Ngk Spark Plug Company, Limited

Ryuichi Ohno

Tomoaki Kato

Katsutoshi Nakayama

Tatsunori Yamada

Tomoyuki Igarashi

Provided is a method for manufacturing a spark plug, wherein at least one of a center electrode and the ground electrode includes an electrode base material and a columnar noble metal tip welded to the electrode base material. The method includes a laser welding step of applying a pulse oscillation laser to form a plurality of unit fusion portions on a peripheral area of a boundary between the electrode base material and the noble metal tip and welding the electrode base material and the noble metal tip. One unit fusion portion is formed by one-time laser irradiation. In the laser welding step, an irradiation axis of the laser is displaced from a central axis of the noble metal tip in a radial direction of the noble metal tip. When a diameter of the noble metal tip is denoted as a diameter A and an amount of displacement of the irradiation axis of the laser is denoted as X, A/20&#x2266;|X|&#x2266;A/4 is satisfied.

Method for manufacturing spark plug

A spark plug has a center electrode having an electrode base member and a core material which is disposed in the electrode base member and which predominantly contains copper, and a noble metal tip disposed at a forward end of the center electrode, and a fusion portion formed between the noble metal tip, and the electrode base member and the core material. The fusion portion is in contact with the core material in a cross section which is parallel to the center axis of the center electrode and which passes through the center axis and the fusion portion. The fusion portion contains a component of the noble metal tip, a component of the electrode base member, and a copper component forming the core material.

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Aichi, Japan

Ryuichi Ohno