Fuel injection system

Claim 1

A fuel injection system for externally ignited internal combustion engines comprising, in combination: (a) a suction tube for air intake to the engine; (b) an air sensor disposed in said suction tube; (c) an arbitrarily operable butterfly valve disposed in said suction tube in series with said air sensor; (d) a fuel supply conduit; (e) a control pressure conduit; (f) a fuel metering valve connected to said fuel supply conduit and said control pressure conduit for continuously injecting fuel into said suction tube; (g) a control plunger, serving as the movable member of said fuel metering valve, said control plunger being acted upon on one end by said air sensor, and on an opposite end by a return force provided by liquid under constant but arbitrarily variable pressure delivered by said control pressure conduit, for metering a fuel quantity that is proportionate to the quantity of air measured by said air sensor; and (h) at least one pressure control valve in the form of a flat seat valve having a membrane as the movable valve part, said pressure control valve being disposed in said control pressure conduit for varying pressure in said control pressure conduit in dependence on at least one operating parameter of the engine and thereby varying the fuel-air ratio during load changes, and in particular for enriching the fuel-air mixture during full load operation, wherein the pressure control valve includes: (i) a valve membrane; (ii) a control membrane; (iii) two pressure chambers separated from one another by the control membrane; (iv) a pressure conduit connected to a first one of the pressure chambers and to the suction tube downstream of the butterfly valve; (v) a spring chamber; (vi) means defining a throttle bore within the pressure control valve for connecting the spring chamber to the first one of the pressure chambers; (vii) a further pressure conduit connected to the spring chamber and to the suction tube between the air sensor and the butterfly valve; (viii) another pressure conduit connected to a second one of the pressure chambers and to the spring chamber; (ix) a control spring disposed in the first one of the pressure chambers, said control spring acting against the control membrane; (x) a valve spring disposed in the spring chamber, said valve spring acting against the valve membrane; and (xi) a transmission pin disposed between the valve membrane and the control membrane.