| 摘要 |
Between the end windings (12a, 12b) of a coil spring (12), a compressive residual stress area (50) having compressive residual stress is formed from the surface of the wire (40) to a first depth (D1). The end winding (12a) includes a first portion (12a1), a second portion (12a2) and a third portion (12a3). The first portion (12a1) is always in contact with a spring base regardless of the load applied to the coil spring (12). The second portion (12a2) is in contact with the spring base when the load applied to the coil spring (12) is large, and is separated from the spring base when the load is small. The third portion (12a3) is always separated from the spring base regardless of the magnitude of the load. In a region of the end winding (12a) that includes the second portion (12a2), a deep residual stress portion (51) is formed by ultrasonic shot peening. The deep residual stress portion (51) has compressive residual stress from the surface of the wire (40) to a second depth (D2) greater than the first depth (D1). |
