Patent ID: 6655334
Filing Date: 2003-12-02
Classification: F02B,F02F,H01T

Abstract:
An ignition apparatus for use in an internal combustion engine, comprising a spark plug, which comprises a center electrode disposed at a front end portion of an axial hole formed in an insulator, a metallic shell provided outside the insulator, and a ground electrode joined to the metallic shell and forming a spark discharge gap between the ground and center electrodes, and which spark plug is disposable in a plug disposition hole formed in a cylinder head of the internal combustion engine, said cylinder head containing lubricating oils, the ignition apparatus being adapted to induce spark discharge in the spark discharge gap of the spark plug for igniting an air-fuel mixture, the ignition apparatus being characterized in that:the metallic shell of the spark plug comprises a flange portion having a plug seat formed on a front end face thereof and adapted to come in contact with the cylinder head directly or indirectly via another member, and a front end portion extending axially frontward from the plug seat of the flange portion, receivable in the plug disposition hole, and having no thread grooves formed on an outer circumferential surface thereof; and in that a plug hole pipe is provided, which is disposable rearward in relation to the plug seat of the metallic shell and is fixedly attachable to the cylinder head, said plug hole pipe isolating the spark plug from lubricating oils in the cylinder head and causing the plug seat of the metallic shell to be pressed against the cylinder head, whereby the spark plug is fixedly attachable to the cylinder head.