Apparatus for controlling the air-fuel quantity ratio in internal combustion engines

An apparatus for controlling the fuel-air quantity ratio of the operational mixture to be introduced into the combustion chambers of an internal combustion engine including an air flow rate meter disposed in the intake manifold of the engine, a servo device having a working chamber, said air flow rate meter being movable under differential pressure against a substantially constant hydraulic restoring force generated in said servo device working chamber, a fuel supply line, a fuel metering throttle device in said fuel supply line having a metering cross section, and a working chamber, a fuel supply pump for supplying fuel to said fuel supply line, the displacement of said air flow rate meter being arranged to actuate said fuel metering throttle device, a fuel injection pump having at least one pump piston and one pump working chamber connected to said fuel supply line, said fuel injection pump being provided with fuel feed channels leading to injection points in said engine, and including a differential pressure valve whose pressure chambers are subjected to the pressures present at said metering cross section of said fuel metering throttle device, the differential pressure valve maintaining a constant pressure drop at the metering cross section and wherein said working chamber in said fuel metering throttle device upstream of said metering cross section communicates with the fuel supply line, wherein said fuel supply pump is associated with said fuel injection pump, said fuel injection pump having a working chamber and a fuel-filled chamber including the drive means for the pump piston, a pressure control valve, means for communicating the supply side of said fuel supply pump with said pressure control valve for setting a variable supply pressure and with said fuel-filled chamber, means including a flushing throttle for conducting fuel out of said fuel-filled chamber in a pressure-relieved manner via said flushing throttle, a throttle for uncoupling the variable supply pressure of said fuel supply pump, a pressure maintenance valve for setting the pressure becoming effective at least in the working chamber of said fuel metering throttle device downstream of said throttle to a constant value, and means for communicating said injection pump working chamber with said fuel supply line excluding said feed channels.