GB1336605A - Fuel injection systems - Google Patents

Abstract

1336605 Spray carburetters ROBERT BOSCH GmbH 27 Nov 1970 [1 Dec 1969] 56433/70 Heading F1B Fuel injection system for an I.C. engine having separate ignition and continuous injection into the inlet manifold comprises a measuring element and a butterfly throttle valve in series in the inlet manifold, the measuring element being movable against a constant return force to actuate the movable part of a valve which meters a quantity of fuel in proportion to the flow of air through the manifold, the measuring element and the metering valve being connected by a device which changes the relationship between the measuring element and the valve to vary the proportionality between the air and fuel in accordance with at least one engine characteristic. Air flow into the manifold is controlled by a butterfly valve 3 and acts on a plate 2 secured to a lever 4 which rotates about a pivot 5. Pivotally mounted on the lever 4 is a link 6 which moves the spool 7 of a fuel metering valve. Fuel is drawn from a tank 12 by a pump 10 and delivered by a line 13 to a passage 16 which communicates with an annular groove 17 in the spool. According to the position of the spool fuel flows into passages 19, each of which leads to a chamber 18b connected by a duct 23 to an injection nozzle. One side of each of the chambers 18b is formed by a diaphragm 20, which acts as a flap valve on the end surface of the duct 23 and is normally held in the open position by a spring 22. The passage 16 also communicates with chambers 18a, each corresponding with one of the chambers 18b so that the diaphragm 20 is subject to fuel pressure on both sides and the pressure head on the valve remains constant irrespective of the quantity of fuel flowing. The return force acting on the valve spool 7 is provided by the pressure of the fuel through a line 25 and a throttle 24 which damps the movement of the spool. Errors in the proportion of fuel provided, for a given air flow, due to stiffness in the movement of the working parts of the valve are compensated by a regulator 28, consisting of a chamber 33 containing a spring-loaded diaphragm 31 which controls the flow of fuel out of a nozzle 30, connected by a line 27 to the end 26 of the valve body through a throttle 39, which has the effect of damping the movement of the plate 2. The side of the diaphragm remote from the nozzle 30 is connected by a line 35 to the region immediately behind the plate 2, where a constant pressure normally exists provided that the plate 2 has moved freely in response to variation in the air flow due to changes in the position of the butterfly valve 3. If the plate 2 fails to move into the divergent conical part 1a of the inlet pipe to accommodate increased air flow, then the reduced pressure in the region between the plate and the butterfly valve acts on the diaphragm 31 and by allowing more fuel to pass the nozzle 30, reduces the pressure in the chamber 26 so that the spool 7 moves to allow a greater fuel flow to the injectors. The tension of the spring 32 is controlled by a temperature-sensitive element 38, so that additional fuel is supplied when the engine is cold. The position of the link 6 relative to the lever 4 is modified by a cam 40 and roller follower mechanism 41, 42, 43. The cam is rotatable about a spindle 45 in dependence upon the operating conditions of the engine e.g. the pressure downstream of butterfly valve 3, to vary the amount of fuel supplied according to the load on the engine.