GB1485993A - Control arrangement for an ignition system of an internal combustion engine - Google Patents

Abstract

1485993 Ignition system SIEMENS AG 4 Nov 1974 [5 Nov 1973] 47674/74 Heading F1B In an ignition system including an ingnition coil 10c in series with a switching transistor 10f, the control system includes a contact breaker 13, e.g. mechanical, electromagnetic or electro-luminescent, and is effective to render the 'on' time of the switching transistor, and hence the time of energizing the ignition coil, substantially independent of engine speed. As shown, immediately after contact 13 opens, a logic evaluator 12 passes a current through contact units A, C to connect an integrator 11 to a fixed voltage source 5 and to negatively bias the inverting input of an operational amplifier forming part of a voltage comparator 7. The integrator 11 therefore begins to integrate the negative fixed voltage U5, and the voltage comparator 7 produces a constant voltage output fed to the power stage 10 to cause transistor 10b to conduct and hence to turn transistor 10f 'off'. When contact 13 closes, logic evaluator 12 cuts-off the current from control units A and C, connecting integrator 11 to a fixed voltage source 6, and disconnecting voltage source 9 from the comparator 7, so that voltage source 8 becomes effective. The integrator 11 now integrates the positive source U6 in the opposite sense until the integrator output equals that of source 8 when the output from comparator 7 drops to zero switching off transistor 10b, and hence switching 'on' transistor 10f to energize coil 10c for a time until contact 13 again opens, when an ignition spark is produced. A device 16 passes a current through control unit B each time the contact 13 opens, to close a contact b in parallel with the operational amplifier 11a of integrator 11 to reset the integrator. A device 18 ensures that should the contact 13 be closed with the engine idling, the transistor 10b will be switched 'on' to switch transistor 10f 'off' to avoid a continuous power dissipation in the ignition coil. The output voltage of the integrator 11 reaches its saturation value in the engine starting speed range to increase the energy and duration of the ignition spark. The integrator may be a digital counter, and the comparator may be analog or digital.