 and 45 by the control unit 96 and the drive mechanism 98, it is possible to select a region where the sound wave is propagated. Therefore, it is possible to perform spatial control of sound waves.

  FIG. 7 is a sectional view showing the electroacoustic transducer 106 according to the fourth embodiment, and corresponds to FIG. 5 according to the second embodiment. In the electroacoustic transducer 106 according to this embodiment, waveguides 34 and 36 are provided. In addition to the reflecting members 54 and 56, reflecting members 55 and 57 are provided. Further, the reflecting members 54 and 56 are transflective reflecting members. About another point, it is the same as that of the electroacoustic transducer 102 which concerns on 2nd Embodiment.

  As shown in FIG. 7, the electroacoustic transducer 106 includes a waveguide 34 and a reflecting member 55 formed in the waveguide 34. Further, a waveguide 36 and a reflection member 57 formed in the waveguide 36 are provided. The waveguide 34 is provided on the first vibration surface of the oscillation device 10. The waveguide 34 has an open end 51. The waveguide 36 is provided on the second vibration surface of the oscillation device 10. The waveguide 36 has an open end 53.

  The waveguide 34 includes an inner region 114 that forms the oscillation device 10 side and an outer region 124 that forms the opening end 51 side. The waveguide 36 includes an inner region 116 that forms the oscillation device 10 side and an outer region 126 that forms the opening end 53 side. The outer region 124 is located farther from the oscillation device 10 than the outer region 120. The outer region 126 is located farther from the oscillation device 10 than the outer region 122. The angle formed by the outer region 124 and the outer region 126 is not less than 60 ° and not more than 140 °. The angle formed by the outer region 124 and the inner region 114 is not less than 120 ° and not more than 160 °. The angle formed by the outer region 126 and the inner region 116 is not less than 120 ° and not more than 160 °.

  The reflection members 54 and 56 are configured to transmit part of the ultrasonic waves 40 and 45 emitted from the oscillation device 10. For example, a transflective reflection member is formed by forming a transmission hole. The reflection member 55 is located behind the reflection member 54 when viewed from the oscillation device 10. The reflection member 57 is located behind the reflection member 56 when viewed from the oscillation device 10.

  Next, the operation of the electroacoustic transducer 106 according to this embodiment will be described. The ultrasonic waves 40 and 45 emitted from the oscillation device 10 reach the reflecting members 54 and 56, respectively. Since the reflecting members 54 and 56 are transflective reflecting members, some of the ultrasonic waves 40 and 45 are transmitted through the reflecting members 54 and 56. The components of the ultrasonic waves 40 and 45 transmitted through the reflecting members 54 and 56 are reflected by the reflecting members 55 and 57 located behind the reflecting members 54 and 56 and are emitted from the open ends 51 and 53, respectively. On the other hand, the components of the ultrasonic waves 40 and 45 reflected by the reflecting members 54 and 56 are emitted from the open ends 50 and 52, respectively. That is, four ultrasonic components are radiated from the electroacoustic transducer 106. The number of waveguides and the number of reflecting members can be increased or decreased as appropriate. When there are three or more waveguides and reflection members, the reflection members other than the two reflection members located on the outermost side are transflective reflection members.

  Next, the effect of this embodiment will be described. In the electroacoustic transducer 106 according to the present embodiment, since three or more ultrasonic components can be radiated, it is possible to have a wide region in which sound waves propagate. Accordingly, it is possible to perform more advanced sound wave spatial control.

  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 Oscillator 20 Case 30 Waveguide 32 Waveguide 34 Waveguide 36 Waveguide 40 Ultrasonic 45 Ultrasonic 50 Open end 51 Open end 52 Open end 53 Open end 54 Reflective member 55 Reflective member 56 Reflective member 57 Reflective member 60 Piezoelectric Vibrator 62 Piezoelectric body 64 Upper electrode 66 Lower electrode 70 Support member 80 Vibration member 90 Control unit 92 Signal generation unit 96 Control unit 98 Drive mechanism 100 Electroacoustic transducer 102 Electroacoustic transducer 104 Electroacoustic transducer 106 Electroacoustic transducer 110 Inner region 112 Inner region 114 Inner region 116 Inner region 120 Outer region 122 Outer region 124 Outer region 126 Outer region

Claims (9)

An oscillation device;
A first waveguide provided on a first vibration surface of the oscillation device and having a first opening end;
A second waveguide provided on a second vibration surface constituted by a surface opposite to the first vibration surface of the oscillation device, and having a second opening end;
With
The oscillation device emits ultrasonic waves from the first vibration surface toward the first waveguide and from the second vibration surface toward the second waveguide, respectively.
The first waveguide is constituted by a first inner region constituting the oscillation device side and a first outer region constituting the first opening end side,
The second waveguide is composed of a second inner region constituting the oscillation device side and a second outer region constituting the second opening end side,
The electroacoustic transducer having an angle between the first outer region and the second outer region of 60 ° or more and 140 ° or less. The electroacoustic transducer according to claim 1,
A signal generator connected to the oscillation device;
A control unit connected to the signal generation unit and controlling generation of a signal by the signal generation unit;
An electroacoustic transducer further comprising: The electroacoustic transducer according to claim 1 or 2,
The oscillation device is an electroacoustic transducer having a piezoelectric vibrator, a vibration member that restrains the piezoelectric vibrator, and a support member that supports the vibration member. The electroacoustic transducer according to any one of claims 1 to 3,
The angle formed by the first inner region and the first outer region is 120 ° or more and 160 ° or less,
An electroacoustic transducer in which an angle formed by the second inner region and the second outer region is 120 ° or more and 160 ° or less. The electroacoustic transducer according to any one of claims 1 to 4,
Further comprising a housing having the oscillation device inside,
The first opening end and the second opening end are electroacoustic transducers provided on a surface of the casing. The electroacoustic transducer according to any one of claims 1 to 5,
The first waveguide is bent at a junction between the first inner region and the first outer region,
The electroacoustic transducer in which the 1st reflective member which changes the advancing direction of the said ultrasonic wave is formed in the said junction part of a said 1st waveguide. The electroacoustic transducer according to claim 6,
A drive mechanism for moving the first reflective member,
A control unit for controlling the drive mechanism;
An electroacoustic transducer further comprising: The electroacoustic transducer according to claim 7,
The drive mechanism is an electroacoustic transducer that is a MEMS. The electroacoustic transducer according to any one of claims 6 to 8,
A third waveguide provided on the first vibration surface of the oscillation device and having a third opening end;
A second reflecting member formed in the third waveguide;
Further comprising
The third waveguide is composed of a third inner region constituting the oscillation device side and a third outer region constituting the third opening end side,
The third outer region is located farther from the oscillation device than the first outer region;
The first reflecting member is configured to transmit a part of the ultrasonic wave emitted from the oscillation device,
The electroacoustic transducer, wherein the second reflecting member is positioned behind the first reflecting member as viewed from the oscillation device.

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