Hydraulic power transmission device

A hydraulic power transmission device for transmitting power from an engine to a transmission via a fluid, the hydraulic power transmission device comprising:

• a front cover;
• a fluid coupling main body including a turbine that rotates integrally with an input shaft of the transmission, the fluid coupling main body configured to transmit power from the engine to the transmission via the fluid;
• a lock-up device provided between the front cover and the turbine, the lock-up device including a clutch portion, an output-side member, and a plurality of first coil springs, the clutch portion configured to transmit or cut off power from the front cover, the output-side member configured to receive power from the clutch portion, the output-side member coupled to the turbine, and an outer circumferential end portion of the output-side member engaged with each of the plurality of first coil springs;
• and
• a dynamic damper configured to attenuate rotational speed fluctuation from the engine, the dynamic damper including a base plate, an inertial body and an elastic unit, the base plate directly fixed to the output-side member of the lock-up device, the inertial body configured to move in a rotation direction relative to the base plate, the elastic unit including a variable hysteresis torque generation portion and a plurality of second coil springs, the variable hysteresis torque generation portion configured to generate a variable hysteresis torque according to a relative speed difference between the base plate and the inertial body, the plurality of second coil springs coupling the base plate and the inertial body elastically in the rotation direction, wherein
• the base plate is ring-shaped, and has a plurality of openings in an outer circumferential portion with predetermined intervals therebetween in a circumferential direction,
• the variable hysteresis torque generation portion is disposed between two adjacent openings among the plurality of openings in the circumferential direction, and
• the inertial body has
• a first inertia ring and a second inertia ring arranged sandwiching the outer circumferential portion of the base plate in an axial direction, each of the first and second inertia rings having a ring-shape, the first and second inertia rings each including corresponding openings at positions that correspond to the openings of the base plate, and
• the plurality of second coil springs of the elastic unit are housed in the openings of the base plate and the corresponding openings of the first and second inertia rings.