GB1342292A - Pulse generators for controlling an internal combustion engine - Google Patents

Abstract

1342292 Transistor pulse circuits ROBERT BOSCH GmbH 29 April 1971 [30 April 1970 15 Jan 1971] 12170/71 Heading H3T [Also in Division F1] In an internal combustion engine, an electronic pulse generator provides separate sets of control pulses to control the inlet and outlet valves, fuel injection, or the ignition system, both sets being synchronized with the crankshaft, having respective duty ratios which are independent of the crank-shaft speed, and being displaced relative to one another also independently of the crank-shaft speed. In the first (valve controlling) embodiment, engine-produced pulses pass through a bi-stable, a monostable and an integrator (11, 12, 13, Fig. 1, not shown) to produce at the input 31 of Fig. 2 one negative ramp and a positive edge per firing cycle (d, Fig. 3, not shown). The positive edge passes by C43 to T39 base so that T39, 40 switch off and T40 on, the output 33 going positive to commence the valve-operating pulse (g). This also turns off T42, and T37 goes on to clamp T36 emitter at the positive supply (e, 63). Now C43 discharges at constant current through T38 until T39 turns on again and the output pulse (g) stops, T37 also going off to allow T36 emitter to follow the falling input ramp (64). Thus the output pulse width depends upon the constant current in T38, which may be varied by a signal at 32 according to various engine parameters; and it also depends upon the magnitude of the positive edge at T36 emitter, this being in turn dependent upon the level reached by the preceding ramp when the engine-generated trigger pulse arrived, and this is a function of engine speed. By this means the pulse output (g) is made longer at slower speeds to maintain the duty ratio constant. To generate a later pulse to operate the exhaust valve, two more circuits as in Fig. 2 (also, 15, 18, 21 and 16, 19, 22, Fig. 1) provide pulses (h, j) the, latter being longer due to the former (h) being used to inhibit T38 base in the second further circuit (22) and delay discharge of C43 therein. These two pulses are subtacted (24) to give the delayed pulse (k). More such circuits (Fig. 4, not shown) operate more valves. In the second (valve controlling) embodiment, an optoelectronic or electromagnetic transducer 101, Fig. 9, driven by the engine supplies pulses to a counter 112. The different level outputs of the counter are fed through appropriately weighted resistors 113-116 to a summing amplifier 120 which then produces a staircase output voltage 162, Fig. 10, at set levels (E1, E2) of which, threshold switches 123, 124 operate to cause a bi-stable 147 to produce a pulse 174 to operate an inlet valve. An exhaust pulse 176 is similarly produced by 148. The leading and trailing edges of these pulses may be shifted, to allow for operating delay in the valve assemblies, by virtue of an OR gate 190 which triggers a monostable 191 and this inhibits at 192, 193 the pulses 174, 176 during the monostable pulse 175. Thus the leading edge of the valve driving pulse 178, 180 is delayed. To delay the trailing edge the monostable is triggered by the opposite edge of the outputs of bi-stables 147, 148 to generate a pulse (175a, Fig. 14, not shown) which is added to the end of the main pulse (178a) by making 192, 193 into OR gates. Speed dependent advance and retard is effected by a further arrangement in which a switch 105 operated once per firing cycle triggers both a monostable 203, whose output 172 blocks a gate 205 for a time t 2 (which is the longest time delay associated with a given valve) and also a bi-stable 204 which enables a gate 206. Gates 205, 206 pass at the end of t 2 engine-generated pulses from 101 to a counter 208 which counts up, 173, until a second switch 108 resets bi-stable 204, blocking 206 and opening 207 and causing the counter to count down again. When it reaches zero, a gate 210 resets a bi-stable 202 to allow the staircase to start, this having been reset to, and held at, zero by bi-stable 202 being first set by the switch 108. Thus the staircase is delayed by the count down time, which equals the count up time; and as the same number of engine pulses 160 occurs between operation of switches 105, 108 (161, 171) and as pulse 172 has a set time duration, the count up time is inversely proportional to speed. The operation of the valves advances therefore at higher speeds.