Power plants – Internal combustion engine with treatment or handling of... – Having sensor or indicator of malfunction – unsafeness – or...
Reexamination Certificate
2000-11-09
2002-08-06
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Having sensor or indicator of malfunction, unsafeness, or...
C060S274000, C060S276000, C060S285000
Reexamination Certificate
active
06427438
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of evaluating a deteriorated state of a catalytic converter for purifying an exhaust gas which is disposed in the exhaust passage of an internal combustion engine.
2. Description of the Related Art
Generally, catalytic converters such as three-way catalytic converters are disposed in the exhaust passages of internal combustion engines for purifying gas components including HC (hydrocarbon), NOx (nitrogen oxides), etc. contained in the exhaust gas emitted from the internal combustion engines.
Each of the gas components is purified by the catalytic converter at a substantially maximum purification rate when the air-fuel ratio of the exhaust gas upstream of the catalytic converter is of a certain value or a value close thereto. If the actual air-fuel ratio is shifted from the certain value to a fuel-lean value or a fuel-rich value, then the purification rate of the gas component tends to be lowered. The air-fuel ratio of the exhaust gas upstream of the catalytic converter specifically is recognized from the concentration of oxygen in the exhaust gas that enters the catalytic converter and represents the air-fuel ratio of an air-fuel mixture which is burned by the internal combustion engine to produce the exhaust gas. The air-fuel ratio will hereinafter referred to as the air-fuel ratio of the internal combustion engine.
The catalytic converters of the above type are gradually deteriorated, with their purifying capability lowered, due to continued use over time. In order to keep the exhaust gas purified adequately by a catalytic converter, the catalytic converter needs to be replaced with a new one when it is deteriorated to a certain extent. For properly replacing the deteriorated catalytic converter with a new one, it is necessary to rely on a technology to evaluate a deteriorated state of the catalytic converter appropriately.
In recent years, there have been developed exhaust gas sensors, specifically HC sensors and NOx sensors, capable of detecting relatively accurately the concentrations of various gas components, including HC, NOx, etc., to be purified by catalytic converters. Some of these exhaust gas sensors generally have their output levels increasing substantially linearly as the concentrations of the detected gas components increase. The output levels of other exhaust gas sensors decrease as the concentrations of the detected gas components increase. The output characteristics of the exhaust gas sensors of the former type will hereinafter be referred to as positive characteristics, and the output characteristics of the exhaust gas sensors of the latter type will hereinafter be referred to as negative characteristics.
Since the above exhaust gas sensors are capable of detecting the concentrations of gas components that are actually purified by a catalytic converter, i.e., the concentrations of gas components which are directly affected by the deteriorated state of the catalytic converter, the exhaust gas sensors can effectively be used to recognize the deteriorated state of the catalytic converter.
For example, two exhaust gas sensors are disposed respectively upstream and downstream of the catalytic converter, and while the internal combustion engine is in operation, the ratio of output levels of those exhaust gas sensors is determined to directly recognize the purification rate of the gas component detected by the exhaust gas sensors and purified by the catalytic converter. The purification rate decreases as the deterioration of the catalytic converter goes on. Therefore, if the purification rate of the gas component is recognized as described above, then it is possible to appropriately determine the deteriorated state of the catalytic converter.
However, due to the effect of a response delay of the catalytic converter, it is actually difficult to accurately recognize the purification rate of the gas component detected by the exhaust gas sensors and purified by the catalytic converter. Attempts to increase the accuracy of the purification rate that can be recognized by canceling the effect of the response delay of the catalytic converter are liable to be complex.
For the above reasons, there has been a demand for a new technology capable of appropriately determining the deteriorated state of a catalytic converter according to a relatively simple process using exhaust sensors such as HC sensors and NOx sensors.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of appropriately evaluating a deteriorated state of a catalytic converter for purifying an exhaust gas, according to a relatively simple process using an exhaust sensor which detects a gas component such as HC, NOx, or the like to be purified by the catalytic converter.
To achieve the above object, there is provided a method of evaluating a deteriorated state of a catalytic converter which is disposed in an exhaust passage of an internal combustion engine for purifying an exhaust gas flowing through the exhaust passage, using data of the output of an exhaust gas sensor which is disposed downstream of the catalytic converter for detecting the concentration of a particular component of the exhaust gas purified by the catalytic converter while the internal combustion engine is in operation, comprising the steps of identifying the values of parameters contained in a nonlinear function of a predetermined type for expressing the correlating characteristics of the concentration of the particular component detected by the exhaust gas sensor with respect to an air-fuel ratio of the exhaust gas upstream of the catalytic converter, using data of the air-fuel ratio of the exhaust gas upstream of the catalytic converter and the data of the output of the exhaust gas sensor, and evaluating the deteriorated state of the catalytic converter based on the identified values of the parameters.
The quadratic function has an independent variable represented by the air-fuel ratio of the exhaust gas upstream of the catalytic converter, e.g. the output of a sensor for detecting the air-fuel ratio, the air-fuel ratio recognized from the output of the sensor, or a target value of the air-fuel ratio, and a dependent variable represented by the output of the exhaust gas sensor or the concentration of the particular component recognized from the output of the exhaust gas sensor. The nonlinear function may be a function of higher degree, e.g., a quadratic function, a cubic function, or the like. The parameters specifically comprise parameters which determine the configuration of the graph of the nonlinear function. For example, if the nonlinear function is a function of higher degree, e.g., a quadratic function, a cubic function, or the like, then the parameters comprise coefficients of terms of the different degrees and a constant term thereof.
The air-fuel ratio of the exhaust gas upstream of the catalytic converter specifically comprises an air-fuel ratio recognized from the concentration of oxygen contained in the exhaust gas. The air-fuel ratio may be referred to simply as an air-fuel ratio of the internal combustion engine.
The particular component detected by the exhaust gas sensor may comprise HC (hydrocarbon), NOx (nitrogen oxide), or the like. Thus, the exhaust gas sensor may comprise an HC sensor, an NOx sensor, or the like.
In the above identifying step, the values of the parameters of the nonlinear function are identified using data of the air-fuel ratio of the internal combustion engine, i.e., the data of the air-fuel ratio of the exhaust gas upstream of the catalytic converter, and the data of the output of the exhaust gas sensor, i.e., the data of the detected value of the concentration of the particular component, thus determining the nonlinear function which approximately expresses, with an equation, the correlating characteristics of the concentration of the particular component detected by the exhaust gas sensor with respect to the air-fuel ratio of the internal combustion engine, i.
Oshima Yoshikazu
Yasui Yuji
Arent Fox Kintner & Plotkin & Kahn, PLLC
Denion Thomas
Honda Giken Kogyo Kabushiki Kaisha
Nguyen Tu M.
LandOfFree
Method of evaluating deteriorated state of catalytic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of evaluating deteriorated state of catalytic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of evaluating deteriorated state of catalytic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2895379