Importance

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Abstract

An electronic ignition system is disclosed for controlling as a function of at least one selected engine parameter the ignition or spark instants of an internal combustion engine having at least one cylinder with a piston and a rotatable crankshaft coupled to the piston to be rotatably driven as combustions occur within the cylinder at spark instant. The crankshaft has at least one reference position defining a positional relationship of the crankshaft to the cylinder. The electronic ignition system comprises a rotor fixed to rotate with the crankshaft and having a plurality of reference indicia thereon positionally related with respect to the reference position. The reference indicia are disposed at points equally spaced from each other by a predetermined arc of crankshaft rotation about the rotor. At least one of the points has a missing indicium and is disposed in a predetermined relation to the reference position of the crankshaft. A single sensor is disposed at a point fixed in relation to the rotation of the crankshaft for providing a train of sensor signals, each signal occurring in time when each of the plurality of reference indicia rotates past the fixed point. The missing indicium is determined by circuitry responsive to each sensor signal for measuring the arc of crankshaft rotation from the current, corresponding reference indicium and, if the measured arc is greater than the predetermined arc, for providing a missing indicium signal.

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First Claim