Patent GB-1479205-A (GB)
Title: Ignition system for an internal combustion engine
IPC: F02P5/04
Filed: 1974-06-07
Abstract: 1479205 Ignition systems; timing ignition G HARTIG 7 June 1974 [26 July 1973] 25310/74 Heading F1B Apparatus for varying the ignition timing in an internal combustion engine comprises pulse generation means for deriving from a rotating part of the engine a sequence of pulses all of which are of substantially equal length, counting means 8 for performing a succession of counting operations during each of which the number of pulses occurring during a time t is counted, a control device for performing an arithmetical operation on the number of pulses counted during each time t or for altering the time t of the next count in dependence on the number of pulses counted during the preceding counting operation, the result of each arithmetical operation or the number of pulses counted during the altered time t being a reference count representing the angle of spark advance α relative to the top dead centre, counting means, which are the same as or different from the firstmentioned counting means for counting, starting from each reference count, from an arbitrary phase position which is advanced from the top dead centre by an angle # until a predetermined total number of pulses has been counted which represent the angle # and means for causing an ignition spark to be produced each time the predetermined total number of pulses has been counted whereby each spark occurs advanced by the angle α relative to the top dead centre. Fig. 4 shows how the circuit of Fig. 3 can be modified to be in accordance with the invention. The reference numeral 50 indicates a coding matrix which has a series of first inputs 51 and a second series of inputs 52a, 52b, 52c and so on. The inputs 51 are shown as connected to the outputs 10 to 13 of the counter 8. Values of operating parameters of the engine are fed through the inputs 52a, 52b and 52c. These values may represent engine temperature intake manifold vacuum, throttle valve position and so on. The pulses from the transmitter 2 are fed to the counter 8 through a gate 6 which is kept open by the function generator 7 for a predetermined time t. The auxiliary pulse from the transmitter 1 is in such a phase that the take over of the numerical condition of the counter 8 by the counter 18 is just ahead of the arbitrary phase position. The output of the counter 18 passes to a comparator 33. At the predetermined value the comparator delivers a pulse at the output terminal 35, this pulse comprising an ignition pulse. The time t can be changed according to engine parameters for example engine temperature intake manifold vacuum or the temperature of an after-combustion reactor. In a modification, not shown, the coding matrix comprises a quadruple NAND gate which has inverted and non-inverted inputs coupled to counting inputs of the firstmentioned counting means. The output of the NAND gate is connected to an input of a NOR gate which is coupled by at least one other input to a transducer of the engine. In Fig. 7 (not shown) the output 53 of the matrix 50 is no longer connected to the function generator 7 but is used to influence the counter directly without changing the time t. The control pulse which occurs at the output 20 of the transmitter 1 can be fed to the input 24 with a time and/or angle delay. Other embodiments are described. A preferred form of the function generator 7 is described.