A spark plug includes a central electrode member and an outer electrode member. The central electrode member includes a central base and a plurality of electrode prongs extending in an axial direction from the central base. The outer electrode member surrounds the central electrode member. The outer electrode member includes a wall that is radially spaced from the plurality of electrode prongs to allow a series of electric arcs to form between the wall and the plurality of electrode prongs. The outer electrode member and the central electrode member are sized and positioned relative to one another such that a first rate of wear of the outer electrode member, along a longitudinal axis of the spark plug, is substantially equal to a second rate of wear of the central electrode member along the longitudinal axis.

One embodiment is a system comprising an internal combustion engine having one or more non-dedicated cylinders and one or more dedicated EGR cylinders configured to provide EGR to the engine via an EGR loop, a first spark plug coupled to each of the one or more non-dedicated cylinders, and a second spark plug coupled to each of the one or more dedicated EGR cylinders, wherein the second spark plug has a physical or dimensional characteristic that is different from the first spark plug. In certain forms each of the non-dedicated cylinders has only one of a first type of spark plug and each of the dedicated EGR cylinders has only one of a second type of spark plug. One or more of the characteristics that may vary between the first and second types of spark plugs include spark gap, electrode diameter, heat range, and ion sensing capability.

One embodiment is a system comprising an internal combustion engine having one or more non-dedicated cylinders and one or more dedicated EGR cylinders configured to provide EGR to the engine via an EGR loop, a first spark plug coupled to each of the one or more non-dedicated cylinders, and a second spark plug coupled to each of the one or more dedicated EGR cylinders, wherein the second spark plug has a physical or dimensional characteristic that is different from the first spark plug. In certain forms each of the non-dedicated cylinders has only one of a first type of spark plug and each of the dedicated EGR cylinders has only one of a second type of spark plug. One or more of the characteristics that may vary between the first and second types of spark plugs include spark gap, electrode diameter, heat range, and ion sensing capability.

A prechamber sparkplug includes a housing having a nozzle with a prechamber formed therein, and each of a first set and a second set of electrode prongs within the prechamber. The second set of electrode prongs downwardly depend from attachment points to the housing, and form, together with the first set of electrode prongs, spark gaps within the prechamber. Each of the anode-cathode pairs formed by the sets of electrode prongs is spaced radially inward a clearance distance from the prechamber wall to position the spark gaps in a flow of swirled gases. The flow of swirled gases displaces a flame kernel formed at the spark gaps to inhibit quenching.

A spark plug includes a first discharge chip and a second discharge chip which faces the first discharge chip and works to produce an electrical spark therebetween. At least one of the first and second discharge chips is made from material containing iridium, platinum, and tantalum. An amount of platinum in the material is in a range of 5 Wt % to 30 Wt %. An amount of tantalum is in a range of 0.3 Wt % to 7.5 Wt %. Use of such material enhances a wear resistance of the spark plug.

An ignition system has an ignition plug and an ignition control unit that controls the ignition plug. When an engine is in a predetermined operating state, the ignition control unit performs ignition control after top dead center to perform ignition after the compression top dead center. The ignition system has an airflow support structure that facilitates the flow of airflow through a discharge gap at least after the compression top dead center. The ignition system is configured such that due to the airflow support structure and the timing of the ignition, airflow at a flow rate of 5 m/s or more flows through the discharge gap during a spark period after top dead center, which is the generation period of the discharge spark in the ignition control after top dead center.

A method of providing spark ignition for an engine or other equipment having a combustion chamber. A radio frequency wave or a microwave (RF/microwave) generator delivers radio frequency waves or microwaves to a transmit antenna inside the combustion chamber. At least one RF/microwave receive antenna is attached to an internal surface of the combustion chamber and comprises two or more RF/microwave focusing features with a spark gap between them. The transmit antenna wirelessly energizes the receive antenna, which generates a spark between the two focusing features.

[Object] To prevent a sealant from intruding between a flange and a stepped portion during manufacture of a spark plug and to prevent cracking of an insulator during use of the spark plug.

[Solution] A spark plug includes a center electrode including a flange, an insulator having a through-hole extending in an axial-line direction and holding the center electrode, and a sealant filled in the through-hole to fix the flange and the insulator to each other. The insulator includes a stepped portion in which the through-hole reduces a diameter toward a front end side and that supports the flange, and a small-diameter portion that is continuous with a front end side of the stepped portion and in which the diameter of the through-hole is smaller than in the stepped portion. An angle θ1 formed by the stepped portion and a plane perpendicular to the axial line and an angle θ2 formed by the plane perpendicular to the axial line and an opposing surface of the flange opposing the stepped portion satisfies θ1−θ2≥6°. In a cross section including the axial line, a maximum diameter D1 of the flange and a diameter D2 of the through-hole at a rear end of the small-diameter portion in the axial-line direction satisfy 0.15 mm≤(D1−D2)/2.

A spark plug electrode with an electrode tip formed on an electrode base using an additive manufacturing process, such as a powder bed fusion technique. The spark plug electrode includes an intermediate layer located between the electrode tip and the electrode base, where the intermediate layer has a coefficient of thermal expansion (CTE) that is between that of the electrode base and the electrode tip and includes a whole area connection. In some examples, the whole area connection is non-uniform in thickness so that it is thicker in one section than it is in another section.

A spark plug includes: a cylindrical insulator; a center electrode, held on an inner circumferential side of the insulator, protruding from the insulator toward a tip end side; a cylindrical housing holding the insulator on an inner circumferential side; a ground electrode forming a discharge gap between the ground electrode and the center electrode on the inner circumferential side of the housing; and a plug cover provided in a tip end portion of the housing to cover a pre-combustion chamber in which the discharge gap is arranged. The plug cover is provided with an injection hole that communicates the pre-combustion chamber to the outside. The ground electrode includes a discharge-side end portion that faces the discharge gap and a joining-side end portion that is joined to the housing. The discharge-side end portion is arranged further toward a base end side in an axial direction than the joining-side end portion is.