A coil spring is provided in a compressed state between a coupling wall section provided at a clutch guide and an inner-side locking section. The clutch guide is provided with a support section which supports one axial-direction end section of the coil spring from a side opposite to the clutch cover in an axial direction of the clutch guide. The clutch cover is provided with a leading-end protruding section which is projected with respect to the inner-side locking section so as to be inserted in the other axial-direction end section of the coil spring. The leading-end protruding section is inclined, with respect to a direction orthogonal to an axial direction of the clutch cover, toward a support section side, so that the coil spring is curved so as to be convex to the support section side.