Abstract

A magnetogenerator comprises a plurality of permanent magnets arranged orderly on an inner periphery of a fly-wheel with magnetic poles thereof being alternative, a plurality of power generating coils including an ignition power generating coil and arranged within the fly-wheel in opposing relation to the plurality of permanent magnets, and a trigger pole of an angle position detector provided on the fly-wheel. The plurality of permanent magnets include a plurality of adjacently disposed first magnets each having a first peripheral length, a pair of adjacently disposed second magnets disposed adjacent the first magnets peripherally of the fly-wheel and having a second peripheral length longer than the first length by l1 and a pair of third magnets disposed adjacent the second magnets, respectively peripherally, and having a third length shorter than the first length by l1, a position and a peripheral length of the trigger pole being determined such that opposite ends of the trigger pole pass over an electromagnetic pick-up of the angle position detector when a polarity of an output voltage of the ignition power generating coil produced by crossing magnetic flux of the second magnets is changed.