Abstract: An electromagnetic rotation control element, for an idle rotation control device for internal combustion engines, include a magnet housing with at least two magnetic poles and with a rotating armature with an even number of pole pieces that cooperate with magnetic poles, and with a restoring spring that acts on the rotating armature. For the purpose of increasing the influencing possibilities for achieving the required characterizing line of the rotation control device, each pole piece is divided into two pole piece sections, located next to each other in the axial direction and having differently formed contour lines. The one contour line has the shape of an arc of a circle, while the other contour line increasingly deviates from the one pole piece end to the other from this arc of a circle shape.

Abstract: To provide an inherent delayed effect of spark trigger pulses derived from a magnetic transducer in which a salient pole piece of a rotor rotates with respect to a salient pole piece of a stator and, upon juxtaposition, a pulse is induced in a pickup coil magnetically coupled to the rotor-stator circuit, the rotor pole piece is formed to have an arcuate length greater than that of the stator pole piece, with stepped configuration so that, with respect to angle of rotation, the output voltage derived from the coil will have, after passing through zero or null, a half wave which has a portion (C) of decreasing rate of change of absolute value, or differential thereof, and a subsequent and adjacent portion (D) of increasing rate or differential of absolute value with respect to angular change with the sign of the differential remains the same, so that, on slow-speed operation, a trigger circuit set to respond only to the subsequent or adjacent portion will have a voltage induced therein only at a later time, tha