A spark plug is provided which includes a cylindrical metal shell, a cylindrical porcelain insulator retained in the metal shell, a center electrode, and a ground electrode. The center electrode is disposed in the insulator with a head protruding outside a front end surface of the insulator. The ground electrode is joined to the metal shell and includes a gap-defining portion which faces a side surface of a side surface of the center electrode to define a spark gap and also faces the front end surface of the porcelain insulator to define a semi-surface discharge gap for burning off, for example, carbon deposits on the front end surface of the insulator.

A spark plug electrode with one or more electrode tip(s) formed on one or more electrode base(s) using an additive manufacturing process, such as a powder bed fusion technique, such that each electrode tip overhangs an edge of a corresponding electrode base. The spark plug electrode may be a center electrode, a ground electrode, or an annular ground electrode and can be provided according to a number of different configurations. Each electrode tip includes a precious metal-based material, such as an iridium- or platinum-based alloy, and a plurality of laser deposition layers, and each electrode tip can be secured to an electrode base with a weldless joint. An additive manufacturing process is also provided.

A spark plug is provided which includes a cylindrical metal shell, a cylindrical porcelain insulator retained in the metal shell, a center electrode, and a ground electrode. The center electrode is disposed in the insulator with a head protruding outside a front end surface of the insulator. The ground electrode is joined to the metal shell and includes a gap-defining portion which faces a side surface of a side surface of the center electrode to define a spark gap and also faces the front end surface of the porcelain insulator to define a semi-surface discharge gap for burning off, for example, carbon deposits on the front end surface of the insulator.

An ignition device for a combustion chamber of an internal combustion engine includes a first electrode and a second electrode, which is movable with the aid of an actuator. The ignition device is configured to generate a first ignition spark when a contact between the first and second electrode is interrupted. To accomplish this, the second electrode is moved away from the first electrode. A third electrode is also provided, which is spaced apart from the first electrode. With the aid of the third electrode, a second ignition spark can be generated by moving the second electrode away from the other two electrodes. With the three electrodes, the ignition unit is configured to allow the two ignition sparks to pass through a volume formed between the electrodes in the direction transverse to the longitudinal extension of the ignition sparks in the course of the movement of the second electrode.

A multipoint ignition device for igniting an air-fuel mixture in a combustion chamber of an engine includes: an insulating member formed in an annular shape such that an inner periphery thereof faces the combustion chamber; and a plurality of electrodes held on the insulating member so as to form a plurality of ignition gaps in a circumferential direction inside the combustion chamber, wherein the insulating member includes a plurality of divided insulating members formed in divided form, and the divided insulating member close to an intake valve of the engine has a higher thermal conductivity than the divided insulating member close to an exhaust valve of the engine.

The method of creating a metallic electrode on the ceramic insulator of a spark plug with a deposit of additional material using the laser weld deposition method, where this metallic electrode, formed by a diffusion metallic layer (3) of the joint between the weld deposit of the smelted wire and the insulator (1), is in the shape of a ring in the end part of the insulator body (1) around the central electrode (2) of the spark plug.

A multipoint ignition device for igniting an air-fuel mixture in a combustion chamber of an engine includes: an insulating member formed in an annular shape such that an inner periphery thereof faces the combustion chamber; a plurality of electrodes held on the insulating member so as to form a plurality of ignition gaps inside the combustion chamber; a main body portion provided on an outer periphery of the insulating member; and an intermediate member that is provided between the main body portion and the insulating member and has a larger thermal expansion coefficient than the insulating member.

A multipoint ignition device for igniting an air-fuel mixture in a combustion chamber of an engine includes: an insulating member formed in an annular shape such that an inner periphery thereof faces the combustion chamber; and a plurality of electrodes held on the insulating member so as to form a plurality of ignition gaps in a circumferential direction inside the combustion chamber, wherein the insulating member includes a plurality of divided insulating members formed in divided form, and the divided insulating member close to an intake valve of the engine has a higher thermal conductivity than the divided insulating member close to an exhaust valve of the engine.

A multipoint ignition device for igniting an air-fuel mixture in a combustion chamber of an engine includes: an insulating member formed in an annular shape such that an inner periphery thereof faces the combustion chamber; a plurality of electrodes held on the insulating member so as to form a plurality of ignition gaps inside the combustion chamber; a main body portion provided on an outer periphery of the insulating member; and an intermediate member that is provided between the main body portion and the insulating member and has a larger thermal expansion coefficient than the insulating member.

The method of creating a metal electrode on the ceramic insulator of a spark plug with a deposit of additional material using the laser weld deposition method, where this metal electrode, formed by a diffusion metallic layer (3) of the joint between the weld deposit of the smelted wire and the insulator (1), is in the shape of a ring in the end part of the insulator body (1) around the central electrode (2) of the spark plug.