Patent ID: 8267075
Filing Date: 2012-09-18
Classification: H01T

Abstract:
1. An ignition device for an internal combustion engine comprising: a chamber with an opening portion to be open to a cylinder of the internal combustion engine and a bottom surface that is disposed facing the opening portion, the chamber extending in an axial direction of the ignition device; an outer electrode provided around the opening portion; a center electrode that forms the bottom surface of the chamber, wherein when a voltage is applied between the center electrode and the outer electrode, a plasma is produced in the chamber and a plasma jet is injected through the opening portion into the cylinder; a housing that accommodates the center electrode, that is made of a metal, and that is formed integrally with or separately from the outer electrode; an insulating member that supports the center electrode while insulating the center electrode from the housing and the outer electrode; and a screw thread by which the ignition device is screwed into a cylinder head of the internal combustion engine, the screw thread being formed on a periphery of the housing, wherein: the housing includes a small diameter portion, the small diameter portion being disposed in a portion closer to the opening portion of the housing than the screw thread and being disposed closer to the opening portion than the bottom surface of the chamber formed by the center electrode relative to a longitudinal direction of the ignition device; a gasket for keeping the cylinder airtight is disposed at a boundary between the small diameter portion and the other portion of the housing; and a peripheral wall of the chamber is formed by the insulating member.