Patent GB-861534-A (GB)
Title: Improvements in ignition systems for internal combustion engines
IPC: F02P3/045
Filed: 1959-02-20
Abstract: 861,534. Ignition systems. BOSCH G.m.b.H., R. Feb. 20, 1959 [Feb. 22, 1958], No. 5888/59. Class 7(4). The invention relates to an ignition system in which a power transistor is arranged with its output circuit in series with the primary circuit of an ignition coil the ignition spark being produced by blocking the transistor. The timing of the spark is effected by electrical means in accordance with engine speed and throttle valve opening. Referring to Fig. 1, with each rotation of the crank-shaft of the engine the magnets 68 of the armature rotating at half the crank-shaft speed produce in the coil 55 four half cycles of an alternating voltage U 1 . The alternating voltage U 1  applied to the variable resistor 63 results in a current component J 1  which combines with the current J c  flowing through the condenser 62 to form an overall current J 2 . The overall current produces across the resistor 64 of resistance R 2  a voltage drop U 3 =J 2 R 2  leading the generator voltage U 1  by a phase angle which increases the faster the engine runs. Each of the negative halfcycles U 1  produces a control current J 3  which passes through the rectifier 60 and by which the oscillator 35 is brought into its unstable condition as long as no control voltage is acting on the input transistor 40 the transistor 30 and the output transistor 50 operating in phase therewith are conductive while the transistor 40 is blocked. As soon as the current J 3  flowing through the rectifier 60 during the negative half cycles exceeds a very low minimum value the transistor 40 becomes conductive. This greatly raises the potential p of the connecting point P. The potential of the base B of the transistor 50 is made more positive and the transistor 50 is blocked and together therewith the transistor 30. The transistor 50 remains together with the transistor 30 practically non-conducting until the base potential has fallen below the value of the emitter potential owing to the discharge of the condenser 43. At this instant the oscillator returns to the condition in which the input transistor 40 is blocked. When the potential U 2  assumes the direction indicated in Fig. 1 it counteracts the operating voltage applied to the oscillator by the leads 32 and 29. This results in a smaller voltage across the resistor 49 when the transistor 40 is energized by one of the control surges J 3 . In this case the base potential of the transistor 50 is raised less and less high with increasing speed of the engine so that the transistors 50 and 30 are re-energized at an earlier instant. The iron core 26 may be saturated even at the highest speed of the engine. Advance of the ignition with increase of speed is obtained by phase displacement of the control surges J 3  by means of the phase shifter means 61. As shown the slider of the adjustable resistor 63 is connected to the pedal 82 for opening the throttle valve 84. When the pedal is depressed for operating the engine at higher load it simultaneously moves the slider with the throttle valve. The effect of reducing the effective resistance of the resistor 63 is that the total current J 2  has a much smaller angle of lead.