Patent ID: 8899120

Claim:
A linear actuator comprising: a stator assembly having coils obtained by winding a magnet wire arranged on a stator yoke, and pole teeth arranged on an inner periphery of the stator assembly; a rotor rotatably disposed in a hollow of the stator assembly with a gap opposing the pole teeth, the rotor including a ring shaped magnet arranged on an outer periphery of a hollow cylindrical sleeve; a ring shaped retainer disposed at an inner periphery of the sleeve, the retainer having a plurality of through-holes for housing balls; an output shaft having a ball screw groove on at least a portion of an outer periphery of the output shaft for engaging with the balls, the output shaft disposed in the rotor so as to be slidable in an axial direction thereof; a front housing disposed at a front end of the stator assembly, the housing having a groove formed at its inner circumference so as to extend parallel to the length of the output shaft; and a pin secured to the output shaft, the pin lodged in and guided by the groove so as to restrict rotation of the output shaft, wherein the through-holes are arranged in a spiral manner on a circumference of the retainer so as to correspond to the ball screw groove; wherein the retainer comprises a first retainer and a second retainer, and the first retainer and the second retainer are disposed apart from each other in the axial direction; and wherein each of the retainers has a single row of said through-holes formed therein.