Ball screw actuator

A ball screw actuator, comprising:

• a linear guide rail comprising left and right side walls and having 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,
• each of the left and right linear ball bearings comprises an external passage formed by a corresponding one of the side walls of the guide rail and the slider main body, and an internal passage formed to extend in the axial direction inside the slider main body,
• 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, a lubricating oil injection passage, and a lubricating oil supply passage for supplying lubricating oil from the lubricating oil injection passage to the left and right return passages,
• each of the left and right return passages comprises an outer end portion communicating with the corresponding external passage and an inner end portion communicating with the corresponding internal passage, and
• the lubricating oil supply passage communicates with the left and right return passages on a side thereof closer to the outer end portion than to the inner end portion.