JP2012217034A - Oscillation device and portable terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sound pressure level of an oscillation device.SOLUTION: An oscillation device 100 includes: a vibration member 20; and a support member 30 for supporting the vibration member 20 and provided so as to enclose a space 60 on one surface side of the vibration member 20. The support member 30 has a hole 42 widening toward the outer side from the space 60 and a hole 40 narrowing toward the outer side from the space 60 at portions facing the space 60. The space 60 opens to the exterior of the space 60 through the hole 40 and the hole 42.

Description

  The present invention relates to an oscillation device and a portable terminal device.

  As one of the electroacoustic transducers, there is an electrodynamic electroacoustic transducer. The electrodynamic electroacoustic transducer generates vibration amplitude using the action of a magnetic circuit. In addition, as described in Patent Document 1, for example, sound reproduction is performed using a mechanical air pump.

  Further, for example, as described in Patent Documents 2 to 5, there is one that performs sound reproduction using a piezoelectric acoustic element. The device described in Patent Document 2 is to join a piezoelectric element, which is a vibration source, and a vibration film through a vibration transmission member having elasticity. The thing of patent document 3 sticks the nonwoven fabric etc. which cover the leak hole provided in the case which supports a piezoelectric ceramic material to a case with a double-sided tape.

  The thing of patent document 4 is that the base which supports a piezoelectric material, and the horn which improves the directivity of a sound wave are formed with a silicon material. In the device disclosed in Patent Document 5, the upper surface of the case that supports the piezoelectric vibrator is formed in a concave shape, and a sound emitting hole is provided in the concave surface portion.

Japanese translation of PCT publication No. 2003-501849 International Publication WO2005 / 094121 Pamphlet JP-A-8-205289 JP-A-5-292598 JP-A-61-89799

  When the oscillation device is held by the substrate of the electronic device or the like, the vibration film constituting the oscillation device is subjected to an acoustic resistance load by the air filling the space between the vibration film and the substrate or the like. When the vibration membrane is subjected to a load by air, the sound pressure of the oscillation device is attenuated. Therefore, it is required to improve the sound pressure level in the oscillation device.

According to the present invention, a vibrating member;
A support member that supports the vibration member and is provided so as to surround a space on one surface side of the vibration member;
With
The support member has a first hole that widens outward from the space and a second hole that narrows outward from the space in a portion facing the space,
An oscillation device is provided in which the space is opened to the outside of the space through the first hole and the second hole.

  According to the present invention, it is possible to provide a mobile terminal device equipped with the above-described oscillation device.

  According to the present invention, the sound pressure level of the oscillation device can be improved.

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 a comparative example. It is a graph which shows the acoustic characteristic of the oscillation apparatus which concerns on 1st Embodiment and a comparative example. 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.

  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 according to the present embodiment includes a vibration member 20 and a support member 30. The oscillation device 100 is mounted on a mobile terminal device such as a mobile phone.

  The support member 30 is provided so as to support the vibration member 20 and surround the space 60 on one surface side of the vibration member 20. Further, the support member 30 has a hole 42 that widens outward from the space 60 and a hole 40 that narrows outward from the space 60 in a portion facing the space 60. The space 60 is opened to the outside of the space 60 through the hole 40 and the hole 42. Hereinafter, the configuration of the oscillation device 100 will be described in detail.

The vibration member 20 has, for example, a flat plate shape. The vibration member 20 is made of a material having a high elastic modulus with respect to a ceramic that is a brittle material, such as metal or resin, and is made of a general-purpose material such as phosphor bronze or stainless steel. The thickness of the vibration member 20 is preferably 5 to 500 μm. The longitudinal elastic modulus of the vibration member 20 is preferably 1 to 500 GPa. When the longitudinal elastic modulus of the vibration member 20 is excessively low or high, the vibration characteristics and reliability of the oscillation device may be impaired.
As shown in FIG. 1, the support member 30 supports the edge of the vibration member 20.

  As shown in FIG. 1, the oscillation device 100 includes an elastic member 22. The elastic member 22 is provided on the edge of the vibration member 20. Further, the elastic member 22 is provided, for example, on the entire circumference of the vibration member 20. The elastic member 22 is made of, for example, a resin material such as urethane, PET, or polyethylene. The support member 30 supports the vibration member 20 via the elastic member 22.

The oscillation device 100 includes a substrate 32. The substrate 32 fixes the support member 30. The space 60 constitutes a closed space surrounded by the vibration member 20, the elastic member 22, the support member 30, and the substrate 32.
The other surface side of the vibration member 20 is open to the outside. At the time of output of the oscillation device 100, sound waves are output using the other surface of the vibration member 20 as an output surface.

  The holes 40 and the holes 42 provided in the support member 30 are formed in a tapered shape, for example. Moreover, the hole 40 and the hole 42 may be formed in, for example, a step shape. Furthermore, a plurality of holes 40 and holes 42 may be provided. In addition, although the shape of the opening end to the exterior of the void | hole 40 and the void | hole 42 is circular, for example, it is not restricted to this.

  The oscillation device 100 includes a piezoelectric vibrator 10. The oscillation device 100 outputs sound waves by vibrating the vibration member 20 in response to the expansion and contraction motion of the piezoelectric vibrator 10. As shown in FIG. 1, the piezoelectric vibrator 10 is provided on both surfaces of the vibration member 20, for example, and is restrained by the vibration member 20. The piezoelectric vibrator 10 may be provided only on one surface of the vibration member 20 or on the other surface opposite to the one surface.

  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 a piezoelectric body 70, an upper electrode 72, and a lower electrode 74. The piezoelectric body 70 is sandwiched between the upper electrode 72 and the lower electrode 74. The piezoelectric body 70 is polarized in the thickness direction (vertical direction in FIG. 2). The piezoelectric vibrator 10 has, for example, a circle or an ellipse in a plane direction parallel to one surface of the vibration member 20.

The piezoelectric body 70 is made of a material having a piezoelectric effect, for example, lead zirconate titanate (PZT) or barium titanate (BaTiO ₃ ) as a material having high electromechanical conversion efficiency. The thickness of the piezoelectric body 70 is preferably 10 μm to 1 mm. When the thickness is less than 10 μm, the piezoelectric body 70 is made of a brittle material, and thus is easily damaged during handling. On the other hand, when the thickness exceeds 1 mm, the electric field strength of the piezoelectric body 70 is reduced. For this reason, the energy conversion efficiency is reduced.

  The upper electrode 72 and the lower electrode 74 are made of a material having electrical conductivity, for example, silver or a silver / palladium alloy. Silver is a low-resistance general-purpose material and is advantageous from the viewpoint of manufacturing cost and manufacturing process. Further, the silver / palladium alloy is a low resistance material excellent in oxidation resistance and excellent in reliability. The thickness of the upper electrode 72 and the lower electrode 74 is preferably 1 to 50 μm. When the thickness is less than 1 μm, it becomes difficult to form the film uniformly. On the other hand, when the thickness exceeds 50 μm, the upper electrode 72 or the lower electrode 74 serves as a restraint surface with respect to the piezoelectric body 70 and causes a decrease in energy conversion efficiency.

  The oscillation device 100 includes a control unit 90 and a signal generation unit 92. The signal generator 92 is connected to the piezoelectric vibrator 10 and generates an electric signal input to the piezoelectric vibrator 10. The control unit 90 is connected to the signal generation unit 92 and controls signal generation by the signal generation unit 92. The control unit 90 controls the generation of the signal of the signal generation unit 92 based on information input from the outside, whereby the output of the oscillation device 100 can be controlled.

When the oscillation device 100 is used as a parametric speaker, the control unit 90 inputs a modulation signal as a parametric speaker via the signal generation unit 92. In this case, the piezoelectric vibrator 10 uses a sound wave of 20 kHz or more, for example, 100 kHz, as a signal transport wave.
When the oscillation device 100 is used as a normal speaker, the control unit 90 may input the audio signal as it is to the piezoelectric vibrator 10 via the signal generation unit 92.
When the oscillation device 100 is used as a sound wave sensor, the signal input to the control unit 90 is a command signal for oscillating sound waves. When the oscillation device 100 is used as a sound wave sensor, the signal generation unit 92 causes the piezoelectric vibrator 10 to generate a sound wave having a resonance frequency of the piezoelectric vibrator 10.

  The principle of operation of the parametric speaker is as follows. 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. The parametric speaker can form a sound field only around the user, and is excellent from the viewpoint of privacy protection.

Next, the effect of this embodiment will be described. When the space 60 is a closed space, when the vibration member 20 vibrates, the vibration member 20 receives a load of acoustic resistance due to the internal pressure generated in the space 60. In this case, the vibration amplitude of the vibration member 20 is reduced, and the sound pressure level of the oscillation device is attenuated. When the oscillation device 100 is mounted on a mobile terminal device, the space 60 that is the back space of the vibration member 20 becomes narrow, and this problem becomes particularly significant.
According to the present embodiment, the support member 30 provided so as to surround the space 60 is provided with the hole 40 and the hole 42. For this reason, when the vibration member 20 vibrates, the air in the space 60 can be discharged and discharged. Thereby, the internal pressure resistance by the space 60 can be suppressed. Therefore, the sound pressure level of the oscillation device can be improved.

FIG. 3 is a cross-sectional view showing an oscillation device 106 according to a comparative example. As shown in FIG. 3, in the oscillation device 106 according to the comparative example, the hole 48 provided in the support member 30 has a constant width from the space 60 toward the outside.
On the other hand, according to the present embodiment, the air holes 42 provided in the support member 30 are provided so as to become wider from the space 60 toward the outside. Further, the holes 40 provided in the support member 30 are provided so as to become narrower from the space 60 toward the outside. For this reason, as shown in FIG. 1, the air 50 filling the space 60 flows from the hole 42 to the hole 40 and is released from the hole 40. In this way, it is possible to form a circulation path that controls the flow of the air 50 and discharges and enters the air 50. Thereby, the internal pressure resistance from the air 50 filling the space 60 to the vibrating member 20 can be relaxed. Thus, the internal pressure resistance due to the space 60 can be suppressed. Therefore, the sound pressure level of the oscillation device can be improved.

  FIG. 4 is a graph illustrating acoustic characteristics of the oscillation devices according to the first embodiment and the comparative example. FIG. 4 shows the result of measuring the sound pressure level of the demodulated audible sound wave when the oscillation device according to this embodiment and the comparative example is used as a parametric speaker. As shown in FIG. 4, at around 1000 Hz, the oscillation device 100 according to this embodiment has a higher sound pressure level than the oscillation device 106 according to the comparative example. In other frequency bands, the sound pressure level of the oscillation device 100 is approximately the same as or higher than the sound pressure level of the oscillation device 106. Therefore, it can be seen that according to the present embodiment, the sound pressure level can be improved.

In addition, the sound wave output from one surface of the vibration member 20 and the sound wave output from the other surface opposite to the one surface are sound waves having opposite phases. For this reason, when they interfere with each other, the sound wave cancels, causing a decrease in the sound pressure level.
According to the present embodiment, the direction in which the sound wave 52 is emitted can be controlled by forming the circulation path of the air 50. That is, the sound wave 52 output from one surface of the vibration member 20 is radiated from the hole 40 in the same manner as the flow of the air 50. By controlling the radiation direction of the sound wave 52, it is possible to prevent the sound wave 52 output from one surface of the vibration member 20 from interfering with the sound wave output from the other surface opposite to the one surface. Therefore, the sound pressure level of the oscillation device can be improved.

  In the present embodiment, when the oscillation device 100 is used as a parametric speaker, the vibration member 20 outputs an ultrasonic wave of 20 kHz or more. Since the ultrasonic wave has high directivity, interference between the sound wave 52 output from one surface of the vibration member 20 and the sound wave output from the other surface is suppressed. In addition, since the ultrasonic wave has low translation, it is easy to form a radiation path of the sound wave 52. Furthermore, the shape of the hole 40 can be reduced.

  FIG. 5 is a sectional view showing the oscillation device 102 according to the second embodiment, and corresponds to the oscillation device 100 according to the first embodiment. The oscillation device 102 according to the present embodiment has the same configuration as that of the oscillation device 100 according to the first embodiment, except that the sound absorption member 34 is provided.

The sound absorbing member 34 is provided around the open end to the outside of the hole 40. The sound absorbing member 34 is made of, for example, urethane or a sound absorbing material such as glass wool, glass fiber, or aluminum. As shown in FIG. 5, the sound absorbing member 34 is, for example, the outer surface of the support member 30 that supports the vibration member 20 on the inner surface, and at least on the other surface side of the vibration member 20 from the opening end to the outside of the hole 40. Is provided.
In this case, the sound absorbing member 34 is preferable because the sound absorbing member 34 is closer to the open end to the outside of the hole 40 because it easily absorbs the sound wave 52 radiated from the hole 40.
Further, it is preferable that the width of the sound absorbing member 34 is larger than the width of the opening end in the tangential direction at the point closest to the other surface side of the vibration member 20 among the opening ends to the outside of the hole 40. In this case, it is possible to effectively suppress the sound wave 52 radiated from the hole 40 from interfering with the sound wave output from the other surface side of the vibration member 20.
The sound absorbing member 34 may be provided so as to surround the hole 40.

Also in this embodiment, the same effect as that of the first embodiment can be obtained. Further, since the sound absorbing member 34 is formed around the opening end to the outside of the hole 40, the sound wave 52 output from one surface of the vibration member 20 and the sound wave output from the other surface interfere with each other. Can be prevented. This effect is that the sound absorbing member 34 is provided on the outer surface of the support member 30 that supports the vibration member 20 on the inner surface, at least on the other surface side of the vibration member 20 with respect to the opening end to the outside of the hole 40. In some cases, this is particularly noticeable.
Further, according to the present embodiment, the sound wave 52 is emitted from the hole 40 and is not emitted from the hole 42. For this reason, the sound absorbing member 34 only needs to be provided around the opening end to the outside of the hole 40. Therefore, it can be easily manufactured.

  FIG. 6 is a cross-sectional view illustrating 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 has the same configuration as that of the oscillation device 100 according to the first embodiment, except that the shielding member 36 is provided.

  The shielding member 36 is fixed to the support member 30. The vibration member 20, the elastic member 22, the shielding member 36, and the support member 30 form a closed space on the other surface side of the vibration member 20. The shielding member 36 is provided with a plurality of holes 46 for emitting sound waves output from the other surface side.

  Also in this embodiment, the same effect as that of the first embodiment can be obtained. In addition, the sound wave output from the other surface of the vibration member 20 is radiated from the hole 46 provided in the shielding member 36. For this reason, the radiation direction of the sound wave output from the other surface of the vibration member 20 can be controlled. Accordingly, the sound wave 52 output from one surface of the vibration member 20 and the sound wave output from the other surface can be prevented from interfering with each other.

  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 Elastic member 30 Support member 32 Substrate 34 Sound absorbing member 36 Shielding member 40 Hole 42 Hole 46 Hole 48 Hole 50 Air 52 Sound wave 60 Space 62 Space 70 Piezoelectric body 72 Upper electrode 74 Lower electrode 90 Control Unit 92 Signal Generation Unit 100 Oscillator 102 Oscillator 104 Oscillator 106 Oscillator

Claims (8)

A vibrating member;
A support member that supports the vibration member and is provided so as to surround a space on one surface side of the vibration member;
With
The support member has a first hole that widens outward from the space and a second hole that narrows outward from the space in a portion facing the space,
The oscillation device, wherein the space is open to the outside of the space through the first hole and the second hole. The oscillation device according to claim 1,
A substrate for fixing the support member;
The oscillation device that constitutes a closed space surrounded by the vibration member, the support member, and the substrate. The oscillation device according to claim 1 or 2,
An oscillation device comprising a piezoelectric vibrator restrained by the vibration member. The oscillation device according to any one of claims 1 to 3,
The oscillation device in which the first hole and the second hole are formed in a tapered shape. The oscillation device according to any one of claims 1 to 4,
An oscillation device further comprising a sound absorbing member provided around an opening end of the second hole to the outside. The oscillation device according to claim 5,
The vibrating member outputs a first sound wave from the one surface and a second sound wave from the other surface opposite to the one surface,
The sound absorbing member is an outer surface of the support member that supports the vibration member on an inner surface thereof, and is provided at least on the other surface side of the vibration member with respect to the outside opening end of the second hole. apparatus. The oscillation device according to any one of claims 1 to 6,
An elastic member provided on an edge of the vibration member;
The support member is an oscillation device that supports the vibration member via the elastic member.   A portable terminal device on which the oscillation device according to claim 1 is mounted.

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