Ignition coil for internal combustion engine

An ignition coil for applying high voltage to a spark plug that is installed at a bottom of a plug hole of an internal combustion engine, comprising:

• a tube member adapted to fitting to a top opening of the plug hole;
• a housing that has an approximately rectangular shape and is formed integrally with the tube member so that the housing is located above the top opening of the plug hole when the tube member is fitted to the top opening of the plug hole;
• a central core that has an elongated shape and is installed in the housing so that the central core is in parallel with both side surfaces of the housing;
• a primary coil that is wound around the central core;
• a secondary coil that is wound around the primary coil;
• a peripheral core that has a larger size than the central core in a direction of a height of the housing and includes:
• a first side portion and a second side portion that are opposed to a first axial end surface and a second axial end surface, respectively, of the central core in an axial direction of the central core;
• and
• a third side portion and a fourth side portion that are placed to interpose the central core, the primary coil and the secondary coil therebetween to magnetically connect the first side portion to the second side portion;
• an igniter that switches on and off electric power supply to the primary coil;
• and
• a terminal treatment portion that is arranged above or below the first side portion to electrically connect the primary coil to an external electric power source,
• wherein a first center line, which traverses a center of the central core in a longitudinal direction of the central core, is positioned above or below a second center line, which is in parallel with the first center line and traverses a center of the first side portion of the peripheral core.