Patent ID: 8876095
Filing Date: 2014-11-04
Classification: F16F

Abstract:
1. A coil spring comprising: a spring wire that is wound in a coil shape and whose sectional outer basic shape is circular; and a contact face formed between coil inner and outer diameter sections of a sectional outer shape of the spring wire so that coil portions adjacent to each other in a coil axis direction are stabilized when they are brought into contact with each other through the contact face, the sectional outer shape being of the spring wire having the contact face based on the sectional outer basic shape, wherein a flattening of the sectional outer shape with the contact face in the coil axis direction corresponds to a stress ratio that is equal to or lower than a stress ratio of a coil spring whose sectional outer shape is circular, in which“T” and “W” are opposite elements resulting in an inverse relationship, and “T/W” represents the flattening and the flattening is in a range of 0.32<=T/W<=0.83, and wherein the coil spring includes one of either no bearing surface formed by a bearing surface abrasive process or a reduced bearing surface formed by the bearing surface abrasive process to have a reduced abrasive amount, the reduced abrasive amount required to form said bearing surface being equivalent to a reference normal bearing surface formed on a reference normal coil spring having a circular cross section by the bearing surface abrasive process with a reference abrasive amount, the reference abrasive amount being greater than the reduced abrasive amount, wherein the coil shape has a total number of coil turns that is determined according to the flattening of the sectional outer shape in a region below a line of a relationship, the relationship appearing in a state where a coil inner diameter, spring constant, and stress ratio are fixed, between a total number of coil turns and the flattening of the sectional outer shape in the coil spring for which no bearing surface is formed by the bearing surface of the abrasive process or for which the bearing surface is formed by the bearing surface abrasive process with the reduced abrasive amount, said line of the relationship defined so that the coil spring includes no bearing surface or the bearing surface formed by the bearing surface abrasive process has the same solid height as the reference normal coil spring when the coil spring and reference normal coil spring have the total number of coil turns and the flattening on the line of the relationship, the region below the line of the relationship defined so that the flattening in the region is less than the flattening on the line at each total number of coil turns.