An internal combustion engine ignition coil includes: a center core; a primary coil provided on an outer side of the center core; a secondary coil provided on an outer side of the primary coil; and a side core provided on an outer side of the primary coil and the secondary coil and formed by stacked electromagnetic steel sheets, the side core having one contact portion in contact with one end surface of the center core and another contact portion in contact with another end surface of the center core with a magnet therebetween. The side core is composed of a plurality of side core portions fitted to each other to be movable relative to each other in a longitudinal direction of the center core.

An ignition coil has primary and secondary coils, a central core and a pair of split cores. One of the split cores has a first opposing face orthogonal to a coil axial direction X facing a core front end face of the central core in the coil axial direction X. The respective split cores have second opposing surfaces mutually facing each other in a lateral direction Y at a rear end of the central core. At least one of the second opposing surfaces and one of rear end surfaces of the central core contacting the least one of the second opposing surfaces collectively constitute a pair of oblique surfaces and come to close to the other one of the second opposing surfaces in the lateral direction Y as a portion of each of the oblique surfaces recedes further from the first opposing face in the coil axial direction X.

An ignition coil includes a center core, a first core member, and a second core member. The first core member includes a first core-facing portion facing a front core surface of the center core and a first core side portion extending rearward from the first core-facing portion. The second core member includes a second core-facing portion facing a rear core surface of the center core and a second core side portion extending frontward from the second core-facing portion. The first core-facing portion has an end surface contacting a portion of the second core side portion to create a first contact region. Similarly, the second core-facing portion has an end surface contacting a portion of the first core side portion to create a second contact region. The first and second contact regions are shaped to approach frontward close to the first core side portion. This structure enhances productivity of the ignition coil.

An ignition coil includes a primary coil, a secondary coil, a center core, a magnet body and an outer peripheral core. The outer peripheral core is provided with a first opposite side, a second opposite side and a coupling side, the first opposite side facing the magnet body from an opposite side of the center core, the second opposite side facing the center core from the opposite side of the magnet body, the coupling side coupling the first opposite side with the second opposite side. The center core has a magnet side flange portion disposed at an end portion in a magnet body side, protruding in a protrusion direction. A thick portion is formed at both of a part of the first opposite side and a part of the coupling side, and a thickness of the thick portion being larger than a minimum thickness of the second opposite side.

A method is described for the assembly of a magnetic core for a transformer, with the following steps: Cutting sheet metal blanks from transformer sheet, stacking the sheet metal blanks to form magnetic core segments, placing a permanent magnet at one of the magnetic core segments so that the latter is magnetized by the permanent magnet, formation of the magnetic core by placing the remaining magnetic core segments against the permanent magnet, or against a magnetic core segment already magnetized by the permanent magnet. A magnetic core is also disclosed.

An ignition coil includes: a center core; a primary coil wound around the center core; a secondary coil wound around the primary coil; a plurality of side cores, which are arranged around the secondary coil, and are coupled to the center core to form a closed magnetic path; a magnet inserted between the plurality of side cores; an igniter configured to control supply and interruption of a current to the primary coil; a case configured to accommodate the center core, the primary coil, the secondary coil, the plurality of side cores, the magnet, and the igniter; and insulating resin filled in the case. The side cores include a wide portion and a narrow portion. The magnet is inserted into the wide portion. The igniter is arranged between the narrow portion and the case.

An internal combustion engine ignition device comprises: a center core; a primary coil wound on the outside of the center core; a secondary coil wound on the outside of the primary coil; a permanent magnet which abuts against one end of the center core and is magnetized in the inverse direction to the direction of a magnetic flux produced by the energization of the primary coil; a side core which is disposed on the outside of the secondary coil with one end abutted against the permanent magnet and the other end abutted against the center core, the side core cooperating with the permanent magnet to form a closed magnetic path; and a heat-resistant and elastic resin covering the side core with an opening at an outer peripheral side. Heat dissipation from the side core to a housing is improved without adversely affecting the dielectric strength voltage of the secondary coil.

An ignition coil includes a primary coil, a secondary coil, a center core, an outer core, an igniter, a coil case and an electrically-insulative fixation resin. On an interior surface of the coil case on a bottom part side in a mounting direction, there is formed a case-side rib to protrude from the interior surface of the coil case to a high-voltage side in an axial direction. The case-side rib has a taper shape such that the protruding amount of the case-side rib to the high-voltage side in the axial direction increases in the mounting direction toward the bottom part side. The case-side rib is arranged to abut a corner portion of the igniter on the bottom part side in the mounting direction and on a low-voltage side in the axial direction and thereby press the igniter against the outer core.

An ignition coil for use in an internal combustion engine includes a primary coil, a secondary coil, a core, and a magnet. The core creates a closed magnetic circuit through which magnetic flux produced upon energization of the primary coil flows. The core has formed therein a gap through which the magnetic circuit passes. The magnet is disposed in the gap and has magnetic domains whose magnetization vectors are at least partially oriented obliquely relative to a gap direction. The orientation of the magnetization vectors in the magnet minimizes an energy loss when primary energy is transformed into secondary energy.

Obtain an ignition coil in which a magnet is provided at a magnet holding portion which is formed between a first side iron core and a second side iron core, and intervening components which are configured by using a non-magnetic material, are included at facing portions which are provided at end portions of separated surfaces of the first side iron core and separated surfaces of the second side iron core, in a state where the magnet holding portion is formed by using the first side iron core and the second side iron core, and are faced at a surface which is vertical with respect to an axis direction of the side iron cores, and the intervening components have a thickness which is less than a distance between the separated surfaces of the first side iron core and the separated surfaces of the second side iron core.