Patent GB-1456987-A (GB)
Title: Monitoring process for combustion engines
IPC: G06F7/62
Filed: 1973-12-06
Abstract: 1456987 Automatic control of fuel injection in IC engines SOC DES PROCEDES MODERNES D'INJECTION 6 Dec 1973 [6 Dec 1972 4 June 1973 6 June 1973] 56713/73 Headings G3N  In a monitoring, checking or controlling process for a combustion engine a set of physical magnitudes are sampled at a sampling frequency and coded as a number or word segment having a limited number of characters such that the mean value of the word segment over a plurality of samplings represents the mean value of the corresponding physical magnitude. The word segments are then grouped to form a first word, which is converted by a programmed memory into a second word, the second word is converted into a function, the mean value of which represents the mean value of the desired regulation function and the regulation function is converted into a magnitude for controlling the engine. The regulation function may be converted to a non-linear function for generating the control signal. The input signals may be a pulse frequency, which is measured by counting for a predetermined time or a voltage which is measured by counting clock pulses for the time a sawtooth voltage takes to rise to the voltage and may be derived from any device which produces variations which can be converted to this form i.e. variations of capacity inductance or resistance. The output signal may be a voltage, a time duration a numerical value or an angular position.  The input digital signal is produced in a circuit which produces only the most significant bits, the less significant bits being added to the next sample value. Constants may also be subtracted to reduce the number of digits to be handled. As shown, pulses of frequency fx are passed for duration S, (determined by a clock) to divider 2-2 which divides the number of pulses (N) by D. The resulting <SP>N</SP>/ D  pulses are fed to counter 2À3 which is connected to gate 2À4 so that after n pulses gate 2À5 is enabled and the remaining <SP>N</SP>/ D  -n pulses pass to counter 2À6. Reset pulses transfer the value in counter 2À6 to store 2À7 and clear counters 2À3 and 2À6. The value in counter 2À2 remains and is added to the value in the next cycle. If the value N = 204, D = 2 and n = 2. The value in counter 2À6 will be 0 (# 200) for 24 consecutive sampling periods then 1 (# 300) for the 25th period since the residual fours in counter 2À2 will have totalled to 100. The average of these readings is 200 plus <SP>100</SP>/ 25  = 0À04. The voltage measuring circuit treats the clock pulses in a similar manner. A circuit for when fx is about the same as the sampling frequency is described. This circuit prevents loss of pulses during the gap between sample cycles. The general system is shown in Fig. 13. The engine speed is measured as a variable pulse signal fx and pressure as an analogue signal Vx under the control of clock signals which comprise the duration signal S, and two, time spaced reset signals S 2 , S 3  as described above. The signals are combined at 13À6 to form the first word. Programmed memory 13À6 generates the second word from the first according to predetermined equations (for details see specification) and the second word is converted at 13À7 to a function whose mean value is the regulation function. The regulation signal, which may be a fuel injection duration is derived at 13À8. A variable reluctance displacement encoder and associated circuitry for use in the determination of angles relating to engine operation is described.