GB1064857A - Internal combustion engine coil ignition systems - Google Patents

Abstract

1,064,857. Ignition systems. GENERAL MOTORS CORPORATION. Sept. 24, 1964 [Oct.17, 1963], No.38938/64. Heading F1B. In an I. C. engine coil ignition system the primary winding of the coil is energized from a D.C. source through a circuit including a three electrode semi-conductor normally biased to its conductive state, but periodically biased to its non-conductive state by a device operable in synchronism with the engine. The potential of a gate 58 of a controlled rectifier 54, of the type which can be switched on or off by the gate, is made positive with respect to the cathode 60 by a potential divider 81, 77 to make the controlled rectifier conductive. The controlled rectifier has a breakdown rating of approximately 500 to 700 volts. When interrupter contacts 22, 24 are closed the voltage induced in the secondary winding 68 of a pulse transformer 64 is of such polarity as to assist rendering the controlled rectifier conductive. When the contacts are opened a voltage of reverse polarity is induced in the secondary winding 68 sufficient to drive the gate 58 negative with respect to the cathode and render the controlled rectifier non-conductive. This opens the circuit of the primary winding 38 of ignition coil 36 to induce a high voltage in the secondary winding 40 connected through a distributor 30, 32 with the spark plugs 46. When the induced voltage of reverse polarity of the pulse transformer 64 has dissipated, the controlled rectifier will again become conductive even if the contacts 22, 24 are still open. The resistors 67, 77, 81, transformer 64 and controlled rectifier 54 may be connected together to form a single unit and added to an existing conventional ignition circuit. The connection 71 may instead be made between the resistor 67 and the primary winding 66 of pulse transformer 64. The conductor containing resistors 77, 81 may be omitted and a capacitor arranged between an earthed secondary winding 68 and the gate 58 or the secondary winding 68 and earth; in the latter case a resistor is arranged in parallel with the capacitor. Thus, the inter-action of the voltage induced in the secondary winding 68 and the charging and discharging of the capacitor renders the controlled rectifier non-conductive when the contacts 22, 24 open but capable of becoming conductive again before they re-close. In other arrangements, Figs. 5 and 6 (not shown), a PNP or a NPN transistor is used, instead of the rectifier, in a modified circuit which may include a Zener diode connected across the transistor to protect it against voltage transients.