| 摘要 |
In an actuator device which comprises a screw shaft, a nut member, and balls, the nut member moves relatively to the screw shaft in a first axial direction and a second axial direction opposite thereto in a manner such that it is continually subjected to a load in the first axial direction. A ball screw groove of the screw shaft is formed having a loaded surface which is pressed against the balls, on the side of a groove base in the first axial direction. A ball screw groove of the nut member is having a loaded surface which is pressed against the balls, on the side of its groove base in the second axial direction. These loaded surfaces are finished so that their surface roughness is lower than that of the unloaded surfaces.
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