Patent ID: 8033880
Filing Date: 2011-10-11
Classification: H01T

Abstract:
1. A method for manufacturing a spark plug comprising the steps of: (a) preparing a metal shell including an insertion hole penetrating the metal shell in an axial direction, an intended crimping portion formed on an upper end of the insertion hole, a stepped portion of the metal shell which protrudes inwardly from an inner circumference of a lower end portion of the insertion hole and has a diameter smaller than that of the insertion hole, and an intended compressive deformation portion forming a portion of an inner peripheral wall of the insertion hole between the intended crimping portion and the stepped portion of the metal shell; (b) preparing an insulator including a first cylindrical portion of a substantially cylindrical shape, in which a metal terminal is exposed from an upper end thereof in an axial direction, a second cylindrical portion of a substantially cylindrical shape, in which a center electrode is exposed from a lower end thereof in an axial direction, and a stepped portion of the insulator formed between lower ends of the first cylindrical portion and an upper end of the second cylindrical portion; (c) inserting the insulator in the insertion hole of the metal shell; (d) forming the intended crimping portion of the metal shell into a crimping portion; and (e) pressing the lower side portion of the metal shell closer to a position lower than the intended compressive deformation portion, and pressing the crimping portion of the metal shell in an axial direction to compressively deform the intended compressive deformation portion of the metal shell and thereby seal a space between the stepped portion of the metal shell and the stepped portion of the insulator, wherein the step (e) controls a pressing amount of a press in a constant value from the start of compressive deformation to the end thereof.