Abnormality diagnosing device for internal combustion engine and abnormality diagnosing method therefor

Abstract

A temperature of a catalyst disposed in an exhaust system is raised to a target bed temperature by supplying an unburned fuel component to the catalyst. A learned value is updated based upon a catalyst bed temperature under a temperature increase control and the target bed temperature so that the learned value corresponds to a difference between the respective temperatures. Whether the learned value is out of a proper range or not is determined whenever the learned value is updated. Abnormality is determined when determination that the learned value is out of the proper range is made over several successive updates of the learned value.

Description

INCORPORATION BY REFERENCE[0001]The disclosure of Japanese Patent Application No. 2006-168847 filed on Jun. 19, 2006 including the specification, drawings and abstract is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to an abnormality diagnosing device for an internal combustion engine and an abnormality diagnosing method therefor.[0004]2. Description of the Related Art[0005]Conventionally, as an exhaust gas purification system of an internal combustion engine such as, for example, a diesel engine for a vehicle, a system including a particulate matter (PM) filter and a catalytic converter disposed in an exhaust system is known. The PM filter traps PM whose major component is soot. The catalytic converter includes a storage reduction type NOx catalyst for purifying exhaust gas, i.e., nitrogen oxides (NOx). In such an exhaust gas purification system, a temperature increase control is executed to r...

AI Technical Summary

Benefits of technology

[0012]The invention provides an abnormality diagnosing device for an internal combustion engine and an abnormality diagnosing method therefor that avoids incorrect abnormality determination when a temporary abnormality occurs.

[0017]In the aspect, the exhaust system of the internal combustion engine may have a filter for trapping particulate matter. The temperature increase control for increasing the temperature of the catalyst to the target bed temperature may be executed by supplying the unburned fuel component to the catalyst when to burn the particulate matter to regenerate the filter. Thus, reducing the amount of particulate matter trapped in the filter is to less than a prescribed amount.

[0019]In the first aspect, the abnormality diagnosing device may have counting means for increasing a count value when the learned value determining section determines that the learned value has fallen outside of the proper range and resets the count value to an initial value, for example, “0” when the learned value determining section determines that the learned value is in the proper range. The abnormality determining means determines that an abnormality is present when the count value becomes a determination value that is equal to or greater than a value that is incremented at least twice from the initial value, e.g., an integer such as “2”. The counting means can reset the count value to the initial value when the filter regeneration is completed.

Problems solved by technology

The abnormality such that the catalyst bed temperature does not reach the target bed temperature even though the unburned fuel components are supplied to the exhaust system to keep the catalyst bed temperature on the target bed temperature does not necessarily permanently occur but can temporarily occur.

When this occurs, if the abnormality is immediately determined when the learned value falls outside of the proper range, the determination of the abnormality may be incorrect when the temporary abnormality disappears afterwards.

However, according to the construction described above, even though the learned value falls outside of the proper range, the abnormality is not determined unless the learned value falls outside of the proper range over several successive updates of the learned value.

Therefore, the abnormality is not incorrectly determined when the catalyst bed temperature and the target bed temperature are temporarily inconsistent with each other.

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