Abstract: An ignition coil includes a coil part having primary and secondary coils, a center core, and a peripheral core, a connector case part, a seal rubber, and a ventilation passage. The coil part is inserted in a plug hole of an engine, and the case part is outside the plug hole. An axial end of the peripheral core is inserted in an insertion hole of the case part. The peripheral core and an inner wall surface of the insertion hole define a ventilation clearance therebetween. A gap between the case part and the plug hole is sealed with the rubber. The rubber is closely-attached to the plug hole and the case part along its whole circumference. The passage, through which the plug hole is ventilated, includes the clearance and a ventilation hole formed at a certain position of the case part away from the rubber to communicate with the clearance.

Abstract: An ignition coil includes a coil part having primary and secondary coils, a center core, and a peripheral core, a connector case part, a seal rubber, and a ventilation passage. The coil part is inserted in a plug hole of an engine, and the case part is outside the plug hole. An axial end of the peripheral core is inserted in an insertion hole of the case part. The peripheral core and an inner wall surface of the insertion hole define a ventilation clearance therebetween. A gap between the case part and the plug hole is sealed with the rubber. The rubber is closely-attached to the plug hole and the case part along its whole circumference. The passage, through which the plug hole is ventilated, includes the clearance and a ventilation hole formed at a certain position of the case part away from the rubber to communicate with the clearance.

Abstract: An ignition coil includes a coil portion that has a primary coil, a secondary coil, and an outer core. The outer core is arranged on a radially outer side of both the primary coil and the secondary coil. A fitting member, which is in a substantially cylindrical shape, has an inner periphery via which the fitting member is fitted to the outer core. A connector case has a fit hole via which the connector case is fitted to an outer periphery of the fitting member. The connector case connects with an axial end of the coil portion via the fitting member. The fitting member includes an embedded member that is at least partially embedded in the fitting member. The embedded member is formed of a material that is different in Young's modulus from a material constructing the fitting member.

Abstract: An ignition coil includes a coil portion that has a primary coil, a secondary coil, and an outer core. The outer core is arranged on a radially outer side of both the primary coil and the secondary coil. A fitting member, which is in a substantially cylindrical shape, has an inner periphery via which the fitting member is fitted to the outer core. A connector case has a fit hole via which the connector case is fitted to an outer periphery of the fitting member. The connector case connects with an axial end of the coil portion via the fitting member. The fitting member includes an embedded member that is at least partially embedded in the fitting member. The embedded member is formed of a material that is different in Young's modulus from a material constructing the fitting member.