Patent ID: 8356397

Claim:
A manufacturing method of a clutch for an automatic transmission which comprises two clutches provided on an input side of a transmission mechanism to conduct connection/disconnection between of an input shaft and the transmission mechanism, inner peripheral portions of respective drum members of which are connected to a sleeve member connected to the input shaft at different positions in an axial direction, a piston provided between the both drum members on an outer periphery side of the sleeve member, the piston forming an oil-pressure chamber of one of the clutches with the drum member of said one of the clutches, a seal plate provided between the drum member of the other of the clutches and said piston, the seal plate forming a centrifugal balance oil-pressure chamber of said one of the clutches, and a return spring provided between said piston and said seal plate to bias said piston toward the drum member of said one of the clutches in a state in which one end of thereof is received by the drum member of said other of the clutches via the seal plate, the manufacturing method comprising: an insulator attaching step of attaching an insulator to either said piston or said seal plate, wherein when the insulator is attached to said piston the insulator provides electric isolation between said piston and the drum member of said one of the clutches, and wherein when the insulator is attached to said seal plate the insulator provides electric isolation between said seal plate and the drum member of said other of the clutches; a first connecting step of connecting the drum member, to which the electric isolation with said insulator is not applied, to the sleeve member; an assembling step of assembling said piston, return spring and seal plate to the sleeve member to which the drum member has been connected through said first connecting step to form an assembly; and a second connecting step of connecting the drum member, to which the electric isolation with said insulator has been applied, to the sleeve member of said assembly which has been formed through said assembling step with electric welding.