Patent ID: 8636555
Filing Date: 2014-01-28
Classification: H01T

Abstract:
1. A manufacturing method of a spark plug, the spark plug comprising: a center electrode; an insulator having an axial hole extending in an axial direction of the center electrode and retaining the center electrode in a front side of the axial hole in the axial direction; and a cylindrical metal shell surrounding and retaining therein the insulator, the manufacturing method comprising: assembling the insulator in the metal shell by inserting the insulator from an open rear end of the metal shell in the axial direction, wherein said assembling of the metal shell and the insulator includes limiting relative positional displacement between the metal shell and the insulator in a radial direction intersecting with the axial direction in such a manner that the amount of deviation between an axis of the metal shell and an axis of the insulator becomes less than or equal to a predetermined level while allowing relative positional displacement between the metal shell and the insulator in the axial direction, and wherein said limiting includes: providing a first positioning member; bringing a front end portion of the metal shell in the axial direction into contact with the first positioning member to thereby limit displacement of the metal shell in the radial direction; providing a second positioning member movable relative to the first positioning member along the axial direction; and bringing a front end portion of the insulator in the axial direction into contact with the second positioning member to thereby limit displacement of the insulator in the radial direction.