US Patent 10030740 Lock-up device for torque converter

A lock-up device includes an output rotary member rotatable relatively to a clutch portion and coupled to a turbine. A plurality of torque transmission elastic members elastically and rotation-directionally couple the clutch portion and the output rotary member. An intermediate member rotatable relatively to the clutch portion and the output rotary member causes at least two of the plural torque transmission elastic members to act in a series-like manner. A dynamic damper device includes a first inertia ring, a second inertia ring and a plurality of dynamic damper elastic members, the first and second inertia rings axially split and having pairs of accommodation recesses axially opposed to each other, the plural dynamic damper elastic members accommodated in the pairs of the accommodation recesses of the first and second inertia rings and elastically coupling the intermediate member and the first and second inertia rings.