To provide a long-life planetary roller screw hard to be damaged even if relative sliding arises between a screw shaft and a roller and between a nut and the roller.
The planetary roller screw is equipped with the screw shaft 1 having a screw groove 1a on a peripheral surface, a nut 2 formed on an inner peripheral surface with a screw groove 2a opposed to the screw groove 1a of the screw shaft 1, a roller train comprising a plurality of the rollers 3 which are interposed between both the screw grooves 1a, 2a in a freely rolling manner, and two gears 4, 4 engaged with the nut 2. The gears 4, 4 engage with teeth formed at the rollers 3', 3' both ends from among the roller train. At least one of the screw grooves 1a of the screw shaft 1, screw groove 2a of the nut 2 and rolling surface 3a of the roller 3 is coated with a solid-state lubricating film made of at least one of molybdenum disulfide, an organic molybdenum compound, a soft metal and a high-polymer material.
Yoshiaki Naito
Cui Shu Tetsu
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