Prechamber spark plug having an optimized cap, and internal combustion engine

An internal combustion engine, comprising:

• a cylinder having therein a combustion chamber;
• a piston configured to move back and forth;
• an injector configured to introduce a fuel into the combustion chamber;
• and
• a prechamber spark plug including:
• a housing;
• and
• a cap, which defines a prechamber at least partially, and which includes a plurality of through holes that are configured to produce a connection between the prechamber and the combustion chamber of the cylinder, the through holes each having a hole center line;
• wherein:
• the cap includes a recess at a region forming a surface of the cap that (a) faces towards the housing and that (b) abuts the housing at a combustion-chamber-side end of the housing;
• and
• the prechamber spark plug includes at least one of the following features (I)-(IV):
• (I) at least one of the following features (i) and (ii) is provided for one of the through holes:
• (i) a distance from (a) an exit point of the one of the through holes that lies on the hole center line of the one of the through holes to (b) the surface of the recess is in a range of 2 mm to 7 mm;
• and
• (ii) the hole center line of the one of the through holes lies on a same plane as (a) a beginning of an external thread of the housing at a combustion-chamber-side end of the housing facing the combustion chamber and (b) a center axis of the prechamber spark plug, when the housing is completely screwed into a cylinder head of the cylinder;
• (II) the recess is formed by a radially inward step of an exterior surface of the cap;
• (III) the prechamber spark plug is arranged relative to the combustion chamber and to the injector in the cylinder head such that a center axis of a conical spray of fuel, when generated by the injector into the combustion chamber, is, relative to the center axis of the prechamber spark plug, at an angle that is within a range of 30° to 70°;
• and
• (IV) the through holes are oriented relative to the combustion chamber such that a direction of a stream of a tumble flow of the fuel, generated by the movement of the piston in the cylinder, is parallel to and in line with the hole center line of at least one of the through holes for direct reception therein of the stream.