Linear actuator

A linear actuator comprising:

• an output shaft formed with a helical groove;
• a retainer having a cylindrical shape which receives the output shaft therein, and provided with a plurality of concave portions spaced from each other at positions of an inner peripheral surface thereof along the helical groove;
• a pair of sleeves having a cylindrical shape and mounted on a circumference of the retainer from a front side and a rear side in an axial direction;
• a rotor magnet fixed in surrounding relation to the retainer;
• and
• balls which are retained in the plurality of concave portions, respectively,
• wherein when the retainer is rotated, the balls are moved along the helical groove of the output shaft in a state where the balls are retained in the concave portions,
• wherein the pair of sleeves have edge portions opposing each other, and each of the edge portions is provided with a concavo-convex structure,
• wherein the retainer is divided into segments along lines extending substantially parallel to a longitudinal axis thereof such that it includes a first retainer segment, a second retainer segment, and a third retainer segment, and
• wherein the third retainer segment is provided with a protrusion inserted between and in contact with the concavo-convex structures of the sleeves so that the protrusion positions the concavo-convex structures of the pair of sleeves relative to each other and prevents rotation of the pair of sleeves.