| 摘要 |
PROBLEM TO BE SOLVED: To easily secure a required magnetic path section by machining a belt groove in the outer peripheral surface of a drawn outer wall part after reducing the diameter and thickness of the outer wall part of an annular member by rolling to be drawn in the axial direction. SOLUTION: An annular member 1 is so constructed that an annular inner wall part 2 and an annular outer wall part 3 are integrated with each other by a base plate part 4, and the outer wall part 3 of the annular member 1 presses inside a portion except portion adjacent to the base plate part 4 by a flat roller 9 and draw the same up to a designated pulley diameter limited by the cylindrical part 13 of a lower mold 8 to reduce the diameter. Further, the flat roller 9 is pressed toward the outer wall part 3 to be decreased in thickness and drawn by rolling, and ten plural belt grooves 14 are machined according to the outer peripheral surface of a forming roller 14 in the outer periphery of the outer wall part 3 of the annular member 1 by rolling. Thus, a required magnetic path section can be easily secured.
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