Internal-combustion engines – Engine speed regulator – Idle speed control
Reexamination Certificate
2003-03-31
2004-11-30
Kwon, John T. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Idle speed control
C123S339140, C123S676000
Reexamination Certificate
active
06823839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for and a method of controlling the temperature of an exhaust gas sensor disposed in the exhaust passage of an internal combustion engine, and a recording medium storing a program for controlling the temperature of such an exhaust gas sensor.
2. Description of the Related Art
Exhaust gas sensors are often disposed in the exhaust passages of internal combustion engines for detecting a physical quantity as to an exhaust gas component state, such as an exhaust gas component concentration, for the purpose of controlling the operation of the internal combustion engine or monitoring the status of an exhaust gas purifying system. Specifically, an exhaust gas sensor is disposed at a certain location in the exhaust gas passage and has an element sensitive to an exhaust gas component state to be detected, the element being positioned for contact with an exhaust gas flowing through the exhaust passage. For example, an air-fuel ratio sensor such as an O
2
sensor or the like is disposed as an exhaust gas sensor upstream or downstream of an exhaust gas purifying catalyst disposed in the exhaust passage for the purpose of controlling the air-fuel ratio of the internal combustion engine in order to keep well the purifying ability of the catalyst.
Some air-fuel ratio sensors have a built-in heater for heating the active element thereof for increasing the temperature of the element and activating the element to enable the element to perform its essential functions and also removing foreign matter deposited on the element. For example, an air-fuel ratio sensor such as an O
2
sensor or the like usually has an electric heater for heating the active element thereof. After the internal combustion engine has started to operate, the electric heater is energized to increase the temperature of the active element of the O
2
sensor to activate the active element and keep the active element active.
As shown in
FIG. 3
of the accompanying drawings, the O
2
sensor produces an output voltage Vout which changes with a large gradient with respect to a change in the air-fuel ratio of an exhaust gas, i.e., which is highly sensitive to a change in the air-fuel ratio, only in a small range &Dgr; (near a stoichiometric air-fuel ratio) of values of the air-fuel ratio that is represented by an oxygen concentration in the exhaust gas to which the active element is sensitive. A change in the output voltage Vout of the O
2
sensor, i.e., a gradient of the output voltage Vout with respect to the air-fuel ratio, is smaller in air-fuel ratio ranges that are richer and leaner than the highly sensitive range &Dgr;. The output characteristics of the O
2
sensor, i.e., the gradient of the highly sensitive range &Dgr;, etc., vary depending on the temperature of the active element. When the air-fuel ratio is to be controlled using the output voltage from the O
2
sensor, therefore, it is desirable to keep the output characteristics of the O
2
sensor in a desired range as much as possible and hence to keep the temperature of the active element of the O
2
sensor in a desired temperature range as stably as possible for better air-fuel ratio control.
Not only O
2
sensors but also Many exhaust gas sensors have their output characteristics affected by the temperature of the active element. If the internal combustion engine is to be controlled using the output signal from the O
2
sensor, then it is preferable to keep the temperature of the active element of the exhaust gas sensor in a desired temperature range as stably as possible for better engine control. When the active element of the exhaust gas sensor is heated to clean the active element, it is also preferable to keep the temperature of the active element of the exhaust gas sensor in a desired temperature range for a better cleaning effect.
As disclosed in Japanese laid-open patent publication No. 2000-304721 by the applicant of the present application, it is known to estimate the temperature of the active element of an exhaust gas sensor (an air-fuel ratio sensor in the publication) and control the energization of a heater (an electric heater) based on the estimated temperature for thereby keep the temperature of the active element in a desired temperature range to obtain appropriate output characteristics from the exhaust gas sensor. According to the disclosed arrangement, the resistance of the heater is recognized from detected values of a current flowing through the heater and a voltage applied across the heater, and the temperature of the active element is estimated based on the detected resistance of the heater.
The heater is controlled based on only the estimated temperature of the active element. Consequently, when the operating state of an internal combustion engine changes frequently and hence the temperature of the exhaust gas emitted therefrom changes frequently, it is difficult to keep the temperature of the active element in a desired temperature range stably and reliably. This drawback occurs also if the temperature of the active element is detected by a temperature sensor and the heater is controlled based on the detected temperature.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus for and a method of controlling the temperature of the active element of an exhaust gas sensor stably in a desired temperature range even if the temperature of an exhaust gas changes.
Another object of the present invention is to provide a recording medium storing a temperature control program controlling the temperature of the active element of an exhaust gas sensor stably in a desired temperature range even if the temperature of an exhaust gas changes.
To achieve the above objects, there is provided in accordance with a first aspect of the present invention an apparatus for controlling the temperature of an exhaust gas sensor disposed in an exhaust passage of an internal combustion engine and having an active element for contacting an exhaust gas flowing through the exhaust passage and a heater for heating the active element, the apparatus comprising exhaust gas temperature estimating means for sequentially estimating the temperature of the exhaust gas flowing through the exhaust passage, using at least a parameter representative of an operating state of the internal combustion engine, and heater control means for controlling the heater to equalize the temperature of the active element of the exhaust gas sensor with a predetermined target temperature, using an estimated value of the temperature of the exhaust gas from the exhaust gas temperature estimating means.
Similarly, there is also provided in accordance with the first aspect of the present invention a method of controlling the temperature of an exhaust gas sensor disposed in an exhaust passage of an internal combustion engine and having an active element for contacting an exhaust gas flowing through the exhaust passage and a heater for heating the active element, the method comprising the steps of sequentially estimating the temperature of the exhaust gas flowing through the exhaust passage, using at least a parameter representative of an operating state of the internal combustion engine, and controlling the heater to equalize the temperature of the active element of the exhaust gas sensor with a predetermined target temperature, using an estimated value of the temperature of the exhaust gas.
There is also provided in accordance with the first aspect of the present invention a recording medium readable by a computer and storing a temperature control program for being executed by the computer for controlling the temperature of an exhaust gas sensor disposed in an exhaust passage of an internal combustion engine and having an active element for contacting an exhaust gas flowing through the exhaust passage and a heater for heating the active element, the temperature control program comprising an exhaust gas temperature estimating program for enabling the computer to carry
Iwaki Yoshihisa
Yasui Yuji
Honda Giken Kogyo Kabushiki Kaisha
Kwon John T.
Squire Sanders & Dempsey L.L.P.
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