In order to prevent ignition power losses at low engine speeds and further to provide for the use of ignition control signals of both unipolar and bipolar nature, the invention provides that a Schmitt trigger which generates the principal ignition control signal is actuated by the transducer. The switching thresholds of this Schmitt trigger are changeable by a secondary threshold recognition circuit which can shift at least the negative threshold of the principal threshold circuit to more positive values. The invention also includes a delay circuit which prevents the return of the shifted threshold to more negative values. Still further included is a third threshold circuit which is engaged only at some higher engine speed.
The operation of the interrupting switch in the primary circuit of an ignition coil triggers a first timing circuit having a fixed interval or one sometimes modified by engine loading, at the end of which a timing interval signal is generated which lasts for a second interval. The latter is applied to switch a resistor across the timing wave generator to load down its output voltage. In this manner, an engine equipped with a simple ignition shift providing spark advance in the low speed region and then steady or slightly retarding timing thereafter, can be caused to provide a retarding priming shift that sets in at a medium speed, increases and then tapers off with higher speeds so as to cover a speed range in which the engine is particularly sensitive to engine knock and avoiding the inefficiencies which would be necessary if the simple ignition shift system had to be backed off to avoid intersecting the knock boundary. It is also possible to utilize the first timing interval to charge or discharge a capacitor to produce an engine speed signal for biasing the threshold of the interrupter switch for control of the dwell angle with respect to engine speed. Two timing intervals can be determined by a single digital counter reset by each ignition pulse and connected with a decoder set to recognize the ends of successive intervals.
A method for recognition of the power stroke of an internal combustion engine is proposed, in which recognition as to whether a cylinder is currently in the power stroke is possible by means of camparison of a signal that is synchronous with the crankshaft angle and a signal that is modulated by the combustion events of the engine.
The output of a combustion chamber sensor is analyzed in two succeeding time intervals defined in term of crankshaft position by use of a reference mark. The sensor output is compared with prescribed threshold values in the respective intervals, and a logic circuit recognizes whether normal combustion, slow combustion or a combustion failure is present and an engine control, such as fuel injection or ignition timing, or a combination of both is modified accordingly.
An electronic control system for an internal combustion gas engine adapted to control the timing pulse for spark ignition in a single cylinder gas engine wherein precise timing of the spark advance throughout a wide range of engine speeds can be achieved whereby efficient burning of a lean air/fuel mixture in the combustion chamber of the engine can be achieved to minimize undesirable exhaust gas emissions and to increase the operating engine efficiency.
