Patent ID: 7743679

Claim:
A power transmission device that transmits power from a power source via a rotation member that rotates about a predetermined shaft center, the power transmission device comprising: the rotation member, the rotation member including a rim section that includes a plurality of teeth, a boss section, and a disk section extending radially outwards from the boss section to the rim section, the disk section including a plurality of holes in slit form that are formed by being drilled by laser processing, at least one of the holes in slit form having a C shape that defines an inner region of the disk section that is partially enclosed by the at least one of the holes such that an outer region of the disk section that is outside of the at least one of the holes is continuous with the inner region of the disk section via a cut-left-over section of the disk, and a length of a connecting region between the plurality of holes is shorter than a length of the at least one hole.