Patent ID: 7941076

Claim:
A rotor driving force transmission device comprising: a cylindrical rotor; a shaft which is disposed inside the rotor and for driving the rotor to thereby rotate the rotor, the rotor being attached removably in a direction of an axis of the shaft; a large number of gearing reception portions which are coupled integrally with the rotor and formed along an inner circumference of the rotor; at least three arm portions which are disposed radially from the shaft toward the gearing reception portions so that the arm portions can be elastically deformed along the axis of the shaft, each of the arm portions including an engagement tooth portion which is disposed in a tip portion thereof and which can gear with one of the gearing reception portions so as to transmit a driving force of the shaft to the rotor; and a press member which presses the rotor toward gearing portions where the gearing reception portions and the engagement tooth portions gear with each other; wherein: a relation of D 1 <D 2 is established where D 1 designates a diameter of a virtual circle formed by connecting contact points between the engagement tooth portions and the gearing reception portions when the rotor has been attached to gear the gearing reception portions with the engagement tooth portions, and D 2 designates a diameter of a virtual circumscribed circle formed by connecting tips of the engagement tooth portions when the rotor has not been attached yet; and the rotor is pressed toward the gearing portions by the press member so that the gearing reception portions gear with the engagement tooth portions while the arm portions are bent in a direction where the rotor is pressed.