Abstract:
A portable electronic device according to the present invention is provided with a casing formed by joining two cabinets together. A housing chamber for an electric component is recessed on at least either one cabinet and is open toward an inner face of the other cabinet. Mating surfaces located on both the cabinets overlap each other around the housing chamber. A water entry portion leading to a clearance between the mating surfaces is located on an exposed surface exposed to the outside of the casing in an upper part of the casing. A groove extending in a right-left direction along the hosing chamber is recessed on the mating surface of at least either one cabinet of the two cabinets at a position away upward from the housing chamber.

Description:
TECHNICAL FIELD 
     The present invention relates to a portable electronic device such as a mobile phone. 
     BACKGROUND ART 
     For example, a mobile phone employs a waterproof structure in which a waterproof packing is interposed between two cabinets which constitute a casing and compressed by the cabinets to seal the inside of the casing. 
     However, a portable electronic device having a conventional waterproof structure is required to include an additional component such as a waterproof packing. 
     In view of the above, an object of the present invention is to achieve effective waterproofing with a simple configuration in a portable electronic device which has a water entry portion, such as a terminal portion, located on an upper part of a casing. 
     SUMMARY OF THE INVENTION 
     A portable electronic device according to the present invention is provided with a casing formed by joining two cabinets together. A housing chamber for an electric component is recessed on at least one of the two cabinets and is open toward an inner face of the other cabinet. Mating surfaces located on both the two cabinets overlap each other around the housing chamber. A water entry portion leading to a clearance between the mating surfaces is located on an exposed surface exposed to the outside of the casing in an upper part of the casing. 
     A groove extending in a right-left direction along the hosing chamber is recessed on the mating surface of at least one of the two cabinets at a position away upward from the housing chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a mobile phone as an embodiment of the present invention. 
         FIG. 2  is a perspective view illustrating a state in which a cover cabinet is detached from a body cabinet in the mobile phone. 
         FIG. 3  is a perspective view illustrating the state of  FIG. 2  upside down. 
         FIG. 4  is a plan view illustrating the configuration on the inner face side of the body cabinet and the cover cabinet. 
         FIG. 5  is a cross-sectional view taken along line A-A of  FIG. 1 . 
         FIG. 6  is an enlarged cross-sectional view of a part E of  FIG. 5 . 
         FIG. 7  is a cross-sectional view taken along line B-B of  FIG. 1 . 
         FIG. 8  is an enlarged cross-sectional view of a part F of  FIG. 7 . 
         FIG. 9  is a cross-sectional view taken along line C-C of  FIG. 1 . 
         FIG. 10  is an enlarged cross-sectional view of a part G of  FIG. 9 . 
         FIG. 11  is a diagram illustrating the flow of water that has entered a casing. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinbelow, an embodiment in which the present invention is embodied as a mobile phone will be specifically described with reference to the drawings. 
     In the present invention, a face of a casing which faces vertically upward or obliquely upward when a main function of the device is being used (e.g., in a call state in a mobile phone) is defined as an upper face, and an upper part and right and left sides are defined on the basis of the upper face. 
     As illustrated in  FIGS. 1 to 4 , the mobile phone as an embodiment of the present invention is provided with a flat casing  1  which is formed by joining a body cabinet  2  and a cover cabinet  3  both made of synthetic resin together. The cover cabinet  3  is detachably locked to the body cabinet  2  by a hook mechanism. 
     As illustrated in  FIG. 1 , an outer peripheral wall of the body cabinet  2  and an outer peripheral wall of the cover cabinet  3 , the body cabinet  2  and the cover cabinet  3  constituting the casing  1 , abut against each other on right and left side faces  12 ,  12  of the casing  1  as well as on an upper face  11  and a lower face  15  of the casing  1 . 
     A USB port  21  and an earphone jack  22  are located as a terminal portion on the upper face  11  of the casing  1 . A speaker hole  32  is formed on a back face  13  of the casing  1 . A camera  7  is exposed on the back face  13  of the casing  1 . 
     A phone call is made using the mobile phone in such a state that the casing  1  is grasped by the hand with the upper face  11  of the casing  1  facing upward (in an inclined posture or a vertical posture) as illustrated in  FIG. 1 , an earpiece portion  16  which is located on the upper part of the casing  1  as illustrated in  FIG. 3  is brought close to the ear, and a mouthpiece portion  17  which is located on the lower part of the casing  1  as illustrated in  FIG. 3  is brought close to the mouth. 
     As illustrated in  FIG. 2 , a rectangular parallelepiped housing chamber  40  is recessed on the body cabinet  2  and is open toward the inner face of the cover cabinet  3 . A battery  4  as a power source is housed in the housing chamber  40 . A circuit board (not illustrated) is placed on the back of the battery  4 . Locking the cover cabinet  3  to the body cabinet  2  allows the cover cabinet  3  to close the housing chamber  40  of the body cabinet  2 . 
     The camera  7  is arranged on the body cabinet  2 . On the other hand, a photographing window  30  for exposing the camera  7  is open on the cover cabinet  3 . 
     Further, as illustrated in  FIG. 3 , a screen of a display  20  is disposed on a front face  14  of the body cabinet  2 . 
     As illustrated in  FIG. 2 , an upper mating surface  24 , right and left mating surfaces  25 ,  25 , and a lower mating surface  26  are continuously located on the body cabinet  2  along four sides of the housing chamber  40  so as to surround the housing chamber  40 . 
     On the other hand, as illustrated in  FIG. 3 , an upper mating surface  33 , right and left mating surfaces  34 ,  34 , and a lower mating surface  35  are continuously formed on the cover cabinet  3 . 
     When the cover cabinet  3  is locked to the body cabinet  2 , the mating surfaces of the body cabinet  2  overlap the respective mating surfaces of the cover cabinet  3 . 
     That is, as illustrated in  FIGS. 5 to 8 , the upper mating surface  24  of the body cabinet  2  and the upper mating surface  33  of the cover cabinet  3  overlap each other. Further, as illustrated in  FIGS. 9 and 10 , the right and left mating surfaces  25  of the body cabinet  2  and the right and left mating surfaces  34  of the cover cabinet  3  overlap each other. Further, the lower mating surface  26  of the body cabinet  2  and the lower mating surface  35  of the cover cabinet  3  overlap each other. 
     A tiny clearance (H illustrated in  FIG. 1 ) of approximately 0.05 mm is formed between the mating surfaces of the body cabinet  2  and the cover cabinet  3  in consideration of molding accuracy in both the cabinets  2  and  3 . 
     Thus, when the body cabinet  2  and the cover cabinet  3  abut against each other on their outer peripheral walls, the mating surfaces do not push against each other. 
     As illustrated in  FIGS. 2 and 4 , the body cabinet  2  includes a groove  5  which is recessed on the upper mating surface  24  and extends in the right-left direction at a position slightly away from the housing chamber  40 . The respective ends of the groove  5  reach the right and left mating surfaces  25 ,  25 . In  FIG. 4 , an area in which the groove  5  is formed is indicated by hatching. 
     As illustrated in  FIG. 4 , an upper wall face of the groove  5  has an inclination which is gradually lowered toward the right and left directions from a position near the camera  7  as a top. 
     On the other hand, as illustrated in  FIGS. 3 and 4 , the cover cabinet  3  includes two ribs  6 ,  6  which project on the upper mating surface  33  and extend in the right-left direction in a manner to face the groove  5  of the body cabinet  2 . Ends of the ribs  6 ,  6  respectively reach the right and left mating surfaces  34 ,  34 . 
     As illustrated in  FIG. 4 , the two ribs  6 ,  6  have an inclination which is gradually lowered toward the right and left directions from a position near the photographing window  30  as a top. 
     When the cover cabinet  3  is locked to the body cabinet  2 , as illustrated in  FIGS. 5 to 8 , the groove  5  of the body cabinet  2  is closed by the mating surface  24  of the cover cabinet  3 , and a space  50  which extends in the right-left direction is thereby formed. Further, the ribs  6  of the cover cabinet  3  are housed in the groove  5  of the body cabinet  2 , and a tiny clearance of approximately 0.1 mm is thereby formed between the ribs  6  and the inner face (the bottom face and the upper wall face) of the groove  5 . 
     When water enters the mobile phone, for example, through the USB port  21  or the earphone jack  22  located on the upper face  11  of the casing  1 , the speaker hole  32  open on the back face  13  of the casing  1 , or a clearance on an abutment portion  10  between the cabinets  2  and  3  exposed on the upper face  11  of the casing  1  in a process of making a call or performing an input operation in a state in which the casing  1  is grasped by the hand with the upper face  11  of the casing  1  facing upward as illustrated in  FIG. 1 , the water first flows into a clearance between the mating surfaces located above the housing chamber  40  under the action of gravity as indicated by arrows X of  FIG. 11 . 
     Then, the water flows toward the groove  5  located on the lower side by the action of gravity. However, since the clearance between the mating surfaces is significantly smaller than the depth of the groove  5  in a direction perpendicular to the mating surfaces, the water flowing toward the groove  5  is sucked into the clearance by a capillary phenomenon generated in the clearance. As a result, the water flows through the clearance toward both sides of the casing  1  as indicated by arrows Y. 
     A flow path which is inclined downward along the upper wall face of the groove  5  is formed in the clearance. Thus, water inside the clearance smoothly flows through the flow path toward both sides of the body cabinet  2  under the action of gravity. 
     Then, the water flows into the clearances between the mating surfaces located on the right and left sides of the housing chamber  40 , and flows through the clearances toward the lower side as indicated by arrows Z. 
     In this manner, a flow path which bypasses the housing chamber  40  is formed. The water is discharged from the lower part of the casing  1  after flowing through the flow path, or retained inside the flow path and gradually evaporates. Thus, the possibility of water entering the housing chamber  40  of the casing  1  is low. 
     Even when part of water that has flowed into the clearance between the mating surface  24  of the body cabinet  2  and the mating surface  33  of the cover cabinet  3  flows into the groove  5 , the water that has flowed into the groove  5  is retained in the clearance formed between the ribs  6  which project on the mating surface  33  of the cover cabinet  3  and the inner face of the groove  5  which is located on the mating surface  24  of the body cabinet  2 , the clearance being smaller than the depth of the groove  5 , by a capillary phenomenon. Thus, the possibility of water flowing into the housing chamber  40  through the groove  5  is extremely low. 
     Also in a conventional mobile phone, the mating surfaces of the body cabinet  2  and the cover cabinet  3  are formed to surround the housing chamber  40 . However, the groove  5  is not formed on the mating surface  24  in a conventional mobile phone. Thus, water enters the housing chamber  40  through the clearance between the mating surfaces  24  and  33 . 
     The mobile phone of the present invention makes it possible to achieve effective waterproofing using a capillary phenomenon with the simple configuration in which the groove  5  is merely recessed on the mating surface  24  of the body cabinet  2  of the casing  1 . Further, the groove  5  can be formed simultaneously with resin molding for the body cabinet  2 . Thus, the number of components and the number of steps in a manufacturing process are not likely to increase. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           1  casing 
           11  upper face 
           2  body cabinet 
           3  cover cabinet 
           21  USB port 
           22  earphone jack 
           32  speaker hole 
           24  mating surface 
           33  mating surface 
           4  battery 
           40  housing chamber 
           5  groove 
           6  rib