A multipoint spark plug includes side electrodes provided in a pair so as to extend in a lengthwise direction of a tip end portion via a gap, and an intermediate electrode provided in the gap between the pair of side electrodes such that a plurality of ignition gaps are formed in the lengthwise direction of the tip end portion. An electrode holding portion is formed from separate parts that hold the side electrodes and the intermediate electrode, respectively, so as to insulate the side electrodes and the intermediate electrode from the main body portion, and the respective parts thereof project into the combustion chamber from the tip end portion.

A multipoint spark plug includes side electrodes provided in a pair so as to extend in a lengthwise direction of a tip end portion via a gap, and an intermediate electrode provided in the gap between the pair of side electrodes such that a plurality of ignition gaps are formed in the lengthwise direction of the tip end portion. An electrode holding portion is formed from separate parts that hold the side electrodes and the intermediate electrode, respectively, so as to insulate the side electrodes and the intermediate electrode from the main body portion, and the respective parts thereof project into the combustion chamber from the tip end portion.

A ceramic spark plug insulator with improved electrical and mechanical strength.

A ceramic spark plug insulator with improved electrical and mechanical strength.

A metal shell for a spark plug is made from a steel material that has increased carbon content and, in some embodiments, boron as well. The steel material is well-suited for extrusion because of its ductility, while maintaining requisite strength. The spark plug shell may have a reduced outer diameter (OD.sub.HL) at a crimped hot lock region, such as the case when the shell is used in smaller diameter spark plugs, such as M8 and M10 plugs. According to a non-limiting example, the spark plug shell steel material comprises 0.20-0.55 wt % carbon, inclusive.

A method for manufacturing a prechamber spark plug including an external thread and a cap including at least one through-opening. The method includes: providing the prechamber spark plug without a cap and including a cylindrical circumferential surface for the external thread. Mounting the cap, which includes at least one through-opening, in an arbitrary alignment at the prechamber spark plug, and creating the external thread at the circumferential surface in such a way that a thread start and/or a thread end of the external thread is aligned in relation to the through-opening at a predetermined position.

A method for manufacturing a prechamber spark plug including an external thread and a cap including at least one through-opening. The method includes: providing the prechamber spark plug without a cap and including a cylindrical circumferential surface for the external thread. Mounting the cap, which includes at least one through-opening, in an arbitrary alignment at the prechamber spark plug, and creating the external thread at the circumferential surface in such a way that a thread start and/or a thread end of the external thread is aligned in relation to the through-opening at a predetermined position.

A spark plug having multiple spark gaps, where at least one of the spark gaps is located within a prechamber. The spark plug may include a first center wire assembly, a second center wire assembly, an insulator, a metallic shell, a first sparking area with a prechamber cap and a ground electrode for a prechamber spark gap, and a second sparking area with a ground electrode for a main chamber spark gap. The spark plug is designed to maximize engine performance and/or operation by utilizing the multiple spark gaps, where the prechamber spark gap may be used for certain operating conditions where such a spark gap is advantageous and the separate main chamber spark gap may be used for other conditions where a main chamber spark gap is advantageous.

A spark plug having multiple spark gaps, where at least one of the spark gaps is located within a prechamber. The spark plug may include a first center wire assembly, a second center wire assembly, an insulator, a metallic shell, a first sparking area with a prechamber cap and a ground electrode for a prechamber spark gap, and a second sparking area with a ground electrode for a main chamber spark gap. The spark plug is designed to maximize engine performance and/or operation by utilizing the multiple spark gaps, where the prechamber spark gap may be used for certain operating conditions where such a spark gap is advantageous and the separate main chamber spark gap may be used for other conditions where a main chamber spark gap is advantageous.

A prechamber spark plug for an internal combustion engine with the following features: a body with an external thread at its front end for screwing the spark plug into the engine; the external thread has a center line and begins with a thread start at the front end; the body has a passage in which an insulator is fastened and a center electrode protrudes from the front end of this insulator; at the front end of the body, a prechamber-forming cap is provided, which delimits a prechamber and shields the center electrode from a combustion chamber of the engine after the spark plug has been installed in the engine; the cap has at least one opening, which has a predefined orientation in relation to the thread start and is oriented obliquely to the center line of the external thread so as to permit a gas exchange between the prechamber and the space outside the prechamber.