Abstract:
An electronic device includes a case including a fixing portion, a printed board fixed to the fixing portion, a key rubber provided with key tops and fixed to the printed board, and a flexible cable attached to the printed board and bent in a direction different from the surface of the fixing portion to which the printed board is fixed, wherein the key rubber includes a contact portion that is in contact with the folded portion of the flexible cable and subjected to reaction force of the flexible cable, and a locking portion pressed against the case by the reaction force.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-251226 filed on Nov. 9, 2010, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiment discussed herein relates to an electronic device. 
     BACKGROUND 
     An electronic device such as a cellular phone is provided with various keys as an input interface of the device. A user depresses the keys, thereby performing various operations. It is known that electronic devices have a key structure including, for example, contact switches. 
     For example, a key structure including contact switches described in Japanese Laid-open Patent Publication No. 2007-109486 includes a printed board module and a key module disposed on the printed board module. The printed board module includes a printed board with an electronic circuit thereon, and contact switches disposed on the printed board. The key module has, for example, a key rubber and key tops disposed on the key rubber. The key rubber is an elastic member disposed on the printed board module. 
     The key rubber has planar portions, supporting portions, and pushers. The planar portions are disposed opposite to the contact switches. The supporting portions support the planar portions at locations on the printed board module where the contact switches are not provided. The pushers are protrusions formed at positions on the contact switch side surfaces of the planar portions corresponding to the contact switches. The key tops are placed on the surfaces of the planar portions opposite to the surfaces on which the pushers are formed. When a user depresses any one of the key tops, the corresponding planar portion bends, the corresponding pusher depresses the corresponding contact switch, and the contact switch is thereby turned on. 
     In the key structure described in Japanese Laid-open Patent Publication No. 2007-109486, a front case holds the key rubber, thereby preventing the key rubber from coming off. In place of the structure disclosed in Japanese Laid-open Patent Publication No. 2007-109486, a structure may be used in which, in a case of an electronic device, a printed board module is fixed to a placement plate integral with the case, the printed board module is thereby fixed to the case, a key rubber is bonded to the printed board module without placing a front case on the key rubber, key tops are bonded to the key rubber, and the key module is thereby fixed. In this case, the thickness of the case may be reduced. 
     In the case where a key flexible cable is used in order to electrically connecting an electronic circuit formed on a first printed board and an electronic circuit formed on a second printed board, the key flexible cable extends from one end thereof connected to the first printed board, and is folded on the outer side of the end face of a placement plate on which the first printed board is placed, and the other end of the key flexible cable is connected to the second printed board disposed, for example, on the reverse side of the placement plate. 
     If another member, such as a slide module of a cellular phone, is provided in the direction in which the folded portion of the key flexible cable bends due to its own weight, the folded portion may come into contact with the other member and may be pressed toward the key rubber. In this case, the folded portion pressed by the other member presses the key rubber, and as a result, the key rubber may peel off of the printed board module. 
     SUMMARY 
     According to an aspect of the embodiment, an electronic device includes a case including a fixing portion, a printed board fixed to the fixing portion, a key rubber provided with key tops and fixed to the printed board, and a flexible cable attached to the printed board and bent in a direction different from the surface of the fixing portion to which the printed board is fixed, wherein the key rubber includes a contact portion that is in contact with the folded portion of the flexible cable and subjected to reaction force of the flexible cable, and a locking portion pressed against the case by the reaction force. 
     The object and advantages of the invention will be realized and attained by at least the features, elements, and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating the appearance of a cellular phone of a first embodiment in a closed state; 
         FIG. 2  is a perspective view illustrating the appearance of the cellular phone of the first embodiment in an open state; 
         FIG. 3  is an exploded perspective view of the display-side case of the cellular phone of the first embodiment; 
         FIG. 4  is a plan view of the cellular phone of the first embodiment; 
         FIG. 5  is a sectional view illustrating part of the section of the cellular phone of  FIG. 4  taken along line V-V; 
         FIG. 6  is a sectional view of a dome switch portion of a printed board module; 
         FIG. 7  is an enlarged view of a locking pawl portion of the first embodiment; 
         FIG. 8  is a plan view of a cellular phone of a second embodiment; 
         FIG. 9  is a sectional view illustrating part of the section of the cellular phone of  FIG. 8  taken along line IX-IX and; 
         FIG. 10  is an enlarged view of a locking pawl portion of the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the electronic device disclosed in the present application will now be described in detail with reference to the drawings. The disclosed technique is not limited to these embodiments. For example, although in the following embodiments a cellular phone is taken as an example of an electronic device, the following embodiments may be applied not only to a cellular phone but also to an electronic device such as a PDA (Personal Digital Assistant). 
     [First Embodiment ] 
       FIG. 1  is a perspective view illustrating the appearance of a cellular phone of a first embodiment in a closed state.  FIG. 2  is a perspective view illustrating the appearance of the cellular phone of the first embodiment in an open state.  FIG. 3  is an exploded perspective view of the display-side case of the cellular phone of the first embodiment. As illustrated in  FIGS. 1 and 2 , a cellular phone  100  of the first embodiment includes a display-side case  110  and an operation-side case  190 . The display-side case  110  and the operation-side case  190  are connected by a slide module so as to be able to slide relative to each other.  FIG. 1  illustrates a closed state where the display-side case  110  is not slid, and the display-side case  110  and the operation-side case  190  are entirely superimposed on each other.  FIG. 2  illustrates an open state where the display-side case  110  is slid, and the overlap between the display-side case  110  and the operation-side case  190  is minimized. 
     As illustrated in  FIG. 3 , one face of the display-side case  110  is open. The display-side case  110  is provided with a partition wall  111  that divides the interior space of the display-side case  110  into an opening-side space and a bottom-side space. On the opening-side surface of the partition wall  111 , a partition wall  112  is erected that divides the opening-side space into two spaces along the sliding direction of the cellular phone. The partition wall  112  divides the opening-side space into a first space  114  and second space  116  that accommodate components. The first space  114  accommodates a display portion  120 . The second space  116  accommodates a printed board module  130  and a front key module  170  disposed on the printed board module  130 . The printed board module  130  is bonded to the surface of the partition wall  111  with double-sided tape  128 . The front key module  170  is an operation module for performing various operations of the cellular phone  100 . The display portion  120  and the front key module  170  form an open surface of the display-side case  110 . 
     The display portion  120  has a display module  122 , a packing  124 , and a display panel  126  such as a liquid crystal panel. The display module  122  is accommodated on the outer side of the partition wall  111 . The display panel  126  is superimposed over the display module  122  with the packing  124  therebetween. The packing  124  is sandwiched between the display panel  126  and the display module  122  and seals the periphery of the display surface of the display module  122 . Thus, foreign matter may be prevented from getting into the space between the display panel  126  and the display surface of the display module  122 . The packing  124  spaces the display panel  126  from the display surface of the display module  122  and prevents blurring or the like caused by contact between the display surface and the display panel  126 . 
     The printed board module  130  includes a key flexible board  140  and a top tape  160 . The key flexible board  140  is bonded to the surface of the partition wall  111  with the double-sided tape  128 . The top tape  160  is bonded to and covers the front key module  170  side surface of the key flexible board  140 . The key flexible board  140  is a flexible printed board formed of PET sheet or the like. On the key flexible board  140 , a wiring pattern is formed, and a plurality of contact switches such as metal domes  132  and various components such as LEDs (Light Emitting Diodes)  134  are mounted. A flexible printed board is a kind of printed board. 
     The key flexible board  140  is substantially rectangular in shape and has cutouts  142  at the corners at both ends of a long side thereof. On the other long side, cutouts  144  for passing screws  119  are formed. A key flexible cable  148  extends from one of the short sides of the key flexible board  140  toward the outside of the key flexible board  140 . The top tape  160  is formed of PET sheet or the like. The top tape  160  has component holes corresponding to the various components such as LEDs  134  mounted on the key flexible board  140  and is bonded to and covers the surface of the key flexible board  140  and the surfaces of the metal domes  132 . 
     The front key module  170  includes a rectangular key rubber  172  bonded to the printed board module  130 , and a plurality of key tops  174  bonded to the key rubber  172 . The front key module  170  includes a multidirectional input unit  176  bonded to the key rubber  172 , and a cover  178  provided on the key rubber  172 . 
     The key tops  174  are bonded to the key rubber  172  along the three sides of the key rubber  172 . The key tops  174  each have a flange  180 . The flanges  180  protrude from the sides of the key tops  174  facing the middle of the key rubber  172  toward the middle of the key rubber  172 . The multidirectional input unit  176  includes a torus-shaped base portion  182  and a flange  184  protruding from the outer periphery of the base portion  182 . The multidirectional input unit  176  is bonded to substantially the center of the key rubber  172 . The multidirectional input unit  176  is an input unit including a rotating operation type encoder capable of rotating operation, depressing operation, and inclining operation. 
     The cover  178  is a rectangular plate with a through-hole  186  in its center. The base portion  182  of the multidirectional input unit  176  is passed through the through-hole  186 . The cover  178  has screw holes  188  at the four corners of the display-side case  110  side surface thereof. By inserting screws  119  into screw through-holes  118  formed in the back surface of the display-side case  110  and screwing the screws  119  into the screw holes  188 , the cover  178  is fixed to the display-side case  110 . The cover  178  fixed to the display-side case  110  is in contact with the flanges  180  of the key tops  174  and the flange  184  of the multidirectional input unit  176  and prevents the key tops  174  and the multidirectional input unit  176  from coming off. 
     The operation-side case  190  accommodates a key module  190  for performing various operations of the cellular phone  100 . The operation-side case  190  accommodates a main body printed board module on which are mounted components that perform various processing such as signal processing in connection with communication of the cellular phone  100 , and signal processing for displaying characters or an image on the display panel. On the side of the operation-side case  190 , operation keys  194 , for example, for speaker volume control are provided. 
     As illustrated in  FIGS. 1 ,  2 , and  3 , the key structure of the cellular phone  100  of the first embodiment is a flangeless key structure in which no flanges are provided on the display-side case  110  side of the key tops  174 . The key structure of the cellular phone  100  of the first embodiment is a ribless key structure in which no rib (part of the display-side case  110 ) is provided between adjacent key tops  174 . While recent cellular phones are required to be small in size and thickness, the key tops  174  thereof are required to be large so that key operation may be easily performed. The cellular phone  100  of the first embodiment has the flangeless structure and ribless structure and has large key tops  174  so that key operation may be easily performed. In the cellular phone  100  of the first embodiment, in order to reduce the thickness of the cellular phone  100 , a key rubber  172  is bonded to a printed board module  130 , and key tops  174  are bonded to the key rubber  172 . 
     In a cellular phone  100  having the flangeless structure and ribless structure such as the first embodiment, the key tops  174  are not locked in the display-side case  110 , and therefore the key rubber  172  may peel off of the printed board module  130 . The key flexible cable  148  extends from the end of the key flexible board  140  in the direction of the side of the display-side case  110 , passes through a gap  113  formed between the end face of the partition wall  111  and the side of the display-side case  110 , and leads to the reverse side of the partition wall  111 . Thus, the key flexible cable  148  has a folded portion  148   a  located in the gap  113 . The folded portion  148   a  bends due to the weight of the key flexible cable  148 . If another member, for example, the slide module of the cellular phone, is provided in this bending direction, the folded portion  148   a  may come into contact with the other member due to the reaction force of the flexible cable, and may be pressed toward the key rubber  172 . The folded portion  148   a  pressed by the other member presses the key rubber  172 , and as a result, the key rubber  172  may peel off of the printed board module  130 . The details of the printed board module  130  and the front key module  170  of the cellular phone  100  of the first embodiment to deal with this problem will be described. 
       FIG. 4  is a plan view of the cellular phone of the first embodiment.  FIG. 5  is a sectional view illustrating part of the section of the cellular phone of  FIG. 4  taken along line V-V.  FIG. 6  is a sectional view of a dome switch portion of a printed board module.  FIG. 7  is an enlarged view of a locking pawl portion of the first embodiment.  FIG. 5  illustrated the section of the cellular phone  100  taken along line V-V of  FIG. 4 . For convenience in description,  FIG. 5  illustrates the section from the center of the multidirectional input unit  176  to one side of the display-side case  110 . 
     As illustrated in  FIG. 5 , the key rubber  172  has planar portions  172   b  opposite to the metal domes  132  provided on the key flexible board  140 . The key rubber  172  has supporting portions  172   a  that floatingly support the planar portions  172   b  at the ends of the top tape  160  and the flat portions of the top tape  160  where the metal domes  132  are not provided. The key rubber  172  has pushers  172   c  that are protrusions formed at positions on the metal dome  132  side surfaces of the planar portions  172   b  corresponding to the metal domes  132 . The bottom surfaces of the supporting portions  172   a  are bonded to the top tape  160  with double-sided tape  172   h . Key tops  174  are bonded to the surfaces of the planar portions  172   b  opposite to the surfaces on which the pushers  172   c  are formed. 
     The key rubber  172  is entirely formed of an elastic material. In each supporting portion  172   a , a resin portion  172   d  formed of a resin material is provided. In other words, each supporting portion  172   a  is integrally formed by a resin portion  172   d  and an elastic portion  172   i  formed of an elastic material around the resin portion  172   d . The resin portion  172   d  may be formed, for example, of polycarbonate. 
     As illustrated in  FIG. 6 , the top tape  160  to which the tops of the metal domes  132  are preliminarily bonded is bonded to the key flexible board  140 . On the component disposing surface of the key flexible board  140 , a first contact  149   a  is formed at a position corresponding to the edge  132   a  of each metal dome  132 , and a second contact  149   b  is formed at a position corresponding to the top  132   b  of each metal dome  132 . The top  132   b  of each metal dome  132  is bonded to the key flexible board  140  side surface of the top tape  160 . The top tape  160  is bonded to the key flexible board  140  such that the edge  132   a  of each metal dome  132  is in contact with the corresponding first contact  149   a.    
     Normally, the edge  132   a  of each metal dome  132  and the corresponding first contact  149   a  are in contact with each other, and the top  132   b  of each metal dome  132  and the corresponding second contact  149   b  are out of contact with each other. Therefore, the first contact  149   a  and the second contact  149   b  are electrically isolated from each other. When any one of the key tops  174  is depressed by a user, the corresponding pusher  172   c  presses the top  132   b  of the corresponding metal dome  132  with the top tape  160  therebetween, and the metal dome  132  deforms such that the top  132   b  crushes. As a result, the top  132   b  of the metal dome  132  comes into contact with the second contact  149   b , and the first contact  149   a  and the second contact  149   b  are electrically connected. When the user stops depressing the key top  174 , the metal dome  132  returns to its original shape, and the first contact  149   a  and the second contact  149   b  are electrically isolated from each other again. In the first embodiment, the contact switches mounted on the key flexible board  140  are metal domes. However, other types of contact switches, for example, cantilever spring contact switches may also be used. 
     Returning to  FIG. 5 , a printed board  150  is provided on the reverse side of the partition wall  111 . On the printed board  150 , pattern wiring is formed and a connector  152  is mounted. The key flexible cable  148  extends from the end of the key flexible board  140  in the direction of the side of the display-side case  110 , passes through a gap  113  formed between the end face of the partition wall  111  and the side of the display-side case  110 , and leads to the reverse side of the partition wall  111 . Thus, the key flexible cable  148  has a folded portion  148   a  located in the gap  113 . The key flexible cable  148  is folded at the folded portion  148   a  toward the reverse side of the partition wall  111  and is connected to the connector  152 . 
     As illustrated in  FIGS. 5 and 7 , a slide module  156  for sliding the display-side case  110  and the operation-side case  190  relative to each other is provided on the reverse side of the partition wall  111 . The folded portion  148   a  is pressed toward the key rubber  172  by the reaction force of the flexible cable  148  generated by contacting the slide module  156 . From the supporting portion  172   a  formed at the end of the key rubber  172 , a locking pawl  172   e  extends in the direction of the side of the display-side case  110 . The locking pawl  172   e  has a contact portion  172   f  that is in contact with the folded portion  148   a  being pressed by the slide module  156 . On the surface opposite to the contact portion  172   f  of the locking pawl  172   e , a locking portion  172   g  may formed that may engage with a protrusion  110   a  formed on the inner wall of the side of the display-side case  110 . The first embodiment has been described with an example in which the folded portion  148   a  is in contact with and pressed by the slide module  156 . The first embodiment may also be applied to the case where the folded portion  148   a  is in contact with and pressed by another member provided in the bending direction of the folded portion  148   a.    
     In the cellular phone  100  of the first embodiment, the planar portions  172   b , the supporting portions  172   a , the pushers  172   c , and the locking pawl  172   e  are integrally formed of an elastic material. The supporting portion  172   a  at the end of the key rubber  172  and the locking pawl  172   e  are integrally formed by a resin portion  172   d  and an elastic portion  172   i  formed of an elastic material around the resin portion  172   d.    
     According to the cellular phone  100  of the first embodiment, the key rubber  172  may be prevented from peeling off due to the pressure of the folded portion  148   a  of the key flexible cable  148 . Because the slide module  156  is provided in the direction in which the folded portion  148   a  of the key flexible cable  148  bends due to the weight of the key flexible cable  148 , the folded portion  148   a  is pressed toward the key rubber  172  by the reaction force of the flexible cable  148  generated by contacting the slide module  156 . The pressed folded portion  148   a  comes into contact with the contact portion  172   f  of the locking pawl  172   e  and presses the key rubber  172  in the direction in which the key rubber  172  peels off of the printed board module  130 . Because the locking portion  172   g  is formed on the surface opposite to the contact portion  172   f  of the locking pawl  172   e , the locking portion  172   g  engages with the protrusion  110   a  formed on the inner wall of the side of the display-side case  110 . Because the pressing force from the folded portion  148   a  is applied to the protrusion  110   a , the force peeling the key rubber  172  is reduced. According to the cellular phone  100  of the first embodiment, the key rubber  172  may be prevented from peeling off due to the pressure of the folded portion  148   a  of the key flexible cable  148 . 
     According to the cellular phone  100  of the first embodiment, the need to separately providing a member for preventing the key rubber  172  from peeling off due to the pressure of the folded portion  148   a , for example, on the key flexible board  140  is eliminated. Therefore, the first embodiment may contribute to the reduction in thickness of the cellular phone  100 . The member for preventing the key rubber  172  from peeling off is formed, for example, of resin. In the cellular phone  100  of the first embodiment, the printed board module  130  and the key rubber  172  may be fixed to each other by providing a locking pawl  172   e  without depending only on the adhesion force of the double-sided tape  172   h . According to the cellular phone  100  of the first embodiment, because the locking portion  172   g  is formed by the elastic portion  172   i , noise may be prevented from being generated even if the locking portion  172   g  and the protrusion  110   a  rub together. According to the cellular phone  100  of the first embodiment, because the locking portion  172   g  is formed by the elastic portion  172   i , and the elastic portion  172   i  serves as a cushion, the dimension tolerance may be set within a wide range. 
     [Second Embodiment ] 
       FIG. 8  is a plan view of a cellular phone of a second embodiment.  FIG. 9  is a sectional view illustrating part of the section of the cellular phone of  FIG. 8  taken along line IX-IX.  FIG. 10  is an enlarged view of a locking pawl portion of the second embodiment. The second embodiment differs from the first embodiment in the configuration of the key rubber. The other components are the same as those of the first embodiment, and the redundant description thereof will be omitted. 
     As illustrated in  FIG. 9 , a key rubber  272  has planar portions  272   b  opposite to the metal domes  132  provided on the key flexible board  140 . The key rubber  272  has pushers  272   c  that are protrusions formed at positions on the metal dome  132  side surfaces of the planar portions  272   b  corresponding to the metal domes  132 . On the top tape  160 , supporting portions  270  are provided that floatingly support the planar portions  272   b  at the ends of the top tape  160  and the flat portions of the top tape  160  where the metal domes  132  are not provided. The supporting members  270  are bonded to the top tape  160  with double-sided tape  172   h . The planar portions  272   b  are bonded to and cover the supporting portions  270 . Key tops  174  are bonded to the surfaces of the planar portions  272   b  opposite to the surfaces on which the pushers  272   c  are formed. The supporting portions  270  may be formed, for example, of polycarbonate. 
     As illustrated in  FIGS. 9 and 10 , from the supporting portion  270  bonded to the end of the top tape  160 , a locking pawl  270   a  extends in the direction of the side of the display-side case  110 . The locking pawl  270   a  has a contact portion  270   b  that is in contact with the folded portion  148   a  being pressed by the slide module  156 . On the surface opposite to the contact portion  270   b  of the locking pawl  270   a , a locking portion  270   c  may formed that may engage with a protrusion  110   a  formed on the inner wall of the side of the display-side case  110 . The second embodiment has been described with an example in which the folded portion  148   a  is in contact with and pressed by the slide module  156 . The second embodiment may also be applied to the case where the folded portion  148   a  is in contact with and pressed by another member provided in the bending direction of the folded portion  148   a.    
     In the cellular phone of the second embodiment, the supporting portions  270  and the locking pawl  270   a  are integrally formed of a resin material. The planar portions  272   b  and the pushers  272   c  are integrally formed of an elastic material. A resin portion integrally formed by the supporting portions  270  and the locking pawl  270   a  and an elastic portion integrally formed by the planar portions  272   b  and the pushers  272   c  are formed separately. The elastic portion is bonded to the resin portion. 
     According to the cellular phone  100  of the second embodiment, the key rubber  272  may be prevented from peeling off due to the pressure of the folded portion  148   a  of the key flexible cable  148 . Because the slide module  156  is provided in the direction in which the folded portion  148   a  of the key flexible cable  148  bends due to the weight of the key flexible cable  148 , the folded portion  148   a  comes into contact with the slide module  156  and is pressed toward the key rubber  272 . The folded portion  148   a  pressed by the slide module  156  comes into contact with the contact portion  270   b  of the locking pawl  270   a  and presses the key rubber  272  in the direction in which the key rubber  272  peels off of the printed board module  130 . Because the locking portion  270   c  is formed on the surface opposite to the contact portion  270   b  of the locking pawl  270   a , the locking portion  270   c  engages with the protrusion  110   a  formed on the inner wall of the side of the display-side case  110 . Because the pressing force from the folded portion  148   a  is applied to the protrusion  110   a , the force peeling the key rubber  272  is reduced. According to the cellular phone  100  of the second embodiment, the key rubber  272  may be prevented from peeling off due to the pressure of the folded portion  148   a  of the key flexible cable  148 . 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present inventions has been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.