Rotation shaft mechanism of display portion of portable computer

A rotation shaft mechanism adapted for a portable computer having a display portion, a base portion and at least one rotation shaft mechanism arranged between the display portion and the base portion, the rotation shaft mechanism comprising a horizontal shaft assembly and a vertical shaft assembly;

• wherein the horizontal shaft assembly has two horizontal shafts and two eccentric protuberances arranged on the two horizontal shafts, respectively;
• wherein the vertical shaft assembly includes:
• a first component having a first body, a pair of symmetric projective ears perpendicularly projected from two sides of the first body and a cylinder body disposed at a bottom of the first body, and the pair of projective ears having two holes which the horizontal shafts passes through, respectively;
• a second component which the cylinder body is removably mounted on and having two projective wall formed thereon to be corresponding to the two eccentric protuberances of the horizontal shaft assembly, and the first component and the second component interfering with each other so as to rotate synchronously;
• and
• a third component which the second component is mounted on;
• and
• an elastic component surrounded on the cylinder body and disposed between a screw nut screwed at a lower portion of said cylinder body and a bottom face of the third component.