Gear mechanism and webbing retractor

摘要

A gear mechanism for reducing a rotational speed of a driving gear and transferring the reduced rotational speed to a gear to be driven comprises an arbitrary number of gear teeth attached to the driving gear and smaller than the number of teeth determined by a module and a stopper having a stopper surface which is attached to the driving gear so as to be displaced relative to said gear teeth along the axial direction of the driving gear and which draws a circle identical in size to a circle drawn by a locus of rotation of an addendum of each gear tooth upon rotation of the driving gear and meshes with gear teeth of the driven gear upon disengagement of the gear teeth from the teeth of the driven gear so that the rotation of the driven gear is controlled by the stopper. Thus, when the gear teeth are in disengagement with the teeth of the driven gear, the stopper is maintained in meshing engagement with the gear teeth of the driven gear so as to prevent the driven gear from rotating.