Patent ID: 8505399

Claim:
An electric actuator comprising: a cylinder body; a screw shaft which is provided in the cylinder body, and rotated by an electric motor; a nut into which the screw shaft is screwed; a piston rod which moves linearly in accordance with rotation of the screw shaft via the nut; a recess formed on an outer circumferential surface of the nut; a key provided to the recess; a hole which is formed on an outer circumference of a piston part of the piston rod, and into which hole the key is fitted; a tapered portion formed on an inner wall of the cylinder body and to which the key is fitted; and a ring engaging member formed on an end of the piston part towards which part the piston rod retracts, wherein a rear end face of the nut does not contact the engaging member when the piston rod advances, wherein the piston rod advances to move the key outward to cause the key to fit to the tapered portion to block retraction of the piston rod, wherein when the piston rod retracts, the nut retracts and the rear end face of the nut contacts the engaging member, with the result that the piston rod retracts together with the nut and wherein during a transition between the retraction and the advancement of the piston rod, the rear end face of the nut does not contact the piston rod.