Patent ID: 7575106

Claim:
A bicycle wheel driving device comprising: a hub axle; a hub shell with a housing space inside, the hub shell rotatably arranged around the hub axle, and the hub shell having a hub flange on an outside circumference thereof and a cylindrical section arranged axially outwardly with respect to the housing space; and an electric motor disposed inside the housing space of the hub shell and configured to rotate the hub shell with respect to the hub axle; and a roller brake device at least partially arranged within the hub shell and extending outside of the hub shell, the roller brake device further including a stationary bracket configured to be fastened to a bicycle; a cylindrical brake drum arranged to rotate integrally with the hub shell and having a braking surface on an internal circumferential surface thereof, the brake drum including an engaging part that is provided on an external circumferential surface thereof and engages an internal circumferential surface of the cylindrical section of the hub shell, the engaging part including a screw thread oriented in such a direction such that engagement between the brake drum and the hub shell tightens the engaging part when the bicycle wheel is braked while rotating in a direction corresponding to forward movement of the bicycle; a plurality of brake shoes non-rotatably arranged with respect to the stationary bracket and arranged radially inwardly with respect to the cylindrical section of the hub shell at a location axially overlapping with the cylindrical section of the hub shell, each of the brake shoes having a contact surface arranged to selectively contact the braking surface to apply braking action against the brake drum; a force applying member arranged to apply forces against the brake shoes in radially inward directions; and a brake operating unit having a plurality of rollers arranged with spaces there between in a circumferential direction and a cam mechanism that presses the rollers in a radially outward direction when turned to press the brake shoes against the brake drum.