GB1257343A - - Google Patents

Abstract

1,257,343. Automatic speed control. DUCELLIER & CIE. Jan.14, 1969 [Jan.15, 1968; June 24, 1968], No.2083/69. Heading G3R. In order to limit the speed of an I.C. engine, particularly one driving a vehicle, ignition sparks are suppressed whenever the engine exceeds a preset speed. As shown the engine drives a pulse generator 20, 21 coupled to a unit 22 which supplies pulses to an ignition coil 23, the generator is an electromagnetic device but may be replaced by a photo-electric or Hall effect or by a simple contact breaker. An additional pick-up 25 displaced from main pick-up 21 delivers pulses, at a frequency proportional to the speed of the engine, to a monostable multivibrator circuit comprising transistors 1, 7. Each pulse changes the state of the monostable and thus renders a transistor 15 conducting which shorts the output of the main pick-up 21. When the time between pulses from pick-up 25 becomes less than the time constant of the monostable transistor 15 remains permanently conducting and all ignition sparks are suppressed until the speed drops below the limit set by the monostable which is adjustable by a potentiometer 6. In a modification Fig.2 (not shown) the pulses fed to the monostable are derived from the main pick-up 21; this results in only alternate sparks being suppressed. Also the monostable has a fixed time constant and feeds a variable time delay circuit. In a more elaborate circuit Fig.3 (not shown) the pulses from a separate pick-up (or from the main pick-up Fig.4 (not shown) are supplied to a fixed time monostable; when that monostable resets it triggers a variable time constant monostable. A diode gate gives an output when both of these monostables are in their unstable condition indicating an excess speed. The output of the gate triggers a second fixed monostable which controls a fixed time constant circuit to maintain a short on the main pick-up for a fixed time.