Patent ID: 9169880
Filing Date: 2015-10-27
Classification: F16D

Abstract:
1. A method of manufacturing a magnetic path forming member of a driving force transmission apparatus including, an outer rotary member and an inner rotary member that are rotatable relative to each other, multiple clutch discs that are arranged between the outer rotary member and the inner rotary member, and that transmit driving force between the outer rotary member and the inner rotary member with use of frictional force, an electromagnet arranged on one axial side of the clutch discs, an armature that is arranged on another axial side of the clutch discs, and that is attracted toward the electromagnet when the electromagnet is energized, and the magnetic path forming member being included in the outer rotary member, is arranged between the clutch discs and the electromagnet, and forms a magnetic path in cooperation with the electromagnet, the clutch discs and the armature when the electromagnet is energized, the method comprising: heating a radially intermediate portion of a workpiece and made of a magnetic material, to melt the radially intermediate portion from one axial face of the workpiece to another axial face of the workpiece to form a keyhole; and disposing an alloy element in a molten pool around the keyhole to demagnetize a melted portion, thereby providing the magnetic path forming member.