Clutch

A clutch apparatus, comprising:

• a hub configured to be constrained to a rotation shaft;
• a sleeve configured to be straight slidably disposed on an external circumferential surface of the hub;
• a clutch gear configured to be disposed to be relatively rotatable with respect to the rotation shaft;
• a first friction ring configured to be mounted between the clutch gear and the hub and pressed toward the clutch gear to form a frictional force between the clutch gear and the hub to transfer a torque;
• a key configured to be mounted between the sleeve and the hub and transfer a linear displacement of the sleeve to the first friction ring before the sleeve makes contact with the first friction ring;
• and
• a displacement changing portion configured to change a relative rotation displacement of the first friction ring with respect to the hub to an axial linear displacement of the first friction ring,
• wherein the hub is provided with a hub groove accommodating the key, the first friction ring is provided with a first ring protrusion being inserted into the hub groove, and an internal side of the sleeve is provided with a sleeve protrusion integrally formed on the internal side of the sleeve and inserted into the hub groove to press directly the first ring protrusion axially, and
• wherein the displacement changing portion includes:
• a first inclined surface formed, at an end part of the hub groove, facing toward the first friction ring, in a shape in which a width thereof is expanded along a circumferential direction of the hub groove;
• and
• a second inclined surface formed at the first ring protrusion of the first friction ring in parallel with the first inclined surface, to contact with the first inclined surface.