Planetary roller screw type linear motion mechanism and electric braking device

摘要

PROBLEM TO BE SOLVED: To provide a planetary roller screw-type linear motion mechanism which can switch a load conversion rate according to an axial load applied to an object from an outer ring member, and can easily finish a cylinder face with which a planetary roller at an external periphery of a rotating shaft contacts by polishing or the like.SOLUTION: In a planetary roller screw-type linear motion mechanism in which an outer ring member 5 moves to an axial line by the engagement of a spiral protrusion 16 of the outer ring member 5 at an internal periphery and a circumferential groove 17 of a planetary roller 13 at an external periphery, a carrier 14 is supported by an elastic member 35 so as to relatively move to a rotating shaft 8 by a reaction force to a rear side in the axial direction, a tapered face 38 which is friction-engaged with the carrier 14 in a state that the carrier 14 does not relatively move to the rotating shaft 8, and releases the friction engagement with the carrier 14 in a state that the carrier 14 relatively moves to the rotating shaft 8 is formed at an external periphery of the rotating shaft 8, and the tapered face 38 is arranged at the rear side in the axial direction with respect to the planetary roller 13.SELECTED DRAWING: Figure 2