Lockup device of torque converter

A lockup device adapted to be used in a torque converter having a front cover with a friction surface on its inner side, an impeller and a turbine, said lockup device being adapted to be disposed in a space between the turbine and the front cover for mechanically engaging and disengaging the front cover to the turbine, said lockup device comprising:

• a disk-shaped plate member adapted to receive torque from the front cover;
• and
• a damper mechanism arranged at a substantially radially midpoint of said plate member, said damper mechanism arranged to elastically couple said plate member and said turbine in a rotational direction, said damper mechanism including a drive plate secured to one axial side surface of said plate member, a driven plate adapted to be relatively nonrotatably engaged with the turbine and a torsion spring elastically coupling said drive plate and said driven plate in a rotational direction,
• said drive plate having a cutout formed at a position corresponding to a position of said torsion spring, said torsion spring being axially supported by said one axial side surface of said plate member within said cutout.

A torque converter adapted to be used to transmit torque from a power input shaft to an output shaft, said torque converter comprising:

• a front cover being adapted to be coupled to the power input shaft, said front cover being provided at an inner side with a friction surface;
• an impeller connected to said front cover to form a hydraulic chamber together with said front cover;
• a turbine disposed opposite said impeller and disposed inside said hydraulic chamber, said turbine being adapted to be coupled to the output shaft, said front cover and said turbine forming a space therebetween;
• and
• a lockup device disposed in said space for mechanically engaging and disengaging said front cover with respect to said turbine, said lockup device including
• a disk-shaped piston adapted to move within the space in accordance with pressure changes in the space, and adapted to be arranged adjacent to the friction surface of the front cover, and
• a damper mechanism arranged at a substantially radially midpoint of said piston, said damper mechanism arranged to elastically couple said piston and the turbine in a rotational direction, said damper mechanism including a drive plate secured to one axial side surface of said piston, a driven plate adapted to be relatively nonrotatably engaged with the turbine and a torsion spring elastically coupling said drive plate and said driven plate in a rotational direction,
• said drive plate having a cutout formed at a position corresponding to a position of said torsion spring, and said torsion spring being axially supported by said one axial side surface of said piston within said cutout.