Ignition arrangement for internal combustion engine

Claim 1

An ignition arrangement for an internal combustion engine having at least one spark-producing unit, comprising, in combination, an electronic switch having a control electrode, a reference electrode and an output electrode, said control and reference electrodes defining between themselves a control path, and said reference and output electrodes defining between themselves a switching path, said switch having a conductive state and a non-conductive state and being switched from one state to the other whenever the voltage across said control path reaches a predetermined threshold value; electrical energy storing means connected to said Switch and to the spark-producing unit for supplying energy to the latter to cause generation of an ignition spark when said switch undergoes a change from said one state to said other state; A.C. voltage generator means coupled to the engine and operative for generating per combustion cycle at least two A.C. voltage cycles composed of four A.C. voltage half-cycles the first of which is generated in advance of top-dead-center and the second, third and fourth of which are generated in succession after the first; full-wave rectifier means having an input connected to the output of said voltage generator means and having an output connected across said control path for applying said voltage half-cycles in full-wave rectified form, thereacross, and operative in cooperation with said generator means for causing all but the last of said half-cycles to have respective amplitudes reaching said threshold value only when the engine reaches respective predetermined successively lower sppeds and for causing the last of said half-cycles to have an amplitude at least equal to said threshold value when the engine speed is lower than the lowest of said successively lower speeds.