Air/fuel ratio monitoring system in ic engine using oxygen sensor
A system is described for monitoring the air/fuel ratio of an air-fuel mixture supplied to an internal combustion engine. The system consists of: a concentration cell type oxygen sensor means disposed in an exhaust passage of the engine, the oxygen sensor having a laminate of an inner electrode layer, a microscopically porous layer of an oxygen ion conductive solid electrolyte, and an outer electrode layer exposed to exhaust gas, the sensor means producing an output which becomes a high-level voltage signal when the air/fuel ratio is below the stoichiometric ratio of the air-fuel mixture, and which becomes a low-level voltage signal when the air/fuel ratio is above the stoichiometric ratio; judgement means for producing an air/fuel ratio signal which indicates whether the air/fuel ratio is above or below the stoichiometric ratio by comparing the output of the oxygen sensor with a reference voltage; modulating means for producing a modulated voltage signal by subtracting a first fixed voltage from the output of the oxygen sensor when the air/fuel ratio signal indicates that the air/fuel ratio is below the stiochiometric ratio and by adding a fixed definite voltage to the output of the oxygen sensor when the air/fuel ratio signal indicates that the air/fuel ratio is above the stoichiometric ratio; and smoothing means, having a variable time constant, for smoothing the modulated voltage signal to thereby produce a smoothed voltage and for supplying the smoothed voltage to the judgement means as the reference voltage; control means for varying the time constant of the smoothing means as a function of a change in the output of the oxygen sensor.
- Assignee:
- Nissan Motor Co., Ltd., Yokohama
- Patent Number(s):
- US 4601273
- OSTI ID:
- 5476394
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
330100* -- Internal Combustion Engines
CONTROL SYSTEMS
DISPERSIONS
ELECTRIC CONDUCTIVITY
ELECTRIC POTENTIAL
ELECTRICAL PROPERTIES
ELECTRODES
ELECTROLYTES
ENGINES
EXHAUST GASES
EXHAUST SYSTEMS
FLUIDS
FUEL-AIR RATIO
GASEOUS WASTES
GASES
HEAT ENGINES
INTERNAL COMBUSTION ENGINES
IONIC CONDUCTIVITY
LAYERS
MEASURING INSTRUMENTS
METERS
MIXTURES
MODULATION
MONITORING
OXYGEN METERS
PHYSICAL PROPERTIES
POROSITY
SIGNALS
SOLID ELECTROLYTES
STOICHIOMETRY
WASTES