| 摘要 |
PROBLEM TO BE SOLVED: To obtain a coil spring having excellent elastic effect by accommodating an original spring, in which a wire is coiled in several times to a prescribed coil diameter/pitch and has a round cross sectional shape, in a female die, pressing/deforming with using a male die fitting into the female die between the male/female dies in the direction orthogonal to the coil axis and making an oval shape having a large diameter at a center part and a small diameter at both ends. SOLUTION: By coiling a wire to a fixed coil diameter in plural times, an original coils spring 15 having a round cross section is formed, is accommodated in a die recessed part 21 of a female die 20 and is pressed with using a male die 30 fitting into the die recessed part 21 between female/male both dies in the direction orthogonal to the coil axis. The original spring 15 is deformed lat and is formed to an oval shape having a large diameter at the center part and a small diameter at both ends. Tension is applied to an oval coil spring, the torsional deformation generated to a coiled surface is eliminated by deforming the cross section from a round shape to an oval shape, successively, by quenching, an oval coil spring having a fixed pitch is obtained.
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