Abstract:
A biaxial hinge in which a first casing and a second casing of a terminal device can open and close 360 degrees relative to each other, with a simplified structure, enhanced opening and closing speed and an improved operability. A first hinge shaft attached to the second casing via a first attaching plate is rotatable in parallel to a second hinge shaft attached to the first casing via a second attaching plate with help of several joint members. A module for restricting rotation of the first hinge shaft and the second hinge shaft is provided in association with the joint members. The module for restricting rotation includes modules for generating friction torque, modules for sucking, stopper modules for restricting a rotation angle of the first hinge shaft and the second hinge shaft, and a module for synchronously rotating hinge shafts.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a biaxial hinge suitably used in opening and closing a first casing relative to a second casing of a terminal device such as a notebook PC, a mobile PC and a PDA. 
         [0003]    2. Background of the Invention 
         [0004]    Among terminal devices, such as notebook PC, mobile PC and PDA, which comprise a first casing provided with a keyboard portion and a second casing provided with a display portion, uniaxial hinges are sometimes used, wherein the hinges connect the first casing and the second casing, such that both casings can open and close in an upward and downward direction; in other cases biaxial hinges are employed, wherein each of the hinges comprises two axes, wherein the second casing can further rotate with regard to the first casing in a horizontal direction, after the former opens 90 to 180 degrees relative to the latter. The present invention relates to the biaxial hinge of these categories. 
         [0005]    Conventionally, a biaxial hinge of the above-mentioned structure is known, such as the one disclosed in JP Laid-Open Patent Application No. 2009-063039. The biaxial hinge according to the patent document is characterized in that a shaft attached to a first member (first casing) is connected to a further shaft attached to a second member (second casing) via a joint arm, and that a means for generating friction torque is provided on each shaft, and that a link arm is provided; however, the hinge is not so designed that the first member can open more than 180 degrees relative to the second member. 
         [0006]    Therefore, a parent company of this Applicant has proposed a biaxial hinge which can meet the above-mentioned requirements (JP Patent Application No. 2013-247542). The configuration of the biaxial hinge is characterized in that a first hinge shaft attached to the first casing side is coupled in parallel to a second hinge shaft attached to the second casing side, via a first joint member and a second joint member; that the first hinge shaft and the second hinge shaft are provided such that the former can rotate relative to the latter; and that a first means for selectively restricting rotation and a second means for selectively restricting rotation are provided between the first hinge shaft and the second hinge shaft, wherein the first means selectively allow the first hinge shaft to rotate and the second means have similar functions on the second hinge shaft; the first and the second means for selectively restricting rotation are constructed such that both means allow the first and the second casings to open and close in a prescribed sequence between the closed state at 0 degree and the opened state at 360 degrees. 
         [0007]    In the above-mentioned prior art, a first means for selectively restricting rotation comprises a locking member provided between a second joint member and a slide guide member, such that the locking member can slide in an upward and downward direction between a first hinge shaft and a second hinge shaft, wherein the locking member comprises a first cam convex portion in an upper portion and a second cam convex portion in a lower portion; a first means for selectively restricting rotation further comprises a first A locking cam member having a first A cam concave portion and a first B cam concave portion, wherein the first A locking cam member is provided above said locking member, and wherein the first hinge shaft passes through and engages with the first locking cam member, and a first B locking cam member having a second A cam concave portion and a second B cam concave portion, wherein the first B locking cam member is provided below the locking member, wherein the second hinge shaft passes through and engages with the first B locking cam member. On the other hand, a second means for selectively restricting rotation comprises a second A locking cam member attached to the first hinge shaft, wherein a rotation of the second A locking cam member is restrained by the first hinge shaft; a second B locking cam member attached to the second hinge shaft, wherein a rotation of the second B locking cam member is restrained by the second hinge shaft; a movement stopper rotatably provided between the second A locking cam member and the second B locking cam member, wherein the movement stopper engages with the second A locking cam member and the second B locking cam member, under specific conditions depending on a rotation angle of the movement stopper; a first stopper lever rotatably attached to the first hinge shaft to engage with the movement stopper, wherein the first stopper lever is brought into a pressurized contact with the second A locking cam member; and a second stopper lever rotatably attached to the second hinge shaft to engage with the movement stopper, wherein the second stopper lever is brought into a pressurized contact with the second B locking cam member. 
         [0008]    However, a further problem arises, in that there are too many components involved and the structure is too complex, which leads to a high manufacturing cost. A manufacturer of terminal devices such as notebook PC would set very strict demands for reducing the costs of the components of the terminal devices. 
       SUMMARY OF THE INVENTION 
       [0009]    Therefore, an object of the invention is to provide a biaxial hinge in which a first casing and a second casing can open and close 360 degrees relative to each other, with a simplified structure, an enhanced opening and closing speed and an improved operability. 
         [0010]    To achieve the above-mentioned object, a biaxial hinge according to the first aspect of the invention allows a first casing and a second casing to open and close relative to each other. In such biaxial hinge, a first hinge shaft attached to the second casing via a first attaching plate can rotate in parallel to said second hinge shaft attached to said first casing via a second attaching plate with help of a plurality of joint members, and a means for restricting rotation is provided in association with the joint members. The biaxial hinge is characterized in that the means for restricting rotation comprises: means for generating friction torque, wherein one is provided on the first hinge shaft and other on the second hinge shaft; means for sucking, wherein one is provided on the first hinge shaft and other on the second hinge shaft; stopper means, wherein one is provided on the first hinge shaft and other on the second hinge shaft, for restricting a rotation angle of the first hinge shaft and the second hinge shaft; and a means for synchronously rotating hinge shafts which allows one hinge shaft to synchronously rotate with a rotation of other hinge shaft, such that one hinge shaft rotates in a direction opposite to other hinge shaft. 
         [0011]    Here, the present invention can be designed such that a means for synchronously rotating hinge shafts comprises a first gear attached to the first hinge shaft, wherein a rotation of the first gear is restrained, and a second gear meshed with the first hinge shaft and attached to the second hinge shaft, wherein a rotation of the second gear is restrained. 
         [0012]    Still further, the present invention can be designed such that a means for synchronously rotating hinge shafts comprises a first gear attached to the first hinge shaft, wherein a rotation of the first gear is restrained, and a second gear meshed with the first hinge shaft and attached to the second hinge shaft, wherein a rotation of the second gear is restrained, and an intermediate gear provided between said first gear and said second gear and conveying a rotation of one gear to other gear, in order to rotate the first gear and the second gear in different directions. 
         [0013]    Still further, a biaxial hinge according to the present invention is characterized in that the stopper means consists of a first stopper means and a second stopper means. The first stopper means comprises: a first A bearing hole provided in an upper part of a stopper plate member also functioning as a first joint member, wherein the first hinge shaft passes through the first A bearing hole, such that the first hinge shaft can rotate; a first stopper projection provided on the outside of the first A bearing hole; and a first projection provided on the first hinge shaft side, wherein the first projection abuts against the first stopper projection or not, depending on a rotation angle of the first hinge shaft. On the other hand, the second stopper means comprises: a first B bearing hole provided in a lower position of the stopper plate member also functioning as the first joint member, wherein the second hinge shaft passes through said first B bearing hole, such that the second hinge shaft can rotate; a second stopper projection provided on the outside of the first B bearing hole; and a second projection provided on the second hinge shaft, wherein the second projection abuts against the second stopper projection or not, depending on a rotation angle of the second hinge shaft. 
         [0014]    Still further, a biaxial hinge according to the present invention is characterized in that means for generating friction torque consists of a first means for generating friction torque and a second means for generating friction torque. The first means for generating friction torque comprises: a first friction washer attached to the first hinge shaft, wherein a rotation of the first friction washer is restrained and wherein the first friction washer is provided between a gear supporting member also functioning as second joint member and a cam plate member also functioning as third joint member; and a first elastic means provided for bringing the gear supporting member and the cam plate member into pressurized contact with the first friction washer. On the other hand, the second means for generating friction torque comprises: a second friction washer attached to the second hinge shaft, wherein a rotation of said second friction washer is restrained and wherein the second friction washer is provided between a gear supporting member also functioning as second joint member and a cam plate member also functioning as third joint member; and a second elastic means provided for bringing the gear supporting member and the cam plate member into pressurized contact with the second friction washer. 
         [0015]    Still further, a biaxial hinge according to the present invention is characterized in that the means for sucking consists of a first means for sucking and a second means for sucking. The first means for sucking comprises: a first A cam concave portion and a first B cam concave portion, each having a substantially circular arc shape, provided outside on one side of said third A bearing hole of a cam plate member also functioning as third joint member, wherein first hinge shaft rotatably passes through the third A bearing hole; a first cam follower comprising a first A cam convex portion and a first B cam convex portion on a side facing the first A cam concave portion and the first B cam concave portion, wherein a rotation of the first cam follower is restrained by the first hinge shaft, such that the first cam follower is attached to the first hinge shaft; and a first elastic means for bringing the first A cam concave portion into a pressurized contact with the first A cam convex portion on one hand, and the first B cam concave portion into a pressurized contact with the first B cam convex portion on the other. On the other hand, the second means for sucking comprises: a second A cam concave portion and a second B cam concave portion, each having a substantially circular arc shape, provided outside on one side of the third A B bearing hole of a cam plate member also functioning as third joint member, wherein the second hinge shaft rotatably passes through the third B bearing hole; a second cam follower comprising a second A cam convex portion and a second B cam convex portion on a side facing the second A cam concave portion and the second B cam concave portion, wherein a rotation of the second cam follower is restrained by the second hinge shaft, such that the second cam follower is attached to the second hinge shaft; and a second elastic means for bringing the second A cam concave portion into a pressurized contact with the second A cam convex portion on one hand, and the second B cam concave portion into a pressurized contact with the second B cam convex portion on the other. 
         [0016]    Still further, a terminal device according to the seventh aspect is characterized in that it uses the biaxial hinge as described in the foregoing. 
         [0017]    The invention is structured as described in the foregoing, so that the biaxial hinge according to the first aspect of the invention can have an operation and effect that a stopper means can restrict a respective rotation of a first and a second hinge shafts up to a prescribed rotation angle; that a means of generating friction torque can generate a friction torque to stably stop a first and a second casings at any opening and closing angle during their opening and closing operation; that a means for sucking can help the first and the second casings to automatically rotate slightly before the fully opened and fully closed state, so that it helps the first and the second casings to automatically close and maintains their closed state, or it helps the first and the second casings to automatically open and maintains their opened state; and that a means for synchronously rotating hinge shafts can open and close one casing at the same time as another casing, when the latter is opened and closed. 
         [0018]    Still further, the present invention can provide the terminal device which enables the first casing and the second casing to synchronously open and close over a total maximum range of 360 degrees. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIGS. 1A and 1B  show a notebook PC being an example of a terminal device, to which a biaxial hinge according to the invention is attached,  FIG. 1A  being a perspective view of the notebook PC (as seen from the front side) in a state in which a second casing is opened relative to a first casing,  FIG. 1B  a perspective view of the notebook PC (as seen from the rear side) in a state in which a first casing is closed relative to a second casing; 
           [0020]      FIG. 2  is a top perspective view of the biaxial hinge according to the invention as attached to a terminal device; 
           [0021]      FIG. 3  is a perspective view of a biaxial hinge according to the invention; 
           [0022]      FIG. 4  is an exploded perspective view of a biaxial hinge according to the invention; 
           [0023]      FIG. 5  is an enlarged perspective view of a first hinge shaft and a second hinge shaft of a biaxial hinge according to the invention; 
           [0024]      FIG. 6  is an enlarged perspective view of a stopper plate member also functioning as a first joint member of a stopper means of a biaxial hinge according to the invention; 
           [0025]      FIG. 7  is an enlarged perspective view of a first gear and a second gear of a biaxial hinge according to the invention; 
           [0026]      FIGS. 8A and 8B  show an intermediate gear of a biaxial hinge according to the invention,  FIG. 8A  being an enlarged elevation view and  FIG. 8B  being an enlarged perspective view thereof; 
           [0027]      FIG. 9  is an enlarged side view of a gear supporting member of a biaxial hinge according to the invention; 
           [0028]      FIGS. 10A and 10B  show a cam plate member of a biaxial hinge according to the invention,  FIG. 10A  being an enlarged side view and  FIG. 10B  being an enlarged elevation view thereof; 
           [0029]      FIGS. 11A ,  11 B and  11 C show a first cam follower and a second cam follower of a biaxial hinge according to the invention,  FIG. 11A  being an enlarged left side view,  FIG. 11B  being an enlarged elevation view and  FIG. 11C  being an enlarged plan view thereof; 
           [0030]      FIGS. 12A and 12B  show a hinge case of a biaxial hinge according to the invention,  FIG. 12A  being a side view and  FIG. 12B  being a cross section along line A-A of  FIG. 12A ; 
           [0031]      FIGS. 13A and 13B  are explanatory views of a stopper means of a biaxial hinge according to the invention,  FIG. 13A  showing it when a first casing is closed relative to a second casing, and  FIG. 13B  when both a first casing and a second casing are respectively opened 180 degrees from their original position; and 
           [0032]      FIG. 14  is an explanatory view illustrating an operation of a biaxial hinge according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    Hereinafter, based on the drawings, reference is made to the embodiments in which a biaxial hinge according to the invention is applied to a notebook PC as an example of terminal devices. The biaxial hinge according to the invention is not limited to application in a notebook PC, but also applicable to terminal devices, such as a mobile PC, PDA and others, comprising a first casing and a second casing which are coupled to each other, such that the casings can open and close in a range of 180 degrees or more in an upward and downward direction. 
         [0034]      FIGS. 1A and 1B  show a notebook PC  1  being an example of a terminal device using a biaxial hinge according to the invention. The notebook PC  1  comprises a first casing  2  provided with a key board portion  2   a  and a second casing  3  provided with a display portion  3   a , and the casings are coupled via a pair of biaxial hinges  4  and  5  to each other at spots on the right and left sides of their respective rear portions such that the casings can open and close. 
         [0035]    Since both biaxial hinges  4  and  5  have an identical structure, reference will be exclusively made to a biaxial hinge  4  in the following, and not to other biaxial hinge  5 . Of course, biaxial hinge denoted with reference numeral  5  can be manufactured in a manner different from the biaxial hinge  4 , as long as no inconvenience occurs in their operation. 
         [0036]      FIGS. 2 to 12  show an embodiment of a biaxial hinge  4  according to the invention. Specifically in  FIGS. 2 to 5 , a reference numeral  10  and  12  denote a first hinge shaft and a second hinge shaft, respectively. These two elements have identical structure, except that a first hinge shaft  10  has one more attaching holes  10   b  than attaching holes  12   b  of a second hinge shaft  12 . Therefore, the first hinge shaft  10  is shown in  FIG. 5 , and as per the second hinge shaft  12 , its reference numeral only appears in parentheses next to the reference numeral  10 . First, reference is made to a structure of a first hinge shaft  10 : the first hinge shaft comprises, as seen from one end in particular as shown in  FIGS. 4 and 5 , an attaching plate portion  10   a  having a substantially flat cross section, wherein attaching holes  10   b ,  10   b ,  10   b  are provided on its surface; a flange portion  10   c  provided next to the attaching plate portion  10   a ; a circular shaft portion  10   d  provided next to the flange portion  10   c ; a first deformed shaft portion  10   e  provided next to the circular shaft portion  10   d  and having a substantially elliptic cross section with a slightly smaller diameter than the circular shaft portion  10   d ; a second deformed shaft portion  10   f  provided next to the first deformed shaft portion  10   e  and having a substantially elliptic cross section with a slightly smaller diameter than the first deformed shaft portion  10   e ; a male screw portion  10   g  provided next to the second deformed shaft portion  10   f ; and a first projection portion  10   h  provided on an outer circumference of the circular shaft portion  10   d.    
         [0037]    As shown in  FIGS. 2 to 4 , a first attaching plate  11  is attached to an attaching plate portion  10   a ; as per mode of attaching, the former is attached to the latter by caulking respective ends of flanged attaching pins  10   i ,  10   i , as the attaching pins pass through two attaching holes  10   b ,  10   b  of three attaching holes  10   b ,  10   b ,  10   b  of a first hinge shaft  10  and attaching holes  11   a ,  11   a  of the first attaching plate  11 . And then, especially as shown in  FIG. 2 , the first attaching plate  11  is attached using attaching screws  3   c ,  3   c  to a lower surface side of a second casing  3  via attaching holes  11   b ,  11   b  of the first attaching plate  11 . In the meantime, attaching screws can be used instead of the attaching pins  10   i ,  10   i.    
         [0038]    Next, as shown in  FIGS. 2 to 5  as well, a reference numeral  12  denotes a second hinge shaft, which is placed in parallel to a first hinge shaft  10  in upward and downward direction. The second hinge shaft  12  comprises, as seen from one end in particular as shown in  FIGS. 4 and 5 , an attaching plate portion  12   a  having a substantially flat cross section, wherein attaching holes  12   b ,  12   b  are provided on its surface; a flange portion  12   c  provided next to the attaching plate portion  12   a ; a circular shaft portion  12   d  provided next to the flange portion  12   c ; a first deformed shaft portion  12   e  provided next to the circular shaft portion  12   d  and having a substantially elliptic cross section with a slightly smaller diameter than the circular shaft portion  12   d ; a second deformed shaft portion  12   f  provided next to the first deformed shaft portion  12   e  and having a substantially elliptic cross section as well, but with a smaller diameter than the first deformed shaft portion  12   e ; a male screw portion  12   g  provided next to the second deformed shaft portion  12   f ; and a second projection  12   h  provided on an outer circumference of the circular shaft portion  12   d.    
         [0039]    As shown in  FIGS. 2 to 4 , a second attaching plate  13  is attached to an attaching plate portion  12   a ; as per mode of attaching, the former is attached to the latter by caulking respective ends of flanged attaching pins  12   i ,  12   i  as the attaching pins pass through attaching holes  12   b ,  12   b  of a second hinge shaft  12  and attaching holes  13   a ,  13   a  of the second attaching plate  13 . And then, the second attaching plate  13  is attached using attaching screws  2   c ,  2   c  to an upper surface side of a first casing  2  via attaching holes  13   b ,  13   b  of the second attaching plate  13 . In the meantime, attaching screws can be used instead of the attaching pins  12   i ,  12   i.    
         [0040]    Next, reference is made to a means for controlling rotation  4   a  provided between a first hinge shaft  10  and a second hinge shaft  12 , and in particular its components will be described one after another in the following. The means for controlling rotation  4   a  consists of a stopper means  15 , a means for synchronously rotating hinge shafts  16 , an elastic means  21 , a means for generating friction torque  30  and a means for sucking  35 . First, reference is made to the stopper means  15  for restricting a rotation angle of the first hinge shaft  10  and the second hinge shaft  12 . The stopper means  15  comprises a first stopper means  15   a  and a second stopper means  15   b , as shown in  FIGS. 3 ,  4  and  13 . The first stopper means  15   a  comprises a first A bearing hole  14   a  being a part of a stopper plate  14  also functioning as a first joint member, wherein the first A bearing hole  14   a  bears a circular shaft portion  10   d  of a first hinge shaft  10  such that the circular shaft portion can rotate; a first stopper projection  14   c  provided on the outside of the first A bearing hole  14   a ; and a first projection  10   h  provided on an outer circumference of the circular shaft portion  10   d  of the first hinge shaft  10 . The first stopper means  15   a  thus restricts a range of the rotation angle of the first hinge shaft  10  up to 180 degrees. The second stopper means  15   b  comprises a first B bearing hole  14   b  being a part of a stopper plate  14  also functioning as a first joint member, wherein the first B bearing hole  14   b  bears a circular shaft portion  12   d  of a second hinge shaft  12  such that the circular shaft portion can rotate; a second stopper projection  14   d  provided on the outside of the first B bearing hole  14   b ; and a second projection  12   h  provided on an outer circumference of the circular shaft portion  12   d  of the second hinge shaft  12 . The second stopper means  15   b  thus restricts a range of the rotation angle of the second hinge shaft  12  up to 180 degrees. 
         [0041]    Next, reference is made to a means for synchronously rotating hinge shafts  16  provided next to a stopper means  15 . As shown in particular in  FIGS. 3 and 4 , the means for synchronously rotating hinge shafts  16  comprises a first gear  17  being a bevel gear, wherein a first deformed shaft portion  10   e  of a first hinge shaft  10  passes through a deformed insertion hole  17   a  provided in an axial direction on the center of the first gear, such that the first deformed shaft portion engages with the deformed insertion hole; and a second gear  18  being a bevel gear, wherein a first deformed shaft portion  12   e  of a second hinge shaft  12  passes through a deformed insertion hole  18   a  provided in an axial direction on the center of the second gear, such that the first deformed shaft portion engages with the deformed insertion hole. The means for synchronously rotating hinge shafts  16  further comprises a gear supporting member  19  also functioning as a second joint member and comprising a second A bearing hole  19   c  and a second B bearing hole  19   d , wherein the second A bearing hole is provided on an upper projecting portion  19   a  and the second B bearing hole is provided on a lower projecting portion  19   b , the former is provided at an upper part of the gear supporting member and the latter at its lower part, both the projecting portions facing one side, and wherein a second deformed shaft portion  10   f  of a first hinge shaft  10  passes through the first A bearing hole, while a second deformed shaft portion  12   f  of a second hinge shaft  12  passes through the first A bearing hole. The means for synchronously rotating hinge shafts  16  further comprises an intermediate gear  20  comprising an upper supporting shaft  20   a  provided coaxially with a first shaft supporting groove  19   e  provided on a lower side of the upper projecting portion  19   a  of the gear supporting member  19 , a lower supporting shaft  20   b  provided coaxially with a second shaft supporting groove  19   f  provided on an upper side of the lower projecting portion  19   b  of the gear supporting member  19 , an upper bevel tooth portion  20   c  provided at an upper part of the intermediate gear and a lower bevel tooth portion  20   d  provided at a lower part of the intermediate gear, wherein the upper supporting shaft  20   a  is rotatably supported by the first shaft supporting groove, while the lower supporting shaft  20   b —by the second shaft supporting groove, and wherein the first gear  17  meshes with the upper bevel tooth portion  20   c , while the second gear  18  with the lower bevel tooth portion  20   d . In the meantime, the first gear  17  and the second gear  18  have an identical structure, so the first gear  17  only is shown in  FIG. 7 , the reference numeral for the second gear  18  in parentheses being just attached thereto. Still further, reference numerals  17  and  18  denote slip washers. 
         [0042]    Next, reference is made to an elastic means  21  provided on the tip side of a biaxial hinge  4 . The elastic means  21  consists of a first elastic means  21   a  on the first hinge shaft  10  side and a second elastic means  21   b  on the second hinge shaft  10  side. The first elastic means  21   a  comprises a first elastic member  22  consisting of a plurality of disc springs, spring washers or the like, wherein a second deformed shaft portion  10   f  of a first hinge shaft  10  passes through a circular insertion hole  22   a  provided in the first elastic member, and then the disc springs overlap each other; a first backing washer  23  provided next to the first elastic member  22 , wherein the second deformed shaft portion  10   f  passes through a deformed insertion hole  23   a  of the first backing washer to engage with the deformed insertion hole; and a first fastening nut  24  provided next to the first backing washer  23 , wherein a male screw portion  10   g  of the first hinge shaft  10  is screwed into a female screw hole  24   a  of the first fastening nut. 
         [0043]    The second elastic means  21   b  comprises a second elastic member  25  consisting of a plurality of disc springs, spring washers and the like, wherein a second deformed shaft portion  12   f  of a second hinge shaft  12  passes through a circular insertion hole  25   a  provided in the second elastic member, and then the disc springs and the like overlap each other; a second backing washer  26  provided next to the second elastic member  25 , wherein the second deformed shaft portion  12   f  pass through and engage with a deformed insertion hole  26   a  of the second backing washer; and a second fastening nut  27  provided next to the second backing washer  26 , wherein a male screw portion  12   g  of the second hinge shaft  12  is screwed into a female screw hole  27   a  of the second fastening nut. 
         [0044]    As described below, an elastic means  21  as described above applies a pressure contact force to a means for generating friction torque  30  and a means for sucking  35 , so that the former can exert a friction function while the latter a sucking function, when a first hinge shaft  10  and a second hinge shaft  12  rotate respectively. 
         [0045]    Next, reference is made to a means for generating friction torque  30 . As shown in particular in  FIGS. 3 and 4 , the means for generating friction torque  30  and a means for sucking  35  are provided between a means for synchronously rotating hinge shafts  16  and an elastic means  21 . As shown in particular in  FIGS. 2 to 4 , the means for generating friction torque  30  consists of a first means for generating friction torque  30   a  on the first hinge shaft  10  side and a second means for generating friction torque  30   b  on the second hinge shaft  12  side. The first means for generating friction torque  30   a  comprises a first friction washer  32 , wherein the second deformed shaft portion  10   f  of the first hinge shaft  10  passes through and engages with a first deformed insertion hole  32   a  provided at a center in an axial direction of the first friction washer, so that the first friction washer is provided between a gear supporting member  19  and a cam plate member  31 . The first means for generating friction torque  30   a  further comprises a first elastic means  21   a  as above described. In the meantime, a waffle-knurl pattern portion  32   b  is provided on the cam plate member  31  side of the first friction washer  32 . 
         [0046]    The second means for generating friction torque  30   b  comprises a second friction washer  33 , wherein the second deformed shaft portion  12   f  of the second hinge shaft  12  passes through and engages with a second deformed insertion hole  33   a  provided at a center in an axial direction of the second friction washer, so that the second friction washer is provided between a gear supporting member  19  and a cam plate member  31 . The second means for generating friction torque  30   b  further comprises a second elastic means  21   b  as above described. In the meantime, a waffle-knurl pattern portion  33   b  is provided on the cam plate member  31  side of the second friction washer  33 . Still further, though a rotation of a first friction washer  32  is restrained by a first hinge shaft  10 , and the second friction washer  33  by the second hinge shaft  12 , both friction washers can respectively slide in an axial direction. 
         [0047]    Next, a means for sucking  35  is provided next to a means for generating friction torque  30 , in this manner between this and an elastic means  21 . The means for sucking  35  consists of a first means for sucking  35   a  on the first hinge shaft  10  side (above) and a second means for sucking  35   b  on the second hinge shaft  12  side (below). First, the first means for sucking  35   a  comprises a first A cam concave portion  31   c  and a first B cam concave portion  31   d , each having a circular arc shape and provided outward on one side of a third A bearing hole  31   a  (above) of a cam plate member  31  also functioning as third joint member. The first means for sucking  35   a  further comprises a first cam follower  36 , wherein a second deformed shaft portion  10   f  of a first hinge shaft  10  passes through and engages with a deformed insertion hole  36   a  of the first cam follower, so that the second deformed shaft portion is restrained by the deformed insertion hole; the first cam follower further comprises a larger first A cam convex portion  36   b  and a smaller first B cam convex portion  36   c , of which the first A cam convex portion is provided opposite to the first A cam concave portion  31   c , while the first B cam convex portion to the first B cam concave portion  31   d . Still further, the first means for sucking  35   a  comprises a first elastic means  21   a  in contact with the first cam follower  36 , wherein the first elastic means  21   a  brings the first cam follower  36  into a pressurized contact with the cam plate member  31 . 
         [0048]    As per a second means for sucking  35   b , it comprises a second A cam concave portion  31   e  and a second B cam concave portion  31   f , each having a circular arc shape and provided outward on one side of a third A bearing hole  31   b  (below) of a cam plate member  31  also functioning as third joint member. The second means for sucking  35   b  further comprises a second cam follower  37 , wherein a second deformed shaft portion  12   f  of a second hinge shaft  12  passes through and engages with a deformed insertion hole  37   a  of the second cam follower, so that the second deformed shaft portion is restrained by the deformed insertion hole; the second cam follower further comprises a larger second A cam convex portion  37   b  and a smaller second B cam convex portion  37   c , of which the second A cam convex portion is provided opposite to a second A cam concave portion  31   e , while the second B cam convex portion to a second B cam concave portion  31   f . Still further, though a rotation of a first cam follower  36  is restrained by a first hinge shaft  10 , and the second cam follower  37  by the second hinge shaft  12 , both cam followers can respectively slide in an axial direction. 
         [0049]    In the meantime, it is recommended to attach a hinge case  6  to a biaxial hinge  4 , wherein the hinge case houses a means for controlling rotation  4   a  including elements from a stopper plate  14  also functioning as a first joint member to an elastic means  21 . The hinge case  6  has a cross section in the shape of oblong hole and a cylindrical contour, in particular as shown in  FIGS. 2 ,  4 , and  12 . An attaching portion  6   b  is provided in the interior of the hinge case, wherein an attaching hole  6   a  is provided such that such hole crosses the center of the hinge case. A first insertion hole  6   c  is provided above the attaching portion  6   b , wherein a first means for generating friction torque  30   a  and a first means for sucking  35   a  on the first hinge shaft  10  side of the biaxial hinge  4  pass through the first insertion hole, while a second insertion hole  6   d  is provided below the attaching portion  6   b , wherein a second means for generating friction torque  30   b  and a second means for sucking  35   b  on the second hinge shaft  12  side of the biaxial hinge  4  pass through the second insertion hole. Still further, a stopper means  15 , a means for synchronously rotating hinge shafts  16  are housed into a space toward portions of the hinge shafts not housed into the hinge case, while a means for generating friction torque  30  and a means for sucking  35  are both housed into a space beyond the attaching portion  6   b  toward the tip ends of the hinge shafts housed into the hinge case. In this manner, these means are altogether attached to a female screw hole  31   g  provided on a cam plate member  31 . 
         [0050]    Still further, a part of a hinge case  6  is housed into a housing concave portion  2   b  provided on a first casing  2  of a notebook PC  1  and a remaining part of the hinge case  6  into a housing concave portion  3   b  provided on a second casing  2 , when the first casing  2  of a notebook PC  1  is closed relative to the second casing  3 , especially as shown in  FIG. 2 , with both casings are coupled to each other via a biaxial hinge  4  according to the invention. Still further, a hinge case  8  of another biaxial hinge  5  has an identical structure. 
         [0051]    In the following, reference is made to an operation of the biaxial hinge  4  as described above. First, the biaxial hinge  4  according to the present invention is a biaxial hinge for opening and closing the first casing  2  and the second casing  3  relative to each other, wherein the both casings constitute the notebook PC  1  being an example of terminal device. The biaxial hinge is characterized in that the first hinge shaft  10  attached to the first casing  2  side via the first attaching plate  11  is coupled in parallel to the second hinge shaft  12  attached to the second casing  3  side via the second attaching plate  13 , by means of the stopper plate member  14  also functioning as the first joint member, the gear supporting member  19  also functioning as the second joint member and the cam plate member  31  also functioning as the third joint member, such that both hinge shafts can rotate. When the first casing  2  is opened and closed by the operator relative to the second casing  3  (or vice versa), the means for synchronously rotating hinge shafts  16  simultaneously opens and closes the casing not assuming opening and closing operations yet, so that the opening and closing operation can be quickly and easily completed. 
         [0052]    Namely, reference is first made to how the second casing  3  which is e.g. held by one hand of the user opens from its closed state, as shown by the solid line in  FIG. 14 , relative to the first casing  2  which is e.g. held by another hand of the user. The hand holding the second casing  3  rotates clockwise, and the first hinge shaft  10  first rotates clockwise and the first gear  17  does so in the same direction (clockwise). On the other hand, when the first gear  17  rotates clockwise, the intermediate gear  20  rotates counterclockwise via the upper bevel tooth portion  20   c  of the intermediate gear  20  meshed with the first bevel tooth portion  17   b  of the first gear  17  rotating together with first hinge shaft  10 , and the second gear  18  attached to the second hinge shaft  12 , wherein the second bevel tooth portion  18   b  of the second gear  18  meshes with the lower bevel tooth portion  20   d  of the intermediate gear  20 , rotates counterclockwise as well. In this manner, the first hinge shaft  10  rotates in a direction opposite to the rotation direction of the second hinge shaft  12 , and therefore the first casing  2  rotates at the same time as the second casing  3  as well as in a direction opposite to the rotation direction of the latter, which is the opening and closing operation of both casings. Accordingly, as long as the first hinge shaft  10  rotates, the opening and closing operation of the first casing  2  and the second casing  3  can be more easily and quickly completed than in case of a conventional biaxial hinge wherein a rotation of the second hinge shaft  12  is arrested by the means for selectively restricting rotation. In this manner, an improved operability is assured. 
         [0053]    When either the first hinge shaft  10  or the second hinge shaft  12  has rotated 180 degrees from its closed state, a rotation of the hinge shaft having rotated to this angle is arrested by the first stopper means  15   a  or the second stopper means  15   b , and at the same time, a rotation of the other hinge shaft is also arrested, as shown in  FIG. 13 . The action which takes place during the opening operation also follows the reverse procedures during the closing operation from the fully-opened state of the first casing  2  and the second casing  3 . 
         [0054]    Next,  FIG. 14  shows by the imaginary line how the first casing  2  has rotated clockwise to open 180 degrees relative to the second casing  3 . Since the first A cam convex portion  36   b  and the first B cam convex portion  36   c  provided on the first cam follower  36  of the first means for sucking  35   a  fall into the first A cam concave portion  31   c  and the first B cam concave portion  31   d  slightly before an opening angle of 180 degrees, the first casing  2  automatically reaches an opening angle of 180 degrees relative to the second casing  3 . The first means for sucking  35   a  also operates, when the first casing  2  closes from 180 degrees to 0 degree. Alternatively, both operations are also possible. Still further, the means for sucking  35  maintains the closed state of the first casing  2  and the second casing  3  without allowing the first casing  2  and the second casing  3  to automatically open relative to each other, even if no means for latching is provided. 
         [0055]    Still further, the first casing  2  and the second casing  3  synchronously open relative to each other, respectively rotating toward opposite directions, so that the former is opened 360 degrees in total relative to the latter. In this state, as shown by the imaginary line in  FIG. 14 , the first casing  2  overlaps the second casing  3 , with the respective surfaces now facing each other being opposite to the ones facing each other in the closed state. Here, as per the first hinge shaft  10 , the first stopper projection  14   c  of the stopper plate  14  also functioning as first joint member of the stopper means  15  abuts against the first projection  10   h  of the first hinge shaft, as shown in  FIG. 13B , while as per the second hinge shaft  12 , the second stopper projection  14   d  against the second projection  12   h  of the second hinge shaft. In this manner, a further rotation of the first hinge shaft  10  and the second hinge shaft  12  is arrested. 
         [0056]    When the first casing  2  and the second casing  3  open and close relative to each other as described above, the first hinge shaft  10  and the second hinge shaft  12  assume rotating operation one after another; at this point, the first means for generating friction torque  30   a  and the second means for generating friction torque  30   b  simultaneously operate, so that the above-mentioned means generate a friction torque on the first friction washer  32  and the second friction washer  33  at their respective contact surfaces with the gear supporting member  19  also functioning as the second joint member and the cam plate member  31  also functioning as the third joint member. In this manner, these means can assure a stable stopping function of the first casing  2  and the second casing  3  at any angle during the rotation of the casings. 
         [0057]    Still further, the stopper means  15  consists of the first stopper means  15   a  and the second stopper means  15   b . As described above and as shown in  FIGS. 13A and 13B , as per the first stopper means  15   a , when the first hinge shaft  10  has rotated 180 degrees in total, its first projection  10   h  abuts against the first stopper projection  14   c  provided on the stopper plate  14  also functioning as the first joint member, in order to restrict a further rotation of the first hinge shaft; as per the second stopper means  15   b , when the second hinge shaft  12  has rotated 180 degrees in total, its second projection  12   h  abuts against the second stopper projection  14   d  provided on the stopper plate  14  also functioning as the first joint member, in order to restrict a further rotation of the second hinge shaft. 
         [0058]    Still further, as per the means for sucking  35 , the first means for sucking  35   a  and the second means for sucking  35   b  take effect slightly before opening angles of 0 and 180 degrees, namely the first A cam convex portion  36   b  and the first B cam convex portion  36   c  of the first cam follower  36  respectively fall into the first A cam concave portion  31   c  and the first B cam concave portion  31   d  of the cam plate member  31  also functioning as third joint member; on the other hand, the second A cam convex portion  37   b  and the second B cam convex portion  37   c  of the second cam follower  37  respectively fall into the second A cam concave portion  31   e  and the second B cam concave portion  31   f  of the cam plate member  31  also functioning as third joint member. In this manner, the second means for sucking performs a sucking action and rotatably urges the first casing  2  and the second casing  3  to automatically rotate relative to each other in an opening direction. 
         [0059]    Further in addition to the original application of the notebook PC  1 , a variety of additional applications is also available, such as by synchronously rotating the first casing  2  and the second casing  3  relative to each other via the biaxial hinge  4  and folding into the shape substantially of the letter L and into the angle shape, as well as by allowing the both casings to overlap each other to form a flat tablet and turning the second casing  3  to the operator, such that the notebook PC has a function as a tablet PC. 
         [0060]    In the meantime, other embodiments include, though not shown in the drawings, the use of spur gears for a first gear  17  and a second gear  18 , whereby the gears are so designed that they directly mesh with each other, without intervention of an intermediate gear. Still further, the gears can be so designed that they synchronously rotate, one in a direction opposite to the other. Still further, a first elastic member  22  and a second elastic member  25  used for the elastic means  21  can be replaced with compression coil springs and elastic materials made of synthetic resin such as rubber. Still further, even without the hinge cases  6 ,  8 , the function of the biaxial hinges  4 ,  5  is not particularly impaired, but the hinge cases  6 ,  8  in use have an advantage that the biaxial hinges  4 ,  5  as attached to the notebook PC  1  have a neat appearance, since the hinge cases prevent the stopper means  15  from an exposure to the outside, and this also applies to the means for selectively restricting rotation  16 , the means for generating friction torque  30  and means for sucking  35 . 
         [0061]    The present invention is constructed as described above, so that it is suitable for use in a terminal device such as a notebook PC and the like, wherein a first casing and a second casing synchronously open relative to each other, and both casings open and close relative to each other in a range of 360 degrees. The present invention is particularly suitable for use in a notebook PC also functioning as a tablet PC.