Clutch structure

A clutch structure comprising:

• a hub secured to a rotating shaft;
• a sleeve mounted on an outer peripheral surface of the hub and configured to slide linearly;
• a clutch gear mounted on the rotating shaft and configured to rotate relative to the rotating shaft, the clutch gear integrally formed with a clutch cone that protrudes toward the hub while decreasing in an outer diameter of the clutch cone;
• a first friction ring provided between the clutch gear and the hub, the first friction ring configured to be pressed toward the clutch gear so that frictional force is generated between the clutch cone and the hub and consequently a torque is transferred;
• a second friction ring configured to be inhibited from rotating relative to the hub and having an inner surface configured to contact an outer surface of the clutch cone;
• and
• a middle cone configured to be inhibited from rotating relative to the clutch gear, the middle cone having:
• an inner surface configured to contact an outer surface of the second friction ring, and an outer surface configured to contact an inner surface of the first friction ring,
• wherein each of the second friction ring and the middle cone is provided with a friction member on at least one of the inner surface or the outer surface each of the second friction ring and the middle cone.