A spark plug for an internal combustion engine has a cylindrical insulator, a center electrode held inside of the insulator, and, a terminal portion held inside of the insulator and electrically connected to the center electrode. The insulator has a insertion portion arranged closer to the base end side than the housing is, the insertion portion being inserted into a cylindrical plug cap. The insertion portion has a non-fit portion formed at the base end of the insulator, and, a fit portion formed to the head end side of the non-fit portion, an outer diameter of the non-fit portion being equal to or smaller than an inner diameter of the plug cap, the fit portion being fitted in the inner periphery surface of the plug cap.

A spark plug for an internal combustion engine has a cylindrical insulator, a center electrode held inside of the insulator, and, a terminal portion held inside of the insulator and electrically connected to the center electrode. The insulator has a insertion portion arranged closer to the base end side than the housing is, the insertion portion being inserted into a cylindrical plug cap. The insertion portion has a non-fit portion formed at the base end of the insulator, and, a fit portion formed to the head end side of the non-fit portion, an outer diameter of the non-fit portion being equal to or smaller than an inner diameter of the plug cap, the fit portion being fitted in the inner periphery surface of the plug cap.

A spark plug assembly includes a spark plug, where the spark plug includes a high voltage connector, an insulator body, a metallic shell, and an electrical conductor at least partly disposed in the insulator body and the metallic shell. The spark plug assembly includes a detection unit having a transmitter device and a receiver device. The transmitter device is coupled to the spark plug and is electrically disposed between the high voltage connector and the electrical conductor. Further, the transmitter device is configured to draw an excitation current from the electrical conductor. The transmitter device includes an optical signal generator that is configured to generate an optical signal in response to the drawn excitation current. The receiver device is disposed in optical communication with the transmitter device and configured to receive the optical signal from the transmitter device.

A spark plug assembly includes a spark plug, where the spark plug includes a high voltage connector, an insulator body, a metallic shell, and an electrical conductor at least partly disposed in the insulator body and the metallic shell. The spark plug assembly includes a detection unit having a transmitter device and a receiver device. The transmitter device is coupled to the spark plug and is electrically disposed between the high voltage connector and the electrical conductor. Further, the transmitter device is configured to draw an excitation current from the electrical conductor. The transmitter device includes an optical signal generator that is configured to generate an optical signal in response to the drawn excitation current. The receiver device is disposed in optical communication with the transmitter device and configured to receive the optical signal from the transmitter device.

An igniter assembly comprising an ignition coil assembly connected to a firing end assembly by an extension, with a valve assembly disposed in a pressure chamber of the extension, is provided. The valve assembly includes a valve stem biased toward the ignition coil assembly by a spring to seal the pressure chamber. The valve assembly is used to evacuate contents from the pressure chamber by pressing the valve stem toward the spring and allowing contents of the pressure chamber to travel through and past the valve stem and out of the pressure chamber. The valve assembly is also used to fill the pressure chamber with an insulating medium by pressing the valve stem toward the spring and allowing the insulating medium to travel through and past the valve stem and into the pressure chamber after evacuating the contents out of the pressure chamber.

An igniter assembly comprising an ignition coil assembly connected to a firing end assembly by an extension, with a valve assembly disposed in a pressure chamber of the extension, is provided. The valve assembly includes a valve stem biased toward the ignition coil assembly by a spring to seal the pressure chamber. The valve assembly is used to evacuate contents from the pressure chamber by pressing the valve stem toward the spring and allowing contents of the pressure chamber to travel through and past the valve stem and out of the pressure chamber. The valve assembly is also used to fill the pressure chamber with an insulating medium by pressing the valve stem toward the spring and allowing the insulating medium to travel through and past the valve stem and into the pressure chamber after evacuating the contents out of the pressure chamber.

A corona igniter assembly which is designed to reduce the amount of air gaps between insulating components and thus reduce electrical fields concentrated in those air gaps and the associated unwanted corona discharge. The assembly includes a high voltage center electrode surrounded by a ceramic insulator and a high voltage insulator. A dielectric compliant insulator is disposed between the ceramic insulator and the high voltage insulator. A layer of metal is applied to at least one of the insulators, for example the ceramic insulator. A compliant collet formed of a partially resistive material covers a sharp edge of the layer of metal to reduce the electric field and smooth the electric field distribution at the sharp edge of the metal layer.

A corona ignition device is described, with a central electrode, an insulator, in which the central electrode sits, a coil, which is connected to the central electrode, a metal housing, which holds the insulator and surrounds the coil, and a cover, which closes the metal housing at its end facing away from the insulator. According to this disclosure, provision is made for a spring arranged between the cover and the coil. In another aspect, a shield is provided that surrounds the housing and comprises several shell elements which each surround a section of the circumference of the coil.

A corona ignition device is described, with a central electrode, an insulator, in which the central electrode sits, a coil, which is connected to the central electrode, a metal housing, which holds the insulator and surrounds the coil, and a cover, which closes the metal housing at its end facing away from the insulator. According to this disclosure, provision is made for a spring arranged between the cover and the coil. In another aspect, a shield is provided that surrounds the housing and comprises several shell elements which each surround a section of the circumference of the coil.

This invention is concerning an ignition device for an internal combustion engine, wherein a plug boot has a reduced-inner-diameter portion having an inner diameter size smaller than that of the other portion, a spring has a larger diameter portion having a diameter size larger than that of the other portion, and a plurality of reduced clearances each having a width reduced by the reduced-inner-diameter portion and the larger diameter portion are formed between the spring and the inner wall surface of the plug boot.