Patent GB-1529364-A (GB)
Title: Ignition timing apparatus for an internal combustion engine
IPC: F02P17/00
Filed: 1975-10-16
Abstract: 1529364 Ignition systems NISSAN MOTOR CO Ltd 16 Oct 1975 [17 Oct 1974 20 May 1975(2) [4 June 1975] 42419/75 Heading F1B Timing control of the ignition system of an I.C. engine 10 is effected by a knock voltage generating circuit 1 including a microphone 12 for converting the knock sounds into an electric signal which is passed through a band pass filter 20 and peak follower 24 to generate a knock voltage representing a maximum voltage of frequency components of the electric signal within a predetermined frequency band width, a knock level discriminating circuit 2 either a) Fig. 7, producing a retard signal when the knock voltage exceeds a higher predetermined level and or advance signal when the knock voltage falls below a lower predetermined level, or b) Figs. 16, 19, producing an advance or retard signal when the knock voltage exceeds a function voltage according to engine speed and an ignition timing control circuit 3 responsive to the advance and retard signals. As shown in Fig. 7 the signal from the peak follower 24 is fed to the knock level discriminating circuit 2 via a logarithmic amplifier 32 which converts the peak voltages to dB units. In the knock level discriminating circuit the signal is fed to a comparator 36 in which it is compared with higher and lower level signals, the amplitudes of which are engine speed dependant and which are derived from TDC and BDC pick-ups 38a, 38b fed via a wave shaper 40 and a function generator 44. The output from comparator 36 is fed to respective flip-flop circuits 58, 60 of a holding circuit 62, the output signals of which are utilized by a voltage regulator 70 as advance and retard signals. The adjusted and amplified output of regulator 70 is then fed to an ignition timing controller 94. Various circuit diagrams are given for some of the circuit components. Again, Fig. 14, (not shown), a number of band pass filters replace filter 20 and a number of function generators with a function selector (152), replace the generator 44, to compensate for fluctuations in the central frequency of the knocking sound, and variations in the knocking level pattern with respect to engine speed in different engines. As shown in Fig. 16, the comparator 36 compares the knock voltage generating circuit signal with a signal derived from a digital function generator in response to an engine speed pulse signal from a speed detector 180 and a function selector signal 184. When the knock voltage generating circuit signal exceeds the speed responsive signal, the comparator feeds a gate 188 to allow a counter 190 to count the number of appearances of knocking per unit time. This digital count is stored and converted to an analogue voltage at 192, which voltage is compared at 194 with a reference voltage to produce the control signal for the voltage regulator 70 of the ignition timing control circuit 3. Again, Fig. 17, (not shown), control is effected in accordance additionally with the proportion of the rate of non-knocking to the rate of knocking during a unit time, by causing the function generator 182, integrator 186, and comparator 36 to each produce two outputs, (knocking, non- knocking rates), which can be processed so that an analogue computer (200) can produce an output voltage equal to the proportion of one to the other, to be compared with a reference voltage. A digital system is shown in Fig. 19, in which the signal from the digital peak follower 24 is fed to a digital comparator 36 where it is compared with an engine speed derived signal from a digital function generator. The comparator 36 has two outputs, producing a signal respectively when the signal from 24 is larger and smaller than the speed signal. The comparator output is fed to an up/ down counter 218 which actuates the ignition timing controller 92 via a digital to analogue converter 222. Again, Figs. 20, 21, (not shown), mixed analogue/digital circuits may be utilized.