Patent ID: 8899396

Claim:
A clutch device comprising: a clutch mechanism including a friction engagement member capable of rotating relative to a rotating member and a clutch member that is supplied with restoration force in a direction in which the clutch member departs from the friction engagement member by a restoration spring; and a cam mechanism including a cam member incapable of rotating relative to the rotating member; and a cam follower capable of rolling on a cam surface that exists between the cam member and the clutch member, the cam member and the clutch mechanism being arranged in a row along a rotation axis line of the rotating member, and the cam mechanism being configured so that a cam angle of the cam surface is set to an angle that makes torque applied to the clutch member due to reaction force accompanied by friction engagement with the friction engagement member larger than torque applied to the clutch member by thrust force caused by an activation of the cam mechanism, the cam mechanism is configured so that the cam angle is set to an angle that satisfies μm×rm×F<F×rc×(sin θ−μc cos θ)/(cos θ+μc sin θ), where the thrust force and the reaction force are F, the coefficient of static friction of the clutch member to a friction surface of the friction engagement member is μm, the coefficient of rolling friction of the cam follower to the clutch member is μc, the radius of an equivalent friction circle of the clutch member is rm, the radius of an action circle of the cam follower is rc, and the cam angle is θ.