Power plants – Internal combustion engine with treatment or handling of... – Having means analyzing composition of exhaust gas
Reexamination Certificate
2002-05-13
2004-03-30
Argenbright, Tony M. (Department: 3747)
Power plants
Internal combustion engine with treatment or handling of...
Having means analyzing composition of exhaust gas
C060S277000, C073S118040
Reexamination Certificate
active
06711891
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for controlling the air-fuel ratio of an internal combustion engine, and more particularly to an air-fuel ratio control apparatus which is capable of evaluating a deteriorated state of a catalytic converter for purifying an exhaust gas.
2. Description of the Related Art
There have been known various techniques for controlling the air-fuel ratio of an air-fuel mixture to be combusted by an internal combustion engine in order to achieve an appropriate purifying capability of a catalytic converter for purifying exhaust gases, such as a three-way catalytic converter, disposed in the exhaust passage of the internal combustion engine. See, for example, Japanese laid-open patent publication No. 9-324681 or U.S. Pat. No. 5,852,930, and Japanese laid-open patent publication No. 11-153051 or U.S. Pat. No. 6,112,517. According to the disclosed systems, an O
2
sensor (oxygen concentration sensor) is disposed downstream of the catalytic converter, and the air-fuel ratio of an air-fuel mixture is controlled according to a feedback control process (specifically, a sliding mode control process) in order to converge the output of the O
2
sensor to a predetermined target value (constant value).
The catalytic converter is progressively deteriorated and its purifying capability is lowered as the internal combustion engine is used over a long period of time. Therefore, the catalytic converter needs to be replaced with a brand-new catalytic converter when it has been deteriorated to a certain extent. It has thus been desired in the art to be able to adequately evaluate a deteriorated state of a catalytic converter which is combined with an internal combustion engine. Known systems for evaluating a deteriorated state of a catalytic converter are disclosed in Japanese patent No. 2526640 and Japanese laid-open patent publication No. 7-19033, for example. According to these disclosed evaluating systems, when the air-fuel ratio of an air-fuel mixture to be combusted by an internal combustion engine is changed from a leaner value to a richer value or from a richer value to a leaner value, the time required until the output of an O
2
sensor that is positioned downstream of the catalytic converter is inverted and the period in which the output of the O
2
sensor is inserted are measured. The deteriorated state of the catalytic converter is evaluated based on the evaluated values.
The disclosed systems, however, make it difficult to achieve an appropriate purifying capability of the catalytic converter at the time its deteriorated state is evaluated because it is necessary to positively change the air-fuel ratio in order to evaluate the deteriorated state of the catalytic converter. Stated otherwise, it is difficult for the disclosed system to evaluate the deteriorated state of the catalytic converter while at the same time maintaining an appropriate purifying capability of the catalytic converter.
The applicant of the present application has made an effort to develop an apparatus capable of evaluating a deteriorated state of a catalytic converter while controlling an air-fuel ratio to converge the output of an O
2
sensor that is positioned downstream of the catalytic converter to a given target value, i.e., maintaining a good purifying capability of the catalytic converter. For example, reference should be made to Japanese patent application No. 2000-139860 (Japanese laid-open patent publication No. 2000-241349). The disclosed system is based on the fact that the value of a certain parameter which is determined from the data of the output of an O
2
sensor that is positioned downstream of the catalytic converter exhibits characteristic properties as the deterioration of the catalytic converter progresses, and evaluates the deteriorated state of the catalytic converter based on the value of the parameter. The system thus arranged makes it possible to evaluate the deteriorated state of the catalytic converter while maintaining a good purifying capability of the catalytic converter.
In the above arrangements for controlling the air-fuel ratio to converge the output of the O
2
sensor that is positioned downstream of the catalytic converter to a given target value (see Japanese laid-open patent publication No. 9-324681 or U.S. Pat. No. 5,852,930, and Japanese laid-open patent publication No. 11-153051 or U.S. Pat. No. 6,112,517), the target value for the output of the O
2
sensor positioned downstream of the catalytic converter is basically a certain constant value. However, depending on the type of the catalytic converter, it may occasionally preferable to make variable the target value for the output of the O
2
sensor depending on the operating state of the internal combustion engine for the purpose of enabling the catalytic converter to achieve an appropriate purifying capability.
However, a control system for controlling the air-fuel ratio according to the variable target value for the output of the O
2
sensor positioned downstream of the catalytic converter tends to suffer certain drawbacks, given below, with respect to the reliability of the evaluation of the deteriorate state of the catalytic converter at the time of evaluating the deteriorate state of the catalytic converter while at the same time controlling the air-fuel ratio.
Since the output of the O
2
sensor is nonlinear with respect to the oxygen concentration (see the solid-line curve a in
FIG. 2
of the accompanying drawings), if the target value for the output of the O
2
sensor changes, then the output of the O
2
sensor changes differently when it is converged to the target value. As a result, the value of the parameter that is uniquely determined from the data of the output of the O
2
sensor is affected by a factor other than the deteriorate state of the catalytic converter, and the deteriorate state of the catalytic converter which is evaluated based on the value of the parameter tends to become less reliable than expected.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus for controlling the air-fuel ratio of an internal combustion engine to converge the output of an O
2
sensor that is positioned downstream of a catalytic converter to a target value which is variably established depending on the operating state of the internal combustion engine, the apparatus being capable of appropriately evaluating the deteriorated state of the catalytic converter while compensating for adverse effects which are produced by making the target value variable.
To achieve the above object, there is provided in accordance with a first aspect of the present invention an apparatus for controlling the air-fuel ratio of an internal combustion engine, comprising an oxygen concentration sensor disposed downstream of a catalytic converter which is disposed in an exhaust passage of an internal combustion engine, air-fuel ratio manipulating means for manipulating the air-fuel ratio of an air-fuel mixture to be combusted in the internal combustion engine to converge an output of the oxygen concentration sensor to a target value established depending on an operating state of the internal combustion engine, parameter generating means for generating a deterioration evaluating parameter for evaluating a deteriorated state of the catalytic converter according to an algorithm predetermined from data of the output of the oxygen concentration sensor while the air-fuel ratio manipulating means is manipulating the air-fuel ratio of the air-fuel mixture, and deteriorated state evaluating means for correcting the deterioration evaluating parameter depending on an average value of the target value or the output of the oxygen concentration sensor, and evaluating the deteriorated state of the catalytic converter based on the corrected deterioration evaluating parameter.
According to a second aspect of the present invention, there is also provided an apparatus for controlling the air-fuel ratio of an internal combustion engin
Hara Mikio
Kitamura Toru
Uedahira Hideki
Arent Fox Kintner & Plotkin & Kahn, PLLC
Argenbright Tony M.
Honda Giken Kogyo Kabushiki Kaisha
LandOfFree
Apparatus for controlling air-fuel ratio of internal... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for controlling air-fuel ratio of internal..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for controlling air-fuel ratio of internal... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3239455