Patent ID: 8987980
Filing Date: 2015-03-24
Classification: H01T

Abstract:
1. A spark plug comprising: an insulator having an axial hole penetrating the insulator in an axial line direction; a terminal electrode inserted in a rear end side of the axial hole; a center electrode inserted in a front end side of the axial hole; a resistor disposed between the terminal electrode and the center electrode within the axial hole and containing a conductive material and glass; and a glass seal layer disposed in the rear end side of the resistor within the axial hole, said glass seal layer contacting a front end of the terminal electrode and containing a conductive material and glass; wherein the terminal electrode has, at its front end: a recess part opened to the front end side and having a depth of 0.3 mm or greater in a center axis direction of the terminal electrode; and a flat part neighboring the recess part at its outer circumference side, and wherein 0.52≦B/A≦0.91 is satisfied, where A (mm