Measuring and testing – Instrument proving or calibrating – Gas or liquid analyzer
Reexamination Certificate
2001-07-17
2003-10-14
Raevis, Robert (Department: 2856)
Measuring and testing
Instrument proving or calibrating
Gas or liquid analyzer
Reexamination Certificate
active
06631632
ABSTRACT:
The disclosure of Japanese Patent Application No. 2000-225615 filed on Jul. 26, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an intake air oxygen concentration sensor calibration device and method that calibrates an output of an oxygen concentration sensor that is provided in a prescribed arrangement along an intake passageway of an internal combustion engine and detects concentration of oxygen contained in intake air.
2. Description of the Related Art
There is available art that is intended to enhance accuracy in control of the air-fuel ratio of internal combustion engines by providing an oxygen concentration sensor in a prescribed arrangement along an intake passageway of the internal combustion engine to detect oxygen concentration in intake air and using the oxygen concentration data detected for controlling operations of the internal combustion engine. One such arrangement is disclosed in Japanese Patent Application Laid-Open Publication No. 11-2153.
The output of the oxygen concentration sensor, however, varies with time and operating conditions (such as engine loads and purge conditions of trapped fuel) of the internal combustion engine. If control is provided for operations of the internal combustion engine, such as air-fuel ratio control, based on variable outputs as those noted above, it is not possible to provide accurate control, which could result in deteriorated exhaust emissions and driveability.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of this invention to provide an intake air oxygen concentration sensor calibration device and method that calibrates an output of an oxygen concentration sensor that is provided in a prescribed arrangement along an intake passageway and detects concentration of oxygen contained in intake air, thereby allowing control of high accuracy to be provided.
A first aspect of this invention is an intake air oxygen concentration sensor calibration device that is provided with an oxygen concentration sensor provided in a prescribed arrangement along an intake passageway of an internal combustion engine to detect concentration of oxygen contained in intake air, intake passageway pressure detection means that detects pressure in the intake passageway, stable condition determination means that compares the amplitude of fluctuations in intake passageway pressure detected by the intake passageway pressure detection means with a predetermined stable condition criterion value previously stored in memory to determine whether the intake passageway pressure is in a stable condition, calibration coefficient calculation means that calculates a calibration coefficient used to calibrate the output of the oxygen concentration sensor based on the intake passageway pressure detected by the intake passageway pressure detection means and a reference output value of the oxygen concentration sensor previously stored in memory, and calibration means that calibrates the output of the oxygen concentration sensor based on the calibration coefficient calculated by the calibration coefficient calculation means, wherein the stable condition criterion value is set so that the smaller the intake passageway pressure detected by the intake passageway pressure detection means, the smaller the value is, and the greater the intake passageway pressure detected by the intake passageway pressure detection means, the greater the value is, and the calibration coefficient calculation means updates the calibration coefficient when the stable condition determination means determines that the intake passageway pressure remains stable.
According to the first aspect, the stable condition criterion value is set small when the intake passageway pressure detected by the intake passageway pressure detection means stays in a region of small values (and the stable condition criterion value is set large when the intake passageway pressure detected by the intake passageway pressure detection means stays in a region of large values). This permits a precise determination to be made to determine whether the intake passageway pressure remains stable, that is, whether it is in a condition in which, when the calibration coefficient is to be calculated based on the output of the oxygen concentration sensor, the calculation of the calibration coefficient is less susceptible to effects of errors such as a response lag of the oxygen concentration sensor. Results of detection of greater accuracy can therefore be obtained by calibrating the output of the oxygen concentration sensor by using the calibration means while the intake passageway pressure remains stable (or when the calculation of the calibration coefficient is less susceptible to effects of errors such as a response lag of the oxygen concentration sensor).
A second aspect of this invention is an intake air oxygen concentration sensor calibration device that is provided with an oxygen concentration sensor provided in a prescribed arrangement along an intake passageway of an internal combustion engine to detect concentration of oxygen contained in intake air, intake passageway pressure detection means that detects pressure in the intake passageway, calibration coefficient calculation means that calculates a calibration coefficient used to calibrate the output of the oxygen concentration sensor based on the intake passageway pressure detected by the intake passageway pressure detection means and a reference output value of the oxygen concentration sensor previously stored in memory, and calibration means that calibrates the output of the oxygen concentration sensor based on the calibration coefficient calculated by the calibration coefficient calculation means, wherein the calibration coefficient calculation means stores in memory the intake passageway pressure when the calibration coefficient is updated and updates the calibration coefficient only when the intake passageway pressure detected by the intake passageway pressure detection means is greater than the intake passageway pressure when the calibration coefficient was updated last.
According to this second aspect, an error contained in the output of the oxygen concentration sensor accounts for a smaller percentage of the entire output of the oxygen concentration sensor when the output is greater, and the oxygen concentration sensor has a characteristic that the higher the pressure detected, the higher the output it produces even with the same oxygen concentration. It is therefore possible not to update the calibration coefficient when the intake passageway pressure is smaller than that when the calibration coefficient was updated last, thereby maintaining the last calibration coefficient, which is considered to have greater accuracy. When the intake passageway pressure is greater than that when the calibration coefficient was updated last, on the other hand, it is possible to calculate anew the calibration coefficient that has greater accuracy.
A third aspect of this invention is an intake air oxygen concentration sensor calibration device that is provided with an oxygen concentration sensor provided in a prescribed arrangement along an intake passageway of an internal combustion engine to detect concentration of oxygen contained in intake air, intake passageway pressure detection means that detects pressure in the intake passageway, calibration coefficient calculation means that calculates a calibration coefficient used to calibrate the output of the oxygen concentration sensor based on the intake passageway pressure detected by the intake passageway pressure detection means and a reference output value of the oxygen concentration sensor previously stored in memory, and calibration means that calibrates the output of the oxygen concentration sensor based on the calibration coefficient calculated by the calibration coefficient calculation means. The intake air oxygen concentration sensor calibration device according
Matsubara Takuji
Yoshioka Mamoru
Kenyon & Kenyon
Raevis Robert
Toyota Jidosha & Kabushiki Kaisha
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