| 摘要 |
A portion 23 of a cylindrical member 3 projecting from a front end 4a of a plug body 4 has outside diameter D2, which is defined as a smaller diameter than a portion of the metallic, cylindrical member which is fixedly disposed within the metallic, cylindrical plug body (a large-diameter portion 33 of the cylindrical member 3). A front-end-oriented end face 3t is formed in a diameter transition region where the outside diameter changes between the two diameters. In a mounting bore formed in a cylinder head, bore diameter D3 of a dead end portion, against which the front end 4a of the body 4 is pressed, is rendered smaller than outside diameter D1 of a large-diameter portion 33 of the cylindrical member 3. Since the dead end portion prevents movement of the cylindrical member 3, even when the cylindrical member 3 comes off the body 4, the member 3 does not drop into the interior of an engine. <IMAGE> |
