GB1313114A - Method and apparatus for producing trigger pulses - Google Patents

Abstract

1313114 Digital measurements G HARTIG 31 March 1970 [3 April 1969 9 March 1970] 15063/70 Heading G4H [Also in Division F1] In a method of generating a timing pulse for a mechanism with periodic motion relative to a fixed point in that motion, such as for an ignition pulse for an internal combustion engine (ICE) relative to top dead centre, for each period of the motion pulses are generated by the motion which are counted for a predetermined period, which is variable according to, say engine temperature, and then at a predetermined point in the periodic motion the pulses are further counted during a second period until the count reaches a predetermined count whereupon the timing pulse is generated. In the arrangement of Fig. 2 pulse shaper 11 receives repeatedly a series of pulses generated by the movement of the ICE, there being a gap between adjacent series which circuit 12 detects and issues a zeroising pulse to counter 28 and sets gating circuit 17. From the beginning of the next sequence counter 28 counts pulses and either counter 16 or 21, which alternate in counting for successive sequences, count pulses during a period S defined by gating circuits 17, fed by the predetermined period signal S. Circuit 18 extends period S to a whole number of pulses which are gated via gate 19 to counter 16 or alternatively counter 21. Adder 25 or alternatively adder 27 adds the counts accumulating in counter 28 to the count accumulated during period S of the previous sequence in counter 16 or alternatively counter 21. At a predetermined sum the respective adder generates an ignition pulse at output S. The counters 16 and 21 are switched and zeroed by bi-stable 14 in response to the cancel pulse from circuit 12. Circuit 23 alters the criterion for detecting interseries spacing from circuit 12 if counter 16 or counter 21 receives only one pulse during period S, e.g. in slow running of the engine. In another example (Fig. 5) an impulse wheel 50 coupled to the crank-shaft of an ICE generates pulses according to the speed of the engine. A start pulse generated by sensor 55 and tooth 51a zeroes a counter 59 which starts via OR gate 60 a relaxation oscillator 61 whose pulse defines the predetermined period and opens AND gate 57 to permit counting of pulses from sensor 54. The period ends before both sensors 54 and 55 simultaneously sense teeth. When the sensors sense teeth together the counter further counts pulses from AND gate 64 until a predetermined count is reached, at which the timing pulse is outputted on line 65. In another arrangement (Fig. 8, not shown) the sensors are staggered along the line of scanning and a tooth and a gap of extra width indicate start of the predetermined period and the further period of counting respectively.