JP2019161472A - Capacitive sound wave generator and capacitive speaker - Google Patents

Abstract

Provided is a technique capable of reducing a driving voltage of a capacitance type sound wave generator or a capacitance type speaker and suppressing power consumption. A fixed electrode having a plate-like shape and having one or a plurality of through holes provided so as to penetrate in a thickness direction, and a fixed electrode having a plate-like or film-like shape Two vibrating electrodes 12 are disposed so as to face the fixed electrode 11, and at least a central portion of the vibrating electrode 12 is movable with respect to the fixed electrode 11 in the thickness direction. And a connecting member 14 having a plate shape and opposed to the vibration electrode 12 from the opposite side to the fixed electrode 11, and arranged so as to sandwich the vibration electrode 12 with the fixed electrode 11. And two outer fixed electrodes 15 and 16. [Selection diagram] FIG.

Description

  The present invention relates to a capacitive sound wave generator and a capacitive speaker.

  Among sound wave generators, those that are generally used as speakers that output sound waves in the audible range include dynamic speakers, balanced armature speakers, capacitance speakers, and the like. The dynamic type speaker vibrates the cone by electromagnetic driving and has a characteristic that the sound range is wide. On the other hand, the dynamic type speaker has a disadvantage of low response because the mass of the cone to be vibrated is large. In particular, a small speaker such as an earphone has a problem that the responsiveness is further deteriorated because the inertial force of the diaphragm is relatively large. In addition, the balanced armature type speaker vibrates an iron piece by electromagnetic driving, and is characterized in that it is easy to miniaturize and consumes less power, but has a disadvantage that the sound range is narrow.

On the other hand, an electrostatic speaker that solves such a problem is used (see, for example, Patent Documents 1-5). In this capacitive speaker, two fixed electrodes are arranged so as to sandwich the diaphragm. The electrostatic attraction generated between the diaphragm and each fixed electrode is used by charging the diaphragm positively or negatively and charging each fixed electrode by sending an electric signal of the opposite polarity to the diaphragm. Then, the diaphragm is vibrated to output sound waves. Since this capacitance type speaker does not have a coil or the like attached to the diaphragm, high response can be realized. In addition, there is an advantage that the structure is simple and power consumption is low.

Iman Shahoseni, et al, “Electromagnetic MEMS microspeaker for portable electronic devices”, Microsystem Technologies, June 2013, Volume 19. 879-886

US Pat. No. 6,842,964 European Patent Application No. 2410768 European Patent Application No. 2464142 European Patent Application Publication No. 2582156 Japanese Patent No. 3281887

The capacitance type speaker as described above has low power consumption, but it is necessary to apply a high voltage (100 to 200 V) between the vibration electrode and the fixed electrode in order to output a sufficient sound pressure. In addition, in a battery-driven application, a booster circuit that boosts voltage from a low battery voltage (within several volts) is required, which may increase device cost and power consumption. In addition to increasing the voltage between the electrodes, as a means of securing the sound pressure of the capacitive speaker, a method of increasing the electrode area can be considered, but in mobile devices and wearable devices where the speaker size is limited, the area of the speaker There were constraints and cost issues. For the reasons described above, it has been difficult to mount a capacitive speaker in mobile devices and wearable devices that have restrictions on both power consumption and speaker size.

  FIG. 9 shows a schematic configuration of a sound wave generating unit 100 in a general capacitive speaker. In the sound wave generating unit 100, two fixed electrodes 111 are arranged so as to sandwich the diaphragm 112. 10A and 10B, the diaphragm 112 is charged positively or negatively, and an electric signal having a polarity opposite to that of the diaphragm 112 is sent to each fixed electrode 111 to be charged. . As a result, the diaphragm 112 is vibrated using an electrostatic attractive force acting between the diaphragm 112 and each fixed electrode 111, and a sound wave is output. In the sound wave generator 100, the diaphragm 112 can be vibrated in accordance with an electric signal without attaching a coil or the like to the diaphragm 112.

  However, in the sound wave generating unit 100 in the general capacitive speaker as described above, one or a plurality of sound holes 111a are provided in each fixed electrode 111 in order to transmit the sound wave generated by the vibration of the diaphragm 112 to the outside. It was necessary to install. Therefore, the sound holes 111a reduce the surface area of each fixed electrode 111, resulting in a disadvantage that the electrostatic force acting on the diaphragm 112 is reduced. And in order to compensate for the fall of the electrostatic force, it was necessary to raise the voltage applied to the diaphragm 112 and each fixed electrode 111, and there existed a subject that power consumption increased.

  The present invention has been made in view of the above-described problems of the prior art, and its object is to reduce the drive voltage of a capacitive sound wave generator or a capacitive speaker, thereby suppressing power consumption. It is to provide technology that is possible.

The present invention has been made to solve the above-described problem, and has a plate-like shape and a fixed electrode having one or a plurality of through holes provided so as to penetrate in the thickness direction;
A plurality of plate-like or film-like shapes, arranged so as to face the fixed electrode, with the fixed electrode interposed therebetween, and at least a central portion of the fixed electrode being provided to be movable in the thickness direction A vibrating electrode;
A connection member for connecting the plurality of vibration electrodes through the through hole;
A plurality of outer fixed electrodes, each having a plate-like shape and disposed so as to sandwich the vibration electrode together with the fixed electrode by facing the vibration electrode from the side opposite to the fixed electrode;
A capacitive sound wave generator characterized by comprising:

  According to this, the vibration electrode can be vibrated based on the electrostatic force between the fixed electrode in which no sound hole is provided and the two vibration electrodes arranged with the fixed electrode interposed therebetween. Therefore, the area of the electrode for generating an electrostatic force can be increased compared to a conventional sound wave generator in which a plurality of sound holes are provided in the fixed electrode, and the vibrating electrode can be vibrated more efficiently. it can. Here, the fixed electrode has a through-hole through which the connecting member is passed. The area of the through-hole is significantly larger than the total area of the sound holes of the fixed electrode in a normal capacitive sound wave generator. Since it can be made smaller, there is no problem.

  In addition to the above, the present invention has a plurality of outer fixed electrodes arranged so as to sandwich the vibration electrode together with the fixed electrode by facing the vibration electrode from the side opposite to the fixed electrode. The electrostatic force between the outer fixed electrode and the vibrating electrode can also be used for the operation of the vibrating electrode. Thereby, the electrostatic force which acts on a vibration electrode can be strengthened, and a vibration electrode can be operated more efficiently. As a result, the voltage applied to the capacitive sound wave generator can be reduced, and the power consumption can be reduced.

  In the present invention, each of the plurality of vibration electrodes may be moved or deformed in the same direction by an electrostatic attraction generated between the fixed electrode and the outer fixed electrode sandwiching the vibration electrode. Further, acoustic signal input means for applying a voltage to the plurality of vibration electrodes and the plurality of outer fixed electrodes may be further provided. As a result, sound waves can be generated more efficiently, the applied voltage of the sound wave generator can be more reliably reduced, and power consumption can be reduced.

  In the present invention, the fixed electrode and the plurality of outer fixed electrodes may be fixed at the periphery thereof, and at least one of the plurality of vibration electrodes may be fixed at the periphery thereof. According to this, the positions and movements of the fixed electrode, the outer fixed electrode, and the vibration electrode can be further stabilized, and the quality of the sound wave generated by the sound wave generating device can be improved.

Further, in the present invention, the two vibration electrodes and the two outer fixed electrodes,
The acoustic signal input means includes
A positive or negative bias voltage is applied to the two outer fixed electrodes, and an inverted bias voltage obtained by reversing the polarity of the bias voltage is applied to the fixed electrode.
An acoustic signal is converted into an analog signal based on the bias voltage, the inverted bias voltage, or a voltage between the bias voltage and the inverted bias voltage, and an inverted analog signal in which the polarity of the analog signal is inverted is generated. An analog signal and the inverted analog signal may be configured to be applied to the two vibrating electrodes, respectively.

  According to this, each of the plurality of vibration electrodes can be controlled to move in the same direction by the electrostatic attractive force generated between the fixed electrode and the outer fixed electrode that sandwich the vibration electrode. As a result, sound waves can be generated more efficiently, the applied voltage of the sound wave generator can be reduced more reliably, and power consumption can be reduced.

  Further, the present invention comprises the above-described capacitance-type sound wave generator, and is configured to generate sound waves in the audible range by vibrations of the plurality of vibration electrodes by the acoustic signal input means. A capacitive speaker may be used. According to this, it is possible to provide a capacitive speaker that can be mounted on a mobile device or a wearable device with restrictions on both power consumption and speaker size.

  In addition, the means for solving each of the above-described problems can be used in combination as much as possible.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to reduce the drive voltage of a capacitive sound wave generator or a capacitive speaker, and to suppress power consumption.

It is the schematic which shows the sound wave generation part of the electrostatic capacitance type speaker in the Example of this invention. It is the schematic of an electrostatic capacitance type speaker including the acoustic signal input part in the Example of this invention. It is a figure which shows the relationship between the signal by the acoustic signal input part and the action | operation of a sound wave generation part in the Example of this invention. It is a figure which shows the relationship between the input signal and the action | operation of a sound wave generation part in the conventional electrostatic capacitance type speaker. It is sectional drawing of the sound wave generation part of the electrostatic capacitance type speaker in the Example of this invention. It is a figure which shows the manufacturing process of the outer side fixed electrode in the Example of this invention. It is a figure which shows the first half of the manufacturing process of the sound wave generation part of the capacitive speaker in the Example of this invention. It is a figure which shows the second half of the manufacturing process of the sound wave generation part of the capacitive speaker in the Example of this invention. It is the schematic which shows the sound wave generation part of the conventional electrostatic capacitance type speaker. It is a figure which shows the mode of an action | operation of the sound wave generation part of the conventional electrostatic capacitance type speaker.

[Application example]
Hereinafter, application examples of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic diagram of a sound wave generator 10a of a capacitive speaker 10 according to the present invention. In this sound wave generator 10a, two vibration electrodes, a first vibration electrode 12 and a second vibration electrode 13, are arranged so as to sandwich the fixed electrode 11, and the first vibration electrode 12 and the second vibration electrode 13 are: The connection member 14 is connected through the through hole 11 a of the fixed electrode 11. A first outer fixed electrode 15 is provided outside the first vibration electrode 12, and a second outer fixed electrode 16 is provided outside the second vibration electrode 13. That is, the first vibrating electrode 12 is sandwiched between the fixed electrode 11 and the first outer fixed electrode 15. Further, the second vibrating electrode 13 is sandwiched between the fixed electrode 11 and the second outer fixed electrode 16. In the example of FIG. 1, the ends of the fixed electrode 11, the first vibrating electrode 12, the second vibrating electrode 13, the first outer fixed electrode 15, and the second outer fixed electrode 16 are fixed.

  In the capacitive speaker 10, a predetermined voltage is applied to the fixed electrode 11, the first vibrating electrode 12, the second vibrating electrode 13, the first outer fixed electrode 15, and the second outer fixed electrode 16, and the first vibrating electrode 12, the electrostatic force generated between the first outer fixed electrode 15 and the fixed electrode 11, the electrostatic force generated between the second vibrating electrode 13, the second outer fixed electrode 16 and the fixed electrode 11, Are controlled in the same direction. Thereby, the first vibrating electrode 12 can be vibrated using both the electrostatic force between the outer first fixed electrode 15 and the electrostatic force between the fixed electrode 11 and the second vibrating electrode 13. Can be vibrated using both the electrostatic force between the outer second fixed electrode 16 and the electrostatic force between the fixed electrode 11 and the outer second fixed electrode 16.

  Further, in the capacitive speaker 10, no sound hole is provided in the fixed electrode 11 as in the conventional capacitive speaker 100 shown in FIG. 9. Therefore, a stronger electrostatic force can be generated. Thereby, in order to generate the same sound pressure, the applied voltage applied to each electrode can be reduced, and as a result, the power consumption of the capacitive speaker 10 can be reduced. In the capacitive speaker 10, the fixed electrode 11 is provided with a through hole 11a. However, since the through hole 11a is used only for passing the connection member 14, a sound hole for allowing sound waves to pass therethrough. Compared with, the ratio with respect to the surface area of the fixed electrode 11 can be made very small. For this reason, even if the through-hole 11a is provided in the fixed electrode 11, the reduction | decrease width of the electrostatic force by the through-hole 11a is small.

Here, the first vibration electrode 12 and the second vibration electrode 13 in the capacitive speaker 10 may have any configuration as long as at least the central portion is provided so as to be movable in the thickness direction. More specifically, one end of the first vibrating electrode 12 or the second vibrating electrode 13 (in other words, the peripheral portion) is fixed, and the other end is not fixed and is in a free state. Also good. The first vibrating electrode 12 and the second vibrating electrode 13 may be the same material or configuration, or may be different materials or configurations. For example, the first vibrating electrode 1
The second and second vibrating electrodes 13 may be formed of a thin and flexible material film such as parylene, polyethylene (PE), or metallic glass. These films desirably have a thickness of 50 μm or less, and particularly desirably 20 μm or less. The Young's modulus is desirably 80 GPa or less, and particularly desirably 50 GPa.

  The first vibrating electrode 12 and the second vibrating electrode 13 include a central portion made of a hard plate made of metal such as silicon, ceramics, Al, Cu, or Ni, and a peripheral portion made of a flexible and thin material. And the peripheral part thereof may be fixed to the frame-shaped support part. As for the magnitude | size of the center part of the 1st vibration electrode 12 and the 2nd vibration electrode 13, it is desirable that a diameter is 100 micrometers or less. The first vibrating electrode 12 and the second vibrating electrode 13 are entirely made of a hard plate made of metal such as silicon, ceramics, Al, Cu, Ni, etc., and its peripheral portion is framed by a leaf spring or the like. It may be fixed to the support part. The leaf spring or the like may be formed from the same material as the first vibrating electrode 12 or the second vibrating electrode 13 or may be formed from a material that is used.

  The first vibrating electrode 12 and the second vibrating electrode 13 are preferably made of a low-resistance material such as a conductor, but are formed of an insulator in which a conductor layer is coated on at least the surface on the fixed electrode 11 side. It may be. In this case, the conductor layer may be formed of, for example, carbon, metal, silicon doped with impurities, or the like.

  The fixed electrode 11, the first outer fixed electrode 15 and the second outer fixed electrode 16 are preferably formed of a hard plate made of metal such as silicon, ceramics, Al, Cu or Ni. The first vibrating electrode 12 and the second vibrating electrode 13 may be connected by one connecting member 14, but may be connected by a plurality of connecting members 14 in accordance with the number of through holes 11 a. The connecting member 14 is preferably at least partially electrically insulated. The insulated portion of the connection member 14 is preferably made of a polymer such as epoxy resin or benzocyclobutene, ceramics, or the like, and preferably has a resistance value of 1 MΩ or more.

  FIG. 2 shows an overall schematic diagram of the capacitive speaker 10 including the sound wave generator 10a and the acoustic signal input unit 10b. As shown in FIG. 2, the capacitive speaker 10 includes an acoustic signal input unit 10b in addition to the sound wave generation unit 10a. The acoustic signal input unit 10 b includes a bias generation unit 31 and a voltage conversion unit 32. The bias generator 31 generates positive and negative bias voltages and supplies the positive bias voltage to the fixed electrode 11. The bias generator 31 supplies a negative bias voltage to the central portion of the transformer secondary coil in the voltage converter 32, the first outer fixed electrode 15, and the second outer fixed electrode 16.

  The voltage conversion unit 32 receives an acoustic signal from the acoustic input terminal 32a, and uses the acoustic signal as a reference from a negative bias voltage supplied from the bias generation unit 31 as a positive voltage or bias potential higher than the bias potential. Convert to analog signal with low negative voltage. The voltage conversion unit 32 supplies one side of the converted analog signal to the first vibrating electrode 12 and supplies an inverted signal obtained by inverting the polarity of the analog signal to the second vibrating electrode 13. Thereby, the capacitive speaker 10 can operate the first vibrating electrode 12 by using both the electrostatic force between the outer first fixed electrode 15 and the electrostatic force between the fixed electrode 11. . Further, the second vibrating electrode 13 can be operated using both the electrostatic force between the outer second fixed electrode 16 and the electrostatic force between the fixed electrode 11.

In the above description, the sound wave generator 10a has the two vibration electrodes of the first vibration electrode 12 and the second vibration electrode 13, but the number of vibration electrodes is not limited to two. Further, by using more vibration electrodes, a configuration in which a stronger electrostatic force acts on the vibration electrodes may be used. The bias generator 31 supplies not the negative bias voltage but a positive bias voltage or a voltage between the negative bias voltage and the positive bias voltage to the central portion of the transformer secondary coil in the voltage converter 32. You may do it. In this case, the voltage conversion unit 32 uses the positive bias voltage supplied from the bias generation unit 31 or a voltage between the negative bias voltage and the positive bias voltage as a reference, or a voltage higher than that potential. You may make it convert into the analog signal of a low voltage.

<Example>
Next, with reference to FIG. 3, an embodiment of the sound wave generator 10a that operates according to an acoustic signal from the acoustic signal input unit 10b will be described in more detail. FIG. 3A shows an acoustic signal from the acoustic signal input unit 10b. 3 (b) to 3 (c) show the potential of each electrode and the direction and magnitude of the electrostatic force when the acoustic signal at the time t1 to t3 in FIG. 3 (a) is input, respectively. Yes. Here, it is assumed that a bias voltage of ± 50 v is supplied from the bias generator 31 and a sine wave having an amplitude of 100 V is supplied from the voltage converter 32.

  At t <b> 1, as shown in FIG. 3B, −50 V is supplied from the sound pressure conversion unit 32 to the first vibration electrode 12, and +50 V is supplied to the second vibration electrode 13. In that case, since the first outer fixed electrode 15 and the first vibrating electrode 12 are at the same potential, no electrostatic force acts between them. On the other hand, an electrostatic attractive force (force on the right side in the figure) corresponding to a potential difference of 100 V acts on the first vibrating electrode 12 from the fixed electrode 11. As a result, an electrostatic force to the right side in the figure corresponding to a potential difference of 100 V acts on the first vibrating electrode 12. Further, since the fixed electrode 11 and the second vibrating electrode 13 have the same potential, no electrostatic force acts between them. On the other hand, an electrostatic attractive force (force on the right side in the figure) corresponding to a potential difference of 100 V acts on the second outer fixed electrode 16 and the second vibrating electrode 13. As a result, an electrostatic force to the right side in the figure corresponding to a potential difference of 100 V also acts on the second vibrating electrode 12. From the above, at t1, the electrostatic force to the right side in the figure corresponding to the potential difference of 100 V acts on the first vibrating electrode 12 and the second vibrating electrode 13, respectively.

  At t2, as shown in FIG. 3C, the voltage supplied from the sound pressure conversion unit 32 to the first vibration electrode 12 and the second vibration electrode 13 is 0V. In that case, an electrostatic attractive force (force on the left side in the figure) corresponding to a potential difference of 50 V acts on the first outer fixed electrode 15 to the first vibrating electrode 12. On the other hand, an electrostatic attractive force (force on the right side in the figure) corresponding to a potential difference of 50 V acts on the first vibrating electrode 12 from the fixed electrode 11. As a result, the electrostatic attractive force acting on the first vibrating electrode 12 is balanced, and the same state as that in which the electrostatic force does not act is obtained. Further, an electrostatic attractive force (force on the left side in the figure) corresponding to a potential difference of 50 V acts on the second vibrating electrode 13 from the fixed electrode 11. An electrostatic attractive force (force on the right side in the figure) corresponding to a potential difference of 50 V acts on the second outer fixed electrode 16 and the second vibrating electrode 13. As a result, the electrostatic attractive force acting on the second vibrating electrode 13 is balanced, and the same state as when no electrostatic force acts is obtained. As described above, no electrostatic force acts on the first vibrating electrode 12 and the second vibrating electrode 13 at t2.

  At t <b> 3, as shown in FIG. 3D, +50 V is supplied from the sound pressure conversion unit 32 to the first vibration electrode 12, and −50 V is supplied to the second vibration electrode 13. In that case, an electrostatic attractive force (force on the left side in the figure) corresponding to a potential difference of 100 V is applied from the first outer fixed electrode 15 to the first vibrating electrode 12. On the other hand, since the fixed electrode 11 and the first vibrating electrode 12 have the same potential, no electrostatic force acts between them. As a result, an electrostatic force to the left side in the figure corresponding to a potential difference of 100 V acts on the first vibrating electrode 12. Further, an electrostatic attractive force (force on the left side in the figure) corresponding to a potential difference of 100 V acts on the second vibrating electrode 13 from the fixed electrode 11. On the other hand, since the second outer fixed electrode 16 and the second vibrating electrode 13 are at the same potential, no electrostatic force acts between them. As a result, an electrostatic force to the left side in the figure corresponding to a potential difference of 100 V also acts on the second vibrating electrode 13. From the above, at t3, the electrostatic force to the left in the figure corresponding to the potential difference of 100 V acts on the first vibrating electrode 12 and the second vibrating electrode 13, respectively.

  Next, an operation mode of the sound wave generation unit of the conventional sound wave generator 100 shown in FIG. 9 will be described with reference to FIG. FIG. 4A shows an acoustic signal as in FIG. 4 (b) to 4 (c) show the potential of each electrode and the direction and magnitude of the electrostatic force when the acoustic signal at the time t1 to t3 in FIG. 4 (a) is input, respectively. Yes. Here, it is assumed that a sine wave having a bias voltage of ± 50 v and an amplitude of 100 V is supplied to the sound wave generator 100 as in the case described with reference to FIG.

  At t1, as shown in FIG. 4B, 50V is supplied to the left fixed electrode 111 and 50V is supplied to the vibration electrode 112. In that case, since the left fixed electrode 111 and the vibrating electrode 112 are at the same potential, no electrostatic force acts between them. On the other hand, an electrostatic attractive force (force on the right side in the figure) corresponding to a potential difference of 100 V is applied to the vibrating electrode 112 from the right fixed electrode 111. As a result, at t1, an electrostatic force to the right side in the figure corresponding to a potential difference of 100 V acts on the vibrating electrode 112.

  Further, at t2, as shown in FIG. 4C, the voltage supplied to the vibrating electrode 112 is 0V. In that case, an electrostatic attractive force (force on the left side in the figure) corresponding to a potential difference of 50 V is applied from the left fixed electrode 111 to the vibrating electrode 112. On the other hand, an electrostatic attractive force (force on the right side in the figure) corresponding to a potential difference of 50 V acts on the vibrating electrode 112 from the right fixed electrode 111. As a result, at t2, the electrostatic attractive force acting on the vibrating electrode 112 is balanced, and the state is the same as when the electrostatic force does not act.

  At t3, −50 V is supplied to the vibrating electrode 112 as shown in FIG. In this case, an electrostatic attractive force (force on the left side in the figure) corresponding to a potential difference of 100 V acts on the left fixed electrode 111 and the vibrating electrode 112. On the other hand, since the right fixed electrode 11 and the vibrating electrode 112 have the same potential, no electrostatic force acts between them. As a result, at t3, an electrostatic force to the left side in the figure corresponding to a potential difference of 100 V acts on the vibrating electrode 112.

  As can be seen from FIGS. 3 and 4, in this embodiment, the first vibration electrode 12 and the second vibration electrode 13 are connected to each other by inputting an acoustic signal to the first vibration electrode 12 and the second vibration electrode 13. It can be vibrated in the direction, and sound waves can be generated. That is, twice the electrostatic force can be applied to the vibrating electrodes 12 and 13 that vibrate integrally. Furthermore, in this embodiment, the vibrating electrodes 12 and 13 are operated based on the electrostatic force between the fixed electrode 11 provided with no sound hole and the first vibrating electrode 12 and the second vibrating electrode 13. Can do. Therefore, the area of the electrode that generates the electrostatic force can be increased, and the vibrating electrodes 12 and 13 can be vibrated more efficiently than in the past. In other words, in this embodiment, it is possible to generate sound waves of the same sound pressure level with a driving voltage of 1/2 or less compared to the conventional sound wave generating device 100, and the consumption. Electric power can be greatly reduced.

FIG. 5 shows a cross-sectional view of the case where the sound wave generator 10a according to the present embodiment is formed as a MEMS device using a semiconductor manufacturing process. Here, the fixed electrode 11 has a disk shape in a plan view, and has a through hole 11a provided in the center thereof in the thickness direction. The fixed electrode 11 has a terminal 11b at the end. The first vibrating electrode 12 is smaller in diameter than the fixed electrode 11 and has a thin disk shape. The first vibrating electrode 12 is disposed on one surface side of the fixed electrode 11 so as to face the fixed electrode 11. The second vibrating electrode 13 has a disk shape having the same diameter and thickness as the first vibrating electrode 12. The second vibrating electrode 13 is disposed on the other surface side of the fixed electrode 11 so as to face the fixed electrode 11. The connecting member 14 has an elongated rod shape, and connects the first vibrating electrode 12 and the second vibrating electrode 13 through the through hole 11 a of the fixed electrode 11. Both ends of the connecting member 14 are fixed to the central portion of the first vibrating electrode 12 and the central portion of the second vibrating electrode 13, respectively.

  In addition, the support portion 17 is fixed to the first frame body 21 provided so as to surround the first vibration electrode 12, the second frame body 22 provided so as to surround the second vibration electrode 13, and And a fixing member 23 for fixing the electrode 11. The first frame body 21 and the second frame body 22 are arranged so as to sandwich the fixed electrode 11 therebetween. The first frame body 21 is provided with a plurality of leaf springs 24 along the inner peripheral edge, and by fixing the inner peripheral end of each leaf spring 24 to the peripheral edge portion of the first vibrating electrode 12, The vibration electrode 12 is supported.

  The first frame 21 has a terminal 25 at the end. The second frame 22 is provided with a plurality of leaf springs 26 along the inner periphery. The vibration electrode 13 is supported by fixing the inner peripheral end of each leaf spring 26 to the peripheral edge of the second vibration electrode 13. The second frame 22 has a terminal 27 at the end. The fixing member 23 is disposed between the first frame 21 and one surface of the fixed electrode 11 so as to fix the fixed electrode 11 between the first frame 21 and the second frame 22, and A plurality of pieces are fixed between the second frame 22 and the other surface of the fixed electrode 11. The fixing member 23 is fixed to the peripheral edge portion of the fixed electrode 11.

  Thereby, the first vibrating electrode 12 can vibrate in the thickness direction with respect to the fixed electrode 11 via the plate springs 24. The second vibrating electrode 13 can vibrate in the thickness direction with respect to the fixed electrode 11 via each leaf spring 26. The first vibrating electrode 12 and the second vibrating electrode 13 are moved in the same direction by the connecting member 14 and vibrate simultaneously.

  The first outer fixed electrode 15 has a disk shape in plan view and has a plurality of sound holes 15a. The first outer fixed electrode 15 has a terminal 28 at the end. The first outer fixed electrode 15 is disposed on the opposite side of the first vibrating electrode 12 from the fixed electrode 11 so as to face the first vibrating electrode 12. The first outer fixed electrode 15 is fixed to the support portion 17 by a fixing member 34. The second outer fixed electrode 16 has a disk shape having the same thickness as the first outer fixed electrode 15 and has a plurality of sound holes 16a. The second outer fixed electrode 16 has a terminal 29 at the end. The second vibration electrode 13 is disposed on the opposite side of the fixed electrode 11 so as to face the second vibration electrode 13. The second outer fixed electrode 16 is fixed to the second frame 22 by a fixing member 35.

  In the example shown in FIG. 5, the fixed electrode 11, the first vibrating electrode 12, the second vibrating electrode 13, the first outer fixed electrode 15, and the second outer fixed electrode 16 are made of low resistance conductive silicon. . The connecting member 14 is made of conductive silicon at the center, and both ends connected to the first vibrating electrode 12 and the second vibrating electrode 13 are made of insulating epoxy resin SU-8. . The first frame 21 and the second frame 22 are made of low resistance conductive silicon. The fixing members 23, 34, and 35 are made of an insulating epoxy resin SU-8. The terminal 11b of the fixed electrode 11, the terminal 25 of the first frame 21, the terminal 27 of the second frame 22, the terminal 28 of the first outer fixed electrode 15, and the terminal 29 of the second outer fixed electrode 16 are: It consists of a conductive Ti / Au layer.

The first outer fixed electrode 15 and the second outer fixed electrode 16 in the present embodiment are formed by a process as shown in FIG. In FIG. 6, the second outer fixed electrode 16 will be described as an example. First, as shown in FIG. 6A, an oxide film 16c is formed on a silicon substrate 16b. Next, as shown in FIG. 6B, a resist 16d is formed on the oxide film 16c, and a portion corresponding to the sound hole 16a is removed by photolithography. Next, as shown in FIG. 6C, the oxide film 16c corresponding to the sound hole 16a is removed, and the remaining resist 16d is removed. Next, as shown in FIG. 6D, the silicon substrate 16b is etched by DRIE (Deep Reactive Ion Etching) to form a sound hole 16a. Next, as shown in FIG. 6E, the remaining oxide film 16c is removed, an electrode Ti / Au bilayer film 29 is formed by sputtering, and a photosensitive epoxy resin (SU8) is formed by spin coating + photolithography. ) Is formed.

  Next, in FIG. 7, an example of the manufacturing process of the entire sound wave generator 10b shown in FIG. 5 will be described. First, as shown in FIG. 7A, in an SOI (Silicon on Insulator) substrate, a base silicon layer 41 has a thickness of 400 μm, and silicon oxide insulating layers 42 above and below the base silicon layer 41 have a thickness of 5 μm. Layer 43 is formed to a thickness of 20 μm. Since the base silicon layer 41 and the silicon active layer 43 are used as electrodes for generating electrostatic attraction, for example, the resistivity is preferably a low resistance of about 0.02 Ωcm.

  In this embodiment, the silicon active layer 43 of the SOI substrate is etched away to the insulating layer 42 by photolithography and dry etching to form the first vibrating electrode 12 in a circular shape having a diameter of 1000 μm. At this time, a portion not not removed by etching is left as a beam (width 100 μm / length 100 μm), and the first vibration electrode 12 is connected to the outer peripheral portion by four beams to form a spring 24 that supports the first vibration electrode 12. . A Ti / Au bilayer film (Ti 0.3 μm / Au 1 μm) 25 serving as an electrode is formed on the silicon active layer 43 holding the first vibrating electrode 12 by sputtering.

  Next, as shown in FIG. 7B, a photosensitive epoxy resin (SU-8) is formed on the silicon active layer 43 on which the first vibrating electrode 12 is formed to a thickness of 100 μm by a spin coating method. Thereafter, by means of photolithography, the electrode spacer 23 and the connecting member (the connection member (SU-8) are left in the outer peripheral portion 21 surrounding the slit in which the first vibrating electrode 12 is formed and the central portion of the first vibrating electrode 12. (Diameter 100 μm) 14 is formed.

  Next, as shown in FIG. 7C, a 200 μm-thick low-resistance (resistivity 0.02 Ωcm) silicon substrate 44 is bonded to the silicon active layer 43 by SU-8 formed in FIG. 7B. Then, a Ti / Au bilayer film (Ti 0.3 μm / Au 1 μm) 11 b as a second electrode is formed on the silicon substrate 44. Then, as shown in FIG. 7D, a slit having an inner diameter of 120 μm and a width of 20 μm is formed on the silicon substrate 44 at a position facing the connecting member 14 of the silicon active layer 43 bonded to the lower portion by a photolithographic dry etching method. Form.

  Next, as shown in FIG. 7 (e), the low resistance (resistivity 0.02 Ωcm) silicon substrate 45 having a thickness of 400 μm is etched and removed in a slit shape to a depth of 20 μm by photolithography and dry etching. A portion to be the second vibrating electrode 13 is formed in a circular shape having a diameter of 1000 μm. At this time, a portion not removed by etching is left as a beam (width 100 μm / length 100 μm), and the second vibration electrode 13 is connected to the outer peripheral portion by four beams, and a portion that becomes the spring 26 that supports the second vibration electrode 13 is also formed. Form. In addition, a Ti / Au bilayer film (Ti 0.3 μm / Au 1 μm) 27 to be an electrode is formed on the opposite surface of the silicon substrate 45 by etching by sputtering.

  Next, as shown in FIG. 7F, a photosensitive epoxy resin SU-8 is formed to a thickness of 100 μm on the side of the silicon substrate 45 where the second vibrating electrode 13 is formed by a spin coating method, and thereafter In addition, by means of photolithography, the electrode spacer 23 and the connecting member (diameter 100 μm) 14 are left so that the photosensitive epoxy resin SU-8 remains in the outer peripheral portion surrounding the second vibrating electrode 13 and the central portion of the second vibrating electrode 13. Is further formed. The surface on which the photosensitive epoxy resin SU-8 is formed on the silicon substrate 45 is bonded to the silicon substrate 44 so that the first vibrating electrode 12 and the second vibrating electrode 13 face each other.

  Next, as shown in FIG. 8A, the silicon substrate 45 includes the second vibrating electrode 13 and the beam by photolithography and dry etching from the side of the Ti / Au bilayer film (Ti 0.3 μm / Au 1 μm) 27. Etching is removed to the depth where the slit is formed.

  Then, as shown in FIG. 8B, in the SOI (Silicon on Insulator) substrate, a base silicon layer 41 and an insulating layer 42 of silicon oxide include the first vibrating electrode 12 and the beam by photolithography and dry etching techniques. Remove by range.

  Next, as shown in FIG. 8C, the second fixed electrode 16 formed in FIG. 6E and a photosensitive epoxy resin having a thickness of 100 μm are formed on the surface of the silicon substrate 45 opposite to the fixed electrode 11. The fixing member 35 of the (SU-8) layer is bonded. Further, as shown in FIG. 8D, the first fixed electrode 15 formed on the surface opposite to the fixed electrode 11 of the silicon substrate 45 by the same method as in FIG. 6 and a photosensitive epoxy resin having a thickness of 100 μm. The fixing member 34 of the (SU-8) layer is bonded. In this way, the sound wave generator 10a of the capacitive speaker 10 shown in FIG. 5 can be manufactured.

  In the capacitive speaker 10, the through-hole 11 a provided in the central fixed electrode 11 is used only for passing the connection member 14, so that the fixed electrode 11 is compared with the case where a plurality of sound holes are provided. The ratio with respect to the surface area can be made very small. For this reason, power consumption can be suppressed compared with the conventional electrostatic capacity type speaker in which the influence by the sound hole of each fixed electrode is large. In addition, since the first vibration electrode 12 and the second vibration electrode 13 are connected by the connecting member 14 in the capacitive speaker 10, only one of the first vibration electrode 12 and the second vibration electrode 13 is present. It is good also as a structure by which a peripheral part is fixed.

  Note that the first vibrating electrode 12 and / or the second vibrating electrode 13 in the capacitive speaker 10 may be made of a thin film. Even in this case, the first vibrating electrode 12 and / or the second vibrating electrode 13 can be vibrated according to the same principle as shown in FIGS. 1 and 2, and sound waves can be output. The thin film in this case preferably has a thickness of 1 to 50 μm and a diameter of 5 mm or less.

  The capacitive speaker 10 according to the present invention may be used for any application as long as the application generates sound waves. Note that the term “sound wave” in this specification includes not only an acoustic wave having a frequency in the audible range but also an elastic wave having a frequency outside the audible range. The capacitive speaker 10 according to the present invention is configured to generate sound waves in the audible range by vibration of the vibrating body by the audio signal input means, and is configured to generate ultrasonic waves having a frequency higher than the audible range. The ultrasonic generator may be configured as an ultra-low frequency sound generator configured to generate an ultra-low frequency wave having a frequency lower than the audible range. That is, in this specification, the capacitive sound wave generator is specified as a device that generates sound waves having a wide frequency including the audible range, and the capacitive speaker 10 particularly generates sound waves having a frequency in the audible range. It is specified as a device to generate.

  Further, in the above-described embodiments, the case where the capacitive speaker 10 is a MEMS capacitive speaker using a semiconductor manufacturing technology has been described. However, the configuration of the present invention is a capacitive type other than MEMS. The present invention can also be applied to a speaker or a capacitive sound wave generator, for example, a so-called capacitor-type speaker, headphones, earphones, or the like.

In the following, in order to make it possible to compare the configuration requirements of the present invention with the configuration of the embodiment, the configuration requirements of the present invention are described with reference numerals in the drawings.
<Invention 1>
One or a plurality of through-holes (11 having a plate shape and penetrating in the thickness direction)
a fixed electrode (11) having a);
It has a plate-like or film-like shape, and is arranged with the fixed electrode (11) sandwiched so as to face the fixed electrode (11), and at least the central part of the fixed electrode (11) is in the thickness direction A plurality of vibrating electrodes (12, 13) movably provided on the
A connecting member (14) for connecting the plurality of vibrating electrodes (12, 13) through the through hole (11a);
It has a plate-like shape and faces the vibration electrode (12, 13) from the opposite side to the fixed electrode (11), thereby allowing the vibration electrode (12, 13) together with the fixed electrode (11). A plurality of outer fixed electrodes (15, 16) arranged to sandwich,
A capacitive sound wave generator (10), comprising:
<Invention 2>
Each of the plurality of vibrating electrodes (12, 13) has the same direction due to electrostatic attraction generated between the fixed electrode (11) and the outer fixed electrodes (15, 16) sandwiching the vibrating electrode (12, 13). Acoustic signal input means (10b) for applying a voltage to the fixed electrode (11), the plurality of vibrating electrodes (12, 13) and the plurality of outer fixed electrodes (15, 16) so as to move or deform The capacitive sound wave generator according to claim 1, further comprising:
<Invention 3>
The fixed electrode (11) and the plurality of outer fixed electrodes (15, 16) are fixed at the periphery thereof, and at least one of the plurality of vibration electrodes (12, 13) is fixed at the periphery thereof. The electrostatic capacity type sound wave generator according to claim 1 or 2, wherein
<Invention 4>
Two vibrating electrodes (12, 13) and two outer fixed electrodes (15, 16),
The acoustic signal input means (10b)
A positive or negative bias voltage is applied to the two outer fixed electrodes (15, 16), and an inverted bias voltage obtained by inverting the polarity of the bias voltage is applied to the fixed electrode (11).
An acoustic signal is converted into an analog signal based on the bias voltage, the inverted bias voltage, or a voltage between the bias voltage and the inverted bias voltage, and an inverted analog signal in which the polarity of the analog signal is inverted is generated. The capacitive acoustic wave according to any one of claims 1 to 3, characterized in that an analog signal and the inverted analog signal are applied to the two vibrating electrodes (12, 13), respectively. Generator.
<Invention 5>
The capacitive sound wave generating device according to any one of the first to fourth aspects of the present invention, wherein sound waves in an audible range are generated by vibrations of the plurality of vibration electrodes (12, 13) by the acoustic signal input means (10b). A capacitive speaker (10) characterized by being configured to be generated.

DESCRIPTION OF SYMBOLS 10 ... Capacitance type speaker 10a ... Sound wave generation part 10b ... Acoustic signal input part 11 ... Fixed electrode 11a ... Through-hole 11b ... Terminal 12 ... First vibration electrode 13 ... Second vibrating electrode 14 ... Connection member 15 ... First outer fixed electrode 16 ... Second outer fixed electrode 31 ... Bias generator 32 ... Voltage converter 32a ... Audio input terminal

Claims (5)

A fixed electrode having a plate-like shape and having one or a plurality of through holes provided so as to penetrate in the thickness direction;
A plurality of plate-like or film-like shapes, arranged so as to face the fixed electrode, with the fixed electrode interposed therebetween, and at least a central portion of the fixed electrode being provided to be movable in the thickness direction A vibrating electrode;
A connection member for connecting the plurality of vibration electrodes through the through hole;
A plurality of outer fixed electrodes, each having a plate-like shape and disposed so as to sandwich the vibration electrode together with the fixed electrode by facing the vibration electrode from the side opposite to the fixed electrode;
A capacitive sound wave generator characterized by comprising:   The fixed electrodes, the plurality of vibration electrodes, and the plurality of vibration electrodes are moved or deformed in the same direction by electrostatic attraction generated between the fixed electrode and the outer fixed electrode sandwiching the vibration electrodes. The capacitive sound wave generator according to claim 1, further comprising acoustic signal input means for applying a voltage to the plurality of outer fixed electrodes.   The fixed electrode and the plurality of outer fixed electrodes are fixed at a peripheral portion thereof, and at least one of the plurality of vibration electrodes is fixed at the peripheral portion thereof. Capacitance type sound wave generator. Two vibration electrodes and two outer fixed electrodes,
The acoustic signal input means includes
A positive or negative bias voltage is applied to the two outer fixed electrodes, and an inverted bias voltage obtained by reversing the polarity of the bias voltage is applied to the fixed electrode.
An acoustic signal is converted into an analog signal based on the bias voltage, the inverted bias voltage, or a voltage between the bias voltage and the inverted bias voltage, and an inverted analog signal in which the polarity of the analog signal is inverted is generated. 4. The capacitance-type sound wave generator according to claim 1, wherein an analog signal and the inverted analog signal are applied to the two vibrating electrodes, respectively. 5.   5. The capacitive sound wave generator according to claim 1, wherein the sound wave input device is configured to generate sound waves in an audible range by vibrations of the plurality of vibration electrodes by the acoustic signal input means. Capacitance type speaker characterized by

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