Air-fuel ratio control system
An air-fuel ratio control system is disclosed for an internal combustion engine having an O/sub 2/-sensor for detecting the concentration of oxygen of exhaust gases passing through the exhaust passage, an electromagnetic valve for correcting the air-fuel ratio of the air-fuel mixture supplied by a carburetor, a feedback control circuit comprising a judging circuit for judging an output signal of the O/sub 2/-sensor and a driving circuit for driving the electromagnetic valve in dependency on an output signal of the judging circuit for controlling the air-fuel ratio to a value approximately to the stoichiometric air-fuel ratio. A Maximum and minimum value hold circuits respectively hold a maximum and a minimum value in one cycle of output variation of the detector. A first comparator compares the outputs of both hold circuits. A second comparator compares the output of the O/sub 2/-sensor with a predetermined level. A gate circuit is responsive to the output signals of the comparators for producting gate control signals. Switch circuits connect the O/sub 2/-sensor to the judging circuit. The gate circuit and the switch circuits operate such that when the output of the second comparator is high representing an output of the O/sub 2/-sensor is higher than the predetermined level, or when the output of the second comparator is low and the output of the first comparator means is high, the output of the O/sub 2/-sensor is connected to the judging circuit for performing the feedback control irrespective of the level of the detected air-fuel ratio, but when the outputs of both comparators are low, the fixed voltage supply source is connected to the judging circuit.
- Assignee:
- Fuji Jukogyo Kabushiki Kaisha (Japan); Nissan Motor Co., Ltd. (Japan)
- Patent Number(s):
- US 4408584
- OSTI ID:
- 5320623
- Resource Relation:
- Patent Priority Date: Priority date 16 Jul 1980, Japan; Other Information: PAT-APPL-282984
- Country of Publication:
- United States
- Language:
- English
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Air-fuel ratio control system
Air-fuel ratio control system