Abstract: An insulator includes a plug side cylindrical portion having an inner space for accommodating a center electrode and a coil side cylindrical portion extending in a direction departing from a combustion chamber. The high-voltage portion of an ignition coil is entirely accommodated inside the coil side cylindrical portion. According to this arrangement, the coil side cylindrical portion can assure insulation between the high-voltage portion and the low-voltage portion. The portion to be insulated and fixed by an insulating resin is limited only to the secondary winding.

Abstract: An insulator includes a coil side cylindrical portion extending from a plug side cylinder portion in a direction departing from a combustion chamber. One end of the coil side cylindrical portion protrudes in the direction departing from the combustion chamber with respect to a primary winding and a secondary winding. A pressure sensing element is disposed next to the one end of the coil side cylindrical portion. The signal lines of the pressure sensing element are taken out of a casing without passing aside an ignition coil. Thus, the diameter of the casing does not increase. The output signal of the pressure sensing element is not adversely influenced by discharge noises generated from the ignition coil.