JP2012217019A - Oscillation device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillation device, using a piezoelectric element as an oscillation source, that produces a larger output while being prevented from increasing in size.SOLUTION: A first vibrator 10 overlaps with a second vibrator 20 in plan view, and has openings 26. The following equation (1) is satisfied, where: θ is a phase difference between a driving signal, as a reference, input to a second piezoelectric element 24 and a driving signal input to a first piezoelectric element 14; L is a distance between the first vibrator 10 and the second vibrator 20; λ is a wavelength, in the air, of a sound wave of an identical frequency to that of the driving signal; and n is a positive number or 0. L=(n+θ/(2π))×λ...(1)

Description

  The present invention relates to an oscillation device and an electronic apparatus.

  One type of speaker is used as an oscillation source in which a piezoelectric element is fixed on a vibrating member. This type of speaker is characterized in that it is easy to miniaturize compared to an electrodynamic speaker using a voice coil and a magnet.

  In Patent Document 1, in an oscillation device used for an ultrasonic diagnostic apparatus, a plurality of piezoelectric bodies and electrodes are alternately stacked, and the distance between the electrodes is 1 / wavelength of the fundamental resonance vibration wavelength of the piezoelectric body. It is described that it is 4 times.

JP 2002-113007 A

  An oscillation device using a piezoelectric element is difficult to increase the output. For this reason, it is desired to increase the output of the oscillation device without increasing the size of the oscillation device.

  An object of the present invention is to provide an oscillation device and an electronic apparatus that use a piezoelectric element as an oscillation source and can increase the output while suppressing an increase in size.

According to the present invention, a first vibrating member, a first vibrator having a first piezoelectric element provided on the first vibrating member,
A second vibrator member, a second vibrator having a second piezoelectric element provided on the second vibrator member,
Control means for inputting drive signals having the same frequency to the first piezoelectric element and the second piezoelectric element;
With
The second vibrating member overlaps with the first vibrator in a plan view and has an opening,
The phase difference of the drive signal input to the first piezoelectric element when the drive signal input to the second piezoelectric element is used as a reference is θ, and the distance between the first vibrator and the second vibrator is L, an oscillation device that satisfies the following expression (1), where λ is the wavelength of a sound wave having the same frequency as the drive signal.
L = (n + θ / (2π)) × λ (1)

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

  According to the present invention, in an oscillation device using a piezoelectric element as an oscillation source, an output can be increased while suppressing an increase in size.

It is a figure which shows the structure of the oscillation apparatus which concerns on 1st Embodiment. FIG. 2 is a plan view illustrating a configuration of a first vibrator illustrated in FIG. 1. FIG. 3 is a plan view illustrating a configuration of a second vibrator illustrated in FIG. 1. It is a figure which shows the modification of FIG. It is a figure which shows the state which attached the oscillation apparatus shown in FIG. 1 to the electronic device. It is sectional drawing which shows the structure of the oscillation apparatus which concerns on 2nd 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.

(First embodiment)
FIG. 1 is a diagram illustrating the configuration of the oscillation device according to the first embodiment. FIG. 2 is a plan view showing the configuration of the first vibrator 10 shown in FIG. FIG. 3 is a plan view showing the configuration of the second vibrator 20 shown in FIG.

  The oscillation device includes a first vibrator 10, a second vibrator 20, and a control unit 50. The first vibrator 10 includes a first vibrating member 12 and a first piezoelectric element 14. The first piezoelectric element 14 is provided on the first vibrating member 12. The second vibrator 20 includes a second vibrating member 22 and a second piezoelectric element 24. The second piezoelectric element 24 is provided on the second vibrating member 22. The controller 50 inputs drive signals having the same frequency to the first piezoelectric element 14 and the second piezoelectric element 24.

The second vibrator 20 overlaps the first vibrator 10 in plan view and has an opening 26. The phase difference of the drive signal input to the first piezoelectric element 14 with respect to the drive signal input to the second piezoelectric element 24 is θ, and the distance between the first vibrator 10 and the second vibrator 20 is L. When the wavelength of the sound wave having the same frequency as that of the drive signal is λ, the following equation (1) is satisfied. However, n is a positive number or 0.
L = (n + θ / (2π)) × λ (1)
Note that the phase difference θ indicates how much the phase of the drive signal input to the first piezoelectric element 14 is advanced with respect to the drive signal input to the second piezoelectric element 24. Details will be described below.

  The first vibrating member 12 has a sheet shape and vibrates due to vibration generated from the first piezoelectric element 14. The first vibrating member 12 adjusts the basic resonance frequency of the first piezoelectric element 14. 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 first piezoelectric element 14 can be controlled by controlling the rigidity of the first vibrating member 12. The thickness of the first vibrating member 12 is preferably 5 μm or more and 500 μm or less. Moreover, it is preferable that the 1st vibration member 12 is 1 GPa or more and 500 GPa or less in the longitudinal elastic modulus which is a parameter | index which shows rigidity. When the rigidity of the first vibrating member 12 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 first vibrating member 12 is not particularly limited as long as it is a material having a high elastic modulus with respect to the first piezoelectric element 14 that is a brittle material, such as a metal or a resin, but from the viewpoint of workability and cost. From phosphor bronze and stainless steel are preferred.

  The first piezoelectric element 14 is made of, for example, piezoelectric ceramics such as PZT. However, the first piezoelectric element 14 may be formed of a polymer material exhibiting piezoelectricity, such as polyvinylidene fluoride.

  The second vibrating member 22 is formed in the same way as the first vibrating member 12, and the second piezoelectric element 24 is formed in the same way as the first piezoelectric element 14.

  Further, it is preferable that the fundamental resonance frequencies of the first vibrator 10 and the second vibrator 20 are equal to each other. For example, in FIG. 1, the first piezoelectric element 14 and the second piezoelectric element 24 have the same planar shape. However, as shown in FIG. 4, the second piezoelectric element 24 may be larger than the first piezoelectric element 14. good. Conversely, the second piezoelectric element 24 may be smaller than the first piezoelectric element 14.

  As described above, the second vibrator 20 is provided with an opening. In the present embodiment, an opening 26 is provided in the second vibrating member 22. Specifically, the second vibrating member 22 has a plurality of beams extending radially from the center of the second piezoelectric element 24. These beams are arranged at equal intervals. And the part located between each beam is the opening 26. However, the beam constituting the second vibrating member 22 only needs to overlap the second piezoelectric element 24, and does not need to extend to the center of the second piezoelectric element 24.

  The controller 50 inputs drive signals to the first piezoelectric element 14 and the second piezoelectric element 24 as described above. When causing the oscillation device to function as a parametric speaker, the control unit 50 modulates audio data (original signal) input from the outside to generate modulation data for the parametric speaker, and generates a drive signal based on this data. . That is, the first piezoelectric element 14 and the second piezoelectric element 24 are input with drive signals having the same frequency generated from the same original signal. Here, the control unit 50 uses the resonance frequencies of the first vibrator 10 and the second vibrator 20 as the frequency of the modulation signal. The resonance frequency used here is preferably the fundamental resonance frequency.

  In the present embodiment, both the first vibrator 10 and the second vibrator 20 are supported by the same support member 40. The support member 40 has a cylindrical shape, and the outer periphery of the first vibration member 12 and the outer periphery of the first piezoelectric element 14 are fixed to the inner wall of the support member 40.

  FIG. 5 is a diagram illustrating a state where the oscillation device illustrated in FIG. 1 is attached to an electronic device. In the example shown in this figure, the oscillation device is attached to the inner wall of the housing 60 of the electronic device. Specifically, the upper end surface of the support member 40 is attached to the inner wall of the housing 60. A sound hole 62 is provided in the housing 60. The support member 40 includes a sound hole 62 on the inner side in plan view. For this reason, the sound hole 62 faces the first vibrator 10 and the second vibrator 20, and the sound waves generated by the first vibrator 10 and the second vibrator 20 are outside the housing 60 through the sound hole 62. To be emitted.

  Next, the operation and effect of this embodiment will be described. According to the present embodiment, since the second vibrator 20 has the opening 26, the sound wave oscillated from the first vibrator 10 is radiated above the second vibrator 20 through the opening 26. The sound waves generated by the second vibrator 20 overlap. Here, in the present embodiment, the above-described expression (1) is satisfied. For this reason, the sound wave oscillated by the first vibrator 10 has the same phase as the sound wave oscillated by the second vibrator 20 at the timing when it overlaps the sound wave oscillated by the second vibrator 20. In this case, the two sound waves strengthen each other. Therefore, the output of the oscillation device can be increased.

  In addition, since the first vibrator 10 and the second vibrator 20 are stacked, the oscillation device can be downsized as compared with the case where they are arranged on the same plane.

  Therefore, the output of the oscillation device can be increased while suppressing an increase in the size of the oscillation device.

  In the equation (1), when θ = π or θ = 2π, the design of the oscillation device becomes easy.

  In addition, a third vibrator may be provided on the second vibrator 20. In this case, the relationship between the third transducer 20 and the second transducer 20 is the same as the relationship between the second transducer 20 and the first transducer 10.

(Second Embodiment)
FIG. 6 is a cross-sectional view illustrating the configuration of the oscillation device according to the second embodiment. This oscillation device has the same configuration as that of the oscillation device according to the first embodiment except that the first vibrator 10 includes the second vibration member 16.

  In the present embodiment, the vibration member of the first vibrator 10 includes the first vibration member 12 and the second vibration member 16. The first piezoelectric element 14 is provided on the first vibrating member 12. The second vibrating member 16 has a hollow shape in plan view, and the first vibrating member 12 is positioned so as to close the hollow portion. That is, the inner peripheral edge of the second vibration member 16 is fixed to the edge of the first vibration member 12, and the outer peripheral edge of the second vibration member 16 is fixed to the support member 40.

  The second vibration member 16 is formed of a material having lower rigidity than the first vibration member 12, for example, a resin material such as polyethylene or urethane. For this reason, by providing the second vibrating member 16, the edge of the first vibrator 10 can vibrate greatly. Therefore, according to this embodiment, the same effect as that of the first embodiment can be obtained, and the output of the oscillation device can be further increased.

  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.

10 first vibrator 12 first vibration member 14 first piezoelectric element 16 second vibration member 20 second vibrator 22 second vibration member 24 second piezoelectric element 26 opening 40 support member 50 control unit 60 housing 62 sound hole

Claims (5)

A first vibrator having a first vibrating member and a first piezoelectric element provided on the first vibrating member;
A second vibrator having a second vibrating member and a second piezoelectric element provided on the second vibrating member;
Control means for inputting drive signals having the same frequency to the first piezoelectric element and the second piezoelectric element;
With
The second vibrating member overlaps with the first vibrator in a plan view and has an opening,
The phase difference of the drive signal input to the first piezoelectric element when the drive signal input to the second piezoelectric element is used as a reference is θ, and the distance between the first vibrator and the second vibrator is L, an oscillation device that satisfies the following expression (1), where λ is the wavelength of a sound wave having the same frequency as the drive signal. However, n is a positive number or 0.
L = (n + θ / (2π)) × λ (1) The oscillation device according to claim 1,
An oscillation device in which θ = π. The oscillation device according to claim 1,
The oscillation device in which θ = 2π. In the oscillation device according to any one of claims 1 to 3,
The first vibrator has the opening in the first vibration member.   The electronic device which has an oscillation apparatus as described in any one of Claims 1-4.

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