Spark plug and internal combustion engine equipped with the same

A spark plug for an internal combustion engine, the spark plug having an axial direction and comprising:

• a tubular insulator having a tip-side end;
• a center electrode having one side and a tip-side end, the center electrode being disposed inside the insulator with the tip-side end of the center electrode protruding outwardly from the tip-side end of the insulator;
• a tubular housing that has a tip-side end and retains the insulator thereinside;
• a ground electrode having a stationary end and a projection-end edge opposite to the stationary end, and one side;
• and
• a plug cover mounted to the tip-side end of the housing to define a sub-chamber between the plug cover and the tip-side end of the housing,
• wherein:
• the stationary end of the ground electrode is mounted to the tip-side end of the housing;
• the projection-end edge of the ground electrode projects to be located in the sub-chamber such that the one side of the ground electrode serves as a facing side facing the one side of the center electrode, resulting in a discharge gap being formed between the facing side of the ground electrode and the one side of the center electrode;
• the plug cover has formed therethrough at least one injection hole that enables the sub-chamber to communicate with an outside thereof, the at least one injection hole having a center axis;
• the center axis of the at least one injection hole is inclined with respect to a radial direction of the spark plug as viewed in the axial direction of the spark plug;
• the at least one injection hole serves as a ground-directed injection hole arranged to face the facing side of the ground electrode, and an extension line of the center axis of the at least one ground-directed injection hole intersects with the facing side of the ground electrode at an intersection point;
• the facing side of the ground electrode has a closer region closer to the projection-end edge of the ground electrode than the intersection point is;
• and
• the closer region of the facing side intersects with the extension line of the center axis of the ground-directed injection hole at a predetermined angle as viewed in the axial direction of the spark plug, the predetermined angle being an obtuse angle.