Patent ID: 7892134

Claim:
A clutch device comprising: an input member rotatable with drive torque; an output member to which the drive torque is transferred from the input member; a clutch member held in constant connection with one member of the input member or the output member and axially movable to the other member to be intermittently coupled; and an electromagnetic actuator including an electromagnetic solenoid and a plunger axially movable in response to magnetic force generated by the electromagnetic solenoid to axially shift the clutch member; wherein the electromagnetic solenoid is disposed on the one member so as not to relatively move in an axial direction and the one member serves as a part of a magnetic flux path formed by the electromagnetic solenoid, wherein the electromagnetic solenoid, the plunger, and the one member form a complete magnetic flux loop as the magnetic flux path to cause the plunger to provide axially moving force to the clutch member in response to magnetic force generated by the electromagnetic solenoid, and wherein the complete magnetic flux loop is composed of a first loop segment passing through the electromagnetic solenoid, a second loop segment following the first loop segment and passing through the one member, and a third loop segment following the second loop segment and passing through the plunger, the third loop segment being connected to the first loop segment; wherein the one member includes protruding portions each with a circumferential length through which permeates a magnetic flux to the plunger, and the one member is operative such that when the plunger is axially moved in response to magnetic force generated by the electromagnetic solenoid, the plunger is placed in opposition to the protruding portions with a minimal clearance in a radial direction.