Constant energy electronic ignition system

Abstract

A first sensor couples to an internal combustion engine and generates a first set of pulses suitable for ignition firing. A second sensor operates in synchronism to the first sensor producing a second set of multiple pulses, during the interval between a first set of pulses, whose occurrence corresponds to specified angles of engine revolution and whose time duration is inversely related to engine RPM. The second pulse set is processed through a digital-to-analog converter having a staircase output voltage which is representative of instantaneous engine position. The second pulse set is further processed through an integrator, modified to produce an output approximating an inverse, or hyperbolic, functional relationship to the input, whereby output pulses are generated whose peak amplitude is representative of instantaneous engine speed, i.e. RPM. Comparator circuitry produces a trigger signal corresponding to a predetermined relationship between the positive voltage signal and speed pulses. The trigger signal activates a switch which initiates ignition coil dwell time such that the time interval from initiation of dwell time for recharging the coil to the next ignition firing is constant over substantially the entire range of operating RPM's thereby always recharging the coil to the same energy level between firings.