1. Field of the Invention
The present invention relates to a fuel injection system for a spark-ignition internal combustion engine which is operative to mechanically meter a liquid fuel and intermittently inject the metered fuel into the engine.
2. Description of the Prior Art
Systems of various types and structures have been proposed for injecting a fuel such as gasoline into internal combustion engines. The known types of fuel injection systems include an intermittent fuel injection type that includes a rotor with a single orifice formed therein. The rotor is rotated to meter and distribute the fuel to a series of fuel injectors provided for respective engine cylinders.
With the intermittent fuel injection system of the type specified above, a difficulty is encountered that, because of the single orifice formed in the rotor, a prolonged period of time is required for the injection of an amount of fuel through an injector with a result that the fuel cannot be injected within a short period of time in an appropriate stroke of the engine. This difficulty could be overcome by use of a large-sized orifice. With a large-sized orifice, however, the flow of fuel through the orifice per unit of time is increased with a resultant increase of the resistance of each injector to the flow of fuel therethrough. The use of a large-sized orifice, moreover, would cause an adverse effect to uniform fuel supply to respective engine cylinders, because of the unequal pressures in the fuel delivery lines downstream of the orifice which would be caused by different flow characteristics of respective fuel injections.
U.S. Pat. No. 3,996,910 issued Dec. 14, 1976 to Masaaki Noguchi et al. (inventors of the present application) discloses a fuel injection system comprising a fuel metering and distributing device which includes a rotor and a control shaft. Fuel metering and distributing slits or orifices are formed in the control shaft and in the rotor. The orifice in the rotor is brought into overlapping relationship with successive orifices in the control shaft by the rotation of the rotor to meter and distribute the fuel to respective fuel injectors. The area over which the orifice in the rotor is overlapped with each of the orifices in the control shaft is varied in accordance with a variation in an engine operating parameter, such as the rate of engine intake air flow, to control the rate of fuel flow through the overlapped fuel metering and distributing orifices. The angle of rotation of the rotor relative to the control shaft over which angle the orifice in the rotor is communicated with each of the orifices in the control shaft is constant regardless of the rate of engine intake air flow. The fuel injection system of the described structure and arrangement is difficult to manufacture and to satisfy the requirement for the fuel metering accuracy.