GB1300741A - Speed limiting systems for internal combustion engines - Google Patents

Abstract

1300741 Automatic speed control JOSEPH LUCAS (INDUSTRIES) LTD 20 Jan 1970 [3 Feb 1969 12 May 1969] 5607/69 and 24056/69 Heading G3R A system for limiting the speed of an internal combustion engine includes means for timing the intervals between successive openings of a contactbreaker or other switching device. If the interval is less than a predetermined minimum value, ignition spark production is suppressed. In the embodiment of Fig. 1, the primary winding 14 of an ignition coil 15 is connected in series with a contact-breaker 16 across the battery 13 of a road vehicle. A thyristor 36 is connected across the contact-breaker. In use, the contact-breaker is opened and closed in timed relationship to the vehicle engine, and each time it opens, a spark is caused at the appropriate plug 21, provided the thyristor 36 is blocked. This will be the case if the engine speed is below the desired limit since a transistor 33 will be conductive to divert current from the gate of the thyristor. After a spark, current through a filter circuit 22-24 will turn off the transistor 33 for a time determined by a resistor 34 and capacitor 32, but this time is arranged to elapse before the next spark is due, so that the thyristor 36 will by then be blocked again. However, if the engine speed is too high, the contact-breaker 16 will open while the thyristor 36 is still gated on, and no spark will result. A second delay circuit 27, 29 ensures that the thyristor is not gated on until the spark has occurred. In a modification, Fig.2 (not shown), the cathode of the thyristor is connected to the positive line to prevent conduction of the thyristor if the engine stalls. The contact-breaker may be replaced by a semiconductor device.