| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength coil spring capable of restricting a disturbance of roughness at a spring surface and restricting an expansion of stress concentration at a high stress part.SOLUTION: This invention relates to a coil spring 1 of a coil winding with a surface hardness exceeding 900Hv. A surface roughness at an effective winding part including an inter-coil winding side 1a, a coil inner diameter side 1b and a coil outer diameter side 1c in a sectional direction of the coil winding is less than Rz=2 μm. When this is applied as a valve spring and the like and a certain load is received, a stress concentration at a high stress part caused by a disturbance of roughness is restricted against its expansion, its breakage is prevented or restricted and durability of high strength coil spring is remarkably improved.SELECTED DRAWING: Figure 1 |
