Abstract: In a stick coil, there is disclosed an ignition coil for an internal combustion engine which can prevent a crack (a collar leak) from being generated due to a thermal stress. In this ignition coil, the structure is made such that a size (L) of a portion which is in parallel to an axial direction of a primary spool (121) in a projection portion (121b) is larger than a size (T) of a portion which is in parallel to an orthogonal direction to the axial direction of the primary spool (121). Accordingly, a frontal projected area of the projection portion (121b) as seen from a flowing direction of a resin becomes small, a resin flow is hard to get out of order at a time when the resin flows through a portion corresponding to the projection portion (121b) at the forming time, and a convoluted void and a weld are hard to be generated.

Abstract: An ignition coil has a coil case made of an insulating resin, including a head portion, a cylinder portion accommodating a primary coil, and a secondary coil and a high-voltage tower portion for fitting with a spark plug. At least one of those three portions is separately molded and then the portions are assembled to form the coil case. The longitudinal length of each of the three portions is less than a forming flow length of the insulating resin, thereby preventing inferior molding. Further, the structure of each molding die is simpler than that of the coil case for an integral molding. Therefore, the coil case of the ignition coil can be molded readily without molding defects, even when the coil case is elongated, formed thinner, and/or formed with an undercut portion.