Abstract:
Disclosed is an electronic apparatus which can ensure waterproofness or dustproofness when a rectangular electroacoustic transducer is employed, and can prevent both distortion of voice and leakage of sound at the same time. A first casing ( 101 ) of the electronic apparatus has sound holes ( 110 ). A film member ( 103 ) is substantially circular and provided between the sound holes ( 110 ) and an electroacoustic transducer ( 107 ). A planar member ( 105 ) is provided between the film member ( 103 ) and the electroacoustic transducer ( 107 ) and has second sound holes ( 111 ). The electroacoustic transducer ( 107 ) is substantially rectangular and generates voice.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electronic device, and relates, for example, to an electronic device that waterproofs an electroacoustic transducer provided inside a casing. 
       BACKGROUND ART 
       [0002]    Hitherto, a telephone provided with a waterproof film for waterproofing an acoustic part has been known (see Patent Literature 1, for example). 
         [0003]      FIG. 1  is an exploded perspective view of principal parts of conventional electronic device  1  such as a telephone. Conventional electronic device  1  mainly comprises casing  10 , cushion member  11 , film member  12 , cushion member  13 , and electroacoustic transducer  14 . 
         [0004]    Casing  10  has plurality of sound holes  50 , which are through-holes. Sound holes  50  output speech generated from electroacoustic transducer  14  to the exterior of casing  10 . 
         [0005]    Cushion member  11  is provided between casing  10  and film member  12 , and provides a seal between casing  10  and film member  12 . 
         [0006]    Film member  12  is circular viewed from above, and is provided between cushion member  11  and cushion member  13 . Film member  12  prevents water or other liquids from penetrating into the interior of casing  10  from sound holes  50 . 
         [0007]    Cushion member  13  is provided between film member  12  and electroacoustic transducer  14 , and provides a seal between film member  12  and electroacoustic transducer  14 . 
         [0008]    Electroacoustic transducer  14  is a speaker, for example. 
         [0009]    In recent years, as portable terminals such as mobile phones have become smaller in size, rectangular electroacoustic transducers have been used in order to achieve an efficient parts layout inside the casing. 
       CITATION LIST 
     Patent Literature 
     [PTL 1] 
       [0010]    Japanese Patent Application Laid-Open No. HEI8-79865 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0011]    However, if a film member is made rectangular in line with the shape of a rectangular electroacoustic transducer, distances from the center of the surface of the film member to the sides become unequal. Consequently, when the film member vibrates due to speech generated from the electroacoustic transducer, there is a problem of frequency components of various different frequencies being produced, and speech output from the sound holes in the casing being distorted. 
         [0012]    On the other hand, if a round film member is used in the conventional way, speech distortion does not occur since distances from the center of the surface of the film member to peripheral edges become equal. However, if a round film member is still used even though the electroacoustic transducer has been made rectangular, there is a problem of sound leakage occurring due to the creation of a gap between the film member and the electroacoustic transducer. 
         [0013]    It is an object of the present invention to provide an electronic device that can ensure waterproofing and dustproofing, and can prevent both speech distortion and sound leakage at the same time, when a rectangular electroacoustic transducer is used. 
       Solution to Problem 
       [0014]    An electronic device of the present invention employs a configuration having a casing, first sound holes provided in the casing, a substantially rectangular electroacoustic transducer provided inside the casing, a substantially circular film member provided between the first sound holes and the electroacoustic transducer, a planar member provided between the film member and the electroacoustic transducer, and second sound holes provided in the planar member. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0015]    The present invention can ensure waterproofing and dustproofing, and can prevent both speech distortion and sound leakage at the same time, when a rectangular electroacoustic transducer is used. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is an exploded perspective view of principal parts of a conventional electronic device; 
           [0017]      FIG. 2  is an exploded perspective view of principal parts of an electronic device according to an embodiment of the present invention; 
           [0018]      FIG. 3  is a cross-sectional view of an electronic device according to an embodiment of the present invention; 
           [0019]      FIG. 4  is a plan view showing the mutual positional relationship of a film member, electroacoustic transducer, and sound holes according to an embodiment of the present invention; 
           [0020]      FIG. 5  is a plan view showing the mutual positional relationship of a film member, electroacoustic transducer, and sound holes according to an embodiment of the present invention; and 
           [0021]      FIG. 6  is an exploded perspective view of an electronic device according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0022]    Now, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
       Embodiment 
       [0023]      FIG. 2  is an exploded perspective view of principal parts of electronic device  100  according to an embodiment of the present invention. 
         [0024]    Electronic device  100  mainly comprises first casing  101 , cushion member  102 , film member  103 , cushion member  104 , planar member  105 , cushion member  106 , and electroacoustic transducer  107 . Electronic device  100  is, for example, a communication terminal apparatus such as a mobile phone, or a portable TV. Cushion member  102 , film member  103 , cushion member  104 , planar member  105 , cushion member  106 , and electroacoustic transducer  107  are housed in an interior space formed by another casing described later herein that is separate from first casing  101 , and first casing  101 . However, in  FIG. 2 , only a part of first casing  101  is shown, and another casing is not shown. 
         [0025]    First casing  101  has plurality of sound holes  110 , which are through-holes. 
         [0026]    Cushion member  102  is provided between first casing  101  and film member  103 . Cushion member  102  has an adhesive section of double-sided adhesive tape or the like on its upper surface and lower surface, and creates a seal between first casing  101  and film member  103  through the adhesion of the respective adhesive sections to first casing  101  and film member  103 . Cushion member  102  is circular viewed from above, and has circular through-hole  112  in its center. 
         [0027]    Film member  103  is thin film that is approximately circular viewed from above, and is provided between cushion member  102  and cushion member  104 . Film member  103  is formed from a material that allows speech generated from electroacoustic transducer  107  to pass through without being attenuated, and is, for example, a microporous membrane of PTFE or the like. Film member  103  prevents water or other liquids, or dust, that penetrates from sound holes  110 , from further penetrating to electroacoustic transducer  107 . That is to say, film member  103  functions as a waterproof film or dustproof film. The term “approximately circular” here includes a polygonal shape in which distances from the center to the periphery are approximately uniform, including, essentially, various shapes that are approximately circular and that do not give rise to various frequency components that cause speech distortion when they vibrate due to speech. 
         [0028]    Cushion member  104  is provided between film member  103  and planar member  105 . Cushion member  104  has an adhesive section of double-sided adhesive tape or the like on its upper surface and lower surface, and creates a seal between film member  103  and planar member  105  through the adhesion of the respective adhesive sections to film member  103  and planar member  105 . Cushion member  104  is circular viewed from above, and has circular through-hole  114  in its center. 
         [0029]    Planar member  105  is of thin planar shape, and is provided between cushion member  104  and cushion member  106 . Planar member  105  has two sound holes  111 , which are through-holes. The number of sound holes  111  is not limited to two, but may be three or more, or one. 
         [0030]    Cushion member  106  is provided between planar member  105  and electroacoustic transducer  107 . Cushion member  106  has an adhesive section of double-sided adhesive tape or the like on its upper surface and lower surface, and creates a seal between planar member  105  and electroacoustic transducer  107  through the adhesion of the respective adhesive sections to planar member  105  and electroacoustic transducer  107 . Cushion member  106  is rectangular viewed from above, and has rectangular through-hole  115  in its center. 
         [0031]    Electroacoustic transducer  107  is approximately rectangular viewed from above. Electroacoustic transducer  107  is a speaker, for example. In addition to a rectangular shape, the term “approximately rectangular” here includes an octagonal shape with four corners cut obliquely, for example, including, essentially, various shapes that are approximately rectangular and that enable an efficient parts layout to be achieved inside the casing. 
         [0032]      FIG. 3  is a cross-sectional view of electronic device  100 . As shown in  FIG. 3 , inside first casing  101  of electronic device  100 , electroacoustic transducer  107 , cushion member  106 , planar member  105 , cushion member  104 , film member  103 , and cushion member  102  are stacked in that order. Sound holes  110  are provided in first casing  101  so as to be located within range L in which film member  103  and electroacoustic transducer  107  overlap in a plan view (looking downward from above in  FIG. 3 ). Similarly, sound holes  111  are provided in planar member  105  so as to be located within range L in which film member  103  and electroacoustic transducer  107  overlap in a plan view. Also, sound holes  110  are provided at positions in which they mutually overlap with sound holes  111  in a plan view. Film member  103  is located between sound holes  110  and sound holes  111 . However, since film member  103  is formed from a material that allows speech to pass through without being attenuated, speech that has passed through sound holes  111  can be guided to sound holes  110  without being attenuated. 
         [0033]      FIG. 4  is a plan view showing the mutual positional relationship of film member  103 , electroacoustic transducer  107 , and sound holes  110 . From  FIG. 4 , it can be seen that sound holes  110  are located at positions in which they overlap both film member  103  and electroacoustic transducer  107  in a plan view. 
         [0034]      FIG. 5  is a plan view showing the mutual positional relationship of film member  103 , electroacoustic transducer  107 , and sound holes  111 . From  FIG. 5 , it can be seen that sound holes  111  are located at positions in which they overlap both film member  103  and electroacoustic transducer  107  in a plan view. 
         [0035]    Sound holes  110  and sound holes  111  are formed so that the total area of sound holes  111  in the surface of planar member  105  is greater than the total area of sound holes  110  in the surface of first casing  101 . By this means, speech that has passed through sound holes  111  can pass through sound holes  110  without being attenuated. Here, the total area of sound holes  110  can be found by multiplying the area of one sound hole  110  by the total number of sound holes  110 . That is to say, in the case shown in  FIG. 4 , the total area of sound holes  110  can be found by means of equation 1. 
         [0000]      Total area of sound holes 110  S 1=(( r 1÷2)2×π)×10  (Equation 1)
 
         [0036]    where r 1  is the diameter of sound holes  110 . 
         [0037]    Also, the total area of sound holes  111  can be found by multiplying the area of one sound hole  111  by the total number of sound holes  111 . That is to say, in the case shown in  FIG. 5 , the total area of sound holes  111  can be found by means of equation 2. 
         [0000]      Total area of sound holes 111  S 2=(( r 2÷2)2×π)×2  (Equation 2)
 
         [0038]    where r 2  is the diameter of sound holes  111 . 
         [0039]    By this means, sound holes  110  and sound holes  111  are formed so that S 1 ≦S 2 . As long as this condition is satisfied, the shape and number of sound holes  110  and sound holes  111  are not limited to those in this embodiment. 
         [0040]      FIG. 6  is an exploded perspective view of electronic device  100 . Electronic device  100  comprises first casing  101 , intermediate casing  501 , and second casing  502 . 
         [0041]    First casing  101  has a U-shaped cross-section and has sound holes  110 . Cushion member  102 , film member  103 , and cushion member  104  are housed in an interior space formed by first casing  101  and intermediate casing  501 . 
         [0042]    Intermediate casing  501  has, integrally, recessed planar member  105  having sound holes  111 . First casing  101  is attached to intermediate casing  501  so as to cover planar member  105 . Cushion member  102  and film member  103  are placed on recessed planar member  105 , and are covered by first casing  101 . Intermediate casing  501  is attached to second casing  502  so as to cover the upper surface of second casing  502 . 
         [0043]    Second casing  502  has parts layout section  503  on which an electrical circuit pattern (not shown) is formed. Electroacoustic transducer  107 , to which cushion member  106  is attached, is attached to parts layout section  503  and electrically connected to the electrical circuit pattern on parts layout section  503 . 
         [0044]    The method of assembling electronic device  100  will now be described using  FIG. 2  and  FIG. 6 . 
         [0045]    First, cushion member  106  is attached to the outer part of the upper surface of electroacoustic transducer  107 , and electroacoustic transducer  107  is placed on parts layout section  503  of second casing  502  so as to be electrically connected to the electrical circuit pattern on parts layout section  503 . 
         [0046]    Next, film member  103  is attached to planar member  105  by means of cushion member  104  at a position to seal off sound holes  111 . 
         [0047]    Next, first casing  101  is attached to intermediate casing  501  so as to cover planar member  105  of intermediate casing  501 . By this means, film member  103  is attached to first casing  101 , by means of cushion member  102 , in a position to seal off sound holes  110 . 
         [0048]    Next, intermediate casing  501  is attached to second casing  502 . By this means, cushion member  106  is attached to planar member  105 , and electronic device  100  is completed. 
         [0049]    This concludes a description of the method of assembling electronic device  100 . 
         [0050]    In electronic device  100  of this kind, speech output from electroacoustic transducer  107  reaches film member  103  after passing through through-hole  115  of cushion member  106 , sound holes  111 , and through-hole  114  of cushion member  104 , in that order. Then speech that has reached film member  103  passes through film member  103 . At this time, film member  103  vibrates due to the speech passing through. Since film member  103  is circular, speech that passes through film member  103  is not distorted. 
         [0051]    Next, speech that has passed through film member  103  passes through through-hole  112  of cushion member  102  and sound holes  110 , and is output to the exterior of electronic device  100 . 
         [0052]    Water or other liquids, or dust, that penetrates into the interior of electronic device  100  from sound holes  110  passes through through-hole  112  of cushion member  102 . However, water or other liquids, or dust, cannot penetrate further into the interior of electronic device  100  due to film member  103 . 
         [0053]    Thus, according to this embodiment, by providing a planar member provided with sound holes between a casing and an electroacoustic transducer, and also providing a circular film member between the casing and the planar member, waterproofing and dustproofing can be ensured, and both speech distortion and sound leakage can be prevented at the same time, when a rectangular electroacoustic transducer is used. Also, by making the total area of sound holes provided in the planar member in the surface of the planar member greater than the total area of sound holes provided in a first casing in the surface of the first casing, speech generated from the electroacoustic transducer can be output to the exterior without being attenuated. Furthermore, according to this embodiment, by providing a plurality of sound holes in the planar member, a decrease in the strength of the planar member associated with sound hole formation can be reduced. 
         [0054]    In this embodiment, a case has been described in which electroacoustic transducer  107  is a speaker. However, the present invention is not limited to this, and can be applied to any electroacoustic transducer, such as a microphone, receiver, or the like, as well as a speaker. 
         [0055]    In the present invention, a planar member has been assumed to be integral with an intermediate casing. However, the present invention is not limited to this, and a planar member may also be a separate entity from an intermediate casing. 
         [0056]    In this embodiment, a seal is provided between first casing  101  and film member  103 , and film member  103  and planar member  105 , by means of cushion member  102  and cushion member  104  respectively. However, the present invention is not limited to this, and provision may also be made for adhesive sections enabling adhesion to first casing  101  and planar member  105  to be provided on film member  103 , and for cushion member  102  and cushion member  104  to be eliminated. 
         [0057]    The disclosure of Japanese Patent Application No. 2008-139792, filed on May 28, 2008, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0058]    The present invention is suitable for use in an electronic device such as a mobile phone, portable audio player, digital camera, digital video camera, notebook PC, electronic dictionary, portable game machine, portable TV, and so forth.