Abstract:
An electronic apparatus includes a first housing; a second housing; and a coupling unit that openably/closably and rotatably couples the second housing with the first housing. The coupling unit is a biaxial coupling unit having: a rotation axis that vertically extends when the first housing is placed on a horizontal table, and is rotatably coupled to the first housing; and an opening/closing axis that is fixed to the rotation axis, horizontally extends, openably/closably supports the second housing with respect to the first housing, and rotates as the rotation axis rotates. The coupling unit includes a stopper to rotate the rotation axis-only when the second housing is opened with respect to the first housing within a range of rotation-allowing opening angle that allows for rotation.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an electronic apparatus in which a second housing is openably/closably and rotatably coupled with respect to a first housing. 
   2. Description of the Related Art 
   In portable electronic apparatuses such as laptop personal computers and mobile phones, a configuration in which an upper housing having a display screen is openably/closably coupled with respect to a lower housing having a keyboard and a push button has been widely used. Such an electronic apparatus is folded so that the upper housing is laid over the lower housing when the apparatus is carried around, and at the time of operation, the upper housing is opened so that the keyboard and push button may be used; thus the portability of the apparatus is increased without downsizing the keyboard and push button. 
   Further, in recent years, electronic apparatuses have also been known in which an upper housing is openably/closably and rotatably coupled with respect to a lower housing (see, for example, Japanese Patent Application Publication No. 8-191420 and Japanese Patent Application Publication No. 2004-118409). For example, when a number of persons see the display screen of one personal computer, by rotating the upper housing to which a display screen is disposed with respect to the lower housing, the display screen can be easily turned to each person. Moreover, in recent years, in addition to a conventional input operation mode using a keyboard or the like, a tablet mode using a touch pen for touching the display screen and moving on the display screen to enter instructions has been incorporated into a personal computer. Furthermore, in such a personal computer, in addition to a touch panel for giving instructions by contact using a touch pen and a finger, an input device that incorporates an electromagnetic induction-type digitizer on the back of the display screen, and detects the position on the display screen indicated with a stylus pen is also used. In the tablet mode, by rotating the upper housing with respect to the lower housing, and laying the upper housing over the lower housing with the display screen turned outward, the personal computer can be easily carried around, and input with the touch pen becomes easy. In this manner, by openably/closably and rotatably coupling the upper housing with respect to the lower housing, the operability of the electronic apparatus can further be improved. 
   Incidentally, although in an electronic apparatus in which an upper housing is rotatable with respect to a lower housing, it is usually assumed that the upper housing is rotated with the upper housing standing with respect to the lower housing, practically, a user who is not familiar with the operation of the apparatus sometimes rotates the upper housing with the apparatus closed or with the apparatus widely opened, which may cause the upper housing and the lower housing to rub against each other and get damaged, or may cause the breakage of the display screen. Conventionally, although a hook to fix the upper housing to the lower housing is sometimes provided on the top of the display screen in order to prevent the rotation in a closed state, there are problems that the appearance is deteriorated, and a case where the upper housing is rotated with the upper housing widely opened cannot be addressed. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in view of the above circumstances and provides an electronic apparatus that can prevent damages from occurring when a housing is being rotated. 
   An electronic apparatus of the present invention, including: 
   a first housing; 
   a second housing; and 
   a coupling unit that openably/closably and rotatably couples the second housing with the first housing, 
   wherein the coupling unit, 
   which is a biaxial coupling unit having a rotation axis that vertically extends when the first housing is placed on a horizontal table, and is rotatably coupled to the first housing, and an opening/closing axis that is fixed to the rotation axis, horizontally extends, openably/closably supports the second housing with respect to the first housing, and rotates as the rotation axis rotates, 
   the coupling unit includes stoppers to rotate the rotation axis only when the second housing is opened with respect to the first housing within a range of rotation-allowing opening angle that allows for rotation. 
   In the electronic apparatus of the present invention, although the second housing is openably/closably and rotatably coupled to the first housing, the rotation of the second housing is prohibited by the stoppers when the second housing is opened with respect to the first housing beyond the range of rotation-allowing opening angle that allows for rotation. Therefore, a problem that the second housing is rotated with the second housing closed or widely opened with respect to the first housing, and hits an obstacle, which results in the breakage of the second housing, can be prevented. 
   Further, in the electronic apparatus of the present invention, it is preferred that the stoppers are unrotatably supported by the first housing, and each of the stoppers and the rotation axis have a stopper-side fitting section and a rotation axis-side fitting section, respectively, which are fitted into each other in a closed state in which the second housing is laid over the first housing, and 
   the stopper and a second housing assembly, which includes the second housing and the opening/closing axis, have a stopper-side contact member and a second housing-side contact member, respectively, which are brought into contact with each other to release the fit of the stopper-side fitting section into the rotation axis-side fitting section when the second housing is opened within the range of rotation-allowing opening angle from the closed state. 
   When the second housing is in the closed state in which the second housing is laid over the first housing, the stopper-side fitting section and the rotation axis-side fitting section are fitted into each other to prohibit the rotation of the second housing, and when the second housing is opened within the range of rotation-allowing opening angle from the closed state, the stopper-side contact member and the second housing-side contact member are brought into contact with each other to release the fit of the stopper-side fitting section into the rotation axis-side fitting section, allowing the open/closed state of the second housing and the prohibition/release of the rotation of the second housing to be easily interlocked. Further, although conventionally, a lock mechanism to stop rotation is usually provided near the display screen so that the housing is not rotated when the personal computer is carried around with the personal computer closed, in the electronic apparatus of the present invention, in the closed state, the rotation of the second housing is prohibited, allowing the lock mechanism near the display screen to be eliminated, which presents an excellent design advantage. 
   Further, in the electronic apparatus of the present invention, it is preferred that when the second housing is rotated about the rotation axis after the second housing-side contact member is brought into contact with the stopper-side contact member, the contact of the second housing-side contact member with the stopper-side contact member is released, and the release of the fit of the stopper-side fitting section into the rotation axis-side fitting section is kept. 
   According to the preferred electronic apparatus, in a state in which the second housing is opened/closed beyond the range of rotation-allowing opening angle, the rotation of the second housing can be prohibited, on the other hand, when the second housing is opened/closed beyond the range of rotation-allowing opening angle after the second housing is rotated, the rotation of the second housing can be allowed. 
   Furthermore, in the electronic apparatus of the present invention, it is preferred that the stopper-side fitting section is formed of a protruding portion that protrudes upward, and the rotation axis-side fitting section is formed of a depressed portion that opens downward, and into which the protruding portion is fitted, 
   the stopper is energized upward by a spring and the protruding portion is fitted into the depressed portion in the closed state, and the second housing-side contact member pushes down the stopper-side contact member from above to remove the protruding portion from the depressed portion when the second housing is opened within the range of rotation-allowing opening angle from the closed state. 
   In the closed state of the second housing, the protruding portion of the stopper-side fitting section is fitted into the depressed portion of the rotation axis-side fitting section to prohibit the rotation of the second section, and when the second housing is opened within the range of rotation-allowing opening angle from the closed state, the second housing-side contact member provided on the second housing pushes down the stopper-side contact member from above to push down the depressed portion of the stopper-side fitting section, allowing the prohibition/release of the rotation of the second housing to be easily controlled. 
   Furthermore, in the electronic apparatus of the present invention, it is preferred that a set of the stopper-side fitting section and the rotation axis-side fitting section, and a set of the stopper-side contact member and the second housing-side contact member are provided, respectively, on both sides of the center of the rotation axis. 
   The set of the stopper-side fitting section and the rotation axis-side fitting section, and the set of the stopper-side contact member and the second housing-side contact member are provided, respectively, on both sides of the center of the rotation axis, thus allowing the prohibition/release of the rotation of the second housing to be reliably controlled, and preventing the interference of the stopper-side contact member with the second housing-side contact member after the start of rotation of the second housing, which results in achievement of smooth rotation. 
   Further, in the electronic apparatus of the present invention, it is preferred that the stopper-side contact member is made of a stiffer material than that of a portion other than the stopper-side fitting section of the stopper. 
   The stopper-side contact member is made of the stiffer material, thus allowing abrasion due to contact with the second housing-side contact member to be suppressed. 
   Furthermore, in the electronic apparatus of the present invention, it is preferred that the stopper has an arm extending on both sides of the center of the rotation axis, the stopper-side fitting section at a position halfway of the arm, and the stopper-side contact member at an end of the arm. 
   According to the preferred electronic apparatus, the prohibition/release of the rotation of the second housing can be controlled with a simple mechanism. 
   Moreover, in the electronic apparatus of the present invention, it is preferred that the second housing-side contact member is a metal member, and the stopper-side contact member is a resin member having a higher lubricating property than that of the second housing-side contact member. Selecting the material of each contact member in this manner allows generation of flakes from the stopper-side contact member due to the rotation of the second housing to be prevented, and allows malfunction of the electronic apparatus due to the penetration of the flakes into the second housing to be prevented. 
   Further, in the electronic apparatus of the present invention, it is preferred that the second housing has a display screen where information is displayed. 
   Furthermore, in the electronic apparatus of the present invention, it is preferred that the first housing has a keyboard by which instructions corresponding to operation are entered. 
   Moreover, in the electronic apparatus of the present invention, it is preferred that the electronic apparatus is provided with display control means that displays, in a first usage state in which the second housing is opened with respect to the first housing, information in a first display mode in which information is displayed on the display screen with the direction of the rotation axis as the vertical direction, and also displays, in a second usage state in which the second housing is laid over the first housing with the display screen turned outward, information in a second display mode in which information is displayed with the direction perpendicular to the rotation axis as the vertical direction. 
   A tablet personal computer is convenient when it can be used in such a manner that, in a normal usage state (first usage state) using a keyboard or the like, the display screen is used in landscape orientation with the direction of the rotation axis as the vertical direction, and when the tablet function is used (second usage state), the display screen is used in portrait orientation with the direction perpendicular to the rotation axis as the vertical direction. According to the electronic apparatus of the present invention, information can be displayed in the orientation that is suited to each application in the first usage state and the second usage state. 
   According to the present invention, in an electronic apparatus in which two housings are openably/closably and rotatably coupled to each other, damages occurring when the housing is being rotated can be prevented. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exterior perspective view of a personal computer to which an embodiment of the present invention is applied; 
       FIG. 2  is an exterior perspective view showing an electronic apparatus in a state in which a display unit is closed over a main unit; 
       FIG. 3  is an exterior perspective view showing a state in which the display unit is rotated almost 90 degrees with respect to the main unit; 
       FIG. 4  is an exterior perspective view showing a state in which the display unit is laid over the main unit with the display screen turned upward; 
       FIG. 5  is a diagram of the internal configuration of the personal computer; 
       FIG. 6  is a magnified view of a coupling unit; 
       FIG. 7  is a magnified view of the coupling unit in a state in which the display unit is standing with respect to the main unit; 
       FIG. 8  is a magnified view around the coupling unit while the personal computer is being assembled; 
       FIG. 9  is magnified view around the coupling unit in the personal computer that has been assembled; and 
       FIGS. 10(A)  and (B) are diagrams illustrating the method of restricting/releasing the rotation of the display unit in the coupling unit. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An embodiment of the present invention will now be described with reference to the drawings. 
     FIG. 1  is an exterior perspective view of a personal computer to which an embodiment of the present invention is applied. 
   A personal computer  10  shown in  FIG. 1  is provided with an input device that incorporates an electromagnetic induction-type digitizer on the back side of a display screen  31 , and detects the position on the display screen  31  indicated with a stylus pen so as to allow instruction input. Note that, as the input device, a touch panel which is incorporated into the display screen  31  may be used instead of the digitizer and the stylus pen. 
   The personal computer  10  is provided with a main unit  20  and a display unit  30 , and the main unit  20  and the display unit  30  are coupled by a biaxial coupling unit  40  so that the display unit  30  can be opened/closed in the arrow A-A direction, and can be rotated (about the rotation axis perpendicular to the main unit  20 ) in the arrow B-B direction, with respect to the main unit  20 . Note that in the personal computer of the present embodiment, in a state in which the display unit  30  is opened/closed beyond a predetermined specified opening angle (80 to 100 degrees in the present embodiment) with the coupling unit  40 , the rotation of the display unit  30  about the rotation axis is prohibited by a rotation control mechanism. The rotation control mechanism will be described later. The personal computer  10  is shown in  FIG. 1  in a state in which the display unit  30  is opened with respect to the main unit  20  (open state), and the open state corresponds to the first usage state according to the present invention. Further, the main unit  20  corresponds to an example of the first housing according to the present invention, the display unit  30  corresponds to an example of the second housing according to the present invention, and the coupling unit  40  corresponds to an example of the coupling unit according to the present invention. 
   The main unit  20  is provided with a keyboard  21 , a track pad  22 , a left click button  23  and a right click button  24 , as well as a rubber display unit receiver  34  to reduce abrasion due to collision caused when the display unit  30  is opened/closed and rotated. Furthermore, the main unit  20  is provided with, on its one side, an opening/closing cover  26   a  for an optical disk drive  26  where an optical disk such as CDs and DVDs is loaded, driven and accessed, and an eject button  26   b , which is pushed to open the opening/closing cover  26   a , is provided on the opening/closing cover  26   a . The keyboard  21  corresponds to an example of the keyboard according to the present invention. 
   The display unit  30  of the personal computer  10  has the display screen  31  spreading over the front surface thereof. Further, the display unit  30  has push buttons  32  on its right edge under the display screen  31 , and a fingerprint sensor  33 , which recognizes a fingerprint when a person moves his/her finger along the sensor, on its left edge. The display screen  31  corresponds to an example of the display screen according to the present invention. In the open state shown in  FIG. 1 , information is displayed on the display screen  31  with the direction of the rotation axis of the display unit  30  as the vertical direction. 
     FIG. 2  is an exterior perspective view showing the electronic apparatus in a state in which the display unit  30  is closed over the main unit  20 . 
   In  FIG. 2 , the display unit  30  is laid over the main unit  20  with the display screen  31  (see  FIG. 1 ) turned toward the main unit  20 . Hereinafter, this state is referred to as a first closed state. 
   In an open state shown in  FIG. 1 , when the display unit  30  is closed in the arrow A direction, as shown in  FIG. 2 , the display screen  31  is hidden inward, and the back of the display screen  31  is exposed outward, which is in the first closed state. The personal computer  10  can be carried around in the first closed state, which prevents damages and dirt onto the display screen  31 . 
     FIG. 3  is an exterior perspective view showing a state in which the display unit is rotated almost 90 degrees with respect to the main unit. 
   The display unit  30  can be rotated via this state so that the display screen  31  is turned to the side opposite to the keyboard  21 . 
     FIG. 4  is an exterior perspective view showing a state in which the display unit is laid over the main unit so that the display screen is turned upward. 
   The display unit  30  is rotated via an attitude shown in  FIG. 3  so that the display screen  31  is turned to the side opposite to the keyboard  21 , and then the display unit  30  is laid over the main unit  20  with the back of the display screen  31  of the display unit  30  turned toward the main unit  20 , which is in a second closed state shown in  FIG. 4 . The second closed state corresponds to an example of the second usage state according to the present invention. Hereinafter, an operation mode in which the personal computer  10  is used in the second closed state is referred to as a tablet mode. 
   As described above, the display screen  31  is a display screen having a pen input function, which is provided with an electromagnetic induction-type digitizer on the back side thereof, and detects the position indicated on the display screen; the usually adopted usage mode is one in which the personal computer  10  in the tablet mode is held with one arm, and the display screen is operated by holding a pen (not shown) with the hand of the other arm. Considering the relationship with the line of sight when the personal computer  10  in the tablet mode is held with an arm, the display image on the display screen  31  is rotated by 90 degrees compared to the open state shown in  FIG. 1 . That is to say, in the tablet mode, information is displayed on the display screen  31  with the direction perpendicular to the rotation axis of the display unit  30  as the vertical direction. 
   Then, the internal configuration of the personal computer  10  will be described. 
     FIG. 5  is a diagram of the internal configuration of the personal computer  10 . 
   As shown in  FIG. 5 , the personal computer  10  incorporates a CPU  101  that executes various programs, a main memory  102  to which the program stored in a hard disk device  103  is read out to be executed by the CPU  101 , the hard disk device  103  in which the various programs and data are stored, a display mechanism  104  that is responsible for processing information display, an operator  106  that includes the keyboard  21  and the track pad  22 , a small recording medium drive  108  where a small recording medium  200  is loaded and accessed, a CD/DVD drive  109  where a CD-ROM  210  or a DVD is loaded and accessed, an input interface  105  that inputs data from an external device, an output interface  110  that outputs data to an external device, and the fingerprint sensor  33 , which is also shown in  FIG. 1 , and each component is connected to one another through a bas  111 . Note that the display mechanism  104  is composed of a display controller  1041  that controls the orientation of information displayed on the display screen  31  shown in  FIG. 1 , a display device  1042  that displays information on the display screen  31 , and a digitizer  1043  that is mounted on the back of the display screen  31 . The display controller  1041  corresponds to an example of the display control section according to the present invention. 
   Then, the coupling unit  40  will be described in detail. 
     FIG. 6  is a magnified view of the coupling unit  40 . 
     FIG. 6  shows the coupling unit  40  in a state in which the display unit  30  is fully opened with respect to the main unit  20 . The coupling unit  40  includes stoppers  300  that prohibit the rotation of the display unit  30 , a rotation section  400  that rotates the display unit  30  in the arrow B direction in  FIG. 1 , and opening/closing sections  500  that open/close the display unit  30  in the arrow A direction in  FIG. 1 . The stopper  300  corresponds to an example of the stopper according to the present invention, the rotation section  400  corresponds to an example of the rotation axis according to the present invention, and the opening/closing section  500  corresponds to an example of the, opening/closing axis according to the present invention. 
   Each stopper  300  is energized vertically upward (upward in  FIG. 6 ) with respect to the main unit  20 , and has an arm  310  extending from the center of the rotation axis of the display unit  30  to one side. A protrusion  320  protruding vertically upward (upward in  FIG. 6 ) from the end of each arm  310  with respect to the main unit  20  is also provided. The arm  310  is made of a metal material, and the protrusion  320  is made of a resin material having a higher lubricating property than that of the arm  310 . The arm  310  corresponds to the arm according to the present invention, and the protrusion  320  corresponds to an example of the stopper-side contact member according to the present invention. 
   The rotation section  400  has a rotor  410  which serves as the rotation axis of the display unit  30 , and an arm  420  that extends from the rotor  410 , and extends from the center of the rotation axis to both sides, and has the opening/closing sections  500 , which are attached on each side. 
   Each opening/closing section  500  opens/closes the display unit  30  by rotating about the arm  420  of the rotation section  400 , and has a fixture  510  that is fixed to the display unit  30 , and a front section  520  that is formed on a portion of the fixture  510 , and comes into contact with the protrusion  320  on the stopper  300 . The opening/closing section  500  rotates with the arm  420  extending from the rotor  410  when the rotor  410  of the rotation section  400  is rotated. The fixture  510  and the front section  520  provided thereon are made of a metal member as with the arm  420 . The front section  520  corresponds to an example of the second housing-side contact member according to the present invention. The front section  520  has a tapered shape whose peripheral portion coming into contact with the protrusion  320  of the stopper  300  has a predetermined curve to allow the rotation control described later to be achieved. 
   In  FIG. 6 , the fixture  510  of the opening/closing section  500  is laid, the front section  520  is turned forward, and the display unit  30  is fully opened with respect to the main unit  20 . When the display unit  30  is erected, the opening/closing section  500  rotates about the arm  420  to close the display unit  30 . At that time, the front section  520  of the opening/closing section  500  moves downward as the display unit  30  is closed, and gradually pushes down the protrusion  320  of the stopper  300 . 
     FIG. 7  is a magnified view of the coupling unit  40  in a state in which the display unit  30  is standing with respect to the main unit  20 . 
   When the display unit  30  is standing with respect to the main unit  20 , the front section  520  of the opening/closing section  500  is turned vertically downward (downward in  FIG. 6 ) with respect to the main unit  20 , and the protrusion  320  of the stopper  300  is pushed down most. 
     FIG. 8  is a magnified view around the coupling unit while the personal computer  10  is being assembled. 
   As shown in  FIG. 8 , the rotor  410  of the rotation section  400  is housed in the main unit  20 , the arm  310  of the rotation section  400  is housed in the display unit  30 , the fixture  510  of the opening/closing section  500  is fixed to the display unit  30 , the front section  520  of the opening/closing section  500  protrudes from the under surface of the display unit  30 , the arm  310  of the stopper  300  is housed in the main unit  20 , the protrusion  320  of the stopper  300  protrudes from the main unit  20  and faces the front section  520  of the opening/closing section  500 . 
     FIG. 9  is magnified view around the coupling unit in the personal computer  10  that has been assembled. 
   As shown in  FIG. 9 , the side of the main unit  20  that is closer to the coupling unit  40  than the keyboard  21  is covered with a cover  28 , and the rotor  410  of the rotation section  400  and the arm  310  of the stopper  300  are hidden. 
   Basically, the coupling unit  40  is constituted as described above. 
   Then, the method of restricting/releasing the rotation of the display unit  30  in the coupling unit  40  will be described in detail. 
     FIGS. 10(A)  and (B) are diagrams illustrating the method of restricting/releasing the rotation of the display unit  30  in the coupling unit  40 . 
     FIG. 10(A)  schematically shows the configuration of the coupling unit  40  in a state in which the display unit  30  is fully opened with respect to the main unit  20 . 
   The rotor  410  of the rotation section  400  has a depressed portion  401 , which opens downward, and the arm  310  of the stopper  300  has a protruding portion  301 , which protrudes upward, and is fitted into the depressed portion  401  of the rotor  410 . The depressed portion  401  corresponds to an example of the rotation axis-side fitting section according to the present invention, and also corresponds to an example of the depressed portion according to the present invention. Further, the protruding portion  301  corresponds to an example of the stopper-side fitting section, and also corresponds to an example of the protruding portion according to the present invention. 
   When the display unit  30  is widely opened with respect to the main unit  20 , the opening/closing section  500  is laid with respect to the body unit  20 , and the front section  520  of the opening/closing section  500  is not pushing down the protrusion  320  of the stopper  300 . Since the stopper  300  is energized upward by a spring with respect to the main unit  20 , in a state shown in  FIG. 10(A) , the protruding portion  301  of the stopper  300  is fitted into the depressed portion  401  of the rotation section  400  to prohibit the rotation of the rotation section  400 . 
   When the display unit  30  is gradually erected from the state shown in  FIG. 10(A) , the opening/closing section  500  stands with respect to the main unit  20 , and the front section  520  of the opening/closing section  500  starts pushing down the protrusion  320  of the stopper  300 . As a result, the stopper  300  is pushed down, and the protruding portion  301  of the stopper  300  starts disengaging from the depressed portion  401 . 
     FIG. 10(B)  schematically shows the configuration of the coupling unit  40  in a state in which the display unit  30  is standing with respect to the main unit  20 . 
   When the display unit  30  is erected and the opening/closing angle reaches the upper limit of a predetermined specified opening angle (80 to 100 degrees in this example), the protruding portion  301  of the stopper  300  fully disengages from the depressed portion  401 , and the prohibition of the rotation of the rotation section  400  by the stopper  300  is released. In the standing state shown in  FIG. 10(B) , the front section  520  of the opening/closing section  500  is erected with respect to the main unit  20 , thus the stopper  300  is pushed down most. 
   When the display unit  30  is rotated in a state in which the prohibition of the rotation by the stopper  300  is released, the opening/closing section  500  mounted on the arm  420  of the rotation section  400  and fixed to the display unit  30  also rotates with the rotation section  400 . At that time, since a set of the protrusion  320  of the stopper  300  and the front section  520  of the opening/closing section  500 , which are brought into contact with each other, are provided only on both sides of the center of the rotation axis of the rotation section  400 , when the rotation section  400  rotates, the contact of the stopper  300  with the opening/closing section  500  are released, thus allowing smooth rotation to be achieved. 
   When the display unit is further closed from the state shown in  FIG. 10(B) , the opening/closing section  500  is laid forward so as to allow the fixture  510  to face the main unit  20  as compared with  FIG. 10(A) , weakening the force of the front section  520  of the opening/closing section  500  that pushes down the protrusion  320  of the stopper  300 . When the display unit  30  is closed, and the opening/closing angle reaches the lower limit of the predetermined specified opening angle (80 to 100 degrees in this example), the stopper  300  is energized upward by the spring, thus the protruding portion  301  of the stopper  300  is fitted into the depressed portion  401 . 
   In this manner, according to the present embodiment, since the rotation is allowed only when the display unit  30  is at the predetermined specified opening angle (80 to 100 degrees in this example) with respect to the main unit  20 , a problem that the display screen  31  is broken because the display unit  30  is rotated when the display unit  30  is closed or widely opened can be prevented. 
   In addition, as shown in  FIG. 10(B) , since the rotation is prohibited when the display unit  30  is closed with respect to the main unit  20 , a lock mechanism provided in a conventional personal computer to stop the rotation of the display unit  30  need not be provided near the display screen  31 , allowing the design to be improved. 
   Although an example in which the electronic apparatus of the present invention is applied to a tablet personal computer has been described herein, the electronic apparatus of the present invention may be applied to a personal computer without a tablet function, an electronic notepad, and the like.