To provide a planetary roller screw device having excellent operation efficiency for converting rotation motion into linear motion in an axial direction.
The planetary roller screw device is provided with a screw shaft 1 in which a screw groove 1a is formed in its outer circumferential surface, a nut 2 in which a screw groove 2a confronting the screw groove 1a of the screw shaft 1 is formed in its inner circumferential surface, and a roller array consisting of a plurality of rollers 3 rollably interposed between both the screw grooves 1a, 2a. By relative rotation motion of the screw shaft 1 and the nut 2, the screw shaft 1 and the nut 2 move relatively and linearly in the axial direction through rolling of the rollers 3. A lubricant for lubricating between both the screw grooves 1a, 2a and the rollers 3 is provided in the planetary roller screw device and an extreme-pressure agent is added to the lubricant.
Yoshiaki Naito
Cui Shu Tetsu