PROBLEM TO BE SOLVED: To provide a power transmission unit, in which deterioration of a power transmission shaft is suppressed. SOLUTION: The power transmission unit 100, which is fitted to a power transmission shaft 15 rotatable in a predetermined direction and moderates non-constant velocity of the power transmission shaft 15, includes: an input side rotator (clutch 50) provided with an input side locking part (input side clutch pawl 53) at a cylindrical part 51 fitted to the power transmission shaft 15 and rotating together with the power transmission shaft 15; an output side rotator (sprocket 60) fitted with the cylindrical part 51 so that the cylindrical member 51 of the input side rotator as a rotation shaft can be freely rotated and provided with an output side locking part (output side clutch pawl 63) capable of meshing with the input side locking part; and a biasing member (torsional coil spring 70) for biasing the output side rotator in the rotation direction. The input side rotator and the output side rotator are capable of relatively rotating within a predetermined angle range. COPYRIGHT: (C)2013,JPO&INPIT
