SPARK PLUG FOR INTERNAL COMBUSTION ENGINE AND METHOD FOR PRODUCING THE SAME

摘要

Disclosed is a spark plug wherein the ignition property is improved without reducing the durability. A spark plug (1) is provided with a ground electrode (27). The ground electrode (27) is comprised of a main body portion (27A), a projected portion (27B) which is projected from an inner surface (27i) of the main body portion (27A) toward the front end side in a longitudinal direction, and a recessed portion (27C) which is open from an outer surface (27o) of the main body portion (27A) toward the front end side. The main body portion (27A) and the projected portion (27B) are formed from the same material. If the length of the projected portion (27B) from the inner surface (27i) is defined as A (mm), the length of the projected portion (27B) from the front end of the main body portion (27A) in the longitudinal direction of the main body portion (27A) is defined as B (mm), the length of the recessed portion (27C) in the longitudinal direction of the main body portion (27A) is defined as C (mm), the depth of the recessed portion (27C) from the outer surface (27o) is defined as D (mm), and the thickness of the main body portion (27A) is defined as E, then 0.3=A=1.0, 0.0<B=1.4, 0.0<C=2.0, and 0.0<D/E<0.85 are satisfied.