| 主权项 |
1. A suspension spring apparatus comprising:
a lower spring seat;
an upper spring seat; anda coil spring which comprises a wire formed into a helical shape, and arranged in a state in which the coil spring is compressed between the lower spring seat and the upper spring seat,the coil spring comprising a lower end turn portion which is less than one turn from a lower end of the wire, and an upper end turn portion which is less than one turn from an upper end of the wire,at least the lower end turn portion comprising a first portion which is always in contact with the lower spring seat irrespective of magnitude of a load applied to the coil spring, a second portion which contacts the lower spring seat or is separated from the lower spring seat in accordance with the load applied to the coil spring, and a third portion which is always separated from the lower spring seat irrespective of the magnitude of the load,the coil spring comprising:a compressive residual stress portion between the lower end turn portion and the upper end turn portion, a compressive residual stress from a surface of the wire to a first depth being imparted to the compressive residual stress portion, anda deep residual stress portion in a region including the second portion of the lower end turn portion, a compressive residual stress from a surface of the wire to a second depth deeper than the first depth being imparted to the deep residual stress portion. |
