Patent ID: 11404204

Abstract:
An ignition coil for an internal combustion engine includes a plug boot with a hole having a length extending in an axial direction of the ignition coil. The length of the hole has a portion which includes a plurality of small distance-to-center sections and a plurality of large distance-to-center sections which are arranged alternately in a circumferential direction of the hole. Each of the small distance-to-center sections is located at a first distance away from the center of the hole, while each of the large distance-to-center sections is located at a second distance away from the center of the hole. The second distance is larger than the first distance. The small distance-to-center sections are placed to be contactable with an outer periphery of the coil spring. This structure of the ignition coil has enhanced resistance to mechanical vibration of the coil spring and also has enhanced withstand voltage.