US 4,708,777 AGranted

Method and apparatus for controlling heater of a gas sensor

AssigneeNippondenso Co., Ltd.

InventorHiroaki Kuraoka

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Abstract

Energization of a heater built in a gas sensor, such as an oxygen sensor, used in an air/fuel ratio control system of an internal combustion engine, is controlled to maintain the temperature of the same within a desired range. The temperature of the heater is calculated using a measured resistance value of the heater, and engine parameters used for estimating a specific engine operating condition. To this end operating state of the engine is first detected to determine whether it is possible to estimate the actual temperature of the heater, and when possible, a reference resistance value of the heater at a reference temperature such as 0.degree. K. or 0.degree. C. is caluclated using estimated heater temperature and a measured resistance value. Once the initial resistance value is obtained, this is used to calculate actual heater temperature using measured resistance value and a predetermined temperature coefficient.

Claims14

Dependent claims

Apparatus for controlling a heater of a gas sensor used for detecting the concentration of a gas component of exhaust gases from an internal combustion engine, comprising:

(a) a temperature sensor for detecting a temperature relating to said engine;
(b) first means for detecting a particular engine operating condition of thermal equilibrium from which it is possible to estimate the temperature of said heater using said detected temperature relating to said engine;
(c) second means for measuring an actual resistance value of said heater;
(d) third means responsive to said temperature sensor and first and second means for calculating a reference resistance value of said heater at a predetermined reference temperature using said detected temperature relating to said engine and said resistance of said heater at the time said first means detects said particular engine operating condition;
(e) fourth means responsive to said second and third means for calculating the temperature of said heater using said measured heater resistance value, said reference resistance value obtained by said third means, and a predetermined temperature coefficient and for producing a control signal using the calculated heater temperature so that said calculated heater temperature equals a desired temperature;
and
(f) fifth means for controlling the energization of said heater in accordance with said control signal.

4 more elements

A method of controlling a heater of a gas sensor used for detecting the concentration of a gas component of exhaust gases from an internal combustion engine, comprising the steps of:

(a) detecting a temperature relating to said engine;
(b) detecting a particular engine operating condition of thermal equilibrium from which it is possible to estimate the temperature of said heater using said detected temperature relating to said engine;
(c) measuring an actual resistance value of said heater;
(d) calculating a reference resistance value of said heater at a predetermined reference temperature using said temperature relating to said engine and said actual resistance of said heater at the time said particular engine operating condition is detected;
(e) calculating the temperature of said heater using said measured heater resistance value, said reference resistance value, and a predetermined temperature coefficient;
(f) producing a control signal using the calculated heater temperature so that said calculated heater temperature equals a desired temperature;
and
(g) controlling the energization of said heater in accordance with said control signal.

5 more elements

Dependencies are inferred from the claim text.