Ignition coil for internal combustion engine

An ignition coil comprising:

• a primary coil;
• a secondary coil;
• a coil casing comprising a casing body, an accommodating part formed in the casing body and a high voltage tower shaped part having a cylindrical shape, the accommodating part accommodating the primary coil and the secondary coil, the high voltage tower shaped part being formed projecting toward the outside of the casing body, a proximal end part of the high voltage tower shaped part being arranged in contact with a bottom surface of the accommodating part, a tower through hole being formed in the high voltage tower shaped part;
• a resistance member having a cylindrical shape arranged as a movable member in the tower through hole;
• a high voltage cap arranged at the proximal end part of the high voltage tower shaped part so as to prevent communication between the tower through hole and the accommodating part, and the high voltage cap electrically connecting the resistance member with a high voltage terminal connected to the secondary coil;
• and
• an insulation resin member with which the accommodating part is filled, wherein
• a proximal end part of the tower through hole has an inner diameter which is greater than an outer diameter of a maximum outer diameter part of the resistance member, and a distal end part of the tower through hole has an inner diameter which is less than the outer diameter of the maximum outer diameter part of the resistance member, and
• a vent part is formed, through which the proximal end part of the tower through hole communicates with the distal end part of the tower through hole when the resistance member is arranged at a maximum distal end position in the tower through hole.