Patent ID: 7055217

Claim:
A hinge device connecting en attachment portion of a first member constituting a keyboard main body and an attachment portion of a second member constituting a display device, so that said first member and said second member are opened and closed relatively to each other, said attachment portion of said first member having a deformed attachment hole; and said attachment portion of said second member having a deformed attachment hole in common with a central axial direction of said deformed attachment hole of said first member; said hinge device comprising: a cam case fixedly inserted in said deformed attachment hole of said first member; a friction case fixedly inserted in said deformed attachment hole of said second member; a shaft arresting and penetrating through both of said cam case and said friction case in an axial direction, and said cam case fixedly attached to said shaft so as to rotate with said shaft; a cam mechanism fitted on said cam case; a friction mechanism fitted on said friction case; wherein said cam mechanism is composed of: a slider cam attached to said shaft, having cam portion composed of a convex portion and depressed portion provided on one side, being restrained its rotation by said cam case; a cam guide provided between said cam case and said friction case by fixedly inserting in said deformed attachment hole of said friction case, said cam guide having a deformed attachment hole; a fixing cam fixedly inserted in said deformed attachment hole of said cam guide at a position confronting to said slider cam, having cam portion disposed with a convex portion and depressed portion at a position opposite to that of said cam portion of said slider cam, and; an elastic means wound around said shaft and provided inside said cam case for forcing said slider cam slidably toward said fixing cam side; wherein an upper surface of said convex portion or a bottom surface of depressed portion of each of said cam portions of said slider cam formed in a plane portion; wherein said friction mechanism is composed of: a friction ring tightly wound round of said shaft so as to generate a friction torque accompanied with the rotation of said friction case; a viscous oil filled between said friction case and said friction ring.