To realize a quiet, stable engine-starting system by suppressing the drag torque of a sprag.
The rotation transmission device comprises a plurality of sprags 6 and elastic members 4 between an inside member 2 having an outer circumferential cylindrical-face 2a and an outer member 1 having an inner circumferential cylindrical-face 1a. A locking member 12 is provided on one side of the sprag 6 in the axial direction, and can move into/out of a gap between the sprags 6 and the inner circumferential cylindrical-face 1a so as to lock up/unlock the sprags 6. The sprag 6 can be selectively set in a lockable/unlockable state in the inner circumferential cylindrical-face 1a, and if the sprag 6 is separated from the inner circumferential cylindrical-face 1a in idling, the drag torque can be inhibited. With the rotation transmission device provided in the engine-stating system, a pinion gear 8 and a ring gear 9 of a flywheel are no more needed to be fitted/removed with/from each other so that vibration, noises, meshing failure and the like are not caused.
ASHIMORI MASAKO
Torii Kazuhisa
Takayoshi Tagawa
Higashio Masahiro