Impeller shell of torque converter and method of forming the same

摘要

An impeller shell 40a of a torque converter includes a main portion 41, a connection portion 42 and a stepped portion 43. The main portion 41 has a curved inner peripheral surface 41a carrying impeller blades, and is opposed to a turbine 5. The connection portion 42 has a cylindrical form larger in diameter than an outer periphery of the inner peripheral surface 41a, and is fixed to a front cover 3. The stepped portion 43 couples an end of the main portion 41 near an engine to an end of the connection portion 42 near a transmission. A corner portion formed of the inner peripheral surface 41a and a surface 43a near the engine has a radius set to 4 mm or less by preliminary forming by a press and subsequent finish forming by a press.