Ignition apparatus for use in internal combustion engine

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, 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 sufface 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 through press fitting, for 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.

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, 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, for 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, and
• wherein the plug hole pipe comprises a flange portion projecting outward from an outer circumferential surface thereof, and the flange portion is fixedly attachable to the cylinder head, whereby the plug hole pipe is fixedly attachable to the cylinder head.

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, 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, for 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, and
• wherein a cylinder head cover is provided on the cylinder head, and the plug hole pipe and cylinder head cover are adapted such that, in use, the plug hole pipe is held between the cylinder head cover and the cylinder head to thereby be fixedly attached to the cylinder head.

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, 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, for 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,
• said ignition apparatus further comprising an oil seal member provided between the plug hole pipe and the cylinder head.