Measuring and testing – Gas analysis – Gas of combustion
Patent
1994-10-05
1995-10-31
Chilcot, Richard
Measuring and testing
Gas analysis
Gas of combustion
G01N 2716, G01N 27407
Patent
active
054619025
ABSTRACT:
An oxygen sensor heat controlling apparatus includes: a current-limiting type oxygen sensor whose electrical characteristic varies with a change in an oxygen concentration of exhaust gases from an internal combustion engine, and whose alternating current resistance varies with a change in an operating temperature of the sensor; a voltage source connected with the sensor through a resistor to supply a given voltage to the sensor; a differential amplifier having a first input connected with the sensor and a second input connected with the voltage source through the resistor, the amplifier producing at its output an output signal derived from the difference between the given voltage and an output voltage from the sensor, the output signal being representative of the oxygen concentration of the exhaust gases; a first closed loop circuit which connects the output of the amplifier with the first input of the amplifier via a first feedback resistor so as to control a current flow through the sensor; a second closed loop circuit which connects the output of the amplifier with the second input thereof via a second feedback resistor; a heater for heating the sensor; an oscillation detecting circuit for detecting occurrence of an oscillation at the output of the amplifier and for outputting a pulse when the occurrence of the oscillation is detected; and a current control circuit for applying current to the heater when the oscillation has not occurred, and for stopping the application of current to the heater in response to the pulse.
REFERENCES:
patent: 4251225 (1981-02-01), Handa et al.
patent: 4291572 (1981-09-01), Maurer et al.
patent: 4419190 (1983-12-01), Dietz et al.
patent: 4611562 (1986-09-01), Nakano et al.
patent: 4732128 (1988-03-01), Yoshioka et al.
patent: 5279145 (1994-01-01), Suzuki
patent: 5327780 (1994-07-01), Entenmann et al.
Chilcot Richard
Dombroske George M.
Toyota Jidosha & Kabushiki Kaisha
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