US 7,073,256 B2 · Method of manufacturing center electrode for spark plug

Abstract

In a method of manufacturing a center electrode for a spark plug, a core member is press-fitted into a metal cup and, thereafter, a cold-forging process is performed to form a small-diameter portion at a closed end of the metal cup. The small-diameter portion is completely free from deformation which may occur during press-fitting operation. Thus, the small-diameter portion has excellent accuracy in shape. Furthermore, since the press-fitting is performed before the cold-forging of the small-diameter portion, it is possible to increase the press-fitting load or pressure to the extent that the core member and the metal cup are joined together with a sufficient degree of adhesion which will insure the a center electrode to have good thermal conductivity.

Claims16

Dependent claims

A method of manufacturing a center electrode for a spark plug, comprising the steps of:

press-fitting a core member into a metal cup, the metal cup being formed as a hollow cylinder with one end closed, the core member being made of metal having a higher thermal conductivity than the metal cup and being in the form of a solid cylinder free from an enlarged head or a flange and having a uniform outside diameter substantially throughout the length thereof;
and
thereafter, performing a cold-forging process to form a small-diameter portion protruding axially from the closed end of the metal cup, wherein the small-diameter portion is smaller in diameter than a transverse cross-section through the cup and core member assembly from which it protrudes, thereby forming the center electrode.

Dependencies are inferred from the claim text.

Method of manufacturing center electrode for spark plug

Life of this patent

Method of manufacturing center electrode for spark plug

Life of this patent

Abstract

Claims16