A rotation transmission device is provided which is small in play in the rotational direction, can be idled with high reliability and is high in torque capacity.An axially movable control
retainer 19A and a rotatable rotary
retainer 19B are mounted between an outer ring 11 having a cylindrical surface 17 on its inner periphery and an inner ring 12 having
cam surfaces on its outer periphery. An opposed pair of rollers 26 and a
coil spring 27 for biasing the pair of rollers 26 away from each other are received in each pocket 25 defined between bridges 21 and 23 of the respective retainers 19A and 19B. A torque
cam 30 is provided between flanges 20 and 22 of the control
retainer 19A and the rotary retainer 19B, respectively. An armature 41 is coupled to the bridges 21 of the control retainer 19A. An
electromagnet 43 is provided to face a rotor 42 that axially faces the armature 41 so that when the
electromagnet 43 is energized, the control retainer 19A moves toward the rotor 42, and the control retainer 19A and the rotary retainer 19B rotate relative to each other in the direction to reduce the circumferential width of the pockets 25, thereby disengaging the opposed pairs of rollers 26. When the
electromagnet 43 is deenergized, the control retainer 19A moves away from the rotor 42 under the biasing force of the separation spring 44, and the control retainer 19A and the rotary retainer 19B rotate relative to each other in the direction to increase the circumferential width of the pockets 25, thereby engaging the opposed pairs of rollers 26.