PURPOSE: To make assembly work easy and to reduce cost by a structure wherein one or plural easily elastically deformable pawl-shaped projections are formed in one body with a driven gear made of a resin and the pawl-shaped projects are fitted into the annular groove of a stationary shaft.

CONSTITUTION: A driven gear 10 is inserted from a pawl part 12 side onto the stationary shaft 13 which is fixed and supported to a transmission case side in the case of the gear 10 fixing freely rotatably to the shaft 13. The parts 12 are formed to an arm shape which is easily elastically deformable when inserted. A tapered part 16 for guiding is formed just before an annular ring 14 formed to the shaft 13 and since the parts 12 are chamfered 15, the parts 12 are forced along the tapered surface of the part 16 and are thus expanded outward when the gear 10 is inserted onto the fixing part 13 so that the parts 12 of the gear 10 are fitted into the groove 14 of the shaft 13 by the gentle outward elastical deformation of the parts 12.