A spark plug has a spark plug housing of a cylindrical shape, an insulator of a cylindrical shape, a central electrode, a ground electrode and a terminal metal fitting. The insulator has a head part projecting toward a distal end side of the spark plug from the spark plug housing. The central electrode and the ground electrode forms a discharge gap. The terminal metal fitting, electrically connected to the central electrode, has a main body part and an exposed part. The exposed part of the terminal metal fitting has a head part. An outer diameter of the head part of the exposed part is greater than an outer diameter of the main body part. A ratio Dt/Di of not less than 0.8 is satisfied, Di represents an outer diameter of the head part of the insulator and Dt represents an outer diameter of the head part of the exposed part.

A spark plug has a spark plug housing of a cylindrical shape, an insulator of a cylindrical shape, a central electrode, a ground electrode and a terminal metal fitting. The insulator has a head part projecting toward a distal end side of the spark plug from the spark plug housing. The central electrode and the ground electrode forms a discharge gap. The terminal metal fitting, electrically connected to the central electrode, has a main body part and an exposed part. The exposed part of the terminal metal fitting has a head part. An outer diameter of the head part of the exposed part is greater than an outer diameter of the main body part. A ratio Dt/Di of not less than 0.8 is satisfied, Di represents an outer diameter of the head part of the insulator and Dt represents an outer diameter of the head part of the exposed part.

A shielded ignition configuration is provided comprising a non-shield spark plug having an electrode, a spark plug extender having first end configured to mount to the spark plug such that a conductor of the extender makes electrical contact with the spark plug electrode, a second end having a cup configured for connection to a secondary lead such that the conductor makes electrical contact with the secondary lead, and a flange, and at least one retainer configured to engage the flange and cause a lower surface of the flange to engage an upper surface of a valve cover.

A shielded ignition configuration is provided comprising a non-shield spark plug having an electrode, a spark plug extender having first end configured to mount to the spark plug such that a conductor of the extender makes electrical contact with the spark plug electrode, a second end having a cup configured for connection to a secondary lead such that the conductor makes electrical contact with the secondary lead, and a flange, and at least one retainer configured to engage the flange and cause a lower surface of the flange to engage an upper surface of a valve cover.

The present invention relates to a spark plug extension body connecting an ignition coil with a spark plug for a spark ignited internal combustion engine, as well as a method for providing such a spark plug extension body for reduction of partial electrical discharges in the spark plug extension body. In conventional spark plug extensions are coil springs used as electrical conductor against the spark plug terminal and/or ignition coil terminal. These coil springs cause Corona effects and short circuiting requiring replacement of the spark plug extension. With the invention the entire electrical conductor (CR.sub.u, 64, CR.sub.L) is in a rod like form and at least both ends (CR.sub.u, CR.sub.L) of the electrical conductor (CR.sub.u, 64, CR.sub.L) are made as a monolith in a flexible and electrically conducting polymeric material, preferably electrically conducting rubber.

The present invention relates to a spark plug extension body connecting an ignition coil with a spark plug for a spark ignited internal combustion engine, as well as a method for providing such a spark plug extension body for reduction of partial electrical discharges in the spark plug extension body. In conventional spark plug extensions are coil springs used as electrical conductor against the spark plug terminal and/or ignition coil terminal. These coil springs cause Corona effects and short circuiting requiring replacement of the spark plug extension. With the invention the entire electrical conductor (CR.sub.u, 64, CR.sub.L) is in a rod like form and at least both ends (CR.sub.u, CR.sub.L) of the electrical conductor (CR.sub.u, 64, CR.sub.L) are made as a monolith in a flexible and electrically conducting polymeric material, preferably electrically conducting rubber.

The present disclosure relates to a spark plug for engines. The spark plug includes a center electrode and a ground electrode that includes a center void and a ground void respectively. An initial spark gap is formed between the center electrode and the ground electrode. A center electrode initial surface is disposed between the center void and the spark gap and a ground electrode initial surface is disposed between the ground void and the spark gap. The center void and ground void can become exposed through wear of the center electrode initial surface and ground electrode initial surface respectively. When the wear breaches center electrode initial surface and the ground electrode initial surface the wear creates a center first concentration edge and a ground first concentration edge that focus an electrical field and reduces the voltage required for fuel breakdown.

The present disclosure relates to a spark plug for engines. The spark plug includes a center electrode and a ground electrode that includes a center void and a ground void respectively. An initial spark gap is formed between the center electrode and the ground electrode. A center electrode initial surface is disposed between the center void and the spark gap and a ground electrode initial surface is disposed between the ground void and the spark gap. The center void and ground void can become exposed through wear of the center electrode initial surface and ground electrode initial surface respectively. When the wear breaches center electrode initial surface and the ground electrode initial surface the wear creates a center first concentration edge and a ground first concentration edge that focus an electrical field and reduces the voltage required for fuel breakdown.

A connector plug is described for connecting an ignition coil to a spark plug, comprising an electrical conductor, which has a first end for contacting the ignition coil and a second end for contacting the spark plug, and a protective tube, which surrounds the electrical conductor. In accordance with this disclosure it is proposed that the protective tube has a predetermined bending point with a reduced bending stiffness.

A connector plug is described for connecting an ignition coil to a spark plug, comprising an electrical conductor, which has a first end for contacting the ignition coil and a second end for contacting the spark plug, and a protective tube, which surrounds the electrical conductor. In accordance with this disclosure it is proposed that the protective tube has a predetermined bending point with a reduced bending stiffness.