| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of annular expanding structure which can easily form projection and recession configuration on an outer surface through cold forging, and can suppress generation of forging defect, and heat radiating body of LED (light emitting diode) electric bulb. <P>SOLUTION: In the manufacturing method, a heat radiating body 5 of LED electric bulb, which has the projection and recession configuration on its outer peripheral surface, is manufactured by cold forging from slug. Using a first upper die and a first lower die having a first gradient at its tip to give extrusion action, a heavy cup-shaped material having an outer peripheral face expanded into a truncated conical shape and an inner peripheral face which has a stepped part to become an excess margin is formed. Then, using a second lower die to form the projection and recession configuration on the outer peripheral surface, and a second upper die with a second gradient on its side face to give plastic flow of the excess margin on the inner peripheral face toward the projection and recession configuration, the projection and recession configuration and a truncated warhead shaped cavity are formed. The inner peripheral surface is formed as a second step, and the bottom part of the fabricated cup-shaped material is subjected to a piercing step. Suppression of forging defect through two times of extrusion work by the gradient is main characteristics of the method. <P>COPYRIGHT: (C)2011,JPO&INPIT |
