Disc spring manufacturing method, and disc spring

A disc spring comprising

• a spring body formed into an annular shape and having
• an outer circumferential surface facing an outward side in a radial direction,
• an inner circumferential surface facing an inward side in the radial direction,
• an outer circumferential edge that is an end surface on the outward side in the radial direction, and
• an inner circumferential edge that is an end surface on the inward side in the radial direction,
• wherein a compressive residual stress is applied to at least an outer end portion in the radial direction on the inner circumferential surface throughout an entire length in a circumferential direction around a center axis line of the spring body,
• the compressive residual stress is maximized on the inner circumferential surface and decreases toward the outer circumferential surface, and
• a surface roughness of a part of the inner circumferential surface to which the compressive residual stress is applied is smaller than a surface roughness of a part inward therefrom in the radial direction.

A disc spring comprising

• a spring body formed into an annular shape and having
• an outer circumferential surface facing an outward side in a radial direction,
• an inner circumferential surface facing an inward side in the radial direction,
• an outer circumferential edge that is an end surface on the outward side in the radial direction, and
• an inner circumferential edge that is an end surface on the inward side in the radial direction,
• wherein a compressive residual stress is applied to at least an outer end portion in the radial direction on the inner circumferential surface throughout an entire length in a circumferential direction around a center axis line of the spring body,
• the compressive residual stress is maximized on the inner circumferential surface and decreases toward the outer circumferential surface, and
• a hardness of a part of the inner circumferential surface to which the compressive residual stress is applied is higher than a hardness of a part inward therefrom in the radial direction.