Patent GB-1480131-A (GB)
Title: Ignition system for an internal combustion engine
IPC: F02P3/02
Filed: 1974-06-07
Abstract: 1480131 Ignition systems; timing ignition G HARTIG 7 June 1974 [23 July 1973]  25312/74 Heading F1B In a method of controlling the closed angle of an ignition system of an internal combustion engine a main pulse sequence is produced, the pulses of which are synchronized with the rotary movement of the rotating parts of the engine, and an advance angle α by which the ignition spark is to be advanced relatively to the top dead centre is determined by counting the pulses occurring during a time t and subtracting them, as defined in the Specification, from a number of pulses counted during traversing of a larger angle # which extends between the engine top dead centre and an arbitrary phase position advanced relatively thereto. The ignition pulse is produced when the differential angle # - α has been traversed so that the ignition pulse is advanced by the angle α relative to the top dead centre. A trigger angle # which changes in the same manner as the angle α in dependence on the speed of engine rotation extends from an ignition closing position to the top dead centre, and is represented by a number of pulses dependent on the speed of rotation, the pulses representing the angle being subtracted, as defined in the Specification, from those representing the angle # to cause the operating pulse to be produced after the differential angle # - # has been traversed so that the operating pulse occurs advanced by the closed angle # relative to the advance angle α. Referring to Fig. 3 it is assumed that a pulse has appeared at the output of the comparator 33 and has reset the flip-flop 37 corresponding to the end of a closed angle pulse. The pulse on the output 35 passes through a pulse former stage 38 and then appears on the set input 9 of the counter 8 and triggers the function generator 7. The counter 8 is reset by the arrival of the pulse from the former stage 38 whereas the triggering of the function generator 7 is affected only by the end of this pulse. During the time t as determined by the function generator 7 the gate 6 is opened so that the pulses counted in the counter 8 are those derived from the transmitter 2 during the time t. As soon as a pulse appears from the transmitter 1 the counters 18 and 23 receive set pulses at their inputs 24 and 25 respectively enabling them to take over the pulses stored in the counter 8. Reset of the counter 29 to the condition 000 is simultaneously effected through the set input 30. At the end of the pulse from the transmitter 1 the counter 18 starts counting the pulses appearing from the transmitter 2. The comparator 34 is programmed so that it delivers an output signal at the output 36 when the output of the counter 23 has the condition "0010". The output signal of this comparator sets the flip-flop 37 so that the rise of a closed angle pulse appears at the output 41. The ignition coil primary circuit is closed. The circuit is opened at the end of the pulse appearing at the output 41 causing a spark at the gap of a plug. The time t can be changed from the input 40 in dependence on engine parameters such, for example, as engine temperature, manifold vacuum, temperature of an after burner and so on. A number of alternative embodiments are described. Specification 1313114 and United States Specification 3696303 are referred to.