Fuel injection apparatus

Claim 1

A fuel injection apparatus of the type comprising air flow rate detecting means having a servomechanism and a valve opening mechanism for maintaining at a predetermined value the pressure difference across a throttle valve disposed in a suction pipe and detecting the flow rate of air to an internal combustion engine from the degree of opening of said throttle valve, fuel flow rate measuring means disposed in a fuel supply passage and having a fuel measuring gate which is connected to said throttle valve and whose degree of fluidcommunication uniquely corresponds to the degree of opening of said throttle valve, pressure adjusting means for regulating the pressure differences across said fuel measuring gate, a plurality of sensor means for sensing the operating conditions of the engine and for emitting sensed signals, electronic control unit means which receives said sensed signals and emits control signals based on said sensed signals, and a first solenoid valve disposed in a fuel pressure control circuit and adapted to be opened and closed by said control signals which are emitted from said electronic control unit means for adjusting a set value of said pressure adjusting means by the open-close action thereof to compensate the air-fuel ratio so as to adapt to all the operating conditions of said engine, characterized in that said fuel injection apparatus further comprises a second solenoid valve disposed in said fuel pressure control circuit in parallel with the first solenoid valve, said solenoid valve being adapted to be opened and closed by output time ratio of fuel rich and lean signals which are emitted from said electronic control unit means so as to correct the basic air-fuel ratio determined in connection with said servo-mechanism of the air flow rate detecting means and said fuel measuring gate when said engine is in operating condition, thereby maintaining said fuel-air ratio at a desired constant value.