Patent ID: 7930955

Claim:
A screw fastener comprising: a screwdriver that includes a sleeve having an absorption hole configured to absorb a top surface of a screw, a bit housed in the absorption hole and having a tip engageable with a recess of the screw, and a rotation unit configured to rotate the bit with the sleeve; a movement unit configured to move the screwdriver between a container configured to accommodate the screw and a work; a controller configured to control operations of the screwdriver and the movement unit so as to pick up the screw from the container and to fix a part onto the work with the screw; a pressure detector configured to detect a pressure in the absorption hole; a pressure fluctuation unit configured to fluctuate the pressure in the absorption hole according to a rotational position of the sleeve when the center axis of the screw is aligned with the center axis of the bit and a bottom surface of the sleeve is located close to but spaced from the top surface of the screw, wherein the controller aligns the tip of the bit with the recess of the screw based on a detection result of the pressure detector.