A pre-chamber spark plug that includes a shell, and an end cap attached to the shell. Additionally, the pre-chamber spark plug includes an insulator disposed within the shell. In a particular embodiment, a center electrode has a first portion surrounded by the insulator, and a second portion that extends from the insulator into a pre-chamber. The pre-chamber defined by the shell and end cap. In a further embodiment, a ground electrode is attached to the shell. In particular embodiments, the ground electrode is tubular in shape and includes an inner spark surface ring spaced in surrounding relation to the center electrode to create a spark gap, an outer ring attached to the shell, and a plurality of rounded spokes connecting the inner and outer rings. In a particular embodiment, the ground and center electrodes accommodate attachment of precious metal alloys to increase electrode surface life.

An electrode for a spark plug, having an electrode base body and a cylindrical wear part, the wear part having a longitudinal axis that extends from an end face of the wear part, facing the electrode base body, to an end face situated opposite this end face, and the wear part having a first region and a second region, the wear part not being fused in the first region and the wear part being fused in the second region.

An electrode for a spark plug, having an electrode base body and a cylindrical wear part, the wear part having a longitudinal axis that extends from an end face of the wear part, facing the electrode base body, to an end face situated opposite this end face, and the wear part having a first region and a second region, the wear part not being fused in the first region and the wear part being fused in the second region.

A pair of electrode lugs clamp a bar at side surfaces of the bar so as to be electrically connected to the bar. The electrode lugs respectively include a first contact portion and a second contact portion having different front-back lengths. The bar is clamped such that the first contact portion having a short front-back length L1 opposes a back end portion of the bar within a range of the second contact portion having a front-back length L2. The back end surface of the bar is brought into contact with and welded to a front end surface of a metal shell by resistance butt welding. Since the first contact portion of one lug is short and is close to the abutting surfaces, heat dissipation can be reduced and heat concentration can be increased.

An ignition device includes a center electrode, a center dielectric covering the center electrode, a ground electrode disposed so as to form a discharge space with the center dielectric, and a high energy source for applying an AC voltage between the center electrode and the ground electrode to generate a streamer discharge. A distal end portion of the center electrode projects beyond a distal end of the ground electrode to an inside of the combustion chamber of an internal combustion engine to make a dielectric discharge portion. The ground electrode is formed with an airflow inlet and en airflow outlet at a lateral portion thereof for enabling an in-cylinder airflow to be introduced into the discharge space. A distal end portion of the ground electrode projects radially inward to make a ground electrode projecting portion so that a discharge space narrow portion is formed with the dielectric discharge portion.

An ignition device includes a center electrode, a center dielectric covering the center electrode, a ground electrode disposed so as to form a discharge space with the center dielectric, and a high energy source for applying an AC voltage between the center electrode and the ground electrode to generate a streamer discharge. A distal end portion of the center electrode projects beyond a distal end of the ground electrode to an inside of the combustion chamber of an internal combustion engine to make a dielectric discharge portion. The ground electrode is formed with an airflow inlet and en airflow outlet at a lateral portion thereof for enabling an in-cylinder airflow to be introduced into the discharge space. A distal end portion of the ground electrode projects radially inward to make a ground electrode projecting portion so that a discharge space narrow portion is formed with the dielectric discharge portion.

A composite sparking component for a spark plug that has a thin precious metal layer with a series of grooves attached to an underlying base layer. The grooves allow the precious metal layer, and hence the entire composite sparking component, to be more easily bent or formed into a desired shape, while at the same time minimizing the amount of precious metal and providing enhanced sparking sites along the edges of the grooves. In one example, the composite sparking component is a sleeve-shaped component attached to a center electrode. In a different example, the composite sparking component is a ring-shaped component attached to a ground electrode. The precious metal layer may be bonded to the base layer in the form of a bimetal laminate structure, or the precious metal layer can be built on the base layer with the use of additive manufacturing, to cite several possibilities.

A composite sparking component for a spark plug that has a thin precious metal layer with a series of grooves attached to an underlying base layer. The grooves allow the precious metal layer, and hence the entire composite sparking component, to be more easily bent or formed into a desired shape, while at the same time minimizing the amount of precious metal and providing enhanced sparking sites along the edges of the grooves. In one example, the composite sparking component is a sleeve-shaped component attached to a center electrode. In a different example, the composite sparking component is a ring-shaped component attached to a ground electrode. The precious metal layer may be bonded to the base layer in the form of a bimetal laminate structure, or the precious metal layer can be built on the base layer with the use of additive manufacturing, to cite several possibilities.

A tip that contains a noble metal is joined to a joining surface of an electrode base material of a ground electrode via a welded portion. On cross-sections of the tip and the electrode base material in a longitudinal direction of the joining surface, the welded portion has a void above the joining surface, and a continuous distance of the welded portion on the joining surface is less than or equal to 0.5 mm, whereby thermal stress due to a difference in thermal expansion between the tip and the electrode base material can be reduced. A total of continuous distances of the welded portions on the joining surface, are 0.4 times to 0.8 times a length from an end of the tip to another end thereof, whereby joining strength of the welded portion can be assured. Peeling at the tip or falling-off of the tip due to thermal stress can be less likely to occur, whereby durability of the ground electrode can be improved.

A tip that contains a noble metal is joined to a joining surface of an electrode base material of a ground electrode via a welded portion. On cross-sections of the tip and the electrode base material in a longitudinal direction of the joining surface, the welded portion has a void above the joining surface, and a continuous distance of the welded portion on the joining surface is less than or equal to 0.5 mm, whereby thermal stress due to a difference in thermal expansion between the tip and the electrode base material can be reduced. A total of continuous distances of the welded portions on the joining surface, are 0.4 times to 0.8 times a length from an end of the tip to another end thereof, whereby joining strength of the welded portion can be assured. Peeling at the tip or falling-off of the tip due to thermal stress can be less likely to occur, whereby durability of the ground electrode can be improved.