Misfire detecting device for internal combustion engine

Abstract

The invention provides a misfire detecting device for an internal combustion engine that is able to increase an accuracy in detecting the occurrence of misfire having the level at which the exhaust purifying function of the filter is impaired. The occurrence of the misfire having a level at which exhaust purifying function of a catalyst is impaired (OT-level misfire) is detected. Upon the detection of the OT-level misfire, basic OT risk from the misfire is multiplied by a correction coefficient corresponding to the accumulated PM amount on the catalyst. The basic OT risk from the misfire is abasic value of OT risk from the misfire which is set based on the operating condition of the engine. The correction coefficient is set to a smaller value as the accumulated PM amount increases. Therefore, the OT risk from the misfire after the multiplication decreases as the accumulated PM amount increases. Thus, it is possible to increase the accuracy in detecting the occurrence of the OT-level misfire caused by the combustion of the PM from the misfire.

Description

technical field [0001] The invention relates to a misfire detection device for an internal combustion engine. Background technique [0002] Japanese Patent Application Laid-Open No. 5-202799 discloses a misfire detection device that evaluates damage to an exhaust purification device caused by the occurrence of misfire based on the operating state of an internal combustion engine. This conventional device calculates an evaluation value when a misfire occurs during the evaluation period. This evaluation value is calculated in association with the operating state when misfire occurs. In addition, this conventional device sums up the evaluation values ​​calculated during the evaluation period after the evaluation period elapses, and when the total value is equal to or greater than a threshold value, it is determined that a misfire of a level at which the function of the exhaust purification device is impaired has occurred. [0003] prior art literature [0004] patent documen...

AI Technical Summary

Problems solved by technology

In addition, in this conventional device, after the elapse of the evaluation period, the evaluation values ​​calculated during the evaluation period are totaled, and when the total value is equal to or greater than a threshold value, it is determined that a misfire of a level at which the function of the exhaust purification device is impaired has occurred.

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