Patent Publication Number: US-2013243224-A1

Title: Oscillation device and portable device

Description:
TECHNICAL FIELD 
     The present invention relates to an oscillation device used as a speaker, and to a portable device. 
     BACKGROUND ART 
     In recent years, demand for portable terminals such as a cellular phone or a lap-top computer has grown. Particularly, thin portable terminals having sound functions, such as a video phone, a movie player, and a hands-free phone function, as commodity values have been developed. During the development thereof, the requirement for a small-sized and high-output electro-acoustic transducer has increased. In electronic devices such as a cellular phone, an electro-dynamic electro-acoustic transducer has been used as an electro-acoustic transducer. The electro-dynamic electro-acoustic transducer is composed of a permanent magnet, a voice coil, and a vibrating membrane. However, the electro-dynamic electro-acoustic transducer has a limitation in a reduction of thickness thereof due to the operation principle and the structure thereof. Consequently, it is expected to use a piezoelectric vibrator as a parametric speaker. 
     On the other hand, Patent Documents 1, 2, and 3 disclose that a parametric speaker and an electro-dynamic speaker are used in the same acoustic device. 
     RELATED DOCUMENT 
     Patent Documents 
     [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2002-027586 
     [Patent Document 2] Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2004-527968 
     [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2009-010619 
     DISCLOSURE OF THE INVENTION 
     A conductivity-type speaker is thicker than a parametric speaker. For this reason, when an electro-dynamic speaker and a parametric speaker are mounted onto one electronic device, the thickness of an electronic device is determined by the thickness of a conductivity-type speaker. Therefore, when the conductivity-type speaker is used, there is a limitation in a reduction of the thickness of the electronic device. On the other hand, it is essential for a portable device to reduce the thickness thereof in order to improve portability. 
     An object of the present invention is to provide an oscillation device and a portable device that include both a speaker reproducing an audible sound as it is and a parametric speaker, and are capable of a reduction in thickness. 
     According to the invention, there is provided an oscillation device including: a first oscillator including a first piezoelectric vibrator; a second oscillator including a second piezoelectric vibrator; and a control unit that inputs an audio signal of an audible sound to the first oscillator, and inputs a modulation signal of a parametric speaker to the second oscillator. 
     According to the invention, there is provided a portable device including: a first oscillator including a first piezoelectric vibrator; a second oscillator including a second piezoelectric vibrator; and a control unit that inputs an audio signal of an audible sound to the first oscillator, and inputs a modulation signal of a parametric speaker to the second oscillator. 
     According to the invention, it is possible to achieve a reduction in thickness in an oscillation device including both a speaker reproducing an audible sound as it is and a parametric speaker. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned objects, other objects, features and advantages will be made clearer from the preferred embodiments described below, and the following accompanying drawings. 
         FIG. 1  is a diagram illustrating a configuration of an oscillation device according to a first embodiment. 
         FIG. 2  is a plan view illustrating a configuration of a portable device having the oscillation device shown in  FIG. 1 . 
         FIG. 3  is a plan view illustrating a layout of a second oscillation device. 
         FIG. 4  is a cross-sectional view illustrating a configuration of a piezoelectric vibrator in the thickness direction. 
         FIG. 5  is an exploded perspective view illustrating a configuration of a piezoelectric vibrator of an oscillation device according to a second embodiment. 
         FIG. 6  is a diagram illustrating a configuration of an oscillation device according to a third embodiment. 
         FIG. 7  is a diagram illustrating a configuration of an oscillation device according to a fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the embodiments of the invention will be described with reference to the accompanying drawings. In all the drawings, like elements are referenced by like reference numerals and descriptions thereof will not be repeated. 
     First Embodiment 
       FIG. 1  is a diagram illustrating a configuration of an oscillation device according to a first embodiment.  FIG. 2  is a plan view illustrating a configuration of a portable device  300  having the oscillation device shown in  FIG. 1 . The portable device  300  is, for example, a portable communication terminal or a portable game console. The oscillation device shown in  FIG. 1  includes a first oscillator  120 , a second oscillator  112 , and a control unit  50 . The first oscillator  120  includes a first piezoelectric vibrator, and the second oscillator  112  includes a second piezoelectric vibrator. The control unit  50  inputs an audio signal of an audible sound to the first piezoelectric vibrator included in the first oscillator  120 , and inputs a modulation signal of a parametric speaker to the second piezoelectric vibrator of the second oscillator  112 . 
     The oscillation device shown in  FIG. 1  is used as an audio output source of the portable device  300 , for example, as shown in  FIG. 2 . The first oscillator  120  functions as a speaker that outputs an audible sound, and the second oscillator  112  functions as a parametric speaker  110 . The portable device  300  is, for example, a portable communication terminal or a portable acoustic device, and includes a display screen  200 . The first oscillator  120  and the parametric speaker  110  are disposed laterally to the display screen  200 . Specifically, on a housing of the portable device  300 , the first oscillator  120  and the parametric speaker  110  are disposed on the surface on which the display screen is provided, and are located between the display screen and the lateral side of the housing. Since this area of the housing of the portable device  300  is narrow, the planar shapes of the first oscillator  120  and the parametric speaker  110  are rectangular. The long sides of the first oscillator  120  and parametric speaker  110  are directed toward a direction along the edge of the housing of the portable device  300 . Meanwhile, the layout of the parametric speaker  110  and the first oscillator  120  is not limited to the example shown in  FIG. 2 . 
     As shown in  FIG. 1 , the parametric speaker  110  includes a plurality of second oscillators  112 . In the example shown in this drawing, both the second oscillator  112  and the parametric speaker  110  include a vibration member  10 , a piezoelectric vibrator  20 , and a supporting member  40 . 
     The piezoelectric vibrator  20  is formed of materials showing a piezoelectric effect, for example, piezoelectric ceramics. The piezoelectric vibrator  20  included in the first oscillator  120  and the piezoelectric vibrator  20  included in the parametric speaker  110  are different from each other in size. Specifically, the piezoelectric vibrator  20  included in the second oscillator  112  is smaller than the piezoelectric vibrator  20  included in the first oscillator  120 . This is because the second oscillator  112  oscillates an ultrasonic wave, whereas the first oscillator  120  oscillates an audible sound of which wavelength is longer than that of the ultrasonic wave. 
     The vibration member  10  is vibrated by a vibration generated from the piezoelectric vibrator  20 . In addition, the vibration member  10  adjusts the fundamental resonance frequency of the piezoelectric vibrator  20 . The fundamental resonance frequency of a mechanical vibrator depends on load weight and compliance. Since the compliance is a mechanical rigidity of a vibrator, the fundamental resonance frequency of the piezoelectric vibrator  20  can be controlled by controlling the rigidity of the vibration member  10 . Meanwhile, it is preferable that the thickness of the vibration member  10  is equal to or more than 5 μm, and is equal to or less than 500 μm. In addition, it is preferable that the longitudinal elasticity modulus of the vibration member  10 , which is an index of rigidity, is equal to or more than 1 GPa, and is equal to or less than 500 GPa. When the rigidity of the vibration member  10  is excessively low or excessively high, it is possible that the characteristics and reliability thereof as a mechanical vibrator are damaged. Meanwhile, the material constituting the vibration member  10  is not particularly limited insofar as it is a material, such as metal or resin, having a higher elastic modulus with respect to the piezoelectric vibrator  20  which is formed of a brittle material, but phosphor bronze, stainless steel or the like are preferable from the viewpoint of workability or costs. 
     The piezoelectric vibrator  20  is configured such that the entire surface thereof facing the vibration member  10  is fixed to the vibration member  10  by an adhesive. Thereby, the entire surface of the piezoelectric vibrator  20  is constrained by the vibration member  10 . 
     In addition, the oscillation device includes a control unit  50  and a signal generation unit  52  as an oscillation circuit. The signal generation unit  52  generates an electrical signal, e.g. a modulation signal in the parametric speaker, which is input to the piezoelectric vibrator  20  of the second oscillator  112 . A modulation signal transportation wave is an ultrasonic wave having a frequency of equal to or more than 20 kHz, for example, an ultrasonic wave of 100 kHz. In addition, the signal generation unit  52  generates an audio signal of an audible sound and inputs the signal to the first oscillator  120 . The control unit  50  controls the signal generation unit  52  on the basis of audio information which is input from the outside. 
       FIG. 3  is a plan view illustrating a layout of the second oscillator  112  included in the parametric speaker  110 . In the example shown in this drawing, the supporting member  40  has a lattice shape, and has a plurality of openings which are disposed in an array form. The vibration member  10  and the piezoelectric vibrator  20  constituting the second oscillator  112  are fitted into each of the plurality of openings included in the supporting member  40 . The control unit  50  shown in  FIG. 1  controls the directivity of the parametric speaker using a phased array method. Specifically, the control unit  50  controls space in which the demodulation of the parametric speaker is performed by regulating a modulation signal which is input to each of the plurality of second oscillators  112 . Meanwhile, in the example shown in  FIG. 3 , the planar shapes of the vibration member  10  and the piezoelectric vibrator  20  are right-angled tetragonal, for example, rectangular. However, the planar shapes of the vibration members  10  and  20  are not limited thereto. 
       FIG. 4  is a cross-sectional view illustrating a configuration of the piezoelectric vibrator  20  in the thickness direction. The piezoelectric vibrator  20  includes a piezoelectric substance  22 , an upper electrode  24 , and a lower electrode  26 . 
     The piezoelectric substance  22  is polarized in the thickness direction. The material constituting the piezoelectric substance  22  may be any of an inorganic material and an organic material insofar as it is a material having a piezoelectric effect. However, the material having high electro-mechanical conversion efficiency, e.g. piezoelectric zirconate titanate (PZT) or barium titanate (BaTiO 3 ), is preferable. The thickness h 1  of the piezoelectric substance  22  is equal to or more than 10 μm, and is equal to or less than 1 mm, for example. When the thickness h 1  is less than 10 μm, the piezoelectric vibrator  20  could be damaged during the manufacturing of the oscillation device. In addition, when the thickness h 1  exceeds 1 mm, the electro-mechanical conversion efficiency is excessively lowered, and thus a sufficiently large vibration cannot be obtained. The reason is that when the thickness of the piezoelectric vibrator  20  increases, the electric field intensity within the piezoelectric vibrator is inversely proportional thereto and thus decreases. 
     Although the materials constituting the upper electrode  24  and the lower electrode  26  are not particularly limited, for example, silver or silver/palladium can be used. Since silver is used as a versatile electrode material with low-resistance, there is an advantage in a manufacturing process or cost and the like. Since silver/palladium is a low-resistance material excellent in oxidation resistance, there is an advantage from the viewpoint of reliability. In addition, the thickness h 2  of the upper electrode  24  and the lower electrode  26  is not particularly limited, but it is preferable that the thickness h 2  is equal to or more than 1 μm, and is equal to or less than 100 μm. When the thickness h 2  is less than 1 μm, it is difficult to uniformly form the upper electrode  24  and the lower electrode  26 . As a result, the electro-mechanical conversion efficiency could decrease. In addition, when the film thicknesses of the upper electrode  24  and the lower electrode  26  exceed 100 μm, the upper electrode  24  and the lower electrode  26  serve as constraint surfaces with respect to the piezoelectric substance  22 , and thus the energy conversion efficiency could be caused to decrease. 
     Next, the operations and effects of the embodiment will be described. According to the embodiment, the oscillation device includes the parametric speaker  110  and the first oscillator  120 . The first oscillator  120  is a speaker that outputs an audible sound as it is. Both the parametric speaker  110  and the first oscillator  120  output an audio through the vibration of the piezoelectric vibrator  20 . For this reason, since an electro-dynamic speaker is not required to be used, it is possible to reduce the thickness of the oscillation device. Therefore, since the thickness of the portable device  300  can be reduced, the portability of the portable device  300  is also improved. 
     In addition, since the parametric speaker  110  and the first oscillator  120  can be controlled using the same control unit  50  and signal generation unit  52 , it is possible to simplify a control circuit system of the oscillation device. 
     Second Embodiment 
       FIG. 5  is an exploded perspective view illustrating a configuration of the piezoelectric vibrator  20  of an oscillation device according to a second embodiment. The oscillation device according to the embodiment has the same configuration as that of the oscillation device according to the first embodiment, except that the piezoelectric vibrator  20  has a structure in which a plurality of piezoelectric substances  22  and electrodes  24  are alternately laminated. The polarization directions of the piezoelectric substances  22  are switched for each layer, and are alternating with each other. 
     In the embodiment, the same effect as that of the first embodiment can also be obtained. In addition, since the piezoelectric vibrator  20  has a structure in which a plurality of piezoelectric substances  22  and electrodes  24  are alternately laminated, the amount of expansion and contraction of the piezoelectric vibrator  20  increases. Therefore, it is possible to increase an output of the oscillation device. 
     Third Embodiment 
       FIG. 6  is a diagram illustrating a configuration of an oscillation device according to a third embodiment, and corresponds to  FIG. 1  in the first embodiment. The oscillation device according to the embodiment is the same as that of the first embodiment except for the following points. 
     First, the control unit  50  can output an ultrasonic wave for an ultrasonic wave sensor from the second oscillator  112  of the parametric speaker  110 , on the basis of an input of a user of the portable device  300 . The oscillation device includes a detection unit  54 . The detection unit  54  detects an ultrasonic wave having the same frequency as that of the ultrasonic wave for an ultrasonic wave sensor which is output from the second oscillator  112 . The control unit  50  detects an object, e.g. an obstacle located in the vicinity of the portable device  300 , on the basis of the intensity of the ultrasonic wave detected by the detection unit  54 , or on the basis of the time between when a billing information storage unit  112  oscillates an ultrasonic wave and when the detection unit  54  detects the ultrasonic wave, and calculates a distance from the portable device  300  to the object. 
     In the embodiment, the same effect as that of the first embodiment can also be obtained. In addition, it is possible to add a sensor function to the portable device  300  by merely adding the detection unit  54 . 
     Fourth Embodiment 
       FIG. 7  is a diagram illustrating a configuration of an oscillation device according to a fourth embodiment, and corresponds to  FIG. 3  in the first embodiment. The oscillation device according to the embodiment is the same as that of the first embodiment, except that the parametric speaker  110  and the first oscillator  120  are formed using one supporting member  40 . 
     Specifically, the supporting member  40  is provided with a first opening which is relatively large, and a plurality of second openings smaller than the first opening. The vibration member  10  and the piezoelectric vibrator  20  that serve as the first oscillator  120  are fitted into the first opening, and the vibration member  10  and the piezoelectric vibrator  20  that serve as the second oscillator  112  are fitted into the second opening. 
     In the embodiment, the same effect as that of the first embodiment can also be obtained. In addition, since the parametric speaker  110  and the first oscillator  120  can be formed as one module, the oscillation device is incorporated more easily into the portable device  300 . 
     As described above, although the embodiments of the invention have been set forth with reference to the drawings, these are merely illustrative of the invention, and various configurations other than those stated above can be adopted. 
     The application claims priority to Japanese Patent Application No. 2010-245665 filed on Nov. 1, 2010, the content of which is incorporated herein by reference in its entirety.