PURPOSE: To reduce torsional vibration of the output shaft of engine, by inserting an impeller shell fixed to a drive plate and a turbine-blade bearing hub shaft into a recess formed at the rear end portion of crank shaft, and thereby giving various purpose to a fluid coupling means.

CONSTITUTION: Hub shaft 9 is fixed to turbine blades 8 which are disposed in face with pump blades 6 of impeller shell 7 fixed to drive plate 2. The hub shaft 9 is disposed coaxially with the crank shaft 1 and main drive shaft 4, and a projection formed at the front end portion of the hub shaft 9 is inserted into recess 1a formed at the rear end portion of crank shaft 1 by the intermediary of ball bearing 18. On the inside of bush 19 fitted into the recess 1a, there is press fitted a boss 21 coupled with impeller shell 7 in a unitary manner, by the intermediary of O-ring 20. With such an arrangement, various purposes can be given to the fitting of crank shaft 1 and fluid coupling F.