GB1409358A - Arrangement for controlling ignition systems for internal combustion engines - Google Patents

Abstract

1409358 Ignition systems; timing ignition BROWN BOVERI & CIE AG 6 Nov 1973 [10 Nov 1972] 51385/73 Heading F1B An arrangement for controlling an ignition system comprises a rotary member which in use rotates synchronously with the crank-shaft of the internal-combustion engine on which the arrangement is used, marking means a b on the rotary member, sensing means 3 for sensing the marking means as the rotary member rotates, the sensing means being operable to produce signals the intervals between which are dependent on the speed of rotation and the arrangement of the marking means on the rotary member and a discriminator (AND-gate 4) connected to the output of the sensing means and operable in response to the signals to produce an output signal for initiating the storage of ignition energy, the discriminator being arranged in such a manner that the time of occurrence of the output signal varies with the speed of rotation of the rotary member in such a way that the interval between the output signal and the moment of ignition corresponds to the time required for the storage of ignition energy. A reference point 1 is arranged on the rotary member and another sensing means 6 is operable in response to the passage of the reference point to trigger delivery of the stored ignition energy. As shown the rotary member is in the form of a disc and the marking means are in the form of lines at the edge of the disc, the spacing between the lines progressively increasing in the direction in which the disc is rotated. Alternatively the marking means may be magnetic or in the form of an alternating waveform. If the engine is rotating at a slower speed than 6000 revolutions per minute the time interval between signals from the sensor 3 resulting from the first and second markings of a group of markings is of such a magnitude that the time delayed sensor signal produced by the first marking has already vanished at the relevant input of the AND-gate 4 before the undelayed sensor signal produced by the second marking appears at the other input. Therefore no signal is produced at the output of the AND-gate 4. If the crankshaft is rotating at 6000 revolutions per minute, when the second marking a passes the sensor 3 the sensor signal produced thereby is applied without delay to the first input of the AND-gate 4. At the other input of the AND-gate there is applied a time delayed signal of the first marking a so that there is a condition of coincidence at the AND-gate 4 which thus produces an output signal which causes the ignition coil energization to be initiated. If the ignition coil forms part of a blocking oscillator the output of the AND-gate 4 is used to trigger the blocking oscillator. In a modification (not shown), a further sensor is associated with the disc at the 270 degrees position and a time delay stage 5 is omitted. The ignition timing can be raised according to the engine speed.