Patent ID: 11821485

Abstract:
According to one embodiment, a coil spring includes a wire rod with a first end and a second end. The wire rod includes a round section portion including a round first cross section perpendicular to a longitudinal direction of the wire rod, a quadrangle section portion including a quadrangle a second section perpendicular to the longitudinal direction, and a variable section portion formed between the round section portion and the quadrangle section portion of the wire rod. The cross section of the variable section portion varies from circular to quadrangle from the round section portion to the quadrangle section portion. The end turn part of the coil spring includes the quadrangle section portion. The width and thickness of the second cross-section are smaller than the diameter of the first cross-section. The area of the second cross section is smaller than the area of the square inscribed in the circle of diameter of the first cross section.