Static lead correction device for the ignition of an internal combustion engine

Claim 1

Static device for the ignition of internal combustion engines of the two-stroke or four-stroke type, in which the ignition moment depends at least on the rotation speed of the engine crankshaft, said device comprising a spark plug per cylinder of the engine, a distributor mechanism for directing current pulses respectively to each spark plug of each cylinder, a revolving member or cam driven by said crankshaft and comprising at least one active zone and one inactive zone, said cam being placed facing an electronic probe, said electronic probe comprising a bistable oscillator with a fixed frequency disposed facing said cam so that it produces pulses during the passage of the inactive parT thereof and is blocked during the passage of the active part, said oscillator having a rectifying and filtering circuit so that it produces rectangular signals corresponding to the inactive parts of the cam and to both the duration and frequency of which image the rotation speed of the crankshaft, a pulse generating circuit having a fixed time constant smaller than the duration of the rectangular signals and being connected to the rectifying and filtering circuit of said electronic probe, so that rectangular pulses are produced by said pulse generating circuit with the same origin as said rectangular signals and a fixed duration, a first capacitor connected to said pulse generating circuit, so that said first capacitor is charged during a fixed duration corresponding to each one of said pulses, a resistive discharge circuit having at least two discharge resistors connected to said first capacitor so that said capacitor has two discharge time constants, a second capacitor connected to the first capacitor by one of said resistors of the discharge circuit thereof, a first electronic gate also connected to said second capacitor and to said rectifying and filtering circuit of said bistable oscillator, so that said first capacitor is progressively discharged through the two resistors of each discharge circuit from the end of each pulse of a fixed duration according to a first time constant and that the rectangular signals from said rectifying and filtering circuit keep closed said first electronic gate which is open as soon as said signals are interrupted whereby said first capacitor is brought to be discharged according to a second time constant in one only of the two resistances of its discharge circuit and said second capacitor also discharged in dependency of said second time constant of said first capacitor, a second electronic gate placed at the input of a voltage threshold circuit and connected to said second capacitor whereby said gate is closed during the duration of the discharge of said second capacitor function of said second time constant of said first capacitor, and open at the end of said discharge, said voltage threshold circuit comprising a capacitor connected to said second electronic gate and to an ignition circuit connected to said distributor mechanism so that the opening of said second electronic gate puts into action said ignition circuit at the end of discharge of said second capacitor to produce an ignition spark at a moment which is a function both of the duration of the discharge of the second capacitor and of the end of each rectangular signal.