Denso Corporation

Kazuhiko Tanaka

Hirofumi Muranaka

Akihiro Endou

Hirofumi Nishiwaki

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.

Method of manufacturing center electrode for spark plug

An object of the present invention is to disclose an apparatus and method for printing a spark plug, wherein an excellent print quality is obtained and maintained. The printing apparatus comprises: a marking roller for forming an ink film on an intaglio on itself; a transfer roller for transferring the ink film from the intaglio to the spark plug insulator; an ink supply nozzle for supplying the intaglio with the printing ink; and a doctor blade for scratching a surplus ink which does not contribute to form the ink film. the concave depth of the intaglio is made to be between 15 &#x3bc;m and 20 &#x3bc;m, both inclusive, thereby optimizing the ink drying.

Printing apparatus and method for spark plug insulator

A fabrication method of a metal shell to be installed on a park plug is provided which is made up of a small-diameter portion, a large-diameter portion, and a wrapping portion. The wrapping portion is to be wrapped by staking about the spark plug to achieve installation of the metal shell on the spark plug. The method comprises pressing a workpiece with a punch to shape the wrapping portion of the metal shell in a first cold forging process and processing the workpiece to shape the small-diameter portion of the metal shell in a second cold forging process different from the first cold forging process. This produces the metal shell which is less susceptible to cracks when installed on the spark plug and has an increased service life.

Fabrication method of metal shell of spark plug

A manufacturing method is provided that produces a tubular metallic shell for spark plugs. The metallic shell has a tapered part in the outer periphery to provide a seal. The tapered part can be formed into a desired shape by cold forging operation. A first processed part has a first tapered part with a tapering angle A formed in the first processing step. In the second processing step, the first tapered part is transformed into a second tapered part having a tapering angle B. This is accomplished by utilizing a stepped inner cavity with a second molding die with a tapered bearing surface having a tapering angle B which is greater than the tapering angle A. In the third processing step, the second tapered part is transformed into a third tapered part with a tapering angle C. This is accomplished by utilizing a stepped inner cavity with a third molding die with a tapered bearing surface having a tapering angle C which is smaller than the tapering angle B. It also utilizes a third punch having a tip part whose outer diameter is smaller than the outer diameter of the small diameter foot part of the second processed part.

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Kuwana, Japan

Kazuhiko Tanaka