Patent ID: 7810616

Claim:
An electric direct-acting actuator for converting a rotary motion of an electric motor to a linear motion to linearly drive an object to be driven, wherein a plurality of planetary rollers are disposed between a radially outer surface of a rotor shaft of said electric motor and a radially inner surface of an outer ring member fixed in position around said rotor shaft, whereby said planetary rollers are configured to rotate about said rotor shaft while rotating about their own axes when said rotor shaft rotates, a relatively axially moving means is provided between the respective planetary rollers and one of said rotor shaft and said outer ring member for axially and relatively moving said planetary rollers, whereby the rotary motion of said rotor shaft is converted to a linear motion of said planetary rollers, wherein the linear motion of said planetary rollers is transmitted to said object to be driven through thrust bearings for supporting the rotation of said respective planetary rollers about their own axes and a thrust bearing for supporting the rotation of said planetary rollers about the rotor shaft.