Patent ID: 8448764

Claim:
A rotation transmission device comprising: an outer ring having an inner periphery; an inner ring mounted inside the outer ring and having an outer periphery, wherein a cylindrical surface is formed on one of the inner periphery of the outer ring and the outer periphery of the inner ring, and a plurality of circumferentially spaced cam surfaces are formed on the other of the inner periphery of the outer ring and the outer periphery of the inner ring to define a wedge-shaped space between the cylindrical surface and each cam surface, each wedge-shaped space narrowing toward circumferential ends thereof; a control retainer and a rotary retainer disposed between opposed surfaces of the outer ring and the inner ring, each of said retainers having a flange axially facing the flange of the other retainer, and each of said retainers having bridges provided at the radially outer side of the respective flange and arranged circumferentially alternately with the bridges of the other retainer thereby defining pockets between the adjacent bridges, wherein the control retainer is axially slidably and rotatably supported and the rotary retainer is axially immovably and rotatably supported; a torque cam provided between the flanges of the control retainer and the rotary retainer for causing the retainers to rotate relative to each other in a direction to reduce the circumferential width of the pockets when the control retainer is moved in a direction to reduce the distance between the flanges of the respective retainers; a plurality of opposed pairs of rollers, each pair being received in one of the pockets; coil springs disposed respectively in the pockets, each of the coil springs biasing a pair of the rollers away from each other; a torque transmission shaft having one end portion thereof inserted in and coupled to the inner ring by a spline; and an electromagnetic clutch mounted on the torque transmission shaft and including an electromagnet having an electromagnetic coil, said electromagnetic clutch being configured to axially move the control retainer when the electromagnetic coil is energized and deenergized.