Misfire detecting device for internal combustion engine

摘要

A misfire detecting device is provided with a rotation detecting sensor 3 for detecting rotation signals corresponding to the timing of ignition of the cylinders of an engine. The device further includes a control unit which has continuous misfire detecting means for detecting the occurrence of a continuous misfire in the engine and intermittent misfire detecting means for detecting the occurrence of an intermittent misfire in it. Those detecting means operate according to the rotation signals provided by the rotation detecting sensor. When either the continuous misfire detecting means or the intermittent misfire detecting means detects the occurrence of a misfire, it is determined that a misfire has actually occurred in the engine. The continuous misfire determining means has arithmetic means for calculating a rotation variation rate from a deviation in rotation period of one and the same segment of the rotation detecting rotor, and the intermittent misfire detecting means also has arithmetic means for calculating a rotation variation rate from a deviation in rotation period corresponding to the order of combustion of the cylinders, and has misfire detecting threshold values respectively for the cylinders.