One example provides a spark plug including an axial centerline extending between a terminal end and a firing end, an insulative core including a central bore having a first diameter coincident with the axial centerline extending through the insulative core, an insulative nose proximate to the firing end, and a counter bore coincident with the axial centerline and extending axially into the insulative nose, the counter bore having a second diameter greater than the first diameter. A center electrode includes an electrode wire disposed within the central bore and having a first end extending into the counter bore, and an electrode head mechanically and electrically coupled to the first end of the electrode wire, a first portion of the electrode head seated within the counter bore to define an interface with the counter bore to provide a heat transfer path from the electrode head to the insulative core.

A spark plug for an internal combustion engine includes insulating glass having a tubular shape, a central electrode including a tip protruding portion, a housing having a tubular shape, and a plug cover provided over an auxiliary combustion chamber. The plug cover is provided with injection holes through which the auxiliary combustion chamber communicates with the exterior. The central electrode includes a base material and a core material disposed inside the base material and having a higher thermal conductivity than the base material. The core material includes a large diameter portion and a small diameter portion continuously formed on a tip side of the large diameter portion. The small diameter portion has a smaller diameter than the large diameter portion, and includes, in a part of the small diameter portion in an axial direction, a small-diameter columnar portion having a constant diameter. At least a part of the small-diameter columnar portion is disposed further on the tip side of the spark plug than a tip of the insulating glass.

Described is a supply circuit for a corona ignition device, with an input for connection to a direct voltage source, a first converter, a second converter, and an output for connecting a load. The two converters each generate an output voltage, which is provided on its secondary side and exceeds the input voltage. The two converters each contain a transformer that galvanically separates the primary side of the converter from its secondary side. At least one transistor switch is arranged between the input and primary side of the two converters for pulse width-modulation of the input voltage. The primary side of the second converter is connected in parallel with the primary side of the first converter, the secondary side of the second converter is connected in series with the secondary side of the first converter, the secondary sides of the two converters are each bridged in this series connection by at least one diode, so that an output voltage can be provided at the output of the supply circuit even given a failure of one of the two converters.

Described is a supply circuit for a corona ignition device, with an input for connection to a direct voltage source, a first converter, a second converter, and an output for connecting a load. The two converters each generate an output voltage, which is provided on its secondary side and exceeds the input voltage. The two converters each contain a transformer that galvanically separates the primary side of the converter from its secondary side. At least one transistor switch is arranged between the input and primary side of the two converters for pulse width-modulation of the input voltage. The primary side of the second converter is connected in parallel with the primary side of the first converter, the secondary side of the second converter is connected in series with the secondary side of the first converter, the secondary sides of the two converters are each bridged in this series connection by at least one diode, so that an output voltage can be provided at the output of the supply circuit even given a failure of one of the two converters.

A spark plug includes: a cylindrical insulator; a center electrode that is held on an inner circumferential side of the insulator and includes a tip-end protruding portion that protrudes from the insulator toward a tip end side; a cylindrical housing that holds the insulator on an inner circumferential side; and a plug cover that is provided in a tip end portion of the housing so as to cover a pre-combustion chamber in which the tip-end protruding portion is arranged. The plug cover is provided with an injection hole that communicates the pre-combustion chamber to the outside. A positioning portion that performs positioning of the housing and the plug cover in a plug circumferential direction is provided in the housing and the plug cover.

A method for manufacturing a spark plug including a center electrode that extends in an axial direction, a metal shell that is provided around an outer periphery of the center electrode, and a rod-shaped ground electrode whose base end is joined to the metal shell and whose distal end is bent towards an axial-line side. The method comprises a bending step of bending an unbent ground electrode, which is the ground electrode that is not yet bent, by pressing against it a predetermined curved surface of a bend spacer, wherein the bend spacer is formed so as to be divisible into two or more members including a first member and a second member. The first member includes a mounting portion for mounting the bend spacer on a fixing tool and the second member includes the predetermined curved surface that comes into contact with the unbent ground electrode.

A method for manufacturing a spark plug including a center electrode that extends in an axial direction, a metal shell that is provided around an outer periphery of the center electrode, and a rod-shaped ground electrode whose base end is joined to the metal shell and whose distal end is bent towards an axial-line side. The method comprises a bending step of bending an unbent ground electrode, which is the ground electrode that is not yet bent, by pressing against it a predetermined curved surface of a bend spacer, wherein the bend spacer is formed so as to be divisible into two or more members including a first member and a second member. The first member includes a mounting portion for mounting the bend spacer on a fixing tool and the second member includes the predetermined curved surface that comes into contact with the unbent ground electrode.

One example provides a spark plug including a terminal end, a firing end, an axial centerline extending between the terminal end and the firing end, and an insulative core extending between the terminal end and the firing end, the insulative core including an insulative nose proximate to the firing end, and a central bore coincident with the axial centerline extending through the insulative core. A center electrode includes an electrode wire and an electrode head. The electrode head includes an electrode plate, in a plane perpendicular to the axial centerline, the electrode plate having a cross-sectional area greater than a cross-sectional area of the insulative nose, the electrode wire mechanically and electrically connected to the electrode plate, the electrode wire extending from a bottom side of the electrode plate into the central bore at the insulative nose to form an electrical and thermal pathway with the electrode head.

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 electrode base that at least partially surrounds a heat dissipating core, an electrode tip that is formed on the electrode base and includes a precious metal-based material, and a thermal coupling zone that directly thermally couples the electrode tip to the heat dissipating core. In some examples, the electrode tip is formed on an electrode base that has been cut or severed to expose a portion of the heat dissipating core, such that the electrode tip is formed directly on the heat dissipating core using additive manufacturing.

A spark plug for an internal combustion engine includes a housing, an insulator, a center electrode, a ground electrode, and an auxiliary chamber forming portion. The ground electrode faces the center electrode from an outer peripheral side and forms a discharge gap between the ground electrode and the center electrode. An auxiliary chamber is formed inside the auxiliary chamber forming portion. A distance in an axial direction between the discharge gap and a distal end of the auxiliary chamber is equal to or greater than a maximum wall thickness of the auxiliary chamber forming portion. The auxiliary chamber forming portion includes injection holes. The injection holes are formed in a state where openings on an outer side are located closer to a distal end than openings on the auxiliary chamber side. At least one of the injection holes is an injection hole in the axial direction formed along an axial direction of a plug. When viewed in the axial direction of the spark plug, a center of the axial injection hole is eccentric from a central axis of the spark plug toward the discharge gap.