GB903118A - Improvements in or relating to ignition systems for internal combustion engines - Google Patents

Abstract

903,118. Engine control systems. BOSCH G.m.b.H., ROBERT. Dec. 5, 1958 [Dec. 6, 1957], No. 39224/58. Class 40 (1). [Also in Groups XXVII and XL (c)] An ignition system comprises at least one transistor for controlling an ignition surge at the ignition instant and an electronic regulating device adapted to give a variable retardation time relative to a control instant predetermined by a control member for adjusting the ignition timing dependently on the speed and the output taken from the engine. In Fig. 1, the transistor 40 is controlled by the relaxation oscillation device 35. The oscillation device delivers an impulse which varies dependently on the speed and the throttle flap position of the engine 10. The impulse begins when a control switch 37 is closed. In order to explain the mode of operation it is first of all assumed that both the control voltage U 1 produced across the resistor 54 by the winding 63 and rectifiers 65 and the voltage U 2 produced across the resistor 53 by the winding 62 of the generator 60 have the value zero. When the switch 37 is closed, the blocked transistor 45 becomes energized. This produces a drop of voltage across the resistor 56 and the transistor 50 is blocked, at the same time the transistor 40 in the current supply lead to the primary winding 27 of the ignition coil is energized. When the transistor 40 is blocked again, a potential sufficient for ignition is produced in the secondary winding. The transistor 40 is blocked again when the condenser 52 has discharged through the resistor 51 sufficiently for its voltage to drop to the required value. At this moment the transistor 50 is again energized. The drop in voltage across the resistor 59 causes the transistor 45 to return to its blocked condition. The slide of the potentiometer 67 is coupled to the throttle valve (not shown). If the slide is displaced upon adjustment of the throttle valve it takes a portion from the control voltage across the potentiometer 67. Thus the base of the transistor 50 falls to the value at which the transistor becomes energized, at a much earlier instant. The second control voltage U 2 is fully effective even when the engine is operating with part load. The control voltage causes the time of lag Z not to continue with an increasing speed of approximately 1250 r.p.m. onwards along the curve indicated by the broken line 16 in Fig. 4 at full load operation. Instead the curve of the time of lag proceeds from then on at a greatly reduced incline up to approximately 2250 r.p.m. and the time of lag becomes only slightly less. From speeds over 2250 r.p.m. the time of lag greatly diminishes rapidly to the value zero at 3000 r.p.m. In the embodiment of Fig. 7 the oscillation device 35 operates only indirectly on the transistor 40 in the feed circuit of the primary 27, namely by way of a second oscillation device 80, the purpose of which is to control the transistor 40 and to cause it to give the primary winding 27 a current impulse of length independent of the speed of the engine. The battery of Fig. 1 is replaced by the winding 99 of the generator and a bridge rectifier 100 is associated therewith. Circuit component values are quoted in the Specification.