Patent GB-1405848-A (GB)
Title: Internal combustion engines
IPC: F02M23/04
Filed: 1973-01-26
Abstract: 1405848 Automatic control of exhaust gases; fluid regulation ROBERT BOSCH GmbH 26 Jan 1973 [29 Jan 1972] 4069/73 Headings G3H and G3R [Also in Division F I ] The fuel/air ratio supplied to an internal combustion engine is adjusted by a carburetter and bypass combination, the by-pass having a valve operated basically in dependence upon movement of a throttle and additionally by the output of a servo-amplifier. As shown, the by-pass valve 18 is controlled by the position of throttle pedal 30 and by the output of an integrating servo-amplifier 25 which receives inputs from an 02 detector 23 and pre-amplifier 24, a throttle position signal 31 or a speed responsive voltage from 33 derived from a pulse signal from a tacho 32. The output of amplifier 24 is compared with a reference value, preferably corresponding to an air/fuel number of 0.98 (i.e. less than stoichiometric) and the result operates a threshold switch to cause the integrating amplifier to integrate in either an increasing or decreasing direction at a rate determined by either the throttle position or the engine speed. At an appropriate upper or lower level an electric motor is energized to re-position the valve 18, which is of butterfly type, by means of a closed loop positioning system, and thereby alter the amount of air bled round the carburetter. The valve is coupled to the servomotor and to throttle valve 14 via slipping clutches Fig. 2a (not shown) whereby it follows movements of the throttle (possibly via gearing) and the servo causes additional motion of 18 only, not to the throttle. The circuit of 25 is described Fig. 3 (not shown); it comprises operational amplifiers and switching transistors to control the direction of integration. The exhaust gases are purified, first by a thermo-reactor, which comprises a thermally insulated, exhaust manifold 20 and causes secondary combustion, and then by a catalytic reactor 21. The 02 detector is of the platinum type described in Specification No. 1385464 (Division G1) which produces a voltage which changes sharply around an air/fuel number of 1. In an alternative embodiment the by-pass butterfly valve 18 is replaced by an electromagnetic throttle valve of the type shown in Fig. 6 in which the position of a fluid control member 63 is controlled by the output of the integrator to which is added the throttle position signal (replacing the mechanical clutch arrangement) and also the engine speed signal Fig. 5 (not shown). In another alternative Fig. 9 (not shown) a valve having both a moving coil and a stationary coil is used; these coils are both energized by the throttle position and the engine speed signals but one only coil (either) by the additional signal from the integrating amplifier. Valve constructions. As shown in Fig. 6 the controlling member 63 is operated by the action of a moving coil 68 in the gap of a permanent magnet 69, against a return spring 64. The gap of the magnet is shaped as shown at 73 to compensate for non-linearities in the system. In an alternative Fig. 7 (not shown) the member 63 is moved by a shaped armature which co-operates with a fixed electromagnet. In another Fig. 8 (not shown) the member is shaped to correct the non-linearities and to minimize forces upon it; in this case it is located only by flat springs (85/86) placed behind a gas tight diaphragm (82). In a final embodiment Fig. 10 (not shown) the control member is as shown in Fig. 6 but the orifice is contained in an axially moveable spring-loaded member, whose position is controlled by a cam. The cam is actuated by the main engine throttle.