GB1336606A - Fuel ignition systems - Google Patents

Abstract

1336606 Spray carburetters ROBERT BOSCH GmbH 27 Nov 1970 [1 Dec 1969] 56436/70 Heading F1B Fuel injection system for an I.C. engine having spark ignition and continuous injection of fuel into the inlet manifold comprises a throttle valve and a gauging element in series in the manifold, the gauging element being displaced proportionally to the air-flow in the manifold and moving a slidable part of a fuel metering valve against a restoring force provided by a pressure fluid which flows continuously and at constant pressure through a line and acts on a member connected to the slidable part. Combustion air is drawn through a cleaner 2 and acts on a gauging element 4 as it enters a part 3 of the inlet pipe which is divergent in the direction of air flow and is connected by a flexible section 5 to a rigid section 6 containing a butterfly throttle valve 7. The gauging element 4 is fixed to a lever 10 which is pivotally mounted at 9 and has a lug 11 which acts on the movable part 12 of a fuel valve. Fuel is drawn from a tank 18 by , a pump 16 and fed to an annular groove 22a in the valve body, from which ports 22b lead to the bore in which the part 12 slides. A central section of the part 12 is reduced in diameter and allows fuel to pass to outlet ports 25 and through passages 26 to the injection nozzles. Fuel also leaves the annular passage by a duct 22c which leads via an annular groove 22d, ports 22e and a line 27 to a chamber 23 where it acts on the end face of part 12 and provides the force opposing the movement of the gauging element 4. The pressure existing in this chamber is modified by the action of two relief valves. The first is connected to the chamber by a line 27 and comprises a diaphragm 29 closing the outlet of a nozzle 27a. The diaphragm is acted on by a spring 31 which shuts a cap 41, itself supported by a rod 40 which scans a three-dimensional cam 32, which turns with the throttle valve spindle and is attached to a diaphragm 36 acted on by a spring 39. The effect of the spring 39 is reduced by conducting lowpressure from a point downstream of the throttle, through a line 38 to a chamber above the diaphragm. Under full throttle conditions, the tension of spring 31 is at a minimum, so that the restoring force acting on part 12 is reduced and an enriched mixture is provided. In over-run conditions, a strong depression is communicated to chamber 37 so that the cam 32 is lifted, the tension on spring 31 is increased and the restoring force is a maximum, no displacement of the gauging element 4 occurs and no fuel is injected. The second relief valve controls the mixture strength in relation to engine temperature and comprises a line 67 leading to a nozzle 70 closed by a diaphragm 71. A spring 72 abuts a sleeve 76 which is connected to a temperature sensitive element 78, and which controls the flow of air through a by-pass duct 75. When the engine is cold, the pressure in the chamber 23 is reduced so that an enriched mixture is provided. In modification of the device, the cam 32 is replaced either by a linear cam which moves vertically but is not connected to the throttle spindle, or by a disc cam which rotates with the throttle spindle but has no vertical movement. The diaphragm 29 may have an opening through it so that both sides of the diaphragm are at the same pressure as the fuel tank. A spring controlled relief valve may be connected close to the chamber 23 to eliminate the effect of surges in the inlet manifold. Damping of the movement of part 12 may be provided Fig.6 (not shown) by enlarging the chamber 23 and providing on the end of part 12 a disc which is a close fit in the chamber. The chambers on both sides of the disc are connected to the groove 22d through passages which are dimensioned so as to be effective as throttles. The first and second relief valves may be combined into one unit, Fig.7 and 8 (not shown) the parts of the unit acting on opposite ends of a lever which is pivotally mounted intermediate its ends on a cap which acts as an abutment for the spring 31.