Abstract: An ignition coil includes primary and secondary coils, a center core inserted into a center hole of the primary coil and a center hole of the secondary coil, an annular side core that forms a magnetic circuit through which a first magnetic flux A generated by the primary coil by being joined to the center core permeates, and a permanent magnet that is disposed between the center core and the side core and that emits a second magnetic flux B directed opposite to the first magnetic flux A to apply a magnetic bias. The side core includes protruded portions that protrude towards lateral sides of a T-shaped horizontal portion of the center core, and gaps are provided between the lateral sides of the T-shaped horizontal portion of the center core and the protruded portions of the side core.

Abstract: An ignition coil includes primary and secondary coils, a center core inserted into a center hole of the primary coil and a center hole of the secondary coil, an annular side core that forms a magnetic circuit through which a first magnetic flux A generated by the primary coil by being joined to the center core permeates, and a permanent magnet that is disposed between the center core and the side core and that emits a second magnetic flux B directed opposite to the first magnetic flux A to apply a magnetic bias. The side core includes protruded portions that protrude towards lateral sides of a T-shaped horizontal portion of the center core, and gaps are provided between the lateral sides of the T-shaped horizontal portion of the center core and the protruded portions of the side core.

Abstract: An internal combustion engine ignition coil according to the present invention includes: a central iron core; a primary coil disposed on an outer circumference of the central iron core; a secondary coil disposed on an outer circumference of the primary coil; a side iron core disposed on an outer circumference of the secondary coil; and an insulating material sealing the central iron core, the primary coil, and the secondary coil on an inner side of the side iron core. A first layered silicate having a particle diameter less than a winding diameter of the secondary coil is present at a higher concentration in a vicinity of the secondary coil than that in a vicinity of the side iron core in the insulating material. A second layered silicate having a particle diameter greater than the winding diameter of the secondary coil is present at a higher concentration than that of the first layered silicate between the outer circumference side of the secondary coil and the side iron core.

Abstract: An ignition coil includes primary and secondary coils, a center core inserted into a center hole of the primary coil and a center hole of the secondary coil, an annular side core that forms a magnetic circuit through which a first magnetic flux A generated by the primary coil by being joined to the center core permeates, and a permanent magnet that is disposed between the center core and the side core and that emits a second magnetic flux B directed opposite to the first magnetic flux A to apply a magnetic bias. The side core includes protruded portions that protrude towards lateral sides of a T-shaped horizontal portion of the center core, and gaps are provided between the lateral sides of the T-shaped horizontal portion of the center core and the protruded portions of the side core.

Abstract: An ignition coil for an internal combustion engine capable of effectively preventing leakage of noise occurring due to, for example, radio waves or unpleasant sounds generated by a spark discharge is provided. When an elastic O-ring 12, which is a main part of the invention and which is made of a annular elastic resin material, is used as securing means, with a simple structure, it is possible to hold a second cap 9 (on a second electrode side) of an electric noise suppressing resistor 10 and to close a gap formed between an inner wall surface of a resistor accommodation section 4 and the second cap 9 of the electric noise suppressing resistor 10.