Ignition timing for internal combustion engines

Claim 2

An electronic ignition system for an internal combustion engine including means for initiating a spark at a crank-shaft angle whose position between two given limits is determined at any instant in accordance with engine requirements and means for extinguishing the spark at the spark plug at a predetermined crank-shaft angle irrespective of the crank-shaft angle at which the spark is initiated.

Claim 3

An electronic ignition system according to claim 1, including means for generating a beam of electro-magnetic radiation; a radiation sensing device; and means positioned between the radiation generating device and the sensing device to interrupt the radiation, the interrupting means being driven in synchronism with the crank-shaft of the engine such that when the radiation is cut off at a given crank angle this determines the two given limits in which the spark is to be initiated in accordance with the engine requirements and when the radiation is once again received by the sensing device this determines the point at which the spark is extinguished.

Claim 4

An electronic ignition system according to claim 1, including means for generating a first series of voltage pulses in synchronism with the engine revolutions to provide a series of alternate highs and lows; means for generating a second series of voltage pulses at a frequency greatly in excess of the first series; means for counting a given number of the second series of voltage pulses from a given point in relation to the first series of voltage pulses; means for producing an output of a given level from said counting means after said count has been completed; means for detecting the presence of both a signal at said given level from the first pulse generating means and the counting means in order to bring about the initiation of the spark, the extinguishing of the spark being effected when the signal from the first generating means changes to the opposite level; and means for varying the count of the counting means in accordance with engine requirements.

Claim 5

An electronic ignition system according to claim 3, including first and second infra-red radiation sources; first and second photo-transistors associated with the respective first and second infra-red radiation sources; an opaque element having a first set of arcuate apertures therein for producing said first series of voltage pulses and a second set of arcuate apertures for producing the second series of voltage pulses, said opaque element being positioned between the radiation sources and photo-transistors, said first set of arcuate apertures being arranged such that the infra-red radiation is interrupted at a first position before top dead centre to start the count for the precise timing of the spark according to engine requirements, the infra-red radiation being established at a second position which is approximately at top dead centre in order to extinguish the spark irrespective of the position at which it was initiated.

Claim 6

An electronic ignition system according to claim 3, including means for generating the highs of the first series of voltage pulses at 30* before top dead centre of respective cylinders of the engine; means for fixing the maximum advance of the ignition at 26* before top dead centre and the maximum retardation to 6* before top dead centre so that the spark is initiated within this range 26* - 6* before top dead centre according to the engine requirements, and means for generating the lows of the first series of voltage pulses at 0* before top dead centre of respective cylinders of the engine.

Claim 7

An electronic ignition system according to claim 3, wherein the counting means is a frequency divider, and the means for varying the count of this divider is a computer whose digital output is modified in accordance with digital information fed into it in accordance with engine requIrements.

Claim 8

An electronic ignition system according to claim 3, including first and second trigger circuits for fast switching and current amplifying the first and second series of voltage pulses, each trigger circuit comprising a plurality of cascaded transistors arranged to switch in inverse relation to one another so that at any one time at least one transistor is always fully saturated whilst its immediate neighbours are hard off.

Claim 9

An electronic ignition system according to claim 7, including at least one power transistor and one or more pre-amplifying stages between the power transistor and the output from the first trigger and counting means, said power transistor being in series with the primary winding of the ignition coil, whereby the spark is initiated on interruption of the current through the primary winding of the ignition coil on the power transistor becoming non-conductive.

Claim 10

An electronic ignition system according to claim 1 further comprising an ignition coil, said spark extinguishing means comprising means for switching said coil on to extinguish said spark at a first, predetermined crank angle position which is approximately at top dead center and said spark initiating means comprising means for switching off said coil to initiate said spark at a variable crank angle position in advance of said first crank angle position in accordance with the engine requirements.

Claim 11

An electronic ignition system for an internal combustion engine in which the spark is initiated between two given crank angles before top dead centre depending on the speed of and load on the engine at any given instant and in which the spark is extinguished at a predetermined crank angle in relation to top dead centre including means for generating a first series of voltage pulses in synchronism with the engine revolutions to provide a series of alternate highs and lows; first means for fast switching and current amplifying said first series of voltage pulses; means for generating a second series of voltage pulses at a frequency greatly in excess of the first series; second means for fast switching and current amplifying said second series of voltage pulses; means for counting a given number of the second series of voltage pulses from a given point in relation to the first series of voltage pulses; means for producing an output of a given level from said counting means after said count has been completed; means for detecting the presence of both a signal at said given level from the output of the first fast switching and current amplifying means and the counting means in order to bring about the initiation of the spark, the extinguishing of the spark being effected when the signal from the first generating means changes to the opposite level; and means for varying the count of the counting means in accordance with the engine requirements.

Claim 12

An electronic ignition system for an internal combustion engine in which the spark is initiated between two given crank angles before top dead centre depending on the speed of and load on the engine at any given instant and in which the spark is extinguished at a predetermined crank angle in relation to top dead centre including means for generating a first series of voltage pulses in synchronism with the engine revolutions to provide a series of alternate highs and lows; first means for fast switching and current amplifying said first series of voltage pulses; means for generating a second series of voltage pulses at a frequency greatly in excess of the first series; second means for fast switching and current amplifying said second series of voltage pulses; means for counting a given number of the second series of voltage pulses from a given point in relation to the first series of voltage pulses; means for producing an output of a given level from said counting means after said count has been completed; means for detecting the presence of both a signal at said given level from the output of the first fast switching and current amplifying means and the counting means in order to bring about the initiation of the spark, the extinguishing of the spark being effected when the signal from the first generating means changes to the opposite level; and means for varying the count of the counting means in accordance with the engine requirements.

Claim 13

An electronic ignition system according to claim 10, wherein the two limits for the initiation of the spark are 26* and 6* before top dead centre and wherein the spark is extinguished at a predetermined point in the range of from 0* to 5* after top dead centre.

Claim 14

An electronic ignition system according to claim 10, including a darlington pair output stage in series with the primary winding of the ignition coil and one or more pre-amplifying stages between the commoned output of the first means for fast switching and current amplifying and the counting means and the input electrode of the power transistor stage.