GB815564A - Improvements in or relating to fuel injection systems - Google Patents

Abstract

815,564. Spray carburetters; regulating. GENERAL MOTORS CORPORATION. June 21, 1957, No. 19660/57. Classes 7(3) and 7(6) [Also in Group XXIX] An apparatus for forming the combustible charge of an I.C. engine comprises an air induction system 14 having a throttle 18 to control the air flow therethrough and a fuel injection system 10 having a fuel metering device'which controls the fuelair ratio of the charge in accordance with the resultant of pressure differentials caused by the velocity of flow of air and fuel through their respective systems. A tube 55 connects the throat of the venturi 20 to the right hand side of the diaphragm 41, the left hand side of which communicates with the atmosphere. Increase in flow of air through the venturi causes the diaphragm 41 to move the control valve 52 to the right. The diaphragm 43 is subjected to the pressure differential across a restriction 56 in the fuel supply line to a distributer 32, such that an increase in fuel flow tends to move the diaphragm 43 to the left in opposition to the direction of movement caused by increased air flow through the venturi 20. The control valve 52 controls a servo-piston 66 which in turn operates a fuel metering valve 30 regulating the delivery rate of fuel to the distributer from the pump 26. Fuel at pump outlet pressure is also used as the motive fluid for the servo-motor. A pressure relief valve 34 maintains a pre-determined fuel pressure in the fuel injection system. To compensate for flow losses which might produce errors in the air-fuel ratio the restriction 56 may be replaced by a restriction having a variable hydraulic resistance, which varies as a function of the pressure drop across the restriction and hence as the fuel flow rate. A fuel enrichment device may be provided in the form of a second restriction in parallel with the restriction 56, which is brought automatically into operation when the engine is operating at full power. This results in a reduction in the fuel pressure differential across the restriction 56 and consequently in a richer mixture. To provide a richer mixture when the engine is idling a pipe may be provided which is in communication between the right hand side of diaphragm 41 and the induction system downstream of the throttle 18. This pipe is controlled by a valve connected by a lost motion linkage to the throttle actuating mechanism such that when the throttle is in the idling position the valve is opened subjecting the chamber 46 to increased suction and hence increasing the fuel supply. The relief valve 34 may be modified to be responsive to both the fuel pressure in the injection system and the 'air pressure in the induction system downstream of the throttle to maintain a substantially constant differential between these pressures. The distributer 32 includes a rotor 78, driven by the engine at camshaft speed and having an outlet that allows the fuel to be distributed to a cylinder only when its associated intake valve is open. At the outlet of each of the injector lines 76 there is a pressure sensitive check valve 80, which ensures sharp starting and stopping of the fuel flow, the fuel pressure opening the valve against the loading of the spring 114 and the vacuum in the manifold acting on the underside of the valve member.