Two-mass flywheel device

PROBLEM TO BE SOLVED: To exhibit the always proper vibration damping action by providing a first inertia mass joined to a prime mover and a second inertia mass acting on this inertia mass via a torsional vibration damper, and generating frictional joining between both inertia masses via the vibration damper under a settable operation condition. SOLUTION: A flywheel device has a first inertia mass 1 detachably fixed to a crankshaft 4 of an internal combustion engine in a hub 3, and a torsion spring 12 is housed in a chamber 10 defined between an inner wall 6 of a ring 5 of this mass 1 and a cover plate 7. Torque absorbed by this torsion spring 12 is introduced to a hub disc 17 operating as a torque transmitter 25 for a second inertia mass 24. A damping mechanism 105 is attached to this second inertia mass 24, and an actuator of a release device 55 is controlled in driving on the basis of measured quantity measured under a prescribed operation condition by a detecting device 120 arranged in this damping mechanism 105.