SPARK PLUG MANUFACTURING METHOD

摘要

The objective of the present invention is to provide a spark plug manufacturing method that allows, by detecting the presence of a defect of an insulator, a spark plug with an insulator that exhibits a withstand voltage performance to be provided. This spark plug manufacturing method is characterized by involving a step in which an assembly comprising a center electrode, a main metal fitting, and the insulator is placed inside a pressure-resistant container; the pressure inside the pressure-resistant container is brought to an ambient pressure higher than the barometric pressure; and a potential difference is created between the center electrode and the main metal fitting with an insulating oil being present inside a space where the insulating oil is allowed to be present, which being a space surrounded by a packing, the main metal fitting, the insulator, and a virtual plane including the front end surface of the main metal fitting, at least at the position where the distance between a shelf section and the insulator becomes the minimum in order to determine whether or not a defect is present in the insulator.