GB1418932A - Fuel injection systems - Google Patents

Abstract

1418932 Spray carburetters ROBERT BOSCH GmbH 19 Jan 1973 [22 Jan 1972] 2809/73 Heading F1B A fuel injection system for mixture compressing I.C. engines having continuous injection into the intake manifold and separate ignition, said system comprising, a measuring element 3 and an arbitrarily operable throttle valve 6 in series in the intake pipe, the measuring element 3 being arranged to be displaced through a distance proportional to the quantity of air flowing through the intake manifold, against a restoring force, said measuring element being arranged to actuate a movable part 11 of a fuel metering valve 50 which is arranged in a fuel line 14, for metering a fuel quantity proportional to the quantity of air flowing, metering being effected at a constant pressure difference which however varies in dependence upon the values of engine operational characteristics, the pressure difference at the metering valve being variable by means of a hysteresis-free electromagnet system having a permanent magnet and a moving coil armature. The measuring element 3 is mounted on an arm 8 which is pivoted at 9 and which actuates a valve spool 11 of the metering valve 50. Fuel is supplied to the metering valve, by a pump, through a line 14 and reaches the spool through a channel 51. According to the position of the spool, the entrance to channels 53 is uncovered to a greater or lesser extent so that fuel passes into chambers 55 on one side of a diaphragm 56, which acts as a valve-member and co-operates with flat valve seats formed on pipes 58 which lead to individual fuel injectors situated in the intake manifold adjacent the inlet ports of respective cylinders. A branch pipe 60, including a restrictor 61, supplies fuel to chambers 57 formed on the other side of the diaphragm 56. The pressure in these chambers, which tends to press the diaphragm against the valve seats on the pipes 58, is controlled by a valve unit 23, which is responsive to e.g. the oxygen content of the engine exhaust gas. Valve unit 23 consists of a housing divided by a diaphragm 25 into chambers 26 and 27. Chamber 26 is connected to chambers 57 by a line 28 and has an outlet pipe 29, the inner end of which forms a flat valve seat which co-operates with the diaphragm 25. A spring 31 biases the diaphragm to the open position. In the chamber 27 which is connected to the fuel pump by a line 32, is a magnet system 34 comprising a moving coil armature 35, a coil 36, a soft iron core 37, a permanent magnet 38 and a soft iron plate 39 having a core 40 which projects into the immersion coil armature 35. The armature 35 is suspended from a spider-type leaf-spring 41 which is connected by an intermediate member 42 to the diaphragm 25. Operation A sensor e.g. an oxygen probe, detects the amount of oxygen in the exhaust gas and provides an electrical signal which is used to vary the current in the coil 35 and thus the position of the diaphragm 25 so that the rate at which fluid leaks away through the unit 23 is varied, producing a corresponding variation in the pressure in the chambers 57 and hence in the quantity of fuel delivered through the pipes 58 to the injectors.