JP2012015756A - Electronic apparatus and oscillation unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic apparatus that can prevent uncomfortable vibration and noise from being generated in a main body housing.SOLUTION: In the electronic apparatus, a unit frame 231 is mounted by a damping material 232 onto a unit mounting part 111 in a main body housing 110, so even when a piezoelectric vibrator 210 is driven and vibration occurs to the unit frame 231 along with an elastic vibration plate 220, uncomfortable vibration and noise can be prevented from being generated in the main body housing 110.

Description

  The present invention relates to an electronic device that outputs sound, such as a mobile phone terminal, and more particularly to an electronic device that outputs sound with an oscillation unit, and the oscillation unit.

  In recent years, demand for portable electronic devices such as mobile phones and notebook computers has been increasing. In such an electronic device, development of a thin portable terminal whose commercial value is an acoustic function such as a videophone, a video playback, and a hands-free phone is being promoted. Under such development, there is an increasing demand for high-quality sound, small size, and thinness for electroacoustic transducers (speaker devices) that are acoustic components.

  Conventionally, electrodynamic electroacoustic transducers have been used as electroacoustic transducers in electronic devices such as mobile phones. This electrodynamic electroacoustic transducer is composed of a permanent magnet, a voice coil, and a diaphragm.

  However, there is a limit to reducing the thickness of electrodynamic electroacoustic transducers due to their operating principles and structures. On the other hand, Patent Documents 1 and 2 describe using a piezoelectric vibrator as an electroacoustic transducer.

  As another example of an oscillation device using a piezoelectric vibrator, in addition to a speaker device, a sound wave sensor that detects a distance to an object using a sound wave oscillated from the piezoelectric vibrator (see Patent Document 3). Various oscillators and electronic devices are known.

  Furthermore, there is also a proposal of an electronic device in which a vibration member equipped with a piezoelectric vibrator is mounted on a main body housing with a damping material (Patent Document 4).

No. 2007-026736 Table 2007-083497 Japanese Patent Laid-Open No. 03-270282 JP 2005-223410 A

  An oscillating device using a piezoelectric vibrator generates a vibration amplitude by an electrostrictive action by inputting an electric signal by using a piezoelectric effect of a piezoelectric layer. The electrodynamic electroacoustic transducer generates vibration by a piston-type forward / backward movement, whereas the oscillation device using the piezoelectric vibrator has a bending-type vibration state and thus has a small amplitude. For this reason, it is superior in reducing the thickness of the electrodynamic electroacoustic transducer described above.

  However, since the main body housing of a mobile phone or the like is small and made of a thin plate, if the oscillation device is directly fixed inside, the main body housing vibrates due to the vibration of the oscillation device, and unpleasant noise and vibration are generated. Become.

  The present invention has been made in view of the above-described problems, and provides an electronic device and its oscillation unit that can prevent unpleasant vibration and noise of the main body housing with a simple structure. .

  An electronic device according to the present invention includes a main body housing having a flat unit mounting portion, a piezoelectric vibrator having electrode layers formed on the front and back surfaces of the piezoelectric layer, and a piezoelectric vibrator having elasticity. The mounted vibration member, a unit frame that supports the vibration member, an oscillation drive unit that drives the piezoelectric vibrator to oscillate the vibration member, and the unit frame with the vibration member facing the inner surface of the unit mounting unit And a damping material that couples the main body housing to damp vibrations.

  An oscillation unit according to the present invention is an oscillation unit for an electronic device according to the present invention, and includes a piezoelectric vibrator in which an electrode layer is formed on a front surface and a back surface of a piezoelectric layer, and a piezoelectric vibrator having elasticity. A vibration member that is mounted; a unit frame that supports the vibration member; and a damping material that attenuates vibration by connecting the unit frame and the main body housing with the vibration member facing the inner surface of the unit mounting portion. Have.

  In the oscillation device of the present invention, since the unit frame is mounted on the unit mounting portion of the main body housing with the damping material, even if the unit frame vibrates together with the vibration member by driving the piezoelectric vibrator, it is uncomfortable for the main body housing. Generation of vibration and noise can be suppressed.

1 is a schematic longitudinal sectional front view showing a structure of a main part of a mobile phone which is an electronic apparatus according to an embodiment of the present invention. It is a typical top view which shows the external appearance of a mobile telephone. It is a typical vertical front view which shows the structure of the principal part of the mobile telephone of one modification. It is a typical vertical front view which shows the structure of the principal part of the mobile phone of another modification.

  A first embodiment of the present invention will be described below with reference to FIG. 1 and FIG. As shown in FIG. 1, a mobile phone 1000 that is an electronic device of the present embodiment includes a body housing 110 having a flat unit mounting portion 111 and electrode layers on the front and back surfaces of a piezoelectric ceramic 211 that is a piezoelectric layer. 212, 213 formed piezoelectric vibrator 210, elastic vibration plate 220 that is elastic and mounted with piezoelectric vibrator 210, and unit frame 231 that supports elastic vibration plate 220 The unit frame 231 and the main body housing 110 in a state where the elastic vibration plate 220 faces the inner surface of the unit mounting portion 111 and the control unit 240 that is an oscillation driving unit that drives the piezoelectric vibrator 210 to oscillate. And a damping material 232 for damping the vibration.

  More specifically, in the cellular phone 1000 according to the present embodiment, the electroacoustic transducer 200 that is an oscillation unit includes the piezoelectric vibrator 210, the elastic diaphragm 220, the unit frame 231, and the damping material 232 described above. Is formed.

  The electroacoustic transducer 200 is driven by the control unit 240 and outputs audible sound waves. For this reason, a plurality of sound holes 112 are passed through the unit mounting portion 111 of the main body housing 110.

  The damping material 232 is made of, for example, a resin having a higher elastic modulus and a larger internal loss than the main body housing 110 and the unit frame 231.

  The vibration damping material 232 is mounted on the inner surface of the unit mounting portion 111 via a rigid plate 233 having higher rigidity than the main body housing 110, and the vibration damping material 232 is mounted via a rigid plate 234 having higher rigidity than the unit frame 231. The unit frame 231 is attached.

  The main body housing 110 and the unit frame 231 are made of resin, and the rigid plates 233 and 234 are made of metal. The controller 240 drives the piezoelectric vibrator 210 to output audible sound waves.

  The piezoelectric ceramic 211 is not particularly limited, although lead zirconate titanate (PZT) or the like is used. The thickness of the piezoelectric ceramic 211 is not particularly limited, but is preferably 10 μm or more and 500 μm or less.

  For example, when a thin film having a thickness of less than 10 μm is used as a ceramic material that is a brittle material, chipping or breakage occurs due to weak mechanical strength during handling, making handling difficult.

  In addition, when the piezoelectric ceramic 211 having a thickness exceeding 500 μm is used, the conversion efficiency for converting electrical energy into mechanical energy is remarkably lowered, and sufficient performance as the electroacoustic transducer 200 cannot be obtained.

  In general, in the piezoelectric ceramic 211 that generates an electrostrictive effect by inputting an electric signal, the conversion efficiency depends on the electric field strength. Since the electric field strength is expressed by the thickness / input voltage with respect to the polarization direction, an increase in thickness inevitably causes a decrease in conversion efficiency.

  In the piezoelectric vibrator 210 of the present embodiment, electrode layers 212 and 213 are formed on the front surface and the back surface in order to generate an electric field. The electrode layers 212 and 213 are not particularly limited as long as they are electrically conductive materials, but it is preferable to use silver or silver / palladium. Silver is used as a general-purpose electrode layer with low resistance, and has advantages in manufacturing process and cost.

  Further, since silver / palladium is a low-resistance material excellent in oxidation resistance, there is an advantage from the viewpoint of reliability. The thickness of the electrode layers 212 and 213 is not particularly limited, but the thickness is preferably 1 μm or more and 50 μm or less.

  For example, when the thickness is less than 1 μm, since the film thickness is thin, it cannot be uniformly formed, and conversion efficiency may be reduced. As a technique for forming the thin-film electrode layers 212 and 213, there is a method of applying the paste in a paste form.

  However, since the surface state of the polycrystal such as the piezoelectric ceramic 211 is a textured surface, the wet state at the time of application is poor, and there is a problem that a uniform electrode film cannot be formed without a certain thickness.

  On the other hand, when the film thickness of the electrode layers 212 and 213 exceeds 100 μm, there is no particular problem in manufacturing, but the electrode layers 212 and 213 serve as a constraining surface with respect to the piezoelectric ceramic 211 and reduce the energy conversion efficiency. There is a problem.

  The elastic diaphragm 220 resonates due to vibration generated from the piezoelectric vibrator 210. At the same time, the elastic diaphragm 220 has a function of adjusting the basic resonance frequency of the piezoelectric vibrator 210. The fundamental resonance frequency f of the mechanical electroacoustic transducer 200 depends on the load weight and compliance, as shown by the following equation.

[Equation 1]
f = 1 / (2πL√ (mC))
“M” is mass and “C” is compliance.

  In other words, since the compliance is the mechanical rigidity of the electroacoustic transducer 200, this means that the fundamental resonance frequency can be controlled by controlling the rigidity of the piezoelectric vibrator 210.

  For example, the fundamental resonance frequency can be shifted to a low range by selecting a material with a high elastic modulus or reducing the thickness of the elastic diaphragm 220. On the other hand, the fundamental resonance frequency can be shifted to a high range by selecting a material having a high elastic modulus or increasing the thickness of the elastic diaphragm 220.

  The elastic diaphragm 220 is not particularly limited as long as it is a material having a high elastic modulus with respect to a ceramic that is a brittle material such as a metal or a resin, but a general-purpose material such as phosphor bronze or stainless steel from the viewpoint of workability and cost. Is used.

  The thickness of the elastic diaphragm 220 is preferably 5 μm or more and 1000 μm or less. When the thickness is less than 5 μm, there is a problem that mechanical strength is weak, the function as a restraining member is impaired, and the mechanical vibration characteristics of the piezoelectric vibrator 210 are varied between manufacturing lots due to a reduction in processing accuracy.

  In addition, when the thickness exceeds 1000 μm, there is a problem that the restraint on the piezoelectric vibrator 210 due to the increase in rigidity is strengthened, and the vibration displacement amount is attenuated. The elastic diaphragm 220 of the present embodiment preferably has a longitudinal elastic modulus, which is an index indicating the rigidity of the material, of 1 GPa or more and 500 GPa or less. As described above, when the rigidity of the elastic diaphragm 220 is excessively low or excessively high, there is a problem that characteristics and reliability are impaired as a mechanical vibrator.

  Here, the manufacturing method of the electroacoustic transducer 200 of this Embodiment is demonstrated below. First, in the piezoelectric vibrator 210, for example, a piezoelectric ceramic 211 having an outer diameter = φ3 mm and a thickness = 200 μm is formed, and electrode layers 212 and 213 having a thickness of 8 μm are formed on both surfaces of the piezoelectric ceramic 211, respectively.

  For the piezoelectric ceramic 211, a lead zirconate titanate ceramic is used, and for the electrode layers 212 and 213, a silver / palladium alloy (weight ratio 70%: 30%) is used. The piezoelectric ceramic 211 is manufactured by a green sheet method, fired in the atmosphere at 1100 ° C. for 2 hours, and then the piezoelectric ceramic 211 is subjected to polarization treatment. An epoxy adhesive is used for bonding the piezoelectric vibrator 210 and the elastic diaphragm 220.

  Further, in this configuration, ultrasonic waves are oscillated in order to realize sound reproduction that can protect privacy. Here, the principle of a parametric speaker that demodulates modulated ultrasonic waves into audible sounds is used. The piezoelectric vibrator 210 oscillates an ultrasonic wave having a frequency of 20 kHz or more.

  Here, AM (Amplitude Modulation) modulation, DSB (Double Sideband) modulation, SSB (Single-Sideband modulation) modulation, FM (Frequency Modulation) modulated ultrasonic waves are emitted into the air, and the ultrasonic waves enter the air. Sound reproduction is performed on the principle that audible sound appears due to nonlinear characteristics when propagating.

  Non-linearity includes a phenomenon in which the flow changes from laminar flow to turbulent flow when the Reynolds number indicated by the ratio between 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 in a non-linear manner.

  However, the amplitude of the sound wave in the low frequency band is nonlinear, but the amplitude difference is very small, and is usually handled as a phenomenon of linear theory. On the other hand, nonlinearity can be easily observed with ultrasonic waves, and when radiated into the air, harmonics accompanying the nonlinearity are remarkably generated.

  In summary, sound waves are a dense state where molecular groups are mixed in the air, and if it takes time for the air molecules to recover rather than compress, the air that cannot be recovered after compression is continuously propagated air. This is the principle that an audible sound is generated by colliding with a molecule and generating a shock wave.

  Next, the operation principle of the piezoelectric vibrator 210 will be described. The piezoelectric ceramic 211 is made of a piezoelectric plate having two main surfaces as described above, and electrode layers 212 and 213 are formed on each of the main surfaces of the piezoelectric ceramic 211.

  Although the polarization direction of the piezoelectric ceramic 211 is not particularly limited, in the electroacoustic transducer 200 according to the present embodiment, it is upward in the vertical direction (thickness direction of the piezoelectric vibrator 210).

  The piezoelectric vibrator 210 configured in this way has a radial direction in which both main surfaces simultaneously expand or contract when an alternating voltage is applied to the electrode layers 212 and 213 and an alternating electric field is applied. Perform telescopic motion (diameter expansion motion).

  In other words, the piezoelectric vibrator 210 performs a motion that repeats a first deformation mode in which the main surface expands and a second deformation mode in which the main surface contracts. When the piezoelectric vibrator 210 repeats such a motion, the elastic diaphragm 220 uses the elastic effect to generate vertical vibrations due to the inertial action and the restoring action, thereby generating sound waves.

  In the configuration of the present invention, the piezoelectric vibrator 210 oscillates an ultrasonic wave having a frequency of 20 kHz or more. Sound reproduction is performed based on the principle of a so-called parametric speaker that oscillates FM or AM-modulated ultrasonic waves and demodulates the modulated wave to reproduce audible sound using the nonlinear state (dense / dense state) of air. This is to propagate sound waves using the high directivity that is a feature of ultrasonic waves, and it is possible to realize a privacy sound source that can be heard only by the user of the mobile phone 1000.

  As described above, the electroacoustic transducer 200 of the present embodiment is small and can reproduce a large volume. Further, since ultrasonic waves are used, directivity is narrow, and industrial value is great in terms of protecting user privacy.

  That is, the electroacoustic transducer 200 according to the present embodiment has higher rectilinearity of the sound wave than the conventional electroacoustic transducer, and can selectively propagate the sound wave to a position to be transmitted to the user. In summary, the electroacoustic transducer 200 according to the present embodiment can be used as a sound source of an electronic device (for example, a mobile phone, a notebook personal computer, a small game device, etc.). In addition, since the electroacoustic transducer 200 can be prevented from being enlarged and the acoustic characteristics are improved, it can be suitably used for portable electronic devices.

  Nevertheless, in the cellular phone 1000 according to the present embodiment, the unit frame 231 is mounted on the unit mounting portion 111 of the main body housing 110 with the damping material 232. For this reason, even if the piezoelectric vibrator 210 is driven and the unit frame 231 vibrates together with the elastic diaphragm 220, it is possible to suppress generation of unpleasant vibration, noise, and the like in the main body housing 110.

  In addition, since the damping material 232 has a higher elastic modulus and a larger internal loss than the main body housing 110 and the unit frame 231, the vibration conducted from the elastic diaphragm 220 can be satisfactorily suppressed.

  Further, a damping material 232 is mounted on the resin main body housing 110 and the unit frame 231 via rigid plates 233 and 234 made of metal and having high rigidity. For this reason, even if the main body housing 110 and the unit frame 231 are formed of fragile resin, the vibration damping material 232 can satisfactorily suppress vibration.

  The present invention is not limited to the present embodiment, and various modifications are allowed without departing from the scope of the present invention. For example, in the present embodiment, the piezoelectric ceramic 211 such as lead zirconate titanate (PZT) is used as the piezoelectric element of the piezoelectric vibrator 210.

  However, the piezoelectric element is not particularly limited as long as it has a piezoelectric effect, and a material having high electromechanical conversion efficiency, for example, a material such as barium titanate (BaTiO 3) can be used.

  Moreover, in the said form, the damping material 232 was attached to the main body housing 110 and the unit frame 231 via the rigid plates 233 and 234 made of metal and having high rigidity.

  However, the damping material 232 may be directly attached to the main body housing 110 and the unit frame 231 without using the metal-made high-rigidity rigid plates 233 and 234 (not shown).

  Further, the vibration direction of the unit frame 231 may be restricted by the direction restricting mechanism 310 in the direction of coming into contact with and separating from the unit mounting portion 111 as in the electroacoustic transducer 300 illustrated as an oscillation unit in FIG.

  Such a direction regulating mechanism 310 is composed of a guide member that is fixed to one side surface of the rigid plates 233 and 234 and slides on the other side surface. In this case, displacement of the unit frame 231 in the horizontal direction in the figure is suppressed by the direction restricting mechanism 310, so that it is possible to satisfactorily prevent the body housing 110 from generating unpleasant vibration and noise.

  Further, a direction regulating mechanism 410 that regulates the vibration direction of the unit frame 231 may be joined to the back surface of the main body housing 110 as in the electroacoustic transducer 400 illustrated as an oscillation unit in FIG.

  In this case, the direction regulation mechanism 410 may be joined only to the back surface of the main body housing 110, or may be fixed to both the back surface of the main body housing 110 and the side surface of the upper rigid plate 233 in the drawing.

  Moreover, in the said form, the mobile telephone 1000 which outputs an audio | voice with the electroacoustic transducer 200 grade | etc., Was assumed as an electric equipment. However, as an electronic device, an electroacoustic transducer 200 or the like that is an oscillation device, an ultrasonic detection unit that detects an ultrasonic wave that is oscillated from the electroacoustic transducer 200 or the like and reflected by an object to be measured, and a detected ultrasonic wave A sonar (not shown) having a distance measuring unit that calculates the distance from the sound wave to the measurement object can also be implemented.

  Needless to say, the above-described plurality of embodiments and the plurality of modifications can be combined within a range in which the contents do not conflict with each other. In the above-described embodiment, the structure of each part has been specifically described. However, the structure and the like can be variously changed within a range that satisfies the present invention.

110 Main body housing 111 Unit mounting portion 112 Sound hole 200 Electroacoustic transducer 210 Piezoelectric vibrator 211 Piezoelectric ceramic 212, 213 Electrode layer 220 Elastic vibration plate 231 Unit frame 232 Damping material 233 Rigid plate 234 Rigid plate 240 Control unit 300 Electroacoustic Converter 310 Direction restriction mechanism 1000 Mobile phone

Claims (10)

A main body housing having a flat unit mounting portion;
A piezoelectric vibrator having electrode layers formed on the front and back surfaces of the piezoelectric layer;
A vibration member having elasticity and mounted with the piezoelectric vibrator;
A unit frame for supporting the vibrating member;
An oscillation drive unit for driving the piezoelectric vibrator to oscillate the vibration member;
A damping material that damps vibration by connecting the unit frame and the main body housing in a state where the vibration member faces the inner surface of the unit mounting portion;
Electronic equipment having   The electronic device according to claim 1, wherein the damping material has a higher elastic modulus and a larger internal loss than the main body housing and the unit frame.   The electronic device according to claim 1, wherein the damping material is mounted on an inner surface of the unit mounting portion via a rigid plate that is higher in rigidity than the main body housing. The body housing is formed of resin;
The electronic device according to claim 3, wherein the rigid plate is made of metal.   5. The electronic device according to claim 1, wherein the damping material is attached to the unit frame via a rigid plate having rigidity higher than that of the unit frame. The unit frame is formed of resin;
The electronic device according to claim 5, wherein the rigid plate is made of metal.   The electronic device according to claim 1, further comprising a direction regulating mechanism that regulates a vibration direction of the unit frame in a direction in which the unit frame is in contact with and separated from the unit mounting portion.   The electronic apparatus according to claim 1, further comprising an oscillation drive unit that drives the piezoelectric vibrator to output an audible sound wave to the vibration member. An oscillation drive unit that drives the piezoelectric vibrator to output ultrasonic waves to the vibration member;
An ultrasonic detector for detecting the ultrasonic wave oscillated from the oscillation device and reflected by the measurement object;
A distance measuring unit for calculating a distance from the detected ultrasonic wave to the measurement object;
The electronic device according to claim 1, comprising: An oscillation unit for an electronic device according to any one of claims 1 to 9,
A piezoelectric vibrator having electrode layers formed on the front and back surfaces of the piezoelectric layer;
A vibration member having elasticity and mounted with the piezoelectric vibrator;
A unit frame for supporting the vibrating member;
A damping material that damps vibration by connecting the unit frame and the main body housing in a state where the vibration member faces the inner surface of the unit mounting portion;
An oscillation unit having

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