Misfire detecting apparatus for internal combustion engine

A misfire detecting method for an internal combustion engine, comprising the steps of:

• a) detecting a rotational speed parameter indicative of a rotational speed of said engine;
• b) performing a moving averaging calculation with respect to data of the detected rotational speed parameter to calculate an averaged speed parameter, a number of the data being equal to a sampling number (NTDC);
• c) calculating a reference value of the averaged speed parameter;
• d) calculating a relative speed parameter, which is a deviation of the averaged speed parameter corresponding to the rotational speed parameter detected at every predetermined crank angle from the reference value;
• e) calculating an integrated value of the relative speed parameter;
• and
• f) performing a misfire determination based on the integrated value,
• wherein the sampling number (NTDC) is determined by an equation:
• NTDC=720/(N×Dθ)
• where (N) is a number of cylinders of said engine, and (Dθ) is a sampling angular period (degree) of the rotational speed parameter.

A computer program embodied on a computer-readable medium, for causing a computer to implement a misfire detecting method for an internal combustion engine, said misfire detecting method comprising the steps of:

• a) detecting a rotational speed parameter indicative of a rotational speed of said engine;
• b) performing a moving averaging calculation with respect to data of the detected rotational speed parameter to calculate an averaged speed parameter, a number of the data being equal to a sampling number (NTDC);
• c) calculating a reference value of the averaged speed parameter;
• d) calculating a relative speed parameter, which is a deviation of the averaged speed parameter corresponding to the rotational speed parameter detected at every predetermined crank angle from the reference value;
• e) calculating an integrated value of the relative speed parameter;
• and
• f) performing a misfire determination based on the integrated value,
• wherein the sampling number (NTDC) is determined by an equation:
• NTDC=720/(N×Dθ)
• where (N) is a number of cylinders of said engine, and (Dθ) is a sampling angular period (degree) of the rotational speed parameter.