| abstract |
To provide a small spark plug and a method of manufacturing the spark plug that combines fouling resistance and long-term withstand voltage characteristics. An insulator 2 having a leg 30 at its tip side, a center electrode 3, and a metal shell 1 holding the insulator 2 by the engaging convex portion 56; The inner diameter D IN of the convex portion 56, the maximum outer diameter d OUT of the leg portion 30 facing the inner circumferential surface 59 of the engaging convex portion 56, its inner diameter d IN , and an insulator ( Spark plug 100 having a dielectric constant? Of 2) satisfying the following conditions, and two or more kinds of Group 2 element compound powders including Al compound powder, Si compound powder, Mg compound powder and Ba compound powder And a raw material powder containing 0.5 to 4.0 mass% of rare earth compound powder, followed by sintering after press molding to produce an insulator (2). Conditions: (D IN -d OUT ) /2≤0.40 (mm), (d OUT -d IN ) /2≤1.65 (mm) and ε≥9.4 |