Ball screw actuator

A ball screw actuator, comprising:

• a linear guide rail comprising left and right side walls and defining a concave cross-sectional shape;
• a slider disposed between the left and right side walls of the guide rail;
• left and right linear ball bearings which are provided with multiple balls that circulate between the slider and the left and right side walls of the guide rail, and which guide movement of the slider in an axial direction relative to the guide rail;
• a ball screw nut part provided in the slider;
• and
• a ball screw shaft that passes through a through hole provided in the slider in the axial direction and is threadedly engaged with the ball screw nut part provided in the slider via balls,
• wherein the slider comprises a slider main body comprising a ball screw nut part, and ball return members respectively attached to both ends of the slider main body in the axial direction,
• at least one of the ball return members comprises left and right return passages through which each ball of the left and right linear ball bearings moves, the left and right linear ball bearings being provided bilaterally symmetrically with respect to the through hole, a lubricating oil injection passage provided offset to one of left and right sides with respect to the through hole, and a lubricating oil supply passage for supplying lubricating oil from the lubricating oil injection passage to the left and right return passages, and
• the lubricating oil supply passage comprises a first passage that extends from the lubricating oil injection passage to a branch position on a bilateral symmetry line which passes through a center of the through hole, and second passages which are branched left and right from the branch position to respectively extend to the left and right return passages and are bilaterally symmetric.