The present invention relates to a press working process whereby a front cover and an impeller shell are deformed such that corner portions are formed on a blank material whereby the corner portions undergo minimal reductions in thickness. In the press working method, compressive force is applied parallel to the thickness of the blank to circumvent reduction in thickness during the deforming process.
A strong lightweight front cover 11 that prevents distortion of a sliding contact surface when the front cover and impeller shell are welded together is provided. The front cover 11 has a radial flange part 44 and an axial flange part 42 that extends from an outside edge of radial flange part 44. The radial flange part 44 has a sliding contact surface 44a on an axially facing surface thereof for sliding against a friction facing 76. The axial flange part 42 has a connection part 51 that connects to the radial flange part 44 and a welding part that is connected by welding to a pump impeller. The various portions of the front cover 11 have differing rigidities and thicknesses.
A torque converter comprises an impeller shell, a pump impeller integrally formed with the impeller shell, a turbine runner, a stator, a front cover, and at least one of a flanged portion through which a driving power of an engine is transmitted and a ring gear for a starter. The flanged portion is formed on an outer peripheral portion of an outer hull that includes the impeller shell and the front cover. A pilot boss portion is disposed at an axial portion of the front cover and is adapted to be fitted to a crank shaft of the engine, and a sleeve-like oil pump driving shaft is disposed at an axial portion of the impeller shell and is adapted to drive an oil pump. The pilot boss portion is formed integrally with the front cover through a plastic working operation, and the flanged portion formed at a front portion of the outer periphery of the front cover is increased in thickness through a plastic working operation that forms the flanged portion as a lamination.