Patent ID: 8371426

Claim:
A power transmission mechanism that permits power to be transmitted from an external driving source to a rotary shaft of a rotating machine, comprising: a first rotating body that rotates integrally with the rotary shaft of the rotating machine; a second rotating body rotatably supported on a housing of the rotating machine, the second rotating body being coaxially arranged with the first rotating body, wherein the second rotating body receives power from the external driving source, accommodates an electromagnetic coil, and has a cylindrical extended portion; an armature that is arranged to face the second rotating body; and a spring clutch wound about an outer circumference of the first rotating body, an entire outer circumference of the spring clutch being surrounded by the extended portion of the second rotating body, wherein the spring clutch has a first end and a second end, the first end being connected to the first rotating body, and the second end being connected to the armature, wherein supply of current to the electromagnetic coil causes the armature to adhere to the second rotating body, wherein, when the armature rotates, the diameter of the spring clutch is increased such that the spring clutch is pressed against the inner circumferential surface of the extended portion and the first rotating body and the second rotating body are coupled to each other.