Ignition circuit with automatic spark advance

Claim 1

In an ignition system for igniting a combustible charge in an internal combustion engine having at least one cylinder, one spark device for said cylinder and a source of electrical energy and further having circuit means adapted to transfer electrical energy from said source to said spark device at substantially a first crankshaft angle in a timing cycle of said engine when said engine is cranked at low speeds during starting and at substantially a second predetermined crankshaft angle in said timing cycle when said engine is operating at running speeds, said energy transferring circuit means comprising electronic switch means responsive to electrical triggering signals of predetermined polarity and having a predetermined value to switch from a first state to a second state and thereby cause electrical energy to be transferred to said spark device, and trigger circuit means comprising first coil means, second coil means, permanent magnet means and flux circuit means and responsive to relative movement between said flux circuit means and said first and second coil means to generate said triggering signals, said first coil means generating triggering signals having first pulsations of said predetermined polarity and an amplitude that is above said predetermined amplitude at both said cranking speeds and said running speeds to switch said switch means at a first crankshaft angle at said cranking speed, said second coil means generating triggering signals having second pulsations of Said predetermined polarity and an amplitude that is less than said predetermined amplitude at said cranking speeds and above said predetermined amplitude at said running speeds to switch said switch means at said second crankshaft angle at said running speeds, that improvement comprising first coupling circuit means coupling said first coil means to said switch means so that triggering signals of both said predetermined polarity and of an opposite polarity are applied to said switch means from said first coil means at both cranking and running speeds, second coupling circuit means coupling said second coil means to said switch means so that only triggering signals of said predetermined polarity are applied to said switch means from said second coil means at both cranking and running speeds, the impedance of said second coupling means and said second coil means being such that if said first pulsations from said first coil means were shunted through said second coupling means and said second coil means at said cranking speeds the amplitude of said first pulsations might fall below said predetermined amplitude, and wherein said second coupling means includes means for isolating said first coil means from said second coil means with respect to triggering signals of said predetermined polarity generated in said first coil means so that said second coil means does not load said first coil means at said cranking speeds.