US Patent 9369024 Electric linear motion actuator and electric disk brake system

A linear motion actuator has an output member that can be smoothly moved linearly even when lateral moment acts on the output member. A carrier (6) supporting planetary rollers (7) is axially immovable, while an outer ring member (5), as the output member, is axially slidably fitted in the radially inner surface of a cylindrical portion (1a) of a housing (1), and is rotationally fixed to a driven member through keys (22). Hard plating layers are formed on the radially outer surface of a rotary shaft (4), the radially outer surfaces of the planetary rollers (7), including helical grooves (7a), and the surface of a helical rib member (5b) which is fixed to the radially inner surface of the outer ring member (5) forming a helical rib.