Air-fuel ratio control system

Claim 1

A system for controlling the air-fuel ratio of mixture gas supplied to an internal combustion engine, comprising: an air-fuel ratio sensor, selectively applied with a predetermined bias voltage, for producing a characteristic saturation output current depending on concentration of oxygen contained in exhaust gas of said engine; means, responsive to said output current, for controlling said air-fuel ratio of said mixture gas supplied to said engine; and voltage regulation means for suspending function of said controlling means and reducing said bias voltage applied to said sensor when said controlling means determines that said engine requires a rich air-fuel ratio of said mixture gas.

Claim 2

A system for controlling the air-fuel ratio of mixture gas supplied to an internal combustion engine, comprising: an air-fuel ratio sensor, selectively applied with a predetermined bias voltage, for producing a characteristic saturation output current depending on concentration of oxygen contained in exhaust gas of said engine; means, responsive to said output current, for controlling said air-fuel ratio of said mixture gas supplied to said engine; and voltage regulation means for suspending function of said controlling means and reducing said bias voltage applied to said sensor when said controlling means determines that said engine requires a rich air-fuel ratio of said mixture gas.

Claim 6

A system for controlling the air-fuel ratio of mixture gas supplied to an internal combustion engine, comprising: an air-fuel ratio sensor in an exhaust pipe of said engine and selectively applied with a predetermined bias voltage for producing a characteristic saturation output current in accordance with composition of said exhaust gas; a sensor for detecting load on said engine; means for controlling, responsive to said engine-load sensor, said air-fuel ratio to provide an amount of fuel required by said engine and, for correcting, responsive to said air-fuel sensor, said fuel amount to attain a target air-fuel ratio depending on engine operating conditions; and voltage regulation means for reducing said bias voltage applied to said air-fuel ratio sensor when said air-fuel ratio sensor is inactive to thereby reduce physical deterioration of said sensor.

Claim 7

A system for controlling the air-fuel ratio of mixture gas supplied to an internal combustion engine, comprising: an air-fuel ratio sensor in an exhaust pipe of said engine and selectively applied with a predetermined bias voltage for producing a characteristic saturation output current in accordance with composition of said exhaust gas; a sensor for detecting load on said engine; means for controlling, responsive to said engine-load sensor, said air-fuel ratio to provide an amount of fuel required by said engine and, for correcting, responsive to said air-fuel sensor, said fuel amount to attain a target air-fuel ratio depending on engine operating conditions; and voltage regulation means for reducing said bias voltage applied to said air-fuel ratio sensor when said air-fuel ratio sensor is inactive to thereby reduce physical deterioration of said sensor.

Claim 9

A system for controlling the air-fuel ratio of mixture gas supplied to an internal combustion engine, comprising: an air-fuel ratio sensor having a cup-shaped solid electrolytic element with its interior exposed to a reference gas and its exterior exposed to exhaust gas of said engine, said air-fuel ratio sensor being selectively applied with a predetermined bias voltage and producing a characteristic saturation output current in accordance with the concentration of oxygen in said exhaust gas; voltage control means for controlling said bias voltage applied to said sensor; first means for calculating a basic amount of fuel required by said engine in accordance with a plurality of operation paratmeters of said engine; second means for calculating a feedback compensation amount in accordance with said output current of said air-fuel ratio sensor; third means for suspending said feedback compensation of said second means and for reducing said bias voltage applied to said air-fuel ratio sensor, by controlling said voltage control means, when said engine is in a condition requiring a rich mixture gas; and fourth means for determining an actual amount of fuel supply in accordance with said basic amount and said feedback compensation amount and for controlling supply of fuel to said engine in accordance with said determined actual amount.

Claim 10

A system for controlling the air-fuel ratio of mixture gas supplied to an internal combustion engine, comprising: an air-fuel ratio sensor having a cup-shaped solid electrolytic element with its interior exposed to a reference gas and its exterior exposed to exhaust gas of said engine, said air-fuel ratio sensor being selectively applied with a predetermined bias voltage and producing a characteristic saturation output current in accordance with the concentration of oxygen in said exhaust gas; voltage control means for controlling said bias voltage applied to said sensor; first means for calculating a basic amount of fuel required by said engine in accordance with a plurality of operation paratmeters of said engine; second means for calculating a feedback compensation amount in accordance with said output current of said air-fuel ratio sensor; third means for suspending said feedback compensation of said second means and for reducing said bias voltage applied to said air-fuel ratio sensor, by controlling said voltage control means, when said engine is in a condition requiring a rich mixture gas; and fourth means for determining an actual amount of fuel supply in accordance with said basic amount and said feedback compensation amount and for controlling supply of fuel to said engine in accordance with said determined actual amount.