Patent ID: 7710229
Filing Date: 2010-05-04
Classification: H01F

Abstract:
1. An ignition coil for a sparkplug having electrodes, the ignition coil adapted to being electrically connected with a control unit, the ignition coil comprising: primary and secondary coils each having an axial high voltage end adapted to connecting with the sparkplug; an ion current detector for detecting an ion current flowing through the electrodes; a center core provided on a radially inner side of the primary and secondary coils, the center core being formed of a magnetic material; and an outer core provided on a radially outer side of the primary and secondary coils, the outer core being formed of a magnetic material; wherein the center core has an axial low voltage end defining a center low end surface, the outer core has an axial low voltage end defining an outer low end surface, the center low end surface axially protrudes toward an opposite side of the axial high voltage end relative to the outer low end surface, the center low end surface is located at a stagger distance from the outer low end surface with respect to an axial direction of the center core, and the stagger distance is defined such that a detection period correlated to residual magnetic noise in the ion current detection output of the ion current detector is within a system requirement period of the control unit, wherein the stagger distance is equal to or greater than 3 mm, and the stagger distance is equal to or less than 12.5 mm.