| 摘要 |
PURPOSE:To provide a helical spring of long life, by shaping the cross section of a spring wire as an egg resulting from a combination of a semicircle and a semi-ellipse and by setting the ratio of the diameter of the semicircle to the major diameter of the semi-ellipse and the spring constant at prescribed values, respectively, to reduce stress concentration. CONSTITUTION:The cross section of a wire for a helical spring is shaped as a semicircle for the outer portion of the coil and a semi-ellipse which is for the inner portion of the coil and has a minor diameter equal to the diameter B of the semicircle. The ratio A/B of the major diameter A of the egg-shaped cross section of the wire to the diamter B of the semi circle is set at 1.1 or more. The spring constant (k) is determined as k=GB<4>{(2-128/9pi<2>(A/B)<3>-(3- 256/9pi<2>)(A/B)<2>+(2-128/9pi<2>)(A/B)}/8nD<3> where G denotes the modulus of rigidity, (n) the effective number of turns, and D the diameter of the coil on the center of gravity of the cross section. As a result, even if the helical spring is made of a wire with a large ratio A/B, the stress concentration in the inner portion of the coil is well reduced to lengthen the life of the coil. |
