GB1260304A - Fuel injection systems for internal combustion engines - Google Patents

Abstract

1,260,304. Regulating I. C. engine fuel injection. BRICO ENG. Ltd. March 28, 1969 [April 5, 1968(2)], Nos. 16640/68 and 16641/68. Heading F1B. In a fuel injection system for an I.C. engine in which fuel is fed to the engine through electrically operated fuel injectors which are opened intermittently, means responsive to engine overrun conditions are operative during overrun to maintain one or more (but not all) of the injectors closed in one embodiment or, in another embodiment, to open all the injectors only once every nth. cycle of engine operations, where n is a number greater than one. This reduces exhaust pollution. The four-cylinder engine shown in Fig. 1 comprises a fuel injector 1 for each cylinder, each injector being located in the induction passage adjacent the respective inlet valve. The injectors 1 are divided into two groups of two, the injectors of each group being opened intermittently by electrical pulses generated by a respective pulse generator 9A or 9B triggered by a trigger device 8, e.g., a contact assembly driven by the engine. Computers 10 control the pulse duration in accordance with, e.g. manifold pressure, rotational speed and ambient temperature and may also provide fuel enrichment on acceleration or cold starting. The pulse generators and computers may be as described in Specification 1, 107, 989. During engine overrun, i.e., when the throttle 12 is closed and the vehicle is temporarily driving the engine, the depression in the induction passage downstream of the throttle 12 operates a pressure-responsive transducer 13 (comprising a diaphragm controlling a pain of contacts) which operates a transistorized switching device 14 to inhibit operation of the pulse generator 9B, so that the two cylinders associated with the pulse generator 9B take in substantially no fuel while the two other cylinders can be supplied with a richer mixture than would otherwise be desirable. In alternative arrangements, the fuel injectors are opened only on alternate cycles (or every third or fourth cycle) during overrun. As before, overrun may be sensed by means of a transducer 13 (embodying a variable resistor instead of a pair of contacts). Alternatively, the engine speed at overrun may be sensed by a diode pump 16, Fig. 6, which counts the rate of pulses from the engine-driven trigger devices 8A, 8B. The output of the diode pump is fed to a Schmitt trigger 19 via an emitter follower 17 and a throttle switch 18 which is closed when the engine throttle 12 is closed. At overrun, the Schmitt trigger provides a positive-going input to each of two AND gates 24A, 24B. Each AND gate also receives a positive-going input at half the frequency of the trigger input pulses from a respective bi-stable frequency divider 23A or 23B. When each AND gate receives positive-going inputs from both the Schmitt trigger and the respective bi-stable frequency divider, it produces an output signal which is fed via a respective output stage 25A or 25B to the respective pulse generator 9A or 9B. This output signal, the frequency of which is half that of the triggering pulses going directly from the trigger devices 8A, 8B to the pulse generators, inhibits the operation of the respective pulse generator during alternate triggering pulses, whereby each fuel injector is opened only on alternate cycles during overrun.