Fuji Jukogyo Kabushiki Kaisha

Nissan Motor Company Limited

Yoshiaki Ohara

Masaaki Ohgami

Makoto Shikata

Hideo Yabuhara

An air-fuel ratio control system for an internal combustion engine having an emission control system with a three-way catalytic converter for controlling the air-fuel ratio in accordance with the operation of the engine. A throttle sensor for detecting a wide-open throttle operation of the engine and a predetermined voltage supply circuit are provided. A feedback control circuit is provided for controlling the air-fuel ratio to the stoichiometric air-fuel ratio in a normal operating condition. A memorizer circuit memorizes a value corresponding to the control output of the feedback control circuit. A first switch means is actuated by the output of the throttle senor to connect the output of the predetermined voltage supply circuit with the input of the feedback control circuit when acceleration is detected, and to cut off the input of the memorizer circuit for maintaining the stored content thereof. A second switch circuit actuated by the output of the throttle sensor to render the feedback control circuit inoperative as a feedback controller, whereby the air-fuel ratio is controlled by the output of the predetermined voltage supply circuit. After the wide-open throttle operation, the feedback control circuit re-starts with the stored content in the memorizer circuit.

Air-fuel ratio control system

An air-fuel ratio control system for a vehicle powered by an internal combustion engine having an emission control system with a three-way catalytic converter for controlling the air-fuel ratio in accordance with the operation of the engine. A vacuum sensor detects heavy load operation of the engine, and an engine speed detecting circuit and a predetermined voltage supply circuit are provided. The engine speed detecting circuit is so arranged as to produce an output when the engine speed is lower than a predetermined value. A feedback control circuit is provided for controlling the air-fuel ratio to the stoichiometric air-fuel ratio in normal operating conditions. A first switch device is actuated by the output of the vacuum sensor to connect the output of the predetermined voltage supply circuit with the input of the feedback control circuit when heavy load operation is detected and to render the feedback control circuit inoperative. A second switch is to be actuated by the output of the engine speed detecting circuit to stop the control of the air-fuel ratio for supplying a rich air-fuel mixture by the carburetor to the engine.

Air-fuel ratio control system for an internal combustion engine

A system for controlling air-fuel ratio for a carburetor for an internal combustion engine having an induction passage, a throttle valve, an exhaust passage, a detector such as an oxygen sensor for detecting the concentration of oxygen in the exhaust gases, air-fuel mixture supply unit, an on-off electromagnetic valve for correcting the air-fuel ratio of the air-fuel mixture supplied by the air-fuel mixture supply unit and electronic controller. The electronic controller comprises a comparator for comparing the output signal of the detector with a set value, an integrating circuit connected to the comparator, a triangular wave pulse generator, and a driving circuit for producing square wave pulses for driving the on-off electromagnetic valve(s) for output signals of the integrating circuit and of the triangular wave pulse generator for controlling the air-fuel ratio to a value approximately equal to the stoichiometric air-fuel ratio. A constant signal generating circuit is selectively connected operatively to the electronic controller. An engine operation detector for detecting a wide open condition of the throttle valve produces a signal during the wide open condition. A switching circuit operatively connects the constant signal generating circuit to the electronic controller for providing a fixed duty ratio of the valve, and renders the electronic controller non-responsive to the output of the exhaust gas detector. The switching circuit is adapted to be operated by the signal of the engine operation detector. A delay circuit is provided to delay the operation of the switching circuit. Thus, the on-off electromagnetic valve is operated at a fixed duty ratio after the wide open condition continues a predetermined period.

A system for controlling air-fuel ratio for an internal combustion engine having a two-barrel carburetor. An electronic controller compares the output signal of an O.sub.2 sensor with a reference corresponding to stoichiometry and for operating on-off electromagnetic valve(s) for controlling the air-fuel ratio to a value approximately equal to the stoichiometric air-fuel ratio. A constant signal generating circuit is selectively connected to the electronic controller. An engine operation detector is provided for detecting the transition from a heavy load condition to light load condition for producing a signal. A switching circuit operatively connects the constant signal generating circuit to the electronic controller for providing a fixed duty ratio of the valve, and renders the electronic controller non-responsive to the output of the O.sub.2 sensor. A switch actuating circuit is provided to actuate the switch by the output signal of the engine operation detector for a predetermined period. Thus, the on-off electromagnetic valve is operated at a small duty ratio after the heavy load condition for a predetermined period.

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Musashino, Japan

Yoshiaki Ohara