Spark plug including a ground electrode, a center electrode, and a resistor

A spark plug for a gas engine, said spark plug including a ground electrode (4) whose front end is to be placed in a combustion chamber of the gas engine which is driven by gaseous fuel, a metallic shell (3) enclosing a center electrode (5) which has a noble metal tip (18) superior in spark-erosion resistance at a firing portion in which a spark discharge occurs against the ground electrode (4), and a resistor (10) provided within one of the spark plug and a spark plug cap so as to be included in a spark plug voltage circuit which applies a high voltage to the center electrode;

• the noble metal tip having a diameter in a range of 0.5.about.1.5 mm, and the resistor having an electrical resistance in the range of 50-200 k.OMEGA.;
• wherein the metallic shell (3) has a front end (3a), a distance (L) between said front end (3a) and a discharge surface (18a) of the noble metal tip (18) is from 1.5 mm to 5.5 mm, while the ground electrode (4) has a noble metal tip (14) provided thereon to form a spark gap (G) between a discharge surface (14a) of the noble metal tip (14) and the discharge surface (18a) of the noble metal tip (18), the spark gap (G) being from 0.3 mm to 0.5 mm.